摘要:

First-principles local density cluster calculations show that a Schottky junction may be formed in a nanoscale Au–Si(111) systems. The calculated Schottky barrier height value depends on the nanosystem’s geometry and varies from 0.5 to 1.35 eV. The total energy calculations show that the metallic gold/silicon system is unstable if the thickness of the gold is more than 2–3 monolayers. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364298

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on the investigation of a low resistance Pd/Zn/Pd contact top-InGaAsP (&lgr;=1.14 &mgr;m). The contact had a minimum contact resistivity of ∼3×10−7&OHgr; cm2to the substrate doped to 2×1018cm−3. The samples showed rather uniform surface and interfacial morphologies. X-ray studies showed the formation of a PdZn phase for samples annealed below 400 °C and this phase started to decompose at temperatures higher than 400 °C. Pd-III compounds (Pd2Ga5and PdIn3) also started to form for annealing temperatures higher than 400 °C. The ohmic behavior can be understood in terms of the decomposition of the PdZn phase and the formation of Pd-III compounds for samples annealed at 400 °C or higher. The thermal stability of this contact at 400 °C was found to be stable, which is important for device applications. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363974

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report the use of a layered foil as a positron rectifying device for transmission geometry positron moderation and remoderation, thereby increasing the efficiency of such devices. Positron transmission through foils consisting of a 10 nm W layer on top of a 100 nm Mo foil has been measured. The measurements are compared with similar results for a 100 nm W foil. A strong rectifying effect with a forward to reverse current ratio of more than 10 is observed making this type of well matched layered foils an obvious candidate for positron remoderation. Retarding energy spectra of the transmitted positrons were obtained and measurements of Doppler broadening and surface branching ratios were performed to further characterize the foils. The obtained transmission results again reveal the discrepancy in positron implantation profiles for thin foils between experiments and existing theory. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363975

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A microstrip T-transducer excites forward volume magnetostatic waves (MSWs) in a [BiLu]3Fe5O12film. An optical beam is edge coupled into the film and the transverse MSW–optical interaction is observed at high microwave power levels. Using the coupled mode equations, we demonstrate that a T-transducer causes the intensity of the diffracted beam to be a product of terms involving the magneto-optic coupling coefficient(&kgr;)and the phase mismatch between the optical guided modes and the MSWs. Taylor series expansions for&kgr;and the MSW wave number(&bgr;)are used to obtain an analytic expression for the MSW–optical interaction. The dependence on&bgr;causes a shift in the interaction spectrum with increasing power. After correcting for this shift, the residual dependence on power is attributed to a quadratic correction to the dynamic magnetization which in turn affects&kgr;. We demonstrate how the quadratic dependence plays an important role in accurately determining an expansion for the MSW dispersion relation. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363970

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The soft magnetic properties of the nanocrystalline Fe–M–B (M=Zr,Nb) alloys, which exhibit a high saturation flux density(Bs)above 1.5 T as well as a high effective permeability(&mgr;e)above 30 000 at 1 kHz, were found to be improved by adding small amounts of Cu and by optimizing the chemical composition. The addition of Cu to the alloys decreases the bcc grain size. The excellent soft magnetic properties (a high&mgr;eof 100 000 at 1 kHz combined with a highBsof 1.53 T) can be achieved in the region where small grain size, as well as nearly zero-magnetostriction are obtained, which is attained in the compositional range aroundFe84Nb3.5Zr3.5B8Cu1.The soft magnetic properties can be further improved by low temperature annealing before the crystallization treatment, probably as a result of a decreased grain size distribution in the crystallized state. Consequently, the&mgr;ereaches the maximum value of 120 000 for the nanocrystallineFe84Nb3.5Zr3.5B8Cu1alloy. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363976

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Thin films of the ferromagnetic Heusler alloy NiMnSb, of interest for magnetic multilayer devices because of their predicted half-metallic (i.e., 100&percent; spin-polarized) transport properties, have been successfully deposited by rf magnetron sputtering from a single composite target. A novel combination of low argon gas pressure, low deposition rates, and moderate substrate temperatures (250–350 °C) are shown to result in high-quality, low-roughness polycrystalline films of theC1b-type crystal structure, with thicknesses as low as 100 Å, without the need for any post-deposition annealing. The structural properties of these films, determined by x-ray diffraction and atomic force microscopy are presented as a function of deposition conditions. The magnetic properties and resistivity are consistent with bulk MiMnSb, which suggests that they will be effective as spin-polarized conducting layers in multilayer thin-film structures. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363977

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The required bias field of a sperimagnetic film is governed by a finite exchange coupling coefficient (&lgr;) mainly determined by the subnetwork coupling. From the study of a series of (Dy,Tb)FeCo films at compensation composition, it is found that &lgr; is mainly determined by the concentration of the rare earth components. Moreover, the exchange integral between rare earth and transition metal subnetworks can be derived from &lgr; so that the number of uncertain parameters for mean field modeling is reduced. Accordingly, the bias field required for magneto-optical recording is mainly proportional to &lgr; that can be obtained quantitatively from either measurement and/or mean field modeling. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363978

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Spherical, monodispersed, ferromagnetic, metallic particles of different compositions were obtained by the polyol process with a mean radius ranging from 30 nm to 1 &mgr;m. The microwave permeability of metallic particles-dielectric matrix composites were studied in the range of 0.1–18 GHz. In the wide particle size range investigated, a size dependence of the dynamic permeability was observed. Whereas the permeability of micrometer-sized particles shows a single resonance band, the permeability of submicrometer-sized particles exhibits several narrow resonance bands which are shifted to high frequencies with decreasing particle size. This latter behavior was found to be in qualitative agreement with the exchange resonance modes calculated by Aharoni. That theory, however, gives anR−2dependence on particle radius for the resonance frequency instead of theR−0.66dependence observed experimentally. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363979

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Lead zirconate titanate (PZT) thin films were prepared by reactive coevaporation with high-concentration ozone. PZT thin films that demonstrate the highest charge storage density (280 fC/&mgr;m2at 1.5 V for 75-nm-thick film) yet reported have been fabricated. No fatigue was observed after 1011polarization switching cycles even though a Pt electrode is used. A low leakage current of <10−7A/cm2at 1.5 V was attained. These PZT films are promising candidates of an alternative capacitor dielectric for dynamic random access memory (DRAM) and ferroelectric nonvolatile memories. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363980

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Elastic, dielectric, and piezoelectric constant matrix elements of a “single crystalline’’ (SC) film of vinylidene fluoride trifluoroethylene copolymer, P(VDF/TrFE), in which the orthorhombic [001] and [110] axes of fully extended chain crystals are preferentially oriented parallel to the stretching axis and normal to the surface, respectively, were measured at temperatures ranging from 10 K to the Curie point (402–404 K) by using a piezoelectric resonance method. All of the electromechanical coupling factors (k31,k32,k33,k24, andk15) are larger than those of conventional lamellar crystalline films. Some of the matrix elements for a P(VDF/TrFE) single crystal are derived from the measured values of constant matrix elements for the SC film. Some features characteristic of the SC film are revealed. The SC film has a large Young’s modulus for the stretching direction (1/s11) (121 GPa at 10 K). The properties related to the molecular motions along the chain axis, such as 1/s11, shear stiffness constantc55, shear piezoelectric constante15, etc., exhibit strong relaxations around 250 K. The origin of these relaxations in the crystalline phase is discussed. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364300

出版商:AIP    

年代:1997

数据来源: AIP