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  • 1
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Some YBa2Cu3O7-δ films and heterostructures prepared by Chemical Vapor Deposition (CVD) were analyzed in our laboratories by EPMA-EDX or WDX, RBS, SNMS and AES. It was found that in some cases the results of composition analysis can significantly deviate from each other. At least two main reasons for these deviations exist: the different lateral resolution and the application of different reference samples for the calibration.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physica C: Superconductivity and its applications 185-189 (1991), S. 545-546 
    ISSN: 0921-4534
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 3014-3017 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The cobalt reactivity on monocrystalline silicon has been studied for annealing temperatures lower than 500 °C. The techniques used were thermomagnetism measurements and transmission electron microscopy. The results demonstate that the reaction starts during deposition. During annealing the three types of formation kinetics were shown to exist as a function of temperature (20–220 °C, 220–370 °C, 370–420 °C). At the latter temperature the cobalt is completely transformed into CoSi and Co2Si.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1584-1590 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical resistivity of monocrystalline TiSi2, TaSi2, MoSi2, and WSi2 has been measured from 4.2 to 1100 K. These disilicides are metallic, yet there is a remarkable difference in the temperature dependence of their intrinsic resistivities. TiSi2 and TaSi2 are found to exhibit a T5 dependence in the temperature range of 13〈T〈30 K and 15〈T〈28 K, respectively, while MoSi2 and WSi2 show a T3.8 dependence from 15 to 40 K. For TiSi2, along the three crystallographic directions 〈100〉, 〈010〉, and 〈001〉, the phonon contribution to the resistivity was found to be linear in temperature above 300 K. The same behavior was observed for TaSi2 along the 〈0001〉 axis, while a negative deviation from the linearity followed by a quasisaturation was observed with the current, parallel to the 〈101¯0〉 axis. The resistivity data of WSi2 and MoSi2 with the current parallel to 〈001〉 and 〈110〉 crystallographic directions showed a positive deviation from linearity. The data are fitted to several theoretical expressions at low temperatures and in the full range of temperatures. The results are discussed in light of these theories.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 999-1001 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report here a study on the role of crystallinity on the magnetoresistive properties of self-doped La0.8MnO3−δ thin films. Films have been grown by a liquid-source metalorganic chemical vapor deposition technique on two different single crystals: SrTiO3 (001) and Al2O3 (012). Epitaxial films are obtained on strontium titanate and show a high magnetoresistance peak at low fields: maximum magnetoresistive effect in the vicinity of the magnetic transition temperature, and negligible 50 K below. Polycrystalline films are observed on sapphire; they exhibit a lower magnetoresistance of several percent which remains nearly constant over a wide temperature range. Two magnetoresistive regimes can be distinguished in these films: in low fields (up to 5 mT), a strong magnetoresistance is obtained with a sensitivity of 0.28%/mT at 78 K; in higher fields, the magnetoresistance is linear and lower than this obtained in epitaxial films. The role of grain boundaries on the magnetoresistive effect is discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin-film growth and compositional effects of c-axis oriented YBa2Cu3O7−x (YBCO) thin films synthesized by metalorganic chemical vapor deposition have been investigated. The formation of single cation films using tetramethylheptanedionate precursors was shown to be mass controlled, exhibiting a ratio of deposited to evaporated species in the increasing order Ba, Y, and Cu. The physical properties of off-stoichiometric YBCO films deposited on MgO substrates were measured in the compositional range 1.1≤Ba/Y≤2.3 and 1.5≤Cu/Ba≤4.6. While structural properties such as c-axis values and rocking curves appeared unaffected to variations in cation stoichiometry, morphology was observed to be extremely sensitive even to slight changes in composition. Off-stoichiometric layers with Cu/Ba(approximately-greater-than)1.5 were observed to exhibit Cu-rich precipitates embedded in a 1:2:3 YBCO film matrix. The zero-resistivity temperatures were above 77 K for all cation film compositions measured. However, sharp ac-susceptibility transitions were restricted to a more narrow compositional range (1.9〈Cu/Ba〈3.6). The best superconducting properties [Tc=85 K, Jc (77 K)(approximately-greater-than)106 A/cm2] were observed for films with relatively rough surface morphologies (Ba/Y=1.6 and Cu/Ba=3.5). An optimum trade-off between smooth surfaces and superconducting properties was found for Ba/Y=1.5 and Cu/Ba=1.9, yielding Tc=81 K and Jc (77 K)=3×105 A/cm2.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6945-6955 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of the microstructure on the magnetoresistance of polycrystalline manganite (La1−xSrxMnO3) thin films have been investigated. The films have been grown by metalorganic chemical vapor deposition on silicon (001) substrates covered with a native silica layer. Different microstructures were obtained by varying the substrate temperature in the range (550–750 °C). The films exhibit a ferromagnetic/paramagnetic transition around 325 K. The grain size is in the range 20–100 nm and, for deposition temperature lower than 650 °C, weak links appear in the films as the grains are mostly noncohesive. The low-field contribution to the magnetoresistance is independent of the grain size in the studied range. A factor of ∼1.8 is gained in this contribution as the substrate temperature is lowered below 650 °C, which can be related to the occurrence of noncohesive grains in the films. The largest low-field magnetoresistance obtained is about 20% at 22 K (under 0.2 T). The high-field contribution to the total magnetoresistance appears to be independent of the microstructure of the films. Our results are discussed in the framework of spin-dependent transport mechanisms (tunneling or scattering). Finally, the low-temperature (T≤20 K) resistivity upturn observed for all the polycrystalline films is discussed. It can be attributed to activated transport phenomena (Coulomb blockade tunneling or tunneling through impurities, with activation energies on the order of 0.05 meV) or to localized states in the material. © 1999 American Institute of Physics.
    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 63 (1988), S. 732-742 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phosphorus redistribution in a WSi2/polycrystalline-silicon structure after furnace annealing between 600 and 1000 °C was studied. When P is initially introduced into the polycrystalline-silicon, a secondary ion mass spectroscopy analysis shows a nearly equidistribution of the dopant within the sandwich. When the silicide layer is phosphorus implanted, it has been clearly shown that with the refractory metal the dopant forms a tungsten phosphide compound more stable than WSi2 up to a critical temperature Tc. The stability of the phosphide increases with the implanted dose. A complete characterization of the additional phase was obtained by thermal annealing of W-Si-P powders. Several other interesting features on the redistribution of the dopant in the polycrystalline-silicon/silicide structure have been established and discussed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1246-1248 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: (La0.7Sr0.3MnO3/SrTiO3)15 superlattices have been grown by pulsed liquid-injection metalorganic chemical vapor deposition on monocrystalline substrates such as LaAlO3, SrTiO3, and MgO. The pulsed-injection technique allows one to control precisely the amount of precursors delivered to the deposition chamber and thus the thickness of each individual layer. The period of the superlattices depends indeed linearly on the number of injected droplets. In our deposition conditions, the average growth rates are ∼0.130 nm/injection for La0.7Sr0.3MnO3 and 0.042 nm/injection for SrTiO3, with no significant difference as regard to the substrate used. The strain's state of the superlattices depends on the relative thicknesses of the La0.7Sr0.3MnO3 and SrTiO3 layers and also on the substrate used. Finally, the deposition of superlattices with ultrathin interlayers of few unit cells has been demonstrated. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2184-2186 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal expansion coefficients associated with the C49 and C54 crystal directions have been determined by in situ x-ray diffraction analysis of Ti film annealing deposited on Si substrates. Evidence of a clear anisotropy in the C49 coefficients has been obtained: the αb is considerably smaller than αa and αc. The volume expansion is larger in C54: this contributes to reduce to 1.6% at the transformation temperature, the observed 2.0% volume difference at 300 K. The magnitude of the volume discontinuity during transformation is an indication for a first-order transition. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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