Measurements of Molecular Densities in Low Pressure Discharge Plasmas Using Laser Raman Scattering

The possibility of using Raman scattering as a method of molecular density measurements in low pressure discharge plasmas has been investigated. Firstly, the detection limit of Raman signal was examined in low pressure air. It was shown that the Raman scattering from nitrogen molecules was detectabl...

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Bibliographic Details
Published in:Japanese Journal of Applied Physics 1996-10, Vol.35 (10R), p.5509
Main Authors: Song, Yi Bing, Hirakawa, Yuichiro, Uchino, Kiichiro, Muraoka, Katsunori, Sakoda, Tadanori, Yanagishita, Koji, Nakamura, Shizuo
Format: Article
Language:English
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Summary:The possibility of using Raman scattering as a method of molecular density measurements in low pressure discharge plasmas has been investigated. Firstly, the detection limit of Raman signal was examined in low pressure air. It was shown that the Raman scattering from nitrogen molecules was detectable down to 0.06 Pa (particle density of 1.4×10 19 m -3 ) when a photon counting detection system was used. The method was then applied to detect methane and its reaction products in an electron cyclotron resonance plasma operated at a pressure of 50 Pa. Densities of CH 4 , C 2 H 2 , C 2 H 6 and H 2 were absolutely determined using the calibrated data of the optical system. Also, it was clearly demonstrated that the gas composition in the discharge was dependent on gas flow rate. These experimental results showed the usefulness of the method for quantitative measurements of molecular densities in processing plasmas.
ISSN:0021-4922
1347-4065
DOI:10.1143/JJAP.35.5509