Growth ZnO Single Crystal And Film By Atmospheric Pressure Chemical Vapor Deposition

Zinc oxide (ZnO) is one of the wide direct bandgap semiconductors with wurtzite structure, which has a band gap of3.37eV and free exciton binding eneygy of60meV at room temperature. With the excellent photoelectricity, piezoelectric, magnetic, chemical stability and biologic safe properties, ZnO is also one of the candidates for UV photoelectric detectors, sensors, surface acoustic wave devices, short-wave lasers and light emitting diodes, and so on. These make ZnO to be a research hot point in recent years. However, a main handicap of the development of ZnO-based devices is lacking of high quality, low cost and suitable commerce using ZnO crystal and film. To solve this problem, in this thesis, a home made, simplified and low-cost atmosphere pressure chemical vapor depositon (APCVD) syatem was utilized to grow ZnO crystals and films. The special adjusting effects of different factors on the morphology and the optical properties of ZnO was researched, and the high quality ZnO crystals and films were finally gained. The main researching points are listed as follows:1. Adjusting ZnO growth in the APCVD system. This thesis includs the different effects of growth temperatures (800-900℃), substrates (quatz, Si, Al2O3and Au, Pt, ZnO buffer layers), ratio of HCl and NH3(0-∞), concertations of H2O vapor (water temperature60-90℃) and the growth locations (5-35cm from center). The key effects of these factor on ZnO crystal growth are discovered.2. Growth ZnO single crystals on Al2O3substrates in the APCVD system. After adjusting the experimental parameters, hexagonal (0001)-facet ZnO single crystals and high density hexagonal ZnO crystals were respectively achieved. The optical images, X-ray diffusion patterns, Raman and PL spectra showed the wurtzite structure, high element purity and charming optical properties of the ZnO crystal. The lateral growth rate is faster than the vertical rate of ZnO crystals on Al2O3substrate, which was testified by a three-time continuous growth experiment. The mechanism of lateral epitaxy mode was also deeply discussed3. Growth ZnO nanostructured film on ZnO/Al2O3substrate in the APCVD system. The ZnO buffer layers were adopted to reduce the lattice mismatch and enhance the density and uniformity of ZnO nuclei, and large-area nanowall and nanoporous ZnO films were respectively gained. The nano sheets of nano-wall film presented120°assembly angles, and the inner-diameters and the distribution of the nano porous were uniform. The properties and growth mechanisms of the two films were also discussed.4. Growth ZnO continuous film on ZnO/Al2O3substrate in the APCVD system. The crystal structure and growth mechanism of ZnO continuous film were discussed.