bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of the Effect of Irradiation Temperature on the Mechanical Anisotropy of the Zr+ Ion Irradiated Zr-2.5%Nb
Authors: Bose Bipasha , Klassen Robert J. 
Published: April 2011

ABSTRACTWe present here new information on the effect of irradiation temperature on the strength and mechanical anisotropy of Zr-2.5%Nb CANDU pressure tube material. Polished samples aligned normal to the transverse (TN), axial (AN) and radial (RN) directions of the pressure tube were irradiated at 300°C with 8.5 MeV Zr+ ions to assess the effect of concurrent thermal annealing of the irradiation damage. Constant-load micro-indentation creep tests were performed at 25°C at indentation depths from 0.1 to 2.0 μm on the ion irradiated samples.The increase in the initial indentation stress with increasing levels of Zr+ ion irradiation at 300°C was lower than that reported earlier for similar samples exposed to Zr+ irradiation at 25°C. While the anisotropy of the indentation stress decreased significantly with Zr+ ion irradiation, the level of the decrease was reduced when the irradiation was performed at 300oC compared to 25oC. The apparent activation energy ΔG0 of the obstacles that limit the rate of dislocation glide during indentation creep did not change with indentation direction but did increase with increasing levels of Zr+ ion damage. The values of ΔG0 were, again, lower for samples that were irradiated at 300°C than for those irradiated at 25oC.The observed differences in the magnitude of, and the anisotropy of, the initial indentation stress and also the decrease in the apparent activation energy of the indentation creep process of Zr-2.5%Nb samples irradiated with Zr+ ions at 300oC compared to those irradiated at 25oC indicate the effect that concurrent thermal annealing has on the accumulation of irradiation damage. The effect of irradiation temperature on reducing the degree of, and the strength of, irradiation induced crystallographic damage must therefore be considered when predicting the strength and thermal creep behaviour of irradiated nuclear materials.
Simulations of CVD Diamond Film Growth: 2D Models for the identities and concentrations of gas-phase species adsorbing on the surface
Authors: May Paul W. , Mankelevich Yuri A. 
Published: April 2011

ABSTRACTA prerequisite for modelling the growth of diamond by CVD is knowledge of the identities and concentrations of the gas-phase species which impact upon the growing diamond surface. Two methods have been devised for the estimation of this information, and have been used to determine adsorption rates for CxHy hydrocarbons for process conditions that experimentally produce single-crystal diamond, microcrystalline diamond films, nanocrystalline diamond films and ultrananocrystalline diamond films. Both methods rely on adapting a previously developed model for the gas-phase chemistry occurring in a hot filament or microwave plasma reactor. Using these methods, the concentrations of most of the CxHy radical species, with the exception of CH3, at the surface have been found to be several orders of magnitude smaller than previously believed. In most cases these low concentrations suggest that reactions such as direct insertion of C1Hy (y = 0-2) and/or C2 into surface C–H or C–C bonds can be neglected and that such species do not contribute significantly to the diamond growth process in the reactors under study.
Carrier lifetime, diffusion length and mobility in (100) CVD diamond samples pre-treated in an O2/H2-plasma
Authors: Deferme W. , Haenen K. , Nesládek M. , Malinauskas T. , Lubys L. , Jarašiūnas K. 
Published: April 2011

ABSTRACTIn this article, (100) Ib diamond substrates are pre-treated for different durations in an O2/H2-plasma, influencing the etching of defects like unepitaxial crystals, flat top hillocks, and pyramidal hillocks [1-3]. Such procedure is used to prevent those to incorporate into the ~ 100μm thick CVD diamond film, which is subsequently grown on top. While the surface morphology and structure of substrates and films are studied by SEM, the time-resolved Light-Induced Transient Grating (LITG) technique provides information on the excess carrier parameters close to the front surface of the grown layers. This technique is particularly useful as it does not requires a separation of the CVD film from its substrate. It will be shown that O2/H2-plasma treatments of more than 150 minutes but less than 240 minutes largely reduce the incorporation of defects in the bulk of the grown film. This, in turn, influences the carrier dynamics as measured by LITG, but also the surface roughness and growth rate as shown by SEM.
Diamond Nanopit Arrays Fabricated by Room-Temperature Nanoimprinting using Diamond Molds
Authors: Kiyohara Shuji , Kumagai Masaya , Taguchi Yoshio , Sugiyama Yoshinari , Omata Yukiko , Kurashima Yuichi , Takikawa Hirofumi 
Published: April 2011

ABSTRACTWe have investigated the nanopatterning of chemical vapor deposited (CVD) diamond films in room-temperature nanoimprint lithography (RT-NIL), using a diamond nanodot mold. We have proposed the use of polysiloxane as an electron beam (EB) mask and RT-imprint resist materials. The diamond molds of cylinder dot using the RT-NIL process were fabricated with polysiloxane oxide mask in EB lithography technology. The dot in minimum diameter is 500 nm. The pitch between the dots is 2 μm, and dot has a height of about 600 nm. It was found that the optimum imprinting conditions for the RT-NIL : time from spin-coating to imprinting t1 of 1 min , pressure time t2 of 5 min, imprinting pressure P of 0.5 MPa. The imprint depth obtained after the press under their conditions was 500 nm. We carried out the RT-NIL process for the fabrication of diamond nanopit arrays, using the diamond nanodot molds that we developed. The resulting diamond nanopit arrays with 500 nm-diameter and 200 nm-depth after the electron cyclotron resonance (ECR) oxygen ion beam etching were fabricated. The diameter of diamond nanopit arrays was in good agreement with that of the diamond nanodot mold.
Phase Transition and Self-assembly of Lower Diamondoids and Derivatives.
Authors: Xue Yong , Mansoori G. Ali 
Published: April 2011

ABSTRACTApplying ab initio calculation and molecular dynamics simulation methods, we have been calculating and predicting the essential phase transition and self-assembly of two lower diamondoids (adamantane and diamantane), three of their important derivatives (amantadine, memantine and rimantadine), and two organometallic molecules that are built by substituting one hydrogen ion with one sodium ion in both adamantane and diamantine molecules (ADM•Na and Optimized DIM•Na). To study their self-assembly and phase transition behaviors, we built seven different MD simulation systems, and each system consisting of 125 molecules. We obtained self-assembly structures and simulation trajectories for the seven molecules. Radial distribution function studies showed clear phase transitions for the seven molecules. Higher aggregation temperatures were observed for diamondoid derivatives. We also studied the density dependence of the phase transition which demonstrates that the higher the density - the higher the phase transition points.
CVD Diamond Dislocations Observed by X-ray Topography, Birefrengence Image and Cathodoluminesence mapping
Authors: Kato Yukako , Umezawa Hitoshi , Yamaguchi Hirotaka , Teraji Tokuyuki , Shikata Shin-ichi 
Published: April 2011

ABSTRACTSemiconductor epitaxial CVD single crystal diamond is considered a potential material for power devices because of its unique characteristics. In the discussion on the relationship between crystal quality and device performance, the atomic purity and defect concentration have been considered; however, the information on the local stress-strain distribution in a single crystal is not sufficient. In this paper, the dislocation analysis is shown for the suggestion of the established standard dislocation analysis method. The aggregation of mixed dislocations is observed by the analysis by using the birefringence image, cathodoluminescence image and x-ray topography.
Focused Ion Beam Milling of Crystalline Diamonds
Authors: Golnabi Rustin , Lee Won I. , Kim Deok-Yang , Kowach Glen R. 
Published: April 2011

ABSTRACTRecently, a wide range of new applications of diamond materials such as spintronics, field emission, and bio-sensing have been proposed. These applications often require the precise patterning of diamonds, which is not trivial because diamonds are the hardest materials known in nature. Among various patterning techniques, the focused ion beam milling method has been proven to provide flexibility as well as high resolution in the pattern design. In this study, a focused beam of 30 kV Ga+ ions was utilized to create sub-micrometer size patterns out of crystalline diamonds. The sputtering rate, re-deposition, and surface roughening of diamond structure have been closely monitored with various milling parameters during the milling process. Our study revealed a low milling yield of 0.02 μm3/nC, high Ga content re-deposition, and the formation of sub-micron scale terracing on the sidewall of patterned diamonds.
Lithium monolayers on single crystal C(100) oxygen-terminated diamond
Authors: Martin Tomas L. , O’Donnell Kane M. , Shiozawa Hidetsugu , Giusca Cristina E. , Fox Neil A. , Silva S. Ravi P. , Cherns David 
Published: April 2011

ABSTRACTThin lithium layers on oxygenated C(100) boron-doped diamond have been observed using x-ray photoemission spectroscopy. Conductive boron-doped diamond was oxygen-terminated using an ozone cleaner. Lithium was evaporated onto the oxygen-terminated C(100) surface and an as-grown hydrogen terminated surface to a thickness of approximately 50 nm. After washing with deionised water, significant lithium signal is still detected on oxygenated diamond, but not on hydrogenated diamond, indicating a strongly bound lithium-oxygen surface layer is formed, as predicted by recent theoretical modeling.
On the mechanism of charge transfer between neutral and negatively charged nitrogen-vacancy color centers in diamond
Authors: Petrakova Vladimira , Taylor Andrew , Kratochvilova Irena , Fendrych Frantisek , Cigler Petr , Ledvina Miroslav , Kucka Jan , Stursa Jan , Ralis Jan , Vacik Jiri , Nesladek Milos 
Published: April 2011

ABSTRACTThe presented work aims for the development of optically-traceable intracellular nanodiamond sensors, where photoluminescence can be changed by biomolecular attachment/delivery event. High biocompatibility, small size and stable luminescence from its color centers, makes nanodiamond (ND) particles an attractive alternative to molecular dyes for drug-delivery and cell-imaging applications. In our work we study how the surface modification of ND can change ND luminescence spectra. This method can be used as a novel detection tool for remote monitoring of chemical processes in biological systems. We discuss photoluminescence (PL) spectra of oxidized and hydrogenated ND and a single crystal diamond, containing engineered NV centers. The hydrogenation of ND leads to quenching of NV- related luminescence and a PL shift due to changing of occupation from NV- to NV0 states. We model this effect using electrical potential changes at the diamond surface.
Effect of Initial Growth and Seeding Conditions on Boron Doped Hot Filament Diamond Films
Authors: Zimmer Jerry , Hantschel Thomas , Chandler Gerry , Schulze Andreas , Vandervorst Wilfried , Peralta Maria 
Published: April 2011

ABSTRACTBoron doped CVD diamond has been extensively studied in bulk form but little has been published regarding the effects that the initial seeding and growth conditions can have on the characteristics of the initial layer of diamond. This can have a dramatic effect on the performance of the film in applications ranging from AFM probe tips to electrodes used for water purification and other applications. This paper will examine how initial growth conditions and seeding methods can affect the film interface characteristics of doped diamond grown in hot filament CVD reactors.
Crystalline Orientation of PbTiO3 Nanorods Grown by MOCVD Using ZnO Nanorods as a Template
Authors: Fujisawa Hironori , Shimizu Masaru , Kuri Ryohei , Nakashima Seiji , Kotaka Yasutoshi , Honda Koichiro 
Published: April 2011

ABSTRACTPbTiO3-covered ZnO nanorods were grown on Al2O3$\left({11\bar 20} \right)$ by metalorganic chemical vapor deposition (MOCVD), and their crystalline orientation was investigated by x-ray diffraction (XRD). Structural analysis by scanning electron microscopy and XRD revealed that the hexagonal ZnO nanorods had $\left\{ {10\bar 10} \right\}$-side facets. XRD analysis of PbTiO3 thin films on ZnO$\left({10\bar 10} \right)$/Al2O3$\left({10\bar 10} \right)$revealed that PbTiO3 was epitaxially grown on ZnO$\left({10\bar 10} \right)$, showing 6 variants of crystallites with the c-axis tilted either 27o or 69o from the surface normal to the ZnO$\left({10\bar 10} \right)$ plane. Effective piezoelectric coefficients calculated for the 27o and 69o-crystallites using piezoresponse force microscopy confirm that deformation of nanorods and nanotubes contributed to the large electrically-induced strain along the radial direction.
Mechanical Spectroscopy in Advanced TiAl-Nb-Mo Alloys at High Temperature
Authors: Simas Pablo , Schmoelzer Thomas , Nó Maria L. , Clemens Helmut , San Juan Jose 
Published: April 2011

ABSTRACTNew advanced multi-phase γ-TiAl based alloys (TiAl-Nb-Mo), so called TNM alloys, have been developed to promote hot workability and to allow easier processing by conventional forging. However, to control and stabilize the final microstructure, specific processing and further thermal treatments are required. In the present work we used mechanical spectroscopy techniques to obtain a better understanding of the microstructural mechanisms taking place at high temperature applying two different heat treatments. Internal friction spectra and dynamic modulus evolution have been measured in an inverted torsion pendulum up to 1220 K. A stable relaxation peak was observed in both cases at about 1050 K for 1 Hz. Spectra acquired at several frequencies between 0.01 Hz and 3 Hz allow us to measure the activation parameters of this peak. In addition, a high temperature background (HTB) has been observed. This HTB, which has been found to be dependent on thermal treatments, has been analyzed to obtain the apparent activation enthalpy, which seems to be correlated to the creep behavior. Finally, we discuss the relaxation peak and the HTB in terms of the microstructural evolution during thermal treatments.
Reflection High Energy Electron Diffraction and Atomic Force Microscopy Studies of MnxSc(1-x)Alloys Grown on MgO(001) Substrates by Molecular Beam Epitaxy
Authors: Constantin Costel , Chinchore Abhijit , Smith Arthur R. 
Published: April 2011

ABSTRACTThe combination of the molecular beam epitaxy growth method with thein-situreflection high energy electron diffraction measurements currently offers unprecedented control of crystalline growth materials. We present here a stoichiometric study of MnxSc(1-x)[x= 0, 0.03, 0.05, 0.15, 0.25, 0.35, and 0.50] thin films grown on MgO(001) substrates with this growth method. Reflection high energy electron diffraction and atomic force microscopy measurements reveal alloy behavior for all of our samples. In addition, we found that samples Mn0.10Sc0.90and Mn0.50Sc0.50display surface self-assembled nanowires with a length/width ratio of ~ 800 – 2000.
Compositional Dependence of the Compressive Yield Strength of Fe-Nb(-Al) and Co-Nb Laves Phases
Authors: Voß Simon , Palm Martin , Stein Frank , Raabe Dierk 
Published: April 2011

ABSTRACTLarge, defect-free single-phase samples of the hexagonal C14 NbFe2 and Nb(Fe,Al)2, and the cubic C15 NbCo2 Laves phases have been produced by a modified levitation melting technique. The compressive strength of NbFe2 and NbCo2 has been determined in dependence on the Nb content, that of Nb(Fe,Al)2 in dependence on the Al content. The binary phases did not show either a maximum (defect softening) or minimum (defect hardening) in strength when the Nb content was varied. Instead, for both phases an increase of the compressive strength with increasing Nb content is observed.
Radiation-induced Chemical Disorder in Covalent Materials
Authors: Ishimaru Manabu , Zhang Yanwen , Weber William J. 
Published: April 2011

ABSTRACTChemical disorder in ion-irradiated SiC and GaN has been examined by means of transmission electron microscopy. Radial distribution functions obtained by a quantitative analysis of electron diffraction intensities revealed that homonuclear bonds, which do not exist in the crystalline state, are formed in both ion-irradiated specimens. The origin of the homonuclear bonds is quite different between SiC and GaN. The constitute elements mix on the atomic-scale in amorphous SiC, while phase separation induced by irradiation is attributed to the formation of self-bonded Ga atomic pairs in amorphous/nanocrystalline GaN.
Modeling the dislocation-void interaction in a dislocation dynamics simulation
Authors: Queyreau Sylvain , Monnet Ghiath , Wirth Brian D. , Marian Jaime 
Published: April 2011

ABSTRACTIn this paper, we propose a model for dislocation-void interaction in Iron that is amenable to dislocation dynamics simulations. Voids are treated as shearable particles whose shear resistance and thermal activation parameters are obtained from atomistic calculations. The modeling is first validated by direct comparison with molecular dynamics calculations. A good agreement is found especially at 0K and high temperature. The interaction with a random distribution of voids is then investigated.
Study for the Interfacial Effect between a Crawling Cell and a Substrate on Chemotaxis
Authors: Song Jihwan , Kim Dongchoul 
Published: April 2011

ABSTRACTChemotaxis is one of the essential mechanisms responsible for various complex biological processes. For a crawling cell, the interface between the cell and the substrate plays an important role in the chemotactic migration. This paper presents a three-dimensional dynamic model to investigate the effect of the interface between a crawling cell and a substrate on its chemotaxis. The coupled mechanisms of chemotaxis, the surface energy of the cell, and the interface between the cell and the substrate are incorporated into a diffuse interface model. Simulations reveal rich dynamics of a crawling cell associated with the interfacial condition, and confirm the high possibility of adequate predictions.
Thin Nano- and Microcrystalline CVD Diamond Films for Micro-channel Cooling: Thermal and Elastic Properties
Authors: Salenbien Robbe , Sermeus Jan , Pobedinskas Paulius , Glorieux Christ , Haenen Ken 
Published: April 2011

ABSTRACTThin nano- to microcrystalline diamond (N/MCD) films were deposited on silicon substrates using plasma enhanced microwave chemical vapor deposition. Selected layers were covered with a thin metal layer of Cr to enhance their optical absorption characteristics for photothermal and photoacoustic experiments. A heterodyne diffraction method was used to investigate the thermoelastic signatures of the N/MCD layers. While the dispersion of surface acoustic waves turned out to be difficult to determine due to high optical scattering from the diamond crystallites, it was found that a diamond film of ~ 2 μm thick is enhancing the thermal diffusion along the surface.
Multilayer antidiffusion barrier schemes for Schottky and ohmic contact metallisations to InAlN/GaN HEMTs
Authors: Kamińska Eliana , Pasternak Iwona , Borysiewicz Michał A. , Guziewicz Marek , Piotrowska Anna , Dynowska Elżbieta , Jakieła Rafał , Kolkovski Valery , di Forte-Poisson Marie‑Antoinette 
Published: April 2011

ABSTRACTThe reported work focuses on developing antidiffusion barriers capable to increase the thermal stability of metal contacts above 700 C. In the chosen approach, such an antidiffusion barrier consists of several bilayers of materials with different crystalline structures. It has been demonstrated that an interface between such materials effectively blocks the atomic interdiffusion. In this work the following groups of materials were used as the bilayers: ZrB2 and ZrN and TaSiN and TiN. The materials were deposited by means of room temperature sputtering from elemental and compound targets in inert Ar and reactive Ar+N2 atmospheres. The structures were characterised using secondary ion mass spectroscopy depth profiling and scanning electron microscopy cross sectional imaging directly after deposition and after degradation. I-V characteristics were measured and contact resistivities were determined from the circular transmission line method.
Electrochemical Nanopatterning on Copper Surface Using an AFM Cantilever Tip
Authors: Lee Gyudo , Nam Kihwan , Jeong Suho , Jung Huihun , Choi Bumjoon , Lee Sang Woo , Yoon Dae Sung , Eom Kilho , Kwon Taeyun 
Published: April 2011

ABSTRACTIn this paper, we present technique to fabricate nanopatterns on Cu thin films via an electrochemical nanomachining (ECN) using an atomic force microscope (AFM). A conductive AFM cantilever tip (Pt/Ir5 coated) was used to form an electric field between tip and Cu substrate with applying a voltage pulse, resulting in the generation of an etched nanopattern. In order to precisely construct the nanopatterns, an ultra-short pulse was applied onto the Cu film through the AFM cantilever tip. The line width of the nanopatterns (the lateral dimension) increased with increased pulse amplitude, on-time, and frequency. The tip velocity effect on the nanopattern line width was also investigated that the line width is decreased with increasing tip velocity. Experimental results were compared with an equivalent electrochemical circuit model representing an ECN technique. The study described here provides important insight for fabricating nanopatterns precisely using electrochemical methods with an AFM cantilever tip.
High temperature creep strength in a nanodispersion-strengthened ferritic alloy prepared by heavy plastic deformation
Authors: Morris David G. , Muñoz-Morris Maria Antonia 
Published: April 2011

ABSTRACTProcesses of severe plastic deformation have been investigated for a wide range of ductile alloys over the past decade, generally with an objective of refining the microstructural scale, for example the grain size, but have hardly been considered for intermetallics. This presentation discusses processing of a boride-containing Fe3Al alloy using a multidirectional, high-strain and high-temperature forging technique. Iron aluminides with relatively low Al contents can be regarded as Al-rich ferritic steels with outstanding oxidation-corrosion properties. However, as for many ferritic steels, they show poor creep resistance at temperatures above about 600ºC. The deformation processing leads to a material with large grain size and refined dispersion of thermally-stable boride particles. The particles produce a large increase in creep strength under conditions of moderate stresses and low strain rates at temperatures near 700ºC. This high-strain forging technique can be seen as an intermediate processing method between conventional wrought metallurgy and mechanical-alloying powder metallurgy, whereby an initially coarse and inhomogeneous dispersion of second phase is refined and made more homogeneous, and can be considered as a useful processing technique for a wide range of particle-containing materials.