On the role of secondary electron emission in capacitively coupled radio frequency plasma sheath: a theoretical ground

TL;DR

This paper develops a theoretical framework for understanding the behavior of RF plasma sheaths with secondary electron emission, combining analytical, numerical, and simulation methods to analyze sheath properties and effects.

Contribution

It introduces a comprehensive theoretical approach to model RF plasma sheaths with secondary electron emission, validated by kinetic and particle-in-cell simulations.

Findings

Sheath potential depends on secondary emission coefficient and voltage amplitude.

Analytical and numerical models agree with kinetic simulation results.

Ionization effects influence sheath dynamics and are characterized by simulations.

Abstract

We propose a theoretical ground for emissive capacitively coupled radio-frequency plasma sheath under low pressure. The rf sheath is assumed to be collisionless, and oscillates with external source. A known sinusoidal voltage instead of current is taken as prerequisite to derive sheath dynamics. Kinetic studies are performed to determine mean wall potential as a function of secondary emission coefficient and applied voltage amplitude, with which the complete mean DC sheath is resolved. Analytical analyses under homogeneous model and numerical analyses under inhomogeneous model are conducted to deduce real time sheath properties including space potential, capacitance and stochastic heating. Obtained results are validated by a continuum kinetic simulation without ionization. The influences of collisionality and ionization induced by secondary electrons are elucidated with a particle-in-cell simulation, which further formalizes proposed theories and inspires future works.