Silicon whiskers and nanowhiskers

The most important products, which can be synthesized from the vapor phase, are silicon whiskers and nanowhiskers, silicon carbide whiskers and nanowhiskers, short carbon and graphite fibers, and carbon nanotubes. 

Tiny VLS nanowhiskers can be obtained by chemical vapor deposition with less than 1/100th the diameter of ordinary VLS-CVD silicon carbide whiskers by proper selection of the metal catalyst and process conditions. Indeed, these "cobweb" [2] or nanowhiskers have been made with diameters of <20 nm. To the naked eye these whiskers look like a blue cloud created by light scattering similar to that which causes the sky to appear blue. 

Diffusion is the process at the molecular level, and it is determined by the random character of the motion of individual molecules. The rate of diffusion is proportional to the average velocity of molecules. It is not obviously possible to track the diffusion process completely in this temporary framework (about several nanoseconds). Therefore, to increase the diffusion rate in accordance with the model of the diffusion-growth of nanowhiskers and Pick s first law (the flux density of matter is proportional to the diffusion coefficient and concentration gradient), an additional diffusional flux to the base of a whisker is used, that is, the force O, whose direction is perpendicular to the z axis, is applied to the deposited silicon atoms. Correspondingly, this force has the nature of intermolecular interaction. 

It should be noted that the migration of gold from the drop can occur in silicon nanowhiskers at high temperatures. Similar conclusions can be made from the results of simulation. This phenomenon is also observed in simulation of the processes of the growth of whiskers by the Monte Carlo methods [21] and in our calculations (Fig. 5.7). These data also show a good coordination of simulation results with experiments and other methods of computer simulation. 

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