Far-infrared spectroscopy of thermally annealed tungsten silicide films

The far-infrared transmittance spectrum of tungsten silicide has been observed for the first time. WSi2 polycrystalline films were prepared by coevaporation and chemical-vapour deposition on silicon wafers, and subsequently thermally annealed at different temperatures. The observed structures are interpreted, on the basis of the symmetry properties of the crystal, such as infrared-active vibrational modes. Moreover, the marked lineshape dependence on annealing temperature enables this technique to analyse the formation of the solid silicide phases.