Annealing behavior of TiO2-sheathed Ga2O3 nanowires

TiO2-sheathed Ga2O3 one-dimensional (1D) nanostructures were synthesized by thermal evaporation of GaN powders and then sputter-deposition of TiO2. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis results indicate that the Ga2O3 cores are of a single crystal nature with a monoclinic structure while the TiO2 shells are amorphous. Photoluminescence (PL) emission is slightly decreased in intensity by TiO2 coating, but it is significantly increased by thermal annealing in an oxygen atmosphere. The emission peak is also shifted from similar to 500 to similar to 550 nm by oxygen annealing. The increase in the green emission is due to the increase in the concentration of the Ga vacancies in the cores by the inflow of oxygen during oxygen annealing. On the other hand, annealing in a nitrogen atmosphere leads to a red shift of the emission to similar to 700 nm originating from nitrogen doping.