bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrogen Absorption and Desorption by Magnesium-Based Nano-Composite Materials
Authors: Kojima Yoshitsugu , Kawai Yasuaki , Haga Tetsuya 
Published: April 2011

ABSTRACTMgH2 was mechanically milled with nano-Ni (nano-Ni/Al2O3/C) and Ni catalysts (Ni), yielding Mg-based nano-composite materials. X-ray and TEM measurements revealed that nano-Ni particles, which are 6–20 nm size, were dispersed in the MgH2 matrix. The nano-composite material with nano-Ni/Al2O3/C showed excellent properties as compared to that with Ni, a ball-milled MgH2 and the mixture of MgH2 and nano-Ni/Al2O3/C in terms of the H2 desorption and absorption. The nano-composite material with nano-Ni/Al2O3/C desorbed H2 of 4.9–5.8 wt% at 423–473 K, while the mixture could not desorb H2 at the temperature. The H2 absorption capacity at 9 MPa and room temperature in 6 hr. increased from below 0.1 wt% for the mixture to 5.0 wt % for the nano-composite material, approaching a maximum of 6.5 wt% in 70 hr. The catalyst activity was improved with decreasing Ni size. The improved kinetics is indicated by the small activation barrier, the short diffusion path length and the high driving force.
NMR and X-ray Diffraction Studies of Phases in the Destabilized LiH-Si System
Authors: Bowman R. C. , Hwang S.-J. , Ahn C. C. , Vajo J. J. 
Published: April 2011

ABSTRACTHydrogen absorption and desorption isotherms have been measured on ballmilled mixtures of LiH+Si powders to evaluate the thermodynamic parameters of these reversible reactions. The phase compositions at the various stages of reaction have been examined by Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR) of the 7Li, 1H, and 29Si nuclei and powder x-ray diffraction (XRD). The initial mixtures of LiH and Si were found to convert into known Li-Si silicide intermetallics (i.e., Li12Si7, Li7Si3, and Li13Si4) as well as providing evidence for a previously unknown ternary Li-Si-H phase as hydrogen was first desorbed and then absorbed. While the absorption reactions are reversible over portions of the Li-Si-H composition range, incomplete recovery of the original LiH + Si phases was also observed under some test conditions.
Archaeological Copper Smelting at Itziparátzico, Michoacan, Mexico
Authors: Maldonado Blanca E. , Rehren Thilo , Howell Paul R. 
Published: April 2011

ABSTRACTMesoamerican copper metallurgy emerged in West Mexico sometime between A.D. 600 and 800. Over a period of approximately 900 years a wide variety of artifacts, typically decorations and other valuable non-utilitarian goods, were produced. By A.D. 1450, the Tarascan kingdom in the state of Michoacan had become the most important center of pre-Hispanic metalworking. Metallurgy played a significant role in the structure of political and economic power in the Tarascan Empire. Metal adornments used as insignia of social status and public ritual became even more associated with political power. While metal was used for an array of goods, virtually nothing is known about the manufacture and the organization of production of this material. Archaeological research at the site of Itziparátzico, near the modern Tarascan community of Santa Clara del Cobre, has recently located potential production areas where concentrations of smelting slag were recorded.The smelting of ores is almost invariably related to the formation of slags, which form from the various impurities introduced into the smelting process, such as gangue minerals, furnace wall material, and fuel ash. Slag analysis thus has the potential for revealing important information about metallurgical technology. Copper smelting slag recovered from the excavations at Itziparátzico has been analyzed for microstructure and compositional properties using light microscopy, x-ray fluorescence spectrometry (XRF), and scanning electron microscopy with energy-dispersive x-ray spectrometry (SEM/EDS). Preliminary results indicate a smelting technology that used sulfidic ores and highly efficient furnaces. While further archaeological investigations are required to precisely date these activities, this technological information is important for establishing the context and scale of production of copper at the site.
Quantitative and Nanoscale Surface Potential Tracking of Ionic and Organic Adsorbates at sub-Monolayer Coverage
Authors: Eng L. M. , Loppacher Ch. , Zerweck U. 
Published: April 2011

ABSTRACTWe use an improved setup for deducing quantitative surface potential values by means of frequency modulated Kelvin-probe force microscopy (FM-KPFM). This method is sensitive to the electrostatic force gradient rather than the absolute force probed in KPFM so far, and therefore provides both a higher lateral resolution and quantitative values. Furthermore, FM-KPFM allows using cantilevers with high spring constants which even favors both the stability and increased topographic resolution. Here, we apply FM-KPFM to deduce interfacial electrical properties of the sub-monolayer coverage of three adsorbates on metal substrates: lithium chloride films, Copper-porphyrines, and C60 molecules.
A Near-Field Microwave Probe for Quantitative Characterization of Dielectric Thin Films
Authors: Talanov Vladimir V. , Moreland Robert L. , Scherz André , Ming Bin , Schwartz Andrew R. 
Published: April 2011

ABSTRACTWe have developed a novel scanning near-field microwave probe capable of precise quantitative measurements of dielectric constant of thin dielectric films. The technique is noncontact and has a few-micron sampling spot-size. For dielectric films with k<7 and thickness down to 200 nm the probe provides precision and accuracy better than 1% and 5%, respectively. The probe is based on a balanced parallel-plate microwave transmission line operating at 4 GHz. Unlike the apertureless STM- or AFM-based schemes that have been previously employed, our “apertured” approach allows for truly quantitative measurements on a few-micron length scale with result that is insensitive to the material property outside this probing volume.We will present quantitative measurements on a variety of so-called low-k dielectric films, which are of great interest to the semiconductor industry as replacements for SiO2 in interconnect wiring. When the probe is placed in close proximity to the film under test its fringe capacitance is governed by the sample permittivity, the tip geometry, and the tip-sample separation. We measure this capacitance with a resolution down to 30 zF using a microwave resonator. Extraction of the film dielectric constant is based on an original approach providing for removal of the substrate contribution. Bulk Si and a set of variable thickness thermal oxide films are employed to calibrate the probe. There is no need to know the absolute value of the tip-sample separation for either measurement or calibration procedures; this separation must only be kept nominally the same for both measurements, which is achieved by a virtually material independent shear-force distance control.
Development of an Ultra-High Vacuum Scanning Nonlinear Dielectric Microscope and Near Atomic-Scale Observation of Ferroelectric Material Surfaces
Authors: Odagawa Hiroyuki , Cho Yasuo 
Published: April 2011

ABSTRACTThis paper describes a newly developed ultra-high vacuum type scanning nonlinear dielectric microscope (UHV-SNDM) and the results from a ferroelectric LiTaO3 single crystal measured by the UHV-SNDM. In a cleaved (012) surface of LiTaO3 crystal, we can clearly observe a striped pattern with a period of about 0.3 nm and a granular pattern approximately corresponding to the sub-lattice period. From this image, we confirmed that the SNDM can be applied to lattice-level measurement in ferroelectric insulator materials.
High-Resolution Photochemical Reaction Using Triplet-Sensitizer Probes
Authors: Miki Hideki , Otomo Akira , Mashiko Shinro 
Published: April 2011

ABSTRACTWe propose molecular-scale photochemical-reaction control using triplet-triplet (T-T) energy transfer from a donor molecule attached on a probe to an acceptor on an insulator surface. In this work, we studied the feasibility of photochemical reactions on a substrate surface using a triplet sensitizer probe. We observed an efficient T-T energy transfer from Michler's ketone on the substrate to an acceptor molecule, cinnamoyl group, on the other substrate facing it. Approximately a quarter of the cinnamoyl groups were dimerized by triplet sensitization. We used a cone-shaped dendron molecule to avoid sensitizer self-quenching caused by the triplet energy migration within the probe surface. We then confirmed efficient site separation of the cone's focal point by measuring the absorption and fluorescent properties of the rhodamine B attached to the focal point. The generation-three dendrons provide enough distance between the functional sites on the probe to reduce singlet energy transfer and it should control triplet energy migration.
Electronic Properties of Modified Surfaces Using Contact and Non-Contact Scanning Probe Microscopy Techniques and SECM.
Authors: Neufeld Aaron K , O'Mullane Anthony , Bond Alan M 
Published: April 2011

ABSTRACTElectrochemical experiments with tetracyanoquinodimethane (TCNQ) modified electrodes in contact with aqueous copper containing electrolytes leads to the incorporation and expulsion of copper ions. This process occurs concomitantly with nucleation and growth processes and significant crystal fragmentation to produce particles with dimensions of the order of 10's of nanometres. During reduction of TCNQ and intercalation of copper ions, different phases of the semiconducting compound CuTCNQ are formed.[1,2] The preparation of both conducting and insulating substrates coated with electroactive TCNQ and CuTCNQ particles of variable size have been made by dip and spin coating procedures. Results suggest that the phase and hence electronic properties of CuTCNQ is dependent on the size of particles that decorate the electrode surface. Combining atomic force microscope (AFM) based methods that interrogate the morphological and electronic properties of nanometre sized particles with use of a scanning electrochemical microscope (SECM) is a new advance in materials characterisation that has proved highly valuable in understanding the highly complex behaviour of these semi-conducting particles.
Apertureless head: a multipurpose tool really combining atomic force microscopy with powerful means for optical investigations.
Authors: Gavrilyuk Vasily V. , Saunin Serguey A. , Zhizhimontov Vladimir V. , Baukov Victor V. 
Published: April 2011

ABSTRACTAn original instrument intended to integrate the advantages of scanning probe, near and far field optical microscopy is presented. The device named Apertureless Head was specially designed to be incorporated to Ntegra scanning probe laboratory, the powerful analytical instrumentation in the nanotechnology field produced by NT-MDT Company, Russia. The device is supposed to be a powerful tool for high resolution analysis in different fields of investigations such as material sciences (optical and optoelectronic, magnetic, semi- and superconducting materials), polymers and biological sciences (structural biology, molecular and cell biology, microbiology, etc.). Probe tip plane light distributions are calculated and different light propagation schemes are discussed.
Simulations of the electrostatic potential in a thin silicon specimen containing a p-n junction
Authors: Somodi P.K. , Dunin-Borkowski R.E. , Twitchett A.C. , Barnes C.H.W. , Midgley P.A. 
Published: April 2011

ABSTRACTThe measurement of potentials associated with dopant atoms in semiconductors at nanometer spatial resolution using off-axis electron holography is known to be affected by the presence of the surfaces of thin specimens. In particular, the potential across a p-n junction is often found to be lower than would be expected from predicted properties of bulk devices. Here we present simulations of two-dimensional potential profiles within a thin (<1 µm) parallel-sided specimen containing a p-n junction. We find that the potential across the p-n junction is always smaller, when projected through the specimen, than would be expected from the properties of the bulk material. Crucially, the step in potential across the junction is independent of the value of the potential on the surface of the specimen for high dopant concentrations (>1017 cm−3). The simulations are compared with experimental data. Although they can account for some of the reduction in the observed potential, they do not fully explain the experimental results.
Novel approaches for the characterization of electromagnetic fields using electron holography
Authors: Kasama Takeshi , Antypas Yanna , Chong Ryan K.K. , Dunin-Borkowski Rafal E. 
Published: April 2011

ABSTRACTTwo recent developments related to the application of off-axis electron holography to the characterization of magnetic and electrostatic fields in nanoscale materials and devices are described. The first is based on the design and implementation of a three-contact electrical biasing specimen holder that allows electron holograms to be recorded from samples as they are tilted to angles of up to ±70° with voltages applied to them in situ in the electron microscope. The second relates to the prospect of characterizing magnetic vector fields in materials in three dimensions using electron holography.
Suzuki Segregation to Stacking Faults in a Cu-Si alloy
Authors: Mendis B.G. , Jones I.P. , Smallman R.E. 
Published: April 2011

ABSTRACTField Emission Gun Transmission Electron Microscopy (FEG TEM) is used to measure solute atom segregation to stacking faults in a Cu- 7.15 at% Si alloy annealed at temperatures of 275°C, 400°C and 550°C. A highly localised increase in the silicon concentration was detected at the stacking fault plane. Segregation of the higher valence silicon atoms increases the local electron to atom ratio in the crystal thereby lowering the stacking fault energy as expected for a Cu-Si alloy system. Measurements across low angle boundaries showed hardly any change in solute concentration, which suggests that the segregation observed at stacking faults is due to a genuine chemical interaction rather than an elastic interaction which can occur in for example high angle grain boundary segregation. The segregation was greatest for the 275°C annealed alloy, where the enrichment is more than 2 at% Si above matrix composition, and was found to decrease monotonically with increasing temperature. The binding energy, as determined from a McLean isotherm, was measured to be -0.021 eV/atom. This is significantly different to the theoretical estimate of -0.0022 eV/atom, as calculated by data on phase equilibria. This could be due to several reasons including experimental error, assigning thermodynamic data of a bulk phase to a stacking fault and inadequacies in the Suzuki segregation model itself.
Electron Holography as a Tool for Dopant Profile Characterization of Semiconductor Devices
Authors: Matsumoto Takao , Kouguchi Masanari 
Published: April 2011

ABSTRACTWe used electron holography to analyze the dopant profile in a MOS transistor. The overall performance of the holography electron microscope at our laboratory has been confirmed by recording a maximum of 16, 000 numbers of electron interference fringes on a conventional electron microscope film. For thin film specimen preparation, we have developed an FIB system with a modified beam scanning scheme in which a high-frequency analog modulation signal is added to the digital signal of the beam deflector. This has enabled us to smooth the residual surface roughness presumably caused by the glitch-noise of D/A converter and we proved that a nearly atomically smooth surface was obtained as estimated with an AFM and TEM. We used this optimized system to characterize the dopant profile in MOS transistors, and comparisons with the calculated profiles from device simulator have proved that they are in good agreement.
Accurate determination of orientation relationships between ferroelastic domains: the tetragonal to monoclinic transition in LaNbO4 as an example.
Authors: Prytz Ø. , Taftø J. 
Published: April 2011

ABSTRACTLaNbO4 crystallizes in a tetragonal high-temperature phase with space group I41/a, which transforms to a monoclinic phase upon cooling below 500 °C. The low-temperature phase has space group I2/a (C2/c) with a monoclinic angle β=94.1°. This system serves as a useful model of a ferroelastic transition of the 4/mF2/m type using the notation of Aizu [1]. This transition produces ferroelastic domains, the boundaries between which are parallel to the monoclinic b-axis. The orientation of these boundaries relative to the monoclinic a- and c-axes has been predicted by Sapriel [2] for all 94 ferroelastic species, and calculations specifically for the LaNbO4 system have been presented by Jian and Wayman [3].We present an accurate determination of the boundary orientation in LaNbO4 using selected area electron diffraction. The boundary planes are parallel to the (2 0 –5.10)/(5.10 0 2) planes of the two domains, as opposed to the predictions of Jian and Wayman which indicate that the domain boundaries should be oriented parallel to the (2 0 -4.04)/(4.04 0 2) planes. Our experimental results are in good agreement with the results of a previous study [4].Furthermore, we present a simple geometric model for calculating the boundary orientation based only on the unit cell parameters of the monoclinic phase. This model gives a boundary orientation in excellent agreement with our experimental determination.
Synthesis and Microstructures of α-Fe2O3 Bicrystalline Nanowires
Authors: Wang R.M. , Chen Y.F. , Fu Y. Y. , Zhang H. , Kisielowski C. 
Published: April 2011

ABSTRACTNovel Fe2O3 nanowires have been successfully synthesized by a simple oxidation process of pure iron. The microstructure of the Fe2O3 nanowires have been systematically investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM). The investigated materials are found to be stoichiometric rhombohedral α-Fe2O3 with typical diameters of 20–80 nm and lengths up to 20 μm. In addition to known single crystal Fe2O3 nanowires, a great amount of novel bicrystalline nanowires were found with ellipsoidal heads. Investigations indicate that most of the bicrystalline nanowires are twins and their orientation relationship is obtained to be (−1, 1, 10)M//(−1, 1, 10)T, [110]M//[-1-10]T. High resolution TEM with numerical reconstruction of the electron exit wave was used to investigated the atomic structure of the micro-twins. Their growth mechanism is briefly discussed on the basis of solid phase growth process.
Electron Microscopy of the Operation of Nanoscale Devices
Authors: Cumings John , Goldhaber-Gordon David , Zettl A. , McCartney M.R. , Spence J. C. H. 
Published: April 2011

ABSTRACTA transmission electron microscope (TEM) is much more than just a tool for imaging the static state of materials. To demonstrate this, we present work on studying the mechanical and electrical properties of carbon nanotube devices. Multiwall carbon nanotubes are concentrically stacked tubular sheets of graphite, where the spacing between each cylinder is simply the natural spacing of graphite. Using a custom-built in-situ nanomanipulation probe, we have shown that it is possible to slide the nanotube layers in a telescopic extension mode that exhibits low friction, demonstrating the potential of nanotubes as the ultimate synthetic nanobearing. During this telescopic extension, the electrical resistance of the nanotube devices increases, opening the possibility that these devices can also be used as nanoscale rheostats. We also briefly describe work on using electron holography inside a TEM to study the electric field distribution in nanotube field-emission devices and on using a nanotube itself as a biprism for electron holography. These measurements together demonstrate the wealth of information that can be obtained and frontiers that can be opened by putting operational nanodevices inside an electron microscope.
Pair Distribution Function as a Probe for Zeolite Structures
Authors: Martínez-Iñesta María M. , Lobo Raúl F. 
Published: April 2011

ABSTRACTIn this article we describe how we have used the pair distribution function of zeolites to solve complex structural problems. A first study was dedicated to refining the structure of disordered zeolite beta, a zeolite that is used in the alkylation of benzene. A second study is a work in progress geared toward the determination of the mechanism of negative thermal expansion of zeolite chabazite, which has been found to be one of the most contracting materials known. Preliminary results suggest that the individual Si-Ox distances and Ox-Si-Ox angles in the tetrahedral are deformed with temperature while the average tetrahedra dimensions stay constant.
Dynamic Responses in Polymer-Clay Gels
Authors: Loizou Elena , Porcar Lionel , Butler Paul , Malwitz Matthew , Schmidt Gudrun 
Published: April 2011

ABSTRACTThe shear orientation of three polymer-clay gels has been investigated by means of small angle neutron scattering (SANS). The gels have the same polymer and clay concentrations but different polymer molecular weight. The polymer is adsorbed to the clay platelets. While long polymer chains can interconnect several platelets shorter polymer chains cannot. Although the polymer concentration is above c* the polymer chain length and cross linking between clay platelets strongly influence their shear orientation which leads to anisotropy in SANS. Our data suggest that the flow is strong enough to enhance and maintain a continuous increase in the shear orientation of the polymer clay gels only when the polymer chains are long enough to interconnect or strongly entangle between platelets.
X-Ray Diffraction as a Probe for Elastic Strain: Micro- and Nanoscale Investigation of Thin Metal Films
Authors: Spolenak R. 
Published: April 2011

ABSTRACTIn the past years the concept of measuring strain by x-rays has changed significantly. The combination of 3rd generation synchrotron sources, advanced focusing techniques and large area detectors has made it possible to probe volumes smaller than a cubic micron. This devolopment has made it possible to probe microstrains directly without having to rely on highly sophisticated models to evaluate peak broadening effects. This paper will provide a review of the state of art of local strain measurements by x-rays, discuss their limitations, provide an outlook of where the field may be going within the next years and address the most important issues to be solved. Examples will be given for the current limits in terms of resolution in time, space, strain and intensity.
In-Situ Infrared (IR) Detection and Heating of the High Pressure Phase of Silicon during Scratching Test
Authors: Dong Lei , Patten John A. , Miller Jimmie A. 
Published: April 2011

ABSTRACTA novel method of in-situ detection of the high pressure phase transformation of silicon during dead-load scratching is described. The method is based on the simple fact that single crystal silicon is transparent to Infrared light while metallic materials are not. Infrared heating during scratching has been performed to thermally soften and deform the transformed metallic material and some promising results were obtained. The sample material used here is silicon, but the same approach can be applied to germanium and other materials, such as ceramics (SiC), which have appropriate optical properties.