Field emission control by work function modulation in graphene edge cathodes

Abstract

We investigate the potential of nanovacuum devices utilizing graphene edges as field emitters, with their work function modulated by a nearby gate on the graphene surface. Unlike metals, the semi-metallic nature of graphene enables modulation of the Fermi level and work function via the surface field. This modulation alters the potential barrier for field emission. Our simulation study reveals that device operation critically depends on two screening factors—horizontal and vertical. Horizontally, work function modulation occurs when the emitter edge is within the critical screening length from the gate edge. Vertically, the effectiveness of work function modulation diminishes beyond the second layer of multi-layer graphene due to surface field screening by the first layer. Our simulations demonstrate that maintaining the vacuum channel on tens of nanometer scale enables transistor-like operation of the device, with remarkably high cut-off frequencies and maximum oscillation frequencies ranging from 0.45 to 0.71 and 32.9 to 40.5 THz, respectively, under source–drain bias from 90 to 100 V.