The epitaxy of silicon on alumina—structural effects

Epitaxial films of silicon have been grown chemically on α-alumina substrates by two different heterogeneous reactions: (a) the hydrogen reduction of trichlorosilane and (b) the pyrolysis of silane. The films have been studied by electron and x-ray diffraction and electron microscopy, using both replica and transmission techniques. The topics considered have been epitaxial arrangements, nucleation and growth and defect structures. Reasons for the large differences observed between films grown from silane and those from trichlorosilane are suggested. Carrier mobilities in certain films are discussed in terms of defect structures. Finally some rather speculative suggestions are made about a possible epitaxial mechanism for some chemical systems which is based on a symmetry transfer effect.