High-temperature morphological evolution of lithographically introduced cavities in silicon carbide

Internal cavities of controlled geometry and crystallography mere introduce d in 6H silicon carbide single crystals by combining lithographic methods, ion-beam etching, and solid-state diffusion bonding. The morphologic evolut ion of these internal cavities (negative crystals) in response to anneals o f up to 128 h duration at 1900 degreesC was examined using optical microsco py. Surface energy anisotropy and faceting had a strong influence on the ge ometric and kinetic characteristics of evolution. Decomposition of {1210} c avity edges into {101x} facets was observed after 16 h anneals, indicating that (1210) faces are not components of the Wulff shape. The shape evolutio n kinetics of penny-shaped cavities were also investigated. Experimentally observed evolution rates decreased much more rapidly with those predicted b y a model in which surface diffusion was assumed to be rate limiting. This suggested that the development of facets and the associated loss of ledges and terraces during the initial stages of evolution resulted in an evolutio n process limited by the nucleation rate of attachment/detachment sites (le dges) on the facets.