Fast UV photoresponse from Aluminum doped zinc oxysulphide composite nanowires by efficient charge-exchange interactions

For the development of technologically advanced material for the next-generation smart electronic devices, we prepared zinc oxysulphide (ZnOS) composite nanowires (NWs) through a two-step process. The electronic and optical properties of this system are further influenced by doping with aluminium. First, 2 at.% Al-doped ZnO NWs were prepared on Si and then it is subjected to sulphidation process for different time durations. Sulphidation for short duration results in a core-shell structure and ZnOS composite structure was achieved after 4 h of sulphidation. We systematically studied the structural, photoluminescence and UV photoresponse properties of the ZnOS composite NWs to investigate the superiority of this kind of semiconducting composite material. Structural characterization of the ZnOS NWs confirms hexagonal crystalline composite structure with small clusters of ZnS phase. Interestingly, these ZnOS composite NWs emit three different colours of emission in UV, blue and green regions. UV photoluminescence (PL) intensity is found to gradually increase with the increased duration of the sulphidation process. We obtained a significant improvement in the UV photoresponse behaviour of the ZnOS composite NWs compared to the bare doped ZnO NWs. The obtained photoresponse time is much faster (200 ms) than the case of virgin ZnO NWs (similar to several seconds) as well as with high responsivity (0.29 A/W). The observed improved PL and fast UV photoresponse are explained based on hoping charge transfer through the interface and modification of defects that is supported by x-ray photoelectron spectroscopy data. Therefore, prepared ZnOS composite NWs is found to be a technologically advanced material for the application as an efficient UV photosensor.