High performance Cu_2O/ZnO core-shell nanorod arrays synthesized using a nanoimprint GaN template by the hydrothermal growth technique

Abstract

Nanoimprint technology was used to synthesize a series of nanostructures with hexagonal holes on a n-GaN baseplate. The hydrothermal growth technique was then used to produce 1.5-μm n-type ZnO nanorods. Radio frequency reactive magnetron sputtering was employed to grow a 50-nm thick layer of cuprous oxide film over the nanorods to form a p-n Cu2O/ZnO core-shell structure. Based on the different imprint widths and intervals obtained, Cu2O/ZnO heterostructure samples A, B, C, and D showed aperture ratios of 0.0627, 0.0392, 0.0832, and 0.0537, respectively. Scanning electron microscopy and atomic force microscopy indicated that a 50-nm Cu2O film coated the ZnO nanorods, forming a core-shell structure. X-ray diffraction and x-ray rocking curve (XRC) analysis showed that the Cu2O lattice structure had polycrystalline characteristics. The lattice planes of Cu2O were (111) and (220), and Sample C exhibited the narrowest XRC half-height full-width value. Therefore, among the samples obtained, Sample C had the optimal material properties. Measurement of the optical properties of the samples demonstrated that their luminous peak did not change with variations in temperature. Sample C also showed optimal optical properties. High-resolution transmission electron microscopy indicated the presence of a midlayer in the Cu2O/ZnO junction that had a direct impact on the Cu2O lattice arrangement on the top, corner, and side faces of the ZnO nanorods. The sample with the largest aperture ratio exhibited the most favorable optical and material properties. The novel structure obtained can potentially be used in solar cell applications.