摘要:

The effect of processing conditions on the interface state density was evaluated fromC‐Vmeasurements on metal‐oxide‐semiconductor capacitors. The optimum processing condition for the minimum surface state density was found to be related to the postoxidation annealing temperature and time, and was independent of chemical treatments prior to oxidation. Annealing at the optimum condition (i.e., at 350 °C for 1 h in either nitrogen or hydrogen gas, with or without an aluminum pattern on the oxide) reduces the fast surface state density by about one order of magnitude. By using a nitrogen/oxygen plasma, the static dielectric constant of the oxide decreased as the N/O ratio was increased, and nitrogen was incorporated into the oxide. In addition, the fast surface state density was reduced as a result of this nitridation process.

ISSN:0021-8979    

DOI:10.1063/1.337045

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The experimental technique of ultraviolet photoelectron spectroscopy has been applied to a number of merocyanine dyes related in chemical structure. Additionally, polarographic and optical measurements were made on these dyes in solution, and Hu¨ckel molecular orbital calculations were carried out for isolated dye molecules. The observed photoionization threshold decreases with increasing delocalization of &pgr; electrons in the compound. With the use of absorption data, we constructed energy band diagrams for the dyes, assuming that these organic materials exist as molecular solids. Our assumption was supported by the observation that their ionization thresholds correlate well with the polarographic and the computational results. Photoelectron spectroscopy is deemed to provide a powerful method for studying dyes in practical forms.

ISSN:0021-8979    

DOI:10.1063/1.336840

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Fully electromagnetic particle‐in‐cell simulations of Applied‐Bion diodes have been performed using themagiccode. These calculations indicate that Applied‐Bdiodes can be nearly 100% efficient. Furthermore, the simulations exhibit an impedance relaxation phenomenon due to the buildup of electron space charge near the anode which causes a time‐dependent enhancement of the ion emission above the Child–Langmuir value. This phenomenon may at least partially explain the rapidly decreasing impedance that has been observed in Applied‐Bion diode experiments. The results of our numerical simulations will be compared to experimental data on Applied‐Bion diodes and to analytic theories of their operation.

ISSN:0021-8979    

DOI:10.1063/1.336851

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The present paper describes an experiment performed at the National Technical University of Athens, comparing the theoretical Biot–Savart–Lorentz forces with the experimentally measured forces which arise on a part of a single circuit. The comparison is decisive and unique, as it is made for the first time after (1) the elimination of the singular or undetermined forces which inevitably arise in such experiments at the contacts of interacting parts, and (2) a complete systematic error elimination in the measurements themselves. The results, therefore, (a) for the first time treat noncontact forces, (b) are free of the ambiguities which have undermined previous experiments, and (c) indicate that the exerted forces are systematically smaller than the predicted Biot–Savart–Lorentz forces.

ISSN:0021-8979    

DOI:10.1063/1.336863

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

This paper reports the fabrication and lasing characteristics of 1.3‐&mgr;m InGaAsP multiquantum‐well (MQW) buried heterostructure (BH) lasers grown by liquid‐phase epitaxy (LPE) technique. The MQW active region consists of five InGaAsP well layers (&lgr;g=1.3‐&mgr;m,Lz∼200 A˚ and InGaAsP barrier layers (&lgr;g=1.1 &mgr;m,d∼400–600 A˚). These lasers have threshold currents of 15–20 mA at 25 °C, external quantum efficiencies of 50% at 25 °C, andT0values of 130–145 °K in the temperature range of less than 300 °K. The beam divergences perpendicular and parallel to the junction plane were in the narrow range of 10–13°. Furthermore, the polarization‐dependent gain‐current relationship between the TE and TM mode of InGaAsP MQW lasers has been investigated in detail for the first time.

ISSN:0021-8979    

DOI:10.1063/1.336832

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

By using a kinetic model developed for a self‐sustained discharge pumped XeCl laser (B→X, 308 nm) with the Ne/Xe/HCl mixture, we determined operational conditions of the XeCl laser with commonly used pulse width of about 100 ns for attaining efficient lasing. According to the analysis of electron kinetics in the laser discharge, the XeCl* formation, the XeCl* relaxation, and the absorption of theB→Xlaser radiation, it is found that the discharge and kinetic characteristics are affected predominantly by the electron number density which is determined mainly by the ratio of Xe to HCl concentrations. Although the XeCl* formation, the XeCl* collisional quenching, and the absorption of the laser radiation increase with increasing total gas pressure, the optimum Xe and HCl concentrations which are almost independent of the total gas pressure can be determined. Furthermore, since the laser output energy does not increase linearly with the excitation rate, the optimum excitation rate can be determined for a given total gas pressure as it shifts to a higher value with increasing total gas pressure. As a result of the analysis by using the most reliable rate constants and cross sections for the reactions published so far involved in the XeCl laser kinetics, the maximum intrinsic efficiency of 12.5% is found to be obtainable with a 3‐atm laser mixture of 0.2% HCl and 1% Xe in the Ne diluent pumped with an excitation rate of 3.5 MW/cm3.

ISSN:0021-8979    

DOI:10.1063/1.336835

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A theoretical study on the efficiency of chemical oxygen‐iodine laser (COIL) oscillators is described together with experimental data obtained using an efficient COIL system. In order to evaluate chemical oxygen‐iodine laser performance, three types of efficiencies (power conversion efficiency, extractable efficiency, and chemical efficiency) were introduced in this investigation. The dependencies of these efficiencies on initial gas components are investigated by theoretical simulation in which the theoretically attainable values of the efficiencies are also given. The validity of this simulation is confirmed by comparing the results with our experimental data. The experiments yielded a high‐extractable power efficiency of 75%, which is comparable to the theoretically determined attainable value of 88%.

ISSN:0021-8979    

DOI:10.1063/1.336836

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Acoustic power flow in a LiNbO3single crystal was calculated to find the optimal crystal cutting orientation and the wave propagation direction for the efficient excitation of acoustic waves in the crystal. By solving the stiffened Christoffel equations and calculating the acoustic Poynting vectors with piezoelectric effect included, maximum longitudinal acoustic power flow in a 30°Z‐rotated,Y‐cut LiNbO3crystal was found.

ISSN:0021-8979    

DOI:10.1063/1.336837

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A spatial map of the variation of acoustic impedance within a material structure can be made using only its resonance frequencies. We demonstrate this for a 1‐D rod having a diameterDwhich varies along its lengthlby determiningD(l) from fundamental and overtone resonances. We also show how the technique can locate material/processing inhomogeneities in the elastic modulus and/or density on a scale of several parts per thousand for ‘‘stock’’ rods of an aluminum alloy using nondestructive and noncontact testing. And finally, we apply dimensional resonance tomography in new measurement methods to obtain the thermal diffusivity along a rod and the heat transfer coefficient of the rod to its ambient. The latter technique provides quantitative data while allowing an arbitrary and unknown initial temperature distribution, requiring no temperature measurement or Fourier analysis, and can be done in noncontact fashion with the measurement of frequency and time, only.

ISSN:0021-8979    

DOI:10.1063/1.336838

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

An air flow sensor that uses a flow‐induced change of temperature oscillation phase at an air‐solid interface is described and analyzed. The sensor is fabricated on silicon coated with polyimide. The source and detector of temperature oscillations are integrated on the same substrate but spatially separated. A narrow strip of metal film driven by ac is the source. A PbTe thin‐film thermocouple is the detector. Device operation in still air is analyzed and compared with experiment. The temperature oscillation amplitude and phase on an interface with an oscillating strip heat source is derived for interface thermal resistance and for a layered substrate. Interference between thermal oscillations propagating from source to detector through the solid and through the air is predicted and observed with a 53‐&mgr;m‐thick polymide layer. In contrast, with a 16‐&mgr;m‐thick polyimide layer, interference that varies with frequency is not seen, also in agreement with theory. Experimental demonstration of flow response is also reported. Qualitative agreement with the predictions of a time‐of‐flight model of flow response is found.

ISSN:0021-8979    

DOI:10.1063/1.336839

出版商:AIP    

年代:1986

数据来源: AIP