Different void shapes in Si at the SiC thin film / Si ( 111 ) substrate interface

The shape of interfacial voids formed in the epitaxial SiC/Si(111) heterosystem just underneath the SiC film has been investigated using optical microscopy and transmission electron microscopy (TEM). SiC films are grown on Si(111) substrates at two different substrate temperatures (specimen type 1 at 850°C, specimen type 2 at 1050°C) using solid-source molecular-beam epitaxy (MBE). At 850°C substrate temperature the well-known triangular void shape with primary {111} facets is formed in the Si substrate confirming the results already reported by Learn and Khan in 1970. When growing at 1050°C substrate temperature a new void shape showing a hexagonal appearance in the plan-view direction is found. By indexing the hexagonal void planes, other facets with higher surface energies than the usual {111} type facets have been observed leading to a void shape near the equilibrium void shape in a cubic crystal. As in the case of the triangular shaped voids, the formation process of the hexagonal shaped voids should start from the {111} planes, however, due to the higher substrate temperature, planes with higher surface energies are formed in addition.