RELATIONS BETWEEN CRYSTAL-STRUCTURE AND GROWTH-MORPHOLOGY OF BETA-SI3N4

A PBC analysis of beta-Si3N4 has been carried out by computer calculations taking into account the atom positions for F-face identification and bond lengths as a measure of bonding energy for face prominence. A rod-like habit with the prism {100} and the pyramids {101} and {101BAR} has been theoretically deduced, which can be observed on crystals grown under a reducing atmosphere. In the presence of oxides, preferably silica, (001) and (001BAR), which are of K-type, dominate over {101} and {101BAR}. This is attributed to face specific adsorption. The growth rate anisotropy between {100} and (001) and (001BAR) faces can be explained by a model derived from the crystal structure according to the growth theory of Kossel and Stranski. Conclusions are drawn concerning interface roughness and aspect ratio development.