Cavity ring-down spectroscopy of CH and CD radicals in a diamond thin film chemical vapor deposition reactor |
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| Authors: | U Lommatzsch EH Wahl D Aderhold TG Owano CH Kruger RN Zare |
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| Institution: | (1) Department of Chemistry, Stanford University, Stanford, CA 94305, USA, US;(2) Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA, US |
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| Abstract: | A mixture of H2 and CH4 is passed over a hot-wire tungsten filament in a diamond thin film chemical vapor deposition reactor. The resulting CH radicals
are measured in absorption using cavity ring-down spectroscopy (CRDS). The concentration of the CH radicals increases as the
filament is approached. The rotational temperature measurements indicate a large temperature discontinuity between the filament
and the CH in the gas phase. The pathways for CH production were investigated by replacing H2 by D2 in the feed gas mixture, which resulted in the exclusive production of CD. From this observation it is concluded that rapid
H/D isotope exchange dominates in the gas phase. Nonperiodic temporal oscillations in the CH concentration are observed when
a rhenium filament is used in place of a tungsten filament. The oscillations are attributed to the nonperiodic changes in
the amount of carbon at the filament surface.
Received: 21 August 2000 / Accepted: 23 August 2000 / Published online: 23 May 2001 |
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| Keywords: | PACS: 81 15 Gh 82 80 Ch 82 40 Bj |
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