Perturbation of the cathode fall in direct-current glow discharges by particulate contamination

Abstract

Particulate (or ‘‘dust’’) contamination of plasma materials processing discharges is known to reduce yields of the product and to perturb electron transport. Dust preferentially accumulates near the cathode sheath-plasma boundary where energetic electrons accelerated in the cathode fall emanate into the negative glow. In this letter, we theoretically investigate the penetration of the electron flux generated in dc cathode falls through the particulate ‘‘barriers’’ formed by dust contamination. We find that at constant current densities, the plasma responds to the reduction in ionization rate coefficients caused by the particulates by increasing the electric field in the cathode fall. In doing so, the cathode fall voltage increases and cathode fall thickness decreases.