Phase selection in the rare earth silicides

The rare earth silicides form islands with a tetragonal or a hexagonal structure that coexist when grown on the Si(100) surface. We show using medium energy ion scattering that it is possible to selectively grow one of these as a pure phase by controlling the mobility of the rare earth atoms as they are deposited. When dysprosium, holmium, and erbium are deposited onto a liquid nitrogen cooled substrate the hexagonal structural phase is formed after annealing. When erbium and holmium are deposited onto a hot substrate only the tetragonal phase results. For dysprosium silicide growth under conditions of high mobility causes approximately equal numbers of hexagonal and tetragonal islands to form. The system offers a means to obtain fine control over physical properties such as the Schottky barrier height.