GRAZING-INCIDENCE X-RAY PHOTOELECTRON-SPECTROSCOPY FROM MULTILAYER MEDIA - OXIDIZED GAAS(100) AS A CASE-STUDY

At the energies of interest in x-ray photoelectron spectroscopy (XPS), total external reflection of the x-ray beam occurs from a smooth surface at small incidence angles. The penetration of the x rays into the material is strongly attenuated at these angles and surface sensitivity is enhanced in the XPS yields. As the incidence angle is increased, the x rays penetrate more deeply into the material and the XPS signal contains a larger contribution from the bulk. By exploiting this angle-dependent x-ray penetration depth, it is possible to obtain depth-dependent XPS spectra from which the concentration profiles of the photoelectron-emitting atoms can be inferred. In this paper we develop a general formalism for calculating grazing-incidence XPS (GIXPS) yields from multilayer media. A quantitative analysis of GIXPS spectra acquired from an oxidized GaAs(100) surface that was annealed to remove oxidized As will be discussed. The results show that this annealed oxide is composed of Ga2O3 and that the oxide-GaAs substrate interface is rough.