Effects of annealing on the electrical resistivity and transmittance properties of Ga doped ZnO (GZO) thin films deposited on glass by radio frequency (RF) magnetron sputtering were investigated. The electrical resistivity of a GZO thin film is effectively decreased by annealing in a reducing atmosphere such as N 2 z5%H 2 . This is attributed to passivation of grain boundaries and zinc ions by hydrogen atoms resulting in increases in carrier concentration and mobility. However, annealing at a temperature .400uC is less effective. The lowest resistivity of 2 . 3610 24 V cm is obtained by annealing at 400uC in an N 2 z5%H 2 atmosphere. The optical transmittance of the GZO film is improved by annealing regardless of the annealing atmosphere. Annealing in an N 2 z5%H 2 atmosphere widens the optical band gap, while annealing in an O 2 atmosphere makes the band gap narrower, which can be explained as a blue shift phenomenon.
Production of indium oxide (In2O3) whiskers at a very low temperature of 650• C was reported. The synthetic route was comprised of a thermal heating process of a mixture of In and Mg powders. We have investigated the structural properties of the as-synthesized nanowires by using X-ray diffraction and scanning electron microscopy. The product consisted of one-dimensional nanowires, with a crystalline cubic structure of In2O3. The photoluminescence measurement with the Gaussian fitting exhibited visible light emission bands centered at 2.1 eV and 2.8 eV. The peaks of the Raman spectrum were indexed to the modes being associated with cubic In2O3.
Ga 2 O 3 based gas sensors have limited use at a temperature lower than 400 C because of their poor performances at low temperatures. Efforts to further improve their performances at room temperature are necessary. This study examines the sensing properties of surface-nitridated Ga 2 O 3 nanowires toward CO gas. Surface-nitridated Ga 2 O 3 nanowires were fabricated by thermal evaporation of GaN powders followed by thermal nitridation in an NH 3 atmosphere. Scanning electron microscopy and transmission electron microscopy showed that the GaN shell layer in a typical surface-nitridated nanowire had a thickness of $21 nm and excellent shell layer thickness uniformity. Multiple networked surface-nitridated Ga 2 O 3 nanowire sensors showed responses of 160-363% to CO concentrations of 10-200 ppm at 150 C. These responses were 1.6-3.1 fold stronger than those of pristine Ga 2 O 3 nanowire sensors at the same CO concentrations and stronger than those of many pristine metal oxide nanostructures and Ga 2 O 3 /metal oxide core-shell nanowires at similar temperatures. The results showed that the sensitivity of Ga 2 O 3 nanowires could be enhanced by simple ammoniation treatment. The enhanced response of the surface-nitridated Ga 2 O 3 nanowires to CO gas can be explained based on a potential barrier carrier transport mechanism combined with a surface depletion mechanism and excellent shell layer uniformity. Fig. 1 (a) SEM image and (b) XRD pattern of surface-nitridated Ga 2 O 3 nanowires.This journal is
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