1PO4-50 The non-designed cap layer on the top surface of PbZr_0.53Ti_0.47O₃/La_1.85Sr_0.15CuO₄ bilayers revealed by x-ray diffuse-scattering and TEM

Y. Yu 1, S.F. Cui 1, Z.H. Mai 1, T. Liu 2, B.R. Zhao 2, L. Zheng 3, and Q.J. Jia 3. 1 Institute of Physics & Center for Condensed Matter Physics, Chinese Academy of Physics, Beijing 100080, China. 2 National Laboratory for Superconductivity, Institute of Physics & Center for Condensed Matter Physics, Chinese Academy of Physics, Beijing 100080, China. 3 Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Physics, Beijing 100039, China.

Presenting Author: S.F. Cui

It is well known that the surface and interface quality of ferroelectric/high T_c superconducting integrated thin films influences their physical properties and device applications. This "quality" is generally characterized by the root mean square (rms) roughness (s ) measured by x-ray reflectivity. However, x-ray diffuse-scattering can provide another important parameter - the roughness exponent (h), which can spatially characterize the dynamical scaling behavior of the growth of surfaces and interfaces. In this paper we present the study of PbZr_0.53Ti_0.47O₃(PZT)/La_1.85Sr_0.15CuO₄(LSCO) bilayers deposited on SrTiO₃ (001) substrates by r.f./d.c. magnetron sputtering, by x-ray diffuse-scattering and transmission electron-microscope (TEM). First of all we have found that, although the both layers are perovskite oxides, the LSCO layers showtwo-dimensional growth while the PZT layers display a columnar one; Secondly, the surface roughness exponent, h, of the PZT layers decreases with the increase of their layer thickness. This indicates that the atomic diffusion coefficient of the growing surfaces tends todecrease during growth; Thirdly, the electron density profiles revealed byx-ray reflectivity and the TEM observations show that there existnon-designed cap layers in nano-scaleon the upper surfaces of the PZT layers, and their thickness increases withthe increase of sample thickness. The formation mechanism of thenon-designed caps is proposed. The present paper has demonstrated thatx-ray reflectivity and diffuse-scattering combined with electron-microscope can investigate efficiently the growth character of high T_c superconducting andferroelectric oxide thin films.

1PO4-51 Superconducting YBCO (T_c(0)= 92 K) and Bi(2223) (T_c(0) = 110 K) films by dip-coating and melt texturing on Ba₂EuZrO_5.5, A novel substrate for high T_c superconductors

J. Koshy, R. Jose, Asha M. John, and J. James, Regional Research Laboratory (CSIR), Trivandrum, India - 695 019

Presenting Author: J. Koshy

A new complex perovskite ceramic oxide Ba₂EuZrO_5.5 have been synthesised and developed for its use as substrate for YBa₂Cu₃O_7-d and Bi (2223) superconductors. Ba₂EuZrO_5.5 has a complex cubic perovskite structure (A₂BB'O₆) with lattice constant, a = 8.421Å. Ba₂EuZrO_5.5 did not show any phase transition in the temperature range 30 to 1300° C. The dielectric constant and loss factor of Ba₂EuZrO_5.5 are in a range suitable for their use as substrates for microwave applications. X-ray diffraction studies and resistance measurements revealed that both YBa₂Cu₃O_7-d and Bi (2223) superconductors did not show any detectable chemical reaction with Ba₂EuZrO_5.5 even under extreme processing conditions. The superconducting properties of YBa₂Cu₃O_7-d and Bi (2223) were unaffected by the addition of Ba₂EuZrO_5.5 up to 20 vol.% in the superconductor-insulator composite. High quality textured YBa₂Cu₃O_7-d and Bi (2223) thick films were developed on ceramic Ba₂EuZrO_5.5 substrate by dip-coating and partial melting techniques. The YBa₂Cu₃O_7-d thick films on polycrystalline Ba₂EuZrO_5.5 substrate gave a T_c(0) of 92 K and a current density of ~ 1.0x10⁴ A/cm² and Bi(2223) thick film on polycrystalline Ba₂EuZrO_5.5 substrate gave a T_c(0) of 110 K and a current density of ~ 3 x 10³ A/cm² at 77 K and zero magnetic field. Dip-coating and subsequent heating is found to be a very simple and convenient method for the preparation of high quality superconducting films on polycrystalline Ba₂EuZrO_5.5 substrate.

1PO4-52 A New Process to Fabricate (Hg,Re)-1212 Thin Films with Smooth Surface

N. Inoue 1, T. Sugano 1, T. Utagawa 1, X.-J. Wu 1, S. Adachi 1, and K. Tanabe 1, and A. Tsukamoto 2. 1 Superconductivity Research Laboratory, International Superconductivity Technology Center, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062, Japan. 2 Advanced Research Laboratory, Hitachi, Ltd., Kokubunji, Tokyo 185-8601, Japan.

Presenting Author: N. Inoue

We have succeeded in fabricating (Hg,Re)Ba₂CaCu₂O_y ((Hg,Re)-1212) thin films with smooth surface by a new process. The general process for the films consists of depositing precursor films and subsequent annealing in a quartz tube. We found that when the film thickness was less than 100 nm, submicron-size defects such as outgrowths and pinholes decreased significantly in the films. As-fabricated 75-nm-thick films showed a self-field J_c at 77 K as high as 10⁷ A/cm². To prepare thicker films suitable for device applications, we developed a following new method; (1) fabricating smooth films by above-mentioned process, (2) repeating the same process on the films.

150-nm-thick (Hg,Re)-1212 films were fabricated by repeating the 75-nm-thick process. The surface of the obtained films was quite smooth. Submicron-size outgrowths and pinholes were not found apparently by SEM observation of the surface and cross-section. By this new process highly homogeneous films with controlled thickness can be fabricated.

This work was supported by the New Energy and Industrial Technology Development Organization (NEDO) as Collaborative Research and Development of Fundamental Technologies for Superconductivity Applications.

1PO4-53 Preparation of superconducting HgBa₂CaCu₂O_x thin films on the distinct substrates

J.D. Guo, Y.F. Sun, X.L. Xu, and G.C. Xiong, Department of Physics, Peking University, Beijing 100871, P.R. China

Presenting Author: J.D. Guo

Superconducting HgBa₂CaCu₂O_x (Hg-1212) films with a thickness of ~ 0.5 m m have been prepared by means of annealing of mercury-free precursor films on distinct substrates. X-ray diffraction indicates that the films consist of predominantly Hg-1212 phase grains with c-axis orientation. The scanning electron microscope (SEM) pictures for the film surface show the occurrence of layered spiral-like growth feature and rectangular shape platelike grains with a size of 1-3 m m. In electrical transport measurements, the two of as-prepared films exhibit zero resistance temperatures of 120 K and zero-field J_c of 1 x 10⁶ A/cm² at 77 K.

1PO4-54 Preparation and Characterization of Hg-based Superconducting Films Using Stable Mo_0.3Sr₂(Ca_0.7Y_0.3)Cu₂O_x and Re_0.1Ba₂CaCu₂O_y Precursors by Laser Ablation

Z.L. Xiao 1,2, G. Jakob 1, B. Hensel 1, H. Adrian 1, and E.Y. Andrei 2. 1 Institut für Physik,Universität Mainz, D-55099 Mainz, Germany. 2 Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08855.

Presenting Author: Z.L. Xiao

Highly oriented (Hg_0.7Mo_0.3)Sr₂(Ca_0.7Y_0.3)Cu₂O_x and (Hg_0.9Re_0.1)Ba₂CaCu₂O_y superconducting films were prepared on SrTiO₃ substrates using laser ablation and post-Hg-vapor annealing. Due to the stability of Mo_0.3Sr₂(Ca_0.7Y_0.3)Cu₂O_x and Re_0.1Ba₂CaCu₂O_y in air, no special handling was needed during the grinding, mixing and pressing of the precursor targets. Zero-resistance superconducting transition temperatures of 92 K and 107 K were achieved for (Hg_0.7Mo_0.3)Sr₂(Ca_0.7Y_0.3)Cu₂O_x and (Hg_0.9Re_0.1)Ba₂CaCu₂O_y respectively. X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate that the (Hg_0.7Mo_0.3)Sr₂(Ca_0.7Y_0.3)Cu₂O_x films are a-axis oriented while the (Hg_0.9Re_0.1)Ba₂CaCu₂O_y films are c-axis oriented.

1PO4-55 High T_c Superconducting HgBa₂CaCu₂O_y Films Growth on the Y-ZrO₂ Substrates with YBa₂Cu₃O₇ Buffer Layers

Y. Sun, J.D. Guo, X.L. Xu, Y.Z. Wang, and G.C. Xiong, Department of Physics, Peking University, Beijing 100871, P.R. China

Presenting Author: Y. Sun

Superconducting HgBa₂CaCu₂O_y (Hg-1212) films have been fabricated on the (100) Y-ZrO₂ substrates with YBa₂Cu₃O₇ (YBCO) buffer layers by a two-step process. Using this buffer layer reproducible superconducting properties, zero resistance temperatures (T_c) = 115-124K and critical current density (J_c) = 1 - 3 x 10⁵ A/cm² at 100K in zero magnetic field, are obtained. X-ray diffraction q -2q patterns and f scans real that the films grew epitaxially on the YBCO surfaces with c-axis perpendicular to them. 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.

1PO4-56 Screen printed Tl-1223 superconducting thick films

Oliver Heiml, Wolfgang T. König and Gerhard Gritzner, Institut für Chemische Technologie Anorganischer Stoffe, Johannes Kepler Universität, A-4040 Linz, Austria

Presenting Author: G. Gritzner

Highly oriented bismuth- and lead-codoped Tl-1223 superconducting, 5 – 10 µm thick films of the composition (Tl_0.6Bi_0.16Pb_0.24)(Ba_0.1Sr_0.9)₂Ca₂Cu₃O_y were prepared on ZrO₂ substrates by screen printing. Sintering was performed by a two step process with an intermediate uni-axial compaction step to enhance both texturing and density.

T_c(0)-values ranged between 115 K and 118 K with narrow transition widths around 1 K. X-ray diffraction proved the high phase purity of the material. The degree of texturing was calculated from the intensities of the respective XRD peaks.

Optical microscopy in normal and polarized light as well as scanning electron microscopy in combination with EDX were employed to learn about the microstructure of the films. These studies yielded information on the interaction between the film and substrate as well as on the morphology of the superconducting grains and grain contacts, on remaining secondary phases and on the porosities. Large areas and complex patterns could be prepared with relative ease.

Transport critical current densities in the range of 10 kA cm^-2 at 77 K were already obtained. Further improvement in the critical current densities is expected.

1PO4-57 The structural symmetry of Tl-2201 films

H.Q. Chen 1, L.-G. Johansson 1, and Z.G. Ivanov 2. 1 Department of Inorganic Chemistry, University of Göteborg. 2 Department of Microelectronics and Nanoscience, Chalmers University of Technology and University of Göteborg.SE 412 96, Göteborg, Sweden.

Presenting Author: H.Q. Chen

Tl_2-xBa₂CuO₆ (Tl-2201) films with a thallium content of 1.85 and 2.04 were prepared on single crystal LaAlO₃ and SrTiO₃ substrates using a multi-step procedure involving laser ablation. The films were c–axis oriented and epitaxial. The structural symmetry of the films was studied by performing X-ray f -scans. For a film with a thallium content of 1.85, a f scan of the (1,1,10) reflection showed four peaks while a 2q scan of the same reflection exhibited single peak structure. This shows that the film is epitaxial and tetragonal.

A film with a thallium content of 2.04 was also found to be epitaxial. In this case a 2q scan of the corresponding reflection showed that it exhibited a double peak structure. This indicates an orthorhombic splitting of the reflection into (2,0,10) and (0,2,10). The f scan also revealed a small deviation from tetragonal symmetry supporting the conclusion that this film is orthorhombic.

The effect of substrate on the symmetry of the films was also studied.

Tl 2201 films deposited on LaAlO₃ and SrTiO₃ with an average thickness of less than 20nm and with a thallium content of 2.04 still exhibited orthorhombic symmetry.

1PO4-58 Hall Effect of Pr_0.5Ca_0.5Ba₂Cu₃O_7-y Superconducting Thin Films with Different Oxygen Contents

Z.H. Wang, G.J. Lian, Y.F. Sun, and G.C. Xiong, Department of Physics and Mesocscopic Physics National Laboratory, Peking University, Beijing 100871, P.R. China

Presenting Author: Z.H. Wang

Using pulsed laser deposition method, we prepared epitaxial Pr_0.5Ca_0.5Ba₂Cu₃O_7-y (PCBCO) thin films with T_c(R=0)=35.4K. Through in situ annealing in different oxygen pressures at 350 ° C, the thin films with different oxygen contents were obtained. We found that the optimum annealing condition for the highest T_c is in an oxygen pressure of 0.2-0.6 atm. On the contrary, the thin films annealed in 1 atm have lower T_c(R=0)=33.5K, although show smaller resistivity behavior. The relationship between T_c and carrier concentration (N_H=1/eR_H) was studied in the epitaxial films with different oxygen contents. The Hall measurement shows that the thin films with higher T_c(R=0) have more mobile carriers. These results support that the highest T_c is corresponding to an optimum N_H. Anomalous result has been obtained that the oxygen sufficient PCBCO films with less mobile carriers have smaller resistivity. A possible explanation is presented in this paper.

1PO4-59 Small Area Characterization of the Ribbon-like thin films of Bi-2212

Shunichi Arisawa 1,2, Hanping Miao 2, Yoshihiko Takano 1, Yoshimasa Satoh 2,3, Akira Ishii 1, Hiroki Fujii 1,2, Takashi Mochiku 1,2, Takeshi Hatano 1, and Kazumasa Togano 1,2,3. 1 National Research Institute for Metals, 1-2-1 Sengen, Tsukuba-shi, Ibaraki 305-0047, Japan. 2 JST-CREST, Japan. 3 University of Tsukuba, Japan.

Presenting Author: S. Arisawa