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  • 1
    Electronic Resource
    Electronic Resource
    Filament-assisted diamond growth kinetics (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1385-1391 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the growth rate of chemical vapor deposition diamond films under filament-assisted conditions using a microbalance. The pressure was varied from 20 to 200 Torr, and the ratio R of CH4 to H2 was varied from 0.2% to 1%. Raman spectra showed only diamond features for our films. We found that for R(approximately-greater-than)0.2%, where filament carburization was not an issue, the growth rate scaled as Rα, where α is an empirical constant that varies from about 1 at 20 Torr to about 0.5 at 200 Torr. A comparison of these results to predictions of our gas-phase/gas-surface model for diamond growth shows that the model accurately predicts both the value of α and how α varies with pressure. Reasons for the success of our very simple model are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349546
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  • 2
    Electronic Resource
    Electronic Resource
    Reaction kinetics on diamond: Measurement of H atom destruction rates (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1022-1026 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: There is presently a considerable effort to understand the chemistry of diamond film growth by chemical-vapor deposition. The first measurements of reaction kinetics between diamond and a gas-phase species—H atoms—involved in its formation are described. A remarkably simple method to measure H atom concentrations is developed and the method is used to measure γd, the destruction probability of H atoms on diamond at 20 Torr and 1200 K. It is found that γd=0.12, with an estimated uncertainty of a factor of 2. This value is about half that estimated from gas-phase alkane rate constants and very close to that predicted by molecular-dynamics/Monte Carlo calculations. The agreement to within the estimated uncertainty supports the assumption that gas-phase alkane rate constants are essentially transferable to reactions between a diamond surface and gas-phase species. The H atom measurement technique could be useful for studying growth in other chemical-vapor-deposition systems in which hydrogen is in high concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354948
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  • 3
    Electronic Resource
    Electronic Resource
    Thermochemistry on the hydrogenated diamond (111) surface (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2654-2659 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: As part of our effort to control the growth of diamond films by chemical vapor deposition, we are studying the chemical mechanism for conversion of gas phase hydrocarbons into diamond. In this work we analyze the thermochemistry of a number of structures on the hydrogenated diamond (111) surface. We use the MM2 molecular mechanics force field to calculate strain energies, which are due to crowding of adsorbed species on the surface, and we use a group additivity scheme to estimate bond enthalpies and entropies. These data allow calculation of equilibrium structures on the surface and, together with estimates for rate constants, will permit a prediction for the kinetics of diamond formation as a function of growth conditions. We find that a straightforward abstraction/addition mechanism using either CH3 or C2H2 to grow on a hydrogenated (111) surface cannot account for experimentally measured growth rates. We suggest that experimental measurements of growth rates on (111) surfaces are strongly influenced by growth at steps, kinks, and edges on those surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349379
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  • 4
    Electronic Resource
    Electronic Resource
    A mechanism for growth on diamond (110) from acetylene (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 2371-2377 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have proposed a detailed chemical kinetics mechanism for the addition of C2H2 to a (110) diamond surface, which is the fastest growing face. The model contains no adjustable parameters and is based on the hypothesis that diamond surface chemistry may be understood in analogy with gas-phase hydrocarbon chemistry. We calculated a growth rate of 0.03 μm/h, which gives order-of-magnitude agreement with experiments and suggests we have a feasible mechanism for growth on (110) surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462033
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  • 5
    Electronic Resource
    Electronic Resource
    Diamond film quality: Effects of gas phase concentrations on the Raman spectra (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2187-2194 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of diamond films have been grown, all at Tsub=1110 K and atomic H concentrations [H]=3×10−10 mol/cm3. The acetylene and methyl radical concentrations at the substrate surface were varied independently by factors of up to 4 and 10, respectively, by adjusting the pressure and the input methane concentration, and the effects of these variations on the Raman spectra were examined. The linewidth of the 1332 cm−1 diamond feature, the sp2 nondiamond carbon feature, and the luminescence yields all increased with increased [CH3]sub, but varying the [C2H2] had no observable impact. A quantitative relationship is provided between the sp2 content and [CH3]sub. The luminescence peak, which is the most sensitive feature to [CH3]sub, is due to an impurity from the filament. Using micro-Raman spectroscopy, large variations are found in the Raman spectra of adjacent crystals and within a single crystal. We attribute these fluctuations to inhomogeneous and anisotropic strains. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363111
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  • 6
    Electronic Resource
    Electronic Resource
    Pressure and temperature effects on the kinetics and quality of diamond films (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5026-5032 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantitative measurements of the effects of pressure on the kinetics and quality of diamond films grown with hot-filament chemical-vapor deposition are reported. Pressure affects growth kinetics largely because it affects transport of precursors to the growing surface. H and CH3 concentrations at the growth surfaces are determined with a recombination enthalpy technique combined with appropriate transport analyses. The growth rate rises and then falls with increasing pressure, although the concentrations of CH3 and atomic hydrogen at the surface are nearly constant. Both the rise and the fall in growth rate at higher pressure are explained with a chemical kinetics model as due in large part to an increase in substrate temperature at higher pressures. The fall at higher pressure (temperature) is due to the rate of thermal desorption of the CH3 precursor increasing more rapidly with temperature than the competing rate of its incorporation: Once these rates become comparable, higher substrate temperatures lower the incorporation rates, and the growth rate decreases. Previously measured Arrhenius plots for diamond-growth kinetics are explained quantitatively. The quality of the diamond, as determined using Raman and scanning electron micrograph data, falls with increasing pressure and substrate temperature. For the first time, this decline in quality is correlated with experimental temperature, H:CH3 ratio, and C2H2 concentration measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355744
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  • 7
    Electronic Resource
    Electronic Resource
    Observation of a negative electron affinity for boron nitride (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3912-3914 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This study reports UV-photoemission (UPS) measurements made on boron nitride crystals and thin films. The materials examined are commercial grade c-BN powder and thin films of BN deposited with ion beam assisted e-beam evaporation and laser ablation. The thin film samples examined exhibited varying amounts of sp3 (cubic) and sp2 (hexagonal, amorphous) bonding as determined by FTIR measurements. The UPS measurements displayed the spectral distribution of the low energy photoemitted electrons and the total energy width of the spectra. These characteristics can be related to the electron affinity. The measurements on several of the BN powder and thin film samples revealed features in the emission spectra which are indicative of a negative electron affinity (NEA) surface. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115315
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  • 8
    Electronic Resource
    Electronic Resource
    In situ characterization of diamond nucleation and growth (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 416-417 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.100938
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  • 9
    Electronic Resource
    Electronic Resource
    Mechanism for diamond growth from methyl radicals (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2298-2300 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We use a 9-carbon model compound to describe a proposed mechanism for homoepitaxial growth of diamond from methyl radicals on a hydrogenated, electrically neutral (100) surface. We estimate enthalpy and entropy changes for each step in the mechanism using group additivity methods, taking into account the types of bonding and steric repulsions found on the (100) surface. Rate constants are estimated based on analogous reactions for hydrocarbon molecules, while gas phase species concentrations are taken from our previous measurements. The rate equations are then integrated. The method, which contains no adjustable parameters or phenomenological constants, predicts a growth rate of between 0.06 and 0.6 μm/h, depending on the local details of the surface. Uncertainties related to the use of a model compound rather than diamond are discussed. The analysis demonstrates that the proposed mechanism is feasible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102946
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  • 10
    Electronic Resource
    Electronic Resource
    Measurement of stable species present during filament-assisted diamond growth (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1605-1607 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.99925
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