Diameter control of tungsten oxide nanowires as grown by thermal evaporation

Tungsten oxide nanowires with controllable diameter were synthesized on Si substrates by thermal evaporation of tungsten trioxide powder in a tube furnace. Depending on the temperature of the source (900-1000 °C), tungsten oxide W(18)O(49) nanowires with diameters ranging from 10 to 100 nm are obtained with high yield. The exponential dependence of the nanowire diameter on the source temperature leads to an energy of about 2.0 eV. The growth process is discussed; it is believed to be a kinetic effect.