bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure-Property Relationship of Ion-Beam Sputtered Nd-Fe-B Magnetic Thin Films On (111) Silicon
Authors: Nazareth Anthony S. , Chopra Harsh Deep , Sood D. K. , Zmood R. B. 
Published: April 2011

AbstractA focussing grid broad beam Kaufman source, using argon ions on a target of nominal composition Nd2Fei4B has been employed to sputter deposit magnetic thin films of thicknesses ranging from 800 â to 1300 â on silicon-(lll) substrates at room temperature. These films were characterised for their composition depth profile by Rutherford Backscattering Spectroscopy, while x-ray diffraction was used to study the crystallographic structure. Due to a close match between (111) Si with (220) Nd2Fej4B lattice spacings, preferred crystallographic texturing was expected, and experimental results showed a greatly enhanced (220) texture. The degradation in magnetic properties was attributed to the presence of oxygen in the films as indicated by concentration depth profiles. It is premised that another significant role of oxygen may be to relieve the misfit strain across the interface by its incorporation within the Nd2Fej4B phase.
Degradation in Euv Reflectance of Ion-Sputtered Sic Films
Authors: Schwarcz Dan , Keski-Kuha Ritva A.M. 
Published: April 2011

AbstractSilicon Carbide (SiC) formed by chemical vapor deposition (CVD) has the highest reflectivity in the extreme ultraviolet (EUV) of any currently used optical material. The high temperature required for the CVD process, however, limits its suitability for coating optical components. To address this problem thin films have been sputtered onto optical surfaces from CVD βSiC targets. These films, while having reflectivity lower than that of CVD SiC, are nonetheless the best coatings available for reflectance in the spectral region below 1000À. While the initial properties are good, the EUV reflectivity degrades with time after deposition. A relative decrease of about 25% is evident in the reflectivity at 920Â after 2.5 years, and about 85% of this change occurs in the first three months. In fact, a decrease is observed in the minutes following deposition. In this study the degradation is characterized and a mechanism is proposed. Efforts underway to reduce or eliminate the degradation are discussed.
Effect of Surface Roughness on Surface Photochemistry
Authors: Myli Kari B. , Grassian Vicki H. 
Published: April 2011

AbstractPhotoinduced processes on surfaces is of fundamental importance in materials processing. For example, photo-assisted chemical vapor deposition has been used to deposit a number of different materials on solid substrates. The effect of substrate morphology on photoinduced processes can be an important factor in film growth. In order to clarify the role of substrate morphology, in particular surface roughness, on surface photochemistry, we have examined the wavelength dependence of the photodissociation of chlorobenzene and 3-chloropyridine adsorbed on smooth and rough silver surfaces. As discussed below, we have measured a red shift in the photodissociation threshold for these molecules adsorbed on a rough surface relative to a smooth surface. The wavelength dependence of the photodissociation cross-section near the threshold has been measured in order to discern the origin of the red shift.
Si. I-x-y. GexCy Film Formation by Pulsed Excimer Laser Crystallization of Heavily Ge and C Implanted Silicon
Authors: Fogarassy E. , Dentel D. , Grob JJ. , Prévot B. , Stoquert J.P. , Stuck R. 
Published: April 2011

AbstractWe investigate, for the first time, the possibility to crystallize heavily Ge and C implanted silicon substrates by excimer-laser annealing performed in the molten regime. It is demonstrated that the crystalline quality of the laser grown SiGeC alloys strongly depends on the initial dose of implanted carbon.
Germanium Partitioning and Interface Stability During Rapid Solidification of Gesi Alloys
Authors: Brunco D. P. , Thompson Michael O. , Hoglundt D. E. , Aziz M. J. 
Published: April 2011

AbstractThe stability of laser processed GeSi heteroepitaxial alloys on Si to partitioning driven interface instabilities is examined. Existing stability models are extended to include nonequi-librium solidification effects for nondilute alloys and are examined under typical conditions of laser induced solidification. Ge diffusion and partitioning were measured for quantitative input to the models. The Ge liquid-phase diffusivity was determined to be 2.5 x 10-4 cm2/s. The measured velocity-dependent partition coefficients k(v) were fit to the Continuous Growth Model using an equilibrium k of 0.45 and a diffusive speed of 2.7 m/s. Stability calculations based on these values and our extended stability model are presented. Although instabilities at compositions comparable to those experimentally observed to give defective films are predicted, the growth rates of these instabilities appear too slow to destabilize an interface on laser processing time scales. These results suggest that strain or other effects play an important role in the observed defective microstructures.
Modeling of Thermal, Electronic, Hydrodynamic, and Dynamic Deposition Processes for Pulsed-Laser Deposition of Thin Films
Authors: Liu C. L. , Leboeuf J. N. , Wood R. F. , Geohegan D. B. , Donate J. M. , Chen K. R. , Puretzky A. A. 
Published: April 2011

AbstractVarious physical processes during laser ablation of solids for pulsed-laser deposition (PLD) are studied using a variety of computational techniques. In the course of our combined theoretical and experimental effort, we have been trying to work on as many aspects of PLD processes as possible, but with special focus on the following areas: (a) the effects of collisional interactions between the particles in the plume and in the background on the evolving flow field and on thin film growth, (b) interactions between the energetic particles and the growing thin films and their effects on film quality, (c) rapid phase transformations through the liquid and vapor phases under possibly nonequilibrium thermodynamic conditions induced by laser-solid interactions, (d) breakdown of the vapor into a plasma in the early stages of ablation through both electronic and photoionization processes, (c) hydrodynamic behavior of the vapor/plasma during and after ablation. The computational techniques used include finite difference (FD) methods, particle-in-cell model, and atomistic simulations using molecular dynamics (MD) techniques.
Electron Beam Assisted Etching of Single Crystal Diamond Chips
Authors: Taniguchi Jun , Miyamoto Iwao 
Published: April 2011

AbstractIn order to fabricate ultra-precision diamond tools and delineate ultra-fine patterns into diamond chips without adding radiation damage, machining characteristics of diamond chips with electron beam assisted etching (EBAE) has been investigated. This processing mechanism is considered as follows: Oxygen atoms or molecules activated by electron beam bombardment on or near the chip surface react with carbon atoms of the diamond surface, resulting in formation of volatile products such as CO or C02 . An EBAE system composed of a scanning electron microscope (SEM) which has an oxygen introduction system was used to etch synthetic single crystal diamond chips. When a diamond chip was etched at an applied voltage of 10 kV and an irradiation beam current of 1.7nA, the depth of the holes increased with an increase of machining time and the diameter of the holes also increased with an increase of machining time. When a diamond chip was etched at an applied voltage of 10 kV and an irradiation beam current of 1.3nA, the depth and diameter of the etched holes merely increased with an increase of flow rate of oxygen gas ranging from 5 cc/min to 30 cc/min, then the depth decreased rapidly with an increase of oxygen gas. With this processing method, very small holes with a diameter of about 0.5 ∼ 2 /xm, and a depth of about 0.01 ∼ 0.7 fim were obtained. Line and rectagular patterns with several /xm and sub-μum depths were also fabricated.
In-situ Ellipsometry Study of Ion Bombardment Effects on Low Temperature Si Epitaxy by dc Magnetron Sputtering
Authors: Yang Y.H. , Feng G.F. , Katiyar M. , Abelson J.R. 
Published: April 2011

AbstractWe deposit Si films on Si(100) substrates at temperatures of 300 - 350 °C using dc magnetron sputtering, and characterize the structure by in-situ spectroscopic ellipsometry. Changes in the ion or electron bombardment, produced by biasing the sample with respect to the floating potential, are found to exert a strong effect on the kinetics of the crystalline (epitaxial) to amorphous transition for films deposited just below the apparent minimum temperature (350 °C) for sustained epitaxy. At 320°C, the best results are found at the floating potential, which is 25 V below the plasma potential and produces an ion flux equal to the depositing Si flux on the substrate. At +14 V above the floating potential, the volume fraction of crystalline Si decreases exponentially with thickness, and the characteristic decay length is a function of substrate temperature. At -14 V below the floating potential, the deposited film is amorphous with a large void content. These observations demonstrate the subtle tradeoff between enhanced surface mobility and defect creation by low energy ion bombardment.
Dynamic Behavior of Twins In BaTiO3
Authors: Katti Kalpana S. , Sarikaya Mehmet 
Published: April 2011

AbstractThe most prominent lattice defects in barium titanate, i.e., twins on two distinct lattice planes { 111 } and { 110 }, were characterized using dynamic transmission electron microscopy techniques in the image and diffraction modes. In-situ heating experiments from room temperature up to 130°C and then cooling down to -168°C reveal a dependence of { 110 } twins on ferroelectric transition. On the other hand, { 111 } twins are found to be completely stable through the ferroelectric transition and exist in all phases. Streaking is observed in the diffraction spots leading to an estimation of { 1111 twin wall thickness to be about 10Å while no such streaking was observed corresponding to { 1101 twins. Based on these observations and the behavior of the twin boundaries under dynamic heating cycles, an estimate of the twin wall energies indicates that { 111 } walls have three orders of magnitude higher energy than that of { 110 } walls which explains their relative thermal and mechanical stability.
Fabrication and Characterization of NiO Bicrystals
Authors: Chung Yong-Chae , Wuensch Bernhardt J. 
Published: April 2011

AbstractFabrication of NiO bicrystals having Σ5 (310) and Σ13 (510) coincidence-site tilt boundaries was successfully carried out by a CVT (Chemical Vapor Transport) method. The CVT method was a very advantageous way to grow ultra pure crystals since it preferentially transported NiO from the source pellet to the substrate by reaction with a HCl carrying gas. Single crystal MgO was used as a substrate for epitaxial growth of NiO as the readily available MgO crystals have only a 1% lattice mismatch with NiO. Moreover, MgO is soluble in acids while NiO is not. This permitted removal of the substrate crystal after growth to provide a free-standing NiO crystal. Using two single crystals of MgO with the desired tilt orientation as a substrate, NiO bicrystals were fabricated at growth rates greater than 100 μm/hour at 1,400K using 250 torr of HCI(g) as a carrying agent. The purity of the epitaxial NiO crystals was determined by mass spectrometry and neutron activation analysis. The grain boundary in the bicrystals is exactly perpendicular to the (100) growth surface. Highly-reflective facets along the growth direction suggest high mechanical quality. High-resolution transmission electron microscopy of the Σ13 boundary revealed structure at the atomic scale that provided no evidence for segregated phases.
Interface Reaction Enhanced Epitaxial Growth of Barium Ferrite Magnetic Thin Films
Authors: Li Jinshan , Sinclair Robert , Rosenblum Stephen S. , Hayashi Hidetaka 
Published: April 2011

AbstractUsing facing target sputtering, crystalline magnetoplumbite-type barium ferrite (BaFe12O19 or BaM) thin films have been prepared in-situ at a substrate temperature of 640°C without postdeposition annealing. BaM thin films grow randomly if they are directly deposited onto Si or thermally oxidized Si substrates. However, deposited onto a sputtered ZnO layer (∼230Å) on Si substrates, BaM thin films show excellent c-axis out-of-plane texture with a 0.2° c-axis dispersion angle, as indicated by X-ray diffraction (XRD) study. Cross section transmission electron microscopy (TEM) reveals that the textured films epitaxially grow on a transition layer, which is formed between BaM and ZnO. No direct epitaxial relation between BaM and ZnO was observed. This transition layer is identified by TEM and XRD as ZnFe2O4, which, from a structure point of view, reduces the lattice mismatch between BaM and ZnO, and also enhances the c-axis out-of-plane epitaxial growth.
Crystallization Kinetics of Fe-DOPED A1203
Authors: Simpson Todd W. , Mitchell Ian V. , Yu Ning , Nastasi Michael , Mcintyre Paul C. 
Published: April 2011

AbstractTime resolved optical reflectivity (TRR) and Rutherford backscattering spectrometry (RBS) and ion channelling methods have been applied to determine the crystallization kinetics of Fe-doped A1203 in the temperature range of 900-1050°C. Amorphous A1203 films, approximately 250 nm thick and with Fe cation concentrations of 0, 1.85, 2.2 and 4.5%, were formed by e-beam deposition on single crystal, [0001] oriented, A1203 substrates. Annealing was performed under an oxygen ambient in a conventional tube furnace, and the optical changes which accompany crystallization were monitored, in situ, by TRR with a 633nm wavelength laser.Crystallization is observed to proceed via solid phase epitaxy. An intermediate, epitaxial phase of -γ-Al203 is formed before the samples reach the ultimate annealing temperature. The 5% Fe-doped film transforms from γ to α-A1203 at a rate approximately 10 times that of the pure A1203 film and the 1.85% and 2.2% Fe-doped films transform at rates between these two extremes. The Fe-dopants occupy substitional lattice sites in the epilayer. Each of the four sets of specimens displays an activation energy in the range 5.0±0.2eV for the γ,α phase transition.
In Situ Hrem Observation of the Oxidation of Nickel Thin Foils
Authors: Thien-Nga Le , Hutchison J.L. , Derby B. 
Published: April 2011

AbstractGrowth of oxide microcrystals at the edge of nickel grains could be observed using highresolution microscopy. Three types of samples were examined: a nickel-cermet material, and pure annealed nickel, both ion-beam milled; and a standard electropolished nickel foil. Microstructural features, such as crystallite size, facets, orientation relationship and lattice parameter are described.
Heteroepitaxial Diamond Formed on Silicon Wafer Observed by High Resolution Electron Microscopy
Authors: Yang Jie , Lin Zhangda , Wang Li-Xin , Jin Sing , Zhang Ze 
Published: April 2011

AbstractDiamond films with high preferential orientation (111) on silicon (100) crystalline orientation substrates had been obtained by hot-filament chemical vapor deposition (HFCVD) method. X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and high-resolution cross-sectional transmission electron microscopy (HREM) are used to characterizate the structure and morphology of the synthesised diamond films. Diamond (111) plans had been local grown epitaxially on the Si(100) substrate observed by HREM. SEM photographes show that plane diamond crystals have been obtained.
Chemical Widths at Composite Interfaces: Relationships to Structural Widths and Methods for Measurement
Authors: Carpenter R.W. , Bow J.S. , Kim M.J. , Chowdhiury K. Das , Braue W. 
Published: April 2011

AbstractEnergy selected imaging with a Zeiss 912 ω-filter TEM was used to examine grain boundary solute distributions in an Si3N4/SiC(w) ceramic densified with Y2O3 + Al2O3 sintering aid. These results are compared to boundary region solute distributions in the same materials determined by field emission small probe electron energy loss spectroscopy and related methods. The intrinsic higher incident flux of the FEG small probe methods renders them the most useful for high spatial resolution local chemical width measurement. Energy selected imaging is fast and relatively simple for determining elemental distributions in boundaries at low magnifications. The methods are complementary.
Cesium/Oxide Interactions for Ultrathin Films on ∝-Al2O3(0001) and ∝-Al2O3(1102)
Authors: Zavadil Kevin R. , Ing Judith L. 
Published: April 2011

AbstractThe interaction of cesium at the (0001) and (1102) surfaces of sapphire has been investigated using a variety of surface analytical techniques. Reflection mass spectrometric measurements yield initial Cs adsorption probabilities of 0.9 and 0.85 for the unreconstructed (0001) and (1102) surfaces, respectively. The adsorption probability decreases dramatically for these surfaces at critical Cs coverages of 2.0×10 14 and 3.4×1014 atoms/cm2, respectively. Thermally induced reconstruction of the (0001) surface to form an oxygen deficient surface results in a decrease in the initial probability and capacity for Cs adsorption. Low energy electron diffraction (LEED) demonstrates that an intermediate, mixed domain surface yields an initial adsorption probability of 0.5 while a reconstructed surface yields a value of 0.27. Thermal desorption mass spectrometry (TDMS) shows that surface reconstruction eliminates the high binding energy states of Cs (2.7 eV/atom), consistent with the observed changes in adsorption probability. In contrast, reconstruction of the (1102) surface produces only minor changes in Cs adsorption. Xray photoelectron spectroscopy (XPS) indicates that no formal reductive/oxidative chemistry takes place at the interface. We interpret the facile adsorption and strong binding of Cs on sapphire to result from Cs interacting with coordinatively unsaturated oxygen.
Effects of Titanium Doping on Surface Properties of Alumina
Authors: Powers James D. , Kulinsky Lawrence , Kitayama Mikito , Glaeser Andreas M. 
Published: April 2011

AbstractControlled-geometry pore structures were introduced into undoped and Ti-doped sapphire using microfabrication techniques, and subsequently transferred to internal sapphire-sapphire and sapphire-polycrystalline alumina interfaces via hot pressing. The high-temperature evolution of several different types of structures was examined, in order to isolate different surface properties and evolution processes which are of interest during sintering. A study of pore channel breakup showed that Ti strongly stabilizes channels oriented in the sapphire [1100] direction, suggesting a significant alteration of the Wulff plot. In another study, the equilibration rate of isolated pores was enhanced in Ti-doped sapphire; as glassy phases are unlikely in this material, a solid-state diffusion mechanism for this enhancement is suggested. The evolution of pore channels with pre-existent perturbations was also studied, and the results of these studies are presented.
Discontinuous Dissolution of Spinel Precipitates in the Al2O3-Fe2O3 System
Authors: Lee Ho-Yong , Kang Suk-Joong L. 
Published: April 2011

AbstractThe discontinuous dissolution of oxide particles has been investigated in the Al2O3 -Fe2O3 system by changing oxygen partial pressure (PO2) and temperature. In PO2 change experiment, 95Al2O3-5Fe2O3 (in wt%) powder compacts were sintered at 1500°C in PO2=0.001 atm and then annealed at 1500°C in air. In temperature change experiment, 85Al2O3-15Fe2O3 (in wt%) powder compacts were sintered at 1600°C in air and then annealed at 1450°C in air. During annealing the sintered specimens, which contained corundum grains and iron aluminate spinel particles, the grain boundaries migrated concomitantly with the dissolution of spinel particles. A discontinuous dissolution of spinel precipitates thus occurred, when the grain boundary migration of alumina in a two phase mixture of corundum and spinel was induced by PO2 or temperature change. The present result would be a distinct observation of the discontinuous dissolution of precipitates in ceramic systems.
Nanoscale Control of Ferroelectric Domain Structure by AFM
Authors: Gruverman A. , Kolosov O. , Hatano J. , Takahashi K. , Tokumoto H. 
Published: April 2011

AbstractAn atomic force microscope is used for visualization and control of domain structure in the ferroelectric crystal guanidinium aluminum sulfate hexahydrate (GASH). Large built-in domains are delineated due to the tip-sample electrostatic interaction by the force microscope operating in friction mode. It is found that an applied voltage of a particular sign created new domains whereas a potential of opposite sign erased these domains. Domains created by an external electric field are visualised in topography mode due to piezoelectric deformation of the crystal. The dynamics of domain lateral growth has been directly observed with nanoscale resolution.
Oxygen Self-Diffusion In Mgo Grain Boundaries
Authors: Liberatore Michael , Wuensch Bernhardt J. 
Published: April 2011

AbstractOxygen grain boundary diffusion has been studied in low energy (∑5, ∑13) and high energy (asymmetric 16° tilt) MgO grain boundaries. Enhanced diffusion of oxygen was observed in all boundaries, but more so in the general, high energy boundary, by 1 - 2 orders of magnitude. This supports the theory that the better the atomic registry between the adjoining grains the lower the diffusivities in the grain boundary. Also the activation energies for bulk and grain boundary diffusion (in the ∑13 boundaries) were found to be equal to within experimental error. (≈ 3.9eV)
Observation and Characterization of Electric Fields at Grain Boundaries
Authors: Huey B. D. , Bonnell D. A. , Carroll D. L. 
Published: April 2011

AbstractVariations in local electric fields near individual grain boundaries have been observed in TiO2 with an ac, non-contact, atomic force microscopy detection scheme. A lateral, in-plane bias was applied to the sample inducing an electric field gradient. A modified AFM then allowed accurate force and force gradient images of both topography and the electric fields to be measured. The sample-tip separation and bias dependence of the AFM probe response to electrostatic fields are used to derive the relationships that allow quantification of lateral fields. With this technique, observation and quantification of potential barriers and enhancement and depletion widths may be observed, especially as a function of boundary chemistry and orientation. Results are discussed in terms of interface potential barrier models.
Atomic Bonding at Oxide Surfaces
Authors: Henrich Victor E. 
Published: April 2011

AbstractThe fundamental interactions involved in the bonding of atoms and molecules to metal oxides are discussed. Surface defects play a major role in many of those interactions. Both acid/base and oxidation/reduction reactions occur at metal-oxide surfaces, with the latter dominating at point defect sites. The reaction of metals with oxide surfaces is governed largely by the relative heats of formation of the respective oxides, although surface point defects also play an important role. Preliminary studies of ceramic/ceramic interfaces indicate that interfacial interactions are much weaker than for metal/ceramic interfaces.