Growth and characterization of type II ZnO/ZnSe core/shell nanowire arrays

Type II ZnO/ZnSe core/shell nanowire arrays were grown by a two-step chemical vapor deposition. The nanowire arrays with dense nanoislands on the surface are well aligned and normal to the substrate imaged by scanning electron microscopy. The core/shell structure of nanowires was identified by a high-resolution transmission electron microscopy. The structure and composition of the shell were confirmed to be wurtzite ZnSe by x-ray diffraction, Raman scattering and energy-dispersive x-ray spectroscopy. Moreover, an intense emission was observed at 1.89 eV smaller than the band gaps of core and shell materials by photoluminescence, indicating the achievement of the type II band alignment at the interface. This study is expected to contribute to the potential applications in novel photovoltaic devices.