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  • 1
    Electronic Resource
    Electronic Resource
    A two-dimensional molecular dynamics simulation of thin film growth by oblique deposition (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5682-5690 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Atomistic, molecular dynamics simulations are employed to investigate the relationship between film microstructure and deposition conditions (substrate temperature, deposition kinetic energy, and deposition angle). Increasing substrate temperature and deposition kinetic energy leads to fewer voids, smaller voids, smoother surfaces, and higher film density. As the deposition angle increases, the film microstructure changes from a dense film, with few voids, to a microstructure in which nearly colinear tracks of elongated voids form and, finally, to a highly porous structure of well-formed columns. The angle along which the voids are elongated and the orientation of the void tracks are the same and increase monotonically with the deposition angle (the column angles follow the same trend as the deposition angle). Void formation, void alignment into tracks, and the columnar structure are all attributable to shadowing effects, which become more pronounced with increasing deposition angle. The variation of the column/void track angle β with deposition angle α fits well with the classical tangent law at low angles, but is overpredicted by the tangent law at α(approximately-greater-than)60°, consistent with experiment. The column angle β decreases slowly with increasing deposition kinetic energy due to increased surface mobility. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363621
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  • 2
    Electronic Resource
    Electronic Resource
    Void formation during film growth: A molecular dynamics simulation study (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1448-1457 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two-dimensional, nonequilibrium molecular dynamics simulations have been applied to study the structure of thin films grown on single-crystal Lennard-Jones substrates. The principal microstructural features to develop within these films are single vacancies and small voids which tend to be slightly elongated and to be aligned in the growth direction. Both the void volume and the mean surface roughness of the films are found to be decreasing functions of substrate temperature and deposition kinetic energy. Voids are shown to form as a consequence of both surface roughness and shadowing effects. The attraction between deposited atoms and the sides of surface depressions lead to the formation of outgrowths from the sidewalls of the surface depression. These outgrowths shadow the open void beneath them and continue to grow across the voids by interaction with the depositing atoms until a continuous bridge is formed that closes off the void. Since this bridging mechanism leaves behind a surface depression above the closed-off void, new voids tend to form above it. This leads to the alignment of voids along the film growth direction. The spacing of the resultant void tracks is correlated with the wavelength of the surface roughness. Increasing temperature and deposition kinetic energy enhancing surface mobility leads to an increase in the wavelength of the surface roughness and hence an increase in the spacing between void tracks. Edge dislocations tend to form within voids as a natural consequence of the void bridging process, however nondislocated voids are also observed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360983
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  • 3
    Electronic Resource
    Electronic Resource
    Extended ensemble molecular dynamics method for constant strain rate uniaxial deformation of polymer systems (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 4396-4407 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We describe a novel molecular dynamics (MD) method to simulate the uniaxial deformation of an amorphous polymer. This method is based on a rigorously defined statistical mechanics ensemble appropriate for describing an isothermal, displacement controlled, uniaxial stress mechanical test. The total number of particles is fixed and the normal stresses in the direction normal to the applied strain are constant, i.e., an NTLxσyyσzz ensemble. By using the Lagrangian of the extended system (i.e., including additional variables corresponding to the temperature and cross-sectional area fluctuations), we derive a set of equations of motion for the atomic coordinates and the additional variables appropriate to this ensemble. In order to avoid the short MD time step appropriate for the stiff covalent bonds along the polymer chains, we introduce bond length constraints. This is achieved using a variation of the commonly used SHAKE [J. P. Ryckaert, G. Ciccotti, and H. J. C. Berendsen, J. Comp. Phys. 23, 327 (1977)] algorithm. A numerical method for integrating the equations of motion with constraints via a modification of the velocity Verlet [W. C. Swope, H. C. Andersen, P. H. Berens, and K. R. Wilson, J. Chem. Phys. 76, 637 (1982)] algorithm is presented. We apply this new algorithm to the constant strain rate deformation of an amorphous polyethylene in a model containing several distinct polymer chains. To our knowledge, this is the first time that bond length constraints were applied to a macromolecular system together with an extended ensemble in which the simulation cell shape is allowed to fluctuate. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474781
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular dynamics study of isobaric and isochoric glass transitions in a model amorphous polymer (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 7058-7069 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We perform molecular dynamics simulations of the glass transition through isobaric and isochoric cooling of a model polymeric material. In general, excellent agreement between the simulation results and the existing experimental trends is observed. The glass transition temperature (Tg) is found to be a function of pressure under isobaric conditions and specific volume under isochoric conditions. Under both isobaric and isochoric conditions, the trans-state fraction and the torsional contributions to the energy undergo abrupt changes at the glass transition temperature. We analyze these data to show that the glass transition is primarily associated with the freezing of the torsional degrees of the polymer chains which is strongly coupled to the degree of freedom associated with the nonbonded Lennard-Jones potential. We attribute the greater strength of the glass transition under constant pressure conditions to the fact that the nonbonded Lennard-Jones potential is sensitive to the specific volume, which does not change during cooling under isochoric conditions. Comparison of the isochoric and isobaric data demonstrate that the thermodynamic state is independent of cooling path above Tg, while path-dependent below Tg. The simulation data show that the free volume at the isobaric glass transition temperature is pressure dependent. We also find that a glass transition occurs under isochoric conditions, even though the free volume actually increases with decreasing temperature. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478611
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  • 5
    Electronic Resource
    Electronic Resource
    Crosshatched surface morphology in strained III-V semiconductor films (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4093-4098 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The correlation between the surface crosshatched morphology and the interfacial misfit dislocations in strained III-V semiconductor heteroepitaxy has been studied. The surface pattern is clearly seen on samples grown at high temperature (520 °C) and those with small lattice-mismatched (f〈2%) systems. A poorly defined crosshatched morphology was found on layers grown at relatively low temperature (400 °C). As the lattice mismatch of the strained layer becomes larger than 2%, a roughly textured surface morphology is commonly observed in place of actual cross-hatching. Few threading dislocations are observed in the strained layer when the crosshatched pattern develops. It is also noted that the surface crosshatched pattern develops after the majority of the interfacial misfit dislocations are generated. The result suggests that the surface crosshatch pattern is directly related to the generation of interfacial misfit dislocations through glide processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344968
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  • 6
    Electronic Resource
    Electronic Resource
    Stress relaxation and misfit dislocation nucleation in the growth of misfitting films: A molecular dynamics simulation study (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 217-227 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The low-temperature growth and relaxation of misfitting films are analyzed on the basis of two-dimensional molecular dynamics simulations using Lennard–Jones potentials. The temporal evolution of the surface morphology and the mechanisms for misfit dislocation nucleation and stress relaxation are monitored. Pseudomorphic film growth is observed up to a critical thickness. In some cases, the formation of voids within the film relaxes some of the stress. At the critical thickness, dislocations nucleate and relax most of the misfit. The critical thickness increases with decreasing lattice mismatch and depends on the sign of the misfit. The critical thickness of compressively strained films is smaller than that of films with the same magnitude of misfit, but in tension. The mechanism of dislocation nucleation is different in tension and compression and, in all cases, is associated with the roughness of the film surface. In the compressive misfit case, dislocations nucleate by squeezing-out an atom at the base of surface depressions. In the tensile misfit case, however, the nucleation of misfit dislocations involves the concerted motion of a relatively large number of atoms, leading to insertion of an extra lattice (plane) row into an already continuous film. These results show that the critical thickness depends intimately on the film morphology which, in turn, is determined as an integral part of the film growth process. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366676
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  • 7
    Electronic Resource
    Electronic Resource
    The mechanism of texture formation during film growth: The roles of preferential sputtering and shadowing (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3007-3009 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonequilibrium molecular dynamics simulations have been employed to develop a mechanistic model for the development of an out-of-plane (fiber) texture in polycrystalline thin films. The depositing atoms preferentially sputter film atoms from grains with high surface energies. As the film grows, an atomic shadowing mechanism leads to the lateral growth of the grains with a height advantage—eventually leading to the occlusion of randomly oriented grains. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116821
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  • 8
    Electronic Resource
    Electronic Resource
    KINETIC MONTE CARLO SIMULATION OF CHEMICAL VAPOR DEPOSITION (2002)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Materials Research 32 (2002), S. 297-319 
    Details
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The kinetic Monte Carlo method is a powerful tool for exploring the evolution and properties of a wide range of problems and systems. Kinetic Monte Carlo is ideally suited for modeling the process of chemical vapor deposition, which involves the adsorption, desorption, evolution, and incorporation of vapor species at the surface of a growing film. Deposition occurs on a time scale that is generally not accessible to fully atomistic approaches such as molecular dynamics, whereas an atomically resolved Monte Carlo method parameterized by accurate chemical kinetic data is capable of exploring deposition over long times (min) on large surfaces (mm2). There are many kinetic Monte Carlo approaches that can simulate chemical vapor deposition, ranging from coarse-grained model systems with hypothetical input parameters to physically realistic atomic simulations with accurate chemical kinetic input. This article introduces the kinetic Monte Carlo technique, reviews some of the major approaches, details the construction and implementation of the method, and provides an example of its application to a technologically relevant deposition system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.matsci.32.012102.110247
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  • 9
    Electronic Resource
    Electronic Resource
    Simulating Equilibrium Grain Boundary Segregation (1993)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 126-128 (Jan. 1993), p. 23-24 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/59/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.126-128.23.pdf
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  • 10
    Electronic Resource
    Electronic Resource
    Interface Diffusion under an Electric Field. Interface Evolution (1996)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 207-209 (Feb. 1996), p. 109-112 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/01/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.207-209.109.pdf
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