Nano vacuum devices utilizing two dimensional semiconductors and their potential

Abstract

We have explored the potential of nanoscale vacuum channel transistors that utilize the edges of transition-metal dichalcogenides (TMDCs) as field emitters for high-frequency applications. The angstrom-scale thickness of monolayer TMDCs in a two-dimensional structure induces a strong field enhancement effect at the edge, facilitating cold emission. Additionally, their semiconducting nature enables control of the emission current by adjusting the tunneling barrier height through Fermi level control via the gate structure. We analyzed the field emission properties of monolayer TMDCs (MoS₂, MoSe₂, and WS₂), examining their current-voltage characteristics based on Fowler-Nordheim theory within a three-terminal vacuum channel transistor system. In this configuration, the emitter is aligned towards the drain electrode, parallel to the substrate, and the carrier dynamics were investigated in detail within the TMDC channels. We further calculated the screening effect induced by gate bias modulation, taking into account the extent of the monolayer TMDC edge protrusion into the vacuum channel. Additionally, we studied the distinctive modulation of the field enhancement factor, which can be adjusted through gate bias control. Finally, under a source-drain bias of 100 V, the transistors demonstrated both cutoff and maximum oscillation frequencies in the sub-terahertz to terahertz range, confirming their high-frequency operational potential.