摘要:

Films of the highTcBi‐Sr‐Ca‐Cu‐O superconductor have been prepared by organometallic chemical vapor deposition using the volatile metalorganic precursors Cu(acetylacetonate)2, Sr(dipivaloylmethanate)2, and Ca(dipivaloylmethanate)2, and triphenylbismuth. Deposition is carried out at 2 Torr with argon as the carrier gas and oxygen and water vapor as reactants. Film growth rates of 2–3 &mgr;m/h are achieved. After annealing under oxygen, energy dispersive x‐ray analysis and x‐ray diffraction data reveal that such films on [100] single‐crystal MgO consist predominantly of the Bi2(Sr,Ca)3Cu2Ox,Tc=85 K, phase and have preferential orientation of the crystallitecaxes perpendicular to the substrate surface. Four‐probe resistivity measurements reveal the onset of film superconductivity at ∼110 K and zero resistance by 75 K.

ISSN:0003-6951    

DOI:10.1063/1.101481

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Superconducting glass ceramics of Bi0.8Pb0.2SrCaCu1.5Oy(sample A) and BiPb0.2SrCaCu1.5Oy(sample B) have been prepared by using the melt quenching method. It was found that the volume fraction of the highTcphases in sample A annealed at 830 or 840 °C for 250 h was much higher than that in sample B. The annealed (840 °C, 250 h) sample A exhibited superconductivity with aTc(zero) of 100 K and a critical current density (77 K, zero magnetic field) of 120 A/cm2.

ISSN:0003-6951    

DOI:10.1063/1.101482

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The current‐voltage characteristic at 77 K of a constricted thallium‐based highTcsuperconducting sample exhibits Shapiro steps and is modulated by a dc magnetic field. This device operates as a dc superconducting quantum interference device with a maximum critical currentIcof 350 &mgr;A, a dynamic resistance up to 30 &OHgr;, and a transfer parameter as high as 1.5 mV/&Fgr;0for an estimated inductance of 40 pH. The measured spectral density of the flux noise in the white noise region is 1.4×10−10&Fgr;20/Hz. The 1/fnoise at 1 Hz is 2.1×10−7&Fgr;20/Hz and is reduced by a factor of 10 by a synchronous detection. Implications for thin‐film devices are examined.

ISSN:0003-6951    

DOI:10.1063/1.101356

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have studied the effect of visible and near‐infrared light on the electrical properties of superconducting thin films of YBa2Cu3O7−&dgr;. The responses we observe can all be explained in terms of light heating the film to a temperature above the superconducting transition. No evidence that the light directly affects superconductivity was found.

ISSN:0003-6951    

DOI:10.1063/1.101483

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have studied the effect of ion beam irradiation on the microstructure of epitaxial YBa2Cu3O7−&dgr;thin films. The ion beam induced defects are found to cluster in small (<100 A˚) disordered areas. The size and density of the disordered areas are found to increase with the ion fluence. The presence of these small disordered areas can lead to the reduction of phase coherence of the electron pair wave function. Ion beam irradiation is also found to reduce the orthorhombicity of the lattice structure. A new incommensurate superlattice phase due to ion beam induced defect ordering has also been observed.

ISSN:0003-6951    

DOI:10.1063/1.101484

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

An attempt to obtain soft magnetic materials with high saturation magnetic flux density and thermal stability has been carried out with respect to a multilayered type of films containing Fe‐N prepared by two‐source magnetron rf sputtering. The addition of small amounts of elements such as Al is effective in improving soft magnetic properties of Fe‐N films. Multilayered films of Fe‐Al‐N intervened by thin Si‐N layers showed softer magnetic properties than the Fe‐Al‐N single layer films and also showed high thermal stability. Typically, Fe‐Al‐N (500 A˚)/Si‐N (12 A˚) multilayered films exhibited a saturation magnetic flux density of 20 kG, a coercivityHcof 0.3 Oe, and a permeability &mgr; of 1900 at 5 MHz after annealing at 550 °C for 1 h.

ISSN:0003-6951    

DOI:10.1063/1.101561

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

By using high dielectric constant and low‐loss dielectric material such as quartz, alumina, or sapphire and by specifically configuring the waveguide structure, we have succeeded in designing a waveguide for the millimeter/submillimeter wavelength range which yields an attenuation constant for the dominant mode that is more than 100 times below that for an equivalent circular dielectric rod with identical cross‐sectional area. This waveguide takes the form of a thin dielectric ribbon surrounded by lossless dry air and possesses an attenuation constant as low as 20 dB/km. Analytical results on the attenuation constant and field extent of the dominant mode on this ribbon structure for several promising materials are given. Experiments have also been performed on ribbon guides made with rexolite. Excellent agreement was found between predicted and measured results.

ISSN:0003-6951    

DOI:10.1063/1.101485

出版商:AIP    

年代:1989

数据来源: AIP