Ion dynamics in capacitively coupled argon-xenon discharges

TL;DR

This study uses simulations and models to explore how gas mixture ratios and voltage influence ion behavior in argon-xenon plasma discharges, revealing control mechanisms for ion energy and flux.

Contribution

It introduces a detailed analysis of ion dynamics in Ar/Xe plasmas, highlighting the impact of gas mixture and voltage on ion energy distributions and flux control.

Findings

Gas composition shifts ion energy distribution from collisionless to collision dominated.

Gas mixture ratio controls ion flux and surface impingement energy.

Synergy effect observed between argon and xenon ionization processes.

Abstract

An argon-xenon (Ar/Xe) plasma is used as a model system for complex plasmas. Based on this system, symmetric low-pressure capacitively coupled radio-frequency discharges are examined utilizing Particle-In-Cell/Monte Carlo Collisions (PIC/MCC) simulations. In addition to the simulation, an analytical energy balance model fed with the simulation data is applied to analyze the findings further. This work focuses on investigating the ion dynamics in a plasma with two ion species and a gas mixture as background. By varying the gas composition and driving voltage of the single-frequency discharge, fundamental mechanics of the discharge, such as the evolution of the plasma density and the energy dispersion, are discussed. Thereby, close attention is paid to these measures' influence on the ion energy distribution functions at the electrode surfaces. The results show that both the gas composition and the driving voltage can significantly impact the ion dynamics. The mixing ratio of argon to xenon allows for shifting the distribution function for one ion species from collisionless to collision dominated. The mixing ratio serves as a control parameter for the ion flux and the impingement energy of ions at the surfaces. Additionally, a synergy effect between the ionization of argon and the ionization of xenon is found and discussed.