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 °C 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 °C. 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. In a single deposition process, tungsten oxide nanostructures and nanostructured thin films were deposited by Hot‐Wire Chemical Vapor Deposition and subsequently reduced by atomic hydrogen at a temperature of 700 ± 100 °C. Metallic tungsten nanostructures and nanostructured thin films of varying morphology can thus controllable be obtained by this method. The metallic structures were, amongst others, characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction (XRD).