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  • 1
    Electronic Resource
    Electronic Resource
    Thermal analysis of float-zone traveling solvent crystal growth of LaB6 (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 518-528 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We analyze the thermal regime of float-zone traveling solvent crystal growth of LaB6. We construct a one-dimensional analytical approximation of the process taking into account relevant phase diagram, phase transition kinetics, and the effects of natural and Marangoni convection. We show that convection plays a crucial role in the formation of the thermal and mass transfer regimes of the process. First, convection strongly inhibits the temperature inside the melt. Second, convection inhibits even more strongly the mass transfer resistance of the molten zone and the temperature difference between the dissolution and solidification interface. Natural convection depends strongly on the molten zone height so that increase of the molten zone leads to a strong decrease in the temperature difference between solid/liquid interfaces. The action of Marangoni convection on the heat and mass transfer is shown to be considerably stronger; however, its influence does not depend strongly on the molten zone dimensions. It is shown that only the action of Marangoni convection can enhance mass transport between the dissolution and solidification interfaces to a rate sufficient to implement the growth of LaB6 at a pulling rate of 1 cm/h. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362780
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  • 2
    Electronic Resource
    Electronic Resource
    Marangoni convection and enhanced morphological stability in float-zone traveling solvent crystal growth of LaB6 (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6567-6569 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We analyze the problem of onset of morphological instability and the increasing supersaturation gradient in the particular case of float-zone traveling solvent growth of LaB6 crystals in excess of La, taking into account the actual liquidus line on the relevant phase diagram of Storms and Mueller [J. Phys. Chem. 82, 51 (1978)]. We show that the action of Marangoni convection decreases the concentration gradient at the solidification interface and inhibits the morphological instability and the increasing supersaturation gradient. We suggest that this effect allows the implementation of float-zone traveling solvent growth of LaB6 crystals with pulling rates of (approximately-equal-to)1 cm/h without the appearance of defects structures associated with the morphological instability and increasing supersaturation gradient. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363642
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  • 3
    Electronic Resource
    Electronic Resource
    Multiwall carbon nanotubes: Self-organization and inhibition of step-flow growth kinetics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3438-3446 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article the results of a numerical study on the self-organization and inhibition of step-flow growth of carbon nanotubes viewed within the framework of the continuum surface diffusion equation are given. Incorporation constants of C atoms, which differ depending on what side of the step the atom has been chemisorbed prior to incorporation, are considered. These differences can lead to the onset of surface multi-island nucleation in front of a propagating step with decrease in the growth temperature. This effect is able to cause formation of defects in the growing layer and even to inhibit stable step-flow modes of nanotube growth, leading to the formation of misoriented surface nuclei which may be likened to amorphous matter. A diagram distinguishing three characteristic temperature regions for nanotube formation is given: (i) the region where there is no secondary layer nucleation because the surface concentration of adsorbate on the surface of the first layer is not sufficiently high, (ii) the region of successive nucleation and propagation of one layer after another, i.e., stable step-flow growth, and (iii) the region where the nanotube surface is prone to multi-island nucleation, which inhibits stable step-flow growth and causes "amorphization" of the external surface of the nanotube. The simultaneous propagation of multilayer steps coupled by lip–lip interaction is shown to be feasible only if a microkinetic mechanism exists, which effectively redistributes to the edges of internal layers the atoms arriving initially by surface diffusion at the edge of the external layer © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1347407
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  • 4
    Electronic Resource
    Electronic Resource
    Postnucleation surface transport-kinetical phenomena and morphological instability in film deposition from vapor (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2151-2159 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The problem of transition of the postnucleation surface profile to continuous growth in the chemical vapor deposition process is considered. The developed numerical model includes a comprehensive set of transport-kinetical phenomena ongoing on the growth interface taking into account the effect of surface self-shadowing from the impinging species feeding the growth. This effect takes place when the characteristic length scale of surface profiles provided by the nucleation stage is lower than the free mean path of the gas species. The effect is shown to be able to destabilize the surface morphology in cases when the surface concentration is held far from the adsorption–desorption equilibrium and the surface profile length provided by the nucleation stage is considerably larger than the surface diffusion length of the growth species. Conditions under which the postnucleation surface smoothing may take place are specified. Experimentally feasible steps for postnucleation surface smoothing are discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1339209
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  • 5
    Electronic Resource
    Electronic Resource
    Surface carbonization and nucleation during chemical vapor deposition of diamond (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1736-1743 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The model presented considers surface kinetics processes, such as adsorption/desorption of hydrocarbon radicals, thermal dehydrogenation, evaporation, and carbon insertion into silicon, together with the bulk diffusion equation. The calculations performed show that surface protrusions present preferential locations for diamond nucleation due to a superposition of diffusion fluxes of carbon that is able to decrease the carbonization time on the protrusion tips by an order of magnitude compared with the untreated surfaces. This mechanism allows us to explain a number of observations in which the diamond is found to nucleate on the tips of surface protrusions. It is suggested that the surface carbon increases adsorption energy for hydrocarbon species and their concentration in the adlayer, resulting in high supersaturation which provokes nucleation. The analysis also shows that increased methane concentration in the feed gas and lower substrate temperature provide conditions for surface nucleation without a preliminary carbonization stage. The resulting diagram, outlining the operational parameters for both nucleation modes (via or without carbonization) on a Si (1,0,0) surface, is given. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370955
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of nanoscale substrate curvature on growth kinetics and morphology of surface nuclei (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 6673-6679 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results on numerical modeling of the influence of a substrate's nanoscale curvature on nucleation, growth kinetics, and morphological stability of nuclei during thin film vapor deposition are given. The problem is considered within the framework of the continuum surface diffusion equation taking into account the dependence of the adsorption energy, chemical potential, and the relevant surface mass fluxes on the surface curvature, together with the effect of surface self-shadowing from direct collisions from the gas phase and the contribution of readsorption fluxes. The nuclei growth kinetics are described by an Arrhenius type equation. Linear perturbation analysis of the growth model shows that positive nanoscale curvature (a concave surface) is able (i) to considerably increase the prenucleation concentration and thereby to increase the probability of nucleation and even to enable nucleation on substrates which do not have an affinity for nucleation under the given operating conditions, (ii) to increase considerably the growth rate of surface nuclei, and (iii) to lead to dramatic changes in morphology. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369043
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  • 7
    Electronic Resource
    Electronic Resource
    Growth mechanism of carbon nanotube forests by chemical vapor deposition (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2752-2754 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Analysis of kinetics processes involved in carbon nanotube (NT) forest growth during chemical vapor deposition suggests that: (i) carbon species are unable to penetrate to the forest bottom whenever the mean free path in gas is much larger than the typical distance between NTs; instead they collide with NT surfaces, chemisorbing within the top few microns, diffuse along the surface, and feed the growth at nanotube tips, (ii) wherever a catalyst nanoparticle is present, at the substrate or on the nanotube tip, in the postnucleation stage its role in feeding NT growth by C dissolution and bulk diffusion is negligibly small in comparison with the surface diffusion of C species adsorbing on the lateral surface of nanotubes, and (iii) bulk diffusion of C through the catalyst nanoparticle, defining the characteristic times of C penetration to nanoparticle base and surface saturation with C, is shown to play a major role in selection of the initial mode of nanotube nucleation and growth. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1468266
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  • 8
    Electronic Resource
    Electronic Resource
    Coupling of kinetic and transport phenomena in self-organization of C–B–N nanotube growth into sandwich structures (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1446-1448 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A mechanism for self-organization of C–B–N sandwich-like nanotubes with well-separated phases of C and BN [K. Suenaga, C. Colliex, N. Demoncy, A. Loiseau, H. Pascard, F. Willaime, Science 278, 653 (1997)] in arc-discharge is proposed. This mechanism includes (i) the microkinetic self-organization of nanotube growth in step-flow mode combined with a C and BN phase segregation at growth steps and (ii) the self-organization of "macro"-oscillations of impinging fluxes of C and B on the surface of nanotubes, which are caused by the nonuniformity of C and B content in the gas combined with the onset of natural convection, providing repeated transport of emerging nanotubes through regions with abundance in C and B, and leading to nucleation and growth of C and BN layers. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1290600
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  • 9
    Electronic Resource
    Electronic Resource
    Surface diffusion growth and stability mechanism of BN nanotubes produced by laser beam heating under superhigh pressures (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3522-3524 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A growth mechanism for BN nanotubes appearing at superhigh pressures under laser beam heating [D. Golberg, Y. Bando, M. Eremets, K. Takemura, K. Kurashima, and H. Yusa, Appl. Phys. Lett. 69, 2045 (1996)] is proposed based upon consideration of the dependence of the energy of adsorption and surface diffusion on the surface curvature. According to this mechanism, the growth of BN nanotubes is due to surface diffusion along the external surface, which also ensures morphological stability of the open end during growth. It is suggested that the observed nanotube heights are limited by the corresponding diffusion length. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120379
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  • 10
    Electronic Resource
    Electronic Resource
    Nanotube self-organization: Formation by step-flow growth (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 194-196 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth kinetics of carbon nanotubes is considered within the framework of a step-flow kinetics model proposed in 1951 by Burton, Cabrera, and Frank [W. K. Burton, N. Cabrera, and F. C. Frank, Philos. Trans. R. Soc. London, Ser. A 243, 299 (1951)] as a general mechanism for defectless crystal growth. The model reveals that the nucleation of the next layer and its consecutive growth can inhibit the growth of the underlying layers leading to the formation of observed nanotubular "bamboo" structures. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123290
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