Silver nanowires are formed by the thermal reduction of an aqueous silver nitrate solution on the surface of TiO2 thin films. A variety of silver nanostructures including nanowires were prepared by variations in the crystallinity of TiO2 thin films and heat-treatment temperature. Under appropriate conditions, silver nanowires 30-100 nm in diameter and 1-50 Am in length were produced. The nanowires are found only on anatase TiO2 thin films, and the yield of nanowires increases with the anatase crystallinity. While other substrate materials, including rutile TiO2 films, silicon wafers, indium tin oxide glasses, quartz coupons, chemical-vapor deposited diamond thin films, and alloy films, were used under comparable conditions, no silver nanowires were observed. The formation of silver nanowires seems to be related to the photocatalytic properties of anatase TiO2. (c) 2005 American Vacuum Society.