The Influence of Morphological Characteristics of Graphene on Its Field Emission Properties

Abstract

Graphene is one of the most potential field emission cathode materials due to its excellent electrical, thermal, and mechanical properties, as well as rich edge structures. In this paper, we studied the growth parameters of graphene prepared by chemical vapor deposition, and prepared three kinds of morphologies of graphene: single-layer graphene, graphene islands, and graphene with buffer layers, and then we explored the influence of the morphological characteristics of graphene on its field emission properties, and analyzed the mechanism of the morphological characteristics of graphene on its field emission properties through COMSOL. Compared to single-layer graphene, the turn-on field of graphene islands, and graphene with buffer layers was 5.55 V/μm and 5.85 V/μm, respectively. The current density has also been increased to 40.3 μA/cm<sup>2</sup> and 26.4 μA/cm<sup>2</sup>. On the other hand, the field emission currents of single-layer graphene and graphene with buffer layers are more stable. In the 5-hour test, the current density only decreased by 2% and 4%, respectively. COMSOL simulation shows that the morphological characteristics of graphene have a significant impact on the electric field distribution characteristics and heat dissipation capacity. Graphene islands and graphene with buffer layers have exposed edges, leading to local electric field concentration and thus improving field emission properties. Graphene islands are distributed discretely on the substrate, without forming a continuous graphene film and lacking transverse heat dissipation channels, so the accumulation of heat will cause damage to the graphene emitter, and affect the stability of its field emission current. This study would be of great benefit to the understanding of the influence of the morphological characteristics of graphene on its field emission properties, and improving the field emission properties of graphene materials.