Synthesis and photo-sensing properties of Zn–ZnO core–shell nanofibers

Abstract

Single-crystalline Zn–ZnO core–shell nanofibers have been prepared by thermal evaporation of metallic Zn in an oxygen atmosphere. The diameter of the Zn core is 53±1.0nm while the thickness of the outer ZnO shell is 10±1.5nm, both are single crystalline and grow along the [1 1 2¯ 0] direction. Post-growth annealing leads to sublimation and out-diffusion of the Zn core that result in the formation of polycrystalline ZnO nanotubes. Metal-semiconductor-metal photodiodes (PDs) are fabricated by depositing In and Ag interdigitated electrodes on Zn–ZnO core–shell nanofibers. PDs fabricated with In contacts exhibit a maximum responsivity of 2A/W at 300nm. In contrast, PDs fabricated with Ag contacts exhibit a maximum responsivity of 10A/W at 300nm and a much faster decay rate which has been attributed to the formation of a Schottky barrier between Ag and ZnO.