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  • 1
    Electronic Resource
    Electronic Resource
    Many-particle quantum dynamics: An exact algorithm for correlated motion on lattices (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 5318-5333 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The time dependent many-body dynamics of strongly interacting particles on a two-dimensional lattice are studied with the recently developed checkerboard propagator. Application is made to the two-dimensional infinite U Hubbard model at high concentrations, for both fermion and boson systems. The concentration, initial state, and boundary condition dependence of vacancy correlation functions are analyzed, and related to the local densities of states. Quasidissipative behavior of the correlation functions is seen beyond a short initial time scale during which single-particlelike motion is seen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462717
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  • 2
    Electronic Resource
    Electronic Resource
    Quantum relaxation in high density fermion and boson tunneling dynamics: Implications for low temperature anomalous surface diffusion (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 1417-1420 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quantum relaxation behavior for many-particle tunneling systems of interacting identical particles is studied for both fermions and bosons within the infinite U Hubbard model, using a numerically exact checkerboard time propagation. Dependence of relaxation times upon vacancy concentration is obtained, and conclusions for nuclear statistical effects in hydrogen surface diffusion presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461123
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  • 3
    Electronic Resource
    Electronic Resource
    Closed, analytic, boson realizations for Sp(4) (1986)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 27 (1986), S. 1987-1993 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The problem of determing a boson realization for an arbitrary irrep of the unitary simplectic algebra Sp(2d) [or of the corresponding discrete unitary irreps of the unbounded algebra Sp(2d,R)] has been solved completely in recent papers by Deenen and Quesne [J. Deenen and C. Quesne, J. Math. Phys. 23, 878, 2004 (1982); 25, 1638 (1984); 26, 2705 (1985)] and by Moshinsky and co-workers [O. Castaños, E. Chacón, M. Moshinsky, and C. Quesne, J. Math. Phys. 26, 2107 (1985); M. Moshinsky, "Boson realization of symplectic algebras,'' to be published]. This solution is not known in closed analytic form except for d=1 and for special classes of irreps for d〉1. A different method of obtaining a boson realization that solves the full problem for Sp(4) is described. The method utilizes the chain Sp(2d)&supuline;SU(2)×SU(2) ×⋅⋅⋅×SU(2) (d times), which, for d≥4, does not provide a complete set of quantum numbers. Though a simple solution of the missing label problem can be given, this solution does not help in the construction of a mapping algorithm for general d.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.527016
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of an inhomogeneous spatial distribution of defects on the constant photocurrent method (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 6795-6799 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The constant photocurrent method has been widely used in hydrogenated amorphous silicon as an efficient way of determining the optical absorption coefficient in the low-absorption region, and of estimating the defect density in the band gap. However, while the analysis is generally carried out on the assumption of uniform material parameters throughout the sample the experimental situation may fail to approximate that model. We therefore examine the influence on the resolved defect density of an inhomogeneous spatial distribution of defects, and of surface recombination, by means of a steady-state diffusion equation for photoexcited carriers. Differences by as much as a factor of 2 are observed within the range of possible experimental circumstances. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365223
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of light soaking on surface- and bulk-spin densities in hydrogenated amorphous silicon (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1230-1234 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To study the influence of light soaking on surface- and bulk-spin densities in hydrogenated amorphous silicon (a-Si:H) films, we have measured the spin density in the films with thicknesses ranging from 0.02 to 3.9 μm as a function of light-soaking time. It is found that the total spin density in films thinner than 0.1 μm approaches the steady state spin density within a few hours and is increased by only a factor of 2–3 after 12 h strong illumination with light intensity of 3.8 W/cm2. However, for the films thicker than 0.7 μm, the total spin density does not show a tendency to approach the steady state value and is increased by a factor of 10. Furthermore, in order to describe the spatial distribution of the spin density, a simulation, in which the total spin density is composed of the surface-spin density and the bulk-spin density, is carried out. The calculated spatial distribution further supports that light soaking increases the surface-spin density by a factor of 2–3, but the bulk-spin density by a factor of 25 if the bulk-spin density for the annealed state is taken as 4×1015 cm−3. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360363
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of oxygen on the thermal stability of amorphous hydrogenated carbon films (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 1349-1353 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Influence of oxygen on the thermal stability of amorphous hydrogenated carbon (a-C:H) films is investigated by annealing the films at 520, 610, and 670 K in vacuum and in O2 flow, respectively. The a-C:H films used for this study were deposited using microwave plasma from a mixture of 10 sccm pure methane and 100 sccm hydrogen in an electron cyclotron resonance chemical vapor deposition system. It is found that the anneals in O2 gas flow lead to much more prominent variation in film thickness, optical band gap, and IR absorption related to C–H stretching vibration than the anneals in vacuum. Raman scattering and optical absorption indicate that O2 greatly promotes the transformation from polymeric to graphitic microstructure with increasing annealing temperature. Possible conversion of bond structure and the role of O2 in the stability of the films are discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367311
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  • 7
    Electronic Resource
    Electronic Resource
    Deposition of hydrogenated diamond-like carbon films under the impact of energetic hydrocarbon ions (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 5538-5542 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article we studied the influence of bombardment energy of hydrocarbon ions on the properties of hydrogenated diamond-like carbon (DLC) films using x-ray reflectivity, Raman spectroscopy, and Fourier-transform infrared. The DLC films were prepared with an electron cyclotron resonance system using H2 and CH4 gases and the ion energy was tunable through a rf-induced dc bias voltage. It was observed that the surface roughness is increased and C–H bonded hydrogen concentration is decreased with increased ion energy, whereas the mass density, hardness, and sp3/sp2 ratio exhibited optimum values. A thin SiC layer was found to form between the DLC films and silicon substrates. Two proposed carbon deposition mechanisms, i.e., the shallow implantation (subplantation) model and the adsorbed layer model, are examined based on the results obtained in this study. Our results indicate that ion bombardment energy is a critical factor in determining the film properties and the ion subplantation could be an important deposition process even for hydrogenated DLC films. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368599
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  • 8
    Electronic Resource
    Electronic Resource
    Thickness dependence of density of gap states in diamond films studied using space-charge-limited current (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5747-5753 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Structural and electrical characteristics of chemical vapor deposited (CVD) diamond films have been studied as a function of film thickness. The samples comprise a set of codeposited, nominally undoped diamond films with average grain size on the growth surface increasing linearly with the film thickness. Raman scattering analysis reveals a decrease of nondiamond phase and intragrain defects with increasing film thickness. Temperature dependent dc conductivity results indicate that, as the film thickness increases, the Fermi level moves towards the valence band. There is a corresponding decrease in the density of states at the Fermi level, as deduced from the space-charge-limited current in the bulk of the samples. The spatial variation in the density of states through the material closely reflects the changes observed in the structural and electrical properties of the films. Such characteristic has the implication on the application of CVD diamond in the area of electronics. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1360222
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  • 9
    Electronic Resource
    Electronic Resource
    Study of hydrogenated diamond-like carbon films using x-ray reflectivity (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 289-296 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray reflectivity under grazing incidence conditions is a powerful technique to study thin film density, surface roughness, and the multilayer structure without destroying the samples. In this article, we, using x-ray reflectivity technique, have studied the effects of bias voltage and deposition pressure on the mass density, surface and interface roughness of hydrogenated diamond-like carbon (DLC) films. It is observed that the surface roughness increases with increasing the bias voltage and with decreasing the deposition pressure over a wide range. The mass density, hardness and sp3/sp2 ratio deduced from the Raman spectra pass through their maximal values with the bias voltage, while they are increased monotonously with the pressure. A thin SiC layer is found to be formed between the DLC films and silicon substrate. According to our results, the influences of the bias voltage and deposition pressure on the film properties are clearly reflected through hydrocarbon ion energy impinging on the growing surface. Based on the film surface feature as a function of the ion energy, we suggest that the shallow ion implantation (subplantation) process could be a dominant deposition mechanism. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370792
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  • 10
    Electronic Resource
    Electronic Resource
    State resolved rotational relaxation of CS2 in argon free jet (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 3617-3621 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotational relaxation of CS2 in argon free jet was studied using laser-induced fluorescence (LIF). The rotational populations were obtained from LIF detection at 19 different points along the jet axis from 3 to 15 nozzle diameters. On the basis of the energy gap power law, the master equation was solved to fit the experiment results, and the two temperature-independent parameters in the law were determined. The results show that the state-to-state relaxation cross sections vary as the inverse 1.7 power of the energy gap between the initial and the final states. The expressions for the state-to-state relaxation cross sections and the rate constants were written. The relaxation cross sections decrease with increasing temperature over the range of 2–60 K for the CS2+Ar collision. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468590
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