Standing wave instability in large area capacitive discharges operated within or near the gamma mode. (1st November 2022)

• Record Type: Journal Article
• Authors: Lieberman, M A; Kawamura, E; Chabert, P
• Is Part Of: Plasma sources science & technology. Volume 31:Number 11(2022)
• Publication Date: 2022-11-01
• Subjects: large-area -- plasma -- instability -- alpha-to-gamma transition -- capacitive-discharge; Plasma (Ionized gases) -- Periodicals; 530.44
• DOI: 10.1088/1361-6595/aca11f
• Languages: English
• ISSNs: 0963-0252

Abstract

Abstract: Large-area capacitive discharges used for plasma deposition operate in a regime where both electromagnetic and secondary electron emission effects are important. The standing wave shortened wavelength in the presence of plasma depends on the sheath size, and in the γ mode, the secondary electron multiplication controls the sheath physics. Near the α -to- γ transition, and within the γ mode, the sheath width typically varies inversely with the discharge voltage, and large center-to-edge voltage (standing wave) ratios may exist. This can give rise to a standing wave instability, in which the central voltage of the discharge grows uncontrollably, for a given voltage excitation at the discharge edge. Using a simple model, we determine the discharge equilibrium properties, the linearized stability condition, and the nonlinear time evolution. For sufficiently large areas, we show that a discharge equilibrium no longer exists above a critical edge voltage at marginal stability.