Replacement of sulphur with selenium in antimony sulphide thin films

This study aims to determine the extent to which sulphur can be replaced with selenium in the Sb2S3 matrix. The relevance of this work is that this replacement reaction forms the underlying principle for the formation of the ternary compound AgSbSe2 from the binary compound Sb2S3. AgSbSe2 is a compound semiconductor belonging to the I-V-VI2 group that has applications in photovoltaics. Even though there are numerous reports of heating multilayers of Sb2S3/Ag/Se or Sb2S3/Ag2Se/Ag to produce AgSbSe2, none of them have resulted in a pure ternary phase. This study explores the possibilities and limitations of the replacement of sulphur with selenium in antimony sulphide thin film. In this work, selenium is deposited on Sb2S3 layer and the resulting structure is annealed at 200°C. The replacement reaction was found to be incomplete at this temperature. The temperature of annealing could not be increased any further as the elemental selenium could not withstand higher temperatures. Hence, a protective layer of silver was coated on top of the selenium layer, and the temperature of annealing was increased to higher values. X-ray diffraction, scanning electron microscopy-energy dispersive X-ray and X-ray photoelectron spectroscopy were used to characterize the multilayer film.