Vertically aligned ZnO-ZnGa _2O _4 core-shell nanowires: From synthesis to optical properties

摘要

Dense and vertically aligned ZnO-ZnGa _2O _4 core-shell nanowires were synthesized in large scale on a-plane sapphire substrates by a simple two-step chemical vapor deposition method. The synthesized ZnO-ZnGa _2O _4 core-shell nanowires were connected through their base by a thick underlayer of the same material realizing electrical contact of the nanostructured array. X-ray diffraction and transmission electron microscopy analyses of the core-shell nanowires reveal that the ZnO cores and ZnGa _2O _4 shells of the core-shell nanowires are of single-crystal quality and have aligned crystallographic orientations. The ultraviolet-visible diffuse reflectance spectra of the core-shell nanowires showed two sharp edges corresponding to near-bandedge absorption contributed by the ZnO cores and the ZnGa _2O _4 shells. Moreover, the room-temperature photoluminescence spectra of the core-shell nanowires gave three UV emission peaks coming from the ZnGa _2O _4 shells and the ZnO cores. The dense and vertically aligned ZnO-ZnGa _2O _4 core-shell nanowires showing promising photoelectric properties offer an ideal structure for light harvesting applications such as a photoanode in a photoelectrochemical water splitting cell.