bluuebunny/crossref_metadata_2025 huggingface dataset:
Strained layer GaAs1−yPy-AlGaAs and InxGa1−xAs-AlGaAs quantum well diode lasers
Authors: van der Poel C. J. , Ambrosius H. P. M. M. , Linders R. W. M. , Peeters R. M. L. , Acket G. A. , Krijn M. P. C. M.
Published: July 2002

Separate confinement strained layer single quantum well diode lasers on GaAs substrates have been fabricated by low-pressure organometallic vapor phase epitaxy. Laser diode structures with a 90 Å quantum well under compressive strain, composed of InxGa1−xAs with x=0.00–0.17, as well as tensile strain, composed of GaAs1−yPy with y=0.00–0.29, have been studied. The emission wavelength ranges from λ=746 nm for y=0.29 up to λ=962 nm for x=0.17. The strain dependence of the threshold current for broad area devices is studied both experimentally and theoretically as a function of temperature. Regions of optimal laser performance, one for compressive and one for tensile strain, are identified.
A highly processable metallic glass: Zr41.2Ti13.8Cu12.5Ni10.0Be22.5
Authors: Peker A. , Johnson W. L.
Published: July 2002

We report on the properties of one example of a new family of metallic alloys which exhibit excellent glass forming ability. The critical cooling rate to retain the glassy phase is of the order of 10 K/s or less. Large samples in the form of rods ranging up to 14 mm in diameter have been prepared by casting in silica containers. The undercooled liquid alloy has been studied over a wide range of temperatures between the glass transition temperature and the thermodynamic melting point of the equilibrium crystalline alloy using scanning calorimetry. Crystallization of the material has been studied. Some characteristic properties of the new material are presented. The origins of exceptional glass forming ability of these new alloys are discussed.
Atomic resolution scanning tunneling microscopy with a gallium arsenide tip
Authors: Nunes G. , Amer N. M.
Published: July 2002

A scanning tunneling microscope which uses a gallium arsenide tip has been successfully constructed. Atomic resolution is demonstrated by the imaging of the Si(111)-7×7 surface in ultrahigh vacuum. Details of the tip preparation are given and the tip tunneling current characteristics are discussed.
Photoinduced charge transfer and charge carrier generation in polysilane films containing C60 molecules
Authors: Kepler R. G. , Cahill P. A.
Published: July 2002

We have studied charge carrier generation and transport in poly(methylphenylsilane) films containing C60 molecules, and have found that the quantum efficiency for carrier generation is increased by more than an order of magnitude over poly(methylphenylsilane) films not containing C60 and that hole transport is unaffected. We also measured the electroabsorption spectrum of the composite films and found no evidence for charge transfer transitions. We conclude that electrons are transferred from poly(methylphenylsilane) to C60 molecules that have been excited to their lowest energy absorption band at about 2 eV.
Formation of epitaxial Tl2Ba2CaCu2O8 thin films at low temperature in pure argon
Authors: Yan S. L. , Fang L. , Song Q. X. , Yan J. , Zhu Y. P. , Chen J. H. , Zhang S. B.
Published: July 2002

Mirror-like Tl2Ba2CaCu2O8 thin films have been reproducibly prepared on (001)LaAlO3 substrates by dc magnetron sputtering using 80% argon and 20% oxygen and post-annealing at temperatures of 720–760 °C in 1 atm pure argon. X-ray diffraction patterns of θ-2θ scans, φ scans, and Read camera photographs prove that the thin films are strongly textured with the c-axis perpendicular to the substrate surfaces and epitaxially grown to the substrate with Tl2Ba2CaCu2O8(100) parallel to the LaAlO3(100). The zero resistance temperatures are in the range of 105.2–108.6 K for the 0.2–1.0-μm-thick films. The critical current density of 5.3×106 A/cm2 at 77 K has been obtained at zero magnetic field for a 0.4-μm-thick film.
Scanning shearing-stress microscope
Authors: Sasaki A. , Katsumata A. , Iwata F. , Aoyama H.
Published: July 2002

A new scanning probe microscope based on a scanning tunneling microscope (STM) and a frequency shift of an AT cut quartz resonator has been developed. The quartz resonator coupled to a STM sample is oscillated at its resonance frequency. The shift of the resonance frequency corresponds to the strength of the shearing stress in the sample, and is caused by the shearing force interaction between the STM tip and the sample under the tip scanning. The preliminary images presented show simultaneously STM surface topographies and the changes of subsurface shearing stresses in gold thin films. The sensitivity of our microscope is 0.30 N/m for a 0.2-Hz frequency shift of the quartz crystal resonance frequency.
Photon-assisted tunneling in double-barrier superconducting tunnel junctions
Authors: Dierichs M. M. Th. M. , Dieleman P. , Wezelman J. J. , Honingh C. E. , Klapwijk T. M.
Published: July 2002

Double-barrier Nb/Al2O3/Al/Al2O3/Nb tunnel junctions are used as mixing elements in a 345 GHz waveguide mixer. Noise temperatures (double side band) down to 720 K at 3.0 K are obtained without the need to apply a magnetic field to suppress the Josephson current. It is shown that the composite barrier acts as a single barrier for photon-assisted tunneling. Surprisingly, at these frequencies the capacitance of two stacked tunnel barriers is only determined by one barrier.
Study of reactive ion etching-induced damage in GaAs/AlGaAs structures using a quantum well intermixing probe
Authors: Ooi B. S. , Bryce A. C. , Wilkinson C. D. W. , Marsh J. H.
Published: July 2002

We report the damage distribution induced by C2F6 and SiCl4 reactive ion etching (RIE) using quantum wells and quantum well intermixing (QWI) as probes. Photoluminescence emission at 77 K was measured both before and after rapid thermal annealing at 900 °C for 30 s. Our results show that the QWI probing technique can effectively be utilized as a sensitive probe of RIE damage. A damage depth of 650 Å before annealing and blue shifts of up to 65 meV after annealing were obtained in C2F6 RIE regions. A damage depth of 100 Å and blue shifts of up to 30 meV were observed in SiCl4 RIE regions.
Band alignment in GaxIn1−xP/InP heterostructures
Authors: Bensaada A. , Graham J. T. , Brebner J. L. , Chennouf A. , Cochrane R. W. , Leonelli R. , Masut R. A.
Published: July 2002

We report low temperature optical absorption measurements on GaxIn1−xP/InP (x<0.2) multiple quantum wells and strained-layer superlattices. The spectra show several well-defined peaks whose positions can be fitted within an envelope-function formalism including strain effects. We deduce conduction band offsets between the larger gap ternary and smaller gap binary materials ranging from 30 to 50 meV. Since these values are intermediate between the strain-induced shifts for the light- and heavy-hole valence bands, the electrons and heavy holes are localized in the InP layers (type I system), whereas the light holes have their quantum wells in the GaInP layers (type II system).
Schottky enhancement of reacted NiAl/n-GaAs contacts
Authors: Chen C.-P. , Chang Y. A. , Kuech T. F.
Published: July 2002

Schottky enhancement of reacted NiAl/n-GaAs contacts was demonstrated experimentally. The Schottky barrier height increases from 0.83 eV for the as-deposited contacts to 0.96 eV when the contacts were annealed at 400 °C for 1 min. Formation of a high Al content (Al,Ga)As layer at the interface upon annealing was rationalized in terms of a thermodynamic/kinetic model. A (200) dark field cross-sectional transmission electron microscopy image was used to show the presence of high Al content (Al,Ga)As at the interface.
S2Cl2 treatment: A new sulfur passivation method of GaAs surface
Authors: Li Z. S. , Cai W. Z. , Su R. Z. , Dong G. S. , Huang D. M. , Ding X. M. , Hou X. Y. , Wang Xun
Published: July 2002

We have developed a new sulfur passivation method—S2Cl2 treatment, which is quite effective for removing the surface oxide layer of GaAs and passivating the surface with monolayer thick sulfides. Photoluminescence (PL) spectroscopy, Auger electron spectroscopy (AES), and x-ray photoelectron spectroscopy (XPS) are used to study the passivated GaAs (100) surfaces. The results of PL reveal that the PL intensity increases by two orders of magnitude, which is indicative of the reduction of surface recombination velocity of GaAs by this treatment. AES data prove that the sulfurized surface contains S, Ga, As, C, and small amount of Cl atoms but no oxygen signal at all. XPS study shows that sulfur atoms bond to both Ga and As atoms more effectively on S2Cl2 treated surfaces than those passivated by (NH4)2Sx.
InGaAs/GaAs shallow quantum well optical switches grown by metalorganic vapor phase epitaxy
Authors: Lee S. W. , Chu K. U. , Kim S. W. , Park S. , Kwon O’D. , Goossen K. W. , Pei S. S.
Published: July 2002

Optical switches have been fabricated from InGaAs/GaAs shallow quantum well structures grown by metalorganic vapor phase epitaxy. The photocurrent spectra exhibited very sharp room-temperature exciton peaks around 900 nm. Quantum well modulators consisting of such a shallow system showed contrast ratios larger than 2:1 and no sign of strain-induced degradations. The epitaxial quality, however, had some interesting dependence on the choice of substrate dopant.
Tapping mode atomic force microscopy in liquid
Authors: Putman Constant A. J. , Van der Werf Kees O. , De Grooth Bart G. , Van Hulst Niek F. , Greve Jan
Published: July 2002

We show that standard silicon nitride cantilevers can be used for tapping mode atomic force microscopy (AFM) in air, provided that the energy of the oscillating cantilever is sufficiently high to overcome the adhesion of the water layer. The same cantilevers are successfully used for tapping mode AFM in liquid. Acoustic modes in the liquid excite the cantilever. On soft samples, e.g., biological material, this tapping mode AFM is much more gentle than the regular contact mode AFM. Not only is the destructive influence of the lateral forces minimized, but more important, the intrinsic viscoelastic properties of the sample itself are effectively used to ‘‘harden’’ the soft sample.
Dispersion of second-order optical nonlinearity in chromophoric self-assembled films by optical parametric amplification: Experiment and theory
Authors: Lundquist Paul M. , Yitzchaik Shlomo , Zhang Tongguang , Kanis David R. , Ratner Mark A. , Marks Tobin J. , Wong George K.
Published: July 2002

The dispersion of the second-order optical nonlinearity in chromophoric self-assembled stilbazolium films has been characterized in detail as a function of fundamental wavelength from 800 to 1600 nm using an optical parametric amplifier-based measurement system. The second-harmonic generation (SHG) spectrum exhibits a distinctive two-photon resonance at ℏω=1.3 eV (960 nm). The maximum in the second-order susceptibility coincides with a low-energy chromophore-centered charge-transfer one-photon excitation at 480 nm (2.6 eV). The experimental SHG dispersion values compare favorably with theoretical results computed using a semiempirical sum-over-states formalism. These indicate that the χ(2) response is dominated by an excitation along the long axis of the stilbazolium chromophore from the highest occupied to the lowest unoccupied molecular orbital.
Suppression of Zn diffusion due to hydrogen passivation in p -AlGaInP
Authors: Ishibashi Akihiko , Mannoh Masaya , Kidoguchi Isao , Ban Yuzaburoh , Ohnaka Kiyoshi
Published: July 2002

The behaviors of Zn acceptors in p-AlGaInP layer during thermal annealing in AsH3+H2 mixture gas have been investigated. The electrical activities of Zn acceptors were greatly affected by the hydrogen atoms originating from AsH3 during thermal annealing. In addition, from observation of the atomic disordering, hydrogen passivation of Zn acceptors was found to suppress the atomic diffusion. These phenomena can be consistently explained by a simple hydrogen passivation model, which is the termination of dangling bonds by hydrogen atoms.
Local temperature increases during electric-field-induced transistor formation in CuInSe2
Authors: Chernyak Leonid , Cahen David , Zhao S. , Haneman D.
Published: July 2002

Local p-n and p-n-p junction structures can be formed under room-temperature conditions, in CuInSe2 and related materials solely by applying strong electric fields through small contacts. Electromigration of native Cu ions, which was suggested as the mechanism for type conversion, assumes an enhancement in ion mobility of several orders of magnitude. Electric-field-induced local heating was given as one possible cause for such enhancement [Cahen et al., Science 258, 271 (1992)]. Therefore, we have measured the average temperature of and around the contacts to CuInSe2 and Cu0.95Ag0.05InSe2 crystals, during application of the electric field. The measurements were done as a function of the active power dissipated in the system, using two different techniques, viz. infrared emission and contact melting. We find that the temperature around the contact, during the tens of ms of actual structure formation (210–320 °C), is insufficient for significant thermal diffusion. We conclude that electromigration is the dominant mechanism.
Semiconductor characterization with the scanning surface harmonic microscope
Authors: Bourgoin J.-P. , Johnson M. B. , Michel B.
Published: July 2002

The scanning surface harmonic microscope, in which a microwave signal is applied across a tip-sample tunneling gap and higher harmonics are detected, is sensitive to the capacitance/voltage characteristics of semiconductor samples on a nanometer scale. We demonstrate its sensitivity to a wide range of dopant concentrations on Si, and its applications as a dopant profiler. Depletion regions are delineated with remarkable sensitivity, and variations in dopant concentration over a 35-nm scale are discussed. Indications of a 5 nm resolution have been obtained.
Measurement of solid–liquid interface temperature during pulsed excimer laser melting of polycrystalline silicon films
Authors: Xu Xianfan , Grigoropoulos Costas P. , Russo Richard E.
Published: July 2002

A nanosecond time resolution pyrometer has been developed for measuring the transient temperature of thin polycrystalline silicon (p-Si) films irradiated by a pulsed excimer laser. The sample design structure and material optical properties allow direct measurement of the temperature at the solid–liquid phase change interface.
Synthesis of nanometer glass particles by pulsed-laser ablation of microspheres
Authors: Juang Ching-Bo , Cai Hong , Becker Michael F. , Keto John W. , Brock James R.
Published: July 2002

We describe a new method for producing ultrafine glass particles that employs pulsed-laser particle ablation. Pulsed-laser radiation with wavelength of 249 nm was used to ablate 8-μm-diam glass microspheres under normal atmospheric conditions. The ejected particles were collected on silicon substrates for further analysis. Scanning electron micrographs of the samples were analyzed by computer aided image processing to determine the effect of laser fluence on the particle size distribution. Results showed that mean particle diameter, in the range from 60 to 80 nm, was generally inversely proportional to laser fluence. The particle size distributions were closely log-normal with small geometric standard deviations.
Modal analysis of a small surface emitting laser with a selectively oxidized waveguide
Authors: Lear K. L. , Choquette K. D. , Schneider R. P. , Kilcoyne S. P.
Published: July 2002

We describe studies of an index-guided ∼4×3 μm2 vertical cavity surface emitting laser with a cw, room temperature 133 μA threshold current and 53% slope efficiency fabricated using selective wet thermal oxidation to provide optical and electrical confinement. While the device operates strictly single mode, a large number of transverse modes are evident in the subthreshold luminescence observed in both vertical and lateral directions. Despite the lumped nature of the index region, the transverse mode wavelengths agree very well with those predicted for a conventional distributed waveguide structure. Waveguide dimensions and an effective index step of 2% between the active and cladding region are determined by fitting the modal data.
Superhard nanocrystalline composite materials: The TiN/Si3N4 system
Authors: Vepřek S. , Reiprich S. , Shizhi Li
Published: July 2002

Thin films of novel superhard composite materials consisting of TiN nanocrystals in an amorphous Si3N4 matrix have been prepared by means of plasma chemical vapor deposition. The films show a high Vickers hardness of 5000 kg/mm2 and elastic modulus of ≳500 GPa, and they are resistant against oxidation in air up to ≥800 °C. The theoretical background of these unusual properties are briefly discussed and practical rules suggested according to which similar properties should be expected for composites of other ternary systems.
Photovoltaic investigations of interband transitions in SiGe/Si multiple quantum wells
Authors: Wang Jianbao , Gong Dawei , Lu Fang , Sun Henghui , Wang Xun
Published: July 2002

Photovoltaic effect measurements have been carried out for the strained Si1−xGex/Si multiple quantum well samples. The absorption structures of the transitions from heavy-hole ground state (HH0) to the unconfined conduction (EC) states, light-hole ground state to EC states as well as the transitions of phonon (transverse acoustic and transverse optical)-assisted HH0-EC excitons of the sample with x=0.25 are identified by the photovoltaic measurement at the temperature of 18 K. The agreement between the experimental results and the calculations based on simple theoretical models is fairly good. Due to the rapid increase of the background absorption, the structures of the transitions from excited hole subbands to the conduction states are very difficult to identify. For the sample with x=0.5, the absorption related to the defects originated from the partial relaxation of the large misfit strain between Si0.5Ge0.5 and Si gives a great influence upon the identification of the interband absorption structures of the multiple quantum well.
An application of electrothermal feedback for high resolution cryogenic particle detection
Authors: Irwin K. D.
Published: July 2002

A novel type of superconducting transition edge sensor is proposed. In this sensor, the temperature of a superconducting film is held constant by feeding back to its position on the resistive transition edge. Energy deposited in the film is measured by a reduction in the feedback Joule heating. This mode of operation should lead to substantial improvements in resolution, linearity, dynamic range, and count rate. Fundamental resolution limits are below ΔE=√kT2C, which is sometimes incorrectly referred to as the thermodynamic limit. This performance is better than any existing technology operating at the same temperature, count rate, and absorber heat capacity. Applications include high resolution x-ray spectrometry, dark matter searches, and neutrino detection.
Electron beam system for rapid isothermal annealing of semiconductor materials and devices
Authors: McMahon R. A. , Hasko D. G. , Ahmed H.
Published: July 2002

An isothermal processing system using a 2-kW electron beam is described. Processing of areas up to 4×4 in. is achieved by rapidly scanning the beam in the multiple scan mode. An analysis of this method and some typical heating cycles for silicon wafers are presented. There is good agreement between theoretically predicted and experimentally measured temperatures. Additionally, closed-loop operation is demonstrated where an optical pyrometer is used to control the electron beam current. This machine can either process whole wafers, or can sequentially treat a large number of small chips. This enables, for example, the rapid assessment of the annealing behavior of a particular implant by processing chips, cut from the same wafer, under varying conditions. Heating cycles of a fraction of a second to tens of seconds or more, which are not possible with furnaces, at temperatures up to 1000°C or greater have found many applications in semiconductor processing. Two important uses are described in this paper illustrating the potential of the technique. One is the annealing of an arsenic implant in silicon with negligible diffusion and the other is the controlled drive in of arsenic.
Imaging differential polarization microscope with electronic readout
Authors: Mickols William , Tinoco Ignacio , Katz Joseph E. , Maestre Marcos F. , Bustamante Carlos
Published: July 2002

A differential polarization microscope forms two images: one of the transmitted intensity and the other due to the change in intensity between images formed when different polarizations of light are used. The interpretation of these images for linear dichroism and circular dichroism are described. The design constraints on the data acquisition systems and the polarization modulation are described. The advantage of imaging several biological systems which contain optically anisotropic structures are described.
Position measurement with a resolution and noise-limited instrument
Authors: Bobroff Norman
Published: July 2002

A common problem in experimental data analysis is to locate the position of a signal to an accuracy which is substantially less than the actual signal width. By applying maximum likelihood estimation to this problem, this paper derives theoretical limits on the ability to locate signal position. The limiting error in position measurement is shown to be a simple function of the instrument resolution, the density of sample points, and the signal-to-noise ratio of the data. An interesting conclusion is that position information on a much finer scale than the minimum instrument sampling interval is contained in data of modest signal-to-noise ratio. The common procedure of excluding the portion of the data lying below an amplitude threshold to guard against background fluctuations is incorporated in the maximum likelihood analysis. It is shown that selection of the optimum amplitude threshold level depends on the type of noise present in the data, and can be an important factor in position accuracy. The analytical results exhibit close agreement with Monte Carlo simulations of position accuracy in the presence of noise.
Automatic measurement system for photocapacitometry analysis
Authors: Nishizawa Jun-ichi , Koike Masayoshi , Dezaki Kazushi , Shibata Jiro
Published: July 2002

Photocapacitometry analysis and an automatic measurement system by computer are described. Photocapacitance is very useful for the detection and identification of deep levels in semiconductors which correspond to impurity or lattice defects. Photocapacitometry analysis has high sensitivity and high resolution for deep-level detection and can measure the deep levels in the actual device structure, for example p+n (or n+p) junction, Schottky diode, metal-insulator-semiconductor (MIS) diode, and so on without destruction. Photocapacitance (PHCAP) measures the deep levels by photoexcitation without thermal excitation; therefore, the energy range of excitation in PHCAP is wider than that in the thermal excitation method. This system is designed for shortening the measuring time and increasing the measurement accuracy. The measurement sequence is controlled automatically and the data analysis is produced by computer. This system can make it possible to realize high-quality semiconductors and consequently the highly efficient and high-performance semiconductor devices.
Auxiliary circuits for pulse bias and equivalent series resistance measurements with a Boonton 72B capacitance meter
Authors: Gutai Laszlo
Published: July 2002

Pulse bias and equivalent series resistance circuits have been developed to expand the capabilities of a Boonton 72B capacitance meter used in MOS capacitor characterization. With the help of tuned parallel and series LC circuits, pulses of 5 μs length can be applied directly to the capacitor under test, avoiding the built-in bias circuitry of the capacitance meter. The equivalent series resistance measurement circuit, used in a computer-controlled automated measurement system, makes it possible to determine both the real and imaginary components of an unknown impedance rather than the equivalent parallel capacitance only.
Low-cost data-acquisition and processing system for photoacoustic spectroscopy
Authors: McAskill Noel A.
Published: July 2002

The VZ-200 (Laser) home computer has been interfaced to a photoacoustic spectrometer for low-cost data acquisition and processing.
Beam scanning system for a clinical pi-meson beam
Authors: Lam G. K. Y. , Harrison R. W. , Kornelsen R. O. , Skarsgard L. D.
Published: July 2002

A beam delivery system for large uniform dose fields suitable for cancer radiotherapy has been constructed for the TRIUMF pion treatment facility using discrete step beam scanning in three dimensions. The patient on a couch is scanned laterally relative to a pencil beam in a raster fashion. At each spot, the depth dose profile is delivered by range modulations using a range shifter. The operations of the scanning couch and range shifter are synchronized by the use of beam monitor pulses from a beam intensity integrating system. The system is hence versatile enough to handle treatment volume of highly irregular shape and yet is immune to fluctuations in accelerator output.
Multichannel, rapid recording spectrometer
Authors: Dunnam C. R. , Chiu N-S. , Bauer S. H.
Published: July 2002

A microcomputer data-collection system is described based on a 20-element linear photodiode array which is positioned in the focal plane of the exit slit of a grating monochromator. Time-dependent, spectrally resolved signals developed by individual diodes in the array are preamplified and directed to a fast multichannel sampling digitizer subsystem. The maximum throughput is 20 parallel channels per 20-μs conversion period; the resulting single byte data words are temporarily buffered in a fast memory for eventual host CPU read in. The digitizer creates a data file consisting of 20 channels by eight bits by a selectable file length of up to 1024 words. Samples of data collected with this equipment of time-dependent absorption spectra of shock-heated toluene are presented.
Sample manipulator for Auger angular dependence studies
Authors: Barnard W. O. , Snyman H. C. , Auret F. D.
Published: July 2002

A modification to a commercial sample manipulator is described by which the angle between the incoming beam direction and the normal of the sample, as well as the angle of rotation about the normal, can be changed by 60° and 360°, respectively, from the outside of an UHV analysis chamber.
Small low-temperature indium compression feedthroughs
Authors: Kessel Robert , Sapp Richard C.
Published: July 2002

This note describes a small low-temperature indium compression feedthrough for electrical leads.
Molecular origin of background light in Thomson scattering measurements
Authors: McNeill D. H.
Published: July 2002

The plasma background light in Thomson scattering measurements is often far higher than expected for a pure hydrogen plasma. The spectral distribution of light from three plasmas (duration: 1 ms to steady state; electron density: below 1012 to over 1014 cm−3; temperature: below 20 to over 1000 eV) is studied. Signal-to-noise and intensity data from the Thomson scattering systems used on them are compared with analytic estimates to show that in two of these plasmas molecular light dominates the spectrum, while in the other, molecular light is present, but bremsstrahlung is usually more intense. Knowledge of the mechanism for background light can aid in designing detection systems for Thomson scattering and provide information on the neutral species composition and effective charge of the plasma.
Totally automated picosecond transient absorption spectrometer using two photodiode arrays as detectors
Authors: Déclémy Alain , Rullière Claude
Published: July 2002

A totally automated picosecond transient absorption spectrometer is described. This experimental apparatus requires two photodiodes arrays as detectors and a single spectrograph. It takes advantage of the high dynamic range of such detectors. Typical transient spectra are presented. They show the reproducibility and accuracy of this method of time-resolved spectroscopy.
Chemical kinetics at very high pressures. I. Two experimental techniques
Authors: Saluja Preet P. S. , Cameron Colin , Floriano M. Antonio , Lavergne Aurele , McLaurin Graham E. , Whalley Edward
Published: July 2002

Two methods of following chemical reaction rates at very high pressures by means of the electrical conductivity are described. In the first, opposed circular tungsten-carbide anvils are used, with 12-μm sheets of platinum silver soldered to them if the solution is too corrosive for unprotected carbide or if electrode polarization is too high, and the sample is confined by a gasket of epoxy resin and fiberglass. It can be used at pressures up to ∼100 kbar. In the second, a conductance cell was built into a hydraulic piston–cylinder apparatus, and the hydraulic fluid was pressurized by a piston. Measurements were made to 27 kbar and could be made to 45 or 50 kbar if a pressure vessel having a greater ratio of outside to inside diameter were used.
Photographic filter for equalizing spectral output of light sources used with optical multichannel analyzers
Authors: Lewis J. W. , Hug S. J. , Kliger D. S.
Published: July 2002

A probe light source with uniform spectral output is required to obtain constant signal-to-noise ratio in absorption spectra taken with an optical multichannel analyzer. Suitable filters to balance the spectrum of the flash-lamp source discussed here are unavailable. Instead a device is proposed which equalizes the spectrum of the probe source after it has been dispersed by the spectrograph of the optical multichannel analyzer.
Tests of a large air-core superconducting solenoid as a nuclear-reaction-product spectrometer
Authors: Stern R. L. , Becchetti F. D. , Casey T. , Jänecke J. W. , Lister P. M. , Liu W. Z. , Kovar D. G. , Janssens R. V. F. , Vineyard M. F. , Phillips W. R. , Kolata J. J.
Published: July 2002

An air-core superconducting solenoid, with a diameter of 0.2 m and a length of 0.4 m, has been configured for use as a heavy-ion reaction-product spectrometer (E/A≤5 MeV/u) near θ=0 °. The spectrometer has a large solid angle (10–35 msr) and properties suitable for time-of-flight measurements with flight paths ≳ 2 m. The performance of the spectrometer was established using α-particle sources and nuclear-reaction products from heavy-ion collisions. The characteristics of air-core magnets are compared to those of steel-yoke magnets. The simplicity and ease of operation of the air-core magnet, without significant problems from the (axial) fringe fields, suggests that larger air-core magnets with dΩ≥20 msr and capable of focusing ions with E/A≥30 MeV/u are feasible. Other applications of solenoids and combinations of solenoids with radial electric-field lenses (ELCO lenses) are also discussed, including designs which focus more than one charge state simultaneously.
Pulsed NMR probe-monitoring system
Authors: Heeschen W. A. , Alderman D. W. , Grant David M.
Published: July 2002

A simple device for measuring the instantaneous reflected power from a NMR probe is described. It is built from commercially available directional power-meter components coupled to a low-speed oscilloscope. The device can be used to monitor the performance of a probe while data are being acquired. It is particularly useful for adjusting probes whose characteristics change during a high-power pulse because of component heating.
Implementation of an optical multichannel analyzer controller for nanosecond flash photolysis measurements
Authors: Lewis J. W. , Yee G. G. , Kliger D. S.
Published: July 2002

Traditionally optical multichannel analyzers (OMAs) have been turnkey instruments. Controllers are now available which replace the OMA console with the users existing computer. The increased flexibility of this approach comes at the expense of increased involvement in the details of system operation. This is particularly the case for pulsed experiments where the detector is gated on for short periods. We report here implementation of an OMA controller hosted by an IBM personal computer using IEEE-488 communication. A microchannel-plate intensified detector is used in gated mode to collect spectra of intermediates formed by nanosecond laser photolysis. Three different pulsers for intensifier gating are compared. Both conventional absorbance measurements on transparent samples and diffuse reflectance measurements on opaque low-temperature matrices are described. In both cases, however, the samples are sufficiently photostable that noise can be reduced by signal averaging using repeated photolysis of the same sample volume. A second paper describes the additional complexity required for high signal-to-noise measurements on small quantities of photolabile samples.
High-pressure differential thermal analysis/dilatometric apparatus based on an Instron capillary rheometer
Authors: Hsiao B. S. , Shaw M. T. , Samulski E. T.
Published: July 2002

A high-pressure apparatus in the form of a modified Instron capillary rheometer capable of measuring differential thermal analysis (DTA) data and pressure–volume–temperature (P–V–T) relations was constructed in our laboratory. Temperatures from 20 to 370 °C and pressures from 1 to 6000 bar are achievable with a data-acquisition and control system based on an APPLE II+ microcomputer. Measurements of pressure to an accuracy of 1%, temperature of 0.5%, and volume change of 0.1% have been obtained. Software was developed to operate the experiments at fixed heating or cooling rates as well as at a constant pressure or with isothermal pressure sweeps. Polymer samples were compressed into rods preceding the experiment by a vacuum molder to eliminate voids. Low-density polyethylene (LDPE) was run as an example to demonstrate the performance of this pressure apparatus. The results revealed an excellent match between our experimental data and the published data.
Demountable piezoelectric transducer holder for use at low temperatures
Authors: Manning M. B. , Moelter M. J. , Elbaum C.
Published: July 2002

We present a design for a piezoelectric transducer holder for use at low temperatures, which is easily constructed and assembled. Improved acoustic signals with ‘‘ringing’’ eliminated were reliably obtained. The standard problems of demountability, electrical integrity, and leak tightness in the presence of liquid helium at moderate pressures were resolved.
Apparatus for making superlattice Langmuir–Blodgett films with atmosphere and temperature control
Authors: Armen T. , Halperin K. , Dutta P. , Ketterson J. B.
Published: July 2002

We describe an instrument consisting of two adjacent Langmuir troughs and an apparatus capable of dipping substrates in either trough. Such a capability permits the fabrication of Langmuir–Blodgett multilayer films consisting of two alternating components. The troughs are housed in a hermetically sealed enclosure which may be evacuated to permit the establishment of a clean and/or modified (e.g., O2 free) atmosphere. The enclosure is double walled for circulation of thermostating fluid (e.g., ethylene glycol) in order to establish temperatures in the range −30 to 130 °C. The monolayer pressures, film size, and dipping sequence can be controlled manually or by a computer. The surface pressure in each trough is sensed by independent Cahn balances employing filter paper ‘‘Wilhelmy plates’’ in such a manner as to maintain the hermetic seal.
Multidetector electron energy-loss spectrometer for time-resolved surface studies
Authors: Gurney Bruce A. , Ho W. , Richter Lee J. , Villarrubia J. S.
Published: July 2002

The design, construction, and operation of a high-resolution electron energy-loss spectrometer incorporating a multidetector of 96 discrete anodes are described. In conjunction with temperature and pressure perturbations, this fast data-acquisition spectrometer allows studies of surface kinetics and reaction mechanisms by accumulating spectra in as fast as 2 ms. A comprehensive hardware and software system has been developed that permits experimental control and data acquisition with an LSI 11/23 microcomputer. A routine increase in data-acquisition speed of ≊10, when compared to a conventional electron energy-loss apparatus, has been achieved when the spectrometer is operated with 10–20-meV resolution.
Intense ion beam diagnostics for particle beam fusion experiments on PBFA II (invited)
Authors: Leeper R. J. , Stygar W. A. , Maenchen J. , Ruiz C. L. , Kensek R. P. , Johnson D. J. , Lockner T. R. , Bailey J. , Cooper G. , Lee J. R. , Mehlhorn T. A. , Mix L. P. , Stinnett R. W.
Published: July 2002

A review of the diagnostics used at Sandia National Laboratories to measure the parameters of intense proton and lithium beams generated on the PBFA-II accelerator will be presented. These diagnostics consist of several types, namely: Kα x-ray pinhole cameras, a multiframe dE/dx ion pinhole camera, a p-i-n array ion pinhole camera, Thomson parabola spectrographs, a Rutherford magnetic spectrograph, plasma visible spectroscopy, and several nuclear activation diagnostics. These components, when taken together, enable a rather thorough description of the 5-MV, 10-TW ion beams presently being produced. A unique feature of these diagnostics is that they are capable of operating in hard (several MeV) x-ray bremsstrahlung backgrounds of some 109–1010 rad/s. Details of each diagnostic, its integration, data reduction procedures, and recent PBFA-II data will be discussed.
Apparatus for making A/B superlattice Langmuir–Blodgett films
Authors: Lin B. , Peng J. B. , Dutta P. , Ketterson J. B. , Wong G.
Published: July 2002

We report a modification recently made to a Langmuir–Blodgett superlattice apparatus previously described in this journal. The modification permits the preparation of so-called A/B superlattices consisting of the sequence ABAB⋅⋅⋅, where A and B are monolayers of two different film-forming molecules deposited into a multilayer structure.
A novel induction heater for chemical vapor deposition
Authors: Ong C. W. , Wong H. K. , Sin K. S. , Yip S. T. , Chik K. P.
Published: July 2002

We report how an induction cooker for household use can be modified for heating substrate or heating gases to high temperature in a chemical vapor deposition system. Only minor changes of the cooker are necessary. Stable substrate temperature as high as 900 °C was achieved with input power of about 1150 W.
Versatile setup for pressure and temperature-controlled time-resolved emission spectroscopy
Authors: Hiraga Takashi , Uchida Tatsuya , Kitamura Noboru , Kim Haeng-Boo , Ikeda Tomiki , Tazuke Shigeo
Published: July 2002

A versatile instrumental setup for time-resolved emission spectroscopy under variable pressure (1 atm–11 GPa) and variable temperature (77–400 K) was described. This setup, consisting of a diamond (or sapphire) anvil cell, was successfully interphased to a conventional fluorescence spectrometer, a gated diode-array system with nanosecond laser-pulse excitation, and a photon counting system excited with a cw YAG/dye laser system. The form of the sample for measurements can be either solid or liquid. Furthermore, the anvil cell can be used for IR spectroscopy by means of a FTIR spectrometer as well as for qualitative absorption spectroscopy. The performance was checked with a number of examples such as pressure and temperature effect on the time-dependent shift of emission from Ru(bpy)2+3 in viscous solution, pressure effect on a solid binuclear complex of platinum, and fluorescence behaviors of several organic molecules. Scope and limitation of this novel setup were discussed.
A new design of monopole field
Authors: Tu J. Y.
Published: July 2002

This article presents a new structure of monopole field on the basis of the method for obtaining ideal quadrupole fields within closed boundaries to which is applied a continuously varied potential with position. Further optimum design is made according to a large number of computations of boundary potentials by using the finite element method, and three sets of structures, termed as A-1, B-1, and B-2 type, respectively, are proposed. The agreement of the results obtained by a field-plotting method with those of the analysis is satisfactory.
Computer-aided data-acquisition system for thermal gradient mapping and calibrations of high-temperature cavities
Authors: Lutz W. N. , Gillies G. T. , Allison S. W.
Published: July 2002

We have designed, built, and tested a robust, thermocouple-based furnace calibration system having automated data acquisition and processing. The system can be used to produce maps of the thermal fields and gradients inside high-temperature cavities. The apparatus consisted of nine type K thermocouples mounted in a ceramic frame, an analog-to-digital interface board, a computer, NBS traceable calibration instrumentation, and software coded specially for the data acquisition and reduction. The absolute accuracy of the system was ±1.3 °C up to 300 °C, providing that the thermocouples had not previously been exposed to temperatures higher than that. The resolution of its gradient sensing ability was ±0.02 °C mm−1. We present details of its construction and operation, a front-to-back error analysis, and results of its use with a box furnace operated between 50 and 1200 °C.
Extracted beam composition with a mixed isotope feed to a neutral-beam system
Authors: Grisham L. R. , Falter H. D. , Hemsworth R. , Deschamps G.
Published: July 2002

Both the Tokamak Fusion Test Reactor and the Joint European Torus, two large magnetic confinement fusion devices, will use high-powered tritium beams. The suggestion has been made that tritium consumption could be reduced if tritium is only fed into the plasma source and deuterium or hydrogen is used as the neutralization target by operating with deuterium or hydrogen fed independently into the neutralizer. We report on measurements we performed with deuterium and hydrogen, and of the beam contamination that occurs in such an operating mode.
SR high-speed K-edge subtraction angiography in the small animal (abstract)
Authors: Takeda T. , Akisada M. , Nakajima T. , Anno I. , Ueda K. , Umetani K. , Yamaguchi C.
Published: July 2002

To assess the ability of the high-speed K-edge energy subtraction system which was made at beamline 8C of Photon Factory, Tsukuba, we performed an animal experiment. Rabbits were used for the intravenous K-edge subtraction angiography. In this paper, the actual images of the artery obtained by this system, are demonstrated. The high-speed K-edge subtraction system consisted of movable silicon (111) monocrystals, II–ITV, and digital memory system. Image processing was performed by 68000-IP computer. The monochromatic x-ray beam size was 50×60 mm. Photon energy above and below iodine K edge was changed within 16 ms and 32 frames of images were obtained sequentially. The rabbits were anaesthetized by phenobarbital and a 5F catheter was inserted into inferior vena cava via the femoral vein. 1.5 mℓ/kg of contrast material (Conlaxin H) was injected at the rate of 0.5 mℓ/kg/s. TV images were obtained 3 s after the starting point of injection. By using this system, the clear K-edge subtracted images were obtained sequentially as a conventional DSA system. The quality of the images were better than that obtained by DSA. The dynamical blood flow was analyzed, and the best arterial image could be selected from the sequential images. The structures of aortic arch, common carotid arteries, right subclavian artery, and internal thoracic artery were obtained at the chest. Both common carotid arteries and vertebral arteries were recorded at the neck. The diameter of about 0.3–0.4 mm artery could be clearly revealed. The high-speed K-edge subtraction system demonstrates the very sharp arterial images clearly and dynamically.
High flux VUV beamline for photochemical processing study at Photon Factory (abstract)
Authors: Tanaka K. , Kato H. , Kikuchi T. , Yagishita A.
Published: July 2002

Recent progress in photochemical processing involving photochemical etching and photochemical vapor deposition are really remarkable and such processes become the most promising candidates as a next-generation VLSI fabrication technology. Thus the study to elucidate the reaction mechanism of the photochemical processing is of both fundamental and technological importance. In order to promote this study, we have designed and constructed a new beamline at Photon Factory (BL 12C). It consists of three major parts; a prefocusing mirror, a multilayer mirror monochromator, and a differential pumping system. A Pt-coated SiC toroidal mirror (Rh:0.539 m, Rv:490 m) is installed in a prefocusing mirror chamber (18.3 m from the source), accepts 5.0-mrad horizontal and 1.0-mrad vertical divergence of the synchrotron radiation, reflects it 3.8° upward, and focuses it onto the middle of the exit arm of the monochromator (32.3 m from the source). A multilayer mirror, which was designed and fabricated by Yamamoto et al., so as to get high reflectance around 100 eV of photon energy (see the preceding paper), is installed in the monochromator, steers SR beam downward, and selects photon energy by changing an incident angle. With this arrangement, a quasimonochromatic and bright beam is obtained in the energy region 80–100 eV. The output flux is expected to be ∼1015 photons/s⋅10% bw with 200-mA ring current.
Versatile low-cost digital lock-in amplifier suitable for multichannel phase-sensitive detection
Authors: Carrato S. , Paolucci G. , Tommasini R. , Rosei R.
Published: July 2002

A simple computer-controlled digital lock-in amplifier is presented. It has been designed as an interface for a personal computer with a minimum number of components. Its simplicity and the fact that all parameters are computer controlled makes the amplifier well suited for multichannel phase-sensitive detection. A comparison with a commercial analog lock-in amplifier is presented.
Dedicated x-ray scintillation detector for digital subtraction angiography using synchrotron radiation
Authors: Dementiev E. N. , Dolbnya I. P. , Zagorodnikov E. I. , Kolesnikov K. A. , Kulipanov G. N. , Kurylo S. G. , Medvedko A. S. , Mezentsev N. A. , Pindyurin V. F. , Cheskidov V. G. , Sheromov M. A.
Published: July 2002

A one-coordinate x-ray detector for digital subtraction angiography using synchrotron radiation is described. It comprises two x-ray-sensitive lines, each having 128 independent channels of scintillation counters. The detector is designed to simultaneously measure the intensities of two linear monochromatic beams being 8–10 mm distant from each other. The spatial resolution of each line ranges from 0.2 to 2 mm. The maximum counting rate is 6 MHz for each channel, and the detection efficiency of the 33.2-keV quanta is close to 100%. Preliminary results of the testing of the detector channels on synchrotron radiation beam are given.
Exposure instrumentation for the application of x-ray lithography using synchrotron radiation
Authors: Oertel H. , Huber H.-L. , Schmidt M.
Published: July 2002

This paper reviews the recent progress in the development of exposure equipment for x-ray lithography consisting of compact synchrotron radiation source, beamline, and x-ray stepper. This exposure facility is situated door by door to a CMOS-pilot line. The compact storage ring COSY, under assembly in Berlin, is described and calculations are presented, that show that relatively low accumulated current exposure times of some seconds can be expected using a highly sensitive x-ray resist. A simple, inexpensive, and highly reliable beamline has been realized to connect an x-ray stepper and a light source. Several x-ray steppers have been installed for field testing in the nearby lithography laboratory at BESSY, that are equipped with x-ray reflecting mirrors, or a scanning mask and wafer unit for full-field exposure.