Controlled synthesis, morphological, optical and electrical properties of copper-doped zinc oxysulfide nanostructures

Zinc oxysulfide nanostructures may have physical and chemical properties that are different from ZnS or ZnO. Therefore, Cu-doped oxysulfide nanostructures were prepared by vapor transport and their properties were characterized by various techniques. EDAX analysis confirmed the presence of Zn, S, O and Cu in the samples. XRD revealed the formation of mixed phases of hexagonal ZnS, orthorhombic ZnSO4, and hexagonal ZnO that is dependent on Cu content. The undoped sample has nanowire morphology. The increase in Cu doping changed the morphology form NWs to a mixture of NWs and nanoparticles (NPs), and then to NPs. The undoped oxysulfide sample has band gap of 4.08 eV, and the band gap decreased to 3.57 eV at 5% Cu doping. The PL intensity was enhanced upon Cu doping with 5 and 10 at% Cu while it weakened at higher Cu contents. The electrical resistivity decreased with Cu content and a thermally activated semiconducting behavior was reported for all samples.