1. Particle-in-cell simulations of the alpha and gamma modes in collisional nitrogen capacitive discharges.
- Author
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Kawamura, E, Lieberman, M A, Lichtenberg, A J, and Chabert, P
- Subjects
ELECTRON density ,PLASMA sheaths ,ELECTRIC discharges ,NITROGEN ,ELECTRON temperature - Abstract
We perform one-dimensional (1D) particle-in-cell (PIC) simulations to study the α and γ modes in an intermediate pressure 1.6 Torr, 2.5 cm gap capacitive nitrogen discharge driven at 13.56 MHz with current density amplitudes J
0 = 7 to 150 A m−2 . In the α-mode, ion-induced secondary electron emission has minimal effects on the discharge equilibrium, while in the γ-mode, it is essential for sustaining the discharge. As in a previous study of a comparable argon discharge, [Kawamura et al 2020, J. Vac. Sci. Technol. A 38 , 023003], the nitrogen discharge in the α-mode can be described by a 'passive bulk' model in which the ionization is negligible in the central bulk region and is due solely to electron sheath heating. The nitrogen discharge undergoes an α to γ transition in the applied J0 range, characterized by an increase in density and a decrease in electron temperature, sheath widths and sheath voltages. For the γ-mode, we calculate the scalings of the maximum sheath width sm and the rf sheath voltage amplitude V1 with J0 . We compare the PIC results in the α-mode to the passive bulk model (modified for nitrogen), and, in the γ-mode with the expected J0 -V1 and sm -V1 curves. We find good agreement with the simulations in both the α and γ regimes, and the α to γ transition is well predicted by the models. [ABSTRACT FROM AUTHOR]- Published
- 2021
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