Mole fractions of H, CH{sub 3} and other species during filament-assisted diamond growth
- Sandia National Lab., Livermore, CA (United States)
Molecular beam mass spectrometry has been used to quantitatively analyze the composition of the gaseous environment in a hot-filament reactor under diamond-growth conditions. Low concentrations of free-radicals, with mole fractions of as low as 10{sup {minus}5}, can be detected by using the threshold ionization technique. The absolute concentrations are determined by a combination of using the published ionization cross-sections and calibrating the instrument sensitivity. At a filament temperature of 2600 K, the H-atom concentration in the proximity of the growth surface was found to decrease with increasing addition of methane to the feed gas, dropping by more than an order of magnitude when the methane percentage was increased from 0.4% to 7.2%. Concurrent with this decrease, large changes in the concentration of the hydrocarbon species were observed. From the measured mole fractions, the reaction H+CH{sub 4}{longleftrightarrow}H{sub 2}+CH{sub 3} was found to be in nonequilibrium near the surface, with the reverse rate ranging from approximately three to sixteen times larger than the forward rate. The author attributes the cause of this nonequilibrium to heterogeneous reactions on the surface of the substrate.
- OSTI ID:
- 127903
- Report Number(s):
- CONF-920376-; ISSN 0003-0503; TRN: 95:007049-0167
- Journal Information:
- Bulletin of the American Physical Society, Vol. 37, Issue 9; Conference: Meeting of the American Physical Society, Indianapolis, IN (United States), 16-20 Mar 1992; Other Information: PBD: Dec 1992
- Country of Publication:
- United States
- Language:
- English
Similar Records
Experimental measurements and numerical simulations of the gas composition in a hot-filament-assisted diamond chemical-vapor-deposition reactor
Gas-phase kinetics during microwave plasma-assisted diamond deposition: Is the hydrocarbon product distribution dictated by neutral-neutral interactions