Influence of pressure on an asymmetric, radio frequency discharge with methane

Recently, we reported about the influence of flow on deposition rates within an asymmetric, radio frequency (RF) discharge with methane. The plasma expansion of the unconfined discharge was found to contribute strongly to the energy consumed by the film-forming particles. To enhance this macroscopic approach to plasma polymerization by simple evaluation of the deposition rates this work considers the pressure as external parameter. Also pressure was found to influence the expansion of the plasma zone in front of the RF-driven electrode. The introduction of geometrical factors describing the reactor and the plasma geometry enables the identification of the energy consumed within the active plasma zone that solely determines the deposition rates and the activation energy for CH4 discharges. This concept helps to understand plasma polymerization processes such as the transition from a volume- to a corner-dominated discharge as well as comparison and scale-up of reactors. (c) 2006 Elsevier B.V. All rights reserved.