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The use of BaF sub 2 buffer layers for the sputter-deposition of TlCaBaCuO thin-film superconductors

Description: Thin films of the Tl-based superconductors often have relatively poor properties because of film/substrate interdiffusion which occurs during the anneal. We have therefore investigated the use of BaF{sub 2} as a diffusion barrier. TlCaBaCuO thin films were deposited by dc magnetron sputtering onto MgO <100> substrates, both with and without an evaporation-deposited BaF{sub 2} buffer layer, and post-annealed in a Tl over-pressure. Electrical properties of the films were determined by four-point … more
Date: January 1, 1989
Creator: Hubbard, K. M.; Arendt, P. N.; Brown, D. R.; Cooke, D. W.; Elliott, N. E.; Farr, J. D. et al.
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Partner: UNT Libraries Government Documents Department
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Anisotropy of oxygen tracer diffusion in YBa sub 2 Cu sub 3 O sub 7-. delta. single crystals

Description: The crystal structure of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} strongly suggests that the diffusion of oxygen in this material will be highly anisotropic, with diffusion in the ab plane being much faster than diffusion parallel to the c axis, and this has been assumed in most analyses of diffusion in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}. The present data confirm this hypothesis; the diffusion coefficient in the ab plane is several orders of magnitude greater than the diffusion coefficient along th… more
Date: September 1, 1989
Creator: Rothman, S. J.; Routbort, J. L.; Liu, J.-Z.; Downey, J. W.; Thompson, L. J.; Fang, Y. et al.
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Partner: UNT Libraries Government Documents Department
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Electron beam induced oxygen in YBa sub 2 Cu sub 3 O sub 7-x superconductors

Description: Thin foils of bulk YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) superconductors were subjected to electron irradiation in a Transmission Electron Microscope (TEM). The resulting disordering of the oxygen atoms and vacancies in the Cu-O planes was monitored by measuring the splitting of the (110) diffraction spots in the (001) diffraction pattern. Samples were irradiated at 83K with 100, 150, 200 and 300kV electrons. The 100kV electrons did not cause any disordering, even after prolonged irradiation. Th… more
Date: January 1, 1989
Creator: Basu, S.N.; Roy, T.; Mitchell, T.E. & Nastasi, M.
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Influence of ion beam mixing on the growth of high temperature oxide superconducting thin film

Description: The superconducting properties of high temperature superconductor thin films are dependent on the quality of the substrate used to grow these films. In order to maximize the lattice matching between the superconducting film and the substrate, we have used a YBa{sub 2}Cu{sub 3}O{sub 7} thin film deposited on {l angle}100{r angle} SrTiO{sub 3} as a template. The first film was prepared by coevaporation of Y, BaF{sub 2} and Cu on {l angle}100{r angle} SrTiO{sub 3}, followed by an anneal in wet'' o… more
Date: January 1, 1989
Creator: Bordes, N.; Rollett, A.D.; Cohen, M.R. & Nastasi, M.
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Partner: UNT Libraries Government Documents Department
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The influence of the substrate surface on the nucleation and growth of superconducting thin films

Description: The quality of epitaxially grown superconducting thin films is dependent on the nature of the substrate surface. In this study, the surface of <100> oriented SrTiO{sub 3} single crystals was modified by mechanical polishing, thermal annealing and chemical etching. A study of the YBa{sub 2}Cu{sub 3}O{sub 7-x} thin films grown on these substrates showed that high quality superconducting films were obtained when the substrate surface was highly oriented in the <100> direction and was also microsco… more
Date: January 1, 1989
Creator: Basu, S.N.; Bordes, N.; Rollett, A.D.; Cohen, M.R. & Nastasi, M.
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Partner: UNT Libraries Government Documents Department
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Microwave characterization of high-temperature superconductors

Description: Thick (10-15 {mu}m) Tl-Ba-Ca-Cu-O films have been deposited onto yttria-stabilized zirconia and Ag substrates by d.c. magnetron sputtering techniques. Direct deposition onto 1'' diameter yttria-stabilized zirconia yields films with typical 22 GHz surface resistance (R{sub s}) values of 5.2 {plus minus} 2 m{Omega} and 52 {plus minus} 2 m{Omega} at 10 K and 77 K, respectively. For comparison, R{sub s} of Cu at this same frequency is 10 m{Omega} at 4 K and 22 m{Omega} at 77 K. Tl-Ba-Ca-Cu-O films … more
Date: January 1, 1989
Creator: Cooke, D. W.; Gray, E. R.; Arendt, P. N.; Beery, J. G.; Bennett, B. L.; Brown, D. R. et al.
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Partner: UNT Libraries Government Documents Department
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High Resolution-Angle Resolved Photoemission Studies of High Temperature Superconductors

Description: Recent photoemission studies of Y 123 and Bi 2212 performed with high energy and angular resolution have provided detailed information on the nature of the states near the Fermi level. Measurements of the superconducting gap, band dispersion, and the density of states near the Fermi level in the normal state all support a Fermi liquid description of these materials. 5 refs., 4 figs.
Date: August 1, 1989
Creator: Olson, C. G.; Liu, R.; Lynch, D. W.; Veal, B. W.; Chang, Y. C.; Jiang, P. Z. et al.
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Partner: UNT Libraries Government Documents Department
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Rotational magnetic processes in YB sub 2 Cu sub 3 O sub 7

Description: A polycrystalline superconducting thin-disk sample was rotated in a fixed field ({rvec H}) at 4.2 K, and the vector magnitude and orientation of the total magnetization ({rvec M}) were measured as the sample-rotation angle ({Theta}) was slowly cycled between 0 and 360{degree}. The measured {rvec M} was decomposed into a penetrating (vortex) flux component {rvec M}{sub p} that rotates rigidly with the sample at very small {Theta} and a diamagnetic (shielding) component {rvec M}{sub d} that stays… more
Date: January 1, 1989
Creator: Liu, Liwen; Kouvel, J.S.; Brun, T.O. (Illinois Univ., Chicago, IL (USA). Dept. of Physics & Argonne National Lab., IL (USA))
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Partner: UNT Libraries Government Documents Department
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Electronic structure of monoclinic BaBiO sub 3

Description: We present the results of photoemission studies of valence disordered'' monoclinic BaBiO{sub 3} in the photon energy range 15--120 eV. The line-shapes of the valence band photoemission spectra and the Ba contributions to the valence band are very similar to the line shapes of the total density of states and Ba partial density of states, respectively. Oxygen resonance is observed, demonstrating the existence of empty O 2p states. These results support a more covalent rather than a simple ionic p… more
Date: January 1, 1989
Creator: Shen, Z. X.; Lindberg, P. A. P.; Wells, B. O.; Dessau, D. S.; Borg, A.; Lindau, I. et al.
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Partner: UNT Libraries Government Documents Department
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Intergranular and interphase boundaries in ceramics

Description: Interfaces are of great importance in both electronic and structural ceramics. The microstructure and microchemistry of interfaces can be studied by transmission electron microscopy, both high resolution and analytical. Examples are taken from both intergranular and interphase boundaries in ceramics. The former include low angle, twin and 90/degree/ boundaries in YBa/sub 2/Cu/sub 3/O/sub 7/ superconductors. Interphase boundaries include epitactic layers of YBa/sub 2/Cu/sub 3/O/sub 7/on SrTiO/su… more
Date: January 1, 1989
Creator: Mitchell, T.E.; Roy, T. & Unal, O.
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Partner: UNT Libraries Government Documents Department
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Phase separation of holes in antiferromagnets

Description: It is shown that dilute holes in an antiferromagnet are unstable against phase separation into a hole-rich phase and a no-hole phase. When the spin exchange interaction J exceeds a critical value J{sub c}, one phase consists of all holes, the other all electrons. The argument is presented in detail for the t--J model but evidence of phase separation in other models is mentioned. 11 refs.
Date: January 1, 1989
Creator: Emery, V.J.; Kivelson, S.A.; Lin, H.Q. (Brookhaven National Lab., Upton, NY (USA); California Univ., Los Angeles, CA (USA). Dept. of Physics & Brookhaven National Lab., Upton, NY (USA))
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Partner: UNT Libraries Government Documents Department
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Partial reduction of re-oxidation processing of Y-Ba-Cu-O sputtered thin films

Description: Thin films of Y--Ba--Cu--O were produced by rf sputtering of YBa{sub 2}Cu{sub 3}O{sub 7-x} ceramic targets, using a variety of plasma compositions, rf power levels, and substrate temperatures. Post annealing of these films in oxygen produced superconducting films with T{sub c} values between 40--60 K, broad transition widths and semiconductor-like electrical behavior above T{sub c}. Subsequent annealing at 850{degree}C in an inert gas with a residual oxygen partial pressure of {le}10 ppM follow… more
Date: January 1, 1989
Creator: Garzon, F.H.; Beery, J.G.; Wilde, D.K. & Raistrick, I.D.
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Partner: UNT Libraries Government Documents Department
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The formation and analysis of thin film high temperature superconductors

Description: Thin films of high temperature superconductors have been fabricated using a variety of physical vapor deposition techniques. Recent results of HTS thin films produced by coevaporation, sputtering and laser deposition will be briefly reviewed. In addition some examples of the utility of high energy ion backscattering for the analysis of film stoichiometry will be given. 34 refs., 6 figs.
Date: January 1, 1989
Creator: Nastasi, M.; Muenchausen, R. E. & Arendt, P. N.
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Partner: UNT Libraries Government Documents Department
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Microstructures of Y123 films on SrTiO sub 3 , LaGaO sub 3 and LaAlO sub 3

Description: Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) have been used to study the microstructural features of YBa{sub 2}Cu{sub 3}O{sub 7} (hereafter referred to as Y123) films grown on various single crystal substrates by electron beam deposition. The films are all of high quality with the best observed J{sub c} value being 3 {times} 10{sup 7} A{center dot}cm{sup -2} at 7 K. Cross-sectional views in TEM have shown that the morphology of the film depends on its thickness.… more
Date: January 1, 1989
Creator: Roy, T.; Raistrick, I.D. & Mitchell, T.E.
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Partner: UNT Libraries Government Documents Department
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Calculation of the nuclear quadrupole resonance spectra of YBa/sub 2/Cu/sub 3/O/sub 7/minus/x/

Description: Nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) studies on /sup 63,65/Cu have demonstrated the the resonance properties of these nuclei can give important information about the electronic structure of the high temperature superconductor YBa/sub 2/Cu/sub 3/O/sub 7/minus/x/ as well as the exchange coupling energy between the Cu(2) sites. Measurements for various oxygen stoichiometries have given insight into the effect of oxygen content on the valence state of the Cu. In t… more
Date: June 1, 1989
Creator: Winter, N. W. & Violet, C. E.
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Partner: UNT Libraries Government Documents Department
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A Fermi Liquid Electric Structure and the Nature of the Carriers in High-T/sub c/ Cuprates: A Photoemission Study

Description: We have performed angle-integrated and angle-resolved photoemission measurements at 20 K on well-characterized single crystals of high-T/sub c/ cuprates (both 1:2:3-type and 2:2:1:2-type) cleaved in situ, and find a relatively large, resolution limited Fermi edge which shows large amplitude variations with photon energy, indicative of band structure final state effects. The lineshapes of the spectra of the 1:2:3 materials as a function of photon energy are well reproduced by band structure pred… more
Date: January 1, 1989
Creator: Arko, A. J.; List, R. S.; Bartlett, R. J.; Cheong, S. W.; Fisk, Z.; Thompson, J. D. et al.
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Partner: UNT Libraries Government Documents Department
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Copper and oxygen NMR studies on the magnetic properties of YBa sub 2 Cu sub 3 O sub 7-y

Description: Microscopic magnetic properties of the CuO{sub 2} layers in YBa{sub 2}Cu{sub 3}O{sub 7-y} have been investigated from Cu and O NMR experiments on the y{approx equal}0 (T{sub c}=92K) and y=0.37 (T{sub c}=62K) materials. The Knight shift at the planar Cu and the planar oxygen sites are found to be proportional to a common spin susceptibility {chi}{sub s} which depends on temperature and oxygen-content, strongly supporting a single component spin model for the CuO{sub 2} planes. In the y=0.37 mate… more
Date: January 1, 1989
Creator: Takigawa, Masashi.
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Partner: UNT Libraries Government Documents Department
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Characterization of electrically conducting oxides

Description: This report discusses some of the highlights and publications of this years work. Listed below are the areas of interest and progress within the program: The studies of the Ba{sub 2}YCu{sub 3}O{sub 7-x} system have shown that the conduction processes (metallic or small polaron) have little temperature dependence and are almost entirely a function of oxygen stoichiometry. The substitution of 10 to 20 m% Ca and Co into LaCrO{sub 3} has enabled the system to be sintered to >95% TD at 1400{degree}C… more
Date: January 1, 1989
Creator: Anderson, H.U. & Sparlin, D.M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Phonons and charge-transfer excitations in HTS superconductors

Description: Some of the experimental and theoretical evidence implicating phonons and charge-transfer excitations in HTS superconductors is reviewed. It is suggested that superconductivity may be driven by a synergistic interplay of (anharmonic) phonons and electronic degrees of freedom (e.g., charge fluctuations, excitons). 47 refs., 5 figs.
Date: January 1, 1989
Creator: Bishop, A. R.
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Partner: UNT Libraries Government Documents Department
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Anomalous ion-channeling behavior across the superconducting transition in high-T/sub c/ materials

Description: Axial channeling scans with minimum RBS yields of /le/2% were obtained for 1.5 MeV /sup 4/He ions incident along the c-axis in YBa/sub 2/Cu/sub 3/O/sub 7-/delta// and ErBa/sub 2/Cu/sub 3/O/sub 7-/delta// single crystals. Large variations in the FWHM of the (001) channeling dip were observed for temperatures between 30 and 300 K. An abrupt, /approximately/8% increase was measured as the temperature was lowered through the superconducting transition (T/sub c/); the relative increase across T/sub … more
Date: July 1, 1989
Creator: Rehn, L. E.; Sharma, R. P.; Baldo, P. M. & Liu, J. Z.
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Partner: UNT Libraries Government Documents Department
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Studies on ion scattering and sputtering processes relevant to ion beam sputter deposition of multicomponent thin films

Description: Results from computer simulation and experiments on ion scattering and sputtering processes in ion beam sputter deposition of high Tc superconducting and ferroelectric thin films are presented. It is demonstrated that scattering of neutralized ions from the targets can result in undesirable erosion of, and inert gas incorporation in, the growing films, depending on the ion/target atom ass ratio and ion beam angle of incidence/target/substrate geometry. The studies indicate that sputtering Kr{su… more
Date: January 1, 1989
Creator: Auciello, O.; Ameen, M. S.; Kingon, A. I.; Krauss, A. R. & Ray, M. A.
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Partner: UNT Libraries Government Documents Department
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Electron spectroscopy studies of high temperature superconductors: Y/sub 1/minus/x/Pr/sub x/Ba/sub 2/Cu/sub 3/O/sub 7/minus/delta/

Description: We itemize our previous work on high T/sub c/ superconductors, and describe more fully the results of an electron spectroscopy study and impurity Anderson Hamiltonian analysis of the Pr 4f spectrum of Y/sub 1/minus/x/Pr/sub x/Ba/sub 2/Cu/sub 3/O/sub 7/minus/delta/, a system in which superconductivity is quenched as x increases. It has been speculated that Pr has valence 4+, resulting in extra charge in the Cu-O planes, and causing T/sub c/-suppression. We find that the Pr valence is close to 3+… more
Date: January 1, 1989
Creator: Kang, J. S.; Allen, J. W.; Lee, B. W.; Maple, M. B.; Shen, Z. X.; Yeh, J. J. et al.
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Partner: UNT Libraries Government Documents Department
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Real-time method of powder diffraction for non-periodic and nearly periodic materials

Description: The use of high-energy neutrons from pulsed or hot sources allows the method of atomic pair distribution analysis to be applied to the structural determination of crystalline as well as amorphous solids. This method complements the standard crystallographic methods in studying non-periodic aspects of solids with or without long range order. 14 refs., 3 figs.
Date: December 1, 1989
Creator: Egami, T.; Toby, B.H.; Dmowski, T.W. (Pennsylvania Univ., Philadelphia, PA (USA). Dept. of Materials Science and Engineering); Janot, C. (Institut Laue-Langevin, 38 - Grenoble (France)) & Jorgensen, J.D. (Argonne National Lab., IL (USA))
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Partner: UNT Libraries Government Documents Department
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Chemistry and Materials Science Department annual report, 1988--1989

Description: This is the first annual report of the Chemistry & Materials Science (C&MS) Department. The principal purpose of this report is to provide a concise summary of our scientific and technical accomplishments for fiscal years 1988 and 1989. The report is also tended to become part of the archival record of the Department`s activities. We plan to publish future editions annually. The activities of the Department can be divided into three broad categories. First, C&MS staff are assigned by the matrix… more
Date: December 31, 1989
Creator: Borg, Richard J.; Sugihara, Thomas T.; Cherniak, Jay C. & Corey, Cara W.
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Partner: UNT Libraries Government Documents Department
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