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  • 1
    Electronic Resource
    Electronic Resource
    New .kappa.-receptor agonists based upon a 2-[(alkylamino)methyl]piperidine nucleus (1992)
    s.l. : American Chemical Society
    Journal of medicinal chemistry 35 (1992), S. 490-501 
    Details
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jm00081a009
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of oxygen on diamond growth using platinum substrates (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3032-3036 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of gas phase oxygen on chemical vapor deposition diamond growth on Pt substrates was studied using x-ray photoelectron spectroscopy (XPS). Samples were transferred between the diamond growth chamber and an attached ultrahigh vacuum analysis chamber without exposure to air. The time-dependent evolution of surface carbon species was monitored by interrupting growth at specific times and analyzing the surface with XPS. In this paper we compare samples prepared from four different mixtures of H2/CH4/O2. With low gas phase O/C ratios (≤0.5) diamond growth on Pt proceeds by a three-step mechanism: (1) decomposition of surface contaminants to form graphitic carbon, (2) conversion of these graphitic species to stable hydrocarbon species, (3) replacement of hydrocarbons with diamond. At higher gas phase O/C ratios (≥0.75) we observed that the Pt surface had less than 1 ML of carbon. In other words, the surface was very clean, and diamond growth did not occur at a measurable rate. However, once diamond is nucleated on the surface under conditions of low oxygen concentration, diamond growth proceeds readily using a high oxygen feed with O/C=1. We conclude that the addition of oxygen affects diamond formation primarily by decreasing the nucleation rate on metals like Pt. Growth rates of existing diamond films are not strongly affected by oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348590
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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
    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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  • 6
    Electronic Resource
    Electronic Resource
    Thermochemistry on a fluorinated diamond (111) surface (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1949-1951 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have performed calculations to evaluate mechanisms for growth of diamond on fluorinated diamond surfaces. These surfaces are very hard and have excellent tribological properties. Our calculations show that steric repulsion between neighboring F atoms on the fully fluorinated surface studied is small, which−given the strength of C—F bonds−implies that this surface should be chemically very stable. Our analysis also shows that in the absence of hydrogen, growth of diamond on a fluorinated surface is thermodynamically so unfavorable that it will not occur. Finally, diamond growth on fluorinated surfaces could be quite favorable in the presence of hydrogen and hydrocarbons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106145
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of NO Pressure on the Reaction of NO and CO over Rh(111) (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 16344-16350 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100044a022
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  • 8
    Electronic Resource
    Electronic Resource
    Diamond formation on platinum (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5353-5359 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.343729
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