Effect of H 2 O 2 Etching on Properties of Spray‐Deposited Cu 2 NiSnS 4 Thin Films

ABSTRACT Recently, high toxic, cyanide‐based etching methods are used to remove copper‐based impurity phases in quaternary chalcogenide materials. In this study, the hazardous and toxic cyanide etching method is replaced by the novel, eco‐friendly, non‐cyanide etching of spray‐deposited Cu 2 NiSnS 4 thin films for the removal of the Cu x S secondary phase. The CNTS thin films are characterized using different characterization techniques to study the effect of etching on their physico‐chemical properties. The spray‐deposited CNTS thin film synthesized at a substrate temperature of 400 °C and etched by 5% H 2 O 2 solution for 6 min have exhibited the suppression of the Cu x S phase. The 6 min etched CNTS thin film reveals excellent physicochemical properties. The cubic CNTS phase exhibits a crystallite size of 13.7 nm. The suppression of the Cu x S phase is indicated by decreased Raman peak intensity at 472 cm −1 , an optimum band gap of 1.45 eV, and band‐to‐band PL emission at 752 nm. XPS spectrum reveal the presence of Cu, Ni, Sn, and S in +1, +2, +4, and −2 oxidation states, respectively.