Influence of substrate temperature on the morphology and structure of bismuth thin films deposited by magnetron sputtering

The melting point of bismuth is only 271.3 degrees C which has a great influence on the properties of bismuth itself and the bismuth-contained compounds especially at high temperature. In this paper, the bismuth thin films were prepared using magnetron sputtering method and the influence of deposition temperature on the morphology and structure were investigated over a wide range of substrate temperatures from room temperature to near the melting point. The results showed that 160 degrees C is a main watershed for the film growth. When the substrate temperature is below 160 degrees C, the morphology changes a lot from continuous film accumulated mainly by irregular grains to the discontinuous film mainly formed from the isolated polyhedral grains and again to the bimodal grain size distribution of the spherical-polyhedron-shape grains. When the substrate temperature is above 160 degrees C, the morphology of the bimodal grain size distribution has been maintained except for the changes of the large grain size. The XRD results revealed that the crystallite size hardly changes above 160 degrees C begin which the bimodal grain size distribution is just formed. The morphology evolution and growth mechanism of bismuth thin films were also studied based on the existing structure zone diagram model and our experimental results.