Hollow ZnO Nano-cone Synthesis via Catalyst Free MOCVD
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Hollow ZnO Nano-cone Synthesis via Catalyst Free MOCVD Wei Zhang and Karlheinz Strobl CVD Equipment Corporation, 1860 Smithtown Ave., Ronkonkoma, NY 11779 ABSTRACT Zinc oxide is a wide band gap material with excellent semiconducting, photonic and piezoelectric properties. In the past ten years zinc oxide nano-structures such as nanowires and nanorods have received great interest due to their unique dimensional and material properties in the area of photonics, electronics, mechanics, energy recovery, etc. In this paper we report the manufacturing process of a new shape, i.e. hollow hexagonal ZnO nano-cones. We grew them on different kinds of substrate using a low pressure, catalyst free, metal organic chemical vapor deposition (MOCVD) process on a FirstNano EasyTube 3000™ MOCVD system. Nitrogen was used as carrier gas to bring the reactants, DEZ and H2O, to the substrate surface. At the right balance of process temperature and carrier/precursor gas flow rate the ZnO nano-structure transitioned into a hollow hexagonal cones growth mode. The both one and two dimensional aspects of these catalyst free hollow hexagonal ZnO nano-cones, which are novel to the best of our knowledge, could lead to new applications in photonics, near field probing, chemical sensors, quantum confinement, electronic, etc. INTRODUCTION As an important wide band gap semiconducting material, zinc oxide has attracted worldwide attention in the fields of materials science, physics and chemistry [1]. Some of its important properties include wide band gap (3.4 eV), large excitation binding energy (60 meV), polarity of lattices which has no center of inversion symmetry, and chemically stable to 1000⁰C in the atmosphere environment [2]. Therefore, ZnO materials have been used extensively in many areas. For example, they are effective gas sensors for a wide range of gases [3, 4], and they have been used as photocatalysts [5, 6], field emitters [7], optoelectronic devices [8, 9], .etc. Low-dimensional ZnO has been synthesized by vapor-liquid-solid (VLS), vapor-solid (VS), metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE) and sol–gel growth [2, 10–14]. High temperature and metal catalysts are generally needed for the growth of nanowires and nanorods [15]. However, the use of metal catalysts leads to the diffusion of impurities into the nano-structures, which can affect the electrical and optical properties of the resulting nano-structures [16]. Even low defect concentrations affect physical properties of semiconductors, and, hence, unintentionally doped impurities are detrimental to device fabrication. In this study, we report the manufacturing process of a new structure, i.e. hollow hexagonal ZnO nano-cones. We grew them on various substrates using a low pressure, catalyst free, metal organic chemical vapor deposition (MOCVD) process on a FirstNano EasyTube 3000™ MOCVD system. Nitrogen was used as carrier gas. DEZ and H2O were used as reaction precursors. At the right balance of process temperature and carrier/precursor gas flo
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