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Your guide to PVD technology, theory and applications

XPS, X-Ray Photoelectron Spectroscopy

Posted by mark00 On March - 22 - 2010

XPS is used to provide quantitative information regarding the composition from the top 50-100 Å of a sample surface. XPS can also be used to gather information about the chemical bonding at the surface.

This is achieved by irradiating the surface with a beam of monochromatic soft X-rays. This results in the emission of photoelectrons from the surface. An electron spectrometer is then used to analyse the distribution of photoelectron kinetic energies. These photoelectron kinetic energies give a unique ‘fingerprint’ for the particular atom and electron orbit it came from.

XPS equipment at the Institute of Materials Science and Technology Bilkent University

Additionally the atomic orbitals from atoms of the same element in different chemical environments possess slightly different binding energies. These differences are due to the variations in electrostatic screening that are experienced by the core electrons as the valence and conduction electrons are removed from the different atoms. Also differences in the oxidation state, molecular environment and co-ordination number will all give different chemical shifts. The photoelectron binding energy shifts are the main source of chemical information from the surface. instrument with suitable software.

Main XPS features
The maximum analysis depth is 1 – 10 nm and is dependent on the orientation of the sample.

All elements can be detected except the smallest two H and He.

The detection limit is typically 0.1 At. per cent (1000ppm).

Depth profiling can be carried out by using XPS analysis at the same time as Argon ion bombardment. This type of XPS depth profiling will provide chemical state and compositional depth profiles.