Intense boundary emission destroys normal radio-frequency plasma sheath

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.