bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron beam induced annealing of defects in GaAs
Authors: Leamy H. J. , Kimerling L. C.
Published: February 2003

It has recently been shown that minority-carrier injection greatly increases the annealing rate of 1-MeV electron damage in GaAs. Energy deposited during nonradiative recombination at the radiation damage defects has been shown by Kimerling and Lang to be responsible for this effect. We have confirmed this effect in experiments in which carrier injection was achieved by 15–45-keV electron irradiation. The annealing process was monitored during irradiation by measurement of the charge collected at a p-n junction within the material. Carrier lifetime improvements of 100% were observed, and could be produced at rates 100 times faster than those reported by Kimerling and Lang when focused electron beam annealing was employed. Dislocations were observed to act as sinks for the defects. Focused electron beam annealing was employed to ’’write’’ annealed patterns in GaAs.
Elastic properties of a boron-aluminum composite at low temperatures
Authors: Read D. T. , Ledbetter H. M.
Published: February 2003

Elastic properties of a boron-filament-reinforced aluminum-matrix composite were studied experimentally. Assuming transverse-isotropic elastic symmetry, five independent elastic constants were measured using a piezoelectric composite-oscillator method. Two constants, Young’s modulus along the filament axis and the torsional modulus perpendicular to the filament axis, were determined between 300 and 4 K. The composite’s elastic-constant values are between the values of boron and aluminum, but closer to that of aluminum. Along the filament axis, Young’s modulus is 2.30×1011 N/m2. Cooling from 300 to 4 K increases all the elastic stiffnesses by as much as 11%.
Linearly viscoplastic material
Authors: Gillis Peter P. , Jones Stanley E.
Published: February 2003

Viscoplastic material models which are based upon dislocation dynamics are so complex mathematically that they seldom yield closed-form solutions to boundary value problems. Here we examine a material having a linear dependence of dislocation speed on stress. The boundary value problem corresponding to a constant crosshead speed tension test of this material remains highly nonlinear. However, an analytic solution to the problem is found in terms of tabulated functions and this solution is used to demonstrate some of the features of the response of the material during tension testing.
X-ray photoemission spectroscopy studies of Sn-doped indium-oxide films
Authors: Fan John C. C. , Goodenough John B.
Published: February 2003

The In and Sn 3d3/2 and 3d5/2 ESCA peaks and the oxygen 1s peak of Sn-doped In2O3 films were compared with those for In2O3 films and In2O3, SnO, SnO2, and Sn3O4 powders. Comparison of as-grown with sanded surfaces revealed Sn-rich surface layers in.those films having good optical and transport properties. These experimental fins are interpreted with a schematic energy-band model and the assumption that film darkening in Sn-doped In2O3 films is caused by the formation and growth of an Sn3O4-like second phase in the bulk. Suppression of these phase could be accomplished by higher substrate temperatures, which permit equilibrium conditions to be attained. Sn-rich phases to migrate to the films surface, and the tine disproportionates to Sn2+ and Sn4+ ions.
Silicon solar cells on zone-melted silicon/graphite substrates
Authors: Chu T. L. , Chu Shirley S. , Duh K. Y. , Mollenkopf H. C.
Published: February 2003

Polycrystalline-silicon solar cells deposited on graphite substrates by conventional chemical vapor deposition techniques have low conversion efficiencies due to the carrier recombinations at grain boundaries. To reduce the concentration of grain boundaries, silicon layers deposited on graphite substrates have been zone melted to increase substantially the size of silicon crystallites. Using these silicon layers as substrates, solar cells have been deposited in a one-step process by the thermal reduction of trichlorosilane containing appropriate dopants, and AM1 efficiencies of higher than 5% have been obtained for cells of about 6-cm2 area.
Surface-acoustic-wave phase velocities in the b plane of triglycine sulfate
Authors: Sader E. , Harnik E.
Published: February 2003

Surface acoustic waves have been generated in triglycine sulfate crystals and their phase velocities have been measured along various propagation directions in the b plane.
Channel spreading and substrate vaporization in surface-spark discharges
Authors: Beverly III R. E.
Published: February 2003

The extent of luminous plasma spreading over various ceramic substrates is shown to be related to the ease of vaporization of the metallized surface layer and not to the ionization potential of the metallic constituents. Intense prompt bremsstrahlung emission is responsible for initial vaporization of substrate species.
On the nature of dislocation loops in As-implanted and postannealed Si wafers
Authors: Pavlidis P. , Economou N. A. , Christou A.
Published: February 2003

Si wafers were implanted with As ions to a concentration of 1019 atoms/cm3 and subsequently annealed in the temperature range 600–1000 °C in an atmosphere of a low partial pressure of Ar. The surface density of the resulting interstitial dislocation loops was measured. The comparison with electrical measurement data suggests that the extra planes in the loops do not consist, at least in their majority, of As atoms.
Dislocations in silicon layers grown on silicon-ribbon substrates
Authors: McFarlane S. H. , Kressel H. , D’Aiello R. V. , Robinson P. H.
Published: February 2003

Silicon layers deposited on silicon-ribbon substrates have been characterized by x-ray topographic examination of thin cross-section samples cut from the crystals. The generally high dislocation density in the silicon ribbon is not duplicated in the silicon expitaxial layer because the majority of substrate defects are edge dislocations which lie beneath the ribbon surface and are not available to propagate into the layer. Only the inclined dislocations contribute to the dislocation density in the epitaxial layer.
Reply to ’’Comment on ’Comparison of experimental and theoretical carrier concentrations in heavily doped n-type silicon’ ’’
Authors: Finetti M. , Susi E.
Published: February 2003

Some remarks are made about the agreement between the experimental results and the theoretical model of Neumark. It is believed that the presence of an impurity band and of localized tail states is not sufficiently accounted for.
Low-temperature electron mobility in InSb
Authors: Nag B. R. , Dutta G. M.
Published: February 2003

Available experimental values of electron mobility in InSb samples with known impurity concentration are compared with the theoretical values obtained by an iteration technique including the effects of band nonparabolicity, wave-function admixture, electron screening, and all scattering mechanisms. Experimental values for the temperature range 20–77 K are found to agree to within 10% with the theoretical values. Values for conductivity mobility, the Hall ratio, and magnetoresistance are also given for different impurity concentrations and compensation ratios. These values should be useful for obtaining the impurity concentration from the knowledge of the experimental values of these transport coefficients.
Anomalous luminescence from oxidized polyethylene in a high-temperature region
Authors: Nakamura Shuhei , Sawa Goro , Ieda Masayuki
Published: February 2003

Previously, we reported that an anomalous luminescence peak appears around the melting point during warming and cooling in previously oxidized polyethylene following γ irradiation. An additional result is presented, showing that the anomalous luminescence appears in polyethylene only oxidized by an ozonizer without subsequent γ irradiation, though γ irradiation is required for the normal luminescence peak which appears well below the melting point.
Deep levels in GaAlAs-GaAs solar cells
Authors: Shen Lawrence Y. L.
Published: February 2003

The capacitance and transient capacitance of GaAs-GaAlAs solar cells and a GaAs p-n junction have been measured as a function of temperature. A new trap was discovered which could be associated with the presence of GaAlAs.
Kinetics of thin-film reactions between Pb and the AgPd alloy
Authors: Tu K. N.
Published: February 2003

Thin-film reaction between Pb and the Ag-20 at.% Pd alloy in the temperature range 160–200 °C has been studied by x-ray diffraction. The reaction results in the formation of the Pb2Pd compound by depleting Pd from the alloy. The rate of depletion is too fast to be explained by lattice diffusion in the alloy at these temperatures. In fact, it is shown that the intermixing of Ag and Pd to form the alloy by lattice diffusion can only occur around 450 °C. On the other hand, grain-boundary diffusion is faster, but it is not obvious how Pd atoms within the alloy grains can be depleted by grain-boundary diffusion. To overcome this difficulty, a kinetic model with a moving interface has been developed to explain the low-temperature reaction. The model seems to agree quite well with the experimental results.
Growth and structure of rf-sputtered HgS films on NaCl
Authors: Nakada Tokio
Published: February 2003

The growth and structure of rf-sputtered HgS films on NaCl substrates mainly at room temperature have been examined by electron diffraction and transmission electron microscopy. Very thin films (∼20 Å thick) on air-cleaved (001) substrates were epitaxially grown in β-HgS (001), β-HgS (111), and α-HgS (00.1) orientations. The films on air-cleaved (110) and polished (111) substrates were basically polycrystalline β-HgS, and partially grown in parallel orientation to the substrate surfaces. As the film thickness increased to more than approximately 200 Å, α-HgS layers started to grow on the β-HgS films, producing 〈111〉 streaks and many extra reflections in the diffraction patterns. α-HgS films approximately 2000 Å thick had (10.2), (11.0) and (20.7), and (00.1) and (10.1) orientations in the cases where (001), (110), and (111) NaCl substrates were used. These orientations are discussed by using a growth model of which α-HgS layers were grown on the {111} facets of β-HgS layers.
Electron-trapping characteristics of W in SiO2
Authors: Young D. R. , DiMaria D. J. , Bojarczuk N. A.
Published: February 2003

The electron-trapping characteristics of W in SiO2 have been studied using evaporated and ion-implanted W. The evaporated W results indicate a trapping cross section varying from 1.56×10−14 to 4.62×10−14 cm2 depending on the evaporation time. The cross section of the implanted W is 1.06×10−15 cm2. Thermal-detrapping measurements indicate an activation energy of 0.9 eV, whereas optical detrapping is not observed for light energies up to 6 eV. It is not understood why there is this large discrepancy of results. It is also interesting to note that Powell and Beairsto measured a barrier height of 3.6 eV for the W-SiO2 interface.
Desorption from powdered ZnO during electron bombardment and interaction with atomic hydrogen
Authors: Morgen P. , Onsgaard J. H. , Tougaard S.
Published: February 2003

Electron bombardment of ZnO powder leads to desorption of CO2. The presence of CO2 molecules at ZnO surfaces after chemisorption of oxygen was recently established from photodesorption experiments, leading to the conclusion that carbon impurities were active during oxygen chemisorption. Atomic hydrogen has earlier been found to chemisorb on ZnO single crystals, the adsorbed atoms acting as electron donors. We have tried to evaluate the possible influence of carbon impurities on this reaction with ZnO powder. It was found that adsorption of hydrogen atoms causes an increase of conductance, accompanied by desorption of CO and O. No significant desorption of CO2 was found.
The frequency constant for thermal activitation of a ferromagnetic domain wall
Authors: Gaunt P.
Published: February 2003

The equation τ−1=C exp(−E/kT) describes thermal activation over a potential-energy barrier of height E. τ is the ’’waiting time’’ for a successful activation, and C is a frequency constant. The frequency constant is evaluated for a circular segement of ferromagnetic domain wall which breaks away from a central pin. Reaction-rate theory reduces the problem to the calculation of the allowed vibrational frequencies of the wall in pinned and activated states. The minimum value of C is ν1, the ’’intuitive attack frequency’’, which is the number of breakaway attempts made by the wall segment per second. The success rate of these attempts may be increased by an ’’entropy enhancement factor’’ so that C?ν1. The enhancement depends on the pinning constants and is numerically estimated for PtCo and an iron alloy. The maximum allowed value of C is ?1012 sec−1.
Photoacoustic spectroscopy of luminescent solids: Ruby
Authors: Murphy J. C. , Aamodt L. C.
Published: February 2003

Photoacoustic spectroscopy (PAS) is applied to the study of nonradiative processes in luminescent systems. A rate-equation model for this process is developed and applied to interpreting the observed concentration-dependent metastable-level quenching rates in ruby. Successful PAS operation at 77°K is reported.
Optical properties of anodically grown native oxides on some Ga-V compounds from 1.5 to 6.0 eV
Authors: Aspnes D. E. , Schwartz B. , Studna A. A. , Derick L. , Koszi L. A.
Published: February 2003

Complex refractive-index and dielectric function data are given for anodically grown native oxides on GaP, GaAs, and GaSb from 1.5 to 6.0 eV. The absorption thresholds for the oxides on GaAs and GaSb occur at 5.0 and 4.2 eV, respectively, with weak tails extending 0.5 eV to lower energy. The absorption threshold in GaP is not seen but is estimated to be near 7 eV. A comparison of these data with each other and with those for SiO2 and GeO2 suggests a more complex bonding behavior than a simple amorphous phase.
Laminar source flow between parallel porous disks with equal suction and injection in the presence of a magnetic field
Authors: Mishra Shankar Prasad , Muduli Jugal Charan
Published: February 2003

This study represents an attempt to understand the effect of magnetic field on the laminar source flow between infinite porous disks with uniform fluid suction or injection. Solution in the form of an infinite series expansion about the solution at infinite radius has been obtained. Expressions for the velocity, pressure-induced magnetic field, and shear stress are presented and the effect of the cross flow and magnetic field strength is discussed.
The breakdown voltage and discharge extension of long gaps in nitrogen-SF6 and air-SF6 gas mixtures
Authors: Watanabe T. , Takuma T.
Published: February 2003

The breakdown voltage and the extension of the discharge has been investigated for impulse voltages with rod-plane gaps of 30 and 50 cm in nitrogen-SF6 and air-SF6 mixtures at atmospheric pressure. The addition of 0.4–2% SF6 by volume to nitrogen reduced the 50% breakdown voltage V50 for both polarity impulse voltages below the value for pure nitrogen or pure SF6, typically 50% below the pure SF6 level. However, in air-SF6 mixtures the opposite effect was found, and a small addition of SF6 (e.g., 1%) increased V50 by typically 80% above that for pure SF6. The extension of the breakdown path has been studied with an image converter and still cameras. In nitrogen-SF6 mixtures there was a rapid extension of the discharge corresponding to the condition of the minimum breakdown voltage with the 2% SF6 content. The typical discharge extension characteristic in both types of mixtures was an intermittent propagation of the leader accompanied by ball-like regions of corona streamers at the leader tip. For a 50% SF6–nitrogen mixture, typical pause times between the steps were 1 μsec for negative polarity and 0.08 μsec for positive polarity, and the discharge extension to breakdown was two to three times faster for positive impulses.
Propagation of highly aberrated laser beams in nonquadratic plasma waveguides
Authors: Feit M. D. , Fleck J. A. , Morris J. R.
Published: February 2003

The propagation of a laser beam in a plasma column several meters long with a realistic electron density distribution is examined. The electron density distribution is based on laser-beam heating at z=0, but is otherwise uncoupled to the laser beam. The aberrated nature of the resulting lenslike medium leads to essentially aperiodic beam properties, which contrast with the completely periodic properties of Gaussian beams propagating in quadratic lenslike media. The beam is nonetheless stably trapped. These aberrated-beam properties also help to stabilize the beam against axial variations in refractive index.
Dislocation dynamics in the modified Frenkel-Kontorova model
Authors: Earmme Y. Y. , Weiner J. H.
Published: February 2003

An analytical solution is presented for the atomic displacements in the steady motion of a dislocation in the modified Frenkel-Kontorova model. The phenomenon of the breakdown of regular dislocation motion as the dislocation velocity approaches the speed of sound, found by Earmme and Weiner in the same model for γ=1/2 is seen to exist in this model for any γ<1/2, where γ is a measure of the critical shear stress of the perfect crystal, varying from zero to one-half in units of the shear modulus. It is found that for sufficiently low γ a mode of dislocation motion can exist in which the dislocation moves at a high constant speed without exciting any lattice waves and with no applied stress required to maintain the motion. A thorough investigation of the analytical solution for γ=1/2 (and for sufficiently large values of γ<1/2) shows that for some range of dislocation velocity v the dislocation motion is unstable. Furthermore, it appears that for sufficiently low v there does not exist a steady-state solution for γ=1/2. The final steady-state motion achieved is found to depend both on the initial conditions and the loading history. For example it is found that in order to arrive at the no-loss mode of motion, it is necessary to first increase the stress to a sufficiently high value, allow steady motion on the upper branch of the v−σ relation to be established, and then to decrease the stress to zero.
Annealing behavior of In implanted in Si studied by perturbed angular correlation
Authors: Kaufmann E. N. , Kalish R. , Naumann R. A. , Lis S.
Published: February 2003

The perturbed angular correlation technique has been used to study the local environment of 111In implanted to low doses at room temperature into Si as a function of postimplantation annealing temperature. At annealing temperatures corresponding to those where previous electrical measurements have observed reverse annealing behavior, we find evidence for the displacement of In to regions of lattice disorder. This is in contrast to results of ion-beam channeling experiments on heavy group-III impurities in Si which have been interpreted to indicate the displacement of the impurity to a unique regular tetrahedral interstitial site.
Stress in ion-implanted CVD Si3N4 films
Authors: EerNisse E. P.
Published: February 2003

The compressive stress buildup caused in chemical-vapor-deposited (CVD) Si3N4 films by ion implantation is shown to be caused entirely by atomic collision effects, ionization effects being unimportant. The stress introduction rate is shown to be independent of CVD processing variables and O content of the film. The maximum attainable compressive stress change is 3.5×1010 dyn/cm2, resulting in a maximum net compressive stress of 2×1010 dyn/cm2 for films on Si where the as-deposited films inherently have 1.5×1010 dyn/cm2 tensile stress before ion implantation. Results are presented which show that O in the films inhibits thermal annealing of the ion-implantation-induced compressive stress. Results for introduction rate and annealing effects are presented in normalized form so that workers can use the effects for intentional stress level adjustment in the films to reduce probability of cracking and detachment.
Electrical profiling and optical activation studies of Be-implanted GaAs
Authors: McLevige W. V. , Helix M. J. , Vaidyanathan K. V. , Streetman B. G.
Published: February 2003

Differential resistivity and Hall-effect measurements have been utilized to study the annealing behavior and electrical carrier-distribution profiles of Be-implanted GaAs. A maximum of 90–100% electrical activation occurs during 900 °C anneals for implanted Be concentrations less than ∼5×1018 cm−3. For higher fluences, however, a heavily concentration-dependent diffusion is observed, and the measured electrical activation is complicated by outdiffusion of Be into the Si3N4 encapsulant. In these cases, a maximum in the electrical activation appears for annealing near 700 °C. Low-temperature (5 °K) photoluminescence substantiates previous findings that 900 °C annealing results in maximum optical activation and lattice recovery.
Identification of the tetragonal Nb5Ge3 phase in two-phase Nb-Ge superconducting films by electron diffraction
Authors: Santhanam A. T.
Published: February 2003

Magnetization studies of CVD Nb3Ge superconducting films had previously shown that the critical current density (Jc) significantly improved in the presence of a few volume percent of the tetragonal Nb5Ge3 phase. The presence of this tetragonal phase was previously determined by x-ray analysis. In the present study, Nb-Ge films containing the A-15 Nb3Ge phase and the tetragonal Nb5Ge3 phase were examined by transmission electron microscopy (TEM), with a view to determine the size and distribution of the tetragonal phase in the microstructure. This paper describes a procedure by which the Nb5Ge3 phase could be identified in the microstructure using electron diffraction. The Nb5Ge3 particles were present at the grain boundaries as well as within the grains of the A-15 matrix.
Structure and properties of bubble domains in cholesteric-nematic mixtures
Authors: Bhide V. G. , Jain S. C. , Chandra S.
Published: February 2003

The paper reports on the observation and behavior of bubble domains under 50 Hz and 1 kHz ac field in (1) a mixture of homeotropically aligned negative dielectric anisotropic εa<0 nematic and a negative dielectric anisotropic εa<0 cholesteric, (2) a mixture of homeotropically aligned εa<0 nematic and εa≳0 cholesteric, (3) a mixture of homeotropically aligned εa<0 nematic and a compensated cholesteric (a mixture of two cholesterics behaving as a nematic), and (4) a mixture of homeotropically aligned εa≳0 nematic and εa<0 cholesteric over a limited range of p/l. The behavior of the bubble domains in (1), (2), and (3) under a 50-Hz ac field is identical. However, the behavior of bubble domains in (1) and (2) under 1-kHz ac field is different. In (3) we observe certain bubble domains which behave as bubble domains in (1), whereas certain other bubble domains behave as in (2). In the mixture of positive dielectric anisotropic nematic and negative dielectric anisotropic cholesteric, unlike in other cases, bubble domains in a 50-Hz ac field decrease in size on application of the field and on increasing the field further, bubble domains disappear completely. These observations strengthen our belief in the model in which bubble domains are pockets of a cholesteric in a matrix of nematic.
Comparison of the single-crystal elastic constants of Th and a ThC0.063 alloy
Authors: Greiner J. D. , Peterson D. T. , Smith J. F.
Published: February 2003

The elastic constants of a single crystal of pure thorium have been measured over the temperature range 4.2–300 K. Measurements were repeated on the same crystal after sufficient carbon had been added to bring the composition to ThC0.063. The results show that carbon addition strengthens thorium with respect to dilational deformation and with respect to torsional deformation along 〈110〉 directions, but weakens thorium with respect to torsional deformation along 〈100〉 directions. The changes with respect to torsional resistance result in a reduced anisotropy ratio, 2C44/(C11−C12). Carbon addition raises the Debye temperature by only ∼3%. Magnetic susceptibility measurements were made on the crystal both before and after carbon addition. The overall results are in qualitative accord with a directional covalent character for the Th-C bonding interactions.
Nonlinearity in power-output–current characteristics of stripe-geometry injection lasers
Authors: Chinone N.
Published: February 2003

The origins and behaviors of kinks in power-output–injection-current (I-L) curves of stripe-geometry lasers are theoretically investigated. Laser output power is calculated as a function of injection current by solving the carrier diffusion equation and Maxwell’s equation. Transverse modes along the junction plane are assumed to be guided by the injected-carrier-induced gain profile. At low current densities, it is shown that the gain profile is nearly parabolic, resulting in the transverse mode very close to the lowest Hermite-Gaussian distribution. However at high current densities the gain profile is deformed by the stimulated recombination of carriers near the center of the stripe. The resultant mode becomes deformed and penetrates into the low-gain or lossy region. Consequently the mode gain is reduced, and the power saturation (kink) appears in the I-L curves. If there exists an asymmetry in the injection current density profile, it is shown that the optical intensity peak moves along the junction plane and the beam direction shifts from the normal to the laser facets with the increase of the current density. Such theoretical results are qualitatively in good agreement with recent experimental observations and demonstrate that kinks originate from the gain profile deformation and the resultant mode deformation. Investigating the dependence of the output power at which a kink appears on various device parameters such as the stripe width, the amount of current spreading, and the degree of asymmetry, we conclude that the scatter of the output power experimentally observed is caused by the small fluctuations of such device parameters.
Comment on ’’Spinning magnetic fields’’
Authors: Viviani A. , Viviani R.
Published: February 2003

From some remarks on the electric fields induced by a spinning magnetic field, the conclusion is drawn that the results of the old experiments made by Barnett, Kennard, and Pegram could be shown to be wrong only by means of more reliable experimental results. Despite recent statements by Jovan Djurić, there is no theoretical reason why they should prove to be wrong a priori. However, these results cannot be considered as a proof of the nonmoving magnetic lines hypothesis, and different results could not be considered as a proof of the opposite hypothesis. Both hypotheses seem to be oversimplified interpretations of the above results, and a more complete set of experimental data seems to be necessary to formulate the electrodynamics of moving bodies in a more complete way.
High-performance cell for photoacoustic spectroscopy
Authors: Ferrell William G. , Haven Ysbrand
Published: February 2003

A small-volume photoacoustic cell is described in which signal strengths of 400 mV can be achieved at irradiation levels of 35 mW. Thin samples produce a signal of near-triangular waveform when the incident light is a square wave at frequencies of 16 Hz and up.
Uniqueness theorem of a quasistatic magnetic field in a saturable medium
Authors: Steele Charles W.
Published: February 2003

A uniqueness theorem is presented for a quasistatic magnetic field in an isotropic but saturable magnetic field. Suppose in a given region that Maxwell’s equations are satisfied and that B is a steadily increasing function of H. Suppose also that E, D, and φ all have negligible time rates of change (this is the quasistatic assumption). If, in addition, tangential H is prescribed over the boundary of the region, then both B and H are unique in the region. If, in place of tangential H, tangential A is prescribed, then A, B, and H are unique in that region.
Investigations of unidentified laser transitions in Ag II
Authors: Reid R. D. , Gerstenberger D. C. , McNeil J. R. , Collins G. J.
Published: February 2003

We originally reported 33 laser transitions in He-Ag and Ne-Ag mixtures, 23 of which were reported as unidentified. We have since made a more thorough investigation of the laser output and have positively identified five of the unidentified laser transitions as Lyman ghosts. The remainder of the unidentified laser transitions are also believed to be spectrometer ghosts.
Comments on ’’Avalanche buildup time of silicon reach-through photodiodes’’
Authors: Goedbloed J. J.
Published: February 2003

The intrinsic response time τ1 of an electron-initiated avalanche can be about an order of magnitude smaller than the intrinsic response time of a self-sustained avalanche, when the same length of the avalanche region la is considered. For low values of la, the value of τi is noticeably influenced by carrier diffusion.
Reply to ’’Comments on ’Avalanche buildup time of silicon reach-through photodiodes’’ ’
Authors: Kaneda Takao
Published: February 2003

It is indicated that the intrinsic response time τ1 is influenced by carrier diffusion in the narrow avalanche region la≲0.4 μm. The values of τ1 depend upon the injection ratio of hole currents.
Defect structure of 〈100〉 dark lines in the active region of a rapidly degraded Ga1−xAlxAs LED
Authors: Ueda Osamu , Isozumi Shoji , Kotani Tsuyoshi , Yamaoka Toyoshi
Published: February 2003

The 〈100〉 dark-line defects (DLD’s) in the active region of a rapidly degraded Ga1−xAlxAs LED were observed by transmission electron microscopy (TEM). Dislocation networks, which contain dislocation dipoles and a number of dislocation loops, were associated with 〈100〉 DLD’s. The dipole extended in the 〈100〉 or 〈210〉 direction and was extrinsic in character; its Burgers vector was a/2 〈011〉 inclined at 45° to the junction plane. These results were very similar to those of GaAs-Ga1−xAlxAs double-heterostructure (DH) lasers.
The defect levels in p-type silicon doped with manganese
Authors: Evwaraye A. O.
Published: February 2003

Manganese was diffused into p+pn+ silicon diodes at temperatures ranging from 900 to 1150 °C for different times under various quenching conditions. Using transient capacitance spectroscopy, five hole traps associated with manganese in these structures were observed. These defect levels are located at Ev+0.17 eV, Ev+0.33 eV, Ev+0.33 eV, Ev+0.44 eV, and Ev+0.51 eV. The formation of the Ev+0.44 eV and Ev+0.51 eV defect levels depends upon the quenching rate of the devices from the diffusion temperatures. It was observed that the electron irradiation of the manganese-diffused p+pn+ silicon junctions does not produce the characteristic radiation-induced defects seen in boron-doped silicon. The behavior of these defects under heat treatment and their capture cross section for majority carriers will be presented.
The multiple-trapping model and hole transport in SiO2
Authors: Curtis O. L. , Srour J. R.
Published: February 2003

An understanding of the charge-transport process in SiO2 is vital to an understanding of radiation effects in MOS devices. To account for hole transport in SiO2 below room temperature, a stochastic hopping transport model has been employed by others with considerable success. An alternate model is presented here which explains many experimental data in an even more satisfactory fashion. This model is based on multiple trapping at a continuum of trapping levels, the concentrations of which decrease exponentially with energy from the valence band edge. By adjusting the parameters of the model to fit the data at a single temperature, behavior at other temperatures for the same specimen is accurately predicted, including the variation of apparent activation energy with the amount of transport that has occurred. This feature and others which are discussed are not shared by the hopping model previously employed.
The Schottky effect in punch-through diodes
Authors: van de Roer Th. G.
Published: February 2003

The thermionic emission of holes from a metal into a depleted n-type semiconductor is studied in a metal–n-p silicon structure commonly known as a punch-through or Baritt diode. The experimental conditions are such that the current is controlled by image-force lowering of the metal-semiconductor barrier. It is found that the increase of current with electric field obeys the Schottky law. A small oscillatory deviation from this law due to a quantum-mechanical interference has also been found. The barrier height, as determined from these measurements, agrees well with the barrier height for electrons measured on single Schottky-barrier diodes.
Photoionization cross sections in platinum-doped silicon
Authors: Braun Stellan , Grimmeiss H. G. , Spann Klaus
Published: February 2003

Platinum-doped silicon has been investigated using photocurrent and photocapacitance measurements. In all samples, at least two deep energy levels having the same concentration were found, 0.250 eV below the conduction band and 0.355 eV above the valence band, respectively. The other thresholds were 0.908 and 0.82 eV, respectively. The threshold energies of the energy levels add up to values of 1.158 and 1.175 eV, respectively, which are close to the band-gap energy of silicon (1.166 eV) at 80 K. No further deep level impurities could be detected in these samples. In some other samples, up to six different deep energy levels were found with more than two order of magnitude difference in concentration. Although five of these energy levels have been reported in the literature, no proof could be given that they are due to platinum.
Surface rippling induced by surface-tension gradients during laser surface melting and alloying
Authors: Anthony T. R. , Cline H. E.
Published: February 2003

During laser surface melting and alloying, temperature gradients on the melt surface between the laser-beam impact point and the intersection line of the solid-liquid interface with the surface generate surface-tension gradients that sweep liquid away from beam impact point. The resulting flow of liquid creates a depression of the liquid surface beneath the beam and ridging of the liquid surface elsewhere. As the beam passes to other areas of the surface, this distortion of the liquid surface is frozen in, creating a roughened rippled surface. If the laser-beam sweep velocity exceeds a critical velocity, the liquid does not have sufficient time to form ripples, and rippling from surface-tension gradients can be avoided.
Heat treating and melting material with a scanning laser or electron beam
Authors: Cline H. E. , Anthony T. R.
Published: February 2003

A thermal analysis for laser heating and melting materials is derived for a Gaussian source moving at a constant velocity. The resulting temperature distribution, cooling rate distribution, and depth of melting are related to the laser spot size, velocity, and power level. As the power is increased to heat the liquid above the boiling point, a transition to deep penetration welding is described. Calculations are presented for 304-stainless steel which are in agreement with experiment.
Electron energy distributions from GaP with negative electron affinity. I. Emission properties of thermalized electrons
Authors: Piaget C. , Vannimenus J. , Saget P.
Published: February 2003

Photoelectron energy distributions are measured on negative electron affinity (NEA) GaP (100) surfaces for near-band-gap photon energy as a function of the activation conditions with Cs or Cs and O2. X electrons in NEA GaP have a low escape probability unless Cs-O activation is used and the work function reduced to less than 1 eV. Measured energy distribution curves are much broader than for GaAs, up to 0.8 eV (FWHM); their widths are limited by the work function. These results are interpreted by taking into account electron reflection at the surface which enhances the probability of inelastic scattering in the space-charge region. High surface reflection is attributed to the noncentral conduction-band minima of GaP and to Bloch-wave matching conditions at the surface. A multivalley transport model in the space-charge region is presented which includes these effects. Energy distribution widths given by this model are in reasonable agreement with experiment.
Temperature rise induced by a laser beam
Authors: Lax M.
Published: February 2003

The spatial distribution of the temperature rise induced by a laser beam absorbed in a solid is reduced to a one-dimensional integral which is evaluated numerically. The solution for a general laser intensity distribution is specialized to the case of a Gaussian beam. A closed-form expression in terms of tabulated functions is obtained for the maximum temperature rise.
Lamellar devices processed by thermomigration
Authors: Anthony T. R. , Cline H. E.
Published: February 2003

Lamellar structures consisting of alternate p- and n-type silicon layers were fabricated by migrating molten aluminum-rich wires through n-type silicon wafers in a thermal gradient. The recrystallized material deposited behind the molten wires was p type. An aluminum-dopant concentration profile was calculated which was consistent with the measured electrical characteristics of the lamellar structures. Lamellar devices made from these structures can be used as vertical multijunction solar cells, high-voltage diodes, surge protectors, and negative-incremental resistors.
Theory of capacitance and conductance behavior of Schottky-barrier and conducting M-I-S diodes with interface traps
Authors: Fonash Stephen J.
Published: February 2003

A small-signal model is developed for conducting M-I-S structures which is used to explain the general features expected in their parallel equivalent capacitance and parallel equivalent conductance in forward bias. It is shown that effects of the minority band as well as recombination currents very significantly influence the interpretation of this data. Further, it is shown that reported correlation between surface-state densities and metallization material can be explained, at least partially, in terms of barrier height dependence on the metallization.
Double-discharge stabilization of supersonic CO laser mixtures
Authors: Srinivasan G. , Smith J. A.
Published: February 2003

Experiments have been conducted to study the applicability of a cw double-discharge stabilization scheme in conditions appropriate for high-energy lasers in supersonic flows. Steady arc-free volume discharges have been produced in a Mach 3 supersonic flow test cavity using an auxiliary discharge to stabilize the main discharge at low-current densities in N2 and He/CO mixtures. A significant result is the lack of observed plasma E/N changes in response to auxiliary discharge current changes. Also, where glow discharges were obtained, the energy loading achieved was less than the threshold required for laser operation.
Neutron and energetic ion production in exploded polyethylene fibers
Authors: Young F. C. , Stephanakis S. J. , Mosher D.
Published: February 2003

Neutron production in exploded-fiber z-pinch plasmas containing hydrogen or deuterium is reported. Yields in excess of 1010 neutrons have been measured with deuterated fibers. The character of the neutron emission changes from that consistent with a thermal-fusion source for large fiber diameters (100 μm) to one primarily due to energetic ion collisions for small fiber diameters (<25 μm). In the latter case, more than 1013 ions of multi-MeV energies have been observed. This transition in the character of neutron emission is correlated with a fundamental change in the nature of the plasma as evidenced by resistivity measurements.
Stark effect in three-dimensional stochastic electric fields and a static magnetic field of a helium plasma
Authors: Kim S. H.
Published: February 2003

Atomic absorption spectra of the He I plasma in the static magnetic field in the absence of laser radiation are different from spectra in the presence of laser radiation. Especially, it has been theoretically predicted that the spectral shift of the satellite line, which is seen in the latter case, does not exist in the former case. In this paper, the effect of three-dimensional high-frequency electric fields on the σ+, σ−, and π components of the allowed 1 1S0-3 1P1 transition and the forbidden 1 1S0-3 1D2 lines in atomic absorption spectra of the He I plasma in a static magnetic field in the absence of a laser beam is investigated from the coupled equations for the probability amplitudes of atomic states. It is shown that they should give rise to a spectral shift of the allowed lines and satellites about forbidden lines. The calculation reveals that the shift is proportional to the mean-square stochastic electric field, and that the ratio of the intensity of the near satellite to that of the far satellite is different from the ratio obtained by the second-order perturbation theory or the three-level rotating-wave approximation. Discussion is given for the validity of this theory.
Laser beam interaction with plastics
Authors: Slivinsky Sandra H. , Ogle Norman E.
Published: February 2003

An efficient and clean laser process is reported which was developed to replace the mechanical skiving utilized for selectively removing plastic material over metal composites, leaving substrate materials undamaged and undelaminated. A CO2 continuous-wave gas transport laser, with laser intensities exceeding 5×104 W/cm2, was utilized to establish the procedure. The parameters of the appropriate physical model for the material removal are calculated.
A study of copper ions in silver-halide photochromic glasses
Authors: Marquardt C. L. , Giuliani J. F. , Gliemeroth G.
Published: February 2003

Measurements of optical absorption, kinetics, electron-spin resonance, and flash photolysis, as well as x-ray fluorescence and wet-chemical analysis, have been applied to a series of silver-halide photochromic glasses having precisely controlled variations in silver and copper concentrations as well as in the size of the precipitated silver-halide microphases. These combined experimental data have enabled us to clarify the manner in which copper enters the microphases and the mechanisms whereby it affects their photochromic properties. Most notably, we have succeeded in determining the site and valence-state distribution of copper ions, produced by the separation of the microphases. We have demonstrated, for example, that copper enters the silver-halide phase only as cuprous ions, which then act as the dominant hole traps in the photochromic darkening process. Optical absorption of these cuprous ions in the silver-halide phase was also found to make a major contribution to the absorption edge observed in the undarkened photochromic glasses. The increase of thermal fade rate with increasing copper content is discussed in light of these new experimental results.
Penning ionization in doped CO2 TEA lasers
Authors: Reits B. J.
Published: February 2003

A quantitative model is presented which predicts the behavior of the discharge of a CO2 laser gas mixture with a low-ionization seed gas. The basis of the developed model is the assumption of the so-called Penning ionzation mechanism in which metastable nitrogen molecules ionize the seed gas. The developed model will be compared with measurements on an appropriate CO2 laser device. As a result of this study, we describe the successful operation of a simple large-aperture amplifier with a diameter of 12 cm.
Ultrasonic attenuation effects associated with the physical modeling of adhesive bonds
Authors: Meyer Paul A. , Rose Joseph L.
Published: February 2003

The purpose of this work is to examine the effects of selected attenuation functions in adhesive bond modeling problems so that the attenuation in signal processing and interpretation can be treated adequately, and also to determine the significance of attenuation in evaluating bond integrity. Bond models are presently being used to study such problems as improper substrate surface preparation, improper adhesive cure, and chemical segregation of the adhesive. Specific attenuation functions used include some experimentally measured values for real materials, such as polystyrene, Lucite, and rubber, and also a few hypothesized resonant functions based on observed attenuation phenomena in polymeric materials. Results indicate that attenuation effects do not substantially alter the ultrasonic reflection at frequencies lower than 7 MHz. As a result of the study, however, it becomes possible either to eliminate or to amplify attenuation effects by selecting processing techniques for bond inspection. It is also possible to study more sophisticated adhesive bond models with more accurate attenuation functions that could ultimately lead to improved criteria for transducer and signal-processing selection.
Axial density and temperature variations in a magnetically confined arc
Authors: Marhic M. E. , Kwan L. I.
Published: February 2003

Axial variations of electron density ne and temperature Te have been found in magnetically confined arcs assumed by other workers to be axially uniform. Results of measurements using plasma radiation, swiveling water-cooled electrostatic probes, and Thomson scattering of dye laser radiation are presented. The axial variations depend only weakly upon magnetic field strength, arc current, distance between the electrodes, and cathode diameter, but depend strongly upon gas pressure p. Te does not always vary monotonically with distance, but ne usually decreases away from the cathode. For all measurements reported here, 4×1014 <ne<2.2×1015 cm−3 and 0.6 <Te<2.6 eV.
High-current plasma accelerator for the investigation of plasma wall interaction
Authors: Martin C. , Müller K. G. , Tuczek H. , Bieger W. , Gresser H. , Richter F.
Published: February 2003

An accelerator producing quasicontinuous homogeneous plasma beams by means of a traveling wave has been developed. By a special feedback system, beams with a density of the order 1012 cm−3 and ion energies of the order of 100 eV can be produced corresponding to an equivalent current of 240 A. The accelerator is applied to the simulation and investigation of special aspects of the plasma wall interaction.
A new defect-revealing etchant for GaAs
Authors: Greene L. I.
Published: February 2003

A new etchant for n and p bulk GaAs is described. Etching is accomplished through an electrochemical anodic process which uses NH4OH : H2O at a pH of 10.6–13.4. Etching rates depended on the current passed through the solution, while conductivity in turn depended on the pH of the solution. A large number of n+ GaAs polished wafers were characterized with this etching method. Samples etched showed growth-induced striations, dislocations, and twin lamellae. Etching was done on {111}-, {1̄1̄1̄}- {211}-, {511}-, and {110}- as well as {100}-oriented substrates with comparable results.
On the shrinkage of rod-shaped defects in boron-ion-implanted silicon
Authors: Wu Wei-Kuo , Washburn Jack
Published: February 2003

Three different types of rod-shaped defects formed during postimplantation annealing of boron-implanted silicon are distinguished in annealing experiments carried out on transmission electron microscope specimens. It is shown that rod-shaped defects can be boron precipitates, Frank dipoles, or perfect a/2 <110≳ dipoles. All shrink from the ends only during annealing. The temperature dependence of shrinkage rate for the first type was determined by measuring dL/dt at three different temperatures for a given isolated defect. Boron diffusion appeared to be the rate-determining process. The second type, Frank dipoles, were often observed to unfault, transforming into the third type during annealing. At the time of unfaulting the newly formed perfect dipole was always observed to rotate on its glide cylinder to near edge orientation.