| Nanometer-sized semiconductor materials have a wide range of applications in many fields, such as optoelectronics, electronics, nano-electrochemical systems and so on. One-dimensional semiconductor nanomaterials have special physical properties due to the quantum confinement effect and the quantum tunnel effect, they can be used in a short wavelength laser, nanoresonator, field effect transistor, ultra-sensitive gas sensor and field emission devices etc. AIN is III-IV compounds with hexagonal wurtzite structure, which has the largest band gap in III nitrides. Size and dimension effect makes it special physical properties, which is considered a very promising material of semiconductor devices. AIN has high thermal conductivity and high breakdown voltage, meanwhile, it also has many other advantages, such as high mechanical strength, good thermal expansion coefficient, large surface acoustic propagation speed, relatively high piezoelectric constant and very low electron affinity. In an inert atmosphere, it is stable in high temperature.in the air, when the temperature is higher than700℃, it will be oxidized. In addition, when the temperature is higher than1000℃, the AIN can still maintain its mechanical properties and piezoelectric properties. Therefore, AIN nanomaterial has a widespread application. This thesis focuses on the fabrication of AIN nanostructures by means of chemical vapor deposition (CVD) and the basic opt electrical properties research. The main content of this thesis includes the following four parts:1. The controlled synthesize of AIN nanostructure by CVD method. Various kinds of aluminium nitride (AIN) nanostructures were prepared utilizing CVD method at atmospheric pressure. The method is a relatively flexible and practicable method to obtain AIN nanostructures, the chemical composition may vary with the composition of the gas phase. The morphology of as grown1D AIN nanostructures on Si substrates is characterized by SEM. The lattice ordering of AIN nanostructures is observed by high-resolution TEM and SAED to analyze the growth direction and crystallinity of the single crystalline phase. The PL spectra are measured at room temperature using a He-Cd laser with200nm excitation.2. The growth mechanism analysis of AIN nanostructures. We employ the vapor-solid (VS) growth mechanism and Ehrlich-Schwoebel barrier mode to analyze the temperature induced AIN structure transformation. With the increase of temperature, the atoms will get larger energy, and they can drop from the upper layer into the bottom layer, which makes the bottom of the nanowires larger. When the growth time of AIN nanomaterials are the same, the diameter of AIN nanowires grown under higher temperature are larger than those grown under lower temperature. The Tersoff and Tromp model can be used to explain this phenomenon in detail. When AIN nanowires begin to grow, many discrete islands will grow on the substrate surface firstly, and the islands can act as nucleation point in a VS growth of AIN nanorods. At higher temperature, the initial nucleation is bigger. As the growth proceeds, the nucleation will grow into one-dimensional nanostructures, so the size of the initial island will affect the final diameter of AIN nanowires directly.3. Preparation of the PS colloidal template and its mechanism investigation. We prepare the PS colloidal template using single gas-liquid interface self-assemble method, and study the influence of annealing temperature and annealing time on the PS spheres. The different size of the PS has different variation under different annealing conditions. When the colloidal crystal film is prepared, the silicon dioxide sol gel is filled into the space of the PS, and then we can get a patterned Si substrate, that is a small exposed circular substrate, where is the position of the PS balls before moved by the chemical solvent.4. Patterned AIN nanostructure preparation and its properties investigation. Use the patterned substrate to grow AlN nanomaterial. The AIN nanostructures can grow in the exposed substrate in the specific conditions. The patterned structure can greatly improve the opt electrical properties of AlN nanowires in theory, such as:in field emission performance, this kind of patterned structure can reduce the screening effect so as to improve the field emission (FE) properties. |
