Fabrication and Characterization of Ga2O3/ZnO Coaxial Nanowires

Abstract

Ga_2O_3/ZnO coaxial nanowires were synthesized by using a two step process comprised of the thermal evaporation of GaN powders and the sputter-deposition of ZnO. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis results indicated that the cores and the shells of the annealed coaxial nanowires were single crystal monoclinic Ga_2O_3 and amorphous ZnO, respectively. Photoluminescence (PL) measurements showed that the major emission of the Ga_2O_3 nanowires in the green region was increased by the ZnO coating but was slightly decreased by subsequent thermal annealing in an oxidative atmosphere. The oxygen concentration in the Ga_2O_3 core regions increased during the oxygen annealing, leading to increases in the oxygen interstitial and Ga vacancy concentrations, resulting in the enhancement in the green emission. In contrast, the PL emission of the wires was significantly increased, and the emission peak was red-shifted from 540 to ∼590 nm by annealing in a reducing atmosphere, which was presumably attributed to the increases in the oxygen vacancy and Zn interstitial concentrations in the Ga_2O_3 cores.