bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature Sensitivity of Bubble Domains
Authors: Dimyan Magid Y. , Della Torre Edward
Published: February 2004

The temperature sensitivities of bubble domains in the mixed rare-earth orthoferrites and the uniaxial magnetic garnets are derived in terms of the material parameters. For the garnets, there exists an optimum plate thickness of 6lM to minimize the sensitivity, although this minimum is fairly flat from 4lM to 10lM. For the orthoferrites, it is preferable to use as thick a plate as possible subject to other constraints.
Electrical Characteristics of rf-Sputtered Single-Crystal Niobium Films
Authors: Mayadas A. F. , Laibowitz R. B. , Cuomo J. J.
Published: February 2004

It is shown from measurements of the resistivity ratio (RR ≡ resistivity at room temperature divided by resistivity at 10°K), superconducting transition temperature, and transition-temperature width that high-quality single-crystal niobium films can be fabricated by rf sputtering. The observed dependence of RR on sample thickness indicates that the intrinsic electron mean free path increases with thickness. Superconducting characteristics are essentially thickness independent for films thicker than approximately 1000 Å.
Impurity-Sensitive Etchant for Sodium Flouride Crystals
Authors: Davisson J. W.
Published: February 2004

This communication introduces acetic acid as an etchant that can sense distributed impurities in sodium fluoride crystals. It can be used to directly observe impurity reactions in these crystals.
Fatigue Fracture of Polymethylmethacrylate
Authors: Johnson T. A.
Published: February 2004

Two distinct fracture morphologies have been observed in commercial grade polymethylmethacrylate (PMMA) cycled to failure at room temperature in uniaxial loading. In extruded PMMA the fatigue striations are concentric with one origin, increasing in spacing until final fracture occurs. Some of the fatigue striations are serrated owing to the crack being stalled by flaws which are inherent to the material. The region of fatigue crack growth is flat and glassy smooth. In cast PMMA the fatigue striations occur in many localized regions near the surface and are not serrated. There is no apparent regularity to the striations on a scale comparable to the extruded PMMA. It is concluded that the differences in the fatigue fracture surfaces between cast and extruded PMMA reflect a difference in molecular weight.
Growth of p-Type Gallium Antimonide Single Crystals by a Temperature-Gradient Transport Technique
Authors: Rado W. G. , Crawley R. L.
Published: February 2004

Undoped p-type gallium antimonide single crystals were grown by a steady-state temperature-gradient transport method. The melt composition was varied from 0.62 to 0.84 atom fraction Sb. The lowest carrier concentration achieved was 4×1016 holes/cm3, at 300°K. It was concluded that no significant further reduction in carrier concentration is to be expected for GaSb grown from Sb-rich melts under quasiequilibrium conditions.
General Method for Calculating Derivatives of the Lattice Electrostatic Energy
Authors: MacDonald D. E. , Eftis J. , Arkilic G. M.
Published: February 2004

A method for calculating the derivatives of the lattice electrostatic energy is given which is more general, concise, and systematic than any of the calculations previously performed by Fuchs, Cousins, and Suzuki, Granato, and Thomas.
Berg-Barrett X-Ray Observation of Annealing and Laser-Induced Damage in Zinc
Authors: Wu Carl Cm. , Armstrong Ronald W. , Lee Chi H.
Published: February 2004

The Berg-Barrett x-ray diffraction contrast technique has been utilized to study the process of laser-induced damage in a zinc crystal and, also to make observations on the annealing characteristics of the dislocation substructure before and after the laser treatment. Annealing caused individual dislocations to become segmented with various sections of their line lengths becoming parallel to 〈101̄0〉. This preference for a crystallographic orientation of the dislocations seemed related to the equally important observation that the subboundary ``lineage'' structure of the crystals was also largely composed of tilt boundaries of {101̄0} and {112̄0} surfaces. The laser-induced damage required a threshold energy which caused melting, possible vaporization, and appreciable plastic deformation of the matrix material by deformation twinning, nonbasal slip, and microkinking. By comparison with the structural rearrangement observed in the preannealed specimen, the laser-damage zone showed only very retarded changes.
Equation of State of Polystyrene and Polymethylmethacrylate from Ultrasonic Measurements at Moderate Pressures
Authors: Lamberson Donald L. , Asay James R. , Guenther Arthur H.
Published: February 2004

The relationship of ultrasonic velocities to equations of state is addressed for two homogeneous isotropic plastics, polystyrene and polymethylmethacrylate. Ultrasonic velocities were measured at hydrostatic pressures up to 10 kbar and temperatures from ambient to 75°C at an acoustic frequency of 6 MHz. From these data the pressure and temperature dependence of the elastic moduli are calculated. In particular, the bulk modulus is used to compute an equation of state from models proposed by Birch and Murnaghan. The nonlinearity of the bulk modulus at pressures below 10 kbar favors the Birch model. Comparison with shock data shows that the Birch equation of state, determined ultrasonically, agrees quite well with the shock data to pressures well over an order of magnitude in excess of the 10-kbar ultrasonic data for both polystyrene and polymethacrylate.
Dispersion Analysis of Optoacoustic Interactions in Moving Media
Authors: Kong J. A. , Wang L. H.
Published: February 2004

Scattering of electromagnetic waves by an acoustic-wave-modulated moving medium is studied. In the absence of the modulation, the medium is isotropic, homogeneous, and nondispersive in its rest frame of reference. The acoustic wave makes the medium dispersive and the motion renders the medium bianisotropic in the laboratory frame. Dispersion relations are derived. Wave behavior at a moving boundary is also considered.
Dielectric Constants of Quartz
Authors: Bottom Virgil E.
Published: February 2004

The dielectric constants of quartz have been determined by measuring the capacitance per unit area of parallel-plate capacitors made by depositing metallic electrodes on surfaces of thin plates of quartz cut in such a way that the major surfaces are respectively perpendicular and parallel to the optic axis. The effect of fringing of the field at the edges was eliminated by measuring the capacitance per unit area for electrodes of different sizes and extrapolating to infinite area. The dielectric constant measured with the field parallel to the optic axis is K∥=4.60. The constant in the perpendicular direction is K⊥=4.51. Both results are believed to be correct to ±0.2%.
Reduced Sputtering Yields for Two-Phase Ag–Ni and Ag–Co Targets
Authors: Dahlgren S. D. , McClanahan E. D.
Published: February 2004

Sputtering yields of water-cooled two-phase Ag–Ni and Ag–Co targets were found to be much lower than predicted by averaging the yields of the unalloyed metals. The target yields steadily decreased when the Ni or Co content increased from 0 to 30 at. %. Above 30-at. % Ni or Co, the yields did not change and were equal to the respective yields for Ni and Co. Thus, the results indicate that yields may be predictable for some multiphase targets from the yield of the low-yield phase. The unusually low yields were attributed to coating of the high-yield Ag phase with lower-yield Ni or Co during sputtering. Simultaneous coating and sputtering processes reached steady state before removal of 20 μ from freshly prepared non-presputtered Ag–Ni targets even though Ni particles were up to 130 μ in diameter. Quantitative microprobe analysis of one Ag–Ni deposit indicated deposit compositions were nearly the same as target compositions.
Force on a Rectangular Coil Moving above a Conducting Slab
Authors: Reitz John R. , Davis L. C.
Published: February 2004

The force on a rectangular current-carrying coil moving above and parallel to a conducting plate of arbitrary thickness is investigated. Expressions are developed for the lift and drag forces on the coil as a function of speed. Numerical calculations are made for a very thick plate and for plates with thickness of the order of the skin depth. Thick-plate results are compared with experimental measurements of lift and drag on a superconducting coil suspended above a rotating aluminum wheel.
Method for Detecting Fine Structure in the Secondary Electron Emission Yield and the Application to Si(111)
Authors: Goto Keisuke , Ishikawa Kazuo
Published: February 2004

A method has been developed to detect the fine structures which appear in the total secondary electron yield σ and the back-scattering coefficient η as a function of primary electron energy Ep. The method is based on differentiating the σ-vs-Ep or η-vs-Ep curves by Ep by superimposing a small modulating voltage on Ep. To automatically record the σ- (or η-) vs-Ep and dσ/dEp- (or dη/dEp-) vs-Ep curves, the primary electron current was stabilized within ± 0.1% by regulating the temperature of the cathode. Using this method, a large number of fine structures on the σ-vs-Ep and η-vs-Ep curves for a Si(111) single crystal could be detected over the Ep range 20–2000 eV. General features of the fine structures seem to agree with those of the LEED spot intensities, and the fine structures are probably caused by the elastically reflected primaries.
Experimental Investigation of Photoemission from Satellite Surface Materials
Authors: Feuerbacher B. , Fitton B.
Published: February 2004

Photoemission properties were measured for the materials gold, aluminium, stainless steel, vitreous carbon, Aquadag, graphite, silica, and semiconducting indium oxide. The surfaces were treated so as to simulate the conditions actually encountered in space missions. Results are presented on the reflectance, photoyield, and photoelectron energy distributions up to 25 eV, and on the work function. From the yield curves the photoelectron flux under solar irradiation is calculated. Methods are discussed for controlling photoemission both with respect to the number of emitted electrons and their energy distribution.
Electron-Beam Excited Minority-Carrier Diffusion Profiles in Semiconductors
Authors: Hackett W. H.
Published: February 2004

It is shown that electron-beam generation of minority carriers at a semiconductor surface can be used to establish as an exponential minority-carrier diffusion profile Δp (z), measured along the z direction perpendicular to this surface, which is insensitive to possible variations in the surface recombination velocity. This profile can be expressed very simply, Δp (z) = C exp (−z/L), where L is the carrier diffusion length. On the basis of this result, a new measurement technique has been proposed, in which the induced junction current is measured as the electron beam is scanned along an angle-lapped surface of a p-n junction. For a small angle θ between the lapped surface and the junction, the induced current I varies exponentially with scan distance x, I = I0 exp (−x sin θ/L), and provides a direct and accurate determination of the carrier diffusion length L. This technique has been successfully utilized to measure diffusion lengths down to 0.2μ (with 10% accuracy) for GaP, and it should be useful for measuring very short diffusion lengths in other semiconductors.
Motion of Charged Particles in the Normal Section of a Cylindrical Condenser
Authors: Bolduc Léonard , De Celles Michel , Baril Marcel
Published: February 2004

The rotation angle φ of a charged particle in a cylindrical condenser, is evaluated by an exact series expansion which was deduced by De Celles in a previous paper. The derivatives of φ relative to θ (the angle between the radius and the tangent to the trajectory) and E (the kinetic energy of the particle) are deduced and evaluated. Our techniques for the numerical evaluation of the preceding values are discussed and results are presented graphically. Maximum error coming from truncation is treated. The knowledge of φ and its derivatives enable one to calculate the optical properties of a charged particle beam centered on a privileged trajectory. A different expansion for φ, useful for small energies and an algorithm for its calculation, is given.
Calculation of Deposition Profiles and Compositional Analysis of Cosputtered Films
Authors: Hanak J. J. , Lehmann H. W. , Wehner R. K.
Published: February 2004

Expressions have been derived from the Knudsen's cosine law for deposition profiles of finite-sized sputtering targets having the shapes of a segment of an annulus, sector of a disk, and a rectangle. The ability to calculate such profiles simplifies the recently published method of approximate compositional determination of multicomponent films, cosputtered from physically separated targets of different materials. The only data now required to calculate the composition of an entire sputtered film are the dimensions of the sputtering arrangement, the relative position of the targets, and a number of film thickness measurements equal to or greater than the number of sputtering targets.
Influence of Heat Treatment on Aluminum Oxide Films on Silicon
Authors: Kamoshida M. , Mitchell I. V. , Mayer J. W.
Published: February 2004

Properties of aluminum oxide films deposited on silicon by hydrolysis of AlCl3 depend on the growth temperatures. The influence of subsequent heat treatments on the film properties and structures have been investigated in films grown at 700 and 830°C. Etch rates and electron-diffraction patterns indicated that the properties of the films grown at 700°C were not converted to those of the 830°C-grown films even after the heat treatment at 900°C in argon. The amount of residual chlorine in low-temperature films determined by MeV He+ ion backscattering technique, reduced from 2 to 0.9 at.% after the heat treatment at 900°C but still exceeded that (≲0.02 at.%) for the film deposited at 830°C. A small amount of silicon (5 at.% at the surface) diffused through the films deposited at 700°C after the heat treatment at 900°C. In contrast, the 830°C-deposited film did not change following the heat treatment at 900°C in argon atmosphere. Comparisons between the backscattering data obtained from the films treated under oxidizing conditions and those from reference standards indicated oxygen migration through aluminum oxide and growth of an oxide film underneath the aluminum oxide. In addition, at least a part of the new-formed oxide appeared to be comprised of a mixture of aluminum, silicon, and oxygen.
Analysis of Doping Anomalies in GaAs by Means of a Silicon-Oxygen Complex Model
Authors: Weiner M. E. , Jordan A. S.
Published: February 2004

A model based on the formation of silicon-oxygen pairs is proposed to explain a variety of anomalous phenomena associated with GaAs grown in the presence of silicon, SiO2, and/or oxygen. It is suggested that silicon atoms on gallium sites pair with interstitial oxygen atoms, forming a complex which behaves as an acceptor with energy levels near 0.2 and 0.4 eV below the conduction band. It is assumed that the complex can dissociate upon annealing below 850°C by the reaction 2(SiGaOi)−=(SiGaO2)0+SiGa++3e−. This reaction may be reversed at higher temperatures. The electrical and thermochemical properties of such a complex can explain annealing behavior, the occurence of a mobility maximum between 150 and 200°K, site distribution of silicon in p-type silicon-doped GaAs, change from n- to p-type conductivity as a function of Si concentration in GaAs grown from Ga solutions, the formation of I (insulating) layers in GaAs grown by vapor-phase epitaxy, and some of the anomalous behavior observed in GaAs devices. A variety of growth experiments and characterization techniques which could aid in verification of the SiGaOi complex model are suggested.
Copper Precipitate Colonies in Silicon
Authors: Nes E. , Lunde G.
Published: February 2004

The precipitate colonies formed during cooling of silicon single crystals have been shown to be a result of copper precipitation. The experimental technique employed combined neutron activation and autoradiography.
Chemical Effects in Auger Electron Spectroscopy
Authors: Haas T. W. , Grant J. T. , Dooley G. J.
Published: February 2004

The effects of a change in the chemical environment of an atom in a surface region are manifested in several subtle ways on the measured Auger electron spectra. The first, a shift in the energies of the Auger electrons, is the result of charge transfer and is a measure of the valence state of an atom. Examples of this effect are the oxidation results on refractory metals presented here. It is found that measurable changes are found even for submonolayer coverages of oxygen on an otherwise clean surface. The second main effect is a change in the shape of a complex spectrum, which occurs when some of the electrons involved in this Auger process are valence electrons. The best example of this behavior is that of carbon, and it is found that these complex spectra serve as a fingerprint for the identification of the form of the carbon at a surface. Problems and opportunities for the exploitation of both these effects are discussed, the data included here being illustrative of the usefulness of this type of measurement.
Studies of the Use of Gyrotropic and Anisotropic Materials for Mode Conversion in Thin-Film Optical-Waveguide Applications
Authors: Wang Shyh , Shah Manhar , Crow John D.
Published: February 2004

Wave propagation in thin-film optical waveguides using gyrotropic or anisotropic material as substrate is studied. At the film-substrate boundary, the relation between the incident and reflected fields can be expressed in terms of a scattering matrix with matrix elements representing the TE-to-TE and TM-to-TM reflection coefficients and the TE-to-TM and TM-to-TE conversion factors. The property of the scattering matrix is examined, and the condition for continuous and complete mode conversion is derived. Various schemes to achieve complete mode conversion are proposed and the performance characteristics, including the physical dimension and the tolerances in the incident angle and film thickness, for several mode-converting structures are computed and compared. Once the practicability of complete mode conversion is established, it is possible to study the feasibility of practical devices. Various schemes for the realization of such devices as the gyrator, the isolator, the optical switch, and the nondestructive read out are proposed.
Warm-Carrier dc Transport in n Si
Authors: Holm-Kennedy James W. , Champlin K. S.
Published: February 2004

Measurements of the dc current density at 77 °K lattice temperature vs electric field for 26-Ω cm n Si are presented and analyzed to determine the amount of repopulation when the field is applied in the 〈100〉 and 〈110〉 crystallographic directions. A relatively simple and straight-forward technique for computing the energy-relaxation-time dependence on the electric field is proposed and applied to n Si. The electron temperatures vs electric field for several differently oriented conduction-band minima are also calculated. An explanation for the previously observed but unexplained decrease in amount of repopulation above 400 V/cm is given. A new technique for computing the theoretical repopulation-field dependence is also presented and found to give excellent agreement with the experimental results. A theory similar to that used in past literature, but more general, is used in the following experimental determination of the warm-carrier repopulation in n Si.
Preparation, Microstructure, and High-Field Superconducting Properties of Nb3 Sn Doped with Group-III, -IV, -V, and -VI Elements
Authors: Enstrom Ronald E. , Appert John R.
Published: February 2004

The influence of incorporating elements from groups III, IV, V, and VI into vapor-deposited Nb3Sn superconducting ribbon on the critical current density in magnetic fields up to 190 kOe has been examined, and the mechanism of the enhancement of Jc by carbon-containing gases has been investigated. It had been found previously that CO2, CO, and N2, but not O2 or CH4 are effective in increasing Jc. We have now established that the less stable C2H6 and C3H8 are as effective as CO2, and that BCl3 increases Jc to a lesser extent. However, H2S, NH3, and NO decrease Jc compared with an undoped Nb3Sn sample. By optimizing the CO2 concentration in the gas phase, the Jc increase can be as much as a factor of 5; this optimum concentration corresponds to about 2000 ppm carbon in the Nb3Sn vapor-grown layer, as determined by radioactive tracer and mass spectrographic analyses. Since the solid solubility limit of carbon in Nb3Sn is less than 200 ppm, carbon or carbide in excess of this amount is distributed as a second phase probably along subgrain or grain boundaries where it can effectively pin flux lines, and thereby increase Jc. From extrapolations of Jc1/2 vs H, the upper critical fields at 4.2 °K for undoped and BCl3- and C2H6-doped Nb3Sn on stainless-steel substrates are 184, 194, and 196 kOe, respectively, while for CO2-doped Nb3Sn on a Nb substrate it is 225 kOe. α = JcH values ranging from 22 to 32×106 kOeA/cm2 were attained for C3H8-, C2H6-, and CO2-doped Nb3Sn on stainless-steel samples and as high as 42×106 kOeA/cm2 for CO2-doped Nb3Sn on Nb samples. For high- and medium-α materials, α is a function of the applied magnetic field; α/αmax vs H/Hc2 is an approximately parabolic function with a maximum value at H/Hc2 = 0.4 for high-α materials and H/Hc2 = 0.6 for low-α materials. The latter value is in general agreement with theoretical predictions.
Self-Magnetoconcentration Effect in Intrinsic Semiconductors
Authors: Kamarinos G. , Zachariadès M.
Published: February 2004

We show that intrinsic germanium can exhibit a notable self-magnetoconcentration effect at room temperature; this effect is provoked by the self-induced magnetic field when a strong current passes through the semiconductor. We point out the influence of some important parameters such as the carrier lifetime in the sample and the velocities of recombination on the bounding surfaces.
Dynamic Modes in Open Gyromagnetic Waveguides
Authors: de Santis Pietro , Franceschetti Giorgio
Published: February 2004

It is shown that the ``dynamic modes'' of a ferrite rod in vacuum are dielectric modes modified by the presence of the induced magnetic anisotropy. A number of inconsistencies existing in the literature are pointed out.
Behavior of a Pulsed-Discharge Laser with an Intracavity Absorber
Authors: Houston Paul L. , Sutton David G. , Steinfeld Jeffrey I.
Published: February 2004

The asymmetrical pulse usually obtained from a transversely discharged medium-pressure laser may be transformed into a narrower pulse with a higher peak by the incorporation of an absorber into the laser cavity. The experimental results are well predicted by a previously described model for passive Q switching.
Unified Treatment of Acoustoelectric Instabilities in CdS
Authors: Ozaki H. , Furuya N. , Mikoshiba N.
Published: February 2004

A unified model is proposed for the effects of the nonuniformity of samples along the length on the acoustoelectric current instabilities in photoconducting CdS. Various aspects of the current saturation and oscillation are explained by numerical calculations based on the model. A qualitative discussion is also given for the behavior of the current oscillation in semiconducting CdS. A criterion for the current oscillation and a relation between the acoustoelectric oscillation and the Gunn oscillation are obtained by using the impedance function.
Glide Band Formation in Silicon
Authors: Mendelson S.
Published: February 2004

Birfringence and etch pit studies of the initial stages of plastic flow in octagonal-shaped silicon crystals oriented for single slip and compressed at low strain rates in the temperature range 750–800 °C show characteristics quite similar to that found for avalanche behavior and ``Luders-band'' type flow in alkali-halide crystals. The narrow glide bands taper to a single plane at opposite ends and the dislocation morphology, as revealed by their phase retardation birefringence characteristics, is in the form of large concentric loops on neighboring planes with staggered sources in the central region of the band. Calculations show that the stress field from dislocation arrays enhances the formation of neighboring arrays by double cross slip and multiplication, and show how different kinds of defects can form. The enhanced shear stress at the cross-slipped segment is significantly greater if the initial source operates on the surface. The effects of partialized dislocations and various dynamic effects which affect the begining and cessation of glide band formation and broadening are shown to be consistent with avalanche behavior.
Microwave Interferometry in High-Temperature Partially Ionized Dense Gases
Authors: Boschi A. , Merzagora N. , Tamburrano A.
Published: February 2004

The present study emphasizes the applicability of microwave interferometry to partially ionized dense gases, such as the gas mixtures used in MHD energy-conversion experiments. Furthermore, a transmission system is described, which allows coherent microwave transmission through refractory chambers or channels, under extreme conditions of temperature (1000–2000 °K) and pressure (near atmospheric), overcoming the difficulties in the accessibility. The system has been inserted in an arm of a microwave bridge, operating in the ``8-mm'' band and the apparatus has been employed for interferometric measurements of electron densities (within 1011–1013 cm−3) in experiments on the nonequilibrium ionization of Cs–He mixtures.
Lanthanum Hexaboride Electron Emitter
Authors: Ahmed H. , Broers A. N.
Published: February 2004

The emitting properties of hot-pressed high-density lanthanum hexaboride rod cathodes have been measured. A current density of 100 A/cm2 is obtained at a true temperature of 1680°C. Lifetime tests have shown a useful life in excess of 200 h with an emission density of more than 50 A/cm2. The initial buildup of emission from the cathode has been found to be a gradual process and the final emission figures are not obtained until approximately 60 min have elapsed. Subsequently however, the full emission is obtained immediately on heating the cathode to operating temperature. The surface structure on the cathode has been examined with a scanning electron microscope both during the initial buildup of emission and during the operating life of the cathode. It is found that surface evaporation reveals sharp crystalline boundaries at a stage which coincides with the full emission density from the cathode. On heating the cathode to operating temperature without drawing emission, the crystalline nature of the material is revealed by the appearance of faceted hillocks on the surface. This structure is etched away when emission is drawn. There is no evidence to support the theory that lanthanum evaporates from selected emission sites. The whole LaB6 surface evaporates during operation and a certain amount of embedded material is revealed. This material is believed to contain tungsten and it accumulates gradually on the surface as operation continues.
Proximity Effect in Systems of Parallel Conductors
Authors: Smith Glenn S.
Published: February 2004

A procedure is presented for determining the cross-sectional high-frequency current distribution and Ohmic resistance per unit length for systems of parallel round wires carrying equal currents. The additional Ohmic resistance due to the proximity effect is examined for various conductor spacings. An optimum spacing for minimum resistance is determined for systems of conductors with restricted dimensions. Theoretical current distributions are compared with measurements.
Effect of Shock Compression on Electrical Resistivity of Three Polymers
Authors: Champion A. R.
Published: February 2004

The electrical resistivities of polytetrafluoroethylene and high- and low-density polyethylene have been measured during uniaxial shock compression from a few tens of kilobars to several hundred kilobars. For samples greater than 0.25 cm thick, decreases in resistivity of 10–14 orders of magnitude below the resistivity at atmospheric pressure were observed over this pressure range. The measured resistivities were independent of magnitude and polarity of the applied voltage, sample area and thickness, and electrode material as one would expect for a bulk conduction process. At stresses above 200–300 kbars, a further decrease in resistivity was observed as the unloading wave propagated through the sample. For samples thinner than 0.13 cm, an anomalous result was obtained in that no measurable decrease in resistivity occurred during the shock compression.
Approximate Blast Wave Theory and Experimental Data for Shock Trajectories in Linear Explosive-Driven Shock Tubes
Authors: Freiwald D.A.
Published: February 2004

An approximate theory is presented for predicting the trajectories of gas shocks driven by solid high explosives in linear shock tubes. Theoretical calculations are compared to results of experiments, where agreement within 10% is found.
Transport and Photoelectrical Properties of Gallium Arsenide Containing Deep Acceptors
Authors: Brown W.J. , Blakemore J.S.
Published: February 2004

An analysis of Hall-effect and optical measurements shows that Ni, Co, and Mn form relatively deep and compact acceptors in GaAs, with activation energies of 0.20, 0.16, and 0.09 eV, respectively. Conduction by free valence-band holes is augmented at low temperatures by impurity conduction in crystals with heavy doping and strong compensation. The photoabsorption cross section for manganese (which we find to be smaller than hitherto reported) and for cobalt can be viewed as the sum of a Lucovsky-like δ-function potential model for photoionization, and smaller but recognizable contributions due to transitions of holes into the V3 ``split-off'' band, 0.35 eV below the upper valence bands. We have observed the spectral dependence of photoconductivity in these three doped GaAs systems from the intrinsic peak down to the extrinsic threshold.
Convex-Concave Resonators for TEM00 Operation of Solid-State Ion Lasers
Authors: Chesler R.B. , Maydan D.
Published: February 2004

Optical resonators with one convex and one concave mirror offer significant advantages for TEM00 mode operation of solid-state lasers. High efficiency and low sensitivity to perturbations and compactness have been obtained in comparison to other resonator types. The resonators described are characterized by a stability product equal to one-half, with one g parameter greater than unity. An equivalent resonator incorporating an intracavity lens is also described which offers a focused light beam of a selected radius useful for intracavity modulation or nonlinear effects. Experimental results are given for continuously pumped Nd: YAG lasers.
Long-Wavelength Shift in the Operation of Lightly Doped Semiconductor Lasers
Authors: Holonyak N. , Scifres D. R. , Macksey H. M. , Dupuis R. D.
Published: February 2004

The observation of a long-wavelength shift in the peak of the photoemission spectra of lightly doped InP and vapor-expitaxial GaAs is reported. It is shown that this long-wavelength shift of the band-edge emission is due to electron-hole-lattice (EHL) interactions. The samples of this work are volume photoexcited in a low-loss high-Q compound optical cavity which permits the observation of recombination radiation at energies E ≥ Eg, as well as at energies E ≤ Eg.
Electroreflectance and Galvanoluminescence of GaAs
Authors: Bobylev B. A. , Kravchenko A. F. , Loburetz Yu. V. , Salomon S. N.
Published: February 2004

In electroreflectance (ER) using the semiconductor-electrolyte technique (saturated solution, 0.5 N, of NH4NO3 in ethyl alcohol at T ∼ 300 °K), a method of modulation of the surface barrier by single-sign square-wave pulses is proposed. This allows an estimation of the surface equilibrium electric fields. They are 5.6 × 104, 1.1 × 105, and 5.7 × 105 V/cm for n = 1.9 × 1014, 7.1 × 1015, and 3.4 × 1017 cm−3, respectively. The surface of these samples has an inversion layer. In samples with n and p = 1016 − 1018 cm−3, the E0 and E0 + Δ0 peaks are displaced 0.02–0.03 eV to smaller energies relative to E0 of the purest sample, n = 1.9 × 1014 cm−3, which has E0 = Eg = 1.43 eV. This shift might be explained by tailing and impurity banding. In samples with n≳1018 cm−3, ER spectra are distorted and seem to be caused by the Moss-Burstein shift modulation. During ER measurements, galvanoluminescence (GL) appears for both n- and p-type samples. Measurements of GL vs voltage and time were made. GL spectra were measured for some n-type samples which agree with photoluminescence and cathodoluminescence. Maximum emitted power of radiation is ∼ 30 μW with quantum efficiency ∼ 10−4. A hole injection mechanism from the electrolyte qualitatively explains the behavior. During ER measurements by the electrolyte method, it is shown that it is necessary to take into account the appearance of GL since this effect can lead to erroneous ER results.
Coupled-Wave Theory of Distributed Feedback Lasers
Authors: Kogelnik H. , Shank C. V.
Published: February 2004

An analysis of laser action in a periodic structure is presented. A model of two counter-running waves coupled by backward Bragg scattering is used. The resonant frequencies and threshold criteria for the modes of oscillation have been determined for both index and gain periodicities. Analytical approximations are given for both the high- and low-gain cases, and computational results for the intermediate regimes.
Thermoluminescence and Color Centers in rf-Sputtered SiO2 Films
Authors: Hickmott T. W.
Published: February 2004

Thermoluminescent (TL) glow curves of rf-sputtered SiO2 films deposited on silicon have been measured and correlated with optical absorption of the films. As-sputtered SiO2 films are thermoluminescent without further exposure to exciting radiation. Films with a strong optical-absorption band at 7.6 eV (E band) give first-order glow curves. They have a TL center with energy ∼ 0.66 eV and a low-frequency factor s ∼ 104 sec−1, which suggests that trapping centers and recombination centers are physically separated. Irradiation of sputtered SiO2 films with x rays produces complex TL glow curves which have been analyzed by thermal cleaning techniques. Trapping centers with energies of 0.66, 0.84, and 1.04 eV are found. The complexity of TL glow curves in sputtered SiO2 films after x-ray irradiation arises primarily from variations in s, rather than from a broad spectrum of trapping energies. The effect on TL glow curves of annealing SiO2 films in oxygen and forming gas has been studied. When samples with a strong E band are annealed in O2, a decrease in absorption coefficient at 7.6 eV is paralleled by an increase in TL intensity. A trapping center with E ∼ 1.40 eV is produced by annealing of the E band followed by x-ray irradiation. A hyperbolic heating rate 1/T=1/T0 - at, used for all TL measurements, simplified analysis of TL glow curves.
Pulse Delays in TEA CO2 Lasers
Authors: Garside B. K. , Ballik E. A. , Reid J.
Published: February 2004

A novel method is reported for studying the time-dependent gain and cavity losses in a TEA CO2 laser. The technique involves an investigation of the time delay of the onset of lasing with respect to the current pulse in such a laser. Detailed measurements of this time delay as both the laser gain and the cavity loss are varied, in conjunction with a simple theoretical analysis, permit the evaluation of parameters describing the time-dependent gain and the cavity loss. In particular, good values for the peak gain, the rise and fall times of the gain, and the average cavity loss per pass can be obtained. The parameters measured in this way are in agreement with other reported data, where available. The method of investigation reported avoids many of the experimental problems which are involved in the direct measurement of the time-dependent gain using cw CO2 laser techniques. Furthermore, the measurement method described also provides an in situ method of measuring the laser cavity loss.
Superconducting Properties of Nb3 (Al, Ge) Prepared by Vacuum Vapor Deposition of the Elements
Authors: Hammond R. H. , Ralls K. M. , Meyer C. H. , Snowden D. P. , Kelly G. M. , Pereue J. H.
Published: February 2004

Properties of films of the niobium-aluminum-germanium system prepared by simultaneous deposition of the individual constituents are presented. The optimum superconducting material obtained contains a large fraction of the desired A-15 compound and has an as-deposited critical temperature of over 17.8 K. Appropriate annealing increases Tc to above 19 K and probably close to values attained in bulk material. Current capacity is above 105 A/cm2 at 50 kOe. Limitations in sample properties have been caused by the substrate material, either Hastelloy B or niobium. Preliminary indications show that the use of tungsten-coated Hastelloy B will avoid these limitations.
Resonant Motion of Domain Walls in Yttrium Gadolinium Iron Garnets
Authors: Vella-Coleiro G. P. , Smith D. H. , Van Uitert L. G.
Published: February 2004

The radio frequency (rf) susceptibility of a series of yttrium gadolinium iron garnets was investigated in the frequency range 40–160 MHz. Resonant behavior was observed for most compositions, and the effective mass of the domain walls and the Landau-Lifshitz damping parameter were determined. The damping parameter was found to be approximately the same for the yttrium and gadolunium ions with the value λ ≃ 1.6×107 rad sec−1.
Electron Microprobe Analysis of Ion-Implanted CdS
Authors: Govind P. K. , Fraikor F. J.
Published: February 2004

An electron beam microprobe was utilized to study the depth distribution of ion-implanted bismuth in CdS. The results, shown as a plot of relative Bi concentration vs depth, indicate that the bismuth concentration profile is of the type exp(−x/λ). Furthermore, the microprobe data reveal substantially deeper ion penetrations than predicted by LSS range theory.
Sputtering of Iron by Fast Neutrons
Authors: Baer T. S. , Anno J. N.
Published: February 2004

The atomic sputtering by fast neutrons incident upon a thin iron foil target was determined by measuring the activity of radioactive iron atoms collected during continuous exposure of the target to a fast neutron flux of 4.0×1012 neutrons/cm2 sec. The sputtering ratio (atoms of iron sputtered per fast neutron crossing the surface of the target) was found to be (5.7±0.8)×10−3, assuming an isotropic neutron flux.
Multiphonon, Raman, and Two-Photon Excitation of Rare-Earth Ions in Crystals: Photon and Phonon Noise in 10-μ Quantum Counters
Authors: Fong Francis K. , Miller Marvin M.
Published: February 2004

Noise arising from strong laser pumping and 77-K internal phonon noise upconversion in the proposed supposedly noiseless 10-μ quantum counters using rare-earth-doped crystals is described. The discussions are specialized to the crystals states of the Eu3+ ion. It is shown that at the pump power (∼50 kW cm−2) necessary for background-limited 10-μ quantum counter upconversion detection at 77 K, all the three major processes of noise generation discussed are insignificant compared to the background thermal (300 K) radiation considered previously in arriving at realistic theoretical quantum efficiencies of the proposed 10-μ quantum counters.
Elastic Moduli of Cobalt-Iron Single Crystals
Authors: McSkimin H. J. , Andreatch P. , Tisone T. C.
Published: February 2004

Face-centered-cubic (fcc) Co–Fe alloys in the vicinity of 10 at. % Fe form the basis for an important class of semihard magnetic alloys used for memory and switching applications. The elastic properties are important in determining the magnitude of the internal and/or applied stresses resulting from device operation and processing. The work described was undertaken to evaluate the compositional dependence of the elastic stiffness moduli in the fcc range of stability. The elastic stiffness moduli for single crystals of 6, 12, and 14 at. % Fe were measured by an ultrasonic method previously described (Ref. 3). The results for the 6 at. % Fe alloy at 25°C were c11=2.340, c12=1.589, and c44=1.259×1012 dyn/cm2. The stiffness moduli were found to vary only slightly with composition.
Adsorption Kinetics of Cs on GaAs
Authors: Smith D. L. , Huchital D. A.
Published: February 2004

Cesium adsorption on vacuum-cleaved p-GaAs (110) was monitored at 10−10 Torr concurrently by photoemission and x-ray photoelectron spectroscopy (ESCA). Cesium was supplied at R = 6.9×1012 atoms/cm2 sec by a calibrated valved room-temperature Knudsen effusion cell. ESCA results showed that the first monolayer of Cs contains N = 6.2×1014 atoms/cm2, that it adsorbs irreversibly, and that fractional coverage is θ = 1−exp(− Rt/N). Maximum photoyield (hence minimum work function) corresponds to θ = 1. The second layer of Cs decreases photoyield, but is desorbed with a time constant of less than 1 min.
Investigation of an rf Plasma with Symmetrical and Asymmetrical Electrostatic Probes
Authors: Gagné R. R. J. , Cantin A.
Published: February 2004

A capacitively coupled plasma facility and the techniques implemented to solve problems associated with the use of electrostatic probes in rf discharges are described. Supporting experimental results are also presented. A new technique devised to minimize the rf voltage at the plasma-probe junction is explained, and a floating optically coupled capacitive probe arrangement, for accurate measurement of this voltage, is discussed. Description is made of a feedback network which is used to stabilize rf potentials and plasma parameters over periods of several hours. The calibration of a focused X-band microwave interferometer indicates that the presence of the Pyrex plasma container has no noticeable effect on the electron density deduced from phase-shift measurements. At a pressure of 0.7 Torr in argon, space-resolved electron temperatures, deduced from symmetrical and asymmetrical double-probe I-V characteristics, indicate that the electron temperature is radially constant in the plasma column, and has a value which is 25% higher than that predicted by using the von Engel and Steenbeck theory for a similar positive column. The radially integrated charge density profile, deduced from the probe ion current using the collisionless Laframboise theory, agrees within 15% with that estimated from measurements made with a microwave interferometer. Collision-dominated probe theories are also considered and found to be less applicable.
Pulse Repsonse of the Conducting Channel in Thermally Switching Glass Films
Authors: Schuöcker D. , Sabathy W. , Langer H.
Published: February 2004

Investigations of the pulse behavior of relatively thick chalcogenide glass films in the on state showed that a time constant of around 40 μsec is involved in the pulse response. This time constant could be identified as the time constant of heating in the sample by a theoretical analysis based on the model of thermal breakdown for relatively thick films. The difference of pulse behavior of thin films (1 μ) is discussed and the possibility of distinguishing between electronic and thermal switching by use of the pulse behavior is shown.
Propagation of a Nonspherical Thermal Wave
Authors: Pomraning G. C.
Published: February 2004

A radiative diffusion problem which gives rise to a wave front with two-dimensional structure is considered. Particular emphasis is placed on the description of the wave front resulting from a point source of energy liberated instantaneously at the interface between two homogeneous half-spaces. By a combination of similarity and moments methods the problem is reduced to a second-order nonlinear ordinary differential equation describing the position of the wave front. This equation is solved analytically in the almost spherical and highly nonspherical limits. Numerical results for the partition of energy between the two half-spaces are given.
Method of Isentropically Compressing Materials to Several Megabars
Authors: Hawke R. S. , Duerre D. E. , Huebel J. G. , Klapper H. , Steinberg D. J. , Keeler R. N.
Published: February 2004

This paper describes a new method of compressing materials up to pressures of several megabars. A high-intensity magnetic field, obtained by magnetic flux compression, is used to compress a sample contained in a metallic tube. The compression of the sample is slow enough to avoid the generation of shock waves which allows the process to be isentropic. This paper describes the apparatus and several experiments with Lucite samples. Evidence that Lucite was isentropically compressed to a specific volume of about 0.25 is included. The pressure reached is estimated to be ∼4 Mbar.
Microwave Loss in Ultralow-Linewidth Substituted Garnets
Authors: Patton Carl E. , Van Hook H.J.
Published: February 2004

Linewidth measurements from 77 to 300°K and room-temperature off-resonance effective linewidth data at 9 GHz show that the microwave losses in ultralow-loss Ca–V–In substituted YIG and Ca–Ge–In–YIG are completely resolvable in terms of known processes and that only a small part of the loss is due to anisotropy broadening. For the lowest linewidth of 2 Oe observed to date (Ca–Ge–In–YIG), about 0.5 Oe is due to rare-earth impurities, 0.9 Oe is from porosity broadening, and 0.2 Oe is from anisotropy. The remaining 0.4 Oe contribution is comparable to expected ``intrinsic'' single-crystal linewidths.
Radiation Hardening of Thermal Oxides on Silicon by Displacement Damage
Authors: Donovan R. P. , Simons M.
Published: February 2004

High-energy implantation of various ions into thermal oxides on silicon renders these oxides less sensitive to charge buildup when subsequently exposed to ionizing radiation. The reduced sensitivity is primarily a reduction in bias dependence and is attributed to ion-induced displacement damage in the oxide.
Elastic Moduli of Diamond as a Function of Pressure and Temperature
Authors: McSkimin H. J. , Andreatch P.
Published: February 2004

Values of wave velocities and elastic moduli at 25°C were measured for hydrostatic pressures to 20 000 psi (excess over 1 atm). Variations of velocities and moduli at 1 atm were obtained over a temperature range of +50°C to −195.8°C. Adiabatic stiffness moduli (units of 1012 dyn/cm2), their pressure derivatives, and their temperature coefficients (units of 10−5/C), are shown below for 1 atm and 25°C. ModulusValuePressure derivativesTemperature coefficientc1110.79±0.055.98±0.7−1.37±0.2c12 1.24±0.053.06±0.7−5.70±1.5c44 5.78±0.022.98±0.3−1.25±0.1
Dislocation Mobility in Aluminum
Authors: Parameswaran V. R. , Urabe N. , Weertman J.
Published: February 2004

Dislocation velocities in aluminum were measured, using the etch-pit technique of Gilman and Johnston, as a function of stress in the temperature region between liquid-helium temperature and room temperature. The dislocation-damping constant B was calculated at various temperatures from the linear portion of the velocity-vs-stress curve. The value of B decreases with decreasing temperature in the region from room temperature to 30°K. This result agrees with theoretical predictions of the dislocation damping produced by phonon-dislocation interactions. Below 30°K the damping constant B increases with decreasing temperature. This latter result disagrees with the accepted theoretical predictions of dislocation damping produced by electron-dislocation interactions.