Measurements of transient sheaths and rf affected plasma potential

Plasma potential and sheath structure play an important role in many industrial plasma applications. Recent advances in diagnostic techniques, such as laser induced fluorescence and optogalvanic effect, have expanded the understanding of the sheath phenomena in commercial devices, however; two dimensional and time dependent characteristics of those parameters are still poorly understood. The authors present the experimental measurements of the transient sheath near an electrode with sudden negative bias in a collisionless argon plasma. The sheath is found to start as a matrix sheath, then expands to have a greater extent than Child-Languir sheath, and finally contracts to Child-Langmuir sheath. RF effects are also measured in parallel plasma capacitor. The results show that, from DC up to 500 KHz, the plasma potential profiles vary significantly. To avoid rf related complications in plasma production a hot-filament discharge plasma in a multidipole device is used. Typical plasma parameters are n = 10/sup 8/ -- 10/sup 9/ cm/sup -3/, T/sub ./ -- 2 eV, T/sub i/ -- 0.2 eV, P/sub o/ -- 10/sup -4./Torr. Data are obtained using emissive probes with two different techniques--time resolved sampling and time averaged techniques. Scaling with different plasma parameters and boundary conditions are discussed. Data from 0.1 to 1 Torr rf glow discharge plasmas are also discussed