All-chemical high-Jc YBa2Cu3O7 multilayers with SrTiO3 as cap layer

2006 ◽  
Vol 21 (5) ◽  
pp. 1106-1116 ◽  
Author(s):  
A. Pomar ◽  
M. Coll ◽  
A. Cavallaro ◽  
J. Gàzquez ◽  
J.C. González ◽  
...  
Keyword(s):  
Ybco Film ◽  
Growth Conditions ◽  
Critical Currents ◽  
Layer Growth ◽  
Vortex Pinning ◽  
Buffer Layers ◽  
Superconducting Thin Films ◽  
Chemical Solution ◽  
Superconducting Properties ◽  
Chemical Methods

We grew high-quality epitaxial YBa2Cu3O7 (YBCO) superconducting thin films by the trifluoroacetate route on top of chemical solution deposited SrTiO3 buffer layers. We show that high lattice mismatches can be accommodated in heterostructures grown by chemical methods. Clean interfaces were observed between the different layers. The influence of the buffer layer growth conditions on the final superconducting properties was studied in depth. We have proved that the main parameter affecting the YBCO critical currents is the SrTiO3 surface roughness, which promotes the nucleation of a/b axis grains and, as a consequence, the porosity of the YBCO film. On the other hand, an improved dependence of the critical current with perpendicular applied magnetic field was observed. This suggests a strengthened vortex pinning due to a higher density of a/b axis oriented grains.

scholarly journals Effect of Buffer Layer and III/V Ratio on the Surface Morphology of Gan Grown by MBE

1999 ◽  
Vol 4 (S1) ◽  
pp. 417-422 ◽  
Author(s):  
E. C. Piquette ◽  
P. M. Bridger ◽  
R. A. Beach ◽  
T. C. McGill
Keyword(s):  
Surface Morphology ◽  
Buffer Layer ◽  
Flux Ratio ◽  
Plasma Source ◽  
Growth Conditions ◽  
Nitrogen Plasma ◽  
Layer Growth ◽  
Buffer Layers ◽  
Flat Surfaces ◽  
Aln Buffer

The surface morphology of GaN is observed by atomic force microscopy for growth on GaN and AlN buffer layers and as a function of III/V flux ratio. Films are grown on sapphire substrates by molecular beam epitaxy using a radio frequency nitrogen plasma source. Growth using GaN buffer layers leads to N-polar films, with surfaces strongly dependent on the flux conditions used. Flat surfaces can be obtained by growing as Ga-rich as possible, although Ga droplets tend to form. Ga-polar films can be grown on AlN buffer layers, with the surface morphology determined by the conditions of buffer layer deposition as well as the III/V ratio for growth of the GaN layer. Near-stoichiometric buffer layer growth conditions appear to support the flattest surfaces in this case. Three defect types are typically observed in GaN films on AlN buffers, including large and small pits and “loop” defects. It is possible to produce surfaces free from large pit defects by growing thicker films under more Ga-rich conditions. In such cases the surface roughness can be reduced to less than 1 nm RMS.

Epitaxial Growth of Solution-Based Rare-Earth Niobate, RE3NbO7, Films on Biaxially Textured Ni–W Substrates

2005 ◽  
Vol 20 (1) ◽  
pp. 6-9 ◽  
Author(s):  
M. Paranthaman ◽  
M.S. Bhuiyan ◽  
S. Sathyamurthy ◽  
H.Y. Zhai ◽  
A. Goyal ◽  
...  
Keyword(s):  
Rare Earth ◽  
Critical Current Density ◽  
Epitaxial Growth ◽  
Chemical Solution Deposition ◽  
Ybco Film ◽  
Pulsed Laser ◽  
Buffer Layers ◽  
Laser Deposition ◽  
Chemical Solution ◽  
Solution Deposition

A new series of rare earth-niobate, RE3NbO7 (RE=Y,Gd,Eu), buffer layers were developed for the growth of superconducting YBa2Cu3O7−δ (YBCO) films on biaxially textured Ni–W (3 at.%) substrates. Using chemical solution deposition, smooth, crack-free, and epitaxial RE3NbO7 (RE = Y,Gd,Eu) films were grown on cube-textured Ni–W substrate. YBCO film with a critical current density of 1.1 × 106 A/cm2 in self-field at 77 K was grown directly on a single Gd3NbO7-buffered Ni–W substrate using pulsed laser deposition.

scholarly journals Effect of Buffer Layer and III/V Ratio on the Surface Morphology of Gan Grown by MBE

1998 ◽  
Vol 537 ◽  
Author(s):  
E. C. Piquette ◽  
P. M. Bridger ◽  
R. A. Beach ◽  
T. C. McGill
Keyword(s):  
Surface Morphology ◽  
Buffer Layer ◽  
Flux Ratio ◽  
Plasma Source ◽  
Growth Conditions ◽  
Nitrogen Plasma ◽  
Layer Growth ◽  
Buffer Layers ◽  
Flat Surfaces ◽  
Aln Buffer

AbstractThe surface morphology of GaN is observed by atomic force microscopy for growth on GaN and AlN buffer layers and as a function of III/V flux ratio. Films are grown on sapphire substrates by molecular beam epitaxy using a radio frequency nitrogen plasma source. Growth using GaN buffer layers leads to N-polar films, with surfaces strongly dependent on the flux conditions used. Flat surfaces can be obtained by growing as Ga-rich as possible, although Ga droplets tend to form. Ga-polar films can be grown on AlN buffer layers, with the surface morphology determined by the conditions of buffer layer deposition as well as the III/V ratio for growth of the GaN layer. Near-stoichiometric buffer layer growth conditions appear to support the flattest surfaces in this case. Three defect types are typically observed in GaN films on AlN buffers, including large and small pits and “loop” defects. It is possible to produce surfaces free from large pit defects by growing thicker films under more Ga-rich conditions. In such cases the surface roughness can be reduced to less than l nm RMS.

scholarly journals CSD-Grown Y1−xGdxBa2Cu3O7−δ-BaHfO3 Nanocomposite Films on Ni5W and IBAD Technical Substrates

Nanomaterials ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 21 ◽  
Author(s):  
Pablo Cayado ◽  
Hannes Rijckaert ◽  
Manuela Erbe ◽  
Marco Langer ◽  
Alexandra Jung ◽  
...  
Keyword(s):  
Chemical Solution Deposition ◽  
Growth Process ◽  
Growth Conditions ◽  
Coated Conductors ◽  
Nanocomposite Films ◽  
Chemical Solution ◽  
Superconducting Properties ◽  
High Quality ◽  
Solution Deposition ◽  
Structure Morphology

Chemical solution deposition (CSD) was used to grow Y1−xGdxBa2Cu3O7−δ-BaHfO3 (YGBCO-BHO) nanocomposite films containing 12 mol% BHO nanoparticles and various amounts of Gd, x, on two kinds of buffered metallic tapes: Ni5W and IBAD. The influence of the rare-earth stoichiometry on structure, morphology and superconducting properties of these films was studied. The growth process was carefully studied in order to find the most appropriate growth conditions for each composition and substrate. This led to a clear improvement in film quality, probably due to the reduction of BaCeO3 formation. In general, the superconducting properties of the films on Ni5W are significantly better. For x > 0.5, epitaxial ~270 nm thick YGBCO-BHO films with Tc > 93 K and self-field Jc at 77 K ~2 MA/cm² were obtained on Ni5W. These results highlight the potential of this approach for the fabrication of high-quality coated conductors.

Effect of Aluminum Nitride Buffer Layer Temperature on Gallium Nitride Grown by OMVPE

1994 ◽  
Vol 339 ◽  
Author(s):  
L. B. Rowland ◽  
K. Doverspike ◽  
D. K. Gaskill ◽  
J. A. Freitas
Keyword(s):  
Gallium Nitride ◽  
Buffer Layer ◽  
Growth Temperature ◽  
Growth Conditions ◽  
Layer Growth ◽  
Buffer Layers ◽  
Double Crystal ◽  
Relative Crystallinity ◽  
Excitonic Emission ◽  
Aln Buffer

ABSTRACTGallium nitride layers were grown by organometallic vapor phase epitaxy on AlN buffer layers deposited in the range of 450–650°C. The GaN growth conditions were kept constant so that changes in film properties were due only to changes in the buffer layer growth temperature. A monotonie improvement in relative crystallinity as measured by double-crystal X-ray diffraction corresponded with a decrease in buffer layer growth temperature. Improvements in GaN electron transport at 300 and 77 K were also observed with decreasing AlN buffer layer temperature. Photoluminescence spectra for the lowest temperatures studied were dominated by sharp excitonic emission, with some broadening of the exciton linewidth observed as the buffer layer growth temperature was increased. The full width at half maximum of the excitonic emission was 2.7 meV for GaN grown on a 450°C buffer layer. These results indicate that minimizing AlN buffer layer temperature results in improvements in GaN film quality.

Characterization of DyBa2Cu3O7+δ thin Films Prepared by Ozone-Assisted Co-Evaporation Technique

1992 ◽  
Vol 275 ◽  
Author(s):  
T. J. Hsieh ◽  
R. V. Smilgys ◽  
C. K. Chiang ◽  
S. W. Robey ◽  
R. J. Arsenault ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Resistivity ◽  
Substrate Temperature ◽  
Critical Currents ◽  
Superconducting Thin Films ◽  
Superconducting Properties ◽  
Critical Temperatures ◽  
Oriented Films ◽  
Evaporation Technique

ABSTRACTSuperconducting thin films of DyBa2Cu3O7-δ_ are deposited on MgO(100) substrates by an ozone-assisted coevaporation technique. At a relatively low substrate temperature (610°C) and with a fixed ozone flux we prepare highly c-axis oriented films with very good superconducting properties. The critical temperatures of the films are commonly above 85 K with critical currents above 10 5 A/cm2. We report on composition, microstructure, electrical resistivity and critical current of two good films.

PREPARATION OF BUFFER LAYERS ON SAPPHIRE FOR HIGH Tc SUPERCONDUCTING THIN FILMS

1991 ◽  
Vol 05 (19) ◽  
pp. 1267-1273 ◽  
Author(s):  
X. D. WU ◽  
R. E. MUENCHAUSEN
Keyword(s):  
Thin Films ◽  
High Frequency ◽  
Dielectric Constants ◽  
Buffer Layers ◽  
Processing Temperature ◽  
Superconducting Thin Films ◽  
Superconducting Properties ◽  
Stabilized Zirconia ◽  
Low Loss ◽  
High Tc

Sapphire is a preferred substrate for high frequency applications where small dielectric constants and low loss tangents are required. It is also much cheaper than other oxide subsrates such as SrTiO 3, LaAlO 3, NdGaO 3, MgO, and yttria-stabilized zirconia (YSZ) for high T c superconducting thin films. Unfortunately, sapphire is not chemically compatible with the high T c superconductors at the processing temperature required to obtained good superconducting properties. As a result, an appropriate buffer layer on sapphire is required.

scholarly journals Structural properties of MOVPE GaN layers grown by a new multi-buffer aproach

1998 ◽  
Vol 3 ◽  
Author(s):  
J. Kozlowski ◽  
R. Paszkiewicz ◽  
R. Korbutowicz ◽  
M. Panek ◽  
B. Paszkiewicz ◽  
...  
Keyword(s):  
High Temperature ◽  
Electrical Properties ◽  
Buffer Layer ◽  
Growth Conditions ◽  
Optical Microscope ◽  
Lattice Parameter ◽  
Layer Growth ◽  
Buffer Layers ◽  
Molar Ratio ◽  
X Ray

GaN undoped layers of good morphology, good crystallinity and electrical properties were grown on c-plane sapphire substrates by the atmospheric pressure MOVPE technique using a new multi-buffer growth approach. A suitable buffer layer growth technique was worked out which enabled growth of GaN layers with properties superior to those grown in a conventional process scheme. Additional buffer layers, deposited with increasing temperature and increasing V/III molar ratio, were inserted between the low temperature buffer layer and the high temperature GaN layer grown on it. The c and a lattice constants of the high temperature GaN overgrown layer were evaluated from X-ray data. The layer mosaicity and c-lattice parameter variation were determined. The relationship between c and a lattice parameters and the second buffer layer growth scheme has been studied. The effect of second buffer layer growth conditions, buffer layer annealing time as well as the influence of V/III molar ratio during the high temperature GaN deposition on the crystalline and electrical properties of overgrown GaN epitaxial layers are presented. Characterization includes surface morphology examination by SEM and Nomarski optical microscope, X-ray diffraction and C-V measurements.

Microstructure of SrTiO3 buffer layers and itseffects on superconducting properties ofYBa2Cu3O7-δ coated conductors

2004 ◽  
Vol 19 (6) ◽  
pp. 1869-1875 ◽  
Author(s):  
H. Wang ◽  
S.R. Foltyn ◽  
P.N. Arendt ◽  
Q.X. Jia ◽  
J.L. MacManus-Driscoll ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Ion Beam ◽  
Growth Conditions ◽  
Coated Conductors ◽  
Buffer Layers ◽  
Superconducting Properties ◽  
Ybco Films ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron

A thin layer of SrTiO3 (STO) has successfully been used as a buffer layer to grow high-quality superconducting YBa2Cu3O7-δ(YBCO) thick films on polycrystalline metal substrates with a biaxially oriented MgO template produced by ion-beam-assisted deposition. Using this architecture, 1.5-μm-thick YBCO films with an in-plane mosaic spread in the range of 2.5° to 3.5° in full width at half-maximum and critical current density over 2 × 10 6A/cm2 in self-field at 75 K have routinely been achieved. It is interesting to note that the pulsed laser deposition growth conditions of SrTiO3 buffer layers, such as growth temperature and oxygen pressure, have strong effects on the superconducting properties of YBCO. Detailed studies using transmission electron microscopy, scanning electron microscopy, and atomic force microscopy were used to explore the microstructures of STO deposited at different conditions and to understand further their effects on the growth and properties of YBCO films.

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