ELECTRON-ENERGY DISTRIBUTION FUNCTION MEASUREMENTS IN A PLANAR INDUCTIVE OXYGEN RADIO-FREQUENCY GLOW-DISCHARGE

A tuned, cylindrical Langmuir probe was used to measure current-voltage traces in a planar, inductive oxygen, radio frequency glow discharge at several pressures ranging from 0.5 to 10 mT. The plasma potentials were determined from the zero crossings of the trace second derivatives. Positive ion densities were evaluated using orbit motion limited probe theory; electron densities were estimated by integrating the area under the unnormalized distribution function. By applying the Druyvesteyn formula to the digitized probe traces, the electron energy distribution functions were obtained. The distribution functions ranged from Maxwellian at 0.5 mT to almost Druyvesteyn-like at 10 mT.