On the evaluation of field emission parameters of V2O5 and TiO2 nanostructure cathodes

The self-assembled V2O5 and TiO2 nanowires are prepared hydrothermally from vanadium (V) hydroxylamido complex and titanium oxide powder, respectively, and studied for their crystalline phase, morphology, and electron emission characteristics. V2O5 is shown to exhibit an orthorhombic phase with preferential growth of the (010) face along the [010] direction; wire size being diameter 100-400 nm, and length several micrometers. TiO2 nanowires depict a monoclinic beta-phase with a typical diameter of similar to 30 nm. Their bundles serve as potential cathodes giving electron emission following the Fowler-Nordheim (F-N) mechanism but from infinitely small areas with large field enhancement factors. In comparison, beta-TiO2 provides better emission characteristics at similar operating parameters (e.g., low threshold voltage 250-400 V and current density 10(9)-10(13) A m(-2)). The unique properties (viz., tip geometry, roughness, and local field enhancement) of one-dimension (1D) nanowires make them prospective candidates for high-brightness electron sources and development of the display devices [1-7]. A simple procedure developed by the authors is applied successfully in actual evaluation of the field emission parameters from the current-voltage data. This involves F-N formulation with physical considerations like variation of work function, effective emission area, and field enhancement factor [31].