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  • 1
    Electronic Resource
    Electronic Resource
    Experimental measurements and numerical simulations of the gas composition in a hot-filament-assisted diamond chemical-vapor-deposition reactor (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7567-7577 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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 XC, (2) the identity of the inlet carbon source (CH4 versus C2H2), and (3) the surface temperature TS, were studied. For XC≤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 XC, 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 CH3 and C2H2 mole fractions on TS can each be characterized as having an activation energy of 3±1 kcal/mol. Surprisingly, the H-atom mole fraction was independent of TS. 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 XC, 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 ×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. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358525
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  • 2
    Electronic Resource
    Electronic Resource
    A model for the nucleation of diamond clusters on Si(111) substrates (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 1966-1977 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical study of the nucleation, size, and structure of diamond phase carbon clusters on Si(111) substrates is presented. Molecular mechanics analysis has been utilized to predict energetically and entropically feasible pathways for nucleation of the carbon clusters. Several mechanistic pathways for nucleation of carbon clusters are examined with CH3 and/or C2H2 as the nucleation precursors. A possible model for the nucleation mechanism of diamond-phase carbon clusters on the β-SiC(111) surface, which forms epitaxially on Si(111) substrates, is presented. The critical size of the carbon clusters is computed based on the atomistic theory of nucleation and the proposed nucleation mechanisms. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364053
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of temperature and filament poisoning on diamond growth in hot-filament reactors (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3102-3113 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of diamond in a hot-filament reactor has been modeled, and compared with existing experimental data. Studies have been carried out on non-growth systems containing only hydrogen, as well as on systems where the methane concentration at the inlet was varied between 0.4% and 7.2%. The one-dimensional stagnation flow model used here includes detailed gas-phase and surface kinetics. A simple model of filament poisoning has been implemented. The effect of the gas/filament temperature discontinuity on species distributions has also been examined. Gross errors between theory and experiment are obtained when filament poisoning is neglected, but good agreement is found using a simple linear poisoning model. A nonzero temperature discontinuity at the filament produces good overall agreement with experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357492
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  • 4
    Electronic Resource
    Electronic Resource
    Nonlinear stability analysis of the growth surface during diamond chemical vapor deposition (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6061-6071 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The morphological stability of the solid–gas interface under conditions of diffusive transport of reactant species towards the surface during the chemical vapor deposition process is analyzed using linear and nonlinear perturbation theories. The Landau coefficient, which represents the nonlinear growth rate, is calculated using the direct method of undetermined coefficients. A dispersive relation is derived which relates the effects of species diffusive transport towards the growing interface, surface diffusion, and geometrical factors with the stability of perturbations on the interface. The resulting relation is applied to the diamond chemical vapor deposition process. Linear and nonlinear instability of the interface is obtained for diamond chemical vapor deposition conditions. Linear instability increases but the Landau coefficient becomes larger, indicating greater nonlinear stability as the reactor pressure increases, although both linear and nonlinear analyses suggest more stability as the reactor temperature increases. However, during typical diamond growth conditions, it is predicted that the diamond–gas interface is unstable to both infinitesimal and finite amplitude disturbances. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367475
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  • 5
    Electronic Resource
    Electronic Resource
    Thermodynamic analysis of III–V semiconductor alloys grown by metalorganic vapor phase epitaxy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4407-4416 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A thermodynamic analysis has been applied to systematically study III–V semiconductor alloy deposition, including nitrides grown by metalorganic vapor phase epitaxy. The predicted solid compositions of a number of ternary and quaternary alloys, including AlxGa1−xPyAs1−y, are compared with experimental data. For phosphorus-containing alloys, introduction of a parameter f representing incomplete PH3 pyrolysis yields good agreement with experimental data. It is shown that the input mole fraction of the group III metalorganic sources influences the incorporation of P into the solid for these alloys. Solid composition is also calculated for nitride alloys as a function of inlet gas concentration. To date, thermodynamic models have been applied solely to predict N solubility limits for nitride alloys where mixing occurs on the group V sublattice. The present model is used to predict N solid compositions in ternary and quaternary alloys, and it is demonstrated that these values are below the theoretical solubility limits for In-containing nitrides. The role of H2 in the carrier gas is investigated for III–N–V, III–III–N–V, and III–N–V–V systems. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1290740
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  • 6
    Electronic Resource
    Electronic Resource
    Relationship between diamond growth rate and hydrocarbon injector location in direct-current arcjet reactors (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 391-393 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of detailed calculations have been carried out using a stagnation flow model to examine the dependence of diamond growth rate on hydrocarbon injector location in dc arcjet reactors. It is predicted that, for methane feed, growth rate can be increased by as much as 75% by relocating the injector from a position near the plasma torch exit to one near the diamond surface, but outside the boundary layer. As the injector is moved towards the surface from the plasma torch, the concentrations of C and CH3 present at the surface increase. When the injector is located within the boundary layer, the lower atomic hydrogen concentration and short residence time leave most of the injected CH4 unreacted, causing growth rates to drop. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114198
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of diamond growth in subatmospheric dc plasma-gun reactors (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 5803-5820 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of diamond in a subatmospheric dc-arc plasma-jet reactor has been studied theoretically. Full transport equations for this geometry, including gas-phase and surface chemistry, have been solved numerically. The surface-reaction mechanism includes pathways for the incorporation of CH3, C2H2, and C from the gas phase, as well as growth of graphite. The surface mechanism includes full reversibility for all reactions, based on estimates of the thermochemistry. Results are presented for degrees of dissociation of H2 in the plasma gun ranging from 2.6% to 90%, and inlet levels of CH4 spanning 0.1–5.0 mol %. It is seen that CH3 is the predominant growth species when there is little H2 dissociation within the plasma gun, but C becomes the dominant species at higher dissociation levels. The third growth species, C2H2, does not play a role in diamond growth under these conditions when there is less than 1% CH4 in the feed; but, at higher CH4 levels both C and CH3 addition rates drop to 50 times greater than C2H2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354201
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  • 8
    Electronic Resource
    Electronic Resource
    A Newton's method scheme for solving free-surface flow problems (1989)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 1469-1486 
    Details
    ISSN: 0271-2091
    Keywords: Free-surface ; Bubble ; Intermediate Reynolds number ; Newton's method ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A Newton's method scheme is described for solving the system of non-linear algebraic equations arising when finite difference approximations are applied to the Navier-Stokes equations and their associated boundary conditions. The problem studied here is the steady, buoyancy-driven motion of a deformable bubble, assumed to consist of an inviscid, incompressible gas. The linear Newton system is solved using both direct and iterative equation solvers. The numerical results are in excellent agreement with previous work, and the method achieves quadratic convergence.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650091204
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  • 9
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    Bending of Lamellar Microdomains of Block Copolymers on Nonselective Surfaces (2010)
    American Chemical Society
    Details
    Publication Date: 2010-02-09
    Print ISSN: 0024-9297
    Electronic ISSN: 1520-5835
    Topics: Chemistry and Pharmacology , Physics
    Published by American Chemical Society
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  • 10
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    Effects of temperature and filament poisoning on diamond growth in hot‐filament reactors (1994)
    American Institute of Physics
    Details
    Publication Date: 1994-09-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics
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