bluuebunny/crossref_metadata_2025 huggingface dataset:
Small−signal analysis of the gain and noise performance of the Josephson mixer
Authors: Habib Serag E.−D. E.−S. , Dmitrevsky S.
Published: February 2003

The behavior of the voltage−biased Josephosn junction coupled to a general external circuit is studied in the small−signal limit. The Josephson relations are formulated in the frequency domain in the form of an infinite set of difference equations relating the current and voltage amplitudes of different frequency components. The results are subsequently utilized to develop a general theory of the self−oscillating Josephson mixer, including noise. The noise temperature and conversion gain of the mixer are derived taking into consideration the image frequency response. A comparison is made between the operation of the negative−resistance converter in the SC regime and its operation in the OC regime.
Two−dimensional domain walls in ferromagnetic films. I. General theory
Authors: Aharoni Amikam
Published: February 2003

A model with two Ritz parameters, for which the magnetostatic self−energy can be calculated analytically, is presented for the wall separating two antiparallel domains in ferromagnetic films. The other energy terms can be only partly calculated analytically, while part of the calculations must be done by numerical computations. However, these computations are much simpler than in wall studies which relied directly on such computations, and also can be approximated at each stage by the first few terms in an analytic power series. It is shown that the model can be generalized to yield a higher accuracy in the wall structure and energy, but only at the expense of a large complication of the calculation, which
Degradation effect of electron−gun evaporation on diode characteristics
Authors: Wei L. S.
Published: February 2003

Degradation in the I−V characteristics of large−area silicon junction diodes on which a passivating layer of alumina has been deposited by e−gun evaporation is shown to exhibit symptoms of a shortened recombination lifetime. After a simple heat treatment, the original characteristics may be restored. It is believed that the combined effects of the high−intensity radiation produced by the e−gun during evaporation, and traces of the etching solution on the diode surface are responsible for the observed degradation.
Monolithic measurement of optical gain and absorption in PbTe
Authors: Cross Peter S. , Oldham W. G.
Published: February 2003

An integrated technique for measuring optical gain and absorption is described. The gain and absorption coefficients are measured as a function of wavelength in PbTe near the direct band gap (∼5.75 μm at 77 °K). It is possible to measure optical gains of up to 100 cm−1 and absorption coefficients up to 300 cm−1. The usefulness to a theoretical analysis of the well−correlated gain and absorption data obtained by this method is discussed with a comparison of experimental data with a simple parabolic band theory.
Buried optical waveguides in fused silica by high−energy oxygen ion implantation
Authors: Rao E. V. K. , Moutonnet D.
Published: February 2003

Oxygen ion implantations in fused silica in the energy range 0.3−2 MeV with doses ranging from 1014 to 1016 ions/cm2 are conducted at room temperature. The optical parameters of the guides obtained are measured before and after successive annealings with the help of a prism−film coupler. Also, an investigation of the buried nature of these guides is carrier out by conducting the above measurements before and after removing a known thickness of the implanted layer by argon plasma etching. It is reported that the contribution to refractive index increase in the surface region due to ionization effects cannot be ignored during the realization of buried guides by high−energy ion implantation. Also, it is shown that these guides get buried depending on the annealing treatment.
Dislocation characteristics in 1018 steel shock loaded at 104 and 304 kbar
Authors: Huo Donald T. C. , Ma Ching H.
Published: February 2003

The effects of shock loading on dislocation characteristics in 1018 carbon steel were studied at 104 and 304 kbar, respectively. It was found that the dislocation density is lower and its average loop length is longer in specimens shock loaded at 304 kbar. The results are interpreted in terms of the effects of transient phase transformations in specimens shock loaded at 304 kbar and higher specimen temperatures of these same specimens during and immediately after loading.
Radiation loss in the flash method for thermal diffusivity
Authors: Clark III L. M. , Taylor R. E.
Published: February 2003

The boundary radiation heat loss method is investigated for the flash method in measuring thermal diffusivity. Present correction procedures for heat loss are tested experimentally using AXM−5Q (POCO) graphite. In addition, a new method for radiation loss correction is presented based solely on the heating portion of the temperature rise curve. Using the new method, corrections of 35% can be made within a ±3% error. The thermal diffusivity results calculated using the adiabatic expression for various portions of the fractional rise curve and for various heat losses are also presented.
Bubble size distribution measurement by Doppler velocimeter
Authors: Ben−Yosef N. , Ginio O. , Mahlab D. , Weitz A.
Published: February 2003

The size distribution of gas bubbles in water was measured by the measurement of their velocity distribution with a Doppler velocimeter. Sizes from r=15 μm and above were recorded and all the distributions (due to different bubble generators) showed a good fit to the log−normal distribution.
Interfacial parametric ferrohydrodynamics
Authors: Perry M. P. , Jones T. B.
Published: February 2003

When a time−periodic magnetic field with a strong gradient is imposed tangentially at the interface of a ferromagnetic liquid, parametric surface instability may result. Under typical conditions this instability grows to a certain amplitude, where nonlinear dynamic effects become dominant, resulting in a standing−wave pattern. In the linearized small−amplitude limit, the surface dynamics are described by Hill’s equation. The nonlinear magnetization characteristic of the ferrofluid is successfully modeled by the Langevin superparamagnetic theory, using a single−sized particle approximation. The wavelength observed in the nonlinear amplitude limited state is successfully correlated with theory by determining the ’’most unstable wavelength’’, that is, the wavelength with the maximum growth rate for given conditions of applied magnetic field strength and frequency.
Polarized reflected light for constrast enhancement in underexposed radiographs
Authors: Mardix S.
Published: February 2003

Polarized reflected light is used for the examination of underexposed radiographs. In this method a bright image on a dark background is observed and the reflected light intensity from this image is proportional to the exposure. Contrast achieved by this technique is higher than that observed with transmitted light by more than an order of magnitude for very low exposures.
Image reconstruction by using a frequency−sweep method
Authors: Hidaka Takehiko
Published: February 2003

A new image reproduction method is proposed. Using an asymmetric dispersive material, a fixed receiving antenna, and frequency sweeping, we can construct an image reproduction system without the expensive and troublesome mechanical antenna−scanning or array−antenna systems for microwave holography. The principle is that the ray trajectory from the object to the receiving antenna changes with the frequency sweeping if a dispersion prism stands between the object and the fixed receiving antenna; the holographic information along with the prism surface is obtained by frequency sweeping. The experiment at the X band (3−cm wavelength) is described.
Late−time behavior of an iodine photodissociation laser oscillator
Authors: Gusinow M. A. , Freeman J. R.
Published: February 2003

The principal experimental result is a determination of late−time lasing long after the flashlamp output has terminated. A simple model has been constructed which agrees qualitatively with the experimental results. The calculations indicate that diffusive transport may be responsible for the observed late−time lasing.
Phase identification and domain structure in PLZT ceramics
Authors: Keve E. T. , Bye K. L.
Published: February 2003

The poling of certain compositions of PLZT ceramic is shown to cause a phase transition (α→β). The polar β phase can be rhombohedral, tetragonal, or orthorhombic depending upon composition, while phase α is always cubic. Characteristic subgrain domain structure is observed in the β phase for orthorhombic and rhombohedral compositions. Phase α is shown to be optically isotropic in a single−grain thickness. Identification of these phases and the observed domain structure enables the phase transitions
Structural and electrical properties of films sputtered from a Pt cathode in argon−oxygen mixtures
Authors: Bennewitz C. D. , Westwood W. D. , Brown J. D.
Published: February 2003

Films have been deposited on glass and polycrystalline alumina substrates by reactive dc sputtering of platinum in oxygen−argon mixtures. The films properties depend on the oxygen/argon ratio and on the discharge parameters. Whereas the resistivity was 25 μΩ cm in an argon discharge at 5 kV, it was higher than 1.5 Ω cm in an oxygen discharge at 2 kV. Corresponding changes were obtained in the temperature coefficient of resistance; values from +2000 to −25000 ppm/°C were measured. As the resistivity increased, the film density decreased from 21.5 to 15.5 g/cm3. These results are interpreted in terms of a cermetlike film structure consisting of mixtures of Pt and oxides of platinum. X−ray and electron diffraction analysis confirms the presence of a phase isostructural with PdO which is considered to be PtO. This phase decomposes to Pt on heating in air at temperatures above 600 °C and thermogravimetric analysis showed that the film composition changed from Pt to PtO1.3 as the temperature coefficient of resistance changed from +2000 to −11000 ppm/°C. It is porposed that an amorphous PtO2 phase is also present in these films and ESCA spectra have confirmed the presence of Pt, PtO, and PtO2. Analysis of the sputtering discharge characteristics and changes in the gas composition during sputtering are consistent with gettering of oxygen by the sputtered Pt.
Amalgamation in the Ag3Sn−Hg system. I. I
n s
i
t
u observations
Authors: Reynolds C. L. , Wawner F. E. , Wilsdorf H. G. F.
Published: February 2003

I n situ observations of the amalgamation of Ag3Sn are presented. It is shown that the product γ1(Ag2Hg3) and γ2(Sn7−8Hg) phases nucleate homogeneously and heterogeneously, respectively, from a liquid Ag−Sn−Hg solution. The growth of the γ1 phase is shown to be proportional to t1/3 while that for the γ2 phase is proportional to t1/2.
On the direction of electromigration in gold thin films
Authors: Blech I. A. , Rosenberg R.
Published: February 2003

The motion of gold atoms during electromigration in thin films is shown to be in the direction of the electron flow, i.e., from cathode to anode. This is contrary to other observations reported in the literature in which holes are seen in the anode regions. In the present work, holes at the anode were produced by transient annealing effects of nonequilibrium grain structures and not by reversal of the direction of the electromigration. Holes can be regularly produced in either anode or cathode regions depending upon test conditions, preannealing, and heat sinking.
Growth of a smectic A from a bent nematic phase and the smectic light valve
Authors: Cladis P. E. , Torza S.
Published: February 2003

We show that for certain liquid crystals, characterized by very small nematic/smectic−A latent heats, the transition from a nematic phase, held firmly in a bent state, to a smectic−A phase takes place via an intermediate state which is stable in a given temperature range and which we have called ’’striped texture’’. This state consists of a corrugated layer of bent nematic which is sandwiched between two smectic−A layers whose planes are oriented in two different directions. As the temperature of the sample is further decreased, the ’’striped texture’’ becomes unstable. The corrugated layer undergoes axial buckling leading to the final smectic−A ’’honeycomb texture’’. This texture is the scattering phase of Kahn’s smectic light valve. We explain the occurrences of these phenomena on the basis of elastic and surface energy considerations.
Anode crater formation by pulsed arcs
Authors: Vasile M. J. , Kammlott G. W.
Published: February 2003

Anode damage due to short−duration (3 ns−1 μs) arcs between a tungsten cathode and copper, gold, palladium, and platinum anodes has been studied. The electrode arrangement was mounted inside the specimen chamber of a scanning electron microscope so that the surfaces to be discharged, the interelectrode spacing, and the resultant damage were readily observable. The effects of arc current and arc duration on crater dimensions were studied. Anode crater diameters were found to vary as the square root of the arc current for fixed arc duration. A weak dependence of anode crater diameter on arc duration was found at constant current for arcs lasting less than ∼100 ns. The depth of cratering was also measured and relationships between the crater diameter and depth were found for platinum and gold anodes. Large differences in arc crater diameters were not found for each of the anode metals, despite the differences in their thermal properties. The transition from anode to cathode arcs with increasing gap could also be observed and was found to occur between 1.3 and 2.1 μ for a plantinum anode.
Analysis of a monolithic piezoelectric mirror
Authors: Hudgin R. , Lipson S. G.
Published: February 2003

Various applications require an optical mirror whose figure can be changed in a controlled manner as a response to an electrical input signal. This paper presents the theory of such a device, consisting of a single piece of piezoelectric ceramic situated in a nonuniform electric field. The surface deformation is calculated for periodic surface potential distributions on a simple geometric shape. Agreement with experimental results is good.
Elastic interactions between disclination loops and inclusion particles
Authors: Chou Tsu−Wei , Pan Yen−Cheng
Published: February 2003

An analysis is made of the interaction between inclusion particles and disclination loops. Two aspects of this interaction have been taken into consideration, namely, the effects of volumetric mismatch and modulus mismatch. It can be shown that there is no resultant interaction energy between a particle and a twist disclination loop due to volumetric misfit. On the other hand, the interaction between wedge disclination loops and impurity particles with volumetric misfit results in net interaction energy. Closed−form solutions are obtained for the total interaction force as a function of the separation distance between the defects. As to the effects of modulus mismatch, the long−range interactions between second−phase particles and twist disclination loops have been examined. Inclusion particles with shear moduli higher than those of the matrices tend to repel the disclinations. The forces on the disclination line segments are determined by evaluating the Peach−Koehler forces on the dislocation models of disclination loops.
Origin of 1/f noise
Authors: Stephany Joseph F.
Published: February 2003

A source of 1/f noise fitting experimental data is derived from the assumption that the units of the autocorrelation function must be those of power. This assumption results in a complex autocorrelation function. A source of 1/f noise can then be derived from an increase in the observed electron velocity resulting from the action of the applied electronic field on the lattice atoms. This results in the following expression for the 1/f noise power spectrum: S (ω) = (8I20R0/N0) × (m−/m+)1/2(1/ω), where m− and m+ are the effective masses of the electron and lattice atoms, respectively.
Theory of a gas laser with a Gaussian field profile
Authors: Maeda Hisatoshi , Shimoda Koichi
Published: February 2003

A theory for a gas laser with a Gaussian radial field distribution is considered. Rotating wave approximation is adopted to calculate the atomic polarization of the two−level system. An asymmetry of the shape of the Lamb dip and a shift of its center frequency are numerically obtained in the self−consistent laser field.
Photon drag effect in p−type tellurium at 10.6 μm
Authors: Panyakeow S. , Shirafuji J. , Inuishi Y.
Published: February 2003

The longitudinal photon drag effect has been studied in detail on p−type tellurium. From a simple analysis the photon drag effect in p−Te is found to be understood as photon pressure. The temperature dependence of the photon drag effect is well explained by the simple analysis, which can also give the optimum hole concentration to be from 5×1014 to 1×1015 cm−3 at temperatures below 200 K to obtain a maximum photon drag voltage. This model gives the maximum photon drag voltage on a 5−mm−long sample to be 3.5 mV/kW at temperatures below 200 K in agreement with the experiment. The photon drag tensor component σ1133 is estimated to be 3.7×10−11 cm/V at 100 K. A steep decrease in the photon drag voltage at higher temperatures can be much improved by using Te−Se mixed crystals.
Influence of multiple internal reflections and thermal expansion on the effective diffraction efficiency of holograms stored in lithium niobate
Authors: Cornish W. D. , Young L.
Published: February 2003

In experimentally determining the diffraction efficiency of holograms stored in lithium niobate and similar materials by exposure to known amounts of light, it is necessary to take into account multiple internal reflections from the surfaces. In particular, the effective diffraction efficiency is very sensitive to small changes in temperature (∼ 1 °C) such as those which are easily produced by exposure to medium−intensity laser beams.
Lifetime spectra (77 °K) of nitrogen−doped GaAs1−xPx
Authors: Lee M. H. , Holonyak N. , Nelson R. J. , Keune D. L. , Groves W. O.
Published: February 2003

Optical phase−shift lifetime measurements (77 °K) on GaAs1−xPx : N are used to determine the dependence of the lifetime spectrum τ (λ) on crystal composition, N concentration, and donor doping concentration. In the indirect composition region (x≳xc?0.46, 77 °K), lifetime spectra provide a decomposition of the structure of the NN−pair emission peak, showing, in comparison with GaP : N, that the NN−pair structure is, in fact, due mainly to NN3 pairs with some contribution from NN1 pairs. Surprisingly, in spite of As−P disorder, the photoemission spectrum (77 °K) of the ternary GaAs1−xPx : N is found to be narrower than that of the binary GaP : N. Comparison of lifetime data obtained on direct GaAs1−xPx : N (x<xc) with those obtained on the same crystal without N doping shows that the N doping minimizes the effects of the indirect X conduction−band minima and the donor states associated with X near the direct−indirect transition (x≡xc). The lifetime spectrum of GaAs1−xPx : N is found not to be a rapid function of the N concentration. An estimate of the electron scattering and capture time from the conduction band to the NN pairs is obtained and is τ≲0.5 nsec. Comparison of the data on heavily donor−doped GaAs1−xPx : N with those on the same crystal made p type by Zn diffusion shows that the presence of a high electron density in the crystal suppresses radiative recombination on transitions involving the NN−pair states.
Low−temperature irradiation effects in SiO2−insulated MIS devices
Authors: Harari E. , Wang S. , Royce B. S. H.
Published: February 2003

The storage of positive charge in the SiO2 insulator of MIS devices has been studied at both 300 and 80 K. It has been found that additional charge is stored in the oxide as a result of low−temperature x irradiation and behaves differently from that induced by room−temperature irradiation. This additional charge may be removed from the oxide by photodepopulation techniques, field emission, and thermal annealing. The portion of the charge which is present at both 300 and 80 K is shown to be insensitve to these treatments under the same experimental conditions. The experimental data indicate that the observed behavior is not due to positive ion transport within the oxide and strongly suggests that hole transport is occurring. Models for the trapping sites and the role of surface states are discussed.
Reduction of the pumping efficiency in CO2 lasers at high discharge energy
Authors: Ballik E. A. , Garside B. K. , Reid J. , Tricker T.
Published: February 2003

It has frequently been observed that, beyond a certain point, the gain obtained in TE CO2 lasers fails to increase with increasing discharge input energy. This saturation effect could be caused by problems of a secondary nature such as the onset of discharge deterioration, or the effects of increasing gas temperature. On the other hand, an intrinsic property of the discharge may be responsible for this limitation on the pumping efficiency. In this paper, evidence is presented in favor of the latter possibility. Measurements of small−signal gain have been carried out in He : CO2 and He : N2 : CO2 gas mixtures at moderately low pressure in a transversely excited resistor−pin amplifier. It is shown that this system permits the clear separation of the region of discharge deterioration from the onset of gain saturation. Furthermore, auxiliary measurements are undertaken which permit corrections to be made for the effects of increasing gas temperature. The net result is that the discharge pumping effectiveness at high energies falls to values drastically below those obtained at low discharge energies. This saturation effect occurs in a manner consistent with the existence in the discharge of a deexcitation process for the upper laser level. If such a deexcitation process indeed accounts for these observations the cross section must be an order of magnitude higher than the corresponding excitation process.
Low−temperature heat−capacity study of the Y1−xThxFe3 system
Authors: Kunesh C. J. , Narasimhan K. S. V. L. , Butera R. A.
Published: February 2003

Low−temperature heat−capacity measurements between 1.5 and 10 °K have been made on some compounds in the Y1−xThxFe3 system (x=0.1, 0.3, 0.5, 0.7, 0.9, and 1.0). The electronic specific−heat coefficient γ exhibits a maximum at x=0.3. The lattice specific−heat coefficient β increases, while the Debye temperature ϑD decreases with increasing x. The results of this study are in agreement with a model proposed to explain the anomalous magnetic behavior of the Y1−xThxFe3 system. The variation of γ as a function of x is discussed in terms of a band model for the 3d transition metals.
Magnetic properties of some light rare−earth compounds with CsCl structure
Authors: Buschow K. H. J. , de Jong J. P. , Zandbergen H. W. , van Laar B.
Published: February 2003

Neutron−diffraction studies were performed on the compounds PrZn, NdZn, NdMg, and NdAg. The lattice constants were determined at 300 and 4.2 K. For all compounds the CsCl structure was confirmed at room temperature. The compound PrZn was found to be subject to a tetragonal distortion at 4.2 K. A very small tetragonal distortion exists probably also in NdZn and NdMg at 4.2 K. the magnetic moment of the rare−earth component and the magnetic structure type was determined. All compounds are antiferromagnetic at 4.2 K, PrZn and NdMg with the 〈0,0,π〉 structure, NdAg with the 〈π,π,0〉 structure. In view of the generally accepted explanation of the magnetic properties of CsCl−type intermetallics in terms of the RKKY model these findings for PrZn and NdMg are remarkable and form a discrepancy with the ferromagnetic nature of the heavy rare−earth counterparts of these compounds.
Optical radiation damage of SBN materials and pyroelectric detectors at 10.6 μm
Authors: Kruer M. R. , Esterowitz L. , Bartoli F. J. , Allen R. E.
Published: February 2003

Thermal damage of Sr1−xBaxNb2O6 (SBN) crystals and infrared pyroelectric detectors due to 10.6−μm CO2 laser radiation was investigated. Permanent damage in the form of cracking or charring was observed depending on the irradiation conditions. Threshold values of energy density for cracking and charring were determined for SBN crystals of typical detector dimensions as a function of irradiation time. These damage thresholds of SBN are about an order of magnitude larger than the corresponding thresholds previously measured in triglycine sulfate. The energy density thresholds for cracking are independent of irradiation time τ for short times and increase as τ for long times. The time dependence of the cracking thresholds under the particular experimental conditions investigated is described by the empirical equation E0=[3+2400τ/tan−1(82τ)1/2] J/cm2. The charring thresholds are given by the empirical equation E0= (8+470τ1/2) J/cm2. The theoretical models presented for thermally induced damage are in satisfactory agreement with the experimental data. The damage thresholds of commerical SBN pyroelectric detectors were measured and found to correspond to those for SBN crystals.
Simple method of determining the external signal voltage in Josephson junctions
Authors: Somervuo P. , Sirkeinen Y.
Published: February 2003

A simple method is presented to obtain the voltage amplitude which is generated by an external microwave signal in a Josephson junction. The signal power and the efficiency of the coupling may thus be estimated. The method is based on the Bessel function obeying behavior of the constant voltage steps in the junction characteristics using a relatively high irradiating power.
Limiting configuration in dislocation glide through a random array of point obstacles
Authors: Hanson Kenton , Morris J. W.
Published: February 2003

We consider a dislocation in glide through a random array of point obstacles. Several important phenomena, including the critical resolved shear stress at zero temperature and the velocity of thermally activated glide at low temperature or at stress near the critical resolved shear stress, are known to be strongly influenced by the properties of the most stable obstacle configuration encountered by the dislocatton during glide. We devise a limiting technique to estimate the mechanical strength, the distribution of forces, and the mean dislocation segment length in this configuration. The estimates are in good agreement with results
Effects of annealing on profiles of aluminum implanted in silicon carbide
Authors: Lucke William , Comas James , Hubler Graham , Dunning Kenneth
Published: February 2003

The effects of isothermal annealing on the profiles of heavy (4×1016 Al+/cm2 at 60 keV) implantations of Al in SiC were investigated by means of the 27Al(p,γ)28Si nuclear resonance technique. Annealing at 1400 °C for 15 min resulted in the apparent outdiffusion of about 30% of the implanted Al, an accumulation of Al at the surface, and a residual peak at the depth of the as−implanted profile. Subsequent annealing showed continued apparent outdiffusion with the release of Al from trapping sites as the rate−limiting process.
Approximate spherical blast theory including source mass
Authors: Freiwald D. A. , Axford R. A.
Published: February 2003

Equations including source mass are presented for strong spherical blasts in cases where the source mass is not negligible. Analytic solutions are obtained for shock speed, position, and overpressure as a function of radius. Approximations similar to those used in the Taylor−Sedov approximate theory are employed. Shock positions as functions of time are obtained via evaluation of incomplete elliptic integrals. Sample calculations are presented for a laser−initiated 1−MJ (debris energy) pellet microexplosion, and compared to Taylor−Sedov approximate theory solutions.
Study of the enhanced solubility and lattice location of gold impurities in a heavily phosphorus−diffused layer of silicon
Authors: Chou S. L. , Gibbons J. F.
Published: February 2003

The enhanced solubility and lattice location of gold impurities in a heavily phosphorus−diffused layer of silicon have been investigated using the ion−backscattering technique. At a phosphorus surface concentration of 3.3×1020 cm−3, the corresponding gold solubility was found to be about 7×1018 cm−3 at 1100 °C, with the gold impurities being predominantly in substitutional sites. A lightly doped wafer with no phosphorus diffusion had a surface gold concentration of 1.5×1018 cm−3 after 1100 °C gold diffusion, again with the gold impurities being predominantly in substitutional sites. The results are interpreted by considering the contributions of electronic interactions and ion pairing to the enhanced gold solubility in the phosphorus−doped layer, using the simple theory of Reiss and assuming the gold and phosphorus atoms of the ion pair to be in adjacent substitutional sites, as suggested by the experimental data.
Holographic formation of gratings in optical waveguiding layers
Authors: Wood Van E. , Hartman N. F. , Verber C. M. , Kenan R. P.
Published: February 2003

Thick phase gratings were formed photorefractively (through optically induced refractive index changes) in planar optical waveguides by intersecting short−wavelength coherent guided beams. In multimode guides formed by effusing Li from LiNbO3, maximum diffraction efficiencies were 52% at the 0.488−μm write wavelength and 3.1% at 0.633 μm. In a two−mode LiTa1−xNbxO3 guide formed by diffusing Nb into LiTaO3 at 1100 °C, diffraction efficiencies were 65% and 28% at the same two wavelengths, respectively.
Electron trapping in aluminum−implanted silicon dioxide films on silicon
Authors: Johnson Noble M. , Johnson Walter C. , Lampert Murray A.
Published: February 2003

Photoelectric and MOS capacitance−voltage techniques were used to study electron trapping in 1400−Å dry−grown silicon dioxide films that were implanted with aluminum ions at 20 keV to a fluence of 1014 cm−2. The photoinjection of electrons into the implanted oxides resulted in the buildup of negative space charge. Data analysis indicated that all injected electrons had been trapped and that the observed transient responses of the photocurrent and flatband voltage were governed by the electric−field dependence of the photoinjected current. The negative space charge could be annealed either optically by photons of energy exceeding 4 eV or thermally at 350 °C. A 600 °C anneal for 30 min considerably reduced the concentration of electron traps. From this it is concluded that a substantial fraction of the traps were associated with displacement damage created by the ion implantation.
Electrical properties of epitaxially grown InAs0.61P0.39 films
Authors: Li Sheng S. , Anderson Jack R. , Kennedy John K.
Published: February 2003

Study has been made on the effect of the hydrogen carrier gas flow rate on the electron concentration and electron mobility of seven epitaxially grown (undoped) InAs0.61P0.39 samples. The H2 flow rates were varied in the range from 1780 to 515 cm3/min. The electron mobility was found to vary from 7800 to 11300 cm2/V s, and the electron density varied from 1.43×1016 to 1.92×1016 cm−3 at 77 K. Resistivity and Hall effect measurements yielded the Hall coefficient, electron density, and electron mobility as a function of temperature (3 to 300 K) for these specimens. the activation energy of the shallow donor states, the density of donor and acceptor impurities, and the scattering mechanisms (polar optical mode and ionized impurity scatterings) for electrons were analyzed. It was found that the impurity hopping conduction dominates for T<20 K.
Moving spot illumination of semiconductor panels
Authors: Rahnavard M. , Mavaddat R. , Mohajeri M.
Published: February 2003

The excess carrier distribution within a semiconductor illuminated by a moving light spot is determined. The analysis is given for the rectangular and circular light spots moving along a straight line on an infinite semiconductor panel. Graphical presentation is given for the particular
Transient heat transfer characteristics of liquid helium
Authors: Tsukamoto O. , Kobayashi S.
Published: February 2003

The transient heat transfer characteristics of liquid helium are experimentally studied. Critical burnout heat fluxes for pulsive heating are measured, and empirical relations between the critical burnout heat flux and the length of the heat pulse are given. The burnout is detected by observing the super−to−normal transition of the temperature sensor which is a thin lead film prepared on the heated surface by vacuum evaporation.
Model for noncoherent magnetization reversal
Authors: Brady Lynn J.
Published: February 2003

A model is presented for noncoherent magnetization reversal which reconciles experimental and theoretical observations. By its means, the saturation magnetization values of diverse materials and the fields required for their saturation are derived with precision. This includes polycrystalline Fe, Ni, Co, and several of their alloys selected at random from among those listed in the International Critical Tables. Data for these derivations are drawn from the tables referred to. The model is used to determine the energy required for magnetization by domain wall motion, as well as that needed for magnetization reversal in a single−crystal cobalt specimen. Data for these determinations are derived from published measurements made in fields whose strength varies from 0 to 9 kOe. Then, it is used to compute the value of the anisotropy field, HA, of an oriented Sm1/2Pr1/2Co5 specimen. Data for these computations are obtained from measurements made in fields whose strength is limited to 22 kOe. The results obtained support the hypothesis advanced that the strength of the applied field Ha required to saturate a uniaxial magnet in its easy direction of magnetization is given by the relationship, Ha=1/2HA, as K1 becomes much greater than K2. Here, K1 is the first−order and K2 is the second−order anisotropy constant. The phenomenon underlying this observation is explained and, in the process, it is shown that the anisotropy field HA required to saturate a completely oriented magnet and its single−crystal counterpart, in their hard directions, are exactly equal.
Comments on deviations of the penetration depth of niobium from BCS calculations
Authors: Halbritter J.
Published: February 2003

The temperature and frequency dependences of the magnetic field penetration depth λ (T,ω) of superconducting Nb show deviations from the BCS theory. These deviations are discussed. It is indicated that inhomogeneities in Nb can adequately account for them.
Photoeffects in CdTe with acid−grown Te layers
Authors: Zitter R. N. , Chavda D. L.
Published: February 2003

Immersion of CdTe in dilute HNO3 produces a layer of tellurium whose thickness grows with immersion time. These Te−CdTe junctions rectify and are photosensitive. Spectral response measurements show (a) a flat band extending to photon energies of 1.5 eV, characteristic of interband transitions in CdTe, (b) a peak at 1.4 eV in CdTe without a Te layer which disappears as the layer is added, and (c) a peak at 0.59 eV observed only with a Te layer present. The 1.4−eV peak is consistent with reports from electroluminescence experiments, but there are no previous reports of an effect in CdTe with energy near 0.59 eV. The latter peak may result from states created at the Te−CdTe interface.
Noise in single injection diodes. I. A survey of methods
Authors: van Vliet K. M. , Friedmann A. , Zijlstra R. J. J. , Gisolf A. , van der Ziel A.
Published: February 2003

A critical discussion is given of existing methods for the computation of noise in single injection space−charge−limited (SCL) devices: the salami method, the Langevin method, and the impedance field method. In addition, a new method is set forth, which in one form (finite volume divisions Δ3r) presents a lumped network description of noise and electrical parameters, whereas in another form (Δ3r→0) it presents a continuous media transport picture which is characterized by a transfer impedance tensor. The first form ties in with a modified salami method, whereas the second form is the substratum from which the more global impedance field formulas can be derived. A necessary and sufficient condition under which the noise is expressible as generalized Nyquist noise is obtained. For the simplest device, the thermal electron trap−free insulator, this is applied to one−dimensional as well as some three−dimensional geometries.
Nature of an intergranular thin−film phase in a highly non−Ohmic metal oxide varistor
Authors: Wong J. , Rao P. , Koch E. F.
Published: February 2003

A detailed examination by transmission electron microscopy and selected−area diffraction revealed that the thin−film intergranular phase in a highly non−Ohmic multicomponent metal oxide varistor system based on ZnO with small additions of antimony, bismuth, cobalt, manganese, and tin oxides is amorphous and is chemically related to a Bi2O3−rich pyrochlore coexisting in the ceramic.
High−frequency limitation on silicon IMPATT diode: Velocity modulation
Authors: Doumbia I. , Salmer G. , Constant E.
Published: February 2003

The effects of the energy relaxation time on the carrier velocity in silicon semiconductor materials is considered in the millimeter wave range. For this purpose an approximate formula relating the carrier velocity evolution in large−signal operation has been derived. Its influence on the rf output power and efficiency of the silicon IMPATT oscillator is discussed. Numerical results achieved reveal that the velocity modulation is one of the fundamental effects which limit the efficiency and power delivered at high frequencies; for example, at 100 GHz it causes an efficiency diminution which can exceed 30%.
Visual observations on the high−current transition from the constricted to the diffuse MPD arc mode
Authors: Murphree David L. , Carter Richard P.
Published: February 2003

High−speed movies of the continuous change through the high−current transition region from a retrograde constricted MPD arc discharge to a diffuse MPD discharge have been obtained. The occurrence of the high−current diffuse discharge is governed by the behavior of the cathode spots with increasing current and magnetic field. Besides obtaining a relatively uniform discharge distribution between the electrodes with the diffuse arc mode, three other important properties are that (1) the retrograde moving cathode spots distribute uniformly over the cathode when the uniform discharge is obtained, (2) the arc voltage decreases, and (3) the arc voltage noise is greatly reduced.
A simple method of determination of electron density in positive−column He−metal laser discharges
Authors: Mizeraczyk Jerzy K.
Published: February 2003

A new simple method of determination of electron density in positive−column He−metal laser discharges using the double probe is presented. The results obtained are in good agreement with those measured with the microwave cavity technique by other investigators. %
Comment on ’’Traveling wave oscillations in the optical region: A theoretical examination’’
Authors: Mizuno Koji , Ono Shoichi
Published: February 2003

The production of optical oscillations by an interaction involving the slow space−charge wave on an electron beam had been analyzed. Such an analysis is shown to be irrelevant since it requires the optical wavelength to be much larger than the Debye length (λ≫λD), a condition which cannot be met with available electron beams.
Heating of solid targets with laser pulses
Authors: Bechtel J. H.
Published: February 2003

Analytical and numerical solutions to the heat−conduction equation are obtained appropriate to the heating of absorbing media with pulsed lasers. The spatial and temporal form of the temperature is determined using several different models of the laser irradiance. Both surface and volume generation of heat are discussed and the results obtained using each model are compared with each other and with previously known results. It is found that if the depth of thermal diffusion for the laser pulse duration is large compared to the optical attenuation depth, the surface and volume generation models give nearly identical results. However, if the thermal diffusion depth for the laser pulse duration is comparable to or less than the optical attenuation depth, the surface generation model can give significantly different results compared to the volume generation model. Specific numerical results are given for a tungsten target irradiated by pulses of different temporal durations and the implications of the results are discussed with respect to the heating of metals by picosecond laser pulses.
Dynamic tensile strength of glycerol
Authors: Carlson G. A. , Levine H. S.
Published: February 2003

By use of a tensile stress wave 0.1 to 0.4 μsec in duration, generated by pulsed electron−beam energy deposition, the dynamic tensile strength (TS) of glycerol was determined in the 220−350 K temperature range. The TS curve is clearly divided into high− and low−temperature segments at about 262 K. Above this temperature, the TS decreases uniformly from 250 MPa (2.5 kbar) to 34 MPa at 350 K and failure appears to occur by void nucleation and growth. The experimental results are explained by a theory of homogeneous bubble nucleation which takes into account the non−steady−state nature of the experiment. Below the transition temperature, the TS is constant at about 250 MPa and failure is believed to occur by crack nucleation and growth.
Effect of beam intensity on target response to high−intensity pulsed CO2 laser radiation
Authors: Metz S. A. , Hettche L. R. , Stegman R. L. , Schriempf J. T.
Published: February 2003

The mechanical response of various classes of opaque materials exposed in air to high−intensity pulsed 10.6−μm−wavelength laser radiation is described. At beam intensities below approximately 107 W/cm2 (pulse durations of 4×10−3 and 3×10−4 sec), the magnitude of the total impulse delivered to the target is found to depend on the nature of the target material. At intensities greater than approximately 108 W/cm2 (pulse duration of 2×10−5 sec), there is negligible difference in the impulse response of different materials. Moreover, at the higher power densities total impulse delivered to a target by a 0.04−cm2 laser beam is found to be proportional to the physical area of the target up to approximately 8 cm2. These results are correlated with the the interrelationships among the instantaneous laser intensity, the instantaneous pressure generated at the target surface, and the observed state of development of the laser plume. Also reported is a survey of the thermal response of aluminum targets to laser irradiation over this range of power densities. These studies reveal that the apparent thermal coupling coefficient of aluminum remains at the cw value of approximately 3% at incident power densities as great as 105 W/cm2. Between 105 and 107 W/cm2, the optical coupling coefficient goes through a maximum of approximately 6%, then drops to a level close to zero at power densities greater than 108 W/cm2.
Microstructure and phase transformation in a highly non−Ohmic metal oxide varistor ceramic
Authors: Wong Joe
Published: February 2003

The microstructure of a complex multicomponent varistor ceramic based on ZnO with small additions of antimony, bismuth, cobalt, manganese, and tin oxides has been elucidated using a variety of structural techniques. Three crystalline phases are found to coexist in the sintered material. The bulk phase consists of a polycrystalline matrix of ZnO doped with Co(II). The ZnO grains are separated from one another by a Bi2Zn4/3Sb2/3O6 pyrochlore phase which forms a three−dimensional threadlike network, indicative of a liquid phase at high temperatures. A Zn(Zn4/3Sb2/3)O4 spinel constitutes the third phase and forms well−faceted octahedral crystals located frequently at grain boundaries between the ZnO and occasionally within the grains. This phase acts as a grain growth moderator for ZnO by anchoring the boundaries during sintering, but plays no role in the nonlinear characteristic of the varistor. A quasiequilibrium between the pyrochlore and spinel has been established such that formation of the spinel is favored at high temperatures. The over−all varistor microstructure may be described as a three−dimensional series−parallel network of ZnO−pyrochlore junctions.
Gain−induced guiding and astigmatic output beam of GaAs lasers
Authors: Cook D. D. , Nash F. R.
Published: February 2003

We report on experimental evidence for gain−induced guiding and refractive−index antiguiding along the junction plane of stripe−geometry double−heterostructure GaAs lasers. It had previously been found that carrier diffusion out of the active region leads to a gain profile along the junction plane that can be approximated by a parabolic variation. This results in a lowest−order mode having a Gaussian profile, a cylindrical phase front, and a constant radius of curvature. This curvature accounts for the astigmatism always observed in the output beam from stripe−geometry GaAs lasers, where gain guiding dominates index guiding. Experimental determinations of the far−field diffraction angle, ϑ, and the beam width, 2w, at the laser mirror in the junction plane enable us to calculate the parameters characterizing the gain distribution responsible for mode confinement, as well as a negative refractive−index increment which would tend to defocus the mode. The negative index increment, as measured between the center and the edges of the stripe, appears to be related to a competition between a negative free−carrier effect and a positive thermal focusing mechanism. Above threshold, changes in ϑ and w with current imply changes in the gain−guiding mechanism. The theory implies in particular a decrease in gain at the center of the stripe and an increase at the edges with an increase in current.
Boundary conditions on carrier stream surfaces in nondegenerate semiconductor plasmas
Authors: Barybin Anatoly A.
Published: February 2003

On the basis of the polarization description of nondegenerate semiconductor plasmas, the surface model of a semiconductor with charged localized surface states and space−charge layers is treated. Additional boundary conditions are derived from the continuity equation and the motion equation. Attention is focused on the applicability of the boundary transverse displacement of the effective stream boundary. The stiff−boundary model for the crystal surface and the free−boundary model for the quasifree effective surface of the carrier stream in the case of space−charge layers on the crystal surface are discussed. In addition to the condition of a completely reflecting boundary (n⋅j1=0) usually applied to the crystal surface, the opposite condition of a completely absorbing boundary (ρ1=0) is obtained. This latter condition corresponds to the quasifree effective boundary of the carrier stream in the presence of depletion layers.
Quasistatic solution of normal mode problem in semiconductor films without magnetic field
Authors: Barybin Anatoly A.
Published: February 2003

An analysis of normal modes in semiconductor films is presented for the stiff−boundary and free−boundary models. The effects of diffusion and anisotropic differential mobility on carrier wave propagation are investigated. Dispersion equations are analyzed in particular cases. The features of the modes are elucidated and related to results obtained previously.
On the generalized theory of normal mode excitation in electromagnetic and polarized medium waveguides by external sources
Authors: Barybin Anatoly A.
Published: February 2003

A generalized reciprocity theorem valid for electromagnetic waveguides, ferromagnetic media, elastic piezodielectric media, and drifting carrier streams in semiconductors in the presence of mobile carrier collisions with crystal defects is derived. The reciprocity theorem is the basis for obtaining mode orthogonality and normalization relations and excitation equations of normal modes in electromagnetic and polarized medium waveguides. The excitation equations thus obtained are reduced to the form of coupled−mode equations.