bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical properties of InSb-based mixed crystal films
Authors: Amemiya Yoshihito , Terao Hiroshi , Sakai Yoshio
Published: February 2004

High-carrier-mobility InSb-based mixed crystal films, InAsxSb1−x (0<x <0.37) and In1−xGaxSb (0<x <1), were prepared by a vacuum evaporation technique for application to galvanomagnetic devices. Temperature dependence of the Hall coefficients and Hall mobilities were measured at temperatures between 90 and 570 °K. The absolute-zero energy gap estimated from the Hall measurement of the InAsxSb1−x films exhibits a minimum of 0.16 eV at about 35 ∼ 37 mole% InAs. The transport properties of the mixed crystal films are both dominated by an unknown scattering process which decrases the electron mobility of InSb films at low temperatures.
Flux-quantization effects in large inductance loops containing Josephson junctions
Authors: Guéret P.
Published: February 2004

Computer simulations of a flip-flop circuit containing weak links (Josephson junctions) show that extremely small changes in the circuit inductance can lead to drastic differences in the circuit behavior. The effect, which is explained in terms of flux quantization, is not limited to small inductance loops, but is also observable in loops which can contain a large number of flux quanta. It is of importance in connection with the punch-through phenomenon recently reported by Fulton and Dynes.
Electromigration-stimulated motion of a liquid alloy defect in aluminum thin films
Authors: Howard J. K.
Published: February 2004

A large defect ([inverted lazy s]600 μ in diameter) was observed to move below the surface in aluminum thin film at a velocity in excess of 40 μ/h (1.11×10−8 m/sec). X-ray stress topography was used to trace the migration, which was in the direction of electron flow, with dislocations in the silicon (under the aluminum) serving as location references for measuring the velocity. The migration direction and velocity of the subsurface defect were reproduced by forming an Al–Sn eutectic zone in the central part of an aluminum stripe. The movement of a liquid alloy inclusion in solid aluminum film under an electromigration driving force was proposed to explain the experimental observations.
Lattice theory of fracture and crack creep
Authors: Hsieh C. , Thomson R.
Published: February 2004

A quasianalytic solution for the atomic displacements of a discrete two-dimensional lattice containing a crack is obtained. We assume that the force laws are linear up to a critical displacement when the bond snaps, which is the basic assumption of the lattice static approximation. When compared to the classic Griffith continuum description, new results are: (i) a predicted and observable lattice trapping of the crack, (ii) difficulties with the interpretations of the crystal surface energy in a cleavage experiment, and (iii) a predicted characteristic crack creep phenomenon under external constant stress. The present theory shows how two separate ``surface energies'' are inferred from the stress to open and to close a crack, and on our model these energies differ from one another by a large factor of 5.7. The thermodynamic ``surface energy'' is not related to either of these quantities. Experimental verification of the lattice trapping of cracks is thought to be most readily and directly obtained by observations of the creep of a crack under high vacuum conditions.
Time-resolved measurement of an electron-beam distribution function
Authors: Chang J. , Swain D. W. , Mix L. P.
Published: February 2004

We have developed a technique for measuring the electron-beam distribution function as it evolves in phase space. Data illustrating the successful use of this technique are presented. Transit time and other effects which can cause errors using this technique are discussed.
Third-order treatment of combined effects of space charge and external fields on cylindrical ion and electron beams
Authors: Bosi G.
Published: February 2004

Analytical treatments of the space-charge spread of cylindrical beams have been based upon a number of restrictive assumptions. Most of them can be removed and a higher accuracy attained with the help of a suitable relation connecting motion and Maxwell's equations. As previous treatments appear as paraxial approximations, third-order formulas applying to arbitrary field forms have been carried out.
Crystallite size distribution and lattice distortions in polyethylene from analyses of Debye-Scherrer line profiles
Authors: Yoda Osamu , Doi Kenji , Tamura Naoyuki , Kuriyama Isamu
Published: February 2004

Distributions of crystallite sizes and lattice distortions in the direction normal to (110) of the polyethylene crystal are derived from 110 Debye-Scherrer profiles, by means of a Fourier technique developed by one of the present authors. Samples investigated are linear polyethylene powder, single-crystal mats grown at 85 °C and 70 °C, and branched polyethylene powder with a different methyl-group concentration. It is found that in the crystallite size distribution each of the polyethylenes examined has a common peak at about 100, 250, 350, and 450 Å. The presence of branches with lower methyl concentration does not seriously affect the distribution, but at the highest concentration of branches (29 CH3/1000 CH2) peaks at 350 and 450 Å disappear. Lattice distortions in the crystallites of polyethylene cannot be always explained by paracrystalline or strained-lattice-type strain alone, but may be generally expressed by a superposition of them.
Thermal analysis of thin-film micromachining with lasers
Authors: Paek U. C. , Kestenbaum A.
Published: February 2004

Laser micromachining of thin metallic films is promising to become an important processing step in the fabrications of electronic circuits. Important applications range from pattern generation of conductive paths to trimming of thin — film resistors. Since the thin films possess vaporization temperatures which generally are much higher than the melting temperature of the underlying dielectric substrate, short — duration pulses such as those available from Q-switched and cavity-dumped lasers must be used. Use of such short pulses minimizes potential thermal damage to the substrate and adjacent areas in the film. To predict the thermal state of the film and substrate, we have developed a theory which takes into account the heat loss due to conduction into the substrate, and the spatial distribution of the irradiating laser beam and its thermal effects in the film. Neglecting thermal gradients across the thickness of the film, we have been able to obtain a closed-form perturbation solution whose first-order solution accurately describes the temperature for many film thicknesses and pulse lengths. The second-order solution which accounts for conduction in a direction transverse to the laser propagation direction may contribute significatnly to the total temperature profile in some cases, particularly for pulse lengths of microsecond duration and longer. The theoretical analysis may be used to estimate the threshold intensity for vaporization of various thin films deposited on dielectric substrates. Estimation of threshold intensity for thin films of bismuth on Mylar and gold on glass is presented. This predicted threshold intensity for vaporization as derived from our first- and second-order solution compares favorably with limited published experimental results.
Anisotropy in electrical properties of {001} Si/{011̄2} Al2O3
Authors: Hughes A. J. , Thorsen A. C.
Published: February 2004

A detailed investigation of the Hall mobility has been carried out on a series of [inverted lazy s]2-μ-thick n-type {001} Si/{011̄2} Al2O3 films. A specially designed Hall bridge pattern has been used to obtain independent measurements of mobility as a function of current direction in the plane of the film. The data show an anisotropy in the mobility of approximately 9%, with a maximum in mobility occuring along the 〈100〉 Si direction that is parallel to the 〈21̄1̄0〉 Al2O3 direction in the plane of the substrate. This behavior is found to be a consequence, through the piezoresistance effect, of the anisotropic thermal contraction of Al2O3 on cooling from the deposition temperature, which leads to an anisotropic thermally induced stress in the Si.
Amplification of helicon wave in indium antimonide
Authors: Hsieh H. C.
Published: February 2004

The condition for the amplification of the left-hand polarized helicon wave in InSb subject to a parallel applied static electric field E0 and magnetic field B0 is derived from the dispersion relationship. It is shown that the helicon wave in InSb may be amplified in the range of E0 where Ohm's law is valid, provided that the value of B0 and the wave frequency f are proper.
Glow-discharge optical spectroscopy for the analysis of thin films
Authors: Greene J. E. , Whelan J. M.
Published: February 2004

Available techniques for the chemical analysis of epitaxial semiconductor films are limited because of typical sample thicknesses of 0.7–10 μm. The use of glow-discharge optical spectroscopy was investigated as an analytical technique. GaAs was dc sputtered in Ar and the glow discharge monitored for the electroluminescence associated with one or more target elements. The present detection limit for Sn in GaAs is 3×1016 atoms cm−3 for a volume sputtering rate of 1.5×10−5 cm3/min. The luminescent intensities combined with sputtering rates were used to estimate concentration profiles as a function of depth for GaAs1−x Sbx films grown on GaAs. Sputtering yields have been measured for GaAs over the range 0.5–3 kV and found to vary with orientation in the following order: (111)As, (111)Ga, (211), and (110).
Spontaneous polarization of Gd2 (MoO4)3
Authors: Sawaguchi E. , Cross L. E.
Published: February 2004

The spontaneous electric polarization Ps has been measured for Gd2(MoO4)3 over the temperature range from 4.2 °K to the Curie point. Near 4 °K the maximum Ps is slightly less than 0.29 μC/cm2 with a very low temperature coefficient. An electric field enforced phase transition from paraelectric to ferroelectric at temperatures just above zero-field Tc demonstrates the first-order nature of the phase change. Better agreement was found near Tc between Ps and the relation (T − T1)1/3 than between Ps and a Landau-type function.
Light scattering from an exploded lithium wire plasma
Authors: Leonard T. A. , Bach D. R.
Published: February 2004

A thin lithium wire was extruded and exploded in vacuum and the resulting plasma was studied during the first 2 μsec of the discharge. Included in the study were scattering of a Q-switched ruby laser beam, high-speed streak photographs showing the laser-plasma interaction, and time-resolved emission spectra. The low pressure in the discharge chamber of 5×10−5 Torr prevented current shunting and also resulted in a ``clean'' lithium emission spectrum. The electron density calculated from mass conservation and temperature varied from 1017 to 1019 cm−3 as the plasma column oscillated in diameter. These densities matched those obtained from a Fresnel reflection model very well. Broadening or shifting of the scattered light was less than 1 Å and the intensities yielded electron densities from 2×1019 to 1022 cm−3 when interpreted as cooperative electron scattering. The emission spectra from 3500 to 6900 Å showed three Li I, seven Li II, one Li III, and one unidentified line. The spectroscopic temperature obtained from various line ratios averaged about 4 eV, whereas the temperature found from a simple ``snowplow'' model analysis varied from 4 to 25 eV. The electron density measured by Stark broadening of emission lines compared well with the average density obtained through mass conservation.
The investigation of microdefects in high-purity silicon crystals by means of lithium decoration
Authors: de Kock A. J. R. , Boonen P. G. T.
Published: February 2004

The occurrence and nature of microdefects in silicon single crystals have been studied by means of lithium decoration in combination with x-ray transmission topography, ir transmission microscopy, and electrical resistivity measurements. The silicon crystals used were grown with the floating-zone or the pedestal-pulling method and contained different types of lattice defects. The Li diffusions were carried out at 400<TD<730°C. Due to precipitation the Li-donor concentration decreased exponentially with time during annealing. The number of nucleation sites was calculated with the aid of Ham's theory. For TD=400°C precipitation took place exclusively on grown-in lattice defects, such as dislocations and vacancy clusters. At TD=500°C vacancy-oxygen complexes of type (V-30) were formed in a striated distribution, which acted as nucleation sites for Li. These complexes are not formed in crystals doped with hydrogen. For TD≥550°C the precipitation process is dominated by Li precipitation on V-O pairs (A centers).
Determination of the local variation of the magnetic properties of liquid-phase epitaxial iron garnet films
Authors: Hansen P. , Krumme J. -P.
Published: February 2004

This paper supplements and assesses an optical measuring technique for the local determination of the cubic and uniaxial anisotropy fields K1/Ms and Ku/Ms in uniaxial magnetic films reported in a recent paper. Graphs for the quick evaluation of the Ku/Ms values are given. The accuracy of the method is assessed by comparison with FMR measurements. The origin of the nonuniformity in the domain pattern of a (111) LPE garnet film with the chemical composition Y2.5Gd0.5Fe4Ga1O12 grown on a GGG substrate is investigated by local optical measurements of the magnetic film parameters K1/Ms, Ku/Ms, compensation temperature, and magneto-optic Faraday rotation. It is correlated with local structural parameters of the substrate as stress birefringence from ellipsometric measurements and inhomogeneity of the lattice constant measured by x-ray topography.
Exchange-free magnetoelastic plane waves
Authors: Parekh J. P. , Bertoni H. L.
Published: February 2004

The propagation of waves in a magnetoelastic (ME) material is gyrotropic and dispersive, and dependent on the externally applied dc magnetic bias field. As a basis for using these properties in acoustic wave devices employed in electronic systems, a systematic description of the propagation characteristics of exchange—free ME plane waves is given. The propagation characteristics are represented via dispersion diagrams and refractive index diagrams. The polarization of the fields is discussed and numerical examples are presented.
Josephson junction interference grating
Authors: Stuehm D. L. , Wilmsen C. W.
Published: February 2004

The maximum current through multiple Josephson structures as a function of applied magnetic field is presented. Particular emphasis is placed on the Josephson penetration depth effects and geometrical considerations. The symmetrical and asymmetrical current feed two-, three-, four-, and five-junction gratings are analyzed and discussed. The Josephson penetration depth is shown to control the amplitude of the interference and diffraction patterns of the interference grating. In addition the interior-junction-length/interference-loop-area product is shown to control the operating mode of the interference grating. The dependence of the magnetic field sensitivity and interference pattern amplitude on the number of junctions is discussed.
Magnetic and thermal properties of some austenitic stainless steels at low temperatures
Authors: Stutius W. , Dillinger J. R.
Published: February 2004

Measurements of the thermal conductivity λ of some stainless steels (AISI types 304, 304L, 310, 321, and U.S. Steel Tenelon) between 0.4 and 1.6 °K, and of the electrical resistivity and magnetic susceptibility below 295 °K are given. Between 0.7 and 1.6 °K, λ depends linearly on temperature and is given to within ±15% for all samples by λ=0.67T(mW/cm °K). All samples show antiferromagnetic order. The susceptibility of Tenelon is about 20×10−6 emu for all temperatures below 295 °K and is smaller than that for any of the other samples by over an order of magnitude at 4.2 °K.
Carrier transport and current oscillation in Bi12GeO20 in the ``relaxation semiconductor regime''
Authors: Hayakawa H. , Yoshisato Y. , Mikoshiba N.
Published: February 2004

New transport and low-frequency current oscillation phenomena have been observed in a photoexcited Bi12GeO20 single crystal in the temperature range 77–110 K. These phenomena can be explained on the basis of the relaxation semiconductor regime where the dielectric relaxation time exceeds the minority-carrier lifetime. Experiments strongly suggest that sublinear dependencies in the current-voltage characteristic and the current oscillation in the higher bias range are general features of the relaxation regime.
Criterion for determining the origin of Ohmic currents in insulators
Authors: Scher H. , Pai D. , Mort J.
Published: February 2004

For thin insulating layers the observation of a linear I-V curves is often cited as prima facie evidence that the carriers originate from thermal bulk generation. In the present paper we point out that a linear I-V curve can also arise from an emission-limited or contact-controlled current. We present an unambiguous experimental criterion to determine whether a linear I-V curve results from contact emission or bulk generation.
Effects of steady-state electrical discharge on the separation of gas constituents in helium-argon mixture
Authors: Hackam R.
Published: February 2004

A study of gas separation (cataphoresis) has been made in the positive column of a steady-state electric discharge, using the binary mixture 2.2% argon-helium. A glow discharge is initiated in a 0.96-m-long tube of 9.5 mm diameter using a high-voltage stabilized source. The discharge tube employs a brush anode and a brush cathode to obtain uniform discharge and is connected to a bakeable gas handling system. The discharge is scanned spectroscopically from anode to cathode and the emitted spectra of helium (5875) and argon (4152 Å) are monitored. The cataphoresis separation of the constituents is studied with variation of both the gas pressure and the current flowing between the electrodes. It has been found that the ratio of Ar/He increases with increasing distance from anode to cathode. Furthermore, the quality of cataphoresis improves with increasing pressure and current in accordance with theoretical predictions. The effect of the temperature of the walls on the quality of cataphoresis is investigated and found to decrease with increasing temperature in agreement with theory and with Schmeltekopf's experimental study in helium-neon mixtures.
Correcting interface-state errors in MOS doping profile determinations
Authors: Brews J. R.
Published: February 2004

It is shown that the apparent doping profile obtained from a 1/CHF2 vs V plot (where CHF is the high-frequency MOS capacitance and V is the voltage across the capacitor) can be corrected for interface-state effects to obtain a more accurate doping profile. This more accurate doping density, N(w), at distance w from the semiconductor-insulator interface is related to the uncorrected density, N0(w), obtained by neglecting interface states, by N(w)=N0(w) (1−CLF/Cox) (1−CHF/Cox)−1, where CLF is the quasistatic MOS capacitance at the voltage corresponding to the depletion width w and Cox is the oxide capacitance. This scheme is shown to provide the doping profile to within 5% accuracy for distances from three extrinsic Debye lengths out to the maximum depletion width obtainable in thermal equilibrium. Experimental verification of this method is obtained by measuring the doping profile on a single capacitor before and after bias-temperature stress. The same doping profile is obtained in both cases despite a large change in interface-state density.
Ionization rate in GaAs determined from photomultiplication in a Schottky barrier
Authors: Glover G. H.
Published: February 2004

The ionization rate of carriers in GaAs has been determined as a function of field from photocurrent in a Schottky barrier. Analysis of the data is based on a model which includes the effects of junction widening and light absorption in the semiconductor. The results agree well with earlier reported values. The technique may be valuable for obtaining avalanche measurements in semiconductors for which fabrication of p-n junctions is difficult.
Scanning electron microscope observations of the effects of discharges on polyethylene
Authors: Mayoux C. , Ai Bui
Published: February 2004

The surface of sheets of polyethylene was studied by means of a scanning electron microscope in order to compare the effects of corona discharges and those of the constituents of the discharge, i.e., uv radiation and electrons and O+ ions of low energy. The deterioration produced by the O+ ions resembles that produced by the discharge, and the deterioration produced by the electrons and the uv radiation does not. This difference tends to confirm infrared results and the assumption that the ions concentrated at the tip of a discharge erode the surface of the insulating material.
Propagation of stress wave with plastic deformation in metal obeying the constitutive equation of the Johnston-Gilman type
Authors: Kuriyama S. , Kawata K.
Published: February 2004

Many theories have been proposed for the propagation of stress waves in metals. They are classified into three types by the constitutive equation; that is, the Kármán-type theory, the Malvern-type theory, and the Cristescu-type theory. However, these proposed theories are not sufficient to explain certain facts which are found in the impact test of a thin rod consistently. For example, they fail to explain how the front of the stress wave always travels with the elastic-wave velocity even in material prestressed into the plastic region, and the plateau of the uniform plastic strain remains in the neighborhood of the impact end. Therefore, in this paper, the authors apply the Johnston-Gilman-type constitutive equation to the theory of stress-wave propagation and study the propagation of the stress wave produced in a thin rod by an impact of a long duration. The results of analysis account for the above-mentioned two facts consistently, and, moreover, account for other phenomena which occur during the propagation of the stress wave not only in mild steel but also in other metals. From these results, the following conclusions are obtained. It is proper to use the Johnston-Gilman-type constitutive equation for the theory of the stress-wave propagation in mild steel, and it seems that the forms of the constitutive equations of other metals may bear a close resemblance to that of the Johnston-Gilman-type constitutive equation. Though the Johnston-Gilman-type constitutive equation is based on the microscopic mechanisms of the dislocation theory, the theory of stress-wave propagation in which it is used is essentially Malvern's theory, which has a noninstantaneous plastic response to an increase of the stress.
Electrode polarization of ionic conductors
Authors: Macdonald J. Ross
Published: February 2004

A theoretical analysis by Mitoff and Charles of electrode processes for an ionic material is criticized and corrected. These authors introduce three separate capacitances into their equivalent circuit where only one need appear. This frequency-dependent diffusion-discharge capacitance is calculated incorrectly by Mitoff and Charles, and earlier relevant work is ignored. Partial blocking small-signal theory is used to show that Mitoff and Charles's experimental results on three different ionic materials can quite possibly by understood using such an approach, contrary to these authors' expectations.
Thermal expansion of corundum structure Ti2O3 and V2O3
Authors: Eckert L. J. , Bradt R. C.
Published: February 2004

The thermal expansion coefficients of the corundum structure oxides Ti2O3 and V2O3 were measured by elevated-temperature x-ray diffraction techniques, the former to 300 °C and the latter to 1000 °C. Compared with corundum, both of these oxides exhibit deviations in their thermal expansion behavior which may be attributed to electronic interactions of the transition metal cations.
Relative importance of phonon scattering to carrier mobility in Si surface layer at room temperature
Authors: Cheng Y. C. , Sullivan E. A.
Published: February 2004

The room-temperature surface mobility of free carriers in metal-oxide-semiconductor systems has not been satisfactorily explained by treating phonons as the only important scattering mechanism. The present work shows that, in addition to phonon scattering, both Coulombic and surface-roughness scattering must be taken into account. Experimental results are presented showing that, contrary to the prediction of phonon scattering, surface mobility is process dependent, and that a strong correlation is observed between the detailed mobility behavior and the surface-state density and the degree of surface roughness. A theoretical calculation of surface mobility, based on the combined effect of scattering due to phonons, charged centers, and surface roughness, is also presented.
Simple recording Möllenstedt electron-velocity analyzer
Authors: Wellenstein H. F.
Published: February 2004

An electrostatic velocity analyzer of the Möllenstedt type is described in detail, featuring in particular a high efficiency (through-put) and a resolution adjustable from about 0.2 to 30 eV (or more) full width at half-maximum (FWHM). The construction is kept simple by using several commercially available parts. A sweep generator together with a multichannel scaler is utilized to record spectra over an energy range from 0 to 16 000 eV. An experimental calibration technique is described and two energy-loss spectra obtained by electron impact are given to demonstrate the performance of the analyzer.
Magnetic phase transition in Tm2Fe17
Authors: Gubbens P. C. M. , Buschow K. H. J.
Published: February 2004

The magnetization and the Mössbauer effect were studied for Tm2Fe17 as a function of temperature in the range 4.2–350 K. The results indicate a magnetic phase transition near 72 K.
On the effective permittivity characterizing electrical coupling in surface-wave devices
Authors: Fahmy A. H. , Adler E. L.
Published: February 2004

An effective permittivity is defined which characterizes the electrical coupling properties of acoustoelectric surface waves. Relationships are established between this quantity and other parameters, such as Δv/v, used in evaluating active and passive surface-wave devices. A simple method for computing the effective permittivity is described which is shown to be more accurate than other methods used to date.
Energy balance in low-pressure gas discharges
Authors: Vriens L.
Published: February 2004

In the positive column of low-pressure gas discharges, the electron energy distribution can be markedly non-Maxwellian, in particular in the tail of the distribution at low degrees of ionization. A method is described which enables one to account for large deviations from a Maxwellian distribution when calculating collision rates, energy flow terms, excited-state densities, and the radiation output. Illustrative examples are given for Cs–Ar, Ar, and Hg–Ar discharges. Possible extensions and applications of the method are briefly discussed. Analytical formulas are derived for (i) the Coulomb relaxation between the electrons and (ii) the cross sections for ionization from excited states.
Parallel flow of cylindrical beams of charged particles
Authors: Bosi G.
Published: February 2004

The usual geometry of an axially symmetric parallel flow Pierce-type gun is criticized and some shortcomings underlined. The general equation defining the family of field forms ensuring parallel flow is carried out and a particular solution selected. The shape of electrodes providing the chosen field form is calculated in a simple and reliable way.
Steady shock profile in solids
Authors: Prieto F. E. , Renero C.
Published: February 2004

The hydrodynamic equations for a shock wave, propagating in a viscous material, are integrated to obtain an expression for the shock profile under steady conditions. This expression is compared with a similar one reported by other authors, and both are shown to be in reasonable agreement with the available experimental data for shock propagation in aluminum. It is also demonstrated that these expressions for the steady shock profile are different because they are based on different assumptions on the form of the shock-vs-particle velocity relationship. It is finally shown that the linear relation used in the present paper is in better agreement with the experimental data on velocities.
Chromium—rare-earth energy transfer in YAlO3
Authors: Weber M. J.
Published: February 2004

Energy transfer between chromium and rare-earth ions in YAlO3 was investigated from fluorescence excitation spectra and fluorescence decay studies. Rare earths examined include Nd3+, Ho3+, Er3+, Tm3+, and Yb3+. Chromium—to—rare-earth transfer was observed in all cases; evidence of rare-earth—to—chromium transfer was also observed for Ho3+. Phonon-assisted transfer rates are dependent on the energy mismatch of the transitions for the two ions involved. The efficiency of the Cr3+ → Nd3+ energy transfer in YAlO3 was measured at 300°K and found to be greater than in Y3Al5O12 for comparable dopant concentrations. Use of chromium as a sensitizer for rare-earth fluorescence and laser action is discussed.
1730-Å radiation dominated by stimulated emission from high-pressure xenon
Authors: Gerardo J. B. , Johnson A. Wayne
Published: February 2004

Experimental data are presented which demonstrate superfluorescent radiation due to stimulated transitions between the lowest-bound diatomic states of xenon and the repulsive ground state. In this context, superfluorescence describes a condition where, even in the absence of feedback, radiation from the fluorescent medium is dominated by stimulated transitions. The continuum emission spectrum was highly anisotropic and narrowing of the spectrum was observed. The optical gain was greatest at a wavelength of 1730 ± 10 Å, where the experimentally estimated effective gain cross section is 1 × 10−18 cm2.
Optical waveguides in GaAs–AlGaAs epitaxial layers
Authors: Logan R. A. , Reinhart F. K.
Published: February 2004

Optical transmission properties are described for two types of waveguides formed in AlxGa1−xAs–GaAs–Alx Ga1−xAs epitaxial layers. The first consists of long smooth-walled mesas formed by a masking and etching procedure and the second are obtained using an additional etching step to selectively etch the GaAs layer. The latter structure is potentially useful in forming active devices such as modulators since this structure is self-masking for contacting of the top layer by conventional evaporation techniques. The waveguide dimensions are typically 1–30 μm wide, [sine wave] 1 μm thick, and several mm in length. The transmission measurements are quite similar for both types of guides with attenuation as low as [inverted lazy s]2 cm−1 in wide ([inverted lazy s]20 μm) guides but with losses increasing with decreasing width. The loss appears to arise from imperfections and compositional inhomogeneities in the epitaxial layers.
Lateral spread of 31P and 11B ions implanted in silicon
Authors: Okabayashi H. , Shinoda D.
Published: February 2004

The lateral spread of implanted 31P and 11B ions into Si has been measured using ion implantation at oblique incidence and the C-V method. Standard deviations of the lateral spread are 570 and 825 Å for 145-keV and 260-keV 31P ions, respectively, and 725 and 1100 Å for 80-keV and 150-keV 11B ions, respectively. These results are in good agreement with the theoretical values in the literature.
Electron cascade theory in laser-induced breakdown of preionized gases
Authors: Nielsen P. E. , Canavan G. H.
Published: February 2004

Calculations are presented which follow the time evolution of the energy distribution function of electrons interacting with an extensively preionized He gas and a CO2 laser photon field. Explicit account is taken of electron-electron collisions, inelastic and superelastic collisions between electrons and excited species, and inverse bremsstrahlung in the field of ions and neutrals. Computed breakdown thresholds are in agreement with recent data of Brown and Smith.
Laser probing of carrier diffusion dynamics
Authors: Herper J. C. , Palócz I. , Axelrod N. N. , Stern R. A.
Published: February 2004

A new diagnostic technique can be used to measure simultaneously the excess free-carrier lifetime τ and the diffusion length L with spatial resolution in semiconductor samples. The technique uses pulses of above-band-edge light to generate carriers near the sample surface. The carrier density evolution into the bulk is measured by means of the free-carrier absorption of an ir laser beam. Computer fitting the time variation of the absorption at any beam position to the carrier transport equation yields τ and L, enabling the diffusion coefficient D = L2/τ to be evaluated. Using 104-W/cm2 injection light and a 3.39-μm laser probe on a 1500-Ω cm silicon sample yielded bulk values in good agreement with calculated and independently measured values.
Experimental properties of injection lasers. V. Strong polarization
Authors: Sommers H. S.
Published: February 2004

The spontaneous and coherent properties of a laser with strong TE polarization (E parallel to the junction) are measured and discussed in terms of the nonlinear theory of injection lasers. The laser cavity is 330 × 100 × 0.25 μm with a symmetrical double heterojunction, sawed sides, and cleaved facets. Its dispersion is that of the normal modes of a rectangular box. The current dependence of spontaneous emission indicates a modest increase in population inversion across the lasing region, the maximum overdrive papameter reaching only 0.4. The power dependence of the overdrive parameter deduced from the spontaneous emission agrees well with that from the lateral profile of the external beam. Within a rather large uncertainty from several factors, the calculated value of 25% for the extra prorated loss of the TM modes compared to TE modes arising from facet reflection accounts quantitatively for the persistence of complete polarization to maximum safe output. The critical power associated with the optical nonlinearity is around 5 mW per cavity mode, in agreement with other reported values, and is shown to be independent of facet area as predicted.
Preparation and properties of green-light-emitting CdS–CuGaS2 heterodiodes
Authors: Wagner Sigurd
Published: February 2004

Heterodiodes have been prepared by the growth of epitaxial n-type CdS films from the component vapors on p-type CuGaS2 substrates. In dc operation at 77°K, green light is emitted with an external quantum efficiency of 0.1%. For pulsed operation at room temperature, the efficiency is [inverted lazy s]0.001%. The near-band-gap radiation results from electron injection into a semi-insulating CuGaS2 region near the CdS/CuGaS2 interface. This region also controls the forward current of the diodes.
High-temperature annealing in electron-irradiated CdS
Authors: Look David C.
Published: February 2004

The room-temperature irradiation of as-grown n-type CdS by 1-MeV electrons results in an increase in carrier concentration. The damage anneals in the temperature range 250–300°C, and a study of the annealing kinetics reveals an activation energy of about 1.3 eV which is attributed to sulfur-vacancy motion.
Comments on barrier changes in stressed metal-semiconductor contacts
Authors: Fonash Stephen J.
Published: February 2004

Considerable attention has been given to stress effects in M-S contacts. This interest arises out of problems of device technology and out of interest in possible sensor development. This work examines the effects of stress analytically. In particular, barrier height changes with stress are studied and a discussion is presented correlating predicted changes with experimental data. Recent interesting conclusions regarding the shift of surface states and the electron affinity of silicon with stress are examined.
Effects of dc substrate bias on the properties of rf-sputtered amorphous germanium ditelluride films
Authors: Fagen E. A. , Nowicki R. S. , Seguin R. W.
Published: February 2004

We have studied the changes in chemical composition, capture and release of argon, electrical conductivity, and morphology of crystallization which result from changes in dc bias applied to the substrate during the rf sputtering of amorphous thin films of nominally stoichiometric GeTe2. We find (i) a strong increase of Te deficiency with negative bias, (ii) a strong increase in incorporated argon content with negative bias, (iii) a strong correlation between Te deficiency and argon content, (iv) no dependence of argon content on film thickness, (v) violent release of argon under certain circumstances, (vi) scant correlation between argon content and electrical properties, (vii) slightly stronger correlation between compositional variation and electrical properties, (viii) a residuum of unexplained variation in electrical properties, and (ix) morphological variations consistent with departures from stoichiometry. We conclude that the rare-gas content of nonreactively sputtered chalcogenide alloys is largely inactive except insofar as it determines the kinetics of its own release at elevated temperatures, but that control of substrate potential during deposition is nevertheless essential for the attainment of quantitatively reproducible transport properties.
A high-pressure phase of polyethylene and chain-extended growth
Authors: Bassett D. C. , Block S. , Piermarini G. J.
Published: February 2004

Optical and x-ray observations of polyethylene have been made at high pressures and temperatures using a gasketed diamond-anvil cell. The experiments confirm the existence of the high-pressure phase previously postulated by Bassett and Turner. The new phase is hexagonal, with orthohexagonal lattice parameters of a = 8.46 Å and b = 4.88 Å. Comparison with the previously measured volume change indicates that there is a decrease in the c dimension to 2.45 Å per ethylene unit in transforming from orthorhombic to hexagonal structures. The likely implication is that the molecules in the hexagonal phase do not have an all-trans conformation. Chain-extended growth is the result of crystallization from the melt into the hexagonal phase, whereas chain-folded growth is the familiar process of melt crystallization.into the orthorhombic phase. Chain-extended lamellae are observed to grow outwards behind a growing edge with a permanent narrowed profile, showing that the lamellar thickness is determined in a region extending several microns behind the growth front.
Ion-backscattering study of LiOH-to-Li2O conversion on a LiH substrate
Authors: Myers S. M.
Published: February 2004

Elastic proton backscattering has been used to study the mechanism by which LiOH corrosion layers on LiH are converted to Li2O. The concentration-vs-depth profile was measured during vacuum anneals in the temperature range 200–280°C, over which the conversion rate varied by two orders of magnitude. Conversion was found to proceed via two reaction fronts, one advancing from the LiH–LiOH interface, the other from the surface. Both H2 and H2O were evolved during the reaction. The results are interpreted in terms of H2O being formed at both reaction fronts, and then diffusing respectively to the LiH substrate and to the surface. Water reaching the LiH substrate then reacts to produce H2, while H2O at the surface is released. The conversion rate on the LiH substrate is related quantitatively to the static equilibrium pressure of H2O over a mixture of bulk LiOH and Li2O in the absence of LiH. Values for this thermodynamic quantity have been reported in the literature. From the analysis it is concluded that H2O formation at the reaction fronts is the rate-determining step in the conversion. The activation energy for the conversion process is 31 kcal/mole.
High-temperature GaAs single heterojunction laser diodes
Authors: Minden H. T. , Premo R.
Published: February 2004

GaAs single heterojunction laser diodes were prepared by epitaxially growing all the layers of the structure. The doping in the n -type confining layer and the p -type active layer were varied as was the thickness of the active layer. The effect of these device parameters on the temperature variation of the threshold current and efficiency was determined. A correlation was observed between an abrupt increase in the threshold current on one hand and the onset of optical pulse delay effects on the other hand. Coincident changes in the spectrum and far-field pattern were also observed. A dielectric slab model is used to explain the experimental results. It is also postulated that there was a strong saturable absorption mechanism associated with the n -type region.
Optical and electrical properties of boron-implanted amorphous germanium thin films
Authors: Anderson Gordon Wood , Davey John E. , Comas James , Saks Nelson S. , Lucke William H.
Published: February 2004

Amorphous germanium films were implanted to high boron levels, ∼1021/cm3 peak concentrations. Before and after implantation the conductivity measurements fit the relation logσ∼T−1/4 and no evidence of intravalence absorption was observed indicating that the Fermi level was near the center of the band gap. Thermoelectric power measurements indicated that the samples were weakly n type before implantation and p type after implantation. The position of the fundamental absorption edge shifted to lower energy upon implantation and to higher energies upon subsequent anneals. Implanted recrystallized films were strongly p type, exhibited intravalence absorption, and had very low dc activation energies.
Stimulated backscattered Raman anti-Stokes radiation in liquid carbon disulfide
Authors: Kepros John G. , Fowles Grant R.
Published: February 2004

A Q-switched ruby laser was used to study the anti-Stokes Raman radiation scattered at 180° in liquid carbon disulfide. Frequency-doubled ruby light at 3473 Å was used to excite amplifier cells containing either rhodamine B or rhodamine 6G. Several orders of stimulated backscattered Raman anti-Stokes radiation were observed. Some of the higher-order lines were enhanced by a dye amplifier technique for ease of observation. The radiation was observed by means of a Czerny-Turner spectrograph.
Multifilament Nb3Sn conductors
Authors: Deis D. W. , Gavaler J. R. , Shaw B. J.
Published: February 2004

The superconducting and mechanical properties of multifilament Nb3Sn wires prepared by the surface diffusion technique are described. Materials tested were 0.021- and 0.051-cm-diam wires with 392 filaments 6.6 or 16 μ in diameter. Electron microprobe and scanning electron microscope studies of Nb3Sn layer thickness and matrix contamination have been carried out also.
On the origin of the increase in Schottky barrier height with interfacial oxide thickness
Authors: Peckerar Martin
Published: February 2004

Two recent papers have dealt with the observation that the Schottky barrier height, Vb′, of the gold-gallium arsenide system increases linearly with the thickness of an interfacial oxide layer, l. In this paper it is shown how this linear relationship can be derived by considering the cause to be the same as that of the flat-band voltage shift in MOS devices. That is, charge trapped at the oxide-semiconductor interface creates an image charge in the semiconductor bulk. The slope, dVB′/dl, predicted by this analysis is in good agreement with the 1.75×10−6V/cm value experimentally derived. The predicted barrier height also varies linearly with the amount of trapped surface charge, Qss.
Aerosol-particle sizes from light emission during excitation by TEA CO2 laser pulses
Authors: Weeks R. W. , Duley W. W.
Published: February 2004

Preliminary measurements of the time-dependent light emission from aerosol particles (generated from submicron powders of carbon black and alumina) during excitation with pulses from a TEA CO2 laser show that this emission may be simply related to particle size.
Lead laser using lead chloride as a lasant
Authors: Chen Che Jen
Published: February 2004

A lead-vapor laser utilizing lead chloride as a lasant has been investigated. Lasing is attained by means of two consecutive electrical discharges. The maximum output is obtained at a vapor pressure of about 0.3 Torr at a temperature of 500°C, a time delay between electrical discharges of 150 μs, and an output mirror transmittance of 80%. The maximum energy density and power density are respectively 4 μJ cm−3 and 160 W cm−3.
The interpretation of dislocation contrast in x-ray topographs of GaAs1−x Px
Authors: Mader S. , Blakeslee A. E. , Angilello J.
Published: February 2004

Misfit accommodation in epitaxially grown GaAs1−xPx was examined by x-ray topography which shows crosshatch contrast and by transmission electron microscopy which reveals individual misfit dislocations. Of these misfit dislocations 80% are glissile 60° dislocations and the remainder are perfect edge dislocations. Contrast considerations show that the x-ray images are fully compatible with the actual dislocation structure although they cannot resolve the individual dislocations.
Sputtering of chemisorbed gas (nitrogen on tungsten) by low-energy ions
Authors: Winters Harold F. , Sigmund Peter
Published: February 2004

Flash filament techniques and mass spectrometry have been used to measure sputtering yields for nitrogen chemisorbed on tungsten and bombarded with noble-gas ions in the energy range up to 500 eV. The experimental results show that primarily nitrogen atoms rather than molecules are sputtered. Despite a high binding energy (∼6.7 eV/atom), we find high sputtering yields and low threshold energies. The results are found to be in reasonable agreement with simple theoretical estimates. It is sugguested that, in the investigated energy range, adsorbed nitrogen atoms are sputtered primarily as a consequence of direct knock-on collisions with impinging and/or reflected noble-gas ions. Estimates are also given for the yield of nitrogen atoms knocked off by sputtered tungsten atoms. This latter process is expected to dominate at much higher energies.
Photoelectric induced elastomer deformation in PVK-TNF type γ-RUTICON
Authors: Lakatos A. I.
Published: February 2004

In the γ-RUTICON images are created with a spatially sinusoidal deformation of a metallized elastomer which is deposited on top of a photoconductor. The deformation in the elastomer is controlled by the imagewise discharge of the photoconductor when a dc bias is applied between the top metal coating and the bottom transparent electrode. This dynamic process is described in terms of a double-layer linear dielectric model. This model is strictly applicable only in the case where the photoconductivity σp is independent of the applied field. Such is the case in the steady state for PVK-TNF (poly-n-vinylcarbazole-trinitroflourenone) at applied fields ≤2 × 105 V/cm. The model predicts the response time τ of the elastomer to be dependent only upon σp and the dielectric constants εp and εe of the photoconductor and elastomer, respectively. The maximum deformation Dmax at a given applied bias V is a function of the mechanical properties of the metallized elastomer alone. If these parameters are field independent, Dmax is proportional to V2. Experiments confirm most of the theoretical predictions.
Effects of dislocations on the properties of metal SiO2-silicon capacitors
Authors: McCaughan D. V. , Wonsiewicz B. C.
Published: February 2004

The effects of dislocations on the SiO2/Si interface have been studied at dislocation levels of from 104 to 109/cm2. At dislocation levels of 106/cm2 or less the MOS properties are unaffected; at levels from 107 to 109/cm2 the flat-band voltage increases with dislocation density to the point where it is not measurable at 109 dislocations/cm2, being greater than the SiO2 breakdown voltage. No effects on the interface state density are seen.