Morphological optimization of large-area arrays of TiO2 nanowires & nanotubes for enhanced cold field emission: experiment and theory

Abstract

Designed by finite elemental modelling, large-area arrays of TiO2 nanowires and nanotubes with differentiated heights mixed together are synthesized on a planar Ti wafer via hydrothermal methods. Experimental measurements reveal that the TiO2 nanowire/tubes arrays with differentiated heights demonstrate a lower shielding effect and their cold field emission (CFE) performances can be further enhanced by increasing their height/diameter ratios for both the nanowires and nanotubes. Theoretically, the TiO2 nanowires and nanotubes are simplified to a "Zero Thickness Charge Disc (ZTCD)" model, based on which their characteristic macroscopic field enhancement factors (gamma C) are quantified. The theoretically calculated gamma C values are in good agreement with the experimental ones of the TiO2 nanowires and tubes with a series of geometrical parameters. The TiO2 nanowires and nanotubes have promising potential in CFE. The "ZTCD" model is valuable for future research on quasi-one-dimensional field emitters.