Nanowires vapor deposition

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... 

Over the past few years, a large number of experimental approaches have been successfully used as routes to synthesize nanorods or nanowires based on titania, such as combining sol-gel processing with electrophoretic deposition,152 spin-on process,153 sol-gel template method,154-157 metalorganic chemical vapor deposition,158-159 anodic oxidative hydrolysis,160 sonochemical synthesis,161 inverse microemulsion method,162 molten salt-assisted and pyrolysis routes163 and hydrothermal synthesis.163-171 We will discuss more in detail the latter preparation, because the advantage of this technique is that nanorods can be obtained in relatively large amounts. 

The variety of porous solid materials that can be used as templates for nanostructure synthesis has been reviewed by Ozin (1992). In the template-assisted synthesis of nanowires, the pores or voids of the template are filled with the chosen material using a number of approaches. Nanowires have been derived via pressure injection, electrochemical deposition, and vapor deposition, as described in the following sections. 

Figure 19(a) shows the temperature dependence of resistance R(T) for bismuth nanowire arrays (dw = 7 - 200 nm) synthesized by vapor deposition and measured by Heremans et al. (2000). Hong et al. (1999) reported similar resistance measurements on bismuth wires of larger diameters (200 nm to 2, uni) prepared by electrochemical deposition (Fig. 19(b)). These two studies... 

Chemical vapor deposition, nanowires, 179 Cluster structures change in grain size, 5 ion-bombardment technique, 7-8 Cobalt molybdates, hydrodesulfurization catalysts, 2-3... 

Metal pair sites on supports, 63-64 Metalloorganic chemical vapor deposition, nanowires, 179 Metals... 

Kong, Y.C., D.P. Yu, B. Zhang, W. Fang and S.Q. Feng (2001). Ultraviolet-emitting ZnO nanowires synthesized by a physical vapor deposition approach. Applied Physics Letters, 78(4), 407 109. 

Figure 9 Examples of novel materials with potential catalytic applications. From left to right and top to bottom, these pictures represent (a) Ag nanowires. (Reprinted with permission from Ref 63. 2002 American Chemical Society) (h)Ag nanoparticles. (Reprinted with permission from Y. Sim and Y. Xia, Science, 2002, 298, 2176. 2002 AAAS (www.sciencemag.org)) (c) zeolite monolith. (Ref. 67. Reproduced hy permission of Kluwer Academic/Plenum Publishers) (d) zeolite coatings on stainless steel grids. (Ref 68. Reproducedby permission of Wiley-VCH) (e) arrays of Pt nano lithography-made particles on Si02. (Ref. 70. Reproduced by permission of Kluwer Academic/Plenum Publishers) and (f) Ag nanoparticles vapor deposited on an AI2O3 thin film ...

The organometallic route can be extended to the formation of one-dimensional indium materials. On the use of long-chain amines as templates. In and InsSn nano wires have been prepared from the organometallic precursors InCp (Cp = 5115 ) in the presence of UV irradiation. In this case, irradiation is cmcial for the formation of the wires. In nanowires are also produced in the metal organic chemical vapor deposition grown InGaN layers. ... 

The OAG method has a general nature and can be applied to a variety of materials other than Si. Based on the OAG method, we have synthesized nanowires of a wide range of semiconducting materials including Ge [35], GaN [36, 37], GaAs [38, 39], GaP [41], SiG [40], and ZnO (whiskers) [42]. The actual OAG process was activated by laser ablation, hot-filament chemical vapor deposition (HFCVD) or thermal evaporation. 

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