bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrogen passivation of deep metal-related donor centers in germanium
Authors: Pearton S. J. , Tavendale A. J.
Published: February 2003

Germanium samples diffused with Cr, Co, Cd, Te, S, Se, Zr, and Ti were exposed to a low pressure hydrogen plasma for 2 h at 250 °C. Deep level transient spectrocopy profiling revealed that the deep metal-related donor centers could be divided into three classes: those which were either weakly or strongly neutralized to the depth of the hydrogen incorporation and those which were unaffected by hydrogen plasma heat treatment.
Nonlinear quantum transport in semiconductors
Authors: Arora Vijay K.
Published: February 2003

We present a density matrix formalism to study the nonlinearities introduced by an electric field in a bulk semiconductor. In the high-field regime, the energy gained inbetween collisions (intercollision field effect) as well as that gained during a collision (intracollisional field effect) becomes important. Also, the scattering rates become quite high, giving deviations from the well-known Fermi Golden Rule formulation of the scattering events. In the strong damping limit, we obtain an expression for collision width for deformation potential scattering by including the intracollisional field effect. In the limit of a strong intracollisional field effect the collision width may be suppressed, giving rise to the possibility of a ballistic transport. But, for energies appropriate to impact ionization in bulk samples of GaAs, the contribution of intracollisional field effect is negligible.
Effective mass considered as a local property
Authors: Cappelletti P. , Cerofolini G. F. , Pignatel G. U.
Published: February 2003

A new picture for acceptors in silicon is proposed. Based on the assumption that the hydrogen-like model holds true irrespective of the value of ionization energy, it implies an effective mass depending on the impurity. This leads to the prediction of new equilibrium and transport properties for moderately doped p-type silicon.
Formation of high density electron-hole plasma in silicon metal-oxide-semiconductor transistors below 25 °K
Authors: Tewksbury S. K.
Published: February 2003

Freezeout of substrate doping impurities, at T<25 °K for conventional shallow level impurities in silicon, creates an insulating substrate in silicon metal-oxide-semiconductor (MOS) transistors. With the flow of majority carriers (holes for p-type substrates) through the substrate impeded, the accumulated majority carrier density in the MOS transistor surface channel must be provided from the sides of the channel. When switched from strong surface accumulation toward surface inversion, a rapidly responding minority carrier density, injected by the source and drain regions, might act to compensate a more slowly responding majority carrier density in the transistor channel, giving rise to anomalously high minority carrier densities. This picture was previously invoked by the author to explain a low level discrete conductance effect seen in a few devices. The other devices exhibit instead a pronounced current spike, which is described here and further supports the initial high charge densities.
Magnetic properties of biotite micas
Authors: Beausoleil N. , Lavallée P. , Yelon A. , Ballet O. , Coey J. M. D.
Published: February 2003

The magnetic behavior of eight samples of biotite and a lepidomelane was studied in the temperature range 1.5–300 K and analyzed in relation to their chemical composition. The platy morphology of biotite facilitates magnetic measurements with the applied field either in the plane of the sheets (Xe⊥ ) or perpendicular to the plane (Xe∥). At high temperature, the samples obey Curie-Weiss laws, showing typical paramagnetic behavior which is due to the presence of both Fe2+ and Fe3+ ions. However, the susceptibilities are anisotropic (χe⊥/χe∥≂1.25), because of a trigonal contribution to the crystal field which affects only the ferrous ions. Formulae are given which permit the ferrous Curie-Weiss parameters to be derived from the measured susceptibility. At low temperature (T<10 K), three of the biotite samples containing high concentrations of iron (17 to 27 wt. %) undergo an antiferromagnetic transition. The magnetic structure consists of octahedral sheets of iron ions with their moments ferromagnetically coupled in the plane, while the interplane interactions are antiferromagnetic and roughly 30 times weaker. Thus, biotite has both magnetic and structural two-dimensional aspects. We also have observed magnetic aftereffect, and some parasitic ferromagnetism below the transition.
Prediction of transverse-mode selection in double heterojunction lasers by an ambipolar excess carrier diffusion solution
Authors: Delaney Joseph B. , Shurtz II Richard R. , Butler Jerome K.
Published: February 2003

Transverse-mode selection is characterized for GaAs/AlGaAs double heterojunction lasers from optical field and electron/hole interaction. The electron/hole distribution determined from a solution of the ambipolar diffusion equation provides the necessary information about gain/mode coupling to predict the current at threshold. Lasing power out versus current solutions provide information about internal differential quantum efficiency. Theory is matched to experiment for a multimode laser with one heterojunction having a very small index step. It is found that the laser’s characteristics over a temperature and current range are predicted by adjusting the active-layer refractive index as determined from far-field measurements.
Design of double passive modulated mode-locked lasers
Authors: Martinez O. E.
Published: February 2003

A set of equations is obtained that allow the determination of the optimum values for the laser parameters in order to obtain perfect mode-locking by double passive modulation. The double modulation consists of a fast saturable absorber and a passive loss proportional to the mean intensity in the cavity provided by a passively driven electro-optic modulator. The stochastic nature of the emission of conventional passive modulated systems is eliminated if the correct values of the modulation parameters are chosen as predicted by the equations presented here. The predictions given by the equations were compared with previous numerical computations in order to check the validity of certain approximations used. Experimental results obtained confirm the predictions given by said equations.
Surface acoustic wave resonators on a ZnO-on-Si layered medium
Authors: Martin S. J. , Schwartz S. S. , Gunshor R. L. , Pierret R. F.
Published: February 2003

The adaptation of surface acoustic wave resonator technology to a ZnO-on-Si layered medium is presented. Several distributed reflector schemes are considered, including shorted and isolated metallic strips, as well as grooves etched in the ZnO layer. In the case of etched groove reflectors, a first-order velocity perturbation arises due to the dispersive nature of the layered medium. Unique resonator design considerations result from the reflector array velocity and reflectivity characteristics. Transverse mode resonances are characterized and their effect on resonator response eliminated by a novel transducer design. A technique for temperature compensating the devices by use of a thermal SiO2 layer is discussed.
Signal and systems analysis for unsteady heat conduction problems
Authors: Duthoit B. , Leclercq D. , Thery P.
Published: February 2003

A general formulation of heat transfer phenomena based on signal analysis is developed in this article. Starting from the classical matrix formulation of heat transfer through a slab, normal modes are defined. The thermal normal modes are linear combinations of heat flow and temperature variations measured on the external surfaces of the slab. Although normal modes fit to a superposition principle, they do not define thermal signals since the scalar product of heat flow and temperature has no physical meaning. Starting from this classical description, a new formulation of heat transfer based on entropy concept is then stated. The ‘‘entropy production’’ and ‘‘entropy exchanged with outside’’ are expressed in terms of normal coordinates. It is shown how the time distribution of entropy production for the quasi-steady-state of flow can be characterized by a cross-correlation function between the space-average heat flow and its entropy conjugated coordinate. In the same way, the time distribution of entropy exchanged with outside results from a cross-correlation function between a normal coordinate and the corresponding entropy conjugated coordinate. Under unsteady-state conditions, the entropy exchanged with outside can be computed by convoluting the cross-correlation function representative of entropy production and the impulse response of heat transfer through the slab. This new formulation yields to consider thermal signal independently of their actual waveforms, but of their correlation function (i.e., their frequency content). In the experimental part, the theoretical results are extended to include practical problems of heat transfer in building sections exposed to natural weather conditions and internal heating.
Validity of spherical quantitative refractometry: Application to laser-produced plasmas
Authors: Benattar R. , Popovics C.
Published: February 2003

We report an experimental laser technique of quantitative Schlieren imaging of spherical plasmas combined with streak camera recording. We show that quantitative refractometry applies for small values of refraction angles, i.e., when the law giving the refraction angle versus the impact parameter of rays passing through the plasma is a linearly decreasing function.
Time-resolved evolution of laser-produced plasmas in spherical expansion regime
Authors: Benattar R. , Popovics C.
Published: February 2003

We report experimental results deduced from quantitative Schlieren imaging of plasmas combined with streak camera recording. Flat or spherical targets are illuminated with one laser beam, at different wavelengths (1.06 μm, 0.53 μm, 10.6 μm): We show that time-resolved density profiles are more stationary for shorter wavelength. We measure the rear displacement and front expansion of plasmas created on glass microballoons and solid microspheres. Comparison with hydrocode simulations shows that transport is inhibited for 1.06-μm interaction, and that ablation processes are more efficient for shorter wavelength.
Numerical simulation of a disk-shaped electron accelerating electrostatic probe
Authors: Nonnast J. H. , Enoch J.
Published: February 2003

This paper presents a method utilizing the numerical plasma simulation particle-in-cell technique for studying electron accelerating probe characteristics. A probe configuration other than the commonly used plane, cylindrical, or spherical case will be studied; the probe configuration used is that of a disk. Cylindrical geometry is used in the simulation model. One of the advantages of a numerical simulation is the ease with which the details of the system can be examined. Therefore, in addition to the current-voltage characteristics of the static probe, other results are presented such as the time evolution of the plasma properties and studies of the sheath region surrounding the probe.
Charge-state measurements of collectively accelerated heavy ions
Authors: Destler W. W. , Cremer J. T.
Published: February 2003

Thomson spectrometer measurements of the charge states of collectively accelerated light and heavy ions (H, D, He, N, Ne, Ar) are reported. Within experimental error, all charge states are accelerated to the same peak energy for each ion specie. Relative ion flux densities for these ion species are also presented.
X-ray topographic observation of dislocation generation and propagation in InP single crystal grown by the liquid-encapsulated Czochralski technique
Authors: Tohno Shun-ichi , Shinoyama Seiji , Yamamoto Akio , Uemura Chikao
Published: February 2003

Dislocation generation and propagation in InP single crystals grown in the [1̄1̄1̄] direction by the liquid-encapsulated Czochralski (LEC) technique have been studied by means of x-ray diffraction topography. First, the type of dislocations propagating from the seed crystal towards the grown crystal is determined, and the effect of using a necking-in procedure is described. Burgers vector determination indicates that the dislocations are of a sessile type and propagate along the 〈1̄1̄0〉 direction, with the Burgers vector parallel to the 〈11̄0〉 direction. Secondly, the propagation of dislocations that nucleate at the crystal surface during crystal growing is described. It is observed that the dislocations propagate by glide on three oblique downward pointing {111} slip planes, which are inclined in the [1̄1̄1̄] growth direction. A mechanism responsible for the high dislocation densities of crystals grown by the LEC technique is discussed.
Annealing effects on electrical properties of thermal neutron transmutation doped Ge
Authors: Kuriyama K. , Yahagi M. , Iwamura K. , Kim Y. , Kim C.
Published: February 2003

A neutron transmutation doping technique was applied to the high purity n-type germanium with 50 Ω cm (n=5.9×1013/cm3). For a neutron flux density of 5×1011/cm2 s and an irradiation time of 60 min, the doped Ge was converted into p type with 7 Ω cm ( p=3.5×1014/cm3). By neutron irradiation it has been possible to introduce the shallow acceptors resulting from the damage in addition to gallium atoms as acceptors. The recovery of radiation damage was evaluated by the improvements of some electrical properties for various annealing stages. By annealing at 600 °C, a room temperature hole mobility of 2200 cm2/Vs has been achieved at p=6.2×1013/cm3 and ρ=45 Ω cm. And, also, we found that higher mobility holes in p-type Ge play an important role for the weak magnetic field as the lattice atoms recover from the radiation damage. Finally, the direct observation of the recovery of damage was performed by the measurement of channeling effects using a helium ion beam.
Laser-induced donor diffusion in ZnTe
Authors: Tews H. , Schneider M. , Legros R.
Published: February 2003

We report the first experiments on laser-induced donor diffusion in ZnTe. Aluminum, chlorine, and indium are incorporated in ZnTe single crystals from a metal layer at the crystal surface, or from a gas atmosphere during millisecond laser heating. Broad luminescence bands are observed on the irradiated areas of the crystal, which in the case of Cl give a bright and efficient photoluminescence even at room temperature. Our results indicate that a part of the dopant atoms has formed various complexes. The high-energy part of the spectra shows that Li and Ag atoms have been liberated during the laser irradiation from precipitates. The appearance of two lines at 2.361 and 2.357 eV after the irradiation can be explained by the decay of excitons bound to radiation-induced defects, or by the liberation of Au and a second deep acceptor from precipitates.
Otto cycle with saturated steam
Authors: Pozwolski Alexandre E.
Published: February 2003

A mixture of air with saturated vapor is considered. The condensation following the adiabatic expansion of such mixture is described. There are no changes for a Carnot cycle, as expected, but for the Otto cycle a high yield remains possible, even at exceptionally low temperatures.
Diffusion of chromium in silicon during a Sirtl etching process at room temperature
Authors: Lue Juh-Tzeng , Meyer Otto
Published: February 2003

A high concentration of chromium atoms is found to stick to and diffuse into the silicon surface after a Sirtl etch. These impurity atoms can only partly be removed by the conventional HF etching followed by acetone rinsing. Sideways diffusion through the walls of the etched S pits have been proposed to account for this phenomenon.
Hydrogen passivation of grain boundaries in polycrystalline gallium arsenide
Authors: Pearton S. J. , Tavendale A. J.
Published: February 2003

Exposure to a plasma of monatomic hydrogen at 300 °C for periods of 3–5 h is shown to significantly reduce the reverse leakage currents of surface barrier diodes fabricated from polycrystalline GaAs. The neutralization by hydrogen of electrical activity associated with grain boundaries leads to reductions in leakage current of a factor of 50 in material with grain sizes of 150–400 μm, and a factor of 3 in material with a typical grain size of ∼1 mm.
Interface state generation by alternating voltage stress under visible irradiation at the silicon-silicon dioxide interface
Authors: Singh R. J. , Srivastava R. S.
Published: February 2003

The generation of interface states in SiO2 metal-oxide-semiconductor capacitors was observed when the structure was stressed simultaneously by a visible radiation and alternating voltage of relatively large amplitude. A correlation between the number of newly generated interface states and the amplitude of the cycling voltage has been found. Part of the surface states generated by a relatively low ac cycling amplitude were relaxable with time. The cause of the generation of interface states at the silicon-silicondioxide (Si-SiO2) interface has been associated with the hot electrons and holes injected into SiO2 by the comparatively large amplitude of the alternating voltage.
Magnetostatic field calculations in the presence of iron using a Green’s function approach
Authors: Caldwell J. , Zisserman A.
Published: February 2003

An alternative method to that of Caldwell [J. Phys. D 12, 1653 (1979)] is used to calculate the effects of iron on the magnetic field produced by a current-carrying axisymmetric conductor. In this way a neater solution is obtained by constructing the Green’s function from an eigenfunction expansion. Good agreement with the previous results is achieved and an indication is given of the advantages of this Green’s function approach.
Magnetostatic energy of a ferromagnetic cylinder
Authors: Aharoni Amikam
Published: February 2003

The magnetostatic self-energy is expressed in terms of integrals which are easier to manipulate than the conventional Green function of the potential. Specific expressions are derived for a finite ferromagnetic particle, in the form of a right-circular cylinder, which has no volume charge.
Impedance parameters and radiation pattern of two coupled circular microstrip disk antennas
Authors: Habashy T. M. , Ali S. M. , Kong J. A.
Published: February 2003

The current distribution on a two-coupled circular microstrip disk antenna fed by two probes is rigorously derived using the Vector Hankel Transform. It is shown that the current on the two disks is governed by a set of vector integral equations. These equations are solved approximately for the amplitudes of the currents on the two disks, in the limit of thin substrate. Expressions for the self, mutual, and input impedances are then rigorously derived. It is shown that excitation of the odd symmetric TM11 mode can cause the two-disk antennas to act as a better radiator than the single-disk antenna, while the odd antisymmetric modes can cause the two-coupled disk structures to act as a better resonator than the single-disk structure. Expressions for the radiation pattern are then derived, and the impedance parameters and the radiation patterns plotted.
Reflection of electromagnetic waves at a biaxial–isotropic interface
Authors: Njoku Eni G.
Published: February 2003

The reflection of electromagnetic waves at a plane boundary between isotropic and biaxial media has been investigated using the kDB approach. The general case has been considered in which the principal dielectric axes of the biaxial medium are oriented at an arbitary angle to the normal of the plane boundary. In general, two characteristic waves propagate in the biaxial medium, leading to coupling of vertical and horizontal polarizations in the reflected waves. Some special cases are illustrated. The results have applications to problems in remote sensing and integrated optics.
Enhanced indium phosphide substrate protection for liquid phase epitaxy growth of indium-gallium-arsenide-phosphide double heterostructure lasers
Authors: Besomi P. , Wilson R. B. , Wagner W. R. , Nelson R. J.
Published: February 2003

Thermal degradation of indium phosphide (InP) single crystal substrates prior to liquid phase epitaxy growth has been virtually eliminated by using an improved protection technique. The phosphorus partial pressure provided by a Sn-In-P solution localized inside an external chamber surrounding the InP substrate prior to growth prevents thermal damage to the surface. Nomarski contrast photomicrographs, as well as photoluminescence and x-ray diffractometric measurements indicate that InP substrates protected by this method suffer a negligible deterioration, in contrast to the results of the more commonly used cover-wafer method.
Mechanism of spectral absorptance in anodic copper oxide films
Authors: Milgram Alvin A.
Published: February 2003

A study is made of the mechanisms affecting the spectral absorption in anodic copper oxide films. It is shown that the solar absorption is due to the unique surface structure of the anodic oxide film in combination with the optical properties of the basic film component, CuO. The surface structure also affects the spectral absorption in the 4–10 micron region contributing to the thermal emittance. Changing the ratio of CuO/Cu2O in the bulk film composition has a minor effect on the thermal emittance for emittance values of less than 0.10.
Optically induced glide motion of misfit dislocations in InP/In1−xGaxAs1−yPy/InP double heterostructure
Authors: Komiya Satoshi , Yamaguchi Akio , Umebu Itsuo , Kotani Tsuyoshi
Published: February 2003

Motion of misfit dislocations by optical excitation with Nd:YAG laser (1.06 μm) and Kr+ laser (0.647 μm) is studied by spatially resolved photoluminescence imaging technique in InGaAsP/InP double heterostructure wafers. Misfit dislocations are shrunken by optical excitation independently of both lattice mismatch and the light wavelength, though they are in the top InP layer but not in the InGaAsP layer. Misfit dislocations begin to move rapidly above a certain light intensity (threshold), and velocity exponentially increases with increase of the excitation intensity. The threshold decreases with decreasing thickness of the top InP layer. These results suggest that nonradiative recombination of excited carriers results in effective reduction of activation energy for glide motion of dislocation and that the carriers excited in the InGaAsP layer by Nd:YAG laser radiation leak into the top InP layer.
Slowing down and thermalization of sputtered particle fluxes: Energy distributions
Authors: Gras-Marti A. , Valles-Abarca J. A.
Published: February 2003

Particles sputtered from solid targets in plasma deposition systems, under typical vacuum conditions, slow down in collisions with the gas phase. A simple model of particle slowing down along straight-line trajectories, subject to a continuous energy loss process, allows to calculate the energy distributions of the nonthermalized component of the particle flux as a function of the distance to the source. Physically reasonable angular and energetic distributions of the flux at emission are used in the calculations. The implications on the deposited films are discussed, and previous estimates by Meyer et al. [J. Appl. Phys. 52, 5803 (1981)] are commented upon.
Thermionic emission and vaporization behavior of the ternary systems of lanthanum hexaboride containing molybdenum boride, molybdenum diboride, zirconium diboride, gadolinium hexaboride, and neodymium hexaboride
Authors: Storms E. K.
Published: February 2003

The addition of various compounds to LaB6 did not improve the thermionic emission over that of pure LaB6. This experience and general conclusions, which result by considering the vaporization properties of these and other materials, greatly limit the options available to improve the properties of LaB6 by forming a ternary system. The principles which must be considered, in order to simplify future work, are described.
Oxygen segregation in Czochralski silicon growth
Authors: Lin Wen , Hill D. W.
Published: February 2003

Oxygen segregation behavior in silicon is examined via the Czochralski crystal-pulling technique. The current experimental approach provides a constant concentration growth environment from which the effect of growth rate on oxygen incorporation level is examined. The results indicate that the equilibrium segregation coefficient of oxygen is smaller than unity, and is estimated to be ∼0.25.
The influence of gallium on external-diffusion-processed Nb3Sn composites
Authors: Kwon S. , Cogan S. F. , Klein J. D. , Rose R. M.
Published: February 2003

The effect of gallium on the processing and properties of multifilamentary Nb3Sn-based superconducting composites was studied. Diffusion in the copper (bronze) matrix and reaction layer formation were studied in pure copper (bronze) wires, in composites with large (15 μ) fibers, and in composites with ultrafine (0.1 μ) fibers closely spaced. Using the external-diffusion method, Ga was introduced at various stages of the Sn diffusion process. The results show that Ga markedly increased the activity coefficient for Sn in the bronze matrix, to the point where ‘‘uphill’’ diffusion occurs. Thus, Ga can be used to control the Sn distribution. Whether or not Ga additions improve superconducting properties depends crucially on the manner and timing of the addition. Higher critical current densities, particularly at high magnetic fields, were demonstrated for external-diffusion composites. Similar improvements should be feasible for all types of Nb3Sn-based filametary materials using small Ga additions appropriately timed.
The effects of methane in the deposition of superconducting niobium nitride thin films at ambient substrate temperature
Authors: Cukauskas E. J.
Published: February 2003

Thin films of the niobium-carbon-nitrogen system have been prepared at ambient substrate temperature by rf diode reactive sputtering in an argon-nitrogen atmosphere with controlled amounts of methane added to the sputter gas. Superconducting transition temperatures ranged from approximately 11 to 15.85 °K. Auger and x-ray diffraction analysis indicate that all films were of the single phase B1 structure with a small amount of β-phase hexagonal structure in the very low carbon containing films. A correlation of the superconducting properties, room temperature sheet resistance, preferred crystallite orientation, and film composition was observed. The results of this investigation show that high Tc niobium nitride/niobium carbonitride thin films can be prepared at ambient substrate temperatures with the proper amount of nitrogen and methane partial pressures during film deposition. These films have potential application for the fabrication of high Tc Josephson tunnel junctions.
Piezoelectricity and pyroelectricity in polyvinylidene fluoride: Influence of the lattice structure
Authors: Purvis C. K. , Taylor P. L.
Published: February 2003

Piezoelectric and pyroelectric responses of β-phase (Phase I) polyvinylidene fluoride are predicted for a model system of polarizable point dipoles. The model incorporates the influence of the orthorhombic crystal structure by including the dependence of the internal electric field on the lattice parameters. Strong anisotropy in the piezoelectric response under uniaxial stress is predicted as a consequence of the orthorhombic lattice structure. Predictions are found to be in reasonable agreement with room-temperature experimental data.
Light-induced electric permittivity change in the presence of a dc electric field
Authors: Gadomski Wojciech
Published: February 2003

Observation of the full theoretically predicted range of electric permittivity changes induced in nitrobenzene by the simultaneous action of dc and strong optical fields is reported. The influence of the dc field-induced oscillation of the light polarization ellipse on this effect is shown. It is proved that the components of the fourth rank susceptibility tensor of an isotropic medium composed of anisotropic molecules fulfill the permutation symmetry relations.
Photoluminescence and impurity concentration in GaxIn1−xAsyP1−y alloys lattice-matched to InP
Authors: Pearsall T. P. , Eaves L. , Portal J. C.
Published: February 2003

The photoluminescence spectra of GaInAsP alloys are examined as a function of impurity concentration at several different temperatures and alloy compositions. The photoluminescence linewidth depends on both the impurity concentration and temperature, and our experimental results at 295 °K are described by the empirical relation: ND(ΔE) =9.1×1011 exp(ΔE/4.3 ×10−3) cm−3. It is proposed that photoluminescence linewidth can be used for a simple and rapid determination of the impurity concentration for n- and p-type samples whose total impurity concentration lies in the range 1016 cm−3 <ND +NA <1019 cm−3.
Reduced pressure deposited arsenic-doped silicon film and its properties as a diffusion source
Authors: Shibata Kenji , Moriya Takahiko
Published: February 2003

Extremely thin (50∼550 Å) and high-concentration (1×1021∼1×1022 cm−3) arsenic-doped silicon (ADS) films are deposited at a reduced pressure by means of pyrolysis of SiH4 and AsH3. The ADS films are used as an improved diffusion source, which can be alternative to ion implantation. Arsenic drive-in diffusion from ADS film is carried out in an O2 ambient, and the desired junctions are achieved. When the arsenic concentration is above 8×1021 cm−3 and the film thickness above 200 Å, however, arsenic atom pileup at the Si-SiO2 interface, reverse dependence of junction depth on the ADS thickness, and high-density hillocks are observed. The increase in junction depth and the decrease in surface concentration during the subsequent heat treatment at 1000 °C in N2 are remarkable for high arsenic concentration and thick ADS films at low diffusion temperature. A modified simulation program is developed with Si-SiO2 interface moving and concentration-dependent diffusion coefficient. The calculated profiles are in satisfactory agreement with the experimental profiles measured by secondary ion mass spectroscopy.
X-ray photoelectron spectroscopy study of radiation-damaged Si-SiO2 interfaces
Authors: Bertrand P. A. , Fleischauer P. D. , Song Y.
Published: February 2003

A direct observation of interfacial defects caused by electron beam irradiation in a scanning electron microscope of device-quality Si-SiO2 structures has been made by x-ray photoelectron spectroscopy (XPS). Radiation-hard oxides (∼700 Å thick) on Si were subjected to 20-keV electron bombardment and several annealing treatments. The radiation induces defects at the semiconductor-oxide interface that were identified by XPS as Si with 3 bonds to oxygen and 1 dangling bond. The state anneals slowly (in a few days) at room temperature but is removed within 30 min by N2 or forming gas (90% N2+10% H2) anneals at 400 °C. Although electron beam irradiation of thin (45 Å) oxide structures is known to produce interface states with similar properties, this is the first report of XPS identification of states produced on device-quality materials under standard processing conditions (i.e., those used for electron-beam writing).
Quantitative electron microprobe analysis of thin films on substrates with a new Monte Carlo simulation
Authors: Murata Kenji , Kotera Masatoshi , Nagami Koichi
Published: February 2003

A new Monte Carlo simulation has been applied to the electron microprobe analysis of thin films at energies from 1–10 keV. The simulation model utilizes the Mott cross section for elastic scattering and the modified Bethe equation of Rao Sahib–Wittry for energy loss, instead of the screened Rutherford cross section and the standard Bethe equation, respectively. The new model has been examined in comparison with experimental results for the most probable angle of transmitted electrons through a thin film, and also the depth distribution of x-ray production. Finally, the simulation was applied to thickness analysis of both aluminum and gold films on a sapphire substrate. The new results show good agreement with experimental data. It follows that the new Monte Carlo simulation is useful for electron microprobe analysis of elements, especially for heavy materials at relatively low energies.
Barrier composition and electrical properties of high-quality all-niobium Josephson tunnel junctions
Authors: Latta Eberhard E. , Gasser Marcel
Published: February 2003

A fabrication procedure for all-niobium tunnel junctions with oxide tunnel barriers is described. All steps of the tunnel-barrier growth have been characterized in situ with the help of x-ray photoelectron spectroscopy. The chemical composition of the barrier is described, and the properties of devices discussed. The results demonstrate the application potential of these all-refractory junctions.
Charging phenomenon in conductor-insulator composites as displayed by the scanning electron microscope
Authors: Campbell E. R. , Reisner J. H. , Chung K. T.
Published: February 2003

Charging properties in conductor-insulator composites have been studied with the scanning electron microscope. Use of this instrument as a charging and display device demonstrated its usefulness as an analytical technique for describing important properties of composite structures, such as filler dispersion, segregation, orientation, and electrical continuity. These scanning electron microscope charging micrographs can be used to characterize composites with a wide range of particle sizes (100 Å to over 10 μm).
Model calculations for accelerated As ion doping of Si during molecular beam epitaxy
Authors: Bajor G. , Greene J. E.
Published: February 2003

A model is presented for calculating the incorporation probability and steady state depth distribution of accelerated dopants in films deposited from the vapor phase. Terms accounting for thermal sticking probabilities, low-energy implantation, diffusion, surface segregation, and preferential sputtering are included. Model predictions are shown to be in good agreement with Ota’s experimental data [J. Appl. Phys. 51, 1102 (1980)] for the incorporation probability of As, as a function of film-growth temperature and As acceleration energy, in Si films grown by molecular beam epitaxy.
Electron microscopy studies of pulsed electron beam annealing in phosphorus-implanted silicon
Authors: Tholomier M. , Pitaval M. , Ambri M. , Barbier D. , Laugier A.
Published: February 2003

Effects of pulsed electron beam annealing (PEBA) are investigated by computer simulations of a thermal process from a one dimensional heat flow model. Experimental studies are presented for phosphorus-implanted silicon samples. Characterization of PEBA specimens, realized by means of electron channelling patterns observed with a scanning electron microscope (SEM), indicate good regrowth. Comparison made between conventional thermal annealing and pulsed electron beam annealing shows that PEBA removes defects associated with thermal annealing. Crystallographic studies have been made on a series of samples annealed with different fluences (from 1.0 up to 1.6 J/cm2). SEM observations carried out using the electron channelling imaging method and transmission electron microscope (TEM) observations show the existence of dislocations and subgrain boundaries, with a density increasing with fluence. Polygonization seems to indicate that climb as well as glide are active in the dislocation mobility.
XPS and AES studies on iron-oxide-coated Si photoanodes with a negative flatband potential
Authors: Nogami G. , Yamaguchi H. , Maeda G. , Beppu K. , Ueda Y. , Nakamura T.
Published: February 2003

We report the first efficient photoanode with a negative flatband potential, consisting of n-Fe2O3 and n-Si. An anodic current of ∼0.8 mA/cm2 was observed at 0 V SCE in 0.1 M KOH solution under an illumination of ∼60 mW/cm2. A photocurrent rose at ∼−0.3 V SCE under the same condition. An electronbeam evaporation of Fe, followed by its oxidation at 700 °C under 5×10−2 Torr was successful in obtaining an efficient photoanode. The surface structure was analyzed using x-ray photoemission spectroscopy (XPS) and Auger-electron spectroscopy (AES) techniques and capacitance-voltage measurements. XPS spectra revealed that the surface structure was composed of Fe2O3-Fe3O4-Si. XPS signals showed that the SiO2 phase also coexisted at the top surface probably due to interdiffusion of Si. Depth profiles were obtained by the AES technique.
Voltage contrast imaging of barriers in ceramic semiconductors
Authors: Chopra K. L. , Bhushan Bharat , Kashyap S. C.
Published: February 2003

Potential barriers responsible for nonlinear conduction in ZnO ceramic semiconductors (cersems) have been observed by both the intensity and Y-modulation voltage contrast secondary electron microscopy techniques. The barriers exist at a grain-intergranular interface and extend into the conducting ZnO grains. The applied voltage is distributed uniformly across the barriers. No electrical shorting of the barriers has been observed at fields exceeding the breakdown.
Dynamic instabilities in magnetically levitated models
Authors: Chu Donald , Moon Francis C.
Published: February 2003

Experiments are reported demonstrating divergence and flutter instabilities in an electrodynamic maglev vehicle. The conducting guideway consists of L-shaped aluminum segments attached to a rotating wheel and qualitatively simulates the Japanese full scale guideway at Miyazaki. The model vehicle employed rare earth permanent magnets. Quantitative tests for a coupled yaw-lateral vibration show both divergence and flutter. The divergence leads to two stable equilibrium yaw positions, while the flutter instability leads to limit cycle oscillations coupling yaw and lateral motions in the neighborhood of the drag peak. A theoretical model based on actual magnetic force measurements is shown to predict this dynamic behavior as functions of vehicle speed and geometry.
Optically generated light beam deflection
Authors: Roosen Gerald , Sincerbox Glenn T.
Published: February 2003

Light deflection is achieved by optically changing the characteristics of a transient index modulation generated in an optical material by two interfering beams. Using a novel technique to maintain the Bragg condition, diffraction efficiency is kept constant during the whole deflection process.
Deceleration of magnetized laser-produced plasmas by shorting of polarization charge layers
Authors: Parsons C. R. , Jellison G.
Published: February 2003

The flow of low-beta laser-produced plasmas across a magnetic field was studied. When a metallic plate was placed adjacent to the plasma stream, low atomic mass plasmas were confined to a region 17 cm from the target. High mass plasmas were not affected within the limits of the vacuum chamber. These observations confirm E×B drift as the mechanism of cross-field flow.
Compositional fine pattern formation at AlGaAs/GaAs interface by Zn implantation
Authors: Iwai S. , Aoyagi Y. , Iwaki M. , Toyoda K. , Namba S. , Doi A.
Published: February 2003

A new AlGaAs layer was formed on GaAs substrates by Zn implantation into an Al0.4Ga0.6As single heterointerface. The Zn implantation of 1015 cm−2 doses at 200 keV with subsequent annealing at 500 °C for 15 min formed the AlxGa1−xAs layer (x<0.4) graded compositionally to the depth with the thickness of about 300 Å. AlGaAs fine patterns of 2–10 μm wide were formed on GaAs substrates by Zn implantation and with low-temperature, short-time annealing.
Laser chemical vapor deposition of selected area Fe and W films
Authors: Allen S. D. , Tringubo A. B.
Published: February 2003

Localized deposition of thin films of W and Fe in both spot and line geometries has been demonstrated by laser chemical vapor deposition using a CO2 laser and several different gaseous reactants. Although optical self-limiting of the deposit thickness was observed under some irradiation conditions, films several thousand Å thick could be deposited with good physical properties. Radial dimensions were less than or equal to the laser beam diameter (D1/e2 =600 μm).
Degradation of thin tellurium films
Authors: Lee Wen-Yaung , Geiss R. H.
Published: February 2003

Changes in electrical resistance, light transmission, and mass were used to monitor the in-situ degradation rate of thin Te films in room air and in an accelerated temperature-humidity environment. The degradation resistance of Te films was found to depend strongly on the film deposition rate, film thickness, and the presence of a surface oxide layer. It was shown that, in addition to oxidation, weight loss through the formation of some unidentified volatile products also contributed to the degradation of thin Te films. The effects of deposition rate and film thickness were attributed to their influence on the film microstructure.
Atomic concentrations of binary compound thin films on elemental substrates determined by Rutherford backscattering techniques
Authors: Petrov I. , Braun M. , Fried T. , Sätherblom H. E.
Published: February 2003

A method of analysis has been developed by which the atomic composition of binary compound thin films can be determined, using Rutherford backscattering techniques. The advantage of the approach discussed in this paper is that the atomic concentration of the lighter material in the film can be deduced without taking into account the backscattering signals from the lighter element. This is of special importance whenever signals from the lighter element suffer from large statistical errors, or are not observable at all in a backscattering spectrum. A few examples of calculations, done with a developed computer program, as well as some experimental results are presented and discussed. It is shown that the atomic concentration of the lighter element in a compound film generally can be determined with an accuracy of about 5%.
Cleaning chemistry of InSb(100) molecular beam epitaxy substrates
Authors: Vasquez R. P. , Lewis B. F. , Grunthaner F. J.
Published: February 2003

In order to obtain good epitaxial growth, in situ cleaning procedures are necessary. The procedures in use include argon ion bombardment and growth of an oxide passivation layer which is removed in situ by heat treatment. Several chemical cleaning procedures for InSb(100) have been compared, and a new technique based on growth of a chloride—rather than an oxide—over-layer is proposed. The chloride is found to be easily removed at low temperatures (<350 °C), and carbon contamination is minimized. Procedures for growth of the chloride are described, including growth of an oxide followed by nucleophilic substitution by Cl− ions, and direct attack on the substrate by a Cl2 plasma or Cl radicals in solution. In all cases, the film is composed of indium chlorides. In-situ desorption of the chloride formed by the Cl2 plasma is found to give the most reproducibly clean surfaces, as determined by x-ray photoemission spectroscopy.
Interfacial reaction and Schottky barrier between Pt and GaAs
Authors: Fontaine C. , Okumura T. , Tu K. N.
Published: February 2003

The interfacial reaction between Pt films and (100)-oriented n-type GaAs substrates in the temperature range between 350 and 500 °C has been studied by combining transmission electron diffraction and microscopy, glancing-incidence x-ray diffraction, and Rutherford backscattering spectroscopy. The reaction has produced PtGa and PtAs2. The phase PtAs2 has shown a strong preferred orientation on (100)GaAs and it is the phase which dominates the contact to GaAs. The orientation relation has been analyzed by using stereographic projections. Effects of the reaction on the Schottky barrier behavior have been monitored by a combination of current-voltage, capacitance-voltage, and photoresponse measurements. The value of the Schottky barrier height has been determined to be 0.9 eV and no strong variation of the barrier height with annealing has been observed.
Characteristics of TiN gate metal-oxide-semiconductor field effect transistors
Authors: Wittmer M. , Noser J. R. , Melchior H.
Published: February 2003

We have investigated the compatibility of TiN gate electrodes with standard metal-oxide-semiconductor (MOS) processing. Measurements were performed on MOS capacitors to determine the metal work function, flat-band voltage, total interface charge density, mobile oxide charge density, oxide leakage current, and breakdown field. The measurement of the threshold voltage as a function of back bias on TiN gate MOS field effect transistors has revealed device characteristics which compare well with those of standard polysilicon gate devices.
Relationship between x-ray-produced holes and interface states in metal-oxide-semiconductor capacitors
Authors: Hu Genda J. , Johnson Walter C.
Published: February 2003

Metal-silicon dioxide-silicon capacitors were irradiated with soft x rays to 40 krads (SiO2) with different biases (−3 to +12 V) at 83 K. The number of interface states generated after samples were warmed was found to bear a linear relation with the flatband voltage shift measured before warm up. A one-to-one relationship was observed between the number of interface states generated in the central 0.7-eV portion of the Si band gap during a one year storage at room temperature and the number of holes that moved to the Si–SiO2 interface during warm up. Annihilation of the x-ray-generated holes by photoinjection of electrons before warm up prevented the generation of interface states. Both experiments support a cause-and-effect relationship between holes in the oxide and interface states generated in the metal-oxide semiconductor structure.
Effect of Si-Ge buffer layer for low-temperature Si epitaxial growth on Si substrate by rf plasma chemical vapor deposition
Authors: Suzuki S. , Itoh T.
Published: February 2003

Silicon epitaxial growth on the Si-Ge buffer layer at a low substrate temperature by the rf plasma chemical vapor deposition using SiH4 and GeH4 has been investigated. The electron Hall mobility of the homoepitaxial layer grown at 750 °C with a growth rate of 14 Å/sec coincides with that of bulk Si, but for a high growth rate of 33 Å/sec, the mobility was limited to within half the value of bulk Si. However, a small amount of Ge introduced in an initial stage of growth to form the Si-Ge buffer layer improved the crystalline quality of the ensuing Si epitaxial layer with a high growth rate. The electron Hall mobility of the Si layer grown on the Si-Ge buffer layer was a similar value of bulk Si in a low carrier concentration of 6×1015 cm−3. The crystalline quality of the grown Si layers was examined by the combination of Rutherford backscattering spectrometry and transmission electron microscopy.
Specific heat of i
n s
i
t
u superconducting composites
Authors: Eucker S. S. , Verhoeven J. D. , Finnemore D. K.
Published: February 2003

Specific heat measurements have been used to study the electronic excitation spectrum of the Cu regions of in situ prepared Cu-Nb and Cu–Nb3Sn composites having filament dimensions comparable to the superconducting coherence distance. At very low temperatures the major contribution to Cp comes from the electrons in the Cu regions so the excitation spectrum in Cu is easily accessible by this technique. Measurements show that the specific heat is far smaller than that expected if the Cu were normal, indicating that there is a well developed superconducting order parameter of about the size predicted from the de Gennes boundary conditions, i.e., about 0.3 meV. With the application of only a few millitesla, this gap is reduced by at least a factor of 10.