Preparation and annealing of GaN/Cu core-shell nanowires

GaN-core/Cu-shell nanowires were prepared and their annealing behavior was investigated. The thermal annealing induced the surface-roughening of the hetero-nanowires due to the agglomeration and generation of cluster-like structures from the Cu-shell layers. X-ray diffraction suggested that the thermal annealing generated CuOx phases. The core GaN nanowires exhibited weak ferromagnetism at 5 K and their coercivity was increased by Cu-sputtering and subsequent thermal annealing at 800 °C. In the Gaussian deconvolution studies, the photoluminescence (PL) spectra exhibited emission bands centered at 2.0 and 3.2 eV, irrespective of the Cu-coating and/or thermal annealing. A mechanism is proposed to explain the significant change in the intensity of the ultraviolet (UV) emission by the combination of Cu-sputtering and annealing at 1000 °C.