bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Weight and Molecular Weight Distribution of Kraft Lignins
Authors: Schmidl Wolfgang , Dong Daojie , Fricke Arthur L.
Published: March 2011

Kraft lignins are the lignin degradation products from kraft pulping. They are complex, heterogeneous polymers with some polar character. The molecular weight of kraft lignins greatly affect the physical properties of black liquors, and are of primary importance in separation from black liquor and in evaluating potential uses.

Several purified kraft lignins from slash pine were analyzed for number average molecular weight by vapor pressure osmometry (VPO), for weight average molecular weight by low angle laser light scattering (LALLS), and for the molecular weight distribution by high temperature size exclusion chromatography (SEC). The lignins were run in Tetrahydrofuran (THF), N, N-Dimethyl Formamide (DMF), DMF with 0.1M LiBr, and pyridine at conditions above the Theta temperature. Experimental methods are discussed.

The results show that VPO may be used to determine Mn for kraft lignins if the purity of the lignins and the identity of the impurities are known. LALLS can be used to determine Mw for kraft lignins if measurements are made at or above the Theta temperature of the lignin-solvent pair. SEC should be used at temperatures at, or above, the Theta temperature of the lignin-solvent pair. Size separation is highly dependent on the solvent used, and DMF is a much better solvent than THF for high temperature SEC. Future work using moment resolution procedures to derive an accurate calibration curve are also discussed.
Continuum Models for the Mechanical Response of Paper and Paper Composites: Past, Present, and Future
Authors: Suhling Jeffrey C.
Published: March 2011

Paper and paper composites are utilized in applications where they are subjected to multiaxial stress states and changing environmental conditions. Such materials exhibit nonlinear anisotropic material behavior which is time dependent and affected adversely by slight changes in moisture content and temperature. At present, lack of adequate theoretical models often hampers the design and development of structurally optimized paper products. Therefore, it has been common practice in the pulp and paper industry to use trial and error, and empirical approaches. Accurate continuum models for the mechanical behavior of paper and paper composites are needed to guide the paper product design process.

In this work, a limited review of the existing methods for modeling the mechanical response of paper and paper composites is given. At first, a brief overview of the goals of current modeling techniques based on hydrogen bond, fiber network, and continuum approaches is presented. The governing equations and capabilities of current continuum models are then discussed in greater detail. Theories which include linear elastic (generalized Hooke's Law), nonlinear elastic (hyperelastic), linear viscoelastic, nonlinear viscoelastic, and inelastic constitutive relations are addressed. Finally, applications of existing continuum theories to the analysis of paper materials in structural configurations are presented. After these discussions, the limitations of the available continuum models are assessed and future research needs are suggested.
The Inter-Relationship Between Paper Structure and Print Quality in Ink Jet Printing
Authors: Oliver John F. , Jones A. Y.
Published: March 2011

This article describes a print quality evaluation of laboratory designed ink jet papers prepared on a dynamic former. A comparison with various plain and coated papers serves to illustrate the potential opportunity for papermakers to exploit novel types of paper structures in the future. The article will also briefly focus on some of the fundamental issues and key paper properties which perturb print quality and govern the capillary absorption of aqueous inks.
Application of Surface Science Techniques to the Understanding of the Colloidal Properties of Papermaking Materials
Authors: Sanders Nicel D. , Schaefer John H. , Bashey Ali R. , McElroy Eric B.
Published: March 2011

Sophisticated surface science techniques long familiar to materials researchers are now being used routinely to characterize the colloids found in papermaking systems. Ion Scattering Spectroscopy (ISS) is used to obtain the surface elemental composition of inorganic filler pigments. Laser light scattering is applied to the determination of particle size and particle charge distribution by way of the methods of Photon Correlation Spectroscopy (PCS) and Doppler Electrophoretic Light Scattering (DELS). The heats and races of interaction of hydrophilic colloids (water soluble polyelectrolytes) with hydrophobic colloids are determined by batch titration microcalorimetry.
Interfacial Aspects of Reinforcement of Wood by Mineral Fibers
Authors: Subramanian R.V. , Park J.M.
Published: March 2011

Significant aspects of fiber reinforcement of wood are introduced. The effectiveness of three different silane coupling agents; one monomeric 3-aminopropyltrimethoxy silane, two polymeric aminosilanes (one dimethoxy- and another trimethoxy substituted), was compared by measurement of interfacial shear strength in silane treated single filament composite (SFC) specimens, under dry and wet conditions. The trimethoxypolymeric silane was found to be inferior to the other two, which warrant further investigation in strength tests with basalt fiber reinforced wood specimens. Acoustic emission measurement during the SFC tests has provided evidence for the sizing effect of polymeric silane coatings, as well as for moisture attack at severe surface flaws on the fiber during silane treatment.
Extruded Wood-Flour Polypropylene Composites: Effect of a Maleated Polypropylene Coupling Agent on Filler-Matrix Bonding and Properties
Authors: Myers George E. , Kolosick Paul C. , Chahyadi Ichwan S. , Coberly Camden A. , Koutsky James A. , Ermer Donald S.
Published: March 2011

Full factorial studies were conducted to determine the effects of a coupling agent (a low molecular weight maleated polypropylene (MAPP)) and other composition and processing variables on the mechanical properties of a wood-flour-filled polypropylene (PP) composite. Effects of MAPP on the bonding between PP and wood veneer were also examined. At less than 1 percent by weight, MAPP produced useful increases in strength and modulus properties of the composite, and this effect was somewhat enhanced by small-particle-size wood flour and multiple extrusions. However, MAPP caused small losses in notched impact energy. High extrusion temperature (190°C to 250°C) had little influence on strength, but it decreased notched impact energy. Peel force between PP and wood veneer was increased by pretreatment with MAPP for aspen, but not for birch, aspen being more porous than birch. The effectiveness of MAPP may therefore be related to its ability to penetrate the wood and form a strongly held hydrophobic layer that is attractive to the PP, thereby increasing both the effective bonding area and mechanical interlocking.
Tem Characterization of Dislocations in GaAs-ON-Si Heterostructures Wite Sjpereatlice Intermediate Iayers
Authors: Soga T. , Nishikawa H. , Jimbo T. , Umeno M.
Published: March 2011

GaAs was grown on Si substrate by metalorganic chemical vapor deposition using GaAs/GaAsP strained layer superlattice (SLS) intermediate layers. The dislocation density decreases at the interface between GaAs and SLS, but does not decrease in the SLS. When GaAs/GaAsP SLS is used as the intermediate layer, a part of the dislocation propagates into the top GaAs layer because of the lattice mismatch of GaAs and SLS. The low etch-pit-density of (3-5) x 105 cm−2 was obtained by using the intermediate layer of GaAs/GaAsP SLS and AlAs/GaAs superlattice with thermal-cycle annealing.
InGaAs/GaAs Graded Superlattices in Photodetectors for Wavelengths Beyond 1 μm
Authors: Mariella R. , Morse J. , Liliental-Weber Z.
Published: March 2011

We have used MBE to grow graded InxGa1−xAs/GaAs superlattices on GaAs substrates as buffers for larger period, constant composition InxGa1−xAs/GaAs superlattices. TEM analysis shows that there are numerous crystal defects associated with the presence of strained layers, but, in many cases, the buffer layers confine these defects to areas outside of the strained-layer superlattices. PIN detectors fabricated from these structures show external quantum efficiencies up to 2.7 %.
Electron Microscopy and Diffraction of the Early Stages of Metal Heteroepitaxy
Authors: Bauer E.
Published: March 2011

The application of some characterization methods to the study of heteroepitaxy is illustrated by recent work in the authors laboratory on the epitaxy of Cu on Mo and W(110). In particular, the use of PEEM and LEEM in the study of the epitaxy of Cu, Au and Co on Si(111) is discussed.
Computer Simulation of the Metal Organic Chemical Vapor Deposition of CdTe
Authors: Kang S. , Jasinski T.J. , Tompa G.S. , Stall R.A.
Published: March 2011

The optimization of chemical vapor deposition processes requires an understanding of the influence of various process parameters on the deposition of thin films. A recently developed computer simulation tool provides a powerful means to develop this understanding. This paper describes the use of the computer program, FLUENT, to study the gas flow, temperature, and chemical species distributions during the deposition of CdTe. Numerical results are reported for two operating conditions for an EMCORE vertical high-speed rotating disk growth reactor and are compared to experimental data. The influence of process parameters is discussed. The effects of the addition of significant amounts of Hg (several percent) to the process gas is evaluated.
Role of Si1−xGex Buffer Layer in Determining Electrical Characteristics of Modulation-Doped p-Si0. 5Ge0.5/Ge/Si1−xGex Heterostructures
Authors: Murakami Eiichi , Etoh Hiroyuki , Nishida Akio , Nakagawa Kiyokazu , Miyao Masanobu
Published: March 2011

Electrical characteristics of modulation-doped p-Si0.5Ge0.5/Ge/Si1−x Gex heterostructures are examined in relation to Si fraction (1−X) and thickness (dB)of the buffer layer (Si1−xGex), using Raman spectroscopy and transmission electron microscopy. Strain-induced enhancement of hole mobility and concentration is observed in 1-X≦0.25. However, their decrease in 1-X≦0.25 and for small dB values is also observed, which is attributed to the increase in threading dislocations. As a result, a maximum hole mobility of 7600 cm2/Vs at 77 K is obtained at 1-X=0.25 and dB=1μm.
Defect Reduction of Cvd-Grown Cubic SiC Epitaxial Films on Off-Axis Si(100) Substrates with a Novel Off-Direction.
Authors: Furukawa Katsuki , Fujii Yoshihisa , Suzuki Akira , Nakajima Shigeo
Published: March 2011

Monocrystalline cubic SiC (β -SiC) thin films with lower defect densities have been epitaxially grown by chemical vapor deposition on off-axis Si (100) substrates with off-directions different from the conventional 〈011〉. Stacking faults of β -SiC films are investigated by the electrolytic etching and SEM observation. The effects of off-direction deviated from 〈011〉 are examined for the first time. The off-angle is fixed at 2 degrees. We find a reduction in defect density with increasing deviation angle θ, of off-direction from [011] toward [011[ (θ = 0 - 45°). The defect density becomes one order of magnitude smaller than that of on-axis (100) substrates. A typical value of the stacking fault density is approximately 6 × 106 cm−2 on the substrate with θ = 30° (film thickness: 24μ m).
Elecitrical Properties of Ion Beam Sputtering Grown Epitaxial Yttria Stabilized Zirconia FIlms on Silicon
Authors: Hesto P. , Pellet C. , Schwebel C. , Dupont-Nivet E. , Noxaic A.Le
Published: March 2011

Yttria stabilized zirconia (YSZ) films have been characterized. The refractive index measured by ellipsometry is about 2.1. The breakdown electric field is greater than 4MV/cm for small area capacitors with a decrease for large area capacitors. This dielectric strength is weakly dependent on the film thickness within the range 0.2-1.lμm. The analysis of the 1MHz C(V) curves by the Terman method leads to a density of interface states of the order of 1012cm−2eV−1 in the middle of the bandgap with an increase near the conduction and the valence bands. The sensitivity of zirconia to the irradiations has been characterized by analysing 1MHz C(V). With or without electric field applied during the irradiations, the Flat-Band voltage shifts are lower for YSZ films than for thermal silicon dioxide films (2 times smaller).
Formation of Pinhole-Free Epitaxial Yttrium Silicide on Silicon(111)
Authors: Siegal Michael P. , Santiago Jorge J. , Graham William R.
Published: March 2011

We report the growth of structurally continuous, pinhole-free epitaxial YSi2−xfilms on Si(l1l) substrates as thin as 30Å. This is accomplished by depositing both yttrium andsiicon in the appropriate stoichiometric ratio onto substrates held near room temperature, which is apparently below the activation energy for the nucleation of a reaction between a deposited Y film and a Si substrate. Diffusion of Si atoms from an evaporation source into a thin Y layer occurs below this barrier energy, allowing the layer by layer formation of YSi2−x without the removal of silicon from the substrate, maintaining a relatively low interface free energy between the growing silicide film and the Si(lll) substrate. Samples have been annealed to 500-900°C to improve epitaxy without the creation of pinholes. Use of the template method allows for the growth of thicker films also free of pinholes.
Temperature Dependence of Compositional Disordering of Gaas-Alas Superlattices During Mev Kr Irradiation
Authors: Bryan R. P. , Miller L. M. , Cockerill T. M. , Coleman J. J. , Klatt J. L. , Averback R. S.
Published: March 2011

The influence of the specimen temperature during MeV Kr irradiation on the extent of compositional disordering in GaAs-AlAs superlattices (SLs) has been determined. We have investigated whether radiation-enhanced diffusion (RED) could be employed to reduce the dose required to completely disorder a SL by ion implanation. Metalorganic chemical vapor deposition grown GaAs-AlAs SLs were implanted with 0.75 MeV Kr to a dose of 2×1016 cm−2 at various sample temperatures ranging from 133 K to 523 K. The extent of disordering induced by the irradiations was determined by Rutherford backscattering spectrometry and secondary ion mass spectrometry. For low temperature irradiations (133 K to 233 K), complete intermixing of the SL is observed. However, the extent of intermixing of the SL decreases with increasing specimen temperature between room temperature and 523 K. We propose two possible explanations to interpret these results: (i) that the amount of ion beam mixing decreases with increasing temperature; and (ii) that the RED coefficient is negative which suggests the existence of a miscibility gap in the GaAs-AlAs SL system.
A Use of Specimens in Form of Tips for In-Situ Experiments in Electron Microscopes (Preparations, Preliminary Results)
Authors: Drechsler M.
Published: March 2011

A long term aim of this study is to overcome the difficulties to use electron microscopes (TEM, SEM) for in situ experiments, which includes (1) a preparation of initially clean surfaces, (2) a use of specimen micro-chambers, (3) in situ heating, (4) devices to produce and analyse reactions and (5) video registration. An interesting step in this direction is the replacement of the usual thin films by specimens in form of tips similar to those used in field emission devices. A tip is first prepared by electrolytic etching. Then the tip is cleaned and shaped in vacuum. This opens the possibility to visualize and measure kinetic phenomena up to higher temperatures than so far (1500 K and more). Examples of results are: (1) Surface matter fluxes and surface self-diffusion can be measured, (2) solid/solid interfaces and their displacements (reactions) can be measured, (3) grain boundary displacements and grain rotations can be measured and (4) periodic electric discharges between electrodes of 0.1 gim on specimens are prepared, visualized and explained.
The Preparation of Fine Particulate for Electron Microscopy Investigations Using Dental Amalgam
Authors: Chumbley L. S. , Laabs F. C. , Sanders S. C.
Published: March 2011

Samples of high Tc superconductors and metal powders have been prepared for Scanning and Transmission Electron Microscopy examination by a novel method. Dental amalgam, commonly used for filling cavities in teeth by dentists, has been used as a binding agent to hold the sample particulate together during sample preparation. The amalgam was pressed into a small rod 3 mmn in diameter and samples were prepared by cutting slices from the rod followed by mechanical grinding and ion milling to perforation. This technique is extremely easy and offers several advantages over other preparation methods. Experiments revealed difficulties due to preferential sputtering yield, but generally these could be overcome and good thermal and electrical properties of the amalgam partially offset the former inconveniences. It should be possible to use this technique for any number of materials, including ceramic materials and small non-spherical particulate.
Problems and Artifacts on Extraction Replicas of Membrane Filters
Authors: Turner S. , Steel E. B. , Landis E. S.
Published: March 2011

For studies of particles suspended in air or water, material is commonly deposited onto membrane filters. Submicrometer particles collected in or on the surface of the filters can be prepared for analysis by TEM by extraction replica methods. To identify the problems and artifacts generated during the preparation process, evaluations were made of replicas prepared internally at NIST and prepared by laboratories involved in the analysis of air-collected asbestos. Problems or artifacts that could affect the counting and analysis of asbestos particles were identified and characterized. Results of evaluations of replicas prepared by eighteen laboratories in an interlaboratory study are summarized.
A Fast and Precise Specimen Preparation Technique for TEM Investigation of Prespecified Areas of Semiconductor Devices
Authors: Romano Albert , Vanhellemont Jan , Bender Hugo
Published: March 2011

In this paper we present a rapid and highly precise plan view and cross-section specimen preparation technique for the localized thinning of semiconductor devices for TEM investigation. No special equipment except the commercially available one is required. Crosssection preparation takes about 6 hours, while plan view takes about 4 hours. Prespecified areas of 0.6 μm wide and 10 μm long can easily be thinned with transparency for CTEM and HREM. Using an iterative ion milling procedure allows to scan a complete device in HREM.
Preparation of Cross Sectional and Plan View TEM Samples of Thin Films on Mgo Substrates with an Additional Chemical Thinning Step
Authors: Rou Shang. H. , Hren Philip. D. , Kingon Angus. I.
Published: March 2011

Single crystal MgO is a common substrate for the deposition of oxide thin films. The conventional cross sectional transmission electron microscopy sample preparation procedure suffers the drawbacks of: 1)- extensive ion milling time; 2) a higher milling rate for the thin films than for the substrate; 3) introduction of artifacts and contamination during ion milling; and 4) generation of excess defects into the substrate during mechanical thinning. An additional chemical thinning step using hot orthophosphoric acid can reduce or eliminate these adverse effects.

This technique can be applied generally to thin film samples deposited on substrates with a low ion milling rate. Furthermore, substrates which are sensitive to mechanical stress and ion beam damage are also suitable for this technique, provided an appropriate chemical polishing solution and compatible epoxy can be found. The unique features of this technique are briefly presented.
A Technique for the Preparation of Thin-Film Cross-Sections for Transmission Electron Microscopy
Authors: Libera M. , Nguyen T. A. , Hwang C.
Published: March 2011

A number of techniques for producing TEM cross-sections of thin films have been described in recent years as the need for improved and more-thorough microstructural study of thin-film materials has grown. We have developed a method for producing such cross-sections which involves little sophisticated equipment other than an ion mill for thinning. Following the method of Bravman and Sinclair (J. Elec. Micrs. Tech 1,53–61 (1984)), the film of interest is either deposited on or epoxied to a silicon wafer and a composite of six silicon beams (=3mm × 25mm × 0.5mm) is fabricated. Slices are cut from this composite perpendicular to the film plane, and each slice is mechanically thinned by a series of simple grinding and polishing steps to ∼ 50–100μm. Dimpling is not necessary. The specimen is mounted onto a slotted TEM grid which provides a vehicle for safe handling, and the specimen is ion milled to perforation. We have found the technique to be relatively fast, reliable, and simple. Its success hinges on minimizing the amount of direct handling required when the specimen is thin and fragile. We present a detailed recipe describing its various steps and show typical results from studies of thin films for data-storage applications.
Ion Channeling Analysis of Disorder
Authors: Picraux S. T.
Published: March 2011

The use of ion channeling to characterize disorder in semiconductors is briefly reviewed. At high defect densities the ion channeling/backscattering technique can give the depth distribution of defects with a resolution ∼ 10 nm. Quantitative analysis of the defect depth profile requires that a single type of defect dominates the scattering of partiicles out of channeling trajectories. This scattering process is characterized by two defect-specific quantities: the direct scattering factor and the dechanneling cross-section. For impurity-associated defects the lattice location of the impurity atoms can be determined to within ∼ 0.1 Å by simultaneously measuring the impurity and host atom signals as a function of tilt angle about channeling directions. The channeling technique can detect a wide range of intrinsic defects including interstitials, dislocations, stacking faults, microtwins, and amorphous clusters. Examples of the application of channeling to study defects in silicon will be given for the cases: 1) hydrogen trapping at defects; 2) ion implantation doping; and 3) epitaxial growth of layers.
Dislocation Nucleation Models From Point Defect Condensations in Silicon and Germanium
Authors: Tan T.Y.
Published: March 2011

The process of dislocation nucleation from point defect condensations in Si(Ge) is discussed. Based on the assumption that during the dislocation nucleation stage, the dominant factor in the configurational energy is the number of dangling bonds per point defect incorporated, rather than the more commonly recognized factor of strain energy, it is possible to model the dislocation nucleation process. In order to minimize the number of dangling bonds, point defects would condense into row configurations elongated in <110>, called intermediate defects (IDC), and then the IDCs would evolute into undissociated 90° edge –, 60°, and Frank partial dislocations.
Characterization of Defects in Silicon Ribbons By Combined Ebic and Hvem
Authors: Strunk Horst , Cunningham Brian , Ast Dieter
Published: March 2011

The electrical properties and crystallographic nature of linear and planar defects in EFG silicon ribbons were studied. A direct correlation between electrical and structural properties was obtained by imaging the same areas first with EBIC and then with HVEM. Coherent twin boundaries were found to be electrically inactive, but higher order twins and other grain boundaries generally enhanced minority carrier recombination. Partial dislocations confined to coherent twin boundaries were usually electrically active, but in certain instances partial dislocations were observed which had no apparent EBIC contrast.
Precipitation of Oxygen and Intrinsic Gettering in Silicon
Authors: TICE W. K. , Tan T. Y.
Published: March 2011

In this review, dislocations introduced by prismatic punching at SiO2precipitate sites in Czochralski silicon are shown to act as metal adsorption centers. Conditions necessary to localize SiO2precipitate and dislocation complexes in wafer regions remote from semiconductor devices are discussed. This localization achieves an intrinsic gettering effect. The application of the intrinsic gettering mechanism to bipolar and MOS device technologies is shown to improve device performance and leakage limited yields.
Convection and Constitutional Supercooling Cells in Laser Annealed Silicon
Authors: Narayan J. , Fletcher J.
Published: March 2011

The formation of convection and constitutional supercooling induced cells has been studied in indium implanted, laser annealed silicon using plan-view and cross-section electron microscopy. The convection cells were associated with the spatial inhomogeneity in the laser pulse, which leads to large temperature gradients in the lateral direction. The average size of constitutional supercooling cells decreases with increasing velocity of solidification, and it also decreases from (111) orientation to (100). The results of a perturbation theory will be discussed, which predicts the cell size and limiting concentration of instability as a function of velocity of solidification.
Tem Investigation of the Microstructure in Laser-Crystallized Ge Films
Authors: Gale Ronald P. , Fan John C. C. , Chapman Ralph L. , Zeiger Herbert J.
Published: March 2011

The crystallite morphology and defect structure of laser-crystallized Ge films have been characterized by transmission (TEM) and scanning (SEM) electron microscopy. The elongated crystallites present in these films have their long axis in the [001] direction. In regions where these crystallites are well aligned with each other, competitive lateral growth and (110) texture are observed. The defects most frequently found are [111] microtwins. A growth model that accounts for the texture and defects is proposed.
Effects Of Damage-Impurity Interaction On Electrical Properties of Se+-Implanted GaAs
Authors: Sadana D. K. , Washburn J. , Strathman M. D. , Booker G. R. , Badawi M. H.
Published: March 2011

Interaction of impurities with the “visible defects” in hot implanted Cr doped semi-insulating (100) GaAs has been investigated. The defects studies were performed using transmission electron microscopy (TEM) and MeV He+ channeled Rutherford backscattering. The defects distribution was obtained by 90° cross-sectional TEM (XTEM). The atomic concentration profiles of Se, and carrier-concentration and mobility profiles were obtained by secondary ion mass spectrometry (SIMS) and Hall measurements in conjunction with chemical stopping, respectively. Comparison of defects, atomic and electrical profiles, showed the formation of secondary defects at and beyond the projected range (Rp), a significant amount of Se+ diffusion beyond Rp, and compensation of electrical carriers caused mainly by the point defects present in hot implanted GaAs.
Fermi Surfaces of Acceptor Intercalated Compounds: Evidence Frov Asf5-Graphite
Authors: Markiewicz R.S. , Lopatin C. , Zahopoulos C.
Published: March 2011

We find that the carrier concentration in Stage II AsF5- graphite can be varied over a wide range, f≃.30–.46. By studying the Fermi surfaces vs. f via magnetooscillations, we find that the band parameters are essentially unchanged from pure graphite. Thus suggests that all stage two compounds should display a universal behavior as a function of f, and we adduce evidence of this from the literature. We further begin an analysis of extra oscillation frequencies. In AsF5-graphite, mixing frequencies are probably caused by Fermi-level modulation (Vinter-Overhauser effect), while a low frequency (β) is associated with a superlattice.
Electronic Transport Properties of Graphite Acceptor Compounds
Authors: Spain Ian L. , Volin Kenneth J.
Published: March 2011

Calculations of the magnetoresistance of graphite acceptor compounds are made using a tight binding model for the carrier dispersion proposed by Blinowski et al, and measured values of the zero-field resistivity. It is shown that, if a reasonable physical model is used for the mobilities, the magnetoresistance cannot be fitted with two- or three-carrier models. Suggestions for the origin of the magnetoresistance are made.
Magnetic Heat Capacity of Stage 2 Graphite-Coc12
Authors: Shayegan M. , Salamanca-Riba L. , Heremans J. , Dresselhaus G. , Issi J-P.
Published: March 2011

The heat capacity Cp of graphite-CoC12 (stage 2) is measured at zero and high (up to 14 T) magnetic fields (H applied in-plane). By suppressing the magnetic contribution to Cp at the highest fields, we are able to decompose Cp into its electronic, lattice, and magnetic contributions. The magnetic heat capacity CM is seen to have a broad peak at ⋍ 9.1 K. The shape of this peak is consistent with the reported Monte Carlo calculations of CM based on a twodimensional xy model.
Ambient Temperature Alkali Metal Transfer in Hydrocarbons - A New Route to Intercalation Compounds and Alloys
Authors: Besenhard J.O. , Kain I. , Klein H.-F. , MöHwald H. , Witty H.
Published: March 2011

Dissolved cobalt(0) complexes of the type [L3L'Co] (L = phosphanes, e.g. PMe3, L' = olefins, e.g. C2H4) are reversibly reduced by alkali metals A (A = Li, K, Rb, Cs)

n[L3L'Co] + A ⇋ A[L3L'Co]

and hence can be used as A-carriers. These carrier complexes A[L3L'Co]n are even soluble in apolar solvents like pentane.

Action of [L3L'Co] plus A in pentane solution on graphite yields binary intercalation compounds ACn. By contrast, conventional ambient temperature A-transfer reagents (e.g. solutions of A in naphthalene-ether or in NH3) require strongly polar solvents and yield ternary intercalation compounds A(solv)yCn.

The “reducing power” of the alkali cobaltates is close to that of free A: alkali-rich phases like 1st stage KC8 or LiC6 or highly doped polyacetylenes (e.g. K(CH)5) are readily prepared. If intercalation of solvated species is unlikely, the A-transfer reactions may also be performed in polar solvents like ethers.
Temperature Gradient Enhancement of Solid State Battery Performance
Authors: Borey Bruce K. , Horne Frederick H.
Published: March 2011

The equations of nonequilibrium thermodynamics are used to investigate how temperature gradients may be utilized to enhance performance of solid state batteries. One result is that the efficiency of a battery with doped cerium oxide as the electrolyte may be increased by imposition of a temperature gradient. This may lead to greater use of electrolytes of appreciable electronic conductivity. Moreover, temperature gradients may be used to increase mobile ion diffusivity in intercalation electrodes during battery discharge and recharge.
In Situ Raman Scattering Studies of the Electrochemical Intercalation of Graphite in Sulfuric Acid
Authors: Olk C.H. , Yeh V. , Holler F.J. , Eklund P.C.
Published: March 2011

In situ Raman scattering studies of the high-frequency carbon intralayer modes in graphite-H2SO4 have been carried out during the electrochemical intercalation of graphite in sulfuric acid. The data show that within an optical depth of ∼ 200 Å the entire c-face undergoes a sudden transition to the next lower stage (n−1) at the moment when the bulk has just completed forming stage n. Raman data collected in the “overcharge” and “overoxidation” regimes of the electrochemical synthesis indicate rapid shifting of the peaks during these times, indicating a significant increase in the oxidation of the carbon layers.
121Sb MöSsbauer Studies of Graphite–SbF5 Intercalation Compounds
Authors: Mcdaniel D. H. , Boolchand P. , Bresser W. J. , Eklund P. C.
Published: March 2011

Stage 2 samples of graphite-SbF5 intercalVtion compounds were prepared by reacting SbF5 with HOPG at 200°C for 5 days. 121Sb Mössbauer spectra taken at 4.2K reveal an intense and narrow feature in the Sb(5+) region and a weak and broad feature in the Sb(3+) region. Interpretation of these data in terms of possible Sb(5+) and Sb(3+) intercalant species is discussed in connection with chemical aspects of intercalation.
121Sb Mössbauer Studies On No2SbF6 Intercalated Graphite
Authors: Boolchand P. , Bresser W. , Mcdaniel D. , Eklund P.C. , Billaud D. , Fischer J.E.
Published: March 2011

We have examined graphite salts of the composition C23nSbF6(CH3NO2)1,7 n = 1,2 by121Sb Mössbauer spectroscopy at 4.2K. The spectra reveal a strong and narrow feature in the Sb5+ region and no evidence of any features in the Sb3+ region. This result is in general accord with the expectation of only Sb5+ in the chemical form of SbF6− anion in the intercalate layers.
Electrical Properties of Sbcl5, Icl, Hno3, and Br2 Intercalated Pitch Based Carbon Fibers
Authors: Natarajan V. , Woollam John A.
Published: March 2011

Highly graphitized pitch based carbon fibers with heat treatment temperatures (HTT) of 2500°C, and 3000°C have been intercalated with SbCl5, ICl, HNO3, and Br2. These were reacted either by themselves alone, or in double sequence (e.g. Br2 followed by SbCl5). The electrical resistivities of individual fibers were then measured in air, and as a function of temperature, to a series of temperatures, to test air and thermal stability. The lowest resistivity found in this sequence so far is 28 micro ohm cm when ICl intercalation was followed by HNO3 reaction. These conductors are sometimes air stable (depending on intercalant) at room temperature and can be heated somewhat, but begin to deintercalate at much lower temperatures than was found for CuCl2 intercalated fibers [1,2]. In comparison with the CuCl2 reaction with pitch fibers, these intercalants react easily, and thesequential intercalations appear to give lower final resistivities.
Optical Reflectance Studies of Stage 1-4 Graphite-Sbcl5 Intercalation Compounds in the Range 0.2-10 eV
Authors: Heinz R. E. , Doll G. , Charron P. , Eklund P. C.
Published: March 2011

We report optical reflectance measurements on stage 1-4 graphite-SbCl5 intercalation compounds in the energy range 0.2 to 10 eV. The data are analyzed using a Kramers-Kroniq relation to determine the parameters describing the intraband and interband contributions to the dielectric functions ∊1(ω) and ∊2(ω). Structure in these functions are compared with recent band calculations by Blinowski et al.
Commensurate-Glass Phase Transitions in Staged Sbcl5-GIC
Authors: Salamanca-Riba L. , Timp G. , Hobbs L.W. , Dresselhaus M.S.
Published: March 2011

An experimental study is reported of the commensurate (√7 × √7)R19.1° to glass phase transition in stages I < n > 4 graphite-SbCl5 using electron and x-ray diffraction. The electron diffraction studies show an in-plane phase transition to a glass at low temperatures. The (00l) x-ray diffraction scans show that the c-axis layered structure of the intercalate is unchanged by the phase transition. A driving mechanism for the commensurate to glass transition is suggested.
Ferroelectric Thin Films on Silicon and Fused Silica Substrates by Sol-Gel Process
Authors: Xu Yuhuan , Chen Ching Jih , Xu Ren , Mackenzie John D.
Published: March 2011

Ferroelectric thin films including undoped and doped PZT (lead zirconate titanate), BaTiO3 (barium titanate), SBN (strontium barium niobate), KNbO3 (potassium niobate), PBN (lead barium niobate), KNSBN (potassium sodium strontium barium niobate), and LiNbO3 (lithium niobate) were made on silicon and fused silica substrates by a sol-gel process. Microstructure and physical (pyroelectric, ferroelectric and optical) properties of these thin films were studied. Transparent and preferentially orientated SBN thin films on fused silica substrates can be obtained by applying a d.c. electric field during heat treatment. A heterojunction effect was observed in ferroelectric thin films on both n-silicon and p-silicon through measurement of I-V characteristics, and by the demonstration of a photocurrent effect.
Processing, Perovskite Phase Development, and Dielectric Properties for Sol-Gel Derived Pb[(Mg1/3Nb2/3)0.9Ti0.1]O3 Thin Layers
Authors: Francis Lorraine Falter , payne D. A.
Published: March 2011

Alkoxide-based solutions were synthesized and used to prepare Pb[(Mg1/3Nb2/3)0.90Ti0.10]O3 (90PMNT) thin layers on platinized Si. A multilayering spin casting method was used. The effects of preparation procedure, additives, and intermediate heat-treatments on perovskite phase content, microstructure development and dielectric properties are reported. The greatest perovskite content (∼99%) and the best dielectric properties (K ≈ 1500–2000, tan∂ ≈ 0.03 at 100 kHz) resulted from rapid thermal processing of individual layers at 800°C. Polarization-reversal measurements are also reported.
Stresses in Ferroelectric Thin Films
Authors: Desu Seshu B.
Published: March 2011

The stresses in rf sputtered BaTiO3 thin films, deposited on both Si and sapphire single crystals, were studied. From the measured total film stress values, both the intrinsic stresses in the film and the elastic coefficients [Ef/(1–vf)] of the film were obtained. BaTiO3 films can be obtained in any stress state (tensile, stress free or compressive) by varying the deposition temperature, deposition pressure, and substrate. At lower temperatures and pressures compressive intrinsic stresses were observed whereas, at high deposition temperatures and pressures intrinsic stresses were tensile in nature. The [Ef/(1–vf)] value approached the single crystal value for films deposited at low pressures and decreased significantly with increasing deposition pressure.
Early Stages of Growth of BaTiO3 Thin-Films
Authors: Norton M. Grant , English Gerald R. , Carter C. Barry
Published: March 2011

Barium titanate (BaTiO3) is of interest for use in a number of thin-film applications in electronic and optoelectronic devices. For these devices the formation of epitactic films of the correct stoichiometry and phase is essential. The substrate is important during the early stages of growth in the establishment of epitaxy, factors such as lattice mismatch, surface preparation and crystallographic orientation can all affect film nucleation and growth. In this study thin-films of BaTiO3 have been formed using the pulsed-laser ablation technique. The early stages of film growth have been studied directly using transmission electron microscopy by examination of very thin films deposited onto specially prepared electron-transparent thin-foil substrates.
Interface Structure and Dielectric Properties of SrTiO3 Thin Film Sputter-Deposited onto Si Substrates
Authors: Matsubara S. , Sakuma T. , Yamamichi S. , Yamaguchi H. , Miyasaka Y.
Published: March 2011

SrTiO3 thin film preparation onto Si substrates using RF magnetron sputtering has been studied for a high capacitance density required for the next generation of LSI's. Structural and chemical analysis on the interface between SrTiO3 film and Si was carried out with cross-sectional TEM, EDX, and AES. Dielectric properties were measured on AuTi/SrTiO3/Si/Ti/Au capacitors. The as-grown dielectric films on Si were analyzed and found to consist of three layers; SiO2, amorphous SrTiO3 and crystalline SrTiO3, from interface toward film surface. By annealing at 600 °C, the amorphous SrTiO3 layer was recrystallized, and consequently the capacitance value increased. A typical specific capacitance was 4.7 fF/μm2 and the leakage current was in the order of 10−8 A/cm2, for 180 nm thick SrTiO3 film. The dielectric constant decreased from 147 to 56 with decreasing SrTiO3 film thickness from 480 nm to 80 nm. This is due to the low dielectric constant SiO2 layer (ε=3.9) at the interface. From the film thickness dependence of the ε value, the SiO2 layer thickness was calculated to be 3.9 nm, which agreed well with the value directly observed in the TEM.

To avoid SiO2 layer formation, barrier layers between SrTiO3 and Si have been studied. Among various refractory and noble metals, RuSi and a multi-layer of Pt/Ti have been found to be promising candidates for the barrier material. When RuSi film or Pt/Ti film was formed between SrTiO3 film and Si substrate, dielectric constant of about 190 was obtained in dependent of the SrTiO3 film thickness in the range of 80–250 nm. Analysis on the barrier layers was performed by means of RBS, XPS and XRD.
Fatigue and Aging in Sol-Gel Derived PZT Thin Films
Authors: Shepherd W.H.
Published: March 2011

Typical fatigue and aging characteristics are reported for thin PZT films prepared using sol-gels. The fatigue process occurs in two steps. There is an initial period, during which the domain matrix of the as formed film is restructured by the cycling and the polarization generally increases, followed by a period in which the polarization decays. The polarization decay may be due, in part, to the formation of dielectric layers at the electrodes. The effects of voltage and temperature on fatigue are reported. Aging is examined as a function of temperature. Measurements of internal bias fields do not support the view that they are the primary cause of aging. Neither fatigue nor aging are temperature sensitive making identification of specific physical processes difficult.
Size Effects in Sputtered PZT Thin Films
Authors: Desu Seshu B. , Peng Chien H. , Kammerdiner Lee , Schuele Paul J.
Published: March 2011

The ferroelectric properties and switching characteristics of rf sputtered PZT thin films were investigated as a function of film thickness (30–300 nm) and grain size. Electron microscopy was used to characterize the film microstructure. The film thickness was measured by ellipsometer. The results were analyzed for the individual contributions of film thickness and crystallite dimension to the size effects on the properties of ferroelectric thin films. A critical discussion of several different models describing the size effects was also presented.
Processing and Structural Characterization of Ferroelectric Thin Films Deposited by Ion Beam Sputtering
Authors: Ameen M. S. , Graettinger T. M. , Rou S. H. , Al-Shareef H. N. , Gifford K. D. , Auciello O. , Kingon A. I.
Published: March 2011

An analysis is presented of the ion beam sputter deposition of ferroelectric KNbO3 and Pb(Zr, Ti)O3 (PZT), and the observed compositional, structural, and microstructural properties of these films. Films are deposited using a specially designed computer-controlled system with ability to produce multicomponent films via layer-by-layer deposition of elemental components. Metal or oxide targets are sequentially exposed to a high current ion beam by means of a rotatable target holder. A quartz crystal resonator provides feedback information on layer thicknesses to the computer. Precise control of film stoichiometry is obtained using this method.

KNbO3, a material possessing a high figure-of-merit for electrooptic applications, has been deposited epitaxially on (100) MgO substrates. The structure of the optically transparent films has been studied with x-ray and electron diffraction, and transmission electron microscopy. The effects of various processing parameters on the microstructure of the films are discussed.

We have demonstrated the ability of the technique to produce multicomponent films and control cation concentration at elevated substrate temperatures for materials such as PZT. The microstructure and associated ferroelectric properties are discussed in relation to processing conditions.
Pulsed Laser Deposition of Metal Dichalcogenides on Stainless Steel
Authors: John P. J. , Dyhouse V. J. , McDevitt N. T. , Safriet A. , Zabinski J. S. , Donley M. S.
Published: March 2011

Films of MoS2 have been successfully deposited on 440C stainless steel using an excimer laser. A comparison was made of films ablated with the laser operating at 193 nm and at 248 nm. The effects of substrate temperature were also studied. X-ray Photoelectron Spectroscopy (XPS) measurements indicated that the films were sulphur rich as compared to single crystal MoS2. Laser Raman measurements indicated that annealing was necessary to obtain crystalline films. All films exhibited coefficients of friction in the neighborhood of 0.03 in a dry nitrogen environment. Coefficients of friction in laboratory air were significantly higher.
Laser Deposition of CdS Thin films on Various Substrates
Authors: Shi L. , Hashishin Y. , Dong S. Y. , Kwok H. S.
Published: March 2011

We have deposited CdS thin films onto substrates such as glass, sapphire and high Tc YBCO superconducting films by Nd:YAG laser evaporation in a vacuum environment. X-ray diffraction, optical and electrical measurements were used to study the deposited CdS films. The films are highly oriented with c-axis perpendicular to the surface and are optically smooth. The effects of laser fluence, substrate temperature on the film quality will be discussed. Additionally, Indium doped CdS films were also grown on sapphire substrates by laser deposition. In-situ resistivity measurements were employed to study the film formation process during laser deposition. A simple model was given to explain the in-situ resistivity data. Finally, a deposition temperature window was found to produce good quality CdS/YBCO heterostructures. The superconducting transition temperature of the YBCO films was degraded to 68K from an original Tc of 85 K after CdS deposition. The degradation of the superconducting properties was found mainly due to the interactions in the interface region.
Crystallization of Molybdenum Disulfide Films Deposited by Pulsed Laser Ablation
Authors: Zabinski J. S. , Donley M. S. , John P. J. , Dyhouse V. J. , Safriet A. J. , McDevitt N. T.
Published: March 2011

Pulsed laser ablation (PLA) is an emerging technology that provides a mechanism to deposit lubricious films and to tailor film properties by the appropriate choice of substrate materials, deposition parameters and post deposition treatments. The properties of MoS2 films deposited by PLA are evaluated as a function of: (1) substrate material, (2) duration of post deposition annealing treatments using 248 nm laser radiation and (3) substrate temperature during deposition. The chemistry and crystal structure of the different films are determined using small angle X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS). The tribological properties of the films are then evaluated as a function of their chemistry and crystal structure.
Stratified Ion Damage and in Situ Regrowth in GaAs/AlAs Heterostructures
Authors: Cullis A G , Eaglesham D J , Jacobson D C , Poate J M , Whitehouse C R , Smith P W
Published: March 2011

The material-dependent manner in which ion damage occurs in AlAs/GaAs heteroepitaxial structures is demonstrated using conventional and high resolution transmission electron microscopy. Both 150keV and 2MeV Si+ ion implants are employed over a wide range of ion doses. Under conditions which yield rapid build-up of lattice damage in GaAs, the AlAs is found to be relatively resistant to structure breakdown. Indeed, the crystalline AlAs exerts a novel protective effect on immediately adjacent regions of the GaAs layers. For high implantation doses amorphous-crystal superlattices are formed in multilayer structures. For the highest ion doses the AlAs lattice begins to be disrupted by a characteristic, boundary-dependent, heterogeneous mechanism. These observations suggest that mobile point defects play a significant role in AlAs in situ restructuring processes.