bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoemission studies of a-SixC1−x:H/a-Si and a-SixC1−x:H/ hydrogenated amorphous silicon heterojunctions
Authors: Evangelisti F. , Fiorini P. , Giovannella C. , Patella F. , Perfetti P. , Quaresima C. , Capozi M.
Published: February 2003

The interfaces between hydrogenated amorphous silicon-carbon alloy and amorphous silicon, both hydrogenated and not, were investigated by photoemission spectroscopy. It is found that the valence-band discontinuity is 0.15±0.1 eV for the amorphous Si case and zero within the experimental uncertainty for the hydrogenated amorphous Si. The relevance of this result for understanding the behavior of the p-i-n amorphous solar cells is discussed.
Heteroepitaxial growth of high mobility InAsP from the vapor phase
Authors: Wang P. J. , Wessels B. W.
Published: February 2003

High quality InAsxP1−x epitaxial layers were heteroepitaxially deposited on InP substrates from the vapor phase using the hydride technique. For phosphorus rich alloys electron mobilities as high as 29 800  cm2/Vs were observed at 77 K. Electrical data indicated that ionized impurity scattering was limiting the mobility at low temperatures since alloys had 77-K mobilities comparable to that of InP grown in this system. Alloys with high electron mobilities could be prepared without deliberate compositional grading.
Interface effects in titanium and hafnium Schottky barriers on silicon
Authors: Taubenblatt Marc A. , Thomson Douglas , Helms C. R.
Published: February 2003

The effect of Si surface contaminants present prior to metal deposition, and that of post-metalization anneals has been investigated for Ti and Hf Schottky barriers on Si. These diodes have been prepared in ultrahigh vacuum, characterized with Auger spectroscopy and measured in situ using internal photoemission, and ex situ using current-voltage measurements. Although barriers to p-type Si as high as 0.9 eV have been reported in the literature for these metals, barriers of 0.72 eV were the highest observed in this investigation, for surfaces contaminated with significant amounts of oxygen.
Effects of annealing on the dark conductivity and photoconductivity of rf sputtered hydrogenated amorphous silicon
Authors: Ozturk M. C. , Thompson M. G.
Published: February 2003

The dark conductivity and photoconductivity of rf sputtered hydrogenated amorphous silicon (a-Si:H) as a function of annealing temperature and hydrogen partial pressure are reported. Isochronal annealing to 350 °C results in a decrease in dark conductivity and an increase in photoconductivity consistent with a reduction in the density of states in the pseudogap. Annealing above 350 °C has the effect of sharply increasing the dark conductivity in more heavily hydrogenated samples and decreasing the photoconductivity. This behavior is associated with the generation of defect states due to hydrogen evolution. The results indicate that annealing rf sputtered a-Si:H below 350 °C can lead to improved electrical properties.
Polar glass ceramics for sonar transducers
Authors: Ting R. Y. , Halliyal A. , Bhalla A. S.
Published: February 2003

Glass ceramics are shown in this study to be a new class of transduction materials for application in sonar transducers. It is found that glass ceramics of Ba2TiSi2O8 have high hydrostatic voltage sensitivity, low dielectric loss, and low dielectric constant. These properties are also shown to be practically independent of pressure up to 35 MPa. The free-field voltage sensitivity of a glass-ceramic prototype hydrophone is higher than that based on a commonly used lead zirconate titanate ceramic element.
Observation of anomalous electrical transport properties in MoSi2 films
Authors: Woerlee P. H. , van Attekum P. M. Th. M. , Hoeben A. A. M. , Hurkx G. A. M. , Wolters R. A. M.
Published: February 2003

We measured the temperature dependence of the electrical resistivity and of the Hall constant for MoSi2 films between 3.5 and 350 K. A behavior quite unusual for a metal was observed. The most striking effect is the proportionality of the resistivity with T 2 for temperatures between 70 and 220 K. Further, we find the Hall constant, which is positive at room temperature, to change sign around 170 K. The bulk resistivity of the MoSi2 at 295 K is deduced to be approximately 18 μΩ cm. We suggest that the observed anomalies and the high resistivity are due to strong s-d scattering.
HgCdTe heterojunction contact photoconductor
Authors: Smith D. L. , Arch D. K. , Wood R. A. , Scott M. Walter
Published: February 2003

A new photoconductor device structure is described utilizing a heterojunction contact which incorporates a higher band-gap HgCdTe alloy between the metal contact and the normal band-gap photoconductor. A theoretical treatment of the heterojunction contact photoconductor (HCP) device shows that carrier sweepout can be virtually eliminated; the calculations predict elimination of ‘‘saturation’’ of responsivity and a very large increase in responsivity. HCP devices were fabricated; experimental results verified the theory in several ways. A responsivity was measured at 80 K of about 450 000 V/W at 30 V/cm and over 1 500 000 V/W at 125 V/cm.
Experimental tests of a moving foil as a high current vacuum opening switch
Authors: Kania D. R. , Zimmermann E. L. , Trainor R. J. , Veeser L. R. , Jones L. A.
Published: February 2003

We report on the first experimental investigation of the use of a magnetically accelerated foil—moving foil—as a vacuum opening switch. One megampere, 60% of the total current, was transferred to a low inductance path in 800 ns.
Direct evidence for the role of gold migration in the formation of dark-spot defects in 1.3-μm InP/InGaAsP light-emitting diodes
Authors: Chin A. K. , Zipfel C. L. , Geva M. , Camlibel I. , Skeath P. , Chin B. H.
Published: February 2003

The results of our previous study of dark-spot defects (DSD’s) in aged 1.3-μm InP/InGaAsP light-emitting diodes (LED’s) have strongly suggested that the defects form as a result of the migration of gold from the p contact into various epitaxial layers. To provide further support for this degradation mechanism, we compare, in this study, the formation of DSD’s in LED’s fabricated with the usual BeAu p metallization and a new platinum p contact. After accelerated aging (200 °C junction temperature, 20 kA/cm2, 3×103 h), DSD’s were observed only in the devices with BeAu contacts, thus directly identifying the active role of gold migration in DSD formation.
Self-developing photoetching of organic films by near UV radiation
Authors: Franke H.
Published: February 2003

Thin films of a photosensitive material based on polymethyl methacrylate have been fabricated on glass substrates. By illumination with light of a photoresist illuminator (300–450 nm) the material can be etched out in the illuminated areas. Film thickness d changes from, e.g., 12 to 4 μm after 20-min illumination. Simultaneously the refractive index n decreases by 2×10−2. Additional annealing treatment causes little further development of n and d patterns. Spatial resolution is limited by lithographic technique and is smaller than 1 μm.
Characterization of semi-insulating liquid encapsulated Czochralski GaAs by cathodoluminescence
Authors: Wakefield B. , Leigh P. A. , Lyons M. H. , Elliott C. R.
Published: February 2003

Characterization of semi-insulating liquid encapsulated Czochralski GaAs by cathodoluminescence in a scanning electron microscope at liquid He temperatures has revealed that the main residual impurity, carbon, is not distributed homogeneously within the material. This may lead to nonuniformities in the electrical properties of the material.
A 14% efficient nonaqueous semiconductor/liquid junction solar cell
Authors: Gibbons James F. , Cogan George W. , Gronet Chris M. , Lewis Nathan S.
Published: February 2003

We describe the most efficient semiconductor/liquid junction solar cell reported to date. Under W-halogen (ELH) illumination, the device is a 14% efficient two-electrode solar cell fabricated from an n-type silicon photoanode in contact with a nonaqueous electrolyte solution. The cell′s central feature is an ultrathin electrolyte layer which simultaneously reduces losses which result from electrode polarization, electrolyte light absorption, and electrolyte resistance. The thin electrolyte layer also eliminates the need for forced convection of the redox couple and allows for precise control over the amount of water (and other electrolyte impurities) exposed to the semiconductor. After one month of continuous operation under ELH light at 100 mW/cm2, which corresponds to the passage of over 70 000 C/cm2, thin-layer cells retained over 90% of their efficiency. In addition, when made with Wacker Silso cast polycrystalline Si, cells yield an efficiency of 9.8% under simulated AMl illumination. The thin-layer cells employ no external compensation yet surpass their corresponding experimental (three-electrode) predecessors in efficiency.
Experimental analysis of a chemical oxygen-iodine laser
Authors: Bonnet J. , David D. , Georges E. , Leporcq B. , Pigache D. , Verdier C.
Published: February 2003

A small scale chemical oxygen-iodine laser is described. The maximum extracted cw laser power is 4 W. Water vapor and molecular iodine concentration measurements are presented in addition to the more usual fluorescence measurements. The effects of water vapor on the extracted laser power, on the dissociation of iodine, and on the quenching of the O2 1Δ–I 2P1/2 system, are observed. It is shown that a relatively large amount of water vapor can be tolerated. An interesting practical consequence is the possibility of lasing at the same power level with less dangerous 30% H2O2 instead of the highly concentrated H2O2 used in previous studies.
Dynamics of optical TE to TM mode conversion in LiNbO3 channel waveguides
Authors: Lam Juan F. , Yen Huan W.
Published: February 2003

We report an analysis of the phenomenon of TE to TM mode conversion in LiNbO3 waveguides. The process is a consequence of the photorefractivity associated with the tensor character of the photovoltaic effect. We predict the existence of a nonlinear phase shift during the energy transfer process as well as a threshold behavior in the dynamics of energy exchange.
Optical bistability and chaos in a semiconductor laser with a saturable absorber
Authors: Kawaguchi Hitoshi
Published: February 2003

Bistable operation and self-sustained pulse oscillation in a semiconductor laser with inhomogeneous excitation are examined. These two characteristics are obtained by the control of the spatial distribution of carrier lifetime in the laser resonator. This laser, which is modulated by injection current, is predicted to have period-doubling bifurcation, and provides a compact optical chaos emitter.
Direct electron beam writing of gallium oxide on GaAs(111) As surfaces
Authors: Alonso M. , Sacedón J. L. , Soria F.
Published: February 2003

In this letter we show the possibility of a direct electron beam writing on GaAs (111) As by electron stimulated oxidation. An estimate of the writing velocity is also given. The analysis of the profiles of the oxide spots by Auger spectroscopy indicates the stability of the gallium oxide formed, and the post-oxidation formation of an As-rich interface.
Nonlocal response to a focused laser beam in one-dimensional Josephson tunnel junctions
Authors: Chang Jhy-Jiun , Ho C. H.
Published: February 2003

A perturbation method is used to calculate the change of the total zero-voltage current ΔIc(y0) flowing through a one-dimensional Josephson tunnel junction due to a focused laser beam irradiated at y0. Nonlocal response of the phase difference function φ as well as the local response of the  amplitude J to the laser beam are included. In the junction configuration we considered, it is found that the nonlocal effect can, depending upon the external magnetic field, make the spatial dependences of ΔIc(y0) and the current distribution different.
Picosecond photoconducting Hertzian dipoles
Authors: Auston D. H. , Cheung K. P. , Smith P. R.
Published: February 2003

The generation transmission, and detection of extremely rapid electromagnetic pulses have been achieved using fast photoconducting materials as time-varying Hertzian dipoles. This approach, which has a measured time response of 1.6 ps, overcomes many of the limitations imposed by transmission line structures, and due to its jitter-free behavior and open geometry is ideally suited for transient electromagnetic measurements of materials.
Investigation of effectiveness of gas flow action on arc discharge initiated in contact breaking
Authors: Azizov E. A. , Akhmerov N. A. , Godonyuk V. A.
Published: February 2003

Heavy-current arc discharges initiated in breaking tubular electrodes were studied. The action of transonic gas flow on discharge electrical characteristics in the case of interelectrode gap monotonic increase was investigated. The electrode mean velocity amounted to 10–40 m/s. All the experiments were carried out on a model of a single-shot circuit breaker with an explosive actuator for breaking a current-carrying element.
Wavelength coverage of lead-europium-selenide-telluride diode lasers
Authors: Partin Dale L. , Thrush Christopher M.
Published: February 2003

Diode lasers made from a new semiconductor material, Pb1−xEuxSeyTe1−y, have recently been developed for sensor applications. This material is grown by molecular beam epitaxy and may be lattice matched to PbTe substrates. Double heterojunction mesa stripe diode lasers have been fabricated and the laser emission energy determined as a function of composition. At 80 K, the emission energy follows the relation E (in eV)=0.219+5.51x. With the range of active region compositions so far explored (up to x=0.046, y=0.054), the wavelength range 6.6–2.6 μm can be covered under pulsed conditions (6.6–3.8 μm cw). Laser operation up to 190 K pulsed, 147 K cw, has been attained with up to 1-mW single mode output power. These devices are useful for spectroscopic measurements of molecules in a gas or adsorbed onto surfaces.
Protection of an interrupted molecular-beam epitaxially grown surface by a thin epitaxial layer of InAs
Authors: Chang Yu-Jeng , Kroemer Herbert
Published: February 2003

When the molecular-beam epitaxial (MBE) growth of GaAs or (Al,Ga)As is interrupted and the surface is exposed to air for other kinds of processing, a high concentration (>2×1011 cm−2) of surface defects tends to form which will show up as highly detrimental interface defects if the MBE growth is subsequently resumed. We show that the surface can be protected by a thin epitaxial layer of InAs, which is highly resistant to many kinds of processing steps, and which can be thermally removed before resumption of growth, leading to an ‘‘invisible’’ restart interface.
Correlation of threshold voltage of implanted field-effect transistors and carbon in GaAs substrates
Authors: Chen R. T. , Holmes D. E. , Asbeck P. M.
Published: February 2003

We have investigated the effect of residual carbon concentration on the threshold voltage (VT) of field-effect transistors (FET’s) fabricated by direct ion implantation with undoped semi-insulating liquid encapsulated Czochralski GaAs. The results show the direct dependence of VT on the carbon concentration. For depletion-mode FET’s, ‖VT‖ decreases linearly as the carbon concentration increases, with a variation of 185 mV in VT for a 1×1016 cm−3 change of carbon concentration, consistent with theory. Our results also show that the radial carbon concentration across crystals is uniform to within about ±6×1014 cm−3; however, the carbon concentration invariably decreases toward the tail of the crystals by 40% or more. As a result, ‖VT‖ tends to increase toward the tail of the crystals.
Optical levitation using single mode fibers and its application to self-centering of microlenses
Authors: Pocholle Jean-Paul , Raffy Jean , Combemale Yves , Papuchon Michel , Roosen G. , Plantegenest M. T.
Published: February 2003

Optical levitation using single mode fibers has been experimentally demonstrated. The use of fibers in levitation experiments presents obvious advantages, in particular, concerning the case with which complicated optical paths can be realized without additional optical components. In addition the microsphere can be accurately deposited on the fiber end by simply controlling the optical guided power. This technique has been used to position microlenses self-centered on the guided mode to improve the coupling efficiency between a semiconductor laser and a single mode fiber.
Pearlescent suspension display concepts
Authors: Bostwick B. D. , Labes M. M.
Published: February 2003

Pearlescent plates whose density is matched to a solvent medium form stable suspensions in which the plate orientation can be switched by magnetic and electric fields. The time frame for these effects is of the order of seconds to minutes, the visual optical effect being a change from a strong reflective pearl essence to a transparent state.
High-speed analog and digital modulation of 1.51-μm wavelength, three-channel buried crescent InGaAsP lasers
Authors: Eisenstein G. , Koren U. , Tucker R. S. , Kasper B. L. , Gnauck A. H. , Tien P. K.
Published: February 2003

The microwave modulation characteristics of 300-μm-long, 1.51-μm wavelength, three-channel buried crescent lasers fabricated on semi-insulating InP substrates have been studied. A small-signal bandwidth of 5.7 GHz has been obtained and digital modulation with pseudorandom sequences at 2 and 4 Gb/s has been demonstrated.
Suppression of preheating in a double foil target irradiated by a 10.6-μm laser
Authors: Nishimura H. , Mima K. , Daido H. , Tateyama R. , Ogura K. , Fujita M. , Nakai S. , Yamanaka C.
Published: February 2003

A new method which suppresses target preheating by hot electrons is proposed. The suppression was verified by means of particle measurements on the rear side of a foil irradiated by a CO2 laser with a thick plate placed in front of the irradiated foil to absorb the energetic electrons which preferentially expand from the critical surface. The results can be explained by the generation of the electrostatic field between the foil and the plate.
Density of two-dimensional electron gas in modulation-doped structure with graded interface
Authors: Grinberg A. A. , Shur M. S.
Published: February 2003

We have calculated the concentration nso of the two-dimensional gas in the AlGaAs/GaAs modulation-doped structures with graded heterointerfaces. Our calculation shows that nso increases with the increase in the grading length WGR at small values of WGR. Depending on composition and doping of the AlGaAs layer the maximum value of nso is achieved for WGR between 20 and 70 Å. An increase in the concentration of the 2-d gas leads to a larger device transconductance and to a large current swing. Hence, the device performance may be improved by grading the heterointerface.
Single longitudinal mode operation of an XeCl laser
Authors: Pacala Thomas J. , McDermid I. Stuart , Laudenslager James B.
Published: February 2003

Single longitudinal mode output from a directly tuned, long pulse, magnetically switched XeCl laser is reported for the first time. Mode control was achieved using spatial aperatures and intracavity etalons. The narrow bandwidth laser output was diffraction limited with an optical pulse width of 30 ns, which would yield a transform limited bandwidth of 30 MHz.
Evidence that the 0.635-eV luminescence band in semi-insulating GaAs is not EL2 related
Authors: Samuelson L. , Omling P. , Grimmeiss H. G.
Published: February 2003

By utilizing the quenching effect of the deep EL2 defect in semi-insulating GaAs in different optical measurements, it has been possible to show that the 0.635-eV photoluminescence band is not related to EL2. The previously observed ‘‘EL2 behavior’’ of this luminescence band is shown to be only an indirect effect where the EL2 level acts as an intermediate step in the excitation process. Evidence is also given that the sharp below-band-gap photoluminescence excitation peak (1.50 eV) which has been regarded as an EL2 feature is actually not related to EL2. A new photoluminescence excitation band with a threshold at ∼1.1 eV is also observed.
Embedded-mirror semiconductor laser
Authors: Laidig W. D. , Lee J. W. , Caldwell P. J.
Published: February 2003

Data are presented demonstrating the operation of a current-injection laser diode with embedded reflectors instead of etched or cleaved facets. The laser structure, grown by molecular beam epitaxy, uses AlAs-GaAs superlattices SL’s in place of conventional AlxGa1−xAs cladding layers. The sample is patterned, etched, and Zn diffused to selectively disorder the SL cladding layers producing a ∼200×∼100 μm rectangular laser cavity embedded in the surrounding AlxGa1−xAs. Following Si3N4 deposition and metallization, the diodes are cut (not cleaved) with intentionally damaged edges. These devices operate as lasers (77 K, pulsed operation) with a mode spacing corresponding to either the ∼100-μm or the ∼200-μm cavity length formed by the selective interdiffusion of the SL cladding layer. This embedded-mirror laser structure may be useful in the development of optical integrated circuits by allowing semiconductor lasers to be monolithically integrated with other optical devices.
Single quantum well lead-europium-selenide-telluride diode lasers
Authors: Partin Dale L.
Published: February 2003

It is desirable to increase the operating temperature of long wavelength lead-chalcogenide diode lasers to simplify cooling system requirements. Recently, double heterostructure Pb1−xEuxSeyTe1−y diode lasers (grown by molecular beam epitaxy) operated up to 147 K cw (180 K pulsed). The output photon energy of these devices is linear with x in the wavelength range 6.6– 2.7 μm. The growth of single quantum well lead-chalcogenide diode lasers is now reported for the first time. These devices had PbTe quantum wells with PbEuSeTe confinement layers. The width of the quantum wells, Lz, was varied from 300 to 250 Å. Strong quantum effects are observed for Lz ≲ 1200 Å because of the small carrier masses (me∼mh∼0.04mo ). The shift in laser emission energy is in approximate agreement with that calculated from a finite square well potential. At low temperatures (≲100 K), these lasers appear to operate on transitions between n=1 states in the conduction and valence bands at threshold. Transitions between the n=2 states require a higher current which decreases with increasing temperature until the laser switches to the n=2 transition at threshold. The threshold current then increases relatively slowly with temperature, yielding cw operation up to 174 K (at 4.41-μm wavelength), and pulsed operation up to 241 K (at 4.01 μm). These are the highest operating temperatures ever reported for lead-chalcogenide diode lasers, and increases their potential usefulness for spectroscopic applications and for long wavelength fiber optics communications.
Detuned loading in coupled cavity semiconductor lasers—effect on quantum noise and dynamics
Authors: Vahala Kerry , Yariv Amnon
Published: February 2003

We derive the modulation and noise properties of a semiconductor laser consisting of an active cavity loaded by a passive cavity. The results indicate that under certain conditions the direct modulation bandwidth can be doubled with simultaneous phase noise reduction as compared to a conventional laser.
Effect of fiber-far-end reflections on intensity and phase noise in InGaAsP semiconductor lasers
Authors: Agrawal G. P. , Olsson N. A. , Dutta N. K.
Published: February 2003

The effect of optical feedback on the intensity-noise spectrum and the longitudinal-mode line shape of a 1.55-μm InGaAsP laser is investigated for reflections arising from the far end of a 7.5-km-long fiber. The intensity noise near the relaxation-oscillation frequency is significantly enhanced by the reflection feedback. Owing to the intercavity coupling, the enhancement is, however, frequency dependent and the noise spectrum exhibits high-contrast modulations with a period corresponding to the fiber-cavity longitudinal-mode separation. A simple rate equation model is used to explain the observed behavior.
Nonelastic acoustic-phonon-electron interactions in Monte-Carlo simulations at low fields
Authors: Hesto F. , Pelouard J-L. , Castagné R. , Pône J-F.
Published: February 2003

Monte-Carlo simulation is an efficient means of investigating electron transport in semiconductors. Nevertheless, the prevailing physical phenomena at low electric fields are usually neglected because a Monte-Carlo algorithm is needed only at rather high fields. It is shown that reaching thermodynamic equilibrium between electrons and crystal lattice in a Monte-Carlo simulation requires only including inelastic interactions with acoustic phonons at the center of the Brillouin zone. Electron energy and velocity distributions at equilibrium resulting from this umproved model are compared with the theoretical Fermi–Dirac distribution.
Nonlinear far-infrared photoconductivity in Ge:Ga
Authors: Leung M. , Drew H. D.
Published: February 2003

We report the observation of photoconductivity in Ge:Ga (NA =3× 1016 cm−3 and 8×1015 cm−3) at 4.2 °K, using high-intensity, far-infrared radiation (I≂10 kW/cm2; λ=496  μm). This observation is unexpected since the impurity ionization potential (Ei =10.97 meV) is greater than the photon energy (hν=2.5 meV). The excitation of holes into the valence band is confirmed by the large decrease in sample resistance (from ∼MΩ to ≤20 Ω) and the decrease in transmission at high intensities. A two-step excitation model matches the behavior of the intensity dependence of the photoconductivity.
Fermi energy control of vacancy coalescence and dislocation density in melt-grown GaAs
Authors: Lagowski J. , Gatos H. C. , Aoyama T. , Lin D. G.
Published: February 2003

We have discovered a striking effect of the Fermi energy on the dislocation density in melt-grown GaAs. Thus, a shift of the Fermi energy from 0.1 eV above to 0.2 eV below its intrinsic value (at high temperature, i.e., near 1100 K) increases the dislocation density by as much as five orders of magnitude. Ther Fermi energy shift was brought about by n-type and p-type doping at a level of about 1017 cm−3 (under conditions of optimum partial pressure of As, i.e., under optimum melt stoichiometry). This effect must be associated with the fact that the Fermi energy controls the charge state of vacancies (i.e., the occupancy of the associated electronic states) which in turn must control their tendency to coalesce and thus the dislocation density. It appears most likely that gallium vacancies are the critical species.
Mobility of the two-dimensional electron gas in GaAs-AlxGa1−xAs heterostructures
Authors: Lin B. J. F. , Tsui D. C. , Paalanen M. A. , Gossard A. C.
Published: February 2003

The mobility of the two-dimensional electron gas in GaAs-Alx Ga1−xAs heterostructures was studied systematically in ten samples with density from 1.33×1011 to 7.8×1011 cm−2 in the temperature range T=4.2–300 K. A theoretical calculation using the variational wave function was carried out for scattering by screened impurity ions, optical phonons, and acoustic phonons through deformation and piezoelectric couplings. Good quantitative agreement between theory and experiment was obtained with no adjustable parameters.
Input impedance of an amplifier based on a dc superconducting quantum interference device
Authors: Hilbert Claude , Clarke John
Published: February 2003

The measured input impedance of an amplifier involving a coil tightly coupled to a dc superconducting quantum interference device (SQUID) is found to depend on the current and flux biases of the SQUID. Variations in the input inductance arise from the reflected dynamic inductance of the SQUID, and are in reasonable agreement with the predictions of an analog simulator. Variations in the input resistance, on the other hand, arise from feedback between the output of the SQUID and the input circuit, and are in approximate agreement with the predictions of a simple model.
Fourier-transform-limited, single-mode picosecond optical pulse generation by a distributed feedback InGaAsP diode laser
Authors: Onodera Noriaki , Ito Hiromasa , Inaba Humio
Published: February 2003

The first generation of bandwidth-limited, single-mode ultrashort optical pulses with excellent coherency from a distributed feedback InGaAsP diode laser at 1.3 μm by the method of strong rf modulation superimposed on the dc bias current is reported. It was realized only by the laser diode itself with no requirement of any other optical elements or external cavity or careful optical control. The measurement of time-bandwidth product of the generated coherent picosecond pulses at 500-MHz modulation gave the value of 0.38 for Lorentzian pulse shape with a full width at half-maximum of nearly 34 ps, which proved definitely the Fourier-transform-limited character. By changing the dc bias current from positive to negative, the pulse width was demonstrated to be continuously controllable over a range of approximately twice to three times depending upon the modulation frequency.
Phase sensitive scanning optical microscope
Authors: Jungerman R. L. , Hobbs P. C. D. , Kino G. S.
Published: February 2003

An electronically scanned optical microscope which quantitatively measures amplitude and phase is described. The system is insenstive to mechanical vibrations. The phase infromation makes it possible to measure surface height variations with an accuracy of better than 100 Å and can also be used to improve the lateral resolution.
Electronic excitations in collision cascades and the ionization of sputtered particles
Authors: Šroubek Z.
Published: February 2003

The electronic temperature Te in collision cascades is calculated for various materials bombarded with keV ions. The calculation is based on a simple form of the electron transport theory. The theoretical values of Te are compared with values inferred from secondary ion mass spectroscopy data.
Growth of MoSi2 with preferential orientation on (100) silicon
Authors: Perio A. , Torres J. , Bomchil G. , Arnaud d’Avitaya F. , Pantel R.
Published: February 2003

Molybdenum has been evaporated under ultrahigh vacuum conditions on (100) silicon wafers. Molybdenum silicide MoSi2 was obtained either by deposition on substrates at room temperature and subsequent annealing in situ at 650 °C or by metal deposition on substrates heated to 650 °C. Structural characterization was carried out by x-ray diffraction and transmission electron microscopy. The silicide resulting from the first operating process is a random, polycrystalline material. On the contrary, growth of MoSi2 with well-defined epitaxial relationship occurs on the heated substrates.
Fine structures in the broadened line of distributed feedback lasers under high-speed direct modulation
Authors: Yoshikuni Yuzo , Matsuoka Takashi , Motosugi George , Yamanaka Naoaki
Published: February 2003

Precise observation of the single longitudinal mode spectrum for distributed feeedback lasers revealed fine structures when the spectrum was broadened by high-speed modulation. A dynamic simulation can explain reasonably the above behavior if the model takes into account the carrier density modulation enhanced by the relaxation oscillation. In this letter, experimental results where both modulation depth and speed were varied are described along with a calculated result.
Back-side illuminated Ga0.47In0.53As photoconductive detectors and associated dark zones
Authors: Chen C. Y. , Cox H. M. , Garbinski P. A. , Hummel S. G.
Published: February 2003

We report the first back-side illuminated Ga0.47In0.53As photoconductive detector. The scheme of back-side illumination has led to an improvement of 1.5 dB in responsivity over front-side illumination. Furthermore, we observed dark zones where responsivities showed a minimum in the vicinity of negative electrodes. Responsivities appeared to peak at the positions beneath the positive electrodes due to a reduction in electron transit time. The upper limit of electrode widths to achieve high-performance back-side illuminated devices was also calculated.
Exact description and data fitting of ion-implanted dopant profile evolution during annealing
Authors: Ghez R. , Oehrlein G. S. , Sedgwick T. O. , Morehead F. F. , Lee Y. H.
Published: February 2003

We solve analytically the problem of dopant redistribution from an arbitrary initial implanted profile. The diffusivity, assumed concentration independent, can be an otherwise arbitrary function of temperature. Next, we derive a closed-form expression for the annealed concentration distribution in the special case of an initial truncated Gaussian. Our solution is valid over a much wider range of experimental conditions than is Seidel and MacRae’s approximation [Trans. AIME 245, 491 (1969)]. We offer a simple, yet precise, criterion for the validity of this approximation, and we guard against its indiscriminate use. Last, we fit short-time annealed P profiles in implanted Si to get an average diffusivity D̄≂3×10−12 cm2/s. We describe simple and accurate one-parameter data-fitting procedures.
An embedded stripe Be-implanted GaAs/GaAlAs double heterostructure laser grown by metalorganic chemical vapor deposition
Authors: Fekete D.
Published: February 2003

A planar GaAs/GaAlAs double heterostructure stripe geometry laser with laterally effective step change of the refraction index is described. The planar structure is achieved by regrowing an embedded stripe selectively on a Be-implanted stripe, using metalorganic chemical vapor deposition. The near-field and the far-field patterns confirm the index guiding mechanism of the light. The threshold current is comparable to those of similar lasers grown by uninterrupted growth process either by liquid phase epitaxy or by metalorganic chemical vapor deposition.
Hydrogen passivation of silicon sheet solar cells
Authors: Tsuo Y. Simon , Milstein Joseph B.
Published: February 2003

Significant improvements in the efficiencies of dendritic web and edge-supported-pulling silicon sheet solar cells have been obtained after hydrogen ion beam passivation for a period of ten minutes or less. We have studied the effects of the hydrogen ion beam treatment with respect to silicon material damage, silicon sputter rate, introduction of impurities, and changes in reflectance. The silicon sputter rate for constant ion beam flux of 0.60±0.05 mA/cm2 exhibits a maximum at approximately 1400-eV ion beam energy.
Variational R-matrix method for quantum tunneling problems
Authors: Le Rouzo Hervé
Published: February 2003

A variational R-matrix method for solving the one-dimensional time-independent Schrödinger equation is presented. The theory is simple and general and applies to an arbitrary potential. As an example, the method is applied to the pedagogically important problem of quantum tunneling through a barrier. Accurate transmission and reflection coefficients are obtained by the variational R-matrix method which compare favorably with the known analytical solutions.
Mathieu functions, a visual approach
Authors: Gutiérrez-Vega J. C. , Rodrı́guez-Dagnino R. M. , Meneses-Nava M. A. , Chávez-Cerda S.
Published: February 2003

The behavior of the Mathieu functions is illustrated by using a variety of plots with representative examples taken from mechanics. We show how Mathieu functions can be applied to describe standing, traveling, and rotating waves in physical systems. Some background is provided on notation and analogies with other mathematical functions. Our goal is to increase the familiarity with Mathieu functions in the scientific and academic community using visualization. For this purpose we adopt a strategy based on visual recognition rather than only looking at equations and formulas.
Illustrating dynamical symmetries in classical mechanics: The Laplace–Runge–Lenz vector revisited
Authors: O’Connell Ross C. , Jagannathan Kannan
Published: February 2003

The inverse square force law admits a conserved vector that lies in the plane of motion. This vector has been associated with the names of Laplace, Runge, and Lenz, among others. Many workers have explored aspects of the symmetry and degeneracy associated with this vector and with analogous dynamical symmetries. We define a conserved dynamical variable α that characterizes the orientation of the orbit in two-dimensional configuration space for the Kepler problem and an analogous variable β for the isotropic harmonic oscillator. This orbit orientation variable is canonically conjugate to the angular momentum component normal to the plane of motion. We explore the canonical one-parameter group of transformations generated by α(β). Because we have an obvious pair of conserved canonically conjugate variables, it is desirable to use them as a coordinate-momentum pair. In terms of these phase space coordinates, the form of the Hamiltonian is nearly trivial because neither member of the pair can occur explicitly in the Hamiltonian. From these considerations we gain a simple picture of dynamics in phase space. The procedure we use is in the spirit of the Hamilton–Jacobi method.
Chaotic pendulum: The complete attractor
Authors: DeSerio Robert
Published: February 2003

A commercial chaotic pendulum is modified to study nonlinear dynamics, including the determination of Poincaré sections, fractal dimensions, and Lyapunov exponents. The apparatus is driven by a simple oscillating mechanism powered by a 200 pulse per revolution stepper motor running at constant angular velocity. A computer interface generates the uniform pulse train needed to run the stepper motor and, with each pulse, reads a rotary encoder attached to the pendulum axle. Ten million readings from overnight runs of 50 000 drive cycles were smoothed and differentiated to obtain the pendulum angle θ and the angular velocity ω at each pulse of the drive. A plot of the 50 000 (θ,ω) phase points corresponding to one phase of the drive system produces a single Poincaré section. Thus, 200 Poincaré sections are experimentally available, one at each step of the drive. Viewed separately, any one of them strikingly illustrates the fractal geometry of the underlying chaotic attractor. Viewed sequentially in a repeating loop, they demonstrate the stretching and folding of phase point density typical of chaotic dynamics. Results for four pendulum damping conditions are presented and compared.
Determination of the mean velocity of a molecule
Authors: Ganci Salvatore
Published: February 2003

A simple experiment for measuring the order of magnitude of the mean thermal velocity of the molecules in the vapor above a shallow dish of fluid is discussed.
Fourier analysis of the spectral properties of multi-mode laser radiation
Authors: Velchev I. , Toulouse J.
Published: February 2003

By using the fast Fourier transform, the spectral and temporal characteristics of multi-mode laser radiation are investigated for different levels of spectral phase coherence. The transition between continuous-wave and mode-locked regimes in lasers is also discussed.
BOWENOID BASAL CELL CARCINOMA OF THE THUMB: A CASE REPORT AND REVIEW OF THE LITERATURE
Authors: Galeano M. , Colonna M. , Lentini M. , Stagno D'Alcontres F.
Published: February 2003

Basal cell carcinoma (BCC) is the most common skin malignancy arising from cells of the basal layer of the epithelium or from the external root sheath of the hair follicle. BCC of the digit is a rare entity. The article presents one such case of bowenoid BCC of the thumb which required amputation at the MP joint.
HAND SURGERY AND THE INTERNET: RESULTS OF A WORLDWIDE SURVEY
Authors: Koch H. , Hubmer M. , Haas F. , Schwarzl F. , Scharnagl E.
Published: February 2003

The opportunities offered by the Internet are employed increasingly in medicine. To obtain data on the extent to which the Internet is used by hand surgeons, survey forms were sent to 1043 participants of the Congress of the IFSSH in Vancouver in 1998. Ninety-four per cent of the respondents use the Internet. Most of the participants use the World Wide Web for literature searches, information on events and to read scientific articles. E-mail is used for general and scientific communication with colleagues and also for transmission of patient-related data. Perceived apprehensions include secure transmission of sensitive data, slow data transmission, and the lack of structure and of an authority to control the contents of the Internet. Virtual congresses and a newsgroup on hand surgery seem to be worthwhile future goals. Some problems pointed out in this survey have already been solved, at least partially, and possible solutions for the rest are discussed.
FACTORS INFLUENCING PROGNOSIS AFTER DIRECT REPAIR OF THE FLEXOR POLLICIS LONGUS TENDON: MULTIVARIATE REGRESSION MODEL ANALYSIS
Authors: Kasashima Toshihiko , Kato Hiroyuki , Minami Akio
Published: February 2003

Few studies have focused on the relevance of early motion exercise on repair of the flexor pollicis longus tendon. We evaluated 29 patients with flexor pollicis longus tendon lacerations treated by direct end-to-end suture, and statistically assessed the clinical factors that influenced the results by using a multivariate logistic regression model. Association with age, vascular damage and timing of repair did not affect the results. Patients with flexor pollicis longus tendon lacerations in zone II or with the tendon stumps retracted proximally had a significantly high risk of unsatisfactory results. Postoperative passive flexion and active extension exercise using rubber bands significantly decreased the risk of unsatisfactory results in these conditions. Results of this study indicate that early postoperative motion is useful after every FPL tendon repair, particularly in patients with zone II laceration or retraction of the proximal tendon stump.
PRIMARY LYMPHOCUTANEOUS NOCARDIOSIS CAUSED BY NOCARDIA OTITIDISCAVIARUM
Authors: Wada Akifusa , Matsuda Shuichi , Kubota Hideaki , Miura Hiromasa , Iwamoto Yukihide
Published: February 2003

A case of primary lymphocutaneous nocardiosis caused by Nocardia otitidiscaviarum in a 69-year-old previously healthy woman is described. The organism was identified in cultures of pus specimens. The patient was treated with a six-month course of oral trimethoprim-sulfamethoxazole chemotherapy following incision and drainage, and the infection completely resolved.
CLASSIFICATION OF HAND SPLINTING
Authors: Wong Simon K. M.
Published: February 2003

The terminology in describing splint or orthosis has been reviewed but there is no one single system adopted universally. Joint efforts by doctors, therapists and orthotists had been set up to review the classification of splint. Four ways of classifying hand splints have been introduced: namely, eponym, acronym, descriptive classification system and the classification system proposed by the American Society of Hand Therapists. These systems include the use of rote memory or logical deduction in grouping of splints. This paper describes the advantages and disadvantages of each classification system. Neither one of the systems stands out to be the best. A combination of the advantages of different systems, such as precision and logical deduction, may be an option for developing a new system. Moreover, communication, documentation and other environmental factors should also be considered.
MANAGEMENT OF SIMPLE FINGER INJURIES: THE SPLINTING REGIME
Authors: Chan Dora Y. L.
Published: February 2003

Mallet finger injury, ligamentous sprain and dislocation of proximal interphalangeal (PIP) joint of fingers are very common types of simple hand injuries. Immediate correction of alignment and protection of the injured area will facilitate early joint movement while maximising functional recovery. This article is to introduce the fabrication of three simple finger splints to tackle these injuries for quick and effective conservative treatment. They are the mallet finger splint, buddy splint and dorsal finger block splint.

The indications and functions of the three types of splints are discussed. The fabrication process will be illustrated; including materials needed, pattern drafting and steps of molding. Wearing regime and precautions will be highlighted to ensure effective patient compliance to splinting programme for the finger injuries.
MANAGEMENT OF STIFF HAND: AN OCCUPATIONAL THERAPY PERSPECTIVE
Authors: Wong Josephine M. W.
Published: February 2003

Joint stiffness, resulting from a variety of complications after hand injuries, remains a common problem. Prolonged swelling, scar formation and shortening of soft tissue after prolonged period of immobilisation are the major causes leading to the loss of joint range of motion. Treatment used to improve the joint stiffness should be integrative and problem-focused. Pressure therapy, active and passive mobilisation through remedial activities and corrective splinting should be started as soon as problems arise. Applying low-load stress through prolonged periods of time onto the shortened tissue at its maximum tolerable range is the main principle in restoration of passive joint range of motion. The greater the joint limitation becomes, the longer the time the splint should be applied. Therapists should understand the process of tissue healing and different functions of splints before a correct and effective splint can be prescribed properly.
PHYSIOLOGICAL AND BIOMECHANICAL PRINCIPLES IN SPLINTING THE TRAUMATISED HANDS
Authors: Fung Boris K. K.
Published: February 2003

The aim of this article is to review the biological sequence of wound repair and the rationale of using splintage to modify the healing process. Appropriate use of splintage and controlled stress can prevent adhesion and periarticular fibrosis. Splinting prescribed at appropriate timing and methods will enhance wound healing and tissue remodelling. In reverse, it will cause permanent damage to the tissues.
Generating Indicative-Informative Summaries with SumUM
Authors: Saggion Horacio , Lapalme Guy
Published: February 2003

We present and evaluate SumUM, a text summarization system that takes a raw technical text as input and produces an indicative informative summary. The indicative part of the summary identifies the topics of the document, and the informative part elaborates on some of these topics according to the reader's interest. SumUM motivates the topics, describes entities, and defines concepts. It is a first step for exploring the issue of dynamic summarization. This is accomplished through a process of shallow syntactic and semantic analysis, concept identification, and text regeneration. Our method was developed through the study of a corpus of abstracts written by professional abstractors. Relying on human judgment, we have evaluated indicativeness, informativeness, and text acceptability of the automatic summaries. The results thus far indicate good performance when compared with other summarization technologies.
Neural Substrates of Perceptual Enhancement by Cross-Modal Spatial Attention
Authors: McDonald John J. , Teder-Sälejärvi Wolfgang A. , Russo Francesco Di , Hillyard Steven A.
Published: February 2003

Orienting attention involuntarily to the location of a sudden sound improves perception of subsequent visual stimuli that appear nearby. The neural substrates of this cross-modal attention effect were investigated by recording event-related potentials to the visual stimuli using a dense electrode array and localizing their brain sources through inverse dipole modeling. A spatially nonpredictive auditory precue modulated visual-evoked neural activity first in the superior temporal cortex at 120–140 msec and then in the ventral occipital cortex of the fusiform gyrus 15–25 msec later. This spatio-temporal sequence of brain activity suggests that enhanced visual perception produced by the cross-modal orienting of spatial attention results from neural feedback from the multimodal superior temporal cortex to the visual cortex of the ventral processing stream.