First-principles study of the electronic properties of graphene nanostructures for high current density cathodes

Graphene is a crystalline allotrope of carbon with 2D properties. Its carbon atoms are densely packed in a nanoscale hexagonal pattern. Graphene has many unusual properties. In this study, the authors study the electronic properties of graphene nanostructures using first-principles or ab initio calculations based on density functional theory as implemented in the Vienna ab initio simulation package in order to explore its applications in field-emission devices. The density of states and work function of graphene nanoribbons are calculated. The work function value is a key parameter in determining the field emission from a cathode surface according to the Fowler-Nordheim theory. For practical applications, the work functions of graphene nanoribbons with different widths and terminating edges, with and without passivation, have been investigated. Specifically, with the decoration of different alkali and alkaline earth metal species, the reduction of the work function has been systematically studied and determined for achieving higher current density emission.