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STRUCTURAL FLUCTUATIONS, ELECTRICAL RESPONSE AND THE RELIABILITY OF NANOSTRUCTURES (FINAL REPORT)

Description: The goal of the research supported by DOE-FG02-01ER45939 was to synthesize a number of experimental and theoretical approaches to understand the relationship between morphological fluctuations, the electrical response and the reliability (failure) of metallic nanostructures. The primary focus of our work was the study of metallic nanowires which we regard as prototypical of nanoscale interconnects. Our research plan has been to link together these materials properties and behaviors by understanding the phenomenon of, and the effects of electromigration at nanometer length scales. The thrust of our research has been founded on the concept that, for nanostructures where the surface-to-volume ratio is necessarily high, surface diffusion is the dominant mass transport mechanism that governs the fluctuations, electrical properties and failure modes of nanostructures. Our approach has been to develop experimental methods that permit the direct imaging of the electromagnetic distributions within nanostructures, their structural fluctuations and their electrical response. This experimental research is complemented by a parallel theoretical and computational program that describes the temporal evolution of nanostructures in response to current flow.
Date: July 31, 2006
Creator: Rous, Philip J.; Williams, Ellen D. & Fuhrer, Michael S.
Partner: UNT Libraries Government Documents Department

Formation mechanism and properties of CdS-Ag2S nanorod superlattices

Description: The mechanism of formation of recently fabricated CdS-Ag{sub 2}S nanorod superlattices is considered and their elastic properties are predicted theoretically based on experimental structural data. We consider different possible mechanisms for the spontaneous ordering observed in these 1D nanostructures, such as diffusion-limited growth and ordering due to epitaxial strain. A simplified model suggests that diffusion-limited growth partially contributes to the observed ordering, but cannot account for the full extent of the ordering alone. The elastic properties of bulk Ag{sub 2}S are predicted using a first principles method and are fed into a classical valence force field (VFF) model of the nanostructure. The VFF results show significant repulsion between Ag{sub 2}S segments, strongly suggesting that the interplay between the chemical interface energy and strain due to the lattice mismatch between the two materials drives the spontaneous pattern formation.
Date: August 11, 2008
Creator: Wang, Lin-Wang; Demchenko, Denis O.; Robinson, Richard D.; Sadtler, Bryce; Erdonmez, Can K.; Alivisatos, A. Paul et al.
Partner: UNT Libraries Government Documents Department

Scanning Tunneling Microscopy Observation of Phonon Condensate

Description: This article discusses results showing that the effective radius of these phonon quasi-bound states, the real-space distribution of phonon standing wave amplitudes, the scattering phase shifts, and the nonlinear intermode coupling strongly depend on the presence of defect-induced scattering resonance.
Date: February 22, 2017
Creator: Altfeder, Igor; Voevodin, Andrey A.; Check, Michael H.; Eichfeld, Sarah M.; Robinson, Joshua A. & Balatsky, Alexander V.
Partner: UNT College of Engineering

Quantum-Confined CdS Nanoparticles on DNA Templates

Description: As electronic devices became smaller, interest in quantum-confined semiconductor nanostructures increased. Self-assembled mesoscale semiconductor structures of II-VI nanocrystals are an especially exciting subject because of their controllable band gap and unique photophysical properties. Several preparative methods to synthesize and control the sizes of the individual nanocrystallites and the electronic and optical properties have been intensively studied. Fabrication of patterned nanostructures composed of quantum-confined nanoparticles is the next step toward practical applications. We have developed an innovative method to fabricate diverse nanostructures which relies on the size and a shape of a chosen deoxyribonucleic acid (DNA) template.
Date: May 1998
Creator: Rho, Young Gyu
Partner: UNT Libraries

Nanoimprinted plasmonic nanocavity arrays

Description: This article demonstrates high resonant absorption of visible light with a plasmonic nanocavity chain structure fabricated through resistless nanoimprinting in metal (RNIM).
Date: June 17, 2013
Creator: Kim, Sangsik; Xuan, Yi; Drachev, Vladimir P.; Varghese, Leo T.; Fan, Li; Qi, Minghao et al.
Partner: UNT College of Arts and Sciences

Templated Self Assemble of Nano-Structures

Description: This project will identify and model mechanisms that template the self-assembly of nanostructures. We focus on a class of systems involving a two-phase monolayer of molecules adsorbed on a solid surface. At a suitably elevated temperature, the molecules diffuse on the surface to reduce the combined free energy of mixing, phase boundary, elastic field, and electrostatic field. With no template, the phases may form a pattern of stripes or disks. The feature size is on the order of 1-100 nm, selected to compromise the phase boundary energy and the long-range elastic or electrostatic interaction. Both experimental observations and our theoretical simulations have shown that the pattern resembles a periodic lattice, but has abundant imperfections. To form a perfect periodic pattern, or a designed aperiodic pattern, one must introduce a template to guide the assembly. For example, a coarse-scale pattern, lithographically defined on the substrate, will guide the assembly of the nanoscale pattern. As another example, if the molecules on the substrate surface carry strong electric dipoles, a charged object, placed in the space above the monolayer, will guide the assembly of the molecular dipoles. In particular, the charged object can be a mask with a designed nanoscale topographic pattern. A serial process (e.g., e-beam lithography) is necessary to make the mask, but the pattern transfer to the molecules on the substrate is a parallel process. The technique is potentially a high throughput, low cost process to pattern a monolayer. The monolayer pattern itself may serve as a template to fabricate a functional structure. This project will model fundamental aspects of these processes, including thermodynamics and kinetics of self-assembly, templated self-assembly, and self-assembly on unconventional substrates. It is envisioned that the theory will not only explain the available experimental observations, but also motivate new experiments.
Date: April 29, 2013
Creator: Suo, Zhigang
Partner: UNT Libraries Government Documents Department

Computational Nanophotonics: Model Optical Interactions and Transport in Tailored Nanosystem Architectures

Description: The program is directed toward development of new computational approaches to photoprocesses in nanostructures whose geometry and composition are tailored to obtain desirable optical responses. The emphasis of this specific program is on the development of computational methods and prediction and computational theory of new phenomena of optical energy transfer and transformation on the extreme nanoscale (down to a few nanometers).
Date: February 21, 2014
Creator: Stockman, Mark & Gray, Steven
Partner: UNT Libraries Government Documents Department

Assembly and actuation of nanomaterials using active biomolecules.

Description: The formation and functions of living materials and organisms are fundamentally different from those of synthetic materials and devices. Synthetic materials tend to have static structures, and are not capable of adapting to the functional needs of changing environments. In contrast, living systems utilize energy to create, heal, reconfigure, and dismantle materials in a dynamic, non-equilibrium fashion. The overall goal of the project was to organize and reconfigure functional assemblies of nanoparticles using strategies that mimic those found in living systems. Active assembly of nanostructures was studied using active biomolecules to drive the organization and assembly of nanocomposite materials. In this system, kinesin motor proteins and microtubules were used to direct the transport and interactions of nanoparticles at synthetic interfaces. In addition, the kinesin/microtubule transport system was used to actively assemble nanocomposite materials capable of storing significant elastic energy. Novel biophysical measurement tools were also developed for measuring the collective force generated by kinesin motor proteins, which will provide insight on the mechanical constraints of active assembly processes. Responsive reconfiguration of nanostructures was studied in terms of using active biomolecules to mediate the optical properties of quantum dot (QD) arrays through modulation of inter-particle spacing and associated energy transfer interaction. Design rules for kinesin-based transport of a wide range of nanoscale cargo (e.g., nanocrystal quantum dots, micron-sized polymer spheres) were developed. Three-dimensional microtubule organizing centers were assembled in which the polar orientation of the microtubules was controlled by a multi-staged assembly process. Overall, a number of enabling technologies were developed over the course of this project, and will drive the exploitation of energy-driven processes to regulate the assembly, disassembly, and dynamic reorganization of nanomaterials.
Date: November 1, 2005
Creator: Spoerke, Erik David; Thayer, Gayle Echo; de Boer, Maarten Pieter; Bunker, Bruce Conrad; Liu, Jun; Corwin, Alex David et al.
Partner: UNT Libraries Government Documents Department

LDRD final report on synthesis of shape-and size-controlled platinum and platinum alloy nanostructures on carbon with improved durability.

Description: This project is aimed to gain added durability by supporting ripening-resistant dendritic platinum and/or platinum-based alloy nanostructures on carbon. We have developed a new synthetic approach suitable for directly supporting dendritic nanostructures on VXC-72 carbon black (CB), single-walled carbon nanotubes (SWCNTs), and multi-walled carbon nanotubes (MWCNTs). The key of the synthesis is to creating a unique supporting/confining reaction environment by incorporating carbon within lipid bilayer relying on a hydrophobic-hydrophobic interaction. In order to realize size uniformity control over the supported dendritic nanostructures, a fast photocatalytic seeding method based on tin(IV) porphyrins (SnP) developed at Sandia was applied to the synthesis by using SnP-containing liposomes under tungsten light irradiation. For concept approval, one created dendritic platinum nanostructure supported on CB was fabricated into membrane electrode assemblies (MEAs) for durability examination via potential cycling. It appears that carbon supporting is essentially beneficial to an enhanced durability according to our preliminary results.
Date: October 1, 2008
Creator: Shelnutt, John Allen; Garcia, Robert M.; Song, Yujiang; Moreno, Andres M. & Stanis, Ronald J.
Partner: UNT Libraries Government Documents Department

Phonon engineering for nanostructures.

Description: Understanding the physics of phonon transport at small length scales is increasingly important for basic research in nanoelectronics, optoelectronics, nanomechanics, and thermoelectrics. We conducted several studies to develop an understanding of phonon behavior in very small structures. This report describes the modeling, experimental, and fabrication activities used to explore phonon transport across and along material interfaces and through nanopatterned structures. Toward the understanding of phonon transport across interfaces, we computed the Kapitza conductance for {Sigma}29(001) and {Sigma}3(111) interfaces in silicon, fabricated the interfaces in single-crystal silicon substrates, and used picosecond laser pulses to image the thermal waves crossing the interfaces. Toward the understanding of phonon transport along interfaces, we designed and fabricated a unique differential test structure that can measure the proportion of specular to diffuse thermal phonon scattering from silicon surfaces. Phonon-scale simulation of the test ligaments, as well as continuum scale modeling of the complete experiment, confirmed its sensitivity to surface scattering. To further our understanding of phonon transport through nanostructures, we fabricated microscale-patterned structures in diamond thin films.
Date: January 1, 2010
Creator: Aubry, Sylvie (Stanford University); Friedmann, Thomas Aquinas; Sullivan, John Patrick; Peebles, Diane Elaine; Hurley, David H. (Idaho National Laboratory); Shinde, Subhash L. et al.
Partner: UNT Libraries Government Documents Department

Nanoscience Research for Energy Needs. Report of the National Nanotechnology Initiative Grand Challenge Workshop, March 16-18, 2004

Description: This document is the report of a workshop held under NSET auspices in March 2004 aimed at identifying and articulating the relationship of nanoscale science and technology to the Nation's energy future.
Date: March 18, 2004
Creator: Alivisatos, P.; Cummings, P.; De Yoreo, J.; Fichthorn, K.; Gates, B.; Hwang, R. et al.
Partner: UNT Libraries Government Documents Department

Complex Systems: Science for the 21st Century

Description: Designed to help define new scientific directions related to complex systems in order to create new understanding about the nano world and complicated, multicomponent structures.
Date: March 6, 1999
Creator: Shank, C. V.; Awschalom, D.; Bawendi, M.; Fr├ęchet, J.; Murphy, D.; Stupp, S. et al.
Partner: UNT Libraries Government Documents Department

Crystal Splitting in the Growth of Bi2S3

Description: Novel Bi{sub 2}S{sub 3} nanostructures with a sheaf-like morphology are obtained via reaction of bismuth acetate-oleic acid complex with elemental sulfur in 1-octadecence. We propose these structures form by the splitting crystal growth mechanism, which is known to account for the morphology some mineral crystals assume in nature. By controlling the synthetic parameters, different forms of splitting, analogous to observed in minerals, are obtained in our case of Bi{sub 2}S{sub 3}. These new and complex Bi{sub 2}S{sub 3} nanostructures are characterized by TEM, SEM, XRD and ED.
Date: June 15, 2006
Creator: Tang, Jing & Alivisatos, A. Paul
Partner: UNT Libraries Government Documents Department

Nanoparticle modifications of photodefined nanostructures for energy applications.

Description: The advancement of materials technology towards the development of novel 3D nanostructures for energy applications has been a long-standing challenge. The purpose of this project was to explore photolithographically defineable pyrolyzed photoresist carbon films for possible energy applications. The key attributes that we explored were as follows: (1) Photo-interferometric fabrication methods to produce highly porous (meso, micro, and nano) 3-D electrode structures, and (2) conducting polymer and nanoparticle-modification strategies on these structures to provide enhanced catalytic capabilities and increase conductivity. The resulting electrodes were then explored for specific applications towards possible use in battery and energy platforms.
Date: October 1, 2011
Creator: Polsky, Ronen; Xiao, Xiaoyin; Burckel, David Bruce; Brozik, Susan Marie; Washburn, Cody M. & Wheeler, David Roger
Partner: UNT Libraries Government Documents Department

Three-Dimensional Carbon Nanostructures for Advanced Lithium-Ion Batteries

Description: This review contains the authors' recent progress on the design and fabrication of 3D carbon nanostructures, their performance in Li-ion batteries (LIBs), and their implementation into large-scale, lightweight, and flexible LIBs.
Date: October 26, 2016
Creator: Kang, Chiwon; Cha, Eunho; Patel, Mumukshu D.; Wu, H. Felix & Choi, Wonbong
Partner: UNT College of Engineering

Probing Compositional Variation within Hybrid Nanostructures

Description: We present a detailed analysis of the structural and magnetic properties of solution-grown PtCo-CdS hybrid structures in comparison to similar free-standing PtCo alloy nanoparticles. X-ray absorption spectroscopy is utilized as a sensitive probe for identifying subtle differences in the structure of the hybrid materials. We found that the growth of bimetallic tips on a CdS nanorod substrate leads to a more complex nanoparticle structure composed of a PtCo alloy core and thin CoO shell. The core-shell architecture is an unexpected consequence of the different nanoparticle growth mechanism on the nanorod tip, as compared to free growth in solution. Magnetic measurements indicate that the PtCo-CdS hybrid structures are superparamagnetic despite the presence of a CoO shell. The use of X-ray spectroscopic techniques to detect minute differences in atomic structure and bonding in complex nanosystems makes it possible to better understand and predict catalytic or magnetic properties for nanoscale bimetallic hybrid materials.
Date: June 22, 2010
Creator: Yuhas, Benjamin D.; Habas, Susan E.; Fakra, Sirine C. & Mokari, Taleb
Partner: UNT Libraries Government Documents Department

"Bottom-up" meets "top-down" : self-assembly to direct manipulation of nanostructures on length scales from atoms to microns.

Description: This document is the final SAND Report for the LDRD Project 102660 - 'Bottomup' meets 'top-down': Self-assembly to direct manipulation of nanostructures on length scales from atoms to microns - funded through the Strategic Partnerships investment area as part of the National Institute for Nano-Engineering (NINE) project.
Date: April 1, 2009
Creator: Swartzentruber, Brian Shoemaker
Partner: UNT Libraries Government Documents Department

Writable graphene: Breaking sp2 bonds with soft X-rays

Description: We study the stability of various kinds of graphene samples under soft x-ray irradiation. Our results show that in single-layer exfoliated graphene (a closer analog to two-dimensional material), the in-plane carbon-carbon bonds are unstable under x-ray irradiation, resulting in nanocrystalline structures. As the interaction along the third dimension increases by increasing the number of graphene layers or through the interaction with the substrate (epitaxial graphene), the effect of x-ray irradiation decreases and eventually becomes negligible for graphite and epitaxial graphene. Our results demonstrate the importance of the interaction along the third dimension in stabilizing the long range in-plane carbon-carbon bonding, and suggest the possibility of using x-ray to pattern graphene nanostructures in exfoliated graphene.
Date: June 9, 2010
Creator: Zhou, S.; Girit, C.; Scholl, A.; Jozwiak, C.; Siegel, D.; Yu, P. et al.
Partner: UNT Libraries Government Documents Department