bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature-Induced Changes in Optical Path Length for a Nd-Doped Glass Rod during Pumping
Authors: Epstein Seymour
Published: January 2005

Frame-camera interferogram data for a neodymium-doped glass rod taken during the laser pumping process have been analyzed in terms of changes in optical path length due to: (1) explicit temperature-induced changes in length and index of refraction, and (2) temperature-induced stress birefringence. Criteria for compatibility of the interferogram data, the formalism, and independently determined values for the phenomenological constants involved are set up and met, after which the temperature over the rod cross section obtains. The minimum in the temperature distribution found accounts for the observed split fringes, and our qualified estimate of the temperature rise at the center of the rod is ∼16°C. Estimates of the changes in optical path length due to the various effects are made, and values for the temperature coefficients of expansion and refractive index of 0.97×10−5/°C±6% and −7.2×10−7/°C±60%, respectively, are submitted.
Theory of Dynamic Optical Distortion in Isotropic Laser Materials
Authors: Riedel E. P. , Baldwin G. D.
Published: January 2005

In this paper, Fermat's principle is applied to the analysis of pump-induced optical distortion in isotropic laser materials. This approach leads to expressions for the slope and trajectories of rays through a laser amplifier rod for a plane-wave input. These results are then used to predict ray refraction, beam divergence, and optical path length through the rod as a function of radius, time, and polarization. The index of refraction of the material is considered to change both as a result of thermal effects and as a result of the presence of an excited ion population.
Measurements of Dynamic Optical Distortion in Nd-Doped Glass Laser Rods
Authors: Baldwin G. D. , Riedel E. P.
Published: January 2005

This paper quantitatively describes the optical distortion in neodymium-doped glass which is induced by pump radiation. We have found the optical path length at 6328 Å dependent on four primary effects: (1) change in physical length; (2) change in refractive index due to temperature rise; (3) change in index resulting from stress; (4) change in index associated with an excited-state population of neodymium ions. Section I presents the experimental techniques used and the results obtained. Included in this section are measurements of optical-path-length variations, pump-induced birefringence, change in physical length, change in refractive index, bulk temperature rise, and the deflection of a pencil of rays. Section II compares the results of Section I with the theory set forth in the previous paper. Good agreement between theory and experiment is achieved provided a term which takes account of the index change associated with an excited-state population of neodymium ions is included. This term arises from the fact that the polarizability of the neodymium ion in its excited 4F3/2 level is different from its value in the 4I9/2 ground level. The inclusion of this new term in the expression for the change in refractive index implies that large optical distortions can exist in ``athermalized'' glass.
Space-Charge-Limited Currents in Copper Phthalocyanine Thin Films
Authors: Sussman Alan
Published: January 2005

Measurements of space-charge-limited currents have been made on evaporated thin films of the compound copper phthalocyanine using Ohmic contacts. A complete study of the current as a function of voltage, temperature, thickness, and illumination indicates that all the results are consistent with the assumption of an exponential distribution of trapping states of the form Nt(E) = kTcP0 exp (E/kTc), where kTcP0 is a parameter related to the total trap density.

Practical techniques for obtaining values for the mobility, density of states, total trap density, trap distribution in the vicinity of the Fermi level, and trap capture cross section are outlined and values reported.
Electrical Properties of Copper Phthalocyanine Thin Films as Influenced by the Ambient
Authors: Sussman Alan
Published: January 2005

Measurements of currents in evaporated thin films of copper phthalocyanine as a function of temperature and ambient have yielded information about the effects of nitrogen, hydrogen, and oxygen ambients on the conductivity, trap density, and mobility. Above a transition voltage the currents are space-charge-limited and can be correlated with a trap distribution that decreases exponentially with energy as the distance from the valence band edge increases. The parameters that govern the distribution as well as the position of the Fermi level depend on sample preparation, and some systematic correlation exists between annealing and the subsequent values of these parameters, based on consideration of the crystal changes that occurs on heating.

The value of the intrinsic conductivity σ0=3(Ω cm)−1 and mobility μ=0.013±0.007 cm2/Vsec have been determined and are found to be relatively independent of preparation and subsequent treatment.
Decorated Dislocations in LiNbO3 and LiTaO3
Authors: Levinstein H. J. , Capio C. D.
Published: January 2005

It has been found that dislocations in LiNbO3 and LiTaO3 single crystals can be decorated by electric-field-enhanced diffusion of platinum or gold into the crystals at temperatures in the order of 600°C with voltages in the range of 250 to 1000 V/cm. To demonstrate the use of the technique, examples of low-angle boundary networks in LiNbO3 and LiTaO3 are shown. The general characteristics of the as-grown dislocation network in a [101̄0]-growth-axis LiNbO3 crystal are described, and the effect of annealing on the dislocation array in LiTaO3 crystals is discussed.
Renormalization and the First-Order Ferroelectric Transition in Perovskites
Authors: Nettleton R. E.
Published: January 2005

A renormalization of the Hamiltonian H, previously devised by Silverman and Joseph to calculate the temperature-dependent ferroelectric-mode frequency in perovskites exhibiting a second-order transition, is extended to the case of a first-order phase change. The extension involves inclusion in H of all anharmonic terms to sixth order which give rise, after a thermal average is taken, to polarization and temperature dependences in the internal energy, which are similar to those appearing in the phenomenological theory of Devonshire. Validity of the latter theory in high electric fields can now be understood as a consequence of field independence of the acoustic modes, which make the dominant contribution to the temperature dependence of the internal energy. Since the optical frequencies must depend on field under these circumstances, so that validity of the Devonshire theory requires that they make little contribution to thermal properties, the optical branch should lie above the acoustic, except in (001) planes where the unstable modes occur which are responsible for the transition. From domain-wall calculations in the tetragonal phase of barium titanate, it is concluded that dispersion is weak in the (001) planes, so that all frequencies with k in such a plane will be low. This suggests that (001) planes should be surfaces of discontinuity in frequency, which leads in turn to the prediction that the electric susceptibility and switching rate in tetragonal barium titanate will exhibit thickness dependence of purely lattice-dynamical origin, with the thickness dependence of the latter exceeding that of the former. The theory thus provides a means of correlating the field and thickness dependence of switching and polarization with the structure and temperature dependence of the lowest transverse optic branch.
Time Dependence of Avalanche Processes in Silicon
Authors: Lee C. A. , Batdorf R. L. , Wiegmann W. , Kaminsky G.
Published: January 2005

An analysis of the time dependence of avalanche processes encountered in silicon junctions, including the effects of different ionization rates and velocities of the two charge carriers, is presented. An earlier analysis of Read was restricted to equal ionization rates and velocities; that restriction has been removed but the frequency limitation of his analysis has been retained here. Various solutions of the generalized differential equation are obtained, including a steady-state solution to a sinusoidal perturbation of the avalanche-field maximum. The important features of this steady-state solution are that it describes the avalanche current for all explicit values of the multiplication M≥1, is valid for highly nonlinear responses to the sinusoidal perturbation, and contains both the in-phase and out-of-phase parts of the fundamental-frequency component of the avalanche response.

The analysis is applied to solid-state photomultipliers, is used to explain an anomalous rectification observed in operating Read structures, and, lastly, the small-signal limit of the avalanche response is compared with susceptance measurements of a uniformly avalanching junction as a function of the multiplication and saturation current over a frequency range of 20 to 200 MHz.
Analysis of the Q Factor, Efficiency, Stability, and the Design of Read Structures in the Nonlinear Range
Authors: Lee C. A. , Batdorf R. L. , Wiegmann W. , Kaminsky G.
Published: January 2005

Using time-dependent solutions of the avalanche current generalized for unequal ionization rates and velocities of the two charge carriers, compact formulas for the Q and the efficiency of the Read structure are derived, which are valid from zero to very large oscillation amplitudes. A method is developed to properly account for the internal-field adjustment (which may be variably positive or negative) that is caused by the nonlinearly rectified avalanche-current component flowing through the drift region. These developments clearly show that the behavior of the Q at intermediate and large signals cannot be correctly derived unless the avalanche analysis retains terms related to both the in-phase and out-of-phase components of the avalanche current.

The behavior of Q vs oscillation amplitude is numerically calculated for a successfully operated prototype and compared with experimental observation. These experimental observations in conjunction with the analytical development also permit an interpretation and assessment of the effects due to inhomogeneities in multiplication found in junctions.

Design considerations of Read structures are discussed, particularly how various parameters that are critical in optimizing the efficiency and stability may be controlled by design of the electric-field distribution of the avalanche. It is shown how advantage may be taken of the asymmetry of ionization rates of the two charge carriers to achieve even higher efficiencies than the 30% Read predicted for the case of equal ionization rates. Finally, certain circuit criteria for achieving dynamic stability are discussed and solutions given.
X-Ray K Absorption Edges of Alloys. I. Correlation to Band Models
Authors: Azároff Leonid V.
Published: January 2005

It is possible to identify portions of the fine structure appearing in the x-ray K absorption edges of pure metals with their respective energy bands. The areas of these portions are proportional to the density of unoccupied states in each band and changes in their occupation density accompanying alloying. Face-centered-cubic Ni, Co, and Fe have similar fine structures that are characteristically different from that of body-centered-cubic Fe. An analysis of the latter suggests that the overlapping 3d+4s+4p bands in α-Fe are split into two sub-bands separated by ∼8 eV. A direct comparison of changes in the areas under the curves of Cu-Ni alloys shows that a systematic decline in Ni 3d holes and Cu 4s holes takes place with increasing copper content. An apparent saturation takes place at 56 at.% copper in agreement with magnetic saturation and NMR measurements.
Dislocation Configurations in Cylindrical Coordinates
Authors: Owen D. R. J. , Mura T.
Published: January 2005

General expressions are derived for the stress components due to an arbitrary continuous distribution of dislocations prescribed in a cylindrical coordinate system. Results are obtained for the stress field of a helical dislocation of uniform shape with the Burgers vector along its axis. The additional energy arising from the interaction of a point defect with the helix is obtained and the behavior of the defect examined.

It is also shown how results for circular dislocation loops are readily obtained from the general expressions and in particular the problem of a rotational loop, which is formed by twisting the two faces of the slip surface relative to each other, is solved.
Magnetic Annealing Effects in Silicon-Doped Garnets
Authors: Hunt Robert P.
Published: January 2005

Many properties of polycrystalline yttrium iron garnet (YIG) and reduced single-crystal YIG have been attributed to the presence of Fe2+ ions which provide mobile electrons that can diffuse locally through the lattice. It was the purpose of this research to study the modification to the low-temperature anisotropy caused by the presence of Fe2+ ions in silicon-doped YIG, Y3Fe5−δSiδO12 with 0<δ<0.18. Silicon-doped YIG demonstrates a time-dependent induced anisotropy proportional to doping when magnetically annealed to low temperatures. The kinetics and temperature dependence of this induced anisotropy have been studied. It is further found that these doped garnets show a constant, high-field component of rotational hysteresis which is both frequency- and temperature-dependent.

The intrinsic, unannealed anisotropy behaves in a novel way. At room temperature the anisotropy coincides with normal YIG, while between 150°K and 300°K | K1 | increases above that of pure YIG Below about 150°K the curves develop asymmetry and appear to be no longer purely cubic. At 4.2°K the easy axis has shifted to the [100] direction (>3% doping) indicative of a change in sign in K1. Silicon-doped lutetium iron garnet and polycrystalline lutetium iron garnet were found to behave in a similar manner.

The results are interpreted in terms of an electron-diffusion model which enables the Fe2+ ion to effectively wander among four nonequivalent octahedral sites. A simple kinetic rate theory is at least partially successful in explaining: (1) the time dependence of the torque curves, (2) the rotational hysteresis, and (3) some of the apparent low-temperature deviations from cubic symmetry.
Study of the Different Operating Modes of an Alkaline-Metal-Plasma Machine by Means of Electric Probes
Authors: Felden M. , Haug R. , Schirmann D.
Published: January 2005

This study includes the design of a fully demountable alkaline-metal-plasma machine. The plasma is produced by contact ionization of alkaline metal vapor on a refractory metal emitter. The properties of this plasma depend on three parameters: emitter temperature, cesium vapor pressure, and potential of an electrode which sets the electric boundary conditions for the medium. Three movable probes analyze the plasma. Measurements are made and results are discussed in terms of the parameters. The first part of the study is devoted to a description of the machine and the probes. The second part analyzes its different operating modes. There are two fundamental modes. The first covers the case where collisions are predominant. The second is a flux mode in which interactions are very improbable. The machine permits continuous transition from the first to the second mode. In the transition zone complex phenomena arise. The study is primarily concerned with an examination of the inflection potentials given by the second derivative of the current-voltage characteristics of the probes. Interpretation of this inflection potential will differ greatly from one operating mode to another.
Thermoelectric and Galvanomagnetic Measurements on (Bi2Te3)5(Bi2Se3)1 (Sb2Te3)18
Authors: Schwartz Richard J.
Published: January 2005

The galvanomagnetic parameters ρ123, ρ1111, ρ1133, ρ1131, and ρ1122 have been measured at 77°K for two samples of p-type (Bi2Te3)5(Bi2Se3)1 (Sb2Te3)18 and the results fitted to a six-ellipsoid model similar to that proposed for Bi2Te3. An anomalous rise in the Hall coefficient with temperature and an apparent change in the effective mass ratios are explained by assuming the existence of impurity banding. The thermal conductivity, thermoelectric power, and electrical resistivity were measured over the temperature range from 77° to 300°K.
Reflection and Transmission of Electromagnetic Waves by a Moving Plasma Medium. II. Parallel Polarizations
Authors: Yeh C.
Published: January 2005

The reflection and transmission of electromagnetic waves by a moving dispersive dielectric half-space or slab are investigated theoretically. The dispersive medium is assumed to be a cold plasma medium. Two cases of the movement are considered: (a) the plasma medium moves parallel to the interface; (b) the plasma medium moves perpendicular to the interface. The electric vector of the incident wave is assumed to be polarized in the plane of incident (parallel polarization). Unlike the normal polarization case which was treated earlier, the reflected and transmitted fields for the present case are functions of the velocity of the moving plasma medium for both cases (a) and (b). An illustrative numerical example is given for case (a) at normal incidence.
Hall-Effect Levels Produced in Te-Doped GaAs Crystals by Cu Diffusion
Authors: Fuller C. S. , Wolfstirn K. B. , Allison H. W.
Published: January 2005

Hall-effect measurements have been made on Te-doped GaAs crystals diffused with known amounts of 64Cu sufficient to convert the crystals to p-type. Energy levels are found above the valence band at 0.123±0.005 eV, 0.145±0.005 eV, 0.166±0.005 eV, 0.19±0.005 eV, and 0.43±0.01 eV. An analysis of the Hall data has been made by means of computer programs. The results may be summarized as follows: (1) Ga vacancies produced during the Cu diffusion associate with and neutralize Te as a compensating center. (2) The ionization energy of the TeCuGa pair is 0.19 eV rather than 0.166 eV as suggested previously.
Experimental Aspects of Tunneling in Metal-Semiconductor Barriers
Authors: Conley J. W. , Tiemann J. J.
Published: January 2005

The electrical characteristics of diodes made from degenerate n-type Ge with either Au or In as the metallic element are reported. The results support a previously published calculation [Phys. Rev. 150, 466 (1966)]. It is significant that the observation can be interpreted quantitatively. Data are presented in terms of the dependence of incremental resistance dv/di or conductance di/dv on applied voltage. Maxima in the incremental resistance predicted to occur at an applied voltage which corresponds to the Fermi degeneracy of the n-type Ge are observed. Data for several values of impurity, density, and temperature are shown to correspond quantitatively with the prediction. However, evidence suggests the importance of band tailing, a feature not included in the calculation. Observation of several additional effects is also reported. Pronounced structure near zero bias appears when the metallic element is in the superconducting state. This is well described by the BCS theory. The threshold for tunneling into the conduction-band minimum Γ2′ was also observed. From this the separation in energy with respect to the L-band minima is determined to be Γ2′−L=0.154±0.003 eV. Anomalous structure at zero bias similar to that observed by others in p-n junctions and metal-oxide-metal structures is reported but not interpreted.
Thermal Properties of Armco Iron
Authors: Shanks H. R. , Klein A. H. , Danielson G. C.
Published: January 2005

The thermal diffusivity and specific heat of Armco iron are reported in the temperature range of 25° to 1000°C. Electrical-resistivity values are reported from −272° to 1000°C. The thermal-diffusivity values as measured by several different methods on the same material are compared. The thermal conductivity is calculated from the thermal diffusivity and specific heat and compared with values reported from direct measurements by other investigators. These measurements were carried out as a contribution to a cooperative program for the characterization of Armco iron as a high-temperature thermal-conductivity standard. Armco iron appears to be a satisfactory thermal-conductivity standard, with an error of 2% or less, from 25° to 700°C; above 700°C the thermal history of the iron sample becomes important and iron is less satisfactory as a standard. Reproducible values above 700°C may still be obtained, but only if the sample has had adequate heat treatment.
Oriented Growth of Semiconductors. V. Surface Features and Twins in Epitaxial Gallium Arsenide
Authors: Holloway H. , Bobb L. C.
Published: January 2005

A study has been made of hillock-like features which sometimes occur on {1, 0, 0} surfaces of epitaxial gallium arsenide. X-ray diffraction topography reveals that the hillocks contain cores of twin which originate at, or near, the epitaxial interface. During growth of the layer the twins can become buried, leaving a surface which is matrix-oriented.
The Absorption of X-Rays by Aluminum at 0.278 keV
Authors: Singer S.
Published: January 2005

We report here measurements which indicate that at 0.278 keV the extrapolated aluminum mass absorption coefficient (24 500 cm2/g) is too small, and that a better value lies in the range 36 000–43 000 cm2/g. This result is consistent with recently reported measurements at higher energies, which indicate that early values of ultra-soft x-ray absorption coefficients were too low.
Spherically Symmetrical Diffusion-Controlled Growth or Dissolution of a Sphere
Authors: Cable M. , Evans D. J.
Published: January 2005

The differential equations describing diffusion-controlled growth or dissolution of an isolated sphere in an infinite body of liquid have been solved numerically assuming constant interface concentration, constant diffusivity, and constant partial specific volume. The results for dissolving spheres are presented in a way which allows change of size with time to be interpolated for wide ranges of values of the two characteristic parameters. The results for growing spheres are compared with the analytical results for growth from zero initial size.
Magnetic Behavior of a Eutectic Alloy Featuring an Aligned Array of Iron Rods
Authors: Albright D. L. , Conard G. P. , Kraft R. W.
Published: January 2005

As-cast and controlled-solidification structures have been produced in the Fe-FeS eutectic. The latter structure consists of an aligned parallel array of Fe rods approximately 2 μ in diameter embedded in and separated by a matrix of FeS. These rods grow with an [001] fiber texture such that the [001] direction coincides with the long direction of the Fe particles. Magnetization and torque results reveal distinct differences between the two structures. The magnetic properties that were determined for the eutectic alloy are interpreted with regard to the multidomain structure of the Fe particles and the relative contributions of the shape anisotropy and crystal anisotropy present in the Fe phase of the solidification structures.
Grüneisen Tensor for Anisotropic Materials
Authors: Key Samuel W.
Published: January 2005

The Grüneisen parameter has been defined as the pressure response in a material to a change in internal energy with the strains held constant. The Grüneisen parameter does not account for the oriented response of anisotropic materials; the Grüneisen tensor is developed to account for this response. The Grüneisen tensor is stated explicitly for several crystal classes. Alpha-quartz is considered as an example of an anisotropic material, and specific values for its Grüneisen tensor are presented.
Theory of Friction Based on Brittle Fracture
Authors: Byerlee James D.
Published: January 2005

A theory of friction is presented that may be more applicable to geologic materials than the classic Bowden and Tabor theory. In the model, surfaces touch at the peaks of asperities and sliding occurs when the asperities fail by brittle fracture. The coefficient of friction, μ, was calculated from the strength of asperities of certain ideal shapes; for cone-shaped asperities, μ is about 0.1 and for wedge-shaped asperities, μ is about 0.15. For actual situations which seem close to the ideal model, observed μ was found to be very close to 0.1, even for materials such as quartz and calcite with widely differing strengths. If surface forces are present, the theory predicts that μ should decrease with load and that it should be higher in a vacuum than in air. In the presence of a fluid film between sliding surfaces, μ should depend on the area of the surfaces in contact. Both effects are observed. The character of wear particles produced during sliding and the way in which μ depends on normal load, roughness, and environment lend further support to the model of friction presented here.
Noise of a Self-Sustaining Avalanche Discharge in Silicon: Low-Frequency Noise Studies
Authors: Haitz Roland H.
Published: January 2005

The noise theory for a self-sustaining avalanche discharge, which was published recently by Hines, is verified experimentally for low frequencies. It was found, in general, that the open-circuit spectral voltage density, 〈u2〉Av/Δf, arises from three contributions: (1) the inherent avalanche noise calculated by Hines and given by 〈u02〉Av/Δf = a2Vb2/I, where a2=3.3×10−20 A/Hz, Vb = breakdown voltage and I = avalanche current; (2) excess noise at low current densities caused by nonuniformities of avalanche breakdown (even in microplasma-free diodes); and (3) excess noise at high current densities which seems to be caused by thermal effects. The temperature dependence of the noise is entirely due to the two excess-noise contributions. The experimental results are discussed with respect to their application in the design of noise generators, low-noise and low-current avalanche diodes, microwave oscillators, and negative-resistance amplifiers.
Paramagnetic Behavior of Nickel-Rich Nickel-Chromium Alloys
Authors: Arajs Sigurds
Published: January 2005

Magnetic susceptibility of nickel-chromium alloys, containing 2.2, 5.6, 7.8, 11.2, 13.3, 16.6, 22.0, and 25.0 at. % chromium, have been studied up to 1500°K. Our data do not exhibit any anomalies of the type observed recently by Chechernikov and Pop from which they inferred the existence of antiferromagnetism in the nickel-rich nickel-chromium solid solutions. In this respect the present measurements are in satisfactory agreement with the older studies by Manders. Small irregularities are observed in the inverse magnetic susceptibility vs temperature curves for 16.6, 22.0, and 25.0 at. % chromium samples. The origin of these observations is not clearly understood but, likely, results from the existence of Ni2Cr phase in these alloys.
Current Transport and Maximum Dielectric Strength of Silicon Nitride Films
Authors: Sze S. M.
Published: January 2005

Measurements of current-voltage characteristics have been performed on Au-Si3N4-Mo and Au-Si3N4-Si (degenerate substrate) structures of various nitride-film thicknesses from 300 Å to 3000 Å and over a range of temperatures. The films are deposited by the process of reaction of SiCl4 with NH3. It is found that at any given temperature and electric field, the current transport is essentially independent of the substrate material, the film thickness, or the polarity of the electrodes.

It is proposed that the current-transport mechanisms are bulk controlled rather than electrode controlled. The conduction-current density, J, is the sum of three contributions: J = J1+J2+J3, where J1∼E exp {−q[φ1 − (qE/πε0εd)½]/ kT}, J2∼E2 exp (−E2/E), and J3∼E exp (−qφ3/kT). At high fields and high temperatures J1 dominates the current conduction (the Poole-Frenkel effect or internal Schottky effect); one obtains a barrier height of (1.3±0.2) V for φ1 and a value of 5.5±1 for the dynamic dielectric constant εd. At high fields and low temperatures J2 dominates as a result of field ionization of trapped electrons (presumably from the same centers as for J1) into the conduction band; one obtains a value for the field E2 of the order of 6×107 V/cm. At low fields and moderate temperatures J3 dominates because of the hopping of thermally excited electrons from one isolated state to another yielding Ohmic characteristics and a thermal-activation energy qφ3 of about 0.1 eV.

At low temperatures the maximum dielectric strength approached ∼107 V/cm. At high temperatures where J1 dominates the current conduction, the maximum dielectric strength, which is limited by thermal instability, decreases as (φ1 − CT)2, where C is a function of the thermal conductivity of the nitride films.
Mass-Spectrometric Study of Sputtering of Single Crystals of GaAs by Low-Energy A Ions
Authors: Comas James , Cooper C. Burleigh
Published: January 2005

Single crystals of GaAs [(110), (111), and (1̄1̄1̄) faces] were sputtered by normally incident low-energy (0–140 eV) argon ions in the source of a mass spectrometer. For each face, approximately 99.4% of the collected ions were neutral Ga and As atomic species; the balance were neutral GaAs molecules. No neutral Ga2, As2 or (GaAs)2 molecules, or negative Ga−, As−, or (GaAs)− ions, with the characteristics of sputtered particles, were detected. Sputtering ``yields'' for the three faces were found to be: ``Y'' (111) ≈ ``Y'' (1̄1̄1̄) > ``Y'' (110).
The Deposition of Atoms Sputtered in an Abnormal Glow Discharge
Authors: Mase H. , Nakaya S. , Hatta Y.
Published: January 2005

Using an optical-transmission method, the deposition of sputtered Ni atoms on a glass collector in an abnormal glow discharge is measured in Ar and Ar-H2 mixture at 5 Torr. The distribution of atoms deposited on a glass collector is found to be determined by the diffusion process of sputtered atoms in the gases. The results show that the sputtering rate is proportional to the square of the current, and the sputtering rate of 100% Ar is about twice as large as that of 70% Ar-30% H2 mixture.
Maximum-Emission Principle and Phase Locking in Multimode Lasers
Authors: Tang C. L. , Statz H.
Published: January 2005

In this paper the phase relationships between self-locked modes in lasers are investigated. The calculations are based on a self-consistency condition. The electric field in the cavity produces in the medium nonlinear polarization terms. These polarization terms may then be considered acting as source terms onto which the mode oscillations lock. The self-consistency condition imposed on the phases arises from the fact that the phase-locked modes must reproduce the originally assumed electric field. We find the calculated phase relationships in essential agreement with earlier predictions based on the maximum-emission principle. The latter principle assumes that the phase relations which maximize the total rate of-stimulated emission should grow most rapidly and should be the ones that establish themselves in lasers. The present paper gives additional evidence for the validity of the maximum-emission principle. In either calculation the basic physical mechanism that is responsible for the phase-locking effect is the nonlinear saturation in the laser medium or some saturable absorber.
Sputtering Experiments with 1- to 5-keV Ar+ Ions. II. Monocrystalline Targets of Al, Cu, and Au
Authors: Robinson Mark T. , Southern A. L.
Published: January 2005

Sputtering yields have been measured during normally incident 1- to 5-keV Ar+ ion irradiation of polycrystalline Au, 〈100〉, 〈110〉, and 〈111〉 Au monocrystals, a 〈111〉 Al monocrystal, and several 〈0kl〉 Cu monocrystals of previously unreported orientations. Onderdelinden's transparency model is found to account satisfactorily for the orientation dependence of the yields of low-index Cu, Au, and Ge crystals. The importance of the recording geometry in governing the appearance of sputtering ejection patterns is demonstrated. The so-called 〈114〉 ejection-pattern spots from 〈111〉 fcc crystals are attributed to assisted focusing sequences along 〈100〉, the most probable ejection direction being shifted because the last focusing ``lens'' is incomplete.
Twinning in Zinc by Indentation
Authors: Yoo Man Hyong , Wei Chuan-Tseng
Published: January 2005

The nucleation and the growth of the {101̄2} 〈101̄1̄〉 type twins in zinc single crystals have been investigated by applying concentrated loads in the [0001̄] direction and on the (0001) surface of such crystals with point indenters as a mechanical means of stress concentration. Assuming the crystals to be a semi-infinite anisotropic elastic medium, the resolved shear stress for the twins to grow is calculated to be 130±50 g/mm2.
Electron Flow in Low-Density Argon Gas Including Space-Charge and Elastic Collisions
Authors: Goldstein Charles M.
Published: January 2005

The characteristics of one-dimensional electron diode with low-pressure argon scattering gas are analyzed by a Monte Carlo method. Experimentally determined differential elastic scattering cross sections, extra-polated to zero energy, are employed. Current-voltage characteristics are compared with those obtained from a hard-sphere collision model. Negative resistance is found for low emission current densities and low pressure as a result of the Ramsauer cross section. The randomization of energy between velocity components is found to be quite large for accelerating potentials and pressure-electrode separation values as low as ½ Torr·cm. The energy dependence of total cross section has a more pronounced effect on the current-voltage curves than nonisotropic scattering.
Anomalous Behavior of the Shear-Sound Velocity under Pressure for Polycrystalline ZnO
Authors: Soga Naohiro , Anderson Orson L.
Published: January 2005

The sound velocities, bulk modulus, and their pressure and temperature derivatives have been measured on a polycrystalline ZnO by means of a pulse-superposition method. The pressure derivatives found from the experiments up to 3 kbar at 25°C are: (dv1/dP)=3.643×10−3 km/sec·kbar, (dvt/dP)=−3.193×10−3 km/sec·kbar, and (dBs/dP)=4.78. The negative value of (dvt/dP) for ZnO is anomalous for crystalline solids. No anomalous behavior was observed in the temperature derivatives near 25°C. They are (dv1/dT)=−1.871×10−4 km/sec·deg, (dvt/dT)=−0.392×10−4 km/sec·deg, and (dBs/dT)=−0.129 kbar/deg. The Grüneisen constant was calculated from the present pressure derivatives of elastic constants and was found to be negative, whereas the value calculated from the thermal-expansion data at 25°C is positive. This result seems to indicate that the thermal expansivity of ZnO may be negative at very low temperatures.
The Strain-Energy Function of a Hyperelastic Material in Terms of the Extension Ratios
Authors: Valanis K. C. , Landel R. F.
Published: January 2005

A simple form of the strain-energy function of natural rubber results if the latter is expressed an an analytic function of the extension ratios rather than the invariants. For incompressible isotropic materials it is postulated that this is a separable symmetric function of the extension ratios, i.e., W = w(λ1) + w(λ2) + w(λ3). This form has been substantiated by critical plots using uniaxial and biaxial data reported in the literature by several investigators. The above form appears to be valid over a wide range of deformations (0.2≤λ≤3.5). An explicit representation of W for this range is given in graphical form. In the more limited range (0.6≤λ≤2.5) w(λ) has the analytic form w=2 μλ (lnλ−1).
Electromagnetic Waves in Longitudinally Magnetized Ferrite Rods
Authors: Schott F. W. , Tao T. F. , Freibrun R. A.
Published: January 2005

Propagation modes for electromagnetic waves in circular ferrite rods magnetized along the axis can be computed exactly by well-known and straightforward procedures; however, three parameters must be specified to define a mode family in the normalized frequency vs axial wavenumber (ω — β) plane. The magnetostatic approximation requires but one parameter, the saturation magnetization normalized with respect to the dc magnetizing field, 4πM0/H0, and thus allows the whole range of solutions to be readily visualized and simply portrayed. The transition from the exact solution to the magnetostatic limit has not been previously studied and is the primary object of these investigations. At the same time it has been found helpful to classify the exact solutions and to suggest an appropriate terminology. Numerical computations have been made and compared with magnetostatic calculations and with other results.
Effect of Background-Gas Impurities on the Formation of Sputtered β-Tantalum Films
Authors: Sosniak J. , Polito W. J. , Rozgonyi G. A.
Published: January 2005

The effect of the gas background in argon glow discharges on the structure of sputtered tantalum films has been studied. The films were deposited in a 240-liter chamber of a conventional oil-diffusion pump system, and in 2-liter chambers of two sputter-ion ultrahigh-vacuum systems. Initial vacua before static sputtering ranged from 1.5×10−10 Torr to 2×10−7 Torr. The gas background generated by the desorption effect of the glow discharge was minimized by presputtering periods of varying duration. The films were found to be mostly beta tantalum, with varying contents of bcc tantalum. The results indicate that the appearance of beta tantalum depends on the substrate temperature, and that the formation of beta tantalum and its resistivity are independent of the gas-background impurities in deposition systems with ultimate pressures between ∼10−10 and ∼10−7 Torr.
Optical Constants of β-Phase NiAl
Authors: Rechtien J. J. , Kannewurf C. R. , Brittain J. O.
Published: January 2005

The optical constants of nine compounds of NiAl ranging in composition from 45.2 at.% Ni to 61.6 at.% Ni have been determined between 0.212 and 1.80 μ. Measurements of the ratio of the reflectance of light polarized parallel to the plane of incidence to the reflectance of light polarized perpendicular to the plane of incidence were made at the following five angles of incidence: 55°, 60°, 65°, 70°, 75°. Data were analyzed by a computerized interation technique to provide values of the high-frequency dielectric constants and the electrical conductivity. Since the measurements were made on mechanically polished surfaces, two annealing experiments were performed to ascertain the effects of surface disturbance; the results showed that the optical properties were essentially unaffected by the annealing treatments. Plots of 2nk show absorption bands at ≈1.5 to 2, 2.5, 4.0, and 5.1 eV and what may be interpreted as free-electron behavior below 1.5 eV. The energy-band structure shows a strong compositional dependence which has been interpreted to be the result of contact between the Fermi surface and a Brillouin-zone boundary.
Diffusional Properties of the Stage-III Defect in Copper. I. Experimental Results
Authors: Thompson D. O. , Buck O. , Barnes R. S. , Huntington H. B.
Published: January 2005

Measurements of the effects of 60Co γ-ray irradiation have been made upon the dislocation internal friction and modulus defect in copper single crystals from 333° to 393°K. It is found that the number of pinning points which are nucleated on the in-grown dislocations by the lattice defects produced by the irradiation depends upon the γ-ray flux, or more directly, upon the concentration of defects in the dislocation core. At the smallest flux level available (1.3×109 photons/cm2/sec), it is found that the dislocation-defect trapping curves are essentially linear, and that the slopes of the linear curves vary exponentially with temperature. These results form the basis of the analyses given in Parts II and III of this series.
Diffusional Properties of the Stage-III Defect in Copper. II. A Model for Defect-Dislocation Interactions
Authors: Thompson D. O. , Buck O. , Huntington H. B. , Barnes P. S.
Published: January 2005

Using the experimental results given in Part I as a guide, a linear model is developed in this Part which describes the interaction of a lattice defect and a dislocation. It is supposed in this model that the defect is free to diffuse between existing (or in-grown) traps such as jogs or dislocation nodal points, and that if the defect is trapped, dislocation climb follows. From a comparison of the results given in Part I and the predictions of the model, values for the ``pipeline'' diffusivity and the strength of the binding of the defects to the in-grown nodal points may be obtained. The numbers so obtained are consistent with values evolved from other techniques for studying atom motions. An estimate for diffusional jog-pair energies is also given.
Diffusional Properties of the Stage-III Defect in Copper. III. Bulk Diffusion
Authors: Thompson D. O. , Buck O.
Published: January 2005

An analysis of the bulk diffusion properties of the stage-III defect is given utilizing the experimental results presented in Part I. It is found that the motion energy of the defect is 0.64±0.03 eV and, in addition, it is shown that this is a true motion energy and not a defect-impurity-atom binding energy. After consideration of the extremely small lattice-defect concentrations used (≤10−12), available information concerning single-vacancy motion energies, and the simple-defect spectrum produced by the γ irradiation, it is concluded that the stage-III defect can only be identified as a freely migrating interstitial atom.
Thermal Diffusivity of Platinum from 300° to 1200°K
Authors: Martin J. J. , Sidles P. H. , Danielson G. C.
Published: January 2005

The thermal diffusivity of five platinum samples with resistivity ratios of 12, 34, 100, 900, and 5000 has been measured from 300° to 1200°K. Only the sample with the resistivity ratio of 12 showed deviations of more than 3% from the average thermal diffusivity of the two purest samples. Thermal conductivity values have been calculated from these results and compared with the results of other investigators. At room temperature most results are in good agreement, but at high temperatures the agreement among different investigators is unsatisfactory. The data from our purest samples indicate that platinum would be suitable for a thermal conductivity standard, but additional measurements should be made by other absolute methods.
Crystal Structure and Stacking Disorder of ZnS Single Crystals Grown from the Melt
Authors: Ebina Atsuko , Takahashi Tadashi
Published: January 2005

The crystal structure of ZnS single crystals grown from melt has been found to be cubic zinc blende by the x-ray analysis of oscillation photographs. However, the x-ray 〈111〉 axis oscillation patterns of the crystals synthesized by various methods are symmetric about the equator line and some spots are elongated along c*, whereas the patterns of natural crystals are asymmetric and sharp. Therefore, it is concluded that the synthetic ZnS crystal contains a considerable amount of stacking disorder in the close-packed planes due to growth faults which result in two orientations in the crystal structure (twin orientations) that repeat with a relatively short periodicity. The value of fault probability occurring in the (111) plane can be obtained by superimposing the observed diffuse diffraction spectra with the ones calculated numerically by a formula proposed by Paterson for the growth fault. This value is also compared with that obtained from the transmission electron micrographs.
Yield Behavior of Dislocation-Free Germanium from 500°C to the Vicinity of the Melting Point
Authors: Patel J. R. , Freeland P. E.
Published: January 2005

The yield behavior of dislocation-free germanium has been measured over its entire plastic range. Crystals of germanium were stressed in tension from 500°C, where the crystals first deform without fracture, to 930°C (7°C below the melting point). Over this entire range a pronounced yield drop is observed. The shapes of the stress-strain curves at the highest and lowest test temperatures are remarkably similar even though the magnitudes differ by about a factor of 40. Both the maximum and flow stresses decrease exponentially with temperature and follow a relation of the form τ = A exp (E/kT). The maximum and flow stresses also were measured at constant temperature over two orders of magnitude change in strain rate. The results are compared with the theoretical predictions of the temperature and strain-rate dependence of the maximum and flow stresses.
Reduction of the Susceptibility to Optically Induced Index Inhomogeneities in LiTaO3 and LiNbO3
Authors: Levinstein H. J. , Ballman A. A. , Denton R. T. , Ashkin A. , Dziedzic J. M.
Published: January 2005

It has been established that LiTaO3 can be made resistant to laser-induced inhomogeneities in the index of refraction at power levels as high as 500 W/cm2. This is accomplished by annealing LiTaO3 in an electric field of 250 V/cm at a temperature of 700°C for ½ h and then cooling the crystal to room temperature with the field on at a rate of 100°C/h. The susceptibility to laser-induced index changes in LiNbO3 is reduced by this treatment but not to the same extent as in LiTaO3. A mechanism is proposed to explain the observed reduction in susceptibility to damage.
Repeated Cold Drawing and Annealing of Polypropylene
Authors: Crystal Richard G. , Hansen David
Published: January 2005

Samples of polypropylene were cold drawn to a maximum extension of five times their original length and then annealed, under no load, at 160°C. Eighty percent of the extension was recovered on annealing. Samples were then redrawn and annealed again repeating the procedure through five drawing cycles. While the first drawing proceeded by neck formation and propagation, subsequent drawings were homogeneous. One hundred percent of the extension in the second and subsequent cold drawings was recovered on annealing. In general the polypropylene became more rubbery with each subsequent cold drawing in the sense that less of the drawing extension was retained after removing the drawing load and the modulus of drawn material decreased while its elastic extensibility increased. Micrographs of sections cut from the polypropylene showed a spherulite structure which was retained throughout the drawing and annealing. After several cycles a distinct Maltese-cross pattern was seen when viewing the sections between crossed polars. Such a pattern is not generally seen with polypropylene spherulites.
Sheet-Resistance Measurement on a Sample with a Circular Hole or on a Circular Sample
Authors: Hall P. M. , Koo J. T.
Published: January 2005

This paper contains calculations of (a) the effect of a circular hole on sheet-resistance readings as measured by a four-point probe; (b) a solution to the generalized four-point probe measurement on a thin circular disk, regardless of the shape, position, and orientation of the probe. The first analysis is intended to aid in the estimation of the effect of pinholes in thin films, and also in certain thin-film circuits where holes have been deliberately made in the substrates. The greatest effect on a linear and evenly spaced four-point probe is found when a hole is just touching one of the potential probes. It is shown that an effect of up to +100% or −40% can result from a hole whose diameter equals the probe spacing, depending upon its position relative to the probes. Analytical expressions are developed for several limiting cases, including that of a straight-edge boundary, in which case the results coincide with earlier work. The second analysis can be used to calculate the sheet resistance of a thin semiconductor wafer, and to evaluate its uniformity. For certain special cases, the present analysis coincides with results obtained elsewhere.