bluuebunny/crossref_metadata_2025 huggingface dataset:
Formulae for the rotational intensity distribution of 5Σ ↔ 5Π (int) transitions in diatomic molecules
Authors: Kovács I. , Antal J.
Published: April 2011

Explicit expressions are obtained for the intensity distribution in the 5Σ ↔ 5Π transitions, where the 5Π state may belong to the coupling case intermediate between Hund's cases (a) and (b). The observed intensity values of the 5Σ ↔ 5Π transition of the CrO molecule are compared with those calculated from the intensity formulae derived, and good agreement is found.
Interference effects in the spectrum of HD: II. The fundamental band for HD–rare gas mixtures
Authors: McKellar A. R. W. , Rich N. H.
Published: April 2011

The absorption spectrum of the fundamental band of HD (λ ≈ 2.7 μm) has been studied at high resolution in mixtures with the rare gases He, Ne, and Ar at low temperatures (77 and 145 K) and moderate densities (<205 amagat). Interference effects that occur between the collision-induced transitions and the dipole-allowed transitions of free HD were analyzed as a function of density and collision-partner. The R(0) and R(1)dipole transitions exhibited large changes in shape and intensity at high densities, but their behaviours were quite different from each other. Like the pure HD samples, the line shapes were well represented by series of Fano profiles, and the density dependences of the lines were well explained by the theory of Herman, Tipping, and Poll. These results should greatly improve the understanding of the physical processes underlying the interference effects.
Interference effects in the spectrum of HD: III. The pure rotational band at 77 K for HD and HD–Ne mixtures
Authors: McKellar A. R. W. , Johns J. W. C. , Majewski W. , Rich N. H.
Published: April 2011

The pure rotational R(0) transition of HD has been studied in pure HD and in HD–Ne mixtures at a temperature of 77 K and at densities between 3 and 123 amagat. Limited measurements of R(1) in pure HD were also made. A value of 8.18 ± 0.26 D was obtained for the R(0) permanent dipole moment of HD, in reasonable agreement with the theoretical value of 8.3 D. However, no evidence for destructive collisional interference effects at high densities was found, and in fact a slight constructive interference was noted. Thus, these results stand in contrast with those for the fundamental band, and with other recent experiments on the pure rotational band, in which destructive interference was invariably measured.
The S0(1) quadrupole line of H2
Authors: Cosmo V. De , Gush H. P. , Halpern M.
Published: April 2011

The frequency, line shape, and intensity of the S0(1) quadrupole absorption line of gaseous H2 have been measured in the pressure range 50–1500 Torr(1 Torr = 133.3 Pa), using a diode laser spectrometer. The line profile exhibits Dicke narrowing, the minimum width at a pressure near 100 Torr being about one-half the Doppler width. The variation of line width with pressure is not in complete agreement with theoretical models. The line frequency extrapolated to zero pressure equals 587.03202 ± 0.00021 cm−1, whereas the quadrupole moment deduced from the integrated intensity of the line equals [Formula: see text].
The electron paramagnetic resonance of methylene
Authors: Bernheim R. A.
Published: April 2011

The electron paramagnetic resonance studies of methylene arc reviewed. The structural information that resulted include verification of the triplet multiplicity of the electronic ground state, the discovery of a bent geometry for the molecule with a bond angle of 134°, measurement of the zero-field or fine-structure splitting parameters, measurement of the g-factor tensor, and measurement of the isotropic and anisotropic 13C hyperfine interaction. The results are compared with recent measurements obtained with laser magnetic resonance techniques and theoretical treatments.
Oxygen absorption in the spectral range 180–300 nm for temperatures to 3000 K and pressures to 50 atm.
Authors: Cann M. W. P. , Shin J. B. , Nicholls R. W.
Published: April 2011

Calculated oxygen absorption coefficients are given for the spectral range 180–300 nm, at a spectral resolution of 0.05 nm (instrumental function half-width) and with a spectral increment of 0.0125 nm. The results are presented for temperatures between 300 and 3000 K, and for pressures between 1 and 50 atm. The spectra were first calculated at high resolution, preserving the natural shape of the spectral lines, using line-by-line techniques and Voigt line shapes. Absorption processes considered include the Schumann–Runge and Herzberg 1 band and continuum systems, including the pressure-dependent component usually ascribed to the formation of the (O2)2 dimer. The results were degraded before use, which allowed several approximations to be introduced into the computing procedures; these are discussed.
The Δk = ±2 "forbidden band" and inversion–rotation energy levels of ammonia
Authors: Urban Š. , D'cunha Romola , Rao K. Narahari , Papoušek D.
Published: April 2011

An entire band of perturbation allowed transitions to the ν4 state of 14NH3 has been assigned in the Fourier transform spectra recorded using a 192-m path length. More than 900 of the forbidden transitions provide necessary information on the spacing between the energy levels with different quantum numbers k, inaccessible from allowed transitions. These data were combined with all other relevant data (MW, submillimetrewave, FIR, IR) published in the literature to derive precise values of inversion–rotation energy levels. This extensive data set completely describes the ground state energy levels of 14NH3 up to quantum number J = 16 for all possible values of the quantum number k.
The 4s ← 1b1 and 3d ← 1b1 Rydberg states of H2O and D2O: Spectroscopy and predissociation dynamics
Authors: Ashfold Michael N. R. , Bayley J. Mark , Dixon Richard N.
Published: April 2011

Two new electronic states of H2O and D2O have been identified in the energy range 84 000–88 000 cm−1 as three-photon resonances in four-photon ionization spectroscopy. Simulations of the rotational intensity distributions using asymmetric top three-photon line strength theory, and rotational analyses, characterize the states as B1 and A2. These Rydberg states are assigned to the excitations 4sa1 ← 1b1[Formula: see text] and 3d2 ← 1b1[Formula: see text] on the basis of equilibrium geometries, quantum defects, and the polarization dependence of their three-photon transition probabilities. The identification of the one-photon forbidden 1A2–1A1 transition, together with published vacuum ultraviolet (VUV) absorption spectra, permits a consistent assignment for all five members of the 3d ← 1b1 complex.The [Formula: see text] and [Formula: see text] states arc predissociatcd via both homogeneous and heterogeneous mechanisms. The homogeneous channel from the [Formula: see text] state shows a dramatic isotope effect, being about two orders of magnitude faster in H2O than from equivalent levels of D2O. The heterogeneous predissociation exhibits irregular vibronic and isotopic dependencies, which can be rationalized in terms of the intercessional role of accidental near resonances with levels of the heavily predissociated [Formula: see text] state. The (000) levels of the [Formula: see text] states of H2O and D2O show contrasting heterogeneous predissociation behaviour, which can be interpreted with a knowledge of the relevant potential energy surfaces and the electronic–rotational Coriolis interactions that couple the states.
Spectroscopic constants for tritiated and deuterated
Authors: Carney Grady D.
Published: April 2011

Theoretical vibration–rotation coefficients for tritiated and deuterated [Formula: see text] are reported for Carney and Porter's ab initio electronic CI potential energy surface. In the calculation of coefficients connecting the zero-point and fundamental states of vibration, accurate vibrational CI wave functions, consisting of 220 configuration functions, were used.
The three lowest ion-pair states of ICl
Authors: Bussières D. , Hoy A. R.
Published: April 2011

The three lowest ion-pair states of the iodine chloride molecule, E(Ω = 0), β(Ω = 1), and D′(Ω = 2), form a coupled triad whose Te'S all lie within 50 cm−1. Transitions to low vibrational levels (ν = 0–2) of D′ are reported for the first time and the analysis of E and β at low ν is expanded considerably. By including the coupling matrix elements explicitly in a nonlinear least squares fit, values for the electronic matrix elements are found that are close to, but slightly less than, the pure precession values.
Characterization of the shallow state of iodine chloride
Authors: Brand J. C. D. , Bussières D. , Hoy A. R. , Jaywant S. M.
Published: April 2011

A weakly bound Ω = 1 state of ICl, [Formula: see text], which converges to the ground state 1(2P3/2) + Cl(2P3/2) of the separated atoms, has been identified and characterized. Spectroscopic constants of this state are Te = 17 338.0(13), ωe = 32.85(48), ωexe = 1.272(40), 103Be = 38.2(13), 104αe = 8.89(34), 105γe = −8.1(20) cm−1, and re = 4.01(6) Å. The dissociation energy De = 219.6 cm−1 is consistent with the value predicted for a Morse function, [Formula: see text]. Transitions [Formula: see text] are allowed owing to homogeneous coupling between ã and the well-defined A(3π1) state; in fact, at medium-long range (r = 6–6.5 Å, D–Gν = 20–30 cm−1), the diabatic ã and A curves cross at a small angle. Principal features of the crossing are explained if the electronic interaction matrix element is ca. 4 cm−1, corresponding to weak coupling. Heterogeneous perturbations of the A and ã states in the range D–Gν < 200 cm−1 are attributed to coupling with high vibrational levels of the ground state X(1Σ+).
Wide-band transducer for acousto-optic Bragg deflector
Authors: Gregoris D. , Ristic V. M.
Published: April 2011

A wide-band transducer for an acousto-optic deflector is described. The transducer is a chirped-frquency interdigital transducer with electrodes tilted to satisfy the isotropic Bragg condition. A simple theoretical model of the device is presented and numerical calculations of the frequency response indicate a wide operational bandwidth. A brief description of a direct optical-projection lithographic system used to fabricate deflectors with minimum electrode widths of ~1 μm is also included.
The influence of wave aberrations: an operator approach
Authors: Ojeda-Castañeda J. , Boivin A.
Published: April 2011

The wave departures from sphericity known as Seidel's primary- or third-order aberrations are represented by a differential operator that modifies the diffraction-limited image. We show that the complex amplitude at any point over the aberrant image can be obtained from certain terms of the Taylor series expansion of the diffraction limited image. This approach allows us to describe the propagation of an aberrant wave front in terms of its aberration coefficients. Furthermore, it can also be applied to implement an optical or an electronic procedure for simulating aberrant images.
L'image tridimensionnelle du point en présence d'aberration sphérique primaire et de filtrage d'amplitude : unitaire ou modal
Authors: Villeneuve Jean-Eudes , Boivin Albéric , Biswas Subhash C.
Published: April 2011

We investigate the point diffraction image arising from an objective lens in the vicinity of its paraxial focus, under the combined influence of spherical aberration, defocusing, and an amplitude filtering of modal TEM00 law. The previous literature pertaining to our subject is first reviewed thoroughly and then we outline a new hybrid formalism that permits an easy computation of the total diffraction image everywhere in the focal region. In this formalism the complex pupil amplitude is developed into a series of Zernike polynomials, the coefficients of which are obtained through the Gauss–Chebyshev method of numerical quadrature. A considerable amount of numerical information has thus been obtained, which will be presented here in graphical form and discussed. Notably we show that our modal filter, combined with an appropriate amount of defocusing, does compensate the existing spherical aberration beyond the supposedly ideal situation represented by the Airy pattern.
Some studies on the growth and properties of Pb1−xSnxTe layers by hot-wall and liquid-phase epitaxy
Authors: Sundaram K. B. , Dalacu N. , Garside B. K.
Published: April 2011

Pb0.92Sn0.08Te layers have been grown by hot-wall and liquid-phase epitaxy techniques. In the hot-wall epitaxy case, layers are grown on BaF2 and Pb0.92Sn0.08Te single-crystal substrates, while in the case of liquid-phase epitaxy, single crystals of PbTe and Pb0.92Sn0.08Te are used. In both cases x-ray Laue diffraction studies indicated the growth of good quality epilayers suitable for device fabrication.
An improved conventional Se–CdO photovoltaic cell
Authors: Champness C. H. , Ghoneim K. , Chen J. K.
Published: April 2011

Studies previously carried out to improve the Se–CdO photovoltaic cell have emphasized optimization of the deposition of the CdO by direct current (DC) reactive sputtering. Attention has now been turned towards improving the deposition, doping, and heat treatment of the polycrystalline selenium base. It has been found that heat treatment of the selenium film on its substrate of aluminum and bismuth in air or oxygen prior to CdO deposition results in an increase in the illuminated open-circuit voltage (Voc) of the cell. The effect increased with increase of annealing temperature from 150 to 195 °C and in going from dry to wet oxygen. No increase in Voc was found by heating in nitrogen. The effect could be due to the formation of higher stoichiometric and hence higher resistivity CdO at the Se–CdO junction, arising from the presence of extra oxygen on the selenium surface.
Photovoltaic performance of thin-film CdS–Cu2S solar cells with electroformed junctions
Authors: Rastogi A. C.
Published: April 2011

Irreproducibility and low conversion efficiency of CdS–Cu2S solar cells fabricated by the chemiplating process are found to be the result of variations in the surface morphology of the textured CdS surface. To counter such problems, a new technique of barrier formation using direct-current (DC) field-assisted control over the reacting ionic species is described. Photovoltaic data on solar cells fabricated in this way display an overall improvement owing to the prevention of deep-intruded Cu2−xS growth along the CdS grain boundaries and a closer approximation to stoichiometry. In addition, with the use of the DC potential as a first-order variable these improved characteristics of the junctions have been found to be less sensitive to the Cu2−xS deposition variables, thus improving general reproducibility. We show data on the cells made by the new technique obtained from spectral response, sheet resistivity, and accelerated life tests.
Optical emission characteristics of (Cu, Ag)In(Se, Te)2 pentenary alloys
Authors: Vanderwel T. M. , McNeil L. P. , Jessop P. E. , Garside B. K.
Published: April 2011

Chalcopyrite alloys with the composition (Cu(1−x)Agx)In(Se(1−z)Tez)2 have been synthesized and characterized. X-ray powder-diffraction measurements show well-defined single-phase material at each composition, verifying complete miscibility. Lattice parameters and differential-thermal-analyser-determined phase-transition temperatures vary smoothly throughout the composition range. Luminescence measurements have been obtained for a large range of excess carrier levels, and characteristics of the electronic band structure have been inferred by comparison of the observed spectra with spectra calculated using a recently developed model.At all compositions, the short, interband, luminescence decay time and the relatively high emission intensity identify the bandgap as direct. The results of the luminescence analysis also indicate that the band structure is dominated by a shallow acceptor ((Ea–Ev) = 10 to 40 meV), except in the AgInSe2 corner where the acceptor concentration drops low enough to allow a donor at (Ec–Ed) = 55 meV to take precedence. Alloying of the group VI anion causes a significant decrease in the bandgap, which drops to almost 100 meV below the minimum monochalcogen value. There is also a large increase in the concentration of the acceptor, which indicates that this acceptor is due to imperfections in the anion face-centered cubic (fcc) sublattice.
Diffusion and annealing effects of crystalline CuInSe2
Authors: Shahidi A. Vahid , Shih I. , Champness C. H.
Published: April 2011

Diffusion and annealing experiments have been made on p-type monocrystalline CuInSe2 samples grown by the directional freezing method. It was found that tellurium diffusion into CuInSe2 produced p-type conduction whereas bismuth diffusion resulted in n-type conduction. Photoconductivity experiments were also made for the first time at 77 K on p-type monocrystalline CuInSe2 samples.
The relation between microstructure and hydrogen content and evolution for hydrogenated amorphous silicon films prepared by magnetron sputtering
Authors: Das S. R. , Charbonneau S. , Williams D. F. , Webb J. B. , MacDonald J. R. , Polk D. R. , Zukotynski S. , Perz J.
Published: April 2011

Amorphous hydrogenated silicon films have been prepared by reactive magnetron sputtering under a variety of preparation conditions. The hydrogen profile for the films measured by an improved 15N bombardment technique shows that hydrogen (H/host) percentages up to 50 can be obtained independent of the film microstructure. The hydrogen partial pressure has the greatest effect on the total hydrogen content. Hydrogen evolution spectra show that smooth films with uniform densities have relatively more complex evolution spectra and evolve proportionately less hydrogen at low temperatures than films with columnar structures. Thermodynamic and diffusion parameters are calculated from hydrogen evolution experiments in the range 20–700 °C. Parameter values are typical, ΔG ~ 1.4–2.1 eV, but low values for ΔH ~ 0.4–0.7 eV are calculated for some low-temperature evolution maxima. Diffusion coefficients are typical of a hopping process. The relationships between these thermodynamic and kinetic parameters are discussed.
The evolution of massive bipolar jets and the birth of H II regions
Authors: Ballys John
Published: April 2011

Observations suggest that outflows of neutral gas are among the first visible signs of the birth of a new star. Stars destined to be of spectral type O or B on the main sequence eventually emit large quantities of ionizing ultraviolet radiation that produce H II regions. The powerful neutral wind associated with the bipolar outflow phase of pre-main-sequence stellar evolution produces cavities in the gas surrounding a newborn star and regulates the escape of ionizing radiation from the vicinity of the star. The birth and early evolution of H II regions is the final phase in the development of bipolar, molecular outflows surrounding massive stars.
High-density gas in bipolar outflow sources and active galactic nuclei
Authors: Persson S. E.
Published: April 2011

The highest density regions near the base of the outflow in young stellar objects with bipolar molecular outflows are discussed. Bright emission lines of Ca II and O I characterize the spectra and lead to estimates of n ~ 1010 cm−3, temperatures of a few thousand Kelvins, and mass motions of several hundred kilometres per second. Typically the rate of momentum transfer within this region fails by more than an order of magnitude to provide the force necessary to drive the molecular outflow on the parsec scale. The overall near-infrared spectra of these young stars are similar to those of certain active galactic nuclei having strong Fe II emission.A comparison is made between the Ca II and O I lines in the infrared core source of the bipolar H II region S106 and in the Seyfert galaxy Mrk 42. The spectra are shown to be scaled versions of each other, and we conclude that the physical conditions are broadly similar in the high-density emission-line regions of these two objects. The Ca II lines appear self-reversed in both objects, but possible Ca II absorption in the underlying galaxy in Mrk 42 compromises the detailed comparison of line shapes. Nevertheless, it is likely that the geometries and velocity fields are also analogous. Derived parameters of the emission-line regions in S106 and the Seyfert galaxies I Zw 1 and Mrk 42 are compared.
Rotating winds and the acceleration of radio jets
Authors: Chakrabarti Sandip K.
Published: April 2011

A wind-type solution is obtained in a general axisymmetric space-time when matter has angular momentum. An application of the solution is suggested in understanding the acceleration of the radio jets as matter flows along the funnel of a thick disk. Because the rotational energy of matter is converted entirely into poloidal energy, the acceleration of matter in a rotating wind is more than what is usually obtained from a flow-tube expansion alone.
Magnetodynamical acceleration of cosmic jets: sweeping-magnetic-twist mechanism
Authors: Uchida Yutaka , Shibata Kazunari
Published: April 2011

Characteristic behavior of cosmic jets predicted by a magnetodynamic mechanism proposed by Uchida and Shibata is discussed in terms of recent observational results of bipolar flows from star-forming regions as examples of low-energy cases. The theoretical model considers the twisting-up of part of the large-scale magnetic field with the driving mechanism being the contracting rotation of the accretion disk around the gravitating center. The twisted field screws out the mass from the surface layers of the disk along the large-scale external field, explaining the observed tuning-fork type of distribution of the cold CO bipolar flows, gradual acceleration of the flows from the vicinity of the disk, and the helical velocity field in the outflows, all of which are not easy to explain by previous hypotheses assuming the wind and blast from the central object. Prospects of application of this mechanism to high-energy jets from active galactic nuclei or such peculiar objects in the galaxy like SS433 or Sco X-1 are discussed from the point of view of the similarity inherent in the mechanism.
Three-dimensional calculation of the mirage effect with a personal computer
Authors: Lepoutre F. , Bein B. K. , Inglehart L. J.
Published: April 2011

Analytical series expansions for the normal and transverse deflections of the mirage effect can be obtained in the case of Gaussian and square-illumination distributions. The conditions of convergence are easy to determine and are found to be compatible with the use of a personal computer. The results totally agree with the numerical integrations previously published.
Theoretical study of the photoacoustic signal produced in a relaxing gas
Authors: Da Silva M. Rebelo
Published: April 2011

The photoacoustic signal generated in a photoacoustic gas cell with rigid wall boundaries is calculated by solving the coupled equations for sound propagation and thermal diffusion in a viscous and relaxing gas. For a cylindrical geometry, monochromatic radiation, and sinusoidal modulation, when a condition of zero heat flow through the lateral walls of the cell is verified, a general expression is found that can be applied whatever the deactivation scheme is for collisional relaxation in the gas. Both resonant and nonresonant modes of operation are considered.
Characterization of vapor and aerosol flows by photothermal methods
Authors: Sontag H. , Tam A. C.
Published: April 2011

Pulsed laser heating is used to label aerosols or absorbing vapors in a flow. In an absorbing vapor, the photothermal heating creates a travelling thermal lens that can be detected by a probe-beam deflection scheme yielding information on flow velocity and the concentration of absorbing species. The absorption by volatile aerosols is detected by transient variation in Mie scattering caused by particle evaporation. In addition, the velocity of a single moving aerosol can be measured by monitoring its infrared thermal emission induced by an excitation laser beam.
Photoacoustic in vivo study of the penetration of sunscreen into human skin
Authors: Giese K. , Nicolaus A. , Sennhenn B. , Kölmel K.
Published: April 2011

Photoacoustic spectroscopy offers the opportunity of detecting the diffusion of light-absorbing drugs into the skin. We report on in vivo measurements on human skin treated with sunscreens. The experimental setup is described, and the transfer properties of the open-ended detector are discussed theoretically and experimentally.
Thermographic methods applied to industrial materials
Authors: Reynolds W. N.
Published: April 2011

Steady-state, or quasi-steady-state thermography is a well-known industrial inspection technique that has not so far been widely used in the nondestructive examination of materials. However, recent advances in infrared thermal-imaging systems have greatly broadened the range of possible uses through video-recording techniques that enable transient thermal distributions to be captured and analyzed very rapidly. In this paper, applications are described to a range on industrial materials, with illustrations of defects in bonded, coated, laminated, and cast structures. Current work is devoted to detailed comparisons with radiographic, ultrasonic, and other techniques as regards speed, effectiveness, and adaptability to manufacturing and testing conditions.
Pulsed photothermoelastic quantitative evaluation of flaws in laminates
Authors: Rousset G. , Lévesque D. , Bertrand L. , Maldague X. , Cielo P.
Published: April 2011

A pulsed photothermoelastic technique for nondestructive testing of layered materials is described. A Fourier-transform signal analysis is presented for a quantitative characterization of subsurface defects. Discrepancies between the experimental results and the data obtained from the thin-plate analytical theory are interpreted through a finite-element numerical model. The effect of the vibrational properties of the whole structure is shown to be particularly important on the spectral features of the thermoelastic signal for small defects.
Analysis of semitransparent layered materials by modulated photothermal radiometry: application to the bonding and thickness control of enamel coatings
Authors: Egee Michel , Dartois Robert , Marx Jean , Bissieux Christian
Published: April 2011

To use modulated photothermal radiometry to control the thermophysical properties of enamel coatings, we first analytically resolve a theoretical model with two finite semitransparent layers and thermal-resistance interface; then we experimentally study several samples with various adhesion properties. The comparison of the experimental results with the calculations allows one, under the present conditions, to point out the possibilities and limits of the method, mainly for the control of coating thickness and delaminations.
Deformation of a liquid surface by laser heating: laser-beam self-focusing and generation of capillary waves
Authors: Hartikainen J. , Jaarinen J. , Luukkala M.
Published: April 2011

The surface deformation of oil by laser heating is presented. The self-focusing of the reflected beam and the generation of capillary waves are observed.
Measurement of Hall mobility in n-channel silicon inversion layer
Authors: Briglio D. R. , Nathan A. , Baltes H. P
Published: April 2011

The Hall mobility of electrons in silicon inversion layers is determined from measurements of the magnetic-field sensitivity of dual-drain n-channel metal oxide semiconductor transistors and comparison with numerical device-modeling results. The variation of the Hall mobility with bias conditions is discussed.
High-frequency wafer-probing techniques
Authors: Rabjohn G. , Wolczanski J. , Surridge R.
Published: April 2011

High-speed digital and microwave circuits have traditionally been tested by dicing wafers and mounting chips into high-frequency test carriers. This process is expensive, time consuming, and destructive. Methods of high-frequency measurement at the wafer stage are very desirable; for example, for wafer mapping, but conventional needle probes cannot be used because of their parasitics. New probe structures based on fine coaxial lines, vertically mounted microstrip lines, and tapered coplanar lines have been reported.For measurement at microwave frequencies (2–20 GHz), we have developed a geometry of a coplanar wave-guide probe that gives better than 10 dB return loss. Individual monolithic components can easily be measured and modelled for inclusion in a circuit simulation.For the measurement of digital circuits, especially those requiring several high-speed signal lines, we have used proprietary microstrip probes. Satisfactory operation up to about 2 Gbit∙s−1 has been observed, the upper bit rate being restricted by the inductance of the probe tip.Microwave-frequency and time-domain measurements of both types of probes have been made and will be discussed. Additionally, examples of the use of these probes for on-wafer measurements of digital and analog circuits will be given.
Mirror formation by chemical etching and microcleaving of InP-based lasers
Authors: Szaplonczay A. , Fox K. , Dyment J. C.
Published: April 2011

This paper outlines two chemical-etch techniques by which processed laser mirrors can be obtained. These are (i) direct etching and (ii) the etching of bridges or cantilevers that can be "microcleaved" to produce small local mirror surfaces. Both techniques rely on the crystallographic selectivity of chemical etchants.Direct etching of mirrors is accomplished using HCl–HNO3–H3PO4–H2SO4 mixtures. This approach produces smooth surfaces with vertical walls in InP and a slight bevel in the GaInAsP active layers. Lasers made with direct etched mirrors showed threshold currents comparable to normal cleaved mirror lasers.For microcleaving, cantilevers were etched in 1–2% Br2–CH3OH solutions initially in InP wafers. Cantilevers, however, could not be obtained directly on double heterostructure InP–InGaAsP lasers with a ternary (GaInAs) capping layer. Owing to severe sideways etching of the ternary under the SiO2 mask, the negative slopes necessary for cantilever formation never developed. To form laser structures, we had to completely remove the ternary top layer from all areas exposed to the Br2– CH3OH etch solution. Properly formed cantilevers were then obtained.
Optical and electrical studies of liquid-encapsulated Czochralski semi-insulating GaAs with different carbon concentrations
Authors: Teh C. K. , Tin C. C. , Weichman F. L.
Published: April 2011

The effects of the presence of carbon over a range of ~1014–1016 cm−3, in liquid-encapsulated Czochralski-grown semi-insulating GaAs have been studied using Fourier-transform infrared (FTIR), photoluminescence spectroscopy, photo-induced transients spectroscopy (PITS), and temperature-dependent Hall-effect measurements. The concentration of the carbon impurity was determined from the absorption line at 582.5 cm−1 on the spectra. From photoluminescence measurements in the temperature range of 4–30 K, the decay signal was found to consist of two parts: the initial decay obeying an exponential behaviour with an activation energy of 15 meV and the subsequent decay obeying a power law of the form t−p with the values of p ranging from 1.4 to 3.5. Results from PITS measurements revealed a broad peak at about 240 K (t2 − t1 = 20 ms; t1/t1 = 5), which could be due to the formation of a free As vacancy or its complexes. The intensity of the EL2 family of emission peaks was directly dependent on the water content of the boric oxide encapsulant used during the growth process. Mobility and resistivity of the samples were also measured and tabulated.
Heterolayer lead-salt diode lasers
Authors: Yang Yonfeng , Garside B. K. , Jessop P. E.
Published: April 2011

Hot-wall epitaxy (HWE) has been used to grow heterostructure lead-salt materials from which low-threshold tunable diode lasers have been made. A new HWE structure consisting of a Pb(Se, Te) layer sandwiched between two lattice-matched (Pb, Sn)Te layers has resulted in lasers of good electrical and material quality, and threshold current densities as low as 200 A∙cm−2 (at 40 K). This occurred even though this structure is expected to be nonconfining to both light and electrical carriers. This result is due to the very rapid interdiffusion of dopant atoms between the epilayers during the growth process. Dopant interdiffusion has been investigated using an etch-back technique combined with hot-point probe measurements to observe changes in the doping profiles of the structures. Very large values for the diffusion constants of dopants have been deduced from these measurements: 2.3 × 10−15 and 1.1 × 10−15 cm2∙s−1 for Bi and Tl, respectively.
Investigation of electrodeposited CuInSe2 films
Authors: Qiu C. X. , Shih I.
Published: April 2011

After a brief review of CuInSe2 films prepared using an electrophoretic technique, results obtained by an electrochemical deposition method will be described. The electrophoretic technique, which is simple, was first investigated and found to be unsuitable for CuInSe2-film deposition. Using the electrochemical deposition method, we obtained uniform and homogeneous CuInSe2 films. The quality of the films was then determined by scanning electron microscopy, electron-probe microanalysis, X-ray diffraction, and secondary-ion mass spectroscopy. Heterojunction cells of the form CdS–CuInSe2 were finally fabricated using the electrodeposited films. The devices showed an active-area AM1 short-circuit current density of more than 30 mA∙cm−2 and a Voc of about 0.2 V.
Low-temperature crystallization of in situ phosphorus-doped low-pressure chemical-vapour deposited amorphous silicon
Authors: Waechter D. , Tarr N. G.
Published: April 2011

A method has been developed for producing low-resistivity phosphorus-doped polysilicon films with a minimum thermal budget. The method involves low-pressure chemical-vapor deposition of amorphous silicon at 560 °C followed by crystallization at 650 °C. Films formed in this manner are compared to films deposited polycrystalline at 627 °C. In both cases, in situ doping is achieved by addition of PH3 diluted in SiH4 to the gas mixture. For a given SiH4: PH3 flow ratio, the phosphorus concentration determined from secondary-ion mass spectroscopy is four times larger in the amorphous-deposited material. Moreover, the resistivity is substantially lower in this material even when the dopant concentrations are similar. The latter result may be due in part to reduced dopant segregation to grain boundaries. The internal strain determined from the Raman line width is larger in the polycrystalline-deposited material but could be reduced by high-temperature annealing.
Growth and annealing of AgInSe2 thin films
Authors: Weir R. D. , Jessop P. E. , Garside B. K.
Published: April 2011

Amorphous thin films of AgInSe2 were grown by rf magnetron sputtering and then crystallized using two forms of optical annealing: laser annealing using a raster-scanned argon laser and heat-pulse annealing using a quartz–halogen heat-lamp system. It was determined that laser annealing of films on amorphous substrates resulted in fine-grained polycrystalline chalcopyrite AgInSe2 thin films with a preferred (112) orientation. The presence of weak X-ray diffraction peaks associated with nonchalcopyrite phases indicated that some segregation had occurred. Heat-pulse annealing of films on single-crystal substrates led to better results. The films were more highly oriented with no evidence of any segregation.
Transverse spin waves in normal and superfluid 3He
Authors: Candela D. , Edwards D. O. , Heff A. , Masuhara N. , Sherrill D. S. , Combescot R.
Published: April 2011

After a brief review of experiment and theory for transverse spin waves in normal liquid 3He, we compare previously published data at 0, 6.3, and 12.3 bar (1 bar = 100 kPa) in superfluid 3He–B with a new version of the theory of Combescot for the spin-wave spectrum. The new theory includes the Fermi-liquid parameters [Formula: see text] and [Formula: see text] (as well as [Formula: see text], which was in the old version). The equations give an excellent fit to the data at 0 bar using values of [Formula: see text] and [Formula: see text] from the normal liquid, and [Formula: see text] from the B-phase susceptibility. At 6.3 bar, the fit is not quite so good, perhaps because of nontrivial strong-coupling effects. At 12.3 bar, the experimental uncertainties make the comparison inconclusive.
Strongly polarized 3He: polarizability and sound velocity
Authors: Bonfait G. , Puech L. , Halperin W. P. , Castaing B.
Published: April 2011

Melting-curve experiments in highly polarized liquid 3He seem to show anomalous behaviour of the susceptibility. We are reminded of how this melting curve is affected by very high magnetic fields and how it is possible to obtain the liquid susceptibility of this polarized liquid using a melting model. To try to confirm the susceptibility behaviour, we have performed sound-velocity measurements in bulk polarized liquid. The results show a clear m2 linear dependence of the sound velocity at 200 mK. This result is compared with available predictions and with previous experimental work and is used to deduce the best experimental requirements for highly polarized 3He studies.
Rotating superfluid 3He
Authors: Fetter Alexander L.
Published: April 2011

The significance of the order parameter is reviewed for the familiar case of vortices in the rotating Bose superfluid 4He. The triplet p-wave Cooper pairing in the Fermi superfluid 3He introduces new and unusual possibilities. In the rotating B phase, all vortices have singular cores, and several different structures have been investigated. In the rotating A phase, an additional feature is a nonsingular vortex with two quanta of circulation.
Experiments with negative ions in rotating superfluid 3He–A
Authors: Lounasmaa O. V. , Simola J. T. , Nummila K. K. , Korhonen J. S. , Skrbek L.
Published: April 2011

Ion-mobility experiments on rotating superfluid 3He–A show that the l-vector texture in the liquid strongly focuses ions to vortex cores and that two different kinds of vortices, with clearly different ion mobilities along their cores, exist in the A phase, depending on the preparation of the rotating state and on the external magnetic field.
Quantum diffusion in solid H2: a short review
Authors: Meyer H.
Published: April 2011

A review is presented on the experimental observations and the theoretical progress made in investigating the quantum diffusion in solid H2. The mechanisms of resonant ortho–para conversion and of quantum tunneling are discussed. It is pointed out that the ortho-H2 clustering reaction process, by which quantum diffusion is detected, needs to be better understood to account for the dependence of the observed reaction-time constant τ on temperature and on ortho-H2 concentration. The general trends in the experimental results are reviewed, and the discrepancies between various determinations of τ are discussed. Further experiments are suggested as well as computer simulations for the clustering procedure. A review is also given on the status of quantum diffusion of HD in solid H2. Recent observations on recombination rates of H and on depolarization rates of muons in H2 that show evidence of quantum effects are briefly mentioned.
Orientational ordering in solid hydrogen
Authors: Sullivan N. S. , Edwards C. M. , Lin Y. , Zhou D.
Published: April 2011

The orientational ordering in solid ortho–para hydrogen mixtures is reviewed with emphasis on dilute mixtures for which a glass-like freezing of the randomly distributed quantum rotators is observed. The interpretation of the various nuclear magnetic resonance experiments used to monitor the relevant order parameters is discussed, and a summary is given of the current consensus and outstanding problems concerning the nature of the ordering in random dilute mixtures.
Spin supercurrents and two-domain precession of magnetization in 3He-B
Authors: Fomin I. A.
Published: April 2011

This is a brief review of recent investigations, both experimental and theoretical, of the phenomena observed in pulsed nuclear magnetic resonance experiments with superfluid 3He-B caused by spin supercurrents flowing in this liquid. Precession of magnetization in 3He-B in a nonuniform magnetic field results in the formation of a two-domain precessing structure, which accounts for the existence and properties of a long-lived induction signal observed in 3He-B. The relaxation of this structure and its small oscillations are discussed in connection with the experiments of Borovik-Romanov et al.
Novel compressional cell for liquid and solid 3He experiments
Authors: Zhao Zuyu , Yang H. Q. , Adenwalla Shireen , Ketterson J. B. , Sarma Bimal K.
Published: April 2011

A pressure compactor has been assembled for spin-polarized liquid and solid 3He experiments. In place of a Kapton diaphragm, a beryllium–copper spring–bellows combination was used to attain a large volume change of 3He. The spring was specially designed and tested to ensure that its displacement at low temperature was a reversible process.
Ferromagnetism of 3He films adsorbed on sintered silver
Authors: Okuda Y. , Fukushima A. , Ikushima A. J.
Published: April 2011

Nuclear magnetic susceptibility of He adsorbed on sintered silver was measured by a superconducting quantum interference detector magnetometer. For the external field of 6G, the susceptibility increased drastically below 1 mK, but then it did not continue to diverge and rolled off below 0.36 mK [Formula: see text]. We looked for a spontaneous magnetization of the present system under zero field (≤ 10 mG) but have seen nothing down to 0.15 mK.
The heat capacity of liquid 3He beyond T3 log T
Authors: Schakel A. M. J. , Calkoen Ch. J. , Weert Ch. G. van
Published: April 2011

The heat capacity of liquid 3He up to 2.5 K is calculated on the basis of a spin-fluctuation model in the context of the Landau theory of Fermi liquids. A good fit of the data is achieved by including the temperature dependence of the magnetic susceptibility and by using a different, smaller, quasi-particle mass. It is also shown that the magnetic susceptibility and the compressibility are analytic functions of the temperature.
Rapid-melting experiments on polarized 3He
Authors: Vermeulen G. A. , Wiegers S. A. J. , Kranenburg C. C. , Jochemsen R. , Frossati G.
Published: April 2011

We report experiments on polarized liquid 3He by using the technique of rapid melting of highly polarized solid 3He. We describe our experimental setup and discuss the production of solid polarized 3He by a slow compression and the subsequent production of liquid polarized 3He by a fast decompression. We conclude that it is by no means straightforward to extract thermodynamic quantities by measuring the melting-curve lowering in rapid-melting experiments. On the other hand, we have obtained moderately polarized liquid 3He (10–20%) at 40 mK with a relaxation time as large as 1000 s, which raises good hopes for the production of polarized superfluid 3He.
Phase-separation temperature of solid 3He–4He mixtures as a function of pressure
Authors: Ehrlich S. N. , Simmons R. O.
Published: April 2011

The pressure dependence (3.01 MPa ≤ P ≤ 4.28 MPa) of the phase-separation temperature of solid mixtures of 3He and 4He has been measured for 3He concentrations of 0.20 and 0.30 using X-ray diffraction. The value determined for the pressure dependence of the critical temperature is compared with the prediction by Mullin and with other experiments.
Silicon oxynitride from microwave plasma: fabrication and characterization
Authors: Blain S. , Klemberg-Sapieha J. E. , Wertheimer M. R. , Gujrathi S. C.
Published: April 2011

Plasma silicon nitride (P-SiN), oxynitride (P-SiON), and silicon dioxide (P-SiO2) films have been prepared from SiH4–NH3–N2O mixtures in a large volume microwave plasma (LMPR, 2.45 GHz) apparatus at TS = 280 °C. Film compositions, determined by X-ray photoelectron spectroscopy and nuclear elastic recoil detection analysis, reveal about 15 at.% hydrogen in P-SiN, <2% in P-SiO2, and intermediate values in P-SiON. Various physicochemical and electrical properties (density, refractive index, intrinsic stress, permittivity, and conductivity) vary systematically with film composition, O/(O + N), determined from the above analyses. The present microwave plasma enhanced chemical vapour deposition (PECVD) films compare favorably with the best PECVD and low pressure chemical vapour deposition (LPCVD) materials reported in the literature.
Characterization of silicon oxide films deposited using tetraethylorthosilicate
Authors: Normandin M. Simard , Emesh I. , D'asti G. , Wilton A. C. de , Pearce N.
Published: April 2011

Silicon dioxide films prepared by plasma enhanced chemical vapour deposition (PECVD) from tetraethylorthosilicate (TEOS) are known to exhibit better step coverage than films prepared from silane chemistry. We have prepared TEOS oxide films under various processing conditions to investigate their electrical properties in view of their applicability to the fabrication of silicon devices. Films deposited using TEOS only and in the presence of an oxidant such as O2 or N2O were prepared. In each case we have submitted some of the samples to a rapid thermal densification cycle in N2. Metal oxide semiconductor (MOS) capacitors with oxide thickness of 50 nm were prepared for the measurements of dielectric strength, leakage current, flat-band voltage, and interface charge density. Several devices were measured to obtain significant statistical data regarding dielectric strength and uniformity of the film properties over the wafer. Thermal SiO2 films of the same thickness were used for comparison. Thicker films (~500 nm) were also prepared for FTIR (Fourier transform infrared) spectroscopy and ERD (elastic recoil detection), for the characterization of the material properties of the films. We have found that rapid thermal annealing (RTA) does not modify the electrical properties of films deposited with O2 or N2O. For the films deposited without oxidant that did not receive RTA, the flat-band voltage is less than −10 V and the interface charge density cannot be calculated reliably. Films deposited in the absence of oxidant that received RTA and films deposited with N2O with and without RTA have Vfb around −5 V and Qf/q of the order of 2E12 cm−2. Films deposited with O2 have Vfb near −0.6 V and Qf/q near 1E11 cm−2; this compares favorably with thermal oxides that have Vfb of −0.3 V and Qf/q near 1E10 cm−2. These oxides can withstand up to 5 MV/cm of electric field. The material analysis reveals that the oxide films prepared in the presence of either oxygen or nitrous oxide have a more ordered structure and contain fewer impurities that the oxide film prepared with TEOS in a nitrogen only ambient.