Characterization and Modeling of DC & RF Breakdown in Microscale Gaps near Vacuum*

Plasma breakdown in both radiofrequency (RF) driven and large-Knudsen number gaps requires lower voltage than the classical Paschen curve predicts. However, while these two regimes have been investigated independently in prior studies, we are unaware of any studies on RF-driven, large-Knudsen number gaps. The present work seeks to unify these two regimes and study the discharge behavior of large-Knudsen number gaps driven at GHz frequencies, thereby allowing very low voltage RF switches and limiters. We have fabricated gold-electrode devices with gaps as small as 100nm that can be operated in a vacuum chamber at DC to GHz frequencies and will report on the experimentally determined breakdown voltage vs. gap size at various pressures from atmospheric down to vacuum (from small-to-large Knudsen numbers) for both DC- and RF-driven devices. We also present simulations of device operation using the Particle-In-Cell Direct Simulation Monte Carlo (PIC-DSMC) electromagnetic plasma code EMPIRE, with a model that has ion-induced Secondary Electron Emission (SEE) and electron impact ionization, as well as Fowler Nordheim field emission and energy-dependent electron-induced SEE.