bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphological Changes in Rod-Shaped Precipitates With Internal Boundaries: Finite Difference Analysis
Authors: Choy Jun-Ho , Hackney S. A. , Lee J. K. 
Published: March 2011

ABSTRACTShape evolution of rod-shaped precipitates due to surface diffusion has been studied under the conditions of constant volume and isotropie interfacial free energy. The shape evolution depends strongly on both the initial aspect ratio and the grain boundary groove angle. For a finite rod with one grain boundary, the morphology evolves into an equilibrium shape made of spherical portions if its aspect ratio and the groove angle are small. Increase in the aspect ratio causes a boundary splitting. For an infinite rod with periodic boundaries, three types of morphological evolutions are observed. When the relationship between the aspect ratio and the groove angle satisfies a certain critical condition, the shape evolves into an equilibrium. If the relationship deviates significantly from this condition, an ovulation process takes place at each location of the internal grain boundaries. When the deviation is intermediate, the morphology undergoes an oscillation in a quasi-dynamic state between the process toward an equilibrium shape and the ovulation process. The ovulation process due to internal grain boundaries is found to precede the Rayleigh spheroidization process.
Kinetics of Explosive Crystallization Phenomena in Amorphous Silicon and Crystal Structure of the Layers Formed
Authors: Glaser E. , Bartsch H. , Andrä G. 
Published: March 2011

ABSTRACTSystematic relations are shown between the parameters controlling explosive crystallization in silicon (temperature, width of a liquid zone, and gradient of melt undercooling), the kinetics of the crystallization process, the predominance of preferential growth directions, and the crystal structure observed. Three typical regions of crystallization are found: (a) cellular growth of a laminated crystalline layer controlled by the formation of high densities of twins at a nearly plane liquid/solid interface, (b) cellular-dendritic growth of crystal lamellae characterized by branching of a curved interface, and (c) formation of a diffuse “slush zone” due to random nucleation in a-Si and grain growth in the liquid zone.
Spinodal Decomposition of the Interface in a Nonlinear Growth Model with Noise
Authors: GoluBovic Leonardo , Karunasiri R. P. U. 
Published: March 2011

ABSTRACTWe consider a non-linear version of Edwards-Wilkinson interface model for the growth in the presence of a collimated partjcie flux. We include both surface tension and surface diffusion relaxation. In a range of positive small values of the surface tension, the interface develops a state which fulfills standard criteria for spinodal decomposition. This suggests the existence of a phase transition from the ordinary state with the interface perpendicular to the incoming flux to a novel, noue.induced state with the interface apontaneously tilted with respect to the direction of the flux.
Impurity Segregation in A/A1−xBx Heterostructures During Liquid Phase Epitaxy
Authors: Cook Stephen J. , Clancy Paillette 
Published: March 2011

ABSTRACTThe segregation behavior of model dopants during liquid phase epitaxy of A/A1−xBx heterostructures is studied using Non-equilibrium Molecular Dynamics computer simulation. Interatomic interactions are modelled using the Lennard-Jones potential and the dopant “B” atoms are assigned to have a different diameter than the host “A” atoms. The extent of segregation as a function of regrowth velocity is found to be well represented by the Continuous Growth Model of Aziz for solidification on the (111) orientation. The mechanism of segregation, however, more closely resembles the physical picture due to Jackson, Gilmer and Leamy.
Surface Microstructural Evolution of Ultrathin films by Real time Spectroscopic Elupsometry
Authors: Collins R. W. , An Ilsinan , Li Y. M. , Wroński C. R. 
Published: March 2011

ABSTRACTVapor deposition of smooth, microstructurally uniform amorphous films on dissimilar substrates requires coalescence of clusters that form during initial nucleation. We have developed techniques that provide sub-monolayer sensitivity to this phenomenon, relying on real time spectroscopie ellipsometry observations during ultrathin film growth (thicknesses < 50 Å). An investigation of tetrahedrally-bonded amorphous semiconductors lends insights into the role of nucleation density and adatom surface diffusion in determining the ultimate atomic-scale roughness on the film.
Simulation of Crystal Growth With Facetted Interfaces
Authors: Roosen Andrew , Taylor Jean E. 
Published: March 2011

ABSTRACTWe present a method for simulation of crystal growth using completely facetted interfaces and the definition of curvature appropriate to such interfaces. The representation of these surfaces, as facets with fixed normal directions, variable distances, and semi-fixed adjacencies, is quite different from that in other methods. It is flexible as to possible growth rules, it appears to avoid the problems involved in measuring curvature and in detecting and making topological changes, and it runs relatively fast. We expect it to be a valid method to approximate growth with any isotropie or anisotropie surface energy and kinetics. The use of the method is demonstrated in dendritic crystal growth and in Ostwald ripening.
Influence of Compression Process on Optical Properties of PDA Langmuir-Blodgett Films
Authors: Yuan Chun-wei , Lu Chun-lin , Liang Yong , Gu Ning , Wei Yu 
Published: March 2011

ABSTRACTIn performing compression-expansion-recompression process during preparation of diacetylene (DA) monolayer, the change in colour of polydiacetylene (PDA) LB films was observed and more ordered structure of the films was achieved. The effect on optical properties could be ascribed to better arrangement of DA monomer which favoured the formation of PDA films in blue-form in polymerization.
Electrochemical Roughening and Annealing of Au(111) Surfaces in Perchloric and Sulfuric Acid Electrolytes Studied by STM
Authors: Hanson Karrie J. , Green Michael P. 
Published: March 2011

ABSTRACTA technique commonly used as the final stage of cleaning gold electrode surfaces is to electrochemically form and reduce a monolayer of oxide on the surface. We have investigated the changes on the Au(111) surface during this procedure using in situ electrochemical scanning tunneling microscopy.
Electrical and Photoelectrochemical Characterization of CDS Particulate Films by Scanning Electrochemical Microscopy, Scanning Tunneling Microscopy, and Scanning Tunneling Spectroscopy
Authors: Zhao Xiao Kang , McCormick Larry , Fendler Janos H. 
Published: March 2011

ABSTRACTCadmium sulfide particulate films have been generated at monolayer interfaces. Controlled and slow infusion of hydrogen sulfide onto compressed monolayers prepared from cadmium arachidate resulted in the formation of covalent metal sulfide bonds at a large number of sites at the monolayer-aqueous interface. The initial nucleation resulted in the downward growth of well-separated, metal-sulfide microclusters which grew in height and width and coalesced into interconnected arrays of semiconductor particles.
X-ray Scattering from Interfaces
Authors: Vlieg E. , Van Der Vegt H. A. 
Published: March 2011

ABSTRACTX-ray diffraction has found an increasing use in the characterization of surface structures. Due to the high penetration depth of X-rays, the technique is also very suitable for the study of buried interfaces. We will give a general outline of the technique, and then discuss two examples concerning epitaxial growth.
In-Situ X-Ray Reflectivity Study on Growth Dynamics of Sputter Deposited Gold on Silicon
Authors: Chiarello R. P. , Kim H. K. , Roberts T. , Miller D. J. , Kampwirth R. T. , Gray K. E. , You H. 
Published: March 2011

ABSTRACTWe performed in-situ x-ray reflectivity measurements to study the growth dynamics of gold sputter deposited onto silicon using an x-ray scattering chamber equipped with a faced magnetron source where the substrate is held at a right angle relative to the sputtering guns. By operating the guns at low power (1 watt) and under 20 mTorr Ar, we could control the gold deposition rate to less than 1Å/sec. The observed x-ray reflectivity for gold deposited onto a silicon substrate at 300 K and 400 K is consistent with nucleated island growth for average gold particle sizes less than 50 Å. Above 50 Å, the reflectivity data indicates that the gold film uniformly covers the silicon surface, and that as the film thickness is increased the gold-vacuum interface gets progressively rougher. Detailed analysis of room temperature data is in progress, as is the temperature dependence on the roughness of the gold vacuum interface.
The Finite Size Effect on The Metal-Insulator Transition of VO2 Films Grown by MOCVD
Authors: Kim Hyung Kook , Chiarello R. P. , You Hoydoo , Chang M. H. L. , Zhang T. J. , LAM D. J. 
Published: March 2011

ABSTRACTWe studied the finite size effect on the metal-insulator phase transition and the accompanying tetragonal to monoclinic structural phase transition of VO2 films grown by MOCVD. X-ray diffraction measurements and electrical conductivity measurements were done as a function of temperature for VO2 films with out-of plane particle size ranging from 60–310Å. Each VO2 film was grown on a thin TiO2 buffer layer, which in turn was grown by MOCVD on a polished sapphire (1120) substrate. The transition was found to be first order. As the out-of plane particle size becomes larger, the transition temperature shifts and the transition width narrows. For the 60Å film the transition was observed at ∼61°C with a transition width of ∼10°C, while for the 310Å film the transition temperature was ∼59°C and the transition width ∼2°C. We also observed thermal hysteresis for each film, which became smaller with increasing particle size.
High-Resolution Leed Study of Intermixing of Fe Films on Au(001) Surface
Authors: He Y.-L. , Wang G.-C. 
Published: March 2011

ABSTRACTUltrathin ferromagnetic Fe films have been grown on an Au(OOl) surface. Using the angular profile measurements of High-Resolution LEED (HRLEED), we show the inho-mogeneities at the interface due to atomic place exchange between Fe and Au atoms can drastically change the angular intensity distributions of diffraction beams. The contributions from the inhomogeneities on the surface can be properly decoupled from the total angular intensity distributions. Through the energy dependent angular profile analysis of diffraction beams, we have quantitatively determined the degree of inhomogeneous atomic intermixing at elevated annealing temperatures.
Electron Microscope Studies of Some Vapor Deposited Materials: Nucleation, Epitaxial Growth and Surface Topography
Authors: Krakow William 
Published: March 2011

ABSTRACTThe nucleation and epitaxial growth of deposits at both low and high temperature substrate conditions and the resulting two and three dimensional growth modes have been investigated using electron diffraction and transmission electron microscopy. At high temperatures, the growth of small particles such as Au, Pt and Ge grown under low rate conditions similar to MBE are revealed by lattice imaging. Using an intermediate bufler layer Ag film, surface growth of (100) and (310) Au thin film layers are revealed by diffraction contrast to be in a step ledge growth regime. While the above investigations were performed ex situ to the microscope vacuum environment, an in situ evaporator has been also been installed on a high resolution electron microscope. Observations can be made in real time of cluster growth from atomic diameters on up. The resulting atomic motion around cluster edges is similar in appearance to surface melting.
Electronic Structure of Defects on Reduced TiO2 (Rutile) Surfaces
Authors: Zhong Qian , Vohs John M. , Bonnell Dawn A. 
Published: March 2011

ABSTRACTSeveral TiO2 (110) surfaces, reduced via different mechanisms, were investigated in ultra-high vacuum using Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) to determine the effect of reduction on the surface atomic and electronic structure. Defect chemistry and its relation to the change of property and structure are discussed.
Growth of Crystalline Superlattices of Aluminum Nitride/Zirconium Nitride on SI(111): Roughness and Layer Interruptions
Authors: Meng W. J. , Heremans J. 
Published: March 2011

ABSTRACTWe report on growth of crystalline superlattices of aluminum nitride/zirconium nitride on aluminum nitride buffered Si(111) substrates. We observed increased buffer layer surface roughness as compared with the buffer/Substrate interface. This roughness in turn influences the quality of the superlattice. We report results of surface morphology examination as a function of growth rate and substrate temperature.
Epitaxial Growth of Bi2Sr2CuO6 Thin Films on Single Crystal Surfaces.
Authors: Matsumoto Takuya , Kawai Tomoji , Kawai Shichio 
Published: March 2011

ABSTRACTEpitaxial growth of Bi2Sr2CuO6 thin films on a SrTiO3, a misoriented SrTiO3 and a Bi2Sr2CaCu2O8 single crystal have been performed using computer-controlled laser molecular beam epitaxy. On the SrTiO3 substrate, the 2201 films consist of two types of domains whose b-axes are perpendicular to each other. In contrast, the 2201 film on the 2212 single crystal has a complete single type of domains. Layer-by-layer growth with a half unit cell thickness of 2201 films is observed.
Crystallization of Amorphous Silicon-Aluminum thin Films: IN-SITU Observation and Thermal Analysis.
Authors: Konno Toyohiko J. , Sinclair Robert 
Published: March 2011

ABSTRACTThe crystallization of sputter-deposited Si/Al amorphous alloys was examined by transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). In-situ high-resolution TEM reveals the existence of an Al layer between the amorphous matrix and the growing crystalline phase. The activation energy for the growth is about 1.2eV, roughly corresponding to the activation energy of Si diffusion in Al. These two observations support the view that a crystallization mechanism, in which an Al buffer layer provides the shortest reaction path, is responsible for the reaction. The product microstructure exhibits secondary crystallization at a higher temperature.
The Importance of Thickness to the Crystallization of Amorphous thin Films
Authors: Cardinale Gregory F. , Farrens S. N. , Howitt D. G. 
Published: March 2011

ABSTRACTThe crystallization of an amorphous thin film, when it is annealed, can be described in terms of the latent heat of the transformation and an activation energy which depends upon the configurational entropy of the surface of the crystallizing interface. An expression is derived for anatase, the low temperature form of titanium oxide, which is consistent with the growth that is observed.
Simulation and Modeling of Kinetics of Silicon Oxidation in the thin Oxide Regime
Authors: Dutta Tirthankar , Ravindra N. M. 
Published: March 2011

ABSTRACTThermal oxidation of Silicon in the thin regime is of vital importance to VLSI device engineers because thin layers of SiO2 are exclusively used as the gate dielectric for high performance of MOS devices. There exists a number of models to explain this kinetics of oxidation. However there is a considerable variance among the reported rate constants, which are supposed to describe the oxidation process. Rather than arriving at an alternative model, the present study aims at simulation of existing models of oxidation in dry oxygen, with a recent set of experimental data and arrive at the best possible model and provide accurate rate constants for oxidation in dry oxygen. These experimental data have been obtained, earlier, using high-resolution transmission electron microscopy (HRTEM) and ellip-sometry techniques to measure thicknesses of silicon oxide, grown at 800° in dry oxygen, in the thickness range of 2–20 nm.
In-Situ TEM Observation of a Structural Change in a Near Σ=3-Twist Boundary In Ordered Cu3Au.
Authors: Tichelaar F. D. , Schapink F. W. 
Published: March 2011

ABSTRACTIn this paper the structure of a (011)-Σ=3 twist boundary in ordered Cu3Au is analysed geometrically. Wrong nearest-neighbour bonds can be avoided by facetting on an atomic scale along common {112} planes, together with a rigid-body translation parallel to one of the facets as measured in earlier work. In the specimen different translational states were found in different areas of the [165]-Σ=3 boundary by transmission electron microscopy (TEM). One of the translations was in agreement with the model, the other was associated with a presumably energetically more unfavourable structure. The in situ observation at 230 °C of the motion of the dislocation separating the different boundary areas was associated with a transformation of the boundary structure with the higher energy into the more favourable structure. Therefore, it is likely that the driving force of the dislocation motion was a difference in boundary energy.
Shape Transformations of Ge Precipitates in Al
Authors: Lours P. , Westmacott K. H. , Dahmen U. 
Published: March 2011

ABSTRACTGe precipitates in Al-Ge alloys have been observed to undergo a transformation in shape during in-situ temperature cycling in a high voltage electron microscope. Octahedral precipitates with a parallel-cube orientation relationship spheroidized on heating and refaceted to the octahedral shape on cooling. This shape transformation was essentially conservative if the temperature excursions were kept small. These observations are discussed in terms of an interface roughening transformation.
The Role of Surface Stress in the Faceting of Stepped Si(111) Surfaces
Authors: Williams Ellen D. , Phaneuf R. J. , Bartelt N. C. , Świe¸ch W. , Bauer E. 
Published: March 2011

ABSTRACTThe nucleation and growth of facets on stepped Si(111) have been observed in real time using the newly developed technique of low-energy electron microscopy (LEEM). The results show that the growth of an isolated facet spontaneously stops at a well-defined size. This is a surprise as classical theories of the growth of linear facets predict a continuous growth, which would only be limited by collisions with neighboring facets. We review predictions that elastic interactions between surface regions of different structure can stabilize finite size domains and facets. We show that a model in which elastic relaxations caused by the facet boundaries stabilize a finite facet width is entirely consistent with the experimental observations.
The Effect of Initial Growth Conditions on the Tilting of Lattice Planes in InP-ON-GaAs Heterostructures
Authors: Riesz Ferenc , Lischka K. , Rakennus K. , Hakkarainen T. , Pesek A. , Koppensteiner E. 
Published: March 2011

ABSTRACTThe relative misorientation (tilt) between the epilayer and substrate (400) lattice planes of InP epilayers grown by gas-source molecular beam epitaxy on (100) GaAs substrates misoriented towards the (110) plane was studied by high resolution x-ray diffraction. For the growth temperature of 490–500°C, the direction of the relative tilt was nearly coincident with the direction of the substrate lattice plane tilting. In contrary, when a buffer layer was deposited at a lower temperature of 400–450°C prior to growth, an azimuthal rotation of about 45° was found between the directions of the relative tilt and the substrate lattice plane tilting. In order to explain the results, a temperature-dependent anisotropic nucleation model is proposed.
The Interaction of Bulk Defects with Surface Reconstructions
Authors: Dunn D. N. , Marks L. D. , Merkle K. L. 
Published: March 2011

ABSTRACTIt is demonstrated by ultra-high vacuum transmission electron microscopy that subsurface dislocations and stacking faults strongly interact with the Au (001) (5×n) surface reconstruction. This effect is found in both bulk single crystal and thin fílm samples.
Analysis of Faceted Growth Hillocks in MOCVD Grown Epitaxial HgCdTe on GaAs with a Nuclear Microprobe
Authors: Jamieson David N. , Dooley S. P. , Russo S. P. , Johnston P. N. , Pain G. N. , Leech P. W. 
Published: March 2011

ABSTRACTHg1-xCdxTe epitaxial layers on GaAs substrates grown by Metal Organic Chemical Vapour Deposition (MOCVD) display growth defects resembling pyramidal faceted hillocks which appear to originate from defects originally present on the substrate. For <100> oriented GaAs substrates and normal growth conditions, these growth defects have an areal density of 1–1000 mm-2. The size of the hillocks depends on the layer thickness and they have the potential to degrade performance of optoelectronic devices fabricated in the epitaxial layers. Nuclear microprobe analysis, performed with a 2 MeV He+ beam focused to less than 5 μm in diameter, has allowed the hillocks to be imaged with the technique of Channeling Contrast Microscopy (CCM). Channeling spectra, obtained by Rutherford Backseat tering Spectrometry (RBS) of the hillocks themselves, showed that the χmin was 13 %. This was similar to the χmin of the high quality single crystal surrounding material. The CCM images also revealed extensive regions of poor channeling, with shapes that suggested that the regions originally arose from scratches in the substrate. These poor channeling regions were not readily observable by other techniques.
In-Situ Transmission Electron Microscopy of the Etching of Silicon (111) Surfaces by Oxygen
Authors: Gibson J. M. , Ross F. M. 
Published: March 2011

ABSTRACTSilicon (111) surfaces have been etched in-situ in a ultra-high vacuum transmission electron microscope. Surface steps are observed to flow during etching, so that Si atoms are removed only from steps. This is in contrast to the behavior during the formation of an oxide layer reported previously. The nucleation of steps and their interaction with surface impurities is described.
Dissolution and Growth Kinetics of Small Crystals in Liquids
Authors: Uttormark Michael J. , Thompson Michael O. , Clancy Paulette 
Published: March 2011

ABSTRACTMolecular Dynamics simulations of the melting of small crystalline clusters (≃800 atoms) in the liquid have been performed at various temperatures above the equilibrium melting point. The melting rates as functions of size and temperature are derived and compared to that predicted by Classical Nucleation Theory. It is found that the driving force for the melting of clusters does not follow the form assumed in the theory, and that this difference is most apparent for clusters containing less than 300 atoms. The implications of these findings on nucleation phenomenon and possible sources for the discrepancies are discussed.
Diffusion Limited Interface Kinetics in Multicomponent Systems
Authors: Hopfe William D. , Morral J. E. 
Published: March 2011

ABSTRACTThe stability of phases in materials can be related to reactions occurring at their interfaces, for example fiber/matrix reactions in composites. The reaction can be modelled in a simple way, even for multicomponent systems, when it is diffusion controlled and when no intermediate phases form. In the current work a model is proposed that assumes local equilibrium at the interface and small concentration differences in each phase. The physical properties required for the model are the “square root diffusivity” for each phase and the applicable phase diagram. The model is applied to predicting concentration profiles and interface velocities for the reaction of a B2 aluminide containing Ni-34at%Cr-12at%Al with various Ni-rich, gamma solid solutions containing Cr and Al. The example shows how varying the gamma composition can alter the aluminide stability with respect to dissolution or growth. In addition, a simplified form of the model is given for extrapolating experimental interface velocity data.