Synthesis and Characterization of Flowerlike ZnO Nanoneedle Arrays on Si (100)
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1174-V09-08
Synthesis and Characterization of Flowerlike ZnO Nanoneedle Arrays on Si (100) Boqian Yang and Peterxian Feng* Physics Department and Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, PR 00931, U.S.A. * Electronic mail: [email protected]. FAX: (787) 764 4063.
ABSTRACT Flowerlike ZnO nanoneedle arrays have been synthesized on Si (100) substrates by pulsed laser deposition techniques. The tips of the nanoneedles are ~ 20- 50 nm in diameter and their roots are as thick as ~ 50- 100 nm. The nanoneedle arrays grow preferentially along the [0001] direction. Raman spectroscopy shows three first order optical normal modes which confirm wurtzite structure of ZnO nanoneedles. In the low frequency zone, additive modes (92, 122, 163, and 275 cm-1) are observed and can be attributed to zone boundary phonons. ZnO nanoneedle arrays exhibit a strong UV luminescence emission, and two strong peaks at 3.258 eV and 3.288 eV are observed.
INTRODUCTION One-dimensional (1D) nanostructures have attracted much attention due to their potential applications as building blocks for electronics and photonics devices [1, 2], as well as biosensors in life-science applications [3]. ZnO is a versatile material and has been used considerably for its catalytic, electrical, optical, and photochemical properties [4]. Therefore, 1D ZnO nanostructures stimulated intense attention, numerous work were carried out in this decade for the fabrication of nanostructures of various shapes i.e. (nanowires, nanobelts, nanorings, nanotubes, nanodonuts, nanopropellers, etc.) grown by different techniques such as the catalyst assisted thermal evaporation route [5], non-catalytic thermal evaporation route [6], wet chemical route [7] and solvothermal/hydrothermal [8] route, etc. Different types of substrates such as Si [9], sapphire [10], ZnO thin film coated substrate [11], metallic zinc foil [12], etc, have been reported for the self growth of various nanostructures. But due to the low cost and possibility of integration with Si-based microelectronics and microelectromechanical systems, among all the above-mentioned substrates for deposition of ZnO 1D nanostructures, Si (100) is particularly important. In this paper, we report the preparation of 1D ZnO nanoneedle arrays without catalyst by pulsed laser deposition (PLD) techniques. The nanoneedles grow in a flowerlike assembly on the Si (100) substrate. Different tools, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman scattering (RS) were used to investigate the morphological, structural, chemical properties of the ZnO nanostructures. The electron field emission and optical properties of ZnO nanoneedle arrays were also characterized.
EXPERIMENT DETAIL Flower-like ZnO nanoneedles were grown on Si (100) substrates by pulse laser deposition techniques. An ArF Lambda Physik 1000 excimer laser (193 nm, ~20-30 ns, and 10 Hz repetition rate, and 200 mJ pulse energy) was used to ir
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