bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrostatic compression of four corundum-type compounds: α-Al2O3, V2O3, Cr2O3, and α-Fe2O3
Authors: Sato Yosiko , Akimoto Syun-iti
Published: February 2003

Accurate x-ray diffraction experiments for hydrostatic compression of corundum α-Al2O3 and transition-metal sesquioxides with the corundum structure, V2O3, Cr2O3, and α-Fe2O3, were performed using a cubic-anvil type of high-pressure apparatus at room temperature up to about 120 kbar. An isotropic compression of the unit cell was found in α-Al2O3 and Cr2O3. In V2O3 and α-Fe2O3, anisotropic behaviors of compression were observed: The ratio c/a in the hexagonal cell increases in V2O3 and decreases in α-Fe2O3 with increasing pressure. The isothermal bulk modulus KT=1.75±0.03 Mbar of V2O3 is unusually small among the studied compounds with the corundum structure. Values of 2.39±0.04 Mbar and 2.31±0.05 Mbar were calculated for KT of α-Al2O3 and Cr2O3, and a value of 2.31±0.10 Mbar for KT of α-Fe2O3 in the pressure range below 30 kbar.
Segregation and desorption kinetics for evaporation of arsenic from silicon
Authors: Tabe Michiharu , Nakamura Hiroaki
Published: February 2003

A significant role of surface segregation in arsenic out-diffusion from silicon is described. After heat treatment of uniformly arsenic-doped silicon in a H2 ambient, the amount of arsenic atoms segregating at the surface is measured using Auger electron spectroscopy. The experimental results are explained by a new model including the segregation effect in the boundary condition in the diffusion equation. Comparing the new model with previous treatments for out-diffusion phenomena, it is indicated that K which has been defined as an evaporation velocity from the solid to the gas phase should be replaced by k1, the rate of the first-order reaction from the solid to the segregation layer at the surface.
Thermal degradation of InP and its control in LPE growth
Authors: Lum W. Y. , Clawson A. R.
Published: February 2003

Thermal degradation of polished InP surfaces of (001) and (111) B orientations has been investigated. These specimens show severe deterioration when annealed under conditions typically used in the LPE growth of InP and InGaAsP layers. We have successfully controlled the decomposition of InP substrates in LPE growth by introducing minute amounts of phosphine gas (PH3) into the flowing hydrogen ambient. A temperature-dependent threshold concentration has been determined above which no thermal degradation is observed.
Quasisteady theory of nonequilibrium droplet evaporation and condensation
Authors: Lou Y. S. , Yang L. S.
Published: February 2003

Using the moment method of Maxwell and quasisteady approximation, an analytical study is performed to obtain useful results for the problem of transient condensation on and evaporation from spherical liquid (or solid) droplets, when the liquid (or solid) phase is not in equilibrium with its surrounding vapor. Unlike the linearized theories, the result of this investigation for the mass flux to or from the droplet surface is obtained for a general case of finite temperature difference between the droplet and its vapor. It is expected, therefore, that the present nonequilibrium theory should be more realistic in predicting the rate of condensation or evaporation phenomena of technological interests.
Influence of a magnetic field on 1/f noise in ambipolar semiconductors: Evidence of its surface origin
Authors: Dilmi T. , Chovet A. , Viktorovitch P.
Published: February 2003

The influence of a transverse magnetic field on the electrical noise in ambipolar semiconductors (like intrinsic and near-intrinsic germanium) is investigated as a function of surface treatment. When the transport of carriers across the sample is governed by the magnetoconcentration effect, it is shown that the very large increase of the 1/f noise is due to 1/f fluctuations of surface recombination velocities. Such fluctuations (which furthermore are proportional to the surface recombination velocity) also account for the most part of the highest frequency noise (beyond the inverse of the carrier effective lifetime).
A simple theory of back-surface-field (BSF) solar cells
Authors: von Roos Oldwig
Published: February 2003

An earlier calculation of the I-V characteristics of solar cells contains a mistake. The current generated by light within the depletion layer is too large by a factor of 2. When this mistake is corrected, not only are all previous conclusions unchanged, but the agreement with experiment becomes better. Results are presented in graphical form of new computations which not only take account of the factor of 2, but also include more recent data on material parameters.
Variations in the carrier concentration in elemental and compound semiconductors utilizing electrolyte electroreflectance: A topographical investigation
Authors: Pollak Fred H. , Okeke Cajetan E. , Vanier P. E. , Raccah Paul M.
Published: February 2003

Utilizing electrolyte electroreflectance we have developed a convenient nondestructive room-temperature technique for evaluating the topographical features of the variations in the carrier concentration across the surface of semiconductors with a spatial resolution of about 100 μm. We report measurements on several element and compound semiconductors including silicon, germanium, GaAs, and InSb. The advantages of this method in relation to other techniques will be discussed.
Electrical conduction of hot carriers in single-injection solid-state diodes with exponential trap distribution
Authors: Sharma Y. K.
Published: February 2003

The regional approximation method is used to evaluate the approximate solutions for the current-voltage characteristic of hot carriers in single-injection solid-state diodes with exponentially distributed traps. It is shown that the (1/2)(l+1) power-law dependence of the current on voltage occurs in the regime dominated by trapped charge.
Modulational instability of a laser beam in a piezoelectric semiconductor
Authors: Guha S. , Sen P. K.
Published: February 2003

Using a hydrodynamic model of a homogeneous plasma, the modulational instability of a laser beam has been studied when the laser beam interacts nonlinearly with a low-frequency transverse acoustic wave in the presence of a transverse magnetostatic field in a heavily doped n-type piezoelectric semiconductor. The instability results in the parametric amplification of the acoustic wave. The threshold electric field necessary for the onset of instability in the absence as well as in the presence of the magnetostatic field and the corresponding growth rates have been obtained analytically. The numerical analysis made for n-InSb at 77 K shows that the necessary laser field can be obtained by irradiating the crystal with a 10.6-μm CO2 laser. A large magnetostatic field lowers the threshold laser field appreciably.
Josephson point-contact resonance responses
Authors: Hagan Patrick S. , Cohen Donald S.
Published: February 2003

The voltage across a dc-current-driven Josephson point contact shunted by a resistive element with an applied small-amplitude ac signal current at frequency ω is calculated. First-order resonances are found to occur whenever +ω or −ω is near the Josephson frequency ω0. Second-order resonances occur whenever ω is near ±ω0/2. Singular perturbation techniques are used to obtain accurate approximate solutions for the contact voltage, in particular solutions when one of the above resonances occurs. These solutions all exhibit frequency (phase) locking when ω is near enough to ±ω0 and ±ω0/2, and frequency pulling otherwise. The regions where frequency locking occurs are obtained.
Pulse shape and laser-energy extraction from e-beam-pumped KrF
Authors: Jacob J. H. , Hsia J. C. , Mangano J. A. , Rokni M.
Published: February 2003

In this paper, detailed comparisons are made between the numerical predictions of a comprehensive KrF kinetics/laser-model computer code and the experimental results from an e-beam-pumped KrF laser. The code and the experimental laser device are described. The inputs to the code are the measured temporally varying e-beam energy and current density, the laser mixture, the optical-cavity output coupling, and the optical gain length. Comparisons include laser output power, laser output pulse shape, and KrF* fluorescence from the laser-cavity sidelight under lasing and nonlasing conditions. Using our numerical model, we have generated a scaling map for the KrF* laser.
Temperature control of multiline oscillation of a TEA CO2 laser
Authors: Endoh A. , Sato T. , Watanabe S. , Kashiwagi H.
Published: February 2003

Irtran-2 and ZnSe were used as temperature-controlled etalons to generate multiline oscillation of a TEA CO2 laser. Different combinations of multilines of the 10.6-μm band were obtained with good reproducibility by temperature controlling these etalons in the laser cavity.
Self-generated magnetic field in CO2-laser-produced plasma
Authors: Kitagawa Y. , Thein Aye , Yamada Y. , Yokoyama M. , Yamanaka C.
Published: February 2003

Measurements have been made of an azimuthal magnetic field spontaneously associated with plasma produced by the irradiation of a CD2 target by an 80-ns CO2-laser pulse. The magnetic field diffuses from an initial source into an ambient nitrogen plasma. Extrapolation of measured data to the initial target surface shows a field intensity of ∼0.6 MG. The diffusion coefficient calculated from the ambient plasma parameters is in accordance with direct experimental data. The diffused field is followed by the expanding laser target plasma. For sufficiently high ambient gas pressure, the field direction is reversed.
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u Auger electron spectroscopy of Si and SiO2 surfaces plasma etched in CF4-H2 glow discharges
Authors: Coburn J. W.
Published: February 2003

I n situ Auger electron spectroscopy has been combined with in situ etch-rate measurements, using quartz crystal microbalances, to study the plasma etching of Si and SiO2 surfaces rf biased at −100 V in CF4-H2 glow discharges. More carbon deposition was observed on the Si surface relative to the SiO2 surface as hydrogen was added to the CF4 plasma. This observation is consistent with a previously suggested model for the large SiO2-to-Si etch-rate ratios observed in CF4-H2 discharges.
Cross polarization of EM waves scattered by an isotropic inhomogeneous moving plasma column
Authors: Cander Ljiljana R. , Stanić Bo?idar V.
Published: February 2003

Interaction of obliquely incident linearly polarized plane electromagnetic waves with a radially inhomogeneous plasma column of infinite length moving uniformly in the axial direction is treated analytically. It is found that the cross-polarized field components disappear at the incident angle Φ0=sin−1(vz/c) (vz is the velocity of the moving plasma column and c is the free-space velocity of light) for the case of an inhomogeneous plasma column with an arbitrary electron density profile. Numerical results for the differential scattering cross sections are obtained for a range of plasma velocities by using the two-point boundary-value method.
The inverse interior Dirichlet problem
Authors: van der Merwe J. P.
Published: February 2003

An infinite number of rotationally symmetrical functions Ψ (r,z) can be found which approximate a given function f (z) on the optical axis 0z (r and z being cylindrical polar coordinates). The Ψ (r,z) are given in the form of a finite Fourier-Bessel series and it is shown how a solution that can be used in electron optical design can be selected by carefully assigning values to the following parameters: the number of terms in the series, the period of the series, and the amount of smoothing introduced. In this way a compromise is established between the quality of the axial approximation, the magnitude of potential gradients to be contended with in zonal regions, and the sizes of apertures allowed. Two-foil, one-foil, and open lenses can be modeled, and given axial potential functions can be accommodated which are either (i) analytic, (ii) continuous but with piecewise continuous z derivatives, or (iii) in the form of a set of experimentally determined values. The method requires no matrix inversion, the computer programming is of a simple nature, and memory requirements are modest enough to allow implementation of the program on small desk-top computers.
Emission of energetic electrons from a Nd-laser-produced plasma
Authors: Armstrong C. M. , Ripin B. H. , Young F. C. , Decoste R. , Whitlock R. R. , Bodner S. E.
Published: February 2003

Absolute spectral measurements of 50–500-keV electrons emitted from a Nd-laser-produced plasma are presented. For normally incident irradiation (1015–1016 W/cm2) onto polystyrene slab targets a total emitted energy of ∼1010 electrons is inferred with a total emitted energy of ∼0.2 mJ. The electron emission is observed to be almost the same both in and out of the plane of polarization. Properties of the emitted spectrum, such as spectral hardness and intensity, are observed to be dependent on the pulse shape and the target material.
An anomalous photocurrent in SnO2-Si heterojunction solar cells
Authors: Rodríguez T. , Maudes J. Sanz , Dehesa C.
Published: February 2003

An anomalous photocurrent observed in reverse-biased SnO2-Si heterojunctions, obtained by spraying, is reported. This current becomes voltage independent above a certain reverse voltage value and is much larger than expected from the number of photopairs generated. The anomalous photocurrent occurs above a minimum voltage value and a minimum number of incident photons, these thresholds being constant for each cell. The anomalous photocurrent is generated under the SnO2 window, its density being larger under the window edge region.
Temperature dependence of the electro-optic Kerr coefficient of nitrobenzene
Authors: Hebner Robert E. , Misakian Martin
Published: February 2003

The Kerr coefficient of nitrobenzene was measured over the temperature range 285–340 K. To within experimental error, the data indicate that the Kerr coefficient can be expressed as a quadratic function of reciprocal temperature. Fitting the data to this quadratic function yields an equation which can be used to correct the response of a pulse-voltage measuring system based on the Kerr effect for variations in the ambient temperature.
Comments on ’’Efficiency of the solid-state engine made with Nitinol memory material’’
Authors: Mohamed H. A. , Banks R. M.
Published: February 2003

A recent calculation of the thermal efficiency of a solid-state engine made with a Ni-Ti alloy (Nitinol) has been criticized with reference to the origin of the work output and the deformation behavior of the material.
Ferromagnetic resonance study of the anisotropy profile in implanted bubble garnets
Authors: Wilts C. H. , Zebrowski J. , Komenou K.
Published: February 2003

A method for determining the magnetic anisotropy profile of an ion-implanted garnet layer is presented. To do this the eigenvalue equation for spin waves is solved numerically for a system consisting of a very thick film with uniform perpendicular anisotropy and a surface layer in which the anisotropy varies through the surface. Results of this calculation are matched to experimental FMR data from samples cut from the same wafer but etched by different amounts. A measurement of the exchange constant in the implanted layer may be possible if two or more surface modes are visible. The anisotropy profiles of samples implanted with 2×1014 Ne+/cm2 at 50, 100, and 150 keV were reconstructed in this manner. The profile was found to show a broad peak centered at a depth somewhat shallower than the projection range for Ne+ at the appropriate energy. The value of the change in anisotropy was shown to match that predicted from a magnetostrictive origin and the measured change in lattice constant in the surface layer. The measured exchange constants in the implanted layer were 1.1×10−7 and 1.7×10−7 ergs/cm for 100- and 150-keV implanted samples, respectively.
Brillouin-scattering studies of polycrystalline and amorphous sputtered films of Fe1−xBx and Co1−xBx
Authors: Malozemoff A. P. , Grimsditch M. , Aboaf J. , Brunsch A.
Published: February 2003

We report on Brillouin-scattering measurements of thermally excited acoustic-surface phonons, and bulk and surface magnons, in sputtered films of Fe1−xBx and Co1−xBx. From the slope of the surface-magnon frequency shift with field we determine g factors of 2.09±0.03 for Fe1−xBx and 2.16±0.03 for Co1−xBx, with no significant trend as a function of composition and no difference between amorphous and polycrystalline materials. The magnetization for pure Fe and Co agree with literature values. The magnetization of sputtered and quenched materials of the same composition are in agreement provided both samples are amorphous. Effective exchange corrections of order Dk2=0.1–0.5 kOe (where D is the spin-wave stiffness and k is a magnon-wave vector) are needed to properly fit the dependence of bulk-magnon frequency shift on field. The magnetization values determined with such fits agree within experimental error with magnetizations obtained from the surface magnons. Possible origins of the Dk2 correction are discussed. In films below about 200 nm in thickness, structure is observed in the bulk-magnon peaks which may be due to standing spin waves. The potential of Brillouin scattering as a tool for thin-film characterization is discussed.
Properties of thin films of Permalloy with rhodium addition for corrosion resistance
Authors: Rice D. W. , Suits J. C.
Published: February 2003

The addition of a small amount of rhodium to thin films of Permalloy substantially improves resistance to atmospheric corrosion with a relatively small degradation of magnetic properties. X-ray photoemission spectroscopy data shows that rhodium, in contrast to chromium, does not change valence during corrosion of these nickel-iron alloys, nor is it enriched at the alloy surface.
Domain-wall behavior in ion-implanted garnet layers for 1-μm bubble devices
Authors: Dove D. B. , Schwarzl S.
Published: February 2003

Bitter pattern observations are reported on domain walls in ion-implanted garnet layers. Particular attention is given to the behavior of charged walls at the edge of nonimplanted disks and other elements and on the response of these walls to varying in-plane fields. The interaction between bubbles and charged walls has been observed and the propagation of bubbles around disks and along propagation tracks has been examined. The crystalline symmetry of the garnet layer has been found to give rise to significant orientation effects on the response of walls to external fields. From a study of wall behavior certain characteristics of bubble motion along propagation paths can be explained.
FMR study of an ion-implanted layer on bubble garnet films
Authors: Mada Junji , Asama Kunihiko
Published: February 2003

Properties of magnetic anisotropy of an ion-implanted layer on [111]-oriented bubble garnet films have been studied in relation to implantation dosages by ferromagnetic resonance techniques. As has been reported, subpeaks generated in the implanted layer were observed in addition to the main peak related to the garnet film itself. The resonant field of these subpeaks showed a strong dependence on the orientation in the (11̄0) plane, whereas dependence was weak in the (111) plane. Data was analyzed under the assumption that signals from the implanted region of specimens are of uniform mode, and it was found that implanted layers of a Y1.33Eu0.2Yb0.57Ca0.9Ge0.9Fe4.1O1 2 film implanted with neon at an energy of 100 keV with dosages ranging from 1.1×1014 to 2.0×1014/cm3 were magnetically uniaxial, the easy axis being the (111) plane and the hard axis, the [111] axis. A precisely defined method for determining implantation-induced anisotropy was developed, and results showed that its magnitude is several 104 erg/cm3. Proton-implanted specimens were also investigated.
Photoluminescence study of laser annealing in phosphorus-implanted and unimplanted silicon
Authors: Nakashima Hisao , Shiraki Yasuhiro , Miyao Masanobu
Published: February 2003

Photoluminescence (PL) measurements are used to study the effects of laser annealing on phosphorus-implanted and unimplanted silicon. PL measurements give a higher threshold energy for annealing than do electrical measurements. Dependence of crystal-quality recovery on dose and laser-annealing energy are examined. The PL intensity of the laser-annealed high-dose (8×1015 cm−2) sample is comparable to that of bulk silicon. On the other hand, laser annealing reduces the PL intensity of unimplanted silicon. These annealing effects are explained in terms of the temperature rise at the sample surface during annealing. In addition, laser annealing of vacuum-deposited amorphous-silicon layers leads to the growth of epitaxial layers with PL intensities as high as bulk silicon.
Doping effects on rake-line formation in LPE growth of AlxGa1−xAs DH lasers
Authors: Logan R. A. , Schumaker N. E. , Henry C. H. , Merritt F. R.
Published: February 2003

The absence or near absence of the active layer in the region of the stripe of a DH laser (rake lines) is one of the more easily assigned causes of poor device yield and performance in semiconductor lasers. A description is given of a scanning photocurrent technique to detect the presence of rake lines and other nonuniformities in DH laser structures with a GaAs top-contacting layer that precludes the use of conventional photoluminescence evaluation. This technique is simple, nondestructive, and of comparable resolution to photoluminescent techniques. The presence of rake lines in DH laser structures is shown to be due to inhibited nucleation of the active-layer growth on the n-type ternary layer. The volatile dopant Te, commonly used to dope n-type ternary layers, enhances the formation of rake lines while the effect is significantly reduced when nonvolatile Sn is used as a dopant.
Nonlinear transmission of fog for laser light
Authors: Friedmann D. , Ariga S. , Ahlborn B.
Published: February 2003

The transmission of a fine fog for iodine laser light (λ=1.315 μ) was investigated. It was found that there is a sharp increase of transmission from 45 to 70% when laser power in excess of 500 kW/cm2 is applied to a fog having a droplet size smaller than 3 μ and a density of 105 N/cm3. This nonlinear transition occurs in a time shorter than ∼10−8 sec.
Depth profile of antimony implanted into diamond
Authors: Braunstein G. , Bernstein T. , Carsenty U. , Kalish R.
Published: February 2003

The depth profiles of 350-keV 121Sb ions implanted at room temperature into diamonds were determined from neutron-activation-layer-removal experiments. Profiles for both random and aligned (〈111〉) implantations were measured. The distribution of antimony ions implanted under channeling conditions was found to be centered somewhat deeper in the crystal than that of Sb ions implanted into a nonaligned diamond. The distribution tail extends in the case of channel implantation far into the crystal, well beyond the region of measurable damage.
Exciton or hydrogen diffusion in SiO2?
Authors: Weinberg Z. A. , Young D. R. , DiMaria D. J. , Rubloff G. W.
Published: February 2003

The appearance of positive interfacial charge at the Si-SiO2 interface in metal (Al) -SiO2-silicon structures illuminated by vacuum ultraviolet (≳ 9 eV) light (Al-negative) or subjected to electron-avalanche injection (Al-positive) has been found to depend on water exposure of the SiO2 layer. This finding raises the possibility that these effects can be explained by the diffusion of water-related species (especially H), rather than by the diffusion of excitons, as has been previously proposed. Although we cannot unambiguously decide whether the source of the vacuum ultraviolet effect is diffusion of excitons or water-related species, it appears more likely that the water enhances the detection efficiency of the diffusing species as they reach the Si-SiO2 interface.
Contact-free conductivity of layered materials: Na β-alumina
Authors: Strom U. , Taylor P. C.
Published: February 2003

The ionic conductivity and its thermal activation energy have been measured in Na β-alumina using a contact-free induced-torque method at frequencies between 1 and 20 Hz and temperatures between 295 and 415 K. The results are in good agreement with the most recent dc contact conductivity measurements.
The frequency-dependent relaxation time of free carriers in InP
Authors: Jensen B.
Published: February 2003

At frequencies higher than 200–300 cm−1 in InP, the classical Drude theory fails to predict the observed wavelength dependence of the absorption coefficient and hence the optical conductivity to which it is proportional. In this paper, the optical conductivity is calculated for InP at 300 °K as a function of frequency and carrier concentration by use of a quantum extension of the Boltzmann transport equation which reduces to the quasiclassical Boltzmann equation in the limit of low frequencies and elastic scattering mechanisms. The conductivity is expressed in terms of a frequency-dependent relaxation time which reduces to a constant in the far infrared. It is given as a function of carrier concentration over the spectral region from 218 to 2180 cm−1 for carrier concentrations from 4.69×1015 to 2.13×1018 cm−3, and used to calculate the reflectivity spectrum over the same range of frequencies and concentrations. The low-frequency limit is used to estimate the dc mobility as a function of concentration, and the effect of compensation on mobility is calculated for the purest materials. Comparison with experimental results is given.
Effects of bulk and surface conductivity on the potential developed by dielectrics exposed to electron beams
Authors: Rotenberg Manuel , Mandell Myron J. , Parks Donald E.
Published: February 2003

The charging and discharging of a dielectric material which has bulk and surface conductivities is discussed. Two model problems are solved. In the first problem, a semi-infinite dielectric plane, attached to an infinite grounded conducting substrate and exposed to a monoenergetic electron beam, is analyzed. Bulk and surface conductivities and secondary emission characteristics are taken into account as parameters. In the second problem the dielectric is charged but the electron beam is shut off so only the bulk and surface conductivities enter the calculation. The principal result of the latter calculation is to show that steep tangential gradients develop in the presence of a surface conductivity during decay, and that for asymptotic times the temporal behavior, for a fixed position, is proportional to t1/2 rather than exponential, as expected in the presence of a bulk conductivity.
Low-temperature operation of multiple quantum-well AlxGa1−xAs-GaAs p-n heterostructure lasers grown by metalorganic chemical vapor deposition
Authors: Vojak B. A. , Kirchoefer S. W. , Holonyak N. , Chin R. , Dupuis R. D. , Dapkus P. D.
Published: February 2003

The phonon-assisted laser operation (4.2–77 °K) of multiple quantum-well AlxGa1−xAs-GaAs heterostructure diodes is described. Laser operation is observed on phonon sidebands ∼36 meV below the lowest confined-particle transitions. Tunnel injection into the confined-particle states, with light emission and negative-resistance regions, is also observed in these multiple quantum-well heterostructures. Two different multiple quantum-well heterostructures grown by metalorganic chemical vapor deposition are described. The first consists of six GaAs quantum wells (Lz∼120 Å) coupled by five AlxGa1−xAs (x∼0.3) layers (∼120 Å), and the second is similar except for a reduction in layer size to ∼50 Å.
Tunnel injection and phonon-assisted recombination in multiple quantum-well AlxGa1−xAs-GaAs p-n heterostructure lasers grown by metalorganic chemical vapor deposition
Authors: Vojak B. A. , Holonyak N. , Chin R. , Rezek E. A. , Dupuis R. D. , Dapkus P. D.
Published: February 2003

Stripe-geometry multiple quantum-well AlxGa1−xAs-GaAs heterostructure laser diodes are described that exhibit tunnel injection with LO phonon participation in the injection and the recombination process. The diodes are constructed by Zn diffusion into n-type AlxGa1−xAs-GaAs heterostructures grown by metalorganic chemical vapor deposition (MO-CVD). At bias voltages V< (1/q) Eg(AlGaAs) in which tunneling is important, laser operation (4.2–77 °K) of these quantum-well diodes is obtained an LO phonon energy (∼36 meV) below the first electron–to–heavy-hole (No. 1 e→hh) confined-particle transitions of the coupled GaAs quantum wells (six wells, Lz∼120 Å). In the normal injection bias range V∼ (1/q) Eg(AlGaAs), recombination radiation is identified on the No. 2 e→hh transitions and an LO phonon energy below the second electron-to-light-hole (No. 2′ e→lh) confined-particle transitions. Phonon involvement in the recombination process is identified also in the range between confined-particle transition 1-1′ and 2.
Influence of a mechanical modulation on electrical transport in point-contact junctions
Authors: Thielemans M. , Leo V. , Deltour R. , Mehbod M.
Published: February 2003

The influence of a mechanical modulation of the barrier thickness has been studied theoretically in metal-insulator-metal (MIM) point-contact junctions for different conduction mechanisms: thermoionic, tunnel, and constriction (tiny metallic microbridges) transport currents. Experiments have been carried out between 95 and 300 K on Au-Al2O3-Al systems. In the presence of a dc component, the alternating electrical current generated in the junction by the barrier modulation has been phase detected and analyzed with respect to the I-V characteristic, the junction dynamic resistance, the modulation amplitude, and the temperature. As predicted in the theoretical analysis, the results demonstrate that the tunneling current in the point-contact junction is very sensitive to the mechanical modulation.
ESR centers, interface states, and oxide fixed charge in thermally oxidized silicon wafers
Authors: Caplan Philip J. , Poindexter Edward H. , Deal Bruce E. , Razouk Reda R.
Published: February 2003

The ESR Pb center has been observed in thermally oxidized single-crystal silicon wafers, and compared with oxide fixed charge Qss and oxidation-induced interface states Nst. The Pb center is found to be located near the interface on (111) wafers. Its g anisotropy is very similar to that of known bulk silicon defects having SiIII bonded to three other Si atoms; the Pb unpaired electron orbital, however, is exclusively oriented normal to the (111) surface. The Pb center cannot be identified with any other known defect in Si or SiO2; in particular, it is totally unlike the common E′ center of SiO2. In contrast to Qss, both Pb and Nst were found to be greatly reduced by steam oxidation and hydrogen annealing. Both Pb and Nst may be regenerated by subsequent N2 anneals at 500 °C. In a graded series of samples, Pb and Nst are found to be proportional and nearly equal in concentration. This possible confirmation of SiIII at the interface, and correlation with Nst, support the theoretical indication of an SiIII band-gap energy level. The E′ center is unobservable, and if present, exists only in a concentration well below that of Qss. Thus, in addition to a lack of strong correlation with Pb, Qss is evidently not due to E′ centers in their normal charge state. Overall, ESR is judged to be a useful technique for research on silicon wafer defects.
Space-charge generation properties of gold in MOS structures
Authors: Faraone L. , Nassibian A.G. , Simmons J.G.
Published: February 2003

The generation lifetime, capture cross section, and thermal emission rates for the gold acceptor level in bulk silicon have been studied using MOS techniques. The experimental methods used were the pulsed high-frequency capacitance-time and nonequilibrium linear-voltage-ramp techiniques at various temperatures. By correlating the results of the above measurements, the capture cross section σ and trap energy Et of the gold acceptor state were determined as a function of temperature in the range 235–265 °K. It was observed that σ increases with increasing temperature and has a value of the order of 1.0×10−15 cm2. On the other hand, the trap energy Et was found to decrease with increasing temperature, suggesting that it varies in unison with the silicon energy gap. Finally, from the above results the thermal emission rates en and ep were determined, with the assumption that the degeneracy factor and gA=1. For the temperature range investigated, the ratio en/ep varied from 30 at 235 °K to 20 at 265 °K.
First-order reflection coefficient of surface acoustic waves from thin-strip overlays
Authors: Datta Supriyo , Hunsinger Bill J.
Published: February 2003

The problem of surface-wave reflection at thin-strip overlays occurs frequently in signal-processing devices. Grooved array reflectors employ strip overlays of the same material as the substrate, while metallic transducers incorporate strips of a material different from the substrate. A simple model for calculating the reflection coefficient of thin overlays is described, based on the normal-mode analysis developed by Auld. Calculated values are in close agreement with reported experimental values for grooves in ST-X quartz and Y-Z lithium niobate, and for aluminum on ST-X quartz.
Thermophoresis: The mass transfer mechanism in modified chemical vapor deposition
Authors: Simpkins P. G. , Greenberg-Kosinski S. , MacChesney J. B.
Published: February 2003

The mass transfer of particulates of silica and germania is characteristic of the MCVD process for preparing optical fiber preforms. Here, after considering a number of alternatives, it is suggested that the dominant mechanism of mass transfer is thermophoresis, i.e., diffusion due to a large temperature gradient. Analytical arguments are given which support this assertion and compare favorably with experiments carried out in a MCVD apparatus.
Mechanical-stress-induced degradation in homojunction GaAs LED’s
Authors: Zaeschmar G. , Speer R. S.
Published: February 2003

The thermal stress in an LED caused by junction heating has been calculated. It is shown theoretically that the change of light output with time is proportional to the third power of thermal stress in the junction. This result is experimentally verified. Mechanical-stress experiments demonstrate that degradation may occur by means of mechanical stress alone. Using the two-path model for the quantum efficiency and the time dependence of the stress-induced lattice-defect concentration, a degradation formula is derived which can be verified to fit the behavior of many LED’s. The characteristic tapering off seen in most degradation curves can be attributed to strain hardening (dislocation pinning). A dark-line-defect progression is observed.
The influence of metallic impurities on the tungsten bromine regenerative cycle of linear quartz bromine lamps
Authors: Yannopoulos L. N. , Wolfe A. L.
Published: February 2003

The role of bromine-reactive common metallic impurities on the life and output of a quartz bromine lamp has been examined. A series of tests with one lamp type showed that impurities such as Fe, Ni, Cr, and Cu reacted with bromine and formed stable bromides that deposited at the cooler end sections of the quartz bulb. If the minimum temperature of this deposit zone was increased from ∼300 to ≳ 500 °C during lamp burning, these deposits became volatile and the regenerative cycle became functional for those cases where the metallic-impurity–to–bromine ratio was high and had previously affected the cycle. The metallic impurities were identified in the deposits; their release was also monitored during lamp burning. A thermochemical interpretation of the results of the tests and analytical findings is presented.
Gallium-field-ion emission from liquid point anodes
Authors: Mair G. L. R. , von Engel A.
Published: February 2003

The principal processes controlling the emission of charged and neutral particles and complexes from positive liquid-gallium points for voltages at or above ∼5 kV are briefly summarized. The components of the extractor and collector current and the fluctuations of the latter are investigated as well as the dependence of the currents on retarding and accelerating potentials that are applied to the collector. The effect of secondary electrons released from the collector by the impact of fast positive ions is examined as well as the suppression of these electrons by means of reversing or deflecting electric or magnetic fields of moderate magnitude. Feeble emission of visible light is observed at the collector surface when condensed gallium evaporates under bombardment of fast particles. The formation and life of protrusions and of the flow of neutral atoms and droplets are discussed.
Analysis of the energy broadening in an electron-beam system
Authors: El-Kareh A. B. , Smither M. A.
Published: February 2003

The Boersch effect is calculated for two electron-beam configurations: an ideal lens leading to a single crossover and an electron gun which has no crossover. The results agree with previous work both as to the spatial spreading caused by space charge and the energy broadening due to electron-electron interactions. The energy spread produced in a gun with no crossover is clearly demonstrated and shown as a function of emitting area and beam current.
Resonant absorption in an argon plasma at thermal equilibrium
Authors: Santiago J. , Johnson J. A.
Published: February 2003

The absorption coefficient of an equilibrium argon plasma is computed, avoiding earlier restrictive assumptions, as a function of temperature and electron density. Our results suggest that the diagnostic applications of resonant absorption to temperature estimates are more difficult than previously expected.
Evaluation of defects in InP and InGaAsP by transmission cathodoluminescence
Authors: Chin A. K. , Temkin H. , Mahajan S. , Bonner W. A. , Ballman A. A. , Dentai A. G.
Published: February 2003

We present the results of a defect study of liquid-encapsulated Czochralski grown InP substrates, and InGaAsP grown by liquid-phase epitaxy using the technique of transmission cathodoluminescence (TCL). The TCL image of the dislocations permits an accurate measurement of the dislocation density and an estimate of the minority-carrier diffusion length. In addition to the dislocation density, TCL examines material quality by imaging growth-related defects, e.g., growth striations in InP and stacking faults in InGaAsP.
Anomalous carrier profiles in BF+2-ion-implanted silicon
Authors: Wada Yasuo , Hashimoto Norikazu
Published: February 2003

Anomalous carrier profiles in BF+2-ion-implanted silicon are investigated by the C-V and incremental-sheet-resistivity methods. An anomalous tail extends about twice as deep as the normal profile, while the peak carrier concentration is around 1/100 that of the main peak. The origin of this anomalous tail is investigated by comparing the profiles of B+, B++F+, and BF+2 ions implanted using postacceleration- and preacceleration-type implanters. High-energy B+ ions generated between a mass-separation magnet and a postacceleration tube are found to be responsible for the observed profiles.
Theory of mixed valence: Metals or small gap insulators (invited)
Authors: Martin Richard M. , Allen J. W.
Published: February 2003

Mixed valence systems exhibit an interesting variety of low temperature electronic phenomena, in particular, a remarkable division of the known mixed valence compounds into metallic and insulating groups, exemplified respectively by CePd3 and SmB6. We show that for Sm compounds it is appropriate to use a two-band Hubbard Hamiltonian comprised of a narrow f band with a large Coulomb interaction U, a wide d band with negligible interactions, and f-d hybridization, Coulomb, and exchange interactions. Using the Green’s function decoupling methods of Hubbard, we show that intersite correlations profoundly affect states near the Fermi energy and may lead to a small insulating gap if the two bands contain an even integral number of electrons per rare earth ion, as in stoichiometric SmB6. Magnetic phase transitions are discussed in terms of exchange vs. hybridization energies, and a first order transition from a paramagnetic insulator to a ferro- or ferrimagnetic metal is predicted within the mixed valence regime.
Spin polarization and magnetism in uranium monochalcogenides
Authors: Greuter F. , Eib W. , Erbudak M. , Meier F. , Reihl B.
Published: February 2003

The spin polarization and energy distribution of photoelectrons (hν<11 eV) emitted from single crystals of ferromagnetic US, USe, and UTe are presented. The data yield width and position of cation and anion derived energy bands as well as the antiparallel coupling of f- and d-electrons.
Transition from Pauli paramagnetism to band ferromagnetism in nickel, few atomic layers thick
Authors: Bergmann G.
Published: February 2003

Ni films of a few atomic layers are condensed in UHV at 10 K on metallic substrates of amorphous Pb75Bi25 and crystalline Pb, Cu and Bi. Anomalous Hall effect measurements are used to determine the magnetization and the susceptibility of the films. Ni films with a thickness smaller than two atomic layers possess no magnetic moment but show an enhanced susceptibility. Between two and three atomic layers of Ni the susceptibility diverges and thicker films possess a magnetic moment. The experimental results can be well described with a band model of magnetism. A thin Ni film condensed onto a non-magnetic metal represents a system in which the density of states is changed with thickness, causing a transition from Pauli paramagnetism to band ferromagnetism. In contrast to Ni the ferromagnetic metal Fe possess already for a coverage of 1/6 atomic layer a magnetic moment and shows a paramagnetic behavior.
Composition and stability of iron powders prepared by a borohydride process
Authors: Freitag W. O. , Sharp T. A. , Baltz A. , Suchodolski V.
Published: February 2003

Iron powders have been produced by the reduction of ferrous ion with borohydride and stabilized by a chromating procedure. The saturation moments is 140 to 160 emu/g. The coercivity can be controlled between 375 and 1150 Oe. Remanence is 0.45 to 0.5 for unoriented powders. The powders are fibers up to 3 μm long and 1000 Å wide consisting of agglomerated spherical crystallites 300 to 450 Å in diameter. Chemical analyses show that typical powders contain about 82–85% Fe, 2–3% B, 3% Cr, 5–6% O, and 0.2% H. The moment indicates that only 70% is metallic iron. Measurements up to 100 KG show no superparamagnetic fraction. Fe(OH)2 and FeOOH were identified by electron diffraction in some but not all the preparations. Chromating may result in the removal of some non-magnetic by-products. Following the chromating treatment, water is removed with methanol. Solvent-wet powder containing less than 0.1% water can be stored at least 3 months without loss in moment. Cured films of dispersions in a typical epoxy-type binder lose moment in an accelerated atmosphere test containing SO2 and NO2 at a rate indicating a lifetime of 10 years in a worst-case indoor ambient.
Temperature-dependent magnetic properties of (Y,Sm,Lu,Tm,Ca)3(Fe,Ge)5O12 epitaxial garnet films
Authors: Gualtieri D. M. , Tumelty P. F. , Gilleo M. A.
Published: February 2003

Thulium has been substituted for yttrium in melts for the growth of (Y,Sm,Lu,Ca)3(Fe,Ge)5O12 epitaxial garnet films for the purpose of reducing the magnitude of the temperature coefficient αbc of the bubble collapse field. As an extension of previous substitutions [J. E. Davies, G. Galli, and J. C. Suits, J. Appl. Phys. 49, 1859 (1978)] of Tm for Lu to smaller bubble diameters, growth conditions were adjusted to produce films of nearly identical thickness (1.40 μm) and characteristic length (0.222 μm at 25°C) for Tm substitutions up to 0.25 atoms in the formula unit. This substitution was found to decrease the magnitude of αbc as measured at 50°C by approximately 0.04%/°C⋅Tm atom. Anisotropy remains nearly constant with Tm substitution.
Discrimination of domain wall states by bubble collapse time
Authors: Konishi S. , Shibata N. , Shimaya M. , Fukuzawa Y. , Narita K.
Published: February 2003

The discrimination of bubble states by dynamic bubble collapse was studied for 5 and 3 μm bubble films. We obtained bias field margin of 6 Oe for the 5 μm bubble film (S=1H and S=0), and about 10 Oe for 3 μm bubble films (S=1H and S= (120)). The discrimination was also tried for 3 μm bubble YY-propagation pattern chips, for which we got about 8 Oe of bias field margin. Demonstrated was this collapse discrimination for ’’1111...’’ ’’0000...’’, and ’’1010...’’ bubble patterns utilizing an on-chip bubble annihilator.
Transverse mass of a bubble in a rotating gradient
Authors: Slonczewski J. C.
Published: February 2003

We propose principles for interpreting magnetic-bubble dynamics in a rotating-gradient experiment when no external in-plane field is present. If the orbit of the bubble is circular, simultaneous determinations of radius and phase lag with respect to the drive may be interpreted to measure the mobility coefficient and the velocity-momentum [V=V (P)] relation. Investigation of the stability of the circular orbit shows that in one limiting case the segments of V (P) having a positive slope will be accessible to experiment. We illustrate dependences of V on P expected for static bubbles with 1) small numbers of vertical Bloch lines, 2) horizontal Bloch lines, and 3) large numbers of vertical Bloch lines. We conclude that rotating-gradient measurements can determine the Bloch-line structure of the circulating bubble. The basically new element present in such experiments is the transverse component of effective bubble mass, which differs from the longitudinal component and will be much greater than the Döring mass whenever Bloch lines are present.
Dynamic behavior of isolated straight stripe domain in rare earth iron garnet films
Authors: Iwata S. , Shiomi S. , Uchiyama S.
Published: February 2003

The dynamic behavior of an isolated straight stripe domain is reported in garnet films with relatively low damping. In the low drive field region, the translation velocity increases linearly with drive field, then it breaks down over a peak velocity followed by repeated increase and decrease of the velocity with increasing drive field. The peak velocity and the critical field for velocity breakdown are increased by a static in-plane field applied parallel to the walls of stripe domain, while they are scarcely influenced by an in-plane field applied perpendicular to them. In case of ion-implanted film, the peak velocity as well as the critical field depend on the direction of the magnetization within the walls. These experimental results are interpreted quantitatively by a model in which the nucleation, the propagation and the punch-through of the horizontal Bloch lines are considered.
Experimental investigation of the interaction potential of domain walls with localized stress fields in epitaxial garnet films
Authors: Schultz L. , Ahn K. Y.
Published: February 2003

Localized stress fields which are present at the edges of evaporated layers pin domain walls. In the experiments Cr layers on epitaxial EuGaYIG films were primarily used to study these effects. Since the domain walls are pinned at the layer edges, magnetic bubbles can be pinned with their centers either inside or outside the layer. To pull off the bubbles a pulsed field gradient established by parallel conductor lines was applied. In total, five different interaction forces can be distinguished. The pinning forces are proportional to the stress in the film, i.e. the layer thickness, and independent of the layer width as long as the width exceeds the bubble diameter. For edges with a normal parallel to 〈110〉 the pinning is symmetric for both edges whereas for 〈211〉 there is an asymmetry. Most of these effects agree qualitatively with theoretical predictions by Dishman et al., which are based on perturbations of the domain wall energy through inverse magnetostriction.