Physics and chemistry in a glow dielectric barrier discharge at atmospheric pressure: diagnostics and modelling

Abstract

Glow dielectric barrier discharge (GDBD) appears as an attractive solution to realise an atmospheric pressure cold plasma process suitable for all the surface treatments including thin film coatings. Such a development requires a large understanding of the GDBD physics and chemistry. The objective of this work is to contribute to that understanding. From the analysis of electrical measurements, time resolved emission spectroscopy, short exposure time pictures and numerical model results, it is shown that GDBD which are discharges due to a Townsend initiation and not to a streamer coupling, transit from Townsend to subnormal glow discharge during the current increase. Depending on the maximum current density, they can be considered as a glow or a Townsend discharge. In a glow discharge, the memory effect from one discharge to the following one is based on electrons and ions trapped in the positive column while in a Townsend discharge, it is metastables which stay in the gas and create electrons through cathode secondary emission. In all the cases, the ionisation has to be slowed down by a significant contribution of Penning ionisation.