摘要:

As nickel and silicon have no absorption edges in the “water window” (2.4–4.4 nm), these materials form suitable components for multilayers to be applied as optical components in this wavelength region. The practical feasibility of using these components is limited by their chemical reactivity, resulting in intermixing at the interfaces. A procedure, based on the application of ion implantation and ion beam mixing, has been developed to produce silicon nitride and nickel silicide layers. As these processes also cause ion etching, an additional reduction of the surface roughness of the layers has been observed. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366213

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In this article, an analytical model for Type I magnetic contrast enhancement in the scanning electron microscope, achieved by sample tilting, is presented. The model accounts for the energy filtering of the secondary electrons emitted from the sample. The results showed that the optimum sample tilt angle for maximum contrast is a function of the field-distance integral. For small field-distance integrals less than10−7 Tm,corresponding to a weak magnetic field situation, the optimum sample tilt is close to 0°. For large field-distance integrals, the optimum sample tilt angle increases and approaches 45° for a field-distance integral of8×10−6 Tm.©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366214

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A new method for the detection of the geometrical information by the scanning tunneling microscope is proposed. In addition to the bias voltage, a small ac modulation is applied. The nonlinear dependence of the transmission coefficient on the applied voltage is used to generate harmonics. The ratio of the harmonics to the dc current is found to give the width between the sample and the probe, i.e., the geometrical information. This method may be useful to measure materials, where the local-spatial-density of states may change notably from place to place. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366215

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Thermal expansion of the sample or tip in a laser-assisted scanning tunneling microscope (STM) junction can obstruct the study of other phenomena related with STM–light interactions, when photoinduced currents are analyzed. In this article, we show that the thermal contribution is proportional to the average tunneling current and that this can be used to distinguish it from other contributions. Simultaneous tunneling current–voltage and photoinduced current–voltage curves are recorded for highly oriented pyrolitic graphite and gold samples with a Pt tip. We have done the measurements for two different polarizations of the incident beam. We show that theI–Vcurves can be used to discriminate between different mechanisms that appear, producing photoinduced currents. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366216

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A sinusoidal model is proposed to analyze the thermodynamic processes of gas parcels oscillating in a regenerator. The regenerator is considered equivalent to a bundle of capillary tubes with large thermal capacities. With perfect thermal contact between the gas and tube wall and the proper phase shift between velocity and pressure, the overall effect of a gas parcel oscillating in the capillary in one cycle is that it absorbs heat from one lengthwise part of the wall and delivers heat to the other part of the wall within its range of displacement. Each gas parcel working in the regenerator undergoes a thermodynamic cycle. When the work flow is in the same direction as the temperature gradient of the regenerator, it undergoes a heat engine cycle. Otherwise it undergoes a refrigeration cycle. The regenerator can work as a heat engine or as a refrigerator. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366217

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A novel methodology is presented for extraction of the semiconductor electron and hole mobility-lifetime products by x- and &ggr;-ray spectroscopy analysis. The methodology is based on the analysis of spectroscopy results, namely themaximaland theaveragecharge collection efficiencies as discussed below, for different photon energies at various bias voltages. The methodology enables the evaluation of both electron and hole mobility-lifetime products without the need to use &agr; particle measurements. The evaluation is carried out by a single parameter fitting of the models analyzed in this study. Mobility-lifetime products for CdZnTe substrates grown by Bridgman and high pressure Bridgman (HPB) methods are reported and compared. Typical values of&mgr;e⋅&tgr;e=2⋅10−3and&mgr;h⋅&tgr;h=1⋅10−5 cm2/Vare extracted for HPB grown CdZnTe with 10&percent; Zn concentration. Values of&mgr;e⋅&tgr;e=9⋅10−4and&mgr;h⋅&tgr;h=1⋅10−7 cm2/Vare obtained for CdZnTe with 10&percent; Zn concentration grown by the Bridgman method. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366218

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We demonstrate a simple method for plasmon surface polariton coupling. A dielectric layer sinusoidally modulated in height (dielectric grating) on top of a metal layer is used as the dispersive element for the momentum coupling between the incoming photon and the plasmon surface polariton. Hence, no modulation of the metal surface is necessary. This coupling method is used to study the thermal decomposition of dielectric gratings. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366258

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The realization of efficient red, green, blue (RGB) light emission can be achieved by covering a blue light emitter with color-converting dye/matrix layers. We present theoretical calculations and experimental data of an electroluminescence device based on parahexaphenyl, an organic semiconducting material, which emits bright blue light when used as an active layer in a thin film device. The waveguiding effects in the various layers making up the RGB device are investigated in order to maximize the brightness, and optimize the angular light intensity distribution of the external emitted light. Quantum efficiencies (QE) for green color conversion of 48&percent;, and red conversion of 13&percent; from blue emission were determined by calculating over all emission angles and confirmed by experimental QE measurements. The efficiency can be drastically improved when the device layers are directly coupled to each other by refractive index matching, where color-conversion efficiencies of 90&percent; for blue to green and 80&percent; for blue to red can be achieved. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366219

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We describe the numerical procedure for calculating three-dimensional profiles of temperature in a multilayer stack illuminated by a laser beam, and model the crystallization and amorphization kinetics for phase-change rewritable media. Experimental methods have been used to determine indirectly the probabilities of nucleation and growth forGe2Sb2Te5alloy. Some of the fundamental behaviors of phase-change erasable media, such as the crystallization of as-deposited amorphous phase, amorphization of supercooled liquid, and recrystallization of quenched amorphous phase, have been illustrated based on our three-dimensional temperature calculations and the model kinetics. The calculated transient reflectance behavior of as-depositedGe2Sb2Te5amorphous films in a single layer and in a quadrilayer stack, as well as the erasure behavior ofGe2Sb2Te5alloy in a quadrilayer disk are in good agreement with experimental observations. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366220

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

This article presents a general mixed displacement-pressure formulation to analyze the dynamic behavior of anisotropic open porous materials. This formulation is obtained in the time domain without neglecting the acceleration terms related to the fluid phase of the porous medium. The derivation of the presented formulation uses Coussy’s description of porous materials. For isotropic media and harmonic motions, the developed general mixed formulation reduces to the common set of equations of motion used in acoustics which results directly from Biot’s equations. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366221

出版商:AIP    

年代:1997

数据来源: AIP