2D transition metal dichalcogenides nanosheets as gate modulated cold electron emitters

We report a detailed investigation of the field emission properties of transition metal dichalcogenides, namely MoS
2
and WSe
2
, taking advantage of an experimental setup realized inside a scanning electron microscope equipped with nano-manipulated probe-tips, used for positioning a tip-shaped anode at a nanometric distance from the emitting surface. For n-type WSe
2
monolayer on Si/SiO
2
substrate, we show that electrons can be extracted also from the flat part of the flake with a current intensity up to few nanoamperes. More interestingly, we demonstrate that the field emission current can be modulated by the back-gate voltage that controls the n-type doping of the WSe
2
monolayer. Similarly, we demonstrate that monolayer MoS
2
flakes are suitable for gate-controlled field emission devices, opening the way to the development of new field emission transistors based on ultrathin materials.