bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laser Ablation Process and Growth Control of Oxide Thin Films in Laser Molecular Beam Epitaxy
Authors: Kawai T. , Nismkawa H. , Koguchi K. , Kanai M. 
Published: April 2011

ABSTRACTIn order to study mechanism of laser ablation, the time-of-flight spectra of monovalent ions generated by ablation of alkaline earth metals are measured. The obtained spectra show that the ion generation is caused by 5-, 4- and 3-photon processes for Ca, Sr and Ba, respectively, when ArF excimer laser is used as a light source. This behavior suggests that laser ablation of alkaline earth metals is triggered by excitation of electrons at the highest inner-core level. Control of layer-by-layer growth processes by monitoring emission from the ablation plume is also reported. The emission measurement is utilized for estimation of each layer thickness in layer-by-layer growth. This conventional technique is very effective for automatic control of layer-by-layer growth.
Pulsed Laser Deposition and Crystallization of Transparent Conducting Thin Films
Authors: Phillips H. M. , Yunjun Li , Zhaoqi Bi , Binglin Zhang 
Published: April 2011

ABSTRACTTransparent conducting thin films of approximately 1000-2000 Å were deposited on glass, quartz and silicon substrates using standard pulsed laser deposition techniques with two different targets (Sn and SnO2) and with three different laser wavelengths (1.06, 0.532 and 0.266 urn) from a Q-switched Nd:YAG laser. Composite films of SnO2 and Sn with high optical transmission were obtained using a Sn target and a background oxygen pressure of 20 Pa with optical transmission over most of the visible spectrum exceeding 80%. Electrical resistivities of approximately 10-2 Ω-cm were obtained. Using SnO2 targets, predominantly amorphous phase SnO2 films were deposited on Si substrates and then transformed into polycrystalline Sn3O4 by laser induced crystallization (λ = 1.06 μm). The electrical resistivity of these films was also permanently reduced by a factor greater than 1000.
Pulsed Laser Deposition of SrBi2Ta2O9 Thin Films for Nonvolatile Memory Applications
Authors: Werner S. , Thomas D. , Streiffer S.K. , Auciello O. , Kingon Angus I. 
Published: April 2011

ABSTRACTFerroelectric SrBi2Ta2U9 (SBT) thin films were synthesized by pulsed laser deposition (PLD) on platinized silicon substrates held at different substrate temperatures, from targets with different compositions. It was necessary to anneal films deposited at low temperature (525°C) at elevated temperatures in an oxygen atmosphere in order to achieve properties comparable to SBT thin films grown by the sol-gel technique. Polarization – electric field hysteresis loops showed saturation in the 2-5 V range with a remnant polarization 2Pr = 8-13 µC/cm2. Capacitors showed negligible fatigue up to 1010 switching cycles.
Investigation of Electronic Excitation Crystallization Enhancement in Amorphous Gesb Films Upon Ultrashort Laser Pulse Irradiation
Authors: Solis J. , Afonso C.N. , Hyde S.C.W. , Barry N.P. , French P.M.W. 
Published: April 2011

ABSTRACTPulsed laser induced crystallization of amorphous GeSb films has been studied as a function of the laser pulse duration. The energy density crystallization threshold has been determined for pulses in the range from 400 fs to 8 ns. The threshold is observed to increase substantially for pulse durations in the ns range due to the existence of heat flow through the substrate while the pulse is still being absorbed. The energy density crystallization threshold remains constant within the experimental resolution as the pulse duration is decreased down to 800 fs. For the shortest pulse length used, (400 fs), a decrease in the threshold is observed, suggesting the possible existence of electronic excitation enhanced crystallization.
Laser Crystallization and Annealing of Ferroelectric Thin Films
Authors: Zhu J.S. , Lu X.M. , Liu X. , Tian W. , Yang Z. , Wang Y.N. 
Published: April 2011

ABSTRACTFerroelectric PbZr0.44Ti0.56O3 film with pure ferroelectric phase was fabricated by Ar3+ and KrF laser crystallization technique from as-deposited amorphous films, with the substrate at room temperature. Laser annealing technique was also used to improve the quality of BaTiO3 (BT) films.
Excimer-Laser Crystallization of Patterned Si Films At High Temperatures Via Artificially Controlled Super-Lateral Growth
Authors: Song H. Jin , Im James S. 
Published: April 2011

ABSTRACTBased on the artificially controlled super-lateral growth approach, we have developed a novel excimer-laser-based high-substrate-temperature method for producing single-crystal Si islands on SiO2. By irradiating a photolithographically preconfigured sample, complete melting of an Si film is induced only at precisely predesignated locations within patterned and physically isolated islands. An intentionally incompletely melted section within each island initiates lateral growth of crystalline grains. A “bottleneck” portion of the island permits only one of the laterally growing grains to propagate into the main portion of the island. The low nucleation-to-growth-rate ratios that are attainable with high substrate temperatures (1000–1200 °C) can lead to nearly unlimited lateral growth distances; with a proper combination of the substrate temperature and the island dimension, the main area of an island—up to 50×50 μm2 in area—is readily converted into a large single-crystal region.
Laser-Controlled Etching of (Al,Ga)As Epitaxial Layers
Authors: Chong T.C. , Lu Y.F. , Lee A. 
Published: April 2011

ABSTRACTWe report a systematic study of laser-controlled etching behaviors of AlxGa1−xAs epitaxial layers (x from 0 to 0.5) by varying parameters such as laser power, beam scanning speed, beam duty cycle, number of scans and different doping types and concentrations. The laser source was an argon ion laser emitting at 514.5 n-type layers were found to be significantly higher than those for p-type layers. Generally, higher etch rates were observed for layers with higher aluminium mole fraction. The etch rate was found to increase at an exponential rate with the laser power for CW beam, but this increase became linear when a chopped laser beam was used. The dependence of etch rates on different conditions can be largely accounted for by the differences in the built-in electric field at the surface as well as differences in the laser-induced local temperature rise in the layers.
Visible Luminescence from Laser-Induced Stain- and Dry Etched Silicon
Authors: Dimova-Malinovska D. , Tzolov M. , Malinowski N. 
Published: April 2011

ABSTRACTLight emitting silicon has been prepared by Ar laser (514.5 nm) induced stain etching and Nd:YAG impulse (532 nm) laser irradiation in air. Photoluminescence (PL), IR and XPS spectra have been studied. The intensity and position of the PL depend on the power or the energy and the duration of laser beam treatment during the etching. Correlation between the PL and chemical bonding is discussed.
Laser - Assisted Synthesis of Unique Graded Surface Composites
Authors: Singh R.K. , Fitz-Gerald J. 
Published: April 2011

ABSTRACTWe have developed a novel laser assisted method to fabricate unique modified surface composites which have industrial applications ranging from improved adhesion of coatings to improved bio-compatibility. The surface consists of two materials with linear variation in composition, thus leading to linear variation in thermal expansion coefficients. The fabrication process is based on the use of a pulsed excimer laser with an energy fluence near the ablation threshold. Using this method we have been able to create adherent diamond coatings on cutting tool materials, high surface area bio-compatible hydroxyapatite ceramics and Mo/W surface composites. This process has also increased the adhesion of coatings in large thermal mismatched systems like diamond on steel substrates.
Laser Induced Nanofabrication on Titanium Thin Films
Authors: Huey B.D. , Bonnell D.A. , Akhsakhalian A.D. , Gorbunov A.A. , Sewing A. , Pompe W. 
Published: April 2011

ABSTRACTIllumination of titanium thin films with an argon-ion laser has been used to fabricate nanometer scale features by localized oxidation. The laser induces a temperature gradient in the metal film, within which oxidation may occur. Due to the non-linearity of the reaction with temperature, the reaction zone can be laterally confined to regions narrower than the diffraction limit of optical resolution. Scanning probe microscopy indicates widths ranging from 105 to 600 nm and heights of 0.8 to 30 nm. The possibility of forming novel structures is demonstrated.
Laser-induced Reactions in a Deep UV Resist System: Studied with Picosecond Infrared Spectroscopy
Authors: Lippert T. , Koskelo A. , Stoutland P. O. 
Published: April 2011

ABSTRACTOne of the most technologically important uses of organic photochemistry is in the imaging industry where radiation-sensitive organic monomers and polymers are used in photoresists. A widely-used class of compounds for imaging applications are diazoketones; these compounds undergo a photoinduced Wolff rearrangement to form a ketene intermediate which subsequently hydrolyses to a base-soluble, carboxylic acid. Another use of organic molecules in polymer matrices is for dopant induced ablation of polymers. As part of a program to develop diagnostics for laser-driven reactions in polymer matrices, we have investigated the photo-induced decomposition of 5-diazo-2,2-dimethyl-l,3-dioxane-4,6-dione (5-diazo Meldrum's acid, DM) in a PMMA matrix using picosecond infrared spectroscopy. In particular, irradiation of DM with a 60 ps 266 nm laser pulse results in immediate bleaching of the diazo infrared band (v = 2172 cm-1). Similarly, a new band appears within our instrument response at 2161 cm-1 (FWHM = 29 cm-1) and is stable to greater than 6 ns.; we assign this band to the ketene photoproduct of the Wolff rearrangement. Using deconvolution techniques we estimate a limit for its rate of formation of τ < 20 ps. The linear dependence of the absorbance change with the pump power (266 nm) even above the threshold of ablation suggest that material ejection take place after 6ns.
Influence of the Shape and Size of ahe Laser Spot on the Spatial Distribution of the Plasma Plume
Authors: Mele A. , Giardini Guidont A. , Kelly R. , Miotello A. , Orlando S. 
Published: April 2011

ABSTRACTPulsed laser deposition may be accomplished by irradiating a target with a high intensity laser pulse. The flux of particles moving from the target to the substrate obeys gas-dynamic laws when the density of the emitted particles exceeds ∼1 monolayer/(10 ns). The angular distribution of the plume, which depends on various factors, will strongly affect the deposit characteristics. It has been found that an intensified CCD camera can be successfully used to analyze laterally in two orthogonal directions the profile of the expanding plume. A marked influence of laser spot dimension and shape on plume dynamics is observed for laser ablation of a number of materials such as metals, semiconductors and high Tc superconductors.
Study of Glass Transition Based on the Fragmentation Model
Authors: Masaki Y. , Kitagawa A. , Suzuki M. 
Published: April 2011

ABSTRACTGlass transition phenomena for a fictive V2-VI3 compound have been described on the basis of fragmentation model in which glass materials begin to fragmentize at a certain temperature and the fragment size becomes small with increasing temperature. By a numerical calculation, the heating rate dependence of glass transition temperature was clearly presented, and fragment sizes at glass transition and melting temperature were estimated as 1.4μm and 20Å respectively. Further, thermodynamic aspects were discussed using the model and it was concluded that the glass transition is a sort of the first order transition.
On the Shape Evolution of Coherent Precipitates: Discrete Atom Method
Authors: Lee Jong K. , Choy Jun H. 
Published: April 2011

ABSTRACTMorphological evolution of coherent precipitates with arbitrary transformation strain is studied via a discrete atom method. With a purely dilatational misfit strain, a soft precipitate tends to have a plate-like equilibrium shape, whereas a hard precipitate takes up a shape of high symmetry such as a circle. If the stiffness is comparable between the matrix and precipitate, however, the equilibrium shape depends on the degree of anisotropy, misfit strain, size, and interfacial energy. Shape bifurcation phenomena from circular to rectangular shapes are also revealed during clustering. With either a tetragonal misfit strain of mixed signs or a pure shear misfit strain, a precipitate takes up a plate-like shape whose major axis lies along the direction containing an invariant line in accordance with the continuum elasticity prediction. Both elastic anisotropy and elastic inhomo-geneity exert little influence on the preferred orientation relationship. With a misfit strain of combined shear and dilatation, a precipitate follows an orientation and shape dictated by both components of the misfit strain.
Simulation by Cellular Automata of the Crystallization of a Matrix Containing a Mobile Second Phase
Authors: Shelton R.K. , Dunand D.C. 
Published: April 2011

ABSTRACTTwo-dimensional cellular automaton computer simulations were carried out to model the geometric interaction between growing matrix grains and mobile, equiaxed particles, thus simulating crystallization (respectively, recrystallization, phase transformation or solidification) of a material containing mobile particles. As a result of particle pushing by growing grains, particle accumulation at grain boundaries and triple-points and concomitant particle depletion within grains occurs. A range of grain nucleation rate, particle area fractions and particle settling rate was investigated under continuous grain nucleation conditions. While these parameters do not change the crystallization kinetics or grain size or shape, they strongly affect the particle spatial distribution and clustering during and after crystallization.
Observation of Crystallization, Precipitation, and Phase Transformation Phenomena in Si Rich Titanium Silicide Thin Films
Authors: Domenicucci A. , Gifford G. , Clevenger L.A. 
Published: April 2011

ABSTRACTCrystallization, precipitation, and phase transformation phenomena were observed in titanium suicide thin film samples during in situ heating experiments in a transmission electron microscope. The as-deposited TixSiy films were 110 nm in thickness with a composition of 1 Ti to 2.33 Si. Crystallization of the C49 phase was followed isothermally near the sputter deposition temperature. The movement of individual grain boundaries was recorded so that a “velocity of crystallization” could be calculated. The precipitation of excess silicon from the C49 phase was first observed in the 650°C to 750°C temperature range. The precipitates were predominantly of the incoherent type, with a smaller number existing at the grain boundaries. Ostwald ripening then occurred up to the C49 to C54 phase transformation which was accompanied by a dramatic increase in grain size. Grain boundary movement during the phase transformation was such that large precipitates, which were originally at C49-C49 boundaries, ended up within resulting C54 crystals. Many of these larger precipitates were found to exist as epitaxial “islands” at the TiSi2/Si substrate interface.
Competitive Phase Selection in Fe-Ni Alloy Droplets
Authors: Gärtner F. , Norman A. F. , Assadi H. , Greer A. L. 
Published: April 2011

ABSTRACTIn the solidification of Fe-Ni droplets (≤ 30 at.% Ni), the selection of different microstructures is dominated by the competition between the bcc and ccp phases. In drop-tube experiments ccp is the primary phase in some dilute (up to 7at% Ni) alloys although the bcc phase is favoured by a lower free energy and by a lower interfacial energy with the liquid. Competitive dendrite growth is a possible explanation for the formation of primary ccp. Comprehensive thermodynamic (CALPHAD) and kinetic modelling is undertaken to understand the growth competition. The origin of the observed primary phases is discussed.
Order-Disorder Transformations in the σ3 (111)/[110] Symmetrical Tilt Boundary in Tungsten
Authors: Wang Gui Jin , Vitck V. 
Published: April 2011

ABSTRACTThe structure of the σ3 (111)/[110] symmetrical tilt boundary in tungsten was modeled by molecular statics using Finnis-Sinclair type many body potentials. Several multiple structures have been found which are composed of two types of structural units and the interaction energy between these units is negative. Hence, order-disorder structural transitions may occur in the boundary with structures being ordered and/or disordered mixtures of the two units. The uansilion temperature is found to be 1158K if only the internal energy and configurational entropy arc included when evaluating the free energy. However, the transition temperature is 782K if the vibrational entropy is also incorporated. This demonstrates that the vibrational contribution to the entropy may be as important as the configurational contribution when considering the inierfacial transformations.
Energetics of Manganese Oxides
Authors: Fritsch S. , Navrotsky A. 
Published: April 2011

ABSTRACTThe energetics of some manganese oxides : pyrolusite ΜnO2, bixbyite Μn2O3, hausmannite Μn3O4 and manganosite MnO were studied by transposed temperature drop calorimetry and high temperature drop solution calorimetry in molten 2PbOB2O3 at 977 K. The enthalpies of oxidation at 298 K in the Mn-O system, determined by appropriate thermodynamic cycles, are (in kJ/mol O2) : −441.4 ± 5.8 for the reaction 6 MnO + O2 -> 2 Mn3O4, −201.8 ± 8.7 for 4 Mn3O4 + O2 -> 6 Mn2O3 and −162.1 ± 7.2 for 2 Mn2O3 + O2 -> 4 ΜnO2 These values agree very well with previous data obtained by equilibrium ρθ2 measurements and indicate that direct calorimetrie measurements are well suited to obtain reliable enthalpy of formation data for oxides containing manganese in the 2+, 3+ and 4+ states. The phase diagram of the Mn-O system was calculated using these new values of enthalpies.
In Situ Cross-Sectional Scanning Tunneling Microscopy Sample Preparation Technique
Authors: Kim Y.-C. , Nowakowski M. J. , Seidman D. N. 
Published: April 2011

ABSTRACTA novel in situ sample cleavage technique has been developed for fabricating specimens for cross-sectional scanning tunneling microscopy (XSTM) applications. This technique can be easily adapted to any ultrahigh vacuum (UHV) STM that has a coarse motion capability. A conducting diamond STM tip is used to create micron long scratches on Ge/GaAs or GaAs {001 }-type surfaces. These {001} surfaces are imaged with STM to observe scratch characteristics, and GaAs samples are cleaved to reveal {110}-type faces. Atomic resolution images of {110}-type GaAs surfaces are readily and reproducibly obtained.
Microstructural Evolution of Co2GaAs Thin Film on GaAs Substrate
Authors: Shin D.W. , Park C.G. , Kwak J.S. , Baik H.K. 
Published: April 2011

ABSTRACTInterfacial reactions and epitaxial growth of the microstructure between cobalt thin film and (100)-oriented GaAs substrate have been studied, using X-ray diffraction, transmission electron microscopy and EDS analysis. Cobalt thin films were deposited by e-beam evaporation, and were subsequently annealed at 400 °C.The reaction layer evolved due to the annealing was identified as the ternary phase, Co2GaAs, that was grown epitaxially on the substrate. The new orientation relationship between Co2GaAs and GaAs substrate was found as <110>Co2GaAs // <100>GaAs and {001}Co2GaAs // {011}GaAs. These results can be well explained upon matching the unit cells of Co2GaAs and GaAs. Upon the annealing at 600°C, the Co2GaAs phase is usually decomposed to stable binary phases, CoGa and CoAs.
The Effect of Substrate Misorientation on the Evolution of Surface Morphology in Epitaxially Grown CaF2/Si(111) Heterostructures
Authors: Kim B. M. , Soss S. R. , Overney R. M. , Schowalter L. J. 
Published: April 2011

ABSTRACTWe have studied the effect of substrate misorientation on the evolution of surface morphology in lattice-mismatched heterostructures for molecular beam epitaxial growth of a thin insulator (CaF2) on vicinal Si(111) surfaces with in-situ reflection high energy electron diffraction (RHEED) and ex-situ atomic force microscopy (AFM). At a substrate temperature of 770 °C, CaF2 growth is initiated by the formation of a reacted CaF layer followed by the complete overgrowth of an additional CaF2 monolayer (ml). However, CaF2 growth beyond these two ml depends on the degree of miscut of the Si substrate. On Si substrates tilted toward the [112] by a miscut angle ≥ 0.5°, the atomic step edges on the Si surface bunch together forming flat terraces that are ∼200 nm wide. In this case, the CaF2 growth beyond 2 ml proceeds by the nucleation and lateral propagation of thick CaF2 islands (whose height is determined by the step bunches) along the bunched step edges to eventually form a complete overlayer. For CaF2 films grown on substrates with a miscut angle < 0.5°, the CaF2 layer remains relatively uniform without the formation of thick islands. With further deposition, evidence for a dense network of misfit dislocations is observed on the surface of the CaF2 film.
Coarsening and Slope Selection During Crystal Growth and Etching of Ge(001)
Authors: Jay Chey S. , Van Nostrand Joseph E. , Cahill David G. 
Published: April 2011

ABSTRACTThe evolution of surface morphology during low temperature crystal growth by molecular beam epitaxy and etching by low-energy ions is characterized by in-situ scanning tunneling microscopy. Epitaxial growth of Ge(001) at low temperatures in the vicinity of 155°C produces a pattern of growth mounds while etching at temperatures near 270°C produces a pattern of low aspect ratio pits. The characteristic in-plane length scale of the surface roughness d increase with a power law dependence on time but the exponent depends on temperature and process. Prior to the onset of amorphous growth, the amplitude of the surface roughness G1/2(d/2) increases more rapidly than d; i.e. the slope of the sides of the growth mounds increases with time. By contrast, the ratio of Gl/2(d/2) to d remains nearly constant during ion etching for a wide range of etching times.
On the Roughening of Ceramic Surfaces
Authors: Heffelfinger J. R. , Bench M. W. , Carter C. B. 
Published: April 2011

ABSTRACTThe faceting of single-crystal ceramic surfaces has been investigated by atomic force microscopy, scanning electron microscopy and transmission electron microscopy. Single-crystals of α-Al2O3 (alumina) with different nominal surface orientations were annealed and used as a model system to investigate the faceting of a polished ceramic surfaces. The {1010} orientation of α-alumina, which facets into a hill-and-valley morphology, provides a dramatic representation of the different stages by which a surface facets. This surface starts faceting with the growth of an individual facet. The growth of this facet creates local surface disturbances that promote the nucleation of adjacent facets; thus, domains of faceted surface form on the otherwise smooth surface. Through time, these domains coalesce and the facets coarsen into a hill-and-valley morphology. Surfaces which facet into a terrace-and-step structure, such as (0001) and {1120} surfaces of alumina, are characterized for their progression of surface faceting and are compared with the stages of faceting observed for the {1010} surface.