Spectroscopy Facilities

Technique of XPS

Photoelectrons result from the interaction of electromagnetic radiation with matter. Useful energy range for the exciting radiation is soft X-Ray regime in X-Ray Photoelectron Spectroscopy, XPS, leading to core level electrons excitation and hence to elemental selectivity. Excited photo-electrons are analyzed according to their kinetic energy, which is, at least for core electrons, a fingerprint of the emitting element. Elemental identification is therefore possible (apart from H and He) for core level photoemission. Elements’ relative abundance can in addition be made semi-quantitative or quantitative.
Information on chemical bonds is derived either from core level shifts. Characteristic of the technique is its surface sensitivity (a few monolayers), which, combined with an etching process (usually through sputtering by accelerated noble ions) allows to measure elemental depth distributions.
The most important feature is its ability to provide detailed chemical information on virtually any kind of solid sample, i.e. also on insulating or easily damaged samples. XPS finds wide applications in several fields of science (surface physics, material science, geophysics, nanomaterials, biomaterials, polymers, organic materials,….).