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  • 1
    Electronic Resource
    Electronic Resource
    Limit cycle oscillation in negative differential resistance devices (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2798-2800 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present experimental current-voltage curves for GaAs/AlGaAs resonant tunneling diodes which show complicated multiple step structures when biased into negative differential resistance. We show that these results can be explained as limit cycle oscillations in the nonlinear dynamical system consisting of a negative differential resistance device loaded with a resonant circuit. Two circuit models, a resistor-capacitor-inductor load, and the dispersionless transmission-line load, are discussed. The limit cycles in the second model exhibit a variety of behaviors characteristic of nonlinear systems, such as bifurcations, period doubling, and Devil's Staircases, resulting in good qualitative agreement with experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341583
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular beam epitaxy of superconducting (Rb,Ba)BiO3 (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2120-2122 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The simple cubic perovskite (Rb,Ba)BiO3 can be grown at temperatures below 350 °C by molecular beam epitaxy using a rf plasma atomic oxygen source. Films with superconducting onsets in resistivity as high as 27 K are obtained without annealing. The epitaxy proceeds in the normal (100) orientation on {100} SrTiO3, despite a 10% lattice mismatch. (110) epitaxy and spotty reflection high-energy electron diffraction (RHEED) patterns are obtained on {100} MgO substrates, despite the good lattice match for (100) growth. Streaked and spotty RHEED patterns have been obtained on either substrate. Sticking coefficients for bismuth depend on the growth conditions, indicating that the epitaxy is partially controlled by desorption kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102343
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  • 3
    Electronic Resource
    Electronic Resource
    Elastic scattering centers in resonant tunneling diodes (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 201-203 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of impurities placed in the wells of double-barrier resonant tunneling diodes on the current-voltage characteristics was experimentally determined. Four different double-barrier structures were grown by molecular beam epitaxy with n-type, p-type, undoped, and highly compensated doping in the center of the well. Resonant tunneling devices of various sizes were fabricated, and measured at 77 K. Systematic shifts in the peak position and peak to valley ratios were observed for the different dopant profiles. The shifts in peak position are correctly predicted by a ballistic model which includes the effects of band bending due to ionized impurities in the well. The doped devices showed a systematic decrease in the peak to valley ratio which is not predicted by the ballistic model. By scaling our results, it is apparent that in most cases unintentional background impurities are not sufficient to significantly degrade the current-voltage characteristics of resonant tunneling diodes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100147
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular beam epitaxy of layered Dy-Ba-Cu-O compounds (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1660-1662 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Heteroepitaxial Dy-Ba-Cu-O films have been grown in situ on SrTiO3 substrates using an oxygen plasma beam and elemental source beams in a modified molecular beam epitaxy machine. By periodically shuttering the Dy and Ba beams during growth, flat surfaces of layered Dy-Ba-Cu-O compounds have been obtained. Periodic oscillations in the intensity of the in situ reflection high-energy electron diffraction pattern were observed during shuttered growths. Depending on growth conditions, the as-grown layers have ranged from insulating to superconducting with onset temperatures above 60 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100443
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  • 5
    Electronic Resource
    Electronic Resource
    Growth of high Tc superconducting thin films using molecular beam epitaxy techniques (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1191-1193 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of the high-temperature superconductor DyBa2Cu3O7−x have been grown on SrTiO3 substrates using molecular beam epitaxy techniques. Reflection high-energy electron diffraction patterns observed during deposition indicate incomplete oxidation of copper and growth of oriented metallic copper microcrystals in a matrix of amorphous barium and dysprosium oxides. After post-growth anneal the films exhibited sharp superconducting transitions with zero resistance observed as high as 89 K and critical current densities of 4.8×105 A/cm2 at 4.2 K and 3.9×104 A/cm2 at 77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98729
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  • 6
    Electronic Resource
    Electronic Resource
    Superconductor-insulator-superconductor tunneling in Ba1−xKxBiO3 grain boundaries (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2824-2826 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have prepared single grain boundaries of the superconductor Ba1−xKxBiO3 by growing epitaxial thin films of this compound on SrTiO3 bicrystal substrates. The four-terminal current-voltage characteristics of the grain boundaries showed clear superconductor- insulator-superconductor (SIS) tunneling behavior. The leakage at zero bias was smaller than 0.3% at 4.2 K. The differential conductance displayed sharp symmetric peaks at 2Δ close to 6.5 mV. At higher bias, an increase in conductance proportional to V2 was observed. The temperature dependence of the conductance was found to be in qualitative accord with conventional SIS theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110299
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  • 7
    Electronic Resource
    Electronic Resource
    All-high Tc Josephson tunnel junction: Ba1−xKxBiO3/Ba1−xKxBiO3 junctions (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 95-96 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated all-high Tc superconducting tunnel junctions in the material Ba1−xKxBiO3. The junctions are of very high quality and have a Josephson supercurrent. For the low-resistance junctions, the IcR product approaches the theoretical limit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104402
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  • 8
    Electronic Resource
    Electronic Resource
    Epitaxial solid-solution films of immiscible MgO and CaO (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1341-1343 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Metastable solid solutions in the MgO-CaO system grow readily on MgO at 300 °C by molecular beam epitaxy. The epitaxy displays both the reflection high-energy electron diffraction oscillations characteristic of layer-by-layer growth and the lattice rotations which have been related to island nucleation. Mg1−xCaxO solid solutions grow despite a larger miscibility gap than in any system for which epitaxial solid solutions have been grown. Epitaxial quenching of nonequilibrium solid solutions is possible because of the very low growth temperatures for rock-salt oxides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111928
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  • 9
    Electronic Resource
    Electronic Resource
    Penetration depth, microwave surface resistance, and gap ratio in NbN and Ba1−xKxBiO3 thin films (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 244-246 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report values of the zero temperature magnetic penetration depth λ(0), microwave surface resistance Rs, and gap ratio 2Δ(0)/kBTc in technologically useful thin films of NbN and Ba1−xKxBiO3. A novel analysis technique was used to extract the absolute magnitude of λ(0) and 2Δ(0)/kBTc from shifts in resonant frequency of a parallel-plate resonator. For NbN and Ba1−xKxBiO3 values of λ(0)=3900±200 A(ring) and 3300±200 A(ring) were obtained, respectively. The gap ratios were found to be 2Δ(0)/kBTc=4.1±0.1 and 3.8±0.5, respectively, for Tc=16.3 K in NbN and Tc=17.2 K in Ba1−xKxBiO3. The surface resistance measurements on Ba1−xKxBiO3 represent the lowest values ever reported at microwave frequencies in this material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111517
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  • 10
    Electronic Resource
    Electronic Resource
    Epitaxial Ba1−xKxBiO3 films on MgO: Nucleation, cracking, and critical currents (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1335-1337 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A two-step growth technique is used to obtain (100) oriented Ba1−xKxBiO3 films with good superconducting properties by molecular beam epitaxy. The films are nucleated without potassium at higher temperatures to get the perovskite (100) orientation on (100)MgO. Ba1−xKxBiO3 is then grown at a lower temperature using potassium flux from the decomposition of K2O. The oxygen content of the films is adjusted in a post-growth anneal in oxygen to reduce cracking which can result from oxidation-induced shrinkage. The annealed films have superconducting transitions as narrow as 0.5 K at temperatures between 20 and 25 K. Critical currents in the range of 105 A/cm2 at 4.2 K have been measured by the magnetization hysteresis loop method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104302
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