bluuebunny/crossref_metadata_2025 huggingface dataset:
A generalized thermal model for laser damage in infrared detectors
Authors: Bartoli F. , Esterowitz L. , Allen R. , Kruer M.
Published: February 2003

Four previously published models for laser damage in infrared detectors, based on closed-form solutions to the heat diffusion equation, are reviewed and their limitations discussed. A generalized two-dimensional numerical model based on a finite element technique is presented. This model can be used to calculate damage thresholds whenever the closed-form solutions are not appropriate, and is sufficiently general that it can treat most cases expected to be of interest in laser detector damage. The numerical model is used to calculate thresholds for HgCdTe photovoltaic detectors. Experimentally measured laser damage thresholds are reported for Hg0.8Cd0.2Te crystals whose size and thermal configurations are similar to those of photovoltaic detectors. These thresholds are found to be in good agreement with theoretical values.
Light scattering from nematic liquid crystals during transient time
Authors: Mada H. , Kobayashi S.
Published: February 2003

Measurements of the scattering of He-Ne laser light from nematic liquid crystals during transient time induced by an electric field have been made both on a simple homogeneously aligned cell and a 90° twisted cell. The nematic liquid crystal used in this experiment is a mixture of pentyl-cyano-biphenyl and hexyloxy-cyano-biphenyl of 4 : 1 by weight. The response waveforms of the scattered light intensity are dependent on the scattering angles and on the polarization of both the incident and the outgoing light. Moreover, the scattering distribution pattern depends strongly on the polarization of the light. These results can be partially explained by orientation fluctuations and relaxation of directors.
Spectra and angular distributions of electrons emitted from laser-produced plasmas
Authors: Giovanielli D. V. , Kephart J. F. , Williams A. H.
Published: February 2003

The spectra and angular distributions of high-energy electrons emitted from laser-produced plasmas have been measured. The plasmas were produced using short pulses from both CO2 and Nd : glass lasers to irradiate polyethylene slabs. For a CO2 laser intensity of approximately 3×1014 W/cm2 we find at least an order of magnitude greater energy conversion to high-energy electrons than with a Nd : glass laser intensity of approximately 5×1015 W/cm2. The angular distribution of electron emission is strongly peaked along the target normal (i.e., density gradient) and fine angular structure is observed.
Investigation of reactively sputtered silicon nitride films by complementary use of backscattering and nuclear-reaction microanalysis results
Authors: Rigo Serge , Amsel Georges , Croset Michel
Published: February 2003

The composition and properties of silicon nitride layers deposited by dc reactive sputtering in a mixture of argon and nitrogen slightly contaminated by oxygen traces were studied. Both MeV 4He backscattering and direct observation of nuclear reactions on nitrogen and oxygen were used to analyze the deposits. The films appear uniform with depth. Their stoichiometry and the incorporations of oxygen and argon vary with the partial pressure PN2 of nitrogen. For small values of PN2 there is a large amount of argon (Ar/Si=11%), while the oxygen amounts are low (O/Si<2%); as PN2 increases, an abrupt decrease of argon incorporation (down to Ar/Si 5 2%) is associated with an abrupt increase of oxygen incorporation (up to O/Si=15%). The N/Si ratio increases practically linearly with PN2 up to a saturation value of 1.5 corresponding to an excess of nitrogen with respect to stoichiometric Si3N4. Argon incorporation does not seem to have a large effect on properties of the films such as etching rate, resistivity, and thermal stability which appear, on the other hand, strongly dependent on the N/Si and O/Si values. The mechanisms of dc reactive sputtering are discussed in light of the results.
Principles and applications of elastic scattering with high-energy protons and heavy ions for quantitative microanalysis of metal surfaces, thin layers, and sandwich structures
Authors: Müller P. , Ischenko G.
Published: February 2003

The elastic non-Coulomb and Coulomb scattering of high-energy ions is proposed in useful combination of protons with 4–6 MeV and heavy ions (16O, 12,13C) with 15–35 MeV as effective quantitative and nondestructive spectroscopy of metal surfaces. This method provides analyzing depths of 1–50 μ, high mass or depth resolutions of 100–1000 Å, and selective high sensitivity for hydrogen and light elements up to Si. Successful application is demonstrated by examples measuring superconductors and metals of group V and binary A-15 compounds. The materials of interest for superconducting cavities, tunneling elements, and high field superconductivity like Nb3Sn have been investigated concerning the problems of oxide layers, composition and contamination, thermal treatment, and interfaces.
Pressure transition of AlP to a conductive phase
Authors: Wanagel John , Arnold Volker , Ruoff Arthur L.
Published: February 2003

Van Vechten, using a semi-empirical theoretical approach, has computed the equilibrium pressures at which various III-V compounds as well as C, Si, Ge, Sn, and SiC transform to the metallic β-tin phase. A characteristic of each of the groups BX, AlX, GaX, and InX, where X is a specific metalloid (N, P, As, Sb), is that the theoretical transformation pressure decreases as the atomic number of the metal atom B, Al, Ga, and In increases. The calculated values for the sequence BP, AlP, GaP, and InP are 401, 269, 216, and 141 kbar, respectively. Currently published values are available for GaP at 220 and 240 kbar and for InP at 105–115 kbar. In the present experiment, in which a direct simultaneous electric resistance comparison method is used, it is shown that AlP becomes conductive at a pressure equal to or less than ZnS which has been shown to transform at 150 kbar. Note should be made of the fact that the pressure at which we find AlP to be conductive is clearly considerably less (rather than more) than the pressure at which GaP becomes conductive. Direct simultaneous comparison with GaP in our cell also shows this to be the case. The possibility is suggested that the conductive phase of AlP seen here may not have the β-tin structure for which Van Vechten’s calculations apply, but instead may have the sodium chloride structure for which his calculations do not apply.
Bonding direction and surface-structure orientation on GaAs (001)
Authors: Cho A. Y.
Published: February 2003

An experimental study to determine the orientation of surface structures with respect to atomic-bond direction is presented. The As-stabilized (2×4) and C(2×8), and Ga-stabilized (4×2) and C(8×2) surface structures all have their twofold direction parallel to the plane containing the dangling surface bonds and perpendicular to that of the back bonds.
Electron energy distributions in e-beam generated Xe and Ar plasmas
Authors: Elliott C. J. , Greene A. E.
Published: February 2003

Calculations have been performed to determine the time evolution of electron energy distributions in e-beam generated Xe and Ar plasmas. In these calculations, we have included electron-neutral elastic and inelastic collisions, electron-electron collisions, and electron-ion dissociative recombination. Our results indicate that in equilibrium the distributions can be reasonably approximated by a Maxwellian below the thresholds for inelastic electron-neutral processes. However, above these thresholds, the inelastic processes dominate so that the high-energy tails of the distributions are largely missing. As a result, a model which takes the distribution to be Maxwellian everywhere somewhat underestimates the average energy of the electrons or overestimates the ionization and direct-impact excitation rates. At very early times and after the removal of the e-beam, there can be significant departures from a Maxwellian distribution. Following removal of the e-beam, the electrons equilibrate with the gas; however, this equilibration occurs on a time scale that is long compared to many other processes in noble-gas eximer laser systems.
Elastic and contractile properties of muscle
Authors: Klip Willem
Published: February 2003

The introduction of a special class of materials, called ’’contractile’’ into nonlinear continuum mechanics to represent muscular tissue is suggested and the general constitutive equation is given. For application to different muscles, transversely isotropic contractile material is considered, and for a cylinder (model for papillary muscle) and for a spherical shell (model for the left ventricle of the heart), more explicit expressions for the stress–contraction-strain equations are derived. For the left ventricle an energy density function W is heuristically constructed. Its four constants C, b, β, and Ra can be determined from measurements and are potentially of prognostic and diagnostic value. Energies and pressures calculated with this function for hearts in different conditions of contraction and passive deformation differ, in general, less than 10% from the measured values. An example for a human heart is given. By means of W an exponential function with constants that may come closer to material constants can be constructed.
Thermal conductivity of mica from 1.5 to 4.2 K
Authors: Falco Charles M.
Published: February 2003

The thermal conductivity of mica along the direction parallel to the cleavage planes has been measured in the temperature range 1.5 to 4.2 K.
Photo-Hall effect of CdS : Li single crystals
Authors: Yoshizawa Michio
Published: February 2003

The photo-Hall effect in lithium-doped CdS single crystals has been studied. Samples were prepared by a sublimation recrystallization method. The carrier concentration n was proportional to the excitation intensity, and the Hall mobility obtained was a constant value of about 200 cm2/V sec, at room temperature over the whole excitation region of 100–105 lx. The temperature dependence of the photo-Hall effect was also measured. The results showed unmeasureably low values of the Hall mobility in the temperature region 350–400 K. However, with increasing temperature the Hall mobility and carrier concentration increase again, but the sign of the Hall effect indicates electrons. The p-type CdS has not been obtained, even with an addition of 0.01 wt% of lithium impurity.
Magnetophotoconductivity of semi-insulating GaAs a function of light intensity
Authors: Nomicos C. D. , Euthymiou P. C. , Papaioannou G. I.
Published: February 2003

The effect of the magnetophotoconductivity of semi-insulating GaAs has been investigated as a function of light intensity at room temperature. If the magnetic field deflects the photocarriers towards the volume of the specimen, a decrease in the pure magnetophotoconductivity is obtained when the illumination decreases, reaching the zero value and then changing signs with a further decrease in the illumination. The same thing occurs, but with the opposite sign for the pure magnetophotoconductivity, when the magnetic field deflects the photocarriers towards the surface of the specimen. These give information about the behavior of the effective carrier lifetimes for the illuminated and nonilluminated layer of the specimen.
Diffusion profiles in ion-exchanged waveguides
Authors: Wood Van E.
Published: February 2003

Recent observations of quadratic dependence of refractive-index change with depth in waveguides formed on the surface of soda-lime glass by ion exchange with molten silver nitrate are shown to be reasonably consistent with expectations based on the theory of ion-exchange diffusion, assuming a fixed surface silver concentration.
Hall effect in rare-earth–transition-metal amorphous alloy films
Authors: Mimura Y. , Imamura N. , Kushiro Y.
Published: February 2003

The Hall effect in amorphous RE-TM (RE=Gd, Tb, Dy; TM=Fe, Ni) films with a perpendicular magnetization easy axis was measured. It was found that amorphous RE-Fe films exhibited a remarkable extraordinary Hall effect as observed previously for Gd-Co sputtered films, and that the observed Hall effect behavior depended much less on the RE element. It was also found that the Hall voltage in Gd-Ni films was two orders of magnitude smaller than that in RE-Fe films. These observations suggest that the TM plays a dominant role in the anomalous Hall voltage in RE-TM alloy systems.
Rate-equation dynamics of passively mode-locked quasicontinuous lasers: Perturbation theory of a ring laser
Authors: New G. H. C. , Rea D. H.
Published: February 2003

The initial build-up of mode locking in a passively mode-locked quasicontinuous laser is studied theoretically. A ring cavity which contains a composite medium exhibiting saturable amplification, saturable absorption, and linear losses is analyzed in the rate-equation approximation by means of a perturbation technique. Conditions for mode locking are derived and compared with the results obtained from similar models employed by other authors. Computer solutions are presented which are in good agreement both with the theoretical analysis and with experimental findings. The applicability of the theory to lasers having the conventional two-mirror configuration is briefly considered.
Excitation of electromagnetic waves from a rotating annular relativistic e-beam
Authors: Sprangle P.
Published: February 2003

Propagation of a thin rotating relativistic electron beam through a circular waveguide is shown to excite both the transverse-electric and transverse-magnetic modes of the guide. The beam is guided by and rotates symmetrically about a constant uniform external magnetic field. Both the synchronous and cyclotron modes associated with the beam can interact with either waveguide mode to excite electromagnetic radiation. The dispersion relations for the four coupling processes are derived and analyzed. Finally, application of this mechanism to the generation of intense microwave radiation is discussed in the light of recent experiments.
Mobility changes produced by electron irradiation of n-type Hg1−xCdxTe
Authors: Green Barry A. , Leadon Roland E. , Mallon Charles E.
Published: February 2003

Irradiation of n-type bulk Hg1−xCdxTe (x?0.2) with 5-MeV electrons at low temperatures produces an increase in the carrier density and variation in the carrier mobility. Some of the samplkes that were irradiated showed an initial increase in mobility with fluence, followed by a decrease, whereas others showed a montonically decreasing mobility. Isochronal annealing of all of the samples caused the mobility–vs–carrier-density curves to roughly retrace themselves as the carrier density decreased with annealing. However, for a given carrier density, the mobility on the annealing leg of the curves was consistently larger than the mobility on the irradiation leg. In this paper, these trends are explained by a combination of degeneracy, nonparabolic bands, and different degrees of initial compensation in the samples. Analysis of the data permits a qualitative determination of the initial compensation, the relative introduction rates for donor and acceptor states by the radiation, and their relative annealing rates. The mobility analysis is also shown to be consistent with the lifetime behavior of the samples.
Theoretical optimization and parametric study of n-on-p AlxGa1−xAs-GaAs graded band-gap solar cell
Authors: Hutchby James A. , Fudurich Richard L.
Published: February 2003

A comprehensive theoretical model of the graded band-gap AlxGa1−xAs-GaAs solar cell is used to optimize the n-on-p cell. The model includes power losses due to surface, bulk, and junction minority-carrier recombination, series resistance, and photon reflection from an SiO antireflection coating of optimum thickness. The optimized cell has a junction depth/graded band-gap layer thickness of 1.0 μm, respective donor and acceptor concentrations of 4×1017 and 2×1017 cm−3, and a surface AlAs mole fraction of x=0.35. The optimized graded band-gap cell has an air-mass-zero efficiency of 17.7% (not corrected for a 13% front surface contact area) and is shown to be less sensitive than a similar n-on-p GaAs cell to material degradation in the form of decreased minority-carrier diffusion lengths and increased surface-recombination velocity.
Distribution of dopant in SiO2-Si
Authors: Av-Ron M. , Shatzkes M. , Burkhardt P. J. , Cadoff I.
Published: February 2003

The distribution of dopant in SiO2-Si during dry thermal oxidation and postoxidation anneal is studied. Analytical expressions for the distribution functions are derived, on the assumptions that the oxide film grows in accordance with the t1/2 law and that before oxidation the dopant is uniformly distributed in the silicon. Cases in which tn≠t1/2 are discussed, with particular attention to the effect of n≳1/2 on the distribution of the dopant in the oxide. Calculations are provided for boron, describing its distribution in the oxide and in the silicon as a function of postoxidation anneal. Some experimental results concerning the distribution of boron in the silicon are provided for various oxide thicknesses, oxidation temperatures, and anneal times. These results were obtained from spreading-resistance measurements.
PbTe and Pb0.8Sn0.2Te epitaxial films on cleaved BaF2 substrates prepared by a modified hot-wall technique
Authors: Kasai I. , Bassett D. W. , Hornung J.
Published: February 2003

PbTe and Pb0.8Sn0.2Te epitaxial films have been grown on cleaved BaF2 substrates by a modified hot-wall technique. Relatively fast growth rates of 3–5 μm/h have been used to prepare high-quality epitaxial films between 5 and 13 μm in thickness. Both p- and n-type films have been grown by temperature control of a separate Te reservoir included in the apparatus. Carrier concentrations and mobilities in the orders of 2×1016–7×1017/cm3 and 1–3.3×104 cm2/V sec, respectively, have been measured in the as-grown films at 77 K. Pb0.8Sn0.2Te homojunction and PbTe-Pb0.8Sn0.2Te heterojunction layers have been prepared. Diode elements engraved in the layers by mesa etching have shown R0A products between 19 and 38 Ω cm2 for heterojunction structures at 77 K.
Electrical properties of platinum in silicon as determined by deep-level transient spectroscopy
Authors: Evwaraye A. O. , Sun Edmund
Published: February 2003

Platinum was diffused into p+nn+ and n+pp+ silicon diodes at temperatures ranging from 860 to 910 °C for approximately 1 h. Using deep-level transient spectroscopy, six levels associated with platinum in these silicon devices were detected. Ev+0.19 eV, Ev+0.28 eV, Ev+0.33 eV, Ev+0.41 eV, Ec−0.34 eV, and Ec−0.23 eV. The concentrations, thermal emission rates, and the capture cross sections for majority carriers at these defects are reported. The Ec−0.34 eV level has not been previously characterized but is probably the dominant recombination center.
Long-time polarization currents in metal-oxide varistors
Authors: Philipp H. R. , Levinson Lionel M.
Published: February 2003

The low-frequency (100–10−4 Hz) behavior of metal-oxide varistors is obtained from analysis of the charging and discharging currents which flow upon the application and removal of a step voltage. These results are compared to data for the complex dielectric constant ε=ε′−iε″ obtained using an ac bridge in the frequency range 101–10−1 Hz. The presence of long-time polarization currents dominates the low-field low-temperature (T?0°C) dc response of these devices. When the varistor microstructure is taken into account the curves of ε″ (ω) versus frequency are consistent in slope and magnitude with other published data obtained on a wide variety of dielectric materials.
Shallow acceptor binding energy and lifetime of donor-acceptor pairs in gallium arsenide
Authors: Kamiya Takeshi , Wagner Elmar
Published: February 2003

The wavelength dependence of photoluminescence decay was measured for a donor-acceptor pair in gallium arsenide. Using the observed saturation % of the lifetime for distant pairs, we separated out the nonradiative contribution to the decay time constant. Fitting the experimental radiative recombination rate to the theory offers a precise method of determining the acceptor binding energy to within ±0.1 meV, as was first proposed by Dingle. The acceptor binding energies thus determined of 26.2 meV for carbon and 34.3 meV for silicon are very close to those of 26.4±0.1 and 34.5±0.1 meV evaluated by conduction-band electron–to-neutral-acceptor recombination spectra for the same samples.
Photocapacitance effects of deep traps in epitaxial GaAs
Authors: White A. M. , Dean P. J. , Porteous P.
Published: February 2003

A photocapacitance technique which allows rapid characterization of deep traps in a semiconductor is described. Continuous illumination with light of photon energy slightly below the band gap provides for the occupation of a trap level by both holes and electrons, and at the same time reduces the time constants associated with population changes to typically 0.1 sec. The first feature enables both hole-emission and electron-emission processes to be detected in a single spectrum and the second eliminates the effects of long time constants which could be masked by slow drifts. Sharp features due to individual traps are displayed by electronic differentiation with respect to energy of the photocapacitance signal. Thus we refer to the technique as double source differentiated photocapacitance (DSDP). Our data for deep levels in GaAs show that the variation of cross section with respect to energy is much more rapid than described by the frequently applied Lucovsky theory. This effect can be understood in terms of band structure throughout the reduced zone, as is more appropriately considered for very deep levels. Characteristic differences of the trap distribution for GaAs grown under different conditions are described. A series of traps less than 0.6 eV above the valence band in vapor-phase epitaxial material are not observed in liquid-phase epitaxial material. A strong feature representing a trap ∼0.65 eV below the conduction band mainly in vapor epitaxial material is associated with chromium. It clearly demonstrated that the transitions detected in this optical cross-section DSDP experiment relate not precisely to the band edge, but to points higher in the bands, influenced by the detailed density of states. We find the complementary energies, of peak hole and electron optical-emission processes in the derivative spectra of a given very deep level, total ∼1.9 eV, considerably greater than the minimum (direct) band gap of GaAs and expected value from the Lucovsky model.
Open-circuit voltage of MIS silicon solar cells
Authors: Ponpon J. P. , Siffert P.
Published: February 2003

The open-circuit voltage of MIS solar cells realized on n-type silicon has been investigated. Chemically formed and evaporated SiOx layers have been used for the insulating film. The latter has given the best results on polished samples, since Voc reached 0.55V. The influence of different parameters like n or ΦBn are discussed.
Microwave impedance of superconducting weak links
Authors: Franson J. D. , Mercereau J. E.
Published: February 2003

Calibrated measurements of both the real and imaginary parts of the microwave impedance of proximity coupled superconducting weak links have been made. The measurements were compared with analytic calculations based on several different models for the supercurrent Is and quasiparticle current. For dc bias currents I1 less than the critical current Ic, the experimental results are consistent with the Josephson relation Is=Ic sinφ, where φ is the quantum phase angle. However, for I1≳Ic, the Fourier component of Is at the Josephson frequency is found to be significantly less (∼0.65±0.1) than would be predicted from Is=Ic sinφ, and consistent with Tinkham’s analysis of a phase slip process. The experimental results indicate that the phase-dependent part of the quasiparticle current, if it exists at all, is no more than 10% of the total quasiparticle current. These results do not necessarily contradict previous measurements made on true tunnel junctions because of the fundamental differences between the two types of devices.
Magnetic-flux propagation on a Josephson transmission line
Authors: Scott Alwyn C. , Chu Flora Y. F. , Reible Stanley A.
Published: February 2003

The propagation of magnetic flux pulses along the insulating barrier of a long Josephson junction is investigated both theoretically and experimentally. The theoretical study includes applications of both (i) the recently developed ’’inverse-scattering-transform method’’ (ISTM) to the corresponding sine-Gordon equation in characteristic (light cone) coordinates and (ii) Whitham’s method (WM) of averaged Lagrangian analysis to the sine-Gordon equation in laboratory coordinates. As the number of solitons (flux quanta) in the pulse becomes large, the ISTM becomes numerically unwieldy while WM becomes more accurate; thus these two analytical tools are complementary. WM has the advantage of being readily modified to account for small dissipative effects. Our experimental observations of magnetic-flux propagation were entirely restricted to the ’’large-amplitude limit’’ in which the average of the ac Josephson current is effectively zero. In this limit, WM indicates pulse propagation with linear dissipation. This result has been confirmed on a Josephson transmission line for which it was possible to predict pulse propagation from parameters which were measured independently on small crossed strip junctions.
Overshoot in the translational motion of magnetic bubble domains
Authors: Vella-Coleiro G. P.
Published: February 2003

We report observations of overshoot in the motion of a bubble domain in a pulsed field gradient obtained by high-speed photography and by a technique which enables a photoelectric signal proportional to bubble translation to be derived. At high drive fields, a correlation between the amount of overshoot and the distance moved by the bubble during the field pulse has been observed. At low drive fields, some overshoot has been found to occur in a high-mobility LuGd film, but not in a low-mobility YSm sample.
Detection of stored momentum in magnetic bubbles by a bias jump effect
Authors: Malozemoff A. P. , Maekawa S.
Published: February 2003

A pulse of uniform bias field is applied to an isolated ∼5-μm bubble in a garnet film. The bubble (S=0) was previously propagated by a strong gradient-field pulse. The bubble is observed to jump forward in the same direction as the previous gradient propagation, irrespective of the sign of the bias-field pulse. Subsequent bias pulses may cause further ’’bias jumps’’ of this type until a maximum displacement is reached, which can be many μm in typical cases. Dependence of the bias jumps on the strength and length of the bias-field pulses and also of the previous gradient-field pulses is reported. The shape of the bubbles, observed by high-speed photography during the bias pulse, is elliptical, indicating lower mobility on the sides of the bubble perpendicular to the over-all direction of motion. These results provide evidence for the existence of unwinding Bloch-line pairs which remain in the bubble wall at the end of a gradient propagation. These Bloch lines are shown to be tantamount to a stored bubble momentum, which is released when the bias pulses are applied.
Fully operational write-read-write and random-access optical store
Authors: Hill B. , Krumme J.-P. , Much G. , Riekmann D. , Schmidt J.
Published: February 2003

A write-read-write magneto-optic memory for random access has been made to work as a feasibility model. The memory is an interim result of the development of a 107–108-bit memory. Design aspects and function of the memory as well as experimental results are summarized. Operation for more than 300 h and more than 109 read-write cycles has not given rise to any degradation.
Sensitivity of x-ray film. II. Kodak No-Screen film in the 1–100-keV region
Authors: Dozier C. M. , Brown D. B. , Birks L. S. , Lyons P. B. , Benjamin R. F.
Published: February 2003

The absolute sensitivity of Kodak No-Screen x-ray film was measured for 11 photon energies between 1 and 8 keV using filtered fluorescent radiation. The shapes of the density-vs-exposure curves were observed to be a function of the photon energy. This calibration was demonstrated to be consistent with two earlier calibrations of No-Screen response for photon energies between 5 and 100 keV and with a theoretical model of film sensitivity by Brown, Criss, and Birks.
High-speed silicon avalanche photodiodes with built-in field
Authors: Kanbe Hiroshi , Mizushima Yoshihiko , Kimura Tatsuya , Kajiyama Kenji
Published: February 2003

High-speed silicon avalanche photodiodes for the near-infrared region are reported. Diodes are provided with a built-in field by a graded impurity distribution which accelerates photocarriers in a light-absorption region. The response for a mode-locked Nd : YAG laser pulse is as narrow as 200 psec. Typical quantum efficiency is 0.55 at 0.80 μm and 0.49 at 0.83 μm. The gain-bandwidth product is 460 GHz at a multiplication factor of 400. The built-in field is effective in realizing high-speed avalanche photodiodes with a low breakdown voltage.
Three-color direct superposition for field-ion microscopy
Authors: Melmed A. J. , Carroll J. J.
Published: February 2003

Direct two-component color superposition for field-ion microscopy is extended to three-component color superposition. Details of the method are given and some applications are mentioned.
Anomalous surface resistance of superconductors at finite temperature
Authors: Kartheuser E. , Rodriguez Sergio
Published: February 2003

A theoretical study of the effect of direct ultrasonic generation on the surface impedance of superconductors at temperatures below the critical temperature Tc is presented. The temperature and frequency dependences of the additional surface resistance due to the ionic motion are analyzed using the Pippard and BCS kernels and parabolic electron energy bands.
Nonlinear absorber characteristics and their effects on discrimination amplifiers
Authors: Seka W. , Stüssi E.
Published: February 2003

In an effort to suppress the background intensity surrounding short laser pulses we have investigated the behavior of various discrimination amplifiers. These amplifiers are made up of a sequence of bleachable dyes and amplifiers having an over-all small-signal gain below unity and a large-signal gain above unity. The characteristics of such amplifiers depend strongly on the dye transmission which is itself a function of the particular spatial and temporal profile of the laser pulse propagated through it. This characteristic was investigated experimentally and theoretically. We found 84% transmission at 100 times the saturation intensity of a dye of initial transmission T0=0.2. As a consequence, typical experimental pulse profiles reduce the background suppression efficiency of discrimination amplifiers considerably. However, background suppression of over 2000 is attainable.
Recombination-enhanced annealing of the E1 and E2 defect levels in 1-MeV-electron–irradiated n-GaAs
Authors: Lang D. V. , Kimerling L. C. , Leung S. Y.
Published: February 2003

Recombination-enhanced annealing of the E1 (Ec−0.08 eV) and E2 (Ec−0.18 eV) defect levels in n-GaAs has been studied by deep-level transient spectroscopy (DLTS). The defects are controllably introduced at room temperature by irradiation with 1-MeV electrons. Thermal annealing at reverse and zero bias yields an activation energy of ΔE=1.75±0.17 eV and shows that charge-state effects are not operative. Recombination annealing produces an enhancement of several orders of magnitude in the annealing rate and an activation energy of 0.98±0.10 eV. The annealing reaction obeys first-order kinetics and does not saturate with injection currents up to 350 A/cm2. The relationship of this data to earlier observations of recombination-enhanced annealing (motion) in GaAs and GaP is discussed as well as the possible implications for injection-mode device degradation.
Switching in amorphous boron films under single-pulse conditions
Authors: Turner George W. , Charles Harry K. , Feldman Charles
Published: February 2003

Investigations of switching parameters in amorphous boron thin films containing carbon have been conducted under rapid single-pulse voltage conditions. Measurements were compared with switching parameters determined from low-voltage long-duration signals. Single high-voltage pulses altered virgin samples more than similar samples previously examined under low-voltage (curve-tracer) signals. Delay times and switching times were considerably shorter under the high-voltage pulse condition. Film thickness had, as found previously, little effect on threshold voltage under curve-tracer or long-duration pulses, but had a large effect under rapid high-pulse conditions. At very high voltages and short pulse duration, the switching threshold became field dependent and the switching process became primarily electronic. The results are discussed in terms of an electrothermal model in which the switching process becomes less dominated by thermal effects as the duration of the applied voltage is decreased.
Structural and electrical characteristics of InSb thin films grown by rf sputtering
Authors: Greene J. E. , Wickersham C. E.
Published: February 2003

InSb films have been grown by rf sputtering on cleaved BaF2, CaF2, NaCl, and NaI substrates in addition to polished and annealed (111) -oriented CaF2 wafers. Growth temperatures investigated ranged from 40 to 300 °C, while deposition rates R ranged from 20 to 450 Å/min. The epitaxial temperature for InSb was found to decrease with decreasing deposition rate and decreasing film-substrate lattice mismatch. Stoichiometric single-crystal films were grown on cleaved BaF2 substrates at temperatures as low as 150 °C at R=20 Å/min. Polycrystalline films grown on cleaved CaF2 exhibited a greater degree of preferred orientation than films on polished and annealed CaF2, but the grain size was always less for a given growth temperature. The maximum grain size was related to the film thickness. The electrical properties of 2000-Å-thick polycrystalline InSb films on polished and annealed CaF2 were investigated. The room-temperature electron carrier concentration and Hall mobility of films grown at 300 °C were 4×1017 cm−3 and 200 cm2/V sec, respectively. The dominant charge-scattering mechanism was identified as potential-barrier scattering at either high- or low-angle grain boundaries depending on the grain size of the film.
Low-temperature thermal conductivity and specific heat of a machinable ceramic
Authors: Roth E. P. , Anderson A. C.
Published: February 2003

The thermal conductivity and specific heat of a commercial machinable ceramic have been measured to 0.06 °K. The data are compared with those of other materials commonly used in the construction of cryogenic apparatus. The role of impurities and of crystallites is discussed.
Absorption edge and ion bombardment of silicon nitride
Authors: Stein H. J.
Published: February 2003

The optical absorption edge for chemical-vapor-deposited silicon nitride films on sapphire substrates has been measured for different deposition conditions, and as a function of ion bombardment and subsequent annealing. An exponential form for the absorption edge, consistent with a disorder-limited edge, is observed for all films. While the slope of the absorption edge is independent of the measurement temperature, the energy for the edge decreases with increasing temperature by (2–4) ×10−4 eV/°C. The energy and slope of the absorption edge are lower for films deposited at 760 °C than for films deposited at 1000 °C, and displacement damage introduced by ion bombardment causes a decrease in both the slope and energy for the edge. Ion-bombardment-induced changes saturate when the energy deposition into damage processes is ∼10 eV/atom. The effects of a lower deposition temperature and of ion bombardment upon the absorption edge are attributed to a degradation of short-range order. Annealing of the bombardment-induced effects occurs over a broad temperature range, and the prebombardment absorption edge is essentially recovered by annealing at the deposition temperature.
Effect of the electric arc and the ambient air on the contact resistance of silver, tungsten, and silver-tungsten contacts
Authors: Slade Paul G.
Published: February 2003

Contact pairs of Ag, W, and Ag-W were operated 6000 times in a 20-A 110-V ac circuit. The effect of contact-resistance change was observed by measuring the temperature rise (TR) at the fixed contact while passing the steady-state 20 A. The TR was measured before the switching had begun and after each 1000 operations. A large number of contact pairs were used in order to ensure a good statistical interpretation of the data. The chemical composition of the contact surfaces was measured using a Debye-Scherer x-ray analysis. The distribution of contact resistance for Ag contacts remained the same throughout the experiment. For W contacts, the distribution was initially higher than that for Ag: the result of conductivity and hardness differences. During the switching experiments, the formation of tungsten oxides on the contact surface resulted in high contact-resistance values. For Ag-W, the distribution was initially closer to that for Ag contacts: the result of a thin surface layer of Ag on the Ag-W. During the switching, the Ag-W contact-resistance distribution gradually increased in dispersion and had higher values than those measured for W contacts. The x-ray data showed that not only were tungsten oxides formed, but also there was a high probability that some of the free Ag on the contact surface formed an insulating silver tungstate.
Linear theory of a cold relativistic beam in a strongly magnetized finite-geometry plasma
Authors: Gagne R. R. J. , Shoucri M. M.
Published: February 2003

The linear theory of a finite-geometry cold relativistic beam propagating in a cold homogeneous finite-geometry plasma, is investigated in the case of a strongly magnetized plasma. The beam is assumed to propagate parallel to the external magnetic field. It is shown that the instability which takes place at the Cherenkov resonance ω?kzvb is of the convective type. The effect of the finite geometry on the instability growth rate is studied and is shown to decrease the growth rate, with respect to the infinite geometry, by a factor depending on the ratio of the beam-to-plasma radius.
Characterization and analysis of reentrant hybrid tee
Authors: Hsu Ken-Wang , Ishii T. Koryu
Published: February 2003

The impedance of a reentrant hybrid tee, which is a relatively new component, is newly analyzed employing a recently refined theory. The experiment and the theory explain the mechanism of this reciprocal but asymmetrical transmission device.
Measurement of potential buildup and decay, surface charge density, and charging currents of corona-charged polymer foil electrets
Authors: Moreno R. A. , Gross B.
Published: February 2003

Conventional measurement techniques for the investigation of the behavior of corona-charged polymer foil electrets allow one to determine the equivalent surface charge and the surface potential decay after termination of the charging process. This paper describes a technique which determines charges, currents, and potentials during the charging process. The application of this technique to Teflon and polyethylene foils show the usefullness of the method. The values of transit times and of the trap-modulated mobility for polyethylene are obtained.
Coupled-amplitude analysis for semiconductive nonlinearities of surface acoustic waves and its application to the second harmonic generation of Bleustein-Gulyaev waves
Authors: Ho R. C. , Chen C. L.
Published: February 2003

A perturbation formula is developed to provide a systematic way of analyzing the nonlinear interaction of waves in piezoelectric media. From this perturbation formula, a set of coupled-amplitude equations is obtained for surface acoustic waves coupled with the charge carriers in an adjacent semiconductor. The nonlinear coupling coefficients associated with semiconductive nonlinearities are expressed explicitly in terms of material constants of the piezoelectric substrate and the semiconductor layer, wave vectors, and polarizations of interacting beams. Making use of the coupled-amplitude equations, the generation of second harmonic Bleustein-Gulyaev waves is studied. The dependence of the second harmonic signal on the thickness and resistivity of the semiconductor sample is investigated and compared with the experimental results.
Molecular-field coefficients of rare-earth iron garnets
Authors: Dionne Gerald F.
Published: February 2003

Molecular-field coefficients of several rare-earth iron garnets (Tb, Dy, Ho, Er, and Yb) have been determined by fitting calculated-and-experimental magnetic-moment–vs–temperature curves. For these compositions, spin canting appears to cause a significant reduction in the net moment of the c sublattice. The results are compared with values of coefficients derived from paramagnetic susceptibility measurements and with other values determined without taking into account c-sublattice canting.
Comment on ’’Theory and analyses of the ac characteristics of defect thin-film insulators’’
Authors: Franceschetti Donald R. , Macdonald J. Ross
Published: February 2003

A theory of metal-insulator-metal thin films proposed by Nadkarni and Simmons is examined in relation to earlier treatments. Attention is drawn to approximations inherent in the theory and physical processes not considered by the authors.
Electron diffraction radial distribution study of liquid polyethylene
Authors: Voigt-Martin I. , Mijlhoff F. C.
Published: February 2003

Electron diffraction patterns of liquid polyethylene have been obtained at 140 and 200 °C in the ranges s =0.75 to 23 Å−1 and 1.25 to 20 Å−1, respectively. These data have been utilized to derive radial distribution functions, which at distances above roughly 20 Å show little detail. It was concluded that, since errors never smooth Fourier transforms, the polyethylene melts have a high degree of structural randomness and that conclusions to the contrary derived from diffraction studies must be met with great caution.
Thermodynamic aspects of particle engulfment by solidifying melts
Authors: Omenyi S. N. , Neumann A. W.
Published: February 2003

This study confirms the predominance of surface thermodynamic effects in the process of particle engulfment by solidifying melts for small-diameter particles and slow interface motion. Predictions of a thermodynamic model are compared with actual particle engulfment behavior. It turns out that, in complete quantitative agreement with the thermodynamic predictions, the more hydrophobic particles like Teflon are engulfed at even very slow rates of solidification of naphthalene and biphenyl melts. On the other hand, more hydrophilic particles like nylon are rejected, and hence pushed by the solidification front at low and moderate rates of solidification. Conclusive proof of the importance of surface properties in particle engulfing is offered by the investigation of small siliconed glass spheres and untreated glass spheres; again the hydrophobic siliconed glass spheres were engulfed at all solidification rates and the untreated hydrophilic glass spheres were pushed. Rate phenomena for the engulfment of hydrophilic particles were studied and found to depend also on surface properties. However, comparison of the critical pushing velocities of one and the same particle in the two matrix materials shows, as expected, that fluid mechanic considerations will also be needed in a complete theory of particle engulfment.
Splashing of drops on liquid layers
Authors: Macklin W. C. , Metaxas G. J.
Published: February 2003

The splashing of drops on deep and shallow liquid layers has been investigated experimentally. The liquids used were water and 90 and 60% aqueous solutions of ethanol and glycerol. Simple geometrical models for the splash are used to calculate the various energy terms involved and the energy balance equation has been expressed in terms of the dimensionless Froude, Weber, and Reynolds numbers. Over the ranges of values of these numbers investigated, deep liquid splashing is determined by both the Froude and Weber numbers, while shallow liquid splashing is determined essentially by the Weber number. Data are presented which enable the maximum radius of the cavity and the maximum height of the crown formed during the splash to be calculated in a variety of splash situations.
Ultrasonic measurements at elevated pressures (9 GPa) to determine Poisson’s ratio and other elastic moduli of NaCl and NaF
Authors: Morris C. E. , Jamieson J. C. , Yarger F. L.
Published: February 2003

We have measured simultaneously transit times of longitudinal and transverse ultrasonic waves in NaCl and NaF as a function of ’’quasihydrostatic’’ pressure to 9 GPa. The dimensionless ratio of these transit times yields directly the ratio of the longitudinal to shear velocity. This velocity ratio is independent of sample length. Using third-order elasticity theory a correction for a probable superimposed uniaxial stress component may be made. When done, this allows the direct determination of Poisson’s ratio for each pressure. Shock-wave data are used to obtain other elastic moduli and velocities of shear and longitudinal waves. Apparatus for making these measurements is described and data for NaCl and NaF are presented.
Photoinitiated F2+H2/D2 chain-reaction laser with high electrical efficiency
Authors: Nichols D. B. , Hall R. B. , McClure J. Doyle
Published: February 2003

Performance characteristics are reported for a pulsed HF/DF laser initiated by photodissociation of F2. Laser energy of 292 J is obtained from a 12.8-l active volume for 2.5% HF content at 1-atm total pressure, giving 8.1% chemical efficiency at 29% electrical efficiency. Thirty-three percent electrical efficiency is obtained with and 109-J laser energy. DF lasing produces 144 J with 14% electrical efficiency. Far-field measurements show a uniform beam profile with angular half-angle divergence of 5.5 mrad, in good agreement with the value expected for multimode operation of the large-Fresnel-number stable resonator used.
Deep-level changes associated with the degradation of gallium phosphide red-light-emitting diodes
Authors: Henry C. H. , Daniel Dapkus P.
Published: February 2003

The degradation of LPE GaP red LED’s in forward-bias aging is studied by deep-level capacitance spectroscopy. The decrease of the Zn-O concentration during aging is found to be a major source of degradation. The Zn-O concentration decreased to 62±9% of its undergrade value for samples degraded to 50±8% efficiency when measured at 10 mA. Three deep levels consistently appear during degradation with activation energies for emitting carriers to the majority-carrier band of 0.41±0.04, 0.72±0.07, and 0.97±0.09 eV. Similar deep-level changes were found for LED’s degraded to 50% efficiency when aged at different temperatures and different currents and for LED’s degraded to 50% efficiency which aged at different rates under the same conditions. In contrast to the red LED, two LPE GaP green LED’s, degraded at 250 °C to 50% efficiency, showed no significant deep-level changes.
Time dependence of environmental-contaminant-induced reactions in encapsulated metallurgy. II. Analysis and application of the model
Authors: Ferris-Prabhu A. V.
Published: February 2003

The equations derived in Paper I describing the time to failure caused by reaction of contaminant with encapsulated metallurgy are examined and an approximate equation is developed which enables the influence of various parameters to be analyzed. The approximate and exact equations are solved for representative cases and good agreement is found. The approximate equations can thus be used to advantage either for design, or in predicting future behavior for a given design.