bluuebunny/crossref_metadata_2025_split huggingface dataset:
Focused Ion Beam Fabrication of Individual Carbon Nanotube Devices
Authors: Chow Lee , Chai Guangyu 
Published: April 2011

AbstractFocused ion beam (FIB) techniques have found many applications in nanoscience and nanotechnology applications in recent years. However, not much work has been done using FIB to fabricate carbon nanotube devices. This is mainly due to the fact that carbon nanotubes are very fragile and energetic ion beam from FIB can easily damage the carbon nanotubes. Here we report the fabrication of carbon nanotube (CNT) devices, including electron field emitters, atomic force microscope tips, and nano-pores for biomedical applications. This is made possible by a unique, coaxial configuration consisting of a CNT embedded in a graphitic carbon coating, which was developed by us for FIB processing of carbon nanotubes. The CNT-based atomic force microscope tip has been demonstrated. The electron field emission from the tip and the side wall of CNT will be discussed. We will also report the fabrication of a multiwall carbon nanotube nanopore for future applications.
A Piezoresistive Cantilever Force Sensor for Direct AFM Force Calibration
Authors: Pratt Jon R. , Kramar John A. , Shaw Gordon A. , Smith Douglas T. , Moreland John M. 
Published: April 2011

AbstractWe describe the design, fabrication, and calibration testing of a new piezoresistive cantilever force sensor suitable for the force calibration of atomic force microscopes in a range between tens of nanonewtons to hundreds of micronewtons. The sensor is calibrated using the NIST Electrostatic Force Balance (EFB) and functions either as a force reference or stiffness artifact that is traceable to the International System of Units. The cantilever has evenly spaced fiducial marks along its length. We report stiffnesses that vary quadratically with location, from a high of 12.1 N/m at the first fiducial to a low of 0.394 N/m at the last; with force sensitivities that vary linearly, ranging from 18.1 Ù/mN to 106 Ù/mN. We also test the device to transfer the unit of force to an atomic force microscope, finding that force and stiffness based approaches yield independent estimates of the contact force consistent within 2 % of each other.
Molecular Dynamics Simulation of Thermal Conductivity of Diamondoid Crystals
Authors: Hu Ming , Shenogin Sergei , Keblinski Pawel , Majumdar Arun 
Published: April 2011

AbstractHydrocarbon molecules with diamond structure, called diamondoids have gain considerable interest as promising nanoscale building blocks. Very large mismatch between strong, covalent intramolecular bonding and weak intermolecular bonding suggests interesting phonon related properties for diamondoid crystal. We use molecular dynamics (MD) simulations to examine thermal transport of diamondoid crystals. In particular, thermal conductivity of small molecule adamantine and larger molecule pentamantane crystal is studied by equilibrium and non-equilibrium MD. The thermal conductivity of both materials is low, but comparable with that characterizing fullerene crystal.
Nanoscale Thermal Property of Amorphous SiC: A Molecular Dynamics Study
Authors: Wang Weiqiang , Kalia Rajiv K. , Nakano Aiichiro , Vashishta Priya 
Published: April 2011

AbstractThermal properties of amorphous silicon carbide (a-SiC) at nanometric scales are studied by molecular dynamics (MD) simulations based on an empirical interatomic potential. A scalable parallel MD algorithm is used for studying systems as long as 30nm. To validate the potential, phonon density of states and specific heat of a-SiC are first calculated. Size effects are studied, and errors are estimated for the temperature profile for different system sizes. Simulation time required to achieve steady temperature profiles is also determined. Finally the thermal conductivities of a-SiC at various temperatures are calculated. The results show that thermal conductivities of a-SiC at nanometric scale also agree with Slack's minimum thermal conductivity model.
Dynamic Pathway Models for Ion Transport in Nanostructured Heterolayers
Authors: Adams Stefan , Tan Esther S 
Published: April 2011

AbstractThe influence of local structure variations on the charge transport properties are still not well understood at an atomic level. In this work the experimentally observed drastic conductivity enhancement in epitactic stacks of BaF2:CaF2 heterolayers compared to any of the two fluoride ion conducting phases is reproduced by molecular dynamics simulations and analyzed in detail with particular emphasis on the variation of properties with the distance to the two-phase boundary. Ion mobility varies with the distance to the interface but remains significantly enhanced throughout the modeled layers when compared to bulk materials.The bond valence method is utilized to study correlations between the conductivity enhancement and the microstructure. A time-averaged violation of local electroneutrality postulated in the mesoscopic multiphase model is verified by the bond valence analysis of the molecular dynamics simulation trajectories. The variation of the ion mobility can be related to the extension of clusters of unoccupied accessible pathway regions.
Solid Oxide Fuel Cell with Nanostructured Fuel Electrode
Authors: Ansar Syed Asif , Ilhan Zeynep 
Published: April 2011

AbstractNanostructured YSZ+NiO anodes (fuel electrode) for solid oxide fuel cell (SOFC) were developed by plasma spraying. Influence of processing parameters was correlated with deposit microstructure and properties. During particle in-flight with in the plasma jet, the high temperatures of plasma resulted in an increase in average crystallite size; the nanostructure was, however, conserved. Anodes with well distributed finely porous nanostructure exhibiting high gas permeability, suitable high temperature electronic conductivity, enhanced triple phase boundaries and catalytic activity were produced by controlling plasma enthalpy and velocity. Properties of nanostructured anodes were compared with conventional ones. At room temperature the permeability of nanostructured anodes was an order of magnitude higher than their conventional counter parts whereas in-plane conductivity at 800°C in reducing atmosphere of former was 4% higher than that of the latter. Electrochemical performance of optimized nanostructured anode was compared with conventional NiO+YSZ anodes by testing full cells at 800°C. 9.5 mol% YSZ electrolyte and LSM cathode were deposited onto these anodes for electrochemical testing in static and dynamic conditions. Impedance spectroscopy measurements were performed to collect data on polarization resistance and catalytic behavior of anode layers. Gas and temperature variation on both cells was performed and data was compared. It was established that enlarged reaction zone provided by high specific surface area of nanostructured anodes and finely porous microstructure led to lower activation and concentration polarizations and enhanced cell performance by more than 30% compared to conventional cells. During redox (oxidation and reduction of nickel in anode electrode) cycling the cell composed of nanostructured anode exhibited lower degradation.
Electron Diffuse Scattering Characterization of Perovskite Thin Films
Authors: Pacaud Jerome , Pailloux Frederic 
Published: April 2011

AbstractFor perfect crystal, diffuse scattering is mostly inelastic due to phonons, plasmons and other processes. Thermal diffuse scattering or phonon scattering can lead to large effects in the electron diffraction pattern especially near second order phase transition where phonon softening occurs. Additionally, elastic diffuse scattering comes from structural deviations from a periodic lattice. These structural deviations can be defects, partial ordering of otherwise disordered structure or structural fluctuations. By studying diffuse scattering we can obtain information about the crystal imperfections and dynamics which can not be obtained from other characterization methods.
Ultra-fast High Resolution Microscopy: Options for Pump-probe Methods
Authors: Howie Archie 
Published: April 2011

AbstractRecent applications of scanned probe microscopy are defined often going hand in hand with improved spectroscopy. These methods can provide information about dynamic response extending down towards the femotsecond time scale for resettable, repeatable phenomena and may thus help to fill the gap in the microscopist's coverage of material behavior. Although the use of photon pulses is best developed, ultra-short electron pulses are now available. Various options are therefore to hand in either transmission electron microscopy or scanning transmission electron microscopy operation for combining the spatial resolution of electrons with the spectral selectivity and precision of photons. With purely photon pump-probe operation, good spatial resolution can perhaps be obtained using the tip field-enhancement effect in scanning probe microscopy (SPM) and has also recently been impressively demonstrated in two-photon photo-electron microscopy (PEEM) operation.
Magnetic Chiral Dichroism Studies using Energy Filtered Images
Authors: Snoeck Etienne , Warot-Fonrose Benedicte , Gatel Christophe , Houdellier Florent 
Published: April 2011

AbstractWe present the quantitative measurement of inelastic intensity distributions in diffraction patterns with the aim of studying magnetic materials. The original idea of using inelastic signal in a transmission electron microscope to measure magnetic information has been proposed recently by Schattschneider et al [1] and various experimental set-ups can be imagined [2,3]. We focus on a new experimental configuration which we use to acquire and collect a map of the signal with a high signal-to-noise ratio. We will also present the numerical treatments that need to be performed to get spatially accurate information and energy resolution. We will illustrate our method studying iron single crystal and discuss the effects of the drift and non-isochromaticity corrections.
A Simple and Effective Route to Annihilate Defects in Nanocrystalline SnO2 Thin Films Prepared by Pulsed Laser Deposition
Authors: Chen Zhiwen , Wu C. M. L. , Shek C. H. , Lai J. K. L. , Jiao Z. , Wu M. H. 
Published: April 2011

AbstractThe microstructural defects of nanocrystalline SnO2 thin films prepared by pulsed laser deposition have been investigated using transmission electron microscopy, high-resolution transmission electron microscopy and Raman spectroscopy. Defects inside nanocrystalline SnO2 thin films could be significantly reduced by annealing the SnO2 thin films at 300 °C for 2 h. High-resolution transmission electron microscopy showed that stacking faults and twins were annihilated upon annealing. In particular, the edges of the SnO2 nanoparticles demonstrated perfect lattices free of defects after annealing. Raman spectra also confirmed that annealing the specimen was almost defect-free. By using thermal annealing, defect-free nanocrystalline SnO2 thin films can be prepared in a simple and practical way, which holds promise for applications as transparent electrodes and solid-state gas sensors.
In-Situ Neutron Diffraction Study of Gas Tungsten Arc Welding of a 1018 Plain Carbon Steel
Authors: Gharghouri Michael , Watson Michael J , Dye David , Rogge Ronald B 
Published: April 2011

AbstractIn-situ neutron diffraction measurements of a dynamic Gas Tungsten Arc Welding (GTAW) process have been performed using a unique instrument that establishes steady-state conditions by translating and rotating a cylindrical specimen past a stationary weld torch. The fixed neutron sampling volume is at a constant location with respect to the torch as new material is brought into the fusion zone. We present maps of lattice spacing and integrated intensity as a function of location about the weld torch, which provide insight into the temperature and phase distributions around the weld.
In-situ GISAXS on Nanocomposite Films of CdS Nanoparticles and Polymers
Authors: Di Luccio Tiziana , Carbone Dina , Laera Anna Maria , Peeper Katrin , Mauser Christian , Da Como Enrico 
Published: April 2011

AbstractWe investigated the growth of CdS nanoparticles in polymer films by means of ex-situ and in-situ x-ray scattering experiments using synchrotron radiation. The CdS nanoparticles were synthesized by thermal decomposition of a Cd thiolate precursor dispersed in a cyclic olefin copolymer. The films were deposited by spin coating. Grazing incidence diffraction (GID) reveals the Bragg reflections of the CdS nanoparticles. In-situ diffraction and grazing incidence small angle scattering (GISAXS) experiments were recorded during the thermal treatment of the precursor/polymer films from room temperature up to 250°C. The diffraction curves show that the initial precursor structure is soon lost at 100°C. Correspondingly, the GISAXS data show a peak at a momentum transfer value q ∼ 0.2Å−1 that shifts towards smaller values with the temperature. Under UV excitation the films show photoluminescence in the range 400 – 700 nm.
Investigation on different organic semiconductor/organic dielectric interfaces in pentacene-based thin-film transistors
Authors: Orgiu Emanuele , Taki Mohammad , Fraboni Beatrice , Locci Simone , Bonfiglio Annalisa 
Published: April 2011

AbstractOrganic Thin-Film Transistors (OTFTs) in top-contact configuration and Metal-Insulator-Semiconductor (MIS) structures with different organic dielectrics as the gate insulator have been fabricated using the same organic semiconductor layer, pentacene, in order to investigate the changes in the electrical behavior by varying the interface properties. A gold bottom gate electrode was sputtered on a glass substrate whereas gold source and drain were thermally evaporated onto the pentacene layer. Several organic dielectrics have been tested as insulating layers, namely were poly(vinyl alcohol) (PVA), polyvinyl alcohol with ammonium dichromate (PVAad) as a cross-linking agent, poly (4-vinyl phenol) (PVP), poly(dimethylsiloxane) (PDMS) and poly(methylsilsesquioxane) (pMSSQ). The interesting differences found out by varying the interface confirm that the chemical-physical interaction between semiconductor and dielectric is crucial for the conduction mechanisms of the charge carriers. In particular we observed that the electron traps can influence not only the electron transport, therefore allowing a more or less marked ambipolar behavior, but also affect the hole transport.
Modification on the Unoccupied Electronic Structure of Organic Semiconductor by Alkali Metal
Authors: Ding Huanjun , Park Kiwan , Gao Yongli 
Published: April 2011

AbstractWe have investigated the evolution of both the occupied and unoccupied states for alkali metal (Cs and Na) doped Copper-Phthalocyanine (CuPc) with photoemission and inverse photoemission spectroscopy. As the doping ratio increases, the lowest unoccupied molecular orbital (LUMO) of CuPc shifts downward, reaching the Fermi level. After the saturation, the LUMO intensity decreases monotonically, while a gap state grows in the valence spectra, which gives direct evidence for the origin of the doping-induced gap state in CuPc molecules.
Large Area Processing and Patterning with Ink Jet Technology
Authors: Grove Michael , Hayes Donal , Shah Virang 
Published: April 2011

AbstractPatterning materials over large areas on flexible plastic or metal substrates, and on rigid ones, where multiple layers of different materials are being applied in order to create active devices brings with it the real challenge of accurate materials placement [1]. The additive process of printing expensive functional materials reduces costs associated with the losses of subtractive processing, but focuses the technological necessity on the precision of materials alignments on the target substrates. During the past decade, both materials and their print processing have developed to a near commercial level for optical and electronic devices. Industrial success will be assured when their production enjoys the economies of scale that large area processing can bring. Ink jet technology has developed in the last twenty-five years to a level of sophistication that is now adequate for the challenges of processing large area substrates for optical and electronic devices. Some equipment and processing will be covered in this paper.
Electrical and Optical Properties of High Mobility W-doped In2O3 Thin Films
Authors: Gupta Ram , Ghosh K. , Mishra S. R. , Kahol P. K. 
Published: April 2011

AbstractTransparent conducting oxides (TCO) have been widely used for opto-electronic devices such as light emitting diodes, photo-detectors, touch panels, flat panel displays, and solar cells. Low resistivity, high mobility, and good transparency are the prime requirements for these devices. There is an increasing interest in TCO with high mobility to decrease their electrical resistivity without a significant decrease in the optical transparency. Highly conducting and transparent tungsten doped indium oxide thin films were deposited on quartz substrate by ablating the sintered In2O3 target containing WO3 with a KrF excimer laser (λ = 248 nm and pulsed duration of 20 ns). The effect of growth temperature and oxygen pressure on structural, optical, and electrical properties has been studied. The transparency of the films largely depends on the growth temperature. The electrical properties are found to depend strongly on the growth temperature as well as on oxygen pressure. The temperature dependence resistivity measurement shows the transition from semiconductor to metallic behavior as the growth temperature increases from room temperature to 500 °C. The high mobility (up to 358 cm2V−1s−1), low resistivity (1.1 × 10−4 Ω.cm), and relatively high transmittance of ∼90 % have been observed on the optimized film grown at 500 °C and under oxygen pressure at 1 × 10−6 bar.
III-V Semiconductor Vertical and Tilted Nanowires on Silicon Using Chemical Beam Epitaxy
Authors: Radhakrishnan Gokul , Freundlich Alex , Charlson Joe , Fuhrmann Bodo 
Published: April 2011

AbstractNowadays nanostructures play a vital part in the rapidly expanding areas of photovoltaics. The ability of nanowires to transfer photo-generated carriers rapidly across a solar cell has lead our interest in growth of nanowires . Currently Vapor Liquid Solid (VLS) epitaxy is the most common method used to grow epitaxial vertical nanowires. A metal particle such as gold is used to form a liquid alloy eutectic with the material of a substrate or with material supplied in the vapor phase. In growing semiconductor wires using metal droplets, it has been shown that the wires grow in the (111) direction and have clean facets . Furthermore these wires generally present an undesirable larger pyramidal base at the bottom and there is also evidence of surface migration of the metal catalyst. Thus far, most of the effort in the development of vertical III-V semiconductor nanowires has been limited to homo-polar combinations (e.g. InAs on InP). The ability to fabricate III-V nanowires on silicon could however pave the way toward the monolithic integration of III-V nanostructured solar cells with Si. Here we demonstrate the growth of GaAs and InP nanowires on silicon (111) using gold as the metal seed particle. An ordered array of gold nano dots is integrated on the surface of a silicon substrate using self-assembled polystyrene nanospheres as the Au evaporation template. The size of the gold dots range from 40 nm to 150 nm and the pitch is about 500 nm. The growth of the wires is done by chemical beam epitaxy under a vapour phase environment. Scanning electron microscopy and photoluminescence are used to characterize these nanowires. Wire exhibit high crystallinity and there is an absence of the pyramidal base at the bottom of the nanowire using this technique. Furthermore the study also shows evidence of pregrowth motion of some of the gold particles causing coalescence of nanowires and leading to the development of nanopods and tilted (off-normal) nanowires. Finally in the light of their optical properties the relevance of these wires to photovoltaic applications is discussed.
Fabrication of Copper Indium Diselenide Nanowires
Authors: Phok Sovannary , Rajaputra Suresh , Singh Vijay 
Published: April 2011

AbstractNanostructured semiconductors have received a great deal of attention due to their unusual physical properties. The possibility of controlling these properties by varying the particle size, shape and surface properties is of great interest for nanoscale device applications in microelectronics, non-linear optics and optoelectronics in particular. Copper Indium diselenide (CIS), a p-type semiconductor with a band gap of about 1.04 eV has shown promise as an absorber for photovoltaic cells. Polycrystalline CIS film has been fabricated by various physical and chemical techniques over the past couple of decades. However, the preparation of nanostructured CIS is still challenging due to the fact that CIS tends to agglomerate resulting in large grains. Furthermore, an annealing step is also required to improve the film properties, which results in increased grain size. Here we report a simple, low cost solution to this problem through electrochemical deposition of CIS into the confined nanopores of an anodic aluminum oxide (AAO) template. The nanoporous aluminum oxide template, a few microns thick was prepared by either a one step or a two anodization in oxalic acidic media. CIS was deposited into the nanoporous AAO template by pulsed cathodic electro-deposition from an aqueous mixture. The electrodeposited nanowires had diameter ranging up to 40 nm and length ranging from 600 nm to 5 μm depending on the length of the template. The hybrid nanostructured CIS/AAO was annealed in vacuum at 230ºC for several hours to achieve stoichiometric CuInSe2 phase. The embedded CIS nanowires were characterized by X-ray diffraction and scanning electron microscopy. The optical bandgap was deduced from UV-Vis absorption spectroscopy measurements.
Application of Cylinder Forming Block Copolymers as Templates for Formation of Bit Patterned and Graded Media
Authors: Warke Vishal , Bakker Martin Gerard , Hong Kunlun , Mays Jimmy , Britt Phillip 
Published: April 2011

AbstractBit patterned media, including media fabricated with a gradient in composition, is being developed as a potential path to higher information storage density. The formation of metal nanopillars with 20-30 nm repeat spacing and precisely controlled magnetic properties presents a significant challenge to current fabrication methods. We have been developing cylinder forming block copolymer phases as a method to generate the desired patterns coupled with the processing steps necessary to transfer the pattern into magnetic material. This involves spin coating of the polymer on an appropriate orienting layer, annealing to allow the pattern to form by self-organization of the block copolymer, solvent processing to remove the minority domain, electrodeposition to form a hard mask, followed by ion-milling to transfer the pattern to the magnetic material. We have demonstrated each step in this process and report on the quality of the pattern achieved.