bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulation By Cellular Automata Of The (Re) Crystallization Of A Matrix Containing An Inert Second Phase
Authors: Pezzee C. F. , Dunand D. C. 
Published: March 2011

ABSTRACTTwo-dimensional cellular automata simulations were carried out to study the case of the crystallization (or recrystallization) of a matrix containing an inert, immobile second phase. A range of particle area fractions and aspect ratios were investigated under continuous grain nucleation conditions, assuming that the effect of particles is limited to geometric impingement upon contact with the growing grains. Systematic deviations from the classical Johnson, Mehl, Avrami, Kolmogo-rov equation for single-phase materials are observed with increasing particle aspect ratio and particle fraction. Inert particles also influence both mean size and mean aspect ratio of the final grains.
Two-Stage Crystallization Of Poly (Ether Ether Ketone) And Its Blends With Poly (Ether Imide)
Authors: Chen Hsin-Lung , Porter Roger S. 
Published: March 2011

ABSTRACTThermal Mechanical analysis (TMA) has been used to study the crystallization behavior of poly (ether ether ketone) (PEEK) and its blends with poly (ether imide) (PEI). The two crystallization stages of PEEK are clearly distinguished by measuring the variation of film thickness with time during isothermal crystallization. Upon blending with PEI, the distinction of the two PEEK crystallization stages becomes obscure. This is attributed to the depressions in both nucleation density and spherulite growth rate upon blending with PEI.An Avrami analysis, Modified by considering both primary and secondary crystallization, is used to extract the respective kinetic behavior of these two crystallization stages. The results indicate that the secondary crystallization proceeded slower than the primary crystallization in the diffusion-controlled crystallization region. On the other hand, these two crystallization stages proceeded at comparable rate in the thermodynamically-controlled crystallization region. It is also found in the diffusion-controlled crystallization that blending with PEI induced a larger depression in the secondary crystallization rate than in the primary crystallization rate. Explanations for these observations are proposed and discussed.
High Temperature Dynamic in-Situ Raman Spectral Characterization of Sodium Borosilicate Glasses
Authors: Jillavenkatesa Ajit , Condrate Robert A. 
Published: March 2011

ABSTRACTDynamic Raman spectra of sodium borosilicate glasses containing large amounts of boron oxide have been studied as functions of temperature and holding time. Such characterization enabled measuring the changes in the nature and states of the molecular species that were present in the glasses and their Melts. The data indicate that boroxol rings involving one or more four-coordinated boron ions in the sodium oxide-containing glasses decreased in concentration as they were heated through melt temperatures as was noted earlier for boroxol groups involving three-coordinated boron ions in pure borosilicate compositions.
Study Of Nucleation And Growth Ev Al-Zn Alloys Using TEM
Authors: Sundar G. , Kenik E. A. , Hoyt J. J. , Spooner S. 
Published: March 2011

ABSTRACTNucleation and growth studies were conducted on Al-Zn alloys at several temperatures using transmission electron Microscopy (TEM) with an in-situ furnace. The value of the critical undercooling was established by noting the lowest temperature at which precipitates were no longer observed, following a quench into the two-phase metastable region. These results were compared with the Langer-Schwartz Model of nucleation and growth in which it is predicted that the half-completion time (i.e, the time required for the supersaturation to reach half its initial value) diverges for initial supersaturations which are higher than those predicted by the classical nucleation theory.
Ion Beam Synthesis of Luminescent Si and Ge Nanocrystals in a Silicon Dioxide Matrix
Authors: Atwater H. A. , Shcheglov K. V. , Wong S. S. , Vahala K. J. , Flagan R. C. , Brongersma M. L. , Polman A. 
Published: March 2011

ABSTRACTIon beam synthesis of Si and Ge nanocrystals in an SiO2 Matrix is performed by precipitation from supersaturated solid solutions created by ion implantation. Films of SiO2 on (100) Si substrates are implanted with Si and Ge at doses 1 × 1016/cm2 - 5 × 1016/cm2. IMplanted samples are subsequently annealed to induce precipitation of Si and Ge nanocrystals. Raman spectroscopy and high-resolution transmission electron microscopy indicate a correlation between visible room-temperature photoluminescence and the formation of diamond cubic nanocrystals approximately 2–5 nm in diameter in annealed samples. As-implanted but unannealed samples do not exhibit luminescence. Rutherford backscattering spectra indicate a steepening of implanted Ge profiles upon annealing. Photoluminescence spectra are correlated with annealing temperatures, and compared with theoretical predictions for various possible luminescence Mechanisms, such as radiative recombination of quantum-confined excitons, as well as possible localized state luminescence related to structural defects in SiO2 Potential optoelectronic device applications are also discussed.
Ion Beam Induced Epitaxial Crystallization of Single Crystalline 6H-SiC
Authors: Heera V. , Kögler R. , Skorupa W. , Glaser E. 
Published: March 2011

ABSTRACTFor the first time, ion beam induced epitaxial crystallization (IBIEC) has been found in SiC. The effect of 300 keV Si+ irradiation through an amorphous surface layer in single crystalline 6H-SiC at 477+5°C has been investigated by RBS/C and XTEM. A shrinkage of the amorphous layer was found after ion irradiation at this temperature which is caused by both an ion dose independent thermal regrowth of about 20 nm and an additional ion beam induced epitaxial crystallization with a rate of about 1.5 nm/ 1016 cm−2.
Induced Crystallization In CW Laser-Irradiated Sol-Gel Deposited Titania Films
Authors: Exarhos Gregory J. , Hess Nancy J. 
Published: March 2011

AbstractIsothermal annealing of amorphous TiO2 films deposited from acidic sol-gel precursor solutions results in film densification and concomitant increase in refractive index. Subsequent heating above 300°C leads to irreversible transformation to an anatase crystalline phase. Similar phenomena occur when such amorphous films are subjected to focused cw laser irradiation. Controlled variations in laser fluence are used to density or crystallize selected regions of the film. Low fluence conditioning leads to the evolution of a subtle nanograin-size morphology, evident in AFM images, which appears to retard subsequent film crystallization when such regions are subjected to higher laser fluence. Time-resolved Raman spectroscopy has been used to characterize irradiated regions in order to follow the crystallization kinetics, assess phase homogeneity, and evaluate accompanying changes in residual film stress.
Layer by Layer Amorphization in Si: Temperature, Ion Mass and Flux Effects
Authors: Battaglia A. , Romano G. , Campisano S. U. 
Published: March 2011

ABSTRACTThe layer-by-layer amorphization process is explored in a temperature range in which the kinetics of crystallization can be neglected. It has been found that the pure amorphization rate increases exponentially as the substrate temperature is decreased with an apparent activation energy of 0.48 eV. Moreover the rate increases with both the ion flux and the energy deposited into elastic collisions. A phenomenological model is proposed to explain the experimental results.
A Critical Regime for AMorphization of Ion Implanted Silicon
Authors: Goldberg R. D. , Williams J. S. , Elliman R. G. 
Published: March 2011

ABSTRACTA critical regime has been identified for ion implanted silicon where only slight changes in temperature can dramatically affect the levels of residual damage. In this regime decreases of only 5° C aie sufficient to induce a crystalline-to-amorphous transformation in material which only exhibited the build-up of extended defects at higher temperatures. Traditional Models of damage accumulation and amorphization have proven inapplicable to this regime which exists whenever dynamic defect annealing and damage production are closely balanced. Irradiating ion flux, Mass and fluence have all been shown to influence the temperature—which varies over a range of 300° C for ion species ranging from C to Xe—at which the anomalous behaviour occurs. The influence of ion fluence suggests that complex defect accumulation plays an important role in amorphization. Results are presented which further suggest that the process is nucleation limited in this critical regime.
The Application of Solid Phase Epitaxy for the Incorporation of Substitutional Carbon in Silicon
Authors: Candelaria Jon J. , Watanabe J. K. , Da Vid Theodore N. , Gregory Richard B. , Schroder Dieter K. , Stout Lawrence M. , Cave Nigel G. 
Published: March 2011

ABSTRACTCarbon was substitutionally incorporated into silicon using ion implantation and solid phase epitaxy (SPE) to regenerate a high quality crystalline substrate. Carbon was implanted into Si (100) substrates using a single implant of 25 keV ai doses ranging from 1.75 × 1015 to 1.05 × 1016/cm2. After carbon implantation half of the substrates were amorphized using a silicon implant. All of the wafers were subjected to a 700°C anneal in N2 ambient for 30 Minutes to induce SPE regrowth of the implanted regions. FTIR, SIMS, RBS, and TEM were used to characterize the samples. Results indicate that carbon was substitutionally incorporated into the silicon lattice, but that some carbon did precipitate to form silicon carbide. Post-amorphization improved regrowth of implanted regions in lower dose implanted wafers. Electrical Measurements on diode structures indicate that the band gap was reduced for carbon incorporation at these concentrations.
Trends in Solute Segregation Behavior During Silicon Solidification
Authors: Reitanot Riccardo , Smith Patrick M. , Aziz Michael J. 
Published: March 2011

ABSTRACTAt the high growth rates accessible during pulsed-laser induced melting and solidification and explosive crystallization, crystal growth kinetics are dominated not by equilibrium thermodynamics, but by the atomistic mechanisms by which crystallization proceeds. These Mechanisms can be probed by testing the predictions of solute trapping models based on various crystal/Melt interface structures against Measurements. We have measured the dependence of solute trapping of several group III, IV, and V elements in silicon on both interface orientation and crystallization speed. The Aperiodic Stepwise Growth Model of Goldman and Aziz accurately fits both the velocity and orientation dependence of the solute trapping observed in these systems. The success of the model implies a ledge structure for the crystal/Melt interface and a step-flow mechanism for crystal growth. In addition, we have observed an empirical inverse correlation between the two free parameters (“diffusive speeds”) in this model and the equilibrium solute partition coefficient of a system. This correlation may be used to estimate values of the diffusive speeds for other systems in which solute trapping has not been or cannot be Measured.
Interface Stability During Solid Phase Epitaxy Of Strained GexS1-x Films on Si (100)
Authors: Zeng Xiaobiao , Lee Tan-Chen , Silcox John , Thompson Michael O. 
Published: March 2011

ABSTRACTStrained solid phase epitaxial (SPE) regrowth of amorphous GexSi1-x on Si (100) substrates was studied using time-resolved reflectivity (TRR). Films of CVD-grown Ge0.13Si0.87 on Si were amorphized by Si ion implantation, and subsequently regrown at temperatures between 550°C and 610°. Information on regrowth dynamics and interface roughness evolution was obtained by accurately modeling the complicated TRR data for GexSi1-x regrowth using a Moving, statistically roughening interface. The SPE regrowth rate slowed as the interface crossed into the GexSi1-x layer and the originally planar interface roughened, as confirmed by transmission electron Microscopy. A Minimum in the regrowth velocity was observed after regrowing approximately 60 nm into the GexSi1-x layer; the SPE rate subsequently increased to a final, thickness-dependent velocity that was still below that for pure Si. Upon entering the GexSi1-x layer, the interface roughened quickly to a 15–20 nm amplitude, increasing only slightly more during the remainder of regrowth. The degree of roughening and velocity reduction was found to be dependent on the anneal temperature. In contrast, samples with low Ge concentrations (< 3 at.%) prepared by ion implantation exhibited minimal interface roughening and essentially identical SPE velocities as pure Si.
Nanometer-Scale Oxide Particles in Gesi Films Grown by Wet Oxidation
Authors: Lee Tan-Chen , Soave Robert J. , Shacham-Diamand Yosi Y. , Silcox John 
Published: March 2011

ABSTRACTAmorphous GeSi films with different thicknesses and oxygen contents were electron beam evaporated onto Si (KK)) wafers and wet oxidized at 900 °C for 30 Min. If there was no oxygen in the as-deposited film, an epitaxial GeSi film would be grown after wet oxidation. For the samples with oxygen, epitaxial growth broke down when the thickness of the epitaxy exceeded about 200 A and polycrystalline GeSi films were formed. A dedicated STEM (scanning transmission electron Microscope) was used to characterize the sample after oxidation. STEM BF (bright field), ADF (annular dark field), and energy filtered images revealed the presence of small oxide particles in the polycrystalline GeSi films. X-ray microprobe analysis with a windowless detector was employed to identify the oxide particles. The failure of the epitaxy is explained by the random nucleation and growth of GeSi grains on the oxide particles.
Crystallization of Amorphous Metastable Ceramic PVD-Coatings
Authors: Knotek O. , Löffler F. , Wolkers L. 
Published: March 2011

ABSTRACTCeramic PVD coatings have got very often an X-ray Amorphous structure. This is regarded for all classes of ceramics like covalent and ionic Materials. These Amorphous materials start to crystallize at temperatures about 800 °C, a quite low temperature for the practical use of such Materials. This prevents the propagation of this materials in applications like high temperature wear protection, oxidation resistivity etc.This paper describes several possible techniques to increase the thermal stability of the Amorphous state of ceramic PVD-coatings like A1203 and SiC up to 1200 °C. The best way is the incoporation of an additional element like nitrogen into the thin filmsl. The change of the mechanical properties of alumina leads to new applications like diffusion barriers.
Effects of Glass and Carbon Fiber on Nylon 6,6 Crystallization
Authors: Siangchaew Krisda , Davidson Theodore , Libera Matthew 
Published: March 2011

ABSTRACTThe effects of addition of glass fiber and HMS4 carbon fiber on the crystallization of nylon 6,6 has been investigated using DSC and polarized optical Microscopy (POM). DSC observations indicate that HMS4 fiber lowers the supercooling required to initiate crystallization. A transcrystalline layer is also observed in the near-fiber region of carbon fiber-reinforced composites after DSC. The presence of transcrystallinity and the earlier onset of crystallization for this composite are due to heterogeneous nucleation on carbon fiber surfaces. DSC Measurements of nylon 6,6 with glass fibers show supercoolings similar to those of neat nylon 6,6. Transcrystallinity is also absent in the glass-reinforced composites. These glass fibers appear to be weak nucleation catalysts. Different transcrystalline layer thickness is found to be influenced by thermal processing condition. In addition to transcrystallinity, the HMS4 carbon fiber also influences the bulk morphology of the nylon 6,6.
Multiple Pulse Irradiation Effects in Excimer Laser-Induced Crystallization of Amorphous Si Films
Authors: Kim H. J. , Im James S. 
Published: March 2011

ABSTRACTWe have experimentally Investigated the effects that are associated with Multiple-pulse irradiation in the excimer laser processing of thin Si films on SiO2. Double-pulse irradiation experiments revealed results, which are consistent with that which is known from single-pulse crystallization experiments, and these experiments confirm the applicability of the transformation scenarios, which were derived from single pulse-induced crystallization experiments [1,2]. The results from the Multiple-pulse irradiation experiments clearly show that gradual and substantial grain enlargement can occur — and only occurs — when the irradiation energy density is close to but less than the level that is required to melt the film completely. Based on these findings, we argue that the grain enlargement effect is a near-complete melting phenomenon that is associated with polycrystalline Si films, and we present a grain boundary melting model to account for this phenomenon. A brief discussion on the apparent similarities and physical differences between the observed phenomenon and the solid state grain growth processes is provided herein.
Large Grain Creation and Destruction in Excimer Laser Crystallized Amorphous Silicon
Authors: Boyce J. B. , Anderson G. B. , Fork D. K. , Johnson R. I. , Mei P. , Ready S. E. 
Published: March 2011

ABSTRACTFor fast-pulse laser-crystallized thin-film Si on non-crystalline substrates, the average grain size exhibits a peak as a function excimer laser energy density at a characteristic laserfluence FM. The average grain size increases with increasing laser fluence and can reach a maximum value on the order of 10 pm or about 100 times the film thickness. The grain size then decreases with further increases in fluence. This peak in grain size is accompanied by a similar peak in the Hall electron mobility and x-ray scattering intensity. Our experiments have investigated as-deposited and ion-implanted samples, using a double-scan laser crystallization process. Devices have also been fabricated and studied. The results are consistent with the increase in grain size occurring because of the destruction of nucleation sites with increasing laser fluence (i.e., increased heating and complete Melting). But substrate damage occurs in the vicinity of FM, creating nucleation sites which give rise to small grain sizes in the solidified film. The disruption of the interface causes substantial current leakage through the dielectric of bottom-gate transistors, implying that devices should be laser fabricated below Fm.
Selective Crystallization of A-Si:H Films on Glass
Authors: Yin Aiguo , Fonash Stephen J. 
Published: March 2011

ABSTRACTWe have found that an oxygen plasma exposure of a-Si:H films can cause these films to crystallize with a much lower thermal-budget than that required for the same a-Si:H films without this plasma exposure. Based on this unique finding, a selective area crystallization process has been developed to successfully form patterned polycrystalline Si films. In this study, 1500 Å PECVD a-Si:H films were first covered by 500 Å sputtered SiO2 which was then patterned by lithography to form various islands covered by the SiO2. These patterned films were exposed to an oxygen plasma and were then thermally annealed in a furnace at 600 °C for 6 hours. After this annealing it was found that the islands covered by SiO2 during the oxygen plasma treatment remained a-Si while the oxygen plasma exposed regions were crystallized completely. Both XRD and TEM were used to establish the existance of these controlled regions of a-Si and poly-Si in these films.
Excimer Laser Induced Crystallization of Amorphous Silicon-Germanium Films
Authors: Slaoui A. , Deng C. , Talwar S. , Kramer J. K. , Prevot B. , Sigmon T. W. 
Published: March 2011

ABSTRACTApplication of excimer laser crystallization of Amorphous silicon (a-Si) has introduced a new, interesting potential technology for the fabrication of polycrystalline (poly-Si) thin film transistors. We are currently studying polycrystalline Si1−xGex thin films in order to determine whether this material can lead to improved electrical properties or to better processing requirements when compared with polycrystalline Si films. In this work we analyze by RBS, TEM, Raman spectroscopy and surface reflectance, the structure of thin Amorphous Si1−xGex films after irradiation with a XeCl excimer laser. The Amorphous SiGe films were prepared by evaporation of Si and Ge onto oxidized Si substrates using an electron gun in vaccum. The effects of laser energy fluence during irradiation are investigated. The Amorphous to crystalline transition is followed by in-situ measurement of time-resolved reflectivity.
Kinetics Of Hydrogen Evolution And Crystallization In Hydrogenated Amorphous Silicon Films Studied By Thermal Analysis And Raman Scattering
Authors: Sridhar Nagarajan , Chung D. D. L. , Anderson W. A. , Yu W. Y. , Fu L. P. , Petrou A. 
Published: March 2011

ABSTRACTWe observed the processes of hydrogen evolution and crystallization in hydrogenated Amorphous silicon 0.5–7 μm thick films (deposited by dc glow discharge on Molybdenum) by differential scanning calorimetry (DSC), Raman scattering and thermogravimetric analysis (TGA). Investigation was made as a function of doping, deposition temperature and film thickness. For all the films, an endothermic DSC peak was observed at 694 °C (onset). That this peak was at least partly due to hydrogen evolution was shown by TGA, which showed weight loss beginning at 694 °C, and by evolved gas analysis, which showed hydrogen evolution at 694 °C. This temperature (658–704 °C) increased with increasing heating rate (5–30 °C/min). Doping reduced this temperature from 694 to 625 °C for boron doping and to 675 °C for phosphorous doping. Hydrogen evolution kinetics and FTIR results suggest that the silicon-hydrogen bonding in the intrinsic film was a mixture of SiH and S1H2, and was predominantly SiH in the phosphorous doped films and SiH2 in the boron doped films. Crystallization was independent of silicon-hydrogen bonding in the as-deposited Amorphous silicon film. It was bulk (not interface) induced. No exothermic DSC peak accompanied the crystallization. The film deposition temperature had little effect on the DSC result, but crystallization was enhanced by a higher deposition temperature.
The Mechanism of Excimer Laser-Induced Amorphization of Ultra-Thin Si Films
Authors: Eiumchotchawalit T. , Im James S. 
Published: March 2011

ABSTRACTTo better understand the involved phase transformation Mechanism, we are studying the excimer laser-induced amorphization (ELA) of ultra-thin Si films on oxidized Si substrates. In this paper, we show that the onset of amorphization of hydrogen-free Si films on SiO2 substrates upon increases in the energy density is associated with the onset of complete melting of the film. Once complete melting occurs, further increases in the incident energy density and/or increases in the substrate temperature can lead to incomplete amorphization of the film. Planar view TEM analysis of nearly-amorphized Si films reveals a heterogeneous microstructure, which consists of a mixture of densely dispersed amorphous-like annular regions (∼20 to 40 μm−2), embedded within and typically separated by a region containing finegrained small crystals. Such a cellular microstructure strongly suggests that amorphization occurred not via a homogeneous but via a heterogeneous transformation. In particular, the microstructure paints a scenario in which amorphization proceeded via nucleation of solids, which is then followed by interfacial amorphization. The experimental results unambiguously reveal (1) that the previously proposed criteria of the melt duration and the vertical temperature gradient are irrelevant in determining amorphization of supercooled liquid Si films and (2) that the quenching rate, not surprisingly, is the important parameter.