bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface-temperature measurement during pulsed laser-induced thermal desorption of xenon from a copper film
Authors: Hussla I. , Coufal H. , Träger F. , Chuang T. J.
Published: April 2011

Surface temperatures during pulsed laser-induced thermal desorption of xenon from a 28-mm-thick copper film are determined directly with a pyroelectric calorimeter as the substrate. Simultaneously, time-of-flight data of desorbed xenon atoms are recorded with a quadrupole mass spectrometer. From these data equivalent surface temperatures and heating rates can be derived. The calorimetric temperatures are compared with temperatures derived from time-of-flight data.
Optical-absorption coefficient measurements in solids and liquids using correlation photoacoustic spectroscopy
Authors: Dodgson James T. , Mandelis Andreas , Andreetta Claudio
Published: April 2011

The spectroscopic information related to the optical-absorption coefficients of solids and liquids, which is contained in the signal-magnitude and time-delay channels of cross-correlation photoacoustic spectroscopy (CPAS), has been investigated. Powders of holmium oxide and aqueous solutions of black India ink of variable concentrations were used as solid and liquid samples, respectively. The experimental results were found to be in general agreement with a one-dimensional theoretical model of the CPAS-signal generation.
Fourier-transform photoacoustic spectroscopy: a more complete method for quantitative analysis
Authors: Choquet M. , Rousset G. , Bertrand L.
Published: April 2011

Strong absorption bands of photoacoustic Fourier-transform spectra are often truncated relative to weaker bands owing to signal saturation. To correct this problem, we propose processing both the phase and the amplitude information in the photoacoustic signal. Under certain conditions, easily fulfilled in typical experiments, we are able to calculate the absolute absorption spectrum from the photoacoustic data. Experimental results are given for asbestos fibers (chrysotile).
Water detection in polymer dielectrics using photoacoustic spectroscopy
Authors: Bordeleau A. , Rousset G. , Bertrand L. , Crine J. P.
Published: April 2011

Photoacoustic spectroscopy is used for the detection of sorbed water in two polymers used for their dielectric properties in electric cables: ethylene–propylene rubber and cross-linked polyethylene. The wavelength range is between 2 and 4 μm, where the OH-bond valence vibrations are observable. As the technique used distinguishes between surface and bulk absorption of the infrared beam, correlations have been made with relative humidity, and water content as measured by another technique, and with other studies of water-sorption processes in polymers.
Influence of condenser microphones on phase measurements in photoacoustics at low pressure
Authors: Louis G. , Lepoutre F. , Monchalin J. P.
Published: April 2011

Condenser microphones used as photoacoustic signal detectors exhibit a phase-shift response that depends on both the nature and the pressure of the ambient filling gas. In this paper, we develop a lumped-parameters model of the microphone damping in which the approximations are thoroughly discussed. This model, after taking into account gas-slip effects on the surfaces of the condenser cartridge plates, is shown to accurately describe the response (magnitude and phase) of a commercial condenser microphone (Brüel and Kjaer 4144) for frequencies below 2.2 kHz and ambient pressures between 1.5 × 103 and 6 × 104 Pa.
Photorefractive deflection technique using parallel and overlaping probe and pump beams
Authors: Gagné M. -C. , Galarneau P. , Chin S. L.
Published: April 2011

The present work provides an experimental study of a pulsed photorefractive technique to diagnose the interior of an irradiated region. Results obtained in a mixture of SF6 and Ar are presented to illustrate the experimental technique. Three distinct areas have been studied, (i) The two beams are parallel and their optical axes are coincident (collinear). At this particular position, the probe beam suffers a defocusing effect that is used to align collinearly two laser beams with a precision of ±3 μm. (ii) The two beams are parallel but slightly off axis. In this case, the probe beam suffers a deviation that is the sole result of a rarefaction in the irradiated region followed by the normal thermal equilibration. (iii) The two beams are parallel and slightly overlapping. The probe beam suffers a deviation similar to the preceding one. Moreover, it sees an initial outward-propagating acoustic (density) wave. It is in this particular region that the acoustic perturbation appears. Finaly, the gas mixture used under our experimental conditions is a good candidate for the collinear alignment of several laser beams. The only restrictions are that the pump laser must produce a beam with a symmetrical intensity profile, the other laser beams must be continuous-wave beams, and the gas mixture must be transparent to the latter.
Monitoring energy conversion in photosystem I of cyanobacterial heterocysts by photoacoustic spectroscopy
Authors: Carpentier Robert , Matthijs Hans C. P. , Leblanc Roger M. , Hind Geoffrey
Published: April 2011

Photoacoustic spectroscopy was used to monitor photosynthetic energy storage in heterocysts isolated from the cyanobacterium Anabaena 7120. Three main energy-conversion pathways have been identified in these specialized cells: cyclic electron transport in photosystem I, nitrogen fixation, and respiration. The aim of this study was to define the conditions for estimating their interdependence. The gas phase (air, Ar, N2, H2) under which the sample was prepared or incubated, as well as the presence of electron donors (NADPH, NADH, H2) and KCN (an inhibitor of respiration), determined the relative flux through the pathways. Heterocysts in which respiration and nitrogen fixation are inhibited have afforded a useful system for specific study of cyclic electron transport around photosystem I. Under optimal conditions for photosystem I turnover, photochemical losses of above 20% were found.
Designing a differential cell for in vivo photoacoustic measurements of skin absorbance
Authors: Guy M. , Bernengo J. C.
Published: April 2011

To optimize photoacoustic detection in dermatological applications in vivo, a differential cell with variable-length chambers has been made to study the chamber-volume influence on acoustic response. In this paper, optical problems have been eliminated through exciting each chamber by a thermoacoustic signal. The common-mode rejection ratio (CMRR), which characterizes the performances of the cell in the presence of common noise, has been measured. This ratio increases with the length of each chamber. The main result of this study is that the cell dimensions cannot be reduced to get a maximum signal, because under these conditions the CMRR becomes very poor. Optimization of the cell will, therefore, be obtained by a compromise between sensitivity and CMRR, leading to large chamber volumes.
The study of time-dependent phenomena in materials by impulse-response photoacoustic spectroscopy
Authors: Miller Richard M. , Surtees Graeme R. , Tye Christopher T. , Vickery Ian P.
Published: April 2011

The use of impulse-response photoacoustic signals to monitor time-dependent changes in physicochemical systems is described. The diffusion of a dye through a polymer and the effect of a herbicide on a plant leaf are used to demonstrate the viability of the technique.
Experimental aspects of photothermal radiometry
Authors: Kanstad Svein Otto , Nordal Per-Erik
Published: April 2011

In photothermal radiometry (PTR), the thermal response of a given sample to time-varying illumination is detected via concomitant thermal radiation emanating from the irradiated region, to obtain spectral, structural, and other types of information about the sample. Excitation of the thermal response may be achieved in one of several different pulsing modes, with detection of the thermal reradiation over a wide range of wavelength bands, power levels, and frequencies. To fully exploit the power and versatility of PTR, therefore, it is necessary to choose judiciously the experimental conditions and equipment appropriate in each analytic situation. We discuss general physical aspects of PTR, emphasizing fundamental principles and methodology related to the detection of thermal reradiation. As will be shown, PTR lends itself well to explicit numerical analysis, greatly aiding the design and interpretation of experiments. Particular features relating to the investigation of high-temperature objects will be discussed. A case study is presented on the analysis of thin films on metallic surfaces, at ambient and at elevated temperatures.
Mirage-effect measurement of thermal diffusivity. Part II: theory
Authors: Kuo P. K. , Sendler E. D. , Favro L. D. , Thomas R. L.
Published: April 2011

A three-dimensional theory of a mirage-effect technique for measuring thermal diffusivity of solids is presented. A formula that incorporates sizes and separations of the heating and probe beams; the height of the probe beam above the sample surface; the thermal properties of the sample, the gas, and the backing; and the thickness of the sample is developed. The results are compared with experiments on a bulk sample and on thin slabs of various thicknesses.
Thermal-diffusivity measurements by the converging-thermal-wave technique
Authors: Cielo P. , Utracki L. A. , Lamontagne M.
Published: April 2011

A converging-thermal-wave technique is described for the measurement of thermal diffusivity in bulk or thin-sheet materials. An annular-shaped area is heated by a pulsed laser beam focused on the material's surface through a combination of spherical and conical lenses, and the surface temperature is monitored by an infrared detector focused on the center of the annulus. The converging action of the thermal flux results in a high amplitude of the detected signal with little overheating of the irradiated material. An analysis of such a technique is presented, as well as some experimental results obtained on heterogeneous materials. Several aspects relevant to the practical implementation of such a technique in an industrial environment, such as the effect of surface losses and different noise sources, are discussed.
Inverse determination of the thermal-conductivity profile in steel from the thermal-wave surface data
Authors: Vidberg H. J. , Jaarinen J. , Riska D. O.
Published: April 2011

The inverse scattering problem of determining the thermal-conductivity and heat-capacity profile in steel from surface data on the thermal wave generated by a low-frequency point or line source is formulated and solved. The solution may be used for the determination of the hardening profile. The utility of the solution is demonstrated by numerical examples with synthetic data.
Photothermal nondestructive evaluation of welding seams
Authors: Busse G. , Rief B. , Eyerer P.
Published: April 2011

Scanned photothermal radiometry is used for remote seam inspection. From the signal we can determine seam profiles and distinguish good quality seams from faulty seams.
Photoacoustic study of the thermal diffusivity of metallic glass ribbons
Authors: Kordecki R. , Bein B. K. , Pelzl J.
Published: April 2011

Thermal diffusivities of metallic glass ribbons have been measured at different annealing stages by the photoacoustic method using a gas-coupled microphone. In a symmetrical excitation geometry of the photoacoustic experiment, heat waves were generated by a laser beam at both sides of the foils. Values of thermal diffusivities have been compared with those of the electrical conductivity measured on the same samples.
Study of thin smectic A samples by a photoacoustic technique
Authors: Louis G. , Peretti P. , Billard J. , Mangeot B.
Published: April 2011

First we recall some experimental results about phase transitions in a thermotropic liquid crystal investigated by means of a photoacoustic technique. Then this paper examines the photoacoustic signal as a function of the sample thickness and the modulation frequency for rear-surface illumination of the smectic A sample. The results are consistent with the McDonald and Wetsel model and lead to the determination of thermal diffusivity.
Thermal- and acoustic-wave techniques in scanning electron microscopy
Authors: Balk Ludwig Josef
Published: April 2011

Since their introduction in 1980, thermal- and acoustic-wave techniques utilizing electron-beam excitation, denoted in the following as scanning electron acoustic microscopy (SEAM), have developed to include methods in the realm of scanning electron microscopy (SEM), giving additional and important information on material parameters compared with other SEM techniques. However, the SEAM method still has shortcomings, both theoretically and experimentally. New theories have to consider various principal sound-generation mechanisms, especially for semiconductors, ceramics, and ferromagnets. Furthermore, they must include three-dimensional and time-resolved calculations. From experimental evidence there is obviously the need for additional consideration of nonlinear signal generation. The theoretical discussion has to be supported by experiments; both phase analysis of the SEAM signal with respect to the electron-beam wave form and evaluation of the temporal SEAM behaviour are important for revealing information about the specimen. With special detectors, in situ experiments can be carried out for varying process parameters, as shown for the investigation of steel sheets. The SEAM performance has to be compared to other SEM modes by simultaneous experiments, especially for applications to semiconductors. Finally, extension to gigahertz frequencies and use of tomographic methods should increase the importance of SEAM in future.
Photothermal beam-deflection imaging of vertical interfaces in solids
Authors: McDonald F. Alan , Wetsel Jr. Grover C. , Jamieson Georges E.
Published: April 2011

A new method for calculating signals in photothermal beam-deflection imaging is reviewed and applied to the case of vertical interfaces (cracks or other thermal barriers) in opaque solids. The generality of the approach and the effect of finite probe-beam size are emphasized.
Ion-acoustic microscopy
Authors: Rose D. N. , Turner H. , Legg K. O.
Published: April 2011

This paper details the modifications to an existing ion implanter that were made to adapt it for ion-acoustic microscopy. Results of tests of the technique on samples of cubic zirconia and alumina implanted with nitrogen ions are described. The utility of the technique for monitoring the progress of implantation in metals and ceramics is discussed.
Depth-dependent two-dimensional thermal-wave source profiling in homogeneous media
Authors: Linebarger R. S. , Tittmann B. R. , Richardson J. M. , Marsh K. A.
Published: April 2011

The main thrust of thermal-wave infrared (IR) microscopy has largely been concerned with the characterization of the amplitude and phase of the received IR radiation emitted from the surface of a solid in which thermal waves are propagating. The effort reported herein describes an experiment designed to test the physical validity of a thermal-wave inversion technique. This technique allows one to spatially characterize a thermal-wave source in a homogeneous, isotropic medium, given certain boundary conditions and a priori statistical assumptions. Results for the thermal-wave profiling in an ultrasonically excited thin sheet of mylar are compared with those obtained using an equivalent mathematical model.
Photoacoustic microscopy to detect subsurface features of integrated circuits
Authors: Zhang Shu-Yi , Chen Li
Published: April 2011

Photoacoustic microscopy has been carried out on p-channel metal-oxide semiconductor integrated circuits using laser excitation and piezoelectric detection. The laser heating beam is modulated in the frequency range 25 Hz–300 kHz and is focused with a spot size of about 2 μm. The ultimate resolution of subsurface structure is better than 5 μm. By selecting a suitable operational frequency and phase angle of the photoacoustic signal, we can obtain a photoacoustic image displaying the subsurface features even in the presence of surface features with strong optical contrast.
Detection at a distance of laser-generated ultrasound using a confocal Fabry–Perot interferometer
Authors: Monchalin Jean-Pierre
Published: April 2011

A novel scheme to detect ultrasonic motion at the surface of a solid sample is presented. The surface of the sample is illuminated by a frequency-stabilized laser and the light scattered by the surface is received by a confocal Fabry–Perot interferometer, which demodulates the Doppler shift produced by ultrasound. Experimental results, obtained at a distance of 1.5 m from a machined but not polished steel plate, and excited by ultrasound produced by a laser pulse, are presented.
The converging-surface-acoustic-wave technique: anaylsis and applications to nondestructive evaluation
Authors: Cielo P. , Jen C. K. , Maldague X.
Published: April 2011

Converging surface-acoustic waves (SAW) are generated by irradiating the inspected material with an annular-shaped pulsed laser beam. The converging-SAW pulse arrival is detected by a laser interferometer focused on the center of the annulus, where the converging effect produces a strong amplification of the ultrasonic pulse. This technique can be applied either to the detection of defects or to the characterization of the material by measuring the SAW velocity or attenuation. In this paper we present an analysis of the converging-wave propagation in order to explain some features of the detected signal, such as its shape and amplitude for different positions of the probing beam. A comparison with the signal intensities expected for a diverging as well as a collimated SAW is also presented. Applications of this technique to the characterization of anisotropic materials as well as to the detection of subsurface planar defects are presented and discussed.
Optical detection of photoacoustic pulses in thin silicon wafers
Authors: Sontag H. , Tam A. C.
Published: April 2011

The propagation of photoacoustic pulses in thin silicon wafers is studied by a probe-beam deflection method. A comparison with transducer measurements is made, which suggests the existence of a nonpropagating plate mode. A signal-to-noise analysis is carried out, and the sensitivity of this detection scheme is analyzed for the case of high-frequency broad-band detection.
Nondestructive ion-implant monitoring using laser Raman spectroscopy
Authors: Wilton A. C. de , Simard-Normandin M. , Wong P. T. T.
Published: April 2011

A new Raman technique for monitoring low-dose ion implants is described. The capability for detection of implants of 20– 50 keV B+ (or equivalent [Formula: see text] energies) at doses as low as ~1010 cm−2 is of particular interest. Currently, there are few other noncontact, nondestructive methods of evaluating implant doses below 1013 cm−2 (e.g., Vt-adjust, field, and p-well implants) in patterened production wafers. The feasibility of using the technique for monitoring Vt-adjust implants is demonstrated.Low-energy B+ and [Formula: see text] ion implants in silicon were studied to determine the detection limits of the technique. Samples were analyzed immediately after implantation, without annealing. Implant doses in the range from 3 × 1016 cm−2 to the detection limit of 3 × 1010 cm−2 were characterized in this way. The presence of a surface layer of SiO2 (≤ 100 nm thick) did not interfere with the measurements. A tunable laser was used to optimize the sensitivity to implants of different energies.Since the frequency spectrum of Raman scattering can also provide information on the structure of the damaged region or on the distribution of activated boron and residual ion damage after annealing, Raman spectroscopy shows promise in several applications for in situ process monitoring of ion implantation for very large scale integration technology.
Picosecond Raman light-scattering study of hot carriers in InP
Authors: Wan Kam , Young Jeff F. , SpringThorpe A. J.
Published: April 2011

We demonstrate a novel method of using picosecond time-resolved Raman scattering to study the kinetics of nonequilibrium carriers in semiconductors. A pump–probe technique employing two separate lasers of different intensities, focal-spot sizes, and pulse durations is used to ensure that a plasma of uniform density is probed. The nonequilibrium-carrier density near the surface of a semi-insulating InP sample is estimated by fitting the photoexcited plasmon – longitudinal optic phonon coupled-mode peak in the Raman spectra. The dielectric function used in the calculation includes contributions from intraband transitions of electrons, light holes, and heavy holes as well as from interband transitions of the holes. The temporal evolution of the optically excited carrier population is modelled using a one-dimensional diffusion equation. The ambipolar diffusion constant and the surface-recombination velocity of the nonequilibrium carriers are found to be comparable to estimated values based on extrapolation of equilibrium properties.
Time-resolved photoluminescence of the defect lines in GaAs molecular-beam epitaxy
Authors: Charbonneau S. , Thewalt M. L. W. , Steiner T.
Published: April 2011

A time-resolved photoluminescence study of the defect-induced bound excitons (DIBE) observed in the energy region 1504–1511 meV in high quality molecular-beam epitaxy grown GaAs has been performed. Our results support the model that these lines consist of two distinct recombination processes. Transient resonant excitation of these DIBE demonstrate that the lines i to s can be associated with acceptor – bound exciton transitions.
Electrical characterization of n-InP grown by metal-organic vapour-phase epitaxy
Authors: Benzaquen M. , Walsh D. , Mazaruk K. , Weissfloch P. , Puetz N. , Miner C.
Published: April 2011

At room-temperature, the Hall mobility observed in epitaxic n-InP samples grown by metal-organic vapour-phase epitaxy is often lower than predicted, with a corresponding rise in the electronic concentration. These effects are attributed to the presence of a residual deep donor center that both acts as a strong scatterer and provides the additional electronic excitation observed at high temperature as it ionizes. A binding energy of 215 meV is consistent with both electrical-transport measurements and the observed photoluminescence.
Silicon nitride from microwave plasma: fabrication and characterization
Authors: Tessier Yves , Klemberg-Sapieha J. E. , Poulin-Dandurand S. , Wertheimer M. R. , Gujrathi S.
Published: April 2011

Plasma silicon nitride (P-SiN) films were prepared from SiH4–NH3 mixtures and from ternary mixtures with Ar or N2 in a large-volume microwave plasma apparatus, at substrate temperatures Ts ranging from ambient to 250 °C. Under otherwise nominally identical fabrication conditions, deposition rates were 10 to 25 times greater than those reported by others for radio-or audio-frequency plasmas. Based on film compositions determined by elastic recoil detection, and measurements of such properties as density, refractive index, etch rate in dilute HF, and the moisture permeation coefficient, our best P-SiN films (produced at Ts ≥ 200 °C) were very similar to those reported in the literature.
The preparation of epitaxial InSb films by magnetron sputtering
Authors: Webb J. B. , Halpin C. , Ehrismann J. , Noad J. P.
Published: April 2011

InSb, with its narrow bandgap, has found application in a wide variety of infrared detector applications, ranging from infrared astronomy on the Galileo satellite to tactical weapon guidance systems. However, InSb also demonstrates an extremely high electron mobility, up to 1 000 000 cm2∙V−1∙s−1 at 77 K, which makes it of particular interest for very high-speed circuit applications. In the past, most multilayer InSb structures have been prepared by conventional crystal-growth techniques, including liquid-phase epitaxy, metalorganic chemical vapour deposition, and molecular-beam epitaxy. In this presentation, the preparation of thin epitaxial films of InSb by magnetron sputtering will be discussed. Using this technique, we have deposited good quality epitaxial InSb films on [Formula: see text] InSb and [Formula: see text] GaAs. In this study, the effects of substrate temperature and sputter pressure on film morphology, composition, and growth rate are examined. As well, preliminary measurement of the electrical characteristics of these layers and their crystal quality as determined by X-ray diffraction and large-area electron-channelling pattern analysis are presented.
Comparison of field-effect transistor logic families for a GaAs depletion-mode metal semiconductor field-effect transistor
Authors: Sitch J.
Published: April 2011

Normally-on or depletion-mode field-effect transistors (MESFET) form the basis of the most mature and robust GaAs active-circuit technology. Because of the negative threshold voltage, depletion-mode metal semiconductor field-effect transistors (D-MEFSET) need level shifters to enable the output of one transistor to switch the input of the next. Buffered FET logic (BFL) is the most popular approach leading to gates that are fast and have good output-drive capability, but they occupy a lot of space and consume a lot of power. Capacitor – FET logic (CFL) has about one quarter of the power dissipation of BFL and occupies a similar area of GaAs. CFL is as fast as BFL, but the output-drive capability is inferior.The aim of the work described here is to develop a family of CFL gates that are at least as fast as BFL under all loading conditions while maintaining the power advantage of CFL. Bootstrapping the load increases the speed, but the output drive remains unsatisfactory. A super-buffered arrangement results in the lowest power and good output drive but with a slight reduction in speed compared to BFL. A combination of super buffering and load bootstrapping results in a design that meets all requirements. For example, a CFL gate with 12 mW dissipation gives a delay of 49 ps for a fan-out of unity and a loading factor of 13 ps per fan-out. This is compared with the BFL values of 60 ps with 12 ps per fan-out and 40 mW for a gate with comparable area and input capacitance.The super CFL gates have been used in the design of a 2.4 Gb∙s−1 4: 1 multiplexer, which has been successfully fabricated using a standard depletion-mode foundry process. The total power is approximately two thirds of that which would have been dissipated by a BFL realization.
A manufacturing process for gallium arsenide monolithic microwave integrated circuits
Authors: Dindo S. , North R. , Madge D.
Published: April 2011

Over the last several years, Optotek has successfully developed the capability to design and process high-frequency x-band monolithic microwave integrated circuits. A process for fabricating active devices and passive elements is described. In addition, dc and microwave measurements are presented.
Semi-automatic, volume production of silicon solar cells
Authors: Thomas R. E. , Norman C. E. , Varma S. , Schwartz G. , Absi E. M.
Published: April 2011

A low-cost, high-yield technology for producing single-crystal silicon solar cells at high volumes, and suitable for export to developing countries, is described. The process begins with 100 mm diameter as-sawn single-crystal p-type wafers with one primary flat. Processing steps include etching and surface texturization, gaseous-source diffusion, plasma etching, and contacting via screen printing. The necessary adaptations of such standard processes as diffusion and plasma etching to solar-cell production are detailed. New process developments include a high-throughput surface-texturization technique, and automatic printing and firing of cell contacts.The technology, coupled with automated equipment developed specifically for the purpose, results in solar cells with an average efficiency greater than 12%, a yield exceeding 95%, a tight statistical spread on parameters, and a wide tolerance to starting substrates (including the first 100 mm diameter wafers made in Canada). It is shown that with minor modifications, the present single shift 500 kWp (kilowatt peak) per year capacity technology can be readily expanded to 1 MWp per year, adapted to square and polycrystalline substrates, and efficiencies increased above 13%.
Growth and characterization of GaAs on Si substrates grown by molecular-beam epitaxy
Authors: Mandeville P. , SpringThorpe A. J. , Miner C. J. , Bruce R. A. , Currie J. F. , McAlister S. P.
Published: April 2011

Single-crystal GaAs layers have been grown by molecular beam epitaxy (MBE) on (100) Si substrates. Surface morphology, defect density, and optical and electrical properties have been studied as a function of the growth parameters. The characterization techniques included photoluminescence, Hall effect, cross-sectional transmission electron microscopy, and X-ray diffraction. GaAs metal semiconductor field-effect transitors on Si exhibited transconductances of 128 mS∙mm−1 and current-gain cutoff frequencies as high as 19 GHz. Special heterostructures showed Shubnikov–de Haas oscillations at low temperature and plateaux in the Hall resistance, which confirmed the presence of two-dimensional electron gas in the heterostructure.
Growth and properties of GaxIn1−xAs–GaAs strained layer superlattices grown by low-pressure metal-organic vapour-phase epitaxy
Authors: Roth A. P. , Masut R. A. , Sacilotti M. , D'Arcy P. J. , Sproule G. I. , Mitchell D. F. , LePage Y.
Published: April 2011

We have analyzed the structural and optical properties of GaxIn1−xAs–GaAs strained-layer superlattices (SLS) grown by low-pressure metal-organic vapour-phase epitaxy. Sample uniformity over 2.5 cm × 2.5 cm has been studied by X-ray diffraction and low-temperature photoluminescence. The sample composition and period are uniform in the longitudinal direction (gas-flow direction in the reactor) and in the central portion (1.5 cm) in the transverse direction. On each side, the In composition decreases slightly towards the edges, as shown by an energy shift of the photoluminescence excitonic recombinations. Comparison of experimental and calculated transition energies in a series of samples, taking into account strain and quantization, shows clearly that SLS grown on mismatched buffer layers arc under additional strain. This additional strain is not present when the layer or whole SLS thicknesses exceed a critical value beyond which the mismatch is partially accommodated by misfit dislocations.
All-optical logic in fiber systems using nonlinear refraction
Authors: Normandin R.
Published: April 2011

We describe the realization of a nonlinear all-optical logic gate and modulator for use in fiber-optics communication systems. The physical mechanisms for the optical nonlinearities and their influences on device operation and design are considered. Results are presented for the AND, NOR, NOT, and XOR logic functions with a better than 20 dB contrast ratio. The gates and modulators exhibit exceptional stability, because no resonator, feedback, or stringent wavelength control are needed. Silicon at λ = 1.06 μm has been used for these "proof-of- concept" experiments. The feasibility of picosecond operation, multiplexing, and wavelength translation is discussed.
An improved wide dynamic range silicon photodetector for integration in image sensor arrays
Authors: Doody Brian C. , Chamberlain Savvas G.
Published: April 2011

DALSA Inc., Waterloo, Ont., has designed, simulated, and tested a novel silicon photodetector offering several important performance advantages over current industry-standard devices. Currently available imaging devices offered by various manufacturers are typically sensitive to varying light intensity over three orders of magnitude in optical power, while DALSA's novel design offers a logarithmic response of greater than six orders of magnitude in light intensity.Designed to use to advantage the subthreshold effect of short-channel metal oxide semiconductor field effect transistors, the new device is readily integrated into large arrays featuring charge coupled device readout shift registers and metal oxide semiconductor support circuitry. Several devices designed by DALSA incorporating the new detector have been fabricated and tested, including discrete detectors, linear arrays, and area arrays.This paper discusses the theory of operation and performance of an improved wide dynamic range photodetector. Performance considerations include dynamic range, quantum efficiency, noise and noise equivalent power, responsivity, and speed. This photodetector can be integrated to form silicon image sensor arrays. Experimental results will also be presented that demonstrate a maximum-to-minimum detectable light intensity of greater than 106.
Carrier transport in GaAs Hall-cross devices
Authors: Nathan Arokia , Allegretto Walter , Baltes Henry P. , Smy Tom
Published: April 2011

We present two-dimensional modeling of carrier transport in cross-shaped N-type Hall devices fabricated of a GaAs epitaxial layer on a semi-insulating GaAs substrate. Using a finite-element scheme, we obtain the electrostatic potential and current density in such devices, when operated in the ohmic region and exposed to a magnetic field. In particular, we consider the carrier transport in the device when it is subject to various configurations of discontinuous magnetic induction. In addition, the magnetic response of these cross-shaped Hall devices is analyzed with respect to moving bubble domains.
Characterization of CdS–CuInSe2 solar cells by current–voltage, capacitance–voltage, and capacitance-transient measurements
Authors: Christoforou N. , Leslie J. D. , Damaskinos S.
Published: April 2011

CdS–CuInSe2 solar cells, which have an efficiency of 9%, have been studied by current–voltage, capacitance–voltage, and capacitance-transient measurements over the temperature range 90–380 K. Deep-level transient spectroscopy analysis of the capacitance transient measurements reveals one majority carrier trap with an activation energy of 0.70 ± 0.02 eV. Although the present experiment cannot establish definitely if the trap is in the CdS or CuInSe2 layer, arguments are presented that it is a hole trap in the p-type CuInSe2 layer. Current–voltage measurements indicate a reversible increase in the reverse-bias leakage current with increasing temperature above 300 K. Evidence is presented that suggests that the rectifying barrier height in the CdS–CuInSe2 solar cell decreases rapidly with temperature above 300 K. Capacitance versus voltage measurements suggest that the depiction layer being studied is primarily in the CuInSe2, but the temperature dependence of the ionized charge concentration N(x) cannot be totally explained although one possible cause is suggested.
Dissolution characteristics of poly(methyl methacrylate) as an X-ray resist
Authors: Lehockey E. M. , Wice J. D. , Reid I.
Published: April 2011

A reversion in the dissolution characteristics of X-ray irradiated poly(methyl methacrylate) (PMMA) is shown experimentally, and a model is developed to explain the behaviour. The PMMA has been irradiated with 11 kV Cu X-rays to doses up to 240 μA∙min∙cm−2 at dose rates of 4 and 8 μA∙cm−2. The doses are determined by photoelectron emission and are therefore only relative measurements. The dissolution rate of the irradiated PMMA in a 1:2 developer of methyl isobutyl ketone and isopropyl alcohol is measured as a function of X-ray dose. For the first time, a model is developed that predicts this reversion in the dissolution rate. For the model to predict a reversion point, it is necessary to treat the processes of chain scission and cross-linking as operating on separate sites. The main requirement here is that cross-linked bonds do not become sites for scission. If this requirement is not made, no reversion is predicted.
Implantation ionique à haute énergie du Si dans l'AsGa
Authors: Azelmad A. , Currie J. F. , Yelon A. , Sood P.
Published: April 2011

We present a study of the implantations of 7 MeV Si ions into GaAs at a dose of 1014 ions/cm2. The depth profile of the ions is measured by secondary-ion mass spectroscopy. It is found to be in good agreement with a Monte Carlo calculation based on the Lindhard, Scharff and Schiott model of ion collisions in solids. The penetration depth of the Si ions is Rp = 3.38 μm, with a standard deviation ΔRp = 0.35 μm. The samples are annealed in a rapid annealing oven. A maximal activation of dopants is obtained with a temperature of 850 °C for 20 s. The resistivity and average mobility after this anneal are ρ = 3.48 × 10−3 Ω∙cm and μn = 2800 cm2∙V−1∙s−1. This suggests that the majority of ions are activated.
Diffusion of Ge in GaAs at SiO2-encapsulated Ge–GaAs interfaces
Authors: Kavanagh L. , Magee Charles W.
Published: April 2011

The diffusion of Ge in semi-insulating GaAs was investigated for annealing temperatures in the range 650–800 °C. The samples consisted of electron-beam or metalorganic chemical-vapour deposition deposited Ge–GaAs interfaces encapsulated with SiO2. Ge diffusion profiles, measured with secondary-ion mass spectroscopy (SIMS), had a characteristic plateau and steep slope at the diffusion front, similar to those obtained for Si and Sn diffusion at SiO2-encapsulated GaAs. A saturated-surface concentration of 2 × 1019 atoms∙cm−3 was observed for anneals above 750 °C, likely the solid solubility of Ge in GaAs at these temperatures. Based on the Greiner–Gibbons substitutional-pair diffusion model (Appl. Phys. Lett. 44, 750 (1984)), the Ge-pair diffusion coefficients were calculated from the SIMS data. They ranged from 1 × 10−13 to 3 × 10−12 cm2∙s−1 but varied depending upon the annealing time and sample structure. A new model that eliminates the necessity for paired-Ge diffusion was introduced. It proposed that dissociation and out-diffusion of GaAs into the SiO2 produced a nonequilibrium flux of vacancies into the GaAs. Calculated profiles using a position-dependent Ge diffusion coefficient were shown to fit the SIMS data independent of the type of Ge diffusing species, whether single ions or pairs.
Complementary metal oxide semiconductor compatible high-voltage transistors
Authors: Kempf P. , Hadaway R. , Kolk J.
Published: April 2011

The purpose of this work was to study the implementation of high-voltage transistors using standard 3–5 μm complementary metal oxide semiconductor (CMOS) technology with a minimum of additional photolithographic or implant steps. A fabrication process was designed to accommodate a variety of high-voltage transistors with greater than 450 V breakdown voltage and low-voltage CMOS. Extensive use was made of a two-dimensional device model and a one-dimensional process model to determine suitable process parameters. The necessary conditions to produce a high-voltage double-diffused metal oxide semiconductor (DMOS) structure, as well as both n-well and p-well regions for CMOS transistors, and a thick gate oxide required to sustain the full blocking voltage were the main determinants of the process flow. Lateral DMOS (LDMOS), vertical DMOS (VDMOS), conductivity modulated FET (COMFET), and MOS triac (TRIMOS) devices were fabricated on the same chip as standard CMOS transistors using the developed fabrication sequence. This paper includes the results of the process modelling, device design, and electrical measurements.
A novel GaAs optical waveguide electrooptic modulator
Authors: Belanger M. , Currie J. F. , Maciejko R. , Najafi S. I. , Yelon A.
Published: April 2011

A novel electrooptic modulator, based on GaAs, is proposed. The configuration as well as the operating principle yield high packing density and insensitivity to the material variation.
a-Si:N:H prepared by reactive evaporation in ammonia vapour
Authors: Audas R. D. , Brodie D. E.
Published: April 2011

The reactive evaporation of Si in an ammonia ambient has been used to produce a-Si:N:H thin films. These films are "intrinsic-like" with low room-temperature conductivities (<10−12 S∙cm−1), high activation energies (0.9 eV), and high optical bandgaps (1.9 eV). Films prepared in this manner have been doped using co-evaporation of antimony (n type) and indium (p type). The addition of 2 at.% indium or antimony results in an increase in the room-temperature conductivity by eight and six orders of magnitude respectively. The undoped and doped samples are photoconductive when illuminated with a quartz-halogen source.
Electron paramagnetic resonance of magnetic clusters in Pb1−xGdxTe
Authors: Bartkowski M. , Northcott D. J. , Park J. M. , Reddoch A. H. , Williams D. F. , Lamarche G.
Published: April 2011

Measurements of electron paramagnetic resonance (EPR) and of susceptibility with a superconducting quantum interference device (SQUID) have been performed on Pb0.995Gd0.005Te crystals from 4.2 to 300 K. The EPR spectra consist of two components, one showing the fine structure of Gd3+ ions in a cubic environment and the other a broad line, which we attribute to clusters of interacting Gd ions. The resonant field of the cluster line is almost isotropic under sample rotation in the [Formula: see text] crystallographic plane, while the line width varies by a factor of 2.5 between [100] and 30° from it. This result suggests that an exchange-narrowing mechanism is responsible for the cluster line. The ratio of cluster-line intensity to fine-structure intensity increases with decreasing temperature down to 10 K and then decreases. This decrease may be related to the spin freeze-out seen in ac susceptibility. The line-width broadening of the cluster and the single-ion lines are similar below 20 K, with a higher rate for the cluster line. The Curie–Weiss temperature is negative and small for both clustered and single spins, reflecting a weak antiferromagnetic interaction.
The effect of co-evaporation on ZnS:Mn electroluminescent characteristics
Authors: Fuh A. , Gallinger R. P. , Caporaletti O.
Published: April 2011

We present a discussion of the brightness–voltage (B–V) response of thin-film electroluminescent (TFEL) devices prepared by the simultaneous evaporation of ZnS and Mn (or MnS) using two separate sources. Crystal structure, threshold voltage, saturation brightness, and memory margin of the B–V characteristics have been studied as a function of the deposition rate of dopant material relative to ZnS. Optimum annealing conditions of the devices are also given. These results indicate that co-evaporation can be advantageously employed to fabricate memory TFEL display devices with excellent characteristics.
Convectively driven superfluid turbulence in dilute solutions of 3He in superfluid 4He
Authors: Ecke Robert E. , Haucke Hans , Wheatley John
Published: April 2011

A dilute solution of 3He in superfluid 4He usually behaves as a single-component classical fluid in the context of thermal convection. However, certain convective states can be excited that do not seem to exist in classical convection. These states are characterized by noisy temperature fluctuations and a pronounced decrease in heat transport relative to the classical convecting states. Critical convective-flow fields are observed analogous to critical velocities for superfluid turbulence in pipes. The magnitudes of the average critical velocities for these two types of superfluid turbulence are in good agreement. Also, a quantitative estimate of energy dissipation due to the interaction of normal fluid and quantized vortex lines is consistent with the large decrease in heat transport for the turbulent states. These states are identified as states of convectively driven superfluid turbulence.
Proposed major revision in the millikelvin temperature scale
Authors: Greywall Dennis S.
Published: April 2011

A new millikelvin temperature scale is presented that is based, in part, on the constraint that the normal-phase specific heat of liquid 3He be linear in temperature with a proportionality constant taken from higher temperature specific-heat measurements. The new scale differs considerably from all of the commonly used scales but provides an explanation for the long-standing 3He specific-heat controversy.
Magnetic structure of solid 3He observed by neutron diffraction
Authors: Benoit A. , Bossy J. , Flouquet J. , Schweizer J.
Published: April 2011

Neutron-diffraction measurements have been performed on a 3He crystal below the magnetic-ordering transition. The measurements have allowed, for the first time, the observation of a magnetic signal. They prove directly the occurrence of an antiferromagnetic order with a propagation vector (1/2, 0, 0).
Effective interactions, elementary excitations, and transport in the helium liquids
Authors: Pines David
Published: April 2011

Polarization potentials, the self-consistent fields that describe the primary consequences of the strong atom–atom interaction in the helium liquids, are developed for liquid 4He and 3He. Emphasis is placed on the common physical origin of the effective interactions in all helium liquids, and the hierarchy of physical effects (very short-range atomic correlations, zero-point motion, and the Pauli principle) that determine their strength is reviewed. An overview is then given of the application of polarization potential theory to experiment, including the phonon–maxon–roton spectra of 4He and 3He–4He mixtures, the phonon–maxon spectrum of normal and spin-polarized 3He, and the transport properties of superfluid 4He and of normal and spin-polarized 3He.
Phase slippage and vortex nucleation in the critical flow of superfluid 4He through an orifice
Authors: Varoquaux E. , Avenel O. , Meisel M. W.
Published: April 2011

We describe in detail our phase-slippage experiments in superfluid 4He.
Josephson flow oscillations in superfluid 3He–B
Authors: Monien H. , Tewordt L.
Published: April 2011

Experiments for observing pressure-induced Josephson oscillations in superfluid 4He renewed the interest for analogous experiments in superfluid 3He. The weak coupling of two superfluids is obtained by a small channel with dimensions in the order of the coherence length. The order-parameter matrix in channels with a rectangular cross section is calculated with and without rigid boundary conditions. From the order-parameter functions, the supercurrent J(ϕ) through the orifice, and the Ginzburg–Landau free energy, F(ϕ) is calculated for different cross sections. A new feature of the function J(ϕ) in comparison to the current-phase relationships for superconducting microbridges is the occurrence of two nontrivial zeros of J(ϕ). It turns out that the frequency, ω, of the Josephson flow oscillations, which follow the sudden application of a force ΔF on a diaphragm, depends on ΔF in a way similar to that in which the frequency of the parallel ringing experiment in 3He–A depends on the field step ΔH.
Deep inelastic neutron scattering from quantum liquids
Authors: Sokol P. E.
Published: April 2011

Liquid helium has been studied for many years because of its unusual properties. The large quantum zero-point motion and the quantum statistics of the particles have a strong effect on the behavior of the liquid. Deep inelastic neutron scattering provides a unique tool for studying the microscopic dynamics of these systems. The results of recent experiments on both liquid 3He and 4He are discussed.