bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of misfit strain on properties of ZnO films grown by pulsed laser deposition
Authors: Park M.C. , Yoon W.H. , Lee D.H. , Myoung J.M. , Bae S.H. , Lee S.Y. , Yun I. 
Published: April 2011

AbstractA series of ZnO films with various thicknesses were prepared on (0001) sapphire substrate by pulsed laser deposition (PLD). Scanning electron microscopy (SEM) and x-ray diffraction (XRD) analysis were utilized to investigate the effects of misfit strain on the surface morphology and the crystallinity. The electrical and optical properties of the films were also investigated as a function of the film thickness. It was found that the crystalline quality, electrical and optical properties of the films depended on the film thickness and were improved with increasing the film thickness. This is attributed to the fact that the films thinner than 400 nm are under the severe misfit strain, which decreases as the film thickness increases further.
Intermixing in Ge/Si(001) Islands: Elemental Content and Structure
Authors: Eshed A. , Zhu J. , Yan J. , Beserman R. , Weiss A. H. 
Published: April 2011

AbstractWe have investigated the shapes, thickness, density, composition, and quality of Ge/Si(001) islands grown by solid source molecular beam epitaxy in ultra high vacuum conditions. Nano crystals were formed by means of the Stranski-Krastanow “self assembly” growth mechanism. 5 nm of Ge were deposited on Si(001) substrates, at 500 °C, with deposition rate of 0.5 nm/min. Atomic force microscope measurements reveal islands of various sizes, ranging from 60 nm to 700 nm in diameter. Islands' density found to be correlated with their sizes, with denser areas containing mostly islands of the smaller sizes. Micro Raman spectroscopy, with probing spot of about 0.7 µm diameter, has been used to study the composition, thickness and crystalline quality of the islands. Data were taken at various points on the sample distinguishing between various islands' types. Combined analysis of Raman spectra and the micrographs reveal low amount of alloying (less than 30%) in all types of islands, with the larger islands showing the more amount of intermixing. High crystalline quality of the layers within the islands suggests negligible amount of dislocations.
Low Energy Plasma Enhanced Chemical Vapour Deposition - Plasma Enhanced Deposition of Epitaxial Si and Sige
Authors: Rosenblad Carsten , Kummera Matthias , Deller Hans-Rudolf , Graf Thomas , Dommann Alex , Hackbarth Thomas , Höck Georg , Müller Elisabeth , von Känel Hans 
Published: April 2011

AbstractLow energy plasma enhanced chemical vapour deposition (LEPECVD) is a deposition technique developed for the epitaxy of Si and SiGe at ultra-high deposition rates. Due to a high current plasma discharge composed of low energy particles, a high plasma enhancement can be obtained without any accompanying plasma induced damage of the wafer surface. The most important application of LEPECVD so far is for compositionally graded relaxed SiGe buffer layers. Such relaxed buffer layers are demonstrated with end composition up to pure Ge and with a growth time below 1 hour. A p-type hetero-MOSFET formed in a SiGe channel compressively strained to a Si0.5Ge0.5 relaxed buffer layer, is demonstrated as one example where the high growth rates of LEPECVD allows the synthesis of devices which cannot be produced with an acceptable throughput with conventional deposition methods. The room temperature effective hole mobility of 760 cm2/Vs obtained on such devices demonstrates a high structural and electrical quality of the LEPECVD material.
Shape Transition in Self-Organized InAs/InP Nanostructures
Authors: Gutiérrez H.R. , Cotta M.A. , Carvalho M.M.G. de 
Published: April 2011

AbstractIn this letter we report the transition from self-assembled InAs quantum-wires to quantumdots grown on (100) InP substrates. This transition is obtained when the wires are annealed at the growth temperature. Our results suggest that the quantum-wires are a metastable shape originated from the anisotropic diffusion over the InP buffer layer during the formation of the first InAs monolayer. The wires evolve to a more stable shape (dot) during the annealing. The driving force for the transition is associated with variations in the elastic energy and hence in the chemical potential produced by height fluctuations along the wire. The regions along the wires with no height variations are more stable allowing the formation of complex, self-assembled nanostructures such as dots interconnected by wires.
Morphology of Self-Assembled InAs Quantum Dots on GaAs(001)
Authors: Arciprete F. , Patella F. , Fanfoni M. , Nufris S. , Placidi E. , Schiumarini D. , Balzarotti A. 
Published: April 2011

AbstractWe have followed by Atomic Force Microscopy (AFM) the epitaxial growth of InAs on GaAs(001) starting from the initial formation of a strained two-dimensional wetting layer up to the self-assembled nucleation and growth of 3D nanoparticles. In this work we underline many aspects of the morphology of this system, which substantiate the role either of kinetics on thermodynamics in the process of growth as well as the role of surface instabilities in controlling lateral ordering of the nanoaggregates.
Island and pit formation during growth and annealing of InGaAs/GaAs films
Authors: Riposan A. , Martin G.K.M. , Bouville M. , Falk M. L. , Millunchick J. Mirecki 
Published: April 2011

AbstractThe surface morphology near the onset of 3D roughening of In0.27Ga0.73As/GaAs films was investigated for films both immediately after growth and after annealing. As expected, 3D island nucleation coincides with the onset of strain relaxation at a critical thickness hc. As strain relaxation continues, pits form adjacent to 3D islands. The onset of the pit formation depends on the growth conditions, including the growth temperature and As overpressure, and the areal coverage of 3D islands. On average, pits form only after the area coverage of islands reaches ~50%. The islands and pits coalesce into ripple arrays as the film thickness increases. Films below and above the critical thickness for 3D roughening were annealed to study the stability of islands and pits. For films with thicknesses below hc, initially smooth surfaces evolve into islanded morphologies upon annealing. For films grown above hc which have both islands and pits on the surface, both islands and pits grow and coalesce during annealing. These results suggest that pit formation is favored, but it requires a minimum island coverage and/or wetting layer thickness in order to nucleate.
Atomic Self-ordering in Heteroepitaxially Grown Semiconductor Quantum Dots due to Relaxation of External Lattice Mismatch Strains
Authors: Möck Peter , Topuria Teya , Browning Nigel D. , Nicholas Robin J. , Booker Roger G. 
Published: April 2011

AbstractThermodynamic arguments are presented for the formation of atomic order in heteroepitaxially grown semiconductor quantum dots. From thermodynamics several significant properties of these systems can be derived, such as an enhanced critical temperature of the disorder-order transition, the possible co-existence of differently ordered domains of varying size and orientation, the possible existence of structures that have not been observed before in semiconductors, the occurrence of atomic order over time, and the occurrence of short range order when the growth proceeds at low temperatures. Transmission electron microscopy results support these predictions. Finally, we speculate on the cause for the observed increase in life time of (In,Ga)As/GaAs quantum dot lasers [H-Y. Liu et al., Appl. Phys. Lett. 79, 2868 (2001)].
Strain Accommodation and Relaxation Mechanisms in Epitaxially Grown Manganites
Authors: Casanove Marie-José , Baulès Pierre , Roucau Christian , Magnoux David , Bobo Jean-François , Bibes Manuel , Balcells Lluis , Fontcuberta Josep 
Published: April 2011

AbstractEpitaxial growth of La1-x(SrorCa)xMnO3 manganites (LSMO or LCMO) has been successfully achieved on SrTiO3 (001) and MgO(001) substrates. We report the influence of the deposition conditions, in particular growth rate, annealing and nature of the substrate, on the state of strain in the manganite layers. Fully strained layers are reported at very slow growth rate on SrTiO3 substrates while misfit dislocations are clearly observed in layers grown on MgO and alsoin layers grown on SrTiO3, after annealing at high temperature. Besides, evidence is given for a rhombohedral (respectively orthorhombic) distortion relaxation in LSMO (respectively LCMO) layers. The microstructure of the manganite layers is analyzed taking into account their non-isomorphic growth on the cubic substrates.
Rapid Prototyping of Plastic Micro Devices by Excimerlaser Ablation
Authors: Klotzbuecher Thomas , Mirtaheri Peyman , Braune Torsten 
Published: April 2011

ABSTRACTNowadays the application of micro devices in many fields like e.g. in the life sciences, chemistry and also optics strongly grows in importance. Micro structures often allow efficient processes with low resource consumption and the possibility of high integration. Typical examples are micro and nano titer plates for chemical screening or DNA chips for sequencing, micro mixers and reaction systems for synthesis on demand or micro optical elements like couplers for optical data transmission. Especially plastics are well suited for the cost effective large number fabrication, using high precision mould inserts with injection moulding or hot embossing. Since the micro devices become more and more complex (keywords: lab on a chip and micro total analysis systems, μ-TAS) the fabrication of mould inserts will be more expensive and time consuming. This is the reason why often methods of rapid prototyping are required for design qualification and functionality test purposes during the development. It will be demonstrated that Excimerlaser ablation is a well suited method for rapid prototyping of quasi-three-dimensional micro structures. Almost all polymers can be ablated by the UV laser radiation with very high accuracy, using mask projection techniques. Therefore, the choice of a suited polymer with adapted material properties like for e.g. chemical resistance, optical surface quality or bio-compatibility allows one to account for the requirements of the corresponding application. Moreover, the prototypes can easily be transformed into mould inserts for large number fabrication, using the Laser-LIGA technique. The corresponding technologies will be explained and demonstrated with the aid of several examples, especially taking into account the material aspects.
Laser Direct Writing of Hydrous Ruthenium Dioxide Micro-Pseudocapacitors
Authors: Arnold Craig B. , Wartena Ryan C. , Pratap Bhanu , Swider-Lyons Karen E. , Piqué Alberto 
Published: April 2011

ABSTRACTWe are using a laser engineering approach to develop and optimize hydrous ruthenium dioxide (RuOxHyor RuO2·0.5 H2O) pseudocapacitors. We employ a novel laser forward transfer process, Matrix Assisted Pulsed Laser Evaporation Direct Write (MAPLE-DW), in combination with UV laser machining, to fabricate mesoscale pseudocapacitors and microbatteries under ambient temperature and atmospheric conditions. Thin films with the desired high surface area morphology are obtained without compromising their electrochemical performance. The highest capacitance structures are achieved by depositing mixtures of sulfuric acid with the RuO2·0.5 H2O electrode material. Our pseudocapacitors exhibit linear discharge behavior and their properties scale proportionately when assembled in parallel and series configurations.
Aerosol-Based Direct-Write of Biological Materials for Biomedical Applications
Authors: Marquez Gregory J. , Renn Michael J. , Miller W. Doyle 
Published: April 2011

ABSTRACTApplying life sciences and engineering principles to the study of cells and engineered tissue has resulted in various successes. These endeavors are poised towards development of functional neo-organs used as native tissue substitutes. Concurrent with this goal, research arenas are directed in the general areas of biocompatible polymer scaffolds, biomimmetic extracellular matrices, control of stem cell differentiation, biomolecule signaling, and directed material delivery. Optomec Inc. is developing an aerosol-based direct-write process for deposition of biological materials into three dimensional, micron-scale patterns. The process uses pneumatic atomization to produce aerosol droplets of proteinacious colloidal dispersions and whole cell suspensions. The droplets are entrained in an air stream and deposited with a proprietary deposition tool. The biological materials can be seeded into three dimensional polymer scaffolds and various substrate surfaces. Optomec's direct write process has applicability to the additive fabrication of engineered tissue. Other applications of the direct write tool include rapid prototyping of analytical biosensors, hybrid BioMEMS, and bio-chip microarray devices.
Analysis of Ion Implantation Damage in Silicon Wafers by a Contactless Microwave Diagnostic
Authors: Ahrenkiel Richard K. , Lojek B. 
Published: April 2011

AbstractRapid thermal annealing (RTA) of lattice damage created by heavy ion implantation damage is required to maintain the integrity of semiconductor material used for submicron-integrated circuit devices. A quick, efficient, and contactless diagnostic of the implantation damage is highly desirable in both research and production environments. A contactless measurement technique has been recently applied to this problem that uses a deeply penetrating low-frequency microwave probe frequency operating at 420 MHz. Here, we will demonstrate the use of this high frequency resonance-coupled photoconductive decay (RCPCD) technique, which, when combined with a tunable optical excitation source, enables us to map the radiation damage in boron and arsenic-implanted silicon wafers. We quantify the damage by mapping the minority-carrier lifetime as a function of optical penetration depth. In this work, we quickly and efficiently compared the effectiveness of various RTA processes by the RCPCD diagnostic.
AC Conductivity Based Microstructural Characterization of Yttria Stabilized Zirconia
Authors: Sauti G. , McLachlan D.S. 
Published: April 2011

AbstractAC conductivity experiments, or Impedance Spectroscopy, at temperatures between 100 and 400°C, made on 8 mole % Yttria Stabilized Zirconia (8YSZ) with different grain sizes, are presented. The results are analyzed using Effective Media Theories, the Brick Layer Model and percolation theory. The results obtained are satisfactory, only if the measured frequency dependant complex conductivity parameters of the grains are inserted in the equations.
Combinatorial optimization of atomically controlled growth for oxide films by the carrousel type laser molecular beam epitaxy
Authors: Takahashi R. , Matsumoto Y. , Koinuma H. , Lippmaa M. , Kawasaki M. 
Published: April 2011

AbstractA new combinatorial pulsed laser deposition system has been developed for rapid optimization of epitaxial growth process by using a carrousel type masking plate. Under in-situ monitoring of growing surface with reflection high energy electron diffraction, eight films with different compositions or preparation parameters can be fabricated on a single substrate. By using this system, we have succeeded in the one lot optimization of YBa2Cu3O7-d(YBCO), PrGaO3, SrO and BaO film growths on the B-site (TiO2) terminated SrTiO3(001) substrates. Key results from these experiments include the high sensitivity of YBCO film crystallinity to the laser focusing as well as of growth behavior of epitaxial SrO and BaO films to the crystal habit with the underlying atomic layers.
Characterization of Magnetic and Dielectric Properties on Y-Type Magnetoplumbite Epitaxial thin Films for High Frequency Application
Authors: Ueno K. , Ohkubo I. , Matsumoto Y. , Okazaki N. , Hasegawa T. , Itaka K. , Koinuma H. 
Published: April 2011

AbstractMagnetic films for miniaturization of planar inductors operating at GHz frequencies require high resistivity and high ferro-magnetic resonance frequency. Y type magnetoplumbite Ba2Co2Fe12O22(Co2Y) is a candidate material to meet such requirements because it has about 10 &m resistivity and resonance frequency higher than 2 GHz. Recently we succeeded in the fabrication of Co2Y epitaxial thin film on MgAl2O4 substrate by combinatorial pulsed laser deposition technique [3]. Here, we report on the magnetic and dielectric properties of this film. The DC resistivity of the film was 7.5 &m. The dielectric constant at 1.25 GHz was measured by a microwave microscope to be 11.0. An easy axis coercive force and saturation magnetization were about 145 Oe and 2000 Gauss respectively, being close to those of bulk sample. Furthermore, the magnetic micro domain structures of Co2Y epitaxial thin films were observed by a scanning SQUID microscope.
Scanning Electron-Beam Dielectric Microscopy for the Temperature Coefficient Distribution of Dielectric Materials
Authors: Cho Yasuo 
Published: April 2011

AbstractStudies on scanning electron-beam dielectric microscopy (SEDM) are reported. This microscopy technique is used for determining the temperature coefficient distribution of dielectric materials using an electron-beam as a heat source instead of a light beam as in photothermal dielectric microscopy. This microscopy technique, which has the ability to simultaneously observe SEM images and the material composition by EPMA, has a resolution better than that of photothermal dielectric microscopy. To demonstrate the usefulness of this technique, the two-dimensional image of a two-phase composite ceramic composed of TiO2 and Bi2Ti4O11 is measured. To shorten a measurement time, a new type of SEDM for measuring the real time transient response caused by a single pulsed electron-beam is also successfully developed. Finally, a quantitative measurement method of temperature coefficient is also developed.
Electrostatic Dispensing of Dry Dielectric Materials
Authors: Tupper Malinda M. , Chopinaud Marjorie E. , Ogawa Takamichi , Cima Michael J. 
Published: April 2011

AbstractDispensing micron-scale dielectric materials can be achieved through the use of dielectrophoresis. Electrodes are designed to create a nonuniform electric field. This method is expected to be applicable for transfer of a wide range of dielectric powders as well as small, shaped components. Small, 150 μm diameter silica spheres, as well as sodium fluorescein powder have been dispensed by this method. Selecting the appropriate electrode geometry and electric field intensity controls the amount collected. As little as 1.0 μg of sodium fluorescein powder, and as much as 16 mg of silica beads have been collected, and repeatability within 10 % of the total amount dispensed has been achieved.
Rapid and Quantitative Determination of Crystallization Tendency of Zinc Tellurite Glass Melt by Using Temperature-Gradient Furnace
Authors: Todoroki Shin-ichi , Matsumoto Takehisa , Inoue Satoru 
Published: April 2011

AbstractQuantitative thermal stability test of glass materials against crystallization is accelerated through a vertical temperature-gradient furnace. In the furnace, zinc tellurite glass melt is sucked into a 75cm-long glass capillary tube (ID 1.5 × OD 8 mmø) and the tube is kept inside to be annealed under a temperature gradient of 300~800°C/50cm. The time to precipitate is determined to make a set of T-T-T (Time-Temperature-Transform) diagrams for different composition and thermal hysteresis. Crystallization is not observed for 65TeO2-35ZnO and 70TeO2-30ZnO (mol%) super-cooled glass melt after 4000s annealing but their stability decreased if the melts were once quenched to below their glass transition temperature before the annealing.
Quantitative Structure-Activity Relationships (QSARs) for Materials Science
Authors: Rajan Krishna , Suh Changwon , Rajagopalan Arun , Li Xiang 
Published: April 2011

AbstractThe field of combinatorial synthesis and “artificial intelligence” in materials science is still in its infancy. In order to develop and accelerated strategy in the discovery of new materials and processes, requires the need to integrate both the experimental aspects of combinatorial synthesis with the computational aspects of information based design of materials. In biology and organic chemistry, this has been accomplished by developing descriptors which help to specify “quantitative structure- activity relationships” at the molecular level. If materials science is to adopt these strategies as well, a similar framework of “QSARs” is required. In this paper, we outline some approaches that can lay the foundations for QSARs in materials science.
Continuum Limit of a Step Flow Model of Epitaxial Growth
Authors: Kohn R.V. , Lo T.S. , Yip N.K. 
Published: April 2011

ABSTRACTWe examine a class of step ow models of epitaxial growth obtained from a Burton-Cabrera-Frank (BCF) type approach in one space dimension. Our goal is to derive a consistent contin uummodel for the evolutionof the film surface. Away from peaks and valleys, the surface height solves a Hamilton-Jacobi equation (HJE). The peaks are free boundaries for this HJE. Their evolution must be specified by boundary conditions reecting the micro- scopic physics of nucleation. We inv estigate this boundary condition by numerical simulation of the step ow dynamics using a simple nucleation law. Our results rev ealthe presence of special structures in the profile near a peak; we discuss the relationship between these structures and the contin uumequation. We further address the importance of evaporation for matching the local behavior near the peak to the solution of the contin uum equation.
Coarse-Grained Molecular Dynamics: Dissipation due to Internal Modes
Authors: Rudd Robert E. 
Published: April 2011

ABSTRACTWe describe progress on the issue of pathological elastic wave reflection in atomistic and multiscale simulation. First we briefly r eview Coarse-Grained Molecular Dynamics (CGMD). Originally CGMD was formulated as a Hamiltonian system in which energy is conserved. This formulation is useful for many applications, but recently CGMD has been extended to include generalized Langevin forces. Here we describe how Langevin dynamics arise naturally in CGMD, and we examine the implication for elastic wave scattering.
Convection Effects in Three-Dimensional Dendritic Growth
Authors: Lu Yili , Beckermann C. , Karma A. 
Published: April 2011

ABSTRACTA phase-field model is developed to simulate free dendritic growth coupled with fluid flow for a pure material in three dimensions. The preliminary results presented here illustrate the strong influence of convection on the three-dimensional (3D) dendrite growth morphology. The knowledge of the flow and temperature fields in the melt from the simulations allows for a detailed understanding of the convection effects on dendritic growth.
Computational Investigation of Selective MOVPE of AlxGa1-xAs in Presence of Hcl
Authors: Nemirovskaya Maria , Cavallotti Carlo , Jensen Klavs 
Published: April 2011

ABSTRACTThe deposition of AlGaAs in the presence of HCl was investigated at the macroscopic and mesoscopic scales. Fluid dynamics simulations were first performed in order to study the dependence of the deposition rate on the operating conditions. Unknown gas phase and surface kinetic parameters were estimated by quantum chemistry and transition state computations. The fluxes of all species to the surface were thus computed and provided the input to a kinetic Monte Carlo model used to investigate the morphology evolution of the film.