Detection of ground-state atomic hydrogen in a dc plasma using third-harmonic generation

Third-harmonic generation (THG) was used to monitor ground-state atomic hydrogen H(1s 2S1/2) in a dc plasma system. A 364.6 nm laser beam focused through H2 or CH4/H2 plasmas induced THG at 121.5 nm, near the atomic hydrogen 2p 2PoJ→1s 2S1/2 Lyman-α transition. Both the intensity and frequency shift...

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Bibliographic Details
Published in:Journal of applied physics 1990-10, Vol.68 (8), p.3814-3817
Main Authors: CELII, F. G, THORSHEIM, H. R, BUTLER, J. E, PLANO, L. S, PINNEO, J. M
Format: Article
Language:English
Subjects:
Exact sciences and technology
Physics
Physics of gases, plasmas and electric discharges
Physics of plasmas and electric discharges
Plasma diagnostic techniques and instrumentation
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Summary:Third-harmonic generation (THG) was used to monitor ground-state atomic hydrogen H(1s 2S1/2) in a dc plasma system. A 364.6 nm laser beam focused through H2 or CH4/H2 plasmas induced THG at 121.5 nm, near the atomic hydrogen 2p 2PoJ→1s 2S1/2 Lyman-α transition. Both the intensity and frequency shift of the excitation spectra exhibited dependence on the plasma power. Absolute H atom concentration was estimated by comparing the frequency shift to that obtained in a calibrated microwave discharge flow system. The sensitivity was ∼4×1013 cm−3 (100 ppm). The measured atomic hydrogen densities were substantially less than in other diamond chemical vapor deposition methods and may explain the lower diamond deposition rates obtained with dc plasma systems of this type.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.346263