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  • 1
    Electronic Resource
    Electronic Resource
    TFTR data management system (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1892-1894 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Developments in the tokamak fusion test reactor (TFTR) data-management system supporting data acquisition and off-line physics data reduction are described. Data from monitor points, timing channels, transient recorder channels, and other devices are acquired and stored for use by on-line tasks. Files are transferred off line automatically. A configuration utility determines data acquired and files transferred. An event system driven by file arrival activates off-line reduction processes. A post-run process transfers files not shipped during runs. Files are archived to tape and are retrievable by digraph and shot number. Automatic skimming based on most recent access, file type, shot numbers, and user-set protections maintains the files required for post-run data reduction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139163
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  • 2
    Electronic Resource
    Electronic Resource
    Epitaxial growth of high Tc superconducting Y-Ba-Cu-O thin films on (001)MgO by a chemical spray pyrolysis method (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2523-2526 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A chemical spray pyrolysis method has been applied to grow epitaxial films of a high Tc Y-Ba-Cu-O compound (YBCO) on (001)MgO. Films as thin as 0.6 μm in thickness was found to exhibit excellent superconducting transition behavior. For films up to 2 μm in thickness, typical values of Tc onset, Tc zero and transition width (90%–10%) were measured to be 82, 76, and 1.5 K, respectively. Both plan-view and cross-sectional transmission electron microscopy revealed that the orientation relationships between the epitaxial films and the substrate are [001]YBCO//[001]MgO and (110)YBCO//(200)MgO. Twins, which may be perceived as domains that are rotated 90° along the c axis of the thin films with respect to the substrate, were found to be copiously present. The influences of the configuration of the oriented growth of overlayer thin films on the superconducting properties are addressed. The advantages of the chemical spray pyrolysis in producing superconducting thin films are outlined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342497
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  • 3
    Electronic Resource
    Electronic Resource
    Unique x-ray diffraction pattern at grazing incidence from misfit dislocations in SiGe thin films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 89-96 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Grazing-incidence x-ray diffraction (GIXD) permits the direct measurement of in-plane lattice parameters of SiGe films that are too thin to yield good results from normal-geometry triple-axis techniques. A unique "X''-shaped pattern has been seen in H–K reciprocal space maps of diffracted x-ray intensity from SiGe films that have relaxed via a modified Frank–Read mechanism. Contours of intensity are seen along the 〈110〉 directions from the (4¯00) reciprocal lattice peak with the introduction of the first dislocations. For higher dislocation densities the X-shaped contours are anisotropically distorted and a satellite peak, corresponding to the lattice parameter for a partially relaxed film, becomes identifiable at lower H. In contrast, H–K reciprocal-space contours from thin SiGe films that have relaxed by roughening and subsequent random nucleation of dislocations display broad, oval-shaped contours centered at the (4¯00) reciprocal lattice point for the film. Numeric simulations of GIXD from a variety of dislocation arrangements were performed in order to understand the origin of the X pattern. We show that this pattern arises from an array of long misfit dislocations running in the 〈110〉 directions. The anisotropic distortion of the X pattern arises at higher dislocation densities from orthogonal intersections of dislocations with equal Burgers vector, which are characteristic of dislocation networks generated by the modified Frank–Read mechanism. We also verify that the measured values of the in-plane lattice parameter, together with the out-of-plane lattice parameter determined from the symmetric (004) reflection, lead to accurate calculation of the composition and strain in these SiGe layers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362776
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  • 4
    Electronic Resource
    Electronic Resource
    Computer simulations of self-avoiding polymerized membranes (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 6554-6557 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this letter we propose a hybrid molecular dynamics/Monte Carlo (MD/MC) method to simulate the statistical behavior of tethered and fluid membranes which does not suffer from severe slowing-down problems as in conventional MC and MD methods. A parallel version of the algorithm allows for reliable determination of the scaling behavior of open and closed membranes. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476068
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  • 5
    Electronic Resource
    Electronic Resource
    Inter- and intrachain attractions in solutions of flexible polyelectrolytes at nonzero concentration (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 2669-2679 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Constant temperature molecular dynamics simulations were used to study solutions of flexible polyelectrolyte chains at nonzero concentrations with explicit counterions and unscreened Coulombic interactions. Counterion condensation, measured via the self-diffusion coefficient of the counterions, is found to increase with polymer concentration, but contrary to the prediction of the Manning theory, the renormalized charge fraction on the chains decreases with increasing Bjerrum length without showing any saturation. Scaling analysis of the radius of gyration shows that the chains are extended at low polymer concentrations and small Bjerrum lengths, while at sufficiently large Bjerrum lengths, the chains shrink to produce compact structures with exponents smaller than a Gaussian chain, suggesting the presence of attractive intrachain interactions. A careful study of the radial distribution function of the center-of-mass of the polyelectrolyte chains shows clear evidence that effective interchain attractive interactions also exist in solutions of flexible polyelectrolytes, similar to what has been found for rodlike polyelectrolytes. Our results suggest that the broad maximum observed in scattering experiments is due to clustering of chains. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477989
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  • 6
    Electronic Resource
    Electronic Resource
    A normal incidence p-type strain layer quantum well infrared photodetector with 19.2 μm peak detection wavelength (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1664-1666 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A normal incidence p-type compressively strained layer superlattice (SL) In0.27Ga0.73As/Al0.15Ga0.85As quantum well infrared photodetector with a spectral response peak at 19.2 μm and a cutoff wavelength λc〉20 μm under moderate background illumination have been demonstrated in this work. A responsivity of 50 mA/W and a gain-quantum efficiency product (ηg) of 0.32% at Vb=20 mV and T=40 K were obtained for this device. The device layer structure consists of four InGaAs/AlGaAs SL-absorber layers sandwiched by wide GaAs barrier layers. Results of the responsivity, dark current, noise, background photocurrent measurements, and analysis of the device performance are discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122267
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  • 7
    Electronic Resource
    Electronic Resource
    Modulation-doped n-type Si/SiGe with inverted interface (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1248-1250 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the growth of n-type modulation-doped Si/SiGe with the doped SiGe supply layer underneath the strained Si channel. The mobility and charge density are measured in samples with 2- and 3-nm-thick spacers using gated Hall measurements. A peak room temperature mobility of 2200 cm2/V s is measured at a sheet density of 2.5×1012 cm−2. The measurements indicate a clear mobility modulation especially near threshold. Our layer design allows the gate to induce a sheet charge density of up to 3.2×1012 cm−2, before any significant reduction in the mobility is observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112085
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  • 8
    Electronic Resource
    Electronic Resource
    Ultralow dark current p-type strained-layer InGaAs/InAlAs quantum well infrared photodetector with background limited performance for T≤100 K (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 727-729 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An ultralow dark current normal incidence p-type strained-layer In0.3Ga0.7Al/In0.52Al0.48As quantum well infrared photodetector (PSL-QWIP) grown on (100) semi-insulating InP substrate by molecular beam epitaxy technique for 8–12 μm infrared detection was demonstrated for the first time. This PSL-QWIP shows background limited performance (BLIP) for T≤100 K, which is the highest BLIP temperature ever reported for a QWIP. Due to a 1.5% lattice mismatch between the substrate and quantum well, a biaxial tensile strain was created in the In0.3Ga0.7As well layers. As a result, the light-hole state becomes the ground state for the free hole with small effective mass. The dramatic increase of optical absorption can be attributed to the large in-plane density of states and the small light-hole effective mass as a result of heavy- and light-hole state inversion. The dark current density and BLIP detectivity for this PSL-QWIP were found to be 7×10−8 A/cm2 and 5.9×1010 cm−(square root of)Hz/W, respectively, at λp=8.1 μm, Vb=2 V, and T=77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111964
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  • 9
    Electronic Resource
    Electronic Resource
    Nondestructive photoacoustic detection of exciton resonances in GaAs/AlGaAs multiple quantum well structures (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 745-747 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report nondestructive observations of both heavy-hole and light-hole excitons in the GaAs/AlGaAs multiple quantum wells (MQWs) using photoacoustic spectroscopy. The absorption spectra were measured by the gas-microphone photoacoustic technique with a minimal volume cell and grazing incidence method. Two distinct peaks were clearly observed in the photoacoustic signal and phase spectra of the MQW at room temperature. A photoreflectance measurement for the given MQW structure revealed that two peaks originated from the heavy-hole and light-hole excitonic resonances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111053
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  • 10
    Electronic Resource
    Electronic Resource
    High hole mobility in SiGe alloys for device applications (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3124-3126 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report high hole mobility in modulation-doped SiGe alloys with Ge content up to 80%. The layers which are grown using ultrahigh-vacuum chemical vapor deposition are of high crystalline quality, have smooth surfaces, and have a low density of misfit dislocations. As a result of strain and high Ge content, we have measured hole mobilities in the range of 800–1050 cm2/V s at room temperature, and 3300–3500 cm2/V s at 77 K. The corresponding two-dimensional sheet hole density is about 3×1012 cm−2. Those numbers are, to our knowledge, the highest numbers ever reported for a SiGe alloy. The resistivity of this two-dimensional hole channel at room temperature is, to our knowledge, the lowest for any p-type semiconductor quantum well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111367
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