Synthesis and characterization of ZnO/NiO p–n heterojunctions: ZnO nanorods grown on NiO thin film by thermal evaporation

Abstract The present article describes the synthesis and characterization of ZnO nanostructures grown on a NiO thin film. The structure and morphology of the as-grown film of ZnO nanorods were characterized by scanning electron microscopy, and X-ray diffraction revealing a rather well ordered array of ZnO nanorods aligned normally to the substrate. Photoluminescence spectroscopy was used to study the optical properties providing evidence for several types of defects in the as grown nanostructures. A comparison between the off-resonance Raman spectra of the nanostructures and bulk ZnO showed a number of atypical Raman bands in the former whose origin is discussed in terms of resonantly enhanced LO phonons via the extrinsic Frohlich interaction. p-NiO/n-ZnO heterojunction diodes are currently emerging as attractive materials with potential use in electronic and optoelectronic devices.