bluuebunny/crossref_metadata_2025 huggingface dataset:
X-ray streak-camera study of the dynamics of laser-imploded microballoons
Authors: Key M. H. , Lamb M. J. , Lewis C. L. S. , Moore A. , Evans R. G.
Published: February 2003

The time and space development of the x-ray emission from the irradiated target surface and the implosion core in laser-compressed glass microballoons is recorded by x-ray streak photography. The experimental variation of implosion time with target mass and laser energy is considered and compared with computer modeling of the implosion.
High-current ion beam from a moving plasma
Authors: Dembinski M. , John P. K. , Ponomarenko A. G.
Published: February 2003

High-current ion beams in the 10–20-keV range are extracted from a moving plasma. Current densities up to 2.5 A/cm2 are obtained at the plasma boundary, which is almost an order of magnitude larger than the Bohm current. Total currents of over 100 A are obtained from the plasma. Simple geometric focusing gives current densities ∼200 A/cm2 at the focus.
Chemical origin of the space-charge layer in cuprous oxide front-wall solar cells
Authors: Herion J.
Published: February 2003

Using Auger electron spectroscopy, the region near the front contact of cuprous oxide front-wall solar cells was investigated. In cells showing large photovoltages, a maximum of the copper concentration being by about 4 at.% percent higher than the bulk concentration was observed at a distance of 70 Å from the metal-semiconductor interface. If the photovoltage was low a copper maximum adjacent to the interfacial layer was found, instead. It is concluded that changes of the stoichiometry of cuprous oxide must be taken into account in order to explain the origin of the space-charge layer in Cu2O front-wall cells.
The effects of oxygen doping and subsequent annealing in nitrogen on the structure of polycrystalline silicon
Authors: McGinn Joseph T. , Goodman Alvin M.
Published: February 2003

We have used reflection high-energy electron diffraction (RHEED) to study (i) the structure (surface crystallinity) of semi-insulating polycrystalline silicon (SIPOS) layers having a wide range of oxygen doping and (ii) the effect of subsequent annealing on that structure. Our results are consistent with a model in which (i) excess O exists in the form of silicon oxide at the intergrain boundaries, (ii) the presence of this intergrain oxide tends to prevent grain growth during annealing, and (iii) sufficiently large O doping completely suppresses observable grain growth during annealing.
Minority-carrier generation in n-InP/SiO2 capacitors
Authors: Stannard J. , Henry R. L.
Published: February 2003

Zerbst and DLTS measurements have been used to study the processes active for minority-carrier generation in n-InP/SiO2 capacitors. Surface generation velocities near 104 cm/sec were observed, and generation in the bulk proceeds via a level below midgap which has a large cross section for electron emission. The present capacitors have low leakage but no ’’inversionlike’’ C-V response at low frequency. Comparison with Langmuir film structures having exactly opposed properties indicates minority charge is trapped in the present capacitors for all values of the applied potential.
Optical distortion coefficient of 〈111〉-oriented CaF2 windows at chemical laser wavelengths
Authors: Klein Claude A.
Published: February 2003

Recently, the piezo-optic constants of CaF2 single crystals have been measured in the infrared. These measurements indicate that the critical orientation in the sense of Joiner, Marburger, and Steier is within 1.9°±1.2° from the [111] direction. It follows that 〈111〉-oriented CaF2 laser windows do not exhibit any detectable stress birefringence independently of the polarization of the incident beam. On using the best data currently available on relevant properties of single-crystalline material at 3.39 μm, an evaluation of the optical distortion coefficient χ of 〈111〉-oriented CaF2 yields an exceptionally small value: χ= (1.0±0.6) ×10−6 K−1. On this basis, it is shown that, in principle, a 1-cm-thick AR-coated CaF2 window can handle average energy fluences of at least 300 kJ/cm2 without violating the Maréchal criterion.
Range-resolved measurements of atmospheric ozone using a differential-absorption CO2 laser radar
Authors: Asai Kazuhiro , Itabe Toshikazu , Igarashi Takashi
Published: February 2003

A 9.4-μm CO2 laser radar was used to obtain ozone measurements in the atmosphere with the differential-absorption method. Concentrations of ozone were measured in the horizontal interval from 0.5 to 2 km with 300-m range resolution. The measurement uncertainty varied from about ±15 ppb at 0.5 km to about ±40 ppb at 1.5 km. Experimental results showed good agreement between the ozone concentrations measured with the laser radar and those measured by point monitors at various sites.
A majority-carrier camel diode
Authors: Shannon J. M.
Published: February 2003

A majority-carrier diode concept is described in which current flow is controlled by a potential hump in the bulk of a semiconductor. Devices of this type, called camel diodes, having ideality factors <2 have been realized using low-energy ion implantation.
Photovoltaic effect in Cu/CuGaSe2 Schottky barriers
Authors: Stankiewicz J. , Giriat W.
Published: February 2003

Cu/CuGaSe2 Schottky barriers have been prepared by vacuum deposition of copper on p-type CuGaSe2 single crystals with a resistivity of 10−2 Ω cm. The photovoltaic properties of such cells have been investigated. Under the AM1 condition these cells exhibit a solar-energy conversion efficiency of 3.5%.
The lateral effect of oxidation on boron diffusion in 〈100〉 silicon
Authors: Lin A. M. , Dutton R. W. , Antoniadis D. A.
Published: February 2003

It is found that oxidation of silicon not only enhances the diffusion of the dopants in the regions under oxidized surface but also in the adjacent unoxidized regions. The diffusivity of boron in the narrow unoxidized regions is enhanced by the oxidation with an enhancement decreasing rapidly with the increasing distances from the oxidation regions. The experimental results show that the lateral diffusion length of the oxidation-induced extrinsic point defects that cause this lateral enhancement is 2 μm for temperatures from 900 to 1100 °C. This lateral diffusion length is much shorter than the reported vertical diffusion length (25 μm). Nevertheless, for modern integrated circuit dimensions, the lateral effect of oxidation-enhanced diffusion can have significant effects on device properties and minimum pattern spacings.
Depth dependence of atomic mixing by ion beams
Authors: Tsaur B. Y. , Matteson S. , Chapman G. , Liau Z. L. , Nicolet M-A.
Published: February 2003

Ion backscattering spectrometry has been used to investigate the depth dependence of atomic mixing induced by ion beams. Samples consisting of a thin Pt (or Si) marker a few tens of angstroms thick buried at different depths in a deposited Si (or Pt) layer were bombarded with Xe+ of 300 keV at 2×1016 cm−2 dose and Ar+ of 150 keV at 5×1015cm−2 dose. Significant spreading of the marker was observed as a result of ion irradiation. The amount of spreading was measured as a function of depth of the marker, which was then compared with the deposited energy distribution. Measurements of this kind promise new insight into the nature of the interaction between ion beams and solids.
Textured silicon: A selective absorber for solar thermal conversion
Authors: Gittleman J. I. , Sichel E. K. , Lehmann H. W. , Widmer R.
Published: February 2003

We have used reactive sputter etching to texture the surface of Si wafers. The texturing was in the form of pillars whose diameters and spacing were small compared with the useful solar wavelengths and whose heights were comparable with or larger than these wavelengths. The normal and hemispherical reflectances of textured wafers were measured. The solar absorptance was found to be 0.99 for wavelengths below 1.0 μm. Because of the sharp drop in absorptance for photon energies less than the energy gap, the overall solar absorptance was about 0.85. The calculated thermal emittance was about 0.25 and was primarily due to multiphoton absorption processes normally observed in thick Si crystals. Much smaller values of thermal emittance would be obtained from thin textured films.
Polarization-independent optical directional coupler switch using weighted coupling
Authors: Alferness R. C.
Published: February 2003

We report the first demonstration of a guided-wave polarization-independent electro-optic switch. Using a specially designed weighted Ti-diffused directional coupler with stepped electrodes, we have achieved crosstalk levels below −23 dB for both switch states for arbitrary incident optical polarization.
Laser fluorescence spectroscopy of atomic uranium using a pulsed hollow cathode lamp as a vapor source
Authors: Miron E. , David R. , Erez G. , Lavi S. , Levin L. A.
Published: February 2003

A commercial hollow cathode lamp operated in a pulsed mode is used as a source of atomic uranium for spectroscopic measurements based on laser induced fluorescence. This method is especially convenient for stepwise laser spectroscopy of refractory elements.
The temperature dependence of band-to-band Auger recombination in silicon
Authors: Huldt L. , Nilsson N. G. , Svantesson K. G.
Published: February 2003

The Auger recombination coefficient has been determined from the decay kinetics of highly excited silicon. It was found to be proportional to T0.6, increasing from 3.0×10−31 to 4.6×10−31 cm6s−1 in the temperature interval 195–372 K.
Anomalous energy dissipation of intense focused electron beam in low atomic-number target
Authors: Miyamoto S. , Imasaki K. , Nakai S. , Yamanaka C.
Published: February 2003

An energy distribution of transmitted electrons through thin-foil targets irradiated by a tightly pinched relativistic electron beam has been measured by a multichannel electrostatic particle energy analyzer. The experimental result indicates the existence of an anomalous energy dissipation of beam electron in low-z target.
Debye screening modifications in ponderomotive effects
Authors: Sodha M. S. , Subbarao D.
Published: February 2003

The effective Debye screening length is shown to be increased in the presence of a high-power electromagnetic wave. The consequent modifications in ponderomotive redistributive effects and strong violations of charge neutrality have been shown to be in agreement with recent laser-plasma experiments.
Theory of elastic properties of composite materials
Authors: Berryman James G.
Published: February 2003

A new method of estimating effective macroscopic elastic constants for microscopically inhomogeneous materials is formulated using elastic-wave scattering theory. The self-consistent medium is determined by the condition that the scattered long-wavelength displacement field must vanish on the average. The resulting formulas are simpler to apply than previous methods due to the reduction from tensor to vector equations. Our formulas are automatically symmetric under interchange of constituent labels whereas some other ’’self-consistent’’ formulations for needle and disk inclusions do not possess this property. For spherical inclusions, the standard self-consistent elastic constants are reproduced.
Studies of the Si-SiO2 interface by MeV ion channeling
Authors: Cheung N. W. , Feldman L. C. , Silverman P. J. , Stensgaard I.
Published: February 2003

By performing backscattering-channeling measurements in two different geometries on thin Si crystals thermally oxidized at 800 °C, we have obtained upper and lower limits of the number of reconstructed Si layers at the Si-SiO2 interface. The results indicate an abrupt Si-SiO2 interface with one to two monolayers of Si reconstruction.
Polarization stabilization on single-mode fiber
Authors: Ulrich R.
Published: February 2003

The state of polarization at the output end of a long nominally circular single-mode optical fiber is stabilized by an active control system. It contains a polarimeter and two electromagnetic fiber squeezers which introduce variable amounts of stress birefringence directly into the fiber, compensating for the effects of changing intrinsic fiber birefringence.
Laser-induced recystallization and defects in ion-implanted hexagonal SiC
Authors: Makarov V. V. , Tuomi T. , Naukkarinen K. , Luomajärvi M. , Riihonen M.
Published: February 2003

SiC(6H) crystals amorphized with 14N+-ion implantation were annealed with CO2 laser pulses at intensities of 20–100 MW/cm2. Laser produced crystallization due to residual ray absorption was studied by means of optical spectroscopy, 4He+-ion backscattering spectrometry and channeling as well as Cu Kα1 and synchrotron x-ray diffraction topography. At low laser intensities topographs revealed linear and planar defects, which contributed to increased dechanneling independent of analyzing beam energy. Minimum of lattice disorder, which was in some regions of the laser impact area smaller than that obtained in thermal annealing, was attained at the peak laser intensities of about 50 MW/cm2.
Luminescent p-GaAs grown by zinc ion doped MBE
Authors: Bean J. C. , Dingle R.
Published: February 2003

Low-energy zinc ions have been incorporated in growing MBE GaAs layers producing heavily doped p-type material. As-grown layers retain a substantial amount of radiation damage as indicated by the absence of photoluminescence and low hole mobilities. A postgrowth anneal yields layers with low-temperature luminescence and mobilities comparable to zinc doped LPE epitaxial layers. Annealed layer quality does not depend on substrate growth temperature or ion energy over the ranges 580–650 °C and 100–3000 eV, respectively. The measured zinc ion sticking coefficient has a value of ∼50% and depends only weakly on ion energy. The data suggest that the sticking coefficients are enhanced by a simple ion burial mechanism and not by an electrostatic attraction between the ion and surface atoms.
The emission spectrum from planar-channeled electrons
Authors: Pantell R. H. , Swent R. L.
Published: February 2003

Planar-channeled electrons radiate electromagnetic energy with sharp peaks in the emission spectrum. A model is developed to predict the locations of these peaks, which are shown to correlate well with experimental observations. A by-product of the model is that it provides a sensitive method for determining the interplanar potential energy function in a crystal.
Polarization effects on single-mode optical fiber sensors
Authors: Sheem S. K. , Giallorenzi T. G.
Published: February 2003

In a conventional circular cross-section single-mode fiber, built-in and induced birefringences remove the degeneracy and make the fiber a two-Eigenmode system. We have constructed the first all-fiber interferometric sensor system and have performed preliminary studies on the effects of birefringence in these interferometers. Theoretical analysis and experimental data supporting this analysis are presented for the 3-dB coupler and all-fiber interferometer sensor.
Minority-carrier diffusion coefficients in highly doped silicon
Authors: Dziewior J. , Silber D.
Published: February 2003

Direct experimental determination of minority-carrier mobilities and corresponding diffusion coefficients in highly doped p- and n-type silicon have apparently not been performed until now. We have determined the minority-carrier diffusion coefficient in phosphorus- and boron-doped silicon (doping range 1017–1019 cm−3) at 300 K by measuring the complex diffusion length of minority carriers generated by 10.7-MHz optical excitation. Converted into mobilities by the Einstein relation, the results do not differ significantly from Irvin’s majority-carrier mobilities.
Amphoteric behavior of Ge implants in GaAs
Authors: Yeo Y. K. , Ehret J. E. , Pedrotti F. L. , Park Y. S. , Theis W. M.
Published: February 2003

The electrical properties of Ge-implanted GaAs have been studied. Room-temperature implantation was performed at 120 keV with doses ranging from 5×1012 to 3×1015/cm2. Implanted samples were annealed with pyrolytic Si3N4 encapsulants at temperatures ranging from 700 to 950 °C. It was found that both p- and n-type layers were produced, depending upon ion dose and anneal temperature. For doses of ∼1×1014/cm2 or below, the implanted layer is p type at anneal temperatures up to 950 °C, with electrical activation up to 38%. For doses of ∼1×1015/cm2 or above, the implanted layer is n type at all anneal temperatures, with activation up to 5%. For the intermediate dose of 3×1014/cm2, the conductivity changes from p to n type at an anneal temperature between 900 and 950 °C.
Stability enhancement in electron-beam-sustained excimer laser discharges
Authors: Brown Robert T. , Nighan William L.
Published: February 2003

Techniques are described for prolonging the duration of stable e-beam-controlled excimer laser discharges, including: temporal tailoring of either the discharge voltage or the ionization source and kinetics modification by way of additives. Theoretical and experimental results are presented for KrF* laser discharges.
Modified balanced-bridge switch with two straight waveguides
Authors: Mikami Osamu , Zembutsu Sakae
Published: February 2003

A new balanced-bridge-switch configuration is presented. This configuration has two 3-dB couplers and an electro-optic phase shifter formed only by two parallel straight waveguides. That is, these three regions were directly interconnected through no extra waveguides. The phase shifter was realized by unsynchronizing the phase of two adjacent waveguides by loading a high-index film on one of them. The modified balanced-bridge switch was fabricated in c-plate LiNbO3 using Ti-diffused waveguides and a Se-S–based chalcogenide glass film. Waveguide dimensions were 8-μm width, 5-μm gap, and 16-mm interaction length. Switch characteristics at 1.15- μm wavelength were 3.3 V half-wave voltage, 8.7-dB crosstalk, and 4.2-dB insertion loss.
Metastable 75As concentrations formed by scanned cw e-beam annealing of 75As-implanted silicon
Authors: Regolini J. L. , Sigmon T. W. , Gibbons J. F.
Published: February 2003

The incorporation of 75As into substitutional lattice sites in silicon in excess of 1021 cm−3 is reported. This has been accomplished by both a scanned cw e-beam and a scanned cw laser operating with dwell times in the range of milliseconds. Both electron concentration (using differential van der Pauw) and atom location measurements (using MeV ion channeling) are reported. Standard thermal processing indicates that these layers are metastable.
Properties of conducting transparent oxide films produced by ion plating onto room-temperature substrates
Authors: Howson R. P. , Avaratsiotis J. N. , Ridge M. I. , Bishop C. A.
Published: February 2003

Indium and indium 10% tin oxide films have been produced on room-temperature insulating substrates and have exhibited high conductivities which compare with the best reported for films made at substrate temperatures of 450 °C and higher. They were made by the evaporation and sputtering of the metals in an atmosphere of argon and oxygen onto a substrate which was one electrode of a rf discharge providing surface bombardment of the substrate. The properties of the films were a function of the oxygen partial pressure, the rf bias voltage, the rate of formation, and gas throughput. It was possible to produce films with mobilities up to 40 cm2 V−1 s−1 with carrier densities up to 3×1020 cm−3 and with conductivities up to 5×104 (Ω m)−1, all of which were transparent in the visible region of the spectrum.
Pulsed-electron-beam annealing of polycrystalline-silicon films
Authors: Kamins T. I. , Greenwald A. C.
Published: February 2003

Pulsed-electron-beam annealing of moderately-phosphorus-doped poly-silicon films reduces their resistance below that of thermally annealed films under optimum conditions. In heavily doped films, the electron pulse can cause the effective dopant concentration to exceed that corresponding to solid solubility, but the excess dopant does not stay in solution upon subsequent heat treatment.
Efficiency enhancement in manganese-doped zinc silicate phosphor with AlPO4 substitution
Authors: Chang I. F. , Shafer M. W.
Published: February 2003

Large increases in the efficiency of the conventional P1 phosphor (Zn2SiO4 : Mn) have been achieved by substituting various combinations of III and V oxides for SiO2, e.g., Zn2−yMnySi1−2xAlxPxO4. The photoluminescence efficiency of these phosphors exhibit strong dependence on the AlPO4 substitution concentration x having highest efficiency for x=0.5–1.5%. Cathodoluminescence and decay measurements show that such materials can have CL efficiency greater than the commercial zinc silicates and still have comparable persistence characteristics.
Microstructure of plasma-deposited a-Si : H films
Authors: Knights J. C. , Lujan R. A.
Published: February 2003

Using transmission and scanning electron microscopy, it is shown that plasma deposition of amorphous silicon hydrogen films from silane or silane/argon mixtures proceeds via nucleation and growth of islands of average lateral dimensions ∼100 Å. If these islands do not coalesce into a homogeneous film, subsequent growth produces columnar morphology with low-density interstitial regions. There is a strong correlation between the columnar structure and the presence of nonradiative recombination centers.
XeF ground-state dissociation and vibrational equilibration
Authors: Fulghum S. F. , Feld M. S. , Javan A.
Published: February 2003

The time evolution of the population in XeF ground-electronic-state vibrational levels is studied using a laser-induced fluorescence technique. The results indicate that a quasiequilibrium distribution is rapidly established within the vibrational manifold and that the dissociation rate of the molecular ground state as a whole is (1.4±0.3) ×104 sec−1 Torr.−1.
Optical directional couplers with weighted coupling
Authors: Alferness R. C.
Published: February 2003

We have fabricated optical directional couplers using titanium-diffused waveguides for which the coupling strength is carefully weighted along the device. With a Hamming function weighting, −25-dB transfer response sidelobes have been obtained, a 17-dB reduction over the uniform coupling case. Sidelobe reduction results in a significant increase in the performance of directional coupler filters and switches.
Self-diffusion in intrinsic silicon
Authors: Kalinowski Ludomir , Seguin Remy
Published: February 2003

The silicon self-diffusion in intrinsic silicon was investigated by a new method using stable isotope 30Si and the ion-analyzer technique. The temperature dependence of the diffusion coefficient was obtained in the range from 885 to 1175 °C from which an activation energy 110.6 kcal/mole was obtained.
Ionization coefficients of electrons and holes in InP
Authors: Armiento C. A. , Groves S. H. , Hurwitz C. E.
Published: February 2003

The ionization coefficients of electrons and holes in InP have been determined from photomultiplication measurements on abrupt-junction low-leakage np+ InP avalanche photodiodes. The ionization rate of holes ( β) was found to be greater than that for electrons (α), the ratio varying with peak electric field Em from β/α=3.8 at Em=4.85×105 V cm−1 to β/α=2.7 at Em=6.37×105 V cm−1.
Optical derivative measurements of the electrical parameters for a junction diode
Authors: Paoli Thomas L.
Published: February 2003

A derivative technique is presented to determine optically the electrical parameters of a p-n junction. The method relies upon the saturation produced in the optically generated current delivered to a load resistor as a result of increases in either the average optical power incident on the p-n junction or the dc circuit voltage. Analysis of the dc equivalent circuit shows that the degree of saturation measured by a derivative of the load current allows determination of the junction’s exponential parameter, saturation current, and shunt resistance. The technique is illustrated by application to a silicon avalanche photodiode.
Visualization of the grain-boundary potential barriers of PTC-type BaTiO3 ceramics by cathodoluminescence in an electron-probe microanalyzer
Authors: Ihrig H. , Klerk M.
Published: February 2003

In PTC-type BaTiO3 ceramics the grain-boundary potential barriers can easily be made visible by means of cathodoluminescence in an electron-probe microanalyzer without having a voltage applied. The visualization can be explained in the context of our finding that the intensity of the cathodoluminescence radiation depends sensitively on the number of charge carriers present in the conduction band. Thus, in PTC-type BaTiO3 ceramics, but not in undoped or reduced materials, the deficiency of conduction electrons in the depletion layers at the grain boundaries causes a blackening of the grain-boundary regions. The blackening of the grain boundaries of our PTC ceramics also appears below the Curie point, thus demonstrating the existence of grain-boundary barriers in this temperature range.
Heating-effect minimization in dye lasers
Authors: Matheson Kenneth Lee , Thorne James M.
Published: February 2003

Optical pumping of dye lasers deposits heat nonuniformly in the active medium. Because the refractive index of a liquid or gas is a function of temperature, gradients are created which refract the laser beam. This effect is sometimes serious enough to quench laser action. In this paper, we evaluate the effects caused by optical pumping with a coaxial flashlamp and suggest ultraviolet absorbers and wavelength shifters as materials for minimizing the problem.
Theory of bistability in nonlinear distributed feedback structures
Authors: Winful Herbert G. , Marburger J. H. , Garmire E.
Published: February 2003

We show that optical bistability can occur in a distributed feedback structure with an intensity-dependent refractive index. Analytical expressions for the transmissivity are obtained and a comparison with Fabry-Perot-type devices is presented.
Detection of far-infrared radiation using Rydberg atoms
Authors: Ducas Theodore W. , Spencer William P. , Vaidyanathan A. Ganesh , Hamilton William H. , Kleppner Daniel
Published: February 2003

A new method for detecting far-infrared radiation is demonstrated. The far-infrared radiation induces transitions between highly excited (Rydberg) levels of Na. These transitions can be detected by selective field ionization. The method is capable of providing narrow-band detection with essentially continuous tuning throughout the infrared and far-infrared range. We have detected radiation from a laser source at 496 and 118 μ with a 1-MHz bandwidth. A noise equivalent power of 5×10−15 W/Hz1/2 was measured at 496 μ.
Interferometry of a gas-puff z-pinch plasma
Authors: Shiloh J. , Fisher A. , Bar-Avraham E.
Published: February 2003

A nitrogen laser interferometer is utilized to study the density profile of a gas-puff z-pinch plasma during the implosion stage and the final collapse. The density profile and the plasma stability as a function of the different parameters are reported.
Comparison of dopant incorporation into polycrystalline and monocrystalline silicon
Authors: Monkowski J. R. , Bloem J. , Giling L. J. , Graef M. W. M.
Published: February 2003

The capacitance-voltage (C-V) technique was used to compare the dopant distribution in polycrystalline silicon to that in monocrystalline silicon grown under the same conditions via chemical vapor deposition. Over a doping range extending from approximately 1015 to 1019 cm−3, the polycrystalline and monocrystalline material yielded identical results. These results, in conjunction with those of other investigations, indicate that the concentration and uniformity of dopant in both n- and p-type polycrystalline silicon match those in monocrystalline silicon.
Temperature dependence of the current-voltage characteristics of silicon MIS solar cells
Authors: Shewchun J. , Singh R. , Burk D. , Scholz F.
Published: February 2003

Measurements on the dark I-V characteristics of Al-SiOx- (p-type) Si solar cells as a function of temperature have been used to elucidate one of the possible current conduction mechanisms in MIS solar cells. A good fit is obtained by using the diffusion current mechanism as described previously in our theory of MIS solar cells. There is little evidence in the data on our devices to support the thermionic emission model which is the alternate mode of operation proposed by other investigators.
A Seebeck effect position sensor for CO2 laser beam alignment
Authors: Hammond R. B. , Gruhn C. R.
Published: February 2003

A new concept for a laser position sensor is presented. The device utilizes the Seebeck effect in semiconductors. Results using a Si detector show position linearity and energy linearity of the device signal. A theoretical model explaining the operation of the device is outlined. Applications to pulsed laser beam alignment are discussed.
Optical bistability in semiconductors
Authors: Gibbs H. M. , McCall S. L. , Venkatesan T. N. C. , Gossard A. C. , Passner A. , Wiegmann W.
Published: February 2003

Optical bistability has been observed in a semiconductor for the first time. The bistable etalon consists of a GaAlAs-GaAs-GaAlAs molecular-beam-epitaxially-grown sandwich with 90% reflectivity coatings. The bistability is primarily dispersive with the nonlinear refractive index arising from light-induced changes in exciton absorption. Using light of frequency just below the exciton peak, we observed bistability from 5 to 120 °K with 40-ns turn-off and subnanosecond turn-on times with 1 mW/μm2 holding intensity.
Degenerate four-wave mixing near the band gap of semiconductors
Authors: Jain R. K. , Klein M. B.
Published: February 2003

We present a theoretical calculation and experimental data on the effective third-order susceptibilities χ(3) for degenerate four-wave mixing near the band gap of semiconductors. The closeness of the calculated and experimental values for the effective χ(3) in silicon at 1.06 μm indicates the utility of our simple calculation. The large values of χ(3) indicate the possibility of high-efficiency degenerate four-wave mixing in semiconductors, especially at longer wavelengths.
Negative differential resistance through real-space electron transfer
Authors: Hess K. , Morkoç H. , Shichijo H. , Streetman B. G.
Published: February 2003

A new mechanism is proposed to obtain negative differential resistance in layered heterostructures for conduction parallel to the interface. The mechanism is based on hot-electron thermionic emission from high-mobility GaAs into low-mobility AlxGa1−xAs. Preliminary calculations indicate that high peak-to-valley ratios can be achieved. The transfer speed is estimated to be of the order of 10−11 s. We further show that the concept of hot-electron thermionic emission can be applicable to a variety of devices.
Improvements of current-carrying capacities of the composite-processed Nb3Sn in high magnetic fields
Authors: Sekine H. , Tachikawa K. , Iwasa Y.
Published: February 2003

The Nb3Sn growth rate Hc2 and Jc in high fields (⩾12 T) of composite-processed Nb3Sn are greatly increased by the addition of hafnium to the niobium core. Furthermore, the simultaneous addition of hafnium to the core and gallium to the matrix more significantly enhances Hc2, and Jc in high fields. Jc of the Nb-Hf/Cu-Sn-Ga wire specimens exceeds 1×105 A/cm2 at 17 T, suggesting the possibility of fabricating multifilamentary Nb3Sn composite wires that stand use in fields at least up to 17 T.
Solid-state electrochromic cell with anodic iridium oxide film electrodes
Authors: Dautremont-Smith W. C. , Beni G. , Schiavone L. M. , Shay J. L.
Published: February 2003

A new solid-state electrochromic cell has been fabricated using an anodic iridium oxide film (AIROF) display electrode. The cell has the symmetric sandwich structure AIROF‖Nafion‖AIROF, with the Nafion solid electrolyte opacified by an in situ precipitation technique. A symmetric square-wave voltage of 1.5 V amplitude produces clearly perceivable color changes from pale to dark blue-gray in ≈1 sec when viewed in diffuse reflection. Good open-circuit optical memory is exhibited: (typical loss in attenuation of 8%/day).
Surface-acoustic-wave plate convolvers at 1 GHz
Authors: Colvin R. D. , Carr P. H.
Published: February 2003

Convolution has been performed at 800 MHz and 1 GHz on Y cut, Z propagating and 38° (rotated from +Z) cut, X propagating lithium niobate, respectively. No saturation of the convolved output was observed for an acoustic power of 178 mW/mm. An attenuation of 1.4±0.3 dB/μsec due to a 500-Å Al film was measured at 1 GHz.
Imploding argon plasma experiments
Authors: Stallings C. , Childers K. , Roth I. , Schneider R.
Published: February 2003

The Pithon pulsed electron beam accelerator was used to implode an argon plasma at 4 TW. The plasma was prepared by microwave preionization of an annular column of gas injected between the output electrodes of the pulser. The electrodynamic behavior implied that most of the gas was involved in the pinch. The plasma conditions were inferred from hydrogenlike and heliumlike x-ray emission spectra. Final pinch dimensions were determined from x-ray pinhole photographs and laser shadowgraphs.
Solid solubility of As in Si as determined by ion implantation and cw laser annealing
Authors: Lietoila A. , Gibbons J. F. , Magee T. J. , Peng J. , Hong J. D.
Published: February 2003

Complete electrical activity was obtained by cw laser annealing of 7×1015 As/cm2 implanted into (100) Si at 100 keV. The peak concentration for these implantation conditions is 1.4×1021/cm3, both theoretically and experimentally. However, this peak concentration was found to be thermally unstable, relaxing to a value of 3×1020/cm3 in a period of less than 2 min at 900 °C. If the peak implanted concentration is below 3×1020/cm3, the electrical activation and crystal structure are unaffected by similar thermal processing. We conclude from these data that the solid solubility of As in Si at 900 °C is approximately 3×1020/cm3, which is almost an order of magnitude below the published value.
Theoretical study of the deexcitation of KrF and XeF excimers by low-energy electrons
Authors: Hazi A. U. , Rescigno T. N. , Orel A. E.
Published: February 2003

Cross sections and rate constants for electron deexcitation of the excimer states of KrF and XeF have been calculated using a modified impact parameter method, and large ab initio wave functions. The superelastic processes are dominated by the B→X transitions with thermal rate constants of 7×10−8 and 3×10−8 cm3/sec for XeF and KrF, respectively.
The isotope shift in the 22P states of lithium and spatially resolved laser-induced fluorescence
Authors: Mariella R.
Published: February 2003

Spatially resolved laser-induced fluorescence has been used to observe and measure the isotope shift for atomic lithium in the 22P←22S transitions. A modified saturated absorption spectrum was also obtained for the ’’overlapping’’ transitions. The 7Li-6Li isotope shift in the absence of fine and hyperfine splittings is calculated to be 1 0532±5 MHz.
Time resolved fluorescence of trans-Stilbene in the picosecond regime
Authors: Taylor J. R. , Adams M. C. , Sibbett W.
Published: February 2003

The Synchroscan streak camera system has been used to examine the temperature dependence of the fluorescence decay of trans-Stilbene between -10 and 30 °C. Two components of the fluorescence have been detected; a short one varying between 125 and 64 psec over the range and a much weaker longer one varying from 690 to 1450 psec. The presence of the longer component may indicate a return to the transgeometry following initial photoisomerization.
The depth of defect annihilation in silicon by pulse laser annealing: Experiment and theory
Authors: Jastrzebski L. , Bell A. E. , Wu C. P.
Published: February 2003

Defect annihilation has been observed in silicon as a result of laser annealing using a Q-switched ruby laser. The threshold pulse energy density for defect annihilation was found to be 1 J/cm2 (pulse length ∼25 ns), and the depth of the defect-free region was found to increase with increasing pulse energy. A thermal model was developed which predicts the depth of melting and the recrystallization velocity. The calculated depth of melting was found to be in good agreement with the experimentally determined depth of defect annihilation. The defect annihilation occurs as a direct result of the extremely high recrystallization velocities which are associated with laser annealing with short pulses.
Short-channel MOS FET’s fabricated by self-aligned ion implantation and laser annealing
Authors: Koyanagi M. , Tamura H. , Miyao M. , Hashimoto N. , Tokuyama T.
Published: February 2003

Short-channel MOS FET’s are successfully fabricated using Q-switched ruby laser irradiation on As-implanted sources and drains. Implantation and laser irradiation are both self-aligned by the polysilicon gate electrodes. The threshold-voltage–vs–channel-length relation is improved as a result of the extremely limited lateral diffusion of implanted As atoms.
Multiple-quantum interference superconducting analog-to-digital converter
Authors: Harris Richard E. , Hamilton C. A. , Lloyd Frances L.
Published: February 2003

Multiple-quantum interference in a superconducting interferometer is used for analog-to-digital conversion. The simple fully parallel four-bit converter which is described is the first known use of this effect in a digital circuit. Sampling rates of 2×108 per second were achieved, and much higher rates appear possible.
Current injection GaAs-AlxGa1−xAs multi-quantum-well heterostructure lasers prepared by molecular beam epitaxy
Authors: Tsang W. T. , Weisbuch C. , Miller R. C. , Dingle R.
Published: February 2003

Low-current-threshold room-temperature injection GaAs-AlxGa1−xAs multi-quantum-well (MQW) lasers have been prepared by molecular beam epitaxy. Under pulsed current injection, lasing emission attributed to the n=1 electron-to-light-hole (1 e-lh) confined-particle transition was observed at threshold. Above threshold, lasing emission involving the n=1 electron-to-heavy-hole transition (1 e−hh) became dominant. Single longitudinal mode operation has also been observed for these broad-area MQW lasers. For heat-sink temperatures between 8 and 100 °C, the lasing current threshold Ith for the 1 e−hh transition has an exponential variation with temperature of the form Ith∝ exp(T/T0), where T0=230 °K.
Backward Raman compression of XeCl laser pulse in Pb vapor
Authors: Djeu N.
Published: February 2003

Pulse compression has been observed for the spontaneously generated backward Raman wave in Pb vapor pumped by the XeCl laser. A compression factor in excess of 6.7 was observed with a photon efficiency of 42%.
The scope of effective medium theory for fine metal particle solar absorbers
Authors: Smith G. B.
Published: February 2003

The treatment of an array of small metal particles as a continuous effective medium is shown to be possible for visible and near infrared frequencies at much larger particle sizes and separations than often supposed. Specific upper limits are evaluated for chromium. Results are based on the strongly correlated model. For this, the usual topology, variation, and attenuation of the field strength over average unit cell dimensions are permissible, provided such variations are characteristic of the effective medium as a whole. As wavelength decreases, the leading contribution to diffuse scattering off such composite films should come from terms proportional to λ−8 not the Rayleigh term.
Efficiency of quantum-utilizing solar energy converters in the absence of intraband thermalization
Authors: Ross Robert T.
Published: February 2003

In some photoelectrical and photochemical devices, energy conversion may occur before thermal equilibrium within the electronic bands of the absorber. A statistical thermodynamic argument shows that such hot-transfer devices cannot have an efficiency greater than that of an ideal device in which thermalization precedes energy conversion.
Temperature dependence of the exciton lifetime in high-purity silicon
Authors: Hammond R. B. , Silver R. N.
Published: February 2003

We observe that the exciton lifetime in high-purity silicon is strongly temperature dependent. To describe our data we propose a theory that includes capture, evaporation, and recombination of excitons at neutral impurities. We suggest applications of exciton-decay measurements to the determination of impurity content, capture cross sections, and electron-hole droplet nucleation kinetics.
Deep levels in Ga1−xAlxAs under pressure
Authors: Saxena Ashok K.
Published: February 2003

Hall electron concentration as a function of temperature (80≲T⩽300 K) has been measured on samples of Ga1−xAlxAs with compositions x in the range 0.23⩽x⩽0.32. The measurements are repeated for the same crystals and for various constant hydrostatic pressures to alter their band structure. The results show that a deep level is present in the crystals whose activation energy initially increases with pressure, being 5 and 145 meV for P=0 and 20 kbars, respectively, for x=0.23. For P≳20 kbars, the activation energy decreases monotonically with pressure, reaching a value of 90 meV at 50 kbars. The results show that the deep level is principally associated with the indirect conduction band minima L and X in Ga1−xAlxAs.
Polyacetylene, (CH)x: Photoelectrochemical solar cell
Authors: Chen S. N. , Heeger A. J. , Kiss Z. , MacDiarmid A. G. , Gau S. C. , Peebles D. L.
Published: February 2003

Photoelectrochemical photovoltaic cells have been fabricated using polyacetylene, (CH)x, as the active photoelectrode. Using a sodium polysulfide solution as electrolyte, Voc∼0.3 V and Isc∼40 μA/cm2 were obtained under illumination of approximately 1 sun. Under present conditions, the cell efficiency is limited by the series resistance, the small effective area of the electrode configuration, and the absorbance of the solution.
Temperature dependence of threshold current for quantum-well AlxGa1−xAs-GaAs heterostructure laser diodes
Authors: Chin R. , Holonyak N. , Vojak B. A. , Hess K. , Dupuis R. D. , Dapkus P. D.
Published: February 2003

Data are presented showing that the threshold current density Jth(T) of quantum-well AlxGa1−xAs-GaAs heterostructure laser diodes, grown by MO-CVD, is less temperature dependent than that of conventional DH lasers. T0 in the usual expression Jth∝exp(T/T0) can be high as 437 °C. This behavior is explained in terms of the steplike density of states and the disturbed electron and phonon distribution functions of the quantum-well active region.
A frequency-locked mode-locked cw dye laser for high-resolution spectroscopy in the frequency domain
Authors: Couillaud B. , Ducasse A. , Sarger L. , Boscher D.
Published: February 2003

A synchronously mode-locked cw dye laser suitable for high-resolution spectroscopy in the frequency domain is described. The number of oscillating modes has been reduced to restrict the laser bandwidth to the order of the Doppler width of the molecular transitions. By frequency locking one of the oscillating laser modes to a reference cavity, the linewidth of each mode of the frequency comb has been narrowed to less than 500 kHz. The tuning of the central frequency extends from 5650 to 6300 Å in the case of R6G. The mode spectrum of the laser can be continuously translated in frequency over several gigahertz.
Dependence of laser output on initial photoelectron density in TEA CO2 laser
Authors: Suzuki Shunji , Ishibashi Yuko , Obara M. , Fujioka T.
Published: February 2003

The relationship has been experimentally clarified between UV preionization density and CO2 laser energy under conditions where the initial energy in the main discharge capacitor was held constant. Laser energy increased logarithmicaly with increasing initial electron number density. Initial electron number density increased exponentially as input preionization energy increased.
Interference enhanced Raman scattering from very thin absorbing films
Authors: Connell G. A. N. , Nemanich R. J. , Tsai C. C.
Published: February 2003

A new method of obtaining Raman spectra from a very thin highly absorbing films (α≳105 cm−1) is described. The technique which is termed interference enhanced Raman scattering (IERS) is shown theoretically to produce a gain in the scattered intensity of 10–103 (depending on the optical constants of the material) over that expected from a thick sample using the conventional Raman backscattering configuration. The potential of the method is demonstrated experimentally using tellurium, and a gain of 20 is obtained.
Role of carrier diffusion in lattice heating during pulsed laser annealing
Authors: Yoffa Ellen J.
Published: February 2003

A calculation is presented which demonstrates that diffusion of the hot, dense carriers generated in pulsed laser annealing of Si can substantially reduce the rate at which energy is transferred to the semiconductor lattice near the surface. The extent of the region in which this energy transfer occurs is consequently increased.
Raman scattering in superlattices: Anisotropy of polar phonons
Authors: Merlin R. , Colvard C. , Klein M. V. , Morkoc H. , Cho A. Y. , Gossard A. C.
Published: February 2003

Raman experiments on polar phonons in GaAs-Ga1−xAlxAs superlattices are reported. Other data from the literature, and its interpretation in terms of folding of the phonon Brillouin zone and scattering from q≠0 phonons induced by electronic zone folding, are discussed. An alternative explanation is presented based on optical anisotropy induced by layering. Numerical results show good agreement with experiment.
Quantitative determination of hydrogen in silicon-nitride films using proton-proton scattering
Authors: Paduschek P. , Eichinger P.
Published: February 2003

The hydrogen profiles of silicon-nitride films were measured using the p-p scattering technique with 1.2-MeV protons generated by a small accelerator. In plasma-nitride layers, hydrogen concentrations on the order of 20 at.% were found compared to 7 at.% in low-pressure CVD layers. The depth resolution was found to be 0.1 μm and a sensitivity limit of 10 ppm is estimated.
Crystalline disorder reduction and defect-type change in silicon on sapphire films by silicon implantation and subsequent thermal annealing
Authors: Inoue Tomoyasu , Yoshii Toshio
Published: February 2003

Ion channeling techniques have been utilized to study the improvement of crystalline quality of SOS films by Si implantation and subsequent thermal annealing. Crystalline disorder was greatly reduced when an amorphous layer was formed at the Si/sapphire interface and annealed at temperatures higher than 600 °C. It was shown that the regrowth of the amorphous layer proceeded from the surface toward the inner region. In the 200–400-keV proton channeling measurements, the dechanneled fraction was found to be proportional to the square root of the proton energy in the crystalline improved SOS, whereas as-grown SOS had no energy dependence. This indicates a defect-type change from microtwins to dislocations during the above treatment.
Improvement of polycrystalline silicon solar cells with grain-boundary hydrogenation techniques
Authors: Seager C. H. , Ginley D. S. , Zook J. D.
Published: February 2003

Electron-beam-induced-current– and dark-current–voltage measurements have been made on p/n photovoltaic cells fabricated from polycrystalline silicon. These data have demonstrated that grain-boundary hydrogenation greatly reduces grain-boundary minority carrier recombination and improves diode current-voltage characteristics.
Observation of amorphous silicon regions in silicon-rich silicon dioxide films
Authors: Hartstein A. , Tsang J. C. , DiMaria D. J. , Dong D. W.
Published: February 2003

Raman scattering and optical transmission measurements have been made on chemically vapor-deposited Si-rich SiO2 films. The measurements show segregated regions of amorphous silicon in the as-deposited films. Annealing the films at 1150 °C completely crystallizes the amorphous silicon. Annealing at lower temperatures produces films with both amorphous and crystalline regions.