Sample records for high-temperature superconducting films

  1. High-field magnets using high-critical-temperature superconducting thin films

    DOEpatents

    Mitlitsky, F.; Hoard, R.W.

    1994-05-10

    High-field magnets fabricated from high-critical-temperature superconducting ceramic (HTSC) thin films which can generate fields greater than 4 Tesla are disclosed. The high-field magnets are made of stackable disk-shaped substrates coated with HTSC thin films, and involves maximizing the critical current density, superconducting film thickness, number of superconducting layers per substrate, substrate diameter, and number of substrates while minimizing substrate thickness. The HTSC thin films are deposited on one or both sides of the substrates in a spiral configuration with variable line widths to increase the field. 4 figures.

  2. High-field magnets using high-critical-temperature superconducting thin films

    DOEpatents

    Mitlitsky, Fred; Hoard, Ronald W.

    1994-01-01

    High-field magnets fabricated from high-critical-temperature superconducting ceramic (HTSC) thin films which can generate fields greater than 4 Tesla. The high-field magnets are made of stackable disk-shaped substrates coated with HTSC thin films, and involves maximizing the critical current density, superconducting film thickness, number of superconducting layers per substrate, substrate diameter, and number of substrates while minimizing substrate thickness. The HTSC thin films are deposited on one or both sides of the substrates in a spiral configuration with variable line widths to increase the field.

  3. Growth and Structure of High-Temperature Superconducting Thin Films

    NASA Astrophysics Data System (ADS)

    Achutharaman, Vedapuram Sankar

    High temperature superconducting thin films with atomic scale perfection are required for technological applications and scientific studies on the mechanism of superconductivity. Ozone assisted molecular beam epitaxy (MBE) has been shown to produce in-situ superconducting thin films. To obtain a well-controlled and reproducible process, some components such as the substrate heater and the substrate holder have to be designed to be compatible with high oxygen partial pressures. Also, to ensure precise stoichiometry and precipitate-free films, evaporation sources and temperature controllers have to be designed for better temperature stability. The investigation of the MBE process and the thin films grown by MBE are required to obtain a better understanding of the growth parameters such as the composition of the film, substrate surface structure, substrate temperature and ozone partial pressure. This can be obtained by dynamically monitoring the growth process by in-situ characterization techniques such as reflection high energy electron diffraction (RHEED). Intensity oscillations of the specular RHEED beam have been observed during the growth of RBa_2Cu_3 O_7 (R = Y,Dy) films on SrTiO _3. A model for the origin of these RHEED intensity oscillations will be proposed from extensive RHEED intensity studies. A mechanism for growth of these oxides by physical vapor deposition techniques such as MBE and pulsed laser deposition will also be developed. To verify both the models, the growth of the superconductors will be simulated by the Monte Carlo method and compared with experimental RHEED observations.

  4. Lanthanum gallate substrates for epitaxial high-temperature superconducting thin films

    NASA Astrophysics Data System (ADS)

    Sandstrom, R. L.; Giess, E. A.; Gallagher, W. J.; Segmuller, A.; Cooper, E. I.

    1988-11-01

    It is demonstrated that lanthanum gallate (LaGaO3) has considerable potential as an electronic substrate material for high-temperature superconducting films. It provides a good lattice and thermal expansion match to YBa2Cu3O(7-x), can be grown in large crystal sizes, is compatible with high-temperature film processing, and has a reasonably low dielectric constant and low dielectric losses. Epitaxial YBa2Cu3O(7-x) films grown on LaGaO3 single-crystal substrates by three techniques have zero resistance between 87 and 91 K.

  5. Thin Film Technology of High-Critical-Temperature Superconducting Electronics.

    DTIC Science & Technology

    1983-12-05

    MD- R136 722 THIN FILM TECHNOLOGY OF HIGH-CRITICAL-TEMPERATURE 1/1 SUPERCONDUCTING ELECTRO..(U) WESTINGHOUSE RESEARCH AND DEVELOPMENT CENTER...critical temperature has been demonstrated. Work will continue in a closed system to eliminate the base superconductor degradation, reduce leakage...a 5% decline in Tc has been demonstrated. Work will continue in a closed system to eliminate the base superconductor degradation, reduce leakage and

  6. High-temperature superconductivity in one-unit-cell FeSe films.

    PubMed

    Wang, Ziqiao; Liu, Chaofei; Liu, Yi; Wang, Jian

    2017-04-20

    Since the dramatic enhancement of the superconducting transition temperature (T c ) was reported in a one-unit-cell FeSe film grown on a SrTiO 3 substrate (1-UC FeSe/STO) by molecular beam epitaxy (MBE), related research on this system has become a new frontier in condensed matter physics. In this paper, we present a brief review on this rapidly developing field, mainly focusing on the superconducting properties of 1-UC FeSe/STO. Experimental evidence for high-temperature superconductivity in 1-UC FeSe/STO, including direct evidence revealed by transport and diamagnetic measurements, as well as other evidence from scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES), are overviewed. The potential mechanisms of the enhanced superconductivity are also discussed. There are accumulating arguments to suggest that the strengthened Cooper pairing in 1-UC FeSe/STO originates from the interface effects, specifically the charge transfer and coupling to phonon modes in the TiO 2 plane. The study of superconductivity in 1-UC FeSe/STO not only sheds new light on the mechanism of high-temperature superconductors with layered structures, but also provides an insight into the exploration of new superconductors by interface engineering.

  7. Fluorescence XAS using Ge PAD: Application to High-Temperature Superconducting Thin Film Single Crystals

    NASA Astrophysics Data System (ADS)

    Oyanagi, H.; Tsukada, A.; Naito, M.; Saini, N. L.; Zhang, C.

    2007-02-01

    A Ge pixel array detector (PAD) with 100 segments was used in fluorescence x-ray absorption spectroscopy (XAS) study, probing local structure of high temperature superconducting thin film single crystals. Independent monitoring of individual pixel outputs allows real-time inspection of interference of substrates which has long been a major source of systematic error. By optimizing grazing-incidence angle and azimuthal orientation, smooth extended x-ray absorption fine structure (EXAFS) oscillations were obtained, demonstrating that strain effects can be studied using high-quality data for thin film single crystals grown by molecular beam epitaxy (MBE). The results of (La,Sr)2CuO4 thin film single crystals under strain are related to the strain dependence of the critical temperature of superconductivity.

  8. Growth And Patterning Of High-Tc Superconducting Films

    NASA Technical Reports Server (NTRS)

    Warner, J. D.; Bhasin, K. B.; Varaljay, N. C.; Bohman, D. Y.; Chorey, C. M.

    1992-01-01

    Superconducting films of YBa(2)Cu(3)O(7-delta), having high superconducting-transition temperatures (Tc's), deposited on LaAlO3 substrates and etched into patterns representative of passive microwave devices, with no deterioration of superconducting properties.

  9. Microwave response of high transition temperature superconducting thin films

    NASA Technical Reports Server (NTRS)

    Miranda, Felix Antonio

    1991-01-01

    We have studied the microwave response of YBa2Cu3O(7 - delta), Bi-Sr-Ca-Cu-O, and Tl-Ba-Ca-Cu-O high transition temperature superconducting (HTS) thin films by performing power transmission measurements. These measurements were carried out in the temperature range of 300 K to 20 K and at frequencies within the range of 30 to 40 GHz. Through these measurements we have determined the magnetic penetration depth (lambda), the complex conductivity (sigma(sup *) = sigma(sub 1) - j sigma(sub 2)) and the surface resistance (R(sub s)). An estimate of the intrinsic penetration depth (lambda approx. 121 nm) for the YBa2Cu3O(7 - delta) HTS has been obtained from the film thickness dependence of lambda. This value compares favorably with the best values reported so far (approx. 140 nm) in single crystals and high quality c-axis oriented thin films. Furthermore, it was observed that our technique is sensitive to the intrinsic anisotropy of lambda in this superconductor. Values of lambda are also reported for Bi-based and Tl-based thin films. We observed that for the three types of superconductors, both sigma(sub 1) and sigma(sub 2) increased when cooling the films below their transition temperature. The measured R(sub s) are in good agreement with other R(sub S) values obtained using resonant activity techniques if we assume a quadratic frequency dependence. Our analysis shows that, of the three types of HTS films studied, the YBa2Cu3O(7 - delta) thin film, deposited by laser ablation and off-axis magnetron sputtering are the most promising for microwave applications.

  10. High-temperature superconductivity: A conventional conundrum

    DOE PAGES

    Božović, Ivan

    2016-01-07

    High-temperature superconductivity in ultrathin films of iron selenide deposited on strontium titanate has been attributed to various exotic mechanisms, and new experiments indicate that it may be conventional, with broader implications.

  11. High temperature superconducting thin film microwave circuits: Fabrication, characterization, and applications

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Warner, J. D.; Romanofsky, R. R.; Heinen, V. O.; Chorey, C. M.

    1990-01-01

    Epitaxial YBa2Cu3O7 films were grown on several microwave substrates. Surface resistance and penetration depth measurements were performed to determine the quality of these films. Here the properties of these films on key microwave substrates are described. The fabrication and characterization of a microwave ring resonator circuit to determine transmission line losses are presented. Lower losses than those observed in gold resonator circuits were observed at temperatures lower than critical transition temperature. Based on these results, potential applications of microwave superconducting circuits such as filters, resonators, oscillators, phase shifters, and antenna elements in space communication systems are identified.

  12. High temperature superconducting thin film microwave circuits - Fabrication, characterization, and applications

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Warner, J. D.; Romanofsky, R. R.; Heinen, V. O.; Chorey, C. M.

    1990-01-01

    Epitaxial YBa2Cu3O7 films were grown on several microwave substrates. Surface resistance and penetration depth measurements were performed to determine the quality of these films. Here, the properties of these films on key microwave substrates are described. The fabrication and characterization of a microwave ring resonator circuit to determine transmission line losses are presented. Lower losses than those observed in gold resonator circuits were observed at temperatures lower than critical transition temperature. Based on these results, potential applications of microwave superconducting circuits such as filters, resonators, oscillators, phase shifters, and antenna elements in space communication systems are identified.

  13. High quality superconducting titanium nitride thin film growth using infrared pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Torgovkin, A.; Chaudhuri, S.; Ruhtinas, A.; Lahtinen, M.; Sajavaara, T.; Maasilta, I. J.

    2018-05-01

    Superconducting titanium nitride (TiN) thin films were deposited on magnesium oxide, sapphire and silicon nitride substrates at 700 °C, using a pulsed laser deposition (PLD) technique, where infrared (1064 nm) pulses from a solid-state laser were used for the ablation from a titanium target in a nitrogen atmosphere. Structural studies performed with x-ray diffraction showed the best epitaxial crystallinity for films deposited on MgO. In the best films, superconducting transition temperatures, T C, as high as 4.8 K were observed, higher than in most previous superconducting TiN thin films deposited with reactive sputtering. A room temperature resistivity down to ∼17 μΩ cm and residual resistivity ratio up to 3 were observed in the best films, approaching reported single crystal film values, demonstrating that PLD is a good alternative to reactive sputtering for superconducting TiN film deposition. For less than ideal samples, the suppression of the film properties were correlated mostly with the unintended incorporation of oxygen (5–10 at%) in the film, and for high oxygen content films, vacuum annealing was also shown to increase the T C. On the other hand, superconducting properties were surprisingly insensitive to the nitrogen content, with high quality films achieved even in the highly nitrogen rich, Ti:N = 40/60 limit. Measures to limit oxygen exposure during deposition must be taken to guarantee the best superconducting film properties, a fact that needs to be taken into account with other deposition methods, as well.

  14. Temperature and Microstructural Effects on the Superconducting Properties of Niobium Thin Films

    DOE PAGES

    Beebe, Melissa R.; Valente-Feliciano, Anne -Marie; Beringer, Douglas B.; ...

    2016-11-23

    Here, superconducting thin films have a wide range of dc and RF applications, from detectors to superconducting radio frequency. Amongst the most used materials, niobium (Nb) has the highest critical temperature (TC) and highest lower critical field (HC1) of the elemental superconductors and can be deposited on a variety of substrates, making Nb thin films very appealing for such applications. Here, we present temperature-dependent dc studies on the critical temperature and critical fields of Nb thin films grown on copper and r-plane sapphire surfaces. Additionally, we correlate the dc superconducting properties of these films with their microstructure, which allows formore » the possibility of tailoring future films for a specific application.« less

  15. High-Temperature-Superconductor Films In Microwave Circuits

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Warner, J. D.; Romanofsky, R. R.; Heinen, V. O.; Chorey, C. M.

    1993-01-01

    Report discusses recent developments in continuing research on fabrication and characterization of thin films of high-temperature superconducting material and incorporation of such films into microwave circuits. Research motivated by prospect of exploiting superconductivity to reduce electrical losses and thereby enhancing performance of such critical microwave components as ring resonators, filters, transmission lines, phase shifters, and feed lines in phased-array antennas.

  16. Interface-enhanced high-temperature superconductivity in single-unit-cell FeT e1 -xS ex films on SrTi O3

    NASA Astrophysics Data System (ADS)

    Li, Fangsen; Ding, Hao; Tang, Chenjia; Peng, Junping; Zhang, Qinghua; Zhang, Wenhao; Zhou, Guanyu; Zhang, Ding; Song, Can-Li; He, Ke; Ji, Shuaihua; Chen, Xi; Gu, Lin; Wang, Lili; Ma, Xu-Cun; Xue, Qi-Kun

    2015-06-01

    Recently discovered high-temperature superconductivity in single-unit-cell (UC) FeSe films on SrTi O3 (STO) substrate has stimulated tremendous research interest, both experimental and theoretical. Whether this scenario could be extended to other superconductors is vital in both identifying the enhanced superconductivity mechanism and further raising the critical transition temperature (Tc). Here we successfully prepared single-UC FeT e1 -xS ex(0.1 ≤x ≤0.6 ) films on STO substrates by molecular beam epitaxy and observed U -shaped superconducting gaps (Δ ) up to ˜16.5 meV , nearly ten times the gap value (Δ ˜1.7 meV ) of the optimally doped bulk FeT e0 .6S e0 .4 single crystal (Tc˜14.5 K ). No superconducting gap has been observed on the second UC and thicker FeT e1 -xS ex films at 5.7 K, indicating the important role of the interface. This interface-enhanced high-temperature superconductivity is further confirmed by ex situ transport measurements, which revealed an onset superconducting transition temperature above 40 K, nearly two times higher than that of the optimally doped bulk FeT e0 .6S e0 .4 single crystal. This work demonstrates that interface engineering is a feasible way to discover alternative superconductors with higher Tc.

  17. High Temperature Superconducting Materials Database

    National Institute of Standards and Technology Data Gateway

    SRD 62 NIST High Temperature Superconducting Materials Database (Web, free access)   The NIST High Temperature Superconducting Materials Database (WebHTS) provides evaluated thermal, mechanical, and superconducting property data for oxides and other nonconventional superconductors.

  18. High-frequency applications of high-temperature superconductor thin films

    NASA Astrophysics Data System (ADS)

    Klein, N.

    2002-10-01

    High-temperature superconducting thin films offer unique properties which can be utilized for a variety of high-frequency device applications in many areas related to the strongly progressing market of information technology. One important property is an exceptionally low level of microwave absorption at temperatures attainable with low power cryocoolers. This unique property has initiated the development of various novel type of microwave devices and commercialized subsystems with special emphasis on application in advanced microwave communication systems. The second important achievement related to efforts in oxide thin and multilayer technology was the reproducible fabrication of low-noise Josephson junctions in high-temperature superconducting thin films. As a consequence of this achievement, several novel nonlinear high-frequency devices, most of them exploiting the unique features of the ac Josephson effect, have been developed and found to exhibit challenging properties to be utilized in basic metrology and Terahertz technology. On the longer timescale, the achievements in integrated high-temperature superconductor circuit technology may offer a strong potential for the development of digital devices with possible clock frequencies in the range of 100 GHz.

  19. In-situ deposition of YBCO high-Tc superconducting thin films by MOCVD and PE-MOCVD

    NASA Technical Reports Server (NTRS)

    Zhao, J.; Noh, D. W.; Chern, C.; Li, Y. Q.; Norris, P. E.; Kear, B.; Gallois, B.

    1991-01-01

    Metal-Organic Chemical Vapor Deposition (MOCVD) offers the advantages of a high degree of compositional control, adaptability for large scale production, and the potential for low temperature fabrication. The capability of operating at high oxygen partial pressure is particularly suitable for in situ formation of high temperature superconducting (HTSC) films. Yttrium barium copper oxide (YBCO) thin films having a sharp zero-resistance transition with T(sub c) greater than 90 K and J(sub c) of approximately 10(exp 4) A on YSZ have been prepared, in situ, at a substrate temperature of about 800 C. Moreover, the ability to form oxide films at low temperature is very desirable for device applications of HTSC materials. Such a process would permit the deposition of high quality HTSC films with a smooth surface on a variety of substrates. Highly c-axis oriented, dense, scratch resistant, superconducting YBCO thin films with mirror-like surfaces have been prepared, in situ, at a reduced substrate temperature as low as 570 C by a remote microwave-plasma enhanced metal-organic chemical vapor deposition (PE-MOCVD) process. Nitrous oxide was used as a reactant gas to generate active oxidizing species. This process, for the first time, allows the formation of YBCO thin films with the orthorhombic superconducting phase in the as-deposited state. The as-deposited films grown by PE-MOCVD show attainment of zero resistance at 72 K with a transition width of about 5 K. MOCVD was carried out in a commercial production scale reactor with the capability of uniform deposition over 100 sq cm per growth run. Preliminary results indicate that PE-MOCVD is a very attractive thin film deposition process for superconducting device technology.

  20. Phase diagram and electronic indication of high-temperature superconductivity at 65 K in single-layer FeSe films.

    PubMed

    He, Shaolong; He, Junfeng; Zhang, Wenhao; Zhao, Lin; Liu, Defa; Liu, Xu; Mou, Daixiang; Ou, Yun-Bo; Wang, Qing-Yan; Li, Zhi; Wang, Lili; Peng, Yingying; Liu, Yan; Chen, Chaoyu; Yu, Li; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Chen, Chuangtian; Xu, Zuyan; Chen, Xi; Ma, Xucun; Xue, Qikun; Zhou, X J

    2013-07-01

    The recent discovery of possible high-temperature superconductivity in single-layer FeSe films has generated significant experimental and theoretical interest. In both the cuprate and the iron-based high-temperature superconductors, superconductivity is induced by doping charge carriers into the parent compound to suppress the antiferromagnetic state. It is therefore important to establish whether the superconductivity observed in the single-layer sheets of FeSe--the essential building blocks of the Fe-based superconductors--is realized by undergoing a similar transition. Here we report the phase diagram for an FeSe monolayer grown on a SrTiO3 substrate, by tuning the charge carrier concentration over a wide range through an extensive annealing procedure. We identify two distinct phases that compete during the annealing process: the electronic structure of the phase at low doping (N phase) bears a clear resemblance to the antiferromagnetic parent compound of the Fe-based superconductors, whereas the superconducting phase (S phase) emerges with the increase in doping and the suppression of the N phase. By optimizing the carrier concentration, we observe strong indications of superconductivity with a transition temperature of 65±5 K. The wide tunability of the system across different phases makes the FeSe monolayer ideal for investigating not only the physics of superconductivity, but also for studying novel quantum phenomena more generally.

  1. JETC (Japanese Technology Evaluation Center) Panel Report on High Temperature Superconductivity in Japan

    NASA Technical Reports Server (NTRS)

    Shelton, Duane; Gamota, George

    1989-01-01

    The Japanese regard success in R and D in high temperature superconductivity as an important national objective. The results of a detailed evaluation of the current state of Japanese high temperature superconductivity development are provided. The analysis was performed by a panel of technical experts drawn from U.S. industry and academia, and is based on reviews of the relevant literature and visits to Japanese government, academic and industrial laboratories. Detailed appraisals are presented on the following: Basic research; superconducting materials; large scale applications; processing of superconducting materials; superconducting electronics and thin films. In all cases, comparisons are made with the corresponding state-of-the-art in the United States.

  2. In Situ deposition of YBCO high-T(sub c) superconducting thin films by MOCVD and PE-MOCVD

    NASA Technical Reports Server (NTRS)

    Zhao, J.; Noh, D. W.; Chern, C.; Li, Y. Q.; Norris, P.; Gallois, B.; Kear, B.

    1990-01-01

    Metalorganic Chemical Vapor Deposition (MOCVD) offers the advantages of a high degree of compositional control, adaptability for large scale production, and the potential for low temperature fabrication. The capability of operating at high oxygen partial pressure is particularly suitable for in situ formation of high temperature superconducting (HTSC) films. Yttrium barium copper oxide (YBCO) thin films having a sharp zero-resistance transition with T( sub c) greater than 90 K and Jc approx. 10 to the 4th power A on YSZ have been prepared, in situ, at a substrate temperature of about 800 C. Moreover, the ability to form oxide films at low temperature is very desirable for device applications of HTSC materials. Such a process would permit the deposition of high quality HTSC films with a smooth surface on a variety of substrates. Highly c-axis oriented, dense, scratch resistant, superconducting YBCO thin films with mirror-like surfaces have been prepared, in situ, at a reduced substrate temperature as low as 570 C by a remote microwave-plasma enhanced metalorganic chemical vapor deposition (PE-MOCVD) process. Nitrous oxide was used as a reactant gas to generate active oxidizing species. This process, for the first time, allows the formation of YBCO thin films with the orthorhombic superconducting phase in the as-deposited state. The as-deposited films grown by PE-MOCVD show attainment of zero resistance at 72 K with a transition width of about 5 K. MOCVD was carried out in a commercial production scale reactor with the capability of uniform deposition over 100 sq cm per growth run. Preliminary results indicate that PE-MOCVD is a very attractive thin film deposition process for superconducting device technology.

  3. High Tc superconducting films from metallo-organic precursors

    NASA Astrophysics Data System (ADS)

    Davison, W. W.; Shyu, S. G.; Buchanan, R. C.

    High Tc superconducting films of heavy metal soaps (derived from carboxylic acid precursors) have been prepared on Si and other substrates. The precursors were synthesized and mixed in appropriate molar ratios to form the high Tc compound YBa2Cu3O(7-x), using a high boiling point common solvent base. The precursor solution was deposited by a spin casting technique on the substrates. Film thicknesses of 0.1-1.0 micron were achieved after heat treatment at 550-850 C at not longer than 4 hours. Films were analyzed as to orientation, appropriate phase, interfacial reaction, and superconducting properties.

  4. Techniques for Connecting Superconducting Thin Films

    NASA Technical Reports Server (NTRS)

    Mester, John; Gwo, Dz-Hung

    2006-01-01

    Several improved techniques for connecting superconducting thin films on substrates have been developed. The techniques afford some versatility for tailoring the electronic and mechanical characteristics of junctions between superconductors in experimental electronic devices. The techniques are particularly useful for making superconducting or alternatively normally conductive junctions (e.g., Josephson junctions) between patterned superconducting thin films in order to exploit electron quantum-tunneling effects. The techniques are applicable to both low-Tc and high-Tc superconductors (where Tc represents the superconducting- transition temperature of a given material), offering different advantages for each. Most low-Tc superconductors are metallic, and heretofore, connections among them have been made by spot welding. Most high-Tc superconductors are nonmetallic and cannot be spot welded. These techniques offer alternatives to spot welding of most low-Tc superconductors and additional solutions to problems of connecting most high-Tc superconductors.

  5. Ultrasonic Attenuation of Surface Acoustic Waves in Thin Films of High Transition Temperature Superconducting Niobium-Tin and Niobium-Nitride

    NASA Astrophysics Data System (ADS)

    Fredricksen, Hans Peter

    The ultrasonic attenuation of 600-700 MHz surface acoustic waves by two high T(,c), cubic crystal structure, superconducting thin films has been investigated. The films studied were two, 0.5 (mu) thin, Nb(,3)Sn samples, electron-beam codeposited on LiNbO(,3) and Quartz, and eleven NbN samples from 3 x 10('3) (ANGSTROM) to <(, )200 (ANGSTROM) thin, sputter deposited on LiNbO(,3). The Nb(,3)Sn (Al5 structure) film on Quartz was difficult to measure due to defects in the Quartz caused by the high deposition temperature ((DBLTURN)700(DEGREES)C) used to make the high T(,c) form of the compound. The Nb(,3)Sn film on LiNbO(,3), however, provided information about the transition temperature and energy gap at T = 0 K when the attenuation was measured as a function of temperature in zero magnetic field. A theory is developed to predict the electron-phonon produced normal state attenuation of surface acoustic waves by a thin, loss producing film on a nonattenuating substrate. Using a viscous drag model for the attenuation, the predictions of the theory are compared to the measured normal state attenuation to find the electron mean-free-path for the Nb(,3)Sn film on LiNbO(,3). The attenuation measured for this film as a function of applied magnetic field for four temperatures below T(,c) showed the sample to be an impurity rich type II superconductor with H(,c(,2)) (T = 0 K) = 85 KG, having GLAG theory constants: (kappa)(,2)(t=1) = 28.5 and (kappa)(t=1) = 29.2. The attenuation curves of the nine thickest NbN samples were non-BCS-like and very similar. Measured as a function of temperature only, because we could not reach the high critical fields of the samples, the attenuation showed an initial drop at T(,c) of about 1-2 dB which then leveled off until the temperature was below 0.5 T(,c), where the rate of decrease was much slower than the initial drop. A qualitative description of this behavior is derived from the Kosterlitz-Thouless vortex-antivortex theory. Although the

  6. Ultrafast IR detector response in high Tc superconducting thin films

    NASA Technical Reports Server (NTRS)

    Lindgren, Mikael; Ahlberg, Henrik; Danerud, Martin; Larsson, Anders; Eng, Sverre T.

    1991-01-01

    The response from a high Tc superconducting multielement optical detector made of a laser deposited Y-Ba-Cu-O thin film has been evaluated. Several microscopic and spectroscopic techniques were used to establish the presence of the correct phase of the thin film. Optical pulses from a laser diode at 830 nm and from a Q-switched CO2-laser at 10.6 microns were used. The detector responded to 50 ps (FWHM) pulses. A comparison between dR/dT of the film and the response amplitude as a function of temperature indicated a bolometric response.

  7. High temperature interfacial superconductivity

    DOEpatents

    Bozovic, Ivan [Mount Sinai, NY; Logvenov, Gennady [Port Jefferson Station, NY; Gozar, Adrian Mihai [Port Jefferson, NY

    2012-06-19

    High-temperature superconductivity confined to nanometer-scale interfaces has been a long standing goal because of potential applications in electronic devices. The spontaneous formation of a superconducting interface in bilayers consisting of an insulator (La.sub.2CuO.sub.4) and a metal (La.sub.1-xSr.sub.xCuO.sub.4), neither of which is superconducting per se, is described. Depending upon the layering sequence of the bilayers, T.sub.c may be either .about.15 K or .about.30 K. This highly robust phenomenon is confined to within 2-3 nm around the interface. After exposing the bilayer to ozone, T.sub.c exceeds 50 K and this enhanced superconductivity is also shown to originate from a 1 to 2 unit cell thick interfacial layer. The results demonstrate that engineering artificial heterostructures provides a novel, unconventional way to fabricate stable, quasi two-dimensional high T.sub.c phases and to significantly enhance superconducting properties in other superconductors. The superconducting interface may be implemented, for example, in SIS tunnel junctions or a SuFET.

  8. Epitaxy of mercury-based high temperature superconducting films on oxide and metal substrates

    NASA Astrophysics Data System (ADS)

    Xie, Yi-Yuan

    High-Tc superconducting (HTS) cuprates are highly anisotropic thus epitaxy along certain crystalline directions is essential to realize high-current-carrying capability at temperatures above 77 K. Hg-based HTS (Hg-HTS) cuprates have the record-high Tc up to 135 K, therefore are of great interest for fundamental research and practical applications. However, growth Of epitaxial Hg-HTS films is extremely difficult in conventional thermal-reaction process since Hg is highly volatile. Motivated by this, we first developed a cation-exchange process for growing epitaxial Hg-HTS films, which involves two steps: selection of precursor matrices with predesigned structure and composition followed by cation-exchange processing. New materials are formed via "atomic surgery" on an existing structure rather than thermal reaction among amorphous oxides in conventional process, thus the structural features of the precursor are inherited by the new material. Using epitaxial Tl-based HTS films as precursor and annealing them in Hg-vapor, epitaxial Hg-HTS films with superior quality have been obtained. This success encouraged us to develop epitaxy on metal tapes for coated conductors and On large-area wafers for electronic devices. For coated conductors, we addressed three critical issues: epitaxy on metal substrates, enhancement of in-field Jcs and scale-up in thickness and length. First, using a fabrication scheme that combines two processes: cation-exchange and fast-temperature-ramping-annealing, epitaxial HgBa2CaCu2O6+delta films were grown on rolling-assisted-biaxially-textured Ni substrates buffered with CeO 2/YSZ/CeO2 for the first time. We fabricated HgBa2CaCu 2O6+delta coated conductors with Tc = 122--124 K and self-field Jc > 1 x 106A/cm2 at 92 K which are record-high for HTS coated conductors. Second, we demonstrated improved in-field J cs via overdoping HgBa2CaCu 2O6+delta films (by means Of charge "overdoped"), heavy-ion-irradiation and substrate engineering. Finally

  9. Superconductivity induced in iron telluride films by low-temperature oxygen incorporation

    NASA Astrophysics Data System (ADS)

    Nie, Y. F.; Telesca, D.; Budnick, J. I.; Sinkovic, B.; Wells, B. O.

    2010-07-01

    We report superconductivity induced in films of the nonsuperconducting, antiferromagnetic parent material FeTe by low-temperature oxygen incorporation in a reversible manner. X-ray absorption shows that oxygen incorporation changes the nominal Fe valence state from 2+ in the nonsuperconducting state to mainly 3+ in the superconducting state. Thus superconductivity in O-doped FeTe occurs in a quite different charge and strain state than the more common FeTe1-xSex . This work also suggests a convenient path for conducting doping experiments in situ with many measurement techniques.

  10. High Tc superconducting IR detectors from Y-Ba-Cu-O thin films

    NASA Technical Reports Server (NTRS)

    Lindgren, M.; Ahlberg, H.; Danerud, M.; Larsson, A.; Eng, M.

    1990-01-01

    A thin-film high-Tc superconducting multielement optical detector made of Y-Ba-Cu-O has been designed and evaluated using optical pulses from a diode laser (830 nm) and a Q-switched CO2-laser (10.6 microns). Different thin films have been tested. A laser deposited film showed the strongest response amplitude for short pulses and responded to an ultrafast, 50 ps wide pulse. Comparisons between dR/dT and response as a function of temperature indicated, however, a bolometric response.

  11. High temperature interface superconductivity

    DOE PAGES

    Gozar, A.; Bozovic, I.

    2016-01-20

    High-T c superconductivity at interfaces has a history of more than a couple of decades. In this review we focus our attention on copper-oxide based heterostructures and multi-layers. We first discuss the technique, atomic layer-by-layer molecular beam epitaxy (ALL-MBE) engineering, that enabled High-T c Interface Superconductivity (HT-IS), and the challenges associated with the realization of high quality interfaces. Then we turn our attention to the experiments which shed light on the structure and properties of interfacial layers, allowing comparison to those of single-phase films and bulk crystals. Both ‘passive’ hetero-structures as well as surface-induced effects by external gating are discussed.more » Here, we conclude by comparing HT-IS in cuprates and in other classes of materials, especially Fe-based superconductors, and by examining the grand challenges currently laying ahead for the field.« less

  12. A high-temperature superconducting transformer with localized magnetic field

    NASA Astrophysics Data System (ADS)

    Volkov, E. P.; Dzhafarov, E. A.

    2013-12-01

    This paper describes a high-temperature superconducting transformer with a bar-type magnetic core and concentric windings with alternating layers, with single-channel and multi-channel arrangements. There is given the design concept of high-temperature superconducting windings of the transformer, made in the form of newly developed first-generation high-temperature superconducting ribbon wires, with localized magnetic field intended for producing maximum transport currents in the windings, as well as for reducing the consumption of a high-temperature superconducting material, cooling agent, and energy losses in these windings.

  13. Room-temperature growth of thin films of niobium on strontium titanate (0 0 1) single-crystal substrates for superconducting joints

    NASA Astrophysics Data System (ADS)

    Shimizu, Yuhei; Tonooka, Kazuhiko; Yoshida, Yoshiyuki; Furuse, Mitsuho; Takashima, Hiroshi

    2018-06-01

    With the eventual aim of forming joints between superconducting wires of YBa2Cu3O7-δ (YBCO), thin films of Nb were grown at room-temperature on SrTiO3 (STO) (0 0 1), a single-crystal substrate that shows good lattice matching with YBCO. The crystallinity, surface morphology, and superconducting properties of the Nb thin films were investigated and compared with those of similar films grown on a silica glass substrate. The Nb thin films grew with an (hh0) orientation on both substrates. The crystallinity of the Nb thin films on the STO substrate was higher than that on the silica glass substrate. X-ray diffraction measurements and observation of the surface morphology by atomic-force microscopy indicated that Nb grew in the plane along the [1 0 0] and [0 1 0] directions of the STO substrate. This growth mode relaxes strain between Nb and STO, and is believed to lead to the high crystallinity observed. As a result, the Nb thin films on the STO substrates showed lower electric resistivity and a higher superconducting transition temperature than did those on the silica glass substrates. The results of this study should be useful in relation to the production of superconducting joints.

  14. Spin fluctuation induced linear magnetoresistance in ultrathin superconducting FeSe films

    DOE PAGES

    Wang, Qingyan; Zhang, Wenhao; Chen, Weiwei; ...

    2017-07-21

    The discovery of high-temperature superconductivity in FeSe/STO has trigged great research interest to reveal a range of exotic physical phenomena in this novel material. Here we present a temperature dependent magnetotransport measurement for ultrathin FeSe/STO films with different thickness and protection layers. Remarkably, a surprising linear magnetoresistance (LMR) is observed around the superconducting transition temperatures but absent otherwise. The experimental LMR can be reproduced by magnetotransport calculations based on a model of magnetic field dependent disorder induced by spin fluctuation. Thus, the observed LMR in coexistence with superconductivity provides the first magnetotransport signature for spin fluctuation around the superconducting transitionmore » region in ultrathin FeSe/STO films.« less

  15. Fluorescence X-ray absorption spectroscopy using a Ge pixel array detector: application to high-temperature superconducting thin-film single crystals.

    PubMed

    Oyanagi, H; Tsukada, A; Naito, M; Saini, N L; Lampert, M O; Gutknecht, D; Dressler, P; Ogawa, S; Kasai, K; Mohamed, S; Fukano, A

    2006-07-01

    A Ge pixel array detector with 100 segments was applied to fluorescence X-ray absorption spectroscopy, probing the local structure of high-temperature superconducting thin-film single crystals (100 nm in thickness). Independent monitoring of pixel signals allows real-time inspection of artifacts owing to substrate diffractions. By optimizing the grazing-incidence angle theta and adjusting the azimuthal angle phi, smooth extended X-ray absorption fine structure (EXAFS) oscillations were obtained for strained (La,Sr)2CuO4 thin-film single crystals grown by molecular beam epitaxy. The results of EXAFS data analysis show that the local structure (CuO6 octahedron) in (La,Sr)2CuO4 thin films grown on LaSrAlO4 and SrTiO3 substrates is uniaxially distorted changing the tetragonality by approximately 5 x 10(-3) in accordance with the crystallographic lattice mismatch. It is demonstrated that the local structure of thin-film single crystals can be probed with high accuracy at low temperature without interference from substrates.

  16. Macroscopic Magnetic Coupling Effect: The Physical Origination of a High-Temperature Superconducting Flux Pump

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Coombs, Tim

    2018-04-01

    We have uncovered at the macroscopic scale a magnetic coupling phenomenon in a superconducting YBa2Cu3O7 -δ (YBCO) film, which physically explains the mechanism of the high-temperature superconducting flux pump. The coupling occurs between the applied magnetic poles and clusters of vortices induced in the YBCO film, with each cluster containing millions of vortices. The coupling energy is verified to originate from the inhomogeneous field of the magnetic poles, which reshapes the vortex distribution, aggregates millions of vortices into a single cluster, and accordingly moves with the poles. A contrast study is designed to verify that, to provide the effective coupling energy, the applied wavelength must be short while the field amplitude must be strong, i.e., local-field inhomogeneity is the crucial factor. This finding broadens our understanding of the collective vortex behavior in an applied magnetic field with strong local inhomogeneity. Moreover, this phenomenon largely increases the controlled vortex flow rate by several orders of magnitude compared with existing methods, providing motivation for and physical support to a new branch of wireless superconducting dc power sources, i.e., the high-temperature superconducting flux pump.

  17. Magnetic Field Enhanced Superconductivity in Epitaxial Thin Film WTe2.

    PubMed

    Asaba, Tomoya; Wang, Yongjie; Li, Gang; Xiang, Ziji; Tinsman, Colin; Chen, Lu; Zhou, Shangnan; Zhao, Songrui; Laleyan, David; Li, Yi; Mi, Zetian; Li, Lu

    2018-04-25

    In conventional superconductors an external magnetic field generally suppresses superconductivity. This results from a simple thermodynamic competition of the superconducting and magnetic free energies. In this study, we report the unconventional features in the superconducting epitaxial thin film tungsten telluride (WTe 2 ). Measuring the electrical transport properties of Molecular Beam Epitaxy (MBE) grown WTe 2 thin films with a high precision rotation stage, we map the upper critical field H c2 at different temperatures T. We observe the superconducting transition temperature T c is enhanced by in-plane magnetic fields. The upper critical field H c2 is observed to establish an unconventional non-monotonic dependence on temperature. We suggest that this unconventional feature is due to the lifting of inversion symmetry, which leads to the enhancement of H c2 in Ising superconductors.

  18. High temperature superconducting composite conductor and method for manufacturing the same

    DOEpatents

    Holesinger, Terry G.; Bingert, John F.

    2002-01-01

    A high temperature superconducting composite conductor is provided including a high temperature superconducting material surrounded by a noble metal layer, the high temperature superconducting composite conductor characterized as having a fill factor of greater than about 40. Additionally, the conductor can be further characterized as containing multiple cores of high temperature superconducting material surrounded by a noble metal layer, said multiple cores characterized as having substantially uniform geometry in the cross-sectional dimensions. Processes of forming such a high temperature superconducting composite conductor are also provided.

  19. High-temperature superconducting nano-meanders made by ion irradiation

    NASA Astrophysics Data System (ADS)

    Amari, P.; Feuillet-Palma, C.; Jouan, A.; Couëdo, F.; Bourlet, N.; Géron, E.; Malnou, M.; Méchin, L.; Sharafiev, A.; Lesueur, J.; Bergeal, N.

    2018-01-01

    In this article, we report on the fabrication of very long {{YBa}}2{{Cu}}3{{{O}}}7 nanowires in a meander shape patterned in a {{CeO}}2-capped thin film by high-energy oxygen ion irradiation. DC and RF characterizations outline the good superconducting properties of the nanowires whose geometry approaches the one used in single photon detectors. Their inductance, which mainly sets the maximum speed of these devices, has been measured on a wide range of temperature by mean of a resonant method. The extracted values are in agreement with the ones calculated from the geometry of the meanders and from the known London penetration depth in {{YBa}}2{{Cu}}3{{{O}}}7 thin films.

  20. Active superconducting devices formed of thin films

    DOEpatents

    Martens, Jon S.; Beyer, James B.; Nordman, James E.; Hohenwarter, Gert K. G.

    1991-05-28

    Active superconducting devices are formed of thin films of superconductor which include a main conduction channel which has an active weak link region. The weak link region is composed of an array of links of thin film superconductor spaced from one another by voids and selected in size and thickness such that magnetic flux can propagate across the weak link region when it is superconducting. Magnetic flux applied to the weak link region will propagate across the array of links causing localized loss of superconductivity in the links and changing the effective resistance across the links. The magnetic flux can be applied from a control line formed of a superconducting film deposited coplanar with the main conduction channel and weak link region on a substrate. The devices can be formed of any type to superconductor but are particularly well suited to the high temperature superconductors since the devices can be entirely formed from coplanar films with no overlying regions. The devices can be utilized for a variety of electrical components, including switching circuits, amplifiers, oscillators and modulators, and are well suited to microwave frequency applications.

  1. High temperature superconducting fault current limiter

    DOEpatents

    Hull, J.R.

    1997-02-04

    A fault current limiter for an electrical circuit is disclosed. The fault current limiter includes a high temperature superconductor in the electrical circuit. The high temperature superconductor is cooled below its critical temperature to maintain the superconducting electrical properties during operation as the fault current limiter. 15 figs.

  2. High temperature superconducting fault current limiter

    DOEpatents

    Hull, John R.

    1997-01-01

    A fault current limiter (10) for an electrical circuit (14). The fault current limiter (10) includes a high temperature superconductor (12) in the electrical circuit (14). The high temperature superconductor (12) is cooled below its critical temperature to maintain the superconducting electrical properties during operation as the fault current limiter (10).

  3. High-precision measurement of magnetic penetration depth in superconducting films

    DOE PAGES

    He, X.; Gozar, A.; Sundling, R.; ...

    2016-11-01

    We report that the magnetic penetration depth (λ) in thin superconducting films is usually measured by the mutual inductance technique. The accuracy of this method has been limited by uncertainties in the geometry of the solenoids and in the film position and thickness, by parasitic coupling between the coils, etc. Here, we present several improvements in the apparatus and the method. To ensure the precise thickness of the superconducting layer, we engineer the films at atomic level using atomic-layer-by-layer molecular beam epitaxy. In this way, we also eliminate secondary-phase precipitates, grain boundaries, and pinholes that are common with other depositionmore » methods and that artificially increase the field transmission and thus the apparent λ. For better reproducibility, the thermal stability of our closed-cycle cryocooler used to control the temperature of the mutual inductance measurement has been significantly improved by inserting a custom-built thermal conductivity damper. Next, to minimize the uncertainties in the geometry, we fused a pair of small yet precisely wound coils into a single sapphire block machined to a high precision. Lastly, the sample is spring-loaded to exactly the same position with respect to the solenoids. Altogether, we can measure the absolute value of λ with the accuracy better than ±1%.« less

  4. Interface induced high temperature superconductivity in single unit-cell FeSe on SrTiO{sub 3}(110)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhou, Guanyu; Zhang, Ding; Liu, Chong

    2016-05-16

    We report high temperature superconductivity in one unit-cell (1-UC) FeSe films grown on SrTiO{sub 3} (STO)(110) substrate by molecular beam epitaxy. By in-situ scanning tunneling microscopy measurement, we observe a superconducting gap as large as 17 meV on the 1-UC FeSe films. Transport measurements on 1-UC FeSe/STO(110) capped with FeTe layers reveal superconductivity with an onset transition temperature (T{sub C}) of 31.6 K and an upper critical magnetic field of 30.2 T. We also find that T{sub C} can be further increased by external electric field although the effect is weaker than that on STO(001) substrate.

  5. Superconducting properties of ion-implanted gold-silicon thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jisrawi, N.M.

    The superconducting properties of thin Au{sub x}Si{sub 1{minus}x}, films prepared by ion beam implantation and ion beam mixing are studied. The films are prepared by evaporation of single Au layers on Si substrates and mixing them with Si, Ar, or Xe, or by Xe beam mixing of alternate multilayers of Au and Si sputtered on Al{sub 2}O{sub 3} substrates. The superconducting transition temperature and upper critical fields are determined by measuring the temperature and magnetic field dependence of resistivity. Temperatures as low as 20mK and magnetic fields as high as 8 T were used. Superconductivity in these films is discussedmore » in connection with metastable metallic phases that are reportedly produced in the Au-Si system by high quenching rate preparation techniques like quenching from the vapor or the melt or ion implantation. Preliminary structural studies provide evidence for the existence of these phases and near-edge X-ray absorption and X-ray photoelectron spectroscopy measurements indicate a metallic type of bonding from which compound formation is inferred. The quality of the films is strongly dependent on the conditions of implantation. The maximum superconducting transition temperature attained is about 1.2 K. The upper critical fields have a maximum of 6T. An unusual double transition in the field dependence of resistivity is observed at low temperatures. The effect is very pronounced at compositions near x = 0.5 where the maximum {Tc} occurs. A model is presented to explain this result which invokes the properties of the metastable metallic phases and assumes the formation of more than two such phases in the same sample as the implantation dose increases. The Si-Au interface plays an important role in understanding the model and in interpreting the results of this thesis in general.« less

  6. Probing transport mechanisms of BaFe₂As₂ superconducting films and grain boundary junctions by noise spectroscopy.

    PubMed

    Barone, C; Romeo, F; Pagano, S; Adamo, M; Nappi, C; Sarnelli, E; Kurth, F; Iida, K

    2014-08-22

    An important step forward for the understanding of high-temperature superconductivity has been the discovery of iron-based superconductors. Among these compounds, iron pnictides could be used for high-field magnet applications, resulting more advantageous over conventional superconductors, due to a high upper critical field as well as its low anisotropy at low temperatures. However, the principal obstacle in fabricating high quality superconducting wires and tapes is given by grain boundaries. In order to study these effects, the dc transport and voltage-noise properties of Co-doped BaFe₂As₂ superconducting films with artificial grain boundary junctions have been investigated. A specific procedure allows the separation of the film noise from that of the junction. While the former shows a standard 1/f behaviour, the latter is characterized by an unconventional temperature-dependent multi-Lorentzian voltage-spectral density. Moreover, below the film superconducting critical temperature, a peculiar noise spectrum is found for the grain boundary junction. Possible theoretical interpretation of these phenomena is proposed.

  7. Thermal response of large area high temperature superconducting YBaCuO infrared bolometers

    NASA Technical Reports Server (NTRS)

    Khalil, Ali E.

    1991-01-01

    Thermal analysis of large area high temperature superconducting infrared detector operating in the equilibrium mode (bolometer) was performed. An expression for the temperature coefficient beta = 1/R(dR/dT) in terms of the thermal conductance and the thermal time constant of the detector were derived. A superconducting transition edge bolometer is a thermistor consisting of a thin film superconducting YBaCuO evaporated into a suitable thermally isolated substrate. The operating temperature of the bolometer is maintained close to the midpoint of the superconducting transition region where the resistance R has a maximum dynamic range. A detector with a strip configuration was analyzed and an expression for the temperature rise (delta T) above the ambient due to a uniform illumination with a source of power density was calculated. An expression for the thermal responsibility depends upon the spatial modulation frequency and the angular frequency of the incoming radiation. The problem of the thermal cross talk between different detector elements was addressed. In the case of monolithic HTS detector array with a row of square elements of dimensions 2a and CCD or CID readout electronics the thermal spread function was derived for different spacing between elements.

  8. High-temperature superconducting undulator magnets

    DOE PAGES

    Kesgin, Ibrahim; Kasa, Matthew; Ivanyushenkov, Yury; ...

    2017-02-13

    Here, this paper presents test results on a prototype superconducting undulator magnet fabricated using 15% Zr-doped rare-earth barium copper oxide high temperature superconducting (HTS) tapes. On an 11-pole magnet we demonstrate an engineering current density, J e, of more than 2.1 kA mm -2 at 4.2 K, a value that is 40% higher than reached in comparable devices wound with NbTi-wire, which is used in all currently operating superconducting undulators. A novel winding scheme enabling the continuous winding of tape-shaped conductors into the intricate undulator magnets as well as a partial interlayer insulation procedure were essential in reaching this advancemore » in performance. Currently, there are rapid advances in the performance of HTS; therefore, achieving even higher current densities in an undulator structure or/and operating it at temperatures higher than 4.2 K will be possible, which would substantially simplify the cryogenic design and reduce overall costs.« less

  9. Enhanced superconducting transition temperature in electroplated rhenium

    NASA Astrophysics Data System (ADS)

    Pappas, D. P.; David, D. E.; Lake, R. E.; Bal, M.; Goldfarb, R. B.; Hite, D. A.; Kim, E.; Ku, H.-S.; Long, J. L.; McRae, C. R. H.; Pappas, L. D.; Roshko, A.; Wen, J. G.; Plourde, B. L. T.; Arslan, I.; Wu, X.

    2018-04-01

    We show that electroplated Re films in multilayers with noble metals such as Cu, Au, and Pd have an enhanced superconducting critical temperature relative to previous methods of preparing Re. The dc resistance and magnetic susceptibility indicate a critical temperature of approximately 6 K. The magnetic response as a function of field at 1.8 K demonstrates type-II superconductivity, with an upper critical field on the order of 2.5 T. Critical current densities greater than 107 A/m2 were measured above liquid-helium temperature. Low-loss at radio frequency was obtained below the critical temperature for multilayers deposited onto resonators made with Cu traces on commercial circuit boards. These electroplated superconducting films can be integrated into a wide range of standard components for low-temperature electronics.

  10. Characterizing superconducting thin films using AC Magnetic Susceptibility

    NASA Astrophysics Data System (ADS)

    Mahoney, C. H.; Porzio, J.; Sullivan, M. C.

    2014-03-01

    We present our work on using ac magnetic susceptibility to determine the critical temperature of superconducting thin films. In ac magnetic susceptibility, the thin film is placed between two coils. One coil carries an ac signal, creating a varying external magnetic field. We measure the voltage induced in the pick-up coil on the opposite side of the sample and measure how the sample magnetization changes as the temperature changes. We will present our work to use ac susceptibility to determine critical temperature and superconducting volume fraction. Using our own analysis program, we are able to accurately locate the critical temperatures of the samples and determine the transition width. For the superconducting volume fraction, we etch samples in order to control the thicknesses of the sample and measure how much of the material grown on the surface is superconducting. Supported by NFS grant DMR-1305637.

  11. Fabrication of superconducting nanowires from ultrathin MgB2 films via focused ion beam milling

    NASA Astrophysics Data System (ADS)

    Zhang, Chen; Wang, Da; Liu, Zheng-Hao; Zhang, Yan; Ma, Ping; Feng, Qing-Rong; Wang, Yue; Gan, Zi-Zhao

    2015-02-01

    High quality superconducting nanowires were fabricated from ultrathin MgB2 films by a focused ion beam milling technique. The precursor MgB2 films in 10 nm thick were grown on MgO substrates by using a hybrid physical-chemical vapor deposition method. The nanowires, in widths of about 300-600 nm and lengths of 1 or 10 μm, showed high superconducting critical temperatures (Tc's) above 34 K and narrow superconducting transition widths (ΔTc's) of 1-3 K. The superconducting critical current density Jc of the nanowires was above 5 × 107 A/cm2 at 20 K. The high Tc, narrow ΔTc, and high Jc of the nanowires offered the possibility of making MgB2-based nano-devices such as hot-electron bolometers and superconducting nanowire single-photon detectors with high operating temperatures at 15-20 K.

  12. Variable temperature superconducting microscope

    NASA Astrophysics Data System (ADS)

    Cheng, Bo; Yeh, W. J.

    2000-03-01

    We have developed and tested a promising type of superconducting quantum interference device (SQUID) microscope, which can be used to detect vortex motion and can operate in magnetic fields over a large temperature range. The system utilizes a single-loop coupling transformer, consisting of a patterned high Tc superconducting thin film. At one end of the transformer, a 20 μm diam detecting loop is placed close to the sample. At the other end, a large loop is coupled to a NbTi coil, which is connected to a low Tc SQUID sensor. Transformers in a variety of sizes have been tested and calibrated. The results show that the system is capable of detecting the motion of a single vortex. We have used the microscope to study the behavior of moving vortices at various positions in a YBa2Cu3O7 thin film bridge.

  13. Studies of the Superconducting Transition in the Mo/Au-Bilayer Thin Films

    NASA Technical Reports Server (NTRS)

    Sadleir, John; Smith, Stephen; Iyomoto, naoko; Bandler, Simon; Chervenak, Jay; Brown, Ari; Brekowsky, Regis; Kilbourne, Caroline; Robinson, Ian

    2007-01-01

    At NASA Goddard, microcalorimeter arrays using superconducting transition edge sensor thermometers (TESs) are under development for high energy resolution X-ray astrophysics applications. We report on our studies of the superconducting transition in our Mo/Au-bilayer TES films including: low current measurements of the superconducting bilayer's resistance transition versus temperature on pixels with different normal metal absorber attachment designs and measured temperature scaling of the critical current and critical magnetic field.

  14. Superconducting NbTiN thin films for superconducting radio frequency accelerator cavity applications

    DOE PAGES

    Burton, Matthew C.; Beebe, Melissa R.; Yang, Kaida; ...

    2016-02-12

    Current superconducting radio frequency technology, used in various particle accelerator facilities across the world, is reliant upon bulk niobium superconducting cavities. Due to technological advancements in the processing of bulk Nb cavities, the facilities have reached accelerating fields very close to a material-dependent limit, which is close to 50 MV/m for bulk Nb. One possible solution to improve upon this fundamental limitation was proposed a few years ago by Gurevich [Appl. Phys. Lett. 88, 012511 (2006)], consisting of the deposition of alternating thin layers of superconducting and insulating materials on the interior surface of the cavities. The use of type-IImore » superconductors with Tc > Tc Nb and H c > HcNb, (e.g., Nb 3Sn, NbN, or NbTiN) could potentially greatly reduce the surface resistance (Rs) and enhance the accelerating field, if the onset of vortex penetration is increased above Hc Nb, thus enabling higher field gradients. Although Nb 3Sn may prove superior, it is not clear that it can be grown as a suitable thin film for the proposed multilayer approach, since very high temperature is typically required for its growth, hindering achieving smooth interfaces and/or surfaces. On the other hand, since NbTiN has a smaller lower critical field (H c1) and higher critical temperature (T c) than Nb and increased conductivity compared to NbN, it is a promising candidate material for this new scheme. Here, the authors present experimental results correlating filmmicrostructure with superconducting properties on NbTiN thin film coupon samples while also comparing filmsgrown with targets of different stoichiometry. In conclusion, it is worth mentioning that the authors have achieved thin films with bulk-like lattice parameter and transition temperature while also achieving H c1 values larger than bulk for films thinner than their London penetration depths.« less

  15. Suppression of superconductivity in epitaxial MgB2 ultrathin films

    NASA Astrophysics Data System (ADS)

    Zhang, Chen; Wang, Yue; Wang, Da; Zhang, Yan; Liu, Zheng-Hao; Feng, Qing-Rong; Gan, Zi-Zhao

    2013-07-01

    MgB2 ultrathin films have potential to make sensitive superconducting devices such as superconducting single-photon detectors working at relatively high temperatures. We have grown epitaxial MgB2 films in thicknesses ranging from about 40 nm to 6 nm by using the hybrid physical-chemical vapor deposition method and performed electrical transport measurements to study the thickness dependence of the superconducting critical temperature Tc. With reducing film thickness d, although a weak depression of the Tc has been observed, which could be attributed to an increase of disorder (interband impurity scattering) in the film, the Tc retains close to the bulk value of MgB2 (39 K), being about 35 K in the film of 6 nm thick. We show that this result, beneficial to the application of MgB2 ultrathin films and in accordance with recent theoretical calculations, is in contrast to previous findings in MgB2 films prepared by other methods such as co-evaporation and molecular-beam epitaxy, where a severe Tc suppression has been observed with Tc about one third of the bulk value in films of ˜5 nm thick. We discuss this apparent discrepancy in experiments and suggest that, towards the ultrathin limit, the different degrees of Tc suppression displayed in currently obtained MgB2 films by various techniques may arise from the different levels of disorder present in the film or different extents of proximity effect at the film surface or film-substrate interface.

  16. Microstructures and superconducting properties of high performance MgB2 thin films deposited from a high-purity, dense Mg-B target.

    PubMed

    Li, G Z; Susner, M A; Bohnenstiehl, S D; Sumption, M D; Collings, E W

    2015-12-01

    High quality, c -axis oriented, MgB 2 thin films were successfully grown on 6H-SiC substrates using pulsed laser deposition (PLD) with subsequent in situ annealing. To obtain high purity films free from oxygen contamination, a dense Mg-B target was specially made from a high temperature, high pressure reaction of Mg and B to form large-grained (10~50 µm) MgB 2 . Microstructural analysis via electron microscopy found that the resulting grains of the film were composed of ultrafine columnar grains of 19-30 nm. XRD analysis showed the MgB 2 films to be c -axis oriented; the a -axis and c -axis lattice parameters were determined to be 3.073 ± 0.005 Å and 3.528 ± 0.010 Å, respectively. The superconducting critical temperature, T c,onset , increased monotonically as the annealing temperature was increased, varying from 25.2 K to 33.7 K. The superconducting critical current density as determined from magnetic measurements, J cm , at 5 K, was 10 5 A/cm 2 at 7.8 T; at 20 K, 10 5 A/cm 2 was reached at 3.1 T. The transport and pinning properties of these films were compared to "powder-in-tube" (PIT) and "internal-infiltration" (AIMI) processed wires. Additionally, examination of the pinning mechanism showed that when scaled to the peak in the pinning curve, the films follow the grain boundary, or surface, pinning mechanism quite well, and are similar to the response seen for C doped PIT and AIMI strands, in contrast to the behavior seen in undoped PIT wires, in which deviations are seen at high b ( b = B/B c2 ). On the other hand, the magnitude of the pinning force was similar for the thin films and AIMI conductors, unlike the values from connectivity-suppressed PIT strands.

  17. Reentrant resistive behavior and dimensional crossover in disordered superconducting TiN films

    DOE PAGES

    Postolova, Svetlana V.; Mironov, Alexey Yu.; Baklanov, Mikhail R.; ...

    2017-05-11

    A reentrant temperature dependence of the normal state resistance often referred to as the N-shaped temperature dependence, is omnipresent in disordered superconductors – ranging from high-temperature cuprates to ultrathin superconducting films – that experience superconductor-to-insulator transition. Yet, despite the ubiquity of this phenomenon its origin still remains a subject of debate. Here we investigate strongly disordered superconducting TiN films and demonstrate universality of the reentrant behavior. We offer a quantitative description of the N-shaped resistance curve. We show that upon cooling down the resistance first decreases linearly with temperature and then passes through the minimum that marks the 3D-2D crossovermore » in the system. In the 2D temperature range the resistance first grows with decreasing temperature due to quantum contributions and eventually drops to zero as the system falls into a superconducting state. As a result, our findings demonstrate the prime importance of disorder in dimensional crossover effects.« less

  18. Reentrant Resistive Behavior and Dimensional Crossover in Disordered Superconducting TiN Films.

    PubMed

    Postolova, Svetlana V; Mironov, Alexey Yu; Baklanov, Mikhail R; Vinokur, Valerii M; Baturina, Tatyana I

    2017-05-11

    A reentrant temperature dependence of the normal state resistance often referred to as the N-shaped temperature dependence, is omnipresent in disordered superconductors - ranging from high-temperature cuprates to ultrathin superconducting films - that experience superconductor-to-insulator transition. Yet, despite the ubiquity of this phenomenon its origin still remains a subject of debate. Here we investigate strongly disordered superconducting TiN films and demonstrate universality of the reentrant behavior. We offer a quantitative description of the N-shaped resistance curve. We show that upon cooling down the resistance first decreases linearly with temperature and then passes through the minimum that marks the 3D-2D crossover in the system. In the 2D temperature range the resistance first grows with decreasing temperature due to quantum contributions and eventually drops to zero as the system falls into a superconducting state. Our findings demonstrate the prime importance of disorder in dimensional crossover effects.

  19. Superconducting properties of NbN film, bridge and meanders

    NASA Astrophysics Data System (ADS)

    Joshi, Lalit M.; Verma, Apoorva; Gupta, Anurag; Rout, P. K.; Husale, Sudhir; Budhani, R. C.

    2018-05-01

    The transport properties of superconducting NbN nanostructures in the form of thin film, bridge of width (w) = 50 μm and three meanders of w = 500, 250 and 100 nm have been investigated by resistance (R) measurements in temperature (T) range = 2 -300 K and magnetic field (B) range = 0 - 7 Tesla. The nanostructuring was carried out using Focused Ion Beam (FIB) milling. Reduction of sample width results in significant changes in the normal and superconducting state properties. For instance, the observed metallic behavior in the thin film sample is lost and the normal state resistance increases drastically from 2.4 Ω to 418 kΩ for the 100 nm meander. In the superconducting state, the value of critical temperature Tc (upper critical field Bc2 at T = 0 K) reduces gradually with width reduction, it changes from 13.15 K (42.8 Tesla) in the case of thin film sample to 5.7 K (12.7 Tesla) for the 100 nm meander sample. The superconducting transitions are found to get broader for the bridge sample and the meanders additionally show low-temperature resistive tails. In case of all the samples with reduced width, the transition onsets are found to be rounded at surprisingly high values of T ˜ 25 K >> Tc. These results are discussed in terms of the possible effects of FIB processing and weak localization in our samples.

  20. Damping in high-temperature superconducting levitation systems

    DOEpatents

    Hull, John R [Sammamish, WA

    2009-12-15

    Methods and apparatuses for improved damping in high-temperature superconducting levitation systems are disclosed. A superconducting element (e.g., a stator) generating a magnetic field and a magnet (e.g. a rotor) supported by the magnetic field are provided such that the superconducting element is supported relative to a ground state with damped motion substantially perpendicular to the support of the magnetic field on the magnet. Applying this, a cryostat housing the superconducting bearing may be coupled to the ground state with high damping but low radial stiffness, such that its resonant frequency is less than that of the superconducting bearing. The damping of the cryostat may be substantially transferred to the levitated magnetic rotor, thus, providing damping without affecting the rotational loss, as can be derived applying coupled harmonic oscillator theory in rotor dynamics. Thus, damping can be provided to a levitated object, without substantially affecting the rotational loss.

  1. Electronic origin of high-temperature superconductivity in single-layer FeSe superconductor.

    PubMed

    Liu, Defa; Zhang, Wenhao; Mou, Daixiang; He, Junfeng; Ou, Yun-Bo; Wang, Qing-Yan; Li, Zhi; Wang, Lili; Zhao, Lin; He, Shaolong; Peng, Yingying; Liu, Xu; Chen, Chaoyu; Yu, Li; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Chen, Chuangtian; Xu, Zuyan; Hu, Jiangping; Chen, Xi; Ma, Xucun; Xue, Qikun; Zhou, X J

    2012-07-03

    The recent discovery of high-temperature superconductivity in iron-based compounds has attracted much attention. How to further increase the superconducting transition temperature (T(c)) and how to understand the superconductivity mechanism are two prominent issues facing the current study of iron-based superconductors. The latest report of high-T(c) superconductivity in a single-layer FeSe is therefore both surprising and significant. Here we present investigations of the electronic structure and superconducting gap of the single-layer FeSe superconductor. Its Fermi surface is distinct from other iron-based superconductors, consisting only of electron-like pockets near the zone corner without indication of any Fermi surface around the zone centre. Nearly isotropic superconducting gap is observed in this strictly two-dimensional system. The temperature dependence of the superconducting gap gives a transition temperature T(c)~ 55 K. These results have established a clear case that such a simple electronic structure is compatible with high-T(c) superconductivity in iron-based superconductors.

  2. The 20 GHz circularly polarized, high temperature superconducting microstrip antenna array

    NASA Technical Reports Server (NTRS)

    Morrow, Jarrett D.; Williams, Jeffery T.; Long, Stuart A.; Wolfe, John C.

    1994-01-01

    The primary goal was to design and characterize a four-element, 20 GHz, circularly polarized microstrip patch antenna fabricated from YBa2Cu3O(x) superconductor. The purpose is to support a high temperature superconductivity flight communications experiment between the space shuttle orbiter and the ACTS satellite. This study is intended to provide information into the design, construction, and feasibility of a circularly polarized superconducting 20 GHz downlink or cross-link antenna. We have demonstrated that significant gain improvements can be realized by using superconducting materials for large corporate fed array antennas. In addition, we have shown that when constructed from superconducting materials, the efficiency, and therefore the gain, of microstrip patches increases if the substrate is not so thick that the dominant loss mechanism for the patch is radiation into the surface waves of the conductor-backed substrate. We have considered two design configurations for a superconducting 20 GHz four-element circularly polarized microstrip antenna array. The first is the Huang array that uses properly oriented and phased linearly polarized microstrip patch elements to realize a circularly polarized pattern. The second is a gap-coupled array of circularly polarized elements. In this study we determined that although the Huang array operates well on low dielectric constant substrates, its performance becomes extremely sensitive to mismatches, interelement coupling, and design imperfections for substrates with high dielectric constants. For the gap-coupled microstrip array, we were able to fabricate and test circularly polarized elements and four-element arrays on LaAlO3 using sputtered copper films. These antennas were found to perform well, with relatively good circular polarization. In addition, we realized a four-element YBa2Cu3O(x) array of the same design and measured its pattern and gain relative to a room temperature copper array. The patterns were

  3. Probing transport mechanisms of BaFe2As2 superconducting films and grain boundary junctions by noise spectroscopy

    PubMed Central

    Barone, C.; Romeo, F.; Pagano, S.; Adamo, M.; Nappi, C.; Sarnelli, E.; Kurth, F.; Iida, K.

    2014-01-01

    An important step forward for the understanding of high-temperature superconductivity has been the discovery of iron-based superconductors. Among these compounds, iron pnictides could be used for high-field magnet applications, resulting more advantageous over conventional superconductors, due to a high upper critical field as well as its low anisotropy at low temperatures. However, the principal obstacle in fabricating high quality superconducting wires and tapes is given by grain boundaries. In order to study these effects, the dc transport and voltage-noise properties of Co-doped BaFe2As2 superconducting films with artificial grain boundary junctions have been investigated. A specific procedure allows the separation of the film noise from that of the junction. While the former shows a standard 1/f behaviour, the latter is characterized by an unconventional temperature-dependent multi-Lorentzian voltage-spectral density. Moreover, below the film superconducting critical temperature, a peculiar noise spectrum is found for the grain boundary junction. Possible theoretical interpretation of these phenomena is proposed. PMID:25145385

  4. Damping in high-temperature superconducting levitation systems

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hull, John R.

    2009-12-15

    Methods and apparatuses for improved damping in high-temperature superconducting levitation systems are disclosed. A superconducting element (e.g., a stator) generating a magnetic field and a magnet (e.g. a rotor) supported by the magnetic field are provided such that the superconducting element is supported relative to a ground state with damped motion substantially perpendicular to the support of the magnetic field on the magnet. Applying this, a cryostat housing the superconducting bearing may be coupled to the ground state with high damping but low radial stiffness, such that its resonant frequency is less than that of the superconducting bearing. The dampingmore » of the cryostat may be substantially transferred to the levitated magnetic rotor, thus, providing damping without affecting the rotational loss, as can be derived applying coupled harmonic oscillator theory in rotor dynamics. Thus, damping can be provided to a levitated object, without substantially affecting the rotational loss.« less

  5. High temperature superconducting magnetic energy storage for future NASA missions

    NASA Technical Reports Server (NTRS)

    Faymon, Karl A.; Rudnick, Stanley J.

    1988-01-01

    Several NASA sponsored studies based on 'conventional' liquid helium temperature level superconductivity technology have concluded that superconducting magnetic energy storage has considerable potential for space applications. The advent of high temperature superconductivity (HTSC) may provide additional benefits over conventional superconductivity technology, making magnetic energy storage even more attractive. The proposed NASA space station is a possible candidate for the application of HTSC energy storage. Alternative energy storage technologies for this and other low Earth orbit missions are compared.

  6. A Method for Suppressing Superconductivity of Thin Films

    NASA Astrophysics Data System (ADS)

    Suppula, Tarmo; Pekola, Jukka; Kauppinen, Juha

    2003-03-01

    We have developed a method for suppressing superconductivity of thin films. Thin stripes of cobalt grown by e-gun evaporation and patterned by e-beam lithography were placed in the vicinity of aluminium thin film structures. The cobalt stripes were magnetized at 4.2 K with a superconducting coil and the remanence suppressed superconductivity of the Al stripe at temperatures down to 50 mK at least. The magnetization remained in thermal cycling and in a longer storage at room temperature. Motivation for this work is the Coulomb Blockade Thermometer(CBT)^1 which has to be in a normal state to operate. The CBT sensor contains aluminium which is superconducting at temperatures below 1.4 K. An external magnetic field is not always available or acceptable in cryostats. A small grain of permanent magnet mounted to the sensor is another solution, but suspicious if the sensor is put in strong magnetic fields or if "zero field" environment is required. We have shown that suitably patterned and magnetized Co stripes in the vicinity of tunnel junctions of the CBT can solve this problem. The amount of magnetic material in the sensor, as well as the stray field, is very small. This technique may be useful in other low temperature thin film devices also. 1) Product of Nanoway Ltd.

  7. Common electronic origin of superconductivity in (Li,Fe)OHFeSe bulk superconductor and single-layer FeSe/SrTiO3 films.

    PubMed

    Zhao, Lin; Liang, Aiji; Yuan, Dongna; Hu, Yong; Liu, Defa; Huang, Jianwei; He, Shaolong; Shen, Bing; Xu, Yu; Liu, Xu; Yu, Li; Liu, Guodong; Zhou, Huaxue; Huang, Yulong; Dong, Xiaoli; Zhou, Fang; Liu, Kai; Lu, Zhongyi; Zhao, Zhongxian; Chen, Chuangtian; Xu, Zuyan; Zhou, X J

    2016-02-08

    The mechanism of high-temperature superconductivity in the iron-based superconductors remains an outstanding issue in condensed matter physics. The electronic structure plays an essential role in dictating superconductivity. Recent revelation of distinct electronic structure and high-temperature superconductivity in the single-layer FeSe/SrTiO3 films provides key information on the role of Fermi surface topology and interface in inducing or enhancing superconductivity. Here we report high-resolution angle-resolved photoemission measurements on the electronic structure and superconducting gap of an FeSe-based superconductor, (Li0.84Fe0.16)OHFe0.98Se, with a Tc at 41 K. We find that this single-phase bulk superconductor shows remarkably similar electronic behaviours to that of the superconducting single-layer FeSe/SrTiO3 films in terms of Fermi surface topology, band structure and the gap symmetry. These observations provide new insights in understanding high-temperature superconductivity in the single-layer FeSe/SrTiO3 films and the mechanism of superconductivity in the bulk iron-based superconductors.

  8. Common electronic origin of superconductivity in (Li,Fe)OHFeSe bulk superconductor and single-layer FeSe/SrTiO3 films

    PubMed Central

    Zhao, Lin; Liang, Aiji; Yuan, Dongna; Hu, Yong; Liu, Defa; Huang, Jianwei; He, Shaolong; Shen, Bing; Xu, Yu; Liu, Xu; Yu, Li; Liu, Guodong; Zhou, Huaxue; Huang, Yulong; Dong, Xiaoli; Zhou, Fang; Liu, Kai; Lu, Zhongyi; Zhao, Zhongxian; Chen, Chuangtian; Xu, Zuyan; Zhou, X. J.

    2016-01-01

    The mechanism of high-temperature superconductivity in the iron-based superconductors remains an outstanding issue in condensed matter physics. The electronic structure plays an essential role in dictating superconductivity. Recent revelation of distinct electronic structure and high-temperature superconductivity in the single-layer FeSe/SrTiO3 films provides key information on the role of Fermi surface topology and interface in inducing or enhancing superconductivity. Here we report high-resolution angle-resolved photoemission measurements on the electronic structure and superconducting gap of an FeSe-based superconductor, (Li0.84Fe0.16)OHFe0.98Se, with a Tc at 41 K. We find that this single-phase bulk superconductor shows remarkably similar electronic behaviours to that of the superconducting single-layer FeSe/SrTiO3 films in terms of Fermi surface topology, band structure and the gap symmetry. These observations provide new insights in understanding high-temperature superconductivity in the single-layer FeSe/SrTiO3 films and the mechanism of superconductivity in the bulk iron-based superconductors. PMID:26853801

  9. Process for preparing superconducting film having substantially uniform phase development

    DOEpatents

    Bharacharya, Raghuthan; Parilla, Philip A.; Blaugher, Richard D.

    1995-01-01

    A process for preparing a superconducting film, such as a thallium-barium-calcium-copper oxide superconducting film, having substantially uniform phase development. The process comprises providing an electrodeposition bath having one or more soluble salts of one or more respective potentially superconducting metals in respective amounts adequate to yield a superconducting film upon subsequent appropriate treatment. Should all of the metals required for producing a superconducting film not be made available in the bath, such metals can be a part of the ambient during a subsequent annealing process. A soluble silver salt in an amount between about 0.1% and about 4.0% by weight of the provided other salts is also provided to the bath, and the bath is electrically energized to thereby form a plated film. The film is annealed in ambient conditions suitable to cause formation of a superconductor film. Doping with silver reduces the temperature at which the liquid phase appears during the annealing step, initiates a liquid phase throughout the entire volume of deposited material, and influences the nucleation and growth of the deposited material.

  10. Possibility of high temperature superconducting phases in PdH

    NASA Astrophysics Data System (ADS)

    Tripodi, Paolo; Di Gioacchino, Daniele; Borelli, Rodolfo; Vinko, Jenny Darja

    2003-05-01

    Possible new superconducting phases with a high critical transition temperature (Tc) have been found in stable palladium-hydrogen (PdHx) samples for stoichiometric ratio x=H/Pd⩾1, in addition to the well-known low critical transition temperature (0⩽Tc⩽9) when x is in the range (0.75⩽x⩽1.00). Possible new measured superconducting phases with critical temperature in the range 51⩽Tc⩽295 K occur. This Tc varies considerably with every milli part of x when x exceeds unit. A superconducting critical current density Jc⩾6.1×104 A cm-2 has been measured at 77 K with HDC=0 T.

  11. Sputtered superconducting films of Bi sub 2 Sr sub 2 CaCu sub 2 O sub x made by low-temperature, in-situ growth

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kampwirth, R.T.; Gray, K.E.; Andersen, P.H.

    1989-01-01

    Composite target rf magnetron sputtering has previously been successfully employed to make superconducting films of YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} in-situ at substrate temperatures T{sub s} < 700{degree}C. We report the successful growth of superconducting films of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} on single crystal MgO substrates by a low-temperature process using dc magnetron sputtering from a Bi-enriched composite target. Using a substrate temperature T{sub s} {approx} 645{degree}C, metallic films with a superconducting onset of 90--100K and an extrapolated T{sub c0} = 56K have been obtained. X-ray diffraction shows the films to be c-axis oriented. Electron microscopy reveals that the filmsmore » are not significantly smoother than films which were post-annealed at 865{degree}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. 9 refs., 4 figs., 1 tab.« less

  12. Highly textured oxypnictide superconducting thin films on metal substrates

    NASA Astrophysics Data System (ADS)

    Iida, Kazumasa; Kurth, Fritz; Chihara, Masashi; Sumiya, Naoki; Grinenko, Vadim; Ichinose, Ataru; Tsukada, Ichiro; Hänisch, Jens; Matias, Vladimir; Hatano, Takafumi; Holzapfel, Bernhard; Ikuta, Hiroshi

    2014-10-01

    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 43 K with a self-field critical current density (Jc) of 7.0 × 10 4 A / cm 2 at 5 K, 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.

  13. Superconducting gamma and fast-neutron spectrometers with high energy resolution

    DOEpatents

    Friedrich, Stephan; , Niedermayr, Thomas R.; Labov, Simon E.

    2008-11-04

    Superconducting Gamma-ray and fast-neutron spectrometers with very high energy resolution operated at very low temperatures are provided. The sensor consists of a bulk absorber and a superconducting thermometer weakly coupled to a cold reservoir, and determines the energy of the incident particle from the rise in temperature upon absorption. A superconducting film operated at the transition between its superconducting and its normal state is used as the thermometer, and sensor operation at reservoir temperatures around 0.1 K reduces thermal fluctuations and thus enables very high energy resolution. Depending on the choice of absorber material, the spectrometer can be configured either as a Gamma-spectrometer or as a fast-neutron spectrometer.

  14. Experimental Investigation of a Broadband High-Temperature Superconducting Terahertz Mixer Operating at Temperatures Between 40 and 77 K

    NASA Astrophysics Data System (ADS)

    Gao, Xiang; Du, Jia; Zhang, Ting; Jay Guo, Y.; Foley, Cathy P.

    2017-11-01

    This paper presents a systematic investigation of a broadband thin-film antenna-coupled high-temperature superconducting (HTS) terahertz (THz) harmonic mixer at relatively high operating temperature from 40 to 77 K. The mixer device chip was fabricated using the CSIRO established step-edge YBa2Cu3O7-x (YBCO) Josephson junction technology, packaged in a well-designed module and cooled in a temperature adjustable cryocooler. Detailed experimental characterizations were carried out for the broadband HTS mixer at both the 200 and 600 GHz bands in harmonic mixing mode. The DC current-voltage characteristics (IVCs), bias current condition, local oscillator (LO) power requirement, frequency response, as well as conversion efficiency under different bath temperatures were thoroughly investigated for demonstrating the frequency down-conversion performance.

  15. Research briefing on high-temperature superconductivity

    NASA Astrophysics Data System (ADS)

    1987-10-01

    The research briefing was prepared in response to the exciting developments in superconductivity in ceramic oxide materials announced earlier in 1987. The panel's specific charge was to examine not only the scientific opportunities in high-temperature superconductivity but also the barriers to commercial exploitation. While the base of experimental knowledge on the superconductors is growing rapidly, there is as yet no generally accepted theoretical explanation of their behavior. The fabrication and processing challenges presented by the materials suggest that the period or precommercial exploration for applications will probably extend for a decade or more. Near term prospects for applications include magnetic shielding, the voltage standard, superconducting quantum interference devices, infrared sensors, microwave devices, and analog signal processing. The panel also identified a number of longer-term prospects in high-field and large-scale applications, and in electronics. The United States' competitive position in the field is discussed, major scientific and technological objectives for research and development identified, and concludes with a series of recommendations.

  16. Tuning Superconductivity in FeSe Thin Films via Magnesium Doping.

    PubMed

    Qiu, Wenbin; Ma, Zongqing; Liu, Yongchang; Shahriar Al Hossain, Mohammed; Wang, Xiaolin; Cai, Chuanbing; Dou, Shi Xue

    2016-03-01

    In contrast to its bulk crystal, the FeSe thin film or layer exhibits better superconductivity performance, which recently attracted much interest in its fundamental research as well as in potential applications around the world. In the present work, tuning superconductivity in FeSe thin films was achieved by magnesium-doping technique. Tc is significantly enhanced from 10.7 K in pure FeSe films to 13.4 K in optimized Mg-doped ones, which is approximately 1.5 times higher than that of bulk crystals. This is the first time achieving the enhancement of superconducting transition temperature in FeSe thin films with practical thickness (120 nm) via a simple Mg-doping process. Moreover, these Mg-doped FeSe films are quite stable in atmosphere with Hc2 up to 32.7 T and Tc(zero) up to 12 K, respectively, implying their outstanding potential for practical applications in high magnetic fields. It was found that Mg enters the matrix of FeSe lattice, and does not react with FeSe forming any other secondary phase. Actually, Mg first occupies Fe-vacancies, and then substitutes for some Fe in the FeSe crystal lattices when Fe-vacancies are fully filled. Simultaneously, external Mg-doping introduces sufficient electron doping and induces the variation of electron carrier concentration according to Hall coefficient measurements. This is responsible for the evolution of superconducting performance in FeSe thin films. Our results provide a new strategy to improve the superconductivity of 11 type Fe-based superconductors and will help us to understand the intrinsic mechanism of this unconventional superconducting system.

  17. Fabrication of Large Bulk High Temperature Superconducting Articles

    NASA Technical Reports Server (NTRS)

    Koczor, Ronald (Inventor); Hiser, Robert A. (Inventor)

    2003-01-01

    A method of fabricating large bulk high temperature superconducting articles which comprises the steps of selecting predetermined sizes of crystalline superconducting materials and mixing these specific sizes of particles into a homogeneous mixture which is then poured into a die. The die is placed in a press and pressurized to predetermined pressure for a predetermined time and is heat treated in the furnace at predetermined temperatures for a predetermined time. The article is left in the furnace to soak at predetermined temperatures for a predetermined period of time and is oxygenated by an oxygen source during the soaking period.

  18. High Temperature Semiconductor Process

    NASA Technical Reports Server (NTRS)

    1998-01-01

    A sputtering deposition system capable of depositing large areas of high temperature superconducting materials was developed by CVC Products, Inc. with the support of the Jet Propulsion Laboratory SBIR (Small Business Innovative Research) program. The system was devleoped for NASA to produce high quality films of high temperature superconducting material for microwave communication system components. The system is also being used to deposit ferroelectric material for capacitors and the development of new electro-optical materials.2002103899

  19. Effects of high-energy proton irradiation on the superconducting properties of Fe(Se,Te) thin films

    NASA Astrophysics Data System (ADS)

    Sylva, G.; Bellingeri, E.; Ferdeghini, C.; Martinelli, A.; Pallecchi, I.; Pellegrino, L.; Putti, M.; Ghigo, G.; Gozzelino, L.; Torsello, D.; Grimaldi, G.; Leo, A.; Nigro, A.; Braccini, V.

    2018-05-01

    In this paper we explore the effects of 3.5 MeV proton irradiation on Fe(Se,Te) thin films grown on CaF2. In particular, we carry out an experimental investigation with different irradiation fluences up to 7.30 · 1016 cm‑2 and different proton implantation depths, in order to clarify whether and to what extent the critical current is enhanced or suppressed, what are the effects of irradiation on the critical temperature, resistivity, and critical magnetic fields, and finally what is the role played by the substrate in this context. We find that the effect of irradiation on superconducting properties is generally small compared to the case of other iron-based superconductors. The irradiation effect is more evident on the critical current density Jc, while it is minor on the transition temperature Tc, normal state resistivity ρ, and on the upper critical field Hc2 up to the highest fluences explored in this work. In more detail, our analysis shows that when protons implant in the substrate far from the superconducting film, the critical current can be enhanced up to 50% of the pristine value at 7 T and 12 K; meanwhile, there is no appreciable effect on critical temperature and critical fields together with a slight decrease in resistivity. On the contrary, when the implantation layer is closer to the film–substrate interface, both critical current and temperature show a decrease accompanied by an enhancement of the resistivity and lattice strain. This result evidences that possible modifications induced by irradiation in the substrate may affect the superconducting properties of the film via lattice strain. The robustness of the Fe(Se,Te) system to irradiation-induced damage makes it a promising compound for the fabrication of magnets in high-energy accelerators.

  20. Low cost, formable, high T(sub c) superconducting wire

    NASA Technical Reports Server (NTRS)

    Smialek, James L. (Inventor)

    1991-01-01

    A ceramic superconductivity part such as a wire is produced through the partial oxidation of a specially formulated copper alloy in the core. The alloys contain low level quantities of rare earth and alkaline earth dopant elements. Upon oxidation at high temperature, superconducting oxide phases are formed as a thin film.

  1. Cryogenic deformation of high temperature superconductive composite structures

    DOEpatents

    Roberts, Peter R.; Michels, William; Bingert, John F.

    2001-01-01

    An improvement in a process of preparing a composite high temperature oxide superconductive wire is provided and involves conducting at least one cross-sectional reduction step in the processing preparation of the wire at sub-ambient temperatures.

  2. Process for preparing superconducting film having substantially uniform phase development

    DOEpatents

    Bharacharya, R.; Parilla, P.A.; Blaugher, R.D.

    1995-12-19

    A process is disclosed for preparing a superconducting film, such as a thallium-barium-calcium-copper oxide superconducting film, having substantially uniform phase development. The process comprises providing an electrodeposition bath having one or more soluble salts of one or more respective potentially superconducting metals in respective amounts adequate to yield a superconducting film upon subsequent appropriate treatment. Should all of the metals required for producing a superconducting film not be made available in the bath, such metals can be a part of the ambient during a subsequent annealing process. A soluble silver salt in an amount between about 0.1% and about 4.0% by weight of the provided other salts is also provided to the bath, and the bath is electrically energized to thereby form a plated film. The film is annealed in ambient conditions suitable to cause formation of a superconductor film. Doping with silver reduces the temperature at which the liquid phase appears during the annealing step, initiates a liquid phase throughout the entire volume of deposited material, and influences the nucleation and growth of the deposited material. 3 figs.

  3. Room temperature deposition of sputtered TiN films for superconducting coplanar waveguide resonators

    NASA Astrophysics Data System (ADS)

    Ohya, S.; Chiaro, B.; Megrant, A.; Neill, C.; Barends, R.; Chen, Y.; Kelly, J.; Low, D.; Mutus, J.; O'Malley, P. J. J.; Roushan, P.; Sank, D.; Vainsencher, A.; Wenner, J.; White, T. C.; Yin, Y.; Schultz, B. D.; Palmstrøm, C. J.; Mazin, B. A.; Cleland, A. N.; Martinis, John M.

    2014-01-01

    We present a systematic study of the properties of room temperature deposited TiN films by varying the deposition conditions in an ultra-high-vacuum reactive magnetron sputtering chamber. By increasing the deposition pressure from 2 to 9 mTorr while keeping a nearly stoichiometric composition of Ti1-xNx (x = 0.5) without substrate heating, the film resistivity increases, the dominant crystal orientation changes from (100) to (111), grain boundaries become clearer, and the strong compressive in-plane strain changes to weak tensile in-plane strain. The TiN films absorb a high concentration of contaminants including hydrogen, carbon, and oxygen when they are exposed to air after deposition. With the target-substrate distance set to 88 mm the contaminant levels increase from ˜0.1% to ˜10% as the pressure is increased from 2 to 9 mTorr. The contaminant concentrations also correlate with in-plane distance from the center of the substrate and increase by roughly two orders of magnitude as the target-substrate distance is increased from 88 to 266 mm. These contaminants are found to strongly influence the properties of TiN thin films. For instance, the resistivity of stoichiometric films increases by around a factor of 5 as the oxygen content increases from 0.1% to 11%. These results strongly suggest that the energy of the sputtered TiN particles plays a crucial role in determining the TiN film properties, and that it is important to precisely control the energy of these particles to obtain high-quality TiN films. Superconducting coplanar waveguide resonators made from a series of nearly stoichiometric films grown at pressures from 2 to 7 mTorr show a substantial increase in intrinsic quality factor from ˜104 to ˜106 as the magnitude of the compressive strain decreases from nearly 3800 MPa to approximately 150 MPa and the oxygen content increases from 0.1% to 8%. Surprisingly, the films with a higher oxygen content exhibit lower loss, but care must be taken when

  4. Growth and patterning of laser ablated superconducting YBa2Cu3O7 films on LaAlO3 substrates

    NASA Technical Reports Server (NTRS)

    Warner, J. D.; Bhasin, K. B.; Varaljay, N. C.; Bohman, D. Y.; Chorey, C. M.

    1989-01-01

    A high quality superconducting film on a substrate with a low dielectric constant is desired for passive microwave circuit applications. In addition, it is essential that the patterning process does not effect the superconducting properties of the thin films to achieve the highest circuit operating temperatures. YBa2Cu3O7 superconducting films were grown on lanthanum aluminate substrates using laser ablation with resulting maximum transition temperature (T sub c) of 90 K. The films were grown on a LaAlO3 which was at 775 C and in 170 mtorr of oxygen and slowly cooled to room temperature in 1 atm of oxygen. These films were then processed using photolithography and a negative photoresist with an etch solution of bromine and ethanol. Results are presented on the effect of the processing on T(sub c) of the film and the microwave properties of the patterned films.

  5. Doubling the critical current density in superconducting FeSe 0.5Te 0.5 thin films by low temperature oxygen annealing

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Cheng; Si, Weidong; Li, Qiang

    Iron chalcogenide superconducting thin films and coated conductors are attractive for potential high field applications at liquid helium temperature for their high critical current densities J c, low anisotropies, and relatively strong grain couplings. Embedding flux pinning defects is a general approach to increase the in-field performance of superconductors. However, many effective pinning defects can adversely affect the zero field or self-field J c, particularly in cuprate high temperature superconductors. Here, we report the doubling of the self-field J c in FeSe 0.5Te 0.5 films by low temperature oxygen annealing, reaching ~3 MA/cm 2. In-field performance is also dramatically enhanced.more » In conclusion, our results demonstrate that low temperature oxygen annealing is a simple and cost-efficient post-treatment technique which can greatly help to accelerate the potential high field applications of the iron-based superconductors.« less

  6. Doubling the critical current density in superconducting FeSe 0.5Te 0.5 thin films by low temperature oxygen annealing

    DOE PAGES

    Zhang, Cheng; Si, Weidong; Li, Qiang

    2016-11-14

    Iron chalcogenide superconducting thin films and coated conductors are attractive for potential high field applications at liquid helium temperature for their high critical current densities J c, low anisotropies, and relatively strong grain couplings. Embedding flux pinning defects is a general approach to increase the in-field performance of superconductors. However, many effective pinning defects can adversely affect the zero field or self-field J c, particularly in cuprate high temperature superconductors. Here, we report the doubling of the self-field J c in FeSe 0.5Te 0.5 films by low temperature oxygen annealing, reaching ~3 MA/cm 2. In-field performance is also dramatically enhanced.more » In conclusion, our results demonstrate that low temperature oxygen annealing is a simple and cost-efficient post-treatment technique which can greatly help to accelerate the potential high field applications of the iron-based superconductors.« less

  7. Cuprate High Temperature Superconductors and the Vision for Room Temperature Superconductivity

    NASA Astrophysics Data System (ADS)

    Newns, Dennis M.; Martyna, Glenn J.; Tsuei, Chang C.

    Superconducting transition temperatures of 164 K in cuprate high temperature superconductors (HTS) and recently 200 K in H3S under high pressure encourage us to believe that room temperature superconductivity (RTS) might be possible. In considering paths to RTS, we contrast conventional (BCS) SC, such as probably manifested by H3S, with the unconventional superconductivity (SC) in the cuprate HTS family. Turning to SC models, we show that in the presence of one or more van Hove singularities (vHs) near the Fermi level, SC mediated by classical phonons (kBTc>ℏ×phonon frequency) can occur. The phonon frequency in the standard Tc formula is replaced by an electronic cutoff, enabling a much higher Tc independent of phonon frequency. The resulting Tc and isotope shift plot versus doping strongly resembles that seen experimentally in HTS. A more detailed theory of HTS, which involves mediation by classical phonons, satisfactorily reproduces the chief anomalous features characteristic of these materials. We propose that, while a path to RTS through an H3S-like scenario via strongly-coupled ultra-high frequency phonons is attractive, features perhaps unavailable at ordinary pressures, a route involving SC mediated by classical phonons which can be low frequency may be found.

  8. Degradation of superconducting Nb/NbN films by atmospheric oxidation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Henry, M. David; Wolfley, Steve; Young, Travis

    2017-03-01

    Niobium and niobium nitride thin films are transitioning from fundamental research toward wafer scale manufacturing with technology drivers that include superconducting circuits and electronics, optical single photon detectors, logic, and memory. Successful microfabrication requires precise control over the properties of sputtered superconducting films, including oxidation. Previous work has demonstrated the mechanism in oxidation of Nb and how film structure could have deleterious effects upon the superconducting properties. This study provides an examination of atmospheric oxidation of NbN films. By examination of the room temperature sheet resistance of NbN bulk oxidation was identified and confirmed by secondary ion mass spectrometry. Asmore » a result, Meissner magnetic measurements confirmed the bulk oxidation not observed with simple cryogenic resistivity measurements.« less

  9. High-Temperature Capacitor Polymer Films

    NASA Astrophysics Data System (ADS)

    Tan, Daniel; Zhang, Lili; Chen, Qin; Irwin, Patricia

    2014-12-01

    Film capacitor technology has been under development for over half a century to meet various applications such as direct-current link capacitors for transportation, converters/inverters for power electronics, controls for deep well drilling of oil and gas, direct energy weapons for military use, and high-frequency coupling circuitry. The biaxially oriented polypropylene film capacitor remains the state-of-the-art technology; however, it is not able to meet increasing demand for high-temperature (>125°C) applications. A number of dielectric materials capable of operating at high temperatures (>140°C) have attracted investigation, and their modifications are being pursued to achieve higher volumetric efficiency as well. This paper highlights the status of polymer dielectric film development and its feasibility for capacitor applications. High-temperature polymers such as polyetherimide (PEI), polyimide, and polyetheretherketone were the focus of our studies. PEI film was found to be the preferred choice for high-temperature film capacitor development due to its thermal stability, dielectric properties, and scalability.

  10. Magnetic suspension using high temperature superconducting cores

    NASA Technical Reports Server (NTRS)

    Scurlock, R. G.

    1992-01-01

    The development of YBCO high temperature superconductors, in wire and tape forms, is rapidly approaching the point where the bulk transport current density j vs magnetic field H characteristics with liquid nitrogen cooling will enable its use in model cores. On the other hand, BSCCO high temperature superconductor in wire form has poor j-H characteristics at 77 K today, although with liquid helium or hydrogen cooling, it appears to be superior to NbTi superconductor. Since liquid nitrogen cooling is approx. 100 times cheaper than liquid helium cooling, the use of YBCO is very attractive for use in magnetic suspension. The design is discussed of a model core to accommodate lift and drag loads up to 6000 and 3000 N respectively. A comparison is made between the design performance of a liquid helium cooled NbTi (or BSCCO) superconducting core and a liquid nitrogen cooled YBCO superconducting core.

  11. High temperature superconducting YBCO microwave filters

    NASA Astrophysics Data System (ADS)

    Aghabagheri, S.; Rasti, M.; Mohammadizadeh, M. R.; Kameli, P.; Salamati, H.; Mohammadpour-Aghdam, K.; Faraji-Dana, R.

    2018-06-01

    Epitaxial thin films of YBCO high temperature superconductor are widely used in telecommunication technology such as microwave filter, antenna, coupler and etc., due to their lower surface resistance and lower microwave loss than their normal conductor counterparts. Thin films of YBCO were fabricated by PLD technique on LAO substrate. Transition temperature and width were 88 K and 3 K, respectively. A filter pattern was designed and implemented by wet photolithography method on the films. Characterization of the filter at 77 K has been compared with the simulation results and the results for a made gold filter. Both YBCO and gold filters show high microwave loss. For YBCO filter, the reason may be due to the improper contacts on the feedlines and for gold filter, low thickness of the gold film has caused the loss increased.

  12. Superconductivity of Rock-Salt Structure LaO Epitaxial Thin Film.

    PubMed

    Kaminaga, Kenichi; Oka, Daichi; Hasegawa, Tetsuya; Fukumura, Tomoteru

    2018-06-06

    We report a superconducting transition in a LaO epitaxial thin film with the superconducting transition onset temperature ( T c ) at around 5 K. This T c is higher than those of other lanthanum monochalcogenides and opposite to their chemical trend: T c = 0.84, 1.02, and 1.48 K for LaX (X = S, Se, Te), respectively. The carrier control resulted in a dome-shaped T c as a function of electron carrier density. In addition, the T c was significantly sensitive to epitaxial strain in spite of the highly symmetric crystal structure. This rock-salt superconducting LaO could be a building block to design novel superlattice superconductors.

  13. Miniaturized High-Temperature Superconducting/Dielectric Multilayer Filters for Satellite Communications

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.

    1997-01-01

    Most communication satellites contain well over a hundred filters in their payload. Current technology in typical satellite multiplexers use dual-mode cavity or dielectric resonator filters that are large (approx. 25 to 125 cu in) and heavy (up to 600 g). As the complexity of future advanced electronic systems for satellite communications increases, even more filters will be needed, requiring filter miniaturization without performance degradation. Such improvements in filter technology will enhance satellite performance. To reduce the size, weight, and cost of the multiplexers without compromising performance, the NASA Lewis Research Center is collaborating with industry to develop a new class of dual-mode multilayer filters consisting of YBa2Cu3O7-delta high-temperature superconducting (HTS) thin films on LaAlO3 substrates.

  14. Contribution of ion beam analysis methods to the development of second generation high temperature superconducting wires

    NASA Astrophysics Data System (ADS)

    Usov, I. O.; Arendt, P. N.; Foltyn, S. R.; Stan, L.; DePaula, R. F.; Holesinger, T. G.

    2010-06-01

    One of the crucial steps in the second generation high temperature superconducting wire program was development of the buffer-layer architecture. The architecture designed at the Superconductivity Technology Center at Los Alamos National Laboratory consists of several oxide layers wherein each layer plays a specific role, namely: nucleation layer, diffusion barrier, biaxially textured template, and intermediate layer providing a suitable lattice match to the superconducting Y 1Ba 2Cu 3O 7 (YBCO) compound. This report demonstrates how a wide range of ion beam analysis techniques (SIMS, RBS, channeling, PIXE, PIGE, NRA and ERD) was employed for analysis of each buffer layer and the YBCO film. These results assisted in understanding of a variety of physical processes occurring during the buffer layer fabrication and helped to optimize the buffer-layer architecture as a whole.

  15. Superconductivity in disordered thin films: giant mesoscopic fluctuations.

    PubMed

    Skvortsov, M A; Feigel'man, M V

    2005-07-29

    We discuss the intrinsic inhomogeneities of superconductive properties of uniformly disordered thin films with a large dimensionless conductance g. It is shown that mesoscopic fluctuations, which usually contain a small factor 1/g, are crucially enhanced near the critical conductance g(cF) > 1 where superconductivity is destroyed at T = 0 due to Coulomb suppression of the Cooper attraction. This leads to strong spatial fluctuations of the local transition temperature and thus to the percolative nature of the thermal superconductive transition.

  16. National Action Plan on Superconductivity Research and Development

    NASA Astrophysics Data System (ADS)

    1989-12-01

    The Superconductivity Action Plan pursuant to the Superconductivity and Competitiveness Act of 1988 is presented. The plan draws upon contributions from leaders in the technical community of the Federal Government responsible for research and development in superconductivity programs, as well as from the report of the Committee to Advise the President on Superconductivity. Input from leaders in the private sector was obtained during the formulation and review of the plan. Some contents: Coordination of the plan; Technical areas (high temperature superconductivity materials in general, high temperature superconductivity films for sensors and electronics, magnets, large area high temperature superconductivity films, bulk conductors); and Policy areas.

  17. Superconductivity in epitaxial InN thin films with large critical fields

    NASA Astrophysics Data System (ADS)

    Pal, Buddhadeb; Joshi, Bhanu P.; Chakraborti, Himadri; Jain, Aditya K.; Barick, Barun K.; Ghosh, Kankat; Laha, Apurba; Dhar, Subhabrata; Gupta, Kantimay Das

    2018-04-01

    We report superconductivity in Chemical Vapor Deposition (CVD) and Plasma-Assisted Molecular Beam Epitaxy (PA-MBE) grown epitaxial InN films having carrier density ˜ 1019 - 1020cm-3. The superconducting phase transition starts at temperatures around Tc,onset˜3 K and the resistance goes to zero completely at Tc0 ˜ 1.6 K. The temperature dependence of the critical field HC2(T) does not obey a two fluid Casimir-Gorter (C-G) model rather it is well explained by the 2-D Tinkham model. The extrapolated value of the zero-temperature perpendicular critical field HC2(0) is found to be between 0.25 - 0.9 T, which is ten times greater than that of Indium metal. It may indicate the intrinsic nature of superconductivity in InN films. The angle dependence of critical field is well described by Lawrence-Doniach (L-D) model, which suggest the existence of quasi-2D superconducting layers.

  18. Thin Film Technology of High-Critical-Temperature Superconducting Electronics.

    DTIC Science & Technology

    1985-12-11

    ANALISIS OF THIN-FILM SUPERCONDUCTORS J. Talvacchio, M. A. Janocko, J. R. Gavaler, and A...in the areas of substrate preparation, niobum nitride, nlobium-tin, and molybdenum-rhenium. AN INTEGRATED DEPOSITION AND ANALISI - FACILITT The four...mobility low (64). The voids are separating 1-3 nm clusters of dense deposit. At low deposition temperatures this microstructure will persist near

  19. Vortex variable range hopping in a conventional superconducting film

    NASA Astrophysics Data System (ADS)

    Percher, Ilana M.; Volotsenko, Irina; Frydman, Aviad; Shklovskii, Boris I.; Goldman, Allen M.

    2017-12-01

    The behavior of a disordered amorphous thin film of superconducting indium oxide has been studied as a function of temperature and magnetic field applied perpendicular to its plane. A superconductor-insulator transition has been observed, though the isotherms do not cross at a single point. The curves of resistance versus temperature on the putative superconducting side of this transition, where the resistance decreases with decreasing temperature, obey two-dimensional Mott variable-range hopping of vortices over wide ranges of temperature and resistance. To estimate the parameters of hopping, the film is modeled as a granular system and the hopping of vortices is treated in a manner analogous to hopping of charges. The reason the long-range interaction between vortices over the range of magnetic fields investigated does not lead to a stronger variation of resistance with temperature than that of two-dimensional Mott variable-range hopping remains unresolved.

  20. Ion beam deposition of in situ superconducting Y-Ba-Cu-O films

    NASA Astrophysics Data System (ADS)

    Klein, J. D.; Yen, A.; Clauson, S. L.

    1990-01-01

    Oriented superconducting YBa2Cu3O7 thin films were deposited on yttria-stabilized zirconia substrates by ion beam sputtering of a nonstoichiometric oxide target. The films exhibited zero-resistance critical temperatures as high as 80.5 K without post-deposition anneals. Both the deposition rate and the c lattice parameter data displayed two distinct regimes of dependence on the beam power of the ion source. Low-power sputtering yielded films with large c dimensions and low Tc's. Higher power sputtering produced a continuous decrease in the c lattice parameter and an increase in critical temperatures.

  1. Prospects and progress of high Tc superconductivity for space applications

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R.; Sokoloski, Marty M.

    1991-01-01

    Current research in the area of high temperature superconductivity is organized around four key areas: communications and data, sensors and cryogenics, propulsion and power, and space materials technology. Recently, laser ablated YBa2Cu3O(7-x) films on LaAlO3 produced far superior RF characteristics when compared to metallic films on the same substrate. The achievement has enabled a number of unique microwave device applications, such as low insertion loss phase shifters and high-Q filters. Melt texturing and melt-quenched techniques are being used to produce bulk material with optimized magnetic properties. These yttrium-enriched materials possess enhanced flux pinning characteristics and could lead to prototype cryocooler bearings. Significant progress has also occurred in bolometer and current lead technology. Studies were conducted to evaluate the effect of high temperature superconducting materials on the performance and life of high power magnetoplasma-dynamic thrusters. Extended studies were also performed to evaluate the benefit of superconducting magnetic energy storage for LEO space station, lunar, and Mars mission applications.

  2. Method of forming low cost, formable High T(subc) superconducting wire

    NASA Technical Reports Server (NTRS)

    Smialek, James L. (Inventor)

    1989-01-01

    A ceramic superconductivity part, such as a wire, is produced through the partial oxidation of a specially formulated copper alloy in a core. The alloys contains low level of quantities of rare earth and alkaline earth dopant elements. Upon oxidation at high temperatures, and superconducting oxide phases are formed as a thin film.

  3. Y1Ba2Cu3O(7-delta) thin film dc SQUIDs (superconducting quantum interference device)

    NASA Astrophysics Data System (ADS)

    Racah, Daniel

    1991-03-01

    Direct current superconducting quantum interferometers (SQUIDs) based on HTSC thin films have been measured and characterized. The thin films used were of different quality: (1) Granular films on Sapphire substrates, prepared either by e-gun evaporation, by laser ablation or by MOCVD (metal oxide chemical vapor deposition), (2) Epitaxial films on MgO substrates. Modulations of the voltage on the SQUIDs as a function of the applied flux have been observed in a wide range of temperatures. The nature of the modulation was found to be strongly dependent on the morphology of the film and on its critical current. The SQUIDs based on granular films were relatively noisy, hysteretic and with a complicated V-phi shape. Those devices based on low quality (lowIc) granular films could be measured only at low temperatures (much lower than 77 K). While those of higher quality (granular films with high Ic) could be measured near to the superconductive transition. The SQUID based on high quality epitaxial film was measured near Tc and showed an anomalous, time dependent behavior.

  4. Versatile fluoride substrates for Fe-based superconducting thin films

    NASA Astrophysics Data System (ADS)

    Kurth, F.; Reich, E.; Hänisch, J.; Ichinose, A.; Tsukada, I.; Hühne, R.; Trommler, S.; Engelmann, J.; Schultz, L.; Holzapfel, B.; Iida, K.

    2013-04-01

    We demonstrate the growth of Co-doped BaFe2As2 (Ba-122) thin films on CaF2 (001), SrF2 (001), and BaF2 (001) single crystal substrates using pulsed laser deposition. All films are grown epitaxially despite of a large misfit of -10.6% for BaF2 substrate. For all films, a reaction layer is formed at the interface confirmed by X-ray diffraction and for the films grown on CaF2 and BaF2 additionally by transmission electron microscopy. The superconducting transition temperature of the film on CaF2 is around 27 K, whereas the corresponding values of the films on SrF2 and BaF2 are around 22 K and 21 K, respectively. The Ba-122 on CaF2 shows almost identical crystalline quality and superconducting properties as films on Fe-buffered MgO.

  5. Phase slips in superconducting films with constrictions

    NASA Astrophysics Data System (ADS)

    Chu, Sang L.; Bollinger, A. T.; Bezryadin, A.

    2004-12-01

    A system of two coplanar superconducting films seamlessly connected by a bridge is studied. We observe two distinct resistive transitions as the temperature is reduced. The first one, occurring in the films, shows some properties of the Berezinskii-Kosterlitz-Thouless (BKT) transition. The second apparent transition (which is in fact a crossover) is related to freezing out of thermally activated phase slips (TAPS) localized on the bridge. We also propose a powerful indirect experimental method allowing an extraction of the sample’s zero-bias resistance from high-current-bias measurements. Using direct and indirect measurements, we have determined the resistance R(T) of the bridges within a range of eleven orders of magnitude. Over such broad range the resistance follows a simple relation R(T)=RNexp[-(c/t)(1-t)3/2] , where c=ΔF(0)/kTc is the normalized free energy of a phase slip at zero temperature, t=T/Tc is normalized temperature, and RN is the normal resistance of the bridge.

  6. Research On Bi-Based High-Temperature Superconductors

    NASA Technical Reports Server (NTRS)

    Banks, Curtis; Doane, George B., III; Golben, John

    1993-01-01

    Brief report describes effects of melt sintering on Bi-based high-temperature superconductor system, as well as use of vibrating-sample magnetometer to determine hysteresis curves at 77 K for partially melt-sintered samples. Also discussed is production of high-temperature superconducting thin films by laser ablation: such films potentially useful in detection of signals of very low power.

  7. Inflight resistance measurement on high-T(sub c) superconducting thin films exposed to orbital atomic oxygen on CONCAP-2 (STS-46)

    NASA Technical Reports Server (NTRS)

    Gregory, J. C.; Raiker, G. N.; Bijvoet, J. A.; Nerren, P. D.; Sutherland, W. T.; Mogro-Camperso, A.; Turner, L. G.; Kwok, Hoi; Raistrick, I. D.; Cross, J. B.

    1995-01-01

    In 1992, UAH (University of Alabama in Huntsville) conducted a unique experiment on STS-46 in which YBa2Cu3O7 (commonly known as '1-2-3' superconductor) high-T(c) superconducting thin film samples prepared at three different laboratories were exposed to 5 eV atomic oxygen in low Earth orbit on the ambient and 320 C hot plate during the first flight of the CONCAP-2 (Complex Autonomous Payload) experiment carrier. The resistance of the thin films was measured in flight during the atomic oxygen exposure and heating cycle. Superconducting properties were measured in the laboratory before and after the flight by the individual experimenters. Films with good superconducting properties, and which were exposed to the oxygen flux, survived the flight including those heated to 320 C (600 K) with properties essentially unchanged, while other samples which were heated but not exposed to oxygen were degraded. The properties of other flight controls held at ambient temperature appear unchanged and indistinguishable from those of ground controls, whether exposed to oxygen or not.

  8. Vortex properties of two-dimensional superconducting Pb films.

    PubMed

    Ning, Y X; Song, C L; Wang, Y L; Chen, Xi; Jia, J F; Xue, Q K; Ma, X C

    2010-02-17

    Using low temperature scanning tunnelling microscopy/spectroscopy (STM/STS) we have investigated the vortex behaviours of two-dimensional superconducting Pb films at different thicknesses. STS at the vortex core shows an evolution of electronic states with film thickness. Transition from the clean limit to the dirty limit of superconductivity is identified, which can be ascribed to the decreased electronic mean free path induced by stronger scattering from the disordered interface at smaller thicknesses. A magnetic field dependent vortex core size is observed even for such a low- κ superconductor. The weak pinning induced by surface defects leads to the formation of a distorted hexagonal vortex lattice.

  9. Superconducting FeSe0.1Te0.9 thin films integrated on Si-based substrates

    NASA Astrophysics Data System (ADS)

    Huang, Jijie; Chen, Li; Li, Leigang; Qi, Zhimin; Sun, Xing; Zhang, Xinghang; Wang, Haiyan

    2018-05-01

    With the goal of integrating superconducting iron chalcogenides with Si-based electronics, superconducting FeSe0.1Te0.9 thin films were directly deposited on Si and SiOx/Si substrates without any buffer layer by a pulsed laser deposition (PLD) method. Microstructural characterization showed excellent film quality with mostly c-axis growth on both types of substrates. Superconducting properties (such as superconducting transition temperature T c and upper critical field H c2) were measured to be comparable to that of the films on single crystal oxide substrates. The work demonstrates the feasibility of integrating superconducting iron chalcogenide (FeSe0.1Te0.9) thin films with Si-based microelectronics.

  10. Spatial characterization of the edge barrier in wide superconducting films

    NASA Astrophysics Data System (ADS)

    Sivakov, A. G.; Turutanov, O. G.; Kolinko, A. E.; Pokhila, A. S.

    2018-03-01

    The current-induced destruction of superconductivity is discussed in wide superconducting thin films, whose width is greater than the magnetic field penetration depth, in weak magnetic fields. Particular attention is paid to the role of the boundary potential barrier (the Bin-Livingston barrier) in critical state formation and detection of the edge responsible for this critical state with different mutual orientations of external perpendicular magnetic field and transport current. Critical and resistive states of the film were visualized using the space-resolving low-temperature laser scanning microscopy (LTLSM) method, which enables detection of critical current-determining areas on the film edges. Based on these observations, a simple technique was developed for investigation of the critical state separately at each film edge, and for the estimation of residual magnetic fields in cryostats. The proposed method only requires recording of the current-voltage characteristics of the film in a weak magnetic field, thus circumventing the need for complex LTLSM techniques. Information thus obtained is particularly important for interpretation of studies of superconducting film single-photon light emission detectors.

  11. Excitation of acoustic oscillations in superconducting films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Golub, A.A.

    1973-11-01

    A study is made of the excitation of sound in a superconducting film by electromagnetic waves incident on the surface of the film. It is assumed that the thickness of the film d is much greater than the penetration depth of the field. If the acoustic wave is damped over a distance of the order of d, traveling acoustic waves can be excited in the superconductor; otherwise, standing waves are excited. The low-temperature contribution of acoustic oseillations to the surface resistence of pure superconductors ia calculated. At very low temperatures, the absorption of electromagnetic waves is mainly governed by themore » loss due to acoustic oscillations. (auth)« less

  12. High temperature superconducting synchronous motor design and test

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Schiferl, R.; Zhang, B.; Shoykhet, B.

    1996-10-01

    High horsepower synchronous motors with high temperature superconducting (HTS) field windings offer the potential to cut motor operating losses in half compared to conventional energy efficient induction motors available today. The design, construction and test of a prototype, air core, synchronous motor with helium gas cooled HTS field coils will be described in this paper. The work described is part of a US Department of Energy, Superconductivity Partnership Initiative award. The motor uses a modified conventional motor armature combined with a vacuum insulated rotor that contains the four racetrack-shaped HTS field coils. The rotor is cooled by helium gas somore » that the HTS coils operate at a temperature of 30 K. This paper provides a status report on HTS motor research and development at Reliance Lab., Rockwell Automation that will lead to commercial HTS motors for utility and industrial applications.« less

  13. Superconductivity-related insulating behavior.

    PubMed

    Sambandamurthy, G; Engel, L W; Johansson, A; Shahar, D

    2004-03-12

    We present the results of an experimental study of superconducting, disordered, thin films of amorphous indium oxide. These films can be driven from the superconducting phase to a reentrant insulating state by the application of a perpendicular magnetic field (B). We find that the high-B insulator exhibits activated transport with a characteristic temperature, TI. TI has a maximum value (TpI) that is close to the superconducting transition temperature (Tc) at B=0, suggesting a possible relation between the conduction mechanisms in the superconducting and insulating phases. Tp(I) and Tc display opposite dependences on the disorder strength.

  14. Decoupling of critical temperature and superconducting gaps in irradiated films of a Fe-based superconductor

    NASA Astrophysics Data System (ADS)

    Daghero, Dario; Tortello, Mauro; Ummarino, Giovanni A.; Piatti, Erik; Ghigo, Gianluca; Hatano, Takafumi; Kawaguchi, Takahiko; Ikuta, Hiroshi; Gonnelli, Renato S.

    2018-07-01

    We report on direct measurements of the energy gaps (carried out by means of point-contact Andreev reflection spectroscopy, PCARS) and of the critical temperature in thin, optimally doped, epitaxial films of BaFe2(As1-x P x )2 irradiated with 250 MeV Au ions. The low-temperature PCARS spectra (taken with the current flowing along the c axis) can be fitted by a modified Blonder-Tinkham-Klapwijk model with two nodeless gaps; this is not in contrast with the possible presence of node lines suggested by various experiments in literature. Up to a fluence Φ = 7.3 × 1011 cm-2, we observe a monotonic suppression of the critical temperature and of the gap amplitudes Δ1 and Δ2. Interestingly, while T c decreases by about 3%, the gaps decrease much more (by about 37% and 25% respectively), suggesting a decoupling between high-temperature and low-temperature superconducting properties. An explanation for this finding is proposed within an effective two-band Eliashberg model, in which such decoupling is inherently associated to defects created by irradiation.

  15. Evidence for filamentary superconductivity up to 220 K in oriented multiphase Y-Ba-Cu-O thin films

    NASA Astrophysics Data System (ADS)

    Schönberger, R.; Otto, H. H.; Brunner, B.; Renk, K. F.

    1991-02-01

    We report on the observation of filamentary superconductivity up to 220 K in multiphase Y-Ba-Cu-O materials that are deposited as highly oriented thin films on (110)-SrTiO 3 substrates by laser ablation from ceramic targets. The high temperature zero resistivity states are reproducible after temperature cycling down to 80 K for samples treated by a special oxygenation and ozonization process at 340 K and measured in a pure oxygen atmosphere. Our results on thin films confirm former experiments of J.T. Chen and co-workers obtained on ceramic samples with preferred crystallite orientation. A close connection between superconductivity and structural instabilities of most likely ferroic nature, which are observed more often for YBa 2Cu 3O 7 in a narrow temperature range near 220 K, is suggested.

  16. Ion beam sputtering of in situ superconducting Y-Ba-Cu-O films

    NASA Astrophysics Data System (ADS)

    Klein, J. D.; Yen, A.; Clauson, S. L.

    1990-05-01

    Oriented superconducting YBa2Cu3O7 thin films were deposited on yttria stabilized zirconia and SrTiO3 substrates by ion-beam sputtering of a nonstoichiometric oxide target. The films exhibited zero-resistance critical temperatures as high as 83.5 K without post-deposition anneals. Both the deposition rate and the c-lattice parameter data displayed two distinct regimes of dependence on the beam power of the ion source. Low-power sputtering yielded films with large c-dimensions and low Tc. Higher-power sputtering produced a continuous decrease in the c-lattice parameter and increase in critical temperature. Films having the smaller c-lattice parameters were Cu rich. The Cu content of films deposited at beam voltages of 800 V and above increased with increasing beam power.

  17. Ultra-High Performance, High-Temperature Superconducting Wires via Cost-effective, Scalable, Co-evaporation Process

    PubMed Central

    Kim, Ho-Sup; Oh, Sang-Soo; Ha, Hong-Soo; Youm, Dojun; Moon, Seung-Hyun; Kim, Jung Ho; Dou, Shi Xue; Heo, Yoon-Uk; Wee, Sung-Hun; Goyal, Amit

    2014-01-01

    Long-length, high-temperature superconducting (HTS) wires capable of carrying high critical current, Ic, are required for a wide range of applications. Here, we report extremely high performance HTS wires based on 5 μm thick SmBa2Cu3O7 − δ (SmBCO) single layer films on textured metallic templates. SmBCO layer wires over 20 meters long were deposited by a cost-effective, scalable co-evaporation process using a batch-type drum in a dual chamber. All deposition parameters influencing the composition, phase, and texture of the films were optimized via a unique combinatorial method that is broadly applicable for co-evaporation of other promising complex materials containing several cations. Thick SmBCO layers deposited under optimized conditions exhibit excellent cube-on-cube epitaxy. Such excellent structural epitaxy over the entire thickness results in exceptionally high Ic performance, with average Ic over 1,000 A/cm-width for the entire 22 meter long wire and maximum Ic over 1,500 A/cm-width for a short 12 cm long tape. The Ic values reported in this work are the highest values ever reported from any lengths of cuprate-based HTS wire or conductor. PMID:24752189

  18. Colloquium: High pressure and road to room temperature superconductivity

    NASA Astrophysics Data System (ADS)

    Gor'kov, Lev P.; Kresin, Vladimir Z.

    2018-01-01

    This Colloquium is concerned with the superconducting state of new high-Tc compounds containing hydrogen ions (hydrides). Recently superconductivity with the record-setting transition temperature of Tc=203 K was reported for sulfur hydrides under high pressure. In general, high pressure serves as a path finding tool toward novel structures, including those with very high Tc . The field has a rich and interesting history. Currently, it is broadly recognized that superconductivity in sulfur hydrides owes its origin to the phonon mechanism. However, the picture differs from the conventional one in important ways. The phonon spectrum in sulfur hydride is both broad and has a complex structure. Superconductivity arises mainly due to strong coupling to the high-frequency optical modes, although the acoustic phonons also make a noticeable contribution. A new approach is described, which generalizes the standard treatment of the phonon mechanism and makes it possible to obtain an analytical expression for Tc in this phase. It turns out that, unlike in the conventional case, the value of the isotope coefficient (for the deuterium-hydrogen substitution) varies with the pressure and reflects the impact of the optical modes. The phase diagram, that is the pressure dependence of Tc , is rather peculiar. A crucial feature is that increasing pressure results in a series of structural transitions, including the one which yields the superconducting phase with the record Tc of 203 K. In a narrow region near P ≈150 GPa the critical temperature rises sharply from Tc≈120 to ≈200 K . It seems that the sharp structural transition, which produces the high-Tc phase, is a first-order phase transition caused by interaction between the order parameter and lattice deformations. A remarkable feature of the electronic spectrum in the high-Tc phase is the appearance of small pockets at the Fermi level. Their presence leads to a two-gap spectrum, which can, in principle, be observed with the

  19. Effect of annealing high-dose heavy-ion irradiated high-temperature superconductor wires

    NASA Astrophysics Data System (ADS)

    Strickland, N. M.; Wimbush, S. C.; Kluth, P.; Mota-Santiago, P.; Ridgway, M. C.; Kennedy, J. V.; Long, N. J.

    2017-10-01

    Heavy-ion irradiation of high-temperature superconducting thin films has long been known to generate damage tracks of amorphized material that are of close-to-ideal dimension to effectively contribute to pinning of magnetic flux lines and thereby enhance the in-field critical current. At the same time, though, the presence of these tracks reduces the superconducting volume fraction available to transport current while the irradiation process itself generates oxygen depletion and disorder in the remaining superconducting material. We have irradiated commercially available superconducting coated conductors consisting of a thick film of (Y,Dy)Ba2Cu3O7 deposited on a buffered metal tape substrate in a continuous reel-to-reel process. Irradiation was by 185 MeV 197Au ions. A high fluence of 3 × 1011 ions/cm2 was chosen to emphasize the detrimental effects. The critical current was reduced following this irradiation, but annealing at relatively low temperatures of 200 °C and 400 °C substantially restore the critical current of the irradiated material. At high fields and high temperatures there is a net benefit of critical current compared to the untreated material.

  20. Superconductivity of lanthanum revisited

    NASA Astrophysics Data System (ADS)

    Loeptien, Peter; Zhou, Lihui; Wiebe, Jens; Khajetoorians, Alexander Ako; Wiesendanger, Roland

    2014-03-01

    The thickness dependence of the superconductivity in clean hexagonal lanthanum films grown on tungsten (110) is studied by means of scanning tunneling microscopy (STM) and spectroscopy (STS). Fitting of the measured spectra to BCS theory yields the superconducting energy gaps from which the critical temperatures are determined. For the case of thick, bulk-like films, the bulk energy gap and critical temperature of dhcp lanthanum turn out to be considerably higher as compared to values from the literature measured by other techniques. In thin films the superconductivity is quenched by the boundary condition for the superconducting wavefunction imposed by the substrate and surface, leading to a linear decrease of the superconducting transition temperature as a function of the inverse film thickness. This opens up the possibility to grow lanthanum films with defined superconducting properties.

  1. Superconducting MgB2 films via precursor postprocessing approach

    NASA Astrophysics Data System (ADS)

    Paranthaman, M.; Cantoni, C.; Zhai, H. Y.; Christen, H. M.; Aytug, T.; Sathyamurthy, S.; Specht, E. D.; Thompson, J. R.; Lowndes, D. H.; Kerchner, H. R.; Christen, D. K.

    2001-06-01

    Superconducting MgB2 films with Tc=38.6 K were prepared using a precursor-deposition, ex situ postprocessing approach. Precursor films of boron, ˜0.5 μm thick, were deposited onto Al2O3 (102) substrates by electron-beam evaporation; a postanneal at 890 °C in the presence of bulk MgB2 and Mg metal produced highly crystalline MgB2 films. X-ray diffraction indicated that the films exhibit some degree of c-axis alignment, but are randomly oriented in plane. Transport current measurements of the superconducting properties show high values of the critical current density and yield an irreversibility line that exceeds that determined by magnetic measurements on bulk polycrystalline materials.

  2. High temperature superconductor materials and applications

    NASA Technical Reports Server (NTRS)

    Doane, George B., III.; Banks, Curtis; Golben, John

    1990-01-01

    Research on processing methods leading to a significant enhancement in the critical current densities (Jc) and the critical temperature (Tc) of high temperature superconducting in thin bulk and thin film forms. The fabrication of important devices for NASA unique applications (sensors) is investigated.

  3. Weakly superconducting, thin-film structures as radiation detectors.

    NASA Technical Reports Server (NTRS)

    Kirschman, R. K.

    1972-01-01

    Measurements were taken with weakly superconducting quantum structures of the Notarys-Mercereau type, representing a thin superconductor film with a short region that is weakened in the sense that its transition temperature is lower than in the remaining portion of the film. The structure acts as a superconducting relaxation oscillator in which the supercurrent increases with time until the critical current of the weakened section is attained, at which moment the supercurrent decays and the cycle repeats. Under applied radiation, a series of constant-voltage steps appears in the current-voltage curve, and the size of the steps varies periodically with the amplitude of applied radiation. Measurements of the response characteristics were made in the frequency range of 10 to 450 MHz.

  4. Macroscopic character of composite high-temperature superconducting wires

    NASA Astrophysics Data System (ADS)

    Kivelson, S. A.; Spivak, B.

    2015-11-01

    The "d -wave" symmetry of the superconducting order in the cuprate high temperature superconductors is a well established fact [J. Tsuei and J. R. Kirtley, Rev. Mod. Phys. 72, 969 (2000), 10.1103/RevModPhys.72.969 and D. J. Vanharlingen, Rev. Mod. Phys. 67, 515 (1995), 10.1103/RevModPhys.67.515], and one which identifies them as "unconventional." However, in macroscopic contexts—including many potential applications (i.e., superconducting "wires")—the material is a composite of randomly oriented superconducting grains in a metallic matrix, in which Josephson coupling between grains mediates the onset of long-range phase coherence. [See, e.g., D. C. Larbalestier et al., Nat. Mater. 13, 375 (2014), 10.1038/nmat3887, A. P. Malozemoff, MRS Bull. 36, 601 (2011), 10.1557/mrs.2011.160, and K. Heine et al., Appl. Phys. Lett. 55, 2441 (1989), 10.1063/1.102295] Here we analyze the physics at length scales that are large compared to the size of such grains, and in particular the macroscopic character of the long-range order that emerges. While X Y -superconducting glass order and macroscopic d -wave superconductivity may be possible, we show that under many circumstances—especially when the d -wave superconducting grains are embedded in a metallic matrix—the most likely order has global s -wave symmetry.

  5. Is there a path from cuprates towards room-temperature superconductivity?

    DOE PAGES

    Božović, I.; Wu, J.; He, X.; ...

    2017-09-01

    A brief account is presented of an extensive experiment performed at Brookhaven National Laboratory, aimed at understanding the nature of high-temperature superconductivity in cuprates. Over the course of the last 12 years, over 2000 films of the prototypical high- T c superconductor, La 2-xSr xCuO 4, have been synthesized using atomic-layer-by-layer molecular beam epitaxy (ALL-MBE), characterized by a range of techniques, and patterned into devices. These were then used to measure accurately the key physical parameters in both the superconducting and the normal states, and establish their precise dependence on doping, temperature, and external fields. Our results bring in somemore » great surprises, challenge the commonly held beliefs, rule out many theoretical models, and point to a new path for raising T c even further.« less

  6. The Interface Structure of FeSe Thin Film on CaF2 Substrate and its Influence on the Superconducting Performance.

    PubMed

    Qiu, Wenbin; Ma, Zongqing; Patel, Dipak; Sang, Lina; Cai, Chuanbing; Shahriar Al Hossain, Mohammed; Cheng, Zhenxiang; Wang, Xiaolin; Dou, Shi Xue

    2017-10-25

    The investigations into the interfaces in iron selenide (FeSe) thin films on various substrates have manifested the great potential of showing high-temperature-superconductivity in this unique system. In present work, we obtain FeSe thin films with a series of thicknesses on calcium fluoride (CaF 2 ) (100) substrates and glean the detailed information from the FeSe/CaF 2 interface by using scanning transmission electron microscopy (STEM). Intriguingly, we have found the universal existence of a calcium selenide (CaSe) interlayer with a thickness of approximate 3 nm between FeSe and CaF 2 in all the samples, which is irrelevant to the thickness of FeSe layers. A slight Se deficiency occurs in the FeSe layer due to the formation of CaSe interlayer. This Se deficiency is generally negligible except for the case of the ultrathin FeSe film (8 nm in thickness), in which the stoichiometric deviation from FeSe is big enough to suppress the superconductivity. Meanwhile, in the overly thick FeSe layer (160 nm in thickness), vast precipitates are found and recognized as Fe-rich phases, which brings about degradation in superconductivity. Consequently, the thickness dependence of superconducting transition temperature (T c ) of FeSe thin films is investigated and one of our atmosphere-stable FeSe thin film (127 nm) possesses the highest T c onset /T c zero as 15.1 K/13.4 K on record to date in the class of FeSe thin film with practical thickness. Our results provide a new perspective for exploring the mechanism of superconductivity in FeSe thin film via high-resolution STEM. Moreover, approaches that might improve the quality of FeSe/CaF 2 interfaces are also proposed for further enhancing the superconducting performance in this system.

  7. Relaxation of the resistive superconducting state in boron-doped diamond films

    NASA Astrophysics Data System (ADS)

    Kardakova, A.; Shishkin, A.; Semenov, A.; Goltsman, G. N.; Ryabchun, S.; Klapwijk, T. M.; Bousquet, J.; Eon, D.; Sacépé, B.; Klein, Th.; Bustarret, E.

    2016-02-01

    We report a study of the relaxation time of the restoration of the resistive superconducting state in single crystalline boron-doped diamond using amplitude-modulated absorption of (sub-)THz radiation (AMAR). The films grown on an insulating diamond substrate have a low carrier density of about 2.5 ×1021cm-3 and a critical temperature of about 2 K . By changing the modulation frequency we find a high-frequency rolloff which we associate with the characteristic time of energy relaxation between the electron and the phonon systems or the relaxation time for nonequilibrium superconductivity. Our main result is that the electron-phonon scattering time varies clearly as T-2, over the accessible temperature range of 1.7 to 2.2 K. In addition, we find, upon approaching the critical temperature Tc, evidence for an increasing relaxation time on both sides of Tc.

  8. Sequentially evaporated thin film YBa2Cu3O(7-x) superconducting microwave ring resonator

    NASA Technical Reports Server (NTRS)

    Rohrer, Norman J.; To, Hing Y.; Valco, George J.; Bhasin, Kul B.; Chorey, Chris; Warner, Joseph D.

    1990-01-01

    There is great interest in the application of thin film high temperature superconductors in high frequency electronic circuits. A ring resonator provides a good test vehicle for assessing the microwave losses in the superconductor and for comparing films made by different techniques. Ring resonators made of YBa2Cu3O(7-x) have been investigated on LaAlO3 substrates. The superconducting thin films were deposited by sequential electron beam evaporation of Cu, Y, and BaF2 with a post anneal. Patterning of the superconducting film was done using negative photolithography. A ring resonator was also fabricated from a thin gold film as a control. Both resonators had a gold ground plane on the backside of the substrate. The ring resonators' reflection coefficients were measured as a function of frequency from 33 to 37 GHz at temperatures ranging from 20 K to 68 K. The resonator exhibited two resonances which were at 34.5 and 35.7 GHz at 68 K. The resonant frequencies increased with decreasing temperature. The magnitude of the reflection coefficients was in the calculation of the unloaded Q-values. The performance of the evaporated and gold resonator are compared with the performance of a laser ablated YBa2Cu3O(7-x) resonator. The causes of the double resonance are discussed.

  9. Chemical vapor deposition of high T(sub c) superconducting films in a microgravity environment

    NASA Technical Reports Server (NTRS)

    Levy, Moises; Sarma, Bimal K.

    1994-01-01

    Since the discovery of the YBaCuO bulk materials in 1987, Metalorganic Chemical Vapor Deposition (MOCVD) has been proposed for preparing HTSC high T(sub c) films. This technique is now capable of producing high-T(sub c) superconducting thin films comparable in quality to those prepared by any other methods. The MOCVD technique has demonstrated its superior advantage in making large area high quality HTSC thin films and will play a major role in the advance of device applications of HTSC thin films. The organometallic precursors used in the MOCVD preparation of HTSC oxide thin films are most frequently metal beta-diketonates. High T(sub c) superconductors are multi-component oxides which require more than one component source, with each source, containing one kind of precursor. Because the volatility and stability of the precursors are strongly dependent on temperature, system pressure, and carrier gas flow rate, it has been difficult to control the gas phase composition, and hence film stoichiometry. In order circumvent these problems we have built and tested a single source MOCVD reactor in which a specially designed vaporizer was employed. This vaporizer can be used to volatilize a stoichiometric mixture of diketonates of yttrium, barium and copper to produce a mixed vapor in a 1:2:3 ratio respectively of the organometellics. This is accomplished even though the three compounds have significantly different volatilities. We have developed a model which provides insight into the process of vaporizing mixed precursors to produce high quality thin films of Y1Ba2Cu3O7. It shows that under steady state conditions the mixed organometallic vapor must have a stoichiometric ratio of the individual organometallics identical to that in the solid mixture.

  10. Growth, patterning, and weak-link fabrication of superconducting YBa2Cu3O(7-x) thin films

    NASA Astrophysics Data System (ADS)

    Hilton, G. C.; Harris, E. B.; van Harlingen, D. J.

    1988-09-01

    Thin films of the high-temperature superconducting ceramic oxides have been grown, and techniques for fabricating weak-link structures have been investigated. Films of YBa2Cu3O(7-x) grown on SrTiO3 by a combination of dc magnetron sputtering and thermal evaporation from the three sources have been patterned into microbridges with widths down to 2 microns. Evidence is found that the bridges behave as arrays of Josephson-coupled superconducting islands. Further weak-link behavior is induced by in situ modification of the coupling by ion milling through the bridge.

  11. The first man-loading high temperature superconducting Maglev test vehicle in the world

    NASA Astrophysics Data System (ADS)

    Wang, Jiasu; Wang, Suyu; Zeng, Youwen; Huang, Haiyu; Luo, Fang; Xu, Zhipei; Tang, Qixue; Lin, Guobin; Zhang, Cuifang; Ren, Zhongyou; Zhao, Guomin; Zhu, Degui; Wang, Shaohua; Jiang, He; Zhu, Min; Deng, Changyan; Hu, Pengfei; Li, Chaoyong; Liu, Fang; Lian, Jisan; Wang, Xiaorong; Wang, Lianghui; Shen, Xuming; Dong, Xiaogang

    2002-10-01

    The first man-loading high temperature superconducting Maglev test vehicle in the world is reported. This vehicle was first tested successfully on December 31, 2000 in the Applied Superconductivity Laboratory, Southwest Jiaotong University, China. Heretofore over 17,000 passengers took the vehicle, and it operates very well from beginning to now. The function of suspension is separated from one of propulsion. The high temperature superconducting Maglev provides inherent stable forces both in the levitation and in the guidance direction. The vehicle is 3.5 m long, 1.2 m wide, and 0.8 m high. When five people stand on vehicle and the total weight is 530 kg, the net levitation gap is more than 20 mm. The whole vehicle system includes three parts, vehicle body, guideway and controlling system. The high temperature superconducting Maglev equipment on board is the most important for the system. The onboard superconductors are melt-textured YBaCuO bulks. The superconductors are fixed on the bottom of liquid nitrogen vessels and cooled by liquid nitrogen. The guideway consists of two parallel permanent magnetic tracks, whose surface concentrating magnetic field is up to 1.2 T. The guideway is 15.5 m long.

  12. Superconductivity of lanthanum revisited: enhanced critical temperature in the clean limit.

    PubMed

    Löptien, P; Zhou, L; Khajetoorians, A A; Wiebe, J; Wiesendanger, R

    2014-10-22

    The thickness dependence of the superconducting energy gap ΔLa of double hexagonally close packed (dhcp) lanthanum islands grown on W(110) is studied by scanning tunneling spectroscopy, from the bulk to the thin-film limit. Superconductivity is suppressed by the boundary conditions for the superconducting wavefunction on the surface and W/La interface, leading to a linear decrease of the critical temperature Tc as a function of the inverse film thickness. For the thick, bulk-like films, ΔLa and Tc are 40% larger compared to the literature values of dhcp La as measured by other techniques. This finding is reconciled by examining the effects of surface contamination as probed by modifications of the surface state, suggesting that the large Tc originates in the superior purity of the samples investigated here.

  13. Superconductivity of lanthanum revisited: enhanced critical temperature in the clean limit

    NASA Astrophysics Data System (ADS)

    Löptien, P.; Zhou, L.; Khajetoorians, A. A.; Wiebe, J.; Wiesendanger, R.

    2014-10-01

    The thickness dependence of the superconducting energy gap ΔLa of double hexagonally close packed (dhcp) lanthanum islands grown on W(110) is studied by scanning tunneling spectroscopy, from the bulk to the thin-film limit. Superconductivity is suppressed by the boundary conditions for the superconducting wavefunction on the surface and W/La interface, leading to a linear decrease of the critical temperature Tc as a function of the inverse film thickness. For the thick, bulk-like films, ΔLa and Tc are 40% larger compared to the literature values of dhcp La as measured by other techniques. This finding is reconciled by examining the effects of surface contamination as probed by modifications of the surface state, suggesting that the large Tc originates in the superior purity of the samples investigated here.

  14. Stoichiometry and thickness dependence of superconducting properties of niobium nitride thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Beebe, Melissa R., E-mail: mrbeebe@email.wm.edu; Beringer, Douglas B.; Burton, Matthew C.

    2016-03-15

    The current technology used in linear particle accelerators is based on superconducting radio frequency (SRF) cavities fabricated from bulk niobium (Nb), which have smaller surface resistance and therefore dissipate less energy than traditional nonsuperconducting copper cavities. Using bulk Nb for the cavities has several advantages, which are discussed elsewhere; however, such SRF cavities have a material-dependent accelerating gradient limit. In order to overcome this fundamental limit, a multilayered coating has been proposed using layers of insulating and superconducting material applied to the interior surface of the cavity. The key to this multilayered model is to use superconducting thin films tomore » exploit the potential field enhancement when these films are thinner than their London penetration depth. Such field enhancement has been demonstrated in MgB{sub 2} thin films; here, the authors consider films of another type-II superconductor, niobium nitride (NbN). The authors present their work correlating stoichiometry and superconducting properties in NbN thin films and discuss the thickness dependence of their superconducting properties, which is important for their potential use in the proposed multilayer structure. While there are some previous studies on the relationship between stoichiometry and critical temperature T{sub C}, the authors are the first to report on the correlation between stoichiometry and the lower critical field H{sub C1}.« less

  15. Effects of superconducting film on the defect mode in dielectric photonic crystal heterostructure

    NASA Astrophysics Data System (ADS)

    Hu, Chung-An; Liu, Jia-Wei; Wu, Chien-Jang; Yang, Tzong-Jer; Yang, Su-Lin

    2013-03-01

    Effects of superconducting thin film on the defect mode in a dielectric photonic crystal heterostructure (PCH) are theoretically investigated. The considered structure is (12)NS(21)N, in which both layers 1 and 2 are dielectrics, layer S is a high-temperature superconducting layer, and N is the stack number. The defect mode is analyzed based on the transmission spectrum calculated by using the transfer matrix method. It is found that, in the normal incidence, the defect mode existing in the host PCH of (12)N(21)N will be blue-shifted as the thickness of layer S increases. In addition, the defect mode is also blue-shifted for both TE and TM modes in the case of oblique incidence. The embedded superconducting thin film plays the role of tuning agent for the defect mode of PCH. As a result, the proposed structure can be designed as a tunable narrowband transmission filter which could be of technical use in the optoelectronic applications.

  16. Superconducting thin films of Bi-Sr-Ca-Cu-O by laser ablation

    NASA Astrophysics Data System (ADS)

    Bedekar, M. M.; Safari, A.; Wilber, W.

    1992-11-01

    Superconducting thin films of Bi-Sr-Ca-Cu-O have been deposited by KrF excimer laser ablation. The best in situ films showed a Tc onset of 110 K and a Tc(0) of 76 K. A study of the laser plume revealed the presence of two distinct regimes. The forward directed component increased with fluence and the film composition was stoichiometric in this region. This is in agreement with the results on the 123 system by Venkatesan et al. [1]. The film properties were found to be critically dependent on the substrate temperature and temperatures close to melting gave rise to 2212 and 2223 phases. At lower temperatures, 2201 and amorphous phases were obtained. The film morphology and superconducting properties were a function of the target to substrate distance and the oxygen pressure during deposition and cooling. An increase in the target to substrate distance led to a deterioration of the properties due to the energy consideration for the formation of 2212 and 2223 phases. The best films were obtained using cooling pressures of 700 Torr. The microwave surface resistance of the films measured at 35 GHz dropped below that of copper at 30 K. Film growth was studied using X-ray diffraction and STM/AFM. This work is a discussion of the role of the different variables on the film properties.

  17. High-temperature change of the creep rate in YBa2Cu3O7-δ films with different pinning landscapes

    NASA Astrophysics Data System (ADS)

    Haberkorn, N.; Miura, M.; Baca, J.; Maiorov, B.; Usov, I.; Dowden, P.; Foltyn, S. R.; Holesinger, T. G.; Willis, J. O.; Marken, K. R.; Izumi, T.; Shiohara, Y.; Civale, L.

    2012-05-01

    Magnetic relaxation measurements in YBa2Cu3O7-δ (YBCO) films at intermediate and high temperatures show that the collective vortex creep based on the elastic motion of the vortex lattice has a crossover to fast creep that significantly reduces the superconducting critical current density (Jc). This crossover occurs at temperatures much lower than the irreversibility field line. We study the influence of different kinds of crystalline defects, such as nanorods, twin boundaries, and nanoparticles, on the high-temperature vortex phase diagram of YBCO films. We found that the magnetization relaxation data is a fundamental tool to understand the pinning at high temperatures. The results indicate that high Jc values are directly associated with small creep rates. Based on the analysis of the depinning temperature in films with columnar defects, our results indicate that the size of the defects is the relevant parameter that determines thermal depinning at high temperatures. Also, the extension of the collective creep regime depends on the density of the pinning centers.

  18. Superconducting thin films on potassium tantalate substrates

    DOEpatents

    Feenstra, Roeland; Boatner, Lynn A.

    1992-01-01

    A superconductive system for the lossless transmission of electrical current comprising a thin film of superconducting material Y.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7-x epitaxially deposited upon a KTaO.sub.3 substrate. The KTaO.sub.3 is an improved substrate over those of the prior art since the it exhibits small lattice constant mismatch and does not chemically react with the superconducting film.

  19. Superconducting Thin Films for the Enhancement of Superconducting Radio Frequency Accelerator Cavities

    NASA Astrophysics Data System (ADS)

    Burton, Matthew C.

    Bulk niobium (Nb) superconducting radio frequency (SRF) cavities are currently the preferred method for acceleration of charged particles at accelerating facilities around the world. However, bulk Nb cavities have poor thermal conductance, impose material and design restrictions on other components of a particle accelerator, have low reproducibility and are approaching the fundamental material-dependent accelerating field limit of approximately 50MV/m. Since the SRF phenomena occurs at surfaces within a shallow depth of ˜1 microm, a proposed solution to this problem has been to utilize thin film technology to deposit superconducting thin films on the interior of cavities to engineer the active SRF surface in order to achieve cavities with enhanced properties and performance. Two proposed thin film applications for SRF cavities are: 1) Nb thin films coated on bulk cavities made of suitable castable metals (such as copper or aluminum) and 2) multilayer films designed to increase the accelerating gradient and performance of SRF cavities. While Nb thin films on copper (Cu) cavities have been attempted in the past using DC magnetron sputtering (DCMS), such cavities have never performed at the bulk Nb level. However, new energetic condensation techniques for film deposition, such as High Power Impulse Magnetron Sputtering (HiPIMS), offer the opportunity to create suitably thick Nb films with improved density, microstructure and adhesion compared to traditional DCMS. Clearly use of such novel technique requires fundamental studies to assess surface evolution and growth modes during deposition and resulting microstructure and surface morphology and the correlation with RF superconducting properties. Here we present detailed structure-property correlative research studies done on Nb/Cu thin films and NbN- and NbTiN-based multilayers made using HiPIMS and DCMS, respectively.

  20. Space applications for high temperature superconductivity - Brief review

    NASA Technical Reports Server (NTRS)

    Krishen, Kumar

    1990-01-01

    An overview is presented of materials and devices based on high-temperature superconductivity (HTS) that could have useful space-oriented applications. Of specific interest are applications of HTS technologies to mm and microwave systems, spaceborne and planet-surface sensors, and to magnetic subsystems for robotic, rescue, and docking maneuvers. HTS technologies can be used in optoelectronics, magnetic-field detectors, antennae, transmission/delay lines, and launch/payload coils.

  1. Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Warner, J. D.; Miranda, F. A.; Gordon, W. L.; Newman, H. S.

    1990-01-01

    A novel waveguide power transmission measurement technique was developed to extract the complex conductivity of superconducting thin films at microwave frequencies. The microwave conductivity was taken of two laser ablated YBa2Cu3O(7-delta) thin films on LaAlO3 with transition temperatures of approx. 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values, the penetration depth was found to be approx. 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approx. 24 and 36 micro-Ohms at 36 GHz and 76 K for the two films under consideration. The R sub s values were compared with those obtained from the change in the Q-factor of a 36 GHz Te sub 011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. This technique allows noninvasive characterization of high transition temperature superconducting thin films at microwave frequencies.

  2. High Tc superconducting bolometric and nonbolometric infrared (IR) detectors

    NASA Technical Reports Server (NTRS)

    Lakeou, Samuel

    1994-01-01

    The original workplan for the first year of the project includes the following: establishment of a pilot superconductivity application laboratory at UDC to support the research component of the project; research on the source of electrical noise in High Tc superconducting films in order to optimize the film microstructure and lower the NEP; and lay the foundation of an academic support for exposing UDC students to the theory and application of High Tc superconductivity. Attached to this status report are abstracts and the course description for Introduction to Applications of Superconductivity.

  3. Superconducting thin films of (100) and (111) oriented indium doped topological crystalline insulator SnTe

    DOE PAGES

    Si, W.; Zhang, C.; Wu, L.; ...

    2015-09-01

    Recent discovery of the topological crystalline insulator SnTe has triggered a search for topological superconductors, which have potential application to topological quantum computing. The present work reports on the superconducting properties of indium doped SnTe thin films. The (100) and (111) oriented thin films were epitaxially grown by pulsed-laser deposition on (100) and (111) BaF2 crystalline substrates respectively. The onset superconducting transition temperatures are about 3.8 K for (100) and 3.6 K for (111) orientations, slightly lower than that of the bulk. Magneto-resistive measurements indicate that these thin films may have upper critical fields higher than that of the bulk.more » With large surface-to-bulk ratio, superconducting indium doped SnTe thin films provide a rich platform for the study of topological superconductivity and potential device applications based on topological superconductors.« less

  4. Superconducting thin films of (100) and (111) oriented indium doped topological crystalline insulator SnTe

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Si, Weidong, E-mail: wds@bnl.gov, E-mail: qiangli@bnl.gov; Zhang, Cheng; Wu, Lijun

    2015-08-31

    Recent discovery of the topological crystalline insulator SnTe has triggered a search for topological superconductors, which have potential application to topological quantum computing. The present work reports on the superconducting properties of indium doped SnTe thin films. The (100) and (111) oriented thin films were epitaxially grown by pulsed-laser deposition on (100) and (111) BaF{sub 2} crystalline substrates, respectively. The onset superconducting transition temperatures are about 3.8 K for (100) and 3.6 K for (111) orientations, slightly lower than that of the bulk. Magneto-resistive measurements indicate that these thin films may have upper critical fields higher than that of the bulk. Withmore » large surface-to-bulk ratio, superconducting indium doped SnTe thin films provide a rich platform for the study of topological superconductivity and potential device applications based on topological superconductors.« less

  5. PREFACE: Superconductivity in ultrathin films and nanoscale systems Superconductivity in ultrathin films and nanoscale systems

    NASA Astrophysics Data System (ADS)

    Bianconi, Antonio; Bose, Sangita; Garcia-Garcia, Antonio Miguel

    2012-12-01

    The recent technological developments in the synthesis and characterization of high-quality nanostructures and developments in the theoretical techniques needed to model these materials, have motivated this focus section of Superconductor Science and Technology. Another motivation is the compelling evidence that all new superconducting materials, such as iron pnictides and chalcogenides, diborides (doped MgB2) and fullerides (alkali-doped C60 compounds), are heterostrucures at the atomic limit, such as the cuprates made of stacks of nanoscale superconducting layers intercalated by different atomic layers with nanoscale periodicity. Recently a great amount of interest has been shown in the role of lattice nano-architecture in controlling the fine details of Fermi surface topology. The experimental and theoretical study of superconductivity in the nanoscale started in the early 1960s, shortly after the discovery of the BCS theory. Thereafter there has been rapid progress both in experiments and the theoretical understanding of nanoscale superconductors. Experimentally, thin films, granular films, nanowires, nanotubes and single nanoparticles have all been explored. New quantum effects appear in the nanoscale related to multi-component condensates. Advances in the understanding of shape resonances or Fano resonances close to 2.5 Lifshitz transitions near a band edge in nanowires, 2D films and superlattices [1, 2] of these nanosized modules, provide the possibility of manipulating new quantum electronic states. Parity effects and shell effects in single, isolated nanoparticles have been reported by several groups. Theoretically, newer techniques based on solving Richardson's equation (an exact theory incorporating finite size effects to the BCS theory) numerically by path integral methods or solving the entire Bogoliubov-de Gennes equation in these limits have been attempted, which has improved our understanding of the mechanism of superconductivity in these confined

  6. Dome-shaped magnetic order competing with high-temperature superconductivity at high pressures in FeSe.

    PubMed

    Sun, J P; Matsuura, K; Ye, G Z; Mizukami, Y; Shimozawa, M; Matsubayashi, K; Yamashita, M; Watashige, T; Kasahara, S; Matsuda, Y; Yan, J-Q; Sales, B C; Uwatoko, Y; Cheng, J-G; Shibauchi, T

    2016-07-19

    The coexistence and competition between superconductivity and electronic orders, such as spin or charge density waves, have been a central issue in high transition-temperature (Tc) superconductors. Unlike other iron-based superconductors, FeSe exhibits nematic ordering without magnetism whose relationship with its superconductivity remains unclear. Moreover, a pressure-induced fourfold increase of Tc has been reported, which poses a profound mystery. Here we report high-pressure magnetotransport measurements in FeSe up to ∼15 GPa, which uncover the dome shape of magnetic phase superseding the nematic order. Above ∼6 GPa the sudden enhancement of superconductivity (Tc≤38.3 K) accompanies a suppression of magnetic order, demonstrating their competing nature with very similar energy scales. Above the magnetic dome, we find anomalous transport properties suggesting a possible pseudogap formation, whereas linear-in-temperature resistivity is observed in the normal states of the high-Tc phase above 6 GPa. The obtained phase diagram highlights unique features of FeSe among iron-based superconductors, but bears some resemblance to that of high-Tc cuprates.

  7. Superconductivity above 100 K in single-layer FeSe films on doped SrTiO3.

    PubMed

    Ge, Jian-Feng; Liu, Zhi-Long; Liu, Canhua; Gao, Chun-Lei; Qian, Dong; Xue, Qi-Kun; Liu, Ying; Jia, Jin-Feng

    2015-03-01

    Recent experiments on FeSe films grown on SrTiO3 (STO) suggest that interface effects can be used as a means to reach superconducting critical temperatures (Tc) of up to 80 K (ref. ). This is nearly ten times the Tc of bulk FeSe and higher than the record value of 56 K for known bulk Fe-based superconductors. Together with recent studies of superconductivity at oxide heterostructure interfaces, these results rekindle the long-standing idea that electron pairing at interfaces between two different materials can be tailored to achieve high-temperature superconductivity. Subsequent angle-resolved photoemission spectroscopy measurements of the FeSe/STO system revealed an electronic structure distinct from bulk FeSe (refs , ), with an energy gap vanishing at around 65 K. However, ex situ electrical transport measurements have so far detected zero resistance-the key experimental signature of superconductivity-only below 30 K. Here, we report the observation of superconductivity with Tc above 100 K in the FeSe/STO system by means of in situ four-point probe electrical transport measurements. This finding confirms FeSe/STO as an ideal material for studying high-Tc superconductivity.

  8. Two-Dimensional Superconductivity in the Cuprates Revealed by Atomic-Layer-by- Layer Molecular Beam Epitaxy

    DOE PAGES

    A. T. Bollinger; Bozovic, I.

    2016-08-12

    Various electronic phases displayed by cuprates that exhibit high temperature superconductivity continue to attract much interest. We provide a short review of several experiments that we have performed aimed at investigating the superconducting state in these compounds. Measurements on single-phase films, bilayers, and superlattices all point to the conclusion that the high-temperature superconductivity in these materials is an essentially quasi-two dimensional phenomenon. With proper control over the film growth, high-temperature superconductivity can exist in a single copper oxide plane with the critical temperatures as high as that achieved in the bulk samples.

  9. Method And Apparatus For Evaluatin Of High Temperature Superconductors

    DOEpatents

    Fishman, Ilya M.; Kino, Gordon S.

    1996-11-12

    A technique for evaluation of high-T.sub.c superconducting films and single crystals is based on measurement of temperature dependence of differential optical reflectivity of high-T.sub.c materials. In the claimed method, specific parameters of the superconducting transition such as the critical temperature, anisotropy of the differential optical reflectivity response, and the part of the optical losses related to sample quality are measured. The apparatus for performing this technique includes pump and probe sources, cooling means for sweeping sample temperature across the critical temperature and polarization controller for controlling a state of polarization of a probe light beam.

  10. Intercalated Nanocomposites Based on High-Temperature Superconducting Ceramics and Their Properties

    PubMed Central

    Tonoyan, Anahit; Schiсk, Christoph; Davtyan, Sevan

    2009-01-01

    High temperature superconducting (SC) nanocomposites based on SC ceramics and various polymeric binders were prepared. Regardless of the size of the ceramics’ grains, the increase of their amount leads to an increase of resistance to rupture and modulus and a decrease in limiting deformation, whereas an increase in the average ceramic grain size worsens resistance properties. The SC, thermo-chemical, mechanical and dynamic-mechanical properties of the samples were investigated. Superconducting properties of the polymer ceramic nanocomposites are explained by intercalation of macromolecule fragments into the interstitial layer of the ceramics’ grains. This phenomenon leads to a change in the morphological structure of the superconducting nanocomposites.

  11. Specific heat measurement set-up for quench condensed thin superconducting films.

    PubMed

    Poran, Shachaf; Molina-Ruiz, Manel; Gérardin, Anne; Frydman, Aviad; Bourgeois, Olivier

    2014-05-01

    We present a set-up designed for the measurement of specific heat of very thin or ultra-thin quench condensed superconducting films. In an ultra-high vacuum chamber, materials of interest can be thermally evaporated directly on a silicon membrane regulated in temperature from 1.4 K to 10 K. On this membrane, a heater and a thermometer are lithographically fabricated, allowing the measurement of heat capacity of the quench condensed layers. This apparatus permits the simultaneous thermal and electrical characterization of successively deposited layers in situ without exposing the deposited materials to room temperature or atmospheric conditions, both being irreversibly harmful to the samples. This system can be used to study specific heat signatures of phase transitions through the superconductor to insulator transition of quench condensed films.

  12. Enhanced pinning in superconducting thin films with graded pinning landscapes

    NASA Astrophysics Data System (ADS)

    Motta, M.; Colauto, F.; Ortiz, W. A.; Fritzsche, J.; Cuppens, J.; Gillijns, W.; Moshchalkov, V. V.; Johansen, T. H.; Sanchez, A.; Silhanek, A. V.

    2013-05-01

    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)].

  13. Superconductivity in ion-beam-mixed layered Au-Si thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jisrawi, N.M.; McLean, W.L.; Stoffel, N.G.

    The superconducting properties of thin films made by mixing alternating layers of Au and Si using ion-beam bombardment correlate with the formation of metastable metallic phases in what is otherwise a simple eutectic system. Transmission-electron-microscopy measurements reveal the superconducting phases to be amorphous. Compound formation and the nature of Au-Si bonding in these metastable phases are demonstrated from x-ray photoelectron spectroscopy and from a previous study of x-ray-absorption spectroscopy. After mixing with a beam of Xe ions, multilayered films with an average nominal composition Au{sub {ital x}}Si{sub 1{minus}{ital x}}, where {ital x}=0.2, 0.4, 0.5, 0.72, and 0.8, exhibited superconducting transitionmore » temperatures in the range 0.2--1.2 K. A double transition feature in the magnetic field dependence of the resistivity is attributed to the formation of more than one metastable metallic phase in the same sample as the ion dose increases.« less

  14. Substrates suitable for deposition of superconducting thin films

    DOEpatents

    Feenstra, Roeland; Boatner, Lynn A.

    1993-01-01

    A superconducting system for the lossless transmission of electrical current comprising a thin film of superconducting material Y.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7-x epitaxially deposited upon a KTaO.sub.3 substrate. The KTaO.sub.3 is an improved substrate over those of the prior art since the it exhibits small lattice constant mismatch and does not chemically react with the superconducting film.

  15. Performance of a four-element Ka-band high-temperature superconducting microstrip antenna

    NASA Technical Reports Server (NTRS)

    Richard, M. A.; Bhasin, K. B.; Gilbert, C.; Metzler, S.; Koepf, G.; Claspy, P. C.

    1992-01-01

    Superconducting four-element microstrip array antennas operating at 30 GHz have been designed and fabricated on a lanthanum aluminate (LaAlO3) substrates. The experimental performance of these thin film Y-Ba-Cu-O superconducting antennas is compared with that of identical antenna patterned with evaporated gold. Efficiency measurements of these antennas show an improvement of 2 dB at 70 K and as much as 3.5 dB at 40 K in the superconducting antenna over the gold antenna.

  16. YBa2Cu3O7 thin films on nanocrystalline diamond films for HTSC bolometer

    NASA Technical Reports Server (NTRS)

    Cui, G.; Beetz, C. P., Jr.; Boerstler, R.; Steinbeck, J.

    1993-01-01

    Superconducting YBa2Cu3O(7-x) films on nanocrystalline diamond thin films have been fabricated. A composite buffer layer system consisting of diamond/Si3N4/YSZ/YBCO was explored for this purpose. The as-deposited YBCO films were superconducting with Tc of about 84 K and a relatively narrow transition width of about 8 K. SEM cross sections of the films showed very sharp interfaces between diamond/Si3N4 and between Si3N4/YSZ. The deposited YBCO film had a surface roughness of about 1000 A, which is suitable for high-temperature superconductive (HTSC) bolometer fabrication. It was also found that preannealing of the nanocrystalline diamond thin films at high temperature was very important for obtaining high-quality YBCO films.

  17. Thermal coupling effect on the vortex dynamics of superconducting thin films: time-dependent Ginzburg–Landau simulations

    NASA Astrophysics Data System (ADS)

    Jing, Ze; Yong, Huadong; Zhou, Youhe

    2018-05-01

    In this paper, vortex dynamics of superconducting thin films are numerically investigated by the generalized time-dependent Ginzburg–Landau (TDGL) theory. Interactions between vortex motion and the motion induced energy dissipation is considered by solving the coupled TDGL equation and the heat diffusion equation. It is found that thermal coupling has significant effects on the vortex dynamics of superconducting thin films. Branching in the vortex penetration path originates from the coupling between vortex motion and the motion induced energy dissipation. In addition, the environment temperature, the magnetic field ramp rate and the geometry of the superconducting film also greatly influence the vortex dynamic behaviors. Our results provide new insights into the dynamics of superconducting vortices, and give a mesoscopic understanding on the channeling and branching of vortex penetration paths during flux avalanches.

  18. Kinetic Inductance Photodetectors Based on Nonequilibrium Response in Superconducting Thin-Film Structures

    NASA Technical Reports Server (NTRS)

    Sergeev, A. V.; Karasik, B. S.; Gogidze, I. G.; Mitin, V. V.

    2001-01-01

    While experimental studies of kinetic-inductance sensors have been limited so far by the temperature range near the superconducting transition, these detectors can be very sensitivity at temperatures well below the transition, where the number of equilibrium quasiparticles is exponentially small. In this regime, a shift of the quasiparticle chemical potential under radiation results in the change of the kinetic inductance, which can be measured by a sensitive SQUID readout. We modeled the kinetic inductance response of detectors made from disordered superconducting Nb, NbC, and MoRe films. Low phonon transparency of the interface between the superconductor and the substrate causes substantial re-trapping of phonons providing high quantum efficiency and the operating time of approximately 1 ms at 1 K. Due to the small number of quasiparticles, the noise equivalent power of the detector determined by the quasiparticle generation-recombination noise can be as small as approximately 10(exp -19) W/Hz(exp 1/2) at He4 temperatures.

  19. Dome-shaped magnetic order competing with high-temperature superconductivity at high pressures in FeSe

    DOE PAGES

    Sun, J. P.; Matsuura, K.; Ye, G. Z.; ...

    2016-07-19

    The coexistence and competition between superconductivity and electronic orders, such as spin or charge density waves, have been a central issue in high transition-temperature (T c) superconductors. Unlike other iron-based superconductors, FeSe exhibits nematic ordering without magnetism whose relationship with its superconductivity remains unclear. Moreover, a pressure-induced fourfold increase of T c has been reported, which poses a profound mystery. Here we report high-pressure magnetotransport measurements in FeSe up to ~15 GPa, which uncover the dome shape of magnetic phase superseding the nematic order. Above ~6 GPa the sudden enhancement of superconductivity (T c ≤ 38.3 K) accompanies a suppressionmore » of magnetic order, demonstrating their competing nature with very similar energy scales. Above the magnetic dome, we find anomalous transport properties suggesting a possible pseudogap formation, whereas linear-in-temperature resistivity is observed in the normal states of the high-T c phase above 6 GPa. In conclusion, the obtained phase diagram highlights unique features of FeSe among iron-based superconductors, but bears some resemblance to that of high-T c cuprates.« less

  20. High Tc superconducting materials and devices

    NASA Technical Reports Server (NTRS)

    Haertling, Gene H.

    1990-01-01

    The high Tc Y1Ba2Cu3O(7-x) ceramic materials, initially developed in 1987, are now being extensively investigated for a variety of engineering applications. The superconductor applications which are presently identified as of most interest to NASA-LaRC are low-noise, low thermal conductivity grounding links; large-area linear Meissner-effect bearings; and sensitive, low-noise sensors and leads. Devices designed for these applications require the development of a number of processing and fabrication technologies. Included among the technologies most specific to the present needs are tapecasting, melt texturing, magnetic field grain alignment, superconductor/polymer composite fabrication, thin film MOD (metal-organic decomposition) processing, screen printing of thick films, and photolithography of thin films. The overall objective of the program was to establish a high Tc superconductivity laboratory capability at NASA-LaRC and demonstrate this capability by fabricating superconducting 123 material via bulk and thin film processes. Specific objectives include: order equipment and set up laboratory; prepare 1 kg batches of 123 material via oxide raw material; construct tapecaster and tapecaster 123 material; fabricate 123 grounding link; fabricate 123 composite for Meissner linear bearing; develop 123 thin film processes (nitrates, acetates); establish Tc and Jc measurement capability; and set up a commercial use of space program in superconductivity at LaRC. In general, most of the objectives of the program were met. Finally, efforts to implement a commercial use of space program in superconductivity at LaRC were completed and at least two industrial companies have indicated their interest in participating.

  1. Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Warner, J. D.; Miranda, F. A.; Gordon, W. L.; Newman, H. S.

    1991-01-01

    A novel waveguide power transmission measurement technique was developed to extract the complex conductivity of superconducting thin films at microwave frequencies. The microwave conductivity was taken of two laser ablated YBa2Cu3O(7-delta) thin films on LaAlO3 with transition temperatures of approximately 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values, the penetration depth was found to be approximately 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approximately 24 and 36 micro-Ohms at 36 GHz and 76 K for the two films under consideration. The R sub s values were compared with those obtained from the change in the Q-factor of a 36 GHz Te sub 011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. This technique allows noninvasive characterization of high transition superconducting thin films at microwave frequencies.

  2. Stable superconducting magnet. [high current levels below critical temperature

    NASA Technical Reports Server (NTRS)

    Boom, R. W. (Inventor)

    1967-01-01

    Operation of a superconducting magnet is considered. A method is described for; (1) obtaining a relatively high current in a superconducting magnet positioned in a bath of a gas refrigerant; (2) operating a superconducting magnet at a relatively high current level without training; and (3) operating a superconducting magnet containing a plurality of turns of a niobium zirconium wire at a relatively high current level without training.

  3. Routes to High-Temperature Superconductivity: A Lesson from FeSe/SrTiO3

    NASA Astrophysics Data System (ADS)

    Lee, Dung-Hai

    2018-03-01

    Raising the superconducting transition temperature to a point where applications are practical is one of the most important challenges in science. In this review, we aim at gaining insights on the Tc controlling factors for a particular high-temperature superconductor family - the FeSe-based superconductors. In particular, we discuss the mechanisms by which the Cooper pairing temperature is enhanced from ˜8 K in bulk FeSe to ˜80 K in the interface between an atomic layer of FeSe and SrTiO3. This includes the experimental hints and the theoretical simulation of the involved mechanisms. We end by applying these insights to suggest some possible high-temperature superconducting systems.

  4. Sequentially evaporated thin Y-Ba-Co-O superconducting films on microwave substrates

    NASA Technical Reports Server (NTRS)

    Valco, G. J.; Rohrer, N. J.; Warner, J. D.; Bhasin, K. B.

    1989-01-01

    The development of high T sub c superconducting thin films on various microwave substrates is of major interest in space electronic systems. Thin films of YBa2Cu3O(7-Delta) were formed on SrTiO3, MgO, ZrO2 coated Al2O3, and LaAlO3 substrates by multi-layer sequential evaporation and subsequent annealing in oxygen. The technique allows controlled deposition of Cu, BaF2 and Y layers, as well as the ZrO buffer layers, to achieve reproducibility for microwave circuit fabrication. The three layer structure of Cu/BaF2/Y is repeated a minimum of four times. The films were annealed in an ambient of oxygen bubbled through water at temperatures between 850 C and 900 C followed by slow cooling (-2 C/minute) to 450 C, a low temperature anneal, and slow cooling to room temperature. Annealing times ranged from 15 minutes to 5 hrs. at high temperature and 0 to 6 hr. at 450 C. Silver contacts for four probe electrical measurements were formed by evaporation followed with an anneal at 500 C. The films were characterized by resistance-temperature measurements, energy dispersive X-ray spectroscopy, X-ray diffraction, and scanning electron microscopy. Critical transition temperatures ranged from 30 K to 87 K as a function of the substrate, composition of the film, thicknesses of the layers, and annealing conditions. Microwave ring resonator circuits were also patterned on these MgO and LaAlO3 substrates.

  5. Characterization of polybenzimidazole (PBI) film at high temperatures

    NASA Astrophysics Data System (ADS)

    Hammoud, Ahmad N.; Suthar, J. L.

    1992-04-01

    Polybenzimidazole, a linear thermoplastic polymer with excellent thermal stability and strength retention over a wide range of temperatures, was evaluated for its potential use as the main dielectric in high temperature capacitors. The film was characterized in terms of its dielectric properties in a frequency range of 50 Hz to 100 kilo-Hz. These properties, which include the dielectric constant and dielectric loss, were also obtained in a temperature range from 20 C to 300 C with an electrical stress of 60 Hz, 50 V/mil present. The alternating and direct current breakdown voltages of silicone oil impregnated films as a function of temperature were also determined. The results obtained indicate that while the film remained relatively stable up to 200 C, it exhibited an increase in its dielectric properties as the temperature was raised to 300 C. It was also found that conditioning of the film by heat treatment at 60 C for six hours tended to improve its dielectric and breakdown properties. The results are discussed and conclusions made concerning the suitability of the film as a high temperature capacitor dielectric.

  6. Characterization of polybenzimidazole (PBI) film at high temperatures

    NASA Technical Reports Server (NTRS)

    Hammoud, Ahmad N.; Suthar, J. L.

    1992-01-01

    Polybenzimidazole, a linear thermoplastic polymer with excellent thermal stability and strength retention over a wide range of temperatures, was evaluated for its potential use as the main dielectric in high temperature capacitors. The film was characterized in terms of its dielectric properties in a frequency range of 50 Hz to 100 kilo-Hz. These properties, which include the dielectric constant and dielectric loss, were also obtained in a temperature range from 20 C to 300 C with an electrical stress of 60 Hz, 50 V/mil present. The alternating and direct current breakdown voltages of silicone oil impregnated films as a function of temperature were also determined. The results obtained indicate that while the film remained relatively stable up to 200 C, it exhibited an increase in its dielectric properties as the temperature was raised to 300 C. It was also found that conditioning of the film by heat treatment at 60 C for six hours tended to improve its dielectric and breakdown properties. The results are discussed and conclusions made concerning the suitability of the film as a high temperature capacitor dielectric.

  7. Evaluation of high temperature dielectric films for high voltage power electronic applications

    NASA Technical Reports Server (NTRS)

    Suthar, J. L.; Laghari, J. R.

    1992-01-01

    Three high temperature films, polyimide, Teflon perfluoroalkoxy and poly-P-xylene, were evaluated for possible use in high voltage power electronic applications, such as in high energy density capacitors, cables and microelectronic circuits. The dielectric properties, including permittivity and dielectric loss, were obtained in the frequency range of 50 Hz to 100 kHz at temperatures up to 200 C. The dielectric strengths at 60 Hz were determined as a function of temperature to 250 C. Confocal laser microscopy was performed to diagnose for voids and microimperfections within the film structure. The results obtained indicate that all films evaluated are capable of maintaining their high voltage properties, with minimal degradation, at temperatures up to 200 C. However, above 200 C, they lose some of their electrical properties. These films may therefore become viable candidates for high voltage power electronic applications at high temperatures.

  8. Q factor of megahertz LC circuits based on thin films of YBaCuO high-temperature superconductor

    NASA Astrophysics Data System (ADS)

    Masterov, D. V.; Pavlov, S. A.; Parafin, A. E.

    2008-05-01

    High-frequency properties of resonant structures based on thin films of YBa2Cu3O7 δ high-temperature superconductor are studied experimentally in the frequency range 30 100 MHz. The structures planar induction coils with a self-capacitance fabricated on neodymium gallate and lanthanum aluminate substrates. The unloaded Q factor of the circuits exceeds 2 × 105 at 77 K and 40 MHz. Possible loss mechanisms that determine the Q factor of the superconducting resonant structures in the megahertz range are considered.

  9. Frequency dispersion of nonlinear response of thin superconducting films in the Berezinskii-Kosterlitz-Thouless state

    DOE PAGES

    Dietrich, Scott; Mayer, William; Byrnes, Sean; ...

    2015-02-20

    The effects of microwave radiation on transport properties of atomically thin La 2-xSr xCuO₄ films were studied in the 0.1-20 GHz frequency range. Resistance changes induced by microwaves were investigated at different temperatures (8–15 K) near the superconducting transition. A strong decrease of the nonlinear response is observed within a few GHz of a cutoff frequency ν cut ≈ 2GHz. The expected frequency dependence vastly underestimates the sharpness of this drop. Numerical simulations that assume ac response to follow dc V-I characteristics of the films reproduce well the low frequency behavior, but fail above ν cut. Thus, high-frequency radiation ismore » much less effective in inducing vortex-antivortex dissociation in the oscillating superconducting condensate.« less

  10. Emerging applications of high temperature superconductors for space communications

    NASA Technical Reports Server (NTRS)

    Heinen, Vernon O.; Bhasin, Kul B.; Long, Kenwyn J.

    1990-01-01

    Proposed space missions require longevity of communications system components, high input power levels, and high speed digital logic devices. The complexity of these missions calls for a high data bandwidth capacity. Incorporation of high temperature superconducting (HTS) thin films into some of these communications system components may provide a means of meeting these requirements. Space applications of superconducting technology has previously been limited by the requirement of cooling to near liquid helium temperatures. Development of HTS materials with transition temperatures above 77 K along with the natural cooling ability of space suggest that space applications may lead the way in the applications of high temperature superconductivity. In order for HTS materials to be incorporated into microwave and millimeter wave devices, the material properties such as electrical conductivity, current density, surface resistivity and others as a function of temperature and frequency must be well characterized and understood. The millimeter wave conductivity and surface resistivity were well characterized, and at 77 K are better than copper. Basic microwave circuits such as ring resonators were used to determine transmission line losses. Higher Q values than those of gold resonator circuits were observed below the transition temperature. Several key HTS circuits including filters, oscillators, phase shifters and phased array antenna feeds are feasible in the near future. For technology to improve further, good quality, large area films must be reproducibly grown on low dielectric constant, low loss microwave substrates.

  11. Millimeter-wave surface resistance of laser-ablated YBa2Cu3O(7-delta) superconducting films

    NASA Technical Reports Server (NTRS)

    Miranda, F. A.; Gordon, W. L.; Bhasin, K. B.; Warner, J. D.

    1990-01-01

    The millimeter-wave surface resistance of YBa2Cu3O(7-delta) superconducting films was measured in a gold-plated copper host cavity at 58.6 GHz between 25 and 300 K. High-quality laser-ablated films of 1.2-micron thickness were deposited on SrTiO3 and LaGaO3 substrates. Their transition temperatures were 90.0 and 88.9 K, with a surface resistance at 70 K of 82 and 116 milliohms, respectively. These values are better than the values for the gold-plated cavity at the same temperature and frequency.

  12. Evolution of High-Temperature Superconductivity from a Low-T_{c} Phase Tuned by Carrier Concentration in FeSe Thin Flakes.

    PubMed

    Lei, B; Cui, J H; Xiang, Z J; Shang, C; Wang, N Z; Ye, G J; Luo, X G; Wu, T; Sun, Z; Chen, X H

    2016-02-19

    We report the evolution of superconductivity in an FeSe thin flake with systematically regulated carrier concentrations by the liquid-gating technique. With electron doping tuned by the gate voltage, high-temperature superconductivity with an onset at 48 K can be achieved in an FeSe thin flake with T_{c} less than 10 K. This is the first time such high temperature superconductivity in FeSe is achieved without either an epitaxial interface or external pressure, and it definitely proves that the simple electron-doping process is able to induce high-temperature superconductivity with T_{c}^{onset} as high as 48 K in bulk FeSe. Intriguingly, our data also indicate that the superconductivity is suddenly changed from a low-T_{c} phase to a high-T_{c} phase with a Lifshitz transition at a certain carrier concentration. These results help to build a unified picture to understand the high-temperature superconductivity among all FeSe-derived superconductors and shed light on the further pursuit of a higher T_{c} in these materials.

  13. On local pairs vs. BCS: Quo vadis high-T c superconductivity

    DOE PAGES

    Pavuna, D.; Dubuis, G.; Bollinger, A. T.; ...

    2016-07-28

    Since the discovery of high-temperature superconductivity in cuprates, proposals have been made that pairing may be local, in particular in underdoped samples. Furthermore, we briefly review evidence for local pairs from our experiments on thin films of La 2–xSr xCuO 4, synthesized by atomic layer-by-layer molecular beam epitaxy (ALL-MBE).

  14. Study of flow fractionation characteristics of magnetic chromatography utilizing high-temperature superconducting bulk magnet.

    PubMed

    Fukui, Satoshi; Shoji, Yoshihiro; Ogawa, Jun; Oka, Tetsuo; Yamaguchi, Mitsugi; Sato, Takao; Ooizumi, Manabu; Imaizumi, Hiroshi; Ohara, Takeshi

    2009-02-01

    We present numerical simulation of separating magnetic particles with different magnetic susceptibilities by magnetic chromatography using a high-temperature superconducting bulk magnet. The transient transport is numerically simulated for two kinds of particles having different magnetic susceptibilities. The time evolutions were calculated for the particle concentration in the narrow channel of the spiral arrangement placed in the magnetic field. The field is produced by the highly magnetized high-temperature superconducting bulk magnet. The numerical results show the flow velocity difference of the particle transport corresponding to the difference in the magnetic susceptibility, as well as the possible separation of paramagnetic particles of 20 nm diameter.

  15. Hydrogen Clathrate Structures in Rare Earth Hydrides at High Pressures: Possible Route to Room-Temperature Superconductivity

    NASA Astrophysics Data System (ADS)

    Peng, Feng; Sun, Ying; Pickard, Chris J.; Needs, Richard J.; Wu, Qiang; Ma, Yanming

    2017-09-01

    Room-temperature superconductivity has been a long-held dream and an area of intensive research. Recent experimental findings of superconductivity at 200 K in highly compressed hydrogen (H) sulfides have demonstrated the potential for achieving room-temperature superconductivity in compressed H-rich materials. We report first-principles structure searches for stable H-rich clathrate structures in rare earth hydrides at high pressures. The peculiarity of these structures lies in the emergence of unusual H cages with stoichiometries H24 , H29 , and H32 , in which H atoms are weakly covalently bonded to one another, with rare earth atoms occupying the centers of the cages. We have found that high-temperature superconductivity is closely associated with H clathrate structures, with large H-derived electronic densities of states at the Fermi level and strong electron-phonon coupling related to the stretching and rocking motions of H atoms within the cages. Strikingly, a yttrium (Y) H32 clathrate structure of stoichiometry YH10 is predicted to be a potential room-temperature superconductor with an estimated Tc of up to 303 K at 400 GPa, as derived by direct solution of the Eliashberg equation.

  16. Hydrogen Clathrate Structures in Rare Earth Hydrides at High Pressures: Possible Route to Room-Temperature Superconductivity.

    PubMed

    Peng, Feng; Sun, Ying; Pickard, Chris J; Needs, Richard J; Wu, Qiang; Ma, Yanming

    2017-09-08

    Room-temperature superconductivity has been a long-held dream and an area of intensive research. Recent experimental findings of superconductivity at 200 K in highly compressed hydrogen (H) sulfides have demonstrated the potential for achieving room-temperature superconductivity in compressed H-rich materials. We report first-principles structure searches for stable H-rich clathrate structures in rare earth hydrides at high pressures. The peculiarity of these structures lies in the emergence of unusual H cages with stoichiometries H_{24}, H_{29}, and H_{32}, in which H atoms are weakly covalently bonded to one another, with rare earth atoms occupying the centers of the cages. We have found that high-temperature superconductivity is closely associated with H clathrate structures, with large H-derived electronic densities of states at the Fermi level and strong electron-phonon coupling related to the stretching and rocking motions of H atoms within the cages. Strikingly, a yttrium (Y) H_{32} clathrate structure of stoichiometry YH_{10} is predicted to be a potential room-temperature superconductor with an estimated T_{c} of up to 303 K at 400 GPa, as derived by direct solution of the Eliashberg equation.

  17. Superconducting gap in cuprate high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Verma, Sanjeev K.; Kumari, Anita; Gupta, Anushri; Indu, B. D.

    2018-05-01

    The many body quantum dynamical evaluation of double time thermodynamic electron Green's functions followed by generalized electron density of states (EDOS) is used to study the superconducting gap (SG). The dependence of EDOS on defects, anharmonicity and electron-phonon interactions makes the problem quite complicated and challenging but furnishes the more realistic grounds to study the SG both in conventional and high temperature superconductors (HTS). For simplicity, only electron-phonon interaction has been taken up to evaluate the intricate integral to enumerate the SG for representative cuprate HTS: YBa2Cu3O7-δ and results show 2Δ/kBTc ⋍ 7.2.

  18. The Fabrication Technique and Property Analysis of Racetrack-Type High Temperature Superconducting Magnet for High Power Motor

    NASA Astrophysics Data System (ADS)

    Xie, S. F.; Wang, Y.; Wang, D. Y.; Zhang, X. J.; Zhao, B.; Zhang, Y. Y.; Li, L.; Li, Y. N.; Chen, P. M.

    2013-03-01

    The superconducting motor is now the focus of the research on the application of high temperature superconducting (HTS) materials. In this manuscript, we mainly introduce the recent progress on the fabrication technique and property research of the superconducting motor magnet in Luoyang Ship Material Research Institute (LSMRI) in China, including the materials, the winding and impregnation technique, and property measurement of magnet. Several techniques and devices were developed to manufacture the magnet, including the technique of insulation and thermal conduction, the device for winding the racetrack-type magnet, etc. At last, the superconducting magnet used for the MW class motor were successfully developed, which is the largest superconducting motor magnet in china at present. The critical current of the superconducting magnet exceeds the design value (90 A at 30 K).

  19. Electro-physical properties of superconducting ceramic thick film prepared by partial melting method.

    PubMed

    Lee, Sang Heon

    2013-05-01

    BiSrCaCuO superconductor thick films were prepared at several curing temperatures, and their electro-physical properties were determined to find an optimum fabrication conditions. Critical temperatures of the superconductors were decreased with increasing melting temperature, which was related to the amount of equilibrium phases of the superconducting materials with temperature. The critical temperature of BiSrCaCuO bulk and thick film superconductors were 107 K and 96 K, respectively. The variation of susceptibility of the superconductor thick film formed at 950 degrees C had multi-step-type curve for 70 G externally applied field, whereas, a superconductor thick film formed at 885 degrees C had a single step-type curve like a bulk BiSrCaCuO ceramic superconductor in the temperature-susceptibility curves. A partial melting at 865 degrees C is one of optimum conditions for making a superconductor thick film with a relatively homogeneous phase.

  20. Nodeless pairing in superconducting copper-oxide monolayer films on Bi 2Sr 2CaCu 2O 8+δ

    DOE PAGES

    Zhong, Yong; Wang, Yang; Han, Sha; ...

    2016-07-12

    We report that the pairing mechanism of high-temperature superconductivity in cuprates remains the biggest unresolved mystery in condensed matter physics. To solve the problem, one of the most effective approaches is to investigate directly the superconducting CuO 2 layers. Here, by growing CuO 2 monolayer films on Bi 2Sr 2CaCu 2O 8+δ substrates, we identify two distinct and spatially separated energy gaps centered at the Fermi energy, a smaller U-like gap and a larger V-like gap on the films, and study their interactions with alien atoms by low-temperature scanning tunneling microscopy. The newly discovered U-like gap exhibits strong phase coherencemore » and is immune to scattering by K, Cs and Ag atoms, suggesting its nature as a nodeless superconducting gap in the CuO 2 layers, whereas the V-like gap agrees with the well-known pseudogap state in the underdoped regime. In conclusion, our results support an s-wave superconductivity in Bi 2Sr 2CaCu 2O 8+δ, which, we propose, originates from the modulation-doping resultant two-dimensional hole liquid confined in the CuO 2 layers.« less

  1. Nodeless pairing in superconducting copper-oxide monolayer films on Bi 2Sr 2CaCu 2O 8+δ

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhong, Yong; Wang, Yang; Han, Sha

    We report that the pairing mechanism of high-temperature superconductivity in cuprates remains the biggest unresolved mystery in condensed matter physics. To solve the problem, one of the most effective approaches is to investigate directly the superconducting CuO 2 layers. Here, by growing CuO 2 monolayer films on Bi 2Sr 2CaCu 2O 8+δ substrates, we identify two distinct and spatially separated energy gaps centered at the Fermi energy, a smaller U-like gap and a larger V-like gap on the films, and study their interactions with alien atoms by low-temperature scanning tunneling microscopy. The newly discovered U-like gap exhibits strong phase coherencemore » and is immune to scattering by K, Cs and Ag atoms, suggesting its nature as a nodeless superconducting gap in the CuO 2 layers, whereas the V-like gap agrees with the well-known pseudogap state in the underdoped regime. In conclusion, our results support an s-wave superconductivity in Bi 2Sr 2CaCu 2O 8+δ, which, we propose, originates from the modulation-doping resultant two-dimensional hole liquid confined in the CuO 2 layers.« less

  2. A visualization instrument to investigate the mechanical-electro properties of high temperature superconducting tapes under multi-fields

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Zhang, Xingyi; Liu, Cong; Zhang, Wentao; Zhou, Jun; Zhou, YouHe

    2016-07-01

    We construct a visible instrument to study the mechanical-electro behaviors of high temperature superconducting tape as a function of magnetic field, strain, and temperature. This apparatus is directly cooled by a commercial Gifford-McMahon cryocooler. The minimum temperature of sample can be 8.75 K. A proportion integration differentiation temperature control is used, which is capable of producing continuous variation of specimen temperature from 8.75 K to 300 K with an optional temperature sweep rate. We use an external loading device to stretch the superconducting tape quasi-statically with the maximum tension strain of 20%. A superconducting magnet manufactured by the NbTi strand is applied to provide magnetic field up to 5 T with a homogeneous range of 110 mm. The maximum fluctuation of the magnetic field is less than 1%. We design a kind of superconducting lead composed of YBa2Cu3O7-x coated conductor and beryllium copper alloy (BeCu) to transfer DC to the superconducting sample with the maximum value of 600 A. Most notably, this apparatus allows in situ observation of the electromagnetic property of superconducting tape using the classical magnetic-optical imaging.

  3. A visualization instrument to investigate the mechanical-electro properties of high temperature superconducting tapes under multi-fields.

    PubMed

    Liu, Wei; Zhang, Xingyi; Liu, Cong; Zhang, Wentao; Zhou, Jun; Zhou, YouHe

    2016-07-01

    We construct a visible instrument to study the mechanical-electro behaviors of high temperature superconducting tape as a function of magnetic field, strain, and temperature. This apparatus is directly cooled by a commercial Gifford-McMahon cryocooler. The minimum temperature of sample can be 8.75 K. A proportion integration differentiation temperature control is used, which is capable of producing continuous variation of specimen temperature from 8.75 K to 300 K with an optional temperature sweep rate. We use an external loading device to stretch the superconducting tape quasi-statically with the maximum tension strain of 20%. A superconducting magnet manufactured by the NbTi strand is applied to provide magnetic field up to 5 T with a homogeneous range of 110 mm. The maximum fluctuation of the magnetic field is less than 1%. We design a kind of superconducting lead composed of YBa2Cu3O7-x coated conductor and beryllium copper alloy (BeCu) to transfer DC to the superconducting sample with the maximum value of 600 A. Most notably, this apparatus allows in situ observation of the electromagnetic property of superconducting tape using the classical magnetic-optical imaging.

  4. The contribution of bends and constrictions of a superconducting film to the photon detection by a single-photon superconducting detector

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zotova, A. N., E-mail: zotova@imp.sci-nnov.ru

    2016-05-15

    The contribution of bends and constrictions by a superconducting film to the detection by a single photon superconducting detector is investigated. It has been shown that, for currents smaller than the minimal detection current of a straight film, the detection efficiency of a film with a constriction attains saturation upon an increase in the current, which coincides qualitatively with the behavior of this dependence observed in the experiment. It has also been found that the effect of bends in the film and the external magnetic field on the detection efficiency for low-energy photons is essential, while for high-energy photons nomore » such influence is observed.« less

  5. Thin Film Approaches to the SRF Cavity Problem Fabrication and Characterization of Superconducting Thin Films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Beringer, Douglas

    Superconducting Radio Frequency (SRF) cavities are responsible for the acceleration of charged particles to relativistic velocities in most modern linear accelerators, such as those employed at high-energy research facilities like Thomas Jefferson National Laboratory’s CEBAF and the LHC at CERN. Recognizing SRF as primarily a surface phenomenon enables the possibility of applying thin films to the interior surface of SRF cavities, opening a formidable tool chest of opportunities by combining and designing materials that offer greater performance benefit. Thus, while improvements in radio frequency cavity design and refinements in cavity processing techniques have improved accelerator performance and efficiency – 1.5more » GHz bulk niobium SRF cavities have achieved accelerating gradients in excess of 35 MV/m – there exist fundamental material bounds in bulk superconductors limiting the maximally sustained accelerating field gradient (≈ 45 MV/m for Nb) where inevitable thermodynamic breakdown occurs. With state of the art Nb based cavity design fast approaching these theoretical limits, novel material innovations must be sought in order to realize next generation SRF cavities. One proposed method to improve SRF performance is to utilize thin film superconducting-insulating-superconducting (SIS) multilayer structures to effectively magnetically screen a bulk superconducting layer such that it can operate at higher field gradients before suffering critically detrimental SRF losses. This dissertation focuses on the production and characterization of thin film superconductors for such SIS layers for radio frequency applications. Correlated studies on structure, surface morphology and superconducting properties of epitaxial Nb and MgB2 thin films are presented.« less

  6. Superconducting pairing of topological surface states in bismuth selenide films on niobium

    PubMed Central

    Zhang, Can; Tsuzuki, Akihiro

    2018-01-01

    A topological insulator film coupled to a simple isotropic s-wave superconductor substrate can foster helical pairing of the Dirac fermions associated with the topological surface states. Experimental realization of such a system is exceedingly difficult, however using a novel “flip-chip” technique, we have prepared single-crystalline Bi2Se3 films with predetermined thicknesses in terms of quintuple layers (QLs) on top of Nb substrates fresh from in situ cleavage. Our angle-resolved photoemission spectroscopy (ARPES) measurements of the film surface disclose superconducting gaps and coherence peaks of similar magnitude for both the topological surface states and bulk states. The ARPES spectral map as a function of temperature and film thickness up to 10 QLs reveals key characteristics relevant to the mechanism of coupling between the topological surface states and the superconducting Nb substrate; the effective coupling length is found to be much larger than the decay length of the topological surface states. PMID:29719866

  7. Microwave spectroscopy evidence of superconducting pairing in the magnetic-field-induced metallic state of InO(x) films at zero temperature.

    PubMed

    Liu, Wei; Pan, LiDong; Wen, Jiajia; Kim, Minsoo; Sambandamurthy, G; Armitage, N P

    2013-08-09

    We investigate the field-tuned quantum phase transition in a 2D low-disorder amorphous InO(x) film in the frequency range of 0.05 to 16 GHz employing microwave spectroscopy. In the zero-temperature limit, the ac data are consistent with a scenario where this transition is from a superconductor to a metal instead of a direct transition to an insulator. The intervening metallic phase is unusual with a small but finite resistance that is much smaller than the normal state sheet resistance at the lowest measured temperatures. Moreover, it exhibits a superconducting response on short length and time scales while global superconductivity is destroyed. We present evidence that the true quantum critical point of this 2D superconductor metal transition is located at a field B(sm) far below the conventionally defined critical field B(cross) where different isotherms of magnetoresistance cross each other. The superfluid stiffness in the low-frequency limit and the superconducting fluctuation frequency from opposite sides of the transition both vanish at B≈B(sm). The lack of evidence for finite-frequency superfluid stiffness surviving B(cross) signifies that B(cross) is a crossover above which superconducting fluctuations make a vanishing contribution to dc and ac measurements.

  8. Superconducting Mercury-Based Cuprate Films with a Zero-Resistance Transition Temperature of 124 Kelvin

    NASA Astrophysics Data System (ADS)

    Tsuei, C. C.; Gupta, A.; Trafas, G.; Mitzi, D.

    1994-03-01

    The synthesis of high-quality films of the recently discovered mercury-based cuprate films with high transition temperatures has been plagued by problems such as the air sensitivity of the cuprate precursor and the volatility of Hg and HgO. These processing difficulties have been circumvented by a technique of atomic-scale mixing of the HgO and cuprate precursors, use of a protective cap layer, and annealing in an appropriate Hg and O_2 environment. With this procedure, a zero-resistance transition temperature as high as 124 kelvin in c axis-oriented epitaxial HgBa_2CaCu_2O6+δ films has been achieved.

  9. Superconducting mercury-based cuprate films with a zero-resistance transition temperature of 124 Kelvin.

    PubMed

    Tsuei, C C; Gupta, A; Trafas, G; Mitzi, D

    1994-03-04

    The synthesis of high-quality films of the recently discovered mercury-based cuprate films with high transition temperatures has been plagued by problems such as the air sensitivity of the cuprate precursor and the volatility of Hg and HgO. These processing difficulties have been circumvented by a technique of atomic-scale mixing of the HgO and cuprate precursors, use of a protective cap layer, and annealing in an appropriate Hg and O(2) environment. With this procedure, a zero-resistance transition temperature as high as 124 kelvin in c axis-oriented epitaxial HgBa(2)CaCu(2)O(6+delta) films has been achieved.

  10. Superconductivity in highly disordered dense carbon disulfide

    PubMed Central

    Dias, Ranga P.; Yoo, Choong-Shik; Struzhkin, Viktor V.; Kim, Minseob; Muramatsu, Takaki; Matsuoka, Takahiro; Ohishi, Yasuo; Sinogeikin, Stanislav

    2013-01-01

    High pressure plays an increasingly important role in both understanding superconductivity and the development of new superconducting materials. New superconductors were found in metallic and metal oxide systems at high pressure. However, because of the filled close-shell configuration, the superconductivity in molecular systems has been limited to charge-transferred salts and metal-doped carbon species with relatively low superconducting transition temperatures. Here, we report the low-temperature superconducting phase observed in diamagnetic carbon disulfide under high pressure. The superconductivity arises from a highly disordered extended state (CS4 phase or phase III[CS4]) at ∼6.2 K over a broad pressure range from 50 to 172 GPa. Based on the X-ray scattering data, we suggest that the local structural change from a tetrahedral to an octahedral configuration is responsible for the observed superconductivity. PMID:23818624

  11. Superconductivity in highly disordered dense carbon disulfide.

    PubMed

    Dias, Ranga P; Yoo, Choong-Shik; Struzhkin, Viktor V; Kim, Minseob; Muramatsu, Takaki; Matsuoka, Takahiro; Ohishi, Yasuo; Sinogeikin, Stanislav

    2013-07-16

    High pressure plays an increasingly important role in both understanding superconductivity and the development of new superconducting materials. New superconductors were found in metallic and metal oxide systems at high pressure. However, because of the filled close-shell configuration, the superconductivity in molecular systems has been limited to charge-transferred salts and metal-doped carbon species with relatively low superconducting transition temperatures. Here, we report the low-temperature superconducting phase observed in diamagnetic carbon disulfide under high pressure. The superconductivity arises from a highly disordered extended state (CS4 phase or phase III[CS4]) at ~6.2 K over a broad pressure range from 50 to 172 GPa. Based on the X-ray scattering data, we suggest that the local structural change from a tetrahedral to an octahedral configuration is responsible for the observed superconductivity.

  12. Shock-induced synthesis of high temperature superconducting materials

    DOEpatents

    Ginley, D.S.; Graham, R.A.; Morosin, B.; Venturini, E.L.

    1987-06-18

    It has now been determined that the unique features of the high pressure shock method, especially the shock-induced chemical synthesis technique, are fully applicable to high temperature superconducting materials. Extraordinarily high yields are achievable in accordance with this invention, e.g., generally in the range from about 20% to about 99%, often in the range from about 50% to about 90%, lower and higher yields, of course, also being possible. The method of this invention involves the application of a controlled high pressure shock compression pulse which can be produced in any conventional manner, e.g., by detonation of a high explosive material, the impact of a high speed projectile or the effect of intense pulsed radiation sources such as lasers or electron beams. Examples and a discussion are presented.

  13. A broadband microwave Corbino spectrometer at ³He temperatures and high magnetic fields.

    PubMed

    Liu, Wei; Pan, LiDong; Armitage, N P

    2014-09-01

    We present the technical details of a broadband microwave spectrometer for measuring the complex conductance of thin films covering the range from 50 MHz up to 16 GHz in the temperature range 300 mK-6 K and at applied magnetic fields up to 8 T. We measure the complex reflection from a sample terminating a coaxial transmission line and calibrate the signals with three standards with known reflection coefficients. Thermal isolation of the heat load from the inner conductor is accomplished by including a section of NbTi superconducting cable (transition temperature around 8-9 K) and hermetic seal glass bead adapters. This enables us to stabilize the base temperature of the sample stage at 300 mK. However, the inclusion of this superconducting cable complicates the calibration procedure. We document the effects of the superconducting cable on our calibration procedure and the effects of applied magnetic fields and how we control the temperature with great repeatability for each measurement. We have successfully extracted reliable data in this frequency, temperature, and field range for thin superconducting films and highly resistive graphene samples.

  14. A broadband microwave Corbino spectrometer at 3He temperatures and high magnetic fields

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Pan, LiDong; Armitage, N. P.

    2014-09-01

    We present the technical details of a broadband microwave spectrometer for measuring the complex conductance of thin films covering the range from 50 MHz up to 16 GHz in the temperature range 300 mK-6 K and at applied magnetic fields up to 8 T. We measure the complex reflection from a sample terminating a coaxial transmission line and calibrate the signals with three standards with known reflection coefficients. Thermal isolation of the heat load from the inner conductor is accomplished by including a section of NbTi superconducting cable (transition temperature around 8-9 K) and hermetic seal glass bead adapters. This enables us to stabilize the base temperature of the sample stage at 300 mK. However, the inclusion of this superconducting cable complicates the calibration procedure. We document the effects of the superconducting cable on our calibration procedure and the effects of applied magnetic fields and how we control the temperature with great repeatability for each measurement. We have successfully extracted reliable data in this frequency, temperature, and field range for thin superconducting films and highly resistive graphene samples.

  15. Superconducting Properties of Lead-Bismuth Films Controlled by Ferromagnetic Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Ye, Zuxin; Lyuksyutov, Igor F.; Wu, Wenhao; Naugle, Donald G.

    2011-03-01

    Superconducting properties of lead-bismuth (82% Pb and 18% Bi) alloy films deposited on ferromagnetic nanowire arrays have been investigated. Ferromagnetic Co or Ni nanowires are first electroplated into the columnar pores of anodic aluminum oxide (AAO) membranes. Superconducting Pb 82 Bi 18 films are then quench-condensed onto the polished surface of the AAO membranes filled with magnetic nanowires. A strong dependence of the Pb 82 Bi 18 superconducting properties on the ratio of the superconducting film thickness to the magnetic nanowire diameter and the material variety was observed.

  16. Superconductivity-localization interplay and fluctuation magnetoresistance in epitaxial BaPb1 -xBixO3 thin films

    NASA Astrophysics Data System (ADS)

    Harris, D. T.; Campbell, N.; Uecker, R.; Brützam, M.; Schlom, D. G.; Levchenko, A.; Rzchowski, M. S.; Eom, C.-B.

    2018-04-01

    BaPb1 -xBixO3 is a superconductor, with transition temperature Tc=11 K, whose parent compound BaBiO3 possesses a charge ordering phase and perovskite crystal structure reminiscent of the cuprates. The lack of magnetism simplifies the BaPb1 -xBixO3 phase diagram, making this system an ideal platform for contrasting high-Tc systems with isotropic superconductors. Here we use high-quality epitaxial thin films and magnetotransport to demonstrate superconducting fluctuations that extend well beyond Tc. For the thickest films (thickness above ˜100 nm ) this region extends to ˜27 K , well above the bulk Tc and remarkably close to the higher Tc of Ba1 -xKxBiO3 (Tc=31 K). We drive the system through a superconductor-insulator transition by decreasing thickness and find the observed Tc correlates strongly with disorder. This material manifests strong fluctuations across a wide range of thicknesses, temperatures, and disorder presenting new opportunities for understanding the precursor of superconductivity near the 2D-3D dimensionality crossover.

  17. Detection of s-wave superconductivity on monolayer CuO2 films on Bi2Sr2CaCu2O8+δ.

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Zhong, Yong; Han, Sha; Lv, Yanfeng; Wang, Wenlin; Zhang, Ding; Ding, Hao; Zhang, Yimin; Wang, Lili; He, Ke; Song, Canli; Ma, Xucun; Xue, Qikun

    High temperature superconductivity emerges when the CuO2 layer touches the doped charge reservoir blocks. The redistributed charge carriers at these interfaces condense into coherent Cooper pairs, albeit the exact underlying mechanism is still highly controversial. Targeting at this, we have mimicked the CuO2/charge reservoir interface by depositing the monolayer CuO2 films on optimal doped Bi2Sr2CaCu2O8+δ substrates. Direct investigation on these superconducting CuO2 films, however, yields results in stark contrast with the common recognition. Despite of the well-known V shaped pseudogap, a U shaped gap is identified. This U shaped gap disappears at TC and is indifference to K, Cs and Ag adsorbates, in line with the traditional s-wave superconductivity. In view of these results, we propose that superconductivity in cuprates may indeed stem from the modulation doping induced two dimensional hole liquid, which is confined in the CuO2 layers. NSF and MOST of China.

  18. What is strange about high-temperature superconductivity in cuprates?

    NASA Astrophysics Data System (ADS)

    Božović, I.; He, X.; Wu, J.; Bollinger, A. T.

    2017-10-01

    Cuprate superconductors exhibit many features, but the ultimate question is why the critical temperature (Tc) is so high. The fundamental dichotomy is between the weak-pairing, Bardeen-Cooper-Schrieffer (BCS) scenario, and Bose-Einstein condensation (BEC) of strongly-bound pairs. While for underdoped cuprates it is hotly debated which of these pictures is appropriate, it is commonly believed that on the overdoped side strongly-correlated fermion physics evolves smoothly into the conventional BCS behavior. Here, we test this dogma by studying the dependence of key superconducting parameters on doping, temperature, and external fields, in thousands of cuprate samples. The findings do not conform to BCS predictions anywhere in the phase diagram.

  19. Ultrasensitive interplay between ferromagnetism and superconductivity in NbGd composite thin films

    PubMed Central

    Bawa, Ambika; Gupta, Anurag; Singh, Sandeep; Awana, V.P.S.; Sahoo, Sangeeta

    2016-01-01

    A model binary hybrid system composed of a randomly distributed rare-earth ferromagnetic (Gd) part embedded in an s-wave superconducting (Nb) matrix is being manufactured to study the interplay between competing superconducting and ferromagnetic order parameters. The normal metallic to superconducting phase transition appears to be very sensitive to the magnetic counterpart and the modulation of the superconducing properties follow closely to the Abrikosov-Gor’kov (AG) theory of magnetic impurity induced pair breaking mechanism. A critical concentration of Gd is obtained for the studied NbGd based composite films (CFs) above which superconductivity disappears. Besides, a magnetic ordering resembling the paramagnetic Meissner effect (PME) appears in DC magnetization measurements at temperatures close to the superconducting transition temperature. The positive magnetization related to the PME emerges upon doping Nb with Gd. The temperature dependent resistance measurements evolve in a similar fashion with the concentration of Gd as that with an external magnetic field and in both the cases, the transition curves accompany several intermediate features indicating the traces of magnetism originated either from Gd or from the external field. Finally, the signatures of magnetism appear evidently in the magnetization and transport measurements for the CFs with very low (<1 at.%) doping of Gd. PMID:26725684

  20. Interface-Induced Zeeman-Protected Superconductivity in Ultrathin Crystalline Lead Films

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Wang, Ziqiao; Zhang, Xuefeng; Liu, Chaofei; Liu, Yongjie; Zhou, Zhimou; Wang, Junfeng; Wang, Qingyan; Liu, Yanzhao; Xi, Chuanying; Tian, Mingliang; Liu, Haiwen; Feng, Ji; Xie, X. C.; Wang, Jian

    2018-04-01

    Two-dimensional (2D) superconducting systems are of great importance for exploring exotic quantum physics. The recent development of fabrication techniques has stimulated studies of high-quality single-crystalline 2D superconductors, where intrinsic properties give rise to unprecedented physical phenomena. Here, we report the observation of Zeeman-type spin-orbit interaction protected superconductivity (Zeeman-protected superconductivity) in 4-monolayer (ML) to 6-ML crystalline Pb films grown on striped incommensurate Pb layers on Si(111) substrates by molecular beam epitaxy. An anomalously large in-plane critical field far beyond the Pauli limit is detected, which can be attributed to the Zeeman-protected superconductivity due to the in-plane inversion symmetry breaking at the interface. Our work demonstrates that, in superconducting heterostructures, the interface can induce Zeeman-type spin-orbit interactions and modulate the superconductivity.

  1. Aspects of passive magnetic levitation based on high-T(sub c) superconducting YBCO thin films

    NASA Technical Reports Server (NTRS)

    Schoenhuber, P.; Moon, F. C.

    1995-01-01

    Passive magnetic levitation systems reported in the past were mostly confined to bulk superconducting materials. Here we present fundamental studies on magnetic levitation employing cylindrical permanent magnets floating above high-T(sub c) superconducting YBCO thin films (thickness about 0.3 mu m). Experiments included free floating rotating magnets as well as well-established flexible beam methods. By means of the latter, we investigated levitation and drag force hysteresis as well as magnetic stiffness properties of the superconductor-magnet arrangement. In the case of vertical motion of the magnet, characteristic high symmetry of repulsive (approaching) and attractive (withdrawing) branches of the pronounced force-displacement hysteresis could be detected. Achievable force levels were low as expected but sufficient for levitation of permanent magnets. With regard to magnetic stiffness, thin films proved to show stiffness-force ratios about one order of magnitude higher than bulk materials. Phenomenological models support the measurements. Regarding the magnetic hysteresis of the superconductor, the Irie-Yamafuji model was used for solving the equation of force balance in cylindrical coordinates allowing for a macroscopic description of the superconductor magnetization. This procedure provided good agreement with experimental levitation force and stiffness data during vertical motion. For the case of (lateral) drag force basic qualitative characteristics could be recovered, too. It is shown that models, based on simple asymmetric magnetization of the superconductor, describe well asymptotic transition of drag forces after the change of the magnet motion direction. Virgin curves (starting from equilibrium, i.e. symmetric magnetization) are approximated by a linear approach already reported in literature only. This paper shows that basic properties of superconducting thin films allow for their application to magnetic levitation or - without need of levitation

  2. High- and Mid-temperature Superconducting Sensors for Far IR/Sub-mm Applications in Space

    NASA Technical Reports Server (NTRS)

    Lakew, Brook; Brasunas, J. C.

    2004-01-01

    In this review paper an overview of the potential applications of high Tc (approx. 90 K) superconductors (HTS) and mid-Tc (approx. 39 K) superconductors (MTS) thin films in far IR/Sub-mm thermal detectors is presented. HTSs (YBCO, GdBCO etc.) were discovered in the late 80s while superconductivity in MgB2, an MTS, was discovered in 2001. The sharp transition in transport properties of HTS has allowed the fabrication of composite infrared thermal detectors (bolometers) with better figures of merit than thermopile detectors - thermopiles are currently on board the CIRS instrument on the Cassini mission to Saturn. The potential for developing even more sensitive sensors for IR/Sub-mm applications using MgB2 thin films is assessed. Current MgB2 thin film deposition techniques and film quality are reviewed.

  3. A hidden pseudogap under the 'dome' of superconductivity in electron-doped high-temperature superconductors.

    PubMed

    Alff, L; Krockenberger, Y; Welter, B; Schonecke, M; Gross, R; Manske, D; Naito, M

    2003-04-17

    The ground state of superconductors is characterized by the long-range order of condensed Cooper pairs: this is the only order present in conventional superconductors. The high-transition-temperature (high-T(c)) superconductors, in contrast, exhibit more complex phase behaviour, which might indicate the presence of other competing ground states. For example, the pseudogap--a suppression of the accessible electronic states at the Fermi level in the normal state of high-T(c) superconductors-has been interpreted as either a precursor to superconductivity or as tracer of a nearby ground state that can be separated from the superconducting state by a quantum critical point. Here we report the existence of a second order parameter hidden within the superconducting phase of the underdoped (electron-doped) high-T(c) superconductor Pr2-xCe(x)CuO4-y and the newly synthesized electron-doped material La2-xCe(x)CuO4-y (ref. 8). The existence of a pseudogap when superconductivity is suppressed excludes precursor superconductivity as its origin. Our observation is consistent with the presence of a (quantum) phase transition at T = 0, which may be a key to understanding high-T(c) superconductivity. This supports the picture that the physics of high-T(c) superconductors is determined by the interplay between competing and coexisting ground states.

  4. Processing study of high temperature superconducting Y-Ba-Cu-O ceramics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Safari, A.; Wachtman, J.B. Jr.; Ward, C.

    Processing of the YBa{sub 2}Cu{sub 3}O{sub 6+x} superconducting phase by employing different precursor powder preparation techniques (ball milling, attrition milling) and samples formed by different sintering conditions are discussed. The superconducting phase has been identified by powder x-ray diffraction. The effect of different powder processing and pressing conditions on the structure, density, resistivity and a.c. magnetic susceptibility were studied. Though there is no variation in T{sub c} for all the samples, attrition milled samples show a much lower resistance and less temperature dependence compared to ball milled samples above the superconducting transition temperature up to room temperature. Ball milled samplesmore » were loosely packed with more voids compared to attrition milled samples which are more densely packed with a needle-like structure.« less

  5. Friction Durability of Extremely Thin Diamond-Like Carbon Films at High Temperature

    PubMed Central

    Miyake, Shojiro; Suzuki, Shota; Miyake, Masatoshi

    2017-01-01

    To clarify the friction durability, both during and after the high-temperature heating of nanometer-thick diamond-like carbon (DLC) films, deposited using filtered cathodic vacuum arc (FCVA) and plasma chemical vapor deposition (P-CVD) methods, the dependence of the friction coefficient on the load and sliding cycles of the DLC films, were evaluated. Cluster-I consisted of a low friction area in which the DLC film was effective, while cluster-II consisted of a high friction area in which the lubricating effect of the DLC film was lost. The friction durability of the films was evaluated by statistical cluster analysis. Extremely thin FCVA-DLC films exhibited an excellent wear resistance at room temperature, but their friction durability was decreased at high temperatures. In contrast, the durability of the P-CVD-DLC films was increased at high temperatures when compared with that observed at room temperature. This inverse dependence on temperature corresponded to the nano-friction results obtained by atomic force microscopy. The decrease in the friction durability of the FCVA-DLC films at high temperatures, was caused by a complex effect of temperature and friction. The tribochemical reaction produced by the P-CVD-DLC films reduced their friction coefficient, increasing their durability at high temperatures. PMID:28772520

  6. Friction Durability of Extremely Thin Diamond-Like Carbon Films at High Temperature.

    PubMed

    Miyake, Shojiro; Suzuki, Shota; Miyake, Masatoshi

    2017-02-10

    To clarify the friction durability, both during and after the high-temperature heating of nanometer-thick diamond-like carbon (DLC) films, deposited using filtered cathodic vacuum arc (FCVA) and plasma chemical vapor deposition (P-CVD) methods, the dependence of the friction coefficient on the load and sliding cycles of the DLC films, were evaluated. Cluster-I consisted of a low friction area in which the DLC film was effective, while cluster-II consisted of a high friction area in which the lubricating effect of the DLC film was lost. The friction durability of the films was evaluated by statistical cluster analysis. Extremely thin FCVA-DLC films exhibited an excellent wear resistance at room temperature, but their friction durability was decreased at high temperatures. In contrast, the durability of the P-CVD-DLC films was increased at high temperatures when compared with that observed at room temperature. This inverse dependence on temperature corresponded to the nano-friction results obtained by atomic force microscopy. The decrease in the friction durability of the FCVA-DLC films at high temperatures, was caused by a complex effect of temperature and friction. The tribochemical reaction produced by the P-CVD-DLC films reduced their friction coefficient, increasing their durability at high temperatures.

  7. Observation of dx2-y-Like Superconducting Gap in an Electron-Doped High-Temperature Superconductor

    NASA Astrophysics Data System (ADS)

    Sato, T.; Kamiyama, T.; Takahashi, T.; Kurahashi, K.; Yamada, K.

    2001-02-01

    High-resolution angle-resolved photoemission spectroscopy of the electron-doped high-temperature superconductor Nd2-xCexCuO4 (x = 0.15, transition temperature Tc = 22 K) has found the quasiparticle signature as well as the anisotropic dx2-y-like superconducting gap. The spectral line shape at the superconducting state shows a strong anisotropic nature of the many-body interaction. The result suggests that the electron-hole symmetry is present in the high-temperature superconductors.

  8. Enhancement of the finite-frequency superfluid response in the pseudogap regime of strongly disordered superconducting films

    PubMed Central

    Mondal, Mintu; Kamlapure, Anand; Ganguli, Somesh Chandra; Jesudasan, John; Bagwe, Vivas; Benfatto, Lara; Raychaudhuri, Pratap

    2013-01-01

    The persistence of a soft gap in the density of states above the superconducting transition temperature Tc, the pseudogap, has long been thought to be a hallmark of unconventional high-temperature superconductors. However, in the last few years this paradigm has been strongly revised by increasing experimental evidence for the emergence of a pseudogap state in strongly-disordered conventional superconductors. Nonetheless, the nature of this state, probed primarily through scanning tunneling spectroscopy (STS) measurements, remains partly elusive. Here we show that the dynamic response above Tc, obtained from the complex ac conductivity, is highly modified in the pseudogap regime of strongly disordered NbN films. Below the pseudogap temperature, T*, the superfluid stiffness acquires a strong frequency dependence associated with a marked slowing down of critical fluctuations. When translated into the length-scale of fluctuations, our results suggest a scenario of thermal phase fluctuations between superconducting domains in a strongly disordered s-wave superconductor. PMID:23446946

  9. Enhancement of the finite-frequency superfluid response in the pseudogap regime of strongly disordered superconducting films.

    PubMed

    Mondal, Mintu; Kamlapure, Anand; Ganguli, Somesh Chandra; Jesudasan, John; Bagwe, Vivas; Benfatto, Lara; Raychaudhuri, Pratap

    2013-01-01

    The persistence of a soft gap in the density of states above the superconducting transition temperature Tc, the pseudogap, has long been thought to be a hallmark of unconventional high-temperature superconductors. However, in the last few years this paradigm has been strongly revised by increasing experimental evidence for the emergence of a pseudogap state in strongly-disordered conventional superconductors. Nonetheless, the nature of this state, probed primarily through scanning tunneling spectroscopy (STS) measurements, remains partly elusive. Here we show that the dynamic response above Tc, obtained from the complex ac conductivity, is highly modified in the pseudogap regime of strongly disordered NbN films. Below the pseudogap temperature, T*, the superfluid stiffness acquires a strong frequency dependence associated with a marked slowing down of critical fluctuations. When translated into the length-scale of fluctuations, our results suggest a scenario of thermal phase fluctuations between superconducting domains in a strongly disordered s-wave superconductor.

  10. Room temperature deposition of superconducting NbN for superconductor-insulator-superconductor junctions

    NASA Technical Reports Server (NTRS)

    Thakoor, S.; Leduc, H. G.; Thakoor, A. P.; Lambe, J.; Khanna, S. K.

    1986-01-01

    The deposition of stoichiometric B1-crystal-structure (111) NbN films on glass or sapphire substrates by reactive dc magnetron sputtering is reported. High-purity Ar-N2 mixtures are used in the apparatus described by Thakoor et al. (1985), and typical deposition parameters are given as background pressure about 10 ntorr, voltage -325 V, current 1 A, deposition rate 1.35 nm/s, film thickness 500 nm, P(Ar) 5-17 mtorr, initial P(N2) 2-6 mtorr, and room temperature. The N2 consumption-injection characteristics are studied and found to control NbN formation using well-conditioned Nb targets. Films with transition temperatures 15-16 K are obtained at P(Ar) = 12.9 + or - 0.2 mtorr and P(N2) = 3.7 + or - 0.1 mtorr. SIS junctions of area about 0.001 sq cm fabricated using the NbN films are shown to have I-V characteristics with nonlinearity parameter about 110 and NbN superconducting-gap parameter Delta = about 2.8 meV.

  11. Progress on applications of high temperature superconducting microwave filters

    NASA Astrophysics Data System (ADS)

    Chunguang, Li; Xu, Wang; Jia, Wang; Liang, Sun; Yusheng, He

    2017-07-01

    In the past two decades, various kinds of high performance high temperature superconducting (HTS) filters have been constructed and the HTS filters and their front-end subsystems have been successfully applied in many fields. The HTS filters with small insertion loss, narrow bandwidth, flat in-band group delay, deep out-of-band rejection, and steep skirt slope are reviewed. Novel HTS filter design technologies, including those in high power handling filters, multiband filters and frequency tunable filters, are reviewed, as well as the all-HTS integrated front-end receivers. The successful applications to various civilian fields, such as mobile communication, radar, deep space detection, and satellite technology, are also reviewed.

  12. Evaluation of high temperature superconductive thermal bridges for space borne cryogenic detectors

    NASA Technical Reports Server (NTRS)

    Scott, Elaine P.

    1996-01-01

    Infrared sensor satellites are used to monitor the conditions in the earth's upper atmosphere. In these systems, the electronic links connecting the cryogenically cooled infrared detectors to the significantly warmer amplification electronics act as thermal bridges and, consequently, the mission lifetimes of the satellites are limited due to cryogenic evaporation. High-temperature superconductor (HTS) materials have been proposed by researchers at the National Aeronautics and Space Administration Langley's Research Center (NASA-LaRC) as an alternative to the currently used manganin wires for electrical connection. The potential for using HTS films as thermal bridges has provided the motivation for the design and the analysis of a spaceflight experiment to evaluate the performance of this superconductive technology in the space environment. The initial efforts were focused on the preliminary design of the experimental system which allows for the quantitative comparison of superconductive leads with manganin leads, and on the thermal conduction modeling of the proposed system. Most of the HTS materials were indicated to be potential replacements for the manganin wires. In the continuation of this multi-year research, the objectives of this study were to evaluate the sources of heat transfer on the thermal bridges that have been neglected in the preliminary conductive model and then to develop a methodology for the estimation of the thermal conductivities of the HTS thermal bridges in space. The Joule heating created by the electrical current through the manganin wires was incorporated as a volumetric heat source into the manganin conductive model. The radiative heat source on the HTS thermal bridges was determined by performing a separate radiant interchange analysis within a high-T(sub c) superconductor housing area. Both heat sources indicated no significant contribution on the cryogenic heat load, which validates the results obtained in the preliminary conduction

  13. Laser ablated high T(sub c) superconducting thin YBa2Cu3O(7-x) films on substrates suitable for microwave applications

    NASA Astrophysics Data System (ADS)

    Warner, J. D.; Meola, J. E.; Jenkins, K. A.; Bhasin, K. B.

    1990-04-01

    The development of high temperature superconducting YBa2Cu3O(7-x) thin films on substrates suitable for microwave applications is of great interest for evaluating their applications for space radar, communication, and sensor systems. Thin films of YBa2Cu3O(7-x) were formed on SrTiO3, ZrO2, MgO, and LaAlO3 substrates by laser ablation. The wavelength used was 248 nm from a KrF excimer laser. During deposition the films were heated to 600 C in a flowing oxygen environment, and required no post annealing. The low substrate temperature during deposition with no post annealing gave films which were smooth, which had their c-axis aligned to the substrates, and which had grains ranging from 0.2 to 0.5 microns in size. The films being c-axis aligned gave excellent surface resistance at 35 GHz which was lower than that of copper at 77 K. At present, LaAlO3 substrates with a dielectric constant of 22, appears suitable as a substrate for microwave and electronic applications. The films were characterized by resistance-temperature measurements, scanning electron microscopy, and x ray diffraction. The highest critical transition temperatures (T sub c) are above 89 K for films on SrTiO3 and LaAlO3, above 88 K for ZrO2, and above 86 K for MgO. The critical current density (J sub c) of the films on SrTiO3 is above 2 x 10(exp 6) amperes/sq cm at 77 K. The T(sub c) and J(sub c) are reported as a function of laser power, composition of the substrate, and temperature of the substrate during deposition.

  14. Passive microwave device applications of high T(c) superconducting thin films

    NASA Astrophysics Data System (ADS)

    Lyons, W. G.; Withers, R. S.

    1990-11-01

    Superconductors with a transition temperature T(c) from 40 K to 125 K are analyzed, with focus placed on their behavior around the boiling point of liquid nitrogen (77 K). It is shown that high-T(c) superconductors are similar to conventional type-II superconductors with paired holes instead of paired electrons. The nature of the electromagnetic response of a superconductor is illustrated with a two-fluid model, and surface resistance and conductor loss are assessed. Several microwave applications of high-T(c) superconductors are outlined including a six-pole dielectric loaded cavity filter used in multiplexers on current communication satellites and a four-pole superconducting filter. An implementation of a chirp filter using superconducting striplines with a cascaded array of backward-wave couplers to achieve a downchirp is presented as well as a 60-GHz phased antenna utilizing microstrip lines in the feed network.

  15. Percolating transport in superconducting nanoparticle films

    NASA Astrophysics Data System (ADS)

    Fostner, Shawn; Nande, Amol; Smith, Alex; Martinez Gazoni, Rodrigo; Grigg, Jack; Temst, Kristiaan; Van Bael, Margriet J.; Brown, Simon A.

    2017-12-01

    Nanostructured and disordered superconductors exhibit many exotic fundamental phenomena, and also have many possible applications. We show here that films of superconducting lead nanoparticles with a wide range of particle coverages, exhibit non-linear V(I) characteristics that are consistent with percolation theory. Specifically, it is found that V ∝(I-Ic) a , where a = 2.1 ± 0.2, independent of both temperature and particle coverage, and that the measured critical currents (Ic) are also consistent with percolation models. For samples with low normal state resistances, this behaviour is observable only in pulsed current measurements, which suppress heating effects. We show that the present results are not explained by vortex unbinding [Berezinskii-Kosterlitz-Thouless] physics, which is expected in such samples, but which gives rise to a different power law behaviour. Finally, we compare our results to previous calculations and simulations, and conclude that further theoretical developments are required to explain the high level of consistency in the measured exponents a.

  16. Evaluation of a Three-Channel High-Temperature Superconducting Magnetometer System

    DTIC Science & Technology

    1997-06-01

    achieved by the best commercially available fluxgate magnetometers demonstrated to date and is only surpassed by low temperature superconducting...wire lines carry the analog SQUID magnetometer signal as well as dc power and ground, and the fiberoptic lines carry digital clock and data signals...with the magnetometers mounted on the three-sensor probe used in the sensor evaluated here. This probe is not highly stabilized with respect to the

  17. High temperature superconducting Maglev equipment on vehicle

    NASA Astrophysics Data System (ADS)

    Wang, S. Y.; Wang, J. S.; Ren, Z. Y.; Zhu, M.; Jiang, H.; Wang, X. R.; Shen, X. M.; Song, H. H.

    2003-04-01

    Onboard high temperature superconducting (HTS) Maglev equipment is a heart part of a HTS Maglev vehicle, which is composed of YBaCuO bulks and rectangle-shape liquid nitrogen vessel and used successfully in the first manned HTS Maglev test vehicle. Arrangement of YBaCuO bulks in liquid nitrogen vessel, structure of the vessel, levitation forces of a single vessel and two vessels, and total levitation force are reported. The first manned HTS Maglev test vehicle in the world has operated well more than one year after it was born on Dec. 31, 2000, and more than 23,000 passengers have taken the vehicle till now. Well operation of more than one year proves the reliability of the onboard HTS Maglev equipment.

  18. Superconducting Ti/TiN Thin Films for mm-Wave Absorption

    NASA Astrophysics Data System (ADS)

    Aliane, A.; Solana, M.; Rabaud, W.; Saminadayar, L.; Agnese, P.; Goudon, V.; Dussopt, L.; Vialle, C.; Baghe, E.; Pocas, S.; Carle, L.; Lio Soon Shun, N.; Becker, S.; Reveret, V.; Rodriguez, L.; Hamelin, A.; Poglitsch, A.; Bounissou, S.; Adami, O.

    2018-04-01

    Polarization-sensitive detectors at 120-500 GHz are required for the observation of the cosmic microwave background radiation. In this paper, superconducting thin films based on Ti/TiN bilayers are developed to be integrated as electromagnetic wave absorbers in suspended cooled silicon bolometers. The critical temperature (T c) is tuned in the range of 600-800 mK through the superconductivity proximity effect between Ti and TiN to optimize the absorption of the incident power while minimizing the heat capacity of the system at low temperature. Ti/TiN bilayer samples are fabricated on silicon with two different thicknesses (100/5 and 300/5 nm). Electrical characterizations at low temperature have been performed and revealed the effect of thermal annealing (20-250 °C) on residual stress, T c, critical magnetic field (H c) and resistance above T c. A physical characterization by X-ray photoelectron spectroscopy provides evidences of oxidized states which may explain these effects.

  19. A novel high temperature superconducting magnetic flux pump for MRI magnets

    NASA Astrophysics Data System (ADS)

    Bai, Zhiming; Yan, Guo; Wu, Chunli; Ding, Shufang; Chen, Chuan

    2010-10-01

    This paper presents a kind of minitype magnetic flux pump made of high temperature superconductor. This kind of novel high temperature superconducting (HTS) flux pump has not any mechanical revolving parts or thermal switches. The excitation current of copper coils in magnetic pole system is controlled by a singlechip. The structure design and operational principle have been described. The operating performance of the new model magnetic flux pump has been preliminarily tested. The experiments show that the maximum pumping current is approximately 200 A for Bi2223 flux pump and 80 A for MgB 2 flux pump operating at 20 K. By comparison, it is discovered that the operating temperature range is wider, the ripple is smaller and the pumping frequency is higher in Bi2223 flux pump than those in MgB 2 flux pump. These results indicate that the newly developed Bi2223 magnetic flux pump may efficiently compensate the magnetic field decay in HTS magnet and make the magnet operate in persistent current mode, this point is significant to the magnetic resonance imaging (MRI) magnets. This new flux pump is under construction presently. It is expected that the Bi2223 flux pump would be applied to the superconducting MRI magnets by further optimizing structure and improving working process.

  20. An experimental study of high Tc superconducting microstrip transmission lines at 35 GHz and the effect of film morphology

    NASA Technical Reports Server (NTRS)

    Chorey, C. M.; Bhasin, K. B.; Warner, J. D.; Josefowicz, J. Y.; Rensch, D. B.

    1991-01-01

    Microstrip transmission lines in the form of ring resonators were fabricated from a number of in-situ grown laser ablated films and post-annealed co-sputtered YBa2Cu3O(7-x) films. The properties of these resonators were measured at 35 GHz and the observed performance is examined in light of the critical temperature (Tc) and film thickness, and also the film morphology, which is different for the two deposition techniques. It is found that Tc is a major indicator of the film performance for each growth type, with film thickness becoming important as it decreases towards 1000 A. It is also found that the films with a mixed grain orientation (both a-axis and c-axis oriented grains) have poorer microwave properties as compared with the primarily c-axis oriented material. This is probably due to the significant number of grain boundaries between the different crystallites, which may act as superconducting weak links and contribute to the surface resistance.

  1. An experimental study of high Tc superconducting microstrip transmission lines at 35 GHz and the effect of film morphology

    NASA Technical Reports Server (NTRS)

    Chorey, C. M.; Bhasin, K. B.; Warner, J. D.; Josefowicz, J. Y.; Rensch, D. B.; Nieh, C. W.

    1990-01-01

    Microstrip transmission lines in the form of ring resonators were fabricated from a number of in-situ grown laser ablated films and post-annealed co-sputtered YBa2Cu3O(7-x) films. The properties of these resonators were measured at 35 GHz and the observed performance is examined in light of the critical temperature (Tc) and film thickness and also the film morphology which is different for the two deposition techniques. It is found that Tc is a major indicator of the film performance for each growth type with film thickness becoming important as it decreases towards 100 A. It is also found that the films with a mixed grain orientation (both a axis and c axis oriented grains) have poorer microwave properties as compared with the primarily c axis oriented material. This is probably due to the significant number of grain boundaries between the different crystallites, which may act as superconducting weak links and contribute to the surface resistance.

  2. Superconductivity above 100 K in Bi(Pb)-Ca-Sr-Cu-O films made by thermal decomposition of metal carboxylates

    NASA Astrophysics Data System (ADS)

    Klee, M.; de Vries, J. W. C.; Brand, W.

    1988-11-01

    Superconducting layers in the Bi(Pb)-Ca-Sr-Cu-O system are prepared by thermal decomposition of metal carboxylates. The films are deposited on MgO single crystal and ceramic substrates using a spin-coating and dip-coating process. The Bi-Ca-Sr-Cu-O films consist mainly of the low- Tc phase ( c-axis=3.073 nm), whereas partial substitution of Bi by Pb favours the formation of the high- Tc phase ( c-axis=3.707 nm). Films deposited on MgO (100) are strong c-axis preferentially oriented grown. While the Bi-Ca-Sr-Cu-O films show a step in the resistance versus temperature curve ( Tcf⋍80 K) due to the presence of the low- Tc and the high- Tc phase, the Bi(Pb)-Ca-Sr-Cu-O films have an onset at 110 K and are superconducting at 104 K. The temperature dependence of the critical current indicates that in the Bi-Ca-Sr-Cu-O system weak links of superconductor-isolator-superconductor type are present, while in the Bi(Pb)-Ca-Sr-Cu-O samples the contact is formed by normal-metal barriers. Using magnetic fields up to 5 T, the anisotropy of the resistive transition of the high- Tc phase was studied. In Bi(Pb)-Ca-Sr-Cu-O films the anisotropy ratio is about 18, and the corresponding coherence lengths are ξ ab(0)⋍3.6 nm and ξ c(0)⋍0.2 nm. These values are nearly the same as in the low- Tc phase.

  3. Method of forming superconducting Tl-Ba-Ca-Cu-O films

    DOEpatents

    Wessels, Bruce W.; Marks, Tobin J.; Richeson, Darrin S.; Tonge, Lauren M.; Zhang, Jiming

    1993-01-01

    A method of forming a superconducting Tl-Ba-Ca-Cu-O film is disclosed, which comprises depositing a Ba-Ca-Cu-O film on a substrate by MOCVD, annealing the deposited film and heat-treating the annealed film in a closed circular vessel with TlBa.sub.2 Ca.sub.2 Cu.sub.3 O.sub.x and cooling to form said superconducting film of TlO.sub.m Ba.sub.2 Ca.sub.n-1 Cu.sub.n O.sub.2n+2, wherein m=1,2 and n=1,2,3.

  4. Thin Film Approaches to the SRF Cavity Problem: Fabrication and Characterization of Superconducting Thin Films

    NASA Astrophysics Data System (ADS)

    Beringer, Douglas B.

    Superconducting Radio Frequency (SRF) cavities are responsible for the acceleration of charged particles to relativistic velocities in most modern linear accelerators, such as those employed at high-energy research facilities like Thomas Jefferson National Laboratory's CEBAF and the LHC at CERN. Recognizing SRF as primarily a surface phenomenon enables the possibility of applying thin films to the interior surface of SRF cavities, opening a formidable tool chest of opportunities by combining and designing materials that offer greater benefit. Thus, while improvements in radio frequency cavity design and refinements in cavity processing techniques have improved accelerator performance and efficiency - 1.5 GHz bulk niobium SRF cavities have achieved accelerating gradients in excess of 35 MV/m - there exist fundamental material bounds in bulk superconductors limiting the maximally sustained accelerating field gradient (approximately 45 MV/m for Niobium) where inevitable thermodynamic breakdown occurs. With state of the art niobium based cavity design fast approaching these theoretical limits, novel material innovations must be sought in order to realize next generation SRF cavities. One proposed method to improve SRF performance is to utilize thin film superconducting-insulating-superconducting (SIS) multilayer structures to effectively magnetically screen a bulk superconducting layer such that it can operate at higher field gradients before suffering critically detrimental SRF losses. This dissertation focuses on the production and characterization of thin film superconductors for such SIS layers for radio-frequency applications.

  5. Coexistence of Topological Edge State and Superconductivity in Bismuth Ultrathin Film.

    PubMed

    Sun, Hao-Hua; Wang, Mei-Xiao; Zhu, Fengfeng; Wang, Guan-Yong; Ma, Hai-Yang; Xu, Zhu-An; Liao, Qing; Lu, Yunhao; Gao, Chun-Lei; Li, Yao-Yi; Liu, Canhua; Qian, Dong; Guan, Dandan; Jia, Jin-Feng

    2017-05-10

    Ultrathin freestanding bismuth film is theoretically predicted to be one kind of two-dimensional topological insulators. Experimentally, the topological nature of bismuth strongly depends on the situations of the Bi films. Film thickness and interaction with the substrate often change the topological properties of Bi films. Using angle-resolved photoemission spectroscopy, scanning tunneling microscopy or spectroscopy and first-principle calculation, the properties of Bi(111) ultrathin film grown on the NbSe 2 superconducting substrate have been studied. We find the band structures of the ultrathin film is quasi-freestanding, and one-dimensional edge state exists on Bi(111) film as thin as three bilayers. Superconductivity is also detected on different layers of the film and the pairing potential exhibits an exponential decay with the layer thicknesses. Thus, the topological edge state can coexist with superconductivity, which makes the system a promising platform for exploring Majorana Fermions.

  6. High quality uniform YBCO film growth by the metalorganic deposition using trifluoroacetates

    NASA Astrophysics Data System (ADS)

    Wang, S. S.; Zhang, Z. L.; Wang, L.; Gao, L. K.; Liu, J.

    2017-03-01

    A need exists for the large-area superconducting YBa2Cu3O7-x (YBCO) films with high critical current density for microwave communication and/or electric power applications. Trifluoroacetic metalorganic (TFA-MOD) method is a promising low cost technique for large-scale production of YBCO films, because it does not need high vacuum device and is easily applicable to substrates of various shape and size. In this paper, double-sided YBCO films with maximum 2 in diameter were prepared on LaAlO3 substrates by TFA-MOD method. Inductive critical current densitiy Jc, microwave surface resistance Rs, as well as the microstructure were characterized. A newly homemade furnace system was used to epitaxially grown YBCO films, which can improve the uniformity of YBCO film significantly by gas supply and temperature distribution proper design. Results showed that the large area YBCO films were very uniform in microstructure and thickness distribution, an average inductive Jc in excess of 6 MA/cm2 with uniform distribution, and low Rs (10 GHz) below 0.3 mΩ at 77 K were obtained. Andthe film filter may be prepared to work at temperatures lower than 74 K. These results are very close to the highest value of YBCO films made by conventional vacuum method, so we show a very promising route for large-scale production of high quality large-area YBCO superconducting films at a lower cost.

  7. Quantum and superconducting fluctuations effects in disordered Nb 1- xTa x thin films above Tc

    NASA Astrophysics Data System (ADS)

    Giannouri, M.; Papastaikoudis, C.

    1999-05-01

    Disordered Nb 1- xTa x thin films are prepared with e-gun coevaporation. The influence of the β-phase of tantalum in the critical temperature Tc is observed as a function of the substrate temperature. The measurements of transverse magnetoresistance at various isothermals are interpreted in terms of weak-localization and superconducting fluctuations. From the fitting procedure, the phase breaking rate τφ-1 and the Larkin parameter βL are estimated as a function of temperature. Conclusions about the dominant inelastic scattering mechanisms at various temperature regions as well as for the dominant mechanism of superconducting fluctuations near the transition temperature are extracted.

  8. High-temperature superconductivity using a model of hydrogen bonds.

    PubMed

    Kaplan, Daniel; Imry, Yoseph

    2018-05-29

    Recently, there has been much interest in high-temperature superconductors and more recently in hydrogen-based superconductors. This work offers a simple model that explains the behavior of the superconducting gap based on naive BCS (Bardeen-Cooper-Schrieffer) theory and reproduces most effects seen in experiments, including the isotope effect and [Formula: see text] enhancement as a function of pressure. We show that this is due to a combination of the factors appearing in the gap equation: the matrix element between the proton states and the level splitting of the proton.

  9. Superconductivity in films of Pb/PbSe core/shell nanocrystals.

    PubMed

    Zolotavin, Pavlo; Guyot-Sionnest, Philippe

    2012-09-25

    Superconductivity in films of electronically coupled colloidal lead nanocrystals is reported. The coupling between particles is in situ controlled through the conversion of the oxides present on the surface of the nanoparticles to chalcogenides. This transformation allows for a 10(9)-fold increase in the conductivity. The temperature of the onset of the superconductivity was found to depend upon the degree of coupling of the nanoparticles in the vicinity of the insulator-superconductor transition. The critical current density of the best sample of Pb/PbSe nanocrystals at zero magnetic field was determined to be 4 × 10(3) A/cm(2). In turn, the critical field of the sample shows 50-fold enhancement compared to bulk Pb.

  10. High Temperature Superconducting Compounds

    DTIC Science & Technology

    1992-11-30

    broadened interest in superconductivity in both the engineering and scientific communities. Superconducting materials may be offered as a solution to a...YBa2Cu307- has been made. For yttrium, the tris( isopropoxide ) was used exclusively, while the use of both Ba(O-i-Pr)2 and Ba(OCH2Ch2OEt)2 (prepared in... solutions of Cu(acac)2, Ba(OCH2CH 2OEt)2 , and Y(O-i-Pr)3 were spin coated on SrTiO 3 (100) and fired under oxygen to give oriented (b axis normal to the

  11. Microwave Hybrid Integrated Circuit Applicatins of High Transition Temperature Superconductor

    NASA Astrophysics Data System (ADS)

    Lu, Shih-Lin

    This research work involves microwave characterization of high Tc superconducting (HTS) thin film using microstrip ring resonators, studying the nonlinear properties of HTS thin film transmission lines using two-tone intermodulation technique, coupling mechanisms and coupling factors of microstrip ring resonators side coupled to a microstrip line, two-port S-parameters measurements of GaAs MESFET at low temperature, and the design and implementation of hybrid ring resonator stabilized microwave oscillator using both metal films and superconducting films. A microstrip ring resonators operating at 10 GHz have been fabricated from YBCO HTS thin films deposited on one side of LaAl_2O_3 substrates. Below 60^circ Kelvin the measured unloaded Q of the HTS thin film microstrip ring resonators are more than 1.5 times that of gold film resonators. The two distinct but very close resonance peaks of a ring resonator side coupled to a microstrip line are experimentally identified as due to odd-mode and even-mode coupling. These two mechanisms have different characteristic equivalent circuit models and lead to different coupling coefficients and loaded resonance frequencies. The coupling factors for the two coupling modes are calculated using piecewise coupled line approximations. The two-port S-parameters measurement techniques and GaAs MESFET low temperature DC and microwave characteristics have been investigated. A system errors model including the errors caused by the line constriction at low temperature has been proposed and a temperature errors correction procedure has been developed for the two-port microwave S-parameters measurements at low temperature. The measured GaAs MESFET DC characteristics shows a 20% increase in transconductance at 77^circ K. There is also a 2 db increase in /S21/ at 77^circ K. The microwave oscillator stabilized with both metal and HTS thin film ring resonators have been studied. The tuning ability of the oscillator by a varactor diode has also

  12. Superconductivity in CVD diamond films.

    PubMed

    Takano, Yoshihiko

    2009-06-24

    A beautiful jewel of diamond is insulator. However, boron doping can induce semiconductive, metallic and superconducting properties in diamond. When the boron concentration is tuned over 3 × 10(20) cm(-3), diamonds enter the metallic region and show superconductivity at low temperatures. The metal-insulator transition and superconductivity are analyzed using ARPES, XAS, NMR, IXS, transport and magnetic measurements and so on. This review elucidates the physical properties and mechanism of diamond superconductor as a special superconductivity that occurs in semiconductors.

  13. Localized superconductivity in the quantum-critical region of the disorder-driven superconductor-insulator transition in TiN thin films.

    PubMed

    Baturina, T I; Mironov, A Yu; Vinokur, V M; Baklanov, M R; Strunk, C

    2007-12-21

    We investigate low-temperature transport properties of thin TiN superconducting films in the vicinity of the disorder-driven superconductor-insulator transition. In a zero magnetic field, we find an extremely sharp separation between superconducting and insulating phases, evidencing a direct superconductor-insulator transition without an intermediate metallic phase. At moderate temperatures, in the insulating films we reveal thermally activated conductivity with the magnetic field-dependent activation energy. At very low temperatures, we observe a zero-conductivity state, which is destroyed at some depinning threshold voltage V{T}. These findings indicate the formation of a distinct collective state of the localized Cooper pairs in the critical region at both sides of the transition.

  14. An experimental investigation of high temperature superconducting microstrip antennas at K- and Ka-band frequencies. Ph.D. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Richard, Mark A.

    1993-01-01

    The recent discovery of high temperature superconductors (HTS) has generated a substantial amount of interest in microstrip antenna applications. However, the high permittivity of substrates compatible with HTS results in narrow bandwidths and high patch edge impedances of such antennas. To investigate the performance of superconducting microstrip antennas, three antenna architectures at K and Ka-band frequencies are examined. Superconducting microstrip antennas that are directly coupled, gap coupled, and electromagnetically coupled to a microstrip transmission line were designed and fabricated on lanthanum aluminate substrates using YBa2Cu3O7 superconducting thin films. For each architecture, a single patch antenna and a four element array were fabricated. Measurements from these antennas, including input impedance, bandwidth, patterns, efficiency, and gain are presented. The measured results show usable antennas can be constructed using any of the architectures. All architectures show excellent gain characteristics, with less than 2 dB of total loss in the four element arrays. Although the direct and gap coupled antennas are the simplest antennas to design and fabricate, they suffer from narrow bandwidths. The electromagnetically coupled antenna, on the other hand, allows the flexibility of using a low permittivity substrate for the patch radiator, while using HTS for the feed network, thus increasing the bandwidth while effectively utilizing the low loss properties of HTS. Each antenna investigated in this research is the first of its kind reported.

  15. An electron tunneling study of superconductivity in amorphous Sn(sub 1-x)Cu(sub x) thin films

    NASA Technical Reports Server (NTRS)

    Naugle, D. G.; Watson, P. W., III; Rathnayaka, K. D. D.

    1995-01-01

    The amorphous phase of Sn would have a superconducting transition temperature near 8 K, much higher than that of crystalline Sn with T(sub c) = 3.5 K. To obtain the amorphous phase, however, it is necessary to use a Sn alloy, usually Cu, and quench condense the alloy films onto a liquid He temperature substrate. Alloying with Cu reduces the superconducting transition temperature almost linearly with Cu concentration with an extrapolation of T(sub c) to zero for x = 0.85. Analysis of the tunneling characteristics between a normal metal electrode with an insulating barrier and superconducting amorphous Sn-Cu films provides detailed information on the changes in the electron-phonon coupling which determines T(sub c) in these alloys. The change from very strong electron-phonon coupling to weak-coupling with the increase in Cu content of amorphous Sn-Cu alloys for the range 0.08 is less than or equal to x is less than or equal to 0.41 is presented and discussed in terms of theories of electron-phonon coupling in disordered metals.

  16. Formation of the 110-K superconducting phase in Pb-doped Bi-Sr-Ca-Cu-O thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kula, W.; Sobolewski, R.; Gorecka, J.

    1991-09-15

    Investigation of the 110-K Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub {ital x}} phase formation in superconducting thin films of Bi-based cuprates is reported. The films were dc magnetron sputtered from single Bi(Pb)-Sr-Ca-Cu-O targets of various stoichiometries, and subsequently annealed in air at high temperatures. The influence of the initial Pb content, annealing conditions, as well as the substrate material on the growth of the 110-K phase was investigated. We found that the films, fully superconducting above 100 K could be reproducibly fabricated on various dielectric substrates from Pb-rich targets by optimizing annealing conditions for each initial Pb/Bi ratio. Heavy Pb dopingmore » considerably accelerated formation of the 110-K phase, reducing the film annealing time to less than 1 h. Films containing, according to the x-ray measurement, more than 90% of the 110-K phase were obtained on MgO substrates, after sputtering from the Bi{sub 2}Pb{sub 2.5}Sr{sub 2}Ca{sub 2.15}Cu{sub 3.3}O{sub {ital x}} target and annealing in air for 1 h at 870 {degree}C. The films were {ital c}-axis oriented, with 4.5-K-wide superconducting transition, and zero resistivity at 106 K. Their critical current density was 2 {times} 10{sup 2} A/cm{sup 2} at 90 K, and above 10{sup 4} A/cm{sup 2} below 60 K. The growth of the 110-K phase on epitaxial substrates, such as CaNdAlO{sub 4} and SrTiO{sub 3}, was considerably deteriorated, and the presence of the 80- and 10-K phases was detected. Nevertheless, the best films deposited on these substrates were fully superconducting at 104 K and exhibited critical current densities above 2 {times} 10{sup 5} A/cm{sup 2} below 60 K{minus}one order of magnitude greater than the films deposited on MgO.« less

  17. Superconducting properties of Pb82Bi18 films controlled by ferromagnetic nanowire arrays

    NASA Astrophysics Data System (ADS)

    Ye, Zuxin; Lyuksyutov, Igor F.; Wu, Wenhao; Naugle, Donald G.

    2011-02-01

    The superconducting properties of Pb82Bi18 alloy films deposited on ferromagnetic nanowire arrays have been investigated. Ferromagnetic Co or Ni nanowires are first electroplated into the columnar pores of anodic aluminum oxide (AAO) membranes. Superconducting Pb82Bi18 films are then quench condensed onto the polished surface of the AAO membranes filled with magnetic nanowires. A strong dependence of the Pb82Bi18 superconducting properties on the ratio of the superconducting film thickness to the magnetic nanowire diameter and material variety was observed.

  18. Flexible Microstrip Circuits for Superconducting Electronics

    NASA Technical Reports Server (NTRS)

    Chervenak, James; Mateo, Jennette

    2013-01-01

    Flexible circuits with superconducting wiring atop polyimide thin films are being studied to connect large numbers of wires between stages in cryogenic apparatus with low heat load. The feasibility of a full microstrip process, consisting of two layers of superconducting material separated by a thin dielectric layer on 5 mil (approximately 0.13 mm) Kapton sheets, where manageable residual stress remains in the polyimide film after processing, has been demonstrated. The goal is a 2-mil (approximately 0.051-mm) process using spin-on polyimide to take advantage of the smoother polyimide surface for achieving highquality metal films. Integration of microstrip wiring with this polyimide film may require high-temperature bakes to relax the stress in the polyimide film between metallization steps.

  19. Effects of high temperature and film thicknesses on the texture evolution in Ag thin films

    NASA Astrophysics Data System (ADS)

    Eshaghi, F.; Zolanvari, A.

    2017-04-01

    In situ high-temperature X-ray diffraction techniques were used to study the effect of high temperatures (up to 600°C) on the texture evolution in silver thin films. Ag thin films with different thicknesses of 40, 80, 120 and 160nm were sputtered on the Si(100) substrates at room temperature. Then, microstructure of thin films was determined using X-ray diffraction. To investigate the influence of temperature on the texture development in the Ag thin films with different thicknesses, (111), (200) and (220) pole figures were evaluated and orientation distribution functions were calculated. Minimizing the total energy of the system which is affected by competition between surface and elastic strain energy was a key factor in the as-deposited and post annealed thin films. Since sputtering depositions was performed at room temperature and at the same thermodynamic conditions, the competition growth caused the formation of the {122} < uvw \\rangle weak fiber texture in as-deposited Ag thin films. It was significantly observed that the post annealed Ag thin films showed {111} < uvw \\rangle orientations as their preferred orientations, but their preferred fiber texture varied with the thickness of thin films. Increasing thin film thickness from 40nm to 160nm led to decreasing the intensity of the {111} < uvw \\rangle fiber texture.

  20. Investigation of the superconducting proximity effect (SPE) and magnetic dead layers (MDL) in thin film double layers

    NASA Astrophysics Data System (ADS)

    Tateishi, Go

    When a thin superconducting film (S film) is condensed onto a thin normal conducting film (N film), the first layers of the S film loose their superconductivity. This phenomenon is generally called the "superconducting proximity effect (SPE)". As an investigation of SPE we focus on the transition temperature of extremely thin NS double layers in the thin regime. Normal metal is condensed on top of insulating Sb, then Pb is deposited on it in small steps. The transition temperature is plotted in an inverse Tc-reduction 1/Delta T c =1/(Ts - Tc) versus Pb thickness graph. To compare our experimental results with the theoretical prediction, a numerical calculation of the SN double layer is performed by our group using the linear gap equation. As a result, there are large discrepancies between the experimental and theoretical results generally. The results of the NS double layers can be divided into three groups in terms of their discrepancies between experiment and theory.(1) Non-coupling (Tc = 0 K): N= Mg, Ag, Cu, Au. There are large deviations between experiment and theory by a factor to the order of 2.5. (2) Weak coupling (Tc is low (< 2.5 K)) : N=Cd, Zn, Al. Deviation is present, but only by a factor of 1.5. (3) Intermediate coupling (T c is around half of Pb's (≈ 4.5 K)) : N=In, Sn. The experimental results agree with the theory. Next, we examine the detection of the magnetic dead layer (MDL) of Ni thin films in terms of the anomalous Hall effect (AHE) with several non-magnetic metal substrates. In our results, when Ni film is contact with a polyvalent metal substrate film, the sandwich film has around 2 to 3.5 at.lay. of magnetic dead layers. However we have not observed the magnetic dead Ni layers with the alkali and noble metal substrate film. Finally, we revisit the Pb/Ni system to measure the magnetic scattering of Ni with the method of Weak Localization (WL) to compare with the dephasing rate due to the Tc-reduction. In this series, we use only very thin

  1. Aerospace Applications Of High Temperature Superconductivity

    NASA Astrophysics Data System (ADS)

    Anderson, W. W.

    1988-05-01

    The existence of superconductors with TcOOK (which implies device operating temper-atures the order of Top ≍45K) opens up a variety of potential applications within the aerospace/defense industry. This is partly due to the existence of well developed cooler technologies to reach this temperature regime and partly due to the present operation of some specialized components at cryogenic temperatures. In particular, LWIR focal planes may operate at 10K with some of the signal processing electronics at an intermediate temperature of 40K. Addition of high Tc superconducting components in the latter system may be "free" in the sense of additional system complexity required. The established techniques for cooling in the 20K to 50K temperature regime are either open cycle, expendable material (stored gas with Joule-Thomson expansion, liquid cryogen or solid cryogen) or mechanical refrigerators (Stirling cycle, Brayton cycle or closed cycle Joule-Thomson). The high Tc materials may also contribute to the development of coolers through magnetically levitated bearings or providing the field for a stage of magnetic refrigeration. The discovery of materials with Tc, 90K has generated a veritable shopping list of applications. The superconductor properties which are of interest for applications are (1) zero resistance, (2) Meissner effect, (3) phase coherence and (4) existence of an energy gap. The zero resistance property is significant in the development of high field magnets requiring neglible power to maintain the field. In addition to the publicized applications to rail guns and electromagnetic launcher, we can think of space born magnets for charged particle shielding or whistler mode propagation through a plasma sheath. Conductor losses dominate attenuation and dispersion in microstrip transmission lines. While the surface impedance of a superconductor is non vanishing, significant improvements in signal transmission may be obtained. The Meissner effect may be utilized

  2. Conductor requirements for high-temperature superconducting utility power transformers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pleva, E. F.; Mehrotra, V.; Schwenterly, S W

    High-temperature superconducting (HTS) coated conductors in utility power transformers must satisfy a set of operating requirements that are driven by two major considerations-HTS transformers must be economically competitive with conventional units, and the conductor must be robust enough to be used in a commercial manufacturing environment. The transformer design and manufacturing process will be described in order to highlight the various requirements that it imposes on the HTS conductor. Spreadsheet estimates of HTS transformer costs allow estimates of the conductor cost required for an HTS transformer to be competitive with a similarly performing conventional unit.

  3. Method and apparatus for measuring gravitational acceleration utilizing a high temperature superconducting bearing

    DOEpatents

    Hull, John R.

    2000-01-01

    Gravitational acceleration is measured in all spatial dimensions with improved sensitivity by utilizing a high temperature superconducting (HTS) gravimeter. The HTS gravimeter is comprised of a permanent magnet suspended in a spaced relationship from a high temperature superconductor, and a cantilever having a mass at its free end is connected to the permanent magnet at its fixed end. The permanent magnet and superconductor combine to form a bearing platform with extremely low frictional losses, and the rotational displacement of the mass is measured to determine gravitational acceleration. Employing a high temperature superconductor component has the significant advantage of having an operating temperature at or below 77K, whereby cooling may be accomplished with liquid nitrogen.

  4. High-temperature superconductivity for avionic electronic warfare and radar systems

    NASA Astrophysics Data System (ADS)

    Ryan, Paul A.

    1994-01-01

    The electronic warfare (EW) and radar communities expect to be major beneficiaries of the performance advantages high-temperature superconductivity (HTS) has to offer over conventional technology. Near term upgrades to system hardware can be envisioned using extremely small, high Q, microwave filters and resonators; compact, wideband, low loss, microwave delay and transmission lines; as well as, wideband, low loss, monolithic microwave integrated circuit phase shifters. The most dramatic impact will be in the far term, using HTS to develop new, real time threat identification and response strategy receiver/processing systems designed to utilize the unique high frequency properties of microwave and ultimately digital HTS.

  5. Electronic structure and superconductivity of FeSe-related superconductors.

    PubMed

    Liu, Xu; Zhao, Lin; He, Shaolong; He, Junfeng; Liu, Defa; Mou, Daixiang; Shen, Bing; Hu, Yong; Huang, Jianwei; Zhou, X J

    2015-05-13

    FeSe superconductors and their related systems have attracted much attention in the study of iron-based superconductors owing to their simple crystal structure and peculiar electronic and physical properties. The bulk FeSe superconductor has a superconducting transition temperature (Tc) of ~8 K and it can be dramatically enhanced to 37 K at high pressure. On the other hand, its cousin system, FeTe, possesses a unique antiferromagnetic ground state but is non-superconducting. Substitution of Se with Te in the FeSe superconductor results in an enhancement of Tc up to 14.5 K and superconductivity can persist over a large composition range in the Fe(Se,Te) system. Intercalation of the FeSe superconductor leads to the discovery of the AxFe2-ySe2 (A = K, Cs and Tl) system that exhibits a Tc higher than 30 K and a unique electronic structure of the superconducting phase. A recent report of possible high temperature superconductivity in single-layer FeSe/SrTiO3 films with a Tc above 65 K has generated much excitement in the community. This pioneering work opens a door for interface superconductivity to explore for high Tc superconductors. The distinct electronic structure and superconducting gap, layer-dependent behavior and insulator-superconductor transition of the FeSe/SrTiO3 films provide critical information in understanding the superconductivity mechanism of iron-based superconductors. In this paper, we present a brief review of the investigation of the electronic structure and superconductivity of the FeSe superconductor and related systems, with a particular focus on the FeSe films.

  6. High Temperature Superconducting State in Metallic Nanoclusters and Nano-Based Systems

    DTIC Science & Technology

    2013-12-01

    pr.ac Semenova 1a Russia EOARD ISTC 09-7006/P-4084p Report Date: December 2013 Final Report from 01 October 2010 to 30 September 2013...CONTRACT NUMBER ISTC PPA 4084p 5b. GRANT NUMBER ISTC 09-7006 5c. PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S...discussed in the conventional theory. High Temperature Superconducting State in Metallic Nanoclusters and Nano-Based Systems ISTC Project No. 4084p

  7. Superconductivity of a Sn film controlled by an array of Co nanowires

    NASA Astrophysics Data System (ADS)

    Wei, Zhiyuan; Ye, Zuxin; Rathnayaka, Daya; Lyuksyutov, Igor; Wu, Wenhao; Naugle, Donald

    2012-02-01

    Superconducting properties of a hybrid structure composed of ferromagnetic Co nanowire arrays and a superconducting Sn film have been investigated. Ordered Co nanowires arrays with 60 nm, 150 nm and 200 nm diameter were electroplated into the pores of self organized anodic aluminum oxide (AAO) membranes. Hysteretic dependence of the Sn film superconducting properties on applied magnetic field and critical current enhancement at moderate fields has been observed. This behavior strongly depends on the ratio of the Sn film thickness to the Co nanowire diameter.

  8. Superconductivity of a Sn film controlled by an array of Co nanowires

    NASA Astrophysics Data System (ADS)

    Wei, Z.; Ye, Z.; Rathnayaka, K. D. D.; Lyuksyutov, I. F.; Wu, W.; Naugle, D. G.

    2012-09-01

    Superconducting properties of a hybrid structure composed of ferromagnetic Co nanowire arrays and a superconducting Sn film have been investigated. Ordered Co nanowires arrays with 60 nm, 150 nm and 200 nm diameter were electroplated into the pores of self organized Anodic Aluminum Oxide (AAO) membranes. Hysteretic dependence of the Sn film superconducting properties on applied magnetic field and critical current enhancement at moderate fields has been observed. This behavior strongly depends on the ratio of the Sn film thickness to the Co nanowire diameter.

  9. Design of a 100 kVA high temperature superconducting demonstration synchronous generator

    NASA Astrophysics Data System (ADS)

    Al-Mosawi, M. K.; Beduz, C.; Goddard, K.; Sykulski, J. K.; Yang, Y.; Xu, B.; Ship, K. S.; Stoll, R.; Stephen, N. G.

    2002-08-01

    The paper presents the main features of a 100 kVA high temperature superconducting (HTS) demonstrator generator, which is designed and being built at the University of Southampton. The generator is a 2-pole synchronous machine with a conventional 3-phase stator and a HTS rotor operating in the temperature range 57-77 K using either liquid nitrogen down to 65 K or liquid air down to 57 K. Liquid air has not been used before in the refrigeration of HTS devices but has recently been commercialised by BOC as a safe alternative to nitrogen for use in freezing of food. The generator will use an existing stator with a bore of 330 mm. The rotor is designed with a magnetic core (invar) to reduce the magnetising current and the field in the coils. For ease of manufacture, a hybrid salient pole construction is used, and the superconducting winding consists of twelve 50-turn identical flat coils. Magnetic invar rings will be used between adjacent HTS coils of the winding to divert the normal component of the magnetic field away from the Bi2223 superconducting tapes. To avoid excessive eddy-current losses in the rotor pole faces, a cold copper screen will be placed around the rotor core to exclude ac magnetic fields.

  10. Superconducting High Resolution Fast-Neutron Spectrometers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hau, Ionel Dragos

    2006-01-01

    Superconducting high resolution fast-neutron calorimetric spectrometers based on 6LiF and TiB{sub 2} absorbers have been developed. These novel cryogenic spectrometers measure the temperature rise produced in exothermal (n, α) reactions with fast neutrons in 6Li and 10B-loaded materials with heat capacity C operating at temperatures T close to 0.1 K. Temperature variations on the order of 0.5 mK are measured with a Mo/Cu thin film multilayer operated in the transition region between its superconducting and its normal state. The advantage of calorimetry for high resolution spectroscopy is due to the small phonon excitation energies k BT on the order ofmore » μeV that serve as signal carriers, resulting in an energy resolution ΔE ~ (k BT 2C) 1/2, which can be well below 10 keV. An energy resolution of 5.5 keV has been obtained with a Mo/Cu superconducting sensor and a TiB 2 absorber using thermal neutrons from a 252Cf neutron source. This resolution is sufficient to observe the effect of recoil nuclei broadening in neutron spectra, which has been related to the lifetime of the first excited state in 7Li. Fast-neutron spectra obtained with a 6Li-enriched LiF absorber show an energy resolution of 16 keV FWHM, and a response in agreement with the 6Li(n, α) 3H reaction cross section and Monte Carlo simulations for energies up to several MeV. The energy resolution of order of a few keV makes this novel instrument applicable to fast-neutron transmission spectroscopy based on the unique elemental signature provided by the neutron absorption and scattering resonances. The optimization of the energy resolution based on analytical and numerical models of the detector response is discussed in the context of these applications.« less

  11. Thin film metrology and microwave loss characterization of indium and aluminum/indium superconducting planar resonators

    NASA Astrophysics Data System (ADS)

    McRae, C. R. H.; Béjanin, J. H.; Earnest, C. T.; McConkey, T. G.; Rinehart, J. R.; Deimert, C.; Thomas, J. P.; Wasilewski, Z. R.; Mariantoni, M.

    2018-05-01

    Scalable architectures characterized by quantum bits (qubits) with low error rates are essential to the development of a practical quantum computer. In the superconducting quantum computing implementation, understanding and minimizing material losses are crucial to the improvement of qubit performance. A new material that has recently received particular attention is indium, a low-temperature superconductor that can be used to bond pairs of chips containing standard aluminum-based qubit circuitry. In this work, we characterize microwave loss in indium and aluminum/indium thin films on silicon substrates by measuring superconducting coplanar waveguide resonators and estimating the main loss parameters at powers down to the sub-photon regime and at temperatures between 10 and 450 mK. We compare films deposited by thermal evaporation, sputtering, and molecular beam epitaxy. We study the effects of heating in a vacuum and ambient atmospheric pressure as well as the effects of pre-deposition wafer cleaning using hydrofluoric acid. The microwave measurements are supported by thin film metrology including secondary-ion mass spectrometry. For thermally evaporated and sputtered films, we find that two-level state are the dominant loss mechanism at low photon number and temperature, with a loss tangent due to native indium oxide of ˜ 5 × 10 - 5 . The molecular beam epitaxial films show evidence of the formation of a substantial indium-silicon eutectic layer, which leads to a drastic degradation in resonator performance.

  12. Superconducting fluctuations in molybdenum nitride thin films

    NASA Astrophysics Data System (ADS)

    Baskaran, R.; Thanikai Arasu, A. V.; Amaladass, E. P.; Vaidhyanathan, L. S.; Baisnab, D. K.

    2018-02-01

    MoN thin films have been deposited using reactive sputtering. The change in resistance near superconducting transition temperature at various magnetic fields has been analyzed based on superconducting fluctuations in the system. The Aslamazov and Larkin scaling theory has been utilized to analyze the conductance change. The results indicate that most of the measurements show two dimensional (2D) nature and exhibit scaling behavior at lower magnetic fields (<7T), while a cross over to three dimensional (3D) nature has been clearly observed in measurements at higher fields (>7T). We have also analyzed our data based on the model in which there is no explicit dependence of Tc. These analyses also substantiate a crossover from a 2D nature to a 3D at larger fields. Analysis using lowest Landau level scaling theory for a 2D system exhibit scaling behavior and substantiate our observations. The broadening at low resistance part has been explained based on thermally activated flux flow model and show universal behavior. The dependence of Uo on magnetic field indicates both single and collective vortex behavior.

  13. Crystallographic structure and superconductive properties of Nb-Ti films with an artificially layered structure

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sato, N.

    1990-06-15

    Artificially layered niobium-titanium (Nb-Ti) films with various thickness ratios (3/1--1/3) and periodicities (2--100 A) are made in an argon or in a mixed argon/nitrogen atmosphere by a dc magnetron sputtering method. Films with small periodicities (less than 30 A) have an artificial superlattice structure (ASL) with crystallographic coherence between constituent layers, where Nb and Ti grow epitaxially on the closest planes. The crystallographic structures of films are bcc with the (110) plane parallel to the film for films with the same or a thicker Nb layer than a Ti layer, and hcp with the (001) plane parallel to the filmmore » for films with a thinner Nb layer than a Ti layer. Films with large periodicities have an artificial superstructure (ASS) with only periodic stacking of constituent layers. Films deposited in the Ar/N atmosphere also have the artificially layered structures of ASL or ASS. The artificially layered structure is thermally stable at temperatures up to 500 {degree}C. The superconducting properties of the films depend strongly on the periodicity and thickness ratio of Nb and Ti layers. The dependence of the transition temperature on the periodicity and thickness ratio is qualitatively explained by a proximity effect with a three-region model. Films with periodicities less than 20 A, composed of the same or a thicker Nb layer than a Ti layer, show high transition temperatures (above 9.3 K). The highest {ital T}{sub {ital c}} of about 13.6 K is obtained in the film composed of monatomic layers of constituents deposited in an Ar atmosphere including 30 vol % N.« less

  14. Method and apparatus for connecting high voltage leads to a high temperature super-conducting transformer

    DOEpatents

    Golner, Thomas M.; Mehta, Shirish P.

    2005-07-26

    A method and apparatus for connecting high voltage leads to a super-conducting transformer is provided that includes a first super-conducting coil set, a second super-conducting coil set, and a third super-conducting coil set. The first, second and third super-conducting coil sets are connected via an insulated interconnect system that includes insulated conductors and insulated connectors that are utilized to connect the first, second, and third super-conducting coil sets to the high voltage leads.

  15. High temperature superconductor materials and applications

    NASA Technical Reports Server (NTRS)

    Doane, George B., III. (Editor); Banks, Curtis; Golben, John

    1991-01-01

    One of the areas concerned itself with the investigation of the phenomena involved in formulating and making in the laboratory new and better superconductor material with enhanced values of critical current and temperature. Of special interest were the chemistry, physical processes, and environment required to attain these enhanced desirable characteristics. The other area concerned itself with producing high temperature superconducting thin films by pulsed laser deposition techniques. Such films are potentially very useful in the detection of very low power signals. To perform this research high vacuum is required. In the course of this effort, older vacuum chambers were maintained and used. In addition, a new facility is being brought on line. This latter activity has been replete with the usual problems of bringing a new facility into service. Some of the problems are covered in the main body of this report.

  16. Conversion of microwave signals by superconducting films in the resistive state

    NASA Technical Reports Server (NTRS)

    Yeru, I. I.; Peskovatskiy, S. A.; Sulima, V. S.

    1984-01-01

    The main characteristics of a superconducting thin film microwave mixer, i.e., conversion efficiency and bandwidth are analyzed. The optimum operating regime of the nonlinear element is determined. Results of calculations are compared with the experimental ones. Experimental data on the noise in the superconducting films in a wide frequency range are presented.

  17. Development of Thin Film Ceramic Thermocouples for High Temperature Environments

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D.; Fralick, Gustave C.; Farmer, Serene C.; Sayir, Ali; Blaha, Charles A.; Gonzalez, Jose M.

    2004-01-01

    The maximum use temperature of noble metal thin film thermocouples of 1100 C (2000 F) may not be adequate for use on components in the increasingly harsh conditions of advanced aircraft and next generation launch technology. Ceramic-based thermocouples are known for their high stability and robustness at temperatures exceeding 1500 C, but are typically found in the form of rods or probes. NASA Glenn Research Center is investigating the feasibility of ceramics as thin film thermocouples for extremely high temperature applications to take advantage of the stability and robustness of ceramics and the non-intrusiveness of thin films. This paper will discuss the current state of development in this effort.

  18. High-Temperature, Thin-Film Strain Gages Improved

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Conventional resistance strain gage technology uses "bonded" strain gages. These foil or wire gages are bonded onto the surface of the test article with glue, ceramic cements, or flame-sprayed ceramics. These bonding agents can, in some instances, limit both the degree of strain transmission from the test structure to the gage and the maximum working temperature of the gage. Also, the bulky, bonded gage normally disrupts aerodynamic gas flow on the surface of the test structure because of its intrusive character. To respond to the urgent needs in aeronautic and aerospace research where stress and temperature gradients are high, aerodynamic effects need to be minimized, and higher operational temperatures are required, the NASA Lewis Research Center developed a thin film strain gage. This gage, a vacuum-deposited thin film formed directly on the surface of a test structure, operates at much higher temperatures than commercially available gages do and with minimal disruption of the aerodynamic flow. The gage uses an alloy, palladium-13 wt % chromium (hereafter, PdCr), which was developed by United Technologies Research Center under a NASA contract. PdCr is structurally stable and oxidation resistant up to at least 1100 C (2000 F); its temperature-induced resistance change is linear, repeatable, and not sensitive to the rates of heating and cooling. An early strain gage, which was made of 25-micrometer-diameter PdCr wire and demonstrated to be useable to 800 C, won an R&D 100 award in 1991. By further improving the purity of the material and by developing gage fabrication techniques that use sputter-deposition, photolithography patterning, and chemical etching, we have made an 8- to 10-m PdCr thin-film strain gage that can measure dynamic and static strain to at least 1100 C. For static strain measurements, a 5-m-thick Pt element serves as a temperature compensator to further minimize the temperature effect of the gage. These thin-film gages provide the advantage of

  19. Imaging of current distributions in superconducting thin film structures

    NASA Astrophysics Data System (ADS)

    Dönitz, Dietmar

    2006-10-01

    Local analysis plays an important role in many fields of scientific research. However, imaging methods are not very common in the investigation of superconductors. For more than 20 years, Low Temperature Scanning Electron Microscopy (LTSEM) has been successfully used at the University of Tübingen for studying of condensed matter phenomena, especially of superconductivity. In this thesis LTSEM was used for imaging current distributions in different superconducting thin film structures: - Imaging of current distributions in Josephson junctions with ferromagnetic interlayer, also known as SIFS junctions, showed inhomogeneous current transport over the junctions which directly led to an improvement in the fabrication process. An investigation of improved samples showed a very homogeneous current distribution without any trace of magnetic domains. Either such domains were not present or too small for imaging with the LTSEM. - An investigation of Nb/YBCO zigzag Josephson junctions yielded important information on signal formation in the LTSEM both for Josephson junctions in the short and in the long limit. Using a reference junction our signal formation model could be verified, thus confirming earlier results on short zigzag junctions. These results, which could be reproduced in this work, support the theory of d-wave symmetry in the superconducting order parameter of YBCO. Furthermore, investigations of the quasiparticle tunneling in the zigzag junctions showed the existence of Andreev bound states, which is another indication of the d-wave symmetry in YBCO. - The LTSEM study of Hot Electron Bolometers (HEB) allowed the first successful imaging of a stable 'Hot Spot', a self-heating region in HEB structures. Moreover, the electron beam was used to induce an - otherwise unstable - hot spot. Both investigations yielded information on the homogeneity of the samples. - An entirely new method of imaging the current distribution in superconducting interference devices

  20. Method Producing an SNS Superconducting Junction with Weak Link Barrier

    NASA Technical Reports Server (NTRS)

    Hunt, Brian D. (Inventor)

    1999-01-01

    A method of producing a high temperature superconductor Josephson element and an improved SNS weak link barrier element is provided. A YBaCuO superconducting electrode film is deposited on a substrate at a temperature of approximately 800 C. A weak link barrier layer of a nonsuperconducting film of N-YBaCuO is deposited over the electrode at a temperature range of 520 C. to 540 C. at a lower deposition rate. Subsequently a superconducting counter-electrode film layer of YBaCuO is deposited over the weak link barrier layer at approximately 800 C. The weak link barrier layer has a thickness of approximately 50 A and the SNS element can be constructed to provide an edge geometry junction.

  1. Permanent magnet design for high-speed superconducting bearings

    DOEpatents

    Hull, John R.; Uherka, Kenneth L.; Abdoud, Robert G.

    1996-01-01

    A high temperature superconducting bearing including a permanent magnet rotor levitated by a high temperature superconducting structure. The rotor preferably includes one or more concentric permanent magnet rings coupled to permanent magnet ring structures having substantially triangular and quadrangular cross-sections. Both alternating and single direction polarity magnet structures can be used in the bearing.

  2. A Cryogenic Magnetostrictive Actuator Using a Persistent High Temperature Superconducting Magnet. Part 1; Concept and Design

    NASA Technical Reports Server (NTRS)

    Horner, Garnett; Bromberg, Leslie; Teter, J. P.

    2000-01-01

    Cryogenic magnetostrictive materials, such as rare earth zinc crystals, offer high strains and high forces with minimally applied magnetic fields, making the material ideally suited for deformable optics applications. For cryogenic temperature applications the use of superconducting magnets offer the possibility of a persistent mode of operation, i.e., the magnetostrictive material will maintain a strain field without power. High temperature superconductors (HTS) are attractive options if the temperature of operation is higher than 10 degrees Kelvin (K) and below 77 K. However, HTS wires have constraints that limit the minimum radius of winding, and even if good wires can be produced, the technology for joining superconducting wires does not exist. In this paper, the design and capabilities of a rare earth zinc magnetostrictive actuator using bulk HTS is described. Bulk superconductors can be fabricated in the sizes required with excellent superconducting properties. Equivalent permanent magnets, made with this inexpensive material, are persistent, do not require a persistent switch as in HTS wires, and can be made very small. These devices are charged using a technique which is similar to the one used for charging permanent magnets, e.g., by driving them into saturation. A small normal conducting coil can be used for charging or discharging. Because of the magnetic field capability of the superconductor material, a very small amount of superconducting magnet material is needed to actuate the rare earth zinc. In this paper, several designs of actuators using YBCO and BSCCO 2212 superconducting materials are presented. Designs that include magnetic shielding to prevent interaction between adjacent actuators will also be described. Preliminary experimental results and comparison with theory for BSCCO 2212 with a magnetostrictive element will be discussed.

  3. Exploring the performance of thin-film superconducting multilayers as kinetic inductance detectors for low-frequency detection

    NASA Astrophysics Data System (ADS)

    Zhao, Songyuan; Goldie, D. J.; Withington, S.; Thomas, C. N.

    2018-01-01

    We have solved numerically the diffusive Usadel equations that describe the spatially varying superconducting proximity effect in Ti-Al thin-film bi- and trilayers with thickness values that are suitable for kinetic inductance detectors (KIDs) to operate as photon detectors with detection thresholds in the frequency range of 50-90 GHz. Using Nam’s extension of the Mattis-Bardeen calculation of the superconductor complex conductivity, we show how to calculate the surface impedance for the spatially varying case, and hence the surface impedance quality factor. In addition, we calculate energy-and spatially-averaged quasiparticle lifetimes at temperatures well-below the transition temperature and compare to calculation in Al. Our results for the pair-breaking threshold demonstrate differences between bilayers and trilayers with the same total film thicknesses. We also predict high quality factors and long multilayer-averaged quasiparticle recombination times compared to thin-film Al. Our calculations give a route for designing KIDs to operate in this scientifically-important frequency regime.

  4. Permanent magnet design for high-speed superconducting bearings

    DOEpatents

    Hull, J.R.; Uherka, K.L.; Abdoud, R.G.

    1996-09-10

    A high temperature superconducting bearing including a permanent magnet rotor levitated by a high temperature superconducting structure is disclosed. The rotor preferably includes one or more concentric permanent magnet rings coupled to permanent magnet ring structures having substantially triangular and quadrangular cross-sections. Both alternating and single direction polarity magnet structures can be used in the bearing. 9 figs.

  5. Superconducting properties of Nb-Cu nano-composites and nano-alloys

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Parab, Pradnya, E-mail: pradnyaprb@gmail.com; Kumar, Sanjeev; Bhui, Prabhjyot

    The evolution of the superconducting transition temperature (T{sub c}) in nano-composite and nano-alloys of Nb-Cu, grown by DC magnetron co-sputtering are investigated. Microstructure of these films depends less strongly on the ratio of Nb:Cu but more on the growth temperature. At higher growth temperature, phase separated granular films of Nb and Cu were formed which showed superconducting transition temperatures (T{sub c}) of ~ 7.2±0.5 K, irrespective of the composition. Our results show that this is primarily influenced by the microstructure of the films determined during growth which rules out the superconducting proximity effect expected in these systems. At room temperaturemore » growth, films with nano-scale alloying were obtained at the optimal compositional range of 45-70 atomic% (At%) of Nb. These were also superconducting with a T{sub c} of 3.2 K.« less

  6. High-Density Superconducting Cables for Advanced ACTPol

    NASA Astrophysics Data System (ADS)

    Pappas, C. G.; Austermann, J.; Beall, J. A.; Duff, S. M.; Gallardo, P. A.; Grace, E.; Henderson, S. W.; Ho, S. P.; Koopman, B. J.; Li, D.; McMahon, J.; Nati, F.; Niemack, M. D.; Niraula, P.; Salatino, M.; Schillaci, A.; Schmitt, B. L.; Simon, S. M.; Staggs, S. T.; Stevens, J. R.; Vavagiakis, E. M.; Ward, J. T.; Wollack, E. J.

    2016-07-01

    Advanced ACTPol (AdvACT) is an upcoming Atacama Cosmology Telescope (ACT) receiver upgrade, scheduled to deploy in 2016, that will allow measurement of the cosmic microwave background polarization and temperature to the highest precision yet with ACT. The AdvACT increase in sensitivity is partly provided by an increase in the number of transition-edge sensors (TESes) per array by up to a factor of two over the current ACTPol receiver detector arrays. The high-density AdvACT TES arrays require 70 \\upmu m pitch superconducting flexible cables (flex) to connect the detector wafer to the first-stage readout electronics. Here, we present the flex fabrication process and test results. For the flex wiring layer, we use a 400-nm-thick sputtered aluminum film. In the center of the cable, the wiring is supported by a polyimide substrate, which smoothly transitions to a bare (uncoated with polyimide) silicon substrate at the ends of the cable for a robust wedge wire-bonding interface. Tests on the first batch of flex made for the first AdvACT array show that the flex will meet the requirements for AdvACT, with a superconducting critical current above 1 mA at 500 mK, resilience to mechanical and cryogenic stress, and a room temperature yield of 97 %.

  7. Low temperature superconductor and aligned high temperature superconductor magnetic dipole system and method for producing high magnetic fields

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gupta, Ramesh; Scanlan, Ronald; Ghosh, Arup K.

    A dipole-magnet system and method for producing high-magnetic-fields, including an open-region located in a radially-central-region to allow particle-beam transport and other uses, low-temperature-superconducting-coils comprised of low-temperature-superconducting-wire located in radially-outward-regions to generate high magnetic-fields, high-temperature-superconducting-coils comprised of high-temperature-superconducting-tape located in radially-inward-regions to generate even higher magnetic-fields and to reduce erroneous fields, support-structures to support the coils against large Lorentz-forces, a liquid-helium-system to cool the coils, and electrical-contacts to allow electric-current into and out of the coils. The high-temperature-superconducting-tape may be comprised of bismuth-strontium-calcium-copper-oxide or rare-earth-metal, barium-copper-oxide (ReBCO) where the rare-earth-metal may be yttrium, samarium, neodymium, or gadolinium. Advantageously, alignment of themore » large-dimension of the rectangular-cross-section or curved-cross-section of the high-temperature-superconducting-tape with the high-magnetic-field minimizes unwanted erroneous magnetic fields. Alignment may be accomplished by proper positioning, tilting the high-temperature-superconducting-coils, forming the high-temperature-superconducting-coils into a curved-cross-section, placing nonconducting wedge-shaped-material between windings, placing nonconducting curved-and-wedge-shaped-material between windings, or by a combination of these techniques.« less

  8. High- T c Superconductivity in FeSe at High Pressure: Dominant Hole Carriers and Enhanced Spin Fluctuations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sun, J. P.; Ye, G. Z.; Shahi, P.

    The importance of electron-hole interband interactions is widely acknowledged for iron-pnictide superconductors with high transition temperatures (T c). However, high-T c superconductivity without hole carriers has been suggested in FeSe single-layer films and intercalated iron-selenides, raising a fundamental question whether iron pnictides and chalcogenides have different pairing mechanisms. Here, we study the properties of electronic structure in another high-T c phase induced by pressure in bulk FeSe from magneto-transport measurements and first-principles calculations. With increasing pressure, the low-T c superconducting phase transforms into high-T c phase, where we find the normal-state Hall resistivity changes sign from negative to positive, demonstratingmore » dominant hole carriers in striking contrast to other FeSe-derived high-T c systems. Moreover, the Hall coefficient is remarkably enlarged and the magnetoresistance exhibits anomalous scaling behaviours, evidencing strongly enhanced interband spin fluctuations in the high-T c phase. These results in FeSe highlight similarities with high-T c phases of iron pnictides, constituting a step toward a unified understanding of iron-based superconductivity.« less

  9. High- T c Superconductivity in FeSe at High Pressure: Dominant Hole Carriers and Enhanced Spin Fluctuations

    DOE PAGES

    Sun, J. P.; Ye, G. Z.; Shahi, P.; ...

    2017-04-07

    The importance of electron-hole interband interactions is widely acknowledged for iron-pnictide superconductors with high transition temperatures (T c). However, high-T c superconductivity without hole carriers has been suggested in FeSe single-layer films and intercalated iron-selenides, raising a fundamental question whether iron pnictides and chalcogenides have different pairing mechanisms. Here, we study the properties of electronic structure in another high-T c phase induced by pressure in bulk FeSe from magneto-transport measurements and first-principles calculations. With increasing pressure, the low-T c superconducting phase transforms into high-T c phase, where we find the normal-state Hall resistivity changes sign from negative to positive, demonstratingmore » dominant hole carriers in striking contrast to other FeSe-derived high-T c systems. Moreover, the Hall coefficient is remarkably enlarged and the magnetoresistance exhibits anomalous scaling behaviours, evidencing strongly enhanced interband spin fluctuations in the high-T c phase. These results in FeSe highlight similarities with high-T c phases of iron pnictides, constituting a step toward a unified understanding of iron-based superconductivity.« less

  10. Tunneling probe of fluctuating superconductivity in disordered thin films

    NASA Astrophysics Data System (ADS)

    Dentelski, David; Frydman, Aviad; Shimshoni, Efrat; Dalla Torre, Emanuele G.

    2018-03-01

    Disordered thin films close to the superconductor-insulator phase transition (SIT) hold the key to understanding quantum phase transition in strongly correlated materials. The SIT is governed by superconducting quantum fluctuations, which can be revealed, for example, by tunneling measurements. These experiments detect a spectral gap, accompanied by suppressed coherence peaks, on both sides of the transition. Here we describe the insulating side in terms of a fluctuating superconducting field with finite-range correlations. We perform a controlled diagrammatic resummation and derive analytic expressions for the tunneling differential conductance. We find that short-range superconducting fluctuations suppress the coherence peaks even in the presence of long-range correlations. Our approach offers a quantitative description of existing measurements on disordered thin films and accounts for tunneling spectra with suppressed coherence peaks.

  11. A high-resolution superconducting pressure control system for use at low temperatures

    NASA Astrophysics Data System (ADS)

    Geng, Z. K.; Swanson, D. R.; Nissen, J. A.; Lipa, J. A.

    2000-01-01

    We have developed a high resolution superconducting pressure gauge and controller system capable of stabilizing pressure to within +/-10-8 bar in the range 0-30 bars at temperatures below about 6K. The system consists of two parts: a transducer and a pressure actuator. The transducer is based on the inductive sensing of the position of a diaphragm using superconducting techniques. A rod attached to the center of the diaphragm supports a superconducting plate which is in close proximity to a flat, spiral superconducting coil. A persistent current of about 1 A is trapped in the coil and is coupled to a dc SQUID magnetometer. The magnetometer produces a partially digitized dc output proportional to the change of pressure applied to the diaphragm. Because of the ability of the magnetometer to count magnetic flux quanta, an extremely wide dynamic range can be achieved with high sensitivity and repeatability. The transducer was used to control the pressure of a sample of liquid helium at temperatures near 2 K and pressures from 1-25 bars. The actuator consisted of two parts: a thermally isolated chamber filled with 3He that could be heated and cooled as desired over the range 1.5 to 10 K, and a beryllium-copper diaphragm assembly. This diaphragm had the 3He on one side and the sample helium on the other. A simple servomechanism was used to convert the output signal from the magnetometer to heat applied to the 3He chamber. The system has been operated routinely over the full range of pressures and so far no significant drift has been detected. It is somewhat sensitive to vibration and EMI, but otherwise appears quite robust. Plans have been made to improve the shielding to reduce the EMI susceptibility. The vibration sensitivity can be reduced by making use of a pair of pressure sensing diaphragms acting in opposite directions. .

  12. Thin film thermocouples for high temperature measurement on ceramic materials

    NASA Technical Reports Server (NTRS)

    Holanda, Raymond

    1992-01-01

    Thin film thermocouples have been developed for use on metal parts in jet engines to 1000 C. However, advanced propulsion systems are being developed that will use ceramic materials and reach higher temperatures. The purpose of this work is to develop thin film thermocouples for use on ceramic materials. The thin film thermocouples are Pt13Rh/Pt fabricated by the sputtering process. Lead wires are attached using the parallel-gap welding process. The ceramic materials are silicon nitride, silicon carbide, aluminum oxide, and mullite. Both steady state and thermal cycling furnace tests were performed in the temperature range to 1500 C. High-heating-rate tests were performed in an arc lamp heat-flux-calibration facility. The fabrication of the thin film thermocouples is described. The thin film thermocouple output was compared to a reference wire thermocouple. Drift of the thin film thermocouples was determined, and causes of drift are discussed. The results of high-heating-rate tests up to 2500 C/sec are presented. The stability of the ceramic materials is examined. It is concluded that Pt13Rh/Pt thin film thermocouples are capable of meeting lifetime goals of 50 hours or more up to temperatures of 1500 C depending on the stability of the particular ceramic substrate.

  13. Growth and characterization of few unit-cell NbN superconducting films on 3C-SiC/Si substrate

    NASA Astrophysics Data System (ADS)

    Chang, H. W.; Wang, C. L.; Huang, Y. R.; Chen, T. J.; Wang, M. J.

    2017-11-01

    Superconducting δ-NbN ultrathin film has become a key element in extremely sensitive detector applications in recent decades because of its excellent electronic properties. We have realized the epitaxial growth of ultrathin δ-NbN films on (100)-oriented 3C-SiC/Si substrates by dc reactive magnetron sputtering at 760 °C with a deposition rate of 0.054 nm s-1. High-resolution transmission electron microscope images confirm the excellent epitaxy of these films. Even with a thickness of 1.3 nm (˜3 unit cells), the δ-NbN film shows a superconducting transition above 8 K. Furthermore, our ultrathin δ-NbN films demonstrate a long Ginzburg-Landau superconducting coherent length ({ξ }{{G}{{L}}}(0)> 5 {{nm}}) with a critical current density of about 2.2 MA cm-2, and good stability in an ambient environment.

  14. YBCO High-Temperature Superconducting Filters on M-Plane Sapphire Substrates

    NASA Technical Reports Server (NTRS)

    Sabataitis, J. C.; Mueller, C. H.; Miranda, F. A.; Warner, J.; Bhasin, K. B.

    1996-01-01

    Since the discovery of High Temperature Superconductors (HTS) in 1986, microwave circuits have been demonstrated using HTS films on various substrates. These HTS-based circuits have proven to operate with less power loss than their metallic film counterparts at 77 K. This translates into smaller and lighter microwave circuits for space communication systems such as multiplexer filter banks. High quality HTS films have conventionally been deposited on lanthanum aluminate (LaAlO3) substrates. However, LaAlO3 has a relative dielectric constant (epsilon(sub r)) of 24. With a epsilon(sub r) approx. 9.4-11.6, sapphire (Al2O3) would be a preferable substrate for the fabrication of HTS-based components since the lower dielectric constant would permit wider microstrip lines to be used in filter design, since the lower dielectric constant would permit wider microstrip lines to be used for a given characteristic impedance (Z(sub 0)), thus lowering the insertion losses and increasing the power handling capabilities of the devices. We report on the fabrication and characterization of YBa2Cu3O(7-delta) (YBCO) on M-plane sapphire bandpass filters at 4.0 GHz. For a YBCO 'hairpin' filter, a minimum insertion loss of 0.5 dB was measured at 77 K as compared with 1.4 dB for its gold counterpart. In an 'edge-coupled' configuration, the insertion loss went down from 0.9 dB for the gold film to 0.8 dB for the YBCO film at the same temperature.

  15. Development of high Tc (greater than 100 K) Bi, Tl and Y-based materials as superconducting circuit elements

    NASA Technical Reports Server (NTRS)

    Haertling, Gene; Grabert, Gregory; Gilmour, Phillip

    1994-01-01

    Experimental work on this project over the last four years has resulted in establishing processing and characterization techniques for producing both the Bi-based and Tl-based superconductors in their high temperature (2223) forms. In the bulk, dry pressed form, maximum critical temperatures (Tc) of 108.2 K and 117.8 K, respectively, were measured. Results have further shown that the Bi and Tl-based superconducting materials in bulk form are noticeably different from the Y-based 123 material in that superconductivity is considerably harder to achieve, maintain, and reproduce. This is due primarily to the difficulty in obtaining the higher Tc phase in pure form since it commonly co-exists with other undesirable, lower Tc phases. In particular, it has been found that long processing times for calcining and firing (20 - 200 hrs.) and close control of temperatures which are very near the melting point are required in order to obtain higher proportions of the desirable, high Tc (2223) phase. Thus far, the BSCCO bulk materials has been prepared in uniaxially pressed, hot pressed, and tapecast form. The uniaxially pressed material has been synthesized by the mixed oxide, coprecipitation, and melt quenching processes. The tapecast and hot pressed materials have been prepared via the mixed oxide process. In addition, thick films of BSCCO (2223 phase) have been prepared by screen printing on to yttria and magnesia stabilized zirconia with only moderate success; i.e., superconductivity was achieved in these thick films, but the highest Tc obtained in these films was 89.0 K. The Tc's of the bulk hot pressed, tapecast, and screen printed thick film materials were found to be 108.2, 102.4, and 89.0 K, respectively.

  16. Nb(x)Ti(1-x)N Superconducting-Nanowire Single-Photon Detectors

    NASA Technical Reports Server (NTRS)

    Stern, Jeffrey A.; Farr, William H.; Leduc, Henry G.; Bumble, Bruce

    2008-01-01

    Superconducting-nanowire single-photon detectors (SNSPDs) in which Nb(x)Ti(1-x)N (where x<1) films serve as the superconducting materials have shown promise as superior alternatives to previously developed SNSPDs in which NbN films serve as the superconducting materials. SNSPDs have potential utility in optical communications and quantum cryptography. Nb(x)Ti(1-x)N is a solid solution of NbN and TiN, and has many properties similar to those of NbN. It has been found to be generally easier to stabilize Nb(x)Ti(1-x)N in the high-superconducting-transition temperature phase than it is to so stabilize NbN. In addition, the resistivity and penetration depth of polycrystalline films of Nb(x)Ti(1-x)N have been found to be much smaller than those of films of NbN. These differences have been hypothesized to be attributable to better coupling at grain boundaries within Nb(x)Ti(1-x)N films.

  17. Room temperature, air crystallized perovskite film for high performance solar cells

    DOE PAGES

    Dubey, Ashish; Kantack, Nicholas; Adhikari, Nirmal; ...

    2016-05-31

    For the first time, room temperature heating free growth and crystallization of perovskite films in ambient air without the use of thermal annealing is reported. Highly efficient perovskite nanorod-based solar cells were made using ITO/PEDOT:PSS/CH 3NH 3PbI 3 nanorods/PC 60BM/rhodamine/Ag. All the layers except PEDOT:PSS were processed at room temperature thereby eliminating the need for thermal treatment. Perovskite films were spin coated inside a N-2 filled glovebox and immediately were taken outside in air having 40% relative humidity (RH). Exposure to humid air was observed to promote the crystallization process in perovskite films even at room temperature. Perovskite films keptmore » for 5 hours in ambient air showed nanorod-like morphology having high crystallinity, with devices exhibiting the highest PCE of 16.83%, which is much higher than the PCE of 11.94% for traditional thermally annealed perovskite film based devices. Finally, it was concluded that moisture plays an important role in room temperature crystallization of pure perovskite nanorods, showing improved optical and charge transport properties, which resulted in high performance solar cells.« less

  18. Thin Film Ceramic Strain Sensor Development for High Temperature Environments

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D.; Fralick, Gustave C.; Gonzalez, Jose M.; Laster, Kimala L.

    2008-01-01

    The need for sensors to operate in harsh environments is illustrated by the need for measurements in the turbine engine hot section. The degradation and damage that develops over time in hot section components can lead to catastrophic failure. At present, the degradation processes that occur in the harsh hot section environment are poorly characterized, which hinders development of more durable components, and since it is so difficult to model turbine blade temperatures, strains, etc, actual measurements are needed. The need to consider ceramic sensing elements is brought about by the temperature limits of metal thin film sensors in harsh environments. The effort at the NASA Glenn Research Center (GRC) to develop high temperature thin film ceramic static strain gauges for application in turbine engines is described, first in the fan and compressor modules, and then in the hot section. The near-term goal of this research effort was to identify candidate thin film ceramic sensor materials and provide a list of possible thin film ceramic sensor materials and corresponding properties to test for viability. A thorough literature search was conducted for ceramics that have the potential for application as high temperature thin film strain gauges chemically and physically compatible with the NASA GRCs microfabrication procedures and substrate materials. Test results are given for tantalum, titanium and zirconium-based nitride and oxynitride ceramic films.

  19. Optimisation of growth of epitaxial Tl 2Ba 2Ca 1Cu 2O 8 superconducting thin films for electronic device applications

    NASA Astrophysics Data System (ADS)

    Michael, Peter C.; Johansson, L.-G.; Bengtsson, L.; Claeson, T.; Ivanov, Z. G.; Olsson, E.; Berastegui, P.; Stepantsov, E.

    1994-12-01

    Epitaxial thin films of Tl 2Ba 2Ca 1Cu 2O 8 (Tl-2212) superconductor have been grown on single crystal (100) lanthanum aluminate (LaAlO 3) substrates by a two stage process: laser ablation of a BaCaCuO (0212) sintered target and post-deposition anneal ex-situ in a thallium environment. The films are c-axis oriented with in-plane epitaxy as determined by x-ray diffraction (XRD θ-2θ and φ-scans). Superconducting transition temperatures as high as 105.5K have been obtained both from four-probe resistance and a.c. magnetic susceptibility measurements. Film morphology and chemical composition have been assessed by scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX). Sensitivity of the precursor film to environmental exposure has proven to be a determining factor in the reproducibility of film growth characteristics. The effect of oxygen partial pressure and substrate temperature used in the precursor film synthesis, as well as the thallium annealing temperature and duration, on the growth of Tl-2212 thin films is reported.

  20. High critical current superconducting tapes

    DOEpatents

    Holesinger, Terry G [Los Alamos, NM; Jia, Quanxi [Los Alamos, NM; Foltyn, Stephen R [Los Alamos, NM

    2003-09-23

    Improvements in critical current capacity for superconducting film structures are disclosed and include the use of a superconducting RE-BCO layer including a mixture of rare earth metals, e.g., yttrium and europium, where the ratio of yttrium to europium in the RE-BCO layer ranges from about 3 to 1 to from about 1.5 to 1.

  1. Far-infrared Optical Conductivity Gap in Superconducting MgB2 Films

    NASA Astrophysics Data System (ADS)

    Carnahan, M. A.; Kaindl, R. A.; Chemla, D. S.; Christen, H. M.; Zhai, H. Y.; Paranthaman, M.; Lowndes, D. H.

    2002-03-01

    The prospect of unconventional coupling in the superconductor MgB2 motivates experiments which probe the density of states around the superconducting gap. The frequency and temperature dependent optical conductivity contains important spectroscopic information about the fundamental gap excitations as well as providing a contactless measure of the superconducting condensate. Here we present the first measurements of the far-infrared conductivity of MgB2 over a broad frequency range which spans excitations across its lowest-energy superconducting gap [1]. Thin films of MgB2 are grown on Al_2O3 substrates through e-beam evaporation and subsequent ex-situ annealing [2]. Both the real and imaginary parts of the conductivity are obtained - without recourse to Kramers-Kronig transformations - from terahertz time-domain spectroscopy. Below Tc we observe a depletion of oscillator strength due to the opening of a superconducting gap. We find a gap size of 2Δ ≈ 5 meV. This result, a value which is only half that expected in weak-coupling BCS theory, disfavors a conventional isotropic single-gap scenario. [1] R. Kaindl et al., Phys. Rev. Lett. (to appear). [2] M. Paranthaman et al., Appl. Phys. Lett. 78, 3669 (2001).

  2. Degradation of superconducting properties in MgB2 films by exposure to water

    NASA Astrophysics Data System (ADS)

    Zhai, H. Y.; Christen, H. M.; Zhang, L.; Paranthaman, M.; Fleming, P. H.; Lowndes, D. H.

    2001-07-01

    The effect of water exposure on MgB2 is studied by submerging an 800 nm thick MgB2 film into de-ionized water at room temperature for 1 h, 4 h, 10 h, and 15 h, and by analysing the resulting material using scanning electron microscopy and resistance versus temperature measurements. It is clearly observed that the Tconset of these films (obtained by an ex-situ reaction of an e-beam evaporated boron layer) remains unchanged throughout this process, indicating that at least a portion of the sample retains its original bulk-like properties. The data is consistent with an interpretation in which a portion of the exposed film - likely to be the region closest to the substrate - becomes superconducting only at ~ 25 K. It is possible that this low-Tc region already exists in the as-prepared film, and we observe that its Tc coincides with that of MgB2 films obtained by annealing precursor films prepared by pulsed laser deposition. Therefore the data presented here not only illustrates the degradation of MgB2 in water but also sheds light on the differences and similarities between films obtained via different routes.

  3. High-temperature crystallized thin-film PZT on thin polyimide substrates

    NASA Astrophysics Data System (ADS)

    Liu, Tianning; Wallace, Margeaux; Trolier-McKinstry, Susan; Jackson, Thomas N.

    2017-10-01

    Flexible piezoelectric thin films on polymeric substrates provide advantages in sensing, actuating, and energy harvesting applications. However, direct deposition of many inorganic piezoelectric materials such as Pb(Zrx,Ti1-x)O3 (PZT) on polymers is challenging due to the high temperature required for crystallization. This paper describes a transfer process for PZT thin films. The PZT films are first grown on a high-temperature capable substrate such as platinum-coated silicon. After crystallization, a polymeric layer is added, and the polymer-PZT combination is removed from the high-temperature substrate by etching away a release layer, with the polymer layer then becoming the substrate. The released PZT on polyimide exhibits enhanced dielectric response due to reduction in substrate clamping after removal from the rigid substrate. For Pb(Zr0.52,Ti0.48)0.98Nb0.02O3 films, release from Si increased the remanent polarization from 17.5 μC/cm2 to 26 μC/cm2. In addition, poling led to increased ferroelastic/ferroelectric realignment in the released films. At 1 kHz, the average permittivity was measured to be around 1160 after release from Si with a loss tangent below 3%. Rayleigh measurements further confirmed the correlation between diminished substrate constraint and increased domain wall mobility in the released PZT films on polymers.

  4. High-Temperature, Thin-Film Ceramic Thermocouples Developed

    NASA Technical Reports Server (NTRS)

    Sayir, Ali; Blaha, Charles A.; Gonzalez, Jose M.

    2005-01-01

    To enable long-duration, more distant human and robotic missions for the Vision for Space Exploration, as well as safer, lighter, quieter, and more fuel efficient vehicles for aeronautics and space transportation, NASA is developing instrumentation and material technologies. The high-temperature capabilities of thin-film ceramic thermocouples are being explored at the NASA Glenn Research Center by the Sensors and Electronics Branch and the Ceramics Branch in partnership with Case Western Reserve University (CWRU). Glenn s Sensors and Electronics Branch is developing thin-film sensors for surface measurement of strain, temperature, heat flux, and surface flow in propulsion system research. Glenn s Ceramics Branch, in conjunction with CWRU, is developing structural and functional ceramic technology for aeropropulsion and space propulsion.

  5. Investigation of noble metal substrates and buffer layers for BiSrCaCuO thin films

    NASA Astrophysics Data System (ADS)

    Matthiesen, M. M.; Rubin, L. M.; Williams, K. E.; Rudman, D. A.

    Noble metal buffer layers and substrates for Bi2Sr2CaCu2O8 (BSCCO) films were investigated using bulk ceramic processing and thin-film techniques. Highly oriented, superconducting BSCCO films were fabricated on polycrystalline Ag substrates and on Ag/MgO and Ag/YSZ structures. Such films could not be produced on Au or Pt substrates under any annealing conditions. In addition, superconducting BSCCO films could not be produced on Ag/Al2O3, Ag/SiO2/Si, or Ag/(Haynes 230 alloy) structures using high annealing temperatures (870 C). However, oriented although poorly connected, superconducting BSCCO films were fabricated on Ag/Al2O3 structures by using lower annealing temperatures (820 C). Once lower processing temperatures are optimized, Ag may be usable as a buffer layer for BSCCO films.

  6. Passivation of high temperature superconductors

    NASA Technical Reports Server (NTRS)

    Vasquez, Richard P. (Inventor)

    1991-01-01

    The surface of high temperature superconductors such as YBa2Cu3O(7-x) are passivated by reacting the native Y, Ba and Cu metal ions with an anion such as sulfate or oxalate to form a surface film that is impervious to water and has a solubility in water of no more than 10(exp -3) M. The passivating treatment is preferably conducted by immersing the surface in dilute aqueous acid solution since more soluble species dissolve into the solution. The treatment does not degrade the superconducting properties of the bulk material.

  7. Nucleation of stable superconductivity in YBCO-films

    NASA Astrophysics Data System (ADS)

    Kötzler, J.

    By means of the linear dynamic conductivity, inductively measured on epitaxial films between 30mHz and 30 MHz, the transition line T g (B) to generic superconductivity is studied in fields between B=0 and 19T. It follows closely the melting line T m (B) described recently in terms of a blowout of thermal vortex loops in clean materials. The critical exponents of the correlation length and time near T g (B), however, enem to be dominated by some intrinsic disorder. Columnar defects produced by heavy-ion irradiation up to field-equivalent-doses of B ϕ =10T lead to adisappointing reduction of T g (B→0) while for B>B ϕ the generic line of the pristine film is recovered. These novel results are also discussed in terms of a loop-driven destruction of generic superconductivity.

  8. A Temperature-Stable Cryo-System for High-Temperature Superconducting MR In-Vivo Imaging

    PubMed Central

    Lin, In-Tsang; Yang, Hong-Chang; Chen, Jyh-Horng

    2013-01-01

    To perform a rat experiment using a high-temperature superconducting (HTS) surface resonator, a cryostat is essential to maintain the rat's temperature. In this work, a compact temperature-stable HTS cryo-system, keeping animal rectal temperature at 37.4°C for more than 3 hours, was successfully developed. With this HTS cryo-system, a 40-mm-diameter Bi2Sr2Ca2Cu3Ox (Bi-2223) surface resonator at 77 K was demonstrated in a 3-Tesla MRI system. The proton resonant frequency (PRF) method was employed to monitor the rat's temperature. Moreover, the capacity of MR thermometry in the HTS experiments was evaluated by correlating with data from independent fiber-optic sensor temperature measurements. The PRF thermal coefficient was derived as 0.03 rad/°C and the temperature-monitoring architecture can be implemented to upgrade the quality and safety in HTS experiments. The signal-to-noise ratio (SNR) of the HTS surface resonator at 77 K was higher than that of a professionally made copper surface resonator at 300 K, which has the same geometry, by a 3.79-fold SNR gain. Furthermore, the temperature-stable HTS cryo-system we developed can obtain stable SNR gain in every scan. A temperature-stable HTS cryo-system with an external air-blowing circulation system is demonstrated. PMID:23637936

  9. Comparison study of cable geometries and superconducting tape layouts for high-temperature superconductor cables

    NASA Astrophysics Data System (ADS)

    Ta, Wurui; Shao, Tianchong; Gao, Yuanwen

    2018-04-01

    High-temperature superconductor (HTS) rare-earth-barium-copper-oxide (REBCO) tapes are very promising for use in high-current cables. The cable geometry and the layout of the superconducting tapes are directly related to the performance of the HTS cable. In this paper, we use numerical methods to perform a comparison study of multiple-stage twisted stacked-tape cable (TSTC) conductors to find better cable structures that can both improve the critical current and minimize the alternating current (AC) losses of the cable. The sub-cable geometry is designed to have a stair-step shape. Three superconducting tape layouts are chosen and their transport performance and AC losses are evaluated. The magnetic field and current density profiles of the cables are obtained. The results show that arrangement of the superconducting tapes from the interior towards the exterior of the cable based on their critical current values in descending order can enhance the cable's transport capacity while significantly reducing the AC losses. These results imply that cable transport capacity improvements can be achieved by arranging the superconducting tapes in a manner consistent with the electromagnetic field distribution. Through comparison of the critical currents and AC losses of four types of HTS cables, we determine the best structural choice among these cables.

  10. Superconducting transmission line particle detector

    DOEpatents

    Gray, K.E.

    1988-07-28

    A microvertex particle detector for use in a high energy physic collider including a plurality of parallel superconducting thin film strips separated from a superconducting ground plane by an insulating layer to form a plurality of superconducting waveguides. The microvertex particle detector indicates passage of a charged subatomic particle by measuring a voltage pulse measured across a superconducting waveguide caused by the transition of the superconducting thin film strip from a superconducting to a non- superconducting state in response to the passage of a charged particle. A plurality of superconducting thin film strips in two orthogonal planes plus the slow electromagnetic wave propagating in a superconducting transmission line are used to resolve N/sup 2/ ambiguity of charged particle events. 6 figs.

  11. Superconducting transmission line particle detector

    DOEpatents

    Gray, Kenneth E.

    1989-01-01

    A microvertex particle detector for use in a high energy physic collider including a plurality of parallel superconducting thin film strips separated from a superconducting ground plane by an insulating layer to form a plurality of superconducting waveguides. The microvertex particle detector indicates passage of a charged subatomic particle by measuring a voltage pulse measured across a superconducting waveguide caused by the transition of the superconducting thin film strip from a superconducting to a non-superconducting state in response to the passage of a charged particle. A plurality of superconducting thin film strips in two orthogonal planes plus the slow electromagnetic wave propogating in a superconducting transmission line are used to resolve N.sup.2 ambiguity of charged particle events.

  12. Superconducting transmission line particle detector

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gray, K.E.

    A microvertex particle detector for use in a high energy physic collider including a plurality of parallel superconducting thin film strips separated from a superconducting ground plane by an insulating layer to form a plurality of superconducting waveguides. The microvertex particle detector indicates passage of a charged subatomic particle by measuring a voltage pulse measured across a superconducting waveguide caused by the transition of the superconducting thin film strip from a superconducting to a non- superconducting state in response to the passage of a charged particle. A plurality of superconducting thin film strips in two orthogonal planes plus the slowmore » electromagnetic wave propagating in a superconducting transmission line are used to resolve N/sup 2/ ambiguity of charged particle events. 6 figs.« less

  13. Transport properties of ultrathin BaFe1.84Co0.16As2 superconducting nanowires

    NASA Astrophysics Data System (ADS)

    Yuan, Pusheng; Xu, Zhongtang; Li, Chen; Quan, Baogang; Li, Junjie; Gu, Changzhi; Ma, Yanwei

    2018-07-01

    Superconducting nanowire single-photon detectors (SNSPDs) have an absolute advantage over other types of single-photon detectors, except for the low operating temperature. Therefore, much effort has been devoted to finding high-temperature superconducting materials that are suitable for preparing SNSPDs. Copper-based and MgB2 ultrathin superconducting nanowires have already been reported. However, the transport properties of iron-based ultrathin superconducting nanowires have not been studied. In this work, a 10 nm thick × 200 nm wide × 30 μm long high-quality superconducting nanowire was fabricated from ultrathin BaFe1.84Co0.16As2 films by a lift-off process. The precursor BaFe1.84Co0.16As2 film with a thickness of 10 nm and root-mean-square roughness of 1 nm was grown on CaF2 substrates by pulsed laser deposition. The nanowire shows a high superconducting critical temperature {T}{{c}}{{zero}} = 20 K with a narrow transition width of ΔT = 2.5 K and exhibits a high critical current density J c of 1.8 × 107 A cm-2 at 10 K. These results of ultrathin BaFe1.84Co0.16As2 nanowire will attract interest in electronic applications, including SNSPDs.

  14. Plasma-enhanced pulsed-laser deposition of single-crystalline M o2C ultrathin superconducting films

    NASA Astrophysics Data System (ADS)

    Zhang, Fan; Zhang, Zhi; Wang, Huichao; Chan, Cheuk Ho; Chan, Ngai Yui; Chen, Xin Xin; Dai, Ji-Yan

    2017-08-01

    Transition-metal carbides (TMCs) possess many intriguing properties and inspiring application potentials, and recently the study of a two-dimensional form of TMCs has attracted great attention. Herein, we report successful fabrication of continuous M o2C ultrathin single-crystalline films at 700 ∘C with an approach of plasma-enhanced pulsed-laser deposition. By sophisticated structural analyses, the M o2C films are characterized as single crystal with a rarely reported face-centered cubic structure. In further electrical transport measurements, superconductivity observed in the M o2C films demonstrates a typical two-dimensional feature, which is consistent with Berezinskii-Kosterlitz-Thouless transitions. Besides, large upper critical magnetic fields are discovered in this system. Our work offers an approach to grow large-area and high-quality TMCs at relatively low temperatures. This study may stimulate more related investigations on the synthesis, characterizations, and applications of two-dimensional TMCs.

  15. The creation of high-temperature superconducting cables of megawatt range in Russia

    NASA Astrophysics Data System (ADS)

    Sytnikov, V. E.; Bemert, S. E.; Krivetsky, I. V.; Romashov, M. A.; Popov, D. A.; Fedotov, E. V.; Komandenko, O. V.

    2015-12-01

    Urgent problems of the power industry in the 21st century require the creation of smart energy systems, providing a high effectiveness of generation, transmission, and consumption of electric power. Simultaneously, the requirements for controllability of power systems and ecological and resource-saving characteristics at all stages of production and distribution of electric power are increased. One of the decision methods of many problems of the power industry is the development of new high-efficiency electrical equipment for smart power systems based on superconducting technologies to ensure a qualitatively new level of functioning of the electric power industry. The intensive research and development of new types of electrical devices based on superconductors are being carried out in many industrialized advanced countries. Interest in such developments has especially increased in recent years owing to the discovery of so-called high-temperature superconductors (HTS) that do not require complicated and expensive cooling devices. Such devices can operate at cooling by inexpensive and easily accessible liquid nitrogen. Taking into account the obvious advantages of superconducting cable lines for the transmission of large power flows through an electrical network, as compared with conventional cables, the Federal Grid Company of Unified Energy System (JSC FGC UES) initiated a research and development program including the creation of superconducting HTS AC and DC cable lines. Two cable lines for the transmitted power of 50 MVA/MW at 20 kV were manufactured and tested within the framework of the program.

  16. High-Density Superconducting Cables for Advanced ACTPol

    NASA Technical Reports Server (NTRS)

    Pappas, C. G.; Austermann, J.; Beall, J. A.; Duff, S. M.; Gallardo, P. A.; Grace, E.; Henderson, S. W.; Ho, S. P.; Koopman, B. J.; Li, D.; hide

    2016-01-01

    Advanced ACTPol (AdvACT) is an upcoming Atacama Cosmology Telescope (ACT) receiver upgrade, scheduled to deploy in 2016, that will allow measure- ment of the cosmic microwave background polarization and temperature to the highest precision yet with ACT. The AdvACT increase in sensitivity is partly provided by an increase in the number of transition-edge sensors (TESes) per array by up to a factor of two over the current ACTPol receiver detector arrays. The high-density AdvACT TES arrays require 70 µ m pitch superconducting flexible cables (flex) to connect the detec- tor wafer to the first-stage readout electronics. Here, we present the flex fabrication process and test results. For the flex wiring layer, we use a 400-nm-thick sputtered alu- minum film. In the center of the cable, the wiring is supported by a polyimide substrate, which smoothly transitions to a bare (uncoated with polyimide) silicon substrate at the ends of the cable for a robust wedge wire-bonding interface. Tests on the first batch of flex made for the first AdvACT array show that the flex will meet the requirements for AdvACT, with a superconducting critical current above 1 mA at 500 mK, resilience to mechanical and cryogenic stress, and a room temperature yield of 97%.

  17. Superconducting magnesium diboride films with Tc≈24 K grown by pulsed laser deposition with in situ anneal

    NASA Astrophysics Data System (ADS)

    Christen, H. M.; Zhai, H. Y.; Cantoni, C.; Paranthaman, M.; Sales, B. C.; Rouleau, C.; Norton, D. P.; Christen, D. K.; Lowndes, D. H.

    2001-05-01

    Thin superconducting films of magnesium diboride (MgB 2) with T c≈24 K were prepared on various oxide substrates by pulsed laser deposition followed by an in situ anneal. A systematic study of the influence of various in situ annealing parameters shows an optimum temperature of about 600°C in a background of 0.7 atm of Ar/4%H 2 for layers consisting of a mixture of magnesium and boron. Contrary to ex situ approaches (e.g. reacting boron films with magnesium vapor at ≈900°C), these films are processed at a temperature at which MgB 2 does not decompose rapidly even in vacuum. This may prove enabling in the formation of multilayers, junctions, and epitaxial films in future work. Issues related to the improvement of these films and to the possible in situ growth of MgB 2 at elevated temperature are discussed.

  18. A compact, high temperature nuclear magnetic resonance probe for use in a narrow-bore superconducting magnet

    NASA Astrophysics Data System (ADS)

    Adler, Stuart B.; Michaels, James N.; Reimer, Jeffrey A.

    1990-11-01

    The design of a nuclear magnetic resonance (NMR) probe is reported, that can be used in narrow-bore superconducting solenoids for the observation of nuclear induction at high temperatures. The probe is compact, highly sensitive, and stable in continuous operation at temperatures up to 1050 C. The essential feature of the probe is a water-cooled NMR coil that contains the sample-furnace; this design maximizes sensitivity and circuit stability by maintaining the probe electronics at ambient temperature. The design is demonstrated by showing high temperature O-17 NMR spectra and relaxation measurements in solid barium bismuth oxide and yttria-stabilized zirconia.

  19. Numerical modelling of dynamic resistance in high-temperature superconducting coated-conductor wires

    NASA Astrophysics Data System (ADS)

    Ainslie, Mark D.; Bumby, Chris W.; Jiang, Zhenan; Toyomoto, Ryuki; Amemiya, Naoyuki

    2018-07-01

    The use of superconducting wire within AC power systems is complicated by the dissipative interactions that occur when a superconductor is exposed to an alternating current and/or magnetic field, giving rise to a superconducting AC loss caused by the motion of vortices within the superconducting material. When a superconductor is exposed to an alternating field whilst carrying a constant DC transport current, a DC electrical resistance can be observed, commonly referred to as ‘dynamic resistance.’ Dynamic resistance is relevant to many potential high-temperature superconducting (HTS) applications and has been identified as critical to understanding the operating mechanism of HTS flux pump devices. In this paper, a 2D numerical model based on the finite-element method and implementing the H -formulation is used to calculate the dynamic resistance and total AC loss in a coated-conductor HTS wire carrying an arbitrary DC transport current and exposed to background AC magnetic fields up to 100 mT. The measured angular dependence of the superconducting properties of the wire are used as input data, and the model is validated using experimental data for magnetic fields perpendicular to the plane of the wire, as well as at angles of 30° and 60° to this axis. The model is used to obtain insights into the characteristics of such dynamic resistance, including its relationship with the applied current and field, the wire’s superconducting properties, the threshold field above which dynamic resistance is generated and the flux-flow resistance that arises when the total driven transport current exceeds the field-dependent critical current, I c( B ), of the wire. It is shown that the dynamic resistance can be mostly determined by the perpendicular field component with subtle differences determined by the angular dependence of the superconducting properties of the wire. The dynamic resistance in parallel fields is essentially negligible until J c is exceeded and flux

  20. Vacuum low-temperature superconductivity is the essence of superconductivity - Atomic New Theory

    NASA Astrophysics Data System (ADS)

    Yongquan, Han

    2010-10-01

    The universe when the temperature closest to the Big Bang the temperature should be nuclear. Because, after the big bang, instant formation of atoms, nuclei and electrons between the absolute vacuum, the nucleus can not emit energy. (Radioactive elements, except in fact, radiation Yuan Su limited power emitted) which causes atomic nuclei and external temperature difference are so enormous that a large temperature difference reasons, all external particles became closer to the nucleus, affect the motion of electrons. When the conductor conductivity and thus affect the conductivity, the formation of resistance. Assumption that no particles affect the motion of electrons (except outside the nucleus) to form a potential difference will not change after the vector form, is now talking about the phenomenon of superconductivity, and then to introduce general, the gap between atoms in molecules or between small, valence electron number of high temperature superconducting conductors. This theory of atomic nuclei, but also explain the atomic and hydrogen bombs can remain after an explosion Why can release enormous energy reasons. Can also explain the ``super flow'' phenomenon. natural world. Tel 13241375685

  1. Superconducting critical temperature under pressure

    NASA Astrophysics Data System (ADS)

    González-Pedreros, G. I.; Baquero, R.

    2018-05-01

    The present record on the critical temperature of a superconductor is held by sulfur hydride (approx. 200 K) under very high pressure (approx. 56 GPa.). As a consequence, the dependence of the superconducting critical temperature on pressure became a subject of great interest and a high number of papers on of different aspects of this subject have been published in the scientific literature since. In this paper, we calculate the superconducting critical temperature as a function of pressure, Tc(P), by a simple method. Our method is based on the functional derivative of the critical temperature with the Eliashberg function, δTc(P)/δα2F(ω). We obtain the needed coulomb electron-electron repulsion parameter, μ*(P) at each pressure in a consistent way by fitting it to the corresponding Tc using the linearized Migdal-Eliashberg equation. This method requires as input the knowledge of Tc at the starting pressure only. It applies to superconductors for which the Migdal-Eliashberg equations hold. We study Al and β - Sn two weak-coupling low-Tc superconductors and Nb, the strong coupling element with the highest critical temperature. For Al, our results for Tc(P) show an excellent agreement with the calculations of Profeta et al. which are known to agree well with experiment. For β - Sn and Nb, we found a good agreement with the experimental measurements reported in several works. This method has also been applied successfully to PdH elsewhere. Our method is simple, computationally light and gives very accurate results.

  2. Preparation and substrate reactions of superconducting Y-Ba-Cu-O films

    NASA Astrophysics Data System (ADS)

    Gurvitch, M.; Fiory, A. T.

    1987-09-01

    Multiple metal-target dc magnetron sputter deposition of a metallic YBa2Cu3 alloy in pure Ar followed by ex situ oxygen annealing was used to prepare superconducting films on various substrates. This work particularly examines film-substrate reactions which are degrading to superconductivity. Better superconductors were obtained using predeposited buffer layers, notably on cubic zirconia and MgO substrates covered with Ag and Nb. Best films have Tc = 80 K, metallic resistivities with a resistance ratio of about 2, and a critical current density of greater than about 10 kA/sq cm at 4.2 K.

  3. Fabrication and chemical composition of RF magnetron sputtered Tl-Ca-Ba-Cu-O high Tc superconducting thin films

    NASA Technical Reports Server (NTRS)

    Subramanyam, G.; Radpour, F.; Kapoor, V. J.; Lemon, G. H.

    1990-01-01

    The preparation of TlCaBaCuO superconducting thin films on (100) SrTiO3 substrates is described, and the results of their characterization are presented. Sintering and annealing the thin films in a Tl-rich ambient yielded superconductivity with a Tc of 107 K. The results of an XPS study support two possible mechanisms for the creation of holes in the TlCaBaCuO compound: (1) partial substitution of Ca(2+) for Tl(3+), resulting in hole creation, and (2) charge transfer from Tl(3+) to the CuO layers, resulting in a Tl valence between +3 and +1.

  4. Preparation and Analysis of Platinum Thin Films for High Temperature Sensor Applications

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D.; Laster, Kimala L. H.

    2005-01-01

    A study has been made of platinum thin films for application as high temperature resistive sensors. To support NASA Glenn Research Center s high temperature thin film sensor effort, a magnetron sputtering system was installed recently in the GRC Microsystems Fabrication Clean Room Facility. Several samples of platinum films were prepared using various system parameters to establish run conditions. These films were characterized with the intended application of being used as resistive sensing elements, either for temperature or strain measurement. The resistances of several patterned sensors were monitored to document the effect of changes in parameters of deposition and annealing. The parameters were optimized for uniformity and intrinsic strain. The evaporation of platinum via oxidation during annealing over 900 C was documented, and a model for the process developed. The film adhesion was explored on films annealed to 1000 C with various bondcoats on fused quartz and alumina. From this compiled data, a list of optimal parameters and characteristics determined for patterned platinum thin films is given.

  5. Plasmon and exciton superconductivity mechanisms in layered structures

    NASA Technical Reports Server (NTRS)

    Gabovich, A. M.; Pashitskiy, E. A.; Uvarova, S. K.

    1977-01-01

    Plasmon and exciton superconductivity mechanisms are discussed. Superconductivity in a three layer metal semiconductor metal and insulator semimetal insulator sandwich structure was described in terms of the temperature dependent Green function of the longitudinal (Coulomb) field. The dependences of the superconducting transition temperature on structure parameters were obtained. In a semiconducting film, as a result of interactions of degenerate free carriers with excitons, superconductivity exists only in a certain range of parameter values, and the corresponding critical temperature is much lower than in the plasmon mechanism of superconductivity.

  6. High-temperature superconducting phase of HBr under pressure predicted by first-principles calculations

    NASA Astrophysics Data System (ADS)

    Gu, Qinyan; Lu, Pengchao; Xia, Kang; Sun, Jian; Xing, Dingyu

    2017-08-01

    The high pressure phases of HBr are explored with an ab initio crystal structure search. By taking into account the contribution of zero-point energy (ZPE), we find that the P 4 /n m m phase of HBr is thermodynamically stable in the pressure range from 150 to 200 GPa. The superconducting critical temperature (Tc) of P 4 /n m m HBr is evaluated to be around 73 K at 170 GPa, which is the highest record so far among binary halogen hydrides. Its Tc can be further raised to around 95K under 170 GPa if half of the bromine atoms in the P 4 /n m m HBr are substituted by the lighter chlorine atoms. Our study shows that, in addition to lower mass, higher coordination number, shorter bonds, and more highly symmetric environment for the hydrogen atoms are important factors to enhance the superconductivity in hydrides.

  7. Superconducting transmission line particle detector

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gray, K.E.

    This paper describes a microvertex particle detector for use in a high energy physic collider including a plurality of parallel superconducting thin film strips separated from a superconducting ground plane by an insulating layer to form a plurality of superconducting waveguides. The microvertex particle detector indicates passage of a charged subatomic particle by measuring a voltage pulse measured across a superconducting waveguide caused by the transition of the superconducting thin film strip from a superconducting to a non-superconducting state in response to the passage of a charged particle. A plurality of superconducting thin film strips in two orthogonal planes plusmore » the slow electromagnetic wave propogating in a superconducting transmission line are used to resolve N{sup 2} ambiguity of charged particle events.« less

  8. Preparation and Properties of High-T(sub c) Bi-Pb-Sr-Ca-Cu-O Thick Film Superconductors on YSZ Substrates

    NASA Technical Reports Server (NTRS)

    Hooker, Matthew W.

    1996-01-01

    An evaluation of four firing profiles was performed to determine the optimum processing conditions for producing high-T(sub c) Bi-Pb-Sr-Ca-Cu-O thick films on yttria-stabilized zirconia substrates. Using these four profiles, the effects of sintering temperatures of 830-850 C and soak times of 0.5 to 12 hours were examined. In this study, T-c, zero values of 100 K were obtained using a firing profile in which the films were sintered for 1.5 to 2 hours at 840 to 845 C and then quenched to room temperature. X-ray diffraction analyses of these specimens confirmed the presence of the high-T(sub c) phase. Films which were similarly fired and furnace cooled from the peak processing temperature exhibited a two-step superconductive transition to zero resistance, with T-c,zero values ranging from 85 to 92 K. The other firing profiles evaluated in this investigation yielded specimens which either exhibited critical transition temperatures below 90 K or did not exhibit a superconductive transition above 77 K.

  9. Synthesis and Superconducting Properties of the High Transition Temperature Superconductor BARIUM(1-X) Potassium(x)bismuth Trioxide

    NASA Astrophysics Data System (ADS)

    Folkerts, Timothy John

    A systematic study of Ba_ {1-x}K_ xBiO_3 (BKBO) in the range 0 <= x <= 0.5 is presented in this work, concentrating especially on the superconducting range 0.35 <= x <= 0.5. Samples were studied using powder x-ray diffraction, thermal analysis, magnetization as a function of both temperature and applied field, and resistivity as a function of both temperature and pressure. Particular effort went into producing high quality samples. This proved difficult because of the moisture sensitivity of the starting materials and of the intermediate products, and because of the tendency of the material to phase separate into regions of varying potassium concentrations. Once synthesis techniques were developed which allowed production of high quality samples, systematic studies could be undertaken. The sharpness of the powder x-ray diffraction peaks, along with least squares fits, were used to determine phase purity and to exclude poor quality samples. The lattice parameters of the remaining samples were seen to obey Vegard's Law. Magnetization studies as a function of temperature were used to determine the superconducting transition temperature (T_ c). Onsets for superconductivity were observed as high as 30 K for samples with broad transitions, although samples with sharp transitions had a maximum T_ c of only 28.8 K. This high T_ c, as well as the crystal structure clearly link BKBO to the high T_ c superconductors. Hysteresis measurements were undertaken to determine the upper and lower critical fields, critical currents, and the normal state susceptibility. Estimates of the coherence length, penetration depth, and the electronic contribution to the specific heat based on these measurements agree well with BCS theory. Resistivity data are quit dependent on sample quality, as well as potassium doping. At low potassium concentrations, the material is semiconducting, while at higher potassium concentrations where the material is superconducting, the normal state resistivity of

  10. High-temperature adhesives for bonding polyimide film. [bonding Kapton film for solar sails

    NASA Technical Reports Server (NTRS)

    St.clair, A. K.; Slemp, W. S.; St.clair, T. L.

    1980-01-01

    Experimental polyimide resins were developed and evaluated as potential high temperature adhesives for bonding Kapton polyimide film. Lap shear strengths of Kapton/Kapton bonds were obtained as a function of test temperature, adherend thickness, and long term aging at 575 K (575 F) in vacuum. Glass transition temperatures of the polyimide/"Kapton" bondlines were monitored by thermomechanical analysis.

  11. Superconducting thin-film gyroscope readout for Gravity Probe-B

    NASA Technical Reports Server (NTRS)

    Lockhart, James M.; Cheung, W. Stephen; Gill, Dale K.

    1987-01-01

    The high-resolution gyroscope readout system for the Stanford Gravity Probe-B experiment, whose purpose is to measure two general relativistic precessions of gyroscopes in earth orbit, is described. In order to achieve the required resolution in angle (0.001 arcsec), the readout system combines high-precision mechanical fabrication and measurement techniques with superconducting thin-film technology, ultralow magnetic fields, and SQUID detectors. The system design, performance limits achievable with current technology, and the results of fabrication and laboratory testing to date are discussed.

  12. Impact of oxygen diffusion on superconductivity in YBa2Cu3O7 -δ thin films studied by positron annihilation spectroscopy

    NASA Astrophysics Data System (ADS)

    Reiner, M.; Gigl, T.; Jany, R.; Hammerl, G.; Hugenschmidt, C.

    2018-04-01

    The oxygen deficiency δ in YBa2Cu3O7 -δ (YBCO) plays a crucial role for affecting high-temperature superconductivity. We apply (coincident) Doppler broadening spectroscopy of the electron-positron annihilation line to study in situ the temperature dependence of the oxygen concentration and its depth profile in single crystalline YBCO film grown on SrTiO3 (STO) substrates. The oxygen diffusion during tempering is found to lead to a distinct depth dependence of δ , which is not accessible using x-ray diffraction. A steady state reached within a few minutes is defined by both, the oxygen exchange at the surface and at the interface to the STO substrate. Moreover, we reveal the depth-dependent critical temperature Tc in the as prepared and tempered YBCO film.

  13. Magnetic pinning in a superconducting film by a ferromagnetic layer with stripe domains

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mancusi, D.; Di Giorgio, C.; Bobba, F.

    2014-10-31

    A magnetic study of superconductor/ferromagnet bilayers was performed by hysteresis loops and temperature-dependent magnetization measurements. The superconductor/ferromagnet bilayers consist of a Nb film deposited on a Py film with weak perpendicular magnetic anisotropy. By comparing the temperature-dependent magnetization data obtained on samples with different ferromagnetic layer thickness, a decrease of the magnetic pinning with increasing thickness of the ferromagnetic layer has been found. This is confirmed by the reduction of the Nb film critical current density at low fields extracted by using the magnetic irreversibility of the hysteresis loops. As the ferromagnetic layer exhibits a magnetic structure with stripe domains,more » whose width increases for increasing thickness as observed by magnetic force microscopy (MFM) measurements, we relate the reduction of the superconducting critical current in samples with thicker ferromagnetic layers to a weaker interaction between the vortices guided by the underlying magnetic template.« less

  14. The creation of high-temperature superconducting cables of megawatt range in Russia

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sytnikov, V. E., E-mail: vsytnikov@gmail.com; Bemert, S. E.; Krivetsky, I. V.

    Urgent problems of the power industry in the 21st century require the creation of smart energy systems, providing a high effectiveness of generation, transmission, and consumption of electric power. Simultaneously, the requirements for controllability of power systems and ecological and resource-saving characteristics at all stages of production and distribution of electric power are increased. One of the decision methods of many problems of the power industry is the development of new high-efficiency electrical equipment for smart power systems based on superconducting technologies to ensure a qualitatively new level of functioning of the electric power industry. The intensive research and developmentmore » of new types of electrical devices based on superconductors are being carried out in many industrialized advanced countries. Interest in such developments has especially increased in recent years owing to the discovery of so-called high-temperature superconductors (HTS) that do not require complicated and expensive cooling devices. Such devices can operate at cooling by inexpensive and easily accessible liquid nitrogen. Taking into account the obvious advantages of superconducting cable lines for the transmission of large power flows through an electrical network, as compared with conventional cables, the Federal Grid Company of Unified Energy System (JSC FGC UES) initiated a research and development program including the creation of superconducting HTS AC and DC cable lines. Two cable lines for the transmitted power of 50 MVA/MW at 20 kV were manufactured and tested within the framework of the program.« less

  15. Experiment results of high temperature superconducting Maglev vehicle

    NASA Astrophysics Data System (ADS)

    Wang, J. S.; Wang, S. Y.; Ren, Z. Y.; Jiang, H.; Zhu, M.; Wang, X. R.; Shen, X. M.; Song, H. H.

    2003-04-01

    The first man-loading high temperature superconducting (HTS) magnetic levitation (Maglev) test vehicle in the world has normally operated over one year after its birth on December 31, 2000. Heretofore over 23 000 passengers have taken the vehicle, and it operates very well from first running to now. The HTS Maglev vehicle is over guideway, which consists of two parallel permanent magnetic tracks. The levitation force of the entire Maglev vehicle is measured. Three times measurement results on December 24, 2000, July 1, 2001, and December 24, 2001 are reported respectively, it will be seen from this that the levitation forces do not change nearly after long running. Total levitation force of entire vehicle is 1050 kg at the 8 mm net levitation gap, which the gap between the bottom of liquid nitrogen vessels and guideway face. A measuring equipment of the guidance force of the entire Maglev vehicle is designed and manufactured. The guidance force of the vehicle is obtained by the equipment.

  16. Test of a Nb thin film superconducting detector

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lacquaniti, V.; Maggi, S.; Menichetti, E.

    1993-08-01

    Results from tests of several Nb thin film microstrip superconducting detectors are reported. A preliminary measurement of critical radius of the hot spot generated by 5 MeV [alpha]-particles is compared with simple model predictions.

  17. Superconducting YBa2Cu3O7- δ Thin Film Detectors for Picosecond THz Pulses

    NASA Astrophysics Data System (ADS)

    Probst, P.; Scheuring, A.; Hofherr, M.; Wünsch, S.; Il'in, K.; Semenov, A.; Hübers, H.-W.; Judin, V.; Müller, A.-S.; Hänisch, J.; Holzapfel, B.; Siegel, M.

    2012-06-01

    Ultra-fast THz detectors from superconducting YBa2Cu3O7- δ (YBCO) thin films were developed to monitor picosecond THz pulses. YBCO thin films were optimized by the introduction of CeO2 and PrBaCuO buffer layers. The transition temperature of 10 nm thick films reaches 79 K. A 15 nm thick YBCO microbridge (transition temperature—83 K, critical current density at 77 K—2.4 MA/cm2) embedded in a planar log-spiral antenna was used to detect pulsed THz radiation of the ANKA storage ring. First time resolved measurements of the multi-bunch filling pattern are presented.

  18. Pulsed Laser Deposition of High Temperature Protonic Films

    NASA Technical Reports Server (NTRS)

    Dynys, Fred W.; Berger, M. H.; Sayir, Ali

    2006-01-01

    Pulsed laser deposition has been used to fabricate nanostructured BaCe(0.85)Y(0.15)O3- sigma) films. Protonic conduction of fabricated BaCe(0.85)Y(0.15)O(3-sigma) films was compared to sintered BaCe(0.85)Y(0.15)O(3-sigma). Sintered samples and laser targets were prepared by sintering BaCe(0.85)Y(0.15)O(3-sigma) powders derived by solid state synthesis. Films 1 to 8 micron thick were deposited by KrF excimer laser on porous Al2O3 substrates. Thin films were fabricated at deposition temperatures of 700 to 950 C at O2 pressures up to 200 mTorr using laser pulse energies of 0.45 - 0.95 J. Fabricated films were characterized by X-ray diffraction, electron microscopy and electrical impedance spectroscopy. Single phase BaCe(0.85)Y(0.15)O(3-sigma) films with a columnar growth morphology are observed with preferred crystal growth along the [100] or [001] direction. Results indicate [100] growth dependence upon laser pulse energy. Electrical conductivity of bulk samples produced by solid state sintering and thin film samples were measured over a temperature range of 100 C to 900 C. Electrical conduction behavior was dependent upon film deposition temperature. Maximum conductivity occurs at deposition temperature of 900 oC; the electrical conductivity exceeds the sintered specimen. All other deposited films exhibit a lower electrical conductivity than the sintered specimen. Activation energy for electrical conduction showed dependence upon deposition temperature, it varied

  19. Effects of Surface Electron Doping and Substrate on the Superconductivity of Epitaxial FeSe Films.

    PubMed

    Zhang, W H; Liu, X; Wen, C H P; Peng, R; Tan, S Y; Xie, B P; Zhang, T; Feng, D L

    2016-03-09

    Superconductivity in FeSe is greatly enhanced in films grown on SrTiO3 substrates, although the mechanism behind remains unclear. Recently, surface potassium (K) doping has also proven able to enhance the superconductivity of FeSe. Here, by using scanning tunneling microscopy, we compare the K doping dependence of the superconductivity in FeSe films grown on two substrates: SrTiO3 (001) and graphitized SiC (0001). For thick films (20 unit cells (UC)), the optimized superconducting (SC) gaps are of similar size (∼9 meV) regardless of the substrate. However, when the thickness is reduced to a few UC, the optimized SC gap is increased up to ∼15 meV for films on SrTiO3, whereas it remains unchanged for films on SiC. This clearly indicates that the FeSe/SrTiO3 interface can further enhance the superconductivity, beyond merely doping electrons. Intriguingly, we found that this interface enhancement decays exponentially as the thickness increases, with a decay length of 2.4 UC, which is much shorter than the length scale for relaxation of the lattice strain, pointing to interfacial electron-phonon coupling as the likely origin.

  20. Piezoresistivity of Resin-Impregnated Carbon Nanotube Film at High Temperatures.

    PubMed

    Li, Min; Zuo, Tianyi; Wang, Shaokai; Gu, Yizhuo; Gao, Limin; Li, Yanxia; Zhang, Zuoguang

    2018-06-13

    This paper presents the development of a continuous carbon nanotube (CNT) composite film sensor with a strain detecting range of 0-2% for structural composites. The strain-dependent resistance responses of continuous CNT film and its resin-impregnated composite films were investigated at temperatures as high as 200 °C. The results manifest that impregnation with resin leads to a much larger gauge factor than pristine film. Both the pristine and composite films show an increase in resistivity with increasing temperature. For different composite films, the ordering of gauge factors is consistent with that of the matrix moduli. This indicates that a resin matrix with higher modulus and strong interactions between CNTs/CNT bundles and the resin matrix are beneficial for enhancing the piezoresistive effect. The CNT/PAA composite film has a gauge factor of 4.3 at 150 °C, an order of magnitude higher than the metal foil sensor. Therefore, the CNT composite films have great potential for simultaneous application for reinforcement and as strain sensor to realise a multifunctional composite. © 2018 IOP Publishing Ltd.

  1. Microwave Conductivity of Laser Ablated YBa2Cu3O7-delta Superconducting Films and Its Relation to Microstrip Transmission Line Performance

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Warner, J. D.; Chorey, C. M.; Ebihara, B. T.; Romanofsky, R. R.; Heinen, V. O.

    1990-01-01

    We report on the values of the microwave conductivity in the normal (sigma(subN)) and superconducting (sigma*=sigma(sub1)-j sigma(sub2)) states of two laser ablated YBa2CU3O7(sigma) thin films at 35 GHz, in the temperature range from 20 to 300 K. The films 0.7 and 0.4 micrometers) were deposited on LaA10(sub3) by laser ablation. The conductivity was obtained from the microwave power transmitted through the films and assuming a two-fluid model. Values of sigma(subN) approximately 2.3 X 10(exp5) S/m at room temperature for both films, and of sigma(sub1) approximately 6.3 X 10(exp5) and 4.6 X 10(exp5) S/m at temperatures around 80 K were obtained for the 0.7 and 0.4 micrometer films respectively. For sigma(sub2) values of 4.9 X 10(exp6) and 5.4 X 10(exp6) S/m were obtained for the 0.7 and 0.4 micrometer films at 80 K. The expected conductor losses and Q-factor of a superconducting ring resonator were calculated using these conductivity values. The theoretical values were then compared with the experimental results obtained for a resonator fabricated from one of these films.

  2. Ultra-Low Heat-Leak, High-Temperature Superconducting Current Leads for Space Applications

    NASA Technical Reports Server (NTRS)

    Rey, Christopher M.

    2013-01-01

    NASA Goddard Space Flight Center has a need for current leads used in an adiabatic demagnetization refrigerator (ADR) for space applications. These leads must comply with stringent requirements such as a heat leak of approximately 100 W or less while conducting up to 10 A of electric current, from more than 90 K down to 10 K. Additionally, a length constraint of < 300 mm length and < 50 mm diameter is to be maintained. The need for these current leads was addressed by developing a superconducting hybrid lead. This hybrid lead comprises two different high-temperature superconducting (HTS) conductors bonded together at a thermally and electrically determined optimum point along the length of the current lead. By taking advantage of material properties of each conductor type, employing advanced fabrication techniques, and taking advantage of novel insulation materials, the company was able to develop and fabricate the lightweight, low heat-leak leads currently to NASA's specs.

  3. Synthesis and characterization of high-T(sub c) screen-printed Y-Ba-Cu-O films on alumina

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Simons, Rainee N.; Farrell, D. E.

    1988-01-01

    Thick films of YBa2Cu3O(sub 7-x) have been deposited on highly polished alumina substrates by the screen printing technique. To optimize the post-printing heat treatment, the films were baked at various temperatures for different lengths of time and oxygen-annealed at a lower temperature. The resulting films were characterized by electrical resistivity measurements, x-ray diffraction, and optical and scanning electron microscopy. Properties of the films were found to be highly sensitive to the post-printing thermal treatment. Films baked for 15 min at 1000 C in oxygen were hard, adherent, near single phase, and superconducting with T(sub c)(onset) approx 96 K, T(sub c)(zero) approx 66 K and Delta T sub c (10 to 90 percent) approx 10 K.

  4. Investigation of superconducting interactions and amorphous semiconductors

    NASA Technical Reports Server (NTRS)

    Janocko, M. A.; Jones, C. K.; Gavaler, J. R.; Deis, D. W.; Ashkin, M.; Mathur, M. P.; Bauerle, J. E.

    1972-01-01

    Research papers on superconducting interactions and properties and on amorphous materials are presented. The search for new superconductors with improved properties was largely concentrated on the study of properties of thin films. An experimental investigation of interaction mechanisms revealed no new superconductivity mechanism. The properties of high transition temperature, type 2 materials prepared in thin film form were studied. A pulsed field solenoid capable of providing fields in excess of 300 k0e was developed. Preliminary X-ray measurements were made of V3Si to determine the behavior of cell constant deformation versus pressure up to 98 kilobars. The electrical properties of amorphous semiconducting materials and bulk and thin film devices, and of amorphous magnetic materials were investigated for developing radiation hard, inexpensive switches and memory elements.

  5. Imaging the electron-boson coupling in superconducting FeSe films using a scanning tunneling microscope.

    PubMed

    Song, Can-Li; Wang, Yi-Lin; Jiang, Ye-Ping; Li, Zhi; Wang, Lili; He, Ke; Chen, Xi; Hoffman, Jennifer E; Ma, Xu-Cun; Xue, Qi-Kun

    2014-02-07

    Scanning tunneling spectroscopy has been used to reveal signatures of a bosonic mode in the local quasiparticle density of states of superconducting FeSe films. The mode appears below Tc as a "dip-hump" feature at energy Ω∼4.7kBTc beyond the superconducting gap Δ. Spectra on strained regions of the FeSe films reveal simultaneous decreases in Δ and Ω. This contrasts with all previous reports on other high-Tc superconductors, where Δ locally anticorrelates with Ω. A local strong coupling model is found to reconcile the discrepancy well, and to provide a unified picture of the electron-boson coupling in unconventional superconductors.

  6. Electro-deposition of superconductor oxide films

    DOEpatents

    Bhattacharya, Raghu N.

    2001-01-01

    Methods for preparing high quality superconducting oxide precursors which are well suited for further oxidation and annealing to form superconducting oxide films. The method comprises forming a multilayered superconducting precursor on a substrate by providing an electrodeposition bath comprising an electrolyte medium and a substrate electrode, and providing to the bath a plurality of precursor metal salts which are capable of exhibiting superconducting properties upon subsequent treatment. The superconducting precursor is then formed by electrodepositing a first electrodeposited (ED) layer onto the substrate electrode, followed by depositing a layer of silver onto the first electrodeposited (ED) layer, and then electrodepositing a second electrodeposited (ED) layer onto the Ag layer. The multilayered superconducting precursor is suitable for oxidation at a sufficient annealing temperature in air or an oxygen-containing atmosphere to form a crystalline superconducting oxide film.

  7. Finding new superconductors: the spin-fluctuation gateway to high Tc and possible room temperature superconductivity.

    PubMed

    Pines, David

    2013-10-24

    We propose an experiment-based strategy for finding new high transition temperature superconductors that is based on the well-established spin fluctuation magnetic gateway to superconductivity in which the attractive quasiparticle interaction needed for superconductivity comes from their coupling to dynamical spin fluctuations originating in the proximity of the material to an antiferromagnetic state. We show how lessons learned by combining the results of almost three decades of intensive experimental and theoretical study of the cuprates with those found in the decade-long study of a strikingly similar family of unconventional heavy electron superconductors, the 115 materials, can prove helpful in carrying out that search. We conclude that, since Tc in these materials scales approximately with the strength of the interaction, J, between the nearest neighbor local moments in their parent antiferromagnetic state, there may not be a magnetic ceiling that would prevent one from discovering a room temperature superconductor.

  8. Spin-orbit-coupled superconductivity

    PubMed Central

    Lo, Shun-Tsung; Lin, Shih-Wei; Wang, Yi-Ting; Lin, Sheng-Di; Liang, C.-T.

    2014-01-01

    Superconductivity and spin-orbit (SO) interaction have been two separate emerging fields until very recently that the correlation between them seemed to be observed. However, previous experiments concerning SO coupling are performed far beyond the superconducting state and thus a direct demonstration of how SO coupling affects superconductivity remains elusive. Here we investigate the SO coupling in the critical region of superconducting transition on Al nanofilms, in which the strength of disorder and spin relaxation by SO coupling are changed by varying the film thickness. At temperatures T sufficiently above the superconducting critical temperature Tc, clear signature of SO coupling reveals itself in showing a magneto-resistivity peak. When T < Tc, the resistivity peak can still be observed; however, its line-shape is now affected by the onset of the quasi two-dimensional superconductivity. By studying such magneto-resistivity peaks under different strength of spin relaxation, we highlight the important effects of SO interaction on superconductivity. PMID:24961726

  9. Nematicity, magnetism and superconductivity in FeSe

    NASA Astrophysics Data System (ADS)

    Böhmer, Anna E.; Kreisel, Andreas

    2018-01-01

    Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, T c, ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of these phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. The experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.

  10. Nematicity, magnetism and superconductivity in FeSe.

    PubMed

    Böhmer, Anna E; Kreisel, Andreas

    2018-01-17

    Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, T c , ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of these phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. The experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.

  11. Unconventional high-Tc superconductivity in fullerides

    PubMed Central

    Takabayashi, Yasuhiro; Prassides, Kosmas

    2016-01-01

    A3C60 molecular superconductors share a common electronic phase diagram with unconventional high-temperature superconductors such as the cuprates: superconductivity emerges from an antiferromagnetic strongly correlated Mott-insulating state upon tuning a parameter such as pressure (bandwidth control) accompanied by a dome-shaped dependence of the critical temperature, Tc. However, unlike atom-based superconductors, the parent state from which superconductivity emerges solely by changing an electronic parameter—the overlap between the outer wave functions of the constituent molecules—is controlled by the C603− molecular electronic structure via the on-molecule Jahn–Teller effect influence of molecular geometry and spin state. Destruction of the parent Mott–Jahn–Teller state through chemical or physical pressurization yields an unconventional Jahn–Teller metal, where quasi-localized and itinerant electron behaviours coexist. Localized features gradually disappear with lattice contraction and conventional Fermi liquid behaviour is recovered. The nature of the underlying (correlated versus weak-coupling Bardeen–Cooper–Schrieffer theory) s-wave superconducting states mirrors the unconventional/conventional metal dichotomy: the highest superconducting critical temperature occurs at the crossover between Jahn–Teller and Fermi liquid metal when the Jahn–Teller distortion melts. This article is part of the themed issue ‘Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene’. PMID:27501971

  12. Optimization of Multilayer Laminated Film and Absorbent of Vacuum Insulation Panel for Use at High Temperature

    NASA Astrophysics Data System (ADS)

    Araki, Kuninari; Echigoya, Wataru; Tsuruga, Toshimitsu; Kamoto, Daigorou; Matsuoka, Shin-Ichi

    For the energy saving regulation and larger capacity, Vacuum Insulation Panel (VIP) has been used in refrigerators with urethane foam in recent years. VIP for low temperature is constructed by laminated plastic film, using heat welding of each neighboring part for keeping vacuum, so that the performance decrement is very large under high temperature. But recently high efficiency insulation material is desired for high temperature water holding devices (automatic vending machine, heat pump water heater, electric hot-water pot water, etc.), and we especially focused on cost and ability of the laminated plastic film and absorbent for high temperature VIP. We measured the heatproof temperature of plastic films and checked the amount of water vapor and out coming gas on temperature-programmed adsorption in absorbent. These results suggest the suitable laminated film and absorbent system for VIP use at high temperature, and the long-term reliability was evaluated by measuring thermal conductivity of high temperature. As a result it was found that high-retort pouch of CPP (cast polypropylene film) and adding of aluminum coating are the most suitable materials for use in the welded layers of high-temperature VIPs (105°C).

  13. Vertical Vibration Characteristics of a High-Temperature Superconducting Maglev Vehicle System

    NASA Astrophysics Data System (ADS)

    Jiang, Jing; Li, Ke Cai; Zhao, Li Feng; Ma, Jia Qing; Zhang, Yong; Zhao, Yong

    2013-06-01

    The vertical vibration characteristics of a high-temperature superconducting maglev vehicle system are investigated experimentally. The displacement variations of the maglev vehicle system are measured with different external excitation frequency, in the case of a certain levitation gap. When the external vibration frequency is low, the amplitude variations of the response curve are small. With the increase of the vibration frequency, chaos status can be found. The resonance frequencies with difference levitation gap are also investigated, while the external excitation frequency range is 0-100 Hz. Along with the different levitation gap, resonance frequency is also different. There almost is a linear relationship between the levitation gap and the resonance frequency.

  14. Critical current measurements of high-temperature superconducting short samples at a wide range of temperatures and magnetic fields.

    PubMed

    Ma, Hongjun; Liu, Huajun; Liu, Fang; Zhang, Huahui; Ci, Lu; Shi, Yi; Lei, Lei

    2018-01-01

    High-Temperature Superconductors (HTS) are potential materials for high-field magnets, low-loss transmission cables, and Superconducting Magnetic Energy Storage (SMES) due to their high upper critical magnetic field (H c2 ) and critical temperature (T c ). The critical current (I c ) of HTS, which is one of the most important parameters for superconductor application, depends strongly on the magnetic fields and temperatures. A new I c measurement system that can carry out accurate I c measurement for HTS short samples with various temperatures (4.2-80 K), magnetic fields (0-14 T), and angles of the magnetic field (0°-90°) has been developed. The I c measurement system mainly consists of a measurement holder, temperature-control system, background magnet, test cryostat, data acquisition system, and DC power supply. The accuracy of temperature control is better than ±0.1 K over the 20-80 K range and ±0.05 K when measured below 20 K. The maximum current is over 1000 A with a measurement uncertainty of 1%. The system had been successfully used for YBa 2 Cu 3 O 7-x (YBCO) tapes I c determination with different temperatures and magnetic fields.

  15. Critical current measurements of high-temperature superconducting short samples at a wide range of temperatures and magnetic fields

    NASA Astrophysics Data System (ADS)

    Ma, Hongjun; Liu, Huajun; Liu, Fang; Zhang, Huahui; Ci, Lu; Shi, Yi; Lei, Lei

    2018-01-01

    High-Temperature Superconductors (HTS) are potential materials for high-field magnets, low-loss transmission cables, and Superconducting Magnetic Energy Storage (SMES) due to their high upper critical magnetic field (Hc2) and critical temperature (Tc). The critical current (Ic) of HTS, which is one of the most important parameters for superconductor application, depends strongly on the magnetic fields and temperatures. A new Ic measurement system that can carry out accurate Ic measurement for HTS short samples with various temperatures (4.2-80 K), magnetic fields (0-14 T), and angles of the magnetic field (0°-90°) has been developed. The Ic measurement system mainly consists of a measurement holder, temperature-control system, background magnet, test cryostat, data acquisition system, and DC power supply. The accuracy of temperature control is better than ±0.1 K over the 20-80 K range and ±0.05 K when measured below 20 K. The maximum current is over 1000 A with a measurement uncertainty of 1%. The system had been successfully used for YBa2Cu3O7-x(YBCO) tapes Ic determination with different temperatures and magnetic fields.

  16. Microstructure and high-temperature tribological properties of Si-doped hydrogenated diamond-like carbon films

    NASA Astrophysics Data System (ADS)

    Zhang, Teng Fei; Wan, Zhi Xin; Ding, Ji Cheng; Zhang, Shihong; Wang, Qi Min; Kim, Kwang Ho

    2018-03-01

    Si-doped DLC films have attracted great attention for use in tribological applications. However, their high-temperature tribological properties remain less investigated, especially in harsh oxidative working conditions. In this study, Si-doped hydrogenated DLC films with various Si content were synthesized and the effects of the addition of Si on the microstructural, mechanical and high-temperature tribological properties of the films were investigated. The results indicate that Si doping leads to an obvious increase in the sp3/sp2 ratio of DLC films, likely due to the silicon atoms preferentially substitute the sp2-hybridized carbon atoms and augment the number of sp3 sites. With Si doping, the mechanical properties, including hardness and adhesion strength, were improved, while the residual stress of the DLC films was reduced. The addition of Si leads to higher thermal and mechanical stability of DLC films because the Si atoms inhibit the graphitization of the films at an elevated temperature. Better high-temperature tribological properties of the Si-DLC films under oxidative conditions were observed, which can be attributed to the enhanced thermal stability and formation of a Si-containing lubricant layer on the surfaces of the wear tracks. The nano-wear resistance of the DLC films was also improved by Si doping.

  17. Transport properties of epitaxial films for superconductor NbN and half-metallic Heusler alloy Co2MnSi under high magnetic fields

    NASA Astrophysics Data System (ADS)

    Shigeta, Iduru; Kubota, Takahide; Sakuraba, Yuya; Kimura, Shojiro; Awaji, Satoshi; Takanashi, Koki; Hiroi, Masahiko

    2018-05-01

    Transport properties were investigated for epitaxial films of superconductor NbN and half-metallic Heusler alloy Co2MnSi under high magnetic fields up to 17 T. The superconducting transition temperature Tc of NbN/Co2MnSi/Au trilayer films was determined to be 16.1 K in the absence of magnetic field. Temperature dependence of the resistivity ρ (T) was measured in both magnetic fields parallel and perpendicular to the surface of NbN/Co2MnSi/Au trilayer films. The activation energy U0 (H) for vortex motion of the trilayer films in both magnetic fields was well fitted above 5 T by the similar model with the exponents in the field dependence of the pinning force density. From the resistivity ρ (T) measurements under high magnetic fields, the upper critical field Hc2 (0) at 0 K was also deduced to be μ0 Hc2 ∥ (0) = 23.2 T for the parallel magnetic filed and μ0 Hc2 ⊥ (0) = 15.8 T for the perpendicular magnetic field, respectively. The experimental results under magnetic fields revealed the superconductivity of the NbN layer was affected by the interplay between the superconducting NbN layer and the half-metallic Co2MnSi layer.

  18. Gas Evolution from Insulating Materials for Superconducting Coil of Iter by Gamma Ray Irradiation at Liquid Nitrogen Temperature

    NASA Astrophysics Data System (ADS)

    Idesaki, A.; Koizumi, N.; Sugimoto, M.; Morishita, N.; Ohshima, T.; Okuno, K.

    2008-03-01

    A laminated material composed of glass cloth/polyimide film/epoxy resin will be used as an insulating material for superconducting coil of International Thermonuclear Experimental Reactor (ITER). In order to keep safe and stable operation of the superconducting coil system, it is indispensable to evaluate radiation resistance of the material, because the material is exposed to severe environments such as high radiation field and low temperature of 4 K. Especially, it is important to estimate the amount of gases evolved from the insulating material by irradiation, because the gases affect on the purifying system of liquid helium in the superconducting coil system. In this work, the gas evolution from the laminated material by gamma ray irradiation at liquid nitrogen temperature (77 K) was investigated, and the difference of gas evolution behavior due to difference of composition in the epoxy resin was discussed. It was found that the main gases evolved from the laminated material by the irradiation were hydrogen, carbon monoxide and carbon dioxide, and that the amount of gases evolved from the epoxy resin containing cyanate ester was about 60% less than that from the epoxy resin containing tetraglycidyl-diaminophenylmethane (TGDDM).

  19. The dynamic process and microscopic mechanism of extraordinary terahertz transmission through perforated superconducting films

    PubMed Central

    Wu, J. B.; Zhang, X.; Jin, B. B.; Liu, H. T.; Chen, Y. H.; Li, Z. Y.; Zhang, C. H.; Kang, L.; Xu, W. W.; Chen, J.; Wang, H. B.; Tonouchi, M.; Wu, P. H.

    2015-01-01

    Superconductor is a compelling plasmonic medium at terahertz frequencies owing to its intrinsic low Ohmic loss and good tuning property. However, the microscopic physics of the interaction between terahertz wave and superconducting plasmonic structures is still unknown. In this paper, we conducted experiments of the enhanced terahertz transmission through a series of superconducting NbN subwavelength hole arrays, and employed microscopic hybrid wave model in theoretical analysis of the role of hybrid waves in the enhanced transmission. The theoretical calculation provided a good match of experimental data. In particular, we obtained the following results. When the width of the holes is far below wavelength, the enhanced transmission is mainly caused by localized resonance around individual holes. On the contrary, when the holes are large, hybrid waves scattered by the array of holes dominate the extraordinary transmission. The surface plasmon polaritions are proved to be launched on the surface of superconducting film and the excitation efficiency increases when the temperature approaches critical temperature and the working frequency goes near energy gap frequency. This work will enrich our knowledge on the microscopic physics of extraordinary optical transmission at terahertz frequencies and contribute to developing terahertz plasmonic devices. PMID:26498994

  20. NASA Space applications of high-temperature superconductors

    NASA Technical Reports Server (NTRS)

    Heinen, Vernon O.; Sokoloski, Martin M.; Aron, Paul R.; Bhasin, Kul B.; Wintucky, Edwin G.; Connolly, Denis J.

    1992-01-01

    The application of superconducting technology in space has been limited by the requirement of cooling to near liquid helium temperatures. The only means of obtaining these temperatures has been with cryogenic fluids which severely limit mission lifetime. The development of materials with superconducting transition temperatures above 77 K has made superconducting technology more attractive and feasible for employment in aerospace systems. Here, potential applications of high temperature superconducting technology in cryocoolers, remote sensing, communications, and power systems are discussed.

  1. High-temperature superconductivity from fine-tuning of Fermi-surface singularities in iron oxypnictides.

    PubMed

    Charnukha, A; Evtushinsky, D V; Matt, C E; Xu, N; Shi, M; Büchner, B; Zhigadlo, N D; Batlogg, B; Borisenko, S V

    2015-12-18

    In the family of the iron-based superconductors, the REFeAsO-type compounds (with RE being a rare-earth metal) exhibit the highest bulk superconducting transition temperatures (Tc) up to 55 K and thus hold the key to the elusive pairing mechanism. Recently, it has been demonstrated that the intrinsic electronic structure of SmFe0.92Co0.08AsO (Tc = 18 K) is highly nontrivial and consists of multiple band-edge singularities in close proximity to the Fermi level. However, it remains unclear whether these singularities are generic to the REFeAsO-type materials and if so, whether their exact topology is responsible for the aforementioned record Tc. In this work, we use angle-resolved photoemission spectroscopy (ARPES) to investigate the inherent electronic structure of the NdFeAsO0.6F0.4 compound with a twice higher Tc = 38 K. We find a similarly singular Fermi surface and further demonstrate that the dramatic enhancement of superconductivity in this compound correlates closely with the fine-tuning of one of the band-edge singularities to within a fraction of the superconducting energy gap Δ below the Fermi level. Our results provide compelling evidence that the band-structure singularities near the Fermi level in the iron-based superconductors must be explicitly accounted for in any attempt to understand the mechanism of superconducting pairing in these materials.

  2. High-temperature superconductivity from fine-tuning of Fermi-surface singularities in iron oxypnictides

    NASA Astrophysics Data System (ADS)

    Charnukha, A.; Evtushinsky, D. V.; Matt, C. E.; Xu, N.; Shi, M.; Büchner, B.; Zhigadlo, N. D.; Batlogg, B.; Borisenko, S. V.

    2015-12-01

    In the family of the iron-based superconductors, the REFeAsO-type compounds (with RE being a rare-earth metal) exhibit the highest bulk superconducting transition temperatures (Tc) up to 55 K and thus hold the key to the elusive pairing mechanism. Recently, it has been demonstrated that the intrinsic electronic structure of SmFe0.92Co0.08AsO (Tc = 18 K) is highly nontrivial and consists of multiple band-edge singularities in close proximity to the Fermi level. However, it remains unclear whether these singularities are generic to the REFeAsO-type materials and if so, whether their exact topology is responsible for the aforementioned record Tc. In this work, we use angle-resolved photoemission spectroscopy (ARPES) to investigate the inherent electronic structure of the NdFeAsO0.6F0.4 compound with a twice higher Tc = 38 K. We find a similarly singular Fermi surface and further demonstrate that the dramatic enhancement of superconductivity in this compound correlates closely with the fine-tuning of one of the band-edge singularities to within a fraction of the superconducting energy gap Δ below the Fermi level. Our results provide compelling evidence that the band-structure singularities near the Fermi level in the iron-based superconductors must be explicitly accounted for in any attempt to understand the mechanism of superconducting pairing in these materials.

  3. Rugged superconducting detector for monitoring infrared energy sources in harsh environments

    NASA Astrophysics Data System (ADS)

    Laviano, F.; Gerbaldo, R.; Ghigo, G.; Gozzelino, L.; Minetti, B.; Rovelli, A.; Mezzetti, E.

    2010-12-01

    Broadband electromagnetic characterization of hot plasmas, such as in nuclear fusion reactors and related experiments, requires detecting systems that must withstand high flux of particles and electromagnetic radiations. We propose a rugged layout of a high temperature superconducting detector aimed at 3 THz collective Thomson scattering (CTS) spectroscopy in hot fusion plasma. The YBa2Cu3O7 - x superconducting film is patterned by standard photolithography and the sensing area of the device is created by means of high-energy heavy ion irradiation, in order to modify the crystal structure both of the superconducting film and of the substrate. This method diminishes process costs and resulting device fragility due to membrane or air-bridge structures that are commonly needed for MIR and FIR radiation detection. Moreover the sensing area of the device is wired by the same superconducting material and thus excellent mechanical strength is exhibited by the whole device, due to the oxide substrate. Continuous wave operation of prototype devices is demonstrated at liquid nitrogen temperature, for selected infrared spectra of broadband thermal energy sources. Several solutions, which exploit the advantages coming from the robustness of this layout in terms of intrinsic radiation hardness of the superconducting material and of the needed optical components, are analysed with reference to applications of infrared electromagnetic detectors in a tokamak machine environment.

  4. Development of remountable joints and heat removable techniques for high-temperature superconducting magnets

    NASA Astrophysics Data System (ADS)

    Hashizume, H.; Ito, S.; Yanagi, N.; Tamura, H.; Sagara, A.

    2018-02-01

    Segment fabrication is now a candidate for the design of superconducting helical magnets in the helical fusion reactor FFHR-d1, which adopts the joint winding of high-temperature superconducting (HTS) helical coils as a primary option and the ‘remountable’ HTS helical coil as an advanced option. This paper reports on recent progress in two key technologies: the mechanical joints (remountable joints) of the HTS conductors and the metal porous media inserted into the cooling channel for segment fabrication. Through our research activities it has been revealed that heat treatment during fabrication of the joint can reduce joint resistance and its dispersion, which can shorten the fabrication process and be applied to bent conductor joints. Also, heat transfer correlations of the cooling channel were established to evaluate heat transfer performance with various cryogenic coolants based on the correlations to analyze the thermal stability of the joint.

  5. Controlling T c of Iridium films using interfacial proximity effects

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hennings-Yeomans, R; Chang, CL; Ding, J

    High precision calorimetry using superconducting transition edge sensors requires the use of superconducting films with a suitable T c, depending on the application. To advance high-precision macrocalorimetry, we require low-T c films that are easy to fabricate. A simple and effective way to suppress T c of superconducting Iridium through the proximity effect is demonstrated by using Ir/Pt bilayers as well as Au/Ir/Au trilayers. While Ir/Au films fabricated by applying heat to the substrate during Ir deposition have been used in the past for superconducting sensors, we present results of T c suppression on Iridium by deposition at room temperature in Au/Ir/Au trilayers and Ir/Pt bilayers in the range ofmore » $$\\sim$$20-100~mK. Measurements of the relative impedance between the Ir/Pt bilayers and Au/Ir/Au trilayers fabricated show factor of $$\\sim$$10 higher values in the Ir/Pt case. These new films could play a key role in the development of scalable superconducting transition edge sensors that require low-T c films to minimize heat capacity and maximize energy resolution, while keeping high-yield fabrication methods.« less

  6. Angular dependence of critical current density and magnetoresistance of sputtered high-T{sub c}-films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Geerkens, A.; Frenck, H.J.; Ewert, S.

    1994-12-31

    The angular dependence of the critical current density and the magnetoresistance of high-T{sub c}-films in high and low magnetic fields and for different temperatures were measured to investigate the flux pinning and the superconducting properties. A comparison of the results for the different superconductors shows their increasing dependence on the angle {Theta} between the magnetic field and the c-axis of the film due to the anisotropy of the chosen superconductor. Furthermore the influence of the current direction to the {Theta}-rotation plane is discussed.

  7. Angular dependence of critical current density and magnetoresistance of sputtered high-T(sub c)-films

    NASA Technical Reports Server (NTRS)

    Geerkens, A.; Meven, M.; Frenck, H.-J.; Ewert, S.

    1995-01-01

    The angular dependence of the critical current density and the magnetoresistance of high-T(sub c)-films in high and low magnetic fields and for different temperatures were measured to investigate the flux pinning and the superconducting properties. A comparison of the results for the different superconductors shows their increasing dependence on the angle Theta between the magnetic field and the c-axis of the film due to the anisotropy of the chosen superconductor. Furthermore the influence of the current direction to the Theta-rotation plane is discussed.

  8. High-Temperature Superconductivity

    ScienceCinema

    Peter Johnson

    2017-12-09

    Like astronomers tweaking images to gain a more detailed glimpse of distant stars, physicists at Brookhaven National Laboratory have found ways to sharpen images of the energy spectra in high-temperature superconductors — materials that carry electrical c

  9. NASA space applications of high-temperature superconductors

    NASA Technical Reports Server (NTRS)

    Heinen, Vernon O.; Sokoloski, Martin M.; Aron, Paul R.; Bhasin, Kul B.

    1992-01-01

    The application of superconducting technology in space has been limited by the requirement of cooling to near liquid helium temperatures. The only means of attaining these temperatures has been with cryogenic fluids which severely limits mission lifetime. The development of materials with superconducting transition temperatures (T sub c) above 77 K has made superconducting technology more attractive and feasible for employment in aerospace systems. Potential applications of high-temperature superconducting technology in cryocoolers and remote sensing, communications, and power systems are discussed.

  10. High temperature superconductivity in distinct phases of amorphous B-doped Q-carbon

    NASA Astrophysics Data System (ADS)

    Narayan, Jagdish; Bhaumik, Anagh; Sachan, Ritesh

    2018-04-01

    Distinct phases of B-doped Q-carbon are formed when B-doped and undoped diamond tetrahedra are packed randomly after nanosecond laser melting and quenching of carbon. By changing the ratio of doped to undoped tetrahedra, distinct phases of B-doped Q-carbon with concentration varying from 5.0% to 50.0% can be created. We have synthesized three distinct phases of amorphous B-doped Q-carbon, which exhibit high-temperature superconductivity following the Bardeen-Cooper-Schrieffer mechanism. The first phase (QB1) has a B-concentration ˜17 at. % (Tc = 37 K), the second phase (QB2) has a B-concentration ˜27 at. % (Tc = 55 K), and the third phase (QB3) has a B-concentration ˜45 at. % (Tc expected over 100 K). From geometrical modeling, we derive that QB1 consists of randomly packed tetrahedra, where one out of every three tetrahedra contains a B atom in the center which is sp3 bonded to four carbon atoms with a concentration of 16.6 at. %. QB2 consists of randomly packed tetrahedra, where one out of every two tetrahedra contains a B atom in the center which is sp3 bonded to four carbon atoms with a concentration of 25 at. %. QB3 consists of randomly packed tetrahedra, where every tetrahedron contains a B atom in the center which is sp3 bonded to four carbon atoms with a concentration of 50 at. %. We present detailed high-resolution TEM results on structural characterization, and EELS and Raman spectroscopy results on the bonding characteristics of B and C atoms. From these studies, we conclude that the high electronic density of states near the Fermi energy level coupled with moderate electron-phonon coupling result in high-temperature superconductivity in B-doped Q-carbon.

  11. The arrival of high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Chu, Paul C. W.

    2011-03-01

    The attainment of high temperature superconductivity has been considered a major advancement of modern science. It was the seminal discovery of the first cuprate high temperature superconductor, the Ba-doped La 2 Cu O4 , with a Tc of 35 K in 1986 by Alex Müller and George Bednorz of IBM Zurich Lab, who were awarded the Nobel Prize in 1987, that ushered in the era of cuprate high temperature superconductivity. It was the first liquid nitrogen high temperature superconductor, YBa 2 Cu 3 O7 with a Tc of 93 K discovered in 1987 by Paul C. W. Chu, Maw-Kuen Wu and colleagues in the respective groups at the University of Houston and the University of Alabama at Huntsville that heralded the new era of high temperature superconductivity, drastically changing the psyche of superconductivity research and bringing superconductivity applications a giant step closer to reality. In the ensuing years, many high temperature superconductors have been found, leading to the current record Tc of 134 K which was observed by A. Schilling et al. of ETH in 1993 in HgBa 2 Ca 2 Cu 3 O9 - δ at ambient and later raised to 164 K under 30 GPa by L. Gao et al. In the present talk, I shall briefly recall a few events leading to and during the arrival of high temperature superconductivity. The prospects for future superconductors with higher Tc will also be discussed. Supported in part by U.S. AFOSR, U.S. DoE through ORNL, U.S. AFRL CONTACT through Rice University, the T. L. L. Temple Foundation, the John J. and Rebecca Moores Endowment, and the State of Texas through TCSUH.

  12. Structure, electrical characteristics, and high-temperature stability of aerosol jet printed silver nanoparticle films

    NASA Astrophysics Data System (ADS)

    Rahman, Md Taibur; McCloy, John; Ramana, C. V.; Panat, Rahul

    2016-08-01

    Printed electronics has emerged as a versatile eco-friendly fabrication technique to create sintered nanoparticle (NP) films on arbitrary surfaces with an excellent control over the film microstructure. While applicability of such films for high-temperature applications is not explored previously, herein we report the high-temperature electrical stability of silver (Ag) metal NP films fabricated using an Aerosol Jet based printing technique and demonstrate that this behavior is dictated by changes in the film microstructure. In-situ high temperature (24-500 °C) impedance spectroscopy measurements show that the real part of the impedance increases with increasing temperature up to 150 °C, at which point a decreasing trend prevails until 300 °C, followed again by an increase in impedance. The electrical behavior is correlated with the in-situ grain growth of the Ag NP films, as observed afterwards by scanning electron microscopy and X-ray diffraction (XRD), and could be tailored by controlling the initial microstructure through sintering conditions. Using combined diffraction and spectroscopic analytical methods, it is demonstrated the Aerosol Jet printed Ag NP films exhibit enhanced thermal stability and oxidation resistance. In addition to establishing the conditions for stability of Ag NP films, the results provide a fundamental understanding of the effect of grain growth and reduction in grain boundary area on the electrical stability of sintered NP films.

  13. Critical current density and third-harmonic voltage in superconducting films

    NASA Astrophysics Data System (ADS)

    Mawatari, Yasunori; Yamasaki, Hirofumi; Nakagawa, Yoshihiko

    2002-09-01

    When a sinusoidal drive current I0cos ωt flows in a small coil close to the surface of a superconducting film, third-harmonic voltage V3 cos(3ωt+θ3) is induced in the coil if the film causes a nonlinear response. We have developed an approximate theoretical method yielding the relationships among I0, V3, and θ3, thus providing the scientific basis for a widely used inductive method for measuring the critical current density Jc in large-area superconducting films. Our results show that V3 is near zero when I0 is smaller than a threshold value Ic0∝Jcd, where d is the film thickness. When I0>Ic0, on the other hand, the third-harmonic voltage is expressed as V3 exp(-iθ3)=ωIc0G(I0/Ic0), where G(x) is a scaling function determined by the configuration of the coil. We demonstrate the scaling law of V3/Ic0 vs I0/Ic0 in a YBa2Cu3O7-δ film.

  14. Strain induced superconductivity in the parent compound BaFe2As2

    NASA Astrophysics Data System (ADS)

    Engelmann, J.; Grinenko, V.; Chekhonin, P.; Skrotzki, W.; Efremov, D. V.; Oswald, S.; Iida, K.; Hühne, R.; Hänisch, J.; Hoffmann, M.; Kurth, F.; Schultz, L.; Holzapfel, B.

    2013-12-01

    The discovery of superconductivity with a transition temperature, Tc, up to 65 K in single-layer FeSe (bulk Tc=8 K) films grown on SrTiO3 substrates has attracted special attention to Fe-based thin films. The high Tc is a consequence of the combined effect of electron transfer from the oxygen-vacant substrate to the FeSe thin film and lattice tensile strain. Here we demonstrate the realization of superconductivity in the parent compound BaFe2As2 (no bulk Tc) just by tensile lattice strain without charge doping. We investigate the interplay between strain and superconductivity in epitaxial BaFe2As2 thin films on Fe-buffered MgAl2O4 single crystalline substrates. The strong interfacial bonding between Fe and the FeAs sublattice increases the Fe-Fe distance due to the lattice misfit, which leads to a suppression of the antiferromagnetic spin density wave and induces superconductivity with bulk Tc≈10 K. These results highlight the role of structural changes in controlling the phase diagram of Fe-based superconductors.

  15. The infinite range Heisenberg model and high temperature superconductivity

    NASA Astrophysics Data System (ADS)

    Tahir-Kheli, Jamil

    1992-01-01

    The thesis deals with the theory of high temperature superconductivity from the standpoint of three-band Hubbard models.Chapter 1 of the thesis proposes a strongly coupled variational wavefunction that has the three-spin system of an oxygen hole and its two neighboring copper spins in a doublet and the background Cu spins in an eigenstate of the infinite range antiferromagnet. This wavefunction is expected to be a good "zeroth order" wavefunction in the superconducting regime of dopings. The three-spin polaron is stabilized by the hopping terms rather than the copper-oxygen antiferromagnetic coupling Jpd. Considering the effect of the copper-copper antiferromagnetic coupling Jdd, we show that the three-spin polaron cannot be pure Emery (Dg), but must have a non-negligible amount of doublet-u (Du) character for hopping stabilization. Finally, an estimate is made for the magnitude of the attractive coupling of oxygen holes.Chapter 2 presents an exact solution to a strongly coupled Hamiltonian for the motion of oxygen holes in a 1-D Cu-O lattice. The Hamiltonian separates into two pieces: one for the spin degrees of freedom of the copper and oxygen holes, and the other for the charge degrees of freedom of the oxygen holes. The spinon part becomes the Heisenberg antiferromagnet in 1-D that is soluble by the Bethe Ansatz. The holon piece is also soluble by a Bethe Ansatz with simple algebraic relations for the phase shifts.Finally, we show that the nearest neighbor Cu-Cu spin correlation increases linearly with doping and becomes positive at x [...] 0.70.

  16. Designing heterostructures with higher-temperature superconductivity

    NASA Astrophysics Data System (ADS)

    Le Hur, Karyn; Chung, Chung-Hou; Paul, I.

    2011-07-01

    We propose to increase the superconducting transition temperature Tc of strongly correlated materials by designing heterostructures which exhibit a high pairing energy as a result of magnetic fluctuations. More precisely, applying an effective theory of the doped Mott insulator, we envisage a bilayer Hubbard system where both layers exhibit intrinsic intralayer (intraband) d-wave superconducting correlations. Introducing a finite asymmetry between the hole densities of the two layers such that one layer becomes slightly more underdoped and the other more overdoped, we show a visible enhancement of Tc compared to the optimally doped isolated layer. Using the bonding and antibonding band basis, we show that the mechanism behind this enhancement of Tc is the interband pairing correlation mediated by the hole asymmetry which strives to decrease the paramagnetic nodal contribution to the superfluid stiffness. For two identical layers, Tc remains comparable to that of the isolated layer until moderate values of the interlayer single-particle tunneling term. These heterostructures shed new light on fundamental questions related to superconductivity.

  17. Nematicity, magnetism and superconductivity in FeSe

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bohmer, Anna E.; Kreisel, Andreas

    Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, T c, ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of thesemore » phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. In conclusion, the experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.« less

  18. Nematicity, magnetism and superconductivity in FeSe

    DOE PAGES

    Bohmer, Anna E.; Kreisel, Andreas

    2017-12-15

    Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, T c, ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of thesemore » phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. In conclusion, the experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.« less

  19. SSTAC/ARTS review of the draft Integrated Technology Plan (ITP). Volume 8: Aerothermodynamics Automation and Robotics (A/R) systems sensors, high-temperature superconductivity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Not Available

    Viewgraphs of briefings presented at the SSTAC/ARTS review of the draft Integrated Technology Plan (ITP) on aerothermodynamics, automation and robotics systems, sensors, and high-temperature superconductivity are included. Topics covered include: aerothermodynamics; aerobraking; aeroassist flight experiment; entry technology for probes and penetrators; automation and robotics; artificial intelligence; NASA telerobotics program; planetary rover program; science sensor technology; direct detector; submillimeter sensors; laser sensors; passive microwave sensing; active microwave sensing; sensor electronics; sensor optics; coolers and cryogenics; and high temperature superconductivity.

  20. SSTAC/ARTS review of the draft Integrated Technology Plan (ITP). Volume 8: Aerothermodynamics Automation and Robotics (A/R) systems sensors, high-temperature superconductivity

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Viewgraphs of briefings presented at the SSTAC/ARTS review of the draft Integrated Technology Plan (ITP) on aerothermodynamics, automation and robotics systems, sensors, and high-temperature superconductivity are included. Topics covered include: aerothermodynamics; aerobraking; aeroassist flight experiment; entry technology for probes and penetrators; automation and robotics; artificial intelligence; NASA telerobotics program; planetary rover program; science sensor technology; direct detector; submillimeter sensors; laser sensors; passive microwave sensing; active microwave sensing; sensor electronics; sensor optics; coolers and cryogenics; and high temperature superconductivity.

  1. Unconventional high-Tc superconductivity in fullerides.

    PubMed

    Takabayashi, Yasuhiro; Prassides, Kosmas

    2016-09-13

    A3C60 molecular superconductors share a common electronic phase diagram with unconventional high-temperature superconductors such as the cuprates: superconductivity emerges from an antiferromagnetic strongly correlated Mott-insulating state upon tuning a parameter such as pressure (bandwidth control) accompanied by a dome-shaped dependence of the critical temperature, Tc However, unlike atom-based superconductors, the parent state from which superconductivity emerges solely by changing an electronic parameter-the overlap between the outer wave functions of the constituent molecules-is controlled by the C60 (3-) molecular electronic structure via the on-molecule Jahn-Teller effect influence of molecular geometry and spin state. Destruction of the parent Mott-Jahn-Teller state through chemical or physical pressurization yields an unconventional Jahn-Teller metal, where quasi-localized and itinerant electron behaviours coexist. Localized features gradually disappear with lattice contraction and conventional Fermi liquid behaviour is recovered. The nature of the underlying (correlated versus weak-coupling Bardeen-Cooper-Schrieffer theory) s-wave superconducting states mirrors the unconventional/conventional metal dichotomy: the highest superconducting critical temperature occurs at the crossover between Jahn-Teller and Fermi liquid metal when the Jahn-Teller distortion melts.This article is part of the themed issue 'Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene'. © 2016 The Author(s).

  2. Magnetic Penetration Effects in Small Superconducting Devices

    NASA Technical Reports Server (NTRS)

    Stevenson, T. R.; Adams, J. S.; Balvin, M. A.; Bandler, S. R.; Denis, K. L.; Hsieh, W.-T.; Kelly, D. P.; Nagler, P. C.; Porst, J.-P.; Sadleir, J. E.; hide

    2011-01-01

    The temperature dependent behavior of a superconducting body in an applied magnetic field involves flux penetration/expulsion both from screening currents (within a magnetic penetration depth) and variations in the superconducting order parameter (locally to form vortices or a mixed state, or globally in the Meissner effect). The temperature dependence of the magnetic penetration depth, in particular, has been used to make highly sensitive macroscopic thermometers. For the microscopic device volumes required in sensitive low temperature photon detectors, properties of actual thin film materials, non-uniformity of applied magnetic fields, and the influence of measurement circuit dynamics are complicating factors. We discuss the various penetration effects as demonstrated in a particularly promising combination of material and geometry that we have used to make sensitive x-ray microcalorimeters.

  3. Superconducting nanowire networks formed on nanoporous membrane substrates

    NASA Astrophysics Data System (ADS)

    Luo, Qiong

    Introducing a regular array of holes into superconducting thin films has been actively pursued to stabilize and pin the vortex lattice against external driving forces, enabling higher current capabilities. If the width of the sections between neighboring holes is comparable to the superconducting coherence length, the circulation of the Cooper pairs in around the holes in the presence of a magnetic field can also produce the Little-Parks effect, i.e. periodic oscillation of the critical temperature. These two mechanisms, commensurate vortex pinning enhancement by the hole-array and the critical temperature oscillations of a wire network due to Little-Parks effect can induce similar experimental observations such as magnetoresistance oscillation and enhancement of the critical current at specific magnetic fields. This dissertation work investigates the effect of a hole-array on the properties of superconducting films deposited onto nanoporous substrates. Experiments on anisotropies of the critical temperature for niobium films on anodic aluminum oxide membrane substrates containing a regular hole-array reveal that the critical temperature exhibits two strong anisotropic effects: Little-Parks oscillations whose period varies with field direction superimposed on a smooth background arising from one dimensional confinement by the finite lateral space between neighboring holes. The two components of the anisotropy are intrinsically linked and appear in concert. That is, the hole-array changes the dimensionality of a two-dimensional (2D) film to a network of 1D nanowire network. Network of superconducting nanowires with transverse dimensions as small as few nanometers were achieved by coating molybdenum germanium (MoGe) layer onto commercially available filtration membranes which have extremely dense nanopores. The magnetoresistance, magnetic field dependence of the critical temperature and the anisotropies of the synthesized MoGe nanowire networks can be consistently

  4. Operation and design selection of high temperature superconducting magnetic bearings

    NASA Astrophysics Data System (ADS)

    Werfel, F. N.; Floegel-Delor, U.; Riedel, T.; Rothfeld, R.; Wippich, D.; Goebel, B.

    2004-10-01

    Axial and radial high temperature superconducting (HTS) magnetic bearings are evaluated by their parameters. Journal bearings possess advantages over thrust bearings. High magnetic gradients in a multi-pole permanent magnet (PM) configuration, the surrounding melt textured YBCO stator and adequate designs are the key features for increasing the overall bearing stiffness. The gap distance between rotor and stator determines the specific forces and has a strong impact on the PM rotor design. We report on the designing, building and measuring of a 200 mm prototype 100 kg HTS bearing with an encapsulated and thermally insulated melt textured YBCO ring stator. The encapsulation requires a magnetically large-gap (4-5 mm) operation but reduces the cryogenic effort substantially. The bearing requires 3 l of LN2 for cooling down, and about 0.2 l LN2 h-1 under operation. This is a dramatic improvement of the efficiency and in the practical usage of HTS magnetic bearings.

  5. Tunneling Spectroscopy of Superconducting MoN and NbTiN Grown by Atomic Layer Deposition.

    DOE PAGES

    Groll, Nickolas; Klug, Jeffrey A.; Cao, Chaoyue; ...

    2014-03-03

    A tunneling spectroscopy study is presented of superconducting MoN and Nbo.8Tio.2N thin films grown by atomic layer deposition (ALD). The films exhibited a superconducting gap of 2meV and 2.4meV, respectively, with a corresponding critical temperature of 11.5K and 13.4 K, among the highest reported Tc values achieved by the ALD technique.Tunnel junctions were obtained using a mechanical contact method with a Au tip. While the native oxides of these films provided poor tunnel barriers, high quality tunnel junctions with low zero bias conductance (below rvl0%) were obtained using an artificial tunnel barrier of Ah03 on the film's surface grown exmore » situ by ALD. We find a large critical current density on the order of 4 x 106Ncm2 at T =0.8Tc for a 60 run MoN film and demonstrate conformal coating capabilities of ALD onto high aspect ratio geometries. These results suggest that the ALD technique offers significant promise for thin film superconducting device applications.« less

  6. Tunneling spectroscopy of superconducting MoN and NbTiN grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Groll, Nickolas R.; Klug, Jeffrey A.; Cao, Chaoyue; Altin, Serdar; Claus, Helmut; Becker, Nicholas G.; Zasadzinski, John F.; Pellin, Michael J.; Proslier, Thomas

    2014-03-01

    A tunneling spectroscopy study is presented of superconducting MoN and Nb0.8Ti0.2N thin films grown by atomic layer deposition (ALD). The films exhibited a superconducting gap of 2 meV and 2.4 meV, respectively, with a corresponding critical temperature of 11.5 K and 13.4 K, among the highest reported Tc values achieved by the ALD technique. Tunnel junctions were obtained using a mechanical contact method with a Au tip. While the native oxides of these films provided poor tunnel barriers, high quality tunnel junctions with low zero bias conductance (below ˜10%) were obtained using an artificial tunnel barrier of Al2O3 on the film's surface grown ex situ by ALD. We find a large critical current density on the order of 4 × 106 A/cm2 at T = 0.8Tc for a 60 nm MoN film and demonstrate conformal coating capabilities of ALD onto high aspect ratio geometries. These results suggest that the ALD technique offers significant promise for thin film superconducting device applications.

  7. Synthesis from separate oxide targets of high quality La2-xSrxCuO4 thin films and dependence with doping of their superconducting transition width

    NASA Astrophysics Data System (ADS)

    Cotón, N.; Mercey, B.; Mosqueira, J.; Ramallo, M. V.; Vidal, F.

    2013-07-01

    A series of superconducting La2-xSrxCuO4 thin films, with 0.09 ≲ x ≲ 0.22, is grown over (100)SrTiO3 substrates by means of a novel pulsed laser deposition method devised to increase the homogeneity and control of doping. We employ two separate parent oxide targets that receive ablation shots at arbitrary computer-controlled relative rates, instead of the conventional procedure that uses a single target whose doping determines the one of the film. We characterize the films both through conventional techniques (XRD, SEM, AFM and EDX) and by measuring their superconducting transition with a high-sensitivity SQUID magnetometer. The latter allows one to determine not only their average critical temperatures {\\bar {T}}_{{c}}(x) but also their dispersions due to inhomogeneities, ΔTc(x). For {\\bar {T}}_{{c}}(x) we obtain the conventional parabolic law centered at x = 0.16, plus a Gaussian depression near x = 1/8 with a {\\bar {T}}_{{c}}-height of about 5 K and x-width about 0.03. For ΔTc(x) we obtain, for all the dopings, values among the lowest reported up to now for La2-xSrxCuO4. The ΔTc(x) dependence can be explained in terms of the unavoidable randomness of the positioning of the Sr ions (the so-called intrinsic chemical inhomogeneity) and a separate residual Tc-inhomogeneity contribution of the order of 0.5 K, this last associated with the samples’ structural inhomogeneities and films’ substrate.

  8. High-Tc superconducting materials for electric power applications.

    PubMed

    Larbalestier, D; Gurevich, A; Feldmann, D M; Polyanskii, A

    2001-11-15

    Large-scale superconducting electric devices for power industry depend critically on wires with high critical current densities at temperatures where cryogenic losses are tolerable. This restricts choice to two high-temperature cuprate superconductors, (Bi,Pb)2Sr2Ca2Cu3Ox and YBa2Cu3Ox, and possibly to MgB2, recently discovered to superconduct at 39 K. Crystal structure and material anisotropy place fundamental restrictions on their properties, especially in polycrystalline form. So far, power applications have followed a largely empirical, twin-track approach of conductor development and construction of prototype devices. The feasibility of superconducting power cables, magnetic energy-storage devices, transformers, fault current limiters and motors, largely using (Bi,Pb)2Sr2Ca2Cu3Ox conductor, is proven. Widespread applications now depend significantly on cost-effective resolution of fundamental materials and fabrication issues, which control the production of low-cost, high-performance conductors of these remarkable compounds.

  9. Strong field-matching effects in superconducting YBa2Cu3O7-δ films with vortex energy landscapes engineered via masked ion irradiation

    NASA Astrophysics Data System (ADS)

    Swiecicki, I.; Ulysse, C.; Wolf, T.; Bernard, R.; Bergeal, N.; Briatico, J.; Faini, G.; Lesueur, J.; Villegas, Javier E.

    2012-06-01

    We have developed a masked ion irradiation technique to engineer the energy landscape for vortices in oxide superconductors. This approach associates the possibility to design the landscape geometry at the nanoscale with the unique capability to adjust the depth of the energy wells for vortices. This enabled us to unveil the key role of vortex channeling in modulating the amplitude of the field matching effects with the artificial energy landscape, and to make the latter govern flux dynamics over an unusually wide range of temperatures and applied fields for high-temperature superconducting films.

  10. Large magnetization and high Curie temperature in highly disordered nanoscale Fe2CrAl thin films

    NASA Astrophysics Data System (ADS)

    Dulal, Rajendra P.; Dahal, Bishnu R.; Forbes, Andrew; Pegg, Ian L.; Philip, John

    2017-02-01

    We have successfully grown nanoscale Fe2CrAl thin films on polished Si/SiO2 substrates using an ultra-high vacuum deposition with a base pressure of 9×10-10 Torr. The thickness of thin films ranges from 30 to 100 nm. These films exhibit cubic crystal structure with lattice disorder and display ferromagnetic behavior. The Curie temperature is greater than 400 K, which is much higher than that reported for bulk Fe2CrAl. The magnetic moments of the films varies from 2.5 to 2.8 μB per formula unit, which is larger than the reported bulk values. Thus, the disordered nanoscale Fe2CrAl films exhibit strong Fe-Fe exchange interactions through Fe-Cr-Fe and Fe-Al-Fe layers, resulting in both a large magnetization and a high Curie temperature.

  11. A 350 mK, 9 T scanning tunneling microscope for the study of superconducting thin films on insulating substrates and single crystals.

    PubMed

    Kamlapure, Anand; Saraswat, Garima; Ganguli, Somesh Chandra; Bagwe, Vivas; Raychaudhuri, Pratap; Pai, Subash P

    2013-12-01

    We report the construction and performance of a low temperature, high field scanning tunneling microscope (STM) operating down to 350 mK and in magnetic fields up to 9 T, with thin film deposition and in situ single crystal cleaving capabilities. The main focus lies on the simple design of STM head and a sample holder design that allows us to get spectroscopic data on superconducting thin films grown in situ on insulating substrates. Other design details on sample transport, sample preparation chamber, and vibration isolation schemes are also described. We demonstrate the capability of our instrument through the atomic resolution imaging and spectroscopy on NbSe2 single crystal and spectroscopic maps obtained on homogeneously disordered NbN thin film.

  12. Structure, electrical characteristics, and high-temperature stability of aerosol jet printed silver nanoparticle films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rahman, Md Taibur; McCloy, John; Panat, Rahul, E-mail: rahul.panat@wsu.edu, E-mail: rvchintalapalle@utep.edu

    Printed electronics has emerged as a versatile eco-friendly fabrication technique to create sintered nanoparticle (NP) films on arbitrary surfaces with an excellent control over the film microstructure. While applicability of such films for high-temperature applications is not explored previously, herein we report the high-temperature electrical stability of silver (Ag) metal NP films fabricated using an Aerosol Jet based printing technique and demonstrate that this behavior is dictated by changes in the film microstructure. In-situ high temperature (24–500 °C) impedance spectroscopy measurements show that the real part of the impedance increases with increasing temperature up to 150 °C, at which point a decreasingmore » trend prevails until 300 °C, followed again by an increase in impedance. The electrical behavior is correlated with the in-situ grain growth of the Ag NP films, as observed afterwards by scanning electron microscopy and X-ray diffraction (XRD), and could be tailored by controlling the initial microstructure through sintering conditions. Using combined diffraction and spectroscopic analytical methods, it is demonstrated the Aerosol Jet printed Ag NP films exhibit enhanced thermal stability and oxidation resistance. In addition to establishing the conditions for stability of Ag NP films, the results provide a fundamental understanding of the effect of grain growth and reduction in grain boundary area on the electrical stability of sintered NP films.« less

  13. Microstructure and hardness evolution of nanochannel W films irradiated by helium at high temperature

    NASA Astrophysics Data System (ADS)

    Qin, Wenjing; Wang, Yongqiang; Tang, Ming; Ren, Feng; Fu, Qiang; Cai, Guangxu; Dong, Lan; Hu, Lulu; Wei, Guo; Jiang, Changzhong

    2018-04-01

    Plasma facing materials (PFMs) face one of the most serious challenges in fusion reactors, including unprecedented harsh environment such as 14.1 MeV neutron and transmutation gas irradiation at high temperature. Tungsten (W) is considered to be one of the most promising PFM, however, virtually insolubility of helium (He) in W causes new material issues such as He bubbles and W "fuzz" microstructure. In our previous studies, we presented a new strategy using nanochannel structure designed in the W film to increase the releasing of He atoms and thus to minimize the He nucleation and "fuzz" formation behavior. In this work, we report the further study on the diffusion of He atoms in the nanochannel W films irradiated at a high temperature of 600 °C. More specifically, the temperature influences on the formation and growth of He bubbles, the lattice swelling, and the mechanical properties of the nanochannel W films were investigated. Compared with the bulk W, the nanochannel W films possessed smaller bubble size and lower bubble areal density, indicating that noticeable amounts of He atoms have been released out along the nanochannels during the high temperature irradiations. Thus, with lower He concentration in the nanochannel W films, the formation of the bubble superlattice is delayed, which suppresses the lattice swelling and reduces hardening. These aspects indicate the nanochannel W films have better radiation resistance even at high temperature irradiations.

  14. Quantitative determination of pairing interactions for high-temperature superconductivity in cuprates

    PubMed Central

    Bok, Jin Mo; Bae, Jong Ju; Choi, Han-Yong; Varma, Chandra M.; Zhang, Wentao; He, Junfeng; Zhang, Yuxiao; Yu, Li; Zhou, X. J.

    2016-01-01

    A profound problem in modern condensed matter physics is discovering and understanding the nature of fluctuations and their coupling to fermions in cuprates, which lead to high-temperature superconductivity and the invariably associated strange metal state. We report the quantitative determination of normal and pairing self-energies, made possible by laser-based angle-resolved photoemission measurements of unprecedented accuracy and stability. Through a precise inversion procedure, both the effective interactions in the attractive d-wave symmetry and the repulsive part in the full symmetry are determined. The latter is nearly angle-independent. Near Tc, both interactions are nearly independent of frequency and have almost the same magnitude over the complete energy range of up to about 0.4 eV, except for a low-energy feature at around 50 meV that is present only in the repulsive part, which has less than 10% of the total spectral weight. Well below Tc, they both change similarly, with superconductivity-induced features at low energies. Besides finding the pairing self-energy and the attractive interactions for the first time, these results expose the central paradox of the problem of high Tc: how the same frequency-independent fluctuations can dominantly scatter at angles ±π/2 in the attractive channel to give d-wave pairing and lead to angle-independent repulsive scattering. The experimental results are compared with available theoretical calculations based on antiferromagnetic fluctuations, the Hubbard model, and quantum-critical fluctuations of the loop-current order. PMID:26973872

  15. Fermi Surface Studies and Temperature Dependence of the Electron-Positron Momentum Density in the High Critical Temperature Superconducting Yttrium BARIUM(2) COPPER(3) OXYGEN(7-X) System by Two-Dimensional Acar

    NASA Astrophysics Data System (ADS)

    von Stetten, Eric Carl

    The electron-positron momentum density has been measured by the two dimensional angular correlation of annihilation radiation (2D ACAR) technique for single crystal and polycrystalline (sintered powder) YBa_2 Cu_3O_{7-x} samples. For sintered superconducting and nonsuperconducting samples, the shape and temperature variation of the momentum density was investigated using the high sensitivity 2D ACAR technique. The possible existence of Fermi surfaces (FS's) in the YBa_2Cu _3O_{7-x} system was investigated in high precision 2D ACAR experiments on an oriented (twinned) single crystal superconducting YBa_2Cu _3O_{7-x} (x ~ 0.1) sample, at temperatures above and below the superconducting transition temperature (~85 K). These experiments were performed in the c-axis projection, in order to observe the theoretically predicted cylindrical FS's (if they exist) in a single experiment, without a full reconstruction of the three dimensional momentum density. Large differences were observed between the room temperature 2D ACAR spectra for superconducting and nonsuperconducting sintered powder samples, and smaller differences were observed between the spectra for similarly prepared superconducting samples. For sintered superconducting samples, complex sample dependent temperature variations of the momentum density were observed, in contrast to the small linear temperature variation observed for a sintered powder nonsuperconducting sample. These results are interpreted as manifestations of the theoretically predicted preferential sampling of the linear Cu-O chain region by the positron in the YBa _2Cu_3O _{7-x} system. High precision experiments on the single crystal superconducting sample revealed a nearly isotropic 2D ACAR spectrum, with only four small (~3% of the height at p_{x} = p _{y} = 0) peaks centered along the (110) symmetry lines. A small narrowing of the 2D ACAR spectrum was observed above T_{c}. The Brillouin-zone-reduced momentum density was formed using the "Lock

  16. Cryogenic-temperature profiling of high-power superconducting lines using local and distributed optical-fiber sensors.

    PubMed

    Chiuchiolo, Antonella; Palmieri, Luca; Consales, Marco; Giordano, Michele; Borriello, Anna; Bajas, Hugues; Galtarossa, Andrea; Bajko, Marta; Cusano, Andrea

    2015-10-01

    This contribution presents distributed and multipoint fiber-optic monitoring of cryogenic temperatures along a superconducting power transmission line down to 30 K and over 20 m distance. Multipoint measurements were conducted using fiber Bragg gratings sensors coated with two different functional overlays (epoxy and poly methyl methacrylate (PMMA)) demonstrating cryogenic operation in the range 300-4.2 K. Distributed measurements exploited optical frequency-domain reflectometry to analyze the Rayleigh scattering along two concatenated fibers with different coatings (acrylate and polyimide). The integrated system has been placed along the 20 m long cryostat of a superconducting power transmission line, which is currently being tested at the European Organization for Nuclear Research (CERN). Cool-down events from 300-30 K have been successfully measured in space and time, confirming the viability of these approaches to the monitoring of cryogenic temperatures along a superconducting transmission line.

  17. Depth profiling of superconducting thin films using rare gas ion sputtering with laser postionization

    NASA Astrophysics Data System (ADS)

    Pallix, J. B.; Becker, C. H.; Missert, N.; Char, K.; Hammond, R. H.

    1988-02-01

    Surface analysis by laser ionization (SALI) has been used to examine a high-Tc superconducting thin film of nominal composition YBa2Cu3O7 deposited on SrTiO3 (100) by reactive magnetron sputtering. The main focus of this work was to probe the compositional uniformity and the impurity content throughout the 1800 Å thick film having critical current densities of 1 to 2×106 A/cm2. SALI depth profiles show this film to be more uniform than thicker films (˜1 μm, prepared by electron beam codeposition) which were studied previously, yet the data show that some additional (non-superconducting) phases derived from Y, Ba, Cu, and O are still present. These additional phases are studied by monitoring the atomic and diatomic-oxide photoion profiles and also the depth profiles of various clusters (e.g. Y2O2+, Y2O3+, Y3O4+, Ba2O+, Ba2O2+, BaCu+, BaCuO+, YBaO2+, YSrO2+, etc.). A variety of impurities are observed to occur throughout the film including rather large concentrations of Sr. Hydroxides, F, Cl, and COx are evident particularly in the sample's near surface region (the top ˜100 Å).

  18. Low-Temperature Synthesis of Superconducting Nanocrystalline MgB 2

    DOE PAGES

    Lu, Jun; Xiao, Zhili; Lin, Qiyin; ...

    2010-01-01

    Magnesium diboride (MgB 2 ) is considered a promising material for practical application in superconducting devices, with a transition temperature near 40 K. In the present paper, nanocrystalline MgB 2 with an average particle size of approximately 70 nm is synthesized by reacting LiBH 4 with MgH 2 at temperatures as low as 450 ° C. This synthesis approach successfully bypasses the usage of either elemental boron or toxic diborane gas. The superconductivity of the nanostructures is confirmed by magnetization measurements, showing a superconducting critical temperature of 38.7 K.

  19. Cation disorder and gas phase equilibrium in an YBa 2Cu 3O 7- x superconducting thin film

    NASA Astrophysics Data System (ADS)

    Shin, Dong Chan; Ki Park, Yong; Park, Jong-Chul; Kang, Suk-Joong L.; Yong Yoon, Duk

    1997-02-01

    YBa 2Cu 3O 7- x superconducting thin films have been grown by in situ off-axis rf sputtering with varying oxygen pressure, Ba/Y ratio in a target, and deposition temperature. With decreasing oxygen pressure, increasing Ba/Y ratio, increasing deposition temperature, the critical temperature of the thin films decreased and the c-axis length increased. The property change of films with the variation of deposition variables has been explained by a gas phase equilibrium of the oxidation reaction of Ba and Y. Applying Le Chatelier's principle to the oxidation reaction, we were able to predict the relation of deposition variables and the resultant properties of thin films; the prediction was in good agreement with the experimental results. From the relation between the three deposition variables and gas phase equilibrium, a 3-dimensional processing diagram was introduced. This diagram has shown that the optimum deposition condition of YBa 2Cu 3O 7- x thin films is not a fixed point but can be varied. The gas phase equilibrium can also be applied to the explanation of previous results that good quality films were obtained at low deposition temperature using active species, such as O, O 3, and O 2+.

  20. A high-temperature superconducting Helmholtz probe for microscopy at 9.4 T.

    PubMed

    Hurlston, S E; Brey, W W; Suddarth, S A; Johnson, G A

    1999-05-01

    The design and operation of a high-temperature superconducting (HTS) probe for magnetic resonance microscopy (MRM) at 400 MHz are presented. The design of the probe includes a Helmholtz coil configuration and a stable open-cycle cooling mechanism. Characterization of coil operating parameters is presented to demonstrate the suitability of cryo-cooled coils for MRM. Specifically, the performance of the probe is evaluated by comparison of signal-to-noise (SNR) performance with that of a copper Helmholtz pair, analysis of B1 field homogeneity, and quantification of thermal stability. Images are presented to demonstrate the SNR advantage of the probe for typical MRM applications.

  1. Observations of flux motion in niobium films. [study of magnetic field trapped in superconducting coatings of gyroscope rotor

    NASA Technical Reports Server (NTRS)

    Xiao, Y. M.; Keiser, G. M.

    1991-01-01

    A magnetic field trapped in a superconducting sphere was examined at temperatures from 4.6 K to 5.5 K. The sphere was the rotor of a precision gyroscope and was made of fused quartz and coated with a sputtered niobium film. The rotor diameter was 3.8 cm. The film thickness was 2.5 microns. The tests were carried out at an ambient magnetic field of about 1 mG. Unexpected instability of the trapped field was observed. The experimental results and possible explanations are presented.

  2. Damping and support in high-temperature superconducting levitation systems

    DOEpatents

    Hull, John R [Sammamish, WA; McIver, Carl R [Everett, WA; Mittleider, John A [Kent, WA

    2009-12-15

    Methods and apparatuses to provide improved auxiliary damping for superconducting bearings in superconducting levitation systems are disclosed. In a superconducting bearing, a cryostat housing the superconductors is connected to a ground state with a combination of a damping strip of material, a set of linkage arms to provide vertical support, and spring washers to provide stiffness. Alternately, the superconducting bearing may be supported by a cryostat connected to a ground state by posts constructed from a mesh of fibers, with the damping and stiffness controlled by the fiber composition, size, and mesh geometry.

  3. Large critical current densities and pinning forces in CSD-grown superconducting GdBa2Cu3O7-x -BaHfO3 nanocomposite films

    NASA Astrophysics Data System (ADS)

    Cayado, Pablo; Erbe, Manuela; Kauffmann-Weiss, Sandra; Bühler, Carl; Jung, Alexandra; Hänisch, Jens; Holzapfel, Bernhard

    2017-09-01

    GdBa2Cu3O7-x -BaHfO3 (GdBCO-BHO) nanocomposite (NC) films containing 12 mol% BHO nanoparticles were prepared by chemical solution deposition (CSD) following the TFA route on SrTiO3 (STO) single crystals and buffered metallic tapes supplied by two different companies: Deutsche Nanoschicht GmbH and SuperOx. We optimized the preparation of our GdBCO-BHO solutions with acetylacetone making the film synthesis very robust and reproducible, and obtained 220 nm films with excellent superconducting properties. We show the structural, morphological and superconducting properties of the films after a careful optimization of the processing parameters (growth temperature, oxygen partial pressure and heating ramp). The films reach critical temperatures (T c) of ˜94 K, self-field critical current densities (J c) of >7 MA cm- 2 and maximum pinning force densities (F p) of ˜16 GN m- 3 at 77 K on STO and T c of ˜94.5 K and J c > 1.5 MA cm- 2 on buffered metallic tapes. The transport properties under applied magnetic fields are significantly improved with respect to the pristine GdBCO films. The GdBCO-BHO NC films on STO present epitaxial c-axis orientation with excellent out-of-plane and in-plane texture. The films are, in general, very dense with a low amount of pores and only superficial indentations. On the other hand, we present, for the first time, a systematic study of CSD-grown GdBCO-BHO NC films on buffered metallic tapes. We have used the optimized growth conditions for STO as a reference and identified some limitations on the film synthesis that should be overcome for further improvement of the films’ superconducting properties.

  4. High Energy Density and High Temperature Multilayer Capacitor Films for Electric Vehicle Applications

    NASA Astrophysics Data System (ADS)

    Treufeld, Imre; Song, Michelle; Zhu, Lei; Baer, Eric; Snyder, Joe; Langhe, Deepak

    2015-03-01

    Multilayer films (MLFs) with high energy density and high temperature capability (>120 °C) have been developed at Case Western Reserve University. Such films offer a potential solution for electric car DC-link capacitors, where high ripple currents and high temperature tolerance are required. The current state-of-the-art capacitors used in electric cars for converting DC to AC use biaxially oriented polypropylene (BOPP), which can only operate at temperatures up to 85 °C requiring an external cooling system. The polycarbonate (PC)/poly(vinylidene fluoride) (PVDF) MLFs have a higher permittivity compared to that of BOPP (2.3), leading to higher energy density. They have good mechanical stability and reasonably low dielectric losses at 120 °C. Nonetheless, our preliminary dielectric measurements show that the MLFs exhibit appreciable dielectric losses (20%) at 120 °C, which would, despite all the other advantages, make them not suitable for practical applications. Our preliminary data showed that dielectric losses of the MLFs at 120 °C up to 400 MV/m and 1000 Hz originate mostly from impurity ionic conduction. This work is supported by the NSF PFI/BIC Program (IIP-1237708).

  5. High Temperature - Thin Film Strain Gages Based on Alloys of Indium Tin Oxide

    NASA Technical Reports Server (NTRS)

    Gregory, Otto J.; Cooke, James D.; Bienkiewicz, Joseph M.

    1998-01-01

    A stable, high temperature strain gage based on reactively sputtered indium tin oxide (ITO) was demonstrated at temperatures up to 1050 C. These strain sensors exhibited relatively large, negative gage factors at room temperature and their piezoresistive response was both linear and reproducible when strained up to 700 micro-in/in. When cycled between compression and tension, these sensors also showed very little hysteresis, indicating excellent mechanical stability. Thin film strain gages based on selected ITO alloys withstood more than 50,000 strain cycles of +/- 500 micro-in/in during 180 hours of testing in air at 1000 C, with minimal drift at temperature. Drift rates as low as 0.0009%/hr at 1000 C were observed for ITO films that were annealed in nitrogen at 700 C prior to strain testing. These results compare favorably with state of the art 10 micro-m thick PdCr films deposited by NASA, where drift rates of 0.047%/hr at 1050 C were observed. Nitrogen annealing not only produced the lowest drift rates to date, but also produce the largest dynamic gage factors (G = 23.5). These wide bandgap, semiconductor strain sensors also exhibited moderately low temperature coefficients of resistance (TCR) at temperatures up to 1100 C, when tested in a nitrogen ambient. A TCR of +230 ppm/C over the temperature range 200 C < T < 500 C and a TCR of -469 ppm/C over the temperature range 600 C < T < 1100 C was observed for the films tested in nitrogen. However, the resistivity behavior changed considerably when the same films were tested in oxygen ambients. A TCR of -1560 ppm/C was obtained over the temperature range of 200 C < T < 1100 C. When similar films were protected with an overcoat or when ITO films were prepared with higher oxygen contents in the plasma, two distinct TCR's were observed. At T < 800 C, a linear TCR of -210 ppm/C was observed and at T > 800 C, a linear TCR of -2170 DDm/C was observed. The combination of a moderately low TCR and a relatively large gage

  6. A Cryogenic Magnetostrictive Actuator using a Persistent High Temperature Superconducting Magnet, Part 1: Concept and Design. Part 1; Concept and Design

    NASA Technical Reports Server (NTRS)

    Horner, Garnett C.; Bromberg, Leslie; Teter, J. P.

    2001-01-01

    Cryogenic magnetostrictive materials, such as rare earth zinc crystals, offer high strains and high forces with minimally applied magnetic fields, making the material ideally suited for deformable optics applications. For cryogenic temperature applications, such as Next Generation Space Telescope (NGST), the use of superconducting magnets offer the possibility of a persistent mode of operation, i.e., the magnetostrictive material will maintain a strain field without power. High temperature superconductors (HTS) are attractive options if the temperature of operation is higher than 10 degrees Kelvin (K) and below 77 K. However, HTS wires have constraints that limit the minimum radius of winding, and even if good wires can be produced, the technology for joining superconducting wires does not exist. In this paper, the design and capabilities of a rare earth zinc magnetostrictive actuator using bulk HTS is described. Bulk superconductors can be fabricated in the sizes required with excellent superconducting properties. Equivalent permanent magnets, made with this inexpensive material, are persistent, do not require a persistent switch as in HTS wires, and can be made very small. These devices are charged using a technique which is similar to the one used for charging permanent magnets, e.g., by driving them into saturation. A small normal conducting coil can be used for charging or discharging. Very fast charging and discharging of HTS tubes, as short as 100 microseconds, has been demonstrated. Because of the magnetic field capability of the superconductor material, a very small amount of superconducting magnet material is needed to actuate the rare earth zinc. In this paper, several designs of actuators using YBCO and BSCCO 2212 superconducting materials are presented. Designs that include magnetic shielding to prevent interaction between adjacent actuators will also be described. Preliminary experimental results and comparison with theory for BSSCO 2212 with a

  7. Enhanced critical current in superconducting FeSe0.5Te0.5 films at all magnetic field orientations by scalable gold ion irradiation

    NASA Astrophysics Data System (ADS)

    Ozaki, Toshinori; Wu, Lijun; Zhang, Cheng; Si, Weidong; Jie, Qing; Li, Qiang

    2018-07-01

    The loss-less electrical current-carrying capability of type II superconductors, measured by the critical current density J c, can be increased by engineering desirable defects in superconductors to pin the magnetic vortices. Here, we demonstrate that such desirable defects can be created in superconducting FeSe0.5Te0.5 films by 6 MeV Au-ions irradiations that produce cluster-like defects with sizes of 10-15 nm over the entire film. The pristine FeSe0.5Te0.5 film exhibits a low anisotropy in the angular dependence of J c. A clear improvement in the J c is observed upon Au-ion irradiation for all field orientations at 4.2 K. Furthermore, a nearly 70% increase in J c is observed at a magnetic field of 9 T applied parallel to the crystallographic c-axis at 10 K with little reduction of the superconducting transition temperature T c. Our studies show that a dose of 1 × 1012 Au cm-2 irradiation at a few MeV is sufficient in order to provide a strong isotropic pinning defect landscape in iron-based superconducting films.

  8. Enhanced critical current in superconducting FeSe 0.5 Te 0.5 films at all magnetic field orientations by scalable gold ion irradiation

    DOE PAGES

    Ozaki, Toshinori; Wu, Lijun; Zhang, Cheng; ...

    2018-01-17

    The loss-less electrical current-carrying capability of type II superconductors, measured by the critical current density J c, can be increased by engineering desirable defects in superconductors to pin the magnetic vortices. Here, we demonstrate that such desirable defects can be created in superconducting FeSe 0.5Te 0.5 films by 6 MeV Au-ions irradiations that produce cluster-like defects with sizes of 10–15 nm over the entire film. The pristine FeSe 0.5Te 0.5 film exhibits a low anisotropy in the angular dependence of J c. A clear improvement in the J c is observed upon Au-ion irradiation for all field orientations at 4.2more » K. Furthermore, a nearly 70% increase in J c is observed at a magnetic field of 9 T applied parallel to the crystallographic c-axis at 10 K with little reduction of the superconducting transition temperature T c. Our studies show that a dose of 1×10 12 Au cm –2 irradiation at a few MeV is sufficient in order to provide a strong isotropic pinning defect landscape in iron-based superconducting films.« less

  9. Enhanced critical current in superconducting FeSe 0.5 Te 0.5 films at all magnetic field orientations by scalable gold ion irradiation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ozaki, Toshinori; Wu, Lijun; Zhang, Cheng

    The loss-less electrical current-carrying capability of type II superconductors, measured by the critical current density J c, can be increased by engineering desirable defects in superconductors to pin the magnetic vortices. Here, we demonstrate that such desirable defects can be created in superconducting FeSe 0.5Te 0.5 films by 6 MeV Au-ions irradiations that produce cluster-like defects with sizes of 10–15 nm over the entire film. The pristine FeSe 0.5Te 0.5 film exhibits a low anisotropy in the angular dependence of J c. A clear improvement in the J c is observed upon Au-ion irradiation for all field orientations at 4.2more » K. Furthermore, a nearly 70% increase in J c is observed at a magnetic field of 9 T applied parallel to the crystallographic c-axis at 10 K with little reduction of the superconducting transition temperature T c. Our studies show that a dose of 1×10 12 Au cm –2 irradiation at a few MeV is sufficient in order to provide a strong isotropic pinning defect landscape in iron-based superconducting films.« less

  10. Publisher's Note: High-temperature superconductivity stabilized by electron-hole interband coupling in collapsed tetragonal phase of KFe 2 As 2 under high pressure [Phys. Rev. B 91 , 060508(R) (2015)

    DOE PAGES

    Nakajima, Yasuyuki; Wang, Renxiong; Metz, Tristin; ...

    2015-03-09

    Here, we report a high-pressure study of simultaneous low-temperature electrical resistivity and Hall effect measurements on high quality single-crystalline KFe 2As 2 using designer diamond anvil cell techniques with applied pressures up to 33 GPa. In the low pressure regime, we show that the superconducting transition temperature T c finds a maximum onset value of 7 K near 2 GPa, in contrast to previous reports that find a minimum T c and reversal of pressure dependence at this pressure. Upon applying higher pressures, this T c is diminished until a sudden drastic enhancement occurs coincident with a first-order structural phasemore » transition into a collapsed tetragonal phase. The appearance of a distinct superconducting phase above 13 GPa is also accompanied by a sudden reversal of dominant charge carrier sign, from hole- to electron-like, which agrees with our band calculations predicting the emergence of an electron pocket and diminishment of hole pockets upon Fermi surface reconstruction. Our results suggest the high-temperature superconducting phase in KFe 2As 2 is substantially enhanced by the presence of nested electron and hole pockets, providing the key ingredient of high-T c superconductivity in iron pnictide superconductors.« less

  11. Ultralow 1/f Noise in a Heterostructure of Superconducting Epitaxial Cobalt Disilicide Thin Film on Silicon.

    PubMed

    Chiu, Shao-Pin; Yeh, Sheng-Shiuan; Chiou, Chien-Jyun; Chou, Yi-Chia; Lin, Juhn-Jong; Tsuei, Chang-Chyi

    2017-01-24

    High-precision resistance noise measurements indicate that the epitaxial CoSi 2 /Si heterostructures at 150 and 2 K (slightly above its superconducting transition temperature T c of 1.54 K) exhibit an unusually low 1/f noise level in the frequency range of 0.008-0.2 Hz. This corresponds to an upper limit of Hooge constant γ ≤ 3 × 10 -6 , about 100 times lower than that of single-crystalline aluminum films on SiO 2 capped Si substrates. Supported by high-resolution cross-sectional transmission electron microscopy studies, our analysis reveals that the 1/f noise is dominated by excess interfacial Si atoms and their dimer reconstruction induced fluctuators. Unbonded orbitals (i.e., dangling bonds) on excess Si atoms are intrinsically rare at the epitaxial CoSi 2 /Si(100) interface, giving limited trapping-detrapping centers for localized charges. With its excellent normal-state properties, CoSi 2 has been used in silicon-based integrated circuits for decades. The intrinsically low noise properties discovered in this work could be utilized for developing quiet qubits and scalable superconducting circuits for future quantum computing.

  12. Self-optimized superconductivity attainable by interlayer phase separation at cuprate interfaces.

    PubMed

    Misawa, Takahiro; Nomura, Yusuke; Biermann, Silke; Imada, Masatoshi

    2016-07-01

    Stabilizing superconductivity at high temperatures and elucidating its mechanism have long been major challenges of materials research in condensed matter physics. Meanwhile, recent progress in nanostructuring offers unprecedented possibilities for designing novel functionalities. Above all, thin films of cuprate and iron-based high-temperature superconductors exhibit remarkably better superconducting characteristics (for example, higher critical temperatures) than in the bulk, but the underlying mechanism is still not understood. Solving microscopic models suitable for cuprates, we demonstrate that, at an interface between a Mott insulator and an overdoped nonsuperconducting metal, the superconducting amplitude is always pinned at the optimum achieved in the bulk, independently of the carrier concentration in the metal. This is in contrast to the dome-like dependence in bulk superconductors but consistent with the astonishing independence of the critical temperature from the carrier density x observed at the interfaces of La2CuO4 and La2-x Sr x CuO4. Furthermore, we identify a self-organization mechanism as responsible for the pinning at the optimum amplitude: An emergent electronic structure induced by interlayer phase separation eludes bulk phase separation and inhomogeneities that would kill superconductivity in the bulk. Thus, interfaces provide an ideal tool to enhance and stabilize superconductivity. This interfacial example opens up further ways of shaping superconductivity by suppressing competing instabilities, with direct perspectives for designing devices.

  13. Self-optimized superconductivity attainable by interlayer phase separation at cuprate interfaces

    PubMed Central

    Misawa, Takahiro; Nomura, Yusuke; Biermann, Silke; Imada, Masatoshi

    2016-01-01

    Stabilizing superconductivity at high temperatures and elucidating its mechanism have long been major challenges of materials research in condensed matter physics. Meanwhile, recent progress in nanostructuring offers unprecedented possibilities for designing novel functionalities. Above all, thin films of cuprate and iron-based high-temperature superconductors exhibit remarkably better superconducting characteristics (for example, higher critical temperatures) than in the bulk, but the underlying mechanism is still not understood. Solving microscopic models suitable for cuprates, we demonstrate that, at an interface between a Mott insulator and an overdoped nonsuperconducting metal, the superconducting amplitude is always pinned at the optimum achieved in the bulk, independently of the carrier concentration in the metal. This is in contrast to the dome-like dependence in bulk superconductors but consistent with the astonishing independence of the critical temperature from the carrier density x observed at the interfaces of La2CuO4 and La2−xSrxCuO4. Furthermore, we identify a self-organization mechanism as responsible for the pinning at the optimum amplitude: An emergent electronic structure induced by interlayer phase separation eludes bulk phase separation and inhomogeneities that would kill superconductivity in the bulk. Thus, interfaces provide an ideal tool to enhance and stabilize superconductivity. This interfacial example opens up further ways of shaping superconductivity by suppressing competing instabilities, with direct perspectives for designing devices. PMID:27482542

  14. Properties of Superconducting Mo, Mo2n and Trilayer Mo2n-Mo-Mo2n Thin Films

    NASA Technical Reports Server (NTRS)

    Barrentine, E. M.; Stevenson, T. R.; Brown, A. D.; Lowitz, A. E.; Noroozian, O.; U-Yen, K.; Eshan, N.; Hsieh, W. T.; Moseley, S. H.; Wollack, E. J.

    2014-01-01

    We present measurements of the properties of thin film superconducting Mo, Mo2N and Mo2N/Mo/Mo2N trilayers of interest for microwave kinetic inductance detector (MKID) applications. Using microwave resonator devices, we investigate the transition temperature, energy gaps, kinetic inductance, and internal quality factors of these materials. We present an Usadel-based interpretation of the trilayer transition temperature as a function of trilayer thicknesses, and a 2-gap interpretation to understand the change in kinetic inductance and internal resonance quality factor (Q) as a function of temperature.

  15. Antiferromagnetism, confinement and spin response in the QED(3) effective theory of high-temperature superconductivity

    NASA Astrophysics Data System (ADS)

    Seradjeh, Babak Hosseyni

    In this thesis, we study the effective theory of a phase-fluctuating d-wave superconductor at zero temperature, formulated by quantum electrodynamics in three space-time dimensions (QED3). This theory describes the quantum critical behaviour in underdoped high-temperature superconductors in terms of an emergent gauge field. The gauge field couples minimally to nodal spin degrees of freedom (spinons) at low energies. It is massive in the superconductor but exhibits Maxwell dynamics when superconductivity is destroyed by strong phase fluctuations of the Cooper pairs. We show that, when dynamical chiral symmetry breaking in QED3 is supplemented by residual interactions, namely, the velocity anisotropy around the nodes, short-range repulsion between electrons, and nonlinear effects of dispersion (all irrelevant for the critical behaviour itself), the loss of superconductivity gives rise to an antiferromagnetic state, in accord with observation. Then, we turn to the problem of confinement of spinons outside the superconducting phase. We assume that the gauge group is a compact U(1) and, thus, allows for monopole configurations. In the absence of fermions, the interaction between monopoles is Coulombic, monopoles form a free plasma, and static fermionic charge is confined for all values of the gauge coupling by a linear potential mediated by free monopoles. We show that this permanent confinement survives in the presence of dynamical fermionic matter. This work comprises three separate studies. We first support our claim, for relativistic fermions, by an electrostatic study of the monopole gas. This is backed up by a controlled renormalization group analysis on the equivalent sine-Gordon theory. In the second study, we extend these findings to the non-relativistic case, with a spinon Fermi surface. In the last study, we provide a variational approach to the problem, in agreement with our other works. Finally, we focus our attention on the more practical application of

  16. Architecture for high critical current superconducting tapes

    DOEpatents

    Jia, Quanxi; Foltyn, Stephen R.

    2002-01-01

    Improvements in critical current capacity for superconducting film structures are disclosed and include the use of, e.g., multilayer YBCO structures where individual YBCO layers are separated by a layer of an insulating material such as CeO.sub.2 and the like, a layer of a conducting material such as strontium ruthenium oxide and the like or by a second superconducting material such as SmBCO and the like.

  17. Thin-film nano-thermogravimetry applied to praseodymium-cerium oxide films at high temperatures

    NASA Astrophysics Data System (ADS)

    Schröder, Sebastian; Fritze, Holger; Bishop, Sean; Chen, Di; Tuller, Harry L.

    2018-05-01

    High precision measurements of oxygen nonstoichiometry δ in thin film metal oxides MaOb±δ at elevated temperatures and controlled oxygen partial pressures pO2 are reported with the aid of resonant microbalances. The resonant microbalances applied here consisted of y-cut langasite (La3Ga5SiO14) and CTGS (Ca3TaGa3Si2O14) piezoelectric resonators, operated in the thickness shear mode at ˜5 MHz. Measurements of variations in δ of Pr0.1Ce0.9O2-δ (PCO) films are reported for the oxygen partial pressure range from 10-8 bar to 0.2 bar at 700 °C, and these results were found to be in good agreement with previously reported oxygen nonstoichiometry δ data derived from chemical capacitance studies. The PCO thin-films were deposited via pulsed laser deposition on both sides of the resonators, whose series resonance frequency was tracked, converted into mass changes and, finally, into nonstoichiometry. The nonstoichiometry was observed to reach a plateau as the oxygen partial pressure dropped below about 10-5 bar, the behavior being attributed to the full reduction of Pr to the trivalent state. These resonators enable stable operation up to temperatures above 1000 °C, thereby maintaining high mass resolution suitable for determining oxygen nonstoichiometry variations in thin films deposited on such resonators. For the given experimental conditions, a mass resolution of ˜50 ng was achieved at 700 °C with the CTGS resonator.

  18. Disorder-induced inhomogeneities of the superconducting state close to the superconductor-insulator transition.

    PubMed

    Sacépé, B; Chapelier, C; Baturina, T I; Vinokur, V M; Baklanov, M R; Sanquer, M

    2008-10-10

    Scanning tunneling spectroscopy at very low temperatures on homogeneously disordered superconducting titanium nitride thin films reveals strong spatial inhomogeneities of the superconducting gap Delta in the density of states. Upon increasing disorder, we observe suppression of the superconducting critical temperature Tc towards zero, enhancement of spatial fluctuations in Delta, and growth of the Delta/Tc ratio. These findings suggest that local superconductivity survives across the disorder-driven superconductor-insulator transition.

  19. Molybdenum-rhenium alloy based high-Q superconducting microwave resonators

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Singh, Vibhor, E-mail: v.singh@tudelft.nl; Schneider, Ben H.; Bosman, Sal J.

    2014-12-01

    Superconducting microwave resonators (SMRs) with high quality factors have become an important technology in a wide range of applications. Molybdenum-Rhenium (MoRe) is a disordered superconducting alloy with a noble surface chemistry and a relatively high transition temperature. These properties make it attractive for SMR applications, but characterization of MoRe SMR has not yet been reported. Here, we present the fabrication and characterization of SMR fabricated with a MoRe 60–40 alloy. At low drive powers, we observe internal quality-factors as high as 700 000. Temperature and power dependence of the internal quality-factors suggest the presence of the two level systems from themore » dielectric substrate dominating the internal loss at low temperatures. We further test the compatibility of these resonators with high temperature processes, such as for carbon nanotube chemical vapor deposition growth, and their performance in the magnetic field, an important characterization for hybrid systems.« less

  20. Nanostructured vanadium oxide thin film with high TCR at room temperature for microbolometer

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Lai, Jianjun; Li, Hui; Hu, Haoming; Chen, Sihai

    2013-03-01

    In order to obtain high quality of thermal sensitive material, VOx thin film of high temperature coefficient of resistance (TCR) of 6.5%/K at room temperature has been deposited by reactive ion beam sputtering and post annealing method. AFM and XRD measurements indicate that the VOx thin film with nanostructured crystalline is composed of VO2 and V2O3. The nanostructured VOx microbolometer has been designed and fabricated. The measurement of the film system with TiN absorbing layer indicates that it has about 92% infrared absorption in the range of 8-14 μm. The performance of this bolometer, comparing with that of bolometer with common VOx, has a better result. At 20 Hz frequency and 10 μA bias current, the bolometer with high TCR has reached detectivity of 1.0 × 109 cm Hz1/2/W. It also indicates that this nanostructured VOx thin film has not only a higher TCR but also a lower noise than common VOx thin film without annealing.

  1. Development of semi-rigid cables for low temperature superconducting detectors

    NASA Astrophysics Data System (ADS)

    Kushino, Akihiro; Kasai, Soichi

    We are developing semi-rigid cables for accurate readout of superconducting radiation/particle detectors and other low temperature experiments. The center conductor with a diameter of 0.86 mm is separated with seamless metal outer conductor by dielectric material, polytetrafluoroethylene. We used various metal materials with low thermal conductivity for the electrical conductors such as stainless-steel, cupro-nickel, brass, beryllium-copper, phosphor-bronze, niobium-titanium, and niobium. In addition to the conventional semi-rigid cables, low-pass-filter type cables were manufactured and evaluated to cut the high frequency noise into superconducting detectors. We measured their low thermal conductance and attenuation property up to 10 GHz below the liquid helium temperature.

  2. A high field and cryogenic test facility for neutron irradiated superconducting wire

    NASA Astrophysics Data System (ADS)

    Nishimura, A.; Miyata, H.; Yoshida, M.; Iio, M.; Suzuki, K.; Nakamoto, T.; Yamazaki, M.; Toyama, T.

    2017-12-01

    A 15.5 T superconducting magnet and a variable temperature insert (VTI) system were installed at a radiation control area in Oarai center in Tohoku University to investigate the superconducting properties of activated superconducting materials by fast neutron. The superconductivity was measured at cryogenic temperature and high magnetic field. During these tests, some inconvenient problems were observed and the additional investigation was carried out. The variable temperature insert was designed and assembled to perform the superconducting property tests. without the liquid helium. To remove the heat induced by radiation and joule heating, high purity aluminum rod was used in VTI. The thermal contact was checked by FEM analysis and an additional support was added to confirm the decreasing the stress concentration and the good thermal contact. After the work for improvement, it was affirmed that the test system works well and all troubles were resolved. In this report, the improved technical solution is described and the first data set on the irradiation effect on Nb3Sn wire is presented.

  3. Superconducting properties of nano-sized SiO2 added YBCO thick film on Ag substrate

    NASA Astrophysics Data System (ADS)

    Almessiere, Munirah Abdullah; Al-Otaibi, Amal lafy; Azzouz, Faten Ben

    2017-10-01

    The microstructure and the flux pinning capability of SiO2-added YBa2Cu3Oy thick films on Ag substrates were investigated. A series of YBa2Cu3Oy thick films with small amounts (0-0.5 wt%) of nano-sized SiO2 particles (12 nm) was prepared. The thicknesses of the prepared thick films was approximately 100 µm. Phase analysis by x-ray diffraction and microstructure examination by scanning electron microscopy were performed and the critical current density dependence on the applied magnetic field Jc(H) and electrical resistivity ρ(T) were investigated. The magnetic field and temperature dependence of the critical current density (Jc) was calculated from magnetization measurements using Bean's critical state model. The results showed that the addition of a small amount (≤0.02 wt%) of SiO2 was effective in enhancing the critical current densities in the applied magnetic field. The sample with 0.01 wt% of added SiO2 exhibited a superconducting characteristics under an applied magnetic field for a temperature ranging from 10 to 77 K.

  4. Superconducting Oxide Films for Multispectral Infrared Sensors

    DTIC Science & Technology

    1989-02-07

    films of both low - and high-temperature supercon- resistances below our measurement sensitivity of 4x 10-10 ductors, including BaPb,-Bi2 O.,’ NbN /BN, 2...Simon, " NbN /BN Granular Films - A states, such as normal metal barriers, will improve the noise Sensitive, High-Speed Detector For Pulsed Far- Infrared ...A. W. Kleinsasser, and R. L Sandstrom, "Electron Trap States and Low Frequency Noise in Tunnel Summary and Conclusions Junctions", IREE Trans. nMa n

  5. Oxygen stabilization induced enhancement in superconducting characteristics of high-Tc oxides

    NASA Technical Reports Server (NTRS)

    Wu, M. K.; Chen, J. T.; Huang, C. Y.

    1991-01-01

    In an attempt to enhance the electrical and mechanical properties of the high temperature superconducting oxides, high T(sub c) composites were prepared composed of the 123 compounds and AgO. The presence of extra oxygen due to the decomposition of AgO at high temperature is found to stabilize the superconducting 123 phase. Ag is found to serve as clean flux for grain growth and precipitates as pinning center. Consequently, almost two orders of magnitude enhancement in critical current densities were also observed in these composites. In addition, these composites also show much improvement in workability and shape formation. On the other hand, proper oxygen treatment of Y5Ba6Cu11Oy was found to possibly stabilize superconducting phase with T(sub c) near 250 K. I-V, ac susceptibility, and electrical resistivity measurements indicate the existence of this ultra high T(sub c) phase in this compound. Detailed structure, microstructure, electrical, magnetic and thermal studies of the superconducting composites and the ultra high T(sub c) compound are presented and discussed.

  6. Proximity-Induced Superconductivity and Quantum Interference in Topological Crystalline Insulator SnTe Thin-Film Devices.

    PubMed

    Klett, Robin; Schönle, Joachim; Becker, Andreas; Dyck, Denis; Borisov, Kiril; Rott, Karsten; Ramermann, Daniela; Büker, Björn; Haskenhoff, Jan; Krieft, Jan; Hübner, Torsten; Reimer, Oliver; Shekhar, Chandra; Schmalhorst, Jan-Michael; Hütten, Andreas; Felser, Claudia; Wernsdorfer, Wolfgang; Reiss, Günter

    2018-02-14

    Topological crystalline insulators represent a new state of matter, in which the electronic transport is governed by mirror-symmetry protected Dirac surface states. Due to the helical spin-polarization of these surface states, the proximity of topological crystalline matter to a nearby superconductor is predicted to induce unconventional superconductivity and, thus, to host Majorana physics. We report on the preparation and characterization of Nb-based superconducting quantum interference devices patterned on top of topological crystalline insulator SnTe thin films. The SnTe films show weak anti-localization, and the weak links of the superconducting quantum interference devices (SQUID) exhibit fully gapped proximity-induced superconductivity. Both properties give a coinciding coherence length of 120 nm. The SQUID oscillations induced by a magnetic field show 2π periodicity, possibly dominated by the bulk conductivity.

  7. Fermi-surface reconstruction and the origin of high-temperature superconductivity.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Norman, M. R.; Materials Science Division

    2010-01-01

    copper ion lattice into a d{sup 9} configuration, with one localized hole in the 3d shell per copper site. Given the localized nature of this state, it was questioned whether a momentum-space picture was an appropriate description of the physics of the cuprates. In fact, this question relates to a long-standing debate in the physics community: Since the parent state is also an antiferromagnet, one can, in principle, map the Mott insulator to a band insulator with magnetic order. In this 'Slater' picture, Mott physics is less relevant than the magnetism itself. It is therefore unclear which of the two, magnetism or Mott physics, is more fundamentally tied to superconductivity in the cuprates. After twenty years of effort, definitive quantum oscillations that could be used to map the Fermi surface were finally observed in a high-temperature cuprate superconductor in 2007. This and subsequent studies reveal a profound rearrangement of the Fermi surface in underdoped cuprates. The cause of the reconstruction, and its implication for the origin of high-temperature superconductivity, is a subject of active debate.« less

  8. High growth rate homoepitaxial diamond film deposition at high temperatures by microwave plasma-assisted chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Vohra, Yogesh K. (Inventor); McCauley, Thomas S. (Inventor)

    1997-01-01

    The deposition of high quality diamond films at high linear growth rates and substrate temperatures for microwave-plasma chemical vapor deposition is disclosed. The linear growth rate achieved for this process is generally greater than 50 .mu.m/hr for high quality films, as compared to rates of less than 5 .mu.m/hr generally reported for MPCVD processes.

  9. Local switching of two-dimensional superconductivity using the ferroelectric field effect

    NASA Astrophysics Data System (ADS)

    Takahashi, K. S.; Gabay, M.; Jaccard, D.; Shibuya, K.; Ohnishi, T.; Lippmaa, M.; Triscone, J.-M.

    2006-05-01

    Correlated oxides display a variety of extraordinary physical properties including high-temperature superconductivity and colossal magnetoresistance. In these materials, strong electronic correlations often lead to competing ground states that are sensitive to many parameters-in particular the doping level-so that complex phase diagrams are observed. A flexible way to explore the role of doping is to tune the electron or hole concentration with electric fields, as is done in standard semiconductor field effect transistors. Here we demonstrate a model oxide system based on high-quality heterostructures in which the ferroelectric field effect approach can be studied. We use a single-crystal film of the perovskite superconductor Nb-doped SrTiO3 as the superconducting channel and ferroelectric Pb(Zr,Ti)O3 as the gate oxide. Atomic force microscopy is used to locally reverse the ferroelectric polarization, thus inducing large resistivity and carrier modulations, resulting in a clear shift in the superconducting critical temperature. Field-induced switching from the normal state to the (zero resistance) superconducting state was achieved at a well-defined temperature. This unique system could lead to a field of research in which devices are realized by locally defining in the same material superconducting and normal regions with `perfect' interfaces, the interface being purely electronic. Using this approach, one could potentially design one-dimensional superconducting wires, superconducting rings and junctions, superconducting quantum interference devices (SQUIDs) or arrays of pinning centres.

  10. High temperature superconductor NB3Ga

    NASA Technical Reports Server (NTRS)

    Vieland, L. J.; Wicklund, A. W.

    1973-01-01

    The discovery of superconductivity at 20.3 K in the Nb-Ga system by applying chemical vapor deposition (CVD) techniques to the materials preparation problem is reported. Films on ceramic substrates have been grown with superconducting onsets of up to 20.3 K. Critical fields at 4.2 K in excess of 300 kG and alpha's of 1100,000 T-A/sq cm have been obtained. The results confirm that the outstanding properties of Nb-Ga are due to an equilibrium configuration of the system, namely, the stoichiometric A-15 compound Nb3Ga, which is stable at relatively low temperatures. Practical materials preparation problems center on the codeposition of an adjacent Nb5Ga3 phase and the requirement that the deposition temperature be low. Some ternary alloys were also prepared, with part of the Ga replaced by Sn, Sb, Al, or Ge.

  11. Far-Infrared Optical Conductivity Gap in Superconducting MgB2 Films

    NASA Astrophysics Data System (ADS)

    Kaindl, Robert A.; Carnahan, Marc A.; Orenstein, Joseph; Chemla, Daniel S.; Christen, Hans M.; Zhai, Hong-Ying; Paranthaman, Mariappan; Lowndes, Doug H.

    2002-01-01

    We report the first study of the optical conductivity of MgB 2 covering the range of its lowest-energy superconducting gap. Terahertz time-domain spectroscopy is utilized to determine the complex, frequency-dependent conductivity σ(ω) of thin films. The imaginary part reveals an inductive response due to the emergence of the superconducting condensate. The real part exhibits a strong depletion of oscillator strength near 5 meV resulting from the opening of a superconducting energy gap. The gap ratio of 2Δ0/kBTC~1.9 is well below the weak-coupling value, pointing to complex behavior in this novel superconductor.

  12. IR detector system based on high-Tc superconducting bolometer on SI membrane

    NASA Astrophysics Data System (ADS)

    Burnus, M.; Hefle, G.; Heidenblut, T.; Khrebtov, Igor A.; Laukemper, J.; Michalke, W.; Neff, H.; Schwierzi, B.; Semtchinova, O. K.; Steinbeiss, E.; Tkachenko, A. D.

    1996-06-01

    An infrared detector system based on high-T(subscript c) superconducting (HTS) membrane bolometer is reported. Superconducting transition-edge bolometer has been manufactured by silicon micromachining using an epitaxial GdBa(subscript 2)Cu(subscript 3)O(subscript 7-x) film on an epitaxial yttria- stabilized zirconia buffer layer on silicon. The active area of the element is 0.85 X 0.85 mm(superscript 2). The membrane thickness is 1 micrometers , those of the buffer layer and HTS films are 50 nm. The detectivity of bolometer, D(superscript *), is 3.8 X 10(superscript 9) cm Hz(superscript 1/2) W(superscript -1) at 84.5 K and within the frequency regime 100 < f < 300 Hz. The optical response is 580 V/W at time constant 0.4 ms. This is one of the fastest composite type HTS-bolometer ever reported. The bolometer is mounted on a metal N(subscript 2)-liquid cryostat, which fits the preamplifier. With the volume of N(subscript 2)-reservoir being 0.1 liter, the cryostat holds nitrogen for about 8 hours. Using only wire heater with constant current, the temperature stability of about 0.03 K/h is achieved. The detector system can be used in IR- Fourier spectroscopy at wavelengths longer than the typical operating range of semiconductor detectors (wavelength greater than about 20 micrometers ).

  13. Optimization of superconducting tiling pattern for superconducting bearings

    DOEpatents

    Hull, John R.

    1996-01-01

    An apparatus and method for reducing magnetic field inhomogeneities which produce rotational loss mechanisms in high temperature superconducting magnetic bearings. Magnetic field inhomogeneities are reduced by dividing high temperature superconducting structures into smaller structures, and arranging the smaller structures into tiers which stagger the magnetic field maximum locations of the smaller structures.

  14. The effect of temperature cycling typical of low earth orbit satellites on thin films of YBa2Cu3O(7-x)

    NASA Technical Reports Server (NTRS)

    Mogro-Campero, A.; Turner, L. G.; Bogorad, A.; Herschitz, R.

    1991-01-01

    Thin films of YBa2Cu3O(7-x) (YBCO) were temperature cycled to simulate conditions of a low earth orbit satellite. In one series of tests, epitaxial and polycrystalline YBCO films were cycled between temperatures of +/- 80 C in vacuum and in nitrogen for hundreds of cycles. The room temperature resistance of an epitaxial YBCO film increased by about 10 percent, but the superconducting transition temperature was unchanged. The largest changes were for a polycrystalline YBCO film on oxidized silicon with a zirconia buffer layer, for which the transition temperature decreased by 3 K. An extended test was carried out for epitaxial films. After 3200 cycles (corresponding to about 230 days in space), transition temperatures and critical current densities remained unchanged.

  15. Proceedings of the fourth international conference and exhibition: World Congress on superconductivity. Volume 1

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Krishen, K.; Burnham, C.

    1994-12-31

    The goals of the World Congress on Superconductivity (WCS) have been to establish and foster the development and commercial application of superconductivity technology on a global scale by providing a non-adversarial, non-advocacy forum where scientists, engineers, businessmen and government personnel can freely exchange information and ideas on recent developments and directions for the future of superconductive research. Sessions were held on: accelerator technology, power and energy, persistent magnetic fields, performance characterization, physical properties, fabrication methodology, superconductive magnetic energy storage (SMES), thin films, high temperature materials, device applications, wire fabrication, and granular superconductors. Individual papers are indexed separately.

  16. Thin film growth of the 2122-phase of BCSCO superconductor with high degree of crystalline perfection

    NASA Technical Reports Server (NTRS)

    Raina, K. K.; Narayanan, S.; Pandey, R. K.

    1992-01-01

    Thin films of the 80 K-phase of BiCaSrCu-oxide superconductor having the composition of Bi2Ca1.05Sr2.1Cu2.19O(x) and high degree of crystalline perfection have been grown on c-axis oriented twin free single crystal substrates of NdGaO3. This has been achieved by carefully establishing the growth conditions of the LPE experiments. The temperature regime of 850 to 830 C and quenching of the specimens on the termination of the growth period are found to be pertinent for the growth of quasi-single crystalline superconducting BCSCO films on NdGaO3 substrates. The TEM analysis reveals a single crystalline nature of these films which exhibit 100 percent reflectivity in infrared regions at liquid nitrogen temperature.

  17. Superconducting order parameter fluctuations in NbN/NiCu and NbTiN/NiCu bilayer nanostripes for photon detection

    NASA Astrophysics Data System (ADS)

    Aichner, Bernd; Jausner, Florian; Zechner, Georg; Mühlgassner, Rita; Lang, Wolfgang; Klimov, Andrii; Puźniak, Roman; Słysz, Wojciech; Guziewicz, Marek; Kruszka, Renata; Wegrzecki, Maciej; Sobolewski, Roman

    2017-05-01

    Thermodynamic fluctuations of the superconducting order parameter in NbN/NiCu and NbTiN/NiCu superconductor/ferromagnet (S/F) thin bilayers patterned to microbridges are investigated. Plain NbN and NbTiN films served as reference materials for the analyses. The samples were grown using dc-magnetron sputtering on chemically cleaned sapphire single-crystal substrates. After rapid thermal annealing at high temperatures, the superconducting films were coated with NiCu overlays, using co-sputtering. The positive magnetoresistance of the superconducting single layers is very small in the normal state but with a sharp upturn close to the superconducting transition, a familiar signature of superconducting fluctuations. The fluctuation-enhanced conductivity (paraconductivity) of the NbN and NbTiN single layer films is slightly larger than the prediction of the parameter-free Aslamazov-Larkin theory for order-parameter fluctuations in two-dimensional superconductors. The addition of a ferromagnetic top layer, however, changes the magnetotransport properties significantly. The S/F bilayers show a negative magnetoresistance up to almost room temperature, while the signature of fluctuations is similar to that in the plain films, demonstrating the relevance of both ferromagnetic and superconducting effects in the S/F bilayers. The paraconductivity is reduced below theoretical predictions, in particular in the NbTiN/NiCu bilayers. Such suppression of the fluctuation amplitude in S/F bilayers could be favorable to reduce dark counts in superconducting photon detectors and lead the way to enhance their performance.

  18. High current densities above 100 K in the high-temperature superconductor HgBa2CaCu2O6+δ

    NASA Astrophysics Data System (ADS)

    Krusin-Elbaum, L.; Tsuei, C. C.; Gupta, A.

    1995-02-01

    THE recent discovery1,2 of a family of mercury-based copper oxide superconductors having transition temperatures1-3 above 130 K is of considerable technological interest. But the viability of high-temperature superconductors for many applications will ultimately depend on the size of the current density, Jc, that they are able to support, not only at high temperatures, but also in high magnetic fields. For the cuprate superconductors, and in particular for Hg-based materials, the combination of high transition temperature1-3 and large mass anisotropy implies that the transport properties will be intrinsically limited by large thermal fluctuations and short superconducting coherence lengths4. Here we report that high-quality c-axis-oriented epitaxial films of the compound HgBa2CaCu6O6+δ (Hg-1212; ref. 5) can support large in-plane current densities at temperatures higher than has been achieved for other superconductors. In low magnetic fields oriented normal to the film surface, we find Jc>~107 A cm-2 at 5 K and Jc~ 105 A cm-2 at 110 K, at least an order of magnitude larger than for Bi- or Tl-based films6-11. For in-plane magnetic fields, the critical current (~108 A cm-2) is close to the theoretical limit even at high fields, indicative of strong intrinsic pinning in this compound.

  19. Characterization of Phase-Slip Centers created in superconducting NbxTi1-xN thin films close to Tc

    NASA Astrophysics Data System (ADS)

    Harrabi, Khalil; Maneval, Jean Paul; Maneval Collaboration

    The dissipative states induced by an over-critical (pair-breaking) current in superconducting NbxTi1-xN strips were investigated and characterized in the vicinity of the critical temperature Tc ( 8.7 K). The suppression of superconductivity then occurs locally and leads to the creation of a phase-slip center (PSC). In the case where the over-critical current is applied as a step pulse, the PSC voltage rise is preceded by a nucleation time td which can be analyzed through a Time-Dependent Ginzburg-Landau theory due to Tinkham. In conformity with previous work, we interpret the effective gap relaxation time of the theory as the film cooling time. By consideration of the respective weights of the electron and phonon specific heats, the phonon escape time can be derived from experiments. It is here found to be 1.8 ns for a 20 nm NbTiN film sputtered on polished crystalline Al2O3\\ King Fahd University of Peroleum and Minerals Saudi Arabia.

  20. Percolation effect in thick film superconductors: Using a Bi(Pb)SrCaCuO based paste to prepare a superconducting planar transformer

    NASA Technical Reports Server (NTRS)

    Sali, Robert; Harsanyi, Gabor

    1995-01-01

    A thick film superconductor paste has been developed to study the properties of granulated superconductor materials, to observe the percolation effect and to confirm the theory of the conducting mechanism in the superconducting thick films. This paste was also applied to make a superconducting planar transformer. Due to the T(sub c) and advantageous current density properties the base of the past was chosen to be of Bi(Pb)SrCaCu) system. For contacts a conventional Ag/Pt paste was used. The critical temperature of the samples were between 110 K and 115 K depending on the printed layer thickness. The critical current density -at the boiling temperature of the liquid He- was between 200 - 300 A/sq cm. The R(T) and V(I) functions were measured with different parameters. The results of the measurements have confirmed the theory of conducting mechanism in the material. The percolation structure model has been built and described. As an application, a superconducting planar thick film transformer was planned and produced. Ten windings of the transformer were printed on one side of the alumina substrate and one winding was printed on the other side. The coupling between the two sides was possible through the substrate. The samples did not need special drying and firing parameters. After the preparation, the properties of the transformer were measured. The efficiency ans the losses were determined. Finally, some fundamental advantages and problems of the process were discussed.

  1. Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system.

    PubMed

    Drozdov, A P; Eremets, M I; Troyan, I A; Ksenofontov, V; Shylin, S I

    2015-09-03

    A superconductor is a material that can conduct electricity without resistance below a superconducting transition temperature, Tc. The highest Tc that has been achieved to date is in the copper oxide system: 133 kelvin at ambient pressure and 164 kelvin at high pressures. As the nature of superconductivity in these materials is still not fully understood (they are not conventional superconductors), the prospects for achieving still higher transition temperatures by this route are not clear. In contrast, the Bardeen-Cooper-Schrieffer theory of conventional superconductivity gives a guide for achieving high Tc with no theoretical upper bound--all that is needed is a favourable combination of high-frequency phonons, strong electron-phonon coupling, and a high density of states. These conditions can in principle be fulfilled for metallic hydrogen and covalent compounds dominated by hydrogen, as hydrogen atoms provide the necessary high-frequency phonon modes as well as the strong electron-phonon coupling. Numerous calculations support this idea and have predicted transition temperatures in the range 50-235 kelvin for many hydrides, but only a moderate Tc of 17 kelvin has been observed experimentally. Here we investigate sulfur hydride, where a Tc of 80 kelvin has been predicted. We find that this system transforms to a metal at a pressure of approximately 90 gigapascals. On cooling, we see signatures of superconductivity: a sharp drop of the resistivity to zero and a decrease of the transition temperature with magnetic field, with magnetic susceptibility measurements confirming a Tc of 203 kelvin. Moreover, a pronounced isotope shift of Tc in sulfur deuteride is suggestive of an electron-phonon mechanism of superconductivity that is consistent with the Bardeen-Cooper-Schrieffer scenario. We argue that the phase responsible for high-Tc superconductivity in this system is likely to be H3S, formed from H2S by decomposition under pressure. These findings raise hope for the

  2. In-situ integrated processing and characterization of thin films of high temperature superconductors, dielectrics and semiconductors by MOCVD

    NASA Technical Reports Server (NTRS)

    Singh, R.; Sinha, S.; Hsu, N. J.; Thakur, R. P. S.; Chou, P.; Kumar, A.; Narayan, J.

    1990-01-01

    In this strategy of depositing the basic building blocks of superconductors, semiconductors, and dielectric having common elements, researchers deposited superconducting films of Y-Ba-Cu-O, semiconductor films of Cu2O, and dielectric films of BaF2 and Y2O3 by metal oxide chemical vapor deposition (MOCVD). By switching source materials entering the chamber, and by using direct writting capability, complex device structures like three-terminal hybrid semiconductors/superconductors transistors can be fabricated. The Y-Ba-Cu-O superconducting thin films on BaF2/YSZ substrates show a T(sub c) of 80 K and are textured with most of the grains having their c-axis or a-axis perpendicular to the substrate. Electrical characteristics as well as structural characteristics of superconductors and related materials obtained by x-ray defraction, electron microscopy, and energy dispersive x-ray analysis are discussed.

  3. In-situ integrated processing and characterization of thin films of high temperature superconductors, dielectrics and semiconductors by MOCVD

    NASA Technical Reports Server (NTRS)

    Singh, R.; Sinha, S.; Hsu, N. J.; Thakur, R. P. S.; Chou, P.; Kumar, A.; Narayan, J.

    1991-01-01

    In this strategy of depositing the basic building blocks of superconductors, semiconductors, and dielectrics having common elements, researchers deposited superconducting films of Y-Ba-Cu-O, semiconductor films of Cu2O, and dielectric films of BaF2 and Y2O3 by metal oxide chemical vapor deposition (MOCVD). By switching source materials entering the chamber, and by using direct writing capability, complex device structures like three terminal hybrid semiconductor/superconductor transistors can be fabricated. The Y-Ba-Cu-O superconducting thin films on BaF2/YSZ substrates show a T(sub c) of 80 K and are textured with most of the grains having their c-axis or a-axis perpendicular to the substrate. Electrical characteristics as well as structural characteristics of superconductors and related materials obtained by x-ray deffraction, electron microscopy, and energy dispersive x-ray analysis are discussed.

  4. Characterization of Thick and Thin Film SiCN for Pressure Sensing at High Temperatures

    PubMed Central

    Leo, Alfin; Andronenko, Sergey; Stiharu, Ion; Bhat, Rama B.

    2010-01-01

    Pressure measurement in high temperature environments is important in many applications to provide valuable information for performance studies. Information on pressure patterns is highly desirable for improving performance, condition monitoring and accurate prediction of the remaining life of systems that operate in extremely high temperature environments, such as gas turbine engines. A number of technologies have been recently investigated, however these technologies target specific applications and they are limited by the maximum operating temperature. Thick and thin films of SiCN can withstand high temperatures. SiCN is a polymer-derived ceramic with liquid phase polymer as its starting material. This provides the advantage that it can be molded to any shape. CERASET™ also yields itself for photolithography, with the addition of photo initiator 2, 2-Dimethoxy-2-phenyl-acetophenone (DMPA), thereby enabling photolithographical patterning of the pre-ceramic polymer using UV lithography. SiCN fabrication includes thermosetting, crosslinking and pyrolysis. The technology is still under investigation for stability and improved performance. This work presents the preparation of SiCN films to be used as the body of a sensor for pressure measurements in high temperature environments. The sensor employs the phenomenon of drag effect. The pressure sensor consists of a slender sensitive element and a thick blocking element. The dimensions and thickness of the films depend on the intended application of the sensors. Fabrication methods of SiCN ceramics both as thin (about 40–60 μm) and thick (about 2–3 mm) films for high temperature applications are discussed. In addition, the influence of thermosetting and annealing processes on mechanical properties is investigated. PMID:22205871

  5. Evaluation of high temperature superconductive thermal bridges for space-borne cryogenic infrared detectors

    NASA Technical Reports Server (NTRS)

    Scott, Elaine P.

    1993-01-01

    The focus of this research is on the reduction of the refrigeration requirements for infrared sensors operating in space through the use of high temperature superconductive (HTS) materials as electronic leads between the cooled sensors and the relatively warmer data acquisition components. Specifically, this initial study was directed towards the design of an experiment to quantify the thermal performance of these materials in the space environment. First, an intensive review of relevant literature was undertaken, and then, design requirements were formulated. From this background information, a preliminary experimental design was developed. Additional studies will involve a thermal analysis of the experiment and further modifications of the experimental design.

  6. Fabrication of superconducting MgB2 nanostructures by an electron beam lithography-based technique

    NASA Astrophysics Data System (ADS)

    Portesi, C.; Borini, S.; Amato, G.; Monticone, E.

    2006-03-01

    In this work, we present the results obtained in fabrication and characterization of magnesium diboride nanowires realized by an electron beam lithography (EBL)-based method. For fabricating MgB2 thin films, an all in situ technique has been used, based on the coevaporation of B and Mg by means of an e-gun and a resistive heater, respectively. Since the high temperatures required for the fabrication of good quality MgB2 thin films do not allow the nanostructuring approach based on the lift-off technique, we structured the samples combining EBL, optical lithography, and Ar milling. In this way, reproducible nanowires 1 μm long have been obtained. To illustrate the impact of the MgB2 film processing on its superconducting properties, we measured the temperature dependence of the resistance on a nanowire and compared it to the original magnesium diboride film. The electrical properties of the films are not degraded as a consequence of the nanostructuring process, so that superconducting nanodevices may be obtained by this method.

  7. Coherently coupling distinct spin ensembles through a high critical temperature superconducting resonator

    NASA Astrophysics Data System (ADS)

    Ghirri, Alberto; Bonizzoni, Claudio; Troiani, Filippo; Affronte, Marco

    The problem of coupling remote ensembles of two-level systems through cavity photons is revisited by using molecular spin centers and a high critical temperature superconducting coplanar resonator. By using PyBTM organic radicals, we achieved the strong coupling regime with values of the cooperativity reaching 4300 at 2 K. We show that up to three distinct spin ensembles are simultaneously coupled through the resonator mode. The ensembles are made physically distinguishable by chemically varying the g-factor and by exploiting the inhomogeneities of the applied magnetic field. The coherent mixing of the spin and field modes is demonstrated by the observed multiple anticrossing, along with the simulations performed within the input-output formalism, and quantified by suitable entropic measures.

  8. Optimization of superconducting tiling pattern for superconducting bearings

    DOEpatents

    Hull, J.R.

    1996-09-17

    An apparatus and method for reducing magnetic field inhomogeneities which produce rotational loss mechanisms in high temperature superconducting magnetic bearings are disclosed. Magnetic field inhomogeneities are reduced by dividing high temperature superconducting structures into smaller structures, and arranging the smaller structures into tiers which stagger the magnetic field maximum locations of the smaller structures. 20 figs.

  9. Use of high temperature superconductors in magnetoplasmadynamic systems

    NASA Technical Reports Server (NTRS)

    Reed, C. B.; Sovey, J. S.

    1988-01-01

    The use of Tesla-class high-temperature superconducting magnets may have an extremely large impact on critical development issues (erosion, heat transfer, and performance) related to magnetoplasmadynamic (MPD) thrusters and also may provide significant benefits in reducing the mass of magnetics used in the power processing system. These potential performance improvements, coupled with additional benefits of high-temperature superconductivity, provide a very strong motivation to develop high-temperature superconductivity (HTS) applied-field MPD thruster propulsion systems. The application of HTS to MPD thruster propulsion systems may produce an enabling technology for these electric propulsion systems. This paper summarizes the impact that HTS may have upon MPD propulsion systems.

  10. Response of fractal penetration of magnetic flux to disorder landscape in superconducting films

    NASA Astrophysics Data System (ADS)

    Ye, Zuxin; Li, Qiang; Si, W. D.; Suenaga, M.; Solovyov, V. F.; Johnson, P. D.

    2005-10-01

    Magnetic flux front and induction contours in superconducting YBa2Cu3O7-δ films with defect size stilde ξ (superconducting coherence length) and s≫ξ are studied by magneto-optical imaging. Robust self-affine spatial correlation was observed using scaling analysis in the small pinning disorder-dominated ( stilde ξ) films. The roughness exponent α was determined to be ˜0.66 , independent of numbers of defects (or the film thickness). When the disorder landscape also included a distribution of large defects (s≫ξ) , the flux front and induction contours exhibited self-similarity, with a fractal dimension D determined to be ˜1.33 using the box-counting method. The remarkably different flux penetration patterns were shown to be the manifestation of self-organized criticality at different length scales.

  11. Low-Temperature Postfunctionalization of Highly Conductive Oxide Thin-Films toward Solution-Based Large-Scale Electronics.

    PubMed

    Ban, Seok-Gyu; Kim, Kyung-Tae; Choi, Byung Doo; Jo, Jeong-Wan; Kim, Yong-Hoon; Facchetti, Antonio; Kim, Myung-Gil; Park, Sung Kyu

    2017-08-09

    Although transparent conducting oxides (TCOs) have played a key role in a wide range of solid-state electronics from conventional optoelectronics to emerging electronic systems, the processing temperature and conductivity of solution-processed materials seem to be far exceeding the thermal limitations of soft materials and insufficient for high-perfomance large-area systems, respectively. Here, we report a strategy to form highly conductive and scalable solution-processed oxide materials and their successful translation into large-area electronic applications, which is enabled by photoassisted postfunctionalization at low temperature. The low-temperature fabrication of indium-tin-oxide (ITO) thin films was achieved by using photoignited combustion synthesis combined with photoassisted reduction process under hydrogen atmosphere. It was noteworthy that the photochemically activated hydrogens on ITO surface could be triggered to facilitate highly crystalline oxygen deficient structure allowing significant increase of carrier concentration and mobility through film microstructure modifications. The low-temperature postfunctionalized ITO films demonstrated conductivity of >1607 S/cm and sheet resistance of <104 Ω/□ under the process temperature of less than 300 °C, which are comparable to those of vacuum-deposited and high-temperature annealed ITO films. Based on the photoassisted postfunctionalization route, all-solution-processed transparent metal-oxide thin-film-transistors and large-area integrated circuits with the ITO bus lines were demonstrated, showing field-effect mobilities of >6.5 cm 2 V -1 s -1 with relatively good operational stability and oscillation frequency of more than 1 MHz in 7-stage ring oscillators, respectively.

  12. Superconductivity in BiPbCaSrCuO thin films

    NASA Astrophysics Data System (ADS)

    Fu, S. M.; Yang, H. C.; Chen, F. C.; Horng, H. E.; Jao, J. C.

    1989-12-01

    Thin films of BiPbCaSrCuO sample were prepared by RF sputtering from sintered ceramic targets. Single crystal of MgO(100) was selected as substrate. The sputtering was held at room temperature. Different annealing conditions were carried out to obtain optimum conditions. High temperature resistivity was measured in air to study the thermodynamic reaction of the sintered films. An resistivity anomaly was found in the first heating cycle which suggests a thermodynamic reaction. A temperature dependence of I c was measured to study the coupling of grains in the granular films in different temperature ranges and the results will be discussed.

  13. High-temperature Superconductivity in Diamond Films - from Fundamentals to Device Applications

    DTIC Science & Technology

    2014-12-20

    film is later removed by acid boiling in nitric acid. The laser cutting process is completely based on CNC machine language. Therefore arbitrary...designed Hall bar shapes and converted them in CNC language. Fig 6. Laser Cutter (Alpha) to create holes in the diamond plates (Oxford Lasers). [5...diamond density is not uniform throughout the plate as it appears lighter on the right side. This could be caused by the plasma being of different

  14. High-temperature-superconducting magnetic susceptibility bolometer

    NASA Technical Reports Server (NTRS)

    Brasunas, J.; Lakew, B.; Lee, C.

    1992-01-01

    An infrared detector called the magnetic susceptibility bolometer is introduced which is based on the tmperature dependence of the diamagnetic screening of a high-Tc superconductor film near Tc. Results are reported for the response of a prototype model to modulated blackbody radiation. Possible improvements are discussed as is the potential sensitivity of an improved device.

  15. The Processing of High Temperature Ceramic Superconducting Devices. Volume 1.

    DTIC Science & Technology

    1992-01-31

    assuming frequency squared dependence) for ease of comparison with other measurements. At the low power levels the surface resistance is I 200 micro ...transition temperature is 106K, where the measured resistivity becomes zero. The noimal state resistivity at the transition temperature, 100 micro -ohms...our films at temperatures down t o 4K. A four-point measurement is used, and the criterion of 1 micro -volt per millimeter is usedI to determine

  16. The present status of the high temperature superconducting Maglev vehicle in China

    NASA Astrophysics Data System (ADS)

    Wang, J. S.; Wang, S. Y.; Zeng, Y. W.; Deng, C. Y.; Ren, Z. Y.; Wang, X. R.; Song, H. H.; Wang, X. Z.; Zheng, J.; Zhao, Y.

    2005-02-01

    Since the first successful running of the people-carrying high temperature superconducting (HTS) Maglev test vehicle on 31 December 2000, about 27 000 people have taken it, and the accumulated running distance is about 400 km. The levitation force of the onboard HTS equipment is measured periodically, and new experimental results measured on 5 March 2003 show that the performance of the onboard HTS Maglev equipment is almost the same as that of two years ago. Experimental results indicate that the long-term stability of the HTS Maglev vehicle is good. This further proves the feasibility of the HTS Maglev vehicle for practical transportation. It is worth mentioning that all the results are measured at a low speed; however, investigations of the dynamic performance of the HTS Maglev vehicle at high speed are necessary for practical application. Research on the dynamic performance of the HTS Maglev vehicle is ongoing.

  17. Method and apparatus for forming high-critical-temperature superconducting layers on flat and/or elongated substrates

    DOEpatents

    Ciszek, Theodore F.

    1994-01-01

    An elongated, flexible superconductive wire or strip is fabricated by pulling it through and out of a melt of metal oxide material at a rate conducive to forming a crystalline coating of superconductive metal oxide material on an elongated, flexible substrate wire or strip. A coating of crystalline superconductive material, such as Bi.sub.2 Sr.sub.2 CaCu.sub.2 O.sub.8, is annealed to effect conductive contact between adjacent crystalline structures in the coating material, which is then cooled to room temperature. The container for the melt can accommodate continuous passage of the substrate through the melt. Also, a second pass-through container can be used to simultaneously anneal and overcoat the superconductive coating with a hot metallic material, such as silver or silver alloy. A hollow, elongated tube casting method of forming an elongated, flexible superconductive wire includes drawing the melt by differential pressure into a heated tubular substrate.

  18. Method and apparatus for forming high-critical-temperature superconducting layers on flat and/or elongated substrates

    DOEpatents

    Ciszek, T.F.

    1994-04-19

    An elongated, flexible superconductive wire or strip is fabricated by pulling it through and out of a melt of metal oxide material at a rate conducive to forming a crystalline coating of superconductive metal oxide material on an elongated, flexible substrate wire or strip. A coating of crystalline superconductive material, such as Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8], is annealed to effect conductive contact between adjacent crystalline structures in the coating material, which is then cooled to room temperature. The container for the melt can accommodate continuous passage of the substrate through the melt. Also, a second pass-through container can be used to simultaneously anneal and overcoat the superconductive coating with a hot metallic material, such as silver or silver alloy. A hollow, elongated tube casting method of forming an elongated, flexible superconductive wire includes drawing the melt by differential pressure into a heated tubular substrate. 8 figures.

  19. Highly oriented Bi-based thin films with zero resistance at 106 K

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kula, W.; Sobolewski, R.; Gorecka, J.

    1991-03-01

    This paper reports on fabrication and characterization of nearly single-phase superconducting Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} thin films. The films were dc magnetron sputtered from heavily Pb-doped (Pb/Bi molar ratios up to 1.25), sintered targets on unheated MgO, SrTiO{sub 3}, CaNdAlO{sub 4}, and SrLaAlO{sub 4} single crystals. For the films grown on the (100) oriented MgO substrate, less than 1 hour of annealing in air at 870{degrees} C was sufficient to obtain more than 90% of the 110-K-phase material, with highly c-axis oriented crystalline structure and zero resistivity at 106 K. The films fabricated on the other substrates alsomore » exhibited a narrow superconducting transition and were fully superconducting above 100 K, but they consisted of a mixed-phase material with a large percentage of the 80 K phase.« less

  20. Advances in Thin Film Thermocouple Durability Under High Temperature and Pressure Testing Conditions

    NASA Technical Reports Server (NTRS)

    Martin, Lisa C.; Fralick, Gustave C.; Taylor, Keith F.

    1999-01-01

    Thin film thermocouples for measuring material surface temperature have been previously demonstrated on several material systems and in various hostile test environments. A well-developed thin film fabrication procedure utilizing shadow masking for patterning the sensors elements had produced thin films with sufficient durability for applications in high temperature and pressure environments that exist in air-breathing and hydrogen-fueled burner rig and engine test facilities. However, while shadow masking had been a reliable method for specimens with flat and gently curved surfaces, it had not been consistently reliable for use on test components with sharp contours. This work reports on the feasibility of utilizing photolithography processing for patterning thin film thermocouples. Because this patterning process required changes in the thin film deposition process from that developed for shadow masking, the effect of these changes on thin film adherence during burner rig testing was evaluated. In addition to the results of changing the patterning method, the effects on thin film adherence of other processes used in the thin film fabrication procedure is also presented.

  1. Method of preparing high-temperature-stable thin-film resistors

    DOEpatents

    Raymond, L.S.

    1980-11-12

    A chemical vapor deposition method for manufacturing tungsten-silicide thin-film resistors of predetermined bulk resistivity and temperature coefficient of resistance (TCR) is disclosed. Gaseous compounds of tungsten and silicon are decomposed on a hot substrate to deposit a thin-film of tungsten-silicide. The TCR of the film is determined by the crystallinity of the grain structure, which is controlled by the temperature of deposition and the tungsten to silicon ratio. The bulk resistivity is determined by the tungsten to silicon ratio. Manipulation of the fabrication parameters allows for sensitive control of the properties of the resistor.

  2. Method of preparing high-temperature-stable thin-film resistors

    DOEpatents

    Raymond, Leonard S.

    1983-01-01

    A chemical vapor deposition method for manufacturing tungsten-silicide thin-film resistors of predetermined bulk resistivity and temperature coefficient of resistance (TCR). Gaseous compounds of tungsten and silicon are decomposed on a hot substrate to deposit a thin-film of tungsten-silicide. The TCR of the film is determined by the crystallinity of the grain structure, which is controlled by the temperature of deposition and the tungsten to silicon ratio. The bulk resistivity is determined by the tungsten to silicon ratio. Manipulation of the fabrication parameters allows for sensitive control of the properties of the resistor.

  3. Vortex-antivortex lattices in superconducting films with arrays of magnetic dots

    NASA Astrophysics Data System (ADS)

    Milosevic, M. V.; Peeters, F. M.

    2004-03-01

    Using the numerical approach within the phenomenological Ginzburg-Landau (GL) theory, we investigate the vortex structure of a thin superconducting film (SC) with a regular matrix of out-of-plane magnetized ferromagnetic dots (FD) deposited on top of it. The perturbation of the superconducting order parameter in the SC film as subject of the inhomogeneous magnetic field of the FDs is studied, and various vortex-antivortex configurations are observed, with net vorticity equal zero. In the case of a periodic array of magnetic disks, vortices are confined under the disks, while the antivortices form a rich spectra of lattice states. In the ground state, antivortices are arranged in the so-called matching configurations between the FDs, while other configurational varieties have higher energy. In the metastable regime, the states with fractional number of vortex-antivortex pairs per unit cell are found, some of which with strongly distorted vortex cores. The exact (anti)vortex structure depends on the size, thickness and magnetization of the magnetic dots, periodicity of the FD-rooster and the properties of the SC expressed through the effective Ginzburg-Landau parameter κ ^* . We discuss the further experimental implications, such as magnetic-field-induced superconductivity.

  4. Thickness-modulated tungsten-carbon superconducting nanostructures grown by focused ion beam induced deposition for vortex pinning up to high magnetic fields.

    PubMed

    Serrano, Ismael García; Sesé, Javier; Guillamón, Isabel; Suderow, Hermann; Vieira, Sebastián; Ibarra, Manuel Ricardo; De Teresa, José María

    2016-01-01

    We report efficient vortex pinning in thickness-modulated tungsten-carbon-based (W-C) nanostructures grown by focused ion beam induced deposition (FIBID). By using FIBID, W-C superconducting films have been created with thickness modulation properties exhibiting periodicity from 60 to 140 nm, leading to a strong pinning potential for the vortex lattice. This produces local minima in the resistivity up to high magnetic fields (2.2 T) in a broad temperature range due to commensurability effects between the pinning potential and the vortex lattice. The results show that the combination of single-step FIBID fabrication of superconducting nanostructures with built-in artificial pinning landscapes and the small intrinsic random pinning potential of this material produces strong periodic pinning potentials, maximizing the opportunities for the investigation of fundamental aspects in vortex science under changing external stimuli (e.g., temperature, magnetic field, electrical current).

  5. Inductively-Charged High-Temperature Superconductors And Methods Of Use

    DOEpatents

    Bromberg, Leslie

    2003-09-16

    The invention provides methods of charging superconducting materials and, in particular, methods of charging high-temperature superconducting materials. The methods generally involve cooling a superconducting material to a temperature below its critical temperature. Then, an external magnetic field is applied to charge the material at a nearly constant temperature. The external magnetic field first drives the superconducting material to a critical state and then penetrates into the material. When in the critical state, the superconducting material loses all the pinning ability and therefore is in the flux-flow regime. In some embodiments, a first magnetic field may be used to drive the superconducting material to the critical state and then a second magnetic field may be used to penetrate the superconducting material. When the external field or combination of external fields are removed, the magnetic field that has penetrated into the material remains trapped. The charged superconducting material may be used as solenoidal magnets, dipole magnets, or other higher order multipole magnets in many applications.

  6. Probing the density of states of two-level tunneling systems in silicon oxide films using superconducting lumped element resonators

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Skacel, S. T.; Institut für Mikro- und Nanoelektronische Systeme, Karlsruher Institut für Technologie, Hertzstraße 16, D-76187 Karlsruhe; Kaiser, Ch.

    2015-01-12

    We have investigated dielectric losses in amorphous silicon oxide (a-SiO) thin films under operating conditions of superconducting qubits (mK temperatures and low microwave powers). For this purpose, we have developed a broadband measurement setup employing multiplexed lumped element resonators using a broadband power combiner and a low-noise amplifier. The measured temperature and power dependences of the dielectric losses are in good agreement with those predicted for atomic two-level tunneling systems (TLS). By measuring the losses at different frequencies, we found that the TLS density of states is energy dependent. This had not been seen previously in loss measurements. These resultsmore » contribute to a better understanding of decoherence effects in superconducting qubits and suggest a possibility to minimize TLS-related decoherence by reducing the qubit operation frequency.« less

  7. Superconducting structure

    DOEpatents

    Kwon, Chuhee; Jia, Quanxi; Foltyn, Stephen R.

    2003-04-01

    A superconductive structure including a dielectric oxide substrate, a thin buffer layer of a superconducting material thereon; and, a layer of a rare earth-barium-copper oxide superconducting film thereon the thin layer of yttrium-barium-copper oxide, the rare earth selected from the group consisting of samarium, gadolinium, ytterbium, erbium, neodymium, dysprosium, holmium, lutetium, a combination of more than one element from the rare earth group and a combination of one or more elements from the rare earth group with yttrium, the buffer layer of superconducting material characterized as having chemical and structural compatibility with the dielectric oxide substrate and the rare earth-barium-copper oxide superconducting film is provided.

  8. Superconducting Structure

    DOEpatents

    Kwon, Chuhee; Jia, Quanxi; Foltyn, Stephen R.

    2005-09-13

    A superconductive structure including a dielectric oxide substrate, a thin buffer layer of a superconducting material thereon; and, a layer of a rare earth-barium-copper oxide superconducting film thereon the thin layer of yttrium-barium-copper oxide, the rare earth selected from the group consisting of samarium, gadolinium, ytterbium, erbium, neodymium, dysprosium, holmium, lutetium, a combination of more than one element from the rare earth group and a combination of one or more elements from the rare earth group with yttrium, the buffer layer of superconducting material characterized as having chemical and structural compatibility with the dielectric oxide substrate and the rare earth-barium-copper oxide superconducting film is provided.

  9. Investigation of the strain-sensitive superconducting transition of BaFe1.8Co0.2As2 thin films utilizing piezoelectric substrates

    NASA Astrophysics Data System (ADS)

    Trommler, S.; Hänisch, J.; Iida, K.; Kurth, F.; Schultz, L.; Holzapfel, B.; Hühne, R.

    2014-05-01

    The preparation of biaxially textured BaFe1.8Co0.2As2 thin films has been optimized on MgO single crystals and transfered to piezoelectric (001) Pb(Mg1/3Nb2/3)0.72Ti0.28O3 substrates. By utilizing the inverse piezoelectric effect the lattice parameter of these substrates can be controlled applying an electric field, leading to a induction of biaxial strain into the superconducting layer. High electric fields were used to achieve a total strain of up to 0.05% at low temperatures. A sharpening of the resistive transition and a shift of about 0.6 K to higher temperatures was found at a compressive strain of 0.035%.

  10. Superconductive radiofrequency window assembly

    DOEpatents

    Phillips, Harry Lawrence; Elliott, Thomas S.

    1998-01-01

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly (20) has a superconducting metal-ceramic design. The srf window assembly (20) comprises a superconducting frame (30), a ceramic plate (40) having a superconducting metallized area, and a superconducting eyelet (50) for sealing plate (40) into frame (30). The plate (40) is brazed to eyelet (50) which is then electron beam welded to frame (30). A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator.

  11. Superconductive radiofrequency window assembly

    DOEpatents

    Phillips, H.L.; Elliott, T.S.

    1998-05-19

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The SRF window assembly has a superconducting metal-ceramic design. The SRF window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron beam welded to frame. A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the SRF window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator. 11 figs.

  12. Superconducting radiofrequency window assembly

    DOEpatents

    Phillips, Harry L.; Elliott, Thomas S.

    1997-01-01

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly (20) has a superconducting metal-ceramic design. The srf window assembly (20) comprises a superconducting frame (30), a ceramic plate (40) having a superconducting metallized area, and a superconducting eyelet (50) for sealing plate (40) into frame (30). The plate (40) is brazed to eyelet (50) which is then electron beam welded to frame (30). A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator.

  13. Superconducting radiofrequency window assembly

    DOEpatents

    Phillips, H.L.; Elliott, T.S.

    1997-03-11

    The present invention is a superconducting radiofrequency window assembly for use in an electron beam accelerator. The srf window assembly has a superconducting metal-ceramic design. The srf window assembly comprises a superconducting frame, a ceramic plate having a superconducting metallized area, and a superconducting eyelet for sealing plate into frame. The plate is brazed to eyelet which is then electron beam welded to frame. A method for providing a ceramic object mounted in a metal member to withstand cryogenic temperatures is also provided. The method involves a new metallization process for coating a selected area of a ceramic object with a thin film of a superconducting material. Finally, a method for assembling an electron beam accelerator cavity utilizing the srf window assembly is provided. The procedure is carried out within an ultra clean room to minimize exposure to particulates which adversely affect the performance of the cavity within the electron beam accelerator. 11 figs.

  14. Effect of metallic capping layers on the superconductivity in FeSe thin films.

    NASA Astrophysics Data System (ADS)

    Shibayev, Pavel; Salehi, Maryam; Moon, Jisoo; Oh, Seongshik; Oh Lab Team

    In the past few years, there has been an increased interest in understanding the superconducting behavior of iron selenide (FeSe). Past efforts of others aimed at growing FeSe thin films yielded some success in reaching a Tc of 40K, but at present there is a stark lack of consensus among groups working on this problem. We set a goal of growing FeSe on insulating SrTiO3 (STO) substrates by optimizing both the growth temperature and the protection layer. In our quest to achieve this, we concentrate on keeping track of each compound's structural evolution with temperature via RHEED, an aspect often overlooked in papers describing FeSe growth, thus presenting a unique perspective to tackling this multifaceted challenge. Our group has grown 1, 3, and 30 unit-cell thick FeSe on STO using a state-of-the-art molecular beam epitaxy (MBE) system in our lab. Crucially, we expect to search for superconductivity in FeSe capped by unprecedented metallic protection layers. In addition, the FeSe/STO heterostructures with FeTe protection layers will be grown to enable comparison of existing transport data and scanning tunneling spectra (STS) to data involving our own novel cappings. Support: NSF EFRI Scholars program (1542798), EPiQS Initiative (GBMF4418).

  15. Thin film thermocouples for high temperature turbine application

    NASA Technical Reports Server (NTRS)

    Martin, Lisa C.

    1991-01-01

    The objective is to develop thin film thermocouples (TFTC) for Space Shuttle Main Engine (SSME) components such as the high pressure fuel turbopump (HPFTP) blades and to test TFTC survivability and durability in the SSME environment. The purpose for developing TFTC's for SSME components is to obtain blade temperatures for computational models developed for fluid mechanics and structures. The TFTC must be able to withstand the presence of high temperature, high pressure hydrogen as well as a severe thermal transient due to a cryogenic to combustion temperature change. The TFTC's will eventually be installed and tested on SSME propulsion system components in the SSME test bed engine. The TFTC's were successfully fabricated on flat coupons of MAR-M 246 (Hf+), which is the superalloy material used for HPFTP turbine blades. The TFTC's fabricated on flat coupons survived thermal shock cycling as well as testing in a heat flux measurement facility which provided a rapid thermal transient. The same fabrication procedure was used to deposit TFTC's on HPFTP first stage rotor blades. Other results from the experiments are presented, and future testing plans are discussed.

  16. Enhanced pinning in YBCO films with BaZrO.sub.3 nanoparticles

    DOEpatents

    Driscoll, Judith L.; Foltyn, Stephen R.

    2010-06-15

    A process and composition of matter are provided and involve flux pinning in thin films of high temperature superconductive oxides such as YBCO by inclusion of particles including barium and a group 4 or group 5 metal, such as zirconium, in the thin film.

  17. Development of practical high temperature superconducting wire for electric power application

    NASA Technical Reports Server (NTRS)

    Hawsey, Robert A.; Sokolowski, Robert S.; Haldar, Pradeep; Motowidlo, Leszek R.

    1995-01-01

    The technology of high temperature superconductivity has gone from beyond mere scientific curiousity into the manufacturing environment. Single lengths of multifilamentary wire are now produced that are over 200 meters long and that carry over 13 amperes at 77 K. Short-sample critical current densities approach 5 x 104 A/sq cm at 77 K. Conductor requirements such as high critical current density in a magnetic field, strain-tolerant sheathing materials, and other engineering properties are addressed. A new process for fabricating round BSCCO-2212 wire has produced wires with critical current densities as high as 165,000 A/sq cm at 4.2 K and 53,000 A/sq cm at 40 K. This process eliminates the costly, multiple pressing and rolling steps that are commonly used to develop texture in the wires. New multifilamentary wires with strengthened sheathing materials have shown improved yield strengths up to a factor of five better than those made with pure silver. Many electric power devices require the wire to be formed into coils for production of strong magnetic fields. Requirements for coils and magnets for electric power applications are described.

  18. Effect of Discontinuities and Penetrations on the Shielding Efficacy of High Temperature Superconducting Magnetic Shields

    NASA Astrophysics Data System (ADS)

    Hatwar, R.; Kvitkovic, J.; Herman, C.; Pamidi, S.

    2015-12-01

    High Temperature Superconducting (HTS) materials have been demonstrated to be suitable for applications in shielding of both DC and AC magnetic fields. Magnetic shielding is required for protecting sensitive instrumentation from external magnetic fields and for preventing the stray magnetic fields produced by high power density equipment from affecting neighbouring devices. HTS shields have high current densities at relatively high operating temperatures (40-77 K) and can be easily fabricated using commercial HTS conductor. High current densities in HTS materials allow design and fabrication of magnetic shields that are lighter and can be incorporated into the body and skin of high power density devices. HTS shields are particularly attractive for HTS devices because a single cryogenic system can be used for cooling the device and the associated shield. Typical power devices need penetrations for power and signal cabling and the penetrations create discontinuities in HTS shields. Hence it is important to assess the effect of the necessary discontinuities on the efficacy of the shields and the design modifications necessary to accommodate the penetrations.

  19. High-temperature performance of MoS2 thin-film transistors: Direct current and pulse current-voltage characteristics

    NASA Astrophysics Data System (ADS)

    Jiang, C.; Rumyantsev, S. L.; Samnakay, R.; Shur, M. S.; Balandin, A. A.

    2015-02-01

    We report on fabrication of MoS2 thin-film transistors (TFTs) and experimental investigations of their high-temperature current-voltage characteristics. The measurements show that MoS2 devices remain functional to temperatures of at least as high as 500 K. The temperature increase results in decreased threshold voltage and mobility. The comparison of the direct current (DC) and pulse measurements shows that the direct current sub-linear and super-linear output characteristics of MoS2 thin-films devices result from the Joule heating and the interplay of the threshold voltage and mobility temperature dependences. At temperatures above 450 K, a kink in the drain current occurs at zero gate voltage irrespective of the threshold voltage value. This intriguing phenomenon, referred to as a "memory step," was attributed to the slow relaxation processes in thin films similar to those in graphene and electron glasses. The fabricated MoS2 thin-film transistors demonstrated stable operation after two months of aging. The obtained results suggest new applications for MoS2 thin-film transistors in extreme-temperature electronics and sensors.

  20. Neutron scattering studies of spin-phonon hybridization and superconducting spin gaps in the high temperature superconductor La 2-x(Sr;Ba) xCuO 4

    DOE PAGES

    Wagman, J. J.; Carlo, Jeremy P.; Gaudet, J.; ...

    2016-03-14

    We present time-of-flight neutron-scattering measurements on single crystals of La 2-xBa xCuO 4 (LBCO) with 0 ≤ x ≤ 0.095 and La 2-xSr xCuO 4 (LSCO) with x = 0.08 and 0.11. This range of dopings spans much of the phase diagram relevant to high temperature cuprate superconductivity, ranging from insulating, three dimensional commensurate long range antiferromagnetic order for x ≤ 0.02 to two dimensional (2D) incommensurate antiferromagnetism co-existing with superconductivity for x ≥ 0.05. Previous work on lightly doped LBCO with x = 0.035 showed a clear resonant enhancement of the inelastic scattering coincident with the low energy crossingsmore » of the highly dispersive spin excitations and quasi-2D optic phonons. The present work extends these measurements across the phase diagram and shows this enhancement to be a common feature to this family of layered quantum magnets. Furthermore we show that the low temperature, low energy magnetic spectral weight is substantially larger for samples with non-superconducting ground states relative to any of the samples with superconducting ground states. Lastly spin gaps, suppression of low energy magnetic spectral weight, are observed in both superconducting LBCO and LSCO samples, consistent with previous observations for superconducting LSCO« less

  1. In situ Pulsed Laser Deposition of C-Axis Oriented MgB2 Films and Their Characterization

    NASA Technical Reports Server (NTRS)

    Shinde, Sanjay; Lakew, Brook; Ogale, S. B.; Kulkarni, V. N.; Kale, S. N.; Venkatesan, T.

    2004-01-01

    The recent discovery of an intermetallic superconductor MgB2 has renewed interest in the area of superconductivity not only because of fundamental understanding of superconductivity but also due to its potential applicability in devices such as thermal detectors. Considerable amount of research has been devoted to obtain MgB2 films by an all in situ growth technique. We have grown MgB2 thin films by an all in situ pulsed laser deposition process from pure B and Mg targets. Ultrathin layers of B and Mg were deposited in a multilayer configuration. Hundreds of such Mg-B bilayers with a capping Mg layer on the top were deposited on sapphire substrate. These depositions were done in high vacuum (approx. 10(exp -7) Torr) and at room temperature. After deposition, such a configuration was annealed at high temperature for a short time in a forming gas (4% H2 in Ar). The best films, obtained by this procedure, showed superconducting transition temperature approx. 30 K. These films have been characterized by x-ray diffraction, Rutherford Backscattering Spectrometry, AC susceptibility-, resistivity- (with and without magnetic field) and 1/f noise-measurements. The physical properties of these films will be presented and discussed.

  2. Transport critical current measurement apparatus using liquid nitrogen cooled high-Tc superconducting magnet with variable temperature insert

    NASA Astrophysics Data System (ADS)

    Nishijima, G.; Kitaguchi, H.; Tshuchiya, Y.; Nishimura, T.; Kato, T.

    2013-01-01

    We have developed an apparatus to investigate transport critical current (Ic) as a function of magnetic field and temperature using only liquid nitrogen. The apparatus consists of a (Bi,Pb)2Sr2Ca2Cu3O10 (Bi-2223) superconducting magnet, an outer dewar, and a variable temperature insert (VTI). The magnet, which is operated in depressurized liquid nitrogen, generates magnetic field up to 1.26 T. The sample is also immersed in liquid nitrogen. The pressure in the VTI is controlled from 0.02 to 0.3 MPa, which corresponds to temperature ranging from 66 to 88 K. We have confirmed the long-term stable operation of the Bi-2223 magnet at 1 T. The temperature stability of the sample at high transport current was also demonstrated. The apparatus provides easy-operating Ic measurement environment for a high-Tc superconductor up to 500 A in magnetic fields up to 1 T and in temperatures ranging from 66 to 88 K.

  3. Tuning the band structure and superconductivity in single-layer FeSe by interface engineering.

    PubMed

    Peng, R; Xu, H C; Tan, S Y; Cao, H Y; Xia, M; Shen, X P; Huang, Z C; Wen, C H P; Song, Q; Zhang, T; Xie, B P; Gong, X G; Feng, D L

    2014-09-26

    The interface between transition metal compounds provides a rich playground for emergent phenomena. Recently, significantly enhanced superconductivity has been reported for single-layer FeSe on Nb-doped SrTiO3 substrate. Yet it remains mysterious how the interface affects the superconductivity. Here we use in situ angle-resolved photoemission spectroscopy to investigate various FeSe-based heterostructures grown by molecular beam epitaxy, and uncover that electronic correlations and superconducting gap-closing temperature (Tg) are tuned by interfacial effects. Tg up to 75 K is observed in extremely tensile-strained single-layer FeSe on Nb-doped BaTiO3, which sets a record high pairing temperature for both Fe-based superconductor and monolayer-thick films, providing a promising prospect on realizing more cost-effective superconducting device. Moreover, our results exclude the direct correlation between superconductivity and tensile strain or the energy of an interfacial phonon mode, and highlight the critical and non-trivial role of FeSe/oxide interface on the high Tg, which provides new clues for understanding its origin.

  4. Polycrystalline Superconducting Thin Films: Texture Control and Critical Current Density

    NASA Astrophysics Data System (ADS)

    Yang, Feng

    1995-01-01

    The growth processes of polycrystalline rm YBa_2CU_3O_{7-X} (YBCO) and yttria-stabilized-zirconia (YSZ) thin films have been developed. The effectiveness of YSZ buffer layers on suppression of the reaction between YBCO thin films and metallic substrates was carefully studied. Grown on the chemically inert surfaces of YSZ buffer layers, YBCO thin films possessed good quality of c-axis alignment with the c axis parallel to the substrate normal, but without any preferred in-plane orientations. This leads to the existence of a large percentage of the high-angle grain boundaries in the YBCO films. The critical current densities (rm J_{c}'s) found in these films were much lower than those in single crystal YBCO thin films, which was the consequence of the weak -link effect of the high-angle grain boundaries in these films. It became clear that the in-plane alignment is vital for achieving high rm J_{c }s in polycrystalline YBCO thin films. To induce the in-plane alignment, ion beam-assisted deposition (IBAD) technique was integrated into the conventional pulsed laser deposition process for the growth of the YSZ buffer layers. It was demonstrated that using IBAD the in-plane orientations of the YSZ grains could be controlled within a certain range of a common direction. This ion -bombardment induced in-plane texturing was explained using the anisotropic sputtering yield theory. Our observations and analyses have provided valuable information on the optimization of the IBAD process, and shed light on the texturing mechanism in YSZ. With the in-plane aligned YSZ buffer layers, YBCO thin films grown on metallic substrates showed improved rm J_{c}s. It was found that the in-plane alignment of YSZ and that of YBCO were closely related. A direct correlation was revealed between the rm J_{c} value and the degree of the in-plane alignment for the YBCO thin films. To explain this correlation, a numerical model was applied to multi-grain superconducting paths with different

  5. Interfacial superconductivity in a bi-collinear antiferromagnetically ordered FeTe monolayer on a topological insulator

    NASA Astrophysics Data System (ADS)

    Manna, S.; Kamlapure, A.; Cornils, L.; Hänke, T.; Hedegaard, E. M. J.; Bremholm, M.; Iversen, B. B.; Hofmann, Ph.; Wiebe, J.; Wiesendanger, R.

    2017-01-01

    The discovery of high-temperature superconductivity in Fe-based compounds triggered numerous investigations on the interplay between superconductivity and magnetism, and on the enhancement of transition temperatures through interface effects. It is widely believed that the emergence of optimal superconductivity is intimately linked to the suppression of long-range antiferromagnetic (AFM) order, although the exact microscopic picture remains elusive because of the lack of atomically resolved data. Here we present spin-polarized scanning tunnelling spectroscopy of ultrathin FeTe1-xSex (x=0, 0.5) films on bulk topological insulators. Surprisingly, we find an energy gap at the Fermi level, indicating superconducting correlations up to Tc~6 K for one unit cell FeTe grown on Bi2Te3, in contrast to the non-superconducting bulk FeTe. The gap spatially coexists with bi-collinear AFM order. This finding opens perspectives for theoretical studies of competing orders in Fe-based superconductors and for experimental investigations of exotic phases in superconducting layers on topological insulators.

  6. High Temperature Superconducting Thick Films

    DOEpatents

    Arendt, Paul N.; Foltyn, Stephen R.; Groves, James R.; Holesinger, Terry G.; Jia, Quanxi

    2005-08-23

    An article including a substrate, a layer of an inert oxide material upon the surface of the substrate, (generally the inert oxide material layer has a smooth surface, i.e., a RMS roughness of less than about 2 nm), a layer of an amorphous oxide or oxynitride material upon the inert oxide material layer, a layer of an oriented cubic oxide material having a rock-salt-like structure upon the amorphous oxide material layer is provided together with additional layers such as at least one layer of a buffer material upon the oriented cubic oxide material layer or a HTS top-layer of YBCO directly upon the oriented cubic oxide material layer. With a HTS top-layer of YBCO upon at least one layer of a buffer material in such an article, Jc's of 1.4×106 A/cm2 have been demonstrated with projected Ic's of 210 Amperes across a sample 1 cm wide.

  7. Magnetotransport Properties in High-Quality Ultrathin Two-Dimensional Superconducting Mo2C Crystals.

    PubMed

    Wang, Libin; Xu, Chuan; Liu, Zhibo; Chen, Long; Ma, Xiuliang; Cheng, Hui-Ming; Ren, Wencai; Kang, Ning

    2016-04-26

    Ultrathin transition metal carbides are a class of developing two-dimensional (2D) materials with superconductivity and show great potentials for electrical energy storage and other applications. Here, we report low-temperature magnetotransport measurements on high-quality ultrathin 2D superconducting α-Mo2C crystals synthesized by a chemical vapor deposition method. The magnetoresistance curves exhibit reproducible oscillations at low magnetic fields for temperature far below the superconducting transition temperature of the crystals. We interpret the oscillatory magnetoresistance as a consequence of screening currents circling around the boundary of triangle-shaped terraces found on the surface of ultrathin Mo2C crystals. As the sample thickness decreases, the Mo2C crystals exhibit negative magnetoresistance deep in the superconducting transition regime, which reveals strong phase fluctuations of the superconducting order parameters associated with the superconductor-insulator transition. Our results demonstrate that the ultrathin superconducting Mo2C crystals provide an interesting system for studying rich transport phenomena in a 2D crystalline superconductor with enhanced quantum fluctuations.

  8. High-Temperature High-Current Superconductors: Preparation, Structure, Superconducting Properties, and Flux-Pinning Mechanisms

    NASA Astrophysics Data System (ADS)

    Hu, Shouxiang

    In bulk high-T_{rm c } superconductors, weak links at the grain boundaries and weak flux pinning are the two major causes of low critical current density (J_{ rm c}) at 77 K. In the present study, various processes designed and developed to address these problems are discussed. The novel pressurized-partial -melt-growth process, which leads to a relatively large improvement in the microstructure as well as in the superconducting properties of bulk Y-Ba-Cu-O superconductors, is described. The effects of introducing foreign elements to serve as pinning centers are reported, and the associated anomalous superconducting phenomena are explained on the basis of a detailed study of basic pinning mechanisms related to the presence of small defects. It is demonstrated that in certain cases the pinning force induced by the compression of the vortex line may be comparable to, or even larger than, the usually recognized pinning force due to the condensation energy. Studies of the pinning mechanism corresponding to large boundary defects show that boundary defects associated with certain non-superconducting inclusions and isolated weak links have a very positive role in the enhancement of both the critical current density and the effective activation energy for flux creep. However, even optimized theoretical estimates show that it will be difficult to reach J_ {rm c} values of 5 times 10^5 A/cm^2 at 77 K and H = 1 T by increasing the number of Y_2BaCuO inclusions alone. Although even higher J_{rm c} values may be achieved by introducing other types of defects using alternative approaches such as irradiation, and, probably, chemical doping, the presence of large amount of boundary defects is very important in causing a large increase in the effective activation energy for flux creep. Also studied are the anisotropic electromagnetic features of the grain-aligned YBa_2Cu _3O_{rm x} bulk superconductors. The development of novel processing methods guided by improved understanding

  9. Quantitative magneto-optical analysis of the role of finite temperatures on the critical state in YBCO thin films

    NASA Astrophysics Data System (ADS)

    Albrecht, Joachim; Brück, Sebastian; Stahl, Claudia; Ruoß, Stephen

    2016-11-01

    We use quantitative magneto-optical microscopy to investigate the influence of finite temperatures on the critical state of thin YBCO films. In particular, temperature and time dependence of supercurrents in inhomogeneous and anisotropic films are analyzed to extract the role of temperature on the supercurrents themselves and the influence of thermally activated relaxation. We find that inhomogeneities and anisotropies of the current density distribution correspond to a different temperature dependence of local supercurrents. In addition, the thermally activated decay of supercurrents can be used to extract local vortex pinning energies. With these results the modification of vortex pinning introduced by substrate structures is studied. In summary the local investigation of supercurrent densities allows the full description of the vortex pinning landscape with respect to pinning forces and energies in superconducting films with complex properties under the influence of finite temperatures.

  10. Superconductor-Insulator Transition in NbTiN Films

    NASA Astrophysics Data System (ADS)

    Burdastyh, M. V.; Postolova, S. V.; Baturina, T. I.; Proslier, T.; Vinokur, V. M.; Mironov, A. Yu.

    2017-12-01

    Experimental results indicating a direct disorder-induced superconductor-insulator transition in NbTiN thin films have been reported. It has been shown that an increase in the resistance per square in the normal state is accompanied by the suppression of the critical temperature of the superconducting transition T c according to the fermion mechanism of suppression of superconductivity by disorder. At the same time, the temperature of the Berezinskii-Kosterlitz-Thouless transition is completely suppressed at a nonzero critical temperature and, then, the ground state changes to insulating, which is characteristic of the boson model of suppression of superconductivity by disorder. It has been shown that the temperature dependences of the resistance of insulating films follow the Arrhenius activation law.

  11. Model of vortex dynamics in superconducting films in two-coil measurements of the coherence length

    NASA Astrophysics Data System (ADS)

    Lemberger, Thomas; Loh, Yen Lee

    In two-coil measurements on superconducting films, a magnetic field from a small coil is applied to the center of the film. When the amplitude of the ac field is increased, the film undergoes a transition from the ``Meissner'' state to a state with vortices and antivortices. Ultimately, the vortex density matches the applied magnetic field and field screening is negligible. Experimentally, the field at the transition is related to the superconducting coherence length, although a full theory of the relationship is lacking. We show that the mutual inductance between drive and pickup coils, on opposite sides of the film, as a function of ac field amplitude is well-described by a phenomenological model in which vortices and antivortices appear together in the film at the radius where the induced supercurrent is strongest, and then they move through a landscape of moderately strong vortex pinning sites. Work at OSU supported by DOE-Basic Energy Sciences through Grant No. FG02-08ER46533.

  12. Fabrication Of High-Tc Superconducting Integrated Circuits

    NASA Technical Reports Server (NTRS)

    Bhasin, Kul B.; Warner, Joseph D.

    1992-01-01

    Microwave ring resonator fabricated to demonstrate process for fabrication of passive integrated circuits containing high-transition-temperature superconductors. Superconductors increase efficiencies of communication systems, particularly microwave communication systems, by reducing ohmic losses and dispersion of signals. Used to reduce sizes and masses and increase aiming accuracies and tracking speeds of millimeter-wavelength, electronically steerable antennas. High-Tc superconductors preferable for such applications because they operate at higher temperatures than low-Tc superconductors do, therefore, refrigeration systems needed to maintain superconductivity designed smaller and lighter and to consume less power.

  13. Emergence of superconductivity from the dynamically heterogeneous insulating state in La(2-x)Sr(x)CuO4.

    PubMed

    Shi, Xiaoyan; Logvenov, G; Bollinger, A T; Božović, I; Panagopoulos, C; Popović, Dragana

    2013-01-01

    A central issue for copper oxides is the nature of the insulating ground state at low carrier densities and the emergence of high-temperature superconductivity from that state with doping. Even though this superconductor-insulator transition (SIT) is a zero-temperature transition, measurements are not usually carried out at low temperatures. Here we use magnetoresistance to probe both the insulating state at very low temperatures and the presence of superconducting fluctuations in La(2-x)Sr(x)CuO(4) films, for doping levels that range from the insulator to the superconductor (x  =  0.03-0.08). We observe that the charge glass behaviour, characteristic of the insulating state, is suppressed with doping, but it coexists with superconducting fluctuations that emerge already on the insulating side of the SIT. The unexpected quenching of the superconducting fluctuations by the competing charge order at low temperatures provides a new perspective on the mechanism for the SIT.

  14. Novel voltage signal at proximity-induced superconducting transition temperature in gold nanowires

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Tang, JunXiong; Wang, ZiQiao; Sun, Yi; Sun, QingFeng; Chan, Moses H. W.

    2018-08-01

    We observed a novel voltage peak in the proximity-induced superconducting gold (Au) nanowire while cooling the sample through the superconducting transition temperature. The voltage peak turned dip during warming. The voltage peak or dip was found to originate respectively from the emergence or vanishing of the proximity-induced superconductivity in the Au nanowire. The amplitude of the voltage signal depends on the temperature scanning rate, and it cannot be detected when the temperature is changed slower than 0.03 K/min. This transient feature suggests the non-equilibrium property of the effect. Ginzburg-Landau model clarified the voltage peak by considering the emergence of Cooper pairs of relatively lower free energy in superconducting W contact and the non-equilibrium diffusion of Cooper pairs and quasiparticles.

  15. Superconductivity in highly disordered NbN nanowires.

    PubMed

    Arutyunov, K Yu; Ramos-Álvarez, A; Semenov, A V; Korneeva, Yu P; An, P P; Korneev, A A; Murphy, A; Bezryadin, A; Gol'tsman, G N

    2016-11-25

    The topic of superconductivity in strongly disordered materials has attracted significant attention. These materials appear to be rather promising for fabrication of various nanoscale devices such as bolometers and transition edge sensors of electromagnetic radiation. The vividly debated subject of intrinsic spatial inhomogeneity responsible for the non-Bardeen-Cooper-Schrieffer relation between the superconducting gap and the pairing potential is crucial both for understanding the fundamental issues of superconductivity in highly disordered superconductors, and for the operation of corresponding nanoelectronic devices. Here we report an experimental study of the electron transport properties of narrow NbN nanowires with effective cross sections of the order of the debated inhomogeneity scales. The temperature dependence of the critical current follows the textbook Ginzburg-Landau prediction for the quasi-one-dimensional superconducting channel I c  ∼ (1-T/T c ) 3/2 . We find that conventional models based on the the phase slip mechanism provide reasonable fits for the shape of R(T) transitions. Better agreement with R(T) data can be achieved assuming the existence of short 'weak links' with slightly reduced local critical temperature T c . Hence, one may conclude that an 'exotic' intrinsic electronic inhomogeneity either does not exist in our structures, or, if it does exist, it does not affect their resistive state properties, or does not provide any specific impact distinguishable from conventional weak links.

  16. Complete Fabrication of a Traversable 3 µm Thick NbN Film Superconducting Coil with Cu plated layer of 42m in Length in a Spiral Three-Storied Trench Engraved in a Si Wafer of 76.2 mm in Diameter Formed by MEMS Technology for a Compact SMES with High Energy Storage Volume Density

    NASA Astrophysics Data System (ADS)

    Suzuki, Yasuhiro; Iguchi, Nobuhiro; Adachi, Kazuhiro; Ichiki, Akihisa; Hioki, Tatsumi; Hsu, Che-Wei; Sato, Ryoto; Kumagai, Shinya; Sasaki, Minoru; Noh, Joo-Hyong; Sakurahara, Yuuske; Okabe, Kyohei; Takai, Osamu; Honma, Hideo; Watanabe, Hideo; Sakoda, Hitoshi; Sasagawa, Hiroaki; Doy, Hideyuki; Zhou, Shuliang; Hori, H.; Nishikawa, Shigeaki; Nozaki, Toshihiro; Sugimoto, Noriaki; Motohiro, Tomoyoshi

    2017-09-01

    Based on the concept of a novel approach to make a compact SMES unit composed of a stack of Si wafers using MEMS process proposed previously, a complete fabrication of a traversable 3 µam thick NbN film superconducting coil lined with Cu plated layer of 42m in length in a spiral three-storied trench engraved in and extended over a whole Si-wafer of 76.2 mm in diameter was attained for the first time. With decrease in temperature, the DC resistivity showed a metallic decrease indicating the current pass was in the Cu plated layer and then made a sudden fall to residual contact resistance indicating the shift of current pass from the Cu plated layer to the NbN film at the critical temperature Tc of 15.5K by superconducting transition. The temperature dependence of I-V curve showed the increase in the critical current with decrease in the temperature and the highest critical current measured was 220 mA at 4K which is five times as large as that obtained in the test fabrication as the experimental proof of concept presented in the previous report. This completion of a one wafer superconducting NbN coil is an indispensable step for the next proof of concept of fabrication of series-connected two wafer coils via superconductive joint which will read to series connected 600 wafer coils finally, and for replacement of NbN by high Tc superconductor such as YBa2Cu3O7-x for operation under the cold energy of liquid hydrogen or liquid nitrogen.

  17. Proceedings of the 4th International Conference and Exhibition: World Congress on Superconductivity, Volume 2

    NASA Technical Reports Server (NTRS)

    Krishen, Kumar (Editor); Burnham, Calvin (Editor)

    1995-01-01

    This document contains papers presented at the 4th International Conference Exhibition: World Congress on Superconductivity held June 27-July 1, 1994 in Orlando, Florida. These documents encompass research, technology, applications, funding, political, and social aspects of superconductivity. The areas covered included: high-temperature materials; thin films; C-60 based superconductors; persistent magnetic fields and shielding; fabrication methodology; space applications; physical applications; performance characterization; device applications; weak link effects and flux motion; accelerator technology; superconductivity energy; storage; future research and development directions; medical applications; granular superconductors; wire fabrication technology; computer applications; technical and commercial challenges; and power and energy applications.

  18. Fast superconducting magnetic field switch

    DOEpatents

    Goren, Yehuda; Mahale, Narayan K.

    1996-01-01

    The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles.

  19. Fast superconducting magnetic field switch

    DOEpatents

    Goren, Y.; Mahale, N.K.

    1996-08-06

    The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles. 6 figs.

  20. Processing of La(1.8)Sr(0.2)CuO4 and YBa2Cu3O7 superconducting thin films by dual-ion-beam sputtering

    NASA Astrophysics Data System (ADS)

    Madakson, P.; Cuomo, J. J.; Yee, D. S.; Roy, R. A.; Scilla, G.

    1988-03-01

    High-quality La(1.8)Sr(0.2)CuO4 and YBa2Cu3O7 superconducting thin films, with zero resistance at 88 K, have been made by dual-ion-beam sputtering of metal and oxide targets at elevated temperatures. The films are about 1.0 micron thick and are single phase after annealing. The substrates investigated are Nd-YAP, MgO, SrF2, Si, CaF2, ZrO2-(9 pct)Y2O3, BaF2, Al2O3, and SrTiO3. Characterization of the films was carried out using Rutherford backscattering spectroscopy, resistivity measurements, TEM, X-ray diffraction, and SIMS. Substrate/film interaction was observed in every case. This generally involves diffusion of the substrate into the film, which is accompanied by, for example, the replacement of Ba by Sr in the YBa2Cu2O7 structure, in the case of SrTiO3 substrate. The best substrates were those that did not significantly diffuse into the film and which did not react chemically with the film.

  1. High-kinetic inductance additive manufactured superconducting microwave cavity

    DOE PAGES

    Holland, Eric T.; Rosen, Yaniv J.; Materise, Nicholas; ...

    2017-11-13

    We present that investigations into the microwave surface impedance of superconducting resonators have led to the development of single photon counters that rely on kinetic inductance for their operation, while concurrent progress in additive manufacturing, “3D printing,” opens up a previously inaccessible design space for waveguide resonators. In this manuscript, we present results from the synthesis of these two technologies in a titanium, aluminum, vanadium (Ti-6Al-4V) superconducting radio frequency resonator which exploits a design unattainable through conventional fabrication means. Additionally, we find that Ti-6Al-4V has two distinct superconducting transition temperatures observable in heat capacity measurements. The higher transition temperature ismore » in agreement with DC resistance measurements, while the lower transition temperature, not previously known in the literature, is consistent with the observed temperature dependence of the superconducting microwave surface impedance. From the surface reactance, we extract a London penetration depth of 8 ± 3 μm—roughly an order of magnitude larger than other titanium alloys and several orders of magnitude larger than other conventional elemental superconductors.« less

  2. High-kinetic inductance additive manufactured superconducting microwave cavity

    NASA Astrophysics Data System (ADS)

    Holland, Eric T.; Rosen, Yaniv J.; Materise, Nicholas; Woollett, Nathan; Voisin, Thomas; Wang, Y. Morris; Torres, Sharon G.; Mireles, Jorge; Carosi, Gianpaolo; DuBois, Jonathan L.

    2017-11-01

    Investigations into the microwave surface impedance of superconducting resonators have led to the development of single photon counters that rely on kinetic inductance for their operation, while concurrent progress in additive manufacturing, "3D printing," opens up a previously inaccessible design space for waveguide resonators. In this manuscript, we present results from the synthesis of these two technologies in a titanium, aluminum, vanadium (Ti-6Al-4V) superconducting radio frequency resonator which exploits a design unattainable through conventional fabrication means. We find that Ti-6Al-4V has two distinct superconducting transition temperatures observable in heat capacity measurements. The higher transition temperature is in agreement with DC resistance measurements, while the lower transition temperature, not previously known in the literature, is consistent with the observed temperature dependence of the superconducting microwave surface impedance. From the surface reactance, we extract a London penetration depth of 8 ± 3 μm—roughly an order of magnitude larger than other titanium alloys and several orders of magnitude larger than other conventional elemental superconductors.

  3. High-kinetic inductance additive manufactured superconducting microwave cavity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Holland, Eric T.; Rosen, Yaniv J.; Materise, Nicholas

    We present that investigations into the microwave surface impedance of superconducting resonators have led to the development of single photon counters that rely on kinetic inductance for their operation, while concurrent progress in additive manufacturing, “3D printing,” opens up a previously inaccessible design space for waveguide resonators. In this manuscript, we present results from the synthesis of these two technologies in a titanium, aluminum, vanadium (Ti-6Al-4V) superconducting radio frequency resonator which exploits a design unattainable through conventional fabrication means. Additionally, we find that Ti-6Al-4V has two distinct superconducting transition temperatures observable in heat capacity measurements. The higher transition temperature ismore » in agreement with DC resistance measurements, while the lower transition temperature, not previously known in the literature, is consistent with the observed temperature dependence of the superconducting microwave surface impedance. From the surface reactance, we extract a London penetration depth of 8 ± 3 μm—roughly an order of magnitude larger than other titanium alloys and several orders of magnitude larger than other conventional elemental superconductors.« less

  4. Topological Magnon Bands and Unconventional Superconductivity in Pyrochlore Iridate Thin Films.

    PubMed

    Laurell, Pontus; Fiete, Gregory A

    2017-04-28

    We theoretically study the magnetic properties of pyrochlore iridate bilayer and trilayer thin films grown along the [111] direction using a strong coupling approach. We find the ground state magnetic configurations on a mean field level and carry out a spin-wave analysis about them. In the trilayer case the ground state is found to be the all-in-all-out (AIAO) state, whereas the bilayer has a deformed AIAO state. For all parameters of the spin-orbit coupled Hamiltonian we study, the lowest magnon band in the trilayer case has a nonzero Chern number. In the bilayer case we also find a parameter range with nonzero Chern numbers. We calculate the magnon Hall response for both geometries, finding a striking sign change as a function of temperature. Using a slave-boson mean-field theory we study the doping of the trilayer system and discover an unconventional time-reversal symmetry broken d+id superconducting state. Our study complements prior work in the weak coupling limit and suggests that the [111] grown thin film pyrochlore iridates are a promising candidate for topological properties and unconventional orders.

  5. Transition metal substitutions for Cu in BSCCO: An instructive probe of high temperature superconductivity

    NASA Astrophysics Data System (ADS)

    Schneider, Clinton W.

    1998-12-01

    Single crystals of the high temperature superconductor Bisb2Srsb2Casb1(Cusb{1-x}Msb{x})sb2)Osb{8+delta} have been grown for M = Zn, Ni, Co, Fe, and Pd in order to probe the effect of transition metal impurities on superconducting properties. Samples have been characterized by XRD, electron microprobe, and transport measurements. Measurement of resistance is used to determine the depression of Tsb{c} due to the impurities. We determine a value dTsb{c}/dx = -7.8K/at/for all substituents, independent of magnetic moment. Considered in terms of the Abrikosov-Gorkov theory for impurity scattering in superconductors, this result agrees with a d-wave order parameter and strong coupling.

  6. Magnetic field dependence of high- T c interface superconductivity in L a 1.55 S r 0.45 Cu O 4 / L a 2 Cu O 4 heterostructures

    DOE PAGES

    Gasparov, V. A.; Drigo, L.; Audouard, A.; ...

    2016-07-11

    Heterostructures made of a layer of a cuprate insulator La 2CuO 4 on the top of a layer of a nonsuperconducting cuprate metal La 1.55Sr 0.45CuO 4 show high-T c interface superconductivity confined within a single CuO 2 plane. Given this extreme quasi-two-dimensional quantum confinement, it is of interest to find out how interface superconductivity behaves when exposed to an external magnetic field. With this motivation, we have performed contactless tunnel-diode-oscillator-based measurements in pulsed magnetic fields up to 56 T as well as measurements of the complex mutual inductance between a spiral coil and the film in static fields upmore » to 3 T. Remarkably, we observe that interface superconductivity survives up to very high perpendicular fields, in excess of 40 T. Additionally, the critical magnetic field H m(T) reveals an upward divergence with decreasing temperature, in line with vortex melting as in bulk superconducting cuprates.« less

  7. Low-temperature rapid synthesis and superconductivity of Fe-based oxypnictide superconductors.

    PubMed

    Fang, Ai-Hua; Huang, Fu-Qiang; Xie, Xiao-Ming; Jiang, Mian-Heng

    2010-03-17

    Fe-based oxypnictide superconductors were successfully synthesized at lower reaction temperatures and with shorter reaction times made possible by starting with less stable compounds, which provide a larger driving force for reactions. Using ball-milled powders of intermediate compounds, phase-pure superconductors with T(c) above 50 K were synthesized at 1173 K in 20 min. This method is particularly advantageous for retaining F, a volatile dopant that enhances superconductivity. Bulk superconductivity and high upper critical fields up to 392 T in Sm(0.85)Nd(0.15)FeAsO(0.85)F(0.15) were demonstrated.

  8. A new ring-shape high-temperature superconducting trapped-field magnet

    NASA Astrophysics Data System (ADS)

    Sheng, Jie; Zhang, Min; Wang, Yawei; Li, Xiaojian; Patel, Jay; Yuan, Weijia

    2017-09-01

    This paper presents a new trapped-field magnet made of second-generation high-temperature superconducting (2G HTS) rings. This so-called ring-shape 2G HTS magnet has the potential to provide much stronger magnetic fields relative to existing permanent magnets. Compared to existing 2G HTS trapped- field magnets, e.g. 2G HTS bulks and stacks, this new ring-shape 2G HTS magnet is more flexible in size and can be made into magnets with large dimensions for industrial applications. Effective magnetization is the key to being able to use trapped-field magnets. Therefore, this paper focuses on the magnetization mechanism of this new magnet using both experimental and numerical methods. Unique features have been identified and quantified for this new type of HTS magnet in the field cooling and zero field cooling process. The magnetization mechanism can be understood by the interaction between shielding currents and the penetration of external magnetic fields. An accumulation in the trapped field was observed by using multiple pulse field cooling. Three types of demagnetization were studied to measure the trapped-field decay for practical applications. Our results show that this new ring-shape HTS magnet is very promising in the trapping of a high magnetic field. As a super-permanent magnet, it will have a significant impact on large-scale industrial applications, e.g. the development of HTS machines with a very high power density and HTS magnetic resonance imaging devices.

  9. Transport critical current measurement apparatus using liquid nitrogen cooled high-T(c) superconducting magnet with variable temperature insert.

    PubMed

    Nishijima, G; Kitaguchi, H; Tshuchiya, Y; Nishimura, T; Kato, T

    2013-01-01

    We have developed an apparatus to investigate transport critical current (I(c)) as a function of magnetic field and temperature using only liquid nitrogen. The apparatus consists of a (Bi,Pb)(2)Sr(2)Ca(2)Cu(3)O(10) (Bi-2223) superconducting magnet, an outer dewar, and a variable temperature insert (VTI). The magnet, which is operated in depressurized liquid nitrogen, generates magnetic field up to 1.26 T. The sample is also immersed in liquid nitrogen. The pressure in the VTI is controlled from 0.02 to 0.3 MPa, which corresponds to temperature ranging from 66 to 88 K. We have confirmed the long-term stable operation of the Bi-2223 magnet at 1 T. The temperature stability of the sample at high transport current was also demonstrated. The apparatus provides easy-operating I(c) measurement environment for a high-T(c) superconductor up to 500 A in magnetic fields up to 1 T and in temperatures ranging from 66 to 88 K.

  10. Superconductivity in interacting interfaces of cuprate-based heterostructures

    NASA Astrophysics Data System (ADS)

    Di Castro, Daniele; Balestrino, Giuseppe

    2018-07-01

    Low dimensional superconducting systems have been the subject of numerous studies in the recent past, with the aim of achieving a higher and higher critical temperature (T c ). The recent improvement in film deposition techniques has allowed the realization of artificial heterostructures, with atomically flat surfaces and interfaces, where novel properties appear that are not present in the single constituent. For instance, quasi-2D superconductivity was found at the interface between different oxides. In this review we analyze, in particular, the quasi-2D superconductivity occurring at the interface between two non-superconducting oxides, mostly cuprates. Throughout a comparison of the superconducting properties of different oxide heterostructures and superlattices, we propose a phenomenological explanation of the behavior of the T c as a function of the number of conducting CuO2 planes. This is achieved by introducing two different interactions between the superconducting 2D sheets. This interpretation is finally extended also to standard high T c cuprates, contributing to the solution of the long-standing question of the dependence of T c on the number of CuO2 planes in these systems.

  11. Electrical properties of epitaxial yttrium iron garnet ultrathin films at high temperatures

    NASA Astrophysics Data System (ADS)

    Thiery, N.; Naletov, V. V.; Vila, L.; Marty, A.; Brenac, A.; Jacquot, J.-F.; de Loubens, G.; Viret, M.; Anane, A.; Cros, V.; Ben Youssef, J.; Beaulieu, N.; Demidov, V. E.; Divinskiy, B.; Demokritov, S. O.; Klein, O.

    2018-02-01

    We report a study on the electrical properties of 19-nm-thick yttrium iron garnet (YIG) films grown by liquid phase epitaxy on gadolinium gallium garnet single crystal. The electrical conductivity and Hall coefficient are measured in the high-temperature range [300,400] K using a Van der Pauw four-point probe technique. We find that the electrical resistivity decreases exponentially with increasing temperature following an activated behavior corresponding to a band gap of Eg≈2 eV. It drops to values about 5 ×103Ω cm at T =400 K, thus indicating that epitaxial YIG ultrathin films behave as large gap semiconductors. We also infer the Hall mobility, which is found to be positive (p type) at 5 cm2V-1sec-1 and almost independent of temperature. We discuss the consequence for nonlocal spin transport experiments performed on YIG at room temperature and demonstrate the existence of electrical offset voltages to be disentangled from pure spin effects.

  12. Thin film coatings for space electrical power system applications

    NASA Technical Reports Server (NTRS)

    Gulino, Daniel A.

    1989-01-01

    This paper examines some of the ways in which thin film coatings can play a role in aerospace applications. Space systems discussed include photovoltaic and solar dynamic electric power generation systems, including applications in environmental protection, thermal energy storage, and radiator emittance enhancement. Potential applications of diamondlike films to both atmospheric and space based systems are examined. Also, potential uses of thin films of the recently discovered high-temperature superconductive materials are discussed.

  13. Thin film coatings for space electrical power system applications

    NASA Technical Reports Server (NTRS)

    Gulino, Daniel A.

    1988-01-01

    This paper examines some of the ways in which thin film coatings can play a role in aerospace applications. Space systems discussed include photovoltaic and solar dynamic electric power generation systems, including applications in environmental protection, thermal energy storage, and radiator emittance enhancement. Potential applications of diamondlike films to both atmospheric and space based systems are examined. Also, potential uses of thin films of the recently discovered high-temperature superconductive materials are discussed.

  14. Phase-incoherent superconducting pairs in the normal state of Ba(Fe(1-x)Co(x))₂As₂.

    PubMed

    Sheet, Goutam; Mehta, Manan; Dikin, D A; Lee, S; Bark, C W; Jiang, J; Weiss, J D; Hellstrom, E E; Rzchowski, M S; Eom, C B; Chandrasekhar, V

    2010-10-15

    The normal state properties of the recently discovered ferropnictide superconductors might hold the key to understanding their exotic superconductivity. Using point-contact spectroscopy we show that Andreev reflection between an epitaxial thin film of Ba(Fe(0.92)Co(0.08))₂As₂ and a silver tip can be seen in the normal state of the film up to temperature T∼1.3T(c), where T(c) is the critical temperature of the superconductor. Andreev reflection far above T(c) can be understood only when superconducting pairs arising from strong fluctuation of the phase of the complex superconducting order parameter exist in the normal state. Our results provide spectroscopic evidence of phase-incoherent superconducting pairs in the normal state of the ferropnictide superconductors.

  15. Two gaps make a high-temperature superconductor?

    NASA Astrophysics Data System (ADS)

    Hüfner, S.; Hossain, M. A.; Damascelli, A.; Sawatzky, G. A.

    2008-06-01

    One of the keys to the high-temperature superconductivity puzzle is the identification of the energy scales associated with the emergence of a coherent condensate of superconducting electron pairs. These might provide a measure of the pairing strength and of the coherence of the superfluid, and ultimately reveal the nature of the elusive pairing mechanism in the superconducting cuprates. To this end, a great deal of effort has been devoted to investigating the connection between the superconducting transition temperature Tc and the normal-state pseudogap crossover temperature T*. Here we present a review of a large body of experimental data which suggests a coexisting two-gap scenario, i.e. superconducting gap and pseudogap, over the whole superconducting dome. We focus on spectroscopic data from cuprate systems characterized by T_c^max\\sim 95\\,K , such as Bi2Sr2CaCu2O8+δ, YBa2Cu3O7-δ, Tl2Ba2CuO6+δ and HgBa2CuO4+δ, with particular emphasis on the Bi-compound which has been the most extensively studied with single-particle spectroscopies.

  16. Metalorganic deposition method for forming epitaxial thallium-based copper oxide superconducting films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Olsen, W.L.; Eddy, M.M.; Hammond, R.B.

    1991-12-10

    This patent describes a method for producing a superconducting article comprising an oriented metal oxide superconducting layer containing thallium, optionally calcium, barium and copper, the layer being at least 30 {Angstrom} and having a c-axis oriented normal to a crystalline substrate surface. It comprises coating the crystalline substrate surface with a solution of thallium, optionally calcium, barium and copper carboxylate soaps dispersed in a medium of hydrocarbons of halohydrocarbons with a stoichiometric metal ratio to form the oxide superconducting layer, prepyrolyzing the soaps coated on the substrate at a temperature of 350{degrees} C. or less in an oxygen containing atmosphere,more » and pyrolyzing the soaps at a temperature in the range of 800{degrees} - 900{degrees} C. in the presence of oxygen and an overpressure of thallium for a sufficient time to produce the superconducting layer on the substrate, wherein usable portions of the superconducting layer are epitaxial to the substrate.« less

  17. Microelectronic superconducting crossover and coil

    DOEpatents

    Wellstood, F.C.; Kingston, J.J.; Clarke, J.

    1994-03-01

    A microelectronic component comprising a crossover is provided comprising a substrate, a first high T[sub c] superconductor thin film, a second insulating thin film comprising SrTiO[sub 3]; and a third high T[sub c] superconducting film which has strips which crossover one or more areas of the first superconductor film. An in situ method for depositing all three films on a substrate is provided which does not require annealing steps and which can be opened to the atmosphere between depositions. 13 figures.

  18. Frequency-tunable superconducting resonators via nonlinear kinetic inductance

    NASA Astrophysics Data System (ADS)

    Vissers, M. R.; Hubmayr, J.; Sandberg, M.; Chaudhuri, S.; Bockstiegel, C.; Gao, J.

    2015-08-01

    We have designed, fabricated, and tested a frequency-tunable high-Q superconducting resonator made from a niobium titanium nitride film. The frequency tunability is achieved by injecting a DC through a current-directing circuit into the nonlinear inductor whose kinetic inductance is current-dependent. We have demonstrated continuous tuning of the resonance frequency in a 180 MHz frequency range around 4.5 GHz while maintaining the high internal quality factor Qi > 180 000. This device may serve as a tunable filter and find applications in superconducting quantum computing and measurement. It also provides a useful tool to study the nonlinear response of a superconductor. In addition, it may be developed into techniques for measurement of the complex impedance of a superconductor at its transition temperature and for readout of transition-edge sensors.

  19. Terahertz Mixing Characteristics of NbN Superconducting Tunnel Junctions and Related Astronomical Observations

    NASA Astrophysics Data System (ADS)

    Li, J.

    2010-01-01

    High-sensitivity superconducting SIS (superconductor-insulator-superconductor) mixers are playing an increasingly important role in the terahertz (THz) astronomical observation, which is an emerging research frontier in modern astrophysics. Superconducting SIS mixers with niobium (Nb) tunnel junctions have reached a sensitivity close to the quantum limit, but have a frequency limit about 0.7 THz (i.e., gap frequency of Nb tunnel junctions). Beyond this frequency Nb superconducting films will absorb energetic photons (i.e., energy loss) to break Cooper pairs, thereby resulting in significant degradation of the mixer performance. Therefore, it is of particular interest to develop THz superconducting SIS mixers incorporating tunnel junctions with a larger energy gap. Niobium-nitride (NbN) superconducting tunnel junctions have been long known for their large energy gap, almost double that of Nb ones. With the introduction of epitaxially grown NbN films, the fabrication technology of NbN superconducting tunnel junctions has been considerably improved in the recent years. Nevertheless, their performances are still not as good as Nb ones, and furthermore they are not yet demonstrated in real astronomical applications. Given the facts mentioned above, in this paper we systematically study the quantum mixing behaviors of NbN superconducting tunnel junctions in the THz regime and demonstrate an astronomical testing observation with a 0.5 THz superconducting SIS mixer developed with NbN tunnel junctions. The main results of this study include: (1) successful design and fabrication of a 0.4˜0.6 THz waveguide mixing circuit with the high-dielectric-constant MgO substrate; (2) successful fabrication of NbN superconducting tunnel junctions with the gap voltage reaching 5.6 mV and the quality factor as high as 15; (3) demonstration of a 0.5 THz waveguide NbN superconducting SIS mixer with a measured receiver noise temperature (no correction) as low as five times the quantum limit

  20. Prediction of superconducting iron–bismuth intermetallic compounds at high pressure

    PubMed Central

    Amsler, Maximilian; Naghavi, S. Shahab

    2017-01-01

    The synthesis of materials in high-pressure experiments has recently attracted increasing attention, especially since the discovery of record breaking superconducting temperatures in the sulfur–hydrogen and other hydrogen-rich systems. Commonly, the initial precursor in a high pressure experiment contains constituent elements that are known to form compounds at ambient conditions, however the discovery of high-pressure phases in systems immiscible under ambient conditions poses an additional materials design challenge. We performed an extensive multi component ab initio structural search in the immiscible Fe–Bi system at high pressure and report on the surprising discovery of two stable compounds at pressures above ≈36 GPa, FeBi2 and FeBi3. According to our predictions, FeBi2 is a metal at the border of magnetism with a conventional electron–phonon mediated superconducting transition temperature of T c = 1.3 K at 40 GPa. PMID:28507678