bluuebunny/crossref_metadata_2025_split huggingface dataset:
Defect Cluster Formation in High Energy Displacement Cascades in Copper
Authors: Osetsky Yuri N. , Bacon David J. 
Published: April 2011

ABSTRACTPrimary radiation damage in displacement cascades in metals has been studied extensively by atomistic simulation during the last decade. The variety of defect types observed in cascade simulation is not entirely consistent with experimental data. For example, experiments on copper show a very effective production of stacking fault tetrahedra (SFTs) but this was not observed systematically in cascade simulation. To clarify this and related issues, extensive simulation of displacement cascades in copper have been performed using two different interatomic potentials, a short-range many-body potential and a long-range pair potential. We have studied the damage created by primary knock-on-atoms of energy up to 20keV, i.e. below the energy range for formation of subcascades, at temperatures 100 and 600K. Special attention was paid to cascade statistics and the accuracy of simulation in the collision stage. The former required many simulations for each temperature whereas the latter involved a modification of the simulation method. The results on variety of clusters observed, e.g. SFTs, glissile and sessile interstitial clusters, and faulted and perfect interstitial dislocation loops, lead to conclusions on the effect of the potentials and the significant variation of the number of Frenkel pairs and clustering effects produced in different cascades under the same conditions.
Reordering and Crystallization of Silicon Carbide Amorphized by Neutron Irradiation
Authors: Snead Lance L. , Balden Martin 
Published: April 2011

ABSTRACTDensification and crystallization kinetics of bulk SiC amorphized by neutron irradiation is studied. The temperature of crystallization onset of this highly pure, fully amorphous bulk SiC was found to be between 875-885°C and crystallization is nearly complete by 950°C. In-situ TEM imaging confirms the onset of crystallization, though thin-film effects apparently alter the kinetics of crystallization above this temperature. It requires >1125°C for complete crystallization of the TEM foil. Annealing at temperatures between the irradiation and crystallization onset temperature is seen to cause significant densification attributed to a relaxation, or reordering, of the as-amorphized structure.
Investigation of Irradiation Damage in Silicon Dioxide Polymorphs using Cathodoluminescence Microanalysis.
Authors: Stevens-Kalceff Marion A. 
Published: April 2011

ABSTRACTCathodoluminescence (CL) Microanalysis (spectroscopy and microscopy) provides unique high sensitivity, high spatial resolution information about the defect structure and distribution of defects in wide band gap materials and therefore is an ideal technique with which to investigate the microstructural processes induced by irradiation. CL microanalytical techniques allow the in situ monitoring and post irradiation assessment of electron irradiation induced damage. Changes in the defect structure and surface topography of electron irradiated silicon dioxide polymorphs and related silicates including pure crystal quartz, pure silica glasses, pure amorphous fused quartz and alkali-borosilicate glasses, have been investigated and compared using CL microanalysis and Scanning Probe Microscopy (SPM) techniques. CL and SPM evidence shows all specimens are sensitive to electron irradiation. CL evidence is consistent with the production and micro-segregation of irradiation induced defects. The observed damage is highly correlated with the electron irradiation induced changes in the surface topography of the investigated specimens.
Unusual Change in Columnar Defect Morphology in YBCO upon Annealing
Authors: Yan Y. , Kirk M. A. , Petrean A. , Paulius L. 
Published: April 2011

ABSTRACTWe show evidence from transmission electron microscopy of an unusual change in columnar defect morphology in YBCO upon annealing to 600°C. The disappearance of the nanotwinned, but not the larger scaled thermal twinned, structure is found. A removal of the large fluctuations in the diameter of the amorphous column, preserving a narrow continuous column, is surprisingly discovered. Correlations with magnetization measurements demonstrate the greater efficiency of vortex pinning at 77 K by the annealed defect structure.
Comparison of Experimental and Computational Aspects of Grain Growth in Al-Foil
Authors: Demirel Melik C. , Kuprat Andrew P. , George Denise C. , El-Dasher Bassem S. , Carlson Neil N. , Straub Galen K. , Rollett Anthony D. 
Published: April 2011

ABSTRACTGrain boundary and crystallographic orientation information of an Al-foil with a columnar grain structure is characterized by Electron Backscattered Diffraction (EBSD) technique. The starting microstructure and grain boundary properties are implemented as an input for the three- dimensional grain growth simulation. In the computational model, minimization of the interface energy is the driving force for the grain boundary motion. The computed evolved microstructure is compared with the final experimental microstructure, after annealing at 550 °C. Good agreement is observed between the experimentally obtained microstructure and the simulated microstructure. The constitutive description of the grain boundary properties was based on a 1- parameter characterization of the variation in mobility with misorientation angle.
Atomic and Electronic Structure of High Purity SiC Grain Boundary
Authors: Takuma Eriko , Ichinose Hideki 
Published: April 2011

ABSTRACTFully relaxed SiC grain boundaries were produced by the sublimation re-crystallization method. Several kinds of grain boundaries of bi- and tri-crystals were investigated applying an atomic resolution high-voltage transmission electron microscopy (ARHVTEM). The rotation axis and the rotation angle were common tofrequently observed grain boundaries, which were, respectively, 70.5 degrees and <1120>. But boundary planes differed from each other. It was shown that the atomic bonding direction was continuous across the stable grain boundary.
Mechanism of Deformation by Intervariant Boundary Motion in Shape-Memory Materials
Authors: Pond Robert C. , Celotto Steven 
Published: April 2011

ABSTRACTThe shape-memory effect relies on deformation in the martensitic state by motion of intervariant boundaries in response to an applied stress. A mechanism for this process in terms of interfacial defect generation, motion and interaction is proposed. This mechanism is conservative and is expected to operate with modest applied stresses and without thermal activation. Experimental observations of intervariant boundaries are discussed and atomistic simulations of the mechanism in such boundaries in hexagonal metals are presented.
Dendritic Growth Dynamics: Steady And Oscillatory States
Authors: Frei J.E. , Glicksman M.E. , LaCombe J.C. , Koss M.B. , Giummarra C. , Lupulescu A.O. 
Published: April 2011

ABSTRACTMicrogravity dendritic growth experiments, conducted aboard the space shuttle Columbia (STS-87) in November/December 1997, are analyzed and discussed. In-situ video images now reveal that pivalic acid (PVA) dendrites growing in the diffusion-controlled environment of low-earth orbit exhibit a range of growth behaviors, including steady, transient, and oscillatory states. The observed transient features of the growth process are being studied with the objective of understanding their physical mechanisms. Some transients in the observed growth speed are thought to arise as an intrinsic aspect of the evolving dendritic pattern. Variability in the growth speed observed from a sequence of identical runs at equal supercooling suggests that self-interactions of the dendrite remain important throughout the development of the dendritic pattern. A Greens function analysis of the near-tip diffusion sources contributing to the local field at the tip suggests that strong non-local interactions exist well into the time-dependent side-branch region of real dendrites. Video data obtained at 30 fps allow the first application of discrete Fourier transform methods (Lomb periodograms) to the digitized images of dendritic growths under quiescent microgravity conditions. These observations provide evidence for the appearance of characteristic frequencies in the tip shape and its dynamical behavior. Some of the frequency bands observed coincide closely with the ratio of the dendritic tip growth speed divided by the side branch spacing. Other observed lower frequencies remain as yet unexplained. These data, and their interpretations, are discussed in this paper.
Dislocations in a Partially-Filled Skutterudite
Authors: Harper Jennifer S. , Gronsky Ronald 
Published: April 2011

ABSTRACTThe partially filled skutterudite structure is a candidate thermoelectric material with the capacity for phonon scattering by the decoupled rattling of filling ions. In this transmission electron microscopy investigation of a 1.6%Ce, 1.6%Ni, 4.9%Ge, 22.8%Co, and 69.1%Sb alloy, the structure is confirmed to be of a partially-filled skutterudite, but with a number of defects. Isolated dislocation dipoles, arrays of dislocation dipoles, and a subgrain boundary are observed and characterized. An atomic structure of a dislocation dipole is also proposed, and the effect of such dislocations on thermoelectric properties is discussed.
High-resolution Electron Microscopy of grain Boundary Structures in Yttria-stabilized Cubic Zirconia
Authors: Merkle K. L. , Thompson L. J. , Bai G.-R. , Eastman J. A. 
Published: April 2011

AbstractThe atomic-scale structure of grain boundaries (GBs) in yttria-stabilized cubic zirconia (YSZ) was investigated by high-resolution electron microscopy (HREM). Non-stoichiometric oxides have found a wide range of applications and therefore it is of importance to explore the role of GBs and their atomic-scale relaxation modes. [001] and [110] tilt GBs were examined by HREM in highly textured thin films of YSZ grown by metal-organic chemical vapor deposition (MOCVD). In addition, a special technique was developed to also allow the HREM study of twist and general GBs. GBs and triple junctions show quite dense arrangements of cation atomic columns. The GB core structures in YSZ can be contrasted to the more open structures in stoichiometric cubic oxides, such NiO, which are characterized by a relatively large GB excess volume. This appears to be due to several factors, including the necessary rearrangement of the oxygen sublattice near GBs in a CsCl2 type structure, the redeployment of oxygen vacancies near GBs, and the segregation of Y to the GB. Relative to stoichiometric oxides, such mechanisms provide additional degrees of freedom for atomic relaxations at GBs and the development of low-energy GBs. These additional relaxation modes, which result in GB cation arrangements more akin to metallic systems, are also reflected by Burgers vector dissociations observed in low-angle YSZ GBs.
Channeling Studies of CeO2 and Ce1-xZrxO2 Films on Yttria-Stabilized ZrO2(111)
Authors: Shutthanandan V. , Thevuthasan S. , Kim Y. J. , Peden C.H.F. 
Published: April 2011

AbstractRutherford backscattering spectrometry and channeling techniques have been used to investigate the crystalline quality and interfacial properties of epitaxially grown CeO2 and Ce0.7Zr0.3O2 films on yttria-stabilized ZrO2(111) substrates. Both films appear to have high crystalline quality with minimum yield of Ce in the CeO2and Ce0.7Zr0.3O2 films determined to be 4.7% and 12.1% respectively. Visibility of more Ce atoms to the ion beam at the interface compared to the bulk of the film indicates that both films show significant disorder at the interface. The normalized angular yield curves obtained from Ce and Zr indicate that the Ce atomic rows in the CeO2 film are parallel to the Zr atomic rows in the substrates. Approximately 88% of the Zr atoms substitutionally occupy the Ce cation lattice sites in the Ce0.7Zr0.3O2 film.
Oxides Influence on Electrical Properties of Si and A2B6 Materials.
Authors: Andrukhiv Andrii , Khlvap Galina , Andrukhiv Mikhail , Belosertseva Violetta 
Published: April 2011

AbstractIt has been shown for the first time how atmospheric oxygen eff ects maj or electrical characteristics of MBE grown CdTe thin f ilms and CVD grown p-/p+ Si junction. I-V and C--V barrier-like characteristics indicate presence of CdO/CdTe quasi-3D microheteroj unctions and complexes at p/p+ interface.
Microstructural Effects in the Thermochromic Behavior of VO2/Al/Si Thin Film Heterostructures
Authors: Dovidenko K. , Beasor S. , Topol A. , Efstathiadis H. , Oktyabrsky S. , Shokhor S. , Naar S. , Kaloyeros A.E. 
Published: April 2011

AbstractWe present the results of detailed chemical and structural characterization of the VO2/Al/Si(100) thin film heterostructures fabricated by chemical vapor deposition and physical vapor deposition methods. The presence of the thermochromic behavior in the VO2 layer around 68°C and its correlation with the layer composition and structure are discussed. The study compares the structural and chemical properties of the two types of thin VO2 layers: one which exhibits a metal-insulator phase transition around 68°C, and another which fails to undergo the temperature-induced transition. The study of interfaces was carried out by transmission electron microscopy, and showed the existence of an aluminum oxide interfacial layer between VO2 and Al for the samples with the metal-insulator phase transition. The smooth VO2/Al interface and the presence of more than one VO2 monoclinic polytypes were observed for the CVD films exhibiting no phase transition.
Time Dependent Debonding of Aluminum/Alumina Interfaces under Cyclic and Static Loading
Authors: Kruzic J. J. , McNaney J. M. , Cannon R. M. , Ritchie R. O. 
Published: April 2011

AbstractThe structural integrity of oxide/metal interfaces is important in many applications. While most attention has focused on the debonding of oxide/metal interfaces by conducting strength and fracture toughness tests, very few investigations have looked at time dependant failure of interfaces under cyclic or static loading. Tests have been conducted on sandwich specimens consisting of 5 - 100 micron thick aluminum layers bonded between either polycrystalline or single crystal Al2O3 to determine cyclic fatigue-crack growth, as well as static loaded moisture- assisted crack-growth, properties of Al/Al2O3 interfaces. Under cyclic loading, crack growth was observed to occur predominantly by interfacial debonding, but was also observed to make excursions into the Al2O3. Static loading in a moist environment also caused interfacial cracks to deviate into the Al2O3 or alternatively to arrest. Due to the poor crack growth resistance of the Al2O3, cracks leaving the interface grew at faster rates than those at the interface. Trends in crack trajectories and crack growth rates are explained in terms of the degree of plastic constraint in the aluminum layer, the modulus mismatch, and the effects of environmental mechanisms.
Semiempirical Correlation between the Optical Band Gap of Oxides and Hydroxides and the Electronegativity of Their Constituents
Authors: Quarto Francesco Di , Santamaria Monica , Piazza Salvatore , Sunseri Carmelo 
Published: April 2011

AbstractOn the basis of new experimental results a previous proposed correlation between the optical band gap of oxides and the difference of electronegativity of their constituents is extended to mixed crystalline and amorphous TiO2-Fe2O3 (d,d-metal oxides) as well as to amorphous passive films grown on Al-Ta, Al-Ti, Al-Nb and Al-W alloys (sp,d-metal oxides). Moreover in analogy with previous results on anhydrous oxides, a correlation is proposed between the optical band gap of hydroxides and the electronegativities of their constituents after substituting the electronegativity of hydroxilic group to that of the oxygen. Like in the case of anhydrous oxides, two different interpolation lines have been found for sp-metal and d-metal hydroxides, respectively.
Electronic Structure of Titanium Oxide Crystal Surface with Lithium Atom on the Surface
Authors: Oshikiri M. , Aryasetiawan F. , Boerol M. 
Published: April 2011

AbstractThe electronic structure of the bulk TiO2 in the rutile structure, geometric and electronic structure of two dimensional titanium oxide and lithium titanium oxide layers have been investigated. Not only density functional approach within the local density approximation (LDA) but also GW approach has been tried and the LDA electronic band structures have been compared with the quasiparticle energy structures. The unit cells which include a few atomic layers and open space of more than several angstroms have been used as geometric model of the surface. The surface geometric relaxation has been investigated by the Car-Parrrinello quantum molecular dynamics method based on the plane wave basis with pseudo potential within Becke-Lee-Yang-Parr (BLYP) generalized gradient approximation (GGA) and the quasiparticle energy structure has been obtained by the GW method based on the linearized muffin tin orbital (LMTO) basis with the atomic sphere approximation (ASA). Good applicability of this hybridized first principles approach has been confirmed.
Nanoporous Ceria Films Prepared from Colloidal Suspension
Authors: Petrovsky Vladimir , Gorman Brian , Anderson Harlan U. , Petrovsky Tatiana 
Published: April 2011

AbstractThe influence of porosity and densification on optical properties of films on sapphire substrates that were prepared from water colloidal suspensions of small (∼5nm) particles of ceria was investigated. The colloidal ceria films have initially very porous structure (porosity about 50%) and densification starts at about 600°oC accompanied by grain growth. The concurrence of these two processes makes it difficultto interpret the results of the optical spectrophotometry, but the combination of transmittance and reflectance measurements provides enough data to separate these two influences and to calculate the porosity, particlesize and energy band gap separately. XRD, SEM, ellipsometry and mechanical profilometry were used to confirm the results obtained from the specrophotometric measurements. All these methods gave results, which are in good agreement: the change in the porosity from 50% to 15% and the particle size increased from 5 to 65nm in the temperature region from 400 to 1000°oC. An important result of the investigation is the fact that the main optical properties of the coating such as refractive index and band gap energy depend only on the porosity, but not on the grain size. The grain size influences the scattering properties of the coating, which allows the grain size to be estimated from optical measurements.
An Overview of FeRAM Technology for High Density Applications
Authors: Nagel Nicolas , Mikolajick Thomas , Kasko Igor , Hartner Walter , Moert Manfred , Pinnow Cay-Uwe , Dehm Christine , Mazure Carlos 
Published: April 2011

AbstractFerroelectric random access memories (FeRAMs) are new types of memories especially suitable for mobile applications due to their unique properties such as nonvolatility, small DRAM - like cell size, fast read and write as well as low voltage / low power behavior. Although standard CMOS processes can be used for frontend and backend / metallization processes, FeRAM technology development has to overcome major challenges due to new materials used for capacitor formation. In this paper, advantages and disadvantages of different ferroelectric materials and major development issues for high density applications are discussed. Results of a 0.5μm ferroelectric process using SrBi2Ta2O9 (SBT) as ferroelectric layer, Pt as electrode material, and 2-layer tungsten / aluminum metallization are discussed.
Surface and Size Effects in TGS, NaNO2, and DKDP Nanocrystals
Authors: Romero Juan D. , Fonseca Luis F. , Ramos Rafael , Marqués Manuel I. , Gonzalo Julio A. 
Published: April 2011

AbstractMonte Carlo simulations of some typical order-disorder ferroelectrics such as TGS, NaNO2 and DKDP nanocrystals were studied using a Transverse Ising Model Hamiltonian with four-spins interactions. The microscopic parameters corresponding to this Hamiltonian were adjusted to fit the experimental polarization-temperature curves for each one of the materials in the bulk phase. Then the dependences of the ferroelectric-paraelectric phase transition temperatures, Tc, on the sizes of those crystals were studied with Monte Carlo simulations of the order-disorder system. We report a weak dependence of Tc on the size of the crystal (d) for these materials above d∼6nm. The addition of surface effects showed that the expected lowtemperature shift of Tc due to size effects, can be reverted.
Piezoresponse Measurements for Pb(Zr,Ti)O3 Island Structure Using Scanning Probe Microscopy
Authors: Fujisawa H. , Morimoto K. , Shimizu M. , Niu H. , Honda K. , Ohtani S. 
Published: April 2011

AbstractPiezoresponse measurements using scanning probe microscopy (SPM) were performed for island structures at the initial growth stage of Pb(Zr,Ti)O3 (PZT) (Zr/Ti=0/100, 24/76 and 74/26) thin films prepared by metalorganic chemical vapor deposition(MOCVD). Deposition times were varied from 5s to 7min to control the size of PZT islands. When deposition times were shorter than 3min, (111)-oriented triangular-shaped PZT islands were observed before forming a continuous film. The width and height of PZT islands deposited at 3min were 160 and 70nm for Zr/Ti = 0/100, 100 and 30nm for Zr/Ti = 24/76, and 80 and 20nm for Zr/Ti = 74/26, respectively. The size of islands decreased with increasing the Zr composition. Hysteresis loops due to polarization switching were observed in the phase difference and displacement of piezoresponse measured using scanning probe microscopy (SPM). This result proves that nano-size PZT islands have weak ferroelectricity. The minimum width and height of PZT islands which showed ferroelectricity were 70 and 30nm for Zr/Ti=24/76.
Sensing Properties of Ba1划xLaxNbyTi1划yO3 (x=0.25%, y=0.25%) Thin-Film on SiO2/Si Substrate
Authors: Li B. , Lai P. T. , Li G. Q. , Zeng S. H. , Huang M. Q. 
Published: April 2011

AbstractBarium lanthanum titanate-niobate (Ba1划xLaxNbyTi1划yO3) film deposited on a SiO2/Si substrate by the argon ion-beam sputtering technique has been used to fabricate a thin-film resistor and a metal-insulator-semiconductor (MIS) capacitor by standard integrated-circuit technology. Measurements show that the film resistor has superior sensitivity for visible light and a thermal sensitivity within the range 28∼400 °C, while the MIS capacitor is highly sensitive to relative humidity. The optical absorption spectrum of the film has been measured and the bandgap of the film determined. The effects of test frequency on the impedance of the film resistor at various temperatures and on the humidity-sensitive characteristics of the MIS capacitor have been investigated.