Synthesis And Characterization Of Ga₂O₃nanoparticles By Chemical Vapor Deposition

Nanometer materials with its peculiar optoelectronics, has caused high attentionof people since it comes to the word. It has experienced several stages of thenanocrystals, nanocrystals, nanocomposite materials and nanoassembly materials, andthe application of the nanomaterials with special properties has been the researchfocuses. Now it has achieved some success in the preparation technology ofnanomaterials, for example, SiO₂, TiO₂, CaCO₃, graphite and many metalnanomaterials could already be applied to scale-production, and bas widelyapplication in the electronics industry, biological medicine and environmentalprotection.Monoclinic β-Ga₂O₃is a deep ultraviolet transparent semiconductor oxide, whichhas a direct wide-band gap range from4.8eV to5.1eV and has excellentcharacteristics in optical and electrical. It is highly transparent in the spectral regionbetween350nm to1100nm, and its refractive index range from1.88to1.94. Thesingle crystal’s conductivity could be changed from insulator to the conductor at roomtemperature. Monoclinic β-Ga₂O₃can be used as a deep ultraviolet transparentconductive oxide, high temperature oxygen sensors, light-emitting phosphor, etc., andis a new materials having a huge potential application in optoelectronic devices,transparent oxide electronics and other fields.Now considerable efforts have been exerted to synthesize various β-Ga₂O₃nanostructures, such as nanoparticles, nanowires, nanorods, nanoribbons,andnanocomb, nanograss, nanocoil, etc., using techniques such as carbothermal reduction,physical evaporation, microwave plasma reaction methods, metal-organic chemicalvapor deposition, sol-gel methods, laser ablation method, catalyst support method,catalytic arc discharge method, thermal annealing method, etc. However, most ofthese techniques require complicated equipment and extreme experimental conditions.β-Ga₂O₃nanometerials have been applied to scale-production using the catalytic arcdischarge method and the vapor-solid mechanism. At the same time some problems exist including: unstable product quanlity and low purity. Chemical vapor depositionmethod is a way to form a thin film using various gas reaction. It not only has manyadvantages such as high deposition rate, high purity, less defect and membrane layeretc, and is also suitable to deposited on the complex shaped substrates, which hasbeen widely applied in semiconductor industry.Monoclinic β-Ga₂O₃nanoparticles were successfully fabricated on Si（111）substrates with NiCl2as a catalyst by chemical vapor deposition using metallicgallium and oxygen as sources in this paper. The method requires that the reactantsmust have enough high vapor pressure, but metallic gallium has low vapor pressure.So GaF2is adopted as dispersant in the experiment, which is an inert salts and canimprove vapor pressure of the metal Ga in the way of increasing the metal effectivearea. The morphology, microstructure, composition, and PL of the samples wereexamined using an X-ray diffractometer, Fourier-transform infraredspectrophotometer, scanning electron microscope, high-resolution transmissionelectron microscope, Raman spectroscopy and PL spectrophotometer, respectively.Research results show that monoclinic β-Ga₂O₃nanoparticles with diametersapproximately ranging from0.5μm to1.5μm, has two strong Ga-O vibration infraredabsorption peak at455cm^-1and694cm^-1, and also found in a typical Ga-O vibrationpeak at198cm^-1in Raman spectroscopy. In addition, a broad emission band rangingfrom300nm to650nm is observed in the PL spectra of β-Ga₂O₃nanoparticles,including ultraviolet light, blue light and green light emitting. Sn doped Ga₂O₃nanoparticles are also prepared by chemical vapor deposition method, the results ofscanning electron microscopy show that, Sn-doped Ga₂O₃nanowires are easy tosynthesis at low temperature, and nanoparticles are easy to synthesis at highertemperature. This paper introduces the influence on particle morphology structure andluminescence properties which are affected by different experiment conditionincluding oxidation time, oxidation temperature, concentration of catalyst and Sn-doping. In addition, the formation mechanism of the β-Ga₂O₃nanoparticles isdiscussed and can be explained by the Vapor-Solid growth mechanism.