In situ analysis of the crystallization process of Sb2S3 thin films by Raman scattering and X-ray diffraction

Sb2S3 thin films grown by chemical bath deposition have received increasing interest for its integration into solar cells. However, its crystallization by post-deposition annealing represents a major difficulty owing to its instability at relatively low temperature. We combine in situ Raman scattering at very low laser power with in situ X-ray diffraction over a broad range of annealing temperatures and durations under N-2 atmosphere to elucidate its crystallization process on anatase-TiO2 layers. The thermally activated crystallization is found to systematically involve the intermediate formation of a metallic Sb phase and very often of a senarmontite cubic Sb2O3 phase, both of them vanishing prior to the formation of the stibnite Sb2S3 phase. Compact and continuous 150 nm-thick Sb2S3 thin films with no pyramid-shaped clusters on their top surface are crystallized in the range of 240 to 270 degrees C, namely below the commonly used annealing temperature of 300 degrees C. Their texture is tunable from (420) and (520) to (020) and (200) planes parallel to the surface by raising the annealing temperature owing to a process of abnormal grain growth. The Sb2S3 thin films crystallized at the optimal annealing temperature of 270 degrees C are composed of dense crystallites with a typical size of several tens of nanometers, which is of high interest for their integration into solar cells. (C) 2017 Published by Elsevier Ltd.