Single-phase CZTS thin film prepared by high power impulse magnetron sputtering (HiPIMS): A first attempt

Copper-zinc-tin-sulfide: Cu2ZnSnS4 (CZTS) is a non-toxic and abundant materials that could possibly replace the toxic and rare copper-indium-gallium-selenium (CIGS) materials for the absorber of thin film photovoltaic. However, to-date, the CZTS thin film fabrication process is not yet ready for commercialization due to its complexity of quaternary elements. Here, CZTS thin films were deposited for the first time using high power impulse magnetron sputtering (HiPIMS) technique. Although the fabrication of thin film solar cell using conventional DC and RF sputtering is very common, to date, there is no report on the fabrication CZTS thin film using HiPIMS technique. The aim of using HiPIMS system is to resolve the problem on stoichiometry control in single step magnetron deposition, i.e., less composition of zinc and sulphur. The prepared thin films were then characterized using X-ray diffraction (XRD) and atomic force microscopy (AFM). The thickness of each film was measured using a step profiler and verified with a cross-sectional image obtained by FE-SEM. The XRD pattern showed significant different between film prepared by HiPIMS and conventional RF sputtering on single CZTS (112) peaks. The CZTS crystallite size was in the range of 14-28 nm, rely on the discharge power and deposition time. In average, the root mean square roughness was lower than 2 nm, which is useful for solar cell application. The chemical composition analyzed by EDX showed that the atomic ratio of sulfur/metal < 1, indicating that the thin film prepared by HiPIMS deviated from CZTS stoichiometric.