Transitions between field emission and vacuum breakdown in nanoscale gaps

Abstract

The continuing reduction in device size motivates a more fundamental understanding of breakdown and electron emission for nanoscale gaps. While prior experiments have separately studied breakdown and electron emission in vacuum gaps, no study has comprehensively examined the transitions between these mechanisms. In this study, we measure the current-voltage [Formula: see text] curves for electrodes with different emitter widths for 20–800 nm gaps at vacuum (∼1 μTorr) to measure breakdown voltage and assess electron emission behavior. The breakdown voltage [Formula: see text] increases linearly with increasing gap distance from ∼15 V at 20 nm to ∼220 V at 300 nm and remains nearly constant for larger gaps; [Formula: see text] does not depend strongly on the emitter width. Breakdown can proceed directly from the field emission regime. Nexus theory, which predicts transitions between space-charge limited current (SCLC) and field emission (FE), shows that the experimental conditions are in the Fowler–Nordheim regime and within a factor of 0.7 to the FE-SCLC transition. We also present the results of electrode damage by emission current-induced heating to explain the flattening of [Formula: see text] at larger gaps that was absent in previous experiments for similar gap distances at atmospheric pressure.

The transition from field emission to collisional space-charge limited current with nonzero initial velocity

“…We have recently experimentally and theoretically assessed the transitions between FN, MG, CL, and field emission-driven breakdown for nanoscale gaps at atmospheric pressure 7 and vacuum 56 near the third-order nexus between FN, MG, and CL. Other theories have examined thermo-field emission driven breakdown for microscale gaps at microwave frequencies 57 , 58 , indicating that the electrons undergoing these mechanisms need not only originate from cold cathodes.…”