It was noted that the epitaxial crystallization rates of amorphous Si layers, on crystalline Si substrates which contained a considerable number of H atoms, were markedly increased in the absence of O atoms. This enhanced crystallization occurred during 1MeV Xe ion-beam bombardment at 310C and during furnace annealing in vacuum at temperatures below 450C. Implantation-amorphized Si layers, which were epitaxially grown onto (100) crystalline Si substrates by means of ultra-high vacuum chemical vapor deposition, were epitaxially crystallized by furnace annealing in vacuum at temperatures below 450C. However, implantation-amorphized bulk-crystal Si substrates were not entirely crystallized by the same low-temperature annealing. Nanometer-scale micro-crystallites, which remained in the near-surface region of the amorphous Si layer after 80keV P implantation of the epitaxial Si layer, grew in a 3-dimensional manner during 1MeV Xe-ion bombardment at 310C, but not during furnace annealing at 600C in a dry Ar ambient. This 3-dimensional crystal growth did not occur in implantation-amorphized bulk crystalline Si substrates; even during 1MeV Xe-ion bombardment. Amorphous Si layers which were directly deposited by means of low-pressure chemical vapour deposition crystallized epitaxially during 1MeV Xe-ion bombardment at 310C. All of the results were explained consistently in terms of the presence of a considerable amount of H, as polyhydride, in amorphous Si layers in the absence of O. It was suggested that the mechanism of low-temperature crystallization of amorphous Si which contained H atoms in polyhydride states was closely related, in terms of vacant spaces and dangling bonds, to the mechanism of ion beam-induced epitaxial crystallization.

J.Nakata: Journal of Applied Physics, 1997, 82[11], 5433-45