Photoelectron diffraction effects in XPS angular distributions from GaAs(110) and Ge(110) single crystals

Abstract

Angular distribution measurements of XPS intensities have been made for various spectral lines from GaAs(110) and Ge(110) single-crystal surfaces. Observed angular distribution curves (ADC's) showed steep intensity variations and sharp peaks due to X-ray photoelectron diffraction (XPED) phenomena. The effects of the type of transition process (photoelectron or Auger), electron kinetic energy and crystal structure on the XPED patterns were examined. Considerably different ADC patterns were observed for high-energy photoelectrons and Auger electrons and for low-energy photoelectrons. ADC's for Ga 3 d, As 3 d and Ge 3 d showed almost the same patterns for scans of the type [110] → [100] → [1 1 0], but they showed substantially different patterns for [110] → [11 1 ] → [00 1 ] scans. These features correspond well with the structural characteristics of GaAs and Ge crystals. A discussion of the applicability of XPS angular distribution measurements to the geometric analysis of crystal surfaces is presented.