X-Ray Photoemission Spectroscopy - XPS

General Description

Photoelectrons are generated by illuminating the samples to be investigated with X-Rays. The emitted photoelectrons are collected and analyzed with respect to their intensity and energy distribution. The chemical sensitivity of this measurement technique is given by the element-specific distribution of binding energies of the electronic core levels leading to characteristic energy spectra. The presented X-Ray Photoemission Spectra is taken from a clean Cu crystal as well as ultra thin Fe (~2 mono layers) and Ni (9 mono layers) films on the same Cu crystal featuring separated peaks which belong to individual elements. XPS is - due to the short mean free path (1-4nm) of the excited photoelectrons - rather surface sensitive, as can be recognized by the reduction of the Cu peaks in the spectra in the case of ~11 atomic layers of Fe and Ni on top of the Cu substrate. XPS is highly sensitive to metals.

Measurement Modes

1. Scan Mode
   The chemical composition in a predefined area (ranging from 0.5 to 2mm) on the sample is analysed by XPS. The sample can be sputtered prior to or simultaneously during the measurement process.
2. Depth Profile
   During a continuous Ar-ion sputtering process which removes the sample structure layer-by-layer the element-specific profile across the sample is recorded.

Sample Structure

The dimension of the samples to be investigated should be from 2 by 1 mm to maximum of about 2 inch or 51mm.