Low-temperature growth and characterization of epitaxial ZnO nanorods by metalorganic chemical vapor deposition
- PDF / 254,346 Bytes
- 5 Pages / 585 x 783 pts Page_size
- 32 Downloads / 232 Views
Dong Jun Park and Jeong Yong Lee Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Yusong-gu, Daejon 305-701, Korea (Received 3 April 2007; accepted 16 April 2007)
By injecting additional argon gas, we were able to grow one-dimensional ZnO nanorod arrays with a uniform distribution on a large scale at a low temperature of less than 330 °C by metalorganic chemical vapor deposition. All of the nanorods grown on the sapphire substrate had a 30° in-plane rotation with respect to the substrate and showed the epitaxial characteristics of [101¯0]ZnO //[112¯0]sapphire, despite the low-temperature growth. These ZnO nanorods with high crystalline quality exhibited a high enhancement factor and low turn-on field value, thus having good potential to be used as a field emitter.
I. INTRODUCTION
ZnO-based semiconductors have recently attracted a lot of interest due to their potential applications as light emitters in the ultraviolet (UV) wavelength range. Among the different kinds of ZnO-based semiconductors, one-dimensional (1D) structures including nanowires, nanorods, nanoneedles, etc. have been particularly studied, because of their many physical and chemical advantages, such as their low-temperature growth, high exciton binding energy, low cost, and high resistance to radiation damage.1–4 Early studies on the synthesis of 1D ZnO nanostructures mainly focused on the high-temperature thermal evaporation method using metal catalysts (vapor–liquid– solid mechanism).3,4 It was reported quite recently that ZnO nanorod arrays could be fabricated by metalorganic chemical vapor deposition (MOCVD), the conventional growth system of compound semiconductors, without catalysts using the vapor–solid mechanism.5,6 Vertically well-aligned ZnO nanorods were successfully synthesized on sapphire substrates by a catalyst-free MOCVD in the growth temperature range of 450 to ∼600 °C,5–9 while physical vapor deposition needed a higher growth temperature and the presence of metal catalysts.3,4 The growth of ZnO using MOCVD makes it possible to obtain nanorods with a hexagonal-shaped column and epitaxial characteristics on c-plane sapphire substrates. The a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2007.0248 2032 J. Mater. Res., Vol. 22, No. 7, Jul 2007 http://journals.cambridge.org Downloaded: 03 Apr 2015
field-emission characteristics of the 1D ZnO nanostructures have also been studied to evaluate their potential use as a UV field emitter for displays, due to the lowtemperature process, low emission barrier, high thermal stability, and high saturation velocity.10–15 Moreover, the successful synthesis of nanostructures at low temperature could lead to the expansion of their field of application to other areas, including displays, solar cells, and sensors, because these technologies require the use of soft and transparent substrates such as glass and plastics that cannot tolerate the high-temperature process.13,16,17 However, the low-temperature process
Data Loading...
