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Sample records for mocvd ybco films

  1. Deposition studies and coordinated characterization of MOCVD YBCO films on IBAD-MgO templates.

    SciTech Connect

    Aytug, Tolga; Paranthaman, Mariappan Parans; Heatherly Jr, Lee; Zhang, Yifei; Kim, Kyunghoon; Goyal, Amit; Maroni, V. A.; List III, Frederick Alyious

    2009-01-01

    A recently installed research metal organic chemical vapor deposition (MOCVD) system at Oak Ridge National Laboratory, provided by SuperPower, Inc., has been used to investigate the processing variables of MOCVD YBCO precursors and trends in the resulting properties. Systematic studies of film growth were carried out by optimizing deposition temperature and oxygen flow rate. Structural and superconducting properties of the YBCO films were analyzed by extensive X-ray diffraction, scanning electron microspcopy and transport measurements. The identification of intermediate phase formations after the YBCO precursor transformation was investigated with coordinated reel-to-reel Raman microprobe analysis. With the combination of these characterization techniques, an improved understanding of the growth characteristics of MOCVD YBCO films was established. Finally, critical current densities greater than 2 MA/cm2 for film thicknesses of 0.8 m have been demonstrated.

  2. 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.

  3. 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.

  4. Enhanced flux pinning in MOCVD-YBCO films through Zr-additions:Systematic feasibility studies

    SciTech Connect

    Aytug, Tolga; Paranthaman, Mariappan Parans; Specht, Eliot D; Kim, Kyunghoon; Zhang, Yifei; Cantoni, Claudia; Zuev, Yuri L; Goyal, Amit; Christen, David K; Maroni, Victor A.

    2009-01-01

    Systematic effects of Zr additions on the structural and flux pinning properties of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films deposited by metal-organic chemical vapor deposition (MOCVD) have been investigated. Detailed characterization, conducted by coordinated transport, x-ray diffraction, scanning and transmission electron microscopy analyses, and imaging Raman microscopy have revealed trends in the resulting property/performance correlations of these films with respect to varying mole percentages (mol%) of added Zr. For compositions {le} 7.5 mol%, Zr additions lead to improved in-field critical current density, as well as extra correlated pinning along the c-axis direction of the YBCO films via the formation of columnar, self-assembled stacks of BaZrO{sub 3} nanodots.

  5. Enhanced flux pinning in MOCVD-YBCO films through Zr additions : systematic feasibility studies.

    SciTech Connect

    Aytug, T.; Paranthaman, M.; Specht, E. D.; Zhang, Y.; Kim, K.; Zuev, Y. L.; Cantoni, C.; Goyal, A.; Christen, D. K.; Maroni, V. A.; Chen, Y.; Selvamanickam, V.; ORNL; SuperPower, Inc.

    2010-01-01

    Systematic effects of Zr additions on the structural and flux pinning properties of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films deposited by metal-organic chemical vapor deposition (MOCVD) have been investigated. Detailed characterization, conducted by coordinated transport, x-ray diffraction, scanning and transmission electron microscopy analyses, and imaging Raman microscopy have revealed trends in the resulting property/performance correlations of these films with respect to varying mole percentages (mol%) of added Zr. For compositions {le} 7.5 mol%, Zr additions lead to improved in-field critical current density, as well as extra correlated pinning along the c-axis direction of the YBCO films via the formation of columnar, self-assembled stacks of BaZrO{sub 3} nanodots.

  6. In-situ thin films by MOCVD

    SciTech Connect

    Norris, P.E.; Orlando, G.W. )

    1990-01-01

    This paper reports on the growth of high quality yttrium barium copper oxide (YBCO) thin films by MOCVD. Three MOCVD processes have been studied: a two-step (growth/post anneal) process requiring O{sub 2} anneal at 950--980 C, an in-situ (one step, no post growth anneal) process at 800--850 C and a plasma-enhanced, in-situ process (PE-MOCVD), which is operable at still lower substrate temperatures. The in-situ PE-MOCVD process is of great interest since, to a substantial degree, the growth temperature determines the degree of compatibility of a process with substrate materials and existing device technologies, such as VLSI-SilicoVLSI-Silicon.

  7. Residual stress measurement in YBCO thin films.

    SciTech Connect

    Cheon, J. H.; Singh, J. P.

    2002-05-13

    Residual stress in YBCO films on Ag and Hastelloy C substrates was determined by using 3-D optical interferometry and laser scanning to measure the change in curvature radius before and after film deposition. The residual stress was obtained by appropriate analysis of curvature measurements. Consistent with residual thermal stress calculations based on the thermal expansion coefficient mismatch between the substrates and YBCO film, the measured residual stress in the YBCO film on Hastelloy C substrate was tensile, while it was compressive on the Ag substrate. The stress values measured by the two techniques were generally in good agreement, suggesting that optical interferometry and laser scanning have promise for measuring residual stresses in thin films.

  8. Fast infrared response of YBCO thin films

    NASA Technical Reports Server (NTRS)

    Ballentine, P. H.; Kadin, A. M.; Donaldson, W. R.; Scofield, J. H.; Bajuk, L.

    1990-01-01

    The response to short infrared pulses of some epitaxial YBCO films prepared by sputter deposition and by electron-beam evaporation is reported. The response is found to be essentially bolometric on the ns timescale, with some indirect hints of nonequilibrium electron transport on the ps scale. Fast switching could be obtained either by biasing the switch close to the critical current or by cooling the film below about 20 K. These results are encouraging for potential application to a high-current optically-triggered opening switch.

  9. Fabrication of YSZ buffer layer by single source MOCVD technique for YBCO coated conductor

    NASA Astrophysics Data System (ADS)

    Jun, Byung-Hyuk; Sun, Jong-Won; Kim, Ho-Jin; Lee, Dong-Wook; Jung, Choong-Hwan; Park, Soon-Dong; Kim, Chan-Joong

    2003-10-01

    Yttria stabilized zirconia (YSZ) buffer layers were deposited by a metal organic chemical vapor deposition technique using a single liquid source for the application of YBa 2Cu 3O 7- δ (YBCO) coated conductor. Y:Zr mole ratio was 0.2:0.8, and tetrahydrofuran (THF) was used as a solvent. The (1 0 0) single crystal MgO substrate was used for searching the deposition conditions. Bi-axially oriented CeO 2 and NiO films were fabricated on {1 0 0} <0 0 1> textured Ni substrate by the same method and used as templates. At a constant working pressure of 10 Torr, the deposition temperatures (660-800 °C) and oxygen flow rates (100-500 sccm) were changed to find the optimum deposition condition. The best (1 0 0) oriented YSZ film on MgO was obtained at 740 °C and O 2 flow rate of 300 sccm. For a YSZ buffer layer with this deposition condition on a CeO 2/Ni template, full width half maximum values of the in-plane ( ϕ-scan) and out-of-plane ( ω-scan) alignments were 10.6° and 9.8°, respectively. The SEM image of YSZ film on CeO 2/Ni showed surface morphologies without microcracks. The film deposition rate was about 100 nm/min.

  10. The optical properties of YBCO thin films

    NASA Astrophysics Data System (ADS)

    Wallace, Roger James

    We present strong evidence that there is no specific mid- infrared absorption band in YBCO and a generalised Drude model can be used to explain all of the observed features in the optical spectrum. A high vacuum, low temperature ATR experiment has been used to excite surface plasmons (SPP) on YBCO thin films at different temperatures. We have found that the SPP resonance condition varies systematically with temperature. The temperature dependent dielectric function and optical conductivity of YBCO at 2984nm have been determined. We have shown that the renal and imaginary dielectric function of YBCO, ~ɛ= ɛ1 + iɛ2, at 2984nm, are linearly dependent on temperature: ɛ1(T) = -52 + 0.008T and ɛ1(T) = 4 + 0.1T. We have calculated the optical conductivity, σ(T), and the normal reflectance, ℜ(T): σ(T) = 196 + 4.9T and ℜ(T) = 0.99-7.4 × 10-4T, where temperature is in kelvin and the conductivity is in Ω-1 cm-1. A generalised Drude model has been used to analyse our results. The generalised Drude memory function, M = 1//tau + i/omega/lambda, has been calculated as a function of temperature. The parameters 1/τ and λ can be approximated by 1/τ(T) = 50 + 6.6T and 1 + λ(T) ≅ 1.48 - 0.003T +.35 × 10-5T. These expressions are valid between 100K and 300K. An optical technique for determining the thickness of YBCO thin films has been developed. It has been used in an investigation of laser ablated plasmas. We have observed that the limit of material in the plasma plume is not the same as the limit of the luminosity of the plume. The angular distribution of material can be modelled by a cos n/Theta function over much of the range but a combined cos n/Theta + cos m/Theta function is required to describe the distribution near the visible tip of the plume.

  11. Cobalt disilicide buffer layer for YBCO film on silicon

    SciTech Connect

    Belousov, I.; Rudenko, E.; Linzen, S.; Seidel, P.

    1997-02-01

    The CoSi{sub 2} films were used as buffer layers of YBCO/CoSi{sub 2}/Si(100), YBCO/ZrO{sub 2}/CoSi{sub 2}/Si(100) and YBCO/CeO{sub 2}/YSZ/CoSi{sub 2}/epi-Si/Al{sub 2}O{sub 3} heterostructures in this work. Transition temperatures of YBCO films were obtained up to 86K for YBCO films deposited by laser ablation on the top of CeO{sub 2}/YSZ/CoSi{sub 2}/Si/Al{sub 2}O{sub 3} structure. Local nucleation on the crystal defects of silicon, the phenomenon of lateral directed growth (DLG) and agglomeration of CoSi{sub 2} phase are responsible for grain boundaries (GB) position in CoSi{sub 2} layer and its roughness. The roughness was decreased using an additional Zr film on the top structure.

  12. High-speed growth of YBa2Cu3O7-δ superconducting films on multilayer-coated Hastelloy C276 tape by laser-assisted MOCVD

    NASA Astrophysics Data System (ADS)

    Zhao, Pei; Ito, Akihiko; Kato, Takeharu; Yokoe, Daisaku; Hirayama, Tsukasa; Goto, Takashi

    2013-05-01

    The high-speed epitaxial growth of YBa2Cu3O7-δ (YBCO) superconducting films on multilayer (CeO2/LaMnO3/MgO/Gd2Zr2O7)-coated Hastelloy C276 tape was demonstrated using laser-assisted metal-organic chemical vapour deposition (laser-assisted MOCVD). The preferred orientation of the YBCO films changed from a-axis to c-axis as the deposition temperature was increased from 769 to 913 K. The c-axis-oriented YBCO film exhibited a high critical temperature of 90 K and a high critical current density of 0.5 MA cm-2 even at a high deposition rate of 55 μm h-1.

  13. Effects of oxygen pressure in preparation of insulating Sr 2AlTaO 6 thin films by MOCVD

    NASA Astrophysics Data System (ADS)

    Takahashi, Yoshihiro; Nakajima, Yuuichi; Morishita, Tadataka; Tanabe, Keiichi

    2002-10-01

    Approximately 300-nm-thick insulating Sr 2AlTaO 6 (SAT) films were prepared on 10-μm-thick YBa 2Cu 3O 7- δ (YBCO) films by metalorganic chemical vapor deposition (MOCVD) in the range of oxygen partial pressure from 13 Pa (0.1 Torr) to 667 Pa (5 Torr) for total deposition pressure of 13 hPa (10 Torr). Stoichiometric SAT films with good crystallinity and square-like grains originating from the cubic structure of SAT were obtained for all the oxygen partial pressure conditions. However, extraordinary areas were partially observed on the sample prepared in the low oxygen partial pressure below 67 Pa (0.5 Torr), which are supposed to be caused by unstableness of YBCO surface. Under the highest oxygen partial pressure condition of 667 Pa, the lower tetragonal YBCO film exhibited a Tc of 80 K, indicating a possibility of in situ oxygenation during cooling. It was also confirmed that the SAT film fabricated under this condition has good dielectric properties such as the dielectric constant of approximately 24 and the conductance below 10 -8 S.

  14. Study of high [Tc] superconducting thin films grown by MOCVD

    SciTech Connect

    Erbil, A.

    1990-01-01

    Work is described briefly, which was carried out on development of techniques to grow metal-semiconductor superlattices (artificially layered materials) and on the copper oxide based susperconductors (naturally layered materials). The current growth technique utilized is metalorganic chemical vapor deposition (MOCVD). CdTe, PbTe, La, LaTe, and Bi[sub 2]Te[sub 3] were deposited, mostly on GaAs. Several YBa[sub 2]Cu[sub 3]O[sub 7] compounds were obtained with possible superconductivity at temperatures up to 550 K (1 part in 10[sup 4]). YBa[sub 2]Cu[sub 3]O[sub 7[minus]x] and Tl[sub 2]CaBa[sub 2]Cu[sub 2]O[sub y] thin films were deposited by MOCVD on common substrates such as glass.

  15. Optical response of YBCO thin films and weak-links

    SciTech Connect

    Osterman, D.P.; Drake, R.; Patt, R.; Track, E.K.; Radparvar, M.; Faris, S.M.

    1989-03-01

    The authors have fabricated films of the high temperature superconductor YBCO and measured their response to optical and infrared radiation. This response to light is manifested by a change in the current-voltage characteristics of YBCO weak-links. They find the change to dependent upon film quality, operating point, light chopping frequency, and temperature. Depending on the type of anneal, the superconducting films exhibit metallic or semiconducting resistivity behavior above T/sub c/. The optical responsivity of semiconducting films is larger than that of metallic films. By further annealing, semiconducting films could be converted into metallic films with a concurrent decrease in their optical reponsivity. Some of the measurements have been performed with the films immersed in superfluid helium to allow the separation of non-equilibrium effects from the equilibrium bolometric response.

  16. MOCVD of multimetal and noble metal films

    NASA Astrophysics Data System (ADS)

    Endle, James Patrick

    2000-11-01

    Carbon content in TiN films produced with tetrakis(dimethylamino)titanium (TDMAT) and methylhydrazine or dimethylhydrazine can be controlled at or below 10% with a N/Ti ratio of ˜1.3 at growth temperatures between 573 and 723 K. Post-dosing either hydrazine on a CVD TiN film results in additional N-Ti bonds, indicating a surface reaction between the two precursors occurs. Co-dosing hydrazine-like compounds with larger alkyl ligands than methyl resulted in additional carbon incorporation in the TiN film. A growth system, consisting of a load lock and growth chamber, and a precursor pyrolysis system were designed and built to study metalorganic chemical vapor deposition. Addition of a bubbler and a direct liquid injection system allowed for the vaporization of solid and liquid precursors and solutions of multiple precursors. A precursor pyrolysis system was designed for high and low vapor pressure precursors and high carrier gas flow rates. The systems were used to study (Al,Ti)N and Ir film growth. (Al,Ti)N was used as a template to study the incorporation of elements into a multimetal chemical vapor deposited film using NH3 and a DLI solution of TDMAT and the tris(dimethylarnino)alane dimer (TDMAA) in toluene-NH 3 significantly decreases the decomposition temperature of both precursors. Carbon was reduced by increasing the NH3 partial pressure, and the Al incorporation was increased by increasing the TDMAA/TDMAT ratio in the DLI solution. Exposure to ambient resulted in significant oxygen incorporation and the removal of carbon and nitrogen from the (AI,Ti)N film. Conformal (AI,Ti)N films were produced at 450 K in the presence of NH3 and at 550 K without NH3. The role of O2 in Ir film growth was studied with the newly designed equipment. O2 significantly decreases the decomposition temperature of (MeCp)Ir(COD) below 425 K by preventing a carbonaceous build-up on the iridium film. By decreasing the oxygen partial pressure, the island nucleation and coalescence

  17. Probing the temperature during switching of YBCO films

    NASA Astrophysics Data System (ADS)

    Lehner, A.; Heinrich, A.; Numssen, K.; Kinder, H.

    2002-08-01

    The switching of YBCO thin films under high current load is fundamental for fault current limiters and active power switches. Its mechanism is still under debate, however, with thermal and nonthermal models being discussed. To clarify the situation, we have placed an array of thermometers directly on top of a YBCO strip and have measured the quench propagation with high spacio-temporal resolution. We compare the results with a numerical model of heat diffusion in 3D with temperature dependent material parameters and find nearly quantitative agreement. This confirms thermal runaway as the mechanism of switching.

  18. Deposition of YBCO films by high temperature spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Shields, T. C.; Abell, J. S.; Button, T. W.; Chakalov, R. A.; Chakalova, R. I.; Cai, C.; Haessler, W.; Eickemeyer, J.; de Boer, B.

    2002-08-01

    The fabrication of YBCO coated conductors on flexible textured metallic substrates requires the deposition of biaxially textured buffer layers and superconducting films. In this study we have prepared YBCO thin films on single crystal SrTiO 3 substrates and cube textured Ni substrates by spray pyrolysis. The Ni substrates have been pre-buffered with CeO 2/YSZ/CeO 2, layers deposited by pulsed laser deposition. Spray pyrolysis of nitrate solutions has been performed directly on heated substrates at temperatures between 800 and 900 °C without need for a subsequent annealing step. YBCO films deposited on both types of substrate are biaxially textured. Full width half maximum values determined from φ-scans are 8° and 20° for films on SrTiO 3 and buffered Ni substrates respectively. A transport Jc value of 1.2×10 5 A/cm 2 at 77 K and zero field has been achieved on SrTiO 3 ( T c onset=91 K, ΔTc=6 K). χ ac susceptibility measurements of films on buffered Ni substrates show Tc onsets of 88 K with ΔTc=18 K.

  19. MOCVD of very thin films of lead lanthanum titanate

    SciTech Connect

    Beach, D.B.; Vallet, C.E.

    1995-12-31

    Films of lead lanthanum titanate were deposited using metal-organic chemical vapor deposition (MOCVD) at temperatures between 500 and 550{degrees}C in a hot-wall reactor. The precursors used were Pb(THD){sub 2}, La(THD){sub 3}, and Ti(THD){sub 2}(I-OPr){sub 2} where THD = 2,2,6,6-tetramethyl-3,5-heptanedionate, O{sub 2}C{sub 11}H{sub 19}, and I-OPr = isopropoxide, OC{sub 3}H{sub 7}. The three precursors were delivered to the reactor using a single solution containing all three precursors dissolved in tetraglyme and the precursor solution was volatilized at 225{degrees}C. Films were deposited on Si and Si/Ti/Pt substrates, and characterized using Rutherford Backscattering Spectroscopy (RPS) and X-ray diffraction(XRD). Films deposited at 550{degrees}C had a composition which was close to that of the precursor solution while films deposited at 500{degrees}C were deficient in lanthanum. Even at 500{degrees}C, the desired perovskite phase showed an increase in the intensity of the X-ray lines, but did not change the width of these lines, implying the grain sizes had remained unchanged.

  20. Pulsed laser deposition of YBCO thin films on IBAD-YSZ substrates

    NASA Astrophysics Data System (ADS)

    Li, M.; Ma, B.; Koritala, R. E.; Fisher, B. L.; Venkataraman, K.; Balachandran, U.

    2003-01-01

    High-quality YBa2Cu3O7-x (YBCO) films were fabricated on yttria-stabilized zirconia (YSZ)-buffered Hastelloy C276 substrates by pulsed laser deposition. YSZ was grown by ion-beam-assisted deposition. A thin (approx10 nm) CeO2 layer was deposited before the deposition of YBCO. The crystalline structure and biaxial texture of the YBCO film and the buffer layer were examined by x-ray diffraction 2theta-scan, phi-scan and pole-figure analysis. Epitaxial growth of the YBCO film on the buffer layer was observed. Full width at half maximum (FWHM) value of 7.4° was measured from the phi-scan of YBCO(103). Raman spectroscopy showed compositional uniformity and phase integrity in the YBCO films. Surface morphologies of the YBCO films were examined by scanning electron microscopy. Comparative studies indicated that the CeO2 buffer layer significantly improves the structural alignment and superconducting properties of YBCO films. Tc = 90 K, with sharp transition, and transport Jc = 2.2 × 106 A cm-2 at 77 K in zero-external field were obtained on the 0.5 mum thick YBCO films. The dependence of Jc on the FWHM of the YBCO(103) phi-scan indicated that high Jc is associated with low FWHM.

  1. Liquid phase epitaxy of REBCO (RE=Y, Sm) thick films on YBCO thin film deposited on LAO substrate

    NASA Astrophysics Data System (ADS)

    Guo, L. S.; Chen, Y. Y.; Cheng, L.; Li, W.; Xiong, J.; Tao, B. W.; Yao, X.

    2013-03-01

    By employing YBCO/LAO thin films as seeds, we succeeded in growing REBa2Cu3Ox (REBCO, RE=Y, Sm) thick films via the LPE method in air. Remarkably, a completely covered YBCO thick film with the c-axis orientation was achieved. Moreover, SmBCO LPE films were effectively induced by the YBCO/LAO thin films at a processing temperature of 1055 °C, indicating that the YBCO/LAO thin film possesses a superheating property. Compared with the YBCO/MgO thin film, the YBCO/LAO thin film has a potentially higher thermal stability in LPE, due to its better lattice fitness at the film/substrate interface. On the other hand, compared to the thick films induced by NdGaO3 (NGO) substrates, YBCO/LAO thin-film-seeded thick films have the broad average spacing of about 150 μm between adjacent cracks, almost five times wider than the former, which benefits the practical application in electronic devices. In short, the YBCO/LAO thin film becomes a third promising candidate for inducing REBCO LPE thick films, combined with conventionally used YBCO/MgO thin films and single-crystal NGO substrates.

  2. Vortex creep in TFA-YBCO nanocomposite films

    NASA Astrophysics Data System (ADS)

    Rouco, V.; Bartolomé, E.; Maiorov, B.; Palau, A.; Civale, L.; Obradors, X.; Puig, T.

    2014-11-01

    Vortex creep in YBa2Cu3O7 - x (YBCO) films grown from the trifluoracetate (TFA) chemical route with BaZrO3 and Ba2YTaO6 second-phase nanoparticles (NPs) has been investigated by magnetic relaxation measurements. We observe that in YBCO nanocomposites the phenomenological crossover line from the elastic to the plastic creep regime is shifted to higher magnetic fields and temperatures. The origin of this shift lies on the new isotropic-strong vortex pinning contribution appearing in these nanocomposites, induced by local lattice distortions. As a consequence, we demonstrate that the addition of non-coherent NPs produces a decrease in the creep rate S in most of the phase diagram, particularly, in the range of fields and temperatures (T\\gt 60 K, {{μ }0}H\\gt 0.5 T) relevant for large scale applications.

  3. Lithographic patterning of superconducting YBCO films

    SciTech Connect

    Mishra, S.K.; Pathak, L.C.; Ray, S.K.; Kal, S.; Bhattacharya, D.; Lahiri, S.K.; Chopra, K.L.

    1992-10-01

    Microbridges of YBa{sub 2}Cu{sub 3}O{sub 7} thin films have been fabricated by conventional photolithography and wet chemical etching using EDTA, and by lift-off lithography technique. The variation of etch rate with etch time, etchant temperature, and post-deposition sintering temperature has been studied. It has been shown that both techniques are useful for film patterning. However, an additional sintering step is necessary for the chemically etched sample to regain the original film properties. An order of increase in critical current density is observed for the patterned film. 10 refs., 7 figs.

  4. Synchrotron radiation assistant MOCVD deposition of ZnO films on Si substrate

    NASA Astrophysics Data System (ADS)

    Guangtao, Yang; Guobin, Zhang; Hongjun, Zhou; Zeming, Qi

    2009-06-01

    The growth of ZnO film on Si(1 0 0) substrate has been studied with synchrotron radiation (SR) assisted MOCVD method. The diethylzinc (DEZn) and CO 2 are used as source materials, while Nitrogen is employed as a carrier gas for DEZn. With the assistance of SR the ZnO film can be deposited even at room temperature. XRD, SEM and photoluminescence (PL) studies show that the crystal quality of ZnO films grown with the assistance of SR is higher than that of those without SR assistance. The growth mechanism of ZnO film with the SR assistant MOCVD system is primarily discussed.

  5. In-situ sputtering of YBCO films for microwave applications

    NASA Technical Reports Server (NTRS)

    Ballentine, P. H.; Kadin, A. M.; Mallory, D. S.

    1991-01-01

    RF magnetron sputtering from a single YBCO target onto a heated substrate (700 C) was used to obtain c-axis-oriented 1-2-3 films that are superconducting without a subsequent annealing or oxygenation step, with Tc(R = 0) as high as 88 K on MgO and LaAlO3 substrates. This process uses an 8-in-diameter target in the sputter-up configuration, with a central grounded shield to eliminate negative ion bombardment. It can reproducibly and uniformly cover substrates as large as 3-in across at rates exceeding 1 A/s. Maintaining film composition very close to stoichiometry is essential for obtaining films with good superconducting properties and surface morphology. Optimum films have critical currents of 1 MA/sq cm at 77 K. Measurements of microwave surface resistance based on a stripline resonator indicate low surface resistance for unpatterned YBCO ground planes, but excess loss and a strong power dependence in a patterned center strip.

  6. Scanning Hall probe microscopy of supercurrents in YBCO films

    NASA Astrophysics Data System (ADS)

    Dinner, Rafael Baruch

    High-temperature superconductors were discovered 20 years ago, inspiring dreams of levitating trains fed by superconducting power lines. The cuprates, particularly YBa2Cu3O7-delta (YBCO), still promise to fulfill such applications, but must be made to carry higher current density, Jc, which is limited by the rapid onset of dissipation. The dissipation arises from the movement of magnetic vortices in the material, driven by the magnetic field of the current. It is therefore natural to use magnetic imaging to understand these limits on the current. Initially, I fix a mesoscopic ring of YBCO to a micro-Hall sensor and demonstrate that the sensor is capable of detecting small numbers of vortices. I then proceed with magnetic imaging, constructing a cryogenic scanning Hall probe microscope that combines a 1 x 4 cm scan range with 200 nm positioning resolution by coupling stepper motors to high-resolution drivers and reducing gears. It enables me to image an entire sample, then zoom in on regions of interest, down to the level of an individual quantized vortex. Applying this capability to current-carrying YBCO strips, I generate magnetic movies of the materials' periodic response to applied ac currents. From the movies, I reconstruct current density by inverting the Biot-Savart law, and electric field by approximating dB/dt and using Faraday's law. I thereby obtain complete, space- and time-resolved characterizations of the materials, including maps of ac power losses. After demonstrating this analysis on a single-crystal film, I image two "coated conductors"---YBCO grown on metal tape. I find relatively homogeneous flux penetration in a film grown by pulsed laser deposition (PLD) on an ion beam assisted deposition (IBAD) substrate, which contrasts with the weak-link behavior of grain boundaries in a film grown by metalorganic deposition (MOD) on rolling assisted biaxially textured substrate (RABiTS). Nonetheless, the in-plane meandering of the MOD film's boundaries

  7. Fabrication of YBCO/YSZ and YBCO/MgO thick films using electrophoretic deposition with top-seeded melt growth process

    NASA Astrophysics Data System (ADS)

    Zhu, Ya-Bin; Zhou, Yue-Liang; Wang, Shu-Fang; Liu, Zhen; Zhang, Qin; Chen, Zheng-Hao; Lü, Hui-Bin; Yang, Guo-Zhen

    2004-02-01

    Superconducting thick films were grown on single crystals MgO and YSZ by electrophoretic deposition with Y2BaCuO5(Y211) addition. YBCO thick films were then accomplished by sintering the precursor films above the peritectic temperature. Single crystals of MgO (3×3×0.5 mm3) were used as top-seed to control crystal structure of the thick films. As shown by scanning electron microscopy, the morphologies of YBCO/YSZ and YBCO/MgO thick films are spherulitic texture and platelet type. The critical temperature is ~89 K for the YBCO/YSZ thick film; the onset transition temperature is 86.4 K and the transition width is ~3 K for YBCO/MgO thick film. The critical current densities (as determined by Bean model) are, in A/cm2, 3870 (77 K) for YBCO/YSZ thick films and 2399 (77 K) for YBCO/MgO thick films, which are comparable to the best Jc reported of the thick films prepared by the same method.

  8. Growth process of BaZrO3 doped YBCO films by TFA-MOD method

    NASA Astrophysics Data System (ADS)

    Konya, K.; Masuda, Y.; Teranishi, R.; Kiss, T.; Munetoh, S.; Yamada, K.; Yoshizumi, M.; Izumi, T.

    Crystal growth process of YBa2Cu3O7-X (YBCO) films with BaZrO3 (BZO) pinning centers were investigated to enhance JC property by controlling microstructure of the films. The YBCO films were fabricated by a metal organic deposition (MOD) method using solutions with trifluoroacetates (TFA) and Zr-salts. Quenched films were prepared by cooling them rapidly during crystallization process and crystallized phases were identified by an X-ray diffraction (XRD) measurement. It is indicating that BZO forms at lower temperature than that of YBCO formation and that BZO and BaF2 are crystallized at the similar temperature range around 700°C. Then, we kept the heating temperature which is under 600°C before crystallization temperature of YBCO and investigated the effect of temperature keeping on film growth. In the film kept for more than 3 hours, BZO peak was detected by XRD measurement. However, BZO particles were not observed in the film even kept for 9 hours by transmission electron microscopy (TEM) and energy dispersive X-ray (EDS) analyses. It is indicated that growth rate of BZO is slow at 600°C. On the other hand, smaller YBCO particles and decreasing of surface roughness (Ra) were observed for the film which were kept at 600°C for 3 hours and then crystallized. This result suggests the density of YBCO film is higher than that for YBCO without that process. In summary, it can be considered that YBCO film density become high by temperature keeping process below 600°C before YBCO crystallization and that size of BZO particles are determined by heat treatment at the temperature of above 600°C

  9. On-line characterization of YBCO coated conductors using Raman spectroscopy methods.

    PubMed

    Maroni, V A; Reeves, J L; Schwab, G

    2007-04-01

    The use of Raman spectroscopy for on-line monitoring of the production of superconducting YBa2Cu3O6+X (YBCO) thin films on long-length metal tapes coated with textured buffer layers is reported for the first time. A methodology is described for obtaining Raman spectra of YBCO on moving tape exiting a metal-organic-chemical-vapor-deposition (MOCVD) enclosure. After baseline correction, the spectra recorded in this way show the expected phonons of the specific YBCO crystal orientation required for high supercurrent transport, as well as phonons of non-superconducting second-phase impurities when present. It is also possible to distinguish YBCO films that are properly textured from films having domains of misoriented YBCO grains. An investigation of the need for focus control on moving tape indicated that focusing of the laser on the surface of the highly reflective YBCO films exiting the MOCVD enclosure tends to produce aberrant photon bursts that swamp the Raman spectrum. These photon bursts are very likely a consequence of optical speckle effects induced by a combination of surface roughness, crystallographic texture, and/or local strain within the small grain microstructure of the YBCO film. Maintaining a slightly out-of-focus condition provides the best signal-to-noise ratio in terms of the obtained Raman spectra. In addition to examining moving tape at the post-MOCVD stage, Raman spectra of the film surface can also be recorded after the oxygen anneal performed to bring the YBCO to the optimum superconducting state. Consideration is given to data processing methods that could be adapted to the on-line Raman spectra to allow the tagging of out-of-specification tape segments and, at a more advanced level, feedback control to the MOCVD process. PMID:17456253

  10. On-line characterization of YBCO coated conductors using Raman spectroscopy methods.

    SciTech Connect

    Maroni, V. A.; Reeves, J. L.; Schwab, G.; Chemical Engineering; SuperPower, Inc.

    2007-04-01

    The use of Raman spectroscopy for on-line monitoring of the production of superconducting YBa2Cu3O6+X (YBCO) thin films on long-length metal tapes coated with textured buffer layers is reported for the first time. A methodology is described for obtaining Raman spectra of YBCO on moving tape exiting a metal-organic-chemical-vapor-deposition (MOCVD) enclosure. After baseline correction, the spectra recorded in this way show the expected phonons of the specific YBCO crystal orientation required for high supercurrent transport, as well as phonons of non-superconducting second-phase impurities when present. It is also possible to distinguish YBCO films that are properly textured from films having domains of misoriented YBCO grains. An investigation of the need for focus control on moving tape indicated that focusing of the laser on the surface of the highly reflective YBCO films exiting the MOCVD enclosure tends to produce aberrant photon bursts that swamp the Raman spectrum. These photon bursts are very likely a consequence of optical speckle effects induced by a combination of surface roughness, crystallographic texture, and/or local strain within the small grain microstructure of the YBCO film. Maintaining a slightly out-of-focus condition provides the best signal-to-noise ratio in terms of the obtained Raman spectra. In addition to examining moving tape at the post-MOCVD stage, Raman spectra of the film surface can also be recorded after the oxygen anneal performed to bring the YBCO to the optimum superconducting state. Consideration is given to data processing methods that could be adapted to the on-line Raman spectra to allow the tagging of out-of-specification tape segments and, at a more advanced level, feedback control to the MOCVD process.

  11. Preparation, transport properties and patterning of superconducting YBCO thin films

    NASA Astrophysics Data System (ADS)

    Kataria, N. D.; May, D.; Wolf, H.; Schneider, R.; Niemeyer, J.

    1991-09-01

    The preparation of YBCO thin films by coevaporation and magnetron sputtering is reported. The coevaporated films were fabricated on SrTiO 3 substrates by the codeposition of Y, BaF 2 and Cu at elevated substrate temperature and an ex situ annealing process. Zero resistance T c was as high as 88 K and the critical current density was j c(77K)≈10 5 A/cm 2. The superconducting sputtered films were fabricated in situ using an inverted cylindrical target on Y-stabilized ZrO 2 substrates with T c near 85 K and j c (77K)≈10 6 A/cm 2. The films were structured by a conventional photolithographic technique and chemical etching. The temperature dependence of the resistance R(T) and critical current I c(T) were measured for bridges with different line widths w. Line widths down to 3 μm were patterned on sputtered films by EDTA without any degradation of the superconducting properties, whereas due to the intrinsic surface roughness of the coevaporated films, degradation in the superconducting properties was observed for w < 10μm.

  12. Study of Modified TFA-MOD Method for YBCO Film Growth

    NASA Astrophysics Data System (ADS)

    Li, C. S.; Lu, Y. F.; Zhang, P. X.; Yu, Z. M.; Tao, B. W.; Feng, J. Q.; Jin, L. H.

    The traditional all-TFA precursor solution for coated conductors has sensitivity to the heating rate in pyrolysis process. This sensitivity could be weakened by using a modified precursor solution, which was prepared by the mixture of yttrium trifluoroacetate, barium trifluoroacetate, and copper benzoate. The YBCO films were deposited on buffered NiW substrates (NiW/Y2O3/YSZ/CeO2) with the modified precursor solution. The texture, microstructure and superconducting properties of YBCO films were characterized by X-ray diffraction, scanning electron microscopy and four-probe method, respectively. The YBCO films prepared by modified TFA-MOD method demonstrated high performance.

  13. RF plasma enhanced MOCVD of yttria stabilized zirconia thin films using octanedionate precursors and their characterization

    NASA Astrophysics Data System (ADS)

    Chopade, S. S.; Nayak, C.; Bhattacharyya, D.; Jha, S. N.; Tokas, R. B.; Sahoo, N. K.; Deo, M. N.; Biswas, A.; Rai, Sanjay; Thulasi Raman, K. H.; Rao, G. M.; Kumar, Niranjan; Patil, D. S.

    2015-11-01

    Yttria stabilized zirconia thin films have been deposited by RF plasma enhanced MOCVD technique on silicon substrates at substrate temperature of 400 °C. Plasma of precursor vapors of (2,7,7-trimethyl-3,5-octanedionate) yttrium (known as Y(tod)3), (2,7,7-trimethyl-3,5-octanedionate) zirconium (known as Zr(tod)4), oxygen and argon gases is used for deposition. To the best of our knowledge, plasma assisted MOCVD of YSZ films using octanediaonate precursors have not been reported in the literature so far. The deposited films have been characterized by GIXRD, FTIR, XPS, FESEM, AFM, XANES, EXAFS, EDAX and spectroscopic ellipsometry. Thickness of the films has been measured by stylus profilometer while tribological property measurement has been done to study mechanical behavior of the coatings. Characterization by different techniques indicates that properties of the films are dependent on the yttria content as well as on the structure of the films.

  14. Thermal stability of NdBCO/YBCO/MgO thin film seeds

    NASA Astrophysics Data System (ADS)

    Volochová, D.; Kavečanský, V.; Antal, V.; Diko, P.; Yao, X.

    2016-04-01

    Thermal stability of the Nd1+x Ba2-x Cu3O7-δ (Nd-123 or NdBCO) thin films deposited on MgO substrate, with YBa2Cu3O7-δ (Y-123 or YBCO) buffer layer (NdBCO/YBCO/MgO thin film), has been experimentally studied in order to determine the optimal film thickness acting as seed for bulk YBCO growth. YBCO bulk superconductors with Y2BaCuO5 (Y-211) and CeO2 addition were prepared by the top seeded melt growth process in a chamber furnace using NdBCO/YBCO/MgO thin film seeds of different thicknesses (200-700 nm with 20 nm YBCO buffer layer) and different maximum temperatures, T max. The maximum temperatures varied in the range of 1040 °C-1125 °C. The highest thermal stability 1118 °C was observed in the case of NdBCO/YBCO/MgO thin film of 300 nm thickness. These results are corroborated with differential scanning calorimetry and high temperature x-ray diffraction measurements, as well as microstructure observations.

  15. Precursor evolution and growth mechanism of BTO/YBCO films by TFA—MOD process

    NASA Astrophysics Data System (ADS)

    Wang, Hong-Yan; Ding, Fa-Zhu; Gu, Hong-Wei; Zhang, Teng; Peng, Xing-Yu

    2014-10-01

    In this study, BaTiO3 (BTO)-doped YBCO films are prepared on LaAlO3 (100) single-crystal substrates by metal—organic decomposition (MOD) using trifluoroacetate (TFA) precursor solutions. The critical current density (Jc) of BTO/YBCO film is as high as 10 MA/cm2 (77 K, 0 T). The BTO peak is found in the X-ray diffraction (XRD) pattern of a final YBCO superconductivity film. Moreover, a comprehensive study of the precursor evolution is conducted mainly by X-ray analysis and μ-Raman spectroscopy. It is found that the TFA begins to decompose at the beginning of the thermal process, and then further decomposes as temperature increases, and at 700 °C BTO nanoparticles begin to appear. It suggests that the YBCO film embedded with BTO nanoparticles, whose critical current density (Jc) is enhanced, is successfully prepared by an easily scalable chemical solution deposition technique.

  16. BAF(2) POST-DEPOSITION REACTION PROCESS FOR THICK YBCO FILMS.

    SciTech Connect

    SUENAGA,M.; SOLOVYOV,V.F.; WU,L.; WIESMANN,H.J.; ZHU,Y.

    2001-07-12

    The basic processes of the so-called BaF{sub 2} process for the formation of YBa{sub 2}Cu{sub 3}O{sub 7}, YBCO, films as well as its advantages over the in situ formation processes are discussed in the previous chapter. The process and the properties of YBCO films by this process were also nicely described in earlier articles by R. Feenstra, et al. Here, we will discuss two pertinent subjects related to fabrication of technologically viable YBCO conductors using this process. These are (1) the growth of thick (>> 1 {micro}m) c-axis-oriented YBCO films and (2) their growth rates. Before the detail discussions of these subjects are given, we first briefly discuss what geometrical structure a YBCO-coated conductor should be. Then, we will provide examples of simple arguments for how thick the YBCO films and how fast their growth rates need to be. Then, the discussions in the following two sections are devoted to: (1) the present understanding of the nucleation and the growth process for YBCO, and why it is so difficult to grow thick c-axis-oriented films (> 3 {micro}m), and (2) our present understanding of the YBCO growth-limiting mechanism and methods to increase the growth rates. The values of critical-current densities J{sub c} in these films are of primary importance for the applications,. and the above two subjects are intimately related to the control of J{sub c} of the films. In general, the lower the temperatures of the YBCO formation are the higher the values of J{sub c} of the films. Thus, the present discussion is limited to those films which are reacted at {approx}735 C. This is the lowest temperature at which c-axis-oriented YBCO films (1-3 {micro}m thick) are comfortably grown. It is also well known that the non-c-axis oriented YBCO platelets are extremely detrimental to the values of J{sub c} such that their effects on J{sub c} dwarf essentially all of other microstructural effects which control J{sub c}. Hence, the discussion given below is mainly

  17. Characteristics of CoxTi1-xO2 thin films deposited by MOCVD

    SciTech Connect

    McClure, A.; Kayani, A.; Idzerda, Y.U.; Arenholz, E.; Cruz, E.

    2008-05-09

    This paper deals with the growth and characterization of ferromagnetic cobalt doped TiO{sub 2} thin films deposited by liquid precursor metal organic chemical vapor deposition (MOCVD) using a new combination of the source materials Co(TMHD){sub 3}, tetrahydrofuran (THF), and titanium isopropoxide (TIP). An array of experiments reveals the intrinsic ferromagnetic nature of the grown films, and suggests that the magnetism is not generated by oxygen vacancies.

  18. Significance of microstructure for a MOCVD-grown YSZ thin film gas sensor

    SciTech Connect

    Vetrone, J.; Foster, C.; Bai, G.

    1996-11-01

    The authors report the fabrication and characterization of a low temperature (200--400 C) thin film gas sensor constructed from a MOCVD-grown yttria-stabilized zirconia (YSZ) layer sandwiched between two platinum thin film electrodes. A reproducible gas-sensing response is produced by applying a cyclic voltage which generates voltammograms with gas-specific current peaks and shapes. Growth conditions are optimized for preparing YSZ films having dense microstructures, low leakage currents, and maximum ion conductivities. In particular, the effect of growth temperature on film morphology and texture is discussed and related to the electrical and gas-sensing properties of the thin film sensor device.

  19. Structural and optical characterization of MOCVD-grown ZnO thin films

    NASA Astrophysics Data System (ADS)

    Pagni, O.; James, G. R.; Leitch, A. W. R.

    2004-03-01

    We report on the characterization of ZnO thin films grown by metal organic chemical vapor deposition (MOCVD) using diethyl zinc (DEZ) and tert-butanol (TBOH) as precursors. Substrate temperature proved to be a crucial factor in the crystallization process, as it vastly impacted the structural properties of the samples studied. Highly c-axis oriented films with large grain size (52 nm), low tensile strain (0.6%), uniform substrate coverage and a columnar structure devoid of hexagonal needles were successfully deposited on n-Si (100) substrates. The temperature-dependent luminescence spectra recorded confirmed the excellent quality of the material obtained in this work. Our results so far set TBOH apart as an outstanding oxygen source for the MOCVD growth of ZnO.

  20. Far-infrared Hall Effect in YBCO films

    NASA Astrophysics Data System (ADS)

    Grayson, M.; Rigal, L.; Cerne, J.; Schmadel, D. C.; Drew, H. D.; Kung, P.-J.

    2001-03-01

    In order to gain insight into the so-called "anomalous Hall effect" in Hi Tc superconductors(T.R. Chien, D.A. Brawner, Z.Z. Wang, and N.P. Ong, PRB 43, 6242(1991).) we explore Hall measurements at far-infrared (FIR) frequencies and study the temperature dependence. We separately measure the real and imaginary parts of the magneto-optical response of YBCO thin films to polarized FIR light (15-250 cm-1). The induced rotation of linearly polarized light tells us the real part of the Faraday angle, Re[θ_F(ω)], and the induced dichroism of circularly polarized light tells us Im[θ_F(ω)]. We can then deduce the complex Hall angle without resorting to Kramers-Kronig (K-K) analysis. Since both the Hall angle and the Faraday angle obey sum rules, we can compare to higher frequencies(Cerne, et al., invited talk) and determine additional information about the spectral response at intermediate frequencies. The consistency of these results is verified with K-K analysis.

  1. Nucleation And Growth Of Ba-Reduced Metal Organic Deposited YBCO Films

    SciTech Connect

    Talantsev, E. F.; Xia, J. A.; Strickland, N. M.; Hoffmann, C.; Morgan, S.; Long, N. J.; Rupich, M. W.; Li, X.; Sathyamurthy, S.

    2009-07-23

    In this study, YBCO films were fabricated on RABiTS metal substrates by metal-organic deposition of trifluoroacetates. Precursor solutions were made with different Ba concentrations (Ba/Y = 1.50, 1.70, 1.85, 2.0) with the aim of optimizing the critical current density (J{sub c}). Our results confirmed that YBCO films with Ba/Y = 1.70(J{sub c} = 3.6 MA/cm{sup 2} at T 77 K) have significantly higher J{sub c} than stoichiometric (Ba/Y = 2.0) YBCO (J{sub c} 2.4 MA/cm{sup 2}). Application of low-angle polishing techniques and X-ray diffraction (XRD) studies for quenched (partially reacted) films has shown that YBCO films with Ba/Y = 1.70 nucleate more rapidly than other films, but that the crystal growth rate is increased when the Ba-concentration is increased. These results provide new insights into the physical mechanisms required to achieve high J{sub c} in YBCO.

  2. Synthesis of (Hg,Pb)(Sr,Ba) 2Ca 2Cu 3O z superconducting films via MOCVD and PLD

    NASA Astrophysics Data System (ADS)

    Klimonsky, S. O.; Samoilenkov, S. V.; Gorbenko, O. Yu.; Emelianov, D. A.; Lyashenko, A. V.; Lee, S. R.; Kaul, A. R.; Tretyakov, Yu. D.; Andrianov, D. G.; Kalinov, A. V.; Voloshin, I. F.

    2002-12-01

    (0 0 1)-oriented Sr-containing (Hg,Pb)-1223 films have been synthesised for the first time using the two-step procedure. Hg-free precursor films with the thickness up to 1 μm have been deposited by metalorganic chemical vapor deposition (MOCVD) or pulsed infra-red laser ablation (PLD) and then the films were annealed in a mercury-containing atmosphere in sealed quartz ampoules. No post-annealing in oxygen was used. The phase composition of the PLD-derived films depended crucially on the deposition temperature of the precursor films. MOCVD-derived films contained only very small amounts of non-superconducting phases according to XRD. The Tc=118 K and j c(77 K,0.01 T)=2.5×10 6A/cm 2 have been measured for the MOCVD-derived samples.

  3. Flux pinning properties of YBCO films with nano-particles by TFA-MOD method

    NASA Astrophysics Data System (ADS)

    Masuda, Y.; Teranishi, R.; Matsuyama, M.; Yamada, K.; Kiss, T.; Munetoh, S.; Yoshizumi, M.; Izumi, T.

    Nano-particles were doped into YBCO films as pinning centers by a metal organic deposition (MOD) method using trifluoroacetates. Two types of initial solution with a cation ratio of Y: Ba: Cu = 1: 1.5: 3 were prepared; one with the dispersion of SnO2 particles with the size of 15-25 nm and the other one with the dispersion of smaller ZrO2 particles with the size of under 8 nm, then the solution was spin-coated on CeO2/Gd2Zr2O7/Hastelloy substrates. The coated films were calcined at 430 °C in oxygen atmosphere and crystallized at 780 °C in low oxygen atmosphere. From the results of X-ray diffraction analysis (XRD), peaks of BaSnO3 were observed clearly in the YBCO film by the starting solution with SnO2. On the other hands, little peaks corresponding to BaZrO3 were observed in the film by the solution with ZrO2. Many CuO segregations were recognized at the surface of SnO2 doped YBCO film in comparison to the YBCO film with ZrO2 doping. From these results, it is indicated that most of SnO2 particles in precursors are react with Ba during heating. Critical current density (JC) of the YBCO films by both solutions showed higher performance than that of pure YBCO film in magnetic fields.

  4. The preparation of high-J c Gd0.5Y0.5Ba2Cu3O7‑δ thin films by the MOCVD process

    NASA Astrophysics Data System (ADS)

    Zhao, R. P.; Zhang, F.; Liu, Q.; Xia, Y. D.; Lu, Y. M.; Cai, C. B.; Tao, B. W.; Li, Y. R.

    2016-06-01

    A home-designed metal organic chemical vapor deposition (MOCVD) system has been employed to prepare high critical current density (J c) Gd0.5Y0.5Ba2Cu3O7‑δ (GdYBCO) thin films on LaMnO3/epitaxial MgO/ion beam assisted deposition (IBAD)-MgO/solution deposition planarization (SDP)-Y2O3-buffered Hastelloy tapes; the thin films were directly heated by the Joule effect after applying an heating current (I h ) through the Hastelloy tapes. The effect of the mole ratio of the metal organic sources has been systematically investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses indicated that the GdYBCO films crystallized better and became denser with the increasing of the Cu/Ba ratio from 1.0 to 1.1, yielding a J c at 77 K and 0 T of 200 nm GdYBCO film increasing from 2.5 MA cm‑2 to 7 MA cm‑2. In addition, SEM and energy dispersive spectrometer (EDS) characterizations revealed that more and more outgrowths appeared and the density of the film was reduced with an increase in the Cu/Ba ratio from 1.1 to 1.2. When the I h was 26.8 A and the mole ratio of Gd(tmhd)3, Y(tmhd)3, Ba(tmhd)2 and Cu(tmhd)2 in the precursor was 0.55:0.55:2:2.2, the critical current (I c) of the deposited 200 nm-thick GdYBCO film reached a 140 A cm‑1 width (77 K, 0 T), corresponding to the J c 7 MA cm‑2 (77 K, 0 T).

  5. 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.

  6. Effect of Interfacial Resistance on AC Loss as a Function of Applied AC Field in YBCO Filamentary Conductors

    SciTech Connect

    Duckworth, Robert C; List III, Frederick Alyious; Zhang, Yifei

    2009-01-01

    To reduce ac loss in Y-Ba-Cu-O (YBCO) coated conductors while maintaining current sharing between filaments, an attempt was made to introduce an interfacial resistance between the YBCO filaments and a continuous silver cap layer. The YBCO filaments were produced via laser scribing of MOCVD YBCO films deposited on standard Ion Beam Assisted Deposition (IBAD) templates. After laser scribing, the filaments were exposed to air at room temperature to degrade the YBCO surface. A three micron thick silver cap layer was then and each sample was oxygen annealed at different temperature to produce different interface resistance at the interface between the silver and YBCO. Measurements of the ac loss was measured as a function of applied perpendicular field and frequency revealed a correlation between the reduction in coupling loss and the oxygen annealing temperature.

  7. Continued improvment of large area, in situ sputter deposition of superconducting YBCO thin films

    NASA Technical Reports Server (NTRS)

    Truman, J. K.; White, W. R.; Ballentine, P. H.; Mallory, D. S.; Kadin, A. M.

    1993-01-01

    The deposition of thin films of superconducting YBa2Cu3O7-x onto substrates of up to 3-in diameter by an integrated off-axis sputtering is reported. The substrate is located above the center of an 8-in-diameter YBCO planar target, and, in conjunction with a negative ion shield, negative ion effects are avoided. A large radiant heater provides backside, noncontact heating of the bare substrates. YBCO films have been grown on polished 1-cm2 MgO and LaAlO3 substrates with Tc = 90 K or greater, Jc = 2.5 x 10 exp 6 A/sq cm or greater at 77 K, and microwave surface resistance Rs less than 0.4 micro-ohm at 77 K and 10 GHz. The films have a very smooth surface morphology. Uniformity data for LaAlO3 substrates are less than +/-5 percent in Rs. Thickness uniformity results for 3-in substrates indicate less than 10 percent variation. The growth of epitaxial insulating films for use with YBCO films and application of the YBCO films in microwave devices are briefly discussed.

  8. Effects of thickness on superconducting properties and structures of Y2O3/BZO-doped MOD-YBCO films

    NASA Astrophysics Data System (ADS)

    Ding, Fa-Zhu; Gu, Hong-Wei; Wang, Hong-Yan; Zhang, Hui-Liang; Zhang, Teng; Qu, Fei; Dong, Ze-Bin; Zhou, Wei-Wei

    2015-05-01

    We report the thickness dependence of critical current density (Jc) in YBa2Cu3O7-x (YBCO) films with BaZrO3 (BZO) and Y2O3 additions grown on single crystal LaAlO3 substrates by metalorganic deposition using trifluoroacetates (TFA-MOD). Comparing with pure YBCO films, the Jc of BZO/Y2O3-doped YBCO films was significantly enhanced. It was also found that with the increase of the thickness of YBCO film from 0.25 μm to 1.5 μm, the Ic of BZO/Y2O3-doped YBCO film increased from 130 A/cm to 250 A/cm and yet Jc of YBCO film decreased from 6.5 MA/cm2 to 2.5 M A/cm2. The thick BZO/Y2O3-doped MOD-YBCO film showed lower Jc, which is mainly attributed to the formation of a-axis grains and pores. Project supported by the National Natural Science Foundation of China (Grant No. 51272250), the National Basic Research Program of China (Grant No. 2011CBA00105), the National High Technology Research and Development Program of China (Grant No. 2014AA032702), and the Beijing Natural Science Foundation, China (Grant No. 2152035).

  9. Optimization of fluorine content in TFA-MOD precursor solutions for YBCO film growth

    NASA Astrophysics Data System (ADS)

    Jin, L. H.; Li, C. S.; Feng, J. Q.; Yu, Z. M.; Wang, Y.; Lei, L.; Zhao, G. Y.; Sulpice, A.; Zhang, P. X.

    2016-01-01

    Several low fluorine solutions containing different contents of fluorine were prepared by a chemical process. The fluorine contents in these solutions with respect to the conventional all-trifluoroacetate solution were calculated as 0%, 7.7%, 15.4%, 23.1%, 30.8%, 38.5% and 53.8%. YBa2Cu3O7-x (YBCO) films were deposited on LaAlO3 and CeO2/MgO/Al2O3/Hastelloy substrates using these low fluorine solutions. The phase formation, texture and microstructure of the YBCO films were characterized by x-ray diffraction and scanning electron microscopy. The decomposition mechanism of the low fluorine solution was also discussed. The results indicate that the ratio of F/Ba and the carbon content in decomposed powders could be controlled by adjusting the fluorine content in the precursor solutions. Fluorine had a great influence on the phase transformation, nucleation and growth of YBCO film during the crystallization process. The optimization of fluorine content was in the range of 15.4%-23.1%, which contributed to the good texture, homogeneous microstructure and high J c value of the YBCO crystallized films.

  10. Preparation and characterization of MOCVD thin films of zinc sulphide

    NASA Astrophysics Data System (ADS)

    Osasona, O.; Djebah, A.; Ojo, I. A. O.; Eleruja, M. A.; Adedeji, A. V.; Jeynes, C.; Ajayi, E. O. B.

    1997-03-01

    Thin solid films of stoichiometric zinc sulphide on soda lime glass and stainless steel was deposited by the pyrolysis of bis-(morpholino dithioato-s,s')zinc (C 10H 16N 2O 2S 4Zn) (a single solid source precursor). The band gap of 3.67 eV was obtained by optical absorption spectroscopy. The composition, stoichiometry and thickness were determined by energy dispersive X-ray fluorescence (EDXRF) and Rutherford backscattering spectroscopy (RBS) and the absence of organic remnants in the film is demonstrated by IR spectroscopy and RBS.

  11. Biaxially aligned template films fabricated by inclined-substrate deposition for YBCO-coated conductor applications.

    SciTech Connect

    Ma, B.; Li, M.; Koritala, R. E.; Fisher, B. L.; Erck, R. A.; Dorris, S. E.; Miller, D. J.; Balachandran, U.

    2002-08-12

    Inclined substrate deposition (ISD) has the potential for rapid production of high-quality biaxially textured buffer layers, which are important for YBCO-coated conductor applications. We have grown biaxially textured MgO films by ISD at deposition rates of 20-100 {angstrom}/sec. Columnar grains with a roof-tile surface structure were observed in the ISD-MgO films. X-ray pole figure analysis revealed that the (002) planes of the ISD-MgO films are tilted at an angle from the substrate normal. A small {phi}-scan full-width at half maximum (FWHM) of {approx}9{sup o} was observed on MgO films deposited at an inclination angle of 55{sup o}. In-plane texture in the ISD MgO films developed in the first 0.5 {micro}m from the interface, then stabilized with further increases in film thickness. YBCO films deposited by pulsed laser deposition on ISD-MgO buffered Hastelloy C276 substrates were biaxially aligned with the c-axis parallel to the substrate normal. T{sub c} of 91 K with a sharp transition and transport J{sub c} of 5.5 x 10{sup 5} A/cm{sup 2} at 77 K in self-field were measured on a YBCO film that was 0.46-{micro}m thick, 4-mm wide, 10-mm long.

  12. High critical current YBCO films prepared by an MOD process on RABiTS templates.

    SciTech Connect

    Li, X.; Rupich, M. W.; Kodenkandath, T.; Huang, Y.; Zhang, W.; Siegel, E.; Verebelyi, D. T.; Schoop, U.; Nguyen, N.; Thieme, C.; Chen, Z.; Feldman, D. M.; Larbalestier, D. C.; Holesinger, T. G.; Civale, L.; Jia, Q. X.; Maroni, A.; Rane, M. V.; Chemical Engineering; American Superconductor Corp.; Univ. of Wisconsin; LANL; State Univ. of New York

    2007-06-01

    The metal organic deposition (MOD) of YBCO high temperature superconducting films on RABiTS (rolling assisted biaxially textured substrates) templates has been developed at American Superconductor as a low-cost, scalable manufacturing process for the commercialization of the second generation (2G) HTS wire. The MOD process is based on the deposition of a triflu-oroacetate (TFA) based metal organic precursor film which is converted, in an ex-situ process, to the superconducting YBCO film. A major goal of the development has been achieving high critical currents. This paper reports the preparation and characterization of MOD-YBCO films with critical currents exceeding 500 A/cm-w (77 K, self-field) using a scaleable thick film approach on RABiTS templates. The high critical current films were obtained through optimization of the precursor composition, nucleation and growth conditions. The through-thickness dependence of the critical current density of MOD Alms as a function of film thickness and a correlation of the through-thickness transport properties and microstructure of the thick MOD/RABiTS samples is reported.

  13. Development of Modified MOD-TFA Approach for YBCO Film Growth

    SciTech Connect

    Bhuiyan, Md S; Paranthaman, Mariappan Parans; Sathyamurthy, Srivatsan; Hunt, Rodney Dale; List III, Frederick Alyious; Duckworth, Robert C

    2007-01-01

    Low-cost coated-conductor fabrication methods are essential for various electric-power applications. Metal-organic-deposition (MOD) approach to grow both YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) and buffer layers on textured metal substrates is very promising towards fabrication of lower-cost second generation wires. YBCO coated conductors (CC) are being developed with high critical currents that should be sufficient for their extensive use in power applications. However, the present CC has high energy losses in ac magnetic field that are unacceptable. We have developed a modified MOD precursor route to deposit {approx} 0.8 {micro}m thick YBCO films in a single coat that requires less than one-fifth of the pyrolysis time compared to the traditional MOD approach. We have also developed a filamentization technique of CC using ink-jet printing to reduce ac losses due to applied ac fields. The preliminary results of YBCO films deposited on standard RABiTS template yielded an of 140 A/cm at 77 K and self- field. A modest reduction of ac loss was observed for the solution ink-jet printed filamentary conductor.

  14. Superconducting YBCO thin film on multicrystalline Ag film evaporated on MgO substrate

    NASA Astrophysics Data System (ADS)

    Azoulay, Jacob; Verdyan, Armen; Lapsker, Igor

    Superconducting YBa 2Cu 3O 7-δ films were grown by resistive evaporation on multicrystalline silver film which was evaporated on MgO substrate. A simple inexpensive vacuum system equipped with resistively heated boat was used for the whole process. Silver film was first evaporated on MgO substrate kept at 400°C during the evaporation after which with no further annealing a precursor mixture of yttrium small grains and Cu and BaF2 in powder form weighed in the atomic proportion to yield stoichiometric YBa 2Cu 3O 7 was evaporated. The films thus obtained were annealed at 740°C under low oxygen partial pressure of about 1Pa for 30 minutes to form the superconducting phase. X-ray diffraction and scanning electron microscopy techniques were used for texture and surface analysis. Electrical properties were determined using a standard dc four-probe for electrical measurements. The physical and electrical properties of the YBCO films are discussed in light of the fact that X-ray diffraction measurements done on the silver film have revealed a multicrystalline structure

  15. Raman spectra of MOCVD-grown ferroelectric PbTiO{sub 3} thin films

    SciTech Connect

    Feng, Z.C.; Kwak, B.S. |; Erbil, A.; Boatner, L.A.

    1993-12-31

    Lead titanate (PbTiO{sub 3}) has been grown on a variety of substrates by using the metalorganic chemical vapor deposition (MOCVD) technique. The substrates employed included Si, GaAs, MgO, fused-quartz, sapphire, and KTaO{sub 3}. Raman spectra from these heterostructures are presented. All of the films exhibited the strong, narrow spectral features characteristic of PbTiO{sub 3} perovskite-oxide crystals and indicative of high crystalline quality. The temperature behavior of the Raman modes, including the so-called ``soft-mode,`` was studied. A ``difference-Raman`` technique was used to distinguish the contributions of the PbTiO{sub 3} film and the KTaO{sub 3} single-crystal substrate.

  16. MOCVD growth and structure of PbTiO{sub 3} thin films

    SciTech Connect

    Gao, Y.; Bai, G.; Merkle, K.L.; Chang, H.L.M.; Lam, D.J.

    1993-08-01

    PbTiO{sub 3} thin films grown on (001)MgO and (110)MgO by MOCVD have been characterized by x-ray diffraction and transmission electron microscopy. The PbTiO{sub 3} films deposited on (001)MgO under the optimum conditions always show a bi-layer structure. The top layer of the films near the free surface is c-axis oriented with the orientation relationship (001)[100]PbTiO{sub 3}{parallel}(001)[100]MgO. The bottom layer of the films near the substrate is a-axis oriented with (100)[001]PbTiO{sub 3}{parallel}(001)[100]MgO. 90{degrees} domains were observed, but only in the c-axis oriented layers. The thickness of the a-axis oriented layers near the substrate decreases with decreasing the cooling rate. PbTiO{sub 3} films deposited on (110) MgO, however, are single-layer, epitaxial films with (101)[001]PbTiO{sub 3}{parallel}(110)[001]MgO.

  17. The mechanism of sputter-induced orientation change in YBCO films on MgO (001)

    SciTech Connect

    Huang, Y.; Vuchic, B.V.; Baldo, P.; Merkle, K.L.; Buchholz, D.B.; Mahajan, S.; Lei, J.S.; Markworth, P.R.; Chang, R.P.H.

    1996-12-01

    The mechanisms of the sputter-induced orientation change in YBa{sub 2}Cu{sub 3}O{sub 7{minus}x}(YBCO) films grown on MgO (001) substrates by pulsed organometallic beam epitaxy (POMBE) are investigated by x-ray diffraction. Rutherford backscatter spectroscopy (RBS), cross-section TEM (XTEM) and microanalysis. It is found that the W atom implantation concurring with the ion sputtering plays an important role in effecting the orientation change. This implantation changes the surface structure of the substrate and induces an intermediate layer in the initial growth of the YBCO film, which in turn acts as a template that induces the orientation change. It seems that the surface morphology change caused by ion sputtering has only a minor effect on the orientation change.

  18. Microstructure of YBCO thin films prepared by TFA-MOD method

    NASA Astrophysics Data System (ADS)

    Nagino, I.; Matsumoto, K.; Adachi, H.; Miyata, S.; Yoshizumi, M.; Izumi, T.; Shiohara, Y.

    2010-11-01

    The microstructure of the recently developed coated conductors was investigated by using electron back scatter diffraction pattern (EBSP). We prepared TFA (trifluoroacetates)-MOD (metal organic deposition) derived YBa 2Cu 3O 7-x (YBCO) films on CeO 2/LaMnO 3/IBAD-MgO/Gd 2Zr 2O 7/Hastelloy C276 substrates of 1 cm-width. The EBSP observation showed that there was a difference of surface microstructure between the midsection and the end of TFA-MOD YBCO film layer in the direction of width. This is attributed not to the local difference of the biaxial texture of CeO 2 top layer but to the local difference of growth condition during TFA-MOD process.

  19. Characteristics of the electrical response of YBCO films with different morphologies to optical irradiation

    SciTech Connect

    Frack, E.K.; Madhavrao, L.; Patl, R.; Drake, R.E.; Radparvar, M. )

    1991-03-01

    The authors have fabricated YBCO films of varying thicknesses (300 {Angstrom} - 3000 {Angstrom}) and morphologies, and measured their electrical response to optical radiation. This paper reports on these measurements, emphasizing the dependence on temperature, light chopping frequency, and cryogenic environment. The temperature dependence of the film resistance is determined in part by the film morphology. This morphology may be represented by a simple model consisting of a two-dimensional array of coupled grains. The magnitude of the bolometric response correlates as expected with the sharpness of the superconducting transition. The increased response observed at lower temperatures (non-equilibrium) correlates with the temperature dependence of the resistance above the transition.

  20. Epitaxial growth of YBCO films on metallic substrates buffered with yttria-stabilized zirconia

    NASA Astrophysics Data System (ADS)

    Ma, B.; Li, M.; Fisher, B. L.; Koritala, R. E.; Balachandran, U.

    2002-05-01

    Biaxially textured yttria-stabilized zirconia (YSZ) films were grown on polished Hastelloy C (HC) substrates by ion-beam-assisted deposition (IBAD) and electron-beam evaporation. A water-cooled sample stage was used to dissipate heat generated by the Kaufman ion source and to maintain the substrate temperature below 100 °C during deposition. X-ray pole figures were used for texture analysis. In-plane texture measured from the YSZ (111) φ-scan full-width-at-half-maximum (FWHM) was 13.2° and out-of-plane texture from the YSZ (002) ω-scan FWHM was 7.7°. In-plane texture improved with lowered substrate temperature during IBAD deposition. RMS surface roughness of 3.3 nm was measured by atomic force microscopy. A thin CeO2 buffer layer (≈10 nm) was deposited to improve the lattice match between the YSZ and YBCO films and to enhance the biaxial alignment of YBCO films. YBCO films were epitaxially grown on IBAD-YSZ buffered HC substrates with and without CeO2 buffer layers by pulsed laser deposition (PLD). In-plane texture FWHMs of 12° and 9° were observed for CeO2 (111) and YBCO (103), respectively. Tc=90 K, with sharp transition, and Jc values of ≈2×106 A/cm2 at 77 K in zero field were observed on 0.5-μm-thick, 5-mm-wide, and 1-cm-long samples.

  1. Long-range phase coherence in YBCO ultra-thin films

    SciTech Connect

    Aprili, M.; Lesueur, J.; Quinton, W.A.; Dumoulin, L.

    1996-12-31

    The authors have investigated the resistive transition of YBCO ultra-thin films (thickness from 5 to 50 nm) grown on MgO(100). The amount of disorder increases as the thickness is reduced, leading to a broad transition that can be described using a 3D weakly-coupled Josephson array. Below a critical thickness, this regime seems to dominate even the fluctuating part of the transition (paraconductive region), when the system undergoes a 3D-0D transition.

  2. Enhanced Flux-Pinning in Dy-Doped, MOD YBCO Films on RABiTS

    SciTech Connect

    Goyal, Amit; Li, Jing; Martin, Patrick M; Gapud, Albert Agcaoili; Specht, Eliot D; Paranthaman, Mariappan Parans; Li, X.; Zhang, W.; Kodenkandath, Thomas; Rupich, Marty

    2007-01-01

    Significant enhancements in flux-pinning were obtained for Dy-doped, YBCO films via a metal-organic deposition (MOD) process on rolling-assisted biaxially textured substrates (RABiTS). It has been reported previously that incorporation of excess rare-earth ions during the MOD process, results in improvement of Jc for H//c, however, a decrease in Jc for H//ab is observed. We report here that by altering the processing conditions the reduction in the magnitude of the current peak for H//ab can be minimized while significantly enhancing the random pinning at all field orientations. The result is a YBCO film with significantly reduced anisotropy compared to the typical YBCO films prepared by the MOD process. This is accomplished by incorporating both a high density of stacking faults and (Dy, Y)2O3 nanoparticles which result in the strong pinning for H//ab and a broad pinning peak for H//c respectively.

  3. Effect of Deposition Temperature on the Properties of TIO2 Thin Films Deposited by Mocvd

    NASA Astrophysics Data System (ADS)

    Khalifa, Zaki S.

    2016-02-01

    Crystal structure, microstructure, and optical properties of TiO2 thin films deposited on quartz substrates by metal-organic chemical vapor deposition (MOCVD) in the temperature range from 250∘C to 450∘C have been studied. The crystal structure, thickness, microstructure, and optical properties have been carried out using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), atomic force microscope (AFM), and UV-visible transmittance spectroscopy, respectively. XRD patterns show that the obtained films are pure anatase. Simultaneously, the crystal size calculated using XRD peaks, and the grain size measured by AFM decrease with the increase in deposition temperature. Moreover, the texture of the films change and roughness decrease with the increase in deposition temperature. The spectrophotometric transmittance spectra have been used to calculate the refractive index, extinction coefficient, dielectric constant, optical energy gap, and porosity of the deposited films. While the refractive index and dielectric constant decrease with the increase of deposition temperature, the porosity shows the opposite.

  4. RAPID COMMUNICATION: YBCO thin films prepared by fluorine-reduced metal organic deposition using trifluoroacetates

    NASA Astrophysics Data System (ADS)

    Cui, X. M.; Tao, B. W.; Tian, Z.; Xiong, J.; Liu, X. Z.; Li, Y. R.

    2006-04-01

    Solution deposition is a promising method for YBCO coated conductor fabrication. We developed a new fluorine-reduced 'metal-organic deposition using trifluoroacetates' (TFA-MOD) method with copper acetate as one of the starting materials. Using the fluorine-reduced TFA-MOD method, we were able to get high performance YBCO films with good out-of-plane and in-plane orientations within a shortened calcining time, which was reduced by at least 4 h in comparison with that for the normal TFA-MOD process. Good superconducting properties, with Jc of 2 MA cm-2 at 77 K and Tc of 88.3 K (ΔTc = 0.9 K), have been obtained for 350 nm epitaxial YBCO thin films on LaAlO3 single-crystal substrates. Owing to the low price of copper acetate and the shorter calcining time, fluorine-reduced TFA-MOD is a very effective and cost-cutting process.

  5. Inclined-substrate deposition of biaxially aligned template films for YBCO-coated conductors

    NASA Astrophysics Data System (ADS)

    Ma, B.; Li, M.; Fisher, B. L.; Koritala, R. E.; Balachandran, U.

    2002-10-01

    Inclined-substrate deposition (ISD) of magnesium oxide (MgO) produces biaxially textured template films at high deposition rates. This process is promising for the fabrication of the second-generation superconducting wires. Biaxially aligned MgO films (≈1.5 μm thick) were deposited on polished Hastelloy C276 (HC) substrates by ISD at deposition rates of 20-100 Å/s. Buffer films were subsequently deposited on these template films, and YBCO films were deposited epitaxially on the substrates by pulsed laser deposition. X-ray pole figure analysis and φ- and ω-scans were used for texture characterization. Good in- and out-of-plane textures were observed, with MgO(0 0 2) φ-scan full-width at half maximum (FWHM) of 9.2° and ω-scan FWHM of 5.4°, respectively. Tc of 90 K with a sharp transition, and Jc≈2×10 5 A/cm 2, were obtained on a 0.5 μm thick, 0.5 cm wide, and 1 cm long YBa 2Cu 3O 7- δ (YBCO) film at 77 K in self-field.

  6. Microwave complex conductivity of the YBCO thin films as a function of static external magnetic field

    NASA Astrophysics Data System (ADS)

    Krupka, J.; Judek, J.; Jastrzebski, C.; Ciuk, T.; Wosik, J.; Zdrojek, M.

    2014-03-01

    A sapphire rod resonator operating at microwave frequencies was used to determine the electric properties of 600 nm thick YBCO films in the superconducting state. The rigorous electromagnetic modelling was applied to transform the measured Q-factor and the resonant frequency to the complex conductivity of high accuracy, which was previously shown to describe the intrinsic properties of superconductor thin films in more precise manner than the complex impedance. Static external magnetic field induces typical transition to normal state due to introduction of magnetic vortices into the sample. Observed magnetic hysteresis has the origin in the strong temperature dependent pinning. Additional energy absorption at about 1.5 T was observed.

  7. Co-doping effects of Gd and Ag on YBCO films derived by metalorganic deposition

    NASA Astrophysics Data System (ADS)

    Sun, Meijuan; Liu, Zhiyong; Bai, Chuanyi; Guo, Yanqun; Lu, Yuming; Fan, Feng; Cai, Chuanbing

    2015-12-01

    Y1-xGdxBa2Cu3O7-δ-Ag (x = 0, 0.25, 0.5, 0.75, 1) thin films were prepared on oxide buffered Hastelloy substrates by low fluorine metalorganic depostion (MOD) process. The effects of co-doping of Ag and Gd on the microstructures and superconducting properties of YBCO thin films are investigated with respect to improvement on texture and superconducting performance in case of optimized doping content. It is found that optimum addition of Ag and Gd may lead to better c-axis orientation, superior surface microstructure and finally give rise to much improvement of superconducting performance.

  8. Inclined-substrate deposition of biaxially textured magnesium oxide thin films for YBCO coated conductors.

    SciTech Connect

    Ma, B.; Li, M.; Jee, Y. A.; Koritala, R. E.; Fisher, B. L.; Balachandran, U.; Energy Technology

    2002-02-01

    Highly textured MgO films were grown by the inclined-substrate deposition (ISD) technique at a high deposition rate. A columnar grain with a roofing-tile-shaped surface was observed in these MgO films. X-ray pole figure, and {phi}- and {omega}-scan were used to characterize in-plane and out-of-plane textures. MgO films deposited when the incline angle {alpha} was 55 and 30 degrees exhibited the best in-plane and out-of-plane texture, respectively. High-quality YBCO films were epitaxially grown on ISD-MgO-buffered Hastelloy C substrates by pulsed laser deposition. {Tc}=88 K, with sharp transition, and j{sub c} values of {approx}2x10{sup 5} A/cm{sup 2} at 77 K in zero field were observed on films 5 mm wide and 1 cm long. This work has demonstrated that biaxially textured ISD MgO buffer layers deposited on metal substrates are excellent candidates for fabrication of high-quality YBCO coated conductors.

  9. The annealing effects of V-doped GaN thin films grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Souissi, M.; Bouzidi, M.; El Jani, B.

    2012-02-01

    We have investigated the annealing effect of V-doped GaN (GaN:V) epitaxial layers grown on sapphire by metal organic chemical vapor deposition (MOCVD). The film was annealed at a temperature of 1075 °C for 30 min in N 2 ambient after growth. The structural, surface morphology and optical properties of GaN:V films were studied by high resolution X-ray diffraction (HRXRD), atomic force microscope (AFM) and photoluminescence (PL). The results show that the annealing makes for the destruction in the crystal quality and surface morphology. After thermal annealing, the photoluminescence (PL) measurement showed a reduction of the blue luminescence (BL) band observed in GaN:V at room temperature (RT). The phenomenon is attributed to vanadium diffusion or to the V-related complex dissociation. Near-band-edge (NBE) peak exhibited a red shift after 1075 °C anneal. This is due to the decrease in the level of strain. In the infrared region, we observed the emergence of the line 0.93 eV accompanied by a decrease in the intensity of the 0.82 eV emission. Their possible origins are discussed.

  10. An advanced low-fluorine solution route for fabrication of high-performance YBCO superconducting films

    NASA Astrophysics Data System (ADS)

    Chen, Yuanqing; Wu, Chuanbao; Zhao, Gaoyang; You, Caiyin

    2012-06-01

    We have developed a new low-fluorine solution consisting of non-fluorine (F-free) barium and copper salts, and fluorine-containing yttrium trifluoroacetate. Using this new low-fluorine solution, the BaCO3 phase was avoided in the pyrolyzed precursor films. Instead, CuO, Y and Ba fluorides (YF3 and BaF2) were formed in the precursor films pyrolyzed at 450 °C, which was the same as when an All-TFA solution (prepared using Y, Ba, Cu trifluoroacetates as precursors) or other fluorine-reduced solutions were used. This new kind of low-fluorine solution has only 23% of the fluorine content in an All-TFA solution, and the fluorine content was lower than any other fluorine-reduced solution. Thus, rapid production of YBa2Cu3O7-x (YBCO) films can be easily realized. Using a heating rate of 10 °C min-1 in the pyrolysis process, a high critical current density (Jc) of 5 MA cm-2 (at 77 K, 0 T) was obtained in YBCO films fabricated on LaAlO3 (LAO) single crystal substrates from the new starting solution.

  11. The domain structure features of epitaxial PbTiO{sub 3} thin films prepared by MOCVD

    SciTech Connect

    Bai, G.R.; Chang, H.L.M.; Foster, C.M.; Lam, D.J.

    1992-03-01

    Ferroelectric oxide thin films have attracted great interest in recent years because of their potential applications in numerous electro-optic, pyroelectric, acousto-optical, and nonvolatile memory devices, and a variety of methods such as sputtering, laser ablation, and MOCVD has been used for preparation of the films. Among these ferroelectric materials, the PbTiO{sub 3} thin film has been extensively studied because of its small dielectric constant, large spontaneous polarization, small coercive field, and high Curie temperature of {approximately}500{degrees}C. However, very little work has dealt with the detailed structural properties of the films. In this work, we have prepared epitaxial PbTiO{sub 3} thin films by MOCVD and performed some detailed studies on the structure of the films, particularly those related to the twin domain structure, using X-ray diffraction technique. Based on the comparison of the domain structure features of the films grown at above Curie temperature with those of the films grown at below Curie temperature as well as of bulk PbTiO{sub 3} single crystal, a model is proposed to explain our experimental results.

  12. The domain structure features of epitaxial PbTiO sub 3 thin films prepared by MOCVD

    SciTech Connect

    Bai, G.R.; Chang, H.L.M.; Foster, C.M.; Lam, D.J.

    1992-03-01

    Ferroelectric oxide thin films have attracted great interest in recent years because of their potential applications in numerous electro-optic, pyroelectric, acousto-optical, and nonvolatile memory devices, and a variety of methods such as sputtering, laser ablation, and MOCVD has been used for preparation of the films. Among these ferroelectric materials, the PbTiO{sub 3} thin film has been extensively studied because of its small dielectric constant, large spontaneous polarization, small coercive field, and high Curie temperature of {approximately}500{degrees}C. However, very little work has dealt with the detailed structural properties of the films. In this work, we have prepared epitaxial PbTiO{sub 3} thin films by MOCVD and performed some detailed studies on the structure of the films, particularly those related to the twin domain structure, using X-ray diffraction technique. Based on the comparison of the domain structure features of the films grown at above Curie temperature with those of the films grown at below Curie temperature as well as of bulk PbTiO{sub 3} single crystal, a model is proposed to explain our experimental results.

  13. Effect of Ge on SiC film morphology in SiC/Si films grown by MOCVD

    SciTech Connect

    Sarney, W.L.; Salamanca-Riba, L.; Zhou, P.; Spencer, M.G.; Taylor, C.; Sharma, R.P.; Jones, K.A.

    1999-07-01

    SiC/Si films generally contain stacking faults and amorphous regions near the interface. High quality SiC/Si films are especially difficult to obtain since the temperatures usually required to grow high quality SiC are above the Si melting point. The authors added Ge in the form of GeH{sub 2} to the reactant gases to promote two-dimensional CVD growth of SiC films on (111) Si substrates at 1,000 C. The films grown with no Ge are essentially amorphous with very small crystalline regions, whereas those films grown with GeH{sub 2} flow rates of 10 and 15 sccm are polycrystalline with the 3C structure. Increasing the flow rate to 20 sccm improves the crystallinity and induces growth of 6H SiC over an initial 3C layer. This study presents the first observation of spontaneous polytype transformation in SiC grown on Si by MOCVD.

  14. Defects-induced thermal instability in YBCO films in microwave field

    NASA Astrophysics Data System (ADS)

    Pan, Vladimir M.; Tretiatchenko, Constantin G.; Flis, Victor S.; Komashko, Valentin A.; Pashitskii, Ernst A.; Ivanyuta, Alexander N.; Melkov, Gennadiy A.; Zandbergen, Henny; Svetchnikov, Vassily L.

    2003-05-01

    The heat instability induced by linear defects is assumed to enhance the remarkable difference between microwave properties of YBCO single crystals and thin films due to extended strain fields near out-of-plane edge dislocations. We have shown theoretically and confirmed experimentally that a single dislocation cannot have a strong effect on the surface resistance Rs, but dislocation arrays, which were observed experimentally, can induce the thermal instability, if edge dislocations in the arrays are spaced closer than the heat relaxation length. Ordered dislocation structures provide much higher local temperature perturbation than randomly distributed dislocations.

  15. Comparison of the strain of GaN films grown on MOCVD-GaN/Al2O3 and MOCVD-GaN/SiC samples by HVPE growth

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Shao, Yongliang; Hao, Xiaopeng; Wu, Yongzhong; Qu, Shuang; Chen, Xiufang; Xu, Xiangang

    2011-11-01

    In this paper, GaN films were successfully grown on the samples of MOCVD-GaN/Al2O3 (MGA) and MOCVD-GaN/6H-SiC (MGS) by HVPE method. We compare the strain of GaN films grown on the two samples by employing various characterization techniques. The surface morphology of GaN films were characterized by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The variations of strain characteristic were also microscopically identified using the Z scan of Raman spectroscopy. The Raman peak (E2) shift indicates that the stress enhanced gradually as a function of increasing the measurement depth. The strain of GaN grown on MGA sample is compressive strain, while on MGS is tensile strain. The stress of GaN films grown on MGA and MGS sample are calculated. The difference in the value of stress between calculation and measurement was interpreted.

  16. Study of high {Tc} superconducting thin films grown by MOCVD. Final report, July 1, 1986--April 30, 1990

    SciTech Connect

    Erbil, A.

    1990-12-31

    Work is described briefly, which was carried out on development of techniques to grow metal-semiconductor superlattices (artificially layered materials) and on the copper oxide based susperconductors (naturally layered materials). The current growth technique utilized is metalorganic chemical vapor deposition (MOCVD). CdTe, PbTe, La, LaTe, and Bi{sub 2}Te{sub 3} were deposited, mostly on GaAs. Several YBa{sub 2}Cu{sub 3}O{sub 7} compounds were obtained with possible superconductivity at temperatures up to 550 K (1 part in 10{sup 4}). YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} and Tl{sub 2}CaBa{sub 2}Cu{sub 2}O{sub y} thin films were deposited by MOCVD on common substrates such as glass.

  17. Deposition, characterization, and laser ablation patterning of YBCO thin films

    NASA Astrophysics Data System (ADS)

    Vase, Per; Yueqiang, Shen; Freltoft, Torsten

    1990-12-01

    High quality epitaxial thin films of YBa 2Cu 3O 7 have been deposited on single-crystal MgO(001) substrates by 355 nm Nd:YAG laser ablation. Through a systematic optimization of the deposition parameters, it was found that for a target-substrate distance of 30 mm, the optimal laser intensity, substrate temperature, and deposition oxygen pressure were 300 MW/cm 2, 750 ° C, and 0.5-1.0 mbar, respectively. Microstrips with dimensions down to 10 μm across were fabricated using both a photoresist technique and laser ablation through a metal mask. The superconducting transition takes place over 1 K, and the critical temperature is reproducible within ±1.5 K, the best result being Tc,0 = 90 K. The highest critical current density measured on a 10 X 0.15 μm 2 strips was 4 X 10 6 A/cm 2 at 77 K . Film patterning using laser ablation through a metal mask was studied in detail to investigate the applicability of this method. Etch rates as a function of laser intensity were measured, and the process was followed in situ by on-line monitoring of the film resistivity.

  18. Enhancement of YBCO thin film thermal stability under 1 ATM oxygen pressure by intermediate Cu2O nanolayer.

    PubMed

    Cheng, L; Wang, X; Yao, X; Wan, W; Li, F H; Xiong, J; Tao, B W; Jirsa, M

    2010-06-10

    The melting process of YBa(2)Cu(3)O(x) (YBCO or Y123) films under an oxygen atmosphere was observed in situ by means of high-temperature optical microscopy. The films were classified by pole figure measurement as c-axis oriented, with two different in-plane orientations (denoted as 0 and 45 degrees). In the 45 degrees-oriented films, electron diffraction and high-resolution transmission electron microscopy (HRTEM) detected an intermediate Cu(2)O nanolayer in the vicinity of the interface. The melting mode and the thermal stability of the YBCO thin films with different in-plane orientations were greatly influenced by oxygen partial pressure. Notably, the thermal stability of the 45 degrees-oriented YBCO films dramatically grew with increasing oxygen partial pressure. We attributed this effect to a change in the intermediate Cu(2)O nanolayer thermal stability. We conclude and suggest that the thermal stability of YBCO films can be significantly enhanced by inserting a Cu(2)O buffer nanolayer. PMID:20469891

  19. The finite size effect on the metal-insulator transition of MOCVD grown VO{sub 2} films

    SciTech Connect

    Kim, Hyung Kook; Chiarello, R.P.; You, Hoydoo; Chang, M.H.L.; Zhang, T.J.; Lam, D.J.

    1991-11-01

    We studied the finite size effect on the metal-insulator phase transition and the accompanying tetragonal to monoclinic structural phase transition of VO{sub 2} films grown by MOCVD. X-ray diffraction measurements and electrical conductivity measurements were done as a function of temperature for VO{sub 2} films with out-of-plane particle size ranging from 60--310 {Angstrom}. Each Vo{sub 2} film was grown on a thin TiO{sub 2} buffer layer, which in turn was grown by MOCVD on a polished sapphire (112) substrate. The transition was found to be first order. As the out-of-plane particle size becomes larger, the transition temperature shifts and the transition width narrows. For the 60{Angstrom} film the transition was observed at {approximately}61{degrees}C with a transition width if {approximately}10{degrees}C, while for the 310{Angstrom} film the transition temperature was {approximately}59{degrees}C and the transition width {approximately} 2{degree}C. We also observed thermal hysteresis for each film, which became smaller with increasing particle size.

  20. The finite size effect on the metal-insulator transition of MOCVD grown VO sub 2 films

    SciTech Connect

    Kim, Hyung Kook; Chiarello, R.P.; You, Hoydoo; Chang, M.H.L.; Zhang, T.J.; Lam, D.J.

    1991-11-01

    We studied the finite size effect on the metal-insulator phase transition and the accompanying tetragonal to monoclinic structural phase transition of VO{sub 2} films grown by MOCVD. X-ray diffraction measurements and electrical conductivity measurements were done as a function of temperature for VO{sub 2} films with out-of-plane particle size ranging from 60--310 {Angstrom}. Each Vo{sub 2} film was grown on a thin TiO{sub 2} buffer layer, which in turn was grown by MOCVD on a polished sapphire (112) substrate. The transition was found to be first order. As the out-of-plane particle size becomes larger, the transition temperature shifts and the transition width narrows. For the 60{Angstrom} film the transition was observed at {approximately}61{degrees}C with a transition width if {approximately}10{degrees}C, while for the 310{Angstrom} film the transition temperature was {approximately}59{degrees}C and the transition width {approximately} 2{degree}C. We also observed thermal hysteresis for each film, which became smaller with increasing particle size.

  1. Fabrication of YBCO film approached by the '211 process' in the TFA-MOD method

    NASA Astrophysics Data System (ADS)

    Lim, Jun Hyung; Hern Jang, Seok; Joo, Jinho; Kim, Hyoungsub; Lee, Hee-Gyoun; Hong, Gye-Won; Kim, Chan-Joong

    2006-04-01

    We fabricated YBCO film using a new approach to the TFA-MOD method. In the fabrication process, Y2Ba1Cu1Ox and Ba3Cu5O8 powders were used as precursors (the so called '211 process'), instead of Y-, Ba-, and Cu-based acetates, and dissolved in trifluoroacetic acid followed by calcining and firing heat treatment. Consequently, we successfully synthesized YBCO film and evaluated the phase formation, texture evolution, and critical properties as a function of the calcining and firing temperature and humidity, in order to explore its possible application in coated conductor fabrication. The films were calcined at 430-460 °C and then fired at 750-800 °C in a 0-20% humidified Ar-O2 atmosphere. We observed that the amount of BaF2 phase was effectively reduced and that a sharp and strong biaxial texture formed under a humidified atmosphere, leading to increased critical properties. In addition, we found that the microstructure varied significantly with the firing temperature; the grains grew further, the film became denser, and the degree of texture and phase purity varied as the firing temperature increased. For the film fired at 775 °C after calcining at 460 °C, the critical current was found to be 39 A cm-1 width (the corresponding critical current density is 2.0 MA cm-2), which was probably attributable to such factors as the enhanced phase purity and out-of-plane texture, the moderate film density and grain size, and the crack-free surface.

  2. Compact spherical neutron polarimeter using high-Tc YBCO films

    NASA Astrophysics Data System (ADS)

    Wang, T.; Parnell, S. R.; Hamilton, W. A.; Li, F.; Washington, A. L.; Baxter, D. V.; Pynn, R.

    2016-03-01

    We describe a simple, compact device for spherical neutron polarimetry measurements at small neutron scattering angles. The device consists of a sample chamber with very low (<0.01 G) magnetic field flanked by regions within which the neutron polarization can be manipulated in a controlled manner. This allows any selected initial and final polarization direction of the neutrons to be obtained. We have constructed a prototype device using high-Tc superconducting films and mu-metal to isolate regions with different magnetic fields and tested device performance in transmission geometry. Finite-element methods were used to simulate the device's field profile and these have been verified by experiment using a small solenoid as a test sample. Measurements are reported using both monochromatic and polychromatic neutron sources. The results show that the device is capable of extracting sample information and distinguishing small angular variations of the sample magnetic field. As a more realistic test, we present results on the characterization of a 10 μm thick Permalloy film in zero magnetic field, as well as its response to an external magnetic field.

  3. Effects of Sn-doping on JC- B properties and crystalline structure for YBCO films by advanced TFA-MOD method

    NASA Astrophysics Data System (ADS)

    Miyanaga, Y.; Teranishi, R.; Yamada, K.; Mori, N.; Mukaida, M.; Kiss, T.; Inoue, M.; Nakaoka, K.; Yoshizumi, M.; Izumi, T.; Shiohara, Y.; Nanba, M.; Awaji, S.; Watanabe, K.

    2009-10-01

    To improve JC properties in a magnetic field ( JC- B) of YBa 2Cu 3O 7-δ(YBCO) films by a TFA-MOD (trifluoroacetates metal organic deposition) method, we fabricated YBCO films with SnO 2-doping as artificial pinning centers and investigated the superconducting properties and the crystalline structures. TFA-MOD is expected as a cost-effective method with a non-vacuum system to fabricate YBCO films with high superconducting properties. However, YBCO films have problems that JC decreases in a magnetic field ( B). In this study, the TFA solutions with SnO 2 for pinning centers were used as starting materials. In the transmission electron microscope image, existence of second phase particles with size of 20-30 nm has been observed in the YBCO film. These nano-particles contained Sn-element and distributed randomly in the film. The JC/ JC (self field) values of the SnO 2-doped YBCO films were enhanced in all magnetic field angles. Therefore it is considered that 3D pinning centers of Sn-compounds were introduced into YBCO film.

  4. Temperature distribution in SFCLs based on Au/YBCO films during quenches

    NASA Astrophysics Data System (ADS)

    Kim, Hye-Rim; Sim, Jungwook; Hyun, Ok-Bae

    2006-04-01

    We investigated temperature distribution in SFCLs based on Au/YBa 2Cu 3O 7 (YBCO). SFCLs were fabricated by patterning Au/YBCO thin films grown on sapphire substrates into meander lines by photolithography. A gold film grown on the back side of the substrate was patterned into a meander line, and used as a thermometer. The front meander line was subjected to simulated AC fault currents, and the back line to DC current. Resistance of the front and back meander lines were measured and analyzed. The SFCLs were immersed in liquid nitrogen during the experiment for effective cooling. The temperature at the back side was close to that at the front side, and was closer at lower temperatures. This was observed at all stripes. The oscillatory component of the resistance of the back meander line is smaller than, and out-of-phase with that of the front meander line, which was more pronounced at higher temperatures. These results were analyzed quantitatively with the concept of heat transfer within the SFCL and to surroundings. Solutions for a heat equation explained the temperature distribution in SFCLs quantitatively: data coincided well with the solutions. In addition, quench development near the quench start point could be understood better than before, using the results.

  5. Real-time observation of the melting process of YBCO thin film on MgO substrate

    NASA Astrophysics Data System (ADS)

    J, Hu; X, Yao; L, Rao Q.

    2003-11-01

    In order to study the mechanism of the liquid phase hetero-epitaxial growth, the melting process of YBa2Cu3O7-dgr (YBCO) thin films was observed by high-temperature optical microscopy. During the heating from room temperature to a temperature above the YBCO peritectic temperature (Tp), we surprisingly find that the YBCO thin film with a MgO substrate can be substantially superheated above the Tp of the YBCO oxide (at least 50 °C) at a heating rate of 5 °C min-1. This is a novel superheating phenomenon involved in a peritectic reaction and an oxide material, which is different from one reported in systems of metals and their alloys. After the melting process, x-ray diffraction analysis was performed, which shows that Y2BaCuO5 (Y211) grains are in good alignment on the MgO substrate. The superheating mechanism of the YBCO oxide is discussed.

  6. Effects of heat treatment and film thickness on microstructure and critical properties of YBCO film processed by TFA-MOD

    NASA Astrophysics Data System (ADS)

    Jang, Seok Hern; Lim, Jun Hyung; Lee, Jin Sung; Yoon, Kyung Min; Kim, Kyu Tae; Joo, Jinho; Jung, Seung-Boo; Lee, Hoo-Jeong

    2007-01-01

    We fabricated YBCO film on an LAO substrate using the TFA-MOD method and evaluated the effects of the heat treatment temperature and film thickness on the microstructure, degree of texture, and critical properties. The calcining and firing processes were performed in the temperature ranges of 370-460 °C and 750-800 °C, respectively. We found that the phase purity, grain size and orientation, and degree of texture varied with the calcining and firing temperatures. The films fired at 775 °C after calcining at 400-430 °C showed the highest critical temperature (TC-onset) of 89.5 K and critical current (IC) of 40 A/cm-width, which corresponds to a critical current density (JC) of 1.8 MA/cm2. According to the XRD, pole-figure, SEM images, and Raman analysis, these highest critical properties are probably due to the formation of a purer YBCO phase and stronger biaxial texture. In the multi-coated films, the IC value increased from 39 to 169 A/cm-width as the number of coatings increased from one to four, while the corresponding JC was measured to be in the range of 0.8-1.2 MA/cm2. Both the IC and JC decreased when a further coating was applied due to the degradation of the microstructure.

  7. High velocity vortex channeling in vicinal YBCO thin films

    PubMed Central

    Puica, I.; Lang, W.; Durrell, J.H.

    2012-01-01

    We report on electrical transport measurements at high current densities on optimally doped YBa2Cu3O7−δ thin films grown on vicinal SrTiO3 substrates. Data were collected by using a pulsed-current technique in a four-probe arrangement, allowing to extend the current–voltage characteristics to high supercritical current densities (up to 24 MA cm−2) and high electric fields (more than 20 V/cm), in the superconducting state at temperatures between 30 and 80 K. The electric measurements were performed on tracks perpendicular to the vicinal step direction, such that the current crossed between ab planes, under magnetic field rotated in the plane defined by the crystallographic c axis and the current density. At magnetic field orientation parallel to the cuprate layers, evidence for the sliding motion along the ab planes (vortex channeling) was found. The signature of vortex channeling appeared to get enhanced with increasing electric field, due to the peculiar depinning features in the kinked vortex range. They give rise to a current–voltage characteristics steeper than in the more off-plane rectilinear vortex orientations, in the electric field range below approximately 1 V/cm. Roughly above this value, the high vortex channeling velocities (up to 8.6 km/s) could be ascribed to the flux flow, although the signature of ohmic transport appeared to be altered by unavoidable macroscopic self-heating and hot-electron-like effects. PMID:23482832

  8. High velocity vortex channeling in vicinal YBCO thin films.

    PubMed

    Puica, I; Lang, W; Durrell, J H

    2012-09-01

    We report on electrical transport measurements at high current densities on optimally doped YBa2Cu3O7-δ thin films grown on vicinal SrTiO3 substrates. Data were collected by using a pulsed-current technique in a four-probe arrangement, allowing to extend the current-voltage characteristics to high supercritical current densities (up to 24 MA cm(-2)) and high electric fields (more than 20 V/cm), in the superconducting state at temperatures between 30 and 80 K. The electric measurements were performed on tracks perpendicular to the vicinal step direction, such that the current crossed between ab planes, under magnetic field rotated in the plane defined by the crystallographic c axis and the current density. At magnetic field orientation parallel to the cuprate layers, evidence for the sliding motion along the ab planes (vortex channeling) was found. The signature of vortex channeling appeared to get enhanced with increasing electric field, due to the peculiar depinning features in the kinked vortex range. They give rise to a current-voltage characteristics steeper than in the more off-plane rectilinear vortex orientations, in the electric field range below approximately 1 V/cm. Roughly above this value, the high vortex channeling velocities (up to 8.6 km/s) could be ascribed to the flux flow, although the signature of ohmic transport appeared to be altered by unavoidable macroscopic self-heating and hot-electron-like effects. PMID:23482832

  9. Electron Paramagnetic Resonance (EPR) Studies of Near-Surface Magnetic Properties of YBCO Thin Films

    NASA Astrophysics Data System (ADS)

    Pugel, D. E.; Xia, Y.-M.; Salamon, M. B.; Greene, L. H.

    2000-03-01

    Several thin film planar tunneling experiments are consistent with a broken time-reversal symmetry (BTRS) state [1-4].To compliment tunneling measurements, we have developed a technique to measure electron paramagnetic resonance (EPR) effects of the near-surface region of a superconductor. Preliminary data are consistent with the spontaneous formation of magnetic moments at low temperature on YBCO thin films and may prove to be an important confirmation of BTRS. 1. Covington,M. et al., Phys. Rev. Lett., 79, 277, (1997). 2. Kashiwaya, S. et al., J. Phys. Chem. Solids, 59, 2034, (1997). 3. Krupke, R. and Deutscher,G., Phys. Rev. Lett., 83, 4634, (1999). 4. Lesueur,J., Grison,X., Aprili,M. and Kontos,T., cond-mat/9909212. -------------------------------------------------------------

  10. In-plane orientation effect on the melting behaviour of YBCO thin film.

    PubMed

    Tang, Chen Y; Cai, Yan Q; Yao, Xin; Rao, Qun L; Tao, Bo W; Li, Yan R

    2007-02-21

    By means of high-temperature optical microscopy (HTOM), a 60 °C gap in initial melting temperature between two YBa₂Cu₃O(x) (Y123) thin films was found in situ. Using these two films as seeds, liquid phase epitaxy (LPE) dipping experiments showed the same tendency in the melting behaviour. The in-plane orientation was detected by x-ray diffraction (XRD) pole figure. On the basis of results from HTOM, LPE and XRD, it was unveiled that the interface structure has a predominant influence on the melting mode. A semi-coherent interface suppresses not only the melting growth but also the melting nucleation, while an incoherent interface encourages both of them. (In this work, melting of YBCO refers to the peritectic decomposition of Y123.). PMID:22251590

  11. Growth and conduction mechanism of As-doped p-type ZnO thin films deposited by MOCVD

    SciTech Connect

    Ma, Y.; Gao, Q.; Wu, G.G.; Li, W.C.; Gao, F.B.; Yin, J.Z.; Zhang, B.L.; Du, G.T.

    2013-03-15

    Highlight: ► P-type As-doped ZnO thin films was fabricated by MOCVD after post-growth annealing. ► The formation mechanism of p-ZnO with high hole concentration above 10{sup 19} cm{sup −3} was elucidated. ► Besides As{sub Zn}–2V{sub Zn} complex, C impurities also played an important role in realizing p-ZnO. ► The formations of As{sub O} and O-C-O complex were partially contributed to the p-type ZnO: As films. - Abstract: As-doped p-type ZnO thin films were fabricated by metal organic chemical vapor deposition (MOCVD) after in situ annealing in a vacuum. The p-type conduction mechanism was suggested by the analysis of X-ray photoelectron spectroscopy and ultraviolet photoemission spectroscopy. It was found that most of the As dopants in p-ZnO thin films formed As{sub Zn}–2V{sub Zn} shallow acceptor complex, simultaneously, carbon impurities also played an important role in realizing p-type conductivity in ZnO. Substitutional carbon on oxygen site created passivated defect bands by combining with Ga atoms due to the donor-acceptor pair Coulomb binding, which shifted the valence-band maximum upwards for ZnO and thus increased the hole concentration.

  12. Structural characterization of multi-coated YBCO films processed by metal-organic deposition method

    NASA Astrophysics Data System (ADS)

    Jang, S. H.; Lim, J. H.; Lee, S. Y.; Kim, K. T.; Lee, C. M.; Park, E. C.; Hwang, S. M.; Park, S.; Joo, J.

    2008-09-01

    YBCO films were fabricated using the TFA-MOD process. The effects of film thickness on phase formation, degree of texture, microstructures, and critical properties were evaluated by X-ray diffraction, pole-figure, and transmission electron microscopy. The films were prepared with various thicknesses by producing multi-coated films by repeating the dip-coating and calcining processes. The microstructure and resultant critical current ( Ic) and critical current density ( Jc) varied remarkably with film thickness: the Ic increased from 39 to 169 A/cm-width, while Jc ranged from 0.85 to 0.92 MA/cm 2 with increasing number of coatings from one to three or four. Both values decreased when further coatings were applied as a result of microstructural degradation. It is believed that this decrease in Ic for the multi-coated film is partly due to the presence of a second phase, pores, and poor texture formability. The optimum thickness for maximizing both the Ic and Jc values is believed to be in the range of 1.1-1.7 μm.

  13. Fabrication of GdBa2Cu3O7-δ films by photo-assisted-MOCVD process

    NASA Astrophysics Data System (ADS)

    Li, Wei; Li, Guoxing; Zhang, Baolin; Chou, Penchu; Liu, Suping; Ma, Xiaoyu

    2014-06-01

    Pure GdBa2Cu3O7-δ (GdBCO) films were deposited on (1 0 0)-oriented LaAlO3 (LAO) substrates by photo-assisted metal organic chemical vapor deposition (PhA-MOCVD) technique. The effects of substrate temperature (Ts) and oxygen partial pressure (Po2) on microstructure, growth rate and superconducting critical current density (Jc) were investigated. A dense and no grain boundary visible, single-crystal-like cross-sectional morphology was observed. For the GdBCO film sample obtained at Ts of 810 °C and Po2 of 4 Torr, the full width at half-maximum were 0.08° and 0.41° for out-of-plane and in-plane orientations, respectively. Such low values were similar to that of single crystal GdBCO. Optimally processed GdBCO samples exhibited Jc of 2.5 MA/cm2 at 77 K in self-field. A relatively high growth rate of 0.104 μm/min for the GdBCO film is realized by the PhA-MOCVD technique.

  14. MOCVD growth of magnesium zinc oxide films and nanostructures for photovoltaics

    NASA Astrophysics Data System (ADS)

    Duan, Ziqing

    MgxZn1-xO, which is formed by alloying ZnO with MgO, has been developed as a promising window layer in chalcopyrite thin film solar cells and hybrid polymer solar cells for enhanced open-circuit voltage and solar conversion efficiency because of its bandgap tunability. The surface morphology of MgxZn1-xO layers in those photovoltaic applications plays important roles on the performances of solar cells. Two-dimensional (2-D) dense and smooth film is preferred in the inorganic p-n junction solar cells while one-dimensional (1-D) nanostructures are favorable for the hybrid polymer solar cells. In this dissertation, metal-organic chemical vapor deposition (MOCVD) is used to grow both of MgxZn1-xO polycrystalline 2-D films and single crystalline 1-D nanostructures for solar cells. A low-temperature (~250°C) ZnO buffer layer, followed by the high-temperature (~500°C) growth of MgxZn1-xO, is found to be beneficial for the formation of a 2-D dense and smooth film. On the other hand, a high-temperature (~520°C) ZnO buffer layer followed by a high temperature (530°C-560°C) growth of MgxZn1-xO is needed to grow the 1-D Mg xZn1-xO (0≤x≤0.15) nanostructures on Si. For the first time, 1-D MgxZn1-xO nanostructures (0≤x≤0.1) are sequentially grown on a Ga-doped ZnO (GZO) 2-D film to form the 3-D photoelectrode, which is used to fabricate the P3HT-MgxZn1-xO hybride solar cells. The preliminary testing results of solar cells show that Mg xZn1-xO is promising to be used in hybrid polymer solar cells for the enhancement of open circuit voltage (VOC). MgxZn1-xO (0≤x≤0.1) polycrystalline films are used in Cu2O-MgxZn1-x O heterojunction solar cells. The current density-voltage (J-V) measurements of solar cells under illumination show that VOC, shunt resistance Rsh and the solar conversion efficiency η are improved with increasing of Mg% until 10%. A relatively high solar conversion efficiency, η AM1.5 = 0.71 % with a short circuit current JSC = 3.0 mA/cm 2 and VOC

  15. MOCVD of YBa 2Cu 3O 7-x thin films using a Ba fluorocarbon-based precursor

    NASA Astrophysics Data System (ADS)

    Fröhlich, K.; Šouc, J.; Chromik, S.; Machajdik, D.; Kliment, V.

    1992-11-01

    We have prepared superconducting YBa 2Cu 3O 7- x films by MOCVD using fluorocarbon based Ba(hfa) 2 precursor. The films were deposited at 500°C and annealed in low pressure ( pO2=10 -2Pa) dry oxygen atmosphere as well as in argon/oxygen mixture in the presence of water vapour. The samples on a MgO single crystal substrate had Tc( R=0)=79 K and Jc=10 4 A/cm 2 at T=30 K in zero magnetic field while the film on SrTiO 3, annealed under the same conditions had Tc( R=0)=86 K and Jc reached a value of 10 5 A/cm 2 at T=78 K.

  16. YBCO film deposition on very large areas up to 20 × 20 cm2

    NASA Astrophysics Data System (ADS)

    Kinder, H.; Berberich, P.; Prusseit, W.; Rieder-Zecha, S.; Semerad, R.; Utz, B.

    1997-08-01

    In the last decade we have developed thermal reactive co-evaporation as a technique to produce high quality YBCO and other oxide films of very large size up to 9 inches in diameter. This was achieved by intermittent deposition and reaction with oxygen using a heater which rotates the substrate in and out of an oxygen pocket. Even larger substrates, e. g. coated conductors, cannot be rotated. Therefore we have recently developed a new setup where the substrate is held fixed, and the oxygen pocket is set in linear reciprocation. This technique allows simultaneous deposition on a square of 20×20 cm 2. Moreover, we have developed an instant refill mechanism for the thermal boats, and stable rate control by atomic absorption spectroscopy (AAS), in order to obtain a continuous process suitable for small scale mass production.

  17. YBCO superconducting thin films prepared by vacuum coevaporation without post treatment in oxygen

    SciTech Connect

    Chromik, S.; Strbik, V.; Benacka, S.; Levarsky, J.; Sith, J.; Plecenik, A.; Gazi, S.; Smatko, V.; Schilder, J.

    1989-03-01

    Results on low temperature process in preparation of superconducting thin films YBa/sub 2/Cu/sub 3/O/sub x/ are presented. The YBCO thin films of thickness 0.5-1.0 ..mu..m were prepared by vacuum codeposition of Y, BaO, and Cu not only onto both polycrystalline and single crystal Al/sub 2/O/sub 3/, MgO, and SrTiO/sub 3/ but even on Si+SrTiO/sub 3/ and Si+SiO/sub 2/ substrates. The temperature of substrate was 550 - 580/sup 0/C and partial oxygen pressure in vacuum chamber 10/sup -2/ Pa. The total film growth rate was 1 nm/s with controlled individual rates to yield the desired 1:2:3 composition. The preparation of in situ superconducting thin films was successful with all used substrates. Maximum critical temperature at zero resistance was T/sub ce/ = 85 K, the onset critical temperature T/sub con/ being from 90 to 95 K.

  18. Microstructural, transport, and rf properties of multilayer-deposited YBCO films

    SciTech Connect

    Madhavrao, L.; Track, E.K.; Drake, R.E.; Patt, R.; Hohenwarter, G.K.G.; Radparvar, M. )

    1991-03-01

    This paper reports on thin films of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}x} (YBCO) fabricated by sequential multilayer rf magnetron sputter-deposition from Y{sub 2}O{sub 3}, BaCO{sub 3}, and CuO targets, and post- annealing in oxygen. This approach readily allows precise control of the film stoichiometry and is proven to be promising for applications that require deposition over large areas. Films on different substrates including SrTiO{sub 3}, LaAlO{sub 3}, MgO and sapphire are found to be c-axis oriented for film thicknesses between 300 {Angstrom} and 10,000 {Angstrom}. Transport current densities in the range of 10{sup 6} A/cm{sup 2} are obtained on SrTiO{sub 3} and LaAlO{sub 3} substrates, and in the range of 10{sup 5} A/cm{sup 2} on MgO and sapphire. Transition temperatures of 89 K (resistive) and 87 K (inductive) are obtained repeatably with LaAlO{sub 3} substrates.

  19. In-plane aligned YBCO film on textured YSZ buffer layer deposited on NiCr alloy tape by laser ablation with only O+ ion beam assistance

    NASA Astrophysics Data System (ADS)

    Tang Huang, Xin; Qing Wang, You; Wang, Qiu Liang; Chen, Qing Ming

    2000-02-01

    High critical current density and in-plane aligned YBa2 Cu3 O7-x (YBCO) film on a textured yttria-stabilized zirconia (YSZ) buffer layer deposited on NiCr alloy (Hastelloy c-275) tape by laser ablation with only O+ ion beam assistance was fabricated. The values of the x-ray phi-scan full width at half-maximum (FWHM) for YSZ(202) and YBCO(103) are 18° and 11°, respectively. The critical current density of YBCO film is 7.9 × 105 A cm-2 at liquid nitrogen temperature and zero field, and its critical temperature is 90 K.

  20. Engineered oxide thin films as 100% lattice match buffer layers for YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Akin, Y.; Heiba, Z. K.; Sigmund, W.; Hascicek, Y. S.

    2003-12-01

    One of the most important qualities of buffer layers for RE-BCO coated conductors' growth is close lattice match with RE-BCO. However, there is no natural material with a 100% lattice match with RE-BCO. In this study mixtures of europium oxide (Eu 2O 3) and ytterbium oxide (Yb 2O 3), (Eu 1- uYb u) 2O 3 (0.0⩽ u⩽1.0), were investigated as a candidate buffer layer that could have same lattice parameter as YBa 2Cu 3O 7- δ(YBCO). Because the pseudocubic lattice parameter of Eu 2O 3 is bigger, and that of Yb 2O 3 is smaller than lattice parameter of YBCO, and the mixed oxides with appropriate ratio would have same lattice parameter of YBCO. The mixtures were prepared using metal-organic precursor by sol-gel process, and it was found that all mixed samples are single phase, complete solid solutions, and have same crystal system over the whole range of " u". Lattice parameters of mixed (Eu 1- uYb u) 2O 3 oxide powders were changed between 10.86831 and 10.42828 Å which are lattice parameter of Eu 2O 3 and Yb 2O 3, respectively by changing the ratio of Eu/Yb in the mixture. Phase and lattice parameter analysis revealed that pseudocubic lattice parameter of (Eu 0.893Yb 0.107) 2O 3 is 3.82 Å which is same as the lattice parameter of YBCO. Textured (Eu 0.893Yb 0.107) 2O 3 buffer layers were grown on biaxially textured-Ni (1 0 0) substrates. The solution was prepared from Europium and Ytterbium 2,4-pentadioanate, and was deposited on the Ni substrates using a reel-to-reel sol-gel dip coating system. The textured films were annealed at 1150 °C for 10 min under 4% H 2-Ar gas flow. Extensive texture analysis has been done to characterize the texture of (Eu 0.893Yb 0.107) 2O 3 buffer layers. X-ray diffraction (XRD) of the buffer layer showed strong out-of-plane orientation on Ni tape. The (Eu 0.893Yb 0.107) 2O 3 (2 2 2) pole figure indicated a single cube-on-cube textured structure. The omega and phi scans revealed good out-of-plane and in-plane alignments. The full

  1. Influence of crossing angles of columnar defects on vortex glass transition in YBCO thin films

    NASA Astrophysics Data System (ADS)

    Sueyoshi, T.; Sogo, T.; Yonekura, K.; Fujiyoshi, T.; Mitsugi, F.; Ikegami, T.; Ishikawa, N.; Awaji, S.; Watanabe, K.

    2011-11-01

    To investigate the influence of the crossing angles of columnar defects (CDs) on the in-field properties of the critical current density Jc and the scaling parameter m derived from the isothermal current-voltage characteristics near the glass-liquid transition at B|| c-axis, YBCO thin films were irradiated using the 200 MeV Xe ions at two angles ± θ i relative to the c-axis. For the thin films, the obvious effect of the crossing angle of CDs occurred on the vortex glass-liquid transition more than the Jc properties. On the glass-liquid transition line, two inflection points induced by the c-axis correlated pinning were confirmed even for the samples of θ i = ±45°. In the magnetic field dependence of m, the peak or kink appeared near B/ B ϕ = 1/3 for the smaller crossing angles, whereas that was slightly visible for the samples of θ i = ±45°. In addition, the values of m for the small crossing angle were larger than those for the parallel CD configuration, while those for the larger crossing angle became smaller. These results suggested that the morphologies of correlated pinning centers strongly affect the dynamics of flux lines even in the disordered system such as thin films.

  2. Prolonged laser ablation effects of YBCO ceramic targets during thin film deposition: Influence of processing parameters

    NASA Astrophysics Data System (ADS)

    Tomov, R.; Tsaneva, V.; Tsanev, V.; Ouzounov, D.

    1996-12-01

    Cumulative laser irradiation during high-Tc superconducting thin film pulsed laser deposition (PLD) may have a detrimental effect on film characteristics. Initial decrease of deposition rate and gradual shift of the center of the deposited material spot towards the incoming laser beam were registered on cold glass substrates. Their absorbance was used for evaluation of the film thickness distribution over the substrate area. At the initial stage, two components of the spot could be distinguished along its short axis: central (˜cosn θ, n≫1) and peripherial (˜cos θ), while with cumulative irradiation the thickness followed an overall cosm θ (mYBCO target under prolonged XeCl laser irradiation were studied by EDAX and SEM for different processing parameters — laser fluence and oxygen environment. The results can be consistently explained suggesting the existence of an additional effective ablation threshold imposed by the modified surface relief.

  3. Solid source MOCVD system

    DOEpatents

    Hubert, Brian N.; Wu, Xin Di

    1998-01-01

    A system for MOCVD fabrication of superconducting and non-superconducting oxide films provides a delivery system for the feeding of metalorganic precursors for multi-component chemical vapor deposition. The delivery system can include multiple cartridges containing tightly packed precursor materials. The contents of each cartridge can be ground at a desired rate and fed together with precursor materials from other cartridges to a vaporization zone and then to a reaction zone within a deposition chamber for thin film deposition.

  4. Solid source MOCVD system

    DOEpatents

    Hubert, B.N.; Wu, X.D.

    1998-10-13

    A system for MOCVD fabrication of superconducting and non-superconducting oxide films provides a delivery system for the feeding of metallorganic precursors for multi-component chemical vapor deposition. The delivery system can include multiple cartridges containing tightly packed precursor materials. The contents of each cartridge can be ground at a desired rate and fed together with precursor materials from other cartridges to a vaporization zone and then to a reaction zone within a deposition chamber for thin film deposition. 13 figs.

  5. Strong vortex matching effects in YBCO films with periodic modulations of the superconducting order parameter fabricated by masked ion irradiation

    NASA Astrophysics Data System (ADS)

    Haag, L. T.; Zechner, G.; Lang, W.; Dosmailov, M.; Bodea, M. A.; Pedarnig, J. D.

    2014-08-01

    We report on measurements of the magnetoresistance and of the critical current in thin films of the high-temperature superconductor YBa2Cu3O7-δ (YBCO). A square array of regions with suppressed superconducting order parameter has been created in these films by introducing point defects via irradiation with He+ ions through a silicon stencil mask. In such a structure distinct peaks of the critical current can be observed at commensurate arrangements of magnetic flux quanta with the artificial defect lattice. Concurrently, the magnetoresistance shows pronounced minima. Both observations demonstrate that the strong intrinsic pinning in YBCO can be overcome by a periodic array of ion-damage columns with 300 nm spacing.

  6. The effect of film thickness on critical properties of YBCO film fabricated by TFA-MOD using 211-process

    NASA Astrophysics Data System (ADS)

    Lim, J. H.; Jang, S. H.; Kim, K. T.; Hwang, S. M.; Joo, J.; Lee, H.-J.; Lee, H.-G.; Hong, G.-W.

    2007-10-01

    YBCO films were fabricated by the TFA-MOD method using the "211-process", and the effects of the film thickness on phase formation, microstructure, texture evolution, and critical properties were evaluated. Various film thicknesses ranging from 0.41 μm to 2.14 μm were obtained by repeating the dip coating and calcining processes one to five times. The critical properties varied significantly with the film thickness. The Ic increased from 35 to 105 A/cm-width with increasing the film thickness from 0.41 μm to 1.17 μm. On the other hand, the corresponding Jc remained almost constant in the range of 0.76-0.90 MA/cm2. With further increases in thickness, these values decreased drastically, which was attributed to the degraded microstructure, i.e., the formation of BaF2 and a-axis grains and degraded texture and surface morphology arising from the insufficient heat treatment time. It is believed that the optimum thickness for improving both the Ic and Jc values is approximately 1.17 μm.

  7. Improvements in Crystal Structure of Two Inch Double-Sided YBCO Thin Films by Preseeded Self-Template Layer

    NASA Astrophysics Data System (ADS)

    Li, Yanrong; Liu, Xingzhao; Tao, Bowan; Zhang, Ying; Deng, Xinwu

    2003-03-01

    A self-template layer was employed to improve the crystal structure and microwave properties of large-area double-sided YBCO thin films. Two-inch double-sided YBCO thin films with excellent out-of-plane orientation and lateral homogeneity of microwave surface resistance were prepared by using a preseeded self-template layer. The full width at half maximum (FWHM) value of the rocking curve as low as 0.15° was achieved. The electronic channeling pattern was very sharp, clear and symmetric. The values of microwave surface resistance Rs (75 K, 145 GHz, 0 T) below 55 mΩ were obtained over the entire YBCO thin films on 2-inch LaAlO3 wafers. The majority of the wafer area given in percent has Rs (75 K, 145 GHz, 0 T) values in the range from 15 mΩ to 40 mΩ. The high frequency (HF) power handling capability was demonstrated by a breakdown field higher than 6 mT at 8.5 GHz and 77 K.

  8. Study on the oxygenation process during the heat treatment of TFA-MOD YBCO thin films by in situ resistance measurement

    NASA Astrophysics Data System (ADS)

    Qu, Timing; Xue, Yunran; Feng, Feng; Huang, Rongxia; Wu, Wei; Shi, Kai; Han, Zhenghe

    2013-11-01

    The oxygen content is one key factor to determine the properties of YBa2Cu3O6+y (YBCO) high temperature superconductors. In this study, YBCO thin films were produced by TFA-MOD method. The oxygenation process was carried out at 450 °C for 40 min, in various oxygen partial pressures from 0.01 to 1 atm. An in situ resistance measurement system was built up to record the resistance evolution during the whole heat treatment process. It was found that the resistance decreased exponentially and reached a saturate value in a few minutes during oxygen annealing. It was also found both the balanced resistance and the c-axis length of YBCO decreased with increasing oxygen partial pressure. A defect reaction was found to control the mechanism of the oxygenation process. A porosity assisted oxygen diffusion mechanism was proposed to explain the fast diffusion kinetics of oxygen in MOD YBCO thin films.

  9. Pulsed laser deposition of c-axis untilted YBCO films on c-axis tilted ISD MgO-buffered metallic substrates

    NASA Astrophysics Data System (ADS)

    Li, M.; Ma, B.; Koritala, R. E.; Fisher, B. L.; Venkataraman, K.; Maroni, V. A.; Vlasko-Vlasov, V.; Berghuis, P.; Welp, U.; Gray, K. E.; Balachandran, U.

    2003-05-01

    Biaxially textured MgO template layer was deposited on nontextured metal substrates by inclined-substrate deposition (ISD) at a deposition rate of 24-600 nm/min. c-axis untilted YBa 2Cu 3O 7- x (YBCO) films were deposited on these MgO-buffered substrates by pulsed laser deposition. The crystalline structures of the YBCO films and MgO layers were examined by X-ray pole figure analysis, X-ray φ-scans, and χ-scans. A tilt angle of 33° of the MgO[0 0 1] with respect to the substrate normal and c-axis untilted YBCO films were observed, respectively. Good biaxial texture of these films with full-width-at-half-maximum values of 13.8° and 10.6° for the φ-scans of YBCO(1 0 3) and MgO(2 2 0), respectively, were obtained. Morphologies were examined by scanning electron microscopy, which revealed a unique roof-tile feature and columnar grain growth for the ISD MgO layer. Raman spectroscopy and magneto-optical image technique were also used to evaluate the quality of the YBCO film. An angular dependence of Jc on the direction of an applied magnetic field confirmed the c-axis untilted orientation of the YBCO films. Tc=90 K with sharp transition and Jc=3.0×10 5 A/cm 2 at 77 K in zero field were obtained on 0.4-μm-thick YBCO films.

  10. Initial stages of TiO 2 thin films MOCVD growth studied by in situ surface analyses

    NASA Astrophysics Data System (ADS)

    Brevet, A.; Peterlé, P. M.; Imhoff, L.; Marco de Lucas, M. C.; Bourgeois, S.

    2005-02-01

    In situ chemical surface analyses using X-ray photoelectron spectroscopy (XPS) were performed to understand the initial stages of TiO 2 thin-film MOCVD growth. Deposits on Si (1 0 0), a few nanometres thick, were obtained at a fixed temperature of 650 °C and for two different pressures, 2.9 and 0.05 mbar, using titanium tetraisopropoxide (TTIP) as precursor. Pressure lowering led to a higher deposit growth rate. Reduction of titanium with respect to stoichiometric titanium dioxide and oxidation of the wet-cleaned silicon substrate are observed from decomposition of the Ti 2p and Si 2p peaks. The formation of a TiSi xO y mixed oxide is also pointed out and confirmed by the presence of a characteristic component in the O 1 s peak.

  11. Aspects of passive magnetic levitation based on high-T{sub c} superconducting YBCO thin films

    SciTech Connect

    Schoenhuber, P.; Moon, F.C.

    1995-04-01

    Passive magnetic levitation systems reported in the past were mostly confined to bulk superconducting materials. Here the authors 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, the authors 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.

  12. 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

  13. MOCVD of high quality YBa 2Cu 3O 7-δ thin films using a fluorinated barium precursor

    NASA Astrophysics Data System (ADS)

    Richards, B. C.; Cook, S. L.; Pinch, D. L.; Andrews, G. W.; Lengeling, G.; Schulte, B.; Jürgensen, H.; Shen, Y. Q.; Vase, P.; Freltoft, T.; Spee, C. I. M. A.; Linden, J. L.; Hitchman, M. L.; Shamlian, S. H.; Brown, A.

    1995-02-01

    MOCVD of superconducting YBa 2Cu 3O 7δ thin films using the novel fluorinated barium β-diketonate complex [Ba(TDFND) 2·tetraglyme] 1 in combination with [Y(TMHD) 3] 2 and [Cu(TMHD) 2] is reported. The Ba complex has a low melting point (72°C), is thermally stable to 200°C and allows reproducible and reliable film deposition even when maintained at 145°C for several weeks. Conversion of the fluoride to the oxide is achieved by in situ hydrolysis. Films deposited on SrTiO 3 (100) were characterised by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, rocking curve, ac susceptibility and secondary ion mass spectrometry. Homogeneous layers of YBa 2Cu 3O 7-δ, ≈ 0.25 μm thick, were grown at ≈ 0.13 μm h -1. The films are epitaxial with good c axis orientation. Critical temperatures Tc are typically 91 K and critical current densities c (at 77 K) of ≈ 5 MA cm -2 are reported. SIMS results showing levels of residual fluorine do not exceed 250 ppm.

  14. Growth parameters effect on the electric and thermoelectric characteristics of Bi 2Se 3 thin films grown by MOCVD system

    NASA Astrophysics Data System (ADS)

    Al Bayaz, A.; Giani, A.; Artaud, M. C.; Foucaran, A.; Pascal-Delannoy, F.; Boyer, A.

    2002-06-01

    Bi 2Se 3 thin films were grown by metal organic chemical vapour deposition (MOCVD) on pyrex substrate in an horizontal reactor using Trimethylbismuth (TMBi) and Diethylselinium (DESe) as metal-organic sources. The effect of the growth parameters such as substrate temperature, Tg, and TMBi partial pressure, PTMBi, on the structural, electrical and thermoelectrical properties of Bi 2Se 3 films, has been investigated. We noticed that a high growth temperature is very important for a good orientation of crystallites, which can be directly related to the best values of Hall mobility and Seebeck coefficient found. Therefore, a large stability of the reactions over the substrates with following growth conditions: 455°C⩽ Tg⩽485°C,0.5×10 -4⩽ PTMBi⩽1×10 -4 atm and a total hydrogen flow rate DT=3 slm, is achieved. In these optimal growth conditions, we found a better crystalline structure of Bi 2Se 3 thin films using X-ray diffraction. Thus, these layers always displayed n-type conduction using Hall effect, with carrier concentration close to 2×10 19 cm -3 and maximum values of Hall mobility and Seebeck coefficient of μ=247 cm 2/V s and | α|=120 μV/K respectively. Then, these films appear to be very promising for thermoelectric applications.

  15. Manufacture of YBCO Superconducting Flexible Tapes from Nanoparticle Films Derived from Sedimentation and by Flame Deposition of Nanoparticles from Solution

    SciTech Connect

    Wiesmann, Harold

    2008-02-24

    The objective of this CRADA was to develop the experimental and theoretical basis of a technology to produce yttrium barium copper oxide (YBCO) superconducting flexible tapes derived from nanoparticle metal oxide sols. The CRADA was a joint effort between Oxford Superconducting Technology, Brookhaven National Laboratory and Karpov Institute of Physical Chemistry. The effort was divided into three main tasks, the synthesis of a heteroepitaxial oxide buffer layer, and the manufacture of a flexible biaxially textured metallic substrate and the synthesis of a heteroepitaxial crystalline YBCO layer. The formation of a heteroepitaxial buffer layer was implemented using technology developed at the Karpov Institute of Physical Chemistry for the synthesis, stabilization and deposition of polymer stabilized nanoparticle metal oxide sols. Using this technology, flexible oriented RABiTS nickel tapes, manufactured and supplied by the CRADA partner, Oxford Superconducting Technology, Carteret, New Jersey, were coated with a film of metal oxide nanoparticles. After coating the RABiTS nickel tapes with the nanoparticle sols the nickel tape/nanoparticle composite structure was sintered in order to form a dense crystalline heteroepitaxial oxide layer on the surface of the tape, also known as a ‘buffer’ layer. The final phase of the research was the formation of a heteroepitaxial YBCO layer, grown on top of the metal oxide buffer layer. This work was scheduled to follow the development of the heteroepitaxial oxide buffer layer as described above. Three different polymer stabilized sols, yttrium hydroxide, Y(OH){sub 3}, copper hydroxide, Cu(OH){sub 2}, and barium fluoride, BaF{sub 2}, were synthesized and combined in the appropriate stoichiometric ratio. This metal oxide sol was then be deposited onto the buffer layer and reacted to form a crystalline heteroepitaxial YBCO film ranging from 1–5 microns thick.

  16. Thickness-Dependent Properties of YBCO Films Grown on GZO/CLO-Buffered NiW Substrates

    NASA Astrophysics Data System (ADS)

    Malmivirta, M.; Huhtinen, H.; Zhao, Y.; Grivel, J.-C.; Paturi, P.

    2016-07-01

    To study the role of novel Gd_2 Zr_2 O_7 /Ce_{0.9} La_{0.1} O_2 buffer layer structure on a biaxially textured NiW substrate, a set of YBa_2 Cu_3 O_{7-δ } (YBCO) films with different thicknesses were prepared by pulsed laser deposition (PLD). Interface imperfections as well as thickness-dependent structural properties were observed in the YBCO thin films. The structure is also reflected into the improved superconducting properties with the highest critical current densities in films with intermediate thicknesses. Therefore, it can be concluded that the existing buffer layers need more optimization before they can be successfully used for films with various thicknesses. This issue is linked to the extremely susceptible growth method of PLD when compared to the commonly used chemical deposition methods. Nevertheless, PLD-grown films can give a hint on what to concentrate to be able to further improve the buffer layer structures for future coated conductor technologies.

  17. Anomalous current-voltage characteristics along the c-axis in YBaCuO thin films prepared by MOCVD and AFM lithography

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shuu'ichirou; Kawaguchi, Atsushi; Oda, Shunri

    1997-12-01

    We have proposed a fabrication process of intrinsic Josephson junctions (IJJs) using AFM lithography and successfully obtained IJJs in YBaCuO thin films deposited by MOCVD. A sample shows clear hysteresis and 23 voltage steps related to IJJs in the I- V curve. The maximum width of a step is about 2 mV at 5 K. We discuss the I- V characteristics and estimate the order of the parameters for the IJJ.

  18. BaHfO3 artificial pinning centres in TFA-MOD-derived YBCO and GdBCO thin films

    NASA Astrophysics Data System (ADS)

    Erbe, M.; Hänisch, J.; Hühne, R.; Freudenberg, T.; Kirchner, A.; Molina-Luna, L.; Damm, C.; Van Tendeloo, G.; Kaskel, S.; Schultz, L.; Holzapfel, B.

    2015-11-01

    Chemical solution deposition (CSD) is a promising way to realize REBa2Cu3O7-x (REBCO; RE = rare earth (here Y, Gd))-coated conductors with high performance in applied magnetic fields. However, the preparation process contains numerous parameters which need to be tuned to achieve high-quality films. Therefore, we investigated the growth of REBCO thin films containing nanometre-scale BaHfO3 (BHO) particles as pinning centres for magnetic flux lines, with emphasis on the influence of crystallization temperature and substrate on the microstructure and superconductivity. Conductivity, microscopy and x-ray investigations show an enhanced performance of BHO nano-composites in comparison to pristine REBCO. Further, those measurements reveal the superiority of GdBCO to YBCO—e.g. by inductive critical current densities, J c, at self-field and 77 K. YBCO is outperformed by more than 1 MA cm-2 with J c values of up to 5.0 MA cm-2 for 265 nm thick layers of GdBCO(BHO) on lanthanum aluminate. Transport in-field J c measurements demonstrate high pinning force maxima of around 4 GN m-3 for YBCO(BHO) and GdBCO(BHO). However, the irreversibility fields are appreciably higher for GdBCO. The critical temperature was not significantly reduced upon BHO addition to both YBCO and GdBCO, indicating a low tendency for Hf diffusion into the REBCO matrix. Angular-dependent J c measurements show a reduction of the anisotropy in the same order of magnitude for both REBCO compounds. Theoretical models suggest that more than one sort of pinning centre is active in all CSD films.

  19. Growth mechanism of GaAs1-xSbx ternary alloy thin film on MOCVD reactor using TMGa, TDMAAs and TDMASb

    NASA Astrophysics Data System (ADS)

    Suhandi, A.; Tayubi, Y. R.; Arifin, P.

    2016-04-01

    Metal Organic Chemical Vapor Deposition (MOCVD) is a method for growing a solid material (in the form of thin films, especially for semiconductor materials) using vapor phase metal organic sources. Studies on the growth mechanism of GaAs1-xSbx ternary alloy thin solid film in the range of miscibility-gap using metal organic sources trimethylgallium (TMGa), trisdimethylaminoarsenic (TDMAAs), and trisdimethylaminoantimony (TDMASb) on MOCVD reactor has been done to understand the physical and chemical processes involved. Knowledge of the processes that occur during alloy formation is very important to determine the couple of growth condition and growth parameters are appropriate for yield high quality GaAs1-xSbx alloy. The mechanism has been studied include decomposition of metal organic sources and chemical reactions that may occur, the incorporation of the alloy elements forming and the contaminants element that are formed in the gown thin film. In this paper presented the results of experimental data on the growth of GaAs1-xSbx alloy using Vertical-MOCVD reactor to demonstrate its potential in growing GaAs1-xSbx alloy in the range of its miscibility gap.

  20. Preparation of ZnO:CeO{sub 2-x} thin films by AP-MOCVD: Structural and optical properties

    SciTech Connect

    Torres-Huerta, A.M.; Dominguez-Crespo, M.A.; Brachetti-Sibaja, S.B.; Dorantes-Rosales, H.; Hernandez-Perez, M.A.; Lois-Correa, J.A.

    2010-09-15

    The growth of columnar CeO{sub 2}, ZnO and ZnO:CeO{sub 2-x} films on quartz and AA6066 aluminum alloy substrates by economic atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) is reported. A novel and efficient combination of metal acetylacetonate precursors as well as mild operating conditions were used in the deposition process. The correlation among crystallinity, surface morphology and optical properties of the as-prepared films was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and UV-vis spectroscopy. The synthesized films showed different crystallographic orientations depending on the ZnO and CeO{sub 2} lattice mismatch, cerium content and growth rate. The CeO{sub 2} films synthesized in this work showed plate-like compact structures as a result of the growth process typical of CVD. Both pure and ZnO:CeO{sub 2-x} films were obtained with a hexagonal structure and highly preferred orientation with the c-axis perpendicular to both substrates under the optimal deposition conditions. The microstructure was modified from dense, short round columns to round structures with cavities ('rose-flower-like' structures) and the typical ZnO morphology by controlling the cerium doping the film and substrate nature. High optical transmittance (>87%) was observed in the pure ZnO films. As for the ZnO:CeO{sub 2-x} films, the optical transmission was decreased and the UV absorption increased, which subsequently was affected by an increase in cerium content. This paper assesses the feasibility of using ZnO:CeO{sub 2-x} thin films as UV-absorbers in industrial applications. - Graphical abstract: TEM micrographs and their corresponding SAED pattern obtained for the as-deposited ZnO-CeO{sub 2-x} thin films for a Zn/Ce metallic ratio 16:9.

  1. Studies of proximity-effect and tunneling in YBCO/metal layered films

    NASA Astrophysics Data System (ADS)

    Greene, L. H.; Barner, J. B.; Feldmann, W. L.; Farrow, L. A.; Miceli, P. F.; Ramesh, R.; Wilkens, B. J.; Bagley, B. G.; Tarascon, J. M.; Wernick, J. H.; Giroud, M.; Rowell, J. M.

    1989-12-01

    The short coherence length of the high-T c superconductors, coupled with their tendency to form non-superconducting surface layers, accounts for the difficulty in achieving good tunnel junctions. A proximity layer of a longer coherence length normal metal (N) is expected to “draw out” Cooper pairs. Our goal is to fabricate reproducible, planar tunnel junctions of SNIS layered structures for proximity tunneling spectroscopy. Such structures of YBCO/N/I/Pb and SNS structures of YBCO/N/Pb indicate that the normal metal produces a low resistance contact to the YBCO surface with a supercurrent observed in the SNS. The insulating barrier in the SNIS is reproducible, insulating and continuous: A sharp Pb gap and phonons from the counter-electrode are routinely observed.

  2. Magnetic Pinning in Nb and YBCO Thin Films by Co/Pt Multilayers with Perpendicular Magnetic Anisotropy

    NASA Astrophysics Data System (ADS)

    Cheng, X. M.; Zhu, L. Y.; Chien, C. L.; Cieplak, Marta Z.; Adamus, Z.; Abal'Oshev, A.; Berkowski, M.

    2006-03-01

    Magnetic pinning of vortices has the advantage over intrinsic pinning in that the superconducting critical current can be reversibly tuned by the magnetic field (H). Magnetic pinning by Co/Pt multilayers with perpendicular magnetic anisotropy has been studied in two ferromagnetic/superconducting bilayers of Nb and YBCO with different superconducting properties (e.g. penetration depth λ). Magnetic force microscopy reveals similar magnetization (M) reversal process in the two cases, both exhibiting a large density of narrow residual domains but with different domain width w at the final reversal stage. However, the magnetic pinning, revealed by the M-H loop shape in the superconducting state, is different. The Nb film exhibits an enhancement of M with the strongest effect during the final reversal stage, while the YBCO film shows a suppression of M in the vicinity of central M peak and an enhancement of M in large magnetic fields. These different behaviors are related to the different λ/w ratio in the two cases.

  3. Fabrication of Tunnel Barriers on YBCO Thin Films by Chemical Surface Modification

    NASA Astrophysics Data System (ADS)

    Hentges, P. J.; Pugel, D. E.; Greene, L. H.; Westwood, G.; Pafford, M. M.; Klemperer, W. G.

    2000-03-01

    In the past, information obtained from planar tunneling into YBCO has been limited by superconducting (SC) counter-electrode density of states effects and interface damage. Traditional fabrication methods such as SC Pb deposition [1] and more recent attempts using organic ligand barriers with non-SC Cu counter electrodes [2] lead to an altered YBCO surface. New molecular technology has produced the molecule Zr_13O_8(OPr^n)_24(OH)_12 which binds to the YBCO surface. XPS analysis shows that successive hydrolysis and condensation reactions increases the molecular density on the surface of YBCO, potentially forming a robust ZrO tunneling barrier which allows the deposition of non-SC counter electrodes. Preliminary results on tunnel junctions will be discussed. This work is supported by the Materials Research Laboratory through the Department of Energy DEFG02-ER-45439. P.J.H. and L.H.G. acknowledge support by ONR N00014-97-1-0682. 1. J. M. Valles et al, Phys. Rev. B 44, 11986 (1991) 2. M. Covington et al., Phys. Rev. Lett. 79, 277 (1997)

  4. Preparation of Sr2AlTaO6 Insulating Films on YBa2Cu3O7-δ by Metalorganic Chemical Vapor Deposition with Purified Sr Source

    NASA Astrophysics Data System (ADS)

    Takahashi, Yoshihiro; Zama, Hideaki; Ishimaru, Yoshihiro; Inoue, Nobuyoshi; Wu, Yuan; Morishita, Tadataka; Tanabe, Keiichi

    2002-02-01

    200-nm-thick Sr2AlTaO6 (SAT) insulating films were prepared on 10-μm-thick superconducting YBa2Cu3O7-δ (YBCO) films by metalorganic chemical vapor deposition (MOCVD). By employing a purified Sr(thd)2 metalorganic source, instead of Sr(thd)2-2tetraene, and a higher evaporation temperature, we could reproducibly obtain stoichiometric SAT films with high crystallinity as revealed by the full-width at half maximum value of the SAT (004) X-ray rocking curve which was as small as 0.2°. Moreover, a 200-nm-thick c-axis-oriented YBCO film with a Tc of 90 K and a Jc higher than 107 A/cm2 below 60 K could be grown on the SAT film. These results confirm that the SAT films prepared by MOCVD are suitable for use as insulating layers in high-Tc multilayer electronic devices.

  5. MOCVD of ceramic and metallic films on porous substrates for dense membrane applications

    NASA Astrophysics Data System (ADS)

    Xia, Changfeng

    Fabrication of thin, dense films on porous substrates is of interest for gas separation membranes, membrane reactor, gas sensors and solid oxide fuel cells. In this study, Chemical Vapor Deposition (CVD) was used to deposit CeOsb2-doped Ysb2Osb3-stabilized ZrOsb2, perovskite SrCosb1-xFesbxOsb{3-delta} and copper films on porous substrates for the purposes of fabricating dense inorganic membranes and studying membrane fabrication process. Aerosol-assisted precursor delivery was employed to overcome the drawbacks of conventional precursor delivery and to provide better control in film composition of multicomponent membrane materials. Thin membrane films of CeOsb2-doped Ysb2Osb3-stabilized ZrOsb2 were grown under atmospheric and reduced pressures from the toluene solutions of the precursors of Zr, Y and Ce 2,2,6,6-tetramethyl-3,5-heptanedionate (tmhd). The effects of system pressure on film morphology, structure and gas-tightness were investigated. The film composition was controlled by selecting the right ratios of precursors in the solutions. Thin membrane films of perovskite SrCosb1-xFesbxOsb{3-delta} were grown under atmospheric pressure and reduced pressure from Sr, Co and Fe tmhd precursors. The relationship between film composition and the composition of precursor solution was developed. The effects of deposition pressure on film morphology, structure and gas-tightness were also studied. The influence of phase purity of SrCosb1-xFesbxOsb{3-delta} films by the system total pressure was also studied. Copper films were deposited on porous substrates for the purpose of investigating the membrane fabrication process using Cu as a model material. The film morphology, microstructure, gas-tightness and other physical properties were characterized in a systematic manner. The copper deposition rates were investigated at different precursor concentrations and the deposition temperatures by using Aerosol-Assisted CVD (AACVD) of toluenen solutions of Cu(hfac)sb2 (hfac

  6. Trade-offs of the opto-electrical properties of a-Si:H solar cells based on MOCVD BZO films.

    PubMed

    Chen, Ze; Zhang, Xiao-dan; Liang, Jun-hui; Fang, Jia; Liang, Xue-jiao; Sun, Jian; Zhang, De-kun; Chen, Xin-liang; Huang, Qian; Zhao, Ying

    2015-01-01

    Boron-doped zinc oxide (BZO) films, deposited by metal-organic chemical vapor deposition (MOCVD), have been widely used as front electrodes in thin-film solar cells due to their native pyramidal surface structure, which results in efficient light trapping. This light trapping effect can enhance the short-circuit current density (Jsc) of solar cells. However, nanocracks or voids in the silicon active layer may form when the surface morphology of the BZO is too sharp; this usually leads to degraded electrical properties of the cells, such as open-circuit voltage (Voc) and the fill factor (FF), which in turn decreases efficiency (Eff) [Bailat et al., Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on. IEEE, 2006, vol. 2, pp. 1533-1536]. In this paper, an etching and coating method was proposed to modify the sharp "pyramids" on the surface of the BZO films. As a result, an evident enhancement was achieved for these modified, BZO-based cells' Voc, FF, and Eff, although the Jsc exhibited a small decrease. In order to increase the Jsc and maintain the improved electrical properties (Voc, FF) of the cell, a thin BZO coating, deposited by MOCVD, was introduced to coat the sputtering-treated BZO film. Finally, we optimized the trade-off among the Voc, FF, and Jsc, that is, we identified a regime with an increase of the Jsc as well as a further improvement of the other electrical properties. PMID:25407724

  7. Microstructures and improved J c-H characteristics of Cl-containing YBCO thin films prepared by the fluorine-free MOD method

    NASA Astrophysics Data System (ADS)

    Motoki, Takanori; Shimoyama, Jun-ichi; Ogino, Hiraku; Kishio, Kohji; Roh, Jiyoung; Tohei, Tetsuya; Ikuhara, Yuichi; Horii, Shigeru; Doi, Toshiya; Honda, Genki; Nagaishi, Tatsuoki

    2016-01-01

    Undoped, Cl-doped, (Cl, Hf) co-doped and (Cl, Sn) co-doped YBa2Cu3O y (YBCO) thin films have been prepared by the fluorine-free metal-organic decomposition (FF-MOD) method on SrTiO3(100) single-crystalline substrates. Cross-sectional microstructures of these films were investigated in detail using scanning transmission electron microscopy (STEM). Rectangular-shaped oxychloride precipitates (Ba2Cu3O4Cl2) and fine particles (BaSnO3) were clearly observed in the (Cl, Sn) co-doped films. The magnetic angular dependence of the critical current density (J c-H-θ) of these films was evaluated. The existence of c-axis-correlated type pinning centers was suggested in Cl-containing YBCO films, whereas this type of pinning is not common in MOD-processed films. J c values were enhanced by Cl doping and further by (Cl, Sn) co-doping in all magnetic field directions at 77 K. This improved J c-H-θ property with c-axis-correlated pinning sites is the first report in FF-MOD-processed YBCO films.

  8. Electroluminescent ZnS:Mn films prepared by an MOCVD method based on dithiocarbamate precursors

    NASA Astrophysics Data System (ADS)

    Zavyalova, L. V.; Beletski, A. I.; Svechnikov, G. S.

    1999-05-01

    It is shown that electroluminescent ZnS:Mn films with luminance more than 0268-1242/14/5/013/img6 and luminous efficiency 0268-1242/14/5/013/img7 can be obtained by low-temperature deposition from Mn and Zn dithiocarbamates; subsequent thermal treatment of these films is not necessary. Starting materials were deposited on the substrate heated to a temperature of 220-0268-1242/14/5/013/img8C by spraying organic solution in air at atmospheric pressure. As a result homogeneous polycrystalline layers of ZnS:Mn with a growth rate of 60-0268-1242/14/5/013/img9 have been obtained. The electroluminescent characteristics of the thin films and structures based on various preparation and excitation conditions are presented. The possibility of application of these films as a planar light source is discussed.

  9. Effects of Target-to-Substrate Angle on Off-Axis Sputter Deposition and EPR Studies of Near-Surface Magnetic Properties of YBCO Thin Films

    NASA Astrophysics Data System (ADS)

    Pugel, D. E.; Xia, Y.-M.; Salamon, M. B.; Greene, L. H.

    2000-11-01

    We have determined the dependence of target-to-substrate angle on the elemental concentration of c-axis YBCO thin films. Away from the standard off-axis position, energy distributions of sputtered elements vary spatially within the sputter plume due to the angular dependence of thermalization. Standard materials characterization techniques and angle-dependent Rutherford Backscattering Spectrometry (RBS) demonstrate that films grown away from the standard off-axis geometry produce bulk Y(123) with modified surface morphology and deposition rate. Several thin film planar tunneling experiments are consistent with a broken-time-reversal symmetry (BTRS) state. To compliment tunneling measurements, we measure electron paramagnetic resonance (EPR) of the near-surface region of YBCO thin films. Preliminary data are consistent with the spontaneous formation of magnetic moments at low temperature.

  10. Double-sided reel-to-reel metal-organic chemical vapor deposition system of YBa{sub 2}Cu{sub 3}O{sub 7-δ} thin films

    SciTech Connect

    Zhang, Fei; Xiong, Jie Liu, Xin; Zhao, Ruipeng; Zhao, Xiaohui; Tao, Bowan; Li, Yanrong

    2014-07-01

    Two-micrometer thick YBa{sub 2}Cu{sub 3}O{sub 7-δ} (YBCO) films have been successfully deposited on both sides of LaAlO{sub 3} single crystalline substrates by using a home-made reel-to-reel metal-organic chemical vapor deposition (MOCVD) system, which has two opposite symmetrical shower heads and a special-designed heater. This technique can simultaneously fabricate double-sided films with high deposition rate up to 500 nm/min, and lead to doubling current carrying capability of YBCO, especially for coated conductors (CCs). X-ray diffraction analysis showed that YBCO films were well crystallized and highly epitaxial with the full width at half maximum values of 0.2° ∼ 0.3° for the rocking curves of (005) YBCO and 1.0° for Φ-scans of (103) YBCO. Scanning electron microscope revealed dense, crack-free, slightly rough surface with Ba-Cu-O precipitates. The films showed critical current density (J{sub c}, 77 K, 0 T) of about 1 MA/cm{sup 2}, and overall critical current of 400 A/cm, ascribed to the double-sided structure. Our results also demonstrated that the temperature and composition in the deposition zone were uniform, which made MOCVD preparation of low cost and high performance double-sided YBCO CCs more promising for industrialization.

  11. Surface Passivation for 3-5 Semiconductor Processing: Stable Gallium Sulphide Films by MOCVD

    NASA Technical Reports Server (NTRS)

    Macinnes, Andrew N.; Jenkins, Phillip P.; Power, Michael B.; Kang, Soon; Barron, Andrew R.; Hepp, Aloysius F.; Tabib-Azar, Massood

    1994-01-01

    Gallium sulphide (GaS) has been deposited on GaAs to form stable, insulating, passivating layers. Spectrally resolved photoluminescence and surface recombination velocity measurements indicate that the GaS itself can contribute a significant fraction of the photoluminescence in GaS/GaAs structures. Determination of surface recombination velocity by photoluminescence is therefore difficult. By using C-V analysis of metal-insulator-semiconductor structures, passivation of the GaAs with GaS films is quantified.

  12. Pressure dependence of the photoluminescence from γ-In2Se3 thin films prepared using MOCVD with a single-source precursor

    NASA Astrophysics Data System (ADS)

    Choi, In Hwan; Park, Hyeon Jeong

    2014-05-01

    Single γ-phase In2Se3 films were prepared by using metal-organic chemical-vapor deposition(MOCVD) with a single-source precursor [(Me)2In( μ-SeMe)]2. The basic physical properties of the grown films were examined by using X-ray diffraction, Raman spectroscopy, and photoluminescence spectroscopy at room temperature. The pressure dependence of the photoluminescence spectrum of the In2Se3 films was measured at room temperature. At 1 atm, 2 PL peaks were observed, one at 1.88 eV due to a bound exciton transition and the other at 1.50 eV due to a bound-to-free transition. While the pressure coefficients, at pressures below 1.4 GPa were nearly zero, the pressure coefficients of both PL peaks at pressures above 1.4 GPa were -25 meV/GPa.

  13. Growth condition dependence of Mg-doped GaN film grown by horizontal atmospheric MOCVD system with three layered laminar flow gas injection

    NASA Astrophysics Data System (ADS)

    Tokunaga, H.; Waki, I.; Yamaguchi, A.; Akutsu, N.; Matsumoto, K.

    1998-06-01

    We developed a novel atmospheric pressure horizontal MOCVD system (SR2000) for the growth of III-nitride film. This system was designed for high-speed gas flow in order to suppress thermal convection and undesirable reactant gas reaction. We have grown Mg-doped GaN films using SR2000. We studied the bis-cyclopentadienyl magnesium (Cp 2Mg) flow rate dependence and growth temperature ( Tg) dependence of Mg-doped GaN. As a result, we have obtained p-type GaN film with hole carrier density of 8×10 17 cm -3 with a mobility of 7.5 cm 2/(V s) at the growth condition with Cp 2Mg flow rate of 0.1 μmol/min at Tg of 1025°C.

  14. Control of carbon content in amorphous GeTe films deposited by plasma enhanced chemical vapor deposition (PE-MOCVD) for phase-change random access memory applications

    NASA Astrophysics Data System (ADS)

    Aoukar, M.; Szkutnik, P. D.; Jourde, D.; Pelissier, B.; Michallon, P.; Noé, P.; Vallée, C.

    2015-07-01

    Amorphous and smooth GeTe thin films are deposited on 200 mm silicon substrates by plasma enhanced—metal organic chemical vapor deposition (PE-MOCVD) using the commercial organometallic precursors TDMAGe and DIPTe as Ge and Te precursors, respectively. X-ray photoelectron spectroscopy (XPS) measurements show a stoichiometric composition of the deposited GeTe films but with high carbon contamination. Using information collected by Optical Emission Spectroscopy (OES) and XPS, the origin of carbon contamination is determined and the dissociation mechanisms of Ge and Te precursors in H2 + Ar plasma are proposed. As a result, carbon level is properly controlled by varying operating parameters such as plasma radio frequency power, pressure and H2 rate. Finally, GeTe films with carbon level as low as 5 at. % are obtained.

  15. Growth parameters effect on the thermoelectric characteristics of Bi 2Se 3 thin films grown by MOCVD system using Ditertiarybutylselenide as a precursor

    NASA Astrophysics Data System (ADS)

    Bayaz, A. Al; Giani, A.; Khalfioui, M. Al; Foucaran, A.; Pascal-Delannoy, F.; Boyer, A.

    2003-10-01

    The growth of Bi 2Se 3 thin films by metalorganic chemical vapour deposition (MOCVD) using Trimethylbismuth (TMBi) and a novel Se-precursor: Ditertiarybutylselenide (DTBSe) as bismuth and selenium sources, respectively, is investigated on pyrex substrates. The effect of the growth parameters such as substrate temperature, Tg, and TMBi partial pressure, PTMBi, on the structural, electrical and thermoelectrical properties for the following growth conditions: 440°C⩽ Tg⩽475°C, 0.5×10 -4 atm⩽ PTMBi⩽1×10 -4 atm and a total hydrogen flow rate DT=3 l/mn, of Bi 2Se 3 films has been investigated. The crystallinity versus growth condition ( Tg, PTMBi) using X-ray diffraction was studied and a typical preferential c-orientation was observed. Thus, these layers always displayed n-type conduction using Hall effect measurement. The best electric and thermoelectric characteristics under the optimal growth conditions have been found; μ>250 cm 2/V s, ρ⩽11.8 μΩ m and α=-163.7 μV/K Then, These initial results suggest a significant potential for the MOCVD method to produce good thermoelectrical materials using DTBSe as Se-precursor.

  16. The magnetisation profiles and ac magnetisation losses in a single layer YBCO thin film caused by travelling magnetic field waves

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Coombs, Timothy

    2015-05-01

    This paper studies the magnetisation and ac magnetisation losses caused by a travelling magnetic wave on a single-layer YBCO thin film. This work provides thorough investigations on how the critical magnetic field gradient has been changed by the application of a travelling wave. Several conditions were studied such as zero-field cooling (ZFC), field cooling (FC) and a delta-shaped trapped field. It was found that the travelling wave tends to attenuate the existing critical magnetic field gradients in all these conditions. This interesting magnetic behaviour can be well predicted by the finite element (FEM) software with the E-J power law and Maxwell’s equations. The numerical simulations show that the existing critical current density has been compromised after applying the travelling wave. The magnetisation profile caused by the travelling wave is very different from the standing wave, while the magnetisation based on the standing wave can be interpreted by the Bean model and constant current density assumption. Based on the numerical method, which has reliability that has been solidly proven in the study, we have extended the study to the ac magnetisation losses. Comparisons were made between the travelling wave and the standing wave for this specific YBCO sample. It was found that by applying the magnetic wave of the same amplitude, the ac magnetisation loss caused by the travelling wave is about 1/3 of that caused by the standing wave. These results are helpful in understanding the general magnetism problems and ac magnetisation loss in the travelling magnetic wave conditions such as inside a high temperature superconducting (HTS) rotating machine, etc.

  17. Progress in fabrication of large magnetic sheilds by using extended YBCO thick films sprayed on stainless steel with the HVOF technique

    SciTech Connect

    Pavese, F.; Bergadano, E.; Ferri, D.

    1997-06-01

    Fabricating a full box-type magnetic shield, by spraying a thick film of commercial YBCO powder on stainless steel with the oxygen-fuel high-velocity technique (HVOF, also referred to as {open_quotes}continuous detonation spray{close_quotes} (CDS)), requires the solution of several specific problems since the design stage of the project. The design problems of this type of shield are examined and the results obtained in the early stages of the realization are discussed.

  18. Properties variation with composition of single-crystal Pb(Zr{sub x}Ti{sub 1-x})O{sub 3} thin films prepared by MOCVD

    SciTech Connect

    Foster, C.M.; Bai, G.R.; Li, Z.; Jammy, R.; Wills, L.A.; Hiskes, R.

    1995-12-01

    Single-crystal thin films covering the full range of PZT 0{le}x{le}1 have been deposited by metal-organic chemical vapor deposition (MOCVD). The films were grown on epitaxial, RF-sputter-deposited SrRuO{sub 3} thin film electrodes on (001) SrTiO{sub 3} substrates. X-ray diffraction, energy-dispersive electron spectroscopy and optical waveguiding were used to characterize the crystalline structure, composition, refractive index, and film thickness. We found that the PZT films were single-crystalline for all compositions exhibiting cube-on-cube epitaxy with the substrate with very high degrees of crystallinity and orientation. We report the systematic variations in the optical, dielectric, polarization, and transport properties as a function of composition and the epitaxy-induced modifications in the solid-solution phase diagram of this system. These films exhibited electronic properties which showed clear systematic variations with composition. High values of remnant polarization (30--55 {mu}C/cm{sup 2}) were observed at all ferroelectric compositions. Unlike previous studies, the dielectric constant exhibited a clear dependence on composition with values ranging from 225--650. Coercive fields decreased with increasing Zr concentration to a minimum of 20 kV/cm at the (70/30) composition. In addition, these films exhibited both high resistivity and dielectric-breakdown strength ({approximately}10{sup 13} {Omega}-cm at 100 kV/cm and >300 kV/cm, respectively) without any compensative doping.

  19. EXAFS study on yttrium oxide thin films deposited by RF plasma enhanced MOCVD under the influence of varying RF self-bias

    NASA Astrophysics Data System (ADS)

    Chopade, S. S.; Nayak, C.; Bhattacharyya, D.; Jha, S. N.; Tokas, R. B.; Sahoo, N. K.; Patil, D. S.

    2014-09-01

    Extended X-ray absorption fine structure (EXAFS) and atomic force microscopy (AFM) studies are carried out on yttrium oxide (Y2O3) thin films deposited by radio frequency plasma assisted metalorganic chemical vapor deposition (MOCVD) process at different RF self-bias (-50 V to -175 V with a step of -25 V) on silicon substrates. A (2,2,6,6-tetramethyl-3,5-heptanedionate) yttrium (commonly known as Y(thd)3) precursor is used in a plasma of argon and oxygen gases at a substrate temperature of 350 °C for deposition. To gain profound understanding about influence of RF self-bias on the properties of the deposited Y2O3 thin films, the films are characterized by EXAFS and AFM measurements. From the EXAFS measurements it is observed that oxygen co-ordination is high for the film deposited at the lowest self bias (-50 V) which is due to presence of higher amount of hydroxyl group in the sample. Oxygen coordination however decrease to lower values for the films deposited at self bias of -75 V. Ysbnd O bond length decreases gradually with increase in self bias indicating reduction in hydroxyl content. However there is reduction in bond length for the film deposited at -100 V as compared to other films resulting from structural changes. The disorder factor obtained from EXAFS measurement increases for films deposited at voltages beyond -125 V due to degradation in crystallinity of the films caused by increased bombardment by incident ions. From AFM measurements, it is observed that the surface morphology of the films also change with self bias. The root mean square roughness value and the entropy factor are found to be low for films deposited at lower bias values and increase for films deposited at bias voltages above -100 V.

  20. Chemical Solution Based Epitaxial Oxide Filmes on Biaxially Textured Ni-W Substrates with Improved Out-of-Plane Texture for YBCO Coated Conductors

    SciTech Connect

    Bhuiyan, Md S; Paranthaman, Mariappan Parans; Sathyamurthy, Srivatsan

    2007-01-01

    Epitaxial films of rare-earth (RE) niobates (where the rare earth includes La, Ce, and Nd) and lanthanum tantalate with pyrochlore structures were grown directly on biaxially textured nickel-3 at.% tungsten (Ni-W) substrates using a chemical solution deposition (CSD) process. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis revealed the surface morphology of the films to be smooth and homogeneous. Detailed X-ray diffraction analysis showed that the films of pyrochlore RE niobate and La-tantalate are highly textured with cube-on-cube epitaxy. The overall texture quality of the films was investigated by measuring the full-width half-maximum (FWHM) of the (004) and (222) rocking curves. We observed a sharper texture for both lanthanum niobate (La{sub 3}NbO{sub 7}) and lanthanum tantalate (La{sub 3}TaO{sub 7}) films compared to the underlying Ni-W substrate, though they have a larger lattice misfit with the Ni-W substrates. These results were comparable to the texture improvement observed in vacuum-deposited Y{sub 2}O{sub 3} seed layers. Texture improvement in the seed layer is the key towards obtaining YBCO films with a higher critical current density. Hence, solution-deposited La{sub 3}NbO{sub 7} and La{sub 3}TaO{sub 7} films can be used as a seed layer towards developing all metalorganic-deposited (MOD) buffer/YBCO architectures.

  1. Structural and optical properties of Ga{sub 2}O{sub 3}:In films deposited on MgO (1 0 0) substrates by MOCVD

    SciTech Connect

    Kong Lingyi; Ma Jin; Luan Caina; Zhu Zhen

    2011-08-15

    Ga{sub 2}O{sub 3}:In films with different indium (In) content x [x=In/(Ga+In) atomic ratio] have been deposited on MgO (1 0 0) substrates by metalorganic chemical vapor deposition (MOCVD). Structural analyses revealed that the film deposited with actual In content (x') of 0.09 was an epitaxial film and the films with x'=0.18 and 0.37 had mixed-phase structures of monoclinic Ga{sub 2}O{sub 3} and bixbyite In{sub 2}O{sub 3}. The absolute average transmittance of the obtained films in the visible region exceeded 95%, and the band gap was in the range of 4.74-4.87 eV. Photoluminescence (PL) measurements were performed at room temperature, in which the visible luminescences were strong and could be seen by the naked eye. The strong emissions in the visible light region were proposed to originate from the gallium vacancies, oxygen deficiencies and other defects in these films. - Graphical abstract: Low magnification XTEM (a), HRTEM (b) and SAED (c) micrographs of the interface area between Ga{sub 1.82}In{sub 0.18}O{sub 3} film and MgO substrate have showed the Ga{sub 1.82}In{sub 0.18}O{sub 3} is an epitaxial film. Highlights: > Ga{sub 1.82}In{sub 0.18}O{sub 3} epitaxial film was deposited on MgO(1 0 0) substrate. > The transmittance of the Ga{sub 2}O{sub 3}:In films in the visible region exceeded 95%. > Strong emissions were observed in the photoluminescence measurements of the films.

  2. YBCO COATED CONDUCTORS

    SciTech Connect

    Paranthaman, Mariappan Parans

    2010-01-01

    Since the discovery of high-temperature superconductors (HTS) in 1986, both (Bi,Pb)2Sr2Ca2Cu3O10 (BSCCO or 2223 with a critical temperature, Tc of 110 K) and YBa2Cu3O7- (YBCO or 123 with a Tc of 91 K) have emerged as the leading candidate materials for the first generation (1G) and second generation (2G) high temperature superconductor wires or tapes that will carry high critical current density in liquid nitrogen temperatures [1-7]. The crystal structures and detailed fundamental properties of BSCCO and YBCO superconductors have been reviewed by Matsumoto in a separate chapter in this book. The U.S. Department of Energy s target price for the conductor is close to the current copper wire cost of $10-50/kA-meter, i.e. a meter of copper type conductor carrying 1000 A current costs ~ $ 50 [8]. The long-term goal for the DOE, Office of Electricity, Advanced Conductors and Cables program is to achieve HTS wire in 1000 meters long with current carrying capacity of 1000 A/cm [8]. Robust, high-performance HTS wire will certainly revolutionize the electric power grid and various other electric power equipments as well. Sumitomo Electric Power (Japan) has been widely recognized as the world leader in manufacturing the first-generation HTS wires based on BSCCO materials using the Oxide-Powder-In-Tube (OPIT) over-pressure process [9]. Typically, 1G HTS wires carry critical currents, Ic, of over 200 Amperes (A) in piece lengths of one kilometer lengths at the standard 4 mm width and ~ 200 m thickness. However, due to the higher cost of 1G wire, mainly because of the cost of Ag alloy sheath, the researchers shifted their effort towards the development of YBCO (second generation 2G) tapes in the last fifteen years [1-7]. One of the main obstacles to the ability to carry high critical currents in YBCO films has been the phenomenon of weak links, i.e., grain boundaries formed by the misalignment of neighboring YBCO grains are known to form obstacles to current flow [10]. By

  3. Advanced high temperature superconductor film-based process using RABiTS

    SciTech Connect

    Goyal, A.; Hawsey, R.A.; Hack, J.; Moon, D.

    2000-01-01

    The purpose of this Cooperative Research and Development Agreement (CRADA) between Lockheed Martin Energy Research Corporation (Contractor), Managing contractor for Oak Ridge National Laboratory (ORNL) and Midwest Superconductivity, Inc. (MSI) and Westinghouse Science and Electric Company (WEC) was to develop the basis for a commercial process for the manufacturing of superconducting tape based on the RABiTS technology developed at ORNL. The chosen method for deposition of YBCO films on RABiTS was Metal Organic chemical Vapor Deposition (MOCVD).

  4. Systematic approach to MOCVD processing chemistry for epitaxial Pb(Zr{sub x}Ti{sub 1-x})O{sub 3} thin films

    SciTech Connect

    Foster, C.M.; Jammy, R.; Bai, G.R.

    1996-12-31

    We have developed a simplified and systematic strategy to the MOCVD synthesis of single crystal thin films of Pb(Ti{sub x}Zr{sub 1-x})O{sub 3} for 0.1 {le}x{le}1. The films were prepared on epitaxial SrRuO{sub 3} buffered on SrTiO{sub 3} substrates by using tetraethyl lead, Pb(C{sub 2}H{sub 5}){sub 4}, zirconium t-butoxide, Zr(OC(CH{sub 3}){sub 3}){sub 4} and titanium isopropoxide, Ti(OCH(CH{sub 3}){sub 2}){sub 4} as metal-organic precursors. The synthesis of these single-crystalline films provided excellent model films to study the systematic variations in the optical, dielectric, polarization, and transport properties as a function of composition and the epitaxy induced modifications in the solid solution phase diagram of this system. High values of remnant polarization (30-55 {mu}C/cm{sup 2}) were observed at all ferroelectric compositions. The remnant polarization, coercive fields, and dielectric constant exhibited a clear dependence on composition. These films exhibited both high resistivity and dielectric strength ({approximately} 10{sup 13} {Omega}-cm at 100 kV/cm and >300 kV/cm, respectively).

  5. MOCVD-derived highly transparent, conductive zinc- and tin-doped indium oxide thin films: precursor synthesis, metastable phase film growth and characterization, and application as anodes in polymer light-emitting diodes.

    PubMed

    Ni, Jun; Yan, He; Wang, Anchuang; Yang, Yu; Stern, Charlotte L; Metz, Andrew W; Jin, Shu; Wang, Lian; Marks, Tobin J; Ireland, John R; Kannewurf, Carl R

    2005-04-20

    Four diamine adducts of bis(hexafluoroacetylacetonato)zinc [Zn(hfa)(2).(diamine)] can be synthesized in a single-step reaction. Single crystal X-ray diffraction studies reveal monomeric, six-coordinate structures. The thermal stabilities and vapor phase transport properties of these new complexes are considerably greater than those of conventional solid zinc metal-organic chemical vapor deposition (MOCVD) precursors. One of the complexes in the series, bis(1,1,1,5,5,5-hexafluoro-2,4-pentadionato)(N,N'-diethylethylenediamine)zinc, is particularly effective in the growth of thin films of the transparent conducting oxide Zn-In-Sn-O (ZITO) because of its superior volatility and low melting point of 64 degrees C. ZITO thin films with In contents ranging from 40 to 70 cation % (a metastable phase) were grown by low-pressure MOCVD. These films exhibit conductivity as high as 2900 S/cm and optical transparency comparable to or greater than that of commercial Sn-doped indium oxide (ITO) films. ZITO films with the nominal composition of ZnIn(2.0)Sn(1.5)O(z)() were used in fabrication of polymer light-emitting diodes. These devices exhibit light outputs and current efficiencies almost 70% greater than those of ITO-based control devices. PMID:15826201

  6. Ion-beam-assisted deposition of biaxially aligned yttria-stabilized zirconia template films on metallic substrates for YBCO-coated conductors

    NASA Astrophysics Data System (ADS)

    Ma, B.; Li, M.; Fisher, B. L.; Balachandran, U.

    2002-07-01

    Biaxially textured yttria-stabilized zirconia (YSZ) films were grown on mechanically polished Hastelloy C276 (HC) substrates by ion-beam-assisted deposition and electron-beam evaporation. The surface root-mean-square (RMS) roughness of the polished HC substrates was ≈3 nm, as measured by atomic force microscopy (AFM). A water-cooled sample stage was used to hold the substrate temperature below 100 °C during deposition. RMS roughness of ≈3.3 nm was measured on the deposited YSZ films by AFM. X-ray pole figures were conducted for texture analysis; in-plane texture measured from YSZ (111) φ-scan FWHM was 13.2° and out-of-plane texture from the YSZ (002) ω-scan FWHM was 7.7°. An ≈10 nm thick CeO2 buffer layer was deposited on the YSZ film at 800 °C before YBCO films were ablated by pulsed laser deposition at 780 °C in a 250 mTorr flowing oxygen environment. Good in-plane texture with FWHM ≈ 7° was observed in YBCO films. Tc = 90 K, with sharp transition, and transport Jc of ≈2.2 × 106 A cm-2 were observed in a 0.5 μm thick, 5 mm wide, and 1 cm long sample at 77 K in self-field.

  7. Vaporization of a mixed precursors in chemical vapor deposition for YBCO films

    NASA Technical Reports Server (NTRS)

    Zhou, Gang; Meng, Guangyao; Schneider, Roger L.; Sarma, Bimal K.; Levy, Moises

    1995-01-01

    Single phase YBa2Cu3O7-delta thin films with T(c) values around 90 K are readily obtained by using a single source chemical vapor deposition technique with a normal precursor mass transport. The quality of the films is controlled by adjusting the carrier gas flow rate and the precursor feed rate.

  8. Temperature dependence of the critical current density in proton irradiated YBCO films by magneto-optical analysis

    NASA Astrophysics Data System (ADS)

    Gozzelino, L.; Botta, D.; Cherubini, R.; Chiodoni, A.; Gerbaldo, R.; Ghigo, G.; Laviano, F.; Minetti, B.; Mezzetti, E.

    2004-07-01

    In this paper we present a magneto-optical analysis of local current densities in YBCO films, before and after 3.5 MeV proton irradiation. The main issue consists into measuring and interpreting the temperature dependence of the critical current density (Jc) in samples with different, increasing defect density. Proton irradiation adds more point defects into the as-grown films. The new defect density as well as the related strain-induced modifications of the order parameter are pushed in our experiment up to temperature-modulated damage thresholds. First of all model-independent Jc data were analysed in the framework of different pinning models, all of them based on mechanisms related to the temperature induced change of the effective pinning centre distribution as well as to the shape of single pinning wells. It turns out that in such a framework the fit parameters are, generally speaking, not suitable to interpret the changes of the pinning landscape across the whole investigated temperature range. Then a model based on a vortex distribution across the whole sample, resulting in a current density that mirrors the current through a defect-modulated average short Josephson junction (JJ) row, is successfully tried. The Jc dependence in the whole temperature range and for all the considered defect densities is accounted for by means of a coherent set of fit parameters. It turns out that the chief quantity that allows applying the JJ formalism to a vortex distribution across the defected matrix is a suitably defined temperature-dependent magnetic thickness of the junctions, which substitutes the usual magnetic penetration in JJs.

  9. Electron microscopy study of MOCVD-grown TiO sub 2 thin films and TiO sub 2 /Al sub 2 O sub 3 interfaces

    SciTech Connect

    Gao, Y.; Merkle, K.L.; Chang, H.L.M.; Zhang, T.J.; Lam, D. J.

    1990-11-01

    TiO{sub 2} thin films grown on (11{bar 2}0) sapphire at 800{degree}C by the MOCVD technique have been characterized by transmission electron microscopy. The TiO{sub 2} thin films are single crystalline and have the rutile structure. The epitaxial orientation relationship between the TiO{sub 2} thin films (R) and the substrate (S) has been found to be: (101)(0{bar 1}0){sub R}{parallel}(11{bar 2}0)(0001){sub S}. Growth twins in the films are commonly observed with the twin plane {l brace}101{r brace} and twinning direction {l angle}011{r angle}. Detailed atomic structures of the twin boundaries and TiO{sub 2}/{alpha}-Al{sub 2}O{sub 3} interfaces have been investigated by high-resolution electron microscopy (HREM). When the interfaces are viewed in the direction of (0{bar 1}0){sub R}/(0001){sub S}, the interfaces are found to be structurally coherent in the direction of ({bar 1}01){sub R}/(1{bar 1}00){sub S}, in which the lattice mismatch at the interfaces is about 0.5%. 8 refs., 4 figs.

  10. A low-fluorine solution with a 2:1 F/Ba mole ratio for the fabrication of YBCO films

    NASA Astrophysics Data System (ADS)

    Wu, Wei; Feng, Feng; Zhao, Yue; Tang, Xiao; Xue, Yunran; Shi, Kai; Huang, Rongxia; Qu, Timing; Wang, Xiaohao; Han, Zhenghe; Grivel, Jean-Claude

    2014-03-01

    In previously reported low-fluorine MOD-YBCO studies, the lowest F/Ba mole ratio of the precursor solution was 4.5. Further lowering the F/Ba ratio would bring benefits for the environment, thick film deposition, and an understanding of the heat treatment process. On the other hand, the F/Ba ratio must be at least 2 for full conversion of the Ba-precursor to BaF2 to avoid the formation of BaCO3, which is detrimental to the superconducting performance of YBCO films. In this study, a solution with a 2:1 F/Ba mole ratio was developed, and the fluorine content of this solution was approximately only 10.3% of that used in the conventional TFA-MOD method. Attenuated total reflectance-Fourier transform-infrared spectra (ATR-FT-IR) revealed that BaCO3 was remarkably suppressed in the as-pyrolyzed film—and eliminated at 700 °C. Thus, YBCO films with a critical current density (Jc) of over 5 MA cm-2 (77 K, 0 T, 200 nm thickness) could be obtained on lanthanum aluminate single-crystal substrates. In situ FT-IR spectra showed that no obvious fluorinated gaseous by-products were detected in the pyrolysis step, which indicated that all F atoms might remain in the film as fluorides. X-ray diffraction θ/2θ scans showed the presence of BaF2—but not of Y F3 or CuF2—in films quenched at 400-800 °C. The formation priority of BaF2 over Y F3 and CuF2 was interpreted by examining the chemical equilibrium of the potential reactions. Our study could enlarge the synthesis window of precursor solutions for MOD-YBCO fabrication, and serve as a foundation for continuously and systematically studying the influence of fluorine content in the precursor solutions.

  11. Novel Neo-Pentoxide Precursors for MOCVD Thin Films of TiO(2) and ZrO(2).[1

    SciTech Connect

    Boyle, Timothy J.; Francisco, Laila P.; Gallegos, Jesus J.; Rodriguez, Mark A.; Ward, Timothy L.

    1999-07-14

    Two novel Group IV precursors, titanium (IV) neo-pentoxide, [Ti({mu}-ONep)(ONep){sub 3}]{sub 2} (l), and zirconium (IV) neo-pentoxide, [Zr({mu}-ONep)(ONep){sub 3}]{sub 2} (2), were reported to possess relatively high volatility at low temperatures. These compounds were therefore investigated as MOCVD precursors using a lamp-heated cold-wall CVD reactor and direct sublimation without carrier gas. The ONep derivatives proved to be competitive precursors for the production of thin films of the appropriate MO{sub 2} (M = Ti or Zr) materials in comparison to other metallo-organic precursors. Compound 1 was found to sublime at 120 C with a deposition rate of {approximately}0.350 {mu}m/min onto a substrate at 330 C forming the anatase phase with < 1% residual C found in the final film. Compound 2 was found to sublime at 160 C and deposited as crystalline material at 300 C with < 1% residual C found in the final film. A comparison to standard alkoxide and {beta}-diketonates is presented where appropriate.

  12. Pulsed Laser Deposition of Thin YBCO Films on Faceted YSZ Single Crystal Fibers

    NASA Astrophysics Data System (ADS)

    Snigirev, O.; Chukharkin, M.; Porokhov, N.; Rusanov, S. Y.; Kashin, V. V.; Tsvetkov, V. B.; Kalabukhov, A.; Winkler, D.

    2014-05-01

    Flexible rods of single crystals of 9% Y2O3-stabilized ZrO2 (YSZ) were used as substrates for deposition of high-critical temperature superconducting (HTS) thin films. YSZ fibers were prepared by mini-pedestal method with laser heating and had average diameter of 300 micrometers and 30 mm length. X-ray diffraction analysis demonstrated high crystalline quality of obtained fibers and also indicated the presence of 15° deviation of the fiber axis from the [001] YSZ direction. Thin YBa2Cu3O7-x films were grown by pulsed laser deposition on YSZ rods using CeO2 buffer layer. Films have shown high critical temperature of 90 K with sharp superconducting transition. Critical current density was estimated to about 3×104 A/cm2 at 80 K. Temperature dependence of critical current density suggests granular structure of films with grain size about several microns. Our results demonstrate feasibility of flexible YSZ fibers coated by HTS thin films for practical use.

  13. Photodetectors of slit and sandwich types based on CdS and CdS1-xSex films obtained using MOCVD method from dithiocarbamates

    NASA Astrophysics Data System (ADS)

    Zavyalova, Ludmila V.; Svechnikov, Sergey V.; Tchoni, Vladimir G.

    1997-04-01

    Here we report the results of working out an original, simple in control and not requiring expensive equipment MOCVD-method for depositing films of semiconductor compounds A2B6. Dithiocarbamates (DTC) are used as starting materials. The compounds are stable, easily synthesized, cheap and low toxic. Atoms of metal and sulfur in the DTC are strongly bonded. The DTC could be easily dissolved in various organic solvents. The experimental unit for film deposition comprises a spraying apparatus, a substrate heater, and a quartz cylinder for separation of a reaction zone from ambience. The process of film deposition is carried out in air conditions. Films of CdS, bright-yellow, transparent, having mirror smooth surface at thickness less than 2 mkm and rough surface at thickness 8-12 mkm, were deposited by spraying cadmium dithiocarbamate, that is DTC with radical C2H5, solution in pyridine on substrates heated to 240-280 degrees C. Deposition rate was 60-90 nm/min. Films obtained were of hexagonal modification, polycrystalline, textured, with low, at the level of centipercents content of oxygen and carbon. Slit type photodetectors based on CdS and CdS1-xSex of 1.0 mkm thickness have dark conductivity (sigma) d equals 10-9 divided by 10-8 Ohm-1cm-1 and photoconductivity (sigma) ph equals 10-2 divided by 10-1 Ohm-1cm-1 at 200 lux. Industrially suitable technology for production of photopotentiometer on the base of these films was developed. Sandwich-type photodetectors In2S3 - CdS: Cu, Cl - In with 8-12 mkm thickness have the same value of photoconductivity and the light-to-dark ratio is 106 divided by 107. Based on sandwich-type photodetectors, a hybrid structure of pyroelectric-photodetector as a resonant-type coordinate-sensitive detector was developed.

  14. Nanoplough-constrictions on thin YBCO films made with atomic force microscopy.

    PubMed

    Elkaseh, A A O; Büttner, U; Meincken, M; Hardie, G L; Srinivasu, V V; Perold, W J

    2007-09-01

    Utilizing atomic force microscope (AFM) with a diamond tip, we were able to successfully plough nano-constrictions on epitaxially grown YBa2Cu3O(7-x) thin films deposited on MgO substrates. The thickness, width, and length of the obtained constrictions were in the range of a few 100 nm. Furthermore, we managed to produce a new S-type constriction, of which the dimensions are easier to control than for conventional constrictions. PMID:18019174

  15. Peculiarities in magnetron sputtering of YBCO epitaxial films for applications in superconductor electronics devices

    NASA Astrophysics Data System (ADS)

    Drozdov, Yu. N.; Masterov, D. V.; Pavlov, S. A.; Parafin, A. E.; Yunin, P. A.

    2015-11-01

    We consider the main factors determining the growth of YBa2Cu3O7-δ high- T c superconductor films during magnetron sputtering in the planar axial geometry. Special attention is paid to the increase of the growth rate of the films suitable for superconductor electronics devices. Magnetron sputtering is used for obtaining YBa2Cu3O7-δ films with high structural and electrophysical characteristics for a growth rate up to 200 nm/h, which were used in constructing microwave disk resonators and long Josephson junctions on bicrystal substrates. The unloaded Q factor of cavities exceeds 80000 at a frequency of 7.1 GHz at a temperature of 77 K, which corresponds to the best results in this field. Josephson junction of length 50-350 μm are characterized by critical current density j c = 12-33 kA/cm2 at T = 77 K and j c = 93-230 kA/cm2 at T = 6 K in zero magnetic field. The characteristic voltage I c R n is 0.8-1.96 mV.

  16. Compact spherical neutron polarimeter using high-T(c) YBCO films.

    PubMed

    Wang, T; Parnell, S R; Hamilton, W A; Li, F; Washington, A L; Baxter, D V; Pynn, R

    2016-03-01

    We describe a simple, compact device for spherical neutron polarimetry measurements at small neutron scattering angles. The device consists of a sample chamber with very low (<0.01 G) magnetic field flanked by regions within which the neutron polarization can be manipulated in a controlled manner. This allows any selected initial and final polarization direction of the neutrons to be obtained. We have constructed a prototype device using high-T(c) superconducting films and mu-metal to isolate regions with different magnetic fields and tested device performance in transmission geometry. Finite-element methods were used to simulate the device's field profile and these have been verified by experiment using a small solenoid as a test sample. Measurements are reported using both monochromatic and polychromatic neutron sources. The results show that the device is capable of extracting sample information and distinguishing small angular variations of the sample magnetic field. As a more realistic test, we present results on the characterization of a 10 μm thick Permalloy film in zero magnetic field, as well as its response to an external magnetic field. PMID:27036785

  17. Advanced light-scattering materials: Double-textured ZnO:B films grown by LP-MOCVD

    NASA Astrophysics Data System (ADS)

    Addonizio, M. L.; Spadoni, A.; Antonaia, A.

    2013-12-01

    Double-textured ZnO:B layers with enhanced optical scattering in both short and long wavelength regions have been successfully fabricated using MOCVD technique through a three step process. Growth of double-textured structures has been induced by wet etching on polycrystalline ZnO surface. Our double-layer structure consists of a first ZnO:B layer wet etched and subsequently used as substrate for a second ZnO:B layer deposition. Polycrystalline ZnO:B layers were etched by utilizing diluted solutions of fluoridic acid (HF), chloridric acid (HCl) and phosphoric acid (H3PO4) and their effect on surface morphology modification was systematically investigated. The morphology of the second deposited ZnO layer strongly depended on the surface properties of the etched ZnO first layer. Growth of cauliflower-like texture was induced by protrusions presence on the HCl etched surface. Optimized double-layer structure shows a cauliflower-like double texture with higher RMS roughness and increased spectral haze values in both short and long wavelength regions, compared to conventional pyramidal-like single texture. Furthermore, this highly scattering structure preserves excellent optical and electrical properties.

  18. Nanopatterning and Hot Spot Modeling of YBCO Ultrathin Film Constrictions for THz Mixers

    NASA Astrophysics Data System (ADS)

    Ladret, Romain G.; Degardin, Annick F.; Kreisler, Alain J.

    2013-06-01

    High-TC hot electron bolometers (HEB) are promising THz mixers due to their expected wide bandwidth, large mixing gain, and low intrinsic noise. To achieve this goal, 0.6-μm-size constrictions were patterned on YBaCuO-based, 10-40-nm-thick films grown on (100) MgO substrates, which as previously reported, exhibited good DC superconducting properties. In this paper, we have simulated the DC and mixer characteristics of YBaCuO HEBs with a hot spot model usually dedicated to low-TC devices. For a 100 nm × 100 nm × 10 nm constriction, the expected double sideband noise temperature TN is 2000 K for 5 μW local oscillator (LO) power (G = -13.5 dB conversion gain). For a larger (but more realistic according to YBaCuO aging effects) 600 nm × 1000 nm × 35 nm constriction, TN = 1300 K at 200 μW LO power (G = -12 dB). This approach is expected to allow optimizing the operation of the HEB constriction coupled to a THz planar antenna.

  19. On the reliability of heteronuclear precursors-ligand effects in the Li-MOCVD synthesis of SrTiO3 films.

    PubMed

    Seisenbaeva, Gulaim A; Gohil, Suresh; Kessler, Vadim G; Andrieux, Michel; Legros, Corinne; Ribot, Patrick; Brunet, Magali

    2011-09-01

    Strontium titanate SrTiO3 thin films are highly perspective as gate dielectric material. Difference in volatility of the common homometallic precursors-strontium beta-diketonates and titanium alkoxides remains major hinder for preparation of high quality coatings based on this phase. An attractive alternative in its synthesis by MOCVD is provided by application of heterometallic mixed-ligand complexes, Sr2Ti2(beta-diket)4(OR)8(ROH)x. Mass-spectrometric study reveals, however, that none of these species can be considered a true single-source precursor. The relative stability of the molecules in solution and the congruence of in-situ release of homometallic species on evaporation are, on the other hand, crucial for the quality of the produced films and are strongly influenced by the nature of alkoxide ligands, OR. The historically first discovered representative of this heterometallic family, a sec-alkoxide derivative Sr2Ti2(thd)4(O(i)Pr)8, is in fact unexpectedly unstable, transforming in solution into Sr2Ti(thd)4(O(i)Pr)4((i)PrOH), which explains difficulties in keeping the correct stoichiometry using isopropoxide precursor. The primary alkoxide complexes, Sr2Ti2(thd)4(OR)8(ROH)2, R = Et, (n)Pr are also unstable yielding Sr4Ti2(thd)4(OR)8(ROH)2 on decomposition. The best solution stability and most uniform evaporation was observed for the iso-derivative, Sr2Ti2(thd)4(O(i)Bu)8, permitting to apply it in long term experiments under industrial process conditions. Present contribution provides detailed experimental comparison between and sec-and iso-alkoxide derivatives and sheds light on the influence of the ligand on molecular stability of a precursor and how it influences the quality of the derived oxide film, especially in relation to its electrophysical properties. PMID:22097573

  20. Electron Spin Resonance (ESR) Detection of Broken Time-Reversal Symmetry (BTRS) at Surfaces of YBa_2Cu_3O_7-x (YBCO) Thin Films

    NASA Astrophysics Data System (ADS)

    Pugel, D. E.

    2001-03-01

    High-Tc cuprate surfaces that break the reflection symmetry of the d-wave order parameter support bound excitations at the Fermi energy. The low-temperature (T ~0.1T_c)behavior of these bound excitations, measured as changes in the density of states, has been interpreted as a transition into a BTRS state(M. Covington et al)., Phys. Rev. Lett. 79, 277 (1997)(R. Krupke & G. Deutscher, Phys. Rev. Lett. 83, 4634 (1999).)(L. H. Greene et al)., Physica B, 280, 159 (2000).. A definitive determination of surface BTRS requires a direct measurement of a spontaneous magnetic field. We adapt traditional X-band ( ~9GHz) ESR to directly search for BTRS at surfaces of optimally-doped,oriented YBCO thin films. This technique allows for spatially localized (<50nm), time-resolved (10-11s) measurements of surface magnetic fields. Organic spin probe crystallites, reduced to nanometer-scale diameters, are applied to (110),(103),(001) YBCO, non-superconducting cuprate isostructure (110) PrBa_2Cu_3O_7, and (100),(110) SrTiO3 surfaces. The resonance response of different spin probes on these surfaces is measured as a function of temperature and applied magnetic field direction. Temperature dependence of ESR spectra for these coated surfaces shows an additional magnetic field source appearing below ~10K for only those YBCO surfaces which break reflection symmetry. The transition is independent of applied field direction, indicating an additional field source that is spontaneous in origin. Results indicate a domain structure whose net magnetization points along [001](D. E. Pugel, Y.-M. Xia, M. B. Salamon, & L. H. Greene, Physica C 341-348, 2003 (2000))(D. E. Pugel, M. B. Salamon, M. B. Weissman, & L. H. Greene, Preprint (2000).).

  1. Fabrication and characterization of hybrid Nb-YBCO dc SQUIDs

    SciTech Connect

    Frack, E.K.; Drake, R.E.; Patt, R.; Radparvar, M. )

    1991-03-01

    This paper reports on the fabrication of hybrid low T{sub c}/high T{sub c} dc SQUIDs of two flavors. The first kind utilizes niobium tunnel junctions and a YBCO film strip as the most inductive portion of the SQUID loop. This configuration allows a direct measurement of the inductance of the YBCO microstrip from which the effective penetration depth can be calculated. The successful fabrication of these SQUIDs has required 1. superconducting Nb-to-YBCO contacts, 2. deposition and patterning of an SiO{sub 2} insulation layer over YBCO, and 3. selective patterning of niobium and SiO{sub 2} relative to YBCO. All these process steps are pertinent to the eventual use of YBCO thin films in electronic devices.

  2. Metal-Organic Chemical Vapor Deposition (MOCVD) Synthesis of Heteroepitaxial Pr0.7Ca0.3MnO3 Films: Effects of Processing Conditions on Structural/Morphological and Functional Properties.

    PubMed

    Catalano, Maria R; Cucinotta, Giuseppe; Schilirò, Emanuela; Mannini, Matteo; Caneschi, Andrea; Lo Nigro, Raffaella; Smecca, Emanuele; Condorelli, Guglielmo G; Malandrino, Graziella

    2015-08-01

    Calcium-doped praseodymium manganite films (Pr0.7Ca0.3MnO3, PCMO) were prepared by metal-organic chemical vapor deposition (MOCVD) on SrTiO3 (001) and SrTiO3 (110) single-crystal substrates. Structural characterization through X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM) analyses confirmed the formation of epitaxial PCMO phase films. Energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) characterization was used to confirm lateral and vertical composition and the purity of the deposited films. Magnetic measurements, obtained in zero-field-cooling (ZFC) and field-cooling (FC) modes, provided evidence of the presence of a ferromagnetic (FM) transition temperature, which was correlated to the transport properties of the film. The functional properties of the deposited films, combined with the structural and chemical characterization collected data, indicate that the MOCVD approach represents a suitable route for the growth of pure, good quality PCMO for the fabrication of novel spintronic devices. PMID:26478849

  3. Metal-Organic Chemical Vapor Deposition (MOCVD) Synthesis of Heteroepitaxial Pr0.7Ca0.3MnO3 Films: Effects of Processing Conditions on Structural/Morphological and Functional Properties

    PubMed Central

    Catalano, Maria R; Cucinotta, Giuseppe; Schilirò, Emanuela; Mannini, Matteo; Caneschi, Andrea; Lo Nigro, Raffaella; Smecca, Emanuele; Condorelli, Guglielmo G; Malandrino, Graziella

    2015-01-01

    Calcium-doped praseodymium manganite films (Pr0.7Ca0.3MnO3, PCMO) were prepared by metal-organic chemical vapor deposition (MOCVD) on SrTiO3 (001) and SrTiO3 (110) single-crystal substrates. Structural characterization through X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM) analyses confirmed the formation of epitaxial PCMO phase films. Energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) characterization was used to confirm lateral and vertical composition and the purity of the deposited films. Magnetic measurements, obtained in zero-field-cooling (ZFC) and field-cooling (FC) modes, provided evidence of the presence of a ferromagnetic (FM) transition temperature, which was correlated to the transport properties of the film. The functional properties of the deposited films, combined with the structural and chemical characterization collected data, indicate that the MOCVD approach represents a suitable route for the growth of pure, good quality PCMO for the fabrication of novel spintronic devices. PMID:26478849

  4. ECR plasma enhanced MOCVD system and the plasma role in film epitaxial growth of GaN and AlN

    NASA Astrophysics Data System (ADS)

    Xu, Yin; Gu, Biao

    2002-11-01

    The development of low-dimension structure materials that are very promising for application of electronic device and optoelectronic device depend on the improvement of the technologies of epitaxial growth and characterization. The film growth technology with noninvasive, in situ, real time monitoring is becoming increasingly important as materials structure become more and more complex. A ECR plasma enhanced MOCVD (PEMOCVD) equipment (ESPU-U) with reflection high-energy electron diffraction (RHEED) for the first time has been developed. Multi-cusp Cavity-coupling ECR plasma source was adopted to provide reactive precursors in ESPD-U therefore the growth temperature was decreased and the working pressure was decreased down to the region less than 1Pa,which makes RHEED in situ monitoring possible. In this paper, the structure, key technologies and unique functions of ESPD-U will be introduced systematically. The epitaxial growth of the large lattice mismatch hetero-junction, GaN/ (0001) Al2O3 and AlN/ Al2O3 (0001), by PEMOCVD in the equipment with in situ RHEED monitoring and the important role of plasma in epitaxial growth were investigated. To remove the native oxidation layer producing a fresh substrate surface with atomic level flatness and to establish a template for the epitaxial growth H2(orH2/N2)-plasma cleaning in situ at 550-650¡A~¦ for 2min- 20 min and N2 ¨Cplasma nitriding at 450-550¡A~¦ for 1 min -30min after the cleaning for the surface of (0001) Al2O3 were investigated. Then the epitaxial growth was started by a two-step process including GaN buffer layer growth at low temperature 500¡A~¦- 650¡A~¦ for 20nm and subsequent film growth of GaN and AlN at high temperature 650¡A~¦-700¡A~¦. The films of GaN and AlN were characterized by the RHEED, XRD, AFM. The FWHM of GaN (0002) diffraction peak from 0.5µm thick GaN film was 18 min and the FWHM of AlN (0002) diffraction peak from 0.3µm thick AlN film was 12 min. The details of

  5. Magnetorefractive effect in the La1-xKxMnO3 thin films grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Sukhorukov, Yu. P.; Telegin, A. V.; Bessonov, V. D.; Gan'shina, E. A.; Kaul', A. R.; Korsakov, I. E.; Perov, N. S.; Fetisov, L. Yu.; Yurasov, A. N.

    2014-10-01

    Thin epitaxial La1-хKхMnO3 films were grown using two-stage procedure. Influence of substitution of La3+ ions with K+ ions on the optical and electrical properties of La1-xKxMnO3 films (х=0.05, 0.10, 0.15 и 0.18) has been studied in detail. A noticeable magnetorefractive effect in the films under study was detected in the infrared range. Magnetorefractive effect as well as transverse magneto-optical Kerr effect and magnetoresistance have the maximum in optimally doped sample with x=0.18 corresponding to the highest Curie temperature. The experimental data for compositions close to optimally doped films are in good agreement with the data calculated in the framework of a theory developed for manganites. The resonance-like contribution to magnetoreflection spectra of manganite films has been observed in the vicinity of the phonon bands. It is shown that magnetic and charge inhomogeneities strongly influence on the magneto-optical effects in films. Thin films of La1-xKxMnO3 with the large values of Kerr and magnetorefractive effect are promising magneto-optical material in the infrared range.

  6. Three-Dimensional Bi2Te3 Nanocrystallites Embedded in 2D Bi2Te3 Films Grown by MOCVD

    NASA Astrophysics Data System (ADS)

    You, HyunWoo; Baek, Seung Hyub; Kim, Chang Kyo; Lyeo, Ho-Ki; Park, Chan; Kim, Jin-Sang

    2012-06-01

    Two- (2D) and three-dimensional (3D) growth of nanostructured Bi2Te3 films was performed on 4° tilt (100) GaAs substrates using a metalorganic chemical vapor deposition system. To obtain 3D Bi2Te3 crystallites embedded in 2D planar film, we alternately changed the gas flow rate in the reactor. By repeating two steps, 3D Bi2Te3 crystallites embedded in 2D planar Bi2Te3 film were obtained. The thermoelectric properties in terms of the thermal conductivity, electrical conductivity, and Seebeck coefficient were investigated at room temperature. The thermal conductivities of the nanostructured Bi2Te3 films were from 0.63 W/(m K) to 0.94 W/(m K) at room temperature, which are low compared with that of film without nanostructure [1.62 W/(m K)]. The thermal conductivity of the film was effectively decreased with the decrease of size and increase of density of 3D crystallites. The results of this study open up a new method to fabricate nanostructured thermoelectric films with high thermoelectric figure of merit.

  7. Indium droplet formation in InGaN thin films with single and double heterojunctions prepared by MOCVD

    PubMed Central

    2014-01-01

    Indium gallium nitride (InGaN) samples with single heterojunction (SH) and double heterojunction (DH) were prepared using metal-organic chemical vapor deposition. SH has a layer of InGaN thin film (thicknesses, 25, 50, 100, and 200 nm) grown on an uGaN film (thickness, 2 μm). The DH samples are distinguished by DH uGaN film (thickness, 120 nm) grown on the InGaN layer. Reciprocal space mapping measurements reveal that the DH samples are fully strained with different thicknesses, whereas the strain in the SH samples are significantly relaxed with the increasing thickness of the InGaN film. Scanning electron microscopy results show that the surface roughness of the sample increases when the sample is relaxed. High-resolution transmission electron microscopy images of the structure of indium droplets in the DH sample indicate that the thickness of the InGaN layer decreases with the density of indium droplets. The formation of these droplets is attributed to the insufficient kinetic energy of indium atom to react with the elements of group V, resulting to aggregation. The gallium atoms in the GaN thin film will not be uniformly replaced by indium atoms; the InGaN thin film has an uneven distribution of indium atoms and the quality of the epitaxial layer is degraded. PMID:25024692

  8. Preparation and characterization of Al{sub 2x}In{sub 2−2x}O{sub 3} films deposited on MgO (1 0 0) by MOCVD

    SciTech Connect

    Li, Zhao; Ma, Jin Zhao, Cansong; Du, Xuejian; Mi, Wei; Luan, Caina; Feng, Xianjin

    2015-07-15

    Highlights: • Ternary Al{sub 2x}In{sub 2−2x}O{sub 3} alloy films were deposited on MgO (1 0 0) by MOCVD. • The microstructure of the Al{sub 2x}In{sub 2−2x}O{sub 3} films were studied upon HRTEM. • Al{sub 2x}In{sub 2−2x}O{sub 3} alloy films exhibited great optical transparency in the visible wavelength range. • The band gap of the Al{sub 2x}In{sub 2−2x}O{sub 3} films can be modulated by controlling the Al contents in the samples. - Abstract: The ternary Al{sub 2x}In{sub 2−2x}O{sub 3} films with different compositions x[Al/(Al + In) atomic ratio] have been fabricated on the MgO (1 0 0) substrates by the metal organic chemical vapor deposition (MOCVD) method. The influence of different Al contents on the structural, optical and electrical properties of Al{sub 2x}In{sub 2−2x}O{sub 3} films has been studied. The structural studies reveal a change from single crystalline structure of cubic In{sub 2}O{sub 3} to amorphous as the Al content increases. The average transmittances of all samples in the visible range are over 80%. The optical band gap is observed to increase monotonically from 3.67 to 5.38 eV as the Al content increases from 0.1 to 0.9.

  9. Synthesis of TiO{sub 2} thin films using single molecular precursors by MOCVD method for dye-sensitized solar cells application and study on film growth mechanism

    SciTech Connect

    Nam, Sang Hun; Hyun, Jae-Sung; Boo, Jin-Hyo

    2012-10-15

    For dye-sensitized solar cells application, in this study, we have synthesized TiO{sub 2} thin films at deposition temperature in the range of 300–750 °C by metalorganic chemical vapor deposition (MOCVD) method. Titanium(IV) isopropoxide, (TIP, Ti(O{sup i}Pr){sub 4}) and Bis(dimethylamido)titanium diisopropoxide, (BTDIP, (Me{sub 2}N){sub 2}Ti(O{sup i}Pr){sub 2}) were used as single source precursors that contain Ti and O atoms in the same molecule, respectively. Crack-free, highly oriented TiO{sub 2} polycrystalline thin films with anatase phase were deposited on Si(1 0 0) with TIP at temperature as low as 450 °C. XRD and TED data showed that below 500 °C, the TiO{sub 2} thin films were dominantly grown in the [2 1 1] direction on Si(1 0 0), whereas with increasing the deposition temperature to 700 °C, the main film growth direction was changed to [2 0 0]. Above 700 °C, however, rutile phase TiO{sub 2} thin films have only been obtained. In the case of BTDIP, on the other hand, only amorphous film was grown on Si(1 0 0) below 450 °C while a highly oriented anatase TiO{sub 2} film in the [2 0 0] direction was obtained at 500 °C. With further increasing deposition temperatures over 600 °C, the main film growth direction shows a sequential change from rutile [1 0 1] to rutile [4 0 0], indicating a possibility of getting single crystalline TiO{sub 2} film with rutile phase. This means that the precursor together with deposition temperature can be one of important parameters to influence film growth direction, crystallinity as well as crystal structure. To investigate the CVD mechanism of both precursors in detail, temperature dependence of growth rate was also carried out, and we then obtained different activation energy of deposition to be 77.9 and 55.4 kJ/mol for TIP and BTDIP, respectively. Also, we are tested some TiO{sub 2} film synthesized with BTDIP precursor to apply dye-sensitized solar cell.

  10. The growth and characterization of GaN films on cone-shaped patterned sapphire by MOCVD

    NASA Astrophysics Data System (ADS)

    Liang, Jing; Hongling, Xiao; Xiaoliang, Wang; Cuimei, Wang; Qingwen, Deng; Zhidong, Li; Jieqin, Ding; Zhanguo, Wang; Xun, Hou

    2013-11-01

    GaN films are grown on cone-shaped patterned sapphire substrates (CPSSs) by metal-organic chemical vapor deposition, and the influence of the temperature during the middle stage of GaN growth on the threading dislocation (TD) density of GaN is investigated. High-resolution X-ray diffraction (XRD) and cathode-luminescence (CL) were used to characterize the GaN films. The XRD results showed that the edge-type dislocation density of GaN grown on CPSS is remarkably reduced compared to that of GaN grown on conventional sapphire substrates (CSSs). Furthermore, when the growth temperature in the middle stage of GaN grown on CPSS decreases, the full width at half maximum of the asymmetry (102) plane of GaN is reduced. This reduction is attributed to the enhancement of vertical growth in the middle stage with a more triangular-like shape and the bending of TDs. The CL intensity spatial mapping results also showed the superior optical properties of GaN grown on CPSS to those of GaN on CSS, and that the density of dark spots of GaN grown on CPSS induced by nonradiative recombination is reduced when the growth temperature in the middle stage decreases.

  11. Photoelectron spectroscopy study of AlN films grown on n-type 6H-SiC by MOCVD

    NASA Astrophysics Data System (ADS)

    Liang, F.; Chen, P.; Zhao, D. G.; Jiang, D. S.; Zhao, Z. J.; Liu, Z. S.; Zhu, J. J.; Yang, J.; Liu, W.; He, X. G.; Li, X. J.; Li, X.; Liu, S. T.; Yang, H.; Liu, J. P.; Zhang, L. Q.; Zhang, Y. T.; Du, G. T.

    2016-09-01

    Photoelectron spectroscopy has been employed to analyze the content and chemical states of the elements on the surface of AlN films with different thickness, which are synthesized by metalorganic chemical vapor deposition on the n-type SiC substrates under low pressure. It is found that, besides the carbon and gallium on the AlN surface, the atom percentage of surface oxygen increases from 4.9 to 8.4, and the electron affinity also increases from 0.36 to 0.97 eV, when the thickness of AlN films increase from 50 to 400 nm. Furthermore, accompanying with the high-resolution XPS spectra of the O 1s, it is speculated that surface oxygen may be the major influence on the electron affinity, where the surface oxygen changes the surface chemical states through replacing N to form Al-O bond and Ga-O bond, although there are also a few of Ga and C contaminations in the chemical sate of Ga-O and C-C, respectively.

  12. Nano-engineered defect structures in Ce- and Ho-doped metal-organic chemical vapor deposited YBa2Cu3O6+δ films: Correlation of structure and chemistry with flux pinning performance

    NASA Astrophysics Data System (ADS)

    Aytug, T.; Chen, Z.; Maroni, V. A.; Miller, D. J.; Cantoni, C.; Specht, E. D.; Kropf, A. J.; Zaluzec, N.; Zhang, Y.; Zuev, Y.; Paranthaman, M.

    2011-06-01

    This study reports on the fabrication of metal-organic chemical vapor deposited (MOCVD) YBa2Cu3O6+δ (YBCO) films doped with varying amounts of Ce and Ho and the characterization of their electrical, microstructural, and chemical properties. The films are prepared by vapor phase deposition of a Y-Ba-Cu precursor mix containing controlled amounts of Ce and Ho onto buffered metal strip templates. The comprehensive characterization of these films by critical current measurement, transmission electron microscopy, x-ray diffraction, Raman microspectroscopy, and x-ray absorption spectroscopy provides detailed information about the structure/chemistry/performance relationships and how they vary with varying amounts of Ce and Ho in the YBCO films. The microstructure exhibited by both the Ce-doped and the Ho-doped films contains a high density of crystal basal-plane aligned, fluoritelike precipitates within the YBCO matrix. For optimally doped samples, the influence of these nanocrystalline phases on the flux pinning properties manifests itself as a significant improvement in the critical current density (Jc) for magnetic field orientations that approach being parallel to the ab planes of the YBCO, while no appreciable change is observed in either self-field Jc or applied-field Jc performance in the vicinity of field orientations parallel to the YBCO c-axis. The Ce is almost exclusively concentrated in the fluoritelike nanoprecipitates, while the Ho incorporates into both the planar arrays of nanoprecipitates and the superconducting matrix, where it substitutes for Y in the YBCO lattice. The present findings for Ce and Ho doping are in interesting contrast with our prior findings for Zr-doped MOCVD films due to the fact that the Zr-doped films exhibit columnar precipitate arrays that produce a substantial improvement in Jc for magnetic field orientations parallel to the YBCO c-axis, while no appreciable change is observed in either self-field or applied-field Jc performance

  13. Nano-engineered defect structures in Ce- and Ho-doped metal-organic chemical vapor deposited YBa{sub 2}Cu{sub 3}O{sub 3+{delta} }films : correlation of structure and chemistry with flux pinning performance.

    SciTech Connect

    Aytug, T.; Chen, Z.; Maroni, V. A.; Miller, D. J.; Cantoni, C.; Specht, E. D.; Kropf, A. J.; Zaluzec, N.; Zhang, Y.; Zuev, Y.; Paranthaman, M.

    2011-06-01

    This study reports on the fabrication of metal-organic chemical vapor deposited (MOCVD) YBa{sub 2}Cu{sub 3}O{sub 6+{delta}} (YBCO) films doped with varying amounts of Ce and Ho and the characterization of their electrical, microstructural, and chemical properties. The films are prepared by vapor phase deposition of a Y-Ba-Cu precursor mix containing controlled amounts of Ce and Ho onto buffered metal strip templates. The comprehensive characterization of these films by critical current measurement, transmission electron microscopy, x-ray diffraction, Raman microspectroscopy, and x-ray absorption spectroscopy provides detailed information about the structure/chemistry/performance relationships and how they vary with varying amounts of Ce and Ho in the YBCO films. The microstructure exhibited by both the Ce-doped and the Ho-doped films contains a high density of crystal basal-plane aligned, fluoritelike precipitates within the YBCO matrix. For optimally doped samples, the influence of these nanocrystalline phases on the flux pinning properties manifests itself as a significant improvement in the critical current density (J{sub c}) for magnetic field orientations that approach being parallel to the ab planes of the YBCO, while no appreciable change is observed in either self-field J{sub c} or applied-field J{sub c} performance in the vicinity of field orientations parallel to the YBCO c-axis. The Ce is almost exclusively concentrated in the fluoritelike nanoprecipitates, while the Ho incorporates into both the planar arrays of nanoprecipitates and the superconducting matrix, where it substitutes for Y in the YBCO lattice. The present findings for Ce and Ho doping are in interesting contrast with our prior findings for Zr-doped MOCVD films due to the fact that the Zr-doped films exhibit columnar precipitate arrays that produce a substantial improvement in J{sub c} for magnetic field orientations parallel to the YBCO c-axis, while no appreciable change is observed in

  14. YBCO coated conductors on highly textured Pd-buffered Ni-W tape

    NASA Astrophysics Data System (ADS)

    Celentano, G.; Galluzzi, V.; Mancini, A.; Rufoloni, A.; Vannozzi, A.; Augieri, A.; Petrisor, T.; Ciontea, L.; Gambardella, U.

    2006-06-01

    High critical current density YBa2Cu3O7-x (YBCO) coated conductors were obtained on cube textured Ni-W. The use of a Pd transient layer as a first buffer led to a sharp out-of-plane grains alignment of the CeO2/YSZ/CeO2 buffer layer. YBCO films grown on this template exhibit an out-of-plane orientation with a full width at half maximum of about 3°, less than 50% of the respective starting Ni-W value. Despite the complete interdiffusion between Ni-W and Pd after the YBCO film deposition, the coated conductors exhibit good film adherence as well as a crack free and smooth surface of the YBCO film. YBCO thin films show critical temperature values above than 88 K and a critical current density of 2.1 MA/cm2 at 77 K and self field.

  15. Reel-to-reel fabrication of meter-long YBCO coated conductor

    NASA Astrophysics Data System (ADS)

    Yang, J.; Zhang, H.; Wang, S. M.; Lin, C. G.; Shi, D. Q.; Dou, S. X.

    2011-04-01

    YBa 2Cu 3O 7-δ (YBCO) superconductors were coated on the CeO 2/YSZ/Y 2O 3 buffered Ni-5at%W tapes by a reel-to-reel pulsed laser deposition (PLD). The process of a multi-layer deposition of YBCO film was explored. X-ray diffraction texture measurements showed good both in-plane and out of plane crystalline orientations in YBCO films. The average values calculated at a full width at half maximum (FWHM) of the peaks from phi-scans ( φ) and omega ( ω) scans for one meter-long YBCO tape were 7.49° and 4.71°, respectively. The critical current ( Ic) was over 200 A/cm-width at 77 K and under self-field for meter-long YBCO tape. The critical transition temperature of the YBCO tape was typically as 90.1 K with 0.5 K transition widths.

  16. Effect of Co-doping on Microstructural, Crystal Structure and Optical Properties of Ti1-xCOxO2 Thin films Deposited on Si Substrate by MOCVD Method

    NASA Astrophysics Data System (ADS)

    Supriyanto, E.; Sutanto, H.; Subagio, A.; Saragih, H.; Budiman, M.; Arifin, P.; Sukirno, Barmawi, M.

    2008-03-01

    Ti1-xCOxO2 thin films have been grown on n-type Si(100) substrates by metal organic vapor deposition (MOCVD) using titanium (IV) isopropoxide (TTIP) and tris (2,2,6,6-tetramethyl-3, 5-heptanedionato) cobalt (III) as metal organic precursors. The parameter deposition, such as: bubbler temperature of TTIP Tb(Ti) = 50 °C; substrate temperature Ts = 450 °C; bubbler pressure Pb(Ti) = 260 Torr; flow rate of Ar gas through TTIP precursor Ar(Ti) = 100 sccm (standard cubic centimeters per minute) and flow rate of oxygen gas O2 = 60 sccm were found as optimal deposition parameters. The thin films deposited were have rutile (002) crystal plane, whereas those deposited at other parameter were mixing of anatase and rutile phases. Co dopant with concentration of up to 5.77% was not changes the structure of TiO2. Increase of Co incorporated in thin films was decreasing of band-gap energy.

  17. Hysteretic Dependence of Magnetic Flux Density on Primary AC Current in Flat-Type Inductive Fault Current Limiter with YBCO Thin Film Discs

    NASA Astrophysics Data System (ADS)

    Harada, Masayuki; Yokomizu, Yasunobu; Matsumura, Toshiro

    2014-05-01

    This paper focuses on a flat-type inductive superconducting FCL (FIS-FCL) consisting of a pancake coil and a YBCO thin layer disc. AC current injection experiments and magnetic field analysis were carried out for two kinds of FIS-FCL, single-disc model and double-discs model. In the former, the pancake coil was putted on the YBCO disc. In the latter, the pancake coil was sandwiched with two YBCO discs. The double-discs model cancels out the magnetic flux density more effectively than the single-disc model. In the double-discs model, the superconducting state period is longer than in the single-disc model. Thus, it may be concluded that the double-discs model is considered to be suitable for FIS-FCL.

  18. Critical Current Properties in Longitudinal Magnetic Field of YBCO Superconductor with APC

    NASA Astrophysics Data System (ADS)

    Kido, R.; Kiuchi, M.; Otabe, E. S.; Matsushita, T.; Jha, A. K.; Matsumoto, K.

    The critical current density (Jc) properties of the Artificial Pinning Center (APC) introduced YBa2Cu3O7 (YBCO) films in the longitudinal magnetic field were measured. Y2O3 or Y2BaCuO5 (Y211) was introduced as APCs to YBCO, and YBCO films with APC were fabricated on SrTiO3 single crystal substrate. The sizes of Y2O3 and Y211 were 5-10 nm and 10-20 nm, respectively. As a result, Jc enhancement in the longitudinal magnetic field was observed in Y2O3 introduced YBCO films. However, it was not observed in Y211 introduced YBCO films. Therefore, it was considered that Jc properties in the longitudinal magnetic field were affected by introducing of small size APC, and it was necessary that APC does not disturb the current pathway in the superconductor.

  19. Crystal growth of YBCO coated conductors by TFA MOD method

    NASA Astrophysics Data System (ADS)

    Yoshizumi, M.; Nakanishi, T.; Matsuda, J.; Nakaoka, K.; Sutoh, Y.; Izumi, T.; Shiohara, Y.

    2008-09-01

    The crystal growth mechanism of TFA (trifluoroacetates)-MOD (metal organic deposition) derived YBa 2Cu 3O y has been investigated to understand the process for higher production rates of the conversion process. YBCO films were prepared by TFA-MOD on CeO 2/Gd 2Zr 2O 7/Hastelloy C276 substrates. The growth rates of YBCO derived from Y:Ba:Cu = 1:2:3 and 1:1.5:3 starting solutions were investigated by XRD and TEM analyses. YBCO growth proceeds in two steps of the epitaxial one from the substrate and solid state reaction. The overall growth rate estimated from the residual amounts of BaF 2 with time measured by XRD is proportional to a square root of P(H 2O). The trend was independent of the composition of starting solutions, however, the growth rate obtained from the 1:1.5:3 starting solutions was high as twice as that of 1:2:3, which could not be explained by the composition of BaF 2 included in the precursor films. On the other hand, the growth rate measured from the thickness of the YBCO quenched film at the same process time showed no difference between the samples of 1:2:3 and 1:1.5:3. The epitaxial growth rate of 1:1.5:3 was also the same as the overall growth rate of that, which means there was no solid state reaction to form YBCO after the epitaxial growth. The YBCO growth mechanism was found to be as follows; YBCO crystals nucleate at the surface of the substrate and epitaxially grow into the precursor by layer-by-layer by a manner with trapping unreacted particles. The amounts of YBCO and the unreacted particles trapped in the YBCO film are independent of the composition of the starting solution in this step. Unreacted particles react with each other to form YBCO and pores by solid state reaction as long as there is BaF 2 left in the film. The Ba-poor starting solution gives little BaF 2 left in the film and so the solid state reaction is completed within a short time, resulting in the fast overall growth rate.

  20. MOCVD deposition of YSZ on stainless steels

    NASA Astrophysics Data System (ADS)

    Chevalier, S.; Kilo, M.; Borchardt, G.; Larpin, J. P.

    2003-01-01

    Yttria stabilized zirconia was deposited on stainless steel using the metal-organic chemical vapor deposition (MOCVD) technique, from β-diketonate precursors. The variation of the evaporation temperatures of yttrium and zirconium precursor allowed to control the level of Y within the film. Over the temperature range 125-150 °C, the Y content increased from 2.5 to 17.6 at.%. X-ray diffraction (XRD) analyses evidenced tetragonal phase of zirconia when the Y content was below 8 at.%, and cubic phase for higher concentration. Sputtered neutral mass spectrometry (SNMS) profiles confirmed that the control and stability of Y precursor temperature were of major importance to guarantee the homogeneity of the deposited films.

  1. Development of YBCO-coated conductors for electric power applications

    NASA Astrophysics Data System (ADS)

    Balachandran, U.; Li, M.; Koritala, R. E.; Fisher, B. F.; Ma, B.

    2002-08-01

    Biaxially textured MgO template films have been fabricated on a Ni-based alloy substrate (Hastelloy C276) by inclined-substrate deposition (ISD), using electron beam evaporation, at the high deposition rate of 120-300 nm/min. Buffer films were subsequently deposited on these template films, and YBCO films were finally deposited by pulsed laser deposition (PLD). Crystal textures of the YBCO films were examined by X-ray pole figure, φ- and ω-scans analysis. Good in-plane and out-of-plane textures were observed, with MgO(0 0 2) φ-scan full-width-at-half-maximum (FWHM) of 10.0° and ω-scan FWHM of 5.5°, for a film deposited with an incline angle of 55°. YBCO films were epitaxially grown on ISD MgO-buffered Hastelloy C276 substrates by PLD. Tc of 90 K with sharp transition and transport Jc of ≈1.4×10 5 A/cm 2 were obtained on a 0.5-μm-thick YBCO film at 77 K in zero field.

  2. Grain morphology of YBCO coated superconductors prepared by spin process on Ni substrate

    NASA Astrophysics Data System (ADS)

    Liu, C. F.; Du, S. J.; Yan, G.; Xi, W.; Wu, X.; Pang, Y.; Wang, F. Y.; Liu, X. H.; Feng, Y.; Zhang, P. X.; Wu, X. Z.; Zhou, L.

    2003-04-01

    The YBCO thick films with c-axis preferred orientation were prepared by spin and printing processes on Ni substrates (including cold rolling Ni, cube textured Ni, and cube textured Ni+ self-oxided NiO ). The results show that the chrysanthemum (or spherulite) and polygon morphology grains dominate the microstructure of YBCO films. The chrysanthemum size is about 0.2-0.5 mm range, some reaches 1 mm, and polygon grains normally are placed in the center of the chrysanthemum grains. No chrysanthemum grains appear in the thick films prepared on the substrate with Ag or YBCO intermediate layers.

  3. Oxygen and cation diffusion in YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Tsukui, S.; Koritala, R. E.; Li, M.; Goretta, K. C.; Adachi, M.; Baker, J. E.; Routbort, J. L.

    2003-10-01

    Biaxially textured YBa 2Cu 3O x (YBCO) films 0.3 μm thick were deposited on single-crystal LaAlO 3 and buffered Hastelloy C276 substrates. After annealing in 18O at 400 °C, secondary-ion mass spectrometry was used to determine oxygen-diffusion profiles and several cation-diffusion profiles within the various layers of the conductors. Oxygenation in the YBCO/LaAlO 3 specimen was relatively slow and hours would be required for full oxygenation of the YBCO. Oxygen diffusion was rapid in the coated conductor. It was dominated by diffusion along a- b planes and full oxygenation of a 0.3-μm-thick YBCO layer was achieved in several minutes. Cation interdiffusion was limited in the YBCO/LaAlO 3 specimen, but was significant within the coated conductor. Although Cu diffused out of the superconductor, an SrTiO 3 layer between textured MgO and YBCO limited diffusion of cations from the various substrate layers into the superconductor.

  4. Influence of Al content on the properties of ternary Al{sub 2x}In{sub 2−2x}O{sub 3} alloy films prepared on YSZ (1 1 1) substrates by MOCVD

    SciTech Connect

    Feng, Xianjin; Zhao, Cansong; Li, Zhao; Luo, Yi; Ma, Jin

    2015-10-15

    Highlights: • Al{sub 2x}In{sub 2−2x}O{sub 3} films were prepared on the Y-stabilized ZrO{sub 2} (1 1 1) substrates by MOCVD at 700 °C. • A phase transition from the bixbyite In{sub 2}O{sub 3} structure to the amorphous structure was observed. • The lowest resistivity of 4.7 × 10{sup −3} Ω cm was obtained for the Al{sub 0.4}In{sub 1.6}O{sub 3} film. • Tunable optical band gap from 3.7 to 4.8 eV was obtained. - Abstract: The ternary Al{sub 2x}In{sub 2−2x}O{sub 3} films with different Al contents of x [Al/(Al + In) atomic ratio] have been fabricated on the Y-stabilized ZrO{sub 2} (1 1 1) substrates by metal organic chemical vapor deposition at 700 °C. The structural, electrical and optical properties of the films as a result of different Al contents (x = 0.1–0.9) were investigated in detail. With the increase of Al content from 10% to 90%, a phase transition from the bixbyite In{sub 2}O{sub 3} structure with a single orientation along (1 1 1) to the amorphous structure was observed. The minimum resistivity of 4.7 × 10{sup −3} Ω cm, a carrier concentration of 1.4 × 10{sup 20} cm{sup −3} and a Hall mobility of 9.8 cm{sup 2} v{sup −1} s{sup −1} were obtained for the sample with x = 0.2. The average transmittances for the Al{sub 2x}In{sub 2−2x}O{sub 3} films in the visible range were all over 78% and the optical band gap of the films could be tuned from 3.7 to 4.8 eV.

  5. Characterization of ZnO thin film grown on c-plane substrates by MO-CVD: Effect of substrate annealing temperature, vicinal-cut angle and miscut direction

    NASA Astrophysics Data System (ADS)

    Boukadhaba, M. A.; Fouzri, A.; Sallet, V.; Hassani, S. S.; Amiri, G.; Lusson, A.; Oumezzine, M.

    2015-09-01

    The annealing effects of c-plane sapphire (α-Al2O3) substrate with a nominally vicinal-cut angle α (α < 0.1°, α = 0.25° toward the m-plane (1 0 1 bar 0) and α = 0.25° toward the a-plane (1 1 2 bar 0)) on the quality of epitaxial ZnO films grown by metal organic chemical vapor deposition (MO-CVD) were studied. The atomic steps formed on sapphire substrate surface by annealing at high temperature were analyzed by atomic force microscopy (AFM). The annealing and the miscut direction of sapphire substrate on the microstructural and optical properties for ZnO films were examined by high resolution X-ray diffraction (HR-XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and photoluminescence spectroscopy (PL). Experimental results indicate that the film quality is strongly affected by annealing treatment and miscut direction of the sapphire substrate. X-ray diffraction study revealed that all films exhibit a wurtzite phase and have a c-axis orientation. ZnO films deposited on sapphire substrate (α < 0.1° and α = 0.25° toward the m-plane (1 0 1 bar 0), annealed substrate at 1100 °C), exhibit a low quantity of defects and a quite good vertical and lateral alignment compared to other disorientation plane (α = 0.25° toward the a-plane (1 1 2 bar 0), annealed substrate at 1100 °C). The Lattice parameters a and c slightly decreases for ZnO layer deposited on annealed sapphire substrate with increase the annealing substrate temperature for all samples. AFM image show significant differences between morphologies of samples depending on annealing treatment and miscut direction of substrates but no significant differences on surface roughness have been found. Sapphire annealing at 1100 °C with a nominally vicinal-cut angle α = 0.25° toward the m-plane (1 0 1 bar 0), provides the best optical quality of ZnO film.

  6. Study of the optical properties and structure of ZnSe/ZnO thin films grown by MOCVD with varying thicknesses

    NASA Astrophysics Data System (ADS)

    Jabri, S.; Amiri, G.; Sallet, V.; Souissi, A.; Meftah, A.; Galtier, P.; Oueslati, M.

    2016-05-01

    ZnSe layers were grown on ZnO substrates by the metal organic chemical vapor deposition technique. A new structure appeared at lower thicknesses films. The structural properties of the thin films were studied by the X-ray diffraction (XRD) and Raman spectroscopy methods. First, Raman selection rules are explicitly put forward from a theoretical viewpoint. Second, experimentally-retrieved-intensities of the Raman signal as a function of polarization angle of incident light are fitted to the obtained theoretical dependencies in order to confirm the crystallographic planes of zinc blend ZnSe thin film, and correlate with DRX measurements. Raman spectroscopy has been used to characterize the interfacial disorder that affects energy transport phenomena at ZnSe/ZnO interfaces and the Photoluminescence (PL) near the band edge of ZnSe thin films.

  7. AC and DC transport currents in melt-grown YBCO

    SciTech Connect

    Yi, Z.; Ashworth, S.; Becluz, C.; Scurlock, R.G. )

    1991-03-01

    It has been suggested that the transport J{sub c} in multi-grain samples of bulk YBCO are limited by the intergrain links. This paper reports on preliminary measurements of intergrain currents. The intergrain critical currents in melt grown YBCO do not appear to be as sensitive to the precise crystallographic alignment of adjacent grains a has been reported for thin films. The measured critical current of similar grain boundaries varies widely, between 15000 A/cm{sup 2} and 200A/Cm{sub 2} for adjacent boundaries in the same sample.

  8. Deep Level Defect Studies in MOCVD-Grown In(x)Ga(1-x)As(1-y)N(y) Films Lattice-Matched to GaAs

    SciTech Connect

    Allerman, A.A.; Boeckl, J.J.; Jones, E.D.; Kaplar, R.J.; Kurtz, S.R.; Kwon, D.; Ringel, S.A.

    1999-03-04

    Deep level defects in MOCVD-grown, unintentionally doped p-type InGaAsN films lattice matched to GaAs were investigated using deep level transient spectroscopy (DLTS) measurements. As-grown p-InGaAsN showed broad DLTS spectra suggesting that there exists a broad distribution of defect states within the band-gap. Moreover, the trap densities exceeded 10{sup 15} cm{sup {minus}3}. Cross sectional transmission electron microscopy (TEM) measurements showed no evidence for threading dislocations within the TEM resolution limit of 10{sup 7} cm{sup {minus}2}. A set of samples was annealed after growth for 1800 seconds at 650 C to investigate the thermal stability of the traps. The DLTS spectra of the annealed samples simplified considerably, revealing three distinct hole trap levels with energy levels of 0.10 eV, 0.23 eV, and 0.48 eV above the valence band edge with trap concentrations of 3.5 x 10{sup 14} cm{sup {minus}3}, 3.8 x 10{sup 14} cm {sup {minus}3}, and 8.2 x 10{sup 14} cm{sup {minus}3}, respectively. Comparison of as-grown and annealed DLTS spectra showed that post-growth annealing effectively reduced the total trap concentration by an order of magnitude across the bandgap. However, the concentration of a trap with an energy level of 0.48 eV was not affected by annealing indicating a higher thermal stability for this trap as compared with the overall distribution of shallow and deep traps.

  9. Synthesis and properties of highly c-axis oriented PbTiO3 thin films prepared by and MOCVD method

    NASA Astrophysics Data System (ADS)

    Chen, Xian-Tong; Yamane, Hisanori; Kaya, Kiyoshi

    1992-08-01

    Thin films of PbTiO3 were prepared on MgO(100) substrates by chemical vapor deposition using Pb(C2H5)4 (PbEt) and Ti(OC3H7)4 (TTIP) as sources. With decreasing Pb/Ti molar ratio from 1.2 to 1 the degree of c-axis orientation increased. Highly c-axis oriented PbTiO3 thin films were epitaxially grown at 500°C and 2 kPa. The films were transparent and had a refractive index (n) of 2.64 at 632.8 nm which was about 2% lower than that of a single PbTiO3 crystal (n ≈ 2.7). The films prepared on (100)-oriented Pt electrodes deposited on MgO(100) substrates at 600°C and 2 kPa also showed a prominent c-axis orientation and had a dielectric constant of 90.

  10. Direct deposition of YBCO on polished Ag substrates by pulsed laser deposition.

    SciTech Connect

    Ma, B.; Li, M.; Koritala, R. E.; Fisher, B. L.; Dorris, S. E.; Maroni, V. A.; Miller, D. J.; Balachandran, U.

    2002-09-15

    YBCO thin films were directly deposited on mechanically polished nontextured silver (Ag) substrates at elevated temperature by pulsed laser deposition with various inclination angles of 35, 55, and 72. Strong fiber texture, with the c-axis parallel to the substrate normal was detected by X-ray diffraction pole figure analysis. Atomic force microscopy and scanning electron microscopy images revealed that a few a-axis-oriented grains were dispersed on the top surface of the YBCO films. Transmission electron microscopy revealed dense amorphous layer at the interface between the YBCO film and the Ag substrate. Energy dispersive spectrum analysis indicates that the YBCO film deposited on the Ag substrate is slightly Cu-deficient. A YBCO film deposited at 755 C and an inclination angle of 55 exhibited {Tc} = 90 K. Transport critical current density measured by the four-probe method at 77 K in self-field was 2.7 x 10{sup 5}A/cm2. This work demonstrated a simple and inexpensive method to fabricate YBCO-coated conductors with high critical current density.

  11. Large field emission current from Si-doped AlN film grown by MOCVD on n-type (001) 6H-SiC

    NASA Astrophysics Data System (ADS)

    Liang, F.; Chen, P.; Zhao, D. G.; Jiang, D. S.; Liu, Z. S.; Zhu, J. J.; Yang, J.; Liu, W.; He, X. G.; Li, X. J.; Li, X.; Liu, S. T.; Yang, H.; Zhang, L. Q.; Liu, J. P.; Zhang, Y. T.; Du, G. T.

    2016-05-01

    A large field emission current density of 2.55 A/cm2 at 20.9 V and a low turn-on voltage of 7.28 V is obtained from the Si-doped 50 nm-thick AlN film, synthesized by metalorganic chemical vapor deposition on the n-type SiC substrates, which is the best result reported for AlN film. Accompanying with atomic force surface micro-images, it is found that this current is achieved owing to a blunting process under a high voltage of 95 V, which can lead to a decrease of the root mean square roughness from 4.23 to 1.03 nm.

  12. Equilibrium composition in II?VI telluride MOCVD systems

    NASA Astrophysics Data System (ADS)

    Ben-Dor, L.; Greenberg, J. H.

    1999-03-01

    Thermodynamic calculations, or computer simulation of the equilibrium composition, offer an excellent possibility to reduce drastically the elaborate trial-and-error experimental efforts of finding the optimal preparation conditions for MOCVD processes (temperature T, pressure P, initial composition of the vapors X), to limit them only to the P- T- X field of existence of the solid to be prepared and an acceptable yield of the product. In this communication equilibrium composition was investigated for MOCVD processes of CdTe, ZnTe, HgTe and solid solutions Cd xZn 1- xTe and Hg xCd 1- xTe. A number of volatile organometallic compounds have been used as precursors for MOCVD growth. These are dimethylcadmium (CH 3) 2Cd, DMCd; diethylzinc (C 2H 5) 2Zn, DEZn; diisopropylzinc [CH(CH 3) 2] 2Zn, DiPZn; diethyltellurium (C 2H 5) 2Te, DETe; diisopropyltellurium [CH(CH 3) 2] 2Te, DiPTe; methylallyltellurium CH 3TeCH 2CHCH 2, MATe. A choice of the particular combination of the precursors largely depends on the desired composition of the film to be prepared, especially in cases of solid solutions Cd xZn 1- xTe and Hg xCd 1- xTe where the vapor pressure of the precursors is instrumental for the composition of the vapor in the reaction zone and, ultimately, for the composition x of the solid solution. Equilibrium composition for II-VI telluride MOCVD systems was investigated at temperatures up to 873 K in hydrogen and inert gas atmospheres at pressures up to 1 atm. P- T- X regions of existence were outlined for each of the five materials.

  13. Microwave Absorption Studies on HIGH-Tc Superconductors and Related Materials VII — Esr of Dpph Coated on a Thin BiSrCaCuO Film Fabricated on MgO(100) Substrate

    NASA Astrophysics Data System (ADS)

    Sugawara, K.; Sugimoto, T.; Shiohara, Y.; Tanaka, S.

    ESR of DPPH coated on a Bi-Sr-Ca-Cu-O (BSCCO) film (350 Å thick) fabricated on MgO(100) substrate by MOCVD was studied. Temperature dependence of the ESR peak-to-peak linewidth, ΔHpp, and the effect of applied magnetic field on ΔHpp have been studied below about 100 K. The results were compared with those of ESR of DPPH coated on ceramic Y-Ba-Cu-O samples (powder and bulk) made by the MPMG method. The DPPH ESR for the BSCCO film revealed that ΔHpp was independent of applied magnetic field up to about 9 kG. In addition, no similarity between the temperature dependence of the excess ESR linewidth of the DPPH and that of critical current density was found for the BSCCO film. These results for the BSCCO film are different from those for the MPMG YBCO samples.

  14. Preparation and characterization of YBCO coating on metallic RABiT substrates by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Gonal, M. R.; Prajapat, C. L.; Igalwar, P. S.; Maji, B. C.; Singh, M. R.; Krishnan, M.

    2016-05-01

    Superconducting YBCO films are coated on metallic Rolling Assisted Bi-axially Textured Substrates (RABiTS) Ni-5wt % W (NiW) (002) substrate using pulsed laser deposition (PLD) system. Targets of YBa2Cu3O7-δ (YBCO) and buffer layers of Ceria and 8 mole % Yttria Stabilized Zirconia (YSZ) of high density are synthesized. At each stage of deposition coatings are characterized by XRD. Transport studies show superconducting nature of YBCO only when two successive buffer layers of YSZ and CeO2 are used.

  15. Investigation on orientation, epitaxial growth and microstructure of a-axis-, c-axis-, (103)/(110)- and (113)-oriented YBa2Cu3O7-δ films prepared on (001), (110) and (111) SrTiO3 single crystal substrates by spray atomizing and coprecipitating laser chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Pei; Wang, Ying; Huang, Zhi liang; Mao, Yangwu; Xu, Yuan Lai

    2015-04-01

    a-axis-, c-axis-, (103)/(110)- and (113)-oriented YBa2Cu3O7-δ (YBCO) films were pareared by spray atomizing and coprecipitating laser chemical vapor deposition. The surface of the a-axis-oriented YBCO film consisted of rectangular needle-like grains whose in-plane epitaxial growth relationship was YBCO [100] // STO [001] (YBCO [001] // STO [100]), and that of the c-axis-oriented YBCO film consisted of dense flat surface with epitaxial growth relationship of YBCO [001] // STO [001] (YBCO [100] //STO [100]). For the (103)/(110)-oriented and (113)-oriented YBCO film, they showed wedge-shaped and triangle-shaped grains, with corresponding in-plane epitaxial growth relationship of YBCO [110] // STO [110] (YBCO [010] // STO [010]) and YBCO [100] // STO [100] (YBCO [113] // STO [111], respectively.

  16. Development of YBCO Superconductor for Electric Systems: Cooperative Research and Development Final Report, CRADA Number CRD-04-150

    SciTech Connect

    Bhattacharya, R.

    2013-03-01

    The proposed project will be collaborative in exploration of high temperature superconductor oxide films between SuperPower, Inc. and the National Renewable Energy Laboratory. This CRADA will attempt to develop YBCO based high temperature oxide technology.

  17. Epitaxial Pb(Zr{sub 0.40}Ti{sub 0.60})O{sub 3}/SrRuO{sub 3} and PbTiO{sub 3}/SrRuO{sub 3} multilayer thin films prepared by MOCVD and rf sputtering

    SciTech Connect

    Foster, C.M.; Csencsits, R.; Baldo, P.M.

    1994-12-01

    Epitaxial SrRuO{sub 3} thin films were deposited by RF sputtering on SrTiO{sub 3} or MgO substrates for use as underlying electrodes. On these conductive substrates, epitaxial Pb(Zr{sub 0.35}Ti{sub 0.65})O{sub 3} (PZT) and PbTiO{sub 3} (PT) thin films were, deposited by metalorganic chemical vapor deposition (MOCVD). X-ray diffraction (XRD), RBS channeling (RBS), transmission electron microscopy (TEM) and optical waveguiding were used to characterize phase, microstructure, defect structure, refractive index, and film thickness of the deposited films. The PZT and PT films were epitaxial and c-axis oriented. 90{degree} domains, interfacial misfit dislocations and dislocations and threading dislocations were the primary structural defects, and the films showed a 70% RBS channeling reduction. Hysteresis and dielectric measurements of epitaxial PZT ferroelectric capacitor structures formed using evaporated Ag or ITO glass top electrode showed: a remanent polarization of 46.2 mC/cm{sup 2}, a coercive field of 54.9 KV/cm, a dielectric constant of 410, a bipolar resistivity of {approximately}5.8 {times} 10{sup 9} {Omega}-cm at a field of 275 KV/cm, and a breakdown strength of >400 KV/cm.

  18. Epitaxial Pb(Zr{sub x}Ti{sub 1{minus}x})O{sub 3}/SrRuO{sub 3} (x = 0, 0.35, 0.65) multilayer thin films on SrTiO{sub 3}(100) and MgO(100) prepared by MOCVD and RF sputtering

    SciTech Connect

    Foster, C.M.; Csencsits, R.; Baldo, P.M.; Bai, G.R.; Li, Z.; Rehn, L.E.; Wills, L.A.; Hiskes, R.

    1995-02-01

    Epitaxial SrRuO{sub 3} thin films were deposited on SrTiO{sub 3}(100) and MgO(100) substrates by RF sputtering for use as bottom electrodes and epitaxial buffer layers. On these conductive substrates, epitaxial Pb(Zr{sub x}Ti{sub 1{minus}x})O{sub 3} (PZT; x = 0.35,0.65) and PbTiO{sub 3} (PT; x = 0) thin films were deposited by metalorganic chemical vapor deposition (MOCVD). X-ray diffraction (XRD), RBS channeling (RBS), transmission electron microscopy (TEM) and optical waveguiding were used to characterize the phase, microstructure, defect structure, refractive index, and film thickness of the deposited films. The PZT and PT films were epitaxial and c-axis oriented. 90{degree} domains, interfacial misfit dislocations and threading dislocations were the primary structural defects, and the films showed as high as a 70% RBS channeling reduction. Ferroelectric hysteresis and dielectric measurements of epitaxial PZT ferroelectric capacitor structures formed using evaporated Ag top electrode showed: a remanent polarization of 46.2 {mu}C/cm{sup 2}, a coercive field of 54.9 kV/cm, a dielectric constant of 410, a bipolar resistivity of {approximately}5.8 {times} 10{sup 9} {Omega}-cm at a field of 275 kV/cm, and a breakdown strength of >400 kV/cm. Cyclic fatigue measurements showed that the remanent polarization was maintained for >10{sup 9} cycles.

  19. Nonvacuum Deposition of Silver Doped YBCO Coated Conductor on %100 Lattice Match Buffered Ni Tapes

    NASA Astrophysics Data System (ADS)

    Arda, L.; Cakiroglu, O.; Keskin, S.; Sacli, O. A.

    2007-04-01

    Silver doped YBa2Cu3O7-δ (YBCO) coated conductors were fabricated on Gd1.624Ho0.376O3 (100 % lattice match with YBCO) textured buffer layers on Ni tape by reel-to-reel sol-gel dip coating system. Sample were prepared with different wt(1-5) % Ag doped ratio. The surface morphologies and microstructure of all sample were characterized by ESEM, EDS and XRD. Pole figure texture analyses have been done to characterize texture of buffer layer and YBCO superconducting film . The critical current Ic measurement was performed using four wire method with the 1 μV/cm criterion. The critical current density, Jc was measured to be 2.2 × 104 A/cm2 at 77 K self field for 1 wt % Ag doped YBCO sample.

  20. Effect of CeO{sub 2} buffer layer thickness on the structures and properties of YBCO coated conductors.

    SciTech Connect

    Li, M.; Zhao, X.; Ma, B.; Dorris, S. E.; Balachandran, U.; Maroni, V. A.; Wuhan Univ.

    2007-01-01

    Biaxially textured YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) films were grown on inclined-substrate-deposited (ISD) MgO-textured metal substrates by pulsed laser deposition. CeO{sub 2} was deposited as a buffer layer prior to YBCO growth. CeO{sub 2} layers of different thickness were prepared to evaluate the thickness dependence of the YBCO films. The biaxial alignment features of the films were examined by X-ray diffraction 2{theta}-scans, pole-figure, {phi}-scans and rocking curves of {Omega} angles. The significant influence of the CeO{sub 2} thickness on the structure and properties of the YBCO films were demonstrated and the optimal thickness was found to be about 10 nm. High values of T{sub c} = 91 K and J{sub c} = 5.5 x 10{sup 5} A/cm{sup 2} were obtained on YBCO films with optimal CeO{sub 2} thickness at 77 K in zero field. The possible mechanisms responsible for the dependence of the structure and the properties of the YBCO films on the thickness of the CeO{sub 2} buffer layers are discussed.

  1. Structure and morphology of MgO/YBCO bilayers for biepitaxial junctions

    NASA Astrophysics Data System (ADS)

    Di Chiara, A.; Lombardi, F.; Granozio, F. Miletto; di Uccio, U. Scotti; Valentino, M.; Tafuri, F.; Del Vecchio, A.; De Riccardis, M. F.; Tapfer, L.

    1996-02-01

    (110) MgO thin films have been deposited by RF sputtering on (110) SrTiO 3 and used as buffer layers for YBCO deposition. The MgO films show high morphological quality, as confirmed by X-ray specular reflectivity, and narrow (≈ 1°) X-ray diffraction peaks in the rocking curves measurements. These results are discussed in the framework of an ionic oxide growth model. XRD analyses performed on the bilayer YBCO/MgO (110) confirm the epitaxial growth of the films, with (001) YBCO//(110) MgO. XRD, AFM, SEM measurements are compared with data relative to bilayers deposited on (100) SrTiO 3.

  2. Observation of the nonlinear meissner effect in YBCO thin films: evidence for a D-wave order parameter in the bulk of the cuprate superconductors.

    PubMed

    Oates, D E; Park, S-H; Koren, G

    2004-11-01

    We present experimental evidence for the observation of the nonlinear Meissner effect in high-quality epitaxial yttrium barium copper oxide thin films by measuring their intermodulation distortion at microwave frequencies versus temperature. Most of the films measured show a characteristic increase in nonlinearity at low temperatures as predicted by the nonlinear Meissner effect. We could measure the nonlinear Meissner effect because intermodulation distortion measurements are an extremely sensitive method that can detect changes in the penetration depth of the order of 1 part in 10(5). PMID:15600869

  3. Real-time physico-neural solutions for MOCVD

    SciTech Connect

    Kelkar, A.S.; Mahajan, R.L.; Sani, R.L.

    1995-12-31

    This paper presents an integrated physical neural network approach for the modeling and optimization of a vertical MOCVD reactor. A first-principles physical model for the reactor was solved numerically using the Fluid Dynamics Analysis Package (FIDAP). This transient model included property variation and thermodiffusion effects. Artificial Neural Network (ANN) models were then trained to predict the growth rate profiles within the reactor. The data used to train the network was obtained from FIDAP simulations for combinations of process parameters determined by statistical Design of Experiments (DOE) methodology. It is shown that the trained ANN predicts the behavior of the reactor accurately. Optimum process conditions to obtain a uniform thickness of the deposited film were determined and tested using the ANN model. The results demonstrate the power and robustness of ANNs for obtaining fast on-line responses to changing input conditions. This capability of ANNs is particularly important for implementing run-to-run and on-line control of the MOCVD process.

  4. Soft nanostructuring of YBCO Josephson junctions by phase separation.

    PubMed

    Gustafsson, D; Pettersson, H; Iandolo, B; Olsson, E; Bauch, T; Lombardi, F

    2010-12-01

    We have developed a new method to fabricate biepitaxial YBa2 Cu3 O7-δ (YBCO) Josephson junctions at the nanoscale, allowing junctions widths down to 100 nm and simultaneously avoiding the typical damage in grain boundary interfaces due to conventional patterning procedures. By using the competition between the superconducting YBCO and the insulating Y2 BaCuO5 phases during film growth, we formed nanometer sized grain boundary junctions in the insulating Y2 BaCuO5 matrix as confirmed by high-resolution transmission electron microscopy. Electrical transport measurements give clear indications that we are close to probing the intrinsic properties of the grain boundaries. PMID:21080664

  5. Control of flux pinning in MOD YBCO coated conductor.

    SciTech Connect

    Zhang, W.; Huang, Y.; Li, X.; Kodenkandath, T.; Rupich, M. W.; Schoop, U.; Verebelyi, D. T.; Thieme, C. L. H.; Siegal, E.; Holesinger, T. G.; Maiorov, B.; Civale, L.; Miller, D. J.; Maroni, V. A.; Li, J.; Martin, P. M.; Specht, E. D.; Goyal, A.; Paranthaman, M. P.; American Superconductor Corp.; LANL; ORNL

    2007-06-01

    NTwo different types of defect structures have been identified to be responsible for the enhanced pinning in metal organic deposited YBCO films. Rare earth additions result in the formation of nanodots in the YBCO matrix, which form uncorrelated pinning centers, increasing pinning in all magnetic field orientations. 124-type intergrowths, which form as laminar structures parallel to the ab-plane, are responsible for the large current enhancement when the magnetic field is oriented in the ab-plane. TEM studies showed that the intergrowths emanate from cuprous containing secondary phase particles, whose density is partially controlled by the rare earth doping level. Critical process parameters have been identified to control this phase formation, and therefore, control the f 24 intergrowth formation. This work has shown that through process control and proper conductor design, either by adjusting the composition or by multiple coatings of different functional layers, the desired angular dependence can be achieved.

  6. Photoluminescence of Nitrogen-Doped Zinc Selenide by Photo-Assisted Mocvd.

    NASA Astrophysics Data System (ADS)

    Gillespie, Paul Matthew

    Zinc selenide is a wide band-gap (2.67 eV) II -VI compound semiconductor with potential use as a blue electro-optic device material. Problems with obtaining suitable p-type conductivity have limited device development. Zinc selenide epitaxial films, doped with nitrogen from NH _3, have been grown on gallium arsenide substrates by laser-assisted metal organic chemical vapor deposition (MOCVD). The effect of nitrogen doping was investigated with and without direct surface irradiation incident on the surface from a broad-band light source. Low temperature (8 K) photoluminescence spectroscopy has confirmed the incorporation of nitrogen as a shallow acceptor by the presence of acceptor-bound-excitons and associated donor -acceptor-pair recombination emissions. The MOCVD growth parameters have been optimized based on the presence of characteristic features in the photoluminescence spectra. Growth rate mechanisms have been proposed for both laser-assisted MOCVD and direct-irradiation MOCVD. Simultaneous interaction of the two photo-assisted techniques show that direct irradiation of the surface does not enhance the growth rate under the laser-assisted condition. This confirms that direct surface irradiation growth mechanisms involve the interaction of photo-generated carriers with alkyl groups from the precursors.

  7. Trapped Field Characteristics of Stacked YBCO Thin Plates for Compact NMR Magnets: Spatial Field Distribution and Temporal Stability.

    PubMed

    Hahn, Seungyong; Kim, Seok Beom; Ahn, Min Cheol; Voccio, John; Bascuñán, Juan; Iwasa, Yukikazu

    2010-06-01

    This paper presents experimental and analytical results of trapped field characteristics of a stack of square YBCO thin film plates for compact NMR magnets. Each YBCO plate, 40 mm × 40 mm × 0.08 mm, has a 25-mm diameter hole at its center. A total of 500 stacked plates were used to build a 40-mm long magnet. Its trapped field, in a bath of liquid nitrogen, was measured for spatial field distribution and temporal stability. Comparison of measured and analytical results is presented: the effects on trapped field characteristics of the unsaturated nickel substrate and the non-uniform current distribution in the YBCO plate are discussed. PMID:20585463

  8. A novel MOCVD reactor for growth of high-quality GaN-related LED layers

    NASA Astrophysics Data System (ADS)

    Hu, Shaolin; Liu, Sheng; Zhang, Zhi; Yan, Han; Gan, Zhiyin; Fang, Haisheng

    2015-04-01

    Gallium nitride (GaN), a direct bandgap semiconductor widely used in bright light-emitting diodes (LEDs), is mostly grown by metal-organic chemical vapor deposition (MOCVD) method. A good reactor design is critical for the production of high-quality GaN thin films. In this paper, we presented a novel buffered distributed spray (BDS) MOCVD reactor with vertical gas sprayers and horizontal gas inlets. Experiments based on a 36×2″ BDS reactor were conducted to examine influence of the process parameters, such as the operating pressure and the gas flow rate, on the growth efficiency and on the layer thickness uniformity. Transmission electron microscopy (TEM) and photoluminescence (PL) are further conducted to evaluate quality of the epitaxial layers and to check performance of the reactor. Results show that the proposed novel reactor is of high performance in growing high-quality thin films, including InGaN/GaN multiquantum wells (MQWs) structures.

  9. Role of twin boundaries on vortex pinning of CSD YBCO nanocomposites

    NASA Astrophysics Data System (ADS)

    Rouco, V.; Palau, A.; Guzman, R.; Gazquez, J.; Coll, M.; Obradors, X.; Puig, T.

    2014-12-01

    We study the effect of twin boundaries (TBs) on the critical current density of YBa2Cu3O7-x (YBCO) films and nanocomposites grown on different substrates. Varying both the direction of the current and magnetic field, we show that the TB orientation is a crucial parameter to consider in the optimization of Jc for particular applications. A quantitative and detailed analysis of the role of TBs on vortex dynamics has allowed us to infer that extended TB planes in pristine YBCO films can reduce Jc by 60% at low temperatures due to vortex channeling effects or increase it by a 98% at high temperatures due to directional vortex pinning. Moreover, we demonstrate that TB length and distribution can be strongly modified in YBCO nanocomposites. We observe that TB planes with no vertical coherence are still effective for vortex pinning while are not to create channels for easy vortex flow.

  10. MOCVD for solar cells, a transition towards a chamberless inline process

    NASA Astrophysics Data System (ADS)

    Barrioz, V.; Monir, S.; Kartopu, G.; Lamb, D. A.; Brooks, W.; Siderfin, P.; Jones, S.; Clayton, A. J.; Irvine, S. J. C.

    2015-03-01

    MOCVD has been associated with batch processing of III-V opto-electronic devices for decades, with epitaxial structures deposited on up to 200 mm diameter wafers. Recent development in thin film PV has seen the gap in conversion efficiencies closing in on that of the commonly found multicrystalline Si wafer based PV. To further improve the conversion efficiency of thin film PV towards the theoretical limits of single junction solar cells requires a technique such as MOCVD with scalability potential. Preliminary results on the development of a chamberless inline process are reported for up to 15 cm wide float glass, progressively coating each layer in the CdTe solar cell as the heated substrate passes under each coating head in turn and entirely at atmospheric pressure. Emphasis is made on ensuring that the chamberless coating heads can be operated safely using a combination of nitrogen curtain flows and a balanced exhaust pressure system. Results are also presented on the exclusion of oxygen and moisture from the coating area, achieved using the same gas flow isolation process. This paper also reviews the achievements made to-date in the transfer of the high efficiency batch MOCVD produced CdTe solar cell to the chamberless inline process demonstrating device quality thin films deposition.

  11. Interlayer structure in YBCO-coated conductors prepared by chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Molina-Luna, Leopoldo; Egoavil, Ricardo; Turner, Stuart; Thersleff, Thomas; Verbeeck, Jo; Holzapfel, Bernhard; Eibl, Oliver; Van Tendeloo, Gustaaf

    2013-07-01

    The functionality of YBa2Cu3O7-δ (YBCO)-coated conductor technology depends on the reliability and microstructural properties of a given tape or wire architecture. Particularly, the interface to the metal tape is of interest since it determines the adhesion, mechanical stability of the film and thermal contact of the film to the substrate. A trifluoroacetate (TFA)—metal organic deposition (MOD) prepared YBCO film deposited on a chemical solution-derived buffer layer architecture based on CeO2/La2Zr2O7 and grown on a flexible Ni5 at.%W substrate with a {100}<001> biaxial texture was investigated. The YBCO film had a thickness was 440 nm and a jc of 1.02 MA cm-2 was determined at 77 K and zero external field. We present a sub-nanoscale analysis of a fully processed solution-derived YBCO-coated conductor by aberration-corrected scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS). For the first time, structural and chemical analysis of the valence has been carried out on the sub-nm scale. Intermixing of Ni, La, Ce, O and Ba takes place at these interfaces and gives rise to nanometer-sized interlayers which are a by-product of the sequential annealing process. Two distinct interfacial regions were analyzed in detail: (i) the YBCO/CeO2/La2Zr2O7 region (10 nm interlayer) and (ii) the La2Zr2O7/Ni-5 at.%W substrate interface region (20 nm NiO). This is of particular significance for the functionality of these YBCO-coated conductor architectures grown by chemical solution deposition.

  12. Pd layer on cube-textured substrates for MOD-TFA and PLD YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Mancini, A.; Celentano, G.; Galluzzi, V.; Rufoloni, A.; Vannozzi, A.; Augieri, A.; Ciontea, L.; Petrisor, T.; Gambardella, U.; Longo, G.; Cricenti, A.

    2008-01-01

    Pd films were deposited on rolling assisted biaxially textured substrate (RABiTS) Ni-5 at.% W in order to exploit the Pd effect of the texture sharpening with respect to that of the substrate, for the development of YBa2Cu3O7-x (YBCO) coated conductors. The Pd sharpening effect was relevant in the out-of-plane direction where the reduction for the ω-scans' full width at half maximum (FWHM) ranged from 55 to 65%, depending on the substrate roughness. The obtained minimum values of the FWHM in the transverse rolling direction of the (002) Pd ω-scan and in the (111) Pd phi-scan were of about 2.5° and 5°, respectively. The CeO2/YSZ/CeO2 (YSZ is Y2O3-stabilised ZrO2) heterostructure of the buffer layer was developed by pulsed laser deposition (PLD). In order to transfer the sharp orientation of the Pd film, both the seed CeO2 layer and the YSZ layer were deposited at low temperatures (450 °C), low enough to avoid Pd/Ni-W interdiffusion. The YBCO, films deposited by both PLD and metal-organic deposition (MOD) using metal trifluoroacetate acid (TFA), exhibited rolling direction (005) ω-scan and the (113) phi-scan FWHM values of about 2° and 5°, respectively. In spite of the complete interdiffusion between Ni and Pd during the YBCO film deposition, the coated conductors exhibit good adherence, as well as a smooth and crack-free surface. A zero-resistance critical temperature (TC0) of 90.8 K for the MOD-TFA YBCO films and critical current-density (JC) up to 2.2 MA cm-2 at 77 K and self-field for PLD YBCO films have been obtained.

  13. Fabrication and Characterization of YBCO Coated Conductors by Inclined Substrate Deposition

    SciTech Connect

    Ma, B.; Balachandran, U.; Xu, Y.; Bhattacharya, R.

    2006-03-31

    Inclined substrate deposition (ISD) is an effective method for rapid fabrication of high-quality template layers for YBCO-coated conductors. We have deposited biaxially textured ISD-MgO films on flexible metallic tapes in a reel-to-reel system by electron-beam evaporation at rapid deposition rates, 2-10 nm{center_dot}s-1. Strontium ruthenium oxide (SRO) buffer and YBCO films were grown by pulsed laser deposition (PLD). Pole figure analysis of a meter-long ISD-MgO tape was carried out by X-ray diffraction using a Bruker's D8 DISCOVER equipped with GADDS (general area detection diffraction system). The c-axis of the ISD-MgO film was tilted away from substrate normal. A full-width at half maximum (FWHM) of {approx_equal}10 deg. was observed from the {phi}-scan of the MgO (002) diffraction measured on samples deposited with 35 deg. inclination angle. Surface morphology measured by atomic force microscopy revealed a roof-tile shaped structure for the ISD-MgO films. Through the use of the SRO buffer, biaxial alignment in the YBCO film deposited on the ISD-MgO template was improved. The {phi}-scan FWHM was 5.8 deg. for the YBCO (005) diffraction. We have measured the critical transition temperature Tc = 91 K and transport critical current density Jc >1.6x106 A{center_dot}cm-2 at 77 K in self-field on a SRO-buffered YBCO film grown with ISD-MgO architecture.

  14. MOCVD OF YSZ COATINGS USING ?-DIKETONATE PRECURSORS

    SciTech Connect

    Varanasi, Venu G; Besmann, Theodore M; Hyde, Robin L.; Payzant, E Andrew; Anderson, Timothy J

    2009-01-01

    Metallorganic chemical vapor deposition (MOCVD) was used to fabricate yttria-stabilized zirconia as a thermal barrier coating. The MOCVD precursors were Y(tmhd)3 and Zr(tmhd)4 (tmhd = 2, 2, 6, 6-tetramethyl-3, 5-heptanedianato) and delivered via aerosol assisted liquid delivery (AALD). The maximum tetragonal YSZ coating rate was 14.2 1.3 m h -1 (at 845oC) yielding a layered coating microstructure. The growth was first-order with temperature (T < 827oC) with an apparent activation energy (Ea) of 50.9 4.3 kJ mol -1. Coating efficiency was a maximum of approximately 10% at the highest growth rate.

  15. YBCO superconducting ring resonators at millimeter-wave frequencies

    NASA Technical Reports Server (NTRS)

    Chorey, Christopher M.; Kong, Keon-Shik; Bhasin, Kul B.; Warner, J. D.; Itoh, Tatsuo

    1991-01-01

    Microstrip ring resonators operating at 35 GHz were fabricated from laser ablated YBCO films deposited on lanthanum aluminate substrates. They were measured over a range of temperatures and their performances compared to identical resonators made of evaporated gold. Below 60 Kelvin the superconducting strip performed better than the gold, reaching an unloaded Q approximately 1.5 times that of gold at 25 K. A shift in the resonant frequency follows the form predicted by the London equations. The Phenomenological Loss Equivalence Method is applied to the ring resonator and the theoretically calculated Q values are compared to the experimental results.

  16. Long length oxide template for YBCO coated conductor prepared by surface-oxidation epitaxy method

    NASA Astrophysics Data System (ADS)

    Watanabe, Tomonori; Matsumoto, Kaname; Maeda, Toshihiko; Tanigawa, Toru; Hirabayashi, Izumi

    2001-08-01

    A 50 m long, biaxially textured NiO buffer layer for epitaxial growth ofYBa 2Cu 3O 7- δ (YBCO) film has been fabricated on the long cube textured nickel tape using surface-oxidation epitaxy (SOE) method. The SOE-NiO layers were highly {1 0 0} <0 0 1> textured. The full width at half maximum of 10-14.5° from X-ray φ-scan ( Δφ) was in the range of 10-14.5° through the whole length. The critical current density ( Jc) values exceeding 0.3 MA/cm 2 (77 K, 0 T) have been obtained in short samples of YBCO films on NiO/Ni tapes, by using thin MgO cap layer. Thirty meters long Ni-clad Ni-20wt.%Cr (Ni/NiCr) and Ni-clad austenitic stainless steel (Ni/SS) tapes were also prepared for YBCO coated conductors with higher strength and lower magnetism than those of pure nickel tape. Highly {1 0 0} <0 0 1> textured NiO layers were formed on those textured composite tapes by SOE method as same as on cube textured pure nickel tapes. YBCO films with Jc of 0.1 MA/cm 2 (77 K, 0 T) have been obtained on MgO/SOE-NiO layer of short Ni/NiCr composite tape.

  17. High-rate fabrication of YBCO coated conductors using TFA-MOD method

    NASA Astrophysics Data System (ADS)

    Nakaoka, K.; Yoshizumi, M.; Usui, Y.; Izumi, T.; Shiohara, Y.

    The YBa2Cu3O7-y (YBCO) coated conductors derived from metal-organic deposition (MOD) method using the metal salts of trifluoroacetic acid (TFA) have been developed with high critical current property. The long-length YBCO coated conductors have been fabricated by multi-turn reel-to-reel system. Increasing the thickness per single coating in the multi-turn reel-to-reel system is a cost-effective technique for fabrication of the precursor films in the calcination process. In this work, we have developed a new starting solution consisting of non-fluorine salts of yttrium 4-oxopentanoate and copper 2-ethylhexanoate with focusing on increasing the thickness per single coating for a high-rate fabrication of the YBCO coated conductors by the TFA-MOD method. The critical thickness per single coating of the film fabricated from the new starting solution was 0.54 μm/coat. High critical current of 377 A/cm-width with high critical current density (3.0 MA/cm2) was obtained in the YBCO film fabricated on CeO2 buffered LaMnO3/MgO/Gd2Zr2O-7/HastelloyTM substrates using the new starting solution at the thickness per single coating of 0.42 μm/coat.

  18. The Effects of Grain Boundaries on the Current Transport Properties in YBCO-Coated Conductors

    NASA Astrophysics Data System (ADS)

    Yang, Chao; Xia, Yudong; Xue, Yan; Zhang, Fei; Tao, Bowan; Xiong, Jie

    2015-10-01

    We report a detailed study of the grain orientations and grain boundary (GB) networks in Y2O3 films grown on Ni-5 at.%W substrates. Electron back scatter diffraction (EBSD) exhibited different GB misorientation angle distributions, strongly decided by Y2O3 films with different textures. The subsequent yttria-stabilized zirconia (YSZ) barrier and CeO2 cap layer were deposited on Y2O3 layers by radio frequency sputtering, and YBa2Cu3O7-δ (YBCO) films were deposited by pulsed laser deposition. For explicating the effects of the grain boundaries on the current carry capacity of YBCO films, a percolation model was proposed to calculate the critical current density ( J c) which depended on different GB misorientation angle distributions. The significantly higher J c for the sample with sharper texture is believed to be attributed to improved GB misorientation angle distributions.

  19. The Effects of Grain Boundaries on the Current Transport Properties in YBCO-Coated Conductors.

    PubMed

    Yang, Chao; Xia, Yudong; Xue, Yan; Zhang, Fei; Tao, Bowan; Xiong, Jie

    2015-12-01

    We report a detailed study of the grain orientations and grain boundary (GB) networks in Y2O3 films grown on Ni-5 at.%W substrates. Electron back scatter diffraction (EBSD) exhibited different GB misorientation angle distributions, strongly decided by Y2O3 films with different textures. The subsequent yttria-stabilized zirconia (YSZ) barrier and CeO2 cap layer were deposited on Y2O3 layers by radio frequency sputtering, and YBa2Cu3O7-δ (YBCO) films were deposited by pulsed laser deposition. For explicating the effects of the grain boundaries on the current carry capacity of YBCO films, a percolation model was proposed to calculate the critical current density (J c) which depended on different GB misorientation angle distributions. The significantly higher J c for the sample with sharper texture is believed to be attributed to improved GB misorientation angle distributions. PMID:26497731

  20. Passivation of Flexible YBCO Superconducting Current Lead With Amorphous SiO2 Layer

    NASA Technical Reports Server (NTRS)

    Johannes, Daniel; Webber, Robert

    2013-01-01

    across a thermal gradient with as little flow of heat as possible to make an efficient current lead. By protecting YBCO on a flexible substrate of low thermal conductivity with SiO2, a thermally efficient and flexible current lead can be fabricated. The technology is also applicable to current leads for 4 K superconducting electronics current biasing. A commercially available thin-film YBCO composite tape conductor is first stripped of its protective silver coating. It is then mounted on a jig that holds the sample flat and acts as a heat sink. Silicon dioxide is then deposited onto the YBCO to a thickness of about 1 micron using PECVD (plasma-enhanced chemical vapor deposition), without heating the YBCO to the point where degradation occurs. Since SiO2 can have good high-frequency electrical properties, it can be used to coat YBCO cable structures used to feed RF signals across temperature gradients. The prime embodiment concerns the conduction of DC current across the cryogenic temperature gradient. The coating is hard and electrically insulating, but flexible.

  1. Ordered YBCO sub-micron array structures induced by pulsed femtosecond laser irradiation.

    PubMed

    Luo, C W; Lee, C C; Li, C H; Shih, H C; Chen, Y-J; Hsieh, C C; Su, C H; Tzeng, W Y; Wu, K H; Juang, J Y; Uen, T M; Chen, S P; Lin, J-Y; Kobayashi, T

    2008-12-01

    We report on the formation of organized sub-micron YBa(2)Cu(3)O(7) (YBCO) dots induced by irradiating femtosecond laser pulses on YBCO films prepared by pulse laser deposition with fluence in the range of 0.21 approximately 0.53 J/cm(2). The morphology of the YBCO film surface depends strongly on the laser fluences irradiated. At lower laser fluence (approximately 0.21 J/cm(2)) the morphology was pattern of periodic ripples with sub-micrometer spacing. Slightly increasing the laser fluence to 0.26 J/cm(2) changes the pattern into organized sub-micron dots with diameters ranging from 100 nm to 800 nm and height of 150 nm. Further increase of the laser fluence to over 0.32 J/cm(2), however, appeared to result in massive melting and led to irregular morphology. The mechanism and the implications of the current findings will be discussed. Arrays of YBCO sub-micron dots with T(c) = 89.7 K were obtained. PMID:19065200

  2. Vacuum MOCVD fabrication of high efficience cells

    NASA Technical Reports Server (NTRS)

    Partain, L. D.; Fraas, L. M.; Mcleod, P. S.; Cape, J. A.

    1985-01-01

    Vacuum metal-organic-chemical-vapor-deposition (MOCVD) is a new fabrication process with improved safety and easier scalability due to its metal rather than glass construction and its uniform multiport gas injection system. It uses source materials more efficiently than other methods because the vacuum molecular flow conditions allow the high sticking coefficient reactants to reach the substrates as undeflected molecular beams and the hot chamber walls cause the low sticking coefficient reactants to bounce off the walls and interact with the substrates many times. This high source utilization reduces the materials costs power device and substantially decreases the amounts of toxic materials that must be handled as process effluents. The molecular beams allow precise growth control. With improved source purifications, vacuum MOCVD has provided p GaAs layers with 10-micron minority carrier diffusion lengths and GaAs and GaAsSb solar cells with 20% AMO efficiencies at 59X and 99X sunlight concentration ratios. Mechanical stacking has been identified as the quickest, most direct and logical path to stacked multiple-junction solar cells that perform better than the best single-junction devices. The mechanical stack is configured for immediate use in solar arrays and allows interconnections that improve the system end-of-life performance in space.

  3. Safety-Enclosure System For MOCVD Process Chamber

    NASA Technical Reports Server (NTRS)

    Singletery, James, Jr.; Velasquez, Hugo; Warner, Joseph

    1995-01-01

    Safety-enclosure system filled with nitrogen surrounds reaction chamber in which metallo-organic chemical vapor deposition (MOCVD) performed. Designed to protect against explosions and/or escaping toxic gases and particulates. Gas-purification subsystem ensures during loading and unloading of process materials, interior of MOCVD chamber exposed to less than 1 ppm of oxygen and less than 5 ppm of water in nitrogen atmosphere. Toxic byproducts of MOCVD process collected within inert atmosphere. Enclosure strong enough to contain any fragments in unlikely event of explosion.

  4. Properties of YBCO on LaMnO3-capped IBAD MgO-templates without Homo-epitaxial MgO layer.

    SciTech Connect

    Aytug, Tolga; Paranthaman, Mariappan Parans; Kim, Kyunghoon; Zhang, Yifei; Cantoni, Claudia; Zuev, Yuri L; Goyal, Amit; Thompson, James R; Christen, David K

    2009-01-01

    Previously, it has been well established that in an IBAD architecture for coated conductors, (1) LaMnO3 (LMO) buffer layers are structurally and chemically compatible with an underlying homo-epitaxial MgO layer and (2) high current density YBCO films can be grown on these LMO templates. In the present work, the homo-epi MgO layer has been successfully eliminated and a LMO cap layer was grown directly on the IBAD (MgO) template. The performance of the LMO/IBAD (MgO) samples has been qualified by depositing 1 m-thick YBCO coatings by pulsed laser deposition. Electrical transport measurements of YBCO films on the standard (with homo-epi MgO) and simplified (without homo-epi MgO) IBAD architectures were carried out. The angular dependencies of critical current density (Jc) are similar for both IBAD architectures. XRD measurements indicate good, c-axis aligned YBCO films. Transmission electron microscopy (TEM) images reveal that microstructures of YBCO/LMO/IBAD (MgO) and YBCO/LMO/homo-epi MgO/IBAD (MgO) templates are similar. These results demonstrate the strong potential of using LMO as a single cap layer directly on IBAD (MgO) for the development of a simplified IBAD architecture.

  5. A YBCO RF-SQUID magnetometer and its applications

    NASA Technical Reports Server (NTRS)

    Luwei, Zhou; Jingwu, Qiu; Xienfeng, Zhang; Zhiming, Tank; Yongjia, Qian

    1990-01-01

    An applicable RF-superconducting quantum interference detector (SQUID) magnetometer was made using a bulk sintered yttrium barium copper oxide (YBCO). The temperature range of the magnetometer is 77 to 300 K and the field range 0 to 0.1T. At 77 K, the equivalent flux noise of the SQUID is 5 x 10 to minus 4 power theta sub o/square root of Hz at the frequency range of 20 to 200 Hz. The experiments show that the SQUID noise at low-frequency end is mainly from 1/f noise. A coil test shows that the magnetic moment sensitivity delta m is 10 to the minus 6th power emu. The RF-SQUID is shielded in a YBCO cylinder with a shielding ability B sub in/B sub ex of about 10 to the minus 6th power when external dc magnetic field is about a few Oe. The magnetometer is successfully used in characterizing superconducting thin films.

  6. Characterization of superconducting YBCO/polyacrylonitrile composites

    NASA Astrophysics Data System (ADS)

    Schlesinger, Y.; Mogilko, E.

    1994-10-01

    The elasto-mechanical and transport properties of HTSC YBCO/polyacrylonitrile (PAN) composites have been investigated. The results indicate clearly the effect of PAN presence on the porosity, microstructure, crack-stability and toughness, and grain-surface pinning strength. At 35% PAN fraction an extensive bridgelike linking network develops, which results in a dramatic increase of the crack-stability and an increased fluxon mobility. In contrast to other reported SC/polymer systems, the YBCO/ PAN composite exhibits a transport current resistive transition even at relatively high PAN concentration. A comparison of finegrain and coarse-grain YBCO ceramic characteristics allows a better understanding of the role played by the PAN host.

  7. Contact characteristics for YBCO bulk superconductors

    NASA Astrophysics Data System (ADS)

    Yamamoto, Naoki; Sakai, Tomokazu; Sawa, Koichiro; Tomita, Masaru; Murakami, Masato

    2003-10-01

    We have studied the contact characteristics of two resin-impregnated YBCO (a composite of YBa 2Cu 3O y and Y 2BaCuO 5) bulk superconductors in mechanical contact. A switching phenomenon could be observed at a threshold current or a transfer current value in the V- I curves of the YBCO contact. The transfer current exceeded the previous value of 13.5 A at 77 K in the contact when the sample surfaces were carefully polished. The present results suggest that a pair of YBCO blocks might be applicable to the mechanical persistent current switch for superconducting magnetic energy storage and other superconducting systems run in a persistent current mode.

  8. Modified Lanthanum Zirconium Oxide Buffer for Low-Cost, High Performance YBCO Coated Conductors

    SciTech Connect

    Paranthaman, Mariappan Parans; Sathyamurthy, Srivatsan; Li, Xiaoping; Specht, Eliot D; Wee, Sung Hun; Cantoni, Claudia; Goyal, Amit; Rupich, M. W.

    2010-01-01

    Lanthanum Zirconium Oxide, La2Zr2O7 (LZO) has been developed as a potential replacement barrier layer in the standard RABiTS three-layer architecture of physical vapor deposited CeO2 cap/YSZ barrier/Y2O3 seed/Ni-5W. The main focus of this research is to see (i) whether we can improve further the barrier properties of LZO; (ii) can we widen the LZO composition and still achieve the high performance?; and (iii) is it possible to reduce the number of buffer layers? We report a systematic investigation of the LZO film growth with varying compositions of La:Zr ratio in the La2O3-ZrO2 system. Using metal-organic deposition (MOD) process, we have grown smooth, crack-free, epitaxial thin films of LaxZr1-xOy (x = 0.2-0.6) on standard Y2O3 buffered Ni-5W substrates in short lengths. Detailed XRD studies indicate that a single epitaxial LZO phase without the (111) texture can be achieved in a wider compositional window of x = 0.2-0.6 in LaxZr1-xOy. Both CeO2 cap layers and MOD-YBCO films were grown 2 epitaxially on these modified LZO barriers. Transport property measurements indicate that we can achieve a higher critical current, Ic of 274-292 A/cm at 77 K and self-field on MOD-YBCO films grown on LaxZr1-xOy (x = 0.4-0.6) films. These results indicate that LZO films can be grown with a wider compositional window and still achieve high performance YBCO coated conductors. In addition, epitaxial MOD LaxZr1-xOy (x = 0.25) films were grown directly on biaxially textured Ni-3W substrates. About 3 m thick YBCO films with a Jc of 0.55 MA/cm2 at 77 K and 0.01 T were grown on a single MOD LZO buffered Ni-3W substrate using pulsed laser deposition. This work promises a route for producing simplified buffer architecture for RABiTS based YBCO coated conductors.

  9. Theoretical analysis of a YBCO squirrel-cage type induction motor based on an equivalent circuit

    NASA Astrophysics Data System (ADS)

    Morita, G.; Nakamura, T.; Muta, I.

    2006-06-01

    A HTS induction motor, with a HTS squirrel-cage rotor, is analysed using an electrical equivalent circuit. The squirrel-cage winding in the rotor consists of rotor bars and end rings, and both are considered to be made of YBCO film conductors. A wide range of electric field versus current density in YBCO film is formulated based on the Weibull function, and analysed as a non-linear resistance in the equivalent circuit. It is shown that starting and accelerating torques of the HTS induction motor are improved drastically compared to those of a conventional induction motor. Furthermore, large synchronous torque can also be realized by trapping the magnetic flux in the rotor circuit because of the persistent current mode.

  10. The influence of strain on the dielectric behavior of (Ba, Sr) Ti{sub 1+x}O{sub 3} thin films grown by LS-MOCVD on Pt/SiO{sub 2}/Si.

    SciTech Connect

    Streiffer, S. K.

    1998-10-14

    The strain state and its coupling to dielectric behavior have been investigated for (100) BST thin films deposited on Pt/SiO{sub 2}/Si at 640 C. It is estimated from x-ray diffraction that the in-plane biaxial strain is approximately 0.7%. We postulate that this is of sufficient magnitude to confine any spontaneous polarization to the plane of the film. The thickness-corrected dielectric behavior perpendicular to the substrate for these samples shows evidence of coupling to such an in-plane phase transition at approximately 390K, as manifested by deviation from Curie-Weiss-like behavior at this temperature.

  11. Direct observation of surface plasmons in YBCO by attenuated total reflection of light in the infrared

    NASA Astrophysics Data System (ADS)

    Walmsley, D. G.; Smyth, C. C.; Sellai, A.; McCafferty, P. G.; Dawson, P.; Morrow, T.; Graham, W. G.

    1994-02-01

    Surface plasmons have been observed directly in YBCO films in an Otto-geometry attenuated total reflection measurement at a wavelength of 3.392 μm. The laser deposited films are c-axis oriented on an MgO substrate. This observation confirms theoretical deductions from complex dielectric function data. Measured data have been fitted to a theoretical model and are compared with the optical constants determined by Bozovic [1]. The investigations have been extended to films with other orientations to investigate whether material anisotropy is reflected in the results and non-metallic behaviour is found.

  12. Development of Solution Buffer Layers for RABiTS Based YBCO Coated Conductors

    SciTech Connect

    Paranthaman, Mariappan Parans; Qiu, Xiaofeng; List III, Frederick Alyious; Zhang, Yifei; Li, Xiaoping; Sathyamurthy, Srivatsan; Thieme, C. L. H.; Rupich, M. W.

    2011-01-01

    Abstract The main objective of this research is to find a suitable alternate solution based seed layer for the standard RABiTS three-layer architecture of physical vapor deposited CeO cap/YSZ barrier/Y O seed on Ni-5%W metal tape. In the present work, we have identified CeO buffer layer as a potential replacement for Y O seeds. Using a metal-organic deposition (MOD) process, we have grown smooth, crack-free, epitaxial thin films of CeO (pure and Zr, Cu and Gd-doped) directly on biaxially textured Ni-5W substrates in short lengths. Detailed XRD studies indicate that a single epitaxial CeO phase with slightly improved out-of-plane texture compared to the texture of the underlying Ni-W substrates can be achieved in pure, undoped CeO samples. We have also demonstrated the growth of YSZ barrier layers on pure CeO seeds using sputtering. Both sputtered CeO cap layers and MOD-YBCO films were grown epitaxially on these YSZ-buffered MOD-CeO /Ni-5W substrates. High critical currents per unit width, of 264 A/cm (critical current density, of 3.3 MA/cm ) at 77 K and 0.01 T was achieved for 0.8 m thick MOD-YBCO films grown on MOD-CeO seeds. These results indicate that CeO films can be grown directly on Ni-5W substrates and still support high performance YBCO coated conductors. This work holds promise for a route for producing low-cost buffer architecture for RABiTS based YBCO coated conductors.

  13. Development of Solution Buffer Layers for RABiTS Based YBCO Coated Conductors

    SciTech Connect

    Paranthaman, Mariappan Parans; Qiu, Xiaofeng; Kim, Kyunghoon; Shi, D.; Zhang, Yifei; Li, Xiaoping; Sathyamurthy, Srivatsan; Thieme, C. L. H.; Rupich, M. W.

    2010-01-01

    The main objective of this research is to find a suitable alternate solution based seed layer for the standard RABiTS three-layer architecture of physical vapor deposited CeO2 cap/YSZ barrier/Y2O3 seed on Ni-5%W metal tape. In the present work, we have identified CeO2 buffer layer as a potential replacement for Y2O3 seeds. Using a metal-organic deposition (MOD) process, we have grown smooth, crack-free, epitaxial thin films of CeO2 (both pure and Zr, Cu and Gd-doped) directly on biaxially textured Ni-5W substrates in short lengths. Detailed XRD studies indicate that a single epitaxial CeO2 phase with slightly improved out-of-plane texture compared to the texture of underlying Ni-W substrates can be achieved in pure, undoped CeO2 samples. We have also demonstrated the growth of YSZ barrier layers on pure CeO2 seeds using sputtering. Both sputtered CeO2 cap layers and MOD-YBCO films were grown epitaxially on these YSZ-buffered MOD-CeO2/Ni-5W substrates. High critical currents per unit width, Ic of 264 A/cm (critical current density, Jc of 3.3 MA/cm2) at 77 K and 0.01 T was achieved for 0.8 m thick MOD-YBCO films grown on MOD-CeO2 seeds. These results indicate that CeO2 films can be grown directly on Ni-5W substrates and still support high performance YBCO coated conductors. This work holds promise for a route for producing low-cost buffer architecture for RABiTS based YBCO coated conductors.

  14. Structural defects in trifluoroacetate derived YBa2Cu3O7 thin films

    NASA Astrophysics Data System (ADS)

    Gazquez, J.; Coll, M.; Roma, N.; Sandiumenge, F.; Puig, T.; Obradors, X.

    2012-06-01

    We present an accurate description of the structural defects occurring within YBa2Cu3O7 (YBCO) films grown by chemical solution deposition (CSD) based on metal trifluoroacetates (TFA). Transmission electron microscopy (TEM) is the essential tool to identify and evaluate the microstructural defects that might act as natural pinning centers. Our study of TFA-YBCO thin films shows that the YBCO thin films contain a variety of extended defects, such as intergrowths, twin boundaries and dislocations, mainly in the basal plane. These extended defects and their interaction make up a rich variety of key microstructural features that play an important role in the YBCO thin films physical properties and performance.

  15. Fast epitaxial growth of a-axis- and c-axis-oriented YBa 2Cu 3O 7- δ films on (1 0 0) LaAlO 3 substrate by laser chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Pei; Ito, Akihiko; Tu, Rong; Goto, Takashi

    2011-02-01

    a-axis- and c-axis-oriented YBa2Cu3O7-δ (YBCO) films were epitaxially grown on (1 0 0) LaAlO3 substrates by laser chemical vapor deposition. The preferred orientation in the YBCO film changed from the a-axis to the c-axis with increasing laser powers from 77 to 158 W (the deposition temperatures from 951 to 1087 K). The a-axis-oriented YBCO film showed in-plane epitaxial growth of YBCO [0 0 1]//LAO [0 0 1], and the c-axis-oriented YBCO film showed that of YBCO [0 1 0]//LAO [0 0 1]. A c-axis-oriented YBCO film with a high critical temperature of 90 K was prepared at a deposition rate of 90 μm h-1, about 2-1000 times higher than that of metalorganic chemical vapor deposition.

  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. Diamondlike carbon films as protective coatings for superconducting YBa2Cu3O7 films

    NASA Technical Reports Server (NTRS)

    Ganapathi, L.; Giles, S.; Rao, Rama

    1993-01-01

    We have investigated the use of diamondlike carbon (DLC) films for protecting superconducting YBCO films against degradation from exposure to moisture and acid. YBCO thin films on single crystal LaAlO3 and MgO substrates were deposited by laser ablation followed by DLC encapsulation. DLC films were deposited at pressures ranging from high vacuum to 0.1 Torr He. Substrate temperature was varied from 20 to 100 C during the deposition of DLC. The process compatibility of laser ablation was found convenient to sequentially deposit YBCO and DLC films from high purity stoichiometric targets. Epitaxial YBCO films on (100)LaAlO3 and (100)MgO substrates showed identical superconducting transitions before and after encapsulation by a DLC layer. The encapsulated films showed no degradation due to acid treatment or aging over a period of 45 days.

  18. Radiative efficiency of MOCVD grown QD lasers

    NASA Astrophysics Data System (ADS)

    Mawst, Luke; Tsvid, Gene; Dudley, Peter; Kirch, Jeremy; Park, J. H.; Kim, N.

    2010-02-01

    The optical spectral gain characteristics and overall radiative efficiency of MOCVD grown InGaAs quantum dot lasers have been evaluated. Single-pass, multi-segmented amplified spontaneous emission measurements are used to obtain the gain, absorption, and spontaneous emission spectra in real units. Integration of the calibrated spontaneous emission spectra then allows for determining the overall radiative efficiency, which gives important insights into the role which nonradiative recombination plays in the active region under study. We use single pass, multi-segmented edge-emitting in which electrically isolated segments allow to vary the length of a pumped region. In this study we used 8 section devices (the size of a segment is 50x300 μm) with only the first 5 segments used for varying the pump length. The remaining unpumped segments and scribed back facet minimize round trip feedback. Measured gain spectra for different pump currents allow for extraction of the peak gain vs. current density, which is fitted to a logarithmic dependence and directly compared to conventional cavity length analysis, (CLA). The extracted spontaneous emission spectrum is calibrated and integrated over all frequencies and modes to obtain total spontaneous radiation current density and radiative efficiency, ηr. We find ηr values of approximately 17% at RT for 5 stack QD active regions. By contrast, high performance InGaAs QW lasers exhibit ηr ~50% at RT.

  19. Improvement of Production Rate of YBCO Coated Conductors Fabricated by TFA-MOD Method

    NASA Astrophysics Data System (ADS)

    Nakaoka, K.; Yoshizumi, M.; Usui, Y.; Izumi, T.; Shiohara, Y.

    The metal-organic deposition (MOD) method using trifluoroacetate (TFA) salts is considered to be an effective method for inexpensively fabricating YBa2Cu3O7-y (YBCO) coated conductors with high critical current density property. The long-length TFA-MOD YBCO coated conductors have been fabricated by multi-turn reel-to-reel system. Increasing the thickness per single coating in the multi-turn reel-to-reel system is a cost-effective technique for fabrication of the precursor films in the calcination process since it reduces the number of coatings and shortens the processing time. In this work, we have developed a new starting solution consisting of non-fluorine salts of yttrium propionate and copper 2-ethylhexanoate with focusing on increasing the thickness per single coating for a high-rate fabrication of the YBCO coated conductors by the TFA-MOD method. The critical thickness per single coating of the precursor film fabricated from the new starting solution was improved to 0.44 μm/coat. Furthermore, the addition of diacetoneacrylamide in the new starting solution increased the critical thickness per single coating to 0.79 μm/coat. High critical current of 791 A/cm-width with high critical current density of 2.7 MA/cm2 was obtained using the new starting solution with diacetoneacrylamide at the thickness per single coating of 0.49 μm/coat.

  20. Study of the Nucleation and Growth of YBCO on Oxide Buffered Metallic Tapes

    SciTech Connect

    Solovyov, Vyacheslav

    2009-04-10

    The CRADA collaboration concentrated on developing the scientific understanding of the factors necessary for commercialization of high temperature superconductors (HTS) based on the YBCO coated conductor technology for electric power applications. The project pursued the following objectives: 1. Establish the correlations between the YBCO nuclei density and the properties of the CeO{sub 2} layer of the RABiTS{trademark} template; 2. Compare the nucleation and growth of e-beam and MOD based precursors on the buffered RABiTS{trademark} templates and clarify the materials science behind the difference; and 3. Explore routes for the optimization of the nucleation and growth of thick film MOD precursors in order to achieve high critical current densities in thick films. The CRADA work proceeded in two steps: 1. Detailed characterization of epitaxial ceria layers on “model” substrates, such as (001) YSZ and on RABiTS tapes; and 2. Study of YBCO nucleation on well-defined substrates and on long-length RABiTS.

  1. Rapid processing method for solution deposited YBa 2Cu 3O 7- δ thin films

    NASA Astrophysics Data System (ADS)

    Dawley, J. T.; Clem, P. G.; Boyle, T. J.; Ottley, L. M.; Overmyer, D. L.; Siegal, M. P.

    2004-02-01

    YBa 2Cu 3O 7- δ (YBCO) films, deposited on buffered metal substrates, are the primary candidate for second-generation superconducting (SC) wires, with applications including expanded power grid transmission capability, compact motors, and enhanced sensitivity magnetic resonance imaging. Feasibility of manufacturing such superconducting wires is dependent on high processing speed, often a limitation of vapor and solution-based YBCO deposition processes. In this work, YBCO films were fabricated via a new diethanolamine-modified trifluoroacetic film solution deposition method. Modifying the copper chemistry of the YBCO precursor solution with diethanolamine enables a hundredfold decrease in the organic pyrolysis time required for MA/cm 2 current density ( Jc) YBCO films, from multiple hours to ∼20 s in atmospheric pressure air. High quality, ∼0.2 μm thick YBCO films with Jc (77 K) values ⩾2 MA/cm 2 at 77 K are routinely crystallized from these rapidly pyrolyzed films deposited on LaAlO 3. This process has also enabled Jc (77 K)=1.1 MA/cm 2 YBCO films via 90 m/h dip-coating on Oak Ridge National Laboratory RABiTS™ textured metal tape substrates. This new YBCO solution deposition method suggests a route toward inexpensive and commercializable ∼$10/kA m solution deposited YBCO coated conductor wires.

  2. Self-seeded YBCO welding induced by Ag additives.

    SciTech Connect

    Puig, T.; Rodrigues, P., Jr.; Carrillo, A. E.; Obradors, X.; Zheng, H.; Welp, U.; Chen, L.; Claus, H.; Veal, B. W.; Crabtree, G. W.; Materials Science Division

    2001-11-01

    A new welding procedure for bulk melt-textured YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) superconducting tiles has been developed leading to high quality joints. The welding agent consists of a YBCO-Ag composite, which has a peritectic temperature 40 C lower than YBCO. It is shown that through a proper selection of thermal treatments, the effect of Ag additives can be confined to the immediate welding zone, thus allowing a self-seeded growth process of the YBCO/Ag composite initiated at the adjacent solid YBCO crystals. Local magneto-optical observations, as well as trapped field measurements produced by circulating currents in ring samples, reveal that the critical current across the weld joint is as high as that of bulk melt-textured YBCO.

  3. Anomalous diffusion of Ga and As from semi-insulating GaAs substrate into MOCVD grown ZnO films as a function of annealing temperature and its effect on charge compensation

    SciTech Connect

    Biswas, Pranab; Banerji, P.; Halder, Nripendra N.; Kundu, Souvik; Shripathi, T.; Gupta, M.

    2014-05-15

    The diffusion behavior of arsenic (As) and gallium (Ga) atoms from semi-insulating GaAs (SI-GaAs) into ZnO films upon post-growth annealing vis-à-vis the resulting charge compensation was investigated with the help of x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy. The films, annealed at 600 ºC and 700 ºC showed p-type conductivity with a hole concentration of 1.1 × 10{sup 18} cm{sup −3} and 2.8 × 10{sup 19} cm{sup −3} respectively, whereas those annealed at 800 ºC showed n-type conductivity with a carrier concentration of 6.5 × 10{sup 16} cm{sup −3}. It is observed that at lower temperatures, large fraction of As atoms diffused from the SI-GaAs substrates into ZnO and formed acceptor related complex, (As{sub Zn}–2V{sub Zn}), by substituting Zn atoms (As{sub Zn}) and thereby creating two zinc vacancies (V{sub Zn}). Thus as-grown ZnO which was supposed to be n-type due to nonstoichiometric nature showed p-type behavior. On further increasing the annealing temperature to 800 ºC, Ga atoms diffused more than As atoms and substitute Zn atoms thereby forming shallow donor complex, Ga{sub Zn}. Electrons from donor levels then compensate the p-type carriers and the material reverts back to n-type. Thus the conversion of carrier type took place due to charge compensation between the donors and acceptors in ZnO and this compensation is the possible origin of anomalous conduction in wide band gap materials.

  4. Superconducting, transition, and normal state photoresponse in YBCO observed at different temperatures

    SciTech Connect

    Bluzer, N. ); Fork, D.K.; Geballe, T.H.; Beasley, M.R.; Reizer, M.Y. . Dept. of Applied Physics); Greenfield, S.R.; Stankus, J.J.; Fayer, M. . Dept. of Chemistry)

    1991-03-01

    This paper reports on photoresponse of YBCO films measured with a new technique between 7 K and 200 K. YBCO was exposed to variable fluence ({le}3 {mu}J) 300 fsec 665 nm 2 KHz laser pulses. Photoinduced impedance changes in the samples biased with a dc current exhibited a transient voltage signal. Typically, the voltage signal had a sharp ({lt}50 psec) rise followed by a more gradual decay. Below T{sub c}, the response did not exhibit a simple exponential relaxation time. Relaxation occurred by a serial combination of fast ({approximately}200-700 psec) and slow ({approx}1 nsec) decay time constants. At T{sub c} the photoresponse was the highest and the relaxation time constant was typically greater than 1 nsec.

  5. Hybrid quantum systems with YBCO coplanar resonators and spin ensembles of organic radicals

    NASA Astrophysics Data System (ADS)

    Ghirri, Alberto; Bonizzoni, Claudio; Troiani, Filippo; Cassinese, Antonio; D'Arienzo, Massimiliano; Beverina, Luca; Affronte, Marco

    We have studied the coherent coupling of microwave photons in a superconducting coplanar resonator with a spin ensemble of stable open-shell organic radicals. We fabricated YBCO/sapphire coplanar resonators that show quality factors ~= 3*104 at 1.8 K, that remain remarkably stable in high magnetic field applied parallel to the YBCO film [QL (7 T) = 90% QL (0 T)]. Spin ensembles of (3,5-Dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl organic radical (PyBTM) show sharp EPR linewidth (8 MHz) due to the effect of the exchange narrowing. The frequency of the spin transition is tuned by means of the external magnetic field. We show the achievement of the strong collective coupling with the resonant photons with coupling rates exceeding 90 MHz at 1.8 K.

  6. Introduction of Artificial Pinning Center into PLD-YBCO Coated Conductor on IBAD and Self-Epitaxial CeO2 Buffered Metal Substrate

    SciTech Connect

    Kobayashi, H.; Yamada, Y.; Ishida, S.; Takahashi, K.; Konishi, M.; Ibi, A.; Miyata, S.; Kato, T.; Hirayama, T.; Shiohara, Y.

    2006-03-31

    In order to fabricate YBa2Cu3O7-x (YBCO) coated conductors with high critical current density Jc in magnetic fields, we fabricated YBCO coated conductors with artificial pinning centers by the pulsed laser deposition (PLD) method on a self epitaxial PLD-CeO2 layer and ion-beam assisted deposition (IBAD)-Gd2Zr2O7 (GZO) buffered Hastelloy tape. Artificial pinning centers were introduced by the PLD deposition using the yttria-stabilized zirconia (YSZ) oxide target (nano-dot method) and YBCO target including YSZ particles (mixed target method). In the experiments using YSZ oxide target, YSZ nano-dots were observed. They were approximately 15 nm in height and 10 nm to 70 nm in diameter. We found that the density of nano-dots was controlled by the number of laser pulses. These samples exhibited higher Jc than YBCO films in magnetic fields. Furthermore, a similar improvement of Jc was observed in the experiments using YBCO target including YSZ particles. TEM observation revealed that columnar nano-structure made of BaZrO3 was formed during YBCO deposition and it was effective for pinning. We call this new epitaxial nano-structure 'bamboo structure' from its anisotropic growth and morphology.

  7. Systematic Evaluation of Jc Decrease in Thick Film Coated Conductors

    SciTech Connect

    Alex Ignatiev; Dr. Amit Goyal

    2006-05-10

    Address both thickness dependence of Jc, in thick film YBCO coated conductors through an application of a suite of new measurement techniques to thick film wire samples produced by commercially viable coated conductor technologies.

  8. MOD Buffer/YBCO Approach to Fabricate Low-Cost Second Generation HTS Wires

    SciTech Connect

    Paranthaman, Mariappan Parans; Sathyamurthy, Srivatsan; Bhuiyan, Md S; Martin, Patrick M; Aytug, Tolga; Kim, Kyunghoon; Fayek, Mostafa; Leonard, Keith J; Li, Jing; Zhang, W.; Rupich, Marty

    2007-01-01

    The metal organic deposition (MOD) of buffer layers on RABiTS substrates is considered a potential, low-cost approach to manufacturing high performance Second Generation (2G) high temperature superconducting (HTS) wires. The typical architecture used by American Superconductor in their 2G HTS wire consists of a Ni-W (5 at.%) substrate with a reactively sputtered Y2O3 seed layer, YSZ barrier layer and a CeO2 cap layer. This architecture supports critical currents of over 300 A/cm-width (77 K, self-field) with 0.8 mum YBCO films deposited by the TFA-MOD process. The main challenge in the development of the MOD buffers is to match or exceed the performance of the standard vacuum deposited buffer architecture. We have recently shown that the texture and properties of MOD - La2Zr2Ogamma (LZO) barrier layers can be improved by inserting a thin sputtered Y2O3 seed layer and prepared MOD deposited LZO layers followed by MOD or RF sputtered CeO2 cap layers that support MOD-YBCO films with Ic's of 200 and 255 A/cm-width, respectively. Detailed X-ray and microstructural characterizations indicated that MOD - CeO2 cap reacted completely with MOD YBCO to form BaCeOs. However, sputtered CeO2 cap/MOD YBCO interface remains clean. By further optimizing the coating conditions and reducing the heat-treatment temperatures, we have demonstrated an Ic of 336 A/cm with improved LZO layers and sputtered CeO2 cap and exceeded the performance of that of standard vacuum deposited buffers.

  9. Electrodeposited Biaxially Textured Buffer Layers for YBCO Superconductors

    SciTech Connect

    Bhattacharya, R.; Phok, S.; Zhao, W.; Norman, A.

    2009-06-01

    Non-vacuum electrodeposition (ED) was used to prepare simplified Gd{sub 2}O{sub 3}/Gd{sub 2}Zr{sub 2}O{sub 7} and CeO{sub 2}/Gd{sub 2}Zr{sub 2}O{sub 7} buffer layers on a Ni-W substrate. Post-annealing conditions of electrodeposited precursor films were optimized to obtain high-quality biaxially textured buffer layers. The buffer layers were characterized by X-ray diffraction, optical profiling, and transmission electron microscopy (TEM). The effect of the cap layer thickness on the surface morphology and texture of the buffers was also studied. The microstructure of CeO{sub 2}/Gd{sub 2}Zr{sub 2}O{sub 7} was analyzed and compared to Gd{sub 2}O{sub 3}/Gd{sub 2}Zr{sub 2}O{sub 7}. The high-resolution TEM shows biaxially textured crystalline elctrodeposited Gd{sub 2}O{sub 3} and CeO{sub 2} cap layers on the electrodeposited Gd{sub 2}Zr{sub 2}O{sub 7} layers without any defects. YBa{sub 2}Cu{sub 3}O{sub 7}-delta (YBCO) superconductor was deposited by pulsed laser deposition (PLD) on the simplified ED-Gd{sub 2}O{sub 3}/Gd{sub 2}Zr{sub 2}O{sub 7} and ED-CeO{sub 2}/Gd{sub 2}Zr{sub 2}O{sub 7} buffers. Transport current density of 3.3 MA/cm{sup 2} at 77 K was obtained for PLD YBCO deposited on ED-Gd{sub 2}O{sub 3}/Gd{sub 2}Zr{sub 2}O{sub 7} buffer layers.

  10. Novel tri-modal defect structure in Nb-doped MOCVD YBa2Cu3O7: A paradigm for pinning landscape control

    SciTech Connect

    Aytug, Tolga; Maroni, Victor A.; Chen, Z; Miller, Dean; Kropft, Jeremy; Zaluzec, Nestor J; Zuev, Yuri L; Specht, Eliot D; Paranthaman, Mariappan Parans

    2012-01-01

    Immobilization of vortices, or flux pinning, is both an enduring scientific issue and one of the most important problems in optimizing high temperature superconductors (HTS) for commercial use. Here, we demonstrate a practical approach to the creation of a multi-modal flux pinning landscape in YBa2Cu3O7 (YBCO) films employing an industrially scalable metal organic chemical vapor deposition technique. Through controlled additions of Nb, we have achieved a novel distribution of crystallographic defects that immobilize (pin) vortices in the YBCO matrix. That is, with only the addition of a single dopant element, a tri-modal defect structure that threads through the YBCO matrix laterally (parallel to the ab planes of YBCO), vertically (parallel to the YBCO c-axis), and isotropically in the form of random spherical defects is induced. For optimally doped samples, the influence of these multi-modal nanocrystalline defect structures on the flux pinning properties manifests itself as a superior improvement in the critical current density (Jc) for all magnetic field orientations. The results demonstrate the possibility of achieving an ideal flux pinning landscape (from an orientation and strength viewpoint), which permits the design of HTS wires with fully-tuneable properties by processes suitable for large-scale manufacturing.

  11. A study for designing YBCO power transformer

    NASA Astrophysics Data System (ADS)

    Hayashi, H.; Okamoto, H.; Harimoto, T.; Imayoshi, T.; Tomioka, A.; Bouno, T.; Konno, M.; Iwakuma, M.

    2007-10-01

    It is highly expected that superconducting transformers, which are characterized by incombustibility, light weight, and compactness, will be used practically for equipment in substations and office buildings sited in urban areas. In recent years, remarkable improvements in the performance of YBaCuO (YBCO) tape wire have been seen. This kind of tape wire has the property that its critical current is large in a highly magnetic field; and, its use is expected to reduce AC loss by applying slit processing on the tape wire, contributing to future cost reductions. In addition, the development of efficient, economical cryogenic units is also expected. The authors have developed a conceptual design for a 66 kV/20 MVA power transformer using YBCO tape wires, or an YBCO power transformer. As a result, we were able to identify the transformer's optimal system structure including coil winding comprised of coils and tape wires; and, we confirmed that the devised transformer can made to be both compact and highly efficient.

  12. 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.

  13. AC Loss Reduction in Filamentized YBCO Coated Conductors with Virtual Transverse Cross-cuts

    SciTech Connect

    Zhang, Yifei; Duckworth, Robert C; Ha, Tam T; List III, Frederick Alyious; Gouge, Michael J; Chen, Y; X, Xiong,; Selvamanickam, V.

    2011-01-01

    While the performance of YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO)-based coated conductors under dc currents has improved significantly in recent years, filamentization is being investigated as a technique to reduce ac loss so that the 2nd generation (2G) high temperature superconducting (HTS) wires can also be utilized in various ac power applications such as cables, transformers and fault current limiters. Experimental studies have shown that simply filamentizing the superconducting layer is not effective enough to reduce ac loss because of incomplete flux penetration in between the filaments as the length of the tape increases. To introduce flux penetration in between the filaments more uniformly and further reduce the ac loss, virtual transverse cross-cuts were made in superconducting filaments of the coated conductors fabricated using the metal organic chemical vapor deposition (MOCVD) method. The virtual transverse cross-cuts were formed by making cross-cuts (17 - 120 {micro}m wide) on the IBAD (ion beam assisted deposition)-MgO templates using laser scribing followed by depositing the superconducting layer ({approx} 0.6 {micro}m thick). AC losses were measured and compared for filamentized conductors with and without the cross-cuts under applied peak ac fields up to 100 mT. The results were analyzed to evaluate the efficacy of filament decoupling and the feasibility of using this method to achieve ac loss reduction.

  14. Low-temperature in situ formation of Y-Ba-Cu-O high T sub c superconducting thin films by plasma-enhanced metalorganic chemical vapor deposition

    SciTech Connect

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

    1990-06-04

    Highly textured, highly dense, superconducting YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} thin films with mirror-like surfaces have been prepared, {ital in} {ital situ}, at a reduced substrate temperature as low as 570 {degree}C by a remote microwave plasma-enhanced metalorganic chemical vapor deposition process (PE-MOCVD). Nitrous oxide was used as the oxidizer gas. The as-deposited films grown by PE-MOCVD show attainment of zero resistance at 72 K. PE-MOCVD was carried out in a commercial scale MOCVD reactor.

  15. High-Jc YBa2Cu3O7-δ superconducting film grown by laser-assisted chemical vapor deposition using a single liquid source and its microstructure

    NASA Astrophysics Data System (ADS)

    Zhao, Pei; Ito, Akihiko; Kato, Takeharu; Yokoe, Daisaku; Hirayama, Tsukasa; Goto, Takashi

    2013-09-01

    A YBa2Cu3O7-δ (YBCO) film was prepared on a multilayer-coated Hastelloy C276 substrate by laser-assisted metalorganic chemical vapor deposition using a single liquid source precursor. A c-axis-oriented YBCO film was grown epitaxially on a (100) CeO2 layer at a deposition rate of 11 μm h-1. A screw dislocation and stacking faults were observed in the cross-section of the YBCO film. The critical current density of the YBCO film reached 2.7 MA cm-2.

  16. MOCVD growth of gallium nitride with indium surfactant

    NASA Astrophysics Data System (ADS)

    Won, Dong Jin

    In this thesis research, the effect of indium surfactant on Ga-polar and N-polar GaN films grown at 950 °C by MOCVD on various substrates such as Si-face SiC, bulk GaN, Si(111), and C-face SiC was studied to investigate the stress relaxation mechanism, structural, and optical properties of GaN films which were modified by the indium surfactant. The effect of indium surfactant on GaN films grown on SiC was studied first. In the 1.8 microm thick Ga-polar GaN films grown on lattice-mismatched Si-face SiC substrates utilizing indium surfactant at 950 °C, inverted hexagonal pyramid surface defects, so-called V-defects which consist of six (1011) planes, formed at threading dislocations on the GaN surface, which gave rise to the relaxation of compressive misfit stress in an elastic way. Simultaneously, enhanced surface mobility of Ga and N adatoms with indium surfactant lead to improved 2D growth, which may be contradictory to the formation of surface defects like V-defects. In order to find the driving force for V-defect formation in the presence of indium, a nucleation and growth model was developed, taking into consideration the strain, surface, and dislocation energies modified by indium surfactant. This model found that the V-defect formation can be energetically preferred since indium reduces the surface energy of the (1011) plane, which gives rise to the V-defect formation and growth that can overcome the energy barrier at the critical radius of the V-defect. These Ga-polar GaN films were found to be unintentionally doped with Si. Thus, an investigation into the effect of intentional Si doping at a constant TMIn flow rate on GaN films was also performed. Si turned out to be another important factor in the generation of V-defects because Si may be captured at the threading dislocation cores by forming Si -- N bonds, acting as a mask to locally prevent GaN growth. This behavior appeared to assist the initiation of the V-defect which enables V-defects to easily

  17. Fabrication of high T(sub c) superconductor thin film devices: Center director's discretionary fund

    NASA Technical Reports Server (NTRS)

    Sisk, R. C.

    1992-01-01

    This report describes a technique for fabricating superconducting weak link devices with micron-sized geometries etched in laser ablated Y1Ba2Cu3O(x) (YBCO) thin films. Careful placement of the weak link over naturally occurring grain boundaries exhibited in some YBCO thin films produces Superconducting Quantum Interference Devices (SQUID's) operating at 77 K.

  18. Development of buffer layers by chemical solution deposition for YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Akin, Yalcin

    Short length YBCO coated conductors have been fabricated by vacuum thin film deposition techniques. However, the fabrication process increases the cost, and makes them impractical to use for commercial applications even if they are fabricated in kilometer lengths. YBCO coated conductors could be available in the market with a cheaper price by developing non-vacuum deposition techniques. The objective of this research was to investigate development of buffer layers by chemical solution deposition technique for YBCO coated conductors. Buffer layer structures are mainly used to prevent metal ion diffusion, and to reduce the lattice mismatch between YBCO and the metallic substrate. The technical approach, which was adapted here, is the reel-to-reel sol-gel dip coating process to fabricate long length coatings by developing buffer layers' chemical solutions. Rolling assisted biaxially textured Ni substrates were used for deposition of buffer layers. Cold rolled Ni strips were heat-treated at certain conditions to form biaxially textured structure, which became templates for textured growth of buffer layers that is necessary to obtain high critical current in the coated conductors. CeO2 was chosen as a buffer layers because it has been recognized as one of the best cap layers. Growth of highly textured, crack free, pinhole free and smooth CeO2 buffer layers have been demonstrated by chemical solution deposition technique on biaxially textured substrates. A new buffer layer with pseudocubic lattice parameters matching YBCO, (Eu0.893Yb0.107)2O3, was developed for the first time by using a mixture of Eu2O 3 and Yb2O3 to eliminate lattice mismatch, which adversely affected the critical current of the coated conductors. Highly textured (Eu0.893Yb0.107)2O3 buffer layers were deposited on biaxially textured Ni substrates by chemical solution deposition technique. Finally, the growth of CeO2 and (Eu0.893Yb 0.107)2O3 buffer layers were investigated on oxide layers because both Ce

  19. The role of impurities in LP-MOCVD grown gallium nitride

    SciTech Connect

    Hwang, C.Y.; Li, Y.; Schurman, M.J.; Mayo, W.E.; Lu, Y.; Stall, R.A.

    1996-11-01

    The authors have investigated the relationship of the Hall electron mobility to the background carrier concentration in low pressure MOCVD grown GaN. The highest electron mobility (400 cm{sup 2}/V{center_dot}s) of the unintentionally doped GaN was obtained at a carrier concentration of 1 {times} 10{sup 17} cm{sup {minus}3} and samples with carrier concentrations lower than this exhibited lower mobilities. SIMS analysis shows C and O concentrations in the range of 2--3 {times} 10{sup 16} cm{sup {minus}3} and H in the 2--3 {times} 10{sup 17} cm{sup {minus}3} range. Structural defects, stoichiometry and impurities in the GaN films grown under different conditions are investigated to understand their relationship to the electron Hall mobilities. In particular, different growth temperatures and pressures were used to grow undoped GaN and modify the background doping effect of the impurities.

  20. Novel Superoxygenated Phases in Superconducting Cuprate Thin Films

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Zhang, H.; Gauquelin, N.; Botton, G. A.; McMahon, C.; Hawthorn, D. G.; Wei, J. Y. T.

    The superconducting critical temperature (Tc) of hole-doped cuprates tends to increase with their lattice complexity, which is generally correlated with higher states of oxidation. For YBa2Cu3O7 - δ (YBCO-123), it is known that solid-state reaction in high-pressure oxygen can induce the formation of more complex and oxidized phases such as Y2Ba4Cu7O15 - δ (YBCO-247) and Y2Ba4Cu8O16 (YBCO-248). In this work, we apply this superoxygenation concept of material synthesis to nanoscale thin films which, owing to their large surface-to-volume ratio, are more thermodynamically reactive than bulk samples. Epitaxial thin films of YBCO-123 were grown by pulsed laser deposition on (La , Sr) (Al , Ta) O3 substrates, and post-annealed in up to 500 atm of oxygen at 800C. Our post-annealed films show robust superconducting transitions with Tc ranging from 80 to 93K. Transmission electron microscopy and X-ray absorption spectroscopy were used to probe the lattice structure and oxygen stoichiometry. Our measurements show clear evidence of conversion to YBCO-247 and YBCO-248 in the superoxygenated films, as well as YBCO-125, a novel YBCO phase that has three CuO chains per unit cell and potentially higher Tc. Work supported by NSERC, CFI/OIT, and CIFAR.

  1. High Jc YBCO coated conductors on non-magnetic metallic substrate using YSZ-based buffer layer architecture

    NASA Astrophysics Data System (ADS)

    Celentano, G.; Boffa, V.; Ciontea, L.; Fabbri, F.; Galluzzi, V.; Gambardella, U.; Mancini, A.; Petrisor, T.; Rogai, R.; Rufoloni, A.; Varesi, E.

    2002-08-01

    Biaxially aligned YBa 2Cu 3O 7- δ (YBCO) thick films were deposited by pulsed laser ablation technique on cube textured non-magnetic Ni 89V 11 (Ni-V) substrate, using CeO 2/YSZ/CeO 2/NiO buffer layer architecture. The first NiO seed layer was formed by epitaxial oxidation of the Ni-V substrate. Structural analyses show typical full width at half maximum values of φ- and ω-scans less than 10° and 8°, respectively. The highest value obtained for the critical current density at 77 K and zero magnetic field was 6×10 5 A cm -2, which is close to that obtained for YBCO films grown on CeO 2/NiO buffer layer architecture.

  2. Transport phenomena and the effects of reactor geometry for epitaxial GaN growth in a vertical MOCVD reactor

    NASA Astrophysics Data System (ADS)

    Tseng, Chien-Fu; Tsai, Tsung-Yen; Huang, Yen-Hsiu; Lee, Ming-Tsang; Horng, Ray-Hua

    2015-12-01

    In this study a numerical simulation was carried out to analyze the transport phenomena in a vertical type metal organic chemical vapor deposition (MOCVD) reactor for Gallium Nitride (GaN) growth. The simulated results were compared and validated by experiment. The effects of showerhead design and chamber height are investigated and discussed. It was found that, by properly adjusting the height of the chamber, both the growth rate and film uniformity could be significantly improved. This is attributed to the suppression of the thermal and mass transfer boundary layers by the injection flow of reacting gas mixtures, as well as the confined vertical vortices caused by the geometry of the reduced space. However, inappropriate design of the distance between the showerhead and the susceptor can result in uneven distribution of the organic source in the vicinity of the substrate surface resulting in an uneven growth rate of the GaN film. Consequently, there exists an optimal chamber height that will give the best growth rate and uniformity to the GaN film as discussed in this study. This study provides comprehensive insight into the transport phenomena of GaN growth that includes coupled heat and mass transfer as well as chemical reactions. The results provide important information in a succinct format and enable decisions to be made about the showerhead and the geometrical design and size of a vertical MOCVD reactor.

  3. Raman and x-ray absorption spectroscopy characterization of Zr-doped MOCVD YBa2Cu2O6+delta.

    SciTech Connect

    Maroni, V. A.; Kropf, Arthur J; Aytug, Tolga; Paranthaman, Mariappan Parans

    2010-01-01

    Metal organic chemical vapor deposited YBa2Cu3O6+ (YBCO) films (about 0.9 m thick) containing varying amounts of added zirconium were examined by Raman microscopy and synchrotron x-ray absorption spectroscopy. The self-field and in-field (1 T, B c) Jc performance of the YBCO films at 77 K (reported by the group at Oak Ridge National Laboratory that fabricated the samples) exhibited an increase on going from 0 mol% (m/o) Zr-added to 2.5 m/o Zr-added but then decreased sharply with increasing Zr content. Raman measurements on these films showed that the added Zr had little effect on YBCO cation disorder up to about 7.5 m/o Zr-added. Cation disorder increased while Ba Cu O content remained relatively constant for Zr additions 7.5 m/o. In the region of sharpest descent of Jc with increasing Zr content (2.5 7.5 m/o Zr-added) neither the cation disorder nor the Ba Cu O content showed a systematic variation with Jc. Zirconium K edge x-ray absorption near-edge spectroscopy revealed that virtually all of the added Zr in each sample was present as a BaZrO3-like phase (BZO). The Jc performance of the Zr-added films showed a high correlation with the variations in the next-nearest-neighbor Zr M (M = Zr, Y) scattering path amplitude from the extended x-ray absorption fine structure (EXAFS) and the critical temperature over the full range of Zr additions and with cation disorder at the higher Zr-added levels (>7.5 m/o). There was no obvious correlation with the amount of residual barium cuprate or CuO. Approximate ranges for the BZO particle dimensions estimated from the EXAFS data indicated that the mean particle size gets larger with increasing Zr addition.

  4. Maximum permissible voltage of YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Wen, J.; Lin, B.; Sheng, J.; Xu, J.; Jin, Z.; Hong, Z.; Wang, D.; Zhou, H.; Shen, X.; Shen, C.

    2014-06-01

    Superconducting fault current limiter (SFCL) could reduce short circuit currents in electrical power system. One of the most important thing in developing SFCL is to find out the maximum permissible voltage of each limiting element. The maximum permissible voltage is defined as the maximum voltage per unit length at which the YBCO coated conductors (CC) do not suffer from critical current (Ic) degradation or burnout. In this research, the time of quenching process is changed and voltage is raised until the Ic degradation or burnout happens. YBCO coated conductors test in the experiment are from American superconductor (AMSC) and Shanghai Jiao Tong University (SJTU). Along with the quenching duration increasing, the maximum permissible voltage of CC decreases. When quenching duration is 100 ms, the maximum permissible of SJTU CC, 12 mm AMSC CC and 4 mm AMSC CC are 0.72 V/cm, 0.52 V/cm and 1.2 V/cm respectively. Based on the results of samples, the whole length of CCs used in the design of a SFCL can be determined.

  5. Field Dependent Penetration Depth in YBCO

    NASA Astrophysics Data System (ADS)

    Carrington, A.; Giannetta, R.; Salamon, M. B.; Ginsberg, D. M.; Kim, J. T.

    1997-03-01

    An important step to understanding the nature of superconductivity in cuprate superconductors was the observation of a linear temperature dependence of the penetration depth (λ_ab) in YBCO(W.N. Hardy et al.) Phys. Rev. Lett. 70, 3999 (1993)., which strongly suggests the presence of line nodes in the order parameter, consistent with a d-wave pairing state. Recent theoretical work(S.K. Yip and J.A. Sauls, Phys. Rev. Lett. 69), 2264 (1992). has claimed that the magnetic field dependence of λ_ab at low temperature also uniquely depends on the symmetry of the order parameter. To investigate these effects we have built an apparatus, based on a RF tunnel diode oscillator,to measure with high precision both the temperature and field dependence of λ in small single crystal samples. Particular attention has been paid to reducing extraneous frequency shifts originating from the field/temperature dependence of the oscillator circuit. The sample rests on a moveable stage whose temperature may be varied indepndently of the resonator, so that the background may be measured in-situ. Results will be presented for YBCO at temperatures down to 1.3 K and fields up to H_c1(T), and their implications for the the pairing state in the cuprates discussed. This work was supported by NSF Grant # DMR-89-20538 and STCS/NSF DMR 91-20000.

  6. Developments of superconducting motor with YBCO bulk magnets

    NASA Astrophysics Data System (ADS)

    Hirakawa, M.; Inadama, S.; Kikukawa, K.; Suzuki, E.; Nakasima, H.

    2003-10-01

    We designed and manufactured a superconducting motor with YBCO superconductive bulk magnets. The motor, equipped with YBCO bulks as trapped field magnets and copper coils as armature windings, is an eight-poled synchronous motor of outer rotor type. The bulks are cooled to around 30 K by a refrigerator. This cooling operation is simpler than the other methods like cooling by liquid nitrogen. This paper presents the construction of the motor, the method of cooling bulks and the method of activating YBCO bulk magnets.

  7. From research to manufacture—The evolution of MOCVD

    NASA Astrophysics Data System (ADS)

    Grodzinski, Piotr; Denbaars, Steven P.; Lee, H. C.

    1995-12-01

    The article provides an overview of the manufacturing capabilities of metalorganic chemical vapor deposition (MOCVD) technology and describes its application to the growth and fabrication of devices in three different material groups: AlGaAs/GaAs, AlInGaP, and AlGaN/GaN. Discussed are GaN blue light-emitting diodes (LEDs), AlInGaP red and yellow LEDs, and AlGaAs/GaAs vertical cavity surface-emitting lasers and high-electron-mobility transistors. Based on these examples, the evolution of MOCVD technology from fundamental materials studies and advanced materials development through the early stages of pilot manufacturing and large-volume manufacturing capabilities is demonstrated.

  8. Surface Stoichiometry, Structure, and Kinetics of GaAs MOCVD

    SciTech Connect

    Baucom, K.C.; Creighton, J.R.; Moffat, H.K.

    1999-01-29

    We have used reflectance-difference spectroscopy (RDS) to examine the surface phases of GaAs(100) during metalorganic chemical vapor deposition (MOCVD). Since the identities of two important surface phases were unknown, we determined their structure and stoichiometry using a variety of surface science techniques. The Type III phase is a newly characterized As-rich (1 X 2)-CH{sub 3} reconstruction. The Type II phase is a metastable derivative of the Type I phase. RDS also indicates that the surface during MOCVD has a considerable degree of heterogeneity. Deposition rates were measured over a similar range of conditions and the kinetically-limited regime was found to correlate with the Type III phase. A simple kinetic model was found to quantitatively describe the deposition rates.

  9. Processing of YBCO superconductors for improved levitation force

    SciTech Connect

    Balachandran, U.; Zhong, W.

    1993-05-01

    One objective of the ANL superconductor program is to develop improved processing methods for production of YBCO superconductors with higher levitation forces suitable for low-friction, superconductor/permanent-magnet bearings and flywheel-energy-storage applications. From the standpoint of these applications, melt-processed bulk YBCO superconductors are of considerable interest. Levitation force and flux-pinning properties depend on microstructural features of the superconductors. We have added several chemical species to YBCO to alter the microstructure and have used a seeding technique to induce crystallization during melt processing. In this paper, we discuss the effects of various process parameters, additives, and a seeding technique on the properties of melt-processed bulk YBCO samples and compare the results with solid-state-sintered superconductors.

  10. Splice Resistance Measurements in 2G YBCO Coated Conductor

    SciTech Connect

    Rey, Christopher M; Duckworth, Robert C; Zhang, Yifei

    2009-01-01

    Abstract The Oak Ridge National Laboratory has been investigating the electrical splice resistance of second-generation (2G) YBCO coated conductor. The purpose of the experimental investigation is to study the splice resistance of 2G YBCO coated conductor as a function of: a) operating temperature, b) magnetic field strength (B-field), and c) magnetic field orientation ( ). Understanding the splice resistance with its corresponding variation as a function of surface preparation and operating conditions is essential to the practical implementation of electric utility devices; e.g., motors, generators, transformers, cables, and fault-current limiters, etc. Preliminary test results indicate that the 2G YBCO splice resistance shows a weak temperature dependence and a significantly stronger dependence upon magnetic field strength and magnetic field orientation. Surface preparation conditions are also briefly discussed. Index Terms coated conductor, splice, critical current, YBCO

  11. P-type Ge epitaxy on GaAs (100) substrate grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Jin, Y. J.; Chia, C. K.; Liu, H. F.; Wong, L. M.; Chai, J. W.; Chi, D. Z.; Wang, S. J.

    2016-07-01

    In this work, Ga-doped Geranium (Ge) films have been grown on GaAs (100) substrates by metal-organic chemical vapor deposition (MOCVD). Undesired pillar structures have been observed on the epilayers prepared at relatively lower temperatures. Energy dispersive X-ray spectroscopy (EDX) indicated that the pillars are mainly consisted of Ga atoms, which is totally different from that of the Ge film. It was demonstrated that the pillar structures could be reduced by simply raising the growth temperature while keeping the other growth conditions unchanged. In this regard, the growth mechanism of the pillars was related to the Ge-Ga dimers formed during the growth of p-Ge films. By further studying the influence of a GaAs or Ge buffer layer on the growth of p-Ge layers, we found that the GaAs substrate with lower density of Ga or Ge dangling bonds was helpful in suppressing the formation of the undesired pillar structures.

  12. Fabrication of Filamentary YBCO Coated Conductor by Inkjet Printing

    SciTech Connect

    List III, Frederick Alyious; Kodenkandath, Thomas; Rupich, Marty

    2007-01-01

    Inkjet printing is a potentially low cost, high rate method for depositing precursors for filamentary YBCO coated conductors. The method offers considerable flexibility of filament pattern, width, and thickness. Using standard solution precursors and RABiTSTM substrates, the printing, processing, and properties of some inkjet-derived filamentary YBCO coated conductors for Second Generation (2G) wire are demonstrated on a laboratory scale. Some systematic variations of growth rate and critical transport current with filament width are observed and discussed.

  13. AFM nano-plough planar YBCO micro-bridges: critical currents and magnetic field effects.

    PubMed

    Elkaseh, A A O; Perold, W J; Srinivasu, V V

    2010-10-01

    The critical current (Ic) of YBa2Cu3O7-x (YBCO) AFM plough micro-constrictions is measured as a function of temperature, width and the magnetic flux density (B), which was applied perpendicular to the YBCO ab-plane and surface of the bridges. C-axis oriented thin films of YBa2Cu3O7-x were deposited on MgO substrates using an inverted cylindrical magnetron (ICM) sputtering technique. The films were then patterned into 8-10 micron size strips, using standard photolithography and dry etching processes. Micro-bridges with widths between 1.9 microm to 4.1 microm were fabricated by using atomic force microscope (AFM) nanolithography techniques. Critical current versus temperature data shows a straight-line behavior, which is typical of constriction type Josephson junctions. The Ic versus B characteristics exhibited a modulation, and a suppression of the critical current of up to 84%. It was also found that the critical current increases with increasing constriction width. PMID:21137754

  14. 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

  15. Characterization of phase evolution in YBCO coated conductors produced by the ex situ BaF{sub 2} process.

    SciTech Connect

    Feenstra, R.; List, F. A.; Zhang, Y.; Christen, D. K.; Maroni, V. A.; Miller, D. J.; Feldmann, D. M.; ORNL; Univ. of Wisconsin

    2007-06-01

    Raman microprobe spectroscopy and scanning electron microscopy were used to study the initial nucleation and growth of YBCO in thick precursors by the BaF2 ex situ process. For quenched films of 2 mum thickness, the data indicate a low density of c-axis nuclei near the substrate, apparently due to a reduced oxygen concentration deep inside the precursor layer. Significant non c-axis growth was also observed; the majority of this material nucleates away from the substrate. Measurement of the conversion rate by in situ XRD for films in the range 0.2-2 mum suggest a weak thickness dependence.

  16. Buffer layers for high-Tc thin films on sapphire

    NASA Technical Reports Server (NTRS)

    Wu, X. D.; Foltyn, S. R.; Muenchausen, R. E.; Cooke, D. W.; Pique, A.; Kalokitis, D.; Pendrick, V.; Belohoubek, E.

    1992-01-01

    Buffer layers of various oxides including CeO2 and yttrium-stabilized zirconia (YSZ) have been deposited on R-plane sapphire. The orientation and crystallinity of the layers were optimized to promote epitaxial growth of YBa2Cu3O(7-delta) (YBCO) thin films. An ion beam channeling minimum yield of about 3 percent was obtained in the CeO2 layer on sapphire, indicating excellent crystallinity of the buffer layer. Among the buffer materials used, CeO2 was found to be the best one for YBCO thin films on R-plane sapphire. High Tc and Jc were obtained in YBCO thin films on sapphire with buffer layers. Surface resistances of the YBCO films were about 4 mOmega at 77 K and 25 GHz.

  17. Heavy p-type carbon doping of MOCVD GaAsP using CBrCl3

    NASA Astrophysics Data System (ADS)

    Heidelberger, Christopher; Fitzgerald, Eugene A.

    2016-07-01

    CBrCl3 is shown to be a useful precursor for heavy p-type carbon doping of GaAsxP1-x grown via metalorganic chemical vapor deposition (MOCVD) across a range of compositions. Structural and electrical properties of the GaAsP films were measured for various processing conditions. Use of CBrCl3 decreased the growth rate of GaAsP by up to 32% and decreases x by up to 0.025. The dependence of these effects on precursor inputs is investigated, allowing C-doped GaAsP films to be grown with good thickness and compositional control. Hole concentrations of greater than 2×1019 cm-3 were measured for values of x from 0.76 to 0.90.

  18. The use of metalorganics in the preparation of semiconductor materials. VIII - Feasibility studies of the growth of Group III-Group V compounds of boron by MOCVD

    NASA Technical Reports Server (NTRS)

    Manasevit, H. M.; Hewitt, W. B.; Nelson, A. J.; Mason, A. R.

    1989-01-01

    The MOCVD growth of B-As and B-P films on Si, sapphire, and Si-on-sapphire substrates is described; in this process, trimethylborane (TMB) or triethylborane (TEB) is pyrolyzed in the presence of AsH3 or PH3 in an H2 atmosphere. The procedures employed are outlined, and the results are presented in graphs, tables, and micrographs. It is found that the growth rate of the primarily amorphous films is dependent on the TMB or TEB concentration but approximately constant for TEB and AsH3 at 550-900 C. The nominal compositions of films grown using TMB are given as B(12-16)As2 and B(1-1.3)P. Carbon impurities and significant stress, bowing, and crazing are observed in the films grown on Si substrates, with the highest carbon content in the films grown from TMB and PH3.

  19. Hetero-epitaxy of ε-Ga2O3 layers by MOCVD and ALD

    NASA Astrophysics Data System (ADS)

    Boschi, F.; Bosi, M.; Berzina, T.; Buffagni, E.; Ferrari, C.; Fornari, R.

    2016-06-01

    Growth of gallium oxide thin films was carried out by Metalorganic Chemical Vapor Deposition (MOCVD) at different temperatures. Pure ε-phase epilayers of Ga2O3, with good morphology and structural properties, were obtained, for the first time with this technique, on sapphire at the temperature of 650 °C. XRD analysis performed by high-resolution diffractometry confirmed the good crystallographic quality of the grown layers. At temperatures higher than 700 °C the usual stable β-Ga2O3 phase was obtained. The ε-films were successfully deposited also on (0001)-oriented GaN and (111)- and (001)-oriented 3C-SiC templates, provided that the appropriate temperature was chosen. This indicates that the temperature, rather than substrate structure, is the growth parameter which decides what phase actually forms. The growth proceeds via coalescence of hexagonal islands and is favored when a substrate with an in-plane hexagonal arrangement of the atoms is employed. By applying Atomic Layer Deposition (ALD), epitaxial growth of the ε-phase was achieved at lower temperature, while the overall uniformity resulted improved, even on large sapphire substrates.

  20. Electrical properties of ferroelectric-gate FETs with SrBi2Ta2O9 formed using MOCVD technique

    NASA Astrophysics Data System (ADS)

    Yan, Kang; Takahashi, Mitsue; Sakai, Shigeki

    2012-09-01

    Ferroelectric-gate field-effect transistors (FeFETs) with a Pt/SrBi2Ta2O9/Hf-Al-O/Si gate stack were fabricated using the metal-organic chemical vapor deposition (MOCVD) technique to prepare the SrBi2Ta2O9 (SBT) ferroelectric layer. A good threshold voltage ( V th) distribution was found for more than 90 n-channel FeFETs in one chip with a 170 nm SBT layer owing to the good film uniformity of the SBT layer deposited by MOCVD. The average memory window (Vw^{av}) and the standard deviations ( σ thl, σ thr) of the left- and right-side branches of the drain-gate voltage curves of the FeFETs yielded a Vw^{av}/(σ_{thl} + σ_{thr}) value of 5.45, indicating that the FeFETs can be adapted for large-scale-integration. The electric field, the energy band profile in the gate stack, and the gate leakage current were also investigated at high gate voltages. We found that the effect of Fowler-Nordheim tunneling appeared under these conditions. Because of the tunneling injection and trapping of electrons into the gate insulators, the operation voltage ranges of the FeFETs were limited by this tunneling.

  1. Over-current characteristics of YBCO superconducting cable

    NASA Astrophysics Data System (ADS)

    Wang, X.; Ueda, H.; Ishiyama, A.; Yagi, M.; Mukoyama, S.; Kashima, N.; Nagaya, S.; Shiohara, Y.

    2009-10-01

    To achieve large current capacity and high mechanical flexibility, YBa 2Cu 3O 7 (YBCO) superconducting cables consist of a number of YBCO coated conductors that are assembled and wound spirally on a Cu former. In practical applications, superconducting cables are vulnerable to short-circuit fault currents that are 10-30 times greater than the operating current. Therefore, in order to ensure the stability of YBCO superconducting cables in such a situation and to protect them from the fault currents, it is important to investigate the redistribution of the transport current and electromagnetic coupling between the conductor layer, shield layer, and Cu former. In this study, we carried out experiments on a 10-m-long YBCO model cable, which was manufactured by Furukawa Electric. An over-current with a peak of 31.8 kA rms and a duration of 2.02 s was applied to the model cable. We performed numerical simulations using a novel computer program developed using the 3D finite element method to elucidate the electromagnetic and thermal behavior of the YBCO model cable in the presence of an over-current.

  2. Enhanced 77 K vortex-pinning in Y Ba2Cu3O7-x films with Ba2Y TaO6 and mixed Ba2Y TaO6 + Ba2Y NbO6 nano-columnar inclusions with irreversibility field to 11 T

    NASA Astrophysics Data System (ADS)

    Rizzo, F.; Augieri, A.; Angrisani Armenio, A.; Galluzzi, V.; Mancini, A.; Pinto, V.; Rufoloni, A.; Vannozzi, A.; Bianchetti, M.; Kursumovic, A.; MacManus-Driscoll, J. L.; Meledin, A.; Van Tendeloo, G.; Celentano, G.

    2016-06-01

    Pulsed laser deposited thin Y Ba2Cu3O7-x (YBCO) films with pinning additions of 5 at. % Ba2Y TaO6 (BYTO) were compared to films with 2.5 at. % Ba2Y TaO6 + 2.5 at. % Ba2Y NbO6 (BYNTO) additions. Excellent magnetic flux-pinning at 77 K was obtained with remarkably high irreversibility fields greater than 10 T (YBCO-BYTO) and 11 T (YBCO-BYNTO), representing the highest ever achieved values in YBCO films.

  3. Microstructure dependence of the c-axis critical current density in second-generation YBCO tapes.

    SciTech Connect

    Jia, Y.; Welp, U.; Crabtree, G. W.; Kwok, W. K.; Malozemoff, A. P.; Rupich, M. W.; Fleshler, S.; Clem, J. R.

    2011-10-01

    C-axis current flow in high temperature superconductor (HTS) tape-shaped wires arises in configurations where the local wire axis is not perpendicular to the local magnetic field, such as in power cables with helically wound HTS tapes. The c-axis critical current density J{sub c}{sup c} has been recently found to be orders of magnitude lower than the ab-plane critical current density J{sub c}{sup ab}. Here we report on J{sub c}{sup c} (77 K, sf) values of various YBa{sub 2}Cu{sub 3}O{sub 7}-based (YBCO) tapes with different microstructures. Our results show that the value of J{sub c}{sup c} (77 K, sf) decreases significantly with increasing concentration of ab-plane stacking faults in YBCO thin films and that the critical current anisotropy {gamma} = J{sub c}{sup ab}/J{sub c}{sup c} can reach values as high as 2070, implying that in the highest-anisotropy tape, {approx}20% of the tape width carries c-axis current in a helically wound power cable.

  4. Microstructure dependence of the c-axis critical current density in second generation YBCO tapes

    SciTech Connect

    Jia, Y. Welp, U. Crabtree, G.W.; Kwok, W.K.; Malozemoff, A.P.; Rupich, M.W.; Fleshler, S.; Clem, J.R.

    2011-10-31

    C-axis current flow in high temperature superconductor (HTS) tape-shaped wires arises in configurations where the local wire axis is not perpendicular to the local magnetic field, such as in power cables with helically wound HTS tapes. The c-axis critical current density J{sub c}{sup c} has been recently found to be orders of magnitude lower than the ab-plane critical current density J{sub c}{sup ab}. Here we report on J{sub c}{sup c} (77 K, sf) values of various YBa{sub 2}Cu{sub 3}O{sub 7}-based (YBCO) tapes with different microstructures. Our results show that the value of J{sub c}{sup c} (77 K, sf) decreases significantly with increasing concentration of ab-plane stacking faults in YBCO thin films and that the critical current anisotropy {gamma} = J{sub c}{sup ab}/J{sub c}{sup c} can reach values as high as 2070, implying that in the highest-anisotropy tape, {approx}20% of the tape width carries c-axis current in a helically wound power cable.

  5. MOD approach for the growth of epitaxial CeO2 buffer layers on biaxially textured Ni W substrates for YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Bhuiyan, M. S.; Paranthaman, M.; Sathyamurthy, S.; Aytug, T.; Kang, S.; Lee, D. F.; Goyal, A.; Payzant, E. A.; Salama, K.

    2003-11-01

    We have grown epitaxial CeO2 buffer layers on biaxially textured Ni-W substrates for YBCO coated conductors using a newly developed metal organic decomposition (MOD) approach. Precursor solution of 0.25 M concentration was spin coated on short samples of Ni-3 at%W (Ni-W) substrates and heat-treated at 1100 °C in a gas mixture of Ar-4%H2 for 15 min. Detailed x-ray studies indicate that CeO2 films have good out-of-plane and in-plane textures with full-width-half-maximum values of 5.8° and 7.5°, respectively. High temperature in situ XRD studies show that the nucleation of CeO2 films starts at 600 °C and the growth completes within 5 min when heated at 1100 °C. SEM and AFM investigations of CeO2 films reveal a fairly dense microstructure without cracks and porosity. Highly textured YSZ barrier layers and CeO2 cap layers were deposited on MOD CeO2-buffered Ni-W substrates using rf-magnetron sputtering. Pulsed laser deposition (PLD) was used to grow YBCO films on these substrates. A critical current, Jc, of about 1.5 MA cm-2 at 77 K and self-field was obtained on YBCO (PLD)/CeO2 (sputtered)/YSZ (sputtered)/CeO2 (spin-coated)/Ni-W.

  6. Development of high-Ic processing for low cost YBCO coated conductors by multi-turn reel-to-reel crystallization large furnace for TFA-MOD process

    NASA Astrophysics Data System (ADS)

    Takagi, Y.; Takahashi, Y.; Nakaoka, K.; Yoshizumi, M.; Akagi, N.; Takahashi, S.; Izumi, T.; Shiohara, Y.

    Trifluoroacetates (TFA) -metal organic deposition (MOD) derived YBCO coated conductors are expected for many applications mainly due to cost-efficiency. High Ic and production rate are required for cost reduction in terms of /Am. Improvement of Ic performance and production rate has been studied in this work, focusing on the conversion process of TFA-MOD. YBCO precursor films with desired thickness were prepared by using the multi-turn reel-to-reel (RTR) -system of dip-coating and calcination. The precursor films were heat treated under different conditions including the interim annealing. Crystallization process was performed on the interim annealed samples by using a multi-turn RTR system. The conversion furnace was modified so that improved conditions such as higher gas flow rate, lower total pressure can be used, which improved the production rate in crystallization process to 15 m/h by accelerating YBCO growth rate. Adopting the interim annealing, Ic property increased about 30% compared with that prepared without the interim annealing. X-ray θ-2θ diffraction analysis showed that; the peak intensities of YBCO (005) in interim annealed samples were 1.5 times stronger compared with those prepared without the interim annealing. The interim annealing affected the crystallinity and microstructure, resulting in high Ic. Then, the improved process for crystallization was applied to long tapes fabrication. A 205 m-long YBCO coated conductors fabricated at 15 m/h with interim annealing showed high and uniform Ic performance throughout the tape; Ic(min.)=372 A/cm-w@77 K, s.f., standard deviation = 15.2 A (3.7%). Uniformity along transverse direction was also analyzed by striating a 54 m long tape (199.5 A/5 mm-widths) into 5 filaments and, the Ic value of each filament (1 mm-width) was confirmed to be uniform; 24.3-32.9 A.

  7. MOCVD growth of vertically aligned InGaN nanowires

    NASA Astrophysics Data System (ADS)

    Kuo, H. C.; Su Oh, Tae; Ku, P.-C.

    2013-05-01

    In this work, we report the growth of vertically aligned bulk InGaN nanowires (NWs) on r-plane sapphire substrate by metal organic chemical vapor deposition (MOCVD). Through the optimization process of growth conditions, such as growth temperature and pressure, we obtained high density InGaN NWs consisting of one (0001) polar- and two equivalent {1101} semi-polar planes. We have shown the highest InGaN NWs wire density of 8×108 cm-2,with an average diameter of 300 nm and a length of 2 μm. From results of photoluminescence (PL) at 30 K and 300 K, we observed the intense and broad emission peak from InGaN NWs at around 595 nm, and confirmed that the luminescence could be tuned from 580 nm to 660 nm by controlling the indium flow (TMIn) rate. Our results indicate that MOCVD-grown InGaN NWs can be effective absorbers of the blue-green range of solar spectrum and may be one of the good candidates for high efficiency photovoltaic devices targeting at blue-green photons.

  8. Strong flux pinning enhancement in YBa2Cu3O7-x films by embedded BaZrO3 and BaTiO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Ding, Fa-Zhu; Gu, Hong-Wei; Zhang, Teng; Wang, Hong-Yan; Qu, Fei; Qiu, Qing-Quan; Dai, Shao-Tao; Peng, Xing-Yu

    2013-07-01

    YBa2Cu3O7-x (YBCO) films with embedded BaZrO3 and BaTiO3 nanoparticles were fabricated by metalorganic deposition using trifluoroacetates (TFA-MOD). Both X-ray diffraction and transmission electron microscopy revealed that these BaZrO3 and BaTiO3 nanoparticles had random orientations and were distributed stochastically in the YBCO matrix. The unique combined microstructure enhances the critical current density (Jc) of the BaZrO3/BaTiO3 doped-YBCO films, while keeping the critical transition temperature (Tc) close to that in the pure YBCO films. These results indicate that BaZrO3 and BaTiO3 nanoparticles provide strong flux pinning in YBCO films.

  9. Microstructural features at the interface between laser ablated YBa2Cu3O7 films and LaAlO3 substrates

    NASA Astrophysics Data System (ADS)

    Guo, L. P.; Tian, Y. J.; Liu, J. Z.; Xu, S. F.; Li, L.; Zhao, Z. X.; Chen, Z. H.; Cui, D. F.; Lu, H. B.; Zhou, Y. L.; Yang, G. Z.

    1995-06-01

    The microstructure at the interface between YBa2Cu3O7(YBCO) thin film and (100)LaAlO3 substrate has been investigated by using transmission electron microscopy. It has been observed that two distinct microstructural features existed in the interface: (1) A thin transitional layer of Ba3Al2O6 was frequently observed and the YBCO thin film grown on it showed stacking faults. (2) Sharp interface with no transitional layer was also occasionally observed and the YBCO film grown on it was single crystalline. In rare cases, a low symmetry phase was observed near the surface of the LaAlO3 substrate, however, the distortion caused by the lattice mismatch between this phase and the YBCO did not affect the quality of the YBCO thin film.

  10. Fabrication and characterization of melt-processed YBCO

    SciTech Connect

    Sengupta, S.; Corpus, J.; Gaines, J.R. Jr.; Todt, V.R.; Zhang, X.F.; Miller, D.J.; Varanasi, C.; McGinn, P.J.

    1996-11-01

    Large domain YBCO are fabricated by using a melt processing technique for magnetic levitation applications. A Nd{sub 1+x}Ba{sub 2{minus}x}Cu{sub 3}O{sub y} seed is used to initiate grain growth and to control the orientation of YBCO grains. Samples as large as 2 inch have been fabricated by utilizing this method. Microstructural studies reveals two distinct regions in these levitators due to different growth mechanism along a/b and c axis. Some initial results on the mass production of these levitators are also reported.

  11. Demonstration of High Current Density YBCO Coated Conductors on RE2O3-Buffered Ni Substrates with Two New Alternative Architectures

    SciTech Connect

    Beach, D.B.; Chirayil, T.G.; Christen, D.K.; Cui, X.; Feenstra, R.; Goyal, A.; Kroeger, D.M.; Lee, D.F.; Martin, P.M.; Mathis, J.E.; Morrell, J.S.; Norton, D.P.; Paranthaman, M.; Specht, E.D.; Verebelyi, D.T.

    1999-07-12

    In continuation of our effort to develop single buffer layer architectures for YBCO (YBa2Cu3O7-g) coated tape conductors, we have studied RE2O3 (RE = Y, and rare earths) as candidate materials. Three types of crystal structures including the preferred cubic phase are known for the rare earth oxides. High quality simple cubic RE2O3 buffer layers were grown epitaxiahy on {100}<001> textured Ni substrates using both reactive evaporation and sol-gel processing. Detailed X-ray studies have shown that the Y2O3, Eu2O3, Gd2O3, and Yb2O3 were grown with a single epitaxial orientation. SEM micrographs indicated that both e-beam and sol-gel grown films were dense, continuous and crack free. High Jc YBCO films were grown on RE2O3-buffered Ni substrates with sputtered cap layers. Two new alternative buffer layer architectures were developed. A high Jc of 1.8 MA/cm2 at 77 K and self-field was obtained on YBCO films with a layer sequence of YBCO (pulsed laser deposition)/Yb2O3 (sputtered)/Y2O3 (e-beam)/Ni. Also, a high Jc of over 1 MA/cm2 at 77 K and self-field was obtained on YBCO films with a layer sequence of YBCO (ex-situ BaF2 process)/CeO2 (sputtered)YSZ sputtered)/RE2O3 (sol-gel or e-beam)Ni. The performance of sol-gel grown buffers approached the quality of e-beam grown buffers.

  12. Influence of stress in GaN crystals grown by HVPE on MOCVD-GaN/6H-SiC substrate.

    PubMed

    Zhang, Lei; Yu, Jiaoxian; Hao, Xiaopeng; Wu, Yongzhong; Dai, Yuanbin; Shao, Yongliang; Zhang, Haodong; Tian, Yuan

    2014-01-01

    GaN crystals without cracks were successfully grown on a MOCVD-GaN/6H-SiC (MGS) substrate with a low V/III ratio of 20 at initial growth. With a high V/III ratio of 80 at initial growth, opaque GaN polycrystals were obtained. The structural analysis and optical characterization reveal that stress has a great influence on the growth of the epitaxial films. An atomic level model is used to explain these phenomena during crystal growth. It is found that atomic mobility is retarded by compressive stress and enhanced by tensile stress. PMID:24569601

  13. Influence of stress in GaN crystals grown by HVPE on MOCVD-GaN/6H-SiC substrate

    PubMed Central

    Zhang, Lei; Yu, Jiaoxian; Hao, Xiaopeng; Wu, Yongzhong; Dai, Yuanbin; Shao, Yongliang; Zhang, Haodong; Tian, Yuan

    2014-01-01

    GaN crystals without cracks were successfully grown on a MOCVD-GaN/6H-SiC (MGS) substrate with a low V/III ratio of 20 at initial growth. With a high V/III ratio of 80 at initial growth, opaque GaN polycrystals were obtained. The structural analysis and optical characterization reveal that stress has a great influence on the growth of the epitaxial films. An atomic level model is used to explain these phenomena during crystal growth. It is found that atomic mobility is retarded by compressive stress and enhanced by tensile stress. PMID:24569601

  14. Wrinkling of YBa2Cu3O7-x film prepared by trifluoroacetate metal organic deposition

    NASA Astrophysics Data System (ADS)

    Jin, L. H.; Li, C. S.; Yu, Z. M.; Feng, J. Q.; Zhang, S. N.; Sulpice, A.; Wang, Y.; Zhang, P. X.

    2015-11-01

    YBa2Cu3O7-x (YBCO) films with wrinkles have been fabricated on LaAlO3(1 0 0) substrates by trifluoroacetate metal organic deposition (TFA-MOD). The decomposition behavior of YBCO-TFA gel and the formation mechanism of wrinkles were analyzed by thermal analysis, Fourier transform infrared spectroscopy, and atomic force microscopy. The effects of wrinkles on the texture, microstructure and critical current density of the final crystallized film were also investigated by X-ray diffraction and scanning electron microscopy. The heating rate in the decomposition process was a crucial parameter to control the wavelength and wave amplitude of wrinkles on the surface of YBCO precursor film. Furthermore, the wrinkles of precursor films were transformed into the ridges of crystallized films during the crystallization process. Large ridges resulted in the degradation of texture of YBCO crystallized films. The decrease of critical current density (Jc) of YBCO crystallized films could be ascribed to the formation of ridges, the segregated phases and the degradation of texture. It suggested that the smooth morphology of YBCO precursor films would be beneficial to the enhancement of Jc value.

  15. Microstructure Characteristics of High Lift Factor MOCVD REBCO Coated Conductors With High Zr Content

    SciTech Connect

    Galstyan, E; Gharahcheshmeh, MH; Delgado, L; Xu, AX; Majkic, G; Selvamanickam, V

    2015-06-01

    We report the microstructural characteristics of high levels of Zr-added REBa2Cu3O7-x (RE = Gd, Y rare earth) coated conductors fabricated by Metal Organic Chemical Vapor Deposition (MOCVD). The enhancements of the lift factor defined as a ratio of the in-field (3 T, B parallel to c-axis) critical current density (J(c)) at 30 K and self-field J(c) at 77 K have been achieved for Zr addition levels of 20 and 25 mol% via optimization of deposition parameters. The presence of strong flux pinning is attributed to the aligned nanocolumns of BaZrO3 and nanoprecipitates embedded in REBa2Cu3O7-x matrix with good crystal quality. A high density of BZO nanorods with a typical size 6-8 nm and spacing of 20 nm has been observed. Moreover, the high Zr content was found to induce a high density of intrinsic defects, including stacking faults and dislocations. The correlation between in-field performance along the c-axis and microstructure of (Gd, Y) BCO film with a high level of Zr addition is discussed.

  16. In Situ Fabrication of Reproducible YBCO/Au Planar Tunnel Junctions with an Artificial MgO Barrier

    NASA Astrophysics Data System (ADS)

    Furuyama, Masafumi; Iguchi, Ienari; Shirai, Koji; Kusumori, Takeshi; Ohtake, Hiroaki; Tomura, Shoji; Nasu, Masako

    1990-03-01

    The in situ fabrication of YBCO (YBa2Cu3Oy)/MgO/Au epitaxial planar tunnel junctions with a thin MgO barrier utilizing an electron-beam coevaporation technique is reported. The thickness of the MgO barrier is 3-12 nm and the tunnel resistance shows a strong dependence on barrier thickness. The fabricated tunnel junctions are highly reproducible and controllable. The observed tunnel characteristics contain the gap opening at about 20 mV and the anomaly around zero bias. The tunnel characteristics using the degraded films are also reported.

  17. Growth of epitaxial Y 2O 3 buffer layers on biaxially textured Ni-W substrates for YBCO coated conductors by MOD approach

    NASA Astrophysics Data System (ADS)

    Bhuiyan, M. S.; Paranthaman, M.; Kang, S.; Lee, D. F.; Salama, K.

    2005-06-01

    We have grown epitaxial Y 2O 3 buffer layers on biaxially textured Ni-W substrates for YBCO coated conductors using a newly developed metal organic decomposition (MOD) approach. Y 2O 3 precursor solution of 0.25 M concentration was spin coated on short samples of Ni-3 at.%W (Ni-W) substrates and heat-treated at 1150 °C in a gas mixture of Ar-4% H 2 for an hour. Detailed X-ray studies indicate that Y 2O 3 films have good out-of-plane and in-plane textures with full-width-half-maximum values of 6.22° and 7.51°, respectively. SEM and AFM investigations of Y 2O 3 films reveal a fairly dense and smooth microstructure without cracks and porosity. Highly textured YSZ barrier layers and CeO 2 cap layers were deposited on MOD Y 2O 3-buffered Ni-W substrates using rf-magnetron sputtering. Pulsed laser deposition was used to grow YBCO films on these substrates. A critical current, Jc, of about 1.21 MA/cm 2 at 77 K and self-field was obtained on YBCO (PLD)/CeO 2 (sputtered)/YSZ (sputtered)/Y 2O 3 (spin-coated)/Ni-W.

  18. Investigation of DC current injection effect on the microwave characteristics of HTS YBCO microstrip resonators

    NASA Astrophysics Data System (ADS)

    Nurgaliev, T.; Blagoev, B.; Mateev, E.; Neshkov, L.; Strbik, V.; Uspenskaya, L.; Nedkov, I.; Chromik, Š.

    2014-03-01

    The DC current injection effect from a ferromagnetic (FM) La0.7Sr0.3MnO3 (LSMO) to a high temperature superconducting (HTS) Y1Ba2Cu3O7-x (YBCO) thin film was investigated by the microwave surface impedance measurements in a FM/HTS structure, formed as a microstrip resonator for improving the sensitivity of the experiments. The quality factor and the resonance frequency of this structure were found to strongly depend on the current strength, injected from the LSMO electrode into the HTS microstrip electrode. The magnetic penetration depth and the quasiparticle conductivity of the HTS component were determined to increase under DC current injection process, which in all probability stimulated breaking of Cooper pairs and led to a decrease of the superfluid concentration and an increase of the normal fluid concentration without significantly affecting the relaxation time of the quasiparticles.

  19. Radiation induced modifications on microstructure and related properties of high temperature superconductor YBCO

    NASA Astrophysics Data System (ADS)

    Marhas, Manmeet Kaur; Balakrishnan, K.; Saravanan, P.; Ganesan, V.; Srinivasan, R.; Kanjilal, D.; Mehta, G. K.; Vedwyas, M.; Ogale, S. B.; Pai, S. P.; Ramachandra Rao, M. S.; Pinto, R.; Mohan Rao, G.; Senthilnathan, S.; Mohan, S.

    Role of swift heavy ion irradiation on the modification of transport and structural properties of high temperature superconductors is studied. Good quality YBCO thin films prepared by high pressure oxygen sputtering and laser ablation were used in this investigation. Resistivity and atomic force microscopy (AFM) were mainly used to probe superconducting and microstructural modifications resulted from the irradiation of high energy and heavy ions like 100 MeV oxygen and 200 MeV silver. Radiation induced sputtering or erosion is likely to be a major disastrous component of such high energy irradiation that could be powerful in masking phase coherence effects, atleast in grain boundaries. The extent of damage/nature of defects other than columnar defects produced by swift heavy ions is discussed in the light of AFM measurements. The effect of high energy oxygen ion irradiation is anomalous. A clear annealing effect at higher doses is seen.

  20. High Tc YBCO superconductor deposited on biaxially textured Ni substrate

    DOEpatents

    Budai, John D.; Christen, David K.; Goyal, Amit; He, Qing; Kroeger, Donald M.; Lee, Dominic F.; List, III, Frederick A.; Norton, David P.; Paranthaman, Mariappan; Sales, Brian C.; Specht, Eliot D.

    1999-01-01

    A superconducting article includes a biaxially-textured Ni substrate, and epitaxial buffer layers of Pd (optional), CeO.sub.2 and YSZ, and a top layer of in-plane aligned, c-axis oriented YBCO having a critical current density (J.sub.c) in the range of at least 100,000 A/cm.sup.2 at 77 K.

  1. Testing of an HTS Power Cable Made from YBCO Tapes

    SciTech Connect

    Gouge, Michael J; Duckworth, Robert C; Demko, Jonathan A; Rey, Christopher M; Lindsay, David T; Roden, Mark L; Tolbert, Jerry Carlton

    2007-01-01

    Oak Ridge National Laboratory (ORNL) has designed, built, and tested a 1.25-m-long, prototype high temperature superconducting (HTS) power cable made from second-generation YBa2Cu3Ox (YBCO)-coated conductor tapes. Electrical tests of this cable were performed in liquid nitrogen at 77 K. DC testing of the HTS cable included determination of the V-I curve with a critical current of about 2100 A, which was consistent with the critical currents of the two layers of 4.4-mm wide YBCO tapes. AC testing of the cable was conducted at currents up to about 1500 Arms. The ac losses were determined calorimetrically by measuring the response of a calibrated temperature sensor placed on the former and electrically by use of a Rogowski coil with a lock-in amplifier. Over-current testing was conducted at peak current values up to 4.9 kA for pulse lengths of 0.3-0.5 s. Test results are compared to earlier data from a 1.25-m-long power cable made from 1-cm-wide YBCO tapes and also comparable BSCCO cables. This commercial-grade HTS cable demonstrated the feasibility of second-generation YBCO tapes in an ac cable application.

  2. MOCVD growth of AlGaN UV LEDs

    SciTech Connect

    Han, J.; Crawford, M.H.

    1998-09-01

    Issues related to the MOCVD growth of AlGaN, specifically the gas-phase parasitic reactions among TMG, TMA, and NH{sub 3}, are studied using an in-situ optical reflectometer. It is observed that the presence of the well-known gas phase adduct (TMA: NH{sub 3}) could seriously hinder the incorporation behavior of TMGa. Relatively low reactor pressures (30--50 Torr) are employed to grow an AlGaN/GaN SCH QW p-n diode structure. The UV emission at 360 nm (FWHM {approximately} 10 nm) represents the first report of LED operation from an indium-free GaN QW diode.

  3. MOCVD manifold switching effects on growth and characterization

    NASA Astrophysics Data System (ADS)

    Clark, Ivan O.; Fripp, Archibald L.; Jesser, William A.

    1991-02-01

    A combined modeling and experimental approach is used to quantify the effects of various manifold components on the switching speed in metalorganic chemical vapor deposition (MOCVD). In particular, two alternative vent-run high-speed switching manifold designs suitable for either continuous or interrupted growth have been investigated. Both designs are incorporated in a common manifold, instrumented with a mass spectrometer. The experiments have been performed using nitrogen as the transport gas and argon as the simulated source gas. The advantages and limitations of two designs are discussed. It is found that while constant flow manifold switching systems may have fluid dynamic advantages, care must be taken to minimize sections of the supply manifold with low flow rates if rapid changes in alloy composition are required.

  4. Effect of crystal orientation on anisotropic etching and MOCVD growth of grooves on GaAs

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G.; Landis, Geoffrey A.; Wilt, David M.

    1989-01-01

    Grooves can be formed on GaAs by wet-chemical anisotropic etching of surfaces masked by photoresist stripes. The effect of crystal orientation on the shape of the grooves etched and on subsequent epitaxial growth by MOCVD is presented. The polar lattice increases the complexity of the etching and growth processes. The slow-etch planes defined by anisotropic etching are not always the same as the growth facets produced during MOCVD deposition, especially for deposition on higher order planes.

  5. Study of TiO2 nanomembranes obtained by an induction heated MOCVD reactor

    NASA Astrophysics Data System (ADS)

    Crisbasan, A.; Chaumont, D.; Sacilotti, M.; Crisan, A.; Lazar, A. M.; Ciobanu, I.; Lacroute, Y.; Chassagnon, R.

    2015-12-01

    Nanostructures of TiO2 were grown using the metal oxide chemical vapor deposition (MOCVD) technique. The procedure used induction heating on a graphite susceptor. This specific feature and the use of cobalt and ferrocene catalysts resulted in nanomembranes never obtained by common MOCVD reactors. The present study discusses the preparation of TiO2 nanomembranes and the dependence of nanomembrane structure and morphology on growth parameters.

  6. Thermal diffusion and quench propagation in YBCO pancake coils wound with ZnO and Mylar insulations

    NASA Astrophysics Data System (ADS)

    Sumption, M. D.; Majoros, M.; Susner, M.; Lyons, D.; Peng, X.; Clark, C. F.; Lawless, W. N.; Collings, E. W.

    2010-07-01

    The thermal diffusion properties of several different kinds of YBCO (yttrium barium copper oxide) insulations and the quench properties of pancake coils made using these insulations were studied. Insulations investigated include Nomex, Kapton, and Mylar, as well as insulations based on ZnO, Zn2GeO4, and ZnO-Cu. Nomex, Kapton, and Mylar, chosen for their availability and ease of use, were obtained as thin ribbons, while the ZnO based insulations were chosen for their high thermal conductivity and were applied by a thin film technique. Initially, short stacks of YBCO conductors with interlayer insulation, epoxy, and a central heater strip were made and later measured as regards their thermal conductivity in liquid nitrogen. Subsequently, three different pancake coils were made. The first two were smaller, each using one meter total of YBCO tape present as four turns around a G-10 former. One of these smaller coils used Mylar insulation co-wound with the YBCO tape, the other used YBCO tape onto which ZnO based insulation had been deposited. One larger coil was made which used 12 total meters of ZnO insulated tape and had 45 turns. Temperature gradients were measured and thermal conductivities were estimated from these coils; the results obtained were compared to those for the short stacks. Quench propagation velocity measurements were performed on the coils (77 K, self-field) by applying a DC current and then using a heater pulse to initiate a quench. Radial NZP (normal zone propagation velocity) values (0.02-1 mm s - 1) were two orders of magnitude lower than axial values (~10-20 mm s - 1). Nevertheless, the quenches were generally seen to propagate radially within the coils, in the sense that any given turn in the coil is driven normal by the turn underneath it. This was due to the fact that while the radial NZP is much lower than the NZP along the conductor (~100 ×) the distance by which the normal zone must expand longitudinally is much larger than the distance

  7. Study of superconducting a-axis oriented YBa 2Cu 3O 7-δ thin films deposited on Y 2O 3/YSZ/Si with PrBa 2Cu 3O 7-δ seed layer

    NASA Astrophysics Data System (ADS)

    Rosova, Alica; Chromik, Stefan; Benacka, Stefan; Wuyts, Bart

    1995-02-01

    Epitaxial a-axis oriented YBa 2Cu 3O 7-δ (YBCO) superconducting thin films have been grown by off-axis magnetron sputtering on Y 2O 3/YSZ/Si substrates with PrBa 2Cu 3O 7-δ (PBCO) seed layer. The YBCO thin films were deposited immediately after the on-axis magnetron sputtering of PBCO. XRD analyses show that the a-axis volume fraction for 120 nm thick YBCO films varies with substrate temperature during PBCO deposition and its maximum value is higher than 98%. The TEM study shows the clear dependence between the character of the R- T dependence and the microstructure of our YBCO thin films, which varies with the change of the volume ratio of a-axis to c-maxis oriented YBCO.

  8. X-ray diffraction characterization of thin superconductive films

    SciTech Connect

    Kozaczek, K.J.; Watkins, T.R.; Book, G.W.; Carter, W.B.

    1995-12-31

    The physical and mechanical properties of thin films are often different from the properties of bulk material and are dictated by the film/substrate orientation relationship, crystal anisotropy and crystalgraphic texture of the film. X-ray diffraction texture analysis provides information about preferential film growth and can be used for optimization of deposition parameters and prediction of properties of thin films. An x-ray back reflection technique using the Braga-Brentano geometry with experimental corrections for absorption and defocusing was used to study thin ceramic films deposited by combustion chemical vapor deposition (CCVD). The film/substrate orientation relationships of YBa{sub 2}Cu{sub 3}O{sub x} (YBCO) superconducting thin films deposited via CCVD on single crystal MgO and polycrystalline silver substrates were studied. The as-deposited films on single crystal (100) MgO substrates showed strong preferential growth with the basal plane parallel to the substrate surface (c-axis up growth). Texture analysis showed two in-plane alignment orientations of the film with respect to the substrate, with YBCO [100] and [110] aligned with the [100] MgO substrate. YBCO films deposited on cold-rolled polycrystalline silver displayed c-axis up growth indicating that the orientation of the polycrystalline substrate (brass type texture) did not induce detectable in-plane preferential growth of the YBCO.

  9. A Comparative Study of a Series of Dimethylgold(III) Complexes with S,S Chelating Ligands Used as MOCVD Precursors

    NASA Astrophysics Data System (ADS)

    Turgambaeva, Asiya; Parkhomenko, Roman; Aniskin, Vladimir; Krisyuk, Vladislav; Igumenov, Igor

    Dimethylgold(III) complexes with S,S donor ligands having AuC2S2 coordination core are compared as precursors for gold MOCVD. Three of them are liquids, the fourth one is low-melting compound. They are non-sensitive to air and light, stable under storage, do not require special handling conditions, and show a good volatility and sufficient vaporization stability. Based on monitoring of the gas phase during the programmed heating of the compound vapor in vacuum, in hydrogen and in oxygen presence, the information concerning stability of the precursor in the gas phase and gaseous products of thermolysis was obtained. It was established that decomposition mechanism in the presence of the studied gas- reactants changed in comparison with vacuum only for diethyldithiocarbamate complex. MOCVD experiments have been performed within the temperature range 210-300 oC with and without hydrogen or oxygen. The films obtained in hydrogen presence were more thick indicating higher growth rate. Effect of gas-reactant on the morphology of the films deposited is discussed.

  10. Temperature and Magnetic Field Dependence of Critical Currents in YBCO Coated Conductors with Processing-Induced Variations in Pinning Properties

    SciTech Connect

    Gapud, Albert Agcaoili; Feenstra, Roeland; Christen, David K; Thompson, James R; Holesinger, T. G.

    2005-01-01

    Several applications of high-temperature super-conducting wire require high currents at intermediate magnetic fields B and over a range of orientations; however, such conditions are at present achievable only at low temperatures (-30 K). The goal of this study is to determine the feasibility of higher operating temperatures for these applications by investigating temperature dependent, low- and high-field pinning properties of YBCO coated conductor samples. The YBCO films were grown on RABiTS templates by a PVD ex situ BaF{sub 2} process. Variations in pinning properties were induced by introducing excess yttrium (Y) in the precursor and controllably increasing the growth rate. The main result is a more uniform dependence of J{sub c} over all orientations of B, along with high irreversibility field B{sub irr} and high critical current densities J{sub c}. Results also show that for films with various pinning properties and processed under different conditions the self-field J{sub c} at 77 K is an effective indicator of performance in the temperatures and fields of interest.

  11. RAPID COMMUNICATION: Large-area uniform ultrahigh-Jc YBa2Cu3O7-x film fabricated by the metalorganic deposition method using trifluoroacetates

    NASA Astrophysics Data System (ADS)

    Araki, Takeshi; Yamagiwa, Katsuya; Hirabayashi, Izumi; Suzuki, Katsumi; Tanaka, Shoji

    2001-07-01

    Ultrahigh-Jc YBa2Cu3O7-x (YBCO) films have been successfully fabricated by the metalorganic deposition method using a trifluoroacetate coating solution which is prepared by a newly developed purification technique, the solvent-into-gel (SIG) method. The prepared pure coating solution has less than 0.25% impurities and has a wide flexibility in process conditions to obtain high-Jc YBCO film. Using this feature, we have successfully formed 50 mm diameter YBCO films, which have a critical current density over 10 MA cm-2 (77 K, 0 T) on LaAlO3 single crystalline substrates.

  12. Physical and Material Properties of Yttrium Barium Copper Oxide High Critical Temperature Superconducting Thin Films.

    NASA Astrophysics Data System (ADS)

    Ma, Qiyuan

    1990-01-01

    A simple method of using layered structures and rapid thermal annealing to produce Y_1 Ba_2 Cu_3 O_{7-x} (YBCO) superconducting thin films is presented. Material properties of the films depend strongly on the processing conditions, the film stoichiometry, and the substrates. The films with critical temperature (T_{ rm c}) higher than liquid nitrogen temperature (77 K) have been made on various substrates including magnesium oxide, sapphire, and silicon. The best film was obtained on a MgO substrate with T_{rm c} of 84 K. Silicon diffusion and reaction with oxygen during a high temperature anneal degrade the superconductivity of the film on a Si substrate. Using a buffer layer of gold, the Si-YBCO interaction is greatly reduced. Typical resistivity of the film shows a linear temperature dependence which may be attributed to an electron -phonon interaction. Anisotropic resistance behavior has been observed due to the layered structures. Different metal contacts to the YBCO films have been used to study the chemical and electrical properties of metal-YBCO film interfaces. Gold has been found nonreactive to YBCO film, thus, it has the lowest contact resistivity. Near the T_{rm c}, the contact resistivity of a Au-YBCO contact approaches zero. This may be due to the proximity effect. Other metals such as Pt, Pd, Sn and Ti, react with the YBCO film and form thin oxide layers at the interfaces. The oxide layer acts as an insulating barrier which forbids the proximity effect and causes a large contact resistivity. The structural and electrical properties of the Si-YBCO intermixed film have been studied for different thicknesses of the silicon layers. A novel patterning technique of using Si-YBCO intermixing has been developed for fabricating the YBCO superconducting device structures. A superconductor sample has a critical current value I _{rm c}. Below the I _{rm c} the material is superconducting, and above I_{rm c} the sample has a finite resistance. Based on this effect

  13. Unique magnetic structure of YbCo2Si2

    NASA Astrophysics Data System (ADS)

    Mufti, N.; Kaneko, K.; Hoser, A.; Gutmann, M.; Geibel, C.; Krellner, C.; Stockert, O.

    2016-07-01

    We report on the results of powder and single-crystal neutron diffraction to investigate the magnetic order in YbCo2Si2 below the Néel temperature TN=1.7 K in detail. Two different magnetically ordered phases can clearly be distinguished. At lowest temperatures a commensurate magnetic structure with a propagation vector k1=(0.25 0.25 1 ) is found, while the intermediate phase (T >0.9 K) is characterized by an incommensurate magnetic structure with k2=(0.25 0.086 1 ) . The magnetic structure in YbCo2Si2 is in marked contrast to all other known R Co2Si2 compounds (R = rare earth element) likely due to some itineracy of the Yb 4 f states being responsible for the magnetism.

  14. Temperature dependence of nanoscale friction for Fe on YBCO

    NASA Astrophysics Data System (ADS)

    Altfeder, Igor; Krim, Jacqueline

    2012-05-01

    A magnetic probe microscopy study of levitation and atomic-scale friction is reported for Fe on YBCO (Tc = 92.5 K) in the temperature range 65-293 K. Below Tc, the friction coefficient is constant and exhibits no correlation with the strength of superconducting levitation forces. Above Tc, the friction coefficient increases progressively, and nearly doubles between Tc and room temperature. The results are discussed within the context of the underlying atomic-scale electronic and phononic mechanisms that give rise to friction, and it is concluded that contact electrification and static electricity may play a significant role in the non-superconducting phase. Given that the properties of YBCO can be finely tuned, the results point the way to a variety of interesting studies of friction and superconductors.

  15. Twin engineering for high critical current densities and twin boundary energy measurement in melt processed YBCO

    NASA Astrophysics Data System (ADS)

    Mei, Linfeng

    It has been proven that twin boundaries in YBa2Cu 3O7-delta (YBCO) are effective flux pinning centers. By increasing the twin density of a YBCO sample, it is possible to achieve a high critical current density (Jc). In this work, twin engineering for high critical current densities and strong flux pinning has been achieved in melt processed YBCO by increasing the annealing temperature up to 680°C. When the isothermal oxygenation temperature increases from 450°C to 680°C, the average twin boundary spacing of the samples decreases significantly, and its critical current density and flux pinning force are greatly increased. The prerequisites for twin boundary engineering for high critical current densities and strong flux pinning are also pointed out. For the first time, temperature dependent twin boundary energies (gammatw's) of melt processed YBCO are measured by the twin spacing method and the twin tip or shape method, and the geometrical factor alpha in the twin spacing method is estimated. As expected, the twin boundary energy of YBCO decreases with increasing temperature. In addition, the correlation between Jc and the concentrations of Y2BaCuO5 (211) and Samarium (Sm) in the melt-textured growth (MTG) YBCO has been studied, as well as the distributions of 211 and Sm in the MTG YBCO pellets. All our results can be applied towards microstructure tailoring for a high Jc and strong flux pinning in YBCO, especially in bulk YBCO samples.

  16. Influence of oxygen partial pressure and silver additions on microstructure and related properties of YBCO superconductors

    SciTech Connect

    Singh, J.P.; Joo, J.; Guttschow, R.; Poeppel, R.B.

    1992-02-01

    Microstructure has a great influence on the mechanical and superconducting properties of YBCO. Mechanical properties of YBCO can be improved by both modifying the monolithic microstructure and developing composites of YBCO with silver (Ag). When monolithic YBCO was sintered to high densities ({approx} 91%) at a relatively low temperature ({approx} 910{degrees}C) by controlling oxygen partial pressure during sintering, the result was a small-grain microstructure (average grain size {approx} 5 {mu}m) and hence a high strength of 191 {plus minus} 7 MPa. Addition of Ag as a second phase further improved the strength of YBCO. Composites of YBCO with 10 to 15 vol % Ag has a strength of 225 {plus minus} 6 MPa and a fracture toughness of 3.3 {plus minus} 0.2 MPa{radical}m. These improvements are believed to be due to compressive stresses in the YBCO matrix as a result of thermal mismatch between the YBCO and Ag phases. Furthermore, the Ag particles may provide increased resistance to crack propagation by pinning the crack. On the other hand, addition of Ag as a dopant to substitute for Cu sites in YBCO has a profound but nonmonotonic effect on grain microstructure and the resulting critical current density.

  17. Influence of oxygen partial pressure and silver additions on microstructure and related properties of YBCO superconductors

    SciTech Connect

    Singh, J.P.; Joo, J.; Guttschow, R.; Poeppel, R.B.

    1992-02-01

    Microstructure has a great influence on the mechanical and superconducting properties of YBCO. Mechanical properties of YBCO can be improved by both modifying the monolithic microstructure and developing composites of YBCO with silver (Ag). When monolithic YBCO was sintered to high densities ({approx} 91%) at a relatively low temperature ({approx} 910{degrees}C) by controlling oxygen partial pressure during sintering, the result was a small-grain microstructure (average grain size {approx} 5 {mu}m) and hence a high strength of 191 {plus_minus} 7 MPa. Addition of Ag as a second phase further improved the strength of YBCO. Composites of YBCO with 10 to 15 vol % Ag has a strength of 225 {plus_minus} 6 MPa and a fracture toughness of 3.3 {plus_minus} 0.2 MPa{radical}m. These improvements are believed to be due to compressive stresses in the YBCO matrix as a result of thermal mismatch between the YBCO and Ag phases. Furthermore, the Ag particles may provide increased resistance to crack propagation by pinning the crack. On the other hand, addition of Ag as a dopant to substitute for Cu sites in YBCO has a profound but nonmonotonic effect on grain microstructure and the resulting critical current density.

  18. STANFORD IN-SITU HIGH RATE YBCO PROCESS: TRANSFER TO METAL TAPES AND PROCESS SCALE UP

    SciTech Connect

    Malcolm R. Beasley; Robert H.Hammond

    2009-04-14

    Executive Summary The materials science understanding of high rate low cost processes for Coated Conductor will benefit the application to power utilities for low loss energy transportation and power generation as well for DOD applications. The research in this program investigated several materials processing approaches that are new and original, and are not being investigated elsewhere. This work added to the understanding of the material science of high rate PVD growth of HTSC YBCO assisted by a liquid phase. A new process discovered uses amorphous glassy precursors which can be made at high rate under flexible conditions of temperature and oxygen, and later brought to conditions of oxygen partial pressure and temperature for rapid conversion to YBCO superconductor. Good critical current densities were found, but further effort is needed to optimize the vortex pinning using known artificial inclusions. A new discovery of the physics and materials science of vortex pinning in the HTSC system using Sm in place of Y came at growth at unusually low oxygen pressure resulting in clusters of a low or non superconducting phase within the nominal high temperature phase. The driving force for this during growth is new physics, perhaps due to the low oxygen. This has the potential for high current in large magnetic fields at low cost, applicable to motors, generators and transformers. The technical demands of this project were the motivation for the development of instrumentation that could be essential to eventual process scale up. These include atomic absorption based on tunable diode lasers for remote monitoring and control of evaporation sources (developed under DARPA support), and the utility of Fourier Transform Infrared Reflectivity (FTIR) for aid in the synthesis of complex thin film materials (purchased by a DURIP-AFOSR grant).

  19. Current-Voltage Measurements in a 2G YBCO Coil

    SciTech Connect

    Rey, Christopher M; Duckworth, Robert C

    2007-01-01

    Abstract- The Oak Ridge National Laboratory in collaboration with American Superconductor Corporation and Cryomagnetics Inc. has designed, fabricated, and tested an HTS coil wound with second-generation (2G) YBCO coated conductor tape. The purpose of the HTS coil project was to study the quench characteristics in 2G YBCO coils at 77 K and lower temperatures (~ 30-45 K). These quench characteristics were investigated in both a pool boiling LN2 environment and in a conduction cooled configuration at ~ 30 K and 45 K. Transport critical current (Ic) measurements taken on the very first thermal cycle of the YBCO coil in pool boiling LN2 showed an Ic ~ 31 A corresponding to a central magnetic field of 0.32 T. The measured Ic value was consistent with the calculated value using the calculated maximum perpendicular B-field component and the measured short sample Ic at 77 K. Subsequent Ic measurements taken in the conduction cooling configuration at 34 K and 45 K, showed a steady-state Ic ~ 45-49 A and 38-44 A, respectively. These Ic values were significantly lower than the calculated value assuming a literature derived temperature dependent Ic of the 2G YBCO tape. A steady degradation was observed in the Ic of the coil with each successive thermal cycle. In addition, the coil was also pulse tested up to 1-T in non-steady state transient conditions and for ramp rates varying between 0.01 and 5 A/s. The problems and limitations encountered during testing of this new type of 2G coil is briefly discussed.

  20. 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.

  1. The Effect of Axial Stress on YBCO Coils

    SciTech Connect

    Sampson, W.; Anerella, M.; Cozzolino, J.P.; Gupta, R.C.; Shiroyanagi, Y.; Evangelou, E.

    2011-03-28

    The large aspect ratio of typical YBCO conductors makes them ideal for constructing solenoids from pancake style coils. An advantage of this method is that each subunit can be tested before assembly into the finished magnet. The fact that conductors are available in relatively short lengths is another reason for using such a fabrication technique. The principal drawback is the large number of joints required to connect the coils together. When very high field solenoids such as those contemplated for the muon collider are built in this way the magnetic forces between pancakes can be very large. Extensive measurements have been made on the effect of stress on short lengths of conductor, but there is little or no data on the effect of intercoil loading. The experiment described in this paper was designed to test the ability of YBCO coils to withstand these forces. A spiral wound 'pancake' coil made from YBCO coated conductor has been stressed to a pressure of 100MPa in the axial direction at 77K. In this case axial refers to the coil so that the force is applied to the edge of the conductor. The effect on the critical current was small and completely reversible. Repeatedly cycling the pressure had no measureable permanent effect on the coil. The small current change observed exhibited a slight hysteretic behaviour during the loading cycle.

  2. Superconducting YBa 2Cu 3O 7- δ thin film grown on metallic film evaporated on MgO

    NASA Astrophysics Data System (ADS)

    Verdyan, A.; Azoulay, J.; Lapsker, I.

    2001-03-01

    At present it is commonly accepted that thin film formation of YBa 2Cu 3O 7- δ (YBCO) on conducting substrate is one of the keys to further development of advanced devices in the microelectronic and other applications. We have grown YBCO thin films by resistive evaporation technique on MgO coated with metallic layers (Ni or Ag). A simple inexpensive vacuum system equipped with resistively heated boats for metal and precursor mixture of yttrium, copper and barium fluoride powders was used. X-ray diffraction (XRD) and scanning electron microscopy techniques were used for texture, morphology and surface analyses respectively. Electrical and magnetical properties were determined by a standard dc four-probe method. The way of heating process is shown to be critical parameter in the film quality. The physical and electrical properties of the YBCO films are discussed in light of the fact that XRD measurements done on the metallic buffer layers have revealed a multicrystalline structure.

  3. MOCVD process technology for affordable, high-yield, high-performance MESFET structures. Phase 3: MIMIC

    NASA Astrophysics Data System (ADS)

    1993-01-01

    Under the MIMIC Program, Spire has pursued improvements in the manufacturing of low cost, high quality gallium arsenide MOCVD wafers for advanced MIMIC FET applications. As a demonstration of such improvements, Spire was tasked to supply MOCVD wafers for comparison to MBE wafers in the fabrication of millimeter and microwave integrated circuits. In this, the final technical report for Spire's two-year MIMIC contract, we report the results of our work. The main objectives of Spire's MIMIC Phase 3 Program, as outlined in the Statement of Work, were as follows: Optimize the MOCVD growth conditions for the best possible electrical and morphological gallium arsenide. Optimization should include substrate and source qualification as well as determination of the optimum reactor growth conditions; Perform all work on 75 millimeter diameter wafers, using a reactor capable of at least three wafers per run; and Evaluate epitaxial layers using electrical, optical, and morphological tests to obtain thickness, carrier concentration, and mobility data across wafers.

  4. Influence of Natural Convection and Thermal Radiation Multi-Component Transport in MOCVD Reactors

    NASA Technical Reports Server (NTRS)

    Lowry, S.; Krishnan, A.; Clark, I.

    1999-01-01

    The influence of Grashof and Reynolds number in Metal Organic Chemical Vapor (MOCVD) reactors is being investigated under a combined empirical/numerical study. As part of that research, the deposition of Indium Phosphide in an MOCVD reactor is modeled using the computational code CFD-ACE. The model includes the effects of convection, conduction, and radiation as well as multi-component diffusion and multi-step surface/gas phase chemistry. The results of the prediction are compared with experimental data for a commercial reactor and analyzed with respect to the model accuracy.

  5. Microstructure and properties of YBa2Cu3O7 - delta thin films with BaO precipitates

    NASA Astrophysics Data System (ADS)

    Tian, Y. J.; Guo, L. P.; Li, L.; Zhou, Y. Q.; Yang, Y.; Zhao, Z. X.; Xu, S. F.; Lu, H. B.; Zhou, Y. L.; Chen, Z. H.; Cui, D. F.; Yang, G. Z.

    1994-07-01

    BaO precipitates with sizes between 10-100 nm in laser ablated YBa2Cu3O7-δ (YBCO) thin films on Y-stabilized Zirconia substrates have been identified by x-ray diffraction and transmission electron microscopy. The precipitates exhibit equiaxed shapes and grow epitaxially inside and on the surface of the YBCO films, with (001)BaO plane parallel to the a,b plane of YBCO. Some of these smaller precipitates and BaO/YBCO boundaries probably provide potential pinning sites for magnetic flux lines, which might contribute to the observed increase of critical current density with magnetic field B under B≤500 G in the case of B perpendicular to the c axis of the film.

  6. CVD method for forming B.sub.i -containing oxide superconducting films

    DOEpatents

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

    1994-01-01

    Films of high T.sub.c Bi-Sr-Ca-Cu-O superconductor have been prepared by MOCVD using volatile metal organic precursors and water vapor. The metal organic precursors are volatized along with a bismuth source, such as Bi(C.sub.6 H.sub.5).sub.3, deposited on a heated substrate to form a film, and annealed.

  7. Fabrication of hybrid thin film structures from HTS and CMR materials

    NASA Astrophysics Data System (ADS)

    Sojková, M.; Štrbík, V.; Nurgaliev, T.; Chromik, Š.; Dobročka, E.; Španková, M.; Blagoev, B.; Gál, N.

    2016-03-01

    We present the preparation of bilayers from high-temperature superconductors (HTS) and half-metallic ferromagnetic (FM) manganite with a colossal magnetoresistance (CMR). We used YBa2Cu3O7-x (YBCO) and Tl2Ba2CaCu2O8 (TBCCO) thin films as a HTS material and La0.67Sr0.33MnO3 (LSMO) film as a CMR material. In the case of YBCO/LSMO, we prepared FM/HTS heterostructure for studying the spin-polarized current injection effect on the electrical properties of the YBCO strip in dc or low-frequency regimes and on the microwave characteristics of the strip. For the first time, we report the preparation of a TBCCO/LSMO bilayer. In some applications, the TBCCO offers better parameters (higher working temperature, lower surface resistance, lower 1/f noise) than YBCO.

  8. Substrate effect on thermal stability of superconductor thin films in the peritectic melting.

    PubMed

    Chen, Y Y; Fang, T F; Yan, S B; Yao, X; Tao, B W

    2012-05-31

    Systematic experiments were performed by in situ observation of the YBa(2)Cu(3)O(z) (Y123 or YBCO) melting. Remarkably, the superheating phenomenon was identified to exist in all commonly used YBCO thin films, that is, films deposited on MgO, LaAlO(3) (LAO), and SrTiO(3) (STO) substrates, suggesting a universal superheating mode of the YBCO film. Distinctively, YBCO/LAO films were found to possess the highest level of superheating, over 100 K, mainly attributed to the lattice match effect of LAO substrate, that is, its superior lattice fit with Y123 delaying the Y123 dissolving and inferior lattice matching with Y(2)BaCuO(5) (Y211) delaying the Y211 nucleation. Moreover, strong dependence of the thermal stability on the substrate material for Y123 films was also found to be associated with the substrate wettability by the liquid and the potential element doping from the substrate. Most importantly, the understanding of the superheating behavior is widely valid for more film/substrate constructions that have the same nature as the YBCO film/substrate. PMID:22540312

  9. Thin film cadmium telluride, zinc telluride, and mercury zinc telluride solar cells

    SciTech Connect

    Chu, T.L. )

    1992-04-01

    This report describes research to demonstrate (1) thin film cadmium telluride solar cells with a quantum efficiency of 75% or higher at 0. 44 {mu}m and a photovoltaic efficiency of 11.5% or greater, and (2) thin film zinc telluride and mercury zinc telluride solar cells with a transparency to sub-band-gap radiation of 65% and a photovoltaic conversion efficiency of 5% and 8%, respectively. Work was directed at (1) depositing transparent conducting semiconductor films by solution growth and metal-organic chemical vapor deposition (MOCVD) technique, (2) depositing CdTe films by close-spaced sublimation (CSS) and MOCVD techniques, (3) preparing and evaluating thin film CdTe solar cells, and (4) preparing and characterizing thin film ZnTe, CD{sub 1-x}Zn{sub 1-x}Te, and Hg{sub 1-x}Zn{sub x}Te solar cells. The deposition of CdS films from aqueous solutions was investigated in detail, and their crystallographic, optical, and electrical properties were characterized. CdTe films were deposited from DMCd and DIPTe at 400{degrees}C using TEGa and AsH{sub 3} as dopants. CdTe films deposited by CSS had significantly better microstructures than those deposited by MOCVD. Deep energy states in CdTe films deposited by CSS and MOCVD were investigated. Thin films of ZnTe, Cd{sub 1- x}Zn{sub x}Te, and Hg{sub 1-x}Zn{sub x}Te were deposited by MOCVD, and their crystallographic, optical, and electrical properties were characterized. 67 refs.

  10. A flat cable with resistively joined YBCO stripes

    NASA Astrophysics Data System (ADS)

    Polák, M.; Mozola, P.

    2010-02-01

    A model of a flat AC cable with resistively joined strips of a Y1Ba2Cu3Ox (YBCO)-coated conductor was prepared. I-V curves, losses in AC external magnetic field and losses due to AC transport current at various frequencies up to 453 Hz were measured. The critical current of the cable at 77 K and self-field was ~160 A. It is shown that the resistive losses in the joints between the stripes do not significantly contribute to the total cable losses exposed to an AC external magnetic field.

  11. Investigation of Radiation Affected High Temperature Superconductors - YBCO

    NASA Astrophysics Data System (ADS)

    Veterníková, J.; Chudý, M.; Slugeň, V.; Sojak, S.; Degmová, J.; Snopek, J.

    In this paper, high temperature superconductors are studied in terms of radiation stability, which is necessary for application in fusion reactors. Perspective superconducting materials based on YBCO (Perkovskite structure) were measured by positron annihilation lifetime spectroscopy. Measurements were performed for samples prior to and after fast neutron irradiation in TRIGA MARK II reactor in Vienna. The samples demonstrated accumulation of Cu-O di-vacancies due to the irradiation. Nevertheless, the structure showed regeneration during thermal treatment by defects recombination. Positron spectroscopy results were complemented with values of critical temperature, which also showed changes of superconducting properties after the irradiation and the annealing.

  12. Microstructure and levitation properties of floating zone melted YBCO samples

    SciTech Connect

    Bashkirov, Yu.A.; Fleishman, L.S.; Vdovin, A.B.; Zubritsky, I.A.; Smirnov, V.V.; Vinogradov, A.V.

    1994-07-01

    Radiation zone melting has been used to produce texture in sintered YBCO cylindrical samples. Microstructural analysis by electron microscopy and pole figure measurements reveals that the production process gives rise to a preferential orientation within large domains. D.C. transport measurements show that changes in alignment orientation can result in the inability to carry a transport current. Both a.c. magnetic field shielding and levitation properties are substantially improved by the floating zone melting, the levitation force being increased with the texture domain size growth.

  13. Quench Propagation Studies Using A Small Bifilar YBCO Coil

    SciTech Connect

    Shiroyanagi, Y; Sampson, W; Ghosh, A

    2012-10-03

    Quench propagation was studied in a small bifilar coil wound from YBCO tape. Measurements were made at 77 K in self-field and at 4.2 K with an applied field. The velocity of quench propagation at 4.2 K was observed to be about an order of magnitude faster than at 77 K both in the longitudinal and transverse directions. During the course of this experiment the conductor damage limit characterized by ∫I2dt was also estimated. Details of the experiment and results are presented in this paper

  14. Method for Improving Mg Doping During Group-III Nitride MOCVD

    DOEpatents

    Creighton, J. Randall; Wang, George T.

    2008-11-11

    A method for improving Mg doping of Group III-N materials grown by MOCVD preventing condensation in the gas phase or on reactor surfaces of adducts of magnesocene and ammonia by suitably heating reactor surfaces between the location of mixing of the magnesocene and ammonia reactants and the Group III-nitride surface whereon growth is to occur.

  15. In situ study through electrical resistance of growth rate of trifluoroacetate-based solution-derived YBa2Cu3O7 films

    NASA Astrophysics Data System (ADS)

    Sánchez-Valdés, C. F.; Puig, T.; Obradors, X.

    2015-02-01

    In this work, we have studied by means of in situ electrical measurements the nucleation, growth and sintering stages of epitaxial YBa2Cu3O6+δ (YBCO) superconducting thin films prepared using a chemical solution deposition approach based on metal-organic trifluoroacetate-based (TFA) precursors. Single crystal substrates (LaAlO3 and CeO2/YSZ) were used in this study. Analysis of isothermal time dependences, at different temperatures, of in situ electrical resistance of films allowed to evidence that the growth rate G is strongly temperature dependent, i.e. G is enhanced by a factor ˜15 when going from 700 to 810 °C. Additionally, we demonstrate that adding Ag-TFA in the solution may enhance the growth rate by as much as 50%, as compared to pure YBCO, thus confirming previous assessments of the strong influence of Ag doping on YBCO film growth and microstructure. In situ electrical resistance measurements show as well that an incubation time exists and we infer the origin of its temperature dependence. Finally, a thermodynamic analysis allows proposing a single equation for the growth rate of YBCO films integrating all the relevant processing parameters. Our analysis has validated the solid-gas reaction-diffusion model describing the growth of YBCO films from TFA precursors and thus enlarges the knowledge required to enhance the control of the microstructure and superconducting properties of solution-derived YBCO films.

  16. Formation of superconducting junctions in MT-YBCO

    NASA Astrophysics Data System (ADS)

    Prikhna, T. A.; Gawalek, W.; Novikov, N. V.; Moshchil, V. E.; Sverdun, V. B.; Sergienko, N. V.; Surzhenko, A. B.; Uspenskaya, L. S.; Viznichenko, R.; Kordyuk, A. A.; Litzkendorf, D.; Habisreuther, T.; Krachunovska, S.; Vlasenko, A. V.

    2005-02-01

    The formation of superconducting junctions between MT-YBCO using TmBa2Cu3O7-δ powder as a solder has been studied. The method proposed excludes the step of a very slow cooling (at a rate of several degrees per hour) during seam formation. The heating and cooling rate for joining parts produced from single-domain material without visible cracks (macrocracks) can be rather high (500-1000 K h-1) and a holding time at the highest temperature (1010 °C) of several minutes (0.05 h) is enough to form a reliable junction. Reasonable rates of heating and cooling are however around 100 K h-1 if crack propagation is to be avoided in joined blocks used for practical application. Modelling experiments on rings and studies of the ring properties by vibrating sample magnetometer (VSM), field mapping with a Hall probe and magneto-optical microscopy have shown that superconducting properties of the junction were not lower than that of the joined material (jc of about 30 kA cm-2 was observed in zero field at 77 K) and that the proposed process of joining did not adversely affect the properties of the material. The structure of the resulting junction was in good agreement with the structure of MT-YBCO.

  17. Limitations for the trapped field in large grain YBCO superconductors

    NASA Astrophysics Data System (ADS)

    Eisterer, M.; Haindl, S.; Zehetmayer, M.; Gonzalez-Arrabal, R.; Weber, H. W.; Litzkendorf, D.; Zeisberger, M.; Habisreuther, T.; Gawalek, W.; Shlyk, L.; Krabbes, G.

    2006-07-01

    The actual limitations for the trapped field in YBa2Cu3O7-δ (YBCO) monoliths are discussed. The influence of the sample geometry and of the critical current density on the trapped field is investigated by numerical calculations. The field dependence of the critical current density strongly influences the trapped field. A nonlinear relationship between the sample size, the critical current density and the resulting trapped field is derived. The maximum achievable trapped field in YBCO at 77 K is found to be around 2.5 T. This limit is obtained for reasonable geometries and high but realistic critical current densities. Such high fields have not been reached experimentally so far, due to non-optimized flux pinning and material inhomogeneities. These inhomogeneities can be directly assessed by the magnetoscan technique, and their influence is discussed. Significant differences between the a- and the c-growth sectors were found. Limitations due to cracks and non-superconducting inclusions (e.g. 211 particles) are estimated and found to be candidates for variations of Jc on a millimetre length scale, as observed in experiments.

  18. Bipolar electrical coil based on YBCO bulks: initial tests

    NASA Astrophysics Data System (ADS)

    Alvarez, A.; Suárez, P.; Ceballos, J. M.; Pérez, B.; Werfel, F.; Floegel-Delor, U.

    2008-02-01

    In the field of the application of HTS in electrical motors, most prototypes are made using superconducting coils based on tape and located in the position where copper coils work in a similar conventional motor. Other prototypes use superconducting bulks (usually disk-shaped) in those positions where normal magnets should work in similar conventional motors. But it is very unusual to find designs using electrical coils based on bulks. This is a challenge whose main problem is the difficulty in machining the superconductor bulks to get the proper shape because of the impossibility of bending the material to wind coils. The design of a bipolar single-turn coil made from a superconducting YBCO disk was proposed by the group of Electrical Application of Superconductors, at the University of Extremadura, several years ago to be an element for the design of a modular two-phase inductor for an air core axial-flux motor. The shape of each coil looks like an 'S'. When a current flows through the circuit, two opposite magnetic fields appear in the upper and lower halves of the piece. Until now, attempts to get a good superconducting circuit by cutting a YBCO disk into the required shape have failed because of cracks appearing in the crystal during the process. Last year, our group at the University of Extremadura began to work with ATZ GmbH who have improved the machining process and made the coils. In this paper we present the coil and the first tests carried out.

  19. Low ac loss geometries in YBCO coated conductors and impact on conductor stability

    SciTech Connect

    Duckworth, Robert C; List III, Frederick Alyious; Paranthaman, Mariappan Parans; Rupich, M. W.; Zhang, W.; Xie, Y. Y.; Selvamanickam, V.

    2007-01-01

    Reduction of ac losses in applied ac fields can be accomplished through either the creation of filaments and bridging in YBCO coated conductors or an assembly of narrow width YBCO tapes. The ac losses for each of these geometries were measured at 77 K in perpendicular ac fields up to 100 mT. While ac loss reduction was achieved with YBCO filaments created through laser scribing and inkjet deposition, the assembly of stacked YBCO conductor provides an alternative method of ac loss reduction. When compared to a 4-mm wide YBCO coated conductor with a critical current of 60 A, the ac loss in a stack of 2-mm wide YBCO coated conductors with a similar total critical current was reduced. While the reduction in ac loss in a 2-mm wide stack coincided with the reduction in the engineering current density of the conductor, further reduction of ac loss was obtained through the splicing of the 2-mm wide tapes with low resistance solders. To better determine the practicality of these methods from a stability point of view, a numerical analysis was carried out to determine the influence of bridging and splicing on stability of a YBCO coated conductor for both liquid nitrogen-cooled and conduction cooled geometries.

  20. Raman and x-ray absorption spectroscopy characterization of Zr-doped MOCVD YBa{sub 2}Cu{sub 3}O{sub 6+{delta}}.

    SciTech Connect

    Maroni, V. A.; Kropf, A. J.; Aytung, T.; Paranthaman, M.; Chemical Sciences and Engineering Division; ORNL

    2010-01-01

    Metal-organic chemical vapor deposited YBa{sub 2}Cu{sub 3}O{sub 6+{delta}} (YBCO) films (about 0.9 {micro}m thick) containing varying amounts of added zirconium were examined by Raman microscopy and synchrotron x-ray absorption spectroscopy. The self-field and in-field (1 T, B {parallel} c)J{sub c} performance of the YBCO films at 77 K (reported by the group at Oak Ridge National Laboratory that fabricated the samples) exhibited an increase on going from 0 mol% (m/o) Zr-added to 2.5 m/o Zr-added but then decreased sharply with increasing Zr content. Raman measurements on these films showed that the added Zr had little effect on YBCO cation disorder up to about 7.5 m/o Zr-added. Cation disorder increased while Ba-Cu-O content remained relatively constant for Zr additions {ge} 7.5 m/o. In the region of sharpest descent of J{sub c} with increasing Zr content (2.5-7.5 m/o Zr-added) neither the cation disorder nor the Ba-Cu-O content showed a systematic variation with J{sub c}. Zirconium K edge x-ray absorption near-edge spectroscopy revealed that virtually all of the added Zr in each sample was present as a BaZrO{sub 3}-like phase (BZO). The J{sub c} performance of the Zr-added films showed a high correlation with the variations in the next-nearest-neighbor Zr-M (M = Zr, Y) scattering path amplitude from the extended x-ray absorption fine structure (EXAFS) and the critical temperature over the full range of Zr additions and with cation disorder at the higher Zr-added levels (>7.5 m/o). There was no obvious correlation with the amount of residual barium cuprate or CuO. Approximate ranges for the BZO particle dimensions estimated from the EXAFS data indicated that the mean particle size gets larger with increasing Zr addition.

  1. Broad Temperature Pinning Study of 15 mol.% Zr-Added (Gd, Y)-Ba-Cu-O MOCVD Coated Conductors

    SciTech Connect

    Xu, AX; Khatri, N; Liu, YH; Majkic, G; Galstyan, E; Selvamanickam, V; Chen, YM; Lei, CH; Abraimov, D; Hu, XB; Jaroszynski, J; Larbalestier, D

    2015-06-01

    BaZrO3 (BZO) nanocolumns have long been shown to be very effective for raising the pinning force F-p of REBa2Cu3Ox (REBCO, where RE = rare earth) films at high temperatures and recently at low temperatures too. We have successfully incorporated a high density of BZO nanorods into metal organic chemical vapor deposited (MOCVD) REBCO coated conductors via Zr addition. We found that, compared to the 7.5% Zr-added coated conductor, dense BZO nanorod arrays in the 15% Zr-added conductor are effective over the whole temperature range from 77 K down to 4.2 K. We attribute the substantially enhanced J(c) at 30 K to the weak uncorrelated pinning as well as the strong correlated pinning. Meanwhile, by tripling the REBCO layer thickness to similar to 2.8 mu m, the engineering critical current density J(e) at 30 K exceeds J(e) of optimized Nb-Ti wires at 4.2 K.

  2. Proximity effect in gold-coated YBa(2)Cu(3)O(7-delta) films studied by scanning tunneling spectroscopy.

    PubMed

    Sharoni, Amos; Asulin, Itay; Koren, Gad; Millo, Oded

    2004-01-01

    Scanning tunneling spectroscopy on gold layers overcoating c-axis YBa(2)Cu(3)O(7-delta) (YBCO) films reveals proximity-induced gap structures. The gap size reduces exponentially with the distance from a-axis facets, indicating that the proximity effect is primarily due to the (100) YBCO facets. The penetration depth of superconductivity into the gold is approximately 30 nm, in good agreement with estimations for the dirty limit. The extrapolated gap at the interface is approximately 15 meV, similar to the value of an s-wave component of the order parameter measured at the YBCO surface in recent point-contact experiments. PMID:14754012

  3. Energy band engineering using polarization induced interface charges in MOCVD grown III-nitride heterojunction devices

    NASA Astrophysics Data System (ADS)

    Tripathi, Neeraj

    2011-12-01

    Characteristics of III-nitride based heterojunction devices are greatly influenced by the presence of high density of polarization induced interface charges. Research undertaken in the current doctoral thesis demonstrates the effect of presence of one, three and six sheets of polarization induced charges in three different III-nitride based devices, namely in a photocathode, a high electron mobility transistor (HEMT) and a hyperspectral detector structure. Through a systematic set of experiments and theoretical modeling an in-depth study of the interaction between multiple sheets of polarization induced charges and their impact on energy band profile was undertaken. Various device designs were studied and optimized using device simulations. Subsequently device structures were grown using metallorganic chemical vapor deposition (MOCVD). Growth conditions for III-nitride epilayers were optimized for pressure, temperature and V/III ratio. Devices were fabricated using photolithography and e-beam evaporation. Novel GaN and GaN/AlGaN photocathode structures were developed. First demonstration of effective negative electron affinity (ENEA) in a GaN photocathode without the use of Cs was made. Effect of polarization induced surface charges on photoemission characteristics was successfully explained using simulated energy band diagrams. AlGaN/GaN/AlGaN/SiO2 based back barrier HEMT structures were developed in which bandgap, thin film thicknesses and polarization induced charge density were engineered to demonstrate Normally OFF operation along with the ability to engineer turn ON voltage of the device. Further, AlGaN based tunable hyperspectral detector pixel with 6-heterojunctions, for application in wavelength spectrometry from UV to IR part of the spectrum, was developed. The novel device design used in the hyperspectral detector utilized voltage tunable internal photoemission (IPE) barriers to measure the energy of the incident photon. Detailed IPE measurements were

  4. Enhanced Flux Pinning and Critical Current Density via Incorporation of Self-Assembled Rare-Earth Barium Tantalate Nanocolumns within YBa2Cu3O7-δ Films

    SciTech Connect

    Wee, Sung Hun; Goyal, Amit; Specht, Eliot D; Cantoni, Claudia; Zuev, Yuri L; Selvamanickam, V.; Cook, Sylvester W

    2010-01-01

    We report rare earth barium tantalates, Ba2RETaO6 (BRETO, RE = rare earth elements) as a new class of additives for superior flux-pinning in YBa2Cu3O7- (YBCO) films. BRETO compounds have excellent chemical inertness to and large lattice mismatch with YBCO. This results in phase separation and strain minimization driven self-assembly of BRETO nanocolumns within YBCO films. YBCO+4 vol% Ba2GdTaO6 films show similar Tc to that of an un-doped film of ~ 88.3 K, a higher self-field Jc of 3.8 MA/cm2 at 77 K, and significantly improved in-field Jc higher by a factor of 1.5-6 over entire magnetic field and angular ranges.

  5. Effects of Seed Layer on YBa2Cu3Ox Films Grown by Liquid Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Zama, Hideaki; Miyakoshi, Masayuki; Yamamoto, Hiroshi; Morishita, Tadataka

    1999-11-01

    Crack-free YBa2Cu3Ox (YBCO) films were grown by liquid phaseepitaxy (LPE) on MgO(100) substrates with a YBCO seed layer. Thecrystalline property of LPE was crucially dependent on that of theseed layer. On the purely c-axis-oriented seed layer, reasonable YBCOfilms were grown with a full-width at half maximum of the (005)reflection rocking curve, Δω, of 0.07°. In the case of the seedincluding an a-axis-oriented grain, the value of Δω of LPE films waspoor in reproducibility and larger than 0.1° on average. For thea-axis-oriented seed, no YBCO films grew under the growth conditionsin this study. X-ray topographic observations revealed that thecrystalline quality of MgO substrates limited the Δω of LPE films grownon them.

  6. High-temperature superconducting thin films and their application to superconducting-normal-superconducting devices

    SciTech Connect

    Mankiewich, P.M.

    1993-01-01

    The existence of the proximity effect between the high temperature superconductor YBa[sub 2]Cu[sub 3]O[sub 7] (YBCO) and normal metal thin films has been demonstrated, and this effect has been exploited to produce lithographically fabricated superconducting-normal-superconducting (SNS) Josephson junctions. Improvement of the fabrication processes has led to new methods of in-situ film growth and plasma etching of YBCO, as well a YBCO-compatible processes for the deep-ultraviolet and electron-beam lithography required to fabricate submicron device structures. This proximity effect approach helps to circumvent the short coherence length ([xi] [approximately] 3 nm) characteristic of the high T[sub c] superconductors. In a clean normal metal such as gold or silver the relevant coherence length is governed by the higher Fermi velocity and longer mean free path. A Josephson device containing a normal metal weak link can be longer than an ideal all-YBCO microbridge (dimensions comparable to [xi]). Initially, SNS devices were fabricated and showed evidence for a supercurrent through the normal region. Properly spaced Shapiro steps as a function of microwave frequency were observed. This result was evidence for a proximity effect between a normal metal and YBCO. The fabrication process was not sufficiently reproducible, so new techniques were developed. In-situ film growth and fabrication is desirable to minimize contamination of and damage to the surface of the superconductor. In-situ reactive coevaporation of YBCO was demonstrated. Patterning of these in-situ films in to a structure required the development of a low-damage reactive ion etch. New lithographic techniques were developed to minimize chemical degradation of the superconductor. Deposition of gold onto heated device structures was demonstrated to produce a superior SNS device. The application of YBCO thin films to passive microwave devices and to active superconducting circuits was evaluated.

  7. Influence of YBa2HfO5.5 - 'derived secondary phase' on the critical current density and flux-Pinning force of YBa2Cu3O7-δ thick films

    NASA Astrophysics Data System (ADS)

    Rejith, Pullanhiyodan Puthiyaveedu; Vidya, Sukumariamma; Thomas, Jijimon Kumbukkattu

    2015-12-01

    Enhancement in critical current density (Jc) and flux pinning force (Fp) in superconducting thick films of YBa2Cu3O7-δ (YBCO) added with small quantities of nanopowders of HfO2, BaHfO3 and YBa2HfO5.5, coated on YBa2ZrO5.5 substrate by dip-coating technique is reported. Critical current density measurements were done over an applied magnetic field using standard four probe technique and the results are compared with that of pure YBCO. High critical current density (Jc) of ∼4.84 MA/cm2 at 77 K in self-field was obtained for 2 wt% of YBa2HfO5.5 added YBCO. A systematic increase in Jc observed in YBCO films prepared by the addition of nano HfO2, BaHfO3 and YBa2HfO5.5, attributed to the formation of a non-reacting 'derived secondary phase' YBa2HfO5.5 (YBHO) in the YBCO matrix. YBCO-YBa2HfO5.5 composite thick films have showed eightfold increases in Jc (3.29 MA/cm2) at 77 K and 0.4 T compared to pure YBa2Cu3O7-δ film (0.37 MA/cm2), while maintaining a high transition temperature (Tc). The development of effective pinning centers in nano particle added YBCO thick film have enhanced the flux pinning force from 1.8 GN/m3 for pure YBCO to a maximum value of 13.15 GN/m3 for YBCO-YBa2HfO5.5. X-ray diffraction and energy dispersive spectroscopic analysis confirmed the presence of secondary phase, derived in the matrix.

  8. The coherent gradient sensor for film curvature measurements at cryogenic temperature.

    PubMed

    Liu, Cong; Zhang, Xingyi; Zhou, Jun; Zhou, Youhe; Feng, Xue

    2013-11-01

    Coherent Gradient Sensor (CGS) system is presented for measurement of curvatures and nonuniform curvatures changes in film-substrate systems at cryogenic temperature. The influences of the interface of refrigerator and itself on the interferograms which are accounting for the temperature effect are successfully eliminated. Based on the measurement technique, the thermal stresses (including the radial stress, circumferential stress and shear stress) of superconducting YBCO thin-film are obtained by the extended Stoney's formula during the heating process from 30K to 150K. Take the superconducting YBCO thin film as an example, the thermal stresses of which are gained successfully. PMID:24216858

  9. Crossover from Quantum to Classical Creep in YBCO

    NASA Astrophysics Data System (ADS)

    Shung, E.; Beauchamp, K. M.; Rosenbaum, T. F.; Welp, U.; Crabtree, G. W.

    1996-03-01

    We use a miniature Hall probe array to measure the local magnetization relaxation S in single crystals of YBCO with columnar defects from milliKelvin to tens of Kelvin. In addition to the usual quantum signature of temperature independence of the relaxation, we probe the relationship between S and the critical current density J_c, tuned by varying columnar defect density. S can increase concurrently with Jc in the Bose glass when quantum effects dominate (K. M. Beauchamp et al., Phys. Rev. Lett. 75), 3942 (1995). Moreover, we test recent theoretical predictions of the dependence of the quantum to classical crossover temperature on critical current density (L. Radzihovsky, Phys Rev. Lett. 74), 4923 (1995).

  10. Solution processing of YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} thin films

    SciTech Connect

    Singhal, A.; Paranthaman, M.; Specht, E.D.; Hunt, R.D.; Beach, D.B.; Martin, P.M.; Lee, D.F.

    1997-12-01

    The aim of this work was to develop a non-vacuum chemical deposition technique for YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} (YBCO) coated conductors on rolling-assisted biaxially textured substrates (RABiTS). The authors have chosen the metal-organic decomposition (MOD) and sol-gel precursor routes to grow textured YBCO films. In the MOD process, yttrium 2-ethylhexonate, barium neodecanoate, copper 2-ethylhexonate and toluene were used as the starting reagents. YBCO films processed by the MOD method on SrTiO{sub 3} (100) single crystal substrates were consisted of c and a-axis oriented materials. These films also contained some amount of the random phase. The c and a-axis oriented materials were epitaxial on SrTiO{sub 3} substrates. Films have a T{sub c,onset} of 89K and the best superconducting transition temperature of 63K. Films pyrolyzed at 525 C and subsequently annealed at 780 C in a p(O{sub 2}) of 3.5 {times} 10{sup {minus}4} atm contained YBCO phase predominantly in a-axis orientation. In the sol-gel route, yttrium-isopropoxide, barium metal, copper methoxide and 2-methoxyethanol were used as the starting reagents. Sol-gel YBCO films on SrTiO{sub 3} substrates were epitaxial and c-axis oriented.

  11. Photoreflectance for in-situ characterization of MOCVD growth of semiconductors under micro-gravity conditions

    NASA Technical Reports Server (NTRS)

    Pollak, Fred H.

    1990-01-01

    A contactless electromodulation technique of photoreflectance (PR) was developed for in-situ monitoring of metal-organic chemical vapor deposition (MOCVD) semiconductor growth for micro-gravity applications. PR can be employed in a real MOCVD reactor including rotating substrate (approximately 500 rev/min) in flowing gases and through a diffuser plate. Measurements on GaAs and Ga(0.82)Al(0.18)As were made up to 690 C. The direct band gaps of In(x)Ga(1-x)As (x = 0.07 and 0.16) were evaluated up to 600 C. In order to address the question of real time measurement, the spectra of the direct gap of GaAs at 650 C was obtained in 30 seconds and 15 seconds seems feasible.

  12. Critical current density of YBa2Cu3O7-x films with BaZrO3 inclusions on SrTiO3 and Al2O3 substrates

    NASA Astrophysics Data System (ADS)

    Augieri, A.; Galluzzi, V.; Celentano, G.; Fabbri, F.; Mancini, A.; Rufoloni, A.; Vannozzi, A.; Gambardella, U.; Padeletti, G.; Cusmà, A.; Petrisor, T.; Ciontea, L.

    2008-02-01

    Recently, many efforts have been dedicated to the development of a reliable technology for the introduction of artificial pinning sites in YBa2Cu3O7-x (YBCO) films with the aim of improving the in-field Jc performances. One of the most effective technique resulted to be the inclusion of BaZrO3 (BZO) second phase embedded in the YBCO films. In this contribution we present Jc measurements on BZO-added YBCO films deposited on SrTiO3 (STO) and CeO2-buffered-Al2O3 (ALO) substrates. Samples were deposited by pulsed laser ablation technique using a composite YBCO + 5mol.% BZO target at the optimum conditions for fully oxygenated c-axis oriented YBCO films. Despite of a slight Tc reduction, BZO addition in YBCO-STO films resulted in an improvement of in-field performances with the appearance of a Jc plateau in the low field region which extends up to about 2.5 Tesla irrespective of the temperature at least in the investigated range (down to 65K). On the other hand, samples deposited on ALO did not exhibit any remarkable difference neither in the Jc value nor in the magnetic field dependences as compared with pure YBCO. The presence of 0° (magnetic field parallel to the c-axis) peaks in the Jc. angular behaviour revealed a c-axis correlated character of the pinning forces in BZO added YBCO films grown on both STO and ALO substrates. X-ray diffraction measurements and AFM investigations were carried out in order to determine the influence of BZO addition on films crystalline quality and microstructure.

  13. Final report on LDRD project : outstanding challenges for AlGaInN MOCVD.

    SciTech Connect

    Mitchell, Christine Charlotte; Follstaedt, David Martin; Russell, Michael J.; Cross, Karen Charlene; Wang, George T.; Creighton, James Randall; Allerman, Andrew Alan; Koleske, Daniel David; Lee, Stephen Roger; Coltrin, Michael Elliott

    2005-03-01

    The AlGaInN material system is used for virtually all advanced solid state lighting and short wavelength optoelectronic devices. Although metal-organic chemical vapor deposition (MOCVD) has proven to be the workhorse deposition technique, several outstanding scientific and technical challenges remain, which hinder progress and keep RD&A costs high. The three most significant MOCVD challenges are: (1) Accurate temperature measurement; (2) Reliable and reproducible p-doping (Mg); and (3) Low dislocation density GaN material. To address challenge (1) we designed and tested (on reactor mockup) a multiwafer, dual wavelength, emissivity-correcting pyrometer (ECP) for AlGaInN MOCVD. This system simultaneously measures the reflectance (at 405 and 550 nm) and emissivity-corrected temperature for each individual wafer, with the platen signal entirely rejected. To address challenge (2) we measured the MgCp{sub 2} + NH{sub 3} adduct condensation phase diagram from 65-115 C, at typical MOCVD concentrations. Results indicate that it requires temperatures of 80-100 C in order to prevent MgCp{sub 2} + NH{sub 3} adduct condensation. Modification and testing of our research reactor will not be complete until FY2005. A new commercial Veeco reactor was installed in early FY2004, and after qualification growth experiments were conducted to improve the GaN quality using a delayed recovery technique, which addresses challenge (3). Using a delayed recovery technique, the dislocation densities determined from x-ray diffraction were reduced from 2 x 10{sup 9} cm{sup -2} to 4 x 10{sup 8} cm{sup -2}. We have also developed a model to simulate reflectance waveforms for GaN growth on sapphire.

  14. Radiation effects on p+n InP junctions grown by MOCVD

    NASA Technical Reports Server (NTRS)

    Messenger, Scott R.; Walters, Robert J.; Panunto, M. J.; Summers, Geoffrey P.

    1994-01-01

    The superior radiation resistance of InP over other solar cell materials such as Si or GaAs has prompted the development of InP cells for space applications. The early research on radiation effects in InP was performed by Yamaguchi and co-workers who showed that, in diffused p-InP junctions, radiation-induced defects were readily annealed both thermally and by injection, which was accompanied by significant cell recovery. More recent research efforts have been made using p-InP grown by metalorganic chemical vapor deposition (MOCVD). While similar deep level transient spectroscopy (DLTS) results were found for radiation induced defects in these cells and in diffused junctions, significant differences existed in the annealing characteristics. After injection annealing at room temperature, Yamaguchi noticed an almost complete recovery of the photovoltaic parameters, while the MOCVD samples showed only minimal annealing. In searching for an explanation of the different annealing behavior of diffused junctions and those grown by MOCVD, several possibilities have been considered. One possibility is the difference in the emitter structure. The diffused junctions have S-doped graded emitters with widths of approximately 0.3 micrometers, while the MOCVD emitters are often doped with Si and have widths of approximately 300A (0.03 micrometers). The difference in the emitter thickness can have important effects, e.g. a larger fraction of the total photocurrent is generated in the n-type material for thicker emitters. Therefore the properties of the n-InP material may explain the difference in the observed overall annealing behavior of the cells.

  15. Progress in MOCVD growth of HgCdTe epilayers for HOT infrared detectors

    NASA Astrophysics Data System (ADS)

    Kebłowski, A.; Gawron, W.; Martyniuk, P.; Stepień, D.; Kolwas, K.; Piotrowski, J.; Madejczyk, P.; Kopytko, M.; Piotrowski, A.; Rogalski, A.

    2016-05-01

    In this paper we present progress in MOCVD growth of (100) HgCdTe epilayers achieved recently at the Institute of Applied Physics, Military University of Technology and Vigo System S.A. It is shown that MOCVD technology is an excellent tool in fabrication of different HgCdTe detector structures with a wide range of composition, donor/acceptor doping and without post grown annealing. Particular progress has been achieved in the growth of (100) HgCdTe epilayers for long wavelength infrared photoconductors operated in HOT conditions. The (100) HgCdTe photoconductor optimized for 13-μm attain detectivity equal to 6.5x109 Jones and therefore outperform its (111) counterpart. The paper also presents technological progress in fabrication of MOCVD-grown (111) HgCdTe barrier detectors. The barrier device performance is comparable with state-of-the-art of HgCdTe photodiodes. The detectivity of HgCdTe detectors is close to the value marked HgCdTe photodiodes. Dark current densities are close to the values given by "Rule 07".

  16. Recent progress in MOCVD growth for thermoelectrically cooled HgCdTe medium wavelength infrared photodetectors

    NASA Astrophysics Data System (ADS)

    Gawron, W.; Martyniuk, P.; Kębłowski, A.; Kolwas, K.; Stępień, D.; Piotrowski, J.; Madejczyk, P.; Pędzińska, M.; Rogalski, A.

    2016-04-01

    The authors report on advanced metalorganic chemical vapour deposition (MOCVD) of Hg1-xCdxTe (HgCdTe) structures for high operating temperature, medium wavelength infrared (MWIR) detector application. MOCVD technology with wide range of composition and donor/acceptor doping and without post grown annealing was proved to be an excellent tool for HgCdTe heterostructure epitaxial growth used for uncooled photodetector design. The interdiffused multilayer process (IMP) technique was applied for the HgCdTe deposition. HgCdTe epilayers were grown at 350 °C with Hg source kept at 210 °C. The II/VI mole ratio was assumed in the range from 1.5 to 3 during CdTe/HgTe cycles of the IMP process. The MWIR detectors grown by MOCVD exhibit detectivity ∼7.3 × 1011 Jones at λPEAK = 3.5 μm and T = 230 K being determined by background limited photodetector (BLIP) condition.

  17. New Heteroleptic Copper(II) Complexes as MOCVD Precursors

    NASA Astrophysics Data System (ADS)

    Krisyuk, V. V.; Sysoev, S. V.; Rumyantsev, Y. M.; Prokhorova, S. A.; Maximovskiy, E. V.; Kosinova, M. L.; Igumenov, I. K.

    New volatile heteroleptic copper(II) complexes having beta-ketoiminate (O,N) and diketonate (O,O) ligands in one molecule were tested as precursors for LPCVD of copper films. Saturated vapor pressure was measured and compared for new compounds Cu(ki)(hfa) and Cu(dpk)(hfa), where ki = pentane-2-imino-4-onato, hfa = 1,1,1,5,5,5-hexafluoro-pentane- 2,4-dionato, dpk= 2,2,6,6-tetramethyl-3-iminoheptane-5-onato. The precursors are air stable and non hygroscopic compounds with long shelf life. It was demonstrated that copper metal films can be selectively deposited on metallic surfaces in the presence of hydrogen as a gas-reactant at temperatures of 250, 300, 350 °C and pressure of 20 Torr. Si(100), SiO2 (melted quartz), stainless steel, and Cu, Al, RuO2, Ru and Ta sublayers on Si(100) were tested as substrate materials. Deposited films were analyzed and characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM).

  18. In situ growth of YBa sub 2 Cu sub 3 O sub 7 minus x high Tc superconducting thin films directly on sapphire by plasma-enhanced metalorganic chemical vapor deposition

    SciTech Connect

    Chern, C.S.; Zhao, J.; Li, Y.Q.; Norris, P.; Kear, B.; Gallois, B. )

    1990-08-13

    Highly {ital c}-axis oriented YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} superconducting thin films have been, {ital in} {ital situ}, deposited directly on sapphire substrate by a remote microwave plasma-enhanced metalorganic chemical vapor deposition process (PE-MOCVD). The films were deposited at a substrate temperature of 730 {degree}C followed by a fast cooling. The as-deposited films show attainment of zero resistance at 82 K and have critical current density of 10{sup 4} A/cm{sup 2} at 70 K. ac susceptibility measurement indicated that the films contain a single superconducting phase. PE-MOCVD was carried out in a commercial-scale MOCVD reactor with capability of uniform deposition over 100 cm{sup 2} per growth run.

  19. Thin film cadmium telluride, zinc telluride, and mercury zinc telluride solar cells. Final subcontract report, 1 July 1988--31 December 1991

    SciTech Connect

    Chu, T.L.

    1992-04-01

    This report describes research to demonstrate (1) thin film cadmium telluride solar cells with a quantum efficiency of 75% or higher at 0. 44 {mu}m and a photovoltaic efficiency of 11.5% or greater, and (2) thin film zinc telluride and mercury zinc telluride solar cells with a transparency to sub-band-gap radiation of 65% and a photovoltaic conversion efficiency of 5% and 8%, respectively. Work was directed at (1) depositing transparent conducting semiconductor films by solution growth and metal-organic chemical vapor deposition (MOCVD) technique, (2) depositing CdTe films by close-spaced sublimation (CSS) and MOCVD techniques, (3) preparing and evaluating thin film CdTe solar cells, and (4) preparing and characterizing thin film ZnTe, CD{sub 1-x}Zn{sub 1-x}Te, and Hg{sub 1-x}Zn{sub x}Te solar cells. The deposition of CdS films from aqueous solutions was investigated in detail, and their crystallographic, optical, and electrical properties were characterized. CdTe films were deposited from DMCd and DIPTe at 400{degrees}C using TEGa and AsH{sub 3} as dopants. CdTe films deposited by CSS had significantly better microstructures than those deposited by MOCVD. Deep energy states in CdTe films deposited by CSS and MOCVD were investigated. Thin films of ZnTe, Cd{sub 1- x}Zn{sub x}Te, and Hg{sub 1-x}Zn{sub x}Te were deposited by MOCVD, and their crystallographic, optical, and electrical properties were characterized. 67 refs.

  20. Coaxial line configuration for microwave power transmission study of YBa2Cu3O(7-delta) thin films

    NASA Technical Reports Server (NTRS)

    Chorey, C. M.; Miranda, F. A.; Bhasin, K. B.

    1991-01-01

    Microwave transmission measurements through YBa2Cu3O(7-delta) (YBCO) high-transition-temperature superconducting thin films on lanthanum aluminate (LaAlO3) have been performed in a coaxial line at 10 GHz. LaAlO3 substrates were ultrasonically machined into washer-shaped discs, polished, and coated with laser-ablated YBCO. These samples were mounted in a 50-ohm coaxial air line to form a short circuit. The power transmitted through the films as a function of temperature was used to calculate the normal state conductivity and the magnetic penetration depth for the films.

  1. On the Nature of the Superconducting Transition in YBCO

    NASA Astrophysics Data System (ADS)

    Yethiraj, M.; Crowe, S. J.; McK. Paul, D.; Christen, D. K.; Arai, M.; Yokoo, T.; Porcar, L.; Butler, P. D.

    2007-03-01

    In the high-Tc superconductor YBCO, a transition was observed from a hexagonal FLL at low magnetic field (parallel to the c-axis) to a square configuration at high fields. Also seen was a rapid decrease in the Bragg intensity at low temperature (T). It has been the general belief that both the symmetry change and the T-dependence behaviour was due to the d- wave nature of high-Tc superconductivity. However, we observed that the fall-off in intensity with increasing temperature depended on the strength of the applied external field and that excellent fits to this T-dependence could be obtained by simply multiplying the temperature dependence of the familiar Ginzburg-Landau two-fluid model, appropriate for high-kappa materials conventional superconductors, by an exponential factor exp(-aT), with the field-dependent variable `a' being the only free parameter. The impact of these observations on the symmetry of the order parameter will be discussed.

  2. Temperature dependent phonon mode coupling in YBCO_6.95

    NASA Astrophysics Data System (ADS)

    Stercel, Ferenc; Chung, Jae-Ho; Egami, Takeshi; Mook, Herb; Frost, Chris

    2004-03-01

    While the majority in the field of high-temperature superconductivity believe in the magnetic mechanism, experimental evidence of phonon involvement is increasing. We carried out inelastic neutron scattering measurements of c-axis phonons with a YBa_2Cu_3O_6.95 single crystal at the MAPS of the ISIS facility. We found distinct temperature dependence of the 63 meV apical oxygen phonon mode, which correlates well with that of the in-plane Cu-O bond-stretching phonon mode observed earlier. The result indicates that the coupling between the two modes changes with temperature, similar to the superconducting order parameter. The coupling is mainly due to the Coulomb repulsion between the in-plane oxygen and the apical oxygen. The phonon-induced hole transfer from oxygen to copper introduces attractive force and offsets this repulsion. The observed effect can be explained by the enhancement of offset due to the off-diagonal transfer of Cooper pairs. Thus this observation constitutes the direct confirmation of involvement of the in-plane Cu-O bond-stretching phonons in the superconductivity of YBCO_6.95.

  3. Nanoscale inhomogeneities in yttrium-barium-copper-oxide (YBCO) superconductors

    NASA Astrophysics Data System (ADS)

    Islam, Zahirul; Sinha, S. K.; Lang, J. C.; Liu, X.; Haskel, D.; Moss, S. C.; Srajer, G.; Veal, B. W.; Wermeille, D.; Lee, D. R.; Haeffner, D. R.; Welp, U.; Wochner, P.

    2004-03-01

    X-ray diffraction studies at the Advanced Photon Source reveal that nanoscale inhomogeneities, electronic or structural in origin, form in yttrium-barium-copper-oxide (YBa_2Cu_3O_6+x) superconductors and coexist with the superconducting (SC) state. Diffuse scattering from these inhomogeneous superstructures is due to atomic displacements with respect to equilibrium lattice sites (Z. Islam et al. Phys. Rev. B 66, 92501 (2002)), that are characterized by a wavevector of the form q=(q_x,0,0), where qx varies with hole doping from 2 unit cells (along shorter Cu-O-Cu direction) for very low doping to 4 unit cells at optimal doping. Interestingly, while these superstructures are 3-dimensionally ordered when the SC state is weakened (e.g., at x=0.4), as the doping increases, they become quasi 1D with correlation lengths comparable to SC coherence lengths in these cuprates. Recent first-principles calculations (D. de Fontaine et al., to be published) for the x=0.63 compound show that atomic displacements consistent with experimental data can be the result of ordering of O vacancies in YBCO. Models for various superstructures and their role in the phase diagram will be discussed.

  4. AC Loss Measurements on a 2G YBCO Coil

    SciTech Connect

    Rey, Christopher M; Duckworth, Robert C; Schwenterly, S W

    2011-01-01

    The Oak Ridge National Laboratory (ORNL) is collaborating with Waukesha Electric Systems (WES) to continue development of HTS power transformers. For compatibility with the existing power grid, a commercially viable HTS transformer will have to operate at high voltages in the range of 138 kV and above, and will have to withstand 550-kV impulse voltages as well. Second-generation (2G) YBCO coated conductors will be required for an economically-competitive design. In order to adequately size the refrigeration system for these transformers, the ac loss of these HTS coils must be characterized. Electrical AC loss measurements were conducted on a prototype high voltage (HV) coil with co-wound stainless steel at 60 Hz in a liquid nitrogen bath using a lock-in amplifier technique. The prototype HV coil consisted of 26 continuous (without splice) single pancake coils concentrically centered on a stainless steel former. For ac loss measurement purposes, voltage tap pairs were soldered across each set of two single pancake coils so that a total of 13 separate voltage measurements could be made across the entire length of the coil. AC loss measurements were taken as a function of ac excitation current. Results show that the loss is primarily concentrated at the ends of the coil where the operating fraction of critical current is the highest and show a distinct difference in current scaling of the losses between low current and high current regimes.

  5. Contamination of YBCO bulk superconductors by samarium and ytterbium

    NASA Astrophysics Data System (ADS)

    Volochova, D.; Jurek, K.; Radusovska, M.; Piovarci, S.; Antal, V.; Kovac, J.; Jirsa, M.; Diko, P.

    2014-01-01

    Y-Ba-Cu-O (YBCO, Y-123) single-grain bulk superconductors with a nominal composition Y1.5Ba2Cu3Ox and 1 wt% CeO2 addition were prepared by the optimized Top-Seeded Melt-Growth process. Small single-crystalline pieces cut from the SmBa2Cu3Oy (Sm-123) bulk were used for seeding of epitaxial growth. Wavelength-dispersive spectrometry (WDS) confirmed that prepared samples contain besides samarium from the seed also ytterbium from the substrate. The influence of maximum melting temperature, Tmax and dwell time on the contamination of the bulk samples was studied. Y2BaCuO5 (Y-211) barriers against samarium diffusion from the seed to melted sample were tested. Using a NdBa2Cu3Oz (Nd-123) seed and a combination of Y2O3 and Yb2O3 substrate led to a high critical temperature (Tc(50%) = 91.54 K) of prepared sample.

  6. Planar transmission line resonators from YBa2Cu3O(7-x) thin films and epitaxial SIS multilayers

    NASA Astrophysics Data System (ADS)

    Rauch, W.; Gornik, E.; Valenzuela, A. A.; Soelkner, G.; Fox, F.; Behner, H.; Gieres, G.; Russer, P.

    1993-03-01

    The authors have grown c-axis-oriented YBa2Cu3O(7-x) (YBCO) thin films and epitaxial YBCO/NdAlO3/YBCO trilayers by sputtering. From the YBCO films, coplanar half-wavelength transmission line resonators were patterned. At 77 K the unloaded quality factors of coplanar stripline resonators were up to 2570 at 5.6 GHz. The attenuation constant of such a line was evaluated to be 0.6 dB/m at 77 K and at 5.6 GHz. Coplanar waveguide resonators yielded quality factors up to 1200 at 77 K and at 6.2 GHz resulting in an attenuation constant of 1.8 dB/m. From these measurements the surface resistance values Rs of the films were determined. The lowest Rs was 105 micro-ohms at 77 K and at 6.2 GHz. Trilayer structures with a dielectric as thick as 800 nm were patterned into microstrip resonators. At 50 K the authors measured a quality factor of 85 at 4.7 GHz, resulting in an attenuation of 26 dB/m and a surface resistance of 340 micro-ohms. For thick dielectrics the upper YBCO film already contains significant portions of polycrystalline material.

  7. Chemical solution approaches to YBa2Cu3O7_delta-Au nanocomposite superconducting thin films.

    PubMed

    Martínez-Julián, F; Ricart, S; Pomar, A; Col, M; Abellán, P; Sandiumenge, F; Casanove, M J; Obradors, X; Puig, T; Pastoriza-Santos, I; Liz-Marzán, L M

    2011-04-01

    We explore the feasibility of preparing YBa2CU3O7-Au (YBCO-Au) nanocomposite thin films by chemical solution deposition (CSD). Two approaches were used: (i) A standard in-situ methodology where Au metallorganic salts are added into the precursor solution of YBCO trifluoroacetate (TFA) salts and (ii) a novel approach where stable colloidal solutions of preformed gold nanoparticles (5-15 nm) were homogeneously mixed with TFA-YBCO solutions. A detailed analysis of the microstructure of the films showed that in both cases, there is a strong tendency of gold nanoparticles to migrate to the film surface. However the kinetics of this migration evidences important differences and in the case of preformed nanoparticles their size remains unchanged (a few nanometers) whereas for the in-situ nanocomposites gold ripening leads to large particles (hundreds of nanometers). The grown YBCO-Au films showed good superconducting characteristics (J(c) 2 MA/cm2 at 77 K) but the absence of Au inclusions inside the YBCO matrix explains the fact that no enhancement of vortex pinning was observed. PMID:21776693

  8. Growth study of Ge xSb yTe z deposited by MOCVD under nitrogen for non-volatile memory applications

    NASA Astrophysics Data System (ADS)

    Longo, M.; Salicio, O.; Wiemer, C.; Fallica, R.; Molle, A.; Fanciulli, M.; Giesen, C.; Seitzinger, B.; Baumann, P. K.; Heuken, M.; Rushworth, S.

    2008-11-01

    We report on the bubbler-type MOCVD growth of Ge xSb yTe z (GST) on SiO 2/Si substrates, potentially transferable to phase change memory (PCM) devices. Pure nitrogen was used as the process gas in order to reduce toxicity whilst increasing the simplicity of the process. This systematic study allowed the modification of the growth parameters on SiO 2 to move through initial sub-micrometric crystalline grain deposition on to lateral island growth. Temperature was observed to play a critical role in film quality with strong morphology and island shape/size changes for small thermal variations. Eventually, continuous layers of GST in the hcp phase and composition close to the 2:2:5 were studied. The deposition on different substrates was also investigated. Although crystal nucleation is still far from achieving the target step coverage required for uniform coating of patterned substrates, the electrical sheet resistance of GST films exhibited values corresponding to those expected for chalcogenide materials suitable to be integrated into PCM devices.

  9. Joining of melt-textured YBCO using Tm123 powder as a solder

    NASA Astrophysics Data System (ADS)

    Prikhna, T. A.; Gawalek, W.; Moshchil, V. E.; Sergienko, N. V.; Sverdun, V. B.; Surzhenko, A. B.; Wendt, M.; Litzkendorf, D.; Habisreuther, T.; Vlasenko, A. V.

    2003-04-01

    Model experiments on joining of melt-textured YBa 2Cu 3O 7- δ (MT-YBCO) using rings cut from bulk single domain give the strong proof that the critical current density through the soldered seam obtained using a Tm123 powder as a solder is at the same level as that through the MT-YBCO (34 kA/cm 2 at 77 K in the 0 T field) and that the proposed comparatively short soldering process allows us to obtain soldered bulk with the even higher jc (up to 2.5 T fields at 77 K) than that of the initial unbroken one. The seam structure (including the twinned one) slaved the structure of the jointed MT-YBCO.

  10. Effect of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} film thickness on the dielectric properties of Ba{sub 0.1}Sr{sub 0.9}TiO{sub 3} in Ag/Ba{sub 0.1}Sr{sub 0.9}TiO{sub 3}/YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}/LaAlO{sub 3} multilayer structures

    SciTech Connect

    Zhu Xiaohong; Peng Wei; Li Jie; Chen Yingfei; Tian Haiyan; Xu Xiaoping; Zheng Dongning

    2005-01-01

    Ferroelectric and superconductor bilayers of Ba{sub 0.1}Sr{sub 0.9}TiO{sub 3} (BSTO)/YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO), with different YBCO film thicknesses, have been fabricated in situ by pulsed-laser deposition on 1.2 deg. vicinal LaAlO{sub 3} substrates. The dielectric properties of BSTO thin films were measured with a parallel-plate capacitor configuration in the temperature range of 77-300 K. We observed a strong dependence of the dielectric properties of BSTO thin films on the thickness of the YBCO layer. As the YBCO-film thickness increases, the temperature of the dielectric permittivity maximum of BSTO thin films shifts to higher values, and the leakage current and dielectric loss increase drastically, while the dielectric constant and dielectric tunability decrease remarkably. The results are explained in terms of the transformation in the growth mode of the YBCO layer from two-dimensional step flow to three-dimensional island that leads to significant deterioration in the dielectric properties of BSTO thin films. We propose that improved dielectric properties could be obtained by reasonably manipulating the growth mode of the YBCO layer in the multilayer structures.

  11. Morphology of ZnO grown by MOCVD on sapphire substrates

    NASA Astrophysics Data System (ADS)

    Munuera, C.; Zúñiga-Pérez, J.; Rommeluere, J. F.; Sallet, V.; Triboulet, R.; Soria, F.; Muñoz-Sanjosé, V.; Ocal, C.

    2004-03-01

    A quantitative roughness and microstructural analysis of ZnO grown on sapphire by atmospheric metalorganic chemical vapor deposition (MOCVD) is presented. In order to investigate the influence of the substrate on the morphology, different sapphire orientations have been employed. Scanning force microscopy data have been analyzed for a variety of thicknesses to elucidate, if possible, the growth mechanisms involved in the growth process. Our study reveals significant differences between morphologies depending on whether the substrate surface exhibits steps (misoriented a-, c- and r-planes) or not ( m-plane); however, no major differences on the calculated roughness coefficients have been found.

  12. Investigation of GaP/Si Heteroepitaxy on MOCVD Prepared Si(100) Surfaces

    SciTech Connect

    Warren, Emily L.; Kibbler, Alan E.; France, Ryan M.; Norman, Andrew G.; Olson, Jerry M.; McMahon, William E.

    2015-06-14

    Antiphase-domain (APD) free growth of GaP on Si has been achieved on Si surfaces prepared in situ by etching with AsH3. The pre-nucleation AsH3 etching removes O and C contaminants at a relatively low temperature, and creates a single-domain arsenic-terminated Si surface. The As-As dimer rows are all parallel to the step edges, and subsequent GaP growth by MOCVD retains this dimerization orientation. Both LEED and TEM indicate that the resulting epilayer is APD-free, and could thereby serve as a template for III-V/Si multijunction solar cells.

  13. High quality GaN-based LED epitaxial layers grown in a homemade MOCVD system

    NASA Astrophysics Data System (ADS)

    Haibo, Yin; Xiaoliang, Wang; Junxue, Ran; Guoxin, Hu; Lu, Zhang; Hongling, Xiao; Jing, Li; Jinmin, Li

    2011-03-01

    A homemade 7 × 2 inch MOCVD system is presented. With this system, high quality GaN epitaxial layers, InGaN/GaN multi-quantum wells and blue LED structural epitaxial layers have been successfully grown. The non-uniformity of undoped GaN epitaxial layers is as low as 2.86%. Using the LED structural epitaxial layers, blue LED chips with area of 350 × 350 μm2 were fabricated. Under 20 mA injection current, the optical output power of the blue LED is 8.62 mW.

  14. High critical current density YBa 2Cu 3O 7- δ films on surface-oxidized metallic substrates

    NASA Astrophysics Data System (ADS)

    Matsumoto, Kaname; Kim, SeokBeom; Yamagiwa, Katsuya; Koike, Yoshihiro; Hirabayashi, Izumi; Watanabe, Tomonori; Uno, Naoki; Ikeda, Masaru

    2000-06-01

    YBa 2Cu 3O 7-δ (YBCO) films with high critical current density ( Jc) were fabricated on nickel tapes buffered with bi-axially textured NiO prepared by surface-oxidation epitaxy (SOE). The effects of oxide cap layers, such as YSZ, CeO 2 and MgO, on the SOE-grown NiO were investigated to improve the superconducting properties of the YBCO films on NiO. By inserting a thin MgO cap layer between NiO layer and YBCO film, a Jc of 3×10 5 A/cm 2 (77 K, 0 T) was achieved. This result indicates the potentiality of the SOE method. In this paper, the application of the NiO/Ni substrate to non-vacuum processings, such as metal-organic deposition (MOD) and liquid phase epitaxy (LPE) will be also introduced.

  15. Large area, low microwave surface resistance thin films of YBa 2Cu 3O 7 prepared by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Tian, Y. J.; Lu, H. B.; Xu, S. F.; Chen, Z. H.; Cui, D. F.; Zhou, Y. L.; Zhang, Y. Z.; Li, L.; Yang, G. Z.

    1994-02-01

    YBa 2Cu 3O 7 (YBCO) superconducting thin films were deposited on (100)LaAlO 3 substrates 35 mm in diameter by pulsed laser ablation. The substrates were heated resistively during deposition by a single-crystal Si heater and the laser beam was scanned on the rotating YBCO target. The films exhibited a thickness variation of ±3.7%, with zero resistance temperature Tc0 =90.6±0.6 K, critical current density Jc=2.9±0.9×10 6A/ cm2 at 77 K, and at 10 GHz a surface microwave resistance of <250μΩ at 77 K. The above-mentioned properties showed that high-quality YBCO thin films over a large substrate area can be obtained with this laser ablation system.

  16. Levitation forces of a bulk YBCO superconductor in gradient varying magnetic fields

    NASA Astrophysics Data System (ADS)

    Jiang, J.; Gong, Y. M.; Wang, G.; Zhou, D. J.; Zhao, L. F.; Zhang, Y.; Zhao, Y.

    2015-09-01

    The levitation forces of a bulk YBCO superconductor in gradient varying high and low magnetic fields generated from a superconducting magnet were investigated. The magnetic field intensity of the superconducting magnet was measured when the exciting current was 90 A. The magnetic field gradient and magnetic force field were both calculated. The YBCO bulk was cooled by liquid nitrogen in field-cooling (FC) and zero-field-cooling (ZFC) condition. The results showed that the levitation forces increased with increasing the magnetic field intensity. Moreover, the levitation forces were more dependent on magnetic field gradient and magnetic force field than magnetic field intensity.

  17. Solderability Study of RABiTS-Based YBCO Coated Conductors

    SciTech Connect

    Zhang, Yifei; Duckworth, Robert C; Ha, Tam T; Gouge, Michael J

    2011-01-01

    The solderability of commercially available YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) coated conductors that were made from Rolling Assisted Biaxially Textured Substrates (RABiTS)-based templates was studied. The coated conductors, also known as second-generation (2G) high temperature superconductor (HTS) wires (in the geometry of flat tapes about 4 mm wide), were laminated with copper, brass, or stainless steel strips as stabilizers. To understand the factors that influence their solderability, surface profilometry and scanning electron microscopy were used to characterize the wire surfaces. The solderability of three solders, 52In48Sn, 67Bi33In, and 100In (wt.%), was evaluated using a standard test (IPC/ECA J-STD-002) and with two different commercial fluxes. It was found that the solderability varied with the solder and flux but the three different wires showed similar solderability for a fixed combination of solder and flux. Solder joints of the 2G wires were fabricated using the tools and the procedures recommended by the HTS wire manufacturer. The solder joints were made in a lap-joint geometry and with the superconducting sides of the two wires face-to-face. The electrical resistances of the solder joints were measured at 77 K, and the results were analyzed to qualify the soldering materials and evaluate the soldering process. It was concluded that although the selection of soldering materials affected the resistance of a solder joint, the resistivity of the stabilizer was the dominant factor.

  18. Effect of holding temperature on microstructures and Jc properties of YBa2Cu3O7-X films fabricated by TFA-MOD method

    NASA Astrophysics Data System (ADS)

    Konya, K.; Ootaguro, K.; Nishiyama, T.; Teranishi, R.; Kiss, T.; Yamada, K.; Kaneko, K.; Yoshizumi, M.; Izumi, T.

    2013-11-01

    In this study, we investigated the correlation between microstructures and critical current density (Jc) of YBa2Cu3O7-X (YBCO) films with BaZrO3 (BZO) pinning centers by introducing holding temperature during the crystallization process. Smaller BZO particles and higher in-field Jc were found in the YBCO film with holding temperature than the one without. As a result, films with improved microstructures were successfully fabricated by implementation of additional process, holding temperature, and highly in-field Jc were obtained by introducing smaller BZO particles as artificial pinning centers.

  19. Compound semiconductor native oxide-based technologies for optical and electrical devices grown on gallium arsenide substrates using MOCVD

    NASA Astrophysics Data System (ADS)

    Holmes, Adrian Lawrence

    1999-11-01

    The beginning of the modern microelectronics industry can be traced back to an invention made in 1947 when Bardeen and Brattain created the first semiconductor switch, called a transistor. Several other important discoveries followed; however, two of the more significant were (i) the development of the first planar process using silicon dioxide (SiO2) as a mask for diffusions into silicon by Frosch in 1955, and (ii) the subsequent integration of several transistors in tiny circuits by Kilby in 1958. Due to the superior quality of the SiO2-silicon interface, Si-based metal-oxide-semiconductor (MOS) transistors have primarily been used in integrated circuits. Until recently, compound semiconductors did not have a native oxide of sufficient quality to create similar MOS transistors. In 1990, research performed by Professor Holonyak and his group at the University of Illinois at Urbana-Champaign has led to a high-quality, stable, and insulating native oxide created from aluminum-containing compound semiconductor alloys. This study investigates native oxide films that are formed by the thermal oxidation of AlAs and InAlP epitaxial layers grown lattice-matched on GaAs substrates using metalorganic chemical vapor deposition (MOCVD). The primary goal is to evaluate how these native oxides can help form novel device structures and transistors. To qualify the material properties of these native oxide films, we have used several characterization techniques including photoluminescence, cross-sectional scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Additionally, we have performed leakage current and capacitance-voltage measurements to evaluate the electrical characteristics of the native oxide-semiconductor interface. The kinetics of the thermal oxidation process for both the surface oxidation of InAlP and lateral oxidation of AlAs are studied and contrasted. Aided by this knowledge, we have created a sealed

  20. In-situ superconducting YBa2Cu3O7 thin films grown by ion beam co-deposition

    NASA Astrophysics Data System (ADS)

    James, J. H.; Kellett, B. J.; Gauzzi, A.; Dwir, B.; Pavuna, D.

    1989-12-01

    We present superconducting YBa2C3O7 (YBCO) thin films grown in-situ by three-ion-beam sputtering. Y, Y2O3, Cu, Cu2O, BaF2 and BaCO3 sputter targets have been investigated. The highest quality films were prepared using a BaCO3 target. Auger analysis of films grown using a BaCO3 target show no carbon content. Y2O3 and Cu2O are more suitable than the native metals as sputter targets for YBCO growth as they are much less prone to sputter rate variations with oxygen partial pressure. They also supply oxygen to the growing film. As-deposited YBCO films are metallic (resistivity 240 μΩ cm at 100 K), reflective, and of highly homogeneous composition with TCO transition temperatures of 73 K and transition widths of 15 K. Post-annealing in flowing oxygen improves TCO's to 82 K. Critical currents are in excess of 105 A cm-2 at 77 K. Films are textured with c-axis orientation perpendicular to the (100) SrTiO3 substrate surface. As-deposited superconducting YBCO films have also been prepared on SiO2 and Y2O3 buffer layers on Si wafers.

  1. Unintentional Doping Mechanisms in GaAs/Si Films Grown by Metalorganic Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Deng, Can; Jia, Zhi-Gang; Wang, Yi-Fan; Wang, Qi; Huang, Yong-Qing; Ren, Xiao-Min

    2013-11-01

    To explain different doping effects in a buffer layer, thermally annealed interface, and upper epilayers of GaAs/Si films grown by Metalorganic Chemical Vapor Deposition (MOCVD), the behaviors of unintentional doping in GaAs/Si films are investigated in detail. A third doping mechanism of arsine impurity incorporation during the growth process of GaAs/Si films, apart from conventional mechanisms of gas phase reaction and diffusion from the silicon substrate, is proposed. The experimental results reveal that the doping behavior in the buffer layer studied is determined by the three types of doping mechanisms together. However in the thermally annealed interface and upper epilayers, the third doping mechanism is dominant. According to the third mechanism, the background carrier concentration in GaAs/Si films grown by MOCVD could be properly controlled through the arsine flow rate.

  2. Optical Response in Amorphous GaAs Thin Films Prepared by Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Kiwa, Toshihiko; Kawashima, Ichiro; Nashima, Shigeki; Hangyo, Masanori; Tonouchi, Masayoshi

    2000-11-01

    Femtosecond optical response in GaAs thin films has been studied. We prepared GaAs thin films on MgO substrates and on YBa2Cu3O7-δ (YBCO) thin films using pulsed laser deposition (PLD) at temperatures below 250^\\circC@. A photocarrier lifetime of less than 1 ps is measured for the prepared GaAs thin films using femtosecond time-domain reflectivity change measurements. Pulsed electromagnetic wave [terahertz (THz) radiaiton] containing a frequency component of up to 1 THz is emitted from fabricated photoconductive switches using the prepared thin films. We also evaluated the THz radiation properties emitted from the photoswitches on the YBCO thin films.

  3. Fabrication of GaN nanotubular material using MOCVD with aluminum oxide membrane

    NASA Astrophysics Data System (ADS)

    Jung, Woo-Gwang; Jung, Se-Hyuck; Kung, Patrick; Razeghi, Manijeh

    2006-02-01

    GaN nanotubular material is fabricated with aluminum oxide membrane in MOCVD. SEM, XRD, TEM and PL are employed to characterize the fabricated GaN nanotubular material. An aluminum oxide membrane with ordered nano holes is used as template. Gallium nitride is deposited at the inner wall of the nano holes in aluminum oxide template, and the nanotubular material with high aspect ratio is synthesized using the precursors of TMG and ammonia gas. Optimal synthesis condition in MOCVD is obtained successfully for the gallium nitride nanotubular material in this research. The diameter of GaN nanotube fabricated is approximately 200 ~ 250 nm and the wall thickness is about 40 ~ 50 nm. GaN nanotubular material consists of numerous fine GaN particulates with sizes ranging 15 to 30 nm. The composition of gallium nitride is confirmed to be stoichiometrically 1:1 for Ga and N by EDS. XRD and TEM analyses indicate that grains in GaN nanotubular material have nano-crystalline structure. No blue shift is found in the PL spectrum on the GaN nanotubular material fabricated in aluminum oxide template.

  4. Fabrication of GaN nanotubular material using MOCVD with an aluminium oxide membrane

    NASA Astrophysics Data System (ADS)

    Jung, Woo-Gwang; Jung, Se-Hyuck; Kung, Patrick; Razeghi, Manijeh

    2006-01-01

    GaN nanotubular material is fabricated with an aluminium oxide membrane in MOCVD. SEM, XRD, TEM and PL are employed to characterize the fabricated GaN nanotubular material. An aluminium oxide membrane with ordered nanoholes is used as a template. Gallium nitride is deposited at the inner wall of the nanoholes in the aluminium oxide template, and the nanotubular material with high aspect ratio is synthesized using the precursors of TMG and ammonia gas. Optimal synthesis conditions in MOCVD are obtained successfully for the gallium nitride nanotubular material in this research. The diameter of the GaN nanotube fabricated is approximately 200-250 nm and the wall thickness is about 40-50 nm. GaN nanotubular material consists of numerous fine GaN particulates with size range 15-30 nm. The composition of gallium nitride is confirmed to be stoichiometrically 1:1 for Ga and N by EDS. XRD and TEM analyses indicate that the grains in GaN nanotubular material have a nano-crystalline structure. No blue shift is found in the PL spectrum on the GaN nanotubular material fabricated in an aluminium oxide template.

  5. Superconductivity in the surface of YBa 2Cu 3O 7-δ films. Role of the charge reservoir block on the occurence of the superconductivity in one-unit-cell thick YBa 2Cu 3O 7-δ

    NASA Astrophysics Data System (ADS)

    Shimura, Ken-ichi; Daitoh, Yoshihiro; Yano, Yoshihiko; Terashima, Takahito; Bando, Yoshichika; Matsuda, Yuji; Komiyama, Susumu

    1994-07-01

    We have studied the superconductivity in the surface of c-axis oriented ultrathin films of YBa 2Cu 3O 7-δ (YBCO) using a heterostructure of cap oxide/one-unit-cell thick (1-UCT) YBCO/PrBa 2Cu 3O 7-δ buffer layer/SrTiO 3. Atomic force microscope images of the film have revealed multi-terraces with a height of a unit cell of YBCO, indicating two-dimensional nucleation and growth. From cross-sectional transmission electron microscope observation, it has been revealed that the terminating layer of the film is a CuO layer. Cap oxides of BaO and SrO with NaCl-type structure and BaTiO 3, SrTiO 3, CaTiO 3, PbTiO 3, and CdTiO 3 with perovskite-type structure have the ability to produce superconductivity in 1-UCT YBCO. These cap oxides contain an MO ‘rocksalt’-type layer which is needed to form an MO-CuO-BaO charge reservoir block. It is required for making the superconductivity in 1-UCT YBCO that the lattice mismatch between the cap oxide and YBCO is sufficiently small (⩽6%) and the valence of M is 2+.

  6. Investigation for surface resistance of yttrium-barium-copper-oxide thin films on various substrates for microwave applications

    NASA Astrophysics Data System (ADS)

    Yao, Hongjun

    High temperature superconducting (HTS) materials such as YBCO (Yttrium-Barium-Copper-Oxide) are very attractive in microwave applications because of their extremely low surface resistance. In the proposed all-HTS tunable filter, a layer of HTS thin film on a very thin substrate (100 mum) is needed to act as the toractor that can be rotated to tune the frequency. In order to provide more substrate candidates that meet both electrical and mechanical requirements for this special application, surface resistance of YBCO thin films on various substrates was measured using microstrip ring resonator method. For alumina polycrystalline substrate, a layer of YSZ (Yttrium stabilized Zirconia) was deposited using IBAD (ion beam assisted deposition) method prior to YBCO deposition. The surface resistance of the YBCO thin film on alumina was found to be 22 mO due to high-angle grain boundary problem caused by the mixed in-plane orientations and large FWHM (full width at half maximum) of the thin film. For YBCO thin films on a YSZ single crystal substrate, the surface resistance showed even higher value of 30 mO because of the mixed in-plane orientation problem. However, by annealing the substrate in 200 Torr oxygen at 730°C prior to deposition, the in-plane orientation of YBCO thin films can be greatly improved. Therefore, the surface resistance decreased to 1.4 mO, which is still more than an order higher than the reported best value. The YBCO thin films grown on LaAlO3 single crystal substrate showed perfect in-plane orientation with FWHM less 1°. The surface resistance was as low as 0.032 mO. A tunable spiral resonator made of YBCO thin film on LaAlO3 single crystal substrate demonstrated that the resonant frequency can be tuned in a rang as large as 500 MHz by changing the gap between toractor and substrate. The Q-factor was more than 12,000, which ensured the extraordinarily high sensitivity for the proposed all-HTS tunable filter.

  7. Superconductivity, microstructure of large area YBa 2Cu 3O 7 thin films prepared by pulsed laser ablation (PLA)

    NASA Astrophysics Data System (ADS)

    Li, L.; Tian, Y. J.; Xu, S. F.; Lu, H. B.; Chen, Z. H.; Cui, D. F.; Zhou, Y. L.; Liu, J. Z.; Guo, L. P.; Zhao, Z. X.; Yang, G. Z.

    1994-12-01

    YBa 2Cu 3O 7 (YBCO) superconducting thin films with Tco = 90.6±0.6 K, Jc = (2.9±0.9)x10 6A/cm 2 at 77K and Rs≤250μΩ at 10GHz were deposited on φ35mm substrates by PLA. STM examination showed both spiral and layered island growth. When the substrate-target distance was 30mm, YBCO film contained BaO precipitates with sizes between 10-100nm, equiaxed shapes, which may act as pinning centers.

  8. 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.

  9. Effect of Interim Annealing on Mechanical Strength of TFA-MOD Derived YBCO Coated Conductors

    NASA Astrophysics Data System (ADS)

    Takagi, Y.; Nakaoka, K.; Nakamura, T.; Yoshizumi, M.; Kiss, T.; Izumi, T.; Shiohara, Y.

    TFA-MOD derived YBCO tapes are expected for many applications due to cost-efficiency. In some applications, uniformity and mechanical strength are required for tapes. A 205 m-long YBCO tape was fabricated with high and uniform Ic performance throughout the tape by adopting the interim annealing before the conversion process. The effect of the interim annealing on the crystal growth mechanism of YBCO has been studied focusing on the relationship between the interim annealing conditions and delamination, in this work. Delamination strength was evaluated in the samples prepared with and without interim annealing by the stud pull method. Measurements were carried out on 50 different points for each sample and the results were analyzed statistically. The difference between the two samples was remarkably seen in the delamination strength below 60 MPa. The conventionally annealed sample had more points with low delamination strength below 60 MPa than the interim annealed one. The cross sectional images of both samples observed by SEM showed that there were few pores within the interim annealed superconducting layer, although conventional superconducting layer had many pores. These results suggest that the pores within YBCO layer might be origins to be propagated for delamination at low strength.

  10. Critical currents and dissipative effects in proton-irradiated ceramic YBCO and BISCO

    SciTech Connect

    Mezzetti, E.; Minetti, B. ); Andreone, D. ); Cherubini, R. ); Gherardi, L.; Metra, P. )

    1992-04-01

    Transport properties in pellets of YBCO and BISCO are studied before and after 6.5-MeV proton implantation. The average critical current was strongly enhanced but in one case also weakened, probably due to the unfavorable interaction with the pre-irradiation defect structure. Characteristic parameters are compared and discussed. 17 refs., 3 figs.

  11. Experimental studies of helical solenoid model based on YBCO tape-bridge joints

    SciTech Connect

    Yu, M.; Lombardo, V.; Turrioni, D.; Zlobin, A.V.; Flangan, G.; Lopes, M.L.; Johnson, R.P.; /Fermilab

    2011-06-01

    Helical solenoids that provide solenoid, helical dipole and helical gradient field components are designed for a helical cooling channel (HCC) proposed for cooling of muon beams in a muon collider. The high temperature superconductor (HTS), 12 mm wide and 0.1 mm thick YBCO tape, is used as the conductor for the highest-field section of HCC due to certain advantages, such as its electrical and mechanical properties. To study and address the design, and technological and performance issues related to magnets based on YBCO tapes, a short helical solenoid model based on double-pancake coils was designed, fabricated and tested at Fermilab. Splicing joints were made with Sn-Pb solder as the power leads and the connection between coils, which is the most critical element in the magnet that can limit the performance significantly. This paper summarizes the test results of YBCO tape and double-pancake coils in liquid nitrogen and liquid helium, and then focuses on the study of YBCO splices, including the soldering temperatures and pressures, and splice bending test.

  12. A newly designed ultrasonic spray pyrolysis device to fabricate YBCO tapes

    NASA Astrophysics Data System (ADS)

    Liu, M.; Zhou, M. L.; Zhai, L. H.; Liu, D. M.; Gao, X.; Liu, W.

    2003-04-01

    A newly designed ultrasonic spray pyrolysis device has been manufactured to fabricate YBCO tapes. The apparatus is primarily composed of four zones: the ultrasonic generator, the atomization chamber, the pyrolysis chamber and the rotating equipment. Every part of them is designed and fabricated by us. The whole system costs far less than the ready-made equipment facility in which there is always a vacuum apparatus. This apparatus with processing parameters accurately controlled can fabricate short and long YBCO tapes. In this paper, we mainly focused on how to design and manufacture four parts of the ultrasonic spray pyrolysis. We have deposited c-axis aligned short YBCO tapes on biaxially textured Ag {1 1 0}<1 1 0> substrates with Jc=10 3 A/cm 2 using this method with our device. The method is very promising in terms of its precise control of metal compositions, high deposition rate and low cost non-vacuum approach. Improvements of this technique are being carried out to fabricate long YBCO tapes.

  13. Formation of Self-Assembled Ba2YNbO6 Nanocolumns and their Contribution to Flux-Pinning and Jc in Nb-doped YBa2Cu3O7- Films

    SciTech Connect

    Wee, Sung Hun; Goyal, Amit; Zuev, Yuri L; Cantoni, Claudia; Selvamanickam, V.; Specht, Eliot D

    2010-01-01

    Ba{sub 2}RENbO{sub 6} (RE = rare earth elements including Y) compounds are considered new additives for superior flux-pinning in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films due to their excellent chemical inertness to and large lattice mismatches with YBCO. Simultaneous laser ablation of a YBCO target and a Nb metal foil attached to the surface of the target resulted in epitaxial growth of YBCO films having columnar defects comprised of self-aligned Ba{sub 2}YNbO{sub 6} (BYNO) nanorods parallel to the c-axis of the film. Compared to pure YBCO, YBCO+BYNO films exhibited no T{sub c} reduction as well as superior J{sub c} performance with higher self- and in-field J{sub c} by a factor of 1.5-7 and also exhibited a strong J{sub c} peak for H {parallel} c indicative of strong c-axis correlated flux-pinning.

  14. O 2-annealing effects on dielectric properties of Sr 2AlTaO 6/YBa 2Cu 3O y films

    NASA Astrophysics Data System (ADS)

    Takahashi, Yoshihiro; Zama, Hideaki; Morishita, Tadataka; Tanabe, Keiichi

    2001-08-01

    Approximately 160-nm-thick Sr 2AlTaO 6 (SAT) thin films were prepared by metalorganic chemical vapor deposition on liquid phase epitaxy-grown 60-μm-thick YBa 2Cu 3O 7- δ (YBCO) films. The effects of oxygen postannealing on the dielectric properties of SAT and the superconducting properties of YBCO were investigated. The c-axis length of YBCO decreased from 11.82 to 11.70 Å and its Tc of 90 K was observed after oxidation for 250 h at 500°C in 1 atm O 2 atmosphere, indicating that YBCO is almost fully oxygenated through SAT. Postannealed samples showed reasonably low dielectric constants for SAT of approximately 24 and low conductance of 10 -8 S at 10 5 Hz which corresponds to a loss tangent of 5×10 -4. On the other hand, the SAT films without postannealing exhibited an order of magnitude larger conductance. The improved dielectric properties of the annealed samples are probably attributed to compensation of oxygen defects at the SAT grain boundaries as well as oxidation of the lower YBCO film.

  15. High Temperature Superconducting Thin Films and Their Application to Superconducting-Normal Devices.

    NASA Astrophysics Data System (ADS)

    Mankiewich, Paul M.

    The existence of the proximity effect between the high temperature superconductor YBa_2Cu _3O_7 (YBCO) and normal metal thin films has been demonstrated for the first time, and this effect has been exploited to produce lithographically fabricated superconducting-normal-superconducting (SNS) Josephson junctions. Improvement of the fabrication processes has led to new methods of in-situ film growth and plasma etching of YBCO, as well as YBCO-compatible processes for the deep -ultraviolet and electron-beam lithography required to fabricate submicron device structures. This proximity effect approach helps to circumvent the short coherence length (xi~3 nm) characteristic of the high T_ {c} superconductors. In a clean normal metal such as gold or silver the relevant coherence length is governed by the higher Fermi velocity and longer mean free path. As a result a Josephson device containing a normal metal weak link can be longer than an ideal all -YBCO microbridge (dimensions comparable to xi ). This makes fabrication possible. Initially, SNS devices were fabricated and showed evidence for a supercurrent through the normal region. Properly spaced Shapiro steps as a function of microwave frequency were also observed. This result was evidence for a proximity effect between a normal metal and YBCO. Nevertheless, due to the short coherence length and the sensitivity of the YBCO to damage, the fabrication process was not sufficiently reproducible. As a result, new techniques were developed to enable more reproducible device fabrication. In-situ film growth and fabrication is desirable to minimize contamination of and damage to the surface of the superconductor. In -situ reactive coevaporation of YBCO was demonstrated. Patterning of these in-situ films into a structure required the development of a low-damage reactive ion etch. New lithographic techniques were developed to minimize chemical degradation of the superconductor. Finally, deposition of gold onto heated device

  16. Design and Evaluation of Ybco Cable for the Albany Hts Cable Project

    NASA Astrophysics Data System (ADS)

    Ohya, M.; Yumura, H.; Ashibe, Y.; Ito, H.; Masuda, T.; Sato, K.

    2008-03-01

    The Albany Cable Project's aim is to develop a 350 meter long HTS cable system with a capacity of 800 A at 34.5 kV, located between two substations in the National Grid Power Company's grid. In-grid use of BSCCO HTS cable began on July 20, 2006, and successful long-term operation proceeded as planned. The cable system consists of two cables, one 320 meters long and the other 30 meters, a cable-to-cable splice in a vault, two terminations, and a cooling system. In Phase-II of the Albany project, this autumn, the 30-meter section will be replaced with YBCO cable. The test manufacturing and evaluation of YBCO cable has been carried out using SuperPower's YBCO wires in order to confirm the credibility of the cable design. No degradation of the critical current was found at any stage of manufacture. The fault-current test, involving a 1-meter sample carrying 23 kA at 38 cycles, was conducted under open-bath conditions. The temperature increases at the conductor and shield were comparable to those of the BSCCO core, and no Ic degradation was found after the fault-current test. After the design suitability was confirmed, a 30-meter YBCO cable was manufactured. The critical current of the conductor and the shield were approximately 2.6 kA and 2.4 kA, respectively, almost the same as the design values, considering the wire's Ic and the effect of the magnetic field. The AC loss of the sample cable was 0.34 W/m/phase at 800 Arms and 60 Hz. Following favorable shipping test results, the YBCO cable was shipped to the United States, and arrived at the site in June 2007.

  17. MOCVD growth of N-polar GaN on on-axis sapphire substrate: Impact of AlN nucleation layer on GaN surface hillock density

    NASA Astrophysics Data System (ADS)

    Marini, Jonathan; Leathersich, Jeffrey; Mahaboob, Isra; Bulmer, John; Newman, Neil; (Shadi) Shahedipour-Sandvik, F.

    2016-05-01

    We report on the impact of growth conditions on surface hillock density of N-polar GaN grown on nominally on-axis (0001) sapphire substrate by metal organic chemical vapor deposition (MOCVD). Large reduction in hillock density was achieved by implementation of an optimized high temperature AlN nucleation layer and use of indium surfactant in GaN overgrowth. A reduction by more than a factor of five in hillock density from 1000 to 170 hillocks/cm-2 was achieved as a result. Crystal quality and surface morphology of the resultant GaN films were characterized by high resolution x-ray diffraction and atomic force microscopy and found to be relatively unaffected by the buffer conditions. It is also shown that the density of smaller surface features is unaffected by AlN buffer conditions.

  18. 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.

  19. YBa2Cu3O7-δ superconducting films prepared by low pressure post-annealing

    NASA Astrophysics Data System (ADS)

    Wang, Lianhong; Liu, Chong; Fan, Jing

    2014-12-01

    YBa2Cu3O7-δ precursor films are deposited on 2″ LaAlO3 wafer by the co-evaporation technique using Y, BaF2 and Cu as evaporation sources. After deposition, the films are annealed at low-pressure atmosphere with the composition of oxygen and water vapour. Compared with the normal pressure annealing, it is shown that low pressure can greatly improve the superconducting properties of 2″ YBCO films with thickness larger than 500 nm, as the microcrack on films surface becomes unobservable the microwave surface resistance is greatly reduced. Furthermore, it is also revealed that the optimal processing window for making high quality superconducting YBCO films through ex-situ process is relatively small, therefore the ambient in annealing furnace is crucial important and should be precisely controlled.

  20. Enhanced flux-pinning properties in superconducting YBa2Cu3O(7-delta) thin films with nanoengineering

    NASA Astrophysics Data System (ADS)

    Tsai, Chen-Fong

    Since the discovery of the high temperature superconductor YBa2Cu3O7-delta (YBCO), with transition temperature (Tc = 77 K), above liquid nitrogen point in 1987 many research projects have been dedicated to enhancing the high field performance of this material for practical applications. The 2 nd generation YBCO-based coated conductors are believed to be the most promising approach for commercial applications including power transmission, motors, generators, and high field magnets. With the advances of nanotechnologies, different nanoengineering methods have been demonstrated to enhance the performance of YBCO thin films, include doping with 0-dimensional (0-D) self-assembled nanoparticles, 1-dimensional (1-D) nanorods, and 2-dimensional (2-D) nanolayers. Furthermore, dopants with ferromagnetic properties are also reported to provide enhanced pinning effects by Lorentz force, especially under high-applied magnetic fields. The principle of these methods is to generate high-density defects at the heterogeneous interfaces as artificial pinning centers in an effort to improve the flux-pinning properties. The morphology and dimensions of the nanoinclusions play an important role in pining enhancement. Optimized pinning structures are likely to be located at energetically favorable vortex cores, which form a triangular lattice with dimensions close to the YBCO coherence length xi (xiab ~ 4 nm; xic ~ 0.5 nm at 77 K.) However, it is challenging to achieve small dimensional nanodopants in the vapor deposited YBCO thin films. The purpose of this research is to utilize nanoengineering methods to produce optimized pinning structure in YBCO thin films. In this thesis, we systematically study the effects of different nanoinclusions on the flux-pinning properties of YBCO thin films. The 0-D ferromagnetic Fe 2O3 and CoFe2O4 nanoparticles, 2-D CeO2 multilayers, and tunable vertically aligned nanocomposites (VAN) of (Fe2O3)x:(CeO2) 1-x and (CoFe2O4)x:(CeO2) 1-x systems are introduced

  1. Large-area YBa2Cu3O(7-delta) thin films on sapphire for microwave applications

    NASA Technical Reports Server (NTRS)

    Cole, B. F.; Liang, G.-C.; Newman, N.; Char, K.; Zaharchuk, G.; Martens, J. S.

    1992-01-01

    We have deposited YBa2Cu3O(7-delta) (YBCO) films with low microwave surface resistance (Rs) on 5-cm-diam, oxide-buffered sapphire substrates by planar magnetron sputtering. MgO buffer layers are used on M-plane (1 0 -1 0) sapphire, and R-plane (1 -1 0 2) sapphire is buffered by CeO2. Rs values of 450-620 microhms at 77 K and 10 GHz were measured across an entire 5-cm diam YBCO film on M-plane sapphire. For YBCO on R-plane sapphire, Rs values at 77 K and 10 GHz were 950 microohms for a 5-cm-diam wafer and 700 microohms for 1 x 1 sq cm samples.

  2. Anisotropic electronic structure of in-plane aligned a-axis YBa2Cu3O7-δ thin films

    NASA Astrophysics Data System (ADS)

    Luo, C. W.; Chen, M. H.; Liu, S. J.; Wu, K. H.; Juang, J. Y.; Uen, T. M.; Lin, J.-Y.; Chen, J.-M.; Gou, Y. S.

    2003-09-01

    Polarization-dependent x-ray absorption near-edge spectra (XANES) of the O 1s has been measured on a highly in-plane aligned a-axis YBa2Cu3O7-δ (YBCO) thin film. The in-plane XANES, with the electric field E of the linearly polarized synchrotron light being parallel to the b or c axis of YBCO films (E//b or E//c) were obtained in a normal-incidence alignment. The XANES for E//a was then calculated from the data obtained by varying the angle. The results lend strong support to those obtained by using detwinned YBCO single crystals in all crystalline orientations, including the extrapolated c-axis spectra.

  3. Preparation of dilute magnetic semiconductor films by metalorganic chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Nouhi, Akbar (Inventor); Stirn, Richard J. (Inventor)

    1990-01-01

    A method for preparation of a dilute magnetic semiconductor (DMS) film is provided, wherein a Group II metal source, a Group VI metal source and a transition metal magnetic ion source are pyrolyzed in the reactor of a metalorganic chemical vapor deposition (MOCVD) system by contact with a heated substrate. As an example, the preparation of films of Cd.sub.1-x Mn.sub.x Te, wherein 0.ltoreq..times..ltoreq.0.7, on suitable substrates (e.g., GaAs) is described. As a source of manganese, tricarbonyl (methylcyclopentadienyl) maganese (TCPMn) is employed. To prevent TCPMn condensation during the introduction thereof int the reactor, the gas lines, valves and reactor tubes are heated. A thin-film solar cell of n-i-p structure, wherein the i-type layer comprises a DMS, is also described; the i-type layer is suitably prepared by MOCVD.

  4. Three-dimensional modelling of horizontal chemical vapor deposition. I - MOCVD at atmospheric pressure

    NASA Technical Reports Server (NTRS)

    Ouazzani, Jalil; Rosenberger, Franz

    1990-01-01

    A systematic numerical study of the MOCVD of GaAs from trimethylgallium and arsine in hydrogen or nitrogen carrier gas at atmospheric pressure is reported. Three-dimensional effects are explored for CVD reactors with large and small cross-sectional aspect ratios, and the effects on growth rate uniformity of tilting the susceptor are investigated for various input flow rates. It is found that, for light carrier gases, thermal diffusion must be included in the model. Buoyancy-driven three-dimensional flow effects can greatly influence the growth rate distribution through the reactor. The importance of the proper design of the lateral thermal boundary conditions for obtaining layers of uniform thickness is emphasized.

  5. Free-standing GaAs nanowires growth on ITO glass by MOCVD

    NASA Astrophysics Data System (ADS)

    Wu, D.; Tang, X. H.; Olivier, A.; Li, X. Q.

    2015-04-01

    GaAs nanowires (NWs) are directly grown on indium tin oxide (ITO) glass substrate by metalorganic chemical vapour deposition (MOCVD), using Au nanoparticles (NPs) as catalyst. By functionalization of the ITO glass and optimization of the Au NPs deposition time, the Au NPs area density deposited on the ITO glass reaches 92 NP μm-2. Uniform and free-standing GaAs NWs without kinking or worm-shape defects have been grown at 430 °C. More than 96% of the NWs have tilt angles larger than 45° with respect of the substrate. The effects of the growth temperature and the Au NPs size on the GaAs NWs growth rate, the NW diameter, and tapering effect are investigated. These results of GaAs NWs growth are the essential step for understanding III-V NWs integration on transparent conductive oxide coated low cost substrate and developing high efficiencyhybrid solar cells.

  6. Monitoring and Controlling of Strain During MOCVD of AlGaN for UV Optoelectronics

    SciTech Connect

    Han, J.; Crawford, M.H.; Shul, R.J.; Hearne, S.J.; Chason, E.; Figiel, J.J.; Banas, M.

    1999-01-14

    The grown-in tensile strain, due to a lattice mismatch between AlGaN and GaN, is responsible for the observed cracking that seriously limits the feasibility of nitride-based ultraviolet (UV) emitters. We report in-situ monitoring of strain/stress during MOCVD of AlGaN based on a wafer-curvature measurement technique. The strain/stress measurement confirms the presence of tensile strain during growth of AlGaN pseudomorphically on a thick GaN layer. Further growth leads to the onset of stress relief through crack generation. We find that the growth of AlGaN directly on low-temperature (LT) GaN or AlN buffer layers results in a reduced and possibly controllable strain.

  7. Low ohmic contact AlN/GaN HEMTs grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Guodong, Gu; Shaobo, Dun; Yuanjie, Lü; Tingting, Han; Peng, Xu; Jiayun, Yin; Zhihong, Feng

    2013-11-01

    AlN/GaN high-electron-mobility transistors (HEMTs) on SiC substrates were fabricated by metal-organic chemical vapor deposition (MOCVD) and then characterized. An Si/Ti/Al/Ni/Au stack was used to reduce ohmic contact resistance (0.33 Ω·mm) at a low annealing temperature. The fabricated devices exhibited a maximum drain current density of 1.07 A/mm (VGS = 1 V) and a maximum peak extrinsic transconductance of 340 mS/mm. The off-state breakdown voltage of the device was 64 V with a gate—drain distance of 1.9 μm. The current gain extrinsic cutoff frequency fT and the maximum oscillation frequency fmax were 36 and 80 GHz with a 0.25 μm gate length, respectively.

  8. Microstructure of GaN Grown on (111) Si by MOCVD

    SciTech Connect

    Fleming, J.G.; Follstaedt, D.M.; Han, J.; Provencio, P.

    1998-12-17

    Gallium nitride was grown on (111) Si by MOCVD by depositing an AIN buffer at 108O"C and then GaN at 1060 {degrees}C. The 2.2pm layer cracked along {1-100} planes upon cooling to room temperature, but remained adherent. We were able to examine the microstructure of material between cracks with TEM. The character and arrangement of dislocation are much like those of GaN grown on Al{sub 2}O{sub 3}: -2/3 pure edge and - 1/3 mixed (edge + screw), arranged in boundaries around domains of GaN that are slightly disoriented with respect to neighboring material. The 30 nm AIN buffer is continuous, indicating that AIN wets the Si, in contrast to GaN on Al{sub 2}O{sub 3}.

  9. A mathematical representation of a modified stagnation flow reactor for MOCVD applications

    NASA Astrophysics Data System (ADS)

    Dilawari, A. H.; Szekely, J.

    1991-02-01

    Computed results are presented describing the behavior of a modified stagnation point reactor for an MOCVD system, employing a showerhead type gas distributor. The principal findings of the work are the following: (a) By this arrangement, it is possible to obtain a very high spatial uniformity in the deposition rate, in cases better than 0.35% for a five inch diameter wafer. (b) Both the absolute values of the gas velocity and the standoff distance were found to play a critical role in affecting the uniformity of the deposition rate. Indeed a small standoff distance was found to be an essential ingredient in obtaining a good spatial uniformity of the deposit. (c) "An upside down" orientation was found to be helpful in minimizing thermal natural convection and a further refinement was found to be possible by imposing a desired radial distribution on the gas inlet velocity profile.

  10. Growth of AlN nanostructure on GaN using MOCVD

    SciTech Connect

    Loganathan, R.; Ramesh, R.; Jayasakthi, M.; Prabakaran, K.; Kuppulingam, B.; Sankaranarayanan, M.; Balaji, M.; Arivazhagan, P.; Singh, Subra; Baskar, K.

    2015-06-24

    Aluminum nitride (AlN) nanowalls have been epitaxially grown on dislocation assisted GaN/Al{sub 2}O{sub 3} template by metal organic chemical vapor deposition (MOCVD) without any help of metal catalysts. A large number of nanowalls with thicknesses of 1.5-2.0 µm and height 400 nm have been deposited. The AlN nanowalls were found to have a preferred c-axis oriented with a hexagonal crystal structure. The AlN nanowalls and GaN/Al{sub 2}O{sub 3} template have been characterize at room temperature photoluminescence (PL) and high resolution X-ray diffraction (HRXRD)

  11. MOCVD capacitors

    SciTech Connect

    Lanagan, M.T.; Foster, C.

    1997-09-01

    A significant effort within the Department of Energy`s Office of Transportation Technologies and the U.S. Navy`s Power Electronic Building Block (PEBB) project has focused on reducing the size and weight of power electronic devices for electric and hybrid vehicles. Power electronic circuits, which are composed of active switching elements and passive components such as capacitors and inductors, provide motor control, power distribution, and DC/AC conversion functions in electric vehicles. Progress has been made on reducing the size and weight of power electronic components such as MOS-controlled thristors and insulated-gate bipolar transistors. Additional effort on high-power capacitors will be needed for load leveling and filter functions. The objective of this work is to fabricate a new class of high-power capacitors with reduced size and weight. Capacitors will be integrated with semiconductor components of electric motor and actuator control subsystems.

  12. Study of GaP single crystal layers grown on GaN by MOCVD

    SciTech Connect

    Li, Shuti; Liu, Chao; Ye, Guoguang; Xiao, Guowei; Zhou, Yugang; Su, Jun; Fan, Guanghan; Zhang, Yong; Liang, Fubo; Zheng, Shuwen

    2011-11-15

    Highlights: {yields} We investigated the growth of GaP layers on GaN by MOCVD. {yields} A single crystal GaP layer could be grown on GaN. {yields} The V/III ratio played an important role to improve GaP layer quality. {yields} The GaP:Mg layer with hole concentration of 4.2 x 10{sup 18} cm{sup -3} was obtained. -- Abstract: The performance of GaN based devices could possibly be improved by utilizing the good p-type properties of GaP layer and it provides the possibility of the integration of InAlGaN and AlGaInP materials to produce new devices, if high quality GaP compounds can be grown on III-nitride compounds. In this paper, the growth of GaP layers on GaN by metalorganic chemical vapor deposition (MOCVD) has been investigated. The results show that the GaP low temperature buffer layer can provide a high density of nucleation sites for high temperature GaP growth. Using a 40 nm thick GaP buffer layer, a single crystal GaP layer, whose full-width at half-maximum of the (1 1 1) plane measured by double crystal X-ray diffraction is 580'', can be grown on GaN. The V/III ratio plays an important role in the GaP layer growth and an appropriate V/III ratio can improve the quality of GaP layer. The GaP:Mg layer with hole carrier concentration of 4.2 x 10{sup 18} cm{sup -3} has been obtained.

  13. High efficiency cadmium and zinc telluride-based thin film solar cells

    NASA Astrophysics Data System (ADS)

    Rohatgi, A.; Summers, C. J.; Erbil, A.; Sudharsanan, R.; Ringel, S.

    1990-10-01

    Polycrystalline Cd(1-x)Zn(x)Te and Cd(1-x)Mn(x)Te films with a band gap of 1.7 eV were successfully grown on glass/SnO2/CdS substrates by molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD), respectively. Polycrystalline Cd(1-x)Zn(x)Te films grown by MBE resulted in uniform composition and sharp interfaces. However, polycrystalline Cd(1-x)Mn(x)Te films grown by MOCVD showed nonuniform compositions and evidence of manganese accumulation at the Cd(1-x)Mn(x)Te/CdS interface. We found that manganese interdiffuses and replaces cadmium in the CdS film. By improving the CdTe/CdS interface and, thus, reducing the collection function effects, the efficiency of the MOCVD CdTe cell can be improved to about 13.5 percent. MBE-grown CdTe cells also produced 8 to 9 percent efficiencies. The standard CdTe process was not optimum for ternary films and resulted in a decrease in the band gap. Recent results indicate that CdCl2 + ZnCl2 chemical treatment may prevent the band-gap reduction, and that chromate etch (rather than bromine etch) may provide the solution to contact resistance in the ternary cells.

  14. High efficiency cadmium and zinc telluride-based thin film solar cells

    SciTech Connect

    Rohatgi, A.; Summers, C.J.; Erbil, A.; Sudharsanan, R.; Ringel, S. . School of Electrical Engineering)

    1990-10-01

    Polycrystalline Cd{sub 1-x}Zn{sub x}Te and Cd{sub 1-x}Mn{sub x}Te films with a band gap of 1.7 eV were successfully grown on glass/SnO{sub 2}/CdS substrates by molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD), respectively. Polycrystalline Cd{sub 1-x}Zn{sub x}Te films grown by MBE resulted in uniform composition and sharp interfaces. However, polycrystalline Cd{sub 1-x}Mn{sub x}Te films grown by MOCVD showed nonuniform compositions and evidence of manganese accumulation at the Cd{sub 1-x}Mn{sub x}Te/CdS interface. We found that manganese interdiffuses and replaces cadmium in the CdS film. By improving the CdTe/CdS interface and, thus, reducing the collection function effects, the efficiency of the MOCVD CdTe cell can be improved to about 13.5%. MBE-grown CdTe cells also produced 8%--9% efficiencies. The standard CdTe process was not optimum for ternary films and resulted in a decrease in the band gap. Recent results indicate that CdCl{sub 2} + ZnCl{sub 2} chemical treatment may prevent the band-gap reduction, and that chromate etch (rather than bromine etch) may provide the solution to contact resistance in the ternary cells.

  15. Second harmonic generation in ZnO thin films fabricated by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Liu, C. Y.; Zhang, B. P.; Binh, N. T.; Segawa, Y.

    2004-07-01

    Second harmonic generation (SHG) from ZnO thin films fabricated by metalorganic chemical vapor deposition (MOCVD) technique was carried out. By comparing the second harmonic signal generated in a series of ZnO films with different deposition temperatures, we conclude that a significant part of second harmonic signal is generated at the film deposited with appropriate temperature. The second-order susceptibility tensor χ(2)zzz=9.2 pm/V was deduced for a film deposited at 250 °C.

  16. Enhancement of critical current density of YBa2Cu3O7-x thin films by self-assembly of Y2O3 nanoparticles

    SciTech Connect

    Vishwanathan, S.; Gapud, Albert Agcaoili; Varela del Arco, Maria; Abiade, J.; Christen, David K; Pennycook, Stephen J; Kumar, Dhananjay

    2007-01-01

    YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) thin films, possessing high critical current density (J{sub c}), have been synthesized by embedding a homogeneous array of Y2O3 non-superconducting nanoclusters/nanoparticles using a pulsed laser deposition technique. The size, interparticle spacing, and density of Y2O3 nanoparticles in YBCO thin films were tailored by varying the number of laser pulses in order to determine the optimum size for effective immobilization of vortices. Scanning transmission electron microscopy with atomic number contrast and X-ray diffraction techniques were used to determine the size and structure of the nanoparticles. Both techniques indicate that the Y{sub 2}O{sub 3} particles are epitaxial with respect to the surrounding YBCO matrix. The information about pinning of vortices by the nanoparticles was obtained by investigating the behavior of critical current density as a function of temperature and applied field, which in turn determines the vortex density in the sample. The superconducting transition temperature ({Tc}) of YBCO films with the inclusion of nanoparticles was observed to remain almost the same or decrease marginally (1-2 K) with respect to Tc of pure YBCO films deposited under identical conditions. However, JcS of YBCO films embedded with self-assembled nanoparticles were found to be significantly higher than that of pure YBCO films. The Jc enhancement was up to five times in high magnetic field, which is a key requirement for practical application of high-{Tc} materials.

  17. ZnO Films with Very High Haze Value for Use as Front Transparent Conductive Oxide Films in Thin-Film Silicon Solar Cells

    NASA Astrophysics Data System (ADS)

    Hongsingthong, Aswin; Krajangsang, Taweewat; Afdi Yunaz, Ihsanul; Miyajima, Shinsuke; Konagai, Makoto

    2010-05-01

    We successfully increased the haze value of zinc oxide (ZnO) films fabricated using metal-organic chemical vapor deposition (MOCVD) by conducting glass-substrate etching before film deposition. It was found that with increasing the glass treatment time, the surface morphology of ZnO films changed from conventional pyramid-like single texture to greater cauliflower-like multi texture. Further, the rms roughness and the haze value of the films increased remarkably. Using ZnO films with a high haze value as front transparent conductive oxide (TCO) films in hydrogenated microcrystalline silicon (µc-Si:H) solar cells, we improved the quantum efficiency of these cells particularly in the long-wavelength region.

  18. Study of microstructure and electrical properties of bulk YBCO prepared by melt textured growth technique

    SciTech Connect

    Gonal, M. R.; Krishnan, Madangopal; Tewari, R.; Tyagi, A. K.; Gyore, A.; Vajda, I.

    2015-06-24

    Bulk YBCO components were prepared using Melt Texture Growth (MTG) technique. Components were fabricated using MTG by addition of Y{sub 2}BaCuO{sub 5} (Y211) and Ag to YBCO, which leads to improved grain size without affecting superconducting properties. Green compacts prepared by cold isostatic pressing were pre-sintered at 930°C before subjecting melt texturing. Cooling rates lower than 1 °C.h{sup −1} was used, in between (peritectic) temperature of about 995 and 1025°C, to obtain large grained components. Microstructure studies in details were carried out by Scanning Electron Microscope (SEM), Electron Probe Micro Analysis (EPMA), Orientation Imaging Microscope (OIM) and TEM correlated with electrical properties like Critical current density (J{sub c})

  19. T /B scaling without quasiparticle mass divergence: YbCo2Ge4

    NASA Astrophysics Data System (ADS)

    Sakai, Akito; Kitagawa, Kentaro; Matsubayashi, Kazuyuki; Iwatani, Makoto; Gegenwart, Philipp

    2016-07-01

    YbCo2Ge4 is a clean paramagnetic Kondo lattice which displays non-Fermi-liquid behavior. We report a detailed investigation of the specific heat, magnetic Grüneisen parameter (Γmag), and temperature derivative of the magnetization (M ) on a high-quality single crystal at temperatures down to 0.1 K and magnetic fields up to 7 T. Γmag and d M /d T display a divergence upon cooling and obey T /B scaling. Similar behavior has previously been found in several other Yb-based Kondo lattices and related to a zero-field quantum critical point without fine tuning of pressure or composition. However, in the approach of B →0 the electronic heat capacity coefficient of YbCo2Ge4 saturates at low T , excluding ferromagnetic quantum criticality. This indicates that T /B scaling is insufficient to prove a zero-field quantum critical point.

  20. Static Test for a Gravitational Force Coupled to Type 2 YBCO Superconductors

    NASA Technical Reports Server (NTRS)

    Li, Ning; Noever, David; Robertson, Tony; Koczor, Ron; Brantley, Whitt

    1997-01-01

    As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (approx. 10(exp -6) g cc. Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating type II, YBCO superconductor, with the percentage change (0.05 - 2.1 %) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 10' was reported above a stationary (non-rotating) superconductor. In experiments using a sensitive gravimeter, bulk YBCO superconductors were stably levitated in a DC magnetic field. Changes in acceleration were measured to be less than 2 parts in 108 of the normal gravitational acceleration. This result puts new limits on the strength and range of the proposed coupling between static superconductors and gravity.

  1. High-field paramagnetic Meissner effect in melt-textured YBCO

    NASA Astrophysics Data System (ADS)

    Dias, F. T.; Pureur, P.; Rodrigues, P.; Obradors, X.

    2004-08-01

    We present systematic field-cooled magnetization measurements in four directionally solidified samples of YBCO containing different amounts of Y211 precipitates. Fields up to 50 kOe were applied either parallel or perpendicular to the Cu-O 2 atomic planes. At high applied magnetic fields, the paramagnetic Meissner effect (PME) was observed in all of the studied samples, regardless of the field orientation with respect to the crystalline axes. This high-field PME shows some noticeable differences when compared to the most frequently investigated PME at low applied fields. Our results suggest that pinning by Y211 particles is important for explaining the high-field PME of melt-processed YBCO.

  2. Study of YBCO tape anisotropy as a function of field, field orientation and operating temperature

    SciTech Connect

    Lombardo, v.; Barzi, E.; Turrioni, D.; Zlobin, A.V.

    2011-06-01

    Superconducting magnets with magnetic fields above 20 T will be needed for a Muon Collider and possible LHC energy upgrade. This field level exceeds the possibilities of traditional Low Temperature Superconductors (LTS) such as Nb{sub 3}Sn and Nb{sub 3}Al. Presently the use of high field high temperature superconductors (HTS) is the only option available for achieving such field levels. Commercially available YBCO comes in tapes and shows noticeable anisotropy with respect to field orientation, which needs to be accounted for during magnet design. In the present work, critical current test results are presented for YBCO tape manufactured by Bruker. Short sample measurements results are presented up to 14 T, assessing the level of anisotropy as a function of field, field orientation and operating temperature.

  3. Phase Evolution of YBa2Cu3O7-x films by all-chemical solution deposition route for coated conductors

    NASA Astrophysics Data System (ADS)

    Zhao, Yue; Tang, Xiao; Wu, Wei; Grivel, Jean-Claude

    2014-05-01

    In order to understand the all-chemical-solution-deposition (CSD) processes for manufacturing coated conductors, we investigated the phase evolution of YBa2Cu3O7 (YBCO) films deposited by a low-fluorine metal-organic solution deposition (LF-MOD) method on CSD derived Ce0.9La0.1O2/Gd2Zr2O7/NiW. It is shown that the phase transition from the pyrolyzed film to fully converted YBCO film in the LF-MOD process is similar to that in typical trifluoroacetates-metal organic deposition (TFA-MOD) processes even though the amount of TFA in the solution is reduced by almost one half compared with typical TFA-MOD cases. Moreover, we found that the formation of impurities (mainly BaCeO3, NiWO4 and NiO) is strongly related to the annealing temperature, i.e., the diffusion controlled reactions become intensive from 760 oC, which might be connected with the poor structural and superconducting properties of the films deposited at high sintering temperatures. Based on these results, the optimized growth conditions of YBCO films were established, and a high critical current density (Jc) of about 2 MA/cm2 (77 K, self field) is achieved in a 200 nm thick YBCO film in the architecture made by our all CSD route.

  4. Temperature coefficients and radiation induced DLTS spectra of MOCVD grown n(+)p InP solar cells

    NASA Technical Reports Server (NTRS)

    Walters, Robert J.; Statler, Richard L.; Summers, Geoffrey P.

    1991-01-01

    The effects of temperature and radiation on n(+)p InP solar cells and mesa diodes grown by metallorganic chemical vapor deposition (MOCVD) were studied. It was shown that MOCVD is capable of consistently producing good quality InP solar cells with Eff greater than 19 percent which display excellent radiation resistance due to minority carrier injection and thermal annealing. It was also shown that universal predictions of InP device performance based on measurements of a small group of test samples can be expected to be quite accurate, and that the degradation of an InP device due to any incident particle spectrum should be predictable from a measurement following a single low energy proton irradiation.

  5. CHEMICAL SOLUTION DEPOSITION BASED OXIDE BUFFERS AND YBCO COATED CONDUCTORS

    SciTech Connect

    Paranthaman, Mariappan Parans

    2011-01-01

    We have reviewed briefly the growth of buffer and high temperature superconducting oxide thin films using a chemical solution deposition (CSD) method. In the Rolling-Assisted Biaxially Textured Substrates (RABiTS) process, developed at Oak Ridge National Laboratory, utilizes the thermo mechanical processing to obtain the flexible, biaxially oriented copper, nickel or nickel-alloy substrates. Buffers and Rare Earth Barium Copper Oxide (REBCO) superconductors have been deposited epitaxially on the textured nickel alloy substrates. The starting substrate serves as a template for the REBCO layer, which has substantially fewer weak links. Buffer layers play a major role in fabricating the second generation REBCO wire technology. The main purpose of the buffer layers is to provide a smooth, continuous and chemically inert surface for the growth of the REBCO film, while transferring the texture from the substrate to the superconductor layer. To achieve this, the buffer layers need to be epitaxial to the substrate, i.e. they have to nucleate and grow in the same bi-axial texture provided by the textured metal foil. The most commonly used RABiTS multi-layer architectures consist of a starting template of biaxially textured Ni-5 at.% W (Ni-W) substrate with a seed (first) layer of Yttrium Oxide (Y2O3), a barrier (second) layer of Yttria Stabilized Zirconia (YSZ), and a Cerium Oxide (CeO2) cap (third) layer. These three buffer layers are generally deposited using physical vapor deposition (PVD) techniques such as reactive sputtering. On top of the PVD template, REBCO film is then grown by a chemical solution deposition. This article reviews in detail about the list of oxide buffers and superconductor REBCO films grown epitaxially on single crystal and/or biaxially textured Ni-W substrates using a CSD method.

  6. One-step preparation of highly dispersed metal-supported catalysts by fluidized-bed MOCVD for carbon nanotube synthesis

    NASA Astrophysics Data System (ADS)

    Xu, Chunbao; Zhu, Jesse

    2004-11-01

    A new technique of fluidized-bed metal-organic chemical vapour deposition (FB-MOCVD) is developed as a one-step method to prepare highly dispersed metal-supported catalysts for carbon nanotube synthesis. By using ultrafine powder of gamma-alumina (70 nm Sauter mean in size) as the support with Fe(CO)5 and Mo(CO)6 as the metal precursors, Fe/Al2O3, Mo/Al2O3 and Fe-Mo/Al2O3 catalysts have been prepared in an FB-MOCVD reactor. Compared with the conventional catalyst-preparation methods such as impregnation, ion exchange, co-precipitation and co-crystallization, the one-step FB-MOCVD technique is advantageous in many aspects. These include eliminating the solid-liquid separation and the subsequent operations of drying and high-temperature calcination/reduction, thus minimizing the aggregation or the crystalline size-growing problem for the supported metal particles caused by these operations. The metal-supported catalysts obtained by FB-MOCVD are characterized with various techniques including ICP-AES, SEM-EDX, XRD and nitrogen isothermal adsorption. Some catalysts are selected and used for carbon nanotube synthesis by CVD from acetylene (C2H2) in a fluidized bed at 650 or 850 °C. The formation of the entangled multi-walled carbon nanotubes (MWNTs), around 50 nm in outer diameter and 10 nm in inner diameter, and several to tens of microns in length, has been confirmed by the TEM and SEM analyses. High CNT selectivity ({\\ge }95{%} ) with the carbon yield ranging widely from about 10% to over 60%, depending on the type of catalyst used and the CNT deposition temperature, has been demonstrated with TGA tests.

  7. Effect of Au nano-particles doping on polycrystalline YBCO high temperature superconductor

    NASA Astrophysics Data System (ADS)

    Dadras, Sedigheh; Gharehgazloo, Zahra

    2016-07-01

    In this research, we prepared different Au nanoparticles (0.1-2 wt%) doped YBCO high temperature superconductor samples by sol-gel method. To characterize the samples, we used X-Ray diffraction (XRD) and scanning electron microscope (SEM) analysis. Results show the formation of orthorhombic phase of superconductivity for all prepared samples. We observed that by adding Au nanoparticles, the grains' size of the samples reduces from 76 nm to 47 nm as well. The critical current density (Jc) and transition temperature (Tc) were determined using current versus voltage (I-V) and resistivity versus temperature (ρ-T) measurements, respectively. We found that by increasing Au nanoparticles in the compound, in comparison to the pure YBCO sample, the transition temperature, pinning energy and critical current density will increase. Also, the highest Jc is for 1 wt% Au doped YBCO compound that its critical current density is about 8 times more than the Jc of pure one in 0.7 T magnetic field.

  8. Ultrasonic signatures at the superconducting and the pseudogap phase boundaries in YBCO cuprates.

    SciTech Connect

    Shehter, Arkady; Migliori, Albert; Betts, Jonathan B.; Balakirev, Fedor F.; McDonald, Ross David; Riggs, Scott C.; Ramshaw, Brad; Liang, Ruixing; Hardy, Walter N.; Bonn, Doug A.

    2012-08-28

    A major issue in the understanding of cuprate superconductors is the nature of the metallic state from which high temperature superconductivity emerges. Central to this issue is the pseudogap region of the doping-temperature phase diagram that extends from room temperature to the superconducting transition. Although polarized neutron scattering studies hint at magnetic order associated with the pseudogap, there is no clear thermodynamic evidence for a phase boundary. Such evidence has a straightforward physical interpretation, however, it is difficult to obtain over a temperature range wide enough to encompass both the pseudogap and superconducting phases. We address this by measuring the elastic response of detwinned single crystals, an underdoped YBCO{sub 6.60} with superconducting transition at T{sub c} = 61.6K and a slightly overdoped YBCO{sub 6.98} with T{sub c} = 88.0K. We observe a discontinuity in the elastic moduli across the superconducting transition. Its magnitude requires that pair formation is coincident with superconducting coherence (the onset of the Meissner effect). For both crystals the elastic response reveals a phase transition at the pseudogap boundary. In slightly overdoped YBCO that transition is 20K below T{sub c}, extending the pseudogap phase boundary inside the superconducting dome. This supports a description of the metallic state in cuprates where a pseudogap phase boundary evolves into a quantum critical point masked by the superconducting dome.

  9. Field Performance of an Optimized Stack of YBCO Square "Annuli" for a Compact NMR Magnet.

    PubMed

    Hahn, Seungyong; Voccio, John; Bermond, Stéphane; Park, Dong-Keun; Bascuñán, Juan; Kim, Seok-Beom; Masaru, Tomita; Iwasa, Yukikazu

    2011-06-01

    The spatial field homogeneity and time stability of a trapped field generated by a stack of YBCO square plates with a center hole (square "annuli") was investigated. By optimizing stacking of magnetized square annuli, we aim to construct a compact NMR magnet. The stacked magnet consists of 750 thin YBCO plates, each 40-mm square and 80- μm thick with a 25-mm bore, and has a Ø10 mm room-temperature access for NMR measurement. To improve spatial field homogeneity of the 750-plate stack (YP750) a three-step optimization was performed: 1) statistical selection of best plates from supply plates; 2) field homogeneity measurement of multi-plate modules; and 3) optimal assembly of the modules to maximize field homogeneity. In this paper, we present analytical and experimental results of field homogeneity and temporal stability at 77 K, performed on YP750 and those of a hybrid stack, YPB750, in which two YBCO bulk annuli, each Ø46 mm and 16-mm thick with a 25-mm bore, are added to YP750, one at the top and the other at the bottom. PMID:22081753

  10. CuPt-type ordering of MOCVD In{sub 0.49}Al{sub 0.51}P.

    SciTech Connect

    Kosel, T. H.; Hall, D. C.; Dupuis, R. D.; Heller, R. D.; Cook, R. E.

    2002-03-14

    CuPt-type ordering in In{sub 0.49}Al{sub 0.51}P is studied by TEM. The lattice-matched film was grown by MOCVD on a GaAs substrate oriented 10{sup o} off (001) towards [110], at 650 C and 25 nm/min. TEM [110] and [1{bar 1}0] cross-sections (XS) were made by wedge polishing and 2 kV Ar ion milling. In CuPt-type ordering of In{sub 0.52}Ga{sub 0.48}P, alternating In-Ga-In-Ga {l_brace}111{r_brace} planes of group III atoms produce 1/2 {bar 1}11 and 1/2 1{bar 1}1 order spots in the 110 SADP, while the [1{bar 1}0] SADP shows no order spots [1-3]. A few studies have reported this type of order in In{sub 0.49}Al{sub 0.51}P [4]. The 004 BF image of the [1{bar 1}0] XS in Fig. 1 shows uneven light/dark contrast modulation due to phase separation often observed in In{sub 0.52}Ga{sub 0.48}P. There are also light/dark layers marked ML parallel to the film growth plane; such unintentional multilayers have also been observed [5] but their origin is not understood. Order lamellae {approx}1.5 nm thick inclined at a shallow angle to the growth plane overlap the multilayer to produce Moire fringe contrast. Fig. 2 is a DF image showing the thin ordered domains in the [1{bar 1}0] XS, which are inclined at 12{sup o} to the growth plane and 2{sup o} to (001). Fig. 3a shows the absence of order spots in the [1{bar 1}0] SADP, while tilting 26.6{sup o} to [3{bar 1}0] reveals rows of order spots characteristic of CuPt ordering (Fig. 3b). The fact that the domains lie within {approx}2{sup o} of (001) shows that their orientation is crystallographically determined, while the fact that the ''multilayer'' is parallel to the growth plane rather than to (001) shows that it is not crystallographically determined. Most work does not describe domains in the [1{bar 1}0] XS, but Bellon et al. [1] commented that in a [1{bar 1}0] XS their In{sub 0.52}Ga{sub 0.48}P domains were exactly on (001) in a wafer 6{sup o} off (001) towards [110], consistent with our results. The domains and streaked order spots in

  11. On line diagnostics and characterization of thin films deposited by laser ablation of solid oxides precursors of superconductors

    NASA Astrophysics Data System (ADS)

    Giardini-Guidoni, A.; Desimoni, E.; Salvi, A. M.; Teghil, R.; Ambrico, M.; Morone, A.; Piccirillo, S.; Snels, M.

    This work presents the analysis of composite solid targets made by laser irradiation of mixtures of simple oxides and of superconducting YBCO and BISCO. The results are discussed in relation to previous studies on laser cluster ion formation of these materials and their chemical reactivity. The films of ablated materials have been analyzed by XPS and SEM.

  12. Nucleation and mesostrain influence on percolating critical currents of solution derived YBa2Cu3O7 superconducting thin films

    NASA Astrophysics Data System (ADS)

    Obradors, X.; Martínez-Julián, F.; Zalamova, K.; Vlad, V. R.; Pomar, A.; Palau, A.; Llordés, A.; Chen, H.; Coll, M.; Ricart, S.; Mestres, N.; Granados, X.; Puig, T.; Rikel, M.

    2012-11-01

    After briefly reviewing the present understanding of the nucleation process of YBCO films, a new approach is presented to enhance the stability of c-axis nucleation in epitaxial chemical solution deposited YBCO thin films derived from TFA precursors. We show that with silver addition to the TFA precursor c-axis nucleation can be reached in a wide range of temperature thus keeping high percolating Jc. We argue that silver reduces supersaturation and makes more stable the c-axis nuclei without modifying Tc. Additional advantages of silver addition are an enhanced surface smootheness and a reduced porosity of the YBCO films. The second reported topic relates to the discovery of an adverse relationship between percolating Jc and YBCO films mesostrain, as determined through X-ray diffraction line broadening. We show that mesostrain is enhanced in processes leading to inefficient strain healing at grain boundaries, for instance annealing times too short or growth temperatures too low. It is suggested that the strained regions at the low angle grain boundaries lead to a weak link behavior which can be microscopically understood on the basis of pair formation prevention, as proposed by the bond contraction pairing model.

  13. Growth of Highly Epitaxial YBa2Cu3O(7-δ) Films from a Simple Propionate-Based Solution.

    PubMed

    Zhao, Yue; Torres, Pol; Tang, Xiao; Norby, Poul; Grivel, Jean-Claude

    2015-11-01

    Intensive investigations have been conducted to develop epitaxial oxide thin films with superior electromagnetic performance by low-cost chemical solution deposition routes. In this paper, a novel propionate-based precursor solution without involving any other additive was proposed and employed to grow superconducting YBa2Cu3O(7-δ) (YBCO) films on LaAlO3 (LAO) single crystals. The precursor solutions are stable with a long shelf life of up to several months. Since the primary compositions are propionates after evaporating the solvent, the toxic reagents and evolved gases during solution synthesis and heat treatment can be eliminated completely. In this process, rapid pyrolysis and high conversation rate can also be achieved during growth of YBCO films in comparison with the conventional trifluoroacetate metal organic deposition routes. Remarkably, a 210 nm YBCO film exhibits high superconducting performance with a Jc value of 3.7 MA/cm(2) at 77 K, self-field. Nucleation and growth behaviors in the chemical solution process have also been studied. It is revealed that the amount of liquid phase (Ba-Cu-O) is sufficient through the entire thickness within a very short time at high growth temperatures, which results in pronounced densification and fast conversion of the YBCO phase. PMID:26473556

  14. Co-deposited thin films of YBa 2Cu 3O 7-δ-Ag

    NASA Astrophysics Data System (ADS)

    Moshfegh, A. Z.; Wang, Y. Q.; Sun, Y. Y.; Mesarwi, A.; Hor, P. H.; Ignatiev, A.

    1993-12-01

    The fabrication of high-temperature superconducting YBa 2Cu 3O 7-δ-Ag thin films has been investigated using a high-pressure Ag coevaporation-DC sputtering technique. Various analytical techniques including X-ray diffraction (XRD), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), energy dispersive X-ray analysis (EDX), and Tc measurement have been utilized for characterization of the films. Highly reproducible c-oriented (00 l) films have been prepared in-situ at a relatively low growth temperature (≃670°C) by this technique. The transition temperatures Tc gradually decreased with added Ag from 90 K (0 at.% Ag) to 72 K (22.3 at.% Ag) for the films deposited on MgO (100) substrates. X-ray diffraction indicated that the Ag is in the metallic state as a separate phase with respect to the YBCO and that the c-lattice parameter of the grown films remained unchanged with Ag addition. Surface morphology of the YBCO-Ag films exhibited a particulate-type structure with the grain size increasing as the Ag content increased. The temperature coefficient of the normalized resistance, d R( T)/ R(280 K)/d T, was also noticed to decrease for the Ag- containing samples as compared to Ag-free YBCO films. AES depth profiling identified Ag residing mainly at the YBCO/MgO interface. The effect of Ag addition to the films has been described by a particle growth model.

  15. Vapor-gel processing and applications in oxide film depositions

    SciTech Connect

    Chour, K.W.; Xu, R.; Takada, T.

    1995-12-31

    The Vapor-gel processing of oxide films is discussed for the prototypic system of LiTa(OBut{sup n}){sub 6}-LiTaO{sub 3}. It is found that the hydrolysis-polycondensation reaction scheme, commonly used in Sol-gel processing, can be used in a vapor deposition environment. High quality films can be deposited at low temperatures. We present some initial results regarding this deposition method and discuss its advantages and disadvantages as compared with Sol-gel processing and typical MOCVD.

  16. Off-axis sputter deposition of thin films

    SciTech Connect

    Capuano, L.A.; Newman, N. )

    1990-01-01

    Currently there are several techniques for making high Tc thin films, e.g., sputter deposition, laser ablation, coevaporation (including MBE), chemical vapor deposition and solution coating/pyrolysis. Of these techniques, the authors have demonstrated that high-pressure in-situ off-axis rf-magnetron sputter deposition is a simple, relatively inexpensive process capable of reproducibly yielding YBCO superconducting thin films with excellent surface resistance properties. This article describes the off-axis technique, the basic equipment requirements and the performance characteristics of high Tc superconductor films produced using this technique.

  17. Strongly enhanced flux pinning in the YBa2Cu3O7 -x films with the co-doping of BaTiO3 nanorod and Y2O3 nanoparticles at 65 K

    NASA Astrophysics Data System (ADS)

    Wang, Hong-Yan; Ding, Fa-Zhu; Gu, Hong-Wei; Zhang, Teng

    2015-09-01

    YBa2Cu3O7 - x (YBCO) films with co-doping BaTiO3 (BTO) and Y2O3 nanostructures were prepared by metal organic deposition using trifluoroacetates (TFA-MOD). The properties of the BTO/Y2O3 co-doped YBCO films with different excess yttrium have been systematically studied by x-ray diffraction (XRD), Raman spectra, and scanning electron microscope (SEM). The optimized content of yttrium excess in the BTO/Y2O3 co-doped YBCO films is 10 mol.%, and the critical current density is as high as ˜17 mA/cm2 (self-field, 65 K) by the magnetic signal. In addition, the Y2Cu2O5 was formed when the content of yttrium excess increases to 24 mol.%, which may result in the deterioration of the superconducting properties and the microstructure. The unique combination of the different types of nanostructures of BTO and Y2O3 in the doped YBCO films, compared with the pure YBCO films and BTO doped YBCO films, enhances the critical current density (JC) not only at the self-magnetic field, but also in the applied magnetic field. Project supported by the National Natural Science Foundation of China (Grant No. 51272250), the National Basic Research Program of China (Grant No. 2011CBA00105), the National High Technology Research and Development Program of China (Grant No. 2014AA032702), and the Natural Science Foundation of Beijing, China (Grant No. 2152035).

  18. Grain boundary networks in high-performance, heteroepitaxial, YBCO films on polycrystalline, cube-textured metals

    SciTech Connect

    Goyal, Amit; Field, Dr. David; Held, R.; Mannhart, J.

    2011-01-01

    Grain boundaries (GBs) in high-temperature superconductors suppress the critical current density (Jc) dramatically [1-3]. The Jc drops exponentially when GB-misorientation exceeds 4 [3]. To reduce the number of high-angle GBs, fabrication of biaxially-textured, superconducting wires via epitaxial growth on cube-textured metals has been widely investigated [4-6]. Such wires have exhibited very high-Jc in applied magnetic fields despite having a majority of GBs with total misorientations greater than 4 . Here we show that GB networks in these wires have numerous GBs with out-of-plane misorientations > 4 and few boundaries having in-plane misorientations > 4 . The high performance can be explained if the Jc is determined primarily by in-plane misorientations. This supposition was confirmed by in-field transport measurements on artificially fabricated bicrystals of superconductors having only out-of-plane misorientations. Atomic resolution imaging of bicrystals with out-of-plane misorientations show that superconducting ab-planes are continuous across such GBs in contrast to GBs with in-plane misorientations.

  19. Flux Compression in HTS Films

    NASA Astrophysics Data System (ADS)

    Mikheenko, P.; Colclough, M. S.; Chakalov, R.; Kawano, K.; Muirhead, C. M.

    We report on experimental investigation of the effect of flux compression in superconducting YBa2Cu3Ox (YBCO) films and YBCO/CMR (Colossal Magnetoresistive) multilayers. The flux compression produces positive magnetic moment (m) upon the cooling in a field from above to below the critical temperature. We found effect of compression in all measured films and multilayers. In accordance with theoretical calculations, m is proportional to applied magnetic field. The amplitude of the effect depends on the cooling rate, which suggests the inhomogeneous cooling as its origin. The positive moment is always very small, a fraction of a percent of the ideal diamagnetic response. A CMR layer in contact with HTS decreases the amplitude of the effect. The flux compression weakly depends on sample size, but sensitive to its form and topology. The positive magnetic moment does not appear in bulk samples at low rates of the cooling. Our results show that the main features of the flux compression are very different from those in Paramagnetic Meissner effect observed in bulk high temperature superconductors and Nb disks.

  20. Epitaxial Growth Of Y2O3 On Biaxially Textured Ni Tapes Using A Sol-Gel Process For YBCO Coated Conductors

    NASA Astrophysics Data System (ADS)

    Ciontea, L.; Ristoiu, T.; Suciu, R.-C.; Petrisor, T.

    2007-04-01

    A solution processing technique was used to deposit an epitaxial Y2O3 film on (001)[100] cube textured Ni tapes for YBa2Cu3Ox (YBCO) coated conductors manufacturing. The cube texture was developed in Ni by a conventional thermo-mechanical process. A precursor solution of yttrium 2-methoxyethoxide in 2-methoxyethanol was spin-coated on the Ni substrate. The as-deposited amorphous film was thermally treated at 1100°C in a flowing Ar+4%H2 gas mixture. The θ-2θ X-ray spectra revealed predominantly (001) reflections, indicating a high degree of out-of-plane orientation. Pole figures for the (222) Y2O3 reflections demonstrate a single in-plane texture. The out-of-plane and in-plane epitaxial relationship is [400]Y2O3//[200] Ni and [110]Y2O3//[100] Ni, respectively. The full-width-half-maximum (FWHM) of the ω-scans and φ-scans is 6° and 11°, respectively.

  1. Thin films of InP for photovoltaic energy conversion. Final report, July 5, 1979-July 4, 1980

    SciTech Connect

    Manasevit, H. M.; Ruth, R. P.; Moudy, L. A.; Yang, J. J.J.; Johnson, R. E.

    1980-08-01

    Research to develop a low-cost high-efficiency thin-film InP heterojunction solar cell, using the metalorganic chemical vapor deposition (MO-CVD) technique for InP film growth on suitable substrates is reported. Heterostructure devices of CdS/InP, using InP films prepared by CO-CVD, were prepared and characterized. The research effort involved three major technical tasks: (1) materials growth; (2) materials characterization; and (3) device fabrication and characterization. The principal results achieved in the investigations are as follows: (1) temperature-activated orientation-dependent background donor doping was observed in undoped epitaxial InP films; (2) p-type epitaxial InP films were prepared by Zn and by Cd doping during growth; (3) the efficacy of Cd doping was found to vary exponentially with the reciprocal of the deposition temperature in the range 650 to 730/sup 0/C; (4) Cd doping appeared to offer no clear advantages over Zn doping for preparation of p-type InP by the MO-CVD process; (5) GaP grown by MO-CVD was investigated as a possible intermediate-layer material for growth of InP films on low-cost substrates; (6) p/sup +/GaAs polycrystalline layers (p > /sup 19/ cm/sup -3/) were successfully prepared by Zn doping during MO-CVD growth on various low-cost substrates and used as surfaces for growth of p-type polycrystalline InP:Zn layers; (7) nCdS/pInP heterojunction solar cells were prepared by vacuum deposition of CdS onto p-type InP films grown by MO-CVD as well as on InP single-crystal wafers; (8) the best polycrystalline CdS/InP cells were obtained in structures on P/sup +/GaAs:Zn layers on both Mo sheet and Corning Code 0317 Glass; and (9) structure analyses of the Cds films used in the heterojunction cells indicated the presence of polycrystalline hexagonal CdS even in films grown on single-crystal InP films or bulk-wafer substrates. (WHK)

  2. High index of refraction films for dielectric mirrors prepared by metal-organic chemical vapor deposition

    SciTech Connect

    Brusasco, R.M.

    1989-01-01

    A wide variety of metal oxides with high index of refraction can be prepared by Metal-Organic Chemical Vapor Deposition. We present some recent optical and laser damage results on oxide films prepared by MOCVD which could be used in a multilayer structure for highly reflecting (HR) dielectric mirror applications. The method of preparation affects both optical properties and laser damage threshold. 10 refs., 8 figs., 4 tabs.

  3. A synergistic approach to environmental concerns in large scale MOCVD processes

    SciTech Connect

    Thompson, A.G.; Tompa, G.S.; Zawadzki, P.A.; McKee, M.; Beckham, C.; Powers, A.; Gurary, A.; Moy, K.; Schumaker, N.E.

    1994-12-31

    Processes used in the production of epitaxial III-V semiconducting materials employ a wide variety of materials that are environmentally hazardous. As production volumes increase, the need to manage these materials becomes a serious concern. As the leading supplier of production scale single and multi-wafer MOCVD systems, EMCORE has taken the approach of minimizing the generation of waste by designing a reactor for high reactant utilization efficiency, and then trapping the remainder so that the exhaust stream is clean. They have paid particular attention to both operational efficiency and operator safety. The trapped materials are reduced to an inert state for subsequent commercial disposal; this is particularly important for phosphorus, which can be highly flammable if improperly handled. The reactor chamber deposits occur below the wafer level and typically are cleaned only after several hundred deposition cycles. These factors contribute to a quick cycle time and high uptime, both of which increase throughput. These issues become more important as the reactor size is increased and when multiple shifts are utilized. These points are exemplified by the operational experience with the new Enterprise series, which holds four 100 mm wafers (or seventeen 50mm wafers) per run. The authors will discuss the progressive trapping of solid As and P compounds and those hydride gases which are not completely decomposed in the reaction chamber. The use of computer modeling to scale the process to larger dimensions and to optimize the deposition conditions will also be discussed.

  4. Wurtzite InP nanowire arrays grown by selective area MOCVD

    SciTech Connect

    Chu, Hyung-Joon; Yeh, Ting-Wei; Stewart, Lawrence; Dapkus, P. Daniel

    2010-06-22

    InP nanowires are a unique material phase because this normally zincblende material forms in the wurtzite crystal structure below a critical diameter owing to the contribution of sidewalls to the total formation energy. This may allow control of the carrier transport and optical properties of InP nanowires for applications such as nano scale transistors, lasers and detectors. In this work, we describe the fabrication of InP nanowire arrays by selective area growth using MOCVD in the diameter range where the wurtzite structure is formed. The spatial growth rate in selective area growth is modeled by a diffusion model for the precursors. The proposed model achieves an average error of 9%. Electron microscopy shows that the grown InP nanowires are in the wurtzite crystal phase with many stacking faults. The threshold diameter of the crystal phase transition of InP nanowires is larger than the thermodynamic estimation. In order to explain this tendency, we propose a surface kinetics model based on a 2×2 reconstruction. This model can explain the increased tendency for wurtzite nanowire formation on InP (111)A substrates and the preferred growth direction of binary III-V compound semiconductor nanowires.

  5. MOCVD synthesis of group III-nitride heterostructure nanowires for solid-state lighting.

    SciTech Connect

    Wang, George T.; Creighton, James Randall; Talin, Albert Alec

    2006-11-01

    Solid-state lighting (SSL) technologies, based on semiconductor light emitting devices, have the potential to reduce worldwide electricity consumption by more than 10%, which could significantly reduce U.S. dependence on imported energy and improve energy security. The III-nitride (AlGaInN) materials system forms the foundation for white SSL and could cover a wide spectral range from the deep UV to the infrared. For this LDRD program, we have investigated the synthesis of single-crystalline III-nitride nanowires and heterostructure nanowires, which may possess unique optoelectronic properties. These novel structures could ultimately lead to the development of novel and highly efficient SSL nanodevice applications. GaN and III-nitride core-shell heterostructure nanowires were successfully synthesized by metal organic chemical vapor deposition (MOCVD) on two-inch wafer substrates. The effect of process conditions on nanowire growth was investigated, and characterization of the structural, optical, and electrical properties of the nanowires was also performed.

  6. Process control of MOCVD growth for LEDs by in-situ photoluminescence

    NASA Astrophysics Data System (ADS)

    Prall, C.; Haberland, K.; Kaspari, C.; Brunner, F.; Weyers, M.; Rueter, D.

    2016-03-01

    Development and manufacturing of LED structures is still driven by production cost reduction and performance improvements. Therefore, in-situ monitoring during the epitaxial process plays a key role in view of further yield improvement and process optimization. With the continuing trend towards larger wafers, stronger bow and increased aspherical curvature are additional challenges the growers have to face, leading to non-uniform LED-emission. Compared to traditional in-situ metrology like curvature measurement and near UV pyrometry, in-situ photoluminescence measurements can provide a more direct access to the quantum well emission already during growth. In this paper we show how in-situ photoluminescence measurements can be used in a production type multi-wafer MOCVD system to characterize the quantum well emission already during growth. We also demonstrate how deviations from the desired wavelength can be detected and corrected in the same growth run. Since the method is providing spatially resolved line-scans across the wafer, also the uniformity of the emission wavelength can be characterized already during growth. Comparison of in-situ and ex-situ photoluminescence data show excellent agreement with respect to wavelength uniformity on 4 inch wafers.

  7. High Growth Rate YSZ Thermal Barrier Coatings Deposited by MOCVD Demonstrate High Thermal Cycling Lifetime

    SciTech Connect

    Varanasi, Venu G; Besmann, Theodore M; Payzant, E Andrew; Pint, Bruce A; Lothian, Janet L; Anderson, Timothy J

    2011-01-01

    Yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBC) were prepared by metalorganic chemical vapor deposition (MOCVD) using Y(OBut{sup n}){sub 3}, Zr(OBut{sup n}){sub 4} precursors and O{sub 2} carrier gas. A thermodynamic analysis guided experiments by optimizing elemental molar (n) stoichiometric ratios for the (Zr-Y-O-C-H system). This analysis showed single-phase YSZ was favored at 950 C, 1 kPa, n{sub O}/(n{sub Y} + n{sub Zr}) > 30, n{sub Y}/(n{sub Y} + n{sub Zr}) = 0.06-0.10 (fixed n{sub C}, n{sub H}). Experimental YSZ growth had multiple phases (fcc, monoclinic), had a relatively high growth rate (43 {micro}m/h, 1005 C), had an Arrhenius dependence (845-950 C, E{sub a} = 53.8 {+-} 7.9 kJ/mol), had columnar grains (SEM analysis), and had a coating through-thickness n{sub Y}/(n{sub Y} + n{sub Zr}) = 0.04 (EPMA analysis). Doubling the inlet yttrium precursor mole fraction resulted in fcc YSZ growth with a coating through-thickness n{sub Y}/(n{sub Y} + n{sub Zr}) = 0.07. Hot-insertion thermal cycling of YSZ coatings on FeCrAlY bond coats showed >1000 h lifetime, matching current standards for EB-PVD YSZ coatings.

  8. MOCVD growth of AlGaInP at atmospheric pressure using triethylmetals and phosphine

    NASA Astrophysics Data System (ADS)

    Ikeda, M.; Nakano, K.; Mori, Y.; Kaneko, K.; Watanabe, N.

    1986-09-01

    (Al xGa 1- x) 0.5In 0.5P quaternary alloy has been successfully grown by conventional atmospheric-pressure MOCVD using triethylaluminum, triethylgallium, triethylindium and phosphine as source materials. The relationship between photoluminescence (PL) line width and lattice mismatch ( {δa}/{a}) was examined. PL spectra at 4 K showed a line width narrower than 12 meV for layers with x less than 0.3 ( {δa}/{a ⩽ 1×10 -3}. Very narrow, down to 10 Å thick (A1 0.5Ga 0.50.5In 0.5P/Ga 0.5In 0.50.5Ga 0.5) 0.5In 0.5P quantum wells have been grown with no growth interruption at the heterojunction. 4 K PL spectra from 30 Å thick GaInP double quantum wells separated by 5, 10 and 20 Å thick A1GaInP barrier layers had a single peak, suggesting that no cluster on any significant size was formed in the A1GaInP alloy. An A1GaInP/GaInP double heterostructure laser operated continuously at room temperature with an emission wavelength from 670 to 680 nm.

  9. Effects of Au on the Growth of ZnO Nanostructures on Si by MOCVD

    NASA Astrophysics Data System (ADS)

    Cong, Chen; Fan, Lu Yang; Ping, He Hai; Wei, Wu Ke; Zhen, Ye Zhi

    2013-08-01

    The effects of Au on the growth of ZnO nanostructures on Si by metal organic chemical vapor deposition (MOCVD) at a relatively low temperature (450°C) were investigated. The experimental results showed that Au nanoparticles played a critical role during the growth of the ZnO nanostructures and affected their morphology and optical properties. It was found that Au nanoparticles particularly affected the nucleation of ZnO nanostructures during the growth process and the Au-assisted growth mechanism of ZnO nanostructures should be ascribed to the vapor-solid (VS) mechanism. The formation of a nanoneedle may be attributed to a more reactive interface between Au and ZnO, which leads to more zinc gaseous species absorbed near the interface. Different nucleation sites on ZnO nuclei resulted in the disorder of ZnO nanoneedles. Moreover, the crystalline quality of nano-ZnO was improved due to the presence of Au, according to the smaller full width at half maximum (FWHM) of the low-temperature exciton emission. We confirmed that ZnO nanoneedles showed better crystalline quality than ZnO nanorods through the HRTEM images and the SAED patterns. The reason for the improvement of the crystalline quality of nano-ZnO may be due to the less lattice mismatch.

  10. Temperature-dependent growth of LaAlO{sub 3} films on YBa{sub 2}Cu{sub 3}O{sub 7} C-axis films for multilayer structures

    SciTech Connect

    Hawley, M.E.; Houlton, R.J.; Raistrick, I.A.; Garzon, F.H.

    1995-01-01

    Fabrication of ultra smooth films, free of micro-shorts, is essential to the development of High Temperature Superconducting (HTS) thin film devices. One such example is a SNS junction consisting of two HTS layers separated by a uniformly smooth continuous barrier material. Other schemes under consideration require multilayer structures of up to 5 - 7 epitaxially grown layers of complex oxide material. Successful fabrication of such devices necessitates understanding the epitaxial growth of polycrystalline oxide films on polycrystalline film templates. Toward this end we have developed a set of deposition parameters that produce high quality epitaxial insulating layers suitable for HTS device applications. All films in this study were grown by off-axis RF magnetron sputter deposition. LaAlO{sub 3} films were deposited over MgO grown YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) c-axis thin films at temperatures ranging from 200 to 700C and on virgin substrates at 600C. Atomic Force Microscopy, eddy current measurements, and x-ray diffraction techniques were used to monitor the effect of growth conditions on the resulting film crystallinity, nanostructure, and electrical properties. Ex-situ interrupted growth characterization of these materials has yielded new insight into the processes that control the growth mechanism and resulting microstructure. All films were polycrystalline. Below 600C, LaAlO{sub 3} films were not epitaxial while films grown at 650C showed some <200> orientation. The shape of the underlying YBCO film is most clearly evident for the film grown at 400C. Surface roughness depended on the appearance of crystals on the film surface. The superconducting properties of the underlying YBCO film required O{sub 2} annealing prior to deposition of the LaAlO{sub 3} layer.

  11. Micro-machined thin film hydrogen gas sensor, and method of making and using the same

    NASA Technical Reports Server (NTRS)

    DiMeo, Jr., Frank (Inventor); Bhandari, Gautam (Inventor)

    2001-01-01

    A hydrogen sensor including a thin film sensor element formed, e.g., by metalorganic chemical vapor deposition (MOCVD) or physical vapor deposition (PVD), on a microhotplate structure. The thin film sensor element includes a film of a hydrogen-interactive metal film that reversibly interacts with hydrogen to provide a correspondingly altered response characteristic, such as optical transmissivity, electrical conductance, electrical resistance, electrical capacitance, magnetoresistance, photoconductivity, etc., relative to the response characteristic of the film in the absence of hydrogen. The hydrogen-interactive metal film may be overcoated with a thin film hydrogen-permeable barrier layer to protect the hydrogen-interactive film from deleterious interaction with non-hydrogen species. The hydrogen sensor of the invention may be usefully employed for the detection of hydrogen in an environment susceptible to the incursion or generation of hydrogen and may be conveniently configured as a hand-held apparatus.

  12. Protection of high temperature superconducting thin-films in a semiconductor processing environment

    SciTech Connect

    Xu, Yizi; Fiske, R.; Sanders, S.C.; Ekin, J.W.

    1996-12-31

    Annealing studies have been carried out for high temperature superconductor YBaCuO{sub 7{minus}{delta}} in a reducing ambient, in order to identify insulator layer(s) that will effectively protect the superconducting film in the hostile environment. While a layer of magnesium oxide (MgO) sputter deposited directly on YBaCuO{sub 7{minus}{delta}} film provides some degree of protection, the authors found that a composite structure of YBCO/SrTiO{sub 3}/MgO, where the SrTiO{sub 3} was grown by laser ablation immediately following YBCO deposition (in-situ process), was much more effective. They also address the need for a buffer layer between YBCO and aluminum (Al) during annealing. Al is most commenly used for semiconductor metalization, but is known to react readily with YBCO at elevated temperatures. The authors found that the most effective buffer layers are platinum (Pt) and gold/platinum (Au/Pt).

  13. Metal-organic chemical vapour deposition of polycrystalline tetragonal indium sulphide (InS) thin films

    NASA Technical Reports Server (NTRS)

    Macinnes, Andrew N.; Cleaver, William M.; Barron, Andrew R.; Power, Michael B.; Hepp, Aloysius F.

    1992-01-01

    The dimeric indium thiolate /(t Bu)2In(mu-S sup t Bu)/2 has been used as a single-source precursor for the MOCVD of InS thin films. The dimeric In2S2 core is proposed to account for the formation of the nonequilibrium high-pressure tetragonal phase in the deposited films. Analysis of the deposited films has been obtained by TEM, with associated energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy.

  14. A water-free metal organic deposition method for YBa2Cu3O7-δ thin film fabrication

    NASA Astrophysics Data System (ADS)

    Huang, Rongxia; Feng, Feng; Wu, Wei; Xue, Yunran; Zhang, Yanyi; Shi, Kai; Qu, Timing; Zhao, Yongjie; Wang, Xiaohao; Zhang, Xiaowen; Han, Zhenghe

    2013-11-01

    During the fabrication of YBa2Cu3O7-δ (YBCO) thin films via the metal organic deposition (MOD) method, the water content of the precursor solution should be reduced to prevent precipitation and other detriment. In most of the reported MOD-YBCO studies, water was used as a solvent, and vacuum distillation was utilized to reduce the water content of the precursor solution. In this study, we propose a water-free MOD method using propionic anhydride and methanol as the solvents. The crystal water of raw precursor salts was removed by heating, and the water content in the final precursor solution was as low as 0.2 wt%. Using this solution with low fluorine content and the optimized maximum temperature of pyrolysis, the final YBCO thin films about 250 nm thick had the critical current density (Jc) of 3.8 MA cm-2 (77 K, self-field). The water content of the precursor solution was further reduced to less than 10-2 wt% by vacuum distillation. According to the Jc performance, thermal analysis, x-ray diffraction investigations, and morphology observations, no significant improvement was found for the final YBCO thin films fabricated by the distilled solution, indicating that vacuum distillation is not necessary in the water-free MOD method.

  15. Thin films of InP for photovoltaic energy conversion. Third quarterly technical progress report, December 29, 1979-March 28, 1980

    SciTech Connect

    Manasevit, H M; Ruth, R P; Moudy, L A; Yang, J J.J.; Johnson, R E

    1980-04-01

    A research study is being conducted for the purpose of developing a low-cost high-efficiency thin-film InP heterojunction solar cell based on InP films grown by the metalorganic chemical vapor deposition (MO-CVD) process on suitable substrates. Heterostructure devices of CdS/InP (and possibly indium tin oxide/InP) are to be prepared at Stanford University under subcontract, using the MO-CVD InP films grown at Rockwell. The work of the third quarter of the program is summarized. Experiments continued on evaluation of GaP as an intermediate layer material for subsequent growth of InP films on various substrate materials, and Cd (obtained from dimethylcadmium) was evaluated as a p-type dopant (an alternative to Zn obtained from diethylzinc) for InP films made by the MO-CVD process. A preliminary x-ray diffraction analysis was conducted of the crystallographic structure of the vacuum-deposited CdS films prepared at Stanford as part of the process of fabricating CdS/InP heterojunction solar cells. A group of CdS/InP heterostructure cells involving vacuum-deposited CdS and p-type epitaxial InP films grown by MO-CVD was prepared and evaluated. High J/sub 0/ values and low fill factors were observed in all of the cells, resulting in AM1.5 efficiencies in the 2 to 5 percent range. (WHK)

  16. Investigating Links Between Enhanced Inhomogeneity and Robustness of the Superconducting State in Severely Underdoped, Ultrathin CaYBCO

    NASA Astrophysics Data System (ADS)

    Steers, Stanley; Lemberger, Thomas; Baker, Brian

    Multiple experiments in recent years have shown evidence for intrinsic inhomogeneity in the cuprate superconductors upon approach to the superconductor to insulator transition (SIT). We present experimental evidence of anomalous suppression of both the diamagnetic response and the resistivity in ultrathin Ca-doped YBCO over tens of Kelvin. We then present further experiments to investigate to what extent this suppression is related to increased inhomogeneity upon approach to the SIT. Finally, we compare these results in CaYBCO to experiments in other cuprate compounds from the literature.

  17. Measurement of oxygen disorder and nano-twin microstructure associated with columnar defects in YBCO.

    SciTech Connect

    Yan, Y,

    1998-12-18

    Studies of defects generated by high energy (>1 GeV) heavy ion irradiation in high-Tc superconductors have been performed by transmission electron microscopy (TEM). Our study shows that high dose irradiation leads to the formation of nano-twins, by which the columnar defects are connected. An analysis of the local Fourier components of the image intensity in [001] lattice images indicates that these new ''twin'' boundaries are much more diffuse than pre-existing twin boundaries in YBCO. The mechanism of the formation of nano-twin boundaries on {l_brace}110{r_brace} planes and their possible relation to superconducting properties are discussed.

  18. Fabrication and test of short helical solenoid model based on YBCO tape

    SciTech Connect

    Yu, M.; Lombardo, V.; Lopes, M.L.; Turrioni, D.; Zlobin, A.V.; Flanagan, G.; Johnson, R.P.; /MUONS Inc., Batavia

    2011-03-01

    A helical cooling channel (HCC) is a new technique proposed for six-dimensional (6D) cooling of muon beams. To achieve the optimal cooling rate, the high field section of HCC need to be developed, which suggests using High Temperature Superconductors (HTS). This paper updates the parameters of a YBCO based helical solenoid (HS) model, describes the fabrication of HS segments (double-pancake units) and the assembly of six-coil short HS model with two dummy cavity insertions. Three HS segments and the six-coil short model were tested. The results are presented and discussed.

  19. Substrate Surface Decoration With CeO2 Nanoparticles: An Effective Method for Improving Flux Pinning in YBa2Cu3O7 Films

    SciTech Connect

    Aytug, Tolga; Paranthaman, Mariappan Parans; Gapud, Albert Agcaoili; Kang, Sukill; Varela del Arco, Maria; Martin, Patrick M; Raitano, J. M.; Chan, S. W.; Thompson, James R; Christen, David K

    2007-01-01

    We have demonstrated improved critical current density, J{sub c}, in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films through a controlled study of substrate surface modifications with nano-sized second-phase pre-formed CeO{sub 2} particles. Nanoparticles were applied to single crystal SrTiO{sub 3} surfaces using suspension-based techniques prior to YBCO film growth. With the introduction of CeO{sub 2} nanoparticles, YBCO films showed more robust field dependence at intermediate fields (J{sub c} {infinity} B{sup -{infinity}}), where a smaller power law exponent of {alpha} {approx} 0.3 is obtained. The self-field J{sub c}(77 K, B{parallel}c) values of the YBCO films on reference and CeO{sub 2} modified substrates are 1.1 and 1.9 MA/cm2; and at 1 Tesla 0.1 and 0.52 MA/cm2, respectively. Consistent with this {alpha}-value, angular field dependent J{sub c} and transmission electron microscopy studies indicate the presence of c-axis aligned correlated defects in these modified samples.

  20. Optical properties of InGaN grown by MOCVD on sapphire and on bulk GaN

    NASA Astrophysics Data System (ADS)

    Osinski, Marek; Eliseev, Petr G.; Lee, Jinhyun; Smagley, Vladimir A.; Sugahara, Tamoya; Sakai, Shiro

    1999-11-01

    Experimental data on photoluminescence of various bulk and quantum-well epitaxial InGaN/GaN structures grown by MOCVD are interpreted in terms of a band-tail model of inhomogeneously broadened radiative recombination. The anomalous temperature-induced blue spectral is shown to result from band-tail recombination under non-degenerate conditions. Significant differences are observed between epilayers grown on sapphire substrates and on GaN substrates prepared by the sublimination method, with no apparent evidence of band tails in homoepitaxial structures, indicating their higher crystalline quality.

  1. Fabrication of low-density GaN/AlN quantum dots via GaN thermal decomposition in MOCVD

    PubMed Central

    2014-01-01

    With an appropriate high anneal temperature under H2 atmosphere, GaN quantum dots (QDs) have been fabricated via GaN thermal decomposition in metal organic chemical vapor deposition (MOCVD). Based on the characterization of atomic force microscopy (AFM), the obtained GaN QDs show good size distribution and have a low density of 2.4 × 108 cm-2. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the GaN QDs were formed without Ga droplets by thermal decomposition of GaN. PMID:25136276

  2. Optoelectronic and structural properties of InGaN nanostructures grown by plasma-assisted MOCVD

    NASA Astrophysics Data System (ADS)

    Seidlitz, Daniel; Senevirathna, M. K. I.; Abate, Y.; Hoffmann, A.; Dietz, N.

    2015-09-01

    This paper presents optoelectronic and structural layer properties of InN and InGaN epilayers grown on sapphire templates by Migration-Enhanced Plasma Assisted Metal Organic Chemical Vapor Deposition (MEPA-MOCVD). Real-time characterization techniques have been applied during the growth process to gain insight of the plasma-assisted decomposition of the nitrogen precursor and associated growth surface processes. Analyzed Plasma Emission Spectroscopy (PES) and UV Absorption Spectroscopy (UVAS) provide detection and concentrations of plasma generated active species (N*/NH*/NHx*). Various precursors have been used to assess the nitrogen-active fragments that are directed from the hollow cathode plasma tube to the growth surface. The in-situ diagnostics results are supplemented with ex-situ materials structures investigation results of nanoscale structures using Scanning Near-field Optical Microscopy (SNOM). The structural properties have been analyzed by Raman spectroscopy and Fourier transform infrared (FTIR) reflectance. The Optoelectronic and optical properties were extracted by modeling the FTIR reflectance (e.g. free carrier concentration, high frequency dielectric constant, mobility) and optical absorption spectroscopy. The correlation and comparison between the in-situ metrology results with the ex-situ nano-structural and optoelectronic layer properties provides insides into the growth mechanism on how plasma-activated nitrogen-fragments can be utilized as nitrogen precursor for group III-nitride growth. The here assessed growth process parameter focus on the temporal precursor exposure of the growth surface, the reactor pressure, substrate temperature and their effects of the properties of the InN and InGaN epilayers.

  3. Characterization of high-purity arsine and gallium arsenide epilayers grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Feng, Jun; Clement, Ryan; Raynor, Mark

    2008-11-01

    Impurities present in the metal organic chemical vapor deposition (MOCVD) process gases and precursors can have a significant effect on the performance of III-V compound semiconductor devices. High-purity arsine purified using chemical, adsorption and distillation techniques, has been characterized for impurities by using high sensitivity gas analysis methods and low temperature photoluminescence (PL) of GaAs epilayers. Permanent gas, hydrocarbon and dopant impurities can all be removed using these purification methods to below the detection limit of instrumentation (low nmol mol -1-pmol mol -1, depending on method). Capability to remove water vapor to single digit nmol mol -1 levels is also demonstrated and cylinder depletion studies show that gas-phase arsine, with consistently low H 2O, can be delivered from the cylinder, even well after phase break. Low temperature PL measurements are made on 10 μm GaAs/GaAs grown with three different arsine sources. Well-resolved near-band emission characteristics of high-purity n-type GaAs is obtained with high-purity distilled arsine. PL of epilayers grown with less pure arsine show the presence of Ge as well as elevated levels of Mg and Zn, incorporated from the trimethylgallium. The incorporation of O from an arsine cylinder containing H 2O at 200 nmol mol -1 results in reduced full width at half maximum (FWHM) of the near-band emission and decreased ( D0, X) and ( F, X) intensity, highlighting the importance of minimizing H 2O impurity.

  4. Study of carrier recombination transient characteristics in MOCVD grown GaN dependent on layer thickness

    SciTech Connect

    Gaubas, E. Čeponis, T.; Jasiunas, A.; Jelmakas, E.; Juršėnas, S.; Kadys, A.; Malinauskas, T.; Tekorius, A.; Vitta, P.

    2013-11-15

    The MOCVD grown GaN epi-layers of different thickness have been examined in order to clarify a role of surface recombination, to separate an impact of radiative and non-radiative recombination and disorder factors. The microwave probed –photoconductivity (MW-PC) and spectrally resolved photo-luminescence (PL) transients were simultaneously recorded under ultraviolet (UV) light 354 nm pulsed 500 ps excitation. The MW-PC transients exhibited the carrier decay components associated with carrier decay within micro-crystals and the disordered structure on the periphery areas surrounding crystalline columns. Three PL bands were resolved within PL spectrum, namely, the exciton ascribed UV-PL band edge for hν>3.3 eV, blue B-PL band for 2.5 < hν < 3.0 eV and yellow Y-PL band with hν < 2.4 eV. It has been obtained that intensity of UV-PL band increases with excitation density, while intensity of B-PL band is nearly invariant. However, intensity of the Y-PL increases with reduction of the excitation density. The Y-PL can be associated with trapping centers. A reduction of UV excitation density leads to a decrease of the relative amplitude of the asymptotic component within the MW-PC transients and to an increase of the amplitude as well as duration of the yellow spectral band (Y-PL) asymptotic component. Fractional index α with values 0.5 < α < 0.8 was evaluated for the stretched-exponent component which fits the experimental transients determined by the disordered structure ascribed to the periphery areas surrounding the crystalline columns.

  5. 500 V/200 A fault current limiter modules made of large-area MOD-YBa2Cu3O7 thin films with high-resistivity Au-Ag alloy shunt layers

    NASA Astrophysics Data System (ADS)

    Yamasaki, H.; Arai, K.; Kaiho, K.; Nakagawa, Y.; Sohma, M.; Kondo, W.; Yamaguchi, I.; Matsui, H.; Kumagai, T.; Natori, N.; Higuchi, N.

    2009-12-01

    We developed 500 Vrms/ 200 Arms superconducting thin-film fault current limiter (FCL) modules that can withstand high electric fields (E>30 Vrms cm-1) by using large-area YBa2Cu3O7 (YBCO) thin films with high-resistivity Au-Ag alloy shunt layers. Au-Ag alloy films about 60 nm thick were sputter-deposited on YBCO/CeO2/sapphire films (2.7 cm × 20 cm) prepared using a fluorine-free MOD method. Each 20 cm long Au-Ag/YBCO film was then divided into three segments (each ~5.7 cm long) by four Ag electrodes deposited on the Au-Ag layer, resulting in an effective length of 17 cm. The 500 V/200 A FCL modules were then fabricated by first connecting two of the segmented films in parallel using Ag-sheathed Bi-2223 superconducting tapes and then connecting in parallel an external resistor and a capacitor for each segment to protect the Au-Ag/YBCO film from hot spots. Switching tests using a short-circuit generator revealed that all the modules carried a superconducting ac current of >=237 Arms and that modules prepared with YBCO films having a relatively homogeneous critical current Ic distribution successfully withstood >=515 Vrms for five cycles without any damage. These results demonstrate that (a) the FCL modules fabricated here successfully achieved the rated current of 200 Arms and rated voltage of 500 Vrms and (b) total area of the YBCO films on sapphire substrates required for the 500 V/200 A (100 kV A) module was less than one-third that for conventional thin-film FCL modules that use gold shunt layers, leading to the significantly reduced cost of thin-film FCLs. Film damage due to hot spots depended on the difference in Ic between the two parallel-connected films and on the inhomogeneity of the Ic distribution in the film, and is most probably due to nonlinear current flows at the moment of quenching that cause local overheating.

  6. Thin films of InP for photovoltaic energy conversion. Second quarterly technical progress report, September 29, 1979-December 28, 1979

    SciTech Connect

    Manasevit, H M; Ruth, R P; Moudy, L A; Yang, J J.J.; Johnson, R E

    1980-01-01

    A research study is being conducted for the purpose of developing a low-cost high-efficiency thin-film InP heterojunction solar cell based on InP films grown by the metalorganic chemical vapor deposition (MO-CVD) process on suitable substrates. Heterostructure devices of CdS/InP (and possibly indium-tin oxide/InP) are to be prepared at Stanford University using the MO-CVD InP films grown at Rockwell. The work of the second quarter of the program is summarized. Growth parameters have been established using new triethylindium, diethylzinc (DEZn), and PH/sub 3/ sources for the formation of Zn-doped p-type InP films in the modified MO-CVD reactor system. Appropriately doped films have been prepared and sent to Stanford for use in deposition of CdS layers. An investigation of the properties of grains and grain boundaries in polycrystalline InP films was begun using several polycrystalline film/substrate combinations, including tungsten (W) layers produced by roller coating and screen-printing on polycrystalline alumina, and mechanically abraded surfaces of single-crystal bulk InP:Fe wafers. An investigation was also undertaken into the use of GaP as an alternative intermediate-layer material to GaAs on low-cost substrates for subsequent growth of InP films. Auger electron spectroscopy analysis done on a group of specially prepared Zn-treated films of polycrystalline InP indicated the presence of Zn at surfaces of InP:Zn films grown on Al and/or heat-treated in high concentrations of DEZn at approx. 600/sup 0/C. However, no Zn was detected in polycrystalline films grown under deposition conditions that would be expected to produce highly doped p-type epitaxial films if single-crystal substrates were used.

  7. Ion-assisted laser deposition of intermediate layers for YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin film growth on polycrystalline and amorphous substrates

    SciTech Connect

    Reade, R.P.

    1993-11-01

    The growth of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) high-temperature superconductor thin films has largely been limited to deposition on single-crystal substrates to date. In order to expand the range of potential applications, growth on polycrystalline and amorphous substrates is desirable. In particular, the deposition of YBCO thin films with high critical current densities on polycrystalline metal alloys would allow the manufacture of superconducting tapes. However, it is shown that it is not possible to grow YBCO thin films directly on this type of substrate due to chemical and structural incompatibility. This work investigates the use of a yttria-stabilized zirconia (YSZ) intermediate layer to address this problem. An ion-assisted pulsed-laser deposition process is developed to provide control of orientation during the growth of the YSZ layers. The important properties of YBCO and YSZ are summarized and the status of research on thin film growth of these materials is reviewed. An overview of the pulsed-laser deposition (PLD) technique is presented. The use of ion-assisted deposition techniques to control thin film properties is discussed.

  8. An evaluation of phase separated, self-assembled LaMnO3-MgO nanocomposite films directly on IBAD-MgO as buffer layers for flux pinning enhancements in YBa2YCu3O7-& coated conductors

    SciTech Connect

    Polat, Ozgur; Aytug, Tolga; Paranthaman, Mariappan Parans; Leonard, Keith J; Lupini, Andrew R; Pennycook, Stephen J; Meyer III, Harry M; Kim, Kyunghoon; Qiu, Xiaofeng; Cook, Sylvester W; Thompson, James R; Christen, David K; Goyal, Amit; Selvamanickam, V.; Xiong, X.

    2010-01-01

    Technological applications of high temperature superconductors (HTS) require high critical current density, Jc, under operation at high magnetic field strengths. This requires effective flux pinning by introducing artificial defects through creative processing. In this work, we evaluated the feasibility of mixed-phase LaMnO3:MgO (LMO:MgO) films as a potential cap buffer layer for the epitaxial growth and enhanced performance of YBa2Cu3O7-d (YBCO) films. Such composite films were sputter deposited directly on IBAD-MgO templates (with no additional homo-epitaxial MgO layer) and revealed the formation of two phase-separated, but at the same time vertically aligned, self-assembled composite nanostructures that extend throughout the entire thickness of the film. The YBCO coatings deposited on these nanostructured cap layers showed correlated c-axis pinning and improved in-field Jc performance compared to those of YBCO films fabricated on standard LMO buffers. Microstructural characterization revealed additional extended disorder in the YBCO matrix. The present results demonstrate the feasibility of novel and potentially practical approaches in the pursuit of more efficient, economical, and high performance superconducting devices.

  9. Effect of bulk growth temperature on antiphase domain boundary annihilation rate in MOCVD-grown GaAs on Si(001)

    NASA Astrophysics Data System (ADS)

    Barrett, C. S. C.; Martin, T. P.; Bao, X.-Y.; Kennon, E. L.; Gutierrez, L.; Martin, P.; Sanchez, E.; Jones, K. S.

    2016-09-01

    GaAs is a material of interest as a potential buffer layer in future III-V semiconductor-based transistor technologies integrated on Si wafers. The goal of this study was to investigate the effect of growth temperature on the propagation and annihilation of antiphase domain boundaries (APBs) in GaAs films grown on Si(001) by metal-organic chemical vapor deposition (MOCVD). No intentional wafer off-cuts or high temperature pre-growth anneals (>1000 °C) were employed as both of these practices complicate integration with other devices. To evaluate the role of growth temperature on the APB evolution, a 200 nm thick layer of GaAs was grown on the Si at a fixed temperature of 530 °C so that all samples started with the same approximate APB density. Subsequently, 600 nm of GaAs was grown at temperatures varying between 530 °C and 650 °C. Chemical etching combined with scanning electron microscopy (SEM) was used to profile the density of the APBs in each sample as a function of depth. The APB annihilation rate, i.e. the exponential decay rate of APB density with respect to film thickness, increases from 2.6 μm-1 to 10.7 μm-1 as the growth temperature increases from 530 °C to 610 °C and then saturates. The increase in annihilation rate with increasing temperatures suggests that the higher temperatures remove kinetic barriers to the reduction of the overall APB interfacial area. An activation energy of 1.1 eV was extracted using an Arrhenius relationship and likely corresponds to the energy needed for APBs to kink from {110} to higher-index planes, e.g. {112}. Dark field transmission electron microscopy showed that at higher growth temperatures the APBs can shift from vertical {110} habit planes to {112} planes leading to self-annihilation with sufficient thickness.

  10. Test Status for Proposed Coupling of a Gravitational Force to Extreme Type II YBCO Ceramic Superconductors

    NASA Technical Reports Server (NTRS)

    Noever, David; Li, Ning; Robertson, Tony; Koczor, Ron; Brantley, Whitt

    1999-01-01

    As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair electron density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (about 10-6 g/cu cm). Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating Type II, YBCO superconductor, with the percentage change (0.05-2.1%) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 10(exp 4) was reported above a stationary (non-rotating) superconductor. In the present experiments reported using a sensitive gravimeter (resolution <10(exp -9) unit gravity or variation of 10(exp -6) cm/sq s in accelerations), bulk YBCO superconductors were stably levitated in a DC magnetic field (0.6 Tesla) subject to lateral AC fields (60 Gauss at 60 Hz) and rotation. With magnetic shielding, thermal control and buoyancy compensation, changes in acceleration were measured to be less than 2 parts in 10(exp 8) of the normal gravitational acceleration. This result puts new limits on the strength and range of the proposed coupling between high-Tc superconductors and gravity. Latest test results will be reported, along with status for future improvements and prospects.

  11. VOLTAGE DISTRIBUTION AND MECHANICAL STRENGTH IN SPLICE JOINTS MADE FROM AS-MANUFACTURED YBCO COATED CONDUCTORS

    SciTech Connect

    Duckworth, Robert C; Zhang, Yifei; Gouge, Michael J; Rey, Christopher M; Van der Laan, Danko; Clickner, Cam

    2010-01-01

    With recommendations from wire manufacturers as a starting point, a series of solder joints were fabricated and characterized to determine the best method to produce repeatable, low-resistance and high-mechanical-strength splices in as-manufactured, stabilized YBCO coated conductors. From the 2.54 cm long splice joints that were fabricated, parameters such as solder material, stabilization material, fabrication method, and conductor geometry were varied to determine the impact of each on splice joint properties. Results indicate that the lowest resistance splice joints were influenced primarily by the tape orientation in the joint and the stabilization material. The lowest resistances were between 2 10-8 and 1.0 10-7 in 4-mm wide tapes and were obtained from pure copper stabilized tapes oriented with the YBCO layers in closest proximity. The voltage drop along the splice length indicated that only a fraction of the splice length contributes to the splice joint resistance. Mechanical characterization of splice joints showed that the joint resistance remained unchanged under axial stress up to a stress level at which the critical current of the tapes forming the joint degrades irreversibly.

  12. Estimation of magnetic relaxation property for CVD processed YBCO-coated conductors

    NASA Astrophysics Data System (ADS)

    Takahashi, Y.; Kiuchi, M.; Otabe, E. S.; Matsushita, T.; Shikimachi, K.; Watanabe, T.; Kashima, N.; Nagaya, S.

    2010-11-01

    Ion Beam Assist Deposition/Chemical Vapor Deposition(IBAD/CVD)-processed YBCO-coated conductors with high critical current density Jc at high magnetic fields are expected to be applied to superconducting equipments such as superconducting magnetic energy storage (SMES). For application to superconducting magnet in SMES one of the most important properties for superconductors is the relaxation property of superconducting current. In this paper, the relaxation property is investigated for IBAD/CVD-processed YBCO-coated conductors of the superconducting layer in the range of 0.18-0.90 μm. This property can be quantitatively characterized by the apparent pinning potential, U0∗. It is found that U0∗ takes a smaller value due to the two-dimensional pinning mechanism at high magnetic fields for conductor with thinner superconducting layer. Although U0∗ decreases with increasing thickness at low magnetic fields at 20 K, it increases at high magnetic fields. The results are theoretically explained by the model of the flux creep and flow based on the dimensionality of flux pinning. Scaling analysis is examined for the dependence of U0∗ on the magnetic field, temperature and the layer thickness.

  13. The Relationship of Magnetic Stiffness Between Single and Multiple YBCO Superconductors over Permanent Magnet Guideway

    NASA Astrophysics Data System (ADS)

    Lu, Yiyun; Lu, Bingjuan; Wang, Suyu

    2011-09-01

    For YBCO bulk levitating over a permanent magnet guideway (PMG), the magnetic stiffness is connected directly with the pinning properties of the measured sample. An experimental setup has been built to investigate the vertical and lateral magnetic stiffness of five high-temperature superconducting (HTS) bulk arrays over a PMG by two methods: the additive method, i.e., calculating the summation of the measured magnetic stiffness values of each HTS bulk in the array; the direct method, i.e., measuring directly the magnetic stiffness of the HTS bulk array. From the experimental results, it is found that the resultant magnetic stiffness of the HTS bulk array composing of multiple YBCO bulk is related with the magnetic stiffness of each individual single bulk, but the additive method does not predict the magnetic stiffness of the array very well because of the interaction between adjacent HTS bulk. The resultant magnetic stiffness of the HTS bulk array is less than the summation magnetic stiffness of each single HTS bulk. One numerical method is used to calculate the magnetic stiffness for comparing with experimental results. The results may be helpful to the design and optimization of the superconducting magnetic levitation system.

  14. Inkjet printing of multifilamentary YBCO for low AC loss coated conductors

    NASA Astrophysics Data System (ADS)

    Hopkins, S. C.; Joseph, D.; Mitchell-Williams, T. B.; Calleja, A.; Vlad, V. R.; Vilardell, M.; Ricart, S.; Granados, X.; Puig, T.; Obradors, X.; Usoskin, A.; Falter, M.; Bäcker, M.; Glowacki, B. A.

    2014-05-01

    Considerable progress has been made with the development of REBCO coated conductors in recent years, and high performance conductors are available commercially. For many applications, however, the cost remains prohibitive, and AC losses discourage their selection for higher frequency applications. Chemical solution deposition (CSD) methods are attractive for low-cost, scalable preparation of buffer and superconductor layers, and in many respects inkjet printing is the method of choice, permitting non-contact deposition with minimal materials wastage and excellent control of coating thickness. Highly textured coatings of YBCO and Gd-doped CeO2 have previously been reported on buffered metal substrates. Inkjet printing also introduces the possibility of patterning - directly depositing two and three dimensional structures without subtractive processing - offering a low-cost route to coated conductors with reduced AC losses. In this contribution, the inkjet deposition of superconducting YBCO tracks is reported on industrially relevant buffered metal substrates both by direct printing and an inverse patterning approach. In the latter approach, ceria tracks were printed reported, which are a candidate both for resistive filament spacers and buffer layers. TFA-based precursor solutions have been printed on SS/ABAD-YSZ/CeO2 and Ni-W/LZO/CeO2 RABiTS substrates, and the resulting multifilamentary samples characterised by microscopy and scanning Hall probe measurements. The prospects for future inkjet-printed low AC loss coated conductors are discussed, including control of interfilamentary resistivity and bridging, transposed filamentary structures and stabilisation material.

  15. Simulation of the behavior of superconducting YBCO lines at high current densities

    NASA Astrophysics Data System (ADS)

    Antognazza, L.; Decroux, M.; Reymond, S.; de Chambrier, E.; Triscone, J.-M.; Paul, W.; Chen, M.; Fischer, Ø.

    2002-08-01

    We report on the behavior of YBCO lines at high current densities. The experiments are performed, with short constant current pulses, on Au/YBCO/CeO 2 structures grown on 2″ sapphire wafers. We found that a quasi spontaneous highly dissipative state (HDS) appears at a critical current J*, which is also temperature dependent. The initial propagation velocity of the HDS can reach values as high as 150 m/s for a current of 3 Jc. We show experimental evidences that this HDS is driven by the current and does not originate from a thermal runaway of the superconducting line. To confirm these results, we have simulated the thermal behavior of the line, using a calculation based on a finite element method, including the dissipation coming from the flux flow. This model reproduces very well the propagation velocity, and its current dependence, observed experimentally if we include the temperature dependence of J*, whereas the calculated velocities in the case of a purely thermal runaway are one order of magnitude lower.

  16. Thermal conductivity of Zn, Pr and Tb doped YBCO single crystals: Theory and experiment

    SciTech Connect

    Henning, P.F.; Cao, G.; Crow, J.E.

    1995-08-01

    The thermal conductivity K(T) vs temperature has been measured for (Y,Pr)Ba{sub 2}Cu{sub 3}O{sub 7}, (Y,Tb)Ba{sub 2}Cu{sub 3}O{sub 7} and YBa{sub 2}(Cu,Zn){sub 3}O{sub 7} single crystals from 10{le}T{le}280K. For YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO), a strong enhancement in K(T) is observed for T{le}T{sub c} with a peak in K(T) at approximately T{approx}T{sub c}/2 with a sharp change in slope of K(T) at T{sub c}. These results are similar to those reported previously. For the selectively doped YBCO, the peak in K(T) is shifted to lower temperatures and occurs at T{approx}20K independent of T{sub c} and the impurity concentration. In addition, the sharp change in slope of K(T) at T{sub c} is not apparent for the doped crystals. These results are discussed along with a theoretical model for electronic conduction including both impurity and inelastic scattering from spin fluctuations.

  17. The influence of magnetic nano metal oxides doping on structure and electrical properties of YBCO superconductor

    NASA Astrophysics Data System (ADS)

    Salama, A. H.; El-Hofy, M.; Rammah, Y. S.; Elkhatib, M.

    2016-03-01

    Superconductor samples of YBa2Cu3O7-δ (YBCO) + x where x = 0.1, 0.2, 0.3, 0.4 and 0.5 wt% of nano metal oxides namely Cr2O3, Co3O4 and Mn3O4 namely are synthesized by the solid-state reaction route. Both x-ray diffraction and electron microscopy have been employed to study the phase identification and the microstructure of these samples. Transition temperature of the samples has been determined by four probe resistivity measurements. The x-ray diffraction patterns indicate that the gross structure of YBCO does not change with the substitution of three types of nano metal oxides with different doping level. The critical transition temperature (Tc) is found to decrease with the increases of doping level. Mn3O4 has highest Tc value which may be due to flux pinning from some defects and the rapid suppression in Tc with increasing concentration of Mn3O4 may be due to the cooper pair breaking and the hole filling in the CuO2 planes.

  18. Room Temperature Ferromagnetism in Transition Metal Doped CVD-Grown ZnO Films and Nanostructures

    NASA Astrophysics Data System (ADS)

    Hill, D. H.; Gateau, R.; Bartynski, R. A.; Wu, P.; Lu, Y.; Wielunski, L.; Poltavets, V.; Greenblatt, M.; Arena, D. A.; Dvorak, J.; Calvin, S.

    2006-03-01

    We have characterized the chemical, compositional, and magnetic properties of Mn- and Fe-ion implanted epitaxial ZnO films and single crystal nanostructures grown by MOCVD as candidate room temperature diluted magnetic semiconductors. X-ray absorption spectroscopy (SXAS) shows that Mn-implanted films contain Mn^2+ ions which convert to a mixture of Mn^3+ and Mn^4+ upon annealing. Fe-implanted films contain a mixture of Fe^2+ and Fe^3+ which converts to a higher concentration of Fe^3+ upon annealing. XAS and preliminary analysis of EXAFS data indicate that the TM ions are substitutional for Zn. SQUID magnetometry shows that as-implanted films are ferromagnetic at 5K and the annealed films are ferromagnetic at room temperature. X-ray diffraction shows that the annealed films remain epitaxial with excellent long range order. Rutherford backscattering spectrometry indicates a substantial recovery of local order upon annealing as well. The properties of in-situ Fe-doped MOCVD-grown ZnO epitaxial films and nanostructures will also be discussed.

  19. Self-heating technique of metallic substrate for reel-to-reel and double-sided deposition of YBa2Cu3O7- δ films

    NASA Astrophysics Data System (ADS)

    Zhang, Fei; Zhao, Ruipeng; Xue, Yan; Wang, Hui; He, Yuanying; Zhang, Pan; Tao, Bowan; Xiong, Jie; Li, Yanrong

    2016-02-01

    A new, simple, and highly efficient heating technology for metal tape substrates is proposed and applied to reel-to-reel and double-sided film deposition. In this technology, direct electrical current ( I DC) is conducted into the metal layer of oxide-buffered metal substrate to induce heat. Different substrate surface temperatures were achieved by varying I DC from 22 to 25 A. At these temperatures, a series of 1-μm-thick and 5-cm-long YBa2Cu3O7- δ (YBCO) films were fabricated on ion-beam-assisted deposition (IBAD) templates through metal organic chemical vapor deposition. X-ray diffraction analysis on the samples revealed that the YBCO film changed its growth mode from mixed a-axis and c-axis to purely c-axis with increasing I DC. The optimal out-of-plane and in-plane texture reached ~1.4° and 3.5°, respectively. A 30-m-long and 500-nm-thick single-sided YBCO-coated conductor was also prepared through reel-to-reel deposition using the proposed heating method. The fabricated conductor presented homogeneous crystallization and texture and exhibited a critical current density at self-field and 77 K ( J c 77K, 0T ) of 2.8-3.2 MA/cm2. Moreover, 500-nm-thick YBCO films were fabricated simultaneously on both sides of the double-sided IBAD template. The two sides of films demonstrated uniform texture and J c 77K, 0T of 3.2 MA/cm2. Results demonstrated that the proposed substrate heating technology can be used for reel-to-reel and double-sided deposition of YBCO-coated conductors.

  20. Influence of Mg and In on defect formation in GaN; bulk and MOCVD grown samples

    SciTech Connect

    Liliental-Weber, Z.; Benamara, M.; Jasinski, J.; Swider, W.; Washburn, J.; Grzegory, I.; Porowski, S.; Bak-Misiuk, J.; Domagala, J.; Bedair, S.; Eiting, C.J.; Dupuis, R.D.

    2000-11-22

    Transmission electron microscopy studies were applied to study GaN crystals doped with Mg. Both: bulk GaN:Mg crystals grown by a high pressure and high temperature process and those grown by metal-organic chemical-vapor deposition (MOCVD) have been studied. Structural dependence on growth polarity was observed in the bulk crystals. Spontaneous ordering (formation of polytypoids) was observed for growth in the N to Ga polar direction (N polarity). On the opposite site of the crystal (growth in the Ga to N polar direction) Mg-rich pyramidal defects with base on the basal planes and with walls inclined about 45O to these planes, empty inside (pinholes) were observed. A high concentration of these pyramidal defects was also observed in the MOCVD grown crystals. For samples grown with Mg delta doping planar defects were also observed especially at the early stages of growth followed by formation of pyramidal defects. TEM and x-ray studies of InxGa{sub 1{minus}x}N crystals for the range of 28-45% nominal In concentration shows formation of two sub-layers: strained and relaxed, with a much lower In concentration in the strained layer. Layers with the highest In concentration were fully relaxed.

  1. Status of HgCdTe Barrier Infrared Detectors Grown by MOCVD in Military University of Technology

    NASA Astrophysics Data System (ADS)

    Kopytko, M.; Jóźwikowski, K.; Martyniuk, P.; Gawron, W.; Madejczyk, P.; Kowalewski, A.; Markowska, O.; Rogalski, A.; Rutkowski, J.

    2016-06-01

    In this paper we present the status of HgCdTe barrier detectors with an emphasis on technological progress in metalorganic chemical vapor deposition (MOCVD) growth achieved recently at the Institute of Applied Physics, Military University of Technology. It is shown that MOCVD technology is an excellent tool for HgCdTe barrier architecture growth with a wide range of composition, donor/acceptor doping, and without post-grown annealing. The device concept of a specific barrier bandgap architecture integrated with Auger-suppression is as a good solution for high-operating temperature infrared detectors. Analyzed devices show a high performance comparable with the state-of-the-art of HgCdTe photodiodes. Dark current densities are close to the values given by "Rule 07" and detectivities of non-immersed detectors are close to the value marked for HgCdTe photodiodes. Experimental data of long-wavelength infrared detector structures were confirmed by numerical simulations obtained by a commercially available software APSYS platform. A detailed analysis applied to explain dark current plots was made, taking into account Shockley-Read-Hall, Auger, and tunneling currents.

  2. Status of HgCdTe Barrier Infrared Detectors Grown by MOCVD in Military University of Technology

    NASA Astrophysics Data System (ADS)

    Kopytko, M.; Jóźwikowski, K.; Martyniuk, P.; Gawron, W.; Madejczyk, P.; Kowalewski, A.; Markowska, O.; Rogalski, A.; Rutkowski, J.

    2016-09-01

    In this paper we present the status of HgCdTe barrier detectors with an emphasis on technological progress in metalorganic chemical vapor deposition (MOCVD) growth achieved recently at the Institute of Applied Physics, Military University of Technology. It is shown that MOCVD technology is an excellent tool for HgCdTe barrier architecture growth with a wide range of composition, donor /acceptor doping, and without post-grown annealing. The device concept of a specific barrier bandgap architecture integrated with Auger-suppression is as a good solution for high-operating temperature infrared detectors. Analyzed devices show a high performance comparable with the state-of-the-art of HgCdTe photodiodes. Dark current densities are close to the values given by "Rule 07" and detectivities of non-immersed detectors are close to the value marked for HgCdTe photodiodes. Experimental data of long-wavelength infrared detector structures were confirmed by numerical simulations obtained by a commercially available software APSYS platform. A detailed analysis applied to explain dark current plots was made, taking into account Shockley-Read-Hall, Auger, and tunneling currents.

  3. MBE grown high quality GaN films and devices

    NASA Astrophysics Data System (ADS)

    Kim, W.; Aktas, O.; Salvador, A.; Botchkarev, A.; Sverdlov, B.; Mohammad, S. N.; Morkoç, H.

    1997-02-01

    GaN films with much improved structural, transport, and optical properties have been prepared by molecular beam epitaxy using NH 3 as a nitrogen source. Films with a wide range of resistivity, including highly resistive ones, were grown with a chosen growth rate of 1.2 μm/h. The electron mobility in modulation doped structures is about 450 and 850 cm 2/Vs at 300 and 77 K, respectively, with an areal carrier concentration of about 10 13 cm -2. Low temperature luminescence shows A- and B-free-excitons as well as the excited state of the A- and B-excitons, the first known observation, attesting to the quality of the samples. These transition energies are consistent with the best MOCVD samples and represent a sizable reduction of the pandemic zincblende phase in MBE grown films. The high quality of films was demonstrated by the realization of high performance MODFETs and Schottky diodes.

  4. Modification and Conversion of E-beam Co-evaporated Precursors for Fabricating High Critical Current YBa2Cu3O7-x Films

    SciTech Connect

    Zhang, Yifei; Feenstra, Roeland; Cantoni, Claudia; Christen, David K

    2009-01-01

    Ex situ conversion of e-beam co-evaporated precursors was studied in an effort to fabricate high critical current YBCO films using the BaF{sub 2} process. It was shown that an intermediate oxygenation annealing prior to the conversion modifies the precursor crystallinity and promotes c-axis epitaxial growth while randomly-oriented film formation is suppressed. With the modified precursors, a critical current density (J{sub c}, 77 K & 0 T) of 2.1 MA/cm{sup 2} measured by SQUID magnetometry was obtained in 1.8 {micro}m thick YBCO films. This corresponds to an estimated transport critical current I{sub c} of about 500 A/cm-width. The mechanism of the pre-annealing effect was investigated by characterization of the precursors, quenched films, and fully converted films using XRD, SEM, and TEM. Cross-sectional TEM was used to study the early nucleation of YBCO film at the precursor/substrate interface. The significant effect of the precursor modification indicated that, in addition to optimizing conversion processing parameters, modifying the precursor is an effective way to achieve the desired epitaxial film structure and to obtain higher critical currents, I{sub c}.

  5. Feasibility studies of the growth of 3-5 compounds of boron by MOCVD. Final report

    SciTech Connect

    Manasevit, H.M.

    1988-03-01

    Boron-arsenic and boron-phosphorus films have been grown on Si sapphire and silicon-on-sapphire (SOS) by pyrolyzing Group 3 alkyls of boron, i.e., trimethylborane (TMB) and triethylborane (TEB), in the presence of AsH/sub 3/ and PH/sub 3/, respectively, in an H/sub 2/ atmosphere. No evidence for reaction between the alkyls and the hydrides on mixing at room temperature was found. However, the films were predominantly amorphous. The film growth rate was found to depend on the concentration of alkyl boron compound and was essentially constant when TEB and AsH/sub 3/ were pyrolyzed over the temperature range 550 C to 900 C. The films were found to contain mainly carbon impurities (the amount varying with growth temperature), some oxygen, and were highly stressed and bowed on Si substrates, with some crazing evident in thin (2 micron) B-P and thick (5 micron) B-As films. The carbon level was generally higher in films grown using TEB as the boron source. Films grown from PH/sub 3/ and TMB showed a higher carbon content than those grown from AsH/sub 3/ and TMB. Based on their B/As and B/P ratios, films with nominal compositions B/sub12-16 As2/ and B/sub1.1-1.3/ P were grown using TMB as the boron source.

  6. Feasibility studies of the growth of 3-5 compounds of boron by MOCVD

    NASA Technical Reports Server (NTRS)

    Manasevit, H. M.

    1988-01-01

    Boron-arsenic and boron-phosphorus films have been grown on Si sapphire and silicon-on-sapphire (SOS) by pyrolyzing Group 3 alkyls of boron, i.e., trimethylborane (TMB) and triethylborane (TEB), in the presence of AsH3 and PH3, respectively, in an H2 atmosphere. No evidence for reaction between the alkyls and the hydrides on mixing at room temperature was found. However, the films were predominantly amorphous. The film growth rate was found to depend on the concentration of alkyl boron compound and was essentially constant when TEB and AsH3 were pyrolyzed over the temperature range 550 C to 900 C. The films were found to contain mainly carbon impurities (the amount varying with growth temperature), some oxygen, and were highly stressed and bowed on Si substrates, with some crazing evident in thin (2 micron) B-P and thick (5 micron) B-As films. The carbon level was generally higher in films grown using TEB as the boron source. Films grown from PH3 and TMB showed a higher carbon content than those grown from AsH3 and TMB. Based on their B/As and B/P ratios, films with nominal compositions B sub12-16 As2 and B sub1.1-1.3 P were grown using TMB as the boron source.

  7. Deposition of high quality YBa2Cu3O(7-delta) thin films over large areas by pulsed laser ablation with substrate scanning

    NASA Technical Reports Server (NTRS)

    Davis, M. F.; Wosik, J.; Forster, K.; Deshmukh, S. C.; Rampersad, H. R.

    1991-01-01

    The paper describes thin films deposited in a system where substrates are scanned over areas up to 3.5 x 3.5 cm through the stationary plume of an ablated material defined by an aperture. These YBCO films are deposited on LaAlO3 and SrTiO3 substrates with the thickness of 90 and 160 nm. Attention is focused on the main features of the deposition system: line focusing of the laser beam on the target; an aperture defining the area of the plume; computerized stepper motor-driven X-Y stage translating the heated sampler holder behind the plume-defining aperture in programmed patterns; and substrate mounting block with uniform heating at high temperatures over large areas. It is noted that the high degree of uniformity of the properties in each film batch illustrates that the technique of pulsed laser deposition can be applied to produce large YBCO films of high quality.

  8. Thin films of gallium arsenide on low-cost substrates. Final technical report, July 5, 1976-December 5, 1978

    SciTech Connect

    Ruth, R.P.; Dapkus, P.D.; Dupuis, R.D.; Johnson, R.E.; Moudy, L.A.; Yang, J.J.; Yingling, R.D.

    1980-03-01

    The MO-CVD technique was applied to the growth of thin films of GaAs and GaAl As on inexpensive polycrystalline or amorphous substrate materials (primarily glasses and metals) for use in fabrication of large-area low-cost photovoltaic device structures. Trimethylgallium, arsine, and trimethylaluminum are mixed in appropriate concentrations at room temperature in the gaseous state and pyrolyzed at the substrate, which is heated in a vertical reactor chamber to temperatures of 700 to 750/sup 0/C, to produce the desired film composition and properties. Studies of the properties of grain boundaries in polycrystalline GaAs films by the use of transport measurements as a function of temperature indicated that the grain boundary regions are depleted of majority carriers by a large density of neutral traps at the grain boundary interface, causing a barrier to majority carrier flow in the material. Schottky-barrier solar cells of approx. 3 percent efficiency (simulated AM0 illumination, no AR coating) were demonstrated on thin-film polycrystalline GaAs n/n/sup +/ structures on Mo sheet, Mo film/glass, and graphite substrates. Substantial enhancement of average grain size in polycrystalline MO-CVD GaAs films on Mo sheet was obtained by the addition of HCl to the growth atmosphere during deposition. Extensive investigation of polycrystalline thin-film p-n junctions indicated that the forward voltage of such devices is apparently limited to 0.5 to 0.6V. A laboratory-type deposition apparatus for the formation of TiO/sub 2/ antireflection (AR) coatings by pyrolysis of titanium isopropoxide was assembled and tested. Detailed analyses were made of the materials and labor costs involved in the laboratory-scale fabrication of MO-CVD thin-film GaAs solar cells. Details are presented. (WHK)

  9. Process for forming epitaxial perovskite thin film layers using halide precursors

    DOEpatents

    Clem, Paul G.; Rodriguez, Mark A.; Voigt, James A.; Ashley, Carol S.

    2001-01-01

    A process for forming an epitaxial perovskite-phase thin film on a substrate. This thin film can act as a buffer layer between a Ni substrate and a YBa.sub.2 Cu.sub.3 O.sub.7-x superconductor layer. The process utilizes alkali or alkaline metal acetates dissolved in halogenated organic acid along with titanium isopropoxide to dip or spin-coat the substrate which is then heated to about 700.degree. C. in an inert gas atmosphere to form the epitaxial film on the substrate. The YBCO superconductor can then be deposited on the layer formed by this invention.

  10. The short-circuit test results of 6.9 kV/2.3 kV 400 kVA-class YBCO model transformer

    NASA Astrophysics Data System (ADS)

    Tomioka, A.; Otonari, T.; Ogata, T.; Iwakuma, M.; Okamoto, H.; Hayashi, H.; Iijima, Y.; Saito, T.; Gosho, Y.; Tanabe, K.; Izumi, T.; Shiohara, Y.

    2011-11-01

    We are developing an elemental technology for 66 kV/6.9 kV 20 MVA-class power transformer with YBCO conductors. The protection of short-circuit technology is one of the elemental technologies for HTS transformer. Since short-circuit current is much higher than critical current of YBCO tape, there is a possibility that superconducting characteristics may be damaged during short-circuit period. We made a conductor to compose the YBCO tape with copper tape. We manufactured 6.9 kV/2.3 kV 400 kVA-class YBCO model transformer using this conductor and performed short-circuit current test. The short-circuit current of primary winding was 346 A which was about six times larger than the rated current. The I-V characteristics of the winding did not change before and after the test. We may consider this conductor withstands short-circuit current.

  11. Factors associated with biaxial texturing of Cu tapes for YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Kim, Y. H.; Sung, T. H.; Han, S. C.; Han, Y. H.; Jeong, N. H.; Kim, C. J.; Jun, B. H.; Oh, S. S.; Kim, H. S.; Kim, T. H.; No, K. S.

    2007-10-01

    A biaxially textured Cu(2 0 0) tape was used as a substrate for YBCO coated conductors by cold rolling followed by recrystallization heat treatment. In this work, we studied the influence of annealing conditions and final tape thickness on the recrystallization process. Phi (ϕ) scan and omega (ω) scan XRD revealed that the best in-plane and out-of-plane alignment of the Cu tape (thickness 100 μm), measured in terms of full width half maximum (FWHM) values of 6.64° and 4.49°, were obtained by annealing at 800 °C for 30 min. The texture of CeO2 buffer layer thermally-evaporated on the Cu tape was also analyzed.

  12. High-Tc Coated Conductors - Performance of Meter-Long YBCO/IBAD Flexible Tapes

    SciTech Connect

    Foltyn, S.R.; Arendt, P.N.; Dowden, P.C.; DePaula, R.F.; Groves J.R.; Coulter, J.Y.; Jia, Q.; Maley, M.P.; Peterson, D.E.

    1998-09-13

    One meter long tapes based on 50-100 {micro}m thick by 1 cm wide nickel alloy substrates have been coated in a continuous process with a textured yttria-stabilized zirconia layer by ion beam-assisted deposition, followed by a 1-2 {micro}m thick layer of YBCO by pulsed laser deposition. The best result to date is a tape with a critical current (I{sub c}) at 75 K of 96 A over an 87 cm measurement length. The overall critical current density and engineering current density are 1 MA/cm{sup 2} and 10 kA/cm{sup 2}, respectively. Using a special probe, individual I-V curves were generated for each centimeter of tape length in order to investigate longitudinal uniformity of the transport properties: the highest and lowest I{sub c} values fall within a range of {+-}25%.

  13. Magnetization losses in superconducting YBCO conductor-on-round-core (CORC) cables

    NASA Astrophysics Data System (ADS)

    Majoros, M.; Sumption, M. D.; Collings, E. W.; van der Laan, D. C.

    2014-12-01

    Described are the results of magnetization loss measurements made at 77 K on several YBCO conductor-on-round-core (CORC) cables in ac magnetic fields of up to 80 mT in amplitude and frequencies of 50 to 200 Hz, applied perpendicular to the cable axis. The cables contained up to 40 tapes that were wound in as many as 13 layers. Measurements on the cables with different configurations were made as functions of applied ac field amplitude and frequency to determine the effects of their layout on ac loss. In large scale devices such as e.g. Superconducting Magnetic Energy Storage (SMES) magnets, the observed ac losses represent less than 0.1% of their stored energy.

  14. Chemical solution deposition using ink-jet printing for YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Van Driessche, I.; Feys, J.; Hopkins, S. C.; Lommens, P.; Granados, X.; Glowacki, B. A.; Ricart, S.; Holzapfel, B.; Vilardell, M.; Kirchner, A.; Bäcker, M.

    2012-06-01

    This paper reports the successful application of ink-jet printing to the deposition of both continuous coatings and multi-filamentary structures of YBCO. Stable inks have been prepared using both the established TFA-MOD route and novel fluorine-free precursors with appropriate rheological properties for ink-jet printing. Continuous and well textured coatings with lengths exceeding 100 m and a thickness of 0.5 µm have been deposited by electromagnetic ink-jet printing from TFA precursors on LZO-buffered Ni-W substrates and samples have achieved a Jc around 1.5 MA cm-2 (self-field, 77 K). On single crystal substrates, continuous coatings and multi-filamentary structures have been deposited using piezoelectric ink-jet printing both from TFA- and water-based precursors, achieving Jc values up to 3 MA cm-2.

  15. Experimental and numerical study of a YBCO pancake coil with a magnetic substrate

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Kvitkovic, J.; Pamidi, S. V.; Coombs, T. A.

    2012-12-01

    A finite element model for a YBCO pancake coil with a magnetic substrate is developed in this paper. An axial symmetrical H formulation and the E-J power law are used to construct the model, with the magnetic substrate considered by introducing an extra time-dependent term in the formula. A pancake coil is made and tested. The measurement of critical current and transport loss is compared to the model result, showing good consistency. The influence of magnetic substrate in the condition of AC and DC current is studied. The AC loss decreases without a magnetic substrate. It is observed that when the applied DC current approaches the critical current the coil turn loss profile changes completely in the presence of magnetic substrate due to the change of magnetic field distribution.

  16. Magnetic levitation and its application for education devices based on YBCO bulk superconductors

    NASA Astrophysics Data System (ADS)

    Yang, W. M.; Chao, X. X.; Guo, F. X.; Li, J. W.; Chen, S. L.

    2013-10-01

    A small superconducting maglev propeller system, a small spacecraft model suspending and moving around a terrestrial globe, several small maglev vehicle models and a magnetic circuit converter have been designed and constructed. The track was paved by NdFeB magnets, the arrangement of the magnets made us easy to get a uniform distribution of magnetic field along the length direction of the track and a high magnetic field gradient in the lateral direction. When the YBCO bulks mounted inside the vehicle models or spacecraft model was field cooled to LN2 temperature at a certain distance away from the track, they could be automatically floating over and moving along the track without any obvious friction. The models can be used as experimental or demonstration devices for the magnetic levitation applications.

  17. A new method to detect the vortex glass phase and its evidence in YBCO.

    PubMed

    Adesso, M G; Polichetti, M; Pace, S

    2008-09-24

    The evidence of the vortex glass phase has been obtained by analysing the nonlinear magnetic response of type-II superconductors. The method introduced here is based on a combined frequency dependence analysis of the real and imaginary part of the 1st and 3rd harmonics of the AC magnetic susceptibility. The analysis has been performed by taking into account both the components and the Cole-Cole plots (i.e. the imaginary part as a function of the real part). Numerical simulations have been used to identify the fingerprints of the magnetic behaviour in the vortex glass phase. These characteristics allowed the vortex glass phase to be distinguished from the other disordered phases, even those showing similar electrical properties. Finally, this method has been successfully applied to detecting the vortex glass phase in an YBCO bulk melt-textured sample. PMID:21693829

  18. Critical currents of YBCO tapes and Bi-2212 wires at different temperatures and magnetic fields

    SciTech Connect

    Lombardo, V.; Barzi, e.; Turrioni, D.; Zlobin, A.V.; /Fermilab

    2010-08-01

    Design studies for the cooling channel of a Muon Collider call for straight and helical solenoids generating field well in excess of the critical fields of state of the art Low Temperature Superconductors (LTS) such as Nb{sub 3}Sn or NbTi. Therefore, High Temperature Superconductors (HTS) will need to be used for the manufacturing of all or certain sections of such magnets to be able to generate and withstand the field levels at the cryogenic temperatures required by the new machine. In this work, two major High Temperature Superconductors - Bi2212 round wires and YBCO coated conductor tapes - are investigated to understand how critical current density of such conductors scales as a function of external field and operating temperature. This is vital information to make conductor choices depending on the application and to proceed with the design of such magnets.

  19. Calibration of Hall sensor array for critical current measurement of YBCO tape with ferromagnetic substrate

    NASA Astrophysics Data System (ADS)

    Zhu, Yunpeng; Wang, Gang; Liu, Liyuan; Yang, Xinsheng; Zhao, Yong

    2015-12-01

    HAS (Hall sensor array) is a powerful tool to detect the uniformity of HTS (high temperature superconductor) tape through mapping the distribution of remanent or shielding field along the surface of the tape. However, measurement of HTS tape with ferromagnetic parts by HSA is still an issue because the ferromagnetic substrate has influence on the magnetic field around the HTS layer. In this work, a continuous HSA system has been designed to measure the critical current of the YBCO tape with ferromagnetic substrate. The relationship between the remanent field and critical current was calibrated by the finite element method. The result showed that the HSA is an effective method for evaluating the critical current of the HTS tape with ferromagnetic substrate.

  20. (abstract) All Epitaxial Edge-geometry SNS Devices with Doped PBCO and YBCO Normal Layers

    NASA Technical Reports Server (NTRS)

    Barner, J. B.; Hunt, B. D.; Foote, M. C.

    1995-01-01

    We will present our results on tapered-edge-geometry SNS weak link fabricated from c-axis oriented base-, counterelectrode and normal layers using a variety of processing conditions. To date, we have employed a variety of different normal materials (Co-doped YBCO, Y-doped PBCO, Ca-doped PBCO). We have been examining the junction fabrication process in detail and we will present our methods. In particular, we have been examining both epitaxial and non-epitaxial milling mask overlayers and we will present a comparison of both methods. These devices behave similar to the expectations of the resisively shunted junction model and conventional SNS proximity effect models but with some differences which will be discussed. We will present the detailed systematics of our junctions including device parameters versus temperature, rf and dc magnetic response for the various processing conditions.