The effect of heating time on growth of NaxWO3 nanowhiskers

A simple method for synthesis of NaxWO3 nanowhiskers on tungsten thin films with 40 nm thickness sputtered on soda lime substrate as a source of sodium atoms has been reported for the first time. After heat treatment of the W thin films at 650 °C in N2 ambient for different times (15, 80 and 180 min), crystalline NaxWO3 nanowhiskers with [0 0 1] direction were obtained. scanning electron microscopy (SEM), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and optical transmission/reflection measurements were employed to determine various properties of the grown nanowhiskers. Experimental results revealed that size and density of nanowhiskers were dependent on the annealing time and found that the 80-min heat treatment was a proper time for the growth of sodium-doped tungsten oxide nanowhiskers, in our experimental conditions. According to SEM observations, the synthesized nanowhiskers have 70–300 nm in width and 1–10 μm in length. It was also observed that by increasing the heating time to 180 min resulted in diffusion of the nanowhiskers into the substrate.