Microstructural analysis and phase transformation of CuInS₂ thin films during sulfurization

This study reports the preparation of CuInS₂ (CIS) thin films on Mo-coated glass substrates using in situ sulfurization of thermally evaporated Cu-In precursor films in a thermal evaporation chamber. The precursor films were thermally evaporated at 1.2 × 10^-6 Torr and further sulfurization was carried out at 8 Torr of 10% H₂S, balanced by Ar. The precursor Cu-In alloy films consist of three types of layered structures with a fixed total thickness of 800 nm. Different temperature-time profiles were used during the sulfurization processes. Various phases in the films were identified using both X-ray diffractometry (XRD) and Raman spectroscopy, the latter of which reveals additional structural information that cannot be observed in the XRD spectra. Direct evidence showing the growth of CIS phase from an Cu₁₁In₉ phase is shown by TEM images. Although there are minor differences during the growth of these samples that lead to slightly different growth paths, the growth can be described by a general reaction sequence.