bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic response of a cw laser-produced Cs plasma to laser modulations
Authors: Tam A. C.
Published: February 2003

We present a first experimental investigation of the response of a continuous laser-produced Cs plasma to weak modulation of the laser beam. The cw dye laser beam at 6010.49 Å, of ∼0.1 W power, excites the Cs (6P1/2→8D3/2) atomic transition in the present study. At low modulation frequency, the fractional modulation of the transmitted laser beam is greatly reduced from that of the incident beam. At high modulation frequency, the two fractional modulations are nearly equal. We also demonstrate that the normal amplitude fluctuation of the laser beam is greatly reduced after transmission through the plasma. These features of the dynamic response are explained in a simple rate equation analysis.
Thermally induced accumulation of silicon on palladium silicide surfaces as studied by Auger electron spectroscopy
Authors: Oura K. , Okada S. , Hanawa T.
Published: February 2003

A clean surface of a palladium silicide grown on a Si(111) plane has been studied by Auger electron spectroscopy. Heat treatment of the silicide in the temperature range 250–600 °C causes the accumulation of a thin layer of elementary Si over its surface. The accumulated thickness has been estimated to be about 3 Å and does not depend on heating temperatures and periods examined.
A superconducting sampler for Josephson logic circuits
Authors: Hamilton C. A. , Lloyd F. L. , Peterson R. L. , Andrews J. R.
Published: February 2003

A method is described for automating a technique which is used to sample transition duration (rise time) in superconducting logic circuits. The method is based on measuring the time at which a biased Josephson junction switches under the influence of an applied signal. The system transition duration is limited primarily by time jitter which is estimated to be 7 ps. Transition durations of as little as 9 ps have been observed.
Si-SiO2 interface characterization from angular dependence of x-ray photoelectron spectra
Authors: Ishizaka Akitoshi , Iwata Seiichi
Published: February 2003

The Si-SiO2 interface is studied by using ESCA. The sample is a very thin oxide film (0.91 nm thick) on Si substrate. The angular dependence of the Si2p spectrum is measured. The Si2p spectrum is composed of SiSi2p photoelectrons emitted from the Si substrate, Six2p photoelectrons emitted from the transition region at the Si-SiO2 interface, and SiSiO22p photoelectrons emitted from SiO2 film.

It is concluded that the chemical shift for Si atoms in the transition region is 1.6 eV (this value is about one-half of that of SiO2), and that the thickness of the transition region is 0.2–0.3 nm.
Arc annealing of BF+2 implanted silicon by a short pulse flash lamp
Authors: Lue Juh Tzeng
Published: February 2003

Step-junction diodes are obtained from BF+2 implanted silicon irradiated by a single pulse of light from a flash lamp. The FWHM is 100 μs with energy densities ranging from 12.4 to 20.6 J/cm2. The sheet resistance and the I-V characteristic have been used to confirm the annealing process.
Reduction of GaAs surface recombination velocity by chemical treatment
Authors: Nelson R. J. , Williams J. S. , Leamy H. J. , Miller B. , Casey H. C. , Parkinson B. A. , Heller A.
Published: February 2003

Chemisorbed ruthenium ions on the surface of n-GaAs decrease the surface recombination velocity of electrons and holes from 5×105 to 3.5×104 cm/sec. It is shown that the ions, in a one-third monolayer thickness, are confined to the surface and do not form a new junction by diffusing into the GaAs. This use of Ru appears to be the first observation of the reduction of the surface recombination velocity for GaAs by the simple chemisorption of ions.
Quantitative spectroscopy of micron-thick liquid films
Authors: Patel C. K. N. , Tam A. C.
Published: February 2003

We demonstrate a new sensitive spectroscopic technique for highly transparent micron-thick liquid films sandwiched between transparent substrates. A pulsed dye laser irradiates the film, producing (via the optoacoustic effect) a transient ultrasonic wave which is launched into the substrate and detected by a piezoelectric transducer bonded to the substrate. This technique is illustrated by measuring the absorption lines of films of aqueous solutions of rare-earth ion, and absorptions ∼10−5 can be detected presently. This technique should open up new opportunities to study the spectra of chemi- or physi-adsorbed species on surfaces.
Superconducting critical properties and AC losses in a large sample of i
n s
i
t
u formed Cu-Nb3Sn composite
Authors: Bevk J. , Harbison James P. , Habbal F. , Wagner G. R. , Braginski A. I.
Published: February 2003

Critical-current density, upper critical field, and hysteresis ac losses have been evaluated for a large (100-m long) sample of in situ formed Cu-Nb3Sn composite with superconducting volume fraction λ≃0.23. The magnetic field dependence of the critical current, measured in wire and tape samples of different reductions, cannot be explained by a model based on a single pinning mechanism. The enhancement of the pinning force in highly reduced tape composites is attributed to surface flux pinning at the filament-matrix interfaces. Hysteretic ac losses obtained by calorimetric and electronic measuring methods confirmed the results reported previously for small in situ samples.
Focusing and defocusing of neutral atomic beams using resonance-radiation pressure
Authors: Pearson D. B. , Freeman R. R. , Bjorkholm J. E. , Ashkin A.
Published: February 2003

We demonstrate strong focusing and defocusing of a sodium atomic beam using the transverse resonance-radiation pressure of a superimposed cw dye laser beam tuned near the atomic resonance. Focal spot diameters of about 60 μm and a 30-fold increase of the on-axis atomic beam intensity have been obtained. For defocusing, the on-axis intensity can be reduced to less than 10−2 of its original value.
Efficient microwave second harmonic generation and frequency conversion in Fe3+-TiO2
Authors: Yngvesson K. S. , Kollberg E. L.
Published: February 2003

Second harmonic generation from 21.5–26 to 43–52 GHz, using about 280 ppm of Fe3+ spins doped into TiO2 crystals has been investigated. The harmonic generator was tunable by use of magnetic fields of a few kilogauss. The most efficient generation is obtained when there are Fe3+ transitions coincident with both frequencies. We report a conversion efficiency of −45 dB, the best so far obtained with paramagnetic crystals. Evidence was found for more efficient conversion occurring inside the crystal. A similar frequency up-conversion experiment yielded an efficiency of −49 dB. With improved materials, frequency down-converters of similar type show promise as a low-noise detector of near-millimeter waves.
Thermal and impulse coupling to an aluminum surface by a pulsed KrF laser
Authors: Woodroffe J. A. , Hsia J. , Ballantyne A.
Published: February 2003

The amount of heat deposited on an aluminum target after irradiation in air by a KrF laser at 249 nm has been measured to be ∼40% of the incident pulse energy for long pulses (0.5 μsec), moderate flux levels (106–108 W/cm2), and spot diameter ⩾0.5 cm. The impulse generated by the laser has also been measured. Significant impulse levels were observed at low incident fluence levels.
Frequency modulation and demodulation of a 10.6-μm CO2 laser
Authors: Yasuoka Y. , Takahashi T. , Gustafson T. K.
Published: February 2003

Frequency modulation and demodulation in optical communication is done using the 10.6-μm CO2 laser beam as a carrier. A GE-LiNbO3 acousto-optic device and W-Ni point-contact diode are used as a modulator and a detector, respectively. The frequency of the carrier shifts by f0, by driving the modulator with the signal of f0. By using the nonreflected laser beam as a local oscillator, the beat note of f0 is obtained at the receiving station. Present experimental observations have demonstrated this, using the subcarrier of 38 MHz and the signal of 1 MHz as the driving frequencies of the modulator.
Mössbauer spectroscopy of polycrystalline steel fibers
Authors: Lashmore D. S. , Swartzendruber L. J. , Bennett L. H.
Published: February 2003

Polycrystalline steel fibers, commonly known as ’’Schladitz whiskers,’’ produced by thermal decomposition of iron pentacarbonyl in the presence of a magnetic field, have been studied by means of the 57Fe Mössbauer effect. Results show that the fibers are a two-phase alloy of α-Fe and Fe3C. Almost all the carbon present in the fibers is tied up as Fe3C. The magnetic polarization (in zero applied field) is random rather than being aligned along the fiber axis.
Very efficient void formation in ion implanted InSb
Authors: Destefanis G. L. , Gailliard J. P.
Published: February 2003

Ion implantation in InSb forms a surface layer which looks like a sponge. We show that this structure is related to an elevation of the surface by as much as 2 μm.In this perturbated layer, large voids typically 50 Å in diameter were observed by TEM. We have studied the evolution of this void formation as a function of the mass, the energy, and the dose of ions.
Growth of metallic whisker crystals incorporated with field electron emission
Authors: Okuyama F.
Published: February 2003

Metallic whisker crystals were found to grow on the electron-emitting region of a pointed field cathode when it was operated in a vacuum containing metal carbonyl vapors. Metal ions are produced by collisions of carbonyl molecules with field electrons and the rapid growth of the whiskers is controlled by the supply of metal ions to the electron-emitting area. The crystals are basically monocrystalline, and the evidence obtained indicates that they do not contain an axial screw dislocation emerging at their growing tip.
Subtraction of signal overlaps in Rutherford backscattering spectrometry
Authors: Liau Z. L.
Published: February 2003

A technique has been developed to deduce the individual signals from overlapped ones in Rutherford backscattering spectra. Based on the backscattering kinematics, a coordinate shift and a subtraction are carried out between the backscattering spectra taken at two slightly different incident-ion energies. The subtraction eliminates one of the overlapping signals and yields the derivative of the other one, from which the two individual signals are reconstructed unoverlapped. Before the subtraction, a small change in energy scale is used to correct the slight change of signal shape due to the variation of incident-ion energy. This technique has been tested to yield good results in a computer-simulated backscattering experiment on a thin-film structure consisting of 5 layers of Au-Ag alloys.
Preparation of atomically clean silicon surfaces by pulsed laser irradiation
Authors: Zehner D. M. , White C. W. , Ownby G. W.
Published: February 2003

Irradiation of single-crystal silicon with pulsed ruby laser radiation is shown to reduce the levels of C and O surface contaminants to within the detection limits of Auger electron spectroscopy. Similar results were observed following irradiation of Ar sputtered surfaces and surfaces with chemisorbed oxygen. These results show that pulsed laser irradiation can be used to prepare atomically clean Si surfaces in remarkably short processing times.
Semiconductor injection lasers with a circular resonator
Authors: Liao Andrew Shuh-Huei , Wang Shyh
Published: February 2003

Outstanding lasing characteristics of a new GaAs-(GaAl)As ring laser is reported. The basic structure of the new laser includes a circular resonator and straight output branching waveguide. The possibility to eliminate the need for feedback reflectors should make it attractive for integrated optics applications.
Propagation of light ions in a plasma channel
Authors: Olsen J. N. , Johnson D. J. , Leeper R. J.
Published: February 2003

An intense beam of light ions has been propagated 50 cm in a wire-initiated plasma channel in a background of 40 Torr of D2 gas. A magnetically insulated ion diode was used on the Hydra accelerator (0.3 TW, 1 MV) to inject the beam into the plasma channel. Propagation efficiencies of 80–90% were inferred from carbon activation measurements.
Collective acceleration of metallic ions
Authors: Adler Richard J. , Nation John A.
Published: February 2003

Preliminary results of collective acceleration of aluminum and iron ions from metal foils are presented. Aluminum ions of up to 15 MeV have been produced from a 0.6-MeV electron beam. Results also suggest that all particle species accelerated reach the same velocity (∼0.035c), indicating that the acceleration may occur in a moving potential well.
Pyroelectric glass-ceramics
Authors: Gardopee G. J. , Newnham R. E. , Halliyal A. G. , Bhalla A. S.
Published: February 2003

Highly oriented surface layers of lithium disilicate crystals were grown by crystallizing glasses of composition Li2Si2O5 in a temperature gradient. The polar c axes of the crystallites were oriented parallel to the temperature gradient and perpendicular to the sample surface. The pyroelectric response of the glass-ceramic crystallized in a thermal gradient was approximately four times larger than that of a touramaline crystal of similar dimensions. The time dependence of the pyroelectric signal obeys the thin-film equivalent circuit model developed by Chynoweth.
A simple technique for determining the stress at the Si/SiO2 interface
Authors: Borden Peter G.
Published: February 2003

A simple technique for measuring the stress at the Si/SiO2 interface is described. This involves etching a groove in the silicon, using the SiO2 layer as a mask. The SiO2 overhang, resulting from etch undercutting, is not constrained by the Si/SiO2 bond and assumes a periodic shape. Measurement of the amplitude and period gives the strain required to conform the SiO2 to the silicon. This allows calculation of the interface stress and the strain in the silicon. For 280 nm of SiO2 on (110) Si, the SiO2 strain is 9×10−3, the interface stress is 6×109dyne/cm2, and the silicon strain 3×10−3, in agreement with previously reported values.
Influence of a thin gold surface layer on the electrochromic behavior of WO3 films
Authors: Haranahalli A. R. , Dove D. B.
Published: February 2003

A new WO3 electrochromic cell structure is described that gives rise to an enhanced rate of coloration. In the electrochromic cells described, a thin gold film has been deposited upon the WO3 film, enabling potentials to be measured or applied at the WO3-electrolyte interface. By applying external voltages on the gold film during coloration and bleaching, the response times have been decreased by a factor of 20 to less than 50 ms.
cw carbon monoxide laser with rf excitation in the supersonic flow
Authors: Schock W. , Schall W. , Hügel H. , Hoffmann P.
Published: February 2003

A cw CO laser with rf discharge transverse to the supersonic flow is described. Using segmented electrodes an electric power density of 33 W/cm3 or 0.15 eV/CO molecule is deposited in a homogeneous arc-free plasma at 7 Torr. At a laser power of 60 W the emission occurs predominantly on the V=5→4 and 4→3 transitions.
Composition control of GaxIn1−xAs films grown by MBE onto InP substrates
Authors: Norris M. T.
Published: February 2003

The molecular beam epitaxial growth of the ternary alloy GaInAs onto (100) oriented InP substrates has been investigated with it being established that, although epitaxial film growth can be achieved over a wide range of substrate temperatures, high-quality layers of composition simply related to the incident flux levels can only be grown in the narrow range Ts=400–430 °C. Film growth below Ts=400 °C was found to result in degradation of electrical properties, while deposition above Ts=430 °C resulted in compositional inhomogeneity.
Gain-dependent noise temperature of Josephson parametric amplifiers
Authors: Feldman M. J. , Levinsen M. T.
Published: February 2003

We describe a novel noise mechanism which should effect all externally pumped parametric amplifiers. The theory is developed specifically for the four-wave Josephson paramp. We predict a noise temperature rising in direct proportion to the amplifier gain; this prediction agrees perfectly with all previously published data for both the three- and four- wave Josephson amplifiers. An explicit expression for the noise temperature of the four-wave device is derived and compared to previous experiments.
Displaced hysteresis loop and microstructure of Cu-Mn-Al alloys
Authors: Narita Kenji , Koga Shinji , Motowaki Yoshihiro
Published: February 2003

The 44.7Cu-20.6Mn-34.7A1 (at. %) alloy aged at 300 °C for 1 h, which exhibits the high coercive force of 5–6 kOe at 300 K, has been found to show displaced hysteresis loop when it is cooled to 77 K in a magnetic field. The displaced hysteresis loop is believed to be due to the statistical fluctuations in the local Mn concentration and the coexistence of ferromagnetic and antiferromagnetic interactions between Mn atoms of different separation.
Effects of a finite melt on the thickness and composition of liquid phase epitaxial InGaAsP and InGaAs layers grown by the diffusion-limited step-cooling technique
Authors: Cook L. W. , Tashima M. M. , Stillman G. E.
Published: February 2003

The thickness of InGaAsP (λg=1.15 μm) and InGaAs (λg=1.68 μm) liquid phase epitaxial layers grown on (100) InP substrates by the step-cooling technique has been measured as a function of growth time. (λg is defined as the wavelength corresponding to the energy gap of the epitaxial layer.) For growth times much less than the shortest diffusion time τi=l2/Di of the melt constituents, where l is the melt height and Di is the diffusivity of each component in the melt, the thickness is consistent with diffusion-limited theory, and the composition is constant. The time at which the growth rate deviates sharply from diffusion-limited theory and beyond which constant composition growth can no longer be maintained has been determined for the melt size used in our experiments and can be estimated for any melt size.
Forward- and reverse-bias tunneling effects in N+P silicon solar cells
Authors: Garlick G. F. J. , Kachare A. H.
Published: February 2003

Excess currents due to field-assisted tunneling in both forward and reverse bias directions have been observed in n+-p silicon solar cells. These currents arise from the effect of conducting paths produced in the depletion layer by n+ diffusion and cell processing. Forward-bias data indicate a small potential barrier with height ∼0.04 eV at the n+ end of conducting paths. Under reverse bias, excess tunneling currents involve a potential barrier at the p end of the conducting paths, the longer paths being associated with smaller barrier heights and dominating at the lower temperatures. Low-reverse-bias data give energy levels of ∼0.11 eV for lower temperatures (253–293 K) and ∼0.35 eV for higher temperatures (293–380 K). A model is suggested to explain the results.
Selective laser annealing
Authors: Fowler Alan B. , Hodgson R.T.
Published: February 2003

We have demonstrated that amorphous silicon films can be laser recrystallized selectively over diffused heavily doped lines in silicon substrates. The laser wavelength (1.06 μm) is chosen so that much more energy is absorbed in the heavily doped regions of the crystal than in the neighboring lightly doped regions. In this way, lines narrower than the 2.5-μm diffused width have been recrystallized with the recrystallized regions registered on the diffusions with no masking and with no alignment.
Pulse-width stabilization of a synchronously pumped mode-locked dye laser
Authors: Rotman S. R. , Roxlo C. B. , Bebelaar D. , Salour M. M.
Published: February 2003

Using an analog feedback loop acting on the mode-locker frequency of a synchronously pumped mode-locked dye laser, we have observed a substantial decrease of pulse-width variations at frequencies up to 10 kHz at the cost of an increase in higher-frequency noise. A digital loop acting on the cavity length decreased noise at low frequencies. Using these methods, we have generated reproducible and stabilized frequency-tunable subpicosecond pulses, and have determined the effects of noise in the mode-locking frequency of the pumping Ar+ laser and drift in the cavity length of the dye laser.
Efficient sequence-frequency generation in a parametric fiber-optic oscillator
Authors: Hill K. O. , Kawasaki B. S. , Fujii Y. , Johnson D. C.
Published: February 2003

An optical fiber parametric oscillator pumped by 1.06-μm radiation and emitting light in a sequence of five wavelengths is reported. The oscillation wavelengths are approximately equispaced in energy and span the interval from 0.52 to 1.63 μm. A conversion efficiency of 25% for the pump frequency into the other frequencies is obtained. Other sequences with up to nine upconverted wavelengths in the same interval have also been observed.
Laser-induced chemical vapor deposition of polycrystalline Si from SiCl4
Authors: Baranauskas V. , Mammana C. I. Z. , Klinger R. E. , Greene J. E.
Published: February 2003

Polycrystalline Si films with average grain sizes of ∼8 μm have been grown by laser-induced chemical vapor deposition from SiCl4. A cw CO2 laser operated at 10.6 μm was used to provide local heating of quartz substrates in an otherwise cool reactor to initiate the endothermic decomposition reaction. Deposition rates of 5.1 μm/min were obtained for films grown at an incident laser power of 18.9 W, resulting in sharply defined mesa structures due to the occurrence of the reverse reaction, etching of free Si, at cooler regions of the substrate surface closer to the edge of the 6-mm irradiated zone. The diameter of the mesas was 1.4 mm with thicknesses up to 26 μm. Three modes of film growth, depending on the incident laser power, were observed.
Charge collection and spectral response of amorphous-silicon solar cells
Authors: Bell R. O.
Published: February 2003

Current generation in hydrogenated amorphous silicon, a-Si(H), was found to be predominately from the space-charge region. The mobility-lifetime (μτ) products were the order of 5×10−10 cm2/V for both holes and electrons. It was necessary to consider trapping and recombination of the optically generated carriers in the space charge region to interpret solar cell and spectral response data.
Optical emission from Ga ionization at a field emitter
Authors: Kuk Young , Sakurai T. , Culbertson R. J. , Robertson G. H.
Published: February 2003

When gallium is ionized on the cap of a field emitter, the optical emission emerges from right at the cap of the emitter. This optical emission was spectroscopically studied using an optical multichannel analyzer with a resolution of 1.3 Å over the range 1850–6500 Å.The dominant emission is due to Ga I radiation and is likely due to the two-body collision between atomic gallium and electrons.
A model for the width dependence of electromigration lifetimes in aluminum thin-film stripes
Authors: Kinsbron E.
Published: February 2003

Aluminum thin-film conductors with a variety of linewidths (1–8 μ) were stressed at high temperature (200 °C) and high current density (2×106 A cm−2) to determine the dependence on the linewidth of the time to failure due to electromigration. A new model is based on consideration of the film microstructure and the presence of a stress-induced countercurrent flow of matter in short thin films during passage of electrical current. The model can explain the increase in lifetime observed in stripes with linewidths below 2 μm.
Measurements of heat transfer in microemulsions by laser-induced thermal blooming
Authors: Lalanne J. R. , Sein E. , Buchert J. , Kielich S.
Published: February 2003

In this letter, we describe a variation of the well-known thermal blooming technique used for the measurement of the thermal conductivity in fluids. An IR microsecond laser pulse is used to develop the thermal effect. The decay of the thermal lens is analyzed by a cw nonabsorbed auxiliary wave. This dual-beam technique is for the first time used for studying selective heat transfer in microemulsions.
Electroreflectance of indium gallium arsenide phosphide lattice matched to indium phosphide
Authors: Perea Ernesto H. , Mendez Emilio E. , Fonstad Clifton G.
Published: February 2003

We report the first systematic measurement of the electroreflectance spectra of InuGa1−uPvAs1−v over the range of compositions that lattice-match InP substrates, at room temperature and for energies between 0.7 and 3.5 eV. Analysis of the spectra has enabled us to determine the composition dependence of E0, E0+Δ0, E1, E1+Δ1, Δ0, and Δ1. Experimentally determined values of E0, E0+Δ0, and m*/m0 have been used to predict the values of the g factors for these compounds.
Semiconducting properties of amorphous V2O5 layers deposited from gels
Authors: Bullot J. , Gallais O. , Gauthier M. , Livage J.
Published: February 2003

Colloidal solutions of amorphous V2O5 are used for preparing semiconducting layers. Reasons for the high measured conductivity (σ≃0.8–1.0 Ω−1 cm−1) are discussed. The temperature dependence of σ is analyzed in terms of a temperature-dependent activation-energy model based upon the assumption of a random distribution of the distances between hopping sites.
Tunable vacuum ultraviolet laser action by argon excimers
Authors: Wrobel W.-G. , Röhr H. , Steuer K.-H.
Published: February 2003

Vacuum ultraviolet lasing was achieved in electron-beam-pumped high-density argon gas (25–65 bars). With a diffraction grating, the argon excimer laser (126 nm) could be tuned between 123.2 and 127.4 nm. The line width of the tuned laser was 0.6 nm and the output power ∼1 kW.
Three-dimensional heat flow in the photoacoustic effect
Authors: McDonald F. Alan
Published: February 2003

The theory of the photoacoustic effect is generalized to include three-dimensional heat flow. For typical experimental conditions the predicted photoacoustic signal is precisely the same as that from previous one-dimensional models, subject only to the restriction that thermal waves transverse to the incident beam do not reach the cell walls. This conclusion applies to both thermally thick and thermally thin sample or gas.
Electron density measurement by deflection of a far-infrared beam
Authors: Keren H. , Hirshfield J. L.
Published: February 2003

Electron densities in the range 3×1014<Ne<6×1015 cm−3 have been determined in a laser-initiated linear discharge using a novel far-infrared method. The density was determined by measuring deflections of a 119- and 171-μm far-infrared beam from an optically pumped CH3OH laser. The far-infrared beam was guided both inside and outside of the plasma chamber using dielectric waveguides. The spatial distribution of electron density for peak discharge currents of 2–4 kA and at distances of 8–25 mm from the laser focus on the target was found to be given by Ne (r,ϑ,I) =3×1014I1.9r−2.4 cosω cm−3, where I is the discharge current in kA, r is the radius from the laser focus on the target in cm, and ϑ is the polar angle from the target axis.
Determination of oxygen concentration profiles in silicon crystals observed by scanning IR absorption using semiconductor laser
Authors: Ohsawa A. , Honda K. , Ohkawa S. , Ueda R.
Published: February 2003

Concentration profiles of interstitial oxygen in silicon crystals were determined by scanning IR absorption using PbTe-Pb0.82Sn0.18Te semiconductor laser with the wavelength of 9.04±0.02 μm. IR beam was collimated to be 200 μm in diameter. Czochralski-grown crystals showed a local concentration fluctuation of about 1.8×1017 cm−3 from the average of 1.1×1018 cm−3. This fluctuation corresponds to an oxygen striation in the silicon crystal.
Elastic stiffness and thermal expansion coefficient of BN films
Authors: Retajczyk T. F. , Sinha A. K.
Published: February 2003

Room temperature stresses were found to be tensile for chemical vapor deposition films of the composition B2N and compressive for BN, with all films becoming more tensile with heating. Analyses of the stress-temperature curves of identical films of BN deposited on two different substrate materials yield values of 1.3×1012 dynes/cm2 for the elastic stiffness parameter E/(1−ν) and 1.0 ppm/°C for the thermal expansion coefficient. This technique is of general applicability to thin films and it is believed to be the first practical (nondestructive) means of determining both the elastic stiffness parameter and thermal expansion coefficient of a film.
Very high quantum efficiency GaSb mesa photodetectors between 1.3 and 1.6 μm
Authors: Capasso F. , Panish M. B. , Sumski S. , Foy P. W.
Published: February 2003

In this letter very high quantum efficiency GaSb mesa photodiodes with AlxGa1−xSb windows are reported for the first time. External quantum efficiencies (ηext) of ≃60% at zero bias and of ≃70% at −1 V near 1.3 μm have been obtained without antireflection coatings. More than 80% of the devices from several wafers exhibited ηext⩾50% at λ≃1.3 μm.
Lifetime improvement in Czochralski-grown silicon wafers by the use of a two-step annealing
Authors: Yamamoto K. , Kishino S. , Matsushita Y. , Iizuka T.
Published: February 2003

Minority-carrier lifetime improvement by a two-step annealing has been demonstrated using MOS capacitors fabricated on Czochralski-grown (CZ) silicon wafers. It is shown that an intrinsic gettering effect does not always follow a single annealing in an oxygen-free ambient, even in the wafers containing high oxygen content (∼1018 cm−3). This is probably because nuclei of precipitate-dislocation complexes (PDC) are two small in size to grow into PDC during a single annealing of recent high-grade CZ wafers. In the present study, an additional low-temperature annealing at 800 °C is performed in order to improve the situation. A few critical conditions to the effectiveness of the intrinsic gettering are discussed in connection with the crystalline quality of the wafer.
Elastic wave scattering at long wavelengths
Authors: Tittmann B. R. , Morris W. L. , Richardson J. M.
Published: February 2003

The scattered radiation patterns of spheroidal voids irradiated by longitudinal waves were analyzed in the regime in which the wavelengths are large with respect to the scattering obstacle. The data were acquired using a simple analog device. Agreement between experiment and theory is good, and shows that the shape and size of defects can be estimated using long wavelengths.
Phase transformations in laser-irradiated Au-Si thin films
Authors: von Allmen M. , Lau S. S. , Mäenpää M. , Tsaur B. Y.
Published: February 2003

Laser-pulse-induced melting, interdiffusion, and rapid resolidification are applied to deposited Au-Si thin films of various compositions. It is found that, if 30-ns pulses are used, amorphous Au-Si films can be produced over a compositional range 9–91 at.% Au. The stability of the amorphous phases varies with their composition. Thermal decomposition involves the formation of a single-metastable silicide with a hexagonal structrue. Application of 300-μs laser pulses directly leads to formation of the same compound.
Impact ionization rates for electrons and holes in Ga0.47In0.53As
Authors: Pearsall T. P.
Published: February 2003

We report the determination of the impact ionization rates for holes and electrons in Ga0.47In0.53As with the electric field oriented in the 〈100〉 direction. Our measurements show that the ionization rate for electrons α is greater than that for holes (β) by about a factor of 2 over electric fields ranging from 2.0×105 to 2.5×105 V cm−1 at 295 K.
Effects of bending on the superconducting critical current density of monofilamentary Nb3Sn wires
Authors: Kaiho K. , Luhman T. S. , Suenaga M. , Sampson W. B.
Published: February 2003

Variations in the superconducting current density Jc of the Nb3Sn wires upon bending were measured for a series of monofilamentary wires in which the ratio Rv of the matrix (Cu+Sn) to the core (Nb3Sn,Nb) was changed from 0 to 58. In most cases Jc was found to increase slightly until the bending strain exceeded a value of εirrB , beyond which it severely and irreversibly degraded. For wires with intermediate values of Rv (∼2 to 10), εirrB , calculated by geometrical considerations, was substantially lower than the measured value of the tensile strain εirrT which was required to irreversibly degrade the critical current. The influence of bending strains on Jc can qualitatively be described by considering residual prestrains in the matrix and the core.
Kinetic processes in the electrically excited mercuric-bromide dissociation laser
Authors: Nighan William L.
Published: February 2003

This letter reports the results of an analysis of basic kinetic and plasma processes in fast-pulse (∼100 nsec) electric discharges containing mixtures of the mercuric-bromide molecule, HgBr2, and N2 in a Ne background. Formation of the laser molecule HgBr (B2Σ+) is shown to occur as a result of dissociative excitation transfer following quenching of N2 (A3Σ+u ) by HgBr2.
A master oscillator power amplifier experiment for the determination of the gain coefficient and saturation intensity for an electron-beam-excited KrF amplifier
Authors: Patterson E. L. , Rice J. K. , Tisone G. C.
Published: February 2003

A master oscillator power amplifier (MOPA) experiment using an electron-beam-excited KrF oscillator and amplifier is described. The amplifier gain as a function of input intensity is determined. A comparison of the measured gain with calculations using a steady-state analysis yields a determination of the small-signal gain coefficient and saturation intensity for the amplifier operating with two different gas mixtures. The small-signal gain is found to be more than an order of magnitude larger than the nonsaturable loss, indicating that efficient energy extraction from the amplifier is possible under the high excitation conditions (1.5–6 MW/cm3) of this study.
A new surface-wave acousto-optic time integrating correlator
Authors: Berg N. J. , Abramovitz I. J. , Lee J. N. , Casseday M. W.
Published: February 2003

A new realization of the acousto-optic time-integrating correlator has been constructed. The new device uses a surface-acoustic-wave delay line and is configured so that no separate reference beam is required for coherent detection. Instantaneous bandwidths of 30 MHz and integration times of 30 ms have been achieved. Broadband signals, such as pseudonoise biphase modulated waveforms, with signal-to-noise ratios of −40 dB have been detected. In addition, center frequency, bandwidth, and relative time-difference-of-arrival of these signals can be determined.
Experimental evidence of hydrodynamic instabilities in laser driven implosions
Authors: Key M. H. , Lunney J. G. , Kilkenny J. D. , Lee R. W.
Published: February 2003

Aluminium coated microballoons have been imploded by a two-beam short-pulse Nd laser. The plasma has been examined by space-resolved x-ray spectroscopy which shows that x-ray lines from the aluminium appear in emission from the implosion core. This suggests that the targets are hydrodynamically unstable, which is contrary to expectation for this exploding pusher mode. Possible experimental errors are eliminated.
Improved stacked-structure oxide by laser annealing
Authors: Yaron Giora , Hess LaVerne D.
Published: February 2003

Laser annealing techniques were successfully incorporated into standard MOS processing to improve the quality of oxides grown over polycrystalline silicon (polysilicon). Polysilicon films (5000 Å thick) deposited over 1000 Å SiO2, grown over (100) bulk Si were exposed to a short pulse (20 nsec) of ruby laser radiation at an energy density of 1 J/cm2 and subsequently oxidized at 925 °C. The resulting oxides over the polysilicon were found to have leakage currents which are lower by over three orders of magnitude than oxides grown over polysilicon films which were not laser annealed. C-V measurements taken on the underlying polysilicon-SiO2-Si structure indicate that no deleterious effects were produced in the underlying structure by the laser radiation.
A cw x-ray preionizer for high-repetition-rate gas lasers
Authors: Arai Tsunenori , Obara Minoru , Fujioka Tomoo
Published: February 2003

Continuous-wave x-ray exposure was first used as a preionizer on a pulsed-discharge HF laser. We investigated experimentally the preionization effect of this cw x-ray preionizer on a pulsed HF laser. Although the cw x-ray preionizer resulted in a characteristic performance similar to that of the flash x-ray preionizer, the cw x-ray generator has a much larger dose than a flash x-ray generator. Applicability of a cw x-ray preionizer to a high-repetition-rate pulsed laser was discussed.
Self-sustained pulsations in GaInAsP diode lasers
Authors: Walpole J. N. , Lind T. A. , Hsieh J. J. , Foyt A. G.
Published: February 2003

Self-sustained pulsations in light output have been observed for several GaInAsP double-heterostructure lasers. Although these pulsations are similar to those occurring in AlGaAs lasers, their rate of incidence is much lower and their occurrence does not appear to be increased by aging, in marked contrast to observations for AlGaAs lasers. Most of the GaInAsP lasers exhibiting pulsations appear to have come from a small region of one wafer, suggesting that the pulsations are related to defects originating in the growth process or subsequent fabrication procedures.
Frictional properties of diamondlike carbon layers
Authors: Enke K. , Dimigen H. , Hübsch H.
Published: February 2003

Hard diamondlike carbon layers have been deposited on silicon by rf plasma deposition using acetylene as working gas. For the first time the dependence of the sliding friction coefficient μ on the water vapor content of a nitrogen atmosphere was measured. An increase of μ with increasing humidity has been found, with μ ranging from 0.01 to 0.19. A steel ball was employed as the friction partner. The wear of the layers has been assessed by measuring their durability during friction experiments. It has been shown, contrary to other publications, that the durability has a maximum in the range 0.5–5.0% of relative humidity.
Measurement of isotype heterojunction barriers by C-V profiling
Authors: Kroemer H. , Chien Wu-Yi , Harris J. S. , Edwall D. D.
Published: February 2003

The Debye length smearing that occurs in C-V profiling has precluded the use of C-V profiling from an adjacent Schottky barrier to measure the magnitude of energy band discontinuities at barriers in isotype heterojunctions. It is observed, however, that in such a process both the number of the charge carriers and the moment of their distribution are conserved. This information permits the extraction of values for both the conduction band discontinuity ΔEc and any interface charge density. This technique and experimental results for an LPE-grown n-N GaAs-Al0.3Ga0.7As heterojunction are described. We find ΔEc =0.248 eV, corresponding to about to 0.66ΔEg rather than Dingle’s commonly accepted value 0.85ΔEg . The difference is attributed to compositional grading during LPE growth.
Low temperature liquid phase epitaxy growth for room-temperature cw operation of 1.55-μm InGaAsP/InP double-heterostructure laser
Authors: Takahei K. , Hagai H. , Kawaguchi H.
Published: February 2003

InP-InGaAsP-InP double-heterostructure wafers with 1.5–1.6-μm wavelength range quaternary layers have been grown by liquid phase epitaxy. Any difficulties due to dissolution of the quaternary active layer during the growth of the following InP confining layer are avoided by reducing the liquid phase epitaxy growth temperature to 592 °C, nearly 40° lower than the temperature most frequently used. The lasers fabricated from the wafers operate continuously at 20 °C and emit light at 1.55 μm. The threshold current under cw operation was 250 mA and that under pulsed operation was 160 mA.
Barrier height of Re and Os contacts to n-silicon
Authors: Smirnov A. , Tove P. A. , de Sousa Pires J. , Norde H.
Published: February 2003

Barrier heights between as-deposited (300 °C substrate temperature) Schottky contacts between Re and Os, and 〈100〉 n-Si have been measured, by photoelectric response and analysis of forward I-V data to 0.77 eV for Re, and 0.85 eV for Os. The trend of barrier heights for the 5d series elements, Hf-Ta-W-Re-Os-Ir-Pt-Au is discussed and compared with quantities which have been correlated with the value of the barrier height, viz. work function, electronegativity, and heat of formation for the appropriate silicide. The comparison gives some preference for the simple correlation with work function.
Chemical vapor deposition of ZnO epitaxial films on sapphire
Authors: Tiku S. K. , Lau C. K. , Lakin K. M.
Published: February 2003

A chemical vapor deposition system for the growth of epitaxial (112̄0) ZnO films on (011̄2) sapphire, employing the reaction of zinc vapor and carbon dioxide, was investigated. Growth rates as high as 30 μm/h at a substrate temperature of 700-750 °C were achieved. Films grown on substrates with thin presputtered layers exhibited smooth surfaces and improved crystal perfection as determined by SEM, reflection electron diffraction, and acoustic evaluation. Films had high resistivity which eventually degraded on exposure to atmosphere. Surface acoustic wave interdigital transducers were fabricated on lithium-diffused films, and the electromechanical coupling coefficient of 1.39% was measured for a film thickness to wavelength ratio of 0.13.
Evidence for the segregation of impurities to grain boundaries in multigrained silicon using Auger electron spectroscopy and secondary ion mass spectroscopy
Authors: Kazmerski L. L. , Ireland P. J. , Ciszek T. F.
Published: February 2003

The first direct physical evidence is presented for the segregation of impurities to grain boundary regions in cast and directionally solidified multigrained silicon. Complementary scanning Auger microprobe (SAM) and secondary ion mass spectroscopy (SIMS) techniques are used in conjunction with in situ ultrahigh vacuum fracturing of the multigrained silicon to identify impurities and their localization at the grain boundaries. Both grain and grain boundary regions are exposed for comparative examination under identical experimental conditions. Auger mapping methods are used to show impurity distributions (including C, O, Al, and Ni) at grain boundaries. SIMS provides information on trace impurities that are below the the detectability limits of Auger electron spectroscopy (AES). The impurities, which include C, O, Mg, Al, Ti, Cr, Fe, Co, Ni, Cu, Zn, and Sb, depend upon the growth technique and containing crucible as well as the silicon source material.
Atomic interdiffusion at Au-Al/GaAs interfaces
Authors: Brillson L. J. , Bauer R. S. , Bachrach R. Z. , Hasson Goran
Published: February 2003

A new technique has been developed to probe metal-semiconductor interdiffusion on an atomic scale. With reacted Al atoms as markers at microscopic Au/GaAs (110) interfaces, soft x-ray photoemission studies reveal both Au indiffusion and nonstoichiometric Ga and As outdiffusion at room temperature.
Stress effects in superconducting Cu-V3Ga i
n s
i
t
u composites
Authors: Bevk J. , Habbal F.
Published: February 2003

The effect of the uniaxial tensile stress on the critical-current density Jc, and upper critical field Hc2, of in situ formed Cu-V3Ga composites has been investigated. Jc was found to gradually decrease at stresses greater than ∼200 MPa. The effect is small, amounting to a decrease of only 20% at 16 T and 1 GPa. However, no permanent degradation was observed even at stress levels in excess of 1 GPa. Similarly, Hc2 was found to be rather insensitive to applied stress. The observed decrease of about 0.5 T at 1 GPa was fully recovered after releasing the stress.
Observation of magnetic hysteresis loop of the perminvar type in worked Co-based amorphous alloys
Authors: Aso Koichi , Makino Yoshimi , Uedaira Satoru , Ito Shigeyasu , Hayakawa Masatoshi
Published: February 2003

Magnetic hysteresis loops were measured for polished Co-based Co-Fe amorphous alloys using a longitudinal Kerr effect apparatus. Squared and constricted, or so-called perminvar, loops were observed when the direction of the applied magnetic field was parallel and normal to the direction of polishing in the specimen surface, respectively, where magnetostriction constant λs of the specimen takes a small positive, zero, or fairly small negative value. This feature is remarkably emphasized for the specimen with λs ≃0, while it is inverted for the specimen with a relatively large negative value of λs, at least with λs ≃−1.4×10−6. That is, the easy direction of magnetization is changed into the normal direction to the one of polishing, and the perminvar loop is observed in the direction of polishing.
Experimental temperature and time dependence of implantations: Al in Zn
Authors: Keinonen J. , Anttila A.
Published: February 2003

The range profiles of 60-keV Al→Zn implantations at 25 and −196 °C were measured as a function of time with the intention to test the time and temperature dependence of the implantation. The probing was carried out using the ( p,γ) resonance broadening method. The 25 °C profile was observed to have an increasing surface peaking as a function of time, while by decreasing the target temperature during the implantation to −196 °C, the peaking was avoided.
Magnetic field-induced semimetal-to-semiconductor transition in InAs-GaSb superlattices
Authors: Kawai N. J. , Chang L. L. , Sai-Halasz G. A. , Chang C.-A. , Esaki L.
Published: February 2003

With the application of a magnetic field, we have observed a semimetal-to-semiconductor transition in InAs-GaSb superlattices with closely overlapped subbands of electrons and holes. The transition is manifested in a sharp increase in the magnetoresistance in the quantum limit, where the ground Landau levels associated with the subbands are crossed at the Fermi level, resulting in carrier depletion.
New rectifying semiconductor structure by molecular beam epitaxy
Authors: Allyn C. L. , Gossard A. C. , Wiegmann W.
Published: February 2003

A new unipolar rectifying semiconductor structure is demonstrated. Rectification is produced by an asymmetric potential barrier created by an MBE-grown sawtooth-shaped composition wave of AlxGa1−xAs between layers of n-type GaAs. Single and multiple barriers as well as doped and undoped barriers have been studied and showed rectification. This is the first structure in which rectification has been produced directly by compositional grading.
On a proposed Josephson-effect voltage standard at zero current bias
Authors: Kautz R. L.
Published: February 2003

A voltage standard has been proposed which uses a series array of Josephson junctions locked to rf-induced constant-voltage steps at zero current bias. The feasibility of this proposal is examined in theory and experiment by determining the conditions under which rf-induced steps cros the zero current axis and the stability of phase lock under the zero bias condition.
A direct optical measurement of velocity gradients
Authors: Fermigier M. , Guyon E. , Jenffer P. , Petit L.
Published: February 2003

We describe an experiment which allows the measurement of transverse velocity gradients and laminar and turbulent diffusion. A pulsed laser instantaneously ’’writes’’ a phase grating in a flowing liquid, and is subsequently ’’read’’ by forming its diffraction image with a second laser. Results are presented both in the laminar and turbulent regime for a plane Poiseuille flow.
Linewidth dependence of electromigration in evaporated Al-0.5%Cu
Authors: Vaidya S. , Sheng T. T. , Sinha A. K.
Published: February 2003

The linewidth dependence of electromigration damage has been evaluated for 2.5-cm-long, 1–4-μm-wide, e-gun-evaporated Al-0.5%Cu conductions. It is observed that the ≲1-μm lines are much longer lived than the ≳2-μm lines, reversing the trend at wider widths. These results are rationalized on the basis of the ’’bamboo’’-type grain structure of narrow lines in contrast to the much more heterogeneous structure of the wider meanders.