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  • 1
    Electronic Resource
    Electronic Resource
    Pulsed laser ablation: A new route to synthesize novel superconducting compounds as oriented films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1082-1091 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report here the significance of the pulsed laser ablation technique in stabilizing strained lattices that do not form by the conventional ceramic method and show that the technique offers unique possibilities to probe the structure property relationship in complicated systems. One of such systems is LuBa2Cu3O7−δ; a systematic investigation of structural (in)stability of its superconducting phase is presented here. Our analysis suggests that the system suffers from internal strain due to lower ionic radius of Lu3+; however, the structure can be stabilized only as oriented films on 〈100〉 LaAlO3, 〈100〉 SrTiO3, and 〈100〉 MgO, with excellent superconducting properties (Jc≈5.0×106 A cm−2 at 77 K). We have also investigated similar compounds having their stability close to their crystallographic limit. The important feature of these metastable phases is that they grow only as oriented films. Free energy of epitaxial growth of strained films are investigated and a simple growth model is proposed based on our observation. Importance of this growth model in explaining the superconductor–normal-metal–superconductor type of junctions, observed in high-Tc superconductors is highlighted. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360898
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  • 2
    Electronic Resource
    Electronic Resource
    Two-dimensional growth model for laser-ablated Ag-doped YBa2Cu3O7−x thin films (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5802-5808 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ag-doped YBa2Cu3O7−x (YBCO) thin films using 2–20 wt % Ag-doped YBCO targets have been grown in situ by the laser ablation technique. The improvement in properties in normal and superconducting states of Ag-doped YBCO films has been interpreted using a two-dimensional growth model. The model is simple and is based on widely accepted characteristics of Ag such as its flux action at high temperatures and its nonreactivity with YBCO phase. Experimental evidence in support of the growth model is presented by carrying out microstructural studies and measurements of room-temperature resistivity, critical current density, and microwave surface resistance in superconducting state. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359159
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  • 3
    Electronic Resource
    Electronic Resource
    Silver doping and its influence on the oxygenation during in situ growth of YBa2Cu3O7−x thin films (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1349-1351 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of Ag doping on both oxygenation and deoxygenation during growth of YBa2Cu3O7−x films at 700 °C by pulsed laser deposition has been studied. Experiments show that undoped and Ag-doped films grown at 200 mTorr oxygen pressure and quenched immediately after termination of growth have a superconducting transition temperature Tc of 61 and 86 K, respectively. The high Tc of 86 K obtained with quenched Ag-doped films is thought to be due to both enhanced oxygen incorporation and reduced deoxygenation associated with Ag doping. These results show that Ag-doped YBa2Cu3O7−x films could be crucial for realizing devices based on multilayer structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357802
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  • 4
    Electronic Resource
    Electronic Resource
    Optical spectroscopy study of the role of Ag in laser ablated YBa2Cu3O7−δ thin films (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5204-5205 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have found evidence through optical spectroscopy that AgO is indeed generated in the laser plume during pulsed laser deposition of YBa2Cu3O7−δ (YBCO) thin films using Ag-doped YBCO targets. This supports our earlier conjecture that formation of AgO in the plume and its subsequent dissociation at the elevated substrate temperature (since AgO is unstable above 350 °C) provides active oxygen to the YBCO lattice, thereby increasing oxygen incorporation during growth of YBCO thin films. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359694
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  • 5
    Electronic Resource
    Electronic Resource
    Surface resistance and residual losses of Ag-doped YBa2Cu3O7−δ thin films on sapphire (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 4116-4118 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-quality Ag-doped YBa2Cu3O7−δ thin films have been grown by laser ablation on R-plane 〈11¯02〉 sapphire without any buffer layer. Thin films have been found to be highly c-axis oriented with Tc=90 K, transition width ΔT≤1 K, and transport Jc=1.2×106 A cm−2 at 77 K in self-field conditions. The microwave surface resistance of these films measured on patterned microstrip resonators has been found to be 530 μΩ at 10 GHz at 77 K which is the lowest reported on unbuffered sapphire. Improved in-plane epitaxy and reduced reaction rate between the substrate and the film caused due to Ag in the film are believed to be responsible for this greatly improved microwave surface resistance. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359496
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  • 6
    Electronic Resource
    Electronic Resource
    Surface resistance, residual losses, and granularity in Ag-doped YBa2Cu3O7−δ thin films (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4258-4260 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied microwave surface resistance Rs and residual resistance Rres in undoped and Ag-doped laser ablated thin-film YBa2Cu3O7−δ microstrip resonators on LaAlO3 substrates. While the undoped films showed a frequency dependence Rs∝fp, where p=1.9±1, Ag-doped films showed p=1.6±1 and 1.4±1 for 5 and 10 wt % Ag doping, respectively. Lower p values and higher Rres observed in Ag-doped films indicate a metallic contribution. However, the advantage of Ag-doped films has been shown to be at 77 K at which they not only have a lower Rs but also a low dRs/dT, thus making them superior to undoped films for microwave devices operating at 77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355965
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  • 7
    Electronic Resource
    Electronic Resource
    Microstructural study of yttria stabilized zirconia buffered sapphire for YBa2Cu3O7−δ thin films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 940-946 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Yttria stabilized zirconia (YSZ) buffer layers were grown by rf-magnetron sputtering on the r (11¯02) plane of sapphire for YBa2Cu3O7−δ (YBCO) thin film deposition. Microstructural changes of YSZ buffer layers grown using different sputtering conditions (5, 10, and 20 mTorr; Ar/O2 gas mix ratio of 9:1 and 1:1) were monitored by atomic force microscopy (AFM). Films grown using a lower oxygen partial pressure (5 mTorr) and a higher Ar/O2 ratio (9:1) showed smooth surface morphology and the average surface roughness increased with an increase in oxygen partial pressure. YBCO films in situ grown by pulsed laser deposition on sapphire with a YSZ buffer layer deposited using optimized sputtering parameters (5 mTorr gas pressure, 9:1 Ar/O2 ratio) yielded the highest critical density, Jc≈4.5×106 A cm−2 at 77 K. An excellent correlation between microstructure and Jc has been found and AFM has proved to be important for the study of the microstructure of films. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360876
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  • 8
    Electronic Resource
    Electronic Resource
    Improved microwave performance of Ag-doped Y1Ba2Cu3O7−δ thin film microstrip resonators (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5105-5108 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microwave transmission properties of undoped and Ag-doped laser ablated thin film Y1Ba2Cu3O7−δ microstrip resonators have been studied both on 〈100(approximately-greater-than) MgO and 〈100(approximately-greater-than) LaAlO3 substrates at X-band frequencies. While the Q factor and microwave surface resistance, Rs, of undoped films showed better performance on LaAlO3 as compared to that on MgO, Ag-doped films on LaAlO3 showed far greater improvement as reflected not only by a decrease in Rs but also by a total absence of its microwave power dependence up to 13 dBm at 77 K. These results are explained as due to the influence of Ag in increasing the grain size and grain alignment and thus, significantly decreasing the density of grain boundary weak links which are known to affect the microwave transmission in high temperature superconductor films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353783
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  • 9
    Electronic Resource
    Electronic Resource
    PbTiO3 thin films on Si(100) as potential varistor material (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3637-3639 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have shown that the aqueous sol derived thin films of PbTiO3 on Si(100) substrate exhibit strong varistor type of behavior for certain annealing conditions. Current–voltage (I–V) characteristics depend upon the processing conditions. The behavior is explained by grain boundary limited conduction model. Since the resistance of the grain boundaries varies with the processing conditions, grain boundaries in all samples do not act as potential barriers to the charge carriers. The film postannealed at 700 °C, possessing high nonlinear coefficient (α) with low breakdown voltage per barrier (Egbl), could be used as a protection device in current-sensitive electronic equipment. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120465
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  • 10
    Electronic Resource
    Electronic Resource
    c-axis oriented ferroelectric thin films of PbTiO3 on Si by pulsed laser ablation (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1582-1584 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have deposited single phase c-axis oriented ferroelectric thin films of PbTiO3 on Si(100) by pulsed laser ablation technique in situ. It has been shown that the formation of a nonferroelectric, Pb2Ti2O6 pyrochlore phase at the interface could be avoided by raising the substrate temperature. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116687
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