Enhanced gas selectivity by p-n type competition of ZnO nanorods with varied CuO shells

Abstract

In this work, n-ZnO/p-CuxO and n-Cu:ZnO/n-Zn:CuO core-shell nanorod (NR) arrays were synthesized by depositing CuxO nanoshells with different thickness on surface of ZnO NRs and subsequent annealing. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) show the outer CuxO shells were comprised of Cu2O and CuO nanocrystals before annealing, but they transformed to single-crystalline Zn doped CuO nanoparticles after annealing. X-ray diffraction (XRD) showed the (0002) peaks shift to higher angle after annealing, indicative of diffusion of Cu and replacement of Zn2+ by Cu2+ ions. Room-temperature Gas-sensing measurements show the n-ZnO/p-CuxO core/shell nanostructures with various CuxO thicknesses demonstrating enhanced selectivity for different gases by utilizing the competition of inner n-ZnO and outer p-CuxO. This work proposes an effective route to synthesize n-ZnO/p-CuxO and CZO nanostructures which have great potential in developing room-temperature gas sensors.