XPS is a non-destructive, surface-sensitive spectroscopic technique that measures elemental composition at the parts per thousand range. Peak shifts provide chemical bonding information. The Escalab instrument can also perform ultraviolet PS, for the analysis of the valence band (density of states, work function, highest occupied state), REELS (band gap measurement), ISS (He+ ion scattering for top monolayer analysis), and depth profiling with monatomic argon, or argon clusters.