Argonne National Laboratory

Seminars

Date Title
January 23, 2017
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"On the Solution of Inverse Problems"
Aggelos K. Katsaggelos
Department of EECS, Northwestern University.

Abstract: In this talk, I will briefly present the various activities in the Image and Video Processing Laboratory I am directing, in the EECS Department at Northwestern University.  I will then focus on the presentation of some of our recent results in solving inverse problems, such as, the image recovery, super-resolution, and compressive sensing problems. I will present both analytical and learning approaches for solving such problems.  More specifically, I will first present hierarchical Bayesian approaches for blind deconvolution and image super-resolution. I will then present dictionary approaches for solving the video super-resolution problem as well as the problem of fusing visible and X-ray fluorescence images. Finally, I will present some of our results using deep neural networks for temporal compressive sampling. I will conclude the talk by discussing the impact of learning approaches in solving inverse problems. 

November 28, 2016
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Curved Magnetic Nanomembranes"
Denys Makarov
Helmholtz-Zentrum Dresden-Rossendorf

Abstract: While conventionally magnetic films and structures are fabricated on flat surfaces, the topology of curved surfaces has only recently started to be explored and leads to new fundamental physics as well as applied device ideas. In particular, novel effects occur when the magnetization is modulated by curvature providing a new degree of freedom that leads to new magnetization configurations and is predicted to have major implications on the spin dynamics due to topological constraints for instance in circular tubes and rolls.

Advances in this novel field solely rely on the understanding of the fundamentals behind the modifications of magnetic responses of 3D-curved magnetic thin films. The lack of an inversion symmetry and the emergence of a curvature induced effective anisotropy and Dzyaloshinskii-Moriya interaction are characteristic of curved surfaces, leading to curvature-driven magnetochiral effects and topologically induced magnetization patterning, including unlimited domain wall velocities in hollow tubes, chirality symmetry breaking and Cherenkov-like effects for magnons. In addition to these rich physics, the application potential of 3D-shaped objects is currently being explored as magnetic field sensorics for magnetofluidic applications, spin-wave filters, magneto-encephalography devices and high-speed racetrack memory devices. To this end, the initially fundamental topic of the magnetism in curved geometries strongly benefited from the input of the application-oriented community, which among others explores the shapeability aspect of the curved magnetic thin films. These activities resulted in the development of the family of shapeable magnetoelectronics, which already includes flexible, printable, stretchable and even imperceptible magnetic field sensorics.

These recent developments starting from the theoretical predictions to the fabrication and characterization of 3D-curved magnetic thin films and their application potential are in the focus of this talk. 

November 14, 2016
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Ultrafast X-ray imaging of phase transitions and nanoscale thermal transport"
Haidan Wen
X-ray Sciences Division
Argonne National Laboratory

Abstract: Heterogeneities in condensed matter systems play important roles in determining their functionalities. Although the heterogeneities have been intensively studied in equilibrium, the evolution of heterogeneities driven out of equilibrium has not been understood due to technical challenges of probing ultrasmall on ultrafast time scales. Visualizing dynamical interaction among heterogeneities of multiple degrees of freedom is critical for understanding and subsequently harnessing the mesoscale properties of materials with new or enhanced functionalities. In this talk, I will present two examples to show the recent efforts that allow researchers to image the evolution of structural heterogeneities by time-resolved x-ray diffraction microscopy with 100 ps resolution.  In the first example, the inhomogeneous structural phase transformation was revealed in photo-excited VO2 thin films. The in-plane phase progression is a result of displacive lattice transformation rather than driven by thermal diffusive process. In the second example, a spatially engineered transient strain profile in BaTiO3 films was created by metasurface-enhanced terahertz field excitation and directly visualized by time-resolved x-ray diffraction. The time-dependent strain profile reveals ballistic phonon transport on sub-micrometer length scales. This method provides an ideal tool for studying nanoscale thermal transport. In the end, I will present a static study of 2D transition metal dichalcogenides heterostructures using in-situ photoluminescence and full-field x-ray diffraction microscopy measurements. This example calls the need for a time-solved multimodal x-ray imaging platform for future materials science. 

October 31, 2016
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Deep neural networks for synchrotron X-ray imaging"
Xiaogang Yang
X-ray Sciences Division
Argonne National Laboratory

Abstract: X-ray imaging scans at today's synchrotron light sources can yield thousands of image frames per second at high resolution. Typical data volumes from a single scan are on the order of tens of gigabytes, however for larger specimens this number can be up to three orders of magnitude larger. Moreover, data generation rates will significantly increase after the upgrade of the storage rings that are planned or under development at many synchrotron facilities worldwide. Current and expected data volumes and rates necessitate having reliable, efficient, and fully automated data processing pipelines. Traditional image process models are powerless for the data with complex patterns and noises. The modern researchers solve the large amount of data manually at most of the cases. The deep neural network can emulate the way of human to model the data problem and to process the large datasets automatically. I will present my recent progress of applying the deep neural network to calibrate the tomographic rotation axis, and to segment the fluorescence and TXM images. Its future development will also be discussed..

October 17, 2016
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Integrated Imaging: The Sum is Greater than the Parts"
Amanda Petford-Long
Materials Science Division
Argonne National Laboratory

Abstract: Most natural and manufactured materials are spatially complex and heterogeneous, and their performance is typically linked to this heterogeneity. Bulk analysis methods ignore these realities, but imaging and microscopy offer a way to see the real material in all of its complexity and explore its local behavior. When combined with spectroscopy, diffraction, or other analytical methods they allow one to understand what one sees. One can further watch materials at work in situ or operando using x-ray and electron microscopy, with unparalleled sensitivity to trace elements, chemical speciation, lattice strain, and electron spin, along with 4D visualization capabilities as the temporal dimension is invoked.  However, as powerful as these individual approaches are, usually no single measurement provides all the information needed to understand a material. Argonne’s efforts integrate DOE Scientific User Facilities such as the APS, EMC, CNM with other imaging capabilities at Argonne, and with the analytical and visualization opportunities offered by the MCS, ALCF and related petascale computational and data analysis facilities.
The goal of Argonne’s Integrated Imaging Institute (I3) is twofold: firstly to provide a bridge across these capabilities to couple the full range of Argonne’s imaging methods with simulation results to close the loop between design, simulation, synthesis, characterization, and analysis. Secondly to act as a portal to external partners interested in engaging with Argonne in the area of integrated imaging. In this seminar I will give an update on the projects funded within I3 and discuss how we are taking the Institute forward, and then provide some specific examples taken from my own group’s research on applying a combination of different imaging modalities together with simulation and modeling to address scientific challenges related to magnetic and multiferroic nanostructures.

May 2, 2016
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Integrated Imaging to Understand and Advance Photocatalysis: a Progress Report"
Jeff Guest
Center for Nanoscale Materials
Argonne National Laboratory

Abstract: We will discuss progress during the first year and a half on our I3 project, the objective of which is to simultaneously (1) advance the understanding of elementary processes involved in CO2 reduction to liquid fuel on metal oxide nanoparticles and (2) develop integrated imaging and visualization approaches across complementary microscopy platforms. These aspects are intertwined because developing an understanding of these complex processes requires correlating structure with photocatalytic functioning down to atomic length scales in environments that support these processes.  We are developing a cross-platform sample holder which will allow gas-flow and optical illumination during imaging and allow transfer of the same sample between TEM, SXFM, and UHV STM measurements; ultimately, we are striving to interrogate the identical particle with these approaches.  Experimental and analytical tools are being developed with the goal of lowering the barriers to experimental work that spans several platforms.  Additionally, we are developing theoretical models of our system and performing calculations to develop an understanding of the photocatalytic processes in order to guide the measurements through simulations of images and spectra for the various experimental modalities.  For our investigations, we are focusing on Cu2O nanoparticles because they may hold several advantages for supporting photocatalytic activity beyond TiO2, the reigning standard.

April 11, 2016
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Investigations of topological states in electron wavefunctions and magnetization"
Prof. Benjamin McMorran
Department of Physics,
University of Oregon

Abstract: We use transmission electron microscopy (TEM) to produce and investigate topological states in coherent free electron wavefunctions, and to image topological spin texture in magnetic materials. Electron vortex beams are composed of helical free electron wavefunctions that carry quantized orbital angular momentum (OAM). To produce such free electron states, we use nanofabricated diffraction gratings to holographically imprint a phase vortex with a prescribed topological charge onto free electron matter waves. We investigate the dynamics and properties of these free electron topological states inside a transmission electron microscope (TEM), and are developing methods to utilize these beams for new types of nanoscale measurements of chirality and particle manipulation. We have an interest in applying these beams to the study of magnetic topological features - magnetic Skyrmions in FeGd thin films. Our initial studies of magnetic Skyrmions will be reviewed.

March 21, 2016
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"MAUI: Modeling, Analysis, and Ultrafast Imaging"
Tom Peterka
Mathematics and Computer Science Division
Argonne National Laboratory

Abstract:Maui is an LDRD project researching the combination of light source imaging and molecular dynamics modeling through the common language of data analysis. Integrating ultrafast time-resolved imaging, large-scale molecular dynamics modeling, and in situ data analysis can provide crucial insights for energy research. The temporal behavior of in situ externally stimulated materials beyond equilibrium can lead to breakthroughs, for example, in heat dissipation of next-generation semiconductors, conversion of wasted heat into electricity in thermoelectric materials, and electrochemical processes across liquid-solid interfaces in water purification. All these diverse applications share a common behavior: they transport energy through phonons (sound waves that carry heat) in a time-evolving crystal lattice.

Computing capability in molecular dynamics is growing exponentially at leadership computing facilities. Likewise, new analysis and visualization techniques for 4D and higher-dimensional data are being researched. We have also begun imaging time-evolving lattice dynamics using "pump-probe" experiments. Never before, however, have all three efforts---forward modeling through atomistic simulations, ultrafast imaging, and reverse modeling through reconstruction and analysis---been combined in an interoperable method that provides iterative feedback from each component to the others.

This talk will provide a high-level summary of the first 1-1/2 years of our project, lessons learned, and a glimpse at the second half of the project.

March 7, 2016
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Model-Based Iterative Reconstruction Algorithms for X-ray Absorption and Phase Contrast Tomography"
Aditya Mohan
Department of Electrical and Computer Engineering
Purdue University

Abstract: X-ray absorption and phase contrast tomography are widely used for 3D and 4D characterization of material and biological samples. The conventional approach to reconstruction makes use of analytical inversion methods that make various limiting assumptions about the object and the measurement physics. Furthermore, they are also sensitive to noise and limited data. For instance, the analytical filtered back projection algorithm used in X-ray tomography requires Nyquist sampling of projection data and an unchanging sample. In phase contrast tomography, the analytical phase retrieval algorithms make the near-field assumption for diffraction that limits the spatial resolution and image contrast.

In this talk, I will present model-based iterative reconstruction algorithms for X-ray absorption and phase contrast tomography that makes efficient use of all the available data and is robust to noise. I will present a time interlaced model-based iterative reconstruction (TIMBIR) method which can significantly improve the temporal resolution of time-space reconstructions. TIMBIR is a synergistic combination of two innovations. The first innovation, interlaced view sampling, is a novel approach to data acquisition which distributes the view angles more evenly in time. The second innovation is a 4D model based iterative reconstruction algorithm (MBIR) which can produce time resolved volumetric reconstructions of the sample from the interlaced views. I will also present a model-based iterative reconstruction (MBIR) algorithm for X-ray phase contrast tomography called complex refractive index tomographic iterative reconstruction (CRITIR). CRITIR is based on a non-linear physics based model for X-ray propagation and a prior model for the complex refractive index of the object being imaged. Unlike conventional methods, CRITIR is designed to work within and beyond the near-field diffraction region.

February 22, 2016
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Multimodal Imaging of Batteries"
Doga Gursoy
Xray Sciences Division
Argonne National Laboratory

Abstract: Batteries have had a remarkable effect on the adoption of portable electronic devices. Improving batteries requires understanding the sophisticated interaction of many materials at multiple length scales, ranging from micro (structure of various components, transport of ions/charge) to nano (electronic interactions, local charge accumulation). To address this challenge, we are working on developing multimodal imaging systems including electron microscopy and multiple X-ray microscopy techniques to quantify structure at multiple length-scales. Our goal is to unify data from each "modality" with the new numerical methods in an integrated fashion. This will allow us to understand the nano to micro scale evolution of change in the material as a function of electrochemical cycling. This talk will provide a brief overview of the project and the challenges that lie ahead.

January 8, 2016
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Sub-nm resolved imaging by plasmon-enhanced Raman scattering"
Rui Zhang
Nanoscience and Technology Division
Argonne National Laboratory

Abstract: Visualizing individual molecules with chemical recognition is a longstanding target in catalysis, molecular nanotechnology and biotechnology. Molecular vibrations provide a valuable ‘finger-print’ for such identification. Vibrational spectroscopy based on tip-enhanced Raman scattering allows us to access the spectral signals of molecular species very efficiently via the strong localized plasmonic fields produced at the tip apex. However, the spatial resolution in normal tip-enhanced Raman scattering technique is not adequate for resolving a single molecule chemically. In this talk, I will introduce our recent development of sub-nanometer resolved Raman spectral imaging which is based on a low-temperature and ultrahigh-vacuum scanning tunneling microscope (LT & UHV STM), resolving the inner structure and surface configuration of a single molecule. Such a technique is also able to directly distinguish DNA-bases connected by hydrogen bonding. Our technique provides a new way of directly studying optical processes and photochemistry at the single-molecule scale.

December 14, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"The Materials Data Facility - Data Services to Advance Materials Science Research"
Ben Blaiszik
Computation Institute
University of Chicago

Abstract: In collaboration between Globus, the National Center for Supercomputing Applications (UIUC), and the Center for Hierarchical Materials Design (CHiMaD), we are building the Materials Data Facility (MDF) to advance materials science research. Based on lessons we have learned from direct interactions with materials researchers, we are developing capabilities to promote open data sharing, simplify data publication and curation workflows, encourage data reuse, and provide powerful data discovery interfaces for data of all sizes and sources. Specifically, MDF services will allow individual researchers and institutions to 1) enable publication of large research datasets with flexible policies; 2) grant the ability to publish data directly from local storage, institutional data stores, or from cloud storage, without third-party publishers; 3) build extensible domain-specific metadata and automated metadata ingestion scripts for key data types; 4) develop publication workflows; 5) register a variety of resources for broader community discovery; and 6) access a discovery model that allows researchers to search, interrogate, and build upon existing published data.

November 30, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Large-Scale Parallel Data Analysis and Visualization Using the vl3 Framework"
Silvio Rizzi
Argonne Leadership Computing Facility
Argonne National Laboratory

Abstract: Experimental and observational systems, along with computational simulations, generate vast amounts of data. Scientific visualization and visual analytics are invaluable tools to extract knowledge from these enormous datasets. In this talk we will describe vl3, a framwork for large-scale data analysis and visualization developed at Argonne and University of Chicago. We will cover its application to interactively explore large-scale volumetric (i.e. CT scans, fluid simulations) and particle-based datasets (i.e. molecular dynamics, cosmology). We will also discuss vl3's capability for remote data visualization and streaming ultra-high resolution images to remote displays, including large tile displays.

October 5, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Towards complete and comprehensive fine structural mapping of brains"
Bobby Kasthuri
Nanoscience and Technology Division
Argonne National Laboratory

Abstract: The Kasthuri lab is pioneering new techniques for large volume reconstructions of the fine structure of the nervous system. These developments include: large volume automated electron microscopy, synchrotron source X-ray microscopy to map the cellular composition of entire brains; improving sample preparation for serial electron microscopy in order to increase the efficiency of automated algorithmic tracing of these datasets; and combining electron microscopy with current techniques for interrogating the proteome and the genome.  These tools will be applied in the service of answering the question: how do brains learn as they grow up?  The lab focuses on the synaptic and cellular development of brains as a basis ultimately for understanding the cellular underpinnings of pathologies such as addiction and mental illness.

September 21, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Superresolution, multi-photon and correlative fluorescence / atomic force microscopy of nano- and bio-materials"
Prof Steve Smith
Nanoscience and Nanoengineering, South Dakota School of Mines

Abstract: Our group at SDSMT focuses on spectroscopy and imaging of nano- and bio-materials. A number of specific applications of imaging methods to select nano- and bio-materials will be discussed, these include: Photo-activated Localization microscopy of single Carbohydrate Binding Modules (CBMs) on nano-crystalline cellulose, multi-photon imaging of fluorescent reporters of gene expression in soy bean root nodules, spectroscopic imaging of the surface plasmon polariton enhanced spectral upconversion in rare-earth doped nano-crystals, and simultaneous fluorescence and atomic force microscope imaging of clathrin mediated endocytotic vesicles in unroofed fixed cells. Time permitting, I will discuss our development of a lattice light-sheet microscope for superresolution, near-video rate volumetric imaging in living cells

August 24, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Quantifying mesocale neuroanatomy using X-ray microtomography"
Eva Dyer
Rehabilitation Unit of Chicago and Feinberg School of Medicine, Northwestern University

Abstract: The structure of the brain is constantly being modified due to experience, learning, aging, and in some cases, disease. Understanding the impact of such modifications on brain architecture, at various spatial scales, will have wide reaching impacts. Unfortunately, existing methods for quantifying the neuroanatomical structure of the brain, such as light and electron microscopy (EM), cannot be readily applied to large brain volumes. For this reason, there exists an information gap at the mesoscale: we require new techniques to produce brain maps that characterize the cell shapes, densities, and positions and their long-range projections across large spatial extents.

Synchotron-based X-ray microtomography (XRM) is uniquely poised to fill this gap. Compared to electrons or visible light photons, X-rays undergo very little multiple scattering so that thick samples can be studied at sub-micrometer resolution. Unfortunately, XRM has not been completely adapted to meet the demands of large-scale brain imaging. In this talk, I will describe my efforts to develop new computer vision and machine learning tools for quantifying neuroanatomy using XRM. Our results demonstrate that XRM of samples prepared for electron microscopy produce image stacks with sufficient resolution (~2 micron isotropic) to identify all cell bodies, their sizes, locations and in some cases partial reconstructions of their dendritic processes. We also show that the trajectory of all the vasculature and myelinated axons can also be reconstructed. These results suggest that XRM promises a new avenue for neuroscientists to study the mesoscale architecture of large brain volumes.

August 10, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Atomic mapping of reduced-dimensional materials by phasing coherent Bragg rods for emergent physics and energy systems "
Hua Zhou
Xray Sciences Division
Argonne National Laboratory

Abstract:

The remarkable development of reduced-dimensional materials (i.e. epitaxial heterostructures or Vdw 2D crystals) in the last decade has led to tremendous amounts of new phenomena and properties, which can be effectively harnessed for the design of advanced materials for information and energy applications and accelerating materials integration into advanced devices. A compelling manifestation is oxide heterointerfaces exhibiting fascinating emergent behaviours due to subtle combinative contributions of atomic structures and chemistries near interfacial boundaries. Surface/interface X-ray scattering from modern synchrotron sources integrated with phase retrieval direct methods provides a very powerful toolkit to decipher the subtlety. In this seminar, I will firstly give a brief introduction of how to obtain atomic mapping of reduced-dimensional systems with sub-Ångstrom resolution by phase retrieving coherent Bragg rods, wherein complete atomically structural information hidden, in particular on the COBRA method in combination with the difference map algorithm achieving unprecedented speed of convergence and precision. In the following, I will demonstrate a few recent studies in the exploration of oxide heterointerfaces and epitaxial 2D crystals for information and energy applications by applying the direct method, such as probing fundamental interactions of epitaxial 2D crystals with substrates, revealing structural motifs responsible for 2DEG and superconductivity adjacent with heterointerfaces, differentiating at the atomic-layer level the complicated cation distribution relevant with creating new polar order and enhancing oxygen reduction activities, and depth-resolved mapping oxygen-octahedral connectivity patterns essential with incipient functionalities of heterostructures. In the end, I will give a short commentary on future opportunities in X-ray studies of reduced-dimensional materials enabled by the exciting advancements towards ultimate storage rings, in particular with enhanced high-energy and coherence capabilities.

July 13, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Complementing ultrafast imaging experiments with insights from atomistic simulations "
Kiran Sasikumar
Nanoscience and Technology Division
Argonne National Laboratory

Abstract: Integrating ultrafast imaging with molecular dynamics (MD) simulations can provide crucial insights for energy research. The temporal behavior of externally stimulated materials beyond equilibrium can lead to breakthroughs, for example, in heat dissipation of semiconductors, waste heat energy conversion via thermoelectric materials, and electrochemical processes across solid-liquid interfaces for water purification. Despite the latest advances in imaging and other experimental techniques, such as conducting sub-ten nanometer resolution coherent x-ray diffractive imaging (CXDI) and obtaining time-dependent lattice dynamics measurements in nanomaterials, it is still challenging to design experiments to characterize local environments near nanoscale surface features. Here, MD offers a powerful tool to capture the local reaction kinetics and other physical properties (temperature, pressure, etc.) of localized nanoscale environments. In this presentation, I will focus on how theoretical modeling can be used to decode the underlying mechanisms behind several ultrafast and/or nanoscale-localized processes to complement the observations from experimental imaging techniques. The first part of the talk will be on a joint theoretical-experimental study of multi-electron transfer processes in the context of gold nanocatalysis. The second part of the talk will be on ultrafast vapor nanobubble cavitation around intensely heated nanoparticles along with other examples where MD simulations can complement imaging.

June 29, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Computational Imaging and Illumination for 3D Acquisition: Research at the NU Comp Photo Lab"
Oliver Cossairt
Department of Electrical Engineering and Computer Science
Northwestern University

Abstract: Computational imaging and illumination plays a central role in many modern three-dimensional imaging techniques. In this talk, I will provide an overview of several 3D imaging technologies pioneered by the NU Comp Photo Lab, highlighting 3 main research projects. First, I will introduce a novel structured light technique called Motion Contrast 3D scanning (MC3D) that maximizes bandwidth and light source power to avoid performance trade-offs in structured light 3D acquisition. The technique allows 3D laser scanning resolution with single-shot speed, even in the presence of strong ambient illumination, significant inter-reflections, and highly reflective surfaces. Next, I will present research on Incoherent Holography, which enables 3D digital refocusing by engineering the camera's Point Spread Function (PSF). The technique can be used to capture a hologram without illuminating the scene with a coherent laser, making it possible to acquire holograms even for passively illuminated scenes. Finally, I will introduce our work using photometric stereo to measure the surface shape of several of Paul Gauguin's prints and drawings housed at the Art Institute of Chicago. In this work we characterize surface topology to better understand the artists production methods, helping to resolve longstanding art historical questions about the evolution of Gauguin's printing techniques. 

June 1, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Small Worlds"
Mark Hereld
Mathematics and Computer Science Division
Argonne National Laboratory

Abstract: An interdisciplinary team of scientists at Argonne, The University of Chicago, and Northwestern University is developing a new multi-modal imaging capability for studying complex multi-agent processes in cells and systems of cells. It is composed of integrated hardware, software, and molecular-scale reporters that will enable the study of systems biology problems involving many parts and spanning spatial scales from the nanometer to the millimeter and temporal scales from subseconds to days.  A novel 3D snapshot interferometric holographic microscope (3D-SIHM) is being developed to enable microscopy of dynamic living systems with nanoscale resolution at 25 frames per second. Scanning x-ray fluorescence (XRF) imaging will provide allows sub-micron scale measurements of intact complex systems in their native environment, even if that environment is opaque to visible light. And correlative electron-optical imaging will allow ultra-resolution imaging of whole organisms by transmission electron microscopy (TEM) and 3D spatial correlation with optical imaging from 3D-SIHM. This contingent of capabilities will enable construction of dynamic experiments that can track and correlate interrelated molecular actors in complex processes, while providing detailed corroboration and supplementary data across physical scales with qualitatively different imaging modalities.

May 18, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"New Developments for In-situ Electron Microscopy"
Adam Kammers
Hummingbird Scientfiic

Abstract: Hummingbird Scientific is developing methods for environmental microscopy using cross-correlative microscopy platforms (TEM, SEM, X-Ray, and Optical). Environmental cells (gas, liquid and vapor) allow control of pressure, temperature, and electrical bias. Application examples include corrosion, catalysis and electrochemistry. We will show some examples of work done both commercially and under currently DOE BES grants.

May 4, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Trace: A Middleware for Parallel and Distributed Reconstruction of Tomographic Datasets on High-End Computing Systems"
Tekin Bicer
Mathematics and Computer Science Division
Argonne National Laboratory

Abstract: New technological advancements in scientific instruments, such as detectors and light sources, enable scientists to design complex experimental setups and perform rapid data acquisition. However, analysis of this collected data is a challenging task. First, the implementation of data analysis/reconstruction code is not a trivial process. Second, analysis of the collected data is a highly compute-intensive operation and requires efficient utilization of high-end computing systems. In this work, we propose a high performance reduction-based computing middleware that eases the implementation of parallel image reconstruction and analysis algorithms. The proposed middleware provides an API where different (iterative) algorithms can be plugged-in. We have evaluated our middleware on Mira using different datasets and tomographic reconstruction algorithms. Our experimental results show that the proposed middleware is highly scalable and introduces low overhead to the execution, which enable near-real time data processing and analysis.

April 20, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Atomic-scale Imaging of Optically-Active Nanoscale Systems"
Jeff Guest
Center for Nanoscale Materials
Argonne National Laboratory

Abstract: Optical interactions and photophysical processes hinge on structure and the local environment in nanoscale systems, it is critically important to develop experimental approaches that can characterize these optical properties and correlate them with atomic-scale morphology and electronic structure. Over the past three decades, ultra-high vacuum (UHV) scanning tunneling microscopy/spectroscopy (STM/STS) and associated surface preparation techniques have demonstrated atomic-scale control over nanoscale structures, while single-particle laser spectroscopy has elucidated photophysics, quantum coherence, plasmonic and even opto-magnetic properties on ultrafast time scales and with ultrahigh spectral resolution at the single quantum absorber and emitter level. In this talk, I will describe my early work to address some of these challenges with low temperature near-field microscopy and spectroscopy, and our more ambitious recent efforts to extend these studies to the atomic scale on surfaces by combining UHV STM and single-particle laser spectroscopy. After introducing UHV STM/STS and some representative experiments, I will focus on our work exploring the structure, electronic, and transport properties of donor-acceptor molecular heterojunctions (HJs) self-assembled from C60 and pentacene. Using UHV STM/STS, have resolved a surprising structure and charge transfer in in-plane molecular HJs, and extremely strong (and spatially dependent) rectification in transport for a stacked molecular HJ at the monolayer level.

April 6, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Optical Nano-Imaging of Graphene and Beyond"
Zhe Fei
Center for Nanoscale Materials
Argonne National Laboratory

Abstract: Graphene plasmons, which are collective excitations of Dirac fermions in graphene, are of broad interests in both fundamental research and technological applications. In this talk, I will present the first nano-imaging studies of graphene plasmons using the scanning near-field optical microscopy — a unique technique allowing efficient excitation and high-resolution imaging of graphene plasmons. With this technique, we were able to show that common graphene/SiO2/Si back-gated structures support propagating surface plasmons in the infrared frequencies. The observed plasmons are highly confined surface modes with a wavelength around 200 nm that are conveniently tunable by the back gate voltages [Nano Lett. 11(11), 4701-4705 (2011); Nature 487, 82–85 (2012)]. In addition, we were able to map and characterize grain boundaries inside CVD graphene film by examining the distinct plasmonic interference patterns triggered by these line defects. Our modeling and analysis unveiled unique electronic properties associated with graphene grain boundaries [Nature Nano. 8, 821–825 (2013)]. Furthermore, we investigated graphene nanobubbles created at the graphene/hBN interface. We found that these nanobubbles are ideal for trapping electromagnetic energy by forming plasmonic hotspots with sub-hundred-nanometer spatial confinement and strong field enhancement. Finally, I will show you our recent nano-imaging results of other interesting surface modes in two-dimensional materials beyond graphene.

March 23, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Visualization-driven Materials Science and Engineering for Information and Energy Applications"
Seungbum Hong
Materials Science Division
Argonne National Laboratory

Abstract: During the Renaissance, European scholars developed a clear, concise, and consistent scientific method in which both observation and reason were employed to test more rigorously the theories of universe. Nowadays, with the advancement of microscopy and theory/modeling tools, materials scientists are able to characterize, observe, and validate the behavior of materials under various stimuli and environment, and propose the guideline of materials design for information and energy applications. Here I will present three such examples where I collaborated with various scientist and engineers to tackle important problems in oxide and polymer materials for information and energy applications.

February 23, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room D-172

*Note room change for this seminar only*

"High-Resolution Transmission Electron Microscopy of Advanced Materials with the Correction of Both Spherical- and Chromatic-aberration"
J.G. Wen
Electron Microscopy Center-Center for Nanoscale Materials
Argonne National Laboratory

Abstract: Recent development of correction of both spherical aberration (Cs) and chromatic aberration (Cc) offers a new opportunity to improve imaging capability for various energy-loss regimes. At zero energy-loss regime for conventional high-resolution transmission electron microscopy (HRTEM), amplitude contrast imaging in HRTEM is achieved. The new imaging approach allows us to obtain elemental information in addition to structural information. For low or high energy-loss regimes, we have successfully obtained energy-filtered HRTEM up to 400 eV energy-loss when Cc is corrected. With these newly developed techniques, I will show some examples using aberration-corrected TEM for characterizing advanced materials such as surface layers of catalyst supports, interface structures of ferroelectric superlattice.

February 09, 2015
4:00 p.m.
Bldg. 241 (ESB)
Room C-201

"Synchrotron X-Ray Scanning Tunneling Microscopy: Elemental Fingerprinting of Materials with Sensitivity at the Atomic Limit"
Nozomi Shirato
X-Ray Science Division
Argonne National Laboratory

Abstract: The direct observation of the chemical composition and magnetic properties of nanoscale materials with high spatial resolution has been a long-standing goal. Scanning tunneling microscopy (STM) provides atomic resolution but fails to provide chemical sensitivity in complex situations. X-rays, however, provide that chemical sensitivity. In this talk, we will discuss the development of a novel high-resolution technique, also known as synchrotron X-ray scanning tunneling microscopy (SX-STM). It combines the subnanometer spatial resolution of STM with the chemical, electronic, and magnetic sensitivity of synchrotron X-rays.

Drawing upon experience from a prototype that has been developed at the Advanced Photon Source to demonstrate general feasibility, current work has the goal to drastically increase the spatial resolution of existing state-of-the-art X-ray microscopy from only tens of nanometers down to atomic resolution. By using synchrotron X-rays as a probe and a nanofabricated smart tip of a tunneling microscope as a detector, we have recently achieved elemental fingerprinting of individual nickel clusters on a Cu(111) surface at 2-nm lateral resolution and at the ultimate single-atomic height sensitivity. Moreover, by varying the photon energy, we have succeeded in locally measuring photoionization cross sections of just a single nickel nanocluster, which opens new exciting opportunities for chemical imaging of nanoscale materials.

The availability of direct chemical contrast in STM at the ultimate atomic limit is expected to find applications in nanoscience, material science, and chemistry.

January 29, 2015
10:00 a.m.
Bldg. 241 (ESB)
Room C-201

"Strain Imaging of Nanoscale Semiconductor Heterostructures with X-ray Bragg projection Ptychography"
Martin Holt
Center for Nanoscale Materials
Argonne National Laboratory

Abstract: We report the imaging of nanoscale strain distributions in complementary components of lithographically engineered epitaxial thin film semiconductor channel heterostructures using synchrotron x-ray Bragg Projection Ptychography (BPP). A new phase analysis technique applied to the reconstructed BPP phase images from two laterally adjacent, stressed materials produced lattice strain and lattice rotation maps with a spatial resolution of ~15 nm, a strain sensitivity of better than 0.01%, and an angular resolution of ~0.1mrad.

Bragg projection ptychography is a coherent diffraction X-ray imaging technique capable of mapping structural perturbation, such as strain, in single crystal thin films with nanoscale spatial resolution. In this study, analysis of the orthogonal derivatives of the reconstructed phase maps provides insight into two distinct lattice responses that quantitatively agree with linear elastic predictions. This demonstrates that Bragg ptychography can be used to quantitatively visualize extremely subtle lattice perturbations at the nanoscale under realistic conditions without sectioning or otherwise modifying the boundary conditions of the sample

   

January 15, 2015
10:00 a.m.
Bldg. 241 (ESB)
Room C-201

"Imaging Complex Materials Using Diffraction Tomography"
Jonathan Almer
X-Ray Science Division
Argonne National Laboratory

Abstract: The diffraction tomography technique will be presented and compared/contrasted with related X-ray techniques of absorption-based tomography and high-energy diffraction microscopy (HEDM). Diffraction tomography has been developed at a few synchrotrons worldwide over the past decade, including 1-ID at the Advanced Photon Source. It uses high-energy X-rays along with fast large-area detectors. Diffraction tomography provides a new tool for microstructural mapping, particularly for very fine-grained materials below the resolution of HEDM. Selected applications are presented, including crack-tip mapping in metals and compositional mapping in biomaterials.