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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 47-50 (June 2008), p. 558-561 
    ISSN: 1662-8985
    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
    Notes: We have developed a new method to fabricate poly(diphenylsilylenemethylene)(PDPhSM) matrix nanocomposite thin films containing copper nanoparticles produced by laserablation in this paper. First of all, 1,1,3,3-tetra- phenyl-1,3-disilacyclobutane (TPDC) films weredeposited on 4 cm2 silicon substrates cut from c-Si wafers by conventional vacuum evaporation undera pressure of 3.0×10-5 Torr; then copper nanoparticles were deposited onto the TPDC films by laserablation; finally the TPDC films with copper nanoparticles were heated in an electric furnace in an airatmosphere at 553 K for 10 min to induce ring-opening polymerization of TPDC. The resultsindicated that it is possible to fabricate PDPhSM matrix nanocomposite thin films using coppernanoparticles produced by laser ablation. The morphology and size distribution of coppernanoparticles can be controlled by laser ablation conditions. Also, the polymerization efficiencydepends on the size and chemical state of copper nanoparticles
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 532-533 (Dec. 2006), p. 953-956 
    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
    Notes: The pressure infiltration process of porous preforms by molten metals was investigatednumerically in this paper. The finite element model of heat and mass transfer of the infiltration inliquid infiltration extrusion process was founded by the introduction of a new continuum model offluid in porous medium and a distribution resistance concept. The proposed model can describe thetransient flow behavior of semisolid materials qualitatively. Numerical simulations were developed inparticular for non-isothermal infiltrations which take into account the thermal aspects (the mould, thefibres and the metal are initially preheated at different temperatures). The temperature distribution,infiltration front and infiltration depth in the infiltration area were gained by the simulation ofANSYS/FLOTRAN code. It is shown that the fiber volume fraction and initial temperature have astrong effect on the infiltration process. The simulation results of axisymmetric infiltration have agood agreement with their experimental ones. In addition, the infiltration time was predicted to get theeffective infiltration depth based on the simulation results
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3041-3044 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the observation of the quantum confinement effect by using photothermal deflection spectroscopy (PDS) experiment and the time dependence of optically induced degradation in CdS and CdSe semiconductor-doped glasses. The observed absorption peaks in the PDS experiment, together with a simple model, were used to evaluate the average radius of semiconductor microcrystals. It is found that the estimated average radii of quantum dots are consistent with that obtained from other methods. This result demonstrates that the PDS technique provides an alternative tool for the study of the optical properties of semiconductor microscrystals. The time dependence of the luminescence degradation of the impurity band, which is attributed to the process of Auger ionization, follows a stretched-exponential function. The inconsistency with the previously proposed exponential relaxation may be due to the size distribution of CdS and CdSe microcrystals.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7728-7736 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is found from scanning electron microscopy that the porous silicon samples fabricated under different conditions exhibit different morphologies. Some of them show islands or cracks, but the rest appear to be smooth. It is proposed that the formation of the islands and the cracks depends on the porosity of the porous silicon samples and result from the shrinkage of the porous structure. The photoluminescence spectra of the porous silicon samples also depend on the etching conditions. The peak position of the photoluminescence shifts to higher energy with increasing the porosity of the samples or by rinsing the samples in deionized water for a long time. However, in certain situations the photoluminescence peak shifts to lower energy after the samples are placed in air for a couple of days. It is proposed that not only the quantum size effect but also the transition between oxide levels contribute to the photoluminescence of the porous silicon.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2786-2789 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoconduction of synthetic pyrite FeS2 single crystals with low impurity concentration prepared by chemical vapor transport method is reported over a temperature range from 15 K to 300 K. The energy gap is determined from the photoconductive spectral response by the Moss rule. At room temperature the indirect energy gap is found to be 0.83±0.02 eV. According to the experimental evidence for a sharp antibonding p-like state above the Fermi level of FeS2 reported by Folkerts et al. [J. Phys. C 20, 4135 (1987)], the indirect gap is assigned as the transition between Fe 3d t2g and S 3p σ* states. The temperature variation of the indirect band gap shows a linear dependence between 100 K and 300 K with a negative temperature coefficience equal to 1.0±0.1 meV/K. A distinct feature at higher energy side of the spectrum is observed and attributed to the direct band-gap transition. At temperature lower than 60 K, a very sharp peak around 0.9 eV emerged below the absorption edge. This feature might be associated with the excess carriers induced by the photothermal ionization between the impurity levels and conduction band.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6912-6918 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The material properties of 2-μm-thick InxGa1−xAs epilayers grown on GaAs with 0.28≤x≤1 were investigated. It was found that for x≥0.5, the material quality of the larger lattice-mismatched heterojunction recovers, as evidenced by cross-sectional transmission electron microscopy (XTEM) and double-crystal x-ray diffraction (DXRD). Magnetophotoconductivity measurements were performed on InxGa1−xAs epilayers with 0.75≤x≤1. The dependence of both the cyclotron resonance linewidth and the carrier relaxation time on the material quality is consistent with the XTEM and DXRD results. The transport properties of InxGa1−xAs epilayers with 0.75≤x≤1 were studied using temperature-dependent van der Pauw measurements. It was found that the electron mobility in the low-temperature range is determined by a combination of ionized impurity and dislocation scatterings. The contribution of dislocation scattering to ternary InGaAs epilayers is larger than that to InAs, although InAs has a larger lattice mismatch with respect to GaAs. These four different measurement techniques confirm that the growth mode rather than lattice mismatch determines the density of dislocation for the heteroepitaxy of highly mismatched InxGa1−xAs on GaAs.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 1514-1516 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gap state density distribution in hydrogenated amorphous silicon has been obtained from the effect of light illumination on the dark conductivity. This new technique allows us to determine the bulk density of state distribution within approximately 400 meV below the Fermi level.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 2578-2579 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to explore the creation process of optically induced excess conductivity in compensated a-Si:H films, we investigated the effect of monochromatic light exposure with different photon energies: 2.54, 1.96, 1.17, and 0.95 eV. The experimental results show that the threshold energy is below 0.95 eV. We suggest that the most likely explanation is the introduction of localized states originating from boron-phosphorus complexes.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1277-1278 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Light-induced metastable defects in hydrogenated amorphous silicon can be eliminated by atomic hydrogen at the temperature below which the annealing effect occurs. The resulting material has a very high photosensitivity and stability.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 70-72 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown for the first time that hydrogen passivation can be made by using a photochemical vapor deposition system. Unlike the common methods, this new method of hydrogenation has no electron or ion bombardment, thus the sample surface will not be damaged during processing. The effects of hydrogenation are confirmed by the enhancement of photoluminescence intensity. A strong increase in the luminescence intensity (a factor of 23) has been observed which is comparable to the results of rf glow discharge systems.
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