Advanced Materials Characterization Chapter 8 X-ray Photoelectron Spectroscopy

Advanced Materials Characterization Chapter 8 - by Igor Bello

X-ray photoelectron spectroscopy (XPS) employs a probe of a photon beam to interact with surfaces of solids. The product of the interaction are photoelectrons that carry unique information on the binding energies (BE) of atoms and their chemical states. Atoms and their chemical states are identified based on the BE that are determined from the measurement of kinetic energies of photoelectrons.

XPS is also known as ESCA standing for electron spectroscopy for chemical analysis. The term ESCA was introduced because this technique provides the data on chemical states. The term ESCA was mostly used at the beginning of the XPS development. Another technique that employs ultraviolet (UV) photon beam probes is called ultraviolet photoelectron spectroscopy (UPS). In contrast to XPS, UPS is more surface sensitive and gives information on unoccupied states. Therefore, UPS is a complementing technique to XPS. The primary difference of these analysis techniques is in sources and energies of photons. Since the energy of ultraviolet photons is much lower than that of x-ray, UV photons induce the emission of valence electrons whose binding energy is low, while the emission probability of valence electrons induced by x-ray photons is very low. Accordingly, using photons with different energies allows analysis of different material properties with different surface sensitivity.