Electron and metastable densities in parallel‐plate radio‐frequency discharges
作者:
K. E. Greenberg,
G. A. Hebner,
期刊:
Journal of Applied Physics
(AIP Available online 1993)
卷期:
Volume 73,
issue 12
页码: 8126-8133
ISSN:0021-8979
年代: 1993
DOI:10.1063/1.353451
出版商: AIP
数据来源: AIP
摘要:
Electron densities were measured in continuous and pulse‐modulated, 13.56‐MHz, helium and argon discharges. These measurements were made in a symmetrically driven Gaseous Electronics Conference Reference Cell. Pulse modulation of the applied potential allowed observation of the time required for the electron density to achieve steady state. In general, helium discharges reached steady state in approximately 1.5 ms, taking three to ten times longer than argon discharges under similar operating conditions. As much as a threefold increase of the electron density was observed in the afterglow of a pulse‐modulated helium discharge, indicative of large metastable densities. Absorption spectroscopy was used to measure the helium singlet and triplet metastable densities throughout the volume of the discharge. For a 1.0‐Torr discharge, helium triplet metastable densities at the center of the discharge were as large as 2.5×1011cm−3while the peak singlet density was 3.0×1010cm−3. The steady‐state electron density varied from 3.8×1010cm−3at 50 V to 2.3×1011cm−3at 200 V for the 1.0‐Torr helium discharge.
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