Effect of growth condition on optical characteristics of nanostructure in chemical vapor deposition grown ZnO
Yao-Teng Chuang1*, Jhe-Wei Liou1, Kuan-Kan Hu1, Wei-Yen Woon1
1Department of Physics, National Central University, Taoyuan County, Taiwan
* presenting author:莊曜滕, email:frank77411@gmail.com
Nanomaterials become broadly interesting when associated with its low dimensionality, quantum confinement, and the critical role in potential nanoscale device application, such as field-effect transistors, field emitter, sensors, and resonators. ZnO is a possible candidate for optoelectronics and piezoelectricity effect due to its wide direct band gap (3.37eV) and a large exciton binding energy (60meV) at room temperature. It is therefore an important issue to understand the optical characteristics of different type ZnO nanostructure in order to realize the application in nanodevices.

ZnO nanostructure is fabricated on sapphire and GaN/sapphire substrate with home-made chemical vapor deposition(CVD) system at different oxygen partial pressure (1~10sccm) under temperature from 700 to 800℃. High-resolution X-ray diffractometry, scanning electron microscope, and photoluminescence are utilized for analyzing the characteristics of ZnO nanostructure. Different nanostructure but same crystal orientation can be found on different substrate due to lattice-mismatch and wetting layer difference. Growth rate and aspect ratio of ZnO nanostructure on the same substrate are strongly related to oxygen partial pressure under the same temperature. Although similar n-type doping related photoluminescence peak can be observed on films grown on both substrates, high aspect ratio needle-like nanostructure can only be found on sapphire substrate and only at the top surface of GaN substrate with island-like bottom layer. Specific photoluminescence peaks are identified, which is corresponding to each nanostructure with different aspect ratio.

Keywords: ZnO, chemical vapor deposition, photoluminescence