Homo-epitaxial (100) and (111) films were grown, side-by-side, in a hot-filament reactor at 875C; with and without O. The growth rates and surface morphologies were monitored by means of in situ  Fizeau interferometry and atomic force microscopy, respectively. Penetration twins were observed on the (100) surface, at a low (100)/(111) growth-rate ratio, but not at a high ratio; as expected. Remarkably, penetration twins were not observed on the (111) surfaces; which were dominated by contact twins in both cases.

R.E.Rawles, W.G.Morris, M.P.D’Evelyn: Applied Physics Letters, 1996, 69[26], 4032-4