Low pressure argon plasma created by a microwave surface wave

Abstract

Low pressure (0.01-10Torr) argon discharges created by surface waves, at 2-45 GHz and 100-500 W, are characterized. The radial and axial profiles of the electron temperature and density are determined by single and double probes. An increase in the electron density is related to the absorption of the wave power and to the higher ionization efficiency at high pressures. The developed theories are used to explain the axial distribution of the electron density. The probe measurements confirm the presence of maxwellian electron energy distributions in the ranges of gas pressure and wave power. The discharge parameters, e.g. total power needed to maintain the discharge, the mean power required for maintaining the electron, θ, the average maintaining electric field and the effective electric field ⟨E eff⟩ are computed as a function of the gas pressure (P). Similarity laws for θ/P and E eff/N n are developed as a function of the product of gas pressure and plasma radius.