Nonequilibrium situations in a pulse-modulated Ar–H2 inductively coupled thermal plasma for hydrogen doping

Pulse-modulated inductively coupled plasma (PM-ICP) has been applied to treatment of functional materials. When operating the plasma in pulse-modulated mode, the electron and heavy species temperatures respond to the changes in input power at different time scales. The degree of deviation from equilibrium can be enhanced in such plasma, which in turn affects the behavior of the plasma. The temporal–spatial behavior of thermal and chemical nonequilibrium in an Ar–H2 PM-ICP for hydrogen doping is investigated by means of numerical modeling. The model takes into account time-dependence, two temperatures, and chemical nonequilibrium. Fourteen chemical reactions involving seven species (e, Ar, Ar+, H2, H2+, H, H+) are considered in a chemical kinetics model for estimation of generation rates of the species. The transient distributions of two chemically reactive species, electrons and hydrogen atoms, are also predicted. The time-averaged heavy species temperature and the hydrogen atom density are compared with those obtained at the equivalent power under steady state, with an emphasis to elucidate the benefits of pulse-modulation on materials processing.