A Three-Temperature Zero-Dimensional Model of a Hydrogen Microwave Plasma

A nonequilibrium plasma is numerically simulated in zero-dimension using a three-temperature model for a microwave powered plasma used for diamond film deposition. Two energy equations (electron and vibration) and seven species equations are solved with an approximate accounting for diffusion losses to a substrate surface. Simulations are run at conditions in which the size of the plasma is held constant while varying the pressure and microwave power. Results are given as function of power density and show that the difference in vibrational and translational temperature varies approximately as the inverse of the pressure squared. The electron temperature and electron mole fraction decrease, while the H-atom mole fraction increases with increasing power density. The prediction of H-atom mole fraction is in reasonable agreement with measurements. Also studied is the effect of a non-Maxwellian electron energy distribution function (EEDF), that shows that the H-atom mole fraction and the electron temperature is higher, whereas the electron mole fraction is lower, compared with a Maxwellian EEDF assumption. However, the difference in the H-atom predictions is within experimental accuracy, 187 therefore one cannot use these data to validate the nonequilibrium EEDF.