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

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 (γC) are quantified. The theoretically calculated γC 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.