Metallic Tungsten Nanostructures and Highly Nanostructured Thin Films by Deposition of Tungsten Oxide and Subsequent Reduction in a Single Hot-Wire CVD Process

The synthesis of metallic tungsten nanostructures and highly nanostructured thin films is presented. Crystalline tungsten oxide nanostructures are deposited on glassy carbon substrates kept at 700 100 8C by oxidizing resistively heated tungsten filaments in an air flow under subatmospheric pressures. The internal morphology of the deposited tungsten oxide can be reproducibly controlled by the air pressure. After deposition, the tungsten oxides have been fully reduced to metallic tungsten by atomic hydrogen at a temperature of about 730 8C. Polycrystalline metallic tungsten nanofibers, nanocrystallites, closed crystallite films, and nanogranular films are thus obtained in a single procedure involving deposition and subsequent reduction, at relatively low temperatures.