bluuebunny/crossref_metadata_2025 huggingface dataset:
Optically induced crosstalk in LiNbO3 waveguide switches
Authors: Schmidt R. V. , Cross P. S. , Glass A. M.
Published: February 2003

Observations of optically induced crosstalk drift in LiNbO3 waveguide directional coupler switches at 0.633- and 1.06-μm wavelengths are reported. At 1.06 μm, crosstalk has been observed to remain below −25 dB for optical powers of 1 mW. The drift at 0.633 μm is explained in terms of the photorefractive effect of LiNbO3.
Effects of chemical kinetics of the performance of the atomic iodine laser system
Authors: Fisk George A. , Truby Frank K.
Published: February 2003

Model calculations show that chemical reactions which take place in the active medium of a photolytically pumped iodine laser limit the efficiency with which pump photons are utilized and convert significant amounts of the starting material RI to the unwanted by-products R2 and I2. Laser- and rf-discharge-based methods for regenerating starting materials from by-products are evaluated experimentally. For economical operation of large iodine laser systems, CF3I is presently the best starting material, and a pulsed rf-discharge technique is presently the best one for chemical regeneration. The absorbed energy required to regenerate one CF3I molecule using pulsed rf-discharge techniques is 5.8 eV.
The effect of eddy currents on NMR line shapes in the presence of self-diffusion
Authors: Engardt R. D. , Paine G. H.
Published: February 2003

A theory by Chapman, Rhodes, and Seymour treats the eddy-current effect on NMR line shapes in metals. The objective of the present work is to test the theory in the presence of high self-diffusion rates and also in the presence of moderately large saturation factors. The theory was verified using lithium metal wires at room temperature.
High-gain image intensifier studies of electroluminescence in III–V semiconductors
Authors: Chapman G. N. , Ramage J. C. , Walton A. J.
Published: February 2003

A high-gain multistage image intensifier and microscope are used to study low-current dc electroluminescence in bulk semiconductors. A comparison is made with cathodoluminescence, and preliminary results for Ga1−xAlxAs and GaP are presented. It is shown how the technique gives information about the electrical contacts to a specimen, the electroluminescence spectra at points on a specimen, and the distribution of radiative recombination centers.
Radiative transitions induced in gallium arsenide by modest heat treatment
Authors: Birey Hülya , Sites James
Published: February 2003

Photoluminescence spectra from three species of n-GaAs, lightly Si doped, heavily Si doped, and lightly Te doped, show the onset of additional radiative transitions upon modest annealing in the 550–700 °C range. Etch-back procedures reveal that the new structure is all surface related. It is attributed to the creation of arsenic vacancies at the surface which allow electrical activation of silicon donors, enhance the probability of silicon site exchange, and lead to complex formation involving both donor and acceptor levels.
Microwave generation by intense relativistic electron beams propagating in a circular waveguide
Authors: Etlicher B. , Huetz A. , Buzzi J. M. , Haldenwang P. , Lequeau D.
Published: February 2003

The stability of circular waveguide modes perturbed by a relativistic electron beam is investigated. The electron beam propagates along the waveguide and is guided by an applied uniform axial magnetic field. The electron beam is represented by a distribution of rigid rotators all having the same energy and Larmor radius rL with their guiding centers centered on a circle or radius Rb around the guide axis. Numerical results are presented giving a general view of the competition between synchronous and cyclotron instabilities for TM and TE modes as a function of rL and Rb.
Structure and optical properties of evaporated films of the Cr- and V-group metals
Authors: Nestell J. E. , Christy R. W. , Cohen Mitchell H. , Ruben G. C.
Published: February 2003

Thin films of Cr, Mo, and W rapidly evaporated in high vacuum (5×10−7 Torr) onto room-temperature substrates show anomalously low reflectance (compared to bulk samples). From electron and x-ray diffraction and electron microscopy, we find the normal bcc crystal structure, but with very fine grains. Columnar grains about 100 Å in diameter were separated by a less dense grain-boundary network about 10 Å wide. The measured optical conductivity agrees with an inhomogeneous-medium model that assumes the normal crystalline conductivity for the grain interiors, with model parameters that correlate to the observed columnar grain size. In contrast, V and Nb films rapidly evaporated onto room-temperature substrates have the reflectance of bulk crystalline material. On liquid- nitrogen temperature substrates, however, V and Nb have normal bcc crystal structure but with small flat-plate grains, and the same model, with appropriate parameters, accounts for the optical conductivity. The difference between these two groups apparently depends on residual gases segregated at the grain boundaries in the Cr-group films.
Optical properties of titanium and titanium oxide surfaces
Authors: Wall William E. , Ribarsky M. W. , Stevenson J. R.
Published: February 2003

The near-normal incidence reflectivity of titanium has been measured for photon energies of 2–25 eV under closely controlled surface conditions. Measurements, using synchrotron radiation above 5 eV, were made in ultrahigh vacuum on both clean and in situ oxidized surfaces monitored with Auger spectroscopy. The reflectivity data were Kramers-Kronig analyzed to generate the optical constants. Structure in ε2 appearing in the oxidized surface but absent in the clean surface is related to the oxygen 2p and 2s bands. Some differences in the oxide structure are observed between oxide films grown on titanium exposure to oxygen compared to exposure to an oxygen plasma.
Energy conservation for reflectivity and transmissivity at a very rough surface
Authors: Tsang L. , Kong J. A.
Published: February 2003

The transmissivity and reflectivity obtained from Huygen’s principle and the geometrical optics approach by integration over angular variables over the hemispheres are shown to violate the conservation of energy. Energy conservation is observed when the integration limits are modified. The modified transmissivity and reflectivity have the additional advantage that they can be evaluated with asymptotic methods to bring out explicitly the rough surface effects. This has direct application to passive remote sensing of a rough surface where the emissivity is to be calculated.
Optical and microwave instabilities in injection lasers
Authors: Hakki B. W.
Published: February 2003

We find that the onset of instability in many GaAs DH lasers that are capable of self-induced modulation is always preceded by the strong emission of noise. The longitudinal optical-mode width is fairly narrow, typically 0.1–0.3 Å, when the optical power contains noise. It is only after the optical power exhibits coherent self-induced modulation that the apparent longitudinal mode width increases to 1–2 Å. This apparent increase in longitudinal mode width is attributed to a wavelength that changes periodically (sinusoidally, for small signals) with time. The wavelength oscillation is due to variations in refractive index brought about by oscillations in the carrier concentration. The implication is that in these lasers, the instantaneous longitudinal optical mode width is relatively narrow regardless of the temporal instability of the light output. In addition, it is shown analytically that there is a critical noise level above which a laser becomes unstable, i.e., exhibits coherent self-induced modulation.
Dependence of pattern dimensions on proximity functions in electron beam lithography
Authors: Parikh Mihir
Published: February 2003

The departure from the prescribed dimensions for simple patterns have been calculated as a function of proximity function parameters. Seven sets of proximity function parameters are used in this work. Using these, an attempt is made to delineate the effect of each parameter on variations in pattern dimensions. With parameters appropriate for high incident electron kinetic energies, it is shown that with increasing energy, even though the backward-scattered distribution increases, the proximity effect seems to decrease. Also, effects due to proximity function parameters appropriate to high-Z substrates are also investigated.
Calculation of changes in pattern dimensions to compensate for proximity effects in electron lithography
Authors: Parikh Mihir
Published: February 2003

Calculation of changes in pattern dimensions to compensate for proximity effects in electron lithography have been performed for simple patterns (isolated shapes and lines adjacent to large areas). The formulation of intershape and intrashape proximity effects lead to a set of nonlinear coupled equations. Such equations have been solved iteratively and/or graphically for a variety of cases. Results for isolated lines are in good agreement with empirically determined values that are reportedly being used in electron lithography. Calculated results, for the shapes considered here, can now be used as ’’design rules’’ for pattern generation in electron lithography. The intrinsic quality of corrections (i.e., edge definition) that can be expected from such a technique is discussed. Calculations for interacting shapes show the impracticality of this technique for arbitrary patterns. Despite shortcomings, such a technique may be the only viable technique for electron projection lithography and thus may be useful.
Estimation of sputtering rate by bombardment with argon gas ions
Authors: Okajima Yoshiaki
Published: February 2003

The sputtering rates of single-crystal Si and polycrystalline Ag, Cu, Ni, Ti, and Al were measured. These target materials were bombarded with argon ions accelerated at 10 kV. The sputtered depth after a given interval of bombardment was greatest for Ag, and decreased for the other materials in the following order: Cu, Ni, Ti, Si, and Al. The difference in the sputtering rates of these target materials was investigated on the basis of their binding energies, and the following expression for sputtering rate was obtained experimentally, Sr=K (I/D)(M/Ec)k, where Sr is the sputtering rate, I is the current density of incident argon ions, and D, M, and Ec are the atomic concentration, mass number, and cohesive energy of a target material, respectively. K and k are constants. Sputtering yield (Sy) can be written Sy=K′ (M/Ec)k. The result was compared with experimental data of many target materials already reported. These results were used to estimate the sputtered depth after a given interval in the practical analyses using ion bombardment.
Supersaturated substitutional alloys formed by ion implantation and pulsed laser annealing of group-III and group-V dopants in silicon
Authors: White C. W. , Wilson S. R. , Appleton B. R. , Young F. W.
Published: February 2003

The formation of supersaturated substitutional alloys by ion implantation and rapid liquid-phase-epitaxial regrowth induced by pulsed laser annealing has been studied using Rutherford backscattering, ion channeling analysis. Group-III (Ga, In) and group-V (As, Sb, Bi) dopants have been implanted into single-crystal silicon at doses ranging from 1×1015 to 1×1017/cm2. The samples were annealed with a Q-switched ruby laser (energy density ∼1.5 J/cm2, pulse duration ∼15×10−9 sec). Ion channeling analysis shows that laser annealing incorporates these dopants into substitutional lattice sites at concentrations far in excess of the equilibrium solid solubility. Channeling measurements indicate the silicon crystal is essentially defect free after laser annealing. Also values for the maximum dopant concentration (Cmaxs) that can be incorporated into substitutional lattice sites are determined for our annealing conditions. Dopant profiles determined by Rutherford backscattering are compared to model calculations which incorporate both dopant diffusion in liquid silicon and a distribution coefficient from the liquid. It is necessary to assume an interfacial distribution coefficient (k′) far greater than the equilibrium value k0 to fit the experimental data. The relationship of Cmaxs and k′ to the formation of these supersaturated alloys is discussed.
Active remote sensing of random media
Authors: Zuniga M. , Kong J. A.
Published: February 2003

Analytical results for the bistatic scattering coefficients and the backscattering cross sections have been derived for active remote sensing of earth terrain with the model of bounded random media which accounts for volume-scattering effects. It is found that as a result of the effect of the second boundary, the horizontally polarized return σhh can be greater than the vertically polarized return σvv, whereas for a half-space random medium σvv is always greater than σhh. We illustrate by matching the theoretical results with experimental data collected from vegetation field.
Nickel pigmented anodic aluminum oxide for selective absorption of solar energy
Authors: Andersson Å. , Hunderi O. , Granqvist C. G.
Published: February 2003

Spectrally selective surfaces on Al metal sheets were prepared by dc anodization in dilute phosphoric acid followed by black coloration via ac electrolysis in a bath containing NiSO4. These coatings had good durability, as found from several accelerated tests. The optical performance was studied by the recording of hemispherical reflectance or specular reflectance in conjunction with diffuse light scattering. From these results we extracted a solar absorptance of 0.93–0.96 and a corresponding thermal emittance of 0.10–0.20. The structure of the coatings was investigated by scanning electron microscopy on fractured specimens, Auger electron spectroscopy combined with depth profiling by sputtering, and atomic absorption analysis. Based on this information, a multilayer model was formulated, its most conspicuous feature being a sheath near to the Al interface comprised of metallic Ni particles in an Al2O3 matrix. The optical properties of this layer were described either by the Maxwell Garnett theory or the Bruggeman theory, which are applicable to different microstructures. The latter formulation, together with a matrix technique to account for the multilayer configuration, was capable of giving quantitative agreement with the measured spectral reflectance, especially when reasonable estimates of surface roughness and of particle shape and orientation were invoked.
Determination of the capture probabilities of two deep impurity levels by photoconductive decay
Authors: Kuwano Hiroshi , Abe Miki , Okubo Satoru
Published: February 2003

A general theoretical analysis of the photoconductivity decays is done on the basis of the Shockley Read theory using a two deep impurity model. All of the theoretical equations of the decay curves of the excess conductivity in which the relation between the reciprocal of lifetimes and the capture probabilities are linear and the sample conditions in which these equations should be realized are obtained approximately. Using these equations, the numerical values of the electron capture probabilities αn and βn and the hole capture probability αp for two deep impurity levels in nickel-doped silicon are experimentally determined over a wide range of temperature.
Near ir sensitive electrophotographic receptor
Authors: Ishiwata T. , Fujimaki Y. , Shimizu I. , Kokado H.
Published: February 2003

A double-layered electrophotographic receptor with an extended sensitivity towards near infrared light is reported. Photogenerated holes in a As2Se1.5Te1.5 layer were efficiency transferred into a poly-N-vinylcarbazole layer, by inserting a thin (0.05 μm) amorphous Se layer between them. The injection efficiency at 800 nm was determined to be 4.62×10−2 at the field of 5×105V/cm.
Polycrystalline thin-film CdS liquid junction photovoltaic cell
Authors: Tsou C. C. , Cleveland J. R.
Published: February 2003

Polycrystalline semiconductor materials, as exemplified by spray-deposited and vacuum-deposited cadmium sulfide (CdS) thin films, have been studied in the liquid-junction photovoltaic cell to determine the open-circuit voltage (Voc) and the power conversion efficiency (η). For the spray-deposited film cell (CdS/1.25M NaOH–0.2M Na2S/C), the Voc and η were found to be 0.6 V and 0.038%, respectively. For the vacuum-deposited film cell, the Voc and η were found to be 0.71 V and 0.054%. Both type cells have the anomalous increase of photocurrent with voltage under anodic bias.
Conduction models of semiconducting calcium borate glasses containing iron oxide
Authors: Saleh M. N. , Gawish M. M.
Published: February 2003

The ac electrical resistivity, dielectric constant, and dielectric loss of the calcium borate glass system are investigated in order to determine the conduction models of the system. The glass series contains different iron concentrations in the system of molar composition (70−x)B2O3-30CaO-xFe2O3 with x up to 32%. The electronic properties are measured from 77 to 800 °K in the frequency range from 20 Hz to 100 kHz. The work has proved that the glasses are electronically conducting. The experimental results support the following models of conduction: (a) hopping conduction for glasses containing less than 20 mole% Fe2O3, (b) trap-limited band conduction together with hopping conduction for glasses having Fe2O3 mole% between 20 and 30, and (c) diffusive conduction together with hopping conduction for glasses containing more than 30 mole% Fe2O3.
The open-circuit voltage of N+-N-P high-low-emitter (HLE) junction solar cells in concentrated sunlight
Authors: Shen Wen-Zen , Wu Ching-Yuan
Published: February 2003

Simple analytical expression for the open-circuit voltage of a n+-n-p (p+-p-n) high-low-emitter (HLE) junction solar cell, which is valid for both the low and high levels of optical illuminations, is presented. Based on the principle of superposition, the open-circuit voltage of a n+-n-p high-low-emitter junction solar cell is expressed in terms of the short-circuit current density and the known saturated dark current. Effects of the high-low junction, the energy-gap shrinkage, and the dimensions of the HLE junction solar cell on the open-circuit voltage are included. The numerical results of the derived expression are found to be in good agreements with the exact numerical analysis of Sah et al. The optimal design considerations based on the known characteristics of the open-circuit voltage are also discussed.
A nondestructive acoustic electric field probe
Authors: Migliori A. , Thompson J. D.
Published: February 2003

A new method is described for the nondestructive measurement of electric field and space-charge distributions inside solid or liquid insulators by using a nonstructured acoustic pulse. The integral equation is derived for the response of the dielectric during propagation of an acoustic pulse and some acoustic measurements of electric fields and space charge inside transformer oil and polymethylmethacrylate plastic are described.
Galvanomagnetic properties of Fe3S4
Authors: Nozaki Hiroshi
Published: February 2003

Galvanomagnetic properties of Fe3S4 are studied through electrical resistivity and Hall effect measurements between 4.2 and about 300 K using synthetic thin films prepared by vacuum deposition method. The resistivity is on the order of 10−4–10−3 Ω cm between 4.2 K and room temperature, and has a positive temperature dependence with increasing temperature which can be explained by a metallic conduction. Hall effect reveals that the metallic conduction is mainly due to hole carriers, 0.2±0.1 per formula unit of Fe3S4, independent of temperature. The extraordinary Hall coefficient is positive and is in linear relation to the resistivity above about 130 K. Thermoelectric effect also supports the p-type conduction. Magnetization is 36.0±1.0 emu/gram at 77 K extrapolated to H=∞, which is much smaller than that expected from cations in the spinel structure.
High-field dark currents in thin CVD silicon nitride
Authors: Andrews J. M. , Jackson B. G. , Polito W. J.
Published: February 2003

Thin films of Si3N4 have been prepared by chemical vapor deposition (CVD) onto n+-Si substrates at 875 °C using an ammonia/silane ratio of 200 : 1. In the thickness range 93⩽τ⩽1021 Å, ellipsometric measurements have revealed that the refractive index decreases with film thickness, indicating a graded composition of silicon oxynitride with increasing oxygen content as the Si-Si3N4 interface is approached. Measurements of steady-state dark currents, injected into Si3N4 from negatively biased Al contacts at a constant average field Eav=Vτ−1=6 MV/cm, have been fitted to an empirical relation J=J0 exp(τ0/τ), where τ is the film thickness and τ0=1039 Å. The apparent increase in film conductivity with decreasing thickness τ is attributed to diminished electron trapping as τ approaches the centroid of trapped charge δ∼100 Å. Below approximately 200 Å, CVD Si3N4 films cannot sustain the continuous average field of 6 MV/cm needed for efficient Fowler-Nordheim injection from an Al contact. Thus, the maximum dissipative energy density of CVD Si3N4 has been estimated to be of the order of 10 kW/cm3. Measurements as a function of temperature in the range 276⩽T⩽470 °K indicate that the traps participating in electric field modification of Fowler-Nordheim injection lie in a narrow range 0.16⩽φT⩽0.18 eV below the conduction band of Si3N4.
A model of electromigration failure under pulsed condition
Authors: Schoen J. M.
Published: February 2003

A model of electromigration failure under pulsed constant-current excitation is derived. Starting with Black’s expression for electromigration failure under dc conditions, the fractional lifetime consumed per infinitesimal time interval is defined as a function of film temperature. The fractional lifetime consumed per pulse is then computed assuming that temperature in the film is an exponentially increasing function of time while the pulse is on. Damage relaxation during the pulse off time is characterized by a time constant exhibiting the same activation energy as the dc electromigration lifetime. Film temperature during the pulse off time is assumed to be an exponentially decreasing function of time. On the basis of the choice of the time-temperature dependence, the model presented here is strictly valid only when the pulse on time and pulse off time exceed characteristic thermal response time of the film. Application of the model to the experimental conditions of Miller yields good agreement between the predicted and measured lifetime as a function of pulse duty cycle for a pulse repetition rate of 250 kHz.
Thermal degradation of indium-tin-oxide/p-silicon solar cells
Authors: Goodnick S. M. , Wager J. F. , Wilmsen C. W.
Published: February 2003

Thermal degradation of indium-tin-oxide (ITO)/p-silicon solar cells has been investigated for cells fabricated on both single and polycrystalline silicon. The primary thermal degradation mechanisms was found to be the growth of SiO2 at the ITO/silicon interface resulting from oxygen diffusion through the ITO and not decomposition of the ITO. The degradation rate appears to be limited by surface reaction controlled oxidation since this rate is independent of ITO thickness. The polycrystalline cells were observed to degrade somewhat faster than the single-crystalline cells. The projected cell life at 50 °C due to thermal failure mechanisms exceeds 105 years for both single-crystal and polycrystalline cells.
On the synthesis of metastable A-15 ’’Nb3Si’’ by ion implantation and on its superconducting transition temperature
Authors: Clapp Mireille Treuil , Rose Robert M.
Published: February 2003

The authors have found a new technique for the synthesis of metastable compounds of well-defined composition: namely, ion implantation of a selected element into the desired crystal structure. [M.T. Clapp and R.M. Rose, Appl. Phys. Lett. 33, 205 (1978)]. Starting with a substrate material of A-15 Nb3Al0.9Si0.1, two basic approaches were tried towards the formation of A-15 Nb3Si by Si implantation: (1) direct replacement of the Al by Si and (2) implantation into a surface layer depleted of Al. This latter approach proved to be the most successful. It consisted of removing the Al by a diffusion anneal and replacing the Al deficiency by sequential Si implantations. Upon subsequent heat treatment a surface layer of A-15 Nb3Al0.2Si0.8 was produced. Details of the experimental procedure and a discussion of the superconducting transition temperature measurements of the implanted surfaces are presented.
Dynamic wall deformation in bubble garnet material
Authors: Vural K. , Humphrey F. B.
Published: February 2003

The dynamic diffuse wall (DDW) structure discovered previously in bubble material using high-speed photography has been investigated in detail here. The reflection (Kerr) mode is used to study the wall dynamics at the surfaces and the results are compared to the transmission (Faraday) mode which shows wall dynamics in the bulk of the film. It is clear that the DDW structure is a wall deformation through the thickness of the film. The mechanism for the deformation is based on the spatial variations of in-plane fields at the wall through the film thickness, due to the addition of the stray fields from the divergence of magnetization at the film surfaces and the applied in-plane field. This causes different parts of the wall to move with different velocities. Ion implantation decreases the width of the DDW which has its trailing edge next to the implanted surface by increasing its velocity compared to the trailing edge next to the as-grown surface. Both the drive field and the in-plane field enhance the wall width due to the functional dependence of the wall velocity near the surfaces on these fields. It is easier to form the structure in samples with a lower anisotropy since the surface tension field opposing the deformations is lower in these samples.
Statics of magnetic bubbles in cylindrical coordinates
Authors: Wong Chi Keung , Huang Huei Li
Published: February 2003

We have derived the static spin configurations of the various kinds of bubble domains using the cylindrical coordinate system. The spin deviation from the wall normal and the variation of the wall width and its characteristic length, etc., have been solved and discussed at some length. The present results can be reduced to the corresponding planar wall results at an appropriate limit, with the exception of the stability condition.
Surface modes along two parallel circular ferrite rods magnetized longitudinally
Authors: Meiri Toshimi , Okamoto Naomichi
Published: February 2003

A method is presented for solving the problem of propagation along many parallel ferrite rods magnetized axially. The characteristic determinant is derived from the reciprocity theorem where auxiliary electric and magnetic current sources are suitably selected. Using this method, the dispersion relations and the mode configurations of surface modes along two rods are shown and discussed in detail for both the cases of parallel and antiparallel magnetizations. For each case there generally exists a pair of modes with the same mode number which are backward waves. For the parallel magnetization, the field patterns in the transverse plane are symmetric and antisymmetric, respectively, about the point bisecting the straight-line segment that connects the centers of two rods. For the antiparallel case, the respective modes have the symmetrical and antisymmetrical electric field patterns about the vertical bisector of the same segment; and the results are reversed for the magnetic field patterns. Therefore, the field patterns of the latter first (or second) mode in the half-space exactly coincide with those of the corresponding mode along a single rod over a plane magnetic (or electric) conductor. The latter first mode disappears as the spacing between two rods becomes narrower than a limit. The distributions of the time-averaged power density for all the above modes are found to be symmetric about the above-mentioned vertical bisector. For some modes, there exists a slight local forward power flow in rods, accompanied with a much larger backward flow in the other region. This region with forward flow is found to appear when the strong coupling between two rods occurs. The coupling effects between two rods are more remarkable for the antiparallel case than for the parallel case, and they tend to become weaker for higher modes and for the larger spacing.
Submicron magnetic bubble material of (YSmLu)3(FeGaSc)5O12
Authors: Ohta N. , Ishida F. , Ikeda T. , Sugita Y.
Published: February 2003

A new submicron magnetic bubble garnet of (YSmLu)3 (FeGaSc)5O12 with low saturation induction 4πMs if found. By suitable combination of amounts of Ga and Sc, 4πMs can be kept to a practical minimum. The usefulness of substitution for ferric ions in both tetrahedral and octahedral sites by nonmagnetic ions for the reduction of 4πMs in submicron bubble garnets is shown. For example, films with the following properties are grown: stripe domain width w=0.9 μm; characteristic length l=0.10 μm quality factor q=2.6; and 4πMs=600 G.
Depth profiling of ion-implanted alloys
Authors: Campbell A. B. , Sartwell B. D. , Needham P. B.
Published: February 2003

Proton-induced x-ray emission analysis (PIXEA) and inert gas ion sputtering (IS) have been utilized to generate elemental profiles for three types of ion-implanted iron alloys. The data were fitted (utilizing a computer program) with symmetrical Gaussian profiles yielding values for the range and range straggle. These parameters were then compared with those obtained from the theory of Lindhard, Scharff, and Schiott (LSS). Changes in the profiles due to annealing were investigated, and values for the diffusion coefficient were obtained assuming Fick’s law. For 25-keV Ni+ and Cr+ in iron, the profiles as-implanted, agree reasonably well with LSS theory and exhibit ’’normal’’ diffusion characteristics at 500 °C. For 25-keV Al+ in iron, the profile as implanted is much broader than predicted and exhibits substantial enhanced diffusion at temperatures up to 500 °C.
Structural characteristics of pyrochlore formation
Authors: McCauley Ronald A.
Published: February 2003

By calculating the value of the unknown oxygen positional parameter x for a large number of A3+2B4+2O7 pyrochlores, it was determined that increasing the radius of the A cation in a series of constant B increased the value of x, and that increasing the radius of the B cation in a series of constant A decreased the value of x. The region of pyrochlore formation has a range of x values from 0.404 to 0.432 and contains BO6 polyhedra that closely approach Oh symmetry and AO8 polyhedra that are highly deformed. It was shown that the characteristics of the BO6 polyhedra were the most important in determining whether or not a pyrochlore would form.
Effects of bombardment by low-energy neutral particles on silicon dioxide films
Authors: McCaughan Daniel V. , Kushner R. A. , Simms D. L. , White C. W.
Published: February 2003

Ion bombardment or backsputtering of SiO2 films has been shown to result in severe insulator degradation in device processing. Here we have investigated the effects of low-energy neutral-particle bombardment on device quality SiO2 films and have compared degradation produced by neutral-particle bombardment with that produced by ion bombardment. These results show that (1) neutral-particle bombardment produces substantially less (by two or three orders of magnitude) fixed charge at the SiO2/Si interface than does ion bombardment; (2) the most prominent degradation produced by neutral bombardment is the creation of a large interface state density across the band gap which is not related to a nonuniform charge distribution at the interface; (3) metal-oxide-semiconductor degradation produced by neutral bombardment may be removed by annealing at temperatures ?400 °C. Comparison of oxide charge degradation produced in SiO2 by ion and neutral-particle bombardment suggests that the neutralization processes at the vacuum-SiO2 interface, which take place only in ion bombardment, have the dominant role in this degradation. As a result of these processes, in ion bombarded samples, charge carriers migrate to the SiO2/Si interface in the field across the oxide film. This mechanism is absent in the case of neutral bombardment.
Precursor amplitudes in LiF from shocks propagating in 〈111〉 directions
Authors: Rosenberg Gideon , Duvall G. E.
Published: February 2003

Precursor amplitudes have been measured for impact-produced shock waves traveling in 〈111〉 directions in LiF. Impact pressures range from 30 to 98 kbars and precursor amplitudes for the larger pressures are about 60 kbars for crystals containing approximately 100 ppm Mg and about 50 kbars for undoped crystals. The greatest impact pressure at which elastic response is preserved is about 40 kbars. No precursor decay is evident from the measurements, which include sample thicknesses between 0.3 and 5 mm. Mean precursor decay rates inferred for the first 1/2 mm of travel range up to about 100 kbars/mm. Primary slip systems are not active in this geometry and the shear stress on secondary systems ranges up to 38 kbars at the highest impact pressure. This is still well below theoretical shear strength. Mechanisms for the inferred decay are not identified.
Phase diagram calculations for InuGa1−uPvAs1−v lattice matched to (111−B) InP, in the temperature range 600–660 °C
Authors: Perea Ernesto H. , Fonstad Clifton G.
Published: February 2003

Quaternary layers have been grown by near equilibrium liquid-phase epitaxy (LPE) at 621 °C over the whole range of compositions that lattice match (111-B) InP and modelling of this system is reported. Comparison of experimental results at 621 °C and those of other workers, with phase diagram calculations made with measured binary and ternary interaction parameters, however, show large discrepancies for v<0.5. A modification of the conventional model, in order to fit the experimental data, as a convenient interpolation scheme, is proposed and discussed. The predictions of this modified model are in good agreement with the experiment.
Thin film interaction between titanium and polycrystalline silicon
Authors: Murarka S. P. , Fraser D. B.
Published: February 2003

The low resistivity of the titanium disilicide makes this material attractive for gate and interconnect metallizations. TiSi2 has been formed by reacting Ti films with polycrystalline and monocrystalline silicon in the temperature range 400–1100 °C. The interaction is investigated by use of sheet resistance, x-ray diffraction, and stress measurements. It has been found that Ti and Si react very rapidly to form both TiSi and TiSi2 at temperatures ? 700 °C and only TiSi2 at temperatures ≳ 700 °C. The TiSi2 films are associated with a very low resistivity (∼15 μΩ cm), high tensile stress [∼ (1–2) ×1010 dyn/cm2)], and a rough surface. Silicided structures are mechanically stable. It is proposed that the silicon, as the predominant diffusing species, first diffuses into titanium to completely convert titanium into TiSi and then into TiSi to form TiSi2.
Liquid-phase electroepitaxy: Dopant segregation
Authors: Lagowski J. , Jastrzebski L. , Gatos H. C.
Published: February 2003

A theoretical model is presented which accounts for the dopant segregation in liquid-phase electroepitaxy in terms of dopant transport in the liquid phase (by electromigration and diffusion), the growth velocity, and the Peltier effect at the substrate-solution interface. The contribution of dopant electromigration to the magnitude of the effective segregation coefficient is dominant in the absence of convection; the contribution of the Peltier effect becomes significant only in the presence of pronounced convection. Quantitative expressions which relate the segregation coefficient to the growth parameters also permit the determination of the diffusion constant and electromigration mobility of the dopant in the liquid phase. The model was found to be in good agreement with the measured segregation characteristics of Sn in the electroepitaxial growth of GaAs from Ga-As solutions. For Sn in Ga-As solution at 900 °C the diffusion constant was found to be 4×10−5 cm2/s and the electromigration velocity (toward the substrate with a positive polarity) 2×10−5 cm/s at a current density of 10 A/cm2.
Complex free-carrier profile synthesis by ’’atomic-plane’’ doping of MBE GaAs
Authors: Wood C. E. C. , Metze G. , Berry J. , Eastman L. F.
Published: February 2003

Doping solely during periods when growth was suspended has been used to synthesize profiles not easily achieved by conventional doping techniques. Suspension of growth under arsenic stabilized conditions allows Ge doping to produce n-type complex profiles with reduced autocompensation. At higher temperatures, autocompensation becomes apparent. Under gallium stabilized conditions, heavily autocompensated n-type layers resulted, consistent with a nonunity incorporation coefficient.
LPE growth of GaAs submicron layers from supercooled solution: Layer thickness uniformity within a wafer
Authors: Toyoda Nobuyuki , Mihara Minoru , Hara Tohru
Published: February 2003

The thickness uniformity within a wafer is studied in GaAs LPE layers grown by the horizontal sliding boat techniques. Thickness nonuniformity appears in the sliding direction of a solution when very thin (∼0.3 μm thick) layers are grown from supercooled solutions. Thicker layers are grown on the side which is first brought into contact with the solution. The diffusion theory of LPE growth explains that such thickness distribution is mainly due to transient growth while a supercooled solution slides across the wafer.
Alloying behavior of Ni/Au-Ge films on GaAs
Authors: Ogawa Masaki
Published: February 2003

Alloying behavior of thin Ni/Au-Ge films deposited on a GaAs substrate is investigated by using a microprobe Auger spectrometer and an x-ray diffractometer. The deposited films react with the substrate above 300 °C to form alloys with complex multilayer structure in the 300–400 °C temperature range and alloys with microscopic grain structure above 450 °C. Uniform alloying, accompanied with a smooth interface, is observed and is ascribed to the high reactivity of Ni with GaAs under a solid-solid phase. However, when the sample is annealed in the solid-solid phase, Ni penetrates irregularly into the GaAs substrate, if the annealing duration is too long, causing poor Ohmicity. Rapid Ge moving to the substrate interface is observed at 400 °C and is closely related to the formation of a Ge-doped degenerate layer beneath the contact. The high reliability of the contract, which is obtained when annealed at 500 °C, is explained by the metallurgical stability of the grain structure. Based on the results of this study, some rules for III-V compound semiconductor contact fabrication are proposed.
Raman-induced Kerr effect with nonmonochromatic waves
Authors: Dutta Niloy K.
Published: February 2003

We discuss the theory of Raman-induced Kerr effect (RIKE) when excited by nonmonochromatic waves. The maxima and minima of the lineshape are shifted farther apart when pumped by linearly polarized nonmonochromatic waves. The shift varies linearly with the sum of the pump and probe linewidths. Certain other features are also predicted in agreement with experimental results.
Capacitance-voltage measurements in amorphous Schottky barriers
Authors: Singh Jasprit , Cohen Morrel H.
Published: February 2003

A theory for the capacitance of junctions (in particular, Schottky barriers) made from amorphous semiconductors is presented. It is emphasized that this theory is very different from the usual theory used for crystalline semiconductors. A self-consistent scheme to use the capacitance results to find the density of localized states in the band gap of amorphous semiconductors is developed. This method provides a strong complement to the field-effect technique for finding the density of states. Theoretical calculations are presented to illustrate the procedure and some of its advantages over the field-effect method. The relation to earlier work is discussed.
Spectroscopy of InAs using SAW generated transverse acoustoelectric voltage
Authors: Ayub F. M. Mohammed , Das P.
Published: February 2003

Transverse acoustoelectric voltage has been measured as a function of incident photon energy in an InAs on LiNbO3 SAW delay line structure. A large transition at 1.5 eV is observed, which is confirmed by photocurrent measurement. Application of the large acoustoelectric voltage to image scanning and signal processing is presented.
The rate equations used in irradiation studies
Authors: Gurol Husam
Published: February 2003

The main purpose of this paper is the investigation of the rate equations used in the theories of void nucleation and swelling as well as creep, in situations where random displacement cascades are the major source of point defects. The point-defect concentrations are described by diffusion equations with random source terms to account for the cascades. Using methods from nuclear reactor kinetic theory and averaging over time, the rate equations are derived. It is seen that the rate equations are valid for computing time and spatially averaged point-defect concentrations, regardless of the cascade statistics, if the observation time is greater than the mean time between cascade events in the irradiated material. An alternate approach is suggested for studying pulsed systems with short pulse widths.
A volumetric constitutive law for snow based on a neck growth model
Authors: Brown Robert L.
Published: February 2003

A volumetric constitutive law for snow is developed by considering the deformation of the ice grains and grain bonds which form the porous material. The equations of equilibrium and mass conservation are applied to both the grain body and neck regions to calculate the rate of change of grain geometry and neck geometry. The matrix material, ice, is assumed to be a nonlinear viscoplastic material. Comparison with data shows excellent agreement for a wide range of initial densities and for large volumetric deformations. Calculations are also made to evaluate grain and neck deformation during compaction. The model can be applied to porous metals and foams, although the constitutive law for the matrix material would have to be altered.
Spectroscopic investigation of a lanthanide iodide/mercury arc discharge plasma
Authors: van den Hoek W. J. , Visser J. A.
Published: February 2003

An investigation was made of the distribution of Dy atoms and ions and iodine atoms in the central region (r/R≲0.6) of a DyI3/Hg-arc plasma. The arc is operated horizontally; it is centered magnetically. The mercury pressure is 4.5×105 N m−2, the input power 500 W, the electrode distance 37 mm, and the tube diameter is 15 mm. The temperature profile was determined from the emission of the optically thin Hg 577.0-nm line. The side-on emission distributions of optically thin Dy+ and Dy lines, in combination with the optical absorption of Dy+ resonance lines, indicate a radial depletion of dysprosium at the arc center, which can be explained by a simple model. Combination of experiments and calculations in which ambipolar diffusion is taken into account yields the distribution of Dy atoms and ions in the central region. The distribution of the iodine atoms was determined from the emission of the optically thin I 905.8-nm line. The iodine content of the arc exceeds the dysprosium content by about an order of magnitude. The chemical composition of the arc plasma is discussed. Measurements and calculations on self-reversed Dy lines also show that ambipolar diffusion is a dominant process.
Space-resolved extreme ultraviolet emission from laser-produced plasmas
Authors: Ebrahim N. A. , Richardson M. C. , Doschek G. A. , Feldman U.
Published: February 2003

We have obtained extreme ultraviolet (XUV) spectra of plasmas created by focusing nanosecond CO2 laser pulses onto massive planar targets of Al, Ti, and CH2. The instrument used to obtain these spectra was a normal incidence extreme ultraviolet spectrograph with the entrance slit removed. The concave spherical grating of such a slitless spectrograph diffracts and focuses the XUV radiation, and the resulting images are recorded on Kodak 101 film. The XUV images are therefore space resolved but time averaged over the lifetime of the plasma. The wavelength range covered in these spectra is 200–500 Å. In this range, the emission lines of aluminum are due to transitions between the 2s22pk, 2s2pk+1, and 2pk+2 configurations within the ions from Al V through Al X. For titanium plasmas, emission lines from Ti VII, Ti XI, and Ti XII have been identified. The prominent images obtained from polyethylene plasma result from 2l-3l′ and 2l-4l′ transitions within the C IV ion. The general morphology of the plasma expansion shows that the most highly ionized species (Al X, Ti XII) expand away from the target surface in well-collimated cylindrical structures. These most highly ionized species also exhibit two component structures; one component expanding along the target normal and the second component expanding parallel to the incident laser direction. The images of the low-ionization stages (Al V, Ti VII) are also cylindrical although their spatial extent is much less than the images from the high-temperature ions and they are not as well collimated. The observations are interpreted in terms of particular temperature structures in such plasmas and the presence of self-generated magnetic fields.
Spectroscopy and atomic physics of highly ionized Cr, Fe, and Ni for tokamak plasmas
Authors: Feldman U. , Doschek G. A. , Cheng Chung-Chieh , Bhatia A. K.
Published: February 2003

We consider the spectroscopy and atomic physics for some highly ionized Cr, Fe, and Ni ions produced in tokamak plasmas. Specifically, we consider both allowed and forbidden transitions between levels of the 2s22pk, 2s2pk+1, and 2pk+2 configurations. Forbidden and intersystem wavelengths for Cr and Ni ions are extrapolated and interpolated using the known wavelengths for Fe lines identified in solar-flare plasmas. We present tables of transition probabilities for the B I, C I, N I, O I, and F I isoelectronic sequences, and give collision strengths and transition probabilities for Cr, Fe, and Ni ions of the Be I sequence. Proton excitation rate coefficients for fine-structure transitions in the Be I through F I sequences are tabulated, as well as populations of all levels of the 2s22pk, 2s2pk+1, and 2pk+2 configurations for Cr, Fe, and Ni for the Be I sequences, and for Cr and Ni for the B I-F I sequences. We discuss similarities of tokamak and solar spectra, and show how the atomic data we have presented may be used to determine ion abundances and electron densities in low-density plasmas.
Investigation of stray particle loss in deflection magnet region of neutral beam line
Authors: Kim J. , Menon M. M.
Published: February 2003

Separation of residual charged particles from neutral particles is typically made by a deflection magnet in a neutral beam injection line for heating fusion plasmas. Ionization of energetic neutrals and neutralization of energetic ions in the deflection magnet region due to collisions with the background gas molecules result in a finite amount of particles that are only partially deflected, which we call a ’’stray particles loss.’’ Quantitative determination of the stray particle loss has been made from calorimetric data of beam power deposited along a beam line employing a 40-kV 60-A hydrogen ion source. The stray particle loss is typically 3–5% of the accelerator power and roughly proportional to the background gas pressure. A simple calculation is shown to be in fair agreement with the measurements.