The auger parameter, its utility and advantages: a review

Abstract

Photoelectron lines and X-ray excited Auger lines often exhibit differences in chemical shifts which are a function of the chemical environment of the atom. In particular, for elements which are conductors with inner shell vacancies, the doubly ionized final state results in substantial differences in screening energy, which reflects largely in the Auger line shifts. The Auger parameter, involving measurements of both Auger and photoelectron line energies, provides abundant chemical state information without the necessity or concern for charge correction and work function measurements. Since the change in Auger parameter is equal to twice the change in extra-atomic relaxation energy, it is also a direct measure of the electronic interaction with the surrounding atoms. Data are presented showing systematic variations in Auger parameter values of several cations with the type and number of participating anions. The physical state of the element/ compound, whether solid, gas or in solution, is also shown to profoundly influence the Auger parameter. Finally a number of special situations such as condensed, implanted and adsorbed atoms at solid surfaces and the role of lattice structure in selected oxide systems on the Auger parameter are discussed.