摘要:

Normal state YBa2Cu3O7−&dgr;films, epitaxially grown ‘‘off‐caxis’’ with tilt angles up to 20° are shown to be fast thermoelectric detectors for radiation from UV to far infrared wavelengths. Upon radiation heating of the tilted films a thermoelectric voltage arises due to the anisotropy of the thermopower in YBa2Cu3O7−&dgr;. The response time is limited by the decaying temperature gradient and thus by heat diffusion. For thin films we have measured a response time from ≲1 ns in the UV to ∼5 ns in the far infrared. Because of the wavelength dependent reflectivity, the responsivity of the films varies between 0.5 V/MW and 20 V/MW. Thus, thin tilted YBa2Cu3O7−&dgr;films can be used as fast room temperature detectors over a wide spectral range. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113337

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report evidence for the reduction of long range lattice order caused by slight departures from the optimal growth temperature in fully doped (x≊0.9) YBa2Cu3O6+xfilms deposited by ion‐beam sputtering on ⟨001⟩ SrTiO3. We estimate the characteristic length of this disorder from the broadening &Dgr;&Vthgr; of the ⟨005⟩ x‐ray diffraction rocking curve. The depression of superconductivity and normal conductivity scales as &Dgr;&Vthgr; and disappears when the in‐plane lattice coherence lengthrc∼1/&Dgr;&Vthgr; is larger than ≊10 nm. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113338

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We propose a novel experimental technique for investigating the giant magnetoresistance effect measured with the current perpendicular to the layer plane (the so‐called CPP geometry). Using holographic laser interference nanofabrication techniques and anisotropic etching the surface of semi‐insulating InP substrates is patterned into V‐shaped grooves of 0.2 &mgr;m width. Subsequently, a magnetic multilayer can be evaporated under an angle with the substrate normal, naturally resulting in a CPP‐like magnetoresistance configuration. The technique is illustrated for Co/Cu multilayers, for which we present magnetization and magnetoresistance experiments. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113339

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An aluminum coated tapered optical fiber is rigidly attached to one of the prongs of a highQpiezoelectric tuning fork. The fork is mechanically dithered at its resonance frequency (33 kHz) so that the tip amplitude does not exceed 0.4 nm. A corresponding piezoelectric signal is measured on electrodes appropriately placed on the prongs. As the tip approaches within 20 nm above the sample surface a 0.1 nN drag force acting on the tip causes the signal to reduce. This signal is used to position the optical fiber tip to about 0 to 25 nm above the sample. Shear forces resulting from the tip‐sample interaction can be quantitatively deduced. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113340

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Nonlinear, time‐dependent calculations have been carried out for closed‐cavity gyrotron oscillations using a strongly modulated electron beam. It is found that radiation pulses of width 200 ps can be generated with carrier frequency of 18 GHz at over 10% efficiency. The gyrotron features a tapered wall radius to allow an equidistant spectrum of cavity modes. Evidence of a disruption in locking is found at electron beam currents several times the start oscillation value. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113341

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Simultaneous time and space resolution of the monochromatic vacuum ultraviolet emission from an excimer laser‐ablated plasma has yielded quantitative information on the plasma generation and velocity. From the time‐resolved spectral data, plasma velocities were measured and found to be ∼2.5×106cm/s. The observed radiation time profile at the target surface reflects essentially the dynamics of the laser pulse absorption. Material continues to be ejected from the target for more than 100 ns after the end of the laser pulse. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113342

出版商:AIP    

年代:1995

数据来源: AIP