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  • 1985-1989  (9)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 416-417 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Filament-assisted chemical vapor deposition (CVD) diamond film growth on Si(100) was studied using x-ray photoelectron spectroscopy (XPS) to examine the sample at selected intervals during the nucleation and growth processes. The sample was transferred under vacuum from the growth chamber to the attached XPS analysis chamber without exposure to air. Before growth XPS showed that the Si sample is covered by a layer of SiO2 and carbonaceous residue; however, after 15 min of growth both of these substances are removed and replaced by a distinct SiC layer [Si(2p)=100.3 eV and C(1s)=282.7 eV].
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1605-1607 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured mole fractions of two of the major stable species at the surface of a silicon substrate during filament-assisted diamond growth as a function of the filament-to-substrate distance. Input gases were methane and hydrogen. A quartz probe withdrew gases at the growing surface, and the gases were sampled with an on-line mass spectrometer. Close to the filament the methane is largely consumed, with most of the remaining gas phase carbon in the form of acetylene. Mass spectral results are compared to compositions calculated with a detailed chemical kinetics model. Our initial analysis suggests that diamond growth comes mainly from reaction of acetylene, ethylene, methane, or methyl radical.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2179-2181 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In situ mass spectral measurements of gas composition at the substrate surface were made during filament-assisted diamond growth. The input gases were various mixtures of CH4, O2, and H2 chosen in order to discern the effects of oxygen addition on diamond formation and growth. The gas phase chemistry was modeled as a one-dimensional flow reactor, and the measured and calculated species mole fractions were in good agreement. The model was then used to estimate mole fractions of several atomic and radical species which could not be measured. We find that addition of O2 has only a small effect on the radical mole fractions. However, O2 can reduce the effective initial hydrocarbon mole fraction, which is important because higher quality diamond is grown at a lower initial hydrocarbon mole fraction. Most important, perhaps is that O2 addition leads to the formation of sufficient gas phase OH to remove nondiamond (pyrolytic) carbon from the film. Thus, O2 addition allows diamond films to be grown under composition and temperature conditions which otherwise would produce largely nondiamond carbon.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3044-3048 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used a one-dimensional kinetic analysis to model the gas-phase chemistry that occurred during the diamond growth experiments of Chauhan, Angus, and Gardner [J. Appl. Phys. 47, 4746 (1976)]. In those experiments the weight of diamond seed crystals heated by lamps in a CH4/H2 environment was monitored by a microbalance. No filament or electric discharge was present. Our analysis shows that diamond growth occurred in this system by direct reaction of CH4 on the diamond surface. C2H2 and CH3, which have been proposed as diamond growth species, played no significant role there, although our results do not address their possible contributions in other systems such as filament- or plasma-assisted diamond growth.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5353-5359 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have made in situ mass spectral measurements and x-ray photoelectron spectroscopy (XPS) measurements at the surface of a diamond film growing on a platinum substrate. We measured the concentrations of CH4, C2H4, and C2H2 and detected additional species with from three to ten carbon atoms. The gas-phase chemical kinetics controlling the concentrations of the C1 and C2 species was modeled, and agreement between the calculated and measured concentrations was good. The presence or absence of the platinum foil had no effect on the measured concentrations, showing that heterogeneous chemistry on platinum did not affect the gas-phase environment. XPS spectra were taken during the course of the diamond growth without exposing the platinum foil to air. After exposure to a room-temperature CH4/H2 mixture but before any growth, the platinum surface was mostly covered with graphitic carbon. Once growth was initiated the graphitic layer was gradually replaced by 1–3 monolayers of hydrocarbon material, which did not thicken with time. Finally, the hydrocarbons were replaced or covered by a diamond film. CO titration experiments demonstrated that practically no active platinum atoms were exposed to the gas-phase reactants during growth. This fact explains the lack of activity of the platinum foil.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 20 (1988), S. 939-955 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A flow system has been developed to study relative rate coefficients of hydroxyl radicals reacting with alkanes under conditions relating to tropospheric chemistry. Relative Arrhenius parameters have been measured over the temperature range 243-328 K for pairs of alkanes from a list consisting of n-butane, 2-methylpropane, n-pentane, n-hexane, 2,2- and 2,3-dimethylbutane, 2,3,3-trimethylbutane, and 2,3,4-trimethylpentane.The results have been incorporated into a Structure-Activity Relation for hydroxylalkane reactions which leads to the following group rate coefficients for a temperature range of 240-500 K. \documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{rcl} k_{{\rm prime}}^0 &=& 3.13 \times 10^{ - 12}\, {\rm exp(} - 904/T)\,{\rm cm}^{\rm 3}\, {\rm molecule}^{ - 1}\, {\rm s}^{ - 1} \\ k_{{\rm sec}}^0 &=& 2.45 \times 10^{ - 12} \,{\rm exp(} - 320/T)\,{\rm cm}^{\rm 3}\, {\rm molecule}^{ - 1}\, {\rm s}^{ - 1} \\ k_{{\rm tert}}^0 &=& 1.88 \times 10^{ - 12} \,{\rm cm}^{\rm 3}\, {\rm molecule}^{ - 1}\, {\rm s}^{ - 1} \end{array}$$\end{document}
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 207-218 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photo-oxidation of n-heptane in synthetic air containing methyl nitrite and nitric oxide has been ivestigated in an atmospheric flow reactor. By measuring the total yields of heptyl nitrate products, relative to the depletion of the n-heptane, the rate constant ratio, k3b/k3a has been determined for the reactions: Over the temperature range 253-325 K and at a total pressure of 730 Torr, the following relative Arrhenius equation has been obtained from the present study together with literature data: \documentclass{article}\pagestyle{empty}\begin{document}$$k_{3b} /k_{3a} = (1.4 \pm 1.1) \times 10^{ - 3} \exp [1640 \pm 250)/T]$$\end{document} These results confirm that the formation of alkyl nitrates from the photo-oxidation of n-alkanes arise from a primary reaction between the alkylperoxy radicals and nitric oxide. Furthermore the present experiments show that the lifetime of the intermediate in this type of reaction, presumed to be an alkyl peroxynitrite, ROONO, must be less than a few seconds.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 19 (1987), S. 609-614 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rates of decay of ozone in a large excess of the cycloalkene have been re-measured by an improved experimental procedure, and the following second-order rate constants (cm3 molecule-1 s-1) have been determined in synthetic air at atmospheric pressure: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm O}_3 + {\rm cyclopentene} \longrightarrow {\rm products,}} & {k = (4.97 \pm 0.30) \times 10^{ - 16} {\rm at}} \\ \end{array}291.5{\rm K} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm O}_3 + {\rm cyclohexene} \longrightarrow {\rm products,}} & {k = (1.51 \pm 0.10) \times 10^{ - 16} {\rm at}} \\ \end{array}295{\rm K} $$\end{document} The results are discussed in relation to existing literature data on the kinetics of ozonecycloalkene reactions.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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