Effect of composition on optical properties of co-evaporated Mn/SiO x , Cr/SiO x and Cu/SiO x cermet thin films

Abstract

Optical absorption spectra of amorphous Mn/SiOx, Cr/SiOx, and Cu/SiOx cermet films, 300 nm thick, with compositions from 0 to 25 at% Mn, Cr and Cu, respectively, prepared by co-evaporation at 293 Kin vacuo have been investigated. The linearity of (αħω)1/2 versusħω graphs in the high absorption region for all the cermet films indicates that indirect photon transitions in k-space are involved in the absorption process. Taue's rule is also confirmed. In all cases the optical energy gap decreases significantly with increasing metallic content of the films and the width of the tail of localized states increases.