High SnS phase purity films produced by rapid thermal processing of RF-magnetron sputtered [formula omitted] precursors

Abstract

The work reported below aimed at establishing a suitable route to prepare single phase SnS thin films for photovoltaic applications. The growth approach consisted in the deposition of SnS2-x precursor layers by RF-magnetron sputtering followed by rapid thermal annealing. The samples were placed on a graphite susceptor covered with a transparent glass dome in an atmosphere of N2 + 5%H2S, with and without additional tin sulphide vapour in the atmosphere around the samples. The resulting films were studied by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Raman scattering and spectrophotometry to determine which set of growth conditions yielded the desired properties. In order to minimize the material loss through evaporation, improve the films’ morphology and eliminate the residual SnS2 phase, the use of a transparent glass dome to confine the tin sulphide vapour in a smaller volume over the sample, is an effective approach. Clearly, the material loss was reduced. The samples grown on Mo at a low heating rate of 0.2 °C/s and 500 °C during 5 min showed good properties but still contained residues of the SnS2 phase. By increasing the heating rate to 2 °C/s and above, it was possible to eliminate the SnS2 phase and still maintain a good morphology, thus obtaining single phase SnS films deemed as essential for optimized photovoltaic performance.