bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Microstructure Control of Protein Thin Films Deposited by Pulsed Laser Deposition and Via Colloid Chemical Routes
Authors: Nakayama Sayuri , Taketani Ichiro , Nagare Sanshiro , Senna Mamoru 
Published: April 2011

ABSTRACTProtein thin film (mainly silk fibroin) was prepared by pulsed laser deposition (PLD) with 1064nm IR-beam and via colloid chemical routes. Thickness, surface roughness, and microstructures of the deposited film were examined by quartz crystal microbalance sensor, field emission scanning electron microscope (FE-SEM), and atomic force microscope (AFM). The laser power density was varied systematically for PLD to control the microstructures of the film and the secondary structure (β-sheet, α-helix, or random coil) of the protein. Secondary structure of the target and film was examined by FT-IR. Films prepared by PLD comprise by agglomerated particles with their primary particle size around 30nm. The size of the primary particles was uniform, especially for the film prepared at low laser power density. At low laser power density, proportion of β-sheet increased and that of random coil decreased. Proportion of random coil was also increased by the wet colloidal process. PLD with low power density is most suitable to preserve the secondary structure in the protein thin film.
Systematic Molecular Control of Interfacial Structure in Nanoporous Carbons
Authors: Jian Kengqing , Crawford Gregory P. , Hurt Robert H. 
Published: April 2011

ABSTRACTThe present paper describes a new concept of synthesizing nanoporous carbons that allows control not only of the pore structure, but also of the molecular structure of the internal surfaces. Interfacial molecular control is achieved through the use of discotic liquid crystalline precursors whose molecular orientation on the substrate material is known or can be determined by simple measurements on flat substrate test samples. Here a suite of nanoporous (mesoporous) carbons are synthesized from various porous glass and silica gel templates, and a model is developed to predict the carbon properties from template properties thus allowing systematic template selection.
Intrinsic Friction of Monolayers Adsorbed on Solid Surfaces.
Authors: Bénichou O. , Cazabat A.M. , De Coninck J. , Moreau M. , Oshanin G. 
Published: April 2011

ABSTRACTWe review recent results on intrinsic frictional properties of adsorbed monolayers, composed of mobile hard-core particles undergoing continuous exchanges with a vapor phase. In terms of a dynamical master equation approach we determine the velocity of a biased impure molecule - the tracer particle (TP), constrained to move inside the adsorbed mono-layer probing its frictional properties, define the frictional forces exerted by the monolayer on the TP, as well as the particles density distribution in the monolayer.
Prediction of Transport Properties of Nanosystems and Their Use for Virtual Fabrication of Nanomaterials
Authors: Pozhar Liudmila A. 
Published: April 2011

ABSTRACTFundamental statistical-mechanical expressions for transport coefficients describing transport processes in spatially inhomogeneous systems (such as nanofluids, interfacial systems, atomic clusters, etc.) and derived by the use of the functional perturbation theory (FTP) due to Pozhar and Gubbins (PG) are simplified for the use in engineering and technology. Together with explicit expressions for the charge transport properties of quantum inhomogeneous systems (such as semiconductor quantum dots, wells and wires, artificial atoms/molecules etc.) derived recently, these expressions form a basis for development of algorithms and codes to realize a virtual (i.e., fundamental theory-based, computational) synthesis of nanomaterials with predesigned transport properties for novel nanocluster- or nanopore- based catalysts and adsorbents, integrated nanocircuits, nanoheterostructures, etc.
Aging Effects in Suspensions of Silica Particles
Authors: Selimovic Seila , Hu Yue 
Published: April 2011

ABSTRACTIn our study of the aging phenomena in silica suspensions we immersed precipitated silica particles in methyl-terminated PDMS (silicone oil), mineral oil, and glycerol/water and measured their viscoelastic properties as a function of time. We found that the samples based on silicone oil, initially of a pasty consistence, became fluid-like after a period of about three weeks. Aqueous samples aged much faster than the oily samples. Samples containing mineral oil did not exhibit any changes in viscosity and elasticity. In this paper we discuss a possible mechanism for these aging behaviors.
Slow Relaxation of Spin-Cast Poly(methyl methacrylate) Confined in Thin Films
Authors: Richardson Helen , Sferrazza Michele , Keddie Joseph L. 
Published: April 2011

ABSTRACTAlthough the volume relaxation of bulk homopolymer glasses is thoroughly understood, many questions remain about the volume relaxation of polymers cast from solvent. Furthermore, in polymer thin films, the possible effects of confinement, surfaces and interfaces on relaxation are largely unexplored. Measurements of the film thickness of spin-cast poly(methyl methacrylate) thin films over extended periods of time, using spectroscopic ellipsometry, reveal that the characteristic time for relaxation increases with film thickness. This result is consistent with the idea of enhanced molecular mobility in thin films, and it might reflect the conformation and a reduced extent of entanglements of the polymers when spin-cast from dilute solution.
Dimensional Crossover in the Growth of Depletion Zone in a Rectangular Capillary: Experiments and Monte Carlo Simulations
Authors: Park Sung Hyun , Peng Hailin , Argyrakis Panos , Taitelbaum Haim , Kopelman Raoul 
Published: April 2011

ABSTRACTThe diffusion-limited kinetics of the growth of depletion zone around a static point trap in a thin, long stripe geometry was studied using a laser photobleaching experiment of fluorescein dye inside a rectangular capillary. The dynamics of the depletion zone was monitored by the θ-distance, defined as the distance from the trap to the point where the reactant concentration has been depleted to the specific fraction of its initial bulk value. A dimensional crossover from two dimensions to one dimension, due to the finite width of the reaction zone, was observed. The crossover seems to occur for all θ values concurrently when the depletion zone touches the boundary for the first time, suggesting that the boundary information spreads faster than diffusion. Monte Carlo simulations were performed to support the experimental results. The crossover time (τc) is found to scale with the width (L) of the rectangular reaction zone as τc ∼ L2, as expected from the Einstein's diffusion law.
An Intermediate TCE Nanocomposite Coating for Thermal Barrier Coatings
Authors: Gregory Otto J. , Downey Markus A. , Wnuk Steve , Wnuk Vince 
Published: April 2011

ABSTRACTA NiCoCrAlY /Al2O3 nanocomposite coating was developed for Inconel 718 substrates to improve thermal barrier coatings (TBC's) based on thermally sprayed NiCoCrAlY and alumina. This intermediate TCE coating was deposited by rf sputtering techniques and was instrumental in increasing the fatigue life of both TBC's and thermal spray instrumentation. Combinatorial chemistry techniques were employed to screen a large number of NiCoCrAlY / Al2O3 compositions to yield an optimal composite coating such that the TCE of the metallic bond coat was matched to the ceramic top coat. The resulting combinatorial libraries were thermally fatigued and the composition of the library with the longest fatigue life was determined by X-ray energy dispersive analysis (EDS). A sputtering target of the optimal composition was fabricated by thermal-spraying a mixture of NiCoCrAlY and alumina to simulate the results from the combinatorial chemistry experiments and form a nanocomposite with the desired properties. The sputtered intermediate TCE coating improved the fatigue life of the TBC's by 160% when compared to as-sprayed TBC's formed on Inconel 718 substrates. When a thermally grown oxide was formed on the surface of NiCoCrAlY bond coated substrates prior to deposition of the intermediate TCE coating, a 200% increase in fatigue life was realized. Techniques for extending the fatigue life of other thermal barrier coating systems using this approach will be discussed.
Multilayer structure, stress reduction and annealing of carbon film.
Authors: Ha Peter C.T. , McKenzie D. R. , Doyle D. , McCulloch D. G. , Wuhrer Richard 
Published: April 2011

ABSTRACTCarbon films deposited by filtered cathodic arc show a high compressive stress which limits their thickness because of delamination. We study three methods of relieving the stress in these films. We first determine the dependence of the stress on DC bias up to bias voltages of 1200V and show that the formula of Davis provides a good fit to the data including the stress maximum in the region of 150–200V and the progressive decrease in stress at higher voltages. In the second method, plasma immersion ion implantation (PIII) was used to create multilayer of alternating high density, high stress (PIII on) films and lower density, low stress (PIII off) films. This method enabled thicker structures to be produced. In the third method we made multilayers using amorphous silicon and carbon layers. Annealing of these layers showed that the stress could be reduced to very low values because of the ability of the silicon layers to absorb compressive stress by contracting after the annealing step. The microstructural effects of PIII were studied by transmission and scanning electron microscopy.
The early stages of stress development during epitaxial growth of Ag/Cu multilayers
Authors: Labat S. , Bocquet F. , Bigault T. , Roussel L. , Mikaelian G. , Alfonso C. , Charai A. , Thomas O. 
Published: April 2011

ABSTRACTThe early stages of stress development during epitaxial growth of metal layers with a large misfit in lattice parameters still need in-depth understanding. In this particular study we have focused on Ag-Cu system, which is immiscible and exhibit a large 14% misfit in lattice parameters. Ag/Cu multilayers have been grown by ultrahigh-vacuum evaporation on Si (111) maintained at -20°C, 35°C or 110°C. The thickness of the individual layers is about 100 Å. All the films present the same (111) orientation with a well defined in-plane orientation: <110> Cu or Ag // <110> Si. The stress was monitored during growth with a home-made laser curvature measurement device. The stress vs thickness behaviour is highly asymmetric when comparing Ag/Cu and Cu/Ag. Indeed Ag grown on Cu does not develop any measurable stress at any thickness or temperature, whereas Cu grows on Ag under tensile temperature and thickness-dependent stress. The temperature dependence of this stress relaxation cannot be interpreted with a standard relaxation model including dislocation motion. A possible way to understand the stress temperature dependence is to consider the evolution of microstructure during growth.
Radiation Effects on Hollandite Ceramics developed for Radioactive Cesium Immobilization
Authors: Aubin V. , Caurant D. , Gourier D. , Baffier N. , Esnouf S. , Advocat T. 
Published: April 2011

ABSTRACTProgress on separating the long-lived fission products from the high level radioactive liquid waste (HLW) has led to the development of specific host matrices, notably for the immobilization of cesium. Hollandite (nominally BaAl2Ti6O16), one of the main phases constituting Synroc, receives renewed interest as specific Cs-host wasteform. The radioactive cesium isotopes consist of short-lived Cs and Cs of high activities and Cs with long lifetime, all decaying according to Cs+→Ba2++e- (β) + γ. Therefore, Cs-host forms must be both heat and (β,γ)-radiation resistant. The purpose of this study is to estimate the stability of single phase hollandite under external β and γ radiation, simulating the decay of Cs. A hollandite ceramic of simple composition (Ba1.16Al2.32Ti5.68O16) was essentially irradiated by 1 and 2.5 MeV electrons with different fluences to simulate the β particles emitted by cesium. The generation of point defects was then followed by Electron Paramagnetic Resonance (EPR). All these electron irradiations generated defects of the same nature (oxygen centers and Ti3+ ions) but in different proportions varying with electron energy and fluence. The annealing of irradiated samples lead to the disappearance of the latter defects but gave rise to two other types of defects (aggregates of light elements and titanyl ions). It is necessary to heat at relatively high temperature (T=800°C) to recover an EPR spectrum similar to that of the pristine material. The stability of hollandite phase under radioactive cesium irradiation during the waste storage is discussed.
Experimental and Computational Studies of Ion-Solid Interactions in Silicon Carbide
Authors: Weber William J. , Gao Fei , Devanathan Ram , Jiang Weilin , Zhang Yanwen 
Published: April 2011

ABSTRACTExperimental and computational results on ion-beam-induced defect production, damage accumulation, and thermal recovery in SiC are reviewed. The accumulation and recovery of disorder on the Si and C sublattices have been determined experimentally by ion-channeling methods. Atomic-level simulations are used to determine defect production, cascade-overlap effects, and defect migration energies. Energetic Si and C collision cascades, with energies up to 50 keV, primarily produce single interstitials, mono-vacancies, antisite defects, and small defect clusters. Overlapping of Si and C cascades results in the interaction of defects and clusters that stimulates cluster growth and produces long-range structural disorder. For energetic Au cascades, nanoscale amorphous clusters are produced directly within about 25% of the Au cascades, along with point defects and smaller clusters. The disordering behavior and the changes in volume and elastic modulus obtained experimentally and from molecular dynamics simulations are in good agreement, thus providing atomic-level interpretation of experimentally observed features. Simulations of close-pair production and recombination in SiC indicate that the activation energies for recombination of most close pairs range from 0.24 to 0.38 eV. Multiaxial channeling measurements indicate annealing below 300 K results in relaxation of some interstitials to lower-energy configurations. Long-range migration energies for interstitials and vacancies have likewise been determined by computational methods.
REACE: A New Algorithm for Low Energy Ion Implantation Simulation.
Authors: Shi Xiaokang , Yu Min , Shi Hao , Huang Ru , Zhang Xing , Wang Yangyuan , Zhang Jinyu 
Published: April 2011

ABSTRACTA new method for the acceleration of MD (molecular dynamics) simulation of ion implantation into crystalline targets is presented, named REACE (Rare Event Algorithm with Cascade Effect). This method can speed up the MD simulation of ion implantation with cascade processes. As a result, the time required to perform a simulation with high precision and dose effect is drastically reduced. And many details producing statistical noise in the simulation are simulated in the REACE and help it to be more reasonable and reliable.
The Role Of Ge In Cluster Formation In B And Bf2 Implanted Si Wafers After Ge Pre-Amorphization
Authors: Alper Sahiner M. , Magee Charles W. , Downey Daniel F. , Arevalo Edwin , Woicik Joseph C. 
Published: April 2011

ABSTRACTCluster formation in high dose B, BF2 implanted Si wafers is an important problem in silicon doping, since it is one of the leading causes of the electrical deactivation of the dopant. In this study, we used Ge pre-amorphized, ultra low energy B and BF2 implanted Si wafers in order to probe these clusters from a local structural point of view. Ge K-edge x-ray absorption spectroscopy (XAFS) is a powerful tool in obtaining local structural information around the Ge atom. The effects of different implant species with various implant doses and annealing conditions on the cluster formation are presented using Ge K-edge multi-shell XAFS analysis. The non-linear least-squares fits to the Ge K-edge Fourier Transformed (FT) XAFS data using calculated standards from multiple scattering simulations around the Ge atom reveal formed Ge-B clusters for the Rapid Thermal Processing (RTP) annealed wafers. The results also indicate the laser annealing process on the other hand is blocking the formation of these Ge induced Ge-B clusters.
One and Two-Dimensional Pattern Formation on Ion Sputtered Silicon
Authors: Brown Ari-David , Bola George H. , Aziz Michael J. , Erlebacher Jonah 
Published: April 2011

ABSTRACTThe evolution of surface morphology during ion beam erosion of Si(111) at glancing ion incidence (60° from normal, 500 eV Ar+, 0.75 mA/cm2 collimated beam current) was studied over a temperature range of 500–730° Celsius. Keeping ion flux, incident angle, and energy fixed, it was found that one-dimensional sputter ripples with wavevector oriented perpendicular to the projected ion beam direction form during sputtering at the lower end of the temperature range. For temperatures above approximately 690° Celsius, growth modes both parallel and perpendicular to the projected ion beam direction contribute to the surface morphological evolution. This effect leads to the formation of bumps (“dots”) with nearly rectangular symmetry.
Characterization of “TEMPOS”: A new

T

unable

E

lectronic

M

aterial with

P

ores in

O

xide on

S

ilicon
Authors: Fink Dietmar , Petrov Alexander , Hoppe Kurt , Fahrner Wolfgang R. 
Published: April 2011

ABSTRACTRecently etched heavy ion tracks in MOS devices were filled with (semi)conducting materials to enable charge extraction from, or injection into the conducting channel below the Si/oxide interface, respectively. This leads to a family of novel electronic devices that we denoted as “TEMPOS” structures - that acronym stands for “Tunable Electronic Material with Pores in Oxide on Silicon”. In comparison with MOS-FETs, TEMPOS structures have some unique properties due to their additional parameters such as the track diameter, density, and shape, and the material embedded therein and its spatial distribution. This makes these novel structures much more complex, and it eventually leads to higher compactation of the TEMPOS circuits and to unexpected electronic properties. Depending on the choice of these parameters and the working point of these structures, TEMPOS elements can overtake the function of gatable resistors, condensors, photocells, hygrocells, diodes, sensors, and others. This work concentrates on some basic aspects of TEMPOS and gives some corresponding current /voltage relations and equivalent circuits.
Characterization of Nanoclusters in MgO Created by Means of Ion Implantation.
Authors: van Huis M.A. , van Veen A. , Schut H. , Kooi B.J. , De Hosson J.Th.M. 
Published: April 2011

ABSTRACTMetal nanoclusters (NCs) of lithium, zinc, silver and gold embedded in MgO were created by means of ion implantation of Li, Zn, Ag and Au ions into single crystals of MgO(100) and subsequent thermal annealing. Nanoclusters of the compound semiconductor CdSe were obtained by implantation of both Cd and Se ions. Solid noble gas clusters were formed by Kr ion implantation. Optical and structural properties of the NCs were investigated using optical absorption spectroscopy (OAS), high-resolution X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). The mean nanocluster size is estimated from the broadening of the Mie plasmon optical absorption bands using the Doyle formula. These results are compared with the NC size as obtained from XRD (using the Scherrer formula) and from direct XTEM observations. The three methods are found to be in reasonable agreement with a mean size of 4.0 and 10 nm found for the Au and Ag clusters, respectively. Using TEM observations, the relative interface energies of MgO//Au and MgO//Ag interfaces are also determined. In the case of MgO//Au, they are found not to be in agreement with theoretical predictions in the literature. CdSe nanoclusters were found to adopt different crystal structures dependent on the size. Small ones (<5 nm) appear to have a rock salt structure, larger ones the sphalerite structure. The solid krypton NC's are under high pressure. The pressure of individual Krypton bubbles was determined from the moiré fringes
Study of optical properties and TEM of Nanoparticles in Ni+-implanted Sapphire
Authors: Xiang X. , Zu X.T. , Zhu S. , Wang L.M. 
Published: April 2011

ABSTRACT64-keV Ni ion implantation was performed at room temperature up to a dose of 1×1017 cm-2 in α-Al2O3 single crystals. The charge states, structure and optical properties of metallic embedded Ni nanoparticles were studied by using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and optical spectroscopy, respectively. XPS analysis showed that implanted Ni ions are mainly in charge state of metallic Ni0. Nanoparticles distributed from the surface to 30 nm below the surface were observed in a bright-field cross-sectional image. The size of nanoparticles ranges from 1 to 5 nm in diameter. A selected area electron diffraction (SAED) pattern shows Ni nanoparticles with lattice parameter a = 0.352 nm. A high-resolution electron microscopy (HREM) image indicated the Ni-implanted area had been entirely amorphized. A new broad absorption band centered at 400 nm appeared in the optical absorption spectrum of the as-implanted crystal, due to surface plasma resonance (SPR) of Ni nanoparticles.
Synthesis and Characterization of WOx Nanowires and their Conversion to WS2 Nanotubes
Authors: Dong Lifeng , Maiz Aitor , Jiao Jun 
Published: April 2011

ABSTRACTIn this paper, we report for the first time the conversion of tungsten oxide (WOx) nanowires to tungsten sulfide (WS2) nanotubes using hydrogen (H2) gas and sulfur (S) powder as precursors instead of hydrogen sulfide (H2S) gas. Both the morphology and diameter of WS2 nanotubes were affected by the use of WOx nanowires. The diameter and length of the WOx nanowires were controlled by the growth temperature. A series of experiments confirmed that the higher the temperature was, the larger and longer the diameter and length of the WOx nanowires. When the temperature increased from 600 °C to 800 °C, the nanowire diameter increased from ∼ 15 nm to ∼50 nm. Furthermore, electron microscopy characterization reveals that the conversion of WS2 nanotubes from WOx nanowires started from outside the WOx nanowires and the conversion was not symmetrically uniform along the radial directions of the WOx nanowires.
TEM analysis of stress in GaInAs/(001)InP epitaxial systems.
Authors: Rocher André , Cabié Martiane , Ponchet Anne , Bertru Nicolas 
Published: April 2011

ABSTRACTA Transmission Electron Microscopy analysis of misfit stress based on the Stoney formula is proposed. It is applied to the GaInAs/(001)InP system to determine the residual stress for layers thicker than the critical thickness. The measured stress corresponds well to the value calculated using the elasticity theory and the nominal lattice mismatch: the structure is always nearly fully strained even for an epilayer two times larger than the critical thickness. Very few segments of misfit dislocation are observed indicating that the plastic relaxation is not active yet. A tentative explanation, based on the difficulty to create the core of a misfit dislocation, is explored.