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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial thin films of YBaCuO have been prepared with (1) the a axis perpendicular to (100) SrTiO3 ; (2) the c axis perpendicular to (100) SrTiO3 ; and (3) the [110] axis perpendicular to (110) SrTiO3. Films were fabricated using a multilayer deposition technique involving three electron guns containing Y, BaF2, and Cu under a pressure of 5×10−5 Torr of O2. As deposited films, which contained polycrystalline and amorphous regions, were later annealed in a furnace under a flowing O2-H2 O atmosphere. X-ray diffraction patterns as well as scanning electron microscopy and high-resolution electron microscopy images confirm that the films are highly oriented, essentially epitaxial. The a-axis oriented film exhibits zero resistance at 90 K and a critical current density of 2.9×106 A/cm2 at 4.2 K while the c-axis oriented film exhibits a Tc of 88 K and a Jc of 0.9×107 A/cm2 at 4.2K; the Jc values were determined magnetically. The [110]-orientation film shows the sharpest transition with a transition width of 1 K and zero resistance at 85 K.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 2655-2662 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate that optical second-harmonic generation (SHG) can be successfully used for in situ study of metal/polymer interfaces. With this SHG technique, Cu cluster formation on polyimide by surface diffusion and Cu diffusion into polyimide have been investigated. The diffusion coefficients of Cu clusters into polyimide at various temperatures have been determined from the measured decay of SHG signal with time. The effects of temperature, cluster size, and surface modification on diffusion have also been examined. For T 〈 Tg, the surface diffusion of Cu on polyimide to form clusters dominates over the diffusion into the bulk. The latter process becomes competitive with increasing temperature. When T (approximately-greater-than) Tg, few large-size Cu clusters can be formed on the polyimide surface. Cu diffusion into polyimide bulk can be greatly impeded by either a monolayer of Ti or by Cu clusters implanted in polyimide beforehand. In this case, Cu can wet the modified surface and form an interface between Cu and polyimide with good adhesion.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4620-4625 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Optical second harmonic generation is employed to investigate the adsorption of soluble naphthalene sulfonates from the bulk solution to the air/water interface in the presence of excess counter ions. Both the surface density of surfactant molecules and the surface pressure were measured as functions of surfactant concentration in solution to yield the adsorption isotherm and the surface pressure/area isotherm. The system investigated shows nonideal gas behavior. The ratio of the activity coefficients at the surface and in the bulk is not unity; however both appear to be constant over the concentration range probed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 2315-2323 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Second-order optical nonlinearities of molecules can be strongly affected by the environment. Protonation and aggregation of the dyes 4-amino-4'-nitrostilbene (NS) and hemicyanine (HC), are investigated by second harmonic generation from molecular monolayers floating on water. The observed second-order nonlinearity of such molecules in the form of either a pure monolayer or a monolayer diluted with stearic acid directly reflects the degree of protonation of the molecules. For NS and HC, the variation of the second-order molecular polarizability with protonation is opposite. It is demonstrated that the measured nonlinearity can be used to deduce the effective proton concentration in the surface region. The proton concentration close to a stearic acid monolayer floating on water, for example, is found to be ∼7 orders of magnitude larger than the bulk proton concentration when the latter is low. The effects of stearic acid in diluting a dye molecular monolayer on changing the environment and breaking dye aggregates are discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5030-5032 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The giant magnetoresistance (GMR) effects in sandwiched Co/Cu/Co and Co/CuMn/Co structures have been investigated. The GMR oscillates with the spacer thickness for both cases, but is nearly antiphased. With diluted Mn atoms in the Cu spacer, the GMR curve as a function of the magnetic field changes a lot, and the saturation/switching field for GMR can be reduced greatly compared with that in Co/Cu/Co systems. This may indicate one way to obtain a highly sensitive GMR. © 1999 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 3100-3101 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new amplifier, designed to operate with fast semiconducting bolometers, is presented. Based on current detection of the bolometer signal, it allows one to obtain good sensitivity with response times of about 10 ns without using cryogenic electrical components. The amplifier was used to detect heat pulses propagating in a Si crystal.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3791-3792 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A semiconductor detachable bolometer using a superconducting thin film as coupling medium is described. The film acts as a low pass band filter for the phonons having a frequency below the superconductive gap. A comparison between different coupling media is reported.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 8167-8173 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this study, we correlate various processing conditions with the magnetic properties of CoCrTa/Cr films by varying the substrate preheating, the substrate bias, and the composition of the magnetic target. High Hc CoCrTa/Cr films with thin Cr underlayers were produced by either preheating the substrate or by rf bias sputtering. We found that the sputtering temperature of the magnetic layer plays a far more important role in reducing intergranular exchange coupling and increasing Hc than does the CoCrTa/Cr crystallographic texture. The optimum condition for preparing high Hc films depends on the magnetic target composition. Even though the crystallographic texture does not control Hc, it does have an effect on the ΔM curve which is related to the noise properties of CoCrTa/Cr media. ΔM measurements indicate that {11¯01}Co /{110}Cr textured films may have slightly better noise properties than the films with {112¯0}Co /{200}Cr texture with similar Hc. © 1994 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1388-1398 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental and numerical results are presented on the evolution of stresses and the accompanying changes in the overall curvatures due to the patterning of silicon oxide lines on silicon wafers and subsequent thermal loading. The finite element analysis involves a generalized plane strain formulation, which is capable of predicting the wafer curvatures in directions parallel and perpendicular to the lines, for both the patterning and thermal cycling operations. The predictions compare reasonably well with systematic curvature measurements for several different geometrical combinations of the thickness, width and spacing of the patterned lines. The non-uniform stress fields within the fine lines and the substrate are also analyzed. It is shown both experimentally and theoretically that certain geometries of patterned lines on the substrate induce dramatic shape changes and reversals of curvature in the direction perpendicular to the lines. The mechanistic origin of this effect is identified to be the Poisson effect arising from the anisotropic strain coupling in the patterned structure. © 1996 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 8174-8179 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the CoCrTa/Cr system, it has been postulated that segregation of nonmagnetic constituents to grain boundaries is responsible for the low noise and high coercivity. However, direct experimental evidence is still lacking. In this investigation, we have carried out microstructural studies using transmission electron microscopy (TEM) and atomic resolution transmission electron microscopy (ARTEM) of CoCrTa/Cr films produced under varying processing conditions. We found that the stacking fault density and the degree of crystalline perfection between the faults is most important in increasing the coercivity and improving signal-noise properties as indicated by ΔM measurement. High substrate temperatures and high Cr and Ta concentrations promote the occurrence of the stacking faults in the films. In conjunction with ARTEM results, we propose that these faults provide possible sites for elemental segregation which is partially responsible for reducing the magnetic coupling among the unfaulted hcp regions in the CoCrTa films. We also provide microstructural evidence supporting the picture that the high-frequency mechanical texture lines break the intergranular coupling normal to the texture lines resulting in circumferential anisotropy. Grains are crystallographically correlated to form clusters between the texture lines but such correlation is broken up by the texture lines. This gives rise to an effective shape-induced anisotropy. We believe that the cluster size plays a more important role than does the grain size in determining the magnetic properties of CoCrTa/Cr media. © 1994 American Institute of Physics.
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