Synthesis, Characterization, Optoelectronical Properties And Growth Mechanism Study Of Zinc Based ZnO/ZnS Micro & Nanostructures

ZnO is one of the most important narrow band-gap semiconductors of the third generations. It has great physical chemistry properties in photoelectronic filed. And also because of its piezoelectric, nonlinear, diluted magnetic properties, ZnO has been studied widely in the new researching fields, such as piezoelectronics, spintronics and so on. Moreover, ZnO is abound resources, environment friendly, low cost, chemical and thermal stability (cannot react with air under high temperature), radioresistance and easy to be etched under wet chemical circumstance. All of the properties make ZnO more challenging than the other third-generation semiconductors, SiC and GaN. So, the research on ZnO materials is always the foreland fields in materials science and engineering, in which both of the synthesis of nanostructures and the growth of bulk single crystals.Nanostructure, especially the one dimensional structure has attracted great attention because of its value and application on understanding the basic physical concepts. It also has great value in nanoelectronics and nano-optoelectronics. For example, the nanostructure is an ideal system on researching the electrical transport properties, optical properties, mechanical properties of the materials. Finally, the nanostructure would play an important role on optical interconnection and other functional nanoelectronic or photoelectronic devices. ZnO has its natural superiorities on synthesis of one dimensional nanostructure because of its polarized growth property. In the past decades, the ZnO nanostructures have been synthesized by different techniques and methods. Generally speaking, these methods can be divided into two classes:liquid phase method and vapor phase method. The vapor phase method contains: Pulsed laser deposition (PLD); Chemical vapor deposition (CVD); Chemical transport method; Thermal evaporation method; Metal organic chemical vapor deposition (MOCVD); Carbothermal method and so on. The advantages of vapor phase method are that, it can growth every inorganic nanostructure and nano materials. The weak point is, the reaction should be taken under higher temperature and also this method needs high requirements on equipments. The liquid phase method is an option that provides a more flexible technique and the cost is lower. In the liquid phase method, the growth of ZnO (ZnS) nanostructure was determined by the growth habits of polar crystals. However, it is hard to control the morphology of nanostructure in liquid phase method, and also hard to let the specific nanostructure growth on the substrate which is need in devices. So, it has much value to develop new hydrothermal systems which can synthesis uniform ZnO (ZnS) nanostructure on conductive substrates. It also has great importance in promoting the usage of ZnO (ZnS) on nanotechnology field.Several methods have been developed on the study of large scale ZnO single crystals, such as chemical vapor transportation, high temperature melt method, molten salt growth method and so on. However, these methods have not gone commercial production like the hydrothermal has done. Recently,3 inches ZnO single crystal has been grown through hydrothermal method. But the research on the synthesis of ZnO single crystal is just the study of experiments and theories which took alkali as the mineralizer. Based on the alkali mineralizer, Zn(OH)42- is the growth units of ZnO crystals. The coordination polyhedron growth unit theory has been proposed based on some other crystal growth. The ZnO crystal growth morphology could be predicted through this theory together with the calculation of crystal growth unit stabilization energies. However, it is hard to explain the ZnO nanostructures morphology synthesized by solution method. So, it has great potential to study on the synthesis of ZnO crystals through hydrothermal method, in which different anions or molecules could affect the ZnO crystal growth and morphology.ZnO is a typical polar crystal. The study on ZnO can be extended to other polar crystals. So, the study of the work is based on ZnO, and ZnO nanorod arrays have been synthesized on Zn substrate through a simple hydrothermal system. The properties and defects have been studied through electronic measurement and spectrographic technique. By using different mineralizers, Zn ions and different ligands formed Zn ion complex compounds, and this have effect on the growth of ZnO micro crystals. Explore new mineralization, the ZnO micro crystals have been successfully synthesized under moderate and low temperature. AFM has been carried out for the study of ZnO micro crystal morphology. The main works are as follows:1. Study of the Zn-based ZnO micro-nano structures synthesized by hydrothermal method.The micro- and nanostructures of Zn-based ZnO have been synthesized through hydrothermal method. The microstructure of ZnO has been characterized. We found that the Zn-based ZnO composite structure grown along the ZnO nanocrystals, then the electronic and optic properties of the structure were studied. At last, we made a deep research on the defects enfolded on the ZnO micro- and nanocrystals.2. Study of the Zn-based ZnO micro- and nanostructures synthesized by solvothermal method.The micro- and nanostructures of Zn-based ZnO have been synthesized through solvothermal method, and also the structures have been characterized. The ultraviolet-visible absorption spectra of Zn-based ZnO micro- and nanostructures have been studied. Then we have made a deep research on the synthesis chemical mechanism of ZnS micro- and nanostructures.3. The influence on the growth and features of ZnO micro crystals caused by different ligands in hydrothermal method.Took zinc slab as the Zn resource, and with different mineralizer, we have synthesized different ZnO micro- and nanostructures. The chemical mechanism of ZnO micro- and nanostructures has been studied. The rules of competition coordination between Zn ions and other anions have been clarified.4. The study of chemical mechanism of Zn-based ZnO and ZnS. The coordination rules between Zn ions and other ligands have been studied through the aspect of ligand radius and Pauling electronegativity. We took NaCl (or other chlorides) as the mineralizer, and have grown the ZnO single crystal under hydrothermal method with moderate and low temperature. The ZnO single crystals synthesized under this condition have been characterized by AFM.In conclusion, a homogeneous ZnO or ZnS nanostructure array on zinc slab has been synthesized through a simple hydrothermal and solvothermal method. The features and properties have been characterized. We especially studied the electronic and optic properties of Zn-based ZnO nanorod arrays, and made a deep research on the influences of properties of defects enfolded on the nanorods. We took different mineralizers, and synthesized ZnO micro- and nanostructures of well crystallized and different morphology. The coordination between Zn ions and anions or molecules together with the influence on ZnO single crystals has been studied. We also studied the coordination rules between Zn ions and other ligands, by means of the radius ratio of anion or molecule ligands and Zn ions, and also by means of the electronegativity relative to Zn atoms. The growth of ZnO single crystal under moderate and low temperature has been studied with new mineralizer. All of the studied provide fundamental basis for the research of new ZnO nanostructure devices, such as Solar Cells, chemical and biological sensors. And also be ready for the synthesis of large scale ZnO single crystal under hydrothermal method.