Low-temperature synthesis of large-scale arrays of aligned tungsten oxide nanorods

We report, in this letter, a simple thermal oxidation approach to growing large-scale arrays of aligned tungsten oxide nanorods on planar substrates. By passing a current of similar to50 A through a tungsten spiral coil in a vacuum of similar to3 x 10(-2) Torr, single-crystalline WO2.9 nanorods, similar to20 nm in diameter and similar to400 nm long, were deposited on planar substrates, e.g. Si(001), Si(111), SiO2/Si, glass, and Ag-coated silicon substrates at temperatures below 200degreesC. The nanorods were vertically aligned on the substrates. The structure, optical properties and alignment of the nanorods was investigated by x-ray diffraction and transmission electron microscopes, micro-Raman spectrometer, and scanning electron microscope and x-ray pole figure measurement, respectively. The present study provides an easy way to grow large-scale arrays of aligned tungsten oxide nanorods at relatively low temperatures, which might also be applicable to the growth of other metal oxides.