摘要:

Measurements of TlBaCaCuO‐based dc superconducting quantum interference devices (SQUIDs) performed using a practical feedback circuit gave a flat frequency response and an energy sensitivity of 6×10−30J/Hz at 5 kHz and 77 K with an 80 pH SQUID. Flux‐locked loop operation was demonstrated to be strongly effective in eliminating the magnetic field hysteresis of the SQUID. The SQUIDs were operated in the flux‐locked loop at temperatures over 90 K and the 1/fnoise was found to decrease with increasing temperature near 77 K.

ISSN:0003-6951    

DOI:10.1063/1.101141

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Interfacial interaction between Bi2Sr2CaCu2O8+&dgr;highTcsuperconductor and indium metal has been investigated using photoemission measurements. The results indicate that a sharp interface is possible and the interfacial interaction is restricted to a region of ∼5 A˚ thickness. In this region, there is a substantial CuO and SrO bond breaking.

ISSN:0003-6951    

DOI:10.1063/1.101564

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We study the propagation of terahertz bandwidth electrical pulses on high critical current densityc‐axis oriented YBa2Cu3O7−&dgr;(YBCO) coplanar transmission lines deposited epitaxially on the low dielectric loss substrate lanthanum aluminate (LaAlO3). The losses on the YBCO transmission line are lower than on an equivalent gold line on the same substrate at temperatures below 50 K. At higher temperatures, absorption and dispersion of the ultrashort electrical pulses are observed in reasonable agreement with Mattis–Bardeen theory.

ISSN:0003-6951    

DOI:10.1063/1.101519

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

As a precursor of highTcsuperconductors, glasses in the system BixCaSrCu2Ow(x=1.5,2.7) have been prepared using twin‐roller and metal‐plate quenching procedures. Transition range viscosities have been measured on samples as thin as 0.02 mm using the beam‐bending method with a technical modification. From the viscosity data, the system Bi‐Ca‐Sr‐Cu‐O can be characterized as a ‘‘fragile’’ liquid like the ZrF4‐based fluorides. The possibility of drawing fibers of highTcsuperconductor precursors is discussed on the basis of the temperature dependence of viscosity.

ISSN:0003-6951    

DOI:10.1063/1.101565

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We report the formation of excellent quality epitaxial YBa2Cu3O7films on (100) SrTiO3and (100) ZrO2(yttria stabilized) substrates in the temperature range of 500–650 °C by XECl excimer laser ablation in a 0.2 Torr oxygen ambient. By applying a dc bias voltage of +300 V to an interposing ring, we were able to reduce the substrate temperatures from 650 to 500 °C for obtaining epitaxial films. The quality of the epitaxial films was found to decrease with temperature, particularly below 550 °C. The thickness of the superconducting films was varied from 500 to 5000 A˚ with superconducting transition temperaturesTc(zero resistance) varying from 87 to 90 K for 650 °C deposits. The critical current densityJcof films was found to vary linearly with temperature with values of (zero magnetic field at 77 K) 5.0×106and 1.0×106for films deposited at 650 °C on (100) SrTiO3and (100) yttria‐stabilized zirconia substrates, respectively. X‐ray diffraction, transmission electron microscopy, electron channeling patterns, and Rutherford backscattering (RBS)/channeling showed excellent epitaxial quality of films on both substrates with best values of minimum ion channeling yield of 3.5% on (100) SrTiO3substrates.

ISSN:0003-6951    

DOI:10.1063/1.101520

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Laser surface ablation of polymethylmethacrylate by ultrafast 0.532 &mgr;m pulses is studied using an imaging apparatus with 2 ps resolution. Coherent two‐photon absorption rapidly heats the sample, inducing explosive thermal decomposition. Electron microscopy is used to characterize the damaged surface. Ultrafast imaging shows that surface damage is accompanied by the production of a transient optical filament. The intensity dependence shows that self‐focusing results from an accumulative, rather than instantaneous, relaxation of the transient refractive index. At all intensities, there is a 20 ps delay before ablation commences.

ISSN:0003-6951    

DOI:10.1063/1.101521

出版商:AIP    

年代:1989

数据来源: AIP

ISSN:0003-6951    

DOI:10.1063/1.101103

出版商:AIP    

年代:1989

数据来源: AIP