bluuebunny/crossref_metadata_2025 huggingface dataset:
RESONANT ELECTRON-PHONON SCATTERING IN POLAR SEMICONDUCTORS
Authors: Sher A. , Thornber K. K.
Published: March 2005

It is demonstrated that even in the case of weak polar coupling, certain two-phonon scattering processes lead to rates comparable to one-phonon scattering. This additional scattering will influence the electron distributions and velocity-field characteristics calculated for polar semiconductors.
TRANSPORT PROPERTIES OF SEMI-INSULATING CdTe USING NUCLEAR PARTICLES
Authors: Zanio K. , Akutagawa W. , Mayer J. W.
Published: March 2005

The transient response of semi-insulating CdTe to monoenergetic alpha particles is composed of a fast component, characteristic of trapping, and slow component displaying the release of carriers from traps. It is verified that the shape of the fast component is directly proportional to [1 - exp (-t/τ+)] for electrons where τ+ is the mean free drift time. From an analysis of the shape, τ+ for electrons ranges from 30 to 90 nsec; mobilities from 600 to 1100 cm2/V-sec. On a single-level model thermal and optical excitation data indicate a trapping level at 0.6±0.05 eV from the conduction band.
RELATIONSHIPS BETWEEN THE NONLINEAR ELASTIC CONSTANTS OF MONOCRYSTALLINE AND POLYCRYSTALLINE SOLIDS OF CUBIC SYMMETRY
Authors: Chang Roger
Published: March 2005

The relationships between the third-order elastic constants of monocrystalline and polycrystalline (quasi-isotropic, randomly oriented) solids of cubic symmetry are derived according to elastic strain energy balances assuming negligibly small elastic strain energy contribution from mismatching of the grain boundaries. The relationships between the three third-order isotropic Lamé coefficients (γ1, γ2, γ3, Brugger convention) and the six third-order single-crystal elastic constants are given by: γ1=135(C111+18C112−30C144−12C166+16C123+16C456) γ2=135(C111+4C112+19C144+2C166−5C123−12C456)γ3=135(C111−3C112−9C144+9C166+2C123+9C456). Good agreement was found between the experimentally evaluated γ1, γ2, γ3 values and those derived from the above equations using the six third-order single-crystal elastic constants for bcc columbium at room temperature.
PHYSICAL LIMITATIONS ON THE PERFORMANCE OF VITREOUS SILICA IN HIGH-FREQUENCY ULTRASONIC AND ACOUSTO-OPTICAL DEVICES
Authors: Fraser D. B. , Krause J. T. , Meitzler A. H.
Published: March 2005

The usefulness of vitreous silica in a variety of high-frequency ultrasonic and acousto-optical devices is often limited by the acoustic properties of the material. The purpose of this Letter is to report recent findings on (1) the acoustic loss-vs-frequency dependence for shear waves in vitreous silica and (2) the magnitude of the fluctuation in the shear wave phase velocity. Information on the shear wave propagation characteristics is most important for ultrasonic delay line applications for which the shear mode of propagation is predominantley used.
RAYLEIGH SCATTERING IN AN OPTICALLY ANISOTROPIC MEDIUM
Authors: Gayles J. N. , Lohmann A. W. , Peticolas W. L.
Published: March 2005

When a plane-polarized light beam is passed through an anisotropic medium, the extraordinary ray can become retarded or advanced relative to the ordinary ray. This leads to a periodic longitudinal extinction of (λ/Δn) along the light path which provides a quick accurate visual method for determining the birefringence of a material which is both transparent and a good scatterer of light.
ON A CURRENT INSTABILITY RESULTING FROM THE DIFFUSION OF HOT ELECTRONS
Authors: Dumke W. P.
Published: March 2005

An instability of the electron concentration is predicted in a semiconductor with a nearly saturating drift velocity and a diffusion constant which increases with increasing electric field. A small signal analysis shows under what conditions fluctuations of the carrier concentration will be unstable.
CAUSE OF THE ``DARK-SHEATH'' IN RF PLASMOIDAL DISCHARGES
Authors: Kregel M. D. , Miller A.
Published: March 2005

The ``dark-sheath'' region in plasmoidal discharges is known to be a high field region, and measurements of the relative emission rates from molecular oxygen ions and neutral oxygen atoms show that only the intensity of the molecular ion lines drop sharply in the ``dark-sheath.'' It is proposed that the dark-sheath region occurs because the lifetimes of the excited states of the molecular ions are long enough to permit an appreciable fraction of newly created ions to be swept away by the static electric field prior to radiative de-excitation.
FRAGMENT SHAPES PRODUCED BY HYPERVELOCITY IMPACT AND THEIR LUNAR SIGNIFICANCE
Authors: Jaffe Leonard D.
Published: March 2005

Hypervelocity impacts against porous silicates and against polyethylene produced highly irregular fragments with re-entrant shapes, sometimes rather filamentary. A similar process may operate on the lunar surface.
A LOW-ENERGY ELECTRON DIFFRACTION STUDY OF THE EPITAXIAL SILICON LAYERS ON A Ge(111) SURFACE
Authors: Takeishi Yoshiyuki , Sasaki Isao , Hirabayashi Kanji
Published: March 2005

Silicon atoms were evaporated onto cleaned and annealed Ge(111) surfaces at a rate of 2 × 1014 atoms/cm2 min up to 40 min. Analyses of LEED patterns have revealed, on the substrate at 870°K, truncated tetrahedra consisting of reconstructed {311} and (111) planes, which have a 3 × 1 and a 7 × 7 superstructure, respectively. The 3 × 1 superstructure was observed on cleaned and annealed Si(311) surfaces in an independent experiment.
PARAMETRIC AMPLIFICATION OF ULTRASHORT LASER PULSES
Authors: Glenn W. H.
Published: March 2005

The parametric amplification of a short optical pulse, such as is produced by a mode-locked laser, is treated. The pump signal is also a short optical pulse whose center frequency is twice that of the signal pulse. It is shown that the signal pulse undergoes considerable sharpening. The sharpening is ultimately limited by the mismatch in the group velocities of the pump and signal pulses.
NUCLEAR ULTRASONIC FAST PASSAGE
Authors: Averbuch P. , James L. W. , Mahler R. J.
Published: March 2005

An ultrasonic fast passage experiment is described and the small resulting 16% nuclear spin inversion is explained as an inability to obtain ideal experimental conditions.
ACOUSTIC NONLINEAR FREQUENCY MIXING DETECTED USING OPTICAL BRAGG DIFFRACTION
Authors: Dixon R. W.
Published: March 2005

Nonlinear acoustic sum and difference frequency generation has been observed in fused quartz using the technique of optical Bragg diffraction. The technique possesses significant advantages over direct acoustic detection and should be very useful in other studies of acoustic nonlinearities in optically transparent materials.
ABSOLUTE FREQUENCY MEASUREMENT OF THE 118.6-μm WATER-VAPOR LASER TRANSITION
Authors: Frenkel L. , Sullivan T. , Pollack M. A. , Bridges T. J.
Published: March 2005

The frequency of the 118.6-μm water-vapor laser transition has been measured as 2,527,952.8 MHz in a harmonic mixing experiment. Accuracy of several parts in 108 has been obtained by phase locking the klystron harmonic source to a tunable crystal oscillator and by centering the laser to the Lamb dip.
SPIKES IN THE LIGHT OUTPUT OF ROOM-TEMPERATURE GaAs JUNCTION LASERS
Authors: Roldan R.
Published: March 2005

A regular spiking pattern has been observed in the light output of GaAs injection lasers with a stripe geometry contact. Computer solutions to the rate equations involving the photon density and the inverted population are compared and found to be in good agreement with the experimental results. The rate equations are based on the assumption that a spatially inhomogeneous inversion exists along the resonator length.
ON THE DIELECTRIC CONSTANT OF GaAs AT MICROWAVE FREQUENCIES
Authors: Braslau N.
Published: March 2005

The dielectric constant of GaAs in the range 1.9–13 GHz has been determined from measurements of the fringing capacitance of bulk samples terminating a coaxial line. There is no indication of a large deviation from the low-frequency value recently reported by Larrabee and Hicinbothem, although there may be a small resonance effect near 10 GHz.
CESIUM-GaAs SCHOTTKY BARRIER HEIGHT
Authors: Uebbing John J. , Bell Ronald L.
Published: March 2005

The Schottky barrier height at the interface of cesium metal and vacuum-cleaved p-type GaAs has been found to be 0.63 ± 0.03 eV. These measurements were made photovoltaically at 80°K and indicate that a heavy coverage of cesium leaves the surface roughly intrinsic.
THE WORK FUNCTIONS OF CESIUM ON THE (100) AND (110) ORIENTED FACES OF TUNGSTEN SINGLE CRYSTALS
Authors: Lee T. J. , Blott B. H. , Hopkins B. J.
Published: March 2005

Work-function measurements have been made at room temperature, using the vibrating capacitor technique, on (110) and (100) oriented tungsten single-crystal surfaces both clean and covered with cesium. After complete cesiation the work functions of the two surfaces were, respectively, 2.06 ± 0.01 eV and 1.82 ± 0.01 eV. On the basis of a model involving epitaxial growth of the cesium and a doubling of the lattice constant, the work-function differences between the two surfaces, clean and cesiated, are found to agree well with the predictions of Smoluchowski. Comparison of the present result on the (110) plane, covered with a monolayer of cesium, with a published value for a thick film of cesium indicates that there may be very little contribution to the work function from atoms in the solid other than those in the outermost atomic layer.
RADIATION DAMAGE IN THIN METAL FILMS AT 4.2°K
Authors: Merkle K. L. , Singer L. R.
Published: March 2005

The changes in electrical resistance in thin films of gold, copper, and aluminum upon irradiation with heavy charged particles were studied. As a function of dose, there is a steady increase in resistance and a monotonic decrease in the damage rate. A large part of the initial decrease is due to the size effect; however, at higher defect densities the thin film damage rate approaches bulk values.
GAIN SATURATION FLUX AND STIMULATED EMISSION CROSS SECTION FOR THE 10.6 μ LINE OF CO2
Authors: Hotz David F. , Austin Joseph W.
Published: March 2005

Gain saturation for the 10.6 μ transition of CO2 has been measured in a single-pass configuration and the saturation flux found to be (22±2) W/cm2. Knowledge of the saturation flux and the inversion production rate provides an estimate of 3 × 10-18 cm2 for the stimulated emission cross section of the transition.
ORIENTED GROWTH OF THE INTERFACIAL PtSi LAYER OR BETWEEN Pt AND Si
Authors: Kawamura T. , Shinoda D. , Muta H.
Published: March 2005

The oriented growth of the interfacial PtSi layer between Pt and Si is described. Sputtered Pt onto the (111) Si wafer reacts with Si above 600°C to form PtSi. The interfacial PtSi has the preferred orientation characteristic of the temperature of heat treatment, varying the orientation from [101] at 600°C and 700°C, through [121] at 750°C, to [001] at 800°C. A possible growth mechanism of the interfacial PtSi is proposed on the basis of the atomic layer sequence of each crystallographic direction.
A LEED STUDY OF THE HOMOEPITAXIAL GROWTH OF THICK SILICON FILMS
Authors: Thomas R. N. , Francombe M. H.
Published: March 2005

An in-situ low-energy electron diffraction (LEED) study has been made of the homoepitaxial growth in ultrahigh vacuum of silicon films up to several microns thickness. During growth on (111) at temperatures between 600 and 1000°C the initial Si(111)-7 surface structure of the substrate is retained by the epitaxial film. Below 600°C a mixed Si(111)-7 and Si(111)-5 structure develops in the initial stages of growth and for a given temperature, is preserved as epitaxy proceeds. At temperatures lower than 350°C the LEED data indicate that the film structure becomes amorphous. Epitaxy on (100) occurs at temperatures down to about 300°C. In this case the initial Si(100)-2 surface structure is retained by the film except in the range 650 to 700°C, where a new ordered form of the Si(100)-2 structure is generated.
ELECTROMIGRATION EFFECTS IN ALUMINUM FILM ON SILICON SUBSTRATES
Authors: Howard J. K. , Ross R. F.
Published: March 2005

A new nondestructive method is reported to investigate electromigration-induced void formation in aluminum stripes on silicon substrates. X-ray topography and optical microscopy are employed to characterize void nucleation at or below the film surface. Results are presented to show the correlation between x-ray and optical images of void structures in an aluminum stripe after dc current flow.
CURRENT RUNAWAY AND AVALANCHE EFFECTS IN n—CdTe
Authors: Oliver M. R. , McWhorter A. L. , Foyt A. G.
Published: March 2005

In addition to Gunn oscillations, n—CdTe exhibits a current runaway which is accompanied by light-emitting filaments reaching from contact to contact. The results of diagnostic experiments suggest a current-density controlled differential negative resistivity caused by a bulk avalanche of hole-electron pairs. The avalanche is probably initiated by high-field Gunn domains, but the mechanism that sustains the runaway is not understood.
EXCITED STATE ABSORPTION IN A SATURABLE ABSORBER
Authors: Gibbs W. E. K.
Published: March 2005

Measurements carried out on chloroaluminum phthalocyanine under ruby laser excitation showed that the observed blue fluorescence originated in the second excited singlet state and was excited by transitions from the first excited singlet state. The upper limit of the excitation cross section of this transition was determined and shown to be without effect on the performance of this absorber as a passive Q switch. Two-photon absorption in the chloronaphthalene solvent was also detected.
HOT CARRIER CURRENT OSCILLATIONS IN n-TYPE GERMANIUM
Authors: Heinrich Helmut , Ferry David K.
Published: March 2005

The observation of current oscillations from n-type germanium at electric fields sufficient to produce hot electron current saturation is reported. These oscillations differ from previous reports in that neither a constricted geometry nor avalanche injection from contacts are required.
ASSESSMENT OF LITHIUM-META-NIOBATE FOR NONLINEAR OPTICS
Authors: Midwinter J. E.
Published: March 2005

Techniques for evaluating the quality of single crystals of LiNbO3 by a Twyman-Green interferometer and between crossed polarizers are described and the quality coefficients so obtained are compared with the second-harmonic generation performance measured using a 1.084-μ gas laser. The variations in quality are interpreted in terms of gradients of chemical composition, and a method for partially correcting them is described.
DONOR SURFACE STATES AND BULK ACCEPTOR TRAPS IN SILICON-ON-SAPPHIRE FILMS
Authors: Heiman F. P.
Published: March 2005

It is proposed that the appearance of donor surface states at the silicon-sapphire interface, after heating in moisture or hydrogen, is due to activation of impurities absorbed in the thin glassy layer which exists between the silicon and sapphire. This layer forms during deposition of the silicon films in a hydrogen atmosphere by reduction of the surface layer of sapphire, releasing aluminum into the silicon film. The photoconductivity of silicon-on-sapphire for photon energy below band gap energy is due to acceptor traps located more than 0.65 eV above the valence band.
THERMAL NOISE IN Ge p-ν-p SCL DIODES
Authors: Yamamoto S. , Liu S. T. , van der Ziel A.
Published: March 2005

We measured the noise spectrum between 1 kHz and 60 MHz. At high frequencies the noise seems to reach the limiting value, where g is the differential conductance and n follows from the characteristic.
ENHANCEMENT OF THE MEISSNER EFFECT IN TYPE II SUPERCONDUCTORS BY A HEAT PULSE
Authors: LeBlanc M. A. R. , Griffiths D. J. , Mattes H. G.
Published: March 2005

A transient increase of the temperature of the surface of a type II superconductor cooled in a static magnetic field causes flux expulsion and enhances the final diamagnetic moment. It is argued that a net paramagnetic current is induced at the surface of the specimen during the initial cooling in a static magnetic field. Quenching of this surface current by a heat pulse permits flux expulsion.
RADIAL DENSITY PROFILE AND CRITICAL MAGNETIC FIELD MEASUREMENT FOR THE HELICAL INSTABILITY IN A HOLLOW PLASMA COLUMN
Authors: Reynolds J. F. , Holt E. H. , Jennings W. C. , Noon J. H.
Published: March 2005

The characteristics of the current convective instability in a hollow plasma column are described. Langmuir probe measurements of the radial form of the perturbed electron density reveal that the rotating helix is concentrated towards the outer wall of the discharge vessel. The instability has been shown to occur at a lower critical magnetic field for a hollow plasma cell than for a regular positive column cell of the same dimensions. Neither of these features are considered in previous theoretical work. For both the regular and the hollow positive column, the use of measured electron density profiles in numerically evaluating a stability criterion is shown to give improved agreement between theory and experiment.
SOLID-STATE ACOUSTOELECTRIC LIGHT SCANNER
Authors: Hakki Basil W.
Published: March 2005

Light-emitting p-n junctions are scanned by an acoustic domain traveling at sound velocity in CdS at room temperature. The light elements are heterojunctions formed by depositing p-Cu2S on n-CdS. The acoustic domain is generated in CdS by applying a bias electric field which gives the electrons a drift velocity greater than the shear sound velocity. When the acoustic domain is in the vicinity of a p-n junction, part of the acoustic energy is transformed into light. As the domain travels between consecutive light elements it replenishes its lost acoustic energy from the bias electric field.
SCATTERING OF LIGHT BY ULTRASONIC SURFACE WAVES IN QUARTZ
Authors: Krokstad J. , Svaasand L. O.
Published: March 2005

Experimental results of Raman-Nath scattering of light by ultrasonic surface and volume waves in quartz are presented. The experiments indicate that the presented method will be a valuable tool for studying the effect of discontinuities upon surface wave propagation. It also appears that the phase velocity of the sound waves may be determined with good accuracy.
ULTRASONIC ATTENUATION IN SUPERCONDUCTING TIN AT VARIOUS AMPLITUDES OF THE ULTRASONIC PULSE
Authors: Chaudhuri K. D. , Jain M. C.
Published: March 2005

The effect of amplitude of the ultrasonic pulse on the attenuation of pure and impure single crystals of superconducting tin has been studied for the strained as well as annealed specimens. It has been found that small amplitude favors oscillations and the temperature-dependent attenuation is strongly dependent on the strain content of the specimen and slightly on amplitude.
A NEW AND STABLE NONLINEAR OPTICAL MATERIAL
Authors: Van Uitert L. G. , Singh S. , Levinstein H. J. , Geusic J. E. , Bonner W. A.
Published: March 2005

The nonlinear coefficient d31 of K.6Li.4NbO3 is equal to d31 of LiNbO3. Also, the serious problem of optically induced refractive-index inhomogeneities which has been observed in many nonlinear materials, notably LiNbO3, is not observed in this new material. The electro-optic half-wave voltage of this new material is 930 V.
A NEW METHOD FOR POINT TUNNELING INTO SUPERCONDUCTORS
Authors: von Molnar S. , Thompson W. A. , Edelstein A. S.
Published: March 2005

A novel point tunneling technique for superconductors is reported. This technique employs the intrinsic barrier layer formed between a degenerate GaAs point and the superconducting metal surface. Excellent agreement between theoretical and experimental conductance curves is obtained for polycrystalline lead.
ATMOSPHERIC ABSORPTION OF CO2 LASER RADIATION
Authors: Stephenson John C. , Haseltine William A. , Moore C. Bradley
Published: March 2005

The absorption of CO2 laser radiation by the atmosphere is calculated from laboratory absorption coefficient measurements.
STUDIES OF SUPERCONDUCTING Nb-25% Zr WIRES CARRYING ALTERNATING CURRENT IN AN AXIALLY APPLIED MAGNETIC FIELD
Authors: Taylor Henry F.
Published: March 2005

The application of an axially directed magnetic field has been observed to reduce ac losses considerably in superconducting Nb-25% Zr wires. It has been found that magnetization curves measured with constant-amplitude ac flowing in a wire sample are paramagnetic-shifted with respect to curves measured with no externally supplied current. The presence of an axially applied field has been observed to increase the ac critical current with a maximum at about 2½ kG applied field.
KINETIC MODEL OF TONKS-DATTNER RESONANCES IN A POSITIVE COLUMN
Authors: Baldwin D. E. , Hirshfield J. L.
Published: March 2005

Widely reported resonances in positive columns are described by a kinetic model in which electrons reflected at the sheath provide a plasma wave reflection mechanism which has been lacking in earlier fluid theories. Application of a weak magnetic field is shown experimentally to destroy the resonances when the gyro-radius falls below the dimension of the reflection zone.
SINGLE WAVELENGTH OPERATION OF A PULSED WATER-VAPOR LASER
Authors: Jeffers W. Q.
Published: March 2005

Single wavelength operation on twenty-five emission lines in the range 23 to 57 μ was obtained by using three diffraction gratings to make the laser resonator frequency selective. This technique leads to new emission lines, enhanced output on weak lines, and identical pulse-to-pulse emission intensities. These results show that there are strong interactions among the transitions responsible for laser action. They are quantitatively consistent with the assumption that laser action is due to vibration-rotation transitions of the H2O molecule.
EFFECT OF A HEATED PLATINUM WIRE ON A SEALED CO2 LASER SYSTEM
Authors: Taylor F. M. , Lombardo A. , Eppers W. C.
Published: March 2005

A heated platinum wire was used in a sealed CO2–N2–He laser system, resulting in increases in output power that were dependent on the initial fill pressure of CO2. The system was also filled with a CO2–He mixture and made to lase. Heating of the platinum wire caused a decrease in output power. It was tentatively concluded that the platinum catalyzes the reaction CO + O → CO2, permitting a higher concentration of CO2 in a sealed system than is otherwise possible.
NANOSECOND PULSE GENERATION BY MEANS OF STIMULATED BRILLOUIN SCATTERING
Authors: Alcock A. J. , Michelis C. De
Published: March 2005

Single high-intensity pulses having a duration under 5 nsec have been generated by means of multiple stimulated Brillouin scattering (MSBS) from methanol. This was achieved by placing a liquid cell at one end of a giant-pulse ruby laser cavity and a Fabry-Perot etalon at the other Laser oscillation builds up at a wavelength where the Fabry-Perot provides a high reflectivity and MSBS occurs until the wavelength is shifted to a point at which the Fabry-Perot has a transmission maximum, thus allowing a single pulse of scattered radiation to be coupled out.
ATOMIC PERFECTION AND FIELD EMISSION FROM TUNGSTEN (110) SURFACE
Authors: Plummer E. W. , Rhodin T. N.
Published: March 2005

Field-emission measurements on field-evaporated (110) tungsten were correlated with direct observation of the atomic configuration of the surface for different degrees of perfection. It is concluded that small perturbations of the (110) plane from atomic perfection produce a significant increase in the field-emitted current.
CURRENT OSCILLATIONS IN Co-DOPED Si p-i-n STRUCTURES
Authors: Streetman B. G. , Blouke M. M. , Holonyak N.
Published: March 2005

Current oscillations in the positive resistance region of the forward characteristics of Co-doped Si p-i-n devices are described. The oscillations are sinusoidal, independent of device length, and are strongly affected by optical excitation and deep-level trap properties.
EFFECT OF ULTRASONIC VIBRATIONS OF THE SUBSTRATE ON THE GROWTH OF THIN METAL FILMS
Authors: Chopra K. L. , Randlett M. R.
Published: March 2005

Gold and silver films deposited on rock salt substrates ultrasonically agitated by a 6.5 Mc AT-cut vibrating quartz crystal exhibit enhanced agglomeration and orientation effects. The effect of the ultrasonic field on the growth of a film is essentially similar to that of an elevated substrate temperature.
CONTRIBUTION OF THERMAL NOISE TO THE LINE-WIDTH OF JOSEPHSON RADIATION FROM SUPERCONDUCTING POINT CONTACTS
Authors: Silver A. H. , Zimmerman J. E. , Kamper R. A.
Published: March 2005

The line-width of the Josephson oscillations of a voltage-biased superconducting point contact has been measured between 1.4°K and 8°K, with bias resistors R between 1.7 × 10−10 Ω and 2.6 × 10−5 Ω. Within the experimental accuracy the line-width is proportional to RT, and is consistent with the estimated theoretical value 8kTR/Φ02, where k is Boltzmann's constant and Φ0 is the flux quantum. Line-widths below 0.1 Hz have been observed at 4.2°K for R = 1.7 × 10−10 Ω, providing an experimental upper limit to other noise sources and indicating that this is useful as a voltmeter and thermometer below 10−16 V and 10−4°K.
LASER POWER STABILIZATION BY MEANS OF NONLINEAR ABSORPTION
Authors: Pantell R. H. , Warszawski J.
Published: March 2005

If a medium with an absorption constant that increases with light intensity is placed within a laser interferometer, then fluctuations in the power output of the laser can be decreased. In this manner the typical spiking behavior of a pulsed, solid-state laser can be essentially reduced to a constant output power as a function of time. A material that has the desired property is one that is Rayleigh active, for once threshold is reached for the stimulated Rayleigh effect the absorption at the pump frequency increases with intensity. The threshold for the stimulated Rayleigh effect is low because most of the gain is provided by the laser medium. Spike suppression has been achieved for a pulsed ruby laser by placing a cell containing benzene within the laser interferometer.
THE DETECTION OF VACANCIES IN MOLYBDENITE
Authors: Montet G. L.
Published: March 2005

The etch-decoration method developed to detect lattice vacancies in graphite has been extended to the detection of lattice vacancies in molybdenite. Observations indicate that vacancies occur at sites from which a molybdenum atom is missing and that etch pits developed from these vacancies may be several layers deep; however, gold decoration can reveal step heights one layer deep (6.15 Å).
HOLOGRAPHY WITH TOTAL INTERNALLY REFLECTED LIGHT
Authors: Stetson Karl A.
Published: March 2005

This Letter reports a new technique for making holograms which employs a reference beam that is totally reflected from the air emulsion boundary of the hologram plate. This type of recording permits a very close spacing between the object and the hologram and has several interesting properties. The properties are listed and discussed in this Letter.
OPTICAL SECOND-HARMONIC GENERATION PRODUCED BY INTERACTION OF LASER BEAMS AND DRIFTING CARRIERS IN InAs
Authors: McFee J. H.
Published: March 2005

Second-harmonic generation (λ = 5.3 μ) is observed when dc fields and CO2 laser beams are applied simultaneously to narrow band-gap semiconductors. The nonlinear mechanism responsible for the dc-induced second harmonic is shown to be a mobile-carrier effect, and is ascribed to the nonparabolicity of the conduction bands. The possible application of this effect to the modulation of optical beams is indicated.
FERROELECTRIC AND OPTICAL PROPERTIES OF KSr2Nb5O15
Authors: Giess E. A. , Burns Gerald , O'Kane D. F. , Smith A. W.
Published: March 2005

A new transparent tetragonal crystal, KSr2Nb5O15, of the tungsten bronze type has been found to be ferroelectric with a Curie temperature of ≈160°C. At room temperature the electro-optic coefficient, r∥, is 1.3 × 10−8 cm/V and ε∥ is approximately 1,000.
OPTICAL PULSE COMPRESSION USING BRAGG SCATTERING BY ULTRASONIC WAVES
Authors: Schulz M. B. , Holland M. G. , Davis L.
Published: March 2005

Pulse compression using Bragg scattering of light by an acoustic beam has been demonstrated. An ultrasonic delay line containing a frequency ramp signal is used to scatter monochromatic diverging light. If the incident and divergence angles are properly adjusted, the scattered light is focused and rapidly traverses a slit in front of a photodetector. A 1.16-GHz, 2-μsec pulse has been compressed to 18 nsec. Five-nanosecond compressed pulses should be possible with this scheme.
PULSE COMPRESSION BY BRAGG DIFFRACTION OF LIGHT WITH MICROWAVE SOUND
Authors: Collins J. H. , Lean E. G. H. , Shaw H. J.
Published: March 2005

Pulse compression of a 240-nsec rf pulse, swept linearly over 75 MHz about 1400 MHz, has been accomplished. The method is dependent on self-focusing associated with Bragg diffraction of light by chirped shears waves in optically anisotropic sapphire. Realization of time bandwidth products exceeding 1000, with built-in side lobe suppression, are predicted.
EFFECTS OF INTERNAL INDUCED ABSORPTION ON LASER EMISSION
Authors: Schwartz J. , Naiman C. S. , Chang R. K.
Published: March 2005

Nonlinear materials having induced absorption within a laser yield effects that contrast with bleachable absorbers. Prolonged giant pulses with greater spatial homogeneity have been observed. Mechanisms for induced absorption are suggested, with a simple model of nonlinear effects on laser emission.
TEMPERATURE-INDUCED SPIN REORIENTATION IN RARE EARTH ORTHOFERRITES—HYSTERESIS LOOP STUDIES
Authors: Wolfe R. , Pierce R. D. , Haszko S. E. , Remeika J. P.
Published: March 2005

The spontaneous reorientation of the weak ferromagnetic moment (``temperature-induced spin flop'') in the rare earth orthoferrites is found to take place over a well-defined temperature range. In TmFeO3, this range is 12°K wide and centered at 88°K. Susceptibility peaks have been observed at the ends of this temperature interval where the magnetic easy axis just begins to rotate away from the a or c axis.
CORRELATION STUDY OF A DRIFT WAVE INSTABILITY
Authors: Chung K. , Rose D. J.
Published: March 2005

A drift wave instability in a fairly highly ionized (50–90%) plasma column has been observed and its properties have been readily discovered using real time auto- and cross-correlation techniques.
DIRECT OBSERVATION OF RAPID SELF-DIFFUSION ALONG DISLOCATIONS IN ALUMINUM
Authors: Volin T. E. , Balluffi R. W.
Published: March 2005

Voids were produced by the precipitation of excess quenched-in vacancies in aluminum. The annealing of these voids in thin foil specimens by a self-diffusion mechanism was studied using transmission electron microscopy. The annealing rates of both isolated voids and voids which were connected to the foil surfaces by dislocations were observed. The voids which were hooked up to the surfaces by dislocations annealed out at appreciably higher rates than the isolated voids. The results indicate that the dislocations acted as rapid self-diffusion pipes for the transport of atoms into the voids from the surfaces.
INCLINED REFERENCE ACOUSTIC HOLOGRAPHY
Authors: MacAnally R. B.
Published: March 2005

Acoustic holographic experiments of the Leith-Upatnieks type in which the inclined planar reference is simulated electrically by a simple technique are described. The results graphically illustrate that finite ``film'' resolution introduces ambiguities into acoustic and optical holograms. The experiments were performed at 1 MHz, a frequency suitable for long-range underwater imaging and detection.
ON LASER-INDUCED BREAKDOWN AND FRACTURE IN GLASSES
Authors: Dupont H. , Donzel A. , Ernest J.
Published: March 2005

Phenomena accompanying laser-induced damage in glasses were studied, showing many analogies with laser-induced breakdown in gases. Ionization due to multiphoton absorption, as primary cause for laser-induced damage, is favored by these observations.
ELASTIC SURFACE WAVES IN A LAYERED SYSTEM OF CADMIUM SULFIDE ON GERMANIUM
Authors: Schnitzler Paul
Published: March 2005

The theoretical behavior of the elastic surface wave phase velocities is presented as a function of direction and layer thickness for a CdS layer on the (001) and (011) faces of a semi-infinite crystal of Ge.
CORRELATION BETWEEN ELECTROLUMINESCENCE AND ELECTRON EMISSION OF THIN METAL-OXIDE-METAL SANDWICHES
Authors: Delord J. F. , Johnston K. H. , Coovert R. E. , Pistoulet B. , Roustand C. , Rouzeyre M.
Published: March 2005

Experiments performed on M-O-M sandwiches of Be–BeO–Au and Al–Al2O3–Ag have demonstrated that the electron emission of these so called thin-film ``cathodes'' is actually due to photoemission from the counterelectrode caused by the luminescence of the device.
A TECHNIQUE FOR OBTAINING A NONPSEUDOSCOPIC REAL IMAGE FROM HOLOGRAMS
Authors: Devaney A. J. , Grauling C. R.
Published: March 2005

In this Letter we describe a technique for producing nonpseudoscopic real images from a hologram which was constructed in the normal manner. It is shown that by properly choosing the reconstructing beam it is possible to ``project'' the virtual image thus obtaining a real image. The process is likened to that of imaging the virtual image through a positive lens whose focal length and aperture are directly related to parameters of the reconstructing beam.
A NEW RECORDING TECHNIQUE FOR ACOUSTIC HOLOGRAPHY
Authors: Young J. D. , Wolfe J. E.
Published: March 2005

A new method of recording ultrasonic holograms using deformable films on solid substrates is described. The films have been used to phase-modulate laser light for image reconstruction.
Resistivity and thermoelectric power of NaxCoO2 (x=1.0, 0.7, and 0.6) system
Authors: Kishan H. , Awana V. P. S. , Ansari M. A. , Gupta Anurag , Saxena R. B. , Ganesan V. , Narlikar A. V. , Cardoso C. A. , Nirmala R. , Buddhikot Devendra , Malik S. K.
Published: March 2005

Results of thermoelectric power (S) and electrical resistivity (ρ) measurements are reported on NaxCoO2 compounds with x=1.0, 0.7, and 0.6. These are single-phase compounds crystallizing in the hexagonal structure (space-group P63∕mmc) at room temperature. Thermoelectric power values at 300K (S300K) are ≅80, 39, and 37μV∕K for the x=1.0, 0.7, and 0.6 samples, respectively. The samples with x=0.7 and 1.0 are metallic down to 5K, while the x=0.6 sample is semiconducting. The value of ρ300K for the x=1.0 sample is ∼0.895mΩcm and the power factor (S2∕ρ) is ∼7.04×10−3W∕mK2 which qualifies it as a good thermoelectric material. In the x=1.0 sample, S(T) is positive throughout the 300–5-K temperature range and decreases monotonically to zero as temperature T→0. In contrast, S(T) of the x=0.7 and 0.6 samples changes sign and shows negative values between 90 and 16K before approaching zero as T→0. The anomalous S(T) behavior of the x=0.6 and 0.7 samples, which are coincidentally the precursor materials to the reported superconductivity in this class of materials, indicates a dramatic change in the electronic structure of these compounds on lowering the Na content.
Anisotropic transport behavior in ultrathin epitaxial Fe films on vicinal oxide substrates
Authors: Jin Xuesong , McEvoy Ciaran , Shvets I. V.
Published: March 2005

Step-induced anisotropy of electron transport in ultrathin Fe film was investigated. The Fe films (2 and 10 nm) were deposited on vicinal MgO (100) substrate using molecular-beam epitaxy. It is found that the films with a thickness of 10 and 2 nm are continuous and discontinuous, respectively, which was determined from their resistivity values, the temperature dependency of the resistivity and the V–I curve. The enhanced magnetoresistance in the continuous and the discontinuous films was observed when the current flows parallel and perpendicular to the miscut direction, respectively. We suggest that the atomic steps in the continuous films nucleate additional domain walls acting as scattering centers and the extra scattering was introduced for the current perpendicular to the step edges. The mechanism of the influence of the atomic steps on the electron-transport properties is different in the continuous and discontinuous films. We further suggest that in the discontinuous films, the atomic steps result in the anisotropic growth of the islands and the anisotropy in the transport behavior as a consequence.
Synchronous rectification for contactless power supply utilizing Mn–Zn ferrite core coils
Authors: Miura Hidekazu , Arai Shinsuke , Sato Fumihiro , Matsuki Hidetoshi , Sato Tadakuni
Published: March 2005

Contactless power supply systems transmit electric power by electromagnetic induction with a pair of coils. The efficiency and the output voltage depend on parameters of coils. We studied the best parameter values that realize stable high efficiency contactless power supply. In the application with low output voltage, the voltage drop of the diodes becomes dominant power loss. A synchronous rectification was proposed as a solution of this problem. Our contactless power supply system for an artificial heart operates at 190kHz. We use planar coils with Mn–Zn ferrite cores. Highly stable output voltage and 88% maximum efficiency were realized.
Determining the spin dependent mean free path in Co90Fe10 using giant magnetoresistance
Authors: Shakespear K. F. , Perdue K. L. , Moyerman S. M. , Checkelsky J. G. , Harberger S. S. , Tamboli A. C. , Carey M. J. , Sparks P. D. , Eckert J. C.
Published: March 2005

The spin dependent mean free path in Co90Fe10 is determined as a function of temperature down to 5K using two different spin valve structures. At 5K the spin dependent mean free path for one structure was measured to be 9.4±1.4nm, decreasing by a factor of 3 by 350K. For the other structure, it is 7.5±0.5nm at 5K and decreased by a factor of 1.5 by 350K. In both cases, the spin dependent mean free path approaches the typical thickness of ferromagnetic layers in spin valves at room temperature and, thus, has an impact on the choice of design parameters for the development of new spintronic devices.
A general approach to synthesis of nanoparticles with controlled morphologies and magnetic properties
Authors: Bao Y. , Pakhomov A. B. , Krishnan K. M.
Published: March 2005

We present a systematic approach to fabricate a variety of magnetic nanoparticles with desirable structure and controlled magnetic properties based on our studies of the process kinetics. The morphology of binary alloy particles is dependent on their bulk thermodynamics—for immiscible heterogeneous systems (Co–Au) core-shell structures are obtained while miscible systems (Fe–Pt) lead to alloy nanoparticles. The annealing effects on FePt nanoparticles show that the coercivity and magnetic anisotropy increase dramatically after annealing at temperatures above 650°C. Studies of Co–Au core-shell structure show that the core is magnetic, but the Au shell does not significantly affect its magnetic properties.
Magnetic properties of TlCu2−xFexSe2 crystals
Authors: Felton S. , Nordblad P. , Ronneteg S. , Berger R.
Published: March 2005

The magnetic properties of two compositions of random solutions in the TlCu2−xFexSe2 system with x=0.2 and 0.45 have been investigated by superconducting quantum interference device magnetometry. The crystal structure is of a layer type and ordering due to the iron atoms occurs at low temperatures, with Tc=85K for x=0.2 and Tc=130K for x=0.45. The samples were highly textured crystals and the magnetic moments of both compositions were found to align along the c axis of the structure. The saturation moments were found to be 1.5μB∕Fe for x=0.2 and 0.66μB∕Fe for x=0.45.
Stabilization of ferromagnetic order in epitaxial ultrathin Fe films
Authors: Kipferl W. , Sperl M. , Hagler T. , Meier R. , Bayreuther G.
Published: March 2005

Epitaxial Fe(001) films with thicknesses less than 20 monolayers were grown on epitaxial Au(001) surfaces by molecular beam epitaxy. All films have a fourfold anisotropy and a negligible uniaxial component. In contrast, the magnetic behavior of Fe films on GaAs(001) is governed by a superposition of a dominating uniaxial and a fourfold anisotropy component. The temperature dependence of the spontaneous magnetization MS for T<0.5TC can be well described by Bloch’s T3∕2 law for both systems. With decreasing film thickness the spin wave parameter B increases significantly compared to the bulk in both cases. However, for the same thickness B is reduced in Fe∕GaAs(001) compared to Fe∕Au(001) films. This is attributed to the presence of the strong uniaxial anisotropy in Fe∕GaAs(001) which apparently stabilizes the ferromagnetic order against thermal excitations.
Growth, structure, and magnetism of γ-phase Mn ultrathin films on Cu3Au(100)
Authors: Lin W. C. , Lin L. C. , Chen T. Y. , Wang B. Y. , Song Ker-Jar , Lin Minn-Tsong
Published: March 2005

Ultrathin γ-phase (face-center cubic) Mn films were prepared by epitaxial growth on Cu3Au(100). Kinematic analysis of low energy electron diffraction I∕V showed a structure transformation of Mn films from nearly face-center cubic to face-center tetragonal with increasing coverage. No ferromagnetic signal in Mn∕Cu3Au(100) was observed. For 21 ML capping film of Fe on Mn films, the hysteresis loop of Fe was biased. The bias field for 21MLFe∕15MLMn∕Cu3Au(100) was ∼200Oe at 110 K with the blocking temperature Tb∼300K. This observation of exchange bias substantiates the theoretical prediction of antiferromagnetism in γ-phase Mn.
Signal-to-media-noise ratio improvement of CoCrPt-SiO2 granular perpendicular media by stacked Ru underlayer
Authors: Mukai Ryoichi , Uzumaki Takuya , Tanaka Atsushi
Published: March 2005

In this work we have developed a stacked Ru underlayer and have studied its effects on the improvement of recording performances for CoCrPt-SiO2 granular-type dual-layer perpendicular media. The c-axis distribution ΔΘ50 of the 13.2 nm thick stacked Ru underlayer was 4.5°, which was about 33% smaller than that of Ru monounderlayer with the same thickness. The use of stacked Ru underlayer realized that the recording layer of granular-type media consisted of segregated fine-grain structure with oxide grain boundaries. The signal-to-media-noise ratio (SNR) improvement achieved by the use of the stacked Ru underlayer was indicated when it was compared with the use of Ru monounderlayers. Furthermore, the SNR for monopole head of 8.5 dB at 480 kfci and D50 of 356 kfci were obtained by optimizing the structure of stacked Ru underlayer.
New spectroscopic method for aqueous solutions: Raman ξ-function dispersion for NaClO4 in water
Authors: Walrafen George E.
Published: March 2005

A new Raman method is exemplified by ξ≡−RT[∂ln(Iω∕IREF)∕∂X1]T,P,n2,n3 for ternary NaClO4∕D2O∕H2O, or by ξ≡−RT[∂ln(Iω∕IREF)∕∂X2]T,P for binary NaClO4∕H2O solutions. (Fundamental differences exist between ξ and the chemical potential μ.) Iω is the Raman intensity at ω, IREF is the reference intensity, e.g., at the isosbestic frequency, X2 is the H2O and X1 the small D2O mol fraction, and n2 and n3 are constant mols of H2O and NaClO4, respectively. Maxima (max) and minima (min) were observed in ξ versus ω(cm−1); ξmax−ξmin=Δξmax. Δξmax=8050±100cal∕mol H2O for the coupled, binary solution OH stretch, and Δξmax=4200±200cal∕mol H bond for the decoupled, ternary solution OD stretch. The perchlorate ion breaks the H bonds in water. 8050cal∕mol H2O corresponds to the maximum tetrahedral Δξmax value for two H bonds, i.e., Δξmax=4025cal∕mol H bond, in agreement with the HDO Δξmax=4200±200cal∕mol H bond. [Δξmax is not the H bond enthalpy (energy).] Minima occur in ξ at the peak ω values corresponding to the HDO∕H2O and H2O ices, and maxima in ξ at 2637±5cm−1 (OD) and 3575±10cm−1 (OH) correspond to the peak OD and OH stretching ω values from dense supercritical water. Enthalpy dispersion curves were also determined for saturated, binary, and ternary NaClO4 solutions and for D2O in H2O. The ξ-function method is shown to be applicable to infrared absorbance spectra.
Development of a metal–tip cantilever for noncontact atomic force microscopy
Authors: Akiyama Kotone , Eguchi T. , An T. , Fujikawa Y. , Yamada-Takamura Y. , Sakurai T. , Hasegawa Y.
Published: March 2005

We report on a focused-ion-beam fabrication of a metal–tip cantilever for noncontact atomic force microscopy (AFM) and demonstrate its superior performance by observing atomically resolved AFM images of the Si(111)7×7 surface. Characterization of the tip apex by transmission electron microscope revealed that the tip radius is less than 5nm. Detrimental changes in the resonance frequency and the Q factor of the cantilever due to the attachment of the metal tip are small and do not affect the performance of the AFM imaging. Since the fabrication technique is applicable to any materials, various functional probes can be developed with this method.
Minimizing convection effects to measure diffusion in liquid droplets during high-temperature electrostatic levitation
Authors: Bossuyt Sven , Schroers Jan , Rhim Won-Kyu , Johnson William L.
Published: March 2005

We present an approach to reduce the convective flow in an electrostatically levitated liquid droplet to such an extent that diffusion is the dominant mechanism for mass transport, thus enabling direct measurements of atomic diffusion in reactive liquids at elevated temperatures. Convection is minimized by containerless processing, and reducing temperature variations in the sample. The diffusion tracer is deposited in situ in the electrostatic levitation device used for containerless processing. Uniform noncontact heating of the sample is achieved by laser heating with multiple beams arranged symmetrically, e.g., in a tetrahedral geometry. The expected temperature variations and the resulting convection flows are estimated for a Zr-based glass-forming alloy. The analysis suggests that diffusion experiments are possible throughout the entire undercooled liquid temperature range of this alloy and, in microgravity, up to 50K above the liquidus temperature.
Characterization of GaAsP trap detector for radiometric measurements in ultraviolet wavelength region
Authors: Noorma M. , Kärhä P. , Lamminpää A. , Nevas S. , Ikonen E.
Published: March 2005

A trap detector was constructed of three Schottky-type 10×10mm2 GaAsP photodiodes. The spectral reflectance of the trap detector was calculated from the measured spectral reflectances of a single GaAsP photodiode in the wavelength range between 240 and 600nm, and compared to the measured spectral reflectance of the trap detector at three laser wavelengths. The absolute spectral responsivity of the trap detector was measured. The internal quantum efficiencies (IQE) of the trap detector and a single photodiode were calculated in the wavelength region between 250 and 400nm from the spectral reflectances and responsivities. The comparison revealed reduction of the apparent IQE of the trap detector as compared to the single photodiode at the level of 10%. The spatial uniformity of the responsivity of the trap detector was measured, and the corresponding uncertainty component at 325nm was calculated to be 4×10−4. The effect of moderate ultraviolet exposure at the level of 50mJ∕cm2 on the stability of the responsivity of GaAsP photodiode was studied and found to be below 2×10−3 at all used wavelengths.
Time-resolved photocurrent spectroscopy of the evolution of the electric field in optically excited superlattices and the prospects for Bloch gain
Authors: Lisauskas Alvydas , Blöser Claudia , Sachs Robert , Roskos Hartmut G. , Juozapavičius Aušrius , Valušis Gintaras , Köhler Klaus
Published: March 2005

We report on photocurrent spectroscopy on undoped GaAs∕AlGaAs semiconductor superlattices subjected to femtosecond optical excitation. The evolution of the carrier-drift-induced inhomogeneity of the electric field is studied by tracing the shifting and broadening of Wannier–Stark transitions as a function of delay time and bias field. Based on experimental data and results of numerical simulations, we find that the superlattice rapidly splits into two moving field regions, one with strong field gradient and low electron density, the other with partially screened field at low gradient and high electron density. Concerning future Bloch-gain measurements, we find that gain is expected in spite of the inhomogeneous field if the electron-rich region is not heavily screened. The time window during which Bloch gain exists is determined by the sweep out of the electrons (10–30ps).