Synthesis of Semiconductor Nanowires

There are many top-down fabrication methods which also make it possible to fabricate SiNWs (Teo and Sun 2007 Schmidt et al. 2009 Bandaru and Pichanusakom 2010). Due to processing-related differences, one should distinguish between the fabrication of horizontal nanowires, that is, nanowires lying in the substrate plane (see Fig. 5.8e, f), on the one hand, and the fabrication of vertical 

fabricated through lithographic patterning or chemical synthesis, can be further reduced in diameter through a self-limiting oxidation process. For example, Liu et al. (1994) have shown that with an initial Si pillar diameter of 30 nm, 6-nm Si nanowires can be obtained using this approach. 

Using SiNWs fabricated by various methods, resistive gas sensors (Gao et al. 2010 Field et al. 2011), FET (McAlpine et al. 2007 Paska et al. 2011), Schottky type gas sensors (Skucha et al. 2010), and field-ionized gas sensors (Sadeghian and Islam 2011) have been designed. Examples of such devices 

Type Technology Diameter/length Target gas Threshold limit Res. time References 

R resistive, FET field-effect transistor, S single nanowire, A nanowire ordered array, OA nanowire ordered array 

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Gudiksen MS, Lieber CM (2000) Diameter-selective synthesis of semiconductor nanowires. J Am Chem Soc 122 188... 

Metal particle catalyzed chemical vapor deposition is the most versatile VLS process (Table II) yielding a wide range of single crystal whiskers and nanowhiskers [1-2] [5-6], short amorphous or polycrystalline fibers [1] [7], and nanotubes [8]. Laser ablation of selected metal alloys is a recent VLS process used for the synthesis of semiconductor nanowire [74]. Metal particle catalyzed carbothermal reduction, another VLS process, yields single crystal whiskers [9-10]. Metal catalyzed arc discharge [11], metal particle catalyzed laser ablation [12], and metal particle catalyzed plasma arc discharge [13] yield nanotubes by a VLS mechanism. 

Solution-Liquid-Solid (SLS) growth of semiconductor nanowires by Wang etal. (2006). The synthesis proceeds by a solution-based catalysed growth mechanism in which nanometer-scale metallic droplets catalyse the decomposition of metallo-organic precursors and crystalline nanowire growth. 

Recently, synthesis of semiconductor nanorods (nanowires or nanoflbers) and investigation of their properties have aroused much interest. Ge et al. (2002) showed that irradiation technique can be very useful in this regard as well. Cadmium sulfide (CdS) nanorods were successfully prepared by y-irradiation at room temperature and ambient pressure using urea as the template. X-ray diffraction (XRD) pattern showed that the phase of the product was hexagonal. The mean diameter of the nanorods was about 40 nm and the length was up to about 100 nm. The ratio between the length and the width is as high as 5 2. More importantly, they demonstrated that the successful obtainment of nanorods was determined by not only the presence of urea in the system but also the crystallization rate of urea from the solution. 

Oriented attachment of nanocrystals can be used to make one-dimensional and other complex nanostructures. Thus, nanotubes and nanowires of II-VI semiconductors have been synthesized using surfactants [566]. The nanorods or nanotubes of CdS and other materials produced in this manner actually consist of nanocrystals. The synthesis of Ti02 nanowires from nanoparticles has been reported [567]. 

WaUentina J, Boigstrom MT (2011) Doping of semiconductor nanowires. J Mater Res 26 2142-2156 Wan G, Wang TH (2005) Single-crystalline Sb-doped SnO nanowires synthesis and gas sensor application. Chem Commun 30 3841-3843... 

The approaches used for preparation of inorganic nanomaterials can be divided into two broad categories solution-phase colloidal synthesis and gas-phase synthesis. Metal and semiconductor nanoparticles are usually synthesized via solution-phase colloidal techniques,4,913 whereas high-temperature gas-phase processes like chemical vapor deposition (CVD), pulsed laser deposition (PLD), and vapor transfer are widely used for synthesis of high-quality semiconductor nanowires and carbon nanotubes.6,7 Such division reflects only the current research bias, as promising routes to metallic nanoparticles are also available based on vapor condensation14 and colloidal syntheses of high-quality semiconductor nanowires.15... 

Duan, X. Lieber, C. M. 2005. Semiconductor nanowires Rational synthesis. In Dekker Encyclopedia of Nanoscience and Nanotechnology, edited by Schwarz J. A., Marcel Dekker, Inc., New York. 

Morales, A. M. Lieber, C. M. 1998. A laser ablation method for the synthesis of crystalline semiconductor nanowires. Science 279 208-211. 

The process begins with the synthesis of different semiconductor nanomaterials (e.g., single-walled carbon nanotubes and single-crystalline nanowires/... 

Yang XH, Wu QS, Li L, Ding YP, Zhang GX (2005) Controlled synthesis of the semiconductor CdS quasi-nanospheres, nanoshuttles, nanowires and nanotubes by the reverse micelle systems with different surfactants. Colloids Surf A 264 172-178... 

Duan, X., and Lieber, C. M., General synthesis of compound semiconductor nanowires. Adv. Mater. 12,298 (2000). 

Solution-Liquid-Solid Process Buhro and coworkers [276], have developed a low temperature solution-liquid-solid (SLS) method for the synthesis of highly crystalline nanowires of III-V semiconductors [276, 327]. In a typical procedure, a metal (e.g., In, Sn, Bi) with a low melting point was used as a catalyst, and the de-... 

Fundamental aspects of vapor-liquid-solid (VLS) semiconductor nanowire growth are presented here. The synthesis of VLS semiconductor has been extended to different reaction media and pathways from the early chemical vapor deposition (CVD) approach, including solution-liquid-solid (SLS) and supercritical fluid-liquid-solid (SFLS), laser-catalyzed growth, and vapor-liquid-solid-epitaxy. The properties of nanowires grown by these VLS embodiments are compared. In this entry, VLS growth of nanowire heterostructures and oriented and hyperbranched arrays is examined. In addition, surface passivation and functionalization are assessed, and the importance of these techniques in the progress toward VLS produced nanowire devices is detailed. 

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