The results of scanning tunnelling microscopic and molecular dynamics annealing studies (based upon quantum-mechanically derived interatomic forces and a semi-empirical density functional approach) were combined in order to analyze surface structures. The experimentally obtained scanning tunnelling microscopic images of (100) and (111) faces of polycrystalline films revealed 1 x 1, (3 x 3)R30 and possibly 2 x 1 structures. The (100) faces exhibited a stable 2 x 1 reconstruction, with dimer formation. Surface structures, with and without adsorbed H, were determined and their stability was investigated by using molecular dynamics simulated annealing techniques. The bulk-like and (3 x 3)R30 structures, observed on grown (111) facets, were attributed to the 2 different single atomic (111) layers. This supported proposed growth mechanisms in which the 2 alternating single atomic layers grew in turn, rather than simultaneously.

T.Frauenheim, U.Stephan, P.Blaudeck, D.Porezag, H.G.Busmann, W.Zimmermann-Edling, S.Lauer: Physical Review B, 1993, 48[24], 18189-202