bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetic model of the XeBr rare-gas monohalide excimer laser
Authors: Hart G. A. , Searles S. K.
Published: February 2003

A kinetic model of the XeBr rare-gas monohalide excimer laser is presented. Agreement of predicted and observed side emission from low-pressure Xe:Br2 mixtures was used to determine rate constants for the formation of XeBr* from Xe* and Br2 (2.0±0.4×10−9 cm3/sec) and the quenching of XeBr* by Br2 (8±2×10−10 cm3/sec), as well as the radiative lifetime of XeBr* (17.5±2.5 nsec).
Photoelastic effect in piezoelectric semiconductor: ZnO
Authors: Sasaki H. , Tsubouchi K. , Chubachi N. , Mikoshiba N.
Published: February 2003

The photoelastic tensor elements of the piezoelectric semiconductor ZnO were measured by the comparative acousto-optic diffraction method (reference material, fused quartz) at an acoustic frequency of 250 MHz and an optical wavelength of 0.633 μm. Two crystals with different conductivities, one is highly conductive and the other is highly resistive, were used as samples. The measured photoelastic tensor elements for piezoactive strains are different between these two samples. The difference is explained by the electro-optic contribution to the photoelasticity induced by the electric field accompanying the piezoactive acoustic wave in the highly resistive sample and its screening by free carriers in the highly conductive sample. The contribution of the rotation of the volume element to the photoelasticity has been also observed in photoelastic tensor elements for shear strains.
Raman spectrometric determination of additive concentration in high-silica-content glasses
Authors: Kato Daisuke
Published: February 2003

For the evaluation of optical fiber material by Raman spectrometry, the Raman spectra of B2O3-doped high-silica-content glass and four TiO2-doped high-silica-content glasses are studied extensively making reference to that of pure fused silica. Extra Raman bands at about 935 cm−1 are found commonly in the high-silica-content glasses and assigned to the motion of the nonbridging oxygen. The theory of Raman spectrometry of high-silica-content glasses is developed and it is verified experimentally with TiO2-doped high-silica-content glass.
Infrared detection and mixing in heavily doped Schottky-barrier diodes
Authors: van der Ziel A.
Published: February 2003

Transit-time and series-resistance effects in heavily doped Schottky-barrier diodes operating in the thermionic mode are evaluated by applying the laws of vacuum tube electronics to the space-charge region and by incorporating the treatment of the series-resistance effect into the discussion. It is assumed that the field distribution in the space-charge region is linear, that collisions in the space-charge region can be neglected, and that the signals are so small thatr the equations of motion can be linearized. The case of uniform field distribution is also briefly dealt with; the results are not significantly different from the linear field case. At a frequency equal to three times the plasma frequency of the bulk semiconductor the detection and mixing efficiency is about 0.25 times the low-frequency value. The effect of the high-frequency conductance of the space-charge region turns out to be quite small when the series-resistance effect is taken into account; the performance is then determined by a single transit-time factor ‖g (jω) ‖2 and a series-resistance factor that is independent of transit time. The effect of tunneling on the device performance is discussed briefly. Satisfactory detection and mixing performance seems feasible for the 10–40-μm wavelength range.
Double-heterostructure GaAs-AlxGa1−xAs [110] p-n-junction-diode modulator
Authors: McKenna J. , Reinhart F. K.
Published: February 2003

The properties of the lowest-order modes that can propagate in a double heterostructure (DH) made optically anisotropic by the electric field of a p-n junction are calculated by exactly solving Maxwell’s equations and also by using coupled-mode theory. The results of these two treatments are in excellent agreement. The theories are then applied to study the behavior of a polarization modulator device. It is shown that this device should perform excellently as a modulator with large extinction ratios obtained with relatively small applied voltage swings and with low power consumption. Finally we report on the actual fabrication of such a device and show that its behavior is in excellent agreement with theory. For devices only 1 mm long the observed half-wave voltage was 12 V and the corresponding extinction ratios considerably larger than 100. The device can also be integrated with DH lasers.
Diffraction of discrete x-ray frequencies from germanium atoms in crystals
Authors: Das Gupta K.
Published: February 2003

Two distinct Kossel lines and two additional Kossel-type lines are generated by the {220} reflections of germanium single crystals irradiated by Cu and Mo radiation. The wavelengths of these lines as calculated from the observed Bragg angles are 1.134, 1.246, 1.391, and 1.544 Å corresponding to energies of 10.931, 9.949, 8.912, and 8.029 keV, respectively. The lines appearing at 1.134 and 1.246 Å are due to Kβ1 and Kα1,2 of germanium. The Kossel-type lines of wavelengths 1.391 and 1.544 Å are of lower-energy value than germanium Kα, and therefore cannot be classified as regular Kossel lines.
Crazing of graphite and lithium niobate on ion bombardment
Authors: Primak William
Published: February 2003

Crazing patterns extending beyond the areas of natural graphite crystals bombarded with 140-keV H+, D+, or He+ ions were examined under the interference microscope and identified as elongated narrow protuberances. They are attributed to radiation blistering and gas migration along dislocations. Similar patterns were found on ion-bombarded lithium niobate plates.
Observation of vibrationally excited nitrogen with a simplified electron transmission apparatus
Authors: Michejda J. A. , Burrow P. D.
Published: February 2003

A simple electron transmission apparatus is used to observe vibrationally excited N2 in the first two vibrational levels. The method is based on the pronounced peaks appearing in the total electron scattering cross section in the range of energy 2–4 eV. Because of the wide spacing between these peaks, good energy resolution is not required and measurements can be performed without an electron monochromator.
An equivalent circuit for Landau damping
Authors: Pécseli H. L.
Published: February 2003

An equivalent circuit simulating the effect of Landau damping in a stable plasma-loaded parallel-plate capacitor is presented. The circuit contains a double infinity of LC components. The transition from stable to unstable plasmas is simulated by the introduction of active elements into the circuit.
Laser heterodyne apparatus for measurements of liquid surface properties—Theory and experiments
Authors: Hård S. , Hamnerius Y. , Nilsson O.
Published: February 2003

An apparatus has been developed, which measures the laser light scattering from thermally excited surface capillary waves of liquids. Such measurements do not cause any mechanical or thermal disturbances of the surface under study (a low-power cw He-Ne laser is used). This is especially important in the study of film-covered surfaces which are biologically interesting. Our heterodyne technique apparatus uses a grating to create a well-controlled local oscillator light beam. This is the main difference between our apparatus and those of previous workers. Compared with these apparatuses the sensitivity and resolution are considerably improved in the measured spectra, from which liquid properties such as surface tension and viscosity are calculated. A quantitative analytical theory is developed which permits optimization of the measuring set up and it is demonstrated that the predicted resolution and sensitivity are obtained in the practical measurements. It is demonstrated with higher accuracy than in earlier light scattering measurments that for a number of liquids the standard capillary wave theory correctly predicts the measured spectra. The surface tension and viscosity of water as calculated from our measurements agree within 2% and 10%, respectively, with the values known from standard mechanical measurements.
Measurement of parameters in a mode-locked and frequency-doubled Nd : YAG laser using relaxation oscillations
Authors: Kennedy C. J. , Barry J. D. , Rice R. R.
Published: February 2003

The behavior of relaxation oscillations in the presence of a nonlinear loss was used to determine the relevant parameters of an intracavity frequency-doubled and mode-locked Nd : YAG laser. The acousto-optic mode locker was used in a controlled manner to excite the relaxation oscillations which allowed the measurement of the damping time and frequency. Laser output power at 0.53 μm and damping time is consistent with recent theory.
Wall depletion effect of population at upper laser level on optical gain in CO2-He waveguide lasers
Authors: Shirahata Hiromichi , Fujioka Tomoo
Published: February 2003

The wall depletion effect of CO2 molecules at the excited (00°1) level has been taken into consideration for the calculation of the optical gain of CO2-He waveguide lasers having a circular discharge tube and a parallel-plate discharge tube. The simplified equations for obtaining the wall depletion rate for these two discharge tubes are presented and they are found to be in good agreement with the exact values. The numerical calculation revealed the presence of an optimum radius and height of discharge tubes as a function of gas pressure, mixing ratio of the laser gases, tubing materials, and the shape of the discharge tubes. The numerically computed small-signal gain has been found in good agreement with the experimentally observed values.
Collision-induced transitions in neon
Authors: Siebeneck H. J. , Bergmann Ernest E.
Published: February 2003

The interaction of 6328-Å laser radiation with excited atoms in a He-Ne gas discharge leads to a sizeable change in the population of the 3s2 and 2p4 levels of Ne. Population of levels connected to the upper and lower laser levels through radiative and nonradiative electronic and/or atomic collisional processes will be perturbed also by the population changes of these two levels. By studying the intensity changes of spontaneous emission from the 3s2 and 3s3 levels as a function of current and pressure, we obtained the total relative atomic and electronic deexcitation rates of the 3s3 level. We also studied the collisional coupling between the 3s2 and 4d4 levels of Ne (the ion cores of which are in two different states) to find the total atomic and electronic deexcitation rates for the 4d4 level. The electronic coupling between these two levels was found to be weaker than between the 3s2 and 3s3 levels, suggestive of a weak selection rule.
CO chain-reaction chemical laser. II. Computer modeling
Authors: Lilenfeld H. V. , Jeffers W. Q.
Published: February 2003

The previous companion paper has shown the potential for development of the CO chain-reaction laser. Given the importance of this development, the CO chemical laser modeling code was extended to describe this device. The improved model has been shown to accurately predict both the essential chemical and optical properties of the experimental device. Specifically, the chemical chain length, gain coefficients, and power-output predictions are in very good agreement with experiment. Finally, the model predicts efficient operation of CO chain-reaction laser at high cavity pressures.
Optical resonance of a two-level atomic system
Authors: Nayfeh Munir H. , Nayfeh Ali H.
Published: February 2003

The method of multiple scales is used to derive a solution of the damped optical Bloch equations of a two-level atomic system due to a strong pulsed field. The time dependence of the oscillations of the atomic inversion influenced by detuning and power broadening is found. The population inversion consists, in general, of three terms: a quasisteady term, quasisteady term that decays with time, and an oscillatory term that also decays with time. In the limit of constant fields, the solution of Torrey for damped systems and that of Rabi for undamped systems are recovered. For an adiabatic switching of the field, the solution for undamped systems reduces to that of Crisp in the adiabatic following limit. An equation describing the field envelope is derived for an arbitrary amount of detuning. At exact resonance, this equation reduces to a pendulum equation, in agreement with previous analyses.
A study of germanium/SiO2 MIS structures by the use of secondary ion mass spectrometry
Authors: Wang K. L. , Storms H. A.
Published: February 2003

Secondary ion mass spectrometry has been used to investiage CVD SiO2-germanijm MIS structures under various annealing conditions using several standards. For samples annealed in oxygen at 600°C, a GeO2 film was formed between germanium and SiO21. Germanosilicate glass was found in the interface when the samples were subsequently annealed in Ar at 800°C. The oxidation of gamanium and formation of GeO2 or germanosilicate glass under these annealing conditions results in a lower interface state density. For samples annealed in Ar or a 10% H2-90% N2 forming gas, only a very thin GeO2 layer was presented and a very small difference in film thickness was observed. Such a small difference cannot explain fully the higher increase in interface state density when samples were annealed in forming gas. The investigation of hydrogen concentration indicates a hydrogen pileup near the germanium, is probably responsible for the high observed interface state density. Metallization, particulary with Al, complicates the studies. Furthermore, the release of hydrogen during the Al evaporation contributes to a high interface state density for samples annealed in forming gas. The effects of direct and recoiled ion implantation on the depth resolution during profiling is discussed. In addition, it is demonstrated that the profiling of contaminants may be used to identify the origins of contamination introduced during the processing.
Study of electron traps in n-GaAs grown by molecular beam epitaxy
Authors: Lang D. V. , Cho A. Y. , Gossard A. C. , Ilegems M. , Wiegmann W.
Published: February 2003

Electron trapping centers in n-GaAs grown by molecular beam epitaxy (MBE) have been studied by deep-level transient capacitance spectroscopy (DLTS). At least nine different electron traps are observed with energies ranging from 0.08 to 0.85 eV from the conduction band. Total electron trap concentrations in various samples range from the low 1014 cm−3 range to the mid 1012 cm−3 range. Studies of samples from various growth systems indicate that these traps are most likely due to chemical impurities. A comparison is made with electron traps in n-GaAs grown by vapor- and liquid-phase epitaxy as well as with the electron traps introduced into n-GaAs by 1-MeV electron irradiation.
Auger recombination and junction resistance in lead-tin telluride
Authors: Emtage P. R.
Published: February 2003

The rate of Auger recombination in materials with a many-valley band structure such as that of PbTe is calculated in this paper. It is found that recombination comes principally from the collision of current carriers in different valleys; the recombination rate can be large at quite low temperatures if the ratio of transverse-to-longitudinal effective masses in a valley is far from unity. The calculated rate sets an upper limit to the resistance of a simple p-n junction in such materials; for material of band gap 0.1. eV, this limit is 6 Ω cm2 at 77 °K.
Electrical effects of SiC inclusions in EFG silicon ribbon solar cells
Authors: Hari Rao C. V. , Bates H. E. , Ravi K. V.
Published: February 2003

The electrical effects of included silicon carbide (SiC) particles in edge-defined film-fed grown silicon ribbons have been examined. By employing a scanning electron microscope operated in the electron-beam-induced current mode, as well as observing the effects of SiC particles on solar-cell characteristics, the electrical activity of particles and particle-generated defects were studied. The influence of SiC particles largely appears to be a result of impurity accumulation around them rather than a direct effect of the inclusions.
Vanadium dioxide current limiters for incandescent lamps
Authors: Miller R. C. , Emtage P. R. , Nalepa P. J.
Published: February 2003

A VO2 resistor, which switches from high to low resistance as it passes through a phase transition at 68 °C, can eliminate the initial current surge when an incandescent lamp is first turned on; this inrush current, which is often harmful, occurs because the cold resistance of the lamp is low. We here analyze the progress of (and the instabilities in) the electrically driven thermal switching of VO2, and determine the size and properties that a current-limiting resistor must have. Current limiters were made from a ceramic with a VO2 base and various additives; such limiters work well, and the steady-state power loss in them is 0.5% for 100-W lamps.
Origin of ’’capacitance’’ in superconducting microbridges
Authors: Song Y.
Published: February 2003

The geometrical interelectrode capacitances of superconducting microbridges are too small to account for the observed hysteresis in their I-V characteristics. We propose a new model of microbridges in finite voltages, in which the relevant time constant is the supercurrent relaxation time τR. From an analysis of the experimental I-V curves it follows that τR can be identified with the pair relaxation time within a numerical factor. By equating τR/2π to the time constant C/G of the shunted Josephson junction model, we obtain values of C in reasonable agreement with those typically obtained from I-V characteristics.
Hard-magnetic properties and microstructure of Sm(Co,Cu)z compounds
Authors: Nagel H. , Perry A. J. , Menth A.
Published: February 2003

Magnetic measurements and metallographic investigations are reported on Sm(Co,Cu)z alloys. The compositions lie between the rare-earth (RE) to transition-metal (TM) ratios of 1 : 5 and 2 : 17 with a content of copper of up to 35% of the TM fraction. The materials were analyzed both in the as-cast and heat-treatment conditions. The remanence BR scales with composition. The coercivity IHc showed a maximum along a tieline from the off-stochiometric Sm(Co0.65Cu0.35)5.6 to the Sm2Co17 phase. In the as-cast state the hysteresis loops are not square. High-temperature homogenization yields ideal demagnetization curves. Subsequent annealing at lower temperatures T resulted in two coercivity peaks as a function of T. The peak temperatures decrease with increasing Cu concentration, e.g., for 35% Cu of TM 450 and 650 °C and for 20% Cu of TM 650 and 850 °C were found. Alloys near the 2 : 17 phase boundary contain 2 : 17 as a massive primary phase in a 1 : 5 matrix. The squareness of the hysteresis loops implies that the 2 : 17 phase itself is magnetically hardened. The results are discussed on a pinning model under consideration of the metallurgical properties of the RE-TM alloys.
Bessel-Fourier series solutions of cylindrically symmetric electrostatic lens potentials
Authors: Wittels N. D. , Jacobsen E. H.
Published: February 2003

We present a method for expressing the electrostatic potential of a cylindrically symmetric electron lens using Bessel-Fourier series. The method consists of partitioning the lens volume into cells and choosing appropriate series solutions made up from the set of functions comprising all possible solutions to Laplace’s equation. The satisfying of boundary conditions and of continuity of the electric field at cell partitions leads to a set of linear equations for the series coefficients. Because the inherent error in these solutions in predictable, it is possible by this scheme to construct solutions which assure a specified accuracy. Moreover, this procedure affords a high degree of flexibility. Two lenses are analyzed by this method in detail.
Precision recording dilatometer with results for cholesteryl nonanoate
Authors: Armitage D. , Price F. P.
Published: February 2003

A capillary dilatometer has been automated by means of a capacitive transducer technique. The precision is 1 : 105 over a range in volume of 4% for a sample volume of 2 ml. Differential scanning dilatometry is achieved by comparing the sample dilatometer with a reference dilatometer. Some results for the density changes associated with the liquid-crystal transformations in cholesteryl nonanoate are presented.
Fluorescence and laser-emission cross sections in NaNdP4O12
Authors: Nakano Jun’ichi , Otsuka Kenju , Yamada Tomoaki
Published: February 2003

As a solid-state laser material, NaNdP4O12 (NNP) single crystals were grown by the top-seeding Kyropoulos method. It belongs to the monoclinic system with space group P21/c-C52h, and the Nd content is 4.24×1021 cm−3. Fluorescence was examined at room temperature and at 77 °K. The lifetime of the 4F3/2 level was measured to be 110±10 μs. A cw laser action was confirmed at room temperature. The laser emission was linearly polarized along the c axis. The effective emission cross section was measured to be σc=2.1×10−19 cm2.
Temperature changes of the photoelastic effect of NaCl, KCl, and KBr
Authors: Kato Eiji , Saji Yoshiro
Published: February 2003

The Brillouin spectra of NaCl, KCl, and KBr were observed in the temperature range ∼50–300 °K. From the measurements of scattered light intensity and the frequency shift, the temperature change of the photoelastic effect were determined. From these results and thermodynamical calculations, the temperature change of ∂n/∂TP of these crystals were also determined. The result showed the same shapes as NaF, obtained from the measurements of the refractive index by previous workers.
Injection of ions into thin insulating films from a glow discharge
Authors: Carlson D. E.
Published: February 2003

A glow discharge has been used to inject positive ions into thin films of SiO2 on Si at moderate temperatures (∼320 °C). The electrical properties of the films are drastically altered by the ion-injection process.
Thermomigration of aluminum-rich liquid wires through silicon
Authors: Cline H. E. , Anthony T. R.
Published: February 2003

High-temperature thermomigration of aluminum-rich droiplets in silicon has resulted in droplet migration rates up to 10 cm/day. These unexpectedly high rates are an order of magnitude greater than those previously reported in the literature. The large enhancement of droplet migration rates at high temperatures is shown to be caused by a substantial increase in the flow of liquid across the droplet and by a favorable variation in the change of the composition of the liquid at high temperatures. The variation of droplet velocity with droplet size is reported over a large range of droplet sizes and temperatures for both the 〈100〉 and 〈111〉 migration directions in silicon. The undersaturation and supersaturation required to make a (111) silicon plane dissolve and deposit, respectively, are calculated from the data. Finally, from the velocity of large droplets, the liquid interdiffusion coefficient for the aluminum-silicon system is determined.
Equivalent electrical circuit of a multielectrode composite piezoceramic disk
Authors: Adelman N. T.
Published: February 2003

An analysis is made for the radial vibrations of a thin multielectrode piezoelectric disk composed of N ferroceramic materials bonded at their cylindrical interfaces. Resonant and antiresonant eigenfrequency equations are derived, and an equivalent electrical circuit of the transducer is developed from the admittance matrix. Numerical solutions are presented for the fundamental resonant frequencies and corresponding effective electromechanical coupling factors of a uniformly polarized two-electrode PZT-4 disk with nonzero interelectrode spacing.
Ferroelastic behavior in Ba2Ge2TiO8
Authors: Kimura Masakazu , Utsumi Kazuaki , Nanamatsu Satoshi
Published: February 2003

A Ba2Ge2TiO8 crystal is found to exhibit ferroelastic behavior. Optical, thermal, and elastic studies indicate that the phase transition occurs at about 810 °C. The wedge-shaped twin domains disappear above the phase transition temperature. The twinned crystal is detwinned by an exchange of orthorhombic axes a and b under the application of a compressive stress of 250 kg/cm2 at room temperature and of 100 kg/cm2 at 700 °C.
Thermal redistribution of impurities in silicon-on-sapphire: Theoretical development
Authors: Maldonado C. D. , Mandel G. , Kinoshita G.
Published: February 2003

A solution to the problem of redistribution of impurities in a finite silicon slab has been determined using the Green’s function for the diffusion equation in a transformed coordinate system. This solution can be used to predict the spatial distribution of the impurity concentration profiles corresponding to different values of time during drive-in and thermal oxidation occurring in the fabrication of silicon-on-sapphire (SOS) devices. A computer program based on the solution has been developed and applied to illustrative examples where the initial impurity distributions arise from single and double ion implants of boron or phosphorus in silicon. Numerical results which predict the redistribution of these initial distributions during thermal oxidation are presented. In a future paper, theoretical predictions based on the solution of the present paper will be used to correlate experimental data on the redistribution of impurities in SOS.
Energy loss of low-energy 40Ca ions in carbon
Authors: Shane K. C. , Laumer H. , Seaman G. G.
Published: February 2003

The energy loss of 40Ca in carbon at less than 335 keV energy has been measured by detecting the energy of Doppler-shifted γ rays from recoiling Ca ions. The energy loss mechanism can best be described as 1.17 and 0.67 times the theoretical values for electronic and nuclear stopping, although the theoretical values also give acceptable fits to the data.
Temperature dependence of the resistivity and the Hall coefficient of thin bismuth film
Authors: Hsu L. S. , Chang Y. Y. , Young C. S. , Tseng P. K.
Published: February 2003

Temperature dependence measurements of Hall coefficients and resistivity were carried out on thin bismuth films (∼1500 Å thickness) of various heat-treating histories. The results show that the perfectness of the thin-film crystal correlates with the temperature dependence of resistivities and that of Hall coefficients if the evaporation condition, film thickness, and the substrate material of thin films are identical. Also it shows that the perfectness of the thin-film crystal depends on the history of heat treatment as well as the surface condition of the substrate.
Crystal structure of cerium above 50 kbar
Authors: Schaufelberger Ph.
Published: February 2003

I n-situ x-ray data has been obtained on 99.99% pure cerium at 50 and 52 kbar with the use of a Bragg-Brentano parafocusing x-ray reflection technique under quasihydrostatic conditions, with a thermal cycling procedure. Our results, based upon 22 experimental diffraction lines, indicate that cerium metal exhibits a definite crystallographic transition from fcc to hcp symmetry at 51±1 kbar with a ?7% volume reduction. Previous results are discussed in light of indexing reliability calculations.
Thermal conductivity of some rubbers under pressure by the transient hot-wire method
Authors: Andersson P.
Published: February 2003

The transient hot-wire method was used to determine the effect of fillers on the thermal conductivities of different rubbers in the pressure range up to 0.2 GPa at 300 K. The fillers, carbon black and ZnO, both strongly increase the absolute conductivity values but the relative pressure reponses are only slightly affected. The thermal conductivities increase linearly with pressure, and the pressure coefficients are in the range 1.0–1.6 per GPa for all the rubbers studied. The thermal conductivity of a filled rubber is analyzed in terms of contributions from the filler and the pure rubber. The experimental results show a stronger increase in conductivity with the percentage of filler than predicted by theory.
Effect of sputtering on the strength of silicate glasses
Authors: Mecholsky J. J. , Rice R. W. , Anderson G. W. , Sigel G. H.
Published: February 2003

Biaxial tensile strengths of radio frequency and ion-beam sputtered silicate glass disks were ≳100% over as-received polished disks. Fracture surface analysis, correlated with the fracture stress, showed failure to originate within the depressions formed from sputtering. Thus sputtering itself limits the increased strength of silicate glasses initially obtained by sputtering away the surface layer containing mechanically introduced flaws.
The unloading and reloading behavior of shock-compressed polymethyl methacrylate
Authors: Schuler K. W. , Nunziato J. W.
Published: February 2003

Samples of polymethyl methacrylate (PMMA) have been shock compressed to ?0.82 GPa and then further compressed by a reloading wave which approximately doubled the initial compressive stress. The reloading waves were observed to be acceleration waves rather than shocks. Assuming the material is Maxwellian, these waves have been analyzed to determine certain material properties characterizing the stress-strain response of the material. These properties were found to be different than those obtained from previously reported unloading waves also propagating in shock-compressed PMMA at ?0.82 GPa. This difference in stress-strain response supports the existence of a yield-type phenomenon previously suggested in PMMA at ?0.75 GPa.
Comparison of silicon solar cell efficiency for space and terrestrial use
Authors: Rittner E. S. , Arndt R. A.
Published: February 2003

The efficiency of silicon p-n junction photovoltaic cells for solar energy conversion is higher in terrestrial use than in space use by an amount which can be as high as 25%. The power output in terrestrial use is nevertheless lower than in space use because of the lower solar intensity. The explanation for the higher efficiency is that, on traversal of the sunlight through the earth’s atmosphere, water vapor and carbon dioxide absorb energy primarily at wavelengths in the near infrared to which the solar cell is not sensitive. In the present paper a quantitative evaluation of this hypothesis is carried out by numerical determination of the total integrated power and of the number of photons/sec capable of creating hole-electron pairs corresponding to known solar power distributions for air masses 0, 1, 2, and 3 and by translation of the results into lossless cell efficiencies. The efficiency for silicon cells at air mass 1 for the case of no absorption bands proves to be the same as for air mass 0, whereas in the absorbing case the terrestrial efficiency is about 10% higher. Also for the absorbing case, as the air mass is increased, the efficiency relative to the space case increases to 15% at air mass 2 and 16% at air mass 3. Measurements of short-circuit current, efficiency, and incident solar power under air mass 2 conditions during the period from mid-November 1975 to early January 1976 have been carried out on a variety of silicon solar cells including conventional satellite cells, violet cells, and COMSAT nonreflective cells. For relatively clear atmospheric conditions, efficiency enhancements relative to space conditions of 11–12% were observed for both direct radiation and the sum of direct and sky radiation. Under hazy atmospheric conditions, efficiency enhancements of from 15–19% were observed. It is concluded than wavelength selective attenuation mechanisms (e.g., infrared absorption by water vapor and carbon dioxide and scattering, predominantly in the infrared, by suspended particulate matter and water droplets) which attenuate the total solar power to a greater degree than the power to which the solar cell is sensitive will produce a higher conversion efficiency for terrestrial use than for space use. However, the higher terrestrial efficiency implies only that, as the sunlight is attenuated by transmission impairments, the cell power output falls off more slowly than the solar power input.
Luminescence properties of Be-implanted GaAs1−xPx (x∼0.38)
Authors: Chatterjee Pallab K. , McLevige W. V. , Streetman B. G.
Published: February 2003

Radiative recombination in Be-implanted GaAs1−xPx (x∼0.38) is examined using low-temperature photoluminescence and electroluminescence. A luminescence band at 1.955 eV (6 °K) is related to recombination from the conduction band to neutral Be acceptors. The temperature dependence of this emission band indicates the binding energy of the Be acceptor is 35±3 meV. Annealing the Be-implanted GaAs1−xPx with SiO2 or Si3N4 encapsulation at 900 °C is shown to reorder the lattice and produce excellent optical activation. Photoluminescence measurements in conjunction with successive layer removal indicate the implanted Be does not diffuse significantly during the anneal.
Photoluminescence from Si irradiated with 1.5-MeV electrons at 100 °K
Authors: Noonan J. R. , Kirkpatrick C. G. , Streetman B. G.
Published: February 2003

The effects which low-temperature electron irradiation have on the photoluminescence from Si provide new information regarding irradiation-induced defects which participate in radiative recombination. Previous identifications of the 0.8–1.0-eV band with the divacancy and the 0.6–0.8-eV band with the Si-G15 (or K) center are apparently in error. The 0.8–1.0-eV band appears only after anneals above ∼300 °K, whereas the 0.6–0.8-eV band can be detected after 100 °K anneals. The lower-energy band may be due to radiative recombination at an oxygen-modified divacancy or a carbon-oxygen-vacancy complex. The 0.8–1.0-eV band may involve a carbon-related defect. A band between 0.7 and 1.0 eV, which is seen only from boron-doped crystals, may arise from a defect involving boron and intrinsic defects.
Configurations for high-power pulsed CH3F 496-μm lasers
Authors: Plant T. K. , DeTemple T. A.
Published: February 2003

The generation of high-power pulses from optically pumped CH3F at 496 μm was investigated in a simple one-mirror superradiant laser, a dielectric waveguide laser, and an oscillator-amplifier configuration. All three configurations were found to produce linearily polarized temporally smooth pulses with a lowest-order transverse intensity profile. The superradiant mode produced approximately twice the output of the oscillator-amplifier mode while the cavity always produced the lowest output. A maximum FIR output of 2.3 kW corresponding to an energy conversion efficiency of 0.35% was obtained which is 35% of the theoretical maximum.
A barium sodium niobate acousto-optic mode locker/frequency doubler (AOML/FD) for Nd : YAG
Authors: Rice R. R. , Burkhart G. H. , Teague J. R.
Published: February 2003

The use of a single Ba2NaNb5O15 crystal to acousto-optically mode lock and frequency double a Nd : YAG laser is reported. An acoustic transducer was bonded to the crystal to form a standing wave Bragg modulator, and the crystal was mounted in an oven for phase-matched SHG. The acousto-optic figure of merit was measured for several orientations. The characteristics of a TEM00 Nd : YAG laser frequency doubled and mode locked at 500 MHz using an AOML/FD are described.
Optical gating by bleaching-induced polarization anisotropy in organic dyes
Authors: Vahey David W.
Published: February 2003

A light gate based on optically induced polarization anisotropy in cryptocyanine-glycerin compares favorably with a CS2 light gate tested under similar conditions. The organic-dye device is more transmissive at giant-pulse excitation levels up to 10 MW/cm2, where both devices gated 1% of an incident probe beam, and is less sensitive to variations in the intensity of exciting light. A theory based on the anisotropic orientational distribution of excited dye molecules during bleaching is used to explain the data. Fair agreement is obtained if one accounts for the birefringence as well as the absorption anisotropy induced by the exciting pulse.
Small-signal gain modeling for optical pumping of the alkali-xenon and alkali dimer laser transitions
Authors: Palmer A. J.
Published: February 2003

A kinetics model for broadband optical pumping of the alkali–rare-gas and alkali dimer A-to-X laser transitions is developed and is used to compute the small-signal gain coefficient as a function of wavelength for the excimer and dimer bands of all of the alkali-xenon systems. Net gain coefficients of ∼10−3–10−2 cm−1 are predicted on the excimer and dimer bands of all of the alkali-xenon systems for practical values of operating pressure and flashlamp fluxes. For the considered operating conditions, the gain bandwidths of all of the alkali-xenon excimer/dimer systems together span almost the entire wavelength range from roughly 6300 to 12 000 Å.
Electroreflectance measurements of lattice damage in ion implanted GaAs
Authors: Anderson Wayne J. , Park Y. S.
Published: February 2003

The electroreflectance (ER) technique for measuring ion implantation damage is developed and evaluated. The technique is useful for measuring damage profiles in GaAs samples. The ER measurement using the E1 critical point is shown to be primarily sensitive to a depth of 0.008 μm. The damage profiles of S-, Cd-, Be-, and Ne-implanted GaAs samples are determined employing a selective etch technique. The annealing characteristics of these GaAs implants are shown to be dose dependent.
Lithium-ion soft x-ray laser
Authors: Mani S. A. , Hyman H. A. , Daugherty J. D.
Published: February 2003

A two-stage optical-pumping scheme is considered for achieving laser action on the 199-Å lithium-ion resonance line. Incoherent radiation from a CO2 laser-produced plasma preferentially photoionizes the K shell of neutral lithium, producing highly energetic ions in the metastable 1s2s state. A detailed model of the system indicates that with an initial lithium vapor density ∼1014 cm−3, an effective metastability of several nsec can be obtained, allowing a drastic reduction in pumping requirements compared to schemes involving direct pumping of the upper laser level. After a sufficient buildup of metastable ions, a dye laser, tuned to the 9584-Å 1s2s 1S→1s2p 1P transition, is switched on, and lasing at 199 Å occurs due to the stimulated-resonant-Raman anti-Stokes process. At 1014 cm−3 initial vapor density, the resonant-Raman gain is ∼10 cm−1, so that a gain length ∼3 cm should be adequate to demonstrate lasing in a single pass. The dye laser acts as a traveling-wave excitation source, providing a collinear well-collimated x-ray laser beam.
Isothermal equations of state for lithium fluoride
Authors: Kim K. Y. , Chhabildas L. C. , Ruoff A. L.
Published: February 2003

The change in length of 1-m-long LiF single crystal has been determined as a function of hydrostatic pressure up to 7 kbar over the temperature range 28–41°C. The length change has been measured to an accuracy of less than 500 A by using a Fabry-Perot type He-Ne laser interferometer, and under a temperature-controlled environment with temperature variations less than 0.002°C. Several isothermal equations of state, together with those derived from the Born model of ionic solids, have been used in analyzing the pressure-volume data. The isothermal bulk modulus Bo and its pressure derivative B′o at atmospheric pressure and 28.83±0.05 °C obtained from the two-parameter (Bo and B′o) equations of state are Bo=664.5±0.5 kbar and B′o=5.40±0.18, respectively. The present results differ considerably from the static measurements of Bridgman and also of Vaidya and Kennedy, but are in excellent agreement with the values obtained by ultrasonic measurements. Using the two-parameter equations of state, the pressure volume data is extrapolated to ∼5 Mbar in order to compare with the shock wave data and to examine the differences between the various equations of state, which are hardly distinguishable in the low-pressure region. Although the present V/Vo measurements are sufficiently accurate to obtain accurate values of B″o, the present pressure measurements are not (although we believe they are as accurate as is possible at the present time).
Deformed layers observed at the interface between a Sn-doped epitaxial layer and a Cr-doped substrate in GaAs
Authors: Kasano Hiroyuki
Published: February 2003

Interfacial deformed layers existing in GaAs epitaxial wafers are conveniently observed on a {110} cleavage face by means of a room-temperature photoetching technique with a slightly modified Abrahams-Buiocchi etchant. Examination is mainly confined to vapor-grown GaAs samples composed of an 0.4-μ-thick Sn-doped epitaxial layer [n? (6–10) ×1016 cm−3] and a Cr-doped semi-insulating substrate. It is established that the deformed layer results from thermal stress imposed on the arsenic depletion layer generated at the substrate surface in the preheating stage prior to growth. The strain field is found to extend more than 10 μ into the substrate side and even into the epitaxial layer side. Electron mobility in the submicron epitaxial layer is lowered by the presence of this strain field. However, this can be improved from 10 to 30% by annealing. It is also found that dislocations are generated in the deformed layer when the imposed stress is increased by coating the back side of the substrate with a SiO2 film. The dislocation density increases rapidly, but the deformed-layer thickness gradually decreases as the SiO2 film thickness increases. Slip dislocations are generated from the periphery of the epitaxial wafer during the cooling process. This is due to stress concentration at the periphery.
Piezoelectric thin films of rf-sputtered Bi12PbO19
Authors: Mitsuyu T. , Wasa K. , Hayakawa S.
Published: February 2003

Thin films of Bi12PbO19, one of the γ-Bi2O3 family, were prepared on glass and Si substrates by rf sputtering. Films of γ-phase Bi12PbO19 were obtained at the substrate temperature of 450–600 °C. The films were found to be highly oriented with the 〈310〉 axis normal to the substrate surface and exhibited piezoelectricity. The electromechanical coupling factors for the longitudinal mode measured were 0.16–0.22 with the phase velocities of 3600–3800 m/sec.
Vacuum breakdown induced by ionic bombardment of cathode electrode
Authors: Brainard J. P. , Riedel A. A.
Published: February 2003

Ion bombardment of the cathode in a vacuum diode can induce high-voltage breakdown. The breakdown damage at the cathode consists of a central initiation site caused during the high-voltage collapse and a surrounding dendritic etching caused after the voltage collapse. Energy dispersive analysis of the central region shows that when contaminants are observed they are dielectric. Dielectric particles above 10 μ diameter which are deliberately placed on the cathode cause breakdown during ion bombardment. These particles attain fields comparable to their dielectric strength (MV/cm) in μs times from charging during ion bombardment (0.3 A/cm2). The discharging of these particles is believed to initiate interelectrode breakdown.
Corona inception under switching surge for point-to-plane long gaps
Authors: Salama M. M. A. , Parekh H. , Srivastava K. D.
Published: February 2003

This paper describes a method of calculating the corona-inception voltage and its statistical probability for a point-to-plane long gap and under a switching surge of positive polarity. The minimum corona-inception voltage is determined by calculating the number of electrons at the head of the primary avalanche. The statistical probability of corona inception is determined by calculating the critical volumes (or areas) in space at different voltages above the minimum corona-inception voltage. The derivative of the critical volume (or area) with respect to time gives a measure of the statistical probability of corona-inception voltage.
Diffused phase transitions in BaxSr1−xTiO3 single crystals
Authors: Benguigui L. , Bethe K.
Published: February 2003

We measured the dielectric susceptibility and the polarization of three crystals in the system BaxSr1−xTiO3 (x=0.39, 0.26, and x=0.24) which exhibit a diffused ferroelectric phase transition. The results are interpreted using an extension of the Devonshire theory to diffused phase transitions. Diffuseness of the phase transition in BST is not caused by crystalline imperfections but is an inherent feature of this transition.
Gas release from Al2O3 and stainless-steel surfaces under x-ray irradiation
Authors: Brumbach Stephen , Kaminsky Manfred
Published: February 2003

Measurements have been made on the amount and type of gas species released under x-ray irradiation from Al2O3 and stainless-steel surfaces in an ultrahigh vacuum environment. These surfaces had not been degassed but had been held more than 24 h at a background pressure of 1×10−9 Torr prior to irradiation. The energy spectrum of the x rays was characteristic for a tungsten-target bremsstrahlung spectrum for electron energies varying from 15 to 50 keV. The predominant gas species observed mass spectrometrically were CO2 from Al2O3 and O2, CO2, and CO from stainless steel. Mean quantum yields for the release of the species have been determined and are in the range from 3×10−5 to 2×10−3 molecules per number of photons in the bremsstrahlung spectrum. Mean quantum yields were observed to decrease with increasing mean photon energy. The mean photon energy dependence of the mean quantum yield for gas release was correlated with the photon energy dependence of the photon absorption coefficient of the substrate material. The amount of CO2 released was found to be independent of CO partial pressure.
Measurement of structure in the energy distribution of slow secondary electrons from aluminum
Authors: Everhart T. E. , Saeki N. , Shimizu R. , Koshikawa T.
Published: February 2003

The number of secondary electrons per unit energy, N (E), and the derivative dN/dE have been measured carefully for clean and contaminated aluminum using a four-grid hemispherical retarding-field energy analyzer. At primary beam energies of 0.5, 1.0, and 1.5 keV, a broadened curve of N (E) vs energy E was obtained for clean aluminum; the more normal narrow curve was obtained when the surface was contaminated with oxygen. This structure is believed due to plasmon decay excitation of electrons in the solid.
Two-dimensional domain walls in ferromagnetic films. IV. Wall motion
Authors: Aharoni Amikam
Published: February 2003

The Ritz model for the wall separating two antiparallel domains in ferromagnetic films is modified, by the addition of a third Ritz parameter, to contain the extra asymmetry appropriate to a wall in motion. The modification is such that the magnetostatic self-energy is still calculated analytically and the numerical integration involved in the calculation of the exchange-energy term is not more complicated than in the case of the stationary wall. Numerical results are given for 1000-Å-thick uniaxial Permalloy film at zero applied field, for a wall velocity in the range 104 to 105 cm/sec. This is the range in which Schlomann’s approximations led to some ’’critical’’ velocity, only no such critical velocity is encountered here. The difference between the energy of the moving wall and that of the stationary wall changes quite considerably with wall velocity. This means that if one uses the conventional definition for the difference as a kinetic energy, the mass of the wall changes with velocity. Its value ranges between 7×10−11 g/cm2 for a velocity of 104 cm/sec and 4×10−11 g/cm2 for a velocity of 105 cm/sec. But most of this change is in a rather small be taken as an abrupt change that experimentalists would call a critical velocity.