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.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0726107-165957 |
| Date | 26 July 2007 |
| Creators | Jhong, Siao-yi |
| Contributors | Liuwen Chang, Ming-Chi Chou, Jih-Jen Wu |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0726107-165957 |
| Rights | not_available, Copyright information available at source archive |
Page generated in 0.0039 seconds