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P: Fachverband Plasmaphysik

P 9: Simulationsverfahren/Theorie/Modellierung

P 9.2: Fachvortrag

Dienstag, 13. März 2012, 14:30–14:55, V57.01

Electron surface layer at the interface of a plasma and a dielectric wall — •Rafael L. Heinisch, Franz X. Bronold, and Holger Fehske — Institut für Physik, Universität Greifswald

We study the electron adsorbate formed at the interface of a plasma and a dielectric wall. Assuming that electron trapping occurs in the image potential we calculate electron sticking coefficients and desorption times [1]. Moreover, we study the potential and the charge distribution across the interface of a plasma and a dielectric wall [2]. For this purpose, the charge bound to the wall is modelled as a quasi-stationary electron surface layer which satisfies Poisson’s equation and minimizes the grand canonical potential of the wall-thermalized excess electrons. Based on an interface model encompassing the image potential and the surface barrier of the dielectric, we calculate the potential and the electron distribution for MgO, SiO₂ and Al₂O₃ surfaces in contact with a helium discharge. Depending on the electron affinity of the surface, we find two vastly different behaviors. For negative electron affinity, electrons do not penetrate into the wall and a quasi-two-dimensional electron gas is formed in the image potential, while for positive electron affinity, electrons penetrate into the wall and a space charge layer develops in the interior of the dielectric. We also investigate how the electron surface layer – which can be understood as the ultimate boundary of a gas discharge – merges with the bulk of the dielectric.

[1] R. L. Heinisch et al., Phys. Rev. B 81, 155420 (2010), ibid 82, 125408 (2010), ibid 83, 195407 (2011) [2] R. L. Heinisch et al., arXiv 1109.5107