bluuebunny/crossref_metadata_2025 huggingface dataset:
Minority-carrier extraction and accumulation near metal-semiconductor interfaces
Authors: Rahimi S. , Manifacier J.-C. , Henisch H. K.
Published: February 2003

Solution to the transport equations in the realm of ’’small signal theory’’ results in expressions for the electric field, and the excess minority-and majority-carrier densities as functions of distance from an injecting boundary. Two situations are examined for ’’lifetime’’ semiconductors, the ’’trap-free’’ case and the case with monoenergetic traps. With different boundary conditions, the new expressions apply equally to all four nonequilibrium processes: injection, exclusion, accumulation, and extraction. Results on extraction are supported by measurements on single-crystal Ge, before and after neutron bombardment (to introduce traps).
Electrical conductivity and electron-spin resonance in oxidatively stabilized polyacrylonitrile subjected to elevated temperature
Authors: Lerner N. R.
Published: February 2003

The development of electrical conductivity in oxidized polyacrylonitrile (PAN) fiber as a function of heat-treatment temperature has been studied for heat-treatment temperatures in the range 710–950 K. By means of a study of conductivity versus measurement temperature, it is shown that PAN heat treated in vacuum in this temperature range is a semiconductor. The room-temperature conductivity is dominated by the contribution of impurities. The activation energy for the formation of the impurities that contribute to the conductivity is 88 kcal/mole. Electron-spin resonance (ESR) measurements have also been made on these fibers. Studies of the variation of the ESR absorption intensity with temperature reveal that the ESR signal can be analyzed in terms of two components: localized spin centers and charge carriers. The charge-carrier component of the ESR signal is interpreted as being due to the formation of metallic conduction pathways in the polymer. Both the electrical conductivity and the ESR absorption intensity decrease when the samples are aged in air.
Schottky contacts of Gd-Pt and Gd-V alloys on n-Si and p-Si
Authors: Thompson R. , Eizenberg M. , Tu K. N.
Published: February 2003

Alloys of Gd-Pt and Gd-V, both Gd-rich and Pt or V-rich, have been prepared by coevaporation onto n- and p-type Si for Schottky contact formation. Structural and electrical properties of these contacts after various heat treatments have been studied by combining x-ray diffraction, backscattering spectroscopy, and current-voltage measurement. We found that these alloys produced a mixture of silicides on Si; i.e., they formed parallel contacts of GdSi2 and PtSi or GdSi2 and VSi2 to Si. We also found that the sum of apparent Schottky barrier heights of these parallel contacts on n-Si and p-Si is not necessarily equal to the value of the band gap of Si, which we recall is always true for a single phase contact.
Size fluctuations and high-energy laser operation of AlxGa1−xAs-AlAs-GaAs quantum-well heterostructures
Authors: Holonyak N. , Laidig W. D. , Camras M. D. , Hess K. , Burroughs M. S. , Coleman J. J. , Dapkus P. D.
Published: February 2003

In AlxGa1−x As-GaAs quantum-well heterostructures (QWH’s) or superlattices (SL’s) with coupling barrier sizes LB <50 Å, alloy clustering, owing simply to fluctuations in the random Al-Ga arrangement, causes effective changes in quantum-well size and, as a consequence, a decrease in energy and broadening of the confined-particle states. Data are presented showing that actual quantum-well size changes δLz = δLB can be observed, via luminescence or laser spectral shifts, on all-binary, active-region (AlAs-GaAs) QWH’s or SL’s. The small spectral broadening and downward shift indicate a size change δLz = δLB as small as a monolayer for high-energy, all-binary QWH and SL structures grown by metal-organic chemical vapor deposition. Narrow-spectrum cw 300-K laser operation has been realized at λ∼7500 Å, and should be possible to λ≲6785 Å.
The effect of position-dependent dielectric constant on the electric field and charge density in a p-n junction
Authors: Andrews M. Heather , Marshak Alan H. , Shrivastava Ritu
Published: February 2003

One of the effects of heavy doping is that the dielectric constant varies with impurity density, and thus with position. The general form of Poisson’s equation is solved numerically for a Gaussian p-n junction using a model for ε(N) which is consistent with the experimental data reported by Castner. The results indicate that the charge density near the surface where the doping is large is a strong function of ε(N), resulting in a large deviation from the constant ε case. This result may be important when capacitive measurement techniques are used to find device parameters in heavily doped semiconductors. The result also indicates a need to consider ε(N) in the theory of the ionization of impurity atoms.
Electron emission from ion-bombarded aluminum
Authors: Svensson B. , Holmén G.
Published: February 2003

The secondary-electron yield from polycrystalline aluminum induced by protons, noble-gas ions, and aluminum ions has been measured as a function of ion energy in the range of 10 to 350 keV and as a function of angle of ion incidence in the interval of 0 ° to 70 °. The experimental data are compared with a theory of electron emission from solids proposed in our previous works. The agreement is good providing additional support for the theory.
Experimental determination of the particle reflection coefficients of low-energy (100–1500 eV) 3He and 4He atoms from the (110) plane of tungsten
Authors: Amano Jun , Seidman David N.
Published: February 2003

The particle reflection coefficients (RN ) for low-energy (100–1500 eV) implanted 3He and 4He atoms were determined employing the atom-probe field-ion microscope (FIM) technique. The implantations were made in situ at 60 K with the ion beam parallel to the [110] direction, within ±5°, of tungsten; the atom-probe FIM analysis were also performed at 60 K. At this temperature both the 3He and 4He atoms, as shown in our earlier work, are completely immobile. After an implantation, to a given fluence, the value of the particle retention coefficient (TN ) was determined directly from the total measured number of helium atoms retained in the range profile that was parallel to the [110] direction. Then the value of RN was calculated from the relationship RN = 1−TN. The experimental value of RN decreases from ∼0.85 to ∼0.25, as the energy of the incident helium ion beam increases from 100 to 1500 eV. The results are compared with values of RN calculated employing Biersack’s and Haggmark’s TRIM program; the calculated values are in fair agreement with the experimental data between 300 and 1500 eV.
A new low temperature III–V multilayer growth technique: Vacuum metalorganic chemical vapor deposition
Authors: Fraas Lewis M.
Published: February 2003

A new technique for multilayer growth by metalorganic chemical vapor deposition is described. The vacuum metalorganic chemical vapor deposition technique combines the low-temperature growth capability of molecular beam epitaxy with the source handling system of chemical vapor deposition. The viability of the new technique is demonstrated by the growth of high-mobility layers of GaAs, GaAs(1−x)P(x), and Ga(1−x)In(x)As at 570 °C. Room-temperature mobilities of GaAs films as high as 4990 cm2/V s are obtained. Doping of both p-type and n-type films is demonstrated. GaAs shallow homojunction solar cells fabricated with this technique are described. Active-area solar cell efficiencies as high as 19.6% are obtained with 6 ’’suns’’ AM2 concentrated light. This multilayer growth technique is particularly suited to the fabrication of multicolor solar cells.
Selective removal of phosgene impurity from boron trichloride by photochemical dissociation
Authors: Hyer Ronald C. , Freund Samuel M. , Hartford Allen , Atencio Jerry H.
Published: February 2003

Selective ultraviolet photolysis using either a KrF excimer laser or an unfiltered mercury arc lamp has been used to reduce substantially the phosgene impurity in a binary mixture of boron trichloride and phosgene. Infrared spectroscopic analysis of the sample before and after irradiation shows that it is possible to highly purify commercially available boron trichloride with this technique.
The oxygen effect in the growth kinetics of platinum silicides
Authors: Nava F. , Valeri S. , Majni G. , Cembali A. , Pignatel G. , Queirolo G.
Published: February 2003

Silicide formation is strongly affected by the presence of oxygen contained in the metal film. A study has been performed by heating at various times and temperatures samples constituted by a thin Pt film sputter deposited on a silicon substrate. Four different oxygen concentrations were implanted in the Pt film ranging from 1 to 0.1 at.%. The presence of oxygen slows down the growth rate of Pt2Si. At 315 °C in the sample with an oxygen concentration of 1 at.%, about 1000 Å of Pt2Si are formed after 20 min of annealing. During the silicide formation, the oxygen originally contained in the platinum films segregates at the Pt2Si/Pt interface. This accumulation acts as a barrier for the transport of Pt and a new phase, PtSi, can form at the Pt2Si/Si interface. The dose necessary to stop the Pt2Si reaction is about (2–4)×1015 at./cm2 at 315 °C.
Reactive electro-optic Q switching of a CO2 laser
Authors: Marcus S.
Published: February 2003

High-repetition-rate reactive electrooptic Q switching of a CO2 laser was demonstrated. It was shown to be more efficient than a comparable polarization Q switch, but more sensitive to frequency instabilities.
Pd2Si surfaces thermally enriched in silicon: Evidence of new Si:Pd bonds
Authors: Abbati I. , Rossi G. , Braicovich L. , Lindau I. , Spicer W. E. , De Michelis B.
Published: February 2003

Thermally induced Si accumulation onto Pd2Si surfaces has been studied for the first time with synchrotron radiation photoemission. Evidence is given of the formation of strong bonds between Si and Pd in the transition region between Pd2Si and Si. The results are discussed in view of the Pd-Si interfaces prepared by annealing in device technology.
On the intensity of secondary Cu+, Cu+2, and Mo+ ions as a function of bombarding ion energy
Authors: Chakraborty P. , Dey S. D.
Published: February 2003

The effect of Zn+ and Cd+ primary ions with energies between 3 and 10 keV on the emission of secondary Cu+, Cu+2, and Mo+ ions from polycrystalline copper and molybdenum target surfaces has been investigated. It was found that secondary ion intensity increases almost linearly with bombarding ion energy, attains a broad maximum, and then decreases steadily. It has also been observed that the location of the maximum depends strongly on the ion-target combination. The positions of maxima were found to be around 7.5, 6.5, and 5.0 keV for Zn+-Cu, Cd+-Cu, and Cd+-Mo combinations, respectively. Our finding could be experimental evidence of the fact that the nontextured surfaces may become textured under ion bombardment.
Wall clusters in thin soft ferromagnetic configurations
Authors: van den Berg H. A. M. , Vatvani D. K.
Published: February 2003

The wall cluster, which is a new concept in ferromagnetic domain theory, is introduced as a tool for getting a grip on the development of domain structures. A wall cluster consists of an arbitrary number of walls, which have a common intersection line. This paper is confined to wall clusters in thin ferromagnetic layers, such as the permalloy overlayers in bubble devices. Two classes of edge clusters, the intersection of which coincides with one of the edges of the ferromagnetic configuration, are distinguished. The odd-edge cluster bridges the outermost domains by an odd number of walls. The magnetization directions in these exterior domains are parallel. In contradistinction, the outermost domains, in which the tangential components to the edge are opposite, require an even-edge cluster in between. It is shown that the magnetization direction in each of the domains is determined by the position of the walls. The clock sense of the rotation of each successive wall in an edge cluster changes the sign. The transformations of edge clusters are also extensively studied. In particular, the annihilation and the creation of complete clusters are discussed. Cluster creation is a process in which a cluster is generated by a continuous succession of equilibrium states. In this context the definition of the creation line, one from which all the walls of the clusters grow, is of significance. The experimental evidence is given for all aspects of the theory.
New bubble garnet films with orthorhombic magnetic anisotropy and high mobility: (YBi)3(FeGa)5O12 and (YTmBi)3(FeGa)5O12/(110)GGG
Authors: Hibiya Taketoshi , Makino Hiroshi , Konishi Susumu
Published: February 2003

New orthorhombic magnetic anisotropy garnet liquid phase epitaxial films with high mobility and low coercivity, (YBi)3(FeGa)5O12 and (YTmBi)3(FeGa)5O12/(110)GGG, have been successfully obtained. There are no hard bubbles, and wall states are either S = 0, 1, or −1. For 2 μm bubble material (YBi)3(FeGa)5O12/(110)GGG, mobility is μw = 85 m/s Oe and saturation velocity is Vs ≃130 m/s. For 6 μm bubble material (YTmBi)3(FeGa)5O12/(110)GGG, μw = 23 m/s Oe and Vs ≃130 m/s are observed. Vs ≃130 m/s for 2 μm bubble material assures bubble transfer at more than 10 MHz in a current access dual conductor device and utilization of the material for a magneto-optic readout head. Orthorhombic anisotropy for these materials is mostly growth induced. Growth-induced perpendicular anisotropies are not observed for eight other garnet systems on the (110)-GGG. Growth-induced orthorhombic anisotropy energy for Bi containing garnets is discussed using Gyorgy’s phenomenological parameters, A and B, compared with growth-induced anisotropy for (111)-oriented garnet films. A unique behavior of Y3+ in Bi containing garnets supports perpendicular anisotropy for orthorhombic anisotropy materials.
Asymmetric crystal topography of diacetylene and polydiacetylene macroscopic single crystals
Authors: Rosemeier Ronald G. , Green Robert E. , Baughman Ray H.
Published: February 2003

X-ray transmission asymmetric crystal topography was used to investigate the changes in defect structure which occur during the solid-state polymerization of macroscopic single crystals of a diacetylene. Comparison of x-ray topographs made before and after gamma-ray-induced polymerization indicate that lattice strain increases during polymerization, but important defect structures present in monomer crystals are retained in the polymer crystals. A cross-pattern defect structure along 〈201〉 crystallographic directions is typically observed in both monomer and polymer single crystals.
Displacement criterion for amorphization of silicon during ion implantation
Authors: Christel L. A. , Gibbons J. F. , Sigmon T. W.
Published: February 2003

Results of Boltzmann transport equation calculations are used to estimate what fraction of a crystalline silicon lattice must be displaced to cause a crystalline-to-amorphous transition during ion implantation. Comparison of these calculations with experimental MeV He channeling and backscattering results for 150-keV boron implantation at 77 °K indicates that the displacement of about 10% of the lattice will cause amorphization provided the substrate is at a temperature which inhibits self-annealing processes and defect diffusion. The calculations also indicate that the number of atoms displaced is proportional to the deposited energy density, one displacement occurring on average for each 200 eV of deposited energy. Experimental results for room-temperature silicon implantation confirm the fact that higher temperature substrates require a greater fractional displacement of the lattice before amorphization occurs.
Distribution of interatomic spacings in random alloys
Authors: Froyen Sverre , Herring Conyers
Published: February 2003

In a disordered solid solution the interatomic spacings will vary because of fluctuations in the local environment. This paper extends previous theories of these variations for a system in which A and B atoms are distributed at random over the sites of a simple lattice, with atomic fractions x and (1−x), respectively, and for which the differences between A and B in regard to size and interaction characteristics are small enough to be treated in first order only. To this order exact results are derived regarding the statistics of relative positions of AA, AB, and BB near-neighbor pairs: expressions are given especially for the departures for the average spacing of each of these three types of pairs from the corresponding spacing of the mean lattice, and for the mean-square fluctuations of these relative positions about their means. The expressions can be evaluated from the elastic spectrum of the crystal and da/dx, the variation of the lattice constant with composition. For the common cubic lattices, graphs are given for their approximate numerical evaluation from da/dx and the three elastic constants. The elastic-relaxation contribution to the configuration-dependent energy can be evaluated from the same expressions.
Dislocation-free zone model of fracture
Authors: Chang S.-J. , Ohr S. M.
Published: February 2003

Recent observations by electron microscopy have shown that a dislocation-free zone (DFZ) is present between the crack tip and the linear pileup of dislocations in the plastic zone. A singular integral equation is formulated to describe the equilibrium configuration of the dislocations. The distribution function of the dislocations is obtained in terms of elliptic integrals. The condition of compatibility and the elastic stress intensity factor at the crack tip are also derived. At the crack tip the stress varies as 1/√r. It is found that the stress intensity factor K is approximately a function of the length of the DFZ, whereas the externally applied stress approximately determines the length of the plastic zone. Based on the mechanism of dislocation generation at the crack tip proposed by Rice and Thomson, it is shown that the formation of the DFZ is anticipated when the stress intensity factor K is less than a critical stress intensity factor Kg defined for a spontaneous generation of dislocations. The magnitude of Kg relative to the critical stress intensity factor for brittle fracture Kc determines the brittle-ductile nature of a material.
Reactivity of magnesium to hydrogen: A high-pressure analysis of the dissolution enthalpy
Authors: Fromageau R. , Hillairet J. , Ligeon E. , Mairy C. , Revel G. , Tzanétakis P.
Published: February 2003

The temperature variation of the hydrogen solubility in magnesium in equilibrium with H2 gas has been measured mostly with use of a resistometric method, for pressures ranging between 0.1 and 12 MPa. The relative partial enthalpy per gram atom of the interstitially dissolved gas was inferred to be 58±5 kJ mol−1 (0.60±0.05 eV). This experimental finding is compared with previous data. The reaction of magnesium with traces of oxygen or moisture and the possible influence of this effect on the result are discussed also. A further point of discussion deals with the proper separation between hydrogen dissolution and hydride formation.
Clustering in molecular-beam epitaxial AlxGa1−xAs-GaAs quantum-well heterostructure lasers
Authors: Holonyak N. , Laidig W. D. , Camras M. D. , Morkoç H. , Drummond T. J. , Hess K. , Burroughs M. S.
Published: February 2003

The effects of alloy clustering in AlxGa1−xAs-GaAs quantum-well heterostructures (QWH’s) grown by molecular-beam epitaxy (MBE) are investigated. Both low- and high-level photoluminescence data on three of the best MBE QWH lasers are presented. These data indicate that while clustering in AlxGa1−xAs can depend on crystal growth conditions (temperature, stoichiometry, surface chemistry, contamination, etc.), it is to an appreciable extent intrinsic to the alloy. Clustering in AlxGa1−xAs can result from the random distribution of Al and Ga atoms regardless of the method of crystal growth. In addition, this work demonstrates cw 300-K photopumped laser operation of MBE QWH’s, which would not be possible if the distributed and heterointerface defect densities (of unknown amount) were very high.
High-current D− production by charge exchange in sodium
Authors: Hooper E. B. , Poulsen P. , Pincosy P. A.
Published: February 2003

A beam of D− ions has been produced at 7–13 keV, with currents up to 2.2 A, using charge exchange in sodium vapor. The beam profile is bi-Gaussian with angular divergence 0.7°×2.8° and peak current density 15 mA/cm2. The characteristics of the beam are in excellent agreement with predictions based on atomic cross sections. The sodium vapor target is formed by a jet directed across the beam. The sodium density drops rapidly in the beamline downstream from the charge exchange region, decreasing three orders of magnitude in 15 cm. Measurement and analysis of the plasma accompanying the beam demonstrate that plasma densities nearly equal to the beam density are obtained 1 m from the charge exchange medium. The plasma produced in the sodium is thus well confined to the charge exchange region and does not propagate along the beam.
Measurements and calculations of the anomalous energy broadening of a 300-eV electron beam
Authors: McClelland J. J. , Ratliff J. M. , Fink M.
Published: February 2003

Measurements and calculations of the energy full width at half maximum (FWHM) of a 300-eV electron beam are presented as a function of current. The measurements utilize a low-energy telefocus electron gun and a 127° cylindrical energy analyzer. The calculations combine theories of Knauer and Zimmermann with beam envelope determinations obtained from a combination of electron ray tracing and measurements on the beam. The energy width is numerically integrated along the beam envelope, and the FWHM is calculated. The calculations agree in magnitude with the measurements, but there is a discrepancy in the current dependence.
Theory of lossless suppression of filamentation in high-power laser beams
Authors: Felber F. S. , Chernin D. P.
Published: February 2003

This paper supports an earlier suggestion that saturation of the optical nonlinearity of a medium by a plane wave will suppress filamentation of the wave. A variational approach and exact solutions of the slowly-varying-envelope approximation of the linearized wave equation describe the growth of localized filaments on plane waves. The solutions show that a wave will be stable against filamentation if the wave is weak or if it is intense enough to saturate the nonlinearity of the medium. Experiments are proposed to demonstrate suppression of filamentation of CO2 laser beams exceeding 1010 W and Nd laser beams exceeding 1012 W in fully ionized hydrogen plasmas. The beams saturate the nonlinearity of the plasma by ponderomotive forces; absorption is negligible in the rarefied channel produced by the laser. Applications may include lossless filters that remove intensity hot spots from beams or convert mulitmode beams to nearly single mode.
Low-loss polystyrene core-optical fibers
Authors: Kaino Toshikuni , Fujiki Michiya , Nara Shigeo
Published: February 2003

Low-loss plastic optical fibers (POF) have been prepared with the attenuation loss of 114 dB/km at the wavelength of 670 nm employing polystylene core and ethylene-vinylacetate copolymer cladding. The POF can allow the use for short-distance optical signal transmission. The theoretical loss limit of polystylene core POF is calculated to be 70 dB/km at 670 nm.
Helicons in bismuth
Authors: Sharma O. P.
Published: February 2003

We have solved the Vlasov equation for electrons in bismuth in the presence of a helicon wave and have obtained general expressions for the current density. The expressions are valid for arbitrary Larmor radius to wavelength ratio and arbitrary distribution function. The attenuation coefficient of helicon waves turns out to be a function of electron mass tensor and its measurements could be employed to investigate the band structure of bismuth.
Electron transport of n-type CdS single crystals annealed in Cd or In
Authors: Mathur P. C. , Sethi B. R. , Goyal P. K. , Sharma O. P.
Published: February 2003

The effect of high-temperature annealing of as-grown, n-type single crystals of CdS in Cd and In on the electrical transport properties has been studied in the temperature range 77–300 K. It has been found that there is optimum duration of annealing in Cd as well as in In at which the low-temperature mobility of the charge carriers is maximum. For the same annealing duration, the low-temperature mobility in the In-annealed samples is, however, found to be very much lower than that in the Cd-annealed samples. The experimentally measured mobility values in all the samples are found to be lower than the mobility values calculated theoretically using the Brooks-Herring formula. This discrepancy in the case of Cd-annealed samples has been explained by applying the electron-electron correction to the ionized impurity scattering. The mobility in the In-annealed samples, however, is too low to be explained on this basis and the discrepancy in this case has been explained by considering the formation of acceptor complexes.
The role of the blocking structure in hydrogenated amorphous silicon vidicon targets
Authors: Oda Shunri , Saito Keishi , Tomita Hisashi , Shimizu Isamu , Inoue Eiichi
Published: February 2003

Vidicon targets based on hydrogenated amorphous silicon (a-Si:H) are investigated. The role of the blocking contact to the photoconductor is discussed and a series of the experiments on the photoconductive properties for various kinds of target structures (doping concentration, film thickness) are presented. Without the blocking layer, the device characteristics would suffer not only from the increased dark current level but also from the lower photocarrier transport due to the accumulation of trapped space charge which would distort the internal field. The blocking layer is essential in photoelectric imaging devices to prevent the carrier injection and to sustain the high field in the photogeneration region. The correlations between the device performances and the target structures are also discussed.
Absorption, stimulated emission, and clustering in AlAs-AlxGa1−xAs-GaAs superlattices
Authors: Coleman J. J. , Dapkus P. D. , Camras M. D. , Holonyak N. , Laidig W. D. , Low T. S. , Burroughs M. S. , Hess K.
Published: February 2003

Absorption and photoluminescence data are presented on two AlAs-AlxGa1−xAs-GaAs superlattices (SL’s) grown by metalorganic chemical vapor deposition (MO-CVD). One SL is an 80-period all-binary structure with AlAs barriers and GaAs wells. The other SL consists of 121 periods of AlxGa1−xAs (x∼0.5) barriers and GaAs wells. The effects of clustering in the alloy-barrier SL lead to a spectral shift to lower energy that can be characterized by an effective well size L′z larger than the intended well size of Lz ∼80 Å. Absorption data and low-level photoluminescence data on both SL’s correspond closely to the calculated confined-particle transitions. At high excitation levels, however, stimulated emission, including cw 300-K laser operation, occurs ∼h/ωLO below the lowest (n = 1) confined-particle transitions.
Barrier metal against Ga and Zn out-diffusion in p-GaP/Au:Zn contact system
Authors: Yamashita Masato , Oana Yasuhisa
Published: February 2003

Molybdenum, tungsten, titanium, 10 wt% titanium: tungsten, and tantalum are evaluated as barrier metals for preventing gallium and zinc out-diffusion from alloyed p-GaP/Au:Zn contact system. Secondary-ion mass spectrometry is employed to assess qualitatively the extent of out-diffusion. SIMS analysis indicates that effectiveness of barrier metals decreases in the order of 10 wt% Ti:W≳Ta≫W≳Mo≫Ti. Furthermore, specific contact resistances are determined by accounting for both spreading resistance and series resistance. Among the present metallization systems, 10 wt% Ti:W is proved to be the most suitable barrier metal.
Mathematical modelling of the impedance of a Josephson junction noise thermometer
Authors: Peterson Robert L.
Published: February 2003

Recent experimental work on noise thermometers consisting of a resistively shunted superconducting loop containing a Josephson junction (a resistive SQUID), has shown some novel behavior of the SQUID dc impedance as a function of rf power. We present a mathematical analysis of the intrinsic behavior of a resistive SQUID in the limit of negligible noise and negligible feedback to the rf circuit. A nonlinear, first-order differential equation is thought to be a reasonable descriptor of this system. Because the radio frequency driving the SQUID is much larger than the Josephson frequency, we are able to obtain a pair of equations in which no rf oscillating terms appear, and which are amenable to numerical solution. The dc impedance calculated from these equations has several, but not all, of the experimentally observed features.
Superconductor-normal-superconductor microbridges: Fabrication, electrical behavior, and modeling
Authors: van Dover R. B. , de Lozanne A. , Beasley M. R.
Published: February 2003

Josephson-effect devices consisting of two superconducting thin films coupled by a short nonsuperconducting metallic bridge are investigated in this work. To fabricate these devices we have developed processing techniques which are compatible with refractory superconductors and show promise for the high-Tc A15 materials as well. We describe in detail the electrical behavior of Nb-Au-Nb and Nb-Cu-Nb bridges, which have been made with resistances up to 0.4 Ω and critical current-resistance (i.e., IcRn ) products as high as 0.5 mV. We have modified the usual theoretical model for the critical current in order to account for the actual geometry of our devices thereby obtaining semiquantitative agreement with experiment. A single parameter is used in this analysis to characterize the proximity effect and we find that values inferred from the critical currents of bridges agree well with those inferred from the behavior of the transition temperature of S/N bilayers. Typical current-voltage characteristics are in good agreement with the predictions of the time-dependent Ginzburg-Landau model with rigid boundary conditions. At high dissipations heating is observed and explained by a generalized version of the hotspot model. Finally, we have employed the models for superconductor-normal-superconductor microbridge behavior to evaluate the ultimate potential of this particular weak-link configuration for practical applications.
Dynamic pyroelectric response of polyvinylidene fluoride at low temperatures
Authors: Das-Gupta D. K. , Duffy J. S.
Published: February 2003

The nature of dynamic pyroelectric responses, superimposed on the time-dependent discharge current of weakly poled polyvinylidene fluoride has been studied in the temperature range −55 to −10 °C. The results show that the observed pyroelectricity is of dipolar origin, occurring in the amorphous phase of the polymer.
Intraband magneto-optical studies of InSb-NiSb eutectic
Authors: Chin A. K. , Sievers A. J.
Published: February 2003

A comprehensive magneto-optical study of the light-hole valence band of InSb-NiSb eutectic is presented. Transmission spectra in the Faraday geometry are measured in the spectral region below 350 cm−1 and at the CO2 laser frequency of 933 cm−1. Temperature dependence (from 1.2 to 80 K) and magnetic fields (from zero field to 350 kG) are used to interpret the experimental data. Transitions among acceptor impurity levels are observed in the zero magnetic-field spectra. With an applied magnetic field, intravalence band transitions and transitions from acceptor levels to the valence band are observed. The Luttinger coefficients of the valence band as calculated from the effective masses of the acceptor level to valence-band transitions are γL1 = 30.9, γ̄L = 15.3, and KL = 12.9. From the zero-field positions of the transitions, the ground-state acceptor level is determined to be 83±3 cm−1 above the top of the valence band. Bound hole-phonon coupling is observed in the pinning behavior and nonlinear field dependence of the acceptor to valence-band transitions. Free hole-phonon coupling is observed for the first time in the nonlinear field dependence of the intraband transitions.
Spontaneous emission factor β for injection lasers
Authors: Sommers H. S.
Published: February 2003

The fraction of the spontaneous emission which appears in a given mode of an injection laser is evaluated from first principles. It is directly proportional to the ratio of a current-derivative of the gain to an effective volume of the cavity mode and has a weak dependence on current density.
Numerical simulation of sheath structure and current-voltage characteristics of a conductor-dielectric disk in a plasma
Authors: Chaky R. C. , Nonnast J. H. , Enoch J.
Published: February 2003

We present results of a calculation of current-voltage characteristic curves and voltage profiles for an idealized spacecraft charging configuration. We model a plasma interacting with a conducting disk covered by a charged dielectric, with a portion of the conductor exposed to the ambient magnetospheric plasma. We also model the electrostatics of a conducting ’’button’’ resting on the center of a dielectric disk. The calculation uses a cylindrical particle-in-cell (PIC) particle mover with variable particle number, and the potential is calculated self-consistently using successive over relaxation (SOR). Results of this electrostatic plasma simulation are presented both with and without secondary electron emission from the dielectric.
The glow-to-arc transition in a pulsed high-pressure gas discharge
Authors: Turner R.
Published: February 2003

The glow-to-arc transition that occurs at high repetition rate operation in near-atmospheric pressure, transverse electric gas discharges has been studied experimentally in helium and mixtures of helium and other gases (CO2, CO, Ne, A, Kr, Xe). Various aspects of the discharge including the ionization phase, output power and wavelength (for lasing gas mixtures), electron density, gas current and voltage, visible emission from reaction products, refractive effects in the gas, and the distribution of cathode hot spots, have been measured as the excitation current, repetition rate, and preionization were changed. The effects on the discharge of cathode material, added contaminants, and magnetic field were also observed. The results of these measurements indicate that one of the main causes of the glow-to-arc transition at high repetition rate operation is a thermal instability, similar to the Benard instability, driven by the temperature gradient at the cathode.
A space-charge region model for microscopic steady coronas from points
Authors: Henson Bob L.
Published: February 2003

A mathematical model for microscopic point-to-plane coronas in the steady-state regime has been developed and current-potential relations have been derived from the model. The potential and electric field distributions for the region outside of the corona glow are also predicted. The model is applicable for both gaseous and liquid media. Hyperboloid geometry is assumed for the point and a constant mobility model is asumed for the transport of the charge carriers. The derived relation for the functional dependence of the corona current on point potential is shown to be in agreement with experimental data in helium. Empirical values for some of the parameters of the equations are presented for microscopic coronas in gaseous helium.
Surface pinning of disclinations and the stability of bistable nematic storage displays
Authors: Cheng Julian
Published: February 2003

The attraction of bulk singularities in nematic liquid crystals (NLC) to substrate surfaces depends on the existence of discontinuities in surface topography or alignment. The pinning of disclinations governs the stability of certain bistable configuration displays (BCD’s) by providing an energy barrier against their spontaneous detachment. We will discuss the conditions required for attraction or pinning, using model calculations for strength 1/2 disclinations at tilt-reversal surface junctions. These results are applied to study the stability of (BCD’s) and to devise a scheme for achieving a discrete array of isolated display picture elements (PEL’s) with completely stable boundaries.
Effects of temperature on attenuation of the shock wave precursor in <100≳ LiF
Authors: Vorthman John E. , Duvall George E.
Published: February 2003

Single-crystal 〈100〉 lithium fluoride was cooled, shocked, and the precursor amplitude measured. Comparison with room-temperature experiments indicates that precursor attenuation is enhanced at liquid-nitrogen temperature. This is opposite to what one would expect if precursor decay is caused by the nucleation and growth of dislocations.
Network oxygen exchange during water diffusion in SiO2
Authors: Pfeffer Robert , Ohring Milton
Published: February 2003

In an investigation of the mechanism responsible for the transport of water through SiO2 thin films, we have performed tracer diffusion measurements involving network 18O demonstrating the importance of oxygen exchange between the SiO2 network and molecularly dissolved water. We have found that in the presence of water, bound network oxygen diffuses through SiO2 as a constituent of molecularly dissolved water. Employing methods common to state-of-the-art semiconductor technology, the central region within a thermal oxide layer grown on silicon was enriched with immobile 18O by ion implantation. After heating in atmospheres with different water contents, the extent of 18O diffusion was determined by observing changes in the concentration profile of implanted 19O by means of nuclear resonance profiling making use of the 629-keV resonance of the 18O( p,a) 15N reaction. Diffusions conducted in steam at 1 atm (at temperatures as low as 250 C) showed an activation energy of about 17 kcal/mol, which is close to that originally measured for water permeation in SiO2. Diffusions in both air and dry nitrogen showed a similar activation energy, with respective pre-exponential factors two and three orders of magnitude below the steam value. Diffusion in low-pressure water vapor showed a clearly linear dependence on gas phase water concentration down to 80 ppm. These results are consistent with a model of water diffusion in SiO2 in which the diffusion mechanism is the interstitial transport of dissolved molecular water accompanied by a reversible reaction with silicon-oxygen bonds in the network.
The effects of irradiation and electrolysis on the thermal conductivity of synthetic quartz
Authors: Jalilian-Nosraty M. , Martin J. J.
Published: February 2003

The low-temperature thermal conductivity of Premium Q and Electronic Grade synthetic a-quartz has been measured. Substitutional aluminum is the primary active impurity in Premium Q quartz. Irradiation at room temperature of the unswept Premium Q sample caused a dip in the thermal conductivity near 4 K. This dip can be described by a simple resonant phonon scattering relaxation time with a resonant frequency of 2.75×1012 rad/sec. A room-temperature irradiation of unswept quartz produces both [Ale+]0 and Al-OH centers either of which might cause a resonant phonon scattering. After the premium Q sample was electrolyzed (swept) in hydrogen to remove the alkalis and the [Ale+]0 center and to produce the Al-OH center, the resonant scattering was slightly enhanced. Consequently, the Al-OH center rather than the [Ale+]0 center must be responsible for this scattering. The Electonic Grade sample which has additional OH related defects showed a strongly suppressed thermal conductivity.
Attraction and repulsion of solid particles by solidification fronts. II. Dimensional analysis
Authors: Omenyi S. N. , Neumann A. W. , Martin W. W. , Lespinard G. M. , Smith R. P.
Published: February 2003

A scheme of dimensional analysis is developed for the description of pushing and engulfing of particles by solidification fronts. The nondimensional groups contain all the properties to be believed relevant, such as the critical velocity of engulfing Vc, the free energy of adhesion of the particle, viscosity, densities, thermal conductivities, temperature, specific heat, diffusion coefficient, and particle diameter. The determination of the parameters of the dimensional analysis is based on a substantial body of experimental critical velocity Vc data as a function of particle diameter. These experiments were performed with naphthalene and biphenyl as matrix materials and a range of polymer particles in the particle size range from 10–200 mm. The final relation obtained is tested for internal consistency and the resulting dependence of the critical velocity of engulfing on particle size is compared with experimental results.
Properties of metal/polyacetylene Schottky barriers
Authors: Grant P. M. , Tani T. , Gill W. D. , Krounbi M. , Clarke T. C.
Published: February 2003

Rectifying barriers of undoped and lightly doped trans-(CH)x films with low work function metals have been investigated. I-V and C-V measurements were used to explore the junction properties. The junction characteristics were found to be Schottky-like in the large sense accompanied by significant differences in detail. Using C-V measurements to determine the carrier concentration, we found the carrier mobility to be concentration dependent.
Analytic approximations for degenerate accumulation layers in semiconductors, with applications to barrier lowering in isotype heterojunctions
Authors: Kroemer Herbert
Published: February 2003

The Joyce-Dixon approximation for the Fermi energy in a degenerate semiconductor is used to obtain rapidly converging series expansions for both the potential and the electric field for degenerate accumulation layers in semiconductors, as functions of the electron concentration. The expressions are valid for electron concentrations up to about 20 times the effective density of states. The approximation is applied to Schottky barriers on degenerate semiconductors, where it leads to an increase in the value of the Gummel-Scharfetter correction in the C-V relation for Schottky barriers. A detailed quantitative treatment is given for the barrier lowering in abrupt n-N heterojunctions with increased reverse bias. Both barrier lowering and reverse bias are given as closed-form parametric expressions, with the electron concentration at the bottom of the heterojunction notch as the independent variable.
Surface resistance of superconducting lead TM010 mode cavities fabricated by an inside surface electroplating technique
Authors: Momose Takashi , Akada Katsuhiro , Onodera Yutaka , Yamashita Tsutomu
Published: February 2003

Several superconducting lead cavities in the TM010 mode at 9.7 GHz were investigated at low rf input power (≲3 mW). The cavities were prepared by deep drawing copper substrates and then depositing lead by means of a new electroplating technique to obtain a continuous film on the inside surface of the cavity. Unloaded Q’s on the order of 109 were routinely obtained and the lowest reported residual surface resistance value (2.0×10−8W) for either TM or TE modes was measured at X-band frequencies.
Magnetization curve of zero-anisotropy sphere
Authors: Aharoni Amikam
Published: February 2003

A specific Ritz model is suggested, in which magnetization curls around the outer part of a sphere, while an inner core is saturated. This model is used to calculate the magnetic field dependence of the magnetization in perfect ferromagnetic spheres, with no anisotropy. For sufficiently small radii, the results indicate an infinite permeability at zero applied field, which brings the average magnetization to an appreciable part of its saturation value. This is then followed by an almost linear dependence of the average magnetization on the applied field, practically up to saturation.
Photoluminescence from Mg-implanted, epitaxial, and semi-insulating InP
Authors: Pomrenke Gernot S. , Park Y. S. , Hengehold Robert L.
Published: February 2003

Photoluminescence measurements were made to study the behavior of Mg implants in InP. Mg ions were implanted at an energy of 120 keV into vapor phase epitaxial (VPE) and Fe-doped, semi-insulating (SI) InP at doses of 1×1012–1×1015 cm−2 at room temperature. Encapsulation was with Si3N4 followed by face-down annealing for 15 min at temperatures from 500 to 800 °C. Changes in excitation intensity, temperature, and dosage resulted in the identification of the Mg-related free-to-acceptor and donor-to-acceptor transitions where the Mg ionization energy was calculated to be 39.4 meV. Annealing in the 700 and 800 °C range proved sufficient in moving impurities into substitutional sites and making the implants optically active. Activation, which is strongly dosage dependent, was optimum at an anneal temperature of 750 °C for VPE material, while for SI InP, maximum activation was achieved at 800 °C. A broad, structured emission between 1.20 and 1.38 eV was observed for anneal temperatures of 600 and 700 °C; it disappeared at high fluences through broadening. A shift toward lower energy was observed for the donor-to-acceptor emission in SI InP:Fe in comparison with VPE InP at low excitation intensity.
Laser-induced dielectric breakdown in cryogenic liquids
Authors: Brueck S. R. J. , Kildal Helge
Published: February 2003

Spot size and pulse length dependences of CO2 laser-induced breakdown in the cryogenic liquids N2, O2, CO, and Ar are reported. Parameters which affect the dielectric strengths are identified and the results are compared with previous dc measurements. Diagnostic measurements of photoconductivity, fluorescence and laser-induced pressure (acoustic), and density fluctuations to characterize the breakdown processes are reported.
Quantitative broadband ultrasonic backscatter: An approach to nondestructive evaluation in acoustically inhomogeneous materials
Authors: O’Donnell M. , Miller J. G.
Published: February 2003

In the present paper we investigate the use of a broadband backscatter technique to obtain the frequency dependence of the longitudinal-wave ultrasonic backscatter coefficient from a collection of scatterers in a solid. Measurements of the backscatter coefficient were obtained over the range 0.1<ka<3.0 from model systems consisting of dilute suspensions of randomly distributed crown glass spheres in hardened polyester resin. The results of these measurements were in good agreement with theoretical prediction. Consequently, broadband measurements of the ultrasonic backscatter coefficient may represent a useful approach toward characterizing the physical properties of scatterers in intrinsically inhomogeneous materials such as composites, metals, and ceramics, and may represent an approach toward nondestructive evaluation of these materials.
Group velocity of guided magnetic waves
Authors: Seshadri S. R.
Published: February 2003

The kinematic and the dynamic methods are shown in a general way to yield identical results for the group velocity of guided magnetic waves.
Influence of substrate temperature in laser annealing of arsenic-implanted silicon
Authors: Nakamura Kunio
Published: February 2003

Effect of substrate heating during Q-switched Nd:YAG laser annealing of arsenic-implanted Si has been observed by sheet resistance measurement. Strong dependence on the substrate temperature has been found in annealing with an infrared pulse (1.06 mm). Temperatures above 200 °C are required to electrically activate the implanted impurities for the incident energy density of 4 J/cm2, except when the implantation dose is 1016/cm2. On the other hand, there is less dependence on the substrate temperature in the case of irradiation with a second harmonic pulse (0.53 mm). These results can be explained by a difference in light-absorption mechanisms. Simple calculations based on the model proposed by Allmen et al. explain well the measured data.