Basic Research On The Preparation, Performance Of Gallium Oxide Quasi-one Dimensional Nanomaterials And Application

Quasi-one dimensional (1D) nanomaterials, including nanotube, nanowire, nanobelts, and so on, have enormous potential applications in the nanodevices, photoelectric devices, sensors for its special physical and chemical properties, which has been the focus of nanotechnology. At present, the research on the quasi-one nanomaterials is just in the beginning stage, and has been focused two aspects: how to prepare the quasi-one nanomaterials with effective method; how to test its basic properties of photics, electrics and so on. In this thesis, we study the beta-gallium oxide (β-Ga₂O₃) quasi-one nanomaterials. Above all,β-Ga₂O₃ quasi-one nanomaterials were prepared through microwave plasma. Secondly, we study the photics properties ofβ-Ga₂O₃ nanobelts, and the electrics properties ofβ-Ga₂O₃ nanobelts and nanowires. The major research results can indicate as follows:Theβ-Ga₂O₃ quasi-one nanomaterials were prepared through microwave plasma.β-Ga₂O₃ quasi-one single crystalline nanomaterials, including nanowires, nanobelts, nanosheets, and nanograsses, were synthesized through microwave plasma (600W microwave power) of liquid phase gallium containing H2O in Ar atmosphere using silicon as the substrate. Thereinto, the nanowires with diameters of about 20-30 nm were several tens of microns long and the nanobelts with thickness of about 20-30 nm were tens to hundreds of microns long. Compared with methods in other papers, microwave plasma method decreases the reactive temperature, which can extend to prepare other quasi-one nanomaterials. A kind of novel nanostructure, single-crystal ring-likeβ-Ga₂O₃ nanobelts, called nanorings here, has been synthesized by microwave plasma method. The diameter of nanoring is typical 0.2-1μm, the thickness of nanoring is 10-40nm and the width of nanoring shell is 20-150nm. Finally, the growth mechanism of these quasi-one nanomaterials has been discussed.We demonstrated the formation of well-alignedβ-Ga₂O₃ nanostructures in the presence of arrayed Au catalysts using a simple microwave plasma method. Large well alignment of network layeredβ-Ga₂O₃ nanostructures, which was enclosed by theβ-Ga₂O₃ nanobelts formed on the Au-coated silicon substrate. The formation of the nanostructures was enhanced greatly by the Au catalyst and the growth mechanisms can be attributed to the VLS and VS process.Self-assembly plays an important role in the development of nanotechnology. The orderβ-Ga₂O₃ nanobelts arrayed film can be formed through the evaporation of the solution on the silicon substrate. As the driving force for this self-assembly can be attributed to the capillary force between the particles in the suspension, the lateral capillary force is one of the main factors causing the observed self-assembly ofβ-Ga₂O₃ nanobelts. The influence of the liquid of the droplet and concentration to the self-assembly process were also addressed. The self-assembly technology of the lateral capillary forces maybe extend to drive others quasi-one nanomaterials.The Photoluminescence (PL) ofβ-Ga₂O₃ nanobelts synthesized through microwave plasma under different exciting wave is originally studied, and the morphology and the photoluminescence ofβ-Ga₂O₃ nanobelts under different annealing temperature and annealing time are also discussed. The results show thatβ-Ga₂O₃ nanobelts can emit blue and ultraviolet light under the 250nm exciting wave. The 440nm blue light is originated from the recombination of an electron on a donor formed by oxygen vacancy and a hole on an acceptor formed by gallium vacancy, which recombines to emit a blue photon. The 320nm ultraviolet light is deduced that more electrons on donors might be thermally trapped to the conduction band and more holes on acceptors might be thermally trapped to form hole acceptor with increasing temperature, recombining to emit a UV photon.β-Ga₂O₃ nanobelts can emit blue light under the 325nm exciting wave. The 430nm blue light is also due to recombination of an electron on a donor formed by oxygen vacancy and a hole on an acceptor formed by gallium vacancy. There is no UV emission under 325nm exciting wave because the excitation wavelength (325nm) does not match the UV emission band (320nm), which is not enough energy to emit UV photon. No matter what under the 250nm exciting wave and under the 325nm exciting wave, with the increasing of annealing temperature and annealing time, the PL position ofβ-Ga₂O₃ nanobelts remains unchanged, while the intensity of blue light is decreased and the intensity of ultraviolet light is increased. The annealing does not significantly change the morphology ofβ-Ga₂O₃ nanobelts.We connected the two electrodes withβ-Ga₂O₃ nanobelts and nanowires under 150℃, and then plotted the I-V curve. Under the same drain voltage VSD, along with the gate voltage VG changes negative to positive, the more VG, the more conductance of theβ-Ga₂O₃ nanobelts and nanowires, which showsβ-Ga₂O₃ nanobelts and nanowires are n type semiconductor. The current between the source and the drain can be adjusted by variational gate voltage, which exhibits the characteristics of FET. The value of carrier concentration and mobilityβ-Ga₂O₃ nanowires and nanobelts is estimated 3.2×108cm^-1 and 1.25×10^-2cm²/V·s, 3.6×10¹³cm^-3 and 7.9cm²/V·s, respectively. The gas sensor is composed of self-assemblyβ-Ga₂O₃ nanobelts film drived by capillary force, silver slurry and Pt wire. We obtained electrics properties of the sensors under different temperature and O₂ concentration. The conductance of the sensor becomes high under high temperature and high O₂ concentration, which demonstrates the self-assemblyβ-Ga₂O₃ nanobelts film can construct high O₂ sensor.During the research on quasi-one nanomaterials, based on the current theory and conditions, we found new method to directly prepare several quasi-one nanomaterials, and studiedβ-Ga₂O₃ nanobelts characteristics of photoluminescence,β-Ga₂O₃ nanobelts and nanowires characteristics of electrics properties, and constructed a simple nanodevice of FET. We also constructed sensor using self-assemblyβ-Ga₂O₃ nanobelts film.β-Ga₂O₃ quasi-one nanomaterials have good practical applications in the nano-photoelectric materials and nano-semiconductor materials.