Intense boundary emission destroys normal radio-frequency plasma sheath

TL;DR

This paper reveals that intense boundary emission can eliminate normal RF plasma sheaths, leading to a new plasma state with potential applications in erosion mitigation and plasma processing control.

Contribution

It presents the first evidence that intense boundary emission destroys RF sheaths, introducing a novel plasma regime with distinct particle and energy dynamics.

Findings

Intense boundary emission destroys normal RF sheaths.

A new RF plasma state with bulk plasma bias consumption.

Potential for erosion mitigation and reaction control.

Abstract

Plasma sheath is the non-neutral space charge region that isolates bulk plasma from boundary. Radio-frequency (RF) sheathes are formed when applying RF voltage to electrodes. Generally, applied bias is mainly consumed by RF sheath which shields external field. Here we report first evidence that intense boundary emission destroys normal RF sheath and establishes a novel type of RF plasma where external bias is consumed by bulk plasma instead of sheath. Ions are naturally confined while plasma electrons are unobstructed, generating strong RF current in entire plasma, combined with unique particle and energy balance. Proposed model offers possibility for ion erosion mitigation of plasma-facing component. It also inspires technics for reaction rate control in plasma processing and wave mode conversion.