Effect of local gas heating on a plasma structure driven at radio frequency in a microcell in Ar at atmospheric pressure

Abstract

In a microplasma in Ar confined at atmospheric pressure, driven at 13.56 MHz, we theoretically investigate the whole structure of a low-temperature plasma including the local distribution in gas temperature inside and outside a microcell. The governing equation of gas and wall temperature is combined with our original relaxation continuum model of an rf plasma. We demonstrate that electrons with intermediate energy play an important role in plasma production through stepwise ionization and metastable pooling in the presence of high-density metastables. Next, we examine the enhancement of the net ionization rate through the increase in the local reduced field under a broad minimum of the heated gas density. The atmospheric-pressure microcell plasma will be classified into a new spatiotemporal sustaining mechanism in the capacitively coupled plasma at 13.56 MHz. This work predicts the presence of a nonequilibrium, steady plasma in a microcell even at atmospheric pressure in Ar under appropriate conditions.

Metastable argon atom kinetics in a low-pressure capacitively coupled radio frequency discharge

“…While metastable densities in this range seem to be typical in CCPs operated at low pressure (≲ 1 Torr), orders of magnitude higher densities can be achieved in discharges operated at atmospheric pressure, as done, e.g. in the work reported by Yamasaki et al [92]. In this work, the plasma was ignited in a microcell with characteristic dimensions of ≈1 mm, with a 13.56 MHz RF voltage with 500 V amplitude.…”