Flexible Metal Tapes Research Articles

Performance improvement of iron chalcogenide films grown at high laser repetition rates by pulsed laser deposition

AbstractFor mass production, a high deposition rate is necessary. A powerful approach is to deposit Fe(Se, Te) (FST) superconducting films at a high laser repetition rate by pulsed laser deposition. Hence, the FST films were grown on flexible metallic tapes using pulsed laser deposition at different laser repetition rates to explore the effect of laser repetition rate on the properties. It was found that as the laser repetition rate increases, the crystallinity and stoichiometry of FST films deteriorate, resulting in a degeneration in superconductivity. The critical temperature of the FST film deposited at a high repetition rate of 120 Hz dropped to 12.89 K. Furthermore, high‐performance FST film was successfully deposited at 120 Hz by increasing the substrate temperature with = 16.96 K and = 18.32 K. The self‐field critical current density can reach 1.3 MA/cm2 at 4.2 K. The analysis of the pinning mechanism reveals that normal surface pinning centers play a dominant part in the FST film and are independent of the temperature. The collective pinning theory states that the FST film exhibits δl pinning. The results may offer valuable information for rapid deposition of FST‐coated conductors for industrial production.

Thickness dependence of structural and superconducting properties of Co-doped BaFe2As2 coated conductors

SummaryHigh-quality Co-doped BaFe2As2 thin films with thickness up to 2 μm were realized on flexible metal tapes with LaMnO3 as buffer layers fabricated by an ion beam-assisted deposition technique. Structural analysis indicates that increasing thickness does not compromise the film crystallinity, except for a small amount of impurities. Two types of thickness dependence of critical current density (Jc) were found: one is almost thickness independent in the range of 0.6–1.5 μm and the other is highly thickness dependent. In addition, the maximum value for crucial current Ic at 9 T and 4.2 K is about 55 A/12 mm-W for the 1.5-μm-thick film. Anisotropic Ginzburg–Landau scaling demonstrates that dominant pinning centers develop from correlated to uncorrelated with increasing film thickness. The further theoretical analysis shows that with film thickness increasing the pinning mechanism evolves progressively from a δl pinning to the δTc pinning mechanism.

High‐efficiency single‐junction p‐i‐n GaAs solar cell on roll‐to‐roll epi‐ready flexible metal foils for low‐cost photovoltaics

AbstractWe demonstrate the fabrication and characterization of high‐efficiency, single‐junction p‐i‐n GaAs solar cells, on flexible metal foil with epi‐ready buffer via roll‐to‐roll fabrication. Single‐junction p‐i‐n GaAs solar cells were fabricated using metal–organic chemical vapor deposition (MOCVD). An efficiency greater than 13% was obtained at 1 sun, which is the highest reported efficiency on GaAs photovoltaics directly deposited on metal tapes. This exceeds our previously reported study showcasing 11.5% efficiency on single‐junction p‐n solar cell structure. Improved morphology of p‐i‐n structure compared with p‐n is explained by atomic force microscopy (AFM), scanning electron microscopy (SEM), and helium ion microscopy (HIM) measurements. Time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) analysis showed reduced Zn diffusion in p‐i‐n cell compared with the p‐n cell. We attribute the improvement in efficiency of p‐i‐n cells on flexible metal tapes to the quality of the junction, surface morphology, controlled diffusion of species within the active layers, and increase in absorption due to the optimized intrinsic layer thickness.

Effects of grain boundaries on conversion efficiencies of single-crystal-like GaAs thin-film solar cells on flexible metal tapes

We present a numerical simulation study of the effects of low-angle grain boundaries (GBs) in a single-crystal-like GaAs thin-film material on its photovoltaic performance. Here, 1D and 2D modeling are employed to simulate a solar-cell (SC) device based on the properties of single-crystal-like GaAs thin films grown on metal tape. Properties include minority carriers’ mobility, carrier lifetimes, and diffusion length. The 1D model, by incorporating a uniform biaxially textured GaAs compared to single crystal GaAs, predicts an efficiency ∼21% for average carrier lifetimes of 1 ns. This result is not consistent with an experimental results showing an efficiency of 4.3%. 1D simulation generally works well for the prediction of conventional crystalline SC I-V characteristics, but it fails for newly-developed single-crystal-like GaAs SC devices with different material properties and non-vertical device geometry. Hence, we develop a 2D model to study the effect of localized recombination centers in the material by defining different regions of defective low-angle grain boundaries and single crystalline intra-grains. The 2D model is comparable to the experimental results mainly due to its capability to consider localized material inhomogeneity and lateral carriers dynamic. The effect of grain boundary density on SC performance is studied by 2D modeling. Increasing the grain size of GaAs from 2 μm to 50 μm can improve efficiency from 4.8% to 12.3%. The open-circuit voltage (Voc) shows more sensitivity to varying grain boundary densities than other SC characteristic factors. The 2D model is also employed to study bulk passivation of GBs and suggests that an efficiency of ∼19.5% is achievable in the single-crystal-like GaAs SCs even with a small grain size of 2 μm, if effective grain boundary passivation is applied.

(Invited) Flexible Multifunctional III-N Semiconductor Materials and Devices for Energy Applications

We present recent development in flexible wide-bandgap semiconductor materials and devices. Especially, we focus on mechanically bendable group-III-nitride (III-N) thin-film heterostructures and their photonic, electronic, and energy-harvesting devices in energy applications. The presentation will cover various topics including (1) multi-functionality of flexible III-N devices, (2) direct growth of high-quality single-crystal-like GaN semiconductor thin films on low-cost flexible metal tapes, and (3) piezoelectric generators and sensors for self-powered wearable systems by harvesting and sensing ambient biomechanical energy. Flexible III-N thin-film heterostructures have an implication of more than just mechanically flexible materials. Bendable devices based on III-N heterostructures can be equipped with new functionalities and even further improved performance characteristics using a new concept of active polarization engineering by controlled external strains. We propose to develop multi-functional and/or further-improved-performance devices by utilizing the interactions between electronic and optical properties and mechanical forces in the flexible III-N heterostructures. The concept will enable new mechano-electro-photonic (MEP) devices. We will show by device modeling that new device concept in flexible transistors based on AlGaInN/GaN heterostructure is possible, including modulation of 2-dimensional electron gas (2DEG) density by bending, strain-effect transistors (Figure 1: I-V characteristics of strain-effect transistors), and high-hole-mobility transistors. Furthermore, photon emitters based on flexible III-N heterostructure can result in higher internal quantum efficiency (IQE), higher wall-plug efficiency (WPE), and color modulation by optimum bending conditions (Figure 2: Concept of color-tunable white light-emitting diodes). We study and develop nearly-single-crystalline GaN thin film on flexible metal tapes by a direct deposition technique for the demonstration of a new wide-bandgap semiconductor platform, targeting high-performance yet economical, flexible, and versatile device technology. Data and analysis are presented for the single-crystal-like film, as representatively shown in Figure 3 (Flexible hybrid tape substrate consisting of GaN thin film and Cu tape with crystallinity-transformational buffer layers). Energy harvesters that scavenge biomechanical energy are promising power supply candidates for wearable and implantable electronics. Of the most widely used energy harvesters, piezoelectric generators can generate more electric charge than their triboelectric counterparts with similar device size, thus are more suitable to make compact wearable devices. We develop a flexible piezoelectric generator (F-PEG) with chemically stable and biocompatible III-N thin film. Data and analysis are presented for the flexible III-N F-PEG. We also demonstrate that the F-PEG can directly power electronics such as light-emitting diodes and electric watches, and charge commercial capacitors and batteries to operate an optical pulse sensor, as representatively shown in Figure 4 (Pulse sensor powered by F-PEG and heart rate measurement on a fingertip). Figure 1

Passivation Studies on Single-Junction GaAs Thin Film Solar Cells on Flexible Metal Tapes for Low-Cost Photovoltaics

Despite the high efficiency of III–V solar cells based on gallium arsenide, their usage in large-scale terrestrial application is very limited due to the excessive cost of GaAs and Ge wafers. Herein, we have developed high-quality epitaxial semiconductor thin films on inexpensive flexible metal tapes to overcome the wafer cost as well as to benefit from the lower manufacturing cost of roll-to-roll processing. Metal organic chemical vapor deposition (MOCVD) is used to grow high-quality epitaxial GaAs solar cell structure on “single-crystalline-like” germanium film on epi-ready metal tape. These epitaxial GaAs films exhibit excellent crystalline alignment with high carrier mobility. The fabricated device is further processed for contact deposition via photolithography. Citric acid used for etching GaAs also resulted in effective passivation of the devices. Passivation of GaAs solar cells with various base thicknesses of 1140, 840, and 380 nm and various device sizes has been demonstrated. After passivation,...

Advance and challenge of secondary-generation high- temperature superconducting tapes for high field applications

High-field magnet application is one of most driving forces for the development of high temperature superconducting (HTS) materials. Recently, the magnet consisting of ReBa2Cu3O7- δ based coated conductors (RE123, also called as secondary-generation high-temperature superconducting tapes, 2G-HTS) has exhibited the magnetic field as high as 26.4 T, over than the limit of conventional NbTi-Nb3Sn magnets. As well, an overall superconductor magnet consisting of a 2G-HTS magnet inserted into the background with low temperature superconducting magnetic field of 17 T gave rise to the magnetic field up to 32 T, reaching a new world record with regard of all superconductor magnets. In reality, these breakouts take place thanks to the latest advances in practical HTS materials, showing the promising future for power applications. The great advantages and promising prospects of RE123 coated conductors over than other practical superconducting materials have spurred the related researches and rapid development of this field worldwide recently. The further development, however, will depend on the fundamental properties, producing yield, and optimum performance/price etc. In the present paper we give a brief introduction to RE123 coated conductor and its typical structure, as well as main technical routes for the scale-up preparation. We introduce the status and development for RE123 coated conductors around the world, including the existing research institutions and technologies they employed. In past decade, people have tested a variety of thin film techniques to realize the biaxial textured RE123 coated conductors epitaxially grown on flexible metallic tapes. For the most institutions working on the preparation of RE123 coated conductor, both IBAD and RABiTS have been used as popular technical routes due to their availability of long textured substrates, the feasibility of controlled buffer growth and the potential for cost-effective processing. At the same time, various thin film coating techniques including sputtering, pulse laser deposition (PLD), metallorganic chemical vapor or solution depositions (MOCVD, MOD) are employed to prepare the coated conductors for both buffer layers and superconducting layers. Particularly, some emerged MOD technologies for preparing superconducting layer with organic addition into the precursor solution or reduced fluorine content precursor solution have been addressed, due to their great potential for a cost-effective and rapid technical route to prepare RE123 coated conductor. It is also demonstrated that the considerable efforts for artificial flux pinning in RE123 coated conductor by introducing nanoparticles and substrate surface decoration have effectively improved the J c value of RE123 under applied magnet field. The thickness effect of 2G-HTS is also an important issue, because in most case the critical current density would decrease while the thickness of superconducting layer increases. Such an effect may be suppressed with controlled techniques and microstructures or compositions. The coated conductors may maintain good biaxial texture as the thickness of superconducting layer increase from 1 to 5 μm, leading to huge increase in current-carrying capability of resultant 2G-HTS tape. It is believed that the mechanical properties of 2G-HTS tape are better than 1G-HTS tape, which is very important during the magnet coil winding. Excessive stress relief or Lorentz force would make coils split or deformed. To improve the anisotropy and mechanical properties, people have designed various types of practical conductors with RE123 tape stacks or metal tubes covered. Moreover, the welding technique of 2G-HTS tape is investigated due to importance on improving the usage rate of short tapes. In summary, the present review introduces the state of the art of 2G-HTS tape and relevant key science and technical issues, including the technical routes, artificial flux pinning, field dependence and thickness induced degradation of critical current density, joint technologies, as well as power applications, especially in the field of HTS magnet.

Effects of Sputtering Parameters on AlN Film Growth on Flexible Hastelloy Tapes by Two-Step Deposition Technique.

AlN thin films were deposited on flexible Hastelloy tapes and Si (100) substrate by middle-frequency magnetron sputtering. A layer of Y2O3 films was used as a buffer layer for the Hastelloy tapes. A two-step deposition technique was used to prepare the AlN films. The effects of deposition parameters such as sputtering power, N2/Ar flow rate and sputtering pressure on the microstructure of the AlN thin films were systematically investigated. The results show that the dependency of the full width at half maximum (FWHM) of AlN/Y2O3/Hastelloy on the sputtering parameters is similar to that of AlN/Si (100). The FWHM of the AlN (002) peak of the prepared AlN films decreases with increasing sputtering power. The FWHM decreases with the increase of the N2/Ar flow rate or sputtering pressure, and increases with the further increase of the N2/Ar flow rate or sputtering pressure. The FWHM of the AlN/Y2O3/Hastelloy prepared under optimized parameters is only 3.7° and its root mean square (RMS) roughness is 5.46 nm. Based on the experimental results, the growth mechanism of AlN thin films prepared by the two-step deposition process was explored. This work would assist us in understanding the AlN film’s growth mechanism of the two-step deposition process, preparing highly c-axis–oriented AlN films on flexible metal tapes and developing flexible surface acoustic wave (SAW) sensors from an application perspective.

Fabrication of long REBCO coated conductors by PLD process in China

In China, the First National Key Project on CC Program started in 2009, which was focused on developing hundred meter long class CC tapes based on PLD/RABiTS processes. In this project, SJTU mainly worked on all of functional layer deposition process development. Northwest Institute for Non-ferrous Metal Research worked on RABiTS tape fabrication. At the end of the project in 2011, SJTU successfully fabricated hundred meter long CC tapes with over 300A/cm (at 77K, self field) on RABiTS tapes. To develop high performance CC tapes by PLD/IBAD-MgO processes, a pilot CC fabrication line was set up at Shanghai Superconductor Technology Corporation, Ltd. in 2013. High quality long REBCO coated conductors have been successfully fabricated on flexible polycrystalline metal tapes by PLD plus magnetron sputter and IBAD processes. Under optimized conditions, the IBAD-MgO layers showed pure (001) orientation and excellent in-plane texture. The in-plane phi-scan rocking curve is 4–6 degrees. AFM observation showed MgO layer had very smooth surface. The RMS is less 1nm. On the textured MgO layer, sputter deposited single cerium oxide cap-layer showed pure (001) orientation and excellent in-plane texture of 4–6degree. Reel-to-reel PLD process with high deposition rate was already scaled up to 100m/h tape speed. Hundred meters long coated conductor tapes with over 500A/cm performance have been routinely fabricated. And now, the process optimization for kilometer long coated conductor tapes is underway.

Full CVD Reel‐To‐Reel Process to Obtain Perfectly Oriented Silicon Films on Metal Tapes with Oxide Buffer Layers**

Silicon films with a sharp biaxial texture on low‐cost, flexible metal tapes are prominent materials for cost‐effective photovoltaics. The cost of such materials can be further reduced by the application of easily scalable chemical deposition methods. In the present article, we report on the application of CVD to obtain epitaxial silicon films on Ni alloy tapes with metal‐organic (MO)CVD‐produced buffer layers. Two types of buffer layer architecture are presented, which enable textured silicon growth on textured Ni(Cr,W) alloy and on non‐textured Hastelloy tape. The Si film appears highly textured and demonstrates chemical purity, indicating the possibility of application of proposed Si/buffer/metal heterostructures formed by CVD for the photovoltaic industry.

MgB2 coated conductors directly grown on flexible metallic Hastelloy tapes by hybrid physical–chemical vapor deposition

MgB2 coated conductors (CCs), which can avoid the low packing density problem of powder-in-tube (PIT) processed wires, can be a realistic solution for practical engineering applications. Here we report on the superior superconducting properties of MgB2 CCs grown directly on the flexible metallic Hastelloy tapes without any buffer layer at various deposition temperatures from 520 to 600 °C by using hybrid physical–chemical vapor deposition (HPCVD) technique. The superconducting transition temperatures (Tc) are in the range of 38.5–39.4 K, comparable to bulk samples and high quality thin films. Clear (101) and (002) reflection peaks of MgB2 are observed in the X-ray diffraction patterns without any indication of chemical reaction between MgB2 and Hastelloy tapes. From scanning electron microscopy, it was found that connection between MgB2 grains and voids strongly depend on the growth temperature. A systematic increase in the flux pinning force density and thereby the critical current density with decreasing growth temperature was observed for the MgB2 CCs. The critical current density (Jc) of Jc(5 K, 0 T) ∼107 A/cm2 and Jc(5 K, 2.5 T) ∼105 A/cm2 has been obtained for the sample fabricated at a low growth temperature of 520 °C. The enhanced Jc (H) behavior can be understood on the basis of the variation in the microstructure of MgB2 CCs with growth temperature.

Development of One Meter Long Double-Sided $ \hbox{CeO}_{2}$ Buffered Ni-5at.%W Templates by Reel-to-Reel Chemical Solution Deposition Route

High performance long-length coated conductors fabricated using various techniques have attracted a lot of interest recently. In this work, a reel-to-reel design for depositing double-sided coatings on long-length flexible metallic tapes via a chemical solution method is proposed and realized. The major achievement of the design is to combine the dip coating and drying processes in order to overcome the technical difficulties of dealing with the wet films on both sides of the tape. We report the successful application of the design to fabricate a one-meter-long double side coated CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Ni-5at%W template. The CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> films on both sides exhibit a dense, crack-free morphology, and a high fraction of cube texture on the surface. Homogeneity studies on global texture over the length also reveal that the average full width at half maximum values of the in-plane and out-of-plane orientation on the CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer are 7.2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> and 5.8 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> with standard deviation of 0.26 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> and 0.34 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> , respectively, being indicative of the high quality epitaxial growth of the films prepared in the continuous manner. An all chemical solution derived YBCO <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Low-TFA</sup> /Ce <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.9</sub> La <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.1</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> /CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> structure is obtained on a short sample, demonstrating the possibility of producing long-length texture templates for coated conductors by this low cost deposition route.

Scale Up of Coated Conductor Substrate Process by Reel-to-Reel Planarization of Amorphous Oxide Layers

Substrate surface smoothness comparable to electropolished substrate has been demonstrated by planarization of multilayers of amorphous oxide films on as received flexible metal tapes. An in-plane texture of 6.4 degrees was achieved on short samples after the final buffer process. A critical current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) over 3 MA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> has been achieved on short samples. The planarization process has been scaled up from a few meters previously done by loop coating to be capable of producing 100 meters. 20 m of planarized substrate were processed with standard buffer deposition process and metal organic chemical vapor deposition (MOCVD) manufacturing run. An average in-plane texture of eight to nine degrees was obtained on the entire 20 m piece after the final buffer LMO process. A uniform critical current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) of 160 A was achieved on 15 m. The planarization process has the potential to lead to a reduction in buffer layers and alleviate the burden of hazardous waste generated from the electropolishing process. It is capable of planarization of any substrate alloy, while electropolishing is limited to only a few alloys.

Reactive Co-Evaporation of YBCO for 2G HTS Tapes

AbstractWe present a new reel-to-reel method for growth of high temperature super-conducting (HTS) films by reactive co-evaporation on flexible metal tapes. We have demonstrated proof of principle for this method with a small laboratory-scale setup using 8 cm long tape pieces. YBa2Cu3O7-δ is deposited on ion-beam assisted deposition textured MgO layers on top of flexible polycrystalline metal tapes. Critical current densities at 75.5 K of over 2 MA/cm2 have been achieved in HTS films with over 2 μm in thickness, yielding a self field critical current of 450 A/cm-width. A 4.5 μm thick film had a self field critical current of 590 A/cm. We discuss some practical possibilities for manufacturing of superconducting wire using this process and present new areas of research that are still needed.

Ion-Beam Assist Nano-Texturing of Films

AbstractWe present an ion-beam based fabrication method for growth of single-crystal-like films that does not utilize epitaxy on single crystal substrates. We use ion-beam assisted texturing to obtain biaxial crystalline alignment in a film. This ion-beam assisted deposition (IBAD) texturing can be done on arbitrary, but smooth substrates, including flexible polycrystalline metal tapes. With IBAD texturing of MgO and subsequent homoepitaxial growth we have demonstrated an in-plane mosaic spread FWHM as low as 2° and out-of-plane alignment of 1°. The deposition system we use includes reel-to-reel tape transport for a linear transport of substrate materials through the deposition zones. This allows for high-throughput experimentation via a linear combinatorial experimental design.

Elongated grains in textured substrate tapes and their effect on transport currents in superconductor layers

The development of cube textured flexible metallic substrate tapes is of basic interest for the economic production of YBa2Cu3Ox (YBCO) coated superconductors. Nickel tapes microalloyed with silver were prepared with the specific feature of an elongated grain structure. Cube textured NiO films were grown by surface oxidation epitaxy on these tapes retaining the elongated grains. Further, buffer layers and YBCO were deposited thereon. The YBCO layer transports an up to four times higher critical current density (Jc=2.35MA∕cm2) in the direction of grain elongation compared to the transversal one (Jc=0.55MA∕cm2).

YBCO Coated Conductor Applications - A Texture Problem

YBa2Cu3O7-δ ("YBCO") is a high-temperature ceramic superconductor. Due to its complex layered structure, a strong biaxial texture of the YBCO grains is necessary to achieve technically relevant currents. In this paper, we describe the development of flexible metallic tapes with strong cube texture, providing a lattice-matched template for buffer and YBCO coatings in proper orientation. Texture analysis was performed using electron backscatter diffraction (EBSD).

Synthesis and characterization of Cu-doped SrTiO/sub 3/ powders and sol-gel processed buffer layers on IBAD MgO templates

Copper-doped SrTiO/sub 3/ (STO) powders were processed by conventional bulk preparation techniques to establish solubility limits of Cu in STO. The maximum solubility of Cu in STO was identified to be /spl sim/1%. Epitaxial Cu-doped SrTiO/sub 3/ (STO) buffer layers were then prepared by pulsed laser deposition (PLD) and chemical solution deposition (CSD) on ion-beam-assisted deposition (IBAD) magnesium oxide (MgO) flexible metallic textured tapes. Transmission electron microscopy (TEM) analysis of the /spl sim/100 nm thick buffer layer deposited by PLD showed a smooth Cu-doped STO/MgO interface. Films deposited by CSD had an average film thickness of 30 nm and exhibited growth by heterogeneous nucleation with no secondary reaction phases. YBa/sub 2/Cu/sub 3/O/sub 7-/spl part// (YBCO) films were deposited onto the Cu-doped STO buffer layers by PLD.

Application of solution deposition to fabricate Y-Ba-Cu-O coated conductor

This paper demonstrates the successful application of solution deposition techniques to deposit buffer layers and YBCO films on flexible metal substrates, thus making coated conductor fabrication scalable and cost effective. We present results obtained using strontium titanate buffer layers. These buffer layers, processed on single crystal substrates using solution precursors and heat treated in a reducing atmosphere are highly textured and have a uniform smooth surface. YBCO films, 0.3-0.5 mm thick, deposited on these buffered single crystals using the trifluoroacetate process shows good superconducting properties. YBCO films processed on strontium titanate buffered lanthanum aluminate substrates have an onset of transition around 90-91 K and critical current densities of the order of 10/sup 5/-10/sup 6/ A/cm/sup 2/ at 77 K and self-field. These processing techniques have been extended to textured nickel substrates. These results offer promise for the development of a scalable, solution-based processing route to deposit buffer layers and YBCO films on flexible metallic textured tapes.

High T c superconducting HgBa 2CaCu 2O y films growth on the YZrO 2 substrates with YBa 2Cu 3O 7 buffer layers

Superconducting HgBa 2CaCu 2O y (Hg-1212) films have been fabricated on the (100) YZrO 2 substrates with YBa 2Cu 3O 7 (YBCO) buffer layers by a two-step process. By using of the YBCO buffer layer reproducible superconducting properties, zero resistance temperatures of T c = 115–124K and critical current density of J c = 0.1 –0.3 MA/cm 2 at 100k in zero magnetic field, were obtained. X-ray diffraction θ-2 θ patterns and Φ scans indicated that the films grow epitaxially on the YBCO surfaces with c-axis perpendicular to the substrates. The results demonstrated that YBCO is a good buffer for growing the Hg-cuprate films. This novel method gives a new way to grow the Hg-cuprate films on various substrates, even on flexible metallic tapes.