News & Events

News & Events

Jul, 2016 - Sep, 2016

Speaker: Sasha Chernyshev
Affiliation: University of California--Irvine, USA
Abstract Details: I will discuss quantum order-by-disorder effect and will present an evidence that the non-linear terms in the anisotropic kagome-lattice antiferromagnets can yield a rare example of the ground state that is different from the one favored by thermal fluctuations. The corresponding order selection will be shown to be generated by the topologically non-trivial tunneling processes, yielding a new energy scale in the system. I will also discuss the effect of the non-linear terms in the spectra of the kagome-lattice systems and will provide an analysis of the spectral properties of realistic kagome-lattice antiferromagnets such as Fe-jarosite, for which a remarkable wipe-out effect for a significant portion of the spectrum should exist due to a resonant-like decay processes involving two flat modes. Recent result concerning the spectrum of the kagome-lattice ferromagnets will also be presented."
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Speaker: Dan Zhao
Affiliation: Department of Chemical and Biomolecular Engineering, NUS)
Abstract Details: The large-scale anthropogenic carbon dioxide (CO2) emission has aroused world-wild concerns nowadays. One of the key steps in carbon mitigation is CO2 capture from stationary CO2 emission sources such as power plants. Membrane-based gas separation has been greatly developed in recent years. In order to combine the merits of both polymeric and inorganic membranes, mixed matrix membranes (MMMs) were invented by dispersing porous fillers into continuous polymeric matrices hoping to increase the permeability and selectivity of the resultant membranes while preserving the properties of good mechanical strength and processability of the polymeric matrices. In this presentation, I will introduce our work in preparing MMMs containing lamellar metal-organic frameworks (MOFs) or covalent organic frameworks (COFs) nanosheets with high-aspect-ratio, which exhibit good gas separation performance because of the increased tortuosity of gas permeation paths imposed by lamellar nanosheets. In addition, I will discuss the direct fabrication of ultrathin membranes composed of 2D graphene oxide (GO) or MOF nanosheets. Because of their ultra-small thickness and precisely tunable pore size and functionality, these novel membranes may demonstrate unprecedented gas separation performance with wide applications in clean energy and environmental sustainability.
About the Speaker: Dr. Dan Zhao obtained his BS (2003) and MS (2006) in Polymer Chemistry and Physics from Zhejiang University, and PhD (2010) in Inorganic Chemistry from Texas A&M University. After finishing his postdoctoral training at Argonne National Laboratory, he joined the Department of Chemical & Biomolecular Engineering at National University of Singapore in July 2012 as an Assistant Professor. His research interests include advanced porous materials and membranes with the applications in clean energy and environmental sustainability.
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Speaker: Koji Hara
Affiliation: FUK Co.,LTD.
Abstract Details: Lamination technology is a manufacturing technology expected to expand in accordance with the rapid growth of the touch panel market. Making best use of their technologies, Flexible device manufacturers are enthusiastically developing higher-definition, thinner and more durable products to avoid commoditization of their products and boost their share. To manufacture in mass production, bonding automation is very important for cost, speed and stability. FUK provides innovative Lamination machinery that can digitize Lamination profiles with its numerically controlled process, which was difficult for traditional air-activating systems. This presentation introduces core technologies relating to Roll to Sheet auto machine, 3D lamination and Flexible OLED process, the trend of flexible device manufacturing process including cleansing of touch sensors, and the latest technologies in this field.
About the Speaker: Koji Hara is the General manager of Planning and Market Div. and President of FUK Taiwan Co.,LTD. He joined FUK Corporation in Feb 2010 after leaving a trade company specialized in materials of touch panels and liquid crystal display panels. In FUK, belonging to a market development department, the presenter has been engaged in market research of cutting-edge technology of processing displays such as LCD, touch panels and 3D displays while proposing optical processes or materials that can meet users' needs.
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Speaker: Xie Han
Abstract Details: Graphene has shown the ability in inducing osteogenic differentiation of stem cells. However, the cellular mechanisms involved in this process remain unexplored. Our studies are investigating the biological function of graphene and its derivatives (2D graphene-2DGp, 3D graphene-3DGp and graphene oxide-GO) during their osteogenic and odontogenic differentiation in dental stem cells. All the graphene substrates supported cell attachment and proliferation, and induced osteogenic differentiation of both periodontal stem cells (PDLSC) and dental pulp stem cells (DPSC) into mature osteoblasts with a higher level as compared with glass slide (GL) and polystyrene scaffold (PS). Bone-related genes and proteins (COL I, RUNX2 and OCN) were upregulated regardless the use of osteogenic medium. Remarkably, GO enhanced odontogenic differentiation as well by upregualting dentin-related genes (MSX-1, PAX-9, DMP-1), which was not observed from 2DGp. Meanwhile, stiffness sensitive genes MHY10 and MHY10-V2 were evaluated, and those higher expressions on 2D and 3D graphene suggest that both chemical and physical properties of graphene act synergistically while ruling osteoblastic differentiation of stem cells. These findings broaden the use of graphene substrates in combination with dental materials to improve their bioactivity and beyond."
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Speaker: So Takei
Affiliation: Queens College of the City University of New York, USA
Abstract Details: The ground state of neutral monolayer graphene in a strong perpendicular magnetic field is believed to be the so-called canted antiferromagnetic $ u=0$ quantum Hall state. This state is an insulator for charge transport, but it should behave like a superfluid for transport of the spin component parallel to the magnetic field. Here, we have proposed an experiment to demonstrate this effect.
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Speaker: Dr. Ahmet Avsar
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Speaker: Chris Pakes
Affiliation: La Trobe University, Australia
Abstract Details: When hydrogenated diamond surfaces are exposed to air, electrons are transferred from the diamond into an absorbed water layer resulting in a sub-surface hole accumulation layer and high p-type surface conductivity. This allows hole sheet densities as high as 7 x 1013 cm-2 to be achieved and has led to interest for chemical and biological sensor applications and the development of high-power field effect transistors. Many experiments have reported an exponential decrease in the sheet conductivity as the temperature is reduced, driven by carrier freeze-out, which prohibits the exploration of the electronic behaviour of the system at low temperature. However, we shall show that surface transfer doping of H-terminated diamond occurs with no activation energy so a high sheet conductivity can be maintained at low temperature in low disorder samples consistent with metallic conduction in a conventional two-dimensional Fermi liquid, permitting exploration of extended states in the predicted 2D hole band. Magnetotransport measurements have revealed the presence of quantum corrections in the Drude conductivity arising from phase coherent backscattering in the form of weak localisation and weak anti-localisation, the latter arising from a strong spin-orbit interaction at the diamond surface. By gating the surface-conducting layer, the sheet conductivity may be tuned from insulating to metallic conduction, with a concurrent modulation in the hole sheet density. Through an analysis of the evolution of the phase coherent backscattering effects as the hole sheet density is modulated, we show that the spin-orbit splitting can be engineered from 4.6 – 24.5 meV using an electrostatic gate. We shall discuss the potential to realise devices using H-terminated diamond in which spin coherent transport can be studied.
About the Speaker: Chris Pakes received his Ph.D. from the University of Birmingham (UK) in 1999. He held positions at the National Physical Laboratory (UK) and The University of Melbourne before joining La Trobe University in 2007. He has served as Associate Dean (Research) in the Faculty of Science, Technology and Engineering and in 2014 was appointed inaugural Dean of the La Trobe Graduate Research School. Chris leads La Trobe’s Atom-scale Research Laboratory, using a combination of ultra-high vacuum scanning probe microscopy, synchrotron-based photoemission and low-temperature transport to explore the functionalisation of technologically interesting materials such as diamond, graphene, silicon and organic semiconductors via the chemical modification of the surface and surface transfer doping. His group has a strong focus on the functionalisation of diamond surfaces at the atomic-scale to engineer two-dimensional devices for quantum electronics and spintronics.
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Speaker: Prof. Mark C. Hersam
Abstract Details: Two-dimensional materials have emerged as promising candidates for next-generation electronic and optoelectronic applications. As is common for new materials, much of the early work has focused on measuring and optimizing intrinsic properties on small samples (e.g., micromechanically exfoliated flakes) under idealized conditions (e.g., vacuum and/or cryogenic temperature environments). However, real-world devices and systems inevitably require large-area samples that are integrated with dielectrics, contacts, and other semiconductors at standard temperature and pressure conditions. These requirements are particularly challenging to realize for two-dimensional materials since their properties are highly sensitive to surface chemistry, defects, and the surrounding environment. This talk will thus explore methods for improving the uniformity of solution-processed two-dimensional materials with an eye toward realizing scalable processing of large-area thin-films. For example, density gradient ultracentrifugation allows the solution-based isolation of transition metal dichalcogenides (e.g., MoS2, WS2, MoSe2, and WSe2) and boron nitride with homogeneous thickness down to the single-layer level. Similarly, two-dimensional black phosphorus is isolated in solution with the resulting flakes showing field-effect transistor mobilities and on/off ratios that are comparable to micromechanically exfoliated flakes. In addition to solution processing, this talk will also report on the integration of two-dimensional materials with dielectrics and other semiconductors. In particular, atomic layer deposition of dielectrics on two-dimensional black phosphorus suppresses ambient degradation, thereby preserving electronic properties in field-effect transistors at atmospheric pressure conditions. Finally, gate-tunable p-n heterojunction diodes with Type I and Type II band alignments are demonstrated by integrating n-type single-layer MoS2 with p-type semiconducting single-walled carbon nanotubes and pentacene, respectively.
About the Speaker: Professional Biography of Mark C. Hersam Materials Science and Engineering, Northwestern University 2220 Campus Drive, Evanston, IL 60208-3108 USA Tel: 847-491-2696; Fax: 847-491-7820 E-mail: m-hersam@northwestern.edu WWW: http://www.hersam-group.northwestern.edu/ Mark C. Hersam is the Walter P. Murphy Professor of Materials Science and Engineering and Director of the Materials Research Center at Northwestern University. He also holds faculty appointments in the Departments of Chemistry, Applied Physics, Medicine, and Electrical Engineering and Computer Science. He earned a B.S. in Electrical Engineering from the University of Illinois at Urbana-Champaign (UIUC) in 1996, M.Phil. in Physics from the University of Cambridge in 1997, and a Ph.D. in Electrical Engineering from UIUC in 2000. His research interests include nanofabrication, scanning probe microscopy, semiconductor surfaces, and nanoelectronic materials. As a faculty member, Dr. Hersam has received several awards including the NSF CAREER Award, Beckman Young Investigator Award, ARO Young Investigator Award, ONR Young Investigator Award, Sloan Research Fellowship, Presidential Early Career Award for Scientists and Engineers, TMS Robert Lansing Hardy Award, AVS Peter Mark Award, MRS Outstanding Young Investigator Award, MacArthur Fellowship, and six Teacher of the Year Awards. Dr. Hersam is the co-founder of NanoIntegris, which is a commercial supplier of high performance nanoelectronic materials. Dr. Hersam is a Fellow of MRS, AVS, APS, AAAS, SPIE, and IEEE, and also serves as an Associate Editor of ACS Nano. Dr. Hersam is currently serving as a 2016 U.S. Science Envoy to help inform the White House, the Department of State, and the scientific community about potential opportunities for international scientific cooperation.
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Speaker: Claudia Draxl
Affiliation: Humboldt University of Berlin, Germany
Abstract Details: Ab initio spectroscopy is a powerful combination of quantum-based theories and computer simulations. It covers a wide range of theoretical and computational methods, which go beyond density-functional theory by incorporating many-body effects and interactions that show up in the excited state. This methodology not only allows for analyzing data obtained by experimental probes like photoemission, optical absorption, Raman, infrared, x-ray, and electron-loss spectroscopy, but also for shining light onto the underlying processes. These may be distinctively different depending on the nature and dimensionality of the material. In this talk, I will focus on core excitations, discussing different absorption edges in a variety of systems. These will cover carbon-based materials, ranging from graphene to self-assembled monolayers of molecular switches and inorganic semiconductors, ranging from nitrides to wide-gap oxides. Discuss their exciton binding strength and character, I will show how theory can get insight into the exciting phenomena behind the spectral features.
About the Speaker: Prof. Claudia Draxl is Professor at the Humboldt-Universität zu Berlin and Felllow of the Max Planck Society. Her research is dedicated to condensed-matter theory and computational materials science, spanning theorectical concepts, development of computer codes, as well their application to a variety of materials. Her team is developing exciting - an all-electron full-potential computer package implementing DFT, TDDFT, and many-body perturbation theory. A particular focus is theoretical spectroscopy - the quantum-based description of radiation-matter interaction. Actual research projects concern organic/inorganic hybrid structures, molecular switches on surfaces, thermoelectricity, semiconductor nanostructures, solar-cell materials, organic film-growth, and more.
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Speaker: Gianluca Fiori
Affiliation: University of Pisa, Italy
Abstract Details: In this talk, I will give the perspectives of two-dimensional materials technology, when exploited in realistic applications, ranging from electronic (both digital and Radio Frequency), optoelectronic, and energy applications. This will be done from an engineering point of view. To achieve this goal, I will extensively take advantage of multi-scale simulations, based on ab-initio calculations to extract the main physical parameter at the atomic level (bands, effective masses, Hamiltonians etc.), to be included at a higher level of abstraction to device simulators, and up to circuit level. Such an approach allows to i) provide design guidelines to the fabrication process, suggesting the most promising technological solutions, while discarding those, which clearly show poor performance even in the best case scenario; ii) understand physical effects observed in experiments.
About the Speaker: Gianluca Fiori is with the University of Pisa. His main field of research includes the development of models and codes for the simulation of CMOS transistors with ultra-short channel and innovative devices based on new architectures and new materials. To this purpose, he has developed numerical codes, also through repeated research visits (in 2004, 2005 and 2008) at the Network for Computational Nanotechnology, at Purdue University, (IN-USA). Part of these models have been included into the commercial device simulator ATLAS, within a collaboration, in Autumn 2002, with Silvaco International, one of the worldwide leading developers and vendors of Technology Computer Aided Design (TCAD) software dedicated to Process and Device Simulation. Dr. Fiori has released, under the BSD open-source license, the in-house developed code NanoTCAD ViDES (http://vides.nanotcad.com), which includes most of the physical models implemented during his research activity.
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