Conductivity enhancement by slight indium doping in ZnO nanowires for optoelectronic applications

Undoped and In-doped ZnO nanowires (NWs) have been synthesized by thermal evaporation. The effect of indium doping on the structure, morphology and electrical/optical properties of the as-grown NWs has been investigated. It has been found that the doped NWs are single crystalline along different orientations, preferably in the [0001] growth direction. The peak shifts and broadening in the x-ray diffraction pattern confirm the incorporation of indium into the ZnO lattice. The amount of contents and the valence state of In ions have been investigated through energy dispersive spectroscopy and x-ray spectroscopy, which demonstrate that the In ions are uniformly doped about 2 at% into each NW and are in the +3 oxidation state. In addition, the photoluminescence spectrum for the doped sample having a blue shift in the UV region shows a prominent tuning in the optical band gap. Furthermore, the presence of In dopant in ZnO NWs induces a dramatic decrease in the electrical resistivity of NWs, which makes it potentially applicable for optoelectronics devices.