POSITRON-ANNIHILATION INDUCED AUGER-ELECTRON SPECTROSCOPY STUDIES OF SUBMONOLAYER AU ON CU(100) - DIRECT EVIDENCE FOR POSITRON LOCALIZATIONAT SITES CONTAINING AU ATOMS

Positron annihilation induced Auger electron spectroscopy (PAES) perfo rmed on submonolayer films of Au deposited on Cu(100) provides direct evidence for preferential annihilation with Au atoms. The PAES intensi ty of Au is anomalously large at low surface concentrations (e.g., the PAES signal from Au deposited at 173 K reaches approximately 40% of t he signal obtained for a complete monolayer at approximately 0.07 mono layer). We infer from this behavior and comparisons with model calcula tions that positrons are localized at sites containing many contiguous Au atoms.