Preparation of tungsten oxide nanowires from sputter-deposited WC _x films using an annealing/oxidation process

The self-synthesis of tungsten oxide (W18 O49) nanowires on sputter-deposited W Cx films using a simple annealing/oxidization process was reported. It was found that thermal annealing of W Cx films at 680 °C for 30 min in nitrogen followed by oxidation at 450 °C for 30 min in pure oxygen would yield dense and well-crystallized monoclinic W18 O49 (010) nanowires with a typical length/diameter of about 0.15-0.2 μm10-20 nm. The formation of W18 O49 nanowires is attributed to the nuclei of immature W2 C nanowires experiencing a regrowth process, accompanied by carbon depletion and the oxidization of tungsten during the subsequent oxidization process.