The effect of film composition on the texture and grain size of CUInS2 prepared by chemical spray pyrolysis

Ternary single-source precursors were used to deposit CuInS2 thin films using chemical spray pyrolysis. We investigated the effect of the film composition on texture, secondary phase formation, and grain size. Films with either (112)- or (204/220)-preferred orientation were deposited with most often In-rich composition. The (112)-preferred orientation became more pronounced as die film composition became more In-poor. Films with a (204/220)-preferred orientation were both In-rich and contained a yet unidentified secondary phase. The phase was evaluated as an In-rich compound based on composition analysis and Raman spectroscopy. Further experiments showed that the phase could be removed by depositing a thin Cu layer prior to the growth of CuInS2. Similarly, as-grown Cu-rich (112)-oriented films did not exhibit the In-rich compound. The (204/220) preferred orientation of the film is likely related to the equivalent symmetry between planes of CuInS2 and the In-rich compound. The largest grain size (similar to 0.5 mum) was achieved with Cu-rich (112)-oriented films.