Nanowires silicon

Cui, Y. Zhong, Z. Wang, D. Wang, W. U. Lieber, C. M. 2003. High performance silicon nanowire field effect transistors. Nano Lett. 3 149-152. 

Cui, Y. Lauhon, L. I Gudiksen, M. S. Wang, J. Lieber, C. M. 2001. Diameter-controlled synthesis of single-crystal silicon nanowires. Appl. Phys. Lett. 78 2214-2216. 

Cui, C. and Lieber, C.M., Functional nanoscale electronic devices assembled using silicon nanowire building blocks, Science, 291, 851,2001. 

Measurements of mobility in PS suffer from the fact that the number of free charge carriers is usually small and very sensitive to illumination, temperature and PS surface condition. Hall measurements of meso PS formed on a highly doped substrate (1018 cm3, bulk electron mobility 310 cm2 V-1 s-1) indicated an electron mobility of 30 cm2 V 1 s 1 and a free electron density of about 1013 cm-3 [Si2]. Values reported for effective mobility of electron and hole space charges in micro PS are about five orders of magnitude smaller (10-3 to 10 4 cm2 V 1 s ) [PelO]. The latter values are much smaller than expected from theoretical investigations of square silicon nanowires [Sa9]. For in-depth information about carrier mobility in PS see [Si6]. 

Hepplestone SP, Srivastava GP (2006) The intrinsic lifetime of low-frequency zone-centre phonon modes in silicon nanowires and carbon nanotubes. Applied Surface Science 252 7726-7729. 

Ni thin films were used as catalysts by Jin et al. and Yan etal. to produce amorphous SiNW at 1200°C. No external supplies of Si were needed, but hydrogen gas was used. It was unclear whether the nanowires were amorphous silicon nanowires covered with silica layers, or silica nanowires. 

It is possible that the as-made nanowires contain some crystalline Si core, and subsequent reaction with oxygen in the air results in the formation of silica nanowires. Since hydrogen gas was used in the reaction, pure silicon nanowires were probably made first, followed by oxidation in air. In the following discussion, for simplicity reason we will assume that amorphous SiNW were made during catal)Tic reactions. 

J. D. Holmes, K. P. Johnston, R. C. Doty, and B. A. Korgel, Control of thickness and orientation of solution-grown silicon nanowires. Science 287, 1471-1473 (2000). 

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... 

S. Jin, Q. Li, and C. Lee, Direct growth of amorphous silicon oxide nanowires and crystalline silicon nanowires from silicon wafer, Phys. Status Solidi A—Appl. Res. 188, Rl—R2 (2001). 

S. Hofmann, C. Ducati, Neill, R., S. Piscanec, A. Ferrari, J. Geng, R. Dunin-Borkowski, and J. Robertson, Gold catalyzed growth of silicon nanowires by plasma enhanced chemical vapor... 

C. Li, N. Wang, S. Wong, C. Lee, and S. Lee, Metal silicide/silicon nanowires from metal vapor vacuum arc implantation, Adv. Mater. 14, 218-221 (2002). 

Does anyone actually use nanowires Well, Dr. Ock in Spiderman 2 claimed to use nanowires to connect his neural circuitry to a machine circuit. In fact, silicon nanowires have recently been used to build sensors for DNA. The sensors are designed to detect the presence of mutations in a cystic fibrosis gene. Nano Letters 2004, 4, 51 -54]... 

Li et al. [61] reported a novel method using a sequence-specific label-free DNA sensors based on silicon nanowires (Si-NWs) by measuring the change in the conductance. Kelley s group [62] developed a gold nanowire array (Au-NW) in 15-20 nm diameter range and this array was used for electrochemical DNA detection with the help of the elect-rocatalytic reporter systems, Ru(NH3)6+ and Fe(CN). ... 

It is probable that rather than using self-assembly to add any active molecules to the device architecture, the nanowires used to construct the devices will be precoated with active molecules via spin coating as shown by Lieber in his recent work.53 Specially doped silicon nanowires have also shown interesting properties in crossbar-based devices.54... 

A number of other types of processes that can be considered a form of self-assembly at surfaces are just beginning to appear. The selective oxidation of silicon, followed by etching of the silicon dioxide, as a route to silicon nanowires is an example172 the galvanic deposition of platinum on selenium nanostructures, followed by removal of the selenium, to make nanowalls with complex shapes is a second173,174. 

Quantum confinement could be evidenced on small silicon nanowires [23], Focusing the probe on different diameter nanowires, a blue shift of the silicon L23 edges which was not detected in a spatially average technique such as XAS. Similar LELS spectra could be conclusively interpreted using the boundary charge method [24],... 

Figure 7. EELS L23 silicon edges spectra on various silicon nanowires. (Sun et al., J. Appl. Phys. 90 (2001) 6379 with permission from American Institute of Physics)...

While the discussion in this chapter has focused on molecular layers on single crystal silicon surfaces, the attachment chemistries discussed here could easily be applied to functionalize silicon nanowires or nanoparticles. Silicon nanowires have been shown to exhibit interesting electrical transport characteristics and have been used to fabricate nanoscale pn junctions [95], field effect transistors [96] and biochemical sensors [97-100]. However, all these interesting phenomena have been reported on oxidized silicon nanowires. It is likely that better control over the surface properties, as could be achieved by employing some of the chemistry discussed here, could significantly improve the performance of these nanowire-based devices. From another perspective, silicon nanowires could prove extremely... 

K. Nauka, and R. S. Williams, Sequence-specific label-free DNA sensors based on silicon nanowires , Nano Letters 4, 245 (2004). 

Recently, a laser ablation-condensation technique was used to produce nanometer-sized catalyst clusters to grow nanowires by the VLS method. A schematic of the laser ablation apparatus used by Morales and Lieber (1998) to produce silicon nanowires is shown in Fig. 11. The target consists of silicon and the catalyst material (e.g., Sii AFeA), and a pulsed laser is used to produce nanometer-sized catalyst clusters within a reaction chamber at 1200°C. The ablated materials are carried by an argon gas flow, and the... 

Fig. 10. Schematic illustrating the growth of silicon nanowires by the VLS mechanism.

---