Controlled Structure of Gallium Oxide and Indium Oxide Nanowires
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N11.27.1
Controlled Structure of Gallium Oxide and Indium Oxide Nanowires Hye Jin Chun, Seung Yong Bae1 and Jeunghee Park1 Dept. of Chemistry, Korea University, Seoul 136-701, South Korea 1 Dept. of Material Chemistry, Korea University, Jochiwon 339-700, South Korea ABSTRACT Gallium oxide (Ga2O3) and indium oxide (In2O3) nanostructures were synthesized by chemical vapor deposition (CVD). Ga2O3 nanowires were synthesized using Ga/Ga2O3 mixture and O2. The diameter of the nanowires is 30-80 nm with an average value of 50 nm. They are consisted of single-crystalline monoclinic crystal. While the nanowires grown without catalyst exhibit a significant planar defect, the nanowires grown with nickel catalytic nanoparticles are almost defect-free. The growth direction of the nanowires grown without the catalyst is uniformly [010]. In contrast, the nanowires grown with the catalyst have random growth direction. X-ray diffraction, Raman spectroscopy, and photoluminescence are well correlated with the structural characteristics of the nanowires. The result provides an evidence for the catalyst effect in controlling the structure of nanowires. In2O3 nanostructures were also synthesized in a controlled manner by selecting the catalyst. The reactants were In and In/In2O3 mixture. The nanowires were produced using catalytic Au nanoparticles and Ga. But the unique bifurcated-structure nanobelts were instead grown without Ga. The nanowires have uniform [100] growth direction with rectangular cross-section. We converted the In2O3 nanowires to In2O3-Ga2O3 nanostructures. INTRODUCTION Since the discovery of carbon nanotubes [1], the pseudo-one-dimensional semiconductor nanostructuers are currently the subject of intense research because of the potential for nanoscale electronic and optoelectronic applications [2]. They are expected to exhibit unique physical properties, distinctive from those of the bulk materials. Monoclinic gallium oxide (β-Ga2O3) is an important wide band gap (Eg ≈ 4.9 eV at 300 K) material due to good chemical and thermal stability. It has a variety of applications including transparent conducting oxide [3], optical emitter for UV [4], and gas sensors [5]. The synthesis and characterization of β-Ga2O3 nanostructures have been lately progressed. Various methods, e.g., arc discharge [6], laser ablation [7], thermal oxidation [8], carbothermal reduction [9], were developed by a number of research groups. Indium oxide (In2O3) is another important wide band gap (Eg ≈ 3.6 eV at 300 K) transparent semiconductor. It has been widely used in optoelectronic devices as solar cells [10], flat panel display materials [11], and gas sensors [12]. In2O3 nanostructures were prepared by physical evaporation [13], sol-gel template method [14], an electrodeposition [15], and triblock copolymer template method [16]. However, despite the tremendous amount of syntheses, the control of the structure has not been much achieved yet. In this paper, we report a large-scale synthesis of β-Ga2O3 nanowires, In2O3 nanowires, and In2O3 nanobelts.
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