Optical response of bismuth based thin films synthesized via unbalanced magnetron DC sputtering technique

Bismuth-based thin films were deposited on AISI 316L stainless steel and glass substrates via the unbalanced magnetron DC sputtering technique. Three different configurations of titanium pieces along the bismuth target race track were used in order to evaluate the influence of Ti content on the optical and electrical properties of the films. We used a reactive ambient mixture of Ar:O (80%:20%) and a constant flux of 9 sccm, along with a power of 40 W. Results showed thin films with high homogeneity and smooth surfaces, with several bismuth droplets, in all the different configurations. It was also found that the optical and electrical properties of the thin films are strongly dependent on the preparation conditions, especially the Ti content. Titanium quantities in the parts-per-million range were found only through the micro-proton induced X-Ray emission technique. This small quantity of Ti, as well as the thickness of the thin films, affected the electrical and optical response of the bismuth-based thin films.