New contact design for the ex situ fabrication of small size, low resistivity normal metal contacts to epitaxial c-axis YBCO films

1996 ◽  
Vol 19 (1) ◽  
pp. 105-112 ◽  
Author(s):  
R. Hahn ◽  
M.E. Johansson
Keyword(s):  
Normal Metal ◽  
Ex Situ ◽  
Metal Contacts ◽  
Ybco Films ◽  
Low Resistivity

High critical current MOD ex situ YBCO films on RABiTSTM and MgO-IBAD templates

2003 ◽  
Vol 390 (3) ◽  
pp. 249-253 ◽  
Author(s):  
X. Li ◽  
M.W. Rupich ◽  
W. Zhang ◽  
N. Nguyen ◽  
T. Kodenkandath ◽  
...  
Keyword(s):  
Critical Current ◽  
Ex Situ ◽  
Ybco Films

Liquid mediated growth and the bimodal microstructure of YBa2Cu3O7−δ films made by the ex situ conversion of physical vapor deposited BaF2 precursors

2005 ◽  
Vol 20 (5) ◽  
pp. 1216-1233 ◽  
Author(s):  
T.G. Holesinger ◽  
P.N. Arendt ◽  
R. Feenstra ◽  
A.A. Gapud ◽  
E.D. Specht ◽  
...  
Keyword(s):  
Film Thickness ◽  
Ion Beam ◽  
Transient Liquid Phase ◽  
Conversion Process ◽  
Ex Situ ◽  
Second Phase ◽  
Bimodal Microstructure ◽  
Ybco Films ◽  
Bimodal Structure ◽  
Liquid Phases

YBa2Cu3Oy (YBCO) films produced by the ex situ conversion of BaF2-based precursors deposited by physical vapor deposition on ion-beam assisted deposited (IBAD) yttrium-stabilized zirconia (YSZ) and rolling-assisted biaxially textured substrates (RABiTS) templates are characterized by a bi-axially aligned, laminar grain structure that results from the anisotropic growth characteristics of the YBCO phase and its precipitation from a transient liquid phase during the conversion process. A bimodal microstructure characterizes these films and is defined by large, well-formed YBCO grains with Y2O3 precipitates in the bottom region of the film and small YBCO grains with a high density of stacking faults in the upper half. Ba2Cu3Oy or Ba–O–F/CuO second phase layers were often found between large YBCO grains in the bottom half of the films. YBCO grain sizes exceeded 50 μm within the plane of the film in some cases. Conversely, discrete secondary phases of Y2Cu2O5, Y2O3, and Ba2Cu3Oy/Ba–O–F could be found among the much smaller YBCO grains in the top portion of the bimodal structure. The dividing line of the bimodal structure was generally at one half of the film thickness, although exceptions to this trend were found. The highest critical current densities (Jc) and best film alignments for a given film thickness were found in samples where the layers of Ba2Cu3Oy or Ba–O–F were minimized or eliminated from the films. Samples quenched after partial conversion show the segregation of CuO to the top region of the film and the lateral growth of large YBCO grains from a precursor mix of Y2Cu2O5 and Ba–O–F. The data demonstrate that transient liquid phases are part of the conversion process of BaF2-based YBCO films. The control of both CuO segregation and the amount of liquid phases generated during the initial stages of phase formation is needed for optimizing the ex situ conversion process for high-Jc coated conductors.

Effects of Conversion Parameters on the Transport Properties of YBCO Films in the BaF2 Ex Situ Process

2004 ◽  
Vol 19 (4) ◽  
pp. 1281-1289 ◽  
Author(s):  
J. Yoo ◽  
K.J. Leonard ◽  
D.F. Lee ◽  
H.S. Hsu ◽  
L. Heatherly ◽  
...  
Keyword(s):  
Water Vapor ◽  
Transport Properties ◽  
Buffer Layer ◽  
Dwell Time ◽  
Ex Situ ◽  
Precursor Film ◽  
Processing Temperature ◽  
Vapor Pressures ◽  
Ybco Films ◽  
Conversion Time

The effects of conversion parameters on transport properties of YBa2Cu3O7-δ (YBCO) films on rolling assisted biaxially textured substrates (RABiTS) in the BaF2 ex situ process were investigated for total pressures Ptotal between 0.1 and 1.3 atm, water vapor pressures PH2O between approximately 7 and 70 Torr and processing temperatures TS between 700 and 790 °C. For this study, a 0.3-μm-thick Y–BaF2–Cu–O precursor film was deposited on a 1-cm-wide Ni=3 at.% W RABiTS with a buffer layer architecture of CeO2/YSZ/Y2O3/Ni deposited in single passes in various reel-to-reel systems for each layer. Under the conditions of Ptotal = 0.1 atm, TS = 740 °C and PO2 approximately 150 mTorr, JC > 2 MA/cm2 was obtained at 77 K and self field for PH2O ≤ 20 Torr. At higher PH2O (=70 Torr), however, the maximum attainable JC decreased. In addition, the JC at these higher PH2O dropped rapidly with increased dwell time. The highest JC, 2.5 MA/cm2, was achieved at 730 °C with Ptotal = 0.1 atm and PH2O approximately 7 Torr. Finally, the variation of IC with wet conversion time was performed at each processing temperature.

Proximity-Effect and Tunneling in YBa2Cu3O7/Metal Layered Structures

1989 ◽  
Vol 169 ◽  
Author(s):  
L. H. Greene ◽  
W. L. Feldmann ◽  
J. B. Barrier ◽  
L. A. Farrow ◽  
P. F. Miceli ◽  
...  
Keyword(s):  
Tunnel Junctions ◽  
Normal Metal ◽  
Ex Situ ◽  
Superconducting Thin Films ◽  
Composite Target ◽  
Shapiro Steps ◽  
Target Composition ◽  
Planar Magnetron ◽  
Metal Bilayers

AbstractSuperconducting thin films of YBa2Cu3O7 are prepared in-situ by on-axis, sputter deposition from a single, composite target. Our planar magnetron target composition of Y:Ba:Cu = 1.08:1.76:4.5 sputtered onto MgO at T~750°C in a 600mTorr Ar-O2 atmosphere yields reproducible superconducting films having Tc(R = 0)>80K and stoichiometry 1:2:3, that are shiny and of near epitaxial, crystalline quality. In order to ensure clean interfaces, YBa2Cu3O7/normal metal bilayers (to form SNS' Josephson junctions) and YBa2Cu3O7/normal metal/insulating barrier trilayers (to form SNIS' proximity tunnel junctions) are grown completely in-situ. (The S' = Pb counter electrode is evaporated ex-situ.) A supercurrent and Shapiro steps are observed in microwave irradiated SNS' (N = Ag) small area (5x10-5cm2) junctions. In SNIS' tunnel junctions, high-quality Pb tunneling is observed.

High-Jc YBCO coatings on reel-to-reel dip-coated Gd2O3 seed buffer layers epitaxially fabricated on biaxially textured Ni and Ni-(3at%W-1.7at%Fe) alloy tapes

2001 ◽  
Vol 689 ◽  
Author(s):  
Tolga Aytug ◽  
M. Paranthaman ◽  
S. Sathyamurthy ◽  
B. W. Kang ◽  
D. B. Beach ◽  
...  
Keyword(s):  
Low Cost ◽  
Dip Coating ◽  
Buffer Layers ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
Ybco Films ◽  
Ni Alloy ◽  
Current Densities ◽  
Alloy Metal

ABSTRACTA low-cost, non-vacuum reel-to reel dip-coating system has been used to continuously fabricate epitaxial Gd2O3 buffer layers on mechanically strengthened, biaxially textured Ni- (3at.%W-1.7at%Fe), defined as Ni-alloy, metal tapes. X-ray diffraction analysis of the seed Gd2O3 layers indicated that well textured films can be obtained at processing temperatures (Tp) between 1100 and 1175°C. Processing speed did not significantly affect the crystalline quality of the Gd2O3. Scanning electron microscopy revealed a continuous, dense and crack-free surface morphology for these dip-coated buffers. The Gd2O3 layer thickness led to remarkable differences in the growth characteristics of the subsequent YSZ and CeO2 layers deposited by rfmagnetron sputtering. Epitaxial YBCO films grown by pulsed laser deposition on the short prototype CeO2/YSZ/Gd2O3/Ni-(3at%W-1.7at%Fe) conductors yielded self-field critical current densities (Jc) as high as 1.2×106 A/cm2 at 77 K. Pure Ni tapes were used to asses the viability of dip-coated buffers for long length coated conductor fabrication. The YBCO films, grown on 80 cm long and 1 cm wide CeO2/YSZ/Gd2O3 buffered Ni tapes by the industrially scalable ex-situ BaF2 precursor process, exhibited end-to-end self-field Jc of 6.25×105 A/cm2 at 77 K.

Inductive measurements of λ(T) of bare YBCO films and the proximity effect in YBCO/normal metal bilayers

1995 ◽  
Vol 5 (2) ◽  
pp. 1432-1435 ◽  
Author(s):  
C.W. Schneider ◽  
R.E. Somekh ◽  
J.E. Evetts ◽  
D.J.C. Walker ◽  
I.M. Watson ◽  
...  
Keyword(s):  
Proximity Effect ◽  
Normal Metal ◽  
Ybco Films ◽  
Metal Bilayers

Transport in Mesoscopic Superconductors and Superconducting/Normal Metal Contacts

1998 ◽  
pp. 79-89
Author(s):  
T. Claeson ◽  
P. Delsing ◽  
Z. Ivanov ◽  
S. Kubatkin ◽  
L. Kuzmin ◽  
...  
Keyword(s):  
Normal Metal ◽  
Metal Contacts ◽  
Mesoscopic Superconductors
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