Low-temperature epitaxial crystallization of amorphous GexSi1−x and NiSi2 layers on Si induced by ion irradiation

Abstract

Crystalline GexSi1−x alloy and NiSi2 layers grown on Si substrates and amorphized by ion irradiation at -196°C are shown to recrystallize epitaxially during subsequent high-energy ion irradiation at temperatures of 275 and 45° C, respectively. For GexSi1−x alloys, where the amorphous layer extended into the underlying Si substrate, both commensurate and incommensurate epitaxy were obtained. Furthermore, the dependence of the commensurate/incommensurate transformation on alloy composition was found to be similar to that for layers grown by molecular beam epitaxy. For NiSi2 layers, ion irradiation at 45° C was found to simultaneously crystallize the amorphous NiSi2 layer and amorphize the underlying Si substrate. This is shown to result in a novel layered structure consisting of a crystalline NiSi2 layer which is epitaxially aligned with the (111) Si substrate but separated from it by an amorphous Si layer.