bluuebunny/crossref_metadata_2025 huggingface dataset:
Conduction mechanisms in polysiloxane films deposited by microwave glow discharge
Authors: Okoniewski A. M. , Yelon A.
Published: July 2002

The electrical properties of metal-plasma polymerized polysiloxane-metal structures have been studied in order to establish the mechanisms of carrier transport through polymer layers of thicknesses of about 20–50 nm. Thin layers of polymer were obtained at room temperature by microwave glow discharge in hexamethyldisiloxane vapor. Current-voltage measurements indicate that carrier transport is dominated by the field emission tunneling at 77 K and by thermionic emission at 300 K.
Effect of heat treatment on p-type CdTe crystals and CdS/CdTe heterojunctions formed by chemical vapor deposition
Authors: Nishimura Ko , Bube Richard H.
Published: July 2002

Heat treatment of p-type CdTe:P single-crystal wafers in hydrogen at temperatures between 310 and 475 °C decreases the hole density near the CdTe surface by as much as a factor of 25, and produces an approximately exponential acceptor density profile. Deposition of CdS during the heat treatment prevents most of the decrease in hole density, presumably by acting as a diffusion barrier against diffusing impurities. CdS/CdTe solar cells prepared by chemical vapor deposition of CdS on CdTe single crystals show efficiencies in the 8 to 10% range. Junction capacitance analysis suggests that the bands are bent strongly toward the Fermi level at the surface, with diffusion potential approximately equal to those expected from a simple junction model.
A comparison between arc drops in ignited thermionic converters with and without ion reflections at the emitter
Authors: Lundgren L.
Published: July 2002

The output performance of two thermionic energy converters is compared. One converter has a normal emitter, working with zero field at the emitter which is close to the optimum working point, and the other has a low work function emitter and ion reflection at the emitter. A simple model of the plasma and the sheaths shows that a converter working with a low work function emitter and ion reflections gives a worse performance than a similar converter with a normal emitter.
Structural implications on positron lifetimes in lamellar polyethylene with chain defects
Authors: Baltá Calleja F. J. , Serna J. , Vicente J. , Segovia M. A.
Published: July 2002

New positron lifetime data in a series of isothermally crystallized polyethylene pairs with known concentrations of chain defects, having a lamellar structure, have been measured. The materials were characterized by small-angle and wide-angle x-ray scattering techniques. Positron lifetime data were computer analyzed and only three components could be resolved. It is shown that the annihilation mechanisms can be understood in terms of average distance between lamellar crystals (long period), crystal thickness, and chain defect concentration. The present results confirm, in consonance with the conclusions of other authors, the longest component to be due to ortho-positronium pick-off annihilation. The intermediate component may be ascribed to positronium trapped at the crystal-amorphous interface. The application of a three-state trapping model yields a lifetime of about 900 ps for this state. It is suggested that the shortest component may be due to free positron annihilation, para-positronium self-annihilation, and annihilation of positrons from a tightly bound state localized at the chain defects. An approximate calculation provides lifetime values around 250 ps for this short-lived state.
Current effects in heavy arsenic implants in silicon
Authors: Cerofolini G. F. , Meda L. , Pignatel G. , Queirolo G. , Armigliato A. , Solmi S. , Ottaviani G.
Published: July 2002

Current effects in heavy arsenic implants into silicon protected by a SiO2 layer were studied by Rutherford backscattering, spectrometry, differential sheet resistivity and Hall mobility measurements, Auger electron spectrometry, and transmission electron microscopy. It was found that oxygen atoms recoiled into silicon by the impinging arsenic ions affect the solid-phase epitaxial regrowth during the low-temperature (≂500 °C) postimplant anneal. A complete stopping in the regrowth was noticed in samples implanted at 1016 cm−2 at low current and annealed at 500 °C. These results show that the procedure suggested to obtain high-quality implanted layers, i.e., (1) formation of an amorphous layer with implants at low temperature and (2) solid-phase epitaxy at about 500 °C, is not suitable for implants through a SiO2 layer.
Optical pumping study of GaAs before and after copper diffusion
Authors: Bacquet G. , Bandet J. , Fabre F. , Frandon J. , Paget D.
Published: July 2002

We have investigated the optical-pumping properties of n-type GaAs and the modification of these results produced by compensation of the crystal by diffusion of copper acceptors. The rate of circular polarization and its decrease as a function of a transverse magnetic field have been measured for the various luminescence lines. We obtain the values of lifetime τ and spin-lattice relaxation time T1 of conduction electrons. Whereas T1 does not change upon copper introduction, τ is found to be decreased by two orders of magnitude because copper acts as a killer center. The compensation of the crystal can be characterized in a straightforward manner from the study of the luminescence polarization as a function of energy in the vicinity of the band gap. Finally, the inhomogeneities of the crystal and the local strains can be investigated respectively from the measure of the nonlorentzian tail of the depolarization curve in a transverse magnetic field and of the polarization of acceptor-related luminescence. All these results show that optical-pumping techniques can allow simple nondestructive characterization of semiconductors.
Magnetic properties of nonirradiated and neutron irradiated iron-lead-borate glasses
Authors: Burzo E. , Ursu I. , Ungur D. , Ardelean I. , Nazarov V. M.
Published: July 2002

The results of magnetic measurements performed on xFe2O3(1−x)[yB2O3 PbO] glasses having y=0.5, 1, 2, and 3 and x≤25 mol % Fe2O3 are reported. For identical Fe2O3 content the Curie constants are greater as the PbO content of the glass matrix is higher. This is due to the increase of the fraction of Fe3+ ions as evidenced by Mössbauer effect measurements. As B2O3 content increases, a more random distribution of the ferric ions in the glass matrix takes place. Under the action of fast neutrons some iron ions situated in clusters are displaced and occupy sites more randomly distributed in the B2O3-PbO matrix. In addition, a fraction of ferrous ions is converted to ferric.
Projected range and damage distributions in ion-implanted Al, Si, Al2O3, and GaAs
Authors: Kido Yoshiaki , Kawamoto Junichi
Published: July 2002

Substrates of Al, Si, Al2O3, and GaAs were implanted with 100 to 420-keV Al, Ar, Mn, Ni, Zn, Te, and Xe ions at low temperature of about 100 K. The reduced energies range from 0.2 to 4. The implantation energies were calibrated accurately using a nuclear resonance reaction of 19F( p,αγ)16O. The depth distributions of the implanted ions and the induced damage were determined by means of backscattering (including channeling) combined with computer-simulated spectrum analysis. The results are compared with the theoretical predictions given by Gibbons et al. (GJM) and Winterbon et al. (WSS). For the latter theory, optimum WSS parameters are determined to give a good fit to the experimental data. The systematic investigation reveals that the reduced projected range and damage depth are proportional to reduced energy ε for Al, Si, and Al2O3, whereas they are expressed in the form ε2/3 for GaAs substrates.
SiL core edge fine structure in an oxidation series of silicon compounds: A comparison of microelectron energy loss spectra with theory
Authors: Skiff W. M. , Carpenter R. W. , Lin S. H.
Published: July 2002

Transmission electron energy loss spectra were obtained from small (approximately 100-Å diam) regions of a series of single-phase silicon-containing specimens at 100-keV incident beam energy, using a field emission source transmission electron microscope fitted with a magnetic sector spectrometer. The specimen foils were diamond cubic silicon, α-silicon carbide, α-silicon nitride, and amorphous silica. The SiL near-edge structure depends markedly upon the chemical environment of the silicon. In this paper we show that the changes in near-L-edge structure, including threshold onset energy shift and edge profile, result from bond-induced changes in the valence shell electronic structure of the specimen materials. Extended Hückel molecular orbital theory was used to calculate the valence shell electronic structure of five-atom tetrahedral clusters, with silicon as the central atom and the other atoms noted above in corner positions. Inelastic electron scattering cross sections for silicon 2p and 2s core shell transitions to valence shell excited states were then calculated using the first Born approximation.
Heat loading on the components of multimegawatt ion sources
Authors: Menon M. M. , Tsai C. C. , Whealton J. H. , Schechter D. E.
Published: July 2002

The underlying mechanisms involved in the heat loading on the accelerator grids and plasma chamber components of multimegawatt ion sources are experimentally identified. Utilizing numerical techniques, a new accelerator geometry is designed to minimize the heat loading on various source components and maximize the beam brightness. Measurements on an ion source employing this accelerator geometry, during extraction of quasi-steady-state beam pulses of 3.2-MW power, show significantly reduced heat loadings on all its components.
Gold/Ga0.85Al0.15Sb Schottky diodes
Authors: Gouskov L. , Boustani M. , Luquet H. , Bougnot G. , Bastide L. , Baya’a D.
Published: July 2002

Gold on n-type Ga0.85Al0.15Sb devices were prepared and characterized. Current versus voltage (I-V) and capacitance versus voltage (C-V) measurements are discussed following the classical models of thermionic field emission and metal-insulator-semiconductor devices. The agreement between experimental I-V results and thermionic field emission model is obtained for a barrier height value of 0.73 eV but the parameter N/m*ε (N: carrier concentration; m*: effective mass; ε: dielectric constant) involved in this model is ten times higher than the expected one, deduced from the doping level in the layer and from m* and ε values in Ga0.85Al0.15Sb. In the case of the metal-insulator-semiconductor model, the comparison between the predicted and the experimental values of both the ideality coefficient n and the threshold V0 of C−2 versus reverse bias, allows to deduce the thickness of the surface insulating film δ≂45 Å. As generally observed, the barrier height χ presented to electrons by the insulating layer is small (120 meV) suggesting that tunneling is probably assisted by traps. Deep level transient spectroscopy measurements were made on these diodes. Two electron traps located in the space charge of the GaAlSb layer are found with apparent thermal activation energy of 145 and 390 meV.
Superconductivity of alloy films of Mo and simple metal elements
Authors: Asada Yuji
Published: July 2002

Alloy films of Mo and simple metal elements M(M=Ag, Mg, Sn, Sb, Bi, and Ge) have been produced by coevaporation method on substrates kept at about 80 K and their structure and electrical resistivity have been measured. The Mo-Sn and Mo-Sb films are found to be amorphous superconductors with a superconducting transition temperature of about 6 K at most. The Mo-Bi films are also superconductors but crystalline; they show the same x-ray diffraction pattern as that of hcp Bi. The upper critical field Hc2 has been measured for Mo-Sn and Mo-Sb films. The Hc2 increases linearly with decreasing temperature down to 1.5 K. The value of Hc2 extrapolated to 0 K is found to exceed the paramagnetic limit.
Oxidation of indium in gold-indium alloys
Authors: Pasquevich A. F. , Hoffmann A. , Vianden R. , Wrede U.
Published: July 2002

The oxidation in air of AuIn alloys with low indium content (1 ppm, 0.1 and 1.0 at. %) was investigated with the help of the time-differential perturbed angular correlation technique. From the results it is concluded that the oxidation is external and is independent of solute concentration. While in the concentrated alloys, the oxide formed was In2O3, in the cases of the dilute ones, In-O-Au complexes appeared. From the oxidation rate in the temperature range 300–1000 °C values of the frequency factor A=0.006(10) cm2/s and the activation energy Q=29.0(5) kcal/mol for the diffusion of indium in gold were obtained.
A shock-tube technique for studying pore-pressure propagation in a dry and water-saturated porous medium
Authors: van der Grinten Jos G. M. , van Dongen Marinus E. H. , van der Kogel Hans
Published: July 2002

Wave propagation in a porous column consisting of sand particles is studied by means of a shock-tube technique. Experimental results are presented for both air and water as pore fluids. Quantitative information on pore-pressure amplitudes, wave speeds, and damping is compared with theoretical predictions. Good agreement is obtained for the air-filled pores. For the water-saturated pores the two-wave structure is observed, and the corresponding pressure-amplitude ratio is consistent with the observed first-wave speed. The transient permeability is approximately one-third the steady-state value. Added mass is significant.
Steady-state rf magnetron discharges
Authors: I Lin
Published: July 2002

A study of the steady-state discharges and the spatial distributions of plasma parameters vertical to the magnetic field was made in an rf magnetron with oval cross section. Langmuir probes were used for the major diagnostics. The device generates low-ion energy, high-ion flux stable plasma (Ei∼102 eV, Γi∼5 mA/cm2 at 1 W/cm2 rf power). Ion transport toward the positive sheath is enhanced by the rf induced dc electric field in the uniform glow. The state of the glow is independent of rf power except ion density ni∝ (rf power)α. The voltage drop across the sheath follows V∝(rf power) β with 0<α<β<1. The discharge strongly depends on magnetic field strength and system pressure, and weakly depends on the gas chemistry. Generally, the state of the discharge is determined by charged particle generation, transport and loss processes, and in turn controlled by the system operating parameters. The experimental results obey the conservation laws and the steady-state criterion. The correlations between plasma parameters and system parameters are investigated and discussed.
Calculation of recoil implantation profiles using known range statistics
Authors: Fung C. D. , Avila R. E.
Published: July 2002

A method has been developed to calculate the depth distribution of recoil atoms that result from ion implantation onto a substrate covered with a thin surface layer. The calculation includes first order recoils considering projected range straggles, and lateral straggles of recoils but neglecting lateral straggles of projectiles. Projectile range distributions at intermediate energies in the surface layer are deduced from look-up tables of known range statistics. A great saving of computing time and human effort is thus attained in comparison with existing procedures. The method is used to calculate recoil profiles of oxygen from implantation of arsenic through SiO2 and of nitrogen from implantation of phosphorus through Si3N4 films on silicon. The calculated recoil profiles are in good agreement with results obtained by other investigators using the Boltzmann transport equation and they also compare very well with available experimental results in the literature. The deviation between calculated and experimental results is discussed in relation to lateral straggles. From this discussion, a range of surface layer thickness for which the method applies is recommended.
InP crystal growth on planar SiO2 substrates
Authors: Oku Satoshi , Mori Hidefumi , Ohmachi Yoshiro
Published: July 2002

Orientation-controlled InP microcrystals are grown on planar SiO2 substrates by reacting molten In thin films with vaporized phosphorus in a closed system. Indium phosphide crystals having a (111) texture of about 7 μm in size, grow at the periphery of the In islands when the substrate is heated at 500 °C under a phosphorus vaporizing temperature of 330 °C. When the In thin films are triangularly patterned, the in-plane 〈110〉 crystal direction is aligned parallel to the pattern edges by the capillary force effect between the In liquid and InP crystal.
Individual spatial modes of a phase-locked injection laser array observed through spectral selection and selected with an external mirror
Authors: Andrews J. R. , Paoli T. L. , Streifer W. , Burnham R. D.
Published: July 2002

The oscillating spatial modes of a phase-locked injection laser array are observed by spectrally resolving its far-field radiation pattern. The origin of the observed far fields is not consistent with a uniform array of emitters with equal coupling between the elements. When the array is placed in an external cavity containing a mirror, it is possible to select individual spatial modes of the compound resonator, including the fundamental mode. Operation of a phase-locked laser array in conjunction with an external resonator is shown to be a useful technique for spatial mode selection.
In/Pt ohmic contacts to GaAs
Authors: Marvin Dean C. , Ives Neil A. , Leung Martin S.
Published: July 2002

Graded heterojunction InGaAs ohmic contacts to GaAs have been prepared which show improved electrical and mechanical properties. The improvements result from the use of a thin Pt layer between the In layer and the substrate which controls the reaction of the In and the GaAs. Evidence is also offered that the InAs heterojunction regions are epitaxial.
Brillouin scattering in polystyrene thin-film waveguides
Authors: Janaky T. P. , Narayanaswamy C. K.
Published: July 2002

An account of Brillouin scattering on thin dip-coated polystyrene waveguides has been given. The behavior of the waveguide near the Bragg region is discussed. The Brillouin scattering observed in dip-coated polystyrene films is attributed to the corrugations in the waveguide due to stress birefringence.
Observation of adsorbate-induced surface states by elastic electron tunneling spectroscopy
Authors: LeDuc H. G. , Lambe J. , Thakoor A. P. , Khanna S. K.
Published: July 2002

Electronic structure induced by adsorbates at the interface of Al/AlOx/Au tunnel junctions has been observed by elastic electron tunneling spectroscopy. Strong structures appearing in the tunneling spectra above ∼1 eV after exposure to I, Hg, Bi, and organohalides, have been interpreted in terms of adsorbate-induced surface states. The spectroscopic capabilities of elastic electron tunneling spectroscopy may be useful in the area of chemical detection. In the broader sense, the observation of adsorbate-induced unoccupied electronic states below the vacuum energy, makes elastic electron tunneling spectroscopy a potentially useful technique for the study of surfaces.
Improvement of critical current uniformity in lead-alloy Josephson junctions
Authors: Imamura T. , Hasuo S. , Yamaoka T.
Published: July 2002

A lead-alloy Josephson junction with excellent uniformity of critical currents is proposed. The junction, consisting of a thin Pb-In-Au base electrode and an ε-phase Pb-Bi counterelectrode, is made on a thick Nb electrode. SiO openings, which define the junction area, are formed not after but before deposition of the base electrode. Using this structure, junctions can be formed free from any wet process of photolithography from the base to counter electrodes. Current-voltage (I-V) characteristics of series-connected junctions are measured and uniformity of the critical currents is estimated. Despite I-V characteristics representing large subgap current and small gap voltage, good uniformity of the critical currents is observed. The maximum to minimum spread of critical currents is ±4.1% for a 186-junction chain with a junction area of 5 μm square. A standard deviation of 1.5% is obtained, a value about one-third of that obtained for the conventional lead-alloy junctions.
Elastic, piezoelectric, and dielectric properties of the BaLaGa3O7 crystal
Authors: Soluch W. , Ksiezopolski R. , Piekarczyk W. , Berkowski M. , Goodberlet M. A. , Vetelino J. F.
Published: July 2002

The elastic, piezoelectric, and dielectric constants of single-crystal BaLaGa3O7, which belongs to the 4̄2m class of the tetragonal system, were measured. The six independent elastic constants, two piezoelectric constants, and coupling coefficients were determined using standard resonance-antiresonance measurements and the following results were received (cij in 1011 N/m2): c11=1.78, c12=1.03, c33=1.17, c13=0.88, c44=0.39, c66=0.54, e14=0.29 C/m2, e36=0.10 C/m2, kl14=0.141, and kl36=0.055. The two dielectric constants were measured at low frequency using a three electrode configuration. The relative values of these constants were determined to be εT11/ε0=12.7, εS11/ε0=12.4, εT33/ε0=9.5, εS33/ε0=9.5.
A model for low-temperature luminescence in lithium- and sodium-doped beryllium oxide single crystals
Authors: Cooke D. W. , Jahan M. S. , Alexander C. , Shul’gin B. V.
Published: July 2002

BeO:Li and BeO:Na single crystals have been investigated by thermoluminescence (TL) techniques in the interval 10–300 K. X-irradiated BeO:Na exhibits an intense glow peak at 85 K and a weak one near 46 K. BeO:Li displays intense glow at 72 K. Analyses of the two strong peaks (the weak one was not amenable to analysis) yield the following TL parameters: Tm=72 K, E=0.143 eV, s=1.08×108 sec−1, and l=1.3; Tm=85 K, E=0.197 eV, s=1.05×1010 sec−1, and l=1.2, where E is the thermal activation energy, s is the frequency factor, and l is the order of kinetics. Spectral emission from the two intense glow peaks were similar, characterized by band emission with maxima near 320 and 525 nm. A model consistent with previous TL and magnetic resonance results which adequately describes our data is presented. It is suggested that the main glow peaks are due to holes released at V centers whereby they recombine with F and F+ centers. Recombination at the F center yields 525-nm radiation whereas recombination at the F+ defect produces 320-nm emission. Optical excitation, photobleaching, and phototransfer experiments support this model.
Note on solid-state reaction kinetics: The formation of silicides in ternary systems
Authors: Rothman S. J.
Published: July 2002

The decrease of the formation rate of Ni2Si from Ni-Cr alloys as opposed to its formation from pure Ni is analyzed in terms of a paper published by Carl Wagner in 1952. Some possible ternary diffusion effects are pointed out.
Possibility of mitigating the destructive effects of a thermonuclear explosion by means of materials which absorb light
Authors: Prosser Robert A.
Published: July 2002

Protection against the destructive effects of a thermonuclear explosion requires a substantial defense against the light energy, the shock wave, and the radioactive fallout. Each can produce casualties either directly or indirectly as the result of fires and the destruction of property. Obviously, light can be intercepted by dyes and smoke. The amount of such material required per square mile to permit no more than a first degree burn at ground zero from a 10 MT weapon exploding at an altitude of three miles is calculated. The interaction of the heated air with the shock wave and radioactive debris is explored. It is shown that a substantial degree of protection from them should ensue.
Dynamics of the gas-surface interaction and the mechanism of condensation of RbI molecules incident on NaCl (100) surfaces
Authors: Baker S. , Schoonmaker R. C.
Published: July 2002

Reflection coefficients and complete angular distributions have been measured at angles of incidence between normal and near grazing for thermal beams of RbI molecules which were scattered from clean and beam-covered NaCl (100) surfaces. For fixed angles of incidence and scattering the intensity of scattered molecules was measured as a function of coverage of RbI on the sodium chloride surfaces. Dynamics of the gas-surface interactions are discussed and a mechanism for condensation of RbI is proposed.
Parametric distortion of the optical absorption edge of a magnetic semiconductor by a strong laser field
Authors: Nunes O. A. C.
Published: July 2002

The influence of a strong laser field on the optical absorption edge of a direct-gap magnetic semiconductor is considered. It is shown that as the strong laser intensity increases the absorption coefficient is modified so as to give rise to an absorption tail below the free-field forbidden gap. An application is made for the case of the EuO.
UV laser incorporation of dopants into silicon: Comparison of two processes
Authors: Fogarassy E. P. , Lowndes D. H. , Narayan J. , White C. W.
Published: July 2002

The incorporation properties of implanted or deposited Sb into the Si lattice as a result of irradiation with a pulsed KrF ultraviolet laser have been compared. The surface melting dynamics resulting from laser irradiation have been studied in both cases by time-resolved optical reflectivity. The distribution profiles of the Sb, deduced from Rutherford backscattering spectrometry and ion channeling measurements, show in both cases a maximum substitutional concentration of 2.1×1021 cm−3. Substitutional solubility is limited by interface instabilities which develop during regrowth and lead to the formation of a well-defined cellular structure, as shown by transmission electron microscopy. For the deposited case, we observe a much larger cellular microstructure in addition to the cells induced by interface instabilities. The large cell structure may result from convection-induced instabilities.
Electrical noise induced by unstable flow of elastic polymer solutions through capillaries
Authors: Klason C. , Kubát J.
Published: July 2002

Capillary flow of 0.3% aqueous solutions of poly(ethylene oxide), 4×106 MW, generates a fluctuating electrical signal (noise) between electrodes at the ends of the capillary. The frequency spectra of the noise are approximately of the 1/f α type. Within certain flow rate ranges, two sets of harmonic peaks appear in the spectra. It is shown that these peaks are associated with the transverse and longitudinal modes of motion of the elastic solution entering the capillary. This equivalence has been verified by frequency analysis of the intensity of a laser beam transmitted through the entry region, and by high-speed photography. The noise is assumed to reflect fluctuations in the streaming potential, caused by fluctuations in flow rate.
High-resolution electron microscopy of high-T
c polycrystalline Nb3Ge fabrics
Authors: Kitano Y. , Nissen H.-U. , Wessicken R. , Yin D. , Schauer W.
Published: July 2002

The fabric of high-Tc Nb3Ge superconducting material synthesized by coevaporation in the vacuum has been investigated using 200-kV high-resolution electron microscopy. The grain texture deduced from the high-resolution structure images, which consist of groups of small coaxial Nb3Ge grains (A15 structure) which have one cubic axis [001] in common, is observed and analyzed using the high-resolution structure images. The coaxial grains are related by a rotation of approximately ±30° around the [001] axis. Crystallites of Nb5Ge3 composition having either a D88 structure or D8m structure are distributed at random in the fabric and are coherent with the adjacent Nb3Ge grains. The statistical distribution of grain sizes of each compound is reported. The average grain size of Nb5Ge3 compounds is smaller than half the average size of the Nb3Ge grains.
Observation of thermo-optic and photorefractive effects during acousto-optic interaction in Ti:LiNbO3 waveguides
Authors: Singh J. , Tobin J. R. , De La Rue R. M.
Published: July 2002

This paper describes the observation of thermo-optic and photorefractive effects in an integrated optics spectrum analyzer. The thermo-optic effect arises because of the dissipation of rf power as heat at the interdigital transducer and at the tuning inductor. The results also indicate that a photorefractive effect takes place at λ=6328 Å and power densities ∼50 W/cm2, but in the presence of acoustic power.
Coupling of surface polaritons incident obliquely on a small amplitude grating
Authors: Seshadri S. R.
Published: July 2002

The coupling of the surface polaritons incident obliquely on a small amplitude grating is investigated. The dispersion characteristics in the neighborhood of the band gap are deduced. The splitting of the dispersion curves of the interacting surface polaritons in the wave-number space is determined and compared with the available experimental result.
Metalorganic chemical vapor deposition and photoluminescence of nm GaAs doping superlattices
Authors: Roentgen P. , Goetz K.-H. , Beneking H.
Published: July 2002

Metalorganic chemical vapor deposition of ultrathin doped GaAs multilayer structures is reported. Low-temperature photoluminescence is used as a powerful characterization method. By observing the shift of the effective band gap with varying layer thickness of doping superlattices we demonstrate that highly doped layers which are separated by only 4 nm do not diffuse together during growth.
Electron-beam-induced current investigations of oxygen precipitates in silicon
Authors: Jakubowicz A. , Habermeier H.-U.
Published: July 2002

The electron-beam-induced current contrast from oxygen-induced defects in Czochralski silicon is studied. It is shown that positive and negative contrasts from individual defects can appear. In some cases a reversal of the contrast’s sign is observed when one changes the observation conditions (electron beam current, accelerating voltage).
Extension of the Engel–Brewer metallic correlation to transition metal silicides
Authors: Sivaram S. , Ficalora P. J. , Cadien K. C.
Published: July 2002

The Engel–Brewer theory for transition metals has been extended to transition metal silicides. It is shown that the promoted electronic state correlates well with the properties of the silicides. From these correlations we are able to predict the effect of deviations from stoichiometry on disilicide resistivity and the existence of other silicide crystal structures.
Variable magnetostatic wave delay lines
Authors: Bajpai S. N. , Weinert R. W. , Adam J. D.
Published: July 2002

Theory which predicts the behavior of magnetostatic volume wave propagation in yttrium iron garnet films with the magnetic bias field applied at an arbitrary angle was developed. Measurements performed with the bias field applied in the plane transverse to the propagation direction and the plane defined by the film normal and the direction of propagation, yielded results which were in good agreement with the theory. A variable nondispersive delay line, obtained by varying the direction of the bias field applied to an approximately constant forward volume wave delay line, was demonstrated. The time delay of this device was adjustable over a ±20% delay range and had a bandwidth of ∼150 MHz at x band.
Deep-level electron traps in vapor phase epitaxial GaAs grown with oxygen injection
Authors: Ruby D. S. , Arai K. , Stillman G. E.
Published: July 2002

The effect of oxygen injection on electron traps in undoped epitaxial GaAs grown in a chloride vapor phase epitaxy (VPE) system is studied using deep-level transient spectroscopy (DLTS). The trap concentrations determined from constant-capacitance DLTS agree well with those obtained from low- and high-temperature differential capacitance measurements. Layers grown with successively higher partial pressures of intentionally added oxygen each contain the same four electron traps typically observed in nonintentionally doped n-type VPE layers. Three of these traps are present in concentrations at or below the mid 1011-cm−3 range, while the dominant level known widely as EL2 remains constant at a concentration of (2.5±0.5)×1014 cm−3. However, no additional deep levels due to the oxygen are observed. Although the trap concentrations are independent of the oxygen injection, the amount of unintentional Si incorporated is reduced by almost three orders of magnitude resulting in a fourfold increase in 77-K electron mobility.
Magnon-assisted luminescence in antiferromagnetic manganese carbonate
Authors: Komura H. , Fujima N. , Yamaguchi T. , Ishikawa K.
Published: July 2002

Strong luminescence observed at a low temperature in the antiferromagnetic MnCO3 disappears near the phase transition temperature. It is interpreted as the emission composed of multimagnon and multi-magnon-phonon sidebands associated with a pure electronic transition between 6A1g and 4T1g states of manganese ions. Polarization experiments of the fine structure in this red emission reveal that two kinds of radiative traps participate in the transitions. The integrated intensity of the luminescence is measured as a function of temperature and discussed in terms of a three-level model in which the energy transfer from an intrinsic exciton to impurity-induced levels plays an important role.
Dark line defect growth in optically pumped AlxGa1−xAs laser material
Authors: Schwartz B. D.
Published: July 2002

The growth of dark line defects (DLD’s) has been observed in epitaxial AlGaAs wafers under optical pumping. The growth velocity as a function of optical intensity is given by V=AI1.8. In addition to recombination-enhanced defect motion, stress-induced dislocation glide is shown to contribute to the elongation of DLD’s in 〈100〉 and 〈110〉 directions. A climb mechanism may be responsible for the thickening of DLD’s after growth in 〈100〉 directions. The asymmetric growth of DLD’s between 〈110〉 and 〈11̄0〉 directions is attributed to the existence of α and β dislocations and the absence of 90° rotational symmetry in the zinc-blende structure.
Note on multi-quantum intraband absorption of intense laser light in semiconductors
Authors: Nunes O. A. C.
Published: July 2002

The electron-acoustic phonon scattering in the presence of intense laser light is considered. A kinetic equation for electrons is derived from which the absorption coefficient is obtained. It is shown that in the limit of ultrastrong fields the absorption coefficient is vanishing small as a result of the weakening of the electron-phonon interaction under intense fields.
Comment on ‘‘Characterization of TiO2, LiNb3O8, and (Ti0.65Nb0.35)O2 compound growth observed during Ti:LiNbO3 optical waveguide fabrication’’
Authors: Esdaile R. J.
Published: July 2002

The formation of LiNb3O8 during the preparation of optical waveguides in LiNbO3 has been reported recently. The limited solid solubility of LiNb3O8 in commercially grown crystals of LiNbO3 is illustrated by reference to the appropriate phase diagram. It is suggested that the approach of thermodynamic equilibrium accounts for the formation of the observed LiNb3O8 phase rather than a process involving evaporation of Li.
Transmission electron microscopy and Auger electron spectroscopy of silicon-on-insulator structures prepared by high-dose implantation of nitrogen
Authors: Petruzzello J. , McGee T. F. , Frommer M. H. , Rumennik V. , Walters P. A. , Chou C. J.
Published: July 2002

The effects of substrate temperature and ion dose on silicon-on-insulator structures prepared by nitrogen implantation were characterized by transmission electron microscopy and Auger electron spectroscopy. Substrate temperatures below 200 °C during implantation result in amorphous surface layers that become polycrystalline after annealing. Implantation above 800 °C leaves the surface single crystalline containing a high density of defects. The majority of these defects are removed after annealing. High nitrogen doses (1.6×1018 cm−2 at 150 keV) resulted in two nitride layers separated by a porous region. This porous region may be attributed to the creation of N2 gas. A continuous nitride layer, without a porous region, was formed using a nitrogen dose of 9.4×1017 cm−2. When a nitrogen dose of 4×1017 cm−2 is used, however, it results in a two-phase layer containing amorphous nitride and Si crystallites.
Artificial oxide barriers for NbN tunnel junctions
Authors: Talvacchio J. , Gavaler J. R. , Braginski A. I. , Janocko M. A.
Published: July 2002

Superconducting tunnel junctions have been prepared with NbN-base electrodes, oxidized Al or Mg tunnel barriers, and NbN or Pb counterelectrodes. The tunnel barriers were formed either by thermal oxidation at room temperature or by subjecting the thin overlayers of Al or Mg to a low-energy ion beam in an argon-5% oxygen background. High-quality junctions with Pb counterelectrodes were produced by either method. However, for junctions with NbN counterelectrodes deposited at room temperature, the thermal oxidation resulted in shorts and the ion-beam oxidation resulted in low-leakage junction. X-ray photoelectron spectroscopy measurements of the NbN artificial-oxide bilayers showed that the ion-beam treatment increased the aluminum oxide thickness by the minimum detectable increment, approximately 0.2 nm, and increased the MgO thickness by 1 nm. The superconducting energy gap inferred for NbN counterelectrodes was typically half as large as the gap of the NbN base. Limitations on the gap values of NbN counterelectrodes grown on these barriers were established by measuring the energy gap of films as thin as 7.5 nm.
Linear electro-optic effects in zinc blende semiconductors
Authors: Hernández-Cabrera A. , Tejedor C. , Meseguer F.
Published: July 2002

Linear electro-optic effects in zincblende semiconductors are theoretically analyzed by means of a microscopic simple model without any fitting of parameters. Faust–Henry, second harmonic generation, and linear electro-optic coefficients are obtained from the calculation of the derivatives of the susceptibility with respect to electric fields and ionic displacements. Our results for GaP, GaAs, InP, ZnSe, and ZnTe are in satisfactory agreement with the available experimental information.
Response of lithographic mask structures to intense repetitively pulsed x rays: Dynamic response analysis
Authors: Dym C. L. , Ballantyne A.
Published: July 2002

This paper addresses the issue of the dynamic response of thin lithographic mask structures to thermally induced stress fields. In particular, the impact of repetitively pulsed x-ray sources are examined: the short duration (1–100 nsec) pulses induce large step changes in mask temperatures, which can, in turn, induce a dynamic response. The impact of conductive cooling of the mask is to reduce the repetitively pulsed problem to a series of isolated nearly identical thermal impulses of duration approximately equal to the cooling time. The importance of self-weight and prestress is examined, and an analysis of the nonlinear dynamic response to thermal impulses is described.
Diffusion of hydrogen in Pb β″ alumina
Authors: Bates J. B. , Dudney N. J. , Wang J. C.
Published: July 2002

Hydrogen diffuses into Pb β″ alumina during ion exchange of Na β″ alumina in molten lead halide salts. The hydrogen resides in the lattice as OH− groups with the protons bound at several kinds of sites. The intrinsic diffusion coefficients of hydrogen and deuterium determined from analysis of infrared absorption profiles following isotope exchange are 9.1, 5.3, and 1.1.×10−7 cm2/s at 515, 455, and 350 °C, respectively. These data fit an Arrhenius equation with an activation energy of 0.54 eV and a preexponential factor of 2.67×10−3 cm2/s. Protons are transported through the conduction layers by hopping to adjacent O= ions. The principal contribution to the activation energy is the energy required to break the O–H bond.
Indium tin oxide/gallium arsenide solar cells
Authors: Naseem S. , Coutts T. J.
Published: July 2002

This communication discusses the performance of solar cells based on single-crystal substrates of p-type gallium arsenide (GaAs) and thin films of indium tin oxide (ITO) deposited by rf sputtering. Such devices have previously yielded conversion efficiencies of less than 5% but here, efficiencies of greater than 7% are reported. This is still poor by comparison with devices based on indium phosphide (InP)/ITO and the reason seems to be due to the excessive values and rather low activation energy (ΔE) of J0. The variation of quantum efficiency with wavelength shows a peak at about 80% for a wavelength around 600 nm.
Face-centered-cubic Nb-Si solid solutions produced by picosecond pulsed laser quenching
Authors: Wang W. K. , Spaepen F.
Published: July 2002

Face-centered-cubic Nb100−xSix solid solutions (10≤x≤27) have been produced by 30-ps pulsed laser irradiation, using a Nd:YAG laser with a fluence of about 1 J/cm2. The lattice parameters of these solutions suggest that the solute atoms can be interstitial or substitutional, probably as a result of a change in the quenching conditions.
High-power single longitudinal mode operation of inverted channel substrate planar lasers
Authors: Yang Jane J. , Hong C. S. , Niesen J. , Figueroa L.
Published: July 2002

A high-power GaAs/GaAlAs double heterostructure laser is developed by using the metalorganic chemical vapor deposition technique. The laser has an index-guided, inverted channel substrate planar structure. Linear output power characteristics were observed to ∼80 mW cw on submount without facet coatings. The device operated in a stable single mode to a power >40 mW.
On the Hall effect in polycrystalline semiconductors
Authors: Garcia-Cuenca M. V. , Morenza J. L. , Codina J. M.
Published: July 2002

Some problems involved in the interpretation of Hall-effect measurements in polycrystalline semiconductors have not been resolved, especially when the contribution of the boundaries is appreciable. Using the Herring theory of transport properties in inhomogeneous semiconductors, we present an alternative interpretation to that previously proposed. This model permits the calculation of the Hall coefficient under general conditions.
Temperature dependence of spontaneous emission from AlGaAs-GaAs laser diodes
Authors: Zabrowski D. W. , Rice R. R. , Specht A. P.
Published: July 2002

The relationship between spontaneous and stimulated emission from a variety of AlGaAs-GaAs double-heterostructure laser diodes has been studied as a function of temperature over a range of 10–70 °C. The spontaneous emission varied exponentially with temperature, and we introduce T′0(J) as the characteristic temperature of spontaneous emission. As the temperature was changed, the laser threshold and slope efficiency for a device strongly covaried with spontaneous emission. A moderately high correlation (r>0.75) was obtained between the lasing and spontaneous emission slope efficiencies of 20 randomly selected lasers from different suppliers.
Rheology of microsphere formation and refinement
Authors: Amundson Karl R. , Bousfield Douglas W. , Soong David S.
Published: July 2002

Two important steps in the fabrication of microsphere laser fusion targets have been analyzed by simple mathematical modeling. Volatile-containing droplets emerging from a nozzle with imposed oscillation first undergo a spontaneous blowing process, driven by the evaporation of volatile solvent which pushes the polymeric shell outward. These hollow particles then enter a refinement zone, where a centering process takes place to eliminate eccentricity between the shell internal and external surfaces. The confined vapor partially permeates to the surroundings, allowing shrinkage of the microspheres in this zone to the desired final dimensions and sphericity. Biaxial extensional flow dominates the rheology of micropshere expansion, whereas detailed dynamics of radial flow results in improved concentricity and sphericity. The effects of viscoelasticity on the rate and stress associated with microsphere expansion have been studied using the Newtonian and Maxwell constitutive equations. Simple analytic results to describe microsphere refinement have been obtained for conditions representative of the centering process where Newtonian behavior prevails as the fluid flow is relatively weak.
Diffusion of chromium in gallium arsenide
Authors: Deal M. D. , Stevenson D. A.
Published: July 2002

The diffusion of Cr in GaAs was investigated under both in-diffusion and out-diffusion conditions. In-diffusion sources were CrAs(s)-GaAs(s)-Ga(l), three phase mixtures which, at a given temperature, provide an invariant chemical potential of the components. Unexpectedly deep penetration was observed and complex (two-branch) concentration profiles were often observed. The profiles were successfully modeled using an interstitial/substitutional/dissociative model. Different regimes of diffusion conditions gave rise to fast and slow effective diffusion coefficients. Subtle effects of doping and preannealing under arsenic overpressures confirmed the proposed model and served as a probe to study these subtle differences. Out-diffusion experiments led to slow effective diffusion coefficients, consistent with the diffusion model.
Photoluminescence and x-ray properties of heteroepitaxial gallium arsenide on silicon
Authors: Duncan W. M. , Lee J. W. , Matyi R. J. , Liu H-Y.
Published: July 2002

We report a study of the residual impurities and defects in heteroepitaxial GaAs films grown by molecular-beam epitaxy on 〈100〉 Si substrates. Low-temperature photoluminescence measurements are used to identify residual impurity and deep defect levels in unintentionally doped heteroepitaxial GaAs and compared to homoepitaxial GaAs grown under similar conditions. Scanning Lang x-ray measurements demonstrate that the heteroepitaxial layers are under biaxial tensile stress in the surface parallel direction. The presence of internal tensile stress is also corroborated by double crystal x-ray rocking curve measurement which shows tetragonal compression in the surface perpendicular direction. This is also the first reported use of interferometric techniques for studying photoluminescence properties of a wide-gap semiconductor in the near infrared region.
Plasma-assisted metalorganic chemical vapor deposition of ZnSe films
Authors: Mino Naoki , Kobayashi Masakazu , Konagai Makoto , Takahashi Kiyoshi
Published: July 2002

ZnSe thin films were grown by plasma-assisted metalorganic chemical vapor deposition (MOCVD). Plasma-assisted MOCVD is a technique combining rf glow discharge decomposition (at 13.56 MHz) with conventional metalorganic chemical vapor deposition. This process may offer several advantages such as low-temperature growth, high chemical reactivity, cleaning effect of substrate surface, and good surface morphology. The metalorganic sources used were diethylzinc and diethylselenide. The epitaxial films were obtained at the low substrate temperature of 250 °C by plasma-assisted MOCVD. The grown films showed excellent surface morphology and uniformity over a large area. These films were applied to Al/ZnSe:Mn/ITO (indium tin oxide) dc-operated electroluminescent cells. As a manganese source, di-π-cyclopentadienyl manganese [(C5H5)2Mn] was successfully used.
Growth of GaInAs-InP multiquantum wells on garnet (GGG=Gd3Ga5O12) substrate by metalorganic chemical vapor deposition
Authors: Razeghi M. , Meunier P-L. , Maurel P.
Published: July 2002

Ga0.47In0.53As-InP multiquantum wells grown by low-pressure metalorganic chemical vapor deposition on garnet (GGG=Gd3Ga5O12 with a=12.383 Å) substrates are presented for the first time. The x-ray diffraction pattern shows that the orientation of the epitaxial layer is (111) while the underlying substrate orientation is (100). The photoluminescence at 77 K is due to the GaInAs layers.
Maximum supercooling of silicon encapsulated in SiO2
Authors: Dutartre D.
Published: July 2002

An SiO2-encapsulated silicon-on-silica structure has been used to examine quantitatively the supercooling of Si. Fully melted, isolated Si islands generally exhibit a maximum supercooling of 235 °C, i.e., their freezing occurs at a temperature around 1175 °C. The implications of this behavior for the growth of thin Si films on amorphous substrates via zone melting are presented and briefly discussed.