bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Method to Improve Activation of Implanted Dopants in SiC
Authors: Holland O. W. , Thomas D. K. 
Published: April 2011

ABSTRACTImplantation of dopant ions in SiC has evolved according to the assumption that the best electrical results (i.e., carrier concentrations and mobility) are achieved by using the highest possible processing temperature. This includes implantation at > 600°C followed by furnace annealing at temperatures as high as 1750°C. Despite such aggressive and extreme processing, implantation suffers because of poor dopant activation, typically ranging between < 2%–50% with p-type dopants represented in the lower portion of this range and n-types in the upper. Additionally, high-temperature processing can led to several problems including changes in the stoichiometry and topography of the surface, as well as degradation of the electrical properties of devices. A novel approach for increasing activation of implanted dopants in SiC and lowering the activation temperature will be discussed. This approach utilizes the manipulation of the ion-induced damage to enhance activation of implanted dopants. It will be shown that nearly amorphous layers containing a small amount of residual crystallinity can be recrystallized at temperatures below 900°C with little residual damage. It will be shown that recrystallization traps a high fraction of the implanted dopant residing within the amorphous phase (prior to annealing) onto substitutional sites within the SiC lattice.
Positron Annihilation Spectroscopy and Small Angle Neutron Scattering Characterization of Nanostructural Features in Irradiated Fe-Cu-Mn Alloys
Authors: Wirth B. D. , Asoka-Kumar P. , Howell R. H. , Odette G. R. , Sterne P. A. 
Published: April 2011

ABSTRACTRadiation embrittlement of nuclear reactor pressure vessel steels results from a high number density of nanometer sized Cu-Mn-Ni rich precipitates (CRPs) and sub-nanometer matrix features, thought to be vacancy-solute cluster complexes (VSC). However, questions exist regarding both the composition of the precipitates and the defect character and composition of the matrix features. We present results of positron annihilation spectroscopy (PAS) and small angle neutron scattering (SANS) characterization of irradiated and thermally aged Fe-Cu and Fe-Cu-Mn alloys. These complementary techniques provide insight into the composition and character of both types of nanoscale features. The SANS measurements indicate populations of CRPs and VSCs in both alloys. The CRPs are coarser in the Fe-Cu alloy and the number densities of CRP and VSC increase with the addition of Mn. The PAS involved measuring both the positron lifetimes and the Doppler broadened annihilation spectra in the high momentum region to provide elemental sensitivity at the annihilation site. The spectra in Fe-Cu-Mn specimens thermally aged to peak hardness at 450°C and irradiated at 288°C are nearly identical to elemental Cu. Positron lifetime and spectrum measurements in Fe-Cu specimens irradiated at 288°C clearly show the existence of long lifetime (∼500 ps) open volume defects, which also contain Cu. Thus the SANS and PAS provide a self-consistent picture of nanostructures composed of CRPs and VSCs and tend to discount high Fe concentrations in the CRPs.
Characterizations of Lamellar Interfaces and Segregations in a PST-TiAl Intermetallic Alloy by an Analytical Scanning Transmission Electron Microscope
Authors: Zhao Wei , Luzzi David E. 
Published: April 2011

ABSTRACTPolysynthetically-twinned titanium aluminide (PST-TiAl), a fully lamellar γTiAl + α2-Ti3Al dual-phase alloy, is under evaluation for applications in rotary components in aircraft and automobile industries due to its high specific strength, and a high strength-retention capability at elevated-temperatures. However, the low ductility at room- to mid-high temperatures of the material hinders its application. Additions of certain tertiary elements to the binary TiAl system appear to improve the ductility at room- to mid-high temperatures, thus a balance among strength, ductility, and fracture toughness can be expected. In this article, segregation of tertiary elements to the lamellar interfaces is investigated. Single crystals of a TiAl with 0.6% atomic percentage tertiary additions are grown by an optical float-zone method. Segregation to the lamellar interfaces and the microstructure of the interfaces are investigated. Structures of the lamellar interfaces are characterized, and microchemistry and distribution habits of these elements along the γ+α2 lamellar boundaries as well as the γ-γ lamellar and domain boundaries are analyzed.
High-Resolution Electron Microscopy of Grain Boundary Migration
Authors: Merkle K. L. , Thompson L. J. , Phillipp Fritz 
Published: April 2011

ABSTRACTAtomic-scale grain boundary (GB) migration has been directly observed by high-resolution transmission electron microscopy (HREM). Atomic-scale motion of high-angle tilt GBs as well as twist and general GBs at gold island grains with a number of planar facets has been studied at ambient and elevated temperatures. GB migration mechanisms depend on GB structure and geometry. Strong indications for cooperative effects has been found. In this case, as has been proposed before, atoms may undergo small shifts in their lattice positions to be incorporated into the growing grain in a collective mode. At high temperature and in the absence of a strong driving force such small lattice regions are observed to fluctuate back and forth between the two grains. Faceted GBs typically move in spurts. This appears to be inherent to GB migration, whenever the motion is controlled by different structural entities. For some GB geometries the motion was found to proceed by the lateral propagation of atomic-scale steps.
Evolution of Nanostructure of FeNi(Ti/Cr)N Alloys During Phase Cycling
Authors: Chechenin N. G. , Bronsveld P. M. , Chezan A. R. , Craus C. B. , Boerma D. O. , de Hosson J. Th.M. , Niesen L. 
Published: April 2011

ABSTRACTA possibility to manipulate the microstructure of cold rolled (down to less than 1% of the initial thickness) Fe94Ni4Ti2 and Fe93Ni4 Cr3 foils via inter-phase cycling by nitriding and de-nitriding is investigated. The grains in the as-rolled material had a dominating (001)[110] texture and contained a complicated internal nanostructure due to a dislocation network. The interphase cycling α↔γ'-Fe4N and α↔ε-FexN (x∼3) was investigated as a tool to change or destroy the texture. We observed that the α↔γ'-Fe4N phase transformations weaken but do not erase the texture. A stronger reduction of the texture was obtained in the α↔ε-cycling, where grains with a new orientation appear in XRD scans. During the α↔γ' phase transformation a lamella structure is formed which is coarsening with the number of cycles. It was found that the rates of the α↔γ' and α↔ε interphase transitions were slowing down with the number of cycles. The observation is explained by an increase of kinetic barriers while removing/transforming the rolling-induced defects during the cycling.
Modelling of Phase Transformation During Homogenization of Ternary Aluminum Alloys
Authors: Hofmeister Thorsten , Greven Klaus , Ludwig Andreas , Sahm Peter R. 
Published: April 2011

ABSTRACTThe microstructure determines for the most part mechanical properties of castings. This is the case especially with age-hardening aluminum alloys. To predict the phase transformation in cast parts during and after solidification a sophisticated approach to a coupled modeling of various simulation phenomena is presented. This approach couples a diffusion equation solver which considers the online estimation of thermodynamic equilibria with a macroscopic model for temperature calculation. The coupled micro-model predicts the dendrite solidification of ternary alloys. To simulate the phase transformation in temperature zones below solidification a homogenization model is added. Permanent mould casting experiments with ternary aluminum alloys are used to validate these models.
Influence of Dislocations on Deuteride Formation in Single Crystal Palladium
Authors: Chen W.C. , Heuser Brent J. 
Published: April 2011

ABSTRACTThe effect of dislocations on deuteride formation in the Pd-D system has been investigated with small-angle neutron scattering (SANS). Deuteride precipitation morphologies in well-annealed single crystal Pd and deformed single crystal Pd have been determined with SANS. High densities of dislocations were introduced into the deformed sample by cycling across the deuteride miscibility gap. The characteristic response from small, 20-30 Angstrom thick, plate-like particles has been observed in the SANS measurement of both sample types. We believe these small plates act as precursors to the formation of much larger, tens-of-microns thick incoherent plate-like particles. These much larger deuteride plates have a preferred habit plane that depends on sample type; (100) for the well-annealed matrix and (110) for the deformed matrix.
Origin of Voids at the Interface of Wafer Bonded Sapphire on Sapphire
Authors: Senz Stephan , Kopperschmidt Pascal , Zakharov Nikolai Dimitri 
Published: April 2011

AbstractTwo sapphire (Al2O3, r-cut) wafers were bonded at room temperature. The bonding energy increased during heating up to 1100 °C. The interface was investigated by plan-view and cross-section TEM. The bonding strength after heating to 1100 °C is similar to the bulk bonding strength. A high density of voids at the bonded interface was observed. The voids are elongated along the interface in a pancake shape. The surfaces are low index planes. The volume inside the voids is higher than expected from a model, where a hydrophobic initial bonding is assumed. The strength of initial bonding and the free volume at the interface can be understood, if the sapphire surfaces are hydrophilic and covered by several monolayers of water during initial bonding. During annealing the water diffuses out along the bonded interface and a free volume remains.
In-Situ Tem Analysis of Nanometre-Sized Oxide Precipitates in a Metal Matrix
Authors: Kooi Bart J. , De Hosson Jeff Th.M. 
Published: April 2011

AbstractThe objective of the present work is the in-situ study of the transformation of small oxide precipitates in a metal matrix by conventional and high-resolution transmission electron microscopy (HRTEM). As an example the reduction of Mn3O4 into MnO for nano-sized oxide precipitates in a silver matrix was studied in detail. A convenient method for monitoring the reduction process is shown for a large number of precipitates simultaneously. It is based on two-beam dark-field images showing distinct Moiré patterns for the MnO and the various types of Mn3O4 precipitates embedded within an Ag matrix. A controlling factor of the transformation kinetics appeared to be the rate in which the system can relax the strains due to the accompanying volume reduction of the precipitates. Other interesting aspects of the Mn3O4 to MnO transformation scrutinized and explained were the shape change of the precipitates upon reduction and the fact that mixed Mn3O4/MnO precipitates were only detected within a small temperature/time interval. Ostwald ripening of the MnO precipitates was observed as well.
Structure-Property Relationships of Tin Dioxide Thin Films Grown on Sapphire Substrates by Femtosecond Pulsed Laser Deposition
Authors: Dominguez J. E. , Fu L. , Pan X. Q. 
Published: April 2011

AbstractThe sensitivity of semiconductive tin dioxide (SnO2) to reducing gases is determinedby the electrical conductivity change in the material. This change in conductivity strongly dependson the thickness of the electron depletion layer near the oxide film surface. In this paper we study the effect of crystal defects and interfaces on the electrical properties and the gas sensing performance of SnO2 thin films. SnO2 thin films with the thickness varying from 15 nm to 100 nm were deposited on sapphire substrates with different surface crystallographic orientations by femtosecond pulsed laser deposition. Films grown on the (1012) sapphire (R-cut) are epitaxial, single crystal. High resolution transmission electron microscopy studies showed the existence of a large number of crystal defects including crystallographic shear planes and misfit dislocations at the film/substrate interface. Films grown on the (0001) sapphire substrates (Ccut) are nanocrystalline with (200) texture. The gas sensitivity of the films was measuredin a gas reactor at high temperature. It was found that the sensitivity to reducing gases increases with decreasing film thickness. Electrical transport properties of the SnO2 thin films were investigated byHall effect measurements. Models correlating the microstructures of thin films to electrical properties are proposed.
Nanoscale electromechanical phenomena in ferroelectric thin films
Authors: Ganpule C. S. , Roytburd A. L. , Nagarajan V. , Stanishevsky A. , Melngailis J. , Williams E. D. , Ramesh R. 
Published: April 2011

AbstractFocused ion beam milling was used to fabricate ferroelectric islands in Pb-Zr-Ti-O thin films. The islands ranged in size from 200μm×200μm to 0.3μm×0.3μm. The inverse piezoelectric effect was studied in these islands as a function of their size by tracking the surface displacement of the top electrode of the island (under an applied electric field) using an atomic force microscope (AFM). It was found that there was a substantial increase in the piezoresponse as the size of the island decreased below 100μm×100μm. This increase was attributed to the elastic deformation of the substrate.
Preparation of sub-100nm Thickness PZT thin Films with Chemical Solution Deposition Method for low Voltage Operation
Authors: Lee Yong Kyun , Lee June Key , Kim Chang Jung , Yi Insook , Chung Ilsub 
Published: April 2011

AbstractPZT thin films with a thickness of 70 nm were successfully fabricated using a modified solution combined with PbTiO3 seed layer. Throughout various approaches, we found that the microstructure of PZT thin film plays an important role in determining the electrical properties such as hysteretic properties and leakage currents, particularly when the thickness is below 100 nm. We modified the precursor system to improve the microstructure in PZT thin film. In addition, we also adopted a thin PbTiO3 seed layer to enhance the initial nucleation density. Finally, we could obtain good electric properties similar to those obtained from 240 nm thick PZT film. The hysteretic properties is excellent enough to operate at a low voltage (2V) for a high density FRAM application.
Characterization of Ferroelectric Property of c-axis and non-c-axis Oriented Epitaxially Grown Bismuth Layer-Structured Ferroelectric Thin Films with Different m-numbers Prepared by MOCVD
Authors: Watanabe Takayuki , Sakai Tomohiro , Saiki Atsushi , Saito Keisuke , Chikyo Toyohiko , Funakubo Hiroshi 
Published: April 2011

AbstractEpitaxial thin films of bismuth layer-structured ferroelectrics (BLSF) with different m-numbers, i.e., Bi2VO5.5 (BVO) (m=1), SrBi2Ta2O9 (SBT) (m=2), and Bi4Ti3O12 (BIT) (m=3), were grown by metalorganic chemical vapor deposition (MOCVD). (00l)-oriented films were deposited on (100)SrTiO3. (114)-oriented BVO, (116)-oriented SBT, and (118)-oriented BIT films were deposited on (110)SrTiO3. Moreover, (102)-oriented BVO, (103)-oriented SBT, and (104)-oriented BIT films were deposited on (111)SrTiO3. On (100), (110), and (111)SrTiO3 substrates, c-axis of the deposited films was tilted about 0°, 45°, and 56°, respectively, against perpendicular to the surface of the substrates irrespective of m-number. This suggests the growth of crystallographic equivalent orientation. The distinctive surface morphology originated to the feature of the film orientation was observed. The dielectric constant and the leakage current of c-axis-oriented film was smaller than that of non-c-axis-oriented one, indicating smaller dielectric constant and leakage current along c-axis than a- or b-axes. A larger ferroelectric anisotropy was ascertained for SBT and BIT films. Furthermore, the evaluated spontaneous polarization along a- and c- axes of BIT from the data of the epitaxially grown BIT films well agreed with the reported one for the single crystal. This suggests the ferroelectric property was not strongly affected by the strain in the films.
Ferroelectric and Piezoelectric Properties of Epitaxial Pb(Yb1/2Nb1/2)O3-PbTiO3 Films
Authors: Yoshimura Takeshi , Trolier-McKinstry Susan 
Published: April 2011

Abstract(1°x)Pb(Yb1/2Nb1/2)O3划xPbTiO3 (PYbN-PT, x=0.5) epitaxial films were grown on (001)SrRuO3/(001)LaAlO3 and (111)SrRuO3/(111)SrTiO3 substrates by pulsed laser deposition. (001)PYbN-PT epitaxial films with high phase purity and good crystalline quality were obtained for a wide range of deposition rates (60-90 nm/min) and temperatures (620-680 °C). (111)PYbN-PT films were also obtained at temperatures in the range of 600 °C to 620 °C. The ferroelectric and piezoelectric properties were investigated on both (001) and (111) PYbN-PT films. The remanent polarizations of (001)PYbN-PT and (111)PYbN-PT films were as high as 34 μC/cm2 and 26 μC/cm2, respectively. On (001)PYbN-PT films with a thickness of 900 nm, an e31 coefficient of -13 C/m2 and an aging rate of 2.5% per decade were observed.
Electrophoretic Deposition of Ferroelectric Composites for Applications in Electronic Scanning Systems
Authors: Ngo E. , Joshi P.C. , Cole M. W. , Hubbard C. W. 
Published: April 2011

AbstractWe have investigated the electrophoretic deposition (EPD) as a low cost and conformal method of fabricating barium strontium titanium (BST) based composite thick films. The films were deposited at a controlled rate on platinum substrate in acetone-based slurry under electric bias. Acetone-aerosol OTS surfactant dispersion was used as dispersive medium. Conformal BST based thick films of 10-80 μm were obtained. The dielectric constant and dielectric loss factor of Ba0.60Sr0.40TiO3 and Ba0.60Sr0.40TiO3 – 20wt% compositions were 603.3 and 0.029 and 327.0 and 0.002, respectively. The low frequency electronic properties of the electrophoretic films were also compared with those of the bulk BST ceramics. In addition, the optical and the structural properties of the films are also discussed. The various techniques employed include x-ray diffraction, SEM and surface profilometer.
Macroscopic Actuators Using Thick Piezoelectric Coatings
Authors: Sayer M. , Lockwood G.R. , Olding T.R. , Pang G. , Cohen Lester M. , Ren W. , Mukherjee B.K. 
Published: April 2011

AbstractLarge scale actuated structures often require piezoelectric elements in the thickness range 10-50μm. For manufacturing purposes, the chemical solution deposition of sol gel composites can create such structures using methods compatible with semiconductor fabrication technology. The piezoelectric characteristics of structures fabricated by patterning methods based on the lapping and dicing of bulk ceramic, spray coating and laser machined and micromolded sol gel composites are compared. Laser interferometer measurements on PZT/PZT composites give d33 = 200 pC/N and d31 = 24 pC/N. The design and fabrication of large area voltage actuated mirrors and annular and linear ultrasonic arrays in the frequency range of 50 MHz are demonstrated.
Effect of Laser Energy and Laser Pulses on the Microstructure, Composition and Properties of Barium Strontium Titanate Thin Films Synthesized by Pulsed Laser Deposition
Authors: Fountzoulas Costas G. , Demaree J. D. , McKnight Steven H. 
Published: April 2011

AbstractBarium strontium titanate (BSTO) films were synthesized by the pulsed laser deposition technique (PLD) on silicon substrates at room temperature. The thin films were synthesized at ambient temperature and 30 mT oxygen partial pressure, with 300, 400 and 500 mJ/cm2 laser fluence at 5, 10 and 20 pulses per second on silicon wafer substrates. All films were subsequently post-annealed at 750°C in an continuous oxygen stream. The microstructure, crystallinity and lattice constant of the BSTO films were studied with the aid of atomic force microscopy (FEM) and Glancing Angle X-ray Diffraction analysis (GAXRD). The hardness and modulus of elasticity of the films were studied with the aid of a nanohardness indenter. The film stoichiometry was determined with the aid of Rutherford Backscattering Spectrometry (RBS). The results of this research will be combined with the results of our previous work [1, 2] on the effect of substrate temperature and oxygen partial pressure on the microstructure and properties of the BSTO films in order to construct a structural zone model (SZM) of the BSTO films synthesized by PLD.
Cellular Domain Architecture of Stress-free Epitaxial Ferroelectric Films
Authors: Alpay S. P. , Roytburd A. L. , Nagarajan V. , Bendersky L. A. , Ramesh R. 
Published: April 2011

AbstractEpitaxial ferroelectric films undergoing a cubic-tetragonal phase transformation relax internal stresses due to the structural phase transformation and the difference in the thermal expansion coefficients of the film and the substrate by forming polydomain structures. The most commonly observed polydomain structure is the c/a/c/a polytwin that relieves the internal stresses only partially. Relatively thicker films may completely reduce internal stresses if all three variants of the ferroelectric phase are brought together such that the film has the same in-plane size as the substrate. In this article, we provide experimental evidence on the formation of the 3-domain structure based on transmission electron microscopy in 450 nm thick (001) PbZr0.2Ti0.8O3 films on (001) SrTiO3 grown by pulsed laser deposition. X-ray diffraction studies show that the film is fully relaxed. Experimental data is analyzed in terms of a domain stability map.
Growth of (Ba,Sr)TiO3 Thin Films in a Multi-wafer MOCVD Reactor
Authors: Ehrhart P. , Fitsilis F. , Regnery S. , Jia C. L. , Jin H.Z. , Waser R. , Schienle F. , Schumacher M. , Juergensen H. 
Published: April 2011

AbstractWe report on the performance of a planetary multi-wafer MOCVD reactor which handles 5 six inch wafers simultaneously. The reactor is combined with a liquid delivery system which mixes the liquid precursors from three different sources: 0.35 molar solutions of Ba(thd)2 and Sr(thd)2 and a 0.4 molar solution of Ti(O-i-Pr)2(thd)2. The microstructure and the film stress were investigated by X-ray diffraction and the composition of the films was determined by X-ray fluorescence analysis. As a direct consequence of the reactor design we obtain a high uniformity of the films over 6 inch wafers, as well as high efficiencies for the precursor incorporation. Film growth is discussed within a wide parameter field and the finally achieved electrical properties, e.g., permittivity, loss tangent, leakage current, are discussed in relation to the microstructural properties.