bluuebunny/crossref_metadata_2025 huggingface dataset:
Thickness and density determination of ultrathin solid films comprising multilayer x-ray mirrors by x-ray reflection and fluorescence study
Authors: Zheludeva S. I. , Kovalchuk M. V. , Novikova N. N. , Bashelhanov I. V. , Salaschenko N. N. , Akhsakhalyan A. D. , Platonov Yu. Ya.
Published: July 2002

New possibilities of ultrathin film thickness and density determination are demonstrated by means of x-ray method in the form of x-ray standing wave technique (XSW) and total external fluorescence study (NTEF). Several samples with ultrathin Fe films protected by carbon layers and with bare Fe film on the top have been analyzed. Rh/C LSM was used as an XSW generator to determine the film’s thickness (15–40 Å). Densities were evaluated by NTEF study and came out to be about 85% from that of the bulk material for covered and 45% for bare Fe films. The detailed analysis of E-field intensity distribution over the diffracting medium is presented.
A universal polarimeter for the soft x-ray and vacuum ultraviolet wavelength region
Authors: Gluskin E. S.
Published: July 2002

A universal polarimeter was designed and built to analyze polarization properties of soft x-ray and vacuum ultraviolet radiation from different types of sources. The design, based on the use of multilayer-polarizers, includes an option to monitor the polarization with a 1 kHz frequency. The polarimeter was tested on the U5 undulator beamline at NSLS.
A multiple crystal diffractometer for generation and characterization of circularly polarized x rays at the Photon Factory (invited)
Authors: Ishikawa Tetsuya , Hirano Keiichi , Kanzaki Kiyoshi , Kikuta Seishi
Published: July 2002

A multiple crystal diffractometer for polarization optical experiments in x-ray region was constructed at the Photon Factory. Using an x-ray phase retarder of transmission type in Bragg geometry, tunable-wavelength circular polarized x rays of both helicities were produced with high degree of circular polarization. A method of complete determination of the polarization states in x-ray region was developed with the reverse use of the phase retarder. Polarization switching with a frequency of 0.3 Hz was performed by flipping the phase retarder in a bistable mode. An optical scheme of producing highly intense circular polarizations using the phase retarder and an x-ray undulator is discussed.
New crystal spectrograph designs and their application to plasma diagnostics (invited)
Authors: Förster E. , Gäbel K. , Uschmann I.
Published: July 2002

A special crystal monolith was fabricated for absolute measurements of x-ray wavelength. It consists of two flat quartz plates, accurately cut relative to reflecting net planes, with a fixed distance between them. Absolute wavelengths (i.e., without use of reference lines) of L-shell laser produced spectra of Cu, Ge, As, etc. have been measured in the 7.5–8.5 Å with an accuracy of Δλ/λ=10−5. Our Johann type x-ray spectrometer with a cylindrically bent quartz has been used to reveal line coincidences necessary for photopumping processes. In this scheme source-size influences are smaller, therefore, line profiles have been measured at a spectrometer resolution better than 5000. Because of its focusing in the sagittal plane, a von Hámos type x-ray spectrometer has been used to detect the small x-ray emission of subpicosecond laser-produced plasmas (E=2 mJ, t=100 fs). X-ray spectra of Al both Kα, Kβ lines and Heα-resonance line with its satellites. Finally, a multichannel x-ray microscope has been designed and fabricated. It consists of several two-dimensionally bent crystals where each of them images one x-ray line emitted by a laser-produced plasma. The spatial resolution of x-ray line images is about 5 μm, and the width of the spectral ranges is Δλ/λ=10−4 to 10−2. Thus, the spatial distribution of ions radiating in selected x-ray lines have been found being of interest in the study of population inversions.
Two high brilliance beam lines at the ESRF dedicated to microdiffraction, biological crystallography, and small-angle scattering (invited)
Authors: Riekel C. , Bösecke P. , Sánchez del Río M.
Published: July 2002

Two undulator beam lines will be available at the ESRF for microdiffraction/small-angle scattering (beam line 1) and time-resolved small-angle scattering/biological crystallography (beam line 4). In both cases a separate function optics with a double monochromator and a double focusing mirror have been selected. The general design principles of the two cameras, end station, and data acquisition systems foreseen are discussed.
Vacuum arc ion sources: Some vacuum arc basics and recent results (invited)
Authors: Anders Simone , Anders André , Brown Ian
Published: July 2002

Vacuum arc ion sources have been developed and used in a growing number of laboratories around the world. Primary applications of this high current metal ion source have evolved for metallurgical ion implantation and for accelerator injection. Novel source versions and features have been developed, including an electronically switchable ‘‘partitioned cathode’’ whereby the metal species generated can be switched from pulse to pulse, a combined metal/gaseous source with a long lasting trigger, a low energy (∼1 keV) miniature source version, and a broad beam (50 cm diam extractor) multicathode version. Progress has been made also in characterization and manipulation of the plasma prior to extraction, e.g., in the understanding of the ion charge states produced and the development of macroparticle-removing magnetic filters. Advances in vacuum arc ion source design and operation have been accompanied by a deeper understanding of plasma production in vacuum arc cathode spots, and several features of vacuum arc ion sources can be explained by the specifics of ion formation within the spots. Here we present a short overview of some fundamental vacuum arc processes and examine some of the recent developments in vacuum arc ion source design and application.
Performance of the modified SX-700 plane grating monochromator at the Finnish beamline in MAX-lab
Authors: Aksela S. , Kivimäki A. , Naves de Brito A. , Sairanen O.-P. , Svensson S. , Väyrynen J.
Published: July 2002

A soft x-ray beamline designed principally for gas phase measurements has been constructed and tested at the 550-MeV MAX I electron storage ring in Lund, Sweden. The beamline uses synchrotron radiation from a short 35-period undulator with a magnetic period of 24 mm. The photon energy range of the undulator is about 60–600 eV covering, e.g., the important C, N and O 1s ionization regions. The beamline is based on a modified SX-700 plane grating monochromator with a plane elliptical focusing mirror. The beamline has been tested by measuring total ion and electron yield spectra from the rare gases Kr and Ar in the resonance excitation regions just below the Kr M4,5 and Ar L2,3 ionization thresholds. These results show that the monochromator has very high resolution, E/ΔE≊4800 at 244 eV and ≊7600 at 91 eV, comparable with the best spherical and plane grating monochromators. The beamline is equipped with an effective differential pumping system for the gas phase experiments combined with a refocusing mirror in order to provide a small spot size (φ<1 mm) at the sample region.
A low cost preamplifier for fast pulses from microchannel plates
Authors: Coyle S. T. , Hembree G. G. , Scheinfein M. R.
Published: July 2002

A simple, low cost 3 GHz bandwidth preamplifier suitable for pulse-counting applications utilizing chevron microchannel plate (MCP) detectors has been built with monolithic microwave integrated circuit (MMIC) amplifiers in multiple stages. Its bandwidth matches the rise time of MCP output pulses (<300 ps), thereby maintaining leading edge timing information. The use of MMICs made this device inexpensive and easy to construct.
Precise computation of electron-beam radiation in nonuniform magnetic fields as a tool for beam diagnostics
Authors: Chubar O. V.
Published: July 2002

Visual range radiation emitted by an ultrarelativistic electron beam at bending magnet edges and within elements of the beam optics (steering magnets, quadrupole lenses, etc.) in storage rings is very sensitive to horizontal and vertical angular divergences, transverse sizes, emittances, energy, position, and trajectory tilts of the electron beam. Precise computation of the radiation intensity distributions with due regard for nonzero beam emittances, layout of storage ring magnet structure, and measurement scheme peculiarities allows one to obtain the electron-beam parameters from the measured radiation intensity distributions. The radiation computation technique and the experimental equipment adjusted for the beam diagnostics on the Siberia-1 electron storage ring are described. Experimental results on measurements of the radiation intensity distributions in the Siberia-1 ring and the corresponding electron-beam parameters determined by the method under discussion are presented.
High-brightness beamline for x-ray spectroscopy at the advanced light source
Authors: Perera R. C. C. , Jones G. , Lindle D. W.
Published: July 2002

Beamline 9.3.1 at the Advanced Light Source (ALS) is a windowless beamline, covering the 1–6 keV photon-energy range, designed to achieve the goals of high energy resolution, high flux, and high brightness at the sample. When completed later this year, it will be the first ALS monochromatic hard-x-ray beamline, and its brightness will be an order-of-magnitude higher than presently available in this energy range. In addition, it will provide flux and resolution comparable to any other beamline now in operation. To achieve these goals, two technical improvements, relative to existing x-ray beamlines, were incorporated. First, a somewhat novel optical design for x rays, in which matched toroidal mirrors are positioned before and after the double-crystal monochromator, was adopted. This configuration allows for high resolution by passing a collimated beam through the monochromator, and for high brightness by focusing the ALS source on the sample with unit magnification. Second, a new ‘‘Cowan type’’ double-crystal monochromator based on the design used at NSLS beamline X-24A was developed. The measured mechanical precision of this new monochromator shows significant improvement over existing designs, without using positional feedback available with piezoelectric devices. Such precision is essential because of the high brightness of the radiation and the long distance (12 m) from the source (sample) to the collimating (focusing) mirror. This combination of features will provide a bright, high resolution, and stable x-ray beam for use in the x-ray spectroscopy program at the ALS.
Variable groove-spaced grating monochromator for soft x-ray emission spectroscopy at CAMD/LSU
Authors: Asfaw A. , Ederer D. L. , Zhou L. , Lin L. , Osborn K. , Callcott T. A. , Miyano K. E. , Morikawa E.
Published: July 2002

A grazing incidence monochromator, equipped with a variable groove-spaced plane grating, has been commissioned recently at the Center for Advanced Microstructures and Devices, at Louisiana State University. This high-throughput and moderate-resolution monochromator is used as an excitation source for a soft x-ray emission spectrometer.
Circularly polarized light-induced dichroism in photoelectron diffraction observed with display-type spherical mirror analyzer
Authors: Daimon Hiroshi , Nakatani Takeshi , Imada Shin , Suga Shigemasa , Kagoshima Yasushi , Miyahara Tsuneaki
Published: July 2002

Strong circular dichroism in two-dimensional photoelectron diffraction patterns was observed for the photoelectron from the Si 2p core on the Si(001) surface using a display-type spherical mirror analyzer, although this Si(001) surface has no chirality and magnetism. The forward focusing peaks in the pattern rotate clockwise or counterclockwise when the helicity of the incident circularly polarized light is reversed. This phenomenon offers a new possibility to measure the polarization of the circularly polarized light in situ because the asymmetry is large (about 25%) and clear.
Polarization modulation spectroscopy for magnetic circular dichroism study using a polarizing undulator
Authors: Yagi K. , Yuri M. , Onuki H.
Published: July 2002

We developed a polarization modulation spectroscopy in the extreme ultraviolet (XUV) region for magnetic circular dichroism (MCD) measurements. We used a polarizing undulator with crossed and retarded magnetic fields. It enables us to obtain radiation adjusting the polarization states arbitrarily and rapidly. The undulator is essential in our polarization modulation spectroscopy for MCD study in the XUV region.
Phase-contrast x-ray computed tomography for observing biological specimens and organic materials
Authors: Momose Atsushi , Takeda Tohoru , Itai Yuji
Published: July 2002

A novel three-dimensional x-ray imaging method has been developed by combining a phase-contrast x-ray imaging technique with x-ray computed tomography. This phase-contrast x-ray computed tomography (PCX-CT) provides sectional images of organic specimens that would produce absorption-contrast x-ray CT images with little contrast. Comparing PCX-CT images of rat cerebellum and cancerous rabbit liver specimens with corresponding absorption-contrast CT images shows that PCX-CT is much more sensitive to the internal structure of organic specimens.
Development of a microarea diffraction system by polychromatic synchrotron radiation with the Laue method
Authors: Ohsumi Kazumasa , Hagiya Kenji , Uchida Masaya , Suda Noboru , Miyamoto Masamichi , Kitamura Masao , Ohmasa Masaaki
Published: July 2002

Microarea diffraction equipment has been developed with a micropinhole and an imaging plate using the Laue method combined with polychromatic synchrotron radiation. The crystal structure of 8 μm diam area of olivine [(Mg,Fe)2SiO4] grain included in a thin section of meteorite was successfully refined based on the intensities of Laue spots.
Temperature of the ions produced and trapped in an electron-beam ion trap
Authors: Beiersdorfer P. , Decaux V. , Elliott S. R. , Widmann K. , Wong K.
Published: July 2002

Spectrometers were constructed with nominal resolving power λ/Δλ≤22 000 at a Bragg angle of 45° and were used to measure the temperature of ions produced and trapped in the Livermore electron-beam ion trap facility. A temperature in excess of 500 eV was found for heliumlike Ti20+ ions produced under standard operating conditions for spectroscopy. The temperature was reduced to 130 eV by lowering the trapping potential and electron-beam current. A description of the spectrometers and representative measurements are given.
Monochromator for circularly polarized synchrotron radiation in the energy range of 5–250 eV
Authors: Kamada Masao , Sakai Kusuo , Tanaka Shin-ichiro , Ohara Shigeo , Kimura Shin-ichi , Hiraya Atunari , Hasumoto Masami , Nakagawa Kazumichi , Ichikawa Kouichi , Soda Kazuo , Fukui Kazutoshi , Fujii Yasuo , Ishiguro Eiji
Published: July 2002

A new spherical grating monochromator with translational and rotational assembly including a normal incidence mount (SGM-TRAIN) is under construction at BL 5A of the UVSOR Facility, IMS, and its design concept is reported. The following points have been taken into account in the design: (1) Energy range of 5–250 eV, (2) use both of undulator and bending magnet radiation, (3) linear and circular polarizations, (4) spectral purity, (5) resolution, and (6) length of beamline. It should be stressed that the SGM-TRAIN is useful for experiments where circularly polarized synchrotron radiation is used. Moreover, the SGM-TRAIN has the advantage that the small emittance of storage ring and the large space for a long beamline are not necessary.
A microwave spectrometer with a frequency control system employing a frequency ‘‘scanning window’’ locked to the rotational absorption peak
Authors: Zhu Z. , Matthews I. P. , Samuel A. H.
Published: July 2002

This article reports a microwave spectrometer with a novel technique of locking a frequency ‘‘scanning window’’ [F1,F3] in the radiation source to a microwave rotational absorption peak. The center (F2) of the scanning window is initially locked to the resonant frequency (Fr) of a tunable resonant cavity so that the center of the scanning window may be tuned by changing the resonant frequency of the cavity. Microwaves are then input to a nonresonant gas cell containing the analyte gas at low pressures and by means of Stark modulation the lower sideband (F1,F2) and upper sideband (F2,F3) of the scanning window are amplitude modulated at different phases. After demodulation of the two sidebands, an error signal is derived through addition of the two demodulated signals (being zero when the scanning window exactly overlaps with the absorption peak) and this is used to lock the resonant frequency (Fr) of the tunable cavity (and thus the center (F2) of the scanning window) to the center (F0) of the absorption peak of the analyte gas. For quantitative measurement, a signal is derived through subtraction of the two demodulated signals (being maximum when the center of the scanning window is approximately at the center of the absorption peak). This spectrometer system has been used to measure ethylene oxide gas (absorption line 23.123 GHz) at concentrations up to 100% and water vapor (absorption line 22.235 GHz) at concentrations from −40 °C dewpoint (127 ppm) to 50 °C dewpoint (138,736 ppm). The detect limit of the spectrometer has been tested and found to be approximately 3×10−9 cm−1 (signal-to-noise ratio equal to 2).
High-temperature cylindrical specimen grip for biaxial loading
Authors: Lipetzky P. , Dvorak G. , Stoloff N.
Published: July 2002

A device has been developed for hot-gripping cylindrical specimens subjected to biaxial (tension/torsion) loading. By supporting the specimen very near the hot zone, the influence of thermal stresses on ultimate or yield strength as well as endurance limit can be minimized. This design thus increases the reliability of high-temperature biaxial mechanical properties data for materials, such as ceramics or other brittle composites, which are sensitive to thermal stresses. Features of this apparatus include high-temperature dimensional stability via in situ load pin adjustability and adaptability to various specimen and furnace geometries.
Phase locking of high power microwave oscillators with large injection power ratios
Authors: Zhu Xianyang , Jen Lang , Liu Qingxiang , Du Xingshao
Published: July 2002

An analysis of phase locking between two high power microwave oscillators with large injection power ratios has been developed by making use of the concept of a lumped circuit, which makes it possible to predict the locked relative phases more accurately and provides a more suitable phase-locking condition for most practical cases. Sample phase calculations starting from different initial conditions are presented, which show that the conventional phase-locking theory is sufficient only when the frequency difference between the oscillators is small enough, however, it must be modified when the frequency difference and the power ratios are both large. Moreover, it has also been found that a longer locked time and a wider locking bandwidth are expected by the new results than those obtained by the conventional phase-locking theory.
Apparatus for small angle x-ray scattering measurements of polymer deformation
Authors: Salomons G. J. , Singh M. A. , Gupta J. A. , Foran W. A. , Clarke J. R. , Capel M. S.
Published: July 2002

We present an apparatus which is capable of small-angle x-ray scattering studies of polymer deformation at strain rates ranging from 49.6 μm/s to less than 0.033 μm/s and temperatures ranging from room (≊22 °C) to 120 °C. The system also includes a load cell for measuring the force applied to the sample and a symmetric stretching system to keep the sample centered in the x-ray beam.
Data acquisition system for (e,2e) coincidence experiments
Authors: Waterhouse D. K. , Williams J. F. , Smith P. A.
Published: July 2002

A data acquisition and display system has been developed for the study of electron impact ionization of atoms. Parallel data recording permits simultaneous but independent acquisition, analysis, and display of electron energy-loss spectra from two 180° electron energy spectrometers at single-detector count rates up to 100 kHz as well as their time coincidence spectra for coincidence rates of up to 1 kHz. The system has sufficient energy resolution to clearly observe the post-collision interaction energy shift of argon L23M23M23 Auger transition lines for low excess energy. It can acquire data at excess energies simultaneously from threshold to 30 eV for more than one transition, representing an improvement in experimental efficiency of at least an order of magnitude. Real-time data processing allows for faster experimental optimization and better statistical accuracy of accumulated data. Object-oriented programming in Windows with an IBM 486 computer was used.
X-ray video camera with 10 μm spatial resolution
Authors: Koch Andreas , Riekel Christian
Published: July 2002

A high resolution x-ray video camera has been developed for Synchrotron radiation x-ray microimaging applications. The image from an x-ray converter screen is optically coupled to a charge coupled device. A linespread function of 10 μm full width at half-maximum has been observed. This concept may be extended to the resolution range of 1–100 μm.
Bimodal loop-gap resonator
Authors: Piasecki W. , Froncisz W. , Hyde James S.
Published: July 2002

A bimodal loop-gap resonator for use in electron paramagnetic resonance (EPR) spectroscopy at S band is described. It consists of two identical one-loop–one-gap resonators in coaxial juxtaposition. In one mode, the currents in the two loops are parallel and in the other antiparallel. By introducing additional capacitors between the loops, the frequencies of the two modes can be made to coincide. Details are given concerning variable coupling to each mode, tuning of the resonant frequency of one mode to that of the other, and adjustment of the isolation between modes. An equivalent circuit is given and network analysis carried out both experimentally and theoretically. EPR applications are described including (a) probing of the field distributions with DPPH, (b) continuous wave (cw) EPR with a spin-label line sample, (c) cw electron–electron double resonance (ELDOR), (d) modulation of saturation, and (e) saturation-recovery (SR) EPR. Bloch induction experiments can be performed when the sample extends half way through the structure, but microwave signals induced by Mx and My components of magnetization cancel when it extends completely through. This latter situation is particularly favorable for SR, modulation of saturation, and ELDOR experiments, which depend on observing Mz indirectly using a second weak observing microwave source.
Substrate heater design for film deposition in oxidizing atmosphere
Authors: Pardo F. , Burmeister G. , Guimpel J.
Published: July 2002

A simple substrate heater for oxide film deposition is presented. Its main features are (a) good thermal contact between temperature sensor, heater, and substrate and (b) compatibility with oxidizing atmosphere at high temperatures. The system shows a good response for the deposition conditions necessary in high-Tc cuprate materials.
Development of chemical vapor deposition diamond burrs using hot filament
Authors: Trava-Airoldi V. J. , Corat E. J. , Peña A. F. V. , Leite N. F. , Valera M. C. , Freitas J. R. , Baranauskas V.
Published: July 2002

The fabrication of boring tools (burrs) for dentistry with the use of a hot-filament chemical vapor deposition (CVD) system, to form the diamond abrading structure, is reported here. The diamond was synthesized from a methane/freon gas mixture diluted in hydrogen. Comparative drilling tests with conventional diamond burrs and the CVD diamond burrs in borosilicate glasses demonstrated a lifetime more than 20 times larger for the CVD diamond burrs. Also, heat flow experiments in dentine showed that the CVD diamond burrs induce temperature gradients of the same order as the conventional ones. These characteristics of the CVD diamond burrs are highly desirable for odontological applications where the burrs’ lifetime and the low temperature processing are essential to the quality and comfort of the treatment.
Torsional oscillator magnetometer for high magnetic fields
Authors: Crowell P. A. , Madouri A. , Specht M. , Chaboussant G. , Mailly D. , Lévy L. P.
Published: July 2002

We have designed and constructed a torsional oscillator magnetometer for use in magnetic fields up to 25 T. The anisotropic component of the magnetization is detected by measuring the shift in the resonant frequency of the oscillator, which is fabricated from a single-crystal silicon wafer using micromachining techniques. The frequencies for the oscillators described here are between 100 Hz and 1 kHz and can be measured with a resolution of order 1 part in 108 in a 10 s averaging time, allowing for the detection of magnetic moments of 2×10−11 J/T at 1 T. Our oscillators are optimized for experiments on GaAs-AlGaAs heterostructures, but the method is suitable for any sample with an anisotropic susceptibility. We have applied the technique to two systems, a quasi-one-dimensional spin chain and a two-dimensional electron gas.
High-resolution positron-annihilation-induced Auger electron spectrometer
Authors: Yang S. , Zhou H. Q. , Jung E. , Weiss A. H. , Citrin P. H.
Published: July 2002

Positron-annihilation-induced Auger electron spectroscopy (PAES) uses a beam of low-energy positrons to excite Auger transitions via annihilation of core electrons. This mechanism imbues PAES with a high degree of surface specificity and the ability to eliminate the large collisionally induced secondary-electron background typically present in conventional Auger spectra. Here, we describe a high-resolution PAES system with an energy resolution ΔE/E=2.5%, approximately five times better than previous PAES spectrometers. The system consists of a compact low-energy (∼10 eV) electrostatically focused positron beam and a large cylindrical mirror analyzer. High-resolution PAES spectra from Cu(100) and Ge(100) surfaces are presented to illustrate the capabilities of the system. Energy spectra of secondary electrons and reemitted positrons resulting from bombardment of the surface by low-energy positron are also presented.
A novel scheme of laser interferometer–refractometer with high spatial and temporal resolutions
Authors: Lisitsyn I. V. , Kohno S. , Akiyama H.
Published: July 2002

A novel scheme combining interferometer and refractometer for simultaneous plasma density and plasma density gradient measurements is described. The scheme employs a ribbon laser beam obtained from one-dimensional laser beam expansion by a pair of cylindrical lenses. This beam shape allows measurements at several spatial locations simultaneously. The beam deflection measurements give additional important information on the spatial distribution of plasma density gradient in the direction perpendicular to the major axis of the expanded beam. Fast pin photodiodes are used as light detectors for temporal resolution better than 1 ns. The high power (700 mW) of the argon ion laser allows 0.1° phase resolution and simultaneously 0.1 mrad refractional deflection angle resolution.
An inexpensive, low-energy, ionized gas source for molecular beam epitaxy applications
Authors: Stumborg M. F. , Santiago F. , Chu T. K. , Boulais K. A.
Published: July 2002

Many molecular beam epitaxy (MBE) applications require a source of ionized gas atoms or molecules. However, the high gas pressures and high kinetic energies associated with many standard gas sources can be detrimental to MBE deposition. These disadvantages are addressed here by an ionized gas source fabricated from a common laboratory ionization gauge. The source described here produces 100 eV gas ions while maintaining vacuums of better than 10−8 mbar. This source has the additional advantage of being inexpensive and simple to construct. Design, construction, and operation of the source will be presented.
Optogalvanic laser Doppler velocimetry using the self-mixing effect of CO2 laser
Authors: Choi Jong-Woon , Kim Young-Pyung , Kim Youn-Myung
Published: July 2002

A laser Doppler velocimeter employing a CO2 laser has been developed by using its optogalvanic effect. A change in the electric impedance of a discharge, induced by mixing of a returned wave with an originally existing wave inside the cavity, is employed to detect the Doppler frequency shift. We found that a Doppler frequency shift as much as 60 kHz was detected, and also a good linear relationship between the velocity and the Doppler frequency shift was obtained.
Shear-force detection based on an external cavity laser interferometer for a compact scanning near field optical microscope
Authors: Pfeffer M. , Lambelet P. , Marquis-Weible F.
Published: July 2002

A compact near field optical microscope module is presented, with shear-force detection based on an external cavity laser interferometer. Its Al2O3 structure allows minimal sensitivity towards thermal and mechanical perturbations. Together with a precise and easy-to-handle tip fixation system, involving standard commercially available elements, this module is simple to use, and allows to detect a minimum displacement of 5.9 pmrms/Hz, with a large working distance of 10.5 mm.
Critical current-length product for electromigration induced resistance changes in short Al lines
Authors: Kraayeveld J. R. , Verbruggen A. H. , Willemsen A. W.-J. , Radelaar S.
Published: July 2002

Changes in the electrical resistance induced by electromigration in short (3–100 μm) pure Al lines show a rather well-defined behavior. An applied dc current induces either an increase or a decrease of the resistance. For current densities below a critical value the resistance change saturates with time and the resistance fully recovers when the current is switched off. The length and temperature dependence of the resistance changes indicate that the observed time dependence is determined by grain boundary diffusion along the whole line length. Above the critical current density the resistance changes do not fully recover. Given the inevitable sample-to-sample variations, the product of the critical current density and the line length is constant. The value of this product is in good agreement with values of the constant product of threshold current density and line length found in drift velocity experiments.
Low-resistance Ohmic conduction across compound semiconductor wafer-bonded interfaces
Authors: Kish F. A. , Vanderwater D. A. , Peanasky M. J. , Ludowise M. J. , Hummel S. G. , Rosner S. J.
Published: July 2002

Data are presented demonstrating low-resistance Ohmic conduction across interfaces formed by high-temperature (750–1000 °C) compound semiconductor wafer bonding. Unipolar junctions formed by wafer bonding surfaces consisting of In0.5Ga0.5P/In0.5Ga0.5P, GaP/GaP, GaP/In0.5Ga0.5P, and In0.5Ga0.5P/GaAs are shown to exhibit low-resistance Ohmic conduction for both p- and n-isotype junctions. The achievement of these properties is demonstrated to be critically dependent upon the crystallographic alignment of the bonded wafer surfaces, irrespective of the lattice mismatch between the surfaces. Specifically, we show that the surface orientation of the bonded surfaces must be nominally matched while simultaneously maintaining rotational alignment of the wafers.
Direct measurement of the internal electric field distribution in a multilayer organic light-emitting diode
Authors: Campbell I. H. , Joswick M. D. , Parker I. D.
Published: July 2002

We present a general electroabsorption technique to measure the electric field in each layer of multilayer organic light-emitting diodes. The electroabsorption signal from each layer is identified spectroscopically and measured as a function of dc bias. Measurements were made on three layer devices consisting of a hole transport layer, a light-emitting layer, and an electron transport layer. In reverse bias, without significant charge injection, the dc electric field is uniform throughout the device. In forward bias, the dc electric field is distributed nonuniformly; it is smallest in the light-emitting layer and largest in the hole transport layer. The nonuniform dc electric field distribution is caused by the accumulation of electrons (holes) at the interface between the light-emitting layer and the hole (electron) transport layer. The maximum accumulated charge densities are 2×1012 electrons/cm2 and 3×1011 holes/cm2. These results highlight the carrier blocking role of monopolar transport layers and demonstrate a powerful technique to characterize multilayer organic structures.
Completely passivated high conductivity copper films made by annealing Cu/Al bilayers
Authors: Wang Wei , Lanford W. A. , Murarka S. P.
Published: July 2002

Thin films made by annealing Cu(500 nm)/Al(7 nm)/SiO2/Si are investigated using Rutherford backscattering and resistivity measurements. Annealing these films in a low pressure of oxygen results in the formation of a thin surface layer of hole-free aluminum oxide which protects the underlying copper from oxidation. Even when heated in air at 350 °C for 4 h, no growth of copper oxide is detected. These films have a resistivity as low as 2.4 μΩ cm, comparable to the resistivity of pure copper films (2.1 μΩ cm) made in the same deposition system. The use of such films for microelectronic metallization is briefly discussed.
Photoluminescence and micro-Raman studies of as-grown and high-temperature-annealed KTiOPO4
Authors: Stevens K. T. , Giles N. C. , Halliburton L. E.
Published: July 2002

An emission band has been observed near 820 nm in a series of KTiOPO4 crystals grown by the flux technique. Photoluminescence spectra were obtained at room temperature using an excitation wavelength of 457 nm and a power density of 1.9 kW/cm2. When a crystal was held for 1 h in air at 1000 °C, the intensity of the emission increased by two orders of magnitude. Micro-Raman spectra taken at the same location as the photoluminescence revealed that the high-temperature anneal caused significant decomposition at the KTiOPO4 surface. Potassium, phosphorus, and oxygen evolved from the surface and left TiO2 (anatase). The increase in emission correlated with the amount of anatase created. This enhanced near-infrared emission arises from Ti3+ ions which are formed by reduction in the TiO2 surface layer during the decomposition process. Since the 820-nm emission is observed in as-grown crystals, our data suggest that some reduced TiO2 (rutile or anatase) is formed in the bulk of KTiOPO4 crystals during growth.
Femtosecond intersubband relaxation and population inversion in stepped quantum well
Authors: Sung C. Y. , Norris T. B. , Afzali-Kushaa A. , Haddad G. I.
Published: July 2002

We have investigated intersubband relaxation rates in a stepped quantum well at room temperature using differential transmission spectroscopy with subpicosecond time resolution. The dynamics of the subband populations are derived from the experimentally observed reduction of oscillator strength of the corresponding exciton transitions. In the stepped quantum well the relaxation through longitudinal optical-phonon emission from n=3 to 1 (25 ps) is slower than that from 2 to 1 (220 fs), due to the reduced wave function overlap and larger wave vector required for intersubband scattering. When the n=3 state is pumped, a population inversion between n3 and n2 (which are separated by 7 THz) is observed.
The dose, energy, and time dependence of silicon self-implantation induced transient enhanced diffusion at 750 °C
Authors: Chao H. S. , Griffin P. B. , Plummer J. D. , Rafferty C. S.
Published: July 2002

The short anneal time behavior of transient enhanced diffusion of dopants in silicon is investigated experimentally using a buried boron marker layer structure and varying Si implant doses and implant energies. The diffusion behavior of the marker layer shows that the diffusivity enhancements are, to the first order, independent of the implant conditions at short anneal times, while the overall transient motion increases with increasing implant conditions. The data are analyzed using an interstitial clustering model that includes both cluster evaporation and cluster growth terms.
Ground state exciton lasing in CdSe submonolayers inserted in a ZnSe matrix
Authors: Ledentsov N. N. , Krestnikov I. L. , Maximov M. V. , Ivanov S. V. , Sorokin S. L. , Kop’ev P. S. , Alferov Zh. I. , Bimberg D. , Sotomayor Torres C. M.
Published: July 2002

We study optical properties of ZnMgSSe-ZnCdSe structures with CdSe submonolayers inserted in a ZnSe matrix. Remarkably high exciton oscillator strength is found in ultrashort-period submonolayer CdSe-ZnSe superlattices, as compared to ZnCdSe quantum wells of comparable average width and Cd composition. In conventional ZnCdSe quantum wells the lasing occurs at energies ∼30 meV below the free heavy-hole exciton transition revealed in photoluminescence and in optical reflectance spectra. In the CdSe submonolayer superlattices lasing occurs at energies in the very vicinity of the heavy hole exciton resonance, directly in the region of strongly-enhanced exciton-induced modulation of the reflectance spectrum, and, consequently, refractive index change. We attribute the effects observed to exciton localization by potential fluctuations caused by nanoscale CdSe islands formed during submonolayer deposition.
1/f noise characterization of Ir/p-Si and Ir/p-Si1−xGex low Schottky barrier junctions
Authors: Ouacha H. , Nur O. , Willander M. , Fu Y. , Ouacha A.
Published: July 2002

The electrical noise properties of Ir/p-Si and Ir/p-Si1−xGex (x=0.14) Schottky junctions have been studied. The 1/f noise measurements were performed under forward bias over a wide temperature and frequency ranges. The effect of annealing on the noise properties of these junctions was also investigated. Annealed junction shows higher noise level. This was attributed to the defects formation at the metal/semiconductor interface. From the temperature dependence of the 1/f noise power density, an optimum operating temperature for as deposited and annealed junctions was found. The Hooge parameter, αH, is derived from the experimental data over a wide range of temperature for the deposited junctions. Values of 2.26×10−6 and 1.78×10−6 were obtained at room temperature for Ir/p-Si and Ir/p-Si1−xGex, respectively.
Characterization of Nd:Y3Al5O12 thin films grown on various substrates by pulsed laser deposition
Authors: Ezaki Mizunori , Obara Minoru , Kumagai Hiroshi , Toyoda Koichi
Published: July 2002

Epitaxial Nd-doped yttrium aluminum garnet (NdxY3−xAl5O12 or Nd:YAG) films have been grown on various substrates by pulsed laser deposition for the purpose of fabricating diode-pumped waveguide lasers. The films were characterized by Rutherford backscattering, x-ray diffraction, atomic force microscopy, and photoluminescence measurements. Nd:YAG films on (100) silicon substrate with a large lattice mismatch show oriented stoichiometric growth. On the other hand, Nd:YAG films on garnet substrates (Nd undoped Gd3Ga5O12,Y3Al5O12 and Zr-, Sc-doped Gd3Ga5O12) show epitaxial growth with smooth surfaces. The optical properties of Nd-doped YAG thin films on various substrates were comparable to those of Nd:YAG bulk laser crystal.
Time-resolved luminescence studies of heavily nitrogen doped ZnSe
Authors: Kothandaraman C. , Kuskovsky I. , Neumark G. F. , Park R. M.
Published: July 2002

Time-resolved luminescence data from heavily nitrogen doped ZnSe (total N concentration exceeding mid-1018/cm3) is presented. The luminescence exhibited a decay time and a rise time which increased with decreasing energy of observation. Furthermore, both the decay times and rise times decreased with increasing temperature. These observations are consistent with the following model: (i) a band of states is created due to fluctuations in the ionized impurity concentrations; (ii) a portion of the carriers captured by the shallower impurity states are transferred to deeper states prior to recombination.
Three-dimensional image interaction for nonsmooth emitters
Authors: Mesa G. , Sáenz J. J.
Published: July 2002

We present a generalized image–charge method to calculate the interaction energies of a charge placed between a metallic tip of arbitrary shape and a sample surface. The basic idea is to replace the electrodes by a set of image charges. These charges are adjusted in order to fit the boundary conditions on the surfaces. As an application of the technique, we have calculated the three-dimensional potential barrier (including image interaction) for electron field emission from sharp tips having different geometries. The influence of the presence of a little hemispherical bump on the apex is also discussed.
Self-organized Fe nanowire arrays prepared by shadow deposition on NaCl(110) templates
Authors: Sugawara Akira , Coyle T. , Hembree G. G. , Scheinfein M. R.
Published: July 2002

Iron nanowire arrays have been grown by shadow deposition on a self-organized grating template produced by annealing the sodium chloride (110) surface. The typical wire size as measured using transmission electron microscopy is 45 nm×13 nm×10 μm. The typical wire array period is 90 nm. The magnetic properties were dominated by a strong in-plane shape anisotropy. The hysteresis loops examined by magneto-optical Kerr effect measurements indicated coherent switching, even though the individual wires were isolated from one another.
Epitaxy of Al films on GaN studied by reflection high-energy electron diffraction and atomic force microscopy
Authors: Liu Q. Z. , Shen L. , Smith K. V. , Tu C. W. , Yu E. T. , Lau S. S. , Perkins N. R. , Kuech T. F.
Published: July 2002

Epitaxy of Al films deposited on GaN has been studied using reflection high-energy electron diffraction (RHEED), atomic force microscopy (AFM), x-ray diffraction, and ion channeling techniques. Al (111) films have been found to grow epitaxially on GaN (0001) surfaces with Al 〈21̄1̄〉‖GaN〈21̄1̄0〉. For growth at 15 and 150 °C with a deposition rate of 0.26 Å/s, the epitaxial quality of the film was poor initially, as evidenced by the observation of diffuse RHEED patterns. After a few monolayers, a sharp and streaky RHEED pattern develops and is maintained during subsequent deposition, indicating an improvement in epitaxial quality with a two-dimensional growth mode. AFM studies indicate that the initial GaN surface quality is a significant factor in achieving epitaxial growth, and that the size of Al epitaxial islands increases substantially for higher growth temperatures. X-ray diffraction and ion channeling results confirm the epitaxial nature of the Al films in spite of a significant lattice mismatch of 10.2%.
Giant interdiffusion induced by nitrogen doping in CdZnMgTe/CdZnTe superlattices
Authors: Baron T. , Kany F. , Saminadayar K. , Magnea N. , Cox R. T.
Published: July 2002

CdZnMgTe/CdZnTe superlattices were doped with nitrogen from a dc plasma source during their growth by molecular beam epitaxy. The samples were investigated by photoluminescence, double crystal x-ray diffraction, and secondary ion mass spectroscopy. A very strong intermixing across the quantum well interfaces was observed, producing a homogeneous alloy. The mixing is attributed to cation diffusion assisted by lattice defects generated by the simultaneous presence of Mg and N atoms.
High-frequency response of polymeric light-emitting diodes
Authors: Pal A. J. , Österbacka R. , Källman K.-M. , Stubb H.
Published: July 2002

The frequency dependence of alternating-current polymeric light-emitting diodes has been studied. Langmuir–Blodgett (LB) films of poly(3-hexylthiophene) have been used as the active emitting material sandwiched between LB films of emeraldine base polyaniline to form the device. We have shown that by reducing the thickness of the emitting layer using the LB deposition technique, one can increase the high-frequency operating limit of the device. From the −3 dB frequency, we have calculated the carrier mobility in the emitting polymer layer, and compared it with the Poole–Frenkel model. The electroluminescence and photoluminescence spectra have been studied.
Grain boundary misorientation angles and stress-induced voiding in oxide passivated copper interconnects
Authors: Nucci J. A. , Keller R. R. , Field D. P. , Shacham-Diamand Y.
Published: July 2002

Grain boundary misorientations were determined by electron backscattering diffraction for tantalum-encapsulated, copper interconnects which contained thermal-stress-induced voids. The misorientation angles at voided and unvoided line segments were analyzed for two differently heat treated sample types, which were not equally susceptibile to stress voiding. Unvoided line segments contained a larger percentage of low misorientation angle, lower diffusivity boundaries than regions adjacent to voids. In addition, the more void resistant sample type also contained an overall higher proportion of low misorientation angle boundaries than the sample type which exhibited more voiding. The data provide further support for the importance of local variations in microstructure, which control the kinetics of stress void formation and growth.
Maskless selective growth of InGaAs/InP quantum wires on (100) GaAs
Authors: Ahopelto J. , Sopanen M. , Lipsanen H. , Lourdudoss S. , Rodriguez Messmer E. , Höfling E. , Reithmaier J. P. , Forchel A. , Petersson A. , Samuelson L.
Published: July 2002

A new fabrication process to create InGaAs/InP quantum wires on (100) GaAs substrates is demonstrated. The process is based on the selectivity of the growth of InP on lines created by focused ion beam bombardment, together with the selectivity of the growth of InGaAs on the InP wires. Intense photoluminescene is observed from the wires and the emission shows clear polarization parallel and perpendicular to the wires. Cathodoluminescene images confirm that the luminescence originates from the wires.
Dislocation blocking in InxGa1−xAs (x<0.20) layers grown on GaAs substrates revealed by strain sensitive etching with aqueous CrO3–HF solutions
Authors: MacPherson G. , Goodhew P. J.
Published: July 2002

Results from transmission electron microscopy (TEM), Nomarski interference microscopy and strain sensitive defect etching of epilayers with CrO3 are presented on single InxGa1−xAs (x<0.20) layers grown on GaAs substrates. The epilayer thickness in all the samples grown was significantly greater than the critical thickness (hc) defined by Matthews and Blakeslee [J. W. Matthews and A. E. Blakeslee, J. Cryst. Growth 27, 118 (1974)]. For these layers there should be a significant amount of relaxation with a high level of dislocation interaction observed at or near to the heteroepitaxial interface. It is shown that orthogonal dislocations, and in particular long 60° and edge dislocation segments lying in the epilayer above the interface play an important role in determining the mean free path of glissile 60° dislocations due to the action of large scale dislocation blocking. The level of dislocation blocking is significantly greater than that found by TEM observations. It is shown that etching with CrO3 is an effective method for revealing dislocation blocking over large areas of a wafer (in principle an entire wafer) and these interactions can be easily viewed using Nomarski interference microscopy.
A highly efficient organic second-order nonlinear optical crystal based on a donor-acceptor substituted 4-nitrophenylhydrazone
Authors: Pan Feng , Wong Man Shing , Bösch Martin , Bosshard Christian , Meier Urs , Günter Peter
Published: July 2002

We present a novel organic crystal, 5-(methylthio)-thiophenecarboxaldehyde-4-nitrophenylhydrazone, with a large effective phase-matchable nonlinear optical coefficient, deff=29±3 pm/V at λ=1318 nm. Single crystals of dimensions up to 25×5×5 mm3 were grown. The large off-diagonal nonlinear optical coefficients can be explained with the two-dimensional geometry of the chromophores in the crystal lattice. Our crystal is ideally suited for optic parametric oscillation in the wavelength range from 1000 to 2500 nm.