bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical characterization of solar cells by surface photovoltage
Authors: Goldstein Bernard , Redfield David , Szostak Daniel J. , Carr Lester A.
Published: February 2003

It is shown that under many conditions the surface photovoltage (SPV) can be identified with Voc of a solar cell. Using a Kelvin probe to measure the SPV we have been able to determine several properties of silicon solar cells without recourse to a contact on the front surface and the attendant complications of resistive losses due to external currents. We have further used these techniques in conjunction with sputter etching to ’’profile’’ the potential through a single-crystal solar-cell junction and an amorphous silicon solar cell.
50−nm silicon structures fabricated with trilevel electron beam resist and reactive-ion etching
Authors: Jackel L. D. , Howard R. E. , Hu E. L. , Tennant D. M. , Grabbe P.
Published: February 2003

A trilevel electron beam resist has been used to make 25-nm metal features on thick silicon substrates. Using this metal as a mask for reactive ion etching, silicon structures 0.33 μm deep have been fabricated. The resist consists of a thin upper layer of polymethylmethacrylate (PMMA), a middle layer of Ge, and a lower layer of co-polymer of methylmethacrylate and methacrylic acid, P(MMA/MAA). High-resolution patterns are written in the upper resist layer and are transferred to the lower layers by reactive-ion etching. Completed resist stencils have 300-nm high walls with near-vertical profiles and are suitable for liftoff processing.
Selective niobium anodization process for fabricating Josephson tunnel junctions
Authors: Kroger H. , Smith L. N. , Jillie D. W.
Published: February 2003

A novel process for fabricating refractory sperconducting tunnel junctions is described, which is useful with both deposited and native oxide barriers. The distinguishing feature of the method is that the entire superconductor-barrier-superconductor sandwich is formed before the patterning of any layer. Isolated Josephson junctions are then formed by anodizing through the upper electrode, while the devices themselves are protected by a photoresist mask. Using this process, Nb-Si:H-Nb junctions have been fabricated, whose product of critical current and subgap resistance exceeds 10 mV and whose critical current density varies by about 50% over a 2-in. diameter wafer.
Atomic mixing in ion impact: A collision cascade model
Authors: Matteson S.
Published: February 2003

The phenomenon of atomic mixing due to the impact of energetic ions is described by a model based upon the theory of random flights. The transport of material is shown to be formally analogous to standard diffusion theory. The formal diffusion constant is derived from first principles using power law potentials and the result of elementary range theory. An approximate formula is given, which is valid for dilute impurity transport in an otherwise homogeneous host matrix. Comparison is made to experimental results of ion irradiation.
Pulsed laser modification of SiO2/Si interface properties and minority-carrier lifetime
Authors: Deshmukh V. G. I. , Webber H. C. , McCaughan D. V.
Published: February 2003

Effects of pulsed laser irradiation on the SiO2/Si interface are investigated by means of capacitance-voltage and capacitance-time experiments yielding values of surface state density (Nss), oxide charge (QFC), and minority carrier lifetime (MCL) which prove to be a sensitive probe of the laser damage thresholds. Increases of Nss and QFC and decreases of MCL of two to three orders of magnitude from controlled starting values are observed at incident energy densities from 0.7 to 1.1 J cm−2. Subsequent thermal treatments restore either QFC or both QFC and Nss to control values. The laser method gives a technique for localized lifetime reduction on silicon wafers while maintaining long lifetimes elsewhere on the wafers.
4.3-μm cascade CO2 laser
Authors: Znotins T. A. , Reid J. , Garside B. K. , Ballik E. A.
Published: February 2003

An in-cavity hot CO2 cell is used to obtain 4.3-μm lasing from a cascade process in a conventional CO2 laser. The 4.3-μm laser operates in a Q-switched mode, is line tunable, and has average output powers greater than 100 mW.
Monitoring UF6 photodissociation via laser multiphoton ionization
Authors: Stuke M. , Reisler H. , Wittig C.
Published: February 2003

Laser multiphoton ionization (MPI) is used to detect nascent photoproducts following the UV photodissociation of UF6. Sensitivity is high, and there is no measurable background due to the MPI of parent UF6. The technique is very well suited for monitoring isotopically selective photodissociation on a ’’single shot’’ basis.
Analysis of density perturbations of a freely imploding shell
Authors: Yabe Takashi , Nishiguchi Akio , Ueda Noriaki
Published: February 2003

The time evolution of the density perturbation of a freely imploding shell is simulated by the fluid PIC code for various specific heat ratios. The rough estimation shows that the angular momentum conservation of the perturbed flow may be responsible for the perturbation growth.
Measurement of the diffusion coefficient and recombination effects in germanium by diffraction from optically-induced picosecond transient gratings
Authors: Moss Steven C. , Lindle J. Ryan , Mackey H. J. , Smirl Arthur L.
Published: February 2003

A variation of the excite-and-probe technique is used to measure the picosecond evolution of laser-induced transient gratings that are produced in germanium by the direct absorption of 35-psec optical pulses at 1.06 μm. Grating lifetimes are determined as a function of grating spacing and sample temperature for peak carrier densities of approximately 5×1019 cm−3. A linear diffusion-recombination model for the grating decay provides a good fit to the experimental data and allows the extraction of the diffusion coefficient and places limits on the recombination lifetime.
Epitaxial growth of Ge on 〈100〉 Si by a simple chemical vapor deposition technique
Authors: Kuech T. F. , Mäenpää M. , Lau S. S.
Published: February 2003

The heteroepitaxial growth of Ge on Si substrates by means of a simple chemical vapor deposition (CVD) method is presented. The epitaxial Ge layers were formed by the decomposition of GeH4 in a H2 ambient at substrate temperatures of 500–900 °C. Smooth surface morphologies and high crystalline quality are obtained in the epitaxial Ge layers. Electrical properties of the Ge films and the resulting p-Ge/n-Si heterojunctions were determined. This technique provides a Ge growth method that is compatible with the current CVD processes used in the growth of GaAs.
Low threshold current density InGaAsP/InP lasers grown in a vertical liquid phase epitaxial system
Authors: Tamari N. , Ballman A. A.
Published: February 2003

Threshold current density of InGaAsP/InP double heterostructure lasers made from crystals grown in a vertical liquid phase epitaxial system and emitting at 1.3 μm is given versus active layer thickness. Extremely low normalized threshold current density is observed Jth/d∼1.6kA/cm2 μm, which represents a considerable improvement over state of the art. The lowest threshold density among 80 lasers studied is 1 kA/cm2. Good uniformity over each wafer is found along with consistency of the results among different experiments. Since standard preparation and fabrication techniques are used in this work, it is assumed that favorable thermal conditions existing in the vertical liquid phase epitaxial system might be responsible for these promising results.
Substrate heating and emitter dopant effects in laser-annealed solar cells
Authors: Young R. T. , Wood R. F. , Christie W. H. , Jellison G. E.
Published: February 2003

This letter provides the first experimental evidence that substrate heating during pulsed-laser annealing (PLA) of ion-implanted silicon can significantly improve the electrical properties of the laser recrystalized region due to the reduction of the regrowth velocity. It is also shown that by using the optimum PLA condition, the open-circuit voltage VOC and the fill factor of ion-implanted, laser-annealed solar cells are improved by increasing the emitter dopant concentrations, whereas the short-circuit current JSC remains fairly constant, results which are in qualitative agreement with theoretical predictions.
Chemical etching and cleaning procedures for Si, Ge, and some III-V compound semiconductors
Authors: Aspnes D. E. , Studna A. A.
Published: February 2003

Chemical etching and cleaning procedures that produce the most abrupt dielectric discontinuities between bulk and ambient (cleanest and/or smoothest surfaces) are determined by ellipsometry for single crystals of Si, Ge, and some III-V compounds. Differences among high-symmetry orientations for Si and Ge indicate that preferential etching may be a factor in minimizing the amount of interface material left at a surface.
Electron beam annealing of selenium-implanted gallium arsenide
Authors: Shah N. J. , Ahmed H. , Leigh P. A.
Published: February 2003

The multiply scanned electron beam method has been applied to annealing selenium implanted gallium arsenide. The conditions necessary to give good electrical activation and mobility have been established for doses from 5×1012 to 1×1014 ions cm−2. Partial activation was achieved in uncapped samples for doses of 1×1013 cm−2 and greater. However, to achieve higher activation of these doses, and significant activation of low doses, encapsulation with Si3N4 was necessary. It is shown that rapid electron beam annealing lasting only a few seconds gave equivalent results to conventional furnace annealing methods.
Image force effects on carrier collection in a-Si:H solar cells
Authors: Han Min-Koo , Anderson Wayne A. , Lahri R. , Coleman John
Published: February 2003

A modified carrier collection model of a-Si:H Schottky-barrier solar cells is proposed to explain the falloff of short wavelength carrier collection efficiency. Schottky-barrier lowering due to image force effects alters the potential distribution near the metal-semiconductor interface. This altered potential decreases the carrier collection in a-Si:H solar cells by as much as 30%. Design considerations to improve carrier collection efficiency are also proposed.
Al-Ga disorder in AlxGa1−xAs alloys grown by molecular beam epitaxy
Authors: Miller Robert C. , Tsang Won T.
Published: February 2003

A heterostructure, consisting of two GaAs quantum wells each of 40 Å width separated by a 40-Å Al0.5Ga0.5As barrier, has been grown by molecular beam epitaxy and examined optically for Al-Ga disorder (alloy clustering). The photoluminescent and excitation spectra showed no evidence of clustering, in marked contrast to results on a similar structure grown by metal-organic chemical vapor deposition. Thus any clusters present must be less than 40 Å in diameter. The spectra also support an island-like interface with steps of ∼one monolayer in height and ≳300 Å in lateral extent.
Charge-coupled devices in epitaxial HgCdTe/CdTe heterostructure
Authors: Kim M. E. , Taur Y. , Shin S. H. , Bostrup G. , Kim J. C. , Cheung D. T.
Published: February 2003

An n-channel metal-insulator-semiconductor charge-coupled device has been successfully demonstrated in p-type epitaxial Hg0.7Cd0.3Te (λco≃5.0 μm, 77 K) grown by liquid-phase epitaxy on CdTe substrate. A three-bit, three-phase device was operated at 77 K, yielding a charge transfer efficiency greater than 0.995 between 5 and 50 kHz clock frequencies. Ion-implanted n+/p diodes facilitated signal input and direct output signal detection.
Oxygen effect on the electrical characteristics of polycrystalline silicon films
Authors: Angelucci R. , Dori L. , Severi M.
Published: February 2003

420-nm-thick polycrystalline silicon films doped with phosphorus after atmospheric-pressure deposition have been investigated as a function of deposition rate. A correlation between deposition rate and oxygen content into polysilicon film, as determined by electron microprobe analysis, has been established, which accounts for the deposition rate effects on the electrical properties and grain size of the film. Layers deposited at rates lower than about 40 nm/min are characterized by an oxygen content of the order of 1% in weight, which inhibits grain growth during high-temperature processes and increases sheet resistance by reducing both Hall mobility and carrier concentration.
Evidence for ion-induced hypersonic shock waves for computer simulations of argon ion bombardment of copper
Authors: Webb R. P. , Harrison D. E.
Published: February 2003

A molecular dynamics simulation has been used to study the times at which atoms are ejected during sputtering events. Plots of the atom ejection time versus distance from the impact point indicate that many sputtering events occur along a roughly circular front that propagates outward at hypersonic speed.
Relativistic planar diode in a magnetic field
Authors: Waisman Eduardo M.
Published: February 2003

The exact steady-state solution for the planar relativistic diode in space-charge-limited conditions is given in the presence of magnetic fluxes below magnetic insulation. It is shown that, as in the classical case, at fixed diode voltage the value of the current density reaching the anode goes discontinuously from a finite value to zero as a function of the magnetic flux at the magnetic insulation cut-off point. The limiting current density just below cutoff is given as a function of voltage and gap distance. This steady-state one-dimensional result below and very near the magnetic insulation threshold is in contradiction with experimental observations.
A method of excitation profiling in high-field electroluminescence
Authors: Langer J. M. , Lemańska-Bajorek A. , Suchocki A.
Published: February 2003

A method of quasidirect profiling of impact excitation of electroluminescence in a metal semiconductor junction utilizing the Auger quenching of a localized center luminescence by either free or weakly bound electrons is described. Experimental results obtained on CdF2:Mn,Y Schottky diodes unambiguously prove a spatial separation of the acceleration and collision excitation processes in high-field electroluminescence.
Continuous broadband tuning of an electron-beam-pumped XeF (C→A) laser
Authors: Liegel J. , Tittel F. K. , Wilson W. L. , Marowsky G.
Published: February 2003

Wide-band tuning of a XeF (C→A) excimer laser pumped with a longitudinal electron beam was demonstrated from 455 to 529 nm. The spectral linewidth of the laser emission was ∼5 nm when a prism was used as a wavelength selecting element, and narrowed to ∼1 nm when the prism was replaced by a diffraction grating.
ZnI (B→X) laser: 600–604 nm
Authors: McCown A. W. , Eden J. G.
Published: February 2003

Lasing on several transitions of the B2𝒥→X2𝒥 band of zinc-iodide (ZnI) with wavelengths ranging from 600 to 604 nm has been demonstrated. Pumped by the dissociative excitation of ZnI2 (using an ArF excimer laser), this laser exhibits many of the optical and chemical properties of the HgBr2 blue-green dissociation laser.
Direct measurement of anomalous dispersion by beam steering and a wavefront sensor
Authors: Wang C. P. , Varwig R. L.
Published: February 2003

A direct measurement of laser beam steering resulting from anomalous dispersion in an absorbing medium was achieved with the use of a sensitive wavefront sensor. The experimental setup, which includes a Brewster’s angle absorption cell, a continuous-wave, frequency-scannable hydrogen flouride (HF) chemical laser, an acousto-optical modulator and phase demodulator, and servo- and detection- electronics, is described. The experimental results provided a direct measure of the anomalous dispersion for HF [P1(6) line] that agrees within about 10% with the value deduced from an absorption measurement.
Photoelectrochemical deposition of microscopic metal film patterns on Si and GaAs
Authors: Micheels Ronald H. , Darrow Allan D. , Rauh R. David
Published: February 2003

Microscopic metal film patterns have been imaged on p-Si and n- and p-GaAs by photoelectrochemical deposition from standard aqueous plating solutions. The photodeposition of Cu, Ni, Pd, and Au films was investigated. Resolution exceeding 10 μ has been achieved for deposits of Au on p-GaAs and Cu on p-Si.
Photoluminescence of heavily doped n-type AlxGa1−x As in the indirect energy gap region
Authors: Kaneko Kunio , Ayabe Masaaki
Published: February 2003

Three peaks were found in the photoluminescence spectrum of Te-doped AlxGa1−xAs with x≃0.52 in the indirect energy gap region. A peak at the highest energy, which is higher than the indirect band-gap energy, is caused by direct transition. The emission intensity of the peak depended on the resistivity of the sample and was at a maximum at about 0.1 Ω cm. This relation is similar to a recently reported anomalous relation of the Hall coefficient to the resistivity. The emission intensity of the peak increased with increasing temperature. These luminescence properties can be explained in terms of the enhancement of electron concentration in the Γ conduction band.
Preparation of amorphous silicon films by chemical vapor deposition from higher silanes SinH2n+2(n≳1)
Authors: Gau S. C. , Weinberger B. R. , Akhtar M. , Kiss Z. , MacDiarmid A. G.
Published: February 2003

Amorphous silicon films have been prepared by chemical vapor deposition from higher silanes Sin H2n+2 (n≳1) in the temperature range 380–500 °C. The films show electrical properties comparable to those prepared by the plasma discharge of silanes. Gold Schottky devices were fabricated with internal short-circuit currents of 12 mA/cm2 under AM1 illumination over an area of 2.0 cm2.
Backside-gated modulation-doped GaAs-(AlGa)As heterojunction interface
Authors: Störmer H. L. , Gossard A. C. , Wiegmann W.
Published: February 2003

We present a new kind of gated modulation-doped GaAs-(AlGa)As heterojunction interface. The gate voltage is applied from the backside of the specimen. Gate voltage dependences of the two-dimensional electron concentration and its mobility μ are determined. The density variation is strictly linear in gate voltage, and the mobility follows approximately a law μ∝n5/2 over the explored region. This concept is similar to a junction field-effect transistor but with a two-dimensional channel. Forward bias improves the mobility by ≊50% to ≊120 000 (cm2/V sec).
Electroreflectance and photoluminescence studies of InP epitaxial layers highly doped with selenium
Authors: Raccah P. M. , Rahemi H. , Zehnder J. , Hawrylo F. Z. , Kressel H. , Helman J. S.
Published: February 2003

InP epi-layers heavily doped with Se exhibit very high carrier concentrations (N≳1020 cm−3) together with significant increases of the optical band-gap energy. We show that in these epi-layers (grown by liquid phase epitaxy) the Se concentration XSe varies with the depth. With increasing Se concentration, the optical band gap increases from 1.34 to ∼1.9 eV, where it remains fixed for Se concentrations larger than 1.5 at.%. This increase is very rapid at first owing to the filling of the low mass conduction band. Beyond XSe = 0.1 at.%, we enter the nonarapbolic bands regime and the electrons begin to overflow into the indirect minima. Because of the large density of states available, further increases in free carriers no longer affect the optical gap, which remains close to the indirect gap value (∼1.9 eV).
Sezawa to Rayleigh mode conversion in the ZnO-on-Si surface acoustic wave device configuration
Authors: Melloch M. R. , Gunshor R. L. , Pierret R. F.
Published: February 2003

Conversion of Sezawa surface waves to Rayleigh surface waves by means of an aluminum grating in the metal-ZnO-SiO2-Si surface acoustic wave structure is reported. This conversion must be taken into account in the design of grating structures in ZnO-on-Si devices, such as multistrip couplers, to avoid unwanted stop bands. The conversion also provides a new phenomenological basis for the construction of bandpass filters.
A proposed design for multishell cryogenic laser fusion targets using superconducting levitation
Authors: Glocker David A.
Published: February 2003

A method is described for using the diamagnetism of superconductors to levitate a permanently magnetized fuel pellet within a spherical superconducting shell in a multishell cryogenic laser fusion target. A general expression is derived for the magnetic force on the fuel pellet as a function of its displacement from the center of the outer shell, and is used to calculate the equilibrium displacement due to gravity in a typical case. For a PtCo inner shell with a radius of 50 μm and a thickness of 1 μm, within a superconducting outer shell with a radius of 100 μm, the maximum displacement is 0.54 μm.
Extreme ultraviolet absorption spectroscopy of a backlighted aluminum plasma
Authors: Riordan John C. , Pearlman Jay S.
Published: February 2003

We show that a cold, dense laboratory plasma can be readily characterized by extreme ultraviolet absorption spectroscopy. The plasma is produced by irradiating a thin aluminum foil with a pulsed soft x-ray source. The same source also provides a backlighting continuum for absorption spectroscopy. Time-integrated L-shell spectra obtained with a grazing incidence spectrograph show collisionally broadened absorption lines of A1 IV and A1 V. The spectra provide plasma temperature and electron density measurements of ≳12 eV and 0.6×1021 cm−3, respectively.
Raman study of evaporated and sputtered GexSe1−x glass films
Authors: Griffiths James E. , Sinclair W. Robert
Published: February 2003

Raman spectra of thin film GexSe1−x (x = 0.1, 0.33) glasses shows them to be structurally and compositionally similar on a molecular scale whether prepared by evaporation or sputtering techniques. Their sensitivity as silver-doped photoresist materials correlates directly with information obtained from backscattering Raman experiments on the initially prepared films. Low sensitivity in some films prepared by sputtering onto low-temperature substrates is attributed to film contamination, probably by oxygen containing impurities or by other materials that inhibit formation of optically absorbing Ge–Se bonding networks.
Improved techniques for growth of large-area single-crystal Si sheets over SiO2 using lateral epitaxy by seeded solidification
Authors: Tsaur B-Y. , Fan John C. C. , Geis M. W. , Silversmith D. J. , Mountain R. W.
Published: February 2003

Continuous single-crystal Si sheets over SiO2 with areas of several square centimeters have been produced from poly-Si films by the LESS technique (lateral epitaxy by seeded solidification). Seeding is achieved either with a narrow stripe opening in a recessed SiO2 layer on a single-crystal Si substrate or with an external single-crystal Si seed. N-channel metal-oxide-semiconductor field-effect transistors (MOSFET’s) fabricated in these films exhibit surface electron mobilities as high as 700 cm2/V s.
Recoil oxygen implants and thermal redistribution of oxygen in through-oxide arsenic-implanted Si
Authors: Magee T. J. , Leung C. , Kawayoshi H. , Palkuti L. J. , Furman B. K. , Evans C. A. , Christel L. A. , Gibbons J. F. , Day D. S.
Published: February 2003

The redistribution of recoil oxygen implants produced by the implantation of As ions through oxide layers on Si substrates has been investigated at annealing temperatures in the range 4000–1000 °C. Using transmission electron microscopy and secondary ion mass spectrometry profiling, it has been shown that the implanted (recoil) oxygen is rapidly gettered into residual damage structure at anneal temperatures < 900 °C. At temperatures ⩾ 1000 °C residual damage gettering sites are annihilated, releasing oxygen to migrate toward the Si surface. At the higher-annealing temperatures, oxygen has been shown to outdiffuse rapidly into the overlying (1000 Å) oxide layer on the sample surface.
Asymmetric current effects of 1/f noise in metal to n-InSb contacts with an applied magnetic field
Authors: Vande Voorde P. , Love W. F.
Published: February 2003

Measurements of 1/f noise in metal to n-InSb contacts at 75 K are reported. This is observed to be sensitive to current direction and to external magnetic fields.
Signal enhancement in photothermal imaging produced by three-dimensional heat flow
Authors: Murphy J. C. , Aamodt L. C.
Published: February 2003

Three-dimensional thermal diffusion effects are shown to be important for photothermal imaging. Signal enhancement near thermal boundaries is observed. The effects are applied to locating defects in a crystalline ceramic. A general application to signal enhancement in powders over bulk solids is suggested.
Large gain, negative resistance, and oscillations in superconducting quasiparticle heterodyne mixers
Authors: McGrath W. R. , Richards P. L. , Smith A. D. , van Kempen H. , Batchelor R. A. , Prober D. E. , Santhanam P.
Published: February 2003

We have measured the properties of a superconductor-insulator-superconductor quasiparticle mixer which is operated in the quantum limit. Single sideband conversion gain larger than +4 dB was observed at 36 GHz with a mixer noise temperature T = 9±6 K, which is to be compared with the (Planck) quantum limit h/ω/(k ln 2)≃2.5 K. Complete three-port mixer calculations are presented which are in good agreement with the gain measurements. The dynamic resistance was observed to become infinite and then negative as the source conductance was decreased. This implies that arbitrarily large gain is available. The negative resistance is accompanied by IF oscillations.
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u formed permanent magnet Cu-Fe multifilamentary composites
Authors: Dublon G. , Habbal F. , Bevk J.
Published: February 2003

Cu-30 Vol % Fe multifilamentary composites were produced in situ. Magnetic hysteresis loops of wire and tape composites were obtained at room temperature as a function of both cross-sectional area reduction, up to 99.9996%, and annealing conditions. Hci and (BH)max increase with cross-sectional area reduction, reaching 250 Oe and 0.46 MG Oe, respectively, in the most heavily deformed unannealed samples. On proper annealing, Hci and (BH)max increase dramatically, up to 590 Oe and 1.35 MG Oe, respectively. Considering the simple preparation technique and inexpensive constituent elements, the in situ formed Cu-Fe composites appear to have the potential for permanent magnet applications.
Electro-optical induction of recombination luminescence in an organic photoconductor
Authors: Code R. F. , Popovic Z. D.
Published: February 2003

Recombination luminescence has been observed in particle dispersions of an organic photoconductor (x-H2Pc) by a new electro-optical technique that eliminates the need for double injection electrodes. The method permits independent investigations to be made of the charge carrier photogeneration and recombination processes in a single sample of photoconducting material.
The effect of lithium on the electronic configuration of LixFeV3O8 (0⩽x⩽2)
Authors: Eibschütz M. , Murphy D. W. , Zahurak S. M. , Christian P. A.
Published: February 2003

The reduction of V ions in FeV3O8 from V5+(3d0) and V4+(3d1) to V4+(3d1) and V3+(3d2) by lithiation with n-BuLi has been inferred by 57Fe Mössbauer effect. The Fe is localized and in the Fe3+ state for all x.
Dielectric anomaly in inhomogeneous materials with application to sedimentary rocks
Authors: Sen P. N.
Published: February 2003

A small concentration of thin plate-like insulating material in a conducting host can give rise to anomalously high values of dielectric constant. For a small concentration η of oblate spheroidal grains (a ≪ b = c) with depolarization factor along symmetry (a) axis Ls = 1−δ,δ = πa/2b, the static value of the dielectric constant of rock εs and dc conductivity σ(0) are given for (a) δ<η as σ(0) = δσR/η, εs≅εm/η, and for (b) δ≳η as σ(0)≅σR(1−η/δ), εs≅ηεm/δ2. Case (a) corresponds to the well-known Maxwell–Wagner effect with εs diverging as η→0, and σ(0)→0. Case (b) gives a novel result that εs may diverge for δ≳η≫δ2, with a nonvanishing σ(0). Case (b) is applied to explain frequency and salinity dependences and the large values (∼103, observed at MHz frequencies) of the dielectric constant of conducting sedimentary rocks. Possible reasons for the larger values (∼106) observed experimentally at lower (khz) frequencies are discussed.
Evidence for interdiffusion of hydronium and alkali ions in leached glasses
Authors: Tsong I. S. T. , Houser C. A. , White W. B. , Wintenberg A. L. , Miller P. D. , Moak C. D.
Published: February 2003

The interdiffusion mechanism governing the leaching (or hydration) of glasses is studied using the 19F resonant nuclear reaction. By measuring the number of hydrogen ions in the surface layers of leached glasses, we have identified that a hydronium-sodium ion exchange process is in operation in leached commercial glasses while it is less conclusive as to the exact mechanism responsible for the leaching of simple laboratory binary and ternary glasses.
Solid-phase epitaxial regrowth of ion-implanted layers in GaAs
Authors: Nissim Y. I. , Christel L. A. , Sigmon T. W. , Gibbons J. F. , Magee T. J. , Ormond R.
Published: February 2003

The complete solid-phase epitaxial regrowth of ion-implanted layers in GaAs was obtained during a short (10 min) capless furnace anneal at a temperature of 475 °C. Two factors believed responsible for the incomplete regrowth of layers have been identified. First, the damage density from the implant should not exceed a critical value determined by a Boltzmann calculation. Second, the growth of polycrystalline material from the surface observed by transmission electron microscopy is a competitive mechanism. As+ implants, whose doses and energies were selected to achieve the correct damage density, and to ensure that its value was maintained in the near-surface region, led to a complete recrystallization.
Spectrum-controllable color sensors using organic dyes
Authors: Kudo K. , Moriizumi T.
Published: February 2003

An organic color sensor was fabricated by using p- and n-type dyes. The cell has a layered structure of Zn0/merocyanine/rhodamine B, which acts as an n-p-n- photodiode. The spectral sensitivity of the cell was changed remarkably by bias voltage, and a good separation of the spectral responses was obtained in the visible-spectrum region.
Effect of hydrogen on the diode properties of reactively sputtered amorphous silicon Schottky barrier structures
Authors: Morel D. L. , Moustakas T. D.
Published: February 2003

The diode properties of reactively sputtered hydrogenated amorphous silicon Schottky barrier structures (a-SiHx /Pt) have been investigated. We find a systematic relation between the changes in the open circuit voltage, the barrier height, and the diode quality factor. These results are accounted for by assuming that hydrogen incorporation into the amorphous silicon network removes states from the top of the valence band and sharpens the valence-band tail. Interfacial oxide layers play a significant role in the low hydrogen content, and low band-gap regime.
Electron Hall mobility in GaxIn1−xAsyP1−y calculated with two-longitudinal-optical-phonon model
Authors: Takeda Y. , Littlejohn M. A. , Hauser J. R.
Published: February 2003

GaInAsP lattice matched to InP is known to have two well-resolved InP-like and InGaAs-like longitudinal optical (LO) phonons over the composition range 0<y<1. Here for the first time the electron Hall mobilities in GaInAsP are calculated by the iterative technique taking the scattering due to the two LO phonons into account. The results show a further downward bowing of the mobilities than those calculated with one-LO-phonon model.
Low barrier height Schottky mixer diode using super thin silicon films by molecular beam epitaxy
Authors: Ballamy William C. , Ota Yusuke
Published: February 2003

Low barrier (≲0.4 eV) microwave mixer diodes were fabricated by means of silicon molecular beam epitaxy (Si MBE). Schottky barrier lowering was achieved by using a thin highly doped epitaxial layer to modify the electric field near the surface. The advantages of silicon MBE for these devices arise from the ability to grow epitaxial layers which are very precisely controlled in thickness and in the spatial distribution of dopant. The resulting diodes have both a low barrier height and a very low forward series resistance.
Photoluminescence of carbon-implanted GaAs
Authors: Stringfellow G. B. , Koschel W. , Briones F. , Gladstone J. , Patterson G.
Published: February 2003

The 5-K photoluminescence (PL) spectra of undoped semi-insulating GaAs are observed as a function of carbon implantation dose (after 850°C annealing using a SiO2 cap). Results show that although the intensity of the bound exciton line at 1.514 eV remains fairly independent of carbon concentration up to 1017 cm−3 carbon, the intensity of the conduction band to acceptor peak at ∼1.494 eV increases monotonically with carbon implant dose. This is the first direct confirmation that the 1.494-eV transition is due to carbon. The observed correlation between implanted carbon doses and PL intensities at high excitation levels is the basis of an analytic technique for C assessment in GaAs.
Multiple-path fission-foil nuclear lasing of Ar-Xe
Authors: De Young R. J.
Published: February 2003

Nuclear lasing of Ar 10% Xe at 760 Torr with a thermal neutron flux of 3.5×1016 n/cm2 s has produced an output power of 50 W. Lasing occurred at 2.6 μm in Xe-I. The argon buffer gas is shown to efficiently stop fission fragments at reasonable pressures emitted from 235U3O8 coatings. A unique folded optical path was used to increase the excited gas volume which in turn increases laser output.
Transmission of sound through a porous disk
Authors: Hovem Jens M.
Published: February 2003

The transmission coefficient for sound at an interface between a fluid and a porous medium has been derived. Numerical values are compared with experimental values obtained by Plona [Appl. Phys. Lett. 36, 259 (1980)] who transmitted a short ultrasonic pulse through a porous disk. The good agreement between theory and experiment supports the conclusion that a second compressional wave has been observed.
Laser bonded n-GaAs/p-GaSb heterojunction intercell Ohmic contact
Authors: Yang H. T. , Zehr S. W.
Published: February 2003

An n-GaAs/p-GaSb heterojunction intercell Ohmic contact (IOC) has been formed by a laser bonding procedure. Resistance per unit area of 5×10−3 Ω-cm2 has been obtained as an upper limit. This IOC is able to provide sufficiently good electrical connection between two adjacent subcells of a monolithic multicolor solar converter operating at several hundred suns concentration with the insignificant I2R loss.
Colorless, transparent, c-oriented aluminum nitride films grown at low temperature by a modified sputter gun
Authors: Onishi S. , Eschwei M. , Bielaczy S. , Wang W-C.
Published: February 2003

Colorless, transparent, pure c-oriented AlN films have been deposited on glass substrates, with and without Cr-Au films, utilizing a modified sputter gun. The design of the gun and of the sputtering system helps to keep the growing surface free from charged particle bombardment and excessive heat by radiation. Attention will be focused mainly on the effect of total sputtering pressure on the quality of the AlN films. A very strong magnetic field makes it possible to sputter at pressures as low as 0.133 Pa (1 μTorr). This high vacuum sputtering improves c-orientation, surface smoothness, film color, transparency, deposition rate, and thermal expansion coefficient matching. The deposition rate of the sputter gun is as high as 2.4 μm/h at input power of 300 W.
Grain growth of polycrystalline silicon films on SiO2 by cw scanning electron beam annealing
Authors: Shibata Kenji , Inoue Tomoyasu , Takigawa Tadahiro , Yoshii Shintaro
Published: February 2003

Reduced pressure, chemical vapor deposited polycrystalline silicon films (5000 Å thick) over thermally grown SiO2 on (100) silicon wafers are recrystallized by a scanning electron microscope modified electron beam annealing system. On the basis of transmission electron microscope bright-field images and electron diffraction patterns, large grained polycrystalline silicon films of 20-μm average grain size are obtained after electron beam annealing. Electron beam current, scanning rate, and annealing repetition are found to be important parameters in the recrystallization. Optimum values for them are from 1.6 to 1.9 mA, from 40 to 80 cm/sec, and from 5 to 10 times, respectively.
Low-noise self-pumped Josephson tunnel junction amplifier
Authors: Calander N. , Claeson T. , Rudner S.
Published: February 2003

We have studied the parametric amplification properties of an internally pumped Josephson tunnel junction, where the shunt contained resistive and inductive components. The amplification was, in this case, limited by circuit component values to less than 8 dB at 10 GHz, but it was very stable against variations in bias conditions. The amplifier gain-bandwidth product was large and the noise level very low. We estimated the noise temperature to be less than 50 K, which should make the device attractive for mm-wave amplification.
High-field superconducting properties of the composite-processed Nb3Sn with Nb-Ti alloy cores
Authors: Tachikawa K. , Asano T. , Takeuchi T.
Published: February 2003

The Nb3Sn layer growth rate, the upper critical field and the critical current density in high fields of the composite-processed Nb3Sn are greatly enhanced by the titanium addition to the niobium core. This addition yields a Jc (Nb3Sn layer) value of over 1×105 A/cm2 at 15 T. After the reaction, large amount of titanium is incorporated into the Nb3Sn layer. The optimal amount of titanium addition to the niobium core is about 2 at. %. The Nb-Ti/Cu-Sn composite wire seems to be quite promising for applications in magnetic fields up to at least 15 T.
Temperature dependence of the pyroelectric response of vinylidene fluoride trifluoroethylene copolymer and the effect of its poling conditions
Authors: Yamazaki Hiroki , Ohwaki Junichi , Yamada Takeshi , Kitayama Toyoki
Published: February 2003

Vinylidene fluoride trifluoroethylene copolymer VDF-TrFE was found to be pyroelectric when poled by application of dc high field. Temperature dependence of its pyroelectric response and the effects of poling conditions were investigated. It was shown that there existed a critical temperature at 70 °C above which pyroelectricity vanished. The pyroelectric coefficient increased with the increase in poling temperature with a tendency to saturation. The pyroelectric coefficient of these samples poled above 70 °C were constantly 9 nc/cm2 K, which is significantly larger than that of any other polymers.
The pulsating elastic sphere
Authors: Hazony D.
Published: February 2003

The elastic sphere is shown to develop catastrophic pressures at its center in response to a finite square pulse input. Also shown is an unusual driving point input admittance function.
Optical assessment of the main electron trap in bulk semi-insulating GaAs
Authors: Martin G. M.
Published: February 2003

Near-infrared optical absorption in undoped bulk GaAs ingots is shown to be due essentially to the presence of the main deep donor EL2. Measurement of the corresponding absorption represents the first known method of quantitative determination of that level in semi-insulating material. Furthermore, complete quenching of the corresponding absorption is shown to occur under high intensity illumination. This strong effect, reported for the first time, can be directly related to the existence of a metastable state for the level EL2 presenting a strong lattice relaxation.
Ultrasonic evaluation of austenitic stainless steel welds using shear horizontal waves
Authors: Fortunko C. M.
Published: February 2003

The propagation of horizontally polarized shear (SH) waves through an austenitic stainless steel weld metal-base metal interface is described. It is shown that SH wave probing signals are particularly suitable for nondestructive evaluation of those stainless steel weldments that are very difficult to evaluate using vertically polarized shear and longitudinal wave probing signals. The SH wave technique is demonstrated experimentally on a 304L/316L stainless steel butt weldment using 454-kHz SH wave electromagnetic-acoustic transducers that excite SH wave probing signals at 70° with respect to surface normal.
Wall effect of director deformation in nematic liquid crystals
Authors: Mada Hitoshi
Published: February 2003

We discuss the director deformation near the interface between a liquid crystal and a solid substrate. The gradient of the tilt angle at the interface was measured by Sprokel et al. as a function of an applied voltage; they obtained a larger gradient than that calculated from Frank theory by a factor of about 5. In order to explain the abnormal gradient, we have taken into account the balance of torque at the interface. The gradient of tilt was estimated when the higher voltage is applied to the liquid crystals; the estimated result agrees well with their experimental result.
Energy levels and solubility of interstitial chromium in silicon
Authors: Feichtinger H. , Czaputa R.
Published: February 2003

The electronic level of interstitial Cr in silicon according to the transition Cr0i→Cr+i(3d6→3d5) was determined by correlating the electron paramagnetic resonance (EPR) signal of Cr+ to Hall measurements on identical samples. The procedure gives the donor level located at Ec −0.222±0.005 eV. From the experiments may be inferred that there is no Cr++i state above Ev +0.05 eV. The solubility of interstitial Cr in silicon is retrograde at 1300° and has a maximum value of 5×1015 cm−3.
Direct nuclear-pumped laser amplifier
Authors: Jalufka N. W.
Published: February 2003

A 3He-Xe gas mixture, excited by the 3He(n,p) 3H reaction, has been employed to amplify the output of a 3He-Xe direct nuclear-pumped laser. Lasing occurred on the 2.63-μ of XeI in the oscillator. The oscillator output was reflected through 180 ° and passed through the amplifier system. Power measurements of the oscillator output and the amplifier output show the laser power to be amplified by a factor of 3 for the 3He-Xe system. Amplification by a factor of 5 was obtained for a 3He-CO system.
Multiple beam free-electron lasers and optical klystrons
Authors: Piestrup M. A.
Published: February 2003

A method for the generation and amplification of infrared and optical radiation is presented based on space-charge interaction of electron streams of different momentum. The use of relativistic electrons with low-energy dispersion is found to allow gain to occur at infrared and optical wavelengths.
Formation of amorphous superconducting transition-metal alloys by liquid quenching on hot substrates
Authors: Togano K. , Kumakura H. , Tachikawa K.
Published: February 2003

An improved cooling rate has been achieved by liquid quenching on a hot substrate, which facilitates the preparation of amorphous and metastable crystalline states of refractory-metal-based alloys. The effectiveness has been proved by the experimental results for Mo-Zr and Nb-Si-Ge alloys. A single amorphous phase was obtained from 40–60 at. % Zr. In the Nb-Si-Ge alloy system, amorphous and metastable A15 phases were obtained in a wide composition range. The superconducting properties and thermal stability of these phases have been studied.
Problems with the external diffusion process for producing Nb3Sn-Cu superconducting wire
Authors: Verhoeven J. D. , Gibson E. D. , Cheng C. C.
Published: February 2003

It has been observed that in the external diffusion process for producing Nb3Sn-Cu superconducting wire, dewetting of the Sn layer occurs for layer thicknesses on the order of 6 μm and larger. A mechanism for this dewetting is proposed and it is demonstrated that the problem may be eliminated by formation of an oxide skin on the outer surface of the Sn layer.
Laser sintering of VO2 film
Authors: Mitsuishi Tomokuni , Okabe Katsuya , Sasaki Yoshisato
Published: February 2003

The conventional preparation process of VO2 temperature sensors requires the precise control of ambient atmosphere. This is one of the difficulties in their application to integrated devices. Laser sintering proved to be useful in overcoming this difficulty. Specimens of VO2 film (1.4×1.4×0.04 mm3 in size) printed on alumina substrates changed in electrical resistance by a factor of 102 at about 68 °C with increasing temperature, after exposing them, in open air, to a 2-ms pulse beam from a ruby laser on relaxation oscillation, whose energy density was 6.5 J/cm2.
Optical generation of continuous 76-MHz surface acoustic waves on Y
Z LiNbO3
Authors: Veith G. , Kowatsch M.
Published: February 2003

The efficient generation of continuous surface acoustic waves (SAW) by focusing the radiation of a synchronously pumped mode-locked cw dye laser (mode-locking frequency 76.44 MHz) on the surface of a YZ LiNbO3 crystal is reported. The surface acoustic waves were generated on a small absorbing surface area under varying excitation conditions and detected piezoelectrically by means of a narrowband interdigital SAW transducer, which yielded a voltage responsivity of 1.5 μV/mW cw laser power. The detected electrical signal verified the expected square law dependence of the acoustic power on the incident laser power.
Laser-induced diffusion of oxygen in ZnTe
Authors: Tews H. , Schneider M. , An C.
Published: February 2003

Micro- and millisecond laser annealing of ZnTe monocrystals in a controlled atmosphere shows clearly that oxygen diffuses from an oxygen-rich atmosphere into ZnTe. In the photoluminescence spectra, the typical red oxygen band is observed after annealing. At 2.360 eV, the intense luminescence line from an exciton bound to a Frenkel pair (VZn,Znint) is found.
Stoichiometry-controlled compensation in liquid encapsulated Czochralski GaAs
Authors: Holmes D. E. , Chen R. T. , Elliott K. R. , Kirkpatrick C. G.
Published: February 2003

We show that the electrical compensation of undoped GaAs grown by the liquid encapsulated Czochralski technique is controlled by the melt stoichiometry. The concentration of the deep donor EL2 in the crystal depends on the As concentration in the melt, increasing from about 5×1015 cm−3 to 1.7×1016 cm−3 as the As atom fraction increases from 0.48 to 0.51. Furthermore, we show that the free-carrier concentration of semi-insulating GaAs is determined by the relative concentrations of EL2 and carbon acceptors. As a result, semi-insulating material can be obtained only above a critical As concentration (0.475-atom fraction in our material) where the concentration of EL2 is sufficient to compensate residual acceptors. Below the critical As concentration the material is p type due to excess acceptors.
Silicon/insulator heteroepitaxial structures formed by vacuum deposition of CaF2 and Si
Authors: Ishiwara Hiroshi , Asano Tanemasa
Published: February 2003

Epitaxial growth of CaF2 films onto Si(100) and (111) substrates and the growth of Si films onto the CaF2/Si structure have been investigated. It has been found from ion channeling and backscattering measurements that the optimum growth temperatures at which the crystalline quality of the CaF2 films is excellent range from 600 to 800 °C for Si(111) substrates and from 500 to 600 °C for Si (100). It has also been found that a heteroepitaxial Si/CaF2/Si(111) structure is formed by vacuum deposition of Si onto the heated CaF2/Si(111) structure.
Deep levels in ion-implanted Si after beam annealing
Authors: Sheng N. H. , Mizuta M. , Merz J. L.
Published: February 2003

Deep level transient spectroscopy has been utilized to study the electronic defect levels in cw laser-annealed and scanning electron-beam-annealed Si after ion implantation. For cw laser annealing, a dominant hole trap, whose concentration increases by more than one order of magnitude with increasing laser power, has been measured in slip-free samples. In contrast, only a low concentration of hole traps appears in electron-beam-annealed Si. This laser-induced defect is not stable at room temperature; it decays with time and can be restored by low-temperature thermal annealing. For the furnace-annealed control samples, rapid quenching from sufficiently high temperature into water produces the same defect energy level and annealing characteristic as the laser-induced defect. These annealing characteristics of laser-induced defects and thermally induced, quenched-in defects are tentatively correlated with Fe and Fe-B pair reactions in Si.