Highly luminescent In2S3 thin films with preferred growth direction of [1 0 3]

Abstract In2S3 is one of the fascinating materials for a range of optoelectronic applications due to its suitable bandgap and stability. Nonetheless, its photoluminescence (PL) originating from defect states within its bandgap were hardly reported. In this work, high quality In2S3 thin films on SiO2 substrates were synthesized by using physical vapor deposition of In2S3 powder in a hot-wall Quartz tube-furnace. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy studies of the grown In2S3 films showed that extremely high crystalline quality tetragonal β-In2S3 films were synthesized with preferred growth direction of [1 0 3]. Absorption spectroscopy revealed the In2S3 films have a direct band of ~2.66 eV. Interestingly, our In2S3 films showed an extremely strong PL peak at room temperature at ~1.6 eV. The observed strong PL from our In2S3 films can be attributed to originating from the oxygen isoelectronic substitution at the sulfur site, and its efficiency was affected by oxygen concentrations in In2S3 films. Our In2S3 thin films exhibited remarkably high PL quantum yields (QY) of up to 14% which is comparable to that of GaAs quantum wells (QWs) and CdSe quantum dots (QDs).