摘要:

We describe a 1 THz quasioptical SIS mixer which uses a twin‐slot antenna, an antireflection‐coated silicon hyperhemispherical lens, Nb/Al‐oxide/Nb tunnel junctions, and an aluminum normal‐metal tuning circuit in a two‐junction configuration. Since the mixer operates substantially above the gap frequency of niobium (&ngr;≳2&Dgr;/h∼700 GHz), a normal metal is used in the tuning circuit in place of niobium to reduce the Ohmic loss. The frequency response of the device was measured using a Fourier transform spectrometer and agrees reasonably well with the theoretical prediction. At 1042 GHz, the uncorrected double‐sideband receiver noise temperature is 840 K when the physical temperature of the mixer is 2.5 K. This is the first SIS mixer which outperforms GaAs Schottky diode mixers by a large margin at 1 THz. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115915

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have measured the tunneling conductance of YBa2Cu3O7/Pb planar tunnel junctions fabricated on superconducting (110)‐oriented YBa2Cu3O7thin films exhibiting zero‐resistance superconducting transition temperatures (Tc’s) between 88 and 89.5 K. The conductance is the same as we and other groups have measured on (100)‐ and (103)‐oriented YBa2Cu3O7/Pb junctions and quantitatively different fromc‐axis tunneling. Theab‐plane transport is comparable to that measured in (001)‐oriented YBa2Cu3O7thin films, and the transport anisotropy varies between 65 and 80 from 300 K toTc, respectively. This anisotropy is higher than that previously measured in both (110)‐oriented andc‐axis aligned (100)‐oriented films, but it is comparable to that measured in single crystals. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115916

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The magnetic penetration depth &lgr; of laser ablated 5 wt % Ag‐doped YBa2Cu3O7−&dgr;thin films has been measured in the thickness range 1500–4000 A˚ and in the temperature range 18–88 K using microstrip resonator technique. A correlation of &lgr;(T) with the film microstructure observed with atomic force microscopy has shown that &lgr;(T) depends critically on the film microstructure. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115917

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

HgBa2Ca2Cu3O8+&dgr;(Hg‐1223) superconducting thin films of about 0.3 &mgr;m in thickness have been successfully synthesized. The process involves depositing films (∼ 1 &mgr;m thickness) of Ba2Ca2Cu3Oxon a SrTiO3substrate by pulse laser ablation technique and implanting mercury ions into this deposited film, followed by annealing at oxygen atmosphere. The films so obtained show a relatively wide superconducting transition temperature up to 118 K, as determined magnetically, which is similar to that of underdoping bulk Hg‐1223. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115887

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The transfer function of the imaging process in magnetic force microscopy is calculated theoretically using a reciprocal force based approach. The reciprocal force is that exerted on the sample by the tip, and according to Newton’s third law, is simply equal but opposite to the force exerted on the tip by the sample. The method allows the role of the tip in the imaging process to be represented in a particularly simple fashion, and the system transfer function is shown to depend on the Fourier transform of the field distribution produced by the microscope tip at the surface of that tip, an exponential spacing loss term reflecting the separation of the tip and the sample and finally a loss term dependent on the sample thickness. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115888

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have performed time‐resolved magneto‐optical Kerr effect measurements with picosecond resolution in a pump‐probe experiment using a 30 ps pulsed dye laser (&lgr;=577 nm). Two typical magneto‐optical storage materials were investigated: a Gd13Tb12Fe75amorphous film evaporated on a glass substrate and a Co/Pt multilayer on a Si substrate. Curie‐point thermomagnetic writing has been performed in less than 2 ns with the Co/Pt multilayer, whereas with the amorphous film magnetization reversal could not be observed within 6 ns. These differences in switching times are likely the consequence of the different thermal conductivities of the substrates. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115889

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The acousto‐optic technique presented by Wevers, Devolder, Leroy, and De Meester [Appl. Phys. Lett.66, 1466 (1995)] was based on the information concerning the phase shift between the incident and the reflected ultrasound at critical angles. Two laser beams were used, one being diffracted by the incident ultrasound, the other being diffracted by the reflected ultrasound. Information concerning the geometrical shape of the sample as well as information concerning the thickness of a thin layer could be obtained from measurements in the near‐field of the light diffraction. In this letter it is shown that using only one laser beam, traveling through the intersection region of both ultrasounds, exact thickness information of the layer can be obtained. Theoretical calculations are derived and compared with practical measurements for a 3 &mgr;m copper layer on a stainless‐steel plate. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115890

出版商:AIP    

年代:1996

数据来源: AIP

ISSN:0003-6951    

DOI:10.1063/1.116788

出版商:AIP    

年代:1996

数据来源: AIP