bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced Cytocompatibility Properties of Hydroxyapatite Doped with Trivalent Ions
Authors: Massa Elizabeth A. , Slamovich Elliott B. , Webster Thomas J.
Published: April 2011

Hydroxyapatite (HA) is a bone-like ceramic used as a coating for dental and orthopedic implants. It is well known for its good cytocompatibility properties, but is limited in use due to its high solubility within the body and mechanical properties that differ from surrounding tissue and bone. The present in vitro study investigated a variety of dopants as a way to further enhance the good cytocompatibility properties of HA as well as address these problematic properties. The dopants investigated were divalent (magnesium and zinc) and trivalent (yttrium, lanthanum, indium, and bismuth) ions. Of the trivalent ions, yttrium and indium have smaller ionic radii than calcium. The present study showed osteoblast adhesion to be statistically greater (p < 0.1) on yttrium-doped HA and indium-doped HA than on undoped HA. Since yttrium and indium are both trivalent ions of a smaller ionic radius than calcium, and other ions of different size and charge did not show significant changes in osteoblast adhesion, these results suggest that substituting divalent calcium with a trivalent ion of smaller size encourages osteoblast adhesion.
Complex Material Using β-Cyclodextrins and Nickel-Zinc Ferrite to Obtain a Magnetically Targetable Drug Carrier
Authors: Bocanegra Alberto , Mohallem Nelcy D. S. , Sinisterra Rubén D.
Published: April 2011

In this study we describe the preparation and the characterization of a complex material using β-cyclodextrin covalently bound to Ni-Zn ferrite to obtain a magnetically targetable drug carrier. The physical-chemical characterization was performed through Fourier transformed infrared spectroscopy, X-ray diffraction, XRD, thermal analysis (TG/DTA), and atomic absorption spectroscopy. The results pointed out that β-cyclodextrin is externally covalently bound to Ni-Zn ferrite. However it was also verified that the β-cyclodextrin cavity is free and can include bioactive agents. The most interesting feature of this approach is the combination of magnetic properties and the host:guest technology to obtain an efficient targetable drug carrier system.
Polypeptide Ultrathin Films by Vacuum Deposition: Preparation and Characterization
Authors: Fulghum Timothy M. , Yamagami Hiroyuki , Tanaka Kuniaki , Usui Hiroaki , Shigehara Kiyotaka , Advincula Rigoberto C.
Published: April 2011

Polypeptide ultrathin films covalently grafted on solid substrates have attracted considerable attention in the interfacial polymer science community over the past couple of years. The potential applications of these films ranges from applications in liquid crystal displays, biosensors, optical devices, etc.. Their study may address important biocompatibility issues. We have synthesized polypeptide ultrathin films through the use of the physical vapor deposition technique. We expect to gain better insight into the polymerization process of the NCA monomers, as well as, possible control of the secondary structure.

Through use of the vapor deposition technique and the amino acid n-carboxy anhydride (NCA) benzyl serine we have been able to prepare polymeric amino acids for analysis. Benzyl serine NCA was evaporated in high vacuum at a temperature of 95-130°C. Different substrates have been used to examine the effects of chemical binding sites on polymerization and secondary structure formation. From IR-spectroscopy and optical microscopy it was evident that without a free amine initiator on the surface of the substrate, polymerization would not occur. Analysis of the films with IR and optical microscopy were used to determine optimum deposition and polymerization conditions. The methyl peak around 3000 cm-1, amide peak at 1650 cm-1 and the carbonyl stretching at 1750 cm-1 evidence of the monomer are greatly reduced or disappear in the deposition range of 40-100nm/min.

Analysis of the films with attenuated total reflectance (ATR) Infrared spectroscopy was used to examine the secondary structure. Values of amide 1 peak at 1632 cm-1, representing the carbonyl stretching, and the peak at 1530 cm-1, representing the carbon nitrogen stretching, match with literature values of beta sheet conformation.
The Technological Analysis of RMS Titanic's Coal: The Enhancement of Archaeological Research
Authors: Sheehan Michael S. , Sickels-Taves Lauren B.
Published: April 2011

This research focuses on coal recovered from the debris field created when R.M.S. Titanic sank on 15 April 1912. The primary objectives are to evaluate the variety of different sources of coal represented in the Titanic sample, and to identify the specific location of these sources. The methods used to evaluate the research objectives include a variety of trace element, petrographic, and palynological analyses. The results of this study provide critical insight into the socioeconomic circumstances that contributed to the enormity of the disaster.
Partially fluorinated acrylic copolymers as coatings for stone protection: characterization and surface properties
Authors: Toniolo L. , Volpe C. Della , Brugnara M. , Poli T.
Published: April 2011

In the last decades the conservation and protection of historical buildings, after theincreased atmospheric pollution, became a priority in all industrial countries. The natural stones exposed to a dramatically increased aggressive environment show their durability limits. The necessity to study new protective systems specifically projected to defend the materials according to the peculiar characteristics of each stone substrate. The complex heterogeneity of stone substrates demands an adaptable and efficient shielding strategy in order to satisfy the different protection requirements such as water repellency, permeability, photochemical and thermal stability and transparency. These characteristics, obviously, have to be maintained as long as possible. Such modulated multi-response behaviors can only be attempted with materials based on multifunctional copolymers. Different polymeric materials have been employed as coatings for building materials but these products were always transferred from industrial applications to the conservation of Cultural Heritage without a deep knowledge of their properties and without a real optimization of structures for stone protection.
Technological investigation of luster decorated ancient majolicas
Authors: Padeletti G. , Fermo P. , Gilardoni S.
Published: April 2011

In this work some luster decorated ancient ceramics have been analyzed in order to acquire knowledge about technological procedures in luster production during the Renaissance period in Italy. Luster is a thin decorative metallic film present on the surfaces of some previously glazed ancient majolicas. It was obtained by applying on the majolica surface a mixture containing silver and copper compounds. Subsequently the object was fired in a reducing atmosphere.

It was found that the luster color, red-like or gold-like, depends not only on the chemical composition, determined by Inductively Coupled Plasma Emission Spectroscopy (ICP-OES), but on the dimensions of silver and copper metallic nanoparticles forming the luster too. Nanocrystals' dimensions and structural characteristics were determined by Transmission Electron Microscopy (TEM).

As obtaining a satisfactory luster depends on the composition of the underlying glaze too, the chemical composition of the glazes have been determined and the analytical data were submitted to statistical multivariate analysis.
The Early History of Glassmaking in the Venetian Lagoon: A Microchemical Investigation
Authors: Mass Jennifer L. , Hunt John A.
Published: April 2011

The compositions of well-dated archaeological glasses from the Northern Adriatic have been determined to learn more about the origins of the Renaissance Venetian glassmaking industry. Electron probe microanalysis (EPMA) was used to characterize thirty-seven late antiquity (5th – 7th centuries) glass finds from Torcello, an island located five miles to the northwest of the Rialtine islands that make up modern Venice. The late antiquity glass data was used in conjunction with two groups of medieval glass data, a predominately 6th –10th centuries Torcello group analyzed by Brill and an 8th-14th centuries Venetian lagoon group analyzed by Verità to gain insight into the technological evolution of glassmaking in the lagoon. The three data sets were then examined within the context of archaeological evidence for a medieval glass furnace complex at Torcello. Our data on the late antiquity glasses reveals that a decline in Roman-style glassmaking technology during this period may have contributed to Venice's late medieval and Renaissance glassmaking innovations.
Analysis of Electromigration Extrusion Failure Mode in Damascene Copper Interconnects
Authors: Arnaud Lucile , Tartavel Gérard , Berger Thierry , Mondon François , Truche Robert
Published: April 2011

The electromigration performance of copper damascene interconnects has been studied with respect to hillock formation and is compared to void formation failure mode. The metal lines consisted of Chemical Vapor Deposition (CVD) copper deposited on CVD TiN and capped with SiN. SiO2 was used for copper lines insulation and final passivation. Two line widths (0.5 and 3µm) have been characterized. It is shown that higher activation energy values are obtained for void formation failure mode, respectively Ea = 0.86 eV for wide lines (poly-grain microstructure) and Ea =1.04 eV for narrow lines (quasi-bamboo microstructure) than for extrusion failure mode. Failure analysis performed with a Scanning Electron Microscope (SEM) showed that grain boundaries are active diffusion paths in polycrystalline copper lines whereas interface diffusion is believed to be the main diffusion path in narrow lines. Extrusions are shown to occur at the upper interface of copper damascene lines and to extend laterally as a consequence of cracks in dielectric layers and are thus responsible for short circuit between adjacent lines. Implications on extrapolated lifetimes at operating conditions are discussed.
The Effect of Initial Void Configuration on the Morphological Evolution Under the Action of Normalized Electron Wind Forces
Authors: Oren Ersin Emre , Ogurtani Tarik Omer
Published: April 2011

In these studies a comprehensive picture of void shape evolution dynamics and its strong dependence on the initial configuration has been thoroughly investigated by utilizing hypocycloid algebra to generate four different shapes of main interest. Our mathematical model on the isotropic diffusion and mass accumulation on void surfaces, under the action of applied electrostatic potential and capillary effects, follows a novel irreversible but discrete thermodynamic formalism of interphases and surfaces.

As a result during the intragranual motion, in addition to the crescent-like slit formation, very rich and also unusual void morphological variations such as fragmentations into the daughter voids or inner island generation have been observed under the severe (normalized) electron wind intensities or very long exposure times. In these numerical experiments, the Euler's method of finite differences with an automatic time step self-adjustment has been utilized in combination with a rather powerful and fast indirect boundary element method (IBEM) for the solution of the Laplace equation.
Comparative Study on Wafer-Level and Package-Level Electromigration Reliability for Sub-Quarter Micron Logic Devices
Authors: Park Young B. , Lee Duk W.
Published: April 2011

The effects of Al underlayer between Ti and TiN on the electromigration (EM) lifetime of Al stack film were compared by the package-level and conventional wafer-level EM tests. The higher EM resistance of the Al stacks prepared with Ti underlayer can be best explained by their better Al (111) texture and grain size distribution than those with TiN underlayer. The surface roughness of the underlayer is related to the grain size distribution and surface roughness of Al film.
The Electronic Structure and other Properties of Amorphous Silicon Nitride Investigated with Density Functional Theory
Authors: Kroll Peter
Published: April 2011

Structural models of amorphous silcon nitride, a-Si3N4. consisting of 112-448 atoms were studied using density functional methods. We used continuous random alterating networks with well-defined topology for the respersentation of chemical order in the material as theoretical precursors. The models were optimized within the DFT framework and compared them to one “ab inito derived” model obtained from quenching a hypothetical melt. The strong chemical order is maintained in the network models even after Car-Parrinello molecular dynamic (CPMD) simulations at elevated temperatures for several pico-seconds, In contrast, the “ab initio derived” model exhibits n-N bonds.

The optimized strutures of Si3N4 have between 2.6 and 3.2 g/vm3 and comprise few topological defects only. The dominant defects are ever over-coordinated Si and N atoms and the 2-connected is averaged over a dozen modles is, averaged over a dozen models, about 1%. Some models are even free of three-connected Si. The calculated bulk moduli decrease with decreasing density of the a-Si3N4 model. We furthermore investigated the properties of the material ater alloying elements such as H and O, espically their capacity to reduces interal strain.
Effect of Pulsed Magnetic Fields on Crystallization of Polymers
Authors: Levin Mark N.
Published: April 2011

The effect of pre-crystallization pulsed magnetic field (PMF) treatment of linear flexible-chain polymers on kinetics of their crystallization and structure in the crystalline state has been studied in polydimethylsiloxane (PDMS) and polyethylene oxide (PEO). It was established that the PMF treatment can destruct the initial net of non-chemically bonded “physical nodes” of the polymer and thus turn the melt into a metastable state with the increased sensitivity to regimes of crystallization. The effect revealed can lay the foundation for the development of new effective methods of controlled crystallization of the flexible-chain polymers, including fractionation and crystallization of polymorphic polymers in the chosen structural modification.
Molecular Modeling of Defect Structures in Pentacene
Authors: Miska Paul K. , Drummy Lawrence F. , Martin David C.
Published: April 2011

We have studied defect structures in the crystalline organic molecular semiconductor pentacene. Our investigations included the calculation of free surface energies on low index planes. It was found that that the (001) surface had the lowest energy ∼50 mJ/m2, roughly half that of the other low index planes, (100) and (010) ∼120 mJ/m2 and ∼140 mJ/m2 respectively. These calculations were then compared to experimental data from vapor grown crystals using optical microscopy, Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM). We also modeled dislocations dipoles of varying Burgers vector and dipole length. It was found that dislocations were accommodated by extensive molecular deformation near the defect core, as well as a well defined stacking fault that occurred down the length of the dipole. Finally, we investigated low angle tilt grain boundaries. It was seen that low angle boundaries relaxed through molecular deformation in the first layer of molecules at the boundary as well as bending of the (001) planes.
Interfacial Polymerization of Molecular Squares: Thin Microporous Membranes Featuring Size Selective Transport
Authors: O′Donnell Jodi L. , Keefe Melinda H. , Hupp Joseph T.
Published: April 2011

Flat porphyrin molecules have been linked at right angles, using metal atoms, to create square or open-ended box structures having minimum cavity widths of about 2.4 nm and nominal volumes of ca. 14 nm3. Chemically modified versions of the squares feature reactive hydroxyl groups at the top and bottom of each of the four walls of the box structure. These groups combine readily with acid chloride functionalized molecules to yield robust ester linkages. If the reactions are carried out at a liquid-liquid interface with squares in one layer and difunctional acid chloride linkers in the other, polymer formation occurs at the interface. As with other liquid-liquid interfacial polymerizations, the reaction is self-limiting because transport of reactants is inhibited by membrane formation. Polymer films prepared by this method have controllable thicknesses ranging from about 200 nm to 2 microns. The membranes display size-selective porosity with respect to molecules smaller than the intra-square cavity and blocking behavior with respect to larger molecules. Electrochemical and electrochemiluminescence methods are used to measure qualitative and quantitative sieving behavior by employing a conductive metal or ceramic electrode as an underlying platform. In these and related membranes, selective molecular transport is being engineered for applications such as chemical sensing, energy conversion, and chemical catalysis.
Damaging of a Soft Polymeric Substrate by Crack Propagation Through Its Hard Coating
Authors: George M. , Colin J. , Coupeau C. , Grilhé J.W.
Published: April 2011

Atomic force microscopy observations of the fine structure of cracks have been carried out on Nickel thin films on polyimide substrates under tensile test. For strains of the order of 10%, the cracking of the metallic thin film induces notable damaging of the polymeric substrate. Post-mortem observations of the substrate and finite element simulations of the stress field at the cracks head have been performed to characterize this unexpected damaging: the crack propagation at the film/substrate interface and inside the substrate.
Delamination of Poylmer Coatings from Metal Substrates: Submicroscopic and Molecular Aspects
Authors: Rohwerder M. , Hornung E. , Yu Xing-Wen
Published: April 2011

Delamination of organic coatings from metal surfaces can occur in a number of different ways, e.g. as pure cathodic delamination, as Filiform corrosion or a mixture of these. In fact, in most technical systems the pure cases are the exception and, of course, delamination is usually very slow. It has been shown that in fast delaminating systems the length scales may range between several 100 μm and several millimetres, while in systems which show slow delamination the reaction zones can be confined to submicroscopic distances [1]. This underlines the importance of investigation methods with submicroscopic resolution. As a very promising new technique Scanning Kelvin Probe Force Microscopy (SKPFM) was applied for the investigation of cathodic delamination and filiform corrosion on a submicroscopic scale [1, 2]. Indeed, these first investigations have shown that SKPFM gives basically the same information as the standard Scanning Kelvin Probe (SKP), but with a much improved resolution. It could be shown, for instance, that the extension of the reaction zone seems to be much narrower than would have to be assumed from the SKP measurements. Based on the knowledge about the different delamination types that was obtained from investigations with the standard SKP [3–12] the SKPFM should be the ideal tool to get information on the submicroscopic scale. However, SKPFM alone is not sufficient for revealing the underlying fundamental mechanisms; of even higher importance is the knowledge of the molecular and mesoscopic structure at the buried interface. In this paper a design for suitable model samples is proposed and first results are presented.
Direct Imaging of Nanoparticle Embedding into PS Films
Authors: Teichroeb J.H. , Forrest J.A.
Published: April 2011

Non-contact Atomic Force Microscopy (AFM) was used to study the embedding of 10 nm and 20 nm gold nano-particles into the surface of polystyrene films spin-coated onto silicon substrates. The rate of embedding was determined by measuring the apparent nanosphere height as a function of annealing time. This was accomplished by two different methods. In the first case, each image (after a specific annealing time) is acquired at a different spot on the sample surface. In this case a fairly large (∼40) number of particles were imaged in order to have acceptable statistics. A second method involved the use of a kinematic mounting hot stage that allowed the same spot on the sample to be imaged at each time. This allows the same final precision without the same necessity for imaging large numbers of particles. The results indicate that sub nm resolution is easily obtainable with either technique.
Potential Profile Surveyed Directly by Nanomanipulator with Probing Tip in Al/Poly(3-alkylthiophene)/Au Diodes
Authors: Kaneto K. , Nakagawa M. , Takashima W.
Published: April 2011

The potential profiles along the channel of Al/Poly(3-hexylthiophene), PHT film/Au diode from Al to Au electrodes have been measured directly using nanomanipulator with potential probing tips. The steep potential cliff is observed at the interface of Al/PHT, indicating the existence of depletion layer with higher resistance than that of bulk region. For the forward bias, the resistance at the depletion layer decreased significantly and the potential gradient in the PHT bulk region is observed above the onset bias of 1 V. It is found that the contact resistance of PHT/Au is unexpectedly large in spite of the ohmic behavior and also for Al/PHT at forward bias. The effect of light on the depletion layer will be also mentioned. It is stressed that the contact resistances of PHT and metals are significantly important to improve the performance of organic electronics devices.
The Characterization of Copper-Doped Carbon Aerogels by Transport Properties Measurements
Authors: Fu R.W. , Yoshizawa N. , Hanzawa Y. , Kaneko K. , Santos A. P. , Dresselhaus M. S. , Dresselhaus G. , Satcher J. , Baumann T.
Published: April 2011

Copper-doped carbon aerogels, which were prepared by sol-gel polymerization of a mixture of resorcinol, formaldehyde and copper ions, followed by supercritical drying with liquid CO2 and carbonization at different temperatures under a N2 atmosphere, were characterized by magnetic susceptibility and temperature-dependent conductivity measurements. The experimental results show that the magnetic susceptibilities (χ) of all the copper-doped carbon aerogels are larger than that of the blank carbon aerogel. The temperature-dependent magnetic susceptibilities of the copper-doped carbon aerogels are well fit to a Curie function in the low temperature region (below 45 K). According to the Curie constant obtained, the spin concentration (N) of the copper-doped carbon aerogels was calculated and the results show that the spin concentration of doped samples increases at first with an increase in the copper concentration used in doping, and then drops from the maximum in N and χ when the copper concentration is further increased above 0.1 wt%. Magnetic susceptibility results suggest that copper-doped carbon aerogels carbonized at 800 °C are more disordered than those carbonized at 1000 °C. The conductivity of these copper-doped carbon aerogels is apparently higher than that of the blank carbon aerogel, especially at low temperature (T < 45 K). The temperature-dependent resistivities of both the copper-doped and the blank carbon aerogels follow a linear functional form log ρ(T) ∼ (1/T)1/2 with two distinct regions below and above 45 K, indicating that the conduction of both the copper-doped and the blank carbon aerogels obey a tunneling and/or a hopping mechanism.
Experimental Studies and Physical Model of Efficient, Tunable Injection Using Tunnel-Transparent Dielectric Contacts on Polymer Light-Emitting Devices
Authors: Bakueva Ludmila , Musikhin Sergei , Sargent Edward H. , Shik Alexander
Published: April 2011

Most conducting polymers used for light-emitting devices have a small electron affinity, creating a high barrier for electron injection resulting in low injection efficiency. To improve injection characteristics, we fabricated and investigated multi-layer contacts with a tunneltransparent dielectric layer of nanometer thickness. Polymer layers were prepared by spin coating, and dielectric and metallic contact layers subsequently grown by vacuum deposition. Samples with such multi-layer cathodes demonstrated a current-voltage characteristic with negative differential resistance. At larger applied voltage, electroluminescence was observed with an efficiency larger than for a simple cathode of the same metal. We have developed a model to describe double injection through multi-layer contacts which explains these salient observed features. The increase in injection efficiency is caused by the voltage drop at the dielectric layer, shifting the metal Fermi level relative to the polymer molecular orbitals responsible for carrier transport. The negative differential resistance is explained by the strong dependence of dielectric tunnel transparency on voltage, a dependence which is qualitatively different for electrons and holes. Further flexibility in the functional characteristics of the injecting contacts is achieved through the use of an additional thin metallic layer playing the role of a base electrode, similar to hot-electron transistors with metallic base.
Chemical Structure of MEH-PPV/LiF/Al Interface
Authors: Feng X. D. , Grozea D. , Lu Z. H.
Published: April 2011

We studied the poly [2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)/LiF/Al interface by angle-dependent X-ray photoemission spectroscopy (XPS). The changes in the C1s, O 1s, Al 2p core level spectra, and the evolution of O to C and Li to F atomic ratios at different photoelectron take-off angles were carefully analyzed. A reduced oxygen concentration with a LiF layer at the interface suggests that LiF can help reduce the oxidation of Al. The interface was found rich in Li+ ions, some of which might be attached to MEH-PPV to form “N type” doping. The electron injection layer consists of Li+doped MEH-PPV, LiF, Al oxides, and metallic Al.
Electrochemical Polymerization of Conducting Polymer Coatings on Neural Prosthetic Devices: Nanomushrooms of Polypyrrole Using Block Copolymer Thin Films as Templates
Authors: Yang Junyan , Xiao Yinghong , Martin David C.
Published: April 2011

We have demonstrated a method to rapidly and reliably fabricate arrays based on the self-assembled morphology of block copolymer ultra thin films. An ordered, nanoporous structure obtained from the block copolymer thin films is used a template for the subsequent electrodeposition of conducting polymer nanomushrooms of polypyrrole (PPy). The influence of current density, deposition charge and morphology of the templates and nanostructured conducting polymer coatings has been investigated. The electrical properties of the polymer coatings were studied.
A New Approach to Design Light Emitting Devices Using Electroactive Dyes
Authors: Pan Michael , Patra Amitava , Friend Christopher S. , Lin Tzu-Chau. , Cartwright Alexander N. , Prasad Paras. N. , Burzynski Ryszard
Published: April 2011

Organic electroluminescence (EL) single layer devices using electroactive dyes incorporated in poly-vinylcarbazole (PVK) were fabricated. The molecular structures of the two-photon dyes are the generic D-π-A;, D-π-D, and A-π-A;, structural motif, composed of a diphenylamine donor (D), a distyrylfluorene π-bridge, and an oxadiazole acceptor (A). A single layer type of EL device of ITO/PVK:DYE/Ca/Al was fabricated. The light emission peak and the threshold of the electroluminescence emission depend on the structure and concentration of the dye. The EL intensity increases with the dye concentration and it was found that as the voltage is increased the brightness increases and reaches a value 498 cd/m2 at an applied voltage of 25 V for the D-π-A; dye. We present a physical explanation of this observed behavior and show that this has significant impact on the design of light emitting devices using these organic dyes.
Temperature Dependence of the Electrical Resistivity of Polymerized C60 Thin Films
Authors: Govinthasamy R. , Rhee J. H. , Sharma S. C
Published: April 2011

Highly conducting thin films of C60 were deposited by thermal evaporation in high vacuum on single crystal silicon substrates. The microstructure of the films was characterized by using Atomic Force Microscopy, and laser Raman spectroscopy. The films were polymerized by uv irradiation. The dc electrical resistivities of the as-deposited and uv-polymerized films were measured as functions of temperature between 295 and 17K by the four-probe technique. We present results on the effects of uv-irradiation on the surface microstructure and the temperature dependence of the electrical resistivity of these films.
Raman Spectroscopy Measurements of Interface Effects in C60/Copper-Oxide/Copper
Authors: Li Y. , Rhee J. H. , Singh D. , Sharma S. C
Published: April 2011

We have investigated interface effects in C60/Cu-oxide/Cu structures. C60 thin films were grown under high vacuum by thermal evaporation and the well-known “pentagonal pinch mode” of C60, Ag(2) band was examined by Raman spectroscopy. We observe Raman-active bands centered at 1420, 1448, 1455, and 1465 cm−1 in C60/Cu-oxide/Cu samples with a thin (∼40 nm) C60 overlayer. The 1420, 1448, and 1455 cm−1 Raman bands are not observed in the spectra of pristine C60 powder, copper-oxide substrate, and C60/Cu-oxide/Cu samples with thick (∼1.3 μm) C60 overlayer. We associate these new Raman-active bands with C60/copper-oxide interface.
Gate Bias Modulated Current Flow Analysis at Organic Semiconductor / Metal Interface for Developing High Performance Organic Fet
Authors: Yoshida Manabu , Uemura Sei , Hoshino Satoshi , Kodzasa Takehito , Kamata Toshihide
Published: April 2011

We have developed a current flow analysis system for Field Effect Transistors (FET) using a conductive cantilever of a probe microscope. Using this analysis system, nanoscale current images were observed on a pentacene active layer grown on a bottom electrode in ordinary FETs. When gold (Au) was employed as a bottom electrode, we found the special region around the electrode edge. The current flow hardly occurred in this region. On the other hand, using a conductive polymer (PEDOT) bottom electrode, such a region was not observed. From the detailed observation around the electrode edge, we concluded that the special region would be caused by diffusion of Au particles that evoked heterogeneous pentacene growth, and then the heterogeneity worked as a contact resistance.
Fluctuation Microscopy Studies Of Aluminum Oxides Exposed To CL Ions
Authors: Chen Xidong , Sullivan John , Barbour Charles , Johnson Craig , Zhou Guangwen , Yang Judith
Published: April 2011

Fluctuation electron microscopy studies have been performed on several aluminum oxides exposed to different electrochemical conditions. Little is known about amorphous aluminum oxide structures and their relationship with their passivation behaviors. Corrosion studies have shown that exposure of aluminum oxide films to Cl ions in solution reduces the oxide's passivity, and this results in the onset of pitting corrosion. The physical changes that occur in the oxide as a result of Cl exposure have not been previously identified due to the difficulty in investigating the structure of this amorphous material. Fluctuation microscopy is a new electron microscopy technique that is able to detect the presence of medium range order structures in amorphous systems. In this paper, we will report fluctuation microscopy results on amorphous aluminum oxides that have been exposed to Cl ions in solution and compare them with oxides that have seen no electrolyte exposure or that have been exposed to electrolytes that do not contain Cl-,such as SO42- containing electrolytes. We will also compare the Cl-exposed oxides with oxides that have been implanted with Cl ions. The differences in pitting behaviors for these oxidesare consistent with our previous speculation on the effect of medium range order on the passivation behavior of aluminum oxides grown using ozone.
High-resolution thermoreflectance microscopy
Authors: Thorne S.A. , Ippolito S.B. , Ünlü M.S. , Goldberg B.B.
Published: April 2011

We present very high-resolution thermal microscopy using the technique of thermoreflectance, a non-contact measurement of the temperature in and around active semiconductor devices. By measuring the local change in reflectivity and comparing to the optical index versus temperature for the interface materials, thermoreflectance can determine the local temperature distribution. Thermoreflectance allows us to work at wavelengths much smaller than those used in typical blackbody imaging, and thus the spatial resolution is significantly improved over that of traditional thermal microscopy. In our experimental setup, we have a confocal scanning optical microscope with a tunable laser, where reflected light is detected by a silicon photodiode in a heterodyne scheme. The sample consists of a 600 nm wide poly-silicon wire embedded in silicon dioxide on top of a silicon substrate. Varying the amount and temporal shape of the current through the poly-silicon wire, we generate a controlled thermal profile to test the imaging capability. Our preliminary results indicate sub-micron thermal resolution.
Spatially Resolved Characterization of Electromigration-Induced Plastic Deformation in al (0.5WT% CU) Interconnect
Authors: Barabash R.I. , Ice G.E. , Tamura N. , Patel J.R. , Valek B.C. , Bravman J. C. , Spolenak R.
Published: April 2011

Electromigration during accelerated testing can induce early stage plastic deformation in Al interconnect lines as recently revealed by the white beam scanning X-ray microdiffraction. In the present paper, we provide a first quantitative analysis of the dislocation structure generated in individual micron-sized Al grains during anin-situelectromigration experiment. Laue reflections from individual interconnect grains show pronounced streaking after electric current flow. We demonstrate that the evolution of the dislocation structure during electromigration is highly inhomogeneous and results in the formation of unpaired randomly distributed dislocations as well as geometrically necessary dislocation boundaries. Approximately half of all unpaired dislocations are grouped within the walls. The misorientation created by each boundary and density of unpaired individual dislocations is determined.
Synthesis, Characterization and the gas phase catalytic activity of metal doped nanoporous carbon
Authors: Ayyappan Ponnaiyan , Foley Henry C.
Published: April 2011

Metal doped nanoporous carbon(NPC) materials, based on polyfurfuryl alcohol and polyethylene glycol were synthesized using new method. The characterization were carried out using acid-base titration, PXRD, TEM, diffused reflectance FTIR, SEM and mass spectrometer. Their gas phase catalytic activities were checked by passing CO and H2 through the catalysts. Carbondioxide and methane were the evolved gases when CO was passed through the catalyst, whereas carbonmonoxide and methane are the resultant gases when H2 was taken up by the catalyst.
Characterisation of Nanocrystals by Scanning Capacitance Force Microscopy
Authors: Tallarida Grazia , Spiga Sabina , Fanciulli Marco
Published: April 2011

Scanning capacitance force microscopy is used to localise Sn nanometer sized structures embedded in a silicon oxide thin film. The capacitance variation occurring between probe and sample in presence of a metallic cluster modifies the oscillation amplitude of the AFM probe at twice the frequency of the applied voltage. The extreme localisation of the interaction due to the small geometries involved allows a lateral resolution of few nm. Issues related to the contrast mechanism are discussed with the support 2D finite element calculation of the electric field distribution between probe and sample.
Yellow Luminescence Imaging Of Epitaxial Lateral Overgrown GaN Using Ionoluminescence
Authors: Teo E. J. , Bettiol A. A. , Osipowicz T. , Hao M.S. , Chua S.J. , Liu Y. Y.
Published: April 2011

Luminescence imaging techniques such as Photoluminescence (PL) and Cathodoluminescence (CL) have been extensively used to characterize the optical properties of GaN. However, analysis using these techniques is limited to near surface regions and may not represent bulk material properties. This restricts the understanding of the defect-related yellow luminescence in GaN, which tends to originate at the interface region. In this work, we propose the use of MeV protons to probe several microns into a Epitaxial Lateral Overgrown GaN layer. Monte Carlo simulations of the ionization profile show that MeV ions have a much higher penetration depth than the keV electrons used in CL. The well-defined electronic energy loss peak or ‘Bragg peak’ at the end of range for MeV ions enables us to perform depth resolved imaging of the yellow luminescence distribution. Another advantage of using a MeV ion beam over keV electrons is the relatively small lateral spreading of ions in a material, making it a more suitable technique for providing high-resolution images of any buried defects in GaN.
Optical gain and stimulated emission in silicon nanocrystals
Authors: Dal Negro L. , Cazzanelli M. , Gaburro Z. , Bettotti P. , Pavesi L. , Pacifici D. , Franzò G. , Priolo F. , Iacona F.
Published: April 2011

Time-resolved luminescence measurements on silicon nanocrystal waveguides have revealed a fast recombination dynamics, related to population inversion which leads to net optical gain. The waveguide samples were obtained by thermal annealing of plasma enhanced chemical vapour deposited thin layers of silicon rich oxide Variable stripe length measurements performed on the fast emission signal have shown an exponential growth of the amplified spontaneous emission, with net gain values of about 10 cm-1. Both the fast component intensity and its temporal width revealed threshold behaviour as a function of the incident pump intensity. A modelling of the decay dynamics is suggested within an effective four level rate equation treatment including the delicate interplay among stimulated emission and Auger recombinations.
AFM-based Electrical Characterization of Nano-structures
Authors: Biswas Sujit K. , Schujman Sandra B. , Vajtai Robert , Wei Bingqing , Parker Allen , Schowalter Leo J. , Ajayan Pulickel M.
Published: April 2011

Carbon nanotubes have the potential of being used as interconnects and active semiconducting material in future electronic circuits. It is necessary to study such nano-scale circuits with probes that can make measurements with molecular precision. We describe results using two nanoprobe techniques, namely scanning surface potential microscopy (SSPM), and conductive tip atomic force microscopy (CT-AFM), in the investigation of electrical properties of nanotube circuits. Vertical arrays of multi-walled nanotubes, grown in a porous alumina template with a metal back contact were analyzed. Current mapping confirmed that the nanotubes were electrically connected to the back contact. Isolated single-walled nanotube bundles deposited on an oxidized silicon wafer, and contacted electrically through chromium electrodes were also studied. Contact potential differences between the metal and nanotubes, and the current in some connected nanotubes were measured. Measurements of contact potential with different metals, and the nature of microscopic transport is crucial. Contact potential measurements can also provide fast and reliable characterization of junctions between metallic and semiconducting nanotubes and metals electrodes.
Fabrication of isolated ferroelectric nanostructures
Authors: Bhattacharyya S. , Chattopadhyay Soma , Alexe M.
Published: April 2011

In this report, we explore the possibilities of the fabrication and characterization of ferroelectric nano-structures by various methods. Techniques include the self-assembly route and direct electron beam lithography. The chemical self-assembly route, which adopted the microemulsionmediated synthesis, appeared to be very encouraging for producing very small monodispersed nano particles and powders, with sizes of 10–60 nm. The possibility to form a two dimensional arrangement of these micro droplets was explored with a suitable choice of the substrate material, and the method of coating. For the patterns prepared by the e-beam technique, a strong coupling between two closely spaced nano elements was observed, the spacing between them was found to be the key factor in tailoring their interaction, i.e., whether they would arrange themselves in rod-like pattern or a two dimensional array of isolated squares or circles.
In-situ preparation of polymer-coated zirconia nanoparticles by decomposition of zirconium-tert-butoxide
Authors: Schallehn Michael , Lorenzen Volker , Seydel Johannes , Hahn Horst
Published: April 2011

Nanocrystalline zirconia particles coated with polymers have been prepared by a two step Chemical Vapor Synthesis process using a hot wall reactor to synthesize the nanocrystalline ceramic core and a subsequent RF plasma reactor for the polymer coating. The polymer coating is built up of organic byproducts of the pyrolysis of the zirconia precursor. By using continuous and pulsed plasma deposition and variation of the plasma parameters, such as RF power, period and duty-cycle, the structure and thickness of the polymer coating can be influenced. Typical particle radii are in the range of 3 to 4 nm with radii of the ceramic core in the range of 2 nm and a coating thickness in the range of 1 to 2 nm. The powders have been characterized by FT-IR, XRD, BET and HRTEM. Consequences for the dispersibility are reported.
Growth of Carbon Nanofibers on Electroless Ni-P Alloy Catalyst
Authors: Tsai T.K. , Liu W.L. , Hsieh S.H. , Chen W.J.
Published: April 2011

ABSTRATE

Carbon nanotubes (CNTs) were grown by electroless Ni-P plated on silicon substrate in a microwave heating chemical vapor deposition (CVD) system with methane gas at 700 °C. The CNTs grown on Ni–P catalyst showed random orientation and small diameter around 15–30 nm. Field emission test results indicated that the Ni–P catalyzed-CNTs exhibited excellent field emission properties. The turn-on field was about 0.56 V/μm with an emission current density 10 μA/cm2 and the threshold field was 4.4 V/μm with an emission current density 10 mA/cm2. These excellent field emission properties may be attributed to the random orientation and small diameter of CNTs.
Size Reduction of Clay Particles in Nanometer Dimensions
Authors: Mani Gopinath , Fan Qinguo , Ugbolue Samuel C. , Eiff Isabelle M.
Published: April 2011

This research work focuses on combining ball milling and ultrasonication to produce nano-size clay particles. Our work also emphasizes on increasing the specific surface area of montmorillonite clay particles by reducing the particle size to nanometer dimensions. We have characterized the as-received clay particles by using particle size analysis based on laser diffraction and found that the size of the clay particles is not consistent and the particle size distribution is very broad. However, after the unique treatment and processing, the clay particles were obtained in nanometer dimensions with narrowed particle size distribution.
Effect of Solid-Solution W Addition on the Nanostructure of Electrodeposited Ni
Authors: Iwasaki Hajime , Higashi Kenji , Nieh T. G.
Published: April 2011

Electrodeposition method was employed to produce freestanding Ni-W alloy foils. The foils consist of nanograins. The structure of the foil, e.g. texture, grain morphology, size distribution, and the nature of grain boundaries, were characterized using X-ray diffraction and high-resolution electron microscopy. The deposited foils exhibit an equiaxed nanocrystalline structure having a grain size value of about 6 nm. Two types of grain boundary structure were observed. One type of grain boundary is essentially one atomic layer thin and another type consists of a structureless layer of about 0.5–1 nm in thickness. Angular dark field (Z-contrast) image of the deposited foils showed an inhomogeneous distribution of W solutes. In some local regions, the W content actually exceeds the equilibrium solid solution limit. Many grain boundaries with a structureless layer of about 0.5–1 nm are probably a result of local supersaturation of W.
Hydrogen Stabilization of {111} Nanodiamond
Authors: Barnard A.S. , Marks N.A. , Russo S.P. , Snook I.K.
Published: April 2011

Presented here are results of ab initio Density Functional Theory (DFT) structural relaxations performed on dehydrogenated and monohydrogenated nanocrystalline diamond structures of octahedral {111} and cuboctahedral morphologies, up to approximately 2nm in diameter. Our results in this size range show a transition of dehydrogenated nanodiamond clusters into carbon onion-like structures, with preferential exfoliation of the C(111) surfaces, in agreement with experimental observations. However, we have found that this transition may be prevented by hydrogenation of the surfaces. Bonding between atoms in the surface layers of the relaxed structures, and interlayer bonding has been investigated using Wannier functions.
Biodegradable Polyester / Layered Silicate Nanocomposites
Authors: Maiti Pralay , Batt Carl A. , Giannelis Emmanuel P.
Published: April 2011

Nanocomposites of α-hydroxy polyester, polylactide (PLA) and β-hydroxy polyester, polyhydroxybutyrate (PHB) with layered silicates have been successfully prepared by melt extrusion of PLA and PHB with organically modified montmorillonite (MMT) and fluoromica. The mechanical properties of the nanocomposites are improved compared to the neat polymers. Storage modulus increase up to 40% compared with the pure polymers by adding only 2–3 wt% nanoclay. Biodegradation can be controlled by the choice of the nanoclay used.
Mechanical Behavior of Polymer Nanocomposites: a discrete simulation approach
Authors: Chabert E. , Gauthier C. , Dendievel R. , Chazeau L. , Cavaillé J.-Y.
Published: April 2011

This work reports the dynamic mechanical characterization of nanocomposites based on a poly(butyl acrylate) matrix filled with spherical particles of either polystyrene or silica both of diameter around 100 nm. A discrete numerical simulation, taking into account the microstructure and the nature of contact between reinforcing particles has been developed. This simulation enables to quantify the effect of interactions between filler particles on the elastic modulus, and in a more general sense, to clarify the concept of mechanical percolation. It gives results in very good agreement with experimental data.
Modeling mechanical properties of carbon molecular clusters and carbon nanostructural materials
Authors: Levin Vadim M. , Petronyuk Julia S. , Ponomareva Inna V.
Published: April 2011

The concept of 2D elasticity of a graphene sheet together with the idea of stiffness of a single sp3 bond have been applied to theoretical evaluating elastic properties of diverse carbon states. 2D elastic moduli have been extracted from data on elastic moduli of crystalline graphite. Stiffness of the sp3 bond has been estimated from data on the elastic modulus of diamond. Efficiency of Van-der-Waals interaction has been taken from the elastic modulus C33 of crystalline graphite. Characteristics of single fullerene deformability have been computed by the molecular dynamics method. Theoretical estimations have been performed for single molecular clusters, pristine fullerite, HPHT phases of polymerized C60, etc. The estimations are in good agreement with experimental data on elastic properties and nanoscale structure of carbon states. The approach is effective for establishing interrelation between nanostructure and elastic properties, for prediction and classification of nanostructure in novel carbon materials.