bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical analysis of observed second bulk compressional wave in a fluid-saturated porous solid at ultrasonic frequencies
Authors: Dutta N. C.
Published: February 2003

We show that the second bulk compressional wave observed recently in an experiment by Plona is consistent with the ’’slow’’ compressional wave as predicted by Biot’s theory. We present dispersion and attenuation curves for all of the body waves for Plona’s samples computed as a function of frequency and Biot’s structure factor S. At high frequencies the velocity of the slow compressional wave is approximately equal to Vf/ S1/2, where Vf is the normal compressional-wave velocity in the pore fluid. Thus, from the measured velocities of slow compressional waves one can obtain S. For Plona’s three samples, the predicted structure factors are 2.1, 2.2, and 3.3.
Energy distribution in relativistic electron beams from field-emission diodes
Authors: Shefer R. E. , Bekefi G.
Published: February 2003

Foil and foil-less field emission diodes (current ∼10 kA, voltage ∼1.5 MV) used in free-electron Raman lasers are studied experimentally with the view of reducing the perpendicular energy of the emitted beam. Microwave emission, attributed to a cyclotron instability in the beam, is used as the diagnostic. Removal of the outer portions of the beam leads to a significant reduction in the radiated intensity, indicating an overall improvement in beam quality.
Recrystallization of silicon-on-sapphire by cw Ar laser irradiation: Comparison between the solid- and the liquid-phase regimes
Authors: Golecki I. , Kinoshita G. , Gat A. , Paine B. M.
Published: February 2003

The annealing behavior under cw Ar laser irradiation (LI) has been studied for 0.2–0.5-μm-thick silicon-on-sapphire (SOS) epitaxial films. Analysis by MeV He+ channeling shows that after LI in the solid phase, Si-implanted films, which had a buried amorphous layer beneth ≈30 Å of surface crystal, become crystalline, but are more defective than the original chemically vapor-deposited (CVD) films. By contrast, furnace annealing of similar layers significantly reduces the defect concentrations below the surface crystal, compared to the defect level in CVD SOS. LI of CVD or Si-implanted SOS in the liquid phase reduces the defect concentration throughout the film thickness, but the regrown films are laterally nonuniform and have a high Al content.
Backward wave oscillation in the gyrotron
Authors: Wachtel J. M. , Wachtel E. J.
Published: February 2003

The electron cyclotron maser instability is shown to support backward wave oscillation in a traveling-wave gyrotron. Numerical values for two parameters that identify oscillation thresholds are determined.
Equivalence between fourth sound in liquid He II at low temperatures and the Biot slow wave in consolidated porous media
Authors: Johnson David Linton
Published: February 2003

The theory of acoustic propagation in porous fluid-filled media developed by Biot is applied to the case where superfluid 4He is in the pores (T<1.1 K where there is a negligible amount of normal fluid). For a consolidated (fused) matrix Biot’s slow compressional wave is shown to be identical to the phenomenon known as fourth sound; V(slow wave/fourth sound)=V(fluid)/n. The index of refraction of fourth sound is related to the ’’structure factor’’α, of the Biot theory by n=α1/2, and so use of the superfluid provides a direct means of measuring α in a given sample. Predictions for the velocities of the fast wave, the shear wave, and the slow wave/fourth sound are made for fused gass bead samples in which Plona has previously reported seeing these three waves under the condition of water saturation.
Nb-Al multifilamentary superconducting composites produced by powder processing
Authors: Akihama R. , Murphy R. J. , Foner S.
Published: February 2003

Multifilamentary superconducting Nb-Al composites were produced using powder processing with high overall critical currents Jc at high magnetic fields. A Nb–3 wt. % Al composite, reacted at 800 °C for 16 h, had Jc ≳104 A/cm2 at 14 T at 4.2 K. Jc was almost independent of strain for strains up to 1.3%.
Carbon-induced amorphous surface layers in Ti-implanted Fe
Authors: Follstaedt D. M. , Knapp J. A. , Picraux S. T.
Published: February 2003

Titanium implantation into high-purity Fe is shown to produce a ternary amorphous surface layer consisting of not only Fe and Ti, but also C. The amorphous layer forms at the surface and grows inward with increasing Ti fluence. The amount of C present also increases with Ti fluence and is believed to be deposited on the surface from the vacuum during implantation and to subsequently diffuse into the sample to produce the amorphous layer. For Ti concentrations ≲10 at.%, the amorphous layer thickness is less than the depth of the implanted Ti, but agrees with C diffusion distances, thus demonstrating that C is an essential constituent of the amorphous phase.
Dynamic range of 106 in depth profiling using secondary-ion mass spectrometry
Authors: Wittmaack K. , Clegg J. B.
Published: February 2003

Limitations in dynamic range previously experienced in SIMS depth profiling are shown to be caused by neutral projectiles present in the primary ion beam. Dynamic ranges of about 106 can be achieved if (i) the final section of the primary beam line and the sample are immersed in a UHV ambient (<10−6 Pa) and (ii) the beam traversing this region is deflected or offset from the gun axis so that energetic neutrals produced in the beam line do not hit the sample.
Structure and compression of crystalline methane at high pressure and room temperature
Authors: Hazen R. M. , Mao H. K. , Finger L. W. , Bell P. M.
Published: February 2003

Methane, CH4, crystallizes in the face-centered cubic metal structure (space group Fm3m) at 15.9 kbar and 20 °C. Cubic unit-cell edges at 16.1, 28.9, 39.5, and 52.1 kbar are 5.4434, 5.3064, 5.1963, and 5.0947 Å, respectively. The isothermal bulk modulus, calculated from a first-order Murnaghan equation of state (K′=4), is 49±9 kbar. Methane transforms to a second as yet unidentified high-pressure solid phase at 52.5 kbar (20 °C).
Arsenic stabilization of InP substrates for growth of GaxIn1−xAs layers by molecular beam epitaxy
Authors: Davies G. J. , Heckingbottom R. , Ohno H. , Wood C. E. C. , Calawa A. R.
Published: February 2003

A new method of cleaning InP substrates under molecular beam epitaxy conditions involving heating to ⩾500 °C in an As4 flux (JAs4 ≃1015–1016 cm−2 s−1) is described. Evidence of surface cleanliness, good morphology, ordered surface reconstruction, and integrity of chemical composition at the interface is given. Lattice-matched layers of Ga0.47In0.53As grown on InP substrates cleaned in this way showed excellent electrical properties: e.g. a room-temperature mobility μ300=8600 cmPu2 V−1 s−1 at n300 =1016 cm−3.
Crystallization-front velocity during scanned laser crystallization of amorphous Ge films
Authors: Chapman Ralph L. , Fan John C. C. , Zeiger Herbert J. , Gale Ronald P.
Published: February 2003

An optical transmission technique has been used to measure the propagation velocity of the crystallization front during scanned laser crystallization of amorphous Ge films on fused-silica substrates. The measurements confirm our theoretical model for the solid-phase amorphous-to-crystalline transformation. According to this model, the periodic structural features of the crystallized films are formed because the crystallization front moves in a series of periodic jumps between rest positions, with the velocity of the front during each jump much higher than the laser scanning velocity. The measured values of the crystallization-front velocity range from 140 to 260 cm/sec, compared with the laser scanning velocity of only 0.5 cm/sec.
Quenching of laser-excited O2(b 1Σ+g) by CO2, H2O, and I2
Authors: Avilés R. G. , Muller D. F. , Houston P. L.
Published: February 2003

The total quenching rates of O2(b 1Σ+g) by CO2, H2O, and I2 have been determined to be (4.53±0.29)×10−13 cm3 molec−1 sec−1, (6.71±0.53)×10−12 cm3 molec−1 sec−1, and (2.04±0.28)×10−11 cm3 molec−1 sec−1, respectively. A pulsed, Raman-shifted dye laser was used to excite a single rotational line of O2(1Σ, v′=0), while subsequent 1Σ→3Σ fluorescence was monitored by a photon counting technique to determine the deactivation rate as a function of the partial pressure of quenching gas. Rate constants for deactivation of O2(1Σ) by CO2 and H2O were found to be consistent with those measured elsewhere, whereas I2 was found to quench O2(1Σ) an order of magnitude more slowly than reported in the literature. The lower total quenching constant for I2 suggests that the reaction O2(1Σ)+I2→O2(3Σ) +2I might not be responsible for dissociation of I2 in the chemical oxygen-iodine laser.
Efficient laser action on the 342-nm band of molecular iodine using ArF laser pumping
Authors: Shaw M. J. , Edwards C. B. , O’Neill F. , Fotakis C. , Donovan R. J.
Published: February 2003

Strong laser action on the 342-nm band of I2 has been obtained by transverse pumping I2/SF6 mixtures at 193 nm with an ArF laser. The highest output energy obtained was 230 mJ at an intrinsic energy conversion efficiency of approximately 30% equivalent to a photon efficiency of greater than 50%.
Confirmation of Biot’s theory
Authors: Berryman James G.
Published: February 2003

Plona’s recent measurements of elastic-wave speeds in a water-saturated porous structure of sintered glass beads are compared quantitatively to the predictions of Biot’s theory. The theoretical predictions lie within the bounds of experimental error (3%) for the fast compressional wave and for the shear wave in all cases. For the slow compressional wave, the theoretically predicted speeds lie within about 10% of the experimental values and increase with increase in porosity as observed. Our model achieves this agreement with no significant free parameters. The frame moduli are estimated using a recently developed self-consistent theory of composite materials. The induced mass of the frame in a water environment is also estimated theoretically.
Measurement of lateral compressive stresses under shock loading
Authors: Gupta Y. M. , Keough D. D. , Henley D. , Walter D. F.
Published: February 2003

Resistance change measurements have been obtained from ytterbium foil gauges, in thin rectangular grooves, placed parallel and normal to the shock front in impact-loaded polymethylmethacrylate (PMMA). Within experimental scatter, the resistance change ratios are in good agreement with the longitudinal and lateral stress ratios obtained from an independent determination in shocked PMMA. These results show the potential for measuring lateral stresses, a development expected to be very useful for shock wave studies.
Open-circuit voltage of induced-junction solar cells
Authors: Alam M. K. , Yeow Y. T.
Published: February 2003

A numerical method is used to evaluate the open-circuit voltage of induced-junction solar cells as a function of substrate doping level and oxide charge. For a given oxide charge there is an optimum doping level at which VOC reaches a maximum. The equilibrium surface potential and the VOC increase with increasing oxide charge. The rate of increase, however, falls off sharply once the semiconductor surface is inverted.
Limitations on luminance characteristics of gas-discharge color display panels
Authors: Mikoshiba Shigeo , Murayama Seiichi
Published: February 2003

Relations between electrical input and optical output of gas-discharge display panels are developed in which resonance radiation from the xenon negative glow is employed to excite phosphor of appropriate color. A panel having optimized cell configuration for maximum luminance can yield white-area luminance of only 10 fL at most when reproducing TV images using a one line at a time addressing technique. The optimization reduces the luminous efficiency to an unrealistically low value.
White photoluminescence of amorphous silicon-carbon alloy prepared by glow-discharge decomposition of tetramethylsilane
Authors: Munekata Hiro , Murasato Shigetaka , Kukimoto Hiroshi
Published: February 2003

An amorphous film of silicon-carbon alloy with approximate composition Si0.1C0.9 was prepared on a fused-quartz, a glass, or a silicon wafer by the glow-discharge decomposition of tetramethylsilane. The film has an optical gap energy as large as 2.8 eV and shows white photoluminescence even at room temperature due to its broad emission band over the whole range of the visible spectrum. The photoluminescence is observable for the films deposited at substrate temperatures below 300 °C.
The use of Young’s modulus to monitor relaxation in metallic glasses
Authors: Kursumovic A. , Scott M. G.
Published: February 2003

The kinetics of change of Young’s modulus E during isothermal relaxation and crystallization of an all-metal glass Cu60Zr40 has been measured by a pulse-echo technique. E increases by about 10% between the as-quenched and fully relaxed states. Crystallization of the glass produces a further 15% increase in E. The kinetics of the relaxation process can be fitted to an expression of the form ΔE=a ln t+b. a)On leave from the Institute of Physics, Saragevo, Yugoslavia.
A direct observation of the trapping of deuterium ions at a grain boundary in tungsten
Authors: Kellogg G. L. , Panitz J. K. G.
Published: February 2003

The imaging atom-probe/field ion microscope has been used to study the trapping of low-energy deuterium ions in tungsten. The experimental results indicate that implanted deuterium does not remain trapped in a tungsten lattice at room temperature for a period of several days unless a defect is present. Time-gated imaging atom-probe images show the first direct correlation between the trapped deuterium and the presence of a grain boundary on an atomic scale. Comparing these results to secondary-ion mass spectrometer and nuclear reaction analyses of simultaneously exposed, flat tungsten, and silicon samples indicates that the imaging atom-probe is sensitive to low levels of hydrogen concentration at lattice defects that are invisible to these other two techniques. The implications of the experiment relating to tokamak plasma-wall and hydrogen embrittlement studies are discussed.
Textured thin-film Si solar selective absorbers using reactive ion etching
Authors: Craighead H. G. , Howard R. E. , Tennant D. M.
Published: February 2003

Solar selective surface photothermal absorbers consisting of thin-film Si with a submicron surface texture have been produced by reactive ion etching an evaporated Si film on a Mo layer. Such surfaces formed on 316 stainless steel and other substrates have solar absorptivities of 0.9 and calculated thermal emissivities of ∼0.2 at 200 °C. These selective surfaces are stable in air to 500 °C.
Measurement of DT neutron-induced activity in glass-microshell laser fusion targets
Authors: Lane Stephen M. , Campbell E. Michael , Bennett Charles
Published: February 2003

Laser fusion targets consisting of DT gas contained in Teflon-coated glass microshells produce 14.1-MeV neutrons that can interact with the 28Si nuclei in the glass to produce radioactive 28Al. Using a very efficient collection-detection scheme that could detect the decay of 10% of the 28Al created, we identified these nuclei by their 1.78-MeV γ ray, which decayed with a 2.2-min half-life. From the number of 28Al nuclei created and the neutron yield the compressed glass areal density was found to be 0.0059 g/cm2.
Optically pumped Iodine monofluoride B3Π(O+)→X1Σ+ laser
Authors: Davis S. J. , Hanko L.
Published: February 2003

An optically pumped iodine monofluoride laser operating on the B3Π(O+)→X2Σ+ system has been demonstrated. Ground-state IF was produced by the reaction of I2+F2 and subsequently excited with a high-energy, broadband dye laser. Lasing was observed on the (2,10), (3,11), (4,9), and (4,10) transitions covering the wavelength range 7200–6500 Å.
A scanning electron microscope study of columnar topography and liquid-crystal alignment on obliquely deposited oxide surfaces at low rates
Authors: Cheng Julian , Boyd G. D. , Storz F. G.
Published: February 2003

We present direct evidence of a columnar topography in obliquely deposited oxide films prepared by thermal and electron beam deposition at low rates. Column size, chaining, and inclination will be described and the correlations with liquid-crystal surface tilt alignment discussed.
Solute trapping by moving interface in ion-implanted silicon
Authors: Campisano S. U. , Foti G. , Baeri P. , Grimaldi M. G. , Rimini E.
Published: February 2003

Experiments are reported for Te and Ag implantation in silicon, as examples of slow and fast diffusers, after furnace or laser annealing. Slow diffusers are substitutionally located at concentrations in great excess of the maximum solid solubility after both processes. Fast diffusers inhibit the solid-phase epitaxial regrowth or are rejected at the sample surface after laser irradiation. Although the epitaxial growth occurs with velocities which differ up to ten orders of magnitude after furnace or laser annealing, the supersaturation is interpreted as due to the same basic mechanism: solute trapping at the moving interface when the residence time is larger than the one monolayer regrowth time. This process is controlled by the diffusion coefficient in the two adjacent phases.
Dielectric hysteresis and rotation of dipoles in polyvinylidene fluoride
Authors: Takahashi Tetsuo , Date Munehiro , Fukada Eiichi
Published: February 2003

Hysteresis curves of the linear dielectric constant, the electric displacement, and the IR absorbance at 1273 cm−1 were observed at −5 °C for a stretched film of polyvinylidene fluoride. The hysteretic polarization was obtained by subtracting the linear electric displacement from the observed electric displacement. Correspondence between hysteretic polarization during the cyclic application of electric field suggests that both originate from rotation of CF2 dipoles in form-I crystals.
High mobility of two-dimensional electrons at the GaAs/n-AlGaAs heterojunction interface
Authors: Hiyamizu S. , Mimura T. , Fujii T. , Nanb K.
Published: February 2003

Mobility of the two-dimensional electron gas as high as 61 500 cm2/V sec, with a carrier concentration of 5.7×1011 cm−2, was obtained at 66 K in a selectively doped GaAs/n-AlGaAs heterojunction structure grown by molecular beam epitaxy. This mobility is a factor of 2–3 larger than any reported so far in similar structures.
Spatially resolved gain measurements in UV preionized homogenous discharge XeCl and KrF lasers
Authors: Watanabe Shuntaro , Alcock A. J. , Leopold K. E. , Taylor R. S.
Published: February 2003

Spatially uniform avalanche discharges of relatively long duration have been obtained in a UV-preionized, high-pressure, rare-gas–halide laser. In the case of XeCl pulse durations as long as 70 ns have been observed. The spatial distribution of the small-signal gain in a plane transverse to the laser axis has been measured. The active discharge cross sections with better than 90% gain uniformity were 2.8×3.0 and 2.8×2.5 cm2 for XeCl and KrF, respectively. The use of neon rather than helium as a buffer gas increased the discharge cross section, and the laser pulse duration resulting in improved laser output energy densities of 4.5 J/l in XeCl and 2.8 J/l in KrF.
Picosecond photoconductivity in radiation-damaged silicon-on-sapphire films
Authors: Smith P. R. , Auston D. H. , Johnson A. M. , Augustyniak W. M.
Published: February 2003

Radiation damage caused by ion implantation is used to control the carrier lifetime in silicon-on-sapphire (SOS) films. Photoconductivity measurements show the relaxation time changes by several orders of magnitude and can be as short as 8 ps. The carrier mobility is found to be at least an order of magnitude higher than amorphous silicon materials with similar relaxation times. A photodetector is described that demonstrates the high-speed capability of these high-defect-density films.
Strain-rate dependence of the effective viscosity under steady-wave shock compression
Authors: Grady D. E.
Published: February 2003

Relationships among Hugoniot pressure, effective viscosity, and strain rate under conditions of steady-wave shock compression are predicted based on the assumption of invariance of a shock property equal to the product of the energy dissipated in shock compression and the rise time of the steady wave. Effective viscosity is found to decrease as η∼ε̇−1/2, while strain rate increases as ε̇∼p4h with Hugoniot pressure. These results are consistent with steady-wave profile measurements on aluminum.
Growth of single-crystal metastable semiconducting (GaSb)1−xGex films
Authors: Cadien K. C. , Eltoukhy A. H. , Greene J. E.
Published: February 2003

Epitaxial metastable (GaSb)1−xGex alloys with compostions across the pseudobinary phase diagram have been grown on (100) GaAs substrates by multitarget rf sputtering. An essential feature allowing the growth of these metastable materials was low-energy ion bombardment of the growing film during deposition to enhance surface diffusion, promote mixing, and preferentially sputter incipient second-phase precipitates. Annealing experiments indicated that the metastable films exhibit good high-temperature stability and that they transform through a continuous series of GaSb-rich and Ge-rich phases in which the solute concentrations decrease until the equilibrium two-phase alloy is obtained. While the calculated free-energy difference between the single-phase metastable and equilibrium states is ∼18 meV, the measured activation barrier for the transformation is ∼3 eV. All films were p-type with room-temperature hole concentrations varying from 1016 to 1019 cm−3 and mobilities between 10 and 720 cm2/ V s, depending on film composition.
Heteroepitaxy of vacuum-evaporated Ge films on single-crystal Si
Authors: Tsaur B.-Y. , Geis M. W. , Fan John C. C. , Gale R. P.
Published: February 2003

Heteroepitaxial Ge films on 〈100〉 and 〈111〉 Si substrates have been prepared by vacuum evaporation. The films were deposited in moderate vacuum (10−6 Torr) at a rate of ∼10 Å/sec, with the substrates heated to 350–750 °C. The crystalline perfection of the films depends on both substrate orientation and temperature. The best films were obtained on 〈100〉 Si substrates heated to 550 °C. Heteroepitaxial GaAs layers of excellent crystal quality have been grown by chemical vapor deposition on such Ge films. GaAs shallow-homojunction solar cells with conversion efficiencies up to 12% at AM1 have been successfully fabricated.
Chemical basis for InP-metal Schottky-barrier formation
Authors: Brillson L. J. , Brucker C. F. , Katnani A. D. , Stoffel N. G. , Margaritondo G.
Published: February 2003

Soft-x-ray photoemission measurements of ultrahigh vacuum-cleaved InP-metal interfaces reveal two classes of microscopic chemical structure. Reactive metal (Al,Ni)-InP interfaces display cation-rich outdiffusion, atomically abrupt microstructure, and low Schottky-barrier height (φSB), while unreactive metal (Au, Cu)-InP interfaces exhibit anion-rich outdiffusion, diffuse microstructure, and high φSB . For InP and other III-V compound semiconductor-metal junctions, chemical bond strength dominates local atomic structure and the type of electrically-active sites produced near the interface. These features can be controlled extrinsically by Al or Ni interlayers.
Amorphous silicon-silicon nitride thin-film transistors
Authors: Powell M. J. , Easton B. C. , Hill O. F.
Published: February 2003

A thin-film field-effect transistor has been fabricated using glow-discharge amorphous silicon as the semiconductor and silicon nitride as the insulator. The transistor operates in the electron (n type) accumulation mode and by changing the gate potential from zero to only 3 V a change in the source-drain conductance of greater than four orders of magnitude is obtained. The results imply upper limits to the density of gap states in amorphous silicon and interface states at the amorphous silicon-silicon nitride interface of 3×1016 cm−3 eV−1 and 5×1011 cm−2 eV−1, respectively.
Synchronously pumped mode-locked CdS platelet laser
Authors: Roxlo C. B. , Salour M. M.
Published: February 2003

We report pulses as short as 8 ps obtained from a mode-locked cw optically-pumped semiconductor laser. The sample was a CdS platelet at a temperature of 95 K longitudinally pumped by a mode-locked Ar+ laser. The output power was 3.2 mW with 8-ps pulses, and powers greater than 10 mW have been observed with 10-ps pulses. Laser performance is quite independent of cavity length as compared to synchronously pumped dye lasers, indicating that passive pulse shaping may be taking place.
Ge-GaAs superlattices by molecular beam epitaxy
Authors: Chang Chin-An , Segmüller Armin , Chang L. L. , Esaki L.
Published: February 2003

We have grown Ge-GaAs superlattices on (100) GaAs by molecular beam epitaxy at ∼400 °C, with individual layer thicknesses ranging from 25 to 1000 Å. Good surface finish and crystalline quality are obtained, except in the lower thickness limit. For configurations where the effect of interdiffusion is shown to be negligible, well-defined periodicity is observed from both x-ray diffraction measurement and Rutherford backscattering spectrometry.
Effects of high angles of convergence on V(z) in the scanning acoustic microscope.
Authors: Sheppard C. J. R. , Wilson T.
Published: February 2003

An investigation is made of the effects of using high numerical aperture acoustic lenses on the V(z) respsonse in acoustic microscopy. Theoretical results are presented for a perfectly reflecting object in an aplanatic system and show marked differences from the paraxial predictions. This suggests that for accurate determination of surface elastic parameters the effects of high angles of convergence should be taken into account.
A note on compositionally modulated Cu-Ni films with lattice-commensurate wavelengths
Authors: Flevaris N. K. , Baral D. , Ketterson J. B. , Hilliard J. E.
Published: February 2003

It has been found that the number and sharpness of the x-ray satellite peaks from Cu-Ni films containing short-wavelength (0.6–11.4 nm) composition modulations (produced by vapor deposition) were strongly dependent on the degree to which the number of monolayers of the components in each period approached integer values. It is demonstrated that this is an important factor in accounting for the difference that has previously been observed between the x-ray spectra from modulated metallic and semi-conductor films.
Time-resolved reflectivity during pulsed-laser irradiation of GaAs
Authors: Lowndes D. H. , Wood R. F.
Published: February 2003

The first comparison of time-resolved reflectivity (TRR) signatures for crystalline and ion implantation amorphized GaAs, during pulsed ruby laser irradiation, is reported. The inferred durations of surface melting are strikingly different for the crystalline and ion-implanted cases. The measurements are in good agreement with the results of thermal melting model calculations for the crystalline case.
3.4-TW performance of a Nd:phosphate glass laser with output aperture of 20 cm
Authors: Kato Y. , Yoshida K. , Kuroda J. , Yamanaka C.
Published: February 2003

A Nd: doped phosphate glass disk amplifier can be scaled to the aperture of 20 cm with the αL product of 4.0. A laser amplifier chain using these high-gain disk amplifiers has delivered output power of 3.4 TW at a pulse width of 100 ps. A very good beam quality has been obtained because of the cleanliness of the optical components.
Single-mode diode laser phase noise
Authors: Dandridge A. , Tveten A. B. , Miles R. O. , Jackson D. A. , Giallorenzi T. G.
Published: February 2003

Measurements have been made of the phase noise of a single-mode diode laser in an unbalanced Michelson interferometer, as a function of optical path difference. The noise increased linearly with increasing optical path difference. The origin of the phase noise is discussed.
Fermi level and surface barrier of GaxIn1−xAs alloys
Authors: Wieder H. H.
Published: February 2003

The surface Fermi level of n-type GaxIn1−xAs alloys is displaced as a function of x from above the conduction band minimum of InAs to the lower half of the band gap of GaAs. Fermi-level pinning is attributed to an As vacancy-related energy level located ∼0.5 eV above the valence band and invariant with x.
Vacancies in Al after pulsed electron beam melting
Authors: Follstaedt D. M. , Wampler W. R.
Published: February 2003

We have used transmission electron microscopy (TEM) to study the retention of vacancies in Al after rapid melting and resolidification of a thin (∼ 3 μm) surface layer using a pulsed (∼50 ns) electron beam. After pulsing and aging at room temperature, TEM examination showed dislocation loops, which are interpreted to be due to the coalescence of the quenched-in vacancies on {111} planes as is the case for the loops observed in earlier furnace quenching studies. Our results indicate that the rapid melting and resolidification leaves a high vacancy concentration (∼100 ppm) in the resolidified Al. Heat transport calculations show that cooling rates for the pulse heated samples (∼108 K/s) are much higher than those achieved by conventional quenching techniques (∼ 104 K/s).
Imaging of dopant regions in silicon with thermal-wave electron microscopy
Authors: Rosencwaig Allan , White Richard M.
Published: February 2003

Thermal-wave electron microscopy has been used at 640-kHz modulation frequency to detect and image P-doped Si regions in a bare Si wafer.
Degenerate four-wave mixing in the nematic phase of a liquid crystal.
Authors: Khoo I. C.
Published: February 2003

We have observed degenerate four-wave mixing process in a nematic liquid-crystal film using low-power cw lasers. The conversion efficiency was measured to be about 10−4 for incident optical intensities on the order of 10 W /cm2. The effect is arttributed to optically induced molecular reorientation.
Acoustic bulk wave composite resonators
Authors: Lakin K. M. , Wang J. S.
Published: February 2003

This letter reports on a new and unique form of acoustic bulk wave resonator composed of a thin film of ZnO sputtered onto a thin Si membrane supporting structure. The piezoelectric ZnO is used to excite a longitudinal bulk wave which reflects from the free surface of the film and membrane. The structure thus forms an acoustical cavity which exhibits parallel and series electrical resonance responses at the ZnO film electrodes for both even and odd order modes. Fundamental resonant frequencies near 500 MHz have been achieved with parallel resonant Q’s over 9000. The temperature coefficient of resonant frequency was found to be −31 ppm for a Si to ZnO thickness ratio of six.
Collection efficiency of low-mobility solar cells
Authors: Reichman Joseph
Published: February 2003

An equation for the collection efficiency (i.e., internal quantum efficiency) is derived that can be used for Schottky barrier, metal-insulator- semiconductor, or semiconductor-electrolyte junction solar cells. It is obtained from an exact solution of the transport equation in the space-charge region and includes the effects of photogenerated majority carriers. It is shown that these carriers can diffuse to the interface and thereby oppose the minority-carrier photocurrent by recombination or emission. This effect is shown to be quite significant in reducing the collection efficiency when the majority-carrier mobility is low and at short wavelengths where the absorption coefficient becomes large.
Reactive ion beam etching of InP with Cl2
Authors: Bösch M. A. , Coldren L. A. , Good E.
Published: February 2003

Reactive ion beam etching of InP with chlorine gas under oblique angles of incidence is reported. This process offers the important advantage of edge profile control. The etch rate is strongly dependent upon the ion energy, manifesting a plateau approaching 0.2 μm/min for a chlorine beam of less than 1 keV. At normal incidence of the ion beam the walls are sloped outward by about 17°. A mesa-type structure with straight, smooth vertical walls has been fabricated by spinning the substrate under oblique ion beam incidence.
Quantum noise theory for the dc SQUID
Authors: Koch Roger H. , Van Harlingen D. J. , Clarke John
Published: February 2003

The noise temperature of a dc superconducting quantum interference device (SQUID) coupled to a tuned input circuit is computed using the complete quantum expression for the equilibrium noise in the shunt resistance of each junction. At T = 0, where the noise reduces to zero-point fluctuations, the noise temperature for an optimized system is hn/kB ln2, where n is the signal frequency. The computation is extended to nonzero temperatures, and it is shown that a SQUID operated at 1K can approach the quantum limit.
X-ray photoemission studies of superficially oxidized cesium antimonide photoemitters
Authors: Bates C. W. , van Atekum Th. M. , Wertheim G. K. , Buchanan D. N. E. , Clements K. E.
Published: February 2003

Superficially oxidized cesium antimonide photoemitting surfaces prepared in ultrahigh vacuum were studied by x-ray photoelectron spectroscopy. Oxidation of Cs3Sb to produce a surface with enhanced photosensitivity converts part of the antimony to elemental antimony and part of the cesium to cesium suboxide. The latter is identified on the basis of an O1 s peak at 531.3 eV, characteristic of Cs11O3. The production of Cs2O is not ruled out in this process since its signature at 527.5 eV is masked by an antimony shake-up peak at 527 eV.
Monolithic two-section GaInAsP/InP active-optical-resonator devices formed by reactive ion etching
Authors: Coldren L. A. , Miller B. I. , Iga K. , Rentschler J. A.
Published: February 2003

Narrow, high-aspect-ratio grooves formed by reactive ion etching (RIE) are shown to be useful as partially transmissive mirrors for coupled active laser-detector, laser-modulator, and laser-etalon two-section monolithic devices. Results emphasize control of the longitudinal mode spectrum by active etalon action.
Study of x-ray preionized avalanche discharge XeCl laser at high gas pressures
Authors: Shao-Chi Lin , Zhi-xiang Bao , Guang-yuan Gong , Yun-sheng Huo , Ju-ping Shu , Shi-qing Tang , Yun-rong Wei , Cheng-en Zheng
Published: February 2003

In an x-ray preionized, transmission-line-driven avalanche-discharge apparatus of approximately 70-nsec electrical length and 0.19-l active volume, we have obtained XeCl laser output pulse energy in excess of 1 J from a relatively lean HCl/Xe/Ne mixture. This corresponds to an output pulse energy density which is greater than 5 J/l. More significantly, the laser output and efficiency are found to increase linearly with the gas pressure up to at least 5 atm with no sign of saturation.
Brillouin scattering from GaS under hydrostatic pressure up to 17.5 GPa
Authors: Polian A. , Besson J. M. , Grimsditch M. , Vogt H.
Published: February 2003

Brillouin scattering in GaS crystals had been measured under hydrostatic pressures up to 17.5 GPa. Frequency shifts of the Brillouin lines give the pressure dependence of the elastic constants C11 and C33, and the index birefringence. Exponents derived from Murnaghan’s equation of state are compared with a Lennard-Jones description of interatomic forces in GaS.
Laser photochemical microalloying for etching of aluminum thin films
Authors: Ehrlich D. J. , Osgood R. M. , Deutsch T. F.
Published: February 2003

A new technique for controlled etching of micrometer-size regions on thin films has been developed. Dopant atoms are deposited on the film surface by UV laser photodissociation of a gas and incorporated by simultaneous heating with a visible laser beam. The process has been demonstrated by laser alloying Al films with Zn to produce localized chemically reactive regions of Zn/Al alloy.
Light-induced dangling bonds in hydrogenated amorphous silicon
Authors: Dersch H. , Stuke J. , Beichler J.
Published: February 2003

After intensive and long illumination of undoped a-Si:H samples the dark ESR signal is considerably enhanced. The g value of 2.0055 and the linewidth DHpp = 6–7 G leads to the conclusion that the light-induced defects are single dangling bonds. They disappear again by thermal anneal at about 220 °C.
Limits of applicability of the depletion approximation and its recent augmentation
Authors: Bartelink D. J.
Published: February 2003

A general analysis of nonuniformly doped, one-dimensional space-charge layers in the Boltzmann approximation is presented from which a direct connection is established to the depletion approximation. An error equation is derived with no additional approximations other than for the neglect of minority-carrier effects for relating the difference between the electric field and potential in depletion approximation and the Boltzmann approximation. From this error equation, the validity of the depletion approximation and its extension to include space-charge effects in the undepleted bulk are evaluated.
A microwave-pumped XeCl* laser
Authors: Mendelsohn A. J. , Normandin R. , Harris S. E. , Young J. F.
Published: February 2003

A XeCl* excimer laser excited by 2-ms-long, 9.375-GHz microwave pulses has been constructed. Spontaneous emission times of ∼500 ns have been observed, while the maximum laser pulse length was 100 ns. The laser pulse length appears to be limited by the buildup of a transient loss.
Pure shear elastic surface wave guided by the interface between two semi-infinite magnetoelastic media
Authors: Camley R. E. , Maradudin A. A.
Published: February 2003

An acoustic shear surface wave can be guided by the interface between two semi-infinite media in contact across a planar interface, if at least one of the two media is magnetoelastic. The dispersion relation for such a wave is obtained in the case that it propagates in a direction normal to the direction of the spontaneous magnetization in each medium, which is assumed to be parallel to the interface. A solution of the dispersion relation is obtained analytically for a particular simple case.
Lack of importance of ambient gases on picosecond laser-induced phase transitions of silicon
Authors: Liu J. M. , Yen R. , Donovan E. P. , Bloembergen N. , Hodgson R. T.
Published: February 2003

A 10-nsec pulsed ruby laser was used to prepare atomically clean silicon surfaces in UHV. With picosecond Nd:YAG laser pulses at 532 amd 266 nm, the amorphous patterns formed on the atomically clean silicon surfaces in UHV were compared with those formed in air and other ambient conditions. Results show that the picosecond laser-induced phase transition of silicon does not depend on the ambient conditions or on the native surface oxide layer of silicon.
Matrix-addressable electrochromic display cell
Authors: Beni G. , Schiavone L. M.
Published: February 2003

We report an electrochromic display cell with intrinsic matrix addressability. The cell, based on a sputtered iridium oxide film (SIROF) and a tantalum-oxide hysteretic counterelectrode, has electrochromic parameters (i.e., response times, operating voltages, and contrast) similar to those of other SIROF display devices, but in addition, has short-circuit memory and voltage threshold. Memory and threshold are sufficiently large to allow, in principle, multiplexing of electrochromic display panels of large-screen TV pixel size.
ϑ-pinch ionization for field-reversed configuration formation
Authors: Armstrong W. T. , Cochrane J. C. , Commisso R. J. , Lipson J. , Tuszewski M.
Published: February 2003

The behavior of a plasma produced by a ringing ϑ-pinch discharge in the presence of a 2.3-kG bias field is examined for the case where the net field passes through zero. Experimental studies, employing internal and external field probes, indicated ∼50% of the initially applied bias flux is excluded by the plasma with this ionization technique. A theoretical model incorporating field diffusion and elastic ion-neutral collisions is used to describe the observed dynamics of the plasma sheath.
A tandem photovoltaic cell using a thin-film polymer electrolyte
Authors: Skotheim T.
Published: February 2003

A tandem photovoltaic cell has been fabricated using a thin-film plastic electrolyte to connect in optical and electrical series an n-type CdS thin-film and a p-type CdTe single crystal. The electrolyte was a thin film of poly(ethylene oxide) with a polysulfide redox couple. An open circuit voltage of 625 mV and a short-circuit current of 35 μA/cm2 were obtained under illumination of 100 mW/cm2 with a xenon lamp. The cell output in the present configuration is limited by the series resistance and insufficient band bending in the semiconductor electrodes due to unfavorable resistance matching of the components.
Origins of acoustic emission in superconducting wires
Authors: Tsukamoto O. , Sinclair M. W. , Steinhoff M. F. , Iwasa Y.
Published: February 2003

Origins of acoustic emission (AE) in superconducting wires have been investigated. Our experimental results indicate that wire motion is a dominant source of AE in current carrying wires, both superconducting and nonsuperconducting. Furthermore, the results show that flux motion, except during flux jumping, produces no discernable acoustic signals. Both of these conclusions differ from the conclusions of earlier AE results, which attributed the major source of AE signals in superconductors and superconducting magnets to flux motion.
Generation of optical pulses shorter than 0.1 psec by colliding pulse mode locking
Authors: Fork R. L. , Greene B. I. , Shank C. V.
Published: February 2003

We report a novel passive mode-locking technique in which two synchronized counterpropagating pulses interact in a thin, saturable absorber to produce a short pulse. Continuous stable trains of pulses shorter than 0.1 psec are obtained using a ring laser configuration.
New method for control of Schottky-barrier height
Authors: Brucker C. F. , Brillson L. J.
Published: February 2003

Ultrathin reactive Al interlayers at ultrahigh vacuum-cleaved Au-CdS, CdSe single-crystal interfaces have been used to continuously tune the effective Schottky-barrier height over the full range reported for metals on these prototypical II-VI semiconductors, i.e., 0–0.8 eV. Measured electrical transport properties are correlated with observed features of atomic interdiffusion chemistry and valence electronic structure.
Induced back-surface field solar cells on p-type silicon substrates
Authors: Tarr N. G. , Pulfrey D. L. , Iles P. A.
Published: February 2003

Recent research has shown that negative-barrier metal insulator semiconductor (MIS) contacts can exhibit the same minority-carrier reflecting properties as diffused back-surface field regions. This letter describes the use of negative-barrier platinum-MIS contacts to form the first induced back-surface field solar cells on p-type silicon substrates.Pt-SiOx -pSi back contacts have been applied both to cells with diffused front junctions and to cells with minority-carrier injecting MIS front junctions. In both cases an enhancement in open-circuit voltage comparable to that obtained with diffused back-surface fields has been observed. The negative-barrier MIS contact has also been found to increase the infrared photocurrent.
Analog-to-digital conversion experiments using a LiNbO3 balanced bridge modulator
Authors: Yamada Syoji , Minakata Makoto , Noda Juichi
Published: February 2003

One-bit electro-optical analog-to-digital conversions of up to 100-MHz signals were carried out in a system using a Ti-diffused LiNbO3 balanced bridge modulator and a 1.15-μm cw He-Ne laser. The modulators have a new configuration with a phase shifter formed by Ti double diffusants and revealed relatively low half-wave voltages and high extinction ratios.
The effect of growth conditions on Si incorporation in molecular beam epitaxial GaAs
Authors: Chai Y. G. , Chow R. , Wood C. E. C.
Published: February 2003

The unity sticking coefficient of Si and the good electrical and optical properties of Si-doped films make Si a near ideal dopant for GaAs grown by molecular beam epitaxy (MBE). However, the incorporation mechanism of Si at high doping levels differs from that at moderate levels. We found that the maximum doping concentration that can be obtained with Si is 6×1018 cm−3. Above this doping concentration Si precipitates, causing a decrease in the free-carrier concentration and the mobility. A detailed discussion of the incorporation mechanism at high doping, and the effects of the substrate temperature and As4/Ga ratio on Si incorporation at moderate doping is presented.
Chaos and noise rise in Josephson junctions
Authors: Pedersen N. F , Davidson A.
Published: February 2003

Digital computer simultations have been used to map parameters of the transition to chaos in an rf current driven Josephson junction. Our results are qualitatively like those reported by others using analog techniques, but differ quantitatively. Our calculations show that the parameters for the onset of chaos are the same as those required for high parametric gain. This leads to the conclusion that the ’’noise rise’’ in Josephson junction parametric amplifiers is due to chaos.
Oxidant transport during steam oxidation of silicon
Authors: Mikkelsen J. C.
Published: February 2003

Secondary ion mass spectrometry was used to measure the 18O profiles in thermally grown SiO2 which had been treated in H2 18O steam. The oxygen isotope exchange between the water and the network proceeds rapidly at 800 °C, completely exchanging a 180-nm film in ∼20 min. Even at 400 and 600 °C, where negligible Si oxidation occurs, the network oxygen can be completely isotopically exchanged. The exchange profiles are analyzed in terms of the competing reactions involving water molecules and the SiO2 network. Similar measurements of the deuterium (D) profiles in D2O-treated films are consistent with diffusion of molecular water and its reaction with the network to transport both hydrogen and oxygen through the thermal oxide. Our results are compared to related studies which used 18O nuclear resonance analysis.
Dependence of electron mobility in modulation-doped GaAs-(AlGa)As heterojunction interfaces on electron density and Al concentration
Authors: Störmer H. L. , Gossard A. C. , Wiegmann W. , Baldwin K.
Published: February 2003

The electron mobility of single modulation-doped GaAs-(AlGa)As heterojunctions is strongly dependent on electron density and Al concentration. A low-temperature persistent photoconductive effect is employed to vary the areal electron density continuously within a single sample by nearly a factor of 3. Over this density range the mobility increases monotonically by as much as a factor of 4, quasilinear with density. At equivalent carrier concentrations heterojunctions with lower Al concentration show higher mobilities. At low temperatures a peak mobility of 365 000 cm2/Vs is found at an areal density of 7.0×1011 cm−2 with an interparticle spacing equivalent to a three-dimensional density of 5.9×1017 cm−3.
Time resolved luminescence of photoexcited p-type gallium arsenide by population mixing
Authors: Rosen D. , Doukas A. G. , Budansky Y. , Katz A. , Alfano R. R.
Published: February 2003

A novel technique in time resolved luminescence spectroscopy called population mixing using a subpicosecond cw mode-locked dye laser has been developed and applied to p-type GaAs at low temperatures. Using this technique the relaxation lifetime for electron recombination was measured to be 39±7 ps for p-type GaAs with Zn at 6×1018 cm−3 hole concentration. This is comparable to the relaxation time measured by a streak camera.
Detection of gas mixing processes by resonant photoacoustic spectroscopy
Authors: Röper J. , Hess P.
Published: February 2003

An apparatus for an accurate, repeated measurement of the acoustic resonance frequencies of a photoacoustic cell is described. The shift of the resonance frequency of the first radial mode, caused by mixing of CH4 and N2 in the resonator, is monitored by repeated recording of the acoustic resonance curves. The time needed to reach the equilibrium concentrations varies between minutes and several days depending on the mixing procedure employed and the composition of the gas mixture. It is shown that condensation of the gases for a short time accelerates the mixing process considerably.