Cu2ZnSnSe4 films by selenization of Sn–Zn–Cu sequential films

This paper deals with the formation of Cu2ZnSnSe4 (CZTS) in the process of selenization of metal precursor layers in elemental selenium vapour. Metallic precursors were sequentially evaported from Sn, Zn and Cu sources. Precursor Sn–Zn–Cu films have a “mesa-like” structure and consist mainly of Cu5Zn8 and Cu6Sn5 phases. It was confirmed that the formation of different binary copper selenides is the dominating process of selenization in elemental Se vapour at temperatures up to 300 °C. The formation of kesterite CZTS films begins at 300 °C and dominates at higher temperatures, always resulting in multiphase films that consist of high-quality Cu2ZnSnSe4 crystals and of a separate phase of ZnSe.