LOW-ENERGY ION-SCATTERING ANALYSIS OF THE SURFACE COMPOSITIONAL CHANGE OF AU3CU(001) INDUCED BY OXYGEN-CHEMISORPTION

The change of the surface composition of Au3Cu(001) induced by oxygen chemisorption was investigated by means of impact collision ion-scattering spectroscopy (ICISS) of time of flight version using 180-degrees scattering of 3 keV Nc+ ions. For the clean surface, the topmost layer was found to be occupied almost completely by Au atoms (approximately 95%) and the second layer by Cu atoms (approximately 95%). Oxygen chemisorption was performed by exposing the crystal surface to atomic oxygen produced on hot-W filament. With the oxygen adsorption. Au in the topmost layer was replaced with Cu and Cu in the second layer with Au, respectively. Almost complete replacement of elements in the first layer was found at high coverages. At low coverages, at least two Cu atoms were induced by one oxygen atom. From the analysis of the polar scans of the ICISS signals, the oxygen was suggested to be located deeply in the 4-fold hollow site.