X-ray photoelectron spectroscopy of oxygen adsorbates on Al(111): Theory experiment

We present the result of polar angle resolved x-ray photoemission spectroscopy on Al (111) /0 and cluster calculations of the 0 (Is) binding energy (BE) for various model situations. In the experimental data two O(ls) peaks are observed, separated by 1.3 eV. The angular behavior (depth-resolution) could indicate that the lower BE peak is associated with an O atom under the surface, and the higher BE peak with an O atom above the surface. Equally, it could indicate oxygen islands on the surface where the perimeter atoms have a higher 0 (Is) BE than the interior atoms. The cluster calculations show that the former interpretation cannot be correct, since an O ads below the surface has a higher calculated O(ls) BE than one above. Cluster calculations simulating oxygen islands are, however, consistent with the experimental data. © 1991, American Vacuum Society. All rights reserved.