Study of Ionization Rate in Microwave Microplasmas by PIC/MCC Simulations

Microwave microplasmas play an important role in numerous areas, such as semiconductor fabrication, combustion, and medicine. On the other hand, microwave breakdown must be suppressed in transmission lines, magnetrons, and MEMS. Both cases require improved prediction of microwave breakdown voltage for micro-/nanoscale gaps
¹
, where the ionization rate is an essential parameter that differs from the classical value for DC fields
²
. Previously, the microwave ionization rate in atmospheric air was written analytically based on the DC equation
³
; however, this formula is invalid for microwave fields at microscale gaps. A comprehensive assessment of the ionization rate with gap distance, pressure, electric field, and frequency is required for incorporation into analytic theories
³
.