bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization, Imaging and Degradation Studies of Quantum Dots in Aquatic Organisms
Authors: Ringwood Amy H , Khambhammettu Sireesha , Santiago Patricia , Bealer Emily , Stogner Michelle , Collins John , Gonsalves Kenneth E
Published: April 2011

There are numerous potential environmental risks of engineered nanoparticles that are not yet well-characterized or understood. Nanoparticles may be introduced into aquatic environments during production processes and also as a result of release following their use in electronic and biological applications. The objectives of these studies were to characterize the behavior of quantum dots (QD) in water, and the accumulation of and toxicity to potential biological receptors in aquatic ecosystems. There are natural differences in environmental factors that may affect the degradation rates of QD’s as well as their toxicity, including temperature, salinity, and pH conditions. To assess the responses under different pH conditions, nonfunctionalized QD’s composed of a Cd/Se core surrounded by a ZnS shell (Evident Technologies) were added to distilled water, at pHs of 4, 6, and 8, and the changes in fluorescent emission spectra over time were determined. Likewise, to determine the effects of salinity on degradation rates, QD’s were added to 0.22 filtered seawater samples of different salinities (10, 20, and 30‰). The accumulation and potential toxicity of QD’s were evaluated using hepatopancreas cells of oysters, Crassostrea virginica.

Fluorescent spectroscopy studies with water and cell samples indicated some degradation in low pH and high salinity waters, but did not indicate that there was increased degradation of QD’s accumulated in cells. Fluorescent confocal microscopy verified that QD’s were accumulated into the hepatopancreas cells. Transmission electron microscopy (TEM) studies verified cellular accumulation, and also indicated some limited degradation of the QD’s by the cells over the short time periods (e.g. hours) used in these preliminary studies. Using a lysosomal destabilization assay, there was some evidence of toxicity to hepatopancreatic cells. These kinds of basic studies are essential for characterizing potential cellular toxicity and addressing the potential impacts of nanoengineered particles on aquatic organisms and basic cellular responses.
Self-assembled Ordered Energetic Composites of CuO Nanorods and Nanowells and Al Nanoparticles with High Burn Rates
Authors: Subramanium Senthil , Hasan Shameem , Bhattacharya Shantanu , Gao Yuanfang , Apperson Steve , Hossain Maruf , Shende Rajesh , Gangopadhyay Shubhra , Redner Paul , Kapoor Deepak , Nicolich Steven
Published: April 2011

Current approaches of mixing fuel and oxidizer nanoparticles or adding fuel nanoparticles to oxidizer gel lead to an overall reduced interfacial area of contact between them and thus, limit their burn rates severely. We have developed an approach of self-assembling fuel nanoparticles around an oxidizer matrix using a monofunctional polymer, poly(4)-vinyl pyridine (P4VP). The polymer has been used to accomplish binding of fuel and oxidizer in a molecularly engineered manner. We use composite of Al-nanoparticles and CuO nanorods for executing this self-assembly. TEM images of this composite confirms the self-assembly of Al-nanoparticles around the oxidizer nanorods. The burn rate of self-assembled composite has been found significantly higher than that of the composite prepared by simple mixing.
Energetic Decomposition of High-Nitrogen Metal Complexes and the Formation of Low-Density Nano-Structured Metal Monoliths
Authors: Tappan Bryce C , Huynh My Hang , Hiskey Michael A. , Chavez David E. , Luther Erik P. , Mang Joseph T. , Son Steven F.
Published: April 2011

Metal complexes of the energetic high-nitrogen ligand, bistetrazole amine (BTA) were ignited in inert environments and their decomposition characteristics were determined. These molecules were found to have the unique properties of a comparatively slow burning rate with very little pressure dependency, unlike most energetic, metal-containing molecules which tend to detonate, rather than burn steadily. This process resulted in unprecedented ultra-low-density, nano-structured, transition metal monoliths, useful as a self-propagating combustion synthesis technique. The resulting nanostructured metal monolithic foams formed in the post flame-front dynamic assembly have remarkably low densities down to 0.011 g cm-3 and extremely high surface areas as high as 270 m2 g-1. In this work we discuss primary the production of iron monoliths, however have produced monolithic nano-porous metal foams via this method with cobalt, copper and silver metals as well. We expect to be able to apply this to many other metals and to be able to tailor the resulting structure significantly.
Reactive Al-Li Powders Prepared by Mechanical Alloying
Authors: Zhu Xiaoying , Schoenitz Mirko , Hoffmann Vern K. , Dreizin Edward L.
Published: April 2011

Mechanically alloyed powders with the composition Al0.7Li0.3 are synthesized. Materials milled for different times are studied using electron microscopy, x-ray diffraction, and thermal analysis. A solid solution of Li in Al (α-phase) is formed with as much as 10 at % of dissolved Li. The LiAl intermetallic δ-phase is readily produced by mechanical alloying but disappears after extended milling times. The final product of milling for 102 hours consists of an x-ray amorphous phase. Mechanically alloyed powders heated in inert environment exhibit several weak exothermic reactions between 420 and 700 K, and two endothermic reactions, around 810 and 870 K. All the observed relaxation processes become less pronounced and eventually become undetectable as the milling time increases and an amorphous material is produced. Ignition experiments performed for the powders coated on an electrically heated filament showed that the powders ignited in the vicinity of 1250 K. An experimental setup for studying combustion of reactive mechanically alloyed powders is developed and initial experimental results are described.
Overview of Nanoscale Energetic Materials Research at Los Alamos
Authors: Son Steven F. , Foley Timothy , Sanders V. Eric , Novak Alan , Tasker Douglas , Asay Blaine W.
Published: April 2011

Metastable Intermolecular Composite (MIC) materials are comprised of a mixture of oxidizer and fuel with particle sizes in the nanometer range. Characterizing their ignition and combustion is an ongoing effort at Los Alamos. In this paper we will present some recent studies at Los Alamos aimed at developing a better understanding of ignition and combustion of MIC materials. Ignition by impact has been studied using a laboratory gas gun using nano-aluminum (Al) and nano-tantalum (Ta) as the reducing agent and bismuth (III) oxide (Bi2O3) as the oxidant. As expected from the chemical potential, the Al containing composites gave higher peak pressures. It was found, for the Al/Bi2O3 system, that impact velocity under observed conditions plays no role in the pressure output until approximately 100 m/s, below which speed, impact energy is insufficient to ignite the reaction. This makes the experiment more useful in evaluating the reactive performance. Replacing the atmosphere on impact with an inert gas reduced both the amount of light produced and the realized peak pressure. The combustion of low-density MIC powders has also been studied. To better understand the reaction mechanisms of burning MIC materials, dynamic electrical conductivity measurements have been performed on a MIC material for the first time. Simultaneous optical measurements of the wave front position have shown that the reaction and conduction fronts are coincident within 160 μm.
Density of RDX Crystals Grown During High Acceleration in an Ultracentrifuge
Authors: Lanzerotti Mary Y. D. , Squillace Richard Z. , Gandzelko Alexander , Sharma Jagadish
Published: April 2011

RDX (cyclotrimethylene-trinitramine) crystals were grown during high acceleration (high g) in an ultracentrifuge. These crystals are found to have a density ∼0.6% greater than 1 g crystals and to have a greatly reduced defect content. The high g crystals should therefore have significantly reduced shock sensitivity as compared to commercial grade RDX. When a RDX saturated acetone solution is accelerated at 200,000 g, the RDX solute molecules move individually through the acetone solvent molecules to form a RDX crystal because the density of the RDX (Theoretical Maximum Density 1.806 g/cc) solute is more dense than the acetone (0.79 g/cc)solvent. Crystal growth is controlled by the g-force. Crystal defects including voids and solution inclusions caused by temperature variation or evaporation at 1 g are minimized and the RDX crystal density increases. A nitrogen pycnometer was used to measure the density of the RDX crystals grown at 1 g and at 200,000 g. The density of the RDX crystals grown at 200,000 g (1.7980±0.0003 g/cc) is found to be greater than the density of RDX crystals grown at 1 g (1.7881±0.0003 g/cc) by 0.0099 g/cc. The density of the high g crystal is 99.6% of the Theoretical Maximum Density of RDX.
A New Approach for Industrial-Scale Production of Carbon Single-Walled Nanotubes
Authors: Harutyunyan A. R. , Mora E. , Tokune T.
Published: April 2011

In the methods reported for continuous synthesis of carbon single-walled nanotubes (SWNTs), the typical production rates are less than 1 g h-1, after purification. Here we report the development of a new technique with higher production rates, up to 6 g h-1, and a scaling capability up to 220 g h-1. SWNTs are produced by vertical floating technique and continuous injection of pre-prepared supported catalyst powder.
Shear Initiated Reactions in Energetic and Reactive Materials
Authors: Meuken Denise , Martines Pacheco Maria , Verbeek Ries , Bouma Richard , Katgerman L
Published: April 2011

Deformation of energetic materials may cause undesired reactions and therefore hazardous situations. The deformation of an energetic material and in particular shear deformation is studied in this paper. Understanding of the phenomena leading to shear initiation is not only necessary to explain for example the response of munitions to intrusions or large deformations imposed in storage and transportation accidents. A fundamental understanding of shear initiation also provides the opportunity to initiate energetic materials in a different and controlled manner, and possibly with a tailored reaction rate of the material. Several small and large scale experiments have been performed in which a shear deformation is imposed onto high explosives as well as thermite based reactive materials. Experiments are numerically simulated in order to correlate small and large scale experiments and understand the initiation mechanisms.
Hydration Effects on the Viscoelastic Properties of Collagen
Authors: Ntim M , Bembey Amanpreet , Ferguson Virginia , Bushby Andrew
Published: April 2011

The manner in which liquid interacts with collagen is unclear, with changes in hydration presenting ambiguity. At present, elastic modulus values for collagen quoted range from MPa to GPa. Dynamic mechanical analysis (DMA) of collagen in isolation provides an insight into the mechanical changes due to altered hydration states.

Changes in the viscoelastic properties of collagen were examined as the material was systematically dehydrated in a series of water:solvent mixes to examine effects of dehydration. The effect of solvents with varying polarity was also examined. Tails from 11-week old wild type mice were used. Mouse tail is a tissue with a well-defined, hierarchical organization of type I collagen. The viscoelastic response of collagen was measured using dynamic mechanical analysis (DMA) in fiber extension mode over the frequency range of 1Hz to 10Hz. Samples were sequentially dehydrated in a series of solvent concentrations: 70% ethanol to 100% ethanol to 100% acetone and 70% ethanol to 70% methanol to 100% methanol for at least 1h. Selectively removing and then replacing water from collagen samples provides insight into the role of water in the ultrastructure of the tissue from the corresponding changes in the experimentally determined elastic modulus and viscous energy.
Chemical Structuring and Materials Design in the Shells of Modern Brachiopods
Authors: Griesshaber Erika , Job Reinhart , Kelm Klemens , Angelika Sehrbrock , Neuser R. D. , Mader Werner , Schmahl Wolfgang W.
Published: April 2011

Compositional and structural variations at various scale levels have been investigated in the shells of the modern brachiopod Megerlia truncata combining transmission electron microscopy (TEM), cathodoluminescence (CL), laser-ablation-inductively-coupled-mass-spectrometric (LA-ICP-MS) and micro-Raman spectroscopical (µRS) analyses. Our results show that these shells can be addressed as hierarchially structured, multi-scaled organic/inorganic fibre composites. A significant chemical as well as a mechanical inhomogeneity is observable within the shells. This occurs on various scale levels ranging from less then one to a few houndred microns. In concert to systematic variations in micro- and nanohardness the µRS and CL analyses reveal a systematic distribution and incorporation of organic material within the shells, which is negligible within the nanocrystalline primary layer but is present in a significant amount in the innermost part of the secondary layer, next to the organic tissue of the animal. Mechanical performance (hardness and fracture toughness) of this biomaterial is mainly determined by textural features, an extreme variation of crystallite size and a purpose oriented interlikage of organic and inorganic components.
Constitutive Modeling of the Stress-Stretch Behavior of Biological Membranes Containing Folded Domains
Authors: Arslan Melis , Boyce Mary C. , Qi Hang J. , Ortiz Christine
Published: April 2011

The mechanical behavior of the red blood cell membrane is governed by the lipid bilayer which resists changes in surface area and the underlying spectrin network which resists changes in shape. The spectrin network can be modeled as an idealized triangulated network. Each spectrin chain consists of folded domains along the length of the chain which can unfold during stretching of the chain. A domain will completely unfold under the application of a chain force of20to35 pNdepending on the rate of imposed chain stretch. During macroscopic stretch of a network, individual chains within the network will experience different levels of chain stretch since the network chains will collectively stretch and rotate to accommodate the imposed stretch. Hence, the stretch on any individual chain will depend on the magnitude and state of macroscopic strain. A microstructurally informed continuum level constitutive model is developed which tracks individual chain deformation behavior as a function of macroscopic strain and also determines the overall macroscopic network stress-strain behavior. Using the introduced continuum approach and statistical mechanics based models of individual chain force-extension behavior, the stress-stretch behavior of the membrane under uniaxial tension is simulated at large stretches and the behavior of the constituent chains is monitored. Domain unfolding occurs within constituent chains during network deformation and the effects of this domain unfolding on the overall macroscopic stress-strain behavior of the network subject to deformation at different strain rates is revealed.
Self-assembled PS-PMMA nanodot array pattern arranged in a parallelogram guide
Authors: Kimura Kaori , Sakurai Masatoshi
Published: April 2011

Mask patterns for XY-type magnetic patterned media using phase separation of polystyrene-polymethylmethacrylate (PS-PMMA) block copolymer were fabricated. Parallelogram guides molded by the nanoimprint lithography controlled the PS-PMMA self-assembling pattern that formed in the guide area. 45nm-pitch defect-free PS-PMMA dot patterns were obtained within a 1μm × 1μm area by optimizing the PS-PMMA film thickness.
Fabrication of Hollow Silica Aerogel Spheres for Direct Drive Inertial Confinement Fusion (ICF) Experiments
Authors: Paguio Reny Richard , Nikroo Abbas , Hund Jared F , Frederick Christopher A. , Jaquez Javier , Takagi Masa , Thi Mary
Published: April 2011

Hollow foam spheres are needed for laser fusion experiments on the OMEGA laser facility at the University of Rochester as part of the demonstration of the feasibility of inertial confinement fusion. Previously polymer based foam and aerogel shells have been produced using resorcinol-formaldehyde (R/F) and divinylbenzene (DVB). In this paper we discuss the development of silica aerogel (SAG) shells. SAG may have the increased robustness, which is important in processing these laser targets. SAG shells were fabricated by the microencapsulation method using a triple orifice droplet generator. This technique allows for precise control of the shell diameter and wall thickness. Reduction of the aerogel gelation time is crucial to fabrication of intact shells with high yield. In addition, the proper choice of the components of the different phases of the microencapsulation process is essential for fabrication of intact SAG shells with proper sphericity and wall uniformity. The density of shells fabricated is approximately 100 mg/cc and the diameter ranges from 700–2000 μm, with a wall thickness of 50–200 μm. Development of a full density permeation barrier for retention of the fusion fuel will also be discussed.
Layer-by-Layer Thin Films of Carbon Nanotubes
Authors: Palumbo Marco , Lee Kye Ung , Ahn Byung Tae , Suri Anil , Coleman Karl , Zeze Dagou , Wood David , Petty Michael C
Published: April 2011

Layer-by-layer films incorporating single-wall carbon nanotubes (SWNTs) with anionic or cationic coatings have been prepared. The process of self-assembly was monitored using the quartz microbalance technique, while the morphology of the resulting thin layers was studied with atomic force microscopy. A variety of different architectures have been built up. The dc conductivities of the thin films, in-plane and out-of-plane, were measured at room temperature and contrasted with reference architectures. The results show clearly that the incorporation of SWNTs into the multilayers resulted in electrically conductive thin films.
Optical Thin Films with Very Low Refractive Index and Their Application in Photonics Devices
Authors: Xi Jingqun , Kim Jong Kyu , Ye Dexian , Juneja Jasbir S. , Lu T.-M. , Lin Shawn-Yu , Schubert E. F.
Published: April 2011

The refractive index contrast in dielectric multilayer structures, optical resonators and photonic crystals is an important figure of merit, which creates a strong demand for high quality thin films with a very low refractive index. SiO2 nano-rod layers with low refractive indices n = 1.08, the lowest ever reported in thin-film materials, is grown by oblique-angle e-beam deposition of SiO2 with vapor incident angle 85 degree. Scanning electron micrographs reveal a highly porous columnar structure of the low-refractive-index (low-n) film. The gap between the SiO2 nano-rods is ≤50 nm, i.e. much smaller than the wavelength of visible light, and thus sufficiently small to make scattering very small. Optical micrographs of the low-n film deposited on a Si substrate reveal a uniform specular film with no apparent scattering. The unprecedented low index of the SiO2 nano-rod layer is confirmed by both ellipsometry measurements and thin film interference measurements. A single-pair distributed Bragg reflector (DBR) employing the SiO2 nano-rod layer is demonstrated to have enhanced reflectivity, showing the great potential of low-n films for applications in photonic structures and devices.
Colloidal Silver Nanoparticle Induced Photoluminescence Quench on the Surface Functionalized Planar Si
Authors: Tay Li-Lin , Rowell Nelson , Boukherroub Rabah
Published: April 2011

The photoluminescence (PL) intensity of undecylenic acid surface functionalized planar Si (001) was investigated in the presence of colloidal Ag nanoparticles. The acid passivated Si surface has a weak PL at 1125 nm. Upon exposure to a Ag nanoparticle sol, the PL quenched exponentially with a characteristic decay time of ∼ 18 minutes. It is known that the metal mediated charge-transfer process provides a pathway for energy decay and leads to a quenching of luminescence in light emitting material. An in-situ study of the surface passivated Si revealed that the Ag nanoparticle was likely to have come into contact or was sited close enough to the semiconductor surface through adsorption to cause effective PL quenching.
Nanofluidic capillaries produced via femtosecond laser induced delamination of thin thermal oxide films from Si(100) substrates
Authors: McDonald Joel Patrick , Mistry Vanita R. , Ray Katherine E. , Yalisove Steven M.
Published: April 2011

Highly selective and repeatable delamination of thermal oxide films from Si(100) substrates has been performed using single and multiple femtosecond laser pulses forming bubbles or blisters. By overlapping the bubbles laterally, tubes or capillaries can be formed with a range of volumes suitable for nanofluidics. By scanning the sample through the laser using an automated translation stage, patterns of tubes with arbitrary complexity can be formed, while the scan velocity can easily control the volume of the tubes. The production time for capillaries in this fashion is considerably less than with other lithographic techniques, while the proximity of the tubes to the underlying silicon substrate yields the possibility for integrated devices. The mechanism responsible for the delamination will be discussed and the optimal laser and sample translation conditions will be presented which provide the most uniform tubes. Atomic force microscopy and optical microscopy of capillaries with a range of volumes will be presented.
Self-organization and Patterning of Multilayers of Molecules
Authors: Salac David , Lu Wei
Published: April 2011

A phase field model is developed to simulate the molecular motion and patterning under the combined actions of dipole moments, intermolecular forces, entropy, and external electric field. The study reveals self-alignment, pattern conformation and the possibility to reduce the domain sizes via a layer by layer approach.
Supramolecular Chemistry at the Liquid/Solid Interface
Authors: De Feyter Steven , Uji-i Hiroshi , Miura Atsushi , Mamdouh Wael , Zhang Jian , van Esch Jan , Feringa Ben , Schenning A. P. H. J. , Meijer E. W. , Wuerthner Frank , De Schryver Frans
Published: April 2011

The liquid/solid interface provides an ideal environment to investigate self-assembly phenomena and scanning tunneling microscopy (STM) is the preferred methodology to probe the structure and the properties of physisorbed monolayers on the nanoscale. Physisorbed monolayers are of relevance in areas such as lubrication, patterning of surfaces on the nanoscale, and thin film based organic electronic devices, to name a few. It's important to gain insight in the factors which control the ordering of molecules at the liquid/solid interface in view of the targeted properties. STM provides detailed insight into the importance of molecule-substrate (epitaxy) and molecule-molecule interactions to direct the ordering of both achiral and chiral molecules on the atomically flat surface. The electronic properties of the self-assembled physisorbed molecules can be probed by taking advantage of the operation principle of STM, revealing spatially resolved intramolecular differences within these physisorbed molecules.
Unconventional Approaches for Advanced Nanotechnology: Functional Patterning and Microfluidic Synthesis
Authors: Choi Kyung , Shea Kenneth , Rogers John
Published: April 2011

Since chemists and materials scientists have been seeking for unconventional routes to synthesize and fabricate novel patterns for applied nanotechnology, we introduced useful functional polymers, which can be patternable on a variety of substrates to fabricate devices with specific functions. We introduce new silicon elastomeric polymers as a stamp material for high fidelity in nano-scale soft lithography. We also fabricated elastic photopatterns by synthesizing photocurable PDMS prepolymers. Photopatternable polymers with specific molecular recognition functions were also employed to fabricate functional patterns with specific functions for our diverse applications.
Control of Colloidal Crystal Growth by External Fields
Authors: von Rhein Elisabeth , Bielawny Andreas , Greulich-Weber Siegmund
Published: April 2011

Synthetic opals serve as templates for the most promising three-dimensional photonic crystals, so-called inverted opals. The time consuming growth of artificial opals by self-assembly of monodisperse sub-micron spheres made of silica or organic materials resulting in fcc and hcp colloidal crystals usually yields in limited crystal qualities. The large scale fabrication and thus their application in photonics suffer from the reproducible growth of defect-free extended bulk crystals. In this paper we propose a sonic wave supported fast colloidal crystal growth in a centrifugal field. White noise acoustic irradiation is thought to realize an artificial temperature allowing particle diffusion during crystal growth.
Growth of Epitaxial Inas Nanowires in a Simple Closed System
Authors: Park Hyun D , Prokes Sharka M , Cammarata Robert C
Published: April 2011

The epitaxial growth of InAs nanowires on an InAs (111) substrate in a sealed quartz tube is described. The method is quite simple and fast, and uses only a bare InAs substrate and a gold colloid coated InAs (111) substrate. High quality InAs nanowires can be produced by this technique.
Amorphization and thermal stability of mechanically alloyed Zr54Cu19Ni8Al8Si5Ti5O1
Authors: Kapaklis Vassilios , Georgiopoulos Athanasios , Schweiss Peter , Politis Constantin
Published: April 2011

In the present work we have intentionally introduced significant amount of oxygen to Zr- based alloys. Samples were prepared either by high energy ball milling of the elemental powders and single phase α-ZrO0.43 at the appropriate stoichiometry, or by melting in an Zr-gettered arc melting facility, in both cases under purified argon atmosphere. The effect of small amounts of oxygen (∼1 at. %) on the amorphization process and the thermal stability of mechanically alloyed Zr54Cu19Ni8Al8Si5Ti5O1 powders and arc melted bulk samples was studied by X-ray diffraction and differential scanning calorimetry. It was found that the introduction of oxygen to the alloy composition does not inhibit the amorphization but enhances greatly the thermal stability of the mechanically alloyed amorphous powders. Compared to samples without oxygen prepared either by arc melting or mechanical alloying, samples with oxygen show an increase of the supercooled liquid region from ΔTx−g=Tx−Tg=117 °C to 141 °C where Tx is the crystallization and Tg the glass transition temperature. The glass transition for the mechanically alloyed samples (Tgma) remains unaffected at 336 °C.
Grain Boundary Structure Evolution in Nanocrystalline Al by Nanoindentation Simulations
Authors: Dupont Virginie , Sansoz Frederic
Published: April 2011

The nanoindentation of a columnar grain boundary (GB) network in nanocrystalline Al has been examined by atomistic simulation. The goal of this study was to gain fundamental understanding on the relationship between structure evolution at GBs and incipient plasticity for indenter tips significantly larger than the average grain size. The nanoindentation simulations were performed by quasicontinuum method at zero temperature. A GB network made of vicinal and high-angle <110> tilt GBs was produced by generating randomly-oriented 5-nm grains at the surface of a 200 nm-thick film of Al. The major findings of this investigation are that (1) nanocrystalline GB networks profoundly impact on the nanoindentation response and cause significant softening effects at the tip/surface interface; (2) GB movement and deformation twins are found to be the predominant deformation modes in columnar Al, in association with shear band formation by GB sliding and intragranular slip, and crystal growth by grain rotation and coalescence; and (3) the cooperative processes during plastic deformation are dictated by the atomic-level redistribution of principal shear stresses in the material.
Atomic-scale simulations of strain localization in a single-component three-dimensional model amorphous solid
Authors: Shi Yunfeng , Falk Michael L
Published: April 2011

Molecular dynamics is used to simulate model non-crystalline solids described by a single-component Dzugutov system. The solids are produced by quenching equilibrium liquids at different cooling rates. These are then tested in uniaxial compression. Samples produced at high cooling rates exhibit homogenous deformation while samples quenched at low cooling rates exhibit localized deformation. Shear bands are shown to correspond to regions of depleted short-range order as determined by a Frank-Kasper criterion.
New transparent conductors anatase Ti1−xMxO2 (M=Nb,Ta): transport and optical properties
Authors: Furubayashi Yutaka , Hitosugi Taro , Yamamoto Yukio , Hirose Yasushi , Otani Makoto , Nakajima Kiyomi , Chikyow Toyohiro , Shimada Toshihiro , Hasegawa Tetsuya
Published: April 2011

We have discovered new transparent conducting oxides (TCOs), anatase Ti1-xMxO2 (M=Nb,Ta), in thin film form. Both films with 0.03 ≤ × ≤ 0.06 showed resistivity of 2−3 × 10−4 Ωcm and internal transmittance of ∼95% in the visible light region (40 nm in thickness), at room temperature. These values are comparable to those of typical TCOs, such as In2−xSnxO3 (ITO).
Photoinduced Solid Phase Transformation in Vanadium Dioxide Films
Authors: Lysenko Sergiy , Vikhnin Valentin , Rua Armando , Fernandez Felix , Liu Huimin
Published: April 2011

Laser induced insulator-to-metal phase transition in VO2 thin films was explored using femtosecond optical pump-probe spectroscopy. The transient reflection and relaxation processes in VO2 were observed during phase transition on 10-11 - 10-9 temporal-scale. Optical generation of carriers in VO2 initiates extremely fast changes in reflectivity which is strongly dependent on pump fluence. Analysis of transient optical properties allows suggesting the excitonic-controlled mechanism responsible for the light-induced phase transition in VO2.
High density BaCeO3 ceramics sintered using microwave irradiation
Authors: Vanetsev Alexander Sergeevitch , Orlov Andrei Vladimirovitch , Tretyakov Yurii Dmitrievitch
Published: April 2011

The goal of this work was to investigate the capabilities of high-power microwaves in manufacture of small-grained barium cerate ceramics. Having compared the samples sintered in the microwave and the thermal fields, we inferred that the microwave sintering occurs at far higher rates. It is also noteworthy that microwave sintering provides a record-breaking low temperature of barium cerate sintering (900°C). Having studied the effect of a microwave field on the microstructure of sintering products, we found that high-power microwave processing significantly reduces the average grain size of barium cerate ceramics.
Magneto-optical Properties of Small Atomic Clusters of Ga and In with As, V and Mn
Authors: Pozhar Liudmila A. , Yeates Alan T. , Szmulowicz Frank , Mitchel William C.
Published: April 2011

The Hartree-Fock (HF) method is used to synthesize virtually (i.e., fundamental theory-based, computationally) small stable atomic clusters of Ga and In with As and V, and an In-based cluster with As and Mn. The electronic energy level structures (ELSs), optical transition energies (OTEs), and charge/spin density distributions of these clusters have been analyzed. It has been shown that the spin of such clusters is collectivized, and that this collectivization is responsible for a dramatic drop in the clusters’ OTEs as compared to those of similar pyramidal clusters that do not contain “magnetic” atoms.
High-Permeability Particles for Magnetic Composites
Authors: Sailer Robert , Jeppson Pamela J , Jarabek Eric L , Sandstrom Joseph A , Al-Badri Zoha , Grier Dean G , Caruso Anthony N , Boudjouk Philip R , Eames Pete , Tondra Mark , Schulz Douglas L
Published: April 2011

Electromagnetic shields and flux concentrators for magnetic sensors could utilize flexible and insulating composites applied using simple thin film deposition methods such as dip-coating, spin-coating, spraying, etc. As the first step towards development of composites with superior performance, efforts focused on isolating nanoparticles with large magnetizations under low fields. In this paper, we provide the results of proof-of-concept studies for two systems: metal-functionalized silicone-based materials (metal-silicone); and, Co-ferrite (Co2+1−xFe2+xFe3+2O4) nanoparticles. The metal-silicone materials studied included a polysiloxane that contained a pendant ferrocene where an optimum saturization magnetization of 5.9 emu/g (coercivity = 11 Oe) was observed. Co-ferrite nanoparticle samples prepared in this study showed unprecendented saturation magnetization (i.e., Ms > 150 emu/g) with low coercivity (Hc ∼ 10 Oe) at room temperature and offer potential application as flux concentrators.
Magnetometer based on the opto-electronic oscillator
Authors: Matsko Andrey , Strekalov Dmitry , Maleki Lute
Published: April 2011

We discuss properties of an all-optical self-oscillating magnetometer based on an opto-electronic oscillator stabilized with an atomic vapor cell. Proof of the principle DC magnetic field measurements characterized with 2 × 10−7 G sensitivity and 1 − 1000 mG dynamic range in one of the schemes are demonstrated.
Length Scale Effect on Deformation and Failure Mechanisms of Ultra-Fine Grained Aluminum
Authors: Hattar Khalid , Han J H , Follstaedt D M , Hearne S J , Saif T A , Robertson I M
Published: April 2011

The deformation and failure processes in ultra-fine and nanograined metals over different length scales have been probed using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) in combination with a micromechanical in situ straining device. This novel straining device affords the opportunity to directly correlate the macroscopic mechanical properties with the microscopic deformation and failure mechanisms. Through use of this device it has been shown that increased film thickness results in a transition between limited plasticity and intergranular fracture to global plasticity and shear failure for deposited aluminum samples of similar grain size but different thickness.
Mechanisms of Grain Growth in Free-Standing Nanograined Gold Thin Films
Authors: Gregg J. A. , Hattar K , Lei C H , Robertson I M
Published: April 2011

Retention of the enhanced properties reported for nanograined metallic systems requires that the nanostructure be insensitive to temperature and deformation. In situ transmission electron microscopy annealing experiments were employed to investigate the structural changes associated with the formation of micron-sized grains in nanograined evaporated gold thin films. This abnormal grain growth occurs randomly throughout the film. Twinning but not dislocation slip occurs in the growing grains until the grain size is in the hundreds of nanometer range. The twins appear to hinder growth and for grain growth to continue the twins must either be annihilated or be able to grow with the grain concurrently.
Molecular Dynamics Simulations of Cluster-size Effect on Sputtering Process with Reactive Gas Cluster Ions
Authors: Aoki Takaaki , Matsuo Jiro
Published: April 2011

To investigate the size-effect of reactive clusters on sputtering processes, we performed molecular dynamics (MD) simulations of reactive cluster ions with various sizes impacting on solid targets. Various sizes of fluorine clusters, (F2)30, (F2)300 and (F2)3000, were irradiated on a Si(100) target at the same total incident energy of 6 keV. These clusters were irradiated on the same target one after another in order to reproduce real experimental conditions such as the accumulation of fluorine atoms in the target. The MD simulations of sequential cluster impacts enabled to perform various statistical analyses regarding the sputtered particles. The study of cluster size distributions showed that the sputtering process by reactive cluster ion impact has similarity with the emission from quasi-liquid materials excited to hyper-thermal conditions by ion bombardment. However, the major sputtered particles were different with each other; Si for (F2)30 (100 eV/atom), SiF2 for (F2)300 (10 eV/atom), and SiF3 for (F2)3000 (1 eV/atom). At the impact of a large size cluster with low incident energy, a large number of Si-F bondings were generated at the cluster-target interface surface, which enhances formation of volatile SiFx compounds with many fluorine atoms. In contrast, a small cluster with high kinetic energy-per-atom could cause the formation of numerous energetic surface atoms at the near surface region, which could be sputtered without being well fluoridated.
Analysis of Successive Focused Ion Beam Slices by Scanning Electron Imaging and 3D Reconstruction
Authors: Yeoh Terence , Ives Neil , Presser Nathan , Stupian Gary , Leung Martin , McCollum John , Hawley Frank
Published: April 2011

An antifuse structure was analyzed using scanning electron microscope imaging and focused ion beam image slicing to generate a form of three-dimensional microscopy. This method reveals nanometer scale features that could not be easily imaged using a single focused ion beam cross-section. A novel end-point detection technique has been developed to control the thickness of the slice to about 2 nm. Voxel imaging and interpretive three-dimensional reconstruction was used to resolve volumes as small as 2 cubic nm3. It was determined that the fusing region for an antifuse is a complex mixture of material phases with an elliptical volume approximately 75 nm in diameter.
Ion-Beam Enhanced Stress-Relaxation of SiGe on SiO2
Authors: Tanaka Masanori , Sadoh Taizoh , Ninomiya Masaharu , Nakamae Masahiko , Enokida Toyotsugu , Miyao Masanobu
Published: April 2011

The Ge condensation by oxidation of SiGe/Si-on-insulator (SOI) structures enabled highly stress relaxed SGOI. However, the relaxation rate obtained in the SiGe layers on insulator (SGOI) abruptly decreased with decreasing SiGe thickness below 50 nm. In order to enhance the relaxation rate in ultra-thin SGOI, the technique combined with H+ irradiation with medium dose (5×1015 cm-2) and post-annealing (1200°C) has been developed. It was demonstrated that highly relaxed (70 %) ultra-thin SGOI with low defect density (<106 cm-2) has been realized by this technique.
Self-assembled nano-dots of heteroepitaxial SiC on Si
Authors: Matsumoto Takashi , Kiuchi Masato , Sugimoto Satoshi , Goto Seiichi
Published: April 2011

Self-assembled silicon carbide (SiC) nano-dots were fabricated on Si wafers by an organometallic ion beam deposition. The self-assembled SiC nano-dots have the shape of a tile, and were heteroepitaxial SiC on Si.
Layer-by-Layer Sputtering and Ultrathin Ion Implantation by Low-Energy Grazing Ion Bombardment
Authors: Dzhurakhalov Abdurauf , Rahmatov Sirojiddin , Teshabaeva Nigorakhon , Yusupov Maqsud
Published: April 2011

The ion sputtering and implantation into GaAs(001) surface at 1-5 keV Se+ grazing ion bombardment have been investigated by computer simulation.The azimuth angular dependencies of sputtering and penetration yield at grazing incidence have been calculated. It was observed that these dependencies correlate the crystal orientation. The depth distributions of 1-5 keV Se ions implanted into GaAs(001) for several azimuth angles of incidence have been presented.
Chemical Behavior and Corrosion Resistance of Medical Grade Titanium after Surface Modification by Means of Ion Implantation Techniques
Authors: Schrempel Frank , Hildebrand Gerhard , Frant Marion , Wesch Werner , Liefeith Klaus
Published: April 2011

This work presents data on topographical structure, chemical surface composition, physicochemical properties and corrosion resistance of medical grade titanium after ion implantation. Pure commercial titanium has been implanted with 30 keV Na-, Ca- and P-ions at fluences of 2.0 × 1017 cm-2 and 1.5 × 1017 cm-2, respectively. Some of the samples were heat treated at 600 °C for 40 min. Atomic force microscopy (AFM) was used for surface analysis. The chemical composition was investigated using Rutherford backscattering spectrometry (RBS). Physicochemical investigations were carried out using contact angle measurements to determine the polarity of the modified titanium surfaces. Moreover, the electrokinetic zeta potentials on a physiological pH value have been determined. Finally, the corrosion resistance was examined in simulated body fluid (SBF) containing 4 g/l bovine serum albumin (BSA) using cyclic voltametry.

Considering the P-implantations, the measured depth distribution of phosphorus agrees well with calculations. For the implantation of Na and Ca, the concentration of implanted atoms in the maximum of the depth distribution is noticeably lower and the distribution extends to larger depths compared to the predictions. This finding is associated with a strong incorporation of oxygen over the whole penetration depth of the implanted ions. According to topographical and chemical changes different contact angles as well as zeta potentials have been detected for the ion implanted surfaces compared to pure titanium. The electrochemical examinations indicate that the implantation has no negative influence on the corrosion resistance in comparison to unmodified medical grade titanium. The results show that ion implantation using certain ions can be used to design tailor-made titanium surfaces from a physicochemical point of view.
Ion irradiation-induced welding of a carbon nanotube to a Si (100) surface
Authors: Kotakoski Jani , Nordlund Kai
Published: April 2011

Carbon nanotubes (CNTs) are one of the possible building blocks for electronic devices in the transition phase from traditional silicon-based microelectronics towards the few-nanometer regime. Remaining problems in integrating CNTs to the existing technology is the low reactivity of the CNT walls which leads to low conductance between CNTs and the other components. Because recent studies have shown that ion irradiation can be used to modify both the electrical and structural properties of CNTs, we propose that it could also be possible to use ion irradiation with low energies to enhance the conductance of these connections. We have used classical molecular dynamics simulations with empirically fitted potentials to examine this possibility by irradiating a single-walled carbon nanotube (SWCNT) on a silicon substrate at room temperature. The nanotube was deposited over a trench created to the silicon substrate so that the nanotube was partly suspended. Low irradiation doses and low energies (0.2 keV − 1.2 keV) were used to ensure that the irradiated CNT will not be destroyed. The simulations were carried out for silicon, carbon and neon ions. Our simulations indicate that ion irradiation will increase the number of covalent bonds between the CNT and the Si substrate. When the irradiation dose and energies are low, the damage caused to the SWCNT atomic network can be tolerable when compared to the improvement in the conductance of the contact regions. Furthermore, as the CNTs have high ability to heal the irradiation-induced damage, it is possible that the irradiation will not have a significant negative effect to the conductivity of the CNT in a system of this type.
High Aspect Ratio Microstructures in LiNbO3 Produced by Ion Beam Enhanced Etching
Authors: Schrempel Frank , Gischkat Thomas , Hartung Holger , Kley Ernst Bernhard , Wesch Werner , Tünnermann Andreas
Published: April 2011

This work presents data on damage evolution, volume expansion and etching behavior of LiNbO3 irradiated with Ar+-ions as a function of irradiation and etching conditions. Single crystals of x- and z-cut LiNbO3 were irradiated at room temperature and 15 K using Ar-ions with energies between 60 and 600 keV and ion fluences between 5 × 1012 and 1 × 1015 cm-2. The damage formation investigated with RBS channeling analysis depends on the crystal cut as well as on the irradiation temperature. Irradiation of z-cut material at 300 K causes complete amorphization at 0.4 dpa (displacements per target atom). In contrast 0.27 dpa are sufficient to amorphize the x-cut LiNbO3. Irradiation at 15 K reduces the number of displacements per atom necessary for amorphization to 0.18 dpa. To study the etching behavior ∼500 nm thick amorphous layers were generated via multiple irradiations with Ar+-ions. Etching was performed in HF-solution of different concentration and at different temperatures. The influence of the irradiation and etching conditions on damage formation and etching of LiNbO3 is discussed. In conclusion, negligible etching of the perfect crystal, high etching rates and high contrast of Ion Beam Enhanced Etching (IBEE) allow the realization of high aspect ratio microstructures in LiNbO3.
Surface Modification of Silicon Nano Mechanical Structures by Carbon Ion Implantation for Post-fabrication Transformation to Silicon Carbide
Authors: Virwani Kumar R , Sood Dinesh K , Elliman Robert G , Malshe Ajay P
Published: April 2011

Internal stresses can cause de-lamination and fracture of coatings and structures and it is well known that ion-implantation can be used to control such behavior through modification of the stress. Here, however, we show that the unique ability of implantation to create controlled stresses in materials by altering both the chemical composition and mechanical properties, combined with an increase in the bending strength of materials, can used to create novel vertical nanostructures. Silicon cantilevers (beams), 193nm thick, 200nm wide and 3μm long, were implanted with carbon ions to create a buried SiCx layers. The internal stresses generated by implantation caused the beams to bend at angles ranging from 10 degrees to greater than 90 degrees, leading to unique vertical nanostructures. This method can be used to create 3-D nano electromechanical systems (NEMS).
Trans-disciplinary Graduate and Refresher Programs for Education, Research and Training in the Fields of Nanoscience and Nanotechnology
Authors: Itoh Tadashi , Akai Hisazumi , Ogawa Hisahito , Diño Wilson Agerico Tan , Ichikawa Satoshi
Published: April 2011

Nanoscience is an area that promises a new understanding of nature, while nanotechnology is the use of nanoscience to build new technologies that will change the world. It has captured the attention of the public, government, and industrial corporations. How it will influence our lives will depend on how we prepare ourselves and our successors. Here we present a brief outline of our effort of education, research and training being taken trans-disciplinarily at Osaka University since 2004, in order to prepare our future scientists, engineers, and industrial leaders in the rapidly flourishing fields of nanoscience and nanotechnology.