Highly crystalline In2S3 thin films epitaxially grown on sapphire substrates

Indium sulfide (In2S3) thin films were deposited on glass and sapphire substrates by physical co-evaporation of the elements. The deposition parameters were varied to optimize the structural properties of the thin films. The sample epitaxially grown on a-sapphire substrate shows the smoothest surface and the highest crystallinity. The optical absorption properties were found to be independent on the deposition parameters and substrate material. We found for In2S3 a weakly pronounced absorption onset at 1.7 eV and a strong one at 2.5 eV, which can be attributed to direct band-band transitions located at 2.1 and 2.7 eV, respectively. Electrical characterization reveals photovoltaic activity with p-ZnCo2O4/n-In2S3 heterodiodes but low performance due to non-ideal heterojunction properties. We further find a strong, persistent photoconductivity, which manifests itself in a strong time-dependence of the dark resistivity after the samples were exposed to light. (C) 2022 Author(s).

Automated summary

In this study, indium sulfide (In2S3) thin films were deposited on glass and sapphire substrates by physical co-evaporation. The structural properties of the films were optimized by varying the deposition parameters. The sample grown epitaxially on an α-sapphire substrate exhibited the smoothest surface and highest crystallinity. The optical absorption properties were found to be independent of the deposition parameters and substrate material. Weak and strong absorption onsets were observed at 1.7 eV and 2.5 eV, respectively, which were attributed to direct band-band transitions at 2.1 eV and 2.7 eV. The electrical characterization revealed photovoltaic activity but low performance due to non-ideal heterojunction properties. A strong and persistent photoconductivity was also observed, resulting in a time-dependent dark resistivity after light exposure.