bluuebunny/crossref_metadata_2025 huggingface dataset:
A laser-type light ion-beam-driven, reactor-size inertial fusion target
Authors: Tahir N. A. , Long K. A.
Published: July 2002

Numerical simulation results of compression and burn of a new inertial confinement fusion (ICF) target, which consists of a hollow DT shell followed by a low-Z Be pusher, are presented. This target contains 3.2 mg of DT fuel and is suitable for use in an ICF reactor system driven by 20–30 MeV lithium ions. A shaped input power pulse with an input energy of 4.7 MJ and a peak power of 250 TW (90 TW/cm2) has been used to implode this target. The overall energy gain is of the order of 120. The problem of symmetry and hydrodynamic stability of the target implosion is also discussed briefly.
Area-selective deposition of organic conducting polymers on semiconductors: Polypyrrole-ZnO system
Authors: Okano Mitsutoshi , Itoh Kiminori , Kikuchi Eiji , Fujishima Akira
Published: July 2002

Area-selective deposition of polypyrrole was successfully performed by three different procedures with electrochemical and photoelectrochemical techniques. These methods are important as tools for organic conducting pattern generation and functionalization of electrode surfaces.
Electron impact dissociation of HgX2 (X=Cl, Br, I)
Authors: Kushawaha V. , Mahmood M.
Published: July 2002

Electron impact dissociation of HgX2 molecules has been studied in the electron energy range of 1–100 eV. By using the most intense band of the B-X system of HgX (X=Cl,Br,I) radicals, emission cross sections have been measured at different energies of the projectile electron. The threshold electron energy for the observation of the B-X band system has been determined to be 7.0, 6.5, and 5.7 eV for HgCl2, HgBr2, and HgI2 molecules, respectively. These energies are in good agreement with values previously reported by other investigators.
Coupled mode theory in a lossy, nonlinear transmission line system
Authors: Hsieh H. C.
Published: July 2002

A method of analysis that uses the coupled mode formulation has been developed to study the coupling phenomenon in a system of two lossy, identical transmission lines. These lines are uniformly coupled and also have uniformly distributed, nonlinear shunt capacitance and series inductance. The transmission lines are excited at one end with two voltage sources of the same frequency but of different amplitude and phase, and are terminated with proper load impedances at the other end. The coupled mode theory has been developed with the aid of quasiharmonic analysis of the codirectional, nonlinear coupled lines. The analytical expressions for the power carried by each mode in the transmission lines can be obtained for a special case of the low loss system in which the phase difference of two coupled modes is assumed to vary slowly with the position along the line. The derived analytical expressions are also used to study the effect of changing input conditions and circuit parameters on the location where relative minima and maxima occur.
Hydrostatic pressure dependence of the exponential optical absorption in Bi12SiO2
Authors: Toyoda T. , Nakanishi H. , Endo S. , Irie T.
Published: July 2002

The optical-absorption spectra in Bi12SiO20 have been measured precisely at various hydrostatic pressure up to 40 kbar, and analyzed in the region below the fundamental absorption edges. It can be seen that the optical-absorption coefficients plotted semilogarithmically vary linearly with photon energy below the fundamental absorption edges at each hydrostatic pressure. The steepness of the absorption edge decreases with increasing pressure up to 10 kbar and then it shows constant value. The broad shoulders below 3.1-eV photon energy are shown, and the optical-absorption coefficients in those regions increase with increasing pressure up to 10 kbar.
Backscattering analysis of electron-beam-induced diffusion of tin in GaAs from dopant emulsions
Authors: Meglicki Zdzislaw , Cohen David D. , Nassibian Armenag G.
Published: July 2002

A scanned electron beam was used to diffuse tin in GaAs from doped emulsions. Rutherford backscattering method was used to investigate the results of the diffusion. The diffusion was greatly enhanced by capping the emulsion with evaporated silicon dioxide.
Kinetics of NiAl3 growth induced by steady-state thermal annealing at the Ni-〈Al〉 interface
Authors: Zhao X.-A. , Yang H.-Y. , Ma E. , Nicolet M.-A.
Published: July 2002

Substrates of large grained aluminum crystals were prepared by the strain annealing technique, and Ni films were vacuum evaporated on these substrates after an in situ sputter cleaning process. Upon thermal annealing of samples in vacuum, a laterally uniform growth of NiAl3 is observed, starting from 330 °C, without any indication of boundary diffusion effects. The aluminide phase grows as (duration)1/2 after an initial incubation period with an activation energy of 1.4 eV, i.e., K=x2/t=0.387 (cm2/s)exp(−1.4 eV/kT) for 600 K<T<650 K. Impurities, either at the interface or inside the Ni film, retard this reaction.
Effect of post-silicidation annealing on TiSi2/p+-n Si junctions
Authors: Delfino M. , Morgan A. E. , Broadbent E. K. , Maillot P. , Sadana D. K.
Published: July 2002

The reverse-bias leakage of TiSi2/p+-n Si junctions is <10 nA/cm2 for 0.1-μm-deep p+-Si with a TiSi2 sheet resistance of 1.7 Ω/sq, and is essentially independent of carrier concentration, and the amount of B consumed during silicidation. Forward-bias current characteristics show that the TiSi2 contacts are ohmic with significant recombination currents and high-level injection at voltages below the series resistance limit. Post-silicidation annealing for 30 min at 920 °C, with or without an overlayer of borophosphosilicate glass, increases the majority-carrier concentration and does not cause B to diffuse out of the Si. Also, minority-carrier lifetimes show a twofold increase after annealing and this results in nearly ideal junctions with leakage that is dominated by diffusion currents. Thus, TiSi2/p+-n Si is thermally stable under conditions that are compatible with glass flow and reflow processing.
Study on high-density recording of an ablative-type optical disk
Authors: Yamazaki Hiroki , Yagi Shougo
Published: July 2002

This paper studies high-density recording on optical disks. The optimal pit diameter and the recording conditions necessary to form low-noise pits are considered. The recording characteristics of a Te-containing plasma polymerized CS2 film (CS2-Te) are studied. This CS2-Te optical disk is shown to be an excellent medium to use in achieving high-density and high-speed storage.
Theory of elastic behavior of composite materials
Authors: Honig E. P. , Wierenga P. E. , van der Linden J. H. M.
Published: July 2002

The theory of Christensen [Mechanics of Composite Materials (Wiley Interscience, New York, 1978)] of the elastic behavior of a composite material with one type of inclusion is extended to the case with more types of inclusions present. A number of special cases is presented, including the extension to viscoelastic systems. Also, the results of Christensen are presented in a more elegant way.
Damage induced by CHF3+C2F6 plasma etching on Si-implanted GaAs(100)
Authors: Shin Sang-Mo , Chung Ho-Kyoon , Chen Chung-Hsu , Tan Kin
Published: July 2002

The damage induced by CHF3+C2F6 plasma etching on GaAs(100) was studied. We exposed GaAs(100) surfaces to various etching conditions and monitored sheet resistance, carrier concentration, and Hall mobility. Significant losses of Hall mobility and carrier concentration, and an increase in sheet resistance were observed only when CHF3 was introduced into the plasma. After annealing at 400 °C for 55 min, sheet resistance was restored nearly to the value obtained before the plasma exposure. We believe that the damage was produced by hydrogen atoms or ions dissociated from CHF3 in the plasma. In contrast to the general belief that plasma etching induces the least damage among dry etching techniques [such as reactive ion etching (RIE) and reactive ion beam etching (RIBE)], our plasma etching damage was comparable to previously reported RIE or RIBE damage.
Determination of effective charges and their composition dependencies in cubic and near-cubic pseudobinary alloys AB1−xCx
Authors: Wakamura Kunio , Arai Toshihiro
Published: July 2002

The effective charge for a pseudobinary mixed crystal has been determined from the phonon frequencies of longitudinal and transverse optical modes. Most of the mixed systems exhibiting one-mode type phonons show the linear composition dependencies, while those of the two-mode type phonon show the nonlinear dependencies. The largest deviation of curves from a linear line is about 20%. The curves are represented by the quadratic equations of composition x with three fitting parameters. The origin of the nonlinearity is qualitatively explained from the electronegativities of substituted and host atoms whose magnitudes vary with the ionic radii. From a large curvature of the dependence in Ga1−xInxP, a two-mode behavior is suggested in contradiction to the previous assignment.
Optical second-harmonic generation from silver at 1.064-μm pump wavelength
Authors: Coutaz J. L. , Maystre D. , Nevière M. , Reinisch R.
Published: July 2002

We present experimental results of second-harmonic generation from a silver mirror at 1.064-μm pump wavelength. The data are well described in the framework of the theory of the nonlinear polarization at the second-harmonic frequency in metals developed by D. Maystre, M. Nevière, and R. Reinisch [Appl. Phys. A 39, 115 (1986)].
Improved shallow p+ diffusion into InGaAsP by a new spin-on diffusion source
Authors: Amann Markus-Christian , Franz Gerhard
Published: July 2002

Shallow p+ diffusion into InGaAsP (λ=1.3 μm) has been improved by employing a new spin-on source based on Zn-doped alumina. Thereby the thermal expansion coefficients of diffusion source and semiconductor are better matched together than in case of the more common Zn-doped silica films. Consequently, besides an excellent mechanical stability of the spin-on films over a wide temperature range, the influence of mechanical stress on the diffusion process is effectively reduced. Applying diffusion temperatures around 600 °C surface hole concentrations above 6×1019 cm−3 and extremely low specific p-contact resistances of 2–3×10−6 Ω cm2 have been achieved.
Optical gain in CdIn2S4
Authors: Beauvais J. , Fortin E.
Published: July 2002

Photoluminescence measurements in the donor-acceptor band of single crystals of CdIn2S4 have displayed optical gain under high extrinsic excitation intensities of the order of 108 W/m2. Gain spectra centered around λ=765 mm have been observed yielding a maximum gain of 2.2 cm−1 at 300 K and about twice that value at 100 K. The results are correlated with kinetics measurements under varying incident intensity, showing a sharp break in the luminescence decay time at exciting intensities corresponding to the onset of gain.
Mechanical properties of anthracene crystals under illumination: Photoplastic effect
Authors: Kojima Kenichi
Published: July 2002

The mechanical properties of the photoplastic effect (PPE) in anthracene crystals were extensively studied. Detailed results of its dependence on strain rates ε̇, strain-rate sensitivity, temperature, and wavelength of exciting light have been obtained, and also the photomemory effect of PPE has been observed. Temperature dependence of PPE showed that the formation energy of physical dimers (photoinduced products) was estimated to be about 0.2 eV. Moreover, the strain-rate dependence of PPE indicated that the change in stress Δτs decreased with increasing strain rates, namely, the strain-rate sensitivity m=Δτs/Δ ln ε̇<0. In addition, the photomemory effect shows that physical dimers were stable at dislocation cores with a long life.
Laser ablation of a polysilane material
Authors: Hansen S. G. , Robitaille T. E.
Published: July 2002

The laser ablation properties of a (50%)-isopropyl methyl–(50%)-n-propyl methyl silane copolymer are examined. Both 193- and 248-nm-pulsed excimer laser radiation cleanly and completely remove this material in vacuum above certain energy thresholds (30 and 50 mJ/cm2, respectively). Under these conditions the ablation properties are quite similar to those reported for typical organic polymers. Below threshold, ablation is less efficient and becomes increasingly inefficient as irradiation continues due to spectral bleaching. In the presence of air, material removal is incomplete even for high-energy densities and long exposures. The ablation rate is shown to be independent of substrate material both above and below threshold.
A continuous representation of the acoustic surface-wave mode shape in arrays of reflecting grooves
Authors: Tiersten H. F. , Song J. T. , Shick D. V.
Published: July 2002

A variational analysis of the reflection of surface waves by arrays of reflecting grooves is presented. The variational condition results in a system of linear algebraic equations relating the amplitudes of the waves on both sides of the edge of a groove. The influence of transverse moding, which is a result of the finite lateral dimension of the grooves, is included in the treatment, but scattering into bulk waves is not considered. Application of the linear algebraic equations across both edges of a typical groove results in a system of transmission equations, which constitutes a linear difference system for the periodic array. A closed-form continuous representation of the mode shape along the transmission path is obtained from the solution of the system of linear difference equations for the periodic array. The continuous representation is particularly convenient for use in the evaluation of perturbation integrals that arise in the calculation of the change in frequency of surface-wave resonators due to biasing states and for many other purposes. When the resonant surface-wave mode has been found, the reduced resonant frequency and phase velocity are obtained by means of a perturbation procedure. Calculated results are presented for grooved arrays on ST-cut quartz.
Real-time x-ray topography on the growth of an Al crystal from melt
Authors: Grange G. , Gastaldi J. , Jourdan C.
Published: July 2002

Aluminium crystals grown from melt in an ultrahigh vacuum chamber have been observed in situ and in real time by using white synchrotron radiation [experiments were performed at the Laboratoire pour l’Utilisation du Rayonnement Electromagnétique (L. U. R. E.), Bâtiment 209c, 91405 Orsay, France]. The shape of the solid-liquid interface is determined by the thermal conditions. The defects are generated by strains extraneous to the fusion-crystallization process. The interfacial area is free from growth dislocations. The dislocations and subboundaries have a tendency to be parallel to the growth axis. Simple 1/2 <011>-type dislocations impinge upon the interfacial plane, proving their stability up to the melting point.
Hydrogen motion in thermally annealed sputter-deposited hydrogenated amorphous silicon
Authors: Bevolo A. J. , Albers M. L. , Shanks H. R. , Shinar J.
Published: July 2002

It is shown that the bulk hydrogen concentration in radio-frequency (rf) sputtered films of hydrogenated amorphous silicon (a-Si:H) can be determined from reflected electron energy-loss spectroscopy signals obtained even during ion beam etching of the film. As a result, depth profiling, with a 50-Å depth resolution of the hydrogen concentration, and with 1 at. % accuracy of the a-Si:Hx/a-Si:Hy multilayer, is achieved. Using this technique to depth profile annealed multilayer samples of rf sputter-deposited a-Si:H, it was found that despite the loss of hydrogen at elevated temperatures the original interface widths are unchanged even after a 500 °C, 1 h anneal. This result contrasts sharply with previous measurements of hydrogen motion in glow-discharge a-Si:H and indicates a significant difference between the two types of a-Si:H with respect to hydrogen motion at elevated temperatures.
Characterization of GaAs layers grown directly on Si substrates by metalorganic chemical vapor deposition
Authors: Pearton S. J. , Vernon S. M. , Abernathy C. R. , Short K. T. , Caruso R. , Stavola M. , Gibson J. M. , Haven V. E. , White A. E. , Jacobson D. C.
Published: July 2002

The electrical and structural properties of GaAs layers grown directly by metalorganic chemical vapor deposition on Si substrates oriented 2° off (100) toward [011] are reported. The uniformity of minority-carrier lifetime in the 2 in.- diam heteroepitaxial wafers is comparable to that in bulk GaAs of the same doping density (2×1016 cm−3). Selective etching of the GaAs layer reveals an etch pit density of ∼108 cm−2, consistent with plan view transmission electron microscopy which shows a defect density of ∼108 cm−2. Rapid annealing at 900 °C for 10 s does not significantly alter the heterointerface abruptness, and at the same time the crystalline quality of the GaAs improves slightly. The deep level concentration in the as-grown layer is ∼1013 cm−3 as determined by capacitance spectroscopy. Finally, the activation characteristics of low dose Si implants (3×1012 cm−2 at 60 keV) are similar to those in high quality bulk GaAs.
Insulating, metallic, or semimetallic electronic nature of XSi2 compounds: Application to WSi2
Authors: Badoz P. A. , Rosencher E. , Torres J. , Fishman G.
Published: July 2002

We present a model which gives a simple interpretation of already published band-structure calculations in transition-metal disilicides (i.e., XSi2, where X stands for Co, Ni, Cr, or W). This approach, based on wave function symmetries, gives physical insight on the insulating, metallic, or semimetallic electronic nature of these silicides. In this theoretical frame, WSi2 is predicted to be a strictly compensated semimetal. Extensive electrical measurements performed on various WSi2 thin films are consistent with this prediction and indicate that the free-carrier density is less than 3×1021 cm−3.
Study of anomalous photovoltaic effect in vacuum-deposited wedge-shaped CdTe films
Authors: Sharma Suresh K. , Srivastava Ram S.
Published: July 2002

Oblique deposition of thin films of CdTe has led to the generation of photovoltages greater than the band gap. CdTe films were obliquely deposited in vacuum onto glass substrates and a number of samples were obtained by varying the deposition parameters. Samples were illuminated with a He-Ne laser and the angle of incidence of the irradiating light was varied. The dependence of the magnitude and sign of the photovoltage on the angle of irradiation may solve the problem of the nature of physical processes in these films that are responsible for the anomalously high photovoltaic effects.
Thermally stimulated persistent conductivity in n-AlGaAs/GaAs heterostructures
Authors: Leybovich I. S. , Rode D. L. , Davis G. A.
Published: July 2002

A new phenomenon, thermally stimulated persistent conductivity, has been observed in n-Al0.3Ga0.7As/GaAs heterostructures. After a heterostructure is cooled from room temperature to low temperatures (120–140 K), the electron concentration and mobility do not stay constant with time. Electron concentration decreases slowly (days), while Hall mobility increases. This effect is attributed to the slow transfer of electrons from the two-dimensional electron gas formed at the heterointerface into deep donors in the AlGaAs.
Determination of ion implantation damage profiles in III-V compounds by means of an electrochemical capacitance-voltage technique
Authors: Tell B. , Brown-Goebeler K. F.
Published: July 2002

Temperature-dependent electrical measurements on light ion bombarded n-type In0.53Ga0.47As established the presence of deep donors. The depth profiles of the net donor concentration of these samples were obtained by the electrochemical capacitance-voltage technique. A simple model was presented to relate these profiles to the ion damage loss mechanism. The capacitance-voltage technique has also been applied to He bombarded n-type InP. Further extensions of this technique are discussed.
Neutron transmutation doping of high-purity InP
Authors: Lee B. , Pan N. , Stillman G. E. , Hess K. L.
Published: July 2002

Transmutation doping of high-purity n-type InP has been used to identify the photothermal ionization photoconductivity peaks due to Sn donors. The results obtained show that Sn and S donors in InP have the same ionization energy and the same ground-state central cell shifts within a resolution of 0.006 meV.
Conduction of heat from a planar wall with uniform surface temperature to a monodispersed suspension of spheres
Authors: Chang Eric Y. , Acrivos Andreas
Published: July 2002

We consider the problem of heat conduction near an isothermal wall in contact with a composite consisting of a matrix containing a random dispersion of spheres having a different thermal conductivity than the matrix. Far away from the wall, i.e., on the macroscopic length scale, the average bulk temperature field is composed of a uniform gradient term plus a constant offset. If the temperature of the wall is set equal to zero, this offset temperature, which would vanish if the composite were replaced everywhere with an effective continuum, provides a measure of the degree to which the continuum hypothesis is inapplicable in describing the heat transfer process near the wall. To this end, we estimate this offset temperature via an effective continuum method to all orders in the inclusion volume fraction c of the composite, as well as find its exact value when c is small. Finally, we illustrate how these results may be applied to other problems in which the continuum assumption becomes invalid using, as an example, the problem of finding the rate of heat conduction from a heated sphere surrounded by a composite.
A study of initial transient phenomena in the chemical vapor deposition process using silane plasma
Authors: Nakayama Yoshikazu , Ohtsuchi Tetsuro , Kawamura Takao
Published: July 2002

Initial transient phenomena in the plasma deposition of hydrogenated amorphous silicon (a-Si:H) film from SiH4 has been studied in terms of an origin and an influence on the device fabrication. The initial transient state (ITS) of plasma over the time ranging from 2 to 40 s is observed as variations of optical emission intensities from SiH and H rather than as double probe currents. A simple model shows that this is caused mainly by the variation of the SiH4 concentration at relatively high rf power as well as at a low SiH4 flow rate. The variation of electron energy distribution is also discussed as a dominant origin at low rf power and high SiH4 flow rate. The predischarge method by which the SiH4 concentration is controlled just before a main discharge is proposed in order to reduce the ITS. A strong influence of the ITS on the field-effect response of the thin-film transistor is observed and can be avoided by the predischarge method.
Titanium-oxide films made by rf diode sputtering from a compound target
Authors: Yang Ming M.
Published: July 2002

This paper describes thin-film stress, stoichiometric ratio, deposition rate, and refractive index of an rf-sputtered titanium-oxide dielectric film. High compressive stresses (1010 dyn/cm2) were obtained, which can be correlated to the argon sputtering gas incorporation and peening effect. The process dependencies of the stoichiometric ratio, deposition rate, and refractive index are also described.
Stability of phase boundaries on thin silicon layers with glass substrates
Authors: Grigoropoulos Costas P. , Buckholz Richard H. , Domoto Gerald A.
Published: July 2002

Phase-change instabilities have been experimentally observed in the laser melting of thin silicon layers on conductive glass substrates. In this study, the polysilicon layer is bounded on the top by a thin layer of glass. This glass covering prevents the occurrence of thermocapillary flows in the silicon melt. A conductive heat-transfer mathematical model is used to predict temperature fields in both the silicon and the glass. Regions of silicon melt are shown to occur; phase-boundary locations are predicted. The stability of the predicted phase boundaries and temperature fields are studied. This analysis shows that the determining factors for stability are the laser power, the shape of the light intensity distribution, and the laser scanning speed. The effect of these parameters on the stability is evaluated. Results from the stability analysis are compared with some experimental results.
Methods for accurate determination of emission rate and trap concentration with application to platinum-doped silicon
Authors: Thurber W. Robert , Lowney Jeremiah R.
Published: July 2002

A procedure for the analysis of junction capacitance was developed which allows one to extract accurate values of emission rate and trap concentration from isothermal transient capacitance measurements. Experiments to demonstrate the procedure were performed on silicon diodes doped with platinum. The capacitance-ratio method of determining the emission rate was used to remove the nonexponentiality due to large trap concentration from the capacitance transients. Arrhenius plots of scaled emission rate gave activation energies of EC−EA=0.2271±0.0002 eV for the platinum acceptor level in n-type silicon and EA−Ev=0.3215±0.0012 eV for the platinum donor level in p-type silicon. A new method for determining the trap concentration is derived and verified by use of simulations and data. This method involves the subtraction of capacitance values obtained from two transients with the same fill voltage, but different reverse voltages. It is much simpler than methods which require iterative solutions of Poisson’s equation and a priori knowledge of the trap energy.
High T
c superconducting B1 phase MoN films prepared by low-energy ion-assisted deposition
Authors: Savvides N.
Published: July 2002

Metastable B1 phase MoN was synthesized by low-energy ion-assisted thin-film growth techniques at deposition temperatures TD =400, 500, and 700 °C. The films were condensed under the action of mixed Ar+ and N2+ ion species at an ion to condensing atom arrival rate ratio of 1.0. For each deposition temperature, films were prepared at various ion energies in the range 2–200 eV. The presence of chemically reactive N2+ ions and the use of low ion energies allow both structural and chemical selectivity, facilitate increased incorporation of nitrogen, and promote ordering of the defect structure of cubic MoN. The films were characterized by x-ray diffraction, by measurements of superconducting temperature Tc and by temperature-dependent resistivity ρ(T). Collectively the film properties strongly depend on ion energy and deposition temperature. The composition, lattice parameter, crystalline preferred orientation, and grain size can be controlled by varying ion energy. The resistivity shows an anomalous temperature dependence that is typical of disordered metals, i.e., electron localization governs electrical conduction with the temperature coefficient of resistivity changing sign according to the Mooij correlation. At optimum deposition conditions the resistivity is metallike (phonon contribution ρthermal >0), Tc=6.2 K, the resistivity ratio RR=1.1, and ρ300 K =120 μΩ cm. Annealing of films at 700 °C causes an improvement in properties with Tc≂12 K, RR=1.7, and ρthermal =60–80 μΩ cm. In films with large thermal resistivities we observe a ρ∼T2 behavior at low temperatures and saturation of resistivity at high temperatures (ρsat =200–280 μΩ cm) which suggest that MoN with the B1 crystal structure is a strongly coupled and disordered high Tc superconductor.
Periodicity and surface flux closure of multipolar 180° Bloch walls
Authors: Hartmann U.
Published: July 2002

The recent calculation of the specific energy associated with Néel singularities in cubic crystals now permits an estimation of the periodicity and self-magnetostatic energy of multipolar 180° Bloch walls. Additionally, it is shown that the slight zigzagging of these walls in the near-surface region of a crystal causes a considerable reduction of the effective free surface charges by an extensive flux closure internal to the crystal
Rotational hysteresis in anisotropic barium and strontium ferrite permanent magnets
Authors: McCurrie R. A. , Jackson S.
Published: July 2002

Measurements of the torque curves and rotational hysteresis energies of anisotropic BaFe12O19 and SrFe12O19 permanent magnets have been made at 293, 178, and 77 K. From the values of the rotational hysteresis integrals it has been concluded that magnetization changes occur by an incoherent mechanism, most probably by domain-wall nucleation and displacement.
Simulation of energy transfer from a glow discharge to a solid surface
Authors: Rapakoulias D. E. , Gerassimou D. E.
Published: July 2002

In this paper, a model simulating the energy transfer from a glow discharge to a metal surface is presented. The model takes into account separately the transfer of each excitation mode of the plasma species: vibrational, translational, rotational, electronic, ionic, secondary electrons, and atom recombination. The case studied is that of a N2 glow discharge heating a W surface. Vibrational excitation transfer appears to be the main channel for the heating of the surface. Recombination on the surface also has an important contribution to the energy transfer from the plasma to the solid. Ions and metastable molecules play a minor role.
X-ray diffraction study of intentionally disordered GaAlAs-GaAs superlattices
Authors: Auvray P. , Baudet M. , Regreny A.
Published: July 2002

A series of six intentionally disordered GaAlAs-GaAs superstructures grown by molecular-beam epitaxy has been investigated using x-ray diffraction techniques. Experimental diagrams show unusual effects increasing with disorder: only nonzero-order satellites are really affected by this kind of disturbance. A mathematical model directly derived from the basic scattering expression is described. By means of this model, which requires for numerical applications the knowledge of the growth sequence, we calculate the diffraction profile of each sample and find a very good agreement with the experiments. We discuss the effect of some changes in the growth sequence and finally show that this model can be used in the general case to take into account the interface roughness or the presence of enlarged wells in ordered superstructures.
Investigation of GaAs/(Al,Ga)As multiple quantum wells grown on Ge and Si substrates by molecular-beam epitaxy
Authors: Reddy U. K. , Houdré R. , Munns G. , Ji G. , Morkoç H. , Longerbone M. , Davis L. , Gu B. P. , Otsuka N.
Published: July 2002

We report photoreflectance studies on GaAs/(Al,Ga)As multiple quantum wells grown on Si and Ge substrates. The sharp spectral features observed from various subband transitions indicate that good epilayer quality can be obtained on nonpolar substrates using suitable growth techniques. The experimental results agree well with calculated values based on the envelope function approximation, when the effect of residual strain resulting from the large difference in thermal expansion between GaAs and Si is taken into account.
The effect of axial temperature profile on the thermal instability in high current-carrying plasmas
Authors: Kuo S. P. , Kuo S. C. , Levi E. , Kunhardt E. E.
Published: July 2002

Current-carrying plasmas exhibit strong temperature gradients in the proximity of bounding electrodes. A modal analysis of the thermal instability shows that a constriction always starts near the electrodes. It is localized there, where the temperature dependence of the thermal and electrical conductivities are assigned parameter values that are characteristic of plasmas in magnetohydrodynamic channels. In the case of practically full ionization and very large pressures, that prevail in arc-driven railguns, the constriction expands axially over the entire length of the discharge.
Ultrasonic study of mechanically alloyed amorphous PdSiCu
Authors: Hikata A. , McKenna M. J. , Elbaum C.
Published: July 2002

Amorphous Pd0.775Si0.165Cu0.060 was produced from powders of the constituent elements by mechanical alloying, and its ultrasonic characteristics are compared with those of the same composition amorphous alloys prepared by conventional rapid solidification. Eight hours of mechanical alloying in the solid state (around room temperature) produced a sample comparable with those obtained by rapid solidification, in terms of the slope of the logarithmic temperature dependence of sound velocity below 1 K and the amplitude dependence of ultrasonic attenuation at 0.3 K. This indicates that very fast solid-state diffusion of atoms has to be operating in the mechanical alloying process.
Superconducting photorelaxation spectroscopy
Authors: Iguchi I. , Kasai Y. , Mochiku T. , Sugishita A.
Published: July 2002

A novel technique termed superconducting photorelaxation spectroscopy is described in detail which utilizes a superconducting tunnel junction for detection of phonons from optically illuminated semiconductors. The method makes use of a lock-in, highly sensitive, detection technique which allows for direct detection of phonons. The system noise is suppressed to the level of 100 pV, enabling one to detect the phonon signal with an S/N ratio of 104. It is demonstrated that the phonon signal detected does not depend upon the chopper frequency, in contrast to conventional photoacoustic spectroscopy. The phonon signal as a function of wavelength of light employing a silver optical reflector yields a clear band-gap structure and modulated structures in the deep-level region consistent with the measurements obtained by other techniques for GaAs and InP wafers. The model for the phonon-detection system with its associated sensitivity is presented. It appears this method will be a very promising technique to study the nonradiative states of semiconductor crystals.
Transmission electron microscopy of (001) ZnTe on (001) GaAs grown by molecular-beam epitaxy
Authors: Petruzzello J. , Olego D. J. , Chu X. , Faurie J. P.
Published: July 2002

The structural properties of [001] ZnTe epitaxial layers grown on [001] GaAs substrates were investigated by transmission electron microscopy. The layers were deposited by molecular-beam epitaxy with thicknesses ranging from 50 to 1800 nm. The layers can be divided into three distinct regions of dislocation arrangements above the interface. The interface consists of an array of misfit dislocations. The separation of these dislocations is about 54 Å and is independent of layer thickness. The first region extends 300 nm towards the surface and consists of a tangle of dislocations. The density of these dislocations increases with layer thickness. The second region, between 600 and 1300 nm above the interface, was found to contain a low density of dislocations. Above 1300 nm, the third region, the dislocation density surprisingly increases again and in addition Te precipitates are detected near the top surface.
Antimony passivation of molecular-beam epitaxially grown GaAs surfaces
Authors: Kerr T. M. , Peacock D. C. , Wood C. E. C.
Published: July 2002

The use of antimony molecular beams to grow passivating films on ‘‘as-grown’’ GaAs surfaces is described. The substrate need not be cooled below 350 °C for deposition as in the case of As4 and not heated above 500 °C for an extended period for removal as in the case of InAs passivation. Good electrical properties of antimony passivated, air exposed, and regrown interfaces were obtained. No degradation in macroscopic defect densities were found with this technique.
Dislocations in Hg1−xCdxTe/Cd1−zZnzTe epilayers grown by liquid-phase epitaxy
Authors: Yoshikawa Mitsuo
Published: July 2002

Misfit and threading dislocations in HgCdTe epitaxial layers grown on (111)B CdTe and CdZnTe substrates by liquid-phase epitaxy have been investigated quantitatively by the etch pitting technique. In the HgCdTe/CdTe heterojunction, it has been found that the misfit dislocations introduced at the initial stage of epitaxial growth move to the 〈111〉 direction and distribute in such a way that they completely accommodate the mismatching strain of the compositional gradient caused by the Hg-Cd interdiffusion. On the other hand, in HgCdTe/CdZnTe heterojunctions, misfit dislocations were found to be pinned by Zn out-diffused from the substrate. For a proper ZnTe mole fraction in the CdZnTe substrate, the linear dislocation-pit density on the (1̄10) cleaved and etched surface was confirmed to decrease to about 1% of that using a CdTe substrate. It has also been found that the density of dislocations threading into the epitaxial layer was determined not by the magnitude of lattice mismatch, but by the dislocation density of the substrate.
Persistent photoconductivity from thin layer amorphous silicon doping modulated superlattices
Authors: Zhang D. H. , Haneman D.
Published: July 2002

Further evidence about the phenomenon of persistent photoconductivity (PPC) in doping modulated amorphous hydrogenated silicon multilayers, has been obtained by studying nipi structures with fixed p- (3.3 nm) and n- (7.7 nm) layer thicknesses but varying i-layer thicknesses. The PPC showed a fairly sharp maximum at i-layer thicknesses of 14 nm, being over 103 times the dark conductivity 10 min after a 20-s light flash at 50 mW cm−2. The decay rates indicate that at least two kinds of trapping centers are involved. From the various phenomena it is proposed that the effect is due to B-P complexes which form deep traps but become shallow after H accretion. Junctions are not directly responsible but different H concentrations in differently doped layers play a key role.
Performance of dry-etched short cavity GaAs/AlGaAs multiquantum-well lasers
Authors: Yuasa Tonao , Yamada Tomoyuki , Asakawa Kiyoshi , Ishii Makoto , Uchida Mamoru
Published: July 2002

Fabrication and lasing characteristics of short cavity GaAs/AlGaAs multiquantum-well (MQW) lasers with dry-etched facets are described in detail. The lasers are fabricated from GaAs/AlGaAs double-heterostructure wafers grown by molecular-beam epitaxy. Fabry–Perot cavities are formed by a reactive ion-beam etching technique with Cl2 plasma. The dependence of lasing characteristics on the cavity length is examined. A threshold current as low as 30 mA is achieved for 20-μm-long cavity MQW lasers with 12 110-Å-thick GaAs wells separated by 11 50-Å-thick Al0.2Ga0.8As barriers. The very short cavity lasers with large mode spacing realize the stable single-longitudinal-mode operation. Furthermore, the lasers show good high-frequency performance. A relaxation oscillation frequency as high as 32 GHz is observed with a 30-μm-long laser. Temperature characteristics are also presented.
Charge state populations in an extreme ultraviolet radiation pumped lithium vapor
Authors: Strobel George L.
Published: July 2002

Charge state populations are calculated evolving from an initially neutral lithium vapor. The vapor is pumped by the passage of an extreme ultraviolet radiation pulse of approximately one microsecond through the lithium. Photoionization and electron induced ionization processes result in a buildup of Li+ and Li++ in the vapor. When recombination is small, a 10% fraction of the atoms will be singly charged, and about 2.4×10−5 of the atoms will be doubly charged for the extreme ultraviolet radiation source considered. The temperature of the vapor can be related to the energy absorbed from the incident extreme ultraviolet radiation pulse. This results in a temperature of about 0.6 eV. Such a plasma is useful for ion diode particle beam fusion experiments.
Flute modes in the shared flux region of a magnetic quadrupole
Authors: Willett Joseph E. , Wu Hsi-Shu
Published: July 2002

A theory is developed for electrostatic waves with frequency ω below the ion bounce frequency ωbi in a plasma confined by a magnetic quadrupole. The dispersion equation for flute modes is derived in the form of a fourth-degree polynomial equation in ω with the effects of temperature gradients, first-order effects of curvature and finite ion Larmor radius, and terms of order ω2/ω2bi included. Growth rate and dispersion curves are calculated for flute modes in the shared flux region of the quadrupole at the University of Manchester Institute of Science and Technology. The present theory predicts an unstable mode with frequencies of the order of 1 kHz propagating in the electron diamagnetic drift direction as observed experimentally.
p/n InP homojunction solar cells with a modified contacting scheme by liquid phase epitaxy
Authors: Choi K. Y. , Shen C. C.
Published: July 2002

p/n InP homojunction solar cells with a modified contacting scheme have been fabricated from wafers grown by liquid phase epitaxy. A p+-In0.53Ga0.47As contacting layer is incorporated in the cell structure to reduce contact resistance and to eliminate surface spiking problems at the front surface. The highest conversion efficiency (total area) obtained under AM0 illumination is 15.0%. The corresponding open-circuit voltage, short-circuit current density, and fill factor for the best cell are 0.866 V, 29.3 mA/cm2, and 81.0%, respectively.
Reply to ‘‘Comment on ‘Quantifying solid-fluid interfacial phenomena in porous rocks with proton nuclear magnetic resonance’ ’’ [J. Appl. Phys. 5
9, 2788 (1986)]
Authors: Schmidt Ehud J.
Published: July 2002

Near orthogonality relations are presented for an inversion algorithm [J. Appl. Phys. 5, 2788 (1986)] utilized in inverting nuclear magnetic resonance relaxation curves to obtain decay rate distributions. These relations are used to determine resolution limitations of this method. Previously reported experimental results which show anomalous magnetization and shifts in the inverted decay rate distributions in porous rocks occurring at 60%–80% water saturation may be the result of a surface tension driven disjointing of the water films along the pore walls.
3D transient eddy current fields using the u-v integral-eigenvalue formulation
Authors: Davey Kent R. , Han Hsiu Chi , Turner Larry
Published: July 2002

The three-dimensional eddy current transient field problem is formulated using the u-v method. This method breaks the vector Helmholtz equation into two scalar Helmholtz equations. Null field integral equations and the appropriate boundary conditions are used to set up an identification matrix which is independent of null field point locations. Embedded in the identification matrix are the unknown eigenvalues of the problem representing its impulse response in time. These eigenvalues are found by equating the determinant of the identification matrix to zero. When the initial transient forcing function is Fourier decomposed into its spatial harmonics, each Fourier component can be associated with a unique eigenvalue by this technique. The true transient solution comes through a convolution of the impulse response, so obtained with the particular external field decay governing the problem at hand. The technique is applied to the FELIX (fusion electromagnetic induction experiments) medium cylinder experiment; computed results are compared with data. A pseudoanalytic confirmation of the eigenvalues so obtained is formulated to validate the procedure.
Losses and mode structure of unstable resonators with spherical mirrors
Authors: Hauck R. , Hodgson N. , Weber H.
Published: July 2002

Losses and near and far field intensity distributions of unstable resonators with equivalent Fresnel numbers in the range up to three have been investigated both experimentally and theoretically. The losses were determined absolutely using a new method for loss measurement. Intensity distributions of lowest loss modes were recorded by means of an image-processing system and compared to numerical solutions of Kirchhoff ’s integral equation of the empty cavity. The experiments were performed with a pulsed Nd-YAG system.
Study on decrease in lasing threshold current of GaAs/AlGaAs single quantum-well lasers through introduction of superlattice waveguide layers
Authors: Yokoyama H. , Iwata H. , Sugimoto M. , Onabe K. , Lang R.
Published: July 2002

A systematic study for evaluating the effect of introducing short-period superlattice waveguide layers on the threshold current of single quantum-well diode lasers is reported. The waveguide layers which consist of short-period GaAs/AlAs superlattices, in place of AlGaAs alloys, resulted in a decrease by a factor of 4–6 in the lasing threshold current density of GaAs/AlGaAs single quantum-well diode lasers of separate confinement heterostructure. A time-resolved photoluminescence study of those laser structures revealed that the threshold current reduction was the result of an improvement of overall nonradiative carrier recombination lifetime of single quantum wells by more than a factor of 10.
The effect of minimum detonation diameter on the mechanism of jet initiation of bare explosives
Authors: Chick M. C. , Bussell T. J.
Published: July 2002

Metal jets generated from 15- and 38-mm-diam-shaped explosive charges were fired into bare samples of the explosives, composition B and H-6. The results showed that a reduction in the jet diameter caused a transition in the mode of initiation from that produced at the sample surface by the impact shock to that produced in the bulk of the explosive by the bow wave from the penetrating jet. The transition is accompanied by a significant change in the explosive’s sensitivity to jets. A simple criterion is proposed for predicting the transition in terms of the minimum diameter of the explosive to support detonation and the diameter of the jet.
Effects of hydrogen chloride on boron acceptor hydrogenation and trap generation-annealing in oxidized silicon irradiated by keV electrons
Authors: Lin Wallace Wan-Li , Sah Chih-Tang
Published: July 2002

The effects of hydrogen chloride (HCl) during oxidation of silicon on the hydrogenation of boron acceptors and generation-annealing of interface and oxide traps are reported in 8-keV electron irradiated aluminum/polycrystalline-silicon/oxide/silicon capacitors. This paper shows (i) boron acceptor hydrogenation also occurs during HCl oxidation, a new finding, (ii) boron acceptor hydrogenation continues after the electron beam was turned off, (iii) interfacial chlorine reduces hydrogen migration to the silicon surface layer, a result also previously observed in capacitors stressed by avalanche injected electrons, and (iv) HCl oxidation significantly reduces the generated and annealed densities of interface and oxide traps by the 8-keV electrons but increases their annealing rate at room temperatures.
Noncollinear magnetic structure of CoFe2O4 small particles
Authors: Haneda K. , Morrish A. H.
Published: July 2002

The magnetic structure of small CoFe2O4 particles has been investigated as a function of the particle size. Samples (in the 10–100 nm size range and up) were prepared by chemical precipitation followed by a heat treatment at relatively low temperatures. Mössbauer spectra of the 57Fe nuclei, obtained with a longitudinal magnetic applied field, unambiguously establish that a noncollinear structure exists that is most pronounced for the smallest particles. The analysis indicates that a surface effect of the crystallites that make up a particle is the origin of this phenomenon. A model is proposed in which the CoFe2O4 crystallites that make up a particle consist of a core with the usual spin arrangement and a boundary surface layer with atomic moments inclined to the direction of the net magnetization. The temperature dependency of this structure is also examined.