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  • 1
    Electronic Resource
    Electronic Resource
    Spin cast thin films of fullerenes and fluorinated fullerenes: Preparation and characterization by x-ray reflectivity and surface diffuse x-ray scattering (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5248-5250 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate that high quality thin films of fullerenes (C60) and fluorinated fullerenes can be prepared from solution by the spin coating technique on float glass or silicon wafers. The films were characterized by x-ray reflectivity and diffuse x-ray scattering. A systematic study of films of different thicknesses allows estimation of the distance between the fullerenes spheres to be 10.9±1 A(ring) in our C60 films. The C60 film-air surface is very smooth. Annealing in air above 90 °C leads to an irreversible increase of the film thickness, which is attributed, at present, to oxidation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350583
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  • 2
    Electronic Resource
    Electronic Resource
    A cryogenic microwave scanning near-field probe: Application to study of high-Tc superconductors (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 4348-4355 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report a vacuum cryogenic (80 K〈T〈350 K), near-field microwave scanning system based on a 90 GHz transmitting/receiving resonant slit antenna with a capacitive measurement of the probe-sample separation. The probe allows local measurement of resistance as a function of temperature with the spatial resolution of 20-50 μm. The mm-wave probe is integrated with the eddy-current probe which allows global measurement of resistance of conducting and superconducting samples. This integrated probe is used for local study of the superconducting transition in high-Tc superconducting thin films. The sensitivity of our present mm-wave probe is sufficient for probing conductivity in the normal state and in the superconducting state close to Tc however not yet sufficient for probing conductivity variations far below superconducting transition temperature. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150078
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  • 3
    Electronic Resource
    Electronic Resource
    Microwave near-field imaging of conducting objects of a simple geometric shape (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 3927-3932 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We study imaging properties of a 90 GHz microwave scanning probe consisting of a thin slit aperture (width of 10–100 μm) in the waveguide endwall. We perform vector measurements of the near-field reflectivity of test samples (conducting dot, strip, half plane, plane) at various probe–sample separations and orientations. Experimental results for small objects agree fairly well with analytical calculations and computer simulations and can be described by a quasistatic model. Experimental results for extended conducting objects show pronounced deviations from the quasistatic model due to excitation of the surface waves. Our experimental results demonstrate several peculiar features which have not been properly addressed in the context of near-field imaging, namely: (i) strong collimation of the fields away from the probe up to a distance equal to the probe width, (ii) very weak phase dependence on distance in the extreme near field, and (iii) excitation of surface waves above conducting surfaces. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289680
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  • 4
    Electronic Resource
    Electronic Resource
    Possible evidence for quantum-size effects in self-assembled ultrathin films containing conjugated copolymers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3082-3088 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present photoluminescence (PL), UV absorption, electroluminescence and x-ray reflectivity studies of self-assembled multilayer films containing alternate layers of conjugated copolymers, and nonconjugated insulating polymers. We show that the PL emission properties of these organic quantum wells can be "tuned'' by a proper choice of the conjugated copolymer and the thickness of the insulating layers. Particularly, some of the self-assembled ultrathin films containing thin (∼7 A(ring)) insulating polymeric layers exhibit a blue shift upon decreasing the thickness of the assembly. The PL shift is roughly proportional to 1/d2 where d is the thickness of the assembly, as expected for confined photogenerated electron-hole pair in an infinite square potential well. In contrast, the PL emission of similar assemblies but containing thick (∼40 A(ring)) insulating layers is independent of the assembly thickness and exhibit emission in the blue. This may suggest a strong spatial confinement. Light emitting diodes based on self-assembled multilayer films with improved efficiency and stability and with threshold voltage as low as 2.6 V could be fabricated. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361250
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  • 5
    Electronic Resource
    Electronic Resource
    Combined interface plasmon polariton and x-ray reflectivity determination of the dielectric tensor in ultrathin liquid crystal films (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3323-3329 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have carried out interface plasmon polariton (IPP) and specular x-ray reflectivity studies of the same multilayer structure containing a thin metallic silver film and a thin (100–600 A(ring)) smectic C* ferroelectric liquid crystal (FLC) film on a glass substrate. An additional thin nylon layer sandwiched between these two films is essential to improve the smectic FLC alignment and its stability. The specular x-ray reflectivity after each stage of layer deposition provides information on the thickness and the electron density of the individual layer. Particularly, this technique allows for the determination of the amplitude and the phase of the electronic density modulation (i.e., the smectic order parameter) of the FLC film. We demonstrate that the x-ray results are essential for the determination of the complex dielectric functions of the FLC film from the shape and the angular position of the IPP resonance. Generally, we have found that for samples with a relatively large smectic order parameter the IPP resonance can be best fitted assuming an anisotropic dielectric tensor and the presence of domains in the FLC film. For well ordered smectic C* films at room temperature, the anisotropy of the dielectric tensor is slightly higher compared to the bulk value and shows a tendency to increase with the decrease of the film thickness in ultrathin films. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360025
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  • 6
    Electronic Resource
    Electronic Resource
    Neutron and x-ray reflectivity studies of self-assembled heterostructures based on conjugated polymers (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 725-732 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutron and x-ray reflectivity studies of modulated heterostructures consisting of alternate layers of conjugated and nonconjugated polymers is described. Such heterostructures are currently being used to fabricate polymer-based light emitting diodes. The heterostructures were prepared by the layer-by-layer self-assembly technique using the precursor of the conjugated polymer, deuterated poly(phenylenevinylene) (D-PPV), and other polyelectrolyte spacers. Heat treatment after the layer assembly converted the pre-D-PPV to a conjugated semiconducting polymer. For the first time in such heterostructures, we were able to observe quasi-Bragg reflections (up to the third order) due to the formation of ordered modulated structures. Both the neutron and the x-ray data were analyzed using the same layer-by-layer model and the same fitting procedure with consistent results. Most importantly, the model and the fitting procedure yield the buried interlayer roughness at the D-PPV/spacer interface. This roughness parameter, of the order of 12±3 Å, was found to be smaller than the thickness of the D-PPV and the spacer layers, suggesting that the length over which interdigitation between neighboring polymer layers occurs is significantly smaller than the spacer layer. We demonstrate that the conversion to conjugated polymer by the heat treatment leads to ∼7% reduction of the repeat unit and the film thickness without significant changes of other structural properties; in fact, the interfacial roughness was somewhat improved. The fabrication of high quality modulated structures with controlled layer thickness and relatively small interfacial roughness may be a first step towards polymer-based multiquantum wells analogous to such devices in inorganic heterostructures. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366744
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  • 7
    Electronic Resource
    Electronic Resource
    Frequency modulation of the superconducting parallel-plate microwave resonator by laser irradiation (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2875-2877 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the effect of chopped laser irradiation (λL=514 nm) on the resonant frequency (f0≈5.4 GHz) of a superconducting parallel-plate resonator (PPR) consisting of two thin epitaxial YBa2Cu3O7−x films. We demonstrate that laser irradiation shifts the resonant frequency of the PPR with negligible change of quality factor. Photoinduced deviation of f0 strongly depends on the chopping frequency and increases linearly with light intensity. The effect of illumination is attributed to the photoinduced change of the kinetic inductance due to laser heating. This effect may be used to produce phase modulation of the superconducting transmission lines. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112521
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  • 8
    Electronic Resource
    Electronic Resource
    Combined millimeter-wave near-field microscope and capacitance distance control for the quantitative mapping of sheet resistance of conducting layers (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2832-2834 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a dual-frequency electromagnetic scanning probe and apply it for quantitative mapping of the sheet resistance of conducting films. The high-frequency (82 GHz) mode is used for image acquisition, while the low-frequency (5 MHz) mode is used for distance control. We measure magnitude and phase of the near-field microwave reflectivity from conducting films of varying thickness and develop a model which accounts fairly well for our results. This brings us to a quantitative understanding of the contrast in the microwave near-field imaging using an aperture probe, and allows us to achieve quantitative contactless characterization of conducting layers with sheet resistance even below 2 Ω. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122605
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  • 9
    Electronic Resource
    Electronic Resource
    Self-assembly of floating magnetic particles into ordered structures: A promising route for the fabrication of tunable photonic band gap materials (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 4168-4170 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report stable ordered arrays of millimeter-size magnetic particles floating on a liquid surface. Self-assembly into a regular two-dimensional lattice results from lateral magnetic interactions between the particles. The lattice constant may be easily tuned by the application of external magnetic field. The array symmetry is designed by using different particle shapes, magnets, and magnet position inside the particle, so that complex symmetries may be achieved. Three-dimensional ordered arrays are obtained in a stack of troughs containing floating magnets. Computer simulations of electromagnetic wave propagation in such three-dimensional structures suggest an opening of a tunable photonic band gap in the microwave range. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125571
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  • 10
    Electronic Resource
    Electronic Resource
    Magnetic-field-modulated microwave reflectivity of high- Tc superconductors studied by near-field mm-wave microscopy (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 1766-1768 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report local studies of magnetic-field-modulated microwave reflectivity (MFMMR) of high-Tc superconductors using a near-field scanning aperture probe operating at 96 GHz. The MFMMR signal appears as a sharp peak at transition temperature and is very useful in identifying superconducting phases in multiphase samples. We show that MFMMR is qualitatively different from such a routine characterization tool as inductive technique. Simultaneous MFMMR and inductive measurements allow us to distinguish between the surface and bulk superconducting properties. The MFMMR technique may be easily extended for the study of giant magnetoresistance materials. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124813
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