bluuebunny/crossref_metadata_2025_split huggingface dataset:
In-Situ Fiberoptic Thermometry Measurements Of Wafer Temperature During Plasma Etching Using An Electron Cyclotron Resonance Source
Authors: Thomas S. , Berg E. W. , Pang S. W. 
Published: April 2011

AbstractThe increase in wafer temperature due to plasma heating during etching has been studied. Si and InP were etched using a high ion density discharge generated by an electron cyclotron resonance source. The wafer temperature was measured in-situ using fiberoptic thermometry as microwave power, rf power, chamber pressure, and gas flow were varied. Wafer temperatures increased with both microwave and rf power, and decreased with chamber pressure. For rf power of 50 W, chamber pressure of 1 mTorr, a source distance of 13 cm, and 10 sccm Ar flow, an increase in microwave power from 50 to 500 W caused the temperature to increase from 62 to 186 °C. Additionally, the use of He flowing at the backside of the wafer for temperature control was analyzed. By setting the backside He pressure at 3 Torr, the temperature increased from 20 °C at the beginning of the etch to only 29 °C after 12 min. Time dependent etch characteristics of InP were studied and related to the wafer temperature measurements. At 100 W microwave power, the InP etch rate increased from 100 to 400 nm/min as the wafer temperature rose from 20 to 150 °C. As the temperature increased above 150 °C, the profile became more undercut and the surface morphology improved. By setting the stage temperature to -100 °C and using 3 Torr He pressure at the backside of the wafer, the InP etch rate remained constant during etching and undercutting was suppressed. For 500 W microwave power, a fast InP etch rate of 2 μm/min was obtained when the wafer temperature was <110 °C, and it increased to over 4 μm/min when the temperature was >150 °C.
Structural Relaxation of Densified Silica Glass by Thermal Annealing
Authors: Kitamura Naoyuki , Fukumi Kohei , Makihara Masaki , Yamashita Hiroshi 
Published: April 2011

ABSTRACTThermal relaxation of glass structure has been studied on silica glasses densified by hot isostatic pressing. Density of the glasses relaxed toward the value of an undensified glass by thermal annealing. Relaxation rates of density of the glasses were measured after the annealing at several temperatures. Fast and slow relaxation processes were found from the analysis by using a stretched exponential relaxation function Φ(t)=exp{−(t/τeffβ}). The slow process becomes dominant after the fast process. Raman scattering spectrum also has been measured through the thermal relaxation. The width of the main band at 450cm−1 increased by the annealing and recovered the value for the undensified glass after the fast process. The bands at 1060 and 1200 cm−1 shifted back to the positions for the undensified glass. The high density state(Δρ/ρ∼0.5%), however, was maintained even after the fast process. From these results, it is deduced that the fast process is due to the recovery of the O3Si-O-SiO3 tilt angle and Si-O-Si bond angle to the mean values for the undensified glass.
Structural Developments in Fragile Glass Forming Oxides
Authors: Masnik J. E. , Nickolayev O. , Kieffer J. , Bass J. D. 
Published: April 2011

ABSTRACTBrillouin light has been used to measure the complex mechanical modulus of the molecular scale structure in oxide melts. The storage modulus reflects the degree of networking and structural integrity, while the loss modulus, which can be attributed to aperiodic motions of structural components, provides a measure of the mobility of these entities. rom the loss modulus it is possible to derive the zero-shear rate viscosity, which is characteristic of a structure in thermodynamic equilibrium, and thereby provide a less encumbered insight into the molecular scale mechanisms that are underlying to the viscous momentum transport.In this paper we compare the visco-elastic behavior of alkali borates and alkali tellurites, particularly in the temperature range between Tg and the equilibrium melting point. While in borates several mechanisms can be identified as contributing to structural relaxation, in tellurites a single mechanism dominates. The assumption of thermo-rheological simplicity, however, is invalid, and a new visco-elastic model has been developed for the description of our results.
Diffusional Dynamics Near the Glass Transition in Amorphous Polymer Thin Films
Authors: Deppe Denise D. , Torkelson John M. 
Published: April 2011

ABSTRACTA novel experimental approach involving the fluorescence nonradiative energy transfer technique is employed to study transport processes in thin polymer films near the glass transition through the measurement of energy transfer efficiency, E. Using a layered thin film sample geometry, values of the small molecule diffusion coefficient, , as low as 8 × 10−16 cm2/sec are measured within diffusion times of 3.5 hours. These studies reveal a significant dependence of both the magnitude and temperature dependence of on diffusant size.
Fractional Debye-Stokes-Einstein Law in Polymeric Liquid Crystals
Authors: Andreozzi L. , Donati C. , Giordano M. , Leporini D. 
Published: April 2011

ABSTRACTThe viscosities of amorphous and semicrystalline polymeric liquid crystals η have been measured by dynamic mechanical analysis. They have been compared with the rotational correlation times of molecular probes, as drawn by Electron Spin Resonance spectroscopy on two different time scales. In all the cases the correlation times of the spinning motion of a cigar-like probes τ| and η are related by a fractional Debye-Stokes-Einstein law, i.e.η| α ηξ, ξ ≤ 1.
Kinetic Roughening of Quenched Xenon Films
Authors: Heilmann Ralf K. , Suter Robert M. 
Published: April 2011

ABSTRACTWe investigate the growth of quenched Xe films formed by deposition onto a cold (15-35K) substrate via in situ measurements of x-ray reflectivity and diffraction. Surface roughness, film density, and crystallinity are determined as a function of Xe film thickness, substrate temperature and Xe flux in order to test for dynamic scaling behavior. Deposition of polycrystalline films with random crystallite orientations is achieved through heating of a grafoil sheet that is enclosed in the sample cell and has previously been covered with bulk Xe. At 16K the films are sufficiently quenched to be stable over several days, while at 25K annealing takes place. Differing atomic mobilities at different temperatures lead to contrasting scaling behavior. The substrate remains unchanged under repeated film deposition and desorption and therefore allows a systematic comparison of different films.
Fractal Growth of Clusters and Pores During Annealing of Aluminum Thin Films Deposited on Silica.
Authors: Fleury Vincent , Balazs Lazlo , Duclos Franck 
Published: April 2011

ABSTRACTAnnealing of anAlthin-film on SiO2 at temperatures in the range 400-660°C leads to a chemical reaction (oxidation ofAland reduction of Si) whih proceeds via irreversible growth of 2-D aggregates which belong to a class of clusters first described in MBE.
Image Analysis and Saxs Characterisation of Mixed Aerogels
Authors: Blacher S. , Tihon Ph. , Pirard R. , Pirard J. P. , Brouers F. , Sahouli B. , Diez B. , Sobry R. , Van den Bosshe G. 
Published: April 2011

ABSTRACTThe fractal structure of SiO2 - ZrO2 mixed aerogel prepared for catalytic purpose is investigated using morphological statistical methods, small angle X-ray scattering and N2 adsorption-desorption measurements. These three methods provide a description of the aerogel structure over several decades.
Verification and Application of a New Adsorption Model for Fractal Surfaces
Authors: Segars Ronald , Piscitelle Louis 
Published: April 2011

ABSTRACTA recently proposed isotherm model for adsorption on fractal surfaces is fitted to a wide range of isotherm data obtained from the literature. All curve fitting attempts produced good fits and the model parameters obtained are shown to be physically reasonable. Also, all significant model parametrs can be obtained from a single isotherm. As expected, when surface roughness is taken into account, the specific surface area determined from monolayer volume may be significantly higher than that obtained using the standard smooth surface isotherm models.
Investigation of Aggregate Structures on Length Scales from About 5 to 10,000 Å
Authors: Schmidt Paul W. , Ehrburger-Dolle Francoise , Pfeifer Peter , Rieker Thomas , Kapoor Yogendra M. , Voss Daniel J. 
Published: April 2011

ABSTRACTSmall-angle x-ray scattering has been used to investigate the structure of some carbon blacks, some silicas, and an alumina-silica catalyst carrier on length scales from about 5 to 10,000 Å. Equations developed for structural studies of fractal and non-fractal aggregates of primary particles have been employed to analyze the scattering data. From the intensity data, the average diameters of the primary particles could be calculated or estimated. Despite the very different origins of the samples and the fact that the average diameters of the particles varied from about 30 to over 1000 Å, the scattered intensities from the samples had many common features. The data showed that the primary particles had a uniform density and were bounded by smooth or fractal surfaces. On length scales greater than the diameters of the primary particles but not more than a few times larger than the average diameters of the aggregates, some of the aggregates were mass fractals, and others were surface fractals.
Modelling of the Structural and Dynamical Properties of Porous Silicon
Authors: Gavartin J. L. , Matthai C. C. 
Published: April 2011

ABSTRACTThe changes in the radial distribution function (RDF) and vibrational density of states (DOS) of porous silicon (p-Si) with change of porosity are studied within a modified diffusion limited aggregation model and molecular dynamics simulations. By decomposing the first peak of the radial distribution function of p-Si on to partial RDFs, for atoms having different coordinations, and partial RDFs, for bonds connecting atoms with different coordinations, we show that appearance of the structure in the first peak of the RDF in p-Si is stipulated by bonds between undercoordinated surface atoms. The vibrational DOS projected on surface atoms are also shown to be different from that corresponding to crystalline phonons. It is characterised by the relative increase of the intensity of vibrations in the acoustic region and by appearance of surface-like vibrations split from the optical band.
Phenomena Rlated to Concurrent Multiple Complex Plane Representations of the Immittance Data
Authors: Alim Mohammad A. 
Published: April 2011

ABSTRACTThe concurrent multiple complex plane representation of the single/multiple semicircular relaxation(s) for the same immittance data provides a choice of selecting simultaneously operative phenomena within a heterogeneous system. The origin of this representation and the selection criteria of the phenomena are highlighted via structure-property-processing relationships. These include the development of a single equivalent circuit model by acquiring knowledge on the type of aterials, history, chemistry, composition, processing variables, microstructures, etc. The correspondence within the complex planes is attributed to the relative magnitudes of the contributing elements in the equivalent circuit model and dominance of the operative phenomena. The limitations concerning the transformation of the data from one complex plane to the other are reviewed, considering Debye/non-Debye conduction processes within the series-parallel microstructural network of electrical paths.
Electrical Properties and Defect Structure in The Sr-Fe-Co-O System
Authors: Ma B. , Chao C.-C. , Park J.-H. , Segret C. U. , Balachandran U. 
Published: April 2011

ABSTRACTThe ceramic Sr-Fe-Co-O has potential use as a membrane in gas separation. This material exhibits high conductivity of both electrons and oxygen ions. It allows oxygen to penetrate at high flux rates without other gas components. Electrical properties are essential to understanding the oxygen transport mechanism and defect structure of this material. By using a gas-tight electrochemical cell with flowing air as the reference environment, we were able to achieve an oxygen partial pressure (P02) as low as 10−16 atm. Total and ionic conductivities of Sr-Fe-Co-O have been studied as a function of P02 at elevated temperature. In air, both total and ionic conductivities increase with temperature, while the ionic transference number is almost independent of temperature, with a value of ≈0.4. Experimental results show that ionic conductivity decreases with decreasing P02 at high P02 (≥10−6 atm). This suggests that interstitial oxygen ions and electron holes are the dominant charge carriers. At 800°C in air, total conductivity and ionic conductivity are 17 and 7 S/cm, respectively. Defect dynamics in this system can be understood by means of the trivalence-to-divalence transition of Fe ions when P02 is reduced. By using the conductivity results, we estimated oxygen penneation through a ceramic membrane made of this material. The calculated oxygen permeability agrees with the experimental value obtained directly from an operating methane conversion reactor.
Dielectric Constant of Sodium Silicate Glasses in Relation to Their Chemical Structure
Authors: Hsieh C. H. , Jain H. 
Published: April 2011

ABSTRACTThe chemical structure of a series of aluminum substituted sodium trisilicate glasses is determined by x-ray photoelectron spectroscopy. It reveals a significant change of the chemical structure around the sodium cations and oxygen anions with the addition of aluminum. A microscopic model is developed to understand the composition dependence of the dielectric constant of these glasses in terms of the changes of chemical structure.
Grain Boundary Dopant and Heat Treatment Effects on the Electrical Properties of Polycrystalline ZnO
Authors: Chen T. D. , Lee J.-R. , Tuller H. L. , Chiang Y.-M. 
Published: April 2011

ABSTRACTSimplified varistor systems of bismuth- and cobalt-doped zinc oxide are studied. A prior study has shown that the distributions of bismuth segregation at the grain boundaries in such samples can be controlled by varying microstructure and heat treatment. Current-voltage and deep level transient spectroscopy measurements were done to evaluate the corresponding electrical properties. Low leakage and α values of ˜30 were attained, despite the nominal, twocomponent doping of these simplified varistors. Moreover, these samples show the signature defects that are found in many multi-dopant, commercial devices: two shallow bulk traps at ˜0.14 eV and ˜0.24 eV and one prominent interfacial trap at ˜1 eV.
Modelling of Electrical Conductivity of n-p Ceramic Composite Using Equivalent Circuits
Authors: Choi Gyeong Man , Jun Seok Taek 
Published: April 2011

ABSTRACTComposition dependence of electrical conductivity of ceramic composite was analyzed using a ZnO(n-type semiconductor)-CuO(p-type semiconductor) composite as a model. The contributions from grain and grain boundaries to the total conductivity of the composite were determined. New equivalent circuits were proposed which represented the distribution and connection of n and p grains and the total electrical conductivity was analyzed using the proposed circuits. Dominant equivalent circuit changed with composition and the total conductivity was determined by the exponential fractional change of two equivalent circuits. Effect of grain size on the grain boundary and total conductivity were also examined.
The Detection And Mapping Of Defects In Organic Coatings Using Local Electrochemical Impedance Methods
Authors: Taylor S. R. , Wittmann M. W. 
Published: April 2011

ABSTRACTCoating failure initiates as a local event at defects which can result from chemical heterogeneities in the resin or physical defects such as bubbles, underfilm deposits, or pinholes. The ability to detect, map the location, as well as make quantitativein-situmeasurements of coating heterogeneities will help identify the source of failure (i.e. coating chemistry, method of application, cure schedule, etc.) and provide insight into the mechanisms of coating degradation. This study used a 5 electrode arrangement to perform local electrochemical impedance spectroscopy (LEIS) on coated steel substrates. Using single frequency measurements, LEIS could successfully detect and map both intentional chemical heterogeneities and physical defects such as subsurface bubbles, underfilm deposits, and pinholes. Efforts to optimize probe design and instrumentation are ongoing.
Y2BaCuO5Addition and Its Effects on Critical Currents in Large grains of YBa2Cu3O7-σ: A Quantitative Microstructural Study
Authors: Chopra Manoj , Meng R. L. , Chu C. W. , Chan Siu-Wai 
Published: April 2011

ABSTRACTThe addition of Y2BaCuO5(211) particles to large grain Yba2Cu3O7−δ(Y123) has significantly improved the critical current (Jc) in this material. Here a systematic quantitative analysis on the effect of the measured 211 present in large grains of Y123 has been performed, after the process of melt texturing, both on a microscopic and a nanoscopic scale with a systematic variation of the initial volume percent of 211 addition. From the correlation between critical current measurements and quantitative microscopy of both (001) and (110) sections, a maximum value of weighted Jcis observed corresponding to a measured Y123 volume percent of 20%. Although an increasing addition of 211 is effective in producing efficient flux pinning sites in the Y123 matrix, percolation paths in the Y123 matrix become limited for supercurrent. Accounting for the loss of liquid phase, we estimate an optimum initial volume of 211 for highest Jc to be 40%. Further correlation between the Jcand the true flux pinning force (Fp) shows a maximum pinning force for an initial 211 addition of 40%. However the pinning efficiency of the superconducting Y123 matrix is found to improve with an increasing 211 addition. Hence an optimum amount of 211 addition is essential for obtaining the best possible electrical characteristics in the superconducting composite.
AC Properties of Carbon Black Filled Polymer Blends
Authors: Brouers F. , Royen I. , Blacher S. , Pirard R. , Gubbels F. , Jerome R. , Sarychev A. 
Published: April 2011

ABSTRACTThe macroscopic electrical properties of carbon black filled polyethylene (PE)/polystyrene (PS) blends depend strongly on the selective localization of carbon black particles in one of the phases of the polyblend. The electrical and dielectric properties of these materials can be understood in the framework of the double percolation theory. It appears that in the vicinity of the carbon black percolation threshold, the electrical conduction is dominated by tunneling. The recent theory of Brouers and Sarychev which includes quantum tunneling in the percolation scaling laws provides the basis for a discussion of the observed frequency dependence of the conductivity and the dielectric constant in the range 10−3 – 106 Hz and its relation to the blend morphology.
Numerical Study of D.C. Conductivity & A.C. Impedance for the Close-Packed Mixture of Hard Spheres
Authors: Han D. G. , Choi G. M. 
Published: April 2011

ABSTRACTUsing a computational methodology, we studied average electrical properties, or, more specifically, d.c. conductivity and a.c. impedance spectra, of macroscopic mixtures of hard spheres numerically. Numerical results were compared with the calculated results of analytic equations which were generally used to describe the d.c. and a.c. electrical properties of composites. It is the purpose of this paper to provide information regarding to the geometrical arrangement effects. It was found that geometrical arrangement effects become more important as the sample size becomes smaller and the filling fraction closer to an effective percolation threshold.
Process-Monitoring Via Impedance Spectroscopy
Authors: Seitz Martin A. , Hirthe Richard W. , Koehler Charles J. 
Published: April 2011

ABSTRACTThe improvement of process yields and efficiency are often dependent upon the availability of sensors that allow real-time in-process control. The sensitivity of impedance techniques to physical, chemical, and microstructural features of a material system offers significant potential in developing real-time sensors. Two examples of how impedance techniques can be used to follow changes in materials throughout out a process are discussed. The first of these involves monitoring the processibility and viability of solder pastes used in surface mount technology. The second example deals with monitoring the state of an ion exchange resin bed as used in water softeners.
AC Conductivity of Crystalline Materials and Glasses Ascribed to ADWPs
Authors: Nowick A. S. , Vaysleyb A. V. , Jain H. , Lu X. 
Published: April 2011

ABSTRACTThe behavior of the frequency dependence of the conductivity, σ(ω), of numerous crystalline materials and glasses is close to an ω1.0 dependence in the limit of low temperatures and/or high frequencies (referred to as the “nearly constant loss”, or NCL, regime). Detailed analysis of this behavior, including the frequency dependence of both ε′ and ε″, shows that it can be described phenomenologically as produced by a broad distribution of asymmetric double-well potentials (ADWPs) with low activation energies. In order to obtain an understanding of the atomic origins of such potentials, we investigate the composition dependence of this behavior in such materials as crystalline CeO2:1%Y3+ ceramics with variable [Y3+] and alkali germanate glasses with variable alkali concentration. The appearance of a discrete loss peak in CeO2: 1%Y3+ helps us understand the ADWPs as due to “off-symmetry” configurations that undergo wiggling motion between adjacent minimum-energy positions.
Control of R7T7 Nuclear Glass Alteration Kinetics Under Saturation Conditions
Authors: Gin S. 
Published: April 2011

AbstractThe hypothesis of French nuclear waste glass disposal in a geological repository implies a comprehensive assessment of all the glass elements liable to participate in controlling the material alteration kinetics. The hypothetical existence of kinetically limiting elements other than silica could account for the observed R7T7 glass behavior in the presence of certain clays, and notably the continued high alteration rates observed even after silica saturation occurs. Flowing experiments with solutions near silica saturation but highly subsaturated with respect to aluminum hydroxide were defined to investigate the possible limiting role of aluminum. Experiments were conducted at different flow rates with the same constant steady-state H4 SiO4 activity for all the tests. The glass dissolution rate was observed to depend on the solution flow rate, indicating that under these conditions the kinetics are not controlled by dissolved silica alone. An additional experiment, in which only the Al(OH)4− activity in solution was allowed to vary, demonstrated the critical role of this element. Several interpretations are discussed.
Surface Characterization of Simulated Low-Level Radioactive Waste Glasses Corroded in Water and LiOH Buffer Solution
Authors: Li H. , Schweiger M. J. , Hrma P. , Feng X 
Published: April 2011

AbstractChemical durability of simulated radioactive low-level waste (LLW) baseline glass, 6- 5412, was found to decrease with the addition of either phosphate or sulfate, or chromium oxide. Scanning electron microscopic study of corroded samples suggests that the effect of these components on glass chemical durability may be attributed to cluster formation of: Na-O-P-O or Na-O-S-O, or (O0)3-Cr3+(O−)3 groups. Preferential corrosion attack was severe on certain corroded sample surface areas that are possibly enriched in these clusters. Durability tests in a solution with LiOH as a buffer suggest that chlorine in the glass slightly improved glass corrosion resistance, while fluorine significantly deteriorated glass corrosion resistance.