Cathode fall model and current-voltage characteristics of field emission driven direct current microplasmas

Abstract

The post-breakdown characteristics of field emission driven microplasma are studied theoretically and numerically. A cathode fall model assuming a linearly varying electric field is used to obtain equations governing the operation of steady state field emission driven microplasmas. The results obtained from the model by solving these equations are compared with particle-in-cell with Monte Carlo collisions simulation results for parameters including the plasma potential, cathode fall thickness, ion number density in the cathode fall, and current density vs voltage curves. The model shows good overall agreement with the simulations but results in slightly overpredicted values for the plasma potential and the cathode fall thickness attributed to the assumed electric field profile. The current density vs voltage curves obtained show an arc region characterized by negative slope as well as an abnormal glow discharge characterized by a positive slope in gaps as small as 10 lm operating at atmospheric pressure. The model also retrieves the traditional macroscale current vs voltage theory in the absence of field emission. V C 2013 AIP Publishing LLC.

Field enhancement factor dependence on electric field and implications on microscale gas breakdown: Theory and experimental interpretation

“…The regions near the tip of such asperities experience an electric field concentration thereby playing a major role in microscale gas breakdown. Traditionally, researchers studying microscale gas breakdown using theory [28,29] or simulations [30][31][32][33] approximate β eff to a value around 50. Assuming a pre-defined value of β eff is done because of the difficulty in directly obtaining β eff for a planar cathode with arbitrary surface roughness distribution.…”

Theory and analysis of operating modes in microplasmas assisted by field emitting cathodes

“…In this regard, the primary goal of this work is to extend the theoretical framework 28 to study microplasma operation at conditions similar to those encountered in the experiments. Specifically, the experimental data are analyzed using the theory of field emission assisted microplasmas.…”

“…While the pre-breakdown regime is characterized by a positively charged gap with significantly higher ion number densities, post-breakdown operation includes a positively charged sheath as well as a quasi-neutral region where the electron and ion number densities are approximately equal. One effort dealing with post-breakdown operation of field emission driven microplasmas was the work by Venkattraman 28 where a sheath model with a linearly varying electric field was used to provide some insights into the current-voltage characteristics of microplasmas with an additional emission mechanism from the cathode. In that work, the author predicted the existence of an abnormal glow mode with a positive differential resistance (dV=dI > 0) and an arc-like mode with a negative differential resistance (dV=dI < 0) in microgaps that are under the influence of field emission.…”

Effect of surface protrusion on plasma sheath properties in atmospheric microdischarges

“…11 A comprehensive analysis of the field distribution and the current emission with the presence of a sharp tip in a finite cathodeanode gap was given by Lin et al 12 Venkattraman investigated the effects of saw-tooth asperity in a channel on the gas breakdown in micro-scale gaps with the field emission mechanism. 13,14 Levko and Raja conducted a fluid modeling of nanosecond pulsed xenon micro-discharge with sphericalprotrusion electrodes. 15 It was previously realized that the discharge behavior depends strongly not only on the cathode dimension, the working gas, or the incident power like in the low-pressure cathodes but also on the electrode material, surface roughness, and protrusions.…”