Papers by Keyword: Gallium Oxide

Abstract: The electrical and optical properties, and microstructures of 100 nm-thick Ga2O3 films fabricated on Al2O3(0001) substrates by a sputtering deposition were investigated. The partial pressure of oxygen was controlled and the substrate temperature was kept to be 500 °C during deposition. With increasing the oxygen partial pressure, the structures of the Ga2O3 films deposited on the substrates were observed to change from amorphous to crystalline (monoclinic β-type Ga2O3). The transmittance of the Ga2O3 films was measured to be more than 80 % at the visible and ultraviolet regions although the electrical resistivity was high. In order to obtain both low electrical resistivity and high transmittance at the ultraviolet regions, the addition of active dopant elements such as Sn into the Ga2O3 films would be required.

Abstract: High purity nanowires are successfully synthesized by chemical vapor deposition. In this work, we have tried synthesis of GaP nanowires with copper oxide catalyst using chemical vapor deposition method involving a metal oxide-assisted vapor-liquid-solid (VLS) growth mechanism. The synthesis process is the same as that described in existing work except for a catalyst. The mixture of GaP and Ga powder was used as GaP source for synthesis of GaP nanowires. And the mixture powder was directly vaporized in the range of 700~1000°C under argon ambient in a furnace. The wire-like products was observed in the range of 800~950°C. The diameter of nanowires increases with increasing synthesis temperature, but reversely, the length of nanowires decreases steadily. The nanowires prepared at 850°C possess perfect wire-like shape and uniform distribution of diameter. The average diameter and length of nanowires are about 50
 and 150, respectively. HRTEM and EDX analysis were carried out to obtain more detailed information of its microstructure. Nevertheless, all condition of processing was set for making the high purity GaP nanowires as existing reported method, the nanowires were identified as well-crystallized gallium oxide nanowires with an amorphous outer layer. It does not accord with existing reported results. This result means that the catalysts play a key role in the growth of nanowires.

Abstract: We have prepared the gallium oxide (Ga2O3) films on sapphire substrates by a thermal evaporation of GaN powders. We have characterized the films by using the x-ray diffraction (XRD), scanning electron microscopy (SEM), and the photoluminescence (PL). SEM and XRD revealed that the deposits were Ga2O3 thin films with monoclinic structure. PL spectrum of Ga2O3 films under excitation at 325 nm showed a blue emission.

Abstract: We have synthesized the high-density Ga2O3 nanowires on gold (Au)-coated silicon substrates using metalorganic chemical vapor deposition. The nanowires exhibited one-dimensional structures having circular cross sections with diameters in the range of 30-200 nm. The energy dispersive x-ray spectroscopy revealed that the nanowires contained elements of Ga and O, without Au-related impurities. X-ray diffraction analysis and high-resolution transmission electron microscopy showed that the Ga2O3 nanowires were crystalline.

Abstract: Beta gallium oxide (β-Ga2O3) ceramics was coupled and reacted with zinc oxide (ZnO) ceramics at 1200oC for 24 h. Energy dispersive X-ray spectroscopy (EDS) analysis revealed the existence of diffusion layer near the interface between β-Ga2O3 and ZnO. Furthermore, the layer showed monochromatic and intense cathodoluminescence (CL) at 3.5 eV. On the other hand, very weak emissions were observed from the out of the layer. The compound in the layer is considered to be an attractive material for ultraviolet optoelectronics.

Abstract: We have studied on the use of a GaN powders for growing gallium oxide (Ga2O3) nanoribbons and nanosheets by the thermal evaporation technique. We used x-ray diffraction, scanning electron microscopy, and transmission electron microscopy to characterize the samples. The results showed that the produced Ga2O3 nanomaterials had single crystalline monoclinic structures. The proportion of wider nanoribbons or nanosheets to nanoribbons increased by increasing the growth temperature and by employing the mixture of GaN and ZnO powders.

Abstract: We have synthesized gallium oxide (Ga2O3) nanomaterials at two different growth temperatures on iridium (Ir)-coated substrates by thermal evaporation of GaN powders. The products consist mainly of nanobelts, with some additional nanosheets. The nanobelts were of a single-crystalline monoclinic Ga2O3 structure. The broad emission photoluminescence band of 900°C-products had a different peak position from that of the 970°C-products.

Abstract: Beta gallium oxide (β-Ga2O3) crystals were grown on β-Ga2O3 ceramics heated by electric current under vacuum at various ambient temperatures. From cathodoluminescence at room temperature, emission peaks at 2.9 and 3.5 eV were clearly observed. With increasing ambient temperature, the relative intensity of ultraviolet emission (3.5 eV) to blue emission (2.9 eV) showed a peak at 400oC. These results suggest that the ambient temperature during the electric current heating of β-Ga2O3 ceramics in vacuum is one of the most effective factors for the ultraviolet emissive β-Ga2O3 crystal.

Abstract: We have demonstrated the production of gallium oxide thin films on various substrates such as Si(111), SiO2, and sapphire by metalorganic chemical vapor deposition using the trimethylgallium (TMGa) as a precursor in the presence of oxygen. The XRD data revealed that the as-deposited gallium oxide films were fully amorphous but very small crystallites with monoclinic structures were found with the thermal annealing at a sufficiently high temperature, regardless of substrate materials. The AFM analysis indicated that the surface roughness increased by the thermal annealing.