Enhanced Photoluminescence and Photoconductivity of ZnO Nanowires with Sputtered Zn

We have sputtered Zn onto quasi-one-dimensional ZnO nanowires (NWs) in order to investigate the effect of Zn diffusion on the photoluminescence and photoconduction properties of ZnO NWs. Elemental mapping clearly indicates higher Zn concentration in the NWs due to diffusion of Zn. The Zn-sputtered NWs show an enhanced ultraviolet emission with 7 nm red shift. Since the ionization energy of Zn-1 is 51 meV, the enhanced PL emission with a red shift is corelated to the coupling between free exciton and zinc interstitials (Zn-1) defects. The photocurrent transients show almost 20 times more photocurrent generation in Zn/ZnO NWs compared to the as-grown NWs. In contrast, the thin him shows no significant change in the photoluminescence and photoconductivity. Based on the photoconductivity and photoluminescence results, we predict that Zn diffusion in the NWs occurs easily compared to the films because of the smaller dimensions of the NWs.