bluuebunny/crossref_metadata_2025 huggingface dataset:
Recombination and reemission of deuterium implanted in stainless steel
Authors: Thomas E. W. , Petrov I. G. , Braun M.
Published: February 2003

During bombardment of a stainless steel sample by 5 keV D+ ions we study simultaneously the reemission of D2 molecules and the depth distribution of deuterium in the target. We determine separately the depth distribution of trapped and mobile deuterium. The mobile component exhibits a uniform density to a depth of 850 Å. A determination is made of the surface recombination rate coefficient relating the emission of free molecules to the density of mobile atoms in the surface. A value of 1.5×10−29 cm4 s−1 is determined for a target at 30 °C. Data are presented up to a 100 °C target temperature and are consistent with previous determinations at higher temperatures. A simple model shows how reemission varies with bombardment fluence and permits a separate evaluation of the recombination rate from the temporal dependence of reemission.
Development of laser diagnostic probes for chemical vapor deposition of InP/InGaAsP epitaxial layers
Authors: Donnelly V. M. , Karlicek R. F.
Published: February 2003

Laser spectroscopic methods have been developed for the detection of PH3, P2, AsH3, As2, InCl, and GaCl, using both tunable-dye-laser induced fluorescence and excimer laser excitation. These are the primary reactants participating in the chemical vapor deposition (CVD) of InP/InGaAsP epitaxial layers. Using a reaction tube designed to simulate a CVD growth reactor, the detection limits measured for all these species are well below those levels typically employed during layer growth. Specific applications are outlined, and several examples are given relating these techniques to conditions expected in InP/InGaAsP layer growth.
Reactions of atomic hydrogen in the deposition of hydrogenated amorphous silicon by glow discharge and reactive sputtering
Authors: Kampas F. J.
Published: February 2003

Three reactions of atomic hydrogen with hydrogenated amorphous silicon (a-Si:H) are proposed in analogy with known gas-phase reactions. These reactions can explain the different rates of hydrogen addition and dangling bond passivation in the deposition of a-Si:H by reactive sputtering; the presence of columnar microstructure and high spin density in a-Si:H deposited by glow discharge from argon-silane mixtures at high power and low silane concentration; and the microcrystalline nature of silicon films deposited by transport in a hydrogen discharge, and from high-power silane-hydrogen mixtures.
Effect of oxygen on chromium-structural defects interaction in ion-implanted gallium arsenide
Authors: Sadana D. K. , Washburn J. , Zee T. , Wilson R. G.
Published: February 2003

The redistribution of chromium in gallium arsenide implanted with either gallium and arsenic or gallium, arsenic, and oxygen and subsequently furnace annealed was studied by secondary ion mass spectrometry. The depth distribution of the residual damage was obtained by cross-sectional transmission electron microscopy. At annealing temperatures of ⩽600 °C, there was a one to one depth correlation between the positions of the damage layers and peaks in the atomic profile of chromium. However, at annealing temperatures of ⩾800 °C such correlations were complicated by oxidation effects.
Fluctuations and thermodynamic properties of anisotropic solids
Authors: Ray John R.
Published: February 2003

We present a direct calculation of fluctuation formulae that relate strain and kinetic energy fluctuations to the adiabatic compliance tensor, the constant stress specific heat, and the constant stress thermal expansion tensor. These fluctuation formulae can be used to determine these quantities in molecular dynamic computer simulations of solids. Also we present a fluctuation formula containing third-order elastic compliances. This higher order fluctuation formula also contains the other elastic properties previously mentioned. The extension to fluctuation formulae containing nth-order elastic properties is straightforward.
Increased power output from N2 laser by addition of BF3
Authors: Mehendale S. C. , Bhawalkar D. D.
Published: February 2003

The output power of a fast transverse electrical discharge excited N2 laser, operating at 3371 Å, was found to increase on addition of BF3. An increase of 25% was observed under optimum conditions without any change in the laser wavelength and the pulse duration.
Reflection of 32–2000 eV deuterium from carbon
Authors: Braun M. , Thomas E. W.
Published: February 2003

Reflection of deuterium from carbon is measured by a technique based on the rise of partial pressure caused by the reflected particles. Data are presented for 32–2000 eV per deuteron incident energies and as a function of angle of incidence. The data are consistent with previous determinations at energies above 1000 eV. A systematic difference in energy dependence is found when the measurements for reflection of deuterium are compared on a reduced energy scale with MARLOWE computer simulations of hydrogen reflection.
Thermal conductivity and specific heat of the chalcogenide salt: Tl3 AsSe3
Authors: Ewbank M. D. , Newman P. R. , Kuwamoto H.
Published: February 2003

The temperature dependence of the thermal conductivity, between 77 and 300 K, and specific heat, between 150 and 550 K, of Tl3AsSe3 are reported. The thermal conductivity is best described as temperature independent and isotropic over the range studied, with a value of approximately 3.5 mW/cm-K. The heat capacity is approximately constant in temperature at the Dulong-Petit limit.
Comment on ’’A photoluminescence study of beryllium-doped GaAs grown by molecular beam epitaxy’’
Authors: Ploog Klaus , Künzel Harald , Collins Douglas M.
Published: February 2003

A recent paper by Scott, Duggan, Dawson, and Weimann on the photoluminescence of beryllium-doped GaAs grown by molecular beam epitaxy is compared and contrasted with earlier studies by Künzel and Ploog. We find that, contrary to a statement by Scott, Duggan, Dawson, and Weimann, the low-temperature photoluminescence spectra of their GaAs samples grown from an As4 source do exhibit new bound exciton lines previously reported by Künzel and Ploog. The source of confusion is identified as an incorrect assignment of near band-gap spectral features of GaAs layers with (NA−ND)≳1016 cm−3 used by Scott, Duggan, Dawson, and Weimann.
Plane shock initiation of detonation in γ-irradiated pentaerythritol tetranitrate
Authors: Dick J. J.
Published: February 2003

The effect of γ irradiation on shock initiation sensitivity of pentaerythritol tetranitrate (PETN) single-crystal explosive was studied experimentally. Shock input strength was 8.6 GPa and detonation transition occurred after 7.3 mm of shock run for as-grown {110} crystals. Other crystals were given γ-ray doses of up to 1 Mrad from a 60Co source. Crystals were sensitized by doses greater that 0.6 Mrad, with 1 Mrad shortening the distance to detonation transition by almost 40%. The initiation process is apparently still of the homogeneous type. Irradiated crystals were studied by optical microscopy. Evidence of the presence of gas molecules produced by decomposition of PETN molecules induced by γ rays was observed. Platelets 20–50 μm in diameter and about 0.25 μm thick were noted inside the crystal 30 days after irradiation. Growth of penny-shaped crack-flaws was observed and attributed to buildup of internal strains generated by the decomposition gas pressure. It is hypothesized that the source of the increased shock sensitivity after irradiation is due to the additional decomposition sites generated by decomposition of PETN molecules by γ-ray excitation. These sites act as additional nuclei for thermal decomposition in the shocked material.
The stability of gaseous nuclei at liquid-solid interfaces
Authors: Forest Tom W.
Published: February 2003

A free energy analysis is used to investigate the stability of gas-vapor nuclei which are trapped in solid surface cavities. The cavities are axisymmetric but otherwise of arbitrary geometry. For a uniform temperature, it is shown that a pre-existing nucleus begins to grow spontaneously when the radius of curvature of the liquid-gas interface reaches a local minimum value. For a range of contact angles this condition implies that the liquid-gas interface is hemispherical. Results are presented for a cavity of specific geometry—the conical cavity.
Carrier compensation at interfaces formed by molecular beam epitaxy
Authors: Kawai N. J. , Wood C. E. C. , Eastman L. F.
Published: February 2003

Ion beam dechanneling, deep-level transient capacitance, and 4 K photoluminescence spectral methods have been used to study carrier compensating centers found at interfaces caused by interrruption of growth and exposure to different media. Defects appear to be related to impurities probably in the form of complexes with vacancies. Excess doping at these interfaces did not decrease the associated resistance to current flow, but increases of doping on either side of the interfaces overcome the resistance problem. A new vertical transistor device is proposed that avoids these interface effects.
Evolution of microstructure in amorphous hydrogenated silicon
Authors: Messier R. , Ross R. C.
Published: February 2003

Hydrogenated α-Si films prepared by rf sputtering were investigated as a function of film thickness (150 Å to 10 μm) and substrate type and roughness. The physical structure was shown to evolve with film thickness as a result of the nucleation, growth, and incomplete coalescence of ’’island’’-like structures which lead to a supernetwork of larger voids. At least four different supernetwork structures of increasing size were identified in the present study. The structural evolution was essentially unaffected by substrate type for this material in which low adatom mobility is the controlling factor. This evolutionary model is expected to have general application to all vapor-deposition processes including glow-discharge decomposition of silane.
A model of dc leakage in ceramic capacitors
Authors: Loh Eugene
Published: February 2003

Data of low-voltage instable capacitors by A. M. Holladay [NASA Conference Publication 2186, Capacitor Techniques, Application and Reliability, 27–31, Feb. 24−25 (1981)], Schottky-like current-voltage characteristics of ’’unreliable’’ capacitors by D. A. Payne [Proceedings of the 1967 International Reliability Physics Symposium, 257–264 (1967)], and stress voltage-dependence of life time of normal capacitors by W. J. Minford, M. A. Yatsko, and W. B. Baker [American Ceramic Society Annual Meeting, Cincinnati, Ohio (1979)] lead to a unified dc leakage model for ceramic capacitors, wherein current-emitting grains subjected to a Poole–Frenkel field ≃105 V/cm are connected by leakage path with ∼102, ∼105, and ∼109 Ω, respectively.
Electrical conduction and breakdown in oxides of polycrystalline silicon and their correlation with interface texture
Authors: Heimann P. A. , Murarka S. P. , Sheng T. T.
Published: February 2003

The electrical properties of oxidized polysilicon (poly-oxide) were measured for samples of various thicknesses, grown from polysilicon which had been doped at temperatures of 900–1000 °C, and oxidized in steam or dry oxygen at temperatures of 850–1050 °C. The electrical conduction can be explained in terms of Fowler-Nordheim tunneling at sites of roughness of the polysilicon/poly-oxide interface, and in terms of deep electron traps near that interface, in agreement with previously published results. We have found additional evidence for such electron traps. We find that higher doping and oxidation temperatures tend to yield oxides with higher breakdown fields, although there is considerable variation among different sets of samples. We observe no significant differences in the polysilicon/poly-oxide interface texture by cross-sectional transmission electron microscopy. However, we find a strong correlation between the applied field necessary for a significant leakage current through the poly-oxide and the applied field which causes breakdown. This finding supports the model that both the leakage current and the oxide breakdown are caused by locally enhanced electric fields within the poly-oxide. The concepts of an enhanced local electric field due to polysilicon/poly-oxide interface roughness and of the formation of electron traps at regions of strong local electric field are used to model the experimentally observed conduction and breakdown processes and to propose additional effects. The electric field enhancement due to a hemispherical protuberance at the interface is calculated analytically.
1/f noise in silicon wafers
Authors: Black R. D. , Weissman M. B. , Restle P. J.
Published: February 2003

The magnitude of 1/ f noise in an ordinary wafer of lightly doped n-type silicon lacking impurity scattering is found to be three orders of magnitude less than the commonly accepted value. The conductivity fluctuations causing the noise are spatially uncorrelated and approximately scalar, as might be expected for a simple trapping model. Varying surface treatments were found to increase the noise, sometimes in clear association with slight I-V nonlinearities, but no sample had resistance fluctuations more than one tenth as large as predicted by the Hooge relation.
Space-charge limited conduction in n+n
n+ amorphous hydrogenated silicon films
Authors: Bhattacharya Enakshi , Guha S. , Krishna K. V. , Bapat D. R.
Published: February 2003

High field conduction in n+nn+ amorphous hydrogenated silicon (α-Si:H) films has been investigated at different temperatures. The results can be explained by assuming space-charge limited conduction (SCLC) with a uniform density of traps. The value of density of states at the Fermi level, g(EF), obtained from the SCLC measurements ranges between 7−9×1016 cm−3 eV−1. Similar values are obtained by measurements of field effect and frequency and temperature dependence of Schottky barrier capacitance on material grown under identical conditions.
Stimulated Brillouin scattering and optical excitation of coherent shear waves
Authors: Nelson Keith A.
Published: February 2003

The theory of stimulated Brillouin scattering is applied to the experimental situation of crossed mode-locked laser pulses, centered at the same frequency, in isotropic and anisotropic materials. It is shown that generation of pure transverse (shear) ultrasonic waves should be possible with reasonable efficiency. In general, any acoustic phonon mode that the material can support— pure shear, quasishear, quasilongitudinal, and pure longitudinal—can be populated coherently. The results permit straightforward determination of the experimental configuration that most effectively couples laser energy to the desired mode. The acoustic frequency can be tuned conveniently from about 3 MHz to 30 GHz in most materials.
Transient hot-strip method for measuring thermal conductivity and specific heat of solids and fluids: Second order theory and approximations for short times
Authors: Gustafsson Silas E. , Ahmed Kamaluddin , Hamdani Abbas J. , Maqsood Asghari
Published: February 2003

The theory of the newly described transient hot-strip method has been developed to include second order terms of the temperature dependence of the electrical resistivity of the hot strip. The theory indicates that second order terms should be included in situations where a high-current pulse is being used. Approximate values of the coefficients for the second order terms have been determined numerically. For times appreciably less than the characteristic time, a simple approximation of the voltage variation as a function of time has been derived and tested experimentally.
Mechanism for the interaction of surface waves with 200-Å nickel films
Authors: Feng I-an , Tachiki M. , Krischer Charles , Levy M.
Published: February 2003

Measurements of the surface wave attenuation of surface wave delay lines coated with nickel films in a magnetic field parallel to the film plane in the frequency range 500–665 MHz exhibit attenuation peaks which depend strongly on film thickness, temperature, and magnetic field. The effect is very strong for 200-Å thick nickel film-coated 618-MHz quartz delay lines at room temperature. The maximum attenuation change is about 40 db/cm. The attenuation can be varied by over 25 db/cm by a magnetic field change of less than 10 Oe. A 665-MHz LiNbO3 delay line coated with a 200-Å nickel film exhibits a maximum attenuation of about 10 db/cm and similar behavior to that seen on the quartz substrate in a magnetic field. Thicker films exhibit similar but smaller attenuation peaks. Attenuation measurements were carried out at various temperatures. In general, the maximum attenuation decreases at lower temperature and the peaks occur at higher field values. Attenuation measurements in a pulsed magnetic field demonstrated that the attenuation follows the magnetic field change in a few microseconds. A theoretical explanation of these experimental results based on the Stoner-Wohlfarth model has been proposed. The low-frequency susceptibility and the imaginary part of the high-frequency susceptibility were calculated in this model and were found to be in qualitative agreement with the experimental curves for the low-frequency susceptibility and the high-frequency surface wave attenuation, respectively. The explanation of the attenuation in this model required an interaction mechanism between the magnetization and the surface wave. Three possible mechanisms are considered in this paper. One of them, the change of the anisotropy energy due to the strain of the wave, appears to give the right order of magnitude for the effect.
Comparison of the experimental results of inverted Lamb dip in a 633-nm He-Ne laser with the theory based on the strong signal formulation
Authors: Kuroda Kazuo , Ogura Iwao
Published: February 2003

The experimental results of the inverted Lamb dip of a 633-nm He-Ne laser with a neon discharge-absorption cell are compared with the theoretical results in detail. The rate equation approximation which is valid for a wide range of the saturation depth is used as a theoretical basis. After the fitting procedure, the theoretical curve approximates the experimental result in good agreement. The parameters, such as the central frequency, the homogeneous linewidth, and the saturation parameter are determined from the best-fit condition. The 12±3-MHz/Torr pressure shift of the central frequency of the laser transition is obtained for 5.3:1 He-Ne mixture.
Ultraviolet light amplification by the cool green phosphorus chemiluminescence flame: PO-diatomic and PO-excimer electronic excited states
Authors: VanZee Richard J. , Khan Ahsan U.
Published: February 2003

Ultraviolet light amplification by the phosphorous chemiluminescence flame is observed in the 200–400-nm region. PO γ-system emission is identified in the light amplification spectrum. Gaps in the amplification spectrum are attributed to the forbidden transitions: 4II→X2II of PO at 30 590 cm−1 and 5Γ1→1,3Γ0 of PO excimer at 28 117 cm−1. Light amplification by the phosphorus chemiluminscence system is interpreted as an incipient lasing action.
Direct observation of laser beam filamentation in an underdense plasma
Authors: Joshi Chan , Clayton Christopher E. , Yasuda Akio , Chen Francis F.
Published: February 2003

By using optical Fourier-transform techniques, we have obtained photgraphs of plasma density striations in the focal region of a 350-MW CO2 laser beam focused by an f/7.5 lens into a plasma with density 0.1nc . The observed spatial frequency and the estimated density change imply that the striated regions are also the regions of self-trapped radiation channels.
Electromagnetic implosion of metal liners
Authors: Marrs R. E. , Wira K.
Published: February 2003

Cylindrical aluminum shells have been imploded at velocities ≳2 mm/μs in a Z-pinch discharge driven by a 100-kJ capacitor bank. The velocity and symmetry of the imploding liners were determined from flash x-ray pictures, and the compression of an axial magnetic field was measured with pickup coils. The results are consistent with numerical calculations of the implosion dynamics. The implosions are symmetric and stable when strongly driven. Buckling is observed in slower implosions
Optimized three-component dye mixtures for achromatic guest-host liquid-crystal displays
Authors: Scheffer Terry J.
Published: February 2003

We apply the matrix representation technique to determine the concentrations of three dye components in the liquid-crystal mixture needed to make a black-and-white guest-host display. This method employs the Newton-Raphson iterative process to match the tristimulus values of the mixture to the tristimulus values of the achromatic color. The color matches are thus metameric rather than spectral and hence depend upon the illuminant type. We give examples which show that practically any yellow, red, and blue dye components can be mixed to obtain a neutral color for a given illuminant, but that such mixtures generally have some coloration when viewed under other illuminant types. By extending the matrix representation technique into six dimensions, we show that it is possible to select optimum dye components according to the width and centroid wavelength of their absorption curves. These optimized components minimize the sensitivity of the neutral color to changes in illuminant type. We demonstrate that displays can be made with three optimized dye components which are achromatic under the extremes of both daylight and incandescent illumination. The absorption bands of these optimized dye components must be about 100 nm wide or wider, and the centroids of their respective absorption curves must be located within the ranges 445±10, 540±10, and 650±10 nm. We find that Heilmeier- and White-and-Taylor-type displays generally require different dye formulations. Examples are given for both display types.
Determination of Burgers vectors of dislocations in synthetic quartz by computer simulation
Authors: Epelboin Y. , Patel J. R.
Published: February 2003

Dislocations in highly perfect quartz crystals have been characterized by correlating experimentally observed section patterns with computer simulations. The Burgers vector observed is the shortest translation vector of the quartz lattice. In cases, such as quartz, where the simple geometrical criteria fail, computer simulation methods are a powerful aid in establishing the Burgers vector of dislocations.
Sensing characteristics of tin oxide thick film gas sensor
Authors: Oyabu Takashi , Osawa Tetsuo , Kurobe Toshiji
Published: February 2003

Thick film gas sensor of tin oxide based materials has been developed by screen printing method, and its sensing characteristics have been examined for some gases. To perform the method, tin oxide fine power with the size about 0.5 μm in diameter was prepared through the fine crystallization in liquid phase, and was mixed with glass frits as a binder and palladium or platinum as a catalyst. This mixed material is used as the paste. With the screen printing method using the paste, the mass production and the sufficient mechanical strength of the sensor can be achieved. The gas sensor of tin oxide incorporated with palladium black as the catalyst shows an excellent selective detection for ethanol and hydrogen gases at the specimen temperature of 250 °C. And the platinum black-doped tin oxide sensor has also a high sensitivity to both gases at the temperature over 350 °C.
Theoretical analysis of single-mode AlGaAs-GaAs double heterostructure lasers with channel-guide structure
Authors: Yang J. J. J. , Dupuis R. D. , Dapkus P. D.
Published: February 2003

This study is concerned with electromagnetic wave propagation in AlGaAs-GaAs double heterojunction lasers with a channel-guide structure. An analytical solution to Maxwell’s equations in a structure of sufficient complexity to describe a channel-guide five-layer laser is presented. Numerical calculations based on the solutions were made for a specific set of parameters obtained from a channel-guide laser grown by metal-organic chemical vapor deposition (MO-CVD) in our laboratory. Some analytical predictions for a fundamental mode oscillation are also included.
Highly reliable and mode-stabilized operation in v-channeled substrate inner stripe lasers on p-GaAs substrate emitting in the visible wavelength region
Authors: Hayakawa T. , Miyauchi N. , Yamamoto S. , Hayashi H. , Yano S. , Hijikata T.
Published: February 2003

Highly reliable and mode-stabilized operation is realized in v-channeled substrate inner stripe (VSIS) lasers emitting in the visible wavelength region. The VSIS lasers with emission wavelengths of 725–790 nm have low threshold currents of 40±5 mA and reproducibly provide fundamental transverse and single longitudinal mode operation up to 20 mW/facet cw. These performances result from the transverse-mode stabilization by a built-in optical waveguide which is self-aligned with an internal current confining channel. Accelerated lifetests and the statistical characterization of reliability were performed on VSIS lasers emitting at 780 nm. The median lifetimes are estimated to be 1.1×106 h for 5 mW/facet, 4.8×104 h for 10 mW/facet, and 1.3×104 h for 15 mW/facet operations at 25 °C. In addition, almost no degradation in modal characteristics has been observed in the devices operated at 5 mW/facet at 50 °C for 4000 h, up to the present. Photoluminescence study was performed in order to clarify the effects of the Te-doped cladding layer on the quality of the active layer.
A perturbation theory for acoustoelastic effects
Authors: Husson D. , Kino G. S.
Published: February 2003

A new perturbation theory for acoustoelastic effects has been derived. The purpose is to deal with inhomogeneous stress states and perturbations of focused acoustic wave beams or wave guide modes. Energy is expressed in terms of third-order elastic constants. Results are derived for perturbation of plane shear waves, plane longitudinal waves, and focused shear and longitudinal wave beams.
Plasma temperature determination from the total intensity of a self-reversed spectral line
Authors: Karabourniotis D. , Karras C. , Drakakis M. , Damelincourt J. J.
Published: February 2003

A method is introduced for determining the temperature of a high-pressure gas discharge from the total intensity of a self-reversed spectral line, if the plasma is in local thermodynamic equilibrium. The structural characteristics of the plasma are determined from observable parameters of the line on the basis of a simplified model for the light source. An application is given with the self-reversed mercury lines 5461, 4358, and 4047 Å emitted from a high-pressure mercury discharge.
Harmonic light emission from CO2 laser-produced plasmas: A link with Brillouin scatter
Authors: Mitchel G. R. , Pépin H. , Johnston T. W.
Published: February 2003

The calorimetric and spectral behavior of second-harmonic light emitted from CO2 laser-produced plasmas in backscatter and near the specular angle is difficult to reconcile with electron Langmuir-ion acoustic wave parametric decay. Resonance absorption and subsequent frequency doubling cannot be excluded, but any model including them is much more complicated than can be supported by the data. Rather, the observed small, angle-dependent frequency shifts of second harmonic light correlate with the frequency shifts of Brillouin scatter at those angles. This suggests that the frequency upconversion is done in regions of the plasma with strong ion acoustic density fluctuations, likely produced by Brillouin scatter.
Characterization of plasma-deposited silicon nitride films by Auger electron spectroscopy and electron energy loss spectroscopy
Authors: Hezel R. , Lieske N.
Published: February 2003

Valence and core electron excitation spectra for amorphous Si nitride films prepared in a glow discharge plasma were measured by low energy electron energy loss spectroscopy (ELS). For comparision, the corresponding spectra were measured on hydrogenated amorphous silicon (a-Si:H). The elemental composition of these films was analyzed using Auger electron spectroscopy (AES). In order to evaluate the influence of hydrogen upon the spectra, comparison of the as-deposited plasma films was made (i) with plasma films annealed at 900 °C, (ii) with pyrolytic Si nitride, and (iii) with ion-bombarded crystalline silicon. Significantly different ELS spectra were obtained for the plasma-deposited films compared to the hydrogen free samples. For plasma Si nitride a new energy loss peak at 8.6 eV was detected and related to the presence of chemically bonded hydrogen. The interband excitations at high energies (EL ≳10 eV) due to Si-N bonds were found to be less pronounced compared to chemical vapor deposited (CVD)Si nitride. For plasma silicon a new energy loss at 8.5 eV was measured which could be attributed to Si-H bonds. The AES experiments revealed a pronounced gettering effect for impurities in plasma Si nitride.
Optical absorption reduction in Bi1Lu2Fe5O12 garnet magneto-optical crystals
Authors: Nelson G. L. , Harvey W. A.
Published: February 2003

The potential magneto-optical efficiency of Bi1Lu2Fe5O12 garnet grown on Gd3Ga5O12 substrates has been significantly improved through doping of the melt to reduce optical absorption. Order of magnitude reductions in near infrared absorption resulted in figure of merits of 26°/dB at 1.06 μM, 180°/dB at 1.15 μM and an estimated 100°/dB at 1.3 μM.
The mechanism of (Hg,Cd)Te anodic oxidation
Authors: Janousek Bruce K. , Carscallen Richard C.
Published: February 2003

It has been determined that anodic oxidation of (Hg,Cd)Te occurs via a dissolution-precipitation mechanism followed by a bulk growth process which involves either interstitial transport of metal cations and/or hydroxyl anion transport via successive jumps. The initial film formation can be understood at least partially in terms of electrochemical parameters and, therefore, can be controlled in a rational manner. For example, stirring the anodization solution during dissolution prohibits film formation due to an increase in the rate of diffusion of ionic species away from the anode. MOS structures fabricated incorporating this electroetch in the passivation process show unique properties which provide evidence for a direct correlation between initial oxide formation and the resultant (Hg,Cd)Te surface electronic properties.
Improved spatial resolution diffusion length measurements in imperfect silicon
Authors: Bell R. O. , Hanoka J. I.
Published: February 2003

The Electron Beam Induced Current (EBIC) method for measuring the minority carrier diffusion length L in semiconductors has been modified to allow for a significant improvement in spatial resolution along the surface of the sample. With this modification, L at a particular point can be determined with spatial resolution close to the limit determined by the electron beam spreading in the semiconductor. The method is particularly suitable for imperfect silicon with L on the order of 50 μm, that is, for silicon often used for solar cells. The use of the method for silicon ribbon which contains dislocations and grain boundaries is illustrated.
Interface state trapping and dark current generation in buried-channel charge-coupled devices
Authors: Saks Nelson S.
Published: February 2003

The effects of interface states on charge transfer efficiency (CTE) are compared in surface-channel and buried-channel charge-coupled devices (CCDs). Although the buried-channel CCD was developed partly to exclude the interaction between signal charge and interface states, this interaction will occur when the amount of signal charge exceeds the buried-channel storage capacity. For this situation, it is shown that CTE measurements may be used to directly and accurately determine the density of interface states in 4-phase buried-channel CCDs, using the same techniques previously developed for surface-channel devices. These measurements have been applied to several different N-buried-channel CCDs, some of which have been fabricated with radiation-hardened oxides, which have been exposed to ionizing radiation. Data from these devices reveal a linear dependence of the interface state electron-hole pair generation rate (i.e., CCD dark current) on the density of interface states. This dependence is the same for all devices studied and does not depend on whether the interface states are intrinsic, created by radiation, or reduced by annealing. From these data, a value for the geometric mean of the interface state electron and hole capture cross sections √(σn σp ) of 5.5×10−16 cm2 is obtained, in excellent agreement with values in the literature obtained by ac conductance and gate-controlled diode measurements.
Compositional changes adjacent to grain boundaries during electrical degradation of a ZnO varistor
Authors: Chiang Yet-Ming , Kingery W. D. , Levinson Lionel M.
Published: February 2003

Compositional changes adjacent to grain boundaries in heavily degraded samples of a ZnO varistor containing the additives Bi and Co have been observed with the scanning transmission electron microscope. A marked asymmetry in the distribution of Bi and Co with respect to the physical location of the boundary is found, consistent with the accumulation of mobile cations on one side of the boundary under the influence of a dc electric field.
Efficient infrared upconversion in GaP
Authors: Gundersen M. A. , Yocom T. A. , Snyder P. G. , Williams P. F.
Published: February 2003

Mechanisms for linear conversion of infrared to visible were investigated in extrinsic GaP. Efficient (1%) conversion of 10 micron to visible was observed in GaP:Zn,O. Several device applications are discussed and a quantum counter scheme involving III–V photocathodes is presented.
Highly conductive and transparent amorphous tin oxide
Authors: Jousse D. , Constantino C. , Chambouleyron I.
Published: February 2003

The physical properties of chemically sprayed tin oxide films have been investigated. The optical and transport behavior of both amorphous and polycrystalline material depends on the reaction temperature. Amorphous films deposited at very low temperatures (Ts=220 °C) possess a conductivity as high as that of the polycrystalline layers. Hall effect measurements and compositional analyses of those amorphous films show that nonintentional chlorine doping is responsible for the increased conductivity. Optical transmission in the visible region of the spectrum is almost as good in amorphous as in polycrystalline material. An antireflecting coating of amorphous tin oxide with an optical gain of 40% has been achieved on silicon wafers. Furthermore, film thickness homogeneity broadens the field of application to various optoelectronic devices.
Anomalous deflection of irradiated cantilevers undergoing blistering
Authors: Primak William , Monahan Emmet
Published: February 2003

Plates which are implanted with ions that segregate to form gaseous occlusions may show a succession of net surface compressional stress and net tensional stress as radiation blistering occurs and the surface exfoliates. Data are given for 140-keV helium ion bombardments of Synroc B, a ceramic compact intended for the incorporation and storage of radioactive wastes, and two of its constituents: perovskite and zirconolite.
Hydrogen passivation of laser-induced defects in germanium
Authors: Pearton S. J. , Tavendale A. J.
Published: February 2003

The passivation by hydrogen of acceptor level defects (Ev +0.17 eV, Ev +0.36 eV) caused by the laser irradiation of single crystal n-type Ge (ND −NA =1.5×1016 cm−3) has been observed using deep level transient spectroscopy. The point defects are neutralized by a 10-min exposure to atomic hydrogen at 150 °C; using conventional thermal annealing, a 2-h heat treatment in H2 at 280 °C is required to produce the same effect.
1.5 μm InGaAsP/InP buried rib waveguide lasers
Authors: Yuasa Tonao , Onabe Kentaro , Ide Yuichi , Isoda Yoichi , Hayashi Junji , Furuse Takao , Sakuma Isamu , Matsumoto Yoshishige
Published: February 2003

InGaAsP/InP double heterostructure lasers with buried rib waveguide structure in which p-quaternary rib waveguide layers surrounded by n-InP are formed adjacent to the active layers, are proposed for the 1.5–1.6 μm wavelength range and have been successfully fabricated by two-step liquid phase epitaxial methods combined with a controlled mesa etching technique. In this structure, the rib waveguide layer can provide carrier confinement as well as lateral optical confinement. The low threshold current of 50 mA was obtained with the external differential quantum efficiencies of about 42% and 36% under pulsed and cw operation, respectively. Stable fundamental transverse mode operation was achieved up to three times the threshold current, and single longitudinal mode cw operation was also observed up to 1.5 times threshold current.
Frequency doubling in a LiNbO3 thin film deposited on sapphire
Authors: Hewig G. H. , Jain K.
Published: February 2003

An rf-sputtered thin film of LiNbO3 on a sapphire substrate was used as a waveguide for optical frequency doubling. Employing a Nd:YAG laser and a tunable dye laser, whose output was used to pump a stimulated Raman cell, the TMω0 → TM2ω2 up-conversion process was investigated in detail, and the phase-matched nature of this process was demonstrated. The conversion efficiency was estimated to be about 10−3.
Characterization of (Ti0.65Nb0.35)O2 compound as a source for Ti diffusion during Ti:LiNbO3 optical waveguides fabrication
Authors: Armenise M. N. , Canali C. , De Sario M. , Carnera A. , Mazzoldi P. , Celotti G.
Published: February 2003

During Ti:LiNbO3 integrated optical waveguide fabrication the (Ti0.65Nb0.35)O2 forms at temperatures ranging from 700 to 950 °C, after the Ti oxidation which occurs owing to Ti reaction with oxygen atoms of the surrounding atmosphere and/or of LiNbO3 substrates. The (Ti0.65Nb0.35)O2 compound has been characterized using scanning electron microscopy, secondary ion mass spectrometry, Auger electron spectroscopy, Rutherford backscattering in channeling conditions, and x-ray diffraction. Results show that the (Ti0.65Nb0.35)O2 phase grows epitaxially on both Z- and Y-cut substrates, the quality depending on both annealing atmosphere and film thickness. The film behaves as a real source for Ti diffusion and consequently is consumed at increasing annealing temperatures and/or times. We did not observe Li-Ti-O compounds, although a small amount of Li was detected in the surface layer.
Orientation-dependent electrodeless breakdown of gas in glass tubes
Authors: Curzon F. L. , Friedmann D. E. , Feeley M.
Published: February 2003

Observations show that the frequency of breakdown of the tube, when it is immersed in a 60-Hz alternating field, is determined by the potential drop along the tube, an effect which can be explained by assuming that the tube wall acts as a lossless guide for the breakdown discharge.
The effect of interfacial traps on the stability of insulated gate devices on InP
Authors: Lile D. L. , Taylor M. J.
Published: February 2003

Measurements of the change in channel current with time following application of a step voltage to the input of enhancement-mode insulated gate Field-Effect Transistors (FETs) on InP are reported. The data indicate that, following an initial steady-state period, the current varies exponentially with inverse temperature and logarithmically with time. This behavior suggests that a thermally activated tunneling process is responsible for the drift in these structures but leaves unanswered the question of the origin of the states responsible. It does appear, however, that, whereas its complete removal may be counterproductive, the proper preparation of the native oxide layer beween the InP and the deposited dielectric may be determinative in the establishment of a low-trap density interface.
Study of magnetism in fine particles of ferric hydroxysulfate by Mössbauer spectroscopy
Authors: Morais P. C. , Neto K. Skeff
Published: February 2003

Experimental results of magnetization and Mössbauer measurements on ferric hydroxysulfate are presented. The method developed in the preparation and characterization of samples is discussed. In the present paper the magnetic properties are explained taking into account the pattern of particle size distribution of the samples in the region of superparamagnetism. The model is described in the molecular-field approximation for randomly dilute magnets.
Optical properties of silver films deposited at low temperatures
Authors: McBreen P. H. , Moskovits M.
Published: February 2003

The reflectance spectrum of quench-condensed silver films was studied as a function of film temperature and thermal history, using an uv-visible stress-modulator ellipsometer. Films deposited at low temperatures were found to exhibit an anomalous absorption in the visible region of the spectrum. This absorption was attenuated and receded to lower wavelengths as the film was annealed. The spectra were successfully reproduced by assuming that films deposited at low temperatures were rough and that the roughness could be modeled by means of a two-dimensional metallic colloid whose optical conduction resonance accounted for the anomalous absorption. The relationship between the surface morphology of these low-temperature condensed films and their ability to give rise to surface-enhanced Raman scattering is discussed.
Donor discrimination and bound exciton spectra in InP
Authors: Dean P. J. , Skolnick M. S.
Published: February 2003

We report detailed studies of the near-gap photoluminescence (NGPL) of refined vapor phase epitaxial (VPE) InP layers, selected to afford the best chance of resolving structure arising from the small chemical shifts between different donor species. Good general correlation was found between electrical data and the quality of the NGPL spectra in a survey of 50 crystals. In particular, the quality of the D+,X bound exciton (BE) and the ‘‘two-electron’’ donor satellites (TEDS) of the D0,Xn BE luminescence components correlated with the 77 °K mobility, known to be dominated by ionized impurity scattering. Use of selective excitation with a narrowed line from a dye laser and magnetic fields to obtain spectral components less subject to inhomogeneous broadening is discussed. The magnetic field is most effective in narrowing the TEDS components. The crystal quality, expressed mainly through the total concentration of shallow donors and acceptors, is apparently just inadequate to obtain line narrowing by selective excitation even in the best available crystals of VPE InP. However, selective excitation is still helpful in removing background luminescence and in enhancing luminescence satellites of particular D0, Xn BE components. Inhomogeneous broadenings of the various electronic states are contrasted. Measurements on both the D0, Xn′ TEDS and D+, X show evidence of only a single donor in the few samples with optimum linewidths. The general difference between these NGPL findings and far infra-red photoconductivity (FIRPC) measurements results from differential incorporation rates for the two most likely inadvertent shallow donor species, Si and S, during the growth of the VPE layers. The energy of the single NGPL donor suggests that it may be Si according to available FIRPC data. Resonantly enhanced Raman scattering (RERS) is observed both amongst the TEDS and through pure electron spin flip transitions. The D+, X and D0,h spectral features are well resolved, and Zeeman spectroscopy is consistent with the D+, X attribution. Approximate electron and hole g values are derived, together with more accurate values of ge from the RERS and of m*e from the TEDS magnetic splittings.
The effects of impurity diffusion and surface damage on oxygen precipitation in silicon
Authors: Fair R. B.
Published: February 2003

The rate of oxygen precipitation in Czochralski-grown silicon with oxygen supersaturation ratios s>5 and s<5 at 1000 °C was studied as a function of surface processing. Reference samples were compared with samples diffused with high-concentration phosphorus or arsenic layers in N2 or O2 ambients. Oxygen precipitation was also studied in samples with air-abraded surfaces. It was found that for s<5, oxygen precipitation was inhibited by the presence of a P diffusion, but not by As diffusion. For s>5 the concentration of oxygen in SiO2 precipitates in P diffused wafers did not equal the change in interstitial oxygen, and a high density of stacking faults were seen in the bulk. It is concluded that the point defects generated from damaged surfaces and P-diffused surfaces are not the same as those generated from an undoped surface during oxidation. A model describing the effect of surface-generated vacancies and silicon self-interstitials on oxygen precipitate nucleation and growth is discussed.
Cadmium telluride films on foreign substrates
Authors: Chu T. L. , Chu Shirley S. , Pauleau Y. , Murthy K. , Stokes E. D. , Russell Phillip E.
Published: February 2003

Thin films of cadmium telluride have been deposited on mullite and tungsten-coated graphite substrates at 500–700 °C by the direct combination of cadmium and tellurium in a hydrogen atmosphere. Their microstructure and crystallographic properties were studied. The importance of controlling the Cd/Te molar ratio in the reaction mixture to obtain nearly stoichiometric films was demonstrated. The electrical properties of nonstoichiometric and nearly stoichiometric films on mullite substrates were measured by the van der Pauw technique. Schottky barriers were used to measure the electrical properties of cadmium telluride films on W/graphite substrates. The effective intragrain minority carrier diffusion length in n-type films was measured by the scanned electron beam method using a Schottky barrier structure.
A study of defects in amorphous silicon films
Authors: Dannefaer S. , Kerr D. , Hogg B. G.
Published: February 2003

Positron lifetime measurements have been performed in an investigation of amorphous silicon films deposited on single-crystal silicon wafers. The amorphous films were produced by evaporation in vacuum or by sputtering in an atmosphere of either pure argon or a mixture of argon and fluorine. All films gave rise to a new lifetime component τ2 having values in the range of 400 to 500 ps. As many as 70% of the positrons annihilating in the film were calculated to be trapped by defects in the film. During isochronal annealing, the τ2 component disappeared around 700 °C for the evaporated films, while it persisted at least up to 1300 °C for the sputtered films. Another lifetime with a value of 2 ns was also observed. This lifetime had a constant intensity of 0.2 to 0.3% for both evaporated silicon and sputtered silicon using argon gas. For the sputtered film using both argon and fluorine, the intensity of this component was increased by a factor of 10 after annealing at 1100–1300 °C.
Quantitative measurements of recombination enhanced dislocation glide in gallium arsenide
Authors: Maeda Koji , Sato Miwa , Kubo Akihisa , Takeuchi Shin
Published: February 2003

Effects of 30-keV electron-beam irradiation on dislocation glide were investigated for α- and β-dislocations in bulk n-GaAs single crystals by cathodoluminescence microscopy using a scanning electron microscope with a bending apparatus in it. At high temperatures above Tc, the electron irradiation has no effect on dislocation velocity v and the temperature dependence v(T) follows an Arrhenius formula v0d exp(−Ed/kT). Below Tc, v(T) under irradiation breaks off the above relation and is enhanced following another Arrhenius formula v0i exp(−Ei/kT). The enhancement effect is completely reversible for individual dislocations. From measurements of irradiation intensity I and stress τ dependences, the dislocation velocity was found to be expressed by a unified formula v=v0d exp[−Ed(τ)/kT ]+v*i(I/I0)0.84  exp{−[Ed(τ)−ΔE]/kT}, which is explained by neither a heating effect nor a charge state effect, but the recombination enhanced defect motion (REDM) mechanism. In view of the REDM mechanism, the ΔE (∼0.7 eV for α-dislocations and ∼1.1 eV for β-dislocations) is related to the energy released upon a nonradiative recombination of generated excess carriers at the dislocations. Based on this postulation, the electronic energy states associated with dislocations are discussed in conjunction with previous, related studies.