I. Stefanovic^1,2, N. Bibinov¹, H.-E. Porteanu³, M. Klute⁴, R.-P. Brinkmann⁴ and P. Awakowicz¹

Published in:

Int. J. Microwave Wireless Technolog., vol. 10, no. 5-6, pp. 700-708 (2018).

Abstract:

A miniature microwave (MMW) inductively coupled plasma (ICP) source is characterized by optical emission spectroscopy and by optical imaging of nitrogen plasma. The MWW source operates in two different modes (H-mode and hybrid-E/H mode) with different plasma parameters and different emission morphologies, depending on the absorbed microwave power (P_abs). The measured spectra of the second positive system (N₂(C-B))and of the first negative system (N₂⁺(B-X)) of nitrogen reveal an electron density n_e = (6.4±1.7)×10¹⁸m^-3 and a gas temperature of T_g = (650±20) K for P_abs = 12 W at a pressure of 1000 Pa. By increasing the absorbed power to P_abs = 78 W the parameters increase to n_e = (3.5±1.7)×10¹⁹m^-3 and T_g = (1600±100) K. The discharge morphology in hybrid and H-mode is different. While in the H-mode the plasma resembles a ‘donuts’ shape, the hybrid mode has a very narrow shape close to the walls and to the gap capacitor of the resonator. For our discharge conditions the power absorption is limited to 158 W, above which the discharge spontaneously switches from H-mode to hybrid mode.

Keywords:

microwave plasma, inductively coupled plasma, E-mode, H-mode, nitrogen plasma,optical emission spectroscopy

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