In-situ monitoring of CuInSe2 thin films growth by light scattering

Abstract

Light scattering spectroscopy, mainly developed for Cu(In,Ga)Se2 thin films growth, has been demonstrated to be an efficient in-situ monitoring tool. It consists of illuminating the substrate surface using a light source and collecting the diffused light with a spectrometer. The on-line information allows monitoring the point of stoichiometry of the grown layer. In this work, we propose an alternative approach of this method, replacing the spectrometer by a standard webcam. This system allows to precisely choose the analyzed area on the substrate surface, which may be the whole sample surface or just a specific zone. We have grown CuInSe2 (CIS) thin films by co-evaporation under vacuum using the three-stage process. We have simultaneously performed CIS growth on both Mo-coated and bare glass substrates within the same growth run, while, on purpose, the scattered light was collected from the Mo-coated substrate. The CIS thin films were characterized by X-ray diffraction, atomic force microscopy, Hall effect measurements, absorption spectroscopy and energy dispersive spectroscopy for composition. By interrupting the CIS growth at different stages of the growth process, we have correlated the scattered light features with the Cu-rich/In-rich transitions and we observe the reproducibility of the scattered light spectra structures.