Mole fractions of H, CH sub 3 , and other species during filament-assisted diamond growth

Journal Article · Mon Sep 16 00:00:00 EDT 1991 · Applied Physics Letters; (United States)

DOI:https://doi.org/10.1063/1.105276· OSTI ID:5277356

Hsu, W L ^[1]

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1. Sandia National Laboratories, Livermore, California (USA)

Molecular beam mass spectrometry has been used to determine the concentrations of several free-radical and stable gaseous species in a hot-filament reactor under diamond-growth conditions. 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. All numerical modeling results that have been reported to date do not include heterogeneous reactions on the filament and have failed to predict or explain these observations. Also from the measured mole fractions, the reaction H+CH{sub 4}{leftrightarrow}H{sup 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. We attribute the cause of this nonequilibrium to heterogeneous reactions on the surface of the substrate.

• OSTI ID: 5277356
• Journal Information: Applied Physics Letters; (United States), Journal Name: Applied Physics Letters; (United States) Vol. 59:12; ISSN APPLA; ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
ALKANES
ALKYL RADICALS
CARBON
CHEMICAL COATING
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMICAL VAPOR DEPOSITION
CRYSTAL GROWTH
DEPOSITION
DIAMONDS
ELEMENTAL MINERALS
ELEMENTS
HYDROCARBONS
HYDROGEN
KINETICS
MASS SPECTROSCOPY
METHANE
METHYL RADICALS
MINERALS
NONMETALS
ORGANIC COMPOUNDS
RADICALS
REACTION KINETICS
SPECTROSCOPY
SURFACE COATING
SYNTHESIS
VERY HIGH TEMPERATURE