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Advances in (Ba,Sr)TiO3 high value capacitors fabricated by chemical solution deposition

Clem, Paul; Brennecka, Geoff; Tuttle, Bruce

This report focuses on our recent advances in the fabrication and processing of barium strontium titanate (BST) thin films by chemical solution deposition for next generation functional integrated capacitors. Projected trends for capacitors include increasing capacitance density, decreasing operating voltages, decreasing dielectric thickness and decreased process cost. Key to all these trends is the strong correlation of film phase evolution and resulting microstructure, it becomes possible to tailor the microstructure for specific applications. This interplay will be discussed in relation to the resulting temperature dependent dielectric response of the BST films.

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TYPE Conference YEAR 2008
OSTI

Dissipation-induced heteroclinic orbits in tippe tops

Proposed for publication in SIAM Review.

Romero, Louis

This paper demonstrates that the conditions for the existence of a dissipation-induced heteroclinic orbit between the inverted and noninverted states of a tippe top are determined by a complex version of the equations for a simple harmonic oscillator: the modified Maxwell-Bloch equations. A standard linear analysis reveals that the modified Maxwell-Bloch equations describe the spectral instability of the noninverted state and Lyapunov stability of the inverted state. Standard nonlinear analysis based on the energy momentum method gives necessary and sufficient conditions for the existence of a dissipation-induced connecting orbit between these relative equilibria.

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TYPE Journal Article YEAR 2008
OSTI

Defect structures created during abnormal grain growth in pulsed-laser deposited nickel

Acta Materialia

Hattar, K.; Follstaedt, David M.; Knapp, J.A.; Robertson, I.M.

The thermal stability of nanograined pulsed-laser deposited nickel was studied by annealing free-standing thin films in situ in a transmission electron microscope. The observed grain growth was sporadic and catastrophic, as expected for abnormal grain growth. The large grains contained a variety of defects that included twins, dislocation lines, small dislocation loops and stacking-fault tetrahedra. This microstructure was developed at annealing temperatures as low as 498 K and was stable at the annealing temperature. The proposed source of the defects and especially the stacking-fault tetrahedra is the grain boundaries, which have excess free volume. This defect source provides insight to the structure of the deposited grain boundaries, which has important consequences for the macroscopic mechanical properties of nanograined pulsed-laser deposited nickel. © 2007 Acta Materialia Inc.

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TYPE Journal Article YEAR 2008
ScopusOSTIDOI

Synthesis and self-assembly of zinc oxide nanoparticles with septahedral morphology

Journal of Materials Research

Bell, Nelson S.; Tallant, David R.; Raymond, Rebecca; Boyle, Timothy

The formation of 10-nm ZnO nanopyramids using a simple synthetic route has been isolated from the reaction of Zn(OAc)2·2H2O in 1,4-butanediol followed by ripening at 90°C. This was accomplished by establishing control over the Ostwald ripening process through the use of a carboxylic acid specific adsorbate. Using a variety of analytical methods, it is proposed that the carboxylate groups in the acetate precursor stabilize the {101} habit planes, creating septahedral shapes or nanopyramids. Particle assembly into crystallographically oriented dimers was observed with high specificity, and the association mechanism is suggested to relate to the crystal polarity and the variation in specific adsorption of the carboxylic acid to the surface facets. These materials are a candidate for biological labeling applications in living cells.

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TYPE Journal Article YEAR 2008
ScopusOSTIDOI

Overview of the dynamic hohlraum X-ray source at Sandia National Laboratories

IEEE Transactions on Plasma Science

Sanford, Thomas W.L.

Progress in understanding the physics of dynamic hohlraums is reviewed for a system that is capable of generating 10 TW of axial radiation for high-temperature (> 200 eV) radiation-flow experiments and inertial confinement fusion capsule implosions. Two-dimensional magneto-hydrodynamic simulation comparisons with data show the need to include wire initiation physics and subsequent discrete-wire dynamics in the simulations if a predictive capability is to be achieved. © 2008 IEEE.

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TYPE SAND Report YEAR 2008
DOIOSTIScopus

Chemical kinetics and mass transport effects in solution-based selective-area growth of ZnO nanorods

Journal of Crystal Growth

Coltrin, Michael E.; Hsu, Julia W.; Scrymgeour, David; Creighton, James R.

We present a combined experimental and modeling study of the dependence of solution-based zinc oxide (ZnO) selective-area growth rates on pattern dimension. Selective growth is achieved by patterning a portion of the substrate with an organic template that inhibits growth. The density of ZnO nanorods and the mass grown per unit area of exposed surface increases as the distance between the exposed growth regions is increased and as the width of the exposed lines is decreased. A 2-D model was developed to calculate selective growth at the exposed surface regions, the loss of reactant material due to a competing reaction in solution, liquid-phase and surface diffusive mass transport to (or on) the growth surface, and the ZnO growth reaction at the surface. To explain the experimental results, we found it necessary to include a reaction by-product in the chemistry model, the desorption of which is the rate limiting step. A relatively simple, three-step reaction mechanism, combined with the species mass transport model, provides a good, semi-quantitative description of the experimental observations in the selective-area growth of ZnO from supersaturated solutions.

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TYPE Journal Article YEAR 2008
OSTIScopus

Displacement and thermal performance of laser-heated asymmetric MEMS actuators

Journal of Microelectromechanical Systems

Serrano, Justin R.; Phinney, Leslie

Optical actuators are fundamental building blocks in the development of all-optical microelectromechanical devices. Photothermally actuated devices are inevitably limited by overheating and device damage resulting from the absorption of laser power. Optimal actuator design requires an efficient use of the applied laser power while minimizing the susceptibility of device damage. Surface micromachined polycrystalline silicon flexure-style optical actuators, which are powered using an 808-nm continuous-wave laser, were evaluated for displacement performance and susceptibility to damage. Actuator displacement is linear with incident power for laser powers below those that cause damage to the irradiated surface, up to a maximum displacement of 7-9 μm. Damage of the irradiated surface causes viscous relaxation of the polysilicon film and leads to recession of the displacement during the heating and additional recession after the optical power is removed. The first spatially resolved temperature measurements during device operation were obtained using micro-Raman thermometry. The temperature measurements revealed the influence of temperature-dependent optical properties in the thermal behavior of the irradiated devices. © 2008 IEEE.

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TYPE Journal Article YEAR 2008
OSTIScopus

Modeling and simulation of blast-induced, early-time intracranial wave physics leading to traumatic brain injury

Taylor, Paul A.

The objective of this modeling and simulation study was to establish the role of stress wave interactions in the genesis of traumatic brain injury (TBI) from exposure to explosive blast. A high resolution (1 mm{sup 3} voxels), 5 material model of the human head was created by segmentation of color cryosections from the Visible Human Female dataset. Tissue material properties were assigned from literature values. The model was inserted into the shock physics wave code, CTH, and subjected to a simulated blast wave of 1.3 MPa (13 bars) peak pressure from anterior, posterior and lateral directions. Three dimensional plots of maximum pressure, volumetric tension, and deviatoric (shear) stress demonstrated significant differences related to the incident blast geometry. In particular, the calculations revealed focal brain regions of elevated pressure and deviatoric (shear) stress within the first 2 milliseconds of blast exposure. Calculated maximum levels of 15 KPa deviatoric, 3.3 MPa pressure, and 0.8 MPa volumetric tension were observed before the onset of significant head accelerations. Over a 2 msec time course, the head model moved only 1 mm in response to the blast loading. Doubling the blast strength changed the resulting intracranial stress magnitudes but not their distribution. We conclude that stress localization, due to early time wave interactions, may contribute to the development of multifocal axonal injury underlying TBI. We propose that a contribution to traumatic brain injury from blast exposure, and most likely blunt impact, can occur on a time scale shorter than previous model predictions and before the onset of linear or rotational accelerations traditionally associated with the development of TBI.

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TYPE SAND Report YEAR 2008
DOIOSTI

Sandia National Laboratories Advanced Simulation and Computing (ASC) : appraisal method for the implementation of the ASC software quality engineering practices: Version 1.0

Turgeon, Jennifer; Minana, Molly A.

This document provides a guide to the process of conducting software appraisals under the Sandia National Laboratories (SNL) ASC Program. The goal of this document is to describe a common methodology for planning, conducting, and reporting results of software appraisals thereby enabling: development of an objective baseline on implementation of the software quality engineering (SQE) practices identified in the ASC Software Quality Plan across the ASC Program; feedback from project teams on SQE opportunities for improvement; identification of strengths and opportunities for improvement for individual project teams; guidance to the ASC Program on the focus of future SQE activities Document contents include process descriptions, templates to promote consistent conduct of appraisals, and an explanation of the relationship of this procedure to the SNL ASC software program.

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TYPE SAND Report YEAR 2008
DOIOSTI

Tape casting of magnesium oxide

Corral, Erica L.; Loehman, Ronald E.; Bencoe, Denise N.

A tape casting procedure for fabricating ceramic magnesium oxide tapes has been developed as a method to produce flat sheets of sintered MgO that are thin and porous. Thickness of single layer tapes is in the range of 200-400 {micro}m with corresponding surface roughness values in the range of 10-20 {micro}m as measured by laser profilometry. Development of the tape casting technique required optimization of pretreatment for the starting magnesium oxide (MgO) powder as well as a detailed study of the casting slurry preparation and subsequent heat treatments for sintering and final tape flattening. Milling time of the ceramic powder, plasticizer, and binder mixture was identified as a primary factor affecting surface morphology of the tapes. In general, longer milling times resulted in green tapes with a noticeably smoother surface. This work demonstrates that meticulous control of the entire tape casting operation is necessary to obtain high-quality MgO tapes.

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TYPE SAND Report YEAR 2008
DOIOSTI
Results 78801–78900 of 99,299
Results 78801–78900 of 99,299