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 (I−V) 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 Vb 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; Vb 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 Vb at larger gaps that was absent in previous experiments for similar gap distances at atmospheric pressure.