Instrumentation for surface studies: XPS angular distributions

The application of XPS angular distribution measurements to surface studies is discussed. The basic principles behind the measurement and interpretation of such angular distributions from solid surfaces are presented, including a review of available experimental data. Effects of electron diffraction (channeling) are neglected, and a macroscopic model including the effects of x-ray refraction and reflection, a non-uniform x-ray flux, a non-constant spectrometer acceptance solid angle, non-uniform surface layer thicknesses, and surface roughness is discussed. The predictions of this model are found to be consistent in several respects with experimental data. The measurement of electron attenuation lengths, surface layer thicknesses, fractional surface layer coverages, and surface roughness characteristics thus all seem feasible from detailed analyses of such angular distributions. (Auth.)