Paul Masih Das and Marija Drndić from the University of Pennsylvania published their research demonstrating in-situ electron-beam gating of monolayer MoS₂ devices using the Hummingbird Scientific electrical biasing TEM sample holder. This work highlights how electron microscopy can actively modulate functional 2D material nanoelectronic devices during in-situ measurement, enabling direct correlation between beam conditions and electrical transport inside the TEM.

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Rather than using a conventional gate electrode, the team employed the TEM electron beam itself as a tunable, non-contact gate. When the 200 keV beam impinged on the suspended silicon nitride (SiNx) membrane supporting the device, it induced substrate charging, creating a positive surface potential that suppressed conductance in the MoS₂ channel. The effect was strong and reversible: conductance suppression of up to 94% and on/off ratios as high as 56 were observed under higher beam currents, with minimal hysteresis when the beam avoided direct exposure of the MoS₂ channel. Critically, when the beam was directed through a micron-scale hole in the SiNx membrane—avoiding substrate charging—no gating occurred, confirming that the field effect originated from beam-induced charging of the insulating window.

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By leveraging the stability and electrical performance of the Hummingbird Scientific electrical biasing TEM sample holder, the researchers established a robust in-situ platform where structural imaging and transistor-like transport measurements occur simultaneously. The results demonstrate that electron-beam-induced substrate charging can function as a controllable gate parameter without complex multi-terminal fabrication, opening new opportunities for studying 2D nanoelectronic devices under direct microscopic observation.

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Reference:

Paul Masih Das & Marija Drndić, ACS Nano, 14, 6, 7389–7397 (2020). DOI: 10.1021/acsnano.0c02908