bluuebunny/crossref_metadata_2025 huggingface dataset:
Generation of coherent current pulses and delayed switching in relaxation GaAs p+-iν-n diodes
Authors: Okushi H.
Published: February 2003

In GaAs p+-ν-n diodes prepared from high-resistivity Cr-doped GaAs, generation of coherent current pulses (CCP) has been observed in the forward bias region Vth?V<Vsw and delayed switching in the region V≳Vsw, where Vth is a threshold voltage for the CCP and Vsw is a threshold voltage for the switching. Coexistence of multiple components of the CCP with different interpulse times and pulse heights has been observed, which indicates that the CCP is caused by the periodic formation and annihilation of the filamentary current path. A double-pulse experiment of the delayed switching has been performed using first and second identical pulses with varying pulse-separation time. For pulse heights slightly larger than Vsw, the delay time of the second pulse (td2) is larger than that of the first pulse (td1). Experimental results show that this peculiar relation td2≳td1 is due to an electronic process. These new nonlinear transport phenomena are closely related to each other. A model based on the concept of the relaxation semiconductor is proposed, taking into account the relationship between the dielectric relaxation time and the diffusion length lifetime in a transient state of the system involving two types of defect centers. Numerical estimations based on the model agree with the experimental values.
Photoinduced anomalous oscillations in reach-through avalanche photodiodes
Authors: Maeda Minoru , Minai Yasuo , Tanaka Mitsuo
Published: February 2003

Some reach-through avalanche photodiodes are found to exhibit anomalous oscillations when illuminated by high-level optical power. Experimental study of the phenomena shows that the anomalous oscillation occurs below a voltage at which the depletion layer begins to extend into the layer. Some relations of oscillation frequency with biasing voltage, optical power density incident on the photosensitive area, and diode parameters are also described. These results should prove useful in the design of a reach-through avalanche photodiode free from anomalous oscillations.
Temperature dependence of microwave SQUID response
Authors: Callegari Alessandro , Deaver Bascom S.
Published: February 2003

The response of a microwave SQUID using a Ta point contact has been measured at various temperatures giving a progression of operating conditions from the nonhysteretic to the hysteretic mode. The responses calculated by Soerensen and by Burhman and Jackel are in good qualitative agreement with the measurements. However, these theories do not appear to account for the response reported by Rachford, Wolf, Nisenoff, and Huang for thin-film bridges. We present a calculation that exhibits explicitly the dependence of the response on Ω=Φ0ν/IcR, where ν is the microwave frequeny, Ic and R are the critical current and resistance of the junction, and Φ0 is the fluxoid quantum, and that agrees with their data and their interpretation of it in terms of a limiting time τ for the supercurrent response with τ∝Δ (T)−1 where Δ (T) is the BCS gap parameter.
Two-frequency excitation for the Ramsey separated oscillatory field method
Authors: Jarvis Stephen , Wineland David J. , Hellwig Helmut
Published: February 2003

It is suggested that the systematic frequency shift due to rf phase difference between the two interaction regions in Ramsey’s separated oscillatory field technique may be eliminated by using different frequencies in the two interaction regions. The technique is briefly described, and the advantages are noted, particularly for frequency standards based on atomic beams.
On the dispersion of a dye with a harmonically varying concentration in the hydromagnetic flow in a channel
Authors: Soundalgekar V. M. , Gupta A. S.
Published: February 2003

An analysis of the dispersion of a dye with a harmonically varying concentration in a magnetohydrodynamic channel flow has been carried out. An estimate is obtained for the axial distance along which the fluctuations in concentration decay in the case of low-frequency input. It is observed that the decay distance for the fluctuations in concentration increases with an increase in the Hartmann number M.
Experimental studies of the large Debye length probe theory in a continuum plasma
Authors: Kamitsuma M. , Chen Sin-Li
Published: February 2003

The Laplace limit probe theory for continuum plasmas, i.e., probe theory under the condition rp/λD→0, where rp is probe radius and λD is Debye length, has been experimentally studied. The results show that the application limit of this theory is rp/λD=0.44 for a spherical probe and rp/λD=0.23 for a cylindrical probe.
Rapid determination of semiconductor doping and flatband voltage in large MOSFET’s
Authors: Lubberts G.
Published: February 2003

A simple method is presented for accurate determination of the semiconductor doping concentration, flatband voltage, and gate-oxide thickness from capacitance measurements on large MOSFET’s. Conventionally, MOS capacitors are used to determine the doping profile from deep-depletion capacitance measurements, which unfortunately require a rapidly varying voltage across the capacitor. It is demonstrated that gate-substrate capacitance of MOSFET’s can be measured conveniently in deep depletion with a slowly varying gate-substrate bias. This is accomplished by reverse biasing the source and drain diodes to prevent the buildup of minority carriers at the semiconductor surface under the gate area. Measurements on MOSFET’s fabricated on n-type 〈111〉 Si gave ND=4.1×1014/cm3, VFB=−1.5 V, and tox=1064 Å, in agreement with resistivity, voltage threshold, and ellipsometry measurements, respectively.
Anomalous microwave-induced voltages across Josephson junctions
Authors: Pech Tibor , Saint-Michel Jacques
Published: February 2003

We have observed that under certain circumstances, in addition to the predictable Josephson voltage, variable anomalous voltages can be induced across a ’’Nb-oxide-Pb’’ type tunnel junction having Cu voltage and current leads fixed by In solder onto the junction’s thin-film electrodes. The analysis of the experimental results shows that the microwave-induced anomalous voltages are due to the combined effect of a contact onto the Nb film and of a contact onto the Pb film which behave quite differently. The induced anomalous voltage may be large or small or even remain undetectable, according to the temperature-dependent quality of the individual contacts. Appearance of anomalous voltages can efficiently be prevented by means of Au contact lands. Precautions should be taken, however, for the preparation of the Au lands, as it is illustrated by an example.
Investigation of ion-implanted GaP layers by ellipsometry
Authors: Dobbs B. C. , Anderson W. J. , Park Y. S.
Published: February 2003

Ion-implanted gallium-phosphide layers have been examined by ellipsometry. This technique provides a nondestructive means of measuring radiation damage. The index of refraction increases with ion dose except when ion-beam-radiation annealing causes a decrease in the extinction coefficient. A marked difference is observed in radiation-damage annealing between light and heavy ions. A computer calculation was performed to investigate the variation in the complex index of refraction due to implanted-ion fluence; agreement with experimental data was obtained.
Shear moduli of a niobium single crystal with hydrogen additions at elevated temperature
Authors: Schlader D. M. , Smith J. F.
Published: February 2003

The independent elastic constants of a niobium single crystal were measured over the temperature range 298–600 K. Concentrations of 1.90 and 4.69 at.% hydrogen were successively introduced at 573 K through a palladium coating. Elastic shear constants were determined at both concentrations. The data show that C44 increases and C′ decreases with increasing hydrogen concentration, but the slopes of both concentration dependences decrease so that the slope of the concentration dependence of the anisotropy ratio is insensitive to temperature. Both increasing temperature and increasing hydrogen concentration tend to move the anisotropy ratio toward unity.
Dislocation damping in Cu-Ni alloys at low temperatures and high strain amplitudes
Authors: Gottschall R. J. , Beshers D. N.
Published: February 2003

Dislocation damping was studied in 〈110〉 Cu crystals containing 0≲c0≲4×10−2 atom fraction Ni at 95≲T≲297 °K, strain amplitudes ε0 from the mid-10−7 to the mid-10−4 range, and frequencies f≈22 kHz. Dislocation interactions with the combined Suzuki-Cottrell atmosphere are analyzed to explain the composition dependence and propose a model for amplitude-independent damping Q−1I in alloys consisting sequentially of (1) the fault narrowing, (2) the escape of one partial, and (3) the complete breakaway from the combined Suzuki-Cottrell atmosphere. Consideration of both the multiplicity of Cottrell pinning sites and the stacking-fault width demonstrate the role of the pinning-point amplification factor in determining the impurity-dislocation binding energy and the distribution of impurities in the combined atmosphere. The transition ε0 from Q−1I to amplitude-dependent damping Q−1H showed a linear correlation with the calculated Suzuki yield stress. Two distinct stages of Q−1H were observed: at the lower ε0, Q−1H1 is thermally activated and characterized by an escape enthalpy of ≈0.04 eV, while at the higher ε0, Q−1H2 is nearly independent of temperature. A qualitative static-hysteresis model is proposed to account for the interaction between dislocations in the breakaway configuration and solid-solution impurities located outside of the Suzuki-Cottrell atmosphere, which predicts a squared hysteresis loop and the observed nearly temperature-independent behavior for Q−1H2.
Control of zinc diffusivity in GaAs0.6P0.4 by multiple implantation
Authors: Stoneham E. B. , Gibbons J. F.
Published: February 2003

Experimental data is presented to show that the diffusion of ion-implanted Zn in GaAs0.6P0.4 can be effectively controlled by the coimplantation of Ga, As, and/or P prior to annealing. The experimental observations are shown to be consistent with the interstitial-substitutional diffusion mechanism for Zn diffusion in III-V semiconductors. This diffusion model is modified to include the effects of Ga, As, or P implants on the Ga vacancy concentration dependence of Zn diffusivity. Coimplantation of B or N with Zn does not affect the diffusion of the Zn the way Ga, As, or P coimplantation does.
Void growth in the early stages of aging and electromigration
Authors: Lloyd J. R. , Nakahara S.
Published: February 2003

High-resolution transmission electron microscopy was used to study the initial stages of the growth of submicroscopic (<50 Å) voids in thin evaporated gold films. These voids were found to grow while aging at room temperature as well as under conditions in which electromigration normally occurs. Room-temperature void growth was attributed to the annihilation of excess vacancies at voids.
Room-temperature conductivity and location of mobile sodium ions in the thermal silicon dioxide layer of a metal–silicon dioxide–silicon structure
Authors: DiMaria D. J.
Published: February 2003

Room-temperature conductivity of mobile Na+ ions in the SiO2 layer of a metal–silicon dioxide–silicon structure is directly shown to be interface limited by use of the photo I-V technique. Na+ ions were found to be located within ?50 Å of the interfaces regardless of field stressing conditions (2–4.5 MV/cm), temperature (20–40 °C), number of ions drifted (up to 2.6×1012 cm−2), or number of temperature-bias cycles used to move Na+ ions back and forth between the interfaces.
The temperature dependence of resistance in aggregate tin films
Authors: Kong W. M. T. , Polan J. S. , Rose K.
Published: February 2003

The temperature dependence of aggregate partially coalesced tin films can be explained by introducing an effective length-to-width ratio S which accounts for the mazelike structure of the film. The deviation of experiment from theory is less than 10% from 4 to 300 °K for films having room-temperature sheet resistances of 5–660 Ω/square. The only adjustable parameters are S and the impurity resistivity ρI. The lattice resistivity of crystal tin, the experimentally determined film thickness, and diffuse surface scattering are used in the theory.
Domain behavior in SmCo3.5Cu1.5 single crystal
Authors: Uehara M.
Published: February 2003

The behavior of the magnetic domains in SmCo3.5Cu1.5 single crystal as a function of applied field, temperature, and time have been studied. The domain reversal depends strongly on the fluctuation of cobalt and copper concentrations. As the reverse field increases, the domains advance gradually into the copper-rich regions. Domain shape is found to be a reflection of microstructure at low temperatures. Aftereffects of magnetization were determined directly by domain observations. The domains grow at constant reverse field due to repeated partial nucleations along the parent walls. This behavior is explained by a thermal activation process.
Properties of electric discharges sustained by a uniform source of ionization
Authors: Lowke John J. , Davies D. Kenneth
Published: February 2003

A theoretical examination is made of the class of discharges which are sustained by a uniform source of electron and ion pairs produced between plane-parallel electrodes. The calculations account for drift, diffusion, and recombination of the charge carriers, ionization of the gas by electrons, and distortion of the applied field due to space charges. It is found that the number and current-density profiles of electrons and positive ions in the gaseous discharge are of three different types, where (i) the electron density is several orders of magnitude lower than the positive-ion density at all interelectrode positions, (ii) a plasma region exists, but the electric field in the plasma is negligible compared with that in both electrode sheaths, and (iii) significant ionization occurs in the cathode-sheath region. Examples of such discharges for which numerical solutions are given are as follows: for type (i), a γ-ray photoionization chamber with a current density j<1 μA/cm2; for type (ii), a fission fragment ionization chamber used as a neutron detector where j∼1 mA/cm2; for type (iii), a discharge similar to that of a gas laser sustained by ionization from an electron beam where j for the laser ∼1 A/cm2. Derived current-voltage characteristics for discharges in argon corresponding to types (i) and (ii) are in reasonable agreement with experiment and also with characteristics derived analytically by considering the cathode-sheath region only and neglecting diffusion and ionization by electrons.
Propagation of ionizing waves in glow discharge
Authors: Suzuki Toshio
Published: February 2003

Ionizing waves were produced along the positive column of a glow discharge in air by applying an impulse voltage to an electrode at one end of the column. Five photomultipliers and three current-sensing coils were used to observe how the waves were affected by the rise time and the magnitude of the applied impulses and by the electron density in the positive column of the glow discharge. It is shown that the speed of the ionizing waves increases with the slope of the applied impulses and with the preexisting electron density. The electron density is augmented about 100–200 times due to the buildup of ionization at the front of the waves. The theory was developed to explain the property of ionizing waves.
Sum-frequency excitation of electron plasma waves
Authors: Willett Joseph E. , Maraghechi Behrooz , Zorinsky Eldon J.
Published: February 2003

Nonlinear mixing of two circularly polarized electromagnetic waves propagating in a plasma along a uniform static magnetic field is considered. Resonant excitation of electron plasma waves is found to be possible at the difference frequency if the incident waves are both extraordinary or both ordinary and at the sum frequency if one incident wave is extraordinary and the other is ordinary. Formulas for the absorption efficiency due to sum-frequency excitation are derived and the results of a numerical study are presented.
Excitations of wave modes and energy loss by a charged particle passing through a plasma sheet
Authors: Swami K. C. , Sharma S. R.
Published: February 2003

Expressions are presented for the field components due to a charged particle passing across a dielectric layer surrounded by the media of different dielectric constants. The case of a cold plasma sheet is discussed in detail. The energy loss due to the space-wave part of the transition radiation has been reported in a previous paper. In the present paper, the energy loss due to the excitation of surface wave modes is considered. For the large thickness, the energy is lost through the surface wave mode which propagates for frequencies less than ωp/√2. However, for thin sheets, two modes are excited in which the radial wave number depends upon the thickness of the plasma sheet. The power flow per unit angular frequency along the radial direction is calculated for both the thick and thin plasma sheet. The contribution of the particle velocity, the layer thickness, and the frequency on the power flow per unit frequency is investigated in detail.
Effects of grain size on cation ordering in sintered Mg-ferrites
Authors: Kimura Toshio , Ichikawa Miyoko , Yamaguchi Takashi
Published: February 2003

The effects of grain size on the isothermal cation ordering in sintered Mg-ferrites have been studied from 400 to 750 °C by thermomagnetic analysis. The observed dependence of ordering behavior on the grain size as well as on the temperature has proposed that the rate-determining process changes from nucleation growth to homogeneous ordering as the temperature increases. The high rates of ordering in fine-grained specimens have been interpreted as due to the increased grain-boundary areas favorable for nucleation. The apparent activation energy of the homogeneous ordering is 36 kcal/mole in the temperature range between 450 and 600 °C.
Theoretical consideration on thermoluminescence response
Authors: Nakajima Toshiyuki
Published: February 2003

A new model is proposed for explaining the unsolved phenomena in the thermoluminescence properties, which are the nonlinear response to exposure, the postirradiation and test-irradiation dose dependences of the sensitization phenomena, the dose effect of the energy dependence, and changes in the shape of the glow curve with the exposure. This model is based on the following assumptions: (1) In the first step of the carrier capture reaction, the sum of the number of trapped carriers in each trapping level is restricted to the number of released carriers, (2) the capture reaction between the released carriers and traps is irreversibly consecutive and follows first-order kinetics, and (3) passage of the charged particle through the phosphor brings about an exothermic effect and reaction temperature is a sum of irradiation and exothermic temperatures. As a result, the number of captured carriers in the ith trapping level is given as a function of irradiation temperature, exothermic temperature, activation energy of the irreversibly consecutive reaction, stopping power and flux of the charged particle in the phosphor, and the number of initial traps. The model can qualitatively explain the unsolved phenomena in thermoluminescence response.
Electromagnetic diffraction of an aperture in a planar conducting screen separating partitioned half-spaces
Authors: Butler Chalmers M. , Howard Allen Q. , Nevels Robert D.
Published: February 2003

A vector integro-differential equation is derived for the problem of electromagnetic diffraction by an aperture in a perfectly conducting planar screen that separates two half-spaces which are, themselves, divided into quarter spaces of differing electromagnetic properties by planar interfaces perpendicular to the screen. The aperture/screen is excited by specified sources located on both sides of the screen. Due to the partitioning of the half-spaces, Sommerfeld integrals appear in the integral-equation kernel. The aperture is specialized to be an infinite slot of uniform width subject to TE and TM (to slot axis) illumination, and the resulting slot equations are solved numerically. Data are presented for representative cases of interest.
The Dirichlet problem in a heterogeneous dielectric
Authors: Mendelson Kenneth S.
Published: February 2003

A Green’s function has been used to discuss the Dirichlet problem in a heterogeneous dielectric. Depending on the boundary condition imposed on the Green’s function, one obtains formal expressions for the potential and the electric field or bounds on the potential and the field components at a point. A formal expression for the effective permittivity of a random statistically homogeneous dielectric has also been obtained. Finally, the Green’s function has been obtained in terms of a Neumann series. A close relation is observed between the Green’s function and the T matrix used in treating effective constants.
Stimulated-emission cross section at 1064 and 1342 nm in Nd : YVO4
Authors: Tucker A. W. , Birnbaum M. , Fincher C. L. , Erler J. W.
Published: February 2003

The stimulated-emission cross sections at 1064 (4F3/2→4I11/2) and 1342 nm (4F3/2→4I13/2) in Nb : YVO4 were determined by measurement of laser thresholds as a function of output mirror reflectivity. Small samples of Nd : YVO4 and Nd : YAG were end pumped at room temperature with a cw 514.5-nm argon ion laser in an almost identical geometrical arrangement which permitted comparative values to be obtained. Assuming that the pumping quantum efficiency of Nd : YVO is similar to that of Nd : YAG, the stimulated-emission cross sections obtained for the 1064- and 1342-nm transitions were respectively 12×10−19 and 6.0×10−19 cm2.
A simple compact high-repetition-rate hydrogen vuv laser for scientific applications
Authors: Goldsmith John E. M. , Knyazev Igor N.
Published: February 2003

The operation of a simple compact high-repetition-rate vuv hydrogen laser is described in detail. The laser uses a Blumlein-type transverse discharge system with a very narrow profiled discharge channel and a low-inductance nitrogen-pressurized triggered spark-gap switch. The laser produces 20−μJ pulses of approximately (1/2) -nsec duration at 1600 Å (corresponding to a peak power of about 40 kW). The dependence of the pulse energy on the operating parameters of the laser is reported. Laser action in nitrogen, neon, and XeF* has also been observed.
Coupling losses in laser resonators containing a hollow rectangular dielectric waveguide
Authors: Avrillier Sigrid , Verdonck Jacques
Published: February 2003

This paper discusses the losses in coupling radiation from the guide into free space and back into the guide for a hollow rectangular dielectric waveguide laser resonator with external spherical mirrors. Computations of the coupling loss for the EH11 lowest-order mode of a square guide, as a function of mirror curvature and position, are presented in the limit of large mirror aperture. It is shown that some mirror positions and radii provide low coupling losses.
Plasma etching A ’’pseudo-black-box’’ approach
Authors: Winters Harold F. , Coburn J. W. , Kay E.
Published: February 2003

A framework for understanding plasma etching has been developed (using the CF4 plasma etching of silicon and silicon compounds as an example) which treats the discharge as a ’’pseudo-black-box’’ which is characterized by a dissociation rate G of the CF4 molecules and a recombination rate R at which CF4 and other inert molecules are re-formed by recombination of the active fragments. Expressions based on the conservation of fluorine and carbon in the system have been derived which relate the concentration of the various species in the effluent gas to the etch rate. This approach provides a semiquantitative understanding of several aspects of plasma etching such as the effects of additive gases and the presence of a much larger ’’loading’’ effect for Si than for SiO2.
Electron-beam-induced current and TEM studies of stacking faults formed by the oxidation of boron-implanted silicon
Authors: Seidel T. E. , Haszko S. E. , Maher D. M.
Published: February 2003

The electron-beam-induced conductivity (EBIC) of emitter-base junctions was studied in a scanning electron microscope, and the image contrast of process-induced stacking faults was investigated by transmission electron microscopy (TEM). Emitter-base (e-b) junctions were formed by phosphorus diffusion into boron-implanted bases on 〈100〉 silicon. The implanted bases were preannealed in an oxidizing atmosphere, which generates stacking faults. The e-b junctions were designed with metal contacts removed such that the active e-b region was ’’open’’ to EBIC analysis. Leaky junctions (i.e., 104 nA/cm2) were found when relatively high concentrations of oxygen were used in the annealing atmosphere (e.g., 10% O2). These junctions exhibited a mottled contrast in the EBIC mode, indicative of a high density of recombination centers. Relatively low-leakage junctions (i.e., 10 nA/cm2) were found when a 1%-O2 atmosphere was used and the junctions contained an occasional stacking fault. These stacking faults exhibited an EBIC contrast characteristic of recombination at partial dislocations bounding the faults. Diffraction-contrast experiments using TEM showed that isolated stacking faults in the base region were extrinsic in nature and were not decorated by heavy metal microprecipitates. The generation currents for ’’clean’’ extrinsic stacking faults were estimated to be in the range 10−2–10−4 nA per stacking fault for these junctions.
Photovoltaic determination of optical-absorption coefficient in CdTe
Authors: Mitchell Kim , Fahrenbruch Alan L. , Bube Richard H.
Published: February 2003

Optical-absorption coefficients for CdTe greater than 103 cm−1, calculated from the spectral-response curve of a CdS/CdTe heterojunction solar cell produced in our laboratory, are in agreement with recent optical measurements on thin films and bulk samples of CdTe. This technique allows high values of absorption coefficient to be measured in bulk samples, bypassing the problems associated with optical measurements in thin films. The high values of absorption coefficient determined for CdTe encourage its use as a thin-film solar-cell material.
Effects of oxidation and nitrogen annealing on ion-implantation-induced interface states in the silicon–silicon dioxide system
Authors: Hess D. W. , Learn A. J.
Published: February 2003

Experiments designed to determine the effects of oxidation and nitrogen annealing on interface states created by argon implantation through thermally grown silicon dioxide films are described. Although these states could be inactivated by a 900 °C hydrogen anneal, they reappeared after short nitrogen or oxygen treatments at 1000 °C. Only oxidations which consumed at least 500 Å of the implantation-damaged silicon surface completely eliminated the states. The oxidation rate of the implanted structures was found to be increased relative to that of the unimplanted controls.
On the electrical resistivity of high-purity nickel
Authors: Wycisk W. , Feller-Kniepmeier M.
Published: February 2003

The dependence of the electrical resistivity of high-purity Ni on circular and longitudinal magnetic fields was determined. In a longitudinal magnetic field of 250 Oe the specific electrical resistivity for a wire of 60 μm diameter was found to be ρ4.2 °K=2.7×10−9 Ω cm. The influence of temperature on the electrical resistivity is determined between 1.5 and 4.2 °K and between 23 and 1130 °C.
Effect of pH on dye-laser output power
Authors: Matsunaga Y. , Ikeda H. , Matsumoto K. , Fujioka T.
Published: February 2003

Experiments have been performed to measure the output power of stimulated emission from acidified or basified solutions of xanthene dyes pumped by a N2 laser. The results showed the laser output power was improved for rhodamine 6G, rhodamine B, pyronin B, fluorescein disodium salt, and fluorescein dipotassium salt by factors of 2.2, 2.8, 1.7, 26.7, and 8.6, respectively.
Mössbauer studies in ZnxMn1−xFe2O4 systems
Authors: Gupta R. G. , Mendiratta R. G.
Published: February 2003

Mössbauser spectra of ZnxMn1−xFe2O4 with x values ranging from 0.0 to 1.0 in steps of 0.1 have been taken at room temperature. The spectrum of Mn0.7Zn0.3Fe2O4 is also taken at 520 °C. A possible explanation for the observed variations in the internal magnetic field, EFG, and the isomer shift is given.
Third-order elastic constants for materials with transversely isotropic symmetry
Authors: Fritz I. J.
Published: February 2003

The scheme of third-order elastic constants (i.e., which constants are nonzero and relations between dependent constants) has been determined for materials possessing transversely isotropic symmetry. There are 20 nonzero constants, and nine of them are independent. The scheme of the mixed third-order elastic constants is also determined by using the equation derived by Brugger, relating the adiabatic and mixed constants. There are 39 nonzero mixed constants, and the relations reducing these to nine independent constants are listed.
Blue light emission by a Pr : LiYF4 − laser operated at room temperature
Authors: Esterowitz L. , Allen R. , Kruer M. , Bartoli F. , Goldberg L. S. , Jenssen H. P. , Linz A. , Nicolai V. O.
Published: February 2003

Room-temperature operation of a solid-state laser has been achieved for the first time in the blue region using Pr : YLF. The 0.2% Pr : YLF crystal was longitudinally pumped at 444 nm using a pulsed dye laser. Laser emission was observed at 479 nm and required a pump-energy density of 8 J/cm2 at threshold.
Interpretation of the spatial and spectral intensities of optically thick resonance lines emitted from a spherical laser-heated plasma
Authors: Apruzese J. P. , Davis J. , Whitney K. G.
Published: February 2003

We present interpretations of computed spatial and spectral intensities of the principal resonance lines emitted from a spherical laser-heated aluminum plasma. Our interpretations are based upon frequency-by-frequency solutions for the radiation transport equation which are coupled to a spherically symmetric time-dependent aluminum plasma model. This model solves the coupled equations for ion and electron temperatures and densities, atomic level populations, and fluid velocities for varying assumptions of energy deposition within the plasma. We find that the HeKα and HKα resonance line profiles and intensities of the Al XII and Al XIII ions emitted during deposition are sensitive to the spatial plasma heating profile. By solving for the emitted H-like Kα line intensities along various lines of sight we generate theoretical ’’pinhole photographs’’ of the emission of this line. These spatial H-like Kα profiles are also very sensitive to the assumed laser deposition distribution. We have also compared our numerical results with those given by the escape-factor formula of Holstein, and we present an escape formula which is more accurate than Holstein’s for large optical depths when the photon sources are approximately uniformly distributed in the plasma sphere.
Precise characterization of the Raman nonlinearity in benzene using nonlinear interferometry
Authors: Owyoung Adelbert , Peercy P. S.
Published: February 2003

Using a newly developed technique which we term two-beam nonlinear interferometry, we report accurate self-consistent determinations of both the real and imaginary parts of the third-order nonlinear optical susceptibility χ11113(−ω,ω,ωo,−ωo) in benzene including resonant Raman contributions from the 992-cm−1 mode. These measurements provide accurate values for the peak Raman cross section, nonlinear refractive index, and electronic hyperpolarizability, thus enabling the direct comparison of Raman, nonlinear refractivity, and frequency-mixing studies.
Ultrafast gating and amplification of broadband optical signals
Authors: Olson G. L. , Busch G. E.
Published: February 2003

The simultaneous picosecond time resolution and amplification of broadband optical signals are described. Appropriately selected laser dye mixtures are shown to provide either broadband or wavelength-selective amplification for arbitrary ultrafast signals. Techniques of picosecond spectroscopy demonstrate that net gains ≳10 and an amplifier bandpass of ∼100 nm are obtained when the dyes DODCI, Rhodamine B, and Rhodamine 6G are used as the active components in the amplifying shutter.
Crosstalk noise from multiple thick-phase holograms
Authors: Burke W. J. , Sheng Ping
Published: February 2003

The crosstalk noise between holograms arising from multiple storage of holograms in the same volume is determined. The noise is measured to be oscillatory with a period greater than that predicted by the theory and to be intermediate in magnitude between the noise levels calculated assuming coherent and incoherent addition of the scattered amplitude from the off-Bragg holograms. It was found that crosstalk noise can be reduced to a level compatible with high-quality (S/N ratio ∼40 dB) readout images at angular spacings (0.1° in air) such that large numbers of holograms can be stored in a given volume.
Composite transition-metal atom superconductivity in a generalized Nb3Ge system
Authors: Cadieu F. J. , Chencinski N. , Rosen C. Z.
Published: February 2003

Data is presented for the variation in superconducting transition temperatures in a generalized Nb3Ge system in which a fraction of Nb atoms have been replaced by the similar 4-d transition-metal atom Mo. It is argued that for a certain composition range, the effective transition-metal atom can be viewed as a composite of Nb and Mo electronic states averaged along the chains in the A15 structure.
Performance of N2/CO2 gasdynamic mixing lasers with various injection techniques
Authors: Schall Wolfgang , Hoffmann Peter , Hügel Helmut
Published: February 2003

The supersonic mixing is the only technique that can exploit the full potential of a thermally excited gasdynamic N2/CO2 laser. A screen-nozzle mixing technique is compared with two other near-throat mixing techniques and is found to be the superior method. Averaged values of the small-signal gain up to 3% cm−1 and specific energies of 10 kJ/kg total mass flow have been measured in a laser channel of 3.5×1.2-cm2 cross section. Characteristics of both gain and extracted power as a function of the nitrogen stagnation temperature and the CO2 mole fraction are discussed for all three types of CO2 injection.
Spectral response of point-contact Josephson junctions
Authors: Tolner H.
Published: February 2003

The spectral response of niobium point-contact Josephson junctions with resistance values R between 1 kΩ and 10 Ω has been measured. For R≳100 Ω the response peaks at maxima of d2V̄/dĪ2, whereas the spectral response peaks at frequencies νR≲200 GHz. Decreasing the resistance by burning-in of the contact, it was found that for underdamped contacts νR∝R−1/3, almost independent of the junction geometry. Tapping the contact, i.e., changing the microscopic properties of the flat contact region (diameter, 5–10 μm), changed the absolute value of νR. Maximum resonant response occurred approximately for critical damping at R=80–100 Ω. The observed behavior is interpreted as resonant detection at the plasma frequency. At low resistance values νR disappears, but additional resonances at ν≳150 GHz appear, some of which could be identified as antenna resonances.
A swept-focus scheme for an ion-beam laser
Authors: Louisell W. H. , Seely J. F. , Shnidman R. , Lax M.
Published: February 2003

A sweep scheme which may be used with an ion-beam laser is investigated. In this scheme, a beam of ions passes through a symmetric electric-quadrupole triplet lens and into a parallel-plate transmission line. A voltage pulse of finite duration (TEM-mode) propagates along the transmission line in the downstream direction with the velocity of light. The ions pass out the end of the transmission line where they are space-charge neutralized and are incident on a target parallel to the transmission-line axis. We show that the point of intersection of the beam with the target moves along the target with the velocity of light due to the voltage pulse. For the beam to remain focused as it hits the target, the focusing potential of the lens must be varied, and we determine the required time variation using the thin-lens approximation. A set of operating parameters is given.
Charge injection from polycrystalline silicon into SiO2 at low fields
Authors: Yun B. H. , Hickmott T. W.
Published: February 2003

Electron injection from polycrystalline silicon into thermal SiO2 at low fields is observed in polycrystalline-silicon–SiO2–Si capacitors. C-V, pulsed-charge injection, and charge-relaxation measurements show that the injected electrons are captured by centers in the SiO2. These trapping centers appear to be located at about 30 Å from the polycrystalline-silicon–SiO2 interface and are characterized by an energy level approximately 0.3 eV above the Fermi level of the degenerate n-type polycrystalline silicon. Annealing of the samples in nitrogen or forming gas strongly affects the charge injection.
Annealing of surface states in polycrystalline-silicon–gate capacitors
Authors: Hickmott T. W.
Published: February 2003

Charge injection at the polycrystalline-silicon–SiO2 interface of phosphorus-doped, polycrystalline-silicon–gate MOS capacitors can cause excess currents during quasistatic C-V measurements and hysteresis in high-frequency C-V curves. The effect of annealing in nitrogen and forming gas at temperatures between 300 and 850 °C on these instabilities as well as on surface states Nss and surface charge Qss has been studied. To distinguish effects occurring at the substrate Si-SiO2 interface from effects occurring at the polycrystalline-silicon–SiO2 interface, measurements are also reported of the effect of annealing Si-SiO2 structures without gate electrodes, in the same temperature range and atmospheres. There is a minimum in Nss after anneal of samples without electrodes in forming gas at 400 °C. Reaction with hydrogen is essential to anneal surface states; thermal anneal is not sufficient. Some reaction, possibly formation of SiO, occurs above 450 °C that increases Nss and may increase Qss. Anneal of polycrystalline-silicon capacitors requires temperatures high enough for hydrogen to diffuse through polycrystalline silicon but low enough that surface states are not generated. A model is discussed that correlates midgap surface states with the B2 band, an optical-absorption band in SiO2 at 5.1 eV. Charge injection at the n-polycrystalline-silicon–SiO2 interface correlates with the E1′ band in SiO2.
Electron-irradiation damage in antimony-doped silicon
Authors: Evwaraye A. O.
Published: February 2003

The electron trapping centers induced by electron irradiation in antimony-doped silicon have been studied by deep-level transient capacitance spectroscopy. Four such traps—E1(Ec−0.17 eV), E2(Ec−0.22 eV), E3(Ec−0.28 eV), and E4(Ec−0.39 eV) —are visible in the spectrum. Of particular interest is the antimony-vacancy pair, E4. The capture cross section for majority carriers at this level is 4.5×10−17 cm−2 at 234 K. The annealing studies of the Sb-V complex indicate first-order kinetics with activation energies of 1.29 and 1.62 eV for the neutral and negative charge states of the complex, respectively. Also, this dependence on the charge state results in the annealing rate at 175 °C being an order of magnitude greater when the Sb-V complex is in the neutral charge state than it is when the complex is in the negative charge state.
Theory of metal-insulator-semiconductor solar cells
Authors: Shewchun J. , Singh R. , Green M. A.
Published: February 2003

Recent reports in the literature indicate that the introduction of an interfacial oxide layer in a Schottky barrier can greatly increase the photovoltaic conversion efficiency of such devices. We propose an explanation for the operation of such solar cells based on the concept that they are minority-carrier nonequilibrium MIS tunnel diodes. Calculations of efficiency as a function of insulator thickness, substrate carrier concentration, surfaces states, and oxide charge are presented. These indicate that a maximum theoretical efficiency of 21% is possible under AM2 illumination for high substrate doping and low interface defect density.
Structure study of multilayer assembly films
Authors: Matsuda A. , Sugi M. , Fukui T. , Iizima S. , Miyahara M. , Otsubo Y.
Published: February 2003

The structures of various multilayer assemblies of cadmium salts of pure and mixed fatty acids have been studied using the x-ray diffraction technique. Model calculations of diffraction patterns for each assembly have indicated that each is an actual reproduction of the designed structure with the chain lengths of composite molecules being invariant.
Composition, structure, and ac conductivity of rf-sputtered calcia-stabilized zirconia thin films
Authors: Croset M. , Schnell J. P. , Velasco G. , Siejka J.
Published: February 2003

Thin 12 mole% calcia-stabilized zirconia CSZ films (500–17 000 Å) were deposited by rf sputtering onto single-crystal silicon substrates. When deposited in an oxygen-containing plasma (more than 0.2% O2 in Kr), such films appeared to be stoichiometric, as verified by nuclear microanalysis; while their structure, analyzed by x rays, appeared to be of the fluorite type. The ac conductivity measured on Al/CSZ/Si structures between 200 and 400 °C suggests an activation energy and a preexponential factor close to that of bulk-sintered material having the same composition. This result tends to prove that conductivity in sputtered CSZ thin films is due to anion-oxygen movement. Preliminary emf measurements on Pt/O2/CSZ/Ni/Si thin-film galvanic cells confirmed this interpretation.
Bloch-line rotation instability during gradient propagation of S=0 bubbles in an in-plane field
Authors: Malozemoff A. P.
Published: February 2003

Recent data by DeLuca and Malozemoff on the gradient propagation of S=0 bubbles in an in-plane field show two peaks in the velocity-vs-drive curve. In this paper the higher-drive peak is accounted for in terms of the well-known horizontal Bloch-line nucleation and punch-through effect, while the lower-drive peak is interpreted as a novel Bloch-line rotation instability. Such an instability can arise in bubbles with two Bloch lines pinned by the in-plane field Hp at opposite sides of the bubble. When the bubble is propagated perpendicular to the in-plane field, one of the Bloch lines is gyrotropically destabilized and can rotate halfway around the perimeter of the bubble. The critical drive field and velocity for this process are calculated to be αHpf and αμHpf, respectively, where α is the Gilbert damping parameter, μ is the linear mobility, and f is a factor between 0.63 and 1. As the Bloch line rotates, the velocity is predicted to drop to a minimum of order 8αμh−1 (2A/π)1/2, where A is the exchange stiffness and h is the film thickness. Eventually a new state is attained with four Bloch lines all of which are gyrotropically and magnetostatically stable.
The attractive and repulsive forces on a lattice screw dislocation
Authors: Jagannadham K.
Published: February 2003

The properties of a lattice screw dislocation in a crystal in the form of a strip or a circular cylinder or an infinite crystal with a circualr hole or in a composite crystal composed of a soft matrix surrounded by a rigid second phase are determined. It is shown that the misfit stress field in the lattice is altered due to the image stress field. Some important conclusions have been arrived at on the image stress field on the dislocation in all the above situations.
Measurement of Faraday rotation in the Implosion Heating Experiment
Authors: Jarboe T. R.
Published: February 2003

A technique for measuring Faraday rotation on the Implosion Heating Experiment (a fast 20-cm-radius theta pinch, with n∼1015/cm3, B∼5 kG) is described. Using a polarized CO2 laser with a nearly crossed analyzer the Faraday rotation is measured at one position in the plasma. The nearly crossed analyzer is used to minimize errors due to refraction. The ℱn dl is measured at the same time and radius using a fractional-fringe interferometer at the He-Ne 633-nm wavelength. From these two measurements the magnetic field is obtained. For comparison the magnetic field is also measured with probes. The results indicate that probes immersed in the plasma are too slow to follow the rapid changes in magnetic field that occur in IHX.
Brewster angle for an E-polarized electromagnetic wave interacting with a moving dielectric medium
Authors: Mukherjee P. K.
Published: February 2003

The Brewster-angle phenomena of total transmission has been investigated with reference to an E-polarized electromagnetic wave interacting with a dielectric half-space moving along the interface. Analytic conditions are derived for the existence of Brewster angles. We also discuss how the Brewster angles are modified by replacing the incident region (in which the incident electromagnetic wave is propagated) with an isotropic or a uniaxially anisotropic plasma. The Brewster angles are found to behave in a remarkably different fashion under various conditions. Numerical results for the Brewster angles, showing their dependence on the nondimensional velocity of the medium β, are presented for several values of the physical parameters.
Empirical T3/2 law for atomic thermal vibration parameters
Authors: Bastow T. J. , Mair Sylvia L. , Wilkins S. W.
Published: February 2003

The Debye-Waller factor, as measured by x-ray and neutron diffraction and Mössbauer techniques, is shown to be of the form a+bT3/2 over an extensive temperature range in a diverse set of crystalline solids. This two-parameter empirical relationship may be interpreted within the framework of the Debye theory, modified to include quasiharmonic effects.
Some aspects of piezoelectricity and pyroelectricity in uniaxially stretched poly(vinylidene fluoride)
Authors: Tamura Masahiko , Hagiwara Sumio , Matsumoto Susumu , Ono Nobuyuki
Published: February 2003

The piezoelectric constant of a uniaxially stretched and polarized poly(vinylidene fluoride) film decreases monotonically with increasing temperature in the range from 65 to 165 °C. After a specimen is cooled under open-circuit conditions, the thermally stimulated current reverses in sign and exhibits a peak at around the glass-transition temperature Tg. Reversible changes in infrared spectra before and after the poling process suggest that the dipoles in the β crystals of poly(vinylidene fluoride) can be aligned along the direction of an applied electric field. The alignment is strongly influenced by the amorphous region; the coercive field in P-E hysteresis curve observed at 50 Hz increases rapidly at around Tg. Under a high electric field, the uniaxially stretched poly(vinylidene fluoride) film behaves above Tg in the same way as ferroelectric ceramics.
Thermal conductivity, electrical resistivity, and Seebeck coefficient of high-purity chromium from 280 to 1000 K
Authors: Moore J. P. , Williams R. K. , Graves R. S.
Published: February 2003

The thermal conductivity λ, electrical resistivity ρ, and Seebeck coefficient S of a high-purity Cr specimen (ρ273/ρ4.2=380) were measured from 285 to 1000 K. The ρ and S of two other Cr specimens (ρ273/ρ4.2=380 and 58) were determined from 300 to 1300 K. The ρ and S results from the three specimens are in excellent agreement and all three properties agree to within experimental uncertainty with previous low-temperature results on the same specimens over the temperature range of overlap. Near T′N (300–320 K), the present λ results are within 0.7% of the previous data and indicate that λρ/T should be smooth to within 1%. At high temperature, the present λ data are about 8% above those of Powell and Tye but the ratios of λρ/T agree to within 2% up to 1000 K. These new data on pure Cr are compared to calculations from standard transport theory and to previous results from W and Mo.