Papers by Keyword: Buffer Layer

Abstract: A new series of ReBiO3 (RBO, Re=Y, Sm or other lanthanide) layers have been prepared on single crystal LaAlO3 or SrTiO3 respectively by a low-cost chemical solution deposition (CSD) method, and their structures have been investigated. With deferent Re element, the ReBiO3 phase has a similar cubic lattice with the pseudo-cubic lattice parameter a’ of about 3.81~3.94Å, which is closely matched to that of the ReBa2Cu3Ox (RBCO). In addition, these ReBiO3 phase are stable when they are sintered on 750~1050°C. After annealed below 850°C in air, highly c-axis oriented ReBiO3 layers can be formed on the (100) plane of single crystal LaAlO3 or SrTiO3. Observed under SEM, these layers appear very dense, smooth, pinhole-free and crack-free morphology. With the matched lattice parameter, lower annealing temperature, good grain-orientation and smooth surface, ReBiO3 layers should be candidates for the buffer layers of RBCO coated conductor. As a proof, a superconducting layer of YBCO has been deposited also by a CSD approach on one of these layers and show good texture and expected superconductivity.

Abstract: A reel-to-reel deposition system was set up for studying YBCO coated conductor. Continuous deposition of multi-layer CeO2/YSZ/Y2O3 buffer layers was carried out on 10mm-width biaxially textured tape of NiW using the reactive dc magnetron sputtering technique. A continuous and uniform buffer layer with good texture was presented over length. For 10–meter-long tapes, the φ-scan FWHM values of Y2O3 (222), YSZ (111), and CeO2 (111) were 7.77°, 7.68° and 7.93°, respectively. The rocking curves showed that the average FWHM values of Y2O3 (004), YSZ (002), and CeO2 (002) were 5.02°, 4.67° and 4.44°, respectively. The microstructure and interfaces of buffer layers were observed by scanning electron microscopy (SEM) and Auger electron spectrum (AES). YBCO layer was prepared by magnetron sputtering technique as well on the short samples.

Abstract: This work reports some new studies related to critical aspects in the development of coated conductors (CC). New bi-axially textured tapes based on commercial copper alloys were fabricated and tested as substrates for LZO buffer layer deposited by chemical solution deposition (CSD). Such a layer form cube texture on NiW5 and Cu55Ni45 with an identical or even better texture than that of the substrate. It was shown that a S c(2x2) sub-layer formed at the metallic surface as a positive effect on the nucleation. The crystallisation of LZO on Cu55Ni45 still has to be improved, being inhibited by trapped C in the film. Recent progresses using our continuous MOCVD system are shown. A CC fabricated by an all MOCVD process has been obtained on SS/YSZIBAD substrate with high transport critical current (170 A/cm-width, at 77 K). It is also shown that LZOMOD can efficiently protect Ni5W RABITS from oxidation during deposition of CeO2 layer by MOCVD under 30-40% O2 partial pressure. This opens the possibility to fabricate a CC on RABITS by MOCVD. This shows that a mixed MOD/MOCVD approach could be efficient. Finally a 2m long CC SS/YSZIBAD has been tested for fault current limiter applications. Best limitation was observed at 86 K where an equivalent energy of 340 J has been dissipated in the CC during 12 ms without apparent damage of the CC. In a subsequent operation, the CC was however destroyed. The causes are discussed in the perspective to design better architectures for this application.

Abstract: Pt/PZT/PbO/Si with the MFIS structure was deposited on the p-type (100) Si substrate by the r.f. magnetron sputtering method with Pb1.1Zr0.53Ti0.47O3 and PbO targets. From the X-ray photoelectron spectroscopy (XPS) results, we could confirm that the partial pressure ratio during PbO deposition affects the interface condition of PbO/Si and the chemical state of Pb existing at the surface of the PZT thin film. The maximum value of the memory window is 3.0 V under the applied voltage of 9V for Pt/PZT (200 nm 400°C)/PbO (80 nm, 300°C)/Si structures with the PbO buffer layer deposited at the partial pressure of 7:3. From these results, we could assume that the PbO buffer layers play a role of the diffusion barrier between the PZT thin film and the Si substrate as well as the seed layer.

Abstract: Superconducting YBa2Cu3O7-δ
(YBCO) films were grown on MgO single crystalline substrates using a BaZrO3 (BZO) buffer layer deposited by a pulsed laser deposition (PLD). Deposition condition has been optimized to obtain good epitaxial BZO film followed by deposition of YBCO superconducting films. The crystallinity and microstructure of epitaxial YBCO/ BZO/ MgO (00l) films were investigated by a two-dimensional x-ray diffraction and a field emission scanning electron microscope. The in-plane (φ-scan) measurements for the BZO films (200 ~ 500 nm thick) grown on MgO substrates revealed a narrow full width half maximum (0φ = 2o). The XRD results exhibited that YBCO films with a BZO buffer layer were well oriented in the [00l] direction perpendicular to the substrate surface. The BZO films also showed homogeneous and dense surface morphologies. By the deposition of a subsequent BZO buffer layer, YBCO was grown epitaxially on MgO with results showing a critical current density (Jc) of ~ 3.3 × 106 A/cm2 and a critical temperature (Tc) of 86 K.

Abstract: A comparative study was presented to demonstrate the clear influence of the different buffer layer (TiN and TiO2) on the HA film. In this study, magnetron sputtering was applied for different film deposition. Nano-indentation was used to examine the mechanical properties of the HA film on both TiN and TiO2 buffer layers. It is found that HA film on TiN buffer layer is harder and the HA film on TiO2 buffers is more rigid. Further more, the simulated body fluid (SBF) soaking test was selected to investigate the properties of the HA/TiN and HA/TiO2 films in the physiological media. The obvious delamination was observed on the surface of HA film on TiN buffer layer, while the surface morphology of HA film on TiO2 buffer layer remained nearly unchanged. The result indicated that TiO2 buffer layer shows a better interfacial bonding to the HA film.

Abstract: Dye-sensitized solar cell (DSSC) is of great interest as one of renewable energy sources. So far, many investigations related to TiO2 electrode, dye, electrolyte, Pt counter electrode, etc. were carried out. Here, we focus on Pt counter electrode for providing an enhanced catalytic property and physical stability. Pt has high-conductivity and superior catalytic properties. However, in case of Pt as counter electrode for DSSC, there exists partial problem due to poor adhesion between Pt and FTO glass. In this work, we tried to enhance the properties of Pt catalyst by two methods; first, the insertion of buffer layer under Pt thin film; second, the heat treatment of Pt films. We report the effect of buffer layer using Cr and Ti and the effect of heat treatment on Pt electrode under 400oC. Electrochemical characteristics of Pt electrodes were measured using electrochemical impedance spectroscopy and cyclic-voltammetry. A degree of electrode reaction, current density, electrode potential and interface resistance, etc were discussed with measured electrochemical data. In comparison with sputtered Pt counter electrode with and without buffer layers, heat-treated Pt counter electrode showed good performance in terms of the current density and interface resistance properties.

Abstract: In this present work, two buffer layers (La2Zr2O7 and CeO2) were deposited by a non-contact computer-controlled ink-jet coating technique with sol-gel precursors on highly textured Ni-5%W Rolling Assisted Biaxially Textured substrates (RABiTS). Lanthanum acetate and cerium acetylacetonate were used as precursors for the LZO and CeO2 sol respectively. After a high temperature heat treatment (heating at 900°C for LZO and at 1100°C for CeO2) under reducing atmosphere, epitaxial textured buffer layers were obtained. XRD and pole figures were used to analyse the texture of the films, the microstructure was analysed by SEM.

Abstract: The influence of a rare earth oxide/yttria-stabilized zirconia (YSZ) double buffer layer structure on the orientation of a perovskite thin film was investigated on (100) silicon substrates. A calcium titanate perovskite film with a mixture of (110) and (100) orientation was grown epitaxially on a YSZ buffer layer. Since rare earth oxides have almost the same chemical nature and different lattice parameters, it is anticipated that the lattice parameter of the buffer layer can be controlled by changing the rare earth element. An (100) oriented epitaxial calcium titanate film was obtained by changing the composition of rare earth oxides on the YSZ/Si substrate.

Abstract: Layered structures of dense porcelain/porous alumina and dense porcelain/porcelainalumina/ porous alumina are designed and their crack propagation behaviors are investigated. As a substrate, the porous alumina, which is prepared by a gel-casting process using the binary slip of alumina powder and PMMA spherical micro-bead, is dried at room temperature for 24 h and then sintered at 1600
for 2 h. Porcelain is coated on the porous alumina substrate and then re-sintered at 987
. Bi- and tri-layered structures are produced by the different dwell times (2 min, 10 min) at re-sintering temperature. There is no delaminating or cracks observed after re-sintering the layered samples. The crack propagation behaviors in the bi- and tri-layered structures are evaluated by micro-indentation. The indentation cracks do not propagate into the porous alumina through interface (porosity; 36~62%) except for another one (porosity; 70%) in the bi-layered samples. In the case of the high porosity bi-layered sample (porosity; 70%), cracks are scattered along the 3-D open-pore channels. However, cracks do not propagate through the interface in the tri-layered samples with a porcelain-alumina buffer layer, because the porcelain-alumina buffer layer plays an important part such as a barrier layer in crack propagation.