bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epitaxial Growth of Metal Fluoride Thin Films by Pulsed-Laser Deposition
Authors: Norton D. P. , Budai J. D. , Chakoumakos B. C. , Geohegan D. B. , Puretzky A. 
Published: April 2011

ABSTRACTWe have investigated the growth of GdLiF4 thin films for optical waveguide applications using pulsed-laser deposition (PLD). Epitaxial, c-axis oriented GdLiF4 films have been grown from undoped GdLiF4 targets in an on-axis PLD geometry on (100) CaF2. These films exhibit a high density of particulates on the surface which are ejected from the target in the ablation process. Growth from Nd-doped polycrystalline GdLiF4 ablation targets results in relatively smooth films with lower particulate densities, as Nd doping significantly increases the optical absorption of GdLiF4 at the ablation laser wavelength of 193 nm and permits efficient pulsed-laser deposition. Optical emission spectra of the ablation pume reveals the presence of atomic fluorine, gadolinium, and lithium, indicating the dissociation of the metal-fluorine bonds in the ablation process. In addition, we find that the residual background oxygen pressure must be sufficiently reduced to avoid the formation of Gd4O3F6 as an impurity oxy-fluoride phase in the films.
Pulsed Laser Ablation of Boron Nitride
Authors: Bae Shin Keon , Min Park Seung , Man Kim Young 
Published: April 2011

ABSTRACTThe probe beam deflection and optical time-of-flight method have been applied to study the dynamics of Nd:YAG laser (266 nm) ablation of pyrolytic boron nitride. Shock wave generation was observed and its velocity was derived by analysis of the acoustic transit time of the acoustic wave produced by laser ablation. The most probable velocities of B and B+ were obtained by optical time-of flight technique. The deposition of boron nitride on silicon substrate by laser ablation was attempted in nitrogen atmosphere. Cubic phase of boron nitride was observed as well as the hexagonal phase.
Raman Studies on Potential substrate Materials of Sr(Al1/2Ta1/2)O3 and Sr(Al1/2Nb1/2)O3 For Htsc
Authors: Tao Ruiwu , Guo A.R. , Tu C.-S. , Siny I. , Katiyar R.S. , Guo Ruyan , Bhalla A.S. 
Published: April 2011

ABSTRACTComplex oxide perovskites, namely strontium aluminum tantalum oxide (SAT) and strontium aluminum niobium oxide (SAN) were recently investigated to be potential substrate materials for HTSC films in microwave applications. Single crystals were prepared by laser heated pedestal growth technique (LHPG). We report Raman vibrational spectrum studies on them for the first time. Order-disorder effects of (Al, Ta) and (Al, Nb) sites were studied with particular interests by comparing Raman spectra of single-crystal samples with ceramic samples. Influences of B sites (Ta and Nb) on O-O modes are discussed in relation to their dielectric properties.
Control of Threshold Voltage on the Excimer Laser Annealed Poly-Si Tfts by Oxygen Plasma Treatment on Poly-Si Surface
Authors: Woo Jae-Ik , Lee Sang-Gul , Moon Dae-Gyu , Hong Chan-Hee , Soh Hoe-Sup 
Published: April 2011

ABSTRACTOxygen plasma treatment was performed on the excimer laser annealed poly-Si surface, followed by gate oxide deposition with low pressure chemical vapor deposition (LPCVD) in order to control the threshold voltage of excimer laser annealed poly-Si thin film transistors (TFTs).Threshold voltages of n-channel TFTs increase from 0.4 to 2.8 V by varying the treatment time from 0 to 7 min. It is shown the effective charge density increased toward negative direction with increase of the treatment time.In addition to the increase of threshold voltage, the oxygen plasma treatment on the Si surface led to an increase in the deposition rate of LPCVD oxide films with an apparent reduction of carbon around the interface between gate insulator and poly-Si film after oxygen plasma treatment.
Excimer-Laser Crystallization of Si Films Via Bi-Directional Irradiation of Dual-Layer Films on Transparent Substrates
Authors: Yoon Jung H. , Im James S. 
Published: April 2011

ABSTRACTIn this paper, we report on a new excimer-laser crystallization (ELC) method that is highly effective in extending the super-lateral growth (SLG) distance and which does not involve any preheating of the substrate. The technique utilizes bi-directional irradiation of a dual layer Si film stack (separated by an oxide layer) deposited on a quartz wafer. The top layer is irradiated with a projection system which transfers a mask image in order to produce grain-boundary-location-controlled (GLC) regions, and the bottom layer, upon irradiation with a uniform beam, acts as a medium that favorably affects the thermal evolution of the top layer. The technique is effective and attractive in that the heating is spatially and temporally localized in an optimal manner. The thermal environment required for extending the SLG distance, as is induced by the melting and solidification of the bottom layer, is physically regulated by the melting temperature of Si, and the enthalpy difference between liquid and solid can be used to initially store and subsequently release heat. Using the method, we were able to attain GLC regions with widths up to 10 μm in 1000-Å Si films without any substrate heating. We elaborate on the applicability of the method to various artificially controlled super-lateral growth (ACSLG) techniques, and discuss process optimization by means of varying the multilayer configuration.
Excimer Laser Beam Interaction with Sintered Y2O3- Doped Aluminium Nitride Ceramic: Fundamentals and Appplication
Authors: Detournay N. , Kolev K. , Robert T. , Brunel M. , Laude L.D. 
Published: April 2011

ABSTRACTSintered aluminium nitride ceramic is most attractive for applications in modern electronic packaging, due to its high thermal conductivity and its high electrical resistivity. Among the sintering additives which are mentioned in the literature, Y2O3 is used most often as sintering accelerator and densificator for AlN commercial ceramics.Since excimer lasers have recently proved to be efficient in ceramic processing for industry, the effects of excimer laser irradiation on sintered Y2O3;rdoped AlN ceramic have been studied in this work. Raman spectroscopy, low-angle X-ray diffraction and scanning electron microscopy equipped with energy-dispersive X-ray analysis are used for characterizing both the initial and processed materials. The results reveal that yttrium-containing phases which are present at the AlN grain boundaries play an essential role in coupling the (λ =248nm) excimer laser beam with sintered material. Moreover, the laser-induced decomposition of these pre-existing complex phases and the subsequent spinel-like formation upon autocatalytic copper (or nickel) deposition are associated with (and explain) the excellent adhesion of the so-formed metal layer onto the ceramic substrate.
Terraced Copper Growth Deposited Onto Teflon AF1600 by The Excimer Laser Irradiation of Cu(hfac)Tmvs
Authors: Popovici D. , Piyakis K. , Sacher E. , Meunier M. 
Published: April 2011

ABSTRACTThe laser chemical vapour deposition (LCVD) of the organometallic precursor Cu(hfac)TMVS (hexafluoroacetylacetonate)(trimethylvinylsilane) is used to grow copper films on a Teflon AF1600 substrate. Exposure to excimer laser radiation at 248 nm results in a terraced copper growth. A simple model, based on interference effects in the Teflon and copper layers, is presented to account for this structure.
Excimer Laser Induced Photolytic Deposition of Aluminum Nitride: Ftlm Growth and Properties
Authors: Radhakrishnan G. , Adams P.M. , Marquez N. 
Published: April 2011

ABSTRACTExcimer laser photolysis has been used for the growth of smooth and well-adhering thin films of aluminum nitride (AlN) on Si, fused quartz, and KBr substrates at temperatures as low as 350 K. The photolysis was carried out at 193 nm, with the laser beam propagating parallel to the substrate. Trimethylamine alane and ammonia were used as gas-phase precursors. The growth rate of these films was investigated as a function of laser fluence. These measurements, as well as other investigations of film growth with and without the photolysis laser, reveal that no AlN film is produced in the absence of laser-induced photolysis of the precursors. The morphology and physical properties of these laser-grown films have been studied by scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Optical absorption spectra of films grown on fused quartz were measured as a function of substrate temperature. A substrate temperature of 350 K was found to be optimum for obtaining good film quality while precluding any effects due to the thermal decomposition of the precursors. The films have excellent dielectric properties as shown by I-V and C-V measurements. The details of AlN film growth using low-temperature gas-phase photolysis at 193 nm and the characterization of these laser grown films will be discussed.
Electron Irradiation-Induced Mechanical Property Changes in Reactor Pressure Vessel Alloys
Authors: Alexander Dale E. , Odette G.R. , Lucas G.E. , Rehn L.E. 
Published: April 2011

ABSTRACTHigh-energy electrons were used to study tensile property changes in simple Fe-Cu and Fe-Cu-Mn alloys irradiated at 288°C. A comparison was made with neutron irradiation data on the same alloys. An apparent effect of alloy chemistry was observed in which the presence of Mn affected embrittlement differently for electron and neutron irradiation. Comparison of previous experimental studies with the present experimental results indicates that electrons may be more efficient than fast neutrons at producing embrittlement.
Electron Beam Induced Crystallisation in Iron (III) Fluoride
Authors: Saifullah M.S.M. , Boothroyd C.B. , Botton G.A. , Humphreys C.J. 
Published: April 2011

ABSTRACTMetal fluorides are excellent candidates as high resolution inorganic resists in electron beam nanolithography. Hence it is important to study their damage characteristics under the electron beam to understand their behaviour as inorganic resists. In this paper the electron beam induced damage process in amorphous FeF3 films deposited by different techniques is investigated using selected area diffraction patterns and time resolved parallel electron energy loss spectroscopy. It is found that fluorine is lost from amorphous FeF3 during irradiation and that the material crystallises mainly to FeF2 with some crystalline FeF3. Time resolved energy loss spectroscopy studies show that the coordination polyhedra in amorphous FeF3 are randomly arranged FeF6 octahedra which arrange themselves to give a long range order in the electron beam during crystallisation to FeF2 and FeF3.
Solidification Behaviour of Al Particles Embedded in an Ni Aluminide Matrix
Authors: O'Reilly K.A.Q , Kim W.T. , Cantor B. 
Published: April 2011

ABSTRACTA hypereutectic Al-40wt%Ni alloy has been manufactured by melt spinning, and the resulting microstructure examined by transmission electron microscopy. As-melt spun hypereutectic Al-40wt%Ni consists of an Ni aluminide matrix and an A1-rich phase distributed in the form of particles with sizes ∼ 50-100 nm, and as an irregular layer at the cell and grain boundaries. Diffraction analysis of the Ni aluminide matrix is consistent with the ASTM x-ray diffraction standard 2θ values for the orthorhombic NiAl3 phase, a=6.6114 Å, b=7.3662 Å andc=4.8112 Å. The solidification nucleation kinetics of Al-rich particles have been examined by heating and cooling experiments in a differential scanning calorimeter over a range of heating and cooling rates. Solidification of the Al-rich phase at the cell and grain boundaries nucleates catalytically on the surrounding Ni aluminide matrix at an undercooling of ∼ 3 K. Analysis of the solidification nucleation kinetics of the Al-rich phase in Al-40wt%Ni supports the hypothesis [1-4] that the classical spherical cap model of heterogeneous nucleation breaks down at low undercoolings and small contact angles.
A Study of the Kinetics and Energetics of Solid State Reactions in Pd/Sn Diffusion Couples
Authors: Chromik R.R. , Cotts E. J. 
Published: April 2011

ABSTRACTUsing differential scanning calorimetry, supplemented by measurements from scanning electron microscopy images, we have investigated solid state reactions in Pd/Sn multilayer composites to form PdSn4 and PdSn3. Planar diffusion couples of Pd and Sn were prepared by means of mechanical co-deformation in a rolling mill. A phase formation sequence was determined using differential scanning calorimetry and x-ray diffraction. Growth of the PdSru phase was studied from room temperature to the melting point of Sn. For temperatures between 430 and 460K diffusion limited growth of PdSn4 was observed. From heat flow data over this limited temperature range, the form of the reaction constant was found to be k2 −k0 exp(−Ea / kbT), where k0= 0.16 cm2/s and &Epsilon;n= 0.8 eV/atom. Also determined was a heat of formation, ΔHf = −27±1 kJ/mol for PdSn4 from Pd and Sn.
Crystallization Kinetics of Rutile Formation from Amorphous Titania Films
Authors: Wiggins M.D. , Nelson M.C. , Atta C.R. 
Published: April 2011

ABSTRACTTitania films with two types of phase composition were sputter deposited on fused silica substrates: Type (I) amorphous+anatase+rutile and Type (II) amorphous+rutile. These films were subjected to various annealing procedures in air. We studied three relevant transitions: 1) amorphous→crystalline (anatase and rutile) at temperature <800 °C, 2) amorphous→mitile at an temperatures, and 3) anatase→rutile in the 750–800 °C temperature range.X-ray diffraction was used for phase identification and crystallographic orientation. The films had a preferred orientation, with (101) anatase and/or (110) rutile planes parallel to the substrate. The activation energy for the amorphous-to-rutile transformation was 0.3 eV. The anatase-to-rutile transformation occurring at 750 °C was modelled using the Avrami relation, which yielded an exponent of unity.From the results of this study, we propose a model for titania crystallization in which site saturation of rutile and/or anatase nuclei already exists in the as-deposited film. Further crystallization upon annealing occurs by one dimensional growth of these nuclei into the amorphous material. If no anatase seeds exist in the as-deposited material, then no anatase will form upon annealing, indicating again that no new nuclei are formed during annealing. In this manner, highly oriented rutile titania films can be produced at temperature below the bulk anatase-to-rutile transformation temperature (750 °C).
Effect of Initial Composition Distribution on the Phase Transformation Behavior in the Fe-Cr-Ni System
Authors: Vitek J. M. , David S. A. 
Published: April 2011

ABSTRACTA finite-difference implicit numerical model was used to study the diffusion-controlled α-γ solid-state phase transformation in the Fe-Cr-Ni system. The influence of a non-uniform initial composition distribution was examined in order to assess the impact that non-uniform solute profiles resulting from solidification may have on subsequent transformation behavior in weldments and castings. A significant impact on the transformation kinetics and transformation path was found in some cases. The factors that affect the degree of influence are discussed.
Kinetic Model of Thermoelastic Martensite Transformation in Niti and NiMn Based Shape Memory Alloys
Authors: Wu K. H. , Shi J.D. , Yang F. , Pu Z. J. 
Published: April 2011

ABSTRACTA new, quantitative model was developed to describe the martensite transformation kinetics of thermoelastic shape memory alloys (SMAs). In addition, a series of experiments were conducted to study the Kinetics of thermoelastic martensite transformation in four SMA systems: NiTi, NiTi-15at%Hf, NiTi-20at%Zr and NiMn-7.5at%Ti alloys. Comparisons between data of the kinetic of martensite transformation with the present theoretic models show that the proposed model is in good agreement and concurs with the experimental data. Also, a comparison of data from the proposed model with data from existing kinetic models, such as Liang's and Magee's [1,7], indicates that the proposed model can better describe the experimental data, including the relationship between dξ(T)/dT and ξ, and dξ(T)/dT and T.
Kinetics of Surface Segregation in Metallic Alloys with First-Principles Interaction Parameters
Authors: Wille L. T. , Ouannasser S. , Dreyssé H. 
Published: April 2011

ABSTRACTWe report the results of Monte Carlo simulations of the kinetics of surface segregation at the (001) face of CuNi and MoW alloys. These two systems were selected because they are based on different lattice structures and show contrasting segregation behavior: CuNi exhibits a monotonie profile, while that of MoW is oscillatory. To describe the energetics we have determined a set of effective cluster interactions (ECI) which govern the ordering or clustering tendencies of these alloys. The ECI were obtained by means of tight-binding electronic structure calculations in which no adjustable or experimentally determined parameters were used. Equilibrium segregation profiles are calculated and a series of quenches are performed. The layer concentrations are studied as a function of time and the existence of metastable phases in the surface region is investigated.
Temperature Dependent Raman Scattering in CsTiOAsO4 Single Crystal
Authors: Guo A.R. , Tu C.-S. , Tao Ruiwu , Katiyar R.S. , Guo Ruyan , Bhalla A.S. 
Published: April 2011

ABSTRACTThe longitudinal (LO) and transverse (TO) A1 vibrational modes have been measured between 30-1200 cm−1 as a function of temperature (30–1240 K) for CsTiOAsO4 (CTA). The frequencies for all corresponding Raman components shifted to lower frequencies on increasing the temperature, however, there is no typical soft-mode like behavior observed in the measured frequency range. The relative intensities of the low frequency bands increase dramatically with increasing temperature due to high mobility of Cs+ ion. A higher symmetry structure taking place above 940K has been confirmed by changes in the phonon spectra.
Development of Microstructure in Rapidly Solidified Intermetallics
Authors: Assadi H. , Greer A. L. 
Published: April 2011

ABSTRACTThe solid-state transformations following rapid solidification of intermetallics can include ordering of primary disordered phase(s), resulting in anti-phase domain boundaries (APDBs). The present work focuses on the Ni-Al system. A qualitative model for solid-state ordering, originally developed by Chen and Khachaturyan [1] has been modified to simulate the APD formation during solidification of a disordered phase. An interpretation is suggested for the formation of various APD patterns observed in sequentially ordered Ni3Al.
Undercooling Experiments in a High Temperature Differential Scanning Calorimeter
Authors: Baricco M. , Ferrari E. , Battezzati L. 
Published: April 2011

ABSTRACTSeveral samples of metals and alloys have been undercooled during scanning in a high temperature DSC. Liquid Ni was undercooled of about 230 K when previously fluxed in molten B2O3. From enthalpy data of melting and solidification as a function of temperature, the excess heat capacity of liquid metals and alloys was evaluated. The specific heat of the liquid is definitely higher than that of the corresponding crystalline phases for glass-forming alloys, whereas it is close to that of the solid for pure metals. The Ni-B system has been studied in detail around the Ni-Ni3B eutectic. On undercooling, a new metastable phase (Ni23B6) was produced. A metastable Ni-B phase diagram has been drawn using data of thermal analysis of several alloys containing the metastable phase.
Analysis of Reflection High Energy Electron Diffraction Pattern of Silicon Carbide Grown on Silicon
Authors: Teichert G. , Pezoldt J. , Cimalla V. , Nennewitz O. , Spiess L. 
Published: April 2011

ABSTRACTRHEED pattern of SiC layers on both (100) and (111)Si grown by carbonization were studied. Different deviations from the single crystalline structure were found ranging from twinning up to changes in the orientation and textured growth. Special attention was drawn on lattice relaxation and morphology evolution during the growth of the formed SiC. Relationships between the occurrence of typical RHEED pattern and the morphology and process parameters are presented.
Misfit Dislocations and Elastic Relaxation
Authors: Strunk H.P , Christiansen S. , Albrecht M. 
Published: April 2011

ABSTRACTPrior to relaxation of misfit strain by formation of misfit dislocations, a growing heteroepitaxial layer can relax elastically by forming surface undulations called ripples. With increasing amplitude of the ripples the misfit strain and thus stress fields grow markedly inhomogeneous, and dislocation formation may thus be triggered in areas of maximum shear stress. The surface directly above such a new dislocation then represents a band of preferential growth and develops into a ridge, which in turn redistributes the strain in the growing layer. This interwoven elastic/plastic relaxation mechanism can comparably easily be deduced from transmission electron and atomic force microscopy studies of SiGe layers grown onto silicon by liquid phase epitaxy. This growth technique exerts only very small driving forces and thus operates very near thermodynamical equilibrium. The local strain tensor and strain energy density are calculated for the actual layer geometries by three dimensional finite element method and provide for quantification of the mechanism.
Investigation of Relationships between Dislocations and Crystal Surface Ledges
Authors: Zimmerman Jonathan A. , Gao Huajian 
Published: April 2011

ABSTRACTMolecular Dynamics (MD) simulations are performed on two-dimensional, triangular lattice models. The program used to perform these simulations was based on codes developed by Farid F. Abraham at the IBM-Almaden Research Center in San Jose, CA and by J.M. Haile, but also contained modifications to increase efficiency. These simulation models contain three constrained sides and a free surface, use a Lennard-Jones 6:12 interatomic potential, and initially exist with various amounts (∼ 5 to 10 %) of compressive strain. Our paper studies the formation of dislocations from atomic ledges during relaxation from a compressive state, as well as the subsequent motion of these dislocations. These simulations are particularly relevant to understanding morphological changes on the surface and nucleation of dislocations in heteroepitaxial thin films.
Effect of the Introduction of a MBE Buffer Layer on the Morphology of InSb Almbe Layers Grown on InP Substrates
Authors: Ferrer J.C. , Cornet A. , Peiró F. , Morante J.R. , Utzmeier T. , Briones F. 
Published: April 2011

ABSTRACTIn this paper we report on the morphology of InSb layers grown by atomic layer molecular beam epitaxy (ALMBE) onto InP substrates at low temperatures (330<T<400°C), comparing the nature and densities of defects with those found in ALMBE InSb films grown over InSb/InP buffer layers grown by molecular beam epitaxy (MBE). The main types of defects for ALMBE direct layers are threading dislocations and stacking faults with similar defect densities along both á110ñ directions. The inclusion of the intermediate InSb/InP MBE grown buffer layers leads to lower threading dislocation densities but higher and anisotropic stacking fault distribution. Moreover, different types of three-dimensional defects appear, which are associated with pyramidal or truncated pyramidal hillocks on the surface. These defects, consisting in twins associations are originated at the InSb/InP MBE interface and they are induced by an anomalous growth of InSb layers. In all the cases, the strain caused by the large lattice mismatch is accommodated by means of a pure edge-type misfit dislocation network placed at the interface.