Vapor Phase Growth of Nanowires

Vapor phase growth is commonly used to produce nanowires. Starting with the simple evaporation technique in an appropriate atmosphere to produce elemental or oxide nanowires, vapor-liquid-solid, vapor-solid and other processes are made use of. 

Carbothermal Reactions It is noteworthy that a variety of oxides, nitrides and elemental nanowires can be synthesized by carbothermal reactions. For example, carbon (activated carbon or carbon nanotubes) in mixture with an oxide produces oxide or suboxide vapor species, which react with other reactants (O2, N2 or NH3) to produce the desired nanowires. Thus GaN nanowires are produced by heating a mixture of Ga203 and carbon in N2 or NH3. Silicon nanowires can also be made by heating Si02 with carbon in a suitable atmosphere. 

(c) HREM image of a fi-S C nanowire prepared by heating the gel containing the activated carbon and silica at 1360 °C in NH3 for 7 h. Reproduced from ref. [301], with permission. 

by using the correct carbon source with the silica gel under carbothermal conditions it is possible to obtain nitride or carbide nanowires. With the carbon nanotubes the reaction follows one step (Step III shown below) to produce Si3N4 nanowires. 

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