Synthesis, Property And Mechanism Of SiC And GaN Semiconductor Nanomaterials And Their Array

Recently, a great of interest in wide band gap semiconductor of SiC, GaN and Ga2O3 quasi one-dimensional nanbmaterials has been stimulated by the discovery of novel properties and the great potential application in the optical, electrical and mechanical field. In this dissertation, quasi one-dimension materials and the arrays of SiC GaN and Ga2O3 nonawires were synthesized and studied systematically. The main results are as follows.Large quantities of high-purity β-SiC nanowires without and with amorphous SiO2 wrapping layers have been synthesized at relatively low temperature and with no confined spaces via a new simple method - the vapor-chemical- reaction approach, in a homemade graphite reaction cell. A mixture of milled Si and SiO2 and C3H6 were employed as starting materials. These two nanostractures were obtained, respectively by controlling the rate of Si and SiO2 powders and other preparation conditions. The analysis results show that both the nanowires without wrapping layers and the center thinner nanowires of the coaxial nanocable with wrapping layers are cubic structure P-SiC single crystalline, whereas the outside wrapping layer of the coaxial nanocable is an amorphous SiO2. In above two nanostructure, β-SiC nanowires axes lie along the <111> direction. Two kinds of possible growth mechanisms are proposed for two different nanostructures. Some unique properties are found in the Raman Scattering Spectra and Photoluminescence Spectra from two p-SiC nanostructures, which are different from previous observation of β-SiC material.Large-scale highly ordered SiC nanowires arrays were prepare in anodic alumina membranes by simple vapor-chemical- reaction approach at 123 0℃. Field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray spectroscopy (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and- high-resolution transmission electron microscopy (HRTEM) indicated that the highly ordered nanostructure arrays consist of single-crystalline cubic p-SiC nanowires in the uniform pores of anodic alumina about 30-60nm in diameter and 8um in length. The nanowire is solid and the periphery is very clean without any coating of amorphous material. The β-SiC nanowires axes lie along the <111> direction and possess a high density of planar defects. The growth mechanism of the ordered nanowires is discussed.Novel 2-D semiconductor SiC nanonetworks have been synthesized at relatively low-temperature via vapor chemical reaction approach in homemade graphite reactioncell. EDX, XRD and HRTEM indicated that the nanowires with diameter of about 20-70nm are single crystalline β-SiC and the growth direction is along [111]. The growth mechanism of β-SiC nanowires networks is discussed.Low-dimensional GaN materials, including nanorings, nanoribbons and smooth nanowires have been synthesized by reacting gallium and ammonia using Ag particles as a catalyst on the substrate of MgO single crystals. FE-SEM, EDX and XRD indicated that the low-dimensional nanomaterials were wurtzite GaN. The growth mechanism of the different morphologies GaN nanomaterials is discussed. New features are found in Raman scatterings for these low-dimensional GaN materials, which are different from the previous observations of GaN materials.Regular arrays of GaN nanorods have been synthesized by reacting gallium and ammonia using Au as a catalyst on MgO single crystal substrate treated by chemical etching. FE-SEM, EDX, XRD, SAED and HRTEM indicated that the regular arrays nanorods were wurtzite single crystal GaN and the nanorods were tapered from the base to their upper end, which compatible with the theoretical result. We suggest that regular tactic square shape with steps on the single crystal MgO and discontinuity of the Au film may play an important role during the formation of regular arrays of GaN nanorods.A new form of GaN nanomaterial-nanotweezers has been obtained by chemical vapor deposition on the specially prepared cubic MgO (100) s...