bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Sputtered Tungsten Silicide as a Micromechanical Material
Authors: Ger Muh-Ling , Brown Richard B.
Published: March 2011

Refractory metal silicides, such as tungsten silicide (WSix), have been used for integrated circuit interconnect and self-aligned MESFET gates because of their low resistivity and thermal and chemical stability. These same characteristics make refractory metal silicides interesting materials for prospective use in micromechanical structures. However, little information on residual stresses, elastic moduli, or other micromechanical properties has been available for refractory metal silicide films.

This paper presents morphology and stress characteristics of sputter-deposited tungsten silicide films, including orientation-dependent variations, as functions of deposition parameters. The biaxial elastic modulus and thermal coefficient of expansion are found for our sputtered films. Stress-measurement methods and annealing are discussed. Released diaphragms of different sizes and shapes, having controlled residual stress, have been fabricated.
Mechanical and Piezoresistive Properties of Graphite-Filled Polyimide Thin Films
Authors: Frazier A. Bruno , Khan M. R. , Allen Mark G.
Published: March 2011

The piezoresistive effect of materials is used as the basis for many types of microsensors. Polyimide, a material widely used in microelectronic fabrication, may be made to exhibit this effect by addition of small graphite particles to form a composite material. Polyimide / graphite based piezoresistive films have the advantage of being spin-castable, plasma-processable, highly chemically resistant, and thermally stable up to 400 °C in nitrogen atmospheres. In this work, piezoresistive polyimide films are formed by addition of various amounts (loadings) of graphite particles one micron in diameter or less to DuPont PI-2555 polyimide. Thin films of these materials are spin-cast on silicon wafers, and an in-situ load-deflection measurement technique is used to evaluate the following film properties: piezoresistive coefficient as a function of both strain and graphite loading; Young's modulus as a function of graphite loading; and residual film stress as a function of graphite loading. The observed piezoresistive coefficient is a strong function of graphite loading, with good piezoresistive properties exhibited in the loading range of 15–25 wt% graphite.
Smart Building Materials which Prevent Damage or Repair Themselves
Authors: Dry Carolyn M.
Published: March 2011

We developed designs in which hollow porous fibers filled with chemicals release them into a matrix over time. A coating covering the fibers is degraded by chemicals, pH change, or broken by structural loading, thus, releasing the chemicals. These stimuli for release are the very agents of environmental attack.

The design to alleviate cracking consists of hollow porous fiberglass fibers containing crack-closing chemicals. The chemicals are released from the fibers when the outer sheath cracks or the fibers flex due to loading. This is the ideal situation in which the agent of environmental degradation, namely loading, is the stimulus to release the repair chemical.

The design to prevent corrosion consists of an anticorrosion chemical in hollow porous polypropylene fibers. Change in chloride ion concentration dissolves the polyol coating and allows the chemical to be released from the fiber wall. The cause of deterioration, change in chloride level which causes corrosion, is the sensor (coating deterioration) and also the activator for the remedial or preventive action (release of anticorrosion chemical).

These are distributed systems responding to environmental stimuli for sensing and repairing when and where they are needed. The control of the amount of chemical released is being researched mainly as a function of coating design and also fiber type.
The Effect of Temperature and Pressure on Residual Stress in LPCVD Polysilicon Films
Authors: Oei D-G. , McCarthy S. L.
Published: March 2011

Measurements of the residual stress in polysilicon films made by Low Pressure Chemical Vapor Deposition (LPCVD) at different deposition pressures and temperatures are reported. The stress behavior of phosphorus (P)-ion implanted/annealed polysilicon films is also reported. Within the temperature range of deposition, 580 °C to 650 °C, the stress vs deposition temperature plot exhibits a transition region in which the stress of the film changes from highly compressive to highly tensile and back to highly compressive as the deposition temperature increases. This behavior was observed in films that were made by the LPCVD process at reduced pressures of 210 and 320 mTORR. At deposition temperatures below 590 °C the deposit is predominantly amorphous, and the film is highly compressive; at temperatures above 610 °C (110) oriented polycrystalline silicon is formed exhibiting high compressive residual stress.
Nonlinear Optical Properties of Organic Photorefractive Polymers
Authors: Moerner W. E. , Walsh C. A. , Silence S. M. , Twieg R. J. , Matray T. J. , Scott J. C. , Lee V. Y. , Miller R. D. , Hache F. , Burland D. M. , Bjorklund G. C.
Published: March 2011

This paper describes the photorefractive properties of a new and growing class of materials exhibiting the effect, doped nonlinear organic polymers. We show directly using a PMMA-based copolymer with a pendant nonlinear nitroaminotolane chromophore doped with a charge transport agent that the presence of photoconductivity and optical nonlinearity are only necessary, but not sufficient to guarantee that a given materials system will yield measurable photorefractive gratings, rather than gratings due to some other process such as photochromism. To prove photorefractivity unequivocally, direct measurement of the spatial phase shift between the intensity pattern and the index modulation is best, and we summarize a convenient way to do this using two-beam coupling and sample translation. In addition to the photorefractive epoxy materials such as bisA-NPDA:DEH reported earlier (Phys. Rev. Lett. 66, 1846 (1991); Proc. SPIE1560, 278 (1992)), a new PMMA-based copolymer with pendant p-nitroaniline chromophores doped with DEH also shows photorefractive grating formation, with writing speed 100 times higher than that for the epoxy material.
Photoconductivity of Photorefractive Polymers
Authors: Scott J. C. , Pautmeier L. Th. , Moerner W. E. , Walsh C. A. , Silence S. M. , Matray T. J. , Twieg R. J.
Published: March 2011

The photorefractive effect has been recently observed by holographic grating formation in optically non-linear polymers molecularly doped with charge transport agents. Grating formation can be understood as a four-step process, the first three of which dictate the photoconductive response: charge generation, mobility and trapping. The fourth step is modulation of the refractive index by the resulting space-charge field, via the electro-optic effect. We present the results of photoconductivity experiments to determine charge generation efficiency, carrier mobility and the kinetics of recombination and trapping, focussing primarily on the epoxy polymer bisphenol-A-diglycidylether 4-nitro-1, 2-phenylenediaminc (bisA-NPDA) doped with the hole transport agent, diethylaminobenzaldehyde-diphenylhydrazone (DEH). The electric field dependence of the generation efficiency and mobility differ in detail from results on other molecularly doped polymers.
Photorefractive, Electro-Optical and Nonlinear Optical Properties of Conjugated Polymers
Authors: Peyghambarian N. , Tamura K. , Kippelen B. , Kawabe Y. , Jarka F. , Mazumdar S. , Guo D. D. , Hall H. K. , Padias A. B.
Published: March 2011

We present experimental and theoretical results on electro-optical properties of some polymeric films. Specifically, we report on our measurements regarding a new, completely polymeric and potentially photorefractive material with a large electro-optic coefficient and photoconductivity. Furthermore, we summarize our investigations of electro-absorption in a DCH polydiacetylene where the important contributions of continuum threshold on the nonlinear and electro-optical properties of conjugated polymers are emphasized.
Introduction to the Theory of Space-Charge Grating Formation in Photoconducting Polymers
Authors: Schildkraut Jay S.
Published: March 2011

Photoconducting electrooptic polymers are a new class of photorefractive material. Most applications of photorefractive materials require the formation of a space-charge grating. The formation of space-charge gratings in photorefractive semiconductors has been studied extensively. We consider the formation of photorefractive gratings in a polymer.
New Amorphous and Crystalline Complexes of Conjugated Aromatic Schiff Base Polymers
Authors: Yang Chen-Jen , Jenekhe Samson A.
Published: March 2011

New soluble amorphous and crystalline complexes of conjugated aromatic Schiff base polymers with diarylphosphates have been prepared and their molecular and electronic structures and morphology characterized by FTIR spectra, electronic absorption spectra, differential scanning calorimetry and x-ray diffraction. The diphenyl phosphate (DPP) or di-m-cresyl phosphate (DCP) complexes of the conjugated polyimines have electronic structures and optical properties that are dramatically different from the pure polymers due to the formation of polyiminium ions on complexation. At diarylphosphate : imine ratio equal to 0.50, amorphous materials are obtained whereas highly crystalline complexes are obtained at the stoichiometric ratio. The potential of complexation in modulating and enhancing the thirdorder nonlinear optical properties of this class of polymers is demonstrated.
A Novel Poling Process for Polymeric Thin Films Exhibiting Second Harmonic Generation
Authors: Barry Stephen E. , Soane David S.
Published: March 2011

Carbon dioxide is used to induce glass transition in amorphous polymer films, allowing efficient alignment of chromophores with an applied electric field. The noncentrosymmetric films thus produced are capable of second harmonic generation (SHG). This method has advantages over previously investigated poling schemes, including poling at ambient temperatures and use of high glass transition temperature polymers. Several polymeric systems have been studied. The chromophrores were either dissolved in the polymer, attached as a side chain, or incorporated into the backbone of the polymer. The SHG of the films was observed as a function temperature. Of the systems studied, polyether sulfone retains SHG capability to the highest temperature. Two different systems had the greatest retention of SHG up to the glass htansition temperature. They were Poly((4-N-ethylene-N-ethylamino)- rz-cyanocinnamate), a polymer which has the chromophore incorporated in the backbone, and 4- (dimethylamino)-4'-(dimesitylboro)azobenzene, a host-guest system with a relatively large chromophore. These and other systems will be discussed.
Electrical Fatigue in Organic Layered Photoconductors
Authors: Pacansky J. , Waltman R. J.
Published: March 2011

The relevance of photochemistry in the electrical fatigue of organic layered photoconductors is discussed. A hole transport molecule DEH undergoes a photocyclization reaction in the charge transport layer to an indazole derivative, causing residual surface charges to persist during light decay. A dye chlorodiane blue, in the presence of DEH, initiates photochemistry at the hole transport/carrier generation interface resulting in chemical consumption of the dye. An activation energy of 15 – 20 kcal/mol is reported for the dye bleaching reaction.
AZO Polymers for Reversible Optical Storage
Authors: Natansohn A. , Rochon P. , Gosselin J. , Xie S.
Published: March 2011

Amorphous high-Tg polymers films containing electron-donor-electronacceptor substituted azobenzene groups can be used as reversible optical storage materials. Optical information can be “written” on the film with a polarized argon laser beam and “read” with a low power HeNe laser. Erasing can be performed with a circularly polarized writing beam. A significant number of writing/erasing cycles can be performed on the same spot. Potential applications in optical memory, holographic storage, waveguides and second harmonic generation are discussed.
Photoinduced Charge Transfer Studies in Bolaamphiphile-Gramicidin-Porphyrin Membranes
Authors: Thompson David H. , Kim J.-M.
Published: March 2011

Synthetic ether-linked bolaform amphiphile vesicles and a novel gramicidin-porphyrin “diad” have been prepared. Photoinduced electron transfer properties of the diad were compared in bilayer (dihexadecylphosphate, DHP) and monolayer (2,2′-0-didecyl-1,1′-0-eicosamethylene-racdiglycero- 3,3′-diphosphoric acid, PS20) membrane vesicles with dithiothreitol sacrificial donor and methyl viologen electron acceptor present on both vesicle membrane surfaces. Although the rates of methyl viologen photoreduction varied depending on the mode of diad orientation within DHP bilayer membranes, photoreduction rates were not orientation-dependent in bolaform membrane vesicles containing the gramicidinporphyrin diad. The relevance of these results on vectorial electron transfer processes in closed membrane systems is briefly discussed.
Estimates of Binding Energies in Complex Crystal Structures
Authors: Jinlong Yang , Kelin Wang , Casula F. , Mula G.
Published: March 2011

A parameter-free technique already proposed by the authors to estimate the binding energy of elementary crystals is here extended to more complex crystal structures. Test calculations are presented here for several families of semiconductors of technological interest, such as XAs (X = Al, Ga, In), InX (X = P, As, Sb) and MgX (X = 0, S, Se). The accuracy of our predictions turns out to be comparable with that of previous results obtained within the local density approximation. The computational advantages of the method will be also discussed.
An Atomistic Computer Simulation of Crack Extension in Cubic Silicon Carbide
Authors: Sawamura Akitaka , Watanabe Yoichi , Yamamoto Ryoichi
Published: March 2011

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An atomistic computer simulation of mode I crack extension in cubic silicon carbide has been performed using a realistic many–body interatomic potential computed by Tersoff. The crack front is parallel to the [110] direction and the crack plane lies in the (111) plane. The stable crack tip configurations were calculated and the effective stress intensity factor and the effective crack tip position were evaluated in the relaxed atomic configuration by the least-square method. The crack was stable over a wide range of the stress intensity factors from 0. 6KG to 3. 4KG, where KG is the Griffith critical stress intensity factor. At 3.5KG an interatomic bond near the tip across the (001) plane ruptured and the crack advanced. When the crack is stable, the effective K is larger than the given K by nearly 0. 2KG to 0.4KG. Crack tip process was also simulated over a range of temperatures. At 1000K. secondary cracks were nucleated and grew like voids around the main crack, and thus the main crack was blunted.
Tight-Binding Lmto Approach to the Electronic Structure and Atomic Configuration in Extended Defects in Metals
Authors: ŠOB M. , Vitek V. , Oh Y.
Published: March 2011

A new quantum-mechanical method capable of determining atomic configurations of extended defects has been developed. The Hamiltonian is constructed using the first-principles tight-binding linear muffin-tin orbital method in the atomic-sphere approximation. A semiempirical correction is employed to describe the effect of electrons in the interstitial region and the repulsive part of the total energy is described by a pair potential. The forces on atoms are calculated by differentiating the corresponding energy terms with respect to atomic positions. The equilibriun configuration is then found by minimizing the total energy. In this approach, the electronic and chemical aspects of defect structures can be accounted for more adequately than when using central-force pair or many-body potentials. In particular, the angular dependence of interatomic forces, which is important in transition metals with unfilled d-bands, is described correctly within the present quantum-mechanical treatment.
Cluster Molecular Dynamics on Massively Parallel Computers
Authors: Nelson K. M. , Smith S. T. , Wille L. T.
Published: March 2011

We report the results of computer simulations of phase transitions in noble-gas clusters. The calculations were performed on a MasPar MP-l massively parallel computer with 8,192 processing elements (PE's). We discuss the efficient implementation of molecular dynamics algorithms for small clusters on this type of architecture. The simulations are based on a classical Lennard-Jones pair potential and follow the temporal evolution of the system by numerically integrating Newton's equations of motion using the Gear algorithm. Because the number of particles is much smaller than the number of PE's, optimal partitioning of the processing element array is an essential and non-trivial task.
Dynamics of Silver Dimer Deposition on Platinum Surfaces
Authors: Blandin P. , Massobrio C. , Buttet J.
Published: March 2011

We present molecular dynamics results on the diffusion properties of Ag monomers and dimers on the (111) surface of Pt. In particular we focus on the behavior of dimers upon collision on the surface with impact energies of 0.5eV and 5eV. We found that the dimer has the largest probability of being found stable on the surface when the temperature is in the range 150K<T<300K, while at T=OK a metastable configuration featuring monomers and dimers is likely to form.
Monte Carlo Simulation of Gas Phase Particle Formation and Sintering
Authors: Akhtar M. Kamal , Pratsinis S. E. , Lipscomb G. G.
Published: March 2011

A Monte Carlo model has been developed to describe the gas phase formation and sintering of nanoclusters. Sintering was incorporated into the model by modifying Kadanoff's algorithm [1] for random particle walks on the surface of the cluster. The effect of restructuring and sintering on cluster-cluster aggregation have been investigated via 2d simulations. In the initial stages the sintering process results in clusters which are compact on small length scales. As time progresses and the clusters become larger, the sintering process slows down and the fractal dimension of the clusters is decreased. The model shows the effect of time and temperature on the specific surface area and size distribution of clusters.
Modelling Growth Morphologies on Different Length Scales
Authors: Iwan J. , Alexander D. , Xiao R.-F. , Rosenberger F.
Published: March 2011

Microscopic morphologies of monocomponent and binary solids growing from melts and vapors are simulated with a Monte Carlo model that accounts for bulk diffusion, interface attachment and detachment kinetics and surface diffusion. The interplay between transport and interface kinetics on morphologies and its effect on microstructures including lamellar spacing, tilted lamellar and oscillatory structures is investigated. An important aspect of these models is the length scale of the simulation.
Mathematical Model of the Bridgman-Stockbarger Method to Growth Semiconductor Single Crystals
Authors: Vega E. , Muiñiz G. , Rabago F.
Published: March 2011

A two dimensional equation has been solved which represents the heat transfer equation for the growth of single crystals system called Bridgman- Stockbarger method. Two variations were analyzed with and without an insulation between heater and cooler. System without an insulation shows stability problems because it's directly affected by the boundary between the cooler and heater region, in this case we obtained a discontinuity in this point. System with an insulation shows higher stability.
Surface Sputtering of Ag{100} by KeV Particle Bombardment
Authors: Chang Che-Chen
Published: March 2011

The atoms emitted from the single-crystal surface due to keV particle bombardment have been characterized using molecular dynamics to simulate the energy dissipation process. The model system in the calculation utilizes a Ag(100) microcrystallite of about 2000 atoms which is bombarded by as many as 1600 incident Ar atoms of 2-keV energy. The surface order is found to be preserved to a certain extent during the bombardment of static particle beams. A preferred direction of ejection is observed for the lower-kinetic-energy atoms (< I eV) sputtered from the second surface layer. Most of these atoms which take off late in the collision cascade originate from positions on the surface within three to four lattice spacings from the point of impact. The ejecting atoms are confined by the top layer atoms which are still located close to their lattice points when the collision cascade subsides. In addition, the angular pattern of ejection changes slightly as the emission energy of detection is varied. We found that the angular pattern of ejection did not vary with the emission energy in the low energy regime, in which the surface structure may be better determined.
Effect of Structural Features on the Statistical Correlation of Dipole Moments on the End-to-End Distance of Polymer Chains
Authors: Galiatsatos Vassilios
Published: March 2011

A recently developed computational methodology allows the quantitative study of the correlation between the end-to-end distance of a polymer chain and its dipole moment. This paper focuses on the further analysis of this correlation and aims in identifying the structural characteristics of the polymer chain that are responsible for the observed behavior of the correlation. We study chains in the independent rotation approximation with symmetric rotational potentials. We focus on two different orientations of the bond dipole moment vector : 010 and 001 (the bond length vector's orientation is [100]).
A Percolation Model for Elastic Softening in Intermetallic Compounds During Solid-State Amorphization
Authors: Massobrio Carlo , Pontikis Vassilis
Published: March 2011

By using isobaric-isothermal molecular dynamics and an n-body effective potential, we show that a dramatic elastic softening precedes the amorphization of NiZr2 occurring on chemically disordering the alloy. Above a critical level of chemical disorder, the shear elastic constant of the alloy increases suddenly up to a value comparable to the one of the amorphous solid obtained by quenching the liquid. This phenomenon occurs at the percolation threshold of the anelastically distorted regions surrounding the antisite defects. The percolation model describes satisfactorily experimental findings concerning the elastic softening and the loss of crystalline order in intermetallic compounds induced by irradiation or hydrogenation.
Entropy of Hydrophobic Hydration: A New Statistical Mechanical Formulation
Authors: Lazaridis Themis , Paulaitis Michael E.
Published: March 2011

A statistical mechanical formulation is presented for the entropy of solution of simple molecules in water. The formulation is based on the Green-Wallace expansion for the entropy in terms of multiparticle correlation functions, which is derived here for rigid polyatomic fluids and for mixtures. With a factorization assumption for the solute-water correlation function we have been able to separate the translational and orientational contributions to the entropy of solution. This approach is applied to an infinitely dilute solution of methane in water. The required correlation functions are obtained by Monte Carlo simulation. The orientational contribution, which is due directly to the orientational asymmetry of water-water interactions, is found to be comparable to the translational contribution. We find that the large entropies and heat capacities of hydrophobic hydration can be accounted for by solute-water correlations alone and that large perturbations in water structure are not required to explain hydrophobic behavior.
A New Parametric Method for the Analysis of Ordering Configurations in Binary Alloys
Authors: Staley T.W. , Matyi R.J.
Published: March 2011

In ordering alloy systems, the overall long-range order parameter does not distinguish the degree to which the component structures are delocalized for different configurations of equal randomness. We define a new parameter, which is sensitive to such differences, by considering the short-range order parameters as a set of statistical moments for geometric variation in the crystal. A computer model has been developed which uses this parameter to analyze finite alloy systems for configurational preferences by a Monte Carlo method. Initial studies have established the parametric range as a function of LRO and nonstoichiometry. Qualitative results correspond well to predictions for ideal systems.
The Fast Multipole Method in Canonical Ensemble Dynamics on Massively Parallel Computers
Authors: Lustig Steven R. , Cristy J.J. , Pensak D.A.
Published: March 2011

The fast multipole method (FMM) is implemented in canonical ensemble particle simulations to compute non-bonded interactions efficiently with explicit error control. Multipole and local expansions have been derived to implement the FMM efficiently in Cartesian coordinates for soft-sphere (inverse power law), Lennard- Jones, Morse and Yukawa potential functions. Significant reductions in execution times have been achieved with respect to the direct method. For a given number, N, of particles the execution times of the direct method scale asO(N2). The FMM execution times scale asO(N) on sequential workstations and vector processors and asymptotically0(logN) on massively parallel computers. Connection Machine CM-2 and WAVETRACER-DTC parallel FMM implementations execute faster than the Cray-YMP vectorized FMM for ensemble sizes larger than 28k and 35k, respectively. For 256k particle ensembles the CM-2 parallel FMM is 12 times faster than the Cray-YMP vectorized direct method and 2.2 times faster than the vectorized FMM. For 256k particle ensembles the WAVETRACER-DTC parallel FMM is 33 times faster than the Cray-YMP vectorized direct method.
Cavities in He-Implanted Si: “Internal” Surface Science
Authors: Follstaedt D. M. , Myers S. M. , Stein H. J.
Published: March 2011

The concept of using internal cavities in semiconductors for surface studies is presented. The microstructures of He-implanted (001) Si are characterized with [110] cross-section TEM, which shows that internal areas 5–7 times that of the specimen front surface are achieved with 1×1017 He/cm2 implanted at 30 keV and annealed at 700 or 800°C. Examples using internal cavities to determine surface bond strengths of other elements adsorbed on Si are indicated. Facets on the cavities are used to examine the equilibrium crystal shape of Si and to measure the ratios of the surface free energies of the observed planes. The {111} planes have the lowest energy, and those of {001} and {110} are 1.09(7) and 1.07(3) times higher, respectively. We also find cavities in He-implanted Ge after annealing that can be used for similar studies.
Influence of Electric Field on the Formation of Neutron, Electron and γ-Ray Radiation Defects in Silicon
Authors: Fengmei Wu , Yi Shi , Zhenzhou Wang , Qiji Lai , Lihua Zhao
Published: March 2011

The influence of an electric field on the formation of radiation-induced defects in silicon irradiated respectively with γ-ray, electrons and neutrons has been investigated using the DLTS method. It is found that the application of an electric field across the p-n junction during irradiation can reduce the formation efficiency of A-centers, divacancies and E3(Ec-0.37 eV) defects, and that the concentration of radiation defects in the junction depletion region is lower than that in the quasineutral bulk. The formation characteristics of radiation defects in the depletion region could be related mainly to the transformation of the charge states of the defects caused by the electric field.
Photoluminescence of Silicon Nanostructures Formed by Ion Beam Implantation
Authors: Redman D. A. , Follstaedt D. M. , Guilinger T. , Kelly M.
Published: March 2011

A new method was used to fabricate nanometer-scale structures in Si for photoluminescence (PL) studies. He ions were implanted to form a dense subsurface layer of small cavities (1–8 nm diameters). The implanted specimens were either annealed in H or anodized with HF to evaluate the quantum confinement model for PL from porous Si. Incomplete passivation apparently prevented PL in the H-annealed specimens. Implantation combined with anodization produced a substantial blue shift relative to anodization alone, which is consistent with quantum confinement.
Synthesis of Critical Point Energies for 1 MeV Electron Irradiated P-Type Silicon
Authors: Russo Onofrio L. , Dumas Katherine A. , Herman Michael H.
Published: March 2011

The critical point energies, E0, E1 and the Lorentz broadening parameter, Γ, for boron doped p-type silicon were obtained by electrolyte-electroreflectance (EER) at 297K and electron beam electroreflectance (EBER) at 297K and 88K. Electron irradiated samples for fluences of 1014 and 1016 e-/cm2 were compared to the samples before irradiation. The value of the low energy weaker structure, Eo and the higher energy main structure, Ei are obtained by the synthesis of two Lorentz line shapes to fit the experimentally obtained composite spectra. The values as determined by EER were all found to increase with radiation as expected. The values for Eo as found by EBER were consistent with those of EER but those of E1 were not.
Metal Induced Crystallization of Amorphous Silicon Thin Films
Authors: Hempel T. , Schoenfeld O. , Veit P.
Published: March 2011

The crystallization behaviour of Ni doped magnetron co-sputtered amorphous silicon thin films (MSP-a-Si(Ni)) has been investigated by means of near infrared-visible-ultraviolet (NIR-VIS-UV) transmission spectroscopy, transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). Using the change in optical transmission spectra of crystallized a-Si(Ni) thin films the crystallization kinetics is described. At the crystallization frontier a needle morphology of single crystals is observed with STEM, which is followed by solid state diffusion of nickel through the amorphous matrix. Using a long term thermal treatment we have studied the formation of expansed monocrystalline networks.
Dose Rate Dependence of the Ion Beam Induced Epitaxial Crystallization in Silicon
Authors: Heera V. , Kögler R. , Skorupa W. , Grötzschel R.
Published: March 2011

The dose rate dependence of 300 keV Si+ ion beam induced epitaxial crystallization (IBIEC) of a 200 nm thick amorphous silicon surface layer at 400°C is investigated in the ion dose rate range from 3 · 1010 up to 3 · 1013cm2s−1. The experimental results are compared with theoretical predictions from several models. Special emphasis is given to the influence of the depth distribution of the nuclear energy deposition on the growth process during both the experiment and the theoretical analysis. According to our experimental results the IBIEC rate is indirectly proportional to the fourth root of the dose rate. This is in excellent agreement with a point defect diffusion model of IBIEC considering pairwise defect annihilation.
Simulator for Dynamic Ion Beam Mixing
Authors: Seidl A. , Fujii K. , Kiuchi M. , Satou M. , Takai M.
Published: March 2011

Dynamic ion beam mixing (simultaneous deposition and ion beam irradiation) was simulated for the first time. Standard Monte Carlo (MC) programs do not account for the steady change of target geometry caused by the layer growth during the process. Therefore a time-step strategy was realized by integrating a MC simulator in a system together with a geometry update module. A comparison between simulation results and XPS and TEM measurements shows reasonable agreement between simulation and measurements.
The Radiation Phase Transitions and the Metamict State of Quartz
Authors: Sayapina O. V. , Koshkin V. M.
Published: March 2011

A model of radiation induced phase transformations in quartz using the old idea of Weissmann and Nakajama is developed. The kinetics of these phase transitions is described taking into account intermediate phase formation. A model of the final radiation induced metamict state of quartz is suggested. The metamict state consists of amorphized matrix SiO2+X, where x ≈0.15 (radioglass), in which pure silicon precipitates are included.
High-Temperature Au Implantation into Ni-Be and Ni-Si Alloys
Authors: James M. R. , Lam N. Q. , Rehn L. E. , Baldo P. M. , Funk L. , Stubbins J. F.
Published: March 2011

The effects of implantation temperature and target composition on the depth distribution of the implanted species were systematically investigated in the present work. Au+ ions were implanted at 300 keV into polycrystalline Ni-Be and Ni-Si alloys at temperatures between 25 and 700 °C to a dose of 1016 cm−2. The depth distributions of Au were analyzed with RBS using He+ at both 1.7 and 3.0 MeV, and those of the other alloying elements by SIMS. Theoretical modeling of compositional redistribution during implantation at elevated temperatures was also carried out with the aid of a comprehensive kinetic model. The analysis indicated that below ∼250 °C, the primary controlling processes were preferential sputtering and displacement mixing, while between 250 and 600 °C radiation-induced segregation was dominant. Above 600 °C, thermal-diffusion effects were most important. A systematic fitting of model calculations to experimental measurements provided values for various defect migration and formation parameters.
A Model to Explain the Variations of “End-of-Range” Defect Densities with Ion Implantation Parameters
Authors: Laanab L. , Bergaud C. , Faye M. M. , Faure J. , Martinez A. , Claverie A.
Published: March 2011

Computer simulations in conjunction with TEM experiments have been used to test the different models usually adopted in the literature to explain the formation of “End Of Range”(EOR) defects which appear after annealing of preamorphized silicon layers. Only one survives careful experimental investigations involving Si+, Ge+, Sn+ amorphization at RT and LNT. The “excess-interstitial” model appears relevant at least for a semi-quantitative explanation of the source of point-defects which after recombination and agglomeration, lead to the formation of these defects. This model may be used for the numerical optimization of conditions for the production of high performances ullra-shallow junctions.
F-Centers and Oxygen-Interstitials in MgO
Authors: Scholz C. , Ehrhart P.
Published: March 2011

MgO single crystals have been irradiated at different temperatures (4 K, 300 K) with electrons of energies varying between 0.3 and 3 MeV. The irradiation induced defects and their reactions during thermal annealing have been investigated by optical absorption spectroscopy and by X-ray diffraction. The relaxation volume (Viel ≈ 1 at.vol. = a3/8) and the migration energy of the interstitial atoms (≈ 1.6 eV) are determined and an ionization induced and thermally assisted migration process is observed for the first time. The relevance of these results for the understanding of the cascade damage observed after neutron- or ion-damage is discussed.
Temperature and Ion-Mass Dependence of Amorphization Dose for Ion Beam Irradiated Zircon (ZrSiO4)
Authors: Wangl L. M. , Ewing R. C. , Weber W. J. , Eby R. K.
Published: March 2011

The temperature dependence of amorphization dose for zircon under 1.5 MeV Kr ion irradiation has been investigated using the HVEM-Tandem Facility at Argonne National Laboratory. Three regimes were observed in the amorphization dose-temperature curve. In the first regime (15 to 300 K), the critical amorphization dose increased from 3.06 to 4.5 ions/nm2. In the second regime (300 to 473 K), there is little change in the amorphization dose. In the third regime (> 473 K), the amorphization dose increased exponentially to 8.3 ions/nm2 at 913 K. This temperature dependence of amorphization dose can be described by two processes with different activation energies (0.018 and 0.31 eV respectively) which are attributed to close pair recombination in the cascades at low temperatures and radiation-enhanced epitaxial recrystallization at higher temperatures. The upper temperature limit for amorphization of zircon is estimated to be 1100 K. The ion-mass dependence of the amorphization dose (in dpa) has also been discussed in terms of the energy to recoils based on data obtained from He, Ne, Ar, Kr, Xe irradiations and a 238Pu-doped sample.
Enhanced Vortex Pinning and Critical Current Density in Proton-Irradiated YBa2Cu3O7-δ Thin Films
Authors: Venturing E. L. , Siegal M. P. , White A. E. , Hou S. Y. , Phillips Julia M.
Published: March 2011

The appropriate fluence of 2.0 MeV H1 ions has been shown previously to enhance the critical current density Jc by a factor of two at a magnetic field of 0.9 tesla in 1000 Å thick epitaxial films of YBa2Cu3O7-δ grown by the ex situ BaF2 process. The as-grown films exhibit single crystal-like behavior in both atomic ordering and Jc versus temperature and magnetic field. TRIM simulations suggest that H+ irradiation generates mainly point delects throughout the crystal structure. We show here that such defects result in an even greater enhancement of Jc for fields above 1 tesla plus a significant increase in the apparent vortex pinning potential deduced from magnetization relaxation data.
Improvement in Tribomechanical Properties of Commercial TiN Coatings by Argon Ion Implantation
Authors: Liu L. J. , Zhou W. C. , Sood D. K. , Manory R.
Published: March 2011

About 2 μm thick commercial coatings of TiN on high speed steel substrates were implanted at RT with Ar ions of 95 keV energy to doses between 0.1–1.0×1017 ions/cm2. An ultramicrohardness machine was used to measure hardness, and a (sapphire) ball-on-disk machine to measure wear, friction and adhesion. Hardness enhancements up to about 50% were observed as dose increased. However, at the highest dose, hardness reduced by nearly 2 times the unimplanted value. Friction coefficient and relative wear are correlated and reduce with ion dose. Films undergo brittle fracture during sliding tests. These results are found to be very sensitive to small changes in relative humidity. All implants lead to improved wear and adhesion as compared to an unimplanted surface. These results are discussed in terms of ion damage, accumulation of Ar gas bubbles and a possible break-up of the TiN phase during ion bombardment.
Orientation of Nitrides in N-Implanted Steels
Authors: Leutenecker R. , Cao-Minh U.
Published: March 2011

The impact of irradiation and stresses onto the preferential orientation of hexagonal ε-nitrides in N-implanted steels is investigated. For this purpose, the contribution of the heterogeneous nucleation, which counteracts a preferential orientation, is varied.
Damage Generation by Electronic Excitations in Crystalline Metals
Authors: Dunlop A. , Lesueur D.
Published: March 2011

EXTENDED ABSTRACT

This paper will give a rapid overview of the main experimental results concerning the effects of high electronic energy deposition in metallic targets and present a tentative model based on the Coulomb explosion mechanism. More detailed reviews have been made recently concerning both the experiments [1–3] and the theoretical model [4].

High levels of localized energy deposition in electronic excitation are easily obtained using GeV heavy ions which during their slowing-down typically transfer a few keV/Å to the electronic system of the target and a few eV/Å in elastic collisions with target nuclei. In insulators and organic materials, it is well-known that both slowing-down processes contribute to damage creation, whereas in metals it has been claimed for a long time that the sole nuclear collisions are involved in damage processes. Although this last assertion remains true for some metals such as Cu, Ag, W, Cu3Au …[2], high levels of electronic excitation can induce a partial annealing of the defects resulting from nuclear collisions in Fe, Ni, Nb, Pt…. lead to additional defect creation in Fe, Co, Zr, Ti… [2] or even to phase transformations in NiZr2 [5], Ni3B[6], NiTi [7], Ti [8]… In the following, we shall only focuss on the last two effects.
Amorphization Kinetics of Zr (Cr,Fe)2 Under Ion Irradiation
Authors: Motta A. T. , Howe L. M. , Okamoto P. R.
Published: March 2011

Thin foils of Zircaloy-4 were irradiated with 350 KeV 40Ar ions in the dual ion beam/HVEM facility at Argonne National Laboratory at 300 – 650 K. The irradiation-induced araorphization of the intermetallic precipitates Zr (Cr, Fe)2 and Zr2 (Ni, Fe) was studied in situ. For Zr (Cr,Fe)2 precipitates the dose-to-amorphization was found to increase exponentially with temperature, with a critical temperature of about 650 K. The amorphization morphology was shown to be homogeneous, with no preferential site for nucleation, in contrast to neutron-irradiation amorphization which started at the precipitate-matrix interface. For Zr2 (Ni,Fe) precipitates it was found that amorphization occurred at 550 K and 600 K, whereas in neutron irradiation no amorphization has been observed at those temperatures. The results are discussed in the context of the previous experimental results of neutron and electron irradiation and likely amorphization mechanisms are proposed.
Effects of Ion Implantation on Crystallization of Amorphous CoSi2
Authors: Hong Q. Z. , Barmak K. , Hong S. Q. , Clevenger L. A.
Published: March 2011

The effects of Si and Kr ion implantation on the crystallization kinetics of amorphous COSi2 have been investigated by differential scanning calorimetry and in situ sheet resistance measurement. Without ion implantation, the crystallization of coevaporated COSi2 is characterized by three dimensional growth from preexisting nuclei. When the as-deposited COSi2 is implanted with Si or Kr ions at liquid nitrogen temperature, the kinetics of the subsequent crystallization is significantly altered. A 180 keV 5×1015 cm−2Si ion implantation increases the crystallization temperature by 34°C. When the Si dose is below 1×1015 cm−2, ion implantation causes a sharp decrease in the crystallization kinetic parameter defined by the Avrami equation. The amount of decrease is shown to scale with the deposited nuclear energy. At higher doses, the kinetic parameter continues to decrease with increasing dose but at a much reduced rate.
Structure Characterization of Metamict and Glassy Lead Phosphates
Authors: Sreeram A. N. , Hobbs L. W.
Published: March 2011

Single crystals of Pb2P2O7 (beam stable under 200 kV TEM electrons to a fluence > 1027 e/m2 and an ionizing dose > 1014 Gy) were rendered metamict (amorphized) with ion-implantation (100 kV P+ ions with several fluences. Pb2P2O7 and PbO·P2O5 glasses were also ion implanted at identical fluences. Radial distribution functions of metamict and glassy phosphates are being generated using energy filtered electron diffraction (EFED) data collected on 100 kV field emission STEM (VG HB-5). Ion-implanted lead phosphate glasses exhibit a significant difference in their FSDP as compared to the non-irradiated ones. XTEM results also show that ion-beam damage layer was around 200 nm deep. XTEM-HREM structure images of ion-implanted single crystals, along with their optical diffraction analysis will be presented and briefly discussed.
Low Energy Focused Ion Beam Processing
Authors: Gamo Kenji
Published: March 2011

Focused ion beam (FIB) techniques have many advantages which stem from being maskless and have attracted much interest for various applications includingin situprocessing. However, reduction of damage and improvement of throughput are problems awaiting solution. For reduction of damage, low energy FIB is promising and for improvement of throughput, understanding of the basic processes and optimization of process parameters based on this understanding is crucial. This paper discusses characteristics of low energy FIB system, ion beam assisted etching and ion implantation, and effect of damage with putting emphasize onin situfabrication. Low energy (0.05–25keV) FIB system being developed forms -lOOnm diameter ion beams and is connected with molecular beam epitaxy system. Many results indicate that low damage, maskless ion beam assisted etching is feasible using low energy beams. Recently it was also shown that for ion beam assisted etching of GaAs, pulse irradiation yields very high etching rate of 500/ion. This indicates that the optimization of the relative ratio of ion irradiation and reactant gas supply as important to achieve high etching rate. Low energy FIB is also important for selective doping for high electron mobility heterostructures of GaAs/GaAlAs, because high mobility is significantly degraded by a slight damage.
Deposition of Nano-Scale Ga Dots onto HF-Treated Si(111) Using a Scanning Tunneling Microscope
Authors: Uesugi Katsuhiro , Sakata Kiyoshi , Kawano Seiji , Yoshimura Masamichi , Yao Takafumi
Published: March 2011

Nano-scale Ga dots are deposited through the decomposition of triethylgallium (TEGa) adsorbed on HF-treated Si(111) surfaces using a scanning tunneling microscope (STM). The deposition of Ga dots of 2–13 nm in diameter is achieved by applying a negative voltage pulse to the sample, while no deposition is observed when a positive voltage pulse is applied. The conditions for Ga deposition are systematically investigated by varying the gap conductance, pulse height, and pulse width. A tentative model for the mechanism of Ga deposition is proposed, in which TEGa molecules are decomposed by the electric field between the tip and the sample.
Pulsed Laser Excited Microwave Photo Conductivity Applications to High Resolution Defect Diagnostics OP Ion and Laser Beam Modified Semiconductor Surface
Authors: Khavroshin D. L. , Manenkov A. A. , Popov S. Yu. , Sokolov S. Yu.
Published: March 2011

A novel diagnostic technique for the studies of semiconductor surfaces is described. Experimental data on nonlocal modification effects in laser produced scribing, doping and annealing of ion implanted GaAs and Si are presented. Mechanisms of nonlocal structural and electric properties changes under modification are analyzed. Nonlocality phenomena are concluded to be universal for any strong modification procedure and very important for microelectronics technology.
Measurements of Melting Velocities in Gold Films on a Picosecond Time Scale
Authors: Homan B. E. , Connery M. T. , Harrison D. E. , Macdonald C. A.
Published: March 2011

Melting velocities were measured in thin gold films by performing pump/probe transmission measurements using a unique picosecond excimer pump and dye laser probe. Monitoring the depth of the liquid by changes in the near psuedo-Brewster's angle transmission allowed for direct measurement of crystal/melt interfacial velocity up to 1500 m/s.
ArF Laser Induced Photochemical Substitution of OH Radicals into Teflon Surface Using Al(OH)3 Solution
Authors: Okoshi M. , Kashiura H. , Miyokawa T. , Toyoda K. , Murahara M.
Published: March 2011

OH radicals were photochemically substituted for fluorine atoms in the teflon surface by using an ArF excimer laser light and an Al(OH)3 solution. This method is simple and can be performed in air atmosphere. In the process, the teflon film was placed on the Al(OH)3 which were dissolved in NaOH water solution; the ArF excimer laser light was irradiated the sample surface and the solution. By irradiating the laser, the surface was defluorinated by the aluminium atoms photodissociated from the Al(OH)3 solution, and the dangling bonds which were formed in the defluorinated surface combined with the OH radicals also photodissociated. The hydrophilic property of the photomodified surface was evaluated by the measurement of the contact angle with water. The defluorination and the OH radicals substitution were inspected by the XPS analysis and the ATR-FTIR measurement.