ON THE (111)[111] PENETRATION TWIN DENSITY IN CVD DIAMOND FILMS

The morphology of isolated crystals and polycrystalline films can thor oughly be influenced by twin nucleation. In order to obtain more insig ht into this rather complicated subject a new theoretical concept, cal led the nucleation surface, is introduced and worked out quantitativel y. The nucleation surface on a given position of a crystal facet is pr oportional to the probability that the given position is overgrown by a twin, which has nucleated at an earlier time. It is calculated in de tail for {111}[111] penetration twins on diamond facets, as a function of the position on the {111} plane and of the geometrical parameter a lpha=root 3 v(100)/v(111). The analytical and numerical results show t hat the twin abundance depends strongly on both parameters. The calcul ations account well for a number of experimental observations. (C) 199 7 Elsevier Science S.A.