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  • 2000-2004  (21)
  • 1975-1979
  • 1965-1969
  • 1950-1954
  • 2001  (21)
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  • 2000-2004  (21)
  • 1975-1979
  • 1965-1969
  • 1950-1954
Year
  • 1
    Electronic Resource
    Electronic Resource
    Amplification of transverse acoustic phonons in quantum well heterostructures with piezoelectric interaction (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3934-3941 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have analyzed amplification of transverse phonons confined in quantum well (QW) heterostructures through piezoelectric electron–phonon interaction with drifting electrons. It was found that this mechanism of interaction couples the low-dimensional electrons and the shear-horizontal (SH) confined phonons. We have studied the electrostatic potential accompanying the SH waves and found that efficient interaction can be achieved for the lowest antisymmetric SH phonon branch in a narrow band of phonon frequencies. For AlGaAs QWs the amplification coefficient was calculated to be on the order of 100 cm−1 in the sub-THz phonon frequency range. These results suggest an electrical method for coherent phonon generation in the technologically well-developed AlGaAs QW heterostructures. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1402145
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  • 2
    Electronic Resource
    Electronic Resource
    CO2 laser–plume interaction in materials processing (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 681-688 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In laser materials processing, localized evaporation caused by focused laser radiation forms a plume of mixed vapor and ambient gas above the material surface. The beam is refracted and absorbed as it traverses the plume, thus modifying its power density on the surface. In this work, plume–beam interaction is studied using an axisymmetric, high-temperature gas-dynamic model of a plume formed by vapor from an iron surface. The beam propagation in the plume is calculated from the paraxial wave equation including absorption and refraction. The simulation results quantify the effects of plasma plume properties on the beam radius and laser power density variations at the material surface. It is shown that absorption and refraction in the plume have significant impacts on the laser–material interaction. Absorption of the beam in the plume has much less direct effect on the power density at the material surface than refraction does. However, absorption is essential for the formation of the plume, without which there is no refraction. Helium gas is more efficient than argon for reducing the beam refraction and absorption effects. Laser energy reflected from the material surface has significant effects on the plume properties. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1329668
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  • 3
    Electronic Resource
    Electronic Resource
    Waldenström's macroglobulinaemia presenting as reticulate purpura and bullae in a patient with hepatitis B virus infection (2001)
    Oxford, UK : Blackwell Science Ltd
    Clinical and experimental dermatology 26 (2001), S. 0 
    Details
    ISSN: 1365-2230
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Cutaneous manifestations of Waldenström's macroglobulinaemia (WM) include purpura, ulcers, urticaria, leukocytoclastic vasculitis, and immunobullous dermatoses. No association has been reported previously of WM and hepatitis B virus (HBV) infection. A 40-year-old female HBV carrier was admitted to hospital because of generalized oedema, oliguria, haematuria, hypertension, fever and blood-tinged sputum. Cutaneous manifestations included generalized petechiae, palpable purpura mainly on the legs, multiple necrotic ulcerations and gangrenous changes on the toes, and necrotic, giant confluent reticulate purpura on the trunk surmounted by several tense bullae. Laboratory investigations revealed monoclonal gammopathy of IgM kappa type (6.7 g/L), membranoproliferative glomerulonephritis associated with HBV infection, Bence Jones proteinuria, and an increased number of abnormal plasmacytoid cells in the bone marrow. Pathologic examination demonstrated immune complex-mediated vasculitis with deposits of IgM in the walls of dermal vessels and secondary subepidermal bulla formation. HBV infection may have caused WM or modified the clinical course in this fatal case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2230.2001.00880.x
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  • 4
    Electronic Resource
    Electronic Resource
    Quantized vibrational modes of nanospheres and nanotubes in the elastic continuum model (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5107-5111 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The properties of nanoscale spheres and tubes are of recent interest due to the discovery of the fullerene molecule and the carbon nanotube. These carbon structures can be modeled as nanoscale spherical or cylindrical shells. In this article, these nanostructures are treated in the thin shell approximation with the elastic properties taken to be those of the graphene sheet. A quantization prescription is applied to the classical elastic modes to facilitate the first calculations of the quantum-mechanical normalizations of selected modes. These modes are shown to be amenable to the study of electron-phonon interactions. Indeed, electron-phonon interaction Hamiltonians are derived. Moreover, it is shown for such a tube of finite length that the electron-phonon interaction strength depends on the axial position. As a special case it is shown that the dispersion relation for the clamped tube depends on the length of the tube. In this article we consider both the vibrational frequencies and the mode quantization for both spherical shell and the nanotube using realistic material parameters. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1356429
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  • 5
    Electronic Resource
    Electronic Resource
    Interlayer coupling field in spin valves with CoFe/Ru/CoFe/FeMn synthetic antiferromagnets (invited) (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7612-7615 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Top synthetic spin valves with structure Ta/NiFe/CoFe/Cu/CoFe(P1)/Ru/CoFe(P2)/FeMn/Ta on Si (100) substrate with natural oxide were prepared by dc magnetron sputtering system. We have changed only the thickness of the free layer and the thickness difference (P1−P2) in the two ferromagnetic layers separated by Ru, and investigated the effect of magnetic film thickness on the interlayer coupling field in a spin valve with a synthetic antiferromagnet. As the free layer thickness decreased from 70 to 20 Å, the interlayer coupling field was increased due to the magnetostatic coupling (orange peel coupling). In the case of the thickness difference in the pinned layers, the interlayer coupling field agreed with the modified Néel model suggested in the top synthetic spin valve structures. However, in the case of tP1=tP2, and tP1=tP2+5 Å, it was found that the interlayer coupling field could not be explained by the modified Néel model. The deviation of the modified Néel model at the dip zone could be due to the large canting of the pinned layers, which depend on applied field and different thickness in synthetic antiferromagnetic structure. The dependence of Cu thickness on the interlayer coupling field was investigated and 10 Oe of the interlayer coupling field was obtained when the Cu thickness is 32 Å. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1361056
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  • 6
    Electronic Resource
    Electronic Resource
    Optical and magneto-optical investigation on electronic structure of ordered ferromagnetic Fe3Pt (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 244-248 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical and magneto-optical properties of ordered Fe3Pt have been investigated by spectroscopic ellipsometry and magneto-optical Kerr spectroscopy. The diagonal component of the optical conductivity tensor of the compound exhibits a broad absorption peak at about 2 eV, which is shifted by about 0.5 eV to lower energies from the corresponding one in pure bcc Fe. The Kerr angle spectrum of the compound disperses quite similarly in both spectral trend and magnitude to that of pure Fe below 3.5 eV but differently above it. The lower-energy shift of the 2-eV-absorption structure of the compound is interpreted as due to the shift of the minority-spin Fe-d states toward EF through the hybridization with Pt-d states. The Kerr effect of the compound is attributable to a large spin-orbit coupling in Pt as well as the well-hybridized spin-polarized bands. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1331064
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  • 7
    Electronic Resource
    Electronic Resource
    Single-electron transistor based on a silicon-on-insulator quantum wire fabricated by a side-wall patterning method (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3812-3814 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose and implement a promising fabrication technology for geometrically well-defined single-electron transistors based on a silicon-on-insulator quantum wire and side-wall depletion gates. The 30-nm-wide silicon quantum wire is defined by a combination of conventional photolithography and process technology, called a side-wall patterning method, and depletion gates for two tunnel junctions are formed by the doped polycrystalline silicon sidewall. The good uniformity of the wire suppresses unexpected potential barriers. The fabricated device shows clear single-electron tunneling phenomena by an electrostatically defined single island at liquid nitrogen temperature and insensitivity of the Coulomb oscillation period to gate bias conditions. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1421081
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  • 8
    Electronic Resource
    Electronic Resource
    Growth and deep ultraviolet picosecond time-resolved photoluminescence studies of AlN/GaN multiple quantum wells (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3690-3692 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: AlN/GaN multiple quantum wells (MQWs) with a well thickness of 26 Å have been grown by metal–organic chemical-vapor deposition. A specially designed photoluminescence (PL) spectroscopy system, which is capable of measuring picosecond time-resolved PL up to 6.2 eV, has been employed to probe the optical properties as well as the carrier transfer and decay dynamics in these MQWs. Optical transitions at 4.039 and 5.371 eV at T=10 K, resulting from the interband recombination between the electrons and holes in the n=1 and n=2 subbands in the wells, have been observed. The band-offset parameter for the AlN/GaN heterostructure has been obtained by comparing the experimental results with the calculations. Carrier dynamics including the relaxation of the electrons and holes from the n=2 and n=1 subband in the conduction and valence bands and the decay lifetimes of the interband transitions have also been measured and analyzed. Detailed subband structures for both the conduction and valence bands in the wells were determined. The implications of our findings on the potential applications of AlN/GaN quantum wells have been discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1377317
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  • 9
    Electronic Resource
    Electronic Resource
    T-shaped ballistic spin filter (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 775-777 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose a semiconductor structure that can filter electron spin without using external magnetic fields. The structure consists of a T-shaped quasi-one-dimensional channel and an electrode placed near the channel intersection to control the spin-orbit interaction for electrons. Our calculations demonstrate that the proposed device can redirect electrons with opposite spins from an unpolarized source to left and right output leads, respectively, and, thus, serve as a spin filter. When the incident electron energy is in resonance with the quasilocalized zero-dimensional states at the intersection, polarization of the transmitted fluxes approaches 100%. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1347023
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  • 10
    Electronic Resource
    Electronic Resource
    Growth and optical properties of InxAlyGa1−x−yN quaternary alloys (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 61-63 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InxAlyGa1−xN quaternary alloys with different In and Al compositions were grown by metalorganic chemical vapor deposition. Optical properties of these quaternary alloys were studied by picosecond time-resolved photoluminescence. It was observed that the dominant optical transition at low temperatures in InxAlyGa1−xN quaternary alloys was due to localized exciton recombination, while the localization effects in InxAlyGa1−xN quaternary alloys were combined from those of InGaN and AlGaN ternary alloys with comparable In and Al compositions. Our studies have revealed that InxAlyGa1−xN quaternary alloys with lattice matched with GaN epilayers (y(approximate)4.8x) have the highest optical quality. More importantly, we can achieve not only higher emission energies but also higher emission intensity (or quantum efficiency) in InxAlyGa1−x−yN quaternary alloys than that of GaN. The quantum efficiency of InxAlyGa1−xN quaternary alloys was also enhanced significantly over AlGaN alloys with a comparable Al content. These results strongly suggested that InxAlyGa1−x−yN quaternary alloys open an avenue for the fabrication of many optoelectronic devices such as high efficient light emitters and detectors, particularly in the ultraviolet region. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1331087
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