bluuebunny/crossref_metadata_2025 huggingface dataset:
REFLECTIVITY THICKNESS CORRECTIONS FOR SILICON DIOXIDE FILMS ON SILICON
Authors: Wesson R. A. , Young H. W. , Pliskin W. A.
Published: March 2005

The interference of light can be used to determine the thickness of thin silicon dioxide films on silicon. This Letter contains corrections to the standard interference formula due to: (1) phase shift at the silicon dioxidesilicon interface and (2) the reflectivity variation at the air-silicon dioxide and silicon dioxide-silicon interfaces. These corrections are calculated as a function of wavelength, order, incident angle, and polarization.
AN EXCITATION MECHANISM FOR THE A+ LASER
Authors: Koozekanani Said H.
Published: March 2005

Direct excitation from the metastable 3p5-4s state of A I to 3p4-4p upper laser state of A II is compared with the two-step excitation from the same metastable state.
EFFECT OF MODE BEATING IN LASER-PRODUCED GAS BREAKDOWN
Authors: Smith David C. , Tomlinson Richard G.
Published: March 2005

Experiments have been carried out which show that the electrical breakdown of gases by optical frequency radiation is independent of the instantaneous intensity fluctuations arising from the interaction of modes present in laser radiation. Gas breakdown thresholds, determined with a single-mode ruby laser and a phase-locked neodymium laser are in substantial agreement with published threshold data for conventional, multiple-mode laser radiation. It was thus determined that the breakdown threshold does not depend upon short term temporal and spatial fluctuations of the power density.
THE SOLID-PHASE TRANSFORMATION IN HAFNIUM
Authors: Bates Glen N. , Barnes George
Published: March 2005

Field-electron emission patterns below and above the solid-phase transformation temperature in hafnium are presented. The transformation temperature was found to be 2030°K confirming results obtained by other methods.
DIGITAL IMAGE FORMATION FROM ELECTRONICALLY DETECTED HOLOGRAMS
Authors: Goodman J. W. , Lawrence R. W.
Published: March 2005

In high precision holographic imagery of weak objects of small angular subtense, electronic detection and digital image formation have distinct advantages. Experiments with a vidicon detector and a PDP-6 computer have yielded reconstructed images of good quality with computation times of five minutes.
THE FARADAY EFFECT AT LOW TEMPERATURES IN TERBIUM ALUMINA SILICATE GLASS
Authors: Daybell Melvin , Overton W. C. , Laquer H. L.
Published: March 2005

The Faraday effect has been studied in a high Verdet-constant terbia-alumina-silicate glass containing 58% Tb2O3 by weight at a number of temperatures down to 2.08°K using the 6328 Å light from a helium-neon laser. The glass is found to be antiferromagnetic with a Curie temperature of -1.16°K. At 2.08°K the observed rotation as a function of H/T fits the Becquerel equation θ = A tanh (μeH/kT) + BH, where μe is 3.5 Bohr magnetons. Because of this small Curie temperature the low-field Verdet constant above liquid nitrogen temperatures follows the simple Curie law within experimental error.
EFFICIENT VISIBLE ELECTROLUMINESCENCE AT 300°K FROM Ga1-xAlxAs p-n JUNCTIONS GROWN BY LIQUID-PHASE EPITAXY
Authors: Rupprecht H. , Woodall J. M. , Pettit G. D.
Published: March 2005

Efficient visible light emitting diodes have been fabricated from Ga1-xAlxAs. Epitaxial layers were obtained by a modified solution growth technique. External quantum efficiencies of up to 3.3% have been measured at room temperature on diodes, which had their emission at 1.70 eV. The switching time for the light emission at 300°K was measured to be 60 nsec.
CARRIER GENERATION AND SWITCHING PHENOMENA IN n—GaAs DEVICES
Authors: Thim H. W. , Knight S.
Published: March 2005

By measuring the steady-state potential distribution in n—GaAs samples with ohmic contacts, very high electric fields have been found near the anode contacts. In samples with n · L (carrier concentration × sample length) products greater than 1012 cm-2, switching from the Gunn mode to a high current, lower (constant) voltage state takes place along with the appearance of a high field at the anode. In samples with n · L products less than 1012 cm-2 the buildup of the high field is accompanied by a sudden increase in current. These high currents are due to carrier generation in a narrow region near the anode.
PASSIVE Q-SWITCHING OF A CO2 LASER
Authors: Wood O. R. , Schwarz S. E.
Published: March 2005

Passive Q-switching of a CO2–N2–He laser has been obtained, using SF6 gas as the saturable absorber. Peak power is 1 kW, in what appears to be a single transverse mode. This is 200 times the CW level for the same configuration and one-fifth that obtained with a mechanical Q switch. Pulse rates are in the range 103 to 104 pulses per sec. Operation is on a single vibrational-rotational line, unlike the case of CW operation.
BROAD-BAND LIGHT AMPLIFICATION IN ORGANIC DYES
Authors: Bass M. , Deutsch T. F.
Published: March 2005

Two organic dyes previously used as liquid lasers, DTTC and cryptocyanine, have been used as broad-band (>300 Å) pulsed light amplifiers in the 7000–8500 Å range. If the input frequency is close to the frequencies of the usual laser oscillations, the latter are quenched and the energy transferred to the frequency being amplified.
SOLUBILITY EFFECTS OF IMPLANTED IONS IN SEMICONDUCTORS
Authors: Marsh O. J. , Mayer J. W. , Shifrin G. A. , Jamba D.
Published: March 2005

Hall effect and sheet resistivity measurements combined with layer removal techniques indicated carrier concentrations for 20-kV antimony implants into silicon that exceed the thermal equilibrium solubility. Annealing caused the carrier concentration to decrease toward solubility values. Supersaturation effects were not observed for gallium implants. For samples annealed at 800 to 900°C, the concentration of carriers increased linearly with implanted dose and leveled off at a value close to the thermal equilibrium solubility.
TRITIUM-LABELED FIELD-INDUCED PROTON TRANSPORT IN SiO2 FILMS
Authors: Hofstein S. R.
Published: March 2005

Tritiated ethanol is adsorbed on the surface of silicon oxide, the oxide is metallized to form an MOS capacitor, and an electric field is applied at elevated temperature to generate ion injection into the oxide film. It is shown that during positive bias-temperature stress, protons, derived from the hydrogens of the ethanol, are transported to the oxide-silicon interface, and that sodium ion transport (examined via neutron activation analysis) is negligible.
SIX dB/CM SINGLE-PASS GAIN AT 7229 Å IN LEAD VAPOR
Authors: Silfvast W. T. , Deech J. S.
Published: March 2005

A method has been developed to measure the single-pass gain of superradiant high-gain pulsed lasers by comparing the intensities of single-pass and double-pass radiation. This method is used on the 7229 Å transition in Pb I and gives a maximum single-pass gain of 63 dB in a 10 cm effective length of lead vapor. The gain is confirmed by line-narrowing measurements and by power output measurements that are related to the theoretical intensities.
HIGH-GAIN LASER LINES IN NOBLE GASES
Authors: Andrade O. , Gallardo M. , Bockasten K.
Published: March 2005

Twenty-four superradiant lines from a pulsed discharge in neon, argon, krypton, and xenon are reported in the wavelength region 8000–29,000 Å. All the lines have been classified as transitions in the neutral spectra. The upper levels are expected to be populated by electron impact or by cascade processes.
A MAGNETOELASTIC TWO-PORT CONFIGURATION IN YIG
Authors: Bennett G. E. , Olson F. A.
Published: March 2005

Two-port magnetoelastic delay performance has been obtained at 1300 MHz in an axially magnetized, [100] oriented YIG rod by injecting longitudinal elastic waves along a [001] axis near the rod end. The polished rod end-face, beveled 28.1° with respect to the rod axis, converts this elastic beam into a linearly polarized shear wave column which propagates down the rod axis. One circularly polarized component of this wave undergoes conventional magnetoelastic conversion and detection to provide the second port.
SINGLE-CRYSTAL SELENIUM FILMS
Authors: Griffiths C. H. , Sang H.
Published: March 2005

Thin continuous single-crystal films of trigonal selenium have been obtained by epitaxial growth from the vapor phase on the (1010) and (0001) faces of tellurium. Transmission electron diffraction and x-ray diffraction measurements indicated the normal trigonal structure and parallel orientation of the selenium on the tellurium. Lattice constants were identical with those found in bulk material.
PHASE SEPARATION IN THE Cu–Ni–Fe SYSTEM; MÖSSBAUER EFFECT EVIDENCE AGAINST DECOMPOSITION BY THE ``SPINODAL MECHANISM''
Authors: Nagarajan A. , Flinn P. A.
Published: March 2005

Mössbauer spectroscopy has been used to investigate the early stages of phase separation in the Cu–Ni.7Fe.3 pseudobinary system. Our results indicate that new phase of composition close to the equilibrium composition is formed early in the decomposition, and grows in amount during transformation. The type of composition fluctuation predicted on the basis of the ``spinodal mechanism'' appears to be absent, and the qualitative nature of the transformation appears to be the same for temperatures above and below the spinodal.
THE NONLINEAR THIRD ORDER DIELECTRIC SUSCEPTIBILITY COEFFICIENTS OF GASES AND OPTICAL THIRD HARMONIC GENERATION
Authors: Rado W. G.
Published: March 2005

The nonresonant third order nonlinear dielectric susceptibility coefficients of several gases were measured in a four wave mixing experiment. These coefficients were used to calculate the amount of third harmonic radiation generated in gases in a focused laser beam. No signal distinguishable from noise was ever seen from gases, although more than 104 times the minimum detectable signal was predicted.
HETERODYNE PERFORMANCE OF MERCURY DOPED GERMANIUM
Authors: Buczek Carl J. , Picus Gerald S.
Published: March 2005

Using optical heterodyne techniques, the response time of a mercury doped germanium detector operated at 4.2°K has been found to be 3.3 nsec and the signal-to-noise ratio measured at 15 MHz is within 4 dB of the quantum noise limit.
THE ORIENTATION OF Cu2S FORMED ON SINGLE CRYSTAL CdS
Authors: Singer Joseph , Faeth Paul A.
Published: March 2005

Extensive penetration by Cu+ into CdS, a reaction used to make the photovoltaic cell Cu2S upon CdS, produces single crystal Cu2S as chalcocite.
A NEW MECHANISM FOR STACKING FAULT GENERATION IN EPITAXIAL GROWTH OF SILICON IN ULTRA-HIGH VACUUM
Authors: Thomas R. N. , Francombe M. H.
Published: March 2005

The homo-epitaxial growth of thick films of silicon, grown by sublimation in vacuo of about 10-10 torr, has been investigated by means of low-energy electron diffraction (LEED) and transmission electron microscopy. In films grown on (111), stacking faults appear at substrate temperatures below 600°C, and increase in density with further decrease in growth temperature. Their appearance is correlated with the development of a mixed Si(111)-5, Si(111)-7 surface structure in this temperature range. It is proposed that these faults are generated by a new mechanism, whereby their nucleation is attributed to the formation of Si(111)-5 domains on the initial Si(111)-7 substrate surface.
ROWS OF DISLOCATION LOOPS IN ALUMINIUM IRRADIATED BY ALUMINIUM IONS
Authors: Henriksen L. , Johansen A. , Koch J. , Andersen H. H. , Cotterill R. M. J.
Published: March 2005

Single-crystal aluminium specimens, irradiated with 50-keV aluminium ions, contain dislocation loops that are arranged in regular rows along 〈 110 〉 directions.
THE DIRECT ABSORPTION EDGE IN COVALENT SOLIDS
Authors: Redfield David , Afromowitz Martin A.
Published: March 2005

Comparative measurements of the absorption edge of p-type GaAs and compensated GaAs over a wide temperature range demonstrate that the shape of the edge in such materials is not dependent on phonon interactions, and is attributable to the state of charge of impurities in the material.
ELASTIC, PIEZOELECTRIC, AND DIELECTRIC PROPERTIES OF LITHIUM TANTALATE
Authors: Smith R. T.
Published: March 2005

Room-temperature values for all six independent elastic coefficients (at constant electric field) and all four independent piezoelectric stress coefficients have been determined from ultrasonic velocity measurements on a single-crystal specimen of lithium tantalate grown by the Czochralski technique. The two independent dielectric constants at constant strain were derived from low-frequency measurements on thin plates of lithium tantalate, in conjunction with the relevant elastic and piezoelectric data. The numerical results have been used to map the deviation of the elastic energy flux vector from the wave propagation direction for plane elastic wave propagation in the YZ crystallographic plane.
ZEEMAN EFFECT STUDIES OF THE WATER-VAPOR LASER OSCILLATING ON THE 118.65 μm TRANSITION
Authors: Tomlinson W. J. , Pollack M. A. , Fork R. L.
Published: March 2005

Zeeman effect studies of the 118.65 μm line of a CW water-vapor laser have shown that the levels involved in the transition have lifetimes between 0.04 and 0.4 μsec and the same total angular momentum, and that the transition has an effective magnetic moment of about 3/4 of a nuclear magneton. These results were obtained by a new spectroscopic technique making explicit use of the saturation behavior of the laser oscillator. This technique enables lifetimes, angular momenta, and magnetic moments to be determined with magnetic field splittings of the order of or less than a tenth of the natural width of the transition.
TEMPERATURE DEPENDENCE AND MODEL OF THE ELECTRO-OPTIC EFFECT IN LiNbO3
Authors: Zook J. D. , Chen D. , Otto G. N.
Published: March 2005

The temperature dependence and the absolute sign of the electro-optic coefficients in single-crystal LiNbO3 were measured in the temperature range of 20°-250°C using a vibrating-mirror Michelson interferometer. The linear electro-optic effect in LiNbO3 is related through a simple model to the quadratic electro-optic effect in paraelectric perovskites. The measured magnitude, sign, and the temperature dependence of the electro-optic effect in this crystal are consistent with this model.
REFLECTIVITY OF YIG AND YGG: OBSERVATION OF CHARGE TRANSFER AND CRYSTAL FIELD TRANSITIONS
Authors: Grant Paul M.
Published: March 2005

The reflectivity spectra of yttrium iron garnet (YIG, Y3Fe5O12) and yttrium gallium garnet (YGG, Y3Ga5O12) have been measured in the energy range 2–7.5 eV. Structure is observed in YIG which can be attributed to charge-transfer-enhanced crystal field transitions and in YGG to critical point transitions.
PREPARATION AND PROPERTIES OF HIGH-PURITY EPITAXIAL GaAs GROWN FROM Ga SOLUTION
Authors: Kang C. S. , Greene P. E.
Published: March 2005

GaAs single crystals were grown epitaxially from Ga solution with carrier concentrations in the 1014 cm-3 range and electron mobilities between 7500 and 9300 cm2/V-sec at 300°K, and 50,000 and 95,000 cm2/V-sec at 77°K. A comparison of the theoretical and experimental curves for the mobility vs temperature indicates that the significant scattering mechanisms are ionized impurities and phonons in the temperature range of 77°K to 430°K. This indicates that the epitaxial layers do not contain other mobility-limiting imperfections to a significant degree. Photoluminescence spectra of the epitaxial layers did not show any emission due to keep lying imperfection levels.
SPACE-CHARGE-LIMITED CURRENTS IN HETEROEPITAXIAL FILMS OF SILICON GROWN ON SAPPHIRE
Authors: Zuleeg R. , Knoll Peter
Published: March 2005

Experimental results are presented on current-voltage relations in heteroepitaxial silicon films grown on sapphire. Above a threshold voltage a current is observed which is proportional to the square of the applied voltage, but inversely proportional to the square of the distance. It is interpreted as space-charge-limited current. The square law dependence with distance is a deviation from the Mott-Gurney law of space-charge-limited current in solids, which predicts I ∝ L−3, and is a consequence of the electrode configuration.
ACOUSTOELECTRIC OSCILLATIONS WITH FIELD-DEPENDENT PERIOD IN INDIUM ANTIMONIDE
Authors: Turner C. W. , Crow J.
Published: March 2005

Experimental observations of acoustoelectric oscillations in [110] and [111] oriented InSb at 77°K in the presence of a transverse magnetic field are described. The period of the oscillations in the [110] samples, equal to the interelectrode transit time of a domain at the shear wave velocity for fields near threshold, increases two- or three-fold for higher electric fields. The possible origin of this anomalous period is discussed.
THE STABILITY OF CYLINDRICAL PERMALLOY FILMS IN AN INHOMOGENEOUS MAGNETIC FIELD
Authors: Rabinovici B. M. , Renton C. A.
Published: March 2005

Measurements of worst-case memory performance, dispersion, and hysteresis have been carried out on permalloy films that have been annealed at elevated temperatures in various applied magnetic fields. It is found that deterioration is most rapid for specimens subjected to inhomogeneous hard-direction fields.
OBSERVATIONS ON THE TENSILE STRENGTH OF ``AMORPHOUS'' BORON
Authors: Wawner Franklin E. , Satterfield Dana B.
Published: March 2005

``Amorphous'' boron filament prepared by chemical-vapor deposition of boron on tungsten has typical tensile strengths of 400–600 kpsi and flexural strengths of the order of 2 Mpsi, contrary to the Weibull relationship which requires that the ratio of these quantities be about 1.4. Tensile strength measurements on sections of these filaments with the tungsten boride core material removed have given numerous values in the range 1 to 1.6 Mpsi, thus demonstrating that the intrinsic strength of the boron in the filament does satisfy the Weibull criterion and that ``amorphous'' boron is one of the strongest materials known.
OBSERVATION OF CHEMICAL-VAPOR-DEPOSITED SILICON ON SAPPHIRE BY TRANSMISSION ELECTRON MICROSCOPY
Authors: Tamura Masao , Nomura Masayoshi
Published: March 2005

The initial stages of the deposition of silicon on very thin sapphire platelets with exact (0001) orientation by the hydrogen reduction of SiCl4 have been observed using transmission electron microscopy.
FRESNEL ZONES AND FIELD ION MICROSCOPY
Authors: Vali W. , Gordon R. L.
Published: March 2005

It is shown that the pattern from a single-crystal tip in a field ion microscope is a collection of Fresnel zone plates. The focal length of a zone is proportional to the interplanar spacing of the set of planes responsible for that zone.
INTERPRETATION OF THE CS2 LASER TRANSITIONS
Authors: Maki Arthur G.
Published: March 2005

The N2–CS2 laser lines are identified as P-branch transitions with J = 28 to 46 for the 001–100 vibrational transition. A population ratio of N001/N100 = 1.07 is determined for the system assuming a temperature of 300°K. The mechanism of selectively populating the 001 level of CS2 is discussed.
DETECTION OF VERY FAINT PREBREAKDOWN LUMINOSITY WAVES IN A POINT-TO-PLANE GAP IMMERSED IN OIL
Authors: MacVicar-Whelan P. J.
Published: March 2005

Very faint luminosity waves traveling at a speed of approximately 3 × 108 cm/sec have been observed in a point-to-plane gap immersed in mineral oil. The waves traveled from both positive and negative points to the plane.
NMR MEASUREMENT OF THE DIFFUSION COEFFICIENT OF PURE ALUMINUM
Authors: Fradin F. Y. , Rowland T. J.
Published: March 2005

Using a radio-frequency field pulse technique which enables measurement of slow atomic diffusion by means of nuclear magnetic resonance we have obtained, for nominally 6–9's pure Al, an activation energy for self-diffusion of 28.75 ± 0.8 kcal/mole. Data was obtained over a range of 5 decades in atomic jump rate (240°C to 550°C) and joins smoothly with other diffusion coefficient measurements at the extremes.
TWO-PHOTON EXCITATION OF FLUORESCENCE BY PICOSECOND LIGHT PULSES
Authors: Giordmaine J. A. , Rentzepis P. M. , Shapiro S. L. , Wecht K. W.
Published: March 2005

Standing wave excitation of two-photon fluorescence in solutions or organic molecules is reported. The observations allow the direct display and measurement of optical pulses as short as 1−2 × 10−2 sec.
PICOSECOND LIGHT PULSE DISPLAY USING TWO DIFFERENT OPTICAL FREQUENCIES
Authors: Rentzepis P. M. , Duguay M. A.
Published: March 2005

A new technique for the display and measurement of picosecond light pulses is demonstrated. Two picosecond pulses, of different optical frequencies, are sent on a collision course in a liquid. They produce strong two-photon fluorescence only in the region where they overlap. This results in the direct display of the pulse shapes over a very weak background. In a different arrangement, the two pulses enter the liquid collinearly and simultaneously, and initially generate strong two-photon fluorescence. Subsequently, as the pulses propagate through the liquid, dispersion causes one pulse to overtake the other and the two-photon fluorescence diminishes. This results in a magnified display of the pulses.
TWO-PHOTON ABSORPTION IN ALKALI HALIDES WITH A PULSED N2 LASER
Authors: Geller M. , Altman D. E. , DeTemple T. A.
Published: March 2005

Two-photon absorption has been observed in alkali halide crystals with a 1 MW superradiant pulse at 3371 Å from a nitrogen gas laser. This multiple quantum process is equivalent to a single-photon absorption in the fundamental absorption edge of the alkali halide with the formation of an exciton and its subsequent trapping at an imperfection to form an F center. The crystals were visibly colored in the regions of high laser flux density. These colored regions, similar to color centers produced by ultraviolet radiation in the exciton region, were bleached by radiation in the F center absorption band.
INTERPRETATION OF HALL EFFECT DATA IN PbS POLYCRYSTALLINE FILMS
Authors: Davis John L. , Greene R. F.
Published: March 2005

The existence of a space-charge layer on the surfaces of the crystallites in PbS photoconducting films is considered. Estimates indicate that observed Hall coefficients may be due to the surface layers rather than to low carrier concentration in the crystallites.
THE TEMPERATURE DEPENDENCE OF STIMULATED BRILLOUIN SCATTERING IN QUARTZ
Authors: Heinicke W. , Winterling G.
Published: March 2005

The threshold power for stimulated Brillouin scattering has been measured from 5° to 300°K in crystalline and fused quartz. There is only a small dependence on temperature. Further threshold measurements in 10 different substances show that instead the threshold depends on the photoelastic properties of the medium. Both facts were predicted by Kroll's dynamical theory. The threshold for stimulated Raman scattering, however, may be strongly temperature dependent as demonstrated for calcite.
THE RELATION BETWEEN STRESS AND STRAIN IN MULTIAXIAL DEFORMATIONS OF ELASTOMERS
Authors: Hutchinson W. D.
Published: March 2005

Using appropriate force and displacement parameters it is shown that the response of elastomers in multiaxial stress fields is identical to their response to uniaxial stresses. These parameters were chosen from consideration of the molecular model assumed in the theory of Kuhn and Grun [Koll. Z., 101, 248 (1942)]. The required force is established to be given by |σ|=(σ¯12+σ¯22+σ¯32)1/2 where the quantities σ¯i are the forces along orthogonal axes on the deformed cross-sectional area; the displacement is given by |e| = (e12 + e22 + e32)1/2 where the quantities ei are the strains along three orthogonal axes. The angle between the force and displacement vectors is found to be independent of the axiality of the stress field.
ENHANCEMENT OF PHOTOELECTRIC QUANTUM EFFICIENCY IN THE NEAR INFRARED
Authors: Crowe K. R. , Gumnick J. L.
Published: March 2005

Enhancement of quantum efficiency has been observed in photocathodes as a result of the application of external electric fields. The magnitude of the enhancement was found to be a function of photon energy.
A NEW, WIDELY AND CONTINUOUSLY TUNABLE, HIGH-POWER PULSED LASER SOURCE
Authors: Carman R. L. , Hanus J. , Weinberg D. L.
Published: March 2005

A pulsed laser source has been developed, which is continuously tunable from 4820 Å to 5790 Å, with power in the kilowatt range, and spectral width ≈14 cm−1. The technique used frequency addition in KDP. One frequency was that of a Nd-glass laser, while the other frequency was selected by phase matching, from the continuum produced by self-focusing and small-scale trapping of the laser beam in CS2. Methods are outlined of extending the wavelength range to ≈50% of the 0.25 μ to 1.0 μ spectrum available with KDP and KD*P.
BULK NEGATIVE DIFFERENTIAL CONDUCTIVITY AND TRAVELING DOMAINS IN n-TYPE GERMANIUM
Authors: Elliott B. J. , Gunn J. B. , McGroddy J. C.
Published: March 2005

Measurements have been made on n-type Ge at 77°K and 27°K, which show the existence of a bulk negative differential conductivity at electric fields above about 3 kV cm−1. This effect is believed to be the cause of previously observed current oscillations, and of traveling domains of high electric field which we have now observed at 27°K.
ACTIVATED TUNGSTEN OXIDE GAS DETECTORS
Authors: Shaver P. J.
Published: March 2005

A method is described for enhancing the sensitivity of the thin films of certain oxides to small amounts of airborne hydrogen and other reducing gases. The quantitative behavior of thin films of platinum-activated tungsten oxide is illustrated.
SIMPLE TECHNIQUE FOR VERY THIN SiO2 FILM THICKNESS MEASUREMENTS
Authors: Pliskin W. A. , Esch R. P.
Published: March 2005

The thickness of films (<900 Å) of silicon dioxide on silicon can be determined by observation near Brewster's angle for silicon with the light polarized in the plane of incidence. Since the intensity of the reflected light increases with thickness for these films, the measurement is made by direct comparison of the light reflected by a sample with a calibrated SiO2 on silicon ``thickness gauge.'' Film thicknesses can be estimated to an accuracy of about±30 Å for thicknesses less than 150 Å and±50 Å for thicknesses between 150 Å and 900 Å.
SINGLE TRANSVERSE MODE PULSED RUBY LASER
Authors: Soncini G. , Svelto O.
Published: March 2005

A special laser cavity made by two roof-top prisms each with roof angle smaller than 90° is described here. Such a cavity has the unique property of giving pure transverse modes of very high quality in pulsed operation.
DIRECT TRANSMISSION ELECTRON MICROSCOPE OBSERVATION OF ELECTROTRANSPORT IN ALUMINUM THIN FILMS
Authors: Blech I. A. , Meieran E. S.
Published: March 2005

Electrotransport in thin Al strips was directly observed by transmission electron microscopy. As expected, hole formation was seen in regions where the electron flow was in the direction of increasing temperature. Hillocks and whiskers were seen to form where the electron flow was in the direction of decreasing temperature. Ciné films taken of the process show the holes to grow predominantly by a transverse movement of narrow fingers which ultimately coalesce and lead to a catastrophic strip burn-out.
THE NONLINEAR OPTICAL PROPERTIES OF Ba2NaNb5O15
Authors: Geusic J. E. , Levinstein H. J. , Rubin J. J. , Singh S. , Van Uitert L. G.
Published: March 2005

The useful nonlinear coefficients of Ba2NaNb5O15 are approximately twice those of LiNbO3. This material is a filled (A sites) structure composition and at room temperature does not have the serious problem of optically induced refractive index inhomogeneities (``optical damage''). Also, the material has unique and reproducible phasematch temperatures. The electro-optic half-wave voltage of this material in the optimum direction is 1570 V.
BLUE LASER EMISSION FROM A FLASHLAMP-EXCITED ORGANIC DYE SOLUTION
Authors: Snavely B. B. , Peterson O. G. , Reithel R. F.
Published: March 2005

Laser emission at 454 mμ has been obtained from 4-methyl umbelliferone in water solution excited by a fast rise time flashlamp.
THE NONLINEAR EFFECT OF ALTERING THE ZEROTH ORDER DENSITY DISTRIBUTION OF A PLASMA
Authors: Hsuan H. C. S. , Ajmera R. C. , Lonngren K. E.
Published: March 2005

By increasing the power of an incident microwave signal on the positive column of a mercury vapor discharge, one observes a nonlinear response. This phenomena can be explained as being due to an alteration of the density which is caused by the externally applied field.
LOCALIZED VIBRATIONAL MODES OF Li AND P IMPURITIES IN GERMANIUM
Authors: Cosand A. E. , Spitzer W. G.
Published: March 2005

Infrared absorption bands due to localized vibrational modes of impurities in germanium are observed at liquid-nitrogen temperature. One pair of bands shows a Li isotope shift from frequencies of 356 cm−1 and 380 cm−1 with 7Li to 379 cm−1 and 405 cm−1 with 6Li; these are attributed to Li paired with Ga. Two bands are associated with the phosphorus: one, at 343 cm−1, is attributed to isolated substitutional phosphorus; the other, at 350 cm−1, is attributed to P–Ga pairs.
ELECTRON IRRADIATION HARDENING OF ALUMINUM-1 AT. % ZINC SINGLE CRYSTALS
Authors: Mifune T. , Meshii M. , Ono Kanji
Published: March 2005

Al-1 at. % Zn single crystals were tensile tested after 1 MeV electron irradiation near 20°K. The increase in the yield stress due to irradiation was proportional to the square root of the electron dose with a proportionality constant similar to that in aluminum. The strain rate sensitivity of the flow stress in stage I increased proportionally to the irradiation induced hardening. The electron irradiation hardening appears to be due to randomly dispersed interstitials acting as obstacles to the movement of dislocations.
EFFECT OF SULFUR ANNEALING PRESSURE ON RESISTIVITY HOMOGENEITY OF CdS SINGLE CRYSTALS
Authors: Parsons M. K. , English F. L.
Published: March 2005

Resistivity inhomogeneities in single-crystal CdS have been studied as a function of sulfur (S2) annealing pressure. The number and severity of the inhomogeneities increase with the value of S2 partial pressure and are believed to be responsible for the deterioration of ultrasonic gain in crystals annealed at pressures much above a critical pressure.
CONTINUOUS OPERATION OF GaAs JUNCTION LASERS ON DIAMOND HEAT SINKS AT 200°K
Authors: Dyment J. C. , D'Asaro L. A.
Published: March 2005

Gallium arsenide stripe geometry junction lasers have now been operated continuously at a heat sink temperature of 200°K, which is the highest yet attained. The improvement is due to higher thermal conductivity resulting from (1) a heat sink made of type IIa diamond with a thermal conductivity of 45 W cm−1 °K−1 at 200°K, (2) an optimized stripe width near 12.5 μm and (3) an unusually thin diffused p region, 2.5 μm deep. This type of laser is unique in that the radiation pattern is Gaussian when measured parallel to the junction plane.
ELECTRIC-FIELD-DEPENDENT LUMINESCENT SPECTRA OF GRADED BAND-GAP SEMICONDUCTORS
Authors: Hill Robert , Williams Ferd
Published: March 2005

Luminescent emission from zinc-cadmium sulfide crystals with graded composition has been investigated. The edge emission spectrum was found to vary linearly with electric field applied parallel to the composition gradient. Possible mechanisms are evaluated, and it is concluded that positive hole transport between regions with different band gaps is responsible for the spectral shift. The effect can be used to determine the product of minority carrier lifetime and mobility.
REFLECTION HIGH-ENERGY ELECTRON DIFFRACTION AND X-RAY EMISSION ANALYSIS OF SURFACES AND THEIR REACTION PRODUCTS
Authors: Sewell P. B. , Cohen M.
Published: March 2005

An apparatus is described in which it is possible to obtain simultaneous reflection high-energy electron diffraction and x-ray emission measurements from surfaces. The ultimate vacuum in the electron diffraction section of the apparatus is <10−9 torr so that both chemical and crystallographic information about clean surfaces and surfaces with adsorbed monolayers or thin film reaction products can be acquired. The sensitivity of the apparatus is illustrated with oxygen on the (001) surface of iron.
Temporary and permanent enhancement of the magnetoimpedance response of amorphous wires
Authors: Rudkowska G. , Clime L. , Ciureanu P. , Yelon A.
Published: March 2005

Melt extracted amorphous wires have a predominantly helical anisotropy due to residual tensile and torsional stresses quenched in the wire during casting. Consequently, their magnetoimpedance (MI) response is inadequate for linear detection of magnetic field. Several methods are used to accomplish this, both temporary (dc current biasing of the wire, tensile stress applied to the wire, or both) and permanent (current annealing of the wire, with or without applying a tensile stress). Their purpose is to optimize the MI response of these wires. The transverse (circumferential) anisotropy of the wire reaches an optimum in magnitude and orientation when a temporary method is used. This optimum can be quenched in the material using a permanent method. The MI response is characterized with the help of three criteria: sensitivity, figure of merit and peak amplitude per wire unit length. Magnetic field sensors with sensitivities as high as 75V∕(Tmm), figures of merit of about 0.5ΩT∕m, and peak amplitudes of 5Ω∕mm were obtained as a result of the enhancement of the MI response.
Beating the superparamagnetic limit of IrMn in ferro-∕antiferromagnet∕artificial antiferromagnet
Authors: Mattheis R. , Steenbeck K.
Published: March 2005

By coupling an artificial antiferromagnet (AAF)(CoFe∕Ru∕CoFe) to a ferro-∕antiferromagnet (F∕AF) system (NiFe∕IrMn) we found a strong increase of the exchange bias blocking temperature, e.g., at 1.5-nm IrMn from 110 to 360 K. By magneto-optical Kerr effect and torquemetry at 10–340 K we determined the exchange bias field He, the coupling energy JF∕AF between ferromagnet and antiferromagnet, and the rotational loss for thickness of IrMn from (0.3 to 3.5) nm. By comparison of both systems we concluded that for small thickness of the AF its superparamagnetic state was overcome due to the increased total anisotropy energy in the system with AAF. In this system exchange bias can be realized at room temperature with vanishing crystalline anisotropy of the antiferromagnet and without rotational loss.
Stress dependence of the differential susceptibility of soft magnetic ribbons
Authors: Kosel J. , Hauser H. , Didosyan Y. , Pertl G.
Published: March 2005

This paper presents a study of the differential susceptibility of soft magnetic magnetostrictive ribbons as a function of applied stress using an original experimental approach that accommodates both tensile and compressive stresses. While tensile stress is applied directly to the sample ribbon, compressive stress is applied to a sandwich structure which contains the sample ribbon and prevents buckling. The results of three different amorphous materials are compared. Additionally, the influence of annealing on the stress sensitivity is investigated for one of the samples.
Enhancement of magnetoresistance with low interlayer coupling by insertion of a nano-oxide layer into a free magnetic layer
Authors: Nam Chunghee , Lee Ki-Su , Cho B. K.
Published: March 2005

We studied the interlayer coupling strength (Hin) and GMR ratio of a spin-valve with the top free layer, separated by a nano-oxide layer (NOL). With the total thickness of the top free layer being fixed at 60Å, the physical properties of the NOL spin-valve were studied with the thickness (tf) of the free layer under the inserted NOL and compared with those of the normal spin-valve with the same thickness as tf. It was found that the spin-valve with NOL has a higher GMR ratio than that of the normal spin-valve at the optimal condition (tf=40Å) after thermal annealing at T=250°C. The NOL spin-valve also shows a lower Hin than that of the optimal normal spin-valve with tf=40Å, which is comparable to that of the normal spin-valve with tf=60Å. This indicates that the enhancement of GMR, while keeping the Hin to be low, can be achieved by inserting a NOL into the top free layer.
Self-ordered growth and magnetic force microscopy study of iron nanoparticles
Authors: Sievers S. , Albrecht M. , Siegner U. , Herweg C. , Freyhardt H. C.
Published: March 2005

We present atomic and magnetic force microscopy measurements on magnetic iron nanoparticles produced by a self-assembly method. The fabrication process is based on the thermal disintegration of iron nanowires deposited on faceted Al2O3 substrates. Arrangement and size of the particles depend on the annealing temperature. For iron this process yields particles with diameters in the range of 100–250 nm. The usage of the prepatterned substrates enforces a linear alignment of the particles. Magnetic force microscopy shows that the particles can be remanently magnetized with external fields of different orientations.
Synthesis and magnetic properties of face-centered-cubic and hexagonal-close-packed Ni nanoparticles through polyol process
Authors: Chinnasamy C. N. , Jeyadevan B. , Shinoda K. , Tohji K. , Narayanasamy A. , Sato K. , Hisano S.
Published: March 2005

The Ni nanoparticles with fcc or hcp phases have been synthesized in tetraethylene glycol by using the modified polyol process. The crystal structure has been controlled by changing the polyol/Ni mole ratio and the reaction temperature. The saturation magnetization of the as-prepared particles depends on the relative volume fraction of the hcp phase. The x-ray diffraction and extended x-ray absorption fine structure studies suggest the formation of pure fcc and hcp Ni phases. The hcp Ni particles show nonmagnetic behavior and thermally stable below 673K.
Armature reaction field and inductances of tubular modular permanent magnet machines
Authors: Wang J. , Howe D. , Amara Y.
Published: March 2005

The paper describes an analytical technique which has been developed to predict the armature reaction field of tubular modular permanent magnet (PM) machines in which the fundamental of the stator magnetomotive force (mmf) has fewer poles than that of the permanent magnet armature, the thrust force being developed by the interaction between a higher-order mmf harmonic with the permanent magnet field. The analytical solution also allows the prediction of the self- and mutual-winding inductances of a tubular modular machine in closed forms and facilitates dynamic modeling, as well as the evaluation of any partial irreversible demagnetization of the magnets which might occur under various operating conditions. The utility and accuracy of the developed technique are demonstrated by extensive finite element analyses and measurements on a nine-slot/ten-pole tubular modular PM machine.
Closure of minor hysteresis loops in disordered antiferromagnetic systems
Authors: Hovorka O. , Friedman G.
Published: March 2005

Closure of quasistatic minor hysteresis loops in disordered Ising-like systems with short-range antiferromagnetic interactions is studied numerically. State of each Ising spin is given by a symmetrical rectangular hysteresis loop. Inherent disorder in the system is modeled by a probability distribution of the spins’ switching thresholds. Numerical implementation of the two-dimensional system shows that minor hysteresis loops do not close at interactions strength above a certain value. Néel’s type mean-field approximation of this system demonstrates a similar behavior with a much more abrupt transition to open minor loops.
Cobalt-doped anatase TiO2: A room temperature dilute magnetic dielectric material
Authors: Griffin K. A. , Pakhomov A. B. , Wang C. M. , Heald S. M. , Krishnan Kannan M.
Published: March 2005

We experimentally investigate the room temperature ferromagnetism observed in insulating Co doped anatase TiO2 thin films grown by sputter deposition. The Co was uniformly incorporated in the lattice as Co(II) with no evidence of Co metal. A series of annealing treatments were carried out to optimize the ferromagnetic ordering and a saturation moment of 1.1μB∕Co atom at 300 K was obtained with UHV annealing at 450 °C. Both as-deposited and annealed films were highly insulating at room temperature. Results show that the ferromagnetism is strongly dependent on the number and distribution of oxygen vacancies in the Co:TiO2 lattice.
Nanocrystalline Fe-Pt-B base hard magnets with high coercive force obtained from amorphous precursor
Authors: Inoue Akihisa , Zhang Wei
Published: March 2005

Nanocomposite alloys of fct γ1-Fe(Co)Pt, fcc γ-Fe(Co)Pt, and Fe(Co)2B phases with good permanent magnet properties have been formed by melt spinning followed by annealing. An amorphous phase was formed for Fe56.25−xCoxPt18.75B25 (x=0–20) alloys by melt spinning. The thermal stability of the amorphous alloys increases gradually with increasing Co content. The structure crystallized by annealing for 900s at 785K consisted of fct γ1-Fe(Co)Pt, fcc γ-Fe(Co)Pt, and Fe(Co)2B phases, and their average grain sizes were about 20nm. The nanocomposite alloys exhibit good hard magnetic properties. As the Co content increases, the coercivity Hci increases, the remanence Br and maximum energy product (BH)max decrease. The Br, reduced remanence Mr∕Ms, Hci, and (BH)max were 0.96T, 0.83, 340kA∕m, and 102.2kJ∕m3, respectively, for the 0at.% Co alloy. Higher coercivity (426kA∕m) was obtained for the 20at.% Co alloy albeit with lower Br(0.68T), Mr∕Ms(0.80), and energy product (66.7kJ∕m3). The good hard magnetic properties for the low Pt-containing alloys are interpreted as resulting from exchange magnetic coupling between nanoscale hard fct γ1-Fe(Co)Pt and soft fcc γ-Fe(Co)Pt or Fe(Co)2B magnetic phase.
A transformer model based on optimized Cauer circuits
Authors: Krah J. H. , Engdahl G.
Published: March 2005

A transformer model is presented where both winding and core were modeled by Cauer circuits in order to take into account eddy currents. The physical property of the magnetic circuit allowed the insertion of a hysteresis model. Thermal effects in the winding insulation were also modeled by a Cauer circuit. The discretization of the circuits was optimized by an iterative method that fits the reluctance of a core part or the impedance of a winding layer to known analytical solutions. This reduced the number of required circuit elements substantially and the accuracy was increased.
Phase behavior and interfacial properties of nonadditive mixtures of Onsager rods
Authors: Shundyak Kostya , van Roij René , van der Schoot Paul
Published: March 2005

Within a second virial theory, we study bulk phase diagrams as well as the free planar isotropic–nematic interface of binary mixtures of nonadditive thin and thick hard rods. For species of the same type, the excluded volume is determined only by the dimensions of the particles, whereas for dissimilar ones it is taken to be larger or smaller than that, giving rise to a nonadditivity that can be positive or negative. We argue that such a nonadditivity can result from modeling of soft interactions as effective hard-core interactions. The nonadditivity enhances or reduces the fractionation at isotropic–nematic (IN) coexistence and may induce or suppress a demixing of the high-density nematic phase into two nematic phases of different composition (N1 and N2), depending on whether the nonadditivity is positive or negative. The interfacial tension between coexisting isotropic and nematic phases shows an increase with increasing fractionation at the IN interface, and complete wetting of the IN2 interface by the N1 phase upon approach of the triple-point coexistence. In all explored cases bulk and interfacial properties of the nonadditive mixtures exhibit a striking and quite unexpected similarity with the properties of additive mixtures of different diameter ratio.
Incorporating variable dielectric environments into the generalized Born model
Authors: Sigalov Grigori , Scheffel Peter , Onufriev Alexey
Published: March 2005

A generalized Born (GB) model is proposed that approximates the electrostatic part of macromolecular solvation free energy over the entire range of the solvent and solute dielectric constants. The model contains no fitting parameters, and is derived by matching a general form of the GB Green function with the exact Green’s function of the Poisson equation for a random charge distribution inside a perfect sphere. The sphere is assumed to be filled uniformly with dielectric medium ϵin, and is surrounded by infinite solvent of constant dielectric ϵout. This model is as computationally efficient as the conventional GB model based on the widely used functional form due to Still et al. [J. Am. Chem. Soc. 112, 6127 (1990)], but captures the essential physics of the dielectric response for all values of ϵin and ϵout. This model is tested against the exact solution on a perfect sphere, and against the numerical Poisson–Boltzmann (PB) treatment on a set of macromolecules representing various structural classes. It shows reasonable agreement with both the exact and the numerical solutions of the PB equation (where available) considered as reference, and is more accurate than the conventional GB model over the entire range of dielectric values.
The merits of the frozen-density embedding scheme to model solvatochromic shifts
Authors: Neugebauer Johannes , Louwerse Manuel J. , Baerends Evert Jan , Wesolowski Tomasz A.
Published: March 2005

We investigate the usefulness of a frozen-density embedding scheme within density-functional theory [J. Phys. Chem. 97, 8050 (1993)] for the calculation of solvatochromic shifts. The frozen-density calculations, particularly of excitation energies have two clear advantages over the standard supermolecule calculations: (i) calculations for much larger systems are feasible, since the time-consuming time-dependent density functional theory (TDDFT) part is carried out in a limited molecular orbital space, while the effect of the surroundings is still included at a quantum mechanical level. This allows a large number of solvent molecules to be included and thus affords both specific and nonspecific solvent effects to be modeled. (ii) Only excitations of the system of interest, i.e., the selected embedded system, are calculated. This allows an easy analysis and interpretation of the results. In TDDFT calculations, it avoids unphysical results introduced by spurious mixings with the artificially too low charge-transfer excitations which are an artifact of the adiabatic local-density approximation or generalized gradient approximation exchange-correlation kernels currently used. The performance of the frozen-density embedding method is tested for the well-studied solvatochromic properties of the n→π* excitation of acetone. Further enhancement of the efficiency is studied by constructing approximate solvent densities, e.g., from a superposition of densities of individual solvent molecules. This is demonstrated for systems with up to 802 atoms. To obtain a realistic modeling of the absorption spectra of solvated molecules, including the effect of the solvent motions, we combine the embedding scheme with classical molecular dynamics (MD) and Car-Parrinello MD simulations to obtain snapshots of the solute and its solvent environment, for which then excitation energies are calculated. The frozen-density embedding yields estimated solvent shifts in the range of 0.20–0.26eV, in good agreement with experimental values of between 0.19 and 0.21eV.
Effect of displacement and distortion of potential energy surfaces and overlapping resonances of electronic transitions on surface-enhanced Raman scattering: Models and ab initio theoretical calculation
Authors: Lee M. T. , Wu D. Y. , Tian Z. Q. , Lin S. H.
Published: March 2005

A previously developed theory for the temperature-dependent resonance Raman scattering is used to study the surface-enhanced Raman scattering. Two models, the displaced oscillator model and the displaced-distorted oscillator model, based on the harmonic potential energy surfaces are carried out to calculate the surface-enhanced Raman scattering excitation profiles of the pyridine molecule adsorbed on a silver electrode, for which the density functional theory method is applied to evaluate the potential energy surfaces of the adsorption structure. In this framework, the distortion effect on the surface-enhanced Raman scattering will be discussed by comparing both models. The overlapping resonance of multiexcited electronic transitions is also studied, in which the interference between electronic transitions has been taken into account. It will be used to study the abnormal band at 1005.6cm−1 with the exciting radiation 457.9 nm.