bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of line-sampling multiframe stroboscopy for dynamic observation of magnetic domains in Si steels
Authors: Shimizu R. , Mase H. , Ikuta T. , Yabumoto M. , Matsuo Y. , Nozawa T.
Published: July 2002

A line-sampling multiframe stroboscopic observation system was attached to a commercial-type 200-kV scanning electron microscope for dynamic observation of ferromagnetic domains in grain-oriented 3% silicon steels with orientation near (110) [001]. This technique has enabled the individual stroboscopic image, at different phases of drive field, to be observed on a display tube simultaneously, leading to a more comprehensive understanding of core-loss characteristics of the silicon steels magnetized at commercial frequency in practical use. The observation has clearly revealed that uniform displacement of domain walls according to the alternating magnetization at commercial frequency leads to lower core losses during operation.
Open-circuit, photoinduced aging of polycrystalline CdSe photoelectrodes in liquid-junction solar cells
Authors: Garuthara Rohana , Tomkiewicz Micha
Published: July 2002

We utilized photoluminescence (PL) spectroscopy under in situ conditions to study slow chemical changes on CdSe/polysulfide liquid-junction solar cells, as a function of aging procedures. The aging conditions were (1) focused light under open-circuit conditions; (2) focused light under short-circuit conditions; and (3) total darkness. For the first time we report that cells do age under open-circuit conditions, and that the decrease in stability and the changes in the PL, with aging time, are similar to those observed for cells which are aged under short-circuit conditions. At the initial stages of the light-induced aging processes, changes in the defect concentration in the photoanode were observed. In addition to the CdSe PL there is a broad PL in the spectral range of 1.7 eV (CdSe) up to 2.4 eV (CdS). This PL is identified to be due to the mixed phase compound of CdSe1−xSx. At the final stages of the aging processes characteristic CdS Raman spectra was detected. Such PL and Raman changes were not detected for the cells which were aged under total darkness. Under ex situ conditions the envelope of two PL spectra due to CdSe and CdSe1−xSx compound changes with the excitation light. Variation of efficiency and PL peak intensity with aging time shows a good correlation between PL peak intensity and the efficiency of the cell.
The nature of p-type conduction in Ca-doped yttrium iron garnet films
Authors: Scarinci F. , Tucciarone A. , Antonini B. , Paroli P.
Published: July 2002

Conductivity and magnetic circular dichroism (MCD) in the near infrared are measured in p-type Ca-doped yttrium iron garnet films. Two MCD components are known to arise in these films, associated with Ca2+ substitution: one peaked at about λ=1.2 μm, the other one at λ=1.6 μm. We show that the center responsible for the λ=1.6 μm component is the only one responsible for the remarkable electrical properties recently reported for these films. The other center provides charge compensation of Ca2+ which is uneffective from the point of view of conduction which may be thus considerably enhanced by inhibiting formation of this center.
Use of alpha sources for hydrogen analysis
Authors: Lanford W. A. , Wielunski L. , Benenson R. E.
Published: July 2002

Nuclear recoil analysis for hydrogen in thin films is demonstrated using radioactive alpha particle sources.
Cation vacancy formation energies in liquid-phase-epitaxial Hg1−xCdxTe
Authors: Shin S. H. , Khoshnevisan M. , Morgan-Pond C. , Raghavan R.
Published: July 2002

Experimental measurements of the cation vacancy formation energies (Ef) of Hg1−xCdxTe were carried out by Hg-annealing and rapid quenching to room temperature, followed by Hall measurements at 77 K. Our observations show that one charge state vacancy is dominant, so that the fractional number n of cation vacancies at temperature T is related exponentially to the energy Ef required to create one vacancy, n=A exp(−Ef/kT). No appreciable temperature dependence of Ef due to temperature variation of the ionization levels and the self-consistent Fermi level is seen. Our measured value for the activation energy is found to be Ef=0.9±0.1 eV, for Hg1−xCdxTe with x=0.21, 0.3, and 0.43. This value is found to be nearly independent of Cd composition x. Theoretical calculations of the p-type carrier concentrations due to cation vacancies in Hg0.8Cd0.2Te yield results which are in good agreement with experimental data. These modeling calculations predict the cation vacancies to be predominantly doubly ionized species at 77 K.
Diffusion and second-order reaction in a cylindrical fiber
Authors: Weling Fredy
Published: July 2002

Many chemical reactions can only take place after a diffusion process involving one of the reagents. This work examines how a reagent A diffuses into a cylindrical fiber containing a uniform distribution of impurities B, when an irreversible second-order reaction A+B→AB can take place. The reaction is considered to be the rate-controlling process. The determination of the different concentration profiles requires the solution of a system of nonlinear partial differential equations for which an approximate solution is derived. It is shown how the diffusion profile of the reagent is modified by the reaction and how the formation of the reaction product depends on the diffusion process. This interdependence is illustrated by some specific examples. For small values of time the concentrations of the diffusing substance A lie below the values one would expect if no reaction took place. This difference depends on the reaction constant k and the number of impurities. The analysis of the differences between in- and out-diffusion experiments is one way of measuring the influence of the reaction on the diffusion process. One possible application of the present model is the description of hydrogen diffusion and hydroxyl formation in optical fibers.
Deposition and characterization of p-type cadmium telluride films
Authors: Chu T. L. , Chu Shirley S. , Firszt F. , Naseem H. A. , Stawski R.
Published: July 2002

The deposition of CdTe films on foreign substrates by the direct combination of the elements in a gasflow system has the flexibility that the conductivity type and electrical resistivity of the film can be controlled by adjusting the composition of the reaction mixture. The deposition and properties of p-type CdTe films are emphasized in this paper because of its importance in thin-film solar cells. Graphite, W/graphite, mullite, and Corning 7059 glass were used as substrates for the deposition process. While CdTe films deposited on W/graphite and mullite substrates could be n or p type, depending on the composition of the reaction mixture, all films deposited on graphite substrates were p type, irrespective of the reactant composition, substrate temperature, or the purification of graphite, suggesting that carbon is electrically active in CdTe. The resistivity of p-type CdTe films on W/graphite and mullite substrates has been controlled for the first time by (1) using a Cd-deficient reaction mixture, and (2) adding dopants (AsH3 or PH3) to the reaction mixture. The resistivity versus composition relation was studied in detail. The optical properties of nearly stoichiometric, Cd-deficient and Te-deficient CdTe films were also investigated.
Properties of a KrF laser with atmospheric-pressure Kr-rich mixture pumped by an electron beam
Authors: Suda Akira , Obara Minoru , Noguchi Akira
Published: July 2002

Atmospheric pressure operation of a KrF laser is suitable for large-aperture laser modules in which several technical limitations on the ICF driver design are overcome by the use of aerodynamic windows instead of the conventional solid optical windows. We experimentally studied atmospheric-pressure operation of the KrF laser pumped by 50-ns electron beams. For a 1-atm mixture of Kr and F2 without diluent, a specific output energy of 4.2 J/1 was obtained with an intrinsic efficiency of 5%, which was comparable to that from normal 10% Kr mixture. According to the results of fluorescence measurements, a large amount of Kr2F* is formed via three-body collisional quenching by high-concentration Kr even in the atmospheric-pressure mixture. Code calculations indicate that a higher excitation rate improves the intrinsic efficiency by reducing three-body quenching especially in Kr-rich mixtures, and that a specific energy in excess of 10 J/1 is realizable.
Current transport and structural model for Li-diffused CdTe low-resistance contacts
Authors: Lee Chun-teh , Bube Richard H.
Published: July 2002

Low-resistance contacts to p-type CdTe have been made by diffusing Li into the CdTe surface before evaporation of Au as the contact metal. The best contact showed a contact resistivity of 2.1×10−3 Ω cm2 at room temperature, and 3.7×10−2 Ω cm2 at liquid N2 temperature, the lowest values reported to date for p-type CdTe. Surface analysis of the Li-diffused surface indicates that the crystalline structure of the CdTe surface has been greatly disturbed and a Te-rich surface layer is produced. Te tends to out-diffuse with time through the Au layer to restore the stoichiometric Te/Cd ratio in the CdTe. A metal-insulator-semiconductor tunnel diode model qualitatively explains the observed current-voltage characteristics of the contacts. Numerical analysis shows good agreement between the calculated contact resistivities and the experimental data. Surface states and fixed charges in the insulator play an important role in the current-voltage characteristics through the modification of metal work function and the distribution of the applied voltage. Contact resistivity increases with decreasing hole concentration, but the effect is small if a high enough density of interface states dominates the properties of the contact.
Infrared characterization of aluminum and hydrogen defect centers in irradiated quartz
Authors: Lipson Herbert G. , Kahan Alfred
Published: July 2002

As-received and 60Co-irradiated cultured quartz is characterized using low-temperature near-infrared Fourier spectroscopy, and peaks associated with as-grown hydroxide (OH) and aluminum hydroxide (Al-OH) point-defect centers are measured. Defect-center distributions are determined from scanning small crystal regions parallel or normal to the crystal-growth axis. Large variations in point defects are observed arising from variations in substitutional and interstitial impurity concentrations along the crystal-growth axis. For the initial radiation doses as-grown OH decreases uniformly across the crystal and forms Al-OH, but Al-OH peak strength varies considerably in different crystal sections. This indicates the possibility of radiation-induced hydrogen diffusion over large distances to compensate nonuniformities in aluminum-ion distribution. With increasing dose as-grown OH may stabilize to a constant level in some crystal regions but deplete in other sections. For some crystals, Al-OH continues to form even after all as-grown OH is depleted, indicating an additional internal hydrogen-ion source. Sweeping (electrodiffusing) an irradiated sample in an air atmosphere restores as-grown OH, retains the radiation-induced Al-OH, and in samples with high as-grown OH concentrations creates a series of small bands in the frequency range of 3450 to 3625 cm−1.
Depth profile and thermal annealing behavior of Bi implanted into an Al/Ti bilayer structure
Authors: Olivieri C. A. , Behar M. , Fichtner P. F. P. , Zawislak F. C. , Fink D. , Biersack J. P.
Published: July 2002

600-keV Bi was implanted into an Al/Ti bilayer structure. There is good agreement between the Bi depth profile measured by Rutherford backscattering and corresponding theoretical prediction (Monte Carlo code trim). After annealing at low temperatures, the pronounced structure of Bi concentration at the Al/Ti interface vanishes, and the buildup of a surface precipitation is observed. At 500 °C annealing, strong Bi diffusion sets in, associated with the intermixing of the substrate components. A thin oxide layer present at the surface acts as a diffusion barrier for Bi, resulting in Bi segregation at the oxide/alloy interface.
Temperature and stress dependence of Young’s modulus in semiconducting barium titanate ceramics
Authors: Mader Gerhard , Meixner Hans , Kleinschmidt Peter
Published: July 2002

In order to study the temperature and stress dependence of Young’s modulus in semiconducting barium titanate ceramics, the longitudinal sound velocity was measured at a frequency of 5 MHz in the temperature range of 20–180 °C. It is striking that at temperatures above the Curie point (Tc=120 °C) the sound velocity reaches values that are 10–20% higher than those at room temperature. Furthermore, a shift of the Curie point of about 2×10−8 K/Pa is observed if uniaxial stress is applied perpendicular to the sound propagation. Both effects can be understood by means of the phenomenological theory of Devonshire.
Mobility and diffusivity for vacancy diffusion in a simple cubic edge dislocation
Authors: Stark J. P.
Published: July 2002

A model of an edge dislocation in a simple cubic crystal is constructed for a [0–10] Burgers vector where vacancy transport along the edge of the extra half plane of ions is considered. The model considers a tight-binding approximation of the vacancy to the compressed region of the core and carries the calculation to the limit of an infinite length of dislocation. As a consequence the limit of the tight-binding approximation becomes exact. Previous comparison of the model with a loosely bound model illustrated the applicability of the tight-binding approximation in all circumstances. Therefore, the model is believed to quite reasonably represent the physical situation. The results of consequence include, unexpectedly, the increase without bounds of the diffusivity and effective charge for electromigration in the limit where the correlation factor becomes zero. The mobility is found to be proportional to the reciprocal of the correlation factor for all jump-frequency responses causing the unusual behavior. The diffusivity becomes large because the number of available vacancies diverges.
Penning ionization ternary gas mixtures for diffuse discharge switching applications
Authors: Nakanishi K. , Christophorou L. G. , Carter J. G. , Hunter S. R.
Published: July 2002

The increase in the total ionization produced by high-energy α particles in Ar/C2F6 mixtures, which have conduction and insulation properties appropriate for use in diffuse discharge switching applications by addition of low ionization energy additives has been quantitatively studied. The energy to produce an electron-positive ion pair (ip) W in C2F6 was found to be 34.7 eV/ip; this rather high value is attributed to the large cross section for electron impact-induced dissociation of C2F6. The W values of Ar/C2F6 mixtures have also been measured and are reported; they increase with increasing C2F6 content. The W values of Ar/C2F6 binary gas mixtures have been found to decrease by addition of C2H2 or 2-C4H8. Quantitative measurements of the W values of the ternary gas mixtures are reported. The amounts of C2H2 or 2-C4H8 in Ar/C2F6, which maximize the increase in total ionization have been estimated; some of these ternary gas mixtures may be useful for diffuse discharge switches sustained by external electron beams. The experimental results on the W values for the binary and ternary gas mixtures studied have been modeled and good agreement has been found between the experimental and the calculated results. From an analysis of the data it has been found that the α-particle energy is partitioned between C2F6 and Ar approximately in the ratio 4.2:1. It has also been found that at the argon pressures employed, the probability of deexcitation of excited argon atoms by C2F6 (or C2H2 or 2-C4H8) molecules is more than three orders of magnitude larger than the probability of radiative deexcitation of the excited argon atoms.
Optical properties of cathodochromic powder screens
Authors: Maszara W. P. , Todd L. T.
Published: July 2002

Melamed’s diffuse reflectance for powdered materials is discussed in conjunction with its application for cathodochromic powder screens. Adaptation of the model was introduced through the modification of geometrical factor xu which is now to be empirically established for given screen. Experimental evidence obtained for cathodochromic bromosodalite well supports proposed modification.
Very low-threshold separate-confinement-heterostructure lasers prepared by liquid phase epitaxy
Authors: Mukai S. , Tsunekawa Y. , Takabe Y. , Yajima H.
Published: July 2002

AlGaAs separate-confinement-heterostructure lasers with low threshold current density (lowest averaged Jth of 317 A cm−2) are reproducibly prepared by liquid phase epitaxy. All optical-cavity layers of the lasers are undoped and their compositions are not graded. The low threshold is attained by increased internal efficiency resulting from effective injection of electrons into the active layer in the thin cavity, as well as by low internal loss of the optical cavity.
Generation of new bound exciton lines by lithium implantation of CdS
Authors: Dagenais M. , Elman B. S. , Sharfin W. F.
Published: July 2002

Sharp new bound exciton optical absorption lines are observed following very low fluence (φ<5×1012 cm−2 room-temperature 7Li implantation of high quality cadmium sulfide platelets. A substantial broadening of the free exciton resonance by the lithium neutral donor impurities is observed. A model of the line shape is proposed.
Spall studies in copper
Authors: Rosenberg Z. , Mayseless M. , Partom Y. , Betser A. A.
Published: July 2002

We have performed a series of planar impact experiments on commercial copper specimens in which the spall phenomenon was investigated. The stress-time histories, as measured at the back of the copper specimens, were compared to calculated ones using a 1-D code with a time-dependent spall model. The model was tested by comparing its predictions with experimental results in which only incipient spall occurred and the agreement between calculated and experimental stress-time histories is good.
Decay kinetics of photoconductivity of PbSnTe doped with indium
Authors: Martinez Antonio , Santiago Francisco , Davis John L. , Houston Bland , Drew H. D.
Published: July 2002

The temporal decay of persistent photoconductivity in PbSnTe films doped with indium were fit using a phenomenological model featuring a quasi-Fermi level-dependent activation energy. The resulting decay curves are nonexponential with a very fast initial relaxation followed by a slower decay due to an increase in the effective activation energy as the quasi-Fermi level decreases. Numerical solutions to the rate equation governing the relaxation were used to fit the data with excellent results. The activation energy in the limit of low carrier densities is found to be 24 meV.
InGaAsP p-i-n photodiodes for optical communication at the 1.3-μm wavelength
Authors: Yi M. B. , Paslaski J. , Lu L-T. , Margalit S. , Yariv A. , Blauvelt H. , Lau K.
Published: July 2002

The preparation and properties of Cd-diffused p-n homojunction InGaAsP photodiodes designed specifically for operation at the 1.3-μm wavelength are described. At a reverse bias of 10 V, the dark current of these diodes was as low as 15 pA. The peak responsivity at 1.3-μm wavelength was 0.7 A/W. An impulse response (full width at half maximum) of 60 ps and a 3-dB bandwidth of 5.5 GHz were achieved.
Optical determination of free-carrier concentration in epitaxial layers of n-type silicon grown on N+ or N− substrates
Authors: Geddo M. , Maghini D. , Stella A. , Cottini M.
Published: July 2002

In this paper it is shown that the optical determination of free-carrier concentration N0 in 5–10 μm thick epitaxial layers of n-type silicon grown on N+ or N− substrates is possible for concentrations ≥2×1016 cm−3 by measuring p-polarized reflected light Rp near the Brewster angle at a wavelength ≂10 μm. Good crystallinity, constant concentration profiles normal to the surface, as well as relatively small differences in the index of refraction with respect to the substrate are essential requirements in order to get high resolution. Good agreement with the angular derivative of Rp is obtained.
Radiation effects in fluoride glasses
Authors: Tanimura K. , Sibley W. A. , Suscavage M. , Drexhage M.
Published: July 2002

Radiation-induced defects in Zr-based fluoride glasses have been characterized using optical absorption and electron spin resonance (ESR) techniques. The optical absorption bands due to interstitial fluorine atoms, the F−2, FCl−, Cl−2 centers, and Zr3+ centers have been identified by correlating optical absorption and ESR measurements. Polarized bleaching experiments indicate that the hole-type centers, and the Zr3+ centers have anisotropic defect configurations. X-ray excitation at 14 K generates a broad, asymmetric emission band at 337 nm (3.68 eV), which is assigned to a localized-excited state similar to that for self-trapped excitons in halide crystals. The intensity of the x-ray induced emission provides further evidence that radiolysis defect production occurs in this material. The optical tail of the radiation-induced Zr3+ absorption affects infrared transmission. Evidence is presented that the CCl4 reactive-atmosphere process introduces a significant amount of Cl− (∼5%) in the glass.
Improvements in stoichiometry and stability of p-CuxS in thin-film CdS solar cells
Authors: Rastogi A. C. , Salkalachen S.
Published: July 2002

To counter the problem of instability, irreproducibility, and low stoichiometry of p-CuxS layers in thin-film CdS solar cells, a new field-assisted chemiplating process of barrier formation is described. Using the dc-forming potential as a first-order variable, nominal deviation from Cu2S composition without any dependence on external process parameters has been obtained. The stability of higher composition CuxS is attributed to the formation of a Cd++, rich barrier layer at the growing CuxS interface towards the CdS side, as inferred from the spectral response and Auger Cu and Cd compositional depth profile of the solar cells.
High-purity AlGaAs grown by molecular beam epitaxy using a superlattice buffer layer
Authors: Hayakawa T. , Suyama T. , Kondo M. , Takahashi K. , Yamamoto S. , Yano S. , Hijikata T.
Published: July 2002

High-purity Al0.3Ga0.7As is grown by molecular beam epitaxy at a high substrate temperature using a superlattice buffer layer in order to trap residual impurities. The unintentionally doped layer is p type with p < 5×1014 cm−3. Photoluminescence spectra at 10 K showed the strong bound-exciton emission to be 3.8 meV wide and extremely weak emission due to residual C and Si. Photoluminescence spectra of successively grown single-quantum wells with different widths demonstrate that residual C and Si are mainly trapped at the interface of the first-grown well.
Image formation in electron thermoelastic acoustic microscopy
Authors: Holstein W. L.
Published: July 2002

The theory of electron beam acoustic imaging with acoustic wave generation through the thermoelastic effect, or electron thermoelastic acoustic microscopy, has been developed in three dimensions. Images are created through two separate processes: acoustic wave (vibration) generation and acoustic wave transmission. Acoustic wave generation through the thermoelastic effect depends on the material’s thermal and elastic properties. Images based on these properties with resolution on the order of 5 μm is possible. The effect of imaging at different frequencies and phase angles is considered, both theoretically and experimentally, with an integrated circuit. Acoustic wave transmission affects the image by introducing vibrational patterns. This phenomenon was studied with aluminum foil. The effect of acoustic transmission on the image can also be used to detect subsurface cracks, delaminations, and voids. The detection of a delamination in glass at a depth of 25 μm is demonstrated.
Charge transport and trapping in silicon nitride-silicon dioxide dielectric double layers
Authors: Manzini S. , Volonté F.
Published: July 2002

Time, electric field, and temperature dependence of the flat-band voltage shift in polysilicon-silicon nitride-(thick) silicon dioxide-silicon capacitors subjected to high field stress has been studied in this paper. A ‘‘turn around’’ effect in the behavior of the flat-band voltage shift versus time is observed, both in the accumulation and in the strong inversion mode, in the full range of temperatures investigated (77 K≤T≤453 K). Early time charge trapping seems to be dominated by transport of carriers, holes or electrons injected at the gate electrode, in the nitride layer. A Poole–Frenkel-active trap for holes is determined to be located at 1.0 eV above the nitride valence-band edge and a Poole-Frenkel-active trap for electrons 1.3 eV below the nitride conduction-band edge. The dark contact current-contact field characteristics at the silicon-silicon dioxide interface are obtained at room temperature for both gate bias conditions. The contact current for positive gate voltage J+ox appears to be dominated by tunneling (Fowler–Nordheim) emission of electrons from the silicon substrate. The contact current for negative gate voltage J−ox is several orders of magnitude smaller than J+ox and is tentatively attributed to tunneling (Fowler–Nordheim) emission of holes from the silicon substrate. The estimated tunneling barrier height for holes is φh0 =4.4±0.1 eV.
Raman instability in n-type piezoelectric semiconducting plasmas
Authors: Ghosh S. , Saxena R. B.
Published: July 2002

The paper aims at the detailed analytical investigation of Raman instability in a magnetoactive n-type cubic piezoelectric semiconducting crystal belonging to class 4̄3m under a geometrical configuration which can also be employed in analyzing the phenomenon under either Voigt or Faraday orientation. The electric vector E0 of the spatially uniform pump electromagnetic wave (applied along the y axis) is normal to the magnetostatic field B0 (along the z axis) as well as to the plane of propagation (x-z plane) of the scattered waves (Ω,k) and (Ω1,k1). The propagation vectors k, k1 (antiparallel to each other) are in the x-z plane making an angle θ with the x axis. The dispersion relation has been obtained by using a hydrodynamic model of the homogeneous, piezoelectric, one-component (electron) semiconducting plasma; and the threshold value of the pump electric field (necessary to achieve physically reasonable growth of the unstable mode) and the growth rate of the unstable Raman mode well above the threshold field have been obtained for isotropic (B0=0) and magnetoactive (B0≠0) plasmas. We have applied our analysis to a specific semiconductor, n-InSb at 77 K, duly irradiated by a pulsed 10.6-μm CO2 laser for numerical estimation. The phase velocity of the growing unstable mode is found to be constant over the whole range of system parameters and equal to the electromagnetic wave velocity in the crystal. The magnitude of threshold electric field decreases with increasing magnetostatic field and decreasing wave vector. The growth rate increases and attains a maximum value at a certain value of the pump intensity, magnetostatic field, and θ; and if these are raised further, growth rate starts decreasing. When the analysis is extended to Voigt and Faraday configurations, the results are not very encouraging.
Wavelength modulation absorption spectroscopy of deep levels in semi-insulating GaAs
Authors: Eetemadi S. M. , Braunstein R.
Published: July 2002

Infrared wavelength modulation absorption spectroscopy was used in the spectral region of 0.3–1.45 eV and the temperature range of 80–300 K, to study deep level impurities and defects in undoped semi-insulating GaAs grown by the liquid encapsulated Czochralski technique. The measurements revealed two resonant type peaks with fine structure near 0.37 and 0.40 eV, as well as thresholds and plateaus at higher energies. The sensitivity of the measurements allows us to give credence to changes in the absorption coefficient at levels ∼10−3 cm−1. The absorption band at 0.37 eV is interpreted as being due to the intra-center transition between levels of accidental iron impurity, split by the crystal field. The absorption band near 0.40 eV, can be annealed out by heat treatment, and is considered to belong to a multilevel defect complex. Utilizing the photo-quenching behavior of the absorption in the spectral region of 0.6–1.4 eV, it was shown that conventional room temperature optical absorption may give erroneous results in measuring the concentration of the EL2 levels, because of appreciable absorption due to other residual deep levels in this spectral region, as revealed by the sensitivity of the wavelength modulation technique.
Deep electron traps near the passivated interface of HgCdTe
Authors: Cotton V. A. , Wilson J. A. , Jones C. E.
Published: July 2002

Electron traps in bulk n-type Hg0.7Cd0.3Te were investigated near the HgCdTe/SiO2 interface by use of deep level transient spectroscopy on metal-insulator-semiconductor structures [D. V. Lang, J. Appl. Phys. 45, 3022 (1974)]. Three electron traps are found with activation energies (relative to the conduction band edge) of 0.12, 0.172, and 0.079 eV, and corresponding capture cross sections of 3.5×10−18, 1.1×10−16, and 1.2×10−18 cm2. Depth profiles from the surface to ∼1.0 μm show the concentration of the 0.172-eV trap to be uniform while the 0.12-eV trap shows a strong depth dependence. It is undetectable at the surface, rising in concentration to twice its bulk value at ∼0.5 μm depth then falling to a value comparable with that of the 0.172-eV trap in the bulk (1 μm). Divalent trapping behavior has also been detected. In this case, the deeper state significantly depopulates, enabling a shallower state to then depopulate [J. S. Blakemore, Semiconductor Statistics (Pergamon, London, 1962), p. 156].
Maskless, selective electroetching for metal patterning
Authors: Chan Winston K.
Published: July 2002

An electroetching technique for maskless patterning of metals is described. The method uses the topography of the surface on which the metal is deposited to delineate the pattern during the electroetch, yielding self-aligned metal features that are burr-free and without undercut. Application of the technique to a one-micron linewidth metal-insulator-semiconductor structure useful for insulated-gate field effect transistors is demonstrated.
Oxidation-enhanced diffusion of ion-implanted boron in heavily phosphorus-doped silicon
Authors: Miyake Masayasu
Published: July 2002

Oxidation-enhanced diffusion (OED) of ion-implanted boron in heavily phosphorus-doped silicon is studied by measuring boron depth profiles using secondary ion mass spectroscopy for phosphorus concentration from intrinsic conditions to 1.2×1020 cm−3. OED is observed for the whole phosphorus concentration range investigated in the present work. However, both the diffusion coefficient in N2 ambient DN and that in dry O2 ambient DO decrease with an increase in substrate phosphorus concentration in extrinsic conditions, i.e., for phosphorus concentration larger than the intrinsic carrier concentration. Diffusion coefficient increment due to OED ΔD(=DO−DN) decreases with an increase in phosphorus concentration. The decrease in ΔD with an increase in phosphorus concentration is attributed to a decrease in excess silicon interstitials due to recombination with acceptor-type vacancies.
Use of paraffins as negative-acting electron-sensitive resists
Authors: Fuchs H. , Petermann J.
Published: July 2002

The effect of generating crosslinks in paraffins by electron impact was utilized to apply these aliphatic hydrocarbons as negative-acting electron-sensitive resists, capable of high structural resolution, anticipated from their low molecular weight. Owing to their chemical stability and relatively high vapor pressure above the melting point, paraffins may be vacuum deposited as thin uniform resist layers. The developing process makes use of the lower vapor pressure of the crosslinked material remaining on the substrate being heated to sublime the unexposed material in vacuum, thus completing an all-dry process.
cw laser processing of semiconductor surfaces
Authors: Moison J. M. , Licoppe C. , Nissim Y. I. , Houzay F.
Published: July 2002

The usefulness of cw laser irradiation for semiconductor surface processing is evaluated. While perfect surface cleaning has not yet been obtained, surface annealing of silicon by this technique equals and even beats classical techniques or pulsed-laser irradiation. cw laser ‘‘writing’’ of fine surface patterns is also demonstrated.
Interface polaritons in layered structures with metallized surfaces
Authors: Kushwaha Manvir S.
Published: July 2002

The magnetoplasma interface polaritons propagating along an interface between a medium (in region II) described by an isotropic frequency-independent dielectric constant ε2 and a semiconductor (in region III) characterized by an anisotropic, frequency-dependent dielectric function εij(ω) are studied. The outer surfaces of the two media (regions II and III) are metallized (in regions I and IV) which serve to ground the tangential components of the electric fields. The electromagnetic field components and the dispersion relation for magnetoplasma interface polaritons are calculated using electromagnetic theory. The field components are then used to derive the expressions for Poynting vectors, energy densities, and energy velocity. The analytical expressions for the dispersion relation and the derived properties are found to be frequency dependent and size dependent. The computed results for metal-vacuum-InSb-metal system with magnetostatic field (B0) perpendicular to the interfaces are illustrated and discussed in detail.
Luminescence behavior of a metallized semiconductor powder
Authors: Sahyun M. R. V. , Brisbois Ronald G.
Published: July 2002

A version of the dead-layer model, originally developed for single crystals, is derived to describe the luminescence behavior of a metallized Zn(Cd)S:Ag phosphor powder. Electron-hole separation occurs only with excitation events capable of leading to free photoelectrons. The potential for the electrons in the deposited ‘‘metal’’ layer may deviate from the metal work function, when chemical modification, e.g., oxidation, of the metal occurs subsequent to deposition. We call particular attention to the dramatic difference in photoluminescence lifetime in the Zn(Cd)S under laser exposure conditions compared with lower intensity xenon flash exposure. Both this observation and the incomplete quenching are rationalized in terms of a double minimum potential surface for hole trapping at the Ag(I) centers.
Monte Carlo simulation of impurity diffusion in thin-film diffusion barriers
Authors: Lavine J. P.
Published: July 2002

A Monte Carlo method is used to simulate grain and grain-boundary diffusion of impurities in thin films. The calculations are performed in two dimensions, and they illustrate some of the mechanisms that may enable thin films to serve as diffusion barriers in semiconductor devices. The effects of the grain-boundary pattern, grain-boundary traps or blockages, and an interface within the thin film are considered. The latter two mechanisms are more effective in stopping impurity diffusion through thin films.
Optical switching mechanisms in type IIa diamond
Authors: Huo Y. S. , Gu X. J. , Code R. F. , Fuh Y. G.
Published: July 2002

The nanosecond optoelectronic switching characteristics of type IIa diamond illuminated by pulsed UV radiation from an excimer laser at λ=193 nm are reported. With sputtered titanium contacts, certain electro-optical conditions produce a secondary current peak which follows the primary photocurrent pulse. When the bias voltage is increased further (with the laser excitation intensity being kept constant), the primary and secondary current pulses merge together, and their combined peak value is observed to have a supralinear increase with respect to bias voltage. The threshold voltages for secondary pulse formation are also shown to decrease with respect to increasing laser excitation intensities. Secondary current pulse formation and decay are shown to be consistent with a model of space-charge-assisted Fowler–Nordheim electron tunneling across the reversed-biased negative Ti/C electrode.
Passivation of ohmic contacts to GaAs during alloying
Authors: Lakhani Amir A.
Published: July 2002

A film of SiO2 was used to passivate Au:Ge:Ni on GaAs during the alloying cycle used to fabricate ohmic contacts. The passivated metallization produced smooth surfaces and interfaces and consistently resulted in a specific contact resistivity of 3×10−6 Ω cm2 over a wide range of alloying times and temperatures. On the other hand, the unpassivated pads exhibited an increasing contact resistivity with increasing alloying times. The sheet resistivity under the metal contact was also found to increase with alloying time when the metallization was not passivated. During the alloying cycle, severe damage to the substrate takes place at the metal-semiconductor interface if the metallization is not passivated. The passivating film of SiO2 remained intact during the heat treatment and its Auger depth profile revealed that it is impermeable to Au, Ge, Ni, Ga, and As at alloying temperatures up to 500 °C. It is proposed that better reproducibility of the specific contact resistivity and improved surface and interface morphologies are due to the suppression of As loss during the heat treatment.
Possible analog gain in a current injection Josephson network
Authors: Biswas J. C. , Dutta Roy S. K.
Published: July 2002

A possible analog gain in Cooper-pair tunneling mode in a current injection Josephson network is theoretically investigated. The network consists of three Josephson junctions A, B, and C, and its gain can be widely controlled by varying the external shunt resistances of junctions B and C. Two different configurations of the planar structure of the network are suggested and their detailed principles of operation are explained. It is expected that the network will function at a higher speed than that possible in an amplifying device working in quasiparticle mode. A comparison between the present network and Faris QUITERON is also given.
Influence of thermal oxide on leakage current for Pb-alloy Josephson junctions
Authors: Yuda Masahiro , Wada Masato , Nakano Jun’ichi
Published: July 2002

The effects of thermal oxide on leakage current of rf-plasma oxidized Pb-In-Au alloy Josephson junctions are examined. The leakage current is small in junctions with thermal oxide grown at low oxygen pressure and for a long period. Current-voltage characteristics at low temperature show that the leakage current magnitude is closely related to the magnitude of the current steps at the gap voltages of electrode materials. Furthermore, optical property investigations of the oxide show that leakage current decreases with a decrease in the oxide absorption coefficients, which are correlated to carrier density. Based on these experimental data, a leakage current model is proposed for Pb-alloy junctions. This model shows that the tunneling current between superconductor and normal metal regions in the oxide barrier causes leakage current.
Void formation in Nb3Sn-Cu superconducting wire produced by the external tin process
Authors: Verhoeven J. D. , Efron A. , Gibson E. D. , Cheng C. C.
Published: July 2002

The tin (Sn) diffusion step for producing Nb3Sn-Cu superconducting wire by the external Sn process was modeled in experiments where either pure Sn or a Cu-Sn alloy was plated on sheets of either pure Cu or a Cu-Sn bronze. Each stage of the three-stage solid-state diffusion process was evaluated and it was found that rows of voids are produced in stage I of the process. These voids coarsen in stages II and III and in the worst case they are observed to coalesce and cause complete spalling away of the Sn-rich diffusion layers. Methods for minimizing void formation and possible causes of the void formation are discussed.
1.3-μm InGaAsP distributed feedback laser
Authors: Dutta N. K. , Napholtz S. G. , Cella T. , Wessel T. , Brown R. L. , Anthony P. J.
Published: July 2002

The fabrication and performance characteristics of 1.3-μm InGaAsP distributed feedback (DFB) double-channel planar buried heterostructure (DCPBH) laser are reported. The lasers utilize a second-order grating with a periodicity of ∼3800 Å for frequency selective feedback. The lasers have threshold currents in the range 25–35 mA at 30 °C. The lasing mode shifts to longer wavelengths with increasing temperature at 1 Å/°C. The dynamic linewidth under 40-mA current modulation is ∼1 Å. The cw linewidth at an output power of 1 mW is ∼90 MHz. A monolithically integrated thermoelectric-controlled laser diode utilizing the DFB-DCPBH laser structure has been fabricated. The emission frequency of the laser can be continuously tuned by ±4 Å using 50-mA controller current.
Hyperbolic heat conduction with temperature-dependent thermal conductivity
Authors: Glass D. E. , Özişik M. N. , McRae D. S. , Vick Brian
Published: July 2002

Hyperbolic heat conduction in a semi-infinite slab with temperature-dependent thermal conductivity is studied numerically, and the results are compared with those obtained from the classical parabolic equation for the following cases: (a) constant applied temperature at x=0.0, (b) constant applied heat flux at x=0.0, and (c) a pulsed heat source released instanteously at t=0.0 in the region 0.0≤x≤Δx adjacent to an insulated boundary. In addition to changing the temperature profiles, the nonlinear thermal conductivity also altered the speed of the thermal front. An increase in the thermal conductivity increased the wave speed, while a decrease in the thermal conductivity decreased the wave speed.
On the thermodynamic efficiency of solar energy converters: Solar cells
Authors: Singh Jai , Foo S. P.
Published: July 2002

Assuming that both source and energy converters are blackbodies and applying thermodynamic balance equations, the net efficiency of a solar cell is derived as a product of two different efficiencies associated, respectively, with the energy absorption and energy conversion into useful work. At room temperature the maximum net efficiency thus obtained is 38%. Efficiencies are calculated at various solar cell temperatures, and results are discussed in view of existing theories.
Metastable Al-Mn phases formed by ion-beam mixing
Authors: Follstaedt D. M. , Knapp J. A.
Published: July 2002

The phases produced by ion-beam mixing of Al/Mn layers were examined as a function of mixing temperature between 30 and 200 °C for 16 at. % Mn. After intermixing of the layers at either 30 or 60 °C with 1×1016 Xe/cm2 at 400 keV, electron diffraction showed amorphous phase formation. However, ion-beam mixing at 100 or 200 °C produced the icosahedral Al(Mn) phase. The crystalline phase Al6Mn can also be formed near the sample surface by ion mixing appropriate concentrations at elevated temperatures. Annealing at successively higher temperatures produced the transformation sequence: amorphous → icosahedral → Al6Mn, which indicates that the icosahedral phase is more stable than the amorphous phase.
Method for measurement of anisotropic electrical conductivities of insulating film
Authors: Tanabe Yoshikazu , Hirota Sumio
Published: July 2002

Measurement of anisotropic electrical conductivities along main axes of insulating film is possible by measuring current flow parallel to the film surface, in which the four-electrode system attached symmetrically to both sides of a film is used. The method is experimentally verified by determining the conductivities of Z-cut and X-cut quartz crystals.
Thermally stimulated current in p-type CuInSe2 thin films
Authors: Datta T. , Noufi R. , Deb S. K.
Published: July 2002

We observe a strong thermally stimulated current (TSC) in p-type CuInSe2 thin films at temperatures from 100 to 350 K. Annealing in air appears to passivate this TSC activity. The passivation is reversible, and the spectra may be partially recovered by reduction. We attribute the three dominant TSC structures to three energy levels, 35, 45, and 100 meV, and we believe that they are associated with intrinsic defects, i.e., vacancies and antisites which are also observed in photoluminescence. We identify oxygen compensation of donors as the cause of the improved transport in CuInSe2 after air annealing.
Hydrogenated amorphous silicon films prepared in cascaded glow discharge reactors
Authors: Panwar O. S. , Dixit P. N. , Bhattacharyya R. , Shah V. V.
Published: July 2002

Plasma decomposition of silane by glow discharge in cascade reactors, which we proposed earlier, yields highly resistive a-Si:H films with appreciable photoconductivity in the second reactor of the cascade. These films have since been characterized by transmission and scanning electron microscopy, Auger electron spectroscopy, infrared spectroscopy as well as by measuring conductivity, photoconductivity, thermoelectric power, optical gap, light-induced changes in conductivity (Staebler–Wronski effect) and density of gap states to see in what respect these two types of films differ. These investigations show that, deposition parameters remaining the same in the two reactors, the films obtained from the first reactor are in no way different from what other workers have reported. The films prepared in the second reactor of the cascade, however, have (i) low dark conductivity (10−13–10−12Ω−1 cm−1), (ii) higher activation energy (0.95–1.05 eV), (iii) higher photosensitivity, (iv) higher optical gap (2.0–2.1 eV), (v) less density of states in the gap, and (vi) are less prone to Staebler–Wronski effect.
Heat-source power requirements for high-quality recrystallization of thin silicon films for electronic devices
Authors: Miaoulis Ioannis N. , Mikić Bora B.
Published: July 2002

An approximate procedure for estimation of the power requirements for the melting and recrystallization of thin silicon films for electronic devices is described. The two heat sources investigated are the laser beam and the graphite strip. The study includes various substrate geometries. The results cover a range of practical interest and are presented in a graphical form for convenient use. The method is verified with existing experimental data.