Growth of rhenium oxide thin films

Rhenium oxide thin films have been grown on stainless steel substrates by DC magnetron sputtering. The stainless steel substrates were biased between −50 and −150 V, and the growth was followed by means of specular reflectance and the derived refractive index and optical absorption. It is shown that the reflectance is a strong function of the bias voltage. There is an initial decrease in the reflectance at −50 V and with further increase in bias voltage there is an increase in reflectance. The refractive index of the films at 600 nm was 2.30±0.02, independent of the biasing conditions, but the optical absorption decreased with increase in bias voltage. The absorption features and the variation in the colour of the films from golden brown to red suggest that the films are mainly ReO3 with some oxygen non-stoichiometry.