PHOTOEMISSION-STUDIES OF AN AL-LI BINARY ALLOY

The surface segregation of Li and the oxidation of a (111) oriented Al -6.5at.%Li binary alloy were studied by synchrotron radiation photoemi ssion. Oxidation of the non-segregated surface leads to four peaks shi fted to higher b.e. than metallic aluminium. plus a fifth peak shifted to lower b.e., ill addition to the metallic peak iii the Al Ip region . nle ii Is and Ai 2p regions indicate that oxygen reacts first with L i, then with both Li and AI, in agreement with earlier studies. The re activity of tbe segregated surface is enhanced due to the increase in concentration of Li at the surface: here also, four chemically shifted peaks appear simultaneously at low oxygen exposures. In addition to t hese features, photoemission from the segregated surface reveals an Al 2p component shifted to lower binding energies relative to the bulk al uminium Al 2p metallic emission for both the clean and oxidized surfac es. These low binding energy components have different origins on the clean and oxidized surfaces. (C) 1997 Elsevier Science B.V.