Using a scanning tunneling microscope (STM), Si nanowires were grown by applying a voltage at a constant current between a Si substrate and a gold STM tip. Silicon atoms were deposited onto a gold tip by field evaporation. The field evaporation rate of silicon atoms was activated by heating the substrate. Silicon nanowire was grown on the gold tip at a substrate temperature of 700 °C. Nanowires could not be grown on a clean tungsten tip when using a gold-free Si substrate. The presence of gold atoms is important for the growth of silicon. Apparently, gold atoms deposited on the silicon substrate by field evaporation reduce the activation energy of field evaporation by attacking Si-Si bonds.