Spatial distributions of electron density and temperature in audio frequency and radio frequency magnetron glow discharges

The spatial distributions of electron density and temperature in parallel plate audio frequency (AF) (40 kHz) and radio frequency (RF) (13.56 MHz) magnetron discharges were obtained using double Langmuir probes. At 30 W and 580 mTorr argon, electron density ranged from 5×108/cm3 to 1.5×109/cm3 and electron temperature ranged from 3.4 to 4.6 eV in the AF discharge. For 30 W net power and 580 mTorr argon in the RF discharge, electron density ranged from 2×109/cm3 to 8×109/cm3 and electron temperature ranged from 2.5 to 3.6 eV. Electron temperature in the AF discharge increases as the discharge axis is approached, and is independent of axial position. In the RF discharge electron temperature increases near the electrode surface. Electron density distributions in both discharges show the influence of magnetic fields, with the maximum electron density occurring at the position where the radial component of the magnetic field (parallel to the electrode surface) is at a maximum. In the AF discharge, this influence is no longer apparent at axial distances from the electrode surface beyond 2.5 cm. In the RF discharge, radial variations in electron density characteristic of magnetic confinement are observed throughout the plasma, even at the center plane between electrodes.