bluuebunny/crossref_metadata_2025 huggingface dataset:
Subthreshold velocity-field characteristic of n-type indium phosphide at 77 K
Authors: Hamilton D. K.
Published: February 2003

Measurements of the subthreshold velocity-field characteristic at 77 K using a direct technique show reasonable agreement with theoretical predictions, but show a lower threshold field. Comparisons of threshold values of field and velocity with extrapolations from other measured and theoretical data are favorable.
Space-charge effects on particle diagnostics of laser-produced plasmas
Authors: Gitomer S. J. , Brysk H.
Published: February 2003

We have considered the interaction between a laser-produced plasma and a grounded conducting cylindrical aperture. Space-charge effects both within and beyond the aperture are treated in an approximate analysis. We apply our results to recent ion pinhole measurements to show that space-charge effects can account for the data obtained.
Effect of ionizing radiation on the optical attenuation in doped silica and plastic fiber-optic waveguides
Authors: Friebele E. J. , Gingerich M. E. , Sigel G. H.
Published: February 2003

The radiation-induced optical attenuation has been measured over a wide range of dose and time in state-of-the-art step- and graded-state 60Co and pulsed electron irradiation. Results are reported for previously uncharacterized silica fibers containing dopants such as Ge,P,B,F,Tl, and Cs. At short times following the irradiation, fibers which contain Ge exhibit an extremely high attenuation that is not observed when these fibers contain P. Recovery is typically more complete in the silica core fibers than in the doped silica core fibers, which can have losses 25–1000 times the intrinsic loss 3 months after an irradiation of 105–106 rad.
Light-sensitive surface-barrier generation of acoustic volume waves
Authors: Holt R. M. , Fossheim K. , Raaen A. M.
Published: February 2003

A new method for generation and detection of acoustic volume waves in nonpiezoelectric dielectrics is described. The acoustic intensity is sensitive to band-gap illumination. Acoustic conversion is observed on inserting the sample in a reentrant cavity, in contact with the center post during application of rf pulses. The induced conversion efficiency builds up with a time constant in the range of seconds to minutes depending on the nature of the metal dielectric contact and on rf pulse repetition rate. Acoustic signals of 75 dB above noise have been generated in KTaO3. Very long storage times are observed. A model for the transducer action based on induced space charge and a surface barrier is proposed, similar to the model of Fossheim and Bjerkan for surface-wave generation in nonpiezoelectric dielectrics. The estimated electromechanical coupling coefficient is comparable to that of piezoelectric LiNbO3 and LiTaO3.
Observation of electron-neutral inverse bremsstrahlung in an electron-beam-sustained discharge
Authors: Alroy Shimshon , Christiansen Walter H.
Published: February 2003

The absorption of 10.6-μ and 2.8-μ radiation by inverse bremsstrahlung in an electron-beam-sustained discharge is measured in several gases as a function of E/N. The experimentally derived absorption cross sections are compared with theoretical predictions and good agreement is shown.
Emission spectrum of the ν3 band of SF6 at 1780 °K
Authors: Bott J. F.
Published: February 2003

The author measured the emission spectrum of the ν3 band of SF6 at 1780 °K in a shock tube. At this high temperature, the emission peaks at a frequency of 907 cm−1 (11.02 μ); at room temperature, the band has a peak intensity at 948 cm−1. Lyman and Nowak observed similar but proportionately smaller shifts of the spectral maximum to lower frequencies at temperatures between 400 and 800 °K. A knowledge of the high-temperature spectral distribution of the ν3 band is important for the design and interpretation of isotope separation experiments in which SF6 is dissociated by selective multiphoton absorption of CO2 laser photons.
The radiative lifetime and quenching of KrF
Authors: Quigley G. P. , Hughes W. M.
Published: February 2003

Excitation of atomic krypton in the presence of molecular fluorine by a wavelength-selective 2.5-ns-long argon excimer photolytic source was used to initiate the reaction sequence resulting in the formation of excited KrF. The radiative lifetime of the KrF* laser transition was found to be 9 ns at the high-pressure limit. This is in good agreement with the calculated values. The rate constant for two-body quenching of KrF* by F2 is 5.7±0.5×10−10 cm3 s−1 and the rate constant for three-body quenching by Kr is 2.9±0.3×10−31 cm3 s−1.
Pressure dependence of the deep level associated with oxygen in n-GaAs
Authors: Zylbersztejn A. , Wallis R. H. , Besson J. M.
Published: February 2003

Transient capacitance measurements have been performed on Schottky barriers on n-GaAs containing the deep electron trap associated with oxygen, as a function of hydrostatic pressure. It is found that the oxygen level separates from the conduction band at a linear rate of 3.8±0.3 meV/kbar. From a comparison with published optical data we conclude that most of this variation comes from a pressure-dependent Frank-Condon shift and that the unoccupied level separates very little from the valence band.
Measurement of forward and reverse signal transfer coefficients for an rf-biased SQUID
Authors: Giffard R. P. , Hollenhorst J. N.
Published: February 2003

Comprehensive measurements of the parameters characterizing an rf-biased SQUID as a linear twoport are described. The behavior of the device corresponds in detail to the predictions of a recently published model of SQUID operation and is unexpectedly similar to that of a conventional reactive parametric amplifier. The measurements have been used to make the first reliable predictions of the noise temperature and optimum source impedance of an rf-biased SQUID.
The role of buffer gases in optoacoustic spectroscopy
Authors: Thomas III Launey J. , Kelly Michael J. , Amer Nabil M.
Published: February 2003

The dependence of an acoustically resonant optoacoustic signal on the molecular weight and thermodynamic and transport properpties of the buffer gas is reported. Our results show that careful selection of such gases can significantly increase the sensitivity and flexibility of optoacoustic spectroscopy. We also demonstrate that such thermodynamic quantities as γ (≡Cp/Cv) and sound velocity can now be measured readily and accurately. Other potential applications are suggested.
The design of efficient broadband wedge transducers
Authors: Fraser J. , Khuri-Yakub B. T. , Kino G. S.
Published: February 2003

A simple coupled-mode theory has been developed for acoustic-surface-wave wedge transducers. Surface-wave transducers have been fabricated to operate on aluminum using water as the wedge material. The measured efficiency was 68% at 2.75 MHz, the theoretical value being 81%. Transducers have also been fabricated to operate on glass with a rubbery solid, RTV 615, as the wedge material. The experimental and theoretical efficiencies of this transducer at 3.2 MHz were 35 and 50%, respectively. The surface-wave leakage coefficient of RTV 615 on glass has been measured and found to be in excellent agreement with theory.
High-efficiency secondary electron emission produced by ions incident on a porous MgO-Ag layer
Authors: Koshida Nobuyoshi , Yoshida Shigetomo
Published: February 2003

High-efficiency secondary electron emission due to incident ions was obtained from a porous MgO-Ag layer prepared from a suspension of MgO, MgCO3 powder, and Ag paste. Field-dependent secondary emission yield larger than unity was achieved under relatively low-energy ion bombardment. The introduction of Ag produces a uniform surface potential and therefore results in a stable secondary emission current. This type of emitter is potentially useful for application in gas-discharge devices.
Photoelectron emission from small particles suspended in air
Authors: Schmidt−Ott A. , Siegmann H. C.
Published: February 2003

Electrical conductivity caused by photoelectron emission from ultrafine particles suspended in a gas has been observed; one obtains information on the concentration as well as on the size of the particles. Furthermore, some bulk and surface properties of small particles not in contact with any substrate can be investigated at any temperature via the photoelectric threshold and the yield of photoelectrons. The method is extremely sensitive, i.e., measurements can be made at a very low particle concentration (∼103 cm−3) and small particle radii (<50 Å).
Interfacial recombination velocity in GaAlAs/GaAs heterostructures
Authors: Nelson R. J. , Sobers R. G.
Published: February 2003

Photoluminescence time-decay measurements on Ga0.5Al0.5As/GaAs double heterostructures were made over a wide range of GaAs active layer thickness and doping levels at room temperature. Observed decay times τ in variously doped GaAs samples range from 10 to 450 nsec. Effects of self-absorption of luminescence and doping level are demonstrated for GaAs layer thickness d≳1 μm. For d<1 μm, the observed decay times are nearly independent of doping level and vary almost linearly with d. The data are interpreted in terms of a small interfacial recombination velocity (Si=450±100 cm/sec) at the Ga0.5Al0.5As/GaAs interface. The value of Si determined here is an average over the doping levels examined.
Intense ion-beam neutralization in free space
Authors: Humphries S.
Published: February 2003

Electron neutralization is a key feature in the propagation of intense ion beams. A one-dimensional sheath solution is given that demonstrates how electrons are captured by a transient ion beam emerging into a field-free vacuum. Conditions for space-charge and current neutralization are discussed. The importance of the electron distribution in determining the minimum spot size of a focused ion beam is considered.
Surface-potential decay in naphthalene
Authors: Campos M. , Giacometti J. A.
Published: February 2003

Surface-potential decay in naphthalene single crystals was measured after a negative corona discharge on the samples. These potential decay curves do not reach zero value, which is attributed to charges which have been trapped on their way through the sample. The value found for the trap-modulated mobility at room temperature was 10−8 cm2 V−1 s−1 and its dependence on temperature was adequately described by an Arrhenius equation, with activation energy of (0.60±0.03) eV.
A high-sensitivity composite poly-(methyl methacrylate) resist
Authors: Horwitz C. M.
Published: February 2003

A composite PMMA resist is described with a linear sensitivity of 10−10 C/cm for a 0.8-μm resist thickness. It uses a simple one-step development process, gives a pronounced undercut profile suitable for metal lift-off, and to date has allowed interline spacings of 1.5 μm in 0.4-μm-thick resist. Some development and exposure characteristics are described.
Grain size dependence in a self-implanted silicon layer on laser irradiation energy density
Authors: Tseng W. F. , Mayer J. W. , Campisano S. U. , Foti G. , Rimini E.
Published: February 2003

The transformation of amorphous Si layers to polycrystalline material induced by Q-switched ruby laser single pulses of 20 and 50 nsec duration has been investigated. The analysis has been performed by transmission electron microscopy and by channeling measurements using 2.0-MeV He+ Rutherford backscattering. The average grain size of the polycrystalline layers increases with the incident energy density of the laser pulse in the range 0.6–1.7 J/cm2. A transition to single-crystal layers is found for incident energy densities around 2.0 J/cm2. The grain size correlates with incident energy density (J/cm2) rather than incident power density (MW/cm2) for these pulse durations.
Transient heat transfer to liquid helium and temperature measurement with a response time in the microsecond region
Authors: Schmidt Curt
Published: February 2003

A method to measure the heat transfer from a solid surface to liquid helium in the transient mode with a time resolution in the microsecond range is described. A monofilamentary NbTi/Cu compound conductor 52 μm in diameter is used as a heater by applying a current ≳Ic and, via the temperature dependence of Ic, as thermometer with a response time below 10 μsec. Transient heat transfer can be described by a heat-flow-independent transfer coefficient h=5 W/cm2 K below a ’’take-off’’ time t1. At t1 the heat-transfer coefficient decreases rapidly due to the onset of film boiling. t1 is related to the heat flow Q by the expression t1∝Q−2.
Oxygen effects on arsenic diffusion in silicon dioxide
Authors: Tsukamoto Katsuhiro , Akasaka Yoichi , Horie Kazuo
Published: February 2003

The diffusion mechanism of arsenic implanted into silicon dioxide is studied by the MeV He+ backscattering method. The diffusion coefficient of elemental arsenic in silicon dioxide is extremely small, i.e., smaller than 1×10−17 cm2/sec at 1200°C. The arsenic diffusivity in silicon dioxide is enhanced by introducing extra oxygen into silicon dioxide from an oxidizing atmosphere or by additional oxygen implantation. Arsenic interacts with the extra oxygen, and an arsenic-oxygen compound might be formed which has a much larger diffusivity than elemental arsenic.
High-field measurements of anisotropy of H
c2 and effect on grain-boundary flux pinning in V3Si
Authors: Foner S. , McNiff E. J.
Published: February 2003

Measurements of the anisotropy δ (T) = (Hc2[100]−Hc2[110])/H̄c2 of single-crystal V3Si are presented which show that δ (T) is small and essentially temperature independent for a variety of crystals with residual resistance ratios from 17 to 60. The effects of δ on flux pinning in V3Si is much smaller than estimated earlier.
Theoretical analysis of the electrically excited KrF laser
Authors: Lacina W. B. , Cohn D. B.
Published: February 2003

The results obtained from a comprehensive theoretical model for an electrically excited laser are compared with experimental data obtained from a large-volume KrF laser device, excited by an e−-beam only, or with enhancement from an electric discharge.
Annealing of Te-implanted GaAs by ruby laser irradiation
Authors: Golovchenko J. A. , Venkatesan T. N. C.
Published: February 2003

A single pulse of ruby laser radiation is shown to cause significant regrowth in the amorphous region of heavily ion-implanted GaAs. The implanted Te atoms and the host material both show good channeling dips, suggesting essentially complete substitutionality of the Te. There has been only a minor redistribution of the tellurium atoms. The resulting local Te concentration in the laser-irradiated sample is more than ten times the known maximum solubility of Te in GaAs.
Transient behavior of a nonlinear Fabry-Perot
Authors: Bischofberger T. , Shen Y. R.
Published: February 2003

We have carried out a theoretical and experimental study on the transient characteristics of a nonlinear Fabry-Perot filled with Kerr liquid. Agreement between theory and experiment is excellent. Characteristic curves for the steady-state operation are deduced.
Variable frequency SAW resonators on ferroelectric-ferroelastics
Authors: Coldren L. A. , Lemons R. A.
Published: February 2003

High-Q SAW grating resonators with tunabilities approaching 1% are possible on certain ferroelectric-ferroelastic crystals such as Gd2(MoO4)3. The resonant frequency is tuned by electronically varying the width of a small domain with different acoustic velocity within the resonator cavity. Experimental results at ∼92.6 MHz are presented.
Formation of strong E-layers by intense electron-beam injection into preformed plasmas
Authors: Smith A. C. , Fleischmann H. H. , Condit W. C.
Published: February 2003

Intense electron-beam injection into preformed plasmas in the RECE-Berta and CHIP devices at Cornell led to the formation of electron layers with 25 and 80% field-reversal strength, and lifetimes of 400 and 150 μsec, respectively. A pronounced ’’stalling’’ of the beam in the vicinity of the injector is observed in RECE-Berta.
A new method for determining the pyroelectric coefficient of thin polymer films using dielectric heating
Authors: Sussner H. , Horne D. E. , Yoon D. Y.
Published: February 2003

Using polarized poly(vinylidene fluoride) films we have demonstrated a new method for determining the pyroelectric coefficient of thin polymer films. In contrast to previous techniques, we utilize the dielectric absorption of the sample itself by applying a radio-frequency pulse to generate heat uniformly throughout the film. The pyroelectric coefficient is obtained without any further calibration by measuring simultaneously the generated charge. Since a spatially uniform temperature increase is achieved in the order of milliseconds, the values obtained represent a true average of the bulk polarization regardless of its spatial distribution.
Fabrication of deep square wave structures with micron dimensions by reactive sputter etching
Authors: Lehmann H. W. , Widmer R.
Published: February 2003

Square wave gratings with periodicities as small as 1.4 μm have been etched into fused quartz by reactive sputter etching in CF4 and CHF3. Grooves with a perfectly rectangular cross section have been etched with a depth of up to 3 μm. The etching is probably due to highly reactive species produced directly on the substrate surface by an ion-induced dissociation process.
Coherent excitation of vibration and direct measurement of the dephasing time with synchronously mode-locked dye lasers
Authors: Lee Chi H. , Ricard D.
Published: February 2003

A new application of a synchronously mode-locked dye laser has been demonstrated. The 1086-cm−1 optical phonon of calcite was coherently excited by the pump and dye laser pulses and its dephasing time measured. The result, 7.1±1 ps at room temperature, agrees well with the Raman linewidth measured on the same sample.
Formation and quenching of XeF* in Ne/Xe/F2 mixtures
Authors: Rokni M. , Jacob J. H. , Mangano J. A. , Brochu R.
Published: February 2003

Recent laser results in XeF* show a considerable improvement when the Ar buffer is replaced by Ne. In this letter we report on the investigations of the formation and quenching processes in typical laser mixtures of Ne/Xe/F2. From our experimental observations, it appears that the Ne ions formed by the fast electrons do not form Xe+ by a direct charge transfer. We have also determined that the two-body quenching of XeF* by Ne is negligible, while the three-body quenching rate constant is 2.5×10−33 cm6/sec. Finally, the three-body quenching rate constant for XeF*+Xe+Ne is 7.8×10−31 cm6/sec.
Electron-beam-controlled discharge HgCl* laser
Authors: Tang Kenneth Y. , Hunter R. O. , Oldenettel J. , Howton C. , Huestis D. , Eckstrom D. , Perry B. , McCusker M.
Published: February 2003

Laser action of HgCl* was observed using an electron-beam-controlled discharge to pump a gas mixture of Hg/Cl2/Ar. An order of magnitude in the fluorescence enhancement was obtained. This gives an excitation efficiency by controlled discharge to be a factor of about 2 higher than that by direct electron-beam pumping. In addition to the previously reported 5576-Å laser transition of HgCl*, a strong transition at 5584 Å was also observed.
InP-GaxIn1−xAsyP1−y double heterostructure for 1.5 μm wavelength
Authors: Nagai Haruo , Noguchi Yoshio
Published: February 2003

InP/GaxIn1−xAsyP1−y/GaxIn1 −x AsyP1−y double-heterostructure LED’s in a 1.5-μm-wavelength region have been fabricated by the LPE method. The half-width value of the spectrum is about 1100 Å, and the external quantum efficiency is 1.5% for undoped active layers of Ga0.28In0.72As0.77P0.23. The threshold current density of the laser oscillation at 1.52 μm and 300 K is 104 A/cm2 μm. No symptom of an initial degradation has been observed.
Distinction between donor and acceptor character of surface states in the Si-SiO2 interface
Authors: Ziegler K.
Published: February 2003

The charge type of interface states is determined utilizing surface potential fluctuations. For thermally grown (111) -oriented n-type silicon, it is shown that the surface states below the conduction band are only donor states. Within the conduction band, an upper limit of 5×1011 possible donor states per cm2 is found. Within and above the valence band, acceptor states are either absent or at most present at a lower level than donor states. An upper limit of 1.6×1011 possible acceptor states per cm2 is obtained in this energy region.
Reactive sputtering of gallium nitride thin films for GaAs MIS structures
Authors: Hariu T. , Usuba T. , Adachi H. , Shibata Y.
Published: February 2003

Amorphous gallium nitride was deposited onto various substrates by reactive sputtering of gallium in nitrogen ambient. Higher pressure up to 2×10−1 Torr is effective in making films closer to the stoichiometric composition. Annealing at 350 °C improves the insulating property of as-deposited films by decreasing dc and ac conductance. The surface-state density and time constant of a GaAs MIS structure, corrected for the dispersive behavior of the insulator, was derived as 7.6×1011 cm−2 eV−1 and 1.9×10−4 sec, respectively. This surface-state density is much lower than that for the native oxide.
Charge retention of MNOS devices limited by Frenkel-Poole detrapping
Authors: Lehovec K. , Fedotowsky A.
Published: February 2003

A simple analytical expression is derived for charge retention in MNOS memory devices assuming that retention loss is limited by Frenkel-Poole release from monoenergetic traps. This model shows that charge retention becomes eventually independent of the initial charge distribution. Experimental data obtained at elevated temperatures confirm this model and provide a trap depth of 1.5 eV, Frenkel-Poole coefficient of about 6×10−4 cm1/2 V−1/2 eV, and effective escape attempt rate factor of 1.2×108 sec−1.
Ion-implanted surface-acoustic-wave guides on lithium niobate
Authors: Hartemann P. , Cauvard P. , Desbois D.
Published: February 2003

Surface-acoustic-wave guides have been obtained by ion-implanting narrow channels on lithium niobate substrates. Guides of different widths have been tested at 150 MHz. Two doses of helium ions at 100 keV have been used. The acoustic power distribution profiles along a guide length close to 21 mm were determined by optical probing. Air-gap silicon convolvers have been implemented with this kind of guide. An external figure of merit equal to −49 dBm has been measured, whereas without guidance the external figure of merit is only close to −61 dBm for the same transducer pattern.
Energy dependence of collisionless multiphoton ionization of D2O molecules by a TEA-CO2 laser
Authors: Chin S. L. , Faubert D.
Published: February 2003

Time-resolved ion spectra of the collisionless ionization of D2O was measured. The ionization was energy density dependent with different thresholds for different species of ions.
Monolithic integration of GaAs-(GaAl)As light modulators and distributed-Bragg-reflector lasers
Authors: Shams Mohammad Kazem , Namizaki Hirofumi , Wang Shyh
Published: February 2003

Integration of an intensity light modulator and a LOC-DBR laser on a single chip has been demonstrated. The injection-type modulator gives a variable loss (or gain) to the laser light, coupled to it via an interconnecting waveguide, and thus modulates its intensity in accordance with the injected current of the modulator. An extinction ratio of more than 10 was obtained.
A new method of fabricating gallium arsenide MOS devices
Authors: Chang R. P. H. , Coleman J. J.
Published: February 2003

A new method of fabricating gallium arsenide MOS devices with improved electrical properties is discussed. The device consists of a gallium arsenide substrate overlaid with a gallium arsenic oxide, a thin aluminum oxide, and a metallic contact. The oxide layers are fabricated using a plasma oxidizing process. These MOS devices show very high breakdown voltages (typically ≈±4×106 V/cm) and have low surface-state densities (≈5×1010 cm−2).
Far-infrared emission from Si-MOSFET’s on high-index surfaces
Authors: Tsui D C. , Gornik E.
Published: February 2003

Voltage-tunable far-infrared emission was observed from n-channel Si-MOSFET’s on high-index surfaces. The emission results from radiative decay of electronic excitations across a minigap in the ground-state subband of the channel. We have observed emission of 10−9 W at 4.4 meV with a linewidth of ∼1 meV. Our results indicate that a voltage-tunable monochromatic source of several times 10−7 W and tuning from ∼1 to ∼20 meV is attainable.
Generation of continuously tunable laser sidebands in the submillimeter region
Authors: Bićanić D. D. , Zuidberg B. F. J. , Dymanus A.
Published: February 2003

Substantial difference- and sum-frequency signals (up to 10−7 W) have been generated and reradiated by mixing the HCN laser radiation at 337 μm with that of a (tunable) millimeter-wave klystron in a metal-semiconductor point-contact or Schottky barrier diode. The magnitude and degree of monochromaticity of the generated power were sufficient for high-resolution spectroscopy as verified by measurements on H2S and CH3OH.
Electron attachment in dilute fluorine-helium mixtures
Authors: Nygaard Kaare J. , Hunter Scott R. , Fletcher John , Foltyn Stephen R.
Published: February 2003

We have made an absolute determination of the electron attachment coefficient η (cm−1) in helium containing 0.1–1% fluorine covering an E/N range from 3Td–17Td. At an estimated average energy of 5 eV we find a rate coefficient equal to (7.5±1.5) ×10−10 cm3/sec.
Effect of beamlet-beamlet interaction on ion optics of multiaperture sources
Authors: Whealton J. H.
Published: February 2003

Space-charge effects of beamlet-beamlet interaction in the unneutralized accelerator region of intense ion sources have been computed. If shielding effects of the electrodes are neglected, the radial space charge of a typical ion source is so great that most of the beam will hit the second electrode or will undergo nonlinear steering. Beam divergence will be an order of magnitude larger than that expected from considerations of spherical aberrations of a single beamlet caused by deviations from Pierce geometry. If shielding effects of the electrodes are sufficiently great that only nearest-neighbor beamlet-beamlet interactions are important, then the outermost beamlets (or those near a water line) will cause a total beam divergence which is the same order of magnitude as that due to single-beamlet spherical aberrations, and far more than the divergence expected from source ion temperature. A solution to this problem is proposed.
Ionic recombination of rare-gas molecular ions X+2 with F− in a dense gas X
Authors: Flannery M. R. , Yang T. P.
Published: February 2003

Rates for the recombination processes X+2+F−+X→[X2F]*+X, (X≡He,Ne,Ar,Kr,Xe) are calculated at 300 K for pressures of the background gas X up to 50 atm. We find rates as high as (2–6) ×10−6 cm3 sec−1 for pressures of 1–8 atm as the gas is varied from Xe to He. The rates are somewhat smaller than those for the corresponding cases involving atomic ions.
High-repetition-rate transverse-flow XeF laser
Authors: Wang C. P.
Published: February 2003

High-repetition-rate (500 pps) laser action in XeF molecules at 351 and 353 nm in a gas mixture of He, Xe, and NF3 has been demonstrated by use of a blowdown-type fast-flow system and thyratron-switched high-repetition-rate pulse generators. The transverse-flow velocity was 14 m/sec across a discharge region of 1×0.4×30 cm at a pressure of 650 Torr. The electric discharge pulse width was 60 nsec. For single-shot operation, laser output energy of 6 mJ/pulse and electric efficiency of 0.25% have been obtained. For high-repetition-rate operation, the output energy per pulse was only 3 mJ as a result of the long charging time constant.
Molecular beam epitaxial writing of patterned GaAs epilayer structures
Authors: Tsang W. T. , Cho A. Y.
Published: February 2003

A technique for achieving molecular beam epitaxial writing of patterned GaAs epilayer structures is described. With this technique, patterned GaAs epilayer structures with controlled thickness profiles, lengthwise varying thickness, featureless and optically smooth sidewalls, and a linewidth as narrow as 10 μm were written. This technique also allows for the first time controlled variation of chemical compositions in the epilayer structure written in a lengthwise direction in the plane of the epilayer.
Surface and subsurface structure of solids by laser photoacoustic spectroscopy
Authors: Wong Y. H. , Thomas R. L. , Hawkins G. F.
Published: February 2003

The new technique of photoacoustic spectroscopy is applied to studies of surface and subsurface structures of solids. In the present case, special attention is focused on silicon-nitride ceramic material, which is used for the manufacturing of turbine blades. Good correlation is obtained between the observed photoacoustic signal and surface microstructure. In addition, the photoacoustic signal shows inhomogeneities that are not visually detected under a microscope.
Backward Raman gain measurements for KrF laser radiation scattered by CH4
Authors: Murray J. R. , Goldhar J. , Szöke A.
Published: February 2003

Backward Raman small-signal gain measurements for a KrF laser scattered by methane gas, including linewidth and pressure dependences, are presented. A 268-nm probe beam is produced from a 249-nm pump beam by superfluorescent emission in a methane cell, and is amplified by a counterpropagating KrF beam at 249 nm in a second methane cell. The results are consistent with theoretical predictions for the backward Raman amplifier.
Electro-optic analog-to-digital conversion using channel waveguide modulators
Authors: Taylor H. F. , Taylor M. J. , Bauer P. W.
Published: February 2003

Some experimental results on the operation of a lithium niobate modulator in a threshold circuit to simulate a bit channel of an analog-to-digital (A/D) converter are presented. Voltages required for π-radian phase retardation were 1.2 and 3.1 V, respectively, for TE and TM excitation. The periodic dependence of modulator intensity on applied voltage is maintained for phase shifts as large as 24π radians in the TE case, which corresponds to 5.6 bits of precision for an A/D converter.
1-mJ line-tunable optically pumped 16 μm laser
Authors: Osgood R. M.
Published: February 2003

A optically pumped CO2 laser, which is excited by a 100-mJ HBr laser, produces 1 mJ of multiline energy per pulse. Extensive stepwise tuning is accomplished by means of an intracavity grating and by using various isotopic forms of CO2. A technique which enables measurement of the CO2 (0110) relaxation time by HBr is described.
Solid solubility of selenium in GaAs as measured by secondary ion mass spectrometry
Authors: Lidow A. , Gibbons J. F. , Deline V. R. , Evans C. A.
Published: February 2003

Secondary ion mass spectrometry profiles of redistributed selenium ion-implanted GaAs samples have been used to determine the solid solubility limit (Css) for this impurity. The data are well approximated by Css=9.5×1023 exp(−1.23±0.02eV/kT) cm−3. It is also shown that carrier concentrations equivalent to this limit can be obtained for annealing temperatures up to 900 °C.
On-time determination of the composition of III-V ternary layers during VPE growth
Authors: Theeten J. B. , Hottier F. , Hallais J.
Published: February 2003

A fast automatic ellipsometer has been used for determining the composition (and the rate of growth in favorable cases) of III-V ternary compound semiconductor layers during their growth in a VPE reactor. The technique is demonstrated on Ga1−xAlxAs and GaAs1−xPx layers grown respectively in an organometallic and a chloride system. The elllipsometric angle ψ is shown to be directly related to the composition and the rate of growth of the layer. The ellipsometric angle Δ contains additional information on the growth mechanisms at the surface of the layer.
A wideband SAW convolver utilizing Sezawa waves in the metal-ZnO-SiO2-Si configuration
Authors: Elliott J. K. , Gunshor R. L. , Pierret R. F. , Day A. R.
Published: February 2003

A monolithic metal-ZnO-SiO2-Si SAW convolver has been developed which not only displays the advantages of the monolithic configuration, but also possesses, due to utilization of high coupling Sezawa waves, a wide bandwidth heretofore only exhibited by LiNbO3 devices. We report here a bandwidth of 30 MHz at an input frequency of 225 MHz with a terminal efficiency of −56.9 dBm. The device displays an electromechanical coupling (Δv/v) of 0.019 which is the largest value yet reported for a ZnO device.
Measurements of kinetic processes in a self-sustained discharge XeF laser
Authors: Gower M. C. , Exberger R. , Rowley P. D. , Billman K. W.
Published: February 2003

The XeF* and F* sidelight emissions, the small-signal gain, and the transient plasma absorption near the laser wavelength have been measured from a XeF self-sustained discharge laser. We conclude that the production of XeF* in its lower vibrational levels requires collisions with He atoms, and that XeF* decays predominantly by radiative processes and He quenching. The transient absorption at the laser wavelength, believed to be due to F−, F*, F*2, and Xe+2, can be as large as ∼1–2%/cm at small-signal gains of ∼8%/cm.
Dopant tracing of terrace growth in GaAs LPE layers
Authors: Fischer B. , Bauser E. , Sullivan P. A. , Rode D. L.
Published: February 2003

Growth terraces on the surface of GaAs liquid phase epitaxial layers leave behind traces of increased doping concentration in the interior of the layer. These traces have been observed on (110) cleavage planes perpendicular to the (100) surface. Spatially resolved photoluminescence, cathodoluminescence, and photoetching have been applied to reveal the traces of the terraces. A fine structure on the photoetched cleavage plane indicates that the increase of thickness of the layer is caused in part by lateral growth of fine terraces traveling across the treads of the high terraces.
Anisotropy of the differential conductivity and of the transverse diffusion coefficient in n-type silicon
Authors: Gasquet D. , Nougier J. P.
Published: February 2003

Measurements of the transverse differential conductivity of hot carriers in semiconductors are performed, for the first time, using an experimental setup described in the present paper. This allows the determination of the transverse diffusion coefficients.
Improved GaAs MESFET with a thin i
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u buffer grown by liquid phase epitaxy
Authors: Kim C. K. , Malbon R. M. , Omori M.
Published: February 2003

Thin undoped layers of GaAs grown directly on GaAs semi-insulating substrates via liquid phase epitaxy (LPE) are shown to exhibit excellent buffering characteristics. Interfacial drift mobilities are shown to be much higher for the multilayer structures employing the thin buffer layer as compared with single-layer structures. GaAs metal semiconductor field-effect transistors (MESFET) fabricated on these LPE multilayer structures are shown to exhibit excellent rf characteristics. Best results include a noise figure of 1.87 dB with an associated gain of 10.6 dB at 12 GHz and a noise figure of 2.4 dB with an associated gain of 6.3 dB at 18 GHz.
Secondary dislocation climb during optical excitation of GaAs laser material
Authors: Woolhouse G. R. , Monemar B. , Serrano C. M.
Published: February 2003

Dislocation glide and climb during optical excitation of GaAs laser material have been studied. A dislocation which has been induced to glide under high excitation can be induced to climb by reducing the incident excitation. The climb proceeds in a distinctly different crystallographic direction to, and at a rate which is five or six orders of magnitude slower than, the glide. Furthermore, only the threading portion of the dislocation experiences climb, a misfit dislocation excited at the same external intensity for the same time undergoes no discernible growth. Transmission electron microscopy examination of the climb region shows that it consists of a highly convoluted giant dislocation dipole. The nature of this giant dipole has been determined by a calibrated technique and it has been shown to grow by vacancy climb. Small coherent precipitate particles have been identified for the first time in the neighborhood of the giant dipole.
A vapor collect method applied to the measurement of magnesium diffusion in tungstened nickel
Authors: Verhoeven J.
Published: February 2003

The diffusion rate of magnesium in tungstened nickel was measured at temperatures between 970 and 1330 K. The method consists of measuring the species and number of atoms collected on a collector in front of the evaporating surface in a well-defined geometrical arrangement under ultrahigh-vacuum conditions. The collected material is analyzed by means of AES. Experiments on the diffusion of magnesium in tungstened nickel yield an activation energy of 57 kcal/mole. The vapor collect method shows great potentialities for the measurement of evaporation rates and its dependence on surface contaminants.
Measurement of anisotropic interfacial interactions between a nematic liquid crystal and various substrates
Authors: Naemura Shohei
Published: February 2003

Wall effects on the Freedericksz transition have been calculated and used to evaluate the interfacial interactions between nematic molecules and substrates. A total reflection method was developed to observe the Freedericksz transition. Both the easy axis and the anchoring strength were measured on the interfaces between MBBA and substrates with several surfactant layers. Experimental results indicate that the polar group of the surfactants plays several roles in their molecular orienting forces.
Elimination of aberrations due to a wavelength shift in holographic microscopy
Authors: Shono Y. , Inuzuka T.
Published: February 2003

The principle of aberrationless reconstruction in holographic microscopy is stated. The aberrations due to the wavelength difference between the recording and reconstruction processes can be eliminated by using a volume hologram. The volume hologram reconstructs the negligibly aberrated image of a very narrow region of the object. By using this effect the whole aberrationless image, which is magnified corresponding to the wavelength shift, can be obtained by rotating the volume hologram during the exposure period in which a photograph of the virtual image is taken.
IBIS: A hollow-cathode multipole boundary ion source
Authors: Forrester A. T. , Goebel D. M. , Crow J. T.
Published: February 2003

The plasma production and containment system for a high-power continuously operating magnetic multipole ion source has been designed and constructed. Preliminary tests on this system prior to high voltage extraction of large beams indicate advantageous performance for neutral-beam injection applications. The source has produced 80 A to the extractor region at 0.33 A/cm2 with a discharge of 330 A at 80 V. Density uniformity is better than 1% over a 16-cm diameter, dropping to −4% at 18 cm, with plasma noise of less than 3%. Gas utilizaion efficiency and atomic (H+) species output are anticipated to be high due to a source length of 40 cm. This quiet efficient performance is attributed to the use of a hollow-tube LaB6 cathode and an improved magnetic multipole confinement system.
Room-temperature operation of lattice-matched InP/Ga0.47In0.53As/InP double-heterostructure lasers grown by MBE
Authors: Miller B. I. , McFee J. H. , Martin R. J. , Tien P. K.
Published: February 2003

Molecular beam epitaxial (MBE) growth of InP/Ga0.47In0.53As/InP double heterostructures has resulted in pulsed room-temperature lasing at 1.65 μm. Thresholds as low as 3.2 kA/cm2 for a 0.6-μm-thick layer has been achieved. These results were achieved by ’’premixing’’ the Ga and In together in a common source oven and precisely monitoring the Ga/In flux ratio during the growth of the Ga0.47In0.53As layer. Cd diffusion from a vapor source allowed us to p dope the top InP layer in the as-grown MBE wafer.
Coherent Raman scattering with three lasers
Authors: Chandra S. , Compaan A. , Wiener-Avnear E.
Published: February 2003

General conditions for four-wave mixing processes are investigated for the three-dimensional geometry. Unlike the standard two-frequency coherent Raman scattering, the use of three laser beams allows great flexibility in the phase-matching condition. Theoretically calculated plots are presented for dispersive and nondispersive media and are compared with experimental results in carbon disulphide and hydrogen gas, respectively.
A dry-etched inorganic resist
Authors: Chang M. S. , Chen J. T.
Published: February 2003

An as-deposited As2S3 thin film is employed as a negative working inorganic resist in lithographic applications. A CF4 plasma is used to etch differentially for pattern delineation. A maximum etch rate ratio of 1.8 between the unexposed and exposed films is obtained. Ag-photodoped As2S3 is found to have a much slower etch rate in the CF4 plasma. Grating patterns have been obtained using this dry process. The extension of this concept to conventional organic polymer resists is considered.
Hydrogen plasma diagnostics by resonant multiphoton optogalvanic spectroscopy
Authors: Ausschnitt C. P. , Bjorklund G. C. , Freeman R. R.
Published: February 2003

Direct pulsed-laser photoionization of neutral atomic hydrogen or deuterium in a discharge plasma is shown to result in large voltage changes across the electrodes. The ground- and excited-state densities and the translational temperature of the H and D atoms within the plasma are probed by this technique.
High-efficiency In1−xGaxAsyP1−y/InP photodetectors with selective wavelength response between 0.9 and 1.7 μm
Authors: Washington M. A. , Nahory R. E. , Pollack M. A. , Beebe E. D.
Published: February 2003

We report In1−xGaxAsyP1−y/InP photodiode detectors with external quantum efficiencies of 50–70% without antireflection coating. The short- and long-wavelength response limits of these very efficient detectors can be compositionally tuned to lie anywhere in the wavelength range 0.9<λ<1.7 μm.
Coupling length adjustment for an optical directional coupler by loading a metal film
Authors: Mikami Osamu , Noda Juichi
Published: February 2003

A simple method for realizing the desired light coupling for an optical directional coupler is presented. This method consists of loading a metal film on one of the waveguides in the undesired coupling region. The effective coupling length, fabricated in c-plate LiNbO3, could be changed from 0 to 3L0 (L0: 0-dB coupling length) by controlling the length of the metal film.
The effect of minor constituents on the electrotransport-induced failure site in thin gold films
Authors: Hummel R. E. , Krumeich B. K. , DeHoff R. T.
Published: February 2003

The presence of small amounts of some solute elements in gold thin films causes a reversal of the failure site during an electrotransport experiment. The effectiveness of a solute element in accomplishing this reversal is not correlated with melting point, solubility, or atomic radius. However, solute elements that produced a reversal in gold films (sodium, indium, barium) all have low ionization energies. Auger electron spectroscopy revealed that sodium from a microscope glass substrate penetrates through a gold film to its free surface during current stressing or during furnace annealing.
Photoacoustics on a microscopic scale
Authors: Wickramasinghe H. K. , Bray R. C. , Jipson V. , Quate C. F. , Salcedo J. R.
Published: February 2003

We have modified a transmission acoustic microscope by replacing the input lens with an optical counterpart. The input to this system comes from a mode-locked and Q-switched Nd : YAG laser at 1.06 μm. Acoustic signals arising from thermoelastic coupling are generated in metallic films at frequencies determined by the modulation envelope of the optical beam. The output acoustic lens and transducer responsive to sound waves at 840 MHz detect the acoustic energy which comes from the heated volume (∼2-μm diameter) near the focal region. The sample is mechanically scanned through the focal point in a raster pattern to record the photoacoustic images. We suggest this as a method for collecting new information on microscopic structures.
Electron collisional laser in Pb+ populated by recombination
Authors: Silfvast W. T. , Szeto L. H. , Wood II O. R.
Published: February 2003

A quasi-steady-state inversion and laser action in the near infrared in Pb+ are shown to occur as a consequence of recombination and subsequent electron collisional thermalization within two ’’bands’’ of atomic energy levels. This demonstrates a mechanism for producing similar inversions at short wavelengths in a recombining plasma where the plasma density may be too high for radiative decay to establish an inversion.
Electrochromism of anodic iridium oxide films on transparent substrates
Authors: Shay J. L. , Beni G. , Schiavone L. M.
Published: February 2003

Anodic iridium oxide films (AIROF’s) can be grown and operated on transparent substrates. Using SnO2-coated glass as the substrate we can monitor large, rapid, and persistent variations of the light intensity transmitted through the AIROF. The voltammogram of the AIROF on SnO2-coated glass is essentially identical to that of an AIROF on iridium. This proves that the electrochemistry producing the coloration does not involve the substrate.
Polycrystal silicon recovery by means of a shaped laser pulse train
Authors: Vitali G. , Bertolotti M. , Foti G.
Published: February 2003

A structure change from a polycrystal to single-crystal layer in ion-implanted Si samples has been obtained by single-pulse ruby-laser irradiation with a power density threshold of about 70 MW cm−2 (pulse length 50 nsec). Under these conditions surface mechanical damage is produced. A laser pulse train shaping technique was adopted to reduce the residual disorder in the layer after laser irradiation and to prevent mechanical damage.
I
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u Ohmic-contact formation to n- and p-GaAs by molecular beam epitaxy
Authors: Tsang W. T.
Published: February 2003

An in situ Ohmic-contact-formation technique for n- and p-GaAs of any resistivity by molecular beam epitaxy was described. The measured specific contact resistances lie between low-10−6 Ω cm2 and mid-10−5 Ω cm2. The contacts were Ohmic for currents in excess of 250 mA tested in both forward and reverse directions. Furthermore, the contact metallization was optically smooth as no sintering or alloying process was needed. Excellent uniformity of electrical quality of the Ohmic contacts on the same sample was obtained.
Oxidation-enhanced diffusion of arsenic and phosphorus in near-intrinsic 〈100〉 silicon
Authors: Antoniadis D. A. , Lin A. M. , Dutton R. W.
Published: February 2003

Oxidation-enhanced diffusion (OED) of phosphorus and arsenic in 〈100〉-oriented silicon has been characterized under low-concentration doping conditions. The first indisputable evidence of arsenic OED in silicon has been obtained. The impurities were introduced by ion implantation, and thermally diffused profiles under oxidized and nonoxidized silicon surfaces were obtained simultaneously. Samples were beveled and the doping profiles were characterized by means of spreading resistance. Because of the close proximity of intrinsically diffused and OED profiles, the relative change in diffusivity could be accurately obtained. Both for phosphorus and arsenic the enhancement decreases as temperature increases, a behavior that is in agreement with previously reported data for boron. On the basis of the present data, it can be concluded that (a) the diffusion mechanisms are basically the same for all three elements and (b) the impurity diffusion mechanism involves two types of point defects in silicon, and the oxidation process increases the concentration of only one of these defects.