Theory of the clean and hydrogenated Al2O3(0001)-(1 x 1) surfaces

We present the results of a first principles investigation of the equilibrium properties of c-plane alpha-Al2O3 surfaces. The stable structure for the 1x1 clean surface is Al terminated with a stoichiometric composition, while other terminations are unstable independent of surface preparation conditions. We discuss the implications of our results in the frame of possible extended reconstructions. For 1 monolayer of H coverage, we find that the preferred structure has OH dimers both perpendicular and nearly parallel to the surface. H-terminated surfaces may form in suitable preparation conditions. We discuss our results in terms of water adsorption and atomic layer epitaxy of alpha-Al2O3(0001). [S0163-1829(99)51848-1].