bluuebunny/crossref_metadata_2025 huggingface dataset:
Interference effects in laser micromachining of thin films on silicon
Authors: Kestenbaum A.
Published: February 2003

Some recent designs of new electronic circuits on silicon have been implemented by laser removal of thin metallic film from the composite structure. The presence of an insulating dielectric region between the thin metallic film and the silicon substrate gives rise to a complex laser-micromachining process whose understanding is crucial to successful applications. In this paper we explore the laser-machining process at 1.06 μm for a tantalum nitride thin-film resistors material on top of a dielectric film on silicon. We experimentally verify the existence of strong optical interference effects in laser machining of these resistors and determine their influence on various laser-trimming parameters. Good correlation is obtained between an analytical model for these interference effects and the experimental data. For structures containing a single SiO2 layer with thickness up to 1 μm between the tantalum film and silicon, it is observed that from a laser-trimming standpoint, a SiO2 thickness of 9000 or 5400 Å is preferred to all others. A selection of either one of these thickness will lead to a wider laser-trimming-process window. These results could, therefore, be viewed as structure design guidelines for laser trimming by material removal at 1.06 μm.
High-temperature mobility analysis of n-type GaAs in the three-valley (Γc6−L
c6−X
c6) model
Authors: Mathur P. C. , Saxena T. K.
Published: February 2003

The mobility of electrons in the central (Γc6) and the satellite valleys (Lc6 and Xc6) of n-type GaAs has been estimated in the temperature range 300–800 K assuming the three-valley Γc6−Lc6−Xc6 model for the conduction band. The relaxation-time technique has been used for calculating the contributions of various types of scatterings to the effective mobility of the charge carriers in different valleys. It has been found that in Γc6 valley the contribution of the Γc6→Xc6 intervalley scattering becomes comparable to the deformation potential scattering (DPS) above 650 K. In the Lc6 valley the contribution of the Lc6→Xc6 intervalley scattering becomes comparable to DPS at temperatures above 650 K. In the Xc6 satellite valley, OPS, DPS, and the Xc6→Lc6 intervalley scattering are found to be important in the entire temperature range. The DPS is found to be relatively more important for this valley as compared to that for the Γc6 and the Lc6 valleys. The results of the calculations have been compared with the available experimental data.
Preliminary investigation of elongational flow of dilute polymer solutions
Authors: Peng S. T. J. , Landel R. F.
Published: February 2003

JAPIA,47,4255,1979
Electrical conductivity and optical absorption studies in superionic RbAg4I5 thin films
Authors: Radhakrishna S. , Hariharan K. , Jagadeesh M. S.
Published: February 2003

Electrical conductivity in thin films of the superionic conductor RbAg4I5 was found to be in very good agreement with the best bulk value (0.27 Ω−1 cm−1). From the conductivity data, the activation energy for Ag+-ion conduction, and the free-ion-like parameters such as the mean free path and lifetime in the excited state have been deduced. The phase transition at 210 °K has also been observed, and the activation energy for conduction before and after the phase transition has been evaluated. Optical absorption studies in these films reveal a well-defined exciton state at 3750 Å at 300 °K. Also, a weak band is observed at 3350 Å on the higher-energy side of the exciton band which appears to be evidence for the existence of large-radius excitons. A broad band observed at 4850 Å has been attributed to the existence of silver colloids in the films. A forbidden internal transition in the Ag+ ion has been observed at 4250 Å.
On the structure of the ferroelectric-paraelectric transformation interface in barium titanate. II. Influence of domain boundaries
Authors: Malis T. , Gleiter H.
Published: February 2003

Transmission electron microscope (TEM) observations have been made on the passage of the broad ferroelectric-paraelectric transformation interface through sets of 90° domains in BaTiO3. They indicate that the domain boundaries widen rapidly at the core of this interface so that the previous discontinuous change in lattice orientation across them is replaced by a continuously fluctuating lattice structure. The nature of this fluctuation rules out a transition to the cubic state via a decreasing short-range-order phenomenon and makes time-dependent switching of individual lattice-cell tetragonality rather unlikely. The 90° domain boundary widening is consistent with recent structural models for domain boundaries in BaTiO3.
Algorithm for solving backreflection Laue patterns of cubic crystals
Authors: Ravindhran K. S. , Siegel H. M. , Johnson R. M. , Wiseman C. D.
Published: February 2003

An algorithm and the accompanying analysis is described for quickly and accurately orienting cubic crystals by Laue x-ray back reflection. This technique utilizes three parameters as inputs: the film-to-specimen distance, the radial distance from the center of the photograph, and the angular displacement from horizontal. The outputs consist of interplanar angles between and indices of the planes producing the diffraction spots as well as the appropriate coordinate positions of the poles of those planes on a Wulff net. Also included is a statistical analysis of the errors involved. By the self-consistent approach employed, interplanar accuracies of ±0.25° are obtained.
Stoichiometry measurements of GaAs by means of 15-MeV He++ backscattering
Authors: Kudo H. , Ochiai Y. , Takita K. , Masuda K. , Seki S.
Published: February 2003

The stoichiometry of heat-treated GaAs crystals was measured over the region about 1 μm below the surface by means of 15-MeV He++ backscattering. Samples were annealed for 1 h at various temperatures between 200 and 900 °C. The annealing-temperature dependence of the concentration ratio of As to Ga in the above-mentioned region shows abrupt change at around 250 °C and at around 800 °C. For annealing at 300–700 °C, this ratio (0.81±0.05) is almost independent of the annealing temperature.
Magnetic properties of zero magnetostrictive amorphous Fe-Co-Si-B alloys
Authors: Kohmoto O. , Ohya K. , Yamaguchi N. , Fujishima H. , Ojima T.
Published: February 2003

The metalloid content dependence of zero magnetostrictive composition of an amorphous (FexCo1−x)100−y(Si0.4B0.6)y alloy in an as-quenched state is experimentally determined. The iron content (x) of the zero magnetostrictive composition was found to decrease with an increase in the metalloid content (y). The Curie temperature and saturation magnetization decrease with an increase in the metalloid content, while crystallization temperature increases. With an increase in the saturation magnetization of the present alloys the coercive force increases as Hc∝M3s.
Pyroelectricity in polyvinylidene fluoride
Authors: Das-Gupta D. K. , Duffy J. S.
Published: February 2003

The magnitude of the pyroelectric coefficient in polyvinylidene fluoride was observed to increase significantly on maintaining the poling field while cooling the samples from elevated poling temperatures to ambient temperature. The results of the measurement of the depolarization currents with repeated thermal cycling of poled specimens from temperatures well above that of poling conditions to 30 °C suggest that dipolar reorientations may be responsible for the pyroelectricity in PVF2. These observations hold for both the conventional poling and the corona charging of PVF2 films, originally containing form 1 and form 2 crystallites.
Potential feedback in field-effect devices
Authors: Gupta Ravendra K.
Published: February 2003

One-dimensional potential profile inside the static induction transistors is analyzed. The potential profile rearranges itself due to negative feedback by a change in gate or drain voltage. The potential barrier shows a nonlinear variation with drain voltage and it tends toward nonexistence as the drain voltage increases, i.e., negative feedback reduces the barrier height. This negative feedback is an important factor in determining the barrier height, which in turn decides the static characteristics of the field-effect devices. Generalized curves of potential profile for field effect, static induction, and analog transistors are presented where secondary effects are neglected. This explains the vacuum-pentode- or vacuum-triode-type characteristics in the unipolar devices.
Spontaneous vibrational modes excited in ferromagnetics by reversible magnetostriction
Authors: Lanotte L. , Luponio C. , Porreca F.
Published: February 2003

Experimental results for magnetostrictive generation of low-frequency standing elastic waves in polycrystalline and amorphous ferromagnetic materials are given. By exciting magnetized samples with bursts of magnetic impulses, extensional and torsional modes of damped wave propagation were observed. These propagation patterns are qualitatively explained by means of the theory of linear magnetoacoustic coupling taking into account the residual stresses alone. A comparison of the magnetomechanical behavior of the materials investigated has been made by studying the conditions of reversible magnetostriction and the magnetic damping. In particular, in the Ni rod, it was possible to clarify the log decrement behavior on the basis of the reversible magnetomechanical permeability and the ΔE effect measured.
Magnetic and corrosion properties of UHV-deposited Fe1−xPdx thin films
Authors: Lee M. H. , Lee W. Y.
Published: February 2003

The magnetic and atmospheric corrosion characteristics of Fe1−xPdx films are discussed. The polycrystalline films are prepared by codeposition in a UHV system using separate electron-beam-heated Fe and Pd sources. Some trends in their properties appear to be connected with the crystal structure which is bcc for x≲0.31 and fcc for higher Pd concentrations. All but films with high Pd content are magnetically soft or nearly so and have an in-plane uniaxial anisotropy. The anisotropy field decreases with increasing deposition temperature and is also smaller for the fcc structure. The coercivity depends principally on film composition and deposition temperature. Perpendicular anisotropy is found in films with high Pd concentrations. The lower Pd content bcc structure is relatively prone to corrosion in a high-humidity atmosphere containing controlled trace quantities of acid-forming pollutants (Cl2, SO2, etc.), but the fcc structures are quite inert. Possible mechanisms governing the relationship of the magnetic, corrosion, and structural properties to the deposition parameters are explored.
Coercivity of γ-Fe2O3 particles growing iron-cobalt ferrite
Authors: Kishimoto M. , Sueyoshi T. , Hirata J. , Amemiya M. , Hayama F.
Published: February 2003

Acicular γ-Fe2O3 particles were heated at 90°C in alkali solution containing Co2+ and Fe2+. The coercivity of the resultant particles remarkably increased with the increasing Co2+/Fe2+ ratio, and in the neighborhood of the Co2+/Fe2+ ratio of 0.4, reached a maximum value. When the particles with a Co2+/Fe2+ ratio of 0.5 were dissolved in hydrochloric acid, the cobalt content and the coercivity were rapidly decreased with increasing dissolved weight. Iron-cobalt ferrite was expected to grow on the surface of γ-Fe2O3 particles. The increase of coercivity was attributed to the iron-cobalt ferrite.
Primary-ion charge compensation in SIMS analysis of insulators
Authors: Wittmaack K.
Published: February 2003

Primary-ion charge compensation by means of simultaneous bombardment of the insulating specimen with a focused beam of low-energy electrons has been investigated. The measurements were performed in a quadrupole-type SIMS instrument which allowed the amount of charging to be measured in situ. The effectiveness of charge neutralization was investigated by monitoring the intensity, the mass resolution, and the line shape of both (positive) atomic and molecular secondary ions. It was found that in the range of electron energies investigated (100–500 eV) the energy has little effect on the amount of charge neutralization (for bombardment of a gadolinium iron garnet sample with 12-keV argon ions). A well-defined minimum electron current was required to provide compensation of the primary ion charge. ’’Supersaturation’’ with electrons caused only a negligible reduction in signal height. Studies with focused ion beams showed that effective neutralization requires compensation of the local primary ion current density. In case of current density compensation the mass resolution observed with insulating specimens is as good as for metals or semiconductors. Possible mechanisms of charge compensation are discussed briefly.
Special functions associated with azimuthally magnetized ferrite rod phase shifters
Authors: Samaddar S. N.
Published: February 2003

Solutions of the differential equation satisfied by the circularly symmetric electric field Eφ in an azimuthally magnetized ferrrite cylinder are given in terms of two infinite series which reduce to Bessel function J1(x) and Neumann function N1(x) in the absence of the dc magnetic field. These results differ from the solutions which have been used in literature associated with ferrite-rod phase shifters. A numerical table is provided for the comparison between the present and the former solutions.
Capless anneal of ion-implanted GaAs in controlled arsenic vapor
Authors: Kasahara J. , Arai M. , Watanabe N.
Published: February 2003

GaAs wafers were implanted with sulfur or silicon ions and annealed at temperatures from 800 to 950 °C under arsenic partial pressure controlled by arsine (AsH3) flow. Electrical characteristics obtained in this method were nearly identical or superior to those obtained with dielectric films. No sign of surface deterioration was observed even after annealing at 950 °C. The implantation into a Cr-doped epitaxial layer resulted in better characteristics than into semi-insulating substrates from a vender. The best doping efficiency of 89% was obtained with a dose of 1×1013 Si+/cm2. The method is simple and reproducible, and suitable for the annealing process in production.
The interfacial layer in MIS amorphous silicon solar cells
Authors: McGill J. , Wilson J. I. B. , Kinmond S.
Published: February 2003

When an insulating layer of TiOx is added beneath the Ni barrier contact of amorphous silicon Schottky diodes, increases are produced in both the open-circuit voltage and the short-circuit current. The former change is explained by an increased barrier height and diode factor, and the latter change is at least partially caused by an increase in the width of the space-charge region.
Effects of indium on the electrical properties of n-type CdS
Authors: Partain L. D. , Sullivan G. J. , Birchenall C. E.
Published: February 2003

Indium doping of nominally pure n-type CdS containing excess Cd can raise the free-carrier concentration by an order of magnitude over the 77–300 °K temperature range even though this increase is only a small fraction of the total concentration of indium impurities included as dopants. At room temperature such doping does not significantly change the mobility from its value in undoped samples. As temperature is lowered toward 77 °K, neutral-impurity-like scattering in the indium-doped samples causes the mobility to become only weakly dependent on temperature. This is in contrast to undoped n-CdS which is dominated by longitudinal polar optical-phonon scattering and piezoelectric scattering that allow the mobility to rise an order of magnitude as temperature is lowered from 300 to 77 °K.
Current-voltage characteristics of ZnO-Bi2O3 heterojunction
Authors: Lou L. F.
Published: February 2003

Thin-film junctions of ZnO-Bi2O3 have been made by sputtering. The junction breakdown voltage ranges from 2.3 to 3.0 V when ZnO is positively biased. A negative resistance usually appears after the breakdown. When ZnO is negatively biased, the current is proportional to an exponential function of the applied voltage with a built-in barrier of roughly 0.8 V. These characteristics and their temperature dependence on being cooled down to 77 °K will be discussed in terms of a qualitative n-n heterojunction with interface states.
Helium migration in alkali germanate glasses
Authors: Shelby J. E.
Published: February 2003

Helium permeability, diffusivity, and solubility have been measured for sodium, potassium, rubidium, and cesium germanate glasses, and for one series of sodium-potassium germanate glasses. In each case, the helium permeability and diffusivity exhibit minima in the property-composition curves. These minima shift to greater alkali oxide content and increase in magnitude in the order Cs, Rb, K, Na-K, Na. These minima result from corresponding maxima in activation energy for helium migration. Helium solubilities do not exhibit similar minima, but rather decrease monotonically with increasing alkali oxide content. These results appear to be related to free-volume changes in the glasses as a function of composition. The inability of the current structural model for these glasses to explain the results of the present study raises questions regarding the validity of that model.
Generation of far-infrared radiation by frequency mixing in insulating GaAs
Authors: Geyer F. F. , Fan H. Y.
Published: February 2003

The generation of far-infrared radiation by frequency mixing has been studied for the case of phase matching by means of the noncollinearity of the generating beams. An exact theoretical treatment has been performed for the case where the laser beams propagate linearly in the sample and for the case where the laser beams follow a zigzag path resulting from multiple internal reflections; the profile of each laser beam entering the sample is taken realistically to be a truncated Gaussian; sample absorption of the generating and generated radiations is taken into account. Previous treatments for the two geometries were approximate; in addition, square profile beams were assumed and the effect of absorption was neglected. Measurements have been made on insulating GaAs; the effects of sample length and sample absorption have been investigated. In contrast to previous work where two separate lasers were used, a single TEA CO2 laser has been modified to provide both generating beams, resulting in a more consistent temporal overlap of the pulses in the two beams. Furthermore, an SF6 saturable absorption cell has been used to select a single longitudinal mode, thereby eliminating the fine structure in pulses of one beam and making the overlap of the pulses from the two beams tractable. The coherence of the generated radiation was measured. The ratio of the theoretical prediction to the experimental results is a factor of ∼6, in comparison with the smallest factor of ∼400 for previous work with pulsed lasers, indicating the significance of the improvements in the experiment and the theory.
Stoichiometry and atomic defects in rf-sputtered SiO2
Authors: Hickmott T. W. , Baglin J. E.
Published: February 2003

Electron microprobe and helium ion backscattering are used to measure the stoichiometry of rf-sputtered SiO2 films at a precision of ?1%. Both oxygen-excess and oxygen-deficient films occur. Optical absorption and electron spin resonance characterize atomic defects in the films. The correlation between stoichiometry and atomic defects is poor. The reproducibility of composition and of atomic defects from run to run, when sputtering conditions are held constant, is good.
Theory of the light-sensitive diode acoustic airgap convolver
Authors: Gautier H. , Maerfeld C. , Tournois P.
Published: February 2003

In this paper we present a theoretical model for the linear and nonlinear coupling between surface acoustic waves and a semiconductor diode array separated from the piezoelectric medium by a thin airgap. We account for the periodic nature of the diode sensor and we discuss the various approximations made. This model yields the convolution efficiency as a function of diode bias, diode charge, or incoming illumination. Two modes of light detection are considered: the photovoltage mode where shining light is equivalent to forward biasing the diodes, and the precharge mode where the photon flux controls the discharge of initially charged up diodes and the remaining charge is read out after the so called photon integration time. Experimental devices have been measured which use pn diode matrices of the vidicon type laid down in close vicinity to a LiNbO3 delay line. We show that the measured data very well compare with the theoretical predictions. In addition we note that light sensitivity thresholds of some 10−2 μW/cm2 have been demonstrated. The light dynamic range reaches 50 dB. In the precharge mode, a higher contrast is obtained over a 10–20-dB range which can be shifted by changing the integration time.
Transverse and longitudinal noise
Authors: Vandamme L. K. J. , Kamp L. P. J.
Published: February 2003

Analytic functions are derived for the spectral noise voltage density between two circular sensor electrodes on a two-dimensional isotropic conductor, placed either transversely or longitudinally to a homogeneous electric field. The sensor electrodes are far removed from both the bias electrodes and the boundaries. The relations have been checked experimentally for 1/f conductivity fluctuations. Both the transverse and longitudinal noise are proportional to I−2ℱs(J⋅J̃)2 ds where J⋅J̃ represents the dot (scalar) product of the homogeneous current density J and the adjoint current density J̃, and the current through the bias electrodes is I. It is found that the transverse noise is somewhat smaller than the longitudinal noise.
Temperature dependence of acoustoelastic amplification in n-InSb
Authors: Davis Jeffrey A.
Published: February 2003

The threshold electric field required to initiate current oscillations in n-InSb has been measured as a function of temperature from 77 to 135 °K. The results are explained under the assumption that a critical constant value for the amplified phonon flux is required for current oscillations within the temperature range covered. Good agreement is found with the theoretical method.
Photoeffects in Fe2O3 sintered semiconductors
Authors: McGregor Kevin G. , Calvin Melvin , Otvos John W.
Published: February 2003

Polycrystalline sintered pellets of α-Fe2O3 have been studied by capacitance and photoelectrochemical techniques. The pellets exhibit (i) photocurrent saturation at a given wavelength with increasing applied voltage, (ii) large dark currents at low applied voltage (0.76 μA cm−2 at +0.2 V SCE), (iii) cathodic and anodic photocurrent transients at low levels of monochromatic irradiation, (iv) photocurrent onset at photon energies greater than 2.1 eV, and (v) flat-band potentials of −0.67 V SCE and pH=4. Capacitance measurements followed a Mott-Schottky relationship indicating a predominance of the semiconductor space-charge layer over surface states and electrolyte effects. No degradation of the semiconductor properties could be observed at pH=4.
Preliminary experiment for stabilizing unmodulated He-Ne laser to an iodine hyperfine component
Authors: Tanaka Keiichi , Morinaga Atsuo
Published: February 2003

First- and third-derivative signals of saturated absorption in iodine 127 molecular vapor are detected by using a frequency-modulated 190-cm-long 633-nm He-Ne laser with a Fox-Smith–type resonator and an iodine absorption cell which is set outside of the resonator. Aiming to stabilize the laser with unmodulated output, a retroreflector-type optical modulator is added to the above system, and the first-derivative signal is obtained by external modulation. Comparing the obtained signal with those obtained by the frequency-modulated laser, possibilities to detect the third-derivative signal by using the optical modulator and to stabilize the unmodulated laser are found.
Electrical properties of CdS–SiO2–Si structures
Authors: Bhattacharyya A. B. , Nahar R. K. , Nagchoudhuri D. , Vasi J.
Published: February 2003

Introducing a passivating layer of SiO2 at the CdS–Si junction is found to improve the I-V characteristics of the heterodiodes. Studies indicate that the reverse-bias characteristics of these structures are determined primarily by the filling and unfilling of interface states at the Si–SiO2 interface. This is substantiated by the temperature dependence of these characteristics. Reverse-bias C-V characteristics show abrupt junctionlike behavior, also controlled by the interface-state charge. Under forward bias, tunneling through the oxide is responsible for conduction.
Fabrication and characterization of i
n s
i
t
u superconducting multifilamentary copper-niobium wires
Authors: Roberge R. , Fihey J. L.
Published: February 2003

I n situ superconducting multifilamentary Cu–17 wt% Nb wires have been produced. The cross-section reduction ratio varied from 1 to 62 500. The critical current density in zero field at liquid-helium temperature dramatically increases from a few hundred amperes per square centimeter in the as-cast condition to a value of 6×105 A/cm2 for the highly reduced wires. A model based on the nonhomogeneous deformation of the niobium network accounts for the observed results. The evolution of the I-V curves from a broad transition to a sharp transition with increasing deformation is explained in terms of the geometry of the niobium chains.
Excitation of a plasma wave by two coaxial Gaussian EM beams
Authors: Sodha M. S. , Govind  , Tewari D. P. , Sharma R. P. , Kaushik S. C.
Published: February 2003

In the present paper we have investigated the excitation of a plasma wave of frequency Δω=ω1∼ω2 in a collisionless hot plasma by two coaxial Gaussian EM beams of frequencies ω1 and ω2 and propagating in the same direction. The mechanism of nonlinearity is assumed to be ponderomotive force arising because of Gaussian intensity distribution of the beams. In the presence of two beams, the nonlinearities introduced by two beams are additive if the difference frequency Δω is comparable to ω1 or ω2 and, hence, cross focusing occurs. For a given power of one beam, the nature of self-focusing becomes considerably modified by changing the power of the second beam. The power associated with the excited plasma wave, which depends on the background electron concentration and the intensity of the two beams, becomes drastically modified with the distance of propagation. The theory presented here is also applicable to a slightly inhomogeneous collisionless hot plasma within the WKB approximation.
Discharge stability in E-beam-sustained rare-gas halide lasers
Authors: Long W. H.
Published: February 2003

The stability of a glow discharge in rare-gas mixtures containing a small fraction of attaching species is examined, using the e-beam-sustained KrF laser discharge as a generic example. The stability limit is shown to lie near the peak of the voltage-current characteristic, while the mode of instability is dependent on external circuit parameters. The calculated maximum discharge voltage is in good agreement with experimental observation over a wide range of e-beam current densities.
Absorption measurements by laser calorimetry
Authors: Rosenstock Herbert B.
Published: February 2003

A solution to the heat equation is given which describes a cylindrical body uniformly heated along its axis. The application considered is the determination of bulk and surface absorption coefficients of the sample material from temperature-vs-time measurements when the heat source is a weakly absorbed narrow light beam. Under certain conditions, the full solution can be greatly simplified and the inference of absorption coefficients thus facilitated; these conditions are discussed and specified quantitatively. Equivalent results for rectangular samples are also given. The utility of the analysis is illustrated by several experimental examples.
Ignition of hydrocarbons by small sparks
Authors: Hill R. D.
Published: February 2003

The heating and growth of a spark channel producing minimum-energy ignition of a propane-air mixture is investigated. The form of the light signal emitted during the initial stage of ignition is derived. The role of spark energy in contributing to stable burning is discussed.
Fuel content characterization and pressure retention measurements of DT-filled laser fusion microballoon targets
Authors: Deckman H. W. , Halpern G. M.
Published: February 2003

We have developed a nondestructive assay of the fule content of deuterium-tritium (DT) -filled microballoon laser fusion targets, which is based on β-particle counting rates. Using a model employing transmission measurements of kilovolt electrons through thin films, observed count rates are correlated with the amount of tritium in the glass walls and hollow interior of the microballoons. It has been shown that gas pressure in balloons can be calculated from tritium content and a knowledge of the initial gas composition since D and T were found to leak at the same rate. This assay technique is primarily applicable for balloons with glass wall thicknesses <1.5 μm where the number of escaping β particles is large compared with the number of x-ray photons generated in the glass. The technique has been applied to measure the pressure retention characteristics of individual targets. At room temperature, the balloons exhibited widely diverse and rapid leakage rates which could not be correlated with a model based on molecular diffusion and the assumption that all balloons had a homogeneous composition. Cryogenic storage greatly reduced the leakage rates with pressure retention half-lives ranging from 5 to approximately 12 years. Finally, it was determined that tritium in the glass wall is trapped and evidence is presented to support the hypothesis that it is uniformly distributed across the shell.
Catastrophe theory: A technique for crack propagation analysis
Authors: Rabinovitch A. , Bahat Dov
Published: February 2003

The catastrophe theory is applied to the analysis of crack propagation. The important parameters and variables of the problem are determined, and a unified picture of the phenomenon is obtained. This model is qualitatively shown to agree with experimental results.
The interaction process for Ag-Al polycrystalline thin-film couples
Authors: Baglin J. E. E. , d’Heurle F. M. , Hammer W.N.
Published: February 2003

The mechanism of the interaction of polycrystalline Ag-Al thin-film couples to form Ag2Al at temperatures from 107 to 221 °C has been studied. Techniques of film characterization included Rutherford backscattering, x-ray diffraction, and SEM. The dependence of the interaction on the grain size of the Ag film (660–7500 Å) was measured. An effective activation energy of 0.86±0.05 eV was found. The reaction is believed to occur initially by nucleation and growth of Ag2Al grains at Ag grain boundaries at the interface; after formation of a continuous Ag2Al layer, the growth of this layer follows a t1/2 law, controlled by diffusion through the grain boundaries of the Ag2Al layer.
LiBixNd1−xP4O12 waveguide laser layer epitaxially grown on LiNdP4O12 substrate
Authors: Nakano Jun’ichi , Kubodera Ken’ichi , Miyazawa Shintaro , Kondo Susumu , Koizumi Hideo
Published: February 2003

A LiBixNd1−xP4O12 laser waveguide was successfully fabricated on a LiNdP4O12 substrate by liquid-phase epitaxy using LiPO3 as flux. cw laser oscillation at 1.05 μm was obtained with Ar ion laser coaxial pumping at room temperature.
Effect of phonon viscosity on dislocation motion in yttrium iron garnet
Authors: Mazumder N. , Roy B.
Published: February 2003

Using Mason’s derivation of the three-phonon loss mechanism, the values of the coefficients of phonon viscosity (shear) η and drag coefficients B have been calculated for yttrium iron garnet (YIG). Further, the compressional viscosity (χ) has also been calculated from the Akhieser loss phenomenon. On comparing the two viscosities (both η and χ), it was found that the shear viscosity plays the prominent role in producing the damping of dislocations in YIG.
Comments on ’’The Anderson-Grüneisen parameter for 16 crystals of cubic symmetry’’
Authors: Ramji Rao R.
Published: February 2003

It is pointed out that the method of calculating the Anderson-Grüneisen parameter from SOEC and TOEC data used by Tripathi et al. was proposed by the author several years ago. In fact, the major part of their paper is a mere duplication of the author’s own paper. No new conclusions were reached in their paper.
Modeling laser-induced diffusion of implanted arsenic in silicon
Authors: Fair Richard B.
Published: February 2003

An approximate theory of laser-induced diffusion in Si is presented. Starting with the concept of molecular motion in liquids, the self-diffusion coefficient of liquid Si at the melting temperature is calculated. By introducing the temperature dependence of diffusivity in the melt, the maximum diffusivity as a function of the laser-power density, the pulse duration, and the As implant dose is derived. Approximate expressions for the depth of melting and the time the Si surface remains molten yield an understanding of the implant dose and the laser-energy dependence of the diffusion depth. Finally, computer simulations of laser-induced diffusions are used to verify that As evaporation occurs to some extent during laser annealing.
Extension of thin-film calculations for films having unlike surface properties
Authors: Ijaz-ur-Rahman
Published: February 2003

The transport coefficients of a thin metal film depend on the properties of the film surfaces and especially on the relative probability of specular and diffuse scattering from each surface. In this paper earlier thin-film calculations have been extended to the case where the two surfaces have different specularity parameters or differ in the value of the critical angle below and above which the specularity parameter has widely different values.
Photoluminescence excitation spectra of AlxGa1−xP alloys
Authors: Sonomura H. , Tanaka K. , Miyauchi T.
Published: February 2003

The photoluminescence excitation spectra of AlxGa1−xP alloys with x=0–0.8 were measured at temperatures between 20 and 145 K. The crystals used in this study were prepared by slow cooling from the Ga-rich Al-Ga-P solution. Two sharp lines, L and H, were observed at 2.305 and 2.314 eV at 80 K. The H line is identified with the A line in GaP, which is due to the N isoelectronic impurity bound exciton. The H line reduced drastically when a small amount of Al was added to the initial solution. This is because the presence of Al in the solution increases the difficulty of nitrogen being introduced into the crystal. The photon energy corresponding to the L line shows that this line is due to the donor bound exciton. The threshold point energy E0 and the L line hardly change until x=0.4; above x=0.4 the energy E0 begins to increase and the L line disappears. It is proposed that small clusters of GaP are formed in the AlxGa1−xP alloy because of a disordered arrangement of the group-III atoms in the sublattice. The size of a cluster is thought to be larger than the exciton radius of 29 Å estimated by the hydrogenlike model.
Growth and electrical properties of sputter-deposited single-crystal GaSb films on GaAs substrates
Authors: Eltoukhy A. H. , Greene J. E.
Published: February 2003

Single-crystal GaSb films have been grown on semi-insulating (100) GaAs substrates using multitarget sputtering to vary the Sb/Ga atomic flux ratio r impinging on the growing film. The effects of systematic variations in growth variables (r, growth temperature, target voltage, and Ar sputtering gas pressure and purity) on the electrical properties of deposited films were evaluated. Temperature-dependent (8–600 °K) Hall coefficient and resistivity measurements were carried out on all films in order to determine the concentration and ionization energies of impurity and point-defect levels. In all cases the Hall-coefficient measurements could be fitted with two acceptor levels and a net concentration of very shallow (<1 meV) acceptors. The deepest acceptor level occurred at 80 meV above the valence-band edge and was associated with electrically active sites on dislocations originating at the film-substrate interface. A second acceptor level occurred at 40 meV above the valence-band edge and was directly related to Sb vacancies or equivalent point-defect complexes. The net concentration of very shallow acceptors was related to both Sb vacancies and donor impurities, probably oxygen. The room-temperature hole-carrier concentration in these films ranged from 5×1015 to 1×1018 cm−3, while the hole mobility was between 1 and 100 cm2/V sec. Analysis of temperature-dependent mobility data showed that the dominant charge-carrier scattering sites were dislocations introduced due to the large film-substrate lattice mismatch, ∼8%.
Photon recycling in Ga1−xAlxAs : Si graded-band-gap LED’s
Authors: Roedel R. J. , Keramidas V. G.
Published: February 2003

It is shown in this study that photon recycling, i.e., photoluminescence resulting from the self-absorption of photons generated by prior luminescence processes, affects the steady-state characteristics of graded-band-gap Ga1−xAlxAs : Si LED’s strongly and of constant-band-gap GaAs : Si LED’s weakly. In Ga1−x Alx As : Si, where the internal quantum efficiency is near unity, photon recycling can enhance the external quantum efficiency (ηext) by 25% or more. Moreover, the effective minority-carrier diffusion length (L) can be augmented by ∼40%. On the other hand, because the internal quantum efficiency in GaAs : Si is considerably less than 100%, the effect of photon recycling on η and L is less pronounced. A theoretical model of photon recycling in both the graded- and constant-band-gap material is formulated and its predictions for the effects on the external quantum efficiency, the diffusion length, and the electroluminescent spectrum are in good agreement with the experimental results.
Thermoelectric power of Nd1−xLax and Ce1−xLax alloys
Authors: Petersen T. S. , Legvold S. , Moorman J. O. , McMasters O. D. , Gschneidner K. A.
Published: February 2003

The thermoelectric power of polycrystalline double hexagonal-close-packed samples of Nd1−xLax and Ce1−xLax has been measured from 2 to 300 K. Single crystals of Nd have also been measured. These results confirm that there are at least two magnetic-transition temperatures in both sets of alloys. Data for Nd affirm there is a Néel temperature at 19.2 K and an incommensurate to commensurate transition at 7.5 K. These features are much less prominent in Ce and Nd thermopower data than corresponding features in the heavy rare earths. There is some anisotropy in the Nd single-crystal data, but the a- and c-axis data are similar in shape. In the Ce-rich Ce-La alloys there is a large positive peak at 75 K and a negative peak at ∼5 K.
Electrical properties of ion-implanted layers in Hg0.79Cd0.21Te
Authors: Margalit S. , Nemirovsky Y. , Rotstein I.
Published: February 2003

The influence of ion-irradiation damage on the electrical properties of Hg0.79Cd0.21Te has been investigated. A large damage-induced n-type conductivity with sheet carrier concentration up to approximately 1014 cm−2 and sheet resistance up to 10 Ω/square at 77 K was found for doses of 1×1015 ions/cm2 at 150 keV. The observed n-type conductivity is produced by various implanted ions regardless of whether they are donors or acceptors. The implanted n-type layer maintains its properties when subjected to temperatures as high as 120 °C. The damage is slightly annealed for this moderate treatment: the conductivity increases slightly, the sheet electron concentration decreases, and the effective mobility increases. The results also show that the implanted layer can be utilized for surface passivation of n-type photoconductors and for making Ohmic contacts to n-type material.
High-purity GaAs and Cr-doped GaAs epitaxial layers by MBE
Authors: Morkoç Hadis , Cho A. Y.
Published: February 2003

Liquid-nitrogen-temperature Hall mobilities of about 105 000 cm2/V sec have been achieved in n-type epitaxial layers grown by molecular beam epitaxy (MBE). The Hall mobility of the p-type epitaxial layers at 78 °K was about 8440 cm2/V sec. The net donor concentration and the net acceptor concentrations for n-type and p-type epitaxial layers were about 4×1014 and 1×1014 cm−3, respectively. The compensation ratio in the n-type epitaxial layers was about 0.4 as determined from the 78 °K electron mobility. Cr-doped GaAs buffer layers for FET’s were grown in a substrate temperature range of 500–640 °C. Sheet resistances in excess of 109 Ω/ ⧠ were achieved when the substrate temperature during the growth was about 580 °C or higher. The amount of Cr that can be incorporated into the epitaxial layer showed a strong substrate temperature dependence.
Temperature variation of the internal voltage in metal/insulator/metal structures with insulating film of barium-stearate
Authors: Kapil A. K. , Singal C. M. , Srivastava V. K.
Published: February 2003

Experimental results on the temperature dependence of the internal voltage in aluminum/(alumina) -barium-stearate/tin sandwich structure have been described in the temperature range 50–0 °C. It is observed that the internal voltage, which arises from the asymmetric nature of the electrodes and due to the dipole field in the alumina film, decreases with decrease of temperature. The observed temperature dependence of the internal voltage has been attributed mainly to the thermal excitation of impurities in the insulating alumina film.
A breakdown-initiated negative-resistance device with MOST-transistor structure
Authors: Yu G. J. , Tsai C. , Yu S. Y.
Published: February 2003

An external controllable dc negative-differential-resistance (NDR) device is presented. The device structure is composed of a conventional MOST and two parasitic transistors, which are internally coupled together. The mechanism of NDR is found to be initiated by both the breakdown phenomena at the drain junction and the negative-feedback circuit from the drain to the gate electrode through an externally connected resistor. Both the experimental observations and qualitative physical interpretations are given.
Effects of plastic deformation on the superconducting specific-heat transition of niobium
Authors: Zubeck R. B. , Barbee T. W. , Geballe T. H. , Chilton F.
Published: February 2003

Effects of plastic deformation on the normal, zero-field, and mixed-state specific heat of the type-II superconductor niobium were experimentally investigated. A high-resolution ac calorimetry technique was developed and used to study the effects of plastic deformation on the specific-heat superconducting transition in fields up to 2750 Oe. A method for the analysis of high-resolution specific-heat data near the superconducting transition is presented and used to determine κ variations (within a material) caused by plastic deformation. The effects of plastic deformation on the bulk superconducting transition temperature and width are also shown. Measurements of the zero-field specific heat show a systematic increase in width of the specific-heat transition with increasing deformation as well as a small increase in Tc. Both κ and the κ variation increase with increasing plastic deformation. The analysis method allows the specific-heat data of the mixed state to be decomposed in a way consistent with previously reported anisotropy data for niobium.
Noise performance and stability of a doubly-degenerate unsaturated SUPARAMP
Authors: Kadlec J.
Published: February 2003

The noise temperature and gain stability of the superconducting unbiased parametric amplifier (SUPARAMP) have been calculated. The results of the analysis suggest that extremely low-noise amplification of signals from cryogenic sources may be achieved. It seems possible to obtain an effective input noise temperature of 1 K for signal frequencies up to 10 GHz, having a stable power gain of 20–30 dB. This paper provides the fundamental design specifications necessary for the construction of a low-noise SUPARAMP.
The cavity-coupled Josephson device
Authors: Longacre Andrew
Published: February 2003

The interaction of a resistance-shunted Josephson junction with a tightly coupled resonant circuit has been examined analytically and in simulation. Parametric dependences are developed and demonstrated for the size of resonance-induced current steps in the device’s V-I curve and the corresponding level of excitation of the resonance.
Magnetic properties and hyperfine interactions in the β‴ phase of potassium ferrite
Authors: Romanov V. P. , Candela G. A. , Roth R. S. , Swartzendruber L. J.
Published: February 2003

The hyperfine field structure and magnetic susceptibility in the temperature range 5–295 K was measured for the β‴ phase of potassium ferrite. Results show that this new phase has an antiferromagnetic ordering similar to the β phase. The hyperfine-interaction parameters have been determined and are compared with those found in magnetite, β-phase potassium ferrite, and barium hexaferrite.
Magnetoelastic-surface waves on YIG substrate
Authors: Komoriya G. , Thomas G.
Published: February 2003

This paper presents the results of an experimental study of the propagation characteristics of magnetoelastic-surface waves (MESW’s) on the (011̄) surface of a 1.5×0.1-cm2 YIG disk and on the (111̄) surface of a 5.1-μm YIG film, and a quantitative analysis of the results. Magnetoelastic-surface waves were excited and detected by means of meander-line transducers which were fabricated through standard photolithography techniques. The waves were excited so as to propagate along [100] and [011] directions on the disk and along the [011] direction on the film. Strongest excitation occurred for the magnetic bias field tangential to the surface and parallel to the direction of propagation. The propagation characteristics were studied at 143.5, 235, and 440 MHz. In addition to the MESW mode, other magnetoacoustic modes, which were stronger than the MESW mode under certain conditions, were also observed. Under certain conditions, as many as a dozen of these other modes, with a wide range of velocities both faster and slower than the MESW’s, were observed. Waves propagating along the [100] direction showed a distinct MESW mode. For the lower frequencies the MESW was the strongest mode excited; at higher frequencies some of the other modes were as much as 5 dB stronger than the MESW mode. For propagation along the [011] direction, the MESW was present, but was always accompanied by other strong magnetoacoustic modes with nearly the same propagation velocity. The strength of both types of modes increased rapidly with excitation frequency, in qualitative agreement with the theory of meander-line excitation. Between 70 and 440 MHz excitation efficiency increased by nearly 30 dB. The experimental results on the disk show that the magnetic bias field required to produce the minimum insertion loss for propagation in the [100] direction was always larger than the bias field for propagation in the [011] direction. An analysis of magnetostatic resonance predicts a difference in the bias field for the two directions of propagation consistent with the measured values. Stripe domains were observed with at least two stable directions in the YIG film. The period of the domains was approximately 4 μm. MESW’s were excited and detected at a magnetic bias field for which a domain structure had disappeared. These observations differ from those of Volluet et al.
ESR study of NiFe2O4 precipitation process from silicate glasses
Authors: Komatsu T. , Soga N. , Kunugi M.
Published: February 2003

The precipitation process of nickel ferrite (NiFe2O4) from silicate glasses has been studied by electron spin resonance (ESR). The ESR linewidth ΔH1/2 and effective g value were measured as functions of heat-treatment temperature and time. Both the linewidth and effective g value change drastically near the glass transition temperature and precipitation temperature. The results are interpreted on the basis of the development of ion ordering, i.e., magnetic-order development, that occurs during the heat treatments.