Controlled growth of silicon nanowires

Using the solid-liquid-solid method, silicon nanowires were grown by annealing the gold-coated silicon substrates under the nitrogen flow. In this method, gold diffused into the silicon substrate upon heating and AuSi alloy formed at their interface. This alloy was melted when temperature increases above their eutectic point and percentage of Si presence in the mixture increased as heating continues. Rapid cooling occurred at the surface of these alloy melted when nitrogen gas was flowed into the chamber. This had caused the phase separation of the silicon from the surface of the alloy droplets and eventually self-arranged to form nanowires. Controlled growth of the nanowires was achieved by manipulating the annealing parameters. Relatively straight nanowires were produced by annealed the sample at 1000°C with nitrogen flow set to 1.5 liters per minute. The as-growth nanowires had diameters varied between 30 and 70nm. Heating duration was used to control the amount and lengths of the nanowires. Heating for 15 minutes produced less amount and shorter nanowires, while a 4-hour heating produced nanowires more than hundreds of microns long and with much larger amount.