Influence of ZnO coating and annealing on the photoluminescence properties of larva-like gallium sulfide nanostructures

This study examined the influence of ZnO coating and annealing on the photoluminescence properties of the Ga2S3 nanostructures. Scanning electron microscopy showed that the Ga2S3/ZnO core–shell nanostructures synthesized using a two-step process consisting of thermal evaporation of Ga metal and S powders and atomic layer-deposition of ZnO had larva-like morphologies. The larva-like Ga2S3 nanostructures synthesized at 700 °C showed strong orange emission. The emission might be due to the localized states associated with S interstitials, Ga vacancies, stacking defects and surface states. The emission peak of the GaS nanostructures was blue-shifted by ZnO coating. The ZnO shell layer thickness corresponding to the ALD cycle of 100 led to the highest emission intensity, which is more than three times higher than that of the uncoated Ga2S3 nanostructures. The emission intensity was further enhanced by annealing in a reducing atmosphere. The origins of the photoluminescence enhancements by ZnO coating and annealing are discussed.