THE INFLUENCE OF ELASTIC-SCATTERING IN OVERLAYERS ON PED FROM PBS SINGLE-CRYSTALS

Monte-Carlo calculations have been used to investigate the influence o f an amorphous overlayer on the photoelectron diffraction pattern from a PbS single crystal substrate. With increasing overlayer thickness D and decreasing elastic scattering length lambda(e) the randomisation of angular distribution increases. The effective randomisation thickne ss D minimising the effect of the photoelectron diffraction on the rel ative intensities to make them suitable for depth-profiling can be fou nd by 2c/D = 1/lambda(e) +1/lambda(i) (lambda(i) = inelastic scatterin g length), where c approximate to 2 for lambda(e) < 2 lambda(i). The c alculations were performed for a broad range of lambda(i), lambda(e) a nd D values. The theoretical data are discussed comparing with experim ental results for the system PbSO4/PbS obtained by UV irradiation of a PbS single crystal on air.