About XPS

The School of Chemistry is pleased to offer an X-ray Photoelectron Spectroscopy (XPS) surface analysis service to universities, individuals and industry.

What can XPS be used for?

X-ray photoelectron spectroscopy (XPS)  is an Ultra high Vacuum (UHV) technique and is suitable for the quantitative determination of elemental composition (atomic %) of elements in the surface region of solid sample.  Additionally, quantitative differentiation of the same element in different chemical environments (e.g. Al metal vs Al2O3 or C-C vs. C=O) can be obtained.

XPS involves irradiating the surface of interest with soft X-rays and analysing the energy of the emitted photoelectrons.  Since these electrons have energies which are typically less than 1500 eV they interact strongly with the material under analysis and can therefore only escape from the top few atomic layers.  The binding energy of the core levels from which the photoelectrons are emitted are sensitive to the number of electrons in the valence band, and so the technique enables chemical state information to be obtained from the top few atomic layers of a surface. Analyses can be applied to all vacuum compatible solid materials whether they are conducting, semi-conductors or insulators.  Layered samples may also be depth profiled in order to investigate the layer distribution.  Additionally, researchers interested in ionic liquids can apply XPS to their samples due to their negligible vapour pressure.

XPS is sensitive to all elements apart from hydrogen and helium and is highly surface sensitive with information typically arising from the top ca. 1-5 nm. Through measurement of the element peak areas and correction with the appropriate sensitivity factors, XPS has a sensitivity for most elements of ca. 0.1 at%.

Further examples ans information on specific XPS related analysis can be found using the left hand menu.