Negative plasma potential in a chamber with a dielectric coated plasma boundary

Abstract

Summary form only given. Negative plasma potentials with respect to a grounded wall that was coated with a dielectric have been achieved in an electropositive plasma confined by a multidipole device. A Langmuir probe was used to measure the density and temperature of the electrons and an emissive probe was used to measure the plasma potential profile near the plasma boundary. For many discharge parameters, the potential profile was that of a typical electropositive sheath, but it was shifted negative due to negative charge accumulated on the plasma-surface boundary. A virtual cathode was observed near the boundary when the neutral pressure, primary electron energy, and/or discharge current were low (for example, 2×10−4 Torr, 60 eV, and 80 mA, respectively). The behavior of the sheath potential was shown to be consistent with that predicted by electron creation and loss balance and a qualitative mechanism for wall charging is presented.