Preparation and characterization of Cu2ZnGeS4 thin films by sulfurizing reactively sputtered precursors

Cu₂ZnGeS₄ (CZGS) thin films were first grown by reactive magnetron co-sputtering technique and post sulfurization. Raman and X-ray diffraction (XRD) examination confirm the synthesized films to be tetragonal stannite CZGS together with ZnS secondary phase. The effect of two manufacturing conditions was investigated: sputtering pressure for precursor deposition and sulfurization temperature. By decreasing the sputtering pressure, the CZGS grain size in the sulfurized films is found to be increased. By increasing the sulfurization temperature, the CZGS grain size is also increased. However, serious voids and pinholes are found in the sample undergoing high sulfurization temperature. The formation of voids and pinholes can be explained by Ge loss via Ge sulfides sublimation. Besides, the M0S2 layer thickness is found dramatically increased after high-temperature sulfurization process.