Gas-phase kinetics during microwave plasma-assisted diamond deposition: Is the hydrocarbon product distribution dictated by neutral-neutral interactions

Journal Article · Thu Oct 01 00:00:00 EDT 1992 · Journal of Applied Physics; (United States)

DOI:https://doi.org/10.1063/1.351470· OSTI ID:7266350

Hsu, W L ^[1]

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1. Sandia National Laboratories, Livermore, California 94550 (United States)

The mole fractions of H, H{sub 2}, CH{sub 3}, CH{sub 4}, and C{sub 2}H{sub 2} that were generated in a microwave plasma under conditions typical for diamond deposition are reported. When the methane percentage in the feed gas was {lt}1%, the measured concentrations were surprisingly similar to those reported for a hot-filament system operated under nearly identical conditions. However, as the methane percentage was increased beyond 1%, a noticeable deviation from the hot-filament results became apparent. In the hot-filament case, surface-induced dissociation of hydrogen on the filament surface was significantly inhibited at this high methane level and lead to a pronounced reduction of the H-atom concentration. But, in the microwave system where dissociation is a homogeneous process, no such reduction was observed. Other observations were: (i) The acetylene concentration scaled as the square of the methyl concentration; (ii) The CH{sub 4}+H{leftrightarrow}CH{sub 3}+H{sub 2} reaction was found to be at the same level of nonequilibrium as in the hot-filament case. These results, plus arguments based on general principles of plasma chemistry, are taken as indications that the hydrocarbon chemistry in the microwave system is as strongly dictated by neutral-neutral reactions as in a thermal system. The primary effect of the plasma is perhaps its role in dissociating hydrogen molecules to H atoms without having to raise the gas temperature significantly.

• DOE Contract Number: AC04-76DP00789
• OSTI ID: 7266350
• Journal Information: Journal of Applied Physics; (United States), Vol. 72:7; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
DIAMONDS
CHEMICAL VAPOR DEPOSITION
PLASMA
CHEMICAL REACTIONS
DISSOCIATION
HYDROGEN
METHANE
MICROWAVE RADIATION
ALKANES
CARBON
CHEMICAL COATING
DEPOSITION
ELECTROMAGNETIC RADIATION
ELEMENTAL MINERALS
ELEMENTS
HYDROCARBONS
MINERALS
NONMETALS
ORGANIC COMPOUNDS
RADIATIONS
SURFACE COATING
360601* - Other Materials- Preparation & Manufacture