2010 International Conference on Enabling Science and Nanotechnology (ESciNano), 1-3 December, 2010, KLCC, MALAYSIA
Aqueous Synthesis of Silicon Nanowire Arrays and Core-shell Structures via Electroless Nanoelectrochemical Process ' L K. Ng , K. Y. Kok, S. S. Zainal Abidin, N. U. Saidin and T. F. Choo
Malaysian Nuclear Agency, Bangi, 43000 Kajang, Selangor D. E. . Email:
[email protected]
A solution growth of silicon nanowires (NWs) and core-shell structures is highly desirable due to low growth temperature and large-area synthesis capability. Silicon demonstrates novel electrochemical properties in aqueous solutions containing hydrofluoric acid which have raised significant research interests due to the complex electrochemical etching behavior involved.
In the present study, we have demonstrated the synthesis of large-area
vertically aligned silicon nanowire (SiNW) arrays (Fig. 1 and 2) in an aqueous solution containing AgN03 and HF on p-type (00 1) Si substrate by self-selective electroless etching process [ 1]. The fabrication process was rather simple and rapid compared to the well-known Vapor-Liquid-Solid (VLS) growth [2] via chemical-vapor deposition (CVD) and other high vacuum techniques. In this work,the temperature of electrolyte and etching duration were varied in order to achieve different stages of nanowire formation. Diameters of the SiNWs obtained varied from 50 nm to 200 nm and their lengths ranged from several to approximately a few tens of !lm, depending on the reaction time and the electrolyte conditions used. Te-Si and Bh Te3-Si core-shell structures (Fig. 3) were subsequently obtained via galvanic displacement of SiNWs in acidic HF electrolytes containing Bi3+ and Bi3+ IHTeO/ ions respectively. The reactions were basically a nanoelectrochemical process due to the difference in redox potentials between the materials. The modified SiNWs of the core-shell structures exhibit roughened surface morphologies and, therefore, have higher surface-to-bulk ratios compared to the unmodified SiNWs, which should have potential applications in sensor, photovoltaic and thermoelectric nanodevices. Growth study on the SiNWs and core-shell structures produced is presented using various microscopy, diffraction and probe-based techniques for structural, morphological and chemical characterizations. References:
[ 1] K. Q. Peng, Y. J. Van, S. P. Gao and J. Zhu, "Synthesis of Large-Area Silicon Nanowire Arrays via Self-Assembling Nanoelectrochemistry", Adv. Mater.,vo\. 14,no. 16,pp 1 1641 167,2002. [2]
S. Wagner and W. C. Ellis, "Vapor-Liquid-Solid Mechanism of Single Crystal Growth", App\. Phys. Lett. 4,pp 89- 90, 1964. R.
ESciNano 2010 - http://www.tke.utm.my/mine/escinan02010
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2010 International Conference on Enabling Science and Nanotechnology (ESciNano), 1-3 December, 2010, KLCC, MALAYSIA
Fig. 1. Top-view SEM images showing typical morphologies of the SiNW arrays synthesized at 40°C for different etching times: (a) 30 min (b) 60 min (c) 90 min and (d) 120 min. Free-ends of the SiNWs bundle into nanoclusters of increasing sizes with longer etching time. EDX trace in the inset shows the purity of the SiNWs in the absence of Ag dendrites.
Fig. 2. Cross-sectional SEM images of the SiNW arrays synthesized at 40°C showing variation in NW length as a function of etching time.
Fig. 3. (a) Te-Si and (b) Bi2 Te3-Si core-shell structures obtained from post-growth modification via galvanic displacement of SiNW arrays and detached single SiNWs respectively at room temperature.
ESciNano 2010 - http://www.tKe.utm.my/mine/escinano2010
