bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Novel Process for Fabricating Force Sensors for Atomic Force Microscopy
Authors: Farooqui M. M. , Evans A. G. R. 
Published: March 2011

ABSTRACTThe new technique of scanned force microscopy which enables imaging surface features with sub nanometre resolution has been made possible by the development of highly sensitive, hysteresis free force sensing cantilevers and the availability extremely sharp probing tips. Such cantilevers with integral tips can be micromachined using IC compatible technology, and several processes have been described in literature for their fabrication. These are based on different etching schemes, and require two or more masking stages. A novel process using a single mask is described here for the fabrication of single crystal silicon cantilevers with integral sensing tips. The cantilever thickness can be tailored to provide a range of force constants and resonant frequencies, and the tip profile can be varied from pyramidal to highly cusped. As only a single mask is used in the fabrication, there are no mask alignment errors and precise location of the tip is thereby achieved. This eliminates any twist in the cantilever during scanning which could give rise to distorted imaging. The complete fabrication process and the mask design is described together with SEM photographs of the first batch of devices, which have been evaluated by retrofitting to a commercial atomic force microscope.
LPCVD Silicon Dioxide Sacrificial Layer Etching for Surface Micromachining
Authors: Monk David J. , Soane David S. , Howe Roger T. 
Published: March 2011

ABSTRACTThe key step in producing a movable microstructure is the controllable sacrificial layer etching process. For the current study, a 1 μm silicon-rich silicon nitride structural layer was deposited on a 2 μm phosphosilicate glass (PSG) sacrificial layer that had been deposited on a single-crystal silicon wafer. Silicon nitride, unlike the more common polycrystalline silicon (poly-Si) structural material, is transparent and, therefore, allows the observation of an etch front in the underlying PSG sacrificial layer. The PSG is an amorphous silicon dioxide, with phosphorus added as a controlled impurity, that can be selectively etched in hydrofluoric acid. Several experiments have been performed with four HF concentrations using these test structures. Diffusion limited etching is observed at long etching times for each concentration. Additional experimental work has been done to determine appropriate kinetic expressions for the PSG/HF reactions.The sacrificial layer etching process has been modeled as a chemical reaction/diffusion system. Constants for the kinetic expression have been found from independent experimental work. This Deal-Grove type model assumes isothermal conditions, constant density solution, onedimensional etching, and the equality of the diffusion and reaction fluxes. The model calculates the HF surface concentration and the length of PSG underetched as a function of time. It fits the data well but requires the use of an unphysical diffusion coefficient. An extension of the Deal-Grove model to nonfirst order kinetics allows for a reasonable estimate of the reactant/product mixture diffusivity in water to be used when fitting the model to experimental data.
Non-Linear Constitutive Properties of Piezoelectric Ceramics
Authors: Cao H. C. , Evans A. G. 
Published: March 2011

ABSTRACTExperiments have been conducted to study the nonlinear constitutive properties of ferroelectric ceramics for large strain operation applications, where the mechanical behavior of the material dictates the overall electromechanical response of the devices. For this purpose, polarization and strain are measured continuously on a compression cuboid. Severe non-linear and hysteretic behavior is observed in these materials. An empirical formulation has been proposed to model the constitutive laws applicable to this non-linear deformation. Physical mechanism is provided, that is attributed to this constitutive law.
Characterization of Pulsed Laser Deposited Zinc Oxide
Authors: Ianno N. J. , McConville L. , Shaikh N. 
Published: March 2011

ABSTRACTThe pulsed laser deposition of zinc oxide films (ZnO) has been studied as a function of laser wavelength, and substrate temperature. The deposited films were characterized by x-ray diffractometry, Auger electron spectroscopy, and scanning electron microscopy. Highly textured (002) ZnO films have been deposited at substrate temperatures of 300 C with laser wavelengths of 532 nm and 248 nm. However, the energy fluence of 248 nm radiation controls the degree of texturing, allowing highly textured films to be deposited at room temperature.Smart structures based on embedded, textured ZnO coated fibers, and wires exhibit excellent piezoelectric response to external stress.
Impact, Friction, and Wear Testing of Microsamples of Polycrystalline Silicon
Authors: Lee Abraham P. , Pisano Albert P. , Lim Martin G. 
Published: March 2011

ABSTRACTThis paper gives an overview of the recent developments in impact, friction, and wear testing of polycrystalline silicon (polysilicon) based micro electromechanical structures. Impact-friction actuated micromechanisms form a new type of actuators. In this type of actuators, lateral resonant structures are retracted by electrostatic comb drives and are propelled forward toward the actuated micromechanism by elastic forces generated by folded beam flexures at frequencies ranging from 10 kHz to 20 kHz. This sequence generates normal impact and tangential friction contact between the two microstructures, raising wear concerns. Two sorts of impact test structures are introduced in this paper, One with a resonant micro impact bumper (MIB) striking a stationary impact wall anchored ofn the substrate. Another is a testing of two MIBs driven to impact each other. Two types of impact actuators are also described, an impact actuated micro angular oscillator (MAO) and a polysilicon micro vibromotor. The vibromotor is a rotor driven by oblique impact on the rim by a converter pointer tip attached to a lateral resonator. Some initial results of impact wear testing as well as static and dynamic friction done by researchers in the field are also described in the paper. Finally, many areas where material scientists can contribute to this field are suggested.
Guest-Host Composite Films Containing Oligomeric Ladder Subunits for χ(3) NLO Applications
Authors: Sapochak Linda , Strohkendl Friedrich , McLean Malcolm R. , Dalton Larry R. , Spangler Charles W. , Nickel Eric G. 
Published: March 2011

ABSTRACTSeveral ladder polymer systems, such as POL and PTL, have displayed large third-order optical nonlinearities. However, these polymers are insoluble in common organic solvents, and as such are not amenable to studies of substituent effects on the nonlinear optical properties. During the past year we have developed synthetic and processing methodology to produce optical quality guest-host composites in polycarbonate, poly(methyl vinyl ether) and most recently polystyrene. In this paper we describe the synthesis of selected guest ladder 5-ring oligomers, and describe the preliminary NLO characterization as thin film composites.
Preparation and Optical Properties of a Reverse-Mode Polymer Dispersed Liquid Crystal Film
Authors: Gotoh Tomohisa , Murai Hideya , Hasegawa Etsuo , Mizoguchi Katsuhiro 
Published: March 2011

ABSTRACTTwo new types of reverse-mode polymer-dispersed liquid crystal films have been developed and successfully produced. The first was produced by UV-curing of a mixture of dual frequency addressable liquid crystal (DFALC) and UV-curable polymers under an applied voltage at a frequency lower than the crossover frequency (fc) of the DFALC. This first type is referred to as a dual frequency type. The second type was produced by injecting a liquid crystal having negative dielectric anisotropy into a specially prepared porous polymer film from which liquid crystal having positive dielectric anisotropy had previously been extracted. The type thus produced through such “negative-for-positive” substitution is referred to as a substitution type. While the dual frequency type can not be driven at a low frequency, substitution type can, which gives it a distinct advantage. Other electro-optic characteristics of the two types of films, including alignment properties of the liquid crystal molecules, are also discussed.
Linear and Non-Linear Optical Properties of (2-Cyano-5-Methoxy-1,4-Phenylenevinylene) and Paraphenylenevinylene Copolymers
Authors: Kim Jang-Joo , Hwang Do-Hoon , Kang Shin-Woong , Shim Hong-Ku 
Published: March 2011

ABSTRACTPoly(CMPV-co-PV) have been synthesized via water soluble sulfonium salt precursor route and their linear and non-linear optical properties were characterized. The electro-optic response was stable up to 100°C when the materials were poled during the elimination. The thermal stability and mechanical strength of PPV and its derivatives, and easy processibility from the precursor polymers suggest a new approach for the molecular design of the 2nd order non-linear optical polymers.
Monoclonal Antibodies as New Macromolecular Hosts for Porphyrins
Authors: Harada Akira , Okamoto Kazutake , Fukushima Hiroyuki , Shiotsuki Keizou , Kamachi Mikiharu 
Published: March 2011

ABSTRACTMonoclonal antibodies against meso-tetrakis(4-carboxyphenyl porphine)(TCPP) were prepared by immunizing Balb/c mice with TCPP bound keyhole limpet hemocyanin covalently and fusing the spleen cells with myeloma cells by using poly(ethylene glycol). The antibodies bind TCPP strongly with the dissociation constants of 10−6−2.5 × 10−7 M. One of the antibodies causes a large shift of the Soret band of TCPP to a longer wavelength and large induced Cotton effects(ICD) on TCPP. Quantitative analyses of the binding of TCPP to the antibody by ICD show that not only one-to-one binding but two-to one(binding site: TCPP) binding occurs in excess of the antibody over TCPP.
Encapsulation and Reactivity of Proteins in Optically Transparent Porous Silicate Glasses Prepared by the Sol-Gel Method
Authors: Yamanaka Stacey A. , Ellerby Lisa M. , Lan Ester H. , Nishida Clinton R. , Nishida Fumito , Dunn Bruce , Valentine Joan Selverstone , Zink Jeffrey I. 
Published: March 2011

ABSTRACTCopper-zinc superoxide dismutase (CuZnSOD), myoglobin, hemoglobin and glucose oxidase are encapsulated in stable, optically transparent, porous, silica glass matrices synthesized under mild conditions using novel sol-gel synthetic techniques. The biomolecules retain their characteristic reactivities and spectroscopic properties. The porous glasses allow transport of small molecules into and out of the glasses at reasonable rates but retain the protein molecules within the pores. The chemical reactions of the immobilized proteins are monitored by means of changes in their visible absorption spectra. Four encapsulated proteins are studied: CuZnSOD reacts with CN−; metmyoglobin is reduced to its deoxy form and then reacts with O2to make the oxy form and CO to make the carbonyl form; methemoglobin is reduced to its deoxy form and reacted with CO to make the carbonyl form; and glucose oxidase is reacted with glucose to make gluconic acid.
Oxygen Configurations and their Effect on Charge Transfer in YBa2Cu3OZ
Authors: Mccormack Ryan , Ceder Gerbrand , Fontaine Didier De 
Published: March 2011

AbstractThe relationship between oxygen structure, charge transfer (hole count), and oxygen content in the YBa2Cu3Oz superconductor is studied by combining Monte-Carlo simulation with existing electronic structure calculations. The present model proposes an expansion of the hole count in terms of oxygen configuration variables for states of an arbitrary degree of order. Calculations of hole count as a function of oxygen content suggest that oxygen ordering is, at least in part, responsible for the observed plateau structure of Tc vs. oxygen content z.
Fracture Modelling of Granular Materials
Authors: Schlangen E. , Van Mier J.G.M. 
Published: March 2011

AbstractA lattice type model is used for simulating fracture processes in concrete and sandstone. Two type of lattices were adopted: a regular triangular lattice and a random lattice. With both lattices the fracture process in four point shear specimens can be simulated. The results are in good agreement with experimental observations. With the regular lattice, where disorder is implemented via a generated grain structure, the typical failure mechanism for granular materials, crack face bridging, is retrieved. With the random lattice, these details cannot be simulated, but the macroscopic crack pattern is obtained correctly with an enormous decrease in the number of elements.
Effects of Hydrogen on the Fracture Properties of Σ9 and Σ11 Tilt Boundaries in Nickel
Authors: Angelo J.E. , Gerberich W.W. , Moody N.R. , Foiles S.M. 
Published: March 2011

AbstractIn this study, the Embedded Atom Method is combined with Monte Carlo and molecular dynamics simulations to study the fracture properties of Σ9 and Σ11 tilt boundaries in nickel. The Monte Carlo simulations are used to simulate the exposure of the bicrystal to a hydrogen environment at 300° C. These simulations establish the equilibrium distribution of hydrogen at the boundaries as a function of far-field concentration. The effect of the hydrogen on the fracture process is then studied with molecular dynamics. It will be shown that the fracture stress of the Σ9 boundary is affected over a wider range of far-field concentrations than the Σ11 boundary, although the Σ11 boundary shows that catastrophic failure occurs when the sample is charged beyond a certain far-field concentration.
Dynamics of Cu Surfaces at High Temperatures
Authors: Stoltze Per 
Published: March 2011

AbstractThe structure and dynamics of Cu(100), Cu(110) and Cu(111) have been studied by Molecular Dynamics simulations using the potential derived from effective medium theory. The formation energy for adatoms is lower for Cu(llO) than for Cu(lO0) or Cu(lll). The relatively high concentration of defects on Cu(11O) makes this surface premelt near the bulk melting point. The surface diffusivity is high for all three surfaces at elevated temperatures, the diffusion mechanism at the disordered surfaces appears to be quite complicated.
Monte Carlo Simulations of Solute-Atom Segregation at [001] Symmetrical Twist Boundaries in the Ni-Pi System
Authors: Udler D. , Seidman D. N. 
Published: March 2011

AbstractAtomistic Monte Carlo simulations utilizing many-body embedded atom method (EAM) potentials have been carried out for a series of symmetrical [001] twist boundaries in Pt-3 at.% Ni and Ni-3 at.% Pt alloy bicrystals at 850 K throughout the misorientation range 0° to 45°. The results demonstrate enhancement of the solute-atom concentration at twist boundaries for both alloys; the interfacial Gibbsian excess is a factor of two greater on the Ni-rich side of the phase diagram. The spatial distributions of solute atoms in the vicinity of the interfaces are found to be markedly different on the two sides of the Ni-Pt phase diagram. For low-angle boundaries on the Pt-rich side solute atoms tend to segregate in hourglass-like regions along the cores of the primary grain boundary screw dislocations, while in the case of Ni-3 at.% Pt they occupy bipyramidal regions centered on the cells of the dislocation grid. The former behavior explains the oscillatory solute-atom concentration profiles nomnal to the plane of an intetface.
Combining Molecular Dynamics and Monte Carlo Simulations to Model Chemical Vapor Deposition: Application to Diamond
Authors: Brenner D.W. , Robertson D.H. , Carty R.J. , Srivastava D. , Garrison B.J. 
Published: March 2011

AbstractGas-surface reactions of the type that contribute to growth during the chemical vapor deposition (CVD) of diamond films are generally completed in picoseconds, well within timescales accessible by molecular dynamics (MD) simulations. For low-pressure deposition, however, the time between collisions for a surface site can be microseconds, which makes direct modeling of CVD crystal growth impossible using standard MD methods. To effectively bridge this discrepancy in timescales, the gas-surface reactions can be modeled using MD trajectories, and then this data can be used to define probabilities in a Monte Carlo algorithm where each step represents a gas-surface collision. We illustrate this approach using the reaction of atomic hydrogen with a diamond (111) surface as an example, where we use abstraction and sticking probabilities generated using classical trajectories in a simple Monte Carlo algorithm to determine the number of open sites as a function of temperature. We also include models for the thermal desorption of hydrogen that predict that growth temperatures are not restricted by the thermal loss of chemisorbed hydrogen.
Monte Carlo Simulations on SIMD Computer Architectures
Authors: Burmester C. P. , Wille L. T. , Gronsky R. 
Published: March 2011

AbstractAlgorithmic considerations regarding the implementation of various materials science applications of the Monte Carlo technique to single instruction multiple data (SIMD) computer architectures are presented. In particular, implementation of the Ising model with nearest, next nearest. and long range screened Coulomb interactions on the SIMD architecture MasPar MP-1 (DEC mpp-12000) series of massively parallel computers is demonstrated. Methods of code development which optimize processor array use and minimize inter-processor communication are presented including lattice partitioning and the use of processor array spanning tree structures for data reduction. Both geometric and algorithmic parallel approaches are utilized. Benchmarks in terms of Monte Carlo updates per second for the MasPar architecture are presented and compared to values reported in the literature from comparable studies on other architectures.
Finite-Temperature Properties From a Single Zero-Temperature Energy Minimization
Authors: Rickman J. M. , Najafabadi R. , Srolovitz D. J. 
Published: March 2011

AbstractA method for calculating the thermodynamic properties of both perfect crystals and defects from a single zero-temperature energy minimization is described. The validity of the method is demonstrated by determining the free energy and the lattice parameter of a perfect Au crystal, as modelled by an embedded-atom method (EAM) potential. In addition, we determine the temperature dependence of the vacancy formation energy and the excess free energy of a (100) free surface.
Molecular Origins of the Unique Conformational Properties of the Polysilanes: A Molecular Dynamics Study of Poly(Di-N-Hexylsilane)
Authors: Welsh William J. , Tersigni Samuel H. , Lin Wangkan 
Published: March 2011

AbstractThe conformational dynamics of a model compound for poly(di-n-hexylsilane) (PDHS) has been explored using the new molecular dynamics program MM3-MD. MM3-MD trajectories at variable temperatures reveal two abrupt conformational transitions, one near -182°C and another near -175°C, associated with two energy barriers on the potential-energy surface. The first transition near -182°C allows shifts in the backbone torsion angle from that defined by the global energy minimum designated off-trans to that corresponding to a statistical collection of torsion angles within the range trans ±30°. The second transition near -175°C allows the backbone torsion angle to explore the remainder of its torsional space. The sidechain dynamics follows a similar pattern. We suggest that the abrupt transition calculated here at -182°C for “gas.phase” PDHS corresponds to that observed for PDHS at -28°C in solution and at 42°C in the solid state.
Scanning Simulation Procedures for Calculation of the Entropy, the Pressure, and the Chemical Potential of Many-Chain Systems
Authors: Meirovitch Hagai 
Published: March 2011

AbstractUsing two simulation techniques, the scanning and the hypothetical scanning methods we study a system of many chains with excluded volume contained in a “box” on a square lattice. With these methods the value of the sampling probability P of a configuration is known and therefore the entropy S can be calculated (S ∼ In P) without the need to resort to thermodynamic integration. Thus, the pressure and the chemical potential can be obtained with high accuracy directly from the entropy using standard thermodynamic relations. Our simulation results are compared to the approximate theories of Flory, Huggins, Miller and Guggenheim and to the recent improved theories of Freed and coworkers.
Formation of Buried Ternary Silicide Layers in Silicon by Ion Beam Synthesis (IBS)
Authors: Panknin D. , Wieser E. , Skorupa W. , Querner G. , Vöhse H. , Albrecht J. 
Published: March 2011

ABSTRACTA buried (Fe1−xCox) Si2 (x < 0.2) layer was formed by two step high dose implantation of Fe and Co into {100}-Si with as well as without intermediate annealing between the implantations. The suicide layer remains semiconducting if the temperature of the post implantation annealing is lower than 850°C. The depth distribution of Fe and Co, the phase composition as well as the microstructure of the layer system was investigated.
Energy Dependence of Amorphization of Ge by Kr Ions
Authors: Birtcher R. C. 
Published: March 2011

ABSTRACTThin Ge specimens have been irradiated with Kr ions of different energies, and the dose required for complete amorphization determined by in situ transmission electron microscopy. Because Ge is directly amorphized by a single energetic Kr ion, onset of amorphization was detected after the lowesi ion doses. The Kr dose required for complete amorphization was found to increase linearly with ion energy over the range 0.5 MeV to 3.5 MeV. With the assumption that the defect density required for amorphization is independent of ion energy, the number of defects produced in a thin specimen by each ion decreases with increasing energy as the reciprocal of the incident ion energy. TRIM calculations indicate that there is a slight decrease in the amount of damage required with increasingion energy.
Mechanism of Dose-Rate Dependence of Electrical Activation in Ion-Implanted GaAs
Authors: Kanayama Toshihiko , Tanoue Hisao 
Published: March 2011

ABSTRACTTo elucidate the mechanism of dose rate (DR) dependence of electrical activation, following two questions are investigated; why the amount of damage remaining after ion bombardment depends on DR and why it affects the electrical activation after high temperature annealing. From the observation that the DR dependence scales with temperature, the activation energy of recovery during ion irradiation has been estimated to be 0.75 and 1.0 eV. A higher DR suppresses the recovery and results in more damage, which in turn delays the electrical activation of implanted impurities.
Ion Species Dependence of Electrical Characteristics in Ion Implanted GaAs
Authors: He L. , Anderson W. A. 
Published: March 2011

ABSTRACTFluorine, boron and oxygen implantation in GaAs has been investigated by electrical characterization using current-voltage (I-V), capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) techniques. Ion implantation at lOOkeV energy was conducted with doses of 1011 and 1012/cm2. Carrier compensation was observed in each implanted sample. The compensation effect strongly depended on ion implantation conditions and ion species. Severe surface damage was also induced which degrades electrical performance. Rapid thermal annealing (RTA) treatment showed the heavier ion implanted samples to be more thermally stable. Defect levels for each implanted species were compared and identified.