Time- and space-resolved radio-frequency plasma electron energy distributions from a displacement-current-based electric probe diagnostic

A displacement-current-based, Langmuir probe technique was developed to measure time-resolved and spatially dependent electron energy distribution functions (EEDF) in a 100 mTorr argon plasma. This diagnostic was designed to take consideration of the changes in displacement current collected at the probe due to changes in the probe tip sheath potential. The EEDFs collected displayed evidence of a time-dependent as well as spatially dependent electron beam component. The beam energy was seen to increase with the instantaneous plasma potential. The electron density was found to be 3.2±1.1×109, 1.0±1.5×1010, and 2.7±1.0×109 cm−3 at locations 0.6, 1.8, and 2.8 cm from the grounded electrode, respectively. Mean electron energies were also spatially dependent, measuring 8.7±0.8, 11.3±1.0, and 6.9±0.7 eV at locations 0.6, 1.8, and 2.8 cm from the grounded electrode, respectively.