The influence of the Ar/O2 ratio on the electron density and electron temperature in microwave discharges

TitleThe influence of the Ar/O2 ratio on the electron density and electron temperature in microwave discharges
Publication TypeJournal Article
Year of Publication2017
AuthorsS. Espinho, S. Hofmann, J.M Palomares, S. Nijdam
JournalPlasma Sources Science and Technology
Volume26
Issue10
Pagination105008
Abstract

The aim of this work is to study the properties of Ar-O-2 microwave driven surfatron plasmas as a function of the Ar/O-2 ratio in the gas mixture. The key parameters are the plasma electron density and electron temperature, which are estimated with Thomson scattering (TS) for O-2 contents up to 50% of the total gas flow. A sharp drop in the electron density from 10(20) m(-3) to approximately 10(18) m(-3) is estimated as the O-2 content in the gas mixture is increased up to 15%. For percentages of O-2 lower than 10%, the electron temperature is estimated to be about 2-3 times higher than in the case of a pure argon discharge in the same conditions (T-e approximate to 1 eV) and gradually decreases as the O-2 percentage is raised to 50%. However, for O-2 percentages above 30%, the scattering spectra become Raman dominated, resulting in large uncertainties in the estimated electron densities and temperatures. The influence of photo-detached electrons from negative ions caused by the typical TS laser fluences is also likely to contribute to the uncertainty in the measured electron densities for high O-2 percentages. Moreover, the detection limit of the system is reached for percentages of O-2 higher than 25%. Additionally, both the electron density and temperature of microwave discharges with large Ar/O-2 ratios are more sensitive to gas pressure variations.

DOI10.1088/1361-6595/aa8d04
Division

MaSF

Department

PSFD

PID

194f016fe8c79b3dd0b062590aecae0e

Alternate TitlePlasma Sources Sci. Technol.

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