Spatially resolved characterization of chemical species and crystal structures in CuInS2 and CuGax Sey thin films using Raman microscopy

This study demonstrates the potential of Raman microscopy in the analysis of thin film cross-sections. Raman maps of the photovoltaic material CuInS 2 (CIS), which was prepared by the spray ion layer gas reaction method, revealed the spatial distribution of two different CIS modifications - chalcopy-rite-type and CuAu I-type CIS - as well as contaminants and segregate with a lateral resolution of approx. 400 nm. Additionally, the chemical heterogeneity of a CuGaSe 2 /CuGa 3 Se 5 bi-layer stack was clearly resolved. Raman microscopy provides a convenient way to simultaneously probe the chemical and structural properties of a sample. Based on Raman spectra, chemical species and even different crystal structures of inorganic compounds can be identified. Knowledge of the distribution of different phases and contaminants in thin films is crucial for further improvements of the coating process.