Synthesis and Raman spectroscopic study of W20O58nanowires

Crystalline W20O58 nanowires were grown on silicon substrates by thermal evaporation of tungsten powders in a flow of argon gas without using any catalyst. Scanning electron microscopy shows that typical nanowires vary from 30 to 100 nm in diameter and around 8 µm in length. X-ray diffraction and high-resolution transmission electron microscopy with electron diffraction study reveal that the nanostructures are crystalline. The laser power effect on the structure change of W20O58 nanowires has also been studied, which shows that W20O58 can be directly oxidized to WO3 very easily only by laser heating.