bluuebunny/crossref_metadata_2025_split huggingface dataset:
Creating Novel Transport Properties in Electric Double Layer Field Effect Transistors Based on Layered Materials
Authors: Ye J. T. , Craciun M. F. , Koshino M. , Russo S. , Kasahara Y. , Yuan H. T. , Shimotani H. , Morpurgo A. F. , Iwasa Y. 
Published: April 2011

ABSTRACTWe present a study on the liquid/solid interface, which can be electrostatically doped to a high carrier density (n~1014 cm-2) by electric-double-layer gating. Using micro-cleavage technique on the layered materials: ZrNCl and graphene, atomically flat channel surfaces can be easily prepared. Intrinsic high carrier density transport regime is accessed at the channel interface of electric double-layer field effect transistor, where novel transport properties are unveiled as the field-induced superconductivity on the ZrNCl with high transition temperature at 15 K, and accessing a high carrier density up to 2×1014 cm-2 in graphene and its multi-layers.
Influence of Quenching Rates on the Transformation of Ternary Phases in Nb-rich γ-TiAl Alloys
Authors: Stark Andreas , Oehring Michael , Pyczak Florian 
Published: April 2011

ABSTRACTIntermetallic γ-TiAl based alloys with additional amounts of the ternary bcc β phase attracted increasing attention in recent years due to their improved workability at elevated temperatures. At lower temperatures the ductile high-temperature β phase can transform to several ordered phases. However, actually available phase diagrams of these multiphase alloys are quite uncertain and the precipitation kinetics of some metastable phases is far from understood.In the present study various transformations of the third phase are observed in situ by means of high-energy x-ray diffraction using synchrotron radiation. A Ti-45Al-10Nb (at.%) specimen is subject to a temperature ramp of repeated heating cycles (700 °C - 1100 °C) with subsequent quenching at different rates. Depending on the quenching rate reversible transformations of the B2-ordered βophase to different ω related phases are observed in Ti-45Al-10Nb. At low quenching rates the hexagonal B82-ordered ωophase is formed while at high quenching rates the metastable intermediate trigonal ω’’ phase can be preserved. The results indicate that the complete transformation from βoto hexagonal B82-ordered ωoconsists of two steps which are both diffusion controlled.
Effect of Microstructure on Cold Workability of Ni3Si base Multi-Phase Intermetallic Alloys
Authors: Kaneno Yasuyuki , Matsuoka Yasuyuki , Takasugi Takayuki 
Published: April 2011

ABSTRACTThe effect of microstructure on cold-rolling workability and tensile properties of Ni3Si (L12)−Ni3Ti (D024)−Ni3Nb (D0a) multi-phase intermetallic alloys was investigated. The cast alloys with different microstructures containing the D024 phase and/or the D0a phase particles in the L12 matrix were homogenized and then cold rolled. For the alloys with the microstructure consisting of coarse plate-like D024 particles in the L12 matrix, serious cracks initiated at the coarse D024 particles in the early stage of the cold rolling process and then propagated, resulting in failure of the rolled plate. On the contrary, for the alloys with the microstructure consisting of fine needle-like D024 precipitates and/or granular-shaped D0a particles, these second phase particles did not spoil the cold workability, leading to successful cold rolling to 90 % reduction. After 90 % cold rolling, the rolled sheets were fully recrystallized at 1173 K for 1 h, resulting in the formation of a fine-grained microstructure. The room-temperature tensile strength and the yield stress of the recrystallized sheet were remarkably enhanced compared with that of the unrolled alloys, possibly due to the fine-grained microstructure as well as the particle hardening. Also, the high-temperature tensile strength and the elongation were improved in the recrystallized sheets compared to an L12 single-phase Ni3(Si,Ti) alloy sheet. Consequently, it was found that the cold rolling and annealing process was beneficial to improve the tensile properties for the present multi-phase intermetallic alloys.
Thermal effects on the Raman spectra of nanodiamonds
Authors: Chaigneau Marc , Girard Hugues A. , Arnault Jean-Charles , Ossikovski Razvigor 
Published: April 2011

ABSTRACTWe report on the influence of the laser heating effect, potentially present in a Raman scattering experiment, on the behaviour of carbon phonon lines in the spectra of nanodiamond particles. Aside from the laser power used in the experiment, the extent of the thermal effect in question depends also on the nanodiamonds origin (obtained through detonation and high pressure high temperature techniques) as well as on the nanoparticles size. Laser heating should be properly taken into account when discussing Raman spectra of carbonaceous species, in particular, prior to addressing peak assignment and possible quantum confinement effects.
Phase Equilibria and Phase Transformations in Molybdenum-Containing TiAl Alloys
Authors: Mayer Svea , Sailer Christian , Nakashima Hirotoyo , Schmoelzer Thomas , Lippmann Thomas , Staron Peter , Liss Klaus-Dieter , Clemens Helmut , Takeyama Masao 
Published: April 2011

ABSTRACTMolybdenum, being a strong β stabilizer, is an important alloying element in TiAl alloys, since a significant volume fraction of the disordered bcc β-phase at elevated temperatures improves the processing characteristics during hot-working. Unfortunately, the effect of Mo on the individual phases and their transition temperatures is not completely known but is necessary for designing engineering applications. In this paper, sections of the Ti-Al-Mo ternary phase diagram derived from thermodynamic calculations as well as experimental data are presented. Further, the phase transition temperatures given by the phase diagrams are compared with results from isothermal heat treatment studies, differential scanning calorimetry measurements and in-situ high-temperature diffraction experiments. Combining all of these results, a revised phase diagram is proposed.
Group theoretical analysis of nitrogen-vacancy center’s energy levels and selection rules
Authors: Maze J. R. , Gali A. , Togan E. , Chu Y. , Trifonov A. , Kaxiras E. , Lukin M. D. 
Published: April 2011

ABSTRACTWe use a group theoretical approach to model the nitrogen-vacancy defect in diamond. In our analysis we clarify several properties of this defect that have been source of controversy such as the ordering of the singlets and the mechanism that leads to spin mixing in the excited state of this defect. In particular, we demonstrate that the ordering of the ground state configuration (e2) is {3A2, 1E, 1A1} and that the spin-spin interaction causes the mixing in the excited state. In addition, we analyze the angular momentum and spin properties of the excited state structure that enables a spin photon entanglement scheme that has been recently demonstrate experimentally. Our description is general and it can be easily applied to other defects in solid-state systems.
Optimization of a Boron Doped Nanocrystalline Diamond Temperature Regulator for Sensing Applications
Authors: Clukers Tim , Van Grinsven Bart , Vandenryt Thijs , Janssens Stoffel D. , Wagner Patrick , De Ceuninck Ward , Thoelen Ronald , Daenen Michaël , Haenen Ken 
Published: April 2011

ABSTRACTRecently, the concept of creating a boron doped nanocrystalline diamond (B-NCD) based temperature regulator for bio-sensing applications was proven. In this work, the next step is taken, i.e. one device working simultaneously as thermistor and heater. In combination with a PID-control., it is possible to create a temperature control, with possible set points going from room temperature till 70°C, with an accuracy exceeding a maximum temperature variation of 0.2 °C. Parallel with steering the temperature by varying the current through the B-NCD film, its resistance is measured with a 4-point measurement from which the temperature can be derived using a calibration curve. This value is the feedback for the PID-control to steer the current used for the regulation.
Structural, Transport, and Magnetic Characterization of NiZr Metallic Glasses with varied Ni/Zr composition
Authors: Isakovic A. F. , Sulejmanovic S. D. , Mihac T. P. , Evans-Lutterodt K. 
Published: April 2011

ABSTRACTThree families of NixZry (x = 28, 36, 38, x + y = 100%) metallic glasses were prepared and examined using X-ray, temperature dependent transport and magnetic field. X-ray characterization shows characteristic diffuse spectrum, except for narrow regions of control samples, where partial crystallization was induced in finite small volumes. Magnetic properties confirm spin-fluctuating paramagnetic-like behavior, which we asses from preliminary Hall coefficient measurements, which is quantitatively different in three sample families. Temperature dependent AC and DC transport measurements were conducted in a broad temperature range from 70 K to 700 K, finding both quantitative and semi-qualitative differences between samples with different Ni/Zr ratio.
Texture Formation of α2-Ti3Al during Hot Forming of γ-TiAl Based Alloys
Authors: Stark Andreas , Gosslar Daniel , Pashkov Nikolai 
Published: April 2011

ABSTRACTIn the present study the α2and the γ texture in a Ti-45Al (at.%) alloy were analyzed by means of x-ray diffraction after hot deformation. The initial Ti-45Al powder compact exhibits a random texture and shows a relatively high amount of α2phase (about 34 vol.%). Various hot compression tests were performed at temperatures ranging from 700 °C to 1100 °C with strain rates of 5·10–4s–1and 5·10–2s–1up to a true deformation of ε = –1.Depending on the deformation temperature the γ-TiAl deformation texture consists of pure deformation components (700 °C) or components completely related to dynamic recrystallization (1100 °C). In contrast to the γ phase the α2phase shows no remarkable changing of the deformation texture with increasing temperature. The α2deformation texture basically consists of a similar component as it is known from hexagonal α-Ti, namely a tilted basal fiber. However, a significant influence of the deformation rate on the α2texture formation is observed at temperatures above 800 °C. With increasing deformation temperature the α2texture strengthens by applying a high deformation rate, whereas it weakens for a low deformation rate. This contrary behavior is attributed to the interaction of the α2and γ phases during texture formation.
Label-free Electrochemical Biosensor Based on Graphene/Ionic Liquid Nanocomposite for the Detection of Organophosphate Pesticides
Authors: Park Tae Jung , Yang MinHo , Choi Bong Gill , Heo Nam Su , Lee Seok Jae , Hong Won Hi , Lee Sang Yup 
Published: April 2011

ABSTRACTThe advanced electrodes for detecting organophosphate pesticides were prepared by modification of the gold (Au) electrode with the reduced graphene oxide/ionic liquid (RGO/IL) nanohybrids. Due to the cationic and anionic parts, the ILs on RGO sheets provide the amount of functional groups for dispersion of hybrids and immobilization of organophosphorus hydrolase (OPH) enzymes. After the immobilization of OPH on the RGO/IL-modified Au electrodes, the modified electrodes represent faster electron transfer than that of Au electrode, resulting in high performance of biosensor with response time (~ 10 s) and sensitivity (4.56 nA μM−1). In addition, the OPH/RGO/IL-modified Au electrode displayed good stability and reproducibility.
Magneto-optics in Diluted Magnetic Semiconductors and in Ferromagnetic-Metal/Semiconductor Hybrids
Authors: Zayets V. , Debnath M. C , Saito H. , Yuasa S. , Ando K. 
Published: April 2011

ABSTRACTThe optical isolator made of diluted magnetic semiconductor and the isolator made of a ferromagnetic-metal/semiconductor hybrid have been developed aiming to integrate nonreciprocal optical devices, such as an optical isolator and optical circulator, into the semiconductor-made optoelectronic integrated circuits,. The Cd1-xMnxTe exhibits a huge Faraday effect and can be grown on a semiconductor substrate. For Cd1-xMnxTe waveguide with a Cd1-xZnxTe/ Cd1-xMnxTe quantum well grown on GaAs substrate we achieved a high Faraday rotation of 2000 deg/cm, a high isolation ratio of 27 dB, a low optical loss of 0.5 dB/cm, and a high magneto-optical figure-of-merit of 2000 deg/dB/kG in a wide 25-nm wavelength range. It was predicted theoretically and proved experimentally the effect of non-reciprocal loss in hybrid semiconductor/ferromagnetic metal waveguides. This effect can be use for new design of waveguide optical isolator. Because of its simplicity and technological compatibility, this design is attractive for the integration into optoelectronic integrated circuits. The magneto-optical figure-of merit of 7% was demonstrated for the AlGaAs passive optical waveguide covered by Co.
Mapping Residual-Stress Distributions in a Laser-Peened Vit-105 Bulk-Metallic Glass Using the Focused-Ion-Beam Micro-Slitting Method
Authors: Winiarski B. , Wang G. , Xie X. , Cao Y. , Shin Y. , Liaw P. K. , Withers P. J. 
Published: April 2011

ABSTRACTMeasuring residual-stresses at the micron scale in glassy materials imposes experimental challenges, particularly when using diffraction, or other conventional laboratory methods, e.g., optical non-contact methods, grid methods, etc. In this short paper, a technique for mapping residual-stress profiles in amorphous materials with high spatial definition is used to measure residual-stresses in a laser-peened and fatigued bulk-metallic glass - Vit-105. The method involves local deposition of nano Pt dots patterns on the mapped region of the specimen and milling of a series of micro-slots of size 15 × 2 × 0.4 μm3 using the focused ion beam of a dual beam Field Emission Gun Scanning Electron Microscope / Focused Ion Gun (FEGSEM/FIB) instrument. The deformation fields in the vicinity of slots are reconstructed by the digital image correlation analyses (DICA) of FEGSEM images recorded during milling. The residual-stresses are inferred by fitting a reference displacement field obtained from finite-element analyses (FEA) with the recorded displacement field. In this way, residual-stress distributions have been characterized as a function of the distance from the laser-peened surface to a depth of 1,200 microns with a spatial resolution of 30 μm. The influence of fatigue loading on the compressive residual-stresses spatial distribution is studied and discussed. It was found that the fatigue loading significantly changes the compressive residual-stress spatial distribution in the laser-peened layer.
Effects of additives on the phase stability of Nb3Si intermetallic compound and mechanical properties of Nb-Si alloy
Authors: Tanahashi Tatsuichi , Miura Seiji , Mohri Tetsuo 
Published: April 2011

ABSTRACTRecently, Nb-Si alloys have attracted attentions as substitutional materials of Ni-based superalloys because of its low density and high melting point. For attaining good room temperature toughness of Nb-Si alloys, proposed is a microstructure-control technique by combining eutectic reaction (L->Nb+Nb3Si) and eutectoid reaction (Nb3Si->Nb+ Nb5Si3) for spheroidizing Nb5Si3 strengthening phase embedded in Nb matrix [1]. For the solid solution strengthening of Nb matrix phase W and Mo are very effective, but Nb3Si phase disappears by adding these elements of as small as 3 at%. In contrast, Ti and Ta stabilize Nb3Si phase. For a further alloy development, establishment of an alloy design based on the control of phase stability of Nb3Si is needed. In the previous study [2], it was revealed that the phase stability of Nb3Si can be controlled by selecting appropriate Ta/Mo ratio. In the present study, this approach is expanded to other combinations of stabilizing and destabilizing elements of Nb3Si, such as Ti and W, Ta and W, and Ti and Mo. Vickers hardness tests were conducted on the heat-treated samples to reveal effects of additives on mechanical properties of Nb-Si alloy.
Quasi-Phase Matching Magneto-Optical Waveguides
Authors: Hutchings David C. , Holmes Barry M. 
Published: April 2011

ABSTRACTPhotonic integration has proved remarkably successful in combining multiple optical devices onto a single chip with the benefits of added functionality, and reduction in costs, arising from the replacement of manual assembly and alignment of individual components with lithographic techniques. However, the incorporation of optical isolators and related non-reciprocal devices within standard optoelectronic wafer platforms is exceptionally challenging. Preferred magneto-optic materials cannot be exploited as waveguide core layers on semiconductor wafers due to a lower refractive index. Another difficulty is the phase velocity mismatch as a consequence of the inherent structural birefringence associated with waveguide geometries.Our approach to the integration of an optical isolator with a III-V semiconductor laser involves combining a nonreciprocal mode converter with a reciprocal mode converter, based on an asymmetric profiled rib waveguide, fabricated by Reactive Ion Etching. We demonstrate that suitably tapered waveguides can be employed to connect the mode converter to other sections thereby avoiding problems caused by mode-matching and reflections from the section interfaces.The nonreciprocal mode converter is formed from a continuation of the III-V semiconductor waveguide core with a magneto-optic upper cladding so that Faraday rotation occurs through the interaction of the evanescent tail. The phase velocity mismatch due to the waveguide birefringence is overcome using a quasi-phase-matching approach. Lithography is used to pattern the top cladding so that the film immediately on top of the waveguide core alternates between magnetooptic and a non-magneto-optic dielectric of a similar refractive index. Our first demonstrations used a dielectric (silica or silicon nitride) patterned by etching, or lift-off, on top of a GaAs rib waveguide, over which was deposited a magneto-optic film. This film was deposited by sputtering from a Ce:YIG target and demonstrated magnetic hysteresis, but, as it was not annealed, it was believed to consist of Ce:YIG and/or gamma iron oxide microcrystallites embedded in an amorphous matrix. With quasi-phase-matching periods of 110–160 μm and a waveguide length of 8 mm, we were able to demonstrate up to 12% non-reciprocal TE- to TM-mode conversion around a wavelength of 1.3 μm using the remanent magnetisation.In order to enhance the magneto-optic effect it is desirable to anneal such films. However the mismatch in thermal expansion coefficients results in a catastrophic failure of samples with large area film coverage. This problem has been shown to be alleviated by patterning the YIG film. Unfortunately wet-etching of YIG also etches (Al)GaAs and, therefore, the development of a lift-off process for YIG deposition has been undertaken. Initial results are promising with ∼100 μm×2.5 μm YIG sections deposited on a GaAs layer which remain intact after an anneal in an oxygen atmosphere.
Displacement cascade decomposition within the Binary Collision Approximation
Authors: Luneville Laurence , Simeone David , Baldinozzi Gianguido , Gosset Dominique 
Published: April 2011

ABSTRACTThe mechanism of damage production in solids during irradiation is of great practical interest in nuclear technology. The need to increase the life time of current nuclear plants as well as extreme conditions (high temperature and high neutron flux) in new generations of nuclear plants leads to have a deep insight into radiation damage in solids. In fact, the slowing down of particles in solids leads to a non homogeneous distribution of defects in solids, giving rise to complex microstructures with unusual properties. Numerous experiments, Molecular Dynamics (MD) and Monte Carlo (MC) simulations have clearly shown that highly damaged areas called displacement cascades are produced by neutron or impinging ions in solids. It is now clearly established that the number and the distribution of these subcascades dictate the long term evolution of the microstructure under irradiation. In this work, we present a new model to calculate the mean number of displacement cascades produced in a mono-atomic solid by an incident particle within the Binary Collision Approximation framework (BCA) taking into account all information extracted from MD simulations. To reach such a goal, the notion of subcascade threshold energy is introduced and discussed on some examples. Within this formalism, we exhibit a new way to estimate the number of defects created in a displacement cascade integrating results of MD simulations of cascades.
Alternative Current Magnetic Permeability of Fe81Ga19 Alloy with Bias Magnetic Fields
Authors: Zhang Hongping , Wu Guangheng , Liu Zheng , Xu Lihong , Wang Lei , Du Zhaofu , Pei Yongmao , Zhao Dongliang 
Published: April 2011

ABSTRACTIn this study, the AC magnetic permeability of polycrystalline Fe81Ga19 alloy (Galfenol), without crystal orientation under both the bias applied fields and frequencies, was investigated by the method of measuring inductance of ring specimens. The results showed that the AC permeability of the alloy can reach more than 160 Gs/Oe under the conditions of low frequencies or quasi-static state. The permeability decreased with the increase of frequency. When the frequency was higher than 6 kHz, the permeability decreased slowly, and gradually stabilized with the increase of frequency. When applying a little of parallel bias magnetic field, the permeability decreases obviously with the increase of frequency. But applying a perpendicular bias magnetic fields, the permeability of the only initial point of the measuring frequency decreases a little compared to the permeability without bias field.
Shark-skin inspired surface engineering on intermetallic titanium aluminides for high temperature applications using the fluorine effect
Authors: Pflumm Raluca , Schütze Michael 
Published: April 2011

ABSTRACTIncreasing demands on technical components for high-temperature applications (e.g. tur-bine blades) promote new developments not only in the field of alloy design, but also in surface engineering. This paper shows that it is possible to structure the surface of intermetallic titanium aluminides in-situ by locally controlled oxidation of the material due to selective doping with fluorine. The aim is to reproduce a shark-skin pattern (parallel riblets with valleys in between) in order to improve the surface aerodynamics. Riblets with widths in the single digit μm range have been generated. The nucleation process, the aspect ratio and the stability of the generated micro-structures are discussed as a function of the substrate composition and the oxidation conditions.
Compression of Micropillars of TiAl Coexisting with Ti3Al
Authors: Fujimura Kazuki , Kishida Kyosuke , Tanaka Katsushi , Inui Haruyuki 
Published: April 2011

ABSTRACTSquare-shaped micropillar of nearly stoichiometric TiAl single crystals with various loading axis orientations were prepared from TiAl PST crystals by focused ion beam (FIB) technique and deformed in compression using a micro hardness testing machine equipped with a flat diamond tip in order to investigate the values of CRSS for the three types of operative deformation modes, namely ${111}1/2&#x003C; 1 \bar 10 &#x003E;$ ordinary slip, ${111}&#x003C; \bar 101 &#x003E;$ superlattice slip and ${111}&#x003C;11\bar 2 &#x003E;$ twinning. The selective activation of the three types of deformation modes was confirmed to be achieved by compression tests of $[\bar 2 11]-, \bar 110- and [\bar 2 12]$-oriented single crystalline micropillars, respectively. The average CRSS values for ordinary slip, superlattice slip and deformation twinning obtained for micropillars with an initial side length between 3.8 and 7.9μm were estimated to be about 145, 284 and 113 MPa, respectively.