bluuebunny/crossref_metadata_2025 huggingface dataset:
High field current induced-positive charge transients in SiO2
Authors: Nissan-Cohen Y. , Shappir J. , Frohman-Bentchkowsky D.
Published: February 2003

The formation of bulk positive charge in SiO2 induced by charge injection and high field conditions is studied in this work, utilizing new experimental methods. Using a dc hot electron injection technique it is shown that the presence of electrons in the SiO2 conduction band is a necessary condition for the positive charge formation. This result rules out field (only) induced mechanisms as possible explanations of high field positive charge generation in SiO2. The positive charge formation and annihilation are found to be governed by the same rate equation, and, therefore, exhibit similar behavior as a function of time. This behavior is consistent with an impact ionization-recombination model, with a recombination cross section σ=2×10−16 cm2 and ionization rate α which is in agreement with previous published values. However, other collision activated mechanisms cannot be ruled out.
Effect of grain size on polycrystalline solar cell fill factor
Authors: Sen K.
Published: February 2003

Theoretical investigation of the influence of grain size on the fill factor of a polycrystalline semiconductor-insulator-semiconductor solar cell is made. It is found that fill factor is degraded with decreasing grain size due to increase in resistivity of the material, increase in the diode quality factor, and decrease in short circuit current. The theoretically predicted results reasonably represent the experimentally observed variations in fill factor as a function of grain size.
Electrical conductivity of thick-film resistors
Authors: Jacoboni Carlo , Rizzi Angela
Published: February 2003

A simulative approach to the calculation of electrical transport in thick-film resistors is presented, in which electrons are considered to hop from and to metallic grains and localized states in the glass. From the diffusion coefficient D, obtained with the simulation, and by means of the Einstein relation, generalized for the system under consideration, the electrical conductivity is derived, which shows a maximum around room temperature. This result can be explained by considering that, at first, the thermal energy favors a mobility increase, but at higher temperatures the effect becomes similar to a normal friction which is not compensated by an increase in carrier density owing to the lack of localized states in the glass outside a fixed energy range around the Fermi level.
Molecular deformation and stress-strain behavior of poly(bisphenol-A-diphenyl sulfone)
Authors: Hong Su-Don , Chung Shirley Y. , Fedors Robert F.
Published: February 2003

Stress-optical studies have been carried out to determine the modes of molecular deformation in poly(bisphenol-A-diphenyl sulfone) and its relationship to stress-strain behavior. Stress and birefringence were measured simultaneously as a function of strain at a strain rate of 0.0133 min−1 in the temperature range −179 to 150 °C. In the temperature range from 150 to −100 °C, measurements were performed using four strain rates, 0.0133 min−1, 0.133, 1.33, and 13.3 min−1 at each testing temperature. The results indicate that the processes involved in the molecular deformation appear to be invariant at temperatures below −100 °C. At higher temperatures, the statistical chain segments participate in the deformation process and the degree of participation increases with increasing temperature. The mechanism controlling the stress-strain response is attributed to chain orientation. The stress-strain response at temperatures below −100 °C is attributed to the temperature dependence of an internal energy contribution associated with conformational changes in the chain segments in response to the applied stress. The observed modest temperature dependence of the stress-strain behavior implies relatively low values for the energy barriers for these conformational rearrangements. The γ transition, which is assigned to the motion of the sulfone group, may be responsible for the conformational rearrangement process.
Light scattering studies of atactic polystyrene through a densification cycle
Authors: Coakley R. W. , Hunt J. L. , Stevens J. R.
Published: February 2003

Rayleigh–Brillouin light scattering studies have been peformed on samples of pure atactic polystyrene which has been subjected to a densification cycle. On reheating the densified glass isobarically at low pressure a significant increase is observed in the Rayleigh intensity in temperature regions associated with motion of the phenyl side groups below Tg ( β relaxation) and with rearrangement of the chain backbone above Tg (α relaxation). This enhanced scattering intensity is attributed to nonuniform density distributions created in the sample as the long chain molecules return to configurations appropriate to the nondensified glass and the equilibrium melt. There is only a slight difference in the values of the hypersonic velocity between the densified and nondensified glasses and no difference in the equilibrium melt.
A coupled mode approach to modulation instability and envelope solitons
Authors: Andersen D. R. , Datta S. , Gunshor R. L.
Published: February 2003

Nonlinear media that support envelope solitons are known to exhibit modulation instability; the modulation depth of an amplitude modulated carrier increases spontaneously and it breaks up into isolated pulses. This paper presents a simple coupled mode approach that shows the transfer of power from the carrier to the sidebands, and clearly brings out the roles played by dispersion and nonlinearity. Using this approach it is shown that line acoustic waves should exhibit this instability; the growth rate of the instability is large enough that an experimental demonstration seems feasible.
Use of wall coated cells in atomic frequency standards
Authors: Frueholz R. P. , Volk C. H. , Camparo J. C.
Published: February 2003

An analysis of the effect of the microwave field distribution on the application of a wall coated, bufferless absorption cell in an atomic frequency standard has been performed. While certain advantages of using such a cell in an atomic frequency standard employing a TE011 microwave cavity have been previously demonstrated, we show that a simple incorporation of this type of cell in a frequency standard using a TE111 microwave cavity would not be advantageous. The role of the microwave field distribution, particularly its phase variation within the cavity, is analyzed and suggestions concerning the use of a wall coated cell in a TE111 microwave cavity as applied to an atomic frequency standard are made.
Formation of H− by scattering H+ on a cesiated polycrystalline tungsten surface
Authors: van Bommel P. J. M. , Geerlings J. J. C. , van Wunnik J. N. M. , Massmann P. , Granneman E. H. A. , Los J.
Published: February 2003

We present measurements on the charge transfer and reflection of H+ ions which are scattered from a cesiated polycrystalline tungsten surface. The particle energy ranges from 400 to 2 keV, the angle of incidence with respect to the surface normal is varied between 65 and 90°. The measured values are compared with data obtained earlier for cesiated monocrystalline tungsten (110). The maximum differential H− fraction of scattered particles in the case of cesiated polycrystalline tungsten is 25%. This value is roughly a factor of 2 lower than that of cesiated monocrystalline tungsten (110). The maximum total conversion efficiency, that is the reflected H− current divided by the incident positive ion current, is 12%. This value is about a factor of 3 lower than that obtained for monocrystalline tungsten (110). The different behavior of the polycrystalline with respect to monocrystalline material cannot be explained theoretically by the difference in work function. Calculated values are a factor of 1.7 higher than the measured ones.
Structure determination of the macromonomer poly(1, 8 nonadiyne) and its crosspolymerized product
Authors: Thakur M. , Lando J. B.
Published: February 2003

Electron diffraction patterns have been obtained from the macromonomer and crosspolymerized crystals of poly(1, 8-nonadiyne). Thin (∼150 Å) crystals of the macromonomer, grown from a chloroform solution, were used for obtaining electron diffraction intensity data. Crosspolymerization resulted from subsequent exposure of these crystals to Co60 γ radiation. Twenty-four reflections for the crosspolymerized sample and 18 for the macromonomer were obtained. Refinement of the structures was accomplished using these data. The unit cells of both the macromonomer and the crosspolymerized material were monoclinic and the space groups P21 and P21/n, respectively.
Strontium nitrite monohydrate: A new pyroelectric nonlinear optic material
Authors: Abrahams S. C. , Liminga R. , Marsh P. , Loiacono G. M.
Published: February 2003

Sr(NO2)2⋅H2O is a newly-characterized material with pyroelectric coefficient p2=20 μC m−2 K−1 and second-order nonlinear dielectric susceptibility about 0.06×10−12 V−1 m at room temperature, in space group P21. Characterization is provided by 42 accurately determined powder diffraction lines. The monoclinic unit cell has dimensions a=12.5831(4), b=8.94941(15), c=4.4860(2) Å, and β=99.111(4)° at 295 K. The linear thermal expansion coefficients at room temperature are α1=37, α2=41, and α3=25×10−6 K−1.
Electric field modulation of photoluminescence in cadmium selenide liquid junction solar cells
Authors: Garuthara Rohana , Tomkiewicz Micha , Silberstein Robert P.
Published: February 2003

We have utilized photoluminescence, modulated by small periodic changes of electrode potential, to study the potential distribution at the surface of single crystal cadmium selenide in contact with an electrolyte. We have shown that at reverse bias and at electrode potentials, not far from the flat-band potential, the modulated photoluminescence is described by the ‘‘dead layer’’ theory, in which the electric field in the space-charge layer quenches completely the photoluminescence in that region. The electrical characterization of the interface, based on modulated photoluminescence, agrees well with more conventional impedance measurements.
Depth profiling of tritium in solids with the nuclear reaction induced by deuteron bombardment
Authors: Okuda Shuichi , Taniguchi Ryoichi , Fujishiro Masatoshi , Satoh Yuji , Hiraoka Eiichi
Published: February 2003

A method for the measurement of depth profiles of tritium in solids has been developed in which the 3H(d,n)4He reaction is used. This method is nondestructive with relatively high depth resolution in the surface region of the solids. The validity of the present method has been supported by the examination of the depth profile measured for a tritium target as is used for a neutron source.
Selective photon emission in bombardment of the fluoride-molecular ions on a Be surface
Authors: Inouye H. , Tanji-Noda K.
Published: February 2003

Relative intensity distribution of the photon emission in the particle sputtering from a metal surface has been assumed to be independent of incident ion species. We have found, however, that the photon emission in the sputtering of Be atoms by the bombardment of boron fluoride and carbon fluoride ions provides different results from those of some other incident ions studied so far. The reason for this selective excitation is not yet understood, but the fluorine atom of the incident molecular ion seems to play an important role in the formation of electronically excited particles in the sputtering processes.
The influence of network topology on time-crosslink density reduction
Authors: Chan Yau-Wai (David) , Aklonis J. J.
Published: February 2003

The time-crosslink density reduction principle asserts that changes in crosslink density of polymer networks are reflected as multiplicative time-scale shifts of the distribution of retardation times in the terminal zone of viscoelastic response. Dramatically differing sensitivities of these shifts to crosslink density changes have been reported. We have proposed that differences in network topology associated with crosslink density changes may be responsible for such behavior. To test this hypothesis we have carried out creep experiments on polyurethane samples where the crosslink density was varied through photodimerization of anthracene molecules which were incorporated into the networks so that specific different topological changes would result. We have found that the coupling of dangling chain ends causes relatively slight shifts in the time scale of the distribution function while shifts associated with crosslink formation are much more substantial. From these results we have concluded that network topological changes accompanying crosslink density variations have strong influences on the quantitative aspects of time-crosslink density reduction.
Pulsed electromagnetic acceleration of exploded wire plasmas
Authors: Peratt Anthony L. , Koert Peter
Published: February 2003

A simple analysis of the dynamic state of a current-conducting high-density plasma column, resulting from an exploded wire between the conductors of a rail-gun accelerator or one or more wires strung between the anode and cathode conductors in a pulsed-power generator diode, is given on the basis of a one-dimensional magnetohydrodynamics model. Spatial distributions of the current density, magnetic field, temperature, and particle density are calculated as well as the temporal current, voltage, and impedance histories. The model self-consistently treats the accelerator load transition through its solid, melt, vapor, and plasma states in the presence of its supply source and feed network. Once formed and accelerated, the plasma state calculations show expansion cooling across the self-induced magnetic field if the Bennett condition is not satisfied. The model predictions are compared to two experimental situations. The first involves the delivery of some hundreds of Joules of stored energy to the wire load. For this case, good agreement between the calculated and observed plasma state is obtained. The second situation involves the delivery of many thousands of Joules to the wire load. For this case and dependent upon the wire mass, diameter, number of wires exploded, their separation, and the pulsed energy electrical wave shapes, the magnetohydrodynamic results can be qualitatively incorrect. The necessity of an electromagnetic particle simulation approach is indicated in order to resolve the magnetic rope-like structure and filamentation observed in the very energetic plasmas.
Anomalous temperature dependence of thermoelectric power of PbTe thin films
Authors: Das V. Damodara , Bhat K. Seetharama
Published: February 2003

PbTe thin films of thicknesses ranging from 400 to 4000 Å have been prepared by vacuum evaporation at a pressure of 5×10−5 Torr on clean glass substrates held at room temperature. The thermoelectromotive force of these films has been measured in the temperature range 300–600 K. It is found that thermoelectric power, SF varies anomalously with temperature, being constant at lower temperatures, and rapidly decreasing at higher temperatures. SF is found to be positive indicating that the samples are p type. The anomalous behavior is explained by assuming that at higher temperatures additional donor levels are generated due to creation and ionization of defects in the system.
Epitaxial GaAs by close space vapor transport
Authors: Chávez F. , Mimila-Arroyo J. , Bailly F. , Bourgoin J. C.
Published: February 2003

The rate of transport of GaAs obtained with the close space vapor transport technique has been investigated as a function of the source (T) and substrate (θ) temperatures and of the source-substrate spacing for two different water vapor pressures (6.6 and ∼10−5 mm Hg) introduced with the H2 gas. Analysis of the results allow us (i) to determine the enthalpy and activation energy (2.1 and 3.1 eV, respectively) associated with the reactions taking place at the source and substrate surfaces and (ii) to deduce the existence of a third reaction occurring in the gas phase, whose activation energy has been measured (2.9 eV). Depending on the water vapor pressure, this third reaction occurs near the source (high water vapor pressure) or near the substrate (low water vapor pressure). We derive the equation governing the rate of transport, from which we calculate this rate per unit of source substrate spacing and of water vapor pressure as a function of both T and θ for constant values of θ and T, respectively.
Inhibiting effect of thermal oxides on the growth of rf-plasma oxides for Pb-alloy Josephson junctions
Authors: Wada Masato , Nakano Jun’ichi , Yanagawa Fumihiko
Published: February 2003

The effect of the thermal oxide existing on a Pb-alloy base electrode on rf-plasma oxidation is investigated. This is carried out by removing the initial thermal oxide progressively and also by forming the thermal oxide after the complete removal of the initial thermal oxide. The electrical measurement of current-voltage characteristics and ellipsometric observation are primarily used to evaluate the junction characteristics and oxide thickness. It is found that the thicker thermal oxide, either the initial thermal oxide removed only slightly or thermal oxide formed by the exposure of the base electrode to oxygen for a longer period, brings about the smaller normal tunnel resistance. This result indicates that the thermal oxide inhibits the growth of the rf-plasma oxide; ion transport during rf-plasma oxidation is presumably inhibited by the presence of the thermal oxide.
Mechanism of catastrophic degradation in InGaAsP/InP double-heterostructure light emitting diodes with Ti/Pt/Au electrodes
Authors: Ueda Osamu , Yamakoshi Shigenobu , Umebu Itsuo , Sanada Tatsuyuki , Kotani Tsuyoshi
Published: February 2003

The mechanism of catastrophic degradation of InGaAsP/InP double-heterostructure light emitting diodes with Ti/Pt/Au electrodes through the application of pulsed large current, is investigated by electroluminescence topography, scanning electron microscopy, energy dispersive x-ray spectroscopy, and transmission electron microscopy. As the degradation is promoted, a dark region is generated in the center of the light emitting area. This then develops through the whole light emitting area. During the generation and the development process of the dark region, no dislocations are generated. The dark region, which develops through the whole light emitting area, consists of amorphous area and nonstructural small grains. There is clear compositional inhomogeneity in the region corresponding to the dark region. However, the electrode metals are not detected. The mechanism of the catastrophic degradation can be explained by local heating at the contact region by large current pulses, melting of the matrix crystal at the current above the degradation current level, and development of the molten region through the whole light emitting area.
Studies of deep levels in Si epitaxy grown by SiCl4–H2 system
Authors: Lou J. C. , Lin M. S. , Wang W. S.
Published: February 2003

The electrical characteristics of a SiCl4-H2–grown silicon epitaxial layer are investigated using the deep level transient spectroscopy (DLTS) and I-V measurement. DLTS results show the existence of two electron traps [Ec−0.41 eV and Ec−(0.66±0.03) eV] and one hole trap [Ev+0.34 eV] in the epitaxial layer. These traps enhance the generation of leakage current in the Si epilayer. The annealing behavior indicates that the activation energy of electron trap Ec−(0.66±0.03) eV is 1.65 eV and the frequency factor is 1.43×1013 sec−1. It also indicates that a 900 °C annealing process can anneal out these deep levels and improve the device performance.
Surface photovoltage measured capacitance: Application to semiconductor/electrolyte system
Authors: Kamieniecki Emil
Published: February 2003

Surface photovoltage measured capacitance (SPMC), a novel technique for determining the properties of semiconducting materials, is introduced. SPMC permits the determination of a semiconductor depletion layer capacitance by measuring changes of the surface potential barrier induced by low intensity chopped light whose photon energy exceeds the band-gap energy. The theory of the SPMC technique is derived, and an equivalent circuit for analyzing the measurements is described. The present technique is compared with the conventional current measured capacitance method, and it is shown that using SPMC the separation of the depletion layer capacitance from the influence of the surface states can be performed by measurements at only one frequency of light modulation. This is a simpler procedure than the frequency dispersion measurement required of conventional capacitance techniques. Measurements of the capacitance-voltage characteristics of a semiconductor/electrolyte system, in particular n-type WS2 exposed to an inert electrolyte, are used as examples to illustrate the capabilities of SPMC.
Long and narrow Josephson tunnel junctions of mixed overlap and inline character
Authors: Olsen O. H. , Samuelsen M. R.
Published: February 2003

A model describing long Josephson junctions of mixed overlap and inline geometry is presented. The shape of the first zero field step is calculated for this model using a perturbation approach. The question of influence of external magnetic field on the maximum supercurrent is investigated for overlap, inline, and mixed overlap-inline geometries. A linear dependence is found for the inline model and for mixed overlap-inline junctions in agreement with experiments.
Effect of twist on wires made from i
n s
i
t
u superconductors
Authors: Carr W. J.
Published: February 2003

The effect of twist on the transverse field hysteresis of in situ superconducting wires is assumed to result from a lowering of the axial critical current density due to anisotropy of critical current density in the material. In weak transverse magnetic fields the twist raises the hysteresis loss, while in stronger fields the twist lowers the loss. It is shown that the axial critical current density determined from hysteresis or magnetic moment measurements in a twisted wire can be lower than the value obtained from transport measurements.
Some effects of elastic stresses and demagnetizing fields on nickel samples
Authors: Bordin G. , Cecchi G. C. , Montanari T.
Published: February 2003

Magnetoelastic measurements have been performed on some tubular Ni samples in order to study the initial magnetization curves as depending on the sequence twist demagnetization or vice versa. The experimental results pointed out that, if the torsion comes before the demagnetization, it causes an anisotropic demagnetization along the compression helix of the torsion. On the contrary, when the demagnetization precedes the torsion, a nucleation and growth of the new domain walls occur. These conclusions are supported by Gavoille theory.
Domain-wall dynamics in garnet films with orthorhombic anisotropy
Authors: Breed D. J. , Nederpel P. Q. J. , de Geus W.
Published: February 2003

The dynamics of domain walls in (110) oriented manganese containing garnet films have been studied. Bubble films and special films in which a single straight domain wall can be stabilized have been prepared. The magnetic anisotropy in these films is orthorhombic and the influence of the in-plane anisotropy field on the maximum domain-wall velocity has been studied. The observed maximum velocities, varying between 40 and 1500 m s−1, are usually considerably lower than the maximum velocities predicted by theory. However, for very high in-plane anisotropy fields the experimental maximum velocities approximate the theoretical ones. From the comparison of different samples it has been concluded that the maximum velocity of the bubbles having no Bloch lines is not very different from the maximum velocity of straight domain walls. Furthermore, it has been shown that the maximum velocity is independent of the film thickness. The influence of external in-plane fields on the maximum velocity also has been studied. In-plane fields in the hard direction of magnetization have no influence on the maximum velocity. In-plane fields small compared with the in-plane anisotropy field increase the maximum velocity considerably if these in-plane fields are applied in the direction perpendicular to the hard axis of magnetization. The influence of stray fields on the maximum velocity is discussed.
Piezomagnetic and elastic properties of metallic glass alloys Fe67CO18B14Si1 and Fe81B13.5Si3.5C2
Authors: Meeks Steven W. , Hill J. Clifton
Published: February 2003

The piezomagnetic and elastic properties of two metallic glass alloys Fe67Co18B14Si1 (Metglas 2605CO) and Fe81B13.5Si3.5C2 (Metglas 2605SC) are presented. The Metglas 2605CO and 2605SC alloys show optimum magnetomechanical coupling coefficient k33, change of Young’s modulus as a function of applied field ΔE/E, and piezomagnetic strain constant d33 values of 0.76, 0.79, 88×10−9 m/A and 0.90, 4.72, 400×10−9 m/A, respectively. The ΔE/E and d33 values of the 2605SC alloy are the largest ever reported. This alloy has a hydrophone figure-of-merit that far exceeds the corresponding value of a commonly used piezoelectric ceramic, PZT4. Both of these commercially available alloys should find considerable use in transduction devices such as sensors or variable acoustic delay lines.
Study of thermally induced active birefringence in Nd:glass laser rods
Authors: Uppal J. S. , Gupta P. D. , Bhawalkar D. D.
Published: February 2003

A study of active birefringence arising due to the thermal stresses in Nd:glass laser rods under different experimental conditions of pumping is reported. The extent of birefringence was measured in terms of depolarization of a pulsed probe beam from a Q-switched Nd:YAG (yttrium aluminum garnet) laser. The maximum depolarization for a 38-mm-diam rod pumped by 12 xenon flash lamps in a circular diffuse reflector configuration was determined to be 2.3%. This value for the depolarization as well as its radial profiles agree well with those determined from a cylindrically symmetric gain profile. In cases of deviation from the cylindrically symmetric pumping, the observed birefringence was found to be more for a clover leaf reflector as compared to that for a circular diffused reflector.
Photoinduced metastable surface effects in boron-doped hydrogenated amorphous silicon films
Authors: Aker B. , Fritzsche H.
Published: February 2003

We observed metastable light-induced conductance changes in p-type hydrogenated amorphous silicon films which are different from those discovered by Staebler and Wronski. In contrast to the large metastable decrease in the dark conductance after prolonged exposure to band-gap light (Staebler–Wronski effect) we observed an increase in the dark conductance by more than a factor of 30 at room temperature. This light-induced increase can be reversed by annealing. The anomalous conductance increase is associated with the presence of a surface oxide layer because it disappears after etching the sample. We find that the enhanced conductance is due to an increase of a hole accumulation layer in the sample caused by a light-induced metastable change in the surface oxide.
Measurements on ablative hole formation process in thin tellurium-selenium alloy films
Authors: Lou D. Y. , Blom G. M.
Published: February 2003

We report on real time measurements of the hole formation process in Te-Se alloy films. The results tend to support a three-step model. First, there is an initiation stage. Energy is absorbed in advance of hole formation. The precise mechanism for hole initiation depend quite sensitively on writing conditions. In some situations the evidence supports a blister formation model. After the hole is initiated, its boundary then propagates out, driven by interfacial energies. Finally, in the terminal phase of hole opening, the continued propagation of the hole boundary becomes limited by the propagation of the melt boundary, until the film material solidifies.
An x-ray diffraction study on the microstructure of Ag–Cd–In (α-phase) alloys
Authors: Reddy S. Venkat , Suryanarayana S. V.
Published: February 2003

X-ray diffractometric profiles of α-phase Ag–5Cd–5In, Ag–10Cd–5In, Ag–20Cd–5In, Ag–25Cd–5In alloys were recorded using a proportional counter for annealed and cold-worked states of the samples. Stacking fault parameters were obtained from the peak shift and peak asymmetry of these profiles. Fourier methods were also applied to the line profiles to evaluate compound fault probability, effective particle size, and rms microstrains for these ternary alloys. It was found that there exists a linear relationship between α(=α′−α″) versus combined solute concentration (Cd+In). The effective particle size De and the rms microstrain 〈ε2〉1/2 along [111] and [100] directions were found to be anisotropic and the anisotropy in the particle size was found to increase with solute concentration. The dislocation density ( ρ) and the ratio of stacking fault energy (γ) to shear modulus ( μ) of these alloys were evaluated.
Dual ion implantation technique for formation of shallow p+/n junctions in silicon
Authors: Tsaur B-Y. , Anderson C. H.
Published: February 2003

To produce thin p+ layers in n-Si substrates, low-energy B+ ions have been implanted into amorphous layers formed by the prior implantation of Si+ ions. Thermal annealing results in recrystallization of the amorphous material by solid-phase epitaxy. After annealing, the B depth profile determined by secondary ion mass spectrometry is close to the calculated profile, transmission electron microscopy shows that the implanted layer is of good crystal quality, and sheet-resistivity measurements show that electrical activation is complete. Diodes with p+/n junctions ∼0.25 μm deep produced by the dual implantation technique show excellent I-V characteristics, with reverse leakage current densities ∼5 and 16 nA/cm2 at −1 and −5 V, respectively. P-channel metal-oxide-semiconductor field-effect transistors fabricated using the dual implantation technique exhibit superior electrical characteristics compared to similar devices fabricated using the conventional single B implant process.
The physical properties of CdS thin films electrodeposited from aqueous diethylene glycol solutions
Authors: Baranski A. S. , Bennett M. S. , Fawcett W. R.
Published: February 2003

Cadmium sulfide films electrodeposited from aqueous diethylene glycol solutions containing elemental sulfur, and either cadmium chloride or cadmium perchlorate have been characterized with respect to both structural and electrical properties. Significant differences have been found between samples grown from solutions containing chloride ions and those grown from solutions containing perchlorate ions. The properties of the CdS films are discussed with respect to their potential use in photovoltaic cells.
Stresses induced in GaAs by TiPt ohmic contacts
Authors: Henein G. E. , Wagner W. R.
Published: February 2003

Measurements of the radius of curvature of GaAs substrates metallized with Ti–Pt bilayer thin films and annealed at 450 °C indicate that the state of stress of the substrate (tension versus compression) at the interface varies with the thickness ratio of the metals. Increasing thicknesses of Ti (Pt) result in increasing tensile (compressive) stresses in the substrate. An appropriate choice of the thickness ratio of Ti/Pt yields an unstressed substrate after annealing. It was found in most cases that extensive plastic deformation occurred in the film during annealing.
Deep levels related to ion-implanted tellurium in silicon
Authors: Kalyanaraman V. , Mohan Chandra M. , Kumar Vikram
Published: February 2003

Deep impurity levels due to ion-implanted tellurium in n–silicon are studied. Two donor levels at Ec−0.13 and Ec−0.56 eV are obtained using deep level transient spectroscopy. Thermal electron capture cross sections for both levels are too large to be measured. Electron photoionization cross section spectrum confirms the Ec−0.56 level and also reveals an excited state 0.45 eV above the ground state.
Low field mobility of 2-d electron gas in modulation doped AlxGa1−xAs/GaAs layers
Authors: Lee K. , Shur M. S. , Drummond T. J. , Morkoç H.
Published: February 2003

We derive a simple analytical formula for the low field electron mobility which uses the 2-d degenerate statistics of the 2-d electron gas. This takes into account the finite width of the depletion layer in (Al,Ga)As for the scattering by remote donors, scattering by the interface charge, and the polar-optical and acoustic deformation potential and piezoelectric scattering. The largest measured value of mobility is determined by scattering due to interface charge in some cases. The ultimate value of the mobility which may be achieved is limited by the acoustic deformation potential and piezoelectric scattering at about 6.5×106 cm2/V s for an interface carrier density of the 2-d electron gas ns0 ≂4×1011 cm−2. Our results agree very well with experimental data obtained in our laboratory as well as other laboratories.
Electron drift velocity in lead telluride at high electric fields
Authors: Chattopadhyay D. , Purkait N. N.
Published: February 2003

Hot electron drift velocity in PbTe at 77 K is calculated by the Monte Carlo method up to a field of 3 kV/cm. The nonparabolic anisotropic nature of the band structure and scattering by polar optic, deformation potential acoustic, and intervalley phonons are incorporated. The anisotropy in the velocity field characteristics is studied by considering fields parallel to the 〈100〉 and 〈110〉 directions. The calculated results are in good agreement with the experimental data in the prebreakdown region. Contrary to a previous result, no negative differential resistance is found to appear in the breakdown region considering transport in the L valleys only.
Electrical conductivity in two phase nickel–nickel oxide mixtures and conductivity of nickel oxide at the nickel–nickel oxide phase boundary
Authors: Tare V. B. , Wagner J. B.
Published: February 2003

The electrical conductivity of sintered pellets of nickel–nickel oxide mixtures of various compositions has been measured as a function of temperature in the range 700–1000 °C. The electrical conductivity of nickel oxide single crystals in air as well as in oxygen pressures corresponding to nickel–nickel oxide equilibrium has also been determined as a function of temperature. The conductivity of nickel–nickel oxide composites decreases initially, attains a minimum at approximately 1 mol % nickel and increases again with the increase in concentration of nickel. The activation energy for conduction remains constant for all compositions containing 20 mol % or less nickel. The variation of conductivity with compositions containing 1–20 mol % nickel is found to be in accordance with Wagner’s model. The decrease in conductivity of nickel oxide with the addition of 1 mol % nickel has been attributed to the trapping of holes from nickel oxide by electrons from the dispersed nickel.
Hole formation in tellurium alloy films during optical recording
Authors: Blom G. M.
Published: February 2003

The material transport phenomena of hole machining, which occur during optical recording, are described for metal films such as elemental tellurium and its alloys. It is shown that the temperature gradient resulting from a focused laser beam creates a minimum in the surface tension at the hottest point of the molten spot. Consequently, a shear stress pulls material from the center of the melt towards the edge, forming a rim. It is demonstrated that the film is thin enough to have all material pulled away, thereby forming a hole and that this occurs in a time frame of about 10–50 ns. Also the cross sectional shape of the rim is modeled. Experimental information corroborating this model is obtained by investigating dropouts, which are created by recording close to the threshold. (A dropout is defined as a missing hole; i.e., it is intended to machine a hole but it fails to open.) The surface profile of dropouts indicates that material has retracted from the center to form a rim. Also, it is shown that dropouts are indeed frozen-in states of the hole opening process. Experimental data on cross sections of rims around fully opened holes and around optical dropouts support the model, showing rounded rims for the first case and very steep edges surrounding dropouts.
Photodynamics and stability of laser active (F+2)A centers
Authors: Schneider Irwin , Pollock Clifford R.
Published: February 2003

In additively colored KCl : Li crystals, the (F+2)A color center laser operates through a photodynamic equilibrium in which UV excitation generates a partial conversion of (F2)A centers to (F+2)A. Evidence is presented which shows that continuous UV exposure is necessary to sustain laser action because of the neutralization of (F+2)A centers which occurs through the capture of F′A center electrons. The bleaching of FA centers results directly from absorption of the 1.3-μm pump radiation. Since the absorption is extremely weak, only modest UV intensities are needed for intense cw laser operation.
Second harmonic generation with surface guided waves in signal processing geometries
Authors: Liao C. , Bundman P. , Stegeman G. I.
Published: February 2003

The nonlinear mixing of two oppositely propagating waves can be used to perform the convolution of two waveforms. We have examined the nonlinear cross sections for this interaction based on waves guided by both dielectric and metal films. The numerical analysis shows that optimum efficiencies are obtained with dielectric film guided waves and that useful cross sections can be obtained with organic nonlinear materials.
Characterization of TiO2, LiNb3O8, and (Ti0.65Nb0.35)O2 compound growth observed during Ti:LiNbO3 optical waveguide fabrication
Authors: Armenise M. N. , Canali C. , De Sario M. , Carnera A. , Mazzoldi P. , Celotti G.
Published: February 2003

TiO2, LiNb3O8, and (Ti0.65Nb0.35)O2 compounds have been observed and characterized during the fabrication of optical waveguides by Ti indiffusion in LiNbO3, performed in a flowing dry O2 atmosphere. Ti oxidizes by reacting with both O atoms of the surrounding atmosphere and of the LiNbO3 substrate. TiO2 formation is followed by LiNb3O8 and (Ti0.65Nb0.35)O2 phase growth. With further increasing in the annealing temperature the TiO2 and LiNb3O8 compounds are consumed and vanish. After 30 min at 950 °C both Y- and Z-cut substrates appear covered only by a uniform and epitaxial (Ti0.65Nb0.35)O2 layer which behaves as the real source for Ti diffusion. The LiNb3O8 formation and dissolution were also observed in samples uncoated with Ti. Similar results were observed in LiNbO3 samples annealed in dry N, Ar, and static air.
Reflective array compressors using 180° reflecting metal dot arrays
Authors: Woods R. C.
Published: February 2003

Recently, a reflective array compressor using 180° grooved reflectors and a 3-dB multistrip coupler has been described. This has the advantage over conventional 90° reflective devices that the surface waves undergo only one reflection instead of two, and so the insertion loss can be low. This paper reports a new device, using surface acoustic waves propagating on YZ LiNbO3, in which the grooves are replaced by metal dot arrays, removing the need for ion-beam milling and—through variation of dot density—providing a simple method of weighting. The devices designed had a time-bandwidth product of 1000, dispersion time of 20 μs, bandwidth of 50 MHz centered at 150 MHz, and a 40-dB sidelobe six-term Taylor amplitude weighting. Compared with dot array devices using 90° reflectors the design is simplified since the velocity and scattering anisotropy, important for 90° reflectors, need not be considered. The surface wave velocity change under the metal dot array is potentially a source of phase error, but it is shown that a simple empirical correction in the mask design is sufficient to reduce this to around 5° rms. Deviation of the weighting characteristic from the ideal is typically of the order ±1 dB.
Elastic wave scattering from irregular voids
Authors: Tittmann B. R. , Domany E. , Opsal J. L. , Newman K. E.
Published: February 2003

Results are presented for elastic wave scattering from irregular voids embedded in Ti alloy by the diffusion bonding process. The defects examined are: two overlapping spherical voids of unequal radii, two overlapping voids consisting of a sphere and a prolate spheroid, and a spherical void with an encircling crack. Representative plots are given for the raw waveforms, magnitude of the deconvolved Fourier transform, and in some cases the time impulse response function. The data are compared to and analyzed in terms of two current theoretical approaches. While good quantitative agreement was observed over certain ranges, the comparisons point to definite (in some cases not unexpected) limitations in either the pertaining theory or experiment or both. The results are discussed with an eye toward applications to nondestructive evaluation.
Analysis of manganin and ytterbium gauge data under shock loading
Authors: Gupta Y. M.
Published: February 2003

Experimental results from previous studies on manganin and ytterbium piezoresistance gauges are analyzed. The gauge stresses and strains for the analysis were approximated from geometrical considerations as suggested in the earlier studies. The results of our analysis lead to conclusions that are significantly different from the previous work. The reasons for these differences are discussed and the requirements for a more rigorous analysis are outlined.
Charging phenomena in the scanning electron microscopy of conductor-insulator composites: A tool for composite structural analysis
Authors: Chung K. T. , Reisner J. H. , Campbell E. R.
Published: February 2003

Useful applications of charging phenomena occuring during scanning electron microscopy (SEM) of conductor-insulator composites have been investigated. Unlike the charging of insulating particles in conventional SEM techniques, the local field effect in a conductive composite enhances the relative secondary electron emission in the isolated conductive grains. This ‘‘reverse’’ charging characteristic was utilized for the mapping of dispersion, orientation and segregation characterization in conductor-insulator composite systems. The charging phenomenon directly reflects the relative electrical continuity of the conductive filler particles in the insulating matrix. The photographic display of the conductive filler arrangement in the composite using this charging phenomenon is termed a SEM charging micrograph. Carbon black/polyvinyl chloride composites with both spherical and chain-like carbon blacks were used in this study. The structural aspects of such composites as revealed by charge display techniques were found to be directly correlatable with the electrical properties of the composites. This technique is applicable to composites with both small (100 Å) and large (over 10 μ) fillers.
X-ray spectral line coincidences between fluorine K- and transition-metal L-series lines
Authors: Burkhalter P. G. , Charatis G. , Rockett P. D.
Published: February 2003

X-ray spectroscopy was performed in the 12–15-Å region, recording L-series lines from selected laser-irradiated transition metals. Line coincidences and near coincidences were identified between Cr, Mn, Fe, and Ni L spectra, and F viii and F ix K-shell lines. Wavelengths were determined to accuracies of 1–3 mÅ and will be utilized in selecting potential pumping candidates in future x-ray lasing schemes. High-resolution x-ray spectra were collected under controlled illumination and target conditions, using 1.05- and 0.527-μm laser excitation with the KMS CHROMA laser. Laser intensity varied from 1.2–2.5×1014 W/cm2 in 200-ps pulses. Three groups of x-ray spectra were collected with highly dispersive x-ray crystals at wave bands centered at 12.643, 13.781, and 14.458 Å, corresponding to H- and He-like lines from fluorine. Two specially designed flat crystal spectrographs employing camera shutters were used with pairs of beryl and thallium acid phthalate (TAP) crystals. The spectra from potential lasant and pump candidates could be recorded on the same spectrogram to aid in identifying x-ray line coincidences. In cases where wavelengths were measured in both the 1.05- and 0.527-μm laser work, agreement within 1–3 mÅ was obtained for the L-series x-ray lines. Within this accuracy range, some five L-series x-ray lines, mostly 2p-3d transitions from the metals Cr, Mn, and Ni, had wavelength values coincident with K-series lines in fluorine.
Monte Carlo studies of attachment in HCl and HCl–N2 mixtures
Authors: Penetrante B. M. , Bardsley J. N.
Published: February 2003

Recent studies of attachment in pure HCl and HCl–N2 mixtures are analyzed by Monte Carlo simulations. The drift velocity and attachment coefficients are calculated as a function of field strength and relative concentration of HCl. Cross sections for momentum transfer, vibrational excitation, and attachment are derived.
Stress measurements using piezoresistance gauges: Modeling the gauge as an elastic-plastic inclusion
Authors: Gupta Y. M.
Published: February 2003

A theoretical framework is provided to analyze and interpret piezoresistance gauge measurements. The analytic developments consist of a phenomenological electromechanical model for piezoresistance and an elastic-plastic inclusion analysis. The combination of these analytic developments can, in principle, explain the main aspects of the gauge response under shock loading. The present work may provide the basis for a complete specification of the stresses in shock wave uniaxial strain experiments and extension of piezoresistance measurements to other loading conditions. Further experiments are required to determine the material constants needed for the model and to permit detailed comparisons with the analytic results.
Metalorganic chemical vapor deposition of undoped In1−xAlxAs on InP
Authors: di Forte-Poisson M. A. , Razeghi M. , Duchemin J. P.
Published: February 2003

In1−x Alx As epitaxial layers were grown on (100) InP substrates by the organometallic vapor phase epitaxy method. Undoped layers with mirror smooth surfaces were obtained for substrate temperatures of 600–650 °C. By adjusting the relative ratio of In and Al, lattice matched In0.52 Al0.48 As epilayers were reproducibly grown on InP substrates. X-ray measurements, scanning Auger analyses, and electron mobilities are presented. These results show that the quality of the epilayers obtained here was comparable to the best reported layers grown by other methods.
Simple model to explain inhomogeneous structures in shocked solids
Authors: Vineyard G. H.
Published: February 2003

A model is proposed to explain observations of inhomogeneous yielding in shocked solids. Instead of seeking hydrodynamic or elastic-plastic instabilities in an initially homogeneous specimen, it is proposed that the material under shock conditions (at pressures well above the yield strength) may be characterized as a viscous medium with initially inhomogeneous viscosity. Such a viscosity might be caused by an inhomogeneous distribution of dislocations. Assuming that the viscosity also decreases with temperature in a simple way, suitably truncated hydrodynamic equations can be solved analytically and predict a tendency toward runaway of temperature and deformation in localized regions.
Extended-defect reduction by uniform heating for P+-implanted Si wafers
Authors: Komatsu Ryosaku , Kajiyama Kenji
Published: February 2003

P was implanted into 76-mm-diam (111) Si wafers at an energy of 40 keV with a dose of 2.54×1016/cm2. An increase in extended defects was found at a high insertion speed of wafer loading into a furnace at 1000–1100 °C in a N2 ambient. The increase was due to nonuniformity in the temperature history and resultant thermal stress in the wafer, though no slip line was observed. The temperature nonuniformity was monitored by thermal-oxide thickness nonuniformity for heating in a dry-O2 ambient. A low insertion speed resulted in uniform heating and reduced extended defects.