Controlled Structure of Zinc Oxide by Means of Side Flow Type MOCVD

Naoki Yoshii, Atsushi Nakamura, Shigetoshi Hosaka, Jiro Temmyo
2008 ECS Transactions   unpublished
We have demonstrated that the ZnO deposited on sapphire (11) (12)(13)(14)(15)(16)(17)(18)(19)(20) substrate is controlled to various structures by side flow type MOCVD at high temperature (above 973 K). We found that the crystal quality of ZnO having film structure is better than that of ZnO nanorod although they are fabricated under the same temperature condition. Also, in the case of ZnO nanorod, it is found that its crystal quality improves dramatically at higher temperature (1073 K).
more » ... xide materials are known to have interesting optical, electrical, and magnetic properties. Among them, zinc oxide (ZnO)-based materials have been investigated for many years due to its wide-direct band gap of 3.37 eV at room temperature and its large exciton binding energy of 60 meV. Recently, much attention has been paid to ZnO nano/micorostructres 1-3 , such as nanowire, nanorod, nanoneedle, and nano/microcone, which are regarded as promising material for new devices, for example ultraviolet (UV) laser, gas sensors. Various kinds of ZnO nanostructures are prepared by chemical vapor deposition (CVD) 4, 5 , sputtering 6 , electrochemical decomposition 7 , thermal evaporation 8 , vapor-liquid-solid (VLS) processes 9 , which are operated at low temperature less than 973 K or with gold (Au) seeds on a substrate so that ZnO nanostructures can be obtained. Among their techniques, CVD, especially metal organic chemical deposition (MOCVD) is thought to be appropriate for commercial production because it has turned out to be excellent growth technique for nitride semiconductors. In the case of ZnO, however, MOCVD technique for ZnO has a problem that metal organic precursors as Zn are highly reactive with O precursors, such as oxygen and water. When the pre-reaction of these sources occurs ZnO powders produce on the substrate, which gives rise to deteriorating the ZnO structure controllability and declining the ZnO crystal quality. Therefore, we have designed the unique side flow type MOCVD system so as to overcome these problems by optimizing the reactor structure and growth condition. In this report, we have demonstrated that the ZnO deposited on sapphire (11-20) substrate is controlled to various structures by side flow type MOCVD at high temperature (above 973 K). In addition, we have investigated the relationship between ZnO structures and their crystal quality.
doi:10.1149/1.2985837 fatcat:x2r65aqxzzewxk3x35ty363s3i