Effects of the annealing atmosphere on the photoluminescence properties of Ga2O3-core/TiO2-shell nanowires

초록

Ga2O3-core/TiO2-shell nanowires have been synthesized by a two step process: thermal evaporation of GaN powder on Au-coated Si substrate and sputter-deposition of TiO2. Transmission electron microscopy and X-ray diffraction analysis results reveal that the Ga2O3 cores and the TiO2 shells are crystalline with monoclinic and tetragonal structures, respectively. Photoluminescence measurements show a red emission peak centered at around 700 nm. Our results also show that coating Ga2O3 nanowires with thin TiO2 layers can significantly enhance the red emission intensity. The PL peak intensity of the Ga2O3/TiO2 coaxial nanowires prepared by sputter-deposition of TiO2 for 1.5 min on Ga2O3 nanowires and then annealing is about 20 times as high as that of Ga2O3 nanowires. X-ray Photoemission spectrometry analysis results suggest that the PL enhancement is attributed to increase in the concentrations of deep levels such as oxygen and titanium interstitials as well as the density of interface states.