bluuebunny/crossref_metadata_2025 huggingface dataset:
Potential of Ultra-High Resolution and Low Voltage Sem for Dynamic Experiments
Authors: Boyes E D
Published: April 2011

A new generation of ultrahigh resolution scanning electron microscope (UHRSEM) is designed to explore the potential for higher resolution imaging and chemical microanalysis from more representative bulk samples. A <0.5nm probe at 30kV and <2.5nm at 1kV have been integrated with high sensitivity energy dispersive x-ray spectrometry (EDX) [1] and a high vacuum (<3×10−8mbar) heating stage (to >1000°C). The sensitivity of surface imaging is generally enhanced at low beam energies. With low voltages and digitally integrated fast scan techniques, conductive coating of an electrically non-conducting sample, such as a ceramic substrate, is no longer a pre-requisite for SEM, and this opens up new possibilities for minimally invasive dynamic in-situ experiments. This paper focuses on metal particle migration and sintering on a ceramic substrate.
Kinetic Study of the Passive Film on 304 Stainless Steel Using a Scanning Tunneling Microscope
Authors: McKrell T. J. , Galligan J. M.
Published: April 2011

The unique capability of the scanning tunneling microscope, STM, for in situ nanoscale electronic measurements has been utilized to establish the nature of the oxide film on 304 stainless steel under HCI, distilled water, and in air. New insights were obtained concerning the kinetics and electronic surface states of the oxide film as a function of exposure time to these environments: quantitative measurements of the corrosion behavior and the stability of the oxide film, as related to observed defects, have been obtained. These findings have resulted in a model which incorporates these new insights with previously established theories concerning oxidized surfaces.
Dynamic Observation of Vortices in Superconductors Using Electron Waves
Authors: Tonomura A.
Published: April 2011

Individual vortices in superconductors were directly and even dynamically observed by using a “coherent” field emission electron beam. Magnetic lines of force of vortices were quantitatively observed in a holographic interference micrograph and their dynamics were observed by Lorentz microscopy. The interaction of vortices with both line- and point-defects was investigated by direct observation.
Localization Phenomena, Photoluminescence and Raman Scattering in nc-Si and nc-Si/a-SiO2 Composites
Authors: veprek S. , Wirschem T. , Rückschloβ M. , Ossadnik C. , Dian J. , Perna S. , Gregora I.
Published: April 2011

We present evidence for the large increase of the band gap due to the quantum localization in nc-Si imbedded in a-SiO2 matrix, which is in agreement with the original theoretical calculations. This, together with additional experimental data explains the large red shift between the onset of the excitation spectra and the photoluminescence. This also provides strong support for the mechanism of the photoluminescence which originates from radiative centers either at the Si/SiO2 interface or within the SiO2 matrix. The strong decrease of the efficiency of the photoluminescence due to a decrease of the thickness of the a-SiO2 grain boundaries is shown and its origin discussed. Delocalization of the photogenerated charge carriers due to ultra thin a-SiO2 is excluded as the cause of this effect. Microwave absorption is used to study the effect of the grain boundaries on the localization and delocalization of photogenerated charge carriers in pure nc-Si together with concomitant phenomena observed in Raman scattering. Finally we show the strong decrease of the photoluminescence decay time to ≤ 500 ps due to molecular-like radiative centers which are formed in the nc-Si/SiO2 composites by appropriate doping.
Towards a Microscopic Interpretation of the Dielectric Function of Porous Silicon
Authors: Rossow U. , Frotscher U. , Aspnes D. E. , Richter W.
Published: April 2011

The dielectric function of porous silicon layers depends strongly on the electronic properties of the nanostructure of the silicon skeleton. In this paper we discuss the main effects, as determined from spectroscopic ellipsometric measurements of the dielectric function of porous layers formed on p-doped material. Finite-size effects and the high inner surface area of the nanostructure lead to relaxation of k-momentum conservation as defined for infinite crystals and therefore to a broadening of the features in <ε> arising from interband critical points. In addition a small threshold energy shift is observed when the percolation of the structure is reduced. However, this shift is too small to explain red photoluminescence as a consequence of a pseudo-direct gap whose energy is blue-shifted by confinement.
Photoluminescence Properties of Er-Doped Porous Silicon
Authors: Hömmerich U. , Wu X. , Namavar F. , Cremins-Costa A. M. , Bray K. L.
Published: April 2011

We present a photoluminescence study of erbium implanted into porous silicon (Er:PSi) with two different Si porosities, a) Er:PSi with a purple appearance and b) with a green-yellow appearance. Er was implanted with a dose of 1×1015 Er/cm2 at 380 keV and annealed at 650°C for 30 minutes. Room-temperature 1.54μm Er3+ emission was observed from both samples. The emission from purple Er:PSi was four times stronger than that from green-yellow Er:PSi. In contrast, visible luminescence from green-yellow Er:PSi was found to be stronger than that from purple Er:PSi. Temperature quenching and power dependence was investigated to elucidate the excitation mechanisms of Er3+ in porous silicon. The results support a correlation between nanostructures of porous Si and 1.54 μm Er3+ luminescence.
Carrier Transport in Silicon Nanocrystallite-Based Multilayer Electroluminescent Devices
Authors: Burr T. A. , Kolenbrander K. D.
Published: April 2011

The electrical and optical properties of light emitting devices employing silicon nanocrystallites as the active material have been studied. Thin films of silicon nanocrystallites were deposited using a pulsed laser ablation supersonic expansion technique. In order to explore their potential for optoelectronic applications, these films have been incorporated into multilayer light emitting devices, using polymer carrier transport layers to enhance their efficiency. Device performance has been found to be weakly temperature dependent, but strongly dependent on the electrical transport properties of the material and the carrier injection mechanisms at the nanocrystal/electrode interface. A systematic study of simple electrode/nanocrystallite/electrode heterostructures has demonstrated that the electrode material and polarity of the applied bias control whether the devices operate in the interface limited or carrier transport limited regimes.
Control of Silicon Nanocrystallite Luminescence Behavior Through Surface Treatments
Authors: Seraphin A. A. , Ngiam S.-T. , Kolenbrander K. D.
Published: April 2011

The visible photoluminescence from thin films of silicon nanocrystallites produced by a pulsed laser ablation supersonic expansion source has been studied to determine the role of particle surface and size in the emission behavior. Variation of nanocrystallite size and surface through a variety of chemical treatments and processing steps has shown that the visible emission can be explained using only a simple quantum confinement model. Particle size has been reduced through a series of acid etch and reoxidation cycles and compared to sample emission wavelength. The role of surface species in determining emission behavior has been studied by chemically altering the surfaces and comparing their surface properties as determined by x-ray photoelectron spectroscopy to their photoluminescence behavior. Nanocrystallite size controls the emission energy, while surface passivation only determines emission intensity, through control of excited carrier recombination pathways.
Theoretical Modelling of the Surface Oxidation of a Silicon Carbide Nanopowder, Based on the v(SiH) Frequency Evolution
Authors: Baraton Marie-Isabelle , Besnainou Sylvette
Published: April 2011

Due to hydrolysis by atmospheric water, the first atomic layer of silicon carbide contains oxygen atoms. The oxygen content on the surface dramatically increases for nanosized SiC powder and strongly affects the overall properties. The presence of SiH groups on the SiC surface, already proven by Fourier transform infrared spectrometry, can be used to investigate the oxidation mechanism. Indeed, the v(SiH) stretching frequency known to strongly depend on the surrounding electronegativity of the silicon atom is directly related to the oxidation degree. Based on our infrared spectroscopic experimental data, ab initio calculations were performed on models representing the SiH surface species in different environments. Using the Hartree-Fock method with 3–21G and 6–31G basis sets, the v(SiH) frequencies were calculated for each model versus the number of substituted oxygen atoms. The comparison with the experimental values led to a discussion of our proposed models and of the SiC surface oxidation mechanism.
Interfacial Defect Control for Infrared Conversion Widening of Silicon Single-Crystal Solar Cells
Authors: Kuznicki Z. T.
Published: April 2011

A multi-interface solar cell design exploiting the parts of solar spectrum heretofore never converted by single-crystal silicon devices seems to be possible with local material modifications combined with a superimposition of hetero-interface transition zones. Possible structural modifications by implantation of a silicon single-crystal target causes a series of “secondary” effects of basic importance from the photovoltaic conversion point of view. The 1800 nm divacancy infrared band activity has revealed totally unknown behavior in the built-in strain field of the inserted α-Si/c-Si hetero-interface. First, even an annealing temperature of 770 K is not enough to quench the divacancy absorption. Next, the elimination of useful band-tail and useless divacancy activities is not coincident, i.e. divacancy absorption can be quenched without too much reduction of the band-tail activity. A relatively important infrared current could be observed experimentally up to 2500 nm and by extrapolation up to about 3500 nm.
Transmission Electron Diffraction Techniques for Nm Scale Strain Measurement in Semiconductors
Authors: Vanhellemont J. , Janssens K. G. F. , Frabboni S. , Smeys P. , Balboni R. , Armigliato A.
Published: April 2011

An overview is given of transmission electron microscopy techniques to address strain with nm scale spatial resolution. In particular the possibilities and limitations of (large angle) convergent beam electron diffraction ((LA)CBED) and electron diffraction contrast imaging (EDCI) techniques are discussed in detail. It will be shown by a few case studies that unique and quantitative information on local strain distributions can be obtained by the combined use of both (LA)CBED and EDCI in correlation with three dimensional finite element simulations of the strain distributions in the thinned specimen.
Analysis of Localized Small Defect in ULSIs
Authors: Fukumoto K. , Maeda H. , Mashiko Y. , Sekine M. , Koyama H.
Published: April 2011

The current leakage generated in a localized area that creates a more serious problem to the ULSI devices was investigated. To clarify the origin of such a current leakage generated at a localized small area, an evaluation technique with a high spatial resolution, high sensitivity and a precise positioning is demanded. We have developed the planar point TEM(Transmission Electron Microscope) technique to enable the structure analysis of a localized small area in ULSI devices. Using this technique and AEM(Analytical Electron Microscope), we revealed one cause of current leakage at a small area in a memory device. It was found that one origin of such leakage is caused by heavy metal precipitation on the localized dislocation. The origin of this dislocation generation is a combination of effects from the crystalline damage during the formation of the oxide sidewall spacer by dry etching and the stresses from the oxide sidewall spacer and the field oxide.
Nanocrystallization Studies in Co and Fe-Rich Amorphous Alloys
Authors: Aburto S. , Jiménez M. , Gómez R. , Marquina V. , Marquina M. L. , Ridaura R. , Santiago P. , Rendon L. , Valenzuela R.
Published: April 2011

Nanocrystallization from Metglas® 2605 SC and Vitrovac® amorphous ribbons were studied by Mössbauer spectroscopy, transmission electron microscopy and differential scanning calorimetry. The spectra showed spin texture. The relative intensities change to a random distribution of spin orientation. New lines appear indicating new magnetic phases. TEM and DSC observations confirmed the crystallization of nanostructured grains.
Evaluation Of Reaction Dynamics Of Film Depositions In Plasma Cvds By Using A Remote Plasma Cvd System
Authors: Wickramanayaka S. , Kitamura K. , Nakanishi Y. , Hatanaka Y.
Published: April 2011

detailed study was carried out in investigating the chemical reaction scheme involved with the deposition of a-SiC:H films by carbosilane sources in a remote hydrogen plasma. As the carbosilane sources, tetramethylsilane (TMS), hexamethyldisilane (HMDS) and tetrakis(trimethylsilyl)silane (TMSS) were used. Depositions were performed in the presence and absence of both UV radiation and H radicals. UV radiation activates only the TMS molecules out of the above three types of molecules in depositing a-SiC:H films. Other two monomers are seen to be activated by hydrogen radicals. It is proposed that the most susceptible bond to be broken at first by hydrogen radical is the Si-Si bond. A reaction model for the formation of a- SiC:H films was presented by considering the Me2Si=CH2 as the film forming precursor.
Diagnostics And Control Of High-Density Etching Plasmas
Authors: Sugai H. , Nakamura K. , Ahn T. H. , Nakamur M.
Published: April 2011

Advanced diagnostics of high-density inductively coupled plasmas (ICPs) are presented supporting the following three proposals of innovative etching modes: First, pulsed plasma etching mode can suppress charge-up on high-aspect-ratio micro-patterns. In order to understand the mechanism, time-resolved measurements of electrons, chlorine atoms and negative ions in a pulsed chlorine ICP are performed. As a result of electron cooling and negative ion yield in afterglow, electrons are found to be accelerated toward a rf-biased electrode, thus neutralizing positive surface charges on that. Second, downstream etching mode using C4F8 gas enables high etch selectivity of SiO2 to Si. The reason for this is qualitatively discussed using comprehensive measurements of spatial distributions of CF3, CF2, CF and F densities in CF4 and C4F8 plasmas. Third, hot wall etching mode also enables high selectibity etching in fluorocarbon plasmas. Radical diagnostics reveal that wall heating dramatically modifies the radical composition of both CF4 and C4F8 plasmas, and it improves the etch selectivity and reproducibility.
Characterization of Materials and Devices by Near-Field Scanning Optical Microscopy
Authors: Goldberg B. B. , Ghaemi H. F. , Ünlü M. S. , Herzog W. D.
Published: April 2011

Near field scanning optical microscopy (NSOM) is a recent technique where a tapered single-mode optical fiber probe is scanned over a sample surface at a height of a fraction of the wavelength. The tapered fiber provides a tiny aperture (a, ˜ 70nm) through which light is coupled and can yield resolutions as high as ˜, λ/40. We have used both room and low-temperature NSOM to study the local spectroscopic characteristics of a wide variety of material systems, from quantum dots and wires, to ordered GaInP, to heterojunctions and optoelectronic devices.

Low temperature near-field photoluminescence spectroscopy was used to study spectral emission maps of a set of samples of GaInP epilayers with varying degrees of ordering. The samples exhibit two peaks, a low energy (LE) and a high energy (HE) peak. Our data are inconsistent with expectations that the LE peak is due to emission from domain boundaries and alternative models will be discussed. NSOM spectral maps can yield information about the spatial dependence of the local optical matrix elements. NSOM data on the emission mode structure of strained (In, Ga)As quantum well lasers has yielded new information on the source kinks in the light response at high currents, while local photocurrent spectroscopy using the tip as a point source of photons provides analysis of the semiconductor layer composition.
Lineshape Analysis of Intersubband Transitions in Multiple Quantum Wells
Authors: Gumbs G.
Published: April 2011

Conduction intersubband transitions between the ground and first excited states in Al0.3Ga0.7As/GaAs multiple quantum wells (MQWs) are studied as a function of the twodimensional electron gas density (0.75 × 1012 ≤ σ ≤ 3.75 × 1012 cm−2) and temperature (5 ≤ T ≤ 300 K). There is no electron tunneling between the wells and well regions are uniformly doped with silicon donors. Theoretically, we have solved the Schrödinger equation containing the self-consistent Hartree potential, in which the z-dependencies of both electron effective mass and dielectric constant, as well as the non-parabolicity in the conduction energy subband dispersion have been taken into consideration. By applying many-body theory which includes the depolarization-shift from a collective dipole moment and the excitonicshift from the negative exchange interaction, we calculate the absorption spectrum as a function of the incident photon energy hw for different values of T and σ. From this, we can quantitatively analyze both T- and σ-dependencies of the peak position and the full width at half-maximum (FWHM) of peak values. The blue-shift or red-shift in the absorption peak position are quantitatively reproduced as either T or σ is reduced. The exchange interaction which depends on σ, will modify the energy subband dispersion. Therefore, the absorption peak will be broadened by the exchange interaction. The T-dependence of broadening from the optical-phonon scattering is also taken into account by a phenomenological model. From the calculated absorption spectrum as a function of o, we have successfully reproduced and explained the σ-dependence of FWHM measured in recent experiments.
Reflectivity Difference Spectra of GaAs and ZnSe (100) Surfaces
Authors: Kim C. C. , Sivananthan S.
Published: April 2011

Using a photoelastic modulator in the optical-bridge configuration, the reflectivity difference was obtained for GaAs and ZnSe (100) surfaces over the photon energy range from 1.5 eV to 6 eV with various azimuthal orientations of the surface. The RD data of GaAs (100) are similar to previously reported data. The RD data of ZnSe (100) are larger by an order of magnitude than those of GaAs (100), possibly due to the larger ionicity of Zn and Se atoms. The distinctive critical point structures and interference patterns shown in the RD spectra of ZnSe (100) suggest that the data, if obtained in real time, could be used to determine the alloy composition, thickness and temperature during growth. The RD data are analyzed using models proposed by Aspnes. The results indicate that the major contribution to the RD spectra of ZnSe (100) are from the surface local field unlike the RD spectra of GaAs (110), whose major contribution is from the bulk spatial distribution.
Optical and Electrical Characterisation of Plasma Processed N-GaAs
Authors: Murtagh M. , Herbert P. A. F. , Kelly P. V. , Crean G. M.
Published: April 2011

A Photoreflectance (PR), Photoluminescence (PL), Raman scattering and Ellipsometry optical characterisation study of He and SiCl4 reactive ion etched 1018cm−3 n-type GaAs is presented. Ellipsometric and PL data reveal significant modifications to the GaAs substrates for the He plasma as a function of etch power and etch gas pressure. Raman data reveal an increase in the depletion depth while the surface electric field data, extracted from PR spectra, decrease with etch severity. This is accounted for by a plasma etch induced decrease in the near surface net carrier density. Ellipsometric and PL measurements of SiCl4 etching reveal evidence of an improvement in the GaAs surface crystallinity while PR and Raman data are consistent with an increase in the surface carrier concentration. Optical characterisation data are correlated with electrical measurements using capacitance-voltage profiling.
Closed-Loop Thickness Control of Resonant-Tunneling Diode Mbe Growth Using Spectroscopic Ellipsometry
Authors: Celii F. G. , Kao Y.-C. , Moise T. S. , Woolsey M. , Harton T. B. , Haberman K.
Published: April 2011

The room temperature electrical characteristics of AlAs/InGaAs/InAs resonant-tunneling diode (RTD) devices are sensitive to sub-monolayer thickness changes, and present a challenging case for closed-loop control. We prepared stacked RTD structures by MBE in which the strained AlAs barrier thicknesses were controlled based on an in situ spectroscopic ellipsometry (SE) system. The short-term and long-term reproducibility of RTDs grown under SE-based control was compared with similar samples grown by “dead-reckoning” (timing-based shutter openings coupled with pre-growth flux calibrations). SE-based calibration can compensate for long-term flux drift, but closed-loop thickness control did not provide a significant improvement over deadreckoning in terms of short-term RTD reproducibility.
Spectroscopic Ellipsometry of Strained Si/Ge Superlattices Grown by Magnetron Sputter Epitaxy
Authors: Guizzetti G. , Patrini M. , Sutter P. , Känel H. Von
Published: April 2011

Spectroscopic ellipsometry was used to characterize several short-period SimGen strained superlattices grown on Si(100) substrates or on graded SixGel-x alloy buffers (strainsymmetrization) by magnetron sputter epitaxy, a novel technique with potential application to industry-scale production of epitaxial Si/Ge heterostructures. Ellipsometric spectra were analyzed within a multilayer model, which included an oxide overlayer, in order to derive the effective dielectric fimctions of the SLs. spectra cannot be simulated by a sequence of Ge+Si slabs and compared to those of the compositionally equivalent alloys showed noticeable differences which can be ascribed to a combination of strain and confinement effects. The results agree with experimental findings and theoretical predictions on analogous SLs grown by MBE, thus confirming the reliability of the used technique to produce good quality SLs.
Optical Characterization of AlxGal-xsb/GaSb Epitaxial Layers
Authors: Lernia S. Di , Geddo M. , Guizzetti G. , Patrini M. , Bosacchi A. , Franchi S. , Magnaninia R.
Published: April 2011

Spectroscopic ellipsometry from 1.4 to 5 eV was used to systematically characterize epitaxial heterostructures AlxGa1-xSb/GaSb for different x concentrations (x≤0.5). The structures were grown by MBE at temperatures and beam equivalent pressure ratios which optimize their lowtemperature photoluminescence properties. Complex dielectric functions of AlxGa1-xSb versus x were derived, for the first time, from the ellipsometric spectra after mathematically removing the oxide overlayer effects. The spectra were analyzed with their second energyderivatives in term of standard analytical lineshapes: in particular the El, E1+Δ1 and E2 critical point energies, broadening and amplitude parameters were derived as a function of x. On this basis we verified that the energy-shift model is appropriate to interpolate for any x≤0.5, thus allowing a nondestructive optical diagnostic of layer thickness and composition of epitaxial heterostructures based on A1xGa1-xSb.
High Performance Of Gettering In Hydrogen Annealed Wafer
Authors: Takeda Ryuji , Hayashi Kenro , Tokuoka Fumio
Published: April 2011

This paper reports on the study of the gettering of nickel contamination in hydrogen annealed CZ-silicon wafers by using method of wet chemical analysis. According to the wet chemical analysis, we believe that the hydrogen annealed wafer is of high quality in the region beneath the surface (DZ) and has a higher gettering ability for nickel compared with conventional CZ wafers. This observation is also in agreement with our MOS C-t measurements.
High Density Plasma Diagnostics For Predictive Model Development
Authors: Eddy C. R. , Douglass S. R.
Published: April 2011

High density plasmas are being increasingly employed in both the deposition of low temperature, high quality passivant films and for highly anisotropic, nanometer-scale pattern transfer. The high degree of control necessary in these processes emphasizes the need for a more complete understanding of the basic physical and chemical mechanisms involved. To this end, a wide range of diagnostic techniques have been employed to characterize electron cyclotron resonance microwave plasmas applied to the etching of semiconductors in both chlorine- and methane-based chemistries. In particular, vacuum ultraviolet spectroscopy has been employed to identify important reactants and, where feasible, measure plasma constituent temperatures (e.g., neutral temperatures range from 0.1–0.3 eV in these plasmas). Langmuir probes, microwave interferometry and microwave electric field probes are used to monitor plasma parameters as a function of process conditions and provide understanding of microwave power deposition. Mass spectroscopy is utilized to characterize the plasma flux incident on the substrate, in terms of mass signature and charge state distribution. This flux is largely ionic with a considerable degree of dissociation, highly appropriate for directional etching. Results from each of these diagnostics are incorporated into an evolving predictive model for highly anisotropic, nanometer-scale etching of semiconductors.
Characterization Of ZnGe(AsxP1-x)2 Crystals By Electrolyte Electroreflectance Spectroscopy
Authors: Angelov Mirko , Goldhahn Rüdiger , Nennewitz Olaf , Schün Silke
Published: April 2011

The influence of the material composition on the optical properties of the quaternary compound semiconductor system ZnGe(AsxP1-x)2 was studied for the first time. The crystals have been synthesized by direct solidification from a stoichiometric melt. X-ray diffraction measurements revealed a chalcopyrite type lattice for the quaternary compound. Closer examination by energy dispersive X-ray microprobe analysis yielded the exact element concentrations for the As and P components. Then electrolyte electroreflectance (EER) spectroscopy was used to determine the energies of the fundamental optical transitions as a function of the composition x. The analysis shows an approximately linear increase of the direct band gap with decreasing As content.

Furthermore, the influence of the composition on the splitting and ordering of the three highest valence bands was investigated by polarization dependent EER measurements. The spectra for two samples with x = 0.42 and 0.77 allowed the determination of the spin orbit parameter Aso and the crystal field parameter Δ;cf by using the quasicubic model. The values were found close to calculated ones, obtained by the same model under the assumption of a precise linear dependence of the band gap on the composition x.
Hydrogen Assisted Remote Plasma Enhanced Chemical Vapor Deposition of Amorphous Silicon Nitride Films
Authors: Santos-Filho P. , Koh K. , Stevens G. , Lucovsky G.
Published: April 2011

We show that in the RPECVD process the addition of a small upstream flow of H2 gas, combined with the He injected into the plasma region of the reactor, promotes chemical exchange between H and D when the material was deposited from deuterated Silane and ammonia and densifies the a- Si:N:H network. We have deposited hydrogenated stoichiometric nitrides with and without H2 injected into the plasma region. For small H2 flows, the deuterated samples show Fourier transform infrared (FTIR) N-D and N-H stretching and bending modes that interchange their populations, as the total bonded hydrogen content in the films remain constant. The hydrogen assisted grown films show, for small H2 flows, a constant amount of bonded-H, an optical index of refraction n=1.85, and reduced etch rate.
Precision of Non-invasive Temperature Measurement by Diffuse Reflectance Spectroscopy
Authors: Wang Zhongze , Kwan Siu L. , Pearsall T. P. , Booth James , Beard Barrett T. , Johnson Shane R.
Published: April 2011

We demonstrate the use of diffuse reflectance spectroscopy as a non-invasive probe for measurement of temperature in real time on Si and GaAs substrates during semiconductor processing. Our results show that the standard deviation of the non-invasive optical technique is less than 0.7 °C for GaAs over the temperature range 50 °C < T< 600 °C with 5-second updates. These results support the notion that non-invasive optical temperature measurement can be used in semiconductor processing with a precision exceeding that of a thermocouple.
An Extended Kalman Filter Based Method for Fast In-Situ Etch Rate Measurements
Authors: Vincent T. L. , Khargonekar P. P. , Terry F. L.
Published: April 2011

The goal of this paper is the presentation of a new algorithm for determining etch rate from single or multiple wavelength reflectometry data. This algorithm is based on techniques from recursive nonlinear estimation theory — Extended Kalman Filtering. A major advantage of our algorithm is extremely high speed. Consequently, it can be used in real-time feedback control applications. The speed advantage also makes it a suitable candidate for full wafer high speed etch rate measurement.
Anomalous Kinetics of the Trapping Reaction in One Dimension Under Steady State Conditions
Authors: Lin Anna L. , Kopelman Raoul
Published: April 2011

We study the A + B→B trapping reaction under steady state conditions for the case in which both A particles and traps(B) are mobile. Using Monte Carlo simulations, we follow the kinetic rate law in one dimension. Anomalies arise due to self-organization of the A particles, which results in a slower steady state reaction rate than is predicted classically. We find a partial order of reaction with respect to trap density of X = 2, and an overall order for the reaction of Z = 3.2. These results are in agreement with other works which predict an exponential rather than an algebraic decay law with respect to the A particle density.
Dynamics of Structural Recovery and Mechanical Response of Polymeric Liquids Near to the Glass Transition
Authors: Colucci D. M. , Schultheisz C. R. , Mckenna G. B.
Published: April 2011

Results from the NIST torsional dilatometer have indicated that after a temperature step from equilibrium, the volume (structure) and mechanical response (physical aging) can evolve at different rates, depending on the temperature history. The torsional dilatometer results have been modeled in two ways. First, it was assumed that the volume and mechanical response are governed by different clocks, with the principle of time-aging time superposition employed to evaluate an aging time shift factor atc from the torsional response, which was then compared to a structural shift factor aδ calculated from the evolution of the volume. These results were also investigated using a thermoviscoelastic model based on rational thermodynamics and configurational entropy; this model does not include an explicit assumption of separate time scales, but different time scales for the structure and mechanical properties appear to arise naturally from the formulation. The results from the thermoviscoelastic model show good qualitative agreement with the torsional dilatometer results, although more material data is needed to make an exact comparison.
Electrokinetic Phenomena in Porous Media
Authors: Pengra David B. , Wong Po-Zen
Published: April 2011

Electrokinetic phenomena, such as electroosmosis (fluid-flow induced by applied electric fields) and streaming potential (the complementary process) are known to exist in brine-saturated porous media, but are very difficult to measure. With modern instrumentation and an ac method, we can now determine these transport coefficients accurately, and use them to characterize the permeability k1, the effective throat radius Re, and the electric potential at the slip-plane, or ζ-potential. Our study shows that permeability can be determined by two different means: by combining the dc values of the streaming potential, electroosmotic pressure and conductivity; or from the frequency response of ac electroosmosis alone. The high sensitivity of the method allows us to measure k over the 0.1–10,000 millidarcy range with less than lOkPa applied pressure. This article reviews some of the basics of electrokinetics and describes our methods. We also discuss effects of brine salinity and possible effects due to the fractal nature of the pore surface.
ATR-FTIR Spectral Investigation of SO2-treated Soda-Lime-Silicate Float Glass
Authors: Senturk U. , Lee D. H. , Condrate R. A. , Varner J. R.
Published: April 2011

The near-surface infrared spectral changes that occurred on a commercial soda-lime-silicate glass, which was heat treated in SO2/H2O/air atmospheres, were measured, in the region 1200 to 600 cm−1, using attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy. Sets of spectra were taken at different angles of incidence of the infrared beam corresponding to successive penetration depths on the surface, hence, giving a surface spectral profile. It was found that the Si-O-Si vibrational band, observed in the region ∼1100 cm−1, is the most affected; with increasing depth the band becomes weaker, depending on the treatment temperature and water content in the treatment atmosphere. The two different sides (the side in contact with the tin bath (tin side) and the opposite side (air side)) were determined to have a different character as a result of the dealkalization treatments.
Electrical Conduction in Relation to Local and Intermediate Range Structure of Rubidium Germanate Glasses
Authors: Jain H. , Kamitsos E. I. , Huang W. C. , Yiannopoulos Y. D.
Published: April 2011

The dependence of dc electrical conductivity of a series of rubidium germanate glasses on rubidium oxide concentration is correlated with the structural information obtained from extended x-ray absorption fine structure analysis, density, x-ray photoelectron, Raman and far infrared absorption spectroscopy. Previously macroscopic molar or excess volume showed the most obvious correlation with the activation energy of conductivity. The present results demonstrate additional importance of the intermediate range structure.
Dynamic Aspects of Frenkel Defect Formation in Silver Chloride and Silver Bromide
Authors: Wilmer D. , Funke K. , Lauxtermann T. , Bennington S. M.
Published: April 2011

Complete ionic conductivity spectra have been taken of solid silver chloride and silver bromide at various temperatures. The spectra contain two new dynamic features: i) a thermally activated Debye-type relaxation which is explained by the frequent hopping of silver ions from their regular lattice sites to adjacent interstial sites and back again, and ii) conductivity maxima at about 500 GHz which are attributed to high-amplitude individual vibrational motions, mostly of the silver ions. – We also report results of a neutron scattering study on silver bromide. These contain thermally activated quasielastic contributions caused by the localized cation back-and-forth hopping and also give evidence of fast correlated movements of neighboring ions.
Study of Chemical Compatibility and Interfacial Resistance Between Oxide Cathode Materials and A LaGao3 –Based Electrolyte for Solid Oxide Fuel Cells
Authors: Wang Weitung , Hellstrom Eric. E.
Published: April 2011

The chemical compatibility of (La0.6Sr0.4)MnO3 (LSM), (La0.6Sr0.4)CoO3 (LSC), (La0.6Sr0.4)(Co0.2Fe0.8)O3 (LSCF), and (La1.7Sr0.3)CuO4 (LSU) as cathode materials with the oxygen conductor (La0.9Sr0.l)(Ga0.8Mg0.2)O3-δ (LSGM) was studied. The interfacial resistance between the cathode materials and LSGM was measured using AC impedance spectroscopy. The same studies were done with yttria-stabilized zirconia (YSZ) electrolyte. The results showed that no new compounds formed between LSGM and the cathode materials LSM, LSC, and LSCF up to at least 1200°C; however, a solid solution formed between the materials. With YSZ, only LSM did not form new compounds, and no solid solutions formed. The interfacial resistance was much lower between all the cathode materials and LSGM than YSZ. The lowest interfacial resistances were for LSC/LSGM and LSCF/LSGM, which are suggested for medium temperature solid oxide fuel cells.
Segmental Relaxation in Crosslinked Rubber
Authors: Roland C. M. , Bero C. A. , Ngai K. L. , Antonietti M.
Published: April 2011

Studies of the local segmental relaxation in rubbery networks reveal a variety of behaviors. In experiments on networks with labeled junctions, whereby the motion of the crosslink site is specifically monitored, the segmental relaxation function broadens, accompanied by a larger activation energy, in a manner well-described by the coupling model of relaxation. The more usual experiment simply measures bulk relaxation, without discriminating among different relaxing entities. For networks, crosslinking introduces a distribution of relaxation behaviors, related to the proximity of a moiety to the junctions. The resulting inhomogeneously broadened relaxation function is difficult to analyze; nevertheless, a heightened sensitivity to temperature (larger activation energy) is exhibited, from which inferences can be made regarding the shape of the relaxation function. Finally, the segmental relaxation of highly crosslinked microgels is ostensibly homogeneous. Interestingly, however, the inverse correlation between the stretch exponent, β, and the activation energy, observed quantitatively in conventional networks, is violated by the microgels.
Effective Transverse Electrical Permittivities of Plain Weave, Twill Weave and Satin Fabric Composites
Authors: Chou T.-W. , Ning Q-G.
Published: April 2011

This paper reports the analytical prediction of effective transverse electrical permittivities of plain weave, twill weave, 4-harness irregular satin, as well as 5-harness and 8-harness satin fabric composites with lossy constituents. Analytical solutions of the effective properties are presented. Numerical examples are given to illustrate the effects of fiber volume fraction and fabric architecture on the composite effective transverse dielectric behavior. Key words: electrical permittivity, plain weave, twill weave, satin weave, fabric composite, analytical solution.
Rigorous Link Between the Electrical and Mechanical Properties of Composite Materials
Authors: Torquato S. , Gibiansky L. V.
Published: April 2011

Cross-property relations that link rigorously the effective electrical conductivity (or dielectric constant) and the effective elastic moduli of two-phase, isotropic composite materials are discussed. The cross-property relations can be optimal in some cases, i.e., they are realized by particular microstructures. The relations are applied to specific two-phase composites as well as to cracked media.
Dielectric Sensors Used in Environmental and Construction Engineering
Authors: Hilhorst M. A. , van Breugel K. , Pluimgraaff D. J. M. h. , Kroesea W. Stenfert
Published: April 2011

Dielectric properties of materials can give insight into the microstructure or concentrations of their constituents and can be determined by measuring the complex impedance of a capacitor formed by a set of electrodes with the material as the dielectric. Measuring frequencies between 1 MHz and 1 GHz appeared to be most informative for soil and concrete. A new dielectric sensor containing an integrated circuit that includes all analog and digital circuitry is described briefly. This sensor is used to demonstrate the potential of dielectric sensor technology for applied materials research in the field in two recently developed applications. One application concerns the determination of the state of hardening of young concrete. The relationship shown is between changes in the dielectric properties and changes in the structure for curing concrete. The other application is a dielectric probe for contaminated site investigation. It appeared to be possible to locate chemically polluted soil layers, such as with chlorinated solvents or oil, using small changes in their dielectric properties.
Formation Features and Electrochemical Behavior of Porous Electropolymeric Films
Authors: Kolzunova L. G. , Kovarskii N. Ya
Published: April 2011

Some features of electroinitiated potentiostatic formation of polymeric films on the cathode in aqueous acrylamide/formaldehyde/zinc chloride and the electrochemical behavior of polymer modified electrode Pt/film have been studied through their voltammetry and impedance characteristics. The mechanism and kinetics of electrochemical depolarizers have been examined on Pt and Pt/film cathodes. The diffusion character of depolarizers and facilitated Red/Ox reactions on the modified Pt electrode were established.
Analysis of Immittance Spectroscopy Data: Model Comparisons, Universality?, and Estimation of Distributions of Activation Energies
Authors: Macdonald J. Ross
Published: April 2011

Immittance spectroscopy [IS] involves the measurement of the small-signal frequency response of dielectrics, semiconductors, electrolytes, biological cells, and polycrystalline, amorphous, and single-crystal electrically conducting materials. Analysis of such data to provide insight into the detailed, microscopic, physicochemical processes present in the full electrode and bulk material system is a crucial part of IS. Background information on IS and a discussion of its strengths and weaknesses are presented. The use of weighted, complex, nonlinear-least-squares for direct data fitting and for the solution of the ill-posed inversion problem of estimating continuous distributions of activation energies for important response models and for experimental data is illustrated. Replacements for the widely used, but incorrect, complexelectric- modulus data-analysis relations proposed long ago by C. T. Moynihan and associates for disordered ionic conductors, are presented and discussed. Recent proposals for various kinds of universal response behavior are examined and found to be unjustified. The present analysis methods are illustrated by applying them to 24°C data on a lithium aluminosilicate glass and to data over a wide temperature range on single-crystal CaTiO3:30%Al3+
Characteristics of Preliminary Waste Forms for Icpp Low Activity Waste (Law) Fractions after Radionuclide Separations
Authors: Vinjamuri Krishna
Published: April 2011

Currently, at the Idaho Chemical Processing Plant (ICPP) there are about 6800 m3 of liquid sodium-bearing and liquid high-level wastes (HLW), and 3800 m3 of solid calcined HLW. One of the waste processing options under consideration includes separation of the HLW into high activity and low activity (LAW) wastes, followed by immobilization. Preliminary glasses were synthesized for the sodium-bearing, alumina-bearing, and the zirconia-bearing LAW fractions after radionuclide separations. The glasses were formed by crucible melting of a mixture of reagent chemicals representative of the LAW waste streams and frit additives at 1200 °C for 5 hours, followed by overnight annealing at 550 °C and furnace cooling of the melt. These glasses were characterized for density, elastic property, viscosity, chemical durability, structural parameters, and glass phase separation. The results are compared with that of the Hanford's standard glass ARM-i, Savannah River's benchmark glass EA, and the ICPP's grout waste form prepared using the simulated non-radioactive sodium-bearing waste fraction.
Redox State and Transition Metal Concentration Effects on Microstructure of Simulated Simplified Glasses for Waste Immobilization
Authors: Kim C.-W. , Muller I. S. , Buechele A. C. , Pegg I. L. , Macedo P. B.
Published: April 2011

Chromium, iron, and nickel are present in many waste-streams from DOE sites. This study considers a simplified lime-aluminosilicate glass system, similar to one proposed for high temperature (1250–1450°C) vitrification of soil and wastes from DOE sites, in which concentrations of Cr, Fe. and Ni are being varied and different redox states induced for selected melting conditions. The solubilities of Cr 2O3 and NiO in the simplified system are determined at 1350°C, 1400°C, and 1450°C. The enthalpies of solution calculated from the solubility data for Cr2O3 and NiO are 12.2 and 15.2 kcal/mol, respectively. The iron redox ratio, Fe2+/Fetotal in selected glasses is determined by Mössbauer Spectroscopy and related to changes in microstructure. The crystallization of eskolaite (Cr2O3) seems to be favored at intermediate states of reduction (Fe2+/Fetotal ≈0.8) in Cr-containing glass at near the solubility limit. Pseudoternary diagrams are plotted for melts in air at 1450°C in which Fe2O3 + SiO2 + X (X = NiO or Cr2O33) is held constant. Time-Temperature-Transformation (TTT) curves are plotted using data from heat treatment studies. Liquidus temperatures of base, 1.5 wt% Cr2O3 glass and 8 wt% NiO, 7 wt% Fe2O3 glass are found to be 1150°C, 1175°C, and 1175°C, respectively.
Plutonium Incineration in LWR's by a Once-Through Cycle with a Rock-Like Fuel
Authors: Degueldre C. , Kasemeyer U. , Botta F. , Ledergerber G.
Published: April 2011

Plutonium incineration in a uranium-free fuel by a once-through burning cycle in LWR’s followed by geological disposal of the rock-like material as a high level waste is discussed here. For burning plutonium of various origins, zirconium oxide is a promising candidate as inert matrix because it is stabilised by rare earth oxides (Er, Ho, Eu … Y) in a single phase solid solution with a stable cubic structure. In this material, selected rare earth isotopes can also act as burnable poisons. The spent fuel may be licensed as waste material on the basis of the inventory, the stability of the material and the behaviour of natural analogue material (e.g. baddeleyite). A fuel composed of 90-80% ZrO2, 7–14% PuO2 and 3–6% Er2O3 (At%), with potential addition of Y2O3 (as additional stabiliser), is suggested for experimental study. Such a fuel employed in LWR's could generate power effectively while transmuting about 95% of the 239Pu
Corrosion Resistance of Ceramic Refractories to Simulated Waste Glasses at High Temperatures
Authors: Xing Shi-Ben , Lin Yijing , Mohr Robert K. , Pegg Ian L.
Published: April 2011

In many vitrification processes, refractory materials are used to contain the waste glass melt. The corrosive nature of the high-temperature melt consumes the waste feed materials but also limits refractory life. As vitrification is applied to more diverse waste streams, and particularly in higher-temperature applications, increasingly severe demands are placed on the refractory materials. A variety of potential refractory materials including Fused-cast AZS, Monofrax K3, Monofrax E, and the Corhart refractories ER1195, ER2161, C1215, C1215Z, Rechrome, and TI 186, were subjected to corrosion testing at 1450°C using the ASTM C-621 procedure. A series of simulated waste glasses was used which included F, Cl, S, Cu, Zn, Pb; these minor components were found to cause significant, and in some cases drastic, increases in corrosion rates. The corrosion tests were conducted over a range of time intervals extending to 144 hrs in order to investigate the kinetics of the corrosion processes. The change of the concentrations of constituents in the glass was monitored by compositional analysis of glass samples and correlated to the observed extent of corrosion; typically, components of the material under test increase with time while key minor components, such as Cu and Pb, decrease. The rate of corrosion of high-zirconia refractories was slowed considerably by adding zirconia to the waste glass composition; this has the added benefit of improving the aqueous leach resistance of the waste form that is produced.