bluuebunny/crossref_metadata_2025 huggingface dataset:
Hole trapping in the bulk of SiO2 layers at room temperature
Authors: DeKeersmaecker R. F. , DiMaria D. J.
Published: February 2003

The first experimental evidence is reported for hole trapping at room temperature in the bulk of dry thermally grown SiO2 layers incorporated into metal-oxide-semiconductor (MOS) structures. The hole traps are generated by ion implantation into the SiO2 layer followed by a high-temperature anneal in nitrogen. Hole avalanche injection from the n-type Si-substrate is used to introduce holes into the SiO2. Electron internal photoemission (photo I-V) measurements are used to locate the trapped positive charge. The magnitude of the cross-over voltage, defined as the gate voltage necessary to suppress electron current injection originating from the metal, is shown to be closely related to the charge location in the oxide. From current measurements in the high-field regime, the hole distribution centroid is calculated and is found to be coincident with earlier determinations of the electron distribution centroid in the oxide of p-type samples which received a similar implantation and annealing. At low applied voltages, it is shown that an oxide with trapped positive bulk charge (holes) will appear to injected electrons as a ’’giant macroscopic potential well’’ where all carriers get trapped by the holes.
Quantitative Auger analysis of Nb-Ge superconducting alloys
Authors: Buitrag Román H.
Published: February 2003

The feasibility of using Auger electron analysis for quantitative analysis was investigated by studying Nb3Ge thin-film Auger data with different approaches. A method base on elemental standards gave consistent quantitative values with reported Nb-Ge data. Alloy sputter yields were also calculated and results were consistent with those for pure elements.
Nature of catalytic impurities in synthetic diamonds. An identification using extended x-ray absorption fine structure
Authors: Wong Joe , Lytle F. W.
Published: February 2003

Identification using the extended x-ray absorption fine structure technique shows that nickel impurities found in synthetic diamonds exist as fcc Ni and contain an estimated amount of 2.7±1.3 at.% carbon in solution.
Laser pulse annealing of ion-implanted GaAs
Authors: Campisano S. U. , Foti G. , Rimini E. , Eisen F. H. , Tseng W. F. , Nicolet M-A. , Tandon J. L.
Published: February 2003

GaAs single-crystals wafers are implanted at room temperature with 400-keV Te+ ions to a dose of 1×1015 cm−2 to form an amorphous surface layer. The recrystallization of this layer is investigated by backscattering spectrometry and transmission electron microscopy after transient annealing by Q-switched ruby laser irradiation. An energy density threshold of about 1.0 J/cm2 exists above which the layer regrows epitaxially. Below the threshold the layer is polycrystalline; the grain size increases as the energy density approaches threshold. The results are analogous to those reported for the elemental semiconductors, Si and Ge. The threshold value observed is in good agreement with that predicted by the simple model successfully applied previously to Si and Ge.
Ultrasonic properties of poly(4-methyl pentene-1)
Authors: Hartmann Bruce
Published: February 2003

Ultrasonic measurements of longitudinal and shear sound speeds and absorptions were made on poly(4-methyl pentene-1) or PMP. The measurements were made at 1.8 MHz and covered the temperature range from 0 to 70 °C. PMP is of interest because it has a lower density (0.835 g/cm3) than any other commercially available high polymer. PMP was found to have a major structural relaxation (the glass transition) at 25 °C. An analysis of the various Grüneisen parameters of the polymer leads to the conclusion that one-fifth of the normal modes of vibration of PMP are interchain rather than intrachain. PMP was evaluated as an acoustic window material and compared with poly(acrylonitrile butadiene styrene) or ABS, another rigid acoustic window material. For an infinitely thick layer of PMP, the reflected signal is 20 dB less than incident, while for ABS the reflected signal is 16 dB less. For plates of finite thickness, PMP is a better acoustic window than ABS at most, but not all, angles of incidence.
Semisintered oxides for pressure-transmitting media
Authors: Onodera Akifumi , Suito Kaichi , Kawai Naoto
Published: February 2003

Several semisintered oxides have been developed for transmitting media able to be employed in multianvil high-pressure vessels. The oxides are MgO, BeO, ZrO2, Al2O3, Fe2O3, and Mg2SiO4, all having porosity of approximately 35–55%. Pressures higher than 220 kbars can be reproducibly generated inside each medium.
Thermal diffusivity measurements at high temperatures by the radial flash method
Authors: Chu F. I. , Taylor R. E. , Donaldson A. B.
Published: February 2003

The flash method has been extended to measure thermal diffusivity in the radial direction at high temperatures, and in the presence of substantial radiation heat losses. Radial effects in this instance, arise because only a small portion of the front surface of the sample is exposed to the energy source. The present effort complements a recently published study in which thermal diffusivity was measured in the axial direction. In that study, substantial radial heat flow and axial radiation heat losses were experienced. Both methods were used to test the same samples of an isotropic material (POCO AXM-5Q graphite) and an anisotropic material (reactor-grade graphite). Results show that thermal diffusivity in the radial direction can be measured for both isotropic and anisotropic material without accounting for the large radiation heat losses. These results are also compared with those based on the conventional flash method using smaller samples.
Silicide formation in thin cosputtered (titanium + silicon) films on polycrystalline silicon and SiO2.
Authors: Murarka S. P. , Fraser D. B.
Published: February 2003

Formation of the silicides of titanium has been investigated by cosputtering titanium and silicon on polycrystalline silicon and oxidized silicon wafers. Alloys with as-deposited Si/Ti atomic ratios of 0.5–8 were sintered in vacuum or hydrogen ambient in the temperature range 400–1000 °C. The Ti-Si interaction in such films was studied by the use of sheet resistance, x-ray diffraction, and stress measurements. It was found that in cases of silicon deficient alloys (e.g., the case of alloys sputtered on oxide with Si/Ti ratio <2) intermetallics Ti5Si3 and TiSi were formed. These intermetallics were stable up to 900 °C. In the presence of polycrystalline silicon and for alloys with Si/Ti ratio ?2, the only intermetallic formed was TiSi2. TiSi2 was responsible for very low resistivity (as low as ∼25 μΩcm) in the films. The volume change associated with silicide formation led to high tensile stresses in the films. It is suggested that in cosputtered films metallurgical interaction occurs locally which leads to small grain size, higher resistivities, and smoother surfaces. For films with excess silicon, up to 4 silicon atoms are accommodated within a unit cell of TiSi2. This suggests a range of solid solubility of silicon in TiSi2.
Interaction of deep-level traps with the lowest and upper conduction minima in InP
Authors: Wada O. , Majerfeld A. , Choudhury A. N. M. M.
Published: February 2003

Deep-level electron traps in bulk, vapor-phase epitaxial (VPE) and liquid-phase epitaxial (LPE) undoped InP crystals are investigated by an extensive method of capacitance measurement. Eight different traps are found in bulk and VPE crystals, and on the other hand no traps are found in LPE crystals. Characteristics of three traps with emission activation energies of ΔEe=0.43, 0.59, and 0.63 eV are analyzed in detail. The absolute energy levels for these traps measured from the lowest Γ conduction minimum are ET=0.34, 0.20, and 0.24 eV, respectively. It is shown that the 0.43-eV trap is coupled to the Γ minimum and that the 0.59- and 0.63-eV traps are coupled to the upper L minima. The capture of Γ electrons by the 0.43-eV trap is found to exhibit a thermally activated capture cross section σ with a barrier energy of ΔEB=0.09 eV. On the contrary, the temperature dependence of capture of L electrons by the 0.59-eV trap is found to be dominated by the temperature dependence of electron density in the L minima and to exhibit a negligible ΔEB for σ. The intervalley energy separation ΔELΓ?0.39 eV is derived and found consistent with the observed emission and capture properties of both of the L-coupled traps. Reasonable agreements are obtained between the capture cross sections derived from capture and from emission experiments, for both the Γ-coupled and L-coupled traps, respectively.
Electron ionization and excitation coefficients for argon, krypton, and xenon in the low E/N region
Authors: Specht L. T. , Lawton S. A. , DeTemple T. A.
Published: February 2003

The electron ionization coefficients for Ar, Kr, and Xe have been measured in the low E/N region [(0.5–4) ×10−16 V cm2] using a drift-tube apparatus. At low field values, the ionization coefficient was found to be anomalously large, a fact attributed to surface photoelectron emission from radiating metastables. This contribution also explains the discrepancy between earlier measurements and recent calculations based on the transport equation. The measurements were analyzed on the basis of two contributions to the ionization rate and calculations of the transport equation, yielding a revised set of inelastic cross sections which differ from earlier ones primarily in the inclusion of shape resonances.
Influence of proton-stripe realization process on the luminescence properties of (AlGa)As double heterostructures
Authors: Rao E. V. K. , Duhamel N.
Published: February 2003

Photoluminescence (PL) measurements using two different incident photon energies (one, higher than both GaAs and AlxGa1−xAs band-gap energies: indirect excitation; the other, higher than GaAs band-gap energy but less than Ga1−xAlxAs band-gap energy: direct excitation) have been conducted on proton-striped double heterostructures (DH) for cw lasers. These measurements performed inside and outside the stripe regions gave the following results: the luminescence from the regions inside the stripe, when measured under indirect excitation conditions is shown to be affected by the proton bombardment; also a simple heat treatment of these layers is found to restore this luminescence to a large extent. Some experimental evidence assuming the presence of nonradiative centers localized in the neighborhood of P-AlxGa1−xAs (confinement layer) and p-GaAs (active layer) heterointerface is presented and discussed.
A mathematical model for calculating effects of back corona in wire-duct electrostatic precipitators
Authors: Lawless Phil A. , Sparks Leslie E.
Published: February 2003

A new mathematical model for the electrical conditions in wire-duct electrostatic precipitators is described. The model is based on the solution of Maxwell’s equations for the electric field components and offers several advantages over numerical solutions of Poisson’s equation. The model is used to calculate the effects of back corona on (1) the voltage-current characteristic, (2) the current-density distribution at the collector plate, and (3) particle collection for five simple mechanisms describing the generation of back corona. Each mechanism is capable of simulating the V-I curves characteristic of precipitators operating in back corona, but two in particular are identified as potential back corona mechanisms on the basis of generating hysteresis in the V-I curves or characteristic current density variations. These mechanisms are consistent with limited experimental data. This method of calculation is useful and can be extended to more complex mechanisms for back corona generation.
Surface- and inner-microdefects in annealed silicon wafer containing oxygen
Authors: Shimura Fumio , Tsuya Hideki , Kawamura Tsutomu
Published: February 2003

Surface- and inner-microdefects examined after a two-step annealing process are compared and related to the intrinsic gettering phenomenon. After the defects are characterized by means of transmission electron microscopy, the defect types (dislocations, precipitates, and stacking faults) and defect structures as well as nature are correlated with the annealing temperature. It is found from the observations that a surface-microdefect is a stacking fault extrinsic in nature possibly caused by a process-induced ’’heavy metal contamination’’ such as copper and that the type of Si-O complex precipitates generated strongly depends on annealing temperatures: <1050°C⋅⋅⋅ platelike cristobalite, 1100°C<⋅⋅⋅ regular octahedral amorphous SiO2. In addition, the mechanism for the formation of these defects is discussed based on electron microscope observations.
Development of hard-elastic solids from glassy polymers
Authors: Moet Abdelsamie , Palley Igor , Baer Eric
Published: February 2003

High-impact polystyrene (HIPS) has been processed into a specific microstructure which exhibited the hard-elastic behavior previously restricted to crystalline polymers. Unidirectionally stacked profuse crazes formed in uniaxially elongated HIPS resembled the row nucleated structures of stacked lamellar aggregates bridged by extended fibrils. Films in this form possessed repeated high recovery from large extension without rupture. Stress-strain and stress-relaxation tests, performed in air and in a variety of liquids, and thermoelastic experiments indicated that this material has similar characteristics to those of hard-elastic crystalline polymers. Our results confirmed that the recovery process of elastic HIPS, like crystalline systems, is composed of an instantaneous component and a time-dependent healing mechanism. The first was found to be energetic in nature and the second conformational (entropic). A mechanism, based on the reversible extensive formation of fresh surface of the craze (or interlamellar) fibrils giving rise to the elastic restorative force, is proposed. Stress-induced sorption and release of liquid, a newly discovered property, is also discussed.
Optical studies of void formation and healing in styrene-isoprene-styrene block copolymers
Authors: O’Connor K. M. , Wool R. P.
Published: February 2003

Void formation is shown to be a significant response of styrene-isoprene-styrene block copolymers under conditions of tensile stress relaxation. When brought to zero stress, these voids are observed to close and heal, restoring the original mechanical properties of the undamaged material. Dark-field optical microscopy and light-transmission photometry have been used to study void formation and healing in the size regime appropriate to optical techniques. As meaured from a reference state of damage, healing was found to increase with time and temperature in the zero-stress state, with an apparent activation energy of 9 kcal/mole. The Mie theory of particle scattering was used to analyze changes in void size and size distribution during the healing process. The results are discussed in terms of possible mechanisms for healing.
A tensorial Hencky measure of strain and strain rate for finite deformations
Authors: Fitzgerald J. Edmund
Published: February 2003

A proper tensorial logarithmic strain measure and its associated time rate of change is developed using an equivalence between the expressions for an isotropic tensor function and the Sylvester-Lagrange formalism. It is shown that the specific Cauchy stress T/ρ is derivable from a potential with respect to this strain measure. A modified stress TF is shown to be derivable from a potential with respect to the left polar decomposition of the deformation gradient. Advantages and disadvantages of this formulation are discussed.
Epitaxial polymerization of (SN)x: Lattice effects on structures and topochemistry
Authors: Rickert Scott E. , Ishida Hatsuo , Lando Jerome B. , Koenig Jack L. , Baer Eric
Published: February 2003

Disulfur dinitride was epitaxially crystallized from the vapor phase on freshly cleaved (100) faces of monovalent alkali halide single crystals. Subsequently, the dimer was polymerized in the solid state, while still on the substrates. This epitaxial polymerization leads to highly oriented crystalline polythiazyl [(SN)x] which shows no evidence of the usual fibrullar morphology. Fibrils of (SN)x have been produced by epitaxial polymerization of a second layer of dimer on a previously polymerized layer. Three new structures of polythiazyl have been observed from crystals grown on NaCl, KBr, and KI. The structures differ significantly from the usual α phase of (SN)x. Because of such large differences in the polymer chain spacing in these forms when compared to the normal form, a new polymerization mode and direction may be involved. The diagnosis of the true effect of water on (SN)x using Fourier-transform infrared spectroscopy (FT-ir) aided in discovering why structural studies from samples exposed to water are impossible.
Fast ion extraction in laser isotope separation
Authors: Hazak G. , Gell Y. , Boneh Y. , Goshen S.
Published: February 2003

An analysis of the E×B scheme for fast ion extraction in laser isotope separation is presented. Using an analytically solvable model and a numerical simulation we have found that the scheme can meet the rather severe time and space restrictions imposed by the large cross section for charge exchange.
Modified radiative transfer theory for a two-layer random medium
Authors: Zuniga M. A. , Kong J. A.
Published: February 2003

Modified radiative transfer (MRT) equations appropriate for electromagnetic wave propagation in bounded random media are derived from the Bethe-Salpeter equation with the ladder approximation and the Dyson equation with the nonlinear approximation. The MRT equations are then solved with the first-order renormalization approximation to obtain analytical results for the backscattering cross sections of a two-layer random medium with arbitrary three-dimensional correlation functions. The coherent effects of the MRT theory are illustrated and comparisons are made with backscattering cross sections obtained with the first Born approximation to the wave equation.
The effect of mismatch on the performance of GaAsSb photodiodes
Authors: Moon R. L.
Published: February 2003

The maximum quantum efficiency of GaAs1−xSbx photodiodes with 0.03 <x<0.11 is shown to decrease as the lattice mismatch between the epitaxial layers and the GaAs (100) substrate increases. Dislocations arising from the mismatch are responsible, but these can be reduced and the performance improved by step-grading. The performance decrease with increasing dislocation density follows the equation developed by Roedel et al., and with this equation an estimate of the performance decrease with mismatch is obtained when the experimental data for dislocation density versus mismatch is used.
Comments on ’’Air breakdown by pulsed laser radiation in the 2.7- and 3.8-μm region’’
Authors: Deka B. K. , Dyer P. E.
Published: February 2003

In a recent paper by Soileau [Appl. Phys. Lett. 35, 309 (1979)], a λ−2 wavelength scaling for air breakdown using various pulsed lasers was reported. The good agreement between this and previously published work not referred to by Soileau is discussed.
Ion-beam induced metastable Pt2Si3 phase. I. Formation, structure, and properties
Authors: Tsaur B. Y. , Mayer J. W. , Tu K. N.
Published: February 2003

A metastable silicide phase with a composition of Pt2Si3 has been obtained by using ion-beam mixing techniques. To form the phase, a thin PtSi film on a Si substrate was first converted into a Si-rich amorphous Pt-Si alloy by implantation with energetic ions through the PtSi-Si interface. The amorphous alloy then transformed into the metastable crystalline phase upon post annealing at 350–500 °C. X-ray diffraction analysis showed that the Pt2Si3 phase has a hexagonal crystal structure with lattice parameters a=3.841 Å and c=11.924 Å and there are ten atoms per unit cell. The phase was unstable at temperatures above 550 °C and transformed back to PtSi and Si. The metastable Pt2Si3 phase was found to exhibit a superconducting transition onset at about 4.2 °K and becomes completely superconductive below 3.6 °K.
Scattering of 5- to 30-keV hydrogen from surfaces
Authors: Harriss J. E. , Young R. , Thomas E. W.
Published: February 2003

Studies have been performed of the energy distribution exhibited by recoil H+ and H− resulting from the impact of 7.5- to 15-keV H+ on targets of Be, C, Cu, Nb, Au, and stainless steel. The scattering geometry involves near grazing incidence and emergence with a scattering angle of 30.4°. Peak flux occurs at higher recoil energies than in previously published studies with large-angle (135°) scattering. The energy spectrum has been shown to be in excellent agreement with the TRIM computer simulation for one case. The charge state distribution of recoils appears to be governed by charge transfer and ionization events in biparticle collisions occurring as the recoil emerges through the surface monolayer. In the study of recoil H+ fragments produced by H+2 impact there is evidence that the collision processes experienced by the fragments are in some way correlated. Recoil spectra due to D+ impact are not the same as for equal energy nor equal velocity H+ impact. The difference is explained and a simple scaling procedure suggested to relate energy spectra for the two isotopes.
Determination of the impact response of PMMA using combined compression and shear loading
Authors: Gupta Y. M.
Published: February 2003

Large amplitude one-dimensional compression and shear wave measurements have been made in polymethyl methacrylate (PMMA). Measurements of shear and longitudinal wave velocities were used to determine the shear modulus, bulk modulus, and the mean stress-volume relations under impact loading. The mean stress-volume relation determined from impact data is considerably stiffer than the static hydrostat often used to interpret shock data and leads to a lower strength in shock wave data. Unlike the quasi-static-uniaxial strain results, the shock data show strength reduction at higher stresses. Measurement of shear wave amplitudes, at different compressive stresses, independently support the strength loss determined from wave velocity analysis. Measurement of shear particle velocity at the impact surface shows that the dynamic friction behavior of PMMA depends on the inelastic material response near the surface.
A theoretical equation of state for methane
Authors: Kerley G. I.
Published: February 2003

A theoretical equation of state for methane is derived and compared with experimental data. The EOS for the solid phase was constructed from the Debye model. The EOS for the fluid phase was constructed from thermodynamic perturbation theory. Tables of the calculated thermodynamic properties are available for temperatures from 20 to 104 K and for densities up to 2.5 g/cm3. Agreement with experiment is good.
Measurement of diffusion length in CuInSe2 and CdS by the electron beam induced current method
Authors: Piekoszewski J. , Castaner L. , Loferski J. J. , Beall J. , Giriat W.
Published: February 2003

The minority-carrier diffusion length Le for electrons in p-CuInSe2 was determined by analyzing the magnitude of the electron beam induced current (EBIC) as a function of distance from the p/n junction in an n-CdS/p-CuInSe2 solar cell whose solar energy conversion efficiency was about 8%. Data obtained for electron beam energies of 10, 20, and 30 keV showed that Le was at least 0.92 μm. Analysis of the data in terms of a model in which the injection process is approximated by a point source results in a value of Le ∼2.5 μm and a surface recombination velocity of about 1.4×106 cm/sec on a as-cut surface. The analysis leads to the inference that the ’’point source’’ is located at a depth equal to about 0.06 times the electron range below the surface on which the beam is incident.
The thermal stability of laser-produced silicide layers
Authors: Wittmer M. , Lüthy W. , von Allmen M.
Published: February 2003

We have studied the thermal stability of laser-reacted Pd and Pt silicides upon post-irradiation annealing in a vacuum furnace. It was found from both Rutherford backscattering and x-ray analysis that thermal annealing at temperatures between 400 and 800 °C for 15 h causes Si to diffuse out of the silicide layer and to grow epitaxially on the single-crystal substrate. Hereby, a single silicide phase tends to form at the expense of the other phases present. The reported compositional changes do not occur during standard heat treatment cycles used in semiconductor device fabrication.
On surface coatings and secondary yield of Nb3Sn and Nb
Authors: Grundner M. , Halbritter J.
Published: February 2003

In rf cavities, Nb3Sn and Nb surfaces show features that have been blamed on unavoidable oxide layers. In addition to the oxidation, physi- and chemisorption take place, which strongly influence the work function and the secondary yield. To measure quantitatively the oxide and sorption layers, x-ray photoelectron spectroscopy (XPS) measurements have been carried out for Nb surfaces subjected to the typical procedures, such as oxipolishing (OP), ultra high vacuum annealing (HT), handling in ’’vacuum,’’ air, H2O, H2O2, CH3OH, or impact of ions and electrons. The XPS results show that all Nb3Sn and Nb surfaces used are coated with a dielectric oxide layer thicker than 2 nm, saturating in growth at 6 nm. These oxides are coated with a sorption layer containing O and C of at least 2 monolayer equivalent (ML), but as much as 10 ML have been observed. The excited states of the oxides and the excited localized states of the Nb2O5-H2O chemisorption state enhance the secondary electron emission, whereas the physisorbed hydrocarbons show enhanced absorption of slow electrons, especially after electron or x-ray induced ’’conditioning.’’ The enhanced secondary emission from the Nb2O5-H2O state positively charges the dielectric, lowering the work function, whereas the enhanced electron absorption of ’’conditioned’’ hydrocarbons negatively charges this region and increases the work function.
On the hygrothermomechanical characterization of polyvinyl acetate
Authors: Knauss W. G. , Kenner V. H.
Published: February 2003

As a part of a program to understand the mechanisms of failure in time-dependent adhesion and film bonding, the creep compliance of polyvinyl acetate (PVAc) in shear has been determined both as a function of temperature and absorbed moisture. Volumetric expansion as a function of temperature or moisture takeup was also measured. We find that practically realizable changes in moisture content affect both the creep compliance and the swelling of PVAc to a degree comparable to that resulting from realistic changes in temperature. For example, the creep rates (histories) at corresponding times for PVAc subjected to 92% relative humidity storage are accelerated by approximately four orders of magnitude over those found for the dry material. Moreover, we find within reasonable experimental error that water concentration affects the time scale of creep like temperature through a concentration-dependent shift factor. An attempt is made at discussing the interrelation of temperature- and moisture-induced volume changes.
Ferroelectric hysteresis effects in poly(vinylidene fluoride) films
Authors: Scheinbeim J. I , Yoon C. H. , Pae K. D. , Newman B. A.
Published: February 2003

Investigations of the piezoelectric response of biaxially oriented poly(vinylidene fluoride) films subjected to a series of static positive and negative poling fields produces a hysteresis curve for d31 and e31 showing the ferroelectric character of phase IV. Examination of changes in the crystalline regions, using differential scanning calorimetry and x-ray methods, of films cycled (statically) through large positive and negative poling fields provides insight into the switching mechanisms of both phase I and phase IV. The experimental results show a cyclic broadening and narrowing of the endothermic melting peaks as the film polarization is switched. Cyclic changes in the intensities of the phase I (110) (200) and phase II (or phase IV) (100), (020), and (110) reflections are also observed.
Rayleigh-Brillouin light scattering from atactic polystyrene at high pressure
Authors: Coakley R. W. , Hunt J. L. , Stevens J. R.
Published: February 2003

Brillouin-frequency shifts have been obtained for atactic polystyrene at pressures up to 2 kbars and temperatures up to 180 °C. The temperature and pressure dependencies of the data have been analyzed. The resulting values of Tg have been found to increase with pressure towards a limit. The temperature dependence of the Brillouin frequencies in the amorphous solid have been separated into a temperature coefficient at constant volume and a volume effect. We comment on the equilibrium entropy theory of Gibbs and DiMarzio using specific volume data from the literature.
Properties of uniform oxygen Czochralski silicon crystals
Authors: Lin Wen , Pearce C. W.
Published: February 2003

The properties of uniformly incorporated oxygen in silicon crystals grown using a modified Czochralski process are described. The impact and advantageous aspects of such crystal properties are demonstrated in terms of impurity gettering and slip retardation during silicon wafer processing.
Refinement of solar absorbing black chrome microstructure and its relationship to optical degradation mechanisms
Authors: Zajac G. , Smith G. B. , Ignatiev A.
Published: February 2003

An in depth characterization of the electrodeposited solar absorber black chrome resulting in refinement of the microstructural model of the coating is presented in light of current studies in valence band Auger electron spectroscopy, x-ray photoelectron spectroscopy, thermal desorption spectroscopy, secondary ion mass spectroscopy, and the chromium electrodeposition mechanism. Through the presented model, the structural and chemical parameters of the coating are linked to its optical response with the degradation of the optical response at elevated temperatures related to changes in these parameters. The degradation process is divided into two distinct phases. First, upon heating to low temperatures (≲300 °C) the chromium hydroxide localized on the surface and within the microstructure of the film decomposes producing H2O and chromium oxide leaving an expected microvoid-metallic particle structure. Heating to temperatures in excess of 300 °C leads to the second degradation phase. The fine chromium crystallites comprising the film undergo oxidation and the metallic chromium component, responsible for the intrinsic optical absorption, is diminished. The optical model of the solar absorbing film has been refined within the effective medium approach to account for the flat response in the visible part of the spectrum.
Parametric conversion of an electron plasma wave into an electromagnetic wave in a piezoelectric semiconductor
Authors: Guha S. , Apte N.
Published: February 2003

The possibility of the excitation of an electromagnetic wave as a consequence of the nonlinear coupling between an electron plasma wave and an acoustic wave in an inhomogeneous piezolectric semiconductor plasma has been analyzed. The nonlinear interaction results in the parametric amplification of acoustic waves. The dispersion relation for such a parametric instability is obtained using a hydrodynamic model of an inhomogeneous semiconductor plasma; it is solved to study the threshold electric field necessary for the onset of instability and the growth rate of the unstable mode well above the threshold as a function of the magnitude of an externally applied magnetostatic field. The numerical analysis has been made for the typical case of n-InSb at 77 K. The threshold electric field is appreciably lowered by the application of a large magnetostatic field, and the growth rate of the unstable mode is found to be 104 times more in a magnetoactive (B0≠0) semiconductor than in an isotropic ( B0=0) crystal.
Optogalvanic spectroscopy and thermal relaxation in high-pressure mercury and sodium arc discharges
Authors: van den Hoek W. J. , Visser J. A.
Published: February 2003

Thermal relaxation processes in high-pressure Hg and Na arc discharges have been studied by measuring the frequency dependence of the optogalvanic effect up to 5000 Hz. The experimental results are interpreted in terms of two linear relaxation processes, using a simple model for the energy flow in the arc. For the Hg arc (400 W dc) the two characteristic times are found to be 4.0×10−4 s and ?4×10−6 s. For the Na arc (180 W dc) only one characteristic time of 5.3×10−5 s is obtained.
Low-energy electron losses by plasmon excitations as control means of the growth of epitaxial layers
Authors: Olivier J.
Published: February 2003

We report the effect of thermal degradation of InP surface on the low-energy electron-loss spectrum: the bulk-plasmon peak of indium metal appears alongside that of InP. We propose the use of this technique to detect metallic microsclusters on; the surface of InP epitaxial layers. An example is given of an epilayer grown by chemical-vapor deposition. The method is applicable to other III-V compounds, and generally to compounds for which a constituent part is a metal capable of segregation.
Preparation and properties of thermally evaporated lead germanate films
Authors: Mansingh Abhai , Krupanidhi S. B.
Published: February 2003

Ferroelectric lead germanate (Pb5Ge3O11) films were fabricated by thermal evaporation on n-type silicon substrates. Characterization of the films was made on the basis of substrate temperature, rate of evaporation, annealing time and temperature, and their interdependence. The crystallinity of the film depends on the substrate temperature; films grown at room temperature are amorphous. At high substrate temperatures crystalline films can be obtained, but the as-grown films which were crystalline in nature were found to be nonferroelectric. The conductivity of these films was very much higher than that of the bulk crystals. This may be attributed to O2 deficiency in the films. The loss of stoichiometry was recovered by annealing the films in an atmosphere of Pb and O2 at 600 °C for 6 h. A clear dielectric anomaly, offset in the dc conductivity near the transition temperature, and good hysteresis loops were observed in the annealed films of thickness ≳1 μm.
Optical and thermal properties of BeO thin films prepared by reactive ionized-cluster beam technique
Authors: Takagi Toshinori , Matsubara Kakuei , Takaoka Hiroshi
Published: February 2003

Preparation of BeO thin films is successfully achieved by the reactive ionized-cluster beam technique developed by the authors. Transparent BeO films with the c-axis preferential orientation which is peculiar to a hexagonal structure are obtained on glass substrates, and single-crystal epitaxial films are formed on sapphire substrates at low substrate temperatures up to 400 °C. Optical and thermal transport properties of films are investigated in detail. A strong reststrahlen reflection peak is observed in the vicinity of wavelength 13.5 μm, from which the frequencies of the transverse and longitudinal vibration modes are determined. Anisotropic lattice thermal conductivities parallel and perpendicular to the c axis of the films are measured, and the values of κ∥ph ?2.6 W/cm deg and κ⊥ph ?0.6 W/cm deg at 300 K are obtained. It is also shown that the thermal conductivities of BeO films are proportional to T−2 below Debye temperature ϑD?1053 K of this material.
Doping characteristics and electrical properties of Be-doped p-type AlxGa1−xAs by liquid phase epitaxy
Authors: Fujita Shigeo , Bedair S.M. , Littlejohn M.A. , Hauser J.R.
Published: February 2003

The liquid phase epitaxial technique has been used to grow Be-doped AlxGa1−xAs in the Al composition range 0<x?0.9, and the doping characteristics and electrical properties of the epilayers have been studied by Hall measurements in the temperature range between 77 and 320 K. The distribution coefficient for Be at 800 °C is about 10 for x<0.4 and decreases to about 1 for x=0.8. High hole concentrations of more than 1018 cm−3 have been easily obtained even in epilayers with an x value as high as 0.9. The acceptor activation energies of the epilayers have been between 10 and 100 meV depending strongly on the x value and NA. The hole Hall mobilities at 300 K are less than 102 cm2/V sec, regardless of Al composition. The variation of the hole mobility with x for the same NA shows that the mobility is controlled by the alloy scattering mechanism. The results obtained in this work suggest that Be can be a useful acceptor in AlxGa1−xAs especially for high x values.
Annealing effects in tunnel junctions (voltage annealing)
Authors: Konkin M. K. , Adler J. G.
Published: February 2003

This paper describes the time-dependent changes which occur in Al-oxide–Pb tunnel junctions as a result of voltage annealing (i.e., keeping a fixed bias across junction electrodes). By examining changes in junction resistance, barrier parameters (barrier thickness, average barrier height, and the separation between barrier heights at the two electrodes) and inelastic electron tunneling (IET) peak intensities, one finds that applying a voltage across the junction causes an accumulation or depletion of positive charge at the Al-oxide interface depending on the polarity of the applied bias. Along with charge redistribution, the voltage-induced electric field also enhances or retards other processes (such as reorientation of surface hydroxyl groups) which normally take place during thermal annealing.
Evaluation of spatial dependence of bulk trap density in MOS devices
Authors: Board Ken , Darwish Mohammed
Published: February 2003

If a linear voltage ramp is applied to a metal-oxide-semiconductor (MOS) device, C-V characteristics are generated which contain information about the donor density, the bulk trap density, and their spatial dependence. In this paper, a technique is presented which allows the spatial dependence of the bulk traps to be obtained. The C-V curves are obtained in digital form and the appropriate manipulation is carried out using a digital computer. The technique is simple and does not require a knowledge of the spatial dependence of the donor density.
Growth of CuInSe2 by molecular beam epitaxy
Authors: Grindle S. P. , Clark A. H. , Rezaie-Serej S. , Falconer E. , McNeily J. , Kazmerski L. L.
Published: February 2003

We have used molecular beam epitaxy to grow CuInSe2 layers on CdS (0001B) and other substrates. Epitaxial growth is obtained at a substrate temperature of 300 °C. The ratio of the arrival rates of copper to indium is the key parameter governing layer stoichiometry. In order to produce low-resistivity p-type layers, the Cu/In arrival rate ratio must be slightly higher than that used to grow nominally stoichiometric layers. This suggests that a different defect is controlling electrical properties, rather than the copper vacancy complex which dominates bulk material. We have fabricated CuInSe2/CdS heterojunctions which show a maximum solar conversion efficiency of ∼5%.
Theory of the singly quasidegenerate Josephson junction parametric amplifier
Authors: Soerensen O. H. , Dueholm B. , Mygind J. , Pedersen N. F.
Published: February 2003

A comprehensive account of the theory of the singly quasidegenerate Josephson junction parametric amplifier is given. In this mode the signal and idler frequencies are both approximately equal to half the pump frequency, and hence the signal and idler channels have a common termination. It is shown that the performance of the amplifier characterized by properties such as gain-bandwidth product, noise temperature, and saturation depends strongly on the embedding microwave circuit. In particular any uncompensated series reactance may deteriorate the overall performance. Internal shot and Johnson noise as well as incident thermal radiation is included in the discussion. It is shown that the noise temperature is virtually independent of noise injected from external sources and that minimum noise temperature is automatically achieved if the amplifier is tuned to maximize the gain-bandwidth product. The analytical results are illustrated by self-consistent numerical solutions of the circuit equations.
Temperature dependence of Mössbauer parameters for Fe57 in NiFe2O4 precipitation process from silicate glass
Authors: Komatsu T. , Soga N.
Published: February 2003

The temperature dependence of Mössbauer parameters (relatively recoil-free fraction, center shift, and quadrupole splitting) for Fe57 in the NiFe2O4 precipitation process from a silicate glass was measured to clarify vibrational properties of Fe3+ ions in the quenched glass (amorphous state) and heat treated specimens (crystalline state) in the temperature range 290–625 K. It was found that the Debye temperature of Fe3+ ions in the quenched glass is smaller than those in the heat treated specimens. It was also found that the vibrational property of Fe3+ ions in the quenched glass can be described by the single Debye model over the entire temperature range. However, anomalies in the temperature dependence of the relatively recoil-free fraction and the correlation between the relatively recoil-free fraction and center shift at high temperatures were observed in the heat treated specimens, and they were related to the presence of anharmonicity in vibrations of Fe3+ ions.
Substrate thickness considerations in electron beam lithography
Authors: Adesida Ilesanmi , Everhart Thomas E.
Published: February 2003

A comprehensive theoretical and experimental study of the spatial distribution of electron energy dissipation in a very thin polymer film for dot, line, and parallel line exposures over a wide range of substrate thickness and exposure dosage is reported. The two Monte Carlo models used in the theoretical calculations are reviewed and the theoretical results obtained are discussed. Experimental fabrication of thin substrates and effective techniques of electron beam lithography on such substrates are described. The concept of equienergy dissipation contours is discussed and then used to compare experimental data with theory. Good agreement between experiment and theory has been obtained. With substrate thickness as a variable, the fundamental influence of electron scattering on the resolution of electron beam lithography has been verified.
Effect of laser spot size on energy balance in laser induced plasmas
Authors: Pant H. C. , Sharma S. , Bhawalkar D. D.
Published: February 2003

The effect of the laser spot size on laser light absorption in laser induced plasmas from solid targets was studied. It was found that at a constant laser intensity on the target, reduction in the laser spot size enhances the net laser energy absorption. It was also observed that the laser light reflection from the target becomes more diffused when the focal spot size is reduced.
Band-gap collapse in uniaxially strained (shocked) elastic germanium
Authors: Harris Paul
Published: February 2003

Assuming elastic Ge above the shock wave Hugoniot elastic limit it is shown that electronic band-gap collapse occurs for symmetry reducing uniaxial strain at approximately 135 kbars.
Preparation of small-area Josephson junction using the scratched edge of a Pb/In layer
Authors: Okuyama K. , Gundlach K. H. , Hartfuss H. J.
Published: February 2003

Superconductor-insulator-superconductor (SIS) Josephson junctions with areas less than 1 μm2 were formed at the scratched edge of the Pb/In electrode. The scratch was made with a razor blade. Notwithstanding the simple technique used for scratching, the yield to get good junction is relatively high. The I-V characteristic with and without 70-GHz radiation is shown.
Tilt angle and mask edge angle dependences of lateral spread of implanted boron ions under mask edge
Authors: Tsuchiya Toshiaki
Published: February 2003

Tilt angle ϑt and mask edge angle ϑe dependences of the lateral spread distribution of implanted boron ions under mask edges are experimentally obtained. To evaluate lateral spread quantitatively, n-MOSFET’s with boron-ion-implanted p+ regions (40 KeV, 2×1013 cm−2) around source and drain n+ layers are fabricated, and threshold voltages of the MOSFET’s are measured and analyzed using two-dimensional computer simulation. Results obtained are that (i) ΔLs/Δϑt (incremental lateral spread width ΔLs / deg of ϑt ) is about 20 Å/deg in the range 5°<ϑt <8°; and (ii) ΔLs/Δϑe is about −3 Å/deg in the range 56°<ϑe <78°. The lateral spread of the p+ regions is also calculated by Runge’s equation modified to incorporate the tilt angle effect by transforming tilt angle into mask shape. Calculated ΔLs/Δϑt agrees well with the experimental value. However, calculated ΔLs/Δϑe is about −50 Å/deg which disagrees with the experimental value. Throughout the present work, it is shown that the new method of evaluating lateral spread by analyzing the threshold voltages of the MOSFET’s is very sensitive, compared with the other methods.
Channeled-proton-induced x-ray measurements of radiation damage in sapphire
Authors: Luera T. F.
Published: February 2003

Channeled-proton-induced x rays (CPIX) were used to measure displacement damage produced in sapphire (α-Al2O3) by ion bombardment at room temperature. A method based on dechanneling theory was developed for the interpretation of CPIX results in terms of numbers of displaced atoms. The results agreed with those obtained with the Rutherford-backscattering-channeling (RBC) technique. The dependence of displacement damage on energy partition was evaluated by selection of ion species and incident energy (20 keV, H+2; 20 keV, He+; 70 keV, N+ and 500 keV, Xe++). Except for H+2 implantation, the net number of displaced atoms at damage levels below saturation was found to depend almost entirely upon the energy deposited into atomic collision processes. For the hydrogen implantations the damage was approximately a factor of 4 higher for equal energy into atomic collisions. Comparison of channeling along the 〈0001〉 and 〈1120〉 directions revealed that aluminum atoms are displaced preferentially into sites along c-axis rows. Ionization-stimulated annealing was investigated with the CPIX technique. Exposure of ion-bombardment-damaged samples to ionizing radiation did not produce annealing measureable by CPIX.
A second-order Korteweg–de Vries equation for a lattice
Authors: Tasi James
Published: February 2003

An analysis is made of the longitudinal response of a semi-infinite lattice with a velocity disturbance at its end. Weakly nonlinear waves are analyzed, with a large acceleration time specified at an end to achieve a maximum disturbance. Nonlinear force interactions of quadratic and cubic form are considered within the lattice. A second-order generalization of the Korteweg–de Vries equation is obtained for the far-field response. The equation contains two stretched coordinates; one for the lowest-order influence of quadratic nonlinearity, and the second for a combination of cubic and the second-order influence of quadratic nonlinearity. Numerical solutions for shock profiles are given to illustrate the first- and second-order effects of quadratic nonlinearity. The combined response with cubic nonlinearity is then illustrated.
On the role of self-interstitials in impurity diffusion in silicon
Authors: Fair R. B.
Published: February 2003

The question of whether the monovacancy or the self-interstitial is the point defect responsible for impurity diffusion is reviewed in the light of buried marker diffusion experiments and irradiation-enhanced diffusion data. It is concluded that coupled vacancy-impurity diffusion is the preferred interpretation, but no definite conclusions can be drawn. However, the role of the self-interstitial in diffusion is proposed through a model which assumes that during oxidation, exchanges can take place between vacancies, self-interstitials, impurity interstitials, and substitutional impurities. By assuming a partial interstitialcy diffusion model it is shown that ?10–20% of the impurity flux during nonoxidizing diffusion conditions is due to impurity interstitials displaced by self-interstitials in equilibrium in the silicon. Calculations of impurity interstitial formation energies are consistent with the degree of oxidation enhanced diffusion measured for boron, phosphorus, and arsenic.