bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of the free-electron density at the onset of laser-induced surface damage
Authors: Alyassini N. , Parks J. H.
Published: February 2003

The rapid transient processes which occur during laser-induced damage to a transparent dielectric surface were studied. A single mode TEM00 ruby laser pulse having ∼12-nsec pulse width was used to damage BSC-2 glass surfaces. An optical probe technique was developed for these studies which used a continuous He-Ne laser to probe the surface reflectivity during, as well as after, the damaging ruby pulse. Changes in the reflected probe intensity were observed and a method was devised to synchronize and correlate the time evolution of the probe variations with the temporal shape of the damaging ruby pulse to within 0.5 nsec. Detailed measurement and analysis of the BSC-2 data reveals a decrease in the specular reflectivity and thus in the index of refraction of the irradiated surface site during the initial 0.5–2.5nsec of the damage process. The enhanced sensitivity provided by probing at the angle of total internal reflection allowed variations in the refractive index of as small as Δn=10−5 to be measured. This index change is shown to be the result of a laser-induced free-electron density which reaches a density of ∼1018–1019/cm3 just prior to catastrophic thermal or structural damage of the irradiated surface site. Several features of the ensuing surface damage processes are discussed.
Dependence of residual damage on temperature during Ar+ sputter cleaning of silicon
Authors: Bean J. C. , Becker G. E. , Petroff P. M. , Seidel T. E.
Published: February 2003

It has been found that the kind and amount of damage produced in silicon following Ar+ ion bombardment at 1.0 keV and the annealing properties of the damage depend strongly on the temperature at which the sputtering is done in the range 25–800 °C. Some of these differences in damage are not evident with surface-sensitive techniques such as LEED, RHEED, or AES, but have been revealed by transmission electron microscopy and by Rutherford ion backscattering. TEM examination of substrates annealed at 800 °C after being sputtered at temperatures in the range 25–800 °C shows an increase in the density and the size of crystal defects with increasing sputtering temperature. Rutherford ion backscattering shows an increase in silicon disorder and in retained argon with increasing sputtering temperature. These results are similar to observations reported for ion implantation at higher energies. Models for damage mechanisms are discussed briefly. It is concluded that for Ar+ ion sputter cleaning of silicon, the silicon should be kept at room temperature or below during sputtering to minimize residual surface damage after annealing.
Size considerations in the design of cells for photoacoustic spectroscopy
Authors: Aamodt L. C. , Murphy J. C. , Parker J. G.
Published: February 2003

The dependence of photoacoustic spectrometer sensitivity on the physical dimensions of the sample cell was investigated for sizes larger than and smaller than the gas thermal diffusion length. The results depend on the thermal properties of the gas and the sample in agreement with an extension of Parker’s theory of photoacoustic signal generation.
Nonlinear elastic interactions between acoustic bulk and surface waves
Authors: Rouvaen J. M. , Torguet R. , Bridoux E. , Bruneel C.
Published: February 2003

A theoretical study of the nonlinear interaction between acoustic bulk and surface waves is presented in this paper. Starting from the nonlinear material elastic equations, a method for computing the scattering efficiency into acoustic bulk and surface waves is given. The wave-vector conservation conditions for resonant interaction are then discussed. Possible applications to nonlinear scanning and signal processing are then studied.
Self-masking selective epitaxy by molecular-beam method
Authors: Nagata Seiichi , Tanaka Tsuneo
Published: February 2003

Using collimated Ga and As4 molecular beams from limited-source apertures, epitaxial GaAs layers were grown selectively by self-masking on preferentially etched GaAs surfaces with a lateral accuracy of 0.1 μm. From edge profile analysis, it is found that (1) the accuracy is limited by preferential growth of an obstruction layer, (2) the surface diffusion length of free Ga is dependent upon As4 arrival rate, and furthermore (3) the length is less than 200 Å in As-rich growth conditions, while in Ga-rich conditions the length is 1900 Å.
The electric strength of hexane vapor and liquid in the critical region
Authors: Sharbaugh A. H. , Watson P. K.
Published: February 2003

The breakdown strength of hexane vapor has been measured above its critical temperature over a wide range of densities (0.001–0.45 g/cm3). Voltage pulses of 10-μsec duration were used for the measurement. Above a density of 0.01 g/cm3 the strength of the vapor is appreciably less than the extrapolated low-pressure results. This departure from Paschen’s Law is believed to be due to field emission from the cathode. Extrapolation of the high-density vapor leads to a breakdown strength in excess of that measured in liquid. Measurements have also been made of breakdown strength under a range of conditions of temperature and pressure near the critical point in both liquid and vapor phases. The breakdown strengths of the liquid are somewhat lower than those of the vapor, but the values converge as one approaches the critical point, and it is suggested that the breakdown mechanisms in liquid and vapor are similar in the vicinity of the critical region.
A localized vibrational mode study of infrared absorption of CdTe : P
Authors: Dutt B. V. , Spitzer W. G.
Published: February 2003

Infrared localized vibrational modes of phosphorus-related point defects are observed in a series of CdTe ingots doped only with P or with P and X, where X is In, Ga, or Al. The dopants were all added during growth by the horizontal Bridgman method. The proposed defects, their point-group symmetries, and the local mode frequencies in cm−1 at 80 °K are as follows: PTe, Td, 322; a neutral P complex, C3v, 269, 308; PTe−InCd, C3v, 305, 331.5; PTe−GaCd, C3v, 301.5, 352.5, 357.5. CdTe : P, Al showed no PTe-AlCd pair bands, which is probably related to the large force constant increases observed for both CdTe : P and CdTe : Al.
Rare-earth dihydride compounds: Lattice thermal expansion and investigation of the thermal dissociation
Authors: Bonnet J. E. , Daou J. N.
Published: February 2003

The lattice parameters of seven rare-earth (La, Nd, Gd, Dy, Er, Tm, Lu) dihydrides are determined between room temperature and a temperature ranging from 500 to 800 °C. The parameter-vs-temperature curves, presenting a ’’knee’’ at temperatures which vary with the rare-earth compound, are fitted by a least-squares method in two separate regions. In the first region, the crystalline properties of dihydrides are compared to those of the parent rare earths. In the second region where a thermal dissociation occurs, we have calculated the formation energy Ef of a point defect. Ef increases with the rare-earth atomic number from 0.25 to 0.7 eV. A law of corresponding states between these rare-earth dihydride compounds is established. The participation of the rare-earth sublattice in the process of hydrogen diffusion and thermal dissociation is predicted.
Surface acoutic wave velocity dispersion induced by radiative absorption
Authors: Parks J. H. , Rockwell D. A.
Published: February 2003

An analysis of the dispersive propagation of surface acoustic waves through a time-dependent thermal gradient induced by radiative absorption is presented. The dispersive phase change of the acoustic wave is shown to depend on the details of the surface absorptive properties of the material. In particular, measurement of such induced phase changes can determine the parameters which characterize the surface depth dependence of the radiarrive absorption coefficient. This analysis is applied to two cases: (i) a strongly absorbing surface layer. The relative sensitivity to bulk and total surface absorption is discussed, as well as the radiative pulse conditions for which the absorption coefficient depth profile can be determined. This technique is applied to published results for 10.6-μm radiative absorption on KCl surfaces for which the total surface layer absorption and the bulk absorption coefficient are individually measured. Additional applicatons to related surface measurements are discussed.
Digital computer simulation of rf sputtering interferometer
Authors: Wang R. H. , Dick G. J. , Mercereau J. E.
Published: February 2003

A digital computer was used to predict the operational characteristics for two models of a superconducting interferometer inductively coupled to an rf tank circuit. The interferometer is modeled by a weak link shunted by a resistor and a superconducting inductor. For a Josephson model, the current iJ and the phase difference across the weak link φ are related by iJ=ic sinφ. We have also examined the consequences of the relationship iJ∝∇φ (1+cosφ) which would result from a modified Aslamazov-Larkin two-phase model, where the supercurrent depends on both the phase difference φ and the phase gradient ∇φ in the weak link. We find that the (1+cosφ) model with the proper boundary condition can reproduce essentially all aspects of the experimental result for interferometers with proximity effect bridges. In particular, the two-phase model is adequate in describing the temperature dependence of the rf response, whereas the Josephson model does not.
Production of uniform field gradients for magnetometers by means of current-carrying strips
Authors: Spal Richard D.
Published: February 2003

Current-carrying strips are a convenient means to produce a uniform field gradient for use in a Faraday magnetometer. An expression is derived for the magnetic field gradient, taking into account the images of the strips in the pole pieces. Tables are presented giving the magnitude and homogeneity of the gradient for various strip widths and locations. The performance in the laboratory of a set of strips is reported.
Optical alignment of impact faces for plate impact experiments
Authors: Kumar P. , Clifton R. J.
Published: February 2003

An optical technique, employing an autocollimator and a 90° precision prism, has been developed for aligning two separated reflective plane surfaces so that they are parallel to an accuracy of approximately 2×10−5 rad. The technique has been used in the alignment of target plates in plate impact experiments.
Reply to ’’Comments on ’Generalized criterion for feasibility of controlled fusion and its application to nonideal D-D systems’’’
Authors: Maglich Bogdan C. , Miller Robert A.
Published: February 2003

An article by Chen et al. criticizes the generalized criterion for controlled fusion. Chen et al. claim to have found errors in the physics in the generalized criterion. We show that these ’’errors’’ are only differences in philosophy about how to account for loss-suppression mechanisms. Many of the conclusions of the generalized criterion, called ’’incorrect’’ by Chen et al., have been published separately by independent workers.
Surface flicker noise in p-n junction diodes at a high injection level
Authors: Sharma Y. K.
Published: February 2003

A theoretical treatment for the flicker noise of a p-n junction at a high injection level has been given. It is shown that the spectral intensity is inversely proportional to the current.
Observation of ultrasonic surface waves on plane and cylindrical solids by optical methods
Authors: Faure Alain , Maze Gérard , Ripoche Jean
Published: February 2003

We present results of observation and velocity measurements of surface waves generated on plane and cylindrical metallic samples submitted to an ultrasonic beam oriented at a slightly greater angle than the second critical angle, which is called the Rayleigh angle. Two different techniques are applied in the experiments. One consists of the visualization of the surfaces of the constant phase of ultrasound in water. The second uses light diffraction by surface-wave corrugations. In this case, the insonified zone is immersed while the observation zone is in contact with the air. This technique allows the determination of the velocity, either directly by measurement of the distance between the diffraction orders or by using the properties of superposition between two echoes. Stainless steel is studied at an ultrasonic frequency near 5 MHz. On the plane surface a unique surface Rayleigh wave is detected. On the cylindrical surface a cylindrical-surface Rayleigh wave is detected in addition to another wave. In the two cases, the velocity of the Rayleigh waves agrees well with the theoretical results: 2875 m/s for a plane and 2900 m/s for a cylinder. The additional cylindrical wave, with a higher velocity (3550 m/s), is assumed to be a circumferential one, and it turns into a higher-velocity wave (4360 m/s) at the transition between a plane and a cylindrical boundary.
Effect of temperature on irradiation-induced dislocation loops in copper
Authors: Larson Bennett C. , Young F. W.
Published: February 2003

The effect of irradiation temperature on irradiation-induced dislocation loops in copper has been studied by x-ray diffuse scattering. Dislocation loop size distributions and total defect concentrations were obtained for irradiations in the temperature range 316–483 °K for neutron doses in the range (1–10) ×1018 n/cm2. The average loop sizes were found to increase with increasing irradiation temperature and increasing neutron dose. The number of point defects stored in the loop distributions tended to saturate at the higher doses and were found to decrease with increasing irradiation temperature. Ambient-temperature measurements made on 4 °K neutron- and electron-irradiated copper indicated the dislocation loops formed during the anneal to room temperature were smaller than those produced by ambient-temperature reactor irradiations.
Trigger temperature of the second-breakdown phenomenon
Authors: Yu S. Y. , Thomas G.
Published: February 2003

This paper presents a theoretical analysis of the second-breakdown phenomenon. The analysis makes the use of the coupled current-continuity, the Fourier heat-flow, and the Poisson equations. The geometry used in the analysis allows the directions of current and heat flow to be separated self-consistently. The trigger temperature is derived and a plot of its variation with respect to applied voltage is given. The approximate expressions for the steady-state voltage states is also given.
Recombination-pumped atomic nitrogen and carbon afterglow lasers
Authors: Cooper G. W. , Verdeyen J. T.
Published: February 2003

It is well established that lasing of atomic nitrogen and carbon can be obtained during the afterglow of an electrical discharge in gas mixtures of either neon or helium containing low partial pressures of N2 or CO. In addition the neon-nitrogen laser has recently been pumped directly by neclear radiation. Microwave quenching experiments have shown conclusively that the afterglow lasers are being pumped directly by the recombination of electron-ion pairs. This result differs from the mechanisms previously proposed for these systems. Measurements comparing the relative sensitivity to the electron temperature of the neon to atomic nitrogen and carbon afterglow light imply that the recombination process pumping these lasers is cllisional-radiative, allowing the recombining ions to be identified as N+ and C+. Since this process is highly compatible with nuclear-radiation-generated plasmas, it is not unreasonable to infer that this process is also the pumping mechanism in the nuclear-excited, neon-nitrogen laser.
Survival of cryogenic laser fusion fuel configurations in fluorescence energy
Authors: Musinski D. L. , Simms R. J. , Henderson T. M.
Published: February 2003

The most troublesome factor affecting the survival of a cryogenic fuel configuration in a laser fusion pellet irradiated by high-power laser beams is the fluorescence energy put out by the amplifier system. Prepulses can be blocked, but the incoherent radiation spontaneously emitted and amplified during lamp pump time is an inherent attribute of any optically pumped laser amplifier system and cannot be completely blocked; its effect on the fuel configuration needs to be examined. The effects of this amplified spontaneous emission (ASE) on cryogenic targets have been recorded at various levels using high-speed photomicrography. The results indicate a high probability of the fuel configuration surviving at the present levels of this ASE energy.
The excitation of anharmonic molecules for steady-state and pulsed radiation
Authors: Steverding B. , Dudel H. P. , Gibson F. P.
Published: February 2003

Excitation levels by multiple-photon absorption are calculated using a quantized model for a classical nonlinear oscillator. Substantial red shifting is necessary in order to reach high vibrational excitation. Increased damping has a linearizing effect and reduces red shifting as well as the excitation. Cross sections for the various excited states are calculated. The decay of the excited molecule to the ground state is discussed. In principle the model can be used to calculate photodissociation.
Effects of low-ionization gas additive along with uv photopreionization on CO2 TEA laser operation
Authors: Morikawa Eiichi
Published: February 2003

The present paper reports an experimental technique for enhancing a high-pressure discharge in a CO2 TEA laser for increasing its output power by using uv irradiation from a series of third needle-plane electrodes, an uv mirror, and an easily ionized gas additive. Laser output energy of 6 J and output peak power of 40 MW at an efficiency of 19% has been obtained in an initial demonstration. Experimentally, it was found that the best results on the laser output radiation were obtained with tri-n-propylamine at a partial pressure of about 0.35 Torr and with p-xylene at a partial pressure of about 0.7 Torr.
Design considerations for high-intensity solar cells
Authors: Dalal Vikram L. , Moore Arnold R.
Published: February 2003

The factors affecting the efficiency of a solar cell change when the solar cell is subjected to concentrated sunlight. In this paper, we examine the effects of high solar intensities on Si and GaAs solar cells. It is shown that the current-collection efficiency in Si solar cells increases at intermediate levels but may be reduced at very high solar intensities due to plasma recombination. Methods to avoid the degradation of efficiency are suggested. The open-circuit voltage increases with concentration, and the rate of increase is faster in Si than in GaAs. The fill factor also increases with concentration, again at a faster rate in Si than in GaAs. Consequently, the efficiency in a Si solar cell under concentration may increase faster than in a GaAs solar cell. The effect of increased temperature is also examined. It is shown that the increase in temperature degrades the efficiency of Si faster than in GaAs. Thermal analysis shows that it is possible to limit the temperature rise to a low value (25 °C) even under 1000 sun concentration by using simple designs of heat sinks. Consequently, there is no significant advantage of GaAs solar cells over Si solar cells for high-intensity operation, except when high temperatures are desired for a complementary thermal system.
A model relating electrical properties and impurity concentrations in semi-insulating GaAs
Authors: Lindquist P. F.
Published: February 2003

The 300 °K resistivity and Hall mobility of semi-insulating GaAs can be understood in terms of a model involving four impurity levels, including the deep acceptor Cr and the deep donor O. Neutral impurity scattering is shown to be an important mechanism in this material, and an empirical expression for this component of the mobility is derived. Comparison of mass-spectrographic and Hall-effect data using this model permits the estimation of the electrically active impurity concentrations. Several cases are discussed in which these estimates lead to predictions of surface conversion which agree well with experiment.
Monte Carlo studies of hot-electron energy distributions in thin insulating films. II. Energy-dependent mean free path and instability
Authors: Baidyaroy S. , Lampert M. A. , Zee B. , Martinelli Ramon U.
Published: February 2003

Monte Carlo calculations are used to study theoretically hot-electron transport through a thin insulating film subjected to a high uniform electric field F. A constant energy-independent mean free path λ leads to a stable steady-state energy distribution for the electrons, characterized by an average steady-state energy Eav,ss. Eav,ss depends on λ, F, and εph, the optical phonon energy associated with scattering of the hot electrons by the lattice. An energy-dependent mean free path λ (E), which increases with increasing electron energy, can lead to energetic runaway of either a relatively small number of electrons in the distribution (quasistability or a bimodal distribution) or the entire distribution (instability). A graphical method has been developed to gain insight into this problem. The method rests on an analysis of the intersections of two curves plotted in the E-λ plane, one curve being the plot of Eav,ss versus λ, where λ is the mean-free-path parameter taken to be constant (energy independent) for each calculation of Eav,ss, the other curve being the plot of the actual functional dependence of λ on E, λ (E). The method is illustrated by several prototypical examples.
Parametric amplification and oscillation at 36 GHz using a point-contact Josephson junction
Authors: Taur Y. , Richards P. L.
Published: February 2003

We have observed doubly degenerate parametric amplification and oscillation at 36 GHz from a single point-contact Josephson junction. The experimental results agree qualitatively with theoretical calculations based on the resistively shunted junction model. The estimated noise temperature of an amplifier with 11 dB net gain is consistent with zero, but has an upper limit of 50 K. Attempts to observe parametric amplification in the singly degenerate mode with a pump frequency of 72 GHz were not successful.
Implosion dynamics of a hemispherical target irradiated by an intense relativistic electron beam
Authors: Widner M. M. , Perry F. C. , Mix L. P. , Chang J. , Toepfer A. J.
Published: February 2003

An intense tightly pinched relativistic electron beam from the Hydra accelerator (250 kA, 800 kV, 80 nsec) was used to produce an ablation driven implosion of a dense hemispherical shell. A laser reflection measurement was used to measure the implosion time and the velocity of the jet of material produced following the implosion. X-ray pinhole photography and optical holography were used to study the uniformity of target loading and ablator motion. Target dynamics was modeled by a two-dimensional Eulerian hydrodynamic code. The results indicated 17–50% of the total beam energy was delivered to the target, where the total beam energies varied between 17 and 20 kj. The uniformity in target loading varied between 20 and 80% from pole to equator. Suggestions are given for improving beam accuracy and target loading uniformity.
VUV emission from high-intensity focused REB discharges into aluminum targets
Authors: Johnson D. J. , Nagel D. J. , Oliphant W. F.
Published: February 2003

The VUV emission from 6061-T6 aluminum targets, exposed to an intense focused electron beam, was examined to study the electron absorption mechanism for a 1-MeV electron beam with a current density of 1 MA/cm2. The VUV emission was observed with aluminum cathode x-ray diodes operated with and without 1/2-μm aluminum filters and a near-normal incidence grating spectrograph. The data obtained are consistent with classical electron deposition and indicate an anode surface temperature of a few eV with the peak temperature occurring at the time of impedance collapse.
The characteristics of a medium current relativistic electron-beam diode
Authors: Swain D. W. , Goldstein S. A. , Mix L. P. , Kelly J. G. , Hadley G. R.
Published: February 2003

In a previous paper we reported observation of ion flow in the Nereus diode. We report here more detailed observations of the diode, employing a Thomson parabola analyzer to measure ion species and energies, a four-pulse holographic interferometer to observe plasma blowoff from the electrodes, and an image-converter streak camera to record total optical radiation and time-resolved emission spectra. The large current on axis (the ’’pinch’’ current) of this diode appears to be caused by rapid local gap closure on axis. A model describing the behavior of this diode is discussed and compared with experimental data.
Firing characteristics of a triggered vacuum gap employing a dielectric coated with a semiconducting layer
Authors: Raju G. R. Govinda , Hackam R. , Benson F. A.
Published: February 2003

Some electrical properties of a triggered vacuum gap (TVG) incorporating five different dielectric materials coated with a semiconducting layer to produce a low surface resistance are studied. The dielectric materials used are high-alumina ceramic, steatite ceramic, barium titanate, silicon carbide, and boron nitride. It has been found that the probability of firing and the time delay to firing of such a TVG are practically independent of the substrate material. The time delay to firing generally decreases with an increase of both the trigger energy and the trigger voltage until saturation is reached. The minimum trigger voltage for successful firing is about 300 V for all substrates except for barium titanate which is higher at 700 V. The higher trigger voltage in the case of barium titanate is attributed to the difficulty of coating this material evenly with the particular semiconducting layer used of colloidal solution of aquadag carbon. A new method is described to rejuvenate a TVG which ceased to operate by applying a ’’keep-alive’’ direct current superimposed on the trigger pulse voltage. A mechanism responsible for this phenomenon is also discussed.
Mobile ions in SiO2: Potassium
Authors: Derbenwick G. F.
Published: February 2003

Mobile potassium ions have been conclusively identified in SiO2 using the high-temperature triangular voltage sweep technique, the bias temperature C-V technique, and ion microprobe studies. The source of the potassium has been found to be the tungsten filaments used for the aluminum gate metallization. Cautions regarding use of the high-temperature triangular voltage sweep technique for measuring mobile ions in MOS structures are discussed.
Mechanics of polymer craze
Authors: Wilczynski A. P. , Liu C. H. , Hsiao C. C.
Published: February 2003

A new model consisting of symmetrical membranes with an enclosed elastic foundation is considered for studying the nature of a polymer craze in a tensile stress field. Both local displacement and stress distribution have been calculated for a linear craze under simple tension.
Ellipsometric studies of environment-sensitive polish layers of glass
Authors: Malin M. , Vedam K.
Published: February 2003

The polishing behavior of vitreous silica and Pyrex is found to be strongly dependent on the ambient (different alcohols) used for polishing. This is manifested by the variations in the thickness and refractive index of the densified layer on the polished surface, which have been detected ellipsometrically. Our measurements on vitreous silica and Pyrex samples have indicated a relation between the number of carbon atoms in the alcohol molecules of the polishing media and the densification of the surface layers. The increased densification has been related to a harder surface which would result in less plastic flow and greater tendency toward fracture during polishing. We found a peak in the densification and hence in the surface hardness of the glasses in hexyl or heptyl alcohol agreeing with studies done on drilling rates and pendulum hardness in these alcohols by Westwood.
Dielectric properties of shock-wave-compressed PZT 95/5
Authors: Lysne P. C.
Published: February 2003

Projectile impact techniques were used to introduce shocks into rectangular bars of the ferroelectric ceramic PZT 95/5. In these experiments the remanent polarization vector was perpendicular to the shock propagation vector. For shock amplitudes greater than 1.6 GPa the specimens were completely depoled, and the permittivity was independent of both the stress and electric fields and it had a value of 9 nF/m. These data indicate that a phase transformation to a nonferroelectric state had occurred. However, the characteristics of the high-stress state are uncertain.
Angular scattering in charge-exchanging beams: Implications for neutral beam formation via negative ions
Authors: Hooper E. B. , Willmann P. A.
Published: February 2003

Coupled Boltzmann equations for particles with two charge states have been solved to describe the angular evolution of a beam which is charge exchanging through collisions with a background vapor. The solutions are applied to the processes D0+Cs→D−+Cs+ and D−+Cs→D0+Cs + e using measured differential cross sections where available. By accelerating and stripping a D− beam, an intense high-energy beam can be formed for thermonuclear fusion experiments and reactors. It is concluded that angular scattering does not place a significant limit on the beam quality, although the cesium line density must be the minimum to reach a charge-state equilibrium in the beam.
Switching measurements on semiconductor-barrier Josephson junctions, isolated and in memory loops
Authors: Lum W. Y. , Van Duzer T.
Published: February 2003

We report here the use of the semiconductor-barrier Josephson junction as the switching component in high-speed digital circuits. We have measured the switching time of a single Pb-Te-Pb junction and the current-transfer time of a memory cell using such a device as the logic switch. The fastest switching time of a rather large junction (0.175×0.175 mm2) is 67 ps and the current-transfer time of a memory cell with loop inductance of 1.05 ×10−10 H is 350 ps. These measured values are comparable with those obtained for oxide tunnel junctions similar dimensions.
The formation of ions in noble-gas/halogen mixtures
Authors: Huber Bernd A. , Miller Thomas M.
Published: February 2003

We have studied positive and negative ions in Xe-Cl2, Xe-Br2, and Ar-Br2 mixtures in a drift-tube mass spectrometer. By varying the partial pressure of the halogen gas, we have been able to identify several ion-molecule reaction channels, and have obtained estimates of reaction rate coefficients in the Xe-Br2 case. In no case did we observe stable noble-gas/halogen complexes to be formed.
New etch pits on GaAs revealed by etching after anodic oxidization
Authors: Matsushita K. , Hariu T. , Adachi H. , Shibata Y.
Published: February 2003

New etch pits, characteristic of crystal orientation, have been observed after etching anodically oxidized GaAs wafers. The etch pits do not always correspond to dislocations originally contained in the wafer and are most likely to indicate structural defects in the transition layer between oxide and GaAs, introduced by anodic oxidization.
Experimental observation of nonreciprocal attenuation of surface waves in yttrium iron garnet
Authors: Daniel Michael R.
Published: February 2003

Measurements are presented of the nonreciprocal attenuation of Rayleigh surface waves propagating parallel with the magnetic field along the 〈111〉 direction in yttrium iron garnet. These measurements are compared with the calculation and confirm that the surface wave attenuation in this material results primarily from the radiation of spin waves into the bulk. The discrepancies which exist in comparing the observed and calculated attenuation levels are thought to arise in Emtage’s calculations when taken only to the first order in the elastic anisotropy.
Time-delayed laser oscillation of a DH diode having an unpumped region
Authors: Iwamoto Kuniakira , Hino Isao
Published: February 2003

An AlxGa1−xAs-AlyGa1−yAs double-heterostructure (DH) superluminescent diode (SLD) having an unpumped absorbing region has shown laser oscillation with a long time delay, amounting to as much as microseconds at a low pumping level. It has been confirmed that this lasing is made possible by two types of band-gap shrinkage, one resulting from the many-body interaction of excited carriers and the other from the temperature rise in the excited region.
Monte Carlo simulation of depth and lateral profiles of boron atoms implanted in polycrystalline silicon
Authors: Shimizu R. , Kang S. T. , Koshikawa T. , Ogata H. , Kanayama K. , Ogata Y. , Akasaka Y. , Horie K.
Published: February 2003

A Monte Carlo calculation technique has been applied to ion implantation. The theory was compared with both the depth distribution of 150-keV boron implanted in silicon, measured with a secondary-ion mass spectrometer (Hitachi IMA-2) and an Auger electron spectrometer (PHI model 5000), and the lateral spread of the implanted boron, measured by Akasaka et al. The results indicate that the theory describes the three-dimensional distribution of boron implanted in polycrystalline silicon at 150 keV with considerable success.
Refractive index of BaTiO3 and SrTiO3 films
Authors: Wöhlecke M. , Marrello V. , Onton A.
Published: February 2003

Experimental data on the wavelength dependence of the refractive index in the wavelength range 0.3–1.0 μm is presented for thin films of BaTiO3 and SrTiO3. The films of thickness 1–4 μm were prepared by sputter deposition at substrate temperatures of 300 to 600 K, resulting in amorphous films at the lower temperatures and ’’microcrystalline’’ films at the higher. Both thin-film phases have a lower index at a given wavelength than the corresponding crystalline value (e.g., at λ=5000 Å, n=2.00, 2.07, and 2.51 for amorphous, microcrystalline, and crystalline BaTiO3, respectively). The dispersion of the refractive index in the thin films follows a single-oscillator model with a higher oscillator energy and smaller oscillator strength than in the crystalline phase.
Construction of energy-band diagrams for amorphous/crystalline heterojunctions
Authors: Chung C. H. , Dunn B.
Published: February 2003

Energy-band diagrams for amorphous/crystalline heterojunctions are constructed by using a method originally developed for crystalline heterojunctions and modifying it accordingly for an amorphous component. The only assumptions made for the amorphous semiconductor involve the determination of the energy gap and the Fermi-level position. The validity of the procedure is shown by the consistent results obtained for the heterojunction energy-band parameters when a given glass is deposited on both n- and p-type silicon. General agreement with previously proposed models is observed.
Theory of a spherical electrostatic probe in a continuum plasma: Analytical models
Authors: Brailsford A. D.
Published: February 2003

A simple physical model of the charge distribution surrounding a biased spherical probe in a quiescent plasma, suggested by the theory of Su and Lam, is used to rederive the probe current-voltage characteristic. The result is compared with that of a slightly different version due to Kiel and with the exact numerical results of Baum and Chapkis. It is shown that if the ratio of the probe radius to the Debye length of the plasma is greater than or of the order of unity, the model calculation is in excellent agreement with the exact results when the dimensionless probe voltage φ*p,=‖eφp/kT‖ in standard notation, is greater than 10, for both thick and thin sheaths. The comparison also provides an assessment of the importance of various additional validity criteria encountered in analytical treatments of the problem.
rf current dependence of the 8.9-GHz impedance of tantalum point-contact Josephson junctions
Authors: Claridge D. E.
Published: February 2003

The complex rf impedance of tantalum point-contact Josephson junctions at 8.9 GHz has been measured as a function of the dc bias current for several values of rf current amplitude. The experimental results agree qualitatively with the predictions of the resistively-shunted-junction model, but discrepancies between the experimental results and the theory suggest that this model does not adequately predict all of the impedance properties of these junctions.
Shock stand-off distance for a sphere
Authors: Shankara T. S. , Sreekanth A. K.
Published: February 2003

The formula &/D=1−{1−[4/(γ+1)2][1/M2+(1/2)(γ−1)]}1/2 is proposed for the stand-off distance of the shock in supersonic or hypersonic flows past a sphere, and is derived from an analogy with the Lorentz transformation.
Comments on ’’electromagnetic interaction with bounded slab media moving normal to the interface’’
Authors: Mukherjee P. K.
Published: February 2003

It is argued that in dealing with electromagnetic interaction with a bounded slab moving perpendicular to the interface with relativistic speed, a correct treatment must take account of the Lorentz contraction of the slab thickness. basis functions of the reducible representation of the system are the following seven Slater functions: the
Laser operation by dissociation of metal complexes. II. New transitions in Cd, Fe, Ni, Se, Sn, Te, V, and Zn
Authors: Chou Mau Song , Cool Terrill A.
Published: February 2003

New laser transitions at 15 wavelengths from 1.454 to 14.54 μ have been observed from eight metal atoms. A double-discharge technique has been employed for the production and excitation of metal atoms by dissociation of metal halides, alkyls, and carbonyls. The possibility of laser action on the Tl(I) 6s2 8p 2P01/2,3/2→6s2 7s 2S1/2 transitions at 6714 and 6550 A° is discussed.
The spectral reflectivity of ion-bombarded surfaces
Authors: Primak William
Published: February 2003

A variety of effects are found to contribute to changes in spectral reflectivity found after bombardment with ions of gaseous species; they cannot be assigned solely to the formation of a gas layer. There may be a change in refractive index and thickness associated with a phase change (e.g., quartz); a decrease in refractive index and an increase of thickness by the introduction of microporosity (e.g., SiC, B4C, Al2O3); an increase in refractive index from the introduction of centers, etc. (e.g., SiC, MgO); an increase of refractive index and a decrease in thickness by compaction (e.g., vitreous silica); or a decrease in refractive index caused by changes in composition (e.g., alkali loss in glasses). Often the chromatic fringes are composites of different fringe systems arising in different parts of the illuminated area; and within any part of an area, there may be more than one cause. These effects are observed in the early stages of bombardment manifested by changes in spacing, phase, amplitude, and level of the chromatic fringes. When a gas layer forms (blistering) the large amplitude of the chromatic fringes associated with it usually dominates the spectral reflectivity at large dose, but this is not always the case (e.g., C1 glass).
C-V and G-V characteristics of ion-implanted MOS structures depending upon the geometrical structure of the implanted region
Authors: Zohta Yasuhito
Published: February 2003

It is found that the capacitance-voltage (C-V) and conductance-voltage (G-V) characteristics of MOS capacitors, into which ions of the opposite conductivity type are implanted, depend strongly upon the geometrical structure of the ion-implanted region. This phenomenon can be analyzed in terms of lateral current flow which connects an inversion layer formed in the ion-implanted region to a surrounding nonimplanted substrate. On the basis of this model, the C-V and G-V characteristics are calculated using a simple equivalent circuit, and general relationships inherent in this model are obtained. MOS capacitors with an ion-implanted layer of different geometries have been prepared to measure their C-V and G-V characteristics. Comparison of experimental measurements with theory substantiates the lateral current flow model.
Gold Si-SiO2 interface traps in MNOS with chemically oxidized 〈100〉 substrate
Authors: Nassibian A. G. , Calligaro R. B.
Published: February 2003

Gold diffusion at 900 °C has been carried out on MNOS samples with chemically grown oxides. Gold diffusion times were 40, 20, and 10 min. The two longer treatments have been found to produce two closely spaced discrete acceptor levels at 0.262 and 0.235 eV above the intrinsic energy level at the Si-SiO2 interface. The charge associated with these traps was of the order of 12×1012 e/cm2 for the upper trap level and 1.5×1012 e/cm2 for the lower trap level. It was found that these traps are detrimental to MNOS device properties.
The effects of heat treatment on dislocation-free oxygen-containing silicon crystals
Authors: Capper P. , Jones A. W. , Wallhouse E. J. , Wilkes J. G.
Published: February 2003

A dislocation-free silicon crystal grown by the Czochralski technique has been heat treated over a wide temperature-time range to explore the basic silicon-oxygen relationship. The processes occurring were followed by carrier-concentration changes and infrared measurements over the range 1.2–25 μ. The infrared absorption changes occurring below 900 °C were found to follow an Arrhenius plot with an activation energy of 0.5±0.03 eV. This value is compared with the results found for other processes occurring on the surface or in bulk silicon and is seen to be low. The changes occurring above 900 °C are in agreement with the generally accepted theory that all the oxygen initially present in the crystal returns to its bound interstitial position. The carrier-concentration changes measured were at variance with currently accepted theories in several respects, particularly at 650 °C, an important temperature since all silicon producers use it to stabilize resistivity for measurement control prior to the thermal cycling experienced during device manufacture. Several experiments are described where slices were thermally cycled to study some of the ’’equilibrium’’ carrier-concentration situations believed to hold. Finally, a general discussion is given of the overall situation concerning the behavior of the various silicon-oxygen complexes believed to exist at the various temperatures. Some speculation is presented as to the interactions of the various Si-O complexes, but it is found that all the results cannot be fully explained on the basis of purely silicon-oxygen interactions and that other effects, particularly those due to carbon, must be taken into consideration.
Cathodoluminescence studies of anomalous ion implantation defect introduction in CdTe
Authors: Norris C. B. , Barnes C. E. , Zanio K. R.
Published: February 2003

Shallow 100-keV Xe+ ion implantations in CdTe are shown to introduce at least two species of 300 K-stable defect complexes to depths of at least several thousand angstroms beyond the calculated projected ion range. The predominant defect species, which is nonradiative in the range 1–1.6 eV, produces severe quenching of the native 1.4-eV cathodoluminescence excited from micron depths. Measurements of the injection level dependence of the quenched 1.4-eV luminescence show that the quenching occurs primarily through the introduction of additional recombination centers rather than through the annihilation of native luminescence centers. Another defect species gives rise to an implantation-induced band near 1.2 eV. The 1.2-eV defects are more localized than the quenching defects and appear to be concentrated primarily at depths of several thousand angstroms beyond the projected ion range. Our experiments, which were performed on Te-rich donor-compensated CdTe, show that the anomalous defect introduction is sensitive to whether the donor doping is present on the Cd sublattice or on the Te sublattice. In comparison to Cl-doped material, In-doped material shows less quenching and a stronger 1.2-eV band. We also find that the production of 300 K-stable quenching centers is enhanced by implanting at 80 rather than 300 K. We conclude that all our results implicate primarily Te vacancies in the anomalous deep introduction of both the quenching centers and the 1.2-eV centers.
Differential relaxation times and diffusivities of hot carriers in isotropic semiconductors
Authors: Nougier J. P. , Rolland M.
Published: February 2003

The differential relaxation time τ (k,F) defined in a previous paper for isotropic semiconductors in the hot-carrier range is shown to depend on the orientation with respect to the field force F. τ (k,F) is expressed using the collision operator and the distribution function. In the Ohmic range τ (k,F=0) is found to be equal to the usual relaxation time τ (k) related to transition probabilities per unit time. Longitudinal τN(k,E) and transverse τn(k,E) differential relaxation times are numerically computed for p-type germanium and are found to be actually different although of the same order of magnitude, namely 10−12–10−13 sec. It is proved that the distribution function for hot carriers may be a displaced Maxwellian only if τ (k) is k independent, which does not hold for most of the situations of physical interest. It is shown that the differential relaxation times involved in longitudinal D∥(E) and transverse D⊥(E) diffusion coefficients are τ∥(k,E) and τ⊥(k,E). D∥(E) and D⊥(E) are numerically computed for p-type germanium and are found to be in excellent agreement with experimental results. Longitudinal and transverse noise temperatures are identical to the electronic temperature for displaced Maxwellian distribution functions.
Thermally stimulated currents of corona-charged abietic acid glass
Authors: Hoshino Yasushi , Tokunaga Yukio
Published: February 2003

Two clearly separated peaks are found in TSC (thermally stimulated current) of corona-charged abietic acid glass. A TSC theory is derived on the basis of the Debye equation and is applied to interpreting this TSC curve. A method of obtaining electrical properties by measuring TSC curves of the samples with various thicknesses is developed and is applied to abietic acid glass. Electrical properties of abietic acid glass are obtained as follows: the dielectric constant is 1.8×10−11 F/m; the electric orientational susceptibility χd is χdε0=1.1×10−11 F/m; the dipole relaxation time is 2.6×10−32 exp(Eτ/kT) sec, Eτ=2.2 eV (45–60 °C); the conductivity is 2.8×1025 exp(−Eγ/kT) (Ω m)−1, Eγ=2.7 eV (75–90 °C). The measured susceptibility agrees approximately with the value estimated by the Langevin-Debye equation.
Electromagnetic scattering by an array of conducting cylinders by finite-difference coupling technique
Authors: Kalhor H. A.
Published: February 2003

A new numerical technique which we call finite-difference coupling is presented for analyzing scattering by an array of conducting cylinders of arbitrary elemental cross section. The method yields the reflected and the transmitted far-field modal amplitudes directly and eliminates the need to evaluate the surface fields initially. Computed numerical results for arrays of thin rectangular strips are compared with results based on other methods of solution. This comparison indicates the capability and the accuracy of the proposed technique. Further results are presented which reveal interesting physical phenomena. The success of the proposed technique makes the analysis of other problems of electromagnetics and a large class of the problems of physics possible. The method should, therefore, be of considerable interest to engineers and applied physicists.