This file was created by the TYPO3 extension publications --- Timezone: CEST Creation date: 2026-05-27 Creation time: 23:58:11 --- Number of references 129 Classical carbenes are highly reactive species that have traditionally been regarded as transient intermediates, making direct structural characterization a challenge. Among them, N-heterocyclic carbenes (NHCs) stand out for their stability and broad applicability, yet atomic-scale insights into their structure and electronic properties remain limited. Here, we report the on-surface single-molecule characterization of a free NHC deposited on ultrathin insulating NaCl layers on Au(111), enabling direct investigation of a reactive carbene in its free form. Using a combination of scanning tunneling microscopy (STM), atomic force microscopy (AFM), and density functional theory (DFT), we resolve its molecular structure and frontier orbital with sub-molecular resolution. We further demonstrate the reactivity of the free NHC through its on-surface complexation with a gold atom. These results demonstrate that real-space techniques enable direct insights into the structure and reactivity of free NHCs, helping to connect molecular properties with their broader functional applications. article 2026 3 26 1521-3773,1433-7851 10.1002/anie.202524266 Angewandte Chemie International Edition Wiley e24266 https://epub.uni-regensburg.de/id/eprint/79056 Ankita Das Tzu‐Chao Hung Andreas Rank Felix Giselbrecht Jonas Schön Mowpriya Das Nikos Doltsinis Saeed Amirjalayer Jascha Repp Frank Glorius We report quantum chemistry calculations performed on superconducting quantum processors for a molecule exhibiting the half-Möbius electronic topology originally introduced by Rončević et al. Using SqDRIFT, a randomized sample-based Krylov quantum diagonalization algorithm, we achieve reliable quantum simulations on active spaces corresponding to 36 orbitals (72 qubits) and extend previous studies up to 50 orbitals (100 qubits). We demonstrate that a systematic increase of active space sizes, which has a concrete impact on the accuracy of the electronic structure description, is achievable with state-of-the-art quantum processors, thus offering a promising path towards practically relevant quantum-assisted electronic-structure calculations. article 2026 3 09 10.48550/arXiv.2603.08696 arXiv 2603.08696 https://epub.uni-regensburg.de/id/eprint/78951 Samuele Piccinelli Stefano Barison Alberto Baiardi Francesco Tacchino Jascha Repp Igor Rončević Florian Albrecht Harry L. Anderson Leo Gross Alessandro Curioni Ivano Tavernelli Stereoisomers of C13Cl2 exhibiting helical orbitals around a ring of carbon atoms were synthesized by atom manipulation on NaCl surfaces. We resolved the enantiomeric geometries of the singlet states by atomic force microscopy and mapped their helical orbital densities by scanning tunnelling microscopy. A π-orbital basis of the helical, non-planar singlets that twists by 90° in one circulation is consistent with a half-Möbius topology. In such a topology, the π-orbital basis changes sign with respect to two circumnavigations and is periodic with respect to four circumnavigations. A quasiparticle on a ring with this boundary condition could be interpreted as carrying a Berry phase of π/2. We demonstrate reversible switching of the topology, between the two singlets of oppositely threaded half-Möbius topology, and the planar, topologically trivial, triplet state. Multireference calculations, including large-scale sample-based ab initio calculations executed on quantum hardware, reveal that the switching is associated with a helical pseudo Jahn-Teller effect. article 2026 3 05 1095-9203,0036-8075 10.1126/science.aea3321 Science - American Association for the Advancement of Science (AAAS) first release https://epub.uni-regensburg.de/id/eprint/78890 Igor Rončević Fabian Paschke Yueze Gao Leonard-Alexander Lieske Lene A. Gödde Stefano Barison Samuele Piccinelli Alberto Baiardi Ivano Tavernelli Jascha Repp Florian Albrecht Harry L. Anderson Leo Gross Phthalocyanines (Pcs) are a class of technologically relevant tetrapyrrolic macrocycles that offer rich photophysical properties as well as excellent tunability by means of chemical functionalization. Among such functionalization strategies, the synthesis of multinuclear, fully fused Pcs – adjacent macrocycles seamlessly fused through a shared aromatic ring into a continuous π-system – is particularly appealing for the preparation of new, exotic, atomically precise carbon frameworks. However, the notoriously low solubility of Pcs typically impedes the synthesis of oligomers beyond trimers. In addition, the positional control for specific units in large low-symmetry frameworks is particularly challenging. In this work, taking advantage of the benefits of on-surface synthesis under ultra-high vacuum (UHV) conditions, we present a strategy that allows the on-surface synthesis of cross-shaped Pc pentamers. This pentamer, which bears two different metal ions with pre-defined positional control, shows a small transport gap of 1.15 eV on Au(111). article 2025 12 18 1521-3773,1433-7851 10.1002/anie.202521922 Angewandte Chemie International Edition 65 Wiley e21922 11 https://epub.uni-regensburg.de/id/eprint/78363 Luis M. Mateo Tzu‐Chao Hung Andreas Rank Raffael Spachtholz Felix Giselbrecht Jonas Schön Leo Gross Jascha Repp Diego Peña Phthalocyanine (Pcs) sind eine Klasse technologisch bedeutender Tetrapyrrol-Makrozyklen, die vielfältige photophysikalische Eigenschaften besitzen und sich durch chemische Funktionalisierung hervorragend maßschneidern lassen. Unter den verschiedenen Funktionalisierungsstrategien ist die Synthese mehrkerniger, vollständig vernetzten Pcs – benachbarte Makrozyklen, die nahtlos über gemeinsame aromatische Ringe zu einem kontinuierlichen π-System verbunden sind – besonders vielversprechend für die Erzeugung neuer, exotischer und atomar präziser Kohlenstoffgerüste. Die meist geringe Löslichkeit von Pcs erschwert jedoch typischerweise die Synthese von Oligomeren mit mehr als drei Einheiten. Zudem stellt die präzise Positionskontrolle einzelner Bausteine in großen, niedrigsymmetrischen Strukturen eine besondere Herausforderung dar. In dieser Arbeit wird die oberflächengestützte Synthese unter Ultrahochvakuumbedingungen (UHV) genutzt, um eine Strategie zur Herstellung kreuzförmiger Pc-Pentamere vorzustellen. Dieses Pentamer, das zwei unterschiedliche Metallionen mit vordefinierter Positionierung enthält, zeigt auf Au(111) eine kleine Transportlücke von 1,15 eV. article 2025 12 18 1521-3757,0044-8249 10.1002/ange.202521922 Angewandte Chemie 138 Wiley e21922 11 https://epub.uni-regensburg.de/id/eprint/78364 Luis M. Mateo Tzu‐Chao Hung Andreas Rank Raffael Spachtholz Felix Giselbrecht Jonas Schön Leo Gross Jascha Repp Diego Peña On-surface synthesis (OSS) offers unique opportunities for fabricating carbon-based nanostructures that are unattainable by conventional wet-chemical synthesis. Despite OSS being extremely successful, the use of coadsorbates to promote reactions remains largely unexplored. In this study, we investigate the role of sodium chloride (NaCl) in promoting the Scholl reaction (oxidative aryl–aryl coupling) of hexaazatriphenylene (HAT) molecules on Au(111), leading to the growth of conjugated azaacene oligomers. Using scanning tunneling microscopy (STM), synchrotron-based X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations, we shed light on the reaction mechanism and the intermediates involved. Upon codeposition on Au(111), NaCl decomposes on the surface, releasing Na atoms that form thermally stable metal-organic complexes, enhancing precursor stability against desorption. This stabilizing effect allows HAT molecules to undergo regioselective intermolecular coupling for polymerization at elevated temperatures. This study highlights the role of alkali metals in on-surface chemical reactions and outlines a strategy for overcoming the precursor-desorption issue. article 2025 11 05 1521-3765,0947-6539 10.1002/chem.202502452 Chemistry – A European Journal 31 Wiley e02452 69 https://epub.uni-regensburg.de/id/eprint/78086 Tim Kratky Xunshan Liu Sebastian Günther Pingo Mutombo Luca Schio Luca Floreano Silvio Decurtins Jascha Repp Pavel Jelinek Shi‐Xia Liu Laerte L. Patera Since its introduction a little over 40 years ago, scanning probe microscopy has advanced to the point that certain compounds can be reliably characterized down to the individual atom. True to its title, this work focuses on investigations of single molecules by means of scanning probe methods, specifically, by scanning tunneling microscopy (STM) and atomic force microcopy (AFM). The former is used for the characterization of the electronic structure of a sample, whereas the sample’s atomic structure can be imaged by means of the latter. In this work, three aspects of scanning probe microscopy are explored. First, the distance- and voltage-dependent contrast of a CO-functionalized STM probe was investigated. For a CO-functionalized tip, a pronounced distance-dependent contrast transition was observed from a predominant p-wave-tip contrast for small tip-sample distances to an s-wave-tip contrast upon increasing the tip-sample distance. In this work, the aforementioned contrast transition was systematically investigated and explained by decay considerations of the tunneling matrix elements for tunneling between tip and sample. The observations were well reproduced by simulations using a fixed ratio of s- to p-wave states located at the apex of the tip. A method for simulating CO-tip STM orbital-density images was proposed that facilitates the comparison between measured and calculated orbital densities. Second, high-resolution AFM for the structural characterization of an incipient soot mixture was performed in order to advance the understanding of the soot-clustering process early in the flame. The AFM measurements were corroborated by orbital-density imaging using STM. Frontier molecular orbitals of the assigned molecular structures were calculated by density functional theory and compared to experimental orbital-density measurements. Besides molecular-mixture characterization, the π-electron localization was calculated for the observed open-shell molecules to explore reaction and clustering pathways. The results give insight into soot formation and could help in developing cleaner combustion processes and mitigating harmful particulate emissions from incomplete combustion. Third, tip-induced dissociation of functional groups was explored. By voltage pulses, up to three nitrene groups were generated by dissociation of azide groups from single molecules. The precursor and its mono-, di- and trinitrene products were characterized by means of AFM and STM. Complementary calculations of exchange couplings suggest an S = 1 ground state for a single nitrene center and ferromagnetic coupling between nitrene centers on individual molecules, indicating high-spin ground states of the generated molecules. thesis_rgbg 2025 10 23 https://epub.uni-regensburg.de/id/eprint/77605 Leonard-Alexander Lieske Electron spin resonance (ESR) is a widely employed spectroscopic technique for studying systems with unpaired electron spins, such as molecular radicals. Typically, many billions of spins are required to get a detectable ESR signal, which is subject to extensive ensemble averaging. Downscaling ESR to a single molecule allows studying the signatures of each individual molecule separately, applicable to biomolecules in their native environment, for example. Single-molecule ESR offers several novel research avenues, such as in quantum sensing with a single molecule. Over the last decades, four different single-molecule ESR approaches have been developed, which rely on either optically detected magnetic resonance or scanning-probe microscopy. An introduction into these four approaches including their deployment in pioneering works will be provided. article 2025 8 19 1521-3773,1433-7851 10.1002/anie.202506539 Angewandte Chemie International Edition 64 Wiley e20250653 37 https://epub.uni-regensburg.de/id/eprint/77554 Lisanne Sellies Jascha Repp Elektronenspinresonanz (ESR) ist eine weit verbreitete spektroskopische Methode zur Untersuchung von Systemen mit ungepaarten Elektronenspins, wie beispielsweise molekularen Radikalen. In der Regel sind viele Milliarden Spins erforderlich, um ein ESR-Signal zu erhalten, das dadurch einer starken Ensemblemittelung unterliegt. Das Herunterskalieren der ESR auf einzelne Moleküle ermöglicht es, die Signaturen der Moleküle einzeln zu messen – etwa bei Biomolekülen in ihrer natürlichen Umgebung. Die Einzelmolekül-ESR eröffnet mehrere neue Forschungsrichtungen, unter anderem im Bereich der Quantendetektion mit einem einzelnen Molekül. In den letzten Jahrzehnten wurden vier verschiedene Ansätze der Einzelmolekül-ESR entwickelt, die entweder auf optisch detektierter Magnetresonanz oder auf Rastersondenmikroskopie beruhen. Hier wird ein Überblick über diese vier Ansätze sowie deren Verwendung in wegweisenden Arbeiten vermittelt. article 2025 8 19 1521-3757,0044-8249 10.1002/ange.202506539 Angewandte Chemie 137 Wiley e202506539 37 https://epub.uni-regensburg.de/id/eprint/77555 Lisanne Sellies Jascha Repp Matter at the atomic-scale is inherently governed by the laws of quantum mechanics. This makes charges and spins confined to individual atoms – and interactions among them – an invaluable resource for fundamental research and quantum technologies alike. However, harnessing the inherent "quantumness" of atomic-scale objects requires that they can be precisely engineered and addressed at the individual atomic level. Since its invention in the 1980s, scanning tunneling microscopy (STM) has repeatedly demonstrated the unrivalled ability to not only resolve but manipulate matter at atomic length scales. Over the past decades, this has enabled the design and investigation of bottom-up tailored nanostructures as reliable and reproducible platforms to study designer quantum physics and chemistry, band topology, and collective phenomena. The vast range of STM-based techniques and modes of operation, as well as their combination with electromagnetic fields from the infrared to microwave spectral range, has even allowed for the precise control of individual charge and spin degrees of freedom. This roadmap reviews the most recent developments in the field of atomically-engineered quantum platforms and explores their potential in future fundamental research and quantum technologies. article 2025 6 21 10.1088/2399-1984/ade6b7 Nano Futures 9 IOP 032001 3 https://epub.uni-regensburg.de/id/eprint/76900 Soo-hyon Phark Bent Weber Yasuo Yoshida Patrick Robert Forrester Robertus Johannes Gerardus Elbertse Joseph A. Stroscio Hao Wang Kai Yang Leo Gross Shantanu Mishra Fabian Paschke Katharina Kaiser Shadi Fatayer Jascha Repp Harry Anderson Diego Peña Florian Albrecht Franz Josef Giessibl Roman Fasel Joaquín Fernández-Rossier Shigeki Kawai Laurence Limot Nicolas Lorente Berthold Jaeck Haonan Huang Joachim Ankerhold Christian R. Ast Martina Trahms Clemens Winkelmann Katharina Jennifer Franke Martina Soldini Glenn Wagner Titus Neupert Felix Küster Souvik Das Stuart Parkin Paolo Sessi Zhenyu Wang Vidya Madhavan Rupert Huber Gagandeep Singh Fabio Donati Stefano Rusponi Harald Brune Eufemio Moreno-Pineda Mario Ruben Wolfgang Wernsdorfer Wantong Huang Kwan Ho Au-Yeung Philip Willke Andreas J. Heinrich Susanne Baumann Sebastian Loth Lukas Maarten Veldman Sander Otte Christoph Wolf Lisanne Sellies Steven R. Schofield Michael E. Flatte Joris G. Keizer Michelle Y. Simmons The charge state plays a critical role in governing the structural, electronic, and chemical properties of molecules. Controlling the charge state of individual molecules provides a powerful tool for exploring fundamental processes, such as redox reactions, selective bond rearrangements, molecular excitations, charge transfer, and modulation of reaction pathways at the single-molecule level. Recent advancements in scanning tunneling microscopy (STM) and atomic force microscopy (AFM) have enabled precise and stable manipulation of molecular charge states, allowing for detailed, high-resolution studies of charge-state-dependent phenomena. In this review, we discuss the principles and methodologies for charge-state control in STM and AFM, with a focus on strategies for stabilizing charge states in a controlled experimental environment. We also examine key advancements in the ability to detect and manipulate intra- and intermolecular charge transfer, providing insights into charge-mediated processes, such as structural rearrangements, electronic states, and reactivity at the atomic scale. Finally, we highlight the potential of charge-state control to probe electronic excited states and resolve spin-coherence in individual molecules. article 2025 6 02 1520-6890,0009-2665 10.1021/acs.chemrev.4c00899 Chemical Reviews 125 American Chemical Society (ACS) 5830-5847 https://epub.uni-regensburg.de/id/eprint/76832 Laerte L. Patera Shadi Fatayer Jascha Repp Leo Gross Während man mittels Tunnelspektroskopie seit Jahrzehnten einzelne Moleküle auf leitenden Oberflächen charakterisieren kann, sind angeregte elektronische Zustände und höhere Ladungszustände nur in einer elektrisch isolierten Umgebung zugänglich. Eine neuartige Tunnelspektroskopie ermöglicht es, elektrisch isolierte Moleküle und deren elektronisch angeregte Zustände zu spektroskopieren. Sie basiert auf Detektion mittels Rasterkraftmikroskopie. article 2025 5 05 1521-3943,0031-9252 10.1002/piuz.202570305 Physik in unserer Zeit 56 Wiley 112-113 3 https://epub.uni-regensburg.de/id/eprint/76834 Jascha Repp Lisanne Sellies Leo Gross Charge-state transitions of a single Cu-phthalocyanine molecule adsorbed on an insulating layer of NaCl on Cu(111) are probed by means of alternate charging scanning tunneling microscopy. Real-space imaging of the electronic transitions reveals the Jahn-Teller distortion occurring upon formation of the first and second anionic charge states. The experimental findings are rationalized by a theoretical many-body model that highlights the crucial role played by the substrate. The latter enhances and stabilizes the intrinsic Jahn-Teller distortion of the negatively charged molecule hosting a degenerate pair of single-particle frontier orbitals. Consequently, two excess electrons are found to occupy, in the ground state, the same localized orbital, despite a larger Coulomb repulsion than the one for the competing delocalized electronic configuration. Control over the charging sequence by varying the applied bias voltage is also predicted. article 2025 4 29 1079-7114,0031-9007 10.1103/PhysRevLett.134.176203 Physical Review Letters 134 American Physical Society (APS) 176203 17 https://epub.uni-regensburg.de/id/eprint/76641 Moritz Frankerl Laerte L. Patera Felix Giselbrecht Thomas Frederiksen Jascha Repp Andrea Donarini The appearance of frontier molecular ion resonances measured with scanning tunneling microscopy (STM)─often referred to as orbital density images─of single molecules was investigated using a CO-functionalized tip in dependence on bias voltage and tip–sample distance. As model systems, we studied pentacene and naphthalocyanine on bilayer NaCl on Cu(111). Absolute tip–sample distances were determined by means of atomic force microscopy (AFM). STM imaging revealed a transition from predominant p- to s-wave tip contrast upon increasing the tip–sample distance, but the contrast showed only small changes as a function of voltage. The distance-dependent contrast change is explained with the steeper decay of the tunneling matrix element for tunneling between two p-wave centers, compared to tunneling between two s-wave centers. In simulations with a fixed ratio of s- to p-wave tip states, we can reproduce the experimental data including the distance-dependent transition from predominant p- to s-wave tunneling contribution. article 2025 1 08 1936-086X,1936-0851 10.1021/acsnano.4c14476 ACS Nano 19 American Chemical Society (ACS) 2641-2650 2 https://epub.uni-regensburg.de/id/eprint/74590 Fabian Paschke Leonard-Alexander Lieske Florian Albrecht C. Julian Chen Jascha Repp Leo Gross Everything, including our own bodies, is built up from atoms and molecules. Understanding their properties is thus crucial for all natural and life sciences as well as for countless applications in engineering. Using an atomic force microscope (AFM), atoms and molecules can be imaged with atomic-scale spatial resolution. Since AFM is based on scanning a physical probe, the tip, across the surface, this tip can also be used to interfere with the sample. For instance, electrons can be steered between the tip and the single molecule under investigation. Molecules can thereby be brought to non-equilibrium states, which play a crucial role in many natural phenomena. Studying such non-equilibrium states with AFM is the topic of this thesis. Two novel methods based on AFM were developed that allow accessing a wide range of properties of non-equilibrium electronic states, of which most were not accessible so far in combination with AFM. First, we introduce an excited-state spectroscopy method that allows extracting the energy levels of ground and excited states for different net charges on the molecule. Thereby, excitation energies can be quantified that are difficult to access otherwise. Furthermore, the molecule can be prepared in specific excited states and the subsequent transitions can be controlled, potentially applicable to induce and study chemical reactions. Second, we demonstrate - for the first time - that electron spin resonance spectroscopy (ESR) signals of single molecules can be measured using AFM. Our method, called ESR-AFM, is based on driving spin transitions between non-equilibrium triplet substates. By combining the spatial resolution of AFM with the isotope sensitivity of ESR, we can locally identify molecules only differing in their isotopic configuration. Moreover, we can coherently manipulate the electron spins of pentacene over tens of microseconds. The high energy resolution of ESR-AFM and the long spin coherence observed represent a leap forward for local studies in the fields of quantum computing and quantum sensing. thesis_rgbg 2024 11 07 https://epub.uni-regensburg.de/id/eprint/59466 Lisanne Sellies In polarizable materials, electronic charge carriers interact with the surrounding ions, leading to quasiparticle behavior. The resulting polarons play a central role in many materials properties including electrical transport, interaction with light, surface reactivity, and magnetoresistance, and polarons are typically investigated indirectly through these macroscopic characteristics. Here, noncontact atomic force microscopy (nc-AFM) is used to directly image polarons in Fe2O3 at the single quasiparticle limit. A combination of Kelvin probe force microscopy (KPFM) and kinetic Monte Carlo (KMC) simulations shows that the mobility of electron polarons can be markedly increased by Ti doping. Density functional theory (DFT) calculations indicate that a transition from polaronic to metastable free-carrier states can play a key role in migration of electron polarons. In contrast, hole polarons are significantly less mobile, and their hopping is hampered further by trapping centers. article 2024 11 01 10.1126/sciadv.adp7833 Science Advances 10 Science eadp7833 44 https://epub.uni-regensburg.de/id/eprint/59495 Jesus Redondo Michele Reticcioli Vit Gabriel Dominik Wrana Florian Ellinger Michele Riva Giada Franceschi Erik Rheinfrank Igor Sokolović Zdenek Jakub Florian Kraushofer Aji Alexander Eduard Belas Laerte L. Patera Jascha Repp Michael Schmid Ulrike Diebold Gareth S. Parkinson Cesare Franchini Pavel Kocan Martin Setvin An increasing number of scanning-probe-based spectroscopic techniques provides access to diverse electronic properties of single molecules. Typically, these experiments can only study a subset of all electronic transitions, which obscures the unambiguous assignment of measured quantities to specific quantum transitions. Here we develop a single-molecule spectroscopy that enables the access to many quantum transitions of different types, including radiative, non-radiative and redox, that is, charge-related, transitions. Our method relies on controlled alternating single-charge attachment and detachment. For read-out, the spin states are mapped to charge states, which we can detect by atomic force microscopy. We can determine the relative energies of ground and excited states of an individual molecule and can prepare the molecule in defined excited states. After a proof-of-principle demonstration of the technique on pentacene, we apply it to PTCDA, the scanning-probe luminescence of which has been interpreted controversially. The method may be used to guide, understand and engineer tip-induced chemical reactions as well as phosphorescence and fluorescence of individual molecules. article 2024 9 26 1748-3395,1748-3387 10.1038/s41565-024-01791-2 Nature Nanotechnology 20 Nature Publishing Group 27-35 1 https://epub.uni-regensburg.de/id/eprint/59277 Lisanne Sellies Jakob Eckrich Leo Gross Andrea Donarini Jascha Repp Bringing optical microscopy to the shortest possible length and time scales has been a long-sought goal, connecting nanoscopic elementary dynamics with the macroscopic functionalities of condensed matter. Super-resolution microscopy has circumvented the far-field diffraction limit by harnessing optical nonlinearities1. By exploiting linear interaction with tip-confined evanescent light fields2, near-field microscopy3,4 has reached even higher resolution, prompting a vibrant research field by exploring the nanocosm in motion5,6,7,8,9,10,11,12,13,14,15,16,17,18,19. Yet the finite radius of the nanometre-sized tip apex has prevented access to atomic resolution20. Here we leverage extreme atomic nonlinearities within tip-confined evanescent fields to push all-optical microscopy to picometric spatial and femtosecond temporal resolution. On these scales, we discover an unprecedented and efficient non-classical near-field response, in phase with the vector potential of light and strictly confined to atomic dimensions. This ultrafast signal is characterized by an optical phase delay of approximately π/2 and facilitates direct monitoring of tunnelling dynamics. We showcase the power of our optical concept by imaging nanometre-sized defects hidden to atomic force microscopy and by subcycle sampling of current transients on a semiconducting van der Waals material. Our results facilitate access to quantum light–matter interaction and electronic dynamics at ultimately short spatio-temporal scales in both conductive and insulating quantum materials. article 2024 5 08 1476-4687,0028-0836 10.1038/s41586-024-07355-7 Nature 629 Springer Nature 329-334 8011 https://epub.uni-regensburg.de/id/eprint/58770 Tom Siday Johannes Hayes Felix Schiegl Fabian Sandner Peter Menden Valentin Bergbauer Martin Zizlsperger Svenja Nerreter Sonja Lingl Jascha Repp Jan Wilhelm Markus A. Huber Yaroslav A. Gerasimenko Rupert Huber In this thesis various methods to study light-matter interaction at the atomic scale are explored. By employing scanning tunneling microscopy (STM) and atomic force microscopy (AFM) the interaction of single molecules with electromagnetic radiation can be investigated with sub-molecular spatial resolution. The first part of this study analyzes the interaction of a single magnesium phthalocyanine (MgPc) molecule with the electric field of an ultrafast terahertz laser pulse. Due to its adsorption geometry on a thin sodium chloride (NaCl) film this molecule acts as a bistable switch, which can be coherently controlled by exerting ultrafast forces with atomic scale precision. The second topic investigated in this thesis is the direct photoexcitation and subsequent toggling motion of a single MgPc molecule. Here the synchronization of optical laser pulses with the oscillating motion of an AFM cantilever allows probing the effects of the direct photoexcitation on the molecule. It was found that the molecule can be switched between its two stable adsorption geometries via photoexcitation, which is attributed to charge exchange between the excited molecule and the STM electrodes. In the third section the effects of photoexcitation on single copper phthalocyanine (CuPc) molecules deposited onto bulk-like NaCl are explored. By employing laser pulses synchronized with the AFM cantilever oscillation single electron photocurrents from individual molecules could be generated and spatially resolved. The final part of this thesis outlines the development and construction of a novel STM design, which is specifically tailored to facilitate experiments with unprecedented spatio-temporal resolution. thesis_rgbg 2024 5 03 https://epub.uni-regensburg.de/id/eprint/54161 Thomas Buchner Defects in atomically thin semiconductors and their moiré heterostructures have emerged as a unique testbed for quantum science. Strong light–matter coupling, large spin–orbit interaction and enhanced Coulomb correlations facilitate a spin–photon interface for future qubit operations and efficient single-photon quantum emitters. Yet, directly observing the relevant interplay of the electronic structure of a single defect with other microscopic elementary excitations on their intrinsic length, time and energy scales remained a long-held dream. Here we directly resolve in space, time and energy how a spin–orbit-split energy level of an isolated selenium vacancy in a moiré-distorted WSe2 monolayer evolves under the controlled excitation of lattice vibrations, using lightwave scanning tunnelling microscopy and spectroscopy. By locally launching a phonon oscillation and taking ultrafast energy-resolved snapshots of the vacancy’s states faster than the vibration period, we directly measure the impact of electron–phonon coupling in an isolated single-atom defect. The combination of atomic spatial, sub-picosecond temporal and millielectronvolt energy resolution marks a disruptive development towards a comprehensive understanding of complex quantum materials, where the key microscopic elementary interactions can now be disentangled, one by one. article 2024 3 14 1749-4893,1749-4885 10.1038/s41566-024-01390-6 Nature Photonics 18 Nature Publishing Group 595-602 6 https://epub.uni-regensburg.de/id/eprint/57920 Carmen Roelcke Lukas Z. Kastner Maximilian Graml Andreas Biereder Jan Wilhelm Jascha Repp Rupert Huber Yaroslav A. Gerasimenko Understanding and controlling decoherence in open quantum systems is of fundamental interest in science, whereas achieving long coherence times is critical for quantum information processing1. Although great progress was made for individual systems, and electron spin resonance (ESR) of single spins with nanoscale resolution has been demonstrated2-4, the understanding of decoherence in many complex solid-state quantum systems requires ultimately controlling the environment down to atomic scales, as potentially enabled by scanning probe microscopy with its atomic and molecular characterization and manipulation capabilities. Consequently, the recent implementation of ESR in scanning tunnelling microscopy5-8 represents a milestone towards this goal and was quickly followed by the demonstration of coherent oscillations9,10 and access to nuclear spins11 with real-space atomic resolution. Atomic manipulation even fuelled the ambition to realize the first artificial atomic-scale quantum devices12. However, the current-based sensing inherent to this method limits coherence times12,13. Here we demonstrate pump-probe ESR atomic force microscopy (AFM) detection of electron spin transitions between non-equilibrium triplet states of individual pentacene molecules. Spectra of these transitions exhibit sub-nanoelectronvolt spectral resolution, allowing local discrimination of molecules that only differ in their isotopic configuration. Furthermore, the electron spins can be coherently manipulated over tens of microseconds. We anticipate that single-molecule ESR-AFM can be combined with atomic manipulation and characterization and thereby paves the way to learn about the atomistic origins of decoherence in atomically well-defined quantum elements and for fundamental quantum-sensing experiments. By using a pump-probe atomic force microscopy detection scheme, electron spin transitions between non-equilibrium triplet states of individual pentacene molecules, as well as the ability to manipulate electron spins over tens of microseconds, is demonstrated. article 2023 12 06 0028-0836,1476-4687 10.1038/s41586-023-06754-6 Nature 624 NATURE PORTFOLIO

BERLIN

64-68 7990 https://epub.uni-regensburg.de/id/eprint/55185 Lisanne Sellies Raffael Spachtholz Sonja Bleher Jakob Eckrich Philipp Scheuerer Jascha Repp The interaction of a molecule with a specific surface has been shown to produce consistent unidirectional motion driven by voltage pulses. The mechanism can even facilitate the transport of molecular cargo. article 2023 9 06 1476-4687,0028-0836 10.1038/d41586-023-02565-x Nature 621 Nature Publishing Group 49-50 7977 https://epub.uni-regensburg.de/id/eprint/54712 Leo Gross Jascha Repp In molecular tunnel junctions, where the molecule is decoupled from the electrodes by few-monolayers-thin insulating layers, resonant charge transport takes place by sequential charge transfer to and from the molecule which implies transient charging of the molecule. The corresponding charge state transitions, which involve tunneling through the insulating decoupling layers, are crucial for understanding electrically driven processes such as electroluminescence or photocurrent generation in such a geometry. Here, we use scanning tunneling microscopy to investigate the decharging of single ZnPc and H2Pc molecules through NaCl films of 3 to 5 monolayers thickness on Cu(111) and Au(111). To this end, we approach the tip to the molecule at resonant tunnel conditions up to a regime where charge transport is limited by tunneling through the NaCl film. The resulting saturation of the tunnel current is a direct measure of the lifetimes of the anionic and cationic states, i.e., the molecule's charge-state lifetime, and thus provides a means to study charge dynamics and, thereby, exciton dynamics. Comparison of anion and cation lifetimes on different substrates reveals the critical role of the level alignment with the insulator's conduction and valence band, and the metal-insulator interface state. Resonant charge transport to and from molecules and their corresponding charge-state transitions are critical to understanding electrically driven processes. Here, the authors investigate the charge-state lifetimes of single molecules through NaCl films of 3 to 5 monolayers thickness. article 2023 8 17 10.1038/s41467-023-40692-1 Nature Communications 14 NATURE PORTFOLIO

BERLIN

4988 1 https://epub.uni-regensburg.de/id/eprint/54598 Katharina Kaiser Leonard-Alexander Lieske Jascha Repp Leo Gross In this thesis three different topics are treated. All these topics are allocated at the cross-section of physics and chemistry. Questions from the field of chemistry are investigated by physical methods, i.e. by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). The first part of this study addresses a detailed structural and electronic investigation of stable organic Blatter radicals. Due to their atomic composition and the associated low spin-orbit coupling and hyperfine interactions, organic radicals are promising candidates for spintronic applications. The second topic deals with tip-induced ether bond fission of different compounds. In this context, the chemical concept of inducing heterolytic bond fission by charging of species is realized with the STM-tip. With this cleaving mechanism, reactive species, such as carbyne model compounds and a p-quinodimethane derivative, could be generated and investigated. In the last section a novel all-electronic AFM-based technique to detect triplet lifetimes is introduced. Using this method, single pentacene triplet lifetimes could be probed and the quenching by closely adsorbed molecular oxygen could be investigated on an atomistic level. All three topics highlight the broad spectrum of AFM/STM applications and its impact on the field of chemistry. thesis_rgbg 2022 12 01 https://epub.uni-regensburg.de/id/eprint/51946 Sophia Sokolov Controlling selectivity of reactions is an ongoing quest in chemistry. In this work, we demonstrate reversible and selective bond formation and dissociation promoted by tip-induced reduction-oxidation reactions on a surface. Molecular rearrangements leading to different constitutional isomers are selected by the polarity and magnitude of applied voltage pulses from the tip of a combined scanning tunneling and atomic force microscope. Characterization of voltage dependence of the reactions and determination of reaction rates demonstrate selectivity in constitutional isomerization reactions and provide insight into the underlying mechanisms. With support of density functional theory calculations, we find that the energy landscape of the isomers in different charge states is important to rationalize the selectivity. Tip-induced selective single-molecule reactions increase our understanding of redox chemistry and could lead to novel molecular machines. article 2022 7 14 0036-8075,1095-9203 10.1126/science.abo6471 Science 377 AMER ASSOC ADVANCEMENT SCIENCE

WASHINGTON

298-301 6603 https://epub.uni-regensburg.de/id/eprint/52628 Florian Albrecht Shadi Fatayer Iago Pozo Ivano Tavernelli Jascha Repp Diego Peña Leo Gross We investigate the interplay of two highly localized, nearly degenerate electronic states, namely, a zero-energy edge mode in a graphene nanoribbon on the one hand and an Abrikosov-Suhl resonance located at a Kondo impurity on the other. On-surface synthesis of the ribbon structures in combination with intercalation of single atom Kondo impurities by atomic manipulation in a scanning tunneling microscope junction offer full control of the atomic geometry of the system. Density functional theory provides the microscopic description to scrutinize the electronic features observed in experiment. We find the interaction of the two localized states and the resulting signatures of Kondo physics to be very sensitive to the placing of the atom, suggesting its use as a laboratory to study the interplay of the Kondo effect with other zero-bias anomalies as well as to tailor these states by controlling the atomic-scale coupling. article 2022 5 06 2469-9950,2469-9969 10.1103/PhysRevB.105.205410 Phys. Rev. B 105 AMER PHYSICAL SOC

COLLEGE PK

205410 https://epub.uni-regensburg.de/id/eprint/52258 Sujoy Karan Tobias Frank Tobias Preis Jonathan Eroms Jaroslav Fabian Ferdinand Evers Jascha Repp Strain-induced on-surface transformations provide an appealing route to steer the selectivity towards desired products. Here, we demonstrate the selective on-surface synthesis of extended all-trans poly(2,6-pyridine) chains on Au(111). By combining high-resolution scanning tunneling and atomic force microscopy, we revealed the detailed chemical structure of the reaction products. Density functional theory calculations indicate that the synthesis of extended covalent structures is energetically favored over the formation of macrocycles, due to the minimization of internal strain. Our results consolidate the exploitation of internal strain relief as a driving force to promote selective on-surface reactions. article 2022 2 16 10.3390/chemistry4010009 Chemistry 4 MDPI 112-117 1 https://epub.uni-regensburg.de/id/eprint/51697 Laerte L. Patera Josef Amler Jascha Repp Spin-polarized defects in 2D materials are attracting attention for future quantum technology applications, but their controlled fabrication is still challenging. Here, the authors report the creation and characterization of effective spin 1/2 defects via the atomically-precise generation of magnetic carbon radical ions in 2D WS2. Atomic spin centers in 2D materials are a highly anticipated building block for quantum technologies. Here, we demonstrate the creation of an effective spin-1/2 system via the atomically controlled generation of magnetic carbon radical ions (CRIs) in synthetic two-dimensional transition metal dichalcogenides. Hydrogenated carbon impurities located at chalcogen sites introduced by chemical doping are activated with atomic precision by hydrogen depassivation using a scanning probe tip. In its anionic state, the carbon impurity is computed to have a magnetic moment of 1 mu(B) resulting from an unpaired electron populating a spin-polarized in-gap orbital. We show that the CRI defect states couple to a small number of local vibrational modes. The vibronic coupling strength critically depends on the spin state and differs for monolayer and bilayer WS2. The carbon radical ion is a surface-bound atomic defect that can be selectively introduced, features a well-understood vibronic spectrum, and is charge state controlled. article 2021 12 15 10.1038/s41467-021-27585-x Nature Communications 12 Nature

BERLIN

7287 1 https://epub.uni-regensburg.de/id/eprint/51241 Katherine A. Cochrane Jun-Ho Lee Christoph Kastl Jonah B. Haber Tianyi Zhang Azimkhan Kozhakhmetov Joshua A. Robinson Mauricio Terrones Jascha Repp Jeffrey B. Neaton Alexander Weber-Bargioni Bruno Schuler Regiospecific C-H activation is a promising approach to achieve extended polymers with tailored structures. While a recent on-surface synthetic approach has enabled regioselective homocoupling of heteroaromatic molecules, only small oligomers have been achieved. Herein, selective C-H activation for dehydrogenative C-C couplings of hexaazatriphenylene by Scholl reaction is reported for the first time. By combining low-temperature scanning tunneling microscopy (STM) and atomic force microscopy (AFM), we revealed the formation of one-dimensional polymers with a double-chain structure. The details of the growth process are rationalized by density functional theory (DFT) calculations, pointing out a cooperative catalytic action of Na and Ag adatoms in steering the C-H selectivity for the polymerization. article 2021 11 17 1433-7851,1521-3773 10.1002/anie.202112798 Angewandte Chemie International Edition 61 Wiley

WEINHEIM

e202112798 5 https://epub.uni-regensburg.de/id/eprint/51056 Xunshan Liu Adam Matej Tim Kratky Jesús I. Mendieta-Moreno Sebastian Günther Pingo Mutombo Silvio Decurtins Ulrich Aschauer Jascha Repp Pavel Jelinek Shi-Xia Liu Laerte L. Patera One-dimensional diffusion of Co adatoms on graphene nanoribbons has been induced and investigated by means of scanning tunnelling microscopy (STM). To this end, the nanoribbons and the Co adatoms have been imaged before and after injecting current pulses into the nanoribbons, with the STM tip in direct contact with the ribbon. We observe current-induced motion of the Co atoms along the nanoribbons, which is approximately described by a distribution expected for a thermally activated one-dimensional random walk. This indicates that the nanoribbons reach temperatures far beyond 100 K, which is well above the temperature of the underlying Au substrate. This model system can be developed further for the study of electromigration at the single-atom level. article 2021 10 23 1530-6984,1530-6992 10.1021/acs.nanolett.1c03073 Nano Letters 21 AMER CHEMICAL SOC

WASHINGTON

8794-8799 20 https://epub.uni-regensburg.de/id/eprint/50890 Tobias Preis Sasha Vrbica Jonathan Eroms Jascha Repp Jan M. van Ruitenbeek Across the natural sciences, most phenomena we encounter trace back to elementary dynamics that, at the same time, occur at extremely small atomic distances (1 Å = 0.000 000 000 1 m) and develop over ultrafast femtosecond time scales (1 fs = 0.000 000 000 000 001 s). To understand and harness these basic processes, such as a transition of a single molecule for example, direct observation and immediate control are vital. To that end, this work demonstrates the first femtosecond videography as well as the first ultrafast electronic and structural control at the atomic scale. Lightwave-driven scanning tunneling microscopy (STM) allows us to track single-molecule vibrations, steer molecular transitions with atomic forces and resolve angstrom-scale near fields – all with sub-optical-cycle temporal precision, for the first time. We apply tip-confined terahertz waveforms in STM to drive one-electron tunneling through a select orbital of a single molecule with combined 0.6 Å and ~100 fs spatio-temporal precision. This process resolves the first single-molecule femtosecond snapshot and tracks a vibration of an individual molecule in space and time. Moreover, to control matter dynamically in the most direct way, we introduce femtosecond atomic forces as a novel stimulus that steers structural motion locally, with atomic precision. The forces – derived from tailored tip-confined electric-field waveforms – push key atoms of a molecular switch to coherently steer a select ultrafast structural rotation. This motion can be driven so vigorously that the switching rate of the molecule is modulated by up to 39%, on the femtosecond scale. To observe such unidirectional transitions, we implement a novel single-shot detection strategy: Ultrafast action spectroscopy monitors every individual switching event of the molecule to resolve the statistics with an accuracy of 0.0001. Finally, we measure the first quantitative, atomically confined near-field waveform, introducing a direct spatio-temporal access to light-matter dynamics at atomic length scales. These novel experiments set the stage for a variety of exciting future studies across the natural sciences, including attosecond and single-spin microscopy and videography of complex reactions, elementary energy exchange as well as local phase transitions that involve order and correlations in solids. thesis_rgbg 2021 9 15 https://epub.uni-regensburg.de/id/eprint/43730 Dominik Peller The nonequilibrium triplet state of molecules plays an important role in photocatalysis, organic photovoltaics, and photodynamic therapy. We report the direct measurement of the triplet lifetime of an individual pentacene molecule on an insulating surface with atomic resolution by introducing an electronic pumpprobe method in atomic force microscopy. Strong quenching of the triplet lifetime is observed if oxygen molecules are coadsorbed in close proximity. By means of single-molecule manipulation techniques, different arrangements with oxygen molecules were created and characterized with atomic precision, allowing for the direct correlation of molecular arrangements with the lifetime of the quenched triplet. Such electrical addressing of long-lived triplets of single molecules, combined with atomic-scale manipulation, offers previously unexplored routes to control and study local spin-spin interactions. article 2021 7 23 0036-8075,1095-9203 10.1126/science.abh1155 Science 373 AMER ASSOC ADVANCEMENT SCIENCE

WASHINGTON

452-456 6553 https://epub.uni-regensburg.de/id/eprint/46426 Jinbo Peng Sophia Sokolov Daniel Hernangómez-Pérez Ferdinand Evers Leo Gross John M. Lupton Jascha Repp High-resolution atomic force microscopy (AFM) and scanning tunneling microscopy (STM) provide a powerful toolbox for the investigation of single molecules. Besides atomically resolved structure elucidation of previously unidentified molecules, the possibility to trigger certain on-surface chemical reactions using the tip of a scanning probe microscope allows for the formation and characterization of novel and highly reactive molecular structures. In this thesis, we first demonstrate the applicability of high-resolution AFM as a method to identify molecular structures from complex mixtures and thereby complement standard analytical techniques in fields other than surface science. We could identify structures and recurring structural motifs in molecules extracted from two different stages of fuel combustion, i.e., incipient and primary soot. The complexity of molecular structures, ranging from small aliphatic chains to large polycyclic aromatic hydrocarbons (PAHs), suggests that aliphatic moieties play a vital role in the physical agglomeration of PAHs during the soot formation process. The abundance of methylene groups in the imaged molecules as well as the presence of molecules with π-radical character could indicate that π-radicals are important in particle inception. They could lead to bond formation between aromatics in primary soot, whereas in incipient soot the molecules should be mainly held together by weak van der Waals forces. These results help to shed light on some of the processes present in soot formation. In addition, we used on-surface synthesis by tip-induced atom manipulation to form and characterize a highly reactive, purely sp-hybridized carbon allotrope (cyclo[18]carbon). Cyclo[18]carbon is highly reactive and has thus not been stably isolated nor characterized before. The prevalent conditions in the microscope, i.e., low temperature, UHV and an inert surface as a support for the molecule can foster its stability after an in situ synthesis. Two different precursors (cyclocarbon oxide C24O6 and bromocyclocarbon C18Br6) were used for the formation of cyclo[18]carbon. By tip-induced unmasking we could form several intermediates, e.g., C22O4/C18Br4 and C20O2/C18Br2, as well as cyclo[18]carbon with a total yield for the complete unmasking of the bromocyclocarbon precursor being about five times higher compared to the one of cyclocarbon oxide (64% vs. 13%). By comparison of experimental and simulated AFM images of different proposed ground state symmetries with varying degree of bond length alternation and bond angle alternation we found that cyclo[18]carbon exhibits a polyynic ground state. However, we cannot distinguish between structures with and without bond angle alternation. In addition, we found that on bilayer NaCl on Cu(111), cyclo[18]carbon exhibits a bistable charge state and charging is accompanied by a distortion of the circular geometry. Because of its high reactivity, cyclo[18]carbon was expected to be a suitable candidate for tip-induced on-surface intermolecular coupling. Indeed, we could trigger covalent bond formation between close-by cyclo[18]carbon molecules/precursors. However, i.a. because of their high mobility on bilayer NaCl, bond formation could not be triggered in a controlled or directed way. Further, we demonstrate first measurements combining high-resolution AFM and STML on molecular systems. The presented experiments aimed at investigating how the optoelectronic properties of a metal-oxide phthalocyanine, in this case VOPc, change upon tip-induced reduction (i.e., dissociation of oxygen). Intact VOPc shows a peak in STML at 1.82 eV, which is in agreement with the expected energy of the Q-band emission. Upon reduction, adsorption position and height change, increasing the interaction between the molecule and the substrate. In addition, NIR and PIR shift up in energy compared to the intact molecule. The change in adsorption could lead to a different degree of luminescence quenching in STML, while a shift in ion resonances could hinder S1 exciton formation by charge injection from the substrate to the molecule. Either way, STML from the reduced species VPc could not be observed. thesis_rgbg 2021 7 02 https://epub.uni-regensburg.de/id/eprint/46133 Katharina Kaiser This thesis characterizes different kinds of graphene nanoribbons (GNRs) from an electronic point of view and thereby tries to bridge the worlds of mesoscopic transport and atomistic aspects. In one part of the thesis, solution-based cove-type GNRs are brought onto mechanically exfoliated hexagonal boron nitride flakes. We observe the formation of ordered GNR domains by means of atomic force microscopy. Employing electron beam lithography and metallization, we contact the GNRs with different metals and measure their I-V-characteristics under ambient conditions. The second part of the thesis investigates atomically precise armchair GNRs that are synthesized on a Au(111) surface under ultra-high vacuum conditions in the chamber of a scanning tunneling microscope (STM). On the one hand, we modify the electronic properties of GNRs by manipulating single Co atoms underneath the GNRs with the help of an STM tip. Differential conductance spectroscopy reveals the appearance of a Kondo-like resonance for certain intercalation sites. The experimental results are compared to density functional theory and tight-binding calculations. On the other hand, we study the diffusion of Co atoms adsorbed on top of the GNRs. We contact the GNRs with an STM tip and inject a current which causes a displacement of the Co atoms. The Co atoms predominantly move along the GNR, rendering the motion one-dimensional. Temperature dependent measurements are performed to extract the Co diffusion rate. thesis_rgbg 2021 2 17 https://epub.uni-regensburg.de/id/eprint/44878 Tobias Preis In this thesis, structural and electronic effects accompanying electron transfer reactions in individual molecules and ordered molecular structures are investigated by means of scanning probe microscopy. The geometrical changes upon charging of individual copper(II)phthalocyanine molecules adsorbed on an ultrathin NaCl layer on a supporting Cu(100) substrate were studied by means of AFM. Making use of charge bistability, we image individual molecules subsequently in their neutral and anionic state and analyze the differences in image contrast due to charging. The observed contrast differences and supporting density functional theory simulations allow us to elucidate the geometrical changes of a molecule upon charging. Further, we investigated self-assembled molecular islands in an insulating environment by means of AFM. By using the AFM tip as a tunable gate, the charge state of the molecular islands was probed and manipulated with single electron control, to gain insight into the distribution of excess electrons within the islands and the role of mutual charge interactions. Depending on the charge state, the we observe stable electron distributions or intra-island electron hopping. This intra-island charge transfer is driven by a local effect of the oscillating tip. From the simultaneous occurrence of charge transfer related features in frequency shift and dissipation of the AFM cantilever we estimate the intra-island tunneling rates. Further, an electrostatic model was used to simulate the probe-dependent electron distribution within an island and rationalize the observed image contrast for specific charge states. Individual perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) and self-assembled PTCDA islands adsorbed on few monolayer thin NaCl films on a supporting conductive substrate were studied by means of scanning probe microscopy. We found that molecules can be switched in both cases by applying voltage pulses. We investigate the changes in the electronic structure and geometric changes upon switching, which indicate that the switching is related to the charging of a molecule. These experiments suggest that the charge is localized at the functional group of a molecule instead of occupying the LUMO. A tentative mechanism for this charge stabilization is proposed based on a strong polaronic interaction with the ionic NaCl surface due the spatial confinement of the excess electron at a molecule’s functional group. thesis_rgbg 2021 1 07

Regensburg

https://epub.uni-regensburg.de/id/eprint/43964 Philipp Thomas Scheuerer Ultrafast lightwave sampling based on scanning tunnelling microscopy is developed to resolve near fields with sub-picosecond time resolution and sub-nanometre spatial resolution. Parameter-free quantitative measurement is achieved by using a single-molecule switch. Tailored nanostructures can confine electromagnetic waveforms in extremely sub-wavelength volumes, opening new avenues in lightwave sensing and control down to sub-molecular resolution. Atomic light-matter interaction depends critically on the absolute strength and the precise time evolution of the near field, which may be strongly influenced by quantum-mechanical effects. However, measuring atom-scale field transients has remained out of reach. Here we introduce quantitative atomic-scale waveform sampling in lightwave scanning tunnelling microscopy to resolve a tip-confined near-field transient. Our parameter-free calibration employs a single-molecule switch as an atomic-scale voltage standard. Although salient features of the far-to-near-field transfer follow classical electrodynamics, we develop a comprehensive understanding of the atomic-scale waveforms with time-dependent density functional theory. The simulations validate our calibration and confirm that single-electron tunnelling ensures minimal back-action of the measurement process on the electromagnetic fields. Our observations access an uncharted domain of nano-opto-electronics where local quantum dynamics determine femtosecond atomic near fields. article 2020 11 1749-4885,1749-4893 10.1038/s41566-020-00720-8 Nature Photonics 15 Nature

BERLIN

143-147 2 https://epub.uni-regensburg.de/id/eprint/44182 Dominik Peller Carmen Roelcke Lukas Z. Kastner Thomas Buchner Alexander Neef Johannes Hayes Franco Bonafé Dominik Sidler Michael Ruggenthaler Angel Rubio Rupert Huber Jascha Repp Polaron formation in conjugated polymers has a major impact on their optical and electronic properties. In polyphenylene, the molecular conformation is determined by a delicate interplay between electron delocalization and steric effects. Injection of excess charges is expected to increase the degree of conjugation, leading to structural distortions of the chain. Here we investigated at the single-molecule level the role of an excess charge in an individual oligophenylene deposited on sodium chloride films. By combining sub-molecular-resolved atomic force microscopy with redox-state-selective orbital imaging, we characterize both structural and electronical changes occurring upon hole injection. While the neutral molecule exhibits a delocalized frontier orbital, for the cationic radical the excess charge is observed to localize, inducing a partial planarization of the molecule. These results provide direct evidence for self-trapping of the excess charge in oligophenylenes, shedding light on the interplay of charge localization and structural distortion. article 2020 10 23 0031-9007,1079-7114 10.1103/PhysRevLett.125.176803 Physical Review Letters 125 AMER PHYSICAL SOC

COLLEGE PK

176803 https://epub.uni-regensburg.de/id/eprint/43974 Laerte L. Patera Fabian Queck-Scharrer Jascha Repp Scanning probe techniques can leverage atomically precise forces to sculpt matter at surfaces, atom by atom. These forces have been applied quasi-statically to create surface structures(1-7)and influence chemical processes(8,9), but exploiting local dynamics(10-14)to realize coherent control on the atomic scale remains an intriguing prospect. Chemical reactions(15-17), conformational changes(18,19)and desorption(20)have been followed on ultrafast timescales, but directly exerting femtosecond forces on individual atoms to selectively induce molecular motion has yet to be realized. Here we show that the near field of a terahertz wave confined to an atomically sharp tip provides femtosecond atomic-scale forces that selectively induce coherent hindered rotation in the molecular frame of a bistable magnesium phthalocyanine molecule. Combining lightwave-driven scanning tunnelling microscopy(21-24)with ultrafast action spectroscopy(10,13), we find that the induced rotation modulates the probability of the molecule switching between its two stable adsorption geometries by up to 39 per cent. Mapping the response of the molecule in space and time confirms that the force acts on the atomic scale and within less than an optical cycle (that is, faster than an oscillation period of the carrier wave of light). We anticipate that our strategy might ultimately enable the coherent manipulation of individual atoms within single molecules or solids so that chemical reactions and ultrafast phase transitions can be manipulated on their intrinsic spatio-temporal scales. The near field of a terahertz wave confined to a scanning probe tip provides femtosecond atomic-scale forces that coherently modulate the switching probability of a molecule between two stable adsorption geometries. article 2020 9 02 0028-0836,1476-4687 10.1038/s41586-020-2620-2 Nature 585 Nature

LONDON

58-62 7823 https://epub.uni-regensburg.de/id/eprint/43676 Dominik Peller Lukas Z. Kastner Thomas Buchner Carmen Roelcke Florian Albrecht Nikolaj Moll Rupert Huber Jascha Repp Due to recent advances in scanning-probe technology, the electronic structure of individual molecules can now also be investigated if they are immobilized by adsorption on nonconductive substrates. As a consequence, different molecular charge states are now experimentally accessible. Thus motivated, we investigate as an experimentally relevant example the electronic and structural properties of a NaCl(001) surface with and without pentacene adsorbed (neutral and charged) by employing density-functional theory. We estimate the polaronic reorganization energy to be E-reorg similar or equal to 0.8 - 1.0 eV, consistent with experimental results obtained for molecules of similar size. To account for environmental effects on this estimate, different models for charge screening are compared. Finally, we calculate the density profile of one of the frontier orbitals for different occupations and confirm the experimentally observed localization of the charge density upon charging and relaxation of molecule-insulator interface from ab initio calculations. article 2020 9 2469-9950,2469-9969 10.1103/PhysRevB.102.115419 Physical Review B 102 AMER PHYSICAL SOC

COLLEGE PK

115419 https://epub.uni-regensburg.de/id/eprint/43728 Daniel Hernangómez-Pérez Jakob Schlör David A. Egger Laerte L. Patera Jascha Repp Ferdinand Evers Strings of gold-organic oligomers of polar units have been formed by on-surface synthesis and investigated with non-contact atomic force microscopy. The mutual alignment of dipoles within the strings is analyzed. While an alternating head-to-tail alignment might be expected from dipolar interactions, a more complicated alignment order is observed. The data suggests that coordination bonding to additional gold adatoms leads to stabilization of parallel pairs of molecules, suppressing a head-to-tail alignment order. article 2020 6 10.1039/D0CC02990D Chemical Communications 56 The Royal Society of Chemistry 7901-7904 57 https://epub.uni-regensburg.de/id/eprint/43343 Sujoy Karan Yan Geng Silvio Decurtins Shi-Xia Liu Jascha Repp This thesis reports on the development and demonstration of a novel experimental technique to investigate heat transport at the atomic and molecular scale. Before this work, there was no method able to reach these length scales in thermal transport experiments. The technique combines highly sensitive heat flux measurements with break junction methods, to simultaneously measure the thermal and electrical conductance of atomic scale contacts. This was achieved by using MEMS structures with an integrated microheater/temperature sensor as suspended substrates for performing break junction experiments in a high-vacuum scanning tunneling microscope. Thanks to the high thermal resistance of the MEMS sensors, the low noise laboratory environment and instrumentation, we obtained state-of-the-art sensitivities of 15 pW/K in a bandwidth of 50 Hz at a temperature difference of 50 K around room temperature. With this technique, we investigated the heat transport properties of atomic gold contacts. For the first time, we observed thermal conductance quantization at room temperature and demonstrated the validity of the Wiedemann-Franz law in single atom contacts. Within the uncertainties of the experiment, we could conclude that ballistic phonon transport in these systems contribute with less than 10% to the overall thermal conductance. We further confirmed these results by investigating platinum quantum point contacts and gold atomic junctions formed with Pt and Pt-Ir tips. Good agreement with the Wiedemann-Franz law was also found for gold-gold junctions in the presence of small organic molecules. These results suggest that heat transport in highly transmitting contacts is dominated by electrons and that phonons plat only a minor role. The experimental technique was further optimized and developed to characterize for the first time the thermal conductance of single organic molecules. We measured thermal transport across two model systems dithiol-oligo(phenylene ethynylene) (OPE3) and octane-dithiol (ODT), finding very good agreement with our theoretical simulations based on the Green’s Function scattering method and the predicted and measured literature values. In the case of ODT, our result fitted well with the thermal transport measurements performed on alkane chains of similar lengths, molecular dynamics and ab-initio simulations, suggesting that transport in this system is mostly dominated by the interface thermal resistance with the electrodes. These studies demonstrate that the experimental technique developed is suitable to investigate heat transport across molecules with different chemical backbones, therefore opening the door to systematic studies of the structure-property relationship. This represents a fundamental step to engineer phonon transport in nanoscale systems. thesis_rgbg 2020 3 09 https://epub.uni-regensburg.de/id/eprint/41047 Nico Mosso Exploiting single electrical charges and their mutual interactions for computation has been proposed as a concept for future nanoelectronics. Controlling and probing charge transfer in electrically isolated atomic-scale structures are fundamental to push its experimental realization. Here, we controllably inject individual excess electrons and study their distribution in a self-assembled structure supported on a nonconductive substrate. The self-assembly ensures structural order down to the atomic scale. Depending on the charge state of the molecular assembly, intermolecular electron hopping and specific electron distributions have been resolved by atomic force microscopy, clarifying the charge-transfer pathways in the tunnel-coupled structure. 'When mutual charge interactions were exploited, control over specific charge distributions in the self-assembled structure has been achieved with single-molecule precision, paving the way toward the design of data processing platforms based on molecular nanostructures. article 2020 2 20 1530-6984,1530-6992 10.1021/acs.nanolett.9b05063 Nano Letters 20 AMER CHEMICAL SOC

WASHINGTON

1839-1845 3 https://epub.uni-regensburg.de/id/eprint/41680 Philipp Scheuerer Laerte L. Patera Jascha Repp In der vorliegenden Arbeit werden Studien an Adsorbaten (Molekülen und Atomen) auf Metallund isolierenden Substraten mittels Rastersondenmikroskopie und –spektroskopie präsentiert. Am System Cu/Cu(111) werden Messungen mit dem Rasterkraftmikroskop, genauer der Kelvin- Kraftspektroskopie an elektronischen Oberflächenzuständen durchgeführt. Mit Hilfe von Simulationen werden Quantenresonatoren entwickelt, welche eine Messung dieser Oberflächenzustände ermöglichen sollen. Umfassende kraftspektroskopische Messungen an den so optimierten und im Experiment umgesetzten Strukturen zeigen im Vergleich mit den Simulationen gute Übereinstimmung. Es zeigt sich jedoch auch, dass die beobachteten Effekte an der Grenze der Nachweisbarkeit liegen. Beim Ladungstransport über eine Grenzfläche zwischen einem Metall und einem organischen Halbleiter spielen die Grenzflächendipole eine entscheidende Rolle. Solche Grenzflächendipole werden hier am Modellsystem Ir(ppy)3/Cu(111) untersucht. Diese Moleküle spielen in der organischen (Opto-)Elektronik eine große Rolle. Rastertunnelmikroskopische Aufnahmen ermöglichen eine geometrische Zuordnung unterschiedlicher Isomere dieses Moleküls und kraftspektroskopische Untersuchungen zur Quantifizierung des Dipols zeigen neue Erkenntnisse zu seiner Ausrichtung für die verschiedenen Isomere. Metall-organische Verbindungen werden in der Literatur grundsätzlich Koordinationsnetzwerke genannt. Der Begriff der Koordination ist in der Chemie dabei wohldefiniert. Hier ist die Fähigkeit der Metall-Atome entscheidend, Ladungen der Liganden (freie Elektronenpaare) aufzunehmen. Mittels Rasterkraft- und Rastertunnelmikroskopie sowie mittels theoretischer Modelle und Simulationen wird hier das Bindungsmotiv metall-organischer Komplexe auf Metalloberflächen eingehend untersucht. Wir beobachten im System Cu+Phenazin/Cu(111) allerdings einen gegenläufigen Ladungstransfer – vom Metall zum Molekül – einhergehend mit einer Verbreiterung und teilweisen Bevölkerung molekularer Grenzorbitale. Dies weist auf eine kovalente Bindung im herkömmlichen donation/back-donation Prinzip hin und schließt koordinative Bindungsmotive aus. Um künftig Experimente an magnetischen Molekülen zu ermöglichen, wird der Aufbau eines Spin-aufgelösten Rastertunnelmikroskops für Temperaturen unter 2 K sowie für Magnetfelder von bis zu 9 T beschrieben. Diese Anlage war bereits in einer ersten Version aufgebaut, jedoch mussten unter anderem im Bereich des Mikroskopkopfes einige konzeptionelle Änderungen geplant, umgesetzt und getestet werden. Diese Anlage befindet sich derzeit in einem weiteren Test, auf welchen – bei positivem Ausgang – erste Experimente an magnetischen Strukturen folgen werden. Die Entwicklung eines neuen Konzepts der Rastermikroskopie, genannt einzel-Elektronen alternierend ladendes Rastertunnelmikroskop (kurz „AC-STM????), ermöglicht erstmals rastertunnelmikroskopische Aufnahmen molekularer Orbitale von vollständig isolierten Molekülen unter Kontrolle des Redox-Übergangs. Dabei tunnelt ein einzelnes Elektron zwischen einer leitfähigen, geerdeten Spitze und einem Molekül hin und her, wobei netto kein Ladungstransfer stattfindet. Auf die für Rastertunnelaufnahmen benötigten leitfähigen Substrate kann somit verzichtet werden. Am System Pentacen/NaCl wird die Machbarkeit dieser Technik demonstriert und am Maßstab bisheriger Rastertunnelabbildungen bewertet. Aus dieser neuartigen Methode ergeben sich vollkommen neue Möglichkeiten. Einzelne RedoxÜbergänge kontrolliert abbilden zu können, wird anhand der Ausprägung des Jahn-Teller Effekts im System Cu-Phthalocyanin/NaCl gezeigt. Weiter wird die Lokalisierung molekularer Orbitale durch statische Polaronen an einer tetrathiafulvalen-Verbindung auf NaCl untersucht. Ebenfalls am System Cu-Phthalocyanin/NaCl werden durch Umladungen hervorgerufene Änderungen des Adsorptionswinkels beobachtet. Weiter kann diese Technik mit herkömmlichen rasterkraftmikroskopischen Methoden kombiniert werden, um neben elektronischen auch geometrische Informationen zu erhalten. Diesbezüglich werden Ladungsinjektionen an Phenylketten auf NaCl untersucht. Es kann festgestellt werden, dass die molekularen Orbitale geladener Spezies stark lokalisiert sind und geometrische Änderungen dieser Ketten ebenfalls nur lokal zu beobachten sind. Zuletzt wird demonstriert, wie am System Cu-Phthalocyanin/NaCl auch höhere Ladungszustände nach Injektion zweier zusätzlicher Elektronen untersucht und die jeweiligen elektronischen Übergänge abgebildet werden können. thesis_rgbg 2019 12 20 https://epub.uni-regensburg.de/id/eprint/38271 Fabian Queck-Scharrer Intramolecular structural relaxations occurring upon electron transfer are crucial in determining the rate of redox reactions. Here, we demonstrate that subangstrom structural changes occurring upon single-electron charging can be quantified by means of atomically resolved atomic force microscopy (AFM) for the case of single copper(II)phthalocyanine (CuPc) molecules deposited on an ultrathin NaCl film. Imaging the molecule in distinct charge states (neutral and anionic) reveals characteristic differences in the AFM contrast. In comparison to density functional theory simulations these changes in contrast can be directly related to relaxations of the molecule's geometric structure upon charging. The dominant contribution arises from a nonhomogeneous vertical relaxation of the molecule, caused by a change in the electrostatic interaction with the surface. article 2019 8 0031-9007,1079-7114 10.1103/PhysRevLett.123.066001 Physical Review Letters 123 AMER PHYSICAL SOC

COLLEGE PK

066001 https://epub.uni-regensburg.de/id/eprint/40671 Philipp Scheuerer Laerte L. Patera Felix Simbürger Fabian Queck Ingmar Swart Bruno Schuler Leo Gross Nikolaj Moll Jascha Repp Intermediate states arc elusive to many experimental techniques due to their short lifetimes. Here, by performing single-electron alternate charging scanning tunneling microscopy of molecules on insulators, we accessed a charged intermediate state involved in the rapid toggling of individual metal phthalocyanines deposited on NaCl films. By stabilizing the transient species, we reveal how electron injection into the lowest unoccupied molecular orbital leads to a pronounced change in the adsorption geometry, characterized by a different azimuthal orientation. This observation allows clarifying the nature of the toggling process, unveiling the role of transient ionic states involved into fundamental processes occurring at interfaces. article 2019 7 0031-9007,1079-7114 10.1103/PhysRevLett.123.016001 Physical Review Letters 123 AMER PHYSICAL SOC

COLLEGE PK

016001 https://epub.uni-regensburg.de/id/eprint/40474 Laerte L. Patera Fabian Queck Philipp Scheuerer Nikolaj Moll Jascha Repp The interplay of adsorption geometry and interface dipoles of the transition-metal complex \molecule\ on Cu(111) was studied using low-temperature scanning probe microscopy and density-functional-theory calculations. We find that the orientation of the molecule's intrinsic dipole moment with respect to the surface has a strong influence to the total energy of the different configurations, where the most stable one has the molecular dipole moment pointing out of the surface plane along the surface normal. Adsorption-induced redistribution of charges results in an additional dipole moment that also points out of the surface plane for all configurations. Submolecularly resolved maps of the resulting local contact potential difference suggest that any in-plane dipole moment is very effectively screened. article 2019 6 2040-3372,2040-3364 10.1039/C9NR00934E Nanoscale 11 The Royal Society of Chemistry 12695-12703 26 https://epub.uni-regensburg.de/id/eprint/40400 Fabian Queck Florian Albrecht Pingo Mutombo Ondřej Krejčí Pavel Jelinek Alastair McLean Jascha Repp The adsorption geometry and the electronic structure of a Blatter radical derivative on a gold surface were investigated by a combination of high-resolution noncontact atomic force microscopy and scanning tunneling microscopy. While the hybridization with the substrate hinders direct access to the molecular states, we show that the unpaired-electron orbital can be probed with angstrom ngstrom resolution by mapping the spatial distribution of the Kondo resonance. The Blatter derivative features a peculiar delocalization of the unpaired-electron orbital over some but not all moieties of the molecule, such that the Kondo signature can be related to the spatial fingerprint of the orbital. We observe a direct correspondence between these two quantities, including a pronounced nodal plane structure. Finally, we demonstrate that the spatial signature of the Kondo resonance also persists upon noncovalent dimerization of molecules. article 2019 5 22 1433-7851,1521-3773 10.1002/anie.201904851 Angewandte Chemie International Edition 58 Wiley

WEINHEIM

11063-11067 32 https://epub.uni-regensburg.de/id/eprint/40239 Laerte L. Patera Sophia Sokolov Jonathan Low Louis Campos Latha Venkataraman Jascha Repp Bisher galt, dass Rastertunnelmikroskopie eine leitfähige Probe erfordert – dies ist nun überholt. Bei der von unserer Gruppe an der Universität Regensburg entwickelten Methode werden nicht mehr die tunnelnden Elektronen in die Probe abgeleitet, sondern diese tunneln ausschließlich zwischen der Spitze des Instruments und einem einzelnen Molekül hin und zurück. Detektiert werden dabei die einzelnen Elektronen anhand ihrer Kraftwirkung auf die Spitze. Diese neue Variante der Rastersondenmikroskopie ermöglicht das Abbilden von Molekülorbitalen in unterschiedlichen Ladungszuständen des Moleküls. article 2019 5 0031-9252,1521-3943 10.1002/piuz.201970304 Physik in unserer Zeit 50 Wiley-VCH 110-111 3 https://epub.uni-regensburg.de/id/eprint/40227 Philipp Scheuerer Fabian Queck Laerte L. Patera Jascha Repp The planar heterocyclic molecules 1,6,7,12-tetraazaperylene on a Ag(111) metal substrate show different charging characteristics depending on their local environment: next to vacancies in self-assembled islands, molecules can be charged by local electric fields, whereas their charge state is fixed otherwise. This enables the activation of selected molecules inside islands by vacancy creation from scanning-probe-based manipulation. This concept allows for combining the precise mutual atomic-scale alignment of molecules by self-assembly, on one hand, and the implementation of specific functionality into otherwise homogeneous monolayers, on the other. Activated molecules in the direct neighborhood influence each other in their charging characteristics, suggesting their use as molecular quantum cellular automata. Surprisingly, only very few interacting molecules exhibit a rich spectroscopic signature, which offers the prospect of implementing complex functionality in such structures in the future. article 2019 4 01 1530-6984,1530-6992 10.1021/acs.nanolett.8b03960 Nano Letters 19 AMER CHEMICAL SOC

WASHINGTON

2750-2757 5 https://epub.uni-regensburg.de/id/eprint/40036 Nemanja Kocić Dominik Blank Paula Abufager Nicolas Lorente Silvio Decurtins Shi-Xia Liu Jascha Repp Stable organic radicals have potential applications for building organic spintronic devices. To fulfill this potential, the interface between organic radicals and metal electrodes must be well characterized. Here, through a combined effort that includes synthesis, scanning tunneling microscopy, X-ray spectroscopy, and single-molecule conductance measurements, we comprehensively probe the electronic interaction between gold metal electrodes and a benchtop stable radical-the Blatter radical. We find that despite its open-shell character and having a half-filled orbital close to the Fermi level, the radical is stable on a gold substrate under ultrahigh vacuum. We observe a Kondo resonance arising from the radical and spectroscopic signatures of its half-filled orbitals. By contrast, in solution-based single-molecule conductance measurements, the radical character is lost through oxidation with charge transfer occurring from the molecule to metal. Our experiments show that the stability of radical states can be very sensitive to the environment around the molecule. article 2019 3 1530-6984,1530-6992 10.1021/acs.nanolett.9b00275 Nano Letters 19 AMER CHEMICAL SOC

WASHINGTON

2543-2548 4 https://epub.uni-regensburg.de/id/eprint/38447 Jonathan Z. Low Gregor Kladnik Laerte L. Patera Sophia Sokolov Giacomo Lovat Elango Kumarasamy Jascha Repp Luis M. Campos Dean Cvetko Alberto Morgante Latha Venkataraman Electron transfer plays a crucial part in many chemical reactions(1,2), including photosynthesis, combustion and corrosion. But even though redox-state transitions change the electronic structure of the molecules involved, mapping these changes at the single-molecule level is challenging. Scanning tunnelling microscopy provides insights into the orbital structure(3) of single molecules and their interactions(4,5), but requires the use of a conductive substrate that keeps molecules in a given charge state and thereby suppresses redox-state transitions. Atomic force microscopy can be used on insulating substrates to obtain structural(6) and electrostatic(7,8) information but does not generally access electronic states. Here we show that when synchronizing voltage pulses that steer electron tunnelling between a conductive atomic force microscope tip and a substrate with the oscillation of the tip, we can perform tunnelling experiments on non-conductive substrates and thereby map the orbital structure of isolated molecules as a function of their redox state. This allows us to resolve previously inaccessible electronic transitions in space and energy and to visualize the effects of electron transfer and polaron formation on individual molecular orbitals. We anticipate that our approach will prove useful for the investigation of complex redox reactions and charging-related phenomena with sub-angstrom resolution. article 2019 2 13 0028-0836,1476-4687 10.1038/s41586-019-0910-3 Nature 566 Nature

LONDON

245-248 7743 https://epub.uni-regensburg.de/id/eprint/38332 Laerte L. Patera Fabian Queck Philipp Scheuerer Jascha Repp The bonds in metal organic networks on surfaces govern the resulting geometry as well as the electronic properties. Here, we study the nature of these bonds by forming phenazine-copper complexes on a copper surface by means of atomic manipulation. The structures are characterized by a combination of scanning probe microscopy and density functional theory calculations. We observed an increase of the molecule-substrate distance upon covalent bond formation and an out-of-plane geometry that is in direct contradiction with the common expectation that these networks are steered by coordination bonds. Instead, we find that a complex energy balance of hybridization with the substrate, inhomogeneous Pauli repulsion, and elastic deformation drives the phenazine-copper interaction. Most remarkably, this attractive interaction is not driven by electron acceptor properties of copper but is of completely different donation/back-donation mechanism between molecular pi-like orbitals and sp-like metal states. Our findings show that the nature of bonds between constituents adsorbed on surfaces does not have to follow the common categories. article 2018 9 0002-7863,0002-7863 10.1021/jacs.8b06765 Journal of the American Chemical Society 140 AMER CHEMICAL SOC

WASHINGTON

12884-12889 40 https://epub.uni-regensburg.de/id/eprint/37743 Fabian Queck Ondřej Krejčí Philipp Scheuerer Felix Bolland Michal Otyepka Pavel Jelinek Jascha Repp Intermolecular single-electron transfer on electrically insulating films is a key process in molecular electronics(1-4) and an important example of a redox reaction(5,6). Electron-transfer rates in molecular systems depend on a few fundamental parameters, such as interadsorbate distance, temperature and, in particular, the Marcus reorganization energy(7). This crucial parameter is the energy gain that results from the distortion of the equilibrium nuclear geometry in the molecule and its environment on charging(8,9). The substrate, especially ionic films(10), can have an important influence on the reorganization energy(11,12). Reorganization energies are measured in electrochemistry(13) as well as with optical(14,15) and photoemission spectroscopies(16,17), but not at the single-molecule limit and nor on insulating surfaces. Atomic force microscopy (AFM), with single-charge sensitivity(18-22), atomic-scale spatial resolution(20) and operable on insulating films, overcomes these challenges. Here, we investigate redox reactions of single naphthalocyanine (NPc) molecules on multilayered NaCl films. Employing the atomic force microscope as an ultralow current meter allows us to measure the differential conductance related to transitions between two charge states in both directions. Thereby, the reorganization energy of NPc on NaCl is determined as (0.8 +/- 0.2) eV, and density functional theory (DFT) calculations provide the atomistic picture of the nuclear relaxations on charging. Our approach presents a route to perform tunnelling spectroscopy of single adsorbates on insulating substrates and provides insight into single-electron intermolecular transport. article 2018 4 16 1748-3387,1748-3395 10.1038/s41565-018-0087-1 Nature Nanotechnology 13 Nature

LONDON

376-380 https://epub.uni-regensburg.de/id/eprint/37128 Shadi Fatayer Bruno Schuler Wolfram Steurer Ivan Scivetti Jascha Repp Leo Gross Mats Persson Gerhard Meyer Sequential tunneling of electrons through a single chlorine vacancy on a multilayer NaCl film on Cu(100) in the junction of a non-contact atomic force microscope with a conductive tip can lead to a negative damping of the cantilever. The characteristic features in the damping signal as a function of NaCl-layer thickness, tip position and tip-sample bias can be explained in a simple rate-equation model for the sequential tunneling process through the double-barrier tunnel junction. The first barrier results from the vacuum gap between tip and vacancy and its tunneling rate is tuned by the tip position and the applied bias. The second barrier results from the NaCl film and its tunneling rate is governed by the film's thickness. The current-induced damping is strongest if the two tunneling rates through each of the barriers individually are both comparable to the cantilever's oscillation frequency. The damping signal can be employed for detecting subfemtoampere tunneling currents and furthermore, maps of the damping signal can be used to inspect the mesoscopic tip shape. The observed and described current-induced damping should be a common phenomenon in non-contact atomic force microscopy for double-barrier tunnel junction geometries. (C) 2018 Published by Elsevier B.V. article 2018 3 0039-6028,1879-2758 10.1016/j.susc.2018.02.011 Surface Science 678 ELSEVIER SCIENCE BV

AMSTERDAM

112-117 https://epub.uni-regensburg.de/id/eprint/36819 Wolfram Steurer Jascha Repp Leo Gross Gerhard Meyer This thesis describes the investigation of fundamental properties of molecules in the tunnelling junction using combined scanning tunneling (STM) and atomic force microscopy (AFM). In this work, five different experimental topics are addressed. A reduction of the single-particle level spacing of two frontier orbitals enables the manifestation of strong electron-correlation effects in single molecules. In this regime conduction exhibits a spatial signature fundamentally different from what a single particle picture would predict. Individual molecules at the edges of self-assembled islands temporarily change their charge state due to the presence of the electric field from a scanning-probe tip. Close to the threshold voltage for a charge state transition, periodic switching of the charge is directly driven by the cantilever motion in frequency-modulated AFM. A novel concept for the realization of molecular quantum cellular automata is demonstrated. The solution lies in the combination of the creation of perfectly aligned inactive cells by self-assembly as a first and their selective and controlled activation as a second step. A real space investigation of a singly charged molecules adsorbed on an ultrathin insulating film reveals a two-level system that can reversibly change between configurations, resembling the motion of a rocker switch. Selective intermolecular aryl-aryl coupling via dehydrogenative C-H activation occurs on the surface upon thermal annealing. A full atomistic description of the different reaction products based on an unambiguous discrimination between pyrazine and pyridine moieties is presented. thesis_rgbg 2018 1 02 https://epub.uni-regensburg.de/id/eprint/35745 Nemanja Kocić The bottom-up assembly of chiral structures usually relies on a cascade of molecular recognition interactions. A thorough description of these complex stereochemical mechanisms requires the capability of imaging multilevel coordination in real-time. Here we report the first direct observation of hierarchical expression of supramolecular chirality at work, for 10,10′-dibromo-9,9′-bianthryl (DBBA) on Cu(111). Molecular recognition first steers the growth of chiral organometallic chains and then leads to the formation of enantiopure islands. The structure of the networks was determined by noncontact atomic force microscopy (nc-AFM), while high-speed scanning tunnelling microscopy (STM) revealed details of the assembly mechanisms at the ms time-scale. The direct observation of the chirality transfer pathways allowed us to evaluate the enantioselectivity of the interchain coupling. article 2017 9 1463-9084,1463-9076 10.1039/C7CP01341H Physical Chemistry Chemical Physics 19 Royal Society of Chemistry (RSC) 24605-24612 36 https://epub.uni-regensburg.de/id/eprint/36122 Laerte L. Patera Zhiyu Zou Carlo Dri Cristina Africh Jascha Repp Giovanni Comelli The frontier orbital sequence of individual dicyanovinyl-substituted oligothiophene molecules is studied by means of scanning tunneling microscopy. On NaCl/Cud(111), the molecules are neutral, and the two lowest unoccupied molecular states are observed in the expected order of increasing energy. On NaCl/Cud(311), where the molecules are negatively charged, the sequence of two observed molecular orbitals is reversed, such that the one with one more nodal plane appears lower in energy. These experimental results, in open contradiction with a single-particle interpretation, are explained by a manybody theory predicting a strongly entangled doubly charged ground state. article 2017 8 01 0031-9007,1079-7114 10.1103/PhysRevLett.119.056801 Physical Review Letters 119 AMER PHYSICAL SOC

COLLEGE PK

056801 5 https://epub.uni-regensburg.de/id/eprint/36073 Ping Yu Nemanja Kocić Jascha Repp Benjamin Siegert Andrea Donarini Structures of the aromatic N-heterocyclic hexaazatriphenylene (HAT) molecular synthon obtained by surface-assisted self-assembly were analyzed with sub-c resolution by means of noncontact atomic force microscopy (nc-AFM), both in the kinetically trapped amorphous state and in the thermodynamically stable crystalline phase. These results reveal how the crystallization governs the length scale of the network order for non-flexible molecular species without affecting the local bonding schemes. The capability of nc-AFM to accurately resolve structural relaxations will be highly relevant for the characterization of vitreous two-dimensional supramolecular materials. article 2017 7 14 1433-7851,1521-3773 10.1002/anie.201705338 Angewandte Chemie International Edition 56 Wiley

WEINHEIM

10786-10790 36 https://epub.uni-regensburg.de/id/eprint/35915 Laerte L. Patera Xunshan Liu Nico Mosso Silvio Decurtins Shi-Xia Liu Jascha Repp In a recent publication [N. Kocic et al., Nano Lett. 15, 4406 (2015)], it was shown that gating of molecular levels in the field of an oscillating tip of an atomic force microscope can enable a periodic charging of individual molecules synchronized to the tip's oscillatory motion. Here we discuss further implications of such measurements, namely, how the force difference associated with the singleelectron charging manifests itself in atomic force microscopy images and how it can be detected as a function of tip-sample distance. Moreover, we discuss how the critical voltage for the chargestate transition depends on distance and how that relates to the local contact potential difference. These measurements allow also for an estimate of the absolute tip-sample distance. article 2017 2 21 0021-9606,1089-7690 10.1063/1.4975607 The Journal of Chemical Physics 146 AMER INST PHYSICS

MELVILLE

092327 9 https://epub.uni-regensburg.de/id/eprint/35257 Nemanja Kocić Silvio Decurtins Shi-Xia Liu Jascha Repp Scanning probe microscopy (SPM) methods allow for investigations of the atomistic world in real space. While scanning tunneling microscopy (STM) is sensitive to the electronic structure of the sample, its geometry can be explored by means of atomic force microscopy (AFM). Suitable functionalization of the AFM tip enables resolving the chemical structure of individual molecules at low temperatures in ultrahigh vacuum. Combining STM and AFM detection schemes in one setup facilitates simultaneous examination of the electronic and the geometric structure of single (molecular) adsorbates. This work employs SPM with functionalized tips on individual molecules in three topics: The capability of structure determination is widened to non-planar and strongly deformed molecules. The required information is deduced from either full three-dimensional data sets or from images along the adsorbed molecule’s symmetry planes that are perpendicular to the sample surface. On-surface chemical reactions are studied in great detail. For two exemplary cases, we investigate the reaction pathway of a thermally activated planarization reaction, and we examine the interplay of electronic and geometric structure in the tip-induced formation of a metalorganic complex. Finally, we use AFM to image the charge distribution in individual metal-organic molecules with polar bonds. Introducing a novel spectroscopy technique we resolve charge contrast along individual polar bonds. thesis_rgbg 2017 1 02 https://epub.uni-regensburg.de/id/eprint/34481 Florian Albrecht Watching a single molecule move on its intrinsic timescale has been one of the central goals of modern nanoscience, and calls for measurements that combine ultrafast temporal resolution(1-8) with atomic spatial resolution(9-30). Steady-state experiments access the requisite spatial scales, as illustrated by direct imaging of individual molecular orbitals using scanning tunnelling microscopy(9-11) or the acquisition of tip-enhanced Raman and luminescence spectra with sub-molecular resolution(26-28). But tracking the intrinsic dynamics of a single molecule directly in the time domain faces the challenge that interactions with the molecule must be confined to a femtosecond time window. For individual nanoparticles, such ultrafast temporal confinement has been demonstrated(18) by combining scanning tunnelling microscopy with so-called lightwave electronics(1-8), which uses the oscillating carrier wave of tailored light pulses to directly manipulate electronic motion on timescales faster even than a single cycle of light. Here we build on ultrafast terahertz scanning tunnelling microscopy to access a state-selective tunnelling regime, where the peak of a terahertz electric-field waveform transiently opens an otherwise forbidden tunnelling channel through a single molecular state. It thereby removes a single electron from an individual pentacene molecule's highest occupied molecular orbital within a time window shorter than one oscillation cycle of the terahertz wave. We exploit this effect to record approximately 100-femtosecond snapshot images of the orbital structure with sub-angstrom spatial resolution, and to reveal, through pump/probe measurements, coherent molecular vibrations at terahertz frequencies directly in the time domain. We anticipate that the combination of lightwave electronics(1-8) and the atomic resolution of our approach will open the door to visualizing ultrafast photochemistry and the operation of molecular electronics on the single-orbital scale. article 2016 11 10 0028-0836,1476-4687 10.1038/nature19816 Nature 539 Nature

LONDON

263-267 7628 https://epub.uni-regensburg.de/id/eprint/34820 Tyler L. Cocker Dominik Peller Ping Yu Jascha Repp Rupert Huber In recent years atomic force microscopy (AFM) at highest resolution was widely applied to mostly planar molecules, while its application toward exploring species with structural flexibility and a distinct 3D character remains a challenge. Herein, the scope of noncontact AFM is widened by investigating subtle conformational differences occurring in the well-studied reference systems 2H-TPP and Cu-TPP on Cu(111). Different saddle shape conformations of both species can be recognized in conventional constant-height AFM images. To unambiguously identify the behavior of specific molecular moieties, we extend data acquisition to distances that are inaccessible with constant height measurements by introducing vertical imaging, that is, AFM mapping in a plane perpendicular to the sample surface. Making use of this novel technique the vertical displacement of the central Cu atom upon tip-induced conformational switching of Cu-TPP is quantified. Further, for 2H-TPP two drastically different geometries are observed, which are systematically characterized. Our results underscore the importance of structural flexibility in adsorbed molecules with large conformational variability and, consequently, the objective to characterize their geometry at the single-molecule level in real space. article 2016 10 25 1530-6984,1530-6992 10.1021/acs.nanolett.6b03769 Nano Letters 16 AMER CHEMICAL SOC

WASHINGTON

7703-7709 12 https://epub.uni-regensburg.de/id/eprint/34769 Florian Albrecht Felix Bischoff Wilhelm Auwärter Johannes V. Barth Jascha Repp It is known that individual metal atoms on insulating ionic films can occur in several different (meta) stable charge states, which can be reversibly switched in a controlled fashion. Here we show that the diffusion of gold adatoms on NaCl thin films depends critically on their charge state. Surprisingly, the anionic species has a lower diffusion barrier than the neutral one. Furthermore, for the former we observe that the diffusion atop a bilayer of NaCl is strongly influenced by the interface between NaCl and the underlying copper substrate. This effect disappears for a trilayer of NaCl. These observations open the prospect of controlling the diffusion properties of individual metal atoms on thin insulating films. article 2016 9 0031-9007,1079-7114 10.1103/PhysRevLett.117.146102 Physical Review Letters 117 AMER PHYSICAL SOC

COLLEGE PK

146102 https://epub.uni-regensburg.de/id/eprint/34658 Jascha Repp Wolfram Steurer Ivan Scivetti Mats Persson Leo Gross Gerhard Meyer Regioselectivity is of fundamental importance in chemical synthesis. Although many concepts for site-selective reactions are well established for solution chemistry, it is not a priori clear whether they can easily be transferred to reactions taking place on a metal surface. A metal will fix the chemical potential of the electrons and perturb the electronic states of the reactants because of hybridization. Additionally, techniques to characterize chemical reactions in solution are generally not applicable to on-surface reactions. Only recent developments in resolving chemical structures by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) paved the way for identifying individual reaction products on surfaces. Here we exploit a combined STM/AFM technique to demonstrate the on-surface formation of complex molecular architectures built up from a heteroaromatic precursor, tetracyclic pyrazino[2,3-f][4,7]phenanthroline (pap) molecule. Selective intermolecular aryl-aryl coupling via dehydrogenative C-H activation occurs on Au(111) upon thermal annealing under ultrahigh vacuum (UHV) conditions. A full atomistic description of the different reaction products based on an unambiguous discrimination between pyrazine and pyridine moieties is presented. Our work not only elucidates that ortho-hydrogen atoms of the pyrazine rings are preferentially activated over their pyridine equivalents, but also sheds new light onto the participation of substrate atoms in metal-organic coordination bonding during covalent C-C bond formation. article 2016 4 08 10.1021/jacs.5b13461 Journal of the American Chemical Society 138 AMER CHEMICAL SOC

WASHINGTON

5585-5593 17 https://epub.uni-regensburg.de/id/eprint/33632 Nemanja Kocić Xunshan Liu Songjie Chen Silvio Decurtins Ondřej Krejčí Pavel Jelinek Jascha Repp Shi-Xia Liu In the past, current-distance spectroscopy has been widely applied to determine variations of the work function at surfaces. While for homogeneous sample areas this technique is commonly accepted to yield at least qualitative results, its applicability to atomic-scale variations has not been proven neither right nor wrong. Here we benchmark measurements of the current-distance decay constant against the well established Kelvin probe force spectroscopy for four distinctly different cases with atomic-scale variations of the local contact potential. The two techniques yield quite different results. Whereas the maps of the current-distance decay constant are consistent with being topographical artifacts, the Kelvin probe force spectroscopy maps show variations of the local contact potential difference in agreement with expected surface dipoles. This comparison clarifies that maps of the current-distance decay constant are not suited to directly characterize contact potential variations at surfaces on atomic length scales. article 2015 12 1098-0121,1550-235X 10.1103/PhysRevB.92.235443 Physical Review B 92 AMER PHYSICAL SOC

COLLEGE PK

235443 https://epub.uni-regensburg.de/id/eprint/33125 Florian Albrecht Martin Fleischmann Manfred Scheer Leo Gross Jascha Repp article 2015 11 02 1521-3943 (online),0031-9252 (print) 10.1002/piuz.201590099 Physik in unserer Zeit 46 WILEY-VCH Verlag 266-267 6 https://epub.uni-regensburg.de/id/eprint/32720 Jascha Repp Florian Albrecht Martin Fleischmann Manfred Scheer Scanning probe microscopy techniques offer the unique possibility to characterize and manipulate atomic-scale objects atom-by-atom. In this thesis, we study structural and electronic properties of single molecules, defects and atoms on two-monolayer thick NaCl islands on Cu(111) by a combination of low-temperature scanning tunneling microscopy (STM), atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). Specifically, we exploit the enhanced resolution obtained with functionalized tips; a deterministic chemical modification of the last atoms of the scanning probe tip. First, the performance of different tip functionalizations is assessed and based on these findings, the underlying contrast mechanisms in AFM and KPFM could be identified. Next, different molecular model systems are examined to describe how important molecular properties such as chemical structure, bond order, adsorption geometry and intramolacular charge distribution can be measured by AFM. Thereby, current understanding of the qualitative and quantitative AFM and KPFM contrast is pushed forward. Then, we apply atomic-resolution AFM and molecular orbital imaging by STM to identify and characterize synthetic products, purified natural compounds and complex mixtures. Finally, atomic manipulation is used to trigger chemical reactions on single molecules, to generate defect structures on the surface, to control the charge state of adatoms and mechanically actuate an atomic switch implemented by an embedded adatom. thesis_rgbg 2015 10 01 https://epub.uni-regensburg.de/id/eprint/32096 Bruno Schuler Kelvin probe force spectroscopy was used to characterize the charge distribution of individual molecules with polar bonds. Whereas this technique represents the charge distribution with moderate resolution for large tip-molecule separations, it fails for short distances. Here, we introduce a novel local force spectroscopy technique which allows one to better disentangle electrostatic from other contributions in the force signal. It enables one to obtain charge-related maps at even closer tip-sample distances, where the lateral resolution is further enhanced. This enhanced resolution allows one to resolve contrast variations along individual polar bonds. article 2015 8 13 0031-9007,1079-7114 10.1103/PhysRevLett.115.076101 Physical Review Letters 115 AMER PHYSICAL SOC

COLLEGE PK

076101 https://epub.uni-regensburg.de/id/eprint/32349 F. Albrecht Jascha Repp M. Fleischmann M. Scheer M. Ondráček P. Jelínek The formation of extended electron states in one-dimensional nanostructures is of key importance for the function of molecular electronic devices. Here, we study the effects of strong electron-phonon interaction on the formation of extended electronic states in intentionally created Cl vacancy pairs and chains in a NaCl bilayer on Cu(111). The interaction between the vacancies was tailored by fabricating vacancy pairs and chains of different orientation and separation with atomic precision using vertical manipulation. Small vacancy separations led to the formation of quantum-well-like vacancy states and localized interface states. By using scanning tunneling spectroscopy, we measured their energy splitting and broadening as a function of the intervacancy separation. Remarkably, the energy splitting between the vacancy states is enlarged by level repulsion resulting from the phonon dressing of the electronic states, as evidenced by theory. article 2015 6 24 1098-0121,1550-235X 10.1103/PhysRevB.91.235443 Physical Review B 91 AMER PHYSICAL SOC

COLLEGE PK

235443 https://epub.uni-regensburg.de/id/eprint/32012 Bruno Schuler Mats Persson Sami Paavilainen Niko Pavliček Leo Gross Gerhard Meyer Jascha Repp Individual molecules at the edges of self-assembled islands grown on Ag(111) can be deliberately switched hi their Charge state with the electric field from a scanning-probe tip. Close to the threshold voltage for a charge state transition, periodic switching of the charge is directly driven by the cantilever motion in frequency-modulated atomic force microscopy (AFM), as can be deduced from the signature in the measured frequency shift. In this regime, the integrated frequency shift yields the tip sample force that is due to a single additional electron. Further, the signature of the dynamic charging response provides information on the electronic coupling of the molecule to the substrate. In analogy to previous experiments on quantum dots, this may also be used in the future to access excited state properties of single molecules from AFM experiments. article 2015 6 09 1530-6984,1530-6992 10.1021/acs.nanolett.5b00711 Nano Letters 15 AMER CHEMICAL SOC

WASHINGTON

4406-4411 https://epub.uni-regensburg.de/id/eprint/31916 Nemanja Kocić Peter Weiderer Stephan Keller Silvio Decurtins Shi-Xia Liu Jascha Repp We study a thermally activated on-surface planarization reaction by a detailed analysis of the reactant and reaction products from atomically resolved atomic forte microscopy (AFM), images and spectroscopy. The three-dimensional (3D) structure of the reactant, a helical diphenanthrene derivative, requires going beyond constant-height imaging. The characterization in three dimensions is enabled by acquisition and analysis of the AFM signal in a 3D data set. This Way, the structure and geometry of nonplanar molecules as well as their reaction products on terraces and at step edges can be determined. article 2015 6 05 10.1021/jacs.5b03114 Journal of the American Chemical Society 137 AMER CHEMICAL SOC

WASHINGTON

7424-7428 23 https://epub.uni-regensburg.de/id/eprint/31913 Florian Albrecht Niko Pavliček Coral Herranz-Lancho Mario Ruben Jascha Repp Atomic resolution on molecules was obtained by employing functionalized tips, that is, deterministic chemical modifications of the last tip atoms, for NC-AFM. The most widely used tip fuctionalization for this purpose to date is a single CO molecule. Here we review the contrast mechanism and compare different tip functionalizations. Furthermore, we describe the use of NC-AFM with functionalized tips for the identification of molecular structures, the determination of molecular adsorption geometries, bond-order discrimination, and for Kelvin probe force microscopy with sub-molecular resolution. book_section 2015 6 02 978-3-319-15587-6 10.1007/978-3-319-15588-3_12 Noncontact Atomic Force Microscopy: Volume 3 Springer International Publishing Seizo Morita Franz J. Giessibl Ernst Meyer und Roland Wiesendanger 223-246 12 https://epub.uni-regensburg.de/id/eprint/32014 Leo Gross Bruno Schuler Fabian Mohn Nikolaj Moll Jascha Repp Gerhard Meyer We show charge-state manipulation of single Au adatoms on 2-11 monolayer (ML) thick NaCl films on Cu surfaces by attaching or detaching single electrons via the tip of an atomic force microscope (AFM). Tristate charge control (neutral, negatively charged, and positively charged) is achieved. On Cu(100) and Cu(111) supports, charge tristability is achieved independently of the NaCl layer thickness. In contrast, on Cu(311), only Au anions are stable on the thinnest NaCl films, but neutral and positive charge states become sufficiently long lived on films thicker than 4 ML to allow AFM-based charge-state-manipulation experiments. article 2015 1 22 0031-9007,1079-7114 10.1103/PhysRevLett.114.036801 Physical Review Letters 114 AMER PHYSICAL SOC

COLLEGE PK

036801 https://epub.uni-regensburg.de/id/eprint/31246 W. Steurer Jascha Repp L. Gross I. Scivetti M. Persson G. Meyer book_section 2015 978-3-662-47736-6 10.1007/978-3-662-47736-6_33 Physics of Solid Surfaces: Subvolume A 45A Springer Berlin Heidelberg

Berlin, Heidelberg

G. Chiarotti und P. Chiaradia 67-99 3 https://epub.uni-regensburg.de/id/eprint/33241 Gerhard Meyer Leo Gross Jascha Repp The underlying mechanisms of image distortions in atomic force microscopy (AFM) with CO-terminated tips are identified and studied in detail. AFM measurements of a partially fluorinated hydrocarbon molecule recorded with a CO-terminated tip are compared with state-of-the-art ab initio calculations. The hydrogenated and fluorinated carbon rings in the molecule appear different in size, which primarily originates from the different extents of their π-electrons. Further, tilting of the CO at the tip, induced by van der Waals forces, enlarges the apparent size of parts of the molecule by up to 50%. Moreover, the CO tilting in response to local Pauli repulsion causes a significant sharpening of the molecule bonds in AFM imaging. article 2014 10 10.1021/nl502113z Nano Letters 14 American Chemical Society 6127-6131 https://epub.uni-regensburg.de/id/eprint/30842 Nikolaj Moll Bruno Schuler Shigeki Kawai Feng Xu Lifen Peng Akihiro Orita Junzo Otera Alessandro Curioni Mathias Neu Jascha Repp Gerhard Meyer Leo Gross This thesis presents low temperature scanning probe experiments performed in the cross-sectional geometry (X-SPM) on GaAs samples. In particular, three topics have been addressed. First, the GaAs(110) surface has been utilized as a substrate to adsorb iron-II-phthalocyanine molecules. The molecules were probed from scanning tunneling microscopy (STM) and spectroscopy (STS) and were found to be only weakly perturbed by the substrate. This is in analogy to molecules decoupled from a metallic sample by an ultrathin insulating layer and hence offers the possibility to combine single-molecule functionality with the rich versatility of semiconductor physics. Second, we have exploited the possibility to tune molecular resonances via the adsorption position of the individual molecules across an epitaxialy grown heterostructure, where the relative positions of molecular resonances, Fermi level and vacuum level can be tuned with respect to each other. Third, we have used a combination of STM/STS and Kelvin probe force spectroscopy (KPFS) to solve the long-standing problem of tip-induced band bending usually present in STM/STS on semiconducting surfaces due to the penetration of the electrostatic field into the interior of the sample. With this combination of experimental techniques, we revisited individual shallow acceptors buried below the GaAs(110) surface, and found the acceptor-induced enhanced conductance to be present similarly within multiple band bending regimes. thesis_rgbg 2014 6 30 https://epub.uni-regensburg.de/id/eprint/30107 Gerhard Münnich Im Rahmen dieser Arbeit wurde ein Tieftemperatur qPlus-Rasterkraftmikroskop aufgebaut und erfolgreich in Betrieb genommen. Sämtliche Details zum Aufbau der Anlage wurden dokumentiert und die Lösungen aufgetretener Probleme erläutert. Verschiedene Tests wurden durchgeführt, um die Leistung der Anlage zu charakterisieren. Diese zeigten auf, dass die Performance der Anlage zum Zeitpunkt der Inbetriebnahme deutlich besser war als kommerziell erhältliche Anlagen. Dieser Umstand ermöglichte es, qualitativ hochwertige Studien durchzuführen: So konnten in ersten Experimenten die Bindungsgeometrie eines Metall-Molekül-Komplexes und die Konfigurationen des DBTH-Moleküls bestimmt und veröffentlicht werden. Ein weiteres und in dieser Arbeit erstmals veröffentlichtes Projekt war die Untersuchung der van-der-Waals Wechselwirkung zwischen einem Edelgasatom und einem kleinen Molekül. Um ausschließlich die Wechselwirkung zwischen diesen beiden zu detektieren, wurde folgendermaßen vorgegangen: 1. Der Sensor wurde bei Amplituden im sub-Å-Bereich betrieben. Dies führte zu einer hohen Sensitivität für die kurzreichweitige Wechselwirkung. 2. Aus der gemessenen Frequenzverschiebung Δf wurde die laterale Komponente des Kraftfeldes bestimmt und ausgewertet. Dies ist deshalb von Vorteil, da das Substrat nur indirekt in die laterale Kraft eingeht. Um die Bedeutung des Substrats einschätzen zu können, wurden Experimente sowohl auf einer Cu(111)- als auch einer NaCl(2 ML)/Cu(111)-Oberfläche durchgeführt. In der Auswertung der Daten wurde eine laterale Kraft zwischen Xe-Atom und Pentacen-Molekül im pN-Bereich festgestellt. Zusätzlich traten qualitative Unterschiede in Abhängigkeit der verwendeten Substrate auf. So wurde in den Daten, die auf der Cu-Oberfläche genommen wurden, eine Kontrastinversion in den Ebenen parallel zum Molekül beobachtet. Diese war auf der NaCl-Oberfläche nicht zu sehen, stattdessen war die Kraft auf diesem Substrat betragsmäßig etwas größer. Da die Experimente ohne Anlegen einer Spannung durchgeführt werden mussten, war mit Beiträgen durch elektrostatische Wechselwirkung zu rechnen. Aus diesem Grund wurden KPFM-Messungen durchgeführt. Diese ergaben, dass das Molekül die Austrittsarbeit auf der Cu-Oberfläche senkt und es deshalb zu lateral repulsiven Kräften aufgrund der elektrostatischen Wechselwirkung kommt. Dies war die Ursache für die beobachtete Kontrastinversion. Auf der NaCl-Oberfläche änderte sich dagegen die Austrittsarbeit nicht. Der Abstand, innerhalb der die vdW-Wechselwirkung dominant ist, wurde abgeschätzt, indem die dominanten Anteile der elektrostatischen Wechselwirkung von der Berechnung ausgeschlossen wurden. Ein weiteres Projekt befasste sich mit der Korrektur von hochauflösenden AFM-Bildern, welche aufgrund der Verwendung einer funktionalisierten Spitze verzerrt sind. Es wurde gezeigt, dass es möglich ist, die Daten mit der lateralen Komponente der vdW-Kraft zu entzerren. Dazu wurde mit einer CO-terminierten Spitze die geometrische Struktur von Pentacen auf den Oberflächen Cu(111) und NaCl(2 ML)/Cu(111) abgebildet und die Korrekturmethode getestet. Als Korrekturparameter diente die inverse effektive Steifigkeit, welche durch die Kopplung des CO-Moleküls an die Metallspitze bestimmt ist. Die entzerrten Daten zeigten eine sehr gute Übereinstimmung der dargestellten mit den erwarteten Bindungslängen, was belegt, dass die Entzerrung gut anwendbar ist. thesis_rgbg 2014 5 13 https://epub.uni-regensburg.de/id/eprint/29007 Mathias Neu It has been demonstrated that atomic force microscopy imaging with CO-functionalizedtips provides unprecedented resolution, yet it is subject to strong image distortions. Here we propose a method to correct for these distortions. The lateral force acting on the tip apex is calculated from three-dimensional maps of the frequency shift signal. Assuming a linear relationship between lateral distortion and force, atomic force microscopy images could be deskewed for different substrate systems. article 2014 5 07 1098-0121,1550-235X,0556-2805 10.1103/PhysRevB.89.205407 Physical Review B 89 AMER PHYSICAL SOC

COLLEGE PK

205407 20 https://epub.uni-regensburg.de/id/eprint/29910 Mathias Neu Nikolaj Moll Leo Gross Gerhard Meyer Franz J. Giessibl Jascha Repp In scanning tunneling experiments on semiconductor surfaces, the energy scale within the tunneling junction is usually unknown due to tip-induced band bending. Here, we experimentally recover the zero point of the energy scale by combining scanning tunneling microscopy with Kelvin probe force spectroscopy. With this technique, we revisit shallow acceptors buried in GaAs. Enhanced acceptor-related conductance is observed in negative, zero, and positive band-bending regimes. An Anderson-Hubbard model is used to rationalize our findings, capturing the crossover between the acceptor state being part of an impurity band for zero band bending and the acceptor state being split off and localized for strong negative or positive band bending, respectively. article 2013 11 19 0031-9007,1079-7114 10.1103/PhysRevLett.111.216802 Physical Review Letters 111 AMER PHYSICAL SOC

COLLEGE PK

216802 https://epub.uni-regensburg.de/id/eprint/29159 Gerhard Münnich Andrea Donarini Martin Wenderoth Jascha Repp Recently, we reported on the bistable configurational switching of dibenzo[a,h]thianthrene (DBTH) molecules adsorbed on NaCl using combined low-temperature scanning tunneling and atomic force microscopy (STM/AFM). Here, we discuss the intra-molecular contrast in AFM images of the molecules as a function of the tip-molecule distance. Our experiments show that ridges in the frequency shift do not necessarily correlate with chemical bonds in this case of a non-planar molecule. To explain this finding we compare images acquired at different tip-molecule distances to the calculated electron density of the molecules obtained from density functional theory calculations (DFT). In addition, we analyze the probability of finding different configurations after adsorption onto the surface. DBTH molecules in two configurations probed by a CO-functionalized tip. Insets show AFM (left) and STM (right) images of a U molecule. article 2013 8 09 0370-1972,1521-3951 10.1002/pssb.201349229 physica status solidi b 250 WILEY-V C H VERLAG GMBH

WEINHEIM

2424-2430 11 https://epub.uni-regensburg.de/id/eprint/29013 Niko Pavliček Coral Herranz-Lancho Benoit Fleury Mathias Neu Judith Niedenführ Mario Ruben Jascha Repp Scanning probe methods on insulating films offer a rich toolbox to study electronic, structural and spin properties of individual molecules. This work discusses three issues in the field of molecular and organic electronics. A scanning tunneling microscopy (STM) head to be operated in high magnetic fields has been designed and built up. The STM head is very compact and rigid relying on a robust coarse approach mechanism. This will facilitate investigations of the spin properties of individual molecules in the future. Combined scanning tunneling and atomic force microscopy (AFM) studies revealed a reversible molecular switch based on two stable configurations of DBTH molecules on ultrathin NaCl films. AFM experiments visualize the molecular structure in both states. Our experiments allowed to unambiguous determination of the pathway of the switch. Finally, tunneling into and out of the frontier molecular orbitals of pentacene molecules has been investigated on different insulating films. These experiments show that the local symmetry of initial and final electron wave function are decisive for the ratio between elastic and vibration-assisted tunneling. The results can be generalized to electron transport in organic materials. thesis_rgbg 2013 7 11 33 https://epub.uni-regensburg.de/id/eprint/28394 Niko Pavliček Metal-organic complexes were formed by means of inelastic excitations in a scanning tunneling microscope (STM). The electronic structure of the complex was characterized using STM imaging and spectroscopy. By exploiting the symmetry of the complex, its electronic structure can be rationalized from linear combinations of molecular orbitals. The actual bonding geometry, which cannot be inferred from STM alone, was determined from atomic force microscopy images with atomic resolution. Our study demonstrates that the combination of these techniques enables a direct quantification of the interplay of geometry and electronic coupling in metal-organic complexes in real space. article 2013 6 07 10.1021/ja404084p Journal of the American Chemical Society 135 AMER CHEMICAL SOC

WASHINGTON

9200-9203 24 https://epub.uni-regensburg.de/id/eprint/28386 Florian Albrecht Mathias Neu Christina Quest Ingmar Swart Jascha Repp Im Rahmen dieser Arbeit wurde zunächst ein Rasterelektronenmikroskop aufgebaut. Dafür wurde eine zwei-Linsen-Elektronensäule in eine Testkammer eingebaut, in der dann das Mikroskop unter UHV-Bedingungen getestet wurde. Anhand einer Serie aus verschiedenen Phthalocyaninmolekülen sollte der Ladungszustand von Adsorbaten auf einer ultradünnen Isolatorschicht untersucht werden. Durch die Änderung des Metallsubstrats, des zentralen Metallatoms im Molekül, der Dotierung und der Orientierung der Moleküle auf dem Substrat wurden die Ferminiveaus sowie die Energieniveaus der Moleküle variiert. Ziel war es, durch lediglich kleine Veränderungen des Gesamtsystems die energetische Lage von Ferminiveau und Molekülniveaus zu verändern und damit unterschiedliche Ladungskonfigurationen zu erreichen. Mittels Rastertunnelspektroskopie konnten zunächst die positiven wie negativen Ionenresonanzen energetisch lokalisiert werden. Durch das Anlegen einer Vorspannung, die der Energie der jeweiligen Resonanzen entspricht, wurde dann in den STM-Bildern die laterale Verteilung der Molekülorbitaldichte bestimmt und den mittels DFT berechneten Orbitalbildern zugeordnet. Durch das Aufdampfen von Kupferphthalocyanin-Molekülen auf Cu(100) konnte dieses nicht nur permanent negativ geladen werden. Auch die Übergänge zwischen den Ladungszuständen sowie deren Abhängigkeit von der Adsorptionsorientierung wurden charakterisiert. Durch den Jahn-Teller-Effekt wurde zudem die Entartung des LUMO aufgehoben, was eine getrennte Abbildung der beiden Orbitale des vorher entarteten Energieniveaus möglich machte. Im letzten Teil der Arbeit wurde dieser Effekt weiter ausgenutzt. Durch die laterale Manipulation negativ geladener Goldatome in die Nähe des Moleküls konnte die Besetzungsreihenfolge der nun nicht mehr entarteten Orbitale verändert werden. So entsteht ein molekularer Schalter, der durch das elektrische Feld von Goldionen aktiviert wird. thesis_rgbg 2013 4 19 https://epub.uni-regensburg.de/id/eprint/27268 Christof Uhlmann We present spatially resolved vibronic spectroscopy of individual pentacene molecules in a double-barrier tunneling junction. It is observed that even for this effective single-level system the energy dissipation associated with electron attachment varies spatially by more than a factor of 2. This is in contrast to the usual treatment of electron-vibron coupling in the Franck-Condon picture. Our experiments unambiguously prove that the local symmetry of initial and final wave function determines the dissipation in electron transport. DOI: 10.1103/PhysRevLett.110.136101 article 2013 3 26 0031-9007,0031-9007 10.1103/PhysRevLett.110.136101 Physical Review Letters 110 AMER PHYSICAL SOC

COLLEGE PK

136101 13 https://epub.uni-regensburg.de/id/eprint/27964 Niko Pavliček Ingmar Swart Judith Niedenführ Gerhard Meyer Jascha Repp We report on the controlled change of the energetic ordering of molecular orbitals. Negatively charged copper(II)phthalocyanine on NaCl/Cu(100) undergoes a Jahn-Teller distortion that lifts the degeneracy of two frontier orbitals. The energetic order of the levels can be controlled by Au and Ag atoms in the vicinity of the molecule. As only one of the states is occupied, the control of the energetic order is accompanied by bistable changes of the charge distribution inside the molecule, rendering it a bistable switch. article 2013 1 24 1530-6984,1530-6992 10.1021/nl304483h Nano Letters 13 AMER CHEMICAL SOC

WASHINGTON

777-780 13 https://epub.uni-regensburg.de/id/eprint/27688 Christof Uhlmann Ingmar Swart Jascha Repp A low-temperature scanning tunneling microscope was used in conjunction with density functional theory calculations to determine the binding sites and charge states of adsorbed Ga and Mn atoms on GaAs(110). To quantify the adatom charge states (both +1e), the Coulomb interaction with an individual Mn acceptor is measured via tunneling spectroscopy and compared with theoretical predictions. Several methods for positioning these charged adatoms are demonstrated, allowing us to engineer the electrostatic landscape of the surface with atomic precision. article 2013 1530-6984,1530-6992 10.1021/nl400305q Nano Letters 13 AMER CHEMICAL SOC

WASHINGTON

2418-2422 6 https://epub.uni-regensburg.de/id/eprint/62506 David Gohlke Rohan Mishra Oscar D. Restrepo Donghun Lee Wolfgang Windl Jay Gupta A weak perturbation of a single molecule by the supporting substrate is a key ingredient to molecular electronics. Here, we show that individual phthalocyanine molecules adsorbed on GaAs(110) and InAs(111)A surfaces represent prototypes for weakly coupled single-molecule/semiconductor hybrid systems. This is demonstrated by scanning tunneling spectroscopy and bias-dependent images that closely resemble orbital densities of the free molecule. This is in analogy to results for molecules decoupled from a metal substrate by an ultrathin insulating layer and proves a weak electronic molecule-substrate coupling. Therefore, such systems will allow single-molecule functionality to be combined with the versatility of semiconductor physics. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4742977] article 2012 8 08 0021-8979,1089-7550 10.1063/1.4742977 Journal of Applied Physics 112 AMER INST PHYSICS

MELVILLE

034312 3 https://epub.uni-regensburg.de/id/eprint/25734 Gerhard Münnich Florian Albrecht Christophe Nacci Martin Utz Dieter Schuh Kiyoshi Kanisawa Stefan Fölsch Jascha Repp In this thesis work, a combination of low-temperature scanning tunneling microscopy (STM) and atomic force microscopy (AFM) was used to study single atoms and molecules on thin insulating films. We show that noncontact-AFM can yield important additional information for these systems, which had previously been studied only with STM. In particular, we demonstrate that the charge states of single gold adatoms can be detected with Kelvin probe force microscopy (KPFM). Furthermore, it is described how AFM can be used to image the chemical structure of a molecule with atomic resolution if the microscope tip is functionalized with suitable single atoms or molecules. This method was then applied to study the exact geometry of a molecular switch consisting of a single gold atom and a PTCDA molecule, and to help in the elucidation of the structure of an unknown molecule from the deep sea. Finally, we were able to combine the high resolution of our AFM molecular imaging technique with the charge sensitivity of KPFM to directly image for the first time the charge distribution within a single molecule. These investigations show that by combining STM and AFM, the electronic and structural properties of single molecules can be revealed in unprecedented detail. The possibility of directly imaging the chemical structure and the intramolecular charge distribution could lead to new fundamental insights into single-molecule switching and bond formation – processes that are usually accompanied by a structural rearrangement and/or an intra- or intermolecular redistribution of charge. thesis_rgbg 2012 7 16 https://epub.uni-regensburg.de/id/eprint/25245 Fabian Mohn We investigated dibenzo[a,h] thianthrene molecules adsorbed on ultrathin layers of NaCl using a combined low-temperature scanning tunneling and atomic force microscope. Two stable configurations exist corresponding to different isomers of free nonplanar molecules. By means of excitations from inelastic electron tunneling we can switch between both configurations. Atomic force microscopy with submolecular resolution allows unambiguous determination of the molecular geometry, and the pathway of the interconversion of the isomers. Our investigations also shed new light on contrast mechanisms in scanning tunneling microscopy. article 2012 2 23 0031-9007,1079-7114 10.1103/PhysRevLett.108.086101 Physical Review Letters 108 AMER PHYSICAL SOC

COLLEGE PK

086101 8 https://epub.uni-regensburg.de/id/eprint/23512 Niko Pavliček Benoit Fleury Mathias Neu Judith Niedenführ Coral Herranz-Lancho Mario Ruben Jascha Repp Scanning tunneling microscopy (STM) and atomic force microscopy (AFM) of single atoms and molecules on ultrathin insulating films have led to a wealth of novel observations and insights. Based on the reduced electronic coupling to the metallic substrate, these techniques allow the charge state of individual atoms to be controlled, orbitals of individual molecules to be imaged and metal-molecule complexes to be built up. Near-contact AFM adds the unique capabilities of imaging and probing the chemical structure of single molecules with atomic resolution. With the help of atomic/molecular manipulation techniques, chemical binding processes and molecular switches can be studied in detail. article 2012 2 01 10.2533/chimia.2012.10 Chimia 66 SWISS CHEMICAL SOC

BERN

10-15 1/2 https://epub.uni-regensburg.de/id/eprint/25936 Gerhard Meyer Leo Gross Fabian Mohn Jascha Repp On metallic and semiconductor surfaces functional nanostructures can be built with atomic scale precision using the tip of an atomic force microscope/scanning tunneling microscope. In contrast, controlled lateral manipulation on insulators has not been reported. The traditional pushing and pulling based manipulation methods cannot be used for molecules adsorbed on insulating films because of the unfavorable ratio between diffusion barrier and desorption energy. Here, we demonstrate that molecules adsorbed on insulating films can be laterally manipulated in a controlled way by injecting inelastically tunneling electrons at well-defined positions in a molecule. The technique was successfully applied to several different molecules. article 2012 1 17 1530-6984,1530-6984 10.1021/nl204322r Nano Letters 12 AMER CHEMICAL SOC

WASHINGTON

1070-1074 2 https://epub.uni-regensburg.de/id/eprint/23423 Ingmar Swart Tobias Sonnleitner Judith Niedenführ Jascha Repp This outstanding textbook provides an introduction to electronic materials and device concepts for the major areas of current and future information technology. On about 1,000 pages, it collects the fundamental concepts and key technologies related to advanced electronic materials and devices. The obvious strength of the book is its encyclopedic character, providing adequate background material instead of just reviewing current trends. It focuses on the underlying principles which are illustrated by contemporary examples. The third edition now holds 47 chapters grouped into eight sections. The first two sections are devoted to principles, materials processing and characterization methods. Following sections hold contributions to relevant materials and various devices, computational concepts, storage systems, data transmission, imaging systems and displays. Each subject area is opened by a tutorial introduction, written by the editor and giving a rich list of references. The following chapters provide a concise yet in-depth description in a given topic. Primarily aimed at graduate students of physics, electrical engineering and information technology as well as material science, this book is equally of interest to professionals looking for a broader overview. Experts might appreciate the book for having quick access to principles as well as a source for getting insight into related fields. book_section 2012 978-3-527-40927-3 Nanoelectronics and Information Technology: advanced electronic materials and novel devices Wiley-VCH

Aachen

und 282-302 II,12 https://epub.uni-regensburg.de/id/eprint/25935 Gerhard Meyer Leo Gross Jascha Repp Symmetrien spielen in unterschiedlichen Bereich von Physik und Chemie eine dominante Rolle. Sind Moleküle auf Einkristall-Oberflächen adsorbiert, so ist die Gesamtsymmetrie des Systems entscheidend für seine Eigenschaften. Symmetrieüberlegungen sind die Grundlage für viele Auswahlregeln in der Optik. In der Diffusion von Adsorbaten gibt es allerdings keine Auswahlregeln die bestimmte Diffusionsschritte verbieten. Dies bringt die Frage auf, wie groß strukturelle Unterschiede sein müssen damit diese einen signifikanten Einfluss auf die Energielandschaft des adsorbierten Moleküls hat. Der erste Abschnitt dieser Arbeit stellt eine systematische Untersuchung dar, wie die Diffusion auf einer Oberfläche von den Symmetrien der Adsorbate beeinflusst wird. Dazu wurden Cu-tetraazaphthalocyanine (4NCuPc) Moleküle auf einer Isolator-Oberfläche untersucht. Von diesen Molekülen existieren vier unterschiedlich symmetrische Isomere. Trotz dieser lediglich kleinen Unterschiede zwischen den Molekülen, ergaben sich für die vier unterschiedlich Isomere vier qualitativ unterschiedliche Diffusionsmuster, wie anhand von Diffusionsfilmen belegt wurde. Die Wechselwirkungen zwischen Molekül und Substrat bestimmt nicht nur die Diffusion auf der Oberfläche, auch die chemischen und physikalischen Eigenschaften von adsorbierten Molekülen werden von diesen Wechselwirkungen bestimmt. Gerade der Ladungszustand von Adsorbaten ist hier von besonderem Interesse, da dieser eine Vielzahl weiterer Eigenschaften wie den Spin-Zustand des Moleküls aber auch die Wechselwirkung mit anderen Adsorbaten oder dem Substrat bestimmt. Der zweite Abschnitt dieser Arbeit beschäftigt sich mit der Kontrolle des Ladungszustands einzelner Moleküle, adsorbiert NaCl/Cu. Dünne Isolatorfilme wie NaCl entkoppeln Molekül und Metallsubstrat elektronisch. Es gibt zwei unterschiedliche Zustände der adsorbierten Moleküle, die anhand des Streuverhalten des Grenzflächenzustandes sowie spektroskopischer Untersuchungen als unterschiedliche Ladungszustände identifiziert werden konnten. Der Ladungszustand kann durch das gezielte Hinzufügen bzw. Entfernen eines Elektrons durch die Spitze eines Rastertunnelmikroskops kontrolliert werden. Beide Zustände sind stabil; das zusätzliche Elektron verbleibt auf dem Molekül bis es durch einen weiteren Spannungspuls entgegengesetzter Polarität wieder entfernt wird. Im Weiteren wird gezeigt wie Ladungsbistabilität unterschiedlicher Moleküle erreicht werden kann, und ausserdem wie die Tunnelbarriere durch ein einzelnes Molekül durch die Anwesenheit einer zusätzlichen Ladung innerhalb des Moleküls beeinflusst wird. Diese Modifikation der Tunnelbarriere wurde mit intramolekularer Auflösung abgebildet. thesis_rgbg 2011 12 16 https://epub.uni-regensburg.de/id/eprint/22975 Tobias Sonnleitner In chemistry and physics symmetry principles are all important, for example, leading to the selection rules governing optical transitions. We have investigated the influence of the molecular symmetry on the surface potential landscape of molecules in the limit of weak molecule-substrate binding. For this purpose, the induced lateral motion of Cu(II)-tetraazaphthalocyanine molecules, for which four symmetry distinct isomers exist, on NaCl(100) was studied by scanning tunneling microscopy. This nonthermal diffusion induced by inelastic excitations is found to be qualitatively different for all four symmetry distinct isomers, demonstrating that symmetry governs the surface potential landscape. article 2011 10 27 0031-9007,0031-9007 10.1103/PhysRevLett.107.186103 Physical Review Letters 107 AMER PHYSICAL SOC

COLLEGE PK

186103 18 https://epub.uni-regensburg.de/id/eprint/22492 Tobias Sonnleitner Ingmar Swart Niko Pavliček Andreas Pöllmann Jascha Repp article 2011 7 Blick in die Wissenschaft 23 Universitätverlag Regensburg GmbH 28-38 https://epub.uni-regensburg.de/id/eprint/21775 Christoph Strunk Dieter Weiss Jascha Repp Andreas Schäfer Thomas A. Niehaus Tilo Wettig From scanning tunneling microscopy and spectroscopy experiments it is shown that control over the charge-state of individual molecules adsorbed on surfaces can be obtained by choosing a substrate system with an appropriate workfunction. The distribution of the additional charge is studied using difference images. These images show marked intramolecular contrast. article 2011 3 23 1530-6984,1530-6984 10.1021/nl104452x Nano Letters 11 AMER CHEMICAL SOC

WASHINGTON

1580-1584 4 https://epub.uni-regensburg.de/id/eprint/20786 Ingmar Swart Tobias Sonnleitner Jascha Repp This chapter reviews the spectacular manipulations of single atoms and molecules using a low temperature scanning tunnelling microscope (STM). Electronic decoupling of the adsorbed atoms and molecules from a metallic substrate by introducing a thin insulating film of alkali halides (NaCl) enables (i) to control the charge states of single atoms (Au, Ag), (ii) to directly image molecular orbitals, (iii) to image the sequencing steps of molecular reactions, and (iv) to control molecular switching based on a tautomerization reaction. book_section 2011 978-0-08-096355-6 10.1016/B978-0-08-096355-6.00002-7 Atomic and Molecular Manipulation 2 Elsvier

Oxford

Richard E. Palmer Andrew J. Mayne und Gerald Dujardin 15-49 2 https://epub.uni-regensburg.de/id/eprint/25934 Jascha Repp Gerhard Meyer We report on the formation of a metal-molecule complex that can be used as a molecular switch. Using a cryogenic scanning tunneling microscope, a covalent bond was formed reversibly between a gold atom and a perylene-3,4,9,10-tetracarboxylic dianhydride molecule supported by a thin insulating film. The bonded and the nonbonded state of the complex were found to be associated with different charge states, and the switching between the two states was accompanied by a considerable change in the tunneling current. Atomic force microscopy molecular imaging was employed to determine precisely the atomic structure of the complex, and the experimental results were corroborated by density functional theory calculations. article 2010 12 28 0031-9007,0031-9007 10.1103/PhysRevLett.105.266102 Physical Review Letters 105 AMER PHYSICAL SOC

COLLEGE PK

266102 https://epub.uni-regensburg.de/id/eprint/24921 Fabian Mohn Jascha Repp Leo Gross Gerhard Meyer Matthew S. Dyer Mats Persson We present scanning tunneling microscopy (STM)-based single-molecule synthesis of linear metal-ligand complexes starting from individual metal atoms (iron or nickel) and organic molecules (9,10-dicyanoanthracene) deposited on an ultrathin insulating film We directly visualize the frontier molecular orbitals by STM orbital imaging, from which, in conjunction with detailed density functional theory calculations, the electronic structure of the complexes is inferred Our studies show how the order of the molecular orbitals and the spin-state of the complex can be engineered through the choice of the metal atom The high-spin iron complex has a singly occupied delocalized orbital with a large spin-splitting that points to the use of these engineered complexes as modular building blocks in molecular spintronics article 2010 6 07 1530-6984,1530-6984 10.1021/nl100834v Nano Letters 10 AMER CHEMICAL SOC

WASHINGTON

2475-2479 7 https://epub.uni-regensburg.de/id/eprint/25160 Peter Liljeroth Ingmar Swart Sami Paavilainen Jascha Repp Gerhard Meyer Ultrathin insulating films on metal substrates are unique systems for using a scanning tunneling microscope (STM) to study the electron transport properties in the weak-coupling limit. The electronic decoupling provided by the films allows the direct imaging of the unperturbed molecular orbitals, as will be demonstrated in the case of individual pentacene molecules. The coupling between electronic states localized on the adsorbate and optical phonons in a polar insulator has two important implications: Peaks in conductance spectra resulting from resonant tunneling into electronic states of the molecules are significantly broadened by the presence of the insulator. Second, the ionic relaxations in a polar insulator may lead to an interesting charge bistability in atoms and molecules. STM-based molecular manipulation has been used to form a metallo-organic complex as well as to switch the position of the two hydrogen atoms in the inner cavity of single free-base naphthalocyanine molecules. article 2010 6 06 10.2533/chimia.2010.370 Chimia 64 SWISS CHEMICAL SOC

BERN

370-375 6 https://epub.uni-regensburg.de/id/eprint/25161 Jascha Repp Gerhard Meyer In molecular electronics individual molecules serve as electronic devices. In these systems, electron-vibron (e-nu) coupling can be expected to lead to new physical phenomena and potential device functions(1-3). In previous studies of molecular wires, the e-nu coupling occurred as a result of the well-known Franck-Condon principle, for which the Born-Oppenheimer approximation holds. This means that after a vibronic excitation, the electrons and the vibrations evolve independently from each other. Here we show that this simple picture changes markedly when two electronic levels in a molecule are coupled by a molecular vibration(4,5). In molecular wires we observe a non-Born-Oppenheimer regime, for which a coherent coupling of electronic and nuclear motion emerges(6). This phenomenon should occur in all systems with strong electron-vibration coupling and an electronic level spacing of the order of vibrational energies. The coherent coupling of electronic and nuclear motion could be used to implement mechanical control of electron transport in molecular electronics. article 2010 1745-2473,1745-2473 10.1038/NPHYS1802 Nature Physics 6 NATURE PUBLISHING GROUP

LONDON

975-979 12 https://epub.uni-regensburg.de/id/eprint/65534 Jascha Repp Peter Liljeroth Gerhard Meyer Die meisten Eigenschaften von Atomen sind durch die Zahl der Elektronen in ihrer äußeren Hülle bestimmt. Deshalb sind Messungen, die verschiedene Ladungszustände atomar aufgelöst unterscheiden können, von großer Bedeutung für die Grundlagenforschung. Auch für die Entwicklung zukünftiger, miniaturisierter Bauteile der Informationstechnik, die auf Speicherung und Transport einzelner Elektronen basieren soll, sind solche Messungen von fundamentalem Interesse. Unserer Gruppe ist es gelungen, den Ladungszustand von einzelnen Gold- und Silberatomen mit dem Rasterkraftmikroskop zu untersuchen. article 2009 9 09 10.1002/piuz.200990086 Physik in unserer Zeit 40 WILEY-VCH Verlag 225-226 5 https://epub.uni-regensburg.de/id/eprint/32404 Leo Gross Fabian Mohn Gerhard Meyer Jascha Repp Franz J. Giessibl Charge states of atoms can be investigated with scanning tunneling microscopy, but this method requires a conducting substrate. We investigated the charge-switching of individual adsorbed gold and silver atoms (adatoms) on ultrathin NaCl films on Cu(111) using a qPlus tuning fork atomic force microscope (AFM) operated at 5 kelvin with oscillation amplitudes in the subangstrom regime. Charging of a gold atom by one electron charge increases the force on the AFM tip by a few piconewtons. Moreover, the local contact potential difference is shifted depending on the sign of the charge and allows the discrimination of positively charged, neutral, and negatively charged atoms. The combination of single-electron charge sensitivity and atomic lateral resolution should foster investigations of molecular electronics, photonics, catalysis, and solar photoconversion. article 2009 6 12 0036-8075,1095-9203 10.1126/science.1172273 Science 324 AMER ASSOC ADVANCEMENT SCIENCE

WASHINGTON

1428-1431 5933 https://epub.uni-regensburg.de/id/eprint/25162 Leo Gross Fabian Mohn Peter Liljeroth Jascha Repp Franz J. Giessibl Gerhard Meyer Auf der Suche nach immer kleineren elektronischen Geräten greifen die Wissenschaftler nach einzelnen Molekülen als elektronische Bauteile. Naphthalocyanin-Moleküle eignen sich als molekulare Schalter, die man – anders als die bisher bekannten molekularen Schalter – untereinander koppeln kann. article 2008 12 18 10.1002/piuz.200790097 Physik in unserer Zeit 39 WILEY-VCH Verlag 10-11 1 https://epub.uni-regensburg.de/id/eprint/32403 Jascha Repp Peter Liljeroth Gerhard Meyer We report on the direct observations of the effect of quantum confinement of surface-state electrons on atomic diffusion. Confined electronic states induced by open nanoscale resonators [consisting of two parallel monatomic Cu chains on Cu(111)] are studied by means of scanning tunneling microscope measurements and first-principles calculations. Strongly anisotropic diffusion of adatoms around and inside resonators is revealed at low temperatures. The formation of diffusion channels and empty zones is demonstrated. We show that it is possible to engineer atomic diffusion by varying the distance between the resonator walls. article 2008 11 24 0031-9007,1079-7114 10.1103/PhysRevLett.101.226601 Physical Review Letters 101 AMER PHYSICAL SOC

COLLEGE PK

226601 https://epub.uni-regensburg.de/id/eprint/24922 Nikolay N. Negulyaev Valerie S. Stepanyuk Larissa Niebergall Patrick Bruno Wolfram Hergert Jascha Repp Karl-Heinz Rieder Gerhard Meyer Density functional theory (DFT) and low-temperature scanning tunneling microscopy (STM) have been combined to examine the bonding of individual C-60 molecules on Cu(111). Energy-resolved differential-conductance maps have been measured for individual C-60 molecules adsorbed on a Cu(111) surface by means of low-temperature STM, which are compared to and complemented by theoretically computed spectral images. It has been found that C-60 chemisorbs with a six-membered ring parallel to the surface at two different Cu(111) binding sites that constitute two exclusive hexagonal sublattices. On each sublattice, C-60 is bonded in one particular rotational conformer, i.e., C-60 molecules bind to the Cu(111) surface in two different azimuthal orientations differing by 60 depending on which sublattice the binding site belongs to. The binding conformation of C60 and its orientation with regard to the copper surface can be deduced by this joint experimental-theoretical approach. Six possible pairs of C60 configurations on three different Cu surface binding sites have been identified that fulfil the requirements of the two sublattices and are consistent with all experimental and theoretical data. Theory proposes that two of these configuration pairs are most likely. We have found that DFT does not get the binding energy between rotational conformers in the correct order. We also report two different C-60 monolayers on Cu(111): one with alternating orientations of neighboring molecules at low temperature and the other with (4 x 4) structure after annealing above room temperature. article 2008 3 20 1098-0121,1098-0121 10.1103/PhysRevB.77.115434 Physical Review B 77 AMER PHYSICAL SOC

COLLEGE PK

115434 11 https://epub.uni-regensburg.de/id/eprint/25236 J. Andreas Larsson Simon D. Elliott James C. Greer Jascha Repp Gerhard Meyer Rolf Allenspach The bistability in the position of the two hydrogen atoms in the inner cavity of single free-base naphthalocyanine molecules constitutes a two-level system that was manipulated and probed by low-temperature scanning tunneling microscopy. When adsorbed on an ultrathin insulating film, the molecules can be switched in a controlled fashion between the two states by excitation induced by the inelastic tunneling current. The tautomerization reaction can be probed by resonant tunneling through the molecule and is expressed as considerable changes in the conductivity of the molecule. We also demonstrated a coupling of the switching process so that the charge injection in one molecule induced tautomerization in an adjacent molecule. article 2007 8 31 0036-8075,1095-9203 10.1126/science.1144366 Science 317 AMER ASSOC ADVANCEMENT SCIENCE

WASHINGTON

1203-1206 5842 https://epub.uni-regensburg.de/id/eprint/25233 Peter Liljeroth Jascha Repp Gerhard Meyer A combined study using density functional calculations and scanning tunneling microscopy experiments shows that individual silver adatoms on ultrathin sodium chloride films on copper surfaces are stable in three different charge states - neutral, negatively, and positively charged adatoms. The charge states of the individual adatoms were manipulated by voltage pulses. The key parameters determining the stability of various charge states are identified and discussed within a simple model. article 2007 4 25 0031-9007,0031-9007 10.1103/PhysRevLett.98.176803 Physical Review Letters 98 AMERICAN PHYSICAL SOC

COLLEGE PK

176803 https://epub.uni-regensburg.de/id/eprint/24923 Fredrik E. Olsson Sami Paavilainen Mats Persson Jascha Repp Gerhard Meyer Ultrathin insulating films on metal substrates are unique systems for using a scanning tunneling microscope to study the electronic properties of single atoms and molecules that are electronically decoupled from the metallic substrate. Individual gold atoms on an ultrathin insulating sodium chloride film supported by a copper surface exhibit two different charge states, which are stabilized by the large ionic polarizability of the film. The charge state and associated physical and chemical properties such as diffusion can be controlled by adding or removing a single electron to or from the adatom with a scanning tunneling microscope tip. The simple physical mechanism behind the charge bistability in this case suggests that this is a common phenomenon for adsorbates on polar insulating films. In the case of molecules on ultrathin NaCl films, the electronic decoupling allows the direct imaging of the unperturbed molecular orbitals, as will be shown in the case of individual pentacene molecules. article 2006 12 0340-3793,0721-7250,0947-8396 10.1007/s00339-006-3703-0 Applied Physics A: Materials Science & Processing 85 Springer Verlag 399-406 4 https://epub.uni-regensburg.de/id/eprint/25240 Jascha Repp Gerhard Meyer Einzelne Moleküle, die auf ultradünnen Isolatorfilmen adsorbiert sind, bieten eine Spielwiese für Experimente mit dem Rastertunnelmikroskop (RTM).Das Beispiel des Pentazen zeigt, dass diese Experimente die Grenzorbitale der Moleküle ganz direkt abbilden können. Besonders interessant ist dies bei der Synthese neuer Moleküle. Mit dem Tunnelstrom lässt sich ein Gold-Atom chemisch an das Pentazen binden und bildet so einen Gold-Pentazen-Komplex. Dabei verändern sich die Struktur, Energie und Besetzung der Orbitale. Das RTM kann diese Änderungen direkt messen und abbilden. Solche Experimente eröffnen besonders der molekularen Elektronik neue Möglichkeiten. article 2006 11 10.1002/piuz.200601115 Physik in unserer Zeit 37 John Wiley & Sons 266-271 6 https://epub.uni-regensburg.de/id/eprint/25239 Jascha Repp Gerhard Meyer A covalent bond between an individual pentacene molecule and a gold atom was formed by means of single-molecule chemistry inside a scanning tunneling microscope junction. The bond formation is reversible, and different structural isomers can be produced. The single-molecule synthesis was done on ultrathin insulating films that electronically isolated the reactants and products from their environment. Direct imaging of the orbital hybridization upon bond formation provides insight into the energetic shifts and occupation of the molecular resonances. article 2006 5 26 10.1126/science.1126073 Science 312 American Assoc. for the Advancement of Science 1196-1199 5777 https://epub.uni-regensburg.de/id/eprint/25234 Jascha Repp Gerhard Meyer Sami Paavilainen Fredrik E. Olsson Mats Persson article 2005 11 21 1079-7114,0031-9007 10.1103/PhysRevLett.95.225503 Physical Review Letters 95 American Physical Society 225503 https://epub.uni-regensburg.de/id/eprint/24924 Jascha Repp Gerhard Meyer Sami Paavilainen Fredrik E. Olsson Mats Persson The physical properties of ultrathin NaCl overlayers on the stepped Cu(311) surface have been characterized using scanning tunneling microscopy (STM) and spectroscopy, and density-functional calculations. Simulations of STM images and differential conductance spectra were based on the Tersoff-Hamann approximation for tunneling with corrections for the modified tunneling barrier at larger voltages and calculated Kohn-Sham states. Characteristic features observed in the STM images can be directly related to calculated electronic and geometric properties of the overlayers. The measured apparent barrier heights for the mono-, bi-, and trilayers of NaCl and the corresponding adsorption-induced changes in the work function, as obtained from the distance dependence of the tunneling current, are well reproduced and explained by the calculated results. The measurements revealed a large reduction of the tunneling conductance in a large voltage range, resembling a band gap. However, the simulated spectrum showed that only the onset at positive sample voltages may be viewed as a valence-band edge, whereas the onset at negative voltages is caused by the drastic effect of the electric field from the tip on the tunneling barrier. article 2005 2 24 1550-235X,1098-0121 10.1103/PhysRevB.71.075419 Physical Review B 71 American Physical Society 075419 7 https://epub.uni-regensburg.de/id/eprint/25237 Fredrik E. Olsson Mats Persson Jascha Repp Gerhard Meyer article 2005 1 19 1079-7114,0031-9007 10.1103/PhysRevLett.94.026803 Physical Review Letters 94 American Physical Society 026803 https://epub.uni-regensburg.de/id/eprint/24925 Jascha Repp Gerhard Meyer Sladjana M. Stojković André Gourdon Christian Joachim Mit einem Rastertunnelmikroskop lassen sich nicht nur Oberflächen atomar abbilden, es kann auch dazu genutzt werden, Atome auf einer Oberfläche zu manipulieren. Auf diese Weise ist es erstmals gelungen, den Ladungszustand einzelner Goldatome zu verändern, ohne diese dabei seitlich zu verschieben. article 2004 8 30 10.1002/piuz.200490077 Physik in unserer Zeit 35 John Wiley & Sons 207 5 https://epub.uni-regensburg.de/id/eprint/25241 Jascha Repp Gerhard Meyer The nature and control of individual metal atoms on insulators are of great importance in emerging atomic-scale technologies. Individual gold atoms on an ultrathin insulating sodium chloride film supported by a copper surface exhibit two different charge states, which are stabilized by the large ionic polarizability of the film. The charge state and associated physical and chemical properties such as diffusion can be controlled by adding or removing a single electron to or from the adatom with a scanning tunneling microscope tip. The simple physical mechanism behind the charge bistability in this case suggests that this is a common phenomenon for adsorbates on polar insulating films. article 2004 7 23 10.1126/science.1099557 Science 305 American Assoc. for the Advancement of Science 493-495 5683 https://epub.uni-regensburg.de/id/eprint/25235 Jascha Repp Gerhard Meyer Fredrik E. Olsson Mats Persson The scanning tunnelling microscope, initially invented to image surfaces down to the atomic scale, has been further developed in the last few years to an operative tool, with which atoms and molecules can be manipulated at will at low substrate temperatures in different manners to create and investigate artificial structures, whose properties can be investigated employing spectroscopic dI/dV measurements. The tunnelling current can be used to selectively break chemical bonds, but also to induce chemical association. These possibilities give rise to startling new opportunities for physical and chemical experiments on the single atom and single molecule level. Here we provide a short overview on recent results obtained with these techniques. article 2004 6 15 0080-4614,0264-3820,0264-3952,1364-503X 10.1098/rsta.2004.1373 Philosophical transactions of the Royal Society A 362 London : Soc. 1207-1216 1819 https://epub.uni-regensburg.de/id/eprint/25252 Karl-Heinz Rieder Gerhard Meyer Saw W. Hla Francesca Moresco Kai-Felix Braun Karina Morgenstern Jascha Repp Stefan Fölsch Ludwig Bartels article 2004 1 22 1079-7114,0031-9007 10.1103/PhysRevLett.92.036803 Physical Review Letters 92 American Physical Society 036803 https://epub.uni-regensburg.de/id/eprint/24927 Jascha Repp Gerhard Meyer Karl-Heinz Rieder article 2003 11 12 1079-7114,0031-9007 10.1103/PhysRevLett.91.206102 Physical Review Letters 91 American Physical Society 206102 https://epub.uni-regensburg.de/id/eprint/24928 Jascha Repp Gerhard Meyer Karl-Heinz Rieder Per Hyldgaard A highly regular assembly of three-sided pyramids can be fabricated by growing the ionic insulator NaCl on the kinked metal surface Cu(532). Only two pyramid faces are covered by NaCl, resulting in an overall surface structure which is modulated in surface chemical behavior. Scanning tunneling microscopy shows that the underlying restructuring mechanism can be attributed to a clear-cut criterion for enhanced interface stability mediated by electrostatic interactions. This criterion provides a generally applicable guideline to create nano- to mesoscopic surface structures by design. article 2002 10 30 1550-235X,1098-0121 10.1103/PhysRevB.66.161409 Physical Review B 66 American Physical Society 161409(R) 16 https://epub.uni-regensburg.de/id/eprint/25238 Stefan Fölsch Andreas Riemann Jascha Repp Gerhard Meyer Karl-Heinz Rieder We present a combined high-resolution electron diffraction (SPALEED) and scanning tunneling microscopy study of the insulator/metal growth system NaCl/Cu(2 1 1) which is inherently unstable against lateral pattern formation on the nanometer scale. Cu(2 1 1) is a vicinal surface with (1 1 1) terraces and intrinsic (1 0 0) steps (step distance 6.25 Å). This starting surface restructures upon NaCl deposition when the growth temperature exceeds ∼270 K. The initially flat surface is transformed into a periodic one-dimensional hill-and-valley structure consisting of (3 1 1) and (1 1 1) facets. NaCl grows selectively on (3 1 1) facets only, thereby creating a regular surface pattern with alternating stripes of bare Cu and chemically inert NaCl-covered areas. The lateral stripe spacing can be varied from ∼30 Å at 300 K to ∼230 Å at 600 K via the growth/annealing temperature. The present restructuring process is governed by the interplay between energetics and kinetics, namely by (1) the tendency to form (1 0 0)-terminated NaCl layers, (2) energetically favored interfacial matching between NaCl(1 0 0) and Cu(3 1 1), and (3) sufficient mobility of the substrate surface to allow for Cu mass transport. article 2002 1 20 10.1016/S0039-6028(01)01630-2 Surface Science 497 Elsevier 113-126 1-3 https://epub.uni-regensburg.de/id/eprint/25253 Stefan Fölsch Andreas Helms Andreas Riemann Jascha Repp Gerhard Meyer Karl-Heinz Rieder The controlled manipulation with a scanning tunneling microscope (STM) down to the scale of small molecules and single atoms allows the buildup of molecular and atomic nanostructures. In the case of the lateral manipulation of adsorbed species, in which only tip/particle forces are used, three different manipulation modes (pushing, pulling, sliding) can be discerned. Vertical manipulation of Xe and CO is demonstrated, leading to the formation of functionalized tips, which can be used for improved imaging and even to perform vibrational spectroscopy on single molecules. Furthermore, we describe how we have reproduced a full chemical reaction with single molecules, whereby all basic steps, namely, preparation of the reactants, diffusion and association, are induced with the STM tip. article 2001 6 1347-4065,0021-4922 10.1143/JJAP.40.4409 Japanese Journal of Applied Physics 40 Japan Soc. of Applied Physics 4409-4413 1-3 https://epub.uni-regensburg.de/id/eprint/25254 Gerhard Meyer Francesca Moresco Saw W. Hla Jascha Repp Kai-Felix Braun Stefan Fölsch Karl-Heinz Rieder article 2001 1 08 1079-7114,0031-9007 10.1103/PhysRevLett.86.252 Physical Review Letters 86 American Physical Society 252-255 https://epub.uni-regensburg.de/id/eprint/24929 Jascha Repp Stefan Fölsch Gerhard Meyer Karl-Heinz Rieder article 2000 10 02 1079-7114,0031-9007 10.1103/PhysRevLett.85.2981 Physical Review Letters 85 American Physical Society 2981-2984 https://epub.uni-regensburg.de/id/eprint/24930 Jascha Repp Francesca Moresco Gerhard Meyer Karl-Heinz Rieder Per Hyldgaard Mats Persson With the scanning tunneling microscope (STM) it became possible to perform controlled manipulations down to the scale of small molecules and single atoms, leading to the fascinating aspect of creating manmade structures on atomic scale. Here we present a short review of our work in the last five years on atomic scale manipulation investigations. Upon soft lateral manipulation of adsorbed species, in which only tip/particle forces are used, three different manipulation modes (pushing, pulling, sliding) can be discerned. We show that also manipulation of highly coordinated native substrate atoms is possible and demonstrate the application of these techniques as local analytic and synthetic chemistry tools with important consequences on surface structure research. Vertical manipulation of Xe and CO is presented, leading to improved imaging and even chemical contrast with deliberately functionalized tips. For the transfer of CO it is shown that beside tip voltage current effects play also an important role. This is also the case for the dissociation of molecules. With CO transferred deliberately to the tip we have also succeeded to perform vibrational spectroscopy on single molecules. Furthermore, first experiments aiming for the transfer of all manipulation modes to thin insulating films are described. article 2000 4 10 10.1002/(SICI)1438-5171(200004)1:1<79::AID-SIMO79>3.0.CO;2-R Single molecules 1 Wiley-VCH 79-86 1 https://epub.uni-regensburg.de/id/eprint/25255 Gerhard Meyer Jascha Repp Sven Zöphel Kai-Felix Braun Saw W. Hla Stefan Fölsch Ludwig Bartels Francesca Moresco Karl-Heinz Rieder article 2000 1 03 1079-7114,0031-9007 10.1103/PhysRevLett.84.123 Physical Review Letters 84 American Physical Society 123-126 https://epub.uni-regensburg.de/id/eprint/24931 Stefan Fölsch A. Helms Sven Zöphel Jascha Repp Gerhard Meyer Karl-Heinz Rieder We have used molecular level manipulation with a low-temperature scanning tunneling microscope to determine the binding site of CO molecules in the ordered 3x1 phase of COrCu(211). With the help of a molecular manipulation technique, short CO chains and domains with 3x1 periodicity could be formed in a molecule-by-molecule way and investigated at 12 K. The experiments show that the CO molecules always occupy on-top sites at the intrinsic step edges of the Cu(211) surface. One can extrapolate from these experiments directly on the binding sites in the ordered phases of CO on this surface. article 1999 10.1016/S0009-2614(99)00757-5 Chemical Physics Letters 310 Elsevier 145-149 1-2 https://epub.uni-regensburg.de/id/eprint/25261 Sven Zöphel Jascha Repp Gerhard Meyer Karl-Heinz Rieder conference_item 1999 Precision science and technology for perfect surfaces : proceedings of the 9th International Conference on Production Engineering (9th ICPE), Senri Life Science Center, Osaka, Japan, August 29 - September 1, 1999 Proceedings of the ICPE 1999 3 JSPE

Tokyo

Y. Furukawa Y. Mori und T. Kataoka 728 Proceedings of the ICPE 1999 Osaka https://epub.uni-regensburg.de/id/eprint/25256 Gerhard Meyer Jascha Repp Sven Zöphel Karl-Heinz Rieder conference_item 1999 Precision science and technology for perfect surfaces : proceedings of the 9th International Conference on Production Engineering (9th ICPE), Senri Life Science Center, Osaka, Japan, August 29 - September 1, 1999 3 JSPE

Tokyo

Y. Furukawa Y. Mori und T. Kataoka 658-664 Proceedings of the ICPE 1999 Osaka https://epub.uni-regensburg.de/id/eprint/25257 Karl-Heinz Rieder Gerhard Meyer Ludwig Bartels Jascha Repp Saw W. Hla