OBSERVATION OF (ROOT-3X-ROOT-3)R30-DEGREES DIAMOND (111) ON VAPOR-GROWN POLYCRYSTALLINE FILMS

(111) facets of polycrystalline diamond films are investigated on the atomic scale by scanning tunnelling microscopy. Besides bulk-like structures, a (square-root 3 x square-root 3)R30-degrees superstructure is found. Molecular dynamics calculations are performed, which base on quantum mechanically derived interatomic forces. They exhibit stable molecular trimer-structures consistent with the observations. Comparison of the simulation to the experimentally obtained images gives evidence that the trimer structures are formed by reconstruction of a triple-dangling-bond layer and that they are centred at the hollow sites of the single-dangling-bond layer underneath.