A WSe2 vertical field emission transistor

Abstract

We report the first observation of a gate-controlled field emission current from a tungsten diselenide (WSe₂) monolayer, synthesized by chemical-vapour deposition on a SiO₂/Si substrate. Ni contacted WSe₂ monolayer back-gated transistors, under high vacuum, exhibit n-type conduction and drain-bias dependent transfer characteristics, which are attributed to oxygen/water desorption and drain induced Schottky barrier lowering, respectively. The gate-tuned n-type conduction enables field emission, i.e. the extraction of electrons by quantum tunnelling, even from the flat part of the WSe₂ monolayers. Electron emission occurs under an electric field ∼100 V μm⁻¹ and exhibits good time stability. Remarkably, the field emission current can be modulated by the back-gate voltage. The first field-emission vertical transistor based on the WSe₂ monolayer is thus demonstrated and can pave the way to further optimize new WSe₂ based devices for use in vacuum electronics.