Experimental and computational study of the electron power absorption in capacitively coupled neon-oxygen plasmas

Phase Resolved Optical Emission Spectroscopy measurements combined with 1d3v Particle-in-Cell/Monte Carlo Collisions simulations were used to study the electron power absorption in capacitively coupled plasmas in mixtures of neon and oxygen. A wide pressure range (15 Pa - 500 Pa) and a wide mixing range of Ne and O₂ gases (10% - 90%) were considered for a geometrically symmetric plasma reactor with a gap length of 2.5 cm, operated at a driving frequency of 10 MHz and a peak-to-peak voltage of 350 V. Based on the emission / excitation patterns, multiple operation regimes were identified. Localized bright emission features at the bulk boundaries, caused by local maxima in the electronegativity were found at high pressures and high O₂ concentrations. The relative contributions of the ambipolar and the Ohmic electron power absorption were found to vary strongly with the discharge parameters. It was found that the power deposition within the gas causes only a slight increase of the gas temperature above the temperature of the electrodes, which was, however, found to be significant due to the heating of the electrodes by the particles from the plasma.