Easy growth of large-area tungsten oxide nanostructures and their field emission properties

Large area tungsten trioxide (WO3) nanosheets and nanoribbons were synthesized by directly heating tungsten plates covered with potassium iodide (KI). The field emission properties of the as-grown samples were systematically measured. A 10 µA/cm² current density was obtained from both samples under a 5.5 V/µm average field, while the average fields that extracted a current density of 1.0 mA/cm² were 8.2 and 11.1 V/µm for the nanosheets and nanoribbons, respectively. Also, the emission sites were found to distribute uniformly on the whole sample surface. In the preliminary test on the stability, the WO3 nanosheets, which had larger surface area, exhibited better robustness than the WO3 nanoribbons. These findings have demonstrated the application perspectives of nanometer-scale tungsten oxide as future cold electron sources.