摘要:

This article analyzes the structure of the so‐called self‐similar effective medium approximation (SSEMA) which has been proposed for the effective permittivities in multicomponent inhomogeneous materials such as sedimentary rocks. In particular, our interest lies in understanding what kind of geometry is represented by the SSEMA. We show that, in the case of binary disorder, the first constituent is treated in the SSEMA in such a way that its geometrical continuity in space is guaranteed all the way down to the limit of zero proportion while the second constituent remains disjoint. This accounts for the zero percolation thresholds manifest in Archie’s law.

ISSN:0021-8979    

DOI:10.1063/1.332490

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The conduction mechanism in ZnO varistors has been studied assuming thermionic emission as the only way of charge transport. A model elaborated on that basis has been satisfactorily applied to the approximation of theI–UandC–Ucharacteristics and has made it possible to determine the barrier height &Fgr;b(300 K)=0.86 V, the donor concentrationND&bartil;1019cm−3, the effective number of grains between the electrodesg&bartil;20, the position of the Fermi levelEC−EF&bartil;0.07 eV, and the donor levelEC−ED&bartil;0.20 eV. The relative power spectral density of 1/fcurrent fluctuationsSI/I2in the varistors in the ohmic region has been calculated, starting from the mobility fluctuation approach of the 1/fnoise. The calculated linear relationship betweenSI/I2and the varistor resistance in the ohmic region has been confirmed by the experimental results. The calculated 1/fnoise density is in agreement with the observed density.

ISSN:0021-8979    

DOI:10.1063/1.332491

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Peculiar features of Deep Level Transient Spectroscopy (DLTS) measurements on resistive samples are pointed out. Depending on the value of the sample resistance in series with the diode capacitance, the DLTS signal can be strongly reduced and even its sign may be reversed, entailing a possible confusion between majority and minority carrier traps. Means of detecting these effects are discussed and a correction procedure is proposed, based on varying the circuit impedance by means of an additional resistance in series with the sample. Illustrative examples include ion implanted silicon and the case of a germanium bicrystal.

ISSN:0021-8979    

DOI:10.1063/1.332492

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A beam‐plasma type ion source employing an original operating principle has been developed by the present authors. The ion source consists of an ion extraction region with an electron gun, a thin long drift tube as the plasma production chamber, and a primary electron beam collector. An electron beam is effectively utilized for the dual purpose of high density plasma production as a result of beam‐plasma discharge, and high current ion beam extraction with ion space‐charge compensation. A high density plasma of the order of 1011–1013cm−3was produced by virtue of the beam‐plasma discharge which was caused by the interaction between a space‐charge wave on the electron beam and a high frequency plasma wave. The plasma density then produced was 102–103times the density produced only by collisional ionization by the electron beam. In order to obtain a stable beam‐plasma discharge, a secondary electron beam emitted from the electron collector should be utilized. The mechanism of the beam‐plasma discharge was analyzed by use of a linear theory in the case of the small thermal energy of the electron beam, and by use of a quasilinear theory in the case of the large thermal energy. High current ion beams of more than 0.1 A were extracted even at a low extraction voltage of 1–5 kV.

ISSN:0021-8979    

DOI:10.1063/1.332493

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A set of generalized calculated results are presented for both radiative and Auger rates in direct gap semiconductors. Emphasis is on materials with band gaps of 1.3 and 1.55 &mgr;m. The radiative and Auger components of the lifetime at threshold are calculated for several possible materials for a semiconductor laser at these wavelengths based on the best available data for the band structure of these materials. We find that the calculatedT0for these materials lie in the range 49 K–92 K.

ISSN:0021-8979    

DOI:10.1063/1.332494

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A new method is described for evaluation of electric field around rectangular arrays of large charged spheres of alternating sign. It is shown that the arrays can be simulated by three pairs of point charges per unit cell. The relation between spacing of charges, their intensity, and radius of the spheres yields the required field. The method provides superior accuracies for different unit cell proportions, including a cube and rectangular parallelepipeds, with the point charges appropriately arranged so as to satisfy boundary conditions.

ISSN:0021-8979    

DOI:10.1063/1.332495

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We have derived the theory for the electromagnetic transient response of metallic spheres, spherical shells, and composite spheres (composed of two materials with different conductivities). We have related the dominant time constant of the voltage at a secondary coil wound around the samples, with their physical characteristics: conductivity, permeability, and geometrical factors. We show that a thin spherical shell under certain conditions can be considered as one time constant system and we derive the values of the resistance and the inductance of the shell equivalent circuit. We have obtained experimental results for aluminum and brass spheres, and we have evaluated experimentally the effect of different primary coil designs.

ISSN:0021-8979    

DOI:10.1063/1.332496

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The temperature distribution in a rectangular sample as a function of time and position during swept line electron beam (SLEB) annealing has been calculated. Beam penetration effects have been included by using the Monte Carlo method and the temperature distribution has been obtained from Green’s function techniques and the method of images. The effects of various beam parameters on the temperature distribution have been studied. The results are correlated with experimental studies of the electrical activation of Be in GaAs during SLEB annealing. The annealing is shown to be governed by a relation of the form: Activated fraction=(Dwell time)×(3840e−(0.535/kBT)).

ISSN:0021-8979    

DOI:10.1063/1.332497

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The fundamental transmission characteristics of KrF laser radiation (248 nm) through the step‐index‐type fused quartz fiber have been determined. For the step‐index‐type fused quartz fiber used the transmission loss is about 0.5 dB/m at power densities up to 3.9 MW/cm2and 2 dB/m at 100 MW/cm2. One of the applications of this intense UV KrF laser transmission via optical fibers is the development of a gas insulated spark‐gap switch trigger by a KrF laser through a 2‐m‐long optical fiber. As a result, at a voltage 90% of the self‐breakdown voltage and at an illumination power density of 1.2 MW/cm2, a full trigger jitter of less than 5 ns is realized and it corresponds to a 1‐&sgr; jitter of less than 1 ns. The illumination energy is as low as 10 &mgr;J/shot.

ISSN:0021-8979    

DOI:10.1063/1.332489

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

An analysis of laser action in a multielement resonator structure is presented. Resonance wavelengths, threshold gains, energy density distributions, and quality of the modes are obtained from a linear model. A multimode rate equation approach then describes the dynamical behavior and gives absolute values for the modal output. It is shown that structures with only a few active elements can have a high mode selectivity providing single‐longitudinal‐mode operation of semiconductor lasers under high‐frequency current modulation. For example, the suppression of unwanted secondary modes in an eight‐element laser can be larger than 23 dB.

ISSN:0021-8979    

DOI:10.1063/1.332498

出版商:AIP    

年代:1983

数据来源: AIP