bluuebunny/crossref_metadata_2025 huggingface dataset:
cw three-wave mixing in single-mode optical fibers
Authors: Hill K. O. , Johnson D. C. , Kawasaki B. S. , MacDonald R. I.
Published: February 2003

Strong continuous three-wave mixing of 514.5-nm argon laser light in a single-mode fiber is reported. The effect, due to the third-order nonlinearity of silica, has been observed for light whose frequency spectrum consists of either a few discrete monochromatic frequency components separated by ∼1 GHz or a quasicontinuous distribution of frequencies having a spectral envelope ∼4 GHz wide. We show that the effect provides a simple and effective method for measuring the nonlinearity of silica. In the first manifestation of the effect, the nonlinearity mixes the frequency components to produce new frequencies. In the second, multiple mixing occurs that broadens the quasicontinuous spectrum. This manifestation of the effect is large; broadening by a factor of 4 has been observed with lower intensity levels than are required to produce stimulated Brillouin scattering in the same fiber. A theoretical model is presented to describe spectral broadening by three-wave mixing for the case of small broadening. The effect of three-wave mixing on the operation of continuous stimulated Brillouin and Raman oscillators is also discussed. Finally, it is noted that the presence of this effect may constrain the design of long-haul single-mode fiber optical communication trunks.
Full-color photosensitive glass
Authors: Stookey S. Donald , Beall George H. , Pierson Joseph E.
Published: February 2003

New polychromatic (full-color photosensitive) glasses are described in which the full color spectrum is developed by photochemical precipitation of subcolloidal silver too small to scatter light. The brilliant colors are shown to be due to selective light absorption by randomly oriented silver-containing particles having controlled anisotropic shapes. The color photographic process and its chemistry are outlined. Controlled anisotropy is due to photo-silver-nucleated growth of elongated NaF⋅ (Na,Ag) X pyramidal crystallites, concentration of AgX at the apex, and subsequent photoprecipitation of this silver. Resultant colors are primarily a function of exposure flux (intensity × time) employing ultraviolet light (300 nm). The colors can be semiquantitatively described from electromagnetic theory assuming ellipsoidal metal particles suspended in a transparent dielectric medium. An absorption band moves across the visible spectrum as a function of particle eccentricity. Polychromatic glasses can be made having transparency, opacity, or a mixed pattern through photonucleation control of halide crystallite growth, which governs light scattering. Colors may be developed in either clear or opal areas; they can be restricted to the surface of the glass or generated to great depth. The colors appear permanent at ambient temperature and exhibit good thermal stability.
An angular-spectrum approach to contrast in reflection acoustic microscopy
Authors: Atalar Abdullah
Published: February 2003

The scanning acoustic microscope in the reflection mode has proved to be a rather simple and direct means for monitoring the elastic properties of a solid surface. When smooth surfaces of crystalline material are examined in a liquid with a highly convergent sound beam they exhibit a distinct response. This characteristic response, which can be treated as a ’’signature’’, is obtained by recording the output of the microscope as the spacing between the acoustic lens and the object is varied. An angular-spectrum approach is used to derive an expression for this output in terms of the reflectance function. This function has an angular dependence determined by the bulk constants of the material itself. The expression resulting from this treatment can be used to explain the source of contrast in acoustic images.
Small-angle light scattering (SALS) from uniaxially stretched polyvinylidene fluoride
Authors: Das-Gupta D. K. , Shier D. B.
Published: February 2003

Films (mostly of Form 2 crystal structure), 50 μm thick, of polyvinylidene fluoride (PVF2) were uniaxially stretched at 60 °C and then annealed at 120 °C. Small-angle light scattering patterns (SALS) were taken of the samples in the Hv scattering mode (i.e., crossed polarizers). The results show that a four-lobe scattering pattern due to undeformed spherulites changes to an eight-lobe pattern on uniaxial stretching of PVF2 films.
Influence of laser-supported detonation waves on metal drilling with pulsed CO2 lasers
Authors: Stürmer E. , von Allmen M.
Published: February 2003

Drilling of highly reflective metals in an ambient atmosphere with single TEA-CO2-laser pulses of fluences between 300 and 6000 J/cm2 is reported. The drilling process was investigated by measuring the time-resolved laser power reflected specularly from the targets during the interaction and by analyzing the craters produced. Experiments were performed in ambient air, argon, and helium. Target damage was found to be strongly influenced by a laser-supported detonation (LSD) wave in the ambient gas. If the laser fluence exceeded a material-dependent damage threshold (copper: 300 J/cm2), drilling occurred, but the efficiency was inversely related to the duration of the LSD wave. Efficient material removal is possible if the LSD wave can be dissipated within a small fraction of the laser pulse duration. This was achieved by small-F-number focusing of TEM00 laser pulses of 5-μs duration. Replacing the ambient air at the target by a gas of lower density results in a further significant reduction of LSD-wave lifetime, and a correlated increase of the drilling yield. On copper targets a maximum drilling yield of 10−5 cm3/J was observed in ambient helium at a laser fluence of 1 kJ/cm2.
Theory and experiments on rapid melting of metals including alloy effects
Authors: Holsapple K. A. , Schmidt R. M.
Published: February 2003

A theory relating to the response of materials heated rapidly into the melt regime is developed. The theory incorporates features that distinguish pure materials from nonpure materials such as metal alloys. This distinction is based on the observed difference between the liquidus and the solidus temperature at a given pressure. This difference leads to significant terms in the resulting theory that are unique to nonpure materials. Experiments are described that give a direct means of evaluating the theory. Results are given for two aluminum alloys, 1100 and 2024. Limited experimental evidence suggests that significant nonequilibrium effects may distinguish the response of alloys from that of pure materials.
The attenuation of elastic waves by surface inhomogeneities: Rayleigh waves
Authors: Narita Masa-aki , Sakuma Tetsuro , Nakayama Tsuneyoshi
Published: February 2003

We present a theoretical study of the attenuation of Rayleigh waves as a consequence of their interaction with surface inhomogeneities. The frequency and correlation-length dependence of the attenuation rate is calculated explicitly based on a Gaussian-distributed fluctuation for the mass density and for the Lamé coefficients in terms of the Green’s function method. All the surface modes of elastic waves are considered in the attenuation processes.
Optical-absorption intensities of trivalent neodymium in the uniaxial crystal yttrium orthovanadate
Authors: Lomheim T. S. , DeShazer L. G.
Published: February 2003

The Judd-Ofelt (JO) theory was applied to optical-absorption transitions in Nd+3 : YVO4 to obtain intensity parameters (Ω2=5.88×10−20 cm2; Ω4=4.08×10−20 cm2; Ω6=5.11×10−20 cm2) and the radiative lifetime (152 μs) and quantum efficiency (0.72) of the 4F3/2 state. The variations of the absorptions with respect to the optic axis measured for Nd+3 in a uniaxial crystal were taken into account in applying the JO theory. In addition, transition-matrix elements using new intermediate-coupling coefficients were obtained and used in the JO fitting procedure.
An aggregate organic photoconductor. I. Chemical composition, preparation, physical structure, and optical properties.
Authors: Dulmage W. J. , Light W. A. , Marino S. J. , Salzberg C. D. , Smith D. L. , Staudenmayer W. J.
Published: February 2003

An aggregate photoconductive film with a broad spectral sensitivity which is useful for electrophotographic applications is described. It consists of an aryl-substituted thiapyrylium salt (dye) and a dialkylamino-substituted triphenylmethane (sensitizer-carrier–transport component, ST) disperesed in poly(4,4′-isopropylidenediphenyl carbonate). A crystalline complex of the polymer and the dye forms an aggregate as a separate phase. Its formation is accompanied by a red shift in the absorption spectrum and a greatly enhanced photoconductive response which is augmented by the ST component. The aggregate has been simulated by a 2 : 1 complex of dye and 4,4′-isopropylidenediphenyl-bis-phenyl carbonate, a two-unit model of the polymer. Single crystals of the model complex were grown and its structure was determined from x-ray-diffraction data. In the monoclinic (P21/a) crystals, the approximately planar dye cations are arranged 3.44 Å apart in stacks along a and the stacks are arranged in (010) sheets. The carbonate molecules are extended head to tail in chains along a so that substitution of isopropylidene groups for the end hydrogen atoms would result in a polymer. The chains also form (010) sheets and the structure consists of alternating dye and carbonate layers along b. There is no evidence of any bonding interactions between or within the sheets. The model complex crystals are good photoconductors. The optical behavior of the aggregate can be explained as a symmetry-allowed crystal transition derived from the lowest molecular singlet state of the dye. The photoconductive behavior of aggregate films is described in detail in the accompanying paper, hereafter referred to as Paper II.
Intensity and line-shape measurements in inelastic electron tunneling spectroscopy
Authors: Magno R. , Adler J. G.
Published: February 2003

Two techniques for removing the background in inelastic electron tunneling spectroscopy (IETS) have been examined in detail. The first of these uses a polynomial least-squares routine to fit a smooth curve to the data on either side of the IETS peak, while the second relies on differential inelastic electron tunneling spectroscopy (DIETS) to subtract one spectrum from another in order to remove some unwanted IETS peaks. Both procedures were applied to spectra obtained from Al-Pb junctions with the lead normal and superconducting. One finds that it is easier to determine the background when the normal rather than superconducting lead is used, as the superconducting line shape has a broad undershoot. The intensity results shown here indicate that failure to consider the undershoot may result in errors as large as 30%. A comparison of theoretical and experimental line shapes is made for data with both normal and superconducting electrodes.
Sensitivity of MOS structures for contamination with H+, Na+, and K+ ions
Authors: Tangena A. G. , de Rooij N. F. , Middelhoek J.
Published: February 2003

Results of contamination experiments on MOS structures with aqueous solutions of NaCl, KCl, acetic acid, and purified water are presented. A special grid-shaped electrode (Al or polycrystalline Si) was developed for these experiments. Various after-treatments were applied. At temperatures of 250 and 350 °C, the I-V curve shows two distinct peaks caused by ion transport in the oxide. Contamination with H+ and Na+ ions had a pronounced influence on the area of both peaks. The results showed that it is impossible to attribute the first peak to transport of Na+ ions only and the second to that of K+ ions. It is concluded that the first peak results from ion transport under conditions of thermodynamic equilibrium and that the second peak is controlled by the rate with which ions are released from traps at the interfaces. Models for both transport mechanisms are presented.
Influence of deposition conditions on sputter-deposited amorphous silicon
Authors: Pawlewicz W. T.
Published: February 2003

The electrical, optical, and photoelectronic properties of sputter-deposited amorphous silicon films have been systematically related to deposition parameters for the case of pure Ar sputtering gas in an rf diode system. Variation of the sputtering gas pressure from 25 to 150 mTorr controllably and reproducibly increases the film resistivity 3 to 4 orders of magnitude and significantly decreases optical absorption for photon energies ≲1.6 eV. Similar film property improvements can be realized through the use of large substrate-target spacings (∼10 cm) and substrate temperatures ≲500 °C. The film properties, however, are independent of deposition rate between 0.5 and 5 Å sec−1. The influence of gas pressure and substrate-target spacing has been linked to Ar bombardment of the growing film, which appears responsible for both high dangling-bond densities and incorporated gas. The influence of substrate temperature could result from annealing of collision-induced defects as the film grows, or from a decrease in the density of microvoids as reported by Paul et al. for amorphous germanium. The use of deposition conditions which minimize plasma interaction and maximize thermal reorganization results in remarkably good electrical and optical properties for nonhydrogenated amorphous silicon. Using the approach of Lewis et al. the addition of H2 to the Ar sputtering gas produces film properties which are further improved and quite similar to those observed for films prepared by plasma-assisted decomposition of silane.
Reorientation kinetics of the magnetization in a glassy ferromagnet
Authors: Hasegawa Ryusuke
Published: February 2003

The kinetics of reorientation of the magnetization have been studied for a noncrystalline Fe40Ni38Mo4B18 alloy which exhibits high magnetic permeability and low ac core loss at high frequencies (∼500 kHz). It is reported that the activation energy for the reorientation kinetics is about 2 eV, indicating that the alloy is thermomagnetically stable.
Low-coercivity amorphous magnetic alloy films
Authors: Heiman Neil , Hempstead R. D. , Kazama N.
Published: February 2003

It is well known that rapidly quenched bulk samples of amorphous transition-metal–metalloid alloys can be made with high permeability and low coercivity; however, little is known of the magnetic properties of these alloys when prepared by thin-film-deposition techniques. Sputter-deposited films of iron-carbon, iron-silicon-boron, iron-chromium-phosphorus-carbon, cobalt-iron-boron, and cobalt-iron-chromium-phosphorus-boron have been prepared, and it is shown that these films can be made with low coercivity and high saturation magnetization by proper choice of deposition conditions. The magnetic properties of iron-carbon films were found to depend on the sputtering conditions, in particular on the argon-gas pressure. At an argon-gas pressure of 15 μm, films with 70 at.% iron and 30 at.% carbon were obtained with a 4πMs of 12 000 G and coercivities in the range 0.1–0.9 Oe. Films made with higher and lower argon-gas pressure had significantly higher coercivity. Other alloys were prepared to explore corrosion and magnetostriction behavior. Films which were extremely corrosion resistant were deposited from a target of 74 at.% iron, 6 at.% chromium, 13 at.% phosphorus, and 7 at.% carbon. Amorphous films of iron-silicon-boron made in an attempt to find small and/or negative λs possessed large positive λs. Films of CoFe-B were found to have λs?0 and generally excellent magnetic properties. Adding Cr and P to the CoFe-B target did not significantly improve the corrosion resistance of the films.
Picosecond-laser-pulse-duration measurements with a low-light-level electro-optic two-photon fluorescence technique
Authors: Taboada J. , Venable D. D.
Published: February 2003

By combining a self-scanned photodiode array and image intensification, a two-photon fluorescent (TPF) pattern has been recorded on-line for single mode-locked Nd-glass laser pulses. Ultrashort-pulse-duration measurements from the TPF readout were obtained on pulse energies as low as 200 μJ. At these low intensities, the TPF peak-to-background ratio was observed to be close to the ideal value of 3 within experimental error for early pulses in the train. Significant reduction from the ideal peak-to-background ratio was observed for pulses approaching 1 mJ.
Redefinition of the coupling coefficient for surface-acoustic-wave interdigital transducer
Authors: Ristic V. M. , Zuliani M. J. J.
Published: February 2003

The electromechanical coupling coefficient for the surface-acoustic-wave interdigital transducer is defined as the maximum fractional change in the time-averaged energy associated with a particular mode passing from one periodic section to the next. The result is compared with Berlincourt’s expression.
New coupled-waveguide optical modulators with Schottky contacts
Authors: Tada Kunio , Yanagawa Hisaharu
Published: February 2003

Coupled-waveguide optical modulators with Schottky contacts are proposed in two waveguide configurations, namely, in the embedded-waveguide configuration and in the rib-waveguide configuration. It is shown that the heterostructured embedded-waveguide device is suitable for efficient modulation and that the homostructured rib-waveguide device has fairly small modulating power per bandwidth P/Δf in spite of its simpler structure. GaAs homostructured rib-waveguide devices were fabricated, and optical modulation was carried out at a light wavelength of 1.06 μm.
The effect of Mn/Ti surface treatment on voltage-holdoff performance of alumina insulators in vaccum
Authors: Miller H. Craig , Furno Edward J.
Published: February 2003

The treatment of the surface of an alumina insulator with a Mn/Ti coating significantly increases its voltage-holdoff capability. Insulators treated with this coating had vacuum-holdoff voltages about 25% higher than did untreated insulators. During processing (quasimetallizing) the coating penetrates into the alumina, so it is fairly insensitive to damage by abrasion or electrical breakdown. The quasimetallized coatings is also comparable with subsequent metallizing and brazing of the alumina insulator. We conclude that the coating (1) decreases the surface resistivity of the insulator, (2) decreases the insulator’s secondary-electron-emission yield, and (3) makes the surface of the insulator dielectrically more uniform.
Transport phenomena in MHD generators: Effect of boundary layers
Authors: Gupta B. K. , Sharma R. P.
Published: February 2003

An investigation of the effect of velocity/temperature boundary layers on the conductivity and the power output of an MHD generator has been presented in this paper; the analysis is based on the Boltzmann transfer equation. It is seen that the conductivity and the mean power output per unit volume of an MHD generator becomes considerably reduced because of the presence of the velocity and temperature boundary layers. The power output is found to decrease sharply with boundary-layer thickness for low values of the thickness and levels off at larger thicknesses.
Spectral properties of physical processes of Markov-correlated events. I. Theory
Authors: Mazzetti P. , Oldano C.
Published: February 2003

The problem of finding the power spectrum of a physical process consisting of linear superimposed random events is solved under the general condition of events correlated in a Markov chain. The statistical properties of the system are described in terms of a generalized Markov matrix which contains all the information about the correlations existing between elementary events. The conditions for the existence of a line spectrum component are discussed and the line intensity calculated. In paper II, typical examples of application to practical problems are also given.
Spectral properties of physical processes of Markov-correlated events. II. Applications
Authors: Mazzetti P. , Oldano C.
Published: February 2003

The application of the theory developed in paper I to problems of physical interest is considered and developed up to the point of finding the correlation matrix of the problem, thus reducing the complete solution to a matter of numerical computation. The considered cases are of rather large generality and refer to (a) fluctuation processes due to carrier trapping, (b) membrane noise, (c) spectral properties of linear atom chains, and (d) fluctuations in quantum systems whose Hamitonian contains an operator which is a random function of time. In the last case, the most general conditions under which the time evolution of a quantum system can be treated as a Markov process will be found and discussed.
Diamond: An efficient source of soft x rays for high-resolution x-ray lithography
Authors: Nelson David A. , Ruoff Arthur L.
Published: February 2003

An axisymmetric distribution of electrons incident on a carbon target causes heating of the target. The thermal conductivity of the various carbon polymorphs varies rapidly with temperature. We have solved the nonlinear steady-state heat-flow problem. We show that type IIb diamond would be an ideal source for carbon K radiation and that such a static target will sustain a power input of 6.5 kW on an area whose diameter is 1 mm and might, with proper design, operate at an even higher power input on the same area. We show that a power input of 6.5 kW at 6.0 kV on the above area would produce carbon K radiation of sufficient intensity so that the exposure time for PMMA (polymethylmethacrylate, an x-ray resist of extremely high resolution but relatively low sensitivity) is only 1 min for a source-to-substrate distance of 2.54 cm.
KrF(B) quenching by He, Ne, Xe, and NF3
Authors: Eden J. G. , Waynant R. W. , Searles S. K. , Burnham R.
Published: February 2003

Flash photolysis of KrF2 at 193 nm has been utilized to directly measure the quenching rate constants of KrF(B) molecules by He, Ne, Xe, and NF3. Investigation of the large rate constant measured for the KrF(B)+Xe reaction (≳10−9 cm3 sec−1) verified the XeF(B) state to be a product.
Centroid location of implanted ions in the SiO2 layer of MOS structures using the photo I-V technique)
Authors: DiMaria D. J. , Young D. R. , DeKeersmaecker R. F. , Hunter W. R. , Serrano C. M.
Published: February 2003

The centroids for distributions of various ions important in Si technology (Al, P, and As) implanted at energies from 5 to 100 keV and a fluence of 1×1013 cm−2 into 1300–1400-Å-thick SiO2 layers of metal-silicon dioxide-silicon (MOS) structures have been located by using measurements of the photocurrent as a function of the gate voltae which is called the photo I-V technique. This technique senses trapped electrons on sites related to the implanted ions after charging by avalanche injection. A high-temperature (1000 °C in N2 for 30 min) premetallization anneal was used in order to minimize trapping on atomic displacement damage sites which could give a different centroid than that of the ion distribution. Good agreement of the trapped electron centroid deduced from the photo I-V technique with calculations of the ion centroid based on the theory of Lindhard, Scharff, and Schio/tt (LSS) and with independent experimental determinations of the ion centroid from profiles using secondary ion mass spectroscopy (SIMS) or He+ ion backscattering was found in most cases. The photo I-V technique is shown to have distinct advantages over most techniques which directly measure the ion distribution or centroid like SIMS and He+ ion backscattering because of its nondestructive nature, minimally perturbing effect, and extremely low detectability limit of 1011 charges/cm2 or less. The empirical relationship observed by Chu, Crowder, Mayer, and Ziegler for ion implantation into various amorphous insulators between the LSS normalized centroid ρ and the LSS normalized energy ε of ρ=2.7ε has been shown for the first time to be valid for ε?0.4.
The stress field of a dislocation lying in a plate
Authors: Nabarro F. R. N. , Kostlan E. J.
Published: February 2003

The stress field of an edge dislocation lying in the midplane of an isotropic plate of thickness 2a with free surfaces is calculated. The Burgers vector b lies in the plane of the plate. The field is calculated as the sum of two terms: the stresses of the dislocation in an infinite medium together with an array of images which annul the tangential tractions, and the stresses which annul the normal tractions and are derived from a stress function given by a convergent Fourier integral. The long-range bending of the beam depends only on the integral and agrees with Eshelby’s result. The energy of interaction with a similar dislocation at a distance Xa can be expressed by a Fourier integral alone. If this integral is evaluated by the method of residues, the asymptotic form for large X is given by the poles of the integrand with the smallest positive real parts. These do not lie on the imaginary axis; the asymptotic form, therefore, shows damped oscillations ∼3.0075bD sin(1.3843X+0.1175) exp(−3.7488X). The first minimum occurs at X?2.4.
Edge-dislocation displacements in an elastic strip
Authors: Moss William C. , Hoover William G.
Published: February 2003

A Fourier-transform method is used to obtain the displacement field for an edge dislocation. The method reproduces known results and produces new solutions that can be compared with those from atomistic models of edge dislocations.
Mechanism of low-temperature radiation hardening in alkali halides. I. Single halogen interstitials as the hardening agent at low temperature
Authors: Tanimura K. , Fujiwara M. , Okada T. , Hagihara T.
Published: February 2003

The property of single halogen interstitials as the hardening agent has been studied through experiments using KBr doped with alkali impurity. Thermal recovery of the radiation-induced increment of the flow stress Δτ, and the thermal annealing of color centers in KBr : Na and KBr : Li are measured by means of an isochronal pulse-annealing technique. Single-intersititial-type centers, HA and IA centers, decay at nearly the same temperature around 100 K in KBr : Na and around 210 K in KBr : Li, which is accompanied by the decrease of a considerable amount of Δτ in both samples. The effects of optical illumination at 77 K on the thermal recovery of Δτ and on the concentration of color centers are also examined to prove the responsibilities of the HA and IA centers for the hardening effect. It is shown that the IA center is more resistant to dislocation movements than the HA center.
Mechanism of low-temperature radiation hardening in alkali halides. II. Thermal-activation mechanism of the interaction between dislocations and halogen interstitials in KBr
Authors: Tanimura K. , Fujiwara M. , Hagihara T. , Okada T.
Published: February 2003

Interaction between dislocations and radiation-induced halogen interstitials in KBr doped with alkali impurities has been studied in terms of the thermal-activation mechanism of dislocation dynamics. Measurements are made on radiation-induced changes and their thermal recovery of activation volume and flow stress. Temperature dependence of flow stress and activation volume in KBr : Li crystals is also examined at temperatures from 4.2 to 80 K. It is shown that the IA center acts as the short-range obstacle, whereas higher-aggregate interstitials act as the long-range one for moving dislocations. The maximum force and the total activation enthalpy in the interaction betweeen dislocations and IA(Li+) centers are evaluated to be 1.6×10−4 dyn and 0.35 eV, respectively.
Mechanism of low-temperature radiation hardening in alkali halides. III. The elastic interaction of single halogen interstitials with dislocations
Authors: Tanimura K. , Hagihara T. , Fujiwara M. , Okada T.
Published: February 2003

The interaction of single halogen interstitials and dislocations has been studied in terms of their elastic interaction. The linear-elastic calculation is made to show that the maximum force in the I-center–dislocation interaction is greater than that in the case of the H center. This result is shown to be relevant for the elastic interaction of the HA and IA centers with dislocations. We reveal the relation between the maximum interaction force and the magnitude of strain around a defect, and conclude that the greater hardening effect of the interstitial ion than the atom originates from the stronger elastic-interaction force caused by the larger strain around the ion. The hardening effect of the interstitial ion is compared with that of the VK center.
Compression mechanisms in α-quartz structures—SiO2 and GeO2
Authors: Jorgensen J. D.
Published: February 2003

Interatomic distances and angles have been measured at pressures to about 25 kbars for the α-quartz forms of SiO2 and GeO2 using time-of-flight powder neutron diffraction. The data show that the compression of SiO2 results solely from a cooperative rotation or tilting of the SiO4 tetrahedra around their shared oxygen corners, with individual tetrahedra remaining relatively rigid. Conversely, the compression of GeO2 results almost solely from distortions of the individual tetrahedra resulting from changes in O-Ge-O angles with cooperative rotations contributing a negligible amount.
Search for soft phonon modes in Zr2Ni
Authors: Kamitakahara W. A. , Khatamian D. , Smith J. F.
Published: February 2003

Inelastic neutron-scattering measurements have been made on a [ζ00] transverse acoustic phonon branch of Zr2Ni at several temperatures between 300 and 10 K. The experiment was motivated by previous ultrasonic results which showed a large softening of the related elastic constant C66. No phonon softening was observed in our experiment, but a fairly unusual dispersion was noted.
Fabrication of KNdP4O12 laser epitaxial waveguide
Authors: Miyazawa Shintaro , Kubodera Ken’ichi
Published: February 2003

From a novel solution composed of H3PO4, Nd2O3, and K2CO3, KNdP4O12 laser crystals were grown, and the KNdP4O12 laser waveguide was successfully fabricated on a KLaP4O12 substrate by liquid-phase epitaxy using the solution. A laser oscillation at 1.05 μm was obtained with an Ar laser coaxial pumping at room temperature. The crystal growth and epitaxy processes are mainly described.
Measurements of photoinduced transformations in amorphous As2S3 films by optical waveguiding
Authors: Tanaka Keiji , Ohtsuka Yoshihiro
Published: February 2003

Photoinduced changes in refractive index and thickness in evaporated As2S3 films have been measured by means of a prism-coupling technique. The irreversible and reversible structural transformations are associated with increases in the refractive index of 0.133 and 0.029, respectively, at a wavelength of 633 nm. Additionally, a dynamical change in refractive index by 0.003 appears under the band-gap illumination of about 10 mW/cm2. The origin of this change is attributable to a result from photoelectronic excitation. In the irreversible process, the films expand first and subsequently contract as the refractive index increases monotonically, whereas any change in thickness was not detected within an experimental error of ±10 Å for the reversible process.
A new resonant ellipsometric technique for characterizing the interface between GaAs and its plasma-grown oxide
Authors: Theeten J. B. , Aspnes D. E. , Chang R. P. H.
Published: February 2003

At certain wavelengths, depending on the thickness of a thin transparent dielectric layer on an absorbing substrate, a standing-wave condition can be produced that efficiently couples the S wave to the substrate, simulating a cavity resonance in the dielectric and maximizing the complex reflectance ratio. Under these conditions high sensitivity is obtained to the nature of the interface between the dielectric and the substrate. We illustrate the method by applying it to plasma-oxidized GaAs samples using scanning ellipsometry from 1.5 to 5.6 eV. As-grown samples exhibit a composite transition layer at the interface consisting of a mixture of oxide, unoxidized GaAs, and elemental As. A crystalline As layer is formed at the interface by annealing in N2 at 550 °C.
Minority-carrier lifetimes and internal quantum efficiency of surface-free GaAs
Authors: Nelson R. J. , Sobers R. G.
Published: February 2003

Minority-carrier lifetimes, internal quantum efficiencies, and values of the radiative recombination coefficient B are determined from photoluminescence time-decay and external quantum efficiency data taken for LPE GaAs samples (germanium doped or undoped) in the doping range 1.9×1015?p0 ?1×1019 cm−3 at 300 °K. Measurements are made on isotype double heterostructure samples where the optically exicted GaAs layer is bounded by wider-band-gap Ga0.5Al0.5As layers which provide for confinement of minority carriers and also minimize the importance of surface or interfacial recombination on the measured lifetimes. Comparison with time-decay data for samples without the ternary cladding layers shows the dominant effect of surface and substrate recombination on the decay time if confinement layers are not provided. Luminescence decay times are observed from 1.2 nsec for heavily doped samples up to 1.3 μsec for lightly doped samples. Values of the bulk minority-carrier lifetimes, radiative lifetimes, and internal quantum efficiencies are determined. The experimental values for B agree well with existing theory for heavily doped material. For lightly doped material, the experimental B coefficient is larger than expected from the single-electron model.
Photoacoustic determination of the optical absorptance of highly transparent solids
Authors: McDavid J. M. , Lee K. L. , Yee S. S. , Afromowitz M. A.
Published: February 2003

A photoacoustic method has been applied to the quantitative measurement of optical absorption at 10.6 μm in coated and uncoated alkali halide samples having a spatially varying optical absorption. Photoacoustic signals were measured as a function of the chopping frequency of a CO2 laser source. The dependence of the signals on chopping frequency and an absolute electrical calibration of the cell were used to interpret the data. The results are in good agreement with laser calorimetry or infrared transmission measurements on the same samples. Signal fluctuations identified with thermal and source-coherence effects are reported and discussed. The experiments reported here confirm the utility of the photoacoustic technique in the general investigation of optical properties of highly transparent materials.
Relaxation of neodymium in a weakly ionized expanding plasma
Authors: Chen Hao-Lin , Bedford Ray , Borzileri C. , Brunner W. , Hayes M.
Published: February 2003

The laser resonance absorption technique has been used to determine the relaxation rate of electronically excited neodymium vapor during its expansion into vacuum. Significant increases of population into ground and 1128-cm−1 levels were found. Analysis shows that interaction between excited metastable atoms and electrons are much more important for relaxation than atom-atom collisions. The final population of neodymium appears to be frozen at a temperature lower than the surface temperature of melt.
On the displacement fields for double forces in an ellipsoid
Authors: Howard C. J.
Published: February 2003

Townsend has considered the problem of double-force defects distributed uniformly throughout elastically isotropic spheres and has achieved separation of the image displacements from those displacements which would occur in an infinite medium. Here it is shown how a similar separation of the total displacement into the two contributions can be achieved for the case of elastically isotropic ellipsoids containing double-force defects. Townsend’s result is derived as a special case.
Mobility anisotropy determination by the photoelectromagnetic effect: Application to HgI2
Authors: Adduci F. , Baldassarre L. , Minafra A.
Published: February 2003

Combined measurements of the photoelectromagnetic effect and photoconductivity in three different geometries can be used to determine the anisotropy factors (μn∥/μn⊥, μp∥/μp∥) and the mobility ratios (μn∥/μp∥, μn⊥/μp⊥) in anisotropic semiconductors. In the present work this method has been applied to mercuric iodide; previous data on electron mobilities are confirmed, whereas the hole mobility is nearly isotropic.
Photoluminescence of thermally treated n-type Si-doped GaAs
Authors: Lum W. Y. , Wieder H. H.
Published: February 2003

Photoluminescence measurements on Si-doped GaAs single crystals heat treated in vacuum at 400≲T≲800 °C reveal emission peaks at 1.363, 1.409, and 1.487 eV, which correspond to three acceptor levels introduced through the activation of vacancies and the site transfer of Si atoms during the annealing process.
On the exothermic model for the thermoluminescence response
Authors: Nakajima Toshiyuki
Published: February 2003

This study was carried out to obtain some information on the adequacy of the assumptions in an exothermic model, which was proposed for explaining the experimental observation of the sensitivity of the thermoluminescence dosimeter. It is expected from the model that the sensitivity is presented as both increasing and decreasing functions of irradiation temperature. This expected phenomenon was experimentally verified. Further, supralinearity and sublinearity of the thermoluminescence response to the dose could be qualitatively explained with the model. These results lead to the conclusion that the assumptions in the exothermic model are supported.
Transition in amorphous selenium under high pressure
Authors: Gupta Mool C. , Ruoff Arthur L.
Published: February 2003

The phase transition in amorphous selenium under high pressure was studied. The high pressures were generated using a diamond-indentor technique. From the behavior of electrical resistance of amorphous selenium under high pressure, it was found that amorphous selenium at room temperature starts transforming to a crystalline phase when the pressure is near 97 kbar. The effect of temperature on the electronic transition in amorphous selenium under high pressure was also studied. Amorphous selenium was heated to approximately 80 °C; when under a pressure of 26 kbar, it transformed to a conducting phase. The conducting phase was retained for hours at 26 kbar after the temperature was lowered to room temperature.
Viscosity and thermal expansion of lithium aluminosilicate glasses
Authors: Shelby J. E.
Published: February 2003

Viscosity and thermal expansion have been measured for 12 series of lithium aluminosilicate glasses. The compositional dependency of the viscosity, glass-transformation temperature, dilatometric-softening temperature, and refractive index all exhibit an abrupt change in slope at an aluminum-to-lithium ratio between 1.05 and 1.10. The thermal-expansion coefficients of these glasses were found to depend only on the lithium oxide content, i.e., to be independent of the aluminum-to-silicon ratio. These results suggest that the traditional structural model for these glasses must be modified slightly. A new model is proposed which allows some aluminum to act as a modifier in all alkali aluminosilicate glasses.
Thermal conductivity and specific heat of NdP5O14
Authors: Chinn S. R. , Zwicker W. K.
Published: February 2003

Using a dynamic electrical-heating technique, we have measured the thermal conductivity and specific heat of NdP5O14, a high-Nd-concentration laser material. The measured values of the thermal-conductivity tensor elements (in W/cm K) are Λa=2.10×10−2, Λb=9.66×10−3, and Λc=1.40×10−2. The specific heat is 0.141 cal/g K, in excellent agreement with the value of 0.139 cal/g K that we measured by differential scanning calorimetry.
Investigation of ion-beam-sputtered Nb-Ti thin films by complementary use of backscattering and nuclear-reaction microanalysis
Authors: Bouchier Daniel , Gautherin Guy , Agius Bernard , Rigo Serge
Published: February 2003

The composition of superconducting Nb-Ti films deposited by ion-beam sputtering has been studied. Both MeV 4He backscattering and direct observation of nuclear reactions on nitrogen and oxygen were used to determine the composition of the deposits. The films appear to have a uniform composition with depth. The stoichiometry of the Nb-Ti alloy is independent of beam intensity and is equal to that of the target. The oxygen and nitrogen content decrease with the background pressure inside the sputtering chamber and with deposition rate; oxygen contents as low as 0.6 at.% have been obtained. Irrespective of deposition conditions, the argon inclusion was very low. The various mechanisms of incorporation of argon and of the reactive species into ion-beam-sputtered films are discussed taking these results into account.
Liquid-phase electroepitaxy: Growth kinetics
Authors: Jastrzebski L. , Lagowski J. , Gatos H. C. , Witt A. F.
Published: February 2003

On the basis of mass-transport principles, a theoretical model of electroepitaxial growth—current-controlled liquid-phase epitaxy—was developed which defines the contribution of the Peltier effect (at the solid-solution interface) and that of solute electromigration to the overall growth process. According to the model, the contribution of electromigration to growth is dominant in the absence of convection in the solution, whereas the contribution of the Peltier effect can be dominant in the presence of convection. On the basis of the model, expressions were derived which relate quantitatively the growth velocity to growth parameters. The model was found to be in excellent agreement with extensive experimental data on the electroepitaxial growth of GaAs from a Ga-As solution.
Bulk-wave generation due to the nonlinear interaction of surface acoustic waves
Authors: Nakagawa Yasuhiko , Dobashi Tadahiko , Saigusa Yoshihiko
Published: February 2003

The generation of a bulk wave due to the nonlinear interaction of surface acoustic waves transmitted in opposite directions is analyzed. We prepared a ZnO thin-film transducer in the rear side of a 131° Y-X LiNbO3 delay line and succeeded in detecting the bulk wave directly. A good agreement was obtained between theory and experiment with respect to the efficiency of generation.
Deep-level capacitance spectroscopy of nitrogen-doped VPE GaP
Authors: Tell B. , Kuijpers F. P. J.
Published: February 2003

The technique of deep-level capacitance spectroscopy was applied to a number of nitrogen-doped level VPE GaP samples. The thermal emission energies and electron and hole capture cross sections were determined for a dozen deep levels. Using these cross sections along with the measured defect concentrations, high excitation density and low-excitation-density minority-carrier lifetimes are calculated. These calculated values are at least one order of magnitude large than lifetimes determined from optical and SEM techniques. cross sections were determined for a dozen deep levels. Using these cross sections along with the measured defect concentrations, high excitation density, and low-excitation-density minority-carrier lifetimes are calculated. These calculated values are at least one order of magnitude larger than lifetimes determined from optical and SEM techniques.
The effect of electric current on the conductivity of MgO single crystals at temperatures above 1300 K
Authors: Sonder E. , Kelton K. F. , Pigg J. C. , Weeks R. A.
Published: February 2003

Changes in electrical conductivity over the temperature range 1000–1400 K due to treatment of MgO crystals with moderate (1000 V cm−1) electric fields at 1300 or 1400 K have been measured. Although different samples of MgO have different initial conductivities, changes produced by the electric fields are qualitatively similar. After treatments for times of the order to 20 h, the temperature dependence changes and the conductivity decreases by anywhere from a small amount to a factor of 4 at ∼1273 K. This decrease correlates with the electrolytic reduction of impurities in the MgO. More lengthy treatment (more than 100 h) causes the samples to become progressively more conducting until catastrophic failure of the electrical insulating properties occurs. The electric current passed as such failure is approached is more than two orders of magnitude greater than at the beginning of treatment. If the temperature is lowered just before failure with the 1000 V cm−1 still applied and the temperature dependence of the conductivity is subsequently measured, a large excess conductivity is present. However, the temperature dependence (slope of lnσ versus T−1) remains unchanged. The results are discussed in terms of identity of current carriers and conduction mechanisms.
Merocyanine organic solar cells
Authors: Ghosh Amal K. , Feng Tom
Published: February 2003

Recently, we reported on the development of a new thin-film organic solar cell with an AM1 sunlight efficiency of about 0.7% for large area devices (∼1 cm2). This relatively high-efficiency MIS-Schottky barrier-type cell was based on merocyanine type photosensitizing dyes. In this paper we present additional experimental results and develop a comprehensive theoretical model to explain the observed photovoltaic properties. The model incorporates the generation, transport, and surface dissociation of excitons and field-dependent quantum efficiency. The low fill factor of 0.3 was attributed mainly to the field dependence of quantum efficiency. An exciton diffusion length of 60 Å was determined by analyzing the short-circuit photocurrent action spectra using the theoretical model developed. The diffusion potentials for metal/merocyanine Schottky barrier cells for six different metals were determined by C-V measurements; the diffusion potential increases with decreasing work function. As solar cells, these devices have higher efficiencies when there is a very thin interfacial oxide layer between the barrier forming metal and merocyanine.
Role of oxygen in the mechanism of formation of Schottky diodes
Authors: Ponpon J. P. , Siffert P.
Published: February 2003

The formation of the potential barrier at the metal-silicon contact has been investigated. Special emphasis has been given to the study of aging of gold–n-type-silicon Schottky diodes. The behavior of the electrical properties as a function of time of exposure to air has been studied, showing that the increase of the barrier height, from 0.5–0.6 eV up to the typical 0.8-eV value is related to the diffusion of oxygen (or water vapor) from the ambient through the metal contact and its accumulation at the interface. In addition, preliminary results on p-type silicon are reported. A phenomenological model based on the behavior of oxygen with respect to the metal involved is proposed to describe the aging for any metal deposited on n- or p-type silicon.
Superconducting properties of evaporated copper molybdenum sulfide films
Authors: Woollam John A. , Alterovitz Samuel A. , Chi K. C. , Dillon R. O. , Bunshah R. F.
Published: February 2003

Films of copper molybdenum sulfide were produced by coevaporation. Those that were superconducting contained only the ternary compound and free molybdenum. The range of copper content in the ternary compound was as large as that in polycrystalline material, that is, it includes either phase alone, or a mixture of the two phases of this material. This is in contrast with sputtered materials where copper concentration has been limited to a narrower range. The upper critical field and the critical current were measured as functions of external magnetic field, and found to be similar to those of sputtered copper molybdenum sulfide, when the comparison was made for samples having the same amount of copper.