摘要:

The polarization characteristics of light emitting porous Si films is investigated. The degree of polarization increases to well over 20% when the excitation wavelength is at the blue edge of the emission band and decreases with decreasing excitation wavelength. The steady‐state value of the degree of polarization is established in less than 1 &mgr;s. The experimental results bear qualitative agreement with a quantum‐wire model. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114938

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Pulsed terahertz spectroscopy is used to determine the superfluid response of a YBa2Cu3O7−&dgr;film under both thermal and optical stimulation. The coherent, time‐domain technique is used in a novel configuration to directly measure the complex conductivity of the film versus temperature and continuous‐wave laser illumination. At 0.6Tc, the superfluid shows an identical response regardless of whether the stimulus is thermal or optical. This contrasts with the behavior of the superfluid at 0.26Tc, where dramatic differences are observed depending on whether the sample is heated or subjected to optical illumination. It is suggested that these differences arise from an enhanced contribution due to quantum effects, and thus also from a strong temperature dependence of the quasiparticle recombination time at low temperatures. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114939

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Improved strain sensitivity of critical currentsIcof the multicored over the monocored (Bi,Pb)2Sr2Ca2Cu3O10–Ag tapes is shown for bending strains, but not for axial tensile strains. The improved mechanical tolerance is due, in part, to a better alignment of the Bi‐cuprate platelets achieved in the multicored tapes. Furthermore, the difference in the response to these tapes to axial tensile and bending strains is due to the difference in the precise manner in which the strains are applied to the tapes. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114940

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Textured YBa2Cu3O7−xthick films (thickness ≊1 mm) were fabricated by vacuum filtration in an applied magnetic field (H=7 T). Platinum (1 wt %) was incorporated to induce liquid phase‐assisted densification in films fired between 960 and 1030 °C in oxygen. The transport critical current densities (Jct) of films fired to 1030 °C exhibited nearly field insensitive behavior betweenH=0–3 T (H∥c‐axis) at 77 K, withJct≊2500 A/cm2and corresponding critical currents (Ic) of nearly 100 A atH=1 T. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115443

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A novel giant magnetoresistance memory effect has been observed in epitaxial Nd0.7Sr0.3MnOzthin films which have previously been found to exhibit a linear increase in conductivity on first application of magnetic fieldB. The resistivity of the films depends not only on the instantaneous applied field but also on the magnetic history of the sample. AtTwell below the temperatureTp, where the zero‐field resistivity has a peak, the film enters a high‐conductivity state (upon application of a magnetic field) which persists even whenBis reduced to zero. The original ‘‘zero’’ field state is not recovered until the sample is warmed toT∼Tp. Surprisingly, the dc magnetization exhibits only a weak irreversibility while the magnetoconductivity is markedly hysteretic. A possible explanation is proposed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115444

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Nickel–aluminum nitride films were prepared by reactive sputtering of a nickel aluminide plate in a nitrogen plasma. The initial product is a nanocomposite containing the nickel as the nitride, Ni3N, in aluminum nitride. Heating in vacuum to 500 °C causes selective decomposition of the thermally labile nickel nitride leaving the aluminum nitride unaffected. The nickel nanocomposite is of interest for potential applications as recording media, as are other finely divided dispersions of ferromagnetic metals in insulating matrices. The nickel–aluminum nitride nanocomposite shows a moderate coercive field of 35 Oe at 300 K and, in common with ultrafine particles of ferromagnetic materials, shows superparamagnetic behavior. The Ni3N/AlN nanocomposite was subjected to localized heating with the focused beam of an argon‐ion laser; this created features several microns in width that could be imaged with a magnetic force microscope, thus confirming its potential as a high density data storage medium. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115445

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have calculated the spatial distribution of the electrostatic potential created by an unbalanced chargeqin one of the conducting electrodes of a long, uniform, linear array of small tunnel junctions. The distribution describes, in particular, the shape of a topological single‐electron soliton in such an array. An analytical solution obtained for a circular cross‐section model is compared with results of geometrical modeling of a more realistic structure with square cross section. These solutions are very close to one another, and can be reasonably approximated by a simple phenomenological expression. In contrast to the previously accepted exponential approximation, the new result describes the crossover between the linear change of the potential near the center of the soliton to the unscreened Coulomb potential far from the center, with an unexpected ‘‘hump’’ near the crossover point. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115446

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The charge balance in the hot filament method of depositing diamond is explored using a novel experimental arrangement. A correlation between ion activity and the growth of diamond is drawn. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115447

出版商:AIP    

年代:1995

数据来源: AIP