Optical absorption and dispersion in rf-sputtered α-HgS films

The refractive index and the absorption coefficient for sputtered α-HgS films several μm thick were determined in the wavelength region from 0.5 to 2.5 μm by the analysis of transmission and reflection spectra. The results showed that the refractive index for as-deposited films decreased with increasing rf power density; however, after annealing approached the bulk value for the ordinary ray. Optical gap energy for films deposited above 0.8 W/cm2 was determined to be 2.02±0.05 eV, but became smaller with decreasing rf power density. Microprobe analysis showed that the variation in optical properties may well be related to differences in film composition. Edge absorption spectra for stoichiometric films were also measured between 77 and 330 K, and these results were compared with single-crystal data.