bluuebunny/crossref_metadata_2025 huggingface dataset:
Theory of noise investigations on conductors with the four-probe method
Authors: Kleinpenning T. G. M.
Published: February 2003

A general relation is derived for the spectral noise density of the ac open-circuit voltage fluctuations between two point electrodes in a homogeneous conductor with conductivity fluctuations. The conductor is assumed to extend to infinity and a noiseless direct current flows through the conductor via two current electrodes. Besides, the spectral noise density between two point electrodes is calculated for a number of conductors with specified dimensions and specified current electrodes. These theoretical results are compared with experimental results.
The effect of adsorbed gases on the surface conductivity of quartz
Authors: Martin A. D. , McLean K. J.
Published: February 2003

The surface conductivity of fused quartz has been examined. An exponential conductivity dependence upon vapor pressure is found for the highly polar water vapor and ammonia gases, whereas the nonpolar gas of carbon dioxide has no measurable effect. The results are in agreement with an electronic conduction model based on the lowering of the charge carrier activation energy by the presence of an adsorbed polar layer.
Charge centroid in MNOS devices
Authors: Lehovec K. , Fedotowsky A.
Published: February 2003

A concise theoretical expression based on pronounced detrapping is derived for the charge-vs-centroid relationship of an MNOS structure subjected to constant current pulses which include the considerable injected charge levels encountered in practical memory device operation. Good agreement is found with available experimental charge-vs-centroid data obtained at various temperatures, thus enabling determination of Frenkel-Poole coefficient and trap depth. Values so obtained agree with those for bulk silicon nitride. An analytical expression valid for any degree of detrapping is derived for change of centroid with charge in the limit of small injected charge levels. Implications of constant voltage versus constant current charging are discussed.
Flux penetration into doubly-connected loops containing two Josephson junctions
Authors: Blackburn James A. , Smith H. J. T.
Published: February 2003

The properties of a doubly-connected pair of superconducting loops in the presence of an applied magnetic field have been examined. Two Josephson junctions are placed in the rings and serve as channels through which flux quanta may ’’bubble’’. Computer simulations show that three modes are associated with magnetic field penetration into the loop interiors.
Photoinduced effect on the permeability of some mixed garnets
Authors: Hisatake Keizo
Published: February 2003

A photoinduced decrease in permeability at 77 K was investigated for the polycrystalline mixed garnets of (Y1−xRx)3Fe5O12 with 0⩽x⩽1 and R=Eu, Yb, Ho, Tm, Gd, Tb, and Er. The change of the effect is interpreted as simply due to the change in the magnetocrystalline anisotropy of the host material.
Strain effects on magnetic anisotropies in (110) Ni films
Authors: Kuriki Shinya
Published: February 2003

Magnetic anisotropies have been studied for evaporated (110) Ni films before and after removing the films from substrates. The uniaxial anisotropy Ku observed in as-evaporated films decreases drastically in magnitude upon removal from the substrate. The magnetocrystalline anisotropies K1 and K2 have high negative values. A magnetoelastic interaction, assuming an anisotropic planar strain, is applied to Ku and to the perpendicular anisotropy K⊥, from which the strain values in the film are calculated. The calculated strains agree with the strains measured with an x-ray diffractometer in as-evaporated films.
Orbits and fields in the helical wiggler
Authors: Blewett John P. , Chasman R.
Published: February 2003

The ’’helical wiggler’’ is a device in which relativistic electrons pass through a transverse magnetic field whose direction revolves with distance along the beam axis. In this paper we discuss the electron orbits in this device. The field patterns and necessary current distributions are established. Finally, the question is treated as to whether this device can be incorporated into a storage ring without destroying the circulating beam. It is concluded that there is reason to expect satisfactory performance from helical wigglers in storage rings.
An efficient organic crystal for nonlinear optics: methyl- (2,4-dinitrophenyl) -aminopropanoate
Authors: Oudar J. L. , Hierle R.
Published: February 2003

The first member of a new family of materials for nonlinear optics, methyl- (2,4-dinitrophenyl) -amino-2 propanoate (MAP), has been prepared and its linear and nonlinear optical properties have been investigated. High nonlinear coefficients result from the favorable electronic properties of the MAP molecule, as well as its chirality, which ensures a noncentrosymmetrical crystal structure. This material is phase matchable over its entire transparency range, and its figure of merit d2/n3 for parametric interactions is 15 times larger than LiNbO3. The optical damage threshold is higher than 1 GW/cm2 for 10−8-sec pulses at 1.06 μm. The 30% second-harmonic conversion efficiency has been observed in a 1-mm-thick crystal. In addition, we present an extension of the analysis of Maker fringes to monoclinic crystals of point group 2.
Transition moments and integrated intensities of HCN(ν1+ν3) and DCN(ν1+ν3) combination bands
Authors: Finzi Jack , Wang John H. S. , Mastrup F. N.
Published: February 2003

The absolute infrared integrated intensities of HCN(ν1+ν3) and DCN(ν1+ν3) summation bands have been measured using the pressure broadening technique. From the measured integrated intensities, transition moments were determined. The values obtained were 1.1±0.1 cm−2 atm−1 and 0.9±0.1 cm−2 atm−1 at 298 °K, respectively, for the HCN and DCN intensities and 1.8×10−41 erg cm3 and 1.9×10−41 erg cm3 for the square of the transition moments. The values reported are 50 times smaller than the corresponding transition moment for CO2 at 10.6 μm, hence it will be considerably more difficult for the HCN/DCN laser to attain threshold.
A study of the lattice imperfections in Li-diffused GaAs by transmission electron microscopy
Authors: Norris Brian , Narayanan G. H.
Published: February 2003

The lattice imperfections in GaAs single crystals introduced as a result of the in-diffusion of lithium at high temperatures were investigated by using transmission electron microscopy. The effects of diffusion temperature, time, postdiffusion annealing treatments, and the presence of other impurities (primarily Zn at concentration levels of 1×1019 cm−3) in the host crystal, on the defect structure have been determined. The results indicate that when Li-saturated GaAs single crystals are cooled to room temperature following high-temperature diffusion, precipitation of Li occurs readily in the form of tetrahedral particles, the size and density of which decrease with decreases in diffusion temperature. Postdiffusion annealing at temperatures of 600 °C and above caused the formation of additional precipitates, vacancy-type prismatic dislocation loops, and a few extrinsic stacking faults. Diffusion of Li into originally Zn-doped GaAs ([Zn]∼1×1019 cm−3) at 700 °C, on the other hand, did not lead to the formation of Li precipitates; however, a moderately high density of small vacancy-type prismatic loops was observed in the microstructure. On increasing the diffusion temperature to 850 °C the substructure revealed the presence of stacking faults and a small density of precipitates in addition to a number of large vacancy-type prismatic loops. The size density and distribution of these defects were found to be dependent on the diffusion time at 850 °C. The origins of the observed lattice defects have been discussed in the light of the previous localized-vibrational-mode (LVM) infrared spectroscopy measurements on materials with identical chemical composition and thermal history as in the present study. A definite correlation between the microstructural features and defect structure as determined by infrared absorption measurements was found to exist.
Shock loading and unloading in bismuth
Authors: Asay J. R.
Published: February 2003

Shock loading and unloading was performed on bismuth specimens for initial temperatures of 293 and 473 K. Wave velocity profiles transmitted through the specimen were determined with an interferometer system. The maximum pressure achieved at room temperature was sufficient to induce a polymorphic transition to the high-pressure solid phase of bismuth. At elevated temperatures, the pressures obtained in some experiments caused partial melting during shock compression. The stress-volume states achieved during compression at 473 K agree closely with the calculated equilibrium hydrostat, and therefore give direct evidence that melting occurs. The measured initial unloading wave velocities from the shocked state show no major change at the onset of the polymorphic transition. However, a large decrease in the initial unloading wave velocity occurs for partial melting. The volume states achieved during unloading from states of partial melt indicate that refreezing back to the initial solid phase does occur, although there appears to be substantial rate effects associated with refreezing.
Ion-surface interactions in plasma etching
Authors: Coburn J. W. , Winters H. F. , Chuang T. J.
Published: February 2003

The surface chemistry and the etching behavior of silicon and oxidized silicon bombarded with a CF3+ ion beam (50–4000 eV) have been studied using Auger electron spectroscopy, and a quartz-crystal microbalance. The conclusions of this study are as follows: (a) the etch rate of Si caused by CF3+ ion bombardment can be accounted for by physical sputtering; (b) the deposition and removal of carbon at the etched surface may be one of the most important phenomena affecting the operation of plasma-etching systems; and (c) there is reason to believe that ion bombardment of the etched surface enhances the reaction rate of the neutral etching species which are most probably fluorine atoms and CF3 radicals.
Low-work-function surfaces produced by cesium carbonate decomposition
Authors: Briere T. R. , Sommer A. H.
Published: February 2003

Cesium carbonate (Cs2CO3) was heated to the decomposition temperature of approximately 600 °C. The nonvolatile decomposition products were condensed on a nickel substrate while the carbon dioxide was removed by pumping. The deposited material is characterized by an effective work function of between 1.05 and 1.15 eV at 450 K and by photoemission in the visible and near-infrared region of the spectrum. It is suggested that the deposited material consists of Cs2O, possibly Cs2O2, and adsorbed cesium. Silver, evaporated from a heated silver bead, produced the typical photoemissive and thermionic properties of a silver-oxygen-cesium (S-1) photocathode. The material may be of interest for thermionic energy converters and for the formation of silver-oxygen-cesium photocathodes.
The effect of x-ray linewidth on the defocus correction in the Schulz reflection technique for texture measurement
Authors: Holt R. A. , Winegar J. E.
Published: February 2003

The loss of measured intensity with increasing specimen inclination in the Schulz reflection technique for texture determination is due to the increase in the width of the diffracted beam profile with increasing inclination. This increase in width is relatively greater for a sharp rather than broad profile. Since the metallurgical condition affects the width of the profile, it also affects the defocus correction. To make an accurate texture measurement one must determine the defocus correction using a specimen of random texture which has a diffracted beamwidth similar to that of the material of interest.
An x-ray diffraction study on the microstructures of cold-worked fcc Cu-Ni-Zn alloys
Authors: Halder S. K. , De M. , Sen Gupta S. P.
Published: February 2003

The state of cold work in the ternary Cu-Ni-Zn alloy system (fcc) has been investigated by x-ray diffraction from a detailed analysis of the peak shift, peak asymmetry, and peak broadening. Cold working in the system produces an appreciable amount of intrinsic stacking faults which play the most important role in peak broadening as well as in shifting the positions of the diffraction profiles. For the observed peak shift, the other contributing factors (namely, lattice-parameter change and long-range residual stresses) are relatively small. Asymmetry in the profiles is due to the presence of a very small amount of extrinsic stacking fault, and deformation twins have been found to be totally absent. The estimations of domain size, rms strains, and the dislocation density in the alloys have been made from the peak-broadening analysis, and the stacking-fault energy for pure copper has also been evaluated and has been found to be comparable. The presence of the transitional solute Ni from 1 to 15 wt% has a very small influence in altering the microstructural parameters, which, however, vary gradually with the increase of zinc concentration from 24 to 34 wt% uninfluenced by the nickel content in a manner similar to that observed earlier for the binary Cu-Zn system.
Quantitative study of the charge transfer in chemisorption; oxygen chemisorption on ZnO
Authors: Lagowski J. , Sproles E. S. , Gatos H. C.
Published: February 2003

A new experimental approach is presented for studying the charge-transfer process involved in the chemisorption on polar semiconductors. This approach utilizes the surface piezoelectric effect, contact potential difference measurements, and surface photovoltage spectroscopy. From the study of oxygen adsorption on ZnO it was found that the rate of electron transfer varies exponentially with the surface barrier height and is proportional to the oxygen pressure (from 10−3 to 20 Torr). Furthermore, it was found that the charge transfer is characterized by a thermal activation energy of about 0.72 eV. At room temperature this activation energy constitutes the most significant rate-limiting factor and is largely responsible for the extremely slow rate of chemisorption. A model for chemisorption was developed in which the thermal activation is treated as an intermediate nonelectronic step involving metastable activated surface states. Upon capturing electrons from the bulk these states become stable surface states. A rate equation was derived through which the capture cross section of the activated surface states was calculated to be 10−16 cm2, in contrast to the unrealistically small value of 10−29 to 10−22 cm2 obtained with exclusively electronic models.
GaAs double-heterostructure photodetectors
Authors: Merz J. L. , Logan R. A. , McBride P. L. , Sergent A. M.
Published: February 2003

AlxGa1−xAs-GaAs structures grown by LPE have been investigated for optical power conversion at 8500 Å. Comparison is made between single- and double-heterostructure configurations, both in theory and experiment; relative merits of each structure are discussed. Good I-V characteristics have been realized for these devices, with series resistance as low as 0.16 Ω. For small-area (5–6 mm2) devices operating at a few mW power, fill factors between 0.75 and 0.81 and internal quantum efficiencies exceeding 90% have been achieved for each structure investigated. Power conversion efficiencies as high as 46% were obtained at 8500 Å, after correcting for reflection losses; this approaches the theoretical limit for space-charge-limited devices. The devices were also evaluated as solar batteries, with efficiencies of 13–14% reported, corresponding to internal efficiencies as high as 18%.
Optical detection of atmospheric 238U decay products
Authors: Solomon Jerry E.
Published: February 2003

Current and proposed programs involving aerial survey of uranium resources require remote sensing of 238U decay products with high sensitivity. In this paper, we investigate the feasibility of a lidar remote sensing system in the detection of atmospheric 238U decay products. We find that the most likely target species are lead and bismuth. The effective scattering cross sections for Pb and Bi are calculated to be 1.09×10−15 and 3.54×10−17 cm2, respectively, for the relevant optical transitions. System operating characteristics are calculated and displayed in graphical form. We find that it should be possible to detect concentration levels of atomic lead as small as 5–10 atoms cm−3 at a range of 200 m, under rather modest transmitter and receiver requirements.
Power deposition in He from the volumetric 3He(n,p)3H reaction
Authors: De Young R. J. , Winters P. A.
Published: February 2003

Calculations are presented in this paper which show the amount of power that can be expected to be deposited in 3He for typical direct nuclear-pumped (DNP) lasers presently in use. The calculations were performed taking into consideration the cylindrical geometry of the system, the depletion of the thermal flux across the tube cross section, and the energy loss of the protons to the cell walls. If a laser efficiency of 1% is assumed, the results indicate a steady-state laser output of 12.5 kW from a volume of 152.6 cm3 or 82 W/cm3 can be achieved.
Enhancement of the rate of charge-exchange collisions in a He-Cd discharge
Authors: Chinen Seitetsu , Hattori Shuzo
Published: February 2003

Spontaneous emission from the 5337-Å and 5378-Å transitions in Cd(II) was studied in a dc discharge whose positive column was exposed to microwave power. The intensities obtained were at least one and one-half times higher than those expected from input increasing with microwave power superposed. This enhancement is explained on the assumption that the electron temperature also increases with the microwave power.
Measurement of sonic velocity in liquid Refrigerant 12
Authors: Winters W. S. , Merte H.
Published: February 2003

The sonic velocity in subcooled liquid Refrigerant 12 (CCl2F2) was measured at 26.7 °C using an apparatus designed to investigate transients associated with pipe blowdown. The mean value for sonic velocity obtained from 65 measurements was 502 m/s. Sonic velocity obtained from other references are compared to the present measurements using the law of corresponding states.
The influence of dopants on the hardening of GaAs
Authors: Weiss B. L. , Hartnagel H. L.
Published: February 2003

Results are presented here which show that Cr-doped GaAs is harder (i.e., more resistant to damage) than Te-doped GaAs and, subsequently, Zn-doped GaAs.
Compressions of Si, MgO, and ZrSiO4 to 8 GPa as measured with a WC-anvil x-ray apparatus and epoxy pressure medium
Authors: Singh A. K. , Kennedy G. C.
Published: February 2003

The compressions of silicon, magnesium oxide, and zircon have been measured to 8 GPa with a tungsten-carbide opposed-anvil x-ray apparatus using a boron-epoxy gasket and epoxy as a pressure-transmitting medium. For silicon and magnesium oxide, the bulk modulus and its pressure derivative were obtained by fitting a second-degree polynominal to the x-ray data. For zircon, the bulk modulus was determined by fitting an equation of the form (ΔV/V0) = −(P/B0). The values of the bulk modulus and its pressure derivative are B0=99.4±8 GPa, B′0=3.2±1 for silicon; B0=166±10 GPa, B′0=2.5±1 for magnesium oxide; B0=222±20 GPa for zircon. In all the cases, the present values of B0 are in good agreement with those obtained from ultrasonic measurements. On the basis of these results it is suggested that the use of epoxy as a pressure-transmitting medium can greatly reduce the uniaxial stress component and improve the sample-pressure distribution in the study of materials possessing large shear strength.
Isothermal compression and bcc→hcp phase transition of iron-cobalt alloys up to 300 kbar at room temperature
Authors: Papantonis Dimosthenis , Bassett William A.
Published: February 2003

Iron-cobalt alloys with 10, 20, and 40 wt% cobalt have been studied at room temperature under high pressure by means of x-ray diffraction techniques, employing the diamond-anvil pressure cell. The crystallographic x-ray data for the three alloys at zero pressure were obtained using the standard Debye-Scherrer x-ray diffraction technique. The volume-pressure relationship was established and, using the Birch-Murnaghan equation of state, the compressibility β for the above alloys was found to remain constant or increase slightly with increasing cobalt content. This is consistent with the electron dilution theory. The bcc→hcp phase transformation in each alloy was seen visually under the microscope in reflected light and it was found to take place when the pressure increased to 163±5, 195±6, and 290±10 kbar respectively, for the 10, 20, and 40 wt% Fe-Co alloys. The volume change at the transition was found to decrease slightly with increasing cobalt content and the crystallographic axis ratio c/a of the hcp phase of the alloys was found to increase with increasing cobalt content.
Analysis of marker motion in thin-film silicide formation
Authors: Tu K. N.
Published: February 2003

A simple analysis of marker motion in the growth of a single compound layer is given. It has been applied to the growth of Ni2Si silicide between Ni thin films and Si wafers. In the silicide Ni was found to be the dominant diffusing species by the use of implanted Xe markers. The intrinsic diffusivities of Ni and Si in Ni2Si at 325 °C have been determined; DNi=1.7×10−14 cm2/sec and DSi=0.6×10−14 cm2/sec. These are the first measurements of intrinsic diffusivities in thin-film silicides.
Ion-beam-induced atomic mixing
Authors: Haff P. K. , Switkowski Z. E.
Published: February 2003

Calculations based on the diffusion model are presented of atomic mixing by ion bombardment. This mixing is assumed to have its basis, as does sputtering, in the collision cascades generated by the primary beam. Sharp interfaces within a target are seen to be smoothed by ion bombardment. Mixing may place fundamental limits on the resolution of ion microprobes.
Edge localized vibration modes on a rectangular ridge
Authors: Maradudin A. A. , Subbaswamy K. R.
Published: February 2003

We present a theory of elastic waves which propagate along a semi-infinite rectangular ridge made up of a nonpiezoelectric elastic medium, and which are localized at the top and sides of the ridge. Stress-free boundary conditions are incorporated into the calculation by the assumption of position-dependent elastic moduli. The equations of motion of the ridge are solved by expanding each displacement component in a double series, each term of which is a product of a Laguerre function and an orthogonal function specially constructed to be exponentially localized at each end of a finite interval. Dispersion curves for the speeds of these ridge waves, as functions of qd are presented, where q is the wave vector describing their propagation along the ridge and d is the half-width of the ridge. In the limit of large qd, two of these modes approach symmetric and antisymmetric linear combinations of the displacement fields associated with an edge mode localized at each of the two edges of the wedge.
Thermally stimulated currents and dielectric study in amorphous selenium
Authors: Guillaud G. , Fornazero J. , Maitrot M. , Chatain D. , Lacabanne C.
Published: February 2003

Two relaxation modes have been isolated by the thermally-stimulated currents (TSC) technique in vitreous selenium. At about 0 °C, a field-independent TSC peak is observed. It may be explained by the field-independent mobility which has been measured in the same temperature range. This relaxation is thermally actived with the same activation energy as the ac conduction found at low frequency (F<1 kHz) from ac measurements in the same samples. At about −100 °C, a field-dependent TSC peak gives a conductivity varying as ω which agrees fairly well with ac measurements in the same samples above 10 kHz. The field dependency of this TSC peak is well described by the continuous distribution of thermally activated hole-drift mobility which has been measured in the same temperature range, using a time-of-flight technique.
Impurity conduction in transmutation-doped germanium
Authors: Thomas H. C. , Covington Billy
Published: February 2003

Measurements of resistivity in transmutation-doped germanium have been made in the temperature range 1.5–4.2 K during the decay of the electrically active products, thus providing experimental values for the resistivity over an essentially continuously varying range of impurity concentration and compensation ratio. From these values an expression for resistivity as a function of impurity concentration, compensation ratio, activation energy, and temperature has been developed which adequately describes the experimental results of this work as well as those of others.
On generation recombination and trapping kinetics in theories of small-signal electrical response
Authors: Franceschetti Donald R.
Published: February 2003

It is shown that small-signal electrical response results obtained for generation-recombination or trapping rate laws appropriate to a neutral-center dissociation-association mechanism encompasses the electrical response to be expected for other frequently encountered generation-recombination or trapping rate laws under a wide range of conditions. The rate constants appearing in such kinetic expressions are related to a number of differently defined charge-carrier lifetimes employed in the semiconductor and electrochemical literature. The ranges of charge-carrier lifetime characteristic of semiconductors, defect solid ionic conductors, and electrolyte solutions are briefly discussed.
Comment on the residual rf surface resistance of superconductors
Authors: Scharnberg K.
Published: February 2003

The effect of acoustic generation on the residual rf surface resistance Rs of superconductors has recently been discussed with the use of nonlocal theory. The results obtained are higher than the lowest values of Rs found experimentally. Taking proper account of the nonlocal collision drag force reduces the theoretical values well below the experimental results.
Magnetocrystalline anisotropy in Y2Co17, Dy2Co17, and Y2xDy2(1−x)Co17 (x=1/3, 2/3)
Authors: Miller A. E. , D’Silva T. , Shanley J.
Published: February 2003

The anisotropy constant K1 in the intermetallic compounds Y2Co17, Dy2Co17, and two pseudobinaries Y2xDy2(1−x)Co17 (x=1/3,2/3) is determined over the temperature range 77.4–383 °K. This constant is obtained by fitting the measured magnetization curves to the equation for magnetization along the hard axis derived by minimizing the sum of the magnetocrystalline anisotropy energy and the magnetic potential energy. All of the four compounds have an easy basal plane over the entire temperature range. The two pseudobinaries Y2/3Dy4/3Co17 and Y4/3Dy2/3Co17 develop basal-plane anisotropy at low temperatures. The contribution of the Dy sublattice to the anisotropy constant and the saturation magnetization is treated for single-ion behavior.
Spontaneous polarization and pyroelectric effect in KNbO3
Authors: Günter P.
Published: February 2003

The spontaneous polarization Ps of single-domain orthorhombic KNbO3 has been measured with the Camlibel pulse method. A new value of Ps=0.41±0.02 C/m2, which is about 30% larger than the result obtained in hysteresis measurements, has been observed. The temperature dependence of the pyroelectric coeffficient has been measured using a direct method. The temperature dependence of the spontaneous polarization calculated from these measurements is compared with the results of a Devonshire free-energy expansion.
Thermal-depolarization-current study of composites of epoxy resin containing mica flakes
Authors: Tanaka T. , Hayashi S. , Shibayama K.
Published: February 2003

Thermal depolarization current (TDC) has been measured to study the effect of a polymer-filler interface on the behavior of carriers in composites of epoxy resin containing mica flakes. Three peaks near 152 (αC), 106 (βC), and 84 °C (γC) are observed in the composites. The origins of these TDC peaks were investigated. The βC peak can be attributed to dipole orientation polarization associated with the glass transition of resin matrix. The αC and γC peaks depend on the fraction of mica flakes. It is assumed that the γC peak arises from dipole polarization associated with molecular motion in boundary regions between the resin matrix and mica flakes. The behavior of the αC peak is different from that of TDC due to dipole polarization. A large dielectric dispersion corresponding to the αC peak is observed near 60 Hz at 183 °C. The large dielectric increment can be explained by Maxwell-type interfacial polarization.
Minority-carrier lifetime measurements of efficient GaAlAs p-n heterojunctions
Authors: Nishizawa J. , Suto K. , Teshima T.
Published: February 2003

High-efficiency Ga1−xAlxAs p-n heterojunctions have been fabricated by the temperature-difference method (ηRT, 1–3% at 6650 A), and the deep levels which govern the efficiency and the lifetime have been studied by I-V, C-V, photocapacitance, impedance, and electroluminescence measurements. The lifetime obtained by the impedance measurement and the deep-level distribution obtained by the C-V measurement have a correlation. The lifetime for efficient diodes is as low as 1 μs at 80 K. The temperature dependence of the lifetime was also measured. Photocapacitance spectra show a threshold photon energy of 0.65 eV. Arsenic vacancies are proposed for these deep levels.
Fluorescence from the TbCl3-AlCl3 vapor complex system: A potential new gas-phase laser
Authors: Hessler Jan P. , Wagner F. , Williams C. W. , Carnall W. T.
Published: February 2003

We report the first fluorescence spectrum of a lanthanide chloride–aluminum chloride vapor complex and discuss the temperature dependence of the fluorescence lifetime.
Circuit-theoretic treatment for anisotropic elastic waveguides and its application to the design of nonreciprocal thin-film acoustic devices using magnetoelastic material YIG
Authors: Sugimoto M. , Makimoto T.
Published: February 2003

A certain class of anisotropic elastic waveguides are treated from the well-established circuit-theoretic viewpoint. The terminal behavior of propagating waves is represented by a kind of transmission matrix, which is called a mode transfer matrix. Relations between this matrix and the relevant waveguide are examined in some detail with special attention paid to the nonreciprocity. The results are applied to the composition of nonreciprocal thin-film acoustic devices. Using a single-crystal YIG, six fundamental systems are defined as canonical elements in the circuit synthesis, and the mode transfer matrices are obtained under the so-called two-mode approximation. Then, the problem of the circuit design can be treated as a simple 2×2 matrix operation as in the case of the conventional transmission-line circuit synthesis. By cascading selected canonical elements in an appropriate order, the desired nonreciprocal devices can be composed. As examples, a gyrator, a unidirectional mode converter, an isolator, and a circulator are designed.
Orientation effects in the friction of a hard ellipsoid sliding on rubber
Authors: Trachman E. G. , Williams R. , Sheng Ping
Published: February 2003

The friction of a hard object sliding on lubricated rubber is believed to be due mainly to mechanical hysteresis losses in the rubber. We show that, if the object is an ellipsoid, the frictional force should depend on the direction of motion relative to the principal axes. To test this idea, we have done experiments with a diamond stylus, having an ellipsoidal shape, sliding on rubber. As predicted, the frictional drag force is smaller for motion parallel to the long axis than it is for motion parallel to the short axis. For cases where there may be more than a single mechanism that contributes to the friction, this effect can be used to determine the fraction due to hysteresis losses.
Filamentation of a laser beam in a collisional plasma
Authors: Tripathi V. K. , Pitale L. A.
Published: February 2003

In this paper we have studied the filamentation of a laser beam in a collisional plasma when the nonlinearity in the dielectric constant arises due to nonuniform heating and redistribution of electrons. For small-scale fluctuations [r0< (mi/m)1/2 λm, where r0 is the beam radius, mi is the ion mass, m is the electron mass, and λm is the electron mean free path], the energy balance of electrons is mainly determined by thermal conduction. The growth rate of perturbation decreases rapidly with decreasing size of perturbation. For large-scale fluctuations, the energy balance is mainly through collisions and the growth rate decreases with the scale length of perturbation. Maximum growth rate is obtained for some optimum value of scale length. The growth rate also has a maximum for some optimum value of intensity of the main beam.
Experimental study of microwave generation and suppression in a non-neutral e-layer
Authors: Destler W. W. , Hudgings D. W. , Rhee M. J. , Kawasaki S. , Granatstein V. L.
Published: February 2003

Broadband microwave radiation in the X and KA bands was observed from a non-neutral electron layer prepared by passing a 2.5-MeV straight hollow electron beam through a narrow magnetic cusp. The mean beam radius shrank from 6 to 4.5 cm and the beam radial width increased from less than 1 to 2.7 cm in the postcusp e-layer drift region. When the beam was passed through a thin scattering foil prior to cusp transmission, the observed radiation decreased by two orders of magnitude and the beam width and radius remained at values consistent with single-particle calculations. Results are discussed in terms of the negative-mass instability.
Evidence for an ionic toroidal postdischarge environment in the atmospheric-pressure spark discharge
Authors: Coleman David M. , Walters J. P.
Published: February 2003

Experimental evidence is presented which indicates that for a magnesium cathode sampled unidirectionally in an atmospheric-pressure spark discharge, a previously observed toroidally distributed postdischarge environment may be composed substantially of ground-state ionic species.
Electron-temperature and spontaneous-magnetic-field measurements in a laser-irradiated free jet
Authors: Thompson H. M. , Daiber J. W.
Published: February 2003

The output of a Q-switched ruby laser irradiated a freely expanding jet of nitrogen gas. The laser optical axis was collinear with that of the jet. Gaseous breakdown occurred and the remaining energy within the laser pulse heated the plasma and drove forward-travelling waves through the orifice and into the plenum of the jet. The temperature of the electrons within the plasma was measured using relative transmittance of x rays through thin metal-foil spectrometers. The temperature varied as the square of the wave velocity from 60 to 160 eV. Measurements were also made of the spontaneous magnetic field generated in the vicinity of the plasma.
X-ray emission measurements from CO2-laser-created plasmas
Authors: Pépin H. , Grek B. , Rheault F. , Nagel D. J.
Published: February 2003

Results of the interaction of gigawatt nanosecond CO2 pulses with various solid targets are reported. The x-ray emission as a function of focusing is not critical within ± 1 mm of the on-target position. The x-ray intensity has an approximate power law dependance of 2.5 with laser energy for all elements. Densitometer analysis of sections of the x-ray pinhole pictures indicate nonuniformities in the plasma and localized hot spots. Line spectra taken with a Bragg crystal indicate temperatures of 200 eV for 4 J of incident energy. Continuum spectra taken with absorbants show characteristic nonthermal behavior, which may be related to parametric instabilities. The x-ray yield as a function of atomic number exhibits a series of peaks which are similar in position to the predictions of a coronal model.
Design of gravitational antennae for use at 3 m°K
Authors: Kos J. F. , Barton R. , Ramadan B.
Published: February 2003

The design, construction, and testing of a gravitational antenna for use at 3 m°K is discussed. New developments include the ’’weak spring ring’’ and ’’resonant ring’’ mounting systems, and a highly sensitive magnetic detector with remotely controlled continuously variable coupling to the antenna. For a prototype aluminum antenna a value of Q=4×106 was obtained at 4.2 °K and calculations predict a sensitivity sufficient to detect thermal oscillations at 3 m°K.
Accelerated aging and a uniform mode of degradation in (Al,Ga)As double-heterostructure lasers
Authors: Dixon R. W. , Hartman R. L.
Published: February 2003

An investigation of certain of the degradation and accelerated aging characteristics of currently fabricated (Al,Ga)As lasers is described. Our observations of the properties of devices aged at 70 °C, both as light-emitting diodes and as lasers, support two conclusions relevant to degradation: (1) The dominant degradation process in present devices is not lasing related in devices operated at power levels ⩽5 mW/face; (2) laser failure is strongly correlated with an approximately 50% reduction in the spontaneous light emission (at a given current below threshold) from these devices. These inferences are consistent with a spatially uniform mode of laser degradation not, for example, related to dark-line defects. They also imply that an LED mode of laser testing could be effective in identifying and eliminating presently dominating degradation mechanisms, i.e., those limiting continuously operating laser lifetimes to median values of about five years at room temperature. A different degradation mechanism which is operative at elevated temperatures even in unbiased devices has also been identified.
Hologram writing by the photorefractive effect
Authors: Moharam M. G. , Young L.
Published: February 2003

A treatment, using numerical methods, is given for the time development of holograms in lithium niobate and similar materials. The special features of the treatment are that both the feedback effect of the space-charge field on redistribution of electrons and the effect of the hologram in modifying the light pattern which is writing it are included, as is the effect of dark conductivity. The treatment is for uniform illumination of a crystal under constant applied voltage. The bulk photovoltaic effect is included through a ’’virtual field’’, an imaginary ’’built-in’’ field acting on photoreleased electrons. The transport lengths are assumed to be short. It is shown that all the reported forms of time development are reproduced by the model.
Nonradiative ’’large dark spots’’ in AlxGa1−xAs-GaAs heterostructures
Authors: Henry C. H. , Logan R. A.
Published: February 2003

A detailed study of ’’large dark spots’’ (LDS) in heterostructures is carried out. LDS are broad nonradiative regions extending up to several hundred microns away from the site of visible damage to the top surface of the sample. We show that only samples with p-n junctions exhibit LDS. In these samples, most of the photogenerated minority carriers diffuse across the junction. A forward bias develops across the (uncontacted) p-n junction, and photoluminescence arises from the forward junction current. In a damaged sample under uniform illumination, some of the forward current flows to the defect where the carriers recombine nonradiatively. Voltage drops produced by the current flowing (parallel to the junction) to the defect reduce the junction bias and luminescence near the defect. A theory is developed which accounts for the size and shape of the LDS.
GaAs1−yPy heterojunction lasers
Authors: Chin R. , Holonyak N. , Shichijo H. , Groves W. O. , Keune D. L. , Rossi J. A.
Published: February 2003

Data are presented showing that low-threshold (300 °K) visible-spectrum GaAs1−yPy and In1−xGaxP1−zAsz DH laser diodes can be grown on GaAs1−yPy substrates of composition at least as high as y=0.41, which corresponds to a short-wavelength limit of ∼6420 Å for the ternary and ∼6180 Å for the quaternary.
Sensitivity of hologram recording in photorefractive media
Authors: Blotekjaer Kjell
Published: February 2003

An expression is given for the sensitivity of hologram recording in photorefractive media, such as LiNbO3, in the presence of absorption. The energy density required to produce a given diffraction efficiency is given by a material constant multiplied by a function of efficiency and optical density of the crystal. The conditions for optimum efficiency are derived. Some published sensitivities are higher than predicted by theory.
Superconductivity of Nb5Ge3
Authors: Claeson T. , Ivarsson J. , Rasmussen S. E.
Published: February 2003

The superconducting transition temperature of Nb5Ge3 was determined to be 0.30 K. The transition width was 0.14 K. For large pieces of single crystals, wider transitions were registered.
Optical absorption coefficient of (Al0.42Ga0.58)As
Authors: Sommers H. S. , Lockwood H. F.
Published: February 2003

The measured room-temperature absorption coefficient of a high-purity layer of (Al0.42Ga0.58)As is quite similar to that of pure GaAs with energy displaced by 540 meV. It has a plateau in the high-absorption region of about 104 cm−1.
Structural and transport properties of CdS films grown on Si substrates
Authors: Livingstone F. M. , Duncan W. , Baird T.
Published: February 2003

Epitaxial films of CdS have been grown on thermally cleaned single-crystal Si substrates. The films were grown by electron-beam evaporation of CdS powder in a UHV system. X-ray Laue and transmission electron diffraction techniques have been used to examine the structure of the films. It has been found that epitaxial growth occurred on (111) substrates at a deposition temperature of approximately 340 °C. Polycrystalline films were obtained at temperatures below 300 °C on (111) substrates. Films grown on (100) substrates were polycrystalline over the range of deposition temperatures 100–390 °C. The electron transport properties of these films have been studied. The Hall mobility measurements of films grown on (111) substrates gave a value of 320 cm2(V sec)−1 for the epitaxial films, decreasing to approximately 100 cm2(V sec)−1 for polycrystalline films grown at 200 °C. For films grown on 〈100〉 substrates the Hall mobility ranged from 60 cm2(V sec)−1 at 200 °C to approximately 90 cm2(V sec)−1 at 340 °C. The electrical resistivity of the epitaxial films was 20 Ω cm and that of the polycrystalline films ranged from 10 to 300 Ω cm. Photoconductivity measurements of these films showed a relatively high trap density extending to greater than 1 eV above the valence band edge. A peak in the response at 800 nm is thought to be due to that of the Cd vacancies.
A relationship between defect resistivity and bulk resistivity at the melting temperature
Authors: Benedek R.
Published: February 2003

An apparent correlation exists between the specific resistivity of intrinsic point defects (i.e., vacancies and interstitials) and bulk resistivity at the melting temperature for cubic metals. A theory based on the rigid-ion model and Lindemann’s melting criterion is proposed to account for this correlation. The ratio of the defect resistivity to the melting-temperature resistivity is related to the defect-formation volume in an infinite crystal (i.e., without the image-field correction).
High-field electron trapping in SiO2
Authors: Solomon P.
Published: February 2003

When linear voltage ramps were applied to MOS capacitors, the current-vs-voltage (I-V) curves indicated a region of quasisaturation of current, i.e., a ledge in the I-V characteristic. These ledges could be explained by an electron-trapping model. Trap cross sections and concentrations were dependent on sample processing and oxide thickness and were in the 10−19 cm2 and 1012 cm−2 ranges, respectively. Comparison of shifts in the I-V and C-V curves showed that trapped charge to be within about 10 Å of the Si-SiO2 interface.
Some effects of heat treatment and electron irradiation on the cathodoluminescence spectra of CuInS2
Authors: Mittleman S. D. , Loferski J. J. , Wold A.
Published: February 2003

The cathodoluminescence spectra of sulfur-saturated and sulfur-deficient CuInS2 has been studied at 40 and 80 °K over the photon energy range 0.47⩽hν⩽2.0 eV. The spectrum of sulfur-saturated specimens exhibits four distinct bands with maxima at approximately 1.55, 1.20, 0.80, and 0.60 eV. The spectrum of sulfur-deficient samples consists of a band with a main peak at ∼0.60 eV and secondary maxima at ∼0.58 and ∼0.55 eV. When sulfur-saturated samples are heated in vacuum, the spectrum changes gradually from the sulfur-saturated form to the sulfur-deficient form. High-energy (10 MeV) electron irradiation on a sulfur-saturated sample results in a reduction of intensity of the dominant 1.55-eV band and a growth of a broad band with a maximum around 0.80 eV.
Electron energy distributions from GaP with negative electron affinity. II. Near-uv photoemission and secondary emission
Authors: Piaget C. , Saget P. , Vannimenus J.
Published: February 2003

Near-uv photoelectron energy distributions and spectral quantum yields are measured on high-efficiency carbon-free (100) GaP epitaxial layers activated to negative electron affinity (NEA) with Cs or Cs and O2. Energy distributions show that near-uv photoelectrons thermalize at both X and L conduction-band minima even for electrons excited by direct Γv15→Γc1 transitions. A two-valley diffusion model gives an accurate quantitative description of the quantum yields and is consistent with the observed energy distribution curves. Secondary-electron energy distributions are given. Thermalization effects at X and L conduction-band minima are also obvious here, but the proportion of hot electrons is higher than has generally been suspected up to now. The hot electron distributions show structure which corresponds to maxima and minima of the density of states in the conduction band at the surface. This can be used in a simple experiment to measure the amount of band bending at the surface. 1.65 and 1.4 eV are obtained for Cs and Cs-O activated surfaces, respectively.
Sputtering of niobium by energetic neutrons and protons: A round-robin experiment
Authors: Behrisch R. , Harling O. K. , Thomas M. T. , Brodzinski R. L. , Jenkins L. H. , Smith G. J. , Wendelken J. F. , Saltmarsh M. J. , Kaminsky M. , Das S. K. , Logan C. M. , Meisenheimer R. , Robinson J. E. , Shimotomai M. , Thompson D. A.
Published: February 2003

This paper presents the results of a round-robin neutron-sputtering experiment in which six independent research groups have participated. Targets of cold-rolled niobium prepared by two standard techniques were used by all participants. Three participating groups used (d,t) neutrons of about 14.8 MeV, one group used (d,Be) neutrons produced by 40-MeV deutrons on a thick Be target, and two groups used 16-MeV protons in transmission. The emission of micrometer-sized particles was observed by two groups and not observed by the other four. This particle emission was observed by two of the groups who used (d,t) neutrons in their irradiations. Chunk emission was observed for only one of the two standardized target types used in the round robin. The round-robin results support the concept that the neutron-sputtering yield of Nb, including atomic and chunk emission, has an estimated probable value no larger than 10−4 atoms per neutron. However, sputtering yields in the range 1.4×10−5 to ≲2.6×10−3 are reported here. The probable value for the sputtering yield was found to be independent of the two target preparations and the method of analysis, whether or not chunks were observed during analysis.
Thermionic work function of LaB6 single crystals and their surfaces
Authors: Oshima C. , Bannai E. , Tanaka T. , Kawai S.
Published: February 2003

The thermionic work functions and the Richardson constants for LaB6 single crystals have been measured using a diode system with a guard ring under stable thermionic conditions. They are 2.86±0.03 eV, 82 A/cm2 K2 for the (100) plane, 2.68±0.03 eV, 57 A/cm2 K2 for the (110) plane, and 3.4±0.2 eV, 71 A/cm2 K2 for the (111) plane. The (111) faceting on the (110) plane has an important effect on the reduction of the thermionic current from the (110) plane at 5×10−6 Torr.