Experimental study of electron impact ionization in field emission-driven microdischarges

Abstract

Field emission can act as a significant source of primary electrons in direct current microdischarges generated in geometries truly at the microscale (∼1–10 µm). Using field emission as a source of primary electrons, it is possible to produce a stable pre-breakdown Townsend discharge with modestly high current at pressures up to atmospheric. Recent theories for field emission-driven Townsend discharges, or more simply field emission-driven microdischarges, show that the field emission current will be multiplied by electron impact ionization in the electrode gap. In this work, experiments using microfabricated, parallel-plate discharge devices showed that the measured anode current increases exponentially with pressure, consistent with the theory for field emission-driven microdischarges operated in a pre-breakdown regime. Furthermore, extracted average ionization cross-sections on the order of 10−19–10−20 m2 are comparable to those predicted by particle-in-cell/Monte Carlo collision simulations of the same experimental conditions.