Electron density measurements of moderate pressure microwave-generated hydrogen discharges

Abstract

Summary form only given, as follows. The electron density is measured in a moderate pressure (30-60 Torr) hydrogen discharge and hydrogen-methane discharge using a millimetre wave open resonator technique. The measurement of the electron density is important for quantifying the importance of electron dissociation and thermal dissociation of the molecular gas as a function of discharge operating conditions. Specifically, the measured electron density values are key in helping to verify the accuracy of numerical models of the plasma discharge reactor. The hydrogen discharge is generated using a resonant cavity microwave source excited at 2.45 GHz. The input power of 500-1000 watts generates a plasma discharge above a substrate holder located in a quartz dome of 5 cm diameter. The plasma ball or hemisphere was positioned in the center of the millimeter wave open resonator operating in the frequency range of 30-32 GHz. The mm-wave open resonator operates with a quality factor of approximately 10,000. The shift in the resonant frequency of the resonator when the plasma electrons are present allows the determination of the electron density. The electron densities measured were in the range of 5-8/spl times/10/sup 11/ cm/sup -1/ for the pressure range of 30-60 Torr. Electron density measurements for various reactor parameter settings will be presented including the addition of methane gas to the hydrogen discharge.