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  • 1
    Electronic Resource
    Electronic Resource
    The interfacial morphology of strained epitaxial InxGa1−xAs/GaAs (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2224-2230 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructure of strained layers of InxGa1−xAs/GaAs grown by molecular-beam epitaxy has been investigated by transmission electron microscopy. lt was found that the formation of irregular interfacial morphologies of the InxGa1−xAs layers was due to a transition in growth mode from two-dimensional (layer-by-layer growth) to three-dimensional nucleation via island formation. It was also found that the occurrence of irregular growth surfaces of epitaxial layers was dependent upon inhomogeneous lattice strains induced by the formation of islands. A possible role of lattice strain for the formation of irregular growth surfaces was also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348700
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  • 2
    Electronic Resource
    Electronic Resource
    Design and construction of a triple-axis ultrahigh vacuum goniometer (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 306-309 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A triple-axis goniometer was designed and constructed for positioning objects within an ultrahigh vacuum chamber. The goniometer is applied to move a large position-sensitive microchannel plate (MCP) detector which is used for scattering and recoiling imaging spectrometry (SARIS). The goniometer allows the MCP to be independently rotated in horizontal (φ) and vertical (θ) planes as well as translated with respect to a fixed sample position. The angle φ can be varied from 0° to 160° in order to change the scattering angle for SARIS. The angle θ can be varied from 0° to 80°, allowing the MCP to be moved out of the scattering plane. Translation allows the MCP to be moved relative to the sample position over a range of 10–60 cm. All of the movements are driven by computer-controlled stepping motors. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148514
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  • 3
    Electronic Resource
    Electronic Resource
    Coercivity of Ti-modified (α-Fe)-Nd2Fe14B nanocrystalline alloys : The 6th joint magnetism and magnetic materials (MMM)−intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7071-7073 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Coercivity of Ti-modified nanocrystalline (α-Fe)-Nd2Fe14B alloys with soft iron particles embedded in hard Nd2Fe14B matrix was studied. The alloys were prepared by melt spinning and annealing. The grain size of Nd2Fe14B is from 20 to 60 nm, while that of the soft iron particles is 11 to 30 nm. The coercivity of the annealed flakes decreased dramatically with increasing particle size of free iron, following the same tendency of a theoretical calculation by Schrefl et al. For the Ti-alloyed flakes, the 1 at. % Ti-containing ones show the highest coercivity of 11.1 kOe. Its (BH)m value is about 16 MGOe despite lower Nd and B contents than stoichiometric Nd2Fe14B. More Ti addition would deteriorate the coercivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358030
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  • 4
    Electronic Resource
    Electronic Resource
    Evidence of domain-wall pinning in W-doped (NdDy)(FeCo)B sintered magnets : The 6th joint magnetism and magnetic materials (MMM)−intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6834-6836 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Addition of tungsten (1–2 at. %) is very effective in improving coercivity of (Nd,Dy)-(Fe,Co)-B sintered magnets both at room temperature and elevated temperatures in addition to improving thermal stability. Transmission electron microscopy shows that there exists a WFeB precipitate phase inside the Nd2Fe14B (2-14-1) matrix grain. The WFeB phase is plateletlike, and occasionally appears to have its largest dimension running parallel to the c axis of the 2-14-1 matrix phase. The orientation relationship between the WFeB precipitate and the matrix is found to be (102)WFeB(parallel)(220)2-14-1, and [010]WFeB(parallel)[002]2-14-1. Domain walls jump from a position alongside the WFeB particles to a new position alongside others upon turning on magnetic field of the objective lens, as evidenced by Lorentz microscopy, denoting the ability of domain-wall pinning by the strain field around the WFeB precipitate. As a result, this provides extra hindrance to domain-wall motion and leads to enhanced coercivity and thermal stability, particularly at elevated temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358146
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  • 5
    Electronic Resource
    Electronic Resource
    Growth and characterization of high current density, high-speed InAs/AlSb resonant tunneling diodes (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 275-277 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High quality resonant tunneling diodes have been fabricated from the InAs/AlSb material system (InAs quantum well and cladding layers, AlSb barriers) on (100)GaAs substrates. A diode with a 6.4-nm-thick InAs quantum well and 1.5-nm-thick AlSb barriers yielded a room-temperature peak current density of 3.7×105 A cm−2 and peak-to-valley current ratio of 3.2. This corresponds to an available current density of 2.6×105 A cm−2, which is comparable to that of the best In0.53Ga0.47As/AlAs diodes grown on lattice-matched substrates and is three times higher than that of the best GaAs/AlAs diode reported to date. These results were obtained in spite of a 7.2% lattice mismatch between the InAs epilayers and the GaAs substrates, which leads to a measured threading dislocation density of roughly 109 cm−2. The experimental peak voltage and current density are in good agreement with theoretical calculations based on a stationary-state transport model with a two-band envelope function approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104659
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  • 6
    Electronic Resource
    Electronic Resource
    Observation of resonant tunneling in InSb/AlInSb double-barrier structures (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 708-710 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first observation of resonant tunneling in the InSb/AlxIn1−xSb material system. Five samples with InSb quantum well thicknesses ranging from 70 to 110 A(ring) and Al0.5In0.5Sb barrier thicknesses ranging from 22 to 36 A(ring) were grown by molecular beam epitaxy on GaAs(100) substrates at a temperature of 420 °C. The best sample, which had 22-A(ring)-thick barriers and a 110-A(ring)-thick quantum well, displayed a peak-to-valley current ratio of 1.4(3.9) at room temperature (77 K) with a corresponding peak current density of 3.6×104 A/cm2. Transmission electron microscopy revealed threading dislocations, misfit dislocations, and microtwins in the barrier region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104522
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  • 7
    Electronic Resource
    Electronic Resource
    Structure of lattice-strained InxGa1−xAs/GaAs layers studied by transmission electron microscopy (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1420-1422 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The defect structures of strained InxGa1−xAs/GaAs quantum wells with 0.28≤x≤1.00, which were grown by molecular beam epitaxy on GaAs (001), have been investigated by transmission electron microscopy. It was found that with increasing thicknesses of the layers a transition occurred from homogeneous lattice strain to a "periodic'' inhomogeneous lattice strain. This effect was more pronounced with increasing indium content. For thicker layers, misfit dislocations were created which existed together with the periodic inhomogeneous strain. For even thicker layers, dislocation complexes arose which primarily consisted of intersecting stacking faults.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99960
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  • 8
    Electronic Resource
    Electronic Resource
    Energy resolved noise measurements in quantum well infrared photodetectors (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 453-455 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In quantum well infrared photodetectors, the detector dark current usually is composed of a wide range of energies originated from thermionic emission as well as thermally assisted tunneling. Yet, it is a common practice to assign a single noise gain to all electrons irrespective of their energies. This assigned value can only represent the mean since both the hot-electron lifetime and the transit time, whose ratio determines the gain, are energy dependent. In this work, we have resolved the energy dependence of the noise gain using an electron energy filter. We find that although the noise gain increases initially with energy as expected, it reaches a maximum at 0.27 eV above the GaAs conduction band edge, and then decreases and forms a minimum at 0.31 eV. We attribute this decrease to the Γ-L intervalley scattering, which increases the transit time of the electrons. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120784
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  • 9
    Electronic Resource
    Electronic Resource
    Noise characteristics of quantum-well infrared photodetectors at low temperatures (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 206-208 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work, we have performed high-sensitivity measurements on the dark current and the noise current of infrared hot-electron transistors (IHETs) and their constituent quantum-well infrared photodetectors (QWIPs) at 4.2 K. We found that the dominant noise of the QWIPs in this regime is not from the expected shot noise but from the 1/f noise and possibly a bias-independent noise. Part of the 1/f noise is unrelated to impurities in the barrier and is intrinsic to the sequential tunneling mechanism in QWIPs. By filtering out the impurity-assisted tunneling current, the IHETs reduce the dark current and the 1/f noise, and improve the detector sensitivity and uniformity. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125703
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  • 10
    Electronic Resource
    Electronic Resource
    Linker DNA bending induced by the core histones of chromatin (1991)
    s.l. : American Chemical Society
    Biochemistry 30 (1991), S. 8408-8414 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00098a019
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