Demonstration of field emission driven microscale gas breakdown for pulsed voltages using in-situ optical imaging

While multiple studies have explored the mechanism for DC and AC microscale gas breakdown, few have assessed the mechanism for pulsed voltage gas breakdown at the microscale. This study experimentally and analytically investigates gas breakdown for gap widths from 1 μm to 25 μm. Using an electrical-optical measurement system with a spatial resolution of 1 μm and a temporal resolution of 2 ns, we measure the breakdown voltages and determine breakdown morphology as a function of the gap width. An empirical fit shows that the breakdown voltage varies linearly with the gap distance at smaller gaps, agreeing with an analytical theory for DC microscale gas breakdown coupling field emission and Townsend avalanche that shows that the slope is a function of field emission properties. Furthermore, the curved breakdown paths captured between 5 μm and 10 μm demonstrate a similar effective length (∼11.7 μm) independent of the gap width, which is consistent with a “plateau” in breakdown voltage. This indicates that Townsend avalanche alone is insufficient to drive breakdown for these gaps and that ion enhanced field emission must contribute, in agreement with theory. The overall agreement of measured breakdown voltage with theoretical predictions from 1 μm to 25 μm indicates the applicability of DC microscale gas breakdown theory to pulsed breakdown, demonstrating that pulsed voltages induce a similar transition from Townsend avalanche to field emission as DC and AC voltages at the microscale.