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  • 1
    Electronic Resource
    Electronic Resource
    The role of high-pressure sintering in preparing high-quality n-type Nd2−xCexCuO4−y superconductors (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 843-849 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-pressure high-temperature sintering (HHS) under 1.0, 2.0, 4.0, and 6.0 GPa for a short time was directly used to reduce n-type Nd1.85Ce0.15CuO4−y. Superconductors with higher critical temperature were obtained. The samples display lower resistivity, and more metalliclike resistance behavior at normal state with increasing sintering pressure. A small increase of lattice parameter and cell volume was observed via electron and x-ray diffraction. Transmission electron microscopy studies also show that there is a preferential orientation along the c axis among the neighboring grains. This helps get well-matching grain boundaries in the HHS samples. A Cu2O high-pressure phase was found via energy-dispersive x-ray analysis in the sample treated above 5.0 GPa, which is thought to be a deleterious factor for superconductivity. Sintering under suitable pressure not only enhances the intragranular conductivity, but also effectively improves the intergranular links. Finally, via the assumed interstitial oxygen ordering in the T' structure, a possible mechanism of n-type reduction is proposed based on the change in tolerance factor under reduction atmosphere and high pressure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353323
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  • 2
    Electronic Resource
    Electronic Resource
    Comparison of transport scattering and single-particle relaxation times in modulation-doped heterostructures (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 390-394 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transport scattering and single-particle relaxation times which characterize a two-dimensional electron system have been investigated by using thermal neutron irradiation. The ratios of transport scattering time to single-particle relaxation time are observed to vary from 1.7 to 7.8 depending on the electron density. A decrease in single-particle relaxation time is found while the transport scattering time increases as the electron concentrations increase. These phenomena are relevant to the Hall plateau broadening and enhancement of Shubnikov–de Haas oscillations in such an experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357086
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  • 3
    Electronic Resource
    Electronic Resource
    Ordering of Tl and Bi in Bi-doped Tl-1223 high Tc superconductors (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 326-330 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High Tc superconducting materials with nominal compositions of Tl1-xBix(Sr, Ba)2Ca2Cu3O9 (0≤x≤0.5) have been investigated using x-ray powder diffractometry and electron microscopy. It was found that Tl and Bi cations were in an ordered arrangement in the (Tl, Bi)–O atomic layer. Although the proposed supercell is 4a×4b×4c derived from the basic unit cell of the undoped TlBa2Ca2Cu3O9 (Tl-1223), the basic two-dimensional superlattice in the (Tl, Bi)–O layer is 2a×4b or 4a×2b with Bi cations at the center and the corner of the rectangle, giving an ideal and preferred composition with the Tl:Bi ratio of 3:1. Accordingly, the maximum Bi doping for Tl in the solid solution is 25%. The proposed model of the superstructure was supported by computer simulation of electron diffraction patterns. The mechanism of formation of the superstructure is discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362823
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  • 4
    Electronic Resource
    Electronic Resource
    Photoreflectance study of H2S plasma-passivated GaAs surface (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1430-1432 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance is used to study the effect of H2S plasma passivation on the GaAs surface. GaAs samples are treated with a H2S plasma in an electron cyclotron resonance chemical vapor deposition system and in-situ encapsulated with a SiNx film. The surface Fermi level moves towards the conduction band after H2S plasma passivation and a surface state density of 6×1010 cm−2 is achieved under optimal passivation conditions. The surface state density is highly dependent on the sample temperature during passivation. The movement of the surface Fermi level is due to the reduction of the surface state density and not due to a shift of midgap surface states, suggesting that S–Ga bonds play the major role in H2S plasma passivated GaAs surfaces. This work demonstrates the need to measure both the surface Fermi level and the density of surface states. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123572
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  • 5
    Electronic Resource
    Electronic Resource
    Growth of carbon nanotubes on cobalt disilicide precipitates by chemical vapor deposition (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 3297-3299 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have successfully grown carbon nanotubes on cobalt-implanted silicon with various doses. The morphology of such tubes has been examined by scanning electron microscopy, transmission electron microscopy, and Raman scattering. On contrary to the commonly used transition-metal nanoparticle catalysts, nanometer-sized CoSi2 precipitates produced in the as-implanted substrates are believed to act as nucleation centers for the formation of carbon nanotubes. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121629
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  • 6
    Electronic Resource
    Electronic Resource
    Bias independent heavy- and light-hole degeneracy in InGaAs/InGaAsP quantum wells (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 683-685 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a type of strained semiconductor quantum-well structure that exhibits bias-independent heavy- and light-hole degeneracy. This effect is achieved by inserting thin layers of highly strained material in an unstrained quantum well. By adjusting the thickness and the position of the highly tensile strained layers, the quantum confined Stark effect for the heavy and light holes can be engineered separately to control the bias dependent polarization properties. Experimental results on such a structure agree well with the theory. These unique bias-dependent polarization properties have important applications in optoelectronic devices when specific polarization properties are required. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120845
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  • 7
    Electronic Resource
    Electronic Resource
    New family of high Tc superconductors in the (Tl1−xMx)Sr2(Ca1−yYy)Cu2O7−δ system (M=IVA and VA elements) (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2492-2494 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new family of high Tc superconductors with superconducting transition temperatures ranging from 40 to 100 K have been synthesized in the (Tl1−xMx)Sr2 (Ca1−yYy)Cu2O7−δ (M=Ti, Zr, Hf, V, Nb, and Ta) system. Here, we use as an example, vanadium and yttrium substitution into the thallium and calcium sites, respectively, in the parent compound TlSr2CaCu2O7 to demonstrate the substitutional chemistry, crystal structure, and superconductivity for these new superconductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104180
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  • 8
    Electronic Resource
    Electronic Resource
    A novel approach for doping impurity in thin film in situ by dual-beam pulsed-laser deposition (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3659-3661 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Doping techniques are of great importance in developing new materials and devices. We present here a novel approach for doping impurity in thin film by using dual-beam pulsed-laser deposition technique that allows in situ controlling doping under a wide range of conditions. We demonstrated doping Ag in situ in YBa2Cu3O7−δ thin films and for the first time observed long bar-like Ag structures with a length up to 150 μm in the as-deposited films, which may have important application in the fabrication of superconductor-normal metal-superconductor Josephson junctions. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149168
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  • 9
    Electronic Resource
    Electronic Resource
    Intracavity frequency doubling of a continuous wave Ti:sapphire laser with over 70% conversion efficiency (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2463-2465 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Efficient tunable ultraviolet generation by intracavity frequency doubling of a continuous wave Ti:sapphire laser was demonstrated. Maximum output is obtained of 460 mW at 398 nm corresponding to a total infrared-to-ultraviolet conversion efficiency over 70%. High conversion efficiency was resulted from a critically phase-matched, temperature-tuned lithium triborate crystal and a novel resonator design. The observed laser damage of the crystal coatings is also discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113996
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  • 10
    Electronic Resource
    Electronic Resource
    Improvements of microstructural and superconducting properties of Ag-Bi2Sr2CaCu2Ox screen-printed tape by controlled oxygen partial pressure during cooling procedure (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 833-835 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of different cooling procedures, after sintering, on the microstructural and superconducting properties of Bi2Sr2CaCu2Ox (B-2212) screen-printed tapes has been investigated. It was found that the amorphous phase originally present in grain boundaries at the sintering temperature undergoes a conversion to the Bi-2212 phase during slow cooling. However, the excess oxygen absorbed during slow cooling (in 21% oxygen) disturbs the order and ordering process of Bi-2212 crystals, but if the slow cooling process is conducted under monotonically reduced oxygen partial pressure, to ensure that the optimum oxidation state at sintering temperature of the Bi-2212 phase can be retained during the cooling procedure, tapes are then characterized by narrow grain boundaries and the highest Jc value (approximately-greater-than)104 A/cm2 at 77 K and 0 T.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109897
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