bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaction between solid nitrogen and 1–3-keV electrons
Authors: So/rensen H. , Schou J.
Published: February 2003

Experimental studies were made of the interaction between solid nitrogen and beams of 1–3-keV electrons. The projected range for the electrons was measured by means of the mirror-substrate method (gold substrate), giving the result 9.02×1016 E1.75 molecules/cm2 with the energy given in keV. The escape depth for secondary electrons was studied by means of the equivalent-substrate method (carbon substrate). The results varied from 280 Å at 1 keV to 400 Å at 3 keV. Measurements were also made of the secondary-electron-emission coefficient, which varied from 2.3 el/el at 1 keV to 1.2 el/el at 3 keV. At 3 keV, the SEE coefficient is 12 times that for solid deuterium. This is attributed partly to the larger production rate for low-energy electrons in nitrogen and partly to the larger escape probability for these electrons. Moreover, measurements were made of the electron-reflection coefficient, both for solid nitrogen and for the carbon substrate. For nitrogen, it varied from 0.17 el/el at 1 keV to 0.13 el/el at 3 keV, and for carbon it varied from 0.13 to 0.12. The observations are discussed and comparisons made with other theoretical and experimental results. The agreement ranges from good to fair.
A topological analysis of electron transport at n+-n contacts
Authors: Ladbrooke P. H.
Published: February 2003

In attempting to take account of momentum and energy-loss-rate variations throughout the structure of an n+-n contact, the effects of impurity scattering in the n+ region and of diffusion upon the distribution function are hard to quantify exactly. Consequently, there is a need to establish whether the transport of electrons under these conditions differs in any significant way from results which can be derived by numerical analysis using transport equations where the same momentum and energy-loss terms are assumed to apply throughout the entire device. In this paper a topological method is used to show that, when the electric field and electron energy attain constant final values in the bulk, the rise in electron energy after injection remains monotonic with distance. The result is of particular interest to the physical operation of submicron channel microwave FET’s.
Mechanical properties of particulate-filled polyurethane foams
Authors: Barma P. , Rhodes M. B. , Salovey R.
Published: February 2003

The compressive behavior of a rigid polyurethane foam reflects its geometric structure and the physical properties of the matrix polymer. Foam properties may be modified by the inclusion of silica particles in the polymer matrix. These silica particles alter the mechanical properties of the base polymer as well as the geometrical structure of the foam. The yield stress and the modulus of the foam decrease with the initial introduction of the silica filler after which the mechanical properties of the foam increase with increasing filler content. A model is presented expressing the foam yield stress and the modulus as a function of the polymer modulus and the cell parameters. These parameters are l, a cell edge length, and d, a characteristic strut thickness. This results in the expressions, Ef=C″Ep(d/l)4 and σy=-Ep(d/l)4. This model is applicable to either filled or unfilled foams and accommodates changes in the properties of the solid phase, through the use of Ep, as well as changes induced in the cell geometry through the d/l relationship.
Electric-field-induced phase changes in poly(vinylidene fluoride)
Authors: Davis G. T. , McKinney J. E. , Broadhurst M. G. , Roth S. C.
Published: February 2003

The antipolar crystal form of poly(vinylidene fluoride) can be made piezoelectric and pyroelecric by the temporary application of electric fields in excess of 1 MV/cm at room temperature. Infrared and x-ray diffraction data reveal that the polarization occurs in two stages. At fields near 1 MV/cm, a phase transition to a polar form II occurs with presumably no change in chain conformation. Fields near 5 MV/cm cause a change in conformation to produce form I. Our results indicate that at least a portion of the residual polarization occurs within the crystal phase of the polymer.
Temperature control in refractory filaments
Authors: Domann F. E. , May T.
Published: February 2003

An improved method of temperature control for a sample filament is described. The technique is based upon a simple model which equates the electrical power input (i2R) to the power needed to heat the sample plus the power lost by radiation. As an example, the model is applied to a tungsten filament 0.005 in. in diameter, 10 cm long.
Gain measurements of the Ca-Xe charge exchange system
Authors: Michels Charles J. , Chubb Donald L.
Published: February 2003

Charge exchange pumped Ca+ was investigated for possible positive gain at 370.6 and 315.9 nm using a Xe magnetoplasmadynamic (MPD) arc as the Xe+ source. Although charge exchange pumping of the Ca+(5s) and Ca+(4d) levels was observed, no positive gain measurements were observed. A small Xe-Ca charge exchange cross section compared to He-metal laser systems charge exchange cross sections is the most probable reason why positive gain was not observed. The MPD arc, the calcium injection system, the diagnosties for gain, and spontaneous emission measurements and results are described.
Charge transfer pumping of the helium-nitrogen laser at atmospheric pressures in an electrical avalanche discharge
Authors: Collins C. B. , Carroll J. M. , Taylor K. N.
Published: February 2003

An atmospheric electrical avalanche (AEA) laser, stabilized by displacement current preionization, has been developed to support the study of the collisional pumping of the N+2, B→X, electronic transition by the kinetic step He+2+N2+He→N+2(B2Σu)+3He. With proper preionization, the AEA laser has been operated at a pulse repetition frequency (PRF) of 1–30 Hz in an avalanche mode at 100–200 A/cm2 and an E/p of 5 V/cm Torr. At pressures from 1 to 8 atm, an essentially uniform 30-cm3 volume containing a high concentration of He+2 has been produced. Resulting laser output pumped by the charge transfer reaction has exceeded 1 MW peak power at 427.8 nm in a 4-nsec pulse. Efficiency with respect to the instantaneous power conversion has exceeded 2%, and output pulse energies have exceeded 1% of the input pulse of energy dissipated in the laser tube.
Second-order intensity correlations in mode-locked laser pulses by use of the two-quantum photoeffect
Authors: Carlin D. B. , Bennett W. R.
Published: February 2003

Precise studies of the shape of pulses produced by a mode-locked argon-ion laser have been conducted through a method for studying the second-order intensity correlation function based on the two-quantum photoeffect. The method is sensitive enough to permit experimental distinction between commonly assumed theoretical forms for the mode-locked laser pulse shape. The present results imply a pulse shape that is closely Gaussian and a laser line profile which is in good agreement with previous line-broadening studies in the argon-ion system. The method has been used to study isolated pulses extracted from a continuous mode-locked laser by a cavity-dumping technique. Data are presented for spectral distributions, peak intensities, and pulse widths as a function of laser discharge current for such mode-locked cavity-dumped laser pulses.
Near-surface embrittlement of solids by hydrogen—The origin of the Rebinder-Westwood chemomechanical effects
Authors: Cuthrell Robert E.
Published: February 2003

Well-controlled drilling experiments in an ultrahigh-vacuum system indicate that the Rebinder-Westwood environmental effect on the deformation and fracture properties of Pyrex glass may be a result of embrittlement of the near-surface region by hydrogen.
An aggregate organic photoconductor. II. Photoconduction properties
Authors: Borsenberger P. M. , Chowdry A. , Hoesterey D. C. , Mey W.
Published: February 2003

The photoconductive properties of an organic aggregate photoconductor are reported. This material shows both electron and hole conduction. The photogeneration efficiency is field dependent and about 0.5 at 106 V/cm. The field and temperature dependences for hole generation are qualitatively consistent with the Onsager theory of geminate recombination. The corresponding dependences of the electron-generation process are obscured by a field-dependent trapping. Drift mobilities, while not directly measured, appear to be in the range of 10−8 cm2/V s. At fields of 6×104 V/cm, the electron and hole ranges are at least 10−8 cm2/V.
Design and performances of maximum-efficiency single- and double-drift-region GaAs IMPATT diodes in the 3–18-GHz frequency range
Authors: Pribetich J. , Chive M. , Constant E. , Farrayre A.
Published: February 2003

The purpose of this paper is to give the main conclusions of a theoretical study on high-efficiency GaAs IMPATT diodes. First, we intend to choose the best structure to achieve these high efficiencies (HL or LHL doping profile). Then, for this structure, we define the optimum parameters (widths, impurity-concentration values, slope of the transit zone profile) and the optimum operating conditions, allowing us to obtain the maximum efficiency which can be expected for single- and double-drift-region diodes in the 3–18-GHz frequency range. A comparison with the best experimental results for single-drift region structures (HL junction, LHL junction, HL barrier, LHL barrier) corroborates our theoretical predictions.
Nonvolume effect of Rh substitution on the metal-nonmetal transition in NiS
Authors: Sawa T. , Anzai S.
Published: February 2003

The lattice parameters a (x) and c (x), the transition temperature Tt(x), and the heat of transition ΔHt(x) are investigated in the NiAs-type Ni1−xRhxS (the solubility limit is x=0.076). a (x) and c (x) increase with increasing x, while Tt(x) decreases and finally disappears at x=0.072. This behavior is contrasted with those observed on the 3d-transition-metal substitutions and the pressure experiments. Such a difference is understood with the change in the electronic state, at a constant volume (nonvolume effect), due to the 4d-transition-metal impurity substitution. Contributions of the nonvolume effect on this transition are estimated from Tt(x) and ΔHt(x) through the Lidiard model improved by Anzai and Ozawa. They are discussed on the basis of the difference in the electron configurations between the 4d- and 3d-transition-metal elements.
Conduction mechanism in plasma-polymerized tetrafluoroethylene films
Authors: Hetzler U. , Kay Eric
Published: February 2003

The ac conductivity and capacitance of plasma-polymerized tetrafluorethylene were measured over the frequency range 10−3–105 Hz. Experimental evidence is given that the measured conductivity is a bulk phenomenon over the entire frequency range. These measurements show that there are three different conduction processes, each of them dominating in certain frequency and temperature regions. At intermediate frequencies and temperature, a dipole orientation process dominates which gives rise to a large dispersion of the ac conductivity and charge storage in the films. Both ir observations and ESR data as well as the electrical measurements confirmed that -C—O groups formed by oxidation of the films after preparation are responsible for this effect. Concentrations of the order of N×1020 cm−3 were determined from electrical as well as from ir data. Hopping conductivity dominates at high frequencies and low temperatures, whereas at very low frequencies and high temperatures, a frequency-independent dc conductivity is found and ascribed to a Poole-Frenkel emission process.
Electron emission from a liquid metal
Authors: Swanson L. W. , Schwind G. A.
Published: February 2003

A repetitive pulsed electron-emission mode has been observed from a liquid Ga/12% In cathode. Current pulses as high as 250 A with a 2- to 3-nsec rise time have been observed at a repetition rate of 40 to 80 000 pps. Emission occurs from the apex of a field-stabilized cone of the liquid metal which exhibits an incandescent glow corresponding to a temperature rise of ∼1000 °C. A field-emission-initiated explosive-emission process is proposed which involves the formation of a plasma via the volatilization of a small portion of the cone apex.
Comment on ’’A critique of the throughtput limit in mass spectrographs’’
Authors: Alexeff Igor
Published: February 2003

It is felt that the paper by A.T. Forrester et al. is not in disagreement with the paper by I. Alexeff.
Correlation of blister diameter and blister skin thickness for helium-bombarded V
Authors: Kaminsky M. , Das S. K.
Published: February 2003

A correlation of the most probable blister diameter Dmp and mean blister skin thickness t for helium-ion-irradiated annealed polycrystalline and monocrystalline V (100) surfaces yields a relationship Dmp∝t0.89. This relationship is different from the relationship Dmp∝t1.5 suggested by other authors for vanadium. The relationship observed in the present studies does not support the lateral stress model for blister formation, which predicts Dmp∝t1.5. Evidence is presented for blister formation by internal gas pressure, as suggested earlier by the present authors.
Normal-mode analysis for anisotropic elastic waveguides and its application to a Rayleigh-Love wave mode converter
Authors: Sugimoto M. , Makimoto T.
Published: February 2003

Normal-mode analysis is presented to study wave propagation along general anisotropic elastic waveguides. Introducing a concept of material perturbation, normal modes of these general waveguides are successfully examined in terms of those of a conveniently defined ’’reference waveguide’’ with simpler material parameters. Employing the Rayleigh-Ritz variational technique, a coupled-mode equation is deduced, and the solution interprets the desired propagation property as a mode coupling between normal modes of the reference waveguide. Considering the case of two-mode coupling, the mode conversion is analyzed in some detail. The results are applied to the case of a specific waveguide with a YIG film on an isotropic substrate. This example suggests the possibility of a ’’Rayleigh-Love wave mode converter’’. Numerical calculations about some basic properties of this device are presented also.
The line shape of the light scattered by surface acoustic waves upon total internal reflection
Authors: Sarid Dror
Published: February 2003

The light which is scattered by a surface acoustic wave, upon total internal reflection and at a grazing angle, exhibits a pronounced structure which varies as the polarization of the light is rotated and differs for a free or metallized surface. A theory is presented which accounts accurately for the various line shapes measured on a y-z LiNbO3 crystal.
Strength enhancement in thin-layered Al-Cu laminates
Authors: Lehoczky S. L.
Published: February 2003

Multilayered Al-Cu laminates were prepared by vapor deposition in vacuum onto NaCl substrates. The 25 °C stress-strain characteristics were measured for laminates having total thicknesses of 1.0 and 2.0 μm and layer thicknesses ranging from 20 to 1000 nm. For layer thicknesses ≲70 nm, the yield stress of the laminates is 4.2 times larger and the tensile fracture stress is 2.4–3.4 times larger than the values given by the rule of mixtures for Al and Cu. These strength increases are related to the basic physical properties of the metals and are in good agreement with Koehler’s theoretical predictions.
Some properties of evaporated amorphous silicon made with atomic hydrogen
Authors: Miller David L. , Lutz H. , Wiesmann H. , Rock E. , Ghosh A. K. , Ramamoorthy Susila , Strongin Myron
Published: February 2003

We describe measurements on a-Si films made by adding atomic hydrogen during evaporation of silicon. The material has conductivity comparable to that formed by silane decomposition and is also photoconducting. The photocurrent in these initial experiments is smaller than in the bes silane-produced films.
Sputtering yields of boron bombarded by light ions
Authors: Miyagawa S. , Ato Y. , Moriya Y.
Published: February 2003

Boron films have been bombarded by He+ and H+ ions in the medium keV energy range at room temperature. The sputtering yields have been measured for doses of 1017–1018 ions/cm2 using a low-energy nuclear-reaction method, 11B(p,α) αα, near the 163-keV resonance, and distinguished from the erosion induced by blistering and flaking. No significant differences are found between experimental values and theoretical predictions, in contrast to the case of heavy targets bombarded by light ions.
Low noise avalanche photodiodes by channeling of 800-keV boron into 〈110〉 silicon
Authors: Kaneda Takao , Kagawa Shuzo , Yamaoka Toyoshi , Nishi Hidetoshi , Inada Tsuguo
Published: February 2003

Low noise avalanche photodiodes, which have an n+-p-π-p+ structure, are reported. Channeled boron ions (800 keV) in the 〈110〉 of Si are used for forming the p layer. The characteristics of this diode are compared with those fabricated by 800-keV random implantation. Low excess noise factors F=4–5 at a gain of 100 are obtained by using 〈110〉 channeled implantation, whereas F=6–7 for random implantation. By using parallel implantation, the uniformity of channeled distributions of boron ions are found to be fairly good at different locations in a wafer.
Theory of a YIG film filter
Authors: Seshadri S. R.
Published: February 2003

The magnetic-wave interactions in a YIG film having periodically corrugated surfaces are investigated for the case of magnetization perpendicular to the propagation direction and parallel to the length of the corrugations. Simple and asymptotically exact analytical expressions for the characteristics of the resulting wave filter are deduced by a systematic singular-perturbation procedure. Numerical results of the characteristics of the wave filter are obtained and compared with the available experimentally observed values.
Disorder-enhanced Auger recombination in III-V alloys
Authors: Takeshima Masumi
Published: February 2003

Auger-recombination lifetimes of the excess carriers in p-type III-V alloys are calculated as functions of the chemical composition. The Auger transition involving the conduction band, the heavy-hole band, and the spin split-off band is analyzed. The mixing of an s-like state into the valence band, which is induced by disorder in alloys, is taken into account on the basis of the tight-binding picture. It is shown that the disorder effect is especially significant in alloys whose band-gap energy is small, as in InAs1−xSbx. A plot of the lifetime against the chemical composition of GaSb1−xAsx shows a prominent valley at the composition, where the band-gap energy is nearly equal to but a little larger than the spin-orbit splitting.
A simple description and demonstration of parametric echoes
Authors: Korpel A.
Published: February 2003

A general formalism is developed that describes the generation of short- and long-range echoes in an ensemble of independent nonlinear oscillators such as exemplified by piezoelectric powder particles. The basic physical model is one of self-parametric interaction in which a parameter of the oscillating system is modulated by the oscillation in the system itself. The resulting formalism, which is similar to the one used in holography, correctly describes the observed echo phenomena. Moreover, it implies the possibility of more general signal storage, analogous to holography. To test the theory, a model has been built consisting of 20 nonlinear LC circuits. Experimental results confirm the existence of both short- and long-range echoes; some of the more detailed implications of the formalism that concern pulse shape are also borne out by the experiment.
Low-temperature ac properties of metal-oxide varistors
Authors: Levinson Lionel M. , Philipp H. R.
Published: February 2003

Low-temperature (3.5<T<77 °K) measurements of the dielectric constant and dissipation of ZnO ceramic varistors are presented for frequencies f in the range 30<f<105 Hz. A loss peak and dispersion in ε observed at 4 °K are identified as resulting from the two-phase structure of the ZnO varistor (Maxwell-Wagner model). We find the zinc oxide grain resistivity ρZnO∼106 Ω cm in a typical commercial varistor at 4.2 °K. The physical origin of a second loss peak observed in measurements around room temperature is discussed. We show the latter dispersion is not interpretable using a Maxwell-Wagner model for an inhomogeneous conductor.
Electrostatic lens for microscopy
Authors: Yamaguchi S.
Published: February 2003

An electrostatic lens for electron microscopy was devised in which a dielectric was charged with electrons in order to give rise to an electrostatic field. The lens performed well when an electron beam was steadily running through it. It was possible to obtain a diffraction pattern from an object suitable for observation by electron microscopy.
Inverse bremsstrahlung energy absorption in laser-irradiated plasmas
Authors: Krumbein A. D. , Shima Y. , Yatom H.
Published: February 2003

The absorption of laser light was calculated at a number of laser frequencies and intensities in order to determine the effect of using different strong-field expressions for the inverse bremsstrahlung absorption. These results are compared to those from experiments on LiD targets, and it is shown that the strong-field formulation of Shima and Yatom gives results which are closer to the experimental points than either the weak-field expression or an approximation due to Goldman.
On total reflection of electromagnetic waves from moving plasmas
Authors: Kalluri D. , Shrivastava R. K.
Published: February 2003

It is shown how the frequency range for total reflection at the interface between free space and plasma is modified by their relative motion.
Etch pits and dislocation in {1̄012} Czochralski sapphire wafers
Authors: Kim K. M. , McFarlane S. H.
Published: February 2003

The reliability of fused KOH for revealing dislocations in the (1̄012) rhombohedral plane in Czochralski-grown sapphire single crystals was investigated by using x-ray-transmission topography. It was found that the etch pits represent closely the dislocations in the (1̄012) sapphire, although a one-to-one correspondence was not established.
Thick-plate technique for measuring ejecta from shocked surfaces
Authors: Asay J. R.
Published: February 2003

An experimental technique is discussed for measuring the mass-velocity distribution of material ejected from strongly shocked surfaces. The two major advantages of this technique are, first, that it is useful for measuring large amounts of surface ejecta and, second, that it allows a direct determination of the mass-velocity distribution of ejecta, without the need for differentiating experimental data. The method has been applied to a measurement of surface ejecta from shock-loaded porous tungsten.
Minority-carrier-lifetime determination in Hg0.68Cd0.32Te
Authors: Lanir M. , Vanderwyck A. H. B. , Wang C. C.
Published: February 2003

Values for the electron minority-carrier lifetime τn in Hg0.68Cd0.32Te photodiodes were independently determined by two indirect techniques. Measurements of the junction resistance under zero bias at 210 K yield τn=2.3×10−7 sec, and diffusion length measurements give τn=2.9×10−7 sec. These results are in agreement with our calculations for radiative lifetime in p-type Hg0.68Cd0.32Te. Similar measurements on gold-doped material indicate a lifetime shorter by almost three orders of magnitude, and it is suggested that this is due to recombination associated with Shockley-Read centers.
Effect of gold recombination centers on the states at the oxide/silicon interface
Authors: Faraone L. , Nassibian A. G. , Simmons J. G.
Published: February 2003

The effect of gold recombination centers on the trapping state at the silicon/silicon-oxide interface has been studied. The technique involves applying a linear voltage ramp to the device and measuring the resulting I-V characteristic. It is found that at low temperatures (∼230 °K) the technique resolves pronounced structure in the interfacial trap distribution that is not apparent at room temperature. Pronounced peaks in the distribution are reported occurring at EV+0.4 and EV+0.6 eV.
Defect pairing diffusion, and solubility studies in selenium-doped silicon
Authors: Vydyanath H. R. , Lorenzo J. S. , Kröger F. A.
Published: February 2003

Se was diffused into Si doped with various concentrations of the group-III elements B, Ga, Al, or In. Selenium acting as a double donor in silicon is found to pair with all the acceptors from the group-III examined, and the Se-acceptor pairs give rise to a donor level at Ec−0.2 eV. An additional donor level at Ec−0.3 eV is assigned to the first ionization level of selenium in silicon. Solubility of Se in silicon in the temperature range 850–1300 °C has been established through Hall-effect measurements. The diffusion coefficient measurements between 800 and 1250 °C yielded 2.47 exp(−2.84 eV/kT) cm2/sec for the diffusion coefficient of Se, DSe.
Composition dependence of the band gaps of In1−xGaxAs1−yPy quaternary solids lattice matched on InP substrates
Authors: Nakajima Kazuo , Yamaguchi Akio , Akita Kenzo , Kotani Tsuyoshi
Published: February 2003

The In-Ga-As-P quaternary phase diagram required for the growth of lattice-matched In1−xGaxAs1−yPy layers on InP substrates has been determined experimentally at 650 °C. The liquidus isotherms were obtained by the seed-dissolution technique. The solidus iostherms were determined by electron-microprobe analysis performed on surfaces of quaternary epitaxial layers grown on Sn-doped InP (111) B substrates from quaternary saturated melts. Lattice constants of layers were measured by an x-ray-diffraction technique. The liquid-phase-epitaxy growth conditions of lattice-matched In1−xGaxAs1−yPy (0⩽x⩽0.47, 0⩽y⩽1.0) layers on InP were found from the results of the phase diagram and lattice constant measurements. Lattice-matched layers with various band gaps (from 1.34 to 0.74 eV at room temperature) were grown by using these conditions. Band gaps of the layers were determined by photoluminescence measurements at 300 and 77 K. The band gap at each temperature was found to be linearly dependent on alloy-composition parameters x and y and can be expressed as a function of composition by Eg=1.35−1.30x at 300 K and Eg=1.41−1.30x at 77 K. The energy shift between the two band gaps was constant all over the composition and was equal to 0.06 eV.
Transverse 1/f noise in InSb thin films and the signal-to-noise ratio of related Hall elements
Authors: Kotera Nobuo , Shigeta Junji , Oi Tetsu , Nakashima Muneyasu , Sato Kikuji
Published: February 2003

Transverse 1/f noise in approximately 2-μm-thick InSb thin films is investigated experimentally at room temperature. Linear dependence of noise voltage on dc bias current is shown quantitatively. The noise intensity is inversely proportional to the number of conduction electrons in the bulk. The temperature rise of specimens due to Joule heating does not affect the noise intensity coefficient. The coefficient differs from sample to sample, which is reduced by the heat treatment of specimens, but is independent of the doped impurity concentration. As a result, the signal-to-noise ratio of related Hall elements is formulated for the first time for audio magnetic heads applications. The signal-to-noise ratio is nearly 80 dB for a 10-G magnetic field in the audio frequency range.
Thermal reemission of trapped electrons in SiO2
Authors: Ning T. H
Published: February 2003

Electron trapping by neutral trap centers in SiO2 was studied at 77 K and at room temperature, using n-channel silicon-gate IGFET structures. The electrons were injected in the dark using the forward-bias pulsed injection method. The results show that electron trapping by the neutral centers was one to two orders of magnitude more efficient at 77 K than at room temperature; which may be compared with the previously reported electron trapping by Coulomb-attractive centers where the capture cross sections at room temperature and at 77 K were about the same. For injected electron concentrations of less than 1016 cm−2, more than 90% of the electron trapping at 77 K was due to shallow-level centers where the captured electrons were thermally reemitted as the samples were warmed to room temperature. The concentrations of these shallow-level traps in dry, wet, and HCl oxides were about the same, regardless of whether the aluminum evaporation was by electron-beam or by rf heating in a tantalum boat. The capture cross section of these traps at 77 K was estimated to be about 10−15 cm2 at Eox=1×106 V/cm, decreasing slowly with increases in the oxide field. Thermally stimulated reemission measurements were made by monitoring the gate voltage shifts at constant channel conductance. Analyses of the results indicated a broad energy distribution for these shallow-level traps, with a peak at 300±50 meV below the conduction-band edge of SiO2 and a half-width of about 200 meV. A small portion of the enhanced trapping at 77 K was attributable to deep-level centers where the captured electrons were not thermally reemitted at room temperature.
New type of varactor diode consisting of multilayer p-n junctions
Authors: Shirota Shozo , Kaneda Shigeo
Published: February 2003

A study of a new type varactor diode which consists of a semiconductor multilayer structure has been performed. It is shown that such a varactor diode has much stronger nonlinearity in capacitance variation with applied bias voltage than does the conventional varactor due to the two-dimensional expansion of the depletion region. First, the internal behaviors of this diode are investigated in detail by two-dimensional computer simulation. Based on the physical insight obtained by the simulation, an approximate analytical expression for the voltage dependence of capacitance is derived for the purpose of practical design. Then, the proposed structure has been experimentally made from Si, whose capacitance-voltage characteristics are compared with those of the conventional structure made from the same material. Those results substantiate the theoretical predictions.
Studies on superconducting Nb3Sn formed from high-tin-concentration Cu-Sn alloy
Authors: Murase S. , Koike Y. , Shiraki H.
Published: February 2003

Multifilament conductors have been fabricated using niobium tubes with a sheathed tin-copper alloy inside and pure copper matrix outside. These composites have good workability, cold drawn without any intermediate heat treatment. Reactions and their effect upon superconducting properties have been checked for temperatures in the 625–800 °C range and various inner filament sizes ranging from 18 to 1154 μm. The Nb3Sn layer thickness grows as t0.8 in most of the reaction time, which cannot be explained by an ordinary diffusion process. The pinning force is found to be inversely proportional to the square root of the grain size measured through a fractographic technique in the 0.1–0.3-μm range. Also, the activation energy of the Cu/Sn-Cu diffusion couple is obtained as 47 kcal/mol from the reaction-temperature–time relation. These results have been discussed and compared with others.
Transit-time measurements of domain-wall mobilities in YFeO3
Authors: Tsang Ching H. , White Robert L. , White Robert M.
Published: February 2003

Using a transit-time technique, we have measured domain-wall velocities versus applied field H for Bloch, Nêel, and the head-to-head walls in bulk single-crystal bars of yttrium orthoferrite from 150 to 600 °K. Fields as high as 100 Oe were applied and wall velocities exceeding 106 cm/sec were recorded. After correcting for magnetostatic effects, all three walls display a well-defined linear v-H region, with a common mobility μ of 1.2×104 cm/sec Oe at 300 °K. As a function of temperature T the wall mobility varies as 1/T2. From these results it is argued that the mobility arises from thermal spin-wave scattering. Velocities for the three walls become field independent abruptly at vs=4.2×105 cm/sec and maintain this velocity until H exceeds ∼60 Oe, whereupon the velocity again increases. We demonstrate that this ’’saturation’’ at vs is due to the interaction between the wall and the bulk acoustic phonons.
Spin-wave damping of domain walls in YFeO3
Authors: Tsang Ching H. , White Robert L. , White Robert M.
Published: February 2003

The mobility of domain walls in YFeO3 is determined by calculating the damping of the uniform precession or k=0 spin-wave mode. The presence of antisymmetric exchange is explicitly taken into account in obtaining the spin-wave modes. The dominant spin-wave damping mechanism is found to be a four-magnon scattering process. This process leads to a calculated wall mobility that has the same order of magnitude and temperature dependence as that observed.
Determination of crack characteristics from the quasistatic approximation for the scattering of elastic waves
Authors: Teitel S.
Published: February 2003

We extend the work of a previous paper to give a long-wavelength approximation for elastic wave scattering by an elliptical flat crack. Explicit formulas for the far-field scattered amplitudes in this approximation are given for various experimental configurations. These formulas are then applied to give a simple inversion procedure. The orientation and eccentricity of the crack are readily determined from unnormalized scattering data. The size may be determined from an absolute intensity measurement.
Stresses generated by the thermomigration of liquid inclusions in silicon
Authors: Anthony T. R. , Cline H. E.
Published: February 2003

Estimates of the stresses generated in a silicon wafer by thermomigration processing indicate the potential presence of stresses ranging from 1.7×10−1 to 7×103 MPa. The causes of these stresses include the heating and cooling of the wafer, the partial infrared transparency of silicon, thermal edge losses from the periphery of the wafer, the increasing solubility of silicon in the inclusion with increasing temperature, the difference in thermal conductivity between the liquid inclusion and the silicon matrix, the lattice expansion induced by impurity atoms in the dopant trials, the mismatch in thermal expansion coefficients in the Al-Si sandwich at the completion of processing, and inclusions frozen in the wafer. Various ways of decreasing or eliminating these stresses are suggested so that the performance and yield of devices made by thermomigration will be optimized.
Transformation of coordinates associated with linearized supersonic motions
Authors: Shankara T. S. , Nandi Kamal Kanti
Published: February 2003

A Lorentz-like transformation (LLT) is introduced in the supersonic regime which keeps the wave equation invariant and simultaneously fixes the coordinate system to the body, producing small disturbances. Its implications, which appear to be far reaching, are briefly discussed.
Photochemical enrichment of the chlorine and carbon isotopes induced in Freon (CF2Cl2) by CO2 laser pulses
Authors: Fettweis P. , Nève de Mévergnies M.
Published: February 2003

Enrichment of the carbon isotopes by photodissociation or photochemical reaction of Freon (CF2Cl2) induced by a TEA-CO2 laser has been reported recently by several authors. The present work shows that large effects on the chlorine isotopes are also induced. Their laser-wavelength dependence has been measured, and some complementary information on the carbon isotopic effects has been collected. Excitation around 930 cm−1 yields an enrichment in 37Cl in the residual CF2Cl2, and excitation around 1085 cm−1 has an opposite effect, while 13C enrichment is found around both 1090 and 922 cm−1 and 12C enrichment is found around 1065 cm−1. These effects can be qualitatively explained with the known fundamental vibrations ν1 (922 cm−1, stretching mode) and ν6 (992 cm−1, rocking mode) of CF2Cl2. The efficiency of the photodissociations of CF2Cl2 induced by a CO2 laser is evaluated, and an effective threshold energy density of 3 J/cm2 is found at 1089 cm−1.
The Kelvin transformation for a torus
Authors: Cade R.
Published: February 2003

A perturbation method was given recently for solving electrostatic problems involving a conducting torus which is freely charged or influenced by a uniform field parallel to its axis. It was forseen that one limitation of the method, the fact that no external influence other than the one just mentioned is allowable, could be removed in the case of a circular torus (anchor ring) by means of the Kelvin transformation and superposition, and the present paper develops this aspect. A number of presumably new results are given for a torus influenced by a given charge located on its axis, and it is shown how the procedure can be extended for a very general axisymmetric situation involving a given charge distribution.
Guided-wave acousto-optic interaction on nonpiezoelectric substrates
Authors: Yao S. K. , August R. R. , Anderson D. B.
Published: February 2003

Guided-wave acousto-optic diffraction has been demonstrated on a silicon substrate for the first time. The surface acoustic wave is launched from a ZnO/Tab2O5/SiO2/Si multilayered structure, while a Ta2O5/SiO2/Si optical waveguide is used for the acousto-optic interaction. The measured diffraction efficiency is 3.3% per milliwatt of acoustic power. An order-better performance is possible with improved transducer geometry. The silicon-based guided-wave acousto-optic technology is preferred for eventual integration of both optical and electronic components for integrated optical applications such as rf spectrum analyzer and fiber-optical terminals. Experiments with a similar structure on a glass substrate is also reported.
Crystal structure and compression of ruby to 46 kbar
Authors: Finger Larry W. , Hazen Robert M.
Published: February 2003

Crystal structures and lattice constants have been determined for ruby at hydrostatic pressures up to 46 kbar using a gasketed opposed-anvil diamond cell on a four-circle diffractometer. The measured compressibility is slightly anisotropic, having a value of 1.36±0.03×10−4 kbar−1 parallel to c and 1.22±0.03×10−4 kbar−1 perpendicular to c. If a Birch-Murnaghan equation of state is used and K′0 is assumed to be 4, the isothermal bulk modulus is 2.57±0.06 Mbar. Refined atomic coordinates do not change with pressure; therefore, the structure compresses in a uniform manner. This study demonstrates that crystal structures may be determined at high pressure on single crystals with a precision approaching that of room-pressure results.
The viscosity and structural relaxation rate of evaporated amorphous selenium
Authors: Stephens R. B.
Published: February 2003

Certain properties of vacuum-deposited thin films of a-Se were measured and compared with those of melt-quenched Se glass. After annealing in the temperature range 25–50 °C, the creep, heat capacities, and far-infrared behaviors of the vapor-deposited films were indistinguishable from those of melt-quenched specimens. The shear-viscosity η measurements on the films were extended into a temperature range well below that where such data on melt-quenched samples are available. Over this temperature range, 25–35 °C, the T dependence of η of the equilibrated films was well fit by an Arrhenius relation with an activation energy of 130 kcal/mole. The stress and thermal-relaxation rates for annealed films were also measured as functions of T. They are controlled by different sets of relaxation processes and are not directly proportional to the equilibrium η. However, they are in good agreement with each other, except that the thermal-relaxation times are more widely dispersed over a span of about two orders of magnitude. The isothermal relaxation of the films to their equilibrium creep rates, though not a simple exponential decay with a single time constant, can be simply described by a relaxation time τ (t), which is proportional to the instantaneous viscosity η (t). As deposited, the films exhibited glass-transition temperatures as much as 10 °C below those of annealed films. Also they showed a broad exothermic peak at about 50 °C. These results, on annealed and as-deposited films, are consistent with the hypothesis that the various molecular constituents, presumably eight-membered rings and polymeric chains of a-Se, readily interconvert to an equilibrium distribution at temperatures as low as 30 °C. This distribution is temperature dependent and the same in vapor-deposited and melt-quenched a-Se.
Studies of defects in neutron-irradiated p-type silicon by admittance measurements of n+-p diodes
Authors: Tokuda Yutaka , Usami Akira
Published: February 2003

Defects introduced in p-type silicon by neutron irradiation were studied by measuring the admittance of n+-p diodes. It was shown that the energy levels and capture cross sections estimated from the temperature dependence of the admittance had some uncertainty due to the temperature dependence of the concentration of free carriers in the bulk and the high-frequency-junction capacitance. So, we presented the method of determination of the energy levels, capture cross sections, and concentrations of defects from the frequency dependence of the admittance. This method consists of the measurements of G/ω and C as a function of frequency. From this method, assuming that capture cross sections are independent of temperature, the energy levels of Ev+0.16 and Ev+0.36 eV were obtained. For these defects, the calculated values of the hole capture cross section were 2.4×10−14 and 3.7×10−14 cm2, respectively. Comparing with other published data, the energy level of Ev+0.36 eV was found to be correlated with the divacancy.
Impurity effect on grown-in dislocation density of InP and GaAs crystals
Authors: Seki Yasuo , Watanabe Hisao , Matsui Junji
Published: February 2003

Dislocation-free InP and GaAs crystals have been grown by liquid encapsulation by means of an ’’impurity doping’’ procedure. It was found that grown-in dislocations were diminished when the crystals were pulled from melts to which certain kinds of impurities were added. The impurity effect on grown-in dislocation density was examined for Zn, S, and Te in InP, and Zn, S, Te, Al, and N in GaAs. It was found that these impurities were effective for reducing the grown-in dislocation density, except for Zn in GaAs. The effectiveness of impurities for reducing the dislocation density of the crystals was ascribed to the strength of the bonds formed between the substitutional impurity atoms and host crystal atoms surrounding the impurity atoms. The anomaly of Zn in GaAs was presumed to originate from the interstitial Zn.
Basic grain-boundary effects in polycrystalline heterostructure solar cells
Authors: Fraas L. M.
Published: February 2003

A qualitative model describing grain-boundary effects in polycrystalline heterostructure solar cells is presented. Two salient observations of the model are (1) that an accumulated grain boundary in the light-absorbing layer can produce a surface field that serves to reduce grain-boundary recombination and increase device short-circuit current and (2) that the grain boundary in either the window layer or absorber layer should be depleted so as to avoid high device tunneling currents. Avoiding high tunneling currents leads to high device open-circuit voltages. The model describes additional electrical effects and suggests means of controlling and characterizing grain-boundary types.
Boundary effects on the normal-mode responses of linear transversely isotropic piezoelectric materials
Authors: Chen Peter J. , Montgomery Stephen T.
Published: February 2003

In this paper, we examine the coupled electromechanical responses of transversely isotropic linear piezoelectric materials. In particular, we consider the boundary–initial-value problem which is consistent with the transverse- or normal-mode experiment and evaluate the effects of lateral boundary conditions on the electrical output of a rectangular specimen of such a material. The solution of the problem entails the simultaneous solution of the wave equation and the circuit equation. This is accomplished via numerical methods. Our results show that the electrical output of the specimen depends markedly on the lateral boundary conditions in that its value and its duration can either be enhanced or degraded without having to alter the mechanical loading. These observations are of importance, particularly in design considerations and in the interpretation of experimental information.
A diamond radiation detector
Authors: Vermeulen L. A. , Harris A. J.
Published: February 2003

Type-IIb diamonds are partially compensated p-type semiconductors at room temperature. Radiation damage makes such diamonds highly insulating. This effect can be exploited to make a fast radiation detector which is sensitive both to light and charged particles. This is done by confining the radiation damage to a narrow band within the crystal. The decay time is less than 3×10−10 s after illumination with photons of energy 3.68 eV (337 nm). The fact that ’’counting diamonds’’ can now be manufactured from the relatively abundant type-IIb diamonds, both natural and synthetic, will be of some interest, since natural counting diamonds are very rare.
Theory of He+2+O2 charge exchange laser
Authors: Ali A. W.
Published: February 2003

The kinetics of the O+2 first-negative band laser due to near-resonance charge exchange between He+2 and O2 are presented. It can be excited in the afterglow of a discharge in a high-pressure He and O2 mixture (He≫O2). Gain calculation, however, is presented for discharges due to high-energy proton beams advocating their use for high-pressure gas lasers. In addition, a comment is made on the disappearance of 3914 laser lines with increasing N2 density in the He+2+N2 charge exchange laser.
A critical evaluation of the effect of electric fields on the residual structure of vapor-deposited metal films
Authors: Murr L. E. , Sattler M. L.
Published: February 2003

Thin films of Al, Pb, Bi, and Sn representing a range of bulk crystal structures and low-melting-point metals were vacuum-vapor deposited onto air-cleaved (001) NaCl substrates in the presence of dc electric fields applied in the plane of the deposit (using detached electrodes) ranging between 102 and 103 V/cm even considering displacement current effects during evaporation. Such experiments, conducted at room temperature (25 °C) within short vaporization periods in order to avoid thermal-induced enhancement of bulk and surface conductivities in the NaCl substrate, and time-dependent gradient losses, showed no significant or detectable effects on residual microstructures or crystal structure upon examination and comparison of representative film samples that have an approximate thickness of 1200 A by transmission electron microscopy.
Trap depths in the depletion region of single-crystal CdS-Cu2S heterojunctions
Authors: Kobayashi Akihiko
Published: February 2003

The experiment of the admittance spectroscopy was carried out for the single-crystal CdS-Cu2S heterojunction in which the Cu2S was grown chemically on the Cd and S plane of CdS single crystal. The results showed that the concentration of the trapped electrons at the several trapping levels in the depletion layer of the former heterojunction decreases with increasing temperature. The opposite effect, however, was obtained for the latter heterojunction at the temperature below 210 K. The causes for the difference in the heterojunctions will be discussed in this paper.
High domain-wall velocities in (Gd,Lu)3(Fe,Mn,Al)5O12 garnet epilayers with orthorhombic anisotropy
Authors: Breed D. J. , van der Heijden A. M. J. , Logmans H. , Voermans A. B.
Published: February 2003

Garnet films can be given orthorhombic anisotropy by growing films with positive magnetostriction constants under compression on (110) -oriented substrates. The positive magnetostriction is achieved by the incorporation of Mn3+ ions in (Gd,Lu)3Fe5O12 films. In this way bubble films with a strong in-plane anisotropy field are obtained. This in-plane anisotropy increases the maximum velocity of the domain walls to at least 40 000 cm s−1. The domain-wall mobility in these films is about 1500 cm s−1 Oe−1. The dependence of the domain-wall velocity on the anisotropy and on the orientation of the domain wall in the film plane is shown.