Preparation Of ZnO Films By Thermal Evaporation And Their Cathodoluminescence Properties

Zinc oxide is receiving more and more attention for its application in UV light-emitters, aristors, transparent conductors, high power electronics, surface acoustic wave devices, piezoelectric transducers, gas-sensors, and windows for displays and solar cells. It has a room temperature band gap of 3.37eV and an exciton binding energy of 60 meV. The large band gap makes ZnO an excellent candidate for UV and blue light emitters, and the exciton binding energy could enable practical semiconductor lasers with low threshold, even above room temperature. In addition to the above advantages, many other key features of ZnO make it a very good replacement for GaN, availability of wet chemical etching, high resistance to damage from radiation, high thermal conductivity of ZnO, semi-insulating capability, ease of production in thin film form, and high quality production in bulk form for homoepitaxial substrates. Compared with other methods, the thermal evaporation process is quite simple, cost cheap, and high production rate, which makes it a promising method for future application..This thesis aims at establishing optimal parameters for synthesizing ZnO films from pure ZnO powders on Si substrate by thermal evaporation. The structure and properties were characterized by x-ray diffraction (XRD) , Scanning electron microscopy (SEM), man spectrumand cathodoluminescence (CL). The growth mechanisms and cathodoluminescence were discussed.The main contents include:A appropriate temperature zone for growing ZnO films from a source of pure ZnO powders on Si substrate by thermal evaporation was determined by a series of experiments at the evaporating temperature from 1200℃to 1400℃. The film structures were characterzed by XRD and Raman spectrum.The effects of deposition conditions such as the substrate temperature, the ambient conditions and the duration time in the above temperature zone are discussed in considerable details.Oriented growth of the ZnO films were observed by XRD.The films deposited at the conditions of the evaporation temperature of 1380...