bluuebunny/crossref_metadata_2025 huggingface dataset:
Time-of-flight study of chalcogenide glasses chemically modified by bismuth
Authors: Tohge Noboru , Yonesaki Takahiro , Minami Tsutomu
Published: July 2002

The transport process has been studied by the time-of-flight technique for the glasses in the systems Ge20BixSe80−x (x=0–13) and Ge20BixSe70−xTe10 (x=0–11), both of which exhibit n-type conduction in x≥9. The highly dispersive transport was observed for electrons and holes in n-type glasses, as well as in p-type glasses. In both systems, the effective drift mobilities of electrons and holes increased with an increase in the Bi content, accompanied by an increase in steady-state photoconductivity; the trap levels, however, remained almost unchanged for holes and became deeper for electrons. In addition, no large difference was found in the effective drift mobility between electrons and holes in both n- and p-type glasses.
Effects of stress on magnetically induced velocity changes for surface waves in steels
Authors: Kwun H.
Published: July 2002

Results of an experimental investigation of the effects of uniaxial stress on the magnetically induced velocity changes for 5-MHz surface (Rayleigh) waves in specimens of ASTM A-36, SAE 4340, and HY-80 steel are described. Like the magnetically induced velocity changes for ultrasonic shear and longitudinal waves, the magnetically induced velocity changes for surface waves exhibited characteristic stress effects which were dependent on the magnitude and the sign (tensile or compressive) of the stress as well as on the relative orientation of the stress, the magnetic field, and the wave propagation directions. The observed characteristic stress effects indicated potential applicability of the magnetically induced velocity changes for surface waves to nondestructive measurements of residual surface stresses in ferromagnetic structural steels.
Reactive diffusion and superconductivity of Nb3Al multilayer films
Authors: Vandenberg J. M. , Hong M. , Hamm R. A. , Gurvitch M.
Published: July 2002

Thin films of A15 Nb3Al have been prepared by reactive diffusion of sputter-deposited Nb/Al multilayers. The diffusion reactions were studied by in situ annealing x-ray diffraction in the temperature range 50–950 °C. Initially the Nb and Al sublayers react to form the phase NbAl3. This interface reaction prevents the formation of the σ-phase Nb2Al, frequently found as a second phase in A15 Nb3Al materials; NbAl3 reacts with the remaining Nb to form the A15 phase. The highest Tc, 16.2 K measured resistively and 15.2 K inductively, was found in a Nb/Al multilayer with an A15 cell parameter a0=5.195 Å which corresponds to ∼20 at. % Al. From a comparison with previous investigations of the Tc dependence on Al concentration and A15 cell parameter, it is concluded that a small amount of the A15 phase has a higher composition of 22–23 at. % Al.
Computer simulation of electron beams. II. Low-cost beam-current reconstruction
Authors: de Wolf D. A.
Published: July 2002

Reconstruction of current density in electron beams is complicated by distortion of phase space which can require very fine discretization of the beam into trajectories. An efficient discretization of phase space is exploited, using conservation of charge and current in hypertriangle patches, to reconstruct the current density by fitting Gaussians through the distorted hypertriangles. Advantages and limitations are discussed.
A momentum-balance model of electron beam propagation through plasma into vacuum
Authors: Reiser M. , Chang C. R.
Published: July 2002

A model is proposed which links electron beam propagation through plasma into a vacuum with collective ion acceleration from the plasma. Electron reflection from the virtual cathode at the beam front transfers momentum to the ions, and a moving ion channel is formed allowing the electron beam to propagate. A momentum-balance equation is derived, and theoretical results for the ion velocity are in good agreement with the experimental data. Conditions for transverse beam confinement are discussed.
Amorphous phase separation in polypropylene block copolymers as revealed by thermostimulated depolarization measurements. II. Thermal sampling analysis
Authors: Ronarc’h D. , Audren P. , Moura J. L.
Published: July 2002

We achieved a thermal sampling scanning of the β-relaxation region of polypropylene (PP) block copolymers together with the β process of isotactic polypropylene, high-density polyethylene, propylene-ethylene rubber, and part of the PP bloc copolymer soluble in xylene and insoluble in ether. The comparison of activation parameters determined in the above relaxations confirmed the hypotheses drawn from complex spectra studies concerning phase separation and the origin of dielectric relaxations in PP block copolymers. One of the dielectric relaxations of the part of PP block copolymer soluble in xylene and insoluble in ether could be attributed to polypropylene blocks. We related the preexponential factor of the relaxation time to chain environment. Then we discussed the compensation phenomenon in distributed relaxations and the relation between the compensation temperature and variation of thermal expansion coefficient through the compensating relaxation.
Minimum probability of electron-hole pair generation by blackbody radiation
Authors: Wu Cheng-Hsiao
Published: July 2002

Using the small-perturbation assumption that all the useful work is in the form of electron-hole pairs when photons from a blackbody radiation source are incident on a quantum device, we derive the minimum probability of generation of one or more pairs of electron holes. Using the Planck radiation formula for the solar spectrum at 6000 K and for the quantum device at 300 K, this minimum probability is about 0.8 at low photon frequency and approaches the limiting value of 0.95 at high frequency. Its relation to maximum efficiency of a quantum device is discussed.
Characterization of the whiskerlike products formed by hydriding magnesium metal powders
Authors: Herley Patrick J. , Jones William , Vigeholm Bjorn
Published: July 2002

The structure of filamentary crystals produced during the hydriding of magnesium powder has been studied in detail. The needles of small dimensions (typically 0.5 μm in diameter) have been identified by electron analytical techniques to be oriented microcrystals of metallic magnesium. Their formation has been ascribed to the melting of localized aluminum impurities within the bulk magnesium to form a liquid eutectic. In the presence of sublimed magnesium vapor and hydrogen (as a carrier gas) a vapor-liquid-solid mechanism operates to produce a rapid unidirectional extension followed by a slower, two-dimensional growth. As a consequence the needle becomes broader at the tip. In addition, the tip is surmounted by a small Mg-Al eutectic aggregate.
Interface of p-type Hg1−xCdxTe passivated with native sulfides
Authors: Nemirovsky Y. , Burstein L. , Kidron I.
Published: July 2002

The process for forming native sulfide films on p-type Hg1−xCdxTe with x≂0.2–0.3 by anodic sulfidization is described and studied. The analytical, optical, and electrical properties of the resulting interface are reported. The results of Auger electron spectroscopy analysis indicate that homogeneous CdS films with an abrupt interfacial transition are formed on Hg1−xCdxTe with x=0.215–0.290. The measured dispersion of the index of refraction and the dielectric constant of the native sulfide films are consistent with the reported data for bulk CdS. The interface between Hg1−xCdxTe and its native sulfide in combination with deposited ZnS has excellent electrical properties. A low fixed surface state density of the order of Nss ≂5×1010 cm−2, a low concentration of fast surface state density of the order of 5×109 cm−2 eV−1, and a small amount of trapping effects in the sulfide are observed. The MIS capacitors exhibit thermal stability up to 95 °C anneal in vacuum. The main features of the interface of p-HgCdTe utilizing native sulfides are the low fixed surface states and the practically flatband conditions which are imposed for a wide range of composition x and doping level of the substrates. It contrasts with the high fixed positive surface-state density which is observed on interfaces utilizing native oxides of HgCdTe and which invariably invert the surfaces of p-Hg1−xCdxTe. The properties of the interface between Hg1−xCdxTe and its native sulfide suggest potential applications for improving the surface passivation of photovoltaic diodes implemented on p-type Hg1−xCdxTe.
High-energy deuteron beam generated by a plasma focus device
Authors: Yamada Yoshiyuki , Kitagawa Yoneyoshi , Yokoyama Masahiro
Published: July 2002

We measured the energy spectrum and the angular distribution of high-energy deuterons, produced by a plasma focus device both in low- and high-pressure regimes, and obtained 5×1014 fast deuterons (0.3–3 MeV) and their beam current of 8 kA at the low pressure (1.5 Torr). Ion pinhole images confirmed a plasma diode, formed just above the anode surface, accelerating the deuterons to high energies. A beam-target model shows that not the fast deuterons (>330 keV) but the slow deuterons (≲74 keV) contribute to the total neutron yield.
Comparison of pulsed laser and furnace annealing of nitrogen-implanted silicon
Authors: Smith T. P. , Stiles P. J. , Augustnyiak W. M. , Brown W. L. , Hull R. , Jacobson D. C. , Kant R. A.
Published: July 2002

We have studied pulsed ruby laser and furnace annealing of high-dose (D>1017 N/cm2) 50-keV nitrogen-implanted silicon. Using Rutherford backscattering and channeling, transmission electron microscopy, and infrared transmission spectroscopy, we have compared liquid and solid phase regrowth, diffusion, impurity segregation, and nitride formation. As has been previously reported, during furnace annealing at or above 1200 °C nitrogen redistributes and forms a polycrystalline silicon nitride (Si3N4) layer. In contrast, pulsed laser melting produces a buried amorphous layer containing silicon and nitrogen with only very small amounts of polycrystalline silicon nitride below a layer of polycrystalline silicon.
Optoacoustic generation and electrical detection of subnanosecond acoustic pulses
Authors: Sessler G. M. , Gerhard-Multhaupt R. , West J. E. , von Seggern H.
Published: July 2002

The optoacoustic generation and electrical detection of acoustic pulses of about 0.5-ns duration in quartz and in several polymer materials is demonstrated. The ultrasonic pulses are generated by thermoelastic effects and/or ablation due to absorption of 70-ps laser-light pulses in an opaque coupling layer deposited on one of the sample surfaces. Detection of the acoustic pulses is possible by using electrically charged, piezoelectric, or biased samples which yield electrode signals upon transit of the pulses. The acoustic pulses have also have been used to measure ultrasonic velocity and attenuation in various materials.
Quantitative analysis of arsenic-implanted layers in silicon by synchrotron-radiation-excited x-ray fluorescence
Authors: Bowen D. K. , Davies S. T. , Ambridge T.
Published: July 2002

The quantitative analysis of arsenic-implanted silicon using the novel technique of synchrotron radiation x-ray fluorescence (SRXF) is reported. An extension of x-ray fluorescence (XRF) theoretical correction factors to the Gaussian impurity distribution is also presented. In the sample analyzed, the dose of arsenic implant is found to be 2.3×1015 atoms cm−2±0.5×1015 atoms cm−2, in reasonable agreement with the value of 1.0±0.1×1015 atoms cm−2 quoted by the implanters. The method is applicable to the rapid and nondestructive assessment of dose accuracy, uniformity, and reproducibility of a variety of ion-implanted species in various substrates.
Oxide breakdown reliability degradation on Si-gate metal-oxide-semiconductor structure by Al diffusion through polycrystalline silicon
Authors: Hokari Yasuaki
Published: July 2002

Time-zero and time-dependent dielectric breakdowns for thermally grown 60- through 70-Å SiO2 films were studied in two kinds of Si-gate metal-oxide-semiconductor (MOS) capacitors, where Al/polycrystalline silicon (poly-Si) connecting contact hole was formed over the thin gate oxide (type A) and the thick field oxide (type B). Almost the same time-zero dielectric breakdown was obtained in types A and B MOSs annealed at 450 °C for metal sintering. In type A samples, however, pinholes increased for the higher sintering temperature. Time-dependent dielectric breakdown on a type-A MOS depended on the sintering anneal temperature and four orders of magnitude shorter lifetime than that for type-B MOS was observed under 450 °C annealed samples. Auger measurements for a type-A MOS yielded that (i) Al precipitated at the poly-Si/SiO2 interface, caused by Al diffusion through poly-Si film at the Al/poly-Si connecting contact hole area during low temperature anneal for metal sintering, and (ii) Al precipitates were extremely enhanced at the contact hole edge. Unannealed type-A samples showed almost the same good reliability as for type-B MOS. The inferior reliability in a type-A MOS with a metal sintering anneal was concluded to be caused by the Al precipitates at the poly-Si/SiO2 interface.
Calculation of the crack tip opening displacement of a crack lying in a subsurface layer
Authors: Higashida Y. , Kamada K.
Published: July 2002

Crack tip opening displacement of a crack lying parallel to a free surface is calculated by counting the number of dislocations emitted into the plastic zone from a crack tip. A discrete dislocation model was used to simulate the crack, while varying the strength of dislocations so as to satisfy the boundary condition. The result coincides numerically with the predictions made in a previous paper, in which the stress intensity factor appearing in a theory of bulk materials was replaced with the one which includes the surface correction.
Master fabrication for optical-data disks using reactive ion-beam etching
Authors: Graf H. P. , Bösch M. A. , Good E. , Haller H. R. , Hubbard W.
Published: July 2002

A new mastering process for optical-data disks is described. The master disk consists of a glass substrate covered with an indium-oxide film. Reactive ion-beam etching with CCl4 is used to selectively etch the information pits into the indium-oxide layer. Pits with tapered walls are obtained by controlled erosion of the etch mask. This technique allows a better control of the pit shape than the conventional mastering process. Moreover, several metal copies can be made from the same master while conventional masters are destroyed after the first copy is made.
Scalar scattering characteristics of impenetrable, periodic surfaces using the T-matrix method: Effect of medium inhomogeneity
Authors: Lakhtakia Akhlesh , Varadan Vijay K. , Varadan Vasundara V.
Published: July 2002

A general T-matrix is formulated to study the scalar scattering response of an impenetrable, biperiodic surface in the presence of a z-directed medium inhomogeneity, and reductions thereof are discussed. A numerical scheme for constructing potential reflection coefficients used for generating an appropriate Green’s function has also been described. Numerical results presented demonstrate that the effect of the inhomogeneity cannot be ignored without inducing severe errors.
Additional observations on the gallium-X center in neutron-irradiated Si:Ga
Authors: Fischer David W. , Mitchel W. C.
Published: July 2002

In a previous paper we reported the formation of the gallium-X center by neutron irradiation of gallium-doped silicon. Since that report we have investigated a variety of other neutron-irradiated Si:Ga samples using float-zone crystals grown by three different vendors and irradiated at four different reactors. The behavior of Ga-X as a function of irradiation conditions, annealing temperatures (up to 800 °C) and various material properties has been studied by Fourier-transform infrared absorption spectroscopy and temperature dependent Hall-effect measurements. Ga-X was not observed in any of the as-grown samples but was definitely present in every irradiated sample. In all cases it first appears after a 400 °C anneal, reaches maximum concentration after a 600 °C anneal, and then decreases at higher anneal temperatures. The maximum Ga-X concentration observed in any sample appears to be dependent on the carbon concentration in that sample and not on the irradiation conditions. A more detailed Ga-X absorption spectrum was obtained showing lines not previously reported. A binding energy of 57.18±0.03 meV is deduced for the Ga-X ground state.
On electron tunneling in the metal-insulator-semiconductor systems including various electron effective masses
Authors: Majkusiak B. , Jakubowski A.
Published: July 2002

It is shown that in some cases of the metal-insulator-semiconductor systems the electron tunnel current may be expressed in the form of one-dimensional integral with modified ‘‘supply function’’ even if the effective mass is not the same in each region of the system. The proposed formula together with description of the semiconductor space charge region (which is not considered in the paper) may be used for modeling of the electron tunnel current-voltage characteristics, e.g., of the metal–SiO2–Si〈100〉 tunnel diodes. The considerations are based on the electron total energy and transverse wave-vector conservation assumptions.
Cathodoluminescence and transmission electron microscopy studies in thermochemically reduced MgO:Ni crystals
Authors: Ochando M. A. , Llopis J.
Published: July 2002

The effects of thermochemical reduction in nickel-doped MgO crystals have been investigated by cathodoluminescence and transmission electron microscopy. Two cathodoluminescence bands at 410 nm (3.0 eV) and 490 nm (2.5 eV) have been observed. The former band appears only in specimens after reducing treatments and is attributed to anion vacancies. The latter is associated with Ni2+ transitions 1T2g→3A2g. The results are analyzed on the basis of the emission from F-type centers and Ni2+ ions. Transmission electron microscopy confirms the presence of precipitate groups as well as pyramids in specimens after thermochemical reduction.
High-intensity laser-induced vaporization without internal superheating
Authors: Beckett P. M.
Published: July 2002

Laser heating for an infinite solid x>0 is modeled by imposing the heat source distribution E0(1−R)α exp(−αx) within the material. In order to overcome the problem of superheating in the solid, when the intensity is strong enough to cause a change of phase, a ‘‘mushy zone’’ of partially molten material is postulated between the fully liquid and the solid phases. The model is applied to laser heating of a solid, initially at constant temperature, together with ablation of any fully liquefied material. The equations are transformed so as to be amenable to numerical methods and the resulting solutions analyzed. The model seems particularly appropriate to optically thin materials.
Optical study of self-annealing in high-current arsenic-implanted silicon
Authors: Borghesi A. , Chen Chen-Jia , Guizzetti G. , Nosenzo L. , Stella A. , Campisano S. U. , Rimini E.
Published: July 2002

Silicon samples implanted with As in the 1014–1016 cm−2 dose range and at a beam current density of 10 μA cm−2 were analyzed by reflectance and Rutherford backscattering measurements. The E1 and E2 reflectance structures disappear at a dose of 1015 cm−2 and reappear red shifted at 1016 cm−2, as a consequence of the self-annealing during high-dose-rate implantation. The red shift of E1 and E2 has been quantitatively accounted for by calculations in a multilayer damage structure. The free-carrier density determined by the infrared response correlates with the substitutional concentration of As measured by channeling effect. The optical response has been measured in laser annealed samples for comparison.
Stable supermode operation in phase-locked laser diode arrays with three index waveguides
Authors: Matsumoto M. , Taneya M. , Matsui S. , Yano S. , Hijikata T.
Published: July 2002

A phase-locked laser diode array with three index waveguides is described. The array has a novel structure which prevents channels from being etched back. As the result, the waveguide elements in the array are very uniform. A stable 180° phase mode oscillation is obtained up to 50-mW output power in the single longitudinal mode and three supermodes are observed simultaneously above 50-mW output power. The near-field patterns and the far-field patterns of these supermodes are in good agreement with the theoretical results.
Reflection coefficients of large active scatterers
Authors: Cohen Ariel
Published: July 2002

The reflection from large absorbing scatterers having a complex refractive index m=n1−iκ (κ>0), is determined by the Fresnel reflection coefficients. Lasing materials with inverted population or having a complex refractive index m=n1+iκ ‘‘reflect’’ the incident light with different coefficients, since internal reflections must be taken into account. The reflection coefficients for long cylindrical active scatterers are derived as asymptotic results of the theory of light scattering by large tilted cylinders and explained by polarization considerations. The resulting coefficients can be applied to active scatterers with very large reflection coefficients (negative extinctions).
Nonlinear surface polaritons guided by metal films
Authors: Ariyasu J. , Seaton C. T. , Stegeman G. I. , Maradudin A. A. , Wallis R. F.
Published: July 2002

The propagation characteristics of nonlinear waves guided by a metal film that is bounded on one or both sides by media characterized by an intensity-dependent refractive index are discussed. The dispersion relations are solved numerically for both self-focusing and self-defocusing media with nonlinearities typical of InSb at a wavelength of 5.5 μm. In particular, the power dependence of the guided wave wave vector, of the field distributions, and of the wave attenuation are obtained for the multiple wave solutions allowed by the dispersion relations. In the appendix we evaluate the power dependence of the attenuation of s-polarized surface-plasmon polaritons guided by a metal film.
Ion beam impact and penetration of polymethyl methacrylate
Authors: Mladenov G. M. , Braun M. , Emmoth B. , Biersack J. P.
Published: July 2002

Depth distributions of energy dissipation and implantation ranges in the polymer resist polymethyl methacrylate (PMMA) have been calculated by using the TRIM computer code. The relevance of such calculations to experimentally obtained data in connection with ion-beam lithography is discussed. It is concluded that the result of the computer simulations may be of value in order to explain the responsible mechanism for the modification (solubility, erosion rate) of a resist material due to ion irradiation. Experimental results of PMMA erosion during ion irradiation are also presented, showing a strong relationship between the erosion and electronic stopping.
Thermally generated electron traps in boron-implanted, phosphorus-doped silicon
Authors: Jackson Daniel B. , Sah C. T.
Published: July 2002

Observation of six electron traps in boron-implanted, phosphorus-doped silicon following annealing at temperatures near 400 °C is reported. Emission rate, cross section, and thermal activation energy measurements of trapped electrons are reported. Isochronal annealing information indicates that the traps are not present in the as-implanted silicon; they are formed during heat treatment at temperatures near 400 °C. Comparison with previous studies indicated that the trap E200(0.424) [peak temperature (activation energy)] may be an oxygen and/or phosphorus complex, and that a second trap, E145(0.320), may be a phosphorus complex.
Conductance changes in trans-polyacetylene during oxidation
Authors: Ebisawa Fumihiro , Tabei Hisao
Published: July 2002

The conductance of trans-polyacetylene is measured during oxidation using an interdigital microelectrode. The measurements obtained indicate a slight increase in the conductivity during initial exposure in air and then a decrease during oxidation, which is confirmed by the corresponding changes in the infrared absorption spectra. The logarithm of conductivity is inversely proportional to the oxidation time. A proposed model which is derived from Kivelson’s theory predicts the behavior of conductivity as a function of time during oxidation. The experimental data of conductivity is in agreement with the calculated data using this model. The temperature dependence of the conductivity at certain stages also supports the theory that the electrical transport mainly occurs through intersoliton electron hopping. Thus, the electrical transport mechanism during oxidation is clarified.
Josephson 4 K-bit cache memory design for a prototype signal processor. I. General overview
Authors: Henkels W. H. , Geppert L. M. , Kadlec J. , Epperlein P. W. , Beha H. , Chang W. H. , Jaeckel H.
Published: July 2002

This paper presents an overview of the status of a Josephson cache chip design at IBM in the Fall of 1983. Details of the design, organized as 1 K×4 bits, and employing a 2.5-μm niobium edge-junction technology, are found in the subsequent two adjoining papers. This paper presents, in a broader perspective than the adjoining papers, the background, motivation, changes from previous designs, and general difficulties of the design. General considerations related to the fabrication process and design methodology and an overview of components and the system environment are presented. A Pb-predecessor design is used as a point of reference; the discussions emphasize changes to that work. Finally, inherent design difficulties and remaining uncertainties are discussed.
Complex acoustic and electromagnetic resonance frequencies of prolate spheroids and related elongated objects and their physical interpretation
Authors: Überall H. , Moser P. J. , Merchant Barbara L. , Nagl A. , Yoo K. B. , Brown S. H. , Dickey J. W. , D’Archangelo J. M.
Published: July 2002

A numerical calculation of the complex eigenfrequencies of prolate spheroids and ellipsoids, and of finite-length circular cylinders undergoing acoustic or electromagnetic eigenvibrations is reported. While mainly longitudinal eigenvibrations have been studied previously, here we obtained eigenfrequencies of vibrations which contain azimuthal components. These give rise (e.g., for the case of a cylinder) to helical surface waves, and we were able to interpret the corresponding eigenfrequencies in terms of resonances caused by the phase matching of such surface waves as they repeatedly engulf, and propagate around, the vibrating object. Phase and group velocities and absorption coefficients of the surface waves are obtained numerically from the set of complex eigenfrequencies.
Measurement of barrier height and its controlling parameters in bulk barrier diodes
Authors: Chilana G. S. , Gupta R. S. , Srivastava G. P.
Published: July 2002

Bulk barrier diodes are majority carrier diodes, in which the current is given by the thermionic emission of carriers over a barrier present in the bulk of the material. The height of this barrier depends on the dopings of the various layers of the diode, which has a p+np or n+pn structure. In this paper, different ways to determine this barrier height and its controlling parameters, have been suggested by considering the effect of temperature on the current and the applied voltage of the device.
Superconductivity in inhomogeneous (Mo,Rh)-B glasses
Authors: Zöltzer Klaus , Freyhardt Herbert C.
Published: July 2002

The influence was investigated of inhomogeneities, structural relaxation, and valence electron concentration on the superconducting properties of melt-spun (MoxRh100−x)80B20 glasses (x=40, . . . 70). Annealing below the crystallization temperature levels out quenched-in differences in the critical temperature Tc and results in a narrower transition indicating a homogenization of the glass during the heat treatment. Nevertheless, due to the remaining inhomogeneities, the temperature dependence of the upper critical field Bc2 cannot be described by the Ginzburg-Landau-Abrikosov-Gorkov theory, especially not for alloys with higher Mo contents. The changing inhomogeneity distribution during relaxation leads to a different temperature dependence of the transition width ΔB where ΔB is determined from resistive transitions by varying the magnetic field at fixed T. The experimental results, furthermore, indicate that in this system the electronic density of states at the Fermi level can obviously not be calculated from the residual resistivity and (−dBc2/dT)Tc.
Doping effect on carrier mobility in poly-p-phenylenesulfide
Authors: Yun Mun Soo , Yoshino Katsumi
Published: July 2002

The carrier mobility in poly-p-phenylenesulfide (PPS) and the effect of doping are studied by a time-of-flight method. In both nondoped and TCNQ- (7,7,8,8,tetracyanoquinodimethane) doped PPS samples, holes are confirmed to be the predominant carriers from the polarity of a laser-induced charge signal. With increasing TCNQ concentration, the hole mobility increases and its activation energy decreases.
Excimer laser-induced deposition of InP: Crystallographic and mechanistic studies
Authors: Donnelly V. M. , Brasen D. , Appelbaum A. , Geva M.
Published: July 2002

InP thin films have been deposited on several types of substrates via 193-nm excimer laser-induced photochemical decomposition of (CH3)3In and P(CH3)3 gas-phase precursors. The characteristics of the deposited films are studied over a wide range of conditions. A photochemical model is proposed which explains the stoichiometry and rate at which the film deposits. Approximate fluences are given for the onset of (in order of increasing fluence) In-precursor photochemistry, P-precursor photochemistry, CHx photochemistry, laser-induced crystallization, and laser damage. Crystallinity of InP films deposited on (100) InP substrates has been studied by scanning electron microscopy, transmission electron microscopy, and Rutherford backscattering spectroscopy. Films range from amorphous to epitaxial, depending upon conditions (most notably fluence incident on the substrate). The best film deposited at ∼0.1 J/cm2 and at a steady-state temperature of only ∼320 °C had a backscattering spectrum indistinguishable from that of the substrate single crystal. To our knowledge, this is the first report of a 100% photochemically-induced deposition of an epitaxial, III-V compound semiconductor thin film (i.e., no growth in the absence of light), and also the first report of an epitaxial InP film deposited from organometallic precursors at a steady-state temperature below the incongruent decomposition temperature of InP (∼350 °C).
The characterization of indium desorbed Si surfaces for low temperature surface cleaning in Si molecular beam epitaxy
Authors: Yang H. T. , Mooney P. M.
Published: July 2002

To investigate the feasibility of using indium to replace Ga as an agent for silicon surface cleaning at lower substrate temperature in ultrahigh vacuum, we have examined the in-diffusion of indium and the surface defects introduced into silicon for various indium desorption processes. TEM, SEM, AES, SIMS, EDAX, and DLTS, as well as spreading resistance measurements, were used to characterize the samples. For the dynamic desorption case, which simulated the actual cleaning procedure, no significant surface defects were identified, nor was there any indium in the near surface region of the silicon substrate.
Bound excitons in Si-doped GaAs/Al0.22Ga0.78As single quantum wells
Authors: Nomura Y. , Shinozaki K. , Ishii M.
Published: July 2002

GaAs/Al0.22Ga0.78As single quantum wells with localized Si doping were grown by molecular beam epitaxy. Low-temperature (1.8, 4.2 K) photoluminescence due to excitons bound to Si donors, which were located at the center of wells, was observed. The binding energies of the exciton are 1.8–1.3 meV for well widths ranging from 7.4–15.4 nm, and substantially agree with the theoretical results obtained by Kleinman [Phys. Rev. B 28, 871 (1983)].
Measurements of ion temperature and drift energy of hydrogen plasma by neutral beam probe spectroscopy
Authors: Ito Yoshifumi , Tsukuda Kazuhiro , Goto Seiichi , Ishimura Tsutomu
Published: July 2002

The ion temperature and the energy of gross drift motion of a fully ionized hydrogen plasma with a field-reversed configuration are measured from the observed Doppler profile of the Hβ line from charge exchange neutrals which are generated by a pulsed intense hydrogen beam with energy ∼400 eV. At the beam energy, the generated neutrals are almost hydrogen atoms in the ground state and they emit spectral lines via electron impact excitation. A Monte Carlo analysis shows that the obtained Doppler temperature of the charge exchange neutrals agree with the ion temperature within 6% accuracy. The measured ion temperature and drift energy of the plasma are typically 100 and 10 eV, respectively.
Design of accelerator for negative ion beams by computer simulation
Authors: Park T. S. , Lee W. S. , Be S. H.
Published: July 2002

We describe the computer simulation concerning the acceleration of the H− ion beams in the range of 150–450 eV. The method of H− ion production by bombarding the accelerated cluster ion beams with a small glancing incident angle on the cesiated metal surface is proposed. The computation of the spatial distribution and H− ion trajectory in the multiple stage ionizer is carried out by the iterative numerical method of Laplace equation. The numerical simulation indicates nearly 100% of the H− ion beams from the cesiated metal surface will be accelerated and appear in the output.
Magnetic and structural properties of TmnLum multilayer films
Authors: Lowe W. P. , Gyorgy E. M. , McWhan D. B. , Greene L. H. , Feldman W. L. , Rowell J. M.
Published: July 2002

Coherent multilayers of interheavy rare-earth metals have been synthesized by sputtering. The antiferromagnetic-ferromagnetic transition temperature is suppressed with decreasing modulation wavelength in the TmnLum system.
Solution of the continuity equation in planar symmetry cases and assessment of photoluminescence decay
Authors: Misiakos K. , Lindholm F. A. , Neugroschel A.
Published: July 2002

The decay of excess carriers induced in a semiconductor sample by a laser pulse is studied. The decay rate is proved to be independent of the spatial dependence of the hole-electron generation rate provoked by the laser beam. The effect of surface recombination can be minimized by waiting until the response drops to about 1% of its initial value. The accuracy of photoluminescence decay measurements of Auger lifetime is examined in view of this and other criteria developed here.
Incoherent emission of an electron beam in a free electron laser rectangular waveguide
Authors: Elias L. , Gallardo J. , Gregoire D.
Published: July 2002

A calculation is presented of the incoherent radiation emitted by an electron beam of finite radius passing through a linearly polarized magnetic undulator in a rectangular waveguide with perfect conducting walls. This analysis is based on the Fourier component of the Lienard–Wiechert fields. The metallic boundary conditions are exactly incorporated in the formalism by means of the ‘‘image currents’’ method. In the Fresnel approximation, we show that the double infinite sum over ‘‘images’’ is transformed into one over ‘‘vertical modes,’’ consisting of trigonometric functions. The discrete frequency spectrum and angular distribution of the radiation are studied for several energy spread and electron beam radius cases. The predicted radiation patterns provide useful diagnostics to determine the electron beam properties (trajectories, energy and angular spread, betatron oscillation). The amount of relative power emitted on each mode is a gaussian function exp(−an2).
Phase shift of photoacoustic signals from microparticles in liquids
Authors: Kitamori Takehiko , Fujii Masaaki , Sawada Tsuguo , Gohshi Yohichi
Published: July 2002

The wave equation in which the source term is coupled with the thermal energy migration was analyzed, and the physical meaning of the phase of photoacoustic signals generated in turbid solutions was clarified. These theoretical results, partially verified by experiments, showed the possibility for novel thermal characterizations and size measurement methods of microparticles. The theoretical limitation of the size measurement was 102 Å for samples with nonradiative relaxation times of 1 nsec.
Light scattering measurements of diffusional growth of precipitates in nickel- and cobalt-doped MgO
Authors: Bunch R. M. , Unruh W. P. , Iverson M. V.
Published: July 2002

Changes in the sizes of second-phase precipitates in nickel- and cobalt-doped MgO single crystals have been examined in samples which were subjected to progressive thermal anneals at temperatures ranging from 600 to 1500 °C. Precipitate sizes and spatial locations were measured by means of light scattering before and after anneals in flowing argon. Absolute light scattering angular distribution measurements were used to obtain size distributions from a Mie theory deconvolution procedure. Comparison of the Ostwald ripening theory with the annealing time evolution of these precipitates indicates that the predominant growth can be described by a dislocation or grain boundary diffusion ripening mechanism. This mechanism is also consistent with ultramicroscope measurements taken before and after each anneal. The depletion region surrounding these ripening particles has been observed by means of backscattering in the measured angular distributions. Our results for diffusion within boundary regions are D′=(1.19±0.8×10−6 cm2/s)exp(−1.72 eV/kT) for nickel ions and D′=(1.60±0.9×10−7 cm2/s)exp(−1.36 eV/kT) for cobalt ions in MgO. These equations are in agreement with previous diffusion-couple measurements of nonenhanced diffusion in grain-boundary regions in these materials.
Two deep hole traps in boron-implanted phosphorus-doped silicon
Authors: Jackson Daniel B. , Sah C. T.
Published: July 2002

Energy level and concentration profile measurements of two deep hole traps in boron-implanted, phosphorus-doped silicon are reported. The traps are present following annealing at temperatures near 400 °C. The energy levels and emission cross sections of the two traps are EV +(0.671±0.005) eV, (1.7±0.4)×10−15 cm2, and EV +(0.471±0.007) eV, (2.2±0.8)×10−16 cm2. The concentration profiles of both traps are highly peaked at about 0.31 μm from the silicon surface, in good agreement with nuclear energy loss profile calculations.
Asymmetry factors for randomly oriented infinite cylinders
Authors: Cohen Ariel , Haracz Richard D. , Cohen Leonard D.
Published: July 2002

A method is presented for obtaining optical parameters that are relevant to problems of radiative transfer in such fields as polyester fiber insulation and the passage of radiation through aerosol clouds. The concept of the asymmetry factor is generalized to include nonspherical particles in order to calculate the ratio of the power of radiated light into the forward direction to the power of backscattering light. The geometry for scattering from an infinite cylinder randomly oriented is discussed and related to the problem of identifying the forward and backward directions. This geometry is used to calculate the asymmetry factor versus the angle which the cylinder axis makes with the direction of incidence. The asymmetry factor is also plotted as a function of the size parameter of the cylinder for random orientations of the cylinder.
Radii of gyration of single-oriented microparticles from small-angle light scattering
Authors: Fischbach F. A.
Published: July 2002

Gaussian functions characterized by a radius of gyration are shown to approximate the intensity of light diffracted at small angles by opaque single-oriented microparticles. Procedures are presented for obtaining the radii of gyration.
Depth profile of bulk stacking fault radius in Czochralski silicon
Authors: Wada Kazumi , Inoue Naohisa
Published: July 2002

The depth profiles of bulk stacking fault radius formed under the annealed specimen surface of Czochralski silicon wafers have been obtained. It is clearly shown that the depth profiles have been well predicted by the theoretical result. The curve fitting gives the diffusion coefficient of the responsible point defects expressed by D=257 exp[−(2.84±0.66)eV/kT] in the temperature range between 1080 and 1270 °C. It is strongly suggested that vacancies, not self-interstitials, dominate the growth of the bulk stacking faults.
Properties and photovoltaic applications of microcrystalline silicon films prepared by rf reactive sputtering
Authors: Moustakas T. D. , Maruska H. Paul , Friedman R.
Published: July 2002

Undoped, phosphorus-, and boron-doped microcrystalline silicon films were prepared by rf reactive sputtering, and their properties were investigated through structural, optical, and transport measurements. The merits of microcrystalline films for the p and n contacts in photovoltaic devices were demonstrated through the fabrication of single and tandem p-i-n solar-cell structures with best efficiencies between 5 and 6%.
Kinetics of charge trapping in dielectrics
Authors: Wolters D. R. , van der Schoot J. J.
Published: July 2002

Transient electronic conduction in thermally grown SiO2 has been shown to be limited by space-charge evolution. The space charge originates from trapping of the injected species. It induces a field which affects the emission of charges at the injecting electrode. The trapping of charge has been analyzed on the basis of three, essentially different, mechanisms: (1) first order trapping, (2) first order trapping which takes into account that trapped charges repel injected charges, and (3) trapping which increases during injection due to the generation of states. It is shown that implementation of the three trapping mechanisms yields a current versus injected charge plot which is given in the asymptotes by simple logarithmic functions. Intersection of the asymptotes directly yields the value of the capture cross section. From the slopes of the asymptotes the surface density(ies) of the trap(s) can be calculated. The method can be used without, a priori, assuming either the injection mechanism or the trapping mechanism. From the relative position of the intersection points the applicable mechanism can be derived, however. For thermal SiO2 on Si we determined, by this method, values of trap densities and capture cross sections which are typical for water-related traps. Furthermore, we derived that trapping mechanism (2) fits our data best.
Optical investigations of electron transport through GaAs/AlAs heterostructures
Authors: Schlesinger T. E. , Collins R. T. , McGill T. C. , Burnham R. D.
Published: July 2002

We present the results of the application of photoresponse techniques to the study of the transport of electrons past an energy barrier. In this study, the barrier was provided by a thin layer of AlAs sandwiched between GaAs layers. The experiment measures the voltage resulting from the flow of optically excited electrons from one side of the barrier to the other. The voltage is measured as a function of the wavelength of the incident light. We present results obtained for samples with different doping levels, AlAs layer widths, and at various temperatures. We find that for increasing temperatures the voltage spectrum shifts to longer wavelengths, and that for higher doping levels in the GaAs the voltage spectrum shifts to shorter wavelengths. We also present the results of calculations which explain why the observed spectra change as a function of temperature and as the doping level in the GaAs is varied.
Time-dependent ensemble Monte Carlo simulation for planar-doped GaAs structures
Authors: Wang T. , Hess K. , Iafrate G. J.
Published: July 2002

A time-dependent ensemble Monte Carlo simulation has been developed which includes the computation of the self-consistent electric field and electron concentration. The Monte Carlo code is used to study transient and steady-state transport in planar-doped-barrier (PDB) GaAs diodes and transistors. Results are presented for the temporal and spatial evolution of electronic transport through the PDB. We show that (i) average velocities achievable with a PDB are significantly above the steady-state velocities by about a factor of 3, (ii) the rise time of the electric current in the PDB is in the subpicosecond range for diode length below 2000 Å, (iii) a pronounced displacement current dominates the transient electronics at onset of injection, and (iv) polar optical phonon absorption contributes significantly to the thermionic-emission current over the barriers.
Contact charging of insulating polymers
Authors: Pong W. , Brandt D. , He Z. X. , Imaino W.
Published: July 2002

A new model of contact charging based on the change of interfacial dipole energy is proposed. The model can be used to explain the charge exchange between an insulating polymer and a metal with a thin interfacial oxide layer. The energy shift of the polymeric electronic states relative to the metal Fermi level can be associated with the change in interfacial dipole energy. The calculated change in energy for polyethylene in contact with oxidized aluminum is found to be in good agreement with data from photoemission experiments. The results are shown to be useful in improving the existing models for calculating the magnitude of the charge exchange.
Effects of composition and structure on electromigration kinetics in aluminum-alloy thin films
Authors: Felton L. E. , Schwarz J. A. , Pasco R. W. , Norbury D. H.
Published: July 2002

Variations in time to failure data for electromigration processes have shown the importance to conductor design of factors that include composition, grain size, and passivation thickness. Traditionally, these variables have been studied separately. An understanding of the combined effects of these variables is necessary to design reliable conductors. Temperature-ramp resistance analysis to characterize electromigration (TRACE) has been applied to sample groups in which composition, passivation thickness, and grain size were varied. The results of these experiments provide the kinetic parameters for electromigration, and from these values, a calculation is proposed that allows an estimate of the conductors’ resistance to electromigration. The results suggest that the predominant factor controlling electromigration rates is the passivation thickness.
Sn diffusion effects on x-ray diffraction patterns of Pb1−xSnxTe–PbSeyTe1−y superlattices
Authors: Ishida A. , Aoki M. , Fujiyasu H.
Published: July 2002

Three kinds of superlattices consisting of good lattice-matched and -mismatched materials (Pb0.76Sn0.24Te-PbSe0.10Te0.90, Pb0.76Sn0.24Te-PbTe, and Pb0.76Sn0.24Te-PbSe0.18Te0.82 superlattices) were prepared by a hot-wall epitaxy and their high-angle x-ray diffractions were measured. Sn-diffusion effects on the satellite structure are studied and it was found that Sn diffusion increases lattice distortion for lattice-matched Pb0.76Sn0.24Te-PbSe0.10Te0.90 superlattice and for lattice-mismatched Pb0.76Sn0.24Te-PbSe0.18Te0.82 superlattice, on the other hand, decreases it for Pb0.76Sn0.24Te-PbTe superlattice. And it was also found that very large diffusion of Sn occurs during growth even when the substrate temperature is 250 °C.
Memory and switching effects in polycarbonate-graphite composites
Authors: Ezquerra T. A. , Baltá-Calleja F. J. , Rueda D. R. , Plans J.
Published: July 2002

Reproducible memory and switching effects have been detected in polycarbonate-graphite composites. Memory effects are characterized in the range of 0–1 kV/cm. It is suggested that they involve electrothermal and electromechanical phenomena. Switching effects occur above 2 kV/cm and are related to an intrinsic electric breakdown of the material. The threshold field increases with increasing thickness of the composite film. The temperature dependence and level of conductivity reached point toward a prevailing electron tunneling mechanism.