Model for the hydrogen atom flux developed in a microwave plasma jet under diamond synthesis conditions

Abstract

Abstract A model is summarized for the hydrogen atom flux in the effluent of a quartz flow tube which is fed by pure molecular hydrogen and which traverse a waveguide excited at microwave (m.w.) frequency. The high subatmospheric pressure, moderate power, convection-dominated conditions modeled are typical of the plasma jet processes for chemically vapor deposited (CVD) diamond. The plasma sustained in the flow tube is predicted to be ‘thermal” in the sense that thermal dissociation of molecular hydrogen strongly dominates dissociation by electron impact, but not in the sense of rough equality of gas and electron temperatures. Both the m.w. power absorbed by the plasma and the incident m.w. power, minimized by adjustment of a movable short circuit which terminates the waveguide, are determined as functions of atom flux for several values of the parameters (pressure and flow rate) which affect transport of the atoms to the substrate.