bluuebunny/crossref_metadata_2025 huggingface dataset:
Damage profile determination of ion-implanted Si layers by ellipsometry
Authors: Motooka T. , Watanabe K.
Published: February 2003

The damage profile in P+-ion-implanted Si is investigated by ellipsometry. Ellipsometric data are analyzed based on a three-layer model, i.e., SiO2 surface layer–implantation-induced amorphous Si (a-Si) layer–crystal Si (c-Si) substrate. The a-Si layer thickness is estimated for three implantation energies, 100, 50, and 30 keV at a fixed dose of 5×1015 cm−2. It is shown that a consistent interpretation of the data is possible taking into account the finite-width transition region between a-Si and c-Si. Assuming the transition layer to be random mixtures of a-Si and c-Si particles, the optical constant distribution in the transition layer is calculated using the effective medium theory for small particle composites. This model is used to estimate transition layer width.
Elastic interaction of 〈111〉 defects and extended screw dislocation in anisotropic fcc crystals
Authors: Parameswaran V. R. , Bapna M. S.
Published: February 2003

Elastic interaction between extended screw dislocations and tetragonal defects of the 〈111〉 type was studied by computing the energy-distance and the force-distance profiles for several metals using anistropic elasticity theory. The isotropic values of interaction energy and force as the limiting cases of the anistropic values were also obtained. It is shown that both the width of the dislocation and the anisotropy of the crystal significantly affect the energy-distance and the force-distance profiles. From the results obtained, the maximum interaction energy and the hardening coefficients for defect-dislocation interaction were also calculated. These values are compared with experimentally observed hardening in metals.
Transport of spatially inhomogeneous current in a compensated metal under magnetic fields. III. A case of bismuth in longitudinal and transverse magnetic fields
Authors: Yoshida Katsukuni
Published: February 2003

Inhomogeneous current systems in bismuth specimens under longitudinal and transverse magnetic fields have been investigated by solving a boundary-value problem of a rectangular parallelepiped medium to which current electrodes are attached with a finite contact area. The main results are as follows. In a longitudinal field, the current inhomogeneity governed by specimen geometry grows, extending toward the middle part of the specimen, and at the same time the current is condensed around the specimen axis parallel to the magnetic field. This current condensation increases the total resistance and decreases the potential difference measured on a side surface. In a transverse field, conversely, the current inhomogeneity degenerates to be confined in a narrow region near the end surface. Influences of specimen dimensions and electrode contact area are quantitatively discussed.
Piecewise analytic solution of the charge carrier transport equation for nondegenerate semiconductors
Authors: Shirts Randall B. , Gordon Roy G.
Published: February 2003

We present an alternative to conventional finite difference solutions to the transport equations for electrons and holes in nondegenerate semiconductor devices. The equations are solved using piecewise analytic methods in which the electric field is approximated by a linear function in a series of relatively large subintervals, and the continuity and current density equation is solved by transforming it into Weber’s equation. Carrier concentrations are expressed as a linear combination of Weber parabolic cylinder functions in each interval. Selfconsistency is obtained by iterative corrections with Gummel’s method. Computational results are presented for an abrupt P-N+ junction. It is believed that this method is particularly efficient for moderate bias conditions and especially in modeling heterojunction solar photovoltaic devices.
Current-voltage characteristics of amorphous silicon P-N junctions
Authors: Harris A. J. , Walker R. S. , Sneddon R.
Published: February 2003

The forward and reverse current-voltage characteristics of amorphous silicon p-n junction diodes are presented as a function of doping level. A study of the forward characteristics with temperature show that at high doping levels the current is limited by tunnelling through the depletion region via gap states. At the lowest doping levels the diode current is determined by generation-recombination in the depletion region. A similar interpretation is applied to the reverse characteristics. These results are relevant to the use of these diodes both as nonlinear elements in matrix-addressed large-area liquid-crystal displays and thin-film solar cells.
Response times of short Josephson junction and applications to rf SQUID’s
Authors: Ben-Jacob E. , Imry Y.
Published: February 2003

The dynamics of a small Josephson junction, driven either by a current source or by an external flux when the junction is the weak link element of a SQUID ring, were studied. Approximate analytical arguments and numerical simulations were used for the lumped circuit model of the junction. The various characteristic times of these devices were systematically obtained as functions of the parameters G and K of the junction and of the SQUID, respectively. The forms of the flux transitions and the times governing them are obtained for linear and periodic time variations of the external flux on the SQUID. A coupling of the SQUID to an LC circuit was treated. Limitations on the device parameters consistent with fast response, stability, and sensitivity were obtained both for the current driven junction and for the rf SQUID.
Band-to-band Auger effect in GaSb and InAs lasers
Authors: Sugimura Akira
Published: February 2003

Band-to-band Auger recombination for a semiconductor laser is studied theoretically. Auger recombination calculation method is formulated, which may be applicable to a semiconductor with any injected carrier density. Using the formulated equation, injected carrier density dependence, and the temperature dependence of the Auger lifetime for GaSb and InAs are calculated. The temperature dependence of Auger lifetime and the upper limit of the quantum efficiency under laser threshold condition are also discussed. Calculated result shows that Auger recombination affects cw room-temperature operation for an InAs laser considerably.
Backscattered electron energy spectra for thin films from an extension of the Everhart theory
Authors: Sogard M. R.
Published: February 2003

The Everhart theory is used to calculate the energy spectrum of normally incident backscattered electrons from elemental films of arbitrary thickness and atomic number. By means of a simple empirical extension of the theory, approximate agreement with experiment is achieved.
Evaluation of quantum and photoproduct yields in multiple-photon dissociation for isotope separation
Authors: Herman Irving P.
Published: February 2003

A model is constructed which evaluates the minority isotope photoproduct yield and the number of photons required per unit product for isotope separation via infrared multiple-photon dissociation by a Gaussian beam. Under most experimental conditions, these parameters are optimized if the peak central fluence is about twice the saturation fluence. The quantum yield and the photoproduct yield are then both about half that attainable if the same laser energy were instead delivered by a beam with a flat transverse profile. Specific applications to deuterium separation are also discussed.
Limiting efficiencies of ideal single and multiple energy gap terrestrial solar cells
Authors: Henry C. H.
Published: February 2003

The maximum efficiencies of ideal solar cells are calculated for both single and multiple energy gap cells using a standard air mass 1.5 terrestrial solar spectrum. The calculations of efficiency are made by a simple graphical method, which clearly exhibits the contributions of the various intrinsic losses. The maximum efficiency, at a concentration of 1 sun, is 31%. At a concentration of 1000 suns with the cell at 300 K, the maximum efficiencies are 37, 50, 56, and 72% for cells with 1, 2, 3, and 36 energy gaps, respectively. The value of 72% is less than the limit of 93% imposed by thermodynamics for the conversion of direct solar radiation into work. Ideal multiple energy gap solar cells fall below the thermodynamic limit because of emission of light from the forward-biased p-n junctions. The light is radiated at all angles and causes an entropy increase as well as an energy loss.
Regular compositional steps generated in GaAs1−xPx VPE layers
Authors: Kasano Hiroyuki
Published: February 2003

For GaAs VPE layers grown on Ge substrates, it is found that a one-dimensional misfit-dislocation density 1/p is proportional to lattice constant mismatch, just as for compositionally graded GaAs1−xPx layers grown on GaAs substrates. On the basis of these experimental results, lattice constant variation due to compositional change is given in a form explicitly including a compositional step. The compositional step width, calculated from this relationship and observed dislocation density, is about 500 atomic layers. Regular compositional steps, which are unintentionally formed, are actually observed on A-B etched cleavage planes of the graded layers. The observed width of this step is about 0.3 μm. This value roughly agrees with the calculated one. Presumably, the discontinuous change in composition is caused by competition between the following two processes which alternately dominate GaAs1−x Px epitaxial growth: a free-energy increase due to a decrease in arsenic supersaturation in vapor phase and a free-energy increase due to an increase in formation enthalpy of the crystal. Furthermore, in final compositional layers equidistant striae about 3.5 μm wide are observed on A-B etched cleavage planes. The origin of these striae is considered to be misfit dislocations which are generated in graded layers and climb as a result of association with Ga vacancies. Some of the striae are regularly bent in the direction perpendicular to the growth axis by shear stress due to sample bending.
Solar selective black cobalt: preparation, structure, and thermal stability
Authors: Smith G. B. , Ignatiev A. , Zajac G.
Published: February 2003

In the quest for an electroplated selective black coating stable to 500 °C in air, black cobalts have been prepared by three techniques to yield (a) plated cobalt sulphides, (b) plated cobalt oxide-hydroxide, and (c) cobalt oxide prepared by thermal oxidation of electropolated cobalt metal. The optical properties of the various coatings are analyzed before and after exposure to air for extended periods of time at temperatures in the 300 °–500 °C range. The sulfide black cobalt is not acceptable as a high-temperature selective absorber due to severe thermal degradation. The plated oxide is a good selective absorber to about 400 °C, and the thermally oxidized black to a slightly higher temperature, but degrades at 500 °C. Structure studies via scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and x-ray photoemission spectroscopy (XPS) are reported which yield a full account of the coating chemistry before and after heating. The studies reveal that the high solar absorptance of the acceptable black cobalt coatings is due to a continuation of a porous outer layer grading into nondense oxides of cobalt; either CoO or Co3O4, depending on the film. Absorption is intrinsic but not due to metal particles as in black chrome. A limited amount of optical degradation occurs upon heating the oxide black cobalt in air due to oxidation of hydroxide. However, the major degradation problem is shown to be substrate oxidation in contrast to black chrome where film oxidation is the principal problem.
Temperature dependence of stresses in chemical vapor deposited vitreous films
Authors: Shintani Akira , Sugaki Shojiro , Nakashima Hisao
Published: February 2003

Thermal stresses in chemical vapor deposited (CVD) vitreous silicate and phosphosilicate glass (PSG) films on Si substrates are measured in situ from room temperature (RT) to 900 °C. As-deposited films grown at one atmospheric (APCVD) and lower pressures (LPCVD) are found to be inherently under a tensile and compressive stress at RT, respectively. On heating to 500 °C, the tensile component of the stress develops in both CVD films. Tensile stress increases with time at a given temperature. In the range 500–900 °C, the tensile component is reduced with temperature and time. During the cooling process from a temperature between 700 and 900 °C, the stress component of APCVD and LPCVD films changes from tension to compression. With APCVD film, the temperature dependence of the stress in the range RT–500 °C can be represented as a function of phosphorous concentration in mol % P2O5. Temperature and time dependence, and thermal hysteresis are attributable to water content, sintering, and viscoelastic properties of CVD film. These are explained from the viewpoint of glass annealing and softening temperature points.
On the temperature and pressure variation of the static dielectric constant in alkaline earth fluorides
Authors: Varotsos P.
Published: February 2003

By comparing the recent dielectric data of alkaline earth fluorides, at various temperatures and pressures, to a recent model we conclude that the Szigeti charge increases on compression.
Microfilamentary superconducting composites by the external diffusion method: Nb3Sn
Authors: Cogan S. F. , Holmes D. S. , Rose R. M.
Published: February 2003

Microfilamentary superconducting composites of Nb3Sn fibers in bronze matrices were produced by the external diffusion method together with a solution preanneal to suppress Kirkendall porosity. The resulting materials had superior superconducting and mechanical properties at 4.2 °K, carrying overall current densities well over 104 A/cm2 at 15.4 T even for low (12%) superconductor fractions; over 105 A/cm2 at 12 T; and tolerating (in some cases) strains of the order of 2% without degradation, and stresses in the 500–1000 MPa range. There is evidence that finer superconducting filaments can tolerate much greater intrinsic strains without degradation; also, that the composites investigated were not optimized in terms of residual stresses, matrix composition, or filament spacing or size, so that further improvements are possible.
Saturation velocity and in-plane field effect on the velocity in bubble garnet films
Authors: Honda Shigeo , Fukuda Nobuo , Kusuda Tetsuzo
Published: February 2003

The motion equations of an infinite straight wall in a bubble garnet film are introduced for finite viscous damping. The present theory differs from previous work in assuming that the nucleated horizontal Bloch line is stable even in the Neel region of the wall. Theoretical values of the peak velocity Vp and the saturation velocity V0 agree fairly well with the experimental data. In-plane field effects on Vp and V0 have been investigated theoretically also. When the in-plane field is applied perpendicular to the wall plane, Vp increases and V0 decreases slightly. On the other hand, Vp decreases and V0 increases slightly due to the in-plane field parallel to the wall.
Temperature variation of the dielectric properties of bismuth germanate and bismuth germanium oxide
Authors: Link Joseph , Fontanella John , Andeen Carl G.
Published: February 2003

The unclamped complex dielectric constant for bismuth germanium oxide (Bi12GeO20) and bismuth germanate [Bi4(GeO4)3] has been determined at audio frequencies over the temperature range 6–325 K. For bismuth germanate, no dipolar impurities were observed. For bismuth germanium oxide, a strong dipolar impurity has been observed with an activation energy of 0.041 eV and a reciprocal frequency factor of 1.86×10−13 s. The strength of the relaxation is found to be correlated with the coloration of the sample. Possible origins of the relaxation are discussed. The results for the imaginary part of the dielectric constant were used to arrive at corrected values of the real part of the unclamped dielectric constant over the full range of temperatures. While absolute values are accurate to about 1.0%, the precision of the data is better than 0.1% relative to the room-temperature value.
Photoacoustic absorption measurements of optical materials and thin films
Authors: Rosencwaig Allan , Willis J. B.
Published: February 2003

We have developed two photoacoustic methods to perform low absorption measurements on optical components. One method can make measurements in the 10−4–10−5 absorption range, while the other can be used down to the 10−6 range.
The analysis of dislocations in strained III-V semiconductor crystals using elastobirefringence
Authors: Booyens H. , Basson J. H.
Published: February 2003

If the sign of the strain in a III-V crystal is known, it is possible to characterize dislocations in that crystal completely as regards their edge components. The technique for doing this is discussed and applied to the particular case of GaAs substrates on which Ga1−xAlxAs epitaxial layers have been grown by LPE.
Crystallographic and electro-optic properties of cleaved LiNbO3
Authors: Kaminow I. P. , Turner E. H. , Barns R. L. , Bernstein J. L.
Published: February 2003

The absolute orientation of the cleavage plane is determined and is related to standard rectangular coordinates. The electro-optic coefficients appropriate to the cleavage orientation are then calculated and measured in Ti:LiNbO3 waveguides. Additionally, a new measurement of the r51 coefficient in the bulk crystal is reported.
Hydrogen in semi-insulating polycrystalline silicon films
Authors: Knolle W. R. , Maxwell H. R. , Benenson R. E.
Published: February 2003

Infrared (IR) spectroscopy, nuclear reaction analysis (NRA), and Rutherford backscattering (RBS) were used on semi-insulating polycrystalline silicon (SIPOS) films deposited at atmospheric pressure (AP) and low pressure (LP) to determine film composition and hydrogen content. The amount of hydrogen in SIPOS ranges from less than 0.1 at. % H for films annealed in nitrogen at 800 °C for 30 min to 11 at. % H for higher oxygen content LP SIPOS films. For AP SIPOS films, the H content is directly proportional to the O content of the film and is uniformly distributed with depth into the SIPOS film. Based on the absorption cross section, the narrow, very weak 2270-cm−1 peak in the IR is identified as the Si-H absorption. The higher oxygen content LP SIPOS film contains additional H not bound as Si-H. The IR, NRA, and RBS data are interpreted in terms of a structural model involving Si-H and Si-O where the O is nonbridging. The 865-cm−1 peak in the IR is believed due to this nonbridging O-Si interaction.
Elastic constants of tungsten between 4.2 and 77 K
Authors: Stathis James H. , Bolef D. I.
Published: February 2003

The elastic constants of single-crystal tungsten between 4.2 and 77 K have been measured utilizing a sampled continuous-wave technique. The sensitivity of the present technique is such that the temperature dependence Cij(T) below 77 K is explicitly observed for the first time. A diffuse anomaly in CL(T), where CL = 1/2 (C11+C12)+C44, is observed in the temperature range 15–22 K.
Direct measurement of strain in plane impact experiments by a longitudinal resistance gauge
Authors: Rosenberg Z. , Yaziv D. , Partom Y.
Published: February 2003

A method for direct measurement of strain in plane impact experiments is presented. The method is based on recording resistance changes of a longitudinal resistance gauge placed in the target specimen. To demonstrate the validity of the method we conducted a series of plane impact experiments in which manganin and constantan resistance gauges were placed in targets made of different materials. From the experimental results we conclude that the uniaxial strain in the target material can be determined to within an error of Δε=±0.2%.
Flow effects in epitaxial autodoping
Authors: Srinivasan G. R.
Published: February 2003

A quantitative model has been developed to account for the flow effects in epitaxial autodoping for chemical-vapor-deposited films. Analytical expressions are derived for the autodoping variations along and against the direction of flow arising from a diffusion stripe in the substrate. These expressions relate the maximum concentration in the lateral autodoping peak to the distance from the autodoping source and to the carrier gas velocity. Experimental verification of the model is obtained for arsenic autodoping in silicon epitaxial films, which indicates that boundary layer effects are not predominant in the autodoping phenomenon. The analysis also yields a value of 2.5 cm2/sec for the arsenic vapor diffusivity in hydrogen at 1150 °C.
Interpretation of the conductance and capacitance frequency dependence of hydrogenated amorphous silicon Schottky barrier diodes
Authors: Viktorovitch P. , Moddel G.
Published: February 2003

We present a general model of the frequency dependence of conductance and capacitance in a-Si:H Schottky diodes. In order to circumvent several questionable assumptions required in the analysis of capacitance voltage characteristics, the frequency dependence of sputtered a-Si:H devices is measured with no applied dc voltage. We obtain independent, consistent values of the depletion width and of the density of states at the Fermi level and below from both conductance and capacitance at both low and high modulation frequencies. We show that the linear frequency dependence of conductance cannot be attributed to hopping conductance, but rather to the interaction of gap states with free carriers. Our study shows that the interaction kinetics of the states around the Fermi level with the conduction-band carriers is so fast that the response of the diode is limited by the band transport of these carriers, which rapidly thermalize and distribute themselves through the continuum of states from the conduction band to the Fermi level.
Effect of nonparabolicity on transverse magnetoresistance in degenerate piezoelectric semiconductors
Authors: Wu Chhi-Chong , Chen Anna
Published: February 2003

The effect of nonparabolicity on the transverse magnetoresistance of degenerate piezoelectric semiconductors in strong dc magnetic fields has been studied for the case where acoustic phonons are the dominant scattering mechanism. The calculation has been performed taking into account the inelasticities in the electron-phonon scattering due to the finite energy of phonons involved. Results show that the transverse magnetoresistance due to the piezoelectric coupling for the nonparabolic band structure is enhanced much more considerably than that for the parabolic band structure. From our numerical results for the nonparabolic band structure, it can be seen that the piezoelectric coupling plays the same important role for the transverse magnetoresistance as the deformation-potential coupling. We also found that the transverse magnetoresistance for both parabolic and nonparabolic band structures oscillates with the dc magnetic field owing to the degeneracy of the electron gas.
Thermal conversion of GaAs
Authors: Klein P. B. , Nordquist P. E. R. , Siebenmann P. G.
Published: February 2003

The conversion of semi-insulating GaAs to p type as a result of heat treatment in H2 was studied by photoluminescence (PL), secondary-ion mass spectrometry (SIMS), and transport measurements. The SIMS measurements resulted in the direct chemical identification of Mn near the heated surface. The correlation of the SIMS profiles with the results of PL and transport measurements indicated that Mn acceptors are responsible for the type conversion, and that substantial concentrations of Mn(?1017/cm3) are found in thin (1–3 μm) layers near the surface. The results of studies of samples heated under several different conditions showed that the Mn layers were not introduced by contamination from external sources during heat treatment, but were probably due to the presence of a bulk Mn concentration (<3×1015/cm3): during heat treatment the Mn diffuses to the surface, probably assisted by the in diffusion of Ga vacancies, as suggested by Zucca. Photoluminescence profiling measurements and the correlation between the SIMS and PL results indicate that the 1.41-eV PL band that is associated with the type-converted surface is due to recombination at a Mn acceptor on a Ga site, and not at a next-nearest-neighbor arsenic vacancy-amphoteric acceptor complex.
Theory of magnetic surface-wave propagation on a thick YIG slab
Authors: Gupta S. S. , Srivastava N. C.
Published: February 2003

This paper presents an electromagnetic analysis of magnetic surface wave propagation on a thick transversely magnetized YIG slab. The effect of transverse variation of wave field has been taken in account; this leads to hybridization of TE and TM modes. Using the interface model the general dispersion relation has been obtained which reduces to the well-known limiting forms. The numerical results indicate restricted validity of the earlier analyses. Specifically, for any realistic set of parameters, the propagation of surface wave in X band can be satisfactorily described only by the present analysis.
Influence of lateral modes on the first derivative of the I-V characteristic of buried or mesa stripe geometry injection lasers
Authors: Dmochowski J. E. , Dobaczewski L. J.
Published: February 2003

The theoretical model proposed in the paper explains the influence of an inhomogeneous laser radiation in the junction plane upon the behavior of the first derivative I dV/dI above threshold. These inhomogeneities are connected with the existence of lateral modes. Calculations are carried out for modes represented by trigonometric functions for a buried or mesa stripe geometry laser. The condition of constant mode gain causes an increase of the average junction voltage due to the inhomogeneity of the minority carrier concentration in the active layer. This effect is observed as the ’’unsaturated’’ junction voltage above threshold.
Nonlinear acoustic off-axis imaging
Authors: Yeack C. E. , Chodorow M. , Cutler C. C.
Published: February 2003

Nonlinear imaging, in which object acoustic illumination is at a frequency ω and the output is detected at 2ω, has been complicated by competing nonlinear generation from the propagation medium between the object and the output lens. However, recent results with a nonspecular oblique incidence acoustic reflection microscope show interesting object nonlinear generation from polyvinylidine fluoride (PVF)2 and mica in granite. These micrographs will be presented and discussed.
The dynamics of cavity clusters in ultrasonic (vibratory) cavitation erosion
Authors: Hansson I. , Mo/rch K. A.
Published: February 2003

The erosion of solids caused by cavitating liquids is a result of the concerted collapse of clusters of cavities. In vibratory cavitation equipment the clusters grow and collapse adjacent to a solid surface and are typically of hemispherical or cylindrical form. In the present paper the collapse process of these clusters is described and the collapse equations are developed and solved. The theoretical results are compared with results from high-speed photography of the clusters and with the initial stages of cavitation erosion on metal specimens. Experimental and theoretical results show that the collapse of a cavity cluster is driven by the ambient pressure and the collapse proceeds from the outer boundary of the cluster towards its center. During the collapse the pressure at the inward-moving cluster boundary increases continuously, and at the cluster center it rises significantly above the ambient pressure. Therefore the collapse velocity of the individual cavities increases towards the cluster center, which explains that the erosion, being caused by the individual cavities, occurs predominantly in this region. Likewise, the pressure increase at the cluster boundary explains why materials of even high strength can be eroded by collapse of cavity clusters at atmospheric ambient pressure.
Cross sections for the vibrational excitation of the H2(X1∑+g) state via electron collisional excitation of the higher singlet states
Authors: Hiskes J. R.
Published: February 2003

The cross sections are reported for the collisional excitation of the ground state of hydrogen, H2X1∑+g (v″=0), leading to vibrational excitation of all fourteen v″ levels. These cross sections pertain to energetic electron collisions populating the B1∑+u and C1∏±u electronic states which in turn radiate to the X1∑+g(v″) levels. The cross sections are in the range 10−18–10−17 cm2. An estimate is made of contributions from higher states.
Theoretical conversion efficiency of relativistic electron beams into ion beams in the vicinity of a target
Authors: Young T. S. T. , Genuario R. D.
Published: February 2003

In order to reach the power density and total energy required for inertial confinement fusion targets using electron beams, a modular approach employing multiple diodes, plasma channel transport, and relativistic electron beam (REB) overlap is being pursued. This paper reports on an analytic study of the conversion efficiency of REB’s to ions by a combination of magnetic reflection and electrostatic reflexing of the electrons in the overlap region. The initial power density (but not total power) of the incident electron beam in this scheme is reduced by the ratio of electron beam overlap radius to final pellet radius squared, and the required power density gain in the overlap region is relaxed to unity. We find for a uniform REB energy distribution (the most probable distribution function at the overlap radius): (1) the ions cannot reach the full potential of the generator; (2) ion beam conversion efficiency remains low (∼5% in energy) and increases slowly with outer shell thickness; and (3) ion voltage remains almost constant for a wide range of generator voltages.
Influence of uniaxial pressure on the critical temperature for long delays in GaAs junction lasers
Authors: Morosini Maria B. Z. , Patel N. B. , Nunes F. D.
Published: February 2003

In this work we report on the influence of uniaxial pressure applied perpendicularly to junction laser on the behavior of the critical temperature for the onset of long delays in GaAs junction lasers. Experimental data showing this influence for lasers operating in a TE or TM polarization are presented and explained on the basis of a thermal theory of long delays and related phenomena.
Basic Josephson tunnel parameters at microwave frequency—A reassessment
Authors: Feldman M. J. , Rudner S. , Claeson T.
Published: February 2003

A previously published analysis of the magnetic field variation of the reflected microwave power from small unbiased Pb-O-Pb Josephson junctions found strong temperature dependences for the basic tunnel parameters. We reanalyze those measurements employing independent variables, compensating for spurious external reflections, and accounting for noise reduction of the dc critical current. The cosφ amplitude ζ is positive near Tc and becomes negative at lower temperatures. In contrast to the previous work ζ is less sharply peaked, the junction rf resistance varies smoothly, and the capacitance is temperature independent. Our results clearly disagree with recent theoretical work.
Short circuit current in indium tin oxide/silicon solar cells
Authors: Singh R.
Published: February 2003

The short circuit current density Jsc of indium tin oxide/single and polycrystalline silicon solar cells reported by Schunck and Coche [Appl. Phys. Lett. 35, 863 (1979)] is much higher than other silicon solar cells. We have shown that the Jsc reported in the above reference does not represent the true value of these devices.
Electron transport across aluminum/ultrathin silicon oxide/phosphorus implanted silicon barriers
Authors: Kikuchi Akira , Yamamoto Hiroshi , Iwata Seiichi , Ikeda Takahide , Nakata Kensuke
Published: February 2003

Schottky barrier diodes are fabricated on silicon surfaces whose impurity concentrations are controlled by ion implantation techniques. The barriers are produced by electron beam evaporation or sputtering of the metal. The forward characteristics of the diodes show that the forward voltage of Schottky barrier diodes made by sputtering is 50–100 mV larger than those made by electron beam evaporation. Electron spectroscopy for chemical analysis measurements show that, for sputtering, the silicon oxide thickness at the interface between the metal film and silicon substrate is 0.2 nm thicker than for electron beam evaporation. Theoretical and experimental studies of Schottky barrier diodes in which the metal and silicon substrate are separated by a thin layer silicon oxide are reported.
A solution of the Werthamer equation for superconducting tunneling junctions at vanishing temperature (T=0)
Authors: Erné S. N. , Lübbig H.
Published: February 2003

A mathematical model is presented for the retardation of the Werthamer functional for the Josephson tunneling junction to treat the current controlled case. Computational results concerning the current-voltage characteristic make visible an enhanced hysteresis due to the nonlinear frequency response of the tunneling current. In addition, the irreversible flux transition in a SQUID is analyzed: the flux quantum transition time is found to be shorter than predicted by quasiadiabatic models.
Angular dependence of site preference in growth-induced anisotropy
Authors: Josephs Richard M. , Stein Barry F. , Callen Herbert , Bekebrede William R.
Published: February 2003

We have investigated the dependence of the growth-induced anisotropy on the orientation of the crystalline growth face in a series of (YLaEu)3 (FeGa)5 O12 films epitaxially grown so that the growth face normal deviates from the [111] direction in a (11̄0) plane by angles varying from 0° to 14.6°. We have determined the direction of the respective net easy axis tilt angles and have found them all to lie in the (11̄0) tilt planes at angles ranging up to ∼60°. We have also measured the azimuthal dependence of the ferromagnetic resonance field in the film plane for the various samples. The tilt angle data were analyzed using an expansion for the growth induced anisotropy carried to fourth order in β, the direction of the growth face normal. The results of this analysis were used to compute the angular variation of the ferromagnetic resonance field; the results are qualitatively correct in shape although deviating quantitatively by ∼20%. In contrast, the conventional fit to second order in β is qualitatively incorrect.
Domain configuration and equilibrium size of domains in BaTiO3 ceramics
Authors: Arlt G. , Sasko P.
Published: February 2003

The domain structures in BaTiO3 ceramics differ from those of single crystals. The spatial configuration of the domains in the ceramics has been derived from etch patterns. All observed etch patterns can be described by two types of domain configurations. Thin layered domains separated by 90 ° walls are piled up to form sloped stacks. Neighboring stacks are bounded by two types of boundaries. One of them is made up of 90 ° and 180 ° domain walls. The other type has a more complex structure which is not free of polarization charge. In this case the pattern accounts for a head to side relation of polarization vectors. Both structures allow the grain, merely by wall motion, to be easily squeezed to arbitrary deformations up to strains of the order of the spontaneous strain. The elastic energy stored in a mixed wall has been estimated. It shows order of magnitude agreement with the energy of the 90 ° walls if the observed domain size is taken into account.
Numerical study of the near field radiated by an infinitely long slot on circular conducting cylinder
Authors: Shirai Hiroshi , Hongo Kohei
Published: February 2003

The numerical solution of the near field patterns of both axial and circumferential slots on a circular conducting cylinder is obtained. Equiamplitude contours around the cylinder and radial variation of the field along the constant azimuthal coordinates are presented. The calculated results show that the pattern above the slot completely coincide with that of a similarly situated slot in an infinite ground plane.
Comment on ’’Studies in electromagnetic fields and phase constants of a concentric line having a helical inner conductor’’ and ’’An analysis of the wave impedance and the attenuation constants of a concentric line having a helical inner conductor’’
Authors: Sichak W.
Published: February 2003

These recent theoretical papers, by the same authors, derive the quantities given in the titles. The authors used a ’’wire’’ model for the helix, which is supposed to be more rigorous than the ’’tape’’ or ’’sheath’’ models used in papers published 25 or more years ago. By using experimental data from a paper referenced by the authors, it is shown that the sheath model fits the measurements better than the wire model used here.
High-efficiency AlGaAs/GaAs concentrator solar cells by organometallic vapor phase epitaxy
Authors: Saxena R. R. , Aebi V. , Cooper C. B. , Ludowise M. J. , Vander Plas H. A. , Cairns B. R. , Maloney T. J. , Borden P. G. , Gregory P. E.
Published: February 2003

Conversion efficiency of 23% at 369 suns has been achieved for packaged AlGaAs/GaAs solar cells fabricated by organometallic vapor phase epitaxy. The design considerations and the solar cell performance in concentrated sunlight are described.
Aging phenomena of plasma oxidized Pb-alloy Josephson junctions
Authors: Waho Takao , Kuroda Kenichi , Ishida Akira
Published: February 2003

Aging phenomena in I-V characteristics of plasma oxidized Pb-alloy Josephson junctions have been investigated. Aging effect, or decrease in tunneling resistance during room-temperature storage as long as 300 days, was found to be dominated by a single rate-controlling process of activation energy of 0.78 eV. Based on Auger analysis of tunneling layers, it was concluded that the aging effect can be attributed to the compositional variation in the tunneling oxide layer resulting from the conversion from a Pb- and In-oxide mixture into In oxide. A simple phenomenological model is proposed, which well explains the decrease in tunneling resistance upon aging.
Fabrication and characterization of narrow stripe InGaAsP/InP buried heterostructure lasers
Authors: Hirao M. , Doi A. , Tsuji S. , Nakamura M. , Aiki K.
Published: February 2003

InGaAsP/InP buried-heterostructure lasers with a stripe width of 1–2 μm have been fabricated by two-step liquid phase epitaxy and preferential chemical etching. They operate in the fundamental transverse mode at wavelengths of ∼1.3 μm with threshold current as low as 22 mA. The temperature limit for cw operation is 80 °C.
Heterodyne measurements of electron cyclotron emission from Alcator A and absolute submillimeter receiver calibration
Authors: Woskoboinikow P. , Praddaude H. C. , Falconer I. S. , Mulligan W. J.
Published: February 2003

Electron cyclotron emission (ECE) from thermal plasmas in the Alcator A tokamak for harmonics from 2nd through 5th and up to the 7th harmonic for nonthermal plasmas have been observed in the frequency range of 400–800 GHz using a sensitive, low-noise submillimeter heterodyne receiver. The sensitivity of the receiver (∼10−20 W Hz−1) allowed for the measurement of 4th and 5th harmonic ECE from thermal plasmas with Te≊800 eV. The receiver was absolutely calibrated and its field of view was experimentally determined. A careful analysis has been made to relate the receiver calibration to the plasma-emitting volume, taking into account radiation coherence time, wall reflections, polarization scrambling, window losses, and aperture restrictions.
Effect of oxygen on the diffusion of Ni in Pt in Pt-Ni-Pt films
Authors: Chang Chin-An , Chu W. K.
Published: February 2003

We have studied the effect of oxygen on the diffusion of Ni into Pt in the Pt-Ni-Pt films. Below 400 °C, the diffusion rates of Ni into both Pt layers are greatly reduced by oxygen. Above 500 °C, however, Ni rapidly mixes with Pt layers, which leads to the formation of Ni oxide on the Pt surface in the presence of oxygen.
Acceptor implantation in Fe-doped, semi-insulating indium phosphide
Authors: Inada T. , Taka S. , Yamamoto Y.
Published: February 2003

Either magnesium or zinc ions have been implanted in (100)-oriented, Fe-doped, semi-insulating indium phosphide at room temperature or at 250 °C. Channeling effect measurements have revealed that the surface layer is transformed to an amorphous state by room-temperature implants with a dose of mid-1014/cm2. The implantation-induced amorphous layers disappear after 700-°C annealing, but a highly disordered region still remains if these amorphous layers exceed 0.23 μm in thickness. Carrier concentration and mobility profiles for Mg- and Zn-implanted samples have been measured by differential Hall-measurements. A dead layer, where no free carrier is detected, is formed near the implanted surface. The formation of the dead layer could be explained by the existence of the highly disordered region remaining after anneal and/or by the compensation effect due to n-type carriers introduced near the surface by room-temperature implant. It has been also shown that neither the amorphous layer nor the highly disordered region is formed in the samples where implantation is carried out at 250 °C, resulting in the annihilation of the dead layer from the carrier concentration profile.
Transient radiation study of GaAs metal semiconductor field effect transistors implanted in Cr-doped and undoped substrates
Authors: Simons M. , King E. E. , Anderson W. T. , Day H. M.
Published: February 2003

Flash x-ray measurements have been made on GaAs metal semiconductor field effect transistor structures fabricated in both Cr-doped and undoped semi-insulating substrate material in order to characterize the levels responsible for long term transients in these devices. Prominent electron and hole traps with activation energies in the 0.76–0.90-eV range have been identified. The main electron trap, which is present in both Cr-doped and undoped substrates, appears to be primarily responsible for the observed transient response. However, traps related to Cr-doping also contribute to the transient behavior.
Cross-sectional transmission electron microscopy of silicon-silicide interfaces
Authors: Föll F. , Ho P. S. , Tu K. N.
Published: February 2003

The epitaxial interfaces of Si/Pd2Si, Si/NiSi2, and, to a lesser extent, Si/PtSi have been investigated by transmission electron microscopy using cross-sectional specimens. Direct lattice imaging was used to image the Si/Pd2Si and the Si/NiSi2 interfaces. The Si/Pd2Si interface was found to be rather smooth on a macroscopic scale but rough on a atomic scale, whereas the opposite is true for the Si/NiSi2 interface. A twinning relationship between NiSi2 and {111} Si has been observed. The Si/PtSi interface is very rough on a macroscopic scale. Interface dislocations are present in the Pd- and Ni-silicide cases. No evidence for an amorphous interfacial layer has been obtained.
Theory of nonlinear absorption in InSb spin-flip laser
Authors: Nee Tsu-Wei , Scully Marlan O.
Published: February 2003

The strong transient optical absorption in n-InSb Raman spin-flip laser device at 2 °K was interpreted due to the intense laser-generated hot conduction electrons. We present the microscopic theoretical calculation for this nonlinear and nonequilibrium optical effect. By assuming the time-dependent functions for electronic temperature and Fermi energy, the time evolution of the nonequilibrium hot electron distribution during the pulsed laser irradiation is calculated.
Channeling of intense electromagnetic beams
Authors: Lax M. , Batteh J. H. , Agrawal G. P.
Published: February 2003

The atmospheric propagation of a sequence of short intense electromagnetic pulses and their creation of a low density channel in the beam vicinity are considered. A Lagrangian as well as Eulerian description of the electromagnetic pulses is developed to solve Maxwell’s equations in t he paraxial approximation. The hydrodynamic response of the atmosphere is considered in the adiabatic approximation. After a scaling of the electromagnetic and hydrodynamic variable three dimensionless parameters, the pressure parameter, the focusing parameter and the diffraction parameter, emerge which describe the interaction of the pulse with the atmosphere in a convenient way. The electromagnetic equations are solved using the finite-difference method as well as the Fourier transform technique. For the latter method a fast Hankel transform algorithm is used. An explicit inclusion of end-corrections in the Hankel transform algorithm makes our propagation code fast and accurate. We discuss the numerical results and their dependence on the three parameters. Our analysis may find applications in determining the optimum beam parameters for creating a low density channel of specified length.
Measurement of HgXe (30+) fluorescence efficiency in an electron-beam-preionized, volume-stable discharge and comparison with Boltzmann kinetics code calculations
Authors: Hays A. K. , Padrick T. D.
Published: February 2003

A HgXe(30+) fluorescence efficiency of 12±2% was measured in an electron-beam-preionized, volume-stable discharge with an E/N value of 2×10−17 V cm2. This efficiency was obtained for gas mixtures with mercury pressures in the range of 2–10 Torr and a constant xenon pressure of 3000 Torr. This efficiency was compared with Boltzmann-kinetics code calculations. It was found that processes involving molecular mercury formation had to be included in the kinetics code in order to obtain agreement between the measured and calculated HgXe (30+) fluorescence efficiency.
Acoustic emission waveforms from cracking steel: Experiment and theory
Authors: Kline Ronald A. , Green Robert E. , Palmer C. Harvey
Published: February 2003

Acoustic emission monitoring has become a well-recognized technique for the nondestructive evaluation of materials and structures. The usual procedure is to count the number of acoustic emission bursts and record either the total count or the burst rate. A rough measure of the burst amplitude or of the burst duration is obtained by ringdown counting or by peak or threshold detection. In this paper we demonstrate that further information is obtainable from accurate waveform determinations, which can be obtained by our optical method. We find that there is good agreement between at least some natural acoustic emission waveforms and theoretical seismic pulse waveforms.
Comment on ’’A unified explanation for secondary-ion yields and ’’mechanism of the SIMS matrix effect’’
Authors: Wittmaack K.
Published: February 2003

Experimental data on secondary-ions yields recently reported by Deline et al. are analyzed critically. It is shown that whereas the results for oxygen bombardment support earlier findings concerning positive-secondary-ion emission, the negative-ion yields observed under cesium impact reveal previously unknown features. A unified explanation for secondary-ion yields cannot be deduced from the published results. Simple (exponential) laws may be found only under certain experimental conditions or after averaging procedures.
Intense electron-beam excitation of organic dye vapors
Authors: Marowsky G. , Tittel F. K. , Wilson W. L.
Published: February 2003

Experimental studies of electron-beam excitation of organic dye vapors of p-phenylene-bis-(5-phenyl-2-oxazole) POPOP and p-quaterphenyl have demonstrated short-duration high-gain and super-radiant laser behavior accompanied by severe fluorescence quenching due to dye fragmentation. This has been analyzed quantitatively by evaluation of the nitrogen fluorescence, originating from the complete breakdown of the POPOP structure.
Radial distribution of the gain of a CuBr laser
Authors: Kuroda K. , Takahashi H. , Chihara M. , Ogura I.
Published: February 2003

The radial distributions of the gain and the saturation energy density of the 510.6-nm line of a double-pulse CuBr laser were measured. With oven temperature varying from 420 to 480 °C, the distributions of the gain change considerably. At 480 °C the distribution of the gain has a strong peak near the wall of the tube. The peak values of the gain and the saturation energy density are 0.25 cm−1 and 53 μJ/cm2, respectively.