Composition and structure of the Al2O3 {0001}-(1x1) surface

The surface composition, termination, and structure of the Al2O3{0001)-(1 x 1) surface have been determined through the use of time-of-flight scattering and recoiling spectrometry (TOF-SARS), low energy electron diffraction (LEED), and classical ion trajectory simulations. TOF-SARS spectra of scattered and recoiled ions plus fast neutrals were collected as a function of crystal azimuthal rotation angle using 4 keV Ar+ primary ions. The scattering and recoiling imaging code SARIC was used to simulate the azimuthal angle scans as a function of the termination layer and the first-second-layer interatomic spacing. This first-second-layer spacing was determined from the best agreement of the simulated scans with the experimental scans using a reliability, or R, factor analysis. The results lead to the conclusions that there are two domains on the surface that are rotated by 180 degrees. It is found that the surface is terminated in an Al layer which relaxes downward so that the Al first-layer to O second-layer spacing is 0.3 +/- 0.1 Angstrom. This relaxation of 63% from the bulk value can be made possible through a bond length conserving buckling of the O atoms. Hydrogen atoms were present on the surface, even at the annealing temperature of 1100 degrees C. (C) 1997 Elsevier Science B.V.