bluuebunny/crossref_metadata_2025 huggingface dataset:
Atomic hydrogen-induced interface degradation of reoxidized-nitrided silicon dioxide on silicon
Authors: Cartier E. , Buchanan D. A. , Dunn G. J.
Published: July 2002

Remote hydrogen plasma exposure is used to study the transport of atomic hydrogen, H0, through reoxidized-nitrided oxides and SiO2 and to quantify H0-induced degradation of their interfaces with silicon. It is directly demonstrated that (1) H0 is extremely reactive and produces large numbers of interface states; (2) the transport of H0 to the silicon/oxide interface is strongly suppressed in reoxidized-nitrided oxides; and (3) this suppression of the H0 transport is mainly responsible for the much slower interface degradation of reoxidized-nitrided oxides during high-field, hot-electron stress as compared to thermal oxide.
Growth temperature dependence of the Si(001)/SiO2 interface width
Authors: Tang Mau-Tsu , Evans-Lutterodt K. W. , Green M. L. , Brasen D. , Krisch K. , Manchanda L. , Higashi G. S. , Boone T.
Published: July 2002

The growth temperature dependence of the thin thermally oxidized Si(001)/SiO2 interface width was studied using synchrotron x-ray diffraction. Nine samples with oxide thickness of about 100 Å were studied, with growth temperatures ranging from 800 to 1200 °C. The oxides were prepared by rapid thermal oxidation. We found that interfacial roughness decreases linearly with increasing growth temperature, with a measured interface width of 2.84 Å for the sample grown at 800 °C, and 1.76 Å when grown at 1200 °C.
Period-doubling route to chaos in a semiconductor laser subject to optical injection
Authors: Simpson T. B. , Liu J. M. , Gavrielides A. , Kovanis V. , Alsing P. M.
Published: July 2002

Experimental measurements and a single-mode analysis of a quantum-well laser diode subject to strong optical injection are combined to demonstrate that the diode follows a period-doubling route to chaos. All laser parameters used in this model, including the influence of spontaneous emission noise, were experimentally determined based on the four-wave mixing technique. The transition to chaos can be used to reduce the uncertainty in the value of the linewidth enhancement factor.
Tunable quasi-phase matching using dynamic ferroelectric domain gratings induced by photorefractive space-charge fields
Authors: Kewitsch Anthony S. , Segev Mordechai , Yariv Amnon , Salamo Gregory J. , Towe Terrence W. , Sharp Edward J. , Neurgaonkar Ratnakar R.
Published: July 2002

We demonstrate a method of dynamic, tunable quasi-phase matched second-harmonic generation using optically induced polarization gratings with periods equal to twice the coherence length. These gratings increase the peak second-harmonic conversion efficiency by a factor of 17 above a poled strontium barium niobate crystal, to 0.01% for fundamental beam intensities of 0.8 MW cm−2. We generate quasi-phase matching spectral response peaks as narrow as 0.175 nm and tailor the response by writing an ensemble of gratings in the same volume, each of which enhances the second-harmonic generation at a predetermined wavelength.
Electrochemical capacitance-voltage analysis of delta-doped pseudomorphic high electron mobility transistor material
Authors: Stutz C. E. , Jogai B. , Look D. C. , Ballingall J. M. , Rogers T. J.
Published: July 2002

This work shows how electrochemical capacitance-voltage (EC-V) measurements can be used to evaluate delta-doped pseudomorphic high electron mobility transistor material. These EC-V measurements are compared with magnetic-field-dependent Hall effect (M-Hall) measurements and a self-consistent Poisson/k⋅p calculation of the band structure and electron concentration. The EC-V technique can clearly delineate the cap layer, the delta-doped layer, and the InxGa1−xAs channel layer, whereas the M-Hall method characterizes only the cap and InxGa1−xAs channel layers. The amount of electron charge seen by the EC-V and M-Hall measurements show good agreement with theory.
Nonalloyed ohmic contacts on GaN using InN/GaN short-period superlattices
Authors: Lin M. E. , Huang F. Y. , Morkoç H.
Published: July 2002

It is well known that ohmic contacts on GaN, a highly promising material for electronic and optoelectronic devices with a wide band gap of about 3.4 eV, constitute a major obstacle to further development of devices based on this material. We demonstrated a novel scheme of nonalloyed ohmic contacts on GaN using a short-period superlattice (SPS), composed of GaN and narrow band-gap InN, sandwiched between the GaN channel and an InN cap layer. Comparison with a similar layer without the SPS structure indicates that quantum tunneling through the SPS conduction band effectively reduces the potential barrier formed by the InN/GaN heterostructure leading to low contact resistivities. From the transmission-line-method measurements, specific contact resistances as low as 6×10−5 Ω cm2 with GaN doped at about 5×1018 cm−3 have been obtained without any post-annealing. Theoretical estimation based on the SPS tunneling model is consistent with the experiment.
Noise suppression for photorefractive image amplification in the LiNbO3:Fe crystal sheet
Authors: Xu Jingjun , Zhang Guangyin , Liu Simin , Liu Junmin , Men Liqiu
Published: July 2002

The dependence of competition between the forward scattering light and climbing light in the LiNbO3:Fe crystal sheet on the incident angle of the pump light beam is discussed. On the basis of the light climbing and beam size effects, a new method for a low-noise, high-gain image amplification in thin crystal is described.
Experimental comparison of strained quantum-wire and quantum-well laser characteristics
Authors: Tiwari Sandip , Woodall Jerry M.
Published: July 2002

Measured gain compression, differential gain, and damping of strained quantum wire lasers are reported and related to attributes specifically traceable to carrier confinement in two dimensions. A comparison is made with the properties of ridge lasers grown simultaneously. Damping and K factors are found to be comparable in the two structures. The differential gain is found to increase by two orders of magnitude (from 2.1×10−15 to 1.5×10−13 cm2), but the most significant consequence is an order of magnitude increase in gain compression (from 2.5×10−17 to 1.8×10−16 cm3), which limits the bandwidth. Carrier occupation, relaxation, recombination from multiple subbands, intersubband processes, high photon density, and consequent carrier heating and spatial hole burning effects in quantized structures are conjectured to cause some of the observed characteristics.
Pulsed excimer laser ablation of (Pb,La)TiO3 thin films for dynamic random access memory devices
Authors: Rao G. Mohan , Krupanidhi S. B.
Published: July 2002

Polycrystalline (Pb,La)TiO3 thin films were deposited by pulsed excimer laser ablation on Si and Pt coated Si substrates. The crystallinity of the films showed dependence on the annealing temperature and oxygen pressure during ablation. Similar trends reflected in the dielectric behavior in terms of varying dielectric permittivity between 430–620 as the ablation pressure varied between 1 and 100 mTorr. Films exhibited the presence of ferroelectricity in terms of hysteresis in capacitance-voltage characteristic in a metal-ferroelectric-metal configuration. The charge storage density estimated from the polarization measurements was about 10 μC/cm2, while a leakage current density of 10−8 A/cm2 was observed at an applied field of 100 kV/cm.
Comparison of the chemical structure and composition between N2O oxides and reoxidized NH3-nitrided oxides
Authors: Bhat M. , Ahn J. , Kwong D. L. , Arendt M. , White J. M.
Published: July 2002

The chemical structure and composition of ultrathin N2O oxides have been investigated using angle resolved x-ray photoelectron spectroscopy and compared to those of reoxidized NH3-nitrided SiO2. It is found that N2O oxide shows a second nitrogen-related bond (N—O bonds) in close proximity to the SiO2/Si interface in addition to the typically observed Si—N bonds in reoxidized NH3-nitrided SiO2. In addition, the change of the difference between Si 2p and O 1s binding energies in the N2O oxide and reoxidized NH3-nitrided SiO2 with the take-off angle is negligible due to the interfacial nitrogen incorporation.
29.5%-efficient GaInP/GaAs tandem solar cells
Authors: Bertness K. A. , Kurtz Sarah R. , Friedman D. J. , Kibbler A. E. , Kramer C. , Olson J. M.
Published: July 2002

We report on multijunction GaInP/GaAs photovoltaic cells with efficiencies of 29.5% at 1-sun concentration and air mass (AM) 1.5 global and 25.7% 1-sun, AM0. These values represent the highest efficiencies achieved by any solar cell under these illumination conditions. Three key areas in this technology are identified and discussed; the grid design, front surface passivation of the top cell, and bottom surface passivation of both cells. Aspects of cell design related to its operation under concentration are also discussed.
Photoconduction in fullerene films
Authors: Könenkamp R. , Erxmeyer J. , Weidinger A.
Published: July 2002

We report results from a detailed study of photoconduction in C60 films. At low temperatures the photoaction spectra show vibrational coupling to the first electronic transition, indicating that the generation of mobile carriers in the solid involves molecular excitation schemes. The lowest energy transition is found to occur at photon energies of ∼1.8 eV. Below this energy, only weak and field-dependent photoresponse is observed. We attribute this to a tail of localized states related to defects in the film. The edge between localized and extended states approximately coincides with the first vibronic peak. From this peak we find the photoconduction edge of the film to be 1.81±0.01 eV at room temperature in the face-centered-cubic phase and 1.85±0.01 eV in the simple cubic phase below ∼200 K.
〈100〉 dark line defect in II-VI blue-green light emitters
Authors: Guha S. , Cheng H. , Haase M. A. , DePuydt J. M. , Qiu J. , Wu B. J. , Hofler G. E.
Published: July 2002

We have carried out a microstructural study of the 〈100〉 dark line defect that forms during degradation of II-VI blue-green light emitters. We find that these defects lie in or near the ZnCdSe quantum well and do not correspond to a readily observable dislocation network in transmission electron microscopy studies. We speculate that they may consist of point defects or small point defect complexes. We have also carried out estimates of point defect migration rates during device operation that can give rise to such degradation.
Electrical deactivation of arsenic as a source of point defects
Authors: Rousseau P. M. , Griffin P. B. , Plummer J. D.
Published: July 2002

The effect of electrical deactivation of arsenic in silicon has been studied. High concentrations of arsenic were implanted and laser melt annealed, creating boxlike fully electrically active arsenic layers, with no residual implant damage. Wafers were then subjected to low temperature thermal cycles while a buried boron layer monitored point defects. Strong enhancements in the boron diffusion were observed suggesting that arsenic deactivation releases large numbers of interstitials. This is explained by a process where the vacancies required by the deactivated arsenic structures are created through a deactivation assisted Frenkel pair generation process, thus injecting interstitials.
Mechanisms of implant damage annealing and transient enhanced diffusion in Si
Authors: Cowern N. E. B. , van de Walle G. F. A. , Zalm P. C. , Vandenhoudt D. W. E.
Published: July 2002

Interactions between self-interstitials (I) and {113} interstitial defects during annealing of Si implant damage have been studied. At low damage levels diffusion is ultrafast, driven by I released direct from the ion collision cascade. At higher damage levels, free I are quenched by nucleation of {113} defects. We show that the transient enhanced diffusion seen in most previous studies arises from the subsequent dissolution of the {113} defects.
Persistent room-temperature relaxation of InP amorphized and compacted by MeV ion beams
Authors: Cliche L. , Roorda S. , Masut R. A.
Published: July 2002

Ion beam induced deformation and compaction has been observed in InP, amorphized by MeV Se ion implantation. The initial density of amorphous InP is 0.55%±0.05% larger than that of crystalline InP. During a period of two months, most of the excess density is lost in a spontaneous, room-temperature relaxation. This relaxation can be described by two time constants: τ1≊8±2 h and τ2≊14±1 days.
Shock wave and plasma dynamics in a surface discharge flash lamp
Authors: Chazaud F. , Sentis M. L. , Le H. C. , Rigneault H. , Delaporte Ph. C. , Marine W. I.
Published: July 2002

Shock waves and plasma dynamics induced by an open discharge called a ‘‘formed-ferrite-plasma’’ source result in intense radiation from the visible to the vacuum ultraviolet region. An experimental study of both the shock waves and plasma expansions from the ferrite surface has been carried out as a function of electrical energy deposition and of background argon pressure. We show that the propagation of the shock wave is accurately described by the following expression: R=b(E/ρ0)αtn, where R is the distance of the shock front from the surface of the ferrite; E the deposited energy; ρ0 the density of background gas; b, α, and n three constants, and t the time.
Temperature dependence of second harmonic generation from Si(100)(2×1) surfaces
Authors: Jiang H. B. , Liu Y. H. , Lu X. Z. , Wang W. C. , Zheng J. B. , Zhang Z. M.
Published: July 2002

Our experiments on reconstructed Si(100)(2×1) surfaces revealed that the reflected second harmonic (SH) signals at 532 nm originated from the contribution of the electrons in surface states. The SH intensity was inversely proportional to the square of the sample temperature. A preliminary explanation for this temperature dependence was proposed.
In situ photoluminescence spectral study of porous Si in HF aqueous solution
Authors: Wadayama T. , Yamamoto S. , Hatta A.
Published: July 2002

Time-dependent change in the visible luminescence of porous Si immersed in HF aqueous solution was measured in a short acquisition time (5 s) with a charge coupled device detector. Under Ar+ laser light (514.5 nm) irradiation, the photoluminescence band of the porous Si shifted to shorter wavelength accompanying a reduction of the peak intensity. The result suggests that the size of the Si nanostructure is closely related to the gap energy of the porous Si.
On the generation of interface states from electron-hole recombination in metal-oxide-semiconductor capacitors
Authors: Buchanan D. A.
Published: July 2002

In this study, we have measured the interface state generation rate resulting from the recombination of free electrons and trapped holes, which occurs either away from or near the silicon/silicon dioxide interface. For recombination events that occur away from the silicon/silicon dioxide interface (by using hole trapping on bulk-oxide ion-implanted arsenic sites), we find an interface state generation rate of approximately 0.024 states per recombination event. For recombination near the silicon/silicon dioxide, the generation rate increases by more than an order of magnitude to approximately 0.27 states per event. Therefore, interface states are more readily produced from electron/hole recombination events that occur near the Si/SiO2 interface.
Narrowing of the intersubband electroluminescent spectrum in coupled-quantum-well heterostructures
Authors: Faist Jérôme , Capasso Federico , Sirtori Carlo , Sivco Deborah L. , Hutchinson Albert L. , Chu Sung Nee G. , Cho Alfred Y.
Published: July 2002

We show that the introduction of a setback between the active region and the dopants has a dramatic effect on the spectrum of quantum-well intersubband electroluminescence at cryogenic temperatures, namely a strong blue shift and narrowing of the emission line. This is accompanied by a change of line shape from Gaussian to Lorentzian. A remarkable electric-field induced narrowing of the electroluminescent spectrum down to a width of 21 meV is also observed.
Influence of indium segregation on the emission from InGaAs/GaAs quantum wells
Authors: Yu Haiping , Roberts Christine , Murray Ray
Published: July 2002

Indium segregation in InxGa1−xAs/GaAs (0.05<x<0.25) quantum wells grown by molecular beam epitaxy has been investigated using low temperature photoluminescence. Additional features at low energy are evident in some of the spectra that are consistent with trapping of free excitons by In-rich islands at the top interface, which occurs as the result of In segregation.
Transmission electron microscopy observation of interfacial reactions in high-temperature sputtered Al alloy/TiN system
Authors: Okihara M. , Hirashita N. , Hashimoto K. , Onoda H.
Published: July 2002

Transmission electron microscopy was used to study the interfacial reactions and crystallographic structure in high-temperature sputtered Al alloy/TiN system. An intermediate layer and semispherical precipitates were observed as the reaction products during high-temperature sputtering at 500 °C. Electron diffraction analysis indicated that the intermediate layer consisted of hexagonal AlN and cubic TiN. Semispherical precipitates were also found to consist of tetragonal Al3Ti. Additional energy dispersive x-ray spectrometer analysis suggested that the intermediate layer was formed by the diffusion of Al atoms into the TiN film.
Structural study of defects induced during current injection to II–VI blue light emitter
Authors: Tomiya S. , Morita E. , Ukita M. , Okuyama H. , Itoh S. , Nakano K. , Ishibashi A.
Published: July 2002

We have carried out structural studies of nonluminescent areas developed by current injection in ZnMgSSe alloy-based II–VI blue light emitting diodes by electroluminescence topography and transmission electron microscopy. The nonradiative regions, which spread out in the 〈100〉 direction during current injection, consist of a high density of dislocation dipoles and dislocation loops. The source of these defects is the preexisting stacking faults originating at the substrate/epilayer interface. The dipoles themselves are aligned along both of the 〈110〉 directions lying in the {111} plane. Their Burgers vectors were of the type (a/2)〈011〉 inclined at 45° to the (001) junction plane.
Appearance of vertical dihydrides on a silicon surface while dissolving the surface oxide layer in hot water
Authors: Watanabe Satoru , Sugita Yoshihiro
Published: July 2002

Removal of surface oxides from a partially oxidized Si(111) surface, and simultaneous termination of the new dangling bonds by hydrogen in hot water with a 0.004 ppm concentration of dissolved oxygen, was observed. During removal for up to 60 min, vertical dihydrides at step edges appeared on the hydrogen-terminated surface. From observing selective removal of vertical dihydrides from an oxygen-free hydrogen-terminated surface, the appearance of vertical dihydrides at step edges shows the existence of the dihydride creation reaction, while the oxides are dissolved in water.
Picosecond multiwavelength optical parametric generation in lithium triborate
Authors: Liu Xiang , Xu Zuyan , Wu Baichang , Chen Chaungtian
Published: July 2002

The retracing behavior of the phase-matching angle (RBPA) in optical parametric generation (OPG) based on a LiB3O5 (LBO) crystal and pumped at 532 nm by a frequency doubled, passive-active mode-locked Nd:YAG laser is investigated. Two pairs of radiations, which are simultaneously generated in the OPG, are observed and the spectral radiant power of the four tunable beams are obtained, showing good agreement with the theoretical calculation results. Together with the parametric process, two kinds of frequency-mixing waves are produced and this novel multiwavelength interaction phenomenon is analyzed.
Domain topography of antiferromagnetic Cr2O3 by second-harmonic generation
Authors: Fiebig M. , Fröhlich D. , Sluyterman v. L. G. , Pisarev R. V.
Published: July 2002

The interference of the time-invariant magnetic-dipole contribution with the time-noninvariant electric-dipole contribution to the second harmonic (SH) provides a mechanism which is sensitive to the reduction of symmetry of Cr2O3 by antiferromagnetic ordering of spins. A pronounced polarization dependence of the SH on the sign of the order parameter is observed in the 1.7–3.1 eV spectral range. The effect is used to study the domain structure of Cr2O3 by use of a CCD camera. Exposure times in the order of minutes are sufficient to yield a high-resolution image of domains in samples of 10 mm2.
Giant magnetoresistance at 300 K in single crystals of La0.65(PbCa)0.35MnO3
Authors: Liu J. Z. , Chang I. C. , Irons S. , Klavins P. , Shelton R. N. , Song K. , Wasserman S. R.
Published: July 2002

Giant magnetoresistance (GMR) at 300 K and 5.5 T with ΔR/R(0)=74% was observed in single crystals of La0.65(PbCa)0.35MnO3. The maximum GMR occurs exactly at the ferromagnetic–paramagnetic phase transition temperature (Tc). For T<Tc, the R(T) curve is closely related to the M(T) curve. A sign change in the curvatures of R(H) curves below and above Tc has been observed, indicating that two different mechanisms are responsible for the magnetic scatterings of the carriers in two separate temperature regions.
Epitaxial growth of single-crystal (La,Ca)MnO3 thin films
Authors: Zeng X. T. , Wong H. K.
Published: July 2002

Single-crystal films of perovskitelike (La,Ca)MnO3 with very smooth surface were grown epitaxially on (110) NdGaO3 substrates by a simple facing-target sputtering technique. Their in-plane and out-of-plane crystal structures were examined by means of a novel double-crystal x-ray diffraction technique. The c axis of the samples lay in the film plane. All rocking curves were found to have a full width at half-maximum of about 0.01° which is smaller than all reported structure data for ceramic thin films.
Large aperture, high-speed calorimeter for high-energy optical pulses
Authors: Niimura M. , Dooling J. , Zich R. L. , Brock R. N. , York T. M.
Published: July 2002

A radiometric calorimeter is described in which the energy absorber works at the same time as a temperature sensor so that thermal equilibrium for the entire volume of absorber is not required before measuring an incident energy. The achievable frequency response is therefore quite high, and this is not offset by the size and/or damage threshold of energy receiver. The device, formerly called Rat’s Nest Calorimeter (RNC), has been found quite useful for measuring the total energy of modern pulsed lasers with a large beam cross section. The aperture (presently 6 cm) can be increased arbitrarily without degrading the rise time. Excellent stability and high damage threshold (≫439 MW/cm2) result when a thick wire bolometer and amplifier combination is used. Response time (∼9 μs) and spectral flatness are much better than previously reported. Potentials of the RNC for measuring any energy which it absorbs up to 2 kJ at the rise time 60 ns (∼10 MHz) are discussed. The maximum sensitivity of the model 3.5 mJ/cm2 is sufficient to detect the radiative energy emitting from today’s fusion test plasmas.
Use of an optical multichannel analyzer for recording absorption spectra of short-lived transients
Authors: Hunter E. P. L. , Simic M. G. , Michael B. D.
Published: July 2002

Characteristics of an adapted commercial optical multichannel analyzer system for recording of transient absorption spectra in single-shot pulse radiolysis and flash photolysis are described. The features discussed include temporal (2 μs) and spectral (1 nm) resolution, signal-to-noise ratio and its improvement, linearity of response, and wavelength coverage (300–650 nm). The system is intermediate in both cost and capabilities compared to two other methods: (1) recording transient spectra by repetitive pulsing and (2) using an image converter streak camera. This system is convenient for discrimination of small differences in fine structured absorption of spectra short-lived species.
Electrodynamic thermogravimetric analyzer
Authors: Spjut R. Erik , Bar-Ziv Ezra , Sarofim Adel F. , Longwell John P.
Published: July 2002

The design and operation of a new device for studying single-aerosol-particle kinetics at elevated temperatures, the electrodynamic thermogravimetric analyzer (EDTGA), was examined theoretically and experimentally. The completed device consists of an electrodynamic balance modified to permit particle heating by a CO2 laser, temperature measurement by a three-color infrared-pyrometry system, and continuous weighing by a position-control system. In this paper, the position-control, particle-weight-measurement, heating, and temperature-measurement systems are described and their limitations examined.
Beam extraction experiments from microwave ion sources
Authors: Tokiguchi K. , Sakudo N. , Koike H.
Published: July 2002

With the aim of designing a new ion source for ampere-class beams, the beam extraction characteristics of standard coaxial-type microwave ion sources were investigated in detail at energies lower than 10 keV. It was found that this source has the capability of providing Ar+ beams of 200 mA at the acceleration voltage of 7.0 kV and the microwave power of 850 W. The obtainable beam current increases with a decrease of gap width between positive and negative electrodes. Moreover, it is shown that the microwave ion source is suitable for obtaining high-current beams of single-charged ions. Both the plasma source and extraction electrode diameters for 1-A beam are estimated to be about 13 cm. The required microwave power is about 6 kW.
Low-energy diffuse scattering electron-spin polarization analyzer
Authors: Unguris J. , Pierce D. T. , Celotta R. J.
Published: July 2002

A new, compact (approximately fist sized), efficient electron-spin analyzer is described. It is based on low-energy (150 eV) diffuse scattering from a high-Z target, for example, an evaporated polycrystalline Au film opaque to the incident electron beam. By collecting a large solid angle of scattered electrons, a figure of merit S2I/I0=10−4 is achieved with an analyzing power S=0.11. The figure of merit degrades only marginally (<10%) for beams with an energy width of 40 eV or after one month of operation at 10−8 Torr. The electron optical acceptance is of order 100 mm2 sr eV. The details of the design and construction are discussed and its performance is compared to six other spin analyzers. Illustrative results are presented from an application to scanning electron microscopy with polarization analysis (SEMPA) to image magnetic microstructure.
Magnetic field alignment studies for the URAGAN-3 torsatron
Authors: Colchin R. J. , Harris J. H. , Lee D. K. , Rome J. A. , Fedotov S. I. , Ozherel’ev F. I. , Pavlichenko O. S. , Pogozhev D. P. , Zalkind V. M. , Treffert J. D.
Published: July 2002

If the major axes of the helical and vertical field coils of a torsatron plasma confinement device are not aligned to within ∼1% of their major radii, the resulting error field can break up closed magnetic flux surfaces and reduce the effective plasma confinement volume. A novel technique for accurately locating the magnetic symmetry axes of torsatron helical and vertical coil sets to within ∼1 mm using magnetic field measurements near the device major axis (i.e., away from the confinement volume) is described and applied to the URAGAN-3 torsatron. The axis of the vertical field coil set was found to be shifted by ∼1 cm relative to the axis of the helical coil set; this shift could account for the reduced confinement volume observed in previous experiments. The magnetic measurements were repeated after coil repositioning to verify correct alignment.
Formation of negative ions in Cs sputter sources
Authors: Yntema J. L. , Billquist P. J.
Published: July 2002

A surface ionization model with three-body interaction is used to explain the mass spectra of negative ions from Cs sputter sources as well as their time dependence. The importance of the high diffusion rate from radiation-damaged volumes is illustrated and the difficulties these may cause in quantitative mass spectroscopy with Cs sputter sources are discussed. The anomalously large emittance of single negative ions compared to clusters is ascribed to the surface formation and breakup of negative dimers. An example of negative molecule formation which does not proceed by a surface reaction is given.
Heat pulse line-source method to determine thermal conductivity of consolidated rocks
Authors: Fernandez M. , Banda E. , Rojas E.
Published: July 2002

An instrument designed to measure thermal conductivity of consolidated rocks, dry or saturated, using a transient method is presented. The instrument measures relative values of the thermal conductivity, and it needs calibration to obtain absolute values. The device can be used as heat pulse line source and as continuous heat line source. Two parameters to determine thermal conductivity are proposed: TMAX, in heat pulse line source, and SLOPE, in continuous heat line source. Its performance is better, and the operation simpler, in heat pulse line-source mode with a measuring time of 170 s and a reproducibility better than 2.5%. The sample preparation is very simple on both modes. The performance has been tested with a set of ten rocks with thermal conductivity values between 1.4 and 5.2 W m−1 K−1 which covers the usual range for consolidated rocks.
Negative hydrogen ion extraction and electron control in a multipole ion source
Authors: Nightingale M. P. S. , Holmes A. J. T. , Johnson J. D.
Published: July 2002

A dc negative ion facility has been built to study both the mechanisms controlling H− production in multipole volume sources and the design of accelerators for negative ion beams. After a 7.5-cm movement of the extraction aperture position within the ion source, the arc current and source gas pressure were optimized, and an H− current of 10 mA was extracted from a 0.5-cm2 circular aperture in a 30-s pulse from a 100-A, 90-V discharge run at 18.8 mT. This is the first operation of such sources to provide a quasi-dc current of 20 mA cm−2. The installation of an octupole electron trap in the beam forming electrode has lowered the electron current extracted simultaneously with the H− beam by approximately a factor of 4, and this has led to a low H− beam divergence. The application of a small bias voltage of up to 2 V between the beam forming electrode and the anode has reduced this electron current still further (by more than a factor of 10) while maintaining the extracted ion current. It is now possible to extract ion currents from such a source/accelerator configuration that are larger than the accompanying electron current.
Debris collection from implosion of microballoons
Authors: Prussin S. G. , Lane S. M. , Richardson M. C. , Noyes S. G.
Published: July 2002

Recovery of krypton from implosion of glass microballoons has been studied in the development of a radiochemical diagnostic for determination of 〈ρr〉fuel. Collection onto metal surfaces following implosions performed on the OMEGA laser with 1–3 TW (1–2 kJ) of 0.35-μm light is consistent with an ion implantation mechanism. The dependence of the intrinsic collection efficiency on the energy fluence to the collector surface and its variation in implosions carried out under the same nominal conditions indicate ion energies extending to at least 0.1 MeV and energy distribution functions that are sensitive to the details of the implosion dynamics. Intrinsic sticking efficiencies approaching 0.5 can be obtained in the limit of low total energy fluence to the collector surface (≤0.1 J cm−2).
Characteristics of uranium-oxide cathode for neutron streak camera
Authors: Niki H. , Itoga K. , Miyanaga N. , Yamanaka M. , Yamanaka T. , Yamanaka C. , Iida T. , Takahashi A. , Sumita K. , Kinoshita K. , Takiguchi Y. , Hayashi I. , Oba K.
Published: July 2002

Detection efficiency and secondary electron yield of the uranium-oxide cathode for a neutron streak camera were measured and found to be 2.3×10−7–1.6×10−6 events/neutron/μm and 60–150/fission, respectively. These measurements were performed for 14-MeV neutrons from a D-T neutron source (OKTAVIAN) by using neutron-imaging techniques. By defocusing an image due to a single fission event, each electron from the cathode was clearly distinguished, and the number of electrons could be counted. From the neutron images in the streak-mode operation, time dispersions due to the electron transit-time spread fell in the range of estimated values.
Nuclear reaction diagnostics of fast confined and escaping alpha particles
Authors: Cecil F. E. , Medley S. S. , Nieschmidt E. B. , Zweben S. J.
Published: July 2002

The resonant nuclear reactions D(α,γ) 6Li, 6Li(α,γ) 10B, and 7Li(α,γ) 11B are examined as diagnostics of the energy distribution of confined fast alpha particles in tokamak plasmas. Reaction rates for Q=1 D-T plasmas are estimated. The design of and preliminary results from the prototype fusion gamma ray detector on the tokamak fusion test reactor (TFTR) will be presented. The activation reactions 10B(α,n) 13N, 14N(α,γ) 18F, 25Mg(α,p) 28Al, and 27Al(α,p) 30P are similarly examined as diagnostics of fast escaping alpha particles. Count rate estimates for Q=1 D-T plasmas will be presented.
Third-order correlator for point processes
Authors: Basano L. , Ottonello P.
Published: July 2002

We present a triple correlator for point processes in which a long batch of pulses is first recorded by direct memory access (DMA) and subsequently analyzed by a microcomputer. Provision is also made for the retrieval of the second-order correlation function. Applications to the statistical analysis of level crossings by random noise are briefly outlined.
Measurement of the spin-wave instability threshold hcrit in microwave ferrites
Authors: Zhang Y. T. , Patton C. E. , Srinivasan G. , White G. O. , Brower C. J. , Edmondson C. A.
Published: July 2002

Several improvements for a previously described semiautomated system for spin-wave instability threshold measurement in microwave ferrites are described. The effects of sample size, sample position in the microwave cavity, and method of data interpretation on the threshold field hcrit are also reported. The data were obtained by the parallel pumping technique at 8.92 GHz. Sphere-shaped samples of polycrystalline yttrium iron garnet were used for the measurements. The results show that the initial, ‘‘exact’’ instability onset, the ‘‘extrapolated’’ onset from the loss increase above threshold, and the ‘‘visual’’ onset estimate from the above threshold response can vary by more than 0.5 Oe for hcrit values of 3 Oe or so. Large samples, above 1 mm in diameter, lead to an overestimation of hcrit due to errors in the microwave cavity perturbation theory analysis which forms the basis of the measurement. The amount of overestimation is about 0.1 Oe for a diameter of 2 mm and 0.2 Oe at 3 mm. Sample position relative to the cavity end wall does not appear to be critical. Imaging effects are small for hcrit measurements in the YIG-like materials of interest here.
Electroformed nickel for thermometry and heating
Authors: Verbeke O. B. , Spinnewijn J. , Strauven H.
Published: July 2002

The electrical resistance of electroformed nickel films has been measured from 4 to 1373 K. An equation is suggested to represent the data of nickel and other pure metals such as platinum. The influence of the electroforming process on the residual resistance at low temperatures and of oxidation on the high-temperature stability of the nickel has been discussed. An electronic circuit for the simultaneous use of the nickel films as thermometer and heater is given.
New design of absolute gravimeter for continuous observations
Authors: Hanada H. , Tsubokawa T. , Takano S. , Tsuruta S.
Published: July 2002

We describe a new absolute gravimeter, which is suitable for long-term continuous observations. It uses laser interferometry to measure the acceleration of a falling corner cube with reference to atomic standards. Between drops, the corner cube is lifted to the top by rotating the vacuum pipe around a horizontal axis with an angular velocity high enough to keep the cube fixed by centrifugal force. This method has an enormous advantage for making a large number of measurements since there is no complicated mechanism inside the vacuum pipe. This absolute gravimeter seems to have no source of systematic error which will exceed one part in 109 if we can reduce the amplitude of the mechanical vibration to less than about 1.5 nm. We describe here the principle and the results of the experiments that we have made to date.
Ceramic nozzle for molecular acceleration and its temperature measurement
Authors: Danon Albert , Amirav Aviv
Published: July 2002

An all ceramic nozzle is described, based on a watch jewel and having a very small heated volume (V<10−3 cc). Using this nozzle, molecular catalytic and thermal decomposition is minimized; thus, high molecular kinetic energies can be obtained for ‘‘unstable’’ organic molecules. The real nozzle temperature is measured by the variation of its backing pressure with its temperature, keeping constant gas flux conditions. The nozzle is capable of being heated to over 1500 °K with less than 20 W and is thermally isolated from the organic molecule oven that is differentially heated and separately temperature controlled.
CCD camera as a multichannel analyzer for the spectral and azimuthal resolution of Fabry–Pérot fringes
Authors: Bunting C. A. , Carolan P. G. , Forrest M. J. , Noonan P. G. , Sharpe A. C.
Published: July 2002

The Fabry–Pérot interferometer is well known for its very favorable combination of high resolution and throughput. However, the radial dispersion of the spectrum makes multichannel detection difficult. Several systems have been devised that physically split the focal plane into annular elements, but these are normally limited to about ten channels while the Fabry–Pérot has potentially a much higher multichannel capability (e.g., the finesse is typically 20–50). In practice these devices have proved to be difficult to make. We have developed a more efficient and versatile technique where the interference pattern is focused onto a CCD array (640×1024 elements). The data can then be transformed to a circular coordinate system and, for example, provide the means of integrating all the information in selected annular ranges (i.e., a multichannel analyzer). The large number of pixels available enables a working finesse of up to 50 to be realized. The technique is particularly valuable for the detection of partial azimuthal fringes.
Impact response of the shorted quartz gauge to 40 kbar
Authors: Tang Z. P. , Gupta Y. M. , Bellamy P. M.
Published: July 2002

The response of shorted quartz gauges, 1.27 cm in diameter and 0.32-cm thick, to impact loading has been examined. Of particular interest was the increase in current with time, commonly referred to as current ramping. Data on the initial current jump from the present work and from earlier studies have been fitted using a piezoelectric current coefficient, k=(1.92+8.25×10−3σ) ×10−8 C/cm2/kbar. This fit, good to within ±2%, is valid to 40 kbar. The current ramping coefficient α was found to be linear with stress and was fitted over the same stress range as α=0.195+8.24×10−3σ, where σ is in kbar and α is in μs−1. Procedures to use the current and ramping calibration are described.
Titration cell and amalgam electrodes used in automated potentiometric measurements
Authors: Berggren Jan , Börtin Olle , Gobom Sylvia
Published: July 2002

Titration vessels, amalgam electrodes, and other assessments which are used in a computer-operated system for potentiometric titrations are described. The titrator is used to study complex formation in solution by means of high- and low-resistance electrodes and volumetric and coulometric addition of titrants. The computerized procedure is governed by a flexible program for the control of titration procedures, registration of data, and calculations.
Calibration of charged-particle analyzer fields
Authors: Smith John R. , Doggett Wesley O.
Published: July 2002

Calibration of charged-particle analyzer fields using a low-level alpha-particle source is described. Calibration factors for deflection in an electric and in a magnetic field were determined with a relative precision of 1%.
New sensor for measuring thermal conductivity in liquid metal by transient hot wire method
Authors: Nakamura Shin , Hibiya Taketoshi , Yamamoto Fumio
Published: July 2002

A new sensor has been developed for measuring thermal conductivity in liquid metal by transient hot wire method. A wire, which is formed in a thin alumina plate, was used for observing temperature rise of the wire, when a constant input power was applied to it. With this sensor, thermal conductivity for mercury in liquid state was measured at room temperature: 0.0918 W/cm/K. The result was in good agreement with reported values.
Simple overshoot-suppressed digital proportional-integral-derivative temperature controller
Authors: Chan C. K.
Published: July 2002

This note describes a simple but efficient algorithm for a digital PID temperature controller. A special reset mechanism is implemented to suppress the inevitable overshoot in a PID controller.
Design and experimental performance of a pulsed power transformer for liner implosion experiments
Authors: Yugami N. , Mizuguchi Y. , Shimoura K. , Imasaki K. , Miyamoto S. , Nakai S. , Yamanaka C.
Published: July 2002

A pulse power transformer has been designed and tested for pulsed power driven Z-pinch experiments. The transformer has reduced the output impedance of a pulsed power machine ‘‘Reiden IV’’ from 2 to 0.02 Ω. The parasitic inductance at the water/vacuum insulator is minimized by the transformer because of the lower output voltage. Therefore, it is possible to improve liner implosion efficiency. When the liner is impedance matched with the transformer, the efficiency is estimated to be ∼10% according to 0-D calculations of the equation of motion and the circuit equation. In experiments, a high current pulse (∼1 MA) was obtained. This value is twice as high as obtained when no transformer is used. Of key importance in the design of the transformer is the geometry of the secondary coil.
Low-noise interferometer for microwave radiometry
Authors: Timbie P. T. , Wilkinson D. T.
Published: July 2002

A novel type of interferometer has been developed for precision measurements in microwave radiometry. The system employs two low-noise heterodyne receivers based on SIS (superconductor–insulator–superconductor) tunnel junction mixers in the band from 40 to 50 GHz. The rectangular horn antennas have adjacent apertures and are coaligned; the IF outputs of the receivers are multiplied together. The resulting antenna interference pattern has lobes which lead to positive output signals and lobes which give negative output. The radiometer measures the difference in the power from these lobes without beam switching or instrument motion. Other major features are: the cancellation of instrumental signals (horn emission, sidelobe pickup, etc.); very low 1/f noise in the output; and zero output signal when viewing a uniform source. The system achieves a sensitivity of ΔTrms =14.4±1.4 mK/(Hz)1/2 and is used to search for anisotropy in the cosmic background radiation on angular scales between 1° and 5°.
Recoil implantation of radioactive transition metals and their investigation in silicon by deep-level transient spectroscopy
Authors: Achtziger N. , Gottschalk H. , Licht T. , Meier J. , Rüb M. , Reislöhner U. , Witthuhn W.
Published: July 2002

Radioactive isotopes are produced by nuclear reactions in a thin target foil. The recoiling products are directly implanted into samples mounted off-axis to the primary beam. Using proton or α beams and appropriate target foils, radioactive isotopes of Ti, V, Cr, Mn, and Co were implanted. The implantation parameters are presented and compared with other implantation techniques for radioactive isotopes. To demonstrate an application, a deep-level transient spectroscopy measurement on 48V in silicon is presented. Ti and V correlated band-gap levels were observed during the 48V decay.
Magnetic surface mapping with highly transparent screens on the Auburn torsatron
Authors: Hartwell G. J. , Gandy R. F. , Henderson M. A. , Hanson J. D. , Swanson D. G. , Bush C. J. , Colchin R. J. , England A. C. , Lee D. K.
Published: July 2002

In stellarator-type magnetic confinement devices (of which the torsatron is one), the magnetic field is produced entirely by external, current-carrying coils. Two methods for mapping magnetic surfaces in the Auburn torsatron were tested and compared, both of which involve the use of highly transparent screens. The first method consists of coating the screen with a phosphor that emits light when struck by electrons emitted by an electron gun. A pattern representative of a magnetic surface is formed on the screen, and this pattern is recorded photographically. The second method uses an uncoated screen to collect electrons emitted from an emissive probe, which is scanned over a poloidal cross section of the torus. Under certain conditions, the collected current is a constant over a particular magnetic surface so that a contour plot of the current versus position is equivalent to a plot of the magnetic surfaces. Parametric studies of the two methods are presented, and the effectiveness of each technique is discussed.
Comment on ‘‘Mass analyzed secondary ion microscopy’’ [Rev. Sci. Instrum. 5
8, 1789 (1987)]
Authors: Levi-Setti R.
Published: July 2002

A review article in the October 1987 issue of the Review of Scientific Instruments entitled: ‘‘Mass analyzed secondary ion microscopy,’’ by Mark T. Bernius and George H. Morrison, contains a number of incorrect statements and quotations that must be rectified. A table comparing the UC scanning ion microprobe and the Cornell stigmatic ion microscope is presented.
Versatile apparatus for low-energy and hyperthermal energy ion scattering spectroscopies
Authors: McEachern R. L. , Adler D. L. , Goodstein D. M. , Kimmel G. A. , Litt B. R. , Peale D. R. , Cooper B. H.
Published: July 2002

We have designed and constructed an apparatus that combines hyperthermal energy ion scattering (<100 eV) with low-energy ion scattering (a few hundred eV to several keV). The UHV scattering chamber possesses a full range of sample preparation and characterization capabilities, including LEED, Auger spectroscopy, a Kelvin probe for work function measurements, and facilities for gas or alkali-metal deposition. The differentially pumped beamline provides well-collimated, monoenergetic beams of gas or alkali-metal ions ranging in energy from <10 eV to 10 keV. To illustrate the qualitative changes in the scattering behavior observed over this range, we present experimental results for Na+ scattered off the Cu(110) surface with the incident ion energy ranging from 56 eV to 4 keV. We also show a comparison between 1 keV K+ and 1 keV Ar+ scattered from the same surface.
Nonlinearity corrections for amplitude measurement from Hadamard sums application to a rotating polarizer ellipsometer
Authors: Zalczer Gilbert
Published: July 2002

In a perfect system, the amplitude of a sinusoidal signal superimposed on a constant background can be determined from Hadamard sums. The simple computation described here allows us to correct a quadratic nonlinearity in the signal detection. Using this procedure, a commercial rotating-polarizer ellipsometer could be safely operated with signal levels increased by a factor of 15.