Synthesis And Characterization Of One-dimensional ZnO And GaN Materials

Low-dimensional nanostructures are an important research field in current Nano S&T. Large work has been done on the low-dimensional nanomaterials since the discovery of carbon nanotubes in early 1990's by Iijima of NEC Corporation of Japan. It has not only great significance in understanding fundamental physical phenomena, but also promising applications as functional building blocks for nanodevices in optical, optoelectronic, catalytic, piezoelectric fields. ZnO and GaN are two kinds of wide direct band-gap semiconductor materials. They possess abundant structures and unique properties, which make them promising candidates as functional materials in many fields of application. Currently, Study of low-dimensional structures of ZnO and GaN materials has become a focus of interest of many research groupsIn this Thesis, various methods of synthesizing one-dimensional (1D) ZnO and GaN nanostructures have been summarized. Various novel 1D nanostructures of ZnO have been successfully fabricated via thermal evaporation method. GaN nanowires and nanoribbons have been synthesized for the first time. Their growth mechanisms are discussed, and properties characterized. The main research content and results are as follows:(1) Various novel one-dimensional nanostructures of ZnO have been successfully fabricated via thermal evaporation method without catalyst. The proper conditions for synthesis of ZnO ID structures are investigated. It is found that temperature and the flux of carrier gas are two keys in the growth;(2) Al-doped quasi-aligned ZnO nanorods were prepared on Si (111) substrates by thermal evaporation method. The element Al acts as deep-level impurity, which is reflected in our characterization results;(3) Quasi-aligned ZnCdO nanorods were prepared for the first time by using thermal evaporation of Zn and CdCl₂ on Si substrates with the presence of Au catalyst. The maximum Cd content was up to 16.7 at. %, which was significantly larger than the thermodynamic solid solubility limits. It isobserved that with the doping of Cd, the ultraviolet (UV) near-band-edge (NBE) emission was red-shifted to 407nm (3.04eV) from 386nm (3.21eV). the direct modulation of band gap caused by Cd substitution is responsible for the red shift;(4) The Raman Spectra of nanorods were carefully studied. The relations between Raman modes and stress in materials are investigated;(5) GaN one-dimensional nanomaterials are prepared by MOCVD using TMGa and high-purity ammonia as reactants. Ni(NOa)2 is used as the catalyst precursor and plays an key role the synthesizing process of GaN nanorods. The successful preparation of GaN one-dimensional structures by MOCVD using Ni as the catalyst is firstly reported in the nation.