bluuebunny/crossref_metadata_2025 huggingface dataset:
Energy transfer processes in YVO4:Nd3+
Authors: Sardar Dhiraj , Powell Richard C.
Published: February 2003

Laser-excited, time-resolved spectroscopy techniques were used to investigate the characteristics of energy transfer in YVO4:Nd3+ crystals. The temperatuare and time dependencies of the energy transfer rates were determined for both host-sensitized and impurity ion interaction processes. The former process is found to have characteristics consistent with the migration and trapping of localized host excitons whereas the latter process is consistent with multistep energy migration via a two-phonon-assisted electric dipole-dipole interaction mechanism.
Saturation characteristics of p-type semiconductors over the CO2 laser spectrum
Authors: James R. B. , Smith D. L.
Published: February 2003

We present the results of a theory describing the saturation behavior of p-type GaSb, AlAs, AlSb, and InAs for light having a wavelength near 10.6 μm. The dominant absorption mechanism is direct intervalence band transitions where a free hole in the heavy-hole band absorbs a photon and makes a transition to the light-hole band. The decrease in the absorption coefficient with increasing intensity is found to be closely approximated by an inhomogeneously broadened two-level model, and values of the saturation intensity are reported for each material. We analyze the systematic dependence of the saturation intensity on the material parameters. We also report the temperature dependence of the saturation intensity near room temperature.
Monte Carlo calculation approach to quantitative Auger electron spectroscopy
Authors: Ichimura Shingo , Aratama Mikio , Shimizu Ryuichi
Published: February 2003

A Monte Carlo calculation technique based on both the partial wave expansion method for elastic scattering and Krefting and Reimer’s treatment for inelastic scattering was applied for quantitative study by Auger electron spectroscopy. The theory has described the experiment of energy and angular distributions of backscattered electrons with considerable success. Dependence of the Auger signal generation on primary electron energy was investigated with a scanning Auger electron microscope, and the result was compared with the theory for a number of elements of practical interest. Through this, we have found that the present Monte Carlo approach allows us to evaluate contributions of backscattered electrons to Auger signal generation leading to more comprehensive quantitative AES study.
An analytical formula and important parameters for low-energy ion sputtering
Authors: Bohdansky J. , Roth J. , Bay H. L.
Published: February 2003

Sputtering yields for different ions and materials at low ion energies have a similar energy dependence. Due to this similarity, yield data can be characterized by a normalized energy function and two parameters for each ion target combination. One of these parameters is the threshold energy. An energy scaling can be based on this parameter. The other parameter is a multiplication factor. Both parameters depend mainly on the ion and target mass M1 and M2 and on the surface binding energy EB. An analytic expression for the normalized functions and both the parameters is given. This empirical relation also allows an estimate of unknown sputtering data, if M1, M2, and EB are noted. A physical interpretation of the empirical relation is given for the case M1≪M2, as in this case special collision processes which dominate the sputtering can be identified.
The effect of carrier diffusion on laser heating of lightly damaged semiconductors
Authors: Wilcox Jaroslava Z.
Published: February 2003

It has been observed that the surface temperature obtained during laser heating of lightly damaged material is generally considerably lower than the temperature obtained in heavily damaged material. We develop a model which explains this observation by taking into acount the diffusion of the photoexcited carriers. The time evolution of temperature profiles was calculated for pulsed ruby and Nd : YAG illumination of silicon and ruby illumination of GaAs. The material, optical, and electronic properties were varied, according to the material quality. Surface recombination of the carriers was also taken into account. For the same laser power, the induced temperature was lower and the heating times were longer in good-quality materials than in heavily damaged materials. This is because of longer carrier difusion lengths in good-quality material. The effect of the damage on the heating was found to be much more pronounced for Nd : YAG than for ruby irradiation because a larger portion of the ruby laser energy (excess above band gap) is given rapidly to the lattice through quasithermalization inside the semiconductor energy bands. Thermal spikes are formed as the result of the preferential recombination of the carriers at the surface. For a sufficiently fast surface recombination, the temperature profile may develop a secondary maximum in the material interior.
Experimental study of impregnated-cathode behavior, emission, and life
Authors: Palluel P. , Shroff A. M.
Published: February 2003

The evolution of the electron emission of impregnated cathodes has been measured over many thousands of hours of operation at various temperatures in diodes and traveling-wave tubes. Certain physical methods were used to investigate the correlation between these results and the mechanisms of cathode operation: X-ray fluorescence electron microprobe analysis has given a new access to the study of the consumption of the active materials (barium and calcium) at various stages of cathode life. While barium depletes according to the t1/2 law, an approximate t1/3 law found for calcium could result from a two-step process in the barium and calcium chemistry. The formation and desorption of synthetized emissive layers on a nonimpregnated porous tungsten plug in a Becker-type test diode is one way to investigate the properties of emissive surfaces. The behavior of layers synthetized at low temperatures onto active impregnated cathodes suggests a surface equilibrium depending on the chemical nature of the substrate. Emission charts are proposed to compare, over a large range of temperatures, the different types of cathodes, in particular, the characteristics of uncoated and coated ones.
Rhenium film preparation by laser melting
Authors: Takei Koji , Fujimori Susumu , Nagai Kazutoshi
Published: February 2003

A laser melting method for preparing rhenium films on permalloy substrates is proposed. Main processes of the method include melting of pressed rhenium powders on substrates by a pulsed Nd-YAG laser beam to form around 30-μm-thick rhenium films, tightly bound to the substrates. Optimum conditions for the film preparation are investigated by computer simulation and experiments. Changes in density and thermal conductivity of a powder layer at the melting temperature are introduced in the simulation. It is demonstrated that, by using this method, high melting point films can be prepared on low melting point substrates.
The effect of added acetylene on the rf discharge chemistry of C2F6. A mechanistic model for fluorocarbon plasmas
Authors: Truesdale E. A. , Smolinsky G. , Mayer T. M.
Published: February 2003

The effect of added acetylene on the rf discharge chemistry of C2F6 was studied as a function of acetylene concentration. The principle products are HF, CF4, CHF3, C2F4, and CF2 as determined by mass spectrometry. Under conditions typically used for etching SiO2, residence time and power density control the amount of conversion of feed gas to products. Large amounts of polymeric material, with composition (CF)n, are formed in the discharge zone. A chemical model for flourocarbon discharges is proposed, which assumes an equilibrium between dissociation and recombination of flourocarbon fragments and flourine atoms. Polymerization and selective etching of Si and SiO2 in flourocarbon dishcarges containing oxygen or hydrogen additives is interpreted in terms of the proposed model.
An analytical model of a backwall MIS Schottky barrier solar cell
Authors: Krauter B. L. , Soukup R. J.
Published: February 2003

An investigation of the backwall MIS Schottky barrier solar cell model was made. This model incorporates the following factors which, for the most part, determine the behavior of the device: the short circuit current density, the MIS Schottky barrier junction behavior, and resistive losses. The study concentrated on the Al-Al2O3-GaAs-metal structure. Practical energy conversion efficiencies are predicted for this structure for a variety of semiconductor properties ranging from best- to worst-case conditions. Reflection losses are ignored assuming that the proper antireflective coating will minimize these losses. The study of the short circuit current density indicates that the structure must be that of a thin-film semiconductor with maximum current occurring when the GaAs thickness is in the 500-Å to 1.2-μm range, depending on minority carrier diffusion length and surface recombination velocity. The behavior of the Al-Al2O3-GaAs Schottky barrier junction yields an optimum open circuit voltage for an Al2O3 thickness of about 15 Å. The resistive loss study considered both the metal ohmic contact grid structure and the semiconductor resistivity. Conversion efficiencies as high as 6% are predicted for this structure with rather poor electrical properties of the GaAs films, i.e., μn =10 cm2/V sec, μp =1 cm2/V sec, and an infinite surface recombination velocity. Thus, if care is taken in the design and fabrication of a backwall MIS Schottky barrier solar cell, reasonable efficiencies can be achieved even if the semiconductor has poor electrical properties, as expected for a polycrystalline film.
A model of a uniform-temperature thermionic generator
Authors: Suknarowski S.
Published: February 2003

A system generating electromotive force in isothermic conditions has been described. The effect appears against the background of thermionic emission obtained from a couple of electrodes working in a magnetic field.
Electrical properties of proton and deuterium ion implanted n-type GaAs
Authors: Harrison H. B. , Martin A. L.
Published: February 2003

Carrier removal in n-type GaAs induced by proton and deuterium bombardment has been investigated using capacitance-voltage profiling techniques. It is shown that deuterium offers advantages over hydrogen implantation, that ’’cold’’ (30 K) implants are superior to room temperature implants, and that carrier removal depth appears to be dose dependent, or dose and dose rate dependent.
Conversion of two ordinary EM waves into an extraordinary wave in a collisionless magnetoplasma
Authors: Sodha M. S. , Singh Tarsem , Sharma R. P.
Published: February 2003

This paper presents the investigation of the partial conversion of two ordinary EM waves of frequencies ω1 and ω2 into an extraordinary wave at the difference frequency ω1∼ω2 in a collisionless hot magnetoplasma. The effect of changing the strength of the static magnetic field is to modify the ratio of the electrostatic and EM parts of the extraordinary wave being generated.
Diffraction efficiency of the curved-crystal spectrograph
Authors: Brown D. B. , Fatemi M.
Published: February 2003

A method for calculating the diffracting efficiency of the convex curved-crystal spectrograph is presented. Experimental data and calculated values are given for elastically curved potassium acid phthalate (KAP) and plastically curved LiF. The calculation method accounts for extinction and anomalous scattering effects. The principal area of application is expected to be diagnostics of the x radiation emitted by hot plasmas.
Alignment of liquid crystals on obliquely evaporated silicon oxide films
Authors: Armitage David
Published: February 2003

Liquid crystal alignment on thin films obliquely deposited by electron beam evaporation of SiO2 is reported. Films deposited at a glancing angle of 5° give high tilt alignment ?45°, while increasing the deposition angle to 30° gives zero tilt alignment. Scanning electron microscope (SEM) pictures relate surface topography to alignment. The material and temperature dependence of tilt are reported. The tilt is constant through the nematic-smectic A transition.
Effect of radiation on the physical properties of borosilicate glasses
Authors: Shelby J. E.
Published: February 2003

The effect of gamma ray irradiation on the density, refractive index, thermal expansion, and helium permeability of a variety of commercial borosilicate glasses has been measured for doses between 108 and 1011 rad. The radiation-induced densification of these glasses for a constant dose can vary by as much as factor of 30 and appears to increase with increasing boron content of the glass. The refractive index also increases with dose and appears to be related to the change in density via the Lorentz-Lorenz equation. The thermal expansion coefficient decreases with increasing dose for any given glass, and appears to vary inversely with the density change on a universal plot of change in thermal expansion coefficient versus change in density. Although the helium permeability was only measured for a few of the glasses, it appears that it is unaffected by radiation-induced compaction of the glass. These effects are believed to result from the phase-separated morphology of these glasses and from the less rigid nature of the network of one of these phases.
Si(L
V
V) Auger spectra of amorphous Si-oxide, Si-nitride, and Si-oxinitride
Authors: Hezel R. , Lieske N.
Published: February 2003

For amorphous SiO2 and Si3N4 the Auger spectra were measured and an interpretation of the Si(LVV) spectra is given based upon electron energy-level schemes, derived from electron energy-loss spectroscopy results obtained at the same samples. For Si-nitride the effect of oxygen content (O/N from 0.02 to 1) and Ar+ ion bombardment was studied and it is shown that discrepancies between the spectra of different authors are mainly due to these effects.
Soft x-ray vacuum ultraviolet spectroscopy of thin targets heated by enhanced electron energy deposition
Authors: Burns E. J. T. , Chang J. , Farnsworth A. V. , VanDevender J. P. , Widner M. M. , Goldstein Steven A. , Mendel C. W. , Quintenz J. P. , Doschek G. A.
Published: February 2003

Soft x-ray vacuum ultraviolet spectroscopy (10–600 eV) has been used to study relativistic electron beam energy deposition in 6-μm Au foils mounted in two different anode geometries. Experimentally determined thermal electron temperatures of 173 eV and 306 eV are in agreement with calculations assuming electron energy deposition rates of 5×1013 W/g and 1014 W/g for the two geometries. These results are consistent with electrons multipassing through the thin foils several times.
Constitutive equation for porous materials with strength
Authors: Swegle J. W.
Published: February 2003

A constitutive equation for porous materials capable of supporting deviatoric stresses is described. The model incorporates the deviatoric stresses in a physically consistent manner so that the porosity is a function of the complete stress tensor and such phenomena as shear-enhanced pore compaction may be represented. The constitutive equation is based on the physical concept of a closed yield surface in stress space which varies as the material porosity changes. An example of the application of the model to 22% porous 2024 aluminum is given.
Fixed points for pressure calibration above 100 kbars related to semiconductor-metal transitions
Authors: Onodera Akifumi , Ohtani Akihito
Published: February 2003

Pressures assigned to the semiconductor-metal transitions in ZnTe, ZnS, GaAs, and GaP have been determined by detecting the electrical resistance change of the semiconductors while the lattice parameter of standard material NaCl was simultaneously measured with x-ray diffraction techniques. A pressure vessel of the split-octahedron type and various pressure-transmitting media have been employed. Pressures were estimated according to the equation of state for NaCl proposed by Decker. The transition pressures, 1296 kbars for ZnTe, 1557 kbars for ZnS, 1888 kbars for GaAs, and 25310 kbars for GaP, constitute fixed points for pressure calibration above 100 kbars at room temperature.
Anomalous behavior of the Grüneisen parameter in cerium near the high-pressure phase transition
Authors: Ramakrishnan J. , Kennedy George C.
Published: February 2003

Measurements have been made of the value (∂T/∂P)s as a function of pressure up to 32 kbar, at room temperature (296.7 °K), for cerium through its electronic transition at 7.5 kbar. The thermodynamical Grüneisen parameter is calculated using the thermodynamic relation γth=(Bs/T) (∂T/∂P)s, where Bs is the adiabatic bulk modulus. An anomalous increase of γth in the low-pressure phase and a rapid decrease after the transition are obtained for cerium.
Local moment hyperfine studies of the Kondo system PdHxFe0.003
Authors: Brand R. A. , Georges-Gibert H. , Kovacic C.
Published: February 2003

The effect of hydrogen on the Fe giant moment in dilute PdFe and the resulting single moment Kondo and RKKY interactions in PdHxFe is investigated by Mössbauer hyperfine techniques in an external magnetic field. The results show that within a large range of composition within the α′ phase (hydrogen lattice liquid), μ(Fe) remains constant at about 3.9μB, smaller than the 12.6μB in dilute PdFe. The Kondo temperature TK is found to increase with hydrogen, as determined from the usual X=μH/k(T+ϑ) modification to the Brillouin function B1(X) where ϑ=4.5 TK. The dynamic part of the impurity interactions leads to a spin-glass–type spin-spin relaxation, which produces a line broadening in a magnetic field much larger for the outer Mössbauer lines and with a maximum in field at about X=1. At higher concentrations (x=0.76), the saturation HF field decreases, indicating a possible orbital component on μ(Fe); this conforms with certain recent calculations. Above x=0.8, new Mössbauer lines are found, indicating the phase transitions and two-phase regions α′ → β and β → α″ with increasing hydrogen content.
Average field of a laser beam self-focused in a turbulent plasma
Authors: Sodha M. S. , Patel L. A.
Published: February 2003

This paper presents an investigation on the spatial variation of the average field of a laser beam which is self-focused in a plasma having random fluctuations in its electron concentration. The analysis is valid for the arbitrary mechanism of self-focusing nonlinearity, for nonlinearly absorbing and nonuniform plasmas, and for elliptically Gaussian laser beams. The Novikov-Furutsu formalism has been followed to derive a parabolic equation for the average field, and the Akhmanov approach has been employed to solve this equation. It is concluded that the plasma turbulence tends to reduce the field intensity as the laser beam penetrates further. The self-focusing-induced oscillations of the beamwidth parameters and axial intensity become considerably aperiodic in the presence of turbulence; after a sufficient distance of propagation, an oscillating beamwidth parameter (axial intensity) starts increasing (decreasing) monotonically.
Nuclear-induced excimer fluorescence
Authors: Wilson J. W. , Shapiro A.
Published: February 2003

We consider a theoretical calculation of a proposed atomic iodine laser system excited by a nuclear-powered photon source. Overall system efficiency of 1.6% is calculated for the KrF fluorescent system and 2.3% for the Ar2F system. Laser power output of about 30 kW is estimated for a laser tube 1.8 cm in diameter and 60 cm long when used with a fast burst reactor. Such systems should easily scale to very high power.
Depolarization effects in the active remote sensing of random media
Authors: Zuniga M. , Kong J. A. , Tsang L.
Published: February 2003

Backscattering cross sections for depolarization are derived for the active remote sensing of a two-layer random medium. It is shown that the depolarization effects arise as a second-order term in albedo under the Born approximation. The results of the backscattering cross sections are illustrated as functions of frequency and incident angles and used to match experimental data collected from a vegetation field.
Magnetostatic surface wave propagation in a nonuniform magnetic field
Authors: Awai Ikuo , Ikenoue Jun-ichi
Published: February 2003

The propagation characteristics of MSSW in a YIG film are analyzed ray optically considering magnetic field nonuniformity. Significant oscillation of an energy beam is predicted in an ordinary experimental film of thickness 10 μm. The increase of signal frequency and film thickness makes oscillation stronger, and that of applied field and film width makes it weaker.
Experimental studies of the xenon excimer laser at atmospheric pressures and low e-beam excitation rates
Authors: Campbell J. D. , Center R. E.
Published: February 2003

Laser emission measurements are reported for the e-beam excited, near-atmospheric-pressure xenon excimer laser. The laser efficiency was limited to the order of 0.1% by the termination of the stimulated emission well before the end of the e-beam pulse. The premature turnoff was observed under all operating conditions and was not predicted by a modelling code using the same kinetic processes which accurately described fluorescence from e-beam excited xenon. Broad band transient absorption by the gas medium during e-beam excitation was measured. The magnitude of the absorption was less than that predicted for photoionization of the excimers and hence, did not appear large enough to account for the premature turnoff. Temperature increases in mirror coatings due to absorption of the laser radiation and the resulting decrease in mirror reflectivities may account for the observed laser pulse termination.
A surface spark discharge UV light source
Authors: Watanabe Kazuhiro , Obara Minoru , Fujioka Tomoo
Published: February 2003

We have designed and constructed a surface spark discharge UV light source, using a Teflon resin substrate, as a new UV light source for H2/F2 laser initiation. The measurements of the time-integrated spectral characteristics, the radiative UV energy in the region 2700–3900 A, and the lifetime of the surface spark flash in the actual H2/F2 laser mixtures are presented. The experimental results have indicated that the surface spark flash using Teflon has a promising performance for practical use in H2/F2 laser initiation.
Two-stage pumping of three-level Mössbauer gamma-ray lasers
Authors: Baldwin G. C. , Solem J. C.
Published: February 2003

The possibility of creating population inversions in multiline Mössbauer nuclei by a two-stage process, employing neutron capture to generate resonance radiation that then excites states in a separate region, is investigated. Geometrical and kinetic factors and dependences of the interstage coupling on isomer ratios and Mössbauer parameters are determined. Rate equations for one hypothetical and four actual Mössbauer isotopes are solved in an approximation that overestimates the excitation; nevertheless, it is found that the necessary neutron capture rates are thermodynamically unattainable.
Current-crowded carrier confinement in double-heterostructure lasers
Authors: Joyce W. B.
Published: February 2003

The profiles (spatial distributions) of injected carriers and current within a double-heterostructure stripe-geometry laser are described theoretically in a one-dimensional-flow model. The one-dimensional model is solved exactly and found to yield comparatively simple analytical expresions even when both radiative (nonlinear) and nonradiative recombination are operative. In the case of a shallow proton bombardment or an oxide stripe, two coupled current components leak from under the stripe—an Ohmic current in the P layer and a diffusion current in the active region. As an example, these wasted leakage currents are evaluated in detail and seen to depend strongly upon the laser design. Features of this work not present in previous analytical studies include incorporation of radiative recombination (Bn2) and a carrier-concentration-dependent diffusion coefficient, as well as development of a self-consistent solution for the two current components.
Temperature dependence of threshold current for coupled multiple quantum-well In1−xGax P1−zAsz-InP heterostructure laser diodes
Authors: Rezek E. A. , Holonyak N. , Fuller B. K.
Published: February 2003

Data are presented showing that the threshold current density, Jth (T)∝exp(T/T0), of multiple quantum-well InGaPAs-InP heterostructure laser diodes, grown by LPE, exhibits a two-regime behavior similar to that of conventional InGaPAs-InP double-heterojunction lasers. At temperatures below a break-point temperature characteristic of the quaternary alloy, Jth (T) of these multiple quantum-well laser diodes is less temperature dependent (i.e., larger T0, as high as 150 °C) than that of regular quaternary DH lasers. At temperatures above the break-point temperature, Jth (T) is dominated by a poorly understood competing temperature-dependent nonradiative recombination process. In this range the T0 of these multiple quantum-well diodes is similar to that of ordinary InGaPAs-InP DH diodes but, because of the large number of layers and large lower-temperature T0, is not apt to be caused by defects at heterointerfaces.
Effects of interference on couplings in three optical waveguides
Authors: Tsukada Noriaki , Tsujinishi Ryoko , Nagano Munehiko , Tomishima Kazunaru
Published: February 2003

In the interaction of a coupled, three-optical-waveguide system, it is shown that, even when there is no direct coupling between two phase-matched waveguides, the high-efficiency coupling between them can be established by the indirect coupling through the third phase-mismatched waveguide. It is also shown that the coupling between the two phase-matched waveguides, having direct coupling, can be effectively vanished by introducing the third phase-mismatched waveguide.
Tunable single-sideband generation in the infrared
Authors: Schupita Walter , Magerl Gottfried
Published: February 2003

Tunable single sidebands in the infrared were generated by electro-optically mixing a 14–18-GHz tunable microwave and a fixed-frequency CO2 laser signal, both circularly polarized, in a resonant modulator. With 10 W microwave drive power, a peak single-sideband conversion efficiency of 280 μW/W laser power was achieved. Sideband discrimination was 30 dB throughout the tuning range.
Determination of spatial energy deposition in e-beam-pumped laser cells by pressure measurements
Authors: Eckstrom D. J. , Walker H. C.
Published: February 2003

A significant fraction of the energy deposited by electron beams in gases results in heating of the gas, which causes a transient pressure rise in the cell. When the pressure rise is uniform across the height and length of the cell, but varies across the depth, one-dimensional unsteady flow theory applies. Then a fast-response pressure measurement at the back wall of the cell can be interpreted to give the initial spatial pressure distribution. We describe the relationship between time and space coordinates for both low and medium levels of excitation in the cell. Experiments are discussed which illustrate the application of this technique. Analytical predictions using the SANDYL 3-D electron scattering code show basic agreement with the experimental results, but indicate some areas for improvements in the calculations. Intermediate-response pressure measurements are shown to be inadequate to determine the local deposition when the deposition varies markedly across the cell.
Coefficient of performance for finite speed heat pump
Authors: Blanchard C. H.
Published: February 2003

This paper gives the coefficient of performance for a heat pump operated at minimum input power for given output heat power.
Impact damage thresholds in brittle materials impacted by water drops
Authors: Evans A. G. , Ito Y. M. , Rosenblatt M.
Published: February 2003

The damage threshold for brittle materials impacted by water drops has been studied by using a combination of analytic and numerical approaches to obtain solutions for the impact stress fields and dynamic stress intensity factors. It has been shown that expressions for the damage threshold, which consists of the activation of preexistent surface microcracks, can be derived from these solutions. The expressions identify three types of behavior, depending upon the adjacence of the preexistent cracks to the impact center, vis-a-vis their size, and describe the respective roles of the three important target parameters, the fracture toughness, the elastic wave velocity, and the preexistent flaw size. An absolute damage threshold has also been defined. The conditions at this threshold are demonstrated to be reasonably consistent with available threshold measurements.
Nonlinear mode interactions and frequency-jump effects in a doubly tuned oscillator configuration
Authors: Grun J. , Lashinsky H.
Published: February 2003

Frequency-jump effects associated with nonlinear mode competition are investigated in an oscillator configuration consisting of a passive linear resonance system coupled to an active nonlinear resonance system. These effects give rise to a hysteresis pattern whose height and width can be related to system parameters such as the resonance frequencies, dissipation, coupling coefficient, etc. It is noted that these effects offer a novel means of determining these parameters in cases in which conventional techniques may not be desirable or as advantageous. The analysis provides a qualitative explanation of empirical observations in a recent nuclear magnetic resonance experiment [R.S. Timsit and J.M. Daniels, Rev. Sci. Instrum. 47, 953 (1976)]. The results also apply to other nonlinear resonance systems such as lasers, microwave generators, and electronic oscillators.
Combinations of third-order elastic constants of lead
Authors: Powell B. E. , Skove M. J.
Published: February 2003

Lead filamentary crystals have been subjected to finite deformations. The parameter δ associated with deviations from linearity in Hooke’s law in the form ε=s′11σ +δ(s′11σ)2 (where ε is the strain, σ the stress, and s′11 Young’s modulus along the whisker axis) has a value of 4.2±0.6 for four crystals oriented in the 〈110〉 direction. The resulting linear combination of third-order constants is, C111−4.6 C112+3.6 C123+3.1 C144−3.7 C166=4.4×1011 N/m2.
Reply to ’’Comment on ’Anisotropy study of electrical conduction in oriented polymers. I. Analysis of bulk electrical conduction parallel to the surface of film’ ’’
Authors: Hirota S.
Published: February 2003

In reply to Wintle and Chapman, we point out that in the experimental condition, the allowed geometry factor of four-electrode system will be limited within a range of values.
Formation of Ohmic contacts in semiconducting oxides
Authors: Narayan J. , Shukla V. N.
Published: February 2003

A new technique based on deposition of metallic film at room temperature followed by laser irradiation, for the formation of Ohmic Contacts on semiconducting oxides, has been developed. Aluminum or nickel film about 1 μm thick was deposited on n-type polycrystalline barium titanate (BaTi03) substrates and irradiated with Q-switched ruby laser pulses. This technique produces low-resistance Ohmic contacts which do not age and remain stable over a wide temperature range.
Isotopic enhancement in laser-produced plasmas
Authors: Gupta P. D. , Bhatnagar R. , Bhawalkar D. D.
Published: February 2003

This paper reports the investigations carried out on isotopic enrichment in boron oxide plasma produced by a Nd : glass laser giving 20 MW in 30 nsec (FWHM). Energy distributions of various ions in the plasma expanding in vacuum were obtained with an electrostatic ion analyzer. Energies corresponding to peaks of distribution for B+10 and B+11 were found to be different by the ratio of their masses, consistent with hydrodynamic expansion of plasma. An anomalously high ratio of B+10 to B+11 ions as compared to their natural abundance was observed.
I-V and C-V characteristics of Au/TiO2 Schottky diodes
Authors: Szydlo N. , Poirier R.
Published: February 2003

The electrical characteristics of Au/n-TiO2 Schottky diodes have been studied using I-V and C-V measurements. TiO2 samples with working face perpendicular to the c axis are reduced in a vacuum of 10−6 Torr at 800 °C for about 5 h and then quenched. The resistivities are in the range 20–30 Ω cm. The barrier heights deduced from I-V characteristics in agreement with the thermionic emission theory are in the range 0.87–0.94 eV. C-V data yield lower barrier heights and show a frequency dependence attributed to relaxation phenomena occurring in a disturbed layer near the surface. Comparison with results relative to Au/n-SrTiO3 diodes shows that the barrier heights obey the Schottky model for these ionic semiconductors, confirming the role of the electron affinity in the band bending formation.
Anomalous flux penetration into a superconducting loop broken by a damped Josephson junction
Authors: Smith H. J. T. , Hutchinson M.
Published: February 2003

The dynamics of a superconducting circuit of a loop broken by a Josephson junction shunted by a resistive loop is analyzed. Anomalous flux flow behavior predicted by the calculation is discussed.
High-field superconductivity in the Nb-Ti-Zr ternary system
Authors: Ralls K. M. , Rose R. M. , Wulff J.
Published: February 2003

Resistive critical current densities, critical fields, and normal-state electrical resistivities were obtained at 4.2 °K for 55 alloys in the Nb-Ti-Zr ternary alloy system, excepting Ti-Zr binary compositions. The resistive critical field as a function of ternary composition has a saddle point between the Nb-Ti and Nb-Zr binaries, so that ternary alloying in this system is not expected to result in higher critical fields than the binary alloys.
Thermomagnetic analysis of intermetallic phases in mischmetal-cobalt system
Authors: Velu E. M. T. , Subbarao E. C. , Bonda N. R. , Goel D. K. , Gupta K. P. , Majumdar A. K. , Sankar T. A. Padmavathi , Subramanyam J.
Published: February 2003

The thermomagnetic analysis of the intermetallic phases in the mischmetal-cobalt (MM-Co) system was used to (1) establish the identity of the structurally similar 1 : 3, 2 : 7, 5 : 19, and 1 : 5 phases by means of their distinctive Curie temperatures (<20, 61, 270, and 541 °C, respectively), (2) indicate a new magnetic transition at 340 °C between the Tc of 5 : 19 and 1 : 5 phases, (3) provide unambiguous evidence for 5 : 19 and 2 : 17 phases as decomposition products of the in situ eutectoid decomposition of 1 : 5 phase, (4) confirm the existence of a homogeneity region of 1 : 5 phase with Tc varying from 487 to 520 °C with increasing Co, and (5) demonstrate the enhancement of Tc of 1 : 5 when Co replaces Fe.
Field-induced magnetic anisotropy of glassy iron-boron and iron-boron-silicon alloys near the eutectic composition
Authors: Nesbitt E. A. , Hasegawa R. , O’Handley R. C. , Sullivan M. O.
Published: February 2003

Measurements were made on a series of glassy iron–boron alloys to determine the association of the eutectic composition (lowest melting point) and the field-induced magnetic anisotropy. When the boron was increased from 15 to 22 at. %, the magnetic anisotropy was found to increase from 500 to 1300 J/m3. There was no sharp discontinuity in the vicinity of the eutectic. It appears that deviation from the eutectic does not greatly influence the value of the magnetic anisotropy, provided the samples are small and are drastically quenched. Specimens having the eutectic composition had the most reproducible values of anisotropy. The substitution of silicon for some of the boron in these alloys raises their Curie and crystallization temperatures. This makes possible a greater range of heat treating temperatures and permits better stress relief in the alloys. Also, the substitution of silicon permits better control of the magnetic anisotropy. This control may be a factor in obtaining improved magnetic properties since both low coercive force and low hysteresis loss in these materials depend upon obtaining the proper value of uniaxial anisotropy. Compositions that had values of the field-induced anisotropy of 1000 J/m3 had low values of core loss when properly heat treated.
Magnetocrystalline anisotropy in epitaxially grown (Gd,Tm,Y)3(Fe,Ga)5O12 garnet thin films
Authors: Gangulee A. , Kobliska R. J.
Published: February 2003

Single-crystal thin films of gallium-substituted mixed garnets (Gd,Tm,Y)3(Fe,Ga)5O12, grown by liquid phase epitaxy, have been used as drive layer materials in contiguous disk bubble devices; a critical parameter for the selection of a specific composition is the value of the magnetocrystalline anisotropy constant K1. We have measured the values of K1 in a series of epitaxial thin films grown on (100) and (111) oriented gadolinium gallium garnet substrates. K1 in the (100) oriented films were measured both by ferrimagnetic resonance and with an inductive hysteresigraph, whereas only resonance measurements were employed in the (111) oriented films. The values of K1 for each composition, obtained by different methods from films with different orientations, agree reasonably well with each other and are consistent with what would be expected from linear extrapolation of the K1’s of pure rare-earth iron garnets after an empirical correction for gallium substitution.
Magneto-optic Raman scattering of Raman-inactive phonon polaritons
Authors: Heiman D.
Published: February 2003

The possibility of observing Raman-inactive vibrations in solids by coherent Raman spectroscopy via the magneto-optic effect is demonstrated. Although vibrations involving nuclei lying at a center of inversion are Raman inactive in first order, they are infrared active and therefore couple to electromagnetic radiation creating phonon polaritons. The magneto-optic effect permits coupling of laser light to the oscillating magnetic field of the polariton mode. A theory is presented and used to calculate the effective third-order nonlinear susceptibility for this mechanism. The magnitude is then estimated from results of Faraday rotation experiments. The effect is found to be much smaller than for most Raman-active vibrations, yet remains within current detectable limits.
Optical properties of integrally colored anodic oxide films on aluminum
Authors: Granqvist C. G.
Published: February 2003

Integrally colored anodic aluminum oxide consists of a mixture of Al and Al2O3. Published spectral optical properties can be quantitatively understood from an effective medium formalism, provided the Al particles are regarded as spherical and their dielectric permeability is taken to be the same as in the bulk. Implications of these requirements are discussed.
Nonequilibrium solid solutions obtained by heavy ion implantation and laser annealing
Authors: Natsuaki N. , Tamura M. , Tokuyama T.
Published: February 2003

Nonequilibrium solid solubility of P, As, and B in single-crystalline silicon annealed by Q-switched ruby laser pulse irradiation was experimentally investigated for residual defects, lattice strain, and electrical activation of implanted impurities. The maximum solubility obtained without any macroscopically extended defect formation was 2–4 times higher than the thermal equilibrium solubility limit. Above this solubility, precipitates, dislocations, and surface cracks were observed. The highest full activation was realized by P implantation, with carrier concentration up to ∼5×1021/cm3 showing no such defects. Formation mechanisms of the defects are discussed and shown to be attributable to the rapid solidification process of the heavily doped layer and to large impurity-induced misfit stress comparable to the fracture stress.
Phase-locking and microwave impedance of Josephson junctions with linear-periodic current-phase relations
Authors: Fujimaki N. , Okabe Y. , Okamura S.
Published: February 2003

Some types of Josephson junctions such as long microbridges, S-N-S junctions, and junctions with a series palastic inductance are known to have nonsinusoidal current-phase relations which can be approximated by linear-periodic functions. In this paper the equivalent circuit equation of the resistively shunted junction model with linear-periodic current-phase relation is solved. The heights of zeroth and first constant-voltage steps in the I-V characteristics and the impedance at these steps are obtained analytically. This analysis shows that the impedance at the first step lies on a semicircle in the impedance plane with its center at the impedance of the zeroth step. The calculated impedance is compared with the experimental results by Claridge et al. The theory presented here can explain some features of experimental results which differ considerably from predictions based on a sinusoidal current-phase relation. Among these are the value of bias current corresponding to the center of the first step, and the appearance of ’’shoulders’’ in the imaginary part of the impedance at the first step.
Evidence of tunnel-assisted transport in nondegenerate MOS and semiconductor-oxide-semiconductor diodes at room temperature
Authors: Kar S. , Ashok S. , Fonash S. J.
Published: February 2003

Metal-oxide-semiconductor diodes have been fabricated on p-type Wacker polycrystalline silicon with aluminum barrier metal, and semiconductor-oxide-semiconductor diodes have been fabricated by chemical spraying of indium-tin oxide on n-type single-crystal silicon. The current-voltage and capacitance-voltage characteristics of these diodes have been measured at various values of temperature above 300 K and analyzed. The results indicate the likelihood of the primary transport mechanism’s being multistep tunneling instead of thermionic emission or minority carrier injection. The study also stresses the importance of investigating the temperature dependence of electrical characteristics before any firm conclusions may be drawn about the conduction mechanisms in semiconductor junctions.
Thermally stimulated discharge current and dielectric studies on chloranil pellets
Authors: Pillai P. K. C. , Rashmi
Published: February 2003

The mechanisms of polarization in chloranil pellets have been investigated by thermally stimulated discharge and ac dielectric measurements. Polarization was found to be mainly due to trapping of charge carriers at molecular sites and grain boundaries. A small dipolar contribution was also observed. Release of charges from molecular sites and dipolar reorientation occurred at about 120 °C with activation energy 0.8 eV. Charges from grain boundaries were released at a higher temperature (about 158 °C). Activation energy was calculated to be 1.06 eV.
Damped oscillation in a thin film optical slab-type directional coupler covered with a high-index absorbing material
Authors: Sasaki K. , Minami F. , Aoyagi S. , Todaka Y.
Published: February 2003

It is shown that in a thin-film optical slab-type directional coupler, the synchronization condition can be controlled by adjusting the thickness of an additional high-index top layer. Damped oscillation was accompanied by the absorbing property of the top-layer material.
Ultrasonic assessment of cumulative internal damage in filled polymers (II)
Authors: Knollman G. C. , Martinson R. H. , Bellin J. L.
Published: February 2003

An ultrasonic technique previously developed for studying dewetting and cumulative internal damage in filled polymers, such as solid rocket propellents, has been improved. The previous theoretical treatment is here expanded to include internal vacuoles of general spheroidal (rather than spherical) shape. Experimental measurements of sound speed and attenuation in a solid propellant material are utilized together with the modified theoretical model to calculate the internal damage parameters of effective vacuole size and number density as functions of applied uniaxial tensile strain. Results obtained from the model near the point of material failure are in excellent agreement with those provided by independent microscopic observations made on several rupture surfaces of propellant samples stressed to failure.
Gallium arsenide transferred-electron devices by low-level ion implantation
Authors: Anderson W. T. , Dietrich H. B. , Swiggard E. W. , Lee S. H. , Bark M. L.
Published: February 2003

Extended n-type layers have been produced in semi-insulating GaAs by the activation of Si implanted to atomic concentrations as low as 6×1016 cm−3. Active layers were obtained in two types of undoped (no intentional dopants introduced during the growth process) semi-insulating GaAs. These were bulk GaAs grown by the liquid encapsulated Czochralski method and epitaxial layers grown by chemical vapor deposition. Three terminal transferred-electron devices were fabricated in a completely planar geometry. Gunn domain triggering by the gate resulted in dc negative resistance current dropback between 20% and 40%. High-frequency negative resistance was observed in the 2–7 GHz range.
Anisotropic elastic interaction between misfit defects and extended screw dislocations in fcc metals
Authors: Bapna M. S. , Parameswaran V. R.
Published: February 2003

The energy and force of interaction of an extended screw dislocation with spherical and tetragonal defects were calculated for several fcc metals using anisotropic and isotropic elasticity theories. It is shown that anisotropy has a large effect on the magnitude of interaction energy and interaction force, as well as on the shape of the energy-distance and force-distance curves. The maximum value of the interaction energy was always smaller in the anisotropic case than in the isotropic case. But the maximum resisting force to dislocation motion due to defect-dislocation interaction is not always smaller in the anisotropic crystal. Computation of the hardening coefficient at 0 °K for several fcc metals indicates that tetragonal defects cause significantly larger hardening than spherical defects.
High-temperature H2 anneal of interface defects in electron-beam-irradiated MNOS structures
Authors: Schols G. A. , Maes H. E. , Van Overstraeten R. J.
Published: February 2003

A thermal anneal technique is proposed to effectively remove electron beam irradiation damage in metal-nitride-oxide semiconductor structures. Using a high-temperature (800–950 °C) H2 anneal treatment the SiO2 layer is impregnated with hydrogen after the nitride deposition. This leads to very low surface state densities for both thick-oxide and thin-oxide devices. After irradiation the device is given a mild heat treatment at 450 °C in an inert ambient. A complete removal of the radiation-induced fixed charges and surfaces states is observed. The effectiveness of the high-temperature H2 anneal is most pronounced for thin-oxide MNOS structures. The technique is shown also to be effective in case of other types of ionizing radiation.
Blistering of molybdenum-base alloy TZM under helium ion bombardment
Authors: Daly John G. , Sinha M. K.
Published: February 2003

Polycrystalline TZM alloy samples have been irradiated at room temperature with helium ions of energy from 75–350 keV in high vacuum. Irradiation parameters such as ion energy, total dose, and ion flux were varied, and the surfaces were examined in a scanning electron microscope. The critical dose for blister formation was found to lie between 4 and 7×1017 ions cm−2 and is independent of the beam flux in the range 6.7×1013–2×1015 ions cm−2 s−1. However, within this flux range the average blister diameter increases with the flux and the blister number density, and the exfoliation maximizes at an intermediate flux. Blister-cover thickness for TZM is found to be less than that for molybdenum, although the average blister diameter for the two materials differs only at the highest energy used. When the TZM surface is successively bombarded with varying ion energies, blistering is reduced compared to monoenergetic helium bombardment, but this reduction is not as substantial as for pure molybdenum.