bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Solubility Limit of Carbon in Ni3AlC1-x
Authors: Hosoda Hideki , Inamura Tomonari
Published: April 2011

In order to clarify the phase stability of E21-type intermetallic carbides, the maximum solid solubility of carbon in Ni3AlC1-x was evaluated by taking into account the strain energy and the chemical energy for the formation of the Ni6C cluster (EM6C). It was found that the maximum carbon content calculated was 0 at.%C at EM6C≥0, 3.5 at.%C at EM6C = -5 kJ/mol, 6.5 at.%C at EM6C = -10 kJ/mol, 10 at.%C at EM6C = -15 kJ/mol and 13 at.%C at EM6C = -20 kJ/mol, respectively. Experimentally determined maximum carbon contents in Ni3Al in the literature can be explained when EM6C is ranged from -5 to -15 kJ/mol, and the solid solubility is found to be sensitive to EM6C. The attractive interaction between Ni and C seems to be due to covalent bonding. Similar attractive chemical interaction between transition metals and carbon must stabilize E21 phases.
Crystallographic Characteristics of Shape Memory Alloys
Authors: Krishnan Madangopal
Published: April 2011

The martensitic microstructure of shape memory alloys is an aggregate of self accommodating plate groups. The principal character of this aggregate is its demonstration of pseudoplasticity, wherein a macroscopic shape change is brought about by extensive rearrangement and reorientation of the self accommodating martensite variants, and that of microstructural reversibility, wherein the polyvariant microstructure transforms back to the original grain of the parent phase after pseudoplastic deformation. These aspects of the shape memory intermetallic alloys are intriguing and, to a great extent, unsolved. The aim of this paper is to show that the underlying crystallographic interrelationships of the self accommodating microstructure of intermetallic alloys are responsible for the observed effect. The paper will discuss the relation between autocatalytic nucleation and self accommodation, the relation between microstructural reversibility and intervariant interfaces of the martensitic microstructure and the manifestations of microstructural irreversibility using results from the microstructural examination of the self accommodating microstructures.
Structure Analysis of a Long Period Stacking Ordered Phase in Mg-Al-Gd Alloys
Authors: Yokobayashi Hideyuki , Kishida Kyosuke , Inui Haruyuki , Yamasaki Michiaki , Kawamura Yoshihito
Published: April 2011

Crystal structure of a long period stacking ordered (LPSO) phase newly found in Mg-Al-Gd ternary alloys was investigated by scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM). The Mg-Al-Gd LPSO phase was confirmed to be constructed with 6-layer structural blocks, which is similar to the case of the 18R-type LPSO phases in the other Mg-TM-RE alloys. Atomic resolution high-angle annular dark-field (HAADF) STEM imaging revealed that Gd atoms are enriched in four layers instead of two layers and are ordered in a long range within the 6-layer structural block.
Experimental Studies of Bonding Related Properties in Binary Intermetallics by Convergent Beam Electron Diffraction
Authors: Sang X. H. , Kulovits A. , Wiezorek J.
Published: April 2011

Accurate Debye-Waller (DW) factors of chemically ordered β-NiAl (B2, cP2, ${\rm{Pm}}\bar 3 {\rm{m}}$) have been measured at different temperatures using an off-zone axis multi-beam convergent beam electron diffraction (CBED) method. We determined a cross over temperature below which the DW factor of Ni becomes smaller than that of Al of ~90K. Additionally, we measured for the first time DW factors and structure factors of chemically ordered γ1-FePd (L10, tP2, P4/mmm) at 120K. We were able to simultaneously determine all four anisotropic DW factors and several low order structure factors using different special off-zone axis multi-beam convergent beam electron diffraction patterns with high precision and accuracy. An electron charge density deformation map was constructed from measured X-ray diffraction structure factors for γ1-FePd.
Microstructure Analysis of The Channel Regions in Dual Two-phase Intermetallic Alloy Based on The Ni3Al-Ni3V Pseudo-binary Alloy System
Authors: Moronaga T. , Kaneno Y. , Tsuda H. , Takasugi T.
Published: April 2011

Dual two-phase intermetallic alloys based on the Ni3Al-Ni3V pseudo-binary alloy system have been reported to display high phase and microstructure stabilities and good mechanical properties at high temperature and are therefore considered to be used as a next generation type of high temperature structural materials. The microstructure of the dual two-phase intermetallic alloys is composed of primary Ni3Al and the channel (eutectoid) regions consisting of Ni3Al+Ni3V. In this study, the microstructure of the channel regions was investigated by a transmission electron microscope (TEM). The contrasts of the channel regions showed a complicated microstructure in bright-field images. However, the electron beam diffraction consisted of a single set of patterns and the spots did not accompany streaks, indicating that crystallographic coherency among the constituent phases or the domains is very high. It was also shown that the lattice misfit between the a-axis of Ni3Al and the c-axis of Ni3V is larger than that between the a-axis of Ni3Al and the a-axis of Ni3V. From the dark-field observation, it was found that the c-axis of Ni3V domains in the channel regions is oriented perpendicular to the interface between primary Ni3Al and Ni3V. Therefore, it is suggested that the crystallographic orientation of Ni3V in the channel regions is aligned in the manner of lowering an internal stress caused by the lattice misfit between primary Ni3Al precipitates and Ni3V domains.
Density Functional Theory Calculations On Magnetic Properties Of Actinide Compounds
Authors: Heifets Eugene , Gryaznov Denis
Published: April 2011

We have performed a detailed analysis of the magnetic (collinear and noncollinear) order and atomic and electron structures of UO2, PuO2 and UN on the basis of density functional theory with the Hubbard electron correlation correction (DFT+U). We have shown that the 3-k magnetic structure of UO2 is stabilized for the Hubbard parameter value of U=4.6 eV (while J=0.5 eV) when Dudarev’s formalism is used. UO2 keeps cubic shape in this structure. Two O atoms nearest to each U atom in direction of its magnetic moment move toward this U atom. Neither UN nor PuO2 shows the energetical preference for the rhombohedral distortion, in contrast to UO2, and, thus, no complex 3-k magnetic structure in these materials. Both materials have the AFM tetragonal <001> structure at reasonable choice of parameters U and J.
Damage generated by MeV-ion Beams on Titanium Surface in Oxidizing Environment
Authors: Do Ngoc-Long , Bérerd Nicolas , Moncoffre Nathalie , Gorse-Pomonti Dominique
Published: April 2011

The study of the irradiation effects on titanium surfaces in oxidizing environment using multi-charged Argon ions in the MeV range shed into light the following points:-Significant oxide film thickening for the film grown at 500°C under irradiation at 4 and 9 MeV, by comparison with the TiO2 rutile film grown under same environmental conditions without irradiation;-Formation of large round –shaped craters, of diameter approaching 200 nanometers, at the titanium surface under irradiation at 500°C provided that the environment is enough oxidizing or provided that the metal surface is covered by a sufficiently thick oxide film.

Practically, and for the present system, the superficial craterization is observed if the thickness of the superficial oxide is equal to twice that of the native oxide (~3 nm).
Tunneling Currents in Nanoscale high-κ MOS Structures
Authors: Vercik Andrés
Published: April 2011

Further improvements of integrated circuits depend on the continuous downscaling of MOSFET´s, well beyond the limits for which direct tunneling currents are acceptable. These leakage currents affect both the stand-by power dissipation and the formation of the inversion layer ate the semiconductor surface, i.e., the channel formation. The most promising strategy to overcome this problem is the use of high-κ insulator in substitution of or as an additional layer on the traditional silicon dioxide. The aim of this work is using a recently developed theory to describe tunneling from inversion layers for high-κ insulators or stacks and analyze the effects of tunneling current on the thermal equilibrium in these cases.
SANS Study of Carbon Addition in Ti–45Al–5Nb
Authors: Staron P. , Schimansky F.-P. , Scheu C. , Clemens H.
Published: April 2011

The distribution of carbon in Ti–45Al–5Nb–0.5C was studied using small-angle neutron scattering (SANS). In an earlier study, carbon had been found to form small perovskite precipitates in a γ-TiAl alloy without Nb, which significantly increase the strength of the material. In the Nb-containing alloy, however, no strengthening precipitates were observed, but most of the C was found to be homogeneously distributed. Atom probe investigations revealed only few C-enriched regions. The present SANS investigation was carried out to confirm the presence and size distribution of these C-enriched regions in the material. The SANS results show that a small volume fraction of such C-enriched regions is present, while the large number of small precipitates found in the alloy without Nb is indeed missing in the Nb-containing alloy.
Effect of The Refractory Element Additions on Microstructure and Mechanical Property of Two-phase Intermetallic Alloys Based on The Ni3Al-Ni3V Pseudo-binary Alloy System
Authors: Moronaga T. , Ishii S. , Kaneno Y. , Tsuda H. , Takasugi T.
Published: April 2011

Two-phase intermetallic alloys composed of geometrically close packed (GCP) Ni3Al (L12 phase) and Ni3V (D022 phase) have attractive mechanical properties at high temperature, and are therefore considered to be used as high temperature structural materials. In this study, the effect of Ta and Re addition on the microstructure and hardness of two-phase intermetallic alloys was investigated. The addition of Ta remarkably enhanced the hardness due to solid solution hardening of the constituent phases. On the other hand, the addition of Re retarded the formation of the two-phase microstructure, resulting in the lowest hardness in the solution treated condition. By aging at 1223 K, the Ni solid solution in the Re added alloy decomposed to Ni3Al and Ni3V, accompanied by precipitates of a Re-rich phase. Consequently, the hardness rapidly increased with increasing aging time. Simultaneous addition of Ta and Re induced very fine precipitates of a Re-rich phase after aging, and consequently resulted in a higher hardness than by the addition of Ta or Re alone.
Phase-Field Simulation of Antiphase Boundary Migration in Intermetallic Compounds with Solute and Vacancy Segregation
Authors: Koizumi Yuichiro , Yokoi Tatsuya , Ouchi Masayuki , Minamino Yoritoshi , Yoshiya Masato , Allen Samuel M.
Published: April 2011

The effects of solute and vacancy segregation on APB migration in Ti3Al, and their dependence on composition, have been investigated by using a phase-field simulation in which vacancy distribution is taken into account. Al-atoms are depleted and vacancies segregate at APB in stoichiometric Ti3Al (Ti-25Al), whereas Al-atoms segregate and vacancies are depleted in Alrich one (Ti-28Al). The simulation indicates that APB in Ti3Al migrates much faster in Ti-25Al than in Ti-28Al with the effect of vacancy segregation whereas it migrates slightly faster in Ti-28Al than in Ti-25Al in the absence of the effect of vacancy segregation.
Microstructural Studies of Multiphase (Zr,Ti)(V,Cr,Mn,Co,Ni)2 Alloys for NiMH Negative Electrodes
Authors: Bendersky L. A. , Wang K. , Boettinger W. J. , Newbury D. E. , Young K. , Chao B.
Published: April 2011

The solidification microstructures of six Laves-based (Zr,Ti)(TM,Ni)2 alloys (TM= V,Cr, Mn,Co) intended for use as novel negative electrodes in Ni-metal hydride batteries were studied here; these alloys often have their best electrochemical properties when in the cast state. Solidification occurs by dendritic growth of a hexagonal C14 Laves phase followed by peritectic solidification of a cubic C15 Laves phase and formation of a cubic B2 phase in interdendritic regions. The observed sequence of Laves phase C14/C15 upon solidification agrees with predictions using effective compositions and thermodynamic assessments of the ternary systems, Ni-Cr-Zr and Cr-Ti-Zr. The paper also examines the complex internal structure of the interdendritic grains formed by solid-state transformation, which plays an important role in the electrochemical charge/discharge characteristics. By studying one alloy it is shown that the interdendritic grains solidify as a B2 (Ti,Zr)44(Ni,TM)56 phase, and then undergo transformation to Zr7Ni10-type, Zr9Ni11-type and martensitic phases. The transformations obey orientation relationships between the high-temperature B2 phase and the low-temperature Zr-Ni-type intermetallics, and consequently lead to a multivariant structure. Binary Ni-Zr and ternary Ti-Ni-Zr phase diagrams were used to rationalize the formation of the observed domain structure.
The Role of Si and Sb in the Si-Sb-Te Phase-change Material
Authors: Wu Liangcai , Zhou Xilin , Song Zhitang , Ni Henan , Rao Feng , Ren Kun , Peng Cheng , Song Sannian , Zhang Ting , Liu Bo , Feng Songlin , Chen Bomy
Published: April 2011

Sb-rich Si-Sb-Te phase change materials with different Si contents were proposed and fabricated, and the role of Si and Sb in the Si-Sb-Te alloys was discussed. The resistance-temperature and retention properties of the Sb-rich Si-Sb-Te alloys were studied. Devices based on the Sb-rich Si-Sb-Te alloys were fabricated by a 0.18 μm CMOS technology and device properties were studied by pulsed mode resistance-voltage (R-V) measurements. Experimental results show that the crystallization temperature and data retention ability of the Sb-rich Si-Sb-Te alloys were obviously improved with increasing Si content, but the electrical properties degenerate if too much Si was added. Sb is helpful to promote the crystallization process, but excessive Sb decreases the thermal stability. So, in order to obtain practicable Sb-rich Si-Sb-Te phase change materials, suitable Si and Sb contents are required to balance the device performances between electrical switching property and thermal stability or data retention ability.
Interphase Energies and Nonequilibrium Growth of γ-precipitates in Al-Ag: A DFT Study
Authors: Watts D. J. , Johnson D. D. , Finkenstadt Daniel
Published: April 2011

Density-functional theory (DFT) calculations of interphase boundary energies provide useful input for many precipitate growth models in alloy systems [1]. One example is Al-Ag, where a rich variety of precipitate types exist, and the sizes and shapes are determined roughly by a Wulff construction, namely, minimizing surface free energies with respect to geometry. This is only a first approximation, however, as kinetic-considerations and crystallography do not allow for a uniform, isotropic growth. Consequently, a nonequilibrium growth model is developed for γ-plates [2], which attempts to connect semi-coherent (ledge) and incoherent (edge) interface growth rates in a way that incorporates shape and interface energies. Through this connection, we make a DFT model with approximate unit cells that mirror experimental conditions, which gives accurate predictions for precipitate aspect ratios and time-development of nonequilibrium shapes. Starting from an explicit calculation of Suzuki segregation of solute to stacking-faults, we find a mechanism for nucleation of nanoscale γ-plates on quenched defects, identify a bulk structure from a calculated phase diagram that gives the relevant HCP equilibrium precipitate structure occurring at 50 at.% Ag and calculate critical nucleation parameters for γ-precipitate formation. Applications to island-coarsening and lath morphology are also discussed.
Characterization of 14YWT As-Atomized, Milled, Milled and Annealed Powders and HIP Consolidated Alloys
Authors: Cunningham Nicholas J. , Etienne Auriane , Odette G. Robert , Stergar Erich , Wu Yuan , Wirth Brian D.
Published: April 2011

Nanostructured ferritic alloys (NFA) are Fe-Cr based ferritic stainless steels containing an ultrahigh density of very stable Y-Ti-O nanofeatures (NFs) that provide dispersion strengthening and radiation damage resistance for candidate Generation IV and future fusion reactor materials. This work is a small and focused part of a larger collaboration to produce large best practice NFA heats. The powders analyzed were rapidly solidified from a melt containing Fe-14%Cr, 3%W, 0.4%Ti and 0.2%Y by gas atomization in Ar, Ar/O, and He atmospheres. Note this represents a different processing path from conventional NFA production where metallic powders are mechanically alloyed with Y2O3 by ball milling. Electron probe microanalysis (EPMA), atom probe tomography (APT), transmission electron microscopy (TEM) and small angle neutron scattering (SANS) were used to characterize the powders in the as-atomized, ball milled and ball milled and annealed conditions. EPMA showed the Y is heterogeneously distributed and phase separated in all the as atomized powders, but attritor milling for 20 to 40 h is required to mix the Y. Milling also creates a significant quantity of O as well as N contamination. Subsequent powder annealing treatments, typically at 1150°C, result in the precipitation of a high density of NFs. All the annealed powder variants show a bimodal grain size distribution, but TEM and APT show NFs in both large and small grains. Reducing O content added during milling of the Ar atomized powders increased the precipitate size and decreased the number density, adversely affecting the hardness.
Study of Ion Beam Mixing by x ray reflectometry
Authors: Simeone D , Gosset D , Luneville L. , Baldinozzi G , Moncoffre N , Deranlot C.
Published: April 2011

We present in this text a new experimental tool to study the mixing of atoms under irradiation. Based on physics of x ray diffraction, the specular reflectivy of x ray was used to estimate the Auto Correlation Function associated with the electron density gradient. The accuracy of the ACF is around 1 nanometer and does not evolve with the thickness of the probed layer. Thus, this point allows accurately measuring the broadening of the electron density gradient spreading induced by irradiation. Such an accurate profile extracted over a large range of fluences (about 3 decades) would lead to the determination of the functional dependence of this spreading with the fluence. This could allow pointing out the main mechanisms triggering the atomic mixing over large distances when atomic mixing occurring in thermal spikes is washed out.
Phase Equilibria in the Nb-rich Nb-Ti-Si-Cr-Hf alloys
Authors: Yang Ying , Bewlay Bernard P. , Chang Austin
Published: April 2011

Refractory Metal-Intermetallic Composites (RMICs) based on the Nb-Si system have been considered as candidates for the next-generation high temperature materials (i.e. >1200°C). Ti, Cr and Hf have been shown to have beneficial effects on the oxidation resistance and mechanical properties of Nb-Si alloys. The present study has determined phase equilibria in the Nb-rich region of the Nb-Si-Ti-Cr-Hf system via the Calphad approach. The alloying effects of Cr and Hf on the microstructure of Nb-Si-Ti alloys are understood based on isothermal sections, liquidus projections, and solidification curves that were calculated from the thermodynamic models of the Nb-Ti-Si-Cr-Hf system developed in the present study. This work provides important guidelines on the development of new Nb-Si-Ti-Cr-Hf alloys.
Microstructural characterization of copper metallic deposition by electroplating growth for SIP applications
Authors: Durand Céline , Domengès Bernadette , Le Duc Philippe
Published: April 2011

Microstructural characterization (Focused Ion Beam and Transmission Electron Microscopy imaging) was performed on cross-sections of contacts in thick Electro Chemical Deposition copper metallization of System In Package Integrated Circuits. It was shown that the lower growth rate of ECD-Cu in the AlSiCu – barrier Ti – PVD-Cu – ECD-Cu layer stacking is related to a local higher resistivity induced by the presence of a great number of almost planar grain boundaries in the PVD-Cu layer, which are perpendicular to the growth axis. This morphology is a consequence of the almost heteroepitaxial growth of Ti layer on AlSiCu layer.
Crevice Corrosion Behavior of Type 316L Stainless Steel in Gamma-ray Irradiated High-temperature Water
Authors: Nakahara Yukio , Kato Chiaki , Yamamoto Masahiro , Tsukada Takashi , Watanabe Atsushi , Fuse Motomasa
Published: April 2011

Crevice-corrosion tests were performed in gamma-ray irradiated high-temperature water of 288 °C on Type 316L stainless steel. The gamma-ray dose rate was about 30 kGy h−1. Tested specimen surfaces were analyzed using SEM, laser Raman spectroscopy and TEM/EDX. Experimental data were presented in order to show the differences made by the irradiation and crevice-shape simulated structure. Both gamma-ray irradiation and crevice-shape simulated structure changed the corrosion phenomena. On the gamma-ray irradiated crevice-shape simulated surface, α-Fe2O3 particles more than 5 μm in diameter were observed. It suggested that corrosion environment on the crevice-shape simulated surface became severer by gamma-ray irradiation.
Magnetic Tight-Binding Simulations of Defects in Iron
Authors: Soin Preetma K. , Horsfield Andrew P. , Nguyen-Manh Duc
Published: April 2011

We consider a tight binding model for magnetic systems, in which we allow atoms to become charged and to interact via the long ranged Coulomb interaction to a published tight binding model; this is then applied to the study defects in ferromagnetic iron. We encounter several problems with achieving self consistency with existing schemes. To address the issue of instability and slow convergency we developed a robust, efficient scheme for charge and spin self consistency. This is based on minimizing an extended form of the Harris-Foulkes functional which includes spin, leading to a Newton-Raphson iterative procedure. We then apply this to both bulk and defect calculations for iron.
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

We 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

A 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

In 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

We 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

Applying 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

Semiconductor 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

Recently, 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

Thin 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

The 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

Boron 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

PbTiO3-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

New 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

The 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

Large, 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

Chemical 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

In 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

Chemotaxis 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

Thin 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

The 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

In 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

Processes 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.
Routes towards large area, low pressure nanodiamond growth via pulsed microwave linear antenna plasma chemistry
Authors: Liehr Michael , Fendrych František , Taylor Andrew , Nesládek Miloš
Published: April 2011

Current experimental configurations for MW PECVD diamond growth do not allow simple up-scaling towards large areas, which is essential for microelectronic industries and other applications. Another important issue is the reduction of the substrate temperature during diamond growth to enhance the compatibility with wafer processing technologies. Such advantages are provided by MW-linear antenna (LA) plasma applicators, allowing a scalable concept for diamond growing plasmas. In the present work we introduce a novel construction of LA MW applicators designed for nanodiamond growth by using plasmas ranging from continuous wave (CW) to high repetition rates pulsed modes (up to 20 kHz) which advantages are discussed in detail.
Template-Assisted Fabrication of Double-Shelled Nanotubes Composed of Inner Shell Pb(Zr0.52Ti0.48)O3and Outer Shell TiO2by Sol-Gel Process with Spin-Coating Technique
Authors: Choi Y. C. , Cho S. Y. , Bu S. D.
Published: April 2011

Double-shelled nanotubes composed of inner shell Pb(Zr0.52Ti0.48)O3(PZT) and outer shell TiO2are successfully fabricated by a spin coating of each sol-gel solution on porous anodic alumina template. Field emission transmission electron microscopy images show that they have a ~ 10 nm wall thickness. The selected area electron diffraction patterns show that they have two mixed crystalline phases of tetragonal PZT and anatase TiO2. The analyses of scanning transmission electron microscopy equipped with energy dispersive X-ray spectroscopy confirm their uniform distribution of each element.
Analysis of Vacancy Agglomeration Processes by Matusita’s Method for B2 FeAl
Authors: Yoshimi Kyosuke , Tsunekane Masafumi , Maruyama Kouichi
Published: April 2011

In this study, the exothermic DSC peaks observed in rapidly-solidified Fe-44.9at.%Al ribbons and water-quenched Fe-48.5at.%Al single crystals were analyzed by Matusita’s method in order to discuss the kinetics of the agglomeration processes of supersaturated vacancies. Both the nucleation and morphological factors, n and m, respectively were approximately 3 for the rapidly solidified ribbons and were approximately 2 for the water-quenched single crystals. Based on the Matusita’s idea, the m values suggest the growth of 3-dimensional voids in the rapidly solidified ribbons and the growth of 2-dimensional dislocations loops in the single crystals due to the agglomeration of supersaturated vacancies. In addition, the n values suggest that the nuclei of voids and dislocation loops existed in as-quenched samples. These interpretations are in good agreement with the results of TEM observations.