bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancement of interface stability in liquid phase electroepitaxy
Authors: Okamoto A. , Lagowski J. , Gatos H. C.
Published: February 2003

The thermodynamic as well as the dynamic constitutional supercooling criteria are derived for liquid phase electroepitaxy (LPEE) taking into account the Peltier effect and electromigration which control the growth interface temperature and mass transport in the solution, respectively. It is shown that solute transport by electromigration enhances significantly the interface stability during growth. Thus the present treatment explains the experimentally attained stable electroepitaxial growth with velocities as high as 25 μm/min. Furthermore, it defines the geometry of the LPEE configuration and the growth parameters (current density and polarity, temperature and substrate characteristics) which lead to the optimization of surface morphology.
Theory of photocurrent in semiconductor-electrolyte junction solar cells
Authors: El Guibaly F. , Colbow Konrad
Published: February 2003

Expressions are derived for the current-voltage characteristics of semiconductor-electrolyte junctions. Charge transfer kinetics, surface recombination, recombination in the quasineutral region and in the depletion region as well as the effect of the incident illumination on the minority carrier distribution in the semiconductor are included in the model. It is shown that surface transfer velocity for minority carriers is a very important parameter that determines the photocurrent of the cell. The dependence of the photoresponse on the light intensity is shown to be a diagnostic tool in determining the efficiency of charge transfer at the surface.
Static I-V characteristics of static induction transistors
Authors: Gupta Ravendra K.
Published: February 2003

The static induction transfer shows the barrier-temperature-limited operation and exhibits vacuum-triode-type output characteristics. The potential profile defining the device characteristics possesses a potential barrier and it rearranges itself due to negative feedback by a change in gate or drain voltage. The nonexistance of a potential barrier leads to space-charge-limited operation of the device. In the former case, current is exponentially related to the applied terminal voltage through the potential barrier, whereas in the latter case, current gives asumptotic dependence proportional to the applied terminal voltage through the amplification factor. The effect of temperature on static characteristics shows that the static induction transistor can be designed with or without the temperature effect on the output characteristics, or the temperature effect can be canceled by the proper choice of the operating conditions.
Semiconducting and other major properties of gallium arsenide
Authors: Blakemore J. S.
Published: February 2003

This review provides numerical and graphical information about many (but by no means all) of the physical and electronic properties of GaAs that are useful to those engaged in experimental research and development on this material. The emphasis is on properties of GaAs itself, and the host of effects associated with the presence of specific impurities and defects is excluded from coverage. The geometry of the sphalerite lattice and of the first Brillouin zone of reciprocal space are used to pave the way for material concerning elastic moduli, speeds of sound, and phonon dispersion curves. A section on thermal properties includes material on the phase diagram and liquidus curve, thermal expansion coefficient as a function of temperature, specific heat and equivalent Debye temperature behavior, and thermal conduction. The discussion of optical properties focusses on dispersion of the dielectric constant from low frequencies [κ0(300)=12.85] through the reststrahlen range to the intrinsic edge, and on the associated absorption and reflectance behavior. Experimental information concerning the valence and conduction band systems, and on the direct and indirect intrinsic gaps, is used to develop workable approximations for the statitistical weights Nv(T) and Nc(T), and for the intrinsic density. Experimental data concerning mobilities of holes and electrons are briefly reviewed, as is also the vn(E) characteristic for the conduction band system.
The early history of the scanning electron microscope
Authors: Oatley C. W.
Published: February 2003

The article begins with an account of prewar German work, particularly that of von Ardenne, who established the theoretical basis of a scanning electron microscope and constructed an instrument which was primarily intended to overcome chromatic aberration when relatively thick specimens were examined by transmission. Neither this microscope nor a different one built a few years later in the U. S. A. attained sufficient resolution to gain acceptance and the reasons for this are examined. The remainder of the article deals with work carried out in the Cambridge University Engineering Department over the years from 1948 to about 1965, when the first successful commercial instrument was produced. The contributions made by successive research students are explained, as are also the nonscientific factors which influenced the course of the development.
Comment on ‘‘Anisotropic suspension display’’
Authors: Scholten P. C.
Published: February 2003

The display proposed by Beni et al. is shown to need electric fields three orders of magnitude higher than the authors suggested. Although not as serious as with liquid crystal displays, the system would have an angle-of-view problem as well.
High-field conduction in off-stoichiometric SiO2 films
Authors: Falcony C. , Helman J. S.
Published: February 2003

The temperature dependence of the high-field conductivity of SiO2 films with a small atomic excess of Si content is interpreted in terms of a model previously proposed for granular metal films. We have found an excellent quantitative agreement between experimental data and the theory. This agreement clarifies the conduction mechanism in this material and strongly suggests that the Si particles have metallic characteristics. With this interpretation, we are able to determine the volume fraction of the excess Si x, the diameter of the Si grains d, and the interparticle distance s. In the case of samples with an excess of Si atoms of 1% to 3%, we found that x≂0.017, d≂9.5 Å, and s≂20.5 Å.
A symmetrical three-junction superconducting quantum interference device
Authors: Dhong S. H. , Jewett R. E. , Spargo J. W. , Van Duzer T.
Published: February 2003

A new symmetrical 1:2:1 split-fed Superconducting Quantum Interference Device (SQUID) has been designed and experimentally investigated. By laying out the control line symmetrically about the center axis of the device and by moving the Josephson junctions in the device out from underneath the control line, we were able to eliminate virtually all the sources of asymmetry in the path of the control line. This asymmetry causes degradation of the threshold curve of the SQUID over a few periods and renders the conventional three-junction SQUID unsuitable for some applications, such as one Josephson analog-to-digital conversion scheme. By eliminating the sources of asymmetry, we were able to make SQUIDs that showed at least eight almost identical periodic lobes. An additional advantage of the symmetrical SQUID is that the insulating SiO layer which defines the junction windows could be used to provide an insulation between the base electrode and the control line. Thus, the control line was defined at the same time as the counterelectrode. This made it possible to make a symmetrical three-junction SQUID with three layers fewer than the planar-type three junction SQUIDs reported previously.
Kerr effect in solid polymethylmethacrylate and polyethylene
Authors: Kim K. S. , Cheng T. C. , Cooper D. E.
Published: February 2003

Commercial grade polymethylmethacrylate (PMMA) and polyethylene (PE) have been found to exhibit the Kerr effect. The Kerr constants were determined to be ∼0.2×10−14 m/V2 for PMMA (at room temperature) and ∼0.1×10−14 m/V2 for uncrosslinked low-density PE (at 110 °C).
The critical number of photons in free-electron devices: A quantum effect?
Authors: Šoln Josip
Published: February 2003

Within the S matrix approach to the free-electron devices, it is shown that the depletion of photons by the electron beam in the interaction volume stops when the number of photons becomes some critical number, mc. In the linear recoil approximation, the expression for mc (or equivalently for critical photon energy Ec) depends only on kinematics, suggesting that it has a general validity for all kinds of free-electron devices. As two numerical examples of mc, which is inversly proportional to ℏ, are not compatible with infinities, we argue that the origin of mc may be quantum mechanical. Some practical aspects of Ec are also discussed.
Submicron conductor array fabricated by selectively etching a eutectic thin film
Authors: Cline H. E.
Published: February 2003

A submicron conductor array was fabricated without using lithography by selectively etching a recrystallized Al-Al2Cu eutectic alloy thin film. The 2-μ eutectic films were deposited on glass substrates and directionally solidified with both a quartz iodine lamp and a scanning laser at rates between 0.0016 and 0.14 cm/sec. The resulting structure consisted of alternate parallel stripes of the two eutectic phases with a spacing between 0.5 and 4 μ that was controlled by the solidification rate. An array of submicron Al-rich conductors was fabricated by selectively etching away the Al-Al2Cu phase. At the maximum theoretical solidification rate that produces a two-phase aligned eutectic structure, the width of the Al wires would be 100 Å.
A supersonic multikilohertz pulsed HF chemical laser
Authors: Rosenwaks S. , Chuchem D.
Published: February 2003

Operation of a pulsed, multikilohertz-repetition-rate, supersonic HF chemical laser is described. Continuously flowing reactants are premixed and then expanded through a supersonic nozzle to the laser cavity where a pulsed electrical discharge initiates the chemical reaction producing the lasing species. An average power of 12 W has been obtained from a hydrogen/sulfur-hexafluoride/helium mixture. It is suggested that this apparatus can be used to overcome some of the inherent problems in achieving quasi-continuous laser operation based on a chain reaction in fluorine/hydrogen mixtures.
The confined compressive strengths and Young’s moduli of three American coals
Authors: Costantino Marc , Trettenero Stan
Published: February 2003

We report the confined compression strengths and Young’s moduli of coal and roof rock from the Upper Freeport seam, Lucerne No. 6 Mine, Homer City, Pennsylvania, the Lower Kittanning seam, Kitt No. 1 Mine, Phillipi, West Virginia, and the Soldier Canyon seam, Soldier Canyon Mine, Price, Utah. A total of 210 tests to failure in biaxial compression were performed at confining pressures of 0.1, 3.0, and 10.0 MPa. The strengths increase by a factor of 2–3 over the confining pressure range, while the Young’s moduli are about constant. Standard deviations are 10–30% of the mean, emphasizing the need to do many tests. Failure in all three coals is brittle, progressing from dilational to multiplane shear to single-plane shear on increasing confining pressure. Strengths and moduli could not be correlated with such macroscopic inhomogeneities as large cracks, voids, and compositional changes.
Electromigration-induced failure by edge displacement in fine-line aluminum-0.5% copper thin film conductors
Authors: English A. T. , Kinsbron E.
Published: February 2003

Electromigration mass transport rates in Al-0.5% Cu film conductors have been measured by the Blech-Kinsbron technique, and the data extrapolated so as to predict times-to-failure under typical conditions of service, due to open circuit at silicon-to-aluminum contacts. In tests between 260 and 400 °C, average drift velocities ranging from 0.01 to 10 μm/h were measured. The observed activation energy is 0.44 eV for the extra-fine-grained film (grain-boundary diffusion control) but 1.2 eV for the coarser-grained film which had been patterned to form a strip 1.5 μm wide (lattice diffusion control). At a given temperature, transport is much faster in finer- as compared to coarser-grained films. For the extra-fine-grained films deposited by evaporation from an induction-heated source, the predicted time-to-failure in use is well within the normal-service lifetime. The inferred safe current density design level for extra-fine-grained material is well below previously recommended values. We conclude that deposition processes which result in extra-fine-grained aluminum are probably unsuitable for use in integrated circuit fabrication. Even for coarser-grained aluminum conductors, additional work will be required to define conservative current density design limits to avoid contact failure by this mechanism.
Influence of metallurgical factors on superconducting current densities in ‘‘bronze-processed’’ Nb3Sn multifilamentary wires
Authors: Okuda S. , Suenaga M. , Sabatini R. L.
Published: February 2003

A number of metallurgical factors influencing superconducting properties, primarily critical current densities, of bronze-processed Nb3Sn multifilamentary wires were examined for a set of wires in which the ratio of bronze to Nb, R, varied from 2.0 to 3.7. The morphology and the size of the Nb3Sn grains were found to be strongly influenced by R and the temperature at which the compound was formed. A qualitative model for the growth of the compound layer is proposed accounting for the microstructural variations in the wires. The critical-current density Jc of the wires was the highest for those heat treated at 725 °C for 192 h, and was essentially independent of R. The highest Jc was also found in the wires with ∼7-μm filaments, compared with those with ∼3- and ∼15-μm filaments. The decreases in Jc with the reduction of the filament size to 3 μm was correlated with the spread in the distribution of the filament sizes. By examination of the present and the previous data on Jc of multifilamentary Nb3Sn wires, it is concluded that values of Jc of ∼800 A/mm2 at 10 T and ∼500 A/mm2 at 12 T can be easily achieved in bronze-processed wires without an undue amount of effort in fabrication, but to achieve significantly higher values (∼1200 A/mm2 or higher at 10 T) may require extensive quality control in the manufacturing of these composite wires.
Four-dimensional J-B-T-ε critical surface for superconductors
Authors: Ekin J. W.
Published: February 2003

The concept of a superconducting critical surface in a four-dimensional J-B-T-ε space is introduced and from this a critical strain parameter εc is defined in analogy to the usual three superconducting critical parameters: Jc, Bc2, and Tc. Examples of a subset of this surface in a three-dimensional J-B-ε space are presented as a function of temperature for the A15 superconductors, Nb3Sn and V3Ga, utilizing the recently discovered strain scaling law. The usefulness of the J-B-T-ε critical surface in characterizing the interaction of strain with the other three critical parameters and in setting strain limits for the mechanical design of superconducting devices is illustrated.
Photoluminescence of shallow acceptors in Al0.28Ga0.72As
Authors: Ballingall J. M. , Collins D. M.
Published: February 2003

Low-temperature (5K) photoluminescence (PL) of lightly silicon-doped Al0.28Ga0.72As grown by molecular beam epitaxy is presented. Samples with different free electron concentrations are examined over five decades of laser excitation intensity. The PL data and Hall effect measurements verify that the samples are not nearly as compensated (n300K =2.2×1015 cm−3, μ300K =2470 cm2/V s) as samples studied previously by others. Narrow transition linewidth (3 meV) bound exciton recombination, ‘‘defect-induced’’ bound exciton recombination, and two prominent neutral donor-neutral acceptor (DA) peaks are observed. Free-to-bound recombination is distinguished from the DA recombination in the low-excitation intensity spectra. The acceptor ionization energies derived from the data are 33 meV for carbon and 53 meV for silicon. The difference in ionization energy for the carbon acceptor in GaAs (26 meV) and Al0.28Ga0.72As (33 meV) is accounted for by the effective mass theory of Baldereschi and Lipari. Differences among the ionization energy assignments reported in the literature and their probable causes are discusssed.
Study of the thermal conversion of semi-insulating GaAs:Cr with cathodoluminescence, photoluminescence, and secondary ion mass spectrometry
Authors: Yin S. Y. , Wittry D. B.
Published: February 2003

Low-temperature cathodoluminescence and photoluminescence spectra of heat-treated GaAs:Cr are compared and differences are attributed to the difference in excitation depth. Cathodoluminescence spectra at 30 K indicate that the 1.23-eV emission band in the as-grown GaAs:Cr may be associated with a SiGa-VGa complex while emission bands in the heat-treated materials at 1.363 and 1.407 eV may correspond to acceptor levels introduced through the site transfer of silicon. The 1.363-eV peak is strongly correlated with carrier concentration of the converted layer. Secondary ion mass spectrometry depth profiles show that this peak is not due to Cu. It may be due to recombination involving a SiAs-VGa complex.
Pulsed laser heating of silicon: The coupling of optical absorption and thermal conduction during irradiation
Authors: Kwong D. L. , Kim Dae M.
Published: February 2003

Transient laser annealing of semiconductors is examined extensively and the rise in lattice temperature specifically attained in silicon under the influence of a high-power laser beam irradiation is characterized analytically over a wide range of laser wavelengths, intensities, and durations. For the case of silicon, with increasing lattice temperature the optical absorption coefficient is drastically enhanced, while the thermal conductivity is considerably reduced. These two temperature-dependent material parameters are, therefore, strongly coupled during the laser beam irradiation, and the effects of this coupling on the ensuing lattice-temperature rise are examined comprehensively. Specifically, the threshold pulse energy for the onset of surface melting is analytically calculated as a function of both material parameters and operating laser beam characteristics.
Techniques for the correction of topographical effects in scanning Auger electron microscopy
Authors: Prutton M. , Larson L. A. , Poppa H.
Published: February 2003

A number of ratioing methods for correcting Auger images and linescans for topographical contrast are tested using anisotropically etched silicon substrates covered with Au or Ag. Thirteen well-defined angles of incidence are present on each polyhedron produced on the Si by this etching. If N1 electrons are counted at the energy of an Auger peak and N2 are counted in the background above the peak, then N1, N1−N2, (N1−N2)/N2, and (N1−N2)/(N1+N2) are measured and compared as methods of eliminating topographical contrast. The latter method gives the best compensation but can be further improved by using a measurement of the sample absorption current. Various other improvements are discussed.
Laser-generated electron emission from surfaces: Effect of the pulse shape on temperature and transient phenomena
Authors: Lin Jui-teng , George Thomas F.
Published: February 2003

Surface temperatures generated by gaussian, rectangular, and triangular laser pulses are determined by solving a heat diffusion equation. The dependence of the temperature on the pulse shape and, in turn, the dependence of the thermal diffusivity and absorptance on the temperature are investigated. The lifetime of an adspecies on a laser-heated solid (e.g., Cs on W) is estimated in terms of the temperature, the desorption energy, and the coverage. The mechanism of laser-generated electron emission from the adspecies is analyzed by means of the Richardson equation. A condition for generating an intense electron beam is that the laser pulse duration and the rise time of the temperature must be less than the lifetime of the adspecies.
An optimization of monolithic photovoltaic series arrays
Authors: Murray E. M. , Warner R. M.
Published: February 2003

In the design of monolithic series-array solar batteries, a tradeoff between resistance losses and active area losses yields an optimum number of cells for maximum output power. A solution of this problem is presented. This analysis can be applied to any series-array technology. The designer can determine the optimum number of cells for maximum output power. The power tradeoff for a nonoptimum design can also be predicted.
On orientation changes, deformation banding, and dislocation structures in rolled [100](001) oriented iron crystals
Authors: Kuhlmann-Wilsdorf D. , Aernoudt E.
Published: February 2003

The texture formation process, dislocation structures, and deformation bands observed in rolled and cross rolled [100] (001) oriented iron crystals have been interpreted from the viewpoint of fundamental dislocation behavior and the properties of low-angle dislocation boundaries. Full agreement between theoretical expectations and published observations was obtained.
Transport of silica in rare earth iodide arc tubes
Authors: Yamane M. , Suenaga M.
Published: February 2003

In the horizontal operation of dysprosium-thallium and scandium-sodium iodide lamps, the internal surface of the upper portion of the arc tube is etched, causing precipitation on the side and lower portions. This precipitation produces spheroidal outgrowths on the side internal surface and closely bunched fibers on the lower internal surface. These deposits are examined by electron beam microanalysis and micro x-ray diffraction analysis, and are construed to be amorphous SiO2. The transport of silica is found to occur also in a furnace experiment, where dysprosium iodide is heated in an evacuated silica tube held at 750–1150 °C.
Magnetic-field dependence of the Hall factor for isotropic media
Authors: Rode D. L. , Wolfe C. M. , Stillman G. E.
Published: February 2003

The magnetic-field dependence of the Hall factor is investigated theoretically and experimentally. The theory includes arbitrary band structure, carrier degeneracy, and wave functions assuming isotropic media and carriers behaving as spinless Fermions without energy-level quantization. Comparisons between theory and experiments on high-purity GaAs from the low magnetic-field limit to the classical high magnetic-field limit agree to within 0.7 percent.
Interaction between a thin polyethylene target and a relativistic electron beam
Authors: Gazaix M. , Doucet H. J. , Furtlehner J. P. , Lamain H. , Rouillé C.
Published: February 2003

We investigate theoretically and experimentally the possibility of energy deposition enhancement when a relativistic electron beam interacts with a high density plasma. The beam-plasma instability is studied taking into account the angular spread of the beam, the electron-ion collisions, and the density gradients. The beam (500 kV, 250 kA, 50 ns) interacts with a thin CH2 foil. Contrary to previous experiments, the plasma expansion from the foil target is found to be symmetric. The maximum temperature estimated by x-ray diodes is 13 eV. The measured parameters (temperature, density, gradients), together with the theoretical study, show that the beam-plasma instability is ineffective in the expanding target.
CO2-laser-induced deflagration of fuel/oxygen mixtures
Authors: Trott Wayne M.
Published: February 2003

Weakly focused pulsed-CO2-laser radiation has been examined as an ignition source for low-pressure (85–100 Torr), near-stoichiometric fuel/oxygen mixtures containing the following fuels: ethylene, methyl fluoride, methanol, ethanol, dimethyl ether, p-dioxane, n-propyl nitrate, and iso-propyl nitrate. The data analysis includes characterization of the spatially dependent ir absorption in the test cell, calculation of appropriate medium temperatures from the absorbed laser energy, and correlation of observed ignition delay times tig with the calculated temperatures. Effects of hydrodynamic motion on the pressure, density, and temperature profiles of the irradiated samples were modeled using a computer code for two-dimensional wave propagation. Code predictions are in accordance with experimental pressure-time histories obtained using a piezoelectric transducer. Minimum ignition temperatures ranged from 590 K for the iso-propyl nitrate/O2 system to 1645 K for CH3F/O2. The observed functional relationship between tig and temperature T was generally of the form ln tig =A/T+B, where A and B are constants. This relationship follows the form predicted by thermal and degenerate chain ignition theories, viz., ln tig =Eact/ RT+constant, where Eact corresponds to an overall activation energy. Using this relation, derived activation energies are 86, 57, 42, 47, ∼40, 13, and 12 kcal/mole for the CH3F/O2, CH3OCH3/O2, CH3OH/O2, C2H5OH/O2, C4H8O2/O2, n-propyl nitrate/O2, and iso-propyl nitrate/O2 mixtures, respectively. These results are in reasonable agreement with available data from shock-tube and hot air stream injection techniques. In contrast, an anomalous, threshold-like effect was observed for laser ignition of C2H4/O2. The applicability of ignition schemes of this type to time-resolved kinetic spectroscopic studies is briefly discussed.
The high-current vacuum arc in an axial magnetic field: An experimental investigation
Authors: Schellekens Hans
Published: February 2003

A spectroscopic study of the plasma parameters of a high-current vacuum arc in an axial magnetic field shows that the interaction of the particles in the arc is collisional. A previously suggested pressure drop is found to exist. The pressure buildup in the arc may be influenced significantly by ion-neutral friction.
Bubble evolution in a stirred volume of liquid closed to mass transport
Authors: Tikuisis P. , Ward C. A. , Venter R. D.
Published: February 2003

The rate of bubble evolution, and hence the rate of mass transport across a curved liquid-gas interface, has been examined both theoretically and experimentally. A single gas bubble is contained in approximately 1.3 cc of a liquid-gas solution that is closed to mass transport. This condition provides the mechanism by which the gas bubble may be placed initially in a state of stable equilibrium, and thus allow an accurate determination of the system parameters. A stirred liquid condition is achieved by rotating a micro-stir bar within the volume, and the resultant flow pattern is characterized with laser-doppler anemometry. Through an experimental examination on the complete dissolution of nitrogen-gas bubbles in water, the mechanism of mass transport is shown to be consistent with a model comprised of two processes: (1) the primary and rate-limiting process is modelled by the diffusion of gas through an unstirred liquid-boundary layer whose thickness varies with bubble radius; and (2) a second-order limitation is due to the nonequilibrium transport of gas across the phase boundary as predicted by a statistical rate theory expression. The theoretical model is then applied to predict the evolution of a bubble towards a state of stable equilibrium.
Radiation-induced photoconductivity in polymers: Poly(vinylidene fluoride) compared with polyethylene terephthalate
Authors: Kurtz S. R. , Hughes R. C.
Published: February 2003

Transient and dc photoconductivity measurements are presented for two low-mobility dielectrics, poly (vinylidene fluoride) and polyethylene terephthalate. In each case, the data are analyzed using the present models for dispersive transport, and the inadequacies of these theories when applied to these low-mobility dielectrics are illustrated. In this paper we report an anomalously small transient photoresponse in poly (vinylidene fluoride); from our analysis, we attribute this result to the dispersive transport limited drift mobility in this material. Polymer structure and electric field contributions to the radiation-induced conductivity in these dielectrics are also discussed.
Photoconductivity in amorphous Si:H:Cl films
Authors: Augelli V. , Murri R. , Alba N.
Published: February 2003

Amorphous silicon films were deposited in a capacitively coupled glow discharge in SiCl4-H2 mixture. The photoconductivity has been correlated to the discharge pressure p, the substrate temperature Ts , and to the ratio R of SiCl4 flow to the total flow. Moreover, the dependence of the photoconductivity on the wavelength and light intensity has been investigated. These measurements give useful information about the recombination mechanisms and allow one to estimate the position of the Fermi level. Some features of the gap state distribution are obtained by correlating dark conductivity and luminescence results to the photoconductivity ones.
Electrical conduction in two-phase nickel oxide-nickel sulfide mixtures
Authors: Tare V. B. , Wagner J. B.
Published: February 2003

The electrical conductivity of sintered pellets of NiO-Ni3S2 mixtures of various compositions has been measured as a function of temperature in the range 600–800 °C. The electrical conductivity of pure nickel oxide initially heated in known sulfur vapor at 950 °C for 100 h has also been measured as a function of temperature. The conductivity of NiO-Ni3S2 decreases initially, attains a minimum at approximately 5 mole % Ni3S2 and increases again with an increase in concentration of Ni3S2. The activation energy for conduction also follows the same pattern. The conductivity changes from predominantly p type for pure and sulfur saturated NiO to predominantly n type for compositions equal to or greater than 5 mole % Ni3S2. The results have been explained by postulating the trapping of holes at the NiO-Ni3S2 interface by the electrons from Ni3S2. At concentrations higher than or equal to 20 mole % Ni3S2 the conduction is predominantly due to electrons from the Ni3S2 phase. The morphological details of the NiO-Ni3S2 composites have been obtained using scanning electron microscopy. The concentration profiles of nickel and sulfur across the composite were obtained by using Energy Dispersive Analysis of x rays.
MeV-energy As+ implantation into Si: Extended-defect reduction and planar n-p-n transistor fabrication
Authors: Takahashi Mitsutoshi , Konaka Shinsuke , Kajiyama Kenji
Published: February 2003

With 2.5 MeV-As+ implantation into Si, etch-pit density (after annealing) could be lowered below 104 cm−2, whether D was smaller than 5×10−4 or larger than 2×10−2. Here D stands for damage degree in the as-implanted sample [0(single-crystalline)≤D≤1 (amorphous)]. At given doses, D could be controlled to be at its optimal value by wafer temperature (over a range from 25–300 °C). By utilizing such MeV-energy implantation to form buried collector layers, planar n-p-n transistors could be successfully fabricated even without epitaxial growth.
Open tube diffusion of Zn into AlGaAs and GaAs
Authors: Yuan Y-R , Eda Kazuo , Vawter G. Allen , Merz James L.
Published: February 2003

A new method of open tube zinc diffusion into AlGaAs and GaAs using a confined chamber has been developed. The depth and quality of Zn diffusion into GaAs and AlxGa1−xAs (0.1≤x≤0.5) at 700 °C, are compared with the traditional closed tube diffusion process. It is seen that the new process provides for a very well controlled diffusion depth and allows shallow diffusion. The specific resistivity and surface carrier concentration are measured by the Van der Pauw method. The diffusion quality is affected by the choice of solvent metals. Some variations of solvent metals are discussed. This technique is used for improvement of ohmic contacts in monolithic integrated-optical devices.
Atomic layer epitaxy and characterization of CdTe films grown on CdTe (110) substrates
Authors: Pessa M. , Huttunen P. , Herman M. A.
Published: February 2003

It is shown that growth of homoepitaxial CdTe films on CdTe (110) substrates by the atomic layer epitaxy method can lead to high structural perfection. The electronic structure of these films with the thickness of approximately 100 Å was studied at room temperature by means of angle-resolved photoemission. In addition to several bulklike features observed in the spectra an intrinsic surface state is believed to be found at the energy of 0.33 eV below the valence-band maximum for the first time in epitaxially grown II-VI compound semiconductor films. The work function of the films was found to be 5.75 eV±0.05 eV independent of whether the growth was terminated by a Cd pulse or Te2 pulse.
Pb whisker growth from liquid phase on Pb-alloy Josephson device chips
Authors: Takeuchi Y. , Fujiwara K.
Published: February 2003

Whisker growth in water-soluble flux was observed on Pb–In–Au superconducting transmission lines and In–Bi–Sn solder bumps in Pb-alloy Josephson device chips. The whisker species were identified as Pb single crystals. These whiskers were about 3–5-μm thick, straight, and fluted. Their growth rate was as high as 2.5  μm/min.
A second derivative gradiometer integrated with a dc superconducting interferometer
Authors: Carelli P. , Foglietti V.
Published: February 2003

A second derivative dc-SQUID (Superconducting Quantum Interference Device) gradiometer built on a single chip is described. The prototype shows a flux noise of 8×10−6 φ0/(Hz)1/2 and an inductance of 240 pH. The measured imbalance for fields orthogonal to the chip plane is 240 ppm, while the imbalance for transverse fields is below the measured error. The sensitivity of 1.8×10−8 T/m2 (Hz)1/2 is not yet sufficient for practical applications, but the natural improvement of physical parameters that will be made to use the device in an array of detectors is discussed as well.
GaP/AlxGa1−xP heterojunction transistors for high-temperature electronic applications
Authors: Zipperian T. E. , Dawson L. R.
Published: February 2003

Useful bipolar transistor action over the temperature range from −195 to 550 °C has been demonstrated for heterojunction bipolar transistors in the GaP/AlGaP chemical system. This represents the highest temperature at which useful bipolar solid-state transistor action has ever been demonstrated in any material. Improvements in the materials technology and in the understanding of device characteristics at high temperatures were essential to the successful fabrication of these devices. These results demonstrate that the GaP/AlGaP heterojunction system is an excellent technology for active electronic components operated at high temperatures.
Fourier transform infrared spectroscopic detection of frequency shifting in the nonequilibrium glassy state of polymers
Authors: Joss B. L. , Bretzlaff R. S. , Wool R. P.
Published: February 2003

The concept of molecular strain energy is defined. The temperature, crystallinity, molecular strain, and free volume dependence of the nonequilibrium glassy state in PVC is analyzed. Quenched PVC samples were (1) cycled between room temperature and 112 °C and (2) annealed below Tg followed by cycling to 112 °C. The measured spectra were subjected to digital subtraction and Fourier self-deconvolution routines to extract the amorphous-state results from competing effects. It was seen that heating a quenched glass to 112 °C produced a discontinuity Δξ″ in the slope of the 1100 cm−1 skeletal frequency versus temperature curve at Tg. The value of Δξ″ was essentially zero in all slow cooling experiments and after annealing below Tg. A small shift in frequency, Δνiso was observed during isothermal annealing. Theoretical considerations indicate that Δξ″ and Δνiso have both intra- and intermolecular contributions. It is believed that this observational technique might be used to monitor physical aging in the nonequilibrium glassy state of polymers.
Step voltage transient currents in poly(vinylidene fluoride)
Authors: Kaura T. , Nath Rabinder
Published: February 2003

The step voltage current transient characteristics have been studied in poly(vinylidene flouride) as a function of field, temperature, and time. The current peaks have been observed in the current–time characteristics. These peaks have been attributed to the space-charge injection phenomena. Using the space-charge-limited model of current transients the mobility has been estimated to 2.2±0.2×10−9 cm2 v−1 s−1 at 301 K. The analysis of the temperature dependence of mobilities establishes that charge carrier transport in extended states involving trapping is predominant.
An analysis of thickness-extensional trapped energy resonant device structures with rectangular electrodes in the piezoelectric thin film on silicon configuration
Authors: Tiersten H. F. , Stevens D. S.
Published: February 2003

It has recently been shown that highly uniform thin layers can be etched in a small well-defined region of a silicon wafer and that good quality thin piezoelectric films such as zinc-oxide can be deposited along with the electrodes to form high frequency trapped energy resonant device structures. The accompanying analytical work has been for pure thickness vibrations only. In this work an analysis of essentially thickness-extensional trapped energy modes in the thin piezoelectric film on silicon composite structure is performed. It is shown that for small wavenumbers along the plate the dispersion equation is isotropic in the plane of the plate even though the silicon is severely anisotropic in that plane. From the resulting dispersion relation an asymptotic differential equation describing the mode shape along the surface of the composite plate vibrating in the vicinity of a thickness-extensional resonance is obtained along with the associated edge conditions. Since the mode is essentially thickness-extensional, trapping does not usually occur in the electroded regions for the fundamental mode of the flat composite plate. However, by appropriately thickening the silicon outside the electroded regions trapping in the electroded regions can be made to occur for the fundamental mode. Furthermore, in the case of zinc-oxide on silicon, trapping in the electroded regions can be made to occur for the fundamental mode of a flat plate simply by making the zinc-oxide sufficiently thicker than the etched silicon. The aforementioned asymptotic differential equation and edge conditions are applied in the analyses of the steady-state vibrations of trapped energy resonators and acoustically coupled two-pole resonator filters, both with rectangular electrodes. Lumped parameter representations of the admittance in the case of the single-pole device and admittance matrix in the case of the two-pole device, which are valid in the vicinity of resonances, are obtained. The analyses hold for the first few thickness-extensional modes and their accompanying lateral overtones.
Pyroelectric energy conversion: Hysteresis loss and temperature sensitivity of a ferroelectric material
Authors: Olsen Randall B. , Evans Diane
Published: February 2003

Measurements of polarization versus applied electric field have been made on specimens of lead zirconate modified with Sn4+ and Ti4+ as a function of temperature. These data were analyzed to estimate the amount of hysteretic loss which may be encountered in heat-to-electrical conversion using this ferroelectric. The hysteretic loss is determined to be small (8% to 16% of the total electrical energy). Also analyzed was the sensitivity of the electrical energy output to the operating temperature. Eighty percent of the maximum energy production is estimated to be available over a 16 °C range of conversion cycle mean temperatures (for cycles with 25 °C temperature excursions).
Electrical conduction and strain sensitivity in RuO2 thick film resistors
Authors: Carcia P. F. , Suna A. , Childers W. D.
Published: February 2003

We have measured the resistance and strain characteristics of RuO2-based thick film resistors and find that they differ from Ru-based pyrochlore (A2Ru2O7) resistors. The dependence of resistance on RuO2 volume concentration (x), for different (average) particle sizes, obeys a critical conduction expression of the form R=R0/(x−xc)t, with t≊3. The strain dependence of resistance or strain gauge factor (γ) approximately follows the phenomenological expression γ=γ0+Atx/(x−xc), with γ0 between 2 and 3. Pyrochlore resistors obey the same critical conduction behavior, but we had previously found that t≊2. Further, γ is larger for pyrochlore resistors for comparable resistivity and particle size. We account for the differences by postulating that in RuO2 resistors sintered conduction pathways dominate at low resistance, and both sintered interfaces and tunnel junctions contribute to the high resistance behavior. This is in contrast to pyrochlore resistors for which we believe that tunnel junctions always dominate electrical conduction.
Rapid isothermal annealing of boron ion implanted junctions
Authors: Lasky J. B.
Published: February 2003

The minimum annealing time for complete dopant activation of ion implant doses of 2.8×1014 and 2.8×1015 B+/cm2 are found for temperatures ranging from 850 to 1100 °C. For samples annealed at 1100 °C for 10 s and 1000 °C for 15 min electrical characteristics of diodes are correlated with dopant profiles and penetration depth of transmission electron microscope observable defects. Radiation-enhanced diffusion, associated with the ion implant damage, is the major contributor to dopant diffusion for 10-s anneals at 1100 °C. The junction depth produced by annealing for 10 s at 1100 °C is significantly less than that produced by annealing for 15 min at 1000 °C, while the electrical characteristics of the diodes are the same.
Analysis of transient response by means of discrete Fourier transformation
Authors: Ikeda Kousuke , Takaoka Hidetoshi
Published: February 2003

A new method for analyzing time constants is proposed. In this method, discrete Fourier transformation of the transient data is performed, and the time constants for exponential waves are determined through numerical analysis of the Fourier coefficients. One remarkable characteristic of this method is that the analytical region for the time constant is about three orders in scale. Transient response entailing a long time constant can be easily analyzed within a short measurement period of about a tenth the time constant.
The anomalous behavior of the viscosity in molten Au55Pb22.5Sb22.5—an easy glass former—from 400 to 600 °C
Authors: Lord A. E. , Steinberg J.
Published: February 2003

The kinematic viscosity of the molten alloy Au55Pb22.5Sb22.5 was found to be extremely high, ranging from 0.32 S (stokes) at 400 °C to 0.25 S at 475 °C. At 475 °C a very sharp decrease begins, ending with a value of 0.53 cS (centistokes) at 500 °C. An anomaly in the electrical conductivity mimics the viscosity behavior but is broader in temperature. Differential scanning calorimetry reveals a small peak in specific heat in the vicinity of these anomalies.
Optogalvanic spectroscopy of quasi-resonant Penning ionization
Authors: Shuker R. , Ben-Amar A. , Erez G.
Published: February 2003

Quasi-resonant Penning ionization in a Ne–Ca discharge is detected and studied by using the pulsed optogalvanic effect on the neon 1si→2pj transitions. The ensuing signals exhibit extra features which appear at longer times following the signals obtained in pure neon discharge. A phenomenological model is used to describe the signal and to extract an estimate of the Penning cross section, which is on the order of 10−14 cm2. At high discharge currents the Penning contribution becomes unimportant and the related features in the optogalvanic signal disappear. A correlation between the dependence of the emission intensity of certain transitions of Ca and Ca+ related to the Penning effect and the dependence of the optogalvanic signal due to the Penning ionization on the discharge current is demonstrated. A similar correlation between the I–V characteristics and the dependence of the optogalvanic signal on the discharge current is also shown.
Study of defects in optoelectronic materials using a scanning acoustic microscope
Authors: Sulewski P. E. , Dynes R. C. , Mahajan S. , Bishop D. J.
Published: February 2003

We report a study of defects in some optoelectronic material of technological interest using a scanning acoustic microscope (SAM). Acoustic micrographs of InP, CdTe, and InGaAsP were compared with defect maps obtained by etching, cathodoluminescence (CL), or photoluminescence. Inclusions in InGaAsP were visible using the SAM. However, at low acoustic powers dislocations in InP and CdTe and dark line defects in InGaAsP were not visible. It was possible at high acoustic powers to create ‘‘acoustic etch pits’’ in CdTe which corresponded to defect areas as revealed by CL scans.
Acoustical contrast of a dislocation line in an isotropic medium
Authors: Sulewski P. E. , Bishop D. J.
Published: February 2003

In this paper we calculate the acoustical contrast of a dislocation line in an isotropic medium. The power of the reflected acoustic signal pulse as a function of lens to object spacing is called the V(z) curve. We use a model where the acoustic contrast changes are due to changes in the V(z) curve. We calculate the changes in V(z) due to a dislocation line and show that its effect should be vanishingly small consistent with experimental observations.
Ion-induced reaction of Ni–Au bilayers both on Si and on SiO2
Authors: Hung L. S. , Gyulai J. , Mayer J. W.
Published: February 2003

Ion-induced reaction of Au–Ni bilayers both on Si and on SiO2 was investigated using backscattering spectrometry and glancing angle x-ray diffraction. Upon irradiation of a 〈100〉 Si/Au/Ni sample with Xe ions, Au–Si amorphous alloys are formed initially, then Si reacts with Ni to form Ni2Si resulting in a final layered structure of 〈100〉 Si/Au–Si alloy/Ni2Si. In ion mixing of bilayers on SiO2, Au and Ni are completely mixed to form solid solutions with various compositions. The fact that the presence of Si leads to phase separation between Ni2Si and Au–Si alloy rather than dispersion during ion bombardment is mainly due to the presence of thermodynamic forces in ion mixing.
Thin film crystal growth of Si on fused silica: Effects of growth front dynamics on crystallography
Authors: Black Jerry G. , Hawkins William G. , Griffiths Clifford H.
Published: February 2003

Reflective high speed video microphotography was used to study the advance of the resolidification front during CO2 laser melting of encapsulated polycrystalline silicon thin film structures on bulk fused silica substrates. Prepatterned silicon films were laser recrystallized, removed from the substrate, and then examined by transmission electron microscopy. The crystal structure which results from seeded and unseeded growth and from various liquid-solid growth front shapes was characterized. Supercooling of the melt and subsequent dendritic polycrystalline regrowth is observed in cases where nucleation occurs in isolated molten regions. Transmission electron micrographs demonstrate the necessity of providing controlled seeding conditions, such as regrowth through a narrow neck of silicon. A flat liquid-solid interface supports a [111] growth direction whereas concave thermal profiles cause twinning or low angle grain boundaries in the films.
Strain effects associated with SiO layers evaporated onto GaAs
Authors: Booyens H. , Proto G. R. , Basson J. H.
Published: February 2003

Piezobirefringence is employed in a study of the strain fields associated with SiO stripes evaporated onto GaAs and GaP substrates. The stress fields in the substrates due to semi-infinite SiO stripes are calculated and compared with the stress distributions deduced from elastobirefringence studies. The stress distribution in the SiO along the interface is calculated and a technique is proposed to determine the magnitude of the stress in the SiO layer from birefringence measurements on the substrate. The local stresses beneath the SiO layer deduced from the measurements approach the yield stress of the Pb-based alloys used in Josephson Computer technology.