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) heterosy stem just underneath the SiC film has been investigated using optical micro scopy and transmission electron microscopy (TEM). SiC films are grown on Si (111) substrates at two different substrate temperatures (specimen type 1 a t 850 degreesC, specimen type 2 at 1050 degreesC) using solid-source molecu lar-beam epitaxy (MBE). At 850 degreesC substrate temperature, the well-kno wn triangular void shape with primary (111) facets is formed in the Si subs trate, confirming the results already reported by Learn and I(han in 1970. When grown at 1050 degreesC substrate temperature, a new void shape showing a hexagonal appearance in the plan-view direction is found. By indexing th e hexagonal void planes, other facets with higher surface energies than the usual (111) type facets have been observed, leading to a void shape near t he equilibrium void shape in a cubic crystal. As in the case of the triangu lar shaped voids, the formation process of the hexagonal shaped voids shoul d start from the (111) planes, however, due to the higher substrate tempera ture, planes with higher surface energies are formed in addition.