| Along with the development of science and technology, the materials with themore excellent properties are becoming more and more popular and the micromation forthe devices is being current. These promote that the people are greatly interested in theresearch of low-dimensional materials. There are three points in the research oflow-dimensional materials: (1) simplified description on the physical phenomenaoccurred in the three-dimensional materials;(2) to find the unique physical phenomenaand properties of low-dimensional materials;(3) synthesis of new three-dimensionalmaterials from low-dimensional materials. Since the discovery of the carbon nanotubesin 1991, materials with nanotube, nanowire and nanorod structures have beenextensively investigated for their interesting and novel properties. They have uniquestructures. On the other hand, many novel physical properties such as QuantumInterference Effects in electrical properties, Quantum Confinement Effects in opticalproperties and the enhancement of mechanical properties, occur, which are differentfrom the block materials. Nanomaterials are important for basic theory research andpreparation of nano-devices. Take carbon nanotubes for examples, it has been provedthat it can be used to prepare high-light field-emission electron source, nano-leads,nano-cuvettes, nano-probes and nano-balance for weighing up the micrograins. It isfound that single-wall carbon nanotubes have the superconductivity. And that M-Sheterojunction devices, which are made of carbon nanotubes and silicon nanowires,have rectigying effect.Wide-band gap gallium nitride (GaN) is one of the direct gap semiconductors andband gap is 3.4 eV at home temperature. It is the perfect material for preparing blue andgreen light-emission diodes and semiconductor laser. The theory and experiments showthat GaN nanostructures markedly improve the luminescence properties of the devices.These lay a foundation for preparing high-integration and high-quality photoelectrondevices.One-dimensional GaN nanowires were synthesized through replace reaction usingmultiple wall carbon nanotubes (MWNT) as the template in 1997. The nanowires arelong up to tens of micrometers and have the diameters from 4 to 50 nanometers. But thepurity and yield of the production are both low and the preparation method is verycomplicated. GaN nanowires were synthesized through the reaction betweenvapor-phase Ga2O and NH3 using porous Al2O3 as the template in 1999. This method issimple and has a higher yield except that the low purity of the production. Meanwhilethe morphology of so-prepared nanowires are not enough perfect. In 2000, XiaolongChen et al. synthesized smooth and straight GaN nanowires through the reactionbetween metal Ga and NH3 on the LaAlO3, silica and single-crystal MgO substrates.According to the results, Xiaolong Chen et al. first brought up the model of the radialgrowth of a nanowire and analyzed the morphological stability of a nanowire during thevapor–solid (VS) side growth process. In 2003, Joshua Goldberger et al. succeeded insynthesizing the GaN nanotubes array using hexagonal ZnO nanowires as the templates.First GaN layers were deposited onto ZnO nanowires through chemistry vapordeposition mehod. Then ZnO were removed through thermal reduction or evaporationmethod. The thickness of so-prepared nanotubes could been reduced down to 5nanometers, which was less than the Bohr radius of GaN excitons. As a result ofquantum confinement effects, the PL spectra produce blue-shift. These GaN nanotubeshave excellent mechanical strength, electrical and optical properties and have apromising material for nano-capillary electrophoresis, nano-liquid biochemistry,nano-scale electrical devices and optical devices.In this paper, GaN one-dimensional nanostructures were prepared throughmagnetron sputtering and ammoniating progress on Si(111) substrates. The twoexperiment routes are carried out to synthesize GaN one-dimensional nanostructures: (1)GaN nanostructures are synthesized on Si(111) substrates using metal Mg as catalyst;(2)GaN nanostructures are synthesized on MgO middle layer deposited on Si(111)substrates. The morphology, microstructure, and components of nanostructures wereanalyzed through scanning electron microscopy (SEM), transmission electronmicroscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-raydiffraction (XRD), Fourier transformed infrared spectra (FTIR) and X-ray photoelectronspectra (XPS) and so on. The effects on GaN nanostructures, which stem from variousexperimental conditions such as the thickness of the middle layer, ammoniatingtemperature and so on, were discussed. According to the analysis and discussion aboutthe results, we have a primary discussion about the growth progress of GaNnanostructures.It is found that various one-dimensional GaN nanostructures and the ammoniatingtemperature had effects on their morphology and arranging mode. Radial-alignednanowires were found at 950℃and 1050℃. Meanwhile, we made an explanation onthe growth progress of the GaN nanostructures using the model of the radial growth of ananowire brought up by Xiaolong Chen et al.Various shaped GaN nanostructures such as lighthouse-shaped nanowires,sword-like nanostructures and so on were found in the samples prepared on Sisubstrates using MgO middle layers. The nanostructures were synthesized basing on VSmechanism and the defects in the surface of films confined and led to the growth ofnanostructures.Besides, we found the evaporation of GaN nanowires occurred when they werebombarded by electron beam. As a result of bombardment, the morphology of GaNnanowires had great changes. They were compact before being bombarded and thesurfaces took on a honeycomb look after being bombarded. |
PDF Full Text Request