Ultra-Fine ZnO Nanobelts and their Photoluminescence Emission
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Ultra-Fine ZnO Nanobelts and their Photoluminescence emission Aurangzeb Khan and Martin E Kordesch Department of Physics and Astronomy and CMSS Program, Ohio University, Athens OH 45701 ABSTRACT Ultra-Fine ZnO nanobelts are grown via thermal evaporation and condensation method without the use of any catalyst on the substrates. These nanobelts have an average width of about 5.8 nm. Photoluminescence spectra reveal that there is a blue shift in the near band edge ultra violet emission from 381 nm to 367 nm equal to 124 meV. These ultra-fine nanobelts have been studied for size induced optical and electrical properties. INTRODUCTION Semiconductor nanoscale one-dimensional (1D) materials have stimulated intensive research interests due to their importance both in fundamental scientific research and potential nano-electronic applications [1-4]. 1D nanostructure such as nanowires and quantum wires are ideal systems for studying the size and dimensionality dependence of electrical transport, mechanical, and optical properties [5]. Nanowires are expected to play an important role in nanodevice applications. Recently, much progress has been made in applications of nanodevices that use nanowires as building blocks. Silicon nanowires have been used to construct Schottky diodes and InP light emitting diodes made from nanowires [6-8]. Furthermore, GaN and InP nanowires have been used to produced computational circuits, which is an important breakthrough in nanotechnology [9]. GaN and ZnO nanowires have also been used for blue and ultra violet lasers respectively [10,11]. On the other hand, ZnO thin films have also stimulated great research interests, because ZnO is a wide band gap compound, it is cheaply available and it has shown great promise for opto-electronic devices due to their UV and green emission at room temperatures [12]. It is believed that nanostructures with dimensions of a few nanometers will have novel and unique physical and chemical properties due to quantum confinement. It is important to try to synthesis nanowires and nanobelts with smaller dimensionality; there has been some success in making these nanostructures of a few nanometers size in e.g Si [13], and InP [14]. X. Wang et al [15] have successfully synthesized ZnO nanobelts of the size of a few nanometers and used Vapor Liquid Solid (VLS) methods using a catalyst on the substrate and studied their photoluminescence (PL). Here we describe the synthesis of ultra fine ZnO nanobelts without the presence of any catalysts using the thermal evaporation and condensation method and study their Photoluminescence emission.
EXPERIMENTAL ZnO nanobelts have been synthesized by thermal evaporation and condensation method under controlled conditions by heating a mixture of ZnO powder (alfa aesar 99.0 % -325 mesh) and graphite powder (alfa aesar 99 % -300 mesh). The ratio of these powders are 1:1 ( by
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volume ) and put in a quartz boat and then kept in quartz tube (three inches in diameter and 45 inches long) placed horizontally in a conventional t
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