Growth mechanism and characterizations of graphene and ZnO nanostructure

• Main Authors: Chung-Wei Chen, 陳重維
• Other Authors: Gou-Chung Chi
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/17949784411734816218

博士 === 國立中央大學 === 物理研究所 === 100 === In this thesis, we will discuss ZnO material with different orientation grown on various substrates and graphene grown on copper foil by home-made atmospheric pressure chemical vapor deposition. For c-plane ZnO films growth, the thin films were grown on c-plane GaN templates. The surface morphology of ZnO film depended on growth temperature and growth time. From photoluminescence (PL) spectrum, near band edge peak suggest that the film stress could be responsible for the blue shift, which corresponding to the XRD results. For the a-plane ZnO nanowires growth, the ZnO nanowires were grown on a-plane GaN templates without employing any catalyst. The growth mechanism on a-GaN was the Volmer-Weber (VW) mode and differed from the Stranski-Krastanow (SK) mode observed for growth on c-GaN. This difference results from the higher interfacial free-energy on the a-plane between ZnO and GaN than that on the c-plane orientation. m-plane ZnO thin film were successfully grown on m-plane p-GaN and be fabricated a heterosturctured light emitting diodes. I-V measurement result shows the turn on voltage was 6 volt and the electroluminescent emission peak was at 458 nm in room temperature with different injected current. Monolayer and few-layer of high-quality graphene have been grown on copper foils with different H2/ CH4 gas ratio by chemical vapor deposition at 17torr. The combination of UV ozone exposure prior to metal contact deposition and annealing of the contacts produces minimum specific contact resistances values of 7x10-7 Ω-cm2 for Ti/Au on graphene layers on SiO2/Si substrates. This is an attractive option for cleaning the graphene surface without issues related to energetic ions in O2 plasma exposures. For application, graphene sensor showed rapid change in the current when exposed to different O2 concentration ambient at room temperature. These results show the potential of graphene for O2 sensing applications.