Anil Roy, DA- IICT,Gandhinagar,India-382009).
Bhagat,Pramod Singh,Rakesh Dhull,Rajeev Jaiswal).
In this paper we are summarizing the past, present and future of fabrication of nanofibers and nanowires. Some of already explored applications of these are in electronic devices e.g. Field-effect transistors, sensors, detectors and light-emitting diodes etc. and many new are coming up. Semiconductor nanowires are one-dimensional structures, with unique electrical and optical properties e.g. Quantum confinement effects. Fabrication at nanoscale and at low temperature with lot of other constraints is a promising area of research.
The vapor liquid solid (VLS) process is a fundamental mechanism for the growth of nanowires. In this process a small size (5 -100 nm in diameter), high melting point metal (such as Gold and Iron) catalyst particle directs the nanowires growth-direction. It also determines the diameter of the crystalline nanowires. The silica nanowires tend to grow batch by batch. For each batch, numerous nanowires simultaneously nucleate, and they grow nearly at the same rate and in the same direction, and simultaneously stop growing.
Highly aligned and closely packed SiO2 nanowires bunches were synthesized in a high yield by using molten Ga as a catalyst and Si wafers as Si-source via a VLS process. The use of Ga provides opportunities for the development of low temperature VLS routes for nanowires synthesis. By using Ge as a catalyst, carbon nanotubes and GeO2 nanowires can be synthesized at temperature below 800 ˚C. .
The synthesis of nano structure was also accomplished by combining thermal evaporation of SiO powders and laser ablation of Ge target. In the thermal evaporation stage, after oxidation-reduction or disproportionation of SiO to Si + SiO2, condensation of SiO vapor give rise to the oxide assisted growth of silicon nanowires. One also gets various SiO2 nanostructures at different temperature distribution zones.