Effect of sulfurization temperature on the phase purity of Cu2SnS3 thin films deposited via high vacuum sulfurization

In this study, the deposition of Cu2SnS3 (CTS) thin films was carried out at different sulfurization temperatures in the range of 350-550°C under high vacuum of 1 Pa using the sputtered Cu/Sn/Cu metal precursor layers in the sulfur vapor atmosphere. In order to reduce the Sn loss, a particular metal stack of Cu/Sn/Cu was used. Single phase monoclinic (M)-CTS thin film was obtained at 500 °C. The high intensity Raman modes at 292 cm−1 and 350 cm−1 further confirmed the formation of M-CTS. The M-CTS thin film sulfurized at 500 °C showed a composition of Cu/Sn = 1.89 and an optical band gap energy of 0.94 eV. Hall effect measurement of the film sulfurized at 500 °C with Cu/Sn ratio of 1.82 showed an electrical resistivity of 7.30 Ω-cm, carrier concentration of 6.29 × 1017 cm−3, and mobility of 1.36 cm2/Vs. Our results indicate that the copper-poor composition with a stacking order of Cu/Sn/Cu is favored in order to attain the single phase M-CTS.