bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation of a Co3O4 Top Layer in SiO2 Cobalt Containing Coatings Sol-gel Obtained
Authors: Tototzintle-Huitle H. , Ramos-Mendoza A. , Mendoza-Galván A. , González-Hernández J. , Chao B. S. 
Published: April 2011

ABSTRACTSiO2 coatings containing cobalt were prepared on glass substrates using the sol-gel method. It has been found that in coatings with a Si to Co ratio of 1.3, a layer of Co3O4 is formed at the free surface of the coating upon thermal annealings in air. The properties of the coatings were studied using optical, x-ray and Auger depth profile measurements. The thermal annealings in the temperature range of 300 to 500 oC, in steps of 50 oC, were performed for 10 min. Some samples were subjected to an isothermal annealing at 400 °C for different times from 10 to 210 min. From the x-ray diffraction patterns the cubic spinel structure of Co3O4 was detected after the thermal treatments. The optical reflection and transmission spectra for each annealing temperature and annealing time, are described with an air-Co3O4-SiO2:Co2+-substrate system. From this, the cobalt oxide thickness was obtained as a function of the annealing temperature and annealing time. From the Arrhenius plots, in the temperature range studied, it was found that the activation energy for the growth of the cobalt oxide layer is 0.41 eV. The layer thickness follows a parabolic behavior with time, which suggests a diffusion-controlled process. The Auger depth profiles obtained from a sample annealed at 500 °C confirm the optical model used.
Composition-Morphology-Property Relations For Giant Magnetoresistance Multilayers Grown By RF Diode Sputtering
Authors: Zou W. , Wadley H.N.G. , Zhou X.W. , Johnson R.A. , Brownell D. 
Published: April 2011

ABSTRACTA series of experiments have been conducted to evaluate the magnetotransport properties of RF diode sputter deposited giant magnetoresistive (GMR) multilayers with either copper or copper-silver-gold nonferromagnetic (NFM) conducting layers. The study revealed that RF diode deposited multilayers utilizing Cu80Ag15Au5 as the NFM conducting layer posses significantly superior giant magnetoresistance to otherwise identical device architectures that used pure copper as the NFM conducting layer. To explore the origin of this effect, copper and Cu80Ag15Au5 films of varying thickness have been grown under identical deposition conditions and their surface morphology and roughness investigated. Atomic force microscopy revealed significant roughness and the presence of many pinholes in thin pure copper films. The surface roughness of the Cu80Ag15Au5 layers was found to be much less than that of pure copper, and the alloying eliminated the formation of pinholes. Molecular statics estimates of activation barriers indicated that both silver and gold have significantly higher mobilities than copper atoms on a flat copper surface. However, gold is found to be incorporated in the lattice whereas silver tends to segregate (and concentrate) upon the free surface, enhancing its potency as a surfactant. The atomic scale mechanism responsible for silver's surface flattening effect has been explored.
Oscillatory Angular Dependence of Exchange Bias for Epitaxial NiO-Co (001) Bilayers
Authors: Dubourg S. , Bobo J.F. , Warot B. , Snoeck E. , Ousset J.C. 
Published: April 2011

ABSTRACTWe have sputter-deposited NiO-Co bilayers on MgO (001) substrates. NiO grows epitaxially on MgO at 900°C and subsequently the room deposited 80 Åthick Co films have a fcc crystal structure in epitaxy with the oxide underlayer. These samples were warmed up to 300° C and then zero-field or field cooled through the NiO Néel temperature (a 300 Oe magnetic field was applied along the [100] or the [110] MgO axis). Magnetic hysteresis loops were obtained by magneto-optical Kerr effect, the magnetic field being oriented in the plane of the substrate for various angles α with respect to the [100] direction. The usually expected behavior for such experiments is a smooth angular α dependence of the exchange bias HE close to a cosine with only one sign change over 180°. The high crystallographic coherence of our NiO/Co bilayers induces a very unusual oscillatory HE (α) dependence with several sign changes according to the NiO axis field application. Despite of the Co magnetization switching mechanism which is not a pure coherent rotation, we propose a Stoner-Wohlfhart model including four fold anisotropy and unidirectional exchange anisotropy giving a realistic description of these typical magnetic properties.
Epitaxial Growth of Dilute Magnetic Semiconductors: GaMnN and GaMnP
Authors: Overberg Mark E. , Abernathy Cammy R. , Pearton Stephen J. , Sharifi Fred , Hebard Arthur F. , Theodoropoulou Nineta , von Molnar Stephan , Anane Madjid , Xiong Peng 
Published: April 2011

ABSTRACTEpitaxial growth of the dilute magnetic semiconductors GaMnP and GaMnN has been investigated by Gas Source Molecular Beam Epitaxy (GSMBE). GaMnP films grown with < 4.5% Mn show the preferential formation of the second phases MnP and Mn5.64P3, resulting in only a slight deviation from purely diamagnetic behavior. GaMnN films grown on both Al2O3 and Metal-Organic Chemical Vapor Deposition (MOCVD) derived GaN surfaces show strong ferromagnetism when grown with either C codoping or at elevated temperatures to raise the concentration of n-type carriers. Comparable GaMnN films grown under conditions which produce highly resistive material show only paramagnetism, indicating the importance of carrier concentration on the resulting magnetic behavior. The formation of second phases was not observed in the GaMnN material for Mn concentrations less than 9%.
Ferromagnetic Resonance On Metallic Glass Ribbons
Authors: Chipara M. , Toacsen M. , Sorescu M. 
Published: April 2011

ABSTRACTFerromagnetic resonance data on metallic glasses, at room temperature, in X band, are discussed. The spectra were decomposed into two Lorentzian lines and the angular dependence of their main parameters (line width and position) is fully analyzed. It is proved that the usual approaches are not able to describe accurately the experimental data. This behavior is ascribed to the misalignment of the magnetization with respect to the external magnetic field, and successfully tested by using a “relaxed” resonance condition that allows a small misalignment of the magnetization relative to the external magnetic field.
Nanocrystalline and Nanostructured High-Performance Permanent Magnets
Authors: Goll D. , Sigle W. , Hadjipanayis G.C. , Kronmüller H. 
Published: April 2011

ABSTRACTThe rather complex correlation between the microstructure and the magnetic properties is demonstrated for two types of high-quality RE-TM permanent magnets (pms), namely nanocrystalline RE2Fe14B (RE = Nd,Pr) and nanostructured Sm2(Co,Cu,Fe,Zr)17 pms. The detailed analysis of this correlation for both pm materials leads to a quantitative comprehension of the hardening mechanism enabling the optimization of their magnetic properties and temperature dependences. In the case of RE2Fe14B, isotropic bonded pms are fabricated showing maximum energy products in the order of 90 kJ/m3. In the case of Sm2(Co,Cu,Fe,Zr)17, magnets with excellent high-temperature magnetic properties are tailored. Hereby, the investigations in addition provide important clues to the evolution of the characteristic microstructural and magnetic properties and to the role of the involved elements.
Exploring the limits of fast phase change materials
Authors: Wöltgens Han-Willem , Detemple Ralf , Friedrich Inés , Njoroge Walter K. , Thomas Ingo , Weidenhof Volker , Ziegler Stefan , Wuttig Matthias 
Published: April 2011

ABSTRACTIn the last decade a number of chalcogenide alloys, including ternary alloys of GeSbTe and quaternary alloys of InAgSbTe, have been identified which enable fast phase change recording. In the quest for materials with improved phase change kinetics we present two different approaches. By comparing alloys with well-defined stoichiometries the mechanisms which govern the transformation kinetics are determined. Optical and electrical measurements determine the activation energy for crystallization to 2.24 ± 0.11 eV for Ge2Sb2Te5 and to 3.71 ± 0.07 eV for Ge4Sb1Te5, respectively. It is shown that for GeSbTe-alloys with different composition the activation energy increases linearly with increasing Ge content. Power-time- reflectivity change diagrams recorded with a static tester reveal that Ge2Sb2Te5, in agreement with previous data, recrystallizes by the growth of sub critical nuclei, while Ge4Sb1Te5 grows from the crystalline rim surrounding the bit.To speed up the search for faster materials we employ concepts of combinatorial material synthesis by producing films with a stoichiometry gradient. Then laterally resolved secondary neutral mass spectroscopy (SNMS) combined with the static tester are used to identify the composition with superior properties for phase change applications.
Materials Issues in the Development of High Data-Transfer-Rate Phase-Change Compounds
Authors: Lankhorst Martijn H.R. , Borg Herman J. 
Published: April 2011

ABSTRACTA model is presented to calculate glass-transition temperatures. This model in combination with experimental data is used to evaluate archival-life stability of common phase change materials Ge2Sb2Te5 and doped eutectic Sb2Te compositions.On the basis of this model, novel high-data-rate phase change compositions have been identified near and on the pseudo-binary line InSb-GaSb in the ternary system Ga-In-Sb.
Dynamic behavior of azobenzene polyester used for holographic data storage
Authors: Kerekes Árpád , Lörincz E. , Sajti Sz. , Várhegyi P. , Ramanujam P. S. , Hvilsted S. 
Published: April 2011

ABSTRACTDynamic behavior of thin photoaddressable polyester films was studied. The saturation process due to Fourier holographic recording was investigated. Model experiments show an optimal intensity ratio of the object and reference beams, where the highest efficiency occurs. This ratio is inversely proportional to the reference intensity. The material has a significantly higher sensitivity at 407 nm than at 532 nm. For 1 μm thick sample an M# of 0.25 was measurable.
Endo-fullerenes and Doped Bucky Onions as Seed Materials for Solid State Quantum Bits
Authors: Park Seongjun , Srivastava Deepak , Cho Kyeongjae 
Published: April 2011

ABSTRACTTwo different models for solid-state quantum bits have been investigated. Both are based on the nuclear spin of doped atoms in endo-fullerenes or bucky-onions. 1H or 31P have been tested as suitable dopant atoms because they have half nuclear spins. The thermal stability and electronic properties of the dopant atoms and the encapsulating cages have been examined with ab-initio pseudo potential density functional methods, and the results show that both models are suitable for single qubit applications.
Medium-Range Order Structures of Amorphous Diamond-Like Carbon Films
Authors: Chen Xidong , Murray Gibson J. , Sullivan John , Friedmann Tom 
Published: April 2011

ABSTRACTIn this paper, we have studied medium-range order structures in amorphous diamond-like carbon films with fluctuation microscopy. Medium-range order structures are quantified by a specific form of a general four-body correlation. We name this function as a pair-pair alignment correlation function. By analyzing speckle dark-field images taken over different areas as a function of momentum transfer in reciprocal space, we measured the pair-pair alignment correlation function for both thermally annealed samples and unannealed samples. We have found that thermal annealing introduces medium-range order in amorphous diamond-like carbon films, causing more pairs of atoms to be aligned. These results agree with density-functional simulations. Larger-scale simulations will be needed to fully understand our experimental results.
Nano-Structured Amorphous Carbon Films Synthesised Using Decr Plasma
Authors: Golanski André , Grambole Dieter , Hommet Jean , Herrmann Folker , Kern Philippe , McDonnell Liam , Piazza Fabrice , Stoquert Jean-Paul 
Published: April 2011

ABSTRACTA Distributed Electron Cyclotron Resonance plasma reactor powered by a microwave generator operating at 2.45 GHz was used to deposit ta-C:H (Diamond-Like Carbon, DLC) thin films at RT. A graphite sputtering target immersed in an argon plasma was used as carbon source. The Ar plasma density was about 5×1010 cm-3. Single crystal <100> Si substrates were RF biased to a negative voltage of -80 V. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), nuclear reaction analysis (NRA) using the resonance at 6.385 MeV of the reaction: 15N + 1H-→ 12C + 4He + γ, elastic recoil detection analysis (ERDA) and Rutherford backscattering (RBS) were used to investigate the early phase of the growth. The morphology of the films grown at low pressure (0.3 mTorr) is shown to be dominated by stress-mediated nucleation leading to formation of basket-like clusters of circular hillocks 20 nm high surrounded by a planar, mostly sp2 bonded film ∼8 nm thick. With increasing plasma pressure the spatial frequency of the hillocks becomes random and the growth is dominated by the Stranski-Krastanov mode. The XPS data taken at decreasing emergence angles show that the structure of the hillocks is dominated by sp3 bonded carbon. The XPS argon signal disappears at 10° emergence angle indicating that integration of argon occurs mainly within the sp bonded regions. The NRA and ERDA analysis show that the amount of integrated hydrogen decreases with increasing substrate current density. RBS data indicate that increasing bias enhances argon integration.
Physical Interactions of Carbon Nanotubes and Conjugated Polymers
Authors: Dalton A.B. , McCarthy B. , Coleman J. N. , Panhuis M. , Carroll D. L. , Czerw R. , Blau W.J. , Byrne H.J. 
Published: April 2011

ABSTRACTSingle walled carbon nanotubes are shown to interact with a conjugated polymer in a periodic manner. Here this interaction is probed using electron microscopy, scanning tunneling microscopy optical and vibrational spectroscopy. The spectroscopic behaviour of the polymer is seen to be dramatically affected, which is attributed to conformational changes due to the effect of the nanotubes.
Lithium Insertion in Nanoporous Carbon Materials Produced from Carbides
Authors: Kotina I.M. , Lebedev V.M. , Ilves A.G. , Patsekina G.V. , Tuhkonen L.M. , Gordeev S.K. , Yagovkina M.A. , Ekström Thommy 
Published: April 2011

ABSTRACTIn this work, the results of a study of the lithium insertion process in nanoporous carbons (NPC) obtained from carbides (SiC, TiC, Mo2C) by chlorination are presented. Lithium insertion was produced in the temperature range of 30–200 °C via the vacuum deposition and diffusion. The major analytical tools for study included nuclear reaction method and X-ray diffraction. Diffusion coefficients of lithium at this temperature interval were estimated. Possible mechanism of lithium diffusion is discussed. Investigation of phase composition of lithiated samples was carried out at room temperature. Phase composition is found to be dependent on the relationship between deposition and diffusion rates.
Effect of pH on Hydrogen Evolution Yield from Water Dispersing Titania Nanoparticles Enhanced by Gamma Ray
Authors: Seino Satoshi , Yamamoto Takao A. , Fujimoto Ryosuke , Hashimoto Kensuke , Katsura Masahiro , Okuda Shuichi , Okitsu Kenji 
Published: April 2011

ABSTRACTHydrogen gas evolution from water dispersing nanoparticles induced by 60Co gamma-ray irradiation was studied. Nanoparticle of TiO2 with average size of 30 nm was examined. It was indicated that the hydrogen yields were affected significantly by pH of the dispersion. Difference in agglomeration could explain the difference in hydrogen yields. Reactions that enhance the hydrogen yields were discussed, and it was concluded that the radiolysis process is dominant in the total enhancement mechanism.
A Magnetically Ordered Non-Stoichiometric Zinc Ferrite for the Oxidative Dehydrogenation Reactions.
Authors: Toledo J. A. , Nava N. , Sun X. C. , Bokhimi X. 
Published: April 2011

ABSTRACTZnFe2O4nanoparticles were prepared by hydrothermal reduction approach. A considerable amount of α-Fe2O3was segregated in the as-synthesized sample, which diffused into the tetrahedral and octahedral sites of the ZnFe2O4spinel structure with increasing the annealing temperature. The introduction of Fe3+into the tetrahedral positions was observed by Mössbauer spectra. Magnetization measurements showed an unusual ferrimagnetic behavior of the ZnFe2O4phase, even at room temperature, confirming the introduction of Fe3+into the tetrahedral sites of the spinel structure. Catalytic activity measured in the oxidative dehydrogenation of 1-butene reaction increased with increasing annealing temperature, indicating that those interactions of Fe3+in tetrahedral and octahedral positions also promotes the activity and selectivity to butadiene formation.
Bioceramics and Biominerals and Their Nanostructures
Authors: Wen Shulin , Feng Jingwei 
Published: April 2011

ABSTRACTArtificial hydroxyapatite with chemical formula of Ca10(PO4)6(OH)2 is the best as bioceramics due to its composition and structure being similar with inorganic part of hard tissues. The alloys especially with Ti, Ni and Co contents are very promising as a kind of biomaterials due to their high strength and high toughness. The alloys as biomaterials need good final surface properties by proper surface treatment. By using clinical treatment with machining, cleaning, sterilization, we obtained Ti-oxides surface with 4-6 nm in thickness which are very good in property with chemical composition of TiO2 + Ti2O3 + TiO. However, the Ti-alloy with an artificial hydroxyapatite surface is even much better than that with the surface of Ti-oxides due to its high bioactivity. Human bones and human teeth with a chemical composition of Ca10(PO4)6(OH)2 and the structure of hydroxyapatite are commonly considered as bio-mineral. In nature the pears and shells are also a kind of bio-minerals. Our observations showed that human bone is a complex material with a layered composite structure. The hydroxyapatite mineral crystals that reinforce the organic proteinceous component are about 35 nm wide, irregular, plate-like crystals reside initially in the hole zones of the collagen microfibris: later fill available space within the collagen fibrils. At present paper nanostructure features of both bioceramics and biominerals have been characterized with comparison between each other's.
Nanocrystalline Mg-based hydrides for hydrogen storage
Authors: Oelerich W. , Klassen T. , Bormann R. 
Published: April 2011

ABSTRACTHydrogen is the ideal means of energy storage for transportation and conversion of energy in a comprehensive clean-energy concept. However, appropriate storage facilities, both for stationary and for mobile applications, are complicated, because of the very low boiling point of hydrogen (20.4 K at 1 atm) and its low density in the gaseous state (90 g/m3). Furthermore, the storage of hydrogen in liquid or gaseous form imposes safety problems, in particular for mobile applications, e.g. the future zero-emission vehicle. Metal hydrides are a safe alternative for H-storage and, in addition, have a high volumetric energy density that is about 60% higher than that of liquid hydrogen. Mg hydride has a high storage capacity by weight and is therefore favoured for automotive applications. However, so far light metal hydrides have not been considered competitive because of their rather sluggish sorption kinetics. Filling a tank could take several hours. Moreover, the hydrogen desorption temperature of about 300 °C is rather high for most applications. A breakthrough in hydrogen storage technology was achieved by preparing nanocrystalline hydrides using high-energy ball milling. These new materials show very fast aband desorption kinetics within few minutes, thus qualifying lightweight Mg-based hydrides for storage application. In this paper recent detailed results on the sorption behaviour of nanocrystalline Mg and Mg-based alloys are presented. In a following research effort the sorption kinetics of nanocrystalline Mg has been further enhanced by catalyst additions. Furthermore, different transition metals have been added to Mg to achieve a thermodynamic destabilisation of the hydride, thus lowering the desorption temperatures to about 230 °C. The newly developed materials are currently being tested in prototype storage tanks.
Investigation of Nanoelectrodes by Transmission Electron Microscopy
Authors: Kabir M. S. , Magnus Persson S. H. , Yao Yimin , Bourgoin Jean Phillippe , Palacin Serge 
Published: April 2011

ABSTRACTElectrodes for making connections to single molecules and clusters must have separations smaller than 10 nm. They are therefore difficult or impossible to image with atomic force microscopes (AFM) or Scanning Electron Microscopes (SEM). We have fabricated nanoelelectrodes by different methods to contacts nanoclusters and conjugated molecules and investigated their properties in transmission electron microscope (TEM) and their electrical characteristics at room temperature and at 4.2K. The electrodes are made on SiN4 membranes, which is transparent to high energy electrons and which make it possible to image features of a few nanometers in TEM.
Magnetic behavior of coated superparamagnetic iron oxide nanoparticles in ferrofluids
Authors: Voit W. , Kim D. K. , Zapka W. , Muhammed M. , Rao K. V. 
Published: April 2011

ABSTRACTWe present a study on the magnetic behavior of nanosized iron oxide particles coated with different surfactants (sodium oleate, PVA and starch) in a ferrofluid. The effect of the coating material, and different particle concentrations in the ferrofluid have been magnetically investigated to determine the effective magnetic particle size and possible interaction. The superparamagnetic iron oxide particles, synthesized by a controlled co-precipitation technique, are found to contain magnetite (Fe3O4) as a main phase with a narrow physical particle size distribution between 6 and 8 nm. The mean effective magnetic size of the particles in different ferrofluid systems are estimated to be around 4-5 nm which is smaller than the physical particle size. On a 10% dilution in the starch coated ferrofluid we observe a decrease in the blocking temperature.
Current induced organization in thin nanocrystalline gold films during deposition
Authors: Chaoguang P. , Ederth J. , Kish L. B. , Granqvist C. G. 
Published: April 2011

ABSTRACTNanocrystalline gold films were prepared by advanced gas deposition. Electric field induced effects on the film structure during and after deposition was investigated. A dc electric field in the range 2 ≤Ua ≤ 8 V/cm, was applied parallel to the substrate surface and led to changes of film microstructure and resistivity. In another set of experiments, films deposited at Ua = 0 were exposed to electric fields of similar strength after deposition. Film degradation could be understood from a mechanism consistent with a biased-percolation effect. Our results show that it is possible to control the film structure by varying the strength of an applied electric field.
Control and Assessment of Structure and Composition in Bismuth Telluride Nanowire Arrays
Authors: Sander M. S. , Prieto A. L. , Gronsky R. , Sands T. , Stacy A. M. 
Published: April 2011

ABSTRACTDue to effects of reduced dimensionality, Bi2Te3 nanowires are predicted to have increased thermoelectric efficiency relative to bulk Bi2Te3, one of the most efficient thermoelectric materials known. High-density arrays of nanowires have desirable characteristics for accessing nanowire properties in potential applications and also allow for facile nanowire property assessment. Here we describe a fabrication method to produce Bi2Te3 nanowire arrays by direct current electrochemical deposition into porous anodic alumina templates. The characteristics of the arrays have been assessed to determine the composition and structure in the arrays as well as in individual nanowires. Thefabricated arrays have a high-density of uniform diameter (∼40nm), high aspect ratio wires that are stoichiometric, polycrystalline Bi2Te3.