Grazing-incidence x-ray photoemission spectroscopy investigation of oxidized GaAs(100): A novel approach to nondestructive depth profiling

Abstract

When a beam of x rays (∼1 keV) impinges on a flat surface at grazing angles (≲3°) the x rays undergo total external reflection. Under these conditions, the penetration depth of the x rays can become comparable to photoelectron escape depths and the photoelectron yields from the surface are enhanced. As the incidence angle of the x rays is increased, the x-ray penetration depth increases and the photoelectron yields contain a larger contribution from deeper layers within the sample. By exploiting this depth-dependence of photoelectron yields as a function of incident x-ray beam angle, it is possible to obtain information about the depth distribution of the photoelectron emitting atoms. We have used this novel application of grazing-incidence x-ray photoelectron spectroscopy (GIXPS) to study the ultraviolet oxidized GaAs(100) surface. This oxide/GaAs surface is particularly well suited for study with GIXPS because a variety of oxide phases are formed during oxidation and questions concerning stratification of these phases can be addressed. Much insight into the composition and depth-dependence of these oxide phases can be obtained by directly comparing the spectra collected at different x-ray incidence angles.