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KK5.8.1

Controlled growth of nanowires using annealing and pulsed laser deposition Hyun D. Park and Timothy P. Hogan* *Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824-1226 ABSTRACT A new nanowire growth technique using annealing and pulsed laser deposition is described. The technique demonstrates the control in the precise nanowire growth temperature thereby yielding higher quality nanowires than obtained from simple annealing alone. InSb substrate and gold target were used to demonstrate the new technique. The results from the variation of gold deposits from 2.5 mins to 40 mins at the fixed growth temperature of 510 oC are discussed. INTRODUCTION Currently, there are several growth techniques available in the fabrication of nanowires such as laser ablation [1-2], chemical vapor deposition (CVD) [3], simple evaporation [4], and annealing. Growth by annealing a metal coated substrate in particular is a simple way to grow nanowires where it simply uses the substrate itself as the source for growth. Based on this method, silicon [5-6], silicon oxide and gold-silica [7] composite nanowires were previously grown using either gold or nickel film on a Si substrate. Despite the simplicity, the resulting nanowires that have been grown based on this method were all amorphous, and showed morphological instabilities such as tapering as well as kinking. We have also used this annealing growth method in the observed growth of nanowires containing mostly indium by annealing a gold coated InSb substrate [8]. The nanowires were high crystalline structure but showed evidence of tapering, branching, and variation in the chemical composition along the length of the nanowire. There have been reports of aligned amorphous silicon oxide nanowires growth using gallium[9-10] on a Si substrate, but the growth process do not show much control over the diameter of the nanowires and the structural uniformity still requires further improvement. To resolve the morphological instabilities inherent in annealed-grown nanowires, we report in this paper on the new technique that optimizes the annealing growth method by combining the annealing with pulsed laser deposition to produce highly aligned, single crystal nanowires. We demonstrate this new technique by using InSb substrate and gold target. From our previous result, nanowires grown using gold film and InSb substrate contained primarily indium, but we have chosen this material due to the fact that nanowires are easily grown at low temperature as low as 400 oC. The technique based on a simple annealing involves first depositing a metal at room temperature, followed by raising the sample temperature to the desired nanowire growth temperature, and finally lowering the temperature once the annealing is done. Due to the variation in temperature, the technique does not present a well controlled growth environment since the nanowires can potentially grow at temperatures other than at the desired growth temperature leading to morphological instabilitie