Effect of substrate temperature during growth on defect density in bismuth thin films

Abstract

Bismuth thin films of thickness 720±10 Å have been vacuum deposited on clean glass substrates held at various substrate temperatures ranging between 30 ° and 185 °C at a constant deposition rate 0f 3±0.3 Å s. Immediately after the formation of the films, the heat treatment was given to the films in situ. For each film, the resistance was recorded as a function of temperature during the heat treatment. It has been found that the resistance of the films decreases when the temperature increases during the first cycle of heating, and this has been attributed to the removal of defects. During the first cycle of cooling and the next cycle of heating and cooling, it is observed that the resistance first decreases when the temperature increases and then increases as the temperature increases. Using Vand’s theory, from the resistance–temperature data during heat treatment, both defect density and the initial lattice distortion energy spectra have been evaluated. It is observed from these spectra that as the substrate temperature increases the defect density decreases. It is also found that the defects have a mild preference for energies in the range between 1.30 and 1.35 eV. The results have been interpreted on the basis of the influence of the substrate temperature on the nucleation and growth phenomena in thin films.