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  • 1
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.357086
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  • 2
    Digitale Medien
    Digitale Medien
    Model for the quasineutral region capacitance of p/n junction devices (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 8074-8078 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The capacitance associated with free-carrier charge storage in the quasineutral region is a primary factor in limiting the switching speed of p/n junction devices. This capacitance has been conventionally modeled using assumptions such as low-level injection, nondegeneracy, complete impurity ionization, and no space-charge region thickness modulation. These assumptions can give rise to a large error in device modeling, particularly for modern devices with very small geometry and high bias conditions. In this article, a comprehensive quasineutral region capacitance model including relevant device physics is developed. Comparisons between the present and conventional models are made, and the effects of using these two different models on the total capacitance of junction diode are also investigated. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.365414
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  • 3
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.362823
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  • 4
    Digitale Medien
    Digitale Medien
    Magnetic properties of iron and iron platinum alloys synthesized via microemulsion techniques (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5615-5617 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In this article, metallic iron, and iron/platinum alloys nanoparticles have been synthesized via chemical assembly and magnetically characterized. Fabrication of iron and iron/platinum particles was achieved by reducing 0.1 M aqueous metal salts confined in the polar portions of inverse micelles of cetyltrimethylammonium bromide with borohydride. The dc susceptibility of a sample of 8 nm iron nanoparticles exhibits a blocking temperature of 54 K and coercivity of 200 G at 10 K. The presence of the gold coatings prevented oxidation and allowed the samples to be manipulated without additional precautions to prevent oxidation. Two iron/platinum alloys have been synthesized and verified by x-ray powder diffraction and transmission electron microscopy. Magnetic characterization is performed using superconducting quantum interference device magnetometry. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.372468
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  • 5
    Digitale Medien
    Digitale Medien
    Granular growth of Fe3O4 thin films and its antiphase boundaries prepared by pulsed laser deposition (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7398-7400 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Fe3O4 thin film prepared by pulsed laser deposition on Si (100) substrate has been investigated by transmission electron microscopy from plane and cross-sectional views. The thin film, which shows a spinel structure as characterized by selected-area diffraction, is about 180 nm thick with granular growth of particle size about 50 nm. High resolution electron microscopy observations indicate reduced thickness of the native SiO2 layer between the thin film and Si due to rastering of the substrate surface by an unfocused laser beam before the deposition. By using a 220 diffraction spot in two beam condition near the 〈001〉 axis of a single Fe3O4 grain, antiphase boundaries (APBs) inside the grains could be clearly resolved. The existence of APBs in the thin film is consistent with the magnetic experiments including an open hysteresis loop and unsaturated magnetization in relatively high magnetic fields. This study suggests that APBs are not unique to Fe3O4 films grown on MgO substrates. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1358831
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  • 6
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.353323
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  • 7
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1149168
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  • 8
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.104180
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  • 9
    Digitale Medien
    Digitale Medien
    Preparation of Y-Ba-Cu-O high Tc superconducting thin films by plasma-assisted organometallic chemical vapor deposition (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 194-196 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Thin films of the high Tc superconducting Y-Ba-Cu metal oxide have been prepared for the first time by plasma-assisted organometallic chemical vapor deposition using β-diketonate chelates of Y, Ba, and Cu, Y(C11H19O2)3, Ba(C11H19O2)2, and Cu(C11H19O2)2 as starting materials, followed by post-annealing under a reduced pressure of oxygen stream. X-ray diffraction spectra indicate that the films deposited on the yttria-stabilized zirconia (YSZ) substrate have a significant preferential orientation of the crystallite c axis being perpendicular to the substrate surface. Four-probe resistivity measurements reveal the temperature of the onset of superconductivity at 91.6 K and zero resistance by 78.5 K.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.102404
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  • 10
    Digitale Medien
    Digitale Medien
    Self-organized type-II In0.55Al0.45As/Al0.50Ga0.50As quantum dots realized on GaAs(311)A (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3741-3743 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Self-organized In0.55Al0.45As/Al0.50Ga0.50As quantum dots are grown by the Stranski–Krastanow growth mode using molecular beam epitaxy on the GaAs(311)A substrate. The optical properties of type-II InAlAs/AlGaAs quantum dots have been demonstrated by the excitation power and temperature dependence of photoluminescence spectra. A simple model accounting for the size-dependent band gap of quantum dots is given to qualitatively understand the formation of type-II In0.55Al0.45As/Al0.50Ga0.50As quantum dots driven by the quantum-confinement-induced Γ→X transition. The results provide new insights into the band structure of InAlAs/AlGaAs quantum dots. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.126768
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