Vapor nanowire synthesis

A hybrid approach to nanowire synthesis developed by Wu et al. [22] combines laser ablation with a flow reactor process, and has yielded superlattice nanowires of Si/SiGe. The role of the flow furnace is to produce Si nano wires, while the laser ablation process introduces Ge periodically into the vapor. The Ge is absorbed by the catalyst and incorporated into the forming nanowire. Through judicious control of the process, Wu s group has achieved superlattice periodicities of Si/ SiGe of approximately 250 nm. Moreover, the results of this study bode well for superlattice nanowire devices. 

Gu Z, Parans Paranthaman M, Pan Z (2009) Vapor-phase synthesis of gallium phosphide nanowires. Cryst Growth Des 9 525-527... 

Figure 3. Schematic representation of the selective synthesis of metal nanowires and nanoparticles by the Sintering Controlled Synthesis approach, (a) Mesoporous silica, (b) impregnation of mesoporous silica with metal ions, (c) addition of water/alcohol vapors and UV-irradiation, or wet H2-reduction, (d) formation of metal nanowires, (e) dry H2-reduction, (f) formation of metal nanoparticles.

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. 

M. K. Sunkara, S. Sharma, R. Miranda, G. Lian, and E. C. Dickey, Bulk synthesis of silicon nanowires using a low-temperature vapor-liquid-solid method, Appl. Phys. Lett. 19, 1546-1548... 

XRD patterns of Pt/FSM-16 [25] (and HMM-1 [32]) show no significant change at 26 = 1-10° before and after the incorporation of metal nanowires and nanoparticles (Figure 15.7). This indicates that the pore structures and mesoporous channels of FSM-16 (and HMM-1) remained unchanged in the synthesis of the Pt wires and Pt particles [18-20, 23, 24] by wet photo-irradiation with methanol -i- water vapor and dry H2 reduction, respectively. Furthermore, in the high 26 region, typical peaks assigned to Pt fee crystalline are observed for both samples of Pt nanowire/FSM-16 and Pt nanoparticles/FSM-16 [25]. 

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. 

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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