摘要:

Single-phasec-axis alignedLa1.85Sr0.15Cu1−yZnyO4films were grown by pulsed laser deposition with Zn contents up to a value ofyof 0.12. The film properties indicate the existence of defects, in addition to the Zn impurities, that are unintentionally introduced during the film growth. These defects are probably oxygen vacancies, and have a distinctly different effect onTcfrom the Zn. The separation of the two effects resolves earlier ambiguities in the observed rates ofTcdepression. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122602

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We present a model for the description of the resistive transition in hot-electron bolometer mixers. We show that the transition is a property of a superconducting microbridge connected to normal conducting cooling pads. Using the concepts of the superconducting proximity effect, charge-imbalance generation, and Andreev reflection, we have calculated the resistance versus temperature of the device and demonstrate its dependence on the length of the microbridge, both theoretically and experimentally. The analysis reopens the question of the relationship between the resistive transition and the situation in which the device is optimally operated as a heterodyne mixer. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122603

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

SingleCo/Al2O3/NiFeand doubleCo/Al2O3/Co/Al2O3/NiFeplanar tunnel junctions were grown by sputtering and subsequently patterned in a four-step process using optical lithography. TheAl2O3barriers are formed by radio frequency plasma oxidation of 1.5 nm aluminum layers. The double junctions exhibit three clear resistance levels depending on the relative configuration of the magnetizations. Both single and double junctions exhibit maximum magnetoresistance (MR) ratios above 10&percent; at room temperature and 20&percent; at 30 K and a decrease of MR with increasing bias voltage. With regard to its low bias value, the MR is reduced by a factor of 2 at 0.26 V for the single junctions and at values above 0.8 V for the double junctions. The decay of the MR of double junctions with bias voltage is significantly slower than expected from two independent junctions in series. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122604

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We present a dual-frequency electromagnetic scanning probe and apply it for quantitative mapping of the sheet resistance of conducting films. The high-frequency (82 GHz) mode is used for image acquisition, while the low-frequency (5 MHz) mode is used for distance control. We measure magnitude and phase of the near-field microwave reflectivity from conducting films of varying thickness and develop a model which accounts fairly well for our results. This brings us to a quantitative understanding of the contrast in the microwave near-field imaging using an aperture probe, and allows us to achieve quantitative contactless characterization of conducting layers with sheet resistance even below 2 &OHgr;. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122605

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have developed an electron lithography method, hot electron emission lithography, which is capable of printing integrated circuits with an exposure time of only a few seconds. The basic design and fabrication of the patterned electron emitting mask made by standard metal–oxide–semiconductor technology will be discussed, and its applicability in a simple 1:1 e-beam stepper will be demonstrated. Patterns with a minimum feature size of 160 nm have been printed successfully. Further improvements in resolution to 50 nm appear to be possible. ©1998 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.122606

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Effective pyroelectric coefficients as large as 5 &mgr;C/cm2 °C, with peak responsivities at approximately 50 °C, were obtained from compositionally graded barium strontium titanate ferroelectric thin film devices formed on silicon using unbalanced magnetron sputter deposition. These effective pyroelectric coefficients are nearly two orders of magnitude larger than those observed from conventional pyroelectric thin film ferroelectric detectors. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122607

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The classical theory of Cabrera–Mott describes passivation film formation on metals, where they predicted that this film grows as a uniform layer due to a field-enhanced ionic transport mechanism. Here we present experimental evidence, based onin situtransmission electron microscopy of copper oxidation, that the passivation film nucleates and grows as oxide islands, not as a uniform layer. We propose an alternative phenomenological theory to describe passivation film formation, based on island growth followed by coalescence. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122608

出版商:AIP    

年代:1998

数据来源: AIP