Sscvd Preparation Of Zno Thin Films

Zinc oxide (ZnO) is one of the most promising semiconductor materials for ultraviolet laser at room temperature due to its wide direct band gap (Eg=3.37eV) and large excitonic binding energy of 60 meV. ZnO films are commonly grown in polar c (002) direction. The intensity of luminescence of polar ZnO films is not high enough, while nonpolar wurtzite ZnO films provide a promising good performance of luminescence. In this thesis, nonpolar a～b oriented ZnO films have been prepared on Si(100) by single source chemical vapor deposition(SSCVD) using a new kind of solid precursor(Zn_xO_yC_zH_i). The growth mode,structure and photoluminescence of nonpolar ZnO films were studied in detail. The major results are listed as follows:1. The growth mode and structure properties of ZnO films have been studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and atom force microscope (AFM). The results show that the precursor temperature could impact the quality of ZnO films but not the growth mode, while the growth temperature can efficiently improve both growth mode and structure of ZnO films. In this thesis, good nonpolar ZnO films with a～b axis orientation were prepared when precursor temperature was 210℃and growth temperature was 350℃.2. The effect of annealing temperature on both quality and photoluminescence of nonpolar ZnO film was also studied. The conclusion is: it's annealing temperature that induces recrystallizatoin of ZnO films, and in this way, the crystallization and stoichiometic proportion of ZnO films are improved. When the annealing temperature was 700℃, ZnO films has the largest preferred orientiation in (100) orientiation (f(100)), the quality of ZnO crystallite is the best, and the stoichimometic proportion(O/Zn) of ZnO films is 1.02 which means the ZnO films contain excessive O atoms. Photoluminescence results show that deep level emission of ZnO films is the weakest when annealed under 700℃.3. To obtain the details of photoluminescence properties of nonpolar ZnO films, we used He-Cd laser as exciting source. The temperature dependence photoluminescence was first investigated, and the free exciton(E_A) emission peak,neutral-donor bound exciton (A~OX) emission peak and E_a-1LO,E_A-2LO,E_A-3LO and E_A-4LO could be found in the 10K PL spectra. The free exciton emission peak is very strong but the bound exciton emission peak is weak at low temperature, accounting for high crystalline quality of nonpolar ZnO films.4. The relationship between growth mode and the intensity of luminescence was also discussed. Polar ZnO films lead to a strong internal electrostatic because of the spontaneous polarization and piezoelectric effect, and hence decreases the intensity of luminescence. Nonpolar wurtzite ZnO films provide a means of circumventing the physical phenomenon and a good performance of luminescence.