Influence of field emission on microwave microdischarges

Abstract

An instability in the stable operation of microdischarges sustained at microwave frequencies, is investigated by a self-consistent one-dimensional particle-in-cell Monte Carlo collisions model. The instability is caused by the field electron emission from electrodes and is triggered by the high electric fields at the sheaths in a dense microplasma. For an operating frequency of 9 GHz, and electrode gap of 60 µm, the field emission (FE) is not active at the breakdown voltage. However, once a stable dense plasma is produced post-breakdown, a strong sheath results in an electrode electric fields that exceed the threshold for FE causing a runaway in the electron generation in the plasma.