Ex situ structural characterization during the formation of CuInS2 thin films

CuInS2 (CIS) thin films were deposited on Mo-coated glass substrates using in situ sulfurization of thermally evaporated precursor Cu–In alloys. Samples were removed before, during and after the sulfurization for X-ray diffractometry (XRD) and Raman spectroscopy analysis. While various phases, including the desired CIS, can be identified by XRD, we show that only Raman spectroscopy can reveal the existence of the two structure orders of the CIS phase, namely the CuInS2–chalcopyrite and the CuInS2–CuAu metastable structure orders. Furthermore, this study also provides direct evidence to show that the CIS phase grows at the expense of an intermediate Cu11In9 phase.