Study of submonolayer films of Au on Cu(100) using positron annihilation induced Auger Electron Spectroscopy

Abstract

Positron Annihilation induced Auger Electron Spectroscopy (PAES), Electron induced Auger Electron Spectroscopy (EAES) and Low Energy Electron Diffraction (LEED) have been used to study ultrathin film of Au on Cu(100). Temperature induced changes in the top surface compositions in Au/Cu(100) are directly observed in PAES spectra while EAES spectra indicate only minor changes as the sample is warmed from 173K to 423K. A sharp kink at ≊0.06 ML in a plot of Au PAES intensity versus coverage at 173K indicates that the positrons are preferentially sampling Au atoms. Saturation of the Au PAES intensity is observed near 1 monolayer of Au demonstrating the high top layer selectivity of PAES. The surface defect dependence of the PAES intensity is interpreted in terms of the positron localization at surface defects.