Interface Control in All MOD Coated Conductors: Influence on Critical Currents

2005 ◽  
Vol 868 ◽  
Author(s):  
Alberto Pomar ◽  
Mariona Coll ◽  
Andrea Cavallaro ◽  
Jaume Gàzquez ◽  
Narcis Mestres ◽  
...  
Keyword(s):  
Recent Progress ◽  
Critical Currents ◽  
Coated Conductors ◽  
Buffer Layers ◽  
Coated Conductor ◽  
Thermal Treatments ◽  
Interface Quality ◽  
Flat Surfaces ◽  
Interface Control ◽  
Atomically Flat

AbstractIn this work we will report our recent progress in the control of the interface quality between buffer layers and YBCO thin films grown by the trifluoroacetates route (TFA) and how it influences the critical current of the coated conductors. We have mainly focused on vacuum and metalorganic deposited (MOD) fluorite-like CeO2 buffer layers and on MOD perovskite SrTiO3 buffer layers. We will show that for vacuum CeO2 buffer layers, microcracks at the surface can be controlled by the means of thermal treatments. Coated conductors TFA-YBCO/CeO2sputt/YSZ/CeO2/Ni with Jc(77K)˜1MA/cm2 can be grown even in the presence of these microcracks. For MOD SrTiO3 we will show that growing the buffer layer at low temperature reduces surface roughness and multilayers with high critical currents can be achieved. An all-chemical coated conductor has been grown TFA-YBCO/SrTiO3MOD/BaZrO3MOD/NiO-SOE/Ni with promising in-plane texture, Δ φYBCO=6.6°. For MOD CeO2 buffer layers, thermal annealings in oxidizing atmospheres lead to atomically flat surfaces that avoid the typical polycrystalline surfaces observed in MOD CeO2 grown in Ar/H2. High Jc multilayers can be achieved and the first all chemical coated conductor in IBAD tapes TFA-YBCO/CeO2MOD/YSZIBAD/SS has been obtained with Jc(60K)=2.3MA/cm2.

Interface control in all metalorganic deposited coated conductors: Influence on critical currents

2006 ◽  
Vol 21 (09) ◽  
pp. 2176-2184 ◽  
Author(s):  
Alberto Pomar ◽  
Mariona Coll ◽  
Andrea Cavallaro ◽  
Jaume Gàzquez ◽  
Narcis Mestres ◽  
...  
Keyword(s):  
Critical Currents ◽  
Coated Conductors ◽  
Interface Control

The microstructure of continuously processed Yba2Cu3Oy coated conductors with underlying CeO2 and ion-beam-assisted yttria-stabilized zirconia buffer layers

2000 ◽  
Vol 15 (5) ◽  
pp. 1110-1119 ◽  
Author(s):  
T. G. Holesinger ◽  
S. R. Foltyn ◽  
P. N. Arendt ◽  
H. Kung ◽  
Q. X. Jia ◽  
...  
Keyword(s):  
Interfacial Reaction ◽  
Ion Beam ◽  
Misfit Strain ◽  
Critical Currents ◽  
Coated Conductors ◽  
Yttria Stabilized Zirconia ◽  
Buffer Layers ◽  
Inconel 625 ◽  
Microstructural Development ◽  
Stabilized Zirconia

The microstructural development of YBa2Cu3Oy (Y-123) coated conductors based on the ion-beam-assisted deposition (IBAD) of yttria-stabilized zirconia (YSZ) to produce a biaxially textured template is presented. The architecture of the conductors was Y-123/CeO2/IBAD YSZ/Inconel 625. A continuous and passivating Cr2O3 layer forms between the YSZ layer and the Inconel substrate. CeO2 and Y-123 are closely lattice-matched, and misfit strain is accommodated at the YSZ/CeO2 interface. Localized reactions between the Y-123 film and the CeO2 buffer layer result in the formation of BaCeO3, YCuO2, and CuO. The positive volume change that occurs from the interfacial reaction may act as a kinetic barrier that limits the extent of the reaction. Excess copper and yttrium generated by the interfacial reaction appear to diffuse along grain boundaries and intercalate into Y-123 grains as single layers of the Y-247, Y-248, or Y-224 phases. The interfacial reactions do not preclude the attainment of high critical currents (Ic) and current densities (Jc) in these films nor do they affect to any appreciable extent the nucleation and alignment of the Y-123 film.

Critical Currents of Overdoped Co-evaporated YBCO Coated Conductors

2007 ◽  
Vol 1001 ◽  
Author(s):  
Jens Hänisch ◽  
Jonathan Storer ◽  
Chris Sheehan ◽  
Yates Coulter ◽  
Vladimir Matias
Keyword(s):  
Critical Temperature ◽  
Critical Current Density ◽  
Oxygen Content ◽  
Lattice Spacing ◽  
Surface Coverage ◽  
Critical Currents ◽  
Coated Conductors ◽  
Hole Doping ◽  
Coated Conductor ◽  
Ybco Coated Conductors

AbstractCoated conductor samples, prepared by reactive co-evaporation, are investigated with respect to the hole-doping dependence of the critical current density. The samples are annealed in an atmosphere of variable oxygen content after which critical currents, critical temperature and the c-axis lattice spacing are measured. The lattice spacing increases with decreasing oxygen content, consistent with literature data. These co-evaporated samples show hole overdoped behavior with respect to the maximum Tc. The achievable range of hole doping in these samples seems to depend on surface coverage. Both self-field and in-field Jc at 75.5 K have a maximum in the overdoped region but at less than maximum oxygen content. The reason for the overdoping of these samples is discussed briefly in terms of Y-Ba disorder.

Quasi-Barrierless Submolecular Motion in Mechanically Interlocked Carbon Nanotubes

2020 ◽  
Author(s):  
Julia Villalva ◽  
Belén Nieto-Ortega ◽  
Manuel Melle-Franco ◽  
Emilio Pérez
Keyword(s):  
Density Functional ◽  
Close Contact ◽  
Tight Binding ◽  
Energetic Cost ◽  
Molecular Fragments ◽  
Activation Barriers ◽  
Flat Surfaces ◽  
Different Types ◽  
Atomically Flat ◽  
Derivatives Of

The motion of molecular fragments in close contact with atomically flat surfaces is still not fully understood. Does a more favourable interaction imply a larger barrier towards motion even if there are no obvious minima? Here, we use mechanically interlocked rotaxane-type derivatives of SWNTs (MINTs) featuring four different types of macrocycles with significantly different affinities for the SWNT thread as models to study this problem. Using molecular dynamics, we find that there is no direct correlation between the interaction energy of the macrocycle with the SWNT and its ability to move along or around it. Density functional tight-binding calculations reveal small (<2.5 Kcal·mol-1) activation barriers, the height of which correlates with the commensurability of the aromatic moieties in the macrocycle with the SWNT. Our results show that macrocycles in MINTs rotate and translate freely around and along SWNTs at room temperature, with an energetic cost lower than the rotation around the C−C bond in ethane.<br>

Influence of Momentary Annealing on the Nanoscale Surface Morphology of Room Temperature Pulsed Laser Deposited NiO(111) Epitaxial Thin Films on Atomically Stepped Sapphire (0001) Substrates

2013 ◽  
Vol 1507 ◽  
Author(s):  
Ryosuke Yamauchi ◽  
Geng Tan ◽  
Daishi Shiojiri ◽  
Nobuo Tsuchimine ◽  
Koji Koyama ◽  
...  
Keyword(s):  
Thin Films ◽  
Surface Morphology ◽  
Room Temperature ◽  
Pulsed Laser ◽  
Film Surface ◽  
Transient State ◽  
Epitaxial Thin Films ◽  
Flat Surfaces ◽  
Surface Nanostructure ◽  
Atomically Flat

ABSTRACTWe examined the influence of momentary annealing on the nanoscale surface morphology of NiO(111) epitaxial thin films deposited on atomically stepped sapphire (0001) substrates at room temperature in O2 at 1.3 × 10−3 and 1.3 × 10−6 Pa using a pulsed laser deposition (PLD) technique. The NiO films have atomically flat surfaces (RMS roughness: approximately 0.1–0.2 nm) reflecting the step-and-terrace structures of the substrates, regardless of the O2 deposition pressure. After rapid thermal annealing (RTA) of the NiO(111) epitaxial film deposited at 1.3 × 10−3 Pa O2, a periodic straight nanogroove array related to the atomic steps of the substrate was formed on the film surface for 60 s. In contrast, the fabrication of a transient state in the nanogroove array formation was achieved with RTA of less than 1 s. However, when the O2 atmosphere during PLD was 1.3 × 10−6 Pa, random crystal growth was observed and resulted in a disordered rough surface nanostructure after RTA.

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

2003 ◽  
Vol 47 (12) ◽  
pp. 2171-2175 ◽  
Author(s):  
Y. Akin ◽  
Z.K. Heiba ◽  
W. Sigmund ◽  
Y.S. Hascicek
Keyword(s):  
Thin Films ◽  
Coated Conductors ◽  
Buffer Layers ◽  
Oxide Thin Films ◽  
Lattice Match ◽  
Ybco Coated Conductors

Homo- and Hetero-Epitaxial Gallium Nitride Grown by Molecular Beam Epitaxy

1998 ◽  
Vol 537 ◽  
Author(s):  
C.T. Foxon ◽  
T.S. Cheng ◽  
D. Korakakis ◽  
S.V. Novikov ◽  
R.P. Campion ◽  
...  
Keyword(s):  
High Temperature ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Defect Density ◽  
Boundary Structure ◽  
Quantum Well Structures ◽  
Flat Surfaces ◽  
Grain Boundary Structure ◽  
Bulk Gan ◽  
Atomically Flat

AbstractVarious methods have been used to initiate growth by Molecular Beam Epitaxy (MBE) of GaN on sapphire, or other substrates, but there is always a problem with morphology and with a high defect density which results in the formation of a sub-grain boundary structure. We show that by using, homo-epitaxial growth on properly prepared bulk GaN substrates, combined with high temperature growth, we obtain a significant improvement in surface morphology. Growth at sufficiently high temperature leads to a rapid smoothing of the surface and to almost atomically flat surfaces over relatively large areas. Multi-Quantum Well structures grown on such GaN epitaxial films are dislocation free with abrupt interfaces.

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