bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature dependence of critical current superconducting for i
n s
i
t
u composites
Authors: Finnemore D. K. , Ostenson J. E. , Gibson E. D. , Verhoeven J. D. , Doyle T. B.
Published: February 2003

The critical current for in situ prepared Cu-Nb3Sn microfilamentary composites has been measured as a function of both temperature and magnetic field in order to determine the suitability of these materials for superconducting magnets which operate above 4.2 K, either continuously or in brief excursions. A rather simple relation, Jc =AB−1/2 (Bc2−B)2 where A=860 A cm−2T−3/2, describes the data very well. The temperature dependence of Bc2 is the dominant factor controlling Jc(T). Values of Bc2 determined both from low current resistive transitions and from Kramer plot extrapolations give Bc2 =B0(1−t2), where B0 is approximately 19 T. Scaling applies in these materials and the volume flux pinning force goes as B5/2c2 as predicted if the flux line shear modulus controls the flux pinning. The data show that a magnet designed to operate at 4.2 K and 12 T also will operate well at 10 K and 7 T.
Powder-metallurgical preparation and properties of superconducting Nb3Sn and V3Ga microcomposites
Authors: Bormann R.
Published: February 2003

The powder-metallurgical process for the preparation of filamentary Nb3Sn and V3Ga microcomposites is described and compared to alternative processing techniques. Investigations of the thermal stability of the submicron size filamentary structure show that the thickness of the ribbonlike filaments should be in the range between 0.1 and 1 μm for a typical wire diameter of 0.2–0.4 mm to avoid a spheroidization of the filaments during the diffusion treatment. The superconducting properties are comparable to the optimized values of other techniques. Overall critical current densities Jc of a Cu-30 wt. % Nb+Sn composite wire amount to 109 and 1.6×108 A/m2 at fields of 10 and 15 T, respectively, whereas values up to 4×108 A/m2 at 16 T are observed for Cu-30 wt. % V+Ga composites. The mechanical behavior such as tensile strength, and the dependence of the superconducting current carrying capability on tensile stress and strain show a favorable behavior in light of a technical application.
Magnetoacoustic resonance in antiferromagnetic insulators in weak magnetic fields
Authors: Maugin G. A. , Sioké-Rainaldy J.
Published: February 2003

Magnetoacoustic resonance between transverse phonons and magnons is studied analytically on the basis of a set of linearized equations previously deduced from a fully nonlinear, rotationally invariant, thermodynamically admissible theory of uniaxial antiferromagnets of the easy-axis type. The present paper concerns the case where the bias magnetic field is relatively weak and aligned with the axis of symmetry. Various types of dispersion are exhibited depending on whether disturbances propagate along the symmetry axis in the positive or negative direction or orthogonally to this axis. In the first situation, two magnetoacoustic regions are placed in evidence (forward travelling modes), which correspond to the interaction between, or the entanglement of, either left-circularly polarized transverse phonons and the upper magnon branch or right-circularly polarized transverse phonons and the lower magnon branch. The resulting dispersion is thoroughly discussed in an analytical manner in terms of a small parameter which represents globally magnetoelastic couplings. The accompanying magnetoacoustic Faraday effects are also exhibited. In the second situation, longitudinal and slow-transverse phonons propagate independently of magnons, while fast transverse phonons couple by resonance with both upper and lower magnon branches, which provides a direct analogy with resonance phenomena in purely mechanical theories, such as vibrations in rods.
Dielectric behavior of red HgI2 under direct bias
Authors: Regolini Jorge L. , Saura José
Published: February 2003

The dielectric constant and loss were measured at several frequencies and temperatures for red mercuric iodide. The equivalent circuits for the sample, before and after a direct bias has been applied for a long time, are discussed. Complex impedance and loss tangent plots versus frequency and temperature show a contact barrier formation after long time polarization. Results are discussed in terms of gamma radiation detector performance.
Dielectric breakdown of polyethylene in divergent field: Role of dissolved gases and electroluminescence
Authors: Laurent C. , Mayoux C. , Noel S.
Published: February 2003

The dielectric breakdown of polyethylene subjected to a highly divergent electric field has been studied. The samples were held at room temperature and an alternating field of frequency 50 Hz applied. When the material contained only residual gas it was possible to detect light emanating from the bulk of the polymer. It is proposed that this was an electroluminescence of the polyethylene resulting from the recombination of charge carriers injected at the electrode–polymer interface with the deep trapping centers in the polyethylene. The detection of this light required the use of a very sensitive photomultiplier coupled to an optical microscope. When the material contained a dissolved gas in equilibrium, the behavior of the solid was found to depend on the chemical reactivity of the gas and on its electron affinity. In particular, the influence of oxygen has been studied. A model is proposed which accounts for all the experimental results and which underlines the fundamental role played in the prebreakdown process by the gas dissolved in the polymer.
Dark defects in InGaAsP/InP double heterostructure lasers under accelerated aging
Authors: Fukuda M. , Wakita K. , Iwane G.
Published: February 2003

Degradation modes due to dark defects under accelerated aging for InGaAsP/InP double heterostructure lasers are investigated by monitoring pulse threshold current, leak current, absorption coefficient, gain factor, and electroluminescence topograph. Most of the dark defects are dark spot defects (DSD’s) and there are only few 〈100〉 dark line defects. At the initial stage of the degradation, these dark defects scarcely absorb the emitted light, and the reduction of gain factor causes the increase of pulse threshold current. After this stage, dark defects begin to act as absorber of the emitted light. The generation time of such DSD’s strongly depends on the injected current density but only weakly on the junction temperature in the range of 25 ° to 250 °C. The activation energies for the generation time of the first dark spot defect and the growing speed of 〈100〉 dark line defects are estimated to be 0.16 and 0.2 eV, respectively.
New optical recording material for video disc system
Authors: Watanabe Kenjirou , Sato Noboru , Miyaoka Senri
Published: February 2003

The optical characteristics of Sb2Se3 and Sb2Te3 films are changed due to an amorphous-crystalline phase transition below 200 °C. The respective reflectivity of 400 Å Sb2Se3 and 300 Å Sb2Te3 films, each on a Te reflective layer, is increased from 10% to 30% and from 45% to 65% by laser radiation. Using these new materials, optical disc recording of FM video signals by a diode laser has been demonstrated.
Monolithic surface acoustic wave resonator oscillator
Authors: Raju T. A. , Kurahatti N. G. , Dube N. M. , Roy M. K.
Published: February 2003

A monolithic surface acoustic wave (SAW) resonator operating at 156 MHz, in which the frequency controlling element is a Fabry–Perot type of SAW resonator and the gain element is a monolithic SAW amplifier (SiOx/InSb/SiOx structure located inside the SAW resonator cavity) is described and experimental details presented. Based on the existing experimental data, an uhf monolithic ring resonator oscillator is proposed.
Mechanisms of etching and polymerization in radiofrequency discharges of CF4–H2, CF4–C2F4, C2F6–H2, C3F8–H2
Authors: d’Agostino R. , Cramarossa F. , Colaprico V. , d’Ettole R.
Published: February 2003

Some results obtained during the etching of Si or the deposition of fluorocarbon films over Si substrates uncoupled from ground in rf plasmas fed with CF4–H2, C2F6–H2, C3F8–H2 and CF4–C2F4 mixtures are presented. The polymerization process is explained on the basis of a mechanism which involves CF and/or CF2 radicals as building blocks as well as an activation of the polymer surface by means of charged particle bombardment. It is definitively proved that the etch rate of Si depends only on the F-atom concentration, independent of conditions in the various feeds.
Focus waves modes in homogeneous Maxwell’s equations: Transverse electric mode
Authors: Brittingham James Neill
Published: February 2003

This paper presents mathematical formulations for new, three-dimensional, packet-like solutions to the free-space homogeneous Maxwell’s equations. These solutions are real, nonsingular, continuous functions which propagate in a straight line at light velocity. They remain focused for all time. The asymptotic behavior of the fields away from the moving pulse center has a magnitude which decreases as the inverse of the distance from the pulse centers.
1/f fluctuations in diffusion processes of effective space dimension less than one
Authors: Agu Masahiro
Published: February 2003

It is shown that the stationary fluctuations described by the diffusion equation of an effective space dimension less than one have a 1/f spectrum. A physical diffusion model equivalent to such a low dimensional diffusion process is proposed. Here, a singular disturbance of temperature fluctuation is assumed to diffuse with the space-dependent diffusion coefficient D(r)=D0(1+κr−m)θ. Here, D0 is the constant part of the diffusion coefficient and κr−m represents the effect of local temperature enhancement of the background medium caused by the singular disturbance itself, where r is the distance from the singular disturbance at r=0, and m and θ positive constants.
Gaseous products from the reaction of XeF2 with silicon
Authors: Winters Harold F. , Houle F. A.
Published: February 2003

XeF2 was reacted with silicon, and the gaseous products were detected using modulation techniques which made the experiments sensitive only to products which had not collided with a wall. In agreement with previous experiments, SiF4 was found to be the major reaction product. Radicals such as SiF and SiF2 were observed at a much lower level. However, SiF2 was not found to be the dominant species as might have been suspected on the basis of experiments by other workers with atomic fluorine. Bombardment with 2000-eV argon ions enhanced the rate of product formation and decreased the fraction of the products that was SiF4. Production of radical species, in particular SiF2, was enhanced. Collisions of SiF2 with fluorinated, stainless-steel vacuum chamber walls were investigated in order to determine whether the SiF2 radical was converted to SiF4 as suggested by others. Wall reactions were found to be important in some circumstances and not important in others.
Theory of beam induced current characterization of grain boundaries in polycrystalline solar cells
Authors: Donolato C.
Published: February 2003

A theoretical analysis is given of the induced current profiles at grain boundaries in polycrystalline solar cells, as obtained by light or electron beam excitation. The area A and the variance σ2 of the contrast profile of a grain boundary are calculated for realistic generations as functions of the interface recombination velocity vs and the minority carrier diffusion length L. A graphical new procedure is proposed which allows the simultaneous determination of vs and L from the measured values of A and σ. The evaluation of an experimental electron beam induced current profile illustrates the applicability of the theory.
Mode of incorporation of phosphorus in Hg0.8Cd0.2Te
Authors: Vydyanath H. R. , Abbott R. C. , Nelson D. A.
Published: February 2003

Single-crystal samples of phosphorus-doped Hg0.8Cd0.2 Te were annealed at temperatures varying from 450 to 600 °C in different partial pressures of Hg. Hall effect and mobility measurements were performed on the samples cooled to room temperature. All the samples were found to be p type, with the hole concentration being much less than the total concentration of phosphorus present in the crystals. The hole concentration was found to increase with increase in partial pressure of Hg, in contrast to the behavior observed in undoped crystals. Also, the hole concentration obtained in the doped samples at low Hg pressures was less than that in undoped crystals. The 77-K hole mobility of the doped samples was similar to that of undoped samples. All these inferences indicate that phosphorus behaves amphoterically in Hg0.8Cd0.2 Te(s), acting as a single acceptor occupying interstitial and tellurium lattice sites at high Hg pressures, and as a single donor occupying Hg lattice sites at low Hg pressures; at intermediate Hg pressures, the majority of the phosphorus appears to be present as electrically neutral pairs formed from the association of the interstitial and substitutional phosphorus species. At low Hg pressures, a large fraction of the phosphorus appears to be present as positively and negatively charged pairs of substitutional phosphorus and vacancies of Hg. Thermodynamic constants evaluated for the incorporation of the various phosphorus species satisfactorily explain the experimental results.
Effects of interface-potential nonuniformities on carrier transport across silicon grain boundaries
Authors: Thomson D. J. , Card H. C.
Published: February 2003

In an experimental investigation of electronic transport across individual grain boundaries in cast silicon, we have recently arrived at the conclusion that the diffusion potential at the grain boundary may in many cases exhibit appreciable variation over the boundary plane. The present paper describes an interpretation of the experimental observations in terms of a Gaussian distribution of interface potential over the grain-boundary surface, and a majority carrier transport to the boundary which is diffusion limited. In the grain boundaries studied the mean value of the diffusion potential was found to vary from 〈Vd〉 ≂0.70 to 〈Vd〉 ≂0.32 eV and the standard deviation from σ≂0 to σ≂0.11 eV. These values were derived from the change in activation energy with temperature. For the particular grain boundaries with spatial uniformity (σ≂0) excellent agreement of the characteristics with an emission/diffusion model of majority-carrier transport is obtained. It is concluded (i) that it is not generally proper to assume that grain boundaries in cast silicon are spatially uniform and (ii) that the Gaussian distribution model provides a satisfactory first approximation to the spatial variation in grain boundaries.
Determination of semiconductor quasi-Fermi level separation under illumination
Authors: Kar S. , Varma S.
Published: February 2003

Two new experimental techniques are described for the determination of the quasi-Fermi level separation in a semiconductor material, exposed to illumination. In one method, this separation is obtained from the change in the value of the measured high frequency capacitance of a transparent conductor-oxide-silicon structure in strong inversion, with the intensity of optical illumination. In the other method, the quasi-Fermi level separation is obtained from the shift of the experimentally obtained low frequency space-charge capacitance versus the surface potential curve in strong inversion. Results obtained from the two techniques agreed well.
Amorphous to crystalline transformation of Fe81B13.5Si3.5C2
Authors: Prasad B. Bhanu , Bhatnagar Anil K. , Jagannathan R.
Published: February 2003

The crystallization of Fe81B13.5Si3.5C2 (Metglas 2605SC) has been studied by resistivity, differential thermal analysis (DTA), Mössbauer and x-ray techniques, and compared with reported results based on other techniques. The DTA shows in addition to the usual two peaks a third peak at 850 K paralleled by a change in the resistivity measurements at the same temperature. The crystallization is found to take place gradually in the temperature region 750–810 K with ∝-iron precipitating first. Mössbauer studies provide evidence for ∝-Fe, Fe2B, and a species with a hyperfine magnetic field ∼314 kOe which could not be unequivocally established. X-ray data shows evidence for the presence of Fe3C in addition to ∝-Fe and Fe2B.
Model of the Čerenkov laser
Authors: Šoln Josip
Published: February 2003

A model of the (wigglerless Čerenkov laser through the S matrix approach is given. Here the classical electron current due to electrons with straight trajectories interacts with a quantized radiation field in a refractive medium of finite extent. The multiphoton distribution function gives the mean photon multiplicity which in turn yields the gain at a given frequency. The imposition of the quantum recoil yields the full ‘‘quantum mechanical’’ gain from which the usual ‘‘classical’’ gain follows. In an example where the radiation wavelength is 2.5 mm and the refractive index 1.8, we estimate the maximum gain to be about 20%; this suggests that the Čerenkov laser may be an effective radiation source. The effect of the finite interaction time on the gain calculation and a new, possibly quantum, effect of residual photons are also discussed.
Temperature dependence of the resonant frequency of electroded contoured AT-cut quartz crystal resonators
Authors: Stevens D. S. , Tiersten H. F. , Sinha B. K.
Published: February 2003

A system of approximate equations recently obtained for the determination of thermal stresses in electroded piezoelectric plates is applied to contoured AT-cut quartz crystal resonators. The changes in resonant frequency resulting from the thermally induced biasing stresses and strains, the temperature derivatives of the fundamental elastic constants of quartz, and the very important temperature dependence of the thickness piezoelectric constant for the AT cut are determined from an equation for the perturbation of the eigenfrequency of the piezoelectric solution due to a bias. The changes in resonant frequency with temperature are calculated for the fundamental and some of the harmonic overtone thickness modes, which were obtained in a recent analysis of overtone modes in contoured crystal resonators. The influences of both the contouring and the electrode size are clearly exhibited.
Degradation of poly(methyl methacrylate) in CF4 and CF4/O2 plasmas
Authors: Wu B. J. , Hess D. W. , Soong D. S. , Bell A. T.
Published: February 2003

The degradation of poly(methyl methacrylate) films exposed to CF4 and CF4/O2 plasmas in a parallel plate reactor is investigated by means of gel permeation chromatography. Profile results indicate that degradation is high in the top few thousand angstroms, although reductions in molecular weight are observed throughout the 1.5 μm films. Oxygen additions to CF4 generate increases in PMMA etch rates, but molecular weight profiles suggest that degradation is still confined to the film surface. The shifts in molecular weight distribution obtained from plasma degradation experiments are simulated by a random scissioning model.
Measurement of the indices of refraction and the absorption coefficients of dielectric materials in the millimeter wave region
Authors: Ahn B. H.
Published: February 2003

The indices of refraction and absorption coefficients of LiNbO3, LiTaO3, GaAs, and Stycast HiK, a plastic dielectric material, which are used frequently for millimeter wave device fabrication, were measured at 55 and 112.5 GHz using a Fabry-Perot transmission technique in waveguide.
Charge storage in a discontinuous Au film deposited on Si
Authors: Alkabetz E. , Gorodetsky G. , Volterra V.
Published: February 2003

Relatively large Au islands of the order of 1 μm and a density of ∼107/cm2, in coexistence with much smaller Au islands, were deposited on an n-type Si. The observed, randomly distributed Au/Si Schottky junctions, exhibited a diode charge storage with a time constant, RC≊1 ms.
Interface states induced in silicon by tungsten as a result of reactive ion beam etching
Authors: Gildenblat Gennady , Heath Barbara A. , Katz William
Published: February 2003

Interface states induced in silicon by reactive ion beam etching (RIBE) have been investigated using a metal oxide semiconductor capacitance-voltage (MOS-CV) technique, secondary ion mass spectrometry (SIMS), and Rutherford backscattering spectrometry (RBS). RIBE using an ion beam extracted from a C2F6 plasma was used to selectively remove a layer of SiO2 from the surface of single crystal silicon. MOS capacitors formed after the regrowth of a thin SiO2 layer on the silicon showed the presence of a substantial interface state density (Nss =1012–1013 eV−1 cm−2) near the middle of the energy gap of Si. RBS experiments on the Si surfaces exposed to the reactive ion beam showed the presence of tungsten (presumably from the tungsten filaments used to ignite the plasma and neutralize the ion beam). SIMS depth profiles of these samples after reoxidation to form capacitors showed tungsten contamination which was at a maximum at the SiO2-Si interface. The interface state density determined from CV measurements scaled linearly with the tungsten concentration at the interface as determined by SIMS. Interface states were formed only in the case where the Si surface was exposed to the reactive ion beam. As little as 10 nm of SiO2 remaining on the Si surface after RIBE was sufficient to prevent interface states formation.
Magnetoresistance of Pd-Fe and Pd-Ni-Fe alloys
Authors: Hsu Y. , Schmidt J. E. , Gupta M. , Jen S. , Berger L.
Published: February 2003

The electrical resistivity of Pd-Fe alloys has been measured in magnetic fields parallel and perpendicular to the current, for a wide range of alloy compositions. The influence of atomic ordering on the magnetoresistance has been investigated. The ferromagnetic anisotropy of resistance Δρ/ρ0 reaches a maximum value of +9% in the ordered state between 30 and 35 at. % Fe, and +6% in the disordered state between 40 and 60 at. % Fe, at 4.2 K. At 295 K, Δρ/ρ0 never exceeds +1%. Similar measurements have been done on (Pd50 Ni50)100−x Fex for x≤30 at. % Fe. The maximum Δρ/ρ0 value of +7% is obtained for 10 at. % Fe at 4.2 K.
Trapping center parameters in indium selenide single crystals by thermally stimulated current measurements
Authors: Micocci G. , Rizzo A. , Tepore A.
Published: February 2003

Systematic investigations of trapping centers parameters have been carried out on InSe single crystals grown from nonstoichiometric melt, by using a thermally stimulated current (TSC) technique. TSC measurements have been performed between 50 and 300 K, and the results have been analyzed according to different methods. The trap characteristics have been determined. In particular, two levels located at 60 and 160 meV below the conduction band have been investigated in detail. Their capture cross sections have been found to be 1.5×10−23 and 9.2×10−21 cm2, respectively, and their concentrations are 1.9×1017 and 2.3×1016 cm−3, respectively. It is concluded that in these centers retrapping is negligible. One additional level has been found at 340 meV with concentration NT =4.2×1016 cm−3 and capture cross section σ=3.5×10−19 cm2.
Effect of composition on the structure and electrical properties of As-Se-Cu glasses
Authors: Hafiz M. M. , Ibrahim M. M. , Dongol M. , Hammad F. H.
Published: February 2003

As-Se-Cu glasses, with Cu content varying between 5 and 25 at. %, were produced by quenching from the melt. The values of resistivity and activation energy for conduction decreased continuously with increasing the copper content. Memory switching phenomena was observed in glasses containing Cu less than 20 at. %. Glasses containing higher Cu concentration showed a reverse switching cycle. Thermally induced changes in the structural properties have been examined using x-ray diffraction, differential thermal analysis, and scanning electron microscopy. The results were discussed on the basis of thermally induced transformations.
A reevaluation of the meaning of capacitance plots for Schottky-barrier-type diodes
Authors: Fonash S. J.
Published: February 2003

Capacitance–voltage (C-V) data, in the form of 1/C2 versus voltage plots, have long been used to extract information on the space charge region doping and barrier height in Schottky-barrier-type diodes. The meaning of the slope and voltage intercept of these 1/C2 versus voltage plots for reverse-biased diodes is reexamined in this analysis for the case when there is an inadvertent or purposeful interface layer present. The possibility of having interface states, one type of which communicates with the metal and another type of which communicates with the semiconductor, is considered, as is the fact that these two classes of states may, or may not, be able to follow an ac signal. The analysis first assumes that the densities of these states do not vary across the gap; this restriction is later relaxed and the possibility of variable densities of interface states is considered. The results of the analysis differ from those of previous studies. In general, it is found that most sets of interface state characteristics lead to nonlinear 1/C2 plots when an interfacial layer is present. Constant 1/C2 slopes (true straight line plots for all values of reverse bias) are found only if there are no interface states present or only if the states present have a constant density across the gap and follow the metal for all frequencies.
An x-ray diffraction study of lattice imperfection in cold-worked FCC alloys. IV. Copper-germanium (alpha-phase)
Authors: Ghosh S. K. , De M. , Gupta S. P. Sen
Published: February 2003

X-ray Fourier line profile analysis has been performed on four compositions of copper-germanium (FCC) alloys containing 3.05, 6.00, 9.25, and 10.00 at. % of solute germanium. The diffraction profiles from 111, 200, 220, 311, 222, and 400 reflections for both cold-worked and annealed samples in each case have been recorded in a counter diffractometer with Cu radiation using a LiF crystal monochromator. Detailed studies on recorded profiles, considering recent developments in the analyses (as in Papers I–III), for peak shift, peak asymmetry, and peak shapes, have been made in order to evaluate the microstructural parameters characterizing the deformed states of the materials. Both the effects of lattice parameter change (Δa/a0) and long-range residual stress σ are found to be negligible in causing the net peak shifts. Quantitative estimations of intrinsic (α′), extrinsic (α″), and twin ( β) stacking fault probabilities have been made, and results have clearly shown the increased presence of intrinsic faults over the extrinsic ones and a complete absence of deformation twin faults, in accordance with the previous observations (Papers I–III). The values of dislocation density ρ have been evaluated from anisotropic domain sizes and rms microstrains. Considering the two expressions for the stacking fault energy (Williamson and Smallman, 1956; Schramm and Reed, 1975), the stacking fault energy of pure Cu (γ0) has also been estimated.
Photovoltage decay in p-n junction solar cells including the effects of recombinations in the emitter
Authors: Jain S. C. , Ray U. C.
Published: February 2003

The expressions for the open circuit photovoltage decay in a p-n junction solar cell are derived, including the effects of recombinations in the emitter. It is shown that for a cell with base thickness wB≫LB, the base diffusion length, the voltage decay rate for small values of time depends on the emitter dark saturation current JE0; the larger the value of JE0 , the faster is the initial rate of voltage decay. For large values of time, the rate of voltage decay is solely determined by the minority carrier lifetime in the base τB and is independent of JE0 . However, for a cell with wB≲LB, the voltage decay is linear from the very beginning and the decay rate is of the form (kT/e)[(1/τB) +(1/t1)]. The time constant t1 is independent of τB . It, however, depends on the base thickness, the effective back surface recombination velocity, and the emitter dark saturation current JE0 . The value of JE0 depends on emitter thickness, front surface recombination velocity, drift field in the emitter, band-gap narrowing, and Auger recombinations in the emitter.
Spectroscopic Doppler-free methods for measuring the electric and magnetic fields in magnetically insulated ion diodes
Authors: Maron Y. , Litwin C.
Published: February 2003

A two-photon absorption technique is proposed for the measurement of the Stark shift and the Zeeman splitting of the ion energy levels in the diode acceleration gap of a magnetically insulated ion diode for the purpose of determining the local electric and magnetic fields. Various measurement schemes are discussed. The required laser power and linewidth are estimated and found to be attainable by the present day lasers. A measurement of the ion transverse velocities in the diode gap is also proposed.
Boron diffusion during electron pulse annealing of silicon
Authors: Dilhac J. M. , Ganibal C. , Vialaret G. , Martinez A.
Published: February 2003

Results concerning boron diffusion during electron pulsed annealing of silicon are presented. The initial boron profile is realized by successive implantations at 50, 80, and 190 keV. Dopants diffusion is explained theoretically in terms of liquid phase diffusion. Electrical activity is about 100%.
Lateral growth of titanium silicide over a silicon dioxide layer
Authors: Révész P. , Gyimesi J. , Pogány L. , Petõ G.
Published: February 2003

If a silicon dioxide step on a single crystal of silicon covered with titanium is annealed, then, following vertical growth on the silicon part, lateral growth of titanium silicide takes place over the oxide layer. In the temperature range 750–950 °C this lateral growth of Ti–silicide was found to be a linear function of the square root of the annealing time. The activation energy of the lateral growth was found to be 1.89 eV. During lateral growth the Ti–silicide forms a deep spike in the silicon crystal at the SiO2 step.
Effects of space charge on the performance of an orotron
Authors: Leavitt Richard P. , Wortman Donald E.
Published: February 2003

We consider the effects of mutual electronic repulsion in the electron beam in the orontron, based on the general analysis of Gover and Strangle [IEEE J. Quantum Electron. QE-17, 1196 (1981)]. The theory of orotron operation is extended to include space charge effects, and calculations are in good agreement with available experimental results at low (∼6.7 A/cm2) beam current densities. The theory predicts than an output power of 264 W cw may be obtainable at 75 GHz with a beam current density of 50 A/cm2.
Observation of diffraction caustics for ultrasound
Authors: Dong Rui-qi , Adler Laszlo , Doyle P. A.
Published: February 2003

The formation of caustics due to the diffraction of ultrasound is observed by scanning in the shadow region close behind an elliptical obstacle in water. Good agreement is obtained between experiment and the theoretical geometry of the caustic, which is an astroid centered in that shadow region.
Comment on ‘‘Electromagnetic decay into a surface plasma wave and an ion acoustic surface wave in a semi-infinite plasma’’
Authors: Mateev E. , Zhelyazkov I.
Published: February 2003

It is pointed out that the parametric instability of surface modes in a semi-infinite plasma is a four-wave process and the threshold should be ∼0.7(mi/me)1/2 times larger than that found by Yasumoto [J. Appl. Phys. 52, 3238 (1981)].
Solid-phase lateral epitaxy of chemical-vapor-deposited amorphous silicon by furnace annealing
Authors: Kunii Yasuo , Tabe Michiharu , Kajiyama Kenji
Published: February 2003

A single-crystalline silicon-on-insulator structure has been fabricated with solid-phase lateral epitaxy. Chemical-vapor-deposited amorphous silicon (CVD a-Si) deposited on a SiO2 stripe is crystallized by furnace annealing. A new CVD technique (clean CVD) has met the conditions required for solid-phase epitaxy; clean interface and reduction of impurities and microcrystallites in the a-Si film. In the case of a 4-μm-wide SiO2 stripe parallel to the 〈100〉 direction, the entire deposited layer grows epitaxially by low-temperature furnace annealing (550∼650 °C). In the case of a 10-μm-wide SiO2 stripe, the whole surface region also grows epitaxially, although the deep region partially becomes polycrystalline in areas distant from the open substrate surface. The grown-layer crystallinity is improved by subsequent high-temperature annealing.
Defects induced by electron irradiation in InP
Authors: Suski J. , Bourgoin J. C. , Lim H.
Published: February 2003

Schottky diodes made on n-type InP, containing 2×1016 cm−3 free carriers, have been irradiated at room temperature with ∼1 MeV electrons. Using transient capacitance techniques, three electron traps situated at 0.14, 0.24, and 0.41 eV below the conduction band have been detected. Measurement of their introduction rates and comparison with the carrier removal rate measured at 80 K indicate that these traps represent ∼20% of the electrically active defects created by the irradiation. The capture cross section for electrons of the trap at EC −0.24 eV is 3×10−20 cm2.
New insights on the reversal of the site of electromigration failure in gold films doped with alkali
Authors: Hummel R. E. , Matts-Goho S. , DeHoff R. T.
Published: February 2003

The description of current-induced failures in thin film metallizations used in microelectronic devices should not be limited to electron wind arguments. Several failure mechanisms such as grain boundary grooving, thermotransport and electrotransport, may contribute to matter transport under conditions normally encountered in service. Grain boundary grooving is accelerated by doping thin gold films with alkali ions. Pure thin gold stripes which are subjected to a direct current of high density fail near the cathode, whereas similar gold films doped with alkali ions fail near the anode. Experiments utilizing Auger electron spectroscopy show an enrichment of alkali metal near the anode after current stressing. The accumulation of alkali metal at the anode promotes grain boundary grooving and void formation there.
Metal/Insulator/Si structures with low interface state density fabricated by combined ion beam sputtering and atomic hydrogen beam treatment
Authors: Garrigues M. , Blanchet R. , Sibran C. , Viktorovitch P.
Published: February 2003

Ion beam techniques, combining insulator deposition and atomic hydrogen treatment, are used for the fabrication of metal–insulator–silicon (MIS) structures at low temperature (300 °C). SiNxOy and AlNxOy insulating layers are deposited by reactively sputtering either a silicon or an aluminium target with a nitrogen ion beam. The y/x ratio is controlled by introducing pure molecular oxygen in the vicinity of the substrate. The resistivity and dielectric strength of the films increase with the y/x ratio and exceed typically 1016 Ω cm and 2×106 V/cm, respectively. The electrical properties of the MIS devices were investigated by the capacitance/conductance method. The dramatic reduction of the interface state density (below 1011 cm−2 eV−1 with AlNxOy) consecutive to H treatment and annealing in nitrogen at 300 °C, is interpreted on the basis of the formation, weakening, and strengthening of Si–H bonds.
Effect of stainless steel reinforcement on the critical current versus strain characteristic of multifilamentary Nb3Sn superconductors
Authors: Ekin J. W. , Flükiger R. , Specking W.
Published: February 2003

A series of multifilamentary Nb3Sn superconductors were fabricated containing from 0% to 52 vol % stainless steel reinforcement strands as an integral part of the conductor. Critical current versus strain measurements are reported which show that the stainless steel introduces a relatively large compressive prestrain, εm, into the superconductor, ranging from εm ≂0.3% for no stainless steel reinforcement to εm =0.84% for 52 vol % stainless steel. Accompanying this high compressive prestrain in the reinforced conductors is a large degradation of the conductor’s critical current, Ic. The Ic degradation relative to the strain-free value has been measured, for example, to be more than 50% at 13 T for εm =0.64%. Several methods are discussed for reducing the large Ic degradation in A15 superconductors containing internal reinforcement.
Strain dependence of the low-frequency dielectric constants of a few alkali halides
Authors: Balakrishnan Geetha , Srinivasan K. , Srinivasan R.
Published: February 2003

The variation of the low-frequency dielectric constant of NaCl, KCl, and KBr with stress has been determined by subjecting the crystals to uniaxial compressive stresses. Contrary to expectations, the dielectric constant was found to increase on stressing. On n irradiation, the sign of the change in the dielectric constant of the crystals was reversed. This has been attributed to the pinning of the dislocations, whose initial movement under stress might have caused the dielectric constant to increase.
A revised analysis of dry oxidation of silicon
Authors: Fargeix A. , Ghibaudo G. , Kamarinos G.
Published: February 2003

The anamalous initial regime of silicon dry oxidation is properly demonstrated using derivative plots of experimental data. The proposed analysis, based on the physical Grove–Deal approach, infers that this initial regime cannot be explained either by an enhanced diffusivity of the oxidizing species near the Si-SiO2 interface as previously advanced, or by the chemical model of Blanc. In contrast it is shown that the diffusion through the first hundreds of Å of the oxide layer is slowed down. It is suggested that this lower diffusivity is due to compressive stresses in the growing silica.
High efficiency in ‘‘semithermal’’ solar energy converters
Authors: Ross Robert T.
Published: February 2003

A photonic device in which the excited carriers thermally equilibrate both among themselves and with the lattice, but maintain distinct chemical potentials in the ground and excited bands, has the same high ideal efficiency as a converter in which only the carriers are hot. Because the hot carriers need only be removed from the absorber faster than band-to-band transitions, such a ‘‘semithermal’’ device should be more practical than devices in which carriers may not equilibrate with the lattice.
Characterization of mechanochemically polished (111) surface of silicon crystal by diffuse x-ray scattering
Authors: Kashiwagura N. , Harada J. , Ogino M.
Published: February 2003

Diffuse x-ray scattering technique was applied to characterize the surface of a (111) silicon wafer polished mechanochemically. Extra diffuse scattering, which is considered to be attributable to localized strain fields, was detected. The localized lattice distortions were of similar characteristics to those found in a (111) surface lapped with white alundum (No. 2000) and etched by 30∼60 μm [S. Yasuami and J. Harada, J. Appl. Phys. 52, 3989 (1981)]. The thickness of the damaged layer induced by mechanochemical polishing was only about 15 μm, however, which is much smaller than that obtained by lapping (about 100 μm). This is the first observation of the damage left in a mechanochemically polished (111) silicon surface.
Dependence of fluxon dynamics on loaded terminations in long overlap Josephson junctions
Authors: Olsen O. H. , Samuelsen M. R.
Published: February 2003

Fluxon motion in long overlap-geometry Josephson junctions influenced by loaded terminations is investigated. The combination of results from a perturbation method with an approximate expression for the emitted power yields equations describing the fluxon dynamics. The form of the first zero field step is presented for various parameters and the emitted power is calculated.
Fluctuations in semiconductor laser emissions
Authors: Copeland J. A.
Published: February 2003

Fluctuations in the optical power emitted by a semiconductor laser into various spectral lines is due to the large fluctuations in the size of the coherent photon packets started by individual spontaneous-emission photons. These fluctuations persist for nanoseconds and create the partition noise effect observed in high bit-rate optical-fiber systems. Representative output fluctuations in mode power have been obtained by a Monte Carlo technique which simulates the stochastic nature of photon emission. The results give a physical basis for recent experimental observations.
Effect of silicon orientation and hydrogen anneal on tunneling from Si into SiO2
Authors: Weinberg Z. A. , Hartstein A.
Published: February 2003

The issue of transverse momentum conservation in tunneling is examined by photon-assisted-tunneling measurements on metal-oxide-silicon structures. Results are compared for tunneling from silicon of 〈100〉, 〈110〉, and 〈111〉 orientations. The results for 〈100〉 and 〈110〉 are almost identical. For 〈111〉 it is concluded that the interface barrier energy is higher by about 0.5 eV than for 〈100〉 samples. This difference exists only for unannealed samples and is almost eliminated by the 400 °C standard forming gas (10% H2, 90% N2) anneal. The barrier for the 〈111〉 interface has therefore a greater sensitivity to hydrogen than for the other two orientations. The experiments and their consistency with the usual (dark) Fowler-Nordheim tunneling from silicon into SiO2 show that transverse momentum (parallel to the interface) conservation is not observed.
Empirical rule to predict heterojunction band discontinuities
Authors: Katnani A. D. , Margaritondo G.
Published: February 2003

We developed an empirical table of valence-band-edge energy positions for group IV, III-V, and II-VI semiconductors, referred to the valence-band edge of germanium. The energy positions listed in the table were deduced from systematic photoemission measurements of heterojunction valence-band discontinuities performed on semiconducting substrates with Si or Ge overlayers. The table can be used to estimate the valence-band discontinuities of heterojunctions between compound semiconductors, with several advantages and better accuracy with respect to the widely used twenty-year-old electron-affinity rule and to other more recent theories.
Interface trap generation in silicon dioxide when electrons are captured by trapped holes
Authors: Lai S. K.
Published: February 2003

A characteristic interface trap was observed in a hole trapping experiment when electrons were captured by trapped holes injected by an avalanche in the silicon. The observations could be explained by the generation of new electronic states through relaxation of strained bonds which were proposed to be the origin of hole traps. The result is either a weak bond in the network or two dangling bonds with no net charge. The weak bond or dangling bonds give rise to neutral traps in the bulk and interface traps at the interface of the oxide. The presence of interface traps for such defects at the interface is predicted by theoretical calculations.
Tunneling current density j(V) for Pb–In–Au alloy junctions and tunnel barrier modeling
Authors: Magerlein J. H.
Published: February 2003

Tunnel barriers formed by rf oxidation of Pb–In–Au alloys and consisting largely of In2O3 have been studied by measuring the current density as a function of applied voltage j(V) for voltages up to 1 V. The junctions studied here, which were oxidized on Pb- or photoresist-coated rf cathodes, showed no evidence of a barrier height below about 1 eV. A trapezoidal barrier with a height of at least 1 eV and a thickness equal to that of the oxide film, roughly 6 nm, would have a tunneling current far below that observed for these junctions. Furthermore, the measured j(V) curves were inconsistent with those calculated for a trapezoidal barrier, even for a barrier thickness less than the physical oxide thickness. The j(V) curves were, however, similar to those calculated for tunneling through a Schottky barrier in the indium oxide at the interface with the counterelectrode. Such a barrier, which is also suggested by recent measurements of oxide thickness and junction electrical properties at low voltages, might be expected to form between the metal electrodes and In2O3, which can be a degenerately-doped n-type semiconductor.
Guided magnetostatic surface waves on a metallic strip line
Authors: Uehara Masahiro , Yashiro Ken’ichiro , Ohkawa Sumio
Published: February 2003

This paper gives a theoretical analysis for the geometrical configuration of a metallic strip deposited on ferrite film, which is available for MSSW (magnetostatic surface wave) waveguide. Dispersion curves and magnetic potential distributions are presented when the metallic strip of 100 μm wide is placed on the ferrite film of 10 μm thick. Since MSSW propagates along either the top surface with the strip, or the bottom face with no strip depending on its propagating direction, a strip-guided mode is nonreciprocal in the energy trapping effects, the number of guided modes, and the frequency bands.
Mössbauer spectroscopy of amorphous silicon–tin–hydrogen alloys
Authors: Williamson D. L. , Deb S. K.
Published: February 2003

Amorphous–Si1−x Snx :H alloys have been prepared by dc and rf sputtering of composite Si–Sn targets in Ar–H2 gas mixtures. 119Sn conversion electron Mössbauer spectroscopy and x-ray diffraction reveal the Sn to be incorporated into the films in at least four distinct sites, the relative populations of which depend strongly on preparation conditions. The Mössbauer resonance from the substitutional Sn in the a-Si:H matrix is well characterized by a quadrupole splitting of 0.46±0.05 mm/s independent of x and preparation conditions. Experimental procedures have been found such that samples can be produced which contain only the substitutional Sn site.
Raman microprobe study of recrystallization in ion-implanted and laser-annealed polycrystalline silicon
Authors: Nakashima S. , Inoue Y. , Miyauchi M. , Mitsuishi A. , Nishimura T. , Fukumoto T. , Akasaka Y.
Published: February 2003

Implantation-amorphized polycrystalline silicon layers which are directly deposited on single-crystal Si are annealed by a scanning cw laser. The crystallinity of the annealed layers has been examined by a Raman microprobe in combination with polarization measurements. The Raman spectra measured for the specimens annealed at various power levels reveal that the polysilicon layer is regrown liquid epitaxially and is transformed into single crystal at high annealing power levels and that the regrowth at lower power levels is governed by the mixture of solid and liquid epitaxial processes. It is found that for specimens annealed at high power levels the tensile stress in the annealed layer is relaxed to a certain extent, though the weak residual strain still remains. The Raman microprobe spectra from the boundary reigon between the annealed and amorphous layers are recorded by making the probe laser beam traverse the boundary region. This technique enables us to investigate the variation in crystallinity and the regrowth process in the boundary zone which is found to be less than 10 μm width.
Photoluminescence of molecular beam epitaxially grown Ge-doped GaAs
Authors: Bafleur M. , Munoz-Yague A. , Castano J. L. , Piqueras J.
Published: February 2003

The role played by molecular beam epitaxial growth conditions in Ge-doped GaAs and the introduction of deep levels inside the forbidden gap were investigated by means of photoluminescence. Firstly, a qualitative correlation was established between the compensation ratio obtained from Hall measurements and the ratio between the integrated intensity of the conduction band–acceptor transition to that of the donor–valence band. Secondly, two peaks at 1.41 and 1.45 eV, very similar to those introduced by another amphoteric impurity (Si) and systematically found in nearly all the samples, were studied in order to clarify their origin. GeAs appears to be involved in both cases. The intensity of the 1.45 eV line increases with growth temperature which agrees with the assignment to a GeAs–VAs complex already suggested elsewhere. Conversely, the emission intensity at 1.41 eV decreases strongly with increasing growth temperature and the presence of GeAs–Asi and/or GeAs–AsGa complexes is suggested to explain this result.