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  • 1
    Electronic Resource
    Electronic Resource
    Extreme thermal expansion, piezoelectricity, and other coupled field properties in composites with a negative stiffness phase (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 6458-6465 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Particulate composites with negative stiffness inclusions in a viscoelastic matrix are shown to have higher thermal expansion than that of either constituent and exceeding conventional bounds. It is also shown theoretically that other extreme linear coupled field properties including piezoelectricity and pyroelectricity occur in layer- and fiber-type piezoelectric composites, due to negative inclusion stiffness effects. The causal mechanism is a greater deformation in and near the inclusions than the composite as a whole. A block of negative stiffness material is unstable, but negative stiffness inclusions in a composite can be stabilized by the surrounding matrix and can give rise to extreme viscoelastic effects in lumped and distributed composites. In contrast to prior proposed composites with unbounded thermal expansion, neither the assumptions of void spaces nor slip interfaces are required in the present analysis. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1413947
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  • 2
    Electronic Resource
    Electronic Resource
    Metal Schottky barrier contacts to alpha 6H-SiC (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4757-4760 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Formation of Schottky barrier contacts to n-type 6H-SiC for a number of metals chosen to include a variety of physical and chemical properties has been investigated. The metals (Pd, Au, Ag, Tb, Er, Mn, Al, and Mg) were deposited onto room temperature surfaces terminated with a submonolayer coverage of oxygen. The metal/6H-SiC interface chemistry and Schottky barrier height φB during contact formation were obtained with x-ray photoemission spectroscopy; the electrical properties of subsequently formed thick contacts were characterized by current-voltage and capacitance-voltage techniques. The øB values for these metals extend over a wide 1.3 eV range. To a varying degree φB depends on the 6H-SiC crystal face (Si vs C). Mg and Al (Si face of latter) have φB=0.3 eV, a value which is suitable for nonalloyed ohmic contacts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352086
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  • 3
    Electronic Resource
    Electronic Resource
    Hall measurements as a function of temperature on monocrystalline SiC thin films (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6375-6381 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hall measurements were conducted at temperatures up to 1000 K on unintentionally doped n-type β(3C)- and α(6H)-SiC thin films epitaxially grown on both on-axis and vicinal Si (100) and α(6H)-SiC (0001) by chemical vapor deposition. The carrier concentration versus temperature data were analyzed using a compensation model. The β-SiC films grown on Si were highly compensated (NA/ND=0.73–0.98). The compensation ratio was not as large in the SiC films grown on α-SiC (NA/ND=0.36, for β-SiC on α-SiC, and 0.02, for α-SiC on α-SiC). The donor ionization energy for β-SiC on Si was calculated to be 14–21 meV. Analogous values for β- and α-SiC films on α-SiC were 33 and 84 meV, respectively. These values are smaller than those for N determined from photoluminescence studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345159
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of surface state density for GaAs and InAlAs by room temperature photoreflectance (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1765-1767 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Room temperature photoreflectance (PR) was used to investigate the surface state densities of GaAs and In0.52Al0.48As surface intrinsic-n+ structures. The built-in electric field and thus the surface barrier height are evaluated using the observed Franz–Keldysh oscillations in the PR spectra. Based on the thermionic emission theory and current-transport theory, the surface state density as well as the pinning position of the Fermi level can be determined from the dependence of the surface barrier height on the pump beam intensity. Even though this method is significantly simpler, easier to perform, and time efficient compared with other approaches, the results obtained agree with the literature. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370961
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  • 5
    Electronic Resource
    Electronic Resource
    Photoreflectance and photoluminescence spectroscopy of the lattice-matched InGaAs/InAlAs single quantum well (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 920-926 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A lattice-matched In0.53Ga0.47As/In0.52Al0.48As single quantum well (SQW) structure grown by gas source molecular beam epitaxy has been investigated by photoreflectance (PR) and photoluminescence (PL). The PR measurements allowed the observation of interband transitions from the heavy- and light-hole valence subbands to the conduction subbands. The transition energies measured from the PR spectra agree with those calculated theoretically. Two features corresponding to the ground state transition coming from the SQW and the band gap transition generated from the buffer layer are observed in the PL spectra and are in good agreement with the PR data. The effect of the temperature on the transition energies is essentially same as that in the gap transition of the bulk structure. The values of the Varshni coefficients of InGaAs/InAlAs were obtained from the relation between the exciton transition energy and the temperature. The built-in electric field could be determined and located from a series of PR spectra by sequential etching processes. The phase spectra obtained from the PR spectra by the Kramers–Kronig transformation were analyzed in terms of the two-ray model, and calculated the etching depth in each etching, and thus leading to the etching rate. The etching rate obtained from phase shift analysis agrees with that measured by atomic force microscopy. The etching results suggest that a built-in electric field exists at the buffer/substrate interface and it also enables us to determine the etching rate. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1487906
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  • 6
    Electronic Resource
    Electronic Resource
    Transmission electron holography of silicon nanospheres with surface oxide layers (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1296-1298 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Phase images of 20–30-nm-diam silicon spheres were collected by holographic methods in a field-emission transmission electron microscope. The spherical geometry enables the effect of specimen thickness on the electron-wave phase to be separated from the intrinsic Si electron-optical refractive effects allowing a determination of the mean inner potential Φ0. This work finds Φ0=11.9±0.9 V characterizing amorphous Si and 12.1±1.3 V characterizing crystalline Si. The phase images can resolve a 2-nm-thick native oxide layer and give Φ0 for SiO2=10.1±0.6 V. The phase data can quickly recognize a surface layer, and the effect of a surface layer on the determination of the bulk mean potential can be minimized. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118556
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  • 7
    Electronic Resource
    Electronic Resource
    Oxide–GaAs interfacial electronic properties characterized by modulation spectroscopy of photoreflectance (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 2857-2859 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Built-in electric fields and interfacial state densities (Dit) in a series of oxide–GaAs heterostructures fabricated by in situ molecular beam epitaxy were studied using room temperature photoreflectance. The samples investigated were air-, Al2O3–Ga2Ox–, and Ga2O3(Gd2O3)–GaAs. We found that the built-in electric fields are 48, 44, and 38 kV/cm for air-, Al2O3-, and Ga2Ox–GaAs samples, respectively. For the Ga2O3(Gd2O3)–GaAs sample, the built-in electric field is negligibly small, indicating a very low interfacial state density. Estimated by the low field limit criterion, Dit is less than 1×1011 cm−2 eV−1. Our results on the Ga2O3(Gd2O3)–GaAs sample are consistent with the data obtained previously using capacitance–voltage measurements in quasistatic/high frequency modes and photoluminescence measurements. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367047
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  • 8
    Electronic Resource
    Electronic Resource
    Unambiguous photoreflectance determination of electric fields using phase suppression (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3452-3454 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance measurements have been performed on a δ-doped GaAs homojunction. Two Franz–Keldysh oscillation features originating from two different regions (a buffer layer and a top layer) of the structure superimpose with each other in the photoreflectance spectrum. By properly selecting the reference phase, one of the features can be suppressed, thus enabling us to determine the electric fields from the two regions unambiguously. The electric field in the top layer is 3.5±0.2×105 V/cm, which is in good agreement with theoretical calculation. The electric field in the buffer layer is 1.2±0.1×104 V/cm. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115790
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  • 9
    Electronic Resource
    Electronic Resource
    Vertical stress distribution due to an arbitrarily shaped foundation using triangulation and an analytical expression for a triangular loaded region (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 15 (1991), S. 51-60 
    Details
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Using the basic Boussinesq's equation, the expression for the vertical stress distribution (σz) underneath any point on the ground surface due to a general triangular loaded region in a preferred orientation with a linearly varied loading has been successfully derived. When the triangle is not in a preferred orientation, a simple axis transformation is required and the expression will be equally applicable. Based on this expression, σz due to an arbitrarily shaped loaded foundation can simply be determined by first triangulating the loaded area and summing up the contributions from each generated triangular region. The procedures for triangulating and calculating the stress distribution can be simply automated through computer programs.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nag.1610150105
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  • 10
    Electronic Resource
    Electronic Resource
    A numerical model for wave scattering problems in infinite media due to p- and sv-wave incidences (1992)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 33 (1992), S. 1661-1682 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Based on elastic wave motion theory and the superposition concept, a numerical model for wave scattering problems in infinite media due to P-wave and SV-wave incidences is presented in this paper. Since this model is based on a coupled system of finite and infinite elements for simulating wave propagation in infinite media, the complexity of geometry and the variability of material properties in the foundation can be realistically simulated. Through a systematic study of the characteristics of a plane harmonic P-wave and SV-wave incidences on a fixed boundary, the concept of stress increase factors and stress factors which can be used to calculate the generalized stresses on the wave input boundary due to the SV-wave and P-wave incidences is also proposed. The effects of incident wave mode, incident angle and Poisson's ratio in the foundation on the stress increase factors and the stress factors have been studied in detail. Finally, the proposed model has been applied to a half-plane foundation and a semi-circular canyon to calculate SV-wave and P-wave scattering problems. The numerical results obtained show good agreement with the theoretical results and Wong's analytical results.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620330808
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