Zinc oxide (ZnO) has gained many interests in the research of wide band-gap semiconductor materials nowadays. ZnO has attracted much attention because of its high excition bound energy (60meV), and it¡¦s promising to gain application in the field of optoelectronic such as ultraviolet light emitting devices (UV-LED) and laser diode (LD) etc. This study aims to investigate the growth condition of ZnO and to control the growth direction. ZnO was grown on LiAlO2 (LAO) (100) substrates by chemical vapor deposition (CVD) with zinc source Zn(C5H7O2)2. The different reacting temperature from 500¢J to 650¢J and the flow rate of oxygen were studied. In the result of scanning electron microscope (SEM), the surface morphology of ZnO showed two different structures, hexagonal structure and non-hexagonal film structure. And the side view of hexagonal structure showed double layers. The key factor for the transformation of double layers from film to column structure is the equilibrium of growth temperature and substrate stress. The crystals structures and epitaxial relationship were studied by X-ray Diffraction Pattern (XRD), Electron Backscattering Diffraction (EBSD). There are two kinds of ZnO epitaxial growth on LiAlO2 (100) substrate, one is c-plane of ZnO(0001)// LiAlO2 (100) and another one is m-plane of ZnO(10 0)// LiAlO2 (100), the latter one has a smaller lattice mismatch. The results of the strong UV and green emission peaking were shown in photoluminescence (PL) spectrum. Under the control of substrate temperature, c-plane polarized ZnO films were grown at 500 ¢J, and m-plane nonpolar ZnO films were grown at 650¢J. Rectangular structure could be formed between 550¢J and 650¢J. With the increase of substrate temperature, the size of rectangular became larger. At last, uniformed film would be formed at 650¢J. In addition to benefit the formation of m-plane structure, high temperature helps the sideward growth to form uniform film. In the experiment of oxygen flow, we found that c-plane hexagonal structure appeared on the m-plane film while the oxygen flow lowered to 50 sccm. And there were large numbers of oxygen vacancies measured by PL. The oxygen flow of 100 sccm is more suitable to obtain higher quality m-plane film than 400 and 50 sccm. At last, the growth time experiments were done under the growth temperament of 600¢J.Island structures of c-plane and m-plane ZnO combined with the growth time increased, and the island become larger. The XRD measurement showed that crystallinity of ZnO become better with the growth time increased.

In this study, epitaxial ZnO films were grown by chemical vapor deposition (CVD) on LSAT(100) substrate. A high-quality [100] (La0.3,Sr0.7)(Al0.65,Ta0.35)O3 (LSAT) single crystal with the diameter of 60mm was grown by Czochralski pulling technique in our lab. Epi-ready LSAT substrates with rms roughness of 0.30nm ~ 0.35nm were used for all of the experiments. Nonpolar ZnO with [11-20] orientation (a-plane) was directly grown on a (100) LSAT substrate without any buffer layer by chemical vapor deposition (CVD) method. (100) LSAT single crystal substrate is loaded in a 2¡¨ quartz tube inserted to a two-temperature zone furnace. Zinc acetylacetonate hydrate (Zn(C5H7O2)2¡DxH2O, Lancaster) source was vaporized at the lower temperature of 130~140oC. The vapor was carried by a mixture of N2/O2 gas flow into the high temperature zone where the (100) LSAT substrate was located. At first, the pressure of the quartz chamber was pumped to 8¡Ñ10-3 Torr, and then kept at 150 ~ 250 Torr. The flows rates of both O2 and N2 are 500sccm. During the growth, the temperature was varied from 700 to 780oC. The growth conditions were controlled by adjusting the growth temperatures and chamber¡¦s pressures. The overall reaction was: Zn(C5H7O2)2 +12O2¡÷ZnO+ 10CO2 +7H2O Scanning electron microscope [(SEM), JEOL JSM-6330TF)] is used to examine the different surface morphologies of ZnO epitaxial film. The orientation and structure were investigated by X-ray diffraction pattern (XRD) using a Siemens D5000 X-ray diffractometer with a Cu anode at 40 kV and 30 mA. The wavelength of X-ray radiated from the Cu K£\1 is 0.1540 nm. The X-ray scan step is 0.01¢X. A JEOL 3010 scanning transmission electron microscope (STEM) operated at 200kV was employed to characterize the microstructures and orientation of the nonpolar ZnO film. Cross-sectioned TEM samples were prepared using the focus ion beam lift-out method. A Pt layer of about 8nm in thickness was pre-deposited on the sample to prevent charging. Room temperature photoluminescence (RT-PL) measurements were performed using a 325nm He-Cd laser. The emitted light was detected by a Jobin-Yvon TRIAX 550 monochromator with 0.025nm resolution.

Zinc Oxide (ZnO) has great potential for applications on ultraviolet/blue light emitting devices because of high exciton binding energy and low cost. This research use low lattice-mismatched £^-LiAlO2 (LAO) substrate to grow ZnO epitaxial films by chemical vapor deposition (CVD). The first part of the present study deals with effect of processing parameters including temperature of Zinc procuser, sample position and growth temperature on ZnO epilayer. High the precuser temperature and long distance between sample and center of CVD furnace resulted in high growth rates. When growth rate was low, (10 0) ZnO (m-ZnO) was obtained and its crystallinity and luminescence property were poor. After increasing the growth rate to a certain extent, the surface of epilayer was flat and the crystallinity was improved. A further increase of growth rate resulted in a mixture of m-ZnO and c-plane in the ZnO epilayer. Based on the first part of study, the second part was focused on examining the effect of a nanosized buffer layer on inhibiting the nucleation of c-plane ZnO. Results showed that the nucleation of c-plane ZnO was indeed inhibited at low growth temperature. Finally, the crystallinity the optical property of the epilayer were improved by introducing a thick and flat buffer layer of ~170 nm in thickness.