OBSERVATION OF A LOW-BINDING-ENERGY PEAK IN THE 2P CORE-LEVEL PHOTOEMISSION FROM OXIDIZED AL(111)

High-resolution photoemission studies of oxidation of the Al(111) surface have been performed. The appearance of a component at lower binding energy than the metallic bulk Al emission in the Al 2p spectrum at oxygen exposures above approximately 50 langmuir (1 L = 10(-6) Torr s) is argued to be due to Al atoms which do not bond directly to oxygen atoms at the oxide-metal interface. Low-energy electron diffraction initially shows a 1 X 1 structure, which subsequently fades away at higher oxygen exposures, greater-than-or-similar-to 400 L.