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  • 1
    Electronic Resource
    Electronic Resource
    New scaling relation for sputtered NbN films (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 258-261 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A scaling relationship has been discovered between the sputtering rate and the partial pressure of argon PAr, which leaves the superconducting properties of NbN films invariant. As PAr increases for a given sputtering rate, there is a linear reduction of Tc together with a rapid increase, followed eventually by saturation, in Hc2 at 4.2 K. These produce a maximum in Jc (measured at 19 T and 4.2 K) at a particular value of PAr. Films exhibiting nearly the same set of superconducting properties and microstructures can be made at a higher fixed sputtering rate if the values of PAr are multiplied by a constant scale factor. This scaling relation is found to hold for two separate sputtering systems, one of which uses a standard diffusion pump while the other uses an oilless turbo pump. Additional comparisons with the results of others reinforces the conclusion that the scaling relationship is universal and thus may provide some insight into those factors in the sputtering process which are important for determining the superconducting properties and microstructure of sputtered NbN films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342582
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  • 2
    Electronic Resource
    Electronic Resource
    Properties of sputtered superconducting films of Bi2Sr2CaCu2Ox made by low-temperature in situ growth (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2135-2137 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting films of Bi2Sr2CaCu2Ox have been fabricated on single-crystal MgO substrates by a low-temperature in situ process. Using a substrate temperature Ts≈645 °C, metallic films with a superconducting onset of 90–100 K and an extrapolated Tc0=56 K have been obtained. X-ray diffraction shows the films to be c-axis oriented. Electron microscopy reveals that the films are not significantly smoother than films which were post-annealed at 865 °C, and that some segregation into nonsuperconducting phases had occurred. The exact mechanism by which crystallization and superconductivity occurs at such low temperatures is not yet known, but it can be speculated that the surface atoms are less constrained and thus have a smaller energy barrier to overcome in forming a crystal structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102347
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  • 3
    Electronic Resource
    Electronic Resource
    In situ x-ray diffraction study of CoSi2 formation during annealing of a Co/Ti bilayer on Si(100) (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 6730-6732 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray diffraction was performed in situ during annealing of a Co/Ti/Si(001) multilayer, which produced an epitaxial CoSi2 layer. The results indicate that the Ti layer did not stay intact during the reaction, and thus could not act like a membrane, moderating Co/Si interdiffusion. Strongly textured phases (M) formed prior to CoSi2 nucleation, and was unobservable upon completion of the anneal. Nucleation and growth of CoSi2 on Si(001) took place in the presence of M, new Co-Ti-(O) phases that were located at the metal/Si interface, and thus M might play an important role in the perfection of the silicide. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359091
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  • 4
    Electronic Resource
    Electronic Resource
    Resistive measurement of the temperature dependence of the penetration depth of Nb in Nb/AlOx/Nb Josephson junctions (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 8163-8167 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of the penetration depth of Nb films was determined from resistive transitions of Nb/AlOx/Nb Josephson junctions in a constant magnetic field applied parallel to the junction planes. Distinct resistance peaks were observed as temperature decreases and those peaks were found to appear when the total flux threading the junction equals an integral multiple of the flux quantum. From this condition, the penetration depth at those peak positions has been determined. The temperature dependence was well described by either the dirty local limit or the two-fluid model. This method can be useful for a highly fluctuating system such as high-temperature superconductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356515
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  • 5
    Electronic Resource
    Electronic Resource
    Large anisotropy in the upper critical field of sputtered thin films of superconducting Tl-Ba-Ca-Cu-O (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2560-2562 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The upper critical field Bc2 provides the most direct measure of the intrinsic anisotropy of a superconductor. For highly oriented, sputtered thin films of the high-temperature superconductor Tl2Ba2CaCu2Ox, we find a Bc2 anisotropy of at least 70, which exceeds similar measurements on thin films and single crystals of the high-temperature superconductors Bi-Sr-Ca-Cu-O and YBa2Cu3Oy. We discuss why the midpoints of the resistive transitions, used in these measurements, may be appropriate for defining the intrinsic Bc2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100531
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  • 6
    Electronic Resource
    Electronic Resource
    Selective resputtering of bismuth in sputtered Bi-Sr-Ca-Cu-O films (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 3867-3875 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present studies using a dc magnetron in an on-axis configuration to sputter Bi-Sr-Ca-Cu-O films from a composite target. These studies show that bismuth can be preferentially resputtered. The influence of ozone, molecular oxygen, and total pressure on the resputtering of bismuth is investigated and discussed. Ozone, in low concentrations, can dramatically affect the degree of resputtering. By comparing the effects of molecular oxygen and ozone, some insight is gained regarding the possible mechanisms of negative ion formation in the magnetron environment. Based on our results we suggest that molecular oxygen can bring about resputtering primarily by forming O+2, which collides with the target to produce energetic negative oxygen ions. In contrast, ozone may form negative ions by electron impact in the dark space above the target, giving rise to lower-energy negative ions, which can traverse the plasma unneutralized and can be stopped with an applied bias on the sample block. With no added oxidant, negative oxygen ions from the target oxygen may dominate the background resputtering. Similarity is found between our results and those for similar studies on Y-Ba-Cu-O by other workers. Bismuth in Bi-Sr-Ca-Cu-O behaves as barium in Y-Ba-Cu-O with regards to preferential resputtering; furthermore, the response of strontium, calcium, and copper to oxygen in sputtered Bi-Sr-Ca-Cu-O is similar to what is observed for copper in Y-Ba-Cu-O.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349193
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  • 7
    Electronic Resource
    Electronic Resource
    Low-temperature neutron irradiation of magnetron-sputtered NbN films (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3172-3175 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Four types of differently prepared NbN films were irradiated at 4.6 K with fast neutrons to a fluence of 5.3 × 1022 m−2 (E(approximately-greater-than)0.1 MeV). The critical current densities Jc were measured in magnetic fields up to 23 T prior to irradiation, following low-temperature irradiation, and again after an annealing cycle to room temperature. In all films, Jc was found to be completely unchanged by the radiation and annealing treatments in fields up to 15 T, but to increase at higher magnetic fields. At the same time, the upper critical fields Bc2 increased by about 0.5 T (∼2%). Replotting Jc versus reduced field B/Bc2 leads to identical field dependencies also in the high-field range. Hence, the observed increase of Jc is equantitatively explained as a Bc2 effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348557
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  • 8
    Electronic Resource
    Electronic Resource
    Radiation effects in superconducting NbN/AlN multilayer films (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 6327-6330 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of neutron irradiation up to a fluence of 1023 m−2 (E〉0.1 MeV) are reported for sputtered NbN/AlN multilayer films. The superconducting properties change only slightly with neutron fluence. For the best multilayers, which exhibit critical current densities Jc of 〉108 A/m2 at 4.2 K and 20 T, the high-field data show virtually no change in Jc. It is therefore proved experimentally that NbN/AlN multilayers, which exhibit higher Jc than single NbN thin films, exhibit the same extremely radiation-hard, high-field behavior which was reported previously for such NbN films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346876
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  • 9
    Electronic Resource
    Electronic Resource
    Magneto-optical imaging of the first order spin-flop transition in the layered manganite La1.4Sr1.6Mn2O7 (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5043-5045 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spin-flop transition in the antiferromagnetic layered manganite La1.4Sr1.6Mn2O7 was studied using magnetization measurements and a high-resolution magneto-optical imaging technique. We report the direct observation of the formation of ferromagnetic domains appearing at the first order spin-flop transition. The magnetization process proceeds through nucleation of polarized domains at crystal defect sites and not through the expansion of polarized domains due to domain wall motion. A small magnetic hysteresis is caused by the difference between the mechanisms of nucleation and annihilation of domains in the mixed state. These results establish a direct link between the magnetic structure on the atomic scale as seen in neutron scattering and the macroscopic properties of the sample as seen in magnetization and conductivity measurements. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373242
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of layering and doping on the magnetic anisotropy of the layered manganites La2−2xSr1+2xMn2O7 (x=0.3–0.4) (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6621-6623 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetization experiments were performed on a series of single crystals of the bilayer manganites La2−2xSr1+2xMn2O7. The magnetic anisotropy constants were determined by fitting expressions based on the tetragonal anisotropy energy to the magnetization curves. It is shown that there is a significant dipolar contribution to the first order anisotropy constant arising from the layered crystal structure. This contribution determines the magnetization direction in the doping range x=0.32–0.33 where the anisotropy due to the electronic structure is small. With increasing doping the magnetic anisotropy changes from strong uniaxial anong the c axis (K(approximate)2.5×106 erg/cm3) at x=0.3 to strong easy plane (K(approximate)−3.7×106 erg/cm3) at x=0.4 in an almost linear fashion. This evolution is explained through the change of the orbital nature of the eg electrons from predominantly d3z2−r2 to predominantly dx2−y2. On the samples displaying easy-plane anisotropy a small anisotropy in the basal plane of about −7×104 erg/cm3 was determined with (110) being the easy axis. An estimate of the spin-wave gap based on these results is in reasonable agreement with experimental determinations. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1357136
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