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.