bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structures of Bonding Interface by Forming Hydrogen Bridges
Authors: Nagakubo M. , Suzuki H. , Idogaki T. , Hattori T. 
Published: April 2011

AbstractDirect bonding by forming interface hydrogen bridges has been investigated for both combinations of AI.Si and Al.PZT{Pb(Zr,Ti)03). Hydrogen bridges are formed between OH-groups and oxygen atoms on each bonding surface. Therefore, the surface adsorbing of OH-groups (hydrophilic treatment) is required to the pre-treatment of bonding surface. In this study, two ways of conventional hydrophilic treatment by wet-process and novel treatment by the surface bombardment of hydro-ions(H2O+, OH+, O+, and others) in vacuum (dry-process) have been examined.Each bonding surface is contacted in the air after the hydrophilic treatment. In the case of hydrophilic treatment by wet-process, the bonding strength of Al-Si shows about 20 MPa after the heat treatment of above 350°C. As for the dry-process, both combinations of At.Si and AI.PZT are bondable, and their strength shows the similar tendency as wet-process with the time and the temperature of heat treatment. However, the bonding area increases more quickly than the ones of wet process. From the results of SIMS and cross-sectional TEM observation of AlSi bonding interface, it is suggested that these bonding are caused by the hydrogen bond formation without interfacial water molecules.
High Resolution Electron Microscopy and Computer Simulation Studies of the Atomic Structure of Tilt Boundaries in TiO2
Authors: Liu Yaping , Majid Imtiaz , Vander Sande John B. 
Published: April 2011

AbstractThe atomic structure of [001] tilt grain boundaries of Σ25 (210), Σ5 (310), Σ213 (320) and Σ217 (410) in TiO2 (rutile) were studied using high resolution electron microscopy and computer simulation. Regularly separated small steps (1/2 [120] high) and big steps (3/2 [120] high) which contain secondary dislocations were found in the (210) boundary as a result of deviation from the exact Σ5 misorientation and (210) symmetric plane. Similar steps were also found in (310) and (320) boundaries. Flat segments between the steps were found to have very accurate misorientation of their, Σ's and a nearly symmetric boundary plane. Their rigid body translation, volume expansion and relaxed structures were determined by comparing HRTEM images with computer calculated structures and simulated images. An irregular core structure was found in the (410) boundary when its misorientation deviated 2° from the exact Σ17 misorientation.
The Interaction of Twin Boundaries with Grain Boundaries in YBa2Cu3O7-δ
Authors: Wang Jenn-Yue , King Alexander H. 
Published: April 2011

AbstractTwins in YBa2Cu3O7-δ may be “correlated” at [001] tilt grain boundaries (i.e. twin boundaries from one grain may meet twin boundaries from the other grain in quadruple junctions) and the twins may also be narrowed or “constricted” at the boundary. These effects are more pronounced in the regime of small angle grain boundaries. Based on TEM observations, a tentative threshold misorientation angle of approximately 15° is identified, below which there is a significant driving force reducing the system energy by correlation. The energies of various grain boundary domain structures associated with the twins were estimated on the basis of the dislocations they contain. Success has been obtained in explaining twin correlation in symmetrical tilt boundaries.
Orientation Relationships and Interfaces Between Low Symmetry Phases in The Yttria-Alumina System
Authors: Hay R. S. 
Published: April 2011

AbstractInterphase boundaries and orientation relationships for yttria - yttrium-aluminum monoclinic and yttrium-aluminum monoclinic - yttrium-aluminum perovskite eutectics were observed by standard and high resolution TEM techniques. Three and five orientation relationships were found for each system, respectively. These eutectics all had a monoclinic phase and therefore had little potential for high symmetry overlap. In many cases low index planes with similer spacings or spacing multiples were parallel. However, presence of a monoclinic phase made definition of a three-dimensional low index near-CSL very difficult, so a combination of planes corresponding to reciprocal-space directions and zones corresponding to real-space directions were often needed for a geometric description of the orientation relationship. In general, two planes and the real-space direction corresponding to the zone for these planes described the orientation relationships. The disregistry between reciprocal-space coincidence sites was not localized by dislocations large enough to be visible.
Effects of Annealing on The Structure of Ta2N Thin Films Deposited on Al2O3
Authors: Angelo James E. , Moody N.R. , Venkataraman S.K. , Gerberich W.W. 
Published: April 2011

AbstractThe microstructure of Ta2N thin films deposited by d.c. magnetron sputtering on (1120) surface of Al2O3 is investigated using transmission electron microscopy. The effects of exposing the thin film structure to a 600°C air environment are also explored. It will be shown that under the standard deposition conditions, stresses exist in the thin film structure which leads to the formation of a textured structure in the as-deposited Ta2N. Exposure of the thin film structure to an air environment transforms the Ta2N to Ta2O5 in the orthorhombic structure. In addition, evidence for a epitaxial relationship between the Ta2O5 and Al2O3 will be presented.
The Stability of MoSi2 Films in Vacuum and Oxidizing Atmospheres
Authors: Kolaya L.E. , Duquette D.J. , Hudson J.B. 
Published: April 2011

AbstractThe stability of MoSi2, films with respect to mass loss at high temperature has been investigated in vacuum and dry air environments at temperatures up to 1300° C. Samples were sputter deposited films of approximate composition MoSi3, on sapphire substrates. Post heat treatment analysis by X-ray diffraction, scanning electron microscopy, and electron microprobe analysis indicated that the films recrystallized, and that phase separation of the excess silicon from the MoSi2, occurred early in the heating process. With continued heating, silicon was lost from the films by evaporation, leading to the conversion of the films to Mo5Si3. The rate of mass loss was much less in the air environment due to the formation of a SiO2, layer which served as a diffusion barrier to silicon. Evidence of a reaction along the MoSi2,/A12O3 interface was observed visually, but could not be detected chemically.
Low Temperature - High Pressure Oxidation of 3C-SiC
Authors: Caragianis-Broadbridge Christine , Walden Barbara L. , Blaser Juliana , Yang Cleva Ow , Paine David C. 
Published: April 2011

AbstractSingle crystal films of n-type 3C-SiC were hydrothermally processed at pressures ranging from 10 to 70 MPa at 550°C. To study the effects of initial thin film microstructure on hydrothermal processing, two different samples of CVD-grown SiC were studied: one, 200 nm thick, contained low angle boundaries and a high density of planar defects; the other, 3500 nm thick, was planar and contained relatively few defects. Raman Spectroscopy, X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were used to study the chemistry and microstructure of the SiC material both before and after hydrothermal treatment. This study reveals that low temperature (T=550°C) oxidation of single crystal epitaxial SiC is possible but that the resulting oxide film microstructure is strongly dependent on the initial film microstructure and oxidation is greatly enhanced along low angle grain boundaries and on planar defects.
Thermodynamic Stability of Binary Oxides in Contact with Silicon
Authors: Hubbard K. J. , Schlom D. G. 
Published: April 2011

AbstractUsing tabulated thermodynamic data, a comprehensive investigation of the thermodynamic stability of binary oxides in contact with silicon at 1000 K was conducted. Reactions between silicon and each binary oxide at 1000 K, including those involving ternary phases, were considered. Sufficient thermodynamic data exists to conclude that all binary oxides except the following are unstable in contact with silicon at 1000 K: LiO2, the alkaline earth oxides (BeO, MgO, CaO, SrO, and BaO), the column IIIB oxides (Sc2O3, Y2O3, and Re2O3 where Re is a rare earth), ThO2, ZrO2, HfO2, and Al2O3. Of these remaining oxides, sufficient thermodynamic data exists to conclude that MgO, CaO, and ZrO2 are thermodynamically stable in contact with silicon at 1000 K.
Interfaces of Ionically Conducting Materials: Electrochemical Properties
Authors: Maier Joachim 
Published: April 2011

AbstractThis contribution summarizes former results and presents recent findings concerning interfacial properties in solid state ionics but also stresses the model role of ionic conductors for typical ceramic problems. Moreover, recently developed and improved electrochemical techniques allowing spatial resolution are discussed, viz. a two-dimensional impedance spectroscopy as well as a combination of microelectrochemistry and atomic force microscopy.
Growth and Structure of Al/MgO Interfaces
Authors: Wagner T. , Ruhle M. 
Published: April 2011

AbstractThe A1/MgO system has been used as a model system to study growth processes and structure at metal/ceramic interfaces. Aluminum films were grown on air-cleaved MgO (100) substrates in ultra high vacuum (UHV) by molecular beam epitaxy (MBE). The substrates and films were characterized by reflection high energy electron diffraction (RHEED), x-ray diffraction (XRD), conventional transmission electron microscopy (CTEM), and high resolution transmission electron microscopy (HREM). XRD measurements exhibited a pronounced {100} texture. Employing electron diffraction in the TEM on cross sectional samples, we observed the following orientation relationship between Al and MgO: (100)A1 II (100)MgO; [010]A1 II [010]MgO. The atomistic structure of the interface was investigated by HREM. Regions of structural defects can be identified clearly at the interface.
Atomistic Study of Energy and Structure of Surfaces in NiO
Authors: Yan M. , Chen S. P. , Voter A. F. , Mitchell T. E. 
Published: April 2011

AbstractThe structure and energy of surfaces in NiO have been studied by atomistic calculations employing short range Buckingham potentials fitted to properties of NiO. The polarizability of lattice anions is included by using the shell model. The results show that the surface energy depends strongly on surface orientation, and the {100} surface has the lowest energy. Surfaces with higher energy prefer to reconstruct into {100} facets to lower their energy and to stabilize their structure.
Theory on the Structure of Twin Boundaries in La2−x,BaxCuO4
Authors: Cai Zhi-Xiong , Welch David O. 
Published: April 2011

AbstractThe structure of the twin boundary in the low-temperature-orthorhombic phase of La2−xBaxCuO4 is studied using a Landau-type free energy model which reproduces the x − T phase diagram. The La2−xBaxCuO4 compound has a body-centered tetragonal (HTT) structure at high temperatures. Upon cooling it undergoes a structural phase transition to a low-temperature orthorhombic structure (LTO structure) which is caused by the tilting of the CuO6 octahedra about the (110) and (110) directions. Depending on the doping level x, the LTO structure may go through another phase transition at an even lower temperature to a low-temperature tetragonal phase (LTT phase). We find that the existence of LTT phase greatly changes the characteristics of the twin boundary in the LTO phase. LTT phase exists at twin boundaries of the LTO phase at temperatures well above the LTT to LTO transition temperature.
Auger Electron Spectroscopy of Metallic Film/Laser-Irradiated Alumina Couples
Authors: Park Jaewon , Pedraza Anthony J. , Allen William R. 
Published: April 2011

AbstractAuger Electron Spectroscopy (AES) was employed to study metal/ceramic interfaces. Adhesion pull testing showed that a strong bonding between metallic films and alumina substrates is obtained when alumina is laser-irradiated in an oxygen atmosphere before deposition and, after deposition, the couple is annealed at 300°C for 1 h. On the other hand the gold/alumina bonding is extremely weak when laser-irradiation of the substrate is performed in argon-4% H2. Fresh surfaces were exposed for AES at several distances from the metal/ceramic interface by sputtering the specimens in situ after each analysis. In the region of the interface the sputtering rate was slower than in the film in order to minimize any spurious effect due to ion beam bombardment. AES of a gold/alumina couple prepared in this way reveals that the Auger peaks of gold from the film and oxygen and aluminum from the alumina substrate, when the substrate was irradiated in oxygen atmosphere, shift by ∼ 1.5 eV, 1.6eV, and 1.4eV respectively when the analysis area encompasses the metal/ceramic interface. On the other hand, no shift of the Auger peaks are observed at the interface when the laser-irradiation was performed in argon-4%H2. In the case of copper deposited on alumina laser-irradiated in an oxygen atmosphere, an interfacial compound is formed. This compound is a double oxide of aluminum/copper or two separated oxides, and promotes strong copper/alumina bonding.
Band Offsets of InAsxP1−X/InP Strained Layer Quantum Wells Grown by Lp-Movpe Using TBAs
Authors: Beaudoin M. , Masut R.A. , Isnard L. , Desjardins P. , Bensaada A. , L'Espérance G. , Leonelli R. 
Published: April 2011

ABSTRACTLow temperature optical absorption spectra are presented for a series of InAsxP1-x/InP strained layer multiple quantum well structures (0 < x = 0.35) grown by low pressure metal organic vapor phase epitaxy (LP-MOVPE) using trimethylindium (TMIn), tertiarybutylarsine (TBAs) and phosphine as precursors. The well widths and compositions in these structures are determined from high resolution x-ray diffraction and transmission electron microscopy. The absorption spectra are then analyzed by fitting the excitonic peak energy position with transition energies determined from a solution to the Schrödinger equation. We used the envelope function formalism with the Kane bands as the basis wavefunctions and included corrections for non parabolicity. From these fits and elasticity theory, both the bandgap of unstrained InAsxP1-x and the band offsets of these heterostructures are deduced self-consistently. The conduction band offsets are found between 72% and 75% of the total strained bandgap differences.
Epitaxial Growth of Aluminum Nitride on Sapphire and Silicon
Authors: Dovidenko K. , Oktyabrsky S. , Narayan J. , Razeghi M. 
Published: April 2011

ABSTRACTThe microstructural characteristics of wide band gap semiconductor, hexagonal A1N thin films on Si(100), (111), and sapphire (0001) and (10ī2) were studied by transmission electron microscopy (TEM) and x-ray diffraction. The films were grown by MOCVD from TMA1 + NH3 + N2 gas mixtures. Different degrees of film crystallinity were observed for films grown on α-A12O3 and Si substrates in different orientations. The epitaxial growth of high quality single crystalline A1N film on (0001) α-Al2O3 was demonstrated with a dislocation density of about 2*10 10cm−2 . The films on Si(111) and Si(100) substrates were textured with the c-axis of A1N being perpendicular to the substrate surface.
Possible Mechanisms for Photoluminescence in Spark-Processed Si
Authors: Hummel R.E. , Ludwig M.H. , Chang S.-S. 
Published: April 2011

ABSTRACTPossible mechanisms which may explain the strong blue/violet (410 nm) photoluminescence (PL) in spark-processed Si (sp-Si) are critically reviewed and discussed. They include involvement of silicon-oxides, silicon-hydrides, silanol groups, siloxene, and silicon carbide. It is concluded from the experimental evidence that none of the above mechanisms can satisfactorily explain the major contribution(s) to PL in sp-Si.
Lattice Relaxation Effects in Si and GaAs Nanocrystals
Authors: Zhao X. S. , Ge Y. R. , Schroeder J. , Persans P. D. 
Published: April 2011

ABSTRACTRaman scattering results on porous silicon, and silicon and gallium arsenide nanocrystals show that almost all vibrational modes become Raman active and remarkably soft in these nanocrystal systems. The experimental results further demonstrate that the carrier-induced strain effects play an important role on the optical properties of such nanocrystal systems.
Nonlinear Optical Properties of Silicon Nanocrystallites: Effects of Passivation
Authors: Seraphin A.A. , Aranda F.J. , Werwa E. , Rao D.V.G.L.N. , Kolenbrander K.D. 
Published: April 2011

ABSTRACTDegenerate four-wave mixing with picosecond pulses at 532 nm has been used to study the third-order nonlinear optical susceptibility (x(3)) for a series of passivated thin films of silicon nanocrystallites. A pulsed laser ablation supersonic expansion source of isolated silicon nanocrystallites was used to deposit thin films onto inert substrates. These films were subsequently passivated using chemical etches or oxidation steps. We observe a strong dependence of the measured x(3) as a function of the degree of passivation, indicating the fundamental importance of the surface of the nanocrystallite in enabling the nonlinear optical behavior. Systems providing more complete passivation were found to have greatly enhanced X(3) behavior when compared to poorly passivated systems. Surface passivation is also shown to be critical to the visible photoluminescence behavior of the thin films, as poorly passivated nanocrystallites exhibit very weak light emission, while well passivated systems show efficient emission. In both cases, the passivation controls the recombination pathways of excited carriers and determines the material's optical properties.
X-Ray Absorption Spectroscopy and Optical Absorption Studies of the Growth of CdS Nanocrystals in Glass
Authors: Persans P. D. , Lurio L. B. , Pant J. , Olsson R. J. , Yukselici H. , Hayes T. M. 
Published: April 2011

ABSTRACTWe have measured and analyzed optical absorption, Raman scattering and x-ray absorption spectra of CdS nanocrystals grown by solid-state reaction in a borosilicate glass. We observe the appearance and growth of an optical absorption peak which is attributed to CdS nanoparticles. Using x-ray absorption we quantify the progressive replacement of O nearest neighbors of Cd by S with heat treatment and the appearance and growth of a well-defined second nearest neighbor peak.
Calculation of the Electronic Structure of Silicon Nanocrystals
Authors: Hill Nicola A. , Whaley K. Birgitta 
Published: April 2011

ABSTRACTThe densities of states for Si nanocrystals with diameters between 15 and 35 Å are calculated using a time-dependent algorithm within the tight-binding approximation [1]. The calculated effects of surface termination and surface relaxation on the electronic properties of Si are shown. The variation in band-gap with cluster size is calculated for clusters up to 60 Å in diameter.
Luminescence and Resonance Raman Spectroscopy of Indirect Excitons in AgBr Nanocrystals
Authors: Pawlik S. , Stolz H. , Von Der Osten W. 
Published: April 2011

ABSTRACTAgBr nanocrystals with radii R ≈ 2.5 to 5 nm comparable with the exciton Bohr radius are produced in inverse micelles. As compared with bulk AgBr, the exciton emission exhibits a substantial blue shift and enhanced intensity due to the spatial confinement. Besides luminescence, first- and second-order resonance Raman scattering is discovered the occurrence of a zero-phonon process clearly revealing mixing of L with Г point states. From time-resolved measurements, exciton lifetimes of the order of 500 μs are found. They are close to the radiative lifetime in the bulk demonstrating that nonradiative processes are negligible in these nanocrystals. In agreement with state mixing, the total decay rate is found proportional to R−2. A small shift of the TO(L) Raman line with excitation photon energy is analyzed in terms of the wavevector dependent interaction of the quantized exciton states with the dispersive phonon.
First-Principles Calculation of the Optical Properties of Nanocrystalline Silicon
Authors: Hirao Masahiko 
Published: April 2011

ABSTRACTThe electronic structure and optical properties of nanocrystalline silicon were calculated by the first-principles density functional pseudopotential approach. The calculated energy-gap upshift from the bulk-Si value is nearly proportional to the reciprocal of the crystallite size. Dipole transitions across the gap are weakly allowed and the transition elements decrease rapidly with increases in the crystallite size. The apparent lifetime, the time over which the intensity decreases to 1/e of the initial value, decreases sharply from milliseconds to microseconds within a certain temperature range. The effect of dehydrogenation and the structural stability were investigated using an ab initio molecular dynamics technique. When some of the surface hydrogen atoms are removed, subsequent lattice relaxation eliminates dangling bonds. Further dehydrogenation creates mid-gap states due to surface dangling bonds, which act as nonradiative recombination centers. The calculated results are compared with observations of porous Si.
Comparison of Porous Silicon Etched Gently and Under Illumination
Authors: Filios Adam A. , Tsu Raphael 
Published: April 2011

ABSTRACTPorous silicon samples prepared in the dark under "gentle" etching conditions clearly demonstrate effects of quantum confinement, such as a correlation of the photoluminescence peak energy with the downshift of the Raman line from 521 cm−1 for bulk silicon, and a blue shift in the remaining weak photoluminescence after thermal annealing. On the other hand, samples prepared under illumination as well as those heavily etched in the dark, though luminesce brightly, show no significant effects of quantum confinement, suggesting a different dominant mechanism for the observed luminescence.
Post-Anodization Implantation and CVD Techniques for Passivation of Porous Silicon
Authors: Duttagupta S. P. , Tsybeskov L. , Fauchet P. M. , Ettedgui E. , Gao Y. 
Published: April 2011

ABSTRACTProper surface passivation is critical for achieving stable, efficient PL from light-emitting porous silicon (LEPSi). As-anodized LEPSi is passivated by hydrogen which desorbs at a temperature as low as 400 °C. For device purposes, it is necessary that porous Si can tolerate at least 450 °C for post anodization annealing/metallization steps. We have established that, if the hydrogen at the surface is substituted by oxygen, the resulting Si-Ox passivation is significantly more stable. One way of achieving this is to implant low energy/low dose oxygen to form a thin coating of SiO2 on the surface. Post implantation FTIR data report the absence of Si-H peaks. XPS data indicate the formation of nearly stoichiometric SiO2 at the surface. Similar results were achieved by implanting with nitrogen to form Si3N4. As an alternative to implantation, we have deposited thin capping layers of SiO2, Si3N4 and SiC by plasma-enhanced chemical vapor deposition (PECVD) which resulted in a similar degree of passivation. Wafers were pre-treated at 400 °C to remove hydrogen from the surface. Finally, we carried out a low-pressure CVD (LPCVD) oxide deposition on LEPSi. Post implantation/CVD annealing was done at temperatures up to 600 °C. In most cases, little or no change was observed in the resultant PL intensities.