Field Emission Control via Work Function Modulation in Semimetallic Graphene Edge Cathodes.

Graphene, the bandgapless 2D crystal, uniquely combines metal-like conductivity with an electrostatically tunable Fermi level-an ability that conventional metals lack. Here, we exploit this semimetallic property to realize a vacuum edge emitter whose current can be directly modulated through work function control rather than relying on vacuum-channel field reshaping. We demonstrate a graphene edge-emitter nanoscale vacuum transistor with an off-channel gate, enabling spatial separation of emission and control fields and achieving current saturation and low-voltage modulation across a 500 nm vacuum gap. This architecture minimizes interception and leakage while offering a structurally simple and scalable means of accessing direct Fermi-level modulation at the emission site. The device shows stable Fowler-Nordheim tunneling from 10 to 300 K, with gate-tunable emission onset and saturation current. Using small-signal parameters extracted entirely from measured I-V data, we further illustrate, through numerical analysis, that the demonstrated device characteristics are consistent with amplification behavior when placed in canonical circuit topologies. More broadly, the direct work-function modulation strategy provides a general pathway for precise control of vacuum electron emission, with potential relevance for RF, cryogenic, and radiation-resilient electronic systems.