bluuebunny/crossref_metadata_2025 huggingface dataset:
Luminescence from impurities and radiation defects in CdSe and CdS
Authors: Arora B.M. , Compton W. Dale
Published: February 2004

CdSe and CdS platelets annealed in NaCl atmosphere show strong emission attributed to donor-acceptor pair recombination with chlorine as a substitutional donor and sodium as a substitutional acceptor. Upon irradiation with fast neutrons, CdSe : NaCl platelets exhibit a new emission band centered at about 7050 Å. Chlorine-doped CdSe platelets show a weak emission band at the same wavelengths, whose strength increases upon irradiation with neutrons. It is suggested that this new emission also arises from donor-acceptor pair recombination with the donor being a substitutional chlorine and the acceptor a cadmium vacancy associated with a substitutional chlorine.
Pyroelectric voltage response to short infrared laser pulses in triglycine sulphate and strontium-barium niobate
Authors: Shaulov A. , Rosenthal A. , Simhony M.
Published: February 2004

Analysis is given of the voltage response in a pyroelectric sample to ir signals much shorter than the electronic and thermal time constants of the sample. The equation of the response is derived, and the dependence of the various parameters of the response on the frequency and energy of the pulses as well as on the parameters of the sample and on material constants is compared with experiment in triglycine sulphate and strontium-barium niobate. The peak value of the response is found to be independent of the load resistance as well as of the pulse frequency, and proportional to the energy of the signals, provided that the mean temperature of the sample is far enough from the Curie point.
Improved probe-curve evaluation based upon the Self and Shih method applied to positive column in He
Authors: Medicus G.
Published: February 2004

The ion-current evaluation method for collision-influenced probes developed by Self and Shih (SS) and their experimental results in positive-column discharges in He are examined. SS observe a peculiar saturation in the electron (e) component of the probe current—≈ independent of all plasma and probe parameters—which they explain as a plasma effect characteristic for positive columns; attempts to reproduce this saturation in the author's laboratory were unsuccessful. To determine the space potential VS, SS resort to the traditional Langmuir scheme of extrapolating the Te line [≡ asymptote to log Je(V), with Je ≡ e current to the probe] and the (peculiar) saturation current, in spite of the error in Vs which must be expected. In the present paper a ``combination method'' is described for determining Vs from the intersection of the Te line calibrated in density, lognFF(Vf), and the function lognSS(Vf) (≡ plasma density n according to SS with Vf ≡ FP potential as independent variable). With this method the uncertainties in the location of Vs with respect to the knee of the collision-influenced probe curve are avoided, and the accuracy of n is increased (although nss is shown to be remarkably insensitive to errors in Vs). From second-derivative measurements and from the theoretical treatment of the e spectrum in the positive column in He published by a number of authors, it is estimated that the error in n caused by underpopulation of the e spectrum above ≈ 20 eV as compared to a Maxwellian is ≲ 10%. In addition, such error sources as inaccuracies in Ji and Te, e reflection, and e emission from the probe by metastables are discussed. Potential importance of the combination method for studying the location of Vs with respect to the knee of the probe curve under collisional conditions is pointed out.
Flutelike instabilities in a strongly curved magnetic field
Authors: Martin J. G. , Emmert G. , El-Derini Z.
Published: February 2004

For three different distribution functions, the analysis of low-frequency flutelike instabilities of a low-β collisionless plasma immersed in the magnetic field of a line current indicates that the qualitative characteristics of the instabilities are independent of the distribution function. The analysis is valid for arbitrary curvature in the absence of magnetic shear and mirror effects. Numerical results for the growth rate and phase velocity for one of the distribution functions illustrate the behavior of the various instabilities, and comparison with Taylor's minimum-B theorem shows which particles in velocity space provide the energy to drive the instabilities.
Electric field enhanced phase separation and memory switching in amorphous arsenic triselenide
Authors: Thornburg David D. , White Robert M.
Published: February 2004

Electric field enhanced phase separation has been examined in amorphous As2Se3 and has been found to be a viable switching mechanism for this material. A simple theoretical analysis of this process is developed in which the formation of dispersed As clusters precedes the growth of an As filament. The analysis predicts that the switching behavior is field controlled and that devices biased below the point at which they switch instantly will switch at a later time. Measurements of the time for memory switching have been made for a large number of devices biased below ``threshold'' and the mean time for switching has been found to increase exponentially with decreasing applied field.
Deep hole traps in n-type liquid encapsulated Czochralski GaP
Authors: Dishman J. M. , Daly D. F. , Knox W. P.
Published: February 2004

Cathodoluminescence and photoluminescence time-response measurements have been used to study the prominent luminescence bands in n-type GaP grown by the liquid-encapsulated Czochralski (LEC) method. In as-grown crystals, two deep hole traps are identified. An isoelectronic hole trap, ≃0.4 eV above the valence band edge, produces red emission (1.72 eV) due to bound-exciton and pair recombination, while infrared luminescence (1.51 eV) is produced by pair recombination between a deep (≃0.7 eV) acceptorlike center and the donor dopant. In certain heat-treated samples, an additional structured luminescence band is produced at 2.07 eV, which also apparently results from recombination at an isoelectronic center. Resolution of the no-phonon lines of this emission suggests that an exciton is bound by 186 meV to the impurity center created by annealing. Although no positive identification of the chemical nature of these defects has been possible, we find that our results are not inconsistent with previously suggested models in which group-VI donors are complexed with gallium vacancies. Comparisons are also made with similar luminescence bands and defect levels observed in GaP grown by lower-temperature methods. We conclude that the hole traps studied here are not unique to the LEC material, but are apparently greatly enhanced by the LEC growth conditions.
Upper critical field of superconducting NbN films
Authors: Yamashita Tsutomu , Kitahara Shogo , Onodera Yutaka , Goto Yukihiro , Aso Tadao
Published: February 2004

NbN films have been examined with respect to their electrical and superconducting properties. These films are diposited by the dc reactive-sputtering technique under argon gas atmosphere combined with nitrogen. Critical magnetic fields were measured using a pulse magnet. Upper critical magnetic fields ranging from 150 to 290 kOe were observed for these films.
Domain-wall energy in cobalt-rare-earth compounds
Authors: Livingston J. D. , McConnell M. D.
Published: February 2004

We have used polarized light metallography to study magnetic domain configurations in Co5Sm, Co5Y, Co5Ce, and Co5Pr as a function of crystal thickness. From measurements of equilibrium domain widths on thin crystals, we estimate the domain-wall energy in these compounds to be 85, 35, 25, and 40 erg/cm2, respectively. From surface domain observations on bulk crystals, we have also made crude estimates of wall energy for Co5Nd, Co5La, and Co5Gd. From these wall energies and published anisotropy constants, we have calculated exchange constants, domain-wall thicknesses, and critical single-domain particle sizes. We find this critical particle size to be larger for Co5Sm and Co5Gd than for the other compounds, and suggest that this may partly explain why high coercive forces are more easily attained in powders of these two compounds.
Oxide-thickness determination by proton-induced x-ray fluorescence
Authors: Musket R. G. , Bauer W.
Published: February 2004

A discussion of the principles of oxygen surface density and, hence, oxide-thickness determination by proton-induced x-ray flurescence is followed by results of several applications of the technique. This technique has been shown to be useful for oxide thicknesses between ten and a few thousand Å. In practice, monoenergetic proton beams with energies between 100 and 400 keV produced characteristic x rays of all elements near the surface of aluminum, erbium dideuteride, copper, and stainless-steel specimens; these x rays were detected with a high-resolution Si(Li) detector. The oxygen Kα x-ray yields (x rays/proton) for these specimens were calibrated using known oxygen surface densities and, hence, oxide thicknesses on aluminum.
Low-temperature thermal expansion and magnetostriction of Kovar
Authors: Schlosser W. F. , Latal E. , Meincke P. P. M. , Graham G. M. , Colling D. A.
Published: February 2004

The temperature and magnetic field dependence of the thermal expansion coefficient and the magnetostriction of commercial Kovar, an Fe–Ni–Co glass-to-metal sealing alloy, has been measured below 50 K and well into the magnetic saturation region. The measured properties of Kovar show anomalous behavior similar to that found in other Invar-type alloys, and are markedly different from the properties of a pure alloy of about the same composition.
Effects of temperature quenching on silicon slices with and without dislocations
Authors: Gramberg G. , Popp G.
Published: February 2004

Quenching effects on slices of silicon with and without dislocations have been compared using x-ray topography. Much higher stress is required to initiate slip in dislocation-free silicon than in silicon with dislocations. In the former, slip is initiated only at a few disturbed points and, at very high quenching rates, also at the lapped surface. This can be largely avoided by etching off the lapped surface before heat treatment.
Acoustoelectric interaction in degenerately doped piezoelectric semiconductors
Authors: Mosekilde E.
Published: February 2004

The acoustoelectric gain constant is calculated quantum mechanically for arbitrary degeneracy of the electron gas. The requirements of energy and momentum conservation in individual electron-phonon interactions result in a rather sharp reduction of the gain factor when the acoustic wave number exceeds the characteristic linear extension of the electron distribution in reciprocal space. A simple two-band model is developed to describe effects of impurity banding upon the acoustoelectric interaction. According to this model, impurity banding enhances the acoustoelectric coupling and widens the active acoustic spectrum. These effects are associated with the increased density of states near the conduction-band edge and with the presence of electrons of higher momentum effective mass than the conduction-band electrons. At low temperatures it becomes possible for the linear gain factor as a function of acoustic frequency to have two maxima.
Effect of oxidation on the resistivity of Ni–P films
Authors: Pai S. T. , Marton J. P.
Published: February 2004

The oxidation and the resulting changes in the dc resistivity of chemically deposited Ni–P films were studied. The oxidation was found to be a two-stage process. At temperatures below 550°K mainly oxygen diffusion along the grain boundaries takes place, while above this temperature a surface-oxide layer forms. The rates of these processes are similar to those for certain bulk metals. A model to explain the resistivity changes, containing two separate terms with different activation energies, is used to analyze the experimental results. The two terms correspond to the two stages of oxidation. The agreement between calculated and measured resistance values for near-ideal films is satisfactory. We suggest that the model may be applicable to other thin-metal films.
Hydrodynamic dispersion in a single rock joint
Authors: Karadi Gabor M. , Krizek Raymond J. , Castillo Enrique
Published: February 2004

This paper deals with the hydrodynamic dispersion of a contaminant in a single rock joint; the effects of molecular diffusion due to a concentration gradient are considered to be negligible relative to the hydrodynamic effects, and the surfaces of the rock joint are assumed to be geochemically stable. Both laminar and turbulent flow are treated, and the constitutive properties of the contaminant are assumed to be the same as those of the parent fluid. Within this framework and with a knowledge of the boundary condition at the origin, the time-dependent average concentration at any point within the joint can be found by using either (a) a Taylor series expansion or a polynomial approximation for this boundary condition, or (b) an incremental approach based on the principle of superposition. Experimental data are given to substantiate the acceptability of the assumptions employed.
Analysis of unsteady waves in solids
Authors: Chen Peter J. , Graham R. A. , Davison Lee
Published: February 2004

In the present paper the acceleration wave theory applicable to the analysis of unsteady waves is developed. It is noted that a measurement of either the stress or the velocity history at a material point is sufficient to determine the history of the remaining one of these variables and of the strain if the instantaneous sound speed is known. This sound speed can be approximated by the speed determined as the wave passes through the material between closely spaced gauge stations or may be directly calculated from simultaneous measurements of particle velocity and stress at a single station. The present theory permits the analysis of wave-profile data obtained using conventional instrumentation which has a time resolution of a few nanoseconds.
Bragg diffraction by standing ultrasonic waves with application to optical demultiplexing
Authors: Tsai C. S. , Yao S. K.
Published: February 2004

The time-dependent Bragg diffraction by a lossy standing ultrasonic wave has been calculated, emphasizing the effect of acoustic attenuation upon the modulation depth. The effects of acoustic attenuation upon the performance of acousto-optic demultiplexing and multiplexing devices are also discussed. Optical demultiplexing of two simulated 37.5-Mbits/sec PCM channels using a PbMoO4 standing ultrasonic Bragg cell is demonstrated. The performance of the demultiplexer was found to be independent of the polarization of the incident light. Other salient features of the device are discussed.
Magnesium-doped GaAs and Alx Ga1−x As by molecular beam epitaxy
Authors: Cho A. Y. , Panish M. B.
Published: February 2004

Molecular beam epitaxy (MBE) of Mg-doped GaAs and AlxGa1−xAs layers was studied in situ by high-energy electron diffraction and Auger spectrometry. The analysis of the incorporation of Mg into the layers was studied with a Cameca (IMS 300) ion-sputtering mass spectrometer and by Hall-effect determination. It has been demonstrated that the sticking coefficient of Mg increases very rapidly (almost 3 orders of magnitude) under the specific conditions of this experiment when x increases from zero to 0.2, and that controlled p-type doping of GaAs and AlxGa1−xAs with Mg during MBE is possible. A new surface structure (001)−2×2-Mg is observed when a Mg beam impinges on a GaAs or AlxGa1−xAs surface.
Sensitivity of Josephson junctions in video detection of microwave and millimeter-wave radiation
Authors: Ohta Hiroshi
Published: February 2004

The responsivity and the noise equivalent power (NEP) of Josephson junctions in video detection of microwave and millimeter-wave radiation have been calculated. The sensitivity to radiation is assumed to be limited by the rounding of the voltage-current curve due to thermal noise of both the source resistance and the junction resistance. The calculated NEP is at least several tens of times better than any experimentally established.
Ambipolar Diffusion in a Weakly Ionized Unstable Plasma Afterglow
Authors: Ventrice Carl A. , Brown Charles E.
Published: February 2004

The afterglow of a weakly ionized plasma is investigated in the presence of a uniform axial magnetic field, which is varied from 0 to 900 G. Evidence of enhanced diffusion is observed and is associated with instabilities in the afterglow. In those cases for which the afterglow is quiescent, the magnetic field dependence of the transverse ambipolar diffusion coefficient is in agreement with that predicted by classical diffusion theory.
Development of a High-Performance Shock Tube
Authors: Rudderow W. H.
Published: February 2004

A new shock tube using electromagnetic forces to compress and heat the driver gas is described. Measurements of the shock velocity, run time, and electron density using air as the test gas were performed over an initial pressure range 0.1–10.0 Torr. Shock velocities 0.6–3.5 cm/μ sec were measured and found in reasonable agreement with a semiempirical theory. Measurements of the test time with photomultipliers and electrostatic probes indicate test times of 1–10 μ sec. Measurements of radiation emitted by air in the temperature range of 7000–11 000 °K agree with other experimental results. Preliminary radiation measurements at an equilibrium gas temperature of 23 000 °K were performed.
One-Dimensional Theory of Polarization by Shock Waves: Application to Quartz Gauges
Authors: Lysne P. C.
Published: February 2004

Laplace transform techniques were used to solve for the current generated by an air-backed quartz gauge impacted by a much thicker disk of equal mechanical impedance. A nonlinear equation of state, which considers the variations of the piezoelectric factor h11 with strain and electric displacement, the dielectric impermeability β11S with strain, and the elastic stiffness c11D with electric displacement, was used in this solution. The differences between theoretical values of the current and values obtained in shock compression experiments to 18 kbar were on the order of ± 1% for time less than twice the transit time of the gauge. The effects of electromechanical coupling on shock reverberation experiments utilizing active quartz reverberation disks are discussed.
Transient Photocurrent for Field-Dependent Mobilities
Authors: Gill W. D. , Kanazawa K. Keiji
Published: February 2004

The analysis of the transient photoconductivity in insulators having field-dependent mobilities is presented. Two specific electric field dependencies, a simple power law, and an exponential dependence on the square root of the field have been treated in detail. For the exponential dependence, which is of current experimental interest, analysis is carried out for both step-function illumination and pulse illumination.
Domain Wall Pinning as a Source of Magnetic Hardening in Alloys
Authors: Gaunt P.
Published: February 2004

A simple formal model of domain wall pinning by inhomogeneities in ferromagnetic alloys is developed. Particular attention is paid to the variation of coercivity with temperature, and it is shown that the coercive field varies linearly with the temperature of observation for an idealized form of magnetic inhomogeneity. This linear variation is observed in PtCo and SmCo5 alloys and it is estimated that each inhomogeneity changes the wall energy by about 2 × 10−12 erg. The diameter of the inhomogeneities in SmCo5 is estimated to be about 34 Å.
Thermoelectric Power of Ternary Cu–Ni–Zn Alloys
Authors: Brown Robert S. , Azároff Leonid V.
Published: February 2004

The thermoelectric power of three ternary alloys having an electron: atom ratio similar to that of constantan (58Cu42Ni) was found to be large (negative) but less than that of constantan. The thermoelectric power of five other alloys containing a nearly constant amount of zinc also was negative and varied linearly with the amount of nickel present, although the e/a ratio was more than sufficient to fill the 3d holes of nickel. This indicates that the nickel 3d band is not completely filled in these alloys, possibly because of nickel cluster formation.
Calculation of Electron Density in Nonparabolic Bands
Authors: Wood Van E.
Published: February 2004

It is shown that the integral F(ε,η)=2π−1/2 ∫ 0∞y1/2(1+y/ε)1/2(1+2y/ε)dyexp(y−η)+1,which is useful for determining the electron density in a nonparabolic energy band of Kane type, may be evaluated in terms of a Bessel function in the Boltzmann limit and that in the narrow-gap (small ε) limit, an approximation suggested by Bebb and Ratliff is quite accurate.
Effects of Impurity Deionization and Temperature on Carrier Equivalent Lifetime in Diffused Semiconductor Structures
Authors: Bhattacharyya A. B. , Basavaraj T. N.
Published: February 2004

In an inhomogeneously doped semiconductor built-in electrostatic field and mobility gradients result in a minority-carrier equivalent lifetime which is of a few orders lower in magnitude compared to normal lifetime in a homogeneous semiconductor. To find the built-in field it is commonly assumed that all the impurity atoms are fully ionized at room temperature. Since this assumption is not valid in some cases, expressions have been derived for the built-in field and the equivalent lifetime taking deionization into account. It is shown that the consideration of deionization for an exponential distribution results in a nonconstant built-in field. Second, the temperature variation of minority-carrier equivalent lifetime has been studied. To make an analytical study possible, an empirical relation for the minority-carrier mobility in silicon as a function of both temperature and impurity concentration has been proposed. Some typical inhomogeneous silicon layers having exponential, Gaussian, and complementary error-function impurity distributions have been considered. It is shown that the equivalent lifetime may decrease with temperature in some regions of an inhomogeneous layer, contrary to the deductions obtained from the Shockley-Read theory for normal lifetime.
Design of a High-Resolution High-Efficiency Magnetic Spectrometer for Electron Spectroscopy
Authors: Fadley C. S. , Healey R. N. , Hollander J. M. , Miner C. E.
Published: February 2004

A theoretical design study was carried out for a high-resolution high-efficiency double-focusing magnetic spectrometer intended for general use in electron spectroscopy. With the proposed design it should be possible to operate with good intensity at energy resolutions as high as 0.01%. The air-cored system of coils used in the design gives a fieldform with electron-optical properties very close to those of the 1/r field. The design thus has very good focal-plane properties and, in conjunction with a multichannel detector, should yield data-acquisition rates approximately 100 times higher than in single-channel operation. The present design is superior in this respect to any previous air-cored magnetic spectrometer. All coils in the design are of smaller radii than the electron orbits, giving very high access to the source and detector regions. There appear to be no great difficulties in the construction of a spectrometer with this design. Most features of the design compare very favorably with other spectrometers currently used in electron spectroscopy. The effects of extraneous magnetic field perturbations on the performance of double-focusing spectrometers were also calculated.
Electrical Conductivity of Vitreous GeO2
Authors: Böhm Horst
Published: February 2004

Electrical-conductivity measurements were carried out on vitreous GeO2 and the conductivity was measured as a function of frequency and temperature in the following ranges: 1.5 Hz ≤ ν ≤ 108 Hz and − 180°C ≤ T ≤ 600°C. The results are discussed in terms of a phenomenological Debye theory, and it is concluded that the conductivity is due to ionic processes.
Profile Estimation of High-Concentration Arsenic Diffusions in Silicon
Authors: Fair R. B.
Published: February 2004

In order to facilitate surface concentration estimation for arsenic diffusion, a simple expression has been derived which is dependent only upon the junction depth xJ and the sheet resistance Rs: Cs = 1.56 × 1017/xJRs. This equation was derived from experimental mobility data and a polynomial approximation to the solution of the arsenic diffusion equation. Available data on diffusions carried out from five different kinds of arsenic sources indicate that this derived equation for Cs is accurate to within 15% for Cs≳ni.
Luminescence in Liquid-Phase Epitaxy GaAs: Ge Diodes
Authors: Romano-Moran Roberto , Ashley K. L.
Published: February 2004

A low-energy emission band has been observed in Ge-doped GaAs layers grown by liquid-phase epitaxy. 77 °K electroluminescence of junctions with Ge-doped p regions and 80 °K photoluminescence of the p layers show the band to be at about 9200 Å (1.35 eV).
Elastic and Piezoelectric Properties of Ferroelectric 5PbO · 3GeO2 Crystals
Authors: Yamada Tomoaki , Iwasaki Hiroshi , Niizeki Nobukazu
Published: February 2004

The elastic, piezoelectric, and dielectric constants of a new ferroelectric crystal 5PbO · 3GeO2 have been measured. The measurements involve mostly the use of thickness modes in small plates of various crystallographic orientations. The electromechanical coupling factors turn out to be small, which makes this material unattractive for ultrasonic applications. The temperature characteristics of some piezoelectric constants are presented. The piezoelectric constant d31 vanishes above the Curie point (177 °C), while d22 remains constant above and below the Curie point.
Comment on the Electrohydrodynamic Instability in Nematic Liquids
Authors: Aslaksen Erik W.
Published: February 2004

We show that in a nematic liquid carrying an electrolytic current, an infinitesimal stationary distortion of the uniform orientation pattern does not lead to the formation of space charges. This contradicts the basic assumption of the Carr-Helfrich model.
The Structure of Electroplated and Vapor-Deposited Copper Films
Authors: Gangulee A.
Published: February 2004

The structures of electroplated and vapor-deposited copper films have been studied by x-ray diffraction. While there was no evidence of stacking faults in any of these films, the electroplated films were characterized by presence of twins, large thickness-dependent microstrains, and small particle sizes. The vapor-deposited films, on the other hand, showed no twins, smaller microstrains, and large thickness-dependent particle sizes. Analysis of the electrical resistivity of the electroplated films indicated that the twin resistivity of copper is, at most, half of the grain-boundary resistivity.
Optical Modulation of Electron-Beam Landing Energy on Semiconductors
Authors: Foss Norman A.
Published: February 2004

This paper studies charging effects on semiconductors in the resistivity range from 103 to 104 Ω cm. An electron beam is scanned along a semiconductor target parallel to an adjacent metal reference electrode. The leading edge of the beam charges the semiconductor to a level determined by the surface and bulk conductance of the semiconductor. This conductance can be varied by optically exciting carriers in the semiconductor thereby altering the maximum charge-up potential and thus the total electron landing energy. The charge-up potential can be determined by measuring the secondary emission current from the target. It is found that the electron landing energy can be changed by as much as several hundred eV on Si and CdTe targets depending upon the photon input flux.
Theoretical Thermodynamic Properties of Gases at High Temperatures and Densities with Numerical Results for Hydrogen
Authors: Baker J. R. , Swift H. F.
Published: February 2004

The partition function corresponding to an equation of state for a high-temperature high-density gas suggested by Rowlinson has been derived. The equations for selected thermodynamic properties of the gas are obtained from this partition function using statistical thermodynamics. These equations are used to calculate results for the case of hydrogen in the range of temperature between 500 and 3000°K and in the range of density between 1 and 2000 amagat.
Isotope Effect for Self-Diffusion in Single Crystals of α Iron and Correlation Factor of Solute Diffusion in α Iron
Authors: Irmer V. , Feller-Kniepmeier M.
Published: February 2004

The isotope effect in α-iron single crystals of different purity was determined to be Ē778 °C = 0.43 and Ē901 °C=0.46. A dependence on crystal purity or temperature was not found. The correlation factor calculated can be interpreted by a single vacancy mechanism and/or an interstitialcy mechanism. The attempt to calculate the correlation factor for solute diffusion of copper in iron failed, because the diffusion data available in the literature were obtained with iron of different purity.
Structure of Amorphous Silicon Monoxide
Authors: Yasaitis John A. , Kaplow Roy
Published: February 2004

The pair distribution function in amorphous deposited silicon monoxide has been measured at room temperature. The result is not in good agreement with expectations for a mixture of well-defined amorphous silicon and amorphous SiO2. Other possibilities, for which the average number of nearest-neighbor Si–O bonds per atom deviates significantly from 2, can be ruled out. A ring-type structure, consistent with the diffraction results, and also (apparently) with optical data, is suggested as the most likely alternative.
Displacement Fields of Straight Dislocations in Anisotropic Crystals
Authors: Yoo M. H. , Loh B. T. M.
Published: February 2004

A detailed analysis is made of the displacement fields of glissile dislocations of active slip systems in common crystal structures by taking account of elastic anisotropy. Each displacement component can be generally expressed in terms of twelve real coefficients. The cases for which analytic expressions of these coefficients are possible are enumerated. An efficient method of numerical calculation for a general case is introduced, and numerical results for Cu, α-Fe, and Zn are given in polar diagrams. ``Bending'', ``warping'', and ``dimpling'' of lattice planes about the dislocation axes are discussed in terms of radial and angular dependencies of the displacement components normal to Burgers vector. Choices of integration constants are described in accordance with symmetry properties about the dislocation axes.
Thermal Vaporization from the (111) CaF2 Face
Authors: Bezerianos N. , Vook R. W.
Published: February 2004

Electron microscopy replica techniques and photo-optical microscopy were applied in an investigation of the surface morphological changes occurring on the cleaved (111) CaF2 face when the crystals were heated in ultrahigh vacuum and technical vacuum. A characteristic macromorphology consisting of ridges, hills, and valleys was observed. The micromorphology consisted initially of crystallographic micropits and steps which gave way to a crystallographically terraced surface containing terraced hillocks in its final stage. Micropits were rarely observed in ultrahigh vacuum, and then only when air-cleaved crystals were used. The density of the terraced hillocks also was much less in ultrahigh vacuum than in technical vacuum. The results are interpreted and discussed in terms of impurity effects and the theories of thermal vaporization.
Electron-Beam-Deposited Thin Polymer Films: Electrical Properties vs Bombarding Current
Authors: Babcock L. E. , Christy R. W.
Published: February 2004

Polymer films about 150 Å thick were deposited on glass substrates by electron bombardment of tetramethyltetraphenyltrisiloxane (DC704). They were sandwiched between evaporated aluminum electrodes, the top one semitransparent. The capacitance, conductance, and photoconductance of the sandwiches were measured at room temperature as a function of the electron bombarding current which formed the polymer. The polymer thickness was obtained independently from Christy's formula for the rate of formation. The dielectric constant, calculated from the capacitance and thickness, increased with bombarding current up to our maximum current density of 4 mA/cm2, starting from the value 2.6 measured for the bulk liquid DC704. After exposure of the film to air, the values fell to 2.6 regardless of bombarding current. The conductance, which showed an exponential dependence on square root of electric field, was interpreted as field-assisted thermal ionization of donors heavily compensated by acceptors. It increased as the cube of bombarding current, and fell several orders of magnitude on exposure to air. The photocurrent, which increased with photon energy at fixed voltage bias, showed a threshold which fell from 3.5 to 2 eV with increasing bombarding current and a proportionality constant which increased. It was not measured before air exposure. Our conclusion from these results is that with increasing bombarding current, the polymer undergoes an increase in both crosslinking bonds (which contribute to the carrier mobility) and dangling bonds (which function as donors or acceptors). Exposure to air drastically reduces the density of dangling bonds, with donor radicals more susceptible to oxidation than acceptors, but does not much affect the crosslinking.
Anomalous Acoustic Behavior in Dow Corning 200 Fluids
Authors: Beattie A. G.
Published: February 2004

Anomalous acoustic behavior is seen in Dow Corning 200 fluid (chemical name: linear dimethyl polysiloxane). A decrease in the longitudinal acoustic velocity is seen upon warming which may be an order of magnitude greater than the corresponding increase upon cooling. This decrease occurs in the temperature region 230–240°K and its magnitude is found to depend inversely upon the thickness of a film of the fluid. A similar anomaly is seen in the dielectric constant under the same conditions. A model based upon a phase transition in the siloxane chain accounts for this behavior.
Effects of Magnetic Field on Attenuation of Ultrasonic Waves in a Nematic Liquid Crystal
Authors: Wetsel Grover C. , Speer Royce S. , Lowry Bright A. , Woodard Michael R.
Published: February 2004

The effects of the magnitude and direction of a steady magnetic field on the propagation of longitudinal ultrasonic waves in N-(p-methoxybenzylidene)—p-butylaniline have been investigated as a function of frequency and path length. The anisotropy of the measured ultrasonic attenuation is in good agreement with a theory of ultrasonic-wave propagation in nematic liquid crystals based on micropolar continuum mechanics. The variation of the attenuation with frequency from 5–85 MHz is, however, inconsistent with present theories. Measurements of velocity and dispersion are also reported.
Determination of the Ion-Induced Electron Yield from a Statistical Treatment of Pulse-Height Distribution Curves Measured with an Ion-Electron-Scintillation Detector
Authors: Werner H. W. , Berg J. v. d.
Published: February 2004

A statistical analysis of pulse-height distribution curves at the output stage of an ion-electron-scintillation detector has been carried out. It is shown that the average ion-induced yield γ̄ of electrons at the converter can be determined from statistical quantities of the pulse-height distribution curves. Corrections are included for nonuniformity in yield in the different stages and for the fact that particles releasing no secondaries are not counted. The energy dependence, mass dependence, and the isotopy effect found for the γ̄ values determined according to this method are in good agreement with values found in using other methods.
Retraction of Cold-Drawn Polyethylene: Influence of Lamellar Thickness and Density
Authors: Falender James R. , Hansen David
Published: February 2004

The role of crystal morphology in the retraction of oriented linear polyethylene was studied utilizing samples crystallized under conditions controlled to vary, separately, lamellar crystal thickness and density. Samples were oriented in a sample shear deformation to a strain of 4.0 prior to measuring retraction tendency in creep- and relaxation-type tests. Characterizations of specimens were made using wide- and small-angle x-ray techniques. The specific morphological variations were chosen to test the hypothesis that a long-range elastic restoring force can originate in conjunction with deformation of lamellar crystals and the consequent increase in lamellar crystal surface area and surface free energy. The results support this hypothesis.
Anomalous Viscoelastic Behavior of Metallic Glasses of Pd–Si-Based Alloys
Authors: Chen H. S. , Goldstein M.
Published: February 2004

The temperature and the stress dependence of viscoelastic properties of metallic glasses of three compositions: Pd0.795Au0.04Si0.165, Pd0.795Ag0.04Si0.165 and Pd0.775Cu0.06Si0.165 have been studied near the glass temperature. The total retarded tensile compliance of these alloy glasses, J̃d0 is small at low temperature (of the order of glass compliance J̃g) but increases rapidly in a narrow temperature range when the temperature approaches Ta, at which the viscosity of the glass attains 1012 P, and attains a value as high as 200 times the glass compliance J̃g for the Pd0.775Cu0.06Si0.165 glassy alloy, at T > Ta + 15°K. Concurrent with an increase in J̃d0 near Ta, the alloy liquids become non-Newtonian in the stress range employed (σ varies from 6×106 to 3×108 dyn/cm2). The apparent shear activation volume for the viscous flow deduced from the non-Newtonian behavior increases with temperature and attains a value as high as 100 times the atomic volume. These results have been compared with viscoelastic behavior of other types of liquids. It is suggested that the strong temperature dependence of the shear compliance of metallic liquids near Tg may be attributed to some sort of macroscopic structural rearrangements taking place as temperature is changed. The large activation volume of viscous flow seems to imply that the flow mechanism involves a large number of simultaneous atomic displacements in the flow direction.
Transit-Time Oscillations in BARITT Diodes
Authors: Coleman D. J.
Published: February 2004

A new mechanism of microwave power generation, obtained in metal-semiconductor-metal structures with significantly lower noise than Impatt diodes is described. The two metal contacts to the semiconductor form a ``double Schottky barrier'' diode. Carriers are thermionically injected over the forward-biased barrier and drift through the depleted semiconductor to be collected by the reverse-biased barrier. When the transit time of the carriers is roughly three-quarters of the desired microwave period, the structure is shown to have a small-signal microwave negative resistance. Combining the ideas of thermionic injection over a barrier and transit time, we suggest the acronym BARITT (BARrier Injection Transit Time) for the device. The small-signal impedance and noise measure of the device are calculated using several approximations to the actual space-charge distribution and transport properties of this device. A minimum negative Q of about 21 and noise measures significantly less than that of Impatt diodes are predicted. Initial experimental observations of microwave oscillations are given, and reasonable agreement with theory is obtained. In general, the theory predicts well the magnitude of the small-signal negative resistance with a somewhat smaller bandwidth than observed. The experimental small-signal amplifier noise measure of 15 dB is verified with practical values as low as 8 dB predicted.
Magnetization of Small Permalloy Circuit Elements
Authors: Copeland J. A.
Published: February 2004

Small thin-film elements of permalloy are being used in circuits for propagating circular magnetic domains in an adjacent uniaxial wafer. This paper shows that these elements often are not magnetically saturated and, therefore, exhibit pole distributions which depend on the applied field and geometry of the element. Approximate relations are derived from numerical solutions of a number of specific cases to aid the design and understanding of these circuits.
Models and Magnetism in One-Dimensional Systems; Low-Temperature Magnetic Susceptibilities of Dimethylammonium Trichlorocupate (II) and Tetramethylammonium Trichloronickelate (II)
Authors: Gerstein B. C. , Gehring F. D. , Willett R. D.
Published: February 2004

The initial susceptibilities of powder dimethylammonium copper (II) chloride (DMACuCl3) and tetramethylammonium nickel (II) chloride (TMANiCl3) have been measured in the ranges 1.7–91 °K and 1.6–79 °K, respectively. DMACuCl3 exhibited deviations from Curie-Weiss behavior below 10 °K. The deviations were not inconsistent with models based on linear antiferromagnetic interactions. Eight models were used in an attempt to fit these deviations. A least-squares fit of the data to the relation χM=C/(T+θ) − α in the Curie-Weiss region yielded the following values: C=0.437 (0.006), θ=0.317 (0.278), and α=−0.00014 (0.00007). TMANiCl3 exhibited deviations from Curie-Weiss behavior below 30 °K which were not inconsistent with linear ferromagnetic interactions. Two one-dimensional models were used to fit these deviations. A least-squares fit of the data to the relation χM=C/(T+θ) − α in the Curie-Weiss region yielded the following values: C=1.28 (0.34), θ=−4.80 (5.25), and α=0.00010 (0.00379). The differences between the data reported herein and the previously reported magnetic behavior of KCuCl3 and CsNiCl3 indicate the strong possibility that a dominant factor in the magnetic behavior of the latter complexes is interchain interaction.
Study of the Distribution of N2 in Ta and V Using Rotational Hysteresis in the Superconducting Mixed State
Authors: Milne I. , Gibbons D. F.
Published: February 2004

Rotational hysteresis curves of selectively oriented single crystals of tantalum and vanadium were determined in the mixed superconducting state at 2°K, as a function of nitrogen content. Enhanced flux pinning, which varied in magnitude with the nitrogen content, was observed when the magnetic field was parallel to the 〈110〉 directions in vanadium and the 〈100〉 directions in tantalum. These results are consistent with the hypothesis that the nitrogen forms clusters on specific crystallographic planes, determined by the respective elastic anisotropies of the solvent metal.
Energy Relaxation Mechanisms in n-InSb at Low Temperatures
Authors: Whalen J. J. , Westgate C. R.
Published: February 2004

Experimental results for the energy relaxation time in n-InSb as a function of electron concentration in the temperature range 1.5–20°K are presented. These values were determined by measuring the response times of bulk InSb mixers. Analytical results for the energy loss rates to the acoustic modes via deformation potential scattering and piezoelectric scattering are given. The effects of degeneracy and screening are considered. Good agreement between theory and experiment is obtained for the low-concentration material (1.5×1013 cm−3) with a piezoelectric constant e14 equal to 3.0×104 dyn1/2/cm and a deformation potential constant E1 less than or equal to 5.0 eV. However, no single set of values for e14 and E1 accurately describes the temperature dependences of the energy relaxation time for all electron concentrations. The usual polar optical phonon scattering treatment is shown to be adequate; however, a careful comparison of the temperature dependence of the energy relaxation time above 14°K strongly suggests that energy relaxation occurs through the simultaneous emission of two acoustic phonons.
Stacking-Fault Broadening in β-AlNi and Separation of Strain and Fault Effects
Authors: Mohanty G. P. , Yu T. C.
Published: February 2004

Recently determined Fourier coefficient data for cold-worked β-AlNi diffraction peaks were analyzed for stacking-fault contributions using a method of normalization for the coefficients suggested by Rothman and Cohen, and the results were compared to those obtained with conventional normalization. It is shown that the conclusions concerning particle size anisotropy and importance of (110) faulting in β-AlNi remain unchanged irrespective of the normalization procedure. In addition, a modified Warren-Averbach-type graphical procedure is suggested for distinguishing anisotropic fault broadening from similar strain effects, which helps eliminate anisotropic strain scatter inherent to the conventional Warren-Averbach plot and allows a direct comparison between the fault predicted and the experimental coefficients for all reflections.
Compound Formation upon Sensitizing Semitransparent Oxidized Silver Layers by Cesium Vapor
Authors: Stahl H. Adrian
Published: February 2004

Since its discovery, the emission mechanism of the silver-oxygen-cesium photoelectric cathode remained enigmatic. This emitter, conspicuous by a low quantum efficiency (at the infrared peak 0.5% but recently augmented to 1.6%) and a unique long-wavelength threshold 1.2–1.7 μ, is featured by colloidal silver granules superficially oxidized. It is surmised that in the emission of this cathode, the semiconductor cesium oxoargentate (CsAgO)2 plays a significant role.
Effect of Compensation on the Segregation Coefficient as Deduced from Resistivity Measurements
Authors: Padovani F.
Published: February 2004

The influence of compensation on the value of the segregation coefficient as deduced from resistivity measurements along the length of a crystal is considered. An expression relating the apparent value of the segregation coefficient to the degree of compensation is derived and applied to the case of boron and/or phosphorus compensated silicon.
Precipitate Colonies in Silicon
Authors: Nes E. , Washburn J.
Published: February 2004

The precipitate colonies formed during cooling of silicon single crystals have been reinterpreted as being caused by a copper precipitation.
Excitation and Detection of Volume Elastic Modes with Surface Conducting Gratings
Authors: Ristic V. M.
Published: February 2004

This paper concerns excitation and detection of volume elastic modes with surface conducting gratings. First, the generation of volume elastic modes is analyzed along degenerate (pure) and nondegenerate mode axes. It is shown under what conditions a strong volume-wave generation occurs. An experiment aimed at measuring coupling losses, and checking the theory, is described. The paper also includes a brief discussion of the applicability of the results to generation of volume elastic waves in a microwave region.
Measurements on Particle Fluxes from dc Vacuum Arcs Subjected to Artificial Current Zeroes
Authors: Miller H. Craig
Published: February 2004

A mass and energy analyzer capable of time-resolved analysis of the separate constituents of the flux from vacuum arcs near and through current zero has been constructed. The following results are obtained in looking at the radial flux from 50- and 100-A copper arcs subjected to rapidly forced current zeros: (i) A burst of low-energy ions is produced at the time of arc extinction (within the resolving power of the apparatus, <5 μsec), this burst being attributed to the collapse of a potential hump near the cathode. (ii) The presence of copper ions depresses the level of background gas signal, especially for hydrogen.
Surface-Charge Transport in a Multielement Charge-Transfer Structure
Authors: Engeler W. E. , Tiemann J. J. , Baertsch R. D.
Published: February 2004

A two-phase 14-stage transfer shift register has been built and operated which uses the surface-charge transistor structure to effect the transfer of signal charge from one stage to the next. This paper describes the structure and presents preliminary experimental results which characterize its operation as a digital shift register. The shift register is operated in both the complete and partial transfer modes. An analytical solution for the approximate equation of motion of charge under a single electrode plate has been obtained. A key result of the analytical solution is that the characteristic time for transfer of charge out of a full potential well is given by t0=L2/μ(V-VT). A computer simulation of the 14-stage shift register, using the analytical solution for a single stage, is in good agreement with the experimental results.