bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficient LiNbO3 balanced bridge modulator/switch with an ion-etched slot
Authors: Minakata Makoto
Published: February 2003

A simple modified balanced bridge modulator or switch is reported. The modulator is comprised of only straight waveguides and an ion-etched slot used for a conventional phase shifter. The slot excavated at the center of two coupled waveguides solves the coupling of them. 3-dB coupler monitoring is performed here by a metal loading. The modulator is fabricated by diffusing Ti into z-cut LiNbO3. Each patterned waveguide is fabricated by diffusing Ti into z-cut LiNbO3. Each patterned waveguide is 7 μm wide and the spacing is 7 μm. The 3-dB coupler is 2.9 mm long, and the excavated slot is 15 mm long, 4 μm wide, and 4.5 μm deep. The overall length is 20.8 mm. For the TM-like fundamental mode, the half-wave voltage was 2.8 V, the extinction ratio was −15 dB, and the optical insertion loss was as low as 2.6 dB at the 1.15-μm wavelength.
A discharge pumped laser on the C→A transition of XeF
Authors: Burnham R.
Published: February 2003

Direct electrical excitation of laser oscillation centered at 490 nm has been obtained on the C→A transition of XeF in mixtures of He, Xe, and NF3 pumped by a self-sustained discharge. Laser output appears to have been limited by the short time available for the buildup of oscillation in the transient discharge.
Tungsten needles produced by decomposition of hexacarbonyltungsten
Authors: Okuyama F. , Shibata T. , Yasuda N.
Published: February 2003

Tungsten needles grown from hexacarbonyltungsten vapors in a glow-discharge condition are described. The needle growth occurs on a tungsten substrate in a temperature range from nearly room temperature to 1500 °K, but needles produced below and above ∼1100 °K are quite different in morphology and crystalline state. The products at lower temperatures are tungsten particles agglomerated in dendritelike shapes while those at higher temperatures possibly are whiskers.
Planar guarded avalanche diodes in InP fabricated by ion implantation
Authors: Donnelly J. P. , Armiento C. A. , Diadiuk V. , Groves S. H.
Published: February 2003

Planar guarded avalanche diodes in InP have been fabricated using a double-ion-implantation technique. Silicon was selectively implanted into an n-type epitaxial layer to increase the concentration portion of the diode, and beryllium was implanted to form the p-n junction. When appropriately reverse biased, these diodes exhibited uniform avalanche photocurrent gain in the central portion, where the electric field is maximum. With a 1-kΩ load, photoresponse gains as high as 20 were measured, although values of 6 to 8 were more typical. At present, the external photoresponse gain with a fixed load is limited by the shunting effect of the diode’s differential resistance.
A monolithically integrated optical repeater
Authors: Yust M. , Bar-Chaim N. , Izadpanah S. H. , Margalit S. , Ury I. , Wilt D. , Yariv A.
Published: February 2003

A monolithically integrated optical repeater has been fabricated on a single-crystal semi-insulating GaAs substrate. The repeater consists of an optical detector, an electronic amplifier, and a double heterostructure crowding effect laser. The repeater makes use of three metal semiconductor field effect transistors, one of which is used as the optical detector. With light from an external GaAlAs laser incident on the detector, an overall optical power gain of 10 dB from both laser facets was obtained.
The influence of annealing ambient on the shrinkage kinetics of oxidation-induced stacking faults in silicon
Authors: Claeys Cor L. , Declerck Gilbert J. , Van Overstraeten Roger J.
Published: February 2003

The shrinkage behavior of oxidation-induced stacking faults (OSF’s) during an annealing in nitrogen, argon, and hydrogen is studied as a function of both annealing temperature and time. Independent of the used gas atmosphere, the OSF shrinkage rate is characterized by an activation energy of 4.9 eV. To explain the different experimental results, an interstitial model for the stacking fault shrinkage is proposed.
Electron beam coevaporation of superconducting A 15 Nb-Si
Authors: Feldman R. D. , Hammond R. H. , Geballe T. H.
Published: February 2003

Nb3Si films have been prepared with varying deposition rates, substrate temperatures, and added oxygen pressure. The variation of the lattice constant with composition for oxygen doped samples follows the predictions of the Geller radii for A15 structures which are as ordered as allowed by stoichiometry. Comparison with other Nb-based A15’s suggests that the lattice constant of these Nb-rich Nb3Si films may be approaching the minimum value possible for Nb-based A15 structures.
Vapor-phase epitaxial growth of InGaAs lattice matched to (100) InP for photodiode application
Authors: Hyder S. B. , Saxena R. R. , Chiao S. H. , Yeats R.
Published: February 2003

Vapor-phase epitaxial growth of In0.53Ga0.47As lattice matched to (100) -oriented InP substrates is described, and the performance of photodiodes fabricated from this material is presented. Gas-flow conditions for lattice-matched growth with various Ga-CHl flows were established for growth using the hydride process. The effect of substrate temperature on gas-flow ratios necessary for lattice-matched growth was studied over the temperature range 650–750 °C. Growth rates were found to vary from about 8 to about 60 μm/h over this temperature range. The activation energy of surface reaction was determined to be 44 kcal/mole. Photodiodes fabricated from an InP/In0.53Ga0.47As/InP structure showed rise and fall times of ≲1 nsec with quantum efficiencies in excess of 95% at 1.22 μm.
CF4 plasma etching on LiNbO3
Authors: Lee C. L. , Lu C. L.
Published: February 2003

CF4 plasma etching was applied to LiNbO3. Ridge structures as thin as 3 μm were fabricated. The resolution was limited by photolithography Al masks. The etched surface showed an optical quality. A horn structure ridge channel wave guide of a width of 20 μm was also etched, and demonstrated good quality in guiding optical waves.
Optoacoustic phase angle measurement for probing a metal
Authors: Busse G.
Published: February 2003

It is shown that using optoacoustic phase angle scanning rather than amplitude scanning enables precise measurements of subsurface structure in metal. For some applications the method can be an alternative to x-ray imaging.
Electron drift velocities in N2, CO2, and (N2+CO2) laser mixtures
Authors: Sierra Rafael A. , Brooks Howard L. , Nygaard Kaare J.
Published: February 2003

A time-of-flight technique has been used to obtain electron drift velocities in N2, CO2, and N2-CO2 mixtures covering the E/N range 3–93 Td. In the case of the pure gases, excellent agreement with previous work is obtained over the entire E/N range. The mixtures, which are of laser importance, have not been studied previously.
Coherent four-wave scattering in plasmas—application to plasma diagnostics
Authors: Praddaude H. C. , Scudder D. W. , Lax B.
Published: February 2003

An explicit solution for the third-order nonlinear transverse susceptibility and for the scattered power in a collisionless unmagnetized plasma is presented. We show that a consistent second-order approximation of the Vlasov equation that treats on equal footing the electric and the magnetic fields of the electromagnetic waves produces a ponderomotive force term that drives various plasma excitations. In analogy with Thomson scattering from thermal fluctuations, the wavevector and frequency dependence of the scattered power is dominated by the first-order longitudinal susceptibilities of the plasma. Even though the Landau damping may be considerable and the plasma resonances may not be well defined, the coherent nature of this four-photon process produces a considerably enhanced scattered power within a narrow scattering cone. These features make this technique well suited for plasma diagnostics. These techniques are a close counterpart of the coherent anti-Stokes Raman spectroscopy and the Raman-induced Kerr effect spectroscopy used with Raman active transitions in gas, liquid, and solid spectroscopy.
Active pulse shaping in the picosecond domain
Authors: Agostinelli J. , Mourou G. , Gabel C. W.
Published: February 2003

Active pulse shaping in the picosecond domain is reported using a fast Pockels cell controlled by an optically driven GaAs electrical switch. The center is sliced out of a long optical pulse, yielding a 70-psec FWHM pulse with 40-psec rise and fall times.
Nonplanar large optical cavity GaAs/GaAlAs semiconductor laser
Authors: Burnham R. D. , Scifres D. R. , Streifer W. , Peled S.
Published: February 2003

We report pulsed room-temperature operation of a nonplanar large optical cavity semiconductor laser. As a result of a single LPE growth in an etched channeled substrate, a curved cavity is created which guides the laser light in both transverse dimensions. Representative lasers exhibit 50-mA thresholds, 40% differential quantum efficiency, 25-mW power output without kinks, and stable near- and far-field optical patterns.
Efficient tunable H2 Raman laser
Authors: Rabinowitz P. , Stein A. , Brickman R. , Kaldor A.
Published: February 2003

We have obtained 85% quantum conversion by stimulated rotational Raman scattering of CO2 laser radiation in para H2. An output energy in excess of 1 J and a peak power of ∼20 MW was measured at 623 cm−1. The prelimininary measurements suggest that the temporal and spatial coherence of the generated Stokes wave are close to the ideal theoretical limitation.
Composition measurements related to the Cu2S/ZnxCd1−xS heterojunction
Authors: Burton L. C.
Published: February 2003

Composition of zinc and cadmium have been measured for three key regions related to the formation of Cu2S on ZnxCd1−xX by aqueous ion exchange. These are the ion-exchange solution, the resulting Cu2S, and the ZnxCd1−xS near the Cu2S-ZnxCd1−x interface. It is found that the participation of zinc in the ion-exchange reaction is incomplete. Zinc is thus retained in the p-n junction region, and is found mainly in the ZnxCd1−xS just under the interface. This phenomenon helps to account for certain differences between electro-optical properties of Cu2S/CdS and Cu2S/ZnxCd1−xS solar cells.
New experimental evidence of the periodic surface structure in laser annealing
Authors: Oron M. , So/rensen G.
Published: February 2003

This letter presents a study of the nature of the periodic structure observed on the edge of laser-annealed spots on ion-implanted silicon. The direction of the periodic fringes was always found to be about perpendicular to the E vector of the light for linearly polarized beams. No fringe pattern was observed for circular polarization. We suggest that the pattern observed is due to heating by a standing wave resulting from the interference of the impinging wave and a radial (longitudinal) scattered wave.
Imaging of dislocations in InP using transmission cathodoluminescence
Authors: Chin A. K. , Mahajan S. , Ballman A. A.
Published: February 2003

We present an exact one-to-one correspondence between grown-in dislocations revealed as etch pits and dark spots observed on transmission cathodoluminescence images of InP. This correspondence has been demonstrated for heavily tellurium- and sulfur-doped InP. This is the first time that dislocations have been identified and imaged in InP using a luminescence technique.
A model of degradation mechanisms in metal-nitride-oxide-semiconductor structures
Authors: Suzuki Eiichi , Hayashi Yutaka , Yanai Hisayoshi
Published: February 2003

The degradation of a metal-nitride-oxide-semiconductor (MNOS) structure has been investigated using p-channel MNOS transistors with a relatively thick oxide layer. Significant degradation effects, e.g., a negative shift of the threshold voltage Vth or the flatband voltage VFB, an increase in the density of the SiO2-Si interface states, a deformation of the memory hysteresis curve, and increase in hole conduction in the oxide are observed during positive-bias stress to the gate. Based on these experimental results, a model of degradation mechanisms in the MNOS structure, where hole conduction in the oxide results in the degradation, is proposed.
Efficient indium tin oxide/polycrystalline silicon solar cells
Authors: Schunck J. P. , Coche A.
Published: February 2003

ITO/Si-N solar cells have been fabricated by a spraying process at 500 °C on polycrystalline silicon. Electroless nickel plating was used for the back Ohmic contact deposition. Electrical characteristics and spectra response of these heterojunctions are compared to those obtained on monocrystalline silicon. AM1 efficiency of ≃9% (based on active area) is achieved for polycrystalline material. Temperature dependence of open-circuit voltages and short-circuit currents are comparable to those reported for diffused Si junctions and Si-based MIS cells.
High current density Ga+ implantations into Si
Authors: Hart R. R. , Anderson C. L. , Dunlap H. L. , Seliger R. L. , Wang V.
Published: February 2003

The lattice disorder produced in Si by a 59-keV Ga+ ion beam focused to a diameter of 1200 Å and having a current density of 1.2 A/cm2 was compared to that produced by broad area implantations of 59-keV Ga+ at a current density of 0.4 μA/cm2. Based on 140-keV proton backscattering, the disorder produced at the high-dose rate was found to be comparable although deeper than that produced by the low-dose-rate implantations. The depth profile of Ga implanted at 1.2 A/cm2 to a dose of 1.5×1015/cm2 was determined by 280-keV He++ backscattering to be basically consistent with projected range calculations.
Dynamics of Nd : YAG laser annealing of silicon on sapphire
Authors: Lüthy W. , Affolter K. , Weber H. P. , Roulet M. E. , Fallavier M. , Thomas J. P. , Mackowski J.
Published: February 2003

Epitaxial and polycrystalline silicon layers on sapphire have been annealed with Q-switch pulses from a Nd : YAG laser irradiated on the Si surface. Time-resolved optical reflectivity measurements have been performed. The annealing process is shown to be induced by melting and subsequent epitaxial regrowth. The best results were obtained if the whole Si layer was melted, thus allowing the (11̄02) oriented sapphire substrate to act as a seed for recrystallization. In this case commercially available Si-on-sapphire (SOS) wafers with additional Si implantation as well as polycrystalline layers of low-pressure chemical vapor deposited (LPCVD) Si on sapphire could be epitaxially regrown. The same material deposited on amorphous SiO2 did not show epitaxial regrowth, however an increase in size of randomly orientated grains from 60 nm to 1 μm could be achieved.
Small-area high-current-density Josephson junctions
Authors: Howard R. E. , Hu E. L. , Jackel L. D. , Fetter L. A. , Bosworth R. H.
Published: February 2003

Josephson junctions with areas of ∼10−9 cm2 and current densities of 105 A/cm2 are described. The junctions were patterned using a combination of optical lithography and oblique evaporation techniques. The junction width is limited by the lithographic resolution to about 1 μm. The junction length is determined essentially by the base-electrode film thickness and can be as small as 1000 Å. The moderate (∼10 Ω) normal resistances of these junctions combined with their short intrinsic RC times gives them potential for application in nonlatching Josephson logic and in quasiparticle mm-wave mixers.
High T
c refractory thin-film microwave SQUID’s
Authors: Rachford F. J. , Cukauskas E. J.
Published: February 2003

Thin-film SQUID’s fabricated from the high Tc refractory material NbN have been studied at 9.4 GHz. Devices with granular weak links display a Josephson critical current dependence over a wide range of temperatures below Tc. We have observed open loop signal-to-noise ratios as high as 20 000 corresponding to a minimum detectable energy of 1×10−30 J in a 1 Hz bandwidth over a temperature range of several °K. In two samples, the response time was found to be limited by the intrinsic gap response time, τg∼h//2Δ (T). These devices are rugged, stable, cycle well, and have good SQUID properties at both 9.4 GHz and 20 MHz.
High-field transport properties of superconducting A15 Nb–Ge and Nb–Ge–Si compounds
Authors: Païdassi Serge
Published: February 2003

The critical currents of superconducting A15 Nb–Ge and Nb–Ge–Si compounds prepared by CVD have been measured in applied fields up to 18 T. Current densities greater than 105 A cm−2 were obtained at 18 T. These results are discussed with regard to the microstructure of the films which were examined by transmission electron microscopy.
Broadly tunable cw operation of Ni : MgF2 and Co : MgF2 lasers
Authors: Moulton P. F. , Mooradian A.
Published: February 2003

Operation of cw Ni : MgF2 and Co : MgF2 lasers with an external cavity has produced broadly tunable emission in the near infrared. The Ni : MgF2 laser was tuned continuously from 1.61 to 1.74 μm and the Co : MgF2 laser from 1.63 to 2.08 μm. Optical pumping with a 1.32-μm Nd : YAG laser and conduction cooling of the laser crystals to 80 K yielded stable spiking-free TEM00 outputs from both lasers with maximum cw output powers of about 100 mW. The Ni : MgF2 laser was operated with a single-frequency output of 20 mW and was Q switched to generate a peak power output of 140 W at a 100-Hz repetition rate.
Degradation of Ga1−xAlxAs visible diode lasers
Authors: Kajimura T. , Kuroda T. , Yamashita S. , Todokoro H. , Nakamura M. , Mizuishi K. , Umeda J.
Published: February 2003

It is shown that Ga1−xAlxAs visible lasers degrade faster at shorter lasing wavelengths. The degradation in the wavelength region below 730 nm can mainly be attributed to the rapid formation of macroscopic defects in the active region. A notable improvement in life is obtained for these shorter wavelength lasers by Te-doping of the active layer. On the other hand, degradation at above 740-nm results from enhanced facet oxidation due to high AlAs mole fractions in the layers. Facet coatings using SiO2 films effectively suppress facet oxidation. As a result, room-temperature extrapolated lives exceeding 10 000 h are achieved in the wavelength region above 740 nm.
A discrepancy in the elementary theory of MOSFET modeling
Authors: van der Ziel A. , Park H. S. , Liu S. T.
Published: February 2003

The elementary theories of flicker noise in MOSFET’s operating at low drain bias evaluate the spectrum SVeq8f) of the equivalent gate noise emf δVeq under the assumptions of an effective mobility μeff that is independent of the gate voltage Vg and of a carrier number in the channel that varies linearly with the gate voltage. We show here that this introduces an error I2d/[g2m(Vg—VT)2] in the calculated results. Experiments show that this error can be significant, so that it makes some existing interpretations of SVeq(f) doubtful. The error comes about because at a given drain current Id the transconductance gm for large Vg−VT is smaller than the elementary theory predicts. This affects most MOSFET modeling at low drain bias.
A TEM00 far infrared laser with integrated pump laser
Authors: Dyrna P. , Tacke M.
Published: February 2003

A new hybrid far infrared (FIR) laser is described. The output beam has the form of the fundamental Gaussian mode. The radiation is pulsed due to passive Q switching by the FIR laser gas CH3F. This type of resonator is expected to combine excellent FIR beam geometry, stability, and efficiency.
Rates of dissociative attachment of electrons to excited H2 and D2
Authors: Wadehra J. M.
Published: February 2003

Calculations are reported of the contributions of the lowest 2Σ+u and 2Σ+g resonant states to the rates of dissociative attachment of electrons to H2 and D2. For all electron temperatures, the rate is significantly enhanced by vibrational and rotational excitation of the initial molecule. Typically, for an electron temperature of 1.5 eV, the attachment rates for various (v, J) levels are, in cm3 sec−1, 5.4×10−15 for (0,0), 7.2×10−11 for (0,20), and 7.8×10−9 for (8,0), for H2; and 4.5×10−17 for (0,0), 1.4×10−14 for (0,20), and 6.0×10−9 for (11,0), for D2.
Low-temperature annealing behavior of GaAs implanted with Be
Authors: Anderson C. Lawrence , Dunlap H. L.
Published: February 2003

Ion implantation of Be into GaAs, followed by annealing at temperatures above 475 °C, produces layers with strong p-type conductivity and high hole mobility. Maximum electrical activation of the Be is obtained by 550 °C. Be appears to be the only dopant in GaAs which can be electrically activated at such low temperatures following implantation. At temperatures in the range 500–630 °C, satisfactory electrical results can be obtained by annealing in argon or vacuum without encapsulation. Little change in the electrical properties occurs for subsequent encapsulated annealing at temperatures up to 800 °C for the fluences used.
State-of-the-art performance of GaAlAs/GaAs avalanche photodiodes
Authors: Law H. D. , Nakano K. , Tomasetta L. R.
Published: February 2003

Ga0.15Al0.85As/GaAs avalanche photodiodes have been successfully fabricated. The performance of these detectors is characterized by a rise time of less than 35 ps, an external quantum efficiency with an antireflection coating of 95% at 0.53 μm, and a microwave optical gain of 42 dB. The dark current density is in the low-10−8-A/cm2 range at one-half the breakdown voltages, and rises to 1.1×10−4 A/cm2 at 42 dB optical gain.
Revised model of asymmetric p-n junctions
Authors: Redfield David
Published: February 2003

The standard physical model by which p-n junctions in semiconductors are generally analyzed is shown to need significant revisions when applied to strongly asymmetrical junctions, such as commonly used in diffused silicon transistor emitters and solar cells. The potential, field, and space-charge density have much wider spatial distributions on the heavily doped side than generally thought, thus, in effect, widening the ’’junction region’’ there. In addition, Auger processes on that side can reduce the minority-carrier lifetime sufficiently to cause recombination without defects in the widened space-charge region and a consequent excess junction saturation current not previously recognized.
The effect of electron irradiation on the In-X acceptor in In-doped silicon
Authors: Swaminathan V. , Lang J. E. , Hemenger P. M. , Smith S. R.
Published: February 2003

We present the results of low-temperature Hall measurements on 1-MeV-electron-irradiated In-doped Si. It is observed that the concentrations of the acceptor In-X, Nx, and the compensating donor ND increase immediately after irradiation with fluences ranging from 2×1015 to 1016 e/cm2. It is suggested that ND increases after irradiation due to the creation of divacancies, interstitial indium, and interstitial indium–substitutional indium pairs, where the interstitial indium atoms occupy the tetrahedral site. To explain the increase in Nx we propose three possible models for In-X in terms of indium-vacancy pairs, indium interstitials in the split configuration, or indium interstitials in the bond-centered configuration.
Improved electrical mobilities from implanting InP at elevated temperatures
Authors: Davies D. Eirug , Comer J. J. , Lorenzo J. P. , Ryan T. G.
Published: February 2003

InP has been implanted with silicon to investigate the effect of implantation temperature on the postannealed electrical mobility. A significant improvement, by a factor of ∼2, occurs on implanting at 200 °C rather than at room temperature. Dislocations found after the room-temperature but not the 200 °C implants may account for the mobility differences.
Shallow acceptors and p-type ZnSe
Authors: Kosai K. , Fitzpatrick B. J. , Grimmeiss H. G. , Bhargava R. N. , Neumark G. F.
Published: February 2003

Shallow acceptors have been incorporated in ZnSe by liquid-phase epitaxy using Bi as a solvent. Epilayers with Li, Na, N, and P as dopants were proven to be p type by establishing the position of the Fermi level by photocapacitance and photoconductivity measurements, and by measuring the potential drop at biased Schottky barriers.
Observation of two-dimensional electrons in LPE-grown GaAs-AlxGa1−xAs heterojunctions
Authors: Tsui D. C. , Logan R. A.
Published: February 2003

We have observed a two-dimensional electron gas at the interface of asymmetrically doped GaAs-AlxGa1−xAs heterojunctions grown by LPE. Our results demonstrate unequivocally that LPE can be used to grow GaAs-AlxGa1−xAs heterojunctions with interfacial electrical properties comparable to those achieved by MBE.
Laser-irradiation effects on unencapsulated GaAs studied by capacitance spectroscopy
Authors: Yuba Yoshihiko , Gamo Kenji , Murakami Kouichi , Namba Susumu
Published: February 2003

The effect of Q-switched ruby-laser irradiation on unencapsulated unimplanted bulk GaAs has been investigated by means of deep-level transient spectroscopy (DLTS) and C-V carrier profiling. It was found that the concentration of a deep-level center (Ec−0.83 eV) assigned to the A center decreases considerably as a result of laser irradiation, and that no deep levels (electron traps) more than 3×1013/cm3 are induced by the laser irradiation on the uncapped surface at a power level suitable for the recrystallization of an amorphous layer produced by ion implantation. No significant change in the free-carrier profile at a depth deeper than 1500 Å from the surface was observed after the laser irradiation.
Efficient XeF laser excited by a proton beam
Authors: Eden J. G. , Golden J. , Mahaffey R. A. , Pasour J. A. , Waynant R. W.
Published: February 2003

The efficient generation of stimulated emission from XeF at 351 and 353 nm has been achieved by pumping RG/Xe/NF3 gas mixtures (RG=argon, neon, or helium) with an intense (∼10 A cm−2) beam of ∼200-keV protons. For an active medium (T=300 °K) consisting of Ar, Xe, and NF3 at a total pressure of 1 atm and 30% cavity output coupling, the volumetric output, efficiency, and threshold pump power for the laser were determined to be 5–10 J/liter amagat, 1.7±0.7%, and 1.5 MW cm−3, respectively. Much lower efficiencies were obtained for neon and helium diluent mixtures.
Surface analysis of field-ion samples exposed to the plasma of the impurities studies experiment (ISX-A) tokamak
Authors: Kellogg G. L. , Clausing R. E.
Published: February 2003

Measurements of the modifications to the surface of field-emitter samples (tips) exposed to plasma discharges in the impurities studies experiment (ISX-A) tokamak have been carried out for the first time in order to help further identify the physical processes occurring at the tokamak wall during machine operation. The specimen tips were exposed to 40 high-power hydrogen discharges in ISX-A at a position 5.0 cm back from the plasma edge defined by carbon and molybdenum limiters. In contrast to results obtained on silicon samples exposed at a similar location in ISX-A using Rutherford ion backscattering analysis, field-ion images of tungsten tips taken before and after exposure indicate that no structural rearrangement of the specimen near-surface region occurred, even on an atomic scale. Contaminant films 60±10 Å thick, deposited on the specimen surfaces during exposure, were observed in the transmission electron microscope. Control tips, placed in the tokamak during the discharges but shielded from direct plasma exposure, remained free of such deposits. Imaging atom-probe depth profiles into the exposed sample substrates revealed that neither plasma nor impurity species were implanted beyond the deposited surface films. The results from this study are compared with those from earlier analyses of samples exposed in the Princeton large torus (PLT) using similar techniques and also with the results of analyses of macroscopic samples exposed at the same ISX-A location using other surface-sensitive techniques.
Four-wave interactions in acoustoelectric integrating correlators
Authors: Ralston R. W. , Stern E.
Published: February 2003

Four-wave acoustoelectric interactions have been observed in an integrating correlator which provide both significantly improved device performance over that achieved with three-wave interactions and make possible a unique signal-processing function: triple-product correlation. These interactions involve the differential delay, mixing, and time integration of two (ω1, ω2) surface acoustic waves (SAW’s) counterpropagating on a LiNbO3 delay line in the presence of a uniform (ω3=ω1+ω2) pump applied to a PtSi diode array and a stationary wave of charge stored in the diode array. A narrow (∼350 nm) air gap provides coupling of the array to the evanescent rf fields accompanying the SAW’s; thus, the silicon nonlinearities provide local mixing of the three rf fields and a fourth field, at dc, which accompanies the stored charge pattern. Two four-wave interactions have been cascaded (the first creates the stored charge, the second scans the charge pattern) to demonstrate the correlation of a waveform with a time-bandwidth product in excess of 10 000.
Visible photoabsorption by noble-gas trimer ions
Authors: Michels H. H. , Hobbs R. H. , Wright L. A.
Published: February 2003

A study of the electronic structure and photoabsorption characteristics of noble-gas trimer ions has been carried out using quantum mechanical methods. This study includes detailed density functional calculations of the potential energy surfaces for a prototype system, Ar+3, an analysis of the spectroscopic properties of the ground state of this ion, and prediction of the strong absorption bands. Studies in D3h, C2v, and D∞h symmetries were carried out. The lowest state of Ar+3 corresponds to the degenerate 2E′ symmetry with an indicated dissociation energy of 0.17 eV relative to Ar+2 (A 2Σ+u)+Ar (1S0). This trimer ion exhibits a small Jahn-Teller distortion which does not significantly alter our conclusions concerning the ground-state stability or absorption characteristics. A strong and very broad photoabsorption band (λ=480–670 nm) is predicted for the 2E′→2A′1 transition of this trimer ion. This suggests that such species may be important in the analysis of loss mechanisms in visible excimer lasers operating under high-pressure conditions with mixtures containing the noble gases.
Carrier-concentration reduction in high-dose phosphorus-implanted silicon caused by wet-oxygen oxidation
Authors: Yagi K. , Oyu K. , Tamura M. , Tokuyama T.
Published: February 2003

The redistribution of heavily implanted phosphorus atoms (⩾1×1016 ions/cm2) in the silicon substrate has been studied for wet-oxygen oxidation in the temperature range 700–1000 °C. The total carrier concentration of implanted layers is observed to decrease after wet-oxygen oxidation. Electron microprobe measurements show that the observed decrease corresponds to the inclusion of phosphorus atoms into the growing oxide films. Under certain conditions the phosphorus concentration in the substrate after wet-oxygen oxidation is found to be reduced to less than 20% of the as-implanted concentration.
Solid-state epitaxial growth of deposited Si films
Authors: von Allmen M. , Lau S. S. , Mayer J. W. , Tseng W. F.
Published: February 2003

Epitaxial growth by furnace annealing of amorphous Si layers deposited onto 〈100〉 Si substrates is demonstrated. Substrate cleaning prior to the evaporation includes only conventional chemical procedures without any attempt to achieve an atomically clean substrate layer interface. The crystalline quality of the grown layers near the surface is comparable to that of 〈100〉 Si regrown layers amorphized by Si implantation. Residual damage is usually found near the substrate-layer interface. The growth mechanism is believed to be vertical growth of isolated epitaxial columns which subsequently grow laterally to consume the remaining amorphous Si.
Transformation from Ohmic to offset behavior for the on state of an amorphous semiconductor threshold switch for interruptions greater than 12 ns
Authors: Vezzoli Gary C.
Published: February 2003

In measuring the on-state I-V curve of an amorphous semiconductor threshold switch it is essential that the addressing voltage pulse does not allow a subholding voltage interval which is longer than a ’’distribution free carrier lifetime’’ in order that only on-state properties be detected. If the voltage is not allowed to fall beneath the holding level for longer than about 12 ns, the well-known offset barrier of the transient on characteristics (TONC) does not develop, and, instead, the on-state curve is linear and largely temperature independent. The time interval τ1≈12 ns is interpreted as the distribution free carrier lifetime, or the average time interval of subholding voltage during which a sufficient number of carriers can either redistribute across the device, or can recombine into traps, to initiate the development of the offset barrier voltage in the TONC. The offset voltage, or what is called the blocked on state or the transient off state, is thus not a true element of the metal-like on state and is instead representative of the semiconductive intermediate states which bridge the normal off state and the true on state and which may involve a screening condition.
Collective acceleration of carbon ions to 170 MeV
Authors: Destler W. W. , Hoeberling R. F. , Kim H. , Bostick W. H.
Published: February 2003

The collective acceleration of carbon ions to a peak energy in the range 170–200 MeV has been achieved using a 6-MeV 190-kA 100-ns electron beam pulse generated by the Pulserad 1590 facility at Kirtland Air Force Base. Accelerated ions were detected using nuclear activation techniques.
Annealing of phosphorus-ion-implanted silicon using a CO2 laser
Authors: Miyao M. , Ohyu K. , Tokuyama T.
Published: February 2003

Annealing behavior of phosphorus implanted in silicon layers under cw CO2 laser irradiation is investigated. The irradiation time required for full electrical activation is found to depend on the dopant concentration of the substrate. This is because absorption of CO2 laser light is a function of free-carrier concentration in the crystalline substrate. During the experiment, an enhancement of annealing efficiency is observed in the case of a low-resistivity substrate or with bias light (Xe lamp) irradiation. This supports the above explanation.
Characterization of neutron-transmutation doping in silicon by the photoluminescence technique
Authors: Tajima Michio
Published: February 2003

The photoluminescence (PL) technique has been applied to the nondestructive characterization of neutron-transmutation doping in silicon crystals for the first time. We demonstrate the simultaneous determination of B and P concentrations both in the starting materials and in the doped crystals by the PL method. The drastic changes in the PL spectrum due to the neutron irradiation and the subsequent heat treatment reflect the behavior of the radiation damage and the annealing effect.
InGaAsP heterostructure avalanche photodiodes with high avalanche gain
Authors: Nishida Katsuhiko , Taguchi Kenko , Matsumoto Yoshishige
Published: February 2003

Distinct improvements in avalanche-gain and dark-current characteristics have been made in InGaAsP heterostructure APD’s. A planar-type p-n junction is formed in an InP window layer, separated from a light-absorbing InGaAsP layer. This APD structure has yielded an avalanche gain of 3000 and a dark-current density as low a 1 μA/cm2 at 0.5 Vb.
Relationships of electrical properties and melting threshold in laser-annealed ion-implanted silicon
Authors: Wang K. L. , Liu Y. S. , Burman C.
Published: February 2003

This paper describes a study comparing the results of the electrical measurements and the regrowth behavior of ion-implanted silicon annealed with an 80-ns (FWHM) laser pulse at 1.06 μm. Certain correlations were established among the threshold energy density required for melting, the dopant distributions, and the diode junction depth and leakage. It is demonstrated that in order to obtain low-leakage diodes, the anneaing energy density, which depends upon the implant conditions, far exceeds the melting energy density as determined from the transient optical-reflectivity change.
Spray-deposited high-efficiency SnO2/n-Si solar cells
Authors: Feng Tom , Ghosh Amal K. , Fishman Charles
Published: February 2003

SnO2/n-Si solar cells (area=1 and 4 cm2) having AM1 efficiencies of 12.3% on single-crystal silicon and 10.1% on polycrystalline silicon have been fabricated. The tin oxide is deposited by spraying a SnCl4 mixture onto heated silicon substrates. Using this low-cost process, large-area (20-cm2) single-crystal cells having 10% efficiency have also been made. The smaller diffusion length and higher resistivity in the polycrystalline silicon (Wacker) accounts for its lower efficiency as compared to single-crystal cells.
The formation of Ga1−xAlxAs layers on the surface of GaAs during continual dissolution into Ga-Al-As solutions
Authors: Small M. B. , Ghez R. , Potemski R. M. , Woodall J. M.
Published: February 2003

When solid GaAs is placed in an undersaturated solution of Ga, Al, and As, it has been observed that a layer of the solid Ga1−xAlxAs forms on the surface. In the past the presence of this layer has been attributed to a process of regrowth following sufficient dissolution to saturate the solution. On the other hand, an analysis of the kinetics of the situation has suggested that dissolution should be continuous and that the surface layer is formed by solid diffusion. An experiment is reported here in which the solid is forced to dissolve continuously, and a layer of Ga1−xAlxAs of similar thickness to those reported by others has been found to be produced on the surface. Such a layer could not have been produced by regrowth. In order to be produced by solid diffusion, the diffusion coefficient of Al in GaAs must be anomalously high.
Carbon and oxygen role for thermally induced microdefect formation in silicon crystals
Authors: Kishino Seigô , Matsushita Yoshiaki , Kanamori Masaru
Published: February 2003

Thermally induced microdefect formation phenomena are investigated in connection with oxygen and carbon in silicon crystals by using x-ray diffraction, infrared absorption, and etching/optical microscope observation techniques. In order to investigate the carbon and oxygen role for microdefect formation, oxygen-diffused floating-zone-grown silicon crystals, containing various carbon contents, are thermally treated. As a result, it is ascertained that the coexistence of both carbon and oxygen is necessary for the microdefect formation. It is also determined that the critical oxygen concentration for microdefect introduction by the heat treatment is about (5–6) ×1017 cm−3.
SAW dispersion and film-thickness measurement by acoustic microscopy
Authors: Weglein R. D.
Published: February 2003

The reflection acoustic microscope has been used to measure SAW velocity dispersion and to indirectly measure the film thickness in a layered composite consisting of Au on a Si substrate. A quantitative thickness determination was made via the acoustic material signature technique, that is nondestructive and noncontacting. A theoretical prediction of SAW dispersion is in excellent agreement with these measurements.
Ion-beam-induced formation of the PdSi silicide
Authors: Tsaur B. Y. , Lau S. S. , Mayer J. W.
Published: February 2003

Formation of PdSi has been obtained by implanting energetic Xe ions through a thin Pd (or Pd2Si) film on a Si substrate. The PdSi phase was found to form near the Pd2Si-Si interface from Rutherford backscattering measurements. Phase formation was confirmed by glancing-angle x-ray-diffraction analysis. Subsequent thermal annealing at 300–400 °C resulted in successive growth of the phase. A uniform PdSi layer was obtained at the final stage of the annealing and exhibited a sheet resistivity of 18 μΩ cm.
Fabrication of superconducting Nb3Sn-Cu composites
Authors: Verhoeven J. D. , Gibson E. D. , Owen C. V. , Ostenson J. E. , Finnemore D. K.
Published: February 2003

A new process has been developed for the fabrication of multifilamentary composites of Nb3Sn in a Cu matrix. Dendritic Cu-Nb alloys are cast as 2.5-kg billets and extruded to a tube shape. The core of the tube is filled with a Sn–5 wt% Cu alloy, and the assembly is drawn to 0.015-cm-diam wire with no intermediate anneals. Reaction of the wire at 550 °C for two days gives a product suitable for magnets in the 8–14-T range.
On the thermoelectric amplification of sound in semiconductors
Authors: Tenan M. A. , Marotta A. , Miranda L. C. M.
Published: February 2003

The possibility of sound amplification in a semiconductor subjected to an external temperature gradient is discussed. It is shown that for kl≪1 and short-circuited samples, the temperature gradient threshold for amplification varies inversely proportional to (kl)2.
Nonalloyed Ohmic contacts to n-GaAs by pulse-electron-beam-annealed selenium implants
Authors: Mozzi R. L. , Fabian W. , Piekarski F. J.
Published: February 2003

Nonalloyed Ohmic contacts to n-GaAs have been formed by vapor deposition of TiPtAu on pulse-electron-beam-annealed Se-implanted surfaces. Peak carrier concentrations were about 1.2×1019/cm3, yielding a specific contact resistance rc≲6×10−7 Ω cm2.
The effect of substrate orientation on the liquid-solid distribution coefficients for GaxIn1−xAs in the temperature range 600–700 °C
Authors: Pearsall T. P. , Quillec M. , Pollack M. A.
Published: February 2003

We demonstrate that the liquid-solid distribution coefficients depend on the substrate orientation in the growth from the liquid phase of GaxIn1−xAs. The distribution coefficient of Ga for growth on the (100) face was found to be larger than that for growth on the (111B) face over the entire temperature range investigated.
700-h continuous room-temperature operation of AlxGa1−xAs-GaAs heterostructure lasers grown by metalorganic chemical vapor deposition
Authors: Dupuis R. D.
Published: February 2003

Constant-current continuous room-temperature (∼26 °C) operating times greater than 700 h have been achieved for AlxGa1−xAs-GaAs multiple-quantum-well heterostructure injection lasers grown by metalorganic chemical vapor deposition. One device has shown essentially no degradation in its output characteristics during this time.
Deleterious effects of an oxidizing drive-in ambient on implanted arsenic emitters in 〈111〉 silicon
Authors: Parrillo L. C. , Morris B. L.
Published: February 2003

In 〈111〉-oriented silicon, annealing high-dose (∼1×1016/cm2) implanted layers of arsenic in an ambient containing more than a few tenths of 1% oxygen in nitrogen results in dislocation networks that extend well beyond the implanted regions. As the oxygen concentration in the drive-in step is increased, the lateral extent and density of the dislocation loops increases. Electrically, the extended dislocation loops cause leaky emitter-base junctions and also emitter-to-collector leakage of the punch-through type. By controlling the drive-in ambient to 0.1% oxygen in nitrogen, we have prevented the formation of these extended dislocations for arsenic doses up to 2×1016/cm2.
Efficient generation of low-energy positrons
Authors: Mills Allen P.
Published: February 2003

Positrons with a nearly thermal-energy distribution can be generated by moderating the beta-decay spectrum of a radioactive β+ source. The efficiency ε of this process is improved substantially by using a clean single-crystal Cu moderator which has been activated by a one-third monolayer of S. When combined with a low self-absorption 58Co β+ source, this moderator has an efficiency (ε=10−3) which is within a factor of ∼6 of what one would expect based on what is presently known about positron diffusion, slow-positron emission, and the stopping of β particles.
Polarization-rotation and thermal-motion studies via resonant degenerate four-wave mixing
Authors: Steel D. G. , Lind R. C. , Lam J. F. , Giuliano C. R.
Published: February 2003

We report experimental observation of polarization rotation in resonant degenerate four-wave mixing (DFWM) arising from the third-order coupling of the electric fields. This effect allows investigation of molecular motion and its effect on the efficiency of the DFWM. By controlling the pulse width and therefore γ=T0/τp (where T0≡λ/vth) we show quantitative agreement with a third-order density matrix perturbation calculation. In particular, using a CO2 laser at 10.6 μm and SF6 as the nonlinear medium, we show that for γ≫1 (stationary limit) we see no molecular motion and for γ≈1, we see a significant ’’washout’’ of one third–order polarization.
400-Å high aspect-ratio lines produced in poylmethyl methacrylate (PMMA) by ion-beam exposure
Authors: Karapiperis L. , Lee C. A.
Published: February 2003

We report preliminary results on the fabrication of 400- and 2600-Å deep lines in polymethyl methacrylate (PMMA) by means of H+ exposure through a holographically produced fine conformal gold mask.
Evidence of room-temperature sintering in aluminum contacts in vacuum and in oxygen
Authors: Timsit R. S.
Published: February 2003

It is found that the area of metallic contact between two aluminum surfaces grows at room temperature both in ultrahigh vacuum and in an oxygen atmosphere. In vacuum, the growth rate is consistent with the rates predicted from sintering theory; the experimental evidence suggests that sintering is driven by capillary forces and controlled largely by dislocation creep. In oxygen, growth is slower but can be understood qualitatively also in terms of creep-controlled sintering.
Pseudoalloy behavior at interfaces; AgAu
Authors: Wertheim G. K. , Bates C. W. , Wernick J. H. , Buchanan D. N. E.
Published: February 2003

Analysis of mixed metallic layers formed by grain-boundary diffusion shows that atoms at the interface have properties resembling those of a solid solution. Generalization of this result suggests that the sharpness of an interface cannot be defined by electronic properties to better than two atomic layers.
Diffusion and p-type conduction of magnesium impurities in germanium
Authors: Ho L. T.
Published: February 2003

Magnesium has been introduced into germanium by the diffusion technique. After heat treatment, the room-temperature carrier concentration of the sample is of the order of 1015 cm−3. Conversion of the sample conductivity from n type to p type indicates that magnesium behaves like a substitutional double acceptor in germanium. A diffusion profile for magnesium impurities in germanium is presented.
Photoacoustic spectroscopy of chrysotile asbestos using a cw HF laser
Authors: Monchalin J.-P. , Gagné J.-M. , Parpal J.-L. , Bertrand L.
Published: February 2003

We have investigated the feasibility of using a cw HF laser to detect chrysotile asbestos fibers by a photoacoustic technique. We report the photoacoustic spectrum of Canadian chrysotile around its OH absorption band between 3400 and 3800 cm−1. We have verified that the absorption depends strongly on the relative orientation of the laser polarization and the fiber axis, a property which will be invaluable in a detection scheme.
Subsurface structures of solids by scanning photoacoustic microscopy
Authors: Wong Y. H. , Thomas R. L. , Pouch J. J.
Published: February 2003

Definitive experimental evidence is given for the nondestructive detection of subsurface structures of solids by the technique of scanning photoacoustic microscopy (SPAM). In the case of the ceramic materials studied, the thickness of the surface layer probed is dictated by the thermal diffusion length δth which scales as f−1/2. For a chopping frequency f∼100 Hz, δth is on the order of 100 μm. This demonstrates the advantages of SPAM over conventional microscopy in investigating structures beneath the surface.
Annealing kinetics of electron-irradiated GaAs heteroface solar cells in the range 175–200 °C
Authors: Walker G. H. , Conway E. J.
Published: February 2003

Annealing of electron-irradiation damage in GaAs solar cells is important for space applications. This paper describes studies conducted to understand this annealing process. GaAs heteroface solar cells were irradiated with 1×1015 1-MeV electrons/cm2 followed by thermal annealing. An activation energy for annealing of 1.25±0.14 eV and a frequency factor of (3.7±1.9) ×109 sec−1 were determined. A small component of the irradiation damage, which does not anneal measurably at 200 °C, was observed.