bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of blocking contacts on generation-recombination noise and responsivity in intrinsic photoconductors
Authors: Smith D. L.
Published: February 2003

A theory is presented of generation-recombination (g-r) noise, responsivity, and detectivity D* in intrinsic photoconductors, including for the first time the effects of recombination at the contacts as a variable parameter. The contacts are described using a contact recombination velocity. Increasing the blocking at the contacts can significantly increase the responsivity, and also push the detectivity toward the background limited value since blocking contacts increase responsivity and the background contribution to the noise voltage faster than the thermal contribution. Blocking contacts also cause both the responsivity and g-r noise voltage to roll off at lower frequencies. Numerical calculations are presented for X∼0.2 HgCdTe photoconductors. Blocking contacts are found to increase the range of material parameters which can be used to make detectors. For example, under typical conditions, to reach responsivities of 105 V/W and detectivities of 6×1010 cm(Hz)1/2/W at T=77 °K, blocking contacts can increase the maximum allowed carrier density from about 4×1014 to about 2×1015 cm−3, and enlarge the required composition window from about 0.200<x<0.212 to about 0.188<x<0.212 for typical device geometries.
Electrical, thermoelectric, and optical properties of strongly degenerate polycrystalline silicon films
Authors: Jones R. E. , Wesolowski S. P.
Published: February 2003

Low-pressure chemical vapor deposited polycrystalline silicon films 0.45  μm thick were doped to strongly degenerate concentrations (1–2×1020 cm−3) by thermal diffusion of phosphorus. Thermoelectric power, Hall effect, and resistivity measurements were made over the temperature range of 80 to 340 K. The thermopower results were in good agreement with single crystal degenerate semiconductor theory. Additionally, these results, in conjunction with the measured carrier concentration, showed that the scattering relaxation time is inversely proportional to the square root of the carrier energy which is indicative of lattice scattering. The temperature dependence of the resistivity was found to be of the form  ρ=a+bT. The liner term was attributed to acoustic phonon scattering within the grains and the constant term to lattice mismatch at the grain boundaries. Scattering from grain boundary potential barriers due to carrier trapping appeared to play no significant role although this effect dominates at lower doping concentrations. The index of refraction and absorption coefficient in the near infrared and visible were determined from transmission and reflection measurements of doped and undoped polycrystalline silicon films on quartz substrates.
Trapping and surface recombination of ion-implanted deuterium in stainless steel
Authors: Myers S. M. , Wampler W. R. , Besenbacher F.
Published: February 2003

Nuclear-reaction analysis was used to investigate the behavior of deuterium (D) in three austenitic stainless steels following ion implantation with D and He. The D was bound to irradiation defects with a binding enthalpy of 0.23±0.08 eV relative to solution sites. Helium bubbles of diameter ∼1 nm trapped D with a binding enthalpy of 0.42±0.08 eV, presumably through a chemisorptionlike process at the bubble walls. Surface-controlled release of D to the gas phase was characterized over the temperature range 425–575 K, and the rate was found to be proportional to the square of the solution concentration within the matrix. Electropolish oxide reduced the surface release rate by as much as 1000 times from that of an ion-sputtered surface.
Probe penetration in spreading resistance measurements
Authors: Vandervorst W. B. , Maes H. E.
Published: February 2003

The penetration depth of the probe points in spreading resistance measurements is determined. The result—penetration depths of less than 20 nm—enforces the need for a microscopic description instead of a macroscopic treatment. A previously proposed method for evaluating the penetration depth is shown to be inadequate. Experiments are provided which show that abrupt transitions can always be detected independent of the probe load. A reduction of the probe load is found to be only beneficial in obtaining smoother profiles.
Electroluminescence from LiInSe2-GaP heterodiodes
Authors: Kuriyama K. , Igarashi Y.
Published: February 2003

Heterodiodes have been prepared by evaporation of p-type LiInSe2 on n-type GaP. Typical diodes emit orange light (610 nm) under forward bias with external quantum efficiency of 10−4% at 77 K. Electroluminescence spectrum is coincident to the photoluminescence in LiInSe2 crystals.
Photoelectrochemical effect of the anodic oxide of Hg1−xCdxTe
Authors: Laser D. , Silberman J. A. , Spicer W. E. , Wilson J. A.
Published: February 2003

Two aspects of the electrochemical behavior of Hg1−xCdxTe in anodizing solution are presented. The current-voltage relationship for anodically oxidized Hg1−xCdxTe under cathodic bias has been examined and found to be independent of film thickness or substrate composition and carrier type for oxides exceeding 100 Å thick. For samples in solution biased anodically, ultraviolet light absorption results in increased electrode current. Mechanisms for these effects are discussed.
Polycrystalline zinc selenide films deposited by a low-temperature close-spaced-vapor-transport method
Authors: Falcony C. , Sánchez-Sinencio F. , Helman J. S. , Zelaya O. , Menezes C.
Published: February 2003

Polycrystalline films of ZnSe, pure and doped with Cu and Ga, have been deposited by a modified close-spaced-vapor-transport method which requires low temperatures (500 °C) and no subsequent annealing. The resulting grains are of the order of 1 μm. The films were characterized by their photoluminescence emission in the temperature range 10–290 K. The undoped and Cu-doped films display the usual Cu-green and Cu-red and near edge emission bands at low temperatures. In the Ga-doped films only a mildly temperature dependent band centered at ∼620 nm appears at all temperatures. The films have very similar characteristics to those prepared by more sophisticated techniques.
Figure of merit and spatial resolution of superconducting flux transformers
Authors: Duret D. , Karp P.
Published: February 2003

A figure of merit relating the magnetic field in one point of space and the output of a superconducting magnetometer system is introduced. This new figure of merit can be understood as the magnetic field gain provided by a flux transformer. By its definition the gain also takes into account the spatial variation of the magnetic field, i.e., its source. Therefore, the gain is a suitable parameter for the optimization of a flux transformer for measuring fields from given sources. As another topic the spatial resolving power of a flux transformer is studied. A simple discrimination criterion gives the result that two magnetic field sources cannot be resolved even with a point vector magnetometer if the separation of the sources is below a threshold value. A second-order flux transformer optimized with respect to gain and resolving power is finally presented.
Dynamics of laser stimulated etching of germanium by bromine
Authors: Davis Glenn P. , Moore Cameron A. , Gottscho Richard A.
Published: February 2003

The dynamics of laser stimulated etching of Ge by Br2 have been studied by characterization of the desorbed products. The product time-of-flight distribution was measured with a quadrupole mass spectrometer, providing both product identification and velocity analysis. Transient reflectivity measurements were used to determine when the melt threshold for Ge was exceeded. At low Br2 pressure, etching at a rate of ∼0.1–0.2 Å per pulse was observed above the melt threshold. The principal product observed was GeBr2, whose translational energy distribution deviated slightly from Maxwell–Boltzmann: the observed distribution was relatively rich in high-energy species (i.e., hyperthermal).
Compressibility of zeolite 4A is dependent on the molecular size of the hydrostatic pressure medium
Authors: Hazen R. M. , Finger L. W.
Published: February 2003

Unit-cell parameters of synthetic zeolite 4A were determined at several pressures to 4.0 GPa in four different hydrostatic pressure media: ethanol, methanol, glycerol, and an organofluorine compound, C8F16O (FC-75). These data, when combined with previously published results on zeolite in water and a water-bearing 4 : 1 methanol : ethanol mixture, reveal that compression of zeolite depends on the relative sizes of the hydrostatic fluid molecules compared with the structural channels in the zeolite framework. Zeolite 4A is most compressible (ΔV/VΔP =β=0.046 GPa−1) in glycerol and FC-75, which have molecular dimensions that are larger than the zeolite channels. Zeolite is least compressible ( β=0.007 GPa−1) in water, which has a maximum molecular dimension that is significantly smaller than the channel diameter. In methanol and ethanol alcohols, which have intermediate molecular diameters, zeolite 4A also has intermediate compressibility. This zeolite in alcohols, furthermore, progressively undergoes a series of transitions to more compressible states as pressure is raised.
Ferrimagnetic echoes of magnetostatic surface wave modes in ferrite films
Authors: Bucholtz F. , Webb D. C. , Young C. W.
Published: February 2003

This paper presents the first detailed characterization of ferrimagnetic echoes resulting from the nonlinear response of magnetostatic surface waves in a yttrium-iron-garnet film to excitation by two time-resolved rf pulses. Data showing the behavior of the echo as a function of excitation pulse separation time τ, signal pulse power Ps, and pump pulse power Pp is presented. We also show the results of measurements of the spatial variation of the echo response which directly confirm the localized nature of the echo-producing magnetostatic modes. The data is analyzed in terms of (1) the dispersion relation for magnetostatic surface waves in a dielectric layered structure to obtain the dependence of the echo power on wavenumber and position in the sample and (2) the general properties of echoes produced by the anharmonic response of a system of oscillators to obtain the dependence of the echo power on τ, Ps, and Pp.
Thermal oxidation of silicides
Authors: Lie L. N. , Tiller W. A. , Saraswat K. C.
Published: February 2003

Kinetics of thermal oxide growth on silicides MoSi2, WSi2, TaSi2, and TiSi2 deposited over polycrystalline and single-crystal silicon were investigated. Both steam and dry O2 oxidations in the temperature range of 750–1200 °C were examined. An oxidation kinetic model for silicides which accounts for diffusion processes of silicon through the silicide layer and oxidant through the growing oxide, and the interface chemical reaction was developed. This model uses the Deal–Grove silicon oxidation approach. The significantly larger linear rate constants and greatly reduced activation energies of the linear rate constants of silicides in relation to single-crystal silicon oxidations are predicted by this model. The similarity of parabolic rate constants and their activation energies for silicon oxidations is also in excellent agreement with the model.
A comparative study of instruments for measuring the liquid water content of snow
Authors: Denoth A. , Foglar A. , Weiland P. , Mätzler C. , Aebischer H. , Tiuri M. , Sihvola A.
Published: February 2003

Different dielectric sensors for measuring the liquid water content of snow are compared and described in detail. The instruments make use of the significant difference in the dielectric properties of ice and liquid water at radio frequencies; they are operated with frequencies ranging from 1 MHz up to 1.3 GHz. Plate condensers in connection with ac bridges are used as sensors in the frequency range up to 100 MHz whereas open resonators are used in the GHz regime. Test measurements with the different sensors on homogeneous samples like dry sand and mixed and prepared snow showed the same results for the dielectric constant: the discrepancies are less than 1%. In the natural, inhomogeneous snow cover, the special properties of the different sensors appear. Snow wetness is calculated from the measured dielectric constant and the snow density using the model of Polder and van Santen. The comparative field measurements were made with Alpine snow in the Stubai Alps in Austria.
Experiments on the temperature rise in cw-laser-irradiated silicon on sapphire
Authors: Alestig G. , Holmén G.
Published: February 2003

Experiments have been carried out to check the validity of calculated temperature distributions in cw-laser-irradiated silicon on sapphire. Both implanted and unimplanted samples were investigated. The implantations did not significantly change the temperature induced by the laser beam. At low laser scan velocities the agreement between the experiments and the calculations is good, but at high scan velocities the existing theoretical expressions are shown to be inadequate. Some of the problems involved in applying the calculations to an experimental situation are discussed.
Frequency chirp under current modulaton in InGaAsP injection lasers
Authors: Dutta N. K. , Olsson N. A. , Koszi L. A. , Besomi P. , Wilson R. B. , Nelson R. J.
Published: February 2003

We have measured the frequency chirp in gain-guided, weakly index-guided, and strongly index-guided InGaAsP lasers under direct-current modulation. The measured chirp width is largest for gain-guided and smallest for weakly index-guided ridge waveguide lasers. The chirp width for 1.5-μm InGaAsP lasers is about a factor of 2 larger than that for 1.3-μm InGaAsP lasers of the same structure. The frequency chirping results from a modulaton of the carrier density which modulates the effective refractive index of the guided mode. The frequency chirping can introduce a limitation on the performance of single-frequency injection laser sources for high bit-rate digital transmission in fiber communication systems at 1.55 μm.
Origin of the open-circuit voltage in amorphous silicon Schottky-barrier solar cells
Authors: Narasimhan K. L. , Premachandran V.
Published: February 2003

The primary source of photovoltage in a-Si is often taken to lie in the built-in electric field in the semiconductor. In this paper we show that this need not be the case in a-Si Schottky-barrier solar cells. We also show that it is necessary to take into account the conductivity prefactor to estimate correctly the built-in voltage in a-Si cells.
Radioactive preionization in space lasers
Authors: Pereira N. R.
Published: February 2003

Radioactive preionization may have advantages over x-ray or UV preionization when simplicity, power consumption, and weight are at a premium, as in space lasers. Computations show that a few Ci/cm2 of 90Sr in the laser sidewalls or the electrodes results in a homogeneous electron source strength exceeding 1014 cm−3 s−1.
Advances in superfluid helium acoustic microscopy
Authors: Hadimioglu B. , Foster J. S.
Published: February 2003

An acoustic microscope utilizing low-temperature (0.1 K) superfluid helium as the coupling medium has been operated at 8 GHz. At this frequency the sound wavelength in helium is 300 Å. Pulse compression techniques have been used to improve the signal-to-noise ratio of the system. A theoretical and experimental analysis of acoustic transducers operating at 8 GHz is presented. The transducer performance has been optimized for operation in liquid helium with the pulse compression system. The images formed with the microscope demonstrate a lateral resolution of 200 Å with a signal-to-noise ratio of 15 dB. A comparison of acoustic and scanning electron microscope or transmission electron microscope images is given.
Electromagnetic effects of a moving metal sheet in the presence of alternating-current conductors
Authors: Ciric I. R. , Mathur R. M.
Published: February 2003

Exact solutions of the quasistationary magnetic vector potential, forces, power loss, and reactive power for an infinite plane metal sheet moving in the proximity of a distribution of parallel straight wires carrying ac have been obtained by assuming a two-dimensional field. The solutions are valid for both nonmagnetic and magnetic metal sheets, within the linear material characteristics, and for any ratio of the plate thickness to the depth of penetration. Integral expressions are derived for the transfer impedance between filamentary conductors and also more practical thick conductors separated by such moving metal sheets. Quantitative results were obtained for a wide range of system parameters and general conclusions are drawn relative to the dependence of forces, active and reactive powers, and transfer impedances on the ac frequency, velocity, and material properties. The analysis presented can be used for nondestructive testing of metallic sheets in motion and is related to the study of ac systems with moving solid conductors.
Magnetic field perturbations due to a hole in a conducting wall on the ZT-40M reversed-field pinch
Authors: Howell R. B. , Vogel H. F.
Published: February 2003

Radial magnetic field components were measured near a pump port on the ZT-40M Reversed-Field Pinch experiment. The measurements show radial components which are about 20% of the equilibrium field at the wall during the setup portion of the discharge. During the flat top of the toroidal current, radial components, ∼8% of the total field at the wall, are measured. A two-dimensional field diffusion calculation was done to understand the measurements. This gave results which were in basic agreement with the measurements at the position of the probe.
〈ρR〉 measurements in laser-produced implosions using elastically scattered ions
Authors: Kacenjar S. , Goldman L. M. , Entenberg A. , Skupsky S.
Published: February 2003

The measurement of the number of elastically scattered deuterium and tritium ions is shown experimentally to be an effective means of determining the 〈ρR〉 of the fuel in a laser fusion implosion. A method is described for clearly separating the unwanted proton background signal from the desired d and t knockon signals. The details of the analysis are presented for an experiment resulting in a measured 〈ρR〉 of 1.2×10−3 g/cm2.
Optogalvanic effects in a hollow cathode glow discharge plasma
Authors: van Veldhuizen E. M. , de Hoog F. J. , Schram D. C.
Published: February 2003

The hollow cathode glow discharge is a very suitable source to measure the optogalvanic effect (OGE). A detailed study of this effect in neon has been made using a tunable, single-frequency dye laser. It was found that the lower level of the irradiated transition together with the plasma conditions determine the sign of the effect. Three situations occur: the lower level can either be metastable, resonant, or highly excited. With a five-level model taking into account electronic collisions and radiative decay a qualitative description of all the cases found in the experiment can be given. Further, it is shown that from a frequency scan of the OGE, line profiles can be obtained which, under certain conditions, contain the gas temperature in their Doppler part. Temperatures ranging from 700 to 1300 K determined this way are consistent with other results. This method makes it possible to measure the temperature as a function of the position, showing that inside the glow the gas temperature is constant. Finally, the time-dependent OGE is measured and analyzed in terms of ambipolar diffusion. This way an average transport temperature for the plasma electrons in the hollow cathode discharge in neon between 0.2 and 1.2 eV is found.
Photoluminescence of CdTe grown on (001) InSb by molecular beam epitaxy
Authors: Mar H. A. , Salansky N.
Published: February 2003

CdTe films grown by molecular beam epitaxy on (001) InSb from a congruently subliming CdTe compound source were studied by photoluminescence for the presence of chemical impurities and native defects. Photoluminescence data taken at 77 K indicates that the optimum substrate growth temperature for a growth rate of 0.4 μm/h is about 170 °C. Negligible self-activated emission was observed at 77 and 6.5 K. The 6.5-K photoluminescence spectrum is dominated by edge emission at about 797 nm (∼1.55 eV) and this is attributed to recombination through acceptor impurity levels. Band-to-band recombination observed at room temperature and the presence of well-resolved free excitons as well as acceptor- and donor-bound excitons suggest the films are of high quality, but contain significant concentrations of donor and acceptor impurities.
Carrier mobility in polycrystalline silicon under solar illumination
Authors: Joshi D. P. , Srivastava R. S.
Published: February 2003

A new model for the carrier mobility in polycrystalline silicon under solar illumination is presented. The dependence of mobility on temperature and grain size is also investigated theoretically. It is found that at low temperatures or for small grain sizes, the mobility is controlled by the grain-boundary scattering effect. Excellent agreement is observed between theoretical predictions and available experimental data.
The mobility of Na+, Li+, and K+ ions in thermally grown SiO2 films
Authors: Greeuw G. , Verwey J. F.
Published: February 2003

Na+, Li+, and K+ ions have been implanted in thermally grown oxides (Tox =1000 °C) of metal-oxide-silicon structures. The mobilities of the Na+ and Li+ ions have been determined by means of the isothermal transient ionic current method in the temperature range 100–300 °C. The K+ mobility has been obtained by means of triangular voltage sweep measurements in the range 350–450 °C. The results show that the Na+ and the Li+ mobilities are not significantly different. The activation energies of the three measured mobilities are shown to agree with a quantitative model which has been developed by Anderson and Stuart [J. Am. Ceram. Soc. 37, 573 (1954)].
Effect of potential fluctuations on the transport properties and the photoconductivity of compensated semiconductors. Application to semi-insulating GaAs. II. Excess carrier lifetimes and photoconductivity
Authors: Pistoulet B. , Girard P. , Hamamdjian G.
Published: February 2003

In the presence of potential fluctuations, the continuity equations must be averaged over the sample in order to obtain equations involving physically observable transport quantities. The lifetime of the total carrier population, which can be obtained by initial photoconductivity decay time measurements, differs from the photoconductivity lifetime. The lifetime expressions are derived in the cases of band-to-band and Shockley–Read recombinations. Numerical calculations of the excess carrier densities versus flux and temperature are performed for semi-insulating (SI) GaAs, considering one deep level as a recombination center. The analysis is extended to describe various situations taking into account (i) the presence of a trap, and (ii) both the EL2 and Cr recombination centers. Experimental data are discussed.
Study of the Kondo effect and intrinsic electrical conduction in titanium diboride
Authors: Williams R. K. , Becher P. F. , Finch C. B.
Published: February 2003

Electrical resistivity data for seven dense polycrystalline TiB2 samples are reported. The data, which extend from 4.2 to 300 K, all show resistivity minima in the 34 – 47 K range and this is attributed to the Kondo effect. Although the residual resistivity values varied by only a factor of about 2, the strength of the Kondo effect changed by a factor of 15. These differences are related to the effects of processing variables. The ideal resistivity of TiB2 was calculated from the measurements and was found to vary about as T5 at low temperatures. These values can be adequately described by the Bloch–Grüneisen equation, and the characteristic temperature obtained from resistivity, 720 K, is in reasonably good agreement with the Debye temperature from specific heat measurements. A comparison of the electronic scattering part of the Bloch–Grüneisen constant shows that TiB2 is a somewhat better conductor than Ti and the electronic band structures of ZrB2 and Zr help to explain this difference.
Effect of the surface condition on the conductance of hydrogenated amorphous silicon
Authors: Yamaguchi M. , Fritzsche H.
Published: February 2003

We observed that the conductance of undoped hydrogenated amorphous silicon films (a-Si:H) is dominated by an electron accumulation layer at their surface. With increasing oxide thickness the band bending diminishes and then converts to hole accumulation. The surface changes from n type to p type as the result of light exposure. The surface space-charge layer was tested and changed by adsorbate layers of water and oxygen and layers of evaporated Se. It is found that erroneous conclusions will be drawn about the values of the conductivity activation energy, the prefactor, and the Meyer–Neldel relation between these parameters unless the conduction in the surface space-charge layer is eliminated or accounted for.
Current-voltage characteristic of Ti-pSi metal-oxide-semiconductor diodes
Authors: Hanselaer P. L. , Laflère W. H. , Van Meirhaeghe R. L. , Cardon F.
Published: February 2003

The electrical characteristics of Ti-pSi metal-oxide-semiconductor diodes have been studied as a function of temperature and of applied voltage, using conventional Schottky barrier capacitance-voltage (C-V) and current-voltage (I-V) measurements. The results show a strong deviation from those expected from thermionic emission and from the minority carrier injection theory for the current mechanism. Unlike other authors who proposed a multistep recombination-tunneling mechanism, we have stressed that a model based on the inhomogeneity of the barrier height over the diode area predicts a temperature and voltage behavior of the I-V characteristic similar to the recombination-tunneling mechanism. The concept of inhomogeneity proposed by former authors is supported by Auger depth concentration profiles which show an intermixed region of Ti and Si. It is observed that the equilibrium semiconductor band bending exhibits a stronger temperature dependence than expected from the variation of the semiconductor Fermi level.
Ultrafast UV-laser-induced oxidation of silicon: Control and characterization of the Si-SiO2 interface
Authors: Richter H. , Orlowski T. E. , Kelly M. , Margaritondo G.
Published: February 2003

A new low-temperature method of rapidly forming (>100 Å/sec) high-quality patterned silicon dioxide (SiO2) layers up to a thickness of 1 μm on silicon substrates is presented. Ultraviolet pulsed laser excitation in an oxygen environment is utilized. Infrared absorption spectroscopy, capacitance-voltage measurements, and soft x-ray photoemission are employed to characterize the oxide films and the Si-SiO2 interface. No shift, but a significant broadening of the Si-O stretching mode compared with thermally grown oxides is found, indicating that the laser-grown oxide is stoichiometric but with a higher degree of disorder. Similar results are obtained from soft x-ray photoemission data: the bulk of the laser-grown SiO2 shows no sign of SiOx suboxides, while at the interface a layer of SiOx is found of comparable thickness as in thermally grown SiO2. From capacitance-voltage measurements we deduce a fixed oxide charge near the Si-SiO2 interface of 6×1010/cm2 for oxides that have been thermally annealed following the laser-induced growth making this material a candidate for applications in semiconductor devices.
Behavior of electrical conduction of spinel and other insulating oxides in moderate electric fields at high temperature
Authors: Sonder E. , Weeks R. A.
Published: February 2003

It is known that MgO subjected to moderate electric fields at high temperature becomes progressively more conducting till it breaks down. We report a similar phenomenon in spinel. The insulating properties of stoichiometric spinel degrade even more rapidly than those of MgO; commercial spinel, which contains excess aluminum as well as hydrogen, exhibits erratic variations in conductance and general electrical instability, but does not always degrade to breakdown. Other insulating oxides (Al2O3, forsterite, quartz, and Y2O3) maintain their insulating properties when moderate dc electric fields (∼1000 V/cm) are applied at temperatures near 1200 °C.
GaN blue light emitting diodes prepared by metalorganic chemical vapor deposition
Authors: Kawabata Toshiharu , Matsuda Toshio , Koike Susumu
Published: February 2003

The epitaxial layers of GaN have been grown on (0001)-oriented sapphire substrates using metalorganic chemical vapor deposition. The layers with good quality and relatively smooth surface morphology were obtained by enforcing growth in H2 after adherence of nuclei to the substrates in N2 atmosphere. Using this technique, GaN light emitting diodes with metal-insulating n-type structure were fabricated. Two kinds of blue electroluminescence were observed at room temperature with exciting voltage of 4–8 V with emission wavelength of 430 and 488 nm. The external efficiency is about 0.005%.
Characterization of Si-implanted and electron-beam-annealed silicon-on-sapphire using high-resolution electron microscopy
Authors: Smith David J. , Freeman L. A. , McMahon R. A. , Ahmed H. , Pitt M. G. , Peters T. B.
Published: February 2003

Silicon-on-sapphire films have been characterized by high-resolution electron microscopy at 500 kV following silicon implantation and electron beam annealing. The effect of implantation with 1015 Si/cm2 at 190 keV was to amorphize most of the 0.3-μm silicon layer, in particular breaking up the lattice defects originating from the interface. The remaining crystalline surface layer acted as a seed for the recrystallization of the film back to the interface. There was a substantial decrease in the number of lattice defects present in the silicon compared to the as-grown films, although amorphous layers varying in thickness up to 50 Å were formed at the interface. Rutherford backscattering spectrometry measurements of the film crystallinity showed good correlation with the observed microstructural changes.
Dislocations and twins formed in zone melted recrystallized Si on SiO2
Authors: Komem Y. , Weinberg Z. A.
Published: February 2003

The microstructure of encapsulated silicon films recrystallized by zone melting, in a graphite strip-heater oven, was investigated by transmission electron microscopy. In the case where the film crystallized with its surface parallel to the (100) plane the major defects were long arrays of dislocations. These defects have sources of slip dislocations at their beginning point, which is indicative of plastic deformation. In other crystallographic cases, especially where the surface of the film was parallel to the (110) plane, the major defects were twins of the {111} 〈112〉 mode, which are typical to deformation twinning in diamond crystals. Both results indicate that the growth occurs under compressive stress which exists in encapsulated silicon films during their recrystallization. It is proposed that the (100) case can best accommodate the deformation by providing the largest number of slip systems, therefore it is energetically favorable. In the (110) case the reduced number of slip systems gives rise to deformation by twinning.
Step-frequency radar
Authors: Iizuka Keigo , Freundorfer Alois P. , Wu Kam Hung , Mori Hirotaka , Ogura Hisanao , Nguyen Van-Khai
Published: February 2003

The step-frequency radar is proposed as a means of detecting targets imbedded in high loss media. The radar derives information on target distance by exploiting the phase and amplitude characteristics of the returned signal. With a given frequency change, the phase angle change from a faroff target is larger, and therefore its phasor rotates faster, than that from a closeby target. Distance information is conveniently derived by applying the Fast Fourier Transform algorithm. The radar is able to offset an arbitrary distance and zoom to the targets, thereby obtaining fine resolution. With Wiener filtering, the resolution of the radar is high enough to identify the type, as well as the orientation, of the buried targets. A subtraction feature has also been incorporated which allows scattering from unwanted targets to be cancelled out from that of the wanted targets. The radar was successfully demonstrated for the detection and identification of various targets buried in sand, moist clay soils, underwater, as well as for the mapping of thin ice.
Comments on ‘‘Material nonlinear piezoelectric coefficients for quartz’’
Authors: Kittinger E. , Tichý J. , Friedel W.
Published: February 2003

True material nonlinear piezoelectric coefficients must be applicable to the piezoelectric response of a crystal under static as well as under dynamic conditions. Experiments involving the static compression of quartz crystals in suitable geometries indicate that some of the nonlinear piezoelectric constants are considerably smaller than those given by R. Brendel [J. Appl. Phys. 54, 5339 (1983), 55, 608 (1984)].
Light scattering in crystals
Authors: Adomian G. , Rach R.
Published: February 2003

The paper provides solution of the nonlinear partial differential equation ∇2p=k2 sinh p previously obtained by Plint and Breig [J. Appl. Phys. 35, 2745 (1964)] with the objective of confirmation of expected temperature dependence of scattering of light by certain crystals. The solution is of interest both for the experimental problem and as a solution of a nonlinear partial differential equation without customary linearizing assumptions. This is done using Adomian’s decomposition method [G. Adomian, Stochastic Systems (Academic, New York, 1983)]. This has been shown elsewhere in Adomian’s work and numerous following papers to provide a rapidly convergent series solution which is accurate and computable even if strong nonlinearities or stochastic behavior is involved.
Piezoelectric properties and ferroelectric hysteresis effects in uniaxially stretched nylon-11 films
Authors: Mathur S. C. , Scheinbeim J. I. , Newman B. A.
Published: February 2003

Oriented nylon-11 films [initially quenched (δ′ form) or slow cooled (α′ form) from the melt] subjected to a series of static positive and negative poling fields were found to show a hysteresislike behavior of the piezoelectric strain constant d31 and the piezoelectric stress constant e31. This behavior was very similar to that observed in poly(vinylidene fluoride) (PVF2) and attributed to ferroelectric dipole switching, in a previous study. No change in the x-ray diffraction patterns of the δ′-form films was observed after poling. Changes in the x-ray diffraction patterns of the α′-form films after poling were consistent with dipole reorientation in the crystalline regions. In both cases the magnitude of the piezoelectric response of the oriented films was considerably higher than that of the unoriented films. The melting points of the poled films increased significant ly relative to that of the unpoled films with the same thermal history, which may suggest field-induced annealing effects.
Pressure dependence of glass transition temperature of elastomeric glasses
Authors: Pae K. D. , Tang C.-L. , Shin E.-S.
Published: February 2003

The pressure dependence of the glass transition temperature Tg of two elastomers, Solithane 113 and 3,3-bis(azidomethyl)oxetane/tetrahydrofuran (BAMO/THF) has been determined, employing high-pressure differential thermal analysis (HP-DTA) and dielectric techniques, up to 8.5 kbar. The glasses of the elastomers were named the specific (or Pi glass) or the general glass depending on how the glasses were formed. A Pi glass was formed by lowering temperature under a constant pressure (Pi) and the pressure dependency of the Pi glass was determined after changing pressure only in the glassy state. The general glass consists of a series of specific glasses but the Tg is determined only at pressures under which the glass is formed. The Tg for both glasses increased with increasing pressure. However, the Tg for the Pi glass appears to level off at very high pressures while the Tg does not level off for the general glass. Thermodynamic analysis was made to show that for many general glasses dTg/dP=Δβ/(1+n)Δα holds, in which n=1 for Solithane and many other glasses. It is also shown that a modified Gibbs and DiMarzio theory can be used effectively to predict the observed experimental results.
Morphology-structure-property relationships in ultraquenched poly(vinylidene fluoride)
Authors: Hsu C. C. , Geil P. H.
Published: February 2003

Ultraquenching of thin films (∼1000 Å) was used to obtain glassy poly(vinylidene fluoride) (PVF2). Electron microscopy indicates the glass has no structure larger than 20 Å. Electron diffraction indicates crystallization forms from the glass at ∼−30 °C into β form. Rapid crystallization from the glass results in the development of a nodular, microcrystalline morphology which can be changed only by annealing above Tα. Thick films (∼80 μm) could not be ultraquenched to the glass; ultraquenching results in α form crystals in the bulk and β form on the surface. These thicker films were characterized by x-ray diffraction, dynamic mechanical spectroscopy, and differential scanning calorimetry.
Dynamic loss properties of wood
Authors: Wert C. A. , Weller Manford , Caulfield Dan
Published: February 2003

Internal friction and dielectric loss measurements have been made on whole wood, on cellulose, and on lignin. A prominent β peak is seen at 200 K for frequencies around 1 Hz. This peak shifts to lower temperatures (near 160 K) when wood is heated to 475 K. We propose that this shift signifies molecular changes characteristic of the first stages of coalification of wood and lignin. Additional comparisons are made with the macromolecular structure of amber, oil shale, and synthetic polymers.
High-power visible GaAlAs lasers with self-aligned strip buried heterostructure
Authors: Ohtoshi Tsukuru , Kawano Toshihiro , Sasaki Yoshimitsu , Kajimura Takashi , Chinone Naoki , Nakamura Michiharu
Published: February 2003

Transverse-mode-stabilized GaAlAs high-power visible lasers have been developed in such a way as to have a self-aligned strip buried heterostructure. Analysis of their waveguide properties shows that asymmetric AlAs composition in cladding layers, as well as a thin active layer, are important for increasing optical spot size and stabilizing the transverse mode. Lasers with such a waveguide structure operate in the fundamental transverse mode up to an output power as high as 30 mW, and at a lasing wavelength of around 780 nm under cw operation. In addition, fundamental transverse mode operation up to 75 mW under cw conditions has been achieved with optimization of facet reflectivities.
Parameters affecting the performance of a rf excited CO2 waveguide laser
Authors: Sinclair R. L. , Tulip J.
Published: February 2003

This paper summarizes the results of a series of rf gas discharge experiments which were performed to assess the factors which influence the efficient operation of a transversely excited CO2 waveguide laser. Using multiple resonating inductors for impedance matching, the longitudinal voltage variations are shown to be affected by the rf operation frequency and the discharge geometry. The effect of the gas mixture and the rf input power density upon the discharge field to pressure ratio is also investigated.
Theoretical study of long-wavelength laser operation in Ga1−xAlxAsySb1−y
Authors: Takeshima Masumi
Published: February 2003

A theoretical study is done on laser operation in Ga1−xAlxAsySb1−y which is lattice-matched to GaSb. The strongly x-dependent intervalence-band absorption, the almost degenerate conduction-band minima, and the nonradiative Auger recombination are major factors deteriorating the laser operation. The first two factors explain the observation that the threshold current rapidly increases with x. It is shown that the Ga1−xAlxAsySb1−y laser with an adequate value of x is promising as a long-wavelength light source characterized by a weak temperature-dependent and low threshold.
Oscillating field current drive for reversed field pinch discharges
Authors: Schoenberg Kurt F. , Gribble Robert F. , Baker Don A.
Published: February 2003

Oscillating field current drive (OFCD), also known as F-Θ pumping, is a steady-state current drive technique proposed for the reversed field pinch (RFP). Unlike other current drive techniques, which employ high technology, invasive, and power intensive schemes using radio frequency or neutral particle injection, F-Θ pumping entails driving the toroidal and poloidal magnetic field circuits with low-frequency (audio) oscillating voltage sources. Current drive by this technique is a consequence of the strong nonlinear plasma coupling in the RFP. Because of its low frequency and efficient plasma coupling, F-Θ pumping shows excellent promise as a reactor relevant current drive technique. A conceptual and computational study of this concept, including its experimental and reactor relevance, is explored in this paper.
A circuit-oriented quiteron analysis
Authors: Frank David J.
Published: February 2003

A phenomenological circuit model for the quiteron, a three-layer superconducting amplifying device, has been developed which simulates the observed I-V curves reasonably well. The model is used to analyze the behavior of the quiteron for various circuits and a range of parameters. The results show that the quiteron has poor isolation making it difficult to use in logic circuits. Several ways to somewhat reduce this problem are suggested.
Simple derivation of the Bohr–Wheeler spontaneous fission limit
Authors: Reed B. Cameron
Published: February 2003

A simple model for establishing the Bohr and Wheeler limit for Z2/A against spontaneous fission is developed. The physics involved is sufficiently simple to make the model suitable for sophomore students. Beyond showing how fundamental energy considerations lead to a limit for Z2/A, the model helps to make clear the physical origin of the numerical values of the surface and Coulomb terms in the semiempirical mass formula. The resulting limit against spontaneous fission, Z2/A∼60, is in fair agreement with the original Bohr and Wheeler value of ∼48.
An introduction to the autolocalization of a free charged particle
Authors: Kornyushin Y.
Published: February 2003

A simple model for the autolocalization of a free charged particle is presented. The polarization well in the model is deep enough for only one localized level. In dielectric materials with a sufficiently large dielectric constant, two charged identical particles can be localized in one polarization potential well, forming a bipolaron. Although several localized levels can be found in more realistic self-consistent models of this type, the more realistic theories require a high level of knowledge of mathematics. Hence, the proposed model can serve as an introduction to the ideas and concepts of autolocalized states.
DIGITAL NERVE GRAFTING USING THE TERMINAL BRANCH OF POSTERIOR INTEROSSEOUS NERVE: A REPORT OF THREE CASES
Authors: Inoue Shigeru , Ogino Toshihiko , Tsutida Hiroyuki
Published: February 2003

We report three cases of digital nerve grafting using the terminal branch of posterior interosseous nerve.
A RECURRENT CASE OF CARPAL TUNNEL SYNDROME IN HAEMODIALYSIS
Authors: Yamauchi Kenji
Published: February 2003

Herein is described a haemodialysis patient with bilateral carpal tunnel syndrome suffering from recurrence unilaterally after undergoing numerous surgeries of varying methods. On the left side, she received carpal tunnel release via open method in our clinic, and has not suffered from recurrence in eight years. On the right side, she received endoscopic carpal tunnel release twice in seven years, and subsequently underwent open carpal tunnel release in our clinic for recurrence. For carpal tunnel syndrome in haemodialysis patients, we recommend open surgery rather than endoscopic surgery.
MAINTAINING WRIST FUNCTION IN SEVERE RHEUMATOID ARTHRITIS: A CASE STUDY OF REVISION SWANSON WRIST ARTHROPLASTY STAGED VIA A WRIST FUSION IN RHEUMATOID ARTHRITIS
Authors: Mutimer J. N. , Giddins G. E. B.
Published: February 2003

We present a case of revision Swanson wrist arthroplasty staged via a wrist fusion in a patient with rheumatoid arthritis. Due to extensive bone loss in the rheumatoid patient, it may not be possible initially to revise a wrist arthroplasty; however after fusion with a bone graft to regain bone stock we have demonstrated that this is possible. It may even be possible to convert such a fusion to a total wrist arthroplasty.
Human Variation and Lexical Choice
Authors: Reiter Ehud , Sripada Somayajulu
Published: February 2003

Much natural language processing research implicitly assumes that word meanings are fixed in a language community, but in fact there is good evidence that different people probably associate slightly different meanings with words. We summarize some evidence for this claim from the literature and from an ongoing research project, and discuss its implications for natural language generation, especially for lexical choice, that is, choosing appropriate words for a generated text.
Visual Localization Ability Influences Cross-Modal Bias
Authors: Hairston W. D. , Wallace M. T. , Vaughan J. W. , Stein B. E. , Norris J. L. , Schirillo J. A.
Published: February 2003

The ability of a visual signal to influence the localization of an auditory target (i.e., “cross-modal bias”) was examined as a function of the spatial disparity between the two stimuli and their absolute locations in space. Three experimental issues were examined: (a) the effect of a spatially disparate visual stimulus on auditory localization judgments; (b) how the ability to localize visual, auditory, and spatially aligned multi-sensory (visual-auditory) targets is related to cross-modal bias, and (c) the relationship between the magnitude of cross-modal bias and the perception that the two stimuli are spatially “unified” (i.e., originate from the same location). Whereas variability in localization of auditory targets was large and fairly uniform for all tested locations, variability in localizing visual or spatially aligned multisensory targets was much smaller, and increased with increasing distance from the midline. This trend proved to be strongly correlated with biasing effectiveness, for although visual-auditory bias was unexpectedly large in all conditions tested, it decreased progressively (as localization variability increased) with increasing distance from the mid-line. Thus, central visual stimuli had a substantially greater biasing effect on auditory target localization than did more peripheral visual stimuli. It was also apparent that cross-modal bias decreased as the degree of visual-auditory disparity increased. Consequently, the greatest visual-auditory biases were obtained with small disparities at central locations. In all cases, the magnitude of these biases covaried with judgments of spatial unity. The results suggest that functional properties of the visual system play the predominant role in determining these visual-auditory interactions and that cross-modal biases can be substantially greater than previously noted.