bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature and energy dependences of capture cross sections at surface states in Si metal-oxide-semiconductor diodes measured by deep level transient spectroscopy
Authors: Katsube Teruaki , Kakimoto Koichi , Ikoma Toshiaki
Published: February 2003

A new deep level transient spectroscopy technique is presented to determine capture cross sections at metal-oxide semiconductor (MOS) surface states. The technique enables us to determine energy and temperature dependences of capture cross sections separately. Applying this method, electron capture cross sections at surface states in Si MOS diodes were measured and found to have strong energy dependence and rather weak temperature dependence. It was also found that there was an effect to increase the emission rate, which may be attributed to barrier lowering at the Si-SiO2 interface.
Silicon-nitride–gallium-arsenide MIS structures produced by plasma enhanced deposition
Authors: Bayraktaroglu Burhan , Johnson Robert L.
Published: February 2003

Plasma enhanced deposited (PED) silicon-nitride films were used for passivating GaAs surfaces. The electrical properties of the metal-insulator–GaAs structures were studied to determine the interfacial characteristics. Both the bulk and the interfacial properties of PED silicon nitride with GaAs were found to be strongly dependent on the growth parameters. The surface state densities could be lowered considerably by treating the GaAs surface in a N2 and H2 plasma prior to the insulator deposition.
The optical properties of Kapton: Measurement and applications
Authors: Arakawa E. T. , Williams M. W. , Ashley J. C. , Painter L. R.
Published: February 2003

The optical properties of Kapton type H polyimide film, obtained from reflectance measurements, are presented for photon energies from 0.5 to 70 eV. Equations for the energy-loss function, with parameters fixed by the optical data, are employed to calculate mean free paths and stopping powers for low-energy electrons (100 eV to 10 keV) in Kapton. The values obtained show good agreement with those predicted by recently proposed analytical formulae for electron mean free paths and stopping powers in solid organic insulators.
Interferometric electron density measurements of high-density plasmas
Authors: Matsumoto Y. , Koyama K. , Tanimoto M. , Sugiura M.
Published: February 2003

The effects of bending of the light beam due to density gradients on the interferometric density measurements of dense plasmas with various density profiles are estimated. It is indicated that in spite of the original smooth density profile the bending effects may result not only in quantitative errors but also in apparent density modifications such as dips, plateaus, rippling, and steepening. In laser fusion experiments it is very essential to exactly adjust the imaging optics of the interferometer as well as the laser-irradiation optical system. The errors inevitably introduced are also evaluated. It is experimentally shown that an imaging lens must be properly used even in the density measurement of a plasma focus with relatively low density compared with laser plasmas.
Faraday cup analysis of ion beams produced by a dense plasma focus
Authors: Gerdin G. , Stygar W. , Venneri F.
Published: February 2003

The design and performance of a Faraday cup which is used in a time-of-flight technique to measure the energy spectrum of ions accelerated away from the anode of a plasma focus are described. The cup is located in a differentially pumped (<20 μ) chamber which is separated from the main plasma focus chamber by a 0.0457-cm diam hole positioned 16 cm above the anode. This arrangement allows a bias voltage of −400 V to be applied to the cup to stop comoving electrons and permits the observation of deuteron energies down to ∼25 keV.
Laser-initiated channels for ion transport: CO2-laser absorption and heating of NH3 and C2H4 gases
Authors: Olsen J. N.
Published: February 2003

Initiation and guiding of an electrical discharge by CO2-laser heating of a molecular gas can provide a channel suitable for the transport of a light ion beam for inertial-confinement fusion. We report absorption measurements for a CO2 laser tuned to the molecular vibrations of NH3 and C2H4 as a function of gas pressure, laser frequency, and laser energy density. The SATUR laser-gas-interaction code models the details of the absorption saturation process for NH3, calculating gas temperature in the process. The calculation is normalized to absorption data at 0.04 J/cm2 and tested with transmission measurements up to 15 J/cm2 into a 50-cm cell. These calculations are the basis for understanding the electrical breakdown and discharge evolution as observed and simulated in the following report. Of particular importance is the calculation of gas temperature of 1900–2100 °K for 15–35-J/cm2 incident laser energy density.
Effect of silicon dioxide surface-layer thickness on boron profiles for directly aligned implants into (100) silicon
Authors: Myers D. R. , Comas J. , Wilson R. G.
Published: February 2003

We report boron profiles as determined by secondary ion mass spectrometry that result from implantation into (100) silicon at (0.0±0.1) degrees through various thicknesses of thermally grown silicon dioxide. The implants were performed at room temperature at 150 keV to a fluence of 4.0×1013/cm2. The oxide surface layers examined were 7.6, 33.6, 101.5, or 140.0 nm thick as determined by ellipsometry. The boron profile for implantation through the 7.6-nm oxide surface layer was only slightly degraded from that seen for accurately aligned implantations into bare (100)-oriented silicon, while implantation through the three thicker oxides results in profiles similar to those obtained from random equivalent implantations into crystalline silicon. The systematics of the dechanneling of the implanted boron as a function of the thickness of the amorphous surface layer are analyzed and discussed.
Dynamic response of fused quartz in the permanent densification region
Authors: Sugiura H. , Kondo K. , Sawaoka A.
Published: February 2003

A shock wave investigation on fused quartz was performed in the permanent densification region, using a double stage light-gas gun with dc x-ray velocity meter and the electromagnetic particle velocity measurement technique. The elastic limit obtained in this work [(8.81±0.11) GPa] was somewhat lower than the published value. The compression curve obtained was quite different from the published curve and indicated that a rapid volume contraction occured just above the elastic limit. The tetrahedral coordinations seemed to remain at least up to 22 GPa, but above 16 GPa, they would be distorted or in some parts destroyed. The pressure of 16 GPa was considered as the limit of the permanent densification process, and the specific volume at atmospheric pressure interpolated along a hypothetical release adiabat was about 0.32 cm3/g.
Redistribution of Fe in InP during liquid phase epitaxy
Authors: Holmes D. E. , Wilson R. G. , Yu P. W.
Published: February 2003

The behavior of Fe in semi-insulating InP substrates during growth by liquid-phase epitaxy (LPE) was studied using secondary-ion mass spectrometry and photoluminescence measurements in conjunction with ion implantation. The redistribution of Fe at the interface between the substrate and the layer follows diffusion theory. The experimentally determined diffusion coefficient D is 6.8×105 exp[-3.4 (eV)/kT]. Fe accumulates near the surface of the substrate during preheating in the H2 ambient. This accumulation cannot be explained by simple diffusion theory and could be influenced by thermal degradation of the surface.
Conservation of axial momentum in intense ion beam systems
Authors: Adler Richard J.
Published: February 2003

In a number of systems, interaction between electrons and ions results in acceleration of ions. Because of the large ion/electron mass ratio, the efficiency of intense ion beam sources can often be low. A macroscopic momentum conservation law is presented which allows the efficiency of collective accelerators and ion diodes to be evaluated. The application of the equation is straightforward and does not depend on the specific dynamical processes involved. A number of new relations are derived from the basic equation including the efficiency of a collective accelerator, the average ion velocity for collective acceleration in vacuum, the ratio of electron and ion currents in a pinched beam diode, and a relation for current enhancements in magnetically insulated diodes. These relations also serve to elucidate the role of magnetic pressure in intense ion beam systems.
Free-molecule drag on straight chains of uniform spheres
Authors: Chan P. , Dahneke B.
Published: February 2003

A numerical technique has been used to determine the free-molecule drag on a straight chain of uniform spheres moving parallel and perpendicular to its axis. For such a concave-shaped body, certain surface elements are inaccessible to molecules having certain velocity components because these areas are screened by neighboring elements. Likewise, reflected molecules do not always escape directly but may experience more than one reflection due to screening by neighboring elements. Because an analytical solution for the drag seems hopelessly complex, we have used a Monte Carlo method to determine the rate of momentum transfer (drag force) due to the molecular collisions and reflections of large numbers of molecules by following their individual dynamics. The results are discussed in terms of the translation of straight chains having fixed orientation, straight chains undergoing Brownian rotations, and branched and kinked chains.
Semileaky thin-film optical isolator
Authors: Kirsch Steven T. , Biolsi W. A. , Blank S. L. , Tien P. K. , Martin R. J. , Bridenbaugh P. M. , Grabbe P.
Published: February 2003

Two interesting effects have been experimentally demonstrated for the first time: (1) simultaneous reciprocal and nonreciprocal mode conversion to achieve an isolation effect and (2) magneto-optic switching between guided and radiation modes. These effects were observed in connection with the construction of a previously proposed thin-film optical isolator. The isolator consists of a piece of LiNbO3 placed on top of a thin film of yttrium ion garnet (YIG) with a selenium layer to avoid optical contact problems. The isolator, which is 1 cm long, exhibited 10 dB of isolation at λ = 1.15 μm. The observed isolation was better than theoretical predictions and a mysterious isolation direction dependence on mode order was observed. Although the device had 10 dB of insertion loss and required a magnetic field of 40 Oe, with a slight change in wavelength and film composition, it should be possible to reduce the insertion loss and field required to under 1 dB and 0.1 Oe, respectively. These characteristics combined with broad tolerances on film thickness and the length of the isolation region, broadband operation (from λ = 1.1 to 4.5 μm), and easy construction and adjustment make the isolator very attractive for use in integrated optics.
Measurements of the plasma ablated from an end plug in a high-energy ϑ pinch
Authors: Ekdahl C. A. , Commisso R. J. , McKenna K. F.
Published: February 2003

A ruby-laser double-exposure holographic interferometer was used to study the interaction of a ϑ-pinch-generated, hot, dense-plasma column (Te+Ti ∼2–3 keV, n∼1016 cm−3) with solid end plugs inserted to eliminate axial loss of plasma. Radial density profiles showing a peak density on axis of greater than 1018 cm−3 near the plug surface were obtained by Abel inversion of the interferograms. Interferograms showed substantial differences in the density profiles for different plug materials. Strong absorption of the laser light by the Stark-broadened Nii line at 6942 Å was used to estimate the ablated plasma temperature.
Homogeneous-homeotropic fluorescent liquid crystal cells
Authors: Filas R. W. , Labes M. M.
Published: February 2003

Theoretical and experimental contrast ratios are compared for homogeneous-to-homeotropic liquid-crystal cells containing fluorescent dye molecules activated by ultraviolet light. Two-color fluorescent displays are described in which one  active  fluor dissolved in the liquid crystal is used as a UV shutter to switch a passive fluor external to the cell. Contrast ratios of about 8 have been achieved simultaneously for both colors, if two polarizers are used and about 7, if only one polarizer is employed.
As-implanted and redistributed annealed depth distributions, range-energy data, and shape factors for Cr implanted into crystalline GaAs and Si
Authors: Wilson Robert G.
Published: February 2003

Depth distributions, range-energy curves, and the Pearson IV moments are given for Cr implantation into crystalline GaAs and Si as a function of ion energy from 40 to 600 keV at 4×1013 cm−2 fluence, and as a function of ion fluence from 4×1012 to 2×1016 cm−2 at 300-keV ion energy. The nature of the redistribution of these Cr profiles upon annealing at 840 °C for 20 min in both GaAs and in Si are shown and agree qualitatively in the two materials. Two general types of redistribution occur for 4×1013 cm−2 fluence, one for ion energies below and one for energies above about 100 keV.
A nondestructive method to determine the stress distributions of neon-implanted garnet layers
Authors: de Roode W. H. , Smits J. W.
Published: February 2003

A method has been developed for determining the stress profiles of neon-implanted garnet layers. This determination is done nondestructively by computer simulation of rocking curves observed in x-ray double-crystal diffraction. The method has been tested for three different neon implantations at energies of 100, 300, and 500 keV with doses of 1×1014, 2×1014, and 1×1014 ions/cm2, respectively. A comparison is made with an earlier destructive method based on stepwise etching of the layer. In addition the resulting profiles are compared to and show good agreement with profiles obtained from relative etching rates of the implanted films.
The use of Manganin gauges in shock reverberation experiments
Authors: Rosenberg Z.
Published: February 2003

The use of Manganin gouages in shock reverberation experiments is demonstrated in three experimental configurations. In the first one we determine the Hugoniot curve for an epoxy resin, in the 0–8.7-GPa range, by a single experiment using copper as anvil material. In the second we measure the degree of compaction of porous polyurethane from the magnitude of the second shock wave in a reverberation experiment. In the third we determine release states of shocked poly-methyl-methacrylate (PMMA). The results are compared to those obtained by other techniques or by the reverberation technique with quartz transducers.
Ion implantation and low-temperature epitaxial regrowth of GaAs
Authors: Grimaldi M. G. , Paine B. M. , Nicolet M-A. , Sadana D. K.
Published: February 2003

Channeling and transmission electron microscopy have been used to investigate the parameters that govern the extent of damage in ion-implanted GaAs and the crystal quality following capless furnace annealing at low temperature (∼400 °C). The implantation-induced disorder showed a strong dependence on the implanted ion mass and on the substrate temperature during implantation. When the implantation produced a fully amorphous surface layer the main parameter governing the regrowth was the amorphous thickness. Formation of microtwins after annealing was observed when the initial amorphous layer was thicker than 400 Å. Also, the number of extended residual defects after annealing increased linearly with the initial amorphous thickness and extrapolation of that curve predicts good regrowth of very thin (<400 Å) GaAs amorphous layers produced by ion implantation. A model is presented to explain the observed features of the low-temperature annealing of GaAs.
Space-charge aberrations in the photoelectron microscope
Authors: Massey G. A. , Jones M. D. , Plummer B. P.
Published: February 2003

The contributions of space charge to chromatic and trajectory aberrations of accelerating electrons in a laser-illuminated photoelectron microscope are calculated. Average and fluctuating components of the electrostatic forces on the particles are considered spearately. The average forces produce a magnification change but no chromatic spread. Fluctuating effects include relaxation of potential to kinetic energy in a beam obeying Poisson emission statistics, and transverse-to-longitudinal velocity relaxation by multiple scattering. The potential energy relaxation is treated in a new way by modifying the Poisson distribution with position along the beam axis. The field fluctuations produce both chromatic and trajectory spreading effects, the latter being much larger at high currents. The resolution limit is about 500 Å for 30-kV electrons in a beam of 1-A/cm2 current density.
Influence of oxidation parameters on atomic roughness at the Si-SiO2 interface
Authors: Hahn P. O. , Henzler M.
Published: February 2003

The roughness at the interface has been determined quantitatively on an atomic scale after removal of the oxide by LEED (low-energy electron diffraction) in an ultrahigh vacuum. The energy dependant broadening of the diffracted electron beam yields the average size of step-free terraces. Silicon (111) samples have been oxidized under various conditions concerning atmosphere (dry and wet), temperature (800 and 1000 °C), time, pretreatment, and post-treatment. The oxidation produces a roughness, which may be decreased by low oxidation rates and appropriate annealing in nonoxidizing atmosphere. The novel technique of evaluation for the first time shows systematically how oxidation parameters determine the roughness at the interface, which again is important for the performance of metal-oxide-semiconductor (MOS) devices.
Conduction mechanisms and 1/f noise in thick-film resistors with Pb3Rh7O15and Pb 2Ru2O7
Authors: de Jeu W. H. , Geuskens R. W. J. , Pike G. E.
Published: February 2003

Thick-film resistors with Pb3Rh7015 and Pb2Ru20 7 as conductors are considered. These compounds are chemically stable during the firing process of the resistors. The variation of sheet resistivity R ⧠ with volume fraction conductor follows a simple power law. This result cannot be explained by percolation theory in its simple form. The conductivity is found to be independent of frequency up to 10 GHz. In both cases a small positive Hall coefficient is observed which is interpreted as being due to mixed electron and hole conduction. Finally the 1/ f noise is considered, and is found to vary approximately linearly with R⧠. A theoretical model for the 1/f noise in thick-film resistors is presented that accounts for this linear relationship. The observed deviations from linearity indicate that probably tunneling through barriers at the interfaces between the conducting grains is an important factor in determining the conduction.
Simulation of I-V curves of small Josephson tunnel junctions with finite capacitance
Authors: Prober D. E. , Slusky S. E. G. , Henry R. W.
Published: February 2003

Results of digital and analog simulations of the I-V characteristics of small Josephson tunnel junctions are presented for a variety of cases, and are compared with the recent experimental results of Howard et al. [Appl. Phys. Lett. 35, 879 (1979)] on small-area, high-current-density junctions. The lumped-circuit-element model of Stewart and McCumber with an adjustable nonlinear quasiparticle conductance and various capacitance values is employed. The value of junction capacitance inferred from the digital simulation for a 10−9-cm2 junction is 9×10−15 F. This represents a normalized capacitance βc = 0.3 for the junction considered, which had a critical current density ≊105 A/cm2. The inferred capacitance is in agreement with the value extrapolated from previous experimental results. Both digital and analog simulations result in I-V curves which show a previously unreported crossing of the quasiparticle and total current curves. This crossing is due to an averaging in time of the voltage across the nonlinear quasiparticle-conductance channel. The crossing is not seen in the experimental results of Howard et al. Differences between the experimental and simulated I-V curves are discussed.
Electroreflectance studies in Cd1−xMnxTe solid solutions
Authors: Bottka N. , Stankiewicz J. , Giriat W.
Published: February 2003

We present electroreflectance (ER) data near the fundamental absorption edge of Cd1−xMnxTe as a function of temperature and Mn content. We show that the observed weak-field ER structure is associated with the screening of excitons by impact-ionization-generated free carriers. Such a phenomenon has never before been observed in mixed crystals at such high temperatures (300 K). From the increased broadening of the ER structure with composition, we conclude that the excitons have a Wannier-like character for x<0.15 and develop a local bound character for x≳0.15, composition at which the system reaches the percolation critical point. The temperature variation of the energy of transition with composition for x?0.15 is not constant and is believed to be a result of mode softening of the lattice with increased Mn content.
Temporal and radial dependence of laser action in a He-Hg pulsed discharge
Authors: Ninomiya H.
Published: February 2003

In a pulsed discharge, the temporal and radial behavior of the population densities of He(2 1S), He(2 3S), Hg(6 3P2), and Hg(6 3P0) is studied experimentally, and the time variation of the intensity of sidelight of Hg II at the 567.7- and 6 15.0-nm lines is also measured with changing He partial pressure. The temporal and radial behavior of the laser action of a Hg ion laser is explained in terms of the temporal and radial behavior of the reactants in the Penning-like excitation process, and furthermore, it is found that the populations of these reactants are dependent upon the distribution of the electron temperature.
Breakdown field strength of SF6, N2O, SF6+N2, and SF6+N2O
Authors: Govinda Raju G. R. , Hackam R.
Published: February 2003

The breakdown voltages of some electron attaching gases and gas mixtures have been calculated from their fundmental properties such as ionization and attachment cross sections, the momentum transfer cross section, the drift velocity or the mean energy of electrons. The calculated breakdown voltages in SF6, N2O, SF6+N2, and SF6+N2O gas mixtures, on the basis of Maxwellian electron energy distribution, agree very well with the measured values. The good agreement between the calculated and measured values shows that the mean energies of electrons in SF6+N2 corresponds to that of SF6 up to 90% concentration of N2 in the mixture, whereas the mean energies of electrons in SF6+N2O mixtures correspond to that of the majority gas.
Compounds in the Pd-Si and Pt-Si system obtained by electron bombardment and post-thermal annealing
Authors: Majni G. , Nava F. , Ottaviani G. , Danna E. , Leggieri G. , Luches A. , Celotti G.
Published: February 2003

Thin Pt, Pd, Pt2 Si, and Pd2Si films deposited on Si were reacted by using electron beam pulses of 60 nsec duration in the 0.4–2.4 J/cm2 energy density range. Irradiaton of Pd/Si structure produces at the same time PdSi, Pd2Si, Pd3Si, and Pd4Si, while PdSi is the only phase observed starting from the Pd2Si/Si structure. Post-thermal annealing of these layers up to 600 °C induces the growth of Pd2Si phase at the expense of the other phases. PdSi seems to be a metastable phase at least up to 600 °C. PtSi, Pt2Si, Pt3Si compounds are formed after irradiation of Pt/Si structure. Post-thermal annealing at 500 °C produces PtSi. A Si-enriched metastable phase Pt2Si3 is present after irradiation of Pt2Si/Si or PtSi/Si structure. Post-thermal annealing at 450 °C produces the growth of Pt2Si3. Further annealing at 500 °C induces the formation of PtSi and Si polycrystal.
Detection of surface and bulk traps
Authors: von Seggern Heinz
Published: February 2003

A method for determining the geometrical surface trap structure of highly insulating polymer films is presented. We compare ’’open-circuit’’ thermally-stimulated current measurements of corona and electron-beam-charged foils. We present the results for three different polymers: polyfluoroethylenepropylene [Teflon (FEP)], polyethyleneterephthalate [Mylar (PET)], and Polyethylene (PE). For Teflon one observes that the surface traps are energetically shallower than the bulk traps, for Mylar no separate surface traps exist whereas for polyethylene the situation is opposite to Teflon. The spatial resolution of the method is 0.5 μm.
Optimum design for window layer thickness of GaAlAs-GaAs heteroface solar cell regarding the effect of reflection loss
Authors: Yoshikawa Akihiko , Kasai Haruo
Published: February 2003

Optimum design for a window layer thickness of GaAlAs-GaAs heteroface solar cell has been performed regarding the effect of reflection loss. It is shown that the GaAlAs layer thickness greatly affects the reflection characteristics of the cell and that there is an optimum thickness for the GaAlAs layer. Thus the GaAlAs layer thickness must be designed so as to minimize the reflection loss, as well as the absorption loss by the window. Optimum thickness for the GaAlAs layer is about 0.03 μm, and the power reflection loss for the cell with optimized double antireflection (AR) coatings is as low as 1.09 % for AM0 solar radiation.
Optical properties of polycrystalline CdTe films
Authors: Myers T. H. , Edwards S. W. , Schetzina J. F.
Published: February 2003

The optical properties of polycrystalline CdTe films prepared using vacuum sublimation techniques are discussed. Refractive index measurements are reported for the wavelength region 450–2000 nm and compared with single-crystal values. Extinction and absorption coefficient measurements are reported for the strong absorption regime (450–900 nm). uv reflectance measurements are also discussed. New structure in the uv reflectance of many of the film samples is attributed to stacking sequence changes which introduce elements of the hexagonal phase. X-ray diffraction results support this conclusion. The reflectance data are analyzed using Birman’s double-zone scheme and yield some information concerning the band structure of hexagonal CdTe.
A molecular dynamics simulation study of the influence of the ion mass upon atom ejection processes
Authors: Harrison Don E.
Published: February 2003

A molecular dynamics simulation has been used to investigate the ion mass dependence of single-crystal atom ejection. Atom yield ratios, surface damage cross sections, atoms ejected per single ion (ASI) distributions, ejected atom energy distributions, layer yield ratios, and multimer yield ratios have been computed for normally incident Ne, Ar, Cu, Kr, and Xe ion masses on Cu targets for two very different Born-Mayer ion-atom potential functions. Results are compared with experimental data where feasible. The sputtering yield is found to increase with the ion size, as fixed by the ion-atom potential function, not with the ion mass. Experimental ejected atom energy distribution functions should show an ion mass dependence at higher atom energies. The layer yield ratios decrease as the ion mass increases. The heavier ions show no increased tendency to eject clumps of material or to create large, deep craters in the target surface. Atoms driven into the target may make a significant contribution to near-surface depleted zones and crater formation. The multimer yield ratios show very little ion mass dependence. ASI distributions and surface layer damage distributions show how momentum changes at constant ion energy affect the sputtering dynamics.
Periodic surface ripples in laser-treated aluminum and their use to determine absorbed power
Authors: Jain Animesh K. , Kulkarni V. N. , Sood D. K. , Uppal J. S.
Published: February 2003

We report the first observation of surface ripples produced on a metal (pure and implanted A1) during pulsed laser treatment (Nd:glass laser in TEM00 mode, λ = 1.06 μm, 7 ns FWHM). Fringes with a characteristic spacing equal to the incident wavelength are readily seen near the periphery of laser spot, over a narrow region, resulting in an accurate delineation of melt threshold. Comparison with the calculated melt threshold leads to determination of the absorbed power. This method to evaluate the absorbed power can be applied to any material exhibiting surface ripples characteristic of melt threshold.
Use of granular NbN as a superconducting bolometer
Authors: Weiser K. , Strom U. , Wolf S. A. , Gubser D. U.
Published: February 2003

An ultrathin film of granular NbN is used as a superconducting bolometer. The bolometer has a high operating temperature (∼12 K), is very sensitive (∼5000 Ω/deg), and exhibits a fast thermal response time, which is estimated to be less than 10−10 sec.
Ferroelectric behavior and phase transition at 715 K in SrAIF5
Authors: Abrahams S. C. , Ravez J. , Simon A. , Chaminade J. P.
Published: February 2003

The atomic arrangement in SrAlF5 determined by von der Mühll, Andersson, and Galy [Acta Cryst. B 27, 2345, (1971)] is shown to be related to a structure of opposite polarity by atomic displacements no greater than about 0.5 Å. Such displacements, which reverse the spontaneous polarization, lead to a predicted ferroelectric-paraelectric phase transition temperature of 685 K and a spontaneous polarization estimated to be in the range 9–48×10−2 C m−2. SrAlF5 is shown to generate second harmonics with an efficiency about that of quartz. The piezoelectric d33 coefficient varies from sample to sample, in the range 0.1<d33<0.8×10−12 C N−1. A specific-heat anomaly is observed at about 695 K with the dielectric constant exhibiting an anomaly at about 715 K. Nine other members of this AIIBIIIF5 family have been identified. The atomic displacements indicate that this is a family of one-dimensional ferroelectrics.
Laser light absorption in multilayers
Authors: Colinge J. P. , Van de Wiele F.
Published: February 2003

A simple model has been derived, which accounts for the optical effects occurring during the laser processing of stacked thin films and determines the power ratio absorbed by each layer. Experimental data provided by the annealing of a Si-SiO2-polysilicon structure are shown to be in good agreement with theory.
Strains and photovoltaic response in Ta-sputtered Si metal-insulator-semiconductor solar cells
Authors: Lalevic B. , Murty K. , Ito T. , Kalman Z. H. , Weissmann S.
Published: February 2003

Deformation by bending of Si or Si-SiO2 wafers was achieved by sputter deposition of tantalum films. Strains induced at Si-SiO2 interface and in Ta films were investigated using a combination of x-ray diffraction, electron diffraction, and transmission electron microscopy. Thin Ta film deposits had predominantly a fcc structure, while thicker films had the normal bcc structure with certain admixture of fcc. Film strains generated by the coexistence of the polymorph structure were accommodated by formation of misfit dislocations at the film-Si substrate interface. The effect of the induced stress on the electronic parameters characterizing the Si-SiO2 interface was studied in the metal-oxide-semiconductor structure and for the effect on photovoltaic response a metal-insulator-semiconductor solar cell configuration was used. Large changes with increasing stress were observed in the values of recombination time, capture cross section, diffusion length, and in sharply decreased conversion efficiency, fill factor, open-circuit voltage, and short-circuit current.
Fabrication of P+-N-N+ silicon solar cells by simultaneous diffusion of boron and phosphorus into silicon through silicon dioxide
Authors: Jain G. C. , Singh S. N. , Kotnala R. K. , Arora N. K.
Published: February 2003

A process of fabrication of P+-N-N+ silicon solar cells by simultaneous diffusion of boron and phosphorus into N-type silicon through a thermally grown silicon dioxide layer ∼0.1 μm thick is described. The inherent problems of cross doping and usefulness of silicon dioxide in minimizing them are briefly discussed. The process is well suited for large-scale production of P+-N-N+ back surface field silicon solar cells. With this process, the cells fabricated from single-crystalline silicon wafers of 100 Ω cm resistivity have shown open-circuit voltages ∼0.6 V at 28 °C under 100 mW/cm2 (AM1) intensity, and the cells fabricated from polycrystalline silicon wafers of 1–2 mm in grain size and 7–27 Ω cm resistivity have shown conversion efficiencies between 10.4 and 11.4% (AM1) at 28 °C.
Electrically-alterable read-only-memory using Si-rich SiO2 injectors and a floating polycrystalline silicon storage layer
Authors: DiMaria D. J. , DeMeyer K. M. , Serrano C. M. , Dong D. W.
Published: February 2003

Currently, electrically-alterable read-only-memory (EAROM) has become increasingly important for memory and logic operations. A novel EAROM device in a field-effect transistor (FET) configuration, which uses a floating polycrystalline silicon (poly-Si) layer on top of thermal SiO2 and a dual electron injector structure (DEIS) between this floating poly-Si and a control gate poly-Si contact, is described. The DEIS stack consists of sequentially chemically vapor deposited (CVD) layers of Si-rich SiO2 (46% atomic Si), SiO2, and Si-rich SiO2 (46% atomic Si) between the poly-Si layers. Electrons from either poly-Si layer can move to the other poly-Si layer biased at the higher voltage with moderate applied voltages. Thus, the floating poly-Si storage layer can be charged with electrons (’’write’’ operation) or with positive charge (’’erase’’ operation) in milliseconds with negative and positive control gate voltages, respectively. The average electric fields in the intervening CVD SiO2 layer during writing and erasing are 5–6 MV /cm and 4–5 MV/cm, respectively, and voltages from ±10 V to ±40 V can be used depending on the device configuration. The enhanced electron injection in these devices is believed to be controlled by localized electric field distortion at the Si-rich SiO2-SiO2 interface caused by the two phase (Si and SiO2) nature of the Si-rich SiO2. The electrical asymmetry of the DEIS is believed to be due to differences in the interfaces of the bottom and top Si-rich SiO2 injectors with the intervening SiO2 layer. At the low voltages used for the ’’read’’ operation in which the charge state of the floating poly-Si layer is sensed by the FET drain current, no read perturb effects are observed. These structures also show excellent charge retention at low voltages, characteristic of a floating poly-Si storage layer surrounded by SiO2. This excellent retention is due to a characteristic of the Si-rich SiO2 in which it builds up a reversible space-charge layer which collapses the field at the interface with the poly-Si layers and minimizes charge loss or further injection. This field screening phenomenon of the Si-rich SiO2 layers also prevents low-voltage breakdowns (which are believed to be due to irregularities in the field at the cathode) from occurring. These DEIS EAROMs operate at lower power due to the small injected SiO2 currents involved and low applied voltages compared to most commercially available devices which use Si junction avalanche injection which requires large Si currents to charge the floating poly-Si storage layer. These devices are capable of being cycled at least 104 times before pronounced threshold-voltage window collapse due to trapped electron space-charge buildup in the intervening CVD SiO2 layer.
Surface-potential decay in insulators with deep traps
Authors: Campos M. , Giacometti J. A.
Published: February 2003

Surface-potential decay characteristics of corona-charged insulators are analyzed theoretically using a theory developed before by Rudenko. It was assumed that the charges are deposited in the surface of the insulator by a short corona pulse and that some amount of charge is instantaneously injected in the bulk of material. An analytical treatment of the standard transport equations in the presence of traps is presented. The model assumed for the traps is one in which they can be characterized by a single trapping time; liberation from traps was neglected, and also it was assumed that the traps are far from fully occupied. Using the theory it was possible to explain the fast decay of surface potential after a negative corona discharge in naphthalene single crystals. The value found for the trap-modulated mobility at room temperature was 10−8cm2 V−1 s−1 and 110 s for the trapping time used as a parameter. With measurements of thermally stimulated currents, it was possible to find two sets of traps with activation energies of 0.6 and 1.2 eV.
Surface topography and alignment of liquid crystals on rubbed oxide surfaces
Authors: Nakamura Minoru
Published: February 2003

For several nematic liquid crystals (LC’s), the relation between alignments of the LC’s on rubbed oxide surfaces and rubbing pressures of the substrates is given. When the LC’s take a parallel alignment to the surfaces, good homogeneous alignment is achieved at low pressures. High pressure rubbing also produces good homogeneous alignment of LC’s, although alignment is perpendicular to the nonrubbed surfaces. Fine stripes of deposited cloth fibers can be observed on the cloth-rubbed oxide surfaces. The stripes consist of asymmetric projections ranging in the rubbed direction. On the basis of the asymmetric structure formed on the surface, the tilt direction of LC’s and their tilt angles are interpreted.
Evidence for 4f-shell delocalization in praseodymium under pressure
Authors: Mao H. K. , Hazen R. M. , Bell P. M. , Wittig J.
Published: February 2003

Praseodymium metal undergoes a crystallographic phase transformation from a distorted fcc lattice to a distorted hcp structure at a pressure of ≃210 kbar. The phase change is accompanied by a large volume decrease of ≃19%. This decrease is analogous to the volume collapse at the γ-α transition in cerium and thus provides strong evidence for a delocalization of the 4 f2 configuration into a 4f conduction band.
Surface Mössbauer analysis of 38NCD4 steel ion implanted with nitrogen
Authors: Carbucicchio M. , Bardani L. , Tosto S.
Published: February 2003

Surface Mössbauer measurements have been carried out for 38NCD4 steel samples, ion implanted with nitrogen at different doses and currents. It has been found that Fe-N compounds form in a wide range of compositions as aggregates in the steel matrix: from the unaffected base metal to the external surface, steel layers follow one upon the other in which first Fe2+yN with 0.3 ⩽ y < 2.7, then Fe2+xN with 0 ⩽x < 0.3, and finally austenite containing ∼10 at. % nitrogen, predominantly form. Dose decrease decreases the thickness of the above layers, while current variations produce differences in the relative amounts of the various Fe-N compounds.
The surface energy of Si, GaAs, and GaP
Authors: Messmer C. , Bilello J. C.
Published: February 2003

The surface energy of various planes in Si, GaAs, and GaP was measured by the use of a modified spark discharge method, previously used successfully in metals. Surface energy values were determined for the following cleavage planes in these crystals: Si {111}∼1.14 J/m2, Si {110}∼1.9 J/m2, GaAs {110}∼0.86 J/m2, and GaP {110}∼1.9 J/m2. The Si surface energy value was compared with previous experimental measurements. The Si {110}, GaAs {110}, and GaP {110} values were compared only to theoretical estimations, since as far as it is known, the surface energy of these planes have never been measured experimentally. Berg-Barrett x-ray topography and chemical etch pit analysis verified that plastic relaxation did not occur under the test conditions used. The cleavage surface energies determined in this work were in good agreement with previous theoretical estimations. Experimental observations confirmed a lack of plastic energy dissipation and a stability of cleavage propagation which indicated that the measured surface energies were close to the intrinsic values.
Analysis of symmetrical Hall plates with finite contacts
Authors: Versnel W.
Published: February 2003

Hall plates with four equal edge contacts of nonzero lengths, which are invariant for a rotation through 90°, are considered. Analytical formulas for Hall voltage and the Hall mobility, in which the finiteness of the contacts and the magnetic field are taken into account, have been obtained. The numerical calculations involved can be reduced to those of regular integrals. In addition, for a number of symmetrical shapes of Hall plates simple approximations have been derived for the product μB of Hall mobility and magnetic induction. The maximum length is calculated of each contact, for which these approximations are accurate to within 0.5% compared to exact solutions. Numerical data are tabulated in a directly applicable form.
Brillouin instability in longitudinally magnetized n-type piezoelectric semiconductors
Authors: Ghosh S.
Published: February 2003

Stimulated Brillouin scattering of a plane polarized intense electromagentic wave propagating parallel to the applied magnetic field has been investigated analytically in an n-type piezoelectric semiconductor plasma. The general dispersion relation has been obtained and solved for both the cases of scattered electromagnetic waves (i.e., in the cases of left-hand and right-hand circularly polarized waves) to study the threshold condition and the growth rate of the unstable Brillouin mode at a pump amplitude well above the threshold. The relevant experiment has not been reported. Numerical estimates have been made for n-type InSb at 77 K irradiated with a pulsed 10.6-μm CO2 laser to obtain the necessary electric field. The threshold electric field is independent of applied magnetic field, and the growth rate of the unstable Brillouin mode has linear dependence on the magnetic field.
Photocurrent conversion efficiency in a Schottky barrier
Authors: Jarrett H. S.
Published: February 2003

The diffusion equation for an illuminated Schottky barrier is solved for a finite lifetime of photoinjected minority carriers within the barrier. The general solutions are related to parabolic cylinder functions when diffusivity and mobility are constant. These solutions are subject to the usual boundary conditions that at the surface the minority carrier current is proportional to the carrier density and that at the barrier/bulk interface the carrier density and its gradient are continuous. The photoconversion efficiency for a given impurity concentration is completely defined by three parameters: the charge transfer rate at the surface, the optical absorptivity, and the carrier lifetime. These calculations are applicable to many of the oxide semiconductors used as anodes in photoelectrolysis.
Active mode locking of double heterostructure lasers in an external cavity
Authors: van der Ziel J. P.
Published: February 2003

Proton bombarded stripe geometry lasers have been actively mode locked in an external cavity consisting of a lens, a Fabry-Perot etalon, and a mirror. Under optimized conditions, pulses as short as 5.3 psec have been observed from measurement of the second harmonic autocorrelation function. The dependence of the pulse width on external parameters was studied in detail. The pulse width t1/2 decreases with increasing direct current. The functional dependence of the pulse width on current indicates that a saturable absorption mechanism is present in the laser which causes significant pulse shortening. The pulse width decreases with increasing rf current. The pulse width is a sensitive function of the frequency detuning of the applied rf current. The shortest pulses are observed when the applied frequency is less than the round trip frequency of the pulse in the cavity. The frequency dependence of the pulse width was obtained using a long cavity with multiple pulses in the cavity. The shortest pulses occur between 0.9 and 1.4 GHz. The Fabry-Perot etalon limits the emission to a 1.9-Å spectral band. At optimum mode locking the band is ∼30 Å below the peak of the multimode emission obtained without the etalon. The shift of the gain curve to lower enery indicates that additional loss is introduced by the feedback from the external cavity. The experimental results are shown to be in good agreement with a theoretical description of mode locking.
GaAs/AlGaAs distributed feedback-transverse junction stripe laser using a hybrid liquid phase epitaxy/metal-organic chemical vapor deposition growth technique
Authors: Kawanishi H. , Hafich M. J. , Skogman R. A. , Lenz B. S. , Petersen P. E.
Published: February 2003

Room-temperature operation was obtained in a new transverse junction stripe laser with distributed feedback. The wafers were grown by a liquid phase epitaxy/metal-organic chemical vapor deposition (LPE/MO-CVD) hybrid technique. These lasers operated stably in a single longitudinal mode at room temperature under pulsed operation. The temperature dependence of lasing wavelength was dλ/dT = 0.63 Å/°C.
The distorted wave Born approximation: Application to elastodynamics
Authors: Newman K. E. , Teitel S. , Domany E.
Published: February 2003

An approximate theory for scattering of elastic waves by general shaped defects has been developed. A defect of arbitrary shape can be represented by a sphere S and a remainder volume R̄. Using the exact solution for a sphere and treating R̄ as a perturbation, the solution corresponding to the distorted wave Born approximation is obtained. This solution contains nontrivial frequency dependence and phase information. Preliminary comparisons with experiments are presented.
A hollow cathode for doppler-free spectroscopy
Authors: Lawler J. E. , Siegel A. , Couillaud B. , Hänsch T. W.
Published: February 2003

We report the design criteria and performance characteristics of a hollow cathode discharge tube developed especially for high-resolution Doppler-free laser spectroscopy. The cathode has a large bore diameter (2.7 cm) and operates at a relatively low pressure (0.5 Torr of Ar). Very narrow homogeneous linewidths of refractory element transitions have been observed using this device. It is simple to construct, is easily demountable, and requires a small amount of sample material.
Cr3+ sensitized Nd3+: Li-La-phosphate glass laser
Authors: Härig T , Huber G. , Shcherbakov I. A.
Published: February 2003

Room-temperature quasi cw lasing at 1.06 μm was obtained in Li-(La1−x−yNdxCry) -phosphate glass. Thresholds as low as 1 mW and slope efficiencies up to 18% have been measured. Cross pumping of Nd3+ (x = 0.3) via Cr3+ (y = 0.03) yields a transfer efficiency of 0.45. For broadband pump sources, the spectral factor of merit (2.3) raises the slope efficiency over those of Nd3+-only doped laser glasses.
Spectral dependence of the change in refractive index due to carrier injection in GaAs lasers
Authors: Henry C. H. , Logan R. A. , Bertness K. A.
Published: February 2003

The refractive index change caused by changes in the absorption edge of GaAs is determined by analysis of the spontaneous emission spectrum of a buried heterostructure window laser. The spontaneous emission spectrum is converted to a gain spectrum from which changes in the imaginary part of the refractive index can be calculated as the laser is excited from low current up to threshold. The real change in refractive index is then determined by a Kramers-Kronig transformation. The change in refractive index n′ of the GaAs active layer is slightly sublinear with minority carrier density nc. At the laser line, including the calculated contribution of free carriers, Δn′ = −0.025±0.005 and dn′/dnc = −(1.8±0.4)×10−20 cm3 in lasers with carrier densities at threshold estimated as 1.02×1018 cm−3. Near threshold, the ratio of the change in the real index to the change in the imaginary index is about 6.2.
Bounds on the complex permittivity of a two-component composite material
Authors: Milton G. W.
Published: February 2003

A generalization of the bounds obtained by Wiener, Hashin and Shtrikman, and others is derived for complex permittivities. Provided the scale of inhomogeneities in the composite is sufficiently small compared with the wavelength of the applied radiation, the permittivity of the composite is found to lie within a simply constructed region of complex plane. The appropriate region depends on what is known about the composite material. We show that in many cases the region is the most restrictive which can be given, using limited information about the structure of the composite.