Si nanowires

FIG. 20-24 High -resolution TEM image of Si nanowires produced at 500 C and 24.1 MPa in supercritical hexane from gold seed crystals. Inset Electron diffraction pattern indexed for the <111> zone axis of Si indicates <110> growth direction. [Reprinted with permission from Lu et al. Nano Lett., 3(1), 93-99 (2003). Copyright 2003 American Chemical Society. ]... 

SiNW can also be used as sensors. In this case, SiNW of a silicon core without or with a very thin Si02 sheath are preferred. Since oxygen in the air normally reacts with Si, thin Si nanowires will eventually become Si02 nanowires if no protective layers are in place. 

A schematic of the proposed growth model is shown in Fig. 10.23. In this model, Co nanoparticles play a dual catalytic role. On the one hand, they catalyze silane formation by reacting first with silicon to form Co silicides, and then react with hydrogen to form silane while being reduced to Co metal. The second role of Co nanoparticles is their classic catalytic ability of making nanowires by first dissolving the silane and precipitating out Si nanowires. 

J. Westwater, D. P. Gosain, and S. Usui, Si nanowires grown via ttie vapour—liquid—solid reaction, Phys. Status Solidi A—Appl. Res. 165, 37-42 (1998). 

In the last decade there has been considerable and reasonably satisfactory progress in the understanding of the theoretical aspects of the structural, electronic and optical properties of Si nanostructures. Here we have presented the outcomes of our theoretical study of the properties of Si nanosystems, considering Si nanodots, Si nanowires and Si nanoslabs. We have demonstrated, by first-principle calculations, also beyond the single particle approach, that the structural, electronic, and optical properties of the... 

Zhou GW, Li H, Sun HP, Yu DP, Wang YQ, Huang XJ, Chen LQ, Zhang Z. Controlled Li doping of Si nanowires by electrochemical insertion method. Appl Phys Lett 1999 75 2447-2449. 

Recently, the VLS growth method has been extended beyond the gas-phase reaction to synthesis of Si nanowires in Si-containing solvent (Holmes et al, 2000). In this case 2.5-nm Au nanocrystals were dispersed in supercritical hexane with a silicon precursor (e.g., diphenylsilane) under a pressure of 200-270 bar at 500°C, at which temperature the diphenylsilane decomposes to Si atoms. The Au nanocrystals serve as seeds for the Si nanowire growth, because they form an alloy with Si, which is in equilibrium with pure Si. It is suggested that the Si atoms would dissolve in the Au crystals until the saturation point is reached then they are expelled from the particle to form a nanowire with a diameter similar to the catalyst particle. This method has an advantage over the laser-ablated Si nanowire in that the nanowire diameter can be well controlled by the Au particle size, whereas liquid metal droplets produced by the laser ablation process tend to exhibit a much broader size distribution. With this approach, highly crystalline Si nanowires with diameters ranging from 4 nm to 5 nm have been produced by Holmes et al. (2000). The crystal orientation of these Si nanowires can be controlled by the reaction pressure. 

Silicon-based ICs 1961 III-V semi, Si-nanowire, carbon nanotube 2011-2015 Scaling performance power... 

Schmidt V, Senz S, Gosele U (2007) Influence of the Si/Si02 interface on the charge carrier density of Si nanowires. Appl Phys A 86 187-191... 

Imamura G, Kawashima T, Fujii M, Nishimura C, Saitoh T, Hayashi S (2009) Raman characterization of active B-concentration profiles in individual p-type/intrinsic and intrin-sic/p-type Si nanowires. J Phys Chem C 113 10901-10906... 

---