bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical Characterization of Cadmium Telluride Doped Heterostructured Opaline Photonic Crystal
Authors: Solovyev V. G. , Romanov S.G. , Torres C.M. Sotomayor , Gaponik N. , Eychmüller A. , Rogach A. L. 
Published: April 2011

AbstractA double-layer photonic crystal (PhC) possessing incomplete photonic band gap (PBG) has been prepared by successive formation of one opaline film on top of another and subsequent impregnation with CdTe colloidal nanocrystals as the light source. Transmission, reflection and photoluminescence (PL) spectra of this nanocomposite have been measured from 1.8 to 2.5 eV at different angles of the light incidence and detection. The suppression of emission intensity has been found at both stop bands of the PhC heterostructure. Depending on the excitation power, either suppression or enhancement of the emission rate at the stop band has been observed.
Artificial Second Order Non-Linearity in Photonic Crystals.
Authors: Feigel A , Kotler Z. , Sfez B. 
Published: April 2011

AbstractWe describe a technique for obtaining effective second order non-linearity λ2in non centro-symmetric Photonic Crystal made from centro-symmetric materials (e.g. glass, Ge or Si). The effect is based on the electric quadrupole transition, strong electromagnetic mode deformation and different contributions to the volume polarization from different parts of the photonic crystal1.
Plastic Deformation of Thin Films – Bending
Authors: Nozaki T. , Kogure Y. , Doyama Masao 
Published: April 2011

ABSTRACTWidely accepted model of bending of a single crystal suggests that edge dislocations are introduced from both the compressed surface and extended surface. The present study examined this model by molecular dynamics using an embedded potential. Shockley partial dislocations are created on the compressed surface. Due to the characteristics of inter atomic potential, the stress on the compression surface is higher than that on the extended surface.
Stress-Strain Response of Free-Standing Nano-Crystalline Gold Thin-Films
Authors: Gudlavalleti Sauri , Kumar Sharvan , Anand Lallit 
Published: April 2011

ABSTRACTFree-standing gold thin-film tension specimens of thicknesses in the range 500-700 nm were fabricated by e-beam deposition methods. The films have grains which have thicknesses essentially equal to the film thickness, and an in-plane grain-size distribution which is bi-modal, with a collection of small grains with an average size of 130 nm, and another collection of larger grains with an average size of 380 nm. The films possess a strong texture with the {111} crystallographic planes aligned with the plane of the film. The thin-film specimens have been tested in simple tension using a novel testing machine which enables measurement of the elastic-plastic stress-strain response of the films with high resolution. The experiments show that the gold thin-films have an initial yield strength of around 100 MPa, which is followed by rapid strain hardening to a stress level of 360 MPa at a strain of only ~1.2%, at which point the specimens fail abruptly. Transmission electron microscopy (TEM) investigations of the deformed films shows that the rapid strain hardening is attributable to extensive dislocation activity in the larger grains. The reason behind the low ductility in our gold specimens is still unclear, but it may be attributable to the observed lack of dislocation activity in the smaller grains, whose boundaries then serve as easier sites for alternative inelastic mechanisms such as grain boundary sliding and decohesion leading to low macroscopic strains to failure.
Effects of Surface Constraints on Stresses in Heteroepitaxial Films Grown on Compliant Substrates
Authors: Feng Zhaohua , Lovell Edward G. , Engelstad Roxann L. , Kuech Thomas F. 
Published: April 2011

ABSTRACTAs films heteroepitaxially grow on substrates, lattice mismatch strain at the interfaces causes stresses in the films and substrates. These stresses can have deleterious effects on film quality. To facilitate an understanding of defect production and control during growth of films on compliant substrates, transient finite element models were developed to simulate the complete mechanical stress and strain fields. Effects of constraints between the template and handle wafer on the film stresses were examined. The investigation showed that different types of constraints caused stress variations over a large range. Other factors affecting the stresses, such as lattice mismatch strain, wafer radius, film and template thickness, were also assessed.
Structural Properties of Carbon Nitride Films Deposited by Reactive - Pulsed Laser Deposition Technique
Authors: Phani A.R. , Krzanowski J.E. , Nainaparampil J.J. 
Published: April 2011

ABSTRACTCarbon nitride films have been deposited by the reactive pulsed laser deposition technique by ablating carbon in a nitrogen atmosphere at different substrate temperatures and different background pressures of nitrogen. Si(111) and 440C steel substrates were used in the present investigation. Deposited films are uniform and show good adhesion to the substrates. The deposition rates depend on laser fluence, background pressure, and target-substrate distance. The nitrogen concentration in the deposited films increases with increasing background nitrogen gas pressure and laser fluence. Fourier transform infrared spectroscopy has been employed to evaluated CN bonds. X-ray photoelectron spectroscopy has been used to study the composition of the deposited films. X-ray diffraction and atomic force microscopy techniques revealed that the deposited films have an oriented microcrystalline structure after annealing at 900°C with smooth surface. Electronic, mechanical and tribological properties of these films have also been discussed.
Self-Formed Aluminum Nitride Microtubes that Exhibit a Large Bending Stress
Authors: Akiyama Morito , Shobu Kazuhisa , Xu Chao-Nan , Nonaka Kazuhiro 
Published: April 2011

ABSTRACTWe have investigated the aluminum nitride microtubes made of aluminum nitride thin film. Aluminum nitride thin film deposited on aluminum foil forms microtubes of itself at room temperature when the aluminum foil is dissolved in hydrochloric acid solution. The aluminum nitride microtubes exhibit a large bending stress of 1100 94 megapascals. The bending stress is more than three times larger than the bending strength of aluminum nitride bulk. The diameter of the microtubes is proportional to the film thickness. The bending stress is independent of the film thickness and is fixed.
Postbuckled Square Thin Film Membranes Under Differential Pressure
Authors: Kramer Torsten , Paul Oliver 
Published: April 2011

ABSTRACTWe report quantitative results on the load-deflection response of compressively prestressed square membranes under differential pressure. The membranes consist of 0.485 μm and 1.9 μm thick silicon nitride films. For these square membranes we observed a new symmetry transition of the deflection profile between a state without reflection symmetries at small loads to a state with reflection symmetries at sufficiently large loads. The load-deflection response was modeled by finite element simulations covering a wide range of prestrains e0 and pressures using various geometries. From the symmetry transition process, Young's modulus E = (150±5) GPa and the prestrain ε0 = (1.6±0.1) 10-3 of the membrane material was extracted.
Strain Rate Dependent Behavior of Pure Aluminum and Copper Micro-Wires
Authors: El-Deiry P. A. , Vinci R. P. 
Published: April 2011

ABSTRACTIn order to shed light on the role that grain boundaries and dislocations play in anelastic relaxation of thin films and small-scale structures, we measured the effective elastic moduli of 99.99% pure Al and Cu 10 m m diameter micro-wires in the as-received (drawn and slight tempered) and annealed states. Moduli were determined using microtensile tests at various strain rates (6.7x10-6s-1, 1.3x10-5s-1, 2.6x10-5s-1, 4.5x10-5s-1, 2.5x10-4s-1, 4.5x10-4s-1). Focused-ion beam scanning electron microscopy was used for imaging grain sizes. Results from the as-received wires are compared with the annealed wires to illustrate the effects of grain size and dislocation density on effective moduli, which closely relates to grain boundary sliding and dislocation motion, respectively. We conclude that microstructure is more significant than scale in inducing anelasticity in small-scale wires and, by extension, thin films.
Void Intergranual Motion Under the Action of Electromigration Forces in Thin Film Interconnects with Bamboo Structure
Authors: Oren Ersin Emre , Ogurtani Tarik Omer 
Published: April 2011

ABSTRACTThe rigorous formulation of the internal entropy production, and the generalized forces and conjugate fluxes associated with the virtual displacement of a triple junction are presented in multi-component systems. Extensive computer simulations are performed on the void configurational evolution during the intergranual motion; under the actions of capillary and electromigration forces in thin film metallic interconnects with bamboo structure having various grain textures. The texture studies in this work show clearly that there are two different and very distinct modes, namely: the grain boundary carving or tearing mode, and the interconnect edge cutting mode by the oblique slit formation (about 450) on the wind-side of the grain boundary.
Mechanical Behavior of Contact Aluminum Alloy
Authors: Read David T. , Cheng Yi-Wen , McColskey J. David , Keller Robert R. 
Published: April 2011

ABSTRACTWe report the results of tensile tests of thin films of Al-0.5 % Cu deposited on bare silicon. This material was subjected to the complete CMOS fabrication process, including a high-temperature heat treatment. Contact metal makes the electrical connection between the metal wiring and the silicon transistors in a chip. Room-temperature values of yield strength, ultimate tensile strength, and elongation were all lower than the corresponding values found previously for pure electron-beam-evaporated aluminum films. The strengths and elongation decreased slightly as the specimen temperature was raised from 25 to 150°C. The slopes of the stress-strain curves from unloading-reloading runs were lower than the accepted Young's modulus of bulk polycrystalline aluminum. The results are interpreted with the help of scanning and transmission electron microscopy.
Magnetoresistive, Mechanically Hard Superlattices of CrN, NbN, TiN Multilayers Deposited on Monocrystalline Si Wafers
Authors: Wolkenberg Andrzej , Wrzesinska Hanna , Bochenek Andrzej , Tokarz Adam , Nitkiewicz Zygmunt , Przeslawski Tomasz , Ratajczak Jacek , Dluzewski Piotr 
Published: April 2011

ABSTRACTHardness measurements on thin films have to face the problem of the effect of the substrate hardness on the obtained result. Also the method of hardness measurement exerts a considerable influence on the experimental data. Some models, which take such effects into account, are presented. We describe experimental results of hardness measurements made with the Vickers 5g probe. Nitride layers (CrN, TiN, NbN), superlattices composed of these nitrides and thin metal films deposited either on the monocrystalline Si or metallic substrates such as steel or copper have been investigated.We also present measurements of the magnetoresistivity (MR) effect. on superlattices, which consist of the multilayers TiN/NbN deposited on Si substrates. Layers of different thickness of TiN and NbN obtained by the reactive sputtering method with different superlattice period values (L) and number have been studied. The composite hardness of the structures (superlattice on Si) was found to reach 80 GPa and MR value in the best probes was ~80% (for fields from some Gs to kGs). When the supporting thin metallic layer was present, then its influence on the composite hardness was also observed.
Epitaxial Island Growth and the Stranski-Krastanow Transition
Authors: Cullis A.G. , Norris D.J. , Walther T. , Migliorato M.A. , Hopkinson M. 
Published: April 2011

AbstractThe way in which the Stranski-Krastanow epitaxial islanding transition can be controlled by strain due to elemental segregation within the initially-formed flat ‘wetting’ layer is examined in detail. Experimentally measured critical ‘wetting’ layer thicknesses for the InxGa1−xAs/GaAs system (x = 0.25 - 1) are demonstrated to show good agreement with values calculated using a segregation model. The strain energy associated with the segregated surface layer is determined for the complete range of deposited In concentrations using atomistic simulations. The segregation-mediated driving force for the Stranski-Krastanow transition is considered to be important also for all other epitaxial systems exhibiting the transition.
Composition and Structure of Epitaxial CaF2 Layers at the First Stages of Their Growth on Si(111)
Authors: Würz R. , Bohne W. , Fuhs W. , Röhrich J. , Schmidt M. , Schöpke A. , Selle B. 
Published: April 2011

AbstractCaF2 films with thicknesses in the monolayer range (<20 Å) were grown on Si(111) by evaporation from a CaF2 source at UHV conditions. They were characterized ex-situ by Heavy-Ion Elastic Recoil Detection Analysis (HI-ERDA), RBS/Channeling, X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM). The F/Ca ratio of the films was found to depend on the growth temperature Ts and to deviate appreciably from the stoichiometric composition (F/Ca=2). Due to an interface reaction which leads to a CaF-interface layer a change from polycrystalline to epitaxial growth occurs at Ts=450°C. At higher temperature film growth started with a closed layer of CaF on top of which CaF2 layers with an increasing fraction of pinholes were formed. By means of a two-step process at different temperatures, the amount of pinholes could be strongly reduced. It was found, that buffer layers of CaF2 with a CaF interface layer introduced in Au/p-Si contacts enhance the barrier height by as much as 0.36eV to values of 0.64eV.
Evolution of Stress and Relaxation of Strain of Ge and SiGe Alloy Films on Si(001)
Authors: Koch R. , Schulz J. J. , Wassermann B. , Wedler G. 
Published: April 2011

AbstractWe report on real time stress measurements by a sensitive cantilever beam technique of Ge and SiGe Alloy Films on Si(001) in combination with structural investigations by in situ STM (scanning tunneling microscopy) and ex situ AFM (atomic force microscopy). Characteristic features in the stress curves provide detailed insight into the development and relief of the misfit strain as well as the respective growth mode. For the Stranski-Krastanow system Ge/Si(001) the strain relaxation proceeds mainly in two steps: (i) by the formation of 3D islands on top of the Ge wetting layer and (ii) via misfit dislocations in larger 3D islands and upon their percolation. Co-deposition of Si influences the stress behavior drastically. The growth mode changes from Stranski-Krastanow to a kinetic 3D island mode at Si concentrations of about 20% leading to the so far smallest quantum dots of the Ge/Si system.
Atomistic Modeling Of Co Growth On Cu(111)
Authors: Khalil Joseph , Bozzolo Guillermo , Farías Daniel , Parga A.L. Vázquez de , Miguel J.J. de , Miranda R. 
Published: April 2011

AbstractThe BFS method for alloys is applied to the study of Co growth on Cu(111). The parameterization of the Co-Cu system is obtained from first-principles calculations, and tested against known experimental features for low coverage Co deposition on Cu(100) and Cu(111). Atomistic simulations are performed to investigate the behavior of Co on Cu(111) as a function of coverage.
Continuum imit of a tep Flow odel 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. ur goal is to derive a consistent contin uummodel for the ev olutionof the lm surface. Away from peaks and valleys, the surface height solves a Hamilton- acobi equation (H E). he peaks are free boundaries for this H E. heir evolution must be speci ed by boundary conditions re ecting the microscopic physics of nucleation. e investigate this boundary condition by numerical simulation of the step ow dynamics using a simple n ucleationlaw. ur results rev ealthe presence of sp ecial structures in the pro le near a peak; we discuss the relationship between these structures and the contin uumequation. e further address the importance of ev aporationfor matching the local behavior near the peak to the solution of the contin uum equation.
An extended Cahn-Hilliard model for interfaces with cubic anisotropy
Authors: Abinandanan T.A. , Haider F. 
Published: April 2011

AbstractFor studying systems with a cubic anisotropy in interfacial energy σ, we extend the CahnHilliard model by including in it a fourth rank term, which leads to an additional linear term in the evolution equation for the composition field. It also leads to an orientation-dependent effective fourth rank coeficient γ(hkl) in the governing equation for the one-dimensional composition profile across a planar interface. The main effect of a non-negative γ(hkl) is to increase both σ and interfacial width w, each of which, upon suitable scaling, is related to γ(hkl) through a universal scaling function. The anisotropy in the interfacial energy can be large enough to give rise to corners in the Wulff shapes in two dimensions. In particles of finite sizes, the corners get rounded, and their shapes tend towards the Wulff shape with increasing particle size. In the study of unmixing of concentrated alloys, the anisotropy nt only leads to non-spherical particle shapes, but also to strongly elongated morphologies.
Chemical Vapor Deposition by Pulsed Ultrasonic Direct Injection of Liquid Precursors Produces Versatile Method for Creation of Thin Film Circuits and Devices.
Authors: Leiby Mark W. 
Published: April 2011

ABSTRACTWe demonstrate a unique, ultrasonic direct injection method that employs nanophase materials (e.g. polymers, metal-organic and ceramic precursors). By use ofin situprocess control, and modification of process parameters, morphology, and structure may be varied to produce desired characteristics. By sequential application of these strategies one may fabricate MEMS, OLED's, deposit conformal coatings, create surface acoustic wave (SAW) chemical sensors, and many other thin film circuits and devices.
An Integrated Tool for Rapid Prototyping of Electronic Circuits Using a Laser Direct Write Technique
Authors: Mathews Scott A. , Duignan Michael 
Published: April 2011

ABSTRACTA laser-based tool has been developed for the fabrication of electronic circuits. The tool integrates three separate functions on a single platform. These functions are deposition, laser processing, and laser micromachining. Deposition is accomplished by dispersing a target material in a thin layer over a transparent backing layer, holding the target material in close proximity to a receiving substrate, and irradiating the target material from behind with a short pulse UV laser. The UV pulse vaporizes a small amount of the material at the material/backing interface, thereby propelling the remainder of the target material toward the receiving substrate. Patterning is achieved either by translating the receiving substrate, scanning the laser beam, or a combination of the two. After transfer, most materials require some thermal processing: either oven baking or laser sintering. Fabricated circuits have included conductors (Ag, AgPd, AgPt, Cu), resistors (cermet and polymer thick film), and dielectrics (ceramic and polymer thick film). These materials have been patterned with feature sizes as small as 10 m and linear write speeds as high as 1 meter per second. The tool includes an integrated, near IR laser which can be operated both CW and pulsed for thermal processing. Laser sintering of metals, cermet resistors, and ceramic dielectrics has been demonstrated on low temperature, polymer substrates. The localized heating achievable with the laser allows the sintering or annealing of high temperature materials without damaging the underlying substrate. The tool includes a complete, state-of-the-art laser micromachining system, capable of milling recesses, drilling vias, trimming components, and excising circuits. No masks or phototools are required. No photoresists or wet chemistries are needed. The tool does not require a clean room environment. The combined functionality and speed result in a flexible and powerful tool for the rapid prototyping of circuits, and potentially, small scale production.
Direct Write Microbatteries for Next-Generation Microelectronic Devices
Authors: Swider-Lyons Karen E. , Piqué Alberto , Arnold Craig B. , Wartena Ryan C. 
Published: April 2011

ABSTRACTMicrobatteries and integrated microbattery systems are likely to be the sole power source or a power-source component for the next generation of microelectronic devices. As part of the LEAPS (Laser Engineering of Advanced Power Sources) program, custom-designed microbatteries and ultracapacitors will be integrated in microelectronic circuits for optimum performance. The Naval Research Laboratory's Matrix-Assisted Pulsed-Laser Deposition Direct-Write (MAPLE DW) process is used to rapidly fabricate various primary and secondary (non-rechargeable and chargeable) electrochemical power sources. This laser forward-transfer process can be used to transfer any type of battery material and battery material mixtures, including polymers, hydrated oxides, metals, and corrosive electrolytes. Additional laser micromachining capabilities are used to tailor the battery sizes, interfaces, and configurations. Examples are given for planar RuO2 ultracapacitors and stacked alkaline batteries.
Direct-Write Processes as Enabling Tools for Novel Antenna Development
Authors: Irwin Bryan S. , Taylor Robert M. , Wilhelm Michael J. , Church Kenneth H. , Culver James W. , Werner Douglas H. 
Published: April 2011

ABSTRACTSignificant research effort is regularly applied to the goal of reducing the size of radio-frequency antennas while maintaining the entire set of positive attributes of proven but relatively large antennas. Such parameters as frequency response (multiple or single), bandwidth, and complexity of the antenna-driver balun structures require iterative optimization. The direct-write processes now available have enabled the insertion of reactive-loading elements as integral parts of the antenna structure, especially into new conformal designs. These reactive-loading elements were used in conjunction with modern design techniques to achieve antenna devices that were reduced in size to as much as half that of traditional counterparts. The performances of the miniaturized antennas constructed by direct-write methods were evaluated and compared to those of traditional antenna structures.
Microstructural Study and Thermal Modeling of Laser Formed Ti-6Al-4V
Authors: Kelly S.M. , Kampe S.L. 
Published: April 2011

ABSTRACTA two-dimensional thermal model for a commercial laser additive manufacturing (LAM) process has been developed to predict the thermal history of Laser Formed Ti-6Al-4V single line (rib-on-web) builds. The thermal model has been developed to assist in the prediction and interpretation of the as-processed microstructure, which evolves as a result of the complex thermal history that develops as a result of the deposition of multiple layers of material. In the current work, the model is used to show that the presence of layer bands is a result of different regions in the build experiencing varying super b transus time, temperature, and cooling rate conditions within different regions in the build.