1,636 results on '"superconducting thin films"'
Search Results
102. Magnetoresistance Study of c-Axis Oriented YBCO Thin Film.
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CHROBAK, M., WOCHA, W. M., KOWALIKA, M., ZALECKIA, R., GIEBUŁTOWSKIA, M., PRZEWOZNIKA, J., KAPUSTAA, C. Z., and SZWACHTA, G.
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YTTRIUM barium copper oxide films , *MAGNETORESISTANCE measurement , *MAGNESIUM oxide , *PULSED laser deposition , *SUPERCONDUCTING thin films - Abstract
The c-axis orientation YBa2Cu3Oδ thin film was prepared directly on MgO substrate by the pulse laser deposition. The thickness of the film is 170 nm. The superconducting critical temperature is Tc50% = 87:5 K and the width of superconducting transition is ΔT = 1:8 K. The temperature dependences of magnetoresistance were measured up to 90 kOe. The widths of the transition to the superconducting state versus applied magnetic field were derived and they were fitted using the formula: ΔT = CHm +ΔT0. The irreversibility fields as a function of temperature were obtained and fitted by the de Almeida and Thouless-like equation: Hirr = Hirr0(1-T=Tc0)n. The irreversibility field at the liquid nitrogen temperature was calculated and it is Hirr = 43:8 kOe when the applied magnetic field is parallel to the c-axis. [ABSTRACT FROM AUTHOR]
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- 2017
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103. Absence of Magnetic-Field-Induced Effects in the Mid-infrared Transmission of La2−xSrxCuO4 Thin Films
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Bozovic, I
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- 2009
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104. Nonlinear optimal filter technique for analyzing energy depositions in TES sensors driven into saturation.
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Shank, B., Yen, J. J., Cabrera, B., Kreikebaum, J. M., Moffatt, R., Redl, P., Young, B. A., Brink, P. L., Cherry, M., and Tomada, A.
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PARTICLE detectors , *SUPERCONDUCTING thin films , *QUASIPARTICLES , *SUPERCONDUCTIVITY , *CRYOGENICS - Abstract
We present a detailed thermal and electrical model of superconducting transition edge sensors (TESs) connected to quasiparticle (qp) traps, such as the W TESs connected to Al qp traps used for CDMS (Cryogenic Dark Matter Search) Ge and Si detectors. We show that this improved model, together with a straightforward time-domain optimal filter, can be used to analyze pulses well into the nonlinear saturation region and reconstruct absorbed energies with optimal energy resolution. [ABSTRACT FROM AUTHOR]
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- 2014
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105. Epitaxial antiperovskite superconducting CuNNi3 thin films synthesized by chemical solution deposition.
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Zhenzhen Hui, Xianwu Tang, Dingfu Shao, Hechang Lei, Jie Yang, Wenhai Song, Xuebin Zhu, Yuping Sun, and Hongmei Luo
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ATOMIC layer epitaxial growth , *PEROVSKITE synthesis , *SUPERCONDUCTING thin films , *CHEMICAL solution deposition , *TRANSITION metal nitrides , *CARBIDES - Abstract
Epitaxial antiperovskite superconducting CuNNi3 thin films have been grown by chemical solution deposition. The film is a type II superconductor and shows a Tc of 3.2 K with a transition of 0.13 K. The Hc2(0) and ξ0 are estimated to be 8.1 kOe and 201 Å, respectively. [ABSTRACT FROM AUTHOR]
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- 2014
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106. Highly textured oxypnictide superconducting thin films on metal substrates.
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Kazumasa Iida, Kurth, Fritz, Masashi Chihara, Naoki Sumiya, Grinenko, Vadim, Ichinose, Ataru, Ichiro Tsukada, Hänisch, Jens, Matias, Vladimir, Takafumi Hatano, Holzapfel, Bernhard, and Hiroshi Ikuta
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IRON-based superconductors , *SUPERCONDUCTING thin films , *SURFACE texture , *SUBSTRATES (Materials science) , *CRYSTAL grain boundaries , *ION beam assisted deposition - Abstract
Highly textured NdFeAs(O,F) thin films have been grown on ion beam assisted deposition-MgO/Y2O3/Hastelloy substrates by molecular beam epitaxy. The oxypnictide coated conductors showed a superconducting transition temperature (Tc) of 43K with a self-field critical current density (Jc) of 7.0 × 104 A/cm² at 5K, more than 20 times higher than powder-in-tube processed SmFeAs(O,F) wires. Albeit higher Tc as well as better crystalline quality than Co-doped BaFe2As2 coated conductors, in-field Jc of NdFeAs(O,F) was lower than that of Co-doped BaFe2As2. These results suggest that grain boundaries in oxypnictides reduce Jc significantly compared to that in Co-doped BaFe2As2 and, hence biaxial texture is necessary for high Jc. [ABSTRACT FROM AUTHOR]
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- 2014
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107. Persistent current relaxation in polycrystalline superconducting thin films.
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Belevtsov, L. V.
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PERSISTENT currents , *POLYCRYSTALS , *SUPERCONDUCTING thin films , *THICKNESS measurement , *PARTICLE size distribution - Abstract
The relaxation rate of persistent current is studied theoretically in superconducting polycrystalline thin films. It is shown that varying the material parameters of grain anisotropy, grain size and film thickness does guide to a change of the current relaxation rate (CRR) mode. The point of degeneracy of CRR was obtained. The film-thickness dependent maxima are found in the behavior of CRR. [ABSTRACT FROM AUTHOR]
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- 2014
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108. Superconducting MoC thin films with enhanced sheet resistance.
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Trgala, M., Žemlička, M., Neilinger, P., Rehák, M., Leporis, M., Gaži, Š., Greguš, J., Plecenik, T., Roch, T., Dobročka, E., and Grajcar, M.
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SUPERCONDUCTING thin films , *MOLYBDENUM compounds , *ACETYLENE , *MAGNETRON sputtering , *ATOMIC force microscopes , *COPLANAR waveguides - Abstract
In this paper we describe a process of MoC superconducting thin films preparation by reactive magnetron sputtering in argon-acetylene atmosphere. The deposition process was optimized to achieve very smooth superconducting thin films with high sheet resistance. We present the results of four-point resistance measurements in cryostat cooled down to 300 mK. The roughness was measured by the atomic force microscope (AFM). The results are so far promising and enable us to pattern superconducting coplanar waveguide resonator with embedded nanostructures. [ABSTRACT FROM AUTHOR]
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- 2014
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109. Role of MgB2/Cr2O3 nano-interfaces in photoinduced nonlinear optical treatment of the MgB2 superconducting films.
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AlZayed, N. S., Kityk, I. V., Ozga, K., Fedorchuk, A. O., Soltan, S., Shahabuddin, M., and El-Naggar, A.
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CHROMIUM oxide , *NANOSTRUCTURES , *SUPERCONDUCTING thin films , *QUANTUM chemistry , *ELECTRIC fields , *POLARIZATION (Nuclear physics) - Abstract
The calculations of the photoinduced nonlinear optical shift with respect to critical temperature for the MgB 2 superconducting films (pure and doped by Cr) were performed using the first principle quantum chemical simulations. The principal role of the nano-interfaces between the MgB 2 and Cr 2 O 3 was established, and the nano-interfaces have a thickness varying within the 20–30 nm. The latter was done taking into account their long-range ordering additionally aligned by bicolour optical poling. The bicolour poling was performed by the fundamental 10.6 μm laser beam and its doubled frequency coherent second harmonic generation signal. The so formed internal dc-electric field has introduced additional polarization to the media which re-scale the factor of the electron–phonon interaction including the anharmionic one responsible for the occurrence of charge density non-centrosymmetry and the related second order nonlinear optical response. The simulations of the IR induced bicolour treatment were performed both for pure as well as MgB 2 superconducting films doped by Cr 3+. [ABSTRACT FROM AUTHOR]
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- 2014
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110. Dynamics of current-driven phase-slip centers in superconducting strips.
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Berdiyorov, G., Harrabi, K., Oktasendra, F., Gasmi, K., Mansour, A. I., Maneval, J. P., and Peeters, F. M.
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SUPERCONDUCTING thin films , *ENERGY dissipation , *MAGNETIC fields , *FLUX (Energy) , *TEMPERATURE - Abstract
Phase-slip centers/lines and hot spots are the main mechanisms for dissipation in current-carrying superconducting thin films. The pulsed-current method has recently been shown to be an effective tool in studying the dynamics of phase-slip centers and their evolution to hot spots. We use the time-dependent Ginzburg-Landau theory in the study of the dynamics of the superconducting condensate in superconducting strips under external current and zero external magnetic field. We show that both the flux-flow state (i.e., slow-moving vortices) and the phase-slip line state (i.e., fast-moving vortices) are dynamically stable dissipative units with temperature smaller than the critical one, whereas hot spots, which are localized normal regions where the local temperature exceeds the critical value, expand in time, resulting ultimately in a complete destruction of the condensate. The response time of the system to abrupt switching on of the overcritical current decreases with increasing both the value of the current (at all temperatures) and temperature (for a given value of the applied current). Our results are in good qualitative agreement with experiments we have conducted on Nb thin strips. [ABSTRACT FROM AUTHOR]
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- 2014
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111. The Study of Purity Improvement on Tl-1223 Thin Films by DC Sputtering and Post-annealing Method.
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Gao, X., Xie, W., Wang, Z., Zhao, X., He, M., Zhang, X., Yan, S., and Ji, L.
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MAGNETRON sputtering , *SUPERCONDUCTING thin films , *THALLIUM , *X-ray diffraction , *CRITICAL current density (Superconductivity) , *ANNEALING of metals , *CRYSTALLIZATION - Abstract
Un-substituted TlBaCaCuO (Tl-1223)-superconducting thin films have been fabricated on a LaAlO (001) substrate in oxygen by using a two-step method, which includes direct current (DC) magnetron sputtering and post-annealing process. Thallium (Tl) content in amorphous precursor films is found to be important to the crystallization of Tl-superconducting phase. Using the nominal composition of TlBaCaCu O ( δ = 0.1∼0.2) precursor films, the formation is promoted to Tl-1223 and Tl-2223 phase rather than Tl-1212 and Tl-1223 phase with accompanying Tl-rich source pellets. When the annealing process continues, Tl-2223 phase will be converted to Tl-1223 phase at a suitable annealing time and temperature. From the X-ray diffraction pattern, only Tl-1223 (00l) peaks are observed, which shows that the purity of Tl-1223 film is improved significantly by this method. The critical temperature T of Tl-1223 film is characterized at 110 K, and the critical current density J (77 K, T = 0) is up to 1.5 MA/cm. [ABSTRACT FROM AUTHOR]
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- 2014
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112. Determination of London penetration depth from ac susceptibility measurements of a square superconducting thin film.
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Chen, D.-X., Navau, C., Del-Valle, N., and Sanchez, A.
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PENETRATION depth (Superconductors) , *SUPERCONDUCTING thin films , *MEISSNER effect , *SCIENTIFIC apparatus & instruments , *PEARLS , *OPTICAL properties - Abstract
Highlights: [•] We calculate Meissner ac susceptibility of square film as a function of Pearl length. [•] New technique is developed for determining London penetration depth of square films. [•] The technique does not require special instrumentation and complex calculations. [•] Intrinsic and applied superconducting properties may be studied for the same film. [ABSTRACT FROM AUTHOR]
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- 2014
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113. Structural origin of enhanced critical temperature in ultrafine multilayers of cuprate superconducting films.
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Fengshan Zheng, Logvenov, Gennady, Bozovic, Ivan, Yimei Zhu, and Jiaqing He
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THERMAL stresses , *SUPERCONDUCTING thin films , *TRANSMISSION electron microscopy , *MOLECULAR beam epitaxy , *SUBSTRATES (Materials science) - Abstract
The interface layers of La2-xSrxCuO4 (LSCO) thin films epitaxially grown on LaSrAlO4 substrates by molecular beam epitaxy were investigated using transmission electron microscopy (TEM). In single-phase LSCO film, we observed an irregular layering sequence near the interface between the film and the substrate, as well as an abundance of oxygen vacancies in CuO2 layers. A multilayer LSCO film with a high critical temperature (Tc = 44.5 K) showed perfect interfaces between the sublayers. Furthermore, by combining scanning TEM, electron energy-loss spectroscopy, and electron holography, we show that there is little or no interdiffusion between the sublayers. The interfacial defects and oxygen vacancies reduce Tc, while the compressive strain in high-quality multilayers enhances Tc. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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114. Synthesis and transport properties of superconducting thin films of K0.33WO3: Tc reduction due to disorder.
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Wu, Phillip M., Hart, Chris, Luna, Katherine, Munakata, Ko, Tsukada, Akio, Risbud, Subhash H., Geballe, T. H., and Beasley, M. R.
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ANNEALING of semiconductors , *SUPERCONDUCTING thin films , *SCANNING electron microscopy , *CRYSTAL structure , *SPECTRUM analysis - Abstract
Via a two-step deposition and post-annealing procedure, K-doped WO3 thin films with reproducible transport properties are obtained. We observe a larger critical field Hc2 along the c axis, consistent with the picture of the Fermi surface containing one-dimensional bands along this direction. Reducing the film thickness results in a superconductor to insulator transition. Scanning electron microscopy (SEM) images show that KWO3 crystallites become less connected as the deposition time is reduced, providing a microscopic explanation for the transport behavior. In the superconducting films, a resistive anomaly is observed similar to bulk crystals, with a characteristic temperature that shifts lower with decreasing film thickness. The competing electronic effects manifest as a suppression of the density of states at the Fermi level, observed using point contact tunneling spectroscopy, demonstrating that disorder-induced increased Coulomb interactions are present. Using the theory of Belitz for the reduction of Tc due to disorder, we can infer that the film with the highest observed Tc has a relatively large disorder dependent electron-phonon interaction parameter ∼ 1 .2. Understanding microscopically why certain films display higher Tc will aid in the search for the trace high-Tc), superconducting anomalies observed in lightly surface doped bronzes. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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115. Quasiparticle generation efficiency in superconducting thin films.
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Guruswamy, T, Goldie, D J, and Withington, S
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QUASIPARTICLES , *SUPERCONDUCTING thin films , *QUANTUM theory , *THIN films , *PHONONS - Abstract
Thin-film superconductors with thickness ∼30–500 nm are used as non-equilibrium quantum detectors for photons, phonons or more exotic particles. One of the most basic questions in determining their limiting sensitivity is the efficiency with which the quanta of interest couple to the detected quasiparticles. As low temperature superconducting resonators, thin films are attractive candidates for producing quantum-sensitive arrayable sensors and the readout uses an additional microwave probe. We have calculated the quasiparticle generation efficiency ηs for low energy photons in a representative, clean thin-film superconductor (Al) operating well below its superconducting transition temperature as a function of film thickness, within the framework of the coupled kinetic equations described by Chang and Scalapino (1978 J. Low Temp. Phys.31 1–32). We have also included the effect of a lower frequency probe. We show that phonon loss from the thin film reduces ηs by as much as 40% compared to earlier models that considered relatively thick films or infinite volumes. We also show that the presence of the probe and signal enhances the generation efficiency slightly. We conclude that the ultimate limiting noise equivalent power of this class of detector is determined by the thin-film geometry. [ABSTRACT FROM AUTHOR]
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- 2014
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116. Influence of hydrostatic pressure on superconducting properties of niobium thin film.
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Pristáš, Gabriel, Gabáni, Slavomír, Gažo, Emil, Komanický, Vladimír, Orendáč, Matúš, and You, Hoydoo
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NIOBIUM compounds , *HYDROSTATIC pressure , *SUPERCONDUCTING thin films , *CHEMICAL preparations industry , *VACUUM , *DC sputtering , *MAGNETRON sputtering - Abstract
Abstract: We have studied superconducting properties of niobium thin films under hydrostatic pressures up to 3GPa. The films with thickness of 100nm were prepared in the high vacuum DC magnetron sputtering system (with critical temperature TC=8.95K at ambient pressure). The produced high quality films have been characterized using electrical resistivity and magnetization measurements, X-ray diffraction, and atomic force microscope imaging. We have observed increase of TC with increasing value of applied pressure (dTC/dp=73 mK/GPa) up to 3GPa. This observation is different to pressure effect observed on bulk sample of Nb. In this paper we are discussing the origin of this discrepancy. [Copyright &y& Elsevier]
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- 2014
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117. Production and Characterization of BaIrO3 Doped Superconducting YBCO Thin Films by TFA-MOD Method.
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BEKTAŞ, Murat, BİRLİK, Işıl, ÖZCİVAN, Ahmet Nuri, and ÇELİK, Erdal
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BARIUM aluminate ,YTTRIUM barium copper oxide films ,SUPERCONDUCTING thin films ,TRIFLUOROACETIC acid ,METAL organic chemical vapor deposition ,SINGLE crystals ,SPIN coating - Abstract
Copyright of Afyon Kocatepe University Journal of Science & Engineering / Afyon Kocatepe Üniversitesi Fen Ve Mühendislik Bilimleri Dergisi is the property of Afyon Kocatepe University, Faculty of Science & Literature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2014
118. Fabrication of a strain-induced high performance NbN ultrathin film by a Nb5N6 buffer layer on Si substrate.
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Jia, X Q, Kang, L, Gu, M, Yang, X Z, Chen, C, Tu, X C, Jin, B B, Xu, W W, Chen, J, and Wu, P H
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METAL fabrication , *LATTICE dynamics , *SILICON analysis , *CURRENT density (Electromagnetism) , *ELECTRIC properties of nanowires , *SUPERCONDUCTING thin films - Abstract
Lattice mismatch between NbN and silicon (Si) reduces the superconducting properties of NbN film on Si substrate, and this in turn affects the performance of devices such as the hot electron bolometer (HEB) and superconducting nanowire single photon detector (SNSPD). We have found that the superconducting properties of NbN film on Si will be significantly improved by a Nb5N6 buffer layer. The strain of the NbN film was optimized by varying the thickness of the buffer layer. With 30 nm thick Nb5N6, the zero resistance superconducting transition temperature (TC0) of a 6 nm thick NbN film on Si is up to 13.5 K and the critical current density (JC) of the film is more than 107 A cm−2. All the details of preparation, improvement and characteristics of this film are also presented. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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119. Nanostructural defects for effective flux pinning in high-quality Bi2Sr2CaCu2O8+x epitaxial thin films with high critical current density.
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Yamasaki, H and Endo, K
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CRYSTAL defects , *NANOSTRUCTURED materials , *EPITAXIAL layers , *CURRENT density (Electromagnetism) , *SUPERCONDUCTING thin films , *POWER law (Mathematics) , *DISLOCATIONS in crystals - Abstract
The dependence of the critical current density (Jc) and current–voltage (I–V) characteristics on the magnetic field H and temperature T were determined in c-axis-oriented epitaxial Bi2Sr2CaCu2O8+x (Bi2212) thin films prepared by metalorganic chemical vapor deposition. The films showed high Tc(R = 0) ≥ 83 K and high transport Jc > 1010 A m−2 at 10 K, but Jc decreased sharply when a magnetic field was applied in the c direction, except at low temperatures (≤20 K). The n-values (indices of the power-law I–V characteristics) decreased together with Jc, showing that the decrease is caused by thermally activated flux motion. To clarify the flux pinning mechanism operating in the films, nanostructural defects were investigated by transmission electron microscopy (TEM). Cross-sectional TEM images of the thin films revealed that the Bi2212 phase was twinned and that the twin boundary runs either parallel or perpendicular to the ab-plane depending on the region. We observed misfit dislocations at twin boundaries, and other dislocations associated with stacking faults parallel to the ab-plane, as well as anti-phase boundaries. Contrasts corresponding to dislocations parallel to the ab-plane and/or to the anti-phase boundaries were observed in plan-view TEM images, and nanoscale precipitates as observed in some YBa2Cu3O7−y (YBCO) films were almost entirely absent. The temperature dependence of low-field Jc, which was mostly unaffected by the thermally activated flux motion, approximately followed ∼(1−T/Tc)m(1+T/Tc)2 (m = 1.7–2.2). The temperature dependence with m ≈ 2, which can be explained by a simple theoretical model, was recently observed in YBCO thin films in which flux pinning was dominated by linear pins (partial dislocations surrounding stacking faults parallel to the ab-plane). From these results and theoretical considerations on the flux pinning force, we conclude that flux pinning in our Bi2212 films is mainly caused by dislocations parallel to the ab-plane and anti-phase boundaries. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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120. Superconductivity of 132 K in HgBa2Ca2Cu3O8+δ thin films fabricated using a cation exchange method.
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Ji, Lu, Yan, Shaolin, and Wu, Judy Z
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SUPERCONDUCTIVITY , *SUPERCONDUCTING thin films , *CRITICAL current density (Superconductivity) , *LIQUID nitrogen , *EPITAXIAL layers , *THIN films testing - Abstract
A cation exchange method was applied to convert epitaxial TlBa2Ca2Cu3O8 (Tl-1223) and Tl2Ba2Ca2Cu3O10 (Tl-2223) precursor superconducting thin films to epitaxial HgBa2Ca2Cu3O8+δ (Hg-1223) films on LaAlO3 (001) substrates. While the conversion of Tl-1223 to Hg-1223 was partially successful, high-quality epitaxial Hg-1223 films were obtained from Tl-2223 precursor films. A critical transition temperature Tc of up to 132 K has been demonstrated for the Hg-1223 films, which is close to the optimal value of 135 K reported on Hg-1223 bulk samples. The critical current density Jc of the Hg-1223 films was up to 0.25 MA cm−2 at 77 K and self-field. This work represents the first success in achieving the highest-Tc epitaxial Hg-1223 films using the cation exchange method, which are promising candidates for device applications with operational temperatures significantly above the temperature of liquid nitrogen. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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121. Critical current density enhancement of Bi, Pb-2223 thin film fabricated by RF sputtering and post-annealing processes.
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Matsumoto, A and Kitaguchi, H
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CRITICAL current density (Superconductivity) , *SUPERCONDUCTING thin films , *RADIOFREQUENCY sputtering , *SUPERCONDUCTING transitions , *ANISOTROPY , *ANNEALING of semiconductors - Abstract
In this study, the microstructures and superconducting properties of Bi, Pb-2223 thin films on SrTiO3(100) fabricated by radio-frequency (RF) sputtering and annealing have been investigated. Most of the as-deposited films fabricated by RF sputtering did not exhibit a superconducting transition, due to low crystallinity, deviation from the composition of Bi-2223, and low intergrain connectivity. The as-deposited films did not contain Pb. To obtain the Bi, Pb-2223 phase, we annealed the film with Bi, Pb-2223 pellets and powder. After annealing, we confirmed that the thin film contained Pb. A zero-resistance transition temperature of 100 K was obtained in the Bi, Pb-2223 thin film after post-annealing. We observed strong 00l peaks and a sharp quadrupole in x-ray θ–2θ and ϕ-scan measurements. These results suggested that this film consists of a single phase of Bi, Pb-2223 and has a biaxial orientation. The Bi, Pb-2223 thin film had a maximum critical current density of 0.9 × 105 A cm−2 at 77 K in a self-field. Furthermore, Bi, Pb-2223 exhibited very strong anisotropy in its critical current density–magnetic field angle characteristics. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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122. Filtering Properties of Photonic Crystal Dual-Channel Tunable Filter Containing Superconducting Defects.
- Author
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Liu, Jia-Wei, Chang, Tsung-Wen, and Wu, Chien-Jang
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PHOTONIC crystals , *CRYSTAL structure , *CRYSTAL filters , *SUPERCONDUCTING thin films , *DIELECTRICS , *STRONTIUM titanate , *ALUMINUM oxide - Abstract
In this work, we analyze filtering properties in a photonic crystal (PC) dual-channel tunable filter. The filter structure containing twin superconducting thin films is denoted as (1/2)S(2/1)S(1/2). Here, 1 and 2 are dielectrics of SrTiO and AlO, respectively. S and S are two high-temperature superconducting thin films taken to be the typical system, YBaCuO. The two channel frequencies can be designed to locate within the photonic band gap (PBG) of the original PC (1/2). Channel frequencies can be significantly changed by changing N, the stack number of the center PC. With the use of superconducting defects, channel frequencies are temperature-dependent, that is, the filter is thermally tunable. The proposed filter structure is of technical use in superconducting photonic applications at terahertz frequency. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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123. Effect of oxygenation process on flux pinning in pristine and BaHfO3 nanocomposite GdBa2Cu3O7 superconducting thin films
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Jens Hänisch, I. Van Driessche, Bernhard Holzapfel, Kai Ackermann, Hannes Rijckaert, and Ruslan Popov
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History ,Flux pinning ,Nanocomposite ,GD ,Annealing (metallurgy) ,Physics ,Superconducting thin films ,Analytical chemistry ,General Physics and Astronomy ,YBA2CU3O7-DELTA ,Partial pressure ,Oxygenation ,Laser ,DIFFUSION ,Computer Science Applications ,Education ,law.invention ,Chemistry ,law ,ddc:530 ,Angular dependence ,COATED CONDUCTORS - Abstract
Pristine and BaHfO3 (BHO) nanocomposite GdBa2Cu3O7 (GdBCO) superconducting thin films were deposited at 800 °C, 0.4 mbar O2 partial pressure using a Nd:YAG laser (λ=355 nm) with 10 Hz frequency on MgO substrate. The influence of the oxygenation process on flux pinning and electrical transport properties was investigated by changing the annealing temperature (T ann) between 450 °C and 780 °C and the holding time (t hold) between 10 and 30 min. The irreversibility field shows the largest shift toward higher fields for T ann = 450 °C and thus the largest in-field J c. Angular dependence of J c for most of the pristine GdBCO films exhibits a large peak for B‖c, however the sample with T ann = 550 °C has a large peak in the 90°-120° region, i.e. near B ‖ ab. For BHO nanocomposites, a decrease in T ann increases in-field J c by a factor of 2.
- Published
- 2020
124. Tuning the Resistive Switching of Superconducting Films by Geometry Effects
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Nadia Martucciello, Francesco Avitabile, Gaia Grimaldi, Antonio Leo, J. C. Villegier, Angela Nigro, and Sandro Pace
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Materials science ,Photon ,Flux pinning ,superconducting thin films ,Field (physics) ,Nucleation ,Geometry ,02 engineering and technology ,01 natural sciences ,Instability ,Critical currents ,flux pinning ,superconducting detectors ,Electronic, Optical and Magnetic Materials ,Condensed Matter Physics ,Electrical and Electronic Engineering ,Condensed Matter::Superconductivity ,0103 physical sciences ,Electronic ,Optical and Magnetic Materials ,010306 general physics ,Superconductivity ,021001 nanoscience & nanotechnology ,Magnetic field ,Vortex ,0210 nano-technology - Abstract
In a superconducting photon detector, the effective transition to the normal state can be induced by the instability of the flux flow regime. Indeed, in the presence of self-magnetic field, the local suppression of superconductivity induced by photon absorption determines vortex nucleation and flux flow regime, which can make the superconducting state unstable. Understanding such instability can boost the performances of those superconducting devices based on this resistive switching. Here, we present the study of the geometry influence on such instability in NbN and NbTiN ultrathin films. Despite the same patterned microbridge geometry, the two superconductors show different behaviors at very low applied magnetic fields. A comparison with other superconductors outlines the possibility to tune the resistive switching by geometry effects in interesting materials for devices applications. Finally, we also report the influence of the cooling environment on the electric critical power in superconducting thin films.
- Published
- 2018
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125. High efficiency preparation of Bi2Sr2CaCu2O8+δ superconducting thin films by an acetate based Sol-Gel process
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Li Lei, Gaoyang Zhao, Xinxiong Fang, Xiaoqin Liu, and Jiqiang Jia
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Superconductivity ,Materials science ,Superconducting thin films ,Analytical chemistry ,02 engineering and technology ,Partial pressure ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Epitaxy ,01 natural sciences ,Metal ,visual_art ,0103 physical sciences ,visual_art.visual_art_medium ,General Materials Science ,010306 general physics ,0210 nano-technology ,Single crystal ,Phase purity ,Sol-gel - Abstract
Bi2Sr2CaCu2O8+δ (Bi-2212) superconducting thin films with c-axis epitaxial orientation were prepared on LaAlO3 (LAO) single crystal substrates via a Sol-Gel technique using metallic acetates as starting materials. The influence of the growth temperature and oxygen partial pressure (pO2) on the phase purity and superconducting properties of Bi-2212 was discussed. The results show that Bi-2212 films prepared at 820 °C with the pO2 of 1.4 KPa exhibit good in-plane and out-of-plane growth textures and excellent superconducting properties with high critical transition temperature (Tc) of 88 K and narrow transition width (ΔTc) of 4.8 K.
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- 2018
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126. Nonlinear microwave photon occupancy of a driven resonator strongly coupled to a transmon qubit.
- Author
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Palmer, B. S., Novikov, S., Suri, B., Keane, Z. K., Bishop, Lev S., and Wellstood, F. C.
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- *
MICROWAVE photonics , *RESONATORS , *QUBITS , *SUPERCONDUCTING thin films , *JAYNES-Cummings model - Abstract
We measure photon occupancy in a thin-film superconducting lumped element resonator coupled to a transmon qubit at 20 mK and find a nonlinear dependence on the applied microwave power. The transmon-resonator system was operated in the strong dispersive regime, where the ac Stark shift (2χ) due to a single microwave photon present in the resonator was larger than the line width (T) of the qubit transition. When the resonator was coherently driven at 5.474 325 GHz, the transition spectrum of the transmon at 4.982 GHz revealed well-resolved peaks, each corresponding to an individual photon number-state of the resonator. From the relative peak heights we obtain the occupancy of the photon states and the average photon occupancy ... of the resonator. We observe a nonlinear variation of ... with the applied drive power Prf for ... < 5 and compare our results to numerical simulations of the system-bath master equation in the steady state, as well as to a semiclassical model for the resonator that includes the Jaynes-Cummings interaction between the transmon and the resonator. We find good quantitative agreement using both models and analysis reveals that the nonlinear behavior is principally due to shifts in the resonant frequency caused by a qubit-induced Jaynes-Cummings nonlinearity. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
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127. Structural properties of gold modified YBa2Cu3O7−δ thin films.
- Author
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Katzer, C, Westerhausen, M, Uschmann, I, Schmidl, F, Hübner, U, and Seidel, P
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SUPERCONDUCTING thin films , *PULSED laser deposition , *GOLD nanoparticles , *X-ray diffraction , *STOICHIOMETRY , *SCANNING electron microscopy - Abstract
YBa2Cu3O7−δ thin films were prepared by pulsed laser deposition whereby single-crystalline Au nanoparticles were embedded via a self-assembly process out of an initial Au seed layer. The size of the Au nanoparticles was controlled via the initial Au seed layer thickness. During the growth of the YBa2Cu3O7−δ matrix the nanoparticles are partly lifted on top of the YBa2Cu3O7−δ thin film. The inclusion of nanoparticles thus offers the possibility of shunting thin contamination layers on top of the YBa2Cu3O7−δ thin film and even allows contact with the lower electrode in multilayer systems without using difficult etching methods. Using x-ray diffraction and scanning electron microscopy we show that the growth conditions of the YBa2Cu3O7−δ matrix are modified, resulting in less a-axis growth and an enhanced oxygen stoichiometry. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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- View/download PDF
128. Coherent magnetic vortex motion in optically formed channels for easy flow in YBa2Cu3O7−x superconducting thin films.
- Author
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Jukna, A., Steponavičienė, L., Plaušinaitienė, V., Abrutis, A., Maneikis, A., Šliužienė, K., Lisauskas, V., and Sobolewski, Roman
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COHERENCE (Optics) , *VORTEX motion , *CHANNEL flow , *YTTRIUM compounds , *SUPERCONDUCTING thin films , *ELECTRIC properties of metals , *MAGNETIC properties of metals , *MAGNETIC flux - Abstract
We report our results of investigation of electric and magnetic properties of partially oxygen-depleted channels for easy vortex motion in YBa 2Cu 3O 7−x (YBCO) superconducting, 50-μm-wide, and 100-μm-long microbridges at temperatures below the onset of the superconducting state critical temperature Tcon. The channels were produced by means of a laser-writing technique. The writing was performed using a 0.1–0.3 W power, continuous-wave laser radiation focused down to a ~ 5 μm spot on the surface of a superconducting film in a nitrogen gas atmosphere, and resulted in perpendicular stripes (channels) with partial ( x ~ 0.2) reduction of the oxygen content in the YBCO stripe. The oxygen-depleted channels exhibit a depressed Tc and lower both the critical current density and the first critical magnetic field, as compared with the laser-untreated areas. The bias current applied to the bridge self-produced a magnetic flux that penetrated the channels in a form of Abrikosov magnetic vortices that, subsequently, moved coherently (a quasi-Josephson effect) along the channels in the narrow temperature range of 0.943 Tcon–0.98 Tcon and manifested themselves as steps on the current–voltage characteristics of our microbridges. Our results demonstrate that laser-induced formation of artificial channels of the flux flow can be used for a precise control of vortex nucleation and their coherent motion in pre-assigned regions of thin-film YBCO devices. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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129. A water-free metal organic deposition method for YBa2Cu3O7−δ thin film fabrication.
- Author
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Huang, Rongxia, Feng, Feng, Wu, Wei, Xue, Yunran, Zhang, Yanyi, Shi, Kai, Qu, Timing, Zhao, Yongjie, Wang, Xiaohao, Zhang, Xiaowen, and Han, Zhenghe
- Subjects
- *
THERMAL properties , *SUPERCONDUCTING thin films , *METHANOL , *PYROLYSIS , *CRITICAL current density (Superconductivity) , *X-ray diffraction , *CHEMICAL solution deposition - Abstract
During the fabrication of YBa2Cu3O7−δ (YBCO) thin films via the metal organic deposition (MOD) method, the water content of the precursor solution should be reduced to prevent precipitation and other detriment. In most of the reported MOD-YBCO studies, water was used as a solvent, and vacuum distillation was utilized to reduce the water content of the precursor solution. In this study, we propose a water-free MOD method using propionic anhydride and methanol as the solvents. The crystal water of raw precursor salts was removed by heating, and the water content in the final precursor solution was as low as 0.2 wt%. Using this solution with low fluorine content and the optimized maximum temperature of pyrolysis, the final YBCO thin films about 250 nm thick had the critical current density (Jc) of 3.8 MA cm−2 (77 K, self-field). The water content of the precursor solution was further reduced to less than 10−2 wt% by vacuum distillation. According to the Jc performance, thermal analysis, x-ray diffraction investigations, and morphology observations, no significant improvement was found for the final YBCO thin films fabricated by the distilled solution, indicating that vacuum distillation is not necessary in the water-free MOD method. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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130. Superconducting properties of FeSexTe1−x thin film with a composition close to antiferromagnetic ordering.
- Author
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Chen, Li, Huang, Jijie, Tsai, Chen-Fong, Zhu, Yuanyuan, Jian, Jie, Chen, Aiping, Bi, Zhenxing, Khatkhatay, Fauzia, Cornell, Nicholas, Zakhidov, Anvar, and Wang, Haiyan
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SUPERCONDUCTING thin films , *ANTIFERROMAGNETIC materials , *CRITICAL current density (Superconductivity) , *FLUX pinning , *SCANNING transmission electron microscopy - Abstract
In this study Te-rich iron chalcogenide (FeSexTe1−x) thin films with a composition close to antiferromagnetic ordering have been deposited on SrTiO3 (STO) substrates. The superconducting critical transition temperature (Tc) of the FeSe0.1Te0.9 thin film on STO substrate ranges from ∼12.5 to ∼13.3 K. The upper critical field is as high as 114 T, which is much higher than that of the FeSe0.5Te0.5 thin film on STO substrate (∼49 T). The self-field critical current density () at 2 K of 1.8 × 105 A cm−2 is much higher than that of the FeSe0.5Te0.5 thin film, and the FeSe0.1Te0.9 thin film also demonstrates superior pinning properties under applied magnetic field. Compared to FeSe0.5Te0.5, which was considered as the optimum composition, FeSe0.1Te0.9 presents even more promise for high field applications because of its high upper critical field and high critical current density. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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131. A signal input coil made of superconducting thin film for improved signal-to-noise ratio in a high-Tc SQUID-based ultra-low field nuclear magnetic resonance system.
- Author
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Chen, Kuen-Lin, Hsu, Chin-Wei, Ku, Yue-Bai, Chen, Hsin-Hsien, Liao, Shu-Hsien, Wang, Li-Min, Horng, Herng-Er, and Yang, Hong-Chang
- Subjects
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SUPERCONDUCTING thin films , *SUPERCONDUCTING quantum interference devices , *NUCLEAR magnetic resonance , *SUPERCONDUCTING coils , *ELECTRIC inductance measurement , *SIGNAL-to-noise ratio , *THIN films testing - Abstract
Resonant coupling schemes are commonly used in SQUID-based ultra-low field (ULF) nuclear magnetic resonance (NMR) systems to couple the spin relaxation signals from samples to the SQUID. Generally, in NMR systems, a resonant coupling scheme is composed of two solenoid coils which are made of enamel insulated wires and a capacitor connected in series. In this work, we tried to replace the metal solenoid input coil with a planar high-Tc superconducting spiral coil to improve the signal-to-noise ratio (SNR) of the ULF NMR signal. A measurement of the free induction decay signal of water protons was performed to demonstrate the improved performance of the system. This improvement is due to the fact that the planar superconducting spiral coil possesses a higher mutual inductance with the SQUID. Therefore, it is a promising way to enhance the SNR of high-Tc SQUID-based ULF NMR/MRI systems. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
132. Trapped magnetic field profiles of arrays of (Gd,Y)Ba2Cu3Ox superconductor tape in different stacking configurations.
- Author
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Selva, Kavita and Majkic, Goran
- Subjects
- *
SUPERCONDUCTING arrays , *MAGNETIC field effects , *SUPERCONDUCTING thin films , *RARE earth metals , *SUPERCONDUCTING tape , *MAGNETIZATION - Abstract
Trapped magnetic field profiles were investigated in thin film (Gd,Y)Ba2Cu3Ox superconducting tapes stacked in different configurations consisting of three 12 mm wide, 36 mm long tapes per layer. The trapped magnetic field values were found to increase monotonically with the increasing number of tape layers in the stack. A crisscross arrangement of the tapes was found to yield a more uniform trapped-field profile than a straight arrangement of the tapes. Furthermore, the decay rate of the trapped magnetic field as a function of distance from the tape stack surface was found to be lower in the crisscross arrangement. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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133. Pinning enhancement in MgB superconducting thin films by magnetic nanoparticles of FeO.
- Author
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KOPARAN, E, SURDU, A, KIZILKAYA, K, SIDORENKO, A, and YANMAZ, E
- Subjects
- *
MAGNESIUM compounds , *SUPERCONDUCTING thin films , *FLUX pinning , *MAGNETIC nanoparticles , *FERRIC oxide , *ELECTROFORMING , *MAGNETRON sputtering - Abstract
MgB thin films were fabricated on r-plane AlO ( ${1} \overline{{1}} {0} {2})$ substrates. First, deposition of boron was performed by rf magnetron sputtering on AlO substrates and followed by a post-deposition annealing at 850 °C in magnesium vapour. In order to investigate the effect of FeO nanoparticles on the structural and magnetic properties of films, MgB films were coated with different concentrations of FeO nanoparticles by spin coating process. The magnetic field dependence of the critical current density J was calculated from the M-H loops and magnetic field dependence of the pinning force density, f( b), was investigated for the films containing different concentrations of FeO nanoparticles. The critical current densities, J, in 3T magnetic field at 5 K were found to be around 2·7 × 10 A/cm, 4·3 × 10 A/cm, 1·3 × 10 A/cm and 5·2 × 10 A/cm for films with concentrations of 0, 25, 50 and 100% FeO, respectively. It was found that the films coated with FeO nanoparticles have significantly enhanced the critical current density. It can be noted that especially the films coated by FeO became stronger in the magnetic field and at higher temperatures. It was believed that coated films indicated the presence of artificial pinning centres created by FeO nanoparticles. The results of AFM indicate that surface roughness of the films significantly decreased with increase in concentration of coating material. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
134. Proposed Measurement of Spatial Correlations at the Berezinski-Kosterlitz-Thouless Transition of Superconducting Thin Films.
- Author
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Erez, Amir and Meir, Yigal
- Subjects
- *
SUPERCONDUCTING thin films , *PHASE transitions , *COHERENCE (Physics) , *THIN films , *TRAILS - Abstract
The Berezinski-Kosterlitz-Thouless transition is a unique two-dimensional phase transition, separating two phases with exponentially and power-law decaying correlations, respectively. In disordered systems, these correlations propagate along favorable paths, with the transition marking the point where global coherence is lost. Here we propose an experimental method to probe locally these particular paths in superconducting thin films, which exhibit this transition, and demonstrate theoretically that close to the transition the coherence propagates along a ramified network, reminiscent of a percolation transition. We suggest and calculate experimentally accessible quantities that can shed light on the spatial correlations in the system as it approaches the critical point. This approach can be applicable to a variety of phase transitions in disordered systems. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
135. Fabrication of superconducting tantalum nitride thin films using infrared pulsed laser deposition.
- Author
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Chaudhuri, Saumyadip, Maasilta, Ilari J., Chandernagor, Lucie, Ging, Marion, and Lahtinen, Manu
- Subjects
TANTALUM compounds ,METALLIC films ,SUPERCONDUCTING thin films ,PULSED laser deposition ,MANGANESE oxides ,SILICA ,SCANNING electron microscopy ,CRYSTAL structure - Abstract
The authors report the successful fabrication of superconducting tantalum nitride (TaN) thin films using a pulsed laser deposition technique with 1064 nm radiation. Films with thickness ∼100 nm deposited on MgO (100) single crystals and on oxidized silicon (SiO2) substrates exhibited a superconducting transition temperature of ∼8 K and 6 K, respectively. The topography of these films were investigated using atomic force and scanning electron microscopy, revealing fairly large area particulate free and smooth surfaces, while the structure of the films were investigated using θ-2θ and glancing angle x-ray diffraction techniques. For films grown on MgO a face-centered cubic phase of TaN was observed, while films grown on SiO2 exhibited the face-centered cubic as well as a mononitride hexagonal phase. The transition temperature of the TaN deposited on SiO2 was found to be more sensitive to the nitrogen pressure during deposition as compared to the TaN deposited on MgO. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
136. Manifestation of the magnetic moments of Cooper pairs in low-temperature properties of superconducting thin-film rings.
- Author
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Agafonov, A.I.
- Subjects
- *
MAGNETIC moments , *COOPER pair , *LOW temperatures , *SUPERCONDUCTING thin films , *SYMMETRY (Physics) , *SUPERCONDUCTORS - Abstract
Highlights: [•] The pairing symmetry determines the intrinsic magnetic moment of the Cooper pairs. [•] The magnetic moments can be tested in experiments with superconducting film rings. [•] The current-carrying thin-film rings made of the cuprate superconductors, are studied. [•] Finding of the magnetic moments can shed light on the pairing symmetry in cuprates. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
137. Influence of initial pH on the microstructure of YBa2Cu3O7−x superconducting thin films derived from DEA-aqueous sol–gel method.
- Author
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Tang, Xiao, Zhao, Yue, and Grivel, Jean-Claude
- Subjects
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COPPER oxide , *PH effect , *METAL microstructure , *SUPERCONDUCTING thin films , *SOL-gel processes , *AQUEOUS solutions - Abstract
Abstract: A fluorine-free aqueous sol–gel technique was used to fabricate YBCO superconducting thin films. Acetic acid was added in order to modify the complexation process taking place between the metal cations and the organic chelating agents. The electrical resistance and the pH value were used as indicators of the quality of the precursors. When pH=6.5, the precursor solution had the lowest resistance, implying a good ionization of the starting metal elements. By using the optimal precursor, the film was found to have very small sized particles after pyrolysis. Consequently, the annealed YBCO films are characterized by a sharp superconducting transition with a Jc (77K) of 0.25MA/cm2. [Copyright &y& Elsevier]
- Published
- 2013
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138. Realization of Artificial Ice Systems for Magnetic Vortices in a Superconducting MoGe Thin Film with Patterned Nanostructures.
- Author
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Latimer, M. L., Berdiyorov, G. R., Xiao, Z. L., Peeters, F. M., and Kwok, W. K.
- Subjects
- *
SPHEROMAKS , *SUPERCONDUCTING thin films , *NANOSTRUCTURES , *COMPUTER simulation , *LANDAU theory , *CRITICAL currents - Abstract
We report an anomalous matching effect in MoGe thin films containing pairs of circular holes arranged in such a way that four of those pairs meet at each vertex point of a square lattice. A remarkably pronounced fractional matching was observed in the magnetic field dependences of both the resistance and the critical current. At the half matching field the critical current can be even higher than that at zero field. This has never been observed before for vortices in superconductors with pinning arrays. Numerical simulations within the nonlinear Ginzburg-Landau theory reveal a square vortex ice configuration in the ground state at the half matching field and demonstrate similar characteristic features in the field dependence of the critical current, confirming the experimental realization of an artificial ice system for vortices for the first time. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
139. Low Temperature Vortex Dynamics in Superconducting Nb Films Containing Square and Rectangular Arrays of Ni Nanodots.
- Author
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Chiliotte, C. E., Carreira, S. J., Bekeris, V., Gomez, A., Gonzalez, E. M., Prieto, J. L., and Vicent, J. L.
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NIOBIUM alloys , *NICKEL alloys , *VORTEX lattice method , *METALS at low temperatures , *SUPERCONDUCTORS , *TEMPERATURE measurements , *MAGNETIC noise , *MAGNETIC flux - Abstract
We examine the vortex lattice (VL) dynamics in superconducting Nb films containing square and rectangular arrays of Ni nanodots, using ac susceptibility techniques. A remarkable robust feature is the increase in pinning that occurs for magnetic fields that create integer n or half integer flux lines per pinning cell. This phenomenology has been reported in transport experiments performed very close to the sample critical temperature TC. In our contactless experiments we determined vortex mobility and pinning properties in an extended temperature range 0.65 < T/TC < 0.99. This was possible after growing larger samples, in the square millimeters range, with top down techniques. For the square pinning array, matching up to n = 8 was observed and pinning for n = 3, 4 and 5 show different characteristics, in agreement with published simulations. For the rectangular array, some of the matching orders are missing and we do not find clear evidence of a reconfiguration transition, where vortex commensuration changes from a rectangular cell to a square cell, as reported near TC in earlier transport experiments. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
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140. Nonlocal spin correlations mediated by a superconductor.
- Author
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Taewan Noh, Manuel Houzet, Meyer, Julia S., and Chandrasekhar, Venkat
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- *
SUPERCONDUCTING thin films , *CRYOELECTRONICS , *CONSTITUTION of matter , *PARTICLES (Nuclear physics) , *NUCLEAR physics - Abstract
Nonlocal charge correlations induced in two normal metals contacted separately to a superconductor have been studied intensively in the past few years. Here we investigate nonlocal correlations induced by the transfer of pure spin currents through a superconductor on a scale comparable to the superconducting coherence length. As with charge currents, two processes contribute to the nonlocal spin signal: crossed Andreev reflection (CAR), where an electron with spin-up injected from one normal metal into the superconductor results in a hole with spin-down being injected into the second normal metal, and elastic cotunneling (EC), where the electron with spin-up injected from the first normal metal results in an electron with spin-up being injected into the second normal metal. Unlike charge currents, however, the spin currents associated with CAR and EC add due to the fact that the bulk superconductor cannot sustain ε net spin current. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
141. Enhancing the critical current of a superconducting film in a wide range of magnetic fields with a conformal array of nanoscale holes.
- Author
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Wang, Y. L., Latimer, M. L., Xiao, Z. L., Divan, R., Ocola, L. E., Crabtree, G. W., and Kwok, W. K.
- Subjects
- *
SUPERCONDUCTING thin films , *CRITICAL currents , *SUPERCONDUCTIVITY , *MAGNETIC fields , *MAGNETIC flux - Abstract
The maximum current (critical current) a type-II superconductor can transmit without energy loss is limited by the motion of the quantized magnetic flux penetrating into a superconductor. Introducing nanoscale holes into a superconducting film has been long pursued as a promising way to increase the critical current. So far the critical current enhancement was found to be mostly limited to low magnetic fields. Here we experimentally investigate the critical currents of superconducting films with a conformal array of nanoscale holes that have nonuniform density while preserving the local ordering. We find that the conformal array of nanoscale holes provides a more significant critical current enhancement at high magnetic fields. The better performance can be attributed to its arching effect that not only gives rise to the gradient in hole density for pinning vortices with a wide range of densities but also prevents vortex channeling occurring in samples with a regular lattice of holes. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
142. The Effects of Pinning on Critical Currents of Superconducting Films.
- Author
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Simões, R., Venegas, P., and Mello, D.
- Subjects
- *
CRITICAL current density (Superconductivity) , *SUPERCONDUCTING thin films , *DISLOCATION pinning , *MOLECULAR dynamics , *SIMULATION methods & models , *ANISOTROPY - Abstract
Using molecular dynamics simulations, we analyze the effects of artificial periodic arrays of pinning sites on the critical current of superconducting thin films as a function of vortex density. We analyze two types of periodic pinning array: hexagonal and Kagomé. For the Kagome pinning network we make calculations using two directions of transport current: along and perpendicular to the main axis of the lattice. Our results show that the hexagonal pinning array presents higher critical currents than the Kagomé and random pinning configuration for all vortex densities. In addition, the Kagomé networks show anisotropy in their transport properties. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
143. Enhanced pinning in superconducting thin films with graded pinning landscapes.
- Author
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Motta, M., Colauto, F., Ortiz, W. A., Fritzsche, J., Cuppens, J., Gillijns, W., Moshchalkov, V. V., Johansen, T. H., Sanchez, A., and Silhanek, A. V.
- Subjects
- *
SUPERCONDUCTING thin films , *SEMICONDUCTOR quantum dots , *MAGNETIZATION , *MAGNETOOPTICS , *THERMOMAGNETIC effects - Abstract
A graded distribution of antidots in superconducting a-Mo79Ge21 thin films has been investigated by magnetization and magneto-optical imaging measurements. The pinning landscape has maximum density at the sample border, decreasing linearly towards the center. Its overall performance is noticeably superior than that for a sample with uniformly distributed antidots: For high temperatures and low fields, the critical current is enhanced, whereas the region of thermomagnetic instabilities in the field-temperature diagram is significantly suppressed. These findings confirm the relevance of graded landscapes on the enhancement of pinning efficiency, as recently predicted by Misko and Nori [Phys. Rev. B 85, 184506 (2012)]. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
144. Characterization of the thin-film NbN superconductor for single-photon detection by transport measurements.
- Author
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Shi-Zeng Lin, Ayala-Valenzuela, Oscar, McDonald, Ross D., Bulaevskii, Lev N., Holesinger, Terry G., Ronning, Filip, Weisse-Bernstein, Nina R., Williamson, Todd L., Mueller, Alexander H., Hoffbauer, Mark A., Rabin, Michael W., and Graf, Matthias J.
- Subjects
- *
QUASIPARTICLES , *SUPERCONDUCTING thin films , *TRANSMISSION electron microscopy , *SCANNING electron microscopy , *ELECTRICAL resistivity , *MAGNETIC fields , *NIOBIUM nitride - Abstract
The fabrication of high-quality thin superconducting films is essential for single-photon detectors. Their device performance is crucially affected by their material parameters, thus requiring reliable and nondestructive characterization methods after the fabrication and patterning processes. Important material parameters to know are the resistivity, superconducting transition temperature, relaxation time of quasiparticles, and uniformity of patterned wires. In this work, we characterize micropatterned thin NbN films by using transport measurements in magnetic fields. We show that from the instability of vortex motion at high currents in the flux-flow state of the / V characteristic, the inelastic lifetime of quasiparticles can be determined to be about 2 ns. Additionally, from the depinning transition of vortices at low currents, as a function of magnetic field, the size distribution of grains can be extracted. This size distribution is found to be in agreement with the film morphology obtained from scanning electron microscopy and high-resolution transmission electron microscopy images. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
145. Robustness of the Berezinskii-Kosterlitz-Thouless transition in ultrathin NbN films near the superconductor-insulator transition.
- Author
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Jie Yong, Lemberger, T. R., Benfatto, L., Ilin, K., and Siegel, M.
- Subjects
- *
SUPERCONDUCTING transitions , *SUPERCONDUCTING thin films , *ROBUST control , *QUANTUM point contacts , *SUPERFLUIDITY , *CRITICAL point (Thermodynamics) , *NIOBIUM nitride - Abstract
Occurrence of the Berezinskii-Kosterlitz-Thouless (BKT) transition is investigated by superfluid density measurements for two-dimensional (2D) disordered NbN films with disorder level very close to a superconductor-insulator transition (SIT). Our data show a robust BKT transition even near this 2D disorder-tuned quantum critical point. This observation is in direct contrast with previous data on deeply underdoped quasi-2D cuprates near the SIT. As our NbN films approach the quantum critical point, the vortex core energy, an important energy scale in the BKT transition, scales with the superconducting gap, not with the superfluid density, as expected within the standard 2D-.XT model description of BKT physics. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
146. Universal scaling of the order-parameter distribution in strongly disordered superconductors.
- Author
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Lemarie, G., Kamlapure, A., Bucheli, D., Benfatto, L., Lorenzana, J., Seibold, G., Ganguli, S. C., Raychaudhuri, P., and Castellani, C.
- Subjects
- *
SUPERCONDUCTING transitions , *NIOBIUM nitride , *SCANNING tunneling microscopy , *SUPERCONDUCTING thin films , *INHOMOGENEOUS materials - Abstract
We investigate theoretically and experimentally the statistical properties of the inhomogeneous order-parameter distribution (OPD) at the verge of the superconductor-insulator transition (SIT). We find within two prototype fermionic and bosonic models for disordered superconductors that one can identify a universal reseating .of. the OPD. By performing scanning-tunneling microscopy experiments in three samples of NbN with increasing disorder we show that such a reseating also describes the experimental data with excellent accuracy. These results . can provide a breakthrough in our understanding of the SIT. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
147. Infrared vortex-state electrodynamics in type-II superconducting thin films.
- Author
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Xiaoxiang Xi, J. -H. Park, Graf, D., Carr, L., and Tanner, D. B.
- Subjects
- *
ELECTRIC properties of thin films , *ELECTRODYNAMICS , *SUPERCONDUCTING thin films , *REFLECTANCE spectroscopy , *MAGNETIC fields , *OPTICAL conductivity , *NIOBIUM nitride - Abstract
The vortex-state electrodynamics of s-wave superconductors has been studied by infrared spectroscopy. Far-infrared transmission and reflection spectra of superconducting Nb0.5Ti0.5N and NbN thin films were measured in a magnetic field perpendicular to the film surface, and the optical conductivity was extracted. The data show clear reduction of superconducting signature. We consider the vortex state as a two-component effective medium of normal cores embedded in a BCS superconductor. The spectral features are well explained by the Maxwell Garnett theory. Our analysis supports the presence of magnetic-field-induced pair-breaking effects in the superconducting component outside of the vortex cores. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
148. Parametric resonance in tunable superconducting cavities.
- Author
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Wustmann, Waltraut and Shumeiko, Vitaly
- Subjects
- *
TUNABLE lasers , *SUPERCONDUCTING thin films , *SUPERCONDUCTING quantum interference devices , *QUANTUM fluctuations , *QUBITS - Abstract
We develop a theory of parametric resonance in tunable superconducting cavities. The nonlinearity introduced by the superconducting quantum interference device (SQUID) attached to the cavity and damping due to connection of the cavity to a transmission line are taken into consideration. We study in detail the nonlinear classical dynamics of the cavity field below and above the parametric threshold for the degenerate parametric resonance, featuring regimes of multistability and parametric radiation. We investigate the phase-sensitive amplification of external signals on resonance, as well as amplification of detuned signals, and relate the amplifier performance to that of linear parametric amplifiers. We also discuss applications of the device for dispersive qubit readout. Beyond the classical response of the cavity, we investigate small quantum fluctuations around the amplified classical signals. We evaluate the noise power spectrum both for the internal field in the cavity and the output field. Other quantum-statistical properties of the noise are addressed such as squeezing spectra, second-order coherence, and two-mode entanglement. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
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149. Evidence of a full gap in LaFeAsO1-xFx thin films from infrared spectroscopy.
- Author
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Xiaoxiang Xi, Dai, Y. M., Homes, C. C., Kidszun, M., Haindl, S., and Carr, G. L.
- Subjects
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SUPERCONDUCTING thin films , *INFRARED spectroscopy , *LANTHANUM , *IRON , *ARSENIC oxides , *DRUDE theory , *QUASIPARTICLES , *EXPERIMENTS - Abstract
We report conventional and time-resolved infrared spectroscopy on LaFeAsO1-xFx superconducting thin films. The far-infrared transmission can be quantitatively explained by a two-component model including a conventional s-wave superconducting term and a Drude term, suggesting at least one carrier system has a full superconducting gap. Photoinduced studies of excess quasiparticle dynamics reveal a nanosecond effective recombination time and temperature dependence that strongly support a recombination bottleneck in the presence of a full gap. The two experiments provide consistent evidence of a full, nodeless, though not necessarily isotropic, gap for at least one carrier system in LaFeAsO1-xFx. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
150. Analysis of superconducting FeSe thin films deposited by a sputtering technique.
- Author
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Schneider, R., Zaitsev, A. G., Fuchs, D., and Fromknecht, R.
- Subjects
- *
SUPERCONDUCTING thin films , *METAL organic chemical vapor deposition , *CRYSTALLINE electric field , *MAGNESIUM oxide crystals , *STOICHIOMETRY , *POLYCRYSTALLINE semiconductors , *FERMI liquids - Abstract
Superconducting FeSe thin films have been deposited onto (001)-oriented single-crystalline MgO substrates by conventional radio-frequency magnetron co-sputtering of a FeSe target and a pure Se target. The composition of the films is within the homogeneity range of the tetragonal β phase close to stoichiometry. Films with a minimum residual resistivity and a maximum superconducting transition temperature can be prepared within a narrow substrate temperature range from 480 to 510 °C. In contrast to the equilibrium phase diagram the β phase surprisingly exists in thin films deposited at substrate temperatures as high as 680 °C. The polycrystalline tetragonal films grow with a preferred c-axis texture and a tiny admixture of misaligned grains. The temperature-dependent resistivity reveals a low-temperature linear part and a high-temperature part with a pronounced negative curvature. The origin of the non-Fermi liquid behaviour and the underlying electron scattering mechanisms are still unknown so far. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
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