Argonne National Laboratory Center for Nanoscale Materials U.S. Department of Energy

Archive: Seminars 2004

2014 | 2013 | 2012 | 2011 | 2010 | 2009 | 2008 | 2007 | 2006 | 2005 | 2004 | 2003

Nov. 23, 2004

"Three-Dimensional Compositional Imaging at the Atomic Scale: Innovative Atom Probe Tomography," Thomas F. Kelly, Imago Scientific Instruments, hosted by Derrick Mancini

Abstract: Atom probe tomography can provide thre-dimensional atomic-scale structural and compositional analysis of materials that is impossible to duplicate using other high-performance techniques such as TEM and SIMS. In spite of its unique analytical capabilities, the atom probe microscope has historically been used only by a small number of experts to analyze metal specimens that have been formed in the shape of a very sharp needle.

With recent developments in Local Electrode Atom Probe or LEAP® technology by Imago Scientific Instruments, the atom probe’s three-dimensional atomic-scale compositional imaging capabilities are now accessible to non-experts for analysis of a variety of materials. The materials to be analyzed can be prepared in either the traditional needle-shaped geometry or in the form microtips residing on planar surfaces. Imago’s LEAP technology also enables 100 times faster data collection rates and 40 times larger field of view than traditional atom probes. Typical images acquired on the LEAP Microscope have a cross-sectional area of 100 nm and require only minutes of data collection, with the end result being that much larger volumes of material may be rapidly accessed with the atom probe microscope than has previously been possible or practical.

Nov. 15, 2004

"New Approaches to the Synthesis and Assembly of Nanoscale Materials," Teri Odom, Northwestern University, hosted by Eric Isaacs and Al Wagner

Nov. 15, 2004

"Ferroelectricity in PbTiO3 Thin Films," Dillon Fong, hosted by Stephen Streiffer

Abstract: Investigations of intrinsic size effects in ferroelectrics are often hindered by uncontrolled strain and charge effects, which interact strongly with the polarization. As a result, despite decades of effort, the size dependence of the paraelectric-to-ferroelectric phase transition in perovskites remains an unresolved issue. Although the ferroelectric phase was once thought to be unstable in small particles and films, researchers have recently found evidence of ferroelectric behavior in ten-unit-cell-thick Pb(Zr0.2Ti0.8)O3, and theorists have predicted ferroelectricity in even thinner films. Here we report synchrotron X-ray scattering studies of the prototypical ferroelectric perovskite, PbTiO3, grown on (001) SrTiO3 in films as thin as one unit cell. We demonstrate that the ferroelectric phase is stable in a three-unit-cell-thick (1.2-nm) film, with a transition temperature of ~250°C. The effect of the mechanical and electrical boundary conditions on ferroelectric phase stability will also be discussed.

Nov. 10, 2004

“Electronic Transport in Molecule-Electrode Interfaces: Current Understanding and Open Questions,” Vladimiro Mujica, Universidad Central de Venezuela, hosted by Luis Nuñez and Eric Isaacs

Abstract: I will review our current understanding of electronic transport in molecule-electrode interfaces. Relevant topics include the description of tunneling and hopping conduction regimes, the influence of the voltage profile, rectification effects and the influence of the contacts. A more speculative discussion about some open questions and the relevance of the field in molecular electronics will follow, mainly about the role of magnetism and the subject of transport under the combined influence of a voltage bias and a time-dependent field.

Nov. 8, 2004

“Surface Layering in Simple Liquids: Elemental Metals, Binary Alloys and Dielectrics,” Oleg Shpyrko, Harvard University, Department of Physics, hosted by Eric Isaacs

Abstract: Advances in nanotechnology produce a variety of nanoscale-sized objects whose properties are defined predominantly by interfacial and surface physics rather than bulk effects. While most modern surface sciences research deals with solid surfaces, surface behavior of even simple fluids is not sufficiently understood. This presentation will review synchrotron studies of liquid-vapor, liquid-liquid, and liquid-solid interfaces, such as surface-induced atomic layering (crystalline-like ordering of atoms at liquid-vapor interface) recently discovered in a number of elemental metallic liquids, formation of nanoscale wetting film in monotectic binary alloys, and Gibbs adsorption and surface freezing in eutectic binary liquids.

Oct. 19, 2004

"The Three-Dimensional Atom Probe: Materials Characterization of the Atomic Scale," Carl Hatton, Oxford nanoScience Ltd., hosted by Derrick Mancini

Abstract: The three-dimensional atom probe provides a uniquely powerful tool for studying the structure and composition of solids at the atomic level. It consists of three main parts: a field ion microscope, in which the atomic structure of the sample can be imaged; a single-ion sensitivity time-of-flight mass spectrometer, in which the chemical nature of the atoms removed from the specimen can be determined; and a position-sensitive detector system, which enables the original location of the analysed atoms on the specimen surface to be identified. Several million atoms can be removed from a single specimen, thus permitting the reconstruction of the atomic-scale structure and chemical composition of a selected region of the sample in three dimensions. In the presentation the principle of operation, instrumentation details, applications and typical data obtained for the 3D Atom Probe instrument will be outlined.

Oct. 14, 2004

"Exploring Photorefractive Polymer-Dispersed Liquid Crystals using High-Field Scanning Optical Microscopy," Jeffrey Hall, Department of Chemistry, Kansas State University, hosted by Gary Wiederrecht

Abstract: Studies were conducted on photorefractive polymer-dispersed liquid crystal (PRPDLC) films developed in the Higgins group. The PRPDLCs are submicrometer-sized lilquid crystal droplets doped with perylene (photoexcitable electron donor) and N,N’-di(n-octyl-1,4,5,8- naphthalene diimide (electron acceptor), encapsulated in a thin, optically transparent polymer film. Bulk spectroscopy methods were used to verify the photorefractive properties in the photorefractive material. Near-field optical microscopy experiments were performed for the first time on these materials and were used to better understand the mechanism of photorefractivity in single liquid crystal droplets.

July 21, 2004

"Photophysics of Self-Assembled Multichromophoric Arrays," Louise E. Sinks, Northwestern University, Department of Chemistry, hosted by Gary Wiederrecht

Abstract: The self-assembly of perylene-3,4:9,10-bis(dicarboximide) (PDI)- containing molecules has been reported by many groups, including our own. The photophysics of new PDI-containing molecules are presented. These molecules show a tendency to aggregate, which has a large impact on the excited state photophysics of PDI, as illustrated by the dramatic spectral changes in the transient absorption data. Several cases will be discussed, including both energy and electron transferring arrays.

July 14, 2004

"Scattering Studies of the Electron-Doped High-Temperature Superconductor Nd2-xCexCu04," Patrick Mang, Stanford University, Department of Physics, hosted by Eric Isaacs

Abstract: X-ray and neutron scattering are powerful and direct probes of structural and magnetic order and excitations in solids. For example, these techniques have provided valuable insights into the properties of hole-doped high-temperature superconductors. Here I present three investigations of Nd2-xCexCuO4 (NCCO) that extend our knowledge to the important class of the electron-doped superconductors.

June 9, 2004

"Nanoparticle Technologies by Chemistry: From the Basics to the Marketplace," Prof. Helmut Karl Schmidt, Leibniz-Institut für Neue Materialien, hosted by Derrick C. Mancini

Abstract: Nanoparticles show unique properties as they are positioned between single ions or molecules and the corresponding bulk material. The effects of this size are manyfold (e.g., free energy, surface area, diffusion rates or Rayleigh scattering). These effects show an interesting potential for tailoring new materials for new applications. Colloidal synthesis processes as well as milling technologies have been developed for the fabrication of surface chemistry tailored nanoparticles from many systems. The utilization for a series of applications will be shown, for example, high-laser-threshold coatings on plastic, the use of superparamagnetic maghemite nanoparticles that are able to discriminate between healthy and tumor cells and are used for tumor therapy, a concept for photoinduced nanoparticle diffusion for holographic data storage and the fabrication of diffuser foils or tailor-made antimicrobial coatings based on controlled release of silver. The basics of fabrication and processing as well as several successful applications are described.

June 16, 2004

"High-Resolution Study of Pressure-Driven Quantum Critical Point in a CrV Alloy," Minhyea Lee, University of Chicago, Department of Physics, hosted by Eric Isaacs

Abstract: High-fidelity pressure measurements in the zero temperature limit provide a unique opportunity to study the behavior of strongly interacting, itinerant electrons with coupled spin and charge degrees of freedom. Approaching the exactitude that has become the hallmark of experiments on classical critical phenomena, we characterize the quantum critical behavior of the model, elemental antiferromagnet chromium, lightly doped with vanadium. We resolve the sharp doubling of the Hall coefficient at the quantum critical point and trace the dominating effects of quantum fluctuations up to surprisingly high temperatures.

May 14, 2004

"Mesoscopic and Multiscale Simulations of Surface-Bound Nanostructures," Rahul V. Magan, Graduate Research Assistant Department of Chemical Engineering Washington University in St. Louis, hosted by Derrick Mancini

Abstract: Surface-bound nanostructures have attracted considerable interest because of their applications in the fields of materials science, nanotechnology, microelectronics, and biotechnology. Techniques for the synthesis of novel materials with desired properties have been sought with intimate attention to the microscopic structure. Robust modeling and simulation tools can help broaden the capability to synthesize, control, and manipulate these nanostructures. We will discuss the application of experimentally validated mesoscopic and multiscale simulations to describe the relationship between morphology/structure and macroscopic process variables in the context of formation of nanoparticles, nanostructured interfaces, and colloidal deposition.

April 14, 2004

"Low-Energy Magnetism and Field-Induced Ordering in Undoped and Lightly Doped La2-xSrxCuO4," Adrian Gozar, Bell Labs, Lucent Technologies, and University of Illinois, Urbana-Champaign, Department of Physics, hosted by Eric Isaacs

Abstract: I will discuss long-wavelength magnetic excitations in La2-xSrxCuO4 (x < 0.03) detwinned (macroscopically orthorhombic) single crystals, focusing on the magnetic field effects on the antiferromagnetic order and also on the "anisotropic paramagnetic" phase for x = 0 and 0.01. Two kinds of resonances corresponding to gapped magnon branches are seen in the low-energy Raman spectra. The anisotropic properties in magnetic fields of the lower energy mode can be understood in terms of the antisymmetric (Dzyaloshinskii-Moriya) interaction within the AF state. The second magnetic mode, analyzed in terms of in-plane magnetic anisotropy, shows an unconventional behavior within the antiferomagnetic state and led to the finding of collective spin excitations pertaining to another field-induced magnetically ordered state. I will discuss the nature of the ordered state and show that it persists in a 9-Tesla field up to almost 100 K above the Neel temperature in the x = 0.01 crystal.

Mar. 16, 2004

"Organic Nanostructures Derived from Petroleum," Prof. G.A. Mansoori, Ph.D., Department of Chemical Engineering, University of Illinois at Chicago, hosted by Lahsen Assoufid and Derrick Mancini

Abstract: We have been studying formation and measurement of the behavior of such organic nanostructures as diamondoids and asphaltenes that might be formed to serve as elements of nanomaterials and also on synthetic strategies for creating such structures. An investigation of the self-replication (self assembly, micellization, and coacervation) measurements of some well-characterized organic molecules in various media at different concentrations and temperatures are made. A multidisciplinary collaborative study in nanomechanics and intermolecular interactions of molecules forming these nanostructures are in progress.

Mar 10, 2004

"Is There Quantum Fluctuation in Superconducting Nanowires?," Alexey Bezrysadin, Department of Physics, University of Illinois – Urbana, hosted by George Crabtree and Konstantin Matveev

Abstract: Review recent progress in the field of one-dimensional superconductivity. First, the techniques leading to ultrathin wires, with diameters approaching 5 nm, will be discussed. The main results of transport measurements will be presented. In many cases the results are in excellent agreement with the LAMH theory of thermally activated phase slips. Two main quantum phenomena emerged in these experiments: quantum superconductor-insulator phase transition (SIT) and possible quantum phase slips. Possible reasons for the SIT will be discussed. Quantum interference devices made out of ultrathin nanowires will be presented.

Mar. 1, 2004

"The Analysis, Design, and Simulation of Atomistic Systems using Ab Initio Based Methods," Julia Hsu, Sandia National Laboratories, hosted by Gary Wiederrecht and Eric Isaacs

Abstract: Photonic and electronic devices employing organic and molecular materials as the active component are of increasing technological interest and present several unsolved scientific issues. The fabrication and characterization of such devices will require innovative techniques. In particular, the electrical transport across the interface between an organic/molecular material and inorganic metal or semiconductor electrodes is still not well understood, and existing experiments in this area offer many inconsistent results. In this talk, I will describe the use of novel soft nanolithography techniques to fabricate polymer light emitting diodes and molecular junctions, and demonstrate the capability of fabricating nanometer-size features over centimeter-size areas. I will discuss electrical transport in these devices and show that devices made by these novel methods are superior to those fabricated by conventional lithographic and metallization techniques.

Mar. 1, 2004

"The Analysis, Design, and Simulation of Atomistic Systems using Ab Initio Based Methods," Prof. Jorge M. Seminario, Department of Electrical Engineering, University of South Carolina, hosted by Leonidas Ocola

Abstract: The analysis, design, and simulation of molecular electronics systems requires of a theoretical bottom-up approach as an alternative to the top-down or phenomenological approach still used for microelectronics. Our approach consists in the use precise quantum first-principles (ab initio) theories to analyze, design, and simulate molecular electronic devices and systems for molecular electronics in order to obtain precise characteristics of all elements involved on a molecular chip. These ab initio results are used in nonlinear circuit solvers that permit us to combine highly nonlinear devices in a molecular circuit allowing us to determine “programmability” features of molecular devices. If this is the case, the molecules are proposed as potential candidates for chemical synthesis and further more precise analyses are performed including molecular dynamics simulations that allow studying the effects of pressure and temperature on the molecular chip.

Mar. 1, 2004

"The Analysis, Design, and Simulation of Atomistic Systems using Ab Initio Based Methods," Prof. Jorge M. Seminario, Department of Electrical Engineering, University of South Carolina, hosted by Leonidas Ocola

Abstract: The analysis, design, and simulation of molecular electronics systems requires of a theoretical bottom-up approach as an alternative to the top-down or phenomenological approach still used for microelectronics. Our approach consists in the use precise quantum first-principles (ab initio) theories to analyze, design, and simulate molecular electronic devices and systems for molecular electronics in order to obtain precise characteristics of all elements involved on a molecular chip. These ab initio results are used in nonlinear circuit solvers that permit us to combine highly nonlinear devices in a molecular circuit allowing us to determine “programmability” features of molecular devices. If this is the case, the molecules are proposed as potential candidates for chemical synthesis and further more precise analyses are performed including molecular dynamics simulations that allow studying the effects of pressure and temperature on the molecular chip.

Feb. 26, 2004

 

"Self-Assembly of Colloids & Droplet Nanoengineering: A Magical Combination," Manuel Marquez, Ph.D., Los Alamos National Laboratory and The Nanotechnology Lab at Kraft Foods R&D, hosted by Luis Nuñez

Abstract: Herein we describe two approaches for nanoengineered complex droplets and their use as templates for micro- and nanoencapsulation. We will discuss the use of microfluidic devices for the preparation and design of droplets with a very narrow size distribution. In addition, the application of an electric field has allowed for the generation of submicron emulsions by electrospray inside the channels. We will also report and discuss the spontaneous formation of inorganic helices and complex patterns of mixed valent colloidal particles.

Colloidosomes: Selectively Permeable Capsules Composed of Colloidal Particles: We present an approach to fabricate solid capsules with precise control of size, permeability, mechanical strength, and compatibility. The capsules are fabricated by the self-assembly of colloidal particles onto the interface of emulsion droplets. After the particles are locked together to form elastic shells, the emulsion droplets are transferred to a fresh continuous-phase fluid that is the same as that inside the droplets. The resultant structures, which we call "colloidosomes," are hollow, elastic shells whose permeability and elasticity can be precisely controlled. The generality and robustness of these structures and their potential for cellular immunoisolation are demonstrated by the use of a variety of solvents, particles, and contents.

Micro/Nano Encapsulation via Electrified Coaxial Liquid Jets: We report a method to generate steady coaxial nanojets of immiscible liquids with diameters in the range of micrometer/nanometer size. This compound jet is generated by the action of electro-hydrodynamic (EHD) forces with a diameter that ranges from tens of nanometers to tens of micrometers. The eventual nanojet breakup results in an aerosol of monodisperse compound droplets with the outer liquid surrounding or encapsulating the inner one. Following this approach, we have produced monodisperse capsules with diameters varying between 0.05 and 10 micrometers, depending on the running parameters.

Jan. 22, 2004

"Biological Routes to Functional Nanostructures, " Brian Dennis Reiss, Ph.D., The Massachusetts Institute of Technology, hosted by Millie Firestone

Abstract: Viral templates are emerging as one of the most versatile tools in nanoscience. By expressing a random peptide insert on the coat proteins of the virus, peptides can be identified using an evolutionary screening technique, which selectively bind technologically important materials. To date, these materials include magnetic materials, noble metals, semiconductors, and polymers. Once discovered, these peptides can be used to control the nucleation of the desired materials and have been used as capping agents to prepare magnetic nanoparticles, such as FePt, CoPt, SmCo5, and Co using a modified arrested precipitation technique. These nanoparticles are prepared at room temperature under aqueous conditions, and characterization using TEM, SQUID, and X-ray diffraction indicate this is the only viable synthetic route developed to date for the direct preparation of ferromagnetic nanostructures. These filamentous viruses can also be engineered to express the desired peptide in high concentrations along their coat proteins, facilitating the synthesis of nanowires of the desired material. High-temperature annealing of these structures leads to the formation of single-crystal nanowires. Currently, a molecular combing technique and dip-pen lithography are being developed as tools for aligning and organizing these viruses into controlled architectures to facilitate their device applications.

 

U.S. Department of Energy Office of Science | UChicago Argonne LLC
Privacy & Security Notice | Contact Us | Site Map

The Center for Nanoscale Materials is an Office of Science User Facility operated for
the U.S.Department of Energy Office of Science by Argonne National Laboratory