Kinetic model of a low-pressure microwave discharge in O₂-H₂ including the effects of O^- ions on the characteristics for plasma maintenance

A consistent theoretical analysis of a low-pressure (p = 1 Torr) microwave discharge ( MHz and 2450 MHz) in O₂-H₂ is presented. The model is based on the coupled solutions to the homogeneous electron Boltzmann equation and a system of rate balance equations for the dominant neutral and charged particles in the discharge. The sustaining electric field is self-consistently derived from the set of continuity and momentum transfer equations for electrons and ions O₂⁺, O⁺, NO⁺, N₄⁺, and O^-. A deviation from the classical ambipolar diffusion is observed due to the presence of O^- ions. The recombination of O(³P) atoms on the tube walls is taken into account through a Monte-Carlo-like simulation of a sequence of elementary surface processes. This formulation provides results for the mean input power absorbed from the field per electron, , and for the concentrations of and O(³P) in satisfactory agreement with measured data. Other important calculated data such as the concentrations of the ionic species and the percentage contributions of the various ionization mechanisms are also reported.