Control of plasma sheath and its potential by dielectric medium

Abstract

Influence of a dielectric medium on the properties of plasma sheaths is investigated. A theoretical model is developed under the assumption that collisionless plasma is confined by two planar electrodes. A planar dielectric medium with a finite thickness is inserted into the plasma, partitioning it into two pieces. Without a priori assumption about the plasma density, an analytical expression of potential distribution in the plasma-dielectric system is obtained. It is found that the electric potential at the dielectric center in high-density plasma is independent of its position and is a half-value of the applied voltage. The electric potential, field, and the charge density in high-density plasma are inversely proportional to the sum of 4+D/ελ, where D and ε are the thickness and dielectric constant, respectively, of the dielectric medium, and λ is the Debye length of high-density plasmas. In this context, the plasma sheaths may easily be controlled by an appropriate choice of dielectric material and its size.