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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 96 (1994), S. 53-61 
    ISSN: 1434-6036
    Keywords: 61.43.-j ; 61.80.Jh ; 81.30.Bx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In1−x Pd x films with 0.2≦x≦0.75 have been prepared by vapour quenching at 4.2 K or 77 K, respectively. To test whether amorphous (a-) phases can be obtained in this way, the resistance behavior and the electron diffraction patterns of the as-prepared and annealed films were studied insitu. For films withx=0.25 additional information could be acquired from their superconducting behavior. Combining these results one concludes that a-phases exist for the compositional range 0.2≦x≦0.6, which are stable up to crystallization temperaturesT x within the range 250 K≦T x ≦420 K. Irradiation of the crystallized films at low temperatures (4.2 K or 77 K) with heavy ions (350 keV Ar+ or Kr+) leads to complete re-amorphization. Forx=0.67 corresponding to InPd2 a nanocrystalline (n-) phase is obtained by vapour quenching at 77 K as inferred from x-ray diffraction. AtT x =700 K, thesen-films exhibit a drop of the electrical resistance indicating the beginning of significant grain growth. After recooling, Kr+ bombardment at 77 K does not restore the high electrical resistance of the as-quenchedn-film. This result can be used as a criterion when studying quenched films withx=0.625 corresponding to In3Pd5. In this case, a resistance drop is found atT x =600 K, but the diffraction techniques do not allow an uniquevocal distinction between amorphous and nanocrystalline. This becomes possible by low temperature ion irradiation after annealing atT〉T x . The bombardment results in resistance changes, which saturate well-below the value of the as-quenched sample implying nanocrystallinity for the latter. Based on this criterion, a ‘phase’-diagram for quenched In1−x Pd x is provided with 0≦x≦1 containing the newly detecteda- andn-phases.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0630
    Keywords: 68.35.Fx ; 64.60.My ; 81.15.Cd
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Al/Au multilayers (average composition Al2Au, individual layer thicknesses 1 nm Al and 0.71 nm Au) are prepared at 90 K by ion beam sputtering. The electrical resistance of the growing films is monitored in situ. From the results obtained in this way it can be concluded that interface reactions occur transforming the ultrathin layers into an amorphous phase, which is stable up to 255 K. For larger individual layer thicknesses (2.1 nm Au and 3 nm Al), the interface reaction into the amorphous state is incomplete. Based on a simple parallel-resistor model, one finds that the interface reaction into the amorphous phase is restricted to a thickness of less than 3.5 nm. The temperature dependence of the resistance of such thicker multilayers indicates the onset of interdiffusion of the yet unreacted material at T=200 K resulting in the crystalline Al2Au-phase.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-7357
    Keywords: 61.80Jh ; 74.60.Ge ; 74.76.Bz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Isothermal current-voltage (I–V) characteristics of c-axis orientedYBa 2 CU 3 O 7−δ films taken in different external magnetic fields μoH, exhibit voltage jumps at a well defined current density J*(T, H) pointing to a specific instability of the vortex system. Interpreted as Larkin- Ovchinnikov (LO)-instability, this behavior allows to extract the inelastic scattering time Tin of quasiparticles. In the present work, the LO-analysis is applied to study the effect of additional defects on Tin. For this purpose,YBa 2 CU 3 O 7−δ films were irradiated at 77K with increasing fluences Φ of 350 ke V He+ ions. The I-V characteristics were determined in the temperature range 45K 〈 T 〈 80K and in magnetic fields up to 5 Tesla. While J* as well as the superconducting transition temperature Tc are significantly decreased by the ion bombardment, the critical vortex velocity as deduced from LO-theory is much less affected. If the temperature dependence of the extracted scattering times Γin is rescaled by plotting versus the reduced temperature t = T/Tc(Φ), the results for all ion fluences fall on one common curve within the error bars. This leads to the conclusion that a universal quasiparticle density nN(t) dominates the scattering rate 1/Tin.
    Type of Medium: Electronic Resource
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