The plasma–sheath boundary region

TLDR

This review aims to provide a comprehensive overview of the plasma–sheath interface across diverse physical conditions. The authors synthesize historical and recent literature, avoiding mathematical complexity while preserving physical insight, to clarify the structure and evolution of the plasma–sheath boundary. The review identifies gaps in existing explanations and presents original work that reconciles earlier theories into a consistent picture of the plasma–sheath boundary.

Abstract

In this review an attempt is made to give a broad coverage of the problem of joining plasma and sheath over a wide range of physical conditions. We go back to the earliest works quoting them, where appropriate, to understand what those who introduced the various terms associated with the structure of the plasma–sheath had in mind. We try to bring out the essence of the insights that have been gained subsequently, by quoting from the literature selectively, indicating how misunderstandings have arisen. In order to make it accessible to the generality of those currently working in low temperature plasmas we have sought to avoid mathematical complexity but retain physical insight, quoting from published work where appropriate. Nevertheless, in clarifying my own ideas I have found it necessary to do additional original work in order to give a consistent picture. In this way I have sought to bring together work in the late 1920s, the 1960s, and now mindful of the commercial importance of plasma processing, work over the past 15 years that adds to the general understanding.