Growth of Silica Nanowires Catalysed by Pd Ion Implantation into Si(100)
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Growth of Silica Nanowires Catalysed by Pd Ion-Implantation into Si (100) Praveen Kumar Sekhar1, Dinesh. K.Sood 2 and Shekhar Bhansali1 1 Nanomaterials and Nanomanufacturing Research Center,Department of Electrical Engineering, University of South Florida, 4202 E. Fowler Ave.,Tampa, FL 33620, USA 2 School of Electrical and Computer Engineering, RMIT University, 124 La Trobe Street, Melbourne 3000, Australia ABSTRACT Selective synthesis of silica nanowires on silicon wafers catalyzed by Pd ion implantation is reported.Nanoclusters of palladium silicide acts as seeds for nucleation of wires following a Vapor-Liquid-Solid (VLS) growth model. The consumption of silicide towards nanowire growth is confirmed through Rutherford Backscattering Spectrometry (RBS). The influence of growth time, implantation dose and heating temperature on the structure and morphology of the wires is investigated. Optimization of these tunable parameters would be needed to facilitate controlled and directed bottom-up growth of silica nanowires. Such selective synthesis may enable a large number of applications in wide areas of future technologies such as localization of light, low dimensional waveguides for functional microphotonics, scanning near field optical microscopy (SNOM), optical interconnects, sacrificial templates, optical transmission antennae and biosensors. INTRODUCTION Silica nanowires have stimulated a great research interest due to their excellent optical properties [1] and bio-compatibility [2]. Recently silica nanowires have been reported [3] to emit stable and high brightness blue light at energies of 2.65 and 3.0 eV. The intensity of the emission was two orders of magnitude higher than that of porous silicon. An assembly of low-loss silica nanowires into functional microphotonics devices on a low-index nondissipative silica aerogel substrate has recently been reported [4]. These engineered nanowires are currently proposed to be used as contrast enhancement agents in molecular imaging and biomarkers in cancer research with good spatial resolution. Numerous techniques have been researched and investigated in synthesizing silica nanowires. Some of the primary approaches include template directed growth [5], solution based chemistry [6], Langmuir-Blodgett method [7] and gas phase growth (carbothermal reduction, oxide assisted growth, VLS, SLS (solid liquid solid), VS (vapor solid) growth) [8]. The VLS mechanism proposed in 1964 [9] for silicon whisker growth has proved to be very reliable for developing silica nanowires [10-11]. In this method, the cluster acting as a seed for subsequent nanowire growth is commonly synthesized either by annealing thin films or is preformed. Our recent study [12] reported the feasibility of forming nanoclusters in silicon using ion implantation, and using them as seeds for VLS growth of silica nanowires. This novel technique would have several advantages over conventional growth mechanisms. For example, controlled annealing during or after ion implantation can be used to tailor th
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