Nonstoichiometric selenium rich Si(x)Se(1-x) films.

Thermal evaporation of bulk melt-quenched Si(x)Se(1-x) glasses in the range 600-650C yields polycrystalline SiSe2. Above that temperature up to 750C, thin reddish films of Si(x)Se (1-x) condense with x 0.333, well outside the bulk glass forming region, 0.333 = x = 0.40. A structural model for such films involving direct bonding of selenium to silicon to form single phase ring or chain structures is based on analyses of the Raman spectra of these colored films. Both crystalline SiSe2 and Si(x)Se(1-x) films appear to have Tauc band-edge energy values considerably higher than were previously supposed.