Search Results - (Author, Cooperation:I. Takeuchi)
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1Latest Papers from Table of Contents or Articles in PressStaff View
Publication Date: 2018-05-07Publisher: BMJ PublishingElectronic ISSN: 2044-6055Topics: MedicineKeywords: Clinical trials (epidemiology), Open access, NeurologyPublished by: -
2Latest Papers from Table of Contents or Articles in PressC. H. Lee ; N. D. Orloff ; T. Birol ; Y. Zhu ; V. Goian ; E. Rocas ; R. Haislmaier ; E. Vlahos ; J. A. Mundy ; L. F. Kourkoutis ; Y. Nie ; M. D. Biegalski ; J. Zhang ; M. Bernhagen ; N. A. Benedek ; Y. Kim ; J. D. Brock ; R. Uecker ; X. X. Xi ; V. Gopalan ; D. Nuzhnyy ; S. Kamba ; D. A. Muller ; I. Takeuchi ; J. C. Booth ; C. J. Fennie ; D. G. Schlom
Nature Publishing Group (NPG)
Published 2013Staff ViewPublication Date: 2013-10-18Publisher: Nature Publishing Group (NPG)Print ISSN: 0028-0836Electronic ISSN: 1476-4687Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsPublished by: -
3Articles: DFG German National LicensesTakeuchi, I. ; Chang, K. ; Sharma, R. P.
[S.l.] : American Institute of Physics (AIP)
Published 2001Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: We have investigated the microstructure of (Ba, Sr)TiO3 films fabricated from BaF2/SrF2/TiO2 amorphous multilayers. Rutherford backscattering spectroscopy and x-ray diffraction studies show that a controlled thermal treatment can interdiffuse the multilayers so as to create predominantly single-phase epitaxial (Ba, Sr)TiO3 films. A high resolution cross-sectional transmission electron microscopy investigation of the processed films shows that they consist of large epitaxial grains of (Ba, Sr)TiO3 with atomically sharp interfaces with the LaAlO3 substrates. In addition, we have identified regions where polycrystalline and transient phases exist in small pockets in the film matrix. The results here indicate that the combinatorial thin-film synthesis using precursors can produce (Ba, Sr)TiO3 films in combinatorial libraries which exhibit properties similar to those films made by conventional techniques. © 2001 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
4Articles: DFG German National LicensesBhattacharya, S. ; Rajeswari, M. ; Takeuchi, I. ; Trajanovic, Z. ; Li, Qi ; Xi, X. X. ; Venkatesan, T.
[S.l.] : American Institute of Physics (AIP)
Published 1994Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: The optical response of single grain-boundary weak links in superconducting YBCO thin films has been investigated. At temperatures well below the transition temperature, the grain boundary exhibits an optical response which is qualitatively different from transition edge response. Using a resistively shunted-junction model for the grain-boundary weak link, we find that the optical response below the transition temperature can be described by radiation induced thermal modulation of the critical currents of the weak links. The dependence on the bias current and the temperature distinguishes the weak-link optical response from the transition edge optical response. We discuss novel aspects of a potential radiation detector based on grain-boundary weak-link junctions.Type of Medium: Electronic ResourceURL: -
5Articles: DFG German National LicensesDuewer, Fred ; Gao, C. ; Takeuchi, I. ; Xiang, X.-D.
Woodbury, NY : American Institute of Physics (AIP)
Published 1999Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: We have developed a means of tip–sample distance regulation for a scanning evanescent microwave microscope over conductive samples. Changes in resonant frequency and quality factor are measured, where changes in resonant frequency are related to the tip–sample capacitance and changes in quality factor are related to microwave absorption. With the analytical expression of the tip–sample capacitance as a function of tip–sample distance, we can quantitatively regulate the tip–sample separation. We demonstrated simultaneous noncontact imaging of topography and surface resistance with high spatial resolution. © 1999 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
6Articles: DFG German National LicensesChang, H. ; Gao, C. ; Takeuchi, I. ; Yoo, Y. ; Wang, J. ; Schultz, P. G. ; Xiang, X.-D.
Woodbury, NY : American Institute of Physics (AIP)
Published 1998Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: A library of 256 differently doped thin films of (BaxSr1−x)TiO3 (where 0.5〈x〈1.0) was generated on a 1 in.×1 in. LaAlO3 substrate using multistep thin-film deposition techniques together with a quaternary masking strategy. Appropriate postannealing processing afforded high-quality epitaxial thin films. The microwave properties, i.e., dielectric constant and loss tangent, of samples in the library were characterized with a scanning-tip microwave near-field microscope at 1 GHz, and the results were found to be consistent with measurements made with interdigital electrodes. Specific dopants were found to significantly affect the dielectric constant and tangent loss. Tungsten, in particular, reduces the tangent loss. © 1998 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
7Articles: DFG German National LicensesEnhanced magnetoresistance in YBa2Cu3O7/Nd0.7Sr0.3MnO3 heterostructures using magnetic flux focusingDong, Z. W. ; Boettcher, T. ; Chen, C-H. ; Takeuchi, I. ; Rajeswari, M. ; Sharma, R. P. ; Venkatesan, T.
Woodbury, NY : American Institute of Physics (AIP)
Published 1996Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: Enhanced low field magnetoresistance (MR) in Nd0.7Sr0.3MnO3 (NSMO) has been achieved by using high-Tc superconducting flux focusing devices made of YBa2Cu3O7(YBCO)/NSMO heterostructures. Two kinds of flux focusing schemes, gap, and washer devices, have been used where an applied magnetic field is expelled from patterned YBCO pads and focused onto a bridge of NSMO film. Using such a magnetic lens, at temperatures below 77 K ∼800% enhancement in MR=−(RH−R0)/R0 was observed for different samples. This corresponds to more than 10% change in the MR of NSMO in the presence of 200 G. For the maximum MR response in NSMO, the YBCO/NSMO heterostructures were deposited on (100) LaAlO3 substrate by pulsed laser deposition in situ so that the peak resistance temperature (Tp) of NSMO was below the superconducting transition temperature (Tc) of YBCO. © 1996 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
8Articles: DFG German National LicensesOgale, S. B. ; Takeuchi, I. ; Rajeswari, M. ; Greene, R. L. ; Venkatesan, T. ; Choughule, D. D.
Woodbury, NY : American Institute of Physics (AIP)
Published 1995Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: Incorporation of Fe in YBa2Cu3O7−δ matrix during its epitaxial growth on (001) LaAlO3 by pulsed excimer laser ablation is examined. It is shown that oxygen pressure during deposition plays a critical role in the incorporation process and that a low-temperature postsynthesis annealing is essential for complete substitution. Clustering of iron atoms and its control via the anion controlled reactions are identified as the key features in this context. It is also shown by using atomic force microscopy that Fe incorporation influences the surface morphology. These issues are of importance in the formation of cationic defects in multicomponent thin films. © 1995 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
9Articles: DFG German National LicensesMao, S. N. ; Xi, X. X. ; Li, Qi ; Takeuchi, I. ; Bhattacharya, S. ; Kwon, C. ; Doughty, C. ; Walkenhorst, A. ; Venkatesan, T. ; Whan, C. B. ; Peng, J. L. ; Greene, R. L.
Woodbury, NY : American Institute of Physics (AIP)
Published 1993Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: Bilayers of Y1Ba2Cu3O7−x(YBCO)/Nd1.85Ce0.15CuO4−y(NCCO), in which both layers were superconducting, were fabricated in situ by pulsed laser deposition. Using N2O as the reactive gas, we were able to meet the conflicting processing requirements, oxygenation for YBCO, and reduction for NCCO, in the same sample with a specific cooling procedure. The bilayer thin films were c-axis oriented with a transition temperature, Tco, of 88.5 K for YBCO and 18.5 K for NCCO. Supercurrent was observed across the interface of the YBCO and NCCO superconducting layers, indicating the phase coherence between these superconductors.Type of Medium: Electronic ResourceURL: -
10Articles: DFG German National LicensesTakeuchi, I. ; Trajanovic, Z. ; Peng, J. L. ; Li, Z. Y. ; Warburton, P. A. ; Lobb, C. J. ; Venkatesan, T.
Woodbury, NY : American Institute of Physics (AIP)
Published 1995Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: In-plane oriented a-axis heteroepitaxial multilayers consisting of YBa2Cu3O7−x/PrBa2Cu3O7−y bilayers and insulating LaSrGaO4 and Nd2CuO4 on (100) LaSrGaO4 substrates have been fabricated. φ-scan measurements of reflections from (101) Nd2CuO4 and (102) YBa2Cu3O7−x planes display twofold symmetry, indicating in-plane oriented growth of the top and middle layers in superconductor-insulator-superconductor structures for an insulating barrier thickness of 3000 A(ring). For structures with a Nd2CuO4 barrier, both top and bottom layers had Tc(R=0)≥85 K. © 1995 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
11Articles: DFG German National LicensesLow temperature optical response of a single grain boundary in superconducting YBa2Cu3O7−δ thin filmBhattacharya, S. ; Rajeswari, M. ; Takeuchi, I. ; Xi, X. X. ; Mao, S. N. ; Kwon, C. ; Li, Qi ; Venkatesan, T.
Woodbury, NY : American Institute of Physics (AIP)
Published 1993Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: We have investigated the optical response from a single grain boundary in a thin film (∼300 nm) of superconducting YBa2Cu3O7−δ fabricated on bicrystals SrTiO3 substrate. We have studied the temperature, bias current, and magnetic field dependence of the optical response in the temperature range of 15 K≤T≤35 K. We find that the optical response from the single grain boundary in this temperature range can be satisfactorily explained in terms of the optical response of a Josephson weak link. The optical response of the grain boundary is qualitatively similar to that of granular films seen in the earlier studies, indicating that the latter may be dominated by the optical response of grain-boundary weak links.Type of Medium: Electronic ResourceURL: -
12Articles: DFG German National LicensesTrajanovic, Z. ; Takeuchi, I. ; Warburton, P. A. ; Lobb, C. J. ; Venkatesan, T.
Woodbury, NY : American Institute of Physics (AIP)
Published 1995Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: The granularity and surface roughness of a-axis YBa2Cu3O7−x films grown on (100) LaAlO3, (100) SrTiO3, and (100) LaSrGaO4 by pulsed laser deposition has been studied. For fixed deposition conditions, the size and the shape of the grains varied from substrate to substrate, while the mean roughness remained the same. We were able to systematically control the grain size and smoothness of films on LaSrGaO4 and LaAlO3. By gradually reducing the oxygen pressure during the deposition we obtained films with increased grain size and much reduced surface roughness (mean ∼40 A(ring) over 5 ×5 μm2). Cracks observed in the films deposited on LaSrGaO4 at very low O2 pressures (∼20 mTorr) were successfully eliminated for deposition pressures above 40 mTorr. © 1995 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
13Articles: DFG German National LicensesTakeuchi, I. ; Mao, S. N. ; Xi, X. X. ; Petersen, K. ; Lobb, C. J. ; Venkatesan, T.
Woodbury, NY : American Institute of Physics (AIP)
Published 1995Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: Josephson junctions were fabricated at the interface of YBa2Cu3O7−x (YBCO) and Nd1.85Ce0.15CuO4−y (NCCO) in heteroepitaxially grown superconducting bilayers. Devices of various configurations and sizes were fabricated, and they display a resistively shunted junction like I–V characteristics with hysteresis at low temperatures. A clear ac Josephson effect was observed under microwave irradiation, and critical currents were completely suppressible by external magnetic fields. Oxygen diffusion or charge diffusion at the interface are possible origins for the barrier formation. © 1995 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
14Articles: DFG German National LicensesPetersen, K. ; Takeuchi, I. ; Talyansky, V. ; Doughty, C. ; Xi, X. X. ; Venkatesan, T.
Woodbury, NY : American Institute of Physics (AIP)
Published 1995Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: The effect of electric field on ultrathin YBa2Cu3O7−δ grain boundary Josephson junctions has been investigated. A conventional metal insulator superconductor field effect transistor structure consisting of a Pr0.55Y0.45Ba2Cu3O7−δ /YBa2Cu3O7−δ bilayer channel, a crystalline SrTiO3 dielectric, and an Au gate electrode is deposited on a SrTiO3 bicrystal substrate. At high bias current (Ibias(very-much-greater-than)Ic) the observed effect is compatible with a parallel resistor model using a value close to the bulk charge carrier density of YBa2Cu3O7−δ. At low bias current (Ibias≥Ic) an enhanced field effect not compatible with a parallel resistor model is observed. This enhanced effect is related to the field dependent dielectric properties of the crystalline SrTiO3 insulation layer. © 1995 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
15Articles: DFG German National LicensesTakeuchi, I. ; Chang, H. ; Gao, C. ; Schultz, P. G. ; Xiang, X.-D.
Woodbury, NY : American Institute of Physics (AIP)
Published 1998Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: Combinatorial libraries of parallel-plate capacitors, consisting of Pt and La0.5Sr0.5CoO3 electrodes and a doped BaxSr1−xTiO3 dielectric layer, have been fabricated and analyzed to systematically study the effects of dopants on device performance. Epitaxial heterostructure libraries with sharp interfaces were generated from amorphous layers on LaAlO3 substrates. Two hundred and forty different host/dopant combinations were synthesized on a 1/2 in. by 1/2 in. substrate, with 23 capacitors for each combination. Addition of 1.5 mol % W was found to increase the figure of merit (ε/Ileak) 220-fold and reduce the high-frequency (MHz and GHz) loss tangent by fourfold. © 1998 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
16Articles: DFG German National LicensesTakeuchi, I. ; Wei, T. ; Duewer, Fred ; Yoo, Y. K. ; Xiang, X.-D.
Woodbury, NY : American Institute of Physics (AIP)
Published 1997Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: We have explored the low temperature capability of a scanning-tip microwave near-field microscope to study superconductors. The shift in the quality factor of the microscope resonator can be used to obtain the temperature dependence of the surface resistance of a local region under the tip. Patterned YBa2Cu3O7−x films were scanned at various temperatures and surface resistance mapping was performed with high spatial resolution at 1.2 GHz. Superconducting transitions at different positions on a film can be detected. Edge-region defects in wet-etched patterns were observed and were shown to be nonsuperconducting at microwave frequencies at 80 K. © 1997 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
17Articles: DFG German National LicensesTakeuchi, I. ; Warburton, P. A. ; Trajanovic, Z. ; Lobb, C. J. ; Dong, Z. W. ; Venkatesan, T. ; Bari, M. A. ; Booij, W. E. ; Tarte, E. J. ; Blamire, M. G.
Woodbury, NY : American Institute of Physics (AIP)
Published 1996Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: We have fabricated vertical YBa 2Cu3O7−x/PrBa 2Cu3O7−x/YBa 2Cu3O7−x (YBCO/PBCO/YBCO) Josephson junctions using in-plane aligned a-axis oriented YBCO multilayers on (100) LaSrGaO4(LSGO). The Tc's of the device electrodes are typically greater than 80 K. Josephson coupling is observed for barrier thickness up to 800 A(ring). Strong nonlinear I–V characteristics arising from the properties of PBCO are observed for thicker barrier devices. Chip to chip spread in the device characteristics may be intrinsically due to the PBCO barrier. © 1996 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
18Articles: DFG German National LicensesTakeuchi, I. ; Sharma, R. P. ; Choopun, S. ; Lobb, C. J. ; Venkatesan, T.
Woodbury, NY : American Institute of Physics (AIP)
Published 1997Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: We have studied the effect of ion milling on the surface crystallinity of the metal oxide substrates LaAlO3, SrTiO3, and NdGaO3 which are used for fabrication of high-Tc Josephson junctions and circuits. Ion channeling of the milled substrates reveals a damage-induced peak corresponding to a disordered layer of (approximate)60 Å at the surface. Annealing the substrates in oxygen ambient at various temperatures ranging from 600 to 1100 °C resulted in the regrowth of the damaged layer at the surface of the substrates as was indicated by the reduction in size of the surface peak observed in the channeled spectrum, as well as by formation of lattice steps as seen by atomic force microscopy. A significant reduction in the damage peak size and the formation of smooth completed lattice steps are seen only after annealing at temperatures ≥950 °C. © 1997 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
19Articles: DFG German National LicensesTakeuchi, I. ; Lobb, C. J. ; Trajanovic, Z. ; Warburton, P. A. ; Venkatesan, T.
Woodbury, NY : American Institute of Physics (AIP)
Published 1996Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: We have measured magnetic diffraction patterns of critical currents of vertical geometry YBa2Cu3O7−x(YBCO)/Ag/PbIn Josephson junctions made with in-plane aligned a-axis oriented YBCO films. Anisotropic penetration depths in YBCO and the resulting Josephson penetration depths give rise to diffraction patterns which are distinctly different when the magnetic field is applied in two orthogonal directions (b and c). The London penetration depths of YBCO, λb, and λc, are found to be ∼2000 A(ring) and ∼1.2 μm, respectively, at 4.2 K. Intrinsic IcRn products of up to 0.2 mV have been obtained in these junctions. © 1996 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
20Articles: DFG German National LicensesChang, H. ; Takeuchi, I. ; Xiang, X.-D.
Woodbury, NY : American Institute of Physics (AIP)
Published 1999Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: We have generated the thin-film ternary composition spread of (Ba1−x−ySrxCay)TiO3 on an equilateral-triangle-shaped LaAlO3 substrate. Compositional variation within the triangle was achieved by a precisely controlled shutter system inside a pulsed laser deposition chamber, which allows the deposition of precursors with gradient thickness over the length of the substrate. Appropriate postannealing afforded high-quality epitaxial thin films over almost the entire composition region. Mapping of the microwave dielectric properties of the composition-spread chip was performed using a scanning evanescent microwave microscope at 1 GHz. Composition region Ba0.12–0.25Sr0.35–0.47Ca0.32–0.53TiO3 was found to have desirable properties for electronic applications. © 1999 American Institute of Physics.Type of Medium: Electronic ResourceURL: