bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural Design of the Geometrical Shape of Interfaces in Bonded Dissimilar Materials Based on Theoretical Elastic Analysis
Authors: Tateno Masayoshi , Fukuzawa Yasushi , Nagasawa Shigeru , Sakuta Hiroshi 
Published: April 2011

ABSTRACTIn order to evaluate the practical strength of a joint and its fracture mode, it is important to find the stress distribution near the edge of the interface by analyses of strength and fracture. The index of stress singularity based on theoretical analysis is a useful tool to indicate the stress distribution.In this paper, investigations on the evaluation of the practical strength of bonded dissimilar materials based on the stress singularity are carried out. The secant stiffness module, which was used for plastics analysis, was applied to the evaluation of thermal elastoplastic behavior near the interface. Spherical conditions of the interface shape were used for the evaluation of stress behavior and the experiment of bonding strength. The relationship between the index of stress singularity, λ, and the practical strength of the bonded TiB2-Ni system was investigated by comparing theoretical λ, which was determined by substituting the secant stiffness module into Bogy's eigenequation, with the practical strength in the edge angle of the interface between 60° and 90° The correlation factor of the relationship between λ and the practical bonding strength of the TiB2-Ni system was found positive. These results show that the structural design of a geometrical interface which is getting a higher strength joint based on the index of stress singularity is verified experimentally.
Interfacial Engineering in Nanocomposites
Authors: Cantor Brian 
Published: April 2011

ABSTRACTThis paper will present details of interfacial design, structure and properties in a variety of different nanocomposites. The materials discussed include co-sputtered nanoscale Ag/SiO2 and Ag/Si thin films which exhibit novel optoelectronic behaviour, and melt spun nanoscale Pb/Al and Sn/Al sheets which exhibit novel mechanical behaviour. The relationships between processing, structure and properties are discussed for these unusual materials systems.
Z-Contrast STEM Imaging and Ab-Initio Calculations of Grain Boundaries in SrTiO3
Authors: Kim Miyoung , Browning Nigel D. , Pennycook Stephen J. , Sohlberg Karl , Pantelides Sokrates T. 
Published: April 2011

ABSTRACTThe understanding of electrical properties of grain boundaries in perovskites is essential for their application to capacitors, varistors and positive-temperature coefficient resistors. The origin of the electrical activity is generally attributed to the existence of charged defects in grain boundaries, usually assumed to be impurities, which set up a double Schottky barrier as they are screened by dopants in the adjacent bulk crystal. Microscopic understanding of the origin of the grain boundary charge, however, has not been achieved. It is not known yet if the charged grain boundary states are an intrinsic property of a stoichiometric grain boundary, arise from nonstoichiometry, or are caused by impurities. Here, the relation between atomic structure and electronic properties is studied by combining experiment with ab-initio calculations. The starting structures for theoretical calculations were obtained from Z-contrast images combined with electron energy loss spectroscopy to resolve the dislocation core structures comprising the boundary. Dislocation core reconstructions are typical of all grain boundaries so far observed in this material. They avoid like-ion repulsion, and provide alternative sites for cation occupation in the grain boundaries. Optimized atomic positions are found by total energy calculations. Calculated differences in vacancy formation energies between the grain boundaries and the bulk suggest that vacancy segregation can account for the postulated grain boundary charge.
Influence of the Interfacial Properties on the Microstructural Development and Properties of Silicon Nitride Ceramics
Authors: Hoffmann M. J. , Gu H. , Cannon R. M. 
Published: April 2011

ABSTRACTThe influence of the sintering additive system on the grain growth anisotropy of silicon nitride has been studied in the two supersaturated oxynitride glass systems M-Si-Al-O-N (where M = Yb, Gd, Nd, La, and Y) and M-Si-Mg-O-N (where M = Lu, Sm, La, Sc and Y). The glasses contained a low volume fraction of grains and offer the possibility to study grain growth without impingement. Both systems show an increase of the aspect ratio with an increasing cation radius of the rare earth elements. The aspect ratios for the Sc- and Y-based glasses are higher than expected from the ionic radius.Analytical transmission electron microscopy of the bulk glass and grain boundary film between flocculated particles reveals a difference in chemical composition. The larger rare earth cations are enriched in the film and the smaller ones are depleted compared to the bulk composition. The enrichment of the larger cations can be considered as an adsorption layer which reduces the growth rate of the prism planes. Glass systems with smaller cations (Yb, Gd) reveal a pronounced growth of the prism planes and sialon is formed in the outer region of the grains. The interfacial strength which determines the fracture toughness increases with a decreasing cation radius, but the effect is mainly attributed to the sialon formation rather than by the cation itself.
Interfacial Reactions in Ti-6Al-4V with Laser-Embedded SiC Particles and the Origin of Intergranular Corrosion Susceptibility of an Al-Mg Alloy
Authors: Kooi B. J. , De Hosson J.Th.M. 
Published: April 2011

ABSTRACTIn the first part of the paper the microstructure of Ti-6Al-4V with laser embedded SiC particles is explained. The interfacial reaction between Ti and SiC is responsible for the largely improved wear resistance of the Ti alloy. In the second part the phase responsible for the intergranular corrosion susceptibility of an Al-Mg alloy when annealed above 65 °C is identified and possible mechanisms to solve this interfacial problem are proposed.
Epitaxial Realignment of In-Situ Doped Polycrystalline Silicon for Advanced BiCMOS Technologies
Authors: Chang K. , Thomas S.G. , Lee T-C. , Gregory R.B. , O'meara D. , Noering K. , Kirchgessner J. , Fresquet G. , Parker J. , TILLACK B. 
Published: April 2011

AbstractIndustrial feasibility of an in-situ-doped (ISD) polycrystalline Si process using chemical vapor deposition for advanced BiCMOS technologies is presented. ISD As-doped amorphous and polycrystalline Si layers have been deposited on Si substrates at 610°C and 660°C, respectively, with the deposition rate varying from 120 to 128Å /minute. Samples are compared on the basis of having been subjected to a substrate preclean prior to deposition using an HF solution and an in-situ H2 bake. TEM micrographs reveal the presence of a thin (10-15 Å) native oxide at the deposited layer/substrate interface for samples not precleaned. This is confirmed for both the amorphous and polycrystalline Si depositions. However, for the 610°C-deposited samples given the substrate preclean, a polycrystalline structure with partial epitaxial layer growth is observed. Twins and stacking faults are found at the poly Si/single crystal Si interface, causing interfacial roughness. Post-deposition annealing of the Si films typically generates grain growth, but RBS-channeling characterization of the annealed Si provides evidence of some recrystallization, the extent of which is affected by the original growth condition. Analysis shows that the amorphous deposition at 610°C results in a mixture of epitaxial and polycrystalline Si. Epitaxial realignment of the polycrystalline Si film by post deposition annealing can result in significantly improved device performance.
Ni-Induced Selective Nucleation and Solid Phase Epitaxy of Large-Grained Poly-Si on Glass
Authors: Puglisi Rosaria A. , Tanabe Hiroshi , Chen Claudine M. , Atwater Harry A. , Rimini Emanuele 
Published: April 2011

AbstractWe investigated the formation of large-grain polycrystalline silicon films on glass substrates for application in low-cost thin film crystalline silicon solar cells. Since use of glass substrates constrains process temperatures, our approach to form large-grain polycrystalline silicon templates is selective nucleation and solid phase epitaxy (SNSPE). In this process, selective crystallization of an initially amorphous silicon film, at lithographically predetermined sites, enables grain sizes larger than those observed via random crystallization. Selective heterogeneous nucleation centers were created on undoped, 75 nm thick, amorphous silicon films, by masked implantation of Ni islands, followed by annealing at temperatures below 600 °. At this temperature, the Ni precipitates into NiSi2 particles that catalyze the transition from the amorphous to the crystalline Si phase. Seeded crystallization begins at the metal islands and continues via lateral solid phase epitaxy (SPE), thus obtaining crystallized regions of several tens of square microns in one hour. We have studied the dependence of the crystallization rate on the Ni-implanted dose in the seed, in the 5×1015/cm3 - 1016/cm3range. The large grained polycrystalline Si films were then used as a substrate for molecular beam epitaxy (MBE) depositions of 1 [.proportional]m thick Si layers. Transmission electron microscopy (TEM) analysis showed a strong correlation between the substrate morphology and the deposited layer. The layer presented a large grain morphology, with sizes of about 4 [.proportional]m.
Strain Modification of Epitaxial SrRuO3 Films Using Structural Transitions of Ferroelectric BaTiO3 Substrate
Authors: Lee M. K. , Nath T. K. , Eom C. B. , Smoak M. C. , Tsui F. 
Published: April 2011

AbstractElectrical conduction and magnetic behavior of ferromagnetic SrRuO3 (bulk Tc= 160 K) were tuned systematically using the structural transitions of ferroelectric BaTiO3 as the growth template. Abrupt resistivity changes of SrRuO3 were observed at the structural transition temperatures of the BaTiO3substrate. The observed effect appears to originate from the lattice changes of BaTiO3 (cubic to tetragonal at 393K, tetragonal to orthorhombic at 278K, and orthorhombic to rhombohedral at 183K) induced by an expansion of spontaneous polarization axis. The observed phenomenon will be very useful for the fabrication of novel perovskite oxide devices.
Study of the Radiative and Non-Radiative Recombination Processes at Dislocations in Silicon by Photoluminescence and LBIC Measurements
Authors: Pizzini S. , Binetti S. , Acciarri M. , Casati M. 
Published: April 2011

AbstractIt is well known that the sharp, room temperature luminescence emission at 1.54 μm from dislocated silicon has set off a great interest for this material in view of its applications in the third window of optical telecommunications. For this reason the dislocation related luminescence in silicon addressed recently a number of investigation aimed at understanding the mechanism of light emission. The problem is still unsolved as most of the experiments done gave contradictory answers to the main questions open, which concern the intrinsic or extrinsic nature of dislocation luminescence and the effect on it of reconstruction, interaction or passivation processes, possibly assisted by metallic or non-metallic impurities.In order to go more insight on the problem, we started a systematic work on CZ silicon, aimed at understanding the properties of dislocation luminescence. The identification of the energy levels involved in the different dislocation PL bands has been obtained.
Photoreflectance Near-Field Scanning Optical Microscopy
Authors: Paulson Charles , Hawkins Brian , Sun Jingxi , Ellis Arthur B. , Mccaughan Leon , Kuech T. F. 
Published: April 2011

AbstractA novel Near-field Scanning Optical Microscopy (NSOM) technique is used to obtain simultaneous topology, photoluminescence and photoreflectance (PR) spectra. PR spectra from GaAs surfaces were obtained and the local electric fields were calculated. Sub-wavelength resolution is expected for this technique and achieved for PL and topology measurements. Photovoltages, resulting from the high intensity of light at the NSOM tip, can limit the spatial resolution of the electric field determination.
Optical and Microstructural Characterization of Nanocrystalline Silicon Superlattices
Authors: Tsybeskov L. , Grom G. F. , Krishnan R. , Fauchet P. M. , McCaffrey J. P. , Baribeau J.-M. , Sproule G. I. , Lockwood D. J. , Timoshenko V. , Diener J. , Heckler H. , Kovalev D. , Koch F. , Blanton T. N. 
Published: April 2011

AbstractWe present optical and microstructural characterization of nanocrystalline silicon superlattices (nc-Si SLs). Our samples have better than 5 % Si nanocrystal size distribution and a long range order along the direction of growth provided by periodically alternating layers of Si nanocrystals and SiO2. Flat and chemically abrupt nc-Si/SiO2 interfaces with a roughness of < 4Å are confirmed by transmission electron microscopy (TEM), Auger elemental microanalysis, X-ray small angle reflection, and low-frequency Raman scattering. Photoluminescence (PL) in our structures has been studied in details including time-resolved and steady-state PL spectroscopy in a wide range of temperature, excitation wavelength and power. Resonantly excited PL spectra show phonon steps proving that the PL originates in Si nanocrystals. Electrical measurements show signature of phonon-assisted tunneling proving low defect density nc-Si/SiO2 interface.
Optical Properties of Pseudomorphic SnXGe1−x Alloys
Authors: Ragan Regina , Atwater Harry A. 
Published: April 2011

AbstractSnxGe1−x alloys are grown coherent on Ge(001) substrates by conventional molecular beam epitaxy. The lattice mismatch between SnxGe1−x and Ge produces a biaxial compression of the alloy in the plane of the substrate and a uniaxial elongation in the growth direction. The change of Eg resulting from the biaxial compression is modeled with deformation potential theory for coherent SnxGe1−x on Ge(001) and coherent SnxGe1−x on Ge(111). For SnxGe1−x on Ge(001), the decrease in the energy band gap due to strain is small, 16 meV for x = 0.10, and Γ7 and L6 shift uniformly. In the case of SnxGe1−x on Ge(111), Γ7 and L6 do not shift uniformly; a large uniaxial splitting occurs at L6, 200 meV for x = 0.10. Another interesting result of a uniaxial strain along [111] is the absence of a direct to indirect energy band gap transition for x < 0.30. Fourier transform infrared spectroscopy transmission measurements of coherent SnxGe1−x on Ge(001) confirm the strain-induced change in the energy band gap is a small effect.
Micro-Raman Characterization of Unusual Defect Structure in Arsenic-Implanted Silicon
Authors: Tuschel David D. , Lavine James P. 
Published: April 2011

AbstractRaman spectroscopy has often been used to study the damage to semiconductors induced by ion implantation. Off-axis, macro-Raman spectra reveal extensive damage to the silicon lattice, consistent with many literature reports. However, when the same samples were analyzed in the backscattering mode by micro-Raman spectroscopy, evidence was found for orientational dependent lattice damage and an unusual defect structure. P/O micro-Raman spectra reveal the spatially-varying appearance of a band between 505 and 510 cm−1 always accompanied by that of the silicon optical mode at 520 cm−1.
Studies Of Photoreflectance in Cd1−x MnxTe/Cd1−yMnyTe Superlattices
Authors: Chen Chenjia , Wang Xuezhong , Li Haitao , Liang Xiaogan , Chai Guangyu , Ning Zheng , Wang Xun 
Published: April 2011

AbstractPhotoreflectance spectroscopy has been peformed on a series of Cd1−xMnxTe/Cd1−yMnyTe superlattices. Samples were grown on (001) GaAs substrates by molecular-beam epitaxy with different barriers (x=0.3 to 0.8) and wells (y=0 to 0.01). After taking into consideration the strain-induced and quantum confinement effects, the exciton transition energies of the heavy and light holes can be determined using envelope-function calculations. The calculations are in good agreement with the photoreflectance measurement results. These results show that photoreflectance is a powerful probe for the study of quantized state structures in superlattices.
Determination of Optical Properties of Fluorocarbon Polymer Thin Films by a Variable Angle Spectroscopic Ellipsometry
Authors: Lee Kang-Kuk , Park Jin-Goo , Shin Hyung-Jae 
Published: April 2011

AbstractOptical properties of vapor phase (VP) deposited and spin-coated fluorocarbon (FC) thin films on silicon substrates, such as refractive index, extinction coefficient and film thickness were characterized by a variable angle spectroscopic ellipsometry (VASE) in the range of 300–800 nm. A Lorentz model allows us to simulate the optical constants of the FC films with a minimum number of parameters while maintaining Kramers-Kronig (KK) consistency between the real and imaginary parts of the optical constants. FC films are nearly transparent over the visible spectrum, so it is possible to assume k (extinction coefficient) = 0 over part of the visible spectrum in a Cauchy model. To accurately simulate the obtained ellipsometric spectra, we performed a regression analysis in two steps assuming a three-phase and a four-phase model. The regression analysis was performed using the three-phase model and a best-fit mean-squared error (MSE) value of 1.717 (VP deposited FC film, Lorentz model) was obtained. However, the four-phase model was used to improve the best-fit result of 0.531 (VP deposited FC film, Lorentz model). The surface roughness layer was assumed to be a mixture of FC films and voids under the Bruggeman effective medium approximation (EMA). We found that the best-fit MSE was reduced when surface roughness was included.
Optical Properties and Defect Structure of MOVPE InGaN Films
Authors: Cremades A. , Albrecht M. , Ulloa J. M. , Piqueras J. , Strunk H. P. , Hanser D. , Davis R. F. 
Published: April 2011

AbstractA series of 100 nm thick InGaN films with In content up to 14% has been grown by MOVPE on SiC substrates. Optical characterization was carried out by means of reflectance spectrometry, photoluminescence and cathodoluminescence. Optical properties of the samples have been correlated with the microstructural properties measured by atomic force microscopy, transmission electron microscopy and X-ray diffraction data. Results indicate a dependence of the optical properties on the In content in the sample, as well as on the residual stress in the films induced by Indium incorporation. Part of the strain is reduced elastically by formation of pinholes which reach the InGaN/GaN interface, where first misfit dislocations are observed to form. Our results show that luminescence is directly correlated with the strain distribution in the layers. Pinholes are observed to act as nonradiative recombination sites for carriers, while strain relaxation around pinholes may enhance luminescence emission. We discuss the influence of strain with respect to In incorporation, the appearance of piezoelectric fields and effects due to strain induced band bending.
Diamond In-Line Monitors for Synchrotron Experiments
Authors: Bergonzo P. , Tromson D. , Brambilla A. , Mer C. , Guizard B. , Foulon F. 
Published: April 2011

ABSTRACTDiamond polycrystalline films have been synthesised using the Chemical Vapour Deposition (CVD) technique in order to fabricate new types of photo-detectors for the characterisation of x-ray light sources as encountered in synchrotron experiments. Since diamond exhibits a low absorption to low energy x-ray photons, these devices allow beam position monitoring with very little beam attenuation at photon energies as low as 2 keV. We present here diamond based new devices for four different applications, including (i) semitransparent beam intensity and (ii) position monitors with high position resolution (< 2 µm), (iii) beam profile monitors with 20 µm pitch resolution, and (iv) ultra-fast diamond detectors (response time < 100 ps) that enable the intensity and temporal monitoring of fast x-ray pulses. These devices can be used for in-line characterisation of synchrotron beam line experiments for permanent in-situ monitoring of beam instabilities during experiments as well as for synchrotron machine diagnostics.
Resonant x-ray Scattering From the Surface of a Dilute Liquid Hg–Au Alloy
Authors: DiMasi E. , Tostmann H. , Ocko B. M. , Huber P. , Shpyrko O. G. , Pershan P. S. , Deutsch M. , Berman L. E. 
Published: April 2011

ABSTRACTWe present the first resonant x-ray reflectivity measurements from a liquid surface. The surface structure of the liquid Hg-Au alloy system just beyond the solubility limit of 0.14at% Au in Hg had previously been shown to exhibit a unique surface phase characterized by a low-density surface region with a complicated temperature dependence. In this paper we present reflectivity measurements near the Au LIII edge, for 0.2at% Au in Hg at room temperature. The data are consistent with a concentration of Au in the surface region that can be no larger than about 30at%. These results rule out previous suggestions that pure Au layers segregate at the alloy surface.
3-D Measurement of Deformation Microstructure in Al(0.2%)Mg Using Submicron Resolution White x-ray Microbeams
Authors: Larson B.C. , Tamura N. , Chung J.-S. , Ice G.E. , Budai J. D. , Tischler J. Z. , Yang W. , Weiland H. , Lowe W.P. 
Published: April 2011

ABSTRACTWe have used submicron-resolution white x-ray microbeanis on the MHATT-CAT beamline 7-ID at the Advanced Photon Source to develop techniques for three-dimensional investigation of the deformation microstructure in a 20% plane strain compressed Al(0.2%)Mg tri-crystal. Kirkpatrick-Baez mirrors were used to focus white radiation from an undulator to a 0.7 × 0.7 μm2 beam that was scanned over bi- and tri-crystal regions near the triple-junction of the tricrystal. Depth resolution along the x-ray microbeam of less than 5 microns was achieved by triangulation to the diffraction source point using images taken at a series of CCD distances from the microbeam. Computer indexing of the deformation cell structure in the bi-crystal region provided orientations of individual subgrains to ∼0.01°, making possible detailed measurements of the rotation axes between individual cells.
Synchrotron Radiation X-ray Microdiffraction Study of Cu Interconnects
Authors: Zhang X. , Solak H. , Cerrina F. , Lai B. , Cai Z. , Ilinski P. , Legnini D. , Rodrigues W. 
Published: April 2011

ABSTRACTWe have used synchrotron radiation x-ray microdiffraction to study the microstructure and strain variation of copper interconnects. Different types of local microstructures have been found in different samples. Our data show that the Ti adhesion layer has a dramatic effect on Cu microstructure. On site electromigration test has been conducted and strain profile along the same interconnect line was measured before and after this electrical stressing. Cu fluorescence scan was used to find the mass variations along the line. Voids and hillocks can be clearly identified in this scan. x-ray micro-diffraction was used to measure the strain change around the interesting regions.