Growth and Characterization of Cu2MnSnS4 Thin Films Synthesized by Spray Pyrolysis under Air Atmosphere

The direct synthesis of chalcopyrite Cu2MnSnS4 (CMTS) thin films by a spray pyrolysis technique on glass substrates under oxidative conditions (ambient atmosphere and using compressed air as a carrier gas instead of nitrogen) was studied. The effect of the deposition temperature on the structural, chemical composition, and optical and electrical properties of thin films has been assessed. X-ray diffraction study reveals that the tetragonal stannite structure crystallizes with a [112] preferential orientation from 280 up to 360 °C, with its crystallinity correlated with the substrate temperature. However, in addition to its crystallization, traces of secondary phases are observed: a mixture of SnO and CuO at 360 °C prevails on the formation of CuS at 320 °C. Above 360 °C, the oxidant conditions combined with the loss in sulfur lead to the crystallization of only the tenorite CuO. The crystallization of sulfides by spray pyrolysis under air is possible only at relatively low deposition temperature for which the oxidation rate is inefficient compared to the sulfidation rate. Further optical studies of stannite films indicate a high absorption coefficient toward the visible range (>104 cm−1) and an optical band gap of about 1.64–1.85 eV, also depending on the substrate temperature. The CMTS thin films deposited below 360 °C exhibit a moderate electrical resistivity of about Ω·cm at room temperature. The properties of the stannite films synthesized using a spray pyrolysis technique in ambient air are comparable to those of films obtained by spray pyrolysis with nitrogen carrier gas despite the presence of oxides traces, an increase in the deposition temperature improving the microstructure, and its related optical and electrical properties.