Langmuir Probe, Optical, And Mass Characterization Of A Dc Co2-H-2 Plasma

We present a detailed Langmuir probe, optical emission spectroscopy (OES), and quadrupole mass spectrometry (QMS) characterization of a DC CO2-H-2 plasma mixture, complemented by calculations of the electron energy distribution functions (EEDFs) and ionization rates of CO2 plasma with varying H-2 ratios using Boltzmann equation (BE) solver BOLSIG+, assuming a bi-Maxwellian distribution. Both the measured and calculated EEDFs as a function of the H-2 concentration agreed well and showed a bi-Maxwellian distribution. The measured and calculated electron temperatures T-e as a function of the increment in the H-2 concentration (0-100%) increased in the range of 2.5-3.1eV. The measured and calculated electron densities (N-e) as a function of H-2 concentration exhibited the same increasing behavior (approximately 10(10)cm(-3)), which confirms that the mixture composition directly influences the plasma-related parameters and results in a large fraction of H atoms by reaction e + H-2 -> H+H. An ascending T-e would result in higher ionization rates (explaining the observed increase in electron densities), which agrees with the ionization rate behavior obtained by the BE calculation. Both OES and QMS techniques detected the species H (through the lines H-alpha, H-beta, and H gamma), CO, CO2, CO2+, O-2, OH, O, C-2, CO, and CO+. An analysis of the CO/CO2 and O-2/CO2 ratios would clarify that OH is formed from O-2 + H -> OH + O rather than other reactions involving CO species. At a 100% CO2 concentration, CO and O-2 formations proceed in accordance with the stoichiometry of 2CO(2) -> 2CO + O-2.