Twin Formation and Au Segregation During Ion-Beam-Induced Epitaxy of Amorphous Si.

Ion-beam induced epitaxial recrystallization of Au-implanted amorphous silicon at temperatures >400 sup 0 C has been studied. Crystallization was induced using a 2.5 MeV Ar beam. Segregation of Au at the moving crystal/amorphous silicon interface occurs with an interface velocity of 5angstrom/sec. At high Au concentrations, the interface breaks down with the formation of twins. The twinned crystal/amorphous interface then propagates under further irradiation with a reduced interface velocity of 3angstrom/sec. Unusual Au redistribution profiles are obtained as a result of the sudden change in interface morphology. The Au segregation profiles are interpreted on the basis of classical segregation theory with the interfacial segregation coefficient changing from 0.0012 to 0.02 at the onset of twin formation.