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  • 1
    Electronic Resource
    Electronic Resource
    The structure of small nickel clusters. I. Ni3–Ni15 (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 7206-7222 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The geometrical structure of small nickel clusters is probed via molecular adsorption of nitrogen on their surfaces. Nitrogen uptake patterns can be rationalized with the proposed structures if it is assumed that N2 binds to every exposed nickel atom, that the binding energies decrease with increasing metal—metal coordination, and that atoms that are four or less coordinate can bind two nitrogen molecules. In some cases nitrogen adsorption causes a change in cluster structure, usually to one that can accommodate more nitrogen molecules. Cluster structures are proposed for all clusters (bare and nitrogenated) in the 3–15-atom size range except Ni4 and Ni11. The nitrogen uptake for Ni4 is consistent with virtually any structure, and the data for Ni11 could not be interpreted in terms of a specific structure. In general, nickel cluster structures are different from those found for rare gas clusters as well as those derived from bulk packing. A comparison of the experimental results with existing theoretical calculations is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466868
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  • 2
    Electronic Resource
    Electronic Resource
    Monte Carlo simulation of the three-dimensional dilute Widom model of microemulsions (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 1385-1387 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Widom suggested a spin-1/2 Ising model for microemulsions. As a simple model of microemulsions in a porous medium such as sandstone, we simulate it on a randomly dilute simple-cubic lattice with sizes up to 252.3 Our results for the critical demixing temperature are somewhat similar to those of Velgakis in the square lattice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459995
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  • 3
    Electronic Resource
    Electronic Resource
    Pressure effect on the superconducting transition temperature of Dy1−xPrxBa2Cu3O7−δ : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5871-5873 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The pressure effect on the superconducting transition temperature (dTc/dP) has been measured for Dy1−xPrxBa2Cu3O7−δ with x=0, 0.02, 0.05, 0.1, 0.15, 0.2, and 0.3. Although the Tc suppression by Pr is in a different fashion for Y1−xPrxBa2Cu3O7−δ and Dy1−xPrxBa2Cu3O7−δ, the dTc/dP is similar in these two systems, with respect to x. The measured dTc/dP is positive at small x but becomes negative for x≥0.2 which is associated with the pressure effect on the normal-state resistivity (1/R)(dR/dP). The positive (1/R)(dR/dP) at x≥0.2 indicates that the number of carriers is decreasing under pressure and it supports the picture of hole localization through the hybridization of Pr-4f and O-2p bands. The mechanical pressure has a negative effect on Tc for x≥0.2, but chemical pressure has a positive effect on Tc according to the results of chemical substitution. This suggests that the large R (=rare earth element) may possibly reduce the Pr-O distance, and increase the hybridization of Pr-4f and O-2p bands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353556
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  • 4
    Electronic Resource
    Electronic Resource
    Temperature dependence of the reaction of nickel clusters with deuterium (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 2798-2804 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The kinetics of reactions of D2 with Ni9 through Ni14 are studied in a flow-tube reactor over the temperature range 133–413 K. Rate constants for the dissociative chemisorption of the first D2 molecule have been determined. Reaction probabilities are near unity for Ni10–Ni14 and are essentially independent of temperature. For Ni9, the reaction probability is about 5% between 213 and 413 K, but increases below 213 K to ∼50% at 133 K. The possibility that these reactions are mediated by a physisorbed precursor state is discussed. The increase in Ni9 reactivity below 213 K is interpreted as due to an increase in the initial trapping of the D2 molecule on the cluster's surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464161
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  • 5
    Electronic Resource
    Electronic Resource
    Temperature dependence of the reactions of small cobalt clusters with deuterium (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 140-147 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The kinetics of the reactions of cobalt clusters (Con, n=9–21) with deuterium are studied over the temperature range 133–373 K. The measured rate constants for the dissociative addition of the first D2 molecule to Con, and their temperature dependences, are found to be strongly dependent on cluster size. Co10–13 and Co15–17 are relatively reactive, with their reaction rates essentially independent of temperature, suggesting no significant reaction barrier for deuterium chemisorption. The reaction rate of Co20 is nearly constant above 213 K, but increases at lower temperature. For Co9 and Co14, the rate constants increase both at high and low temperatures. An increase at higher temperatures suggests the presence of activation barriers, while increases at low temperatures are interpreted as due to an increase in the initial trapping of D2 onto the clusters' surfaces. For Co18, Co19, and Co21, evidence for more than one isomer at low temperature is found. The experimental results are discussed in terms of cluster geometrical structure and the detailed reaction mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465793
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  • 6
    Electronic Resource
    Electronic Resource
    Conduction-band discontinuities of InxAl1−xAs/In0.53Ga0.47As n-isotype heterojunctions (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4377-4379 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The conduction-band offsets ΔEc of n-isotype InxAl1−xAs/In0.53Ga0.47As heterojunctions, with 0.47〈x≤0.52, grown by molecular-beam epitaxy, lattice matched and pseudomorphically strained on n+-InP substrates, were determined from the capacitance-voltage profiling technique. A more accurate ΔEc value was obtained after the correction for fixed interface charge perturbation. The ΔEc related to the band-gap difference ΔEgs of the heterojunction are found to be ΔEc=0.70ΔEgs. The fixed interface charges are acceptorlike with a density of the order 1010/cm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344908
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  • 7
    Electronic Resource
    Electronic Resource
    Atomic structure at the LaSi2−x/Si(100) interface (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 43-45 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interfaces between Si(100) and LaSi2−x lattices formed by rapid thermal annealing at ∼900 °C for 10 s have been studied using high-resolution transmission electron microscopy. The experimental results show that the C axis of the LaSi2−x unit cell points to the 〈332〉Si direction. A model suggesting the {100} planes of LaSi2−x grown on a {113}Si surface has been put forward to account for the observed tilting growth of LaSi2−x disilicide on the Si(100) surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104235
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  • 8
    Electronic Resource
    Electronic Resource
    As-deposited Sb-doped Bi-Pb-Sr-Ca-Cu-O thin films prepared by pulsed laser deposition (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2591-2593 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting Bi-Pb-Sr-Ca-Cu-O films doped with Sb have been fabricated on MgO single-crystal substrates without post-annealing, using pulsed excimer laser deposition. Deposition at 800 °C in 0.2 Torr oxygen environment from a target doped with Sb yielded as-deposited superconducting films with zero resistance at 70 K. X-ray diffraction data show the films are c-axis oriented 2212 phase material. Scanning electron micrographs indicate that doping with Sb enhances grain growth. These results demonstrate that Sb acts to stabilize the 2212 phase in the as-deposited films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103824
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis under ambient pressure of 80 K superconducting YBa2Cu4O8 powders via coprecipitation (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2426-2428 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sub-micron homogeneous powders of YBa2Cu4O8 having Tc∼80 K were synthesised from aqueous solutions containing Y, Ba, Cu salts, and oxalic acid as a precipitant via a chemical coprecipitation method using triethylamine as a base. An accelerated formation−within 24 h−of nearly single phase YBa2Cu4O8 powders was achieved. The intragrain critical current density at 5 K and H=1 T was determined to be 3.9×107 A/cm2. This process may have considerable potential in the large-scale preparation of YBa2Cu4O8.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104892
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  • 10
    Electronic Resource
    Electronic Resource
    Hemispherical resonator study for surface-emitting InGaAsP/InP lasers (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 432-433 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For making surface-emitting lasers such as InGaAsP/InP double-heterostructure lasers, it is important to select and study the resonator properly. The authors have compared the relative light output power of two different structures, the plane-parallel and the hemispherical resonators. The InGaAsP/InP double-heterostructure was grown by liquid phase epitaxy. The different resonators on the same wafer were fabricated using chemical etching, lithography, evaporation, and other integrated circuit process techniques. Output optical power of the devices with the hemispherical resonator is a factor of 2 larger than those with the plane-parallel resonator. This is because the hemispherical resonator structure has a smaller diffraction loss than the plane-parallel structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102756
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