This letter reports the synthesis of silicon nanowires on iron-patterned silicon substrates in a controlled fashion using a method involving thermal evaporation of pure silicon powder. The positions of these silicon nanowires were controlled by depositing iron in desired areas on the substrates. Transmission electron microscopy, high-resolution transmission electron microscopy, and scanning electron microscopy images indicate that the products are straight crystalline silicon nanowires with diameters of 10-60 nm. The formation mechanism of the nanowires is discussed. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]