bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Influence of Amorphous Nanosized Mo and MoO2 Fillers on the Tribological Properties of Polymer-based Composite Materials
Authors: R.T. Malkhasyan , A.K. Pogosian , V.K. Makaryan , A.R. Isajanyan 
Published: April 2011

ABSTRACTThe problems of the creation of composite polymer-based materials with the use of amorphous nanosized molybdenum and molybdenum dioxide fillers with the particle size of less than 5 nm are considered. The copolymer of formaldehyde and dioxolane (CFD) and the polyphenylene sulphide (PPS) are chosen as polymeric matrixes. A comparative analysis of the tribological properties of composite materials with amorphous nanosized fillers and crystalline microsized analogues is made. It is determined that the use of isotropic nanosized amorphous fillers leads to improved wear-resistance up to three times for CFD-based composites and up to an order for PPS-based ones.
An Analytical Model for the Effect of Elastic Modulus Mismatch on Laminate Threshold Strength
Authors: Paranjpye Alok , Beltz Glenn E. , MacDonald Noel C. 
Published: April 2011

ABSTRACTA scheme for calculating the stress intensity factor at the crack tip in a two-dimensional bimaterial laminate composite has been developed to model the damage tolerance obtained in brittle ceramics by using this geometry. One limitation of the model is its assumption of homogenous elastic properties throughout the composite, limiting the accuracy of predictions it can make about real material systems. Finite element simulations of the same architecture that allow for elastic modulus mismatch give results that are moderately different from those obtained from the homogeneous model. We present an analytical expression for the stress intensity factor around a crack tip in a laminated composite that can take into account the elastic modulus mismatch. To make the problem tractable, the model is based on the assumption that the system behaves as a homogeneous anisotropic material when the stress field at the crack tip arises out of far field tractions applied away from the crack tip. The model improves upon the homogeneous model, giving results that are closer to those from the finite element simulations. We, however, conclude that more work is required to predict the stresses at the tip as the crack approaches a material interface before a complete analytical model can be obtained.
Simulation of Focused Ion Beam Induced Damage Formation in Crystalline Silicon
Authors: Hobler Gerhard , Lugstein Alois , Brezna Wolfgang , Bertagnolli Emmerich 
Published: April 2011

ABSTRACTApplication of focused ion beams (FIB) to circuit modification during design and debugging of integrated circuits is limited by the degradation of active devices due to beam induced crystal damage. In order to investigate FIB induced damage formation theoretically, we have extended our 1-D/2-D binary collision (BC) code IMSIL to allow surface movement due to sputtering. In contrast to other dynamic BC codes, the crystal structure of the target and damage generation during implantation may be taken into account. Using this tool we simulate the milling of trenches in the gate stack of MOSFETs and compare the results with transmission electron microscopy cross sections and charge pumping data. The simulations confirm that damage tails are generated that are a factor of two deeper at relevant defect concentrations than expected by conventional BC simulations. This result is shown to be due to recoil channeling in spite of the fact that a beam-induced surface amorphous layer is present throughout the implant. In addition, we discuss the accuracy of the experimental results and the simulations.
High-Resolution Spectrochemical Analysis of Columnar Defects Formed in Bi2Sr2CaCu2Ox by Swift Heavy Ion Irradiation
Authors: Kano F. , Terasawa M. , Mitamura T. , Kambara T. , Sasaki Y. , Ikuhara Y. 
Published: April 2011

ABSTRACTSingle-crystal specimen of high-temperature superconductor Bi2Sr2CaCu2Ox was irradiated with 3.5 GeV Xe ions at room temperature up to 1.0 × 1011 ion/cm2. Significant enhancement of magnetization by the irradiation was confirmed. The irradiated specimens were studied by using a high-resolution transmission electron microscope with field emission electron gun (FE-TEM), and, also, with an energy dispersive x-ray analyzer (EDS). Columnar defects with diameter of about 6 nm were observed along the incident ion tracks. By nanoscale high-resolution x-ray spectrochemical analysis across the columnar defect, enrichment of Cu and depletion of Bi, Sr and Ca in the columnar defect center, and vice versa in the outskirts of the defect, was found for the first time. Oxygen depletion in the defect, and increased distribution outside of the defect were also found by electron energy loss spectroscopy. This experimental evidence suggests that the columnar defects are formed as a consequence of Coulomb explosion induced by the electronic excitation of the high-energy heavy ions.
“Recovery” Effect of Electron Induced Damage in 4H-SiC Schottky Diodes
Authors: Castaldini A. , Cavallini A. , Rigutti L. , Nava F. , Fuochi P.G. , Vanni P. 
Published: April 2011

ABSTRACTThe effects of electron irradiation on the defects associated electronic levels in Schottky diodes on 4H silicon carbide epilayers grown by chemical vapour deposition were investigated by Deep Level Transient Spectroscopy (DLTS) and Capacitance-Voltage (C-V) characteristics. These investigations were performed before and after irradiation with 8.6 MeV electrons at different doses. After irradiation four new traps with enthalpies equal to (Ec-0.23 eV), (Ec-0.39 eV), (Ec-0.63 eV) and (Ec-0.75 eV) were detected. Their thermal stability, a key point to determine their structure on the basis of recent theoretical and experimental results, was carefully investigated since it was earlier observed that during DLTS temperature runs up to 500 K a slight but significant recovery of a few irradiation-induced levels occurs. This effect was previously observed in literature for the level (Ec-0.70 eV) after thermal treatment at 500 °C [1], but the present results indicate that it involves more than a single level and is also effective at lower temperature. DLTS analyses were also performed from room temperature to liquid nitrogen temperature and vice versa up to 500 K.The annealing kinetics is reported and a few conclusions on the structure of the defects involved in the recovery are drawn. The correlation with the diode charge collection efficiency is also reported.
Ion Beam Processing for Silicon - Based Light Emission
Authors: Skorupa W. , Dekorsy T. , Gebel T. , Helm M. , Lysenko V.S. , Nazarov A.N. , Osiyuk I.N. , Rebohle L. , Schmidt B. , Sun J. M. 
Published: April 2011

ABSTRACTThe development of novel devices for optical communication and integrated sensor applications is mainly focused on their possible integration into dedicated integrated circuits. The main problem concerning integrated optical systems in silicon technology has always been the realization of a highly efficient silicon-based light emitter which is a key requirement to make a real step into the world of integrated optoelectronics.One of the most promising approaches to form such a silicon based light emitter is ion beam processing. In this paper we will report on recent results regarding blue-violet (∼400 nm) and infrared (∼1100 nm) electroluminescence (EL) from ion beam synthesized Ge-rich silicon dioxide layer and Boron-implanted pn-junctions in silicon showing remarkable power efficiencies of 0.5 and 0.12%, respectively. The main effort is devoted to the achievement of a deeper insight into the mechanism of the EL.
RBS, TEM and SEM Characterization of Gold Nanoclusters in TiO2(110)
Authors: Shutthanandan V. , Zhang Y. , Wang C. M. , Young J. S. , Saraf L. , Thevuthasan S. 
Published: April 2011

ABSTRACTNucleation of gold nanoclusters in TiO2(110) single crystal using ion implantation and subsequent annealing were studied by Rutherford backscattering spectrometry /channeling (RBS/C), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Approximately 1000 Au2+/nm2 were implanted at room temperature in TiO2(110) substrates. TEM and SEM measurements reveal that rounded nanoclusters were formed during the implantation. In contrast, subsequent annealing in air for 10 hours at 1275 K promoted the formation of faceted (rectangular shaped) Au nanostructures in TiO2. RBS channeling measurements further reveled that Au atoms randomly occupied the host TiO2 lattice during the implantation. However, it appears that some Au atoms moved to the Ti lattice positions after annealing.
Ion Beam Assisted Deposition
Authors: Hirvonen James K. 
Published: April 2011

ABSTRACTThe beneficial roles energetic ions play in thin film vacuum processes have long been recognized by the vacuum coating community. Optical coaters were among the first to adopt the process in the form of concurrent, low energy, directed ion beam bombardment of physical vapor deposition [electron beam] coatings for producing dense, adherent, robust, and environmentally resistant optical coatings. The international research and development community has also been actively pursuing the study of ion beam assisted deposition (IBAD) for both studying the mechanisms of ion/solid interactions during thin film growth as well as for developing coating protocols for specific application areas, including: tribological coatings, anti-corrosion coatings, optical coatings, superconducting buffer layers and coatings for temperature sensitive substrates such as polymers. This paper will review selected areas of this active field and will attempt to identify emerging application areas.
Radiation-induced Defects in Nonradioactive Natural Minerals: Mineralogical and Environmental Significance
Authors: Calas Georges , Allard Thierry , Balan Etienne , Morin Guillaume , Sorieul Stéphanie 
Published: April 2011

ABSTRACTNatural short-lived radionuclides generate electronic defects in minerals, such as trapped electrons and positive holes, often associated with element impurities, which act as final traps over geological periods. Two main examples will be illustrated. The first example will concern the point defects, which are observed in clay minerals. The high specific surface area makes clay minerals sensitive to the geochemical radiation background and provides a record of the past occurrence of radionuclides in geological systems. In kaolinite, three types of hole-centers are trapped by oxygen atoms linked to Si- or Al-sites. An experimental dosimetry gives the paleodose, which can be used either to assess mean past U-concentration or for kaolinite dating, depending on the available geochemical parameters. The detection of past migrations of radioelements in natural analogues may be used in the safety assessment of radioactive waste disposals. The second example will concern the role of mineral impurities in defect formation and stabilization. Natural fluorites (CaF2) exhibit hole-and electron-centers trapped on several rare earths and oxygen impurities, often present at the ppm level, which are responsible for the wide range of coloration observed in natural fluorites. Ca colloids may form under severe irradiation and give rise to a characteristic absorption. The thermal stability of radiation-induced defects gives constraints on the evolution of fluorites as a function of temperature and time. Other minerals, such as apatite, confirm the importance of impurities in stabilizing radiation-induced defects over geological periods.
Modification of lattice structure and magnetic properties of Fe-Rh alloys by energetic electron irradiation
Authors: Fukuzumi Masafumi , Taniguchi Ryoichi , Komatsu Seiji , Ono Fumihisa , Iwase Akihiro 
Published: April 2011

ABSTRACTIn order to modify the lattice structure and magnetic properties, we irradiate Fe-50at.%Rh alloys with 8 MeV electrons at room temperature. Effects of irradiation are investigated by using Superconducting QUantum Interference Device (SQUID) and X-Ray Diffractometer (XRD).Although the crystal structure is not changed by the irradiation and remains the B2 structure, the lattice parameter increases by about 0.1–0.3 % and the antiferromagnetic(AF)-ferromagnetic(FM) transition temperature decreases by 3–18 deg. with increasing the electron fluence. The present result shows that energetic electron irradiation can be used for the precise control of AF-FM transition temperature of Fe-50at.%Rh alloy.
Proton Beam Irradiation Effects on Magnetic Nanocomposites
Authors: Chipara M. , Zaleski M. J. , Hui D. , Pelecky D. L. , Balascuta S. 
Published: April 2011

ABSTRACTA magnetic nanocomposite material has been obtained by dispersing ball milled magnetic nanoparticles of barium ferrite within a styrene- isoprene- styrene block copolymer, sonicating the solution, and spin coating it onto a quartz crystal. Ferromagnetic resonance spectra of pristine and irradiated magnetic nanocomposites are reported. Although the flux of incoming protons was not large, modifications in the ferromagnetic resonance spectra were noticed. This suggests that the future ultra high-density media would present an enhanced sensitivity to the radiation component of the space environment.
Small-angle x-ray scattering characterization of self-irradiated zircon
Authors: Ríos Susana , Salje Ekhard K. H. 
Published: April 2011

ABSTRACTSmall-angle x-ray scattering (SAXS) measurements were performed on two natural zircons: one with an amorphous content close to 85 %, and the second one x-ray amorphous. Electron density fluctuations were observed in the untreated samples, and studied as a function of various heat-treatments. In the starting material, density fluctuations were found to have a characteristic length-scale of approximately 1 nanometer diameter. Below 800 °C, the SAXS contribution (Q<10 nm-1) showed only a small variation as a function of temperature. Above 800 °C, a strong increase in intensity is observed, accompanied by the precipitation of 2–3 nm zirconia domains. At high enough temperatures, >1000 °C, when the amorphous phase recrystallizes into the starting zircon structure, characteristics of surface-scattering are observed, associated to large zircon regions.
Effects of High-Energy Ion Irradiation in Bismuth Thin Films at Low Temperature
Authors: Chimi Yasuhiro , Ishikawa Norito , Iwase Akihiro 
Published: April 2011

ABSTRACTWe have studied high-energy ion irradiation effects in bismuth by measuring the electrical resistivity at low temperature in relation to its structural change. Bismuth thin films (330–520 Å thick) are irradiated below ∼10 K with energetic (150–200-MeV) heavy ions. The resistivity of the specimen is measured in situ below ∼7.2 K during the irradiation. After the irradiation, annealing behavior of the resistivity is observed up to ∼30 K. The temperature dependence of the resistivity during annealing shows an abrupt increase around 20 K, implying re-crystallization of irradiation-induced amorphous regions. We have tried to detect a superconducting transition which may take place as a result of irradiation-induced amorphization. In the range of the measuring temperature down to ∼4.9 K, resistivity decrease due to superconducting transition has not been observed in the temperature dependence of the resistivity after 200-MeV 197Au ion irradiation up to a fluence of 3.1×1012 cm-2.
Atomic-scale simulations of radiation effects in GaN and carbon nanotubes
Authors: Nordlund K. , Nord J. , Krasheninnikov A. V. , Albe K. 
Published: April 2011

ABSTRACTGallium nitride and carbon nanotubes have received wide interest in the materials research community since the mid-1990's. The former material is already in use in optoelectronics applications, while the latter is considered to be extremely promising in a wide range of materials. Common to both materials is that ion irradiation may be useful for modifying their properties. In this paper we overview our recent molecular dynamics simulations results on ion irradiation of these materials. We employ such potentials to study the basic physics of how ion irradiation affects these materials. In particular we discuss the reasons for the high radiation hardness of GaN, and the surprising nature of vacancies and interstitials in carbon nanotubes.
Correlation and Spectral-Density Roughness Analysis of Surfaces Processed With Gas-Cluster Ion Beams
Authors: Fenner D. B. 
Published: April 2011

ABSTRACTAutocorrelation, height-difference correlation, and power spectral density are used to characterize various surfaces exposed to gas-cluster ion beams (GCIB), as well as for detailed comparison with simulated surfaces which are based on models with stochastic impact and surface mobility mechanisms. This work demonstrates a close correspondance between detailed statistical analysis of AFM images from actual surfaces and the results of the same types of analysis of simulated surfaces. Surface roughness prior to and after GCIB treatment is always found to be essentially fractal in nature. Phenomenological models with both continuum surface mobility and Monte Carlo impact accumulations are presented. Accurate simulation of smoothing requires a combination of these models.
Radiation Damage Characterization in Ar+ Implanted GaN
Authors: Usov I. , Kvit A. , Reitmeier Z. , Davis R. 
Published: April 2011

ABSTRACTDamage microstructure evolution in GaN films implanted with argon ions (Ar+) as a function of implantation temperature was studied by cross-sectional transmission electron microscopy (TEM). After irradiation at room temperature, the implanted layer contained mostly isolated point defects. Implantation at elevated temperatures significantly reduced the number of isolated point defects. Numerous dislocations and regions exhibiting strain-contrast were observed after implantation at 300 °C. Bombardment at 600 °C resulted in formation of a new type of defect. Along with the partial dislocations and the strained regions, precipitates composed of carbon and nitrogen were identified by electron energy loss spectroscopy. These precipitates were formed in the vicinity of the Ar+ projected range where the amount of radiation damage was maximal. The high concentration of defects facilitated redistribution of carbon atoms introduced during the GaN film growth and resulted in the formation of precipitates. No precipitates were observed after implantation at 1000 °C. Consideration of the TEM results in conjunction with ion channeling data showed that presence of the precipitates correlated with a reverse annealing damage accumulation mode, which manifests itself as an increase of backscattering yield with increasing implantation temperature. The results of our study indicated that the carbon impurity in as-grown GaN films enhances the radiation damage accumulation rate and consequently has to be taken into account when ion implantation doping of GaN is performed.
Germanium Island Size Distribution by Atomistic Simulation
Authors: Wagner Richard J. , Gulari Erdogan 
Published: April 2011

ABSTRACTStrained epitaxial growth of Ge on Si(001) produces self-assembled, nanometer scale islands, or quantum dots. We study this growth by atomistic simulation, computing the energy of island structures to determine when and how islanding occurs. The distribution of island sizes on a surface is determined by the relation of island energy to size. Applying the calculated chemical potential to the Boltzmann-Gibbs distribution, we predict size distributions as functions of coverage and temperature. The peak populations around 80 000 atoms (35 nm wide) compare favorably with experiment.
Effects of Growth Sequence on Optical and Structural Properties of InAs/GaAs Quantum Dots Grown by Atomic Layer Molecular Beam Epitaxy
Authors: Song J. D. , Park Y. M. , Shin J. C. , Lim J. G. , Park Y. J. , Choi W. J. , Han I. K. , Cho W. J. , Lee J. I. , Kim H. S. , Park C. G. 
Published: April 2011

ABSTRACTThe influence of growth sequence on optical and structural properties of InAs/GaAs quantum dots (QD) grown by atomic layer epitaxy was investigated systematically. It is found that growth interruption (GI) after In is more effective than non-GI after In in reducing the density of coalescent dots, and reducing the dot width distribution of the QDs. Meanwhile, dot densities are approximately doubled by non-GI after In. GI after As reduces dot height distribution compared with non-GI after As. Generally, GI after In plays a more critical role than GI after As does in formation of the QDs. The sample grown with In/GI/As/GI sequence shows the lowest 300 K-photoluminescence (PL) linewidth (∼30 meV), high PL peak separation between ground and 1st excited level (∼80 meV). From the result, it is known that In/GI/As/GI is the favorable growth sequence among the sample sets. Temperature dependence of PL linewidth shows that the In/GI/As/GI sample is insensitive to cryostat temperature and it is attributed to weak wetting effect. Thinner wetting layers shown in a cross-sectional TEM image supports this.
InNAs and GaInNAs self-assembled quantum dots and lasers grown by solid source molecular beam epitaxy
Authors: Sun Z.Z. , Yoon S.F. , Yew K.C. , Bo B.X. 
Published: April 2011

ABSTRACTSelf-assembled Ga1−xInxNyAs1-y quantum dots were grown on GaAs by solid source molecular beam epitaxy (SSMBE). Introduction of N was achieved by a RF Nitrogen plasma source. Formation of quantum dots by S-K growth mode is confirmed by observation of standard 2D-3D RHEED pattern transition. Atomic force microscopy (AFM) and photoluminescence (PL) measurements were used to characterize the structure and optical properties of GaInNAs quantum dots. High GaInNAs quantum dot density (1010∼1011cm−2) was obtained for different In and N composition (0.3≤ x ≤1, y≤0.01). The effect of surface coverage on dot density, dot size, and optical properties was studied in detail. Adjusting the bandgap confinement by incorporating a GaNAs strain-reduction layer into the GaInNAs dot layer was found to extend the emission wavelength by 170nm. Room temperature pulsed operation is demonstrated for a Ga0.5In0.5N0.01As0.99 quantum dot laser emitting at ∼1.1μm.
First electrically injected QD-MCLED emitting at 1.3 μm, grown by metal organic chemical vapour deposition
Authors: Tasco V. , Todaro M.T. , De Giorgi M. , De Vittorio M. , Cingolani R. , Passaseo A. 
Published: April 2011

ABSTRACTWe present the fabrication of a Quantum Dot Microcavity Light Emitting Diode (QD-MCLED) emitting at 1.3 μm at room temperature. The long wavelength emission is achieved by using for the first time InGaAs QDs directly grown on GaAs, by metal organic chemical vapour deposition. Electroluminescence bright emission, peaked at 1298 nm with a FWHM of 6.5 meV and a line shape independent on the applied bias is found.
Modeling of a Surface Plasmon Polariton Interferometer
Authors: Coello Victor , Søndergaard Thomas , Bozhevolnyi Sergey I. 
Published: April 2011

ABSTRACTWe model the operation of a micro-optical interferometer for surface plasmon polaritons (SPPs) that comprises an SPP beam-splitter formed by equivalent scatterers lined up and equally spaced. The numerical calculations are carried out by using a vector dipolar model for multiple SPP scattering. The SPP beam-splitter is simulated for different angles of the incident SPP beam, radii of the particles, and inter-particle distances in order to find a suitable configuration for realization of a 3dB SPP beam-splitter. The results obtained are in good agreement with experimental data available in the literature. The feasibility of fabricating an interferometer is thereby corroborated and the calculated intensity maps are found rather similar to those experimentally reported.