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  • 1
    Electronic Resource
    Electronic Resource
    Segregation, interface reactions and surface topography of YBa"2Cu"3O"7"-"δ thin films, investigated by Auger depth profiling, microprobe analysis, STM and SEM
    Amsterdam : Elsevier
    Physica C: Superconductivity and its applications 153-155 (1988), S. 1453-1454 
    Details
    ISSN: 0921-4534
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0921-4534(88)90367-X
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  • 2
    Electronic Resource
    Electronic Resource
    Simple piezoelectric translation device (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 368-369 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a piezoelectric device which allows continuous movement and high-resolution micropositioning, without distance limitation. Both mechanical construction and the electronics for the device are very simple. The movement is obtained via a stick-slip mechanism, and steps as small as 10 nm are obtained. A displacement speed of 0.4 mm/s has been attained, and the device was capable of carrying several times its own weight, exerting a horizontal force, or climbing a plane inclined by 7°. Due to its compact construction, the device shows prospects for miniaturization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140206
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  • 3
    Electronic Resource
    Electronic Resource
    Superconducting, microstructural, and grain boundary properties of hot-pressed PbMo6S8 (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4232-4239 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An alternative procedure is outlined for the synthesis of high quality, fine grained PbMo6S8. As the grain size plays an important role on the densification process, which in turn has an influence on the magnitude of Jc, an attempt has been made to produce dense samples from such powders by "Hot Pressing.'' The effect of the hot-pressing temperature on the superconducting, crystallographic, microstructural, and grain boundary characteristics of the ternary compound was evaluated. Scanning electron micrographs and ac-susceptibility measurements indicate that hot pressing (1000–1200 °C) improves the grain connection as a consequence of better densification. However, at higher temperatures (1250–1400 °C) it also precipitates MoS2 as an additional phase. Calorimetric data indicate a continuous broadening, as a function of hot-pressing temperature, of the specific heat jump at Tc. Preliminary investigation on the Tc distribution of the samples shows a progressive degradation, as indicated by a smearing in Tc down at least to 8 K. The deterioration was examined using Auger electron spectroscopy and the results suggest possible compositional variations rather than oxygen defects in the phase. The origin of such behavior is examined on the basis of nonstoichiometry or chemical heterogeneity at the grain surface. In addition, grain boundary contaminants and their role on the superconducting properties are considered. Finally, the often encountered problem of transport Jc limitation in these materials is discussed in terms of interconnectivity of the grains, phases, the presence of secondary phases, impurities, inhomogeneities, and the grain boundary phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352235
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  • 4
    Electronic Resource
    Electronic Resource
    X-ray photoelectron spectroscopy study of thin Ag overlayers on YBa2Cu3O7−xB: Effects of oxygen annealing (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1777-1781 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray photoelectron spectroscopy was used to examine vapor deposited Ag overlayers on YBa2Cu3O7−x thin films and cleaved single-crystal surfaces (x=1), including the effects of subsequent heat treatment in oxygen. The core level spectra of the present tetragonal crystals were found to closely resemble those previously reported for nominally orthorhombic superconducting samples. Minor differences, notably an increased fraction of Cu in the +1 oxidation state and a slightly higher binding energy of the Ba 3d levels, may be attributed to the lower oxygen content of the tetragonal semiconducting phase. Deposition of Ag on clean monocrystal surfaces was found to cause some disruption of CuO bonds at the Ag/YBa2Cu3O7−x interface. We also find weak indications of surface band bending (i.e., Schottky barrier formation) from a uniform shift in the measured binding energies of the substrate core levels upon Ag deposition. Heat treatment in pure oxygen (1 h at 500 °C) of Ag-coated superconducting thin films was found to reduce efficiently the amount of superficial contaminant phases, initially present on the air-exposed thin-film surfaces, and to cause diffusion of Ag to a depth of ∼20 nm into the volume of the material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346608
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  • 5
    Electronic Resource
    Electronic Resource
    Scanning tunneling microscope investigation of (100) and (001) faces of YBa2Cu3O7−δ (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3274-3276 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin as-grown side faces, and edge and corner regions of crystals of the tetragonal precursor phase of the high-temperature superconductor YBa2Cu3O7−δ were studied by scanning tunneling microscopy under scanning electron microscope control of tip positioning. From observed changes in slope of the (100) surface, in particular near the (100)/(001) edges, it was concluded that the (100) and (001) faces have different growth mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342684
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  • 6
    Electronic Resource
    Electronic Resource
    A vertical piezoelectric inertial slider (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 965-967 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed a linear translation device using piezoelectric-induced slip-stick motion. Reproducible single steps of about 30 A(ring), as well as continuous stepping with an overall translation speed of 0.25 mm/s, are routinely realized. The notable feature of this device is that this performance is achieved in the vertical orientation with the translator moving against gravity. This remarkable result is made possible using cycloidal functions instead of sawtooth signals to activate the motion. We have realized a very simple translator which can be used in any orientation with a displacement onset voltage of 15 V. The instrument was successfully tested in the temperature range from 1.6 to 300 K. Since no mechanical connections are required, this design is well suited for many applications, including scanning tunneling microscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141450
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  • 7
    Electronic Resource
    Electronic Resource
    Field emission from broad-area niobium cathodes: Effects of high-temperature treatment (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 892-901 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present results made with a new apparatus for the study of localized field emission (FE) sites on broad-area cathodes. The apparatus is centered around a UHV field emission scanning microscope, consisting of a micromanipulator allowing precision cathode motion, a rotatable holder for broad and microtip anodes, and a fast high-voltage regulator allowing constant-current measurement of a distribution of both weakly and strongly emitting sites. Also included are an in situ scanning electron microscope, and a facility for in situ microfocus Auger analysis as well as scanning Auger microscopy. Samples can be high-temperature annealed without removal from UHV. These tools have been used to study the effects of heat treatment (HT) up to 2000 °C on the FE from nonanodized and anodized Nb cathodes. We find that HT at 800–900 °C increases the density of field emitters at a given electric field. HT at T〉1000 °C reduces the density, while at T≥1400 °C a drastic decrease of the emission occurs. We have repeatedly obtained surfaces of cm2 size which do not emit at 100 MV/m. If such an emission-free surface is heat treated again at 800 °C, new emitters appear. Typically, the physical size of the field emitters is a few μm, although in some cases a larger particle was found and in others no feature was seen at 0.5-μm resolution. A large variety of elements is associated with these particles. We discuss in particular the nature and origin of three types of emitters: (1) sulfur containing particles, (2) carbon particles, both of which were identified as new emitters after a 800 °C HT, and (3) FE sites which are especially resistant against HT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336560
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  • 8
    Electronic Resource
    Electronic Resource
    Electron field emission from intentionally introduced particles on extended niobium surfaces (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 3851-3860 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Field emission properties of microscopic particles of graphite, sulfur, and MoS2 deposited on nonemitting Nb surfaces under ultrahigh vacuum conditions are described. Both graphite and MoS2 particles are shown to emit strongly, with field enhancement factors of the order of 100, in contrast to sulfur particles, which emit only weakly. The emission characteristics are measured locally on the individual sites, and emitting particles are further characterized by microfocus Auger spectroscopy and scanning electron microscopy. Their behavior upon heat treatment was studied, with the main result that both for graphite and MoS2 particles the emission disappears after heating to 1200 °C. The properties of the artificially created emitters are compared with those of naturally occurring field emitters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336727
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  • 9
    Electronic Resource
    Electronic Resource
    Field emission from a metal covered with a semiconducting layer: A model calculation (1990)
    Springer
    Applied physics 50 (1990), S. 331-338 
    Details
    ISSN: 1432-0630
    Keywords: 73 ; 79.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The electron field emission from a metal covered with a thin layer of a semiconductor with electron affinity χ and dielectric constant ɛ is considered. The model takes into account the metal-semiconductor (Schottky) barrier of height ϕb, the conduction current inside the semiconductor, and the band bending at the semiconductor-vacuum interface due to the external field penetration. For thick films under moderately high electric fields, the metal-semiconductor interface does not influence the emission behaviour whereas for thin films, the interface plays an important role, depending on the barrier heights. In particular, for χ/ϕb〈ε2/3 the I–V characteristics will, for strong fields, be dominated by the field emission process at the interface. In such cases important deviations from Fowler-Nordheim behaviour are found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324502
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