CRYSTALLINE EFFECTS ON AUGER AND PHOTOELECTRON EMISSION FROM CLEAN AND CS-COVERED GAAS(110) SURFACES

Angular-resolved Auger electron spectroscopy (ARAES) and X-ray photoelectron diffraction (XPD) are applied to the structural study of (i) cleaved or (ii) sputter-processed GaAs (110) surface and of (iii) the Cs/GaAs interface. Experimental diffraction patterns of Ga and As high-energy Auger electrons are compared to the theoretical angular distribution calculated in the single-scattering, spherical-wave approximation, and with the XPD patterns. The observed crystalline effects in the Auger spectra of the clean surface are discussed in terms of the relative importance of processes related to ingoing and outgoing electrons. The orientational dependence of the backscattering factor is also taken into account and its contribution to the observed crystallographic anisotropy is evaluated. As an example, we report an investigation of the ion-induced surface damage on the (110) cleaved surface processed with Ar+ beams of various energies. AREAES characterization fo the Cs/GaAs (110) interface is also reported. No disruption of the substrate is detected at low coverages, while significant intermixing occurs at Cs saturation.