摘要:

Aninsitumicrowave plasma‐enhanced metalorganic chemical vapor deposition process was used to fabricate highlyc‐axis oriented YBa2Cu3O7−xsuperconducting thin films on metallic Ag substrates. The films were deposited at a reduced substrate temperature of 740 °C in about 270 Pa of N2O ambient. Magnetic susceptibilities versus temperature of the as‐deposited films show attainment of zero resistance of 85 K and composition of single (highTc) phase. X‐ray diffraction measurements reveal that the films deposited at 740 °C have highly preferential orientation of the crystallitecaxes perpendicular to the substrate surface.

ISSN:0003-6951    

DOI:10.1063/1.104400

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Using our recently developed pulsed critical current density (Jc) measuring system, theJcof the highJcmelt‐textured YBa2Cu3O7−&dgr;(Y123) bulk samples has been determined.I‐Vcurves with a voltage resolution of 0.5 &mgr;V were obtained, and transportJc’s along thea‐bplane (Jc∥a‐b) as high as 7.2×1 04A/cm2were extracted. These results are comparable to the values obtained magnetically. On the other hand, transportJcalong thecaxis (Jc∥c) were found to be two orders of magnitude smaller, even though the magneticJc∥cis only about five times smaller thanJc∥a‐b. We suggest that for the high‐temperature superconducting materials which are highly anisotropic, caution should be taken when using the nontransport magnetic methods to determineJc.

ISSN:0003-6951    

DOI:10.1063/1.104401

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have fabricated all‐highTcsuperconducting tunnel junctions in the material Ba1−xKxBiO3. The junctions are of very high quality and have a Josephson supercurrent. For the low‐resistance junctions, theIcRproduct approaches the theoretical limit.

ISSN:0003-6951    

DOI:10.1063/1.104402

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The Grenoble drop tube first experiments and results on pure W and Re droplets are presented. High absolute amounts of undercooling have been reached (530 K for W and 975 K for Re). The solidified samples are single crystals in the case of W and polycrystals in the case of Re. The liquid‐solid interfacial energy is derived from these experiments.

ISSN:0003-6951    

DOI:10.1063/1.104403

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have used the extreme sensitivity of electron tunneling to variations in electrode separation to construct a novel, compact displacement transducer. Electrostatic forces are used to control the separation between the tunneling electrodes, thereby eliminating the need for piezoelectric actuators. The entire structure is composed of micromachined silicon single crystals, including a folded cantilever spring and a tip. Measurements of displacement sensitivity and noise are reported. This device offers a substantial improvement over conventional technology for applications which require compact, highly sensitive transducers.

ISSN:0003-6951    

DOI:10.1063/1.104432

出版商:AIP    

年代:1991

数据来源: AIP