Experimental measurements and numerical simulations of the gas composition in a hot-filament-assisted diamond chemical-vapor-deposition reactor

Journal Article · Thu Dec 01 00:00:00 EST 1994 · Journal of Applied Physics; (United States)

DOI:https://doi.org/10.1063/1.358525· OSTI ID:7181981

McMaster, M C; Hsu, W L ^[1]; Coltrin, M E ^[2]; Dandy, D S ^[3]

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1. Sandia National Laboratories, Livermore, California 94551-0969 (United States)
2. Sandia National Laboratories, Albuquerque, New Mexico 87185-5800 (United States)
3. Department of Chemical Engineering, Colorado State University, Fort Collins, Colorado 80523 (United States)

Molecular-beam mass spectroscopy was used to measure the gas composition near a growing diamond surface in a hot-filament-assisted chemical-vapor-deposition reactor. The dependencies of the gas composition on changes in (1) the carbon mole fraction in the reactor feed [ital X][sub C], (2) the identity of the inlet carbon source (CH[sub 4] versus C[sub 2]H[sub 2]), and (3) the surface temperature [ital T][sub [ital S]], were studied. For [ital X][sub C][le]0.02, the gas composition appeared to be nearly independent of the identity of the inlet hydrocarbon source and depended only on the C/H ratio in the feed gas. At higher values of [ital X][sub C], catalytic poisoning of the hot filament resulted in different product distributions in these two systems. Increasing the surface temperature affected changes in the hydrocarbon composition; the dependencies of the CH[sub 3] and C[sub 2]H[sub 2] mole fractions on [ital T][sub [ital S]] can each be characterized as having an activation energy of 3[plus minus]1 kcal/mol. Surprisingly, the H-atom mole fraction was independent of [ital T][sub [ital S]]. These results suggest that reported temperature sensitivities of film growth properties are primarily due to changes in the kinetics of surface processes rather than changes in the gas composition near the surface. A numerical model of the process is presented. In the study of the compositional change as a function of [ital X][sub C], the code gives good prediction for the methane case but grossly underestimates the methane and methyl concentrations for the acetylene case. The H-atom mole fraction is predicted to increase by [times]7 if the H destruction probability on the diamond surface is expected to have an activation energy of 7.3 kcal/mol. Good agreement with experimental data can be obtained, however, if H loss by lateral transport to the walls is taken into account.

• DOE Contract Number: AC04-76DP00789
• OSTI ID: 7181981
• Journal Information: Journal of Applied Physics; (United States), Vol. 76:11; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CHEMICAL VAPOR DEPOSITION
COMPUTERIZED SIMULATION
DIAMONDS
CATALYTIC EFFECTS
CHEMICAL COMPOSITION
FILAMENTS
GAS ANALYSIS
HYDROCARBONS
MASS SPECTRA
SURFACES
TEMPERATURE DEPENDENCE
THIN FILMS
CARBON
CHEMICAL COATING
DEPOSITION
ELEMENTAL MINERALS
ELEMENTS
FILMS
MINERALS
NONMETALS
ORGANIC COMPOUNDS
SIMULATION
SPECTRA
SURFACE COATING
360601* - Other Materials- Preparation & Manufacture