摘要:

ESCA (electron spectroscopy for chemical analysis) measurement results on thin SiO2/Si samples are examined comprehensively, critically, and in detail to show that it is possible to correlate these results with MOS (metal–oxide–semiconductor) device characteristics such as flatband (threshold) voltage, oxide breakdown field, mobile‐ion density, hole and electron trap density, and hot‐carrier lifetime. Up to now, much effort has been made to detect SiOxphases at SiO2/Si interfaces since they are thought to have a significant effect on MOS device characteristics. However, correlating the SiOxphases with device characteristics is difficult and involves overcoming two problems. First, the chemical state is difficult to determine exactly due to x‐ray irradiation effects. Second, the amount of defects and impurities which influence device characteristics is usually below the ESCA detection limit (1012–1013cm−2) in device‐quality SiO2/Si samples. Investigation of the first problem led to the conclusion that it is possible to correct for these effects from the x‐ray intensity or oxide thickness dependence of the chemical shift. However, accurate (better than ±0.2 eV) chemical state determination is not easy. It is therefore necessary to approach this detection problem from a different viewpoint. Our first attempt involves measuring the ESCA thickness, which decreases when oxide defects like unoxidized Si or uneven thickness (or pinholes) are present, resulting in breakdown field degradation. Our second attempt started while we were studying how to interpret the measured chemical shift. The photoelectron peaks of the SiO2and the Si can be observed to shift due to small amounts of charged defects and impurities, although they cannot be detected as peaks. This method is considered to be especially useful for characterizing ultrathin (a few nm thick) SiO2/Si samples which are difficult to characterize using conventionalC‐V(capacitance–voltage) measurements because of tunneling currents. Accordingly, we discuss the data obtained in steady‐state and transient peak position measurements of SiO2/Si samples containing 1010–1012cm−2of Na (sodium) ions, 1012–1013cm−2of hole and electron traps, and 1014–1021cm−3of impurities such as P (phosphorus) (in the Si). It is shown that a correlation with MOS characteristics is possible. A close scrutiny of various results concerning x‐ray irradiation time, intensity, and oxide thickness dependence of the above peak positions indicates that electric charging during ESCA measurements is correlated to the trap‐capturing process. As MOS characteristics are also related to this process, more studies in this direction are needed and will certainly yield more information on the defects influencing the MOS characteristics and the trap‐capturing mechanism. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362676

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A model for calculating the electron inelastic mean free path and stopping power in insulators in the 50 eV–10 keV energy range is presented. Both valence and core electron contributions have been considered. The valence part has been estimated following the dielectric theory modified to include the energy gap; the core contribution has been evaluated on the basis of the classical binary encounter theory. Inelastic mean free path and stopping power calculations based on this model have been performed for several alkali halides: LiF, NaCl, KCl and CsI. They are compared to existing experimental data and Penn model’s predictions for the mean free path and to Bethe’s values for the stopping power; a fair agreement is found for incident electron energies higher than 100‐200 eV. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361491

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

In order to interpret the experiment of Conde and Bekefi, electron trajectories are studied for a configuration with a reversed axial guide field. In the vicinity of ‘‘antiresonance,’’ electrons are shown to have chaotic trajectories when emitted far enough from the axis. Thus, the interaction efficiency is degraded for most particles. This explains the large dip in radiative power observed and predicted by different simulation codes. The very good efficiency observed in the experiment is explained by a compromise between a high amplitude perpendicular velocity and a regular enough axial momentum for the electrons. It is also explained by the fact that when photons are emitted, the axial kinetic energy is not too much affected. A new situation for which a small peak in efficiency should be observed is predicted. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361492

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The pulse propagation in free electron lasers is treated analytically. A general gain formula including finite pulse effects, high gain corrections, inhomogeneous broadening contributions and the detuning parameter is derived. It is shown that it contains, as particular cases, the already known gain parametrization formulae. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361493

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

High‐peak‐power lasers are typically used as pump sources in nonlinear optical measurements. Intrinsic to these sources are pulse‐to‐pulse output energy instabilities. We report on how pump instabilities affect the measurement of nonlinear susceptabilites and develop theory which relates statistical parameters of a general, arbitrary pump energy probability distribution to those of its correspondingmth harmonic output. The relation leads to a simple method of data analysis whereby pump instabilities can be used as a tool in determining the nonlinear susceptibility of a material. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361494

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

For the transverse magnetic mode, the second‐order Bragg interaction of the guided and the radiated waves is considered for a thin film dielectric waveguide with a corrugated film–cover interface. A set of four canonical equations for the deexcitation and the excitation of the guided waves are derived by employing a quasioptical technique. The governing equations are applied for the treatment of a surface‐emitting distributed feedback laser. Some design criteria are obtained for optimizing the performance of the laser. When these design criteria are used, the laser characteristics are insensitive to small changes in the physical parameters about their designed values. Numerical results are presented to illustrate the performance of the laser. The shape of the surface relief grating is found to play a vital role in determining the gain threshold and the gain margin of the laser. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361495

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The influence of the depolarization effect on the third‐harmonic generation due to intersubband transitions in the near‐triply‐resonant quantum well structures is studied theoretically. Calculations are performed in the framework of the perturbative density‐matrix formulation with relaxation‐time approximation. The results obtained show that the depolarization effect not only shifts the peak in the third‐harmonic‐generation spectrum but also, due to the coupling between different intersubband transitions, can enhance its maximum value. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361496

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

In the article by V. Asch [J. Appl. Phys.37, 2654 (1966)], experiments were performed to study the influence of an electrostatic field on nucleate boiling of Freon-113(R-113). We have found that Asch might not have properly considered the effects of his experimental setup and therefore came to incorrect conclusions concerning electrophoretic and dielectrophoretic forces. Asch's analysis of the electric field distribution led him to conclude that the dielectrophoretic forces were small, however, we show in this article that, in general, there are strong dielectrophoretic forces in the vicinity of the heater wire. This article presents the results from a set of experiments performed with an apparatus similar to that of Asch's with test fluids of R-113 and FC-72. The experimental results show that vapor bubbles can be attracted to either the anode or cathode depending on the potentials with respect to the heater wire on which the boiling takes place. This is contrary to the results obtained by Asch which led him to conclude that the bubbles were always attracted to the anode. The bubble movement appears to be the result of a combination of dielectrophoretic forces (which are very strong but highly localized), electrophoretic forces, and bulk electroconvective flow. Furthermore, the combined effects of these forces away from the wire can lead to unstable behavior. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361497

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The effective conductivity of composites containing aligned spheroids of finite conductivity is determined with the pair interaction rigorously taken into account. The pair interaction is evaluated by solving a boundary‐value problem involving two aligned spheroids with a boundary collocation scheme. Our results are in the form of virial expansion in the inclusion volume fractionf, truncated at theO(f2) term. Effective conductivities obtained from this study agree well with Willis’s [J. Mech. Phys. Solids25, 185 (1977)] bounds and Kim and Torquato’s [J. Appl. Phys.74, 1844 (1993)] first‐passage‐time simulation results. An expression for the effective conductivity tensor based on an equivalent inclusion method originated by Hasselman and Johnson [J. Compos. Mater.21, 508 (1987)] is also derived, from which a criterion for testing the virial expansion validity is constructed. The relevant series ratio is found to be a good measure of intensity of the system thermal interaction. The smaller the value of the series ratio, the better agreement of the virial expansion with the simulation results. Explicit expressions for the second‐order virial expansion for the parallel and perpendicular components of the effective conductivity tensor are tabulated for inclusion aspect ratios 1, 10/9, 2, 5, 10 and phase conductivity ratios &sgr;=0, 0.1, 2, 10, 100, 10 000, and ∞. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361498

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Plasma in the presence of a static magnetic field supports a whistler wave. It is shown that when the static magnetic field is switched off, the energy of the whistler wave is converted into the energy of a helical wiggler magnetic field. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361499

出版商:AIP    

年代:1996

数据来源: AIP