Growth and Characterization of ZnO Nanonail
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Growth and Characterization of ZnO Nanonail H. W. Seo, D. Wang, Y. Tzeng1, N. Sathitsuksanoh2, C. C. Tin, M. J. Bozack, J. R. Williams, and M. Park3 Department of Physics, Auburn University, Auburn, AL 36849 1 Department of Electrical and Computer Engineering, Auburn University, Auburn, AL 36849 2 Department of Chemical Engineering, Auburn University, Auburn, AL 36849 3 Corresponding Author: email ([email protected]) ABSTRACT Zinc oxide (ZnO) is an interesting material for short-wavelength optoelectronics due to its wide band gap. The nanostructures of ZnO are also intriguing since a variety of morphology can be obtained by employing different processing parameters. In our laboratory, ZnO nanonails were successfully synthesized at low temperature using a thermal chemical vapor deposition. The morphology of the sample was studied by using scanning electron microscopy. The shape of the nail head can be controlled from hexagon to quasi-circular shape. X-ray diffraction, Raman scattering, photoluminescence spectroscopy were also performed to analyze the ZnO nanonail. Photoluminescence spectroscopy suggested that the defects in the ZnO nanonail and nanobone are of different nature. INTRODUCTION Zinc oxide (ZnO) has been recognized as a important functional material which have applications in sensors [1], solar cells [2], surface acoustic wave devices [3], and varistors [4]. ZnO is a semiconductor with a large band gap of 3.37 eV and a large exciton binding energy 60 meV compared with thermal energy at room temperature (25 meV), making it a promising material for UV laser and optoelectronic application. In addition, one-dimensional material exhibits novel properties due to the quantum confinement effect or the very large surface to volume ratio of the structure. Recently, there has been a vigorous research activity in the growth of ZnO nanostructures. Some of the well established growth methods for ZnO nanowire and nanoprticle are the vapor-liquid-solid growth [5,6], metal-organic vapor-phase epitaxy (MOVPE) [7,8], plasma-assist chemical vapor deposition [9], metalorganic chemical vapor deposition [10], pulsed laser deposition [ 11 ], and electrophoretic deposition [ 12 ]. In these processes, nanoparticles of Au or Ni are frequently utilized as catalysts. The ZnO nanowires have also been successfully synthesized using thermal evaporation even without a metal catalyst [13]. Recently, Yao et al. has produced needle-like rods with a hexagonal head at 750-800˚C via thermal evaporation [14]. Very recently, Lao et al. have also synthesized a nail shaped nanorods at 950-970˚C using a thermal evaporation and condensation [15]. The nanostructure was named “nanonail” due to the similarity of its morphology to a nail. However, these growth processes require a relatively high temperature, and there is a scarce of optical properties of these samples reported. Therefore, we have successfully synthesized ZnO nanonails at a relatively low temperature (450-500˚C) via thermal CVD process, and performed optical characterizati
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