bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal and Electrical Transport Measurements of Single-Walled Carbon Nanotube Strands
Authors: Borca-Tasciuc Diana-Andra , LeBon Yann , Nanot Claire , Chen Gang , Borca-Tasciuc Theodorian , Cao Anyuan , Vajtai Robert , Ajayan Pulikel M. 
Published: April 2011

ABSTRACTThis work reports temperature dependent thermal and electrical properties characterization of long (mm size) single-walled carbon nanotube strands. Electrical properties are measured using a 4-probe method. Thermal conductivity and specific heat capacity are determined using an AC driven, self-heating method. Normalized values of resistivity, thermal conductivity, specific heat, thermal diffusivity, and the temperature coefficient of resistance are reported. The trends observed in the temperature dependent properties are comparable with previously published data on multi-walled carbon nanotube strands measured with a similar technique.
Macroporous Silica and Alkylene-Bridged Polysilsesquioxane Gels with Templated Nanopores
Authors: Nakanishi Kazuki 
Published: April 2011

ABSTRACTGels with hierarchical well-defined macropores and supramolecularly templated mesopores have been synthesized in the systems of pure silica as well as organic-inorganic hybrids. Cationic surfactants such as alkyltrimethylammonium salts and nonionic surfactants such as poly(ethyleneglycol)-poly(propyleneglycol)- poly(ethyleneglycol) triblock copolymers, EOPOEO, were found to be effective for pure silica system both in inducing the phase separation to give macroporous morphology and in templating the mesopores within a narrow distribution width. The partial introduction of methyl-modified alkoxide into the pure silica system lead to increased phase separation tendency accompanied by the disturbance of the supramolecular templating of mesopores. By contrast, in the 1,2-bis(trimethoxysilyl)ethane systems, poly(ethylene glycol) and EOPOEO were much better additive to induce phase separation in spite of the presence of internal hydrocarbon chain. Combination of well-defined macropores and supramolecularly templated mesopores has been achieved by selecting an appropriate molecular weight and concentration of EOPOEO in the starting composition.
Micromechanics of PS/PB/PS Triblock-Copolymer Films with Lamellar Morphology
Authors: Tzianetopoulou Theodora , Boyce Mary C. 
Published: April 2011

ABSTRACTHighly oriented, near single-crystal lamellar triblock copolymer films with alternating rubbery-glassy layer morphology possess an interesting anisotropy in their mechanical behavior, which can prove to be attractive for various applications. Here, the deformation micromechanics of highly oriented styrene-butadiene-styrene (SBS) lamellar triblock copolymers are investigated. The competing roles of the glassy (PS) and rubbery (PB) phases in the layered configuration are studied with micromechanical finite element based representative volume element (RVE) models subjected to tensile loading at different directions to the lamellar plane. The calculated material response is compared to x-ray and microscopy data from the literature, and proves to be successful in linking the macroscopic material response to the underlying physics of the microstructural evolution. Moreover, the RVE simulations are successful in reproducing the mechanical behavior of highly oriented nano-clay block copolymer nanocomposites. The response of layered-silicate models having 2wt% clay content is compared to the behavior of the respective neat block copolymer (BCP) and to existing experimental data. The ultimate objective is to facilitate these micromechanical models to design hierarchically ordered materials with properties, which will be optimally tailored for different classes of applications.
Anomalous behavior of confined-supercooled water near the bulk water hypothetical 2nd Critical Temperature
Authors: Mansour F. , Dimeo R. M. , Peemoeller H. 
Published: April 2011

ABSTRACTHigh resolution inelastic neutron scattering measurements of the molecular dynamics of deeply supercooled water confined to a porous host, MCM-41 are reported. Results obtained near the critical temperature of water are discussed. Anomalous behavior near and below the glass transition temperature is also presented and discussed. Results are compared to those from earlier studies on supercooled water.
Vibrational Dynamics of the OH Stretching Mode of Water in Reverse Micelles Studied by Infrared Nonlinear Spectroscopy
Authors: Maekawa Hiroaki , Ohta Kaoru , Tominaga Keisuke 
Published: April 2011

ABSTRACTVibrational dynamics of the OH stretching mode of water in the water pool of reverse micelles (H2O/Aerosol OT (AOT)/isooctane) are studied by nonlinear infrared spectroscopy such as transient grating method and three-pulse photon echo peak shift measurements. The W0 value (W0 =[H2O]/[AOT]) is changed from 2 to 40, which corresponds to a water pool diameter of a few nm to about 20 nm. Polarization dependent transient grating experiments show rapid anisotropy decay of the OH stretching mode, which could be due to resonant intra and intermolecular energy transfer. From the three-pulse photon echo peak shift experiments, the spectral diffusion is found to be dependent on W0.
Dynamics of Buried Polymer -polymer Interfaces in Thin Films
Authors: Lurio L. B. , Hu Xuesong , Narayanan Suresh , Jiao Xuesong , Lal Jyotsana 
Published: April 2011

ABSTRACTWe have performed x-ray photon correlation spectroscopy (XPCS) measurements on a polymer-bilayer system comprised of 100 nm polystyrene film on top of an 80 nm polybromostyrene film, supported on a Si substrate. In order to distinguish the dynamics at the top interface from that at the polymer-polymer interface we have performed the measurement at grazing incidence. In this geometry, a standing wave is set up in the film. We derive a relation for the intensity of the standing wave and the resulting diffuse scattering. This model is compared with the measured diffuse scattering from which we extract a value of 0.7±0.4 dyne/cm for the surface tension between PS and PBrS at 180C. XPCS was then measured in each of two standing wave conditions, first where diffuse scattering only occurs at the polymer-vacuum interface and then where it only occurs at the interior polymer-polymer interface. The measured time correlation functions for each of the two interfaces show clear differences, with the polymer-polymer interface exhibiting much slower dynamics.
Mechanical Properties Of Polyaniline / Multi-walled Carbon Nanotube Composite Films
Authors: Ramamurthy P. C. , Harrell W. R. , Gregory R. V. , Sadanadan B. , Rao A. M. 
Published: April 2011

ABSTRACTHigh molecular weight polyaniline / multi-walled carbon nanotube composite films were fabricated using solution processing. Composite films with various weight percentages of multiwalled carbon nanotubes were fabricated. Physical properties of these composites were analyzed by thermogravimetric analysis, tensile testing, and scanning electron microscopy. These results indicate that the addition of multiwalled nanotubes to polyaniline significantly enhances the mechanical properties of the films. In addition, metal–semiconductor (composite) (MS) contact devices were fabricated, and it was observed that the current level in the films increased with increasing multiwalled nanotube content. Furthermore, it was observed that polyaniline containing one weight percent of carbon nanotubes appears to be the most promising composition for applications in organic electronic devices.
Testing Techniques for Mechanical Characterization of Nanostructured Materials
Authors: Koch Carl C. , Scattergood Ronald O. , Linga Murty K. , Guduru Ramesh K. , Trichy Gopinath , Rajulapati Koteswararao V. 
Published: April 2011

ABSTRACTTesting methods are reviewed that can be applied to the small sample sizes which result from many of the processing routes for preparation of nanocrystalline materials. These include the measurement of elastic properties on small samples; hardness, with emphasis on nanoindentation methods; the miniaturized disk bend test (MDBT); the automated ball indentation test (ABI); the shear punch test; and the use of subsize compression and tensile samples.
Solid State Property - Bonding Electron Density – Volume Plasmon Energy Scaling Relationships: Novel AEM Technique for In Situ Diagnostics of Material Properties at the Nanoscale
Authors: Oleshko Vladimir P. , Howe James M. 
Published: April 2011

ABSTRACTQuantized high-frequency (∼1016 Hz) correlated longitudinal electron excitations (plasmons) generated in the energy-loss range 0–50 eV by fast electrons passing through any solid enable one to probe various states of matter. Their energy, Ep, is directly related to the density of valence electrons, thus allowing determination of solid-state properties that are governed by ground-state densities. Universal features and scaling in relations between Ep and the cohesive energy per atomic volume, bonding electron density and elastic constants have been established. The resulting correlations follow the universal binding energy relationship, thus providing new insights into the fundamental nature of structure-property relationships. They allow direct in situ determination of local material properties in an analytical electron microscope, as illustrated by examples utilizing Al- and Ti-based structural alloys.
Xe Precipitates in Aluminum
Authors: Birtcher Robert C. , Donnelly Stephen E. , Morrison Ian , Allen Charles W. , Furuya Kazuo , Song Minghui , Mitsuishi Kazutaka , Dahmen Ulrich 
Published: April 2011

ABSTRACTReal space, high-resolution transmission electron microscopy observations of Xe confined in nanometer size faceted cavities in Al yield information on both the inert gas and the matrix in which it is confined. At room temperature, Xe in such cavities can be liquid or an fcc solid. In larger cavities, Xe within can undergo melting and recrystallization. The Al surface energy can be deduced from the largest Xe nanocrystal at 300 K by setting the corresponding calculated Laplace pressure equal to the equilibrium pressure for melting of Xe, obtained from empirical bulk compression data. These surface energy values are 1.05 J m-2 for {111} facets and 1.10 Jm-2 for {200} facets. Because of the weak interactions, these values correspond to the surface tensions for Al at 300 K.At room temperature, fluid Xe confined in small faceted cavities in aluminum has up to three ordered layers of Xe atoms at the Al interface. Conceptually in a three-dimensionally confined system of sufficiently small size, complete three-dimensional ordering of the fluid may occur. Molecular dynamics simulations have revealed that such ordering would result in fluid Xe confined to a small tetragonal volume solidifying as a body-centered cubic phase on compression.
Experimental Study of Cluster Size Effect with Size-selected Cluster Ion Beam System
Authors: Toyoda Noriaki , Houzumi Shingo , Aoki Takaaki , Yamada Isao 
Published: April 2011

ABSTRACTA size-selected gas cluster ion beam (GCIB) system has been developed to study the size effects of energetic large cluster ion bombardments on a solid surface for the first time. This system equipped a permanent magnet with a magnetic flux density of 1.2 T. There is a sliding detector and sample holder on a guiding rail perpendicular to the incoming cluster beam axis. By locating a sample at a certain position, particular size of cluster ion can be irradiated continuously with affordable ion current density. When the total acceleration energy of Ar-GCIB was 5keV, both amorphous and oxide thickness on Si substrate increased with decreasing cluster size. This result showed good agreement with that obtained from molecular dynamics simulations.
Structure of Cu Ions in (Cu + Halogen or Chalcogen)-Ion Implanted Silica Glasses
Authors: Fukumi Kohei , Chayahara Akiyoshi , Kageyama Hiroyuki , Kitamura Naoyuki , Kadono Kohei , Kinomura Atsushi , Mokuno Yoshiyuki , Horino Yuji , Nishii Junji 
Published: April 2011

ABSTRACTStructure of Cu ions in (Cl+Cu)-, (Br+Cu)-, (I+Cu)-, (S+Cu)- and (Se+Cu)-ion implanted silica glasses has been studied by x-ray absorption and optical absorption spectroscopies. Cu ions formed Cu-O bonds in the as-implanted glasses, due to the homogeneous distribution of Cu ions and the low local concentration of halogen and chalcogen ions in silica glass. Heat treatment at about 600°C caused the formation of bonds between Cu ions and halogen/chalcogen ions without forming Cu halide or chalcogenide crystals. It was deduced that the formation of these bonds was controlled by the diffusion of Cu ions in silica glass. On the other hands, it was inferred that the formation of Cu halide and chalcogenide crystals was controlled not only by the diffusion of halogen/chalcogen ions but also by the diffusion of matrix ions.
Damage Mechanisms of Ion Implanted Bulk (0001) ZnO Single Crystals.
Authors: Adekore B.T. , Usov I. , Patnaik B. , Parikh N. , Davis R.F 
Published: April 2011

ABSTRACTCrystalline damage created by ion-implantation of dopant impurities in ZnO (0001) substrates was characterized as a function of atomic mass of implanted species using triple-axis (2θ-ω/ω) x-ray diffraction and Rutherford backscattering (RBS). The former revealed the presence of implantation-induced strain through the broadening of the isometric and asymmetric 2θ-ω reflections. However, RBS indicated that the damage introduced during implantation of these ions was insufficient to transform the crystalline lattice into a completely amorphous state. Additional XRD characterization as a function of annealing temperature of the implanted materials showed a reduction in the broadening of the isometric reflections, indicating that structural recovery of implanted ZnO crystals can be achieved.
Diffraction Contrast Image Analysis on the Facet Defects of the Laser Diodes Caused by ECR Cleaning Process
Authors: Cheng S.C. , Ouyang M.X. 
Published: April 2011

ABSTRACTCross-sectional and plan-view TEM techniques were used to study the ion beam passivation of 980 nm laser pump diodes. It is found that under certain operation conditions, the ECR cleaning process produces crystal defects in the facets region of the diodes. By TEM diffraction contrast image analysis, the crystal defects are determined as Frank dislocation loops at the {111} planes of the GaAs crystal. The details of the TEM analysis procedures are described in the paper. In order to obtain high quality passivation of the diodes, the parameters of the ECR cleaning process have to be optimized to eliminate the induced defects.
MAS NMR Study on the Microstructural Changes of Zeolite-NaY under Neutron Irradiation
Authors: Chen J. , Beck L. W. , Wang L. M. , Gu B. X. , Ewing R. C. 
Published: April 2011

ABSTRACTThe results of high-resolution solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) indicate the bond angles of Al-O-Si decrease with the increase of neutronirradiation dose, but there are only minor changes for Si-O-Si bond angles in the current dose range studied. This suggests that zeolite with higher Si/Al ratio is more resistant to neutron irradiation damage. It is also found that [AlO6] formed at higher dose range. The ratio of Si/Al changed from 2.57 before neutron irradiation to 2.76 when the dose reached 2.25×1019 n/cm2, which shows that mild dealumination occurred during neutron irradiation. The strontium ion exchange experiments have been conducted for neutron irradiated, thermally treated and original zeolite samples, respectively. It is found that the ion-exchange ability of neutron-irradiated zeolite-NaY is between those of original and heat-treated zeolite samples. The distortion of the framework under neutron irradiation by the decrease of Al-O-Si bond angles and the formation of [AlO6] is partially responsible for the ion-exchange variability variation of zeolite-NaY.
γ - Ray Detectors Based on Composite A1B5C6 Semiconductors
Authors: Khlyap Galina , Andrukhiv Mikhail , Panchenko Ludmila 
Published: April 2011

ABSTRACTMetal-semiconductor structures based on composite semiconductors A1B5C6 are investigated as possible γ-ray detectors. Electric measurements carried out on the samples before the irradiation have exhibited no special peculiarities. After irradiation the analogous investigations have shown dramatic changes of charge carriers transport. Numerical analysis showed the field-current characteristics similar to the p-n-homo-junction: the forward current is described by the power law I∼(Fa)3/2, where Fa stands for applied electric field. Under reverse bias two clear modes of the carriers transport are observed: under the so-called threshold field FTR ∼ 300 V/m the experimental current is governed by quasi-ohmic law I∼(Fa)0.8; as the applied field exceeds the threshold value, the field-current dependence points out the strong trap-assistant tunneling processes: I∼(Fa)5.
Simulations of Electron Diffraction Contrast Images of Nanometer-sized Dislocation Loops
Authors: Zhou Zhongfu , Dudarev Sergei L , Jenkins Michael L , Sutton Adrian P , Kirk Marquis A 
Published: April 2011

ABSTRACTA computer code has been developed to solve numerically the Howie-Basinski equations of electron diffraction theory, and has been applied to simulate diffraction contrast images of small dislocation loops under weak-beam diffraction conditions. In this paper we describe the basis of the code, and apply it to simulate weak-beam images of small loops under a variety of imaging conditions.
Multi-Dot Floating-Gates in MOSFETs for Nonvolatile Memories – Their Ion Beam Synthesis and Morphology
Authors: Müller T. , Heinig K.-H. , Bonafos C. , Coffin H. , Cherkashin N. , Ben Assayag G. , Schamm S. , Zanchi G. , Claverie A. , Tencé M. , Colliex C. 
Published: April 2011

ABSTRACTScalability and performance of current flash memories can be improved substantially by novel devices based on Multi-Dot Floating Gate MOSFETs. The multi-dot layer in the very thin gate oxide can be fabricated CMOS-compatibly by ion beam synthesis (IBS). Here, we present both experimental and theoretical studies on IBS of multi-dot layers consisting of Si nanocrystals (NCs). The NCs are produced by ultra low energy Si+ ion implantation, which causes a high Si supersaturation in the shallow implantation region. During post-implantation annealing, this supersaturation leads to phase separation of the excess Si from the SiO2. Till now, the study of this phase separation suffered from the weak z contrast between Si and SiO2 phases in Transmission Electron Microscopy (TEM). Here, this imaging problem is solved by Energy Filtered Scanning Transmission Electron Microscopy (EFSTEM). Additionally, kinetic lattice Monte Carlo simulations of Si phase separation have been performed and compared with EFSTEM images. It has been predicted theoretically that the morphology of the multi-dot Si floating gate changes with increasing ion fluence from isolated, spherical NCs to percolated spinodal Si pattern. These patterns agree remarkably with EFSTEM images. However, the predicted fluence for spinodal pattern is lower than the experimental one. Because oxidants of the ambient atmosphere penetrate into the as-implanted SiO2, a substantial fraction of the implanted Si is lost due to oxidation.
Fast Neutral Ar Penetration during Gas Cluster Ion Beam Irradiation into Magnetic Thin Films
Authors: Kakuta Shigeru , Seki Toshio , Sasaki Shinji , Furusawa Kenji , Aoki Takaaki , Matsuo Jiro 
Published: April 2011

ABSTRACTAr penetration during gas cluster ion beam (GCIB) irradiation has been investigated using secondary ion mass spectroscopy (SIMS). The concentration of Ar rose to a maximum and then decreased gradually with increasing depth. The depth of the Ar penetration peak increased in proportion to the cube root of the acceleration voltage of GCIB and was independent of ion dose. Ar penetration was attributed to fast neutrals in the GCIB and was successfully suppressed by decreasing the pressure of the space downstream of the GCIB or decreasing the monomer ion density in order to suppress charge transfer collisions.
Controlled Fabrication by LPCVD of Luminescent SiGe/SiO2 (LTO) Very Thin Multilayers
Authors: Rodríguez A. , Sangrador J. , Rodríguez T. , Avella M. , Prieto A. C. , Jiménez J. , Ortiz M. I. , Ballesteros C. 
Published: April 2011

ABSTRACTAmorphous SiGe/SiO2 multilayers with controlled thickness in the range of nanometers have been deposited by LPCVD at low temperature in a single multistep run. Continuous and discontinuous layers have been deposited. No intermixing between the SiGe and SiO2 layers has been observed. As-deposited and crystallized multilayers have been characterized by Raman spectroscopy, Cathodoluminescence and TEM. The luminescence emission is more intense in the discontinuous layers than in the continuous ones.
Laterally Graded Rugate Filters in Porous Silicon
Authors: Foss Sean E. , Finstad Terje G. 
Published: April 2011

ABSTRACTRugate optical reflectance filters with position dependent reflectance peaks in the visible to near infrared spectrum were realized in porous silicon (PS). Filters with strong reflection peaks, near 100%, no detectable higher order harmonics and suppressed sidebands compared to discrete layer filters were obtained by varying the current density continuously and periodically during etching. An in-plane voltage up to 1.5 V was used to obtain refractive index and periodicity change along the filter surface resulting in reflectance peak shifts of up to 100 nm/mm in the direction of the voltage drop. The effect of the lateral change in optical parameters on the filter characteristics is studied by varying the gradient and comparing measurements at different positions with measurements on a non-graded filter. We have observed extra features in the reflectance spectrum of these graded filters compared with reflectance from a non-graded filter which is likely caused by the gradient.
Fabrication of Two-dimensional Nonlinear Photonic Crystal by Electron Beam Lithography
Authors: Kang Chiang Huen , Shen Ze Xiang , Tang Sing Hai 
Published: April 2011

ABSTRACTIn this paper, we present a study on quasi-phase matched (QPM) two-dimensional χ(2) lithium niobate (LN) nonlinear photonic crystal (NPC) for frequency doubling at λ = 1064nm. The NPCs were fabricated by electron beam lithography (EBL) through periodic polarization inversion of the ferroelectric domains and characterized with electrostatic force microscopy (EFM), atomic force microscopy and optical microscopy. Domain inversion occurred through the entire wafer thickness of 0.5mm as EFM images on the +c face of the z-cut wafer showed uniform domain structures throughout the corresponding electron beam irradiated regions of the -c face. In addition, the intended periodicity was observed. Moreover, domain inversion was also seen to have taken place in bulk from the optical images of the chemically etched samples. The EBL technique offers great flexibility in superlattice design and relative ease of fabrication as compared to the conventional poling techniques as pattern transfer is direct without the need for a mask and/or a coating of resist. Besides, micro- or sub-micro scale superlattices corresponding to wavelengths in the visible and into the ultraviolet are highly feasible, restricted only by the transparency of the crystals.
Photonic Quasiperiodic Multilayers of Porous Silicon
Authors: Nava R. , del Río J. A. , Alonso J. C. , Wang C. 
Published: April 2011

ABSTRACTPorous silicon is an efficient photo- and electro-luminescence material and represents a promising candidate for opto-electronic applications. In the last years, porous silicon multilayers with a high enough refractive index contrast have been obtained. In this work, we study the light transmission in Fibonacci multilayers made of porous silicon. The theoretical reflectance spectra are compared with experimental data, observing a good agreement, even though they are extremely fragile when the number of quasiperiodic layers increases. The photoluminescence spectra show evidences of the quasiperiodic structure and in particular, the observed enhancement in comparison with that of single porous silicon layer could be due to the quasiperiodicity.