In Situ 2D MoS₂ Field-Effect Transistors with an Electron Beam Gate

We use the beam of a transmission electron microscope (TEM) to modulate in situ the current–voltage characteristics of a two-terminal monolayer molybdenum disulfide (MoS 2 ) channel fabricated on a silicon nitride substrate. Suppression of the two-dimensional (2D) MoS 2 channel conductance up to 94% is observed when the beam hits and charges the substrate surface. Gate-tunable transistor characteristics dependent on beam current are observed even when the beam is up to tens of microns away from the channel. In contrast, conductance remains constant when the beam passes through a micron-sized hole in the substrate. There is no MoS 2 structural damage during gating, and the conductance reverts to its original value when the beam is turned off. We observe on/off ratios up to ∼60 that are largely independent of beam size and channel length. This TEM field-effect transistor architecture with electron beam gating provides a platform for future in situ electrical measurements.