Enhancement of field emission performance of graphene nanowalls: the role of compound-cathode architecture and anode proximity effect

Abstract

The Schottky Conjecture (SC) suggests the use of a multiscale cathode to increase the local electric field at a field-emitting tip. A similar increase in local field also occurs when the anode is in close proximity to the cathode. The authors take advantage of these twin effects to design a compound cathode consisting of a macroscopic base with a much smaller wire-protrusion having an end-cap. Field emission experiments were performed using two different compound-cathode setups, each consisting of an adjustable-height Kovar wire with graphene nanowalls deposition as the end-cap, and a macroscopic base on which the Kovar wire is mounted. The field emission data was recorded for both compound-cathodes at different anode positions. Experimental results indicate remarkable improvement in field emission current density while adopting an optimized diode architecture. Stable emission was observed and a maximum current density of 46 mA/cm2 was extracted from the sample. An analysis of the experimental data, aided by additional numerical simulations, clearly shows the combined effect of the recently proposed Corrected Schottky Conjecture and the anode proximity effect. It is thus possible to realize an efficient field emitter device by tweaking the geometry of the diode structure.

Keywords

• Graphene nanowalls
• Field emission
• Schottky Conjecture
• Anode-proximity