Characterization of luminescence properties of V2O5-capped ZnSe nanowires.

ZnSe-core/V2O5-shell nanowires were synthesized by the thermal evaporation of ZnSe powders on gold-coated Si (100) substrates followed by the sputter depositon of V2O5. Scanning electron microscopic images showed that the core-shell nanowires were a few tens to a few hundreds of nanometers in diameter and a few hundreds of micrometers in length. Transmission electron microscopy and X-ray diffraction analyses revealed that the core and shell of the core-shell nanowires were single crystal wurtzite-structured ZnSe and amorphous V2O5, respectively. Photoluminescence measurement showed that the core-shell nanowires as-synthesized or annealed in an oxidative atmosphere had a green emission band centered at around 520 nm whereas the as-synthesized ZnSe nanowires and the ZnSe-core/V2O5-shell nanowires annealed in a reducing atmosphere had a yellow emission band centered at around 590 nm. Our results also showed that V2O5 capping with an optimal thickness and subsequent annealing in a reducing atmosphere could significantly enhance the emission intensity of the ZnSe nanowires. In addition, the origins of the enhancement in intensity and the blue shift of the major emission by V2O5 capping are discussed.