Temporal evolution of collisionless sheaths
Abstract
Experimental measurements have been performed to determine the temporal evolution of Langmuir sheaths near an electrode to which a negative step bias is applied in a collisionless argon plasma. The plasma was produced by a hot-filament discharge in a multidipole device. Plasma potential data were obtained using emissive probes with two different techniques: time-resolved sampling and time-averaged techniques. The sheath is found to initially form close to the electrode, to extend to a maximum separation, and to contract to a steady-state value. The time scale required to reach a steady state is close to the time scale of the presheath relaxation. Characteristics of sheaths in RF plasmas are also measured using a parallel-plate plasma capacitor. It is observed that the plasma potential profile has significant variation with frequency, even for frequencies as low as 1 kHz which are far below the ion plasma frequency (about 1 MHz).
- Publication:
-
Journal of Vacuum Science Technology A: Vacuum Surfaces and Films
- Pub Date:
- September 1988
- DOI:
- 10.1116/1.575462
- Bibcode:
- 1988JVSTA...6.2978C
- Keywords:
-
- Collisionless Plasmas;
- Electrostatic Probes;
- Glow Discharges;
- Plasma Frequencies;
- Plasma Oscillations;
- Plasma Sheaths;
- Electric Fields;
- Poisson Equation;
- Waveforms;
- Plasma Physics