bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrohydrodynamic instabilities in nematic liquid-crystal layers aligned by polymeric sheets
Authors: Bortolotti A. , Buttino G. , Zini G.
Published: February 2003

This paper reports that a polymeric sheet can be used as orienting substrate for obtaining regular electrohydrodynamic instabilities in liquid nematic layers. The experimental results, obtained from the Williams domain mode instability, fit well the results of Meyerhofer’s theory, provided appropriate values of the critical frequency are used. The dependence of critical frequency on the type of substrate has not yet been explained.
Comment on ’’Cathodoluminescence studies of anomalous ion implantation defect introduction in ZnTe’’
Authors: Pautrat J. L. , Pfister J. C. , Ligeon E.
Published: February 2003

The long-range migration of lattice defects in ion-implanted ZnTe crystals has been previously discovered and analyzed. From these studies it can be inferred that zinc interstitial is the migrating species.
Reply to ’’Comment on ’Cathodoluminescence studies of anomalous ion implantation defect introduction in ZnTe’ ’’
Authors: Norris C. B.
Published: February 2003

In the light of very recent data, our previous study gives strong evidence that the dominant postrange defects in ion-implanted ZnTe are not zinc interstitials (Zni). The prior Grenoble work is discussed with respect to current knowledge concerning shallow acceptors in ZnTe and the insensitivity of radiotracer measurements to vacancy introduction. It is concluded that the Grenoble results do not conflict with ours in that they provide no direct evidence that Zni dominate the postrange damage in ZnTe.
Selenium implantation in indium phosphide
Authors: Inada Taroh , Taka Shin-ichi , Yamamoto Yasuhiro
Published: February 2003

Selenium implantation has been studied as a means of fabricating n-type layers in Fe-doped, semi-insulating indium phosphide. Channeling measurements using 1.5-MeV He ions have shown that amorphous layers (about 0.1 μm thick) are created by Se implantation at room temperature and these layers recrystallize after annealing at above 700 °C. Differential Hall-effect and sheet-resistivity measurements have revealed that very shallow (<0.1 μm) and highly doped (nmax = ∼2×1019 /cm3) n+ layers can be formed by implantation with 100-keV ions at room temperature and by subsequent annealing at 700 °C. Profile measurements have also indicated that Se ions implanted into elevated temperature InP tend to diffuse in the crystal during the implantation.
Evidence for Cu-related deep states in GaAs, earlier ascribed to Ni
Authors: Kumar V. , Ledebo L-Å.
Published: February 2003

Published data for the energy positions of Ni-related levels in the band gap of GaAs exhibit serious discrepancies. We have studied the properties of Ni-doped GaAs, the Ni being introduced by diffusion or liquid phase epitaxy. These techniques have been used successfully earlier to dope GaAs with Cu or Fe. When Ni is introduced during LPE, no related level is detected. When diffused, the only deep level found has properties identical to those of Cu in GaAs. It is therefore suggested that the level at Ev +0.4 eV in GaAs frequently reported as Ni-related is not due to Ni but to Cu.
Reply to ’’Comment on ’I-V and C-V characteristics of Cr∥H-Pc∥Cr organic sandwich cell’ ’’
Authors: Isett L. C.
Published: February 2003

It is shown that the capacitor-discharge measurement of a two-terminal device, such as a Schottky barrier, must be interpreted with care since the measurement technique does not separate capacitive and conductive components of the current.
The use of Au-Cd alloys to achieve large Schottky barrier heights on CdTe
Authors: Kuech Thomas F.
Published: February 2003

The Schottky barrier height of Cd, Au, and Au-Cd alloys on vacuum cleaved surfaces of n-CdTe was determined by I-V, C-V, and photoresponse techniques. A large barrier of 0.92 eV was found in the case of the Au-Cd alloy contacts. Contacts made with elemental Cd or Au gave barrier heights of 0.45 and 0.65 eV, respectively. The increased barrier height found on Au-Cd alloy contacts may be related to recent UHV observations on Schottky barrier formation where crystal defects play a role in determining the observed barrier height.
Complete collection of minority carriers from the inversion layer in induced junction diodes
Authors: Geist Jon , Liang Eli , Schaefer A. Russell
Published: February 2003

Mechanisms limiting the internal quantum efficiency in various types of oxide-passivated silicon photodiodes are discussed. It is argued that unit internal quantum efficiency is achievable in metallurgical junction, oxide-n+-p-p+ photodiodes, if it is achievable in the inversion layer of induced junction diodes of the same type. Measurements of the variation in response of the latter type of photodiode under both oxide bias and reverse bias are described. The results indicate that 100% collection of the minority carriers generated in the inversion layer is achieved for sufficiently low flux levels. Implantation in the oxide of Na+ ions to augment the trapped positive charge increases the maximum flux level at which 100% collection is observed.
Thermal oxidation of InP in phosphorus pentoxide vapor
Authors: Yamaguchi Masafumi
Published: February 2003

A modified thermal oxidation of InP is proposed. The native oxide films have been thermally grown on InP substrates in phosphorus pentoxide vapor at temperatures ranging from 400 to 500 °C. The oxide films are mainly composed of InPO4. Improved resistivities of the films at room temperature range from 1011 to 1012 Ω cm.
Influence of lattice mismatch on properties of InxGa1−xAs1−yPy layers epitaxially grown on InP substrates
Authors: Shirafuji J. , Tamura A. , Oka K. , Inoue M. , Inuishi Y.
Published: February 2003

Minority carrier (electron) diffusion length, density of electron traps and surface morphology in InxGa1−xAs1−yPy LPE layers grown on InP substrates have been investigated as a function of layer/substrate lattice mismatch. Two kinds of electron traps at Ec−0.60 and 0.67 eV are detected by DLTS measurement in undoped n-type layers (x = 0.77,y = 0.65). Their density is very sensitive to the amount of lattice mismatch. On the contrary, the electron diffusion length in p-type layers (x = 0.84,y = 0.63 at the lattice match condition) with the hole density ranging from 1 to 5×1017 cm−3 is almost independent of the amount of lattice mismatch at least within ±0.4 %. This result is explained in terms of dominant direct recombination process.
Superconductivity in amorphous+crystalline Ti-(Nb or V)-Si-B ductile alloys obtained by rapid quenching from the melt
Authors: Inoue A. , Takahashi Y. , Hoshi A. , Suryanarayana C. , Masumoto T.
Published: February 2003

Ductile superconductors with a duplex structure consisting of amorphous and bcc phases have been found in rapidly quenched alloys of the Ti70−xNb30(Si-B)x and Ti60-xV40(Si-B)x quaternary systems. Continuous ribbons of these alloys were produced in the form of about 1-mm width and 0.02-mm thickness using a modified single roller quenching apparatus. The silicon content in these duplex alloys was limited to the range between about 7 and 19 at. % and the boron content was in the range of about 0 to 9 at. %. The superconducting transition temperature Tc increased with decreasing metalloid content and/or with replacement of silicon by boron. The highest values obtained were 7.3 K for Ti57Nb30Si10B3 and 4.7 K for Ti45V40Si8B7, which are much higher than those of Ti-Nb and Ti-V base amorphous superconductors. The upper critical magnetic field Hc2 and the critical current density Jc for the Ti55Nb30Si7B8 alloy were about 5.1×106 A/m at 4.2 K and of the order 3.5×104 A/cm2 at zero applied field and 4.2 K. Although the superconducting properties of the duplex alloys are still insufficient for practical use, the information that the duplex structure produces a remarkable improvement in the superconducting properties without a detectable change or loss of ductility seems to be very important from the technological point of view.
Equilibrium bubble positions and effective easy axes in implanted garnet films
Authors: Niedoba H. , Puchalska I. B.
Published: February 2003

The disc-bubble method is used to determine bubble equilibrium positions and effective easy axes in garnets with implanted layer. The influence of tilting on the effective easy axes arrangement and charged walls subsistence is discussed. Propagation margins in four directions are measured in nontilted and tilted specimens, and the results are referred to orientation of circuits towards the effective easy axes.
Electromagnetic radiation from line sources interacting with a moving lossy half-space
Authors: Mann D. S. , Mukherjee P. K.
Published: February 2003

The problem of electromagnetic radiation from electric and magnetic line sources interacting with a moving lossy half-space is treated. The line source is oriented normal to the medium motion. The E and the H modes are excited independently in the moving medium by the magnetic and the electric line sources, respectively. Following the standard technique the expressions for the far-zone radiation field and the radiation pattern are obtained for both line sources. It is found that the radiation from an electric line source in vacuum remains practically unaffected by the medium motion as opposed to the case of a magnetic line source in vacuum. Further, when the medium supporting the line source is backed by a perfect conductor, the radiation from a magnetic line source has finite value of unity in both the ϑ = 0 and ϑ = π directions. This result is in contradistinction to the case of a magnetic (or an electric) line source situated in a medium that is backed by a half-space of finite conductivity. Numerical results for the far-zone radiation pattern, referring to both electric and magnetic line sources, are presented for several values of the physical parameters.
Nonlinear absorption due to shallow donors in germanium at 10.6 μm
Authors: McManus J. B. , People R. , Aggarwal R. L. , Wolff P. A.
Published: February 2003

Nonlinear absorption due to shallow donors in phosphorus-doped germanium (ND ≊1.5×1016 cm−3) has been measured at 1.8 °K, using a single-mode CO2 TEA laser operating at 10.6 μm. The absorption coefficient is found to decrease with increasing intensity up to 10 MW/cm2. A simple two-level model provides a good fit to the data and yields values for the donor photoionization, free-carrier absorption, and capture cross sections.
Thermal release of trapped electrons and phosphorescent decay in zinc silicate phosphors
Authors: Yang E. S. , Brownlow J. M.
Published: February 2003

Thermoluminescent (the glow curve) and phosphorescent decay experiments have been performed for a range of manganese activated zinc silicate phosphors. It is observed that the phosphorescent decay time is a nonmonotonic function of temperature when the light output is contributed simultaneously by two energetically adjacent traps. By representing the decay curve with exponential terms, the calculated trap depths can be correlated with the data obtained from the glow-curve experiment. Thus, the apparent contradiction between the relative insensitivity of the decay time with respect to temperature and the thermal activation of traps can be reconciled. In isolated traps, the decay time is always a monotonic function of temperature although the decay curve may not be exponential.
A study of the Si-Au-Ag interface by surface techniques
Authors: Cros A. , Salvan F. , Derrien J.
Published: February 2003

Auger spectroscopy, electron energy loss spectroscopy, and ion depth profiling techniques, under ultrahigh vacuum conditions, have been applied to the study of the formation of the Si-Au-Ag interface. The results show that the presence of gold atoms on the (111) face of a silicon substrate modifies drastically the structure of the silver layer subsequently deposited. At room temperature, from the Si substrate, one finds successively (i) a diffuse zone composed of an Si-Au-Ag alloy, the Ag concentration of which increases progressively (both gold-silver intermixing and silicon atoms diffusion from the bulk contribute to its formation), (ii) a pure silver layer, and (iii) a surface layer where silicon atoms have segregated and formed an Ag-Si alloy. The influence of the predeposited gold layer thickness has been investigated. Similar interface structures are obtained with gold coverage as low as 1.5 monolayers. These peculiar properties must be contrasted with the Si-Ag abrupt interface case where no silicon diffusion takes place. Results can be explained within a qualitative model involving interstitial diffusion of gold. The annealing of a room-temperature-grown interface shows two distinct regimes: for temperatures ≲ 400 °C, both silicon diffusion and gold-silver intermixing are enhanced. Beyond 400 °C, agglomeration of the metal overlayers takes place.
Deadtime effect in a straight channel electron multiplier
Authors: Bouchard C. , Carette J. D.
Published: February 2003

The intermediate state between single pulsing and oscillating cascades of a straight channel electron multiplier operated in ion feedback conditions is studied. The observation of the transient waveforms produced by a large number of superposed pulses of the same height is reported and their behavior is analyzed with the help of an RC equivalent circuit model.
Reactive magnetron sputtering of ZnO
Authors: Khuri-Yakub B. T. , Smits J. G. , Barbee T.
Published: February 2003

A planar magnetron with a zinc target is used to sputter zinc oxide in an oxygen atmosphere. Highly oriented zinc oxide films are obtained on a variety of subtrates such as gold, aluminum, platinum, quartz, and oxidized silicon. The sputtering rate is typically 10–20 μm/h for a substrate temperature of 450–500 °C, a substrate-to-target spacing of 4–7 cm, an oxygen partial pressure of 7 μm, and an input rf power of 1–1.25 kW. The films are evaluated by acoustic measurements, x-ray diffraction, reflection electron diffraction, and scanning electron microscopy.
Properties of space harmonics in a sinusoidally width-modulated rectangular waveguide
Authors: Mallick Amiya Kumar , Sanyal Gitindra Saran
Published: February 2003

The propagation characteristics of a sinusoidally width-modulated rectangular waveguide have been analyzed by solving the appropriate wave equation after reducing it to an eigenvalue equation. Different properties of significant space harmonics are brought out as variants of the operating frequency. The magnitudes and also the phase factors (propagation constants) of the space harmonics have been investigated as the parameters of the signal frequency of the propagating wave. The effects of the depth of modulation of the modulated structure on its propagation constant as well as on the axial variation of the transverse electric field have been successfully examined. Further, the frequency dependence of the characteristic wave impedance of the fundamental space wave of the periodic structure is also presented in this paper.
Transient response of a free-burning discharge: Quantitative model
Authors: Novak Jaroslav P. , Shoucri Magdi M. , Séguin Jean-Nöel
Published: February 2003

The work presented here deals with the application of the theoretical model of the nonequilibrium discharge developed by one of us to a free-burning discharge in argon subjected to a current impulse. The paper includes a description of the system of transport equations and a discussion of the boundary conditions and numerical solutions. The response to a 0.5-μs current ramp from 0.4 to 1.2 A is studied in detail. The variation of the basic parameters, such as the electron density, temperature, heat flux and diffusion velocity, the heavy-particle temperature, and heat flux and the average mass velocity is shown as a function of time and space. Radial profiles of the initial and final states are shown to agree well with the results of the earlier steady-state model.
Misfit dislocation-free In1−xGaxAs1−yPy/InP heterostructure wafers grown by liquid phase epitaxy
Authors: Nakajima Kazuo , Yamazaki Susumu , Komiya Satoshi , Akita Kenzo
Published: February 2003

The conditions to grow misfit dislocation-free In1−xGaxAs1−yPy/InP (0⩽x⩽0.47, 0⩽y⩽1.0) heterostructure wafers were first determined systematically by observing etch pits and x-ray topographs. Etch pits were produced on InP substrates on which an In1−xGaxAs1−yPy layer was grown, and they were observed to find whether misfit dislocations generated or not. Threshold regions for initiation of misfit dislocations into the wafers were determined as a function of both lattice misfit and layer thickness. The misfit dislocation-free regions determined by the etch pit observation of InP was found to be equivalent to the regions where misfit dislocations form in neither InP nor In1−xGaxAs1−yPy . The misfit dislocation-free regions of the quaternary wafers are larger than the region of the ternary In1−xGaxAs/InP wafers by more than three times.
The influence of tin implantation on the oxidation of iron
Authors: Baumvol I. J. R.
Published: February 2003

The high-temperature oxidation of metallic iron implanted with Sn ions at doses between 5×1015 and 5×1016 Sn ions cm−2 is studied in the temperature range from 300 to 500 °C. Ion implantation of Sn reduces the oxidation rate constant of iron up to a factor of 10 at all experimental temperatures. The mechanisms that underlie this process are investigated using physical techniques such as Rutherford backscattering of  4He particles, conversion electron Mössbauer scattering of  57Fe and 119Sn and scanning electron microscopy to analyze the surface of the implanted and oxidized samples. The FeSn2 intermetallic phase was formed in the sample implanted at room temperature. This compound is partially decomposed to the FeSn intermetallic and free Sn in solution in iron when the implanted sample is oxidized at 500°C. Ion implantation produces a surface composition very similar to that obtained with the more conventional methods of tinplating. The observed inhibition of the corrosion is discussed on the basis of this similarity.
Crystal perfection of HgI2 studied by neutron and gamma-ray diffraction
Authors: Yelon W. B. , Alkire R. W. , Schieber M. M. , van den Berg L. , Rasmussen S. E. , Christensen H. , Schneider J. R.
Published: February 2003

The crystalline perfection of wire sawn pieces of vapor grown single crystals of mercuric iodide was compared with the perfection of (00l) cleaved sections of the same crystal from which nuclear radiation detectors have been fabricated. The crystalline perfection was studied using neutron and gamma-ray diffraction rocking curves. Most of the gamma-ray data were obtained using a high intensity source of 153Sm gamma rays with a wavelength of λ = 0.12 Å. Some of the data were obtained using highly penetrating 198Au gamma rays with a shorter wavelength of λ = 0.03 Å. The neutrons had a wavelength of λ = 1.07 Å. It was found that, in terms of the mosaic spread of the crystals, the cleaved detector plates have a much lower crystalline perfection than the thicker uncleaved detector plates. At the same time, the results show that for detectors cut from the same crystal, the one with the lower spectral resolution for radiation detection will also have a lower perfection and larger width of the gamma-ray rocking curve. These results suggest consideration should be given to alternative fabrication procedures for HgI2 nuclear radiation detectors.
Theoretical account for the response of manganin gauges
Authors: Partom Y. , Yaziv D. , Rozenberg Z.
Published: February 2003

We propose a theoretical model to account for the dynamic response of manganin gauges in plane impact experiments. It is based on the concept that the elastoplastic behavior of a polycrystalline material depends significantly on the fact that it is made up of single-crystal grains randomly oriented in space. We refer to this approach as the grains model. By adjusting a single mechanical parameter and three piezoresistance parameters, contained in our model, we are able to reproduce the available experimental calibration curves for manganin.
Diffusion of zinc in gallium arsenide: A new model
Authors: Gösele U. , Morehead F.
Published: February 2003

Experimental results on the diffusion of Zn in GaAs which could not be satisfactorily explained in terms of a Frank–Turnbull mechanism involving vacancies can be understood with a ’’kick-out model’’ in which the equilibrium between interstitial and substitutional Zn is established via gallium interstitials.
The electrical properties of sulphur in silicon
Authors: Brotherton S. D. , King M. J. , Parker G. J.
Published: February 2003

Hall effect and diode C-V type measurements (including DLTS) have been used to study the several levels introduced by sulphur into the upper half of the silicon band gap. Where possible, the electron capture cross section of each level has also been measured. The results are interpreted in terms of two well characterized and reproducibly occurring centers sulphur I (0.18 and 0.38 eV) and sulphur II (0.32 and 0.53 eV). A third center, or variety of close centers, with energy levels of <0.1 eV were also found, but their occurrence was determined by the starting material and diffusion conditions. The centers sulphur I and II were both assumed to be double donors.The observed variations in concentration of sulphur I and sulphur II with diffusion temperature have enabled us to fit previously published results into a consistent pattern.
Ballistic transport in a nonparabolic band structure
Authors: Lee Johnson
Published: February 2003

The orientation dependence of ballistic electron transport in GaAs at room temperature is investigated using the Kane band structure model, which is consistent with the pseudopotential model for values of wave vector k<1.5×109 m−1. It is shown that the variation of the effective mass with group velocity plays a very important role in the conservation of energy relation. The field distribution and the I-V characteristic of a two-terminal ballistic transport GaAs device are determined by solving Poisson’s equation for parabolic and nonparabolic band structures. For comparison, the I-V characteristic of InSb is included also.
Contact charge-transfer lasers
Authors: Dharamsi A. N. , Tulip J.
Published: February 2003

A mechanism for sustaining population inversions in contact charge-transfer complexes in which the ground electronic state is not bound is described. The mechanism relies on picosecond radiationless depletion of the lower laser state. This generates an inversion even when the ground-state potential curve, as plotted against the donor-acceptor distance, is not repulsive vertically below the excited state minimum. Contact charge-transfer lasers would offer high gain, high-energy density, and tunable sources of coherent radiation in the uv and visible. A method for pumping such a laser is examined and applied to the pyrrole-oxygen complex. A rate equation analysis is done and estimates for gain and energy density are presented.
A high-resolution x-ray diagnostic technique using simultaneous diffraction from several planes of acid phthalate crystals
Authors: Burkhalter P. G. , Brown D. B. , Gersten M.
Published: February 2003

An x-ray diagnostic tool was developed for acquiring and interpreting high-resolution spectra for hot-plasma emission from selected elements. A convex, curved potassium acid phthalate (KAP) crystal was used to collect spectral data from an exploded-A1-wire plasma over a wide exposure latitude with the 001, 002, and the 013 planes simultaneously diffracting. The curved-crystal diffraction efficiencies were calculated for these three planes in KAP and evaluated with x-ray line intensities derived from the experimental A1 data. The crystal efficiencies were also computed for two other commonly used acid phthalate crystals rubidium acid phthalate (RAP) and thallium acid phthalate (TAP), to compare with KAP crystals. The calculated efficiencies for the first-order diffraction in KAP, RAP, and TAP agreed with available experimental data.
Angular distribution of sputtered atoms from polycrystalline metal targets
Authors: Tsuge H. , Esho S.
Published: February 2003

Angular distribution of sputtered atoms from polycrystalline metal targets with crystallographic-preferred orientation was measured for 0.5- and 1.0-keV Ar+ ions at incidence angles of 0° and 45°. The distribution was compared with that for a Si (100) single-crystal target. Atoms sputtered from Au, Pt, Al, and NiFe targets are ejected preferentially in the directions of their close packing in the lattice. For the Si target, the distribution is under cosine. These results are explained in terms of the target-surface crystal structure during and after ion bombardment. The surface structure for the metal targets remains essentially unchanged, but not for the Si target. Sputtered-atom ejection along the target normally increases with increasing incident-ion energy. Even at oblique incidence, heavy-target atoms such as Au, appear to have preferentially ejected atoms in the close-packed directions.
Monte Carlo simulation of fast secondary electron production in electron beam resists
Authors: Murata Kenji , Kyser David F. , Ting Chiu H.
Published: February 2003

Monte Carlo calculations of fast secondary electron production have been performed with a hybrid model for the discrete and continuous energy-loss processes. The Moller theory was adopted for the differential inelastic scattering cross-section which determines the production rate of fast secondary electrons. The calculations were made for both a bulk polymethyl methacrylate (PMMA) sample and 4000-Å-thin films of PMMA (with and without a silicon substrate) at 10 and 20 keV. The new model is discussed and comparison made with results obtained from the old model, which is based on the continuous slowing down approximation of Bethe for energy loss and the screened Rutherford equation for elastic angular scattering. The new model predicts a larger absorbed energy density than the old model for an isolated line source exposure on a resist film. The consequences of this fast secondary electron contribution on the ultimate limit in electron lithography is discussed.
Measurement of spectrum, bias dependence, and intensity of spontaneous emission in GaAs lasers
Authors: Henry C. H. , Logan R. A. , Bertness K. A.
Published: February 2003

Spontaneous emission spectra and intensity measurements are made on buried heterostructure lasers with transparent windows above the active stripe. The bias voltage V, where eV is the separation of quasi-Fermi levels, is determined from spectral measurements. The total luminescence intensity increases as exp(eV/nkT), where n changes from 1.0 to about 2 as V increases from 1.3 V to the threshold voltage of 1.415 V. The change in n is due primarily to saturation of the low-energy electron states as a result of electron degeneracy. The spectral determination of bias voltage is justified by the close agreement between the threshold voltage determined by spectral analysis and the voltage determined by extrapolation of directly measured light versus voltage data. Calibration of the absolute radiative rate with optical absorption data yields a predicted radiative recombination current of Jth/d≊5.8 kA cm−2 μm−1, in reasonable agreement with empirical threshold data.
Strain-related degradation phenomena in long-lived GaAlAs stripe lasers
Authors: Robertson M. J. , Wakefield B. , Hutchinson P.
Published: February 2003

Qualified GaAlAs/GaAs oxide isolated stripe geometry DH lasers, degraded at temperatures up to 90 °C, have been examined using the cathodoluminescence (CL) and electron beam induced current (EBIC) modes of the scanning electron microscope, and by transmission electron microscopy in a 1-MeV TEM. The main features observed in the EBIC and CL images in the plane of the heterojunction of the degraded lasers were bright and dark bands running parallel to the stripe, together with brightened mottled regions extending well outside. The separation of the bands and the extent of the mottled region is dependent on the width of the stripe. This general pattern is modified considerably near to the facets of the lasers. Calculations of strain profiles for the different laser types suggested that these phenomena can be explained in terms of a model of operation induced, strain enhanced, defect migration. Small dislocation loops seen at the edges of the stripe, using transmission electron microscopy appear to support this model.
Hollow-core oxide-glass cladding optical fibers for middle-infrared region
Authors: Hidaka T. , Morikawa T. , Shimada J.
Published: February 2003

A new type of middle-infrared optical fiber is proposed in which oxide glass is used as the cladding material to define a hollow core. Several kinds of oxide glasses have refractive indices lower than unity in the frequency range near 1000 cm−1 due to the nearby reasonance of molecular vibration; hence due to the total reflection of the incident laser light from air to the oxide-glass surface, it is expected that the hollow-core optical fiber made with the glass functioning as the cladding will exhibit small transmission loss. A preliminary experiment on a 1-mm-inner diam hollow-core Pb glass optical fiber shows its loss to be 7.7 dB/m at 940 cm−1 for CO2 laser light.
SAW propagation loss mechanism in piezoelectric ceramics
Authors: Jyomura Shigeru , Nagatsuma Kazuyuki , Takeuchi Hiroshi
Published: February 2003

The surface acoustic wave (SAW) propagation loss mechanism of piezoelectric ceramics is examined using lead titanate (PbTiO3) ceramics modified with additives of Nd2O3, MnO2, and In2O3, which have zero temperature coefficients of SAW delay time. The propagation loss L in the frequency range 30 to 300 MHz consists of two parts. One is the Rayleigh scattering loss LS caused by grain, and the other is the true dissipative loss LF caused by internal friction. Thus, total loss results in L(dB/cm) = LS+LF = 3.2×103D3f4+6.8×10−4f2 (where D and f denote average grain size in cm and frequency in MHz, respectively). It is also revealed experimentally that the internal friction causing the latter loss has a close correlation with the dielectric loss through piezoelectric combination. Therefore, materials with fine grain (<0.5 μm) and low dielectric loss (<10−3) must be developed to reduce SAW propagation losses which prevent the piezoelectric ceramics from being used in higher frequency (≳100 MHz) SAW applications. Based on these requirements, fine grained (∼0.5 μm) specimens are fabricated. The propagation losses obtained from these specimens, 9 dB/cm at 100 MHz, are the lowest values ever reported for piezoelectric ceramics. This result suggests that the present ceramics have high potential as materials for high-frequency SAW devices.
Surface acoustic wave and piezoelectric properties of (Pb, Ln) (Ti, Mn)O3 ceramics (Ln = rare earths)
Authors: Ito Yukio , Nagatsuma Kazuyuki , Takeuchi Hiroshi , Jyomura Shigeru
Published: February 2003

The surface acoustic wave (SAW) and piezoelectric properties of PbTi03 ceramics modified by the partial substitution of rare earths for Pb, particularly (Pb, Ln) (Ti, Mn)03 (Ln = La, Ce, Pr, Nd, Sm, or Gd) ceramics, are examined. The effects of the rare earths introduced on these properties are noted. Properties, such as velocities and electromechanical coupling factors, for bulk wave and SAW vary monotonically with the ionic sizes of the rare earths. On the other hand, the temperature coefficient of SAW delay time takes a minimum value when the Ln is Nd. It is shown that the variation of the temperature coefficient with rare earths corresponds well with those of the temperature coefficients of elastic constants CE33 and CE44.
Investigation of shell stability in imploding cylindrical targets
Authors: Sweeney M. A. , Perry F. C.
Published: February 2003

As part of a program to determine the feasibility of inertial confinement fusion (ICF), the physics of implosion stability is being studied. Ablatively-driven double-shell cylinders with and without initial periodic perturbations on the outer edge of the pusher were imploded using a single electron beam. Four-pulse holographic shadowgraphy yielded spatially and temporally resolved images of the implosions. The experiments are in a regime where fluidlike behavior is expected to dominate. A comparison of experimental data on the free-surface motion with two-dimensional, planar-geometry numerical calculations which include materials effects indicates shock-accelerated unstable growth of fabrication irregularities at the perturbed material interface. Peak pressures of 0.26 TPa (2.6 Mbars) are inferred in the high-density pusher material. Both the experiment and the calculation show a decrease in the amplitude of the free-surface perturbations at late time. In the experiment this decrease in amplitude begins earlier and the amount of the decrease is larger because of the enhanced interaction of adjacent perturbations due to convergence. The complex nonlinear development of both intentional and nonintentional target perturbations are demonstrated in the experiments.
Bounds on the transport and optical properties of a two-component composite material
Authors: Milton G. W.
Published: February 2003

An infinite set of bounds on the effective permittivity εe of two-component composite materials is derived. All the bounds can be expressed in terms of a single function g. Analogous bounds apply to the other transport properties of the composite, such as the thermal and electrical conductivities and the magnetic permeability. The work also applies to the optical properties of the composite, provided the wavelength is sufficiently large compared with the structure of the composite. In all cases we find εe is confined to a region of the complex plane bounded by arcs of circles. The appropriate region is determined by what is known about the composite and as more information is known the region becomes progressively smaller. We show that in many cases the region is the most restrictive which can be found using only the known information about the composite material.
Thermionic emission from platinum in hydrocarbon flows at low pressure
Authors: Halpern Bret , Al-Mutaz Ibrahim , Douyon Liselle
Published: February 2003

Thermionic emission from Pt filaments is increased by a factor of 1000 in a flow of hydrocarbons at ∼1 Torr pressure and space-charge-free conditions. The effect can be used to trace the initial stages of hydrocarbon decomposition and carbon deposition, and it has possible application as an automobile exhaust sensor or a gas chromatograph detector.
Forming electrical interconnections through semiconductor wafers
Authors: Anthony T. R.
Published: February 2003

To fabricate electrical interconnections through a semiconductor wafer, an array of holes is laser drilled in the wafer and then a conductor is formed in the holes. Six techniques, including capillary wetting, wedge extrusion, wire insertion, electroless plating, electroforming, and double-sided sputtering and through-hole electroplating were used to form conductors in the array of laser-drilled holes in silicon-on-sapphire (SOS) wafers. These techniques are described, and their respective strengths and weaknesses discussed and compared.
Optical pumping of dye laser with an array of plasma pinches
Authors: Rieger Harry , Kim Kyekyoon
Published: February 2003

Laser activity from a dye (rhodamine 6 G) has been obtained, for the first time, by using an array of plasma pinches as the excitation light source. Description of the experimental setup is presented along with the pumping light and laser pulse traces.
Longitudinal acoustic wave radiated from an arched interdigital transducer
Authors: Kobayashi Kenichi , Moriizumi Toyosaka , Toda Kohji
Published: February 2003

An arched interdigital transducer has been devised for acoustic imaging uses. Two kinds of acoustic beams are radiated into water from the transducer, one of which is radiated at a constant angle independent of the frequency change. The other has a frequency-dependent radiation angle. The two beams follow conical paths and come to a focus on the axis of the arc. The arched transducer with 45 ° aperture angle, consisting of 10 finger pairs, has a conversion loss of about 10 dB and about 150-μm beamwidth for 3 dB down values, at 22.7 MHz.
Low-temperature redistribution and gettering of oxygen in silicon
Authors: Magee T. J. , Leung C. , Kawayoshi H. , Furman B. , Hopkins C. G. , Evans C. A.
Published: February 2003

Redistribution and gettering of mobile oxygen in Si by back surface damage has been investigated at temperatures in the range 300°–500°C for annealing periods of 10–72 h. Using data from transmission electron microscopy, secondary ion mass spectrometry depth profiling, and secondary ion microscopy, it has been shown that oxygen is gettered from the interior of the wafer and pinned along dislocation lines, resulting in increased concentrations of 16O within back surface regions. The process is characterized by an activation energy of 0.92 eV and controlled by stress gradients produced by the damage at the wafer backside.
Static compression of polymethyl methacrylate to 100 GPa
Authors: Chan Kam-Shui , Ruoff Arthur L.
Published: February 2003

Polymethyl methacrylate (PMMA) was compressed in a diamond indentor-flat anvil system to a pressure of 100 GPa (i.e., 1 Mbar). PMMA was found to remain an excellent electrical insulator.
The effect of surface potential fluctuations on surface photovoltage in metal-oxide-semiconductor structures
Authors: Krawczyk S. K. , Jakubowski A.
Published: February 2003

The classical theory of surface photovoltage neglects the presence of surface potential fluctuation at the semiconductor surface. In this letter it is demonstrated that surface potential fluctuations strongly influences the surface photovoltage in metal-oxide-semiconductor structures.
Deep level studies of Hg1−xCdx Te. I: Narrow-band-gap space-charge spectroscopy
Authors: Polla D. L. , Jones C. E.
Published: February 2003

Trapping effects in p-type Hg1−xCdx Te (0.2<x<0.4) have been surveyed using three techniques. These were deep level transient spectroscopy (DLTS), admittance spectroscopy (AS), and thermally stimulated current (TSC). All three techniques were able to identify deep traps in Hg1−xCdx Te even for band gaps less than 0.1 eV. DLTS is best able to characterize deep traps, admittance spectroscopy is able to quickly survey majority-carrier traps, and TSC is limited in Hg1−xCdx Te by leakage currents. Deep traps were seen in all of the samples studies in concentrations of 1014–1016 cm−3. Double pulse DLTS techniques have been used to identify the electron capture cross sections for specific hole traps. This allows the complete characterization of recombination centers. A donor-like Shockley-Read generation-recombination center occurring near midgap may be common to p-type Hg1−xCdx Te, where the doping is due to mercury vacancies.
Deep level studies of Hg1−xCdxTe. II: Correlation with photodiode performance
Authors: Polla D. L. , Reine M. B. , Jones C. E.
Published: February 2003

Trapping parameters measured by deep level transient spectroscopy (DLTS) for several samples of Hg1−xCdxTe doped p type by mercury vacancies have been correlated with photodiode characteristics. The samples are Hg1−xCdxTe with x values of 0.215, 0.305, and 0.320. The DLTS measured parameters are trap energy, concentration, and electron and hole capture cross sections. These parameters are used to calculate minority carrier lifetime and generation-recombination noise current. DLTS has identified Shockley-Read recombination centers which determines the carrier lifetime of p-type Hg1−xCdxTe photodiodes and the resistance-area product detectivity figure of merit.
Deep levels produced by pairs of impurities in InP
Authors: Sankey Otto F. , Dow John D.
Published: February 2003

The major chemical trends in the energy levels of nearest-neighbor-paired, substitutional, sp3-bonded defects in InP are predicted. Schemes for manipulating the deep levels of an isolated impurity by pairing with a second impurity are proposed, and applied to the isolated deep C donor and the deep P-antisite defect in InP.
Carbon-acceptor pair centers (X centers) in silicon
Authors: Jones Colin E. , Schafer David , Scott Walter , Hager R. J.
Published: February 2003

An electrically active complex called the X center has long been known in indium-doped silicon. Similar defects have now been associated with the other Group IIIA elements in silicon. These X centers are acceptors with energies approximately 80% of the corresponding IIIA substitutional atoms energy and with concentrations 10−2 to 10−5 of the corresponding Group IIIA concentration. Doping studies show that the X-center concentrations depend on carbon and fit the reaction As +Cs⇄K X, where As is the substitutional Group IIIA acceptor, Cs is the substitutional carbon, and K is the equilibrium constant. The equilibrium constants as a function of temperature and the complex binding energies have been determined for all of the Group IIIA X centers except Tl. The binding energy for the complex increases from 0.03 eV for the boron–X center to 0.70 eV for the indium–X center. The complexes do not anneal out up to the melting point of silicon and they can be cyclically annealed. Stress studies on the aluminum–X center show that the complex has [111] trigonal orientational symmetry. The dependence on carbon, the stress symmetry, and the high-temperature stability of these centers all suggest a model of these complexes of a nearest-neighbor substitutional carbon-acceptor pair. Mathematical modeling using extended Hückel calculations confirms that this defect should have a single energy level slightly shallower than the substitutional acceptor.
A calculation of susceptibilities of the rare-earth ion in orthoferrite
Authors: Enomura A.
Published: February 2003

The susceptibilities of the rare-earth ion in orthoferrite are calculated in detail by using a diagonal sum method, assuming the crystal-field B20O20+B22O22. The calculated results are compared with experimental data of TbFeO3 and DyFeO3 and it is confirmed that this assumption holds good.
Conductivity modulation in indium oxide films by oxygen pressure variations
Authors: Laser Daniel
Published: February 2003

The electrical conductivity of indium oxide films prepared by reactive evaporation of indium is shown to be modulated by adusting the partial pressure of oxygen over the film after its formation. This effect is attributed to changes in the extent of nonstoichiometry of the oxide, which seems to be caused by the incorporation into or extraction of oxygen from the oxide film. The effect is found to be reversible, temperature-dependent, and to become smaller as the film thickness increases.
The interpretation of ohmic behavior in semi-insulating gallium arsenide systems
Authors: Manifacier J.-C. , Henisch H. K.
Published: February 2003

The paper is concerned with the interpretation of measurements on semi-insulating gallium arsenide and, in particular, with the evaluation of effective bulk resistivities from the results of observations on two-electrode systems. These observations tend to be dominated by injection effects, even when the contacts used are nominally of low resistance. Order-of-magnitude errors can arise from this cause, even though the specimen may appear to exhibit ohmic behavior. Carrier concentration, field- and space-charge contours are calculated on the basis of a model within the realm of a small-signal theory, for conditions which correspond to lifetime, relaxation, and hybrid operating regimes.
Phthalocyanine organic solar cells: Indium/x-metal free phthalocyanine Schottky barriers
Authors: Loutfy R. O. , Sharp J. H. , Hsiao C. K. , Ho R.
Published: February 2003

A thin organic film of polycrystalline particles of x-metal free phthalocyanine (x-H2Pc) dispersed in a polymer binder, when sandwiched between tin oxide (NESA) and indium electrodes, is shown to exhibit a strong photovoltaic effect. The photovoltaic and rectification properties of In/x-H2Pc/NESA sandwich cells are reported. From the photovoltaic action spectra, the active region responsible for electric power generation was found to be confined to the metal/semiconductor interface. A Schottky barrier width of 300 Å was determined, which allows the capture of 30% of solar irradiance. An electron trap density of 3×1017/cm3 and a Schottky barrier built-in potential of 0.63 V are estimated from C-V measurements. At low voltage, the dark current in the forward direction varies exponentially with voltage: from this dependence values of 2×10−9 A/cm2 and 1.3–2.6 for the saturation current J0 and diode quality factor n are determined. At higher voltage, a super quadratic dependence of forward current on voltage indicated that current conduction is limited by an exponentially decreasing distribution of traps. At peak solar power (135 mW/cm2), a power conversion efficiency (η′) of 1.2% to transmitted light has been obtained. The transmittance of the indium electrode approached 2%. The devices exhibit open circuit voltages Voc of 0.45 V and short-circuit currents of 0.2 mA/cm2 at Air Mass Zero (AMO) sunlight. Therefore, the engineering efficiency of our device approached 0.03%. The monochromatic quantum efficiency of free-carrier generation approached 75% at low light level; this diminished to 30% at solar intensities, characteristic of a cell with large series resistance. The effect of pigment loading, cell thickness, light intensity, binder material, dye sensitization, and the nature of barrier electrode has been studied and optimized.
Experimental and theoretical electron mobility of modulation doped AlxGa1−xAs/GaAs heterostructures grown by molecular beam epitaxy
Authors: Drummond T. J. , Morkoç H. , Hess K. , Cho A. Y.
Published: February 2003

Single period modulation doped Alx Ga1−x As/GaAs heterostructures have been grown by MBE and characterized. The incorporation of a thin undoped Alx Ga1−x As layer between the doped Alx Ga1−x As and undoped GaAs layers further improves the electron mobility through the reduction of remote donor scattering. Electron mobilities as high as 8165, 80 900, and 115 000 cm2 V−1 s−1 at 300, 78, and 10 K respectively, for an average sheet electron concentration of 5×1011 cm−2 were obtained. The best mobility was obtained when the undoped Alx Ga1−x As layer thickness was 75 Å for both x = 0.25 and x = 0.33. These figures represent the best mobilities associated with single period Alx Ga1−x As/GaAs structures reported to date. Good agreement between the experiments and mobility calculations have also been obtained. The theory is based on heavily screened remote impurity scattering and quasi-two-dimensional electron-phonon interaction.
Field effect spectroscopy of CdSe-insulator interface states
Authors: Brillson L. J. , Luo F. , Wysocki J.
Published: February 2003

We have developed a new technique termed field effect spectroscopy (FES) to probe semiconductor-insulator interface states optically. It consists of photoconductivity measurements of the semiconductor channel between source and drain of a gated thin-film transistor. By varying the gate voltage and thereby the potential at the insulator-semiconductor interface, one can vary the relative contributions of bulk and interface states to the resistivity of the semiconductor channel. FES results for a variety of Al2O3:CdSe and SiO2:CdSe interface reveal a strong dependence of interface state density on fabrication conditions.
Performance of a N2/CO2 mixing laser by using a rapid mixing technique
Authors: Hara H.
Published: February 2003

The small-signal gain of a N2/CO2 mixing laser was found to depend strongly on the amount of He gas added to N2 gas flow when the distance from a CO2 gas injector was varied. A maximum gain of 8 m−1 and an output power of 5.2 W from 1.2-cm active length were obtained 4 cm downstream from a CO2 gas injector at a gas composition of N2:He:CO2 = 9.0:6.5:14.6 (STP). The influence of the diffusion velocity of CO2 gas to the small-signal gain is also discussed.