Electron density in moderate pressure diamond deposition discharges

The electron density is measured in a microwave plasma-assisted chemical va por deposition diamond reactor at moderate pressures (5-60 Torr) using a mi llimeter-wave open resonator technique. The discharge plasma is generated u sing a resonant cavity excited at the frequency 2.45 GHz. The absorbed inpu t power of 400 W generates a microwave discharge above a substrate holder l ocated in a quartz dome. The discharge, shaped as a plasma ball or hemisphe re, is positioned in the resonant path of the millimeter-wave open resonato r operating at the frequency 32.2 GHz. The millimeter-wave open resonator o perates with a quality factor of approximately 3500. The shift in the reson ant frequency of the resonator when the discharge plasma is present allows the determination of the electron density. The electron densities measured were in the range of (1-6) x 10(11) cm(-3) for the pressure range of 5-60 T orr. Electron density measurements for various reactor parameter settings a re presented for both pure hydrogen and hydrogen-methane mixture discharges . (C) 2000 Elsevier Science S.A. All rights reserved.