California NanoSystems Institute
CNSI
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May 31, 2011

Giovanni Vignale
Curators' Professor of Physics
Theoretical Condensed Matter Physics Research Group
University of Missouri-Columbia
Electric Control of Spin Currents and Spin-Wave Logic
There has been in recent years a tremendous growth of interest in the so-called spin-wave spintronics, in which spin waves - collective excitations of a magnetized material - are used in alternative to individual spin-polarized electrons to perform logical functions. The great appeal of the idea arises mainly from the fact that spin waves in insulating magnets can transport spin currents with extremely low energy dissipation. In this context, an interesting scheme of "spin-wave logic", in which logical operation are implemented at room temperature and GHz frequencies via constructive or destructive interference of spin waves, has been proposed and implemented by several experimental groups. [M.P. Kostylev et al., App. Phys. Lett., 153501 (2005)] The essential element of any spin wave logic device is a spin-wave phase shifter. Phase shift can be achieved by a magnetic field (which changes the wave vector of the wave at given frequency), by a magnetic domain wall, or, more generally, by passing the spin wave through a non-uniform magnetic texture. In our work we introduce a new mechanism, in which the phase of spin waves is controlled by an electric field, via the spin-orbit coupling of this electric field to the electrons that mediate the magnetic interaction. We refer to this new mechanism as magneto-electric control of spin waves. Our microscopic calculations, based on the super-exchange model of magnetism, indicate that the magneto-electric effect is sufficiently large to be used to effectively control spin currents. We apply these findings to the design of a novel spin-wave interferometric device, which works on a topological interference mechanism, analogous to the Aharonov-Casher effect for spin-carrying particles. This device can be used as a building block for room-temperature, low-dissipation logic circuits.

Bio: Giovanni Vignale is Curators' Professor of Physics at the University of Missouri-Columbia. After graduating from the Scuola Normale Superiore in Pisa in 1979 and gaining his PhD at Northwestern University in 1984, he worked as a postdoc at the Max-Planck-Institute for Solid State Research in Stuttgart, Germany and at Oak Ridge National Laboratory in Oak Ridge, Tennessee. He joined the Physics Department at the University of Missouri in 1988 and was elected Fellow of the American Physical Society in 1997. He has been a visiting scientist at the International Centre for Theoretical Physics in Trieste and at the Scuola Normale Superiore in Pisa; a member of the Kavli Institute for Theoretical Physics in Santa Barbara, California, an Ikerbasque Fellow at the European Theoretical Spectroscopy Facility in San Sebastian, Spain, and a Visiting Professor at the Institute for Solid State Physics of the University of Tokyo. Giovanni Vignale's main areas of research are many-body theory and density functional theory of electronic materials and devices.

He is author of two books "Quantum Theory of the Electron Liquid" (Cambridge University Press, 2005) and, "The Beautiful Invisible - Imagination, Creativity and Theoretical Physics" (Oxford University Press, 2011), and is working on a third one "Physics of Electronic Devices" (Cambridge University Press). For further information on research activities see http://web.missouri.edu/~vignaleg/.

May 17, 2011

Paula T. Hammond
Bayer Professor and Executive Officer
Department of Chemical Engineering
Koch Institute for Integrative Cancer Research
Massachusetts Institute of Technology
Associate Editor, ACS Nano

Streaming Video
Building Materials Nanolayer by Nanolayer: From Batteries to Implantable Pharmacies
The alternating adsorption of oppositely charged molecular species, known as the electrostatic layer-by-layer (LbL) process, is a simple and elegant method of constructing highly tailored ultrathin polymer and organic-inorganic composite thin films. We use this method to manipulate transport and function in thin films, enabling the generation of a range of organic and organic-inorganic devices. Several approaches to the controlled manipulation, construction and, in some cases, the controlled deconstruction, degradation or dissolution of multilayers upon specific stimulus will be discussed. A modified form of the automated alternate misting approach is also useful for the incorporation of materials systems and the generation of complex thin film morphologies and architectures. New developments in the rapid assembly of these systems with nanoscale objects such as carbon nanotubes and functionalized nanoparticles, and their practical applications from biomedical implants and modular release vaccine systems to electrochemical energy devices will be addressed. Finally, new advances in the use of LbL to generate smart nanoparticle systems for targeting cancer will be described.

Bio: Professor Paula T. Hammond is the Bayer Chair Professor of Chemical Engineering at the Massachusetts Institute of Technology, and is currently serving as its Executive Officer. She is also a member of MIT's Koch Institute for Integrative Cancer Research, and is a founding member of the MIT Institute for Soldier Nanotechnology. Paula Hammond earned her S.B. in Chemical Engineering from the Massachusetts Institute of Technology in 1984, her M.S. degree from Georgia Institute of Technology in 1988, and her Ph.D. in Chemical Engineering in 1993 from the Massachusetts Institute of Technology. From 1993 to 1995, she held the NSF Postdoctoral Fellowship in Chemistry while working at Harvard University's Chemistry Department.

Her work encompasses two major areas: the development of new biomaterials via nano to microscale fabrication using directed and self-assembly of polymers, including drug delivery thin films with temporal control and novel polymer architectures for targeted nanoparticle drug and gene delivery; and self-assembled materials systems for electrochemical energy devices, including fuel cells, batteries and photovoltaics. Professor Hammond was awarded the NSF Career Award, the EPA Early Career Award, the DuPont Young Faculty Award, and the Junior Bose Faculty Award at MIT. Recently her work in nanomaterials has been recognized and featured in several venues, including the journal Nature, the "Top 100 Science Stories of 2008" in Discover Magazine, the Popular Mechanics Breakthrough Award in 2006, The Economist, Forbes Magazine and Technology Review. Professor Hammond is an Associate Editor for the journal ACS Nano, and serves on the Advisory Board of several additional journals. Other honors include Caltech Kavli Distinguished Lecturer, Radcliffe Fellow at Harvard University, Georgia Tech Outstanding Young Alumni Award, the Lloyd Ferguson Award for Outstanding Young Scientist, and Fellow of the American Physical Society.

May 10, 2011

Dean Ho
Biomedical and Mechanical Engineering
Robert H. Lurie Comprehensive Cancer Center
Northwestern University

Streaming Video
Nanodiamond-Based Therapeutic Delivery Agents for Cancer Therapy
Nanodiamond (ND) surface properties mediate a spectrum of clinically-relevant improvements to drug delivery such as enhanced cancer treatment efficacy and safety. NDs can also be functionalized with a broad array of therapeutics which includes small molecules, proteins, antibodies, and DNA/siRNA for applications in cancer treatment, cardiovascular medicine, wound healing, and beyond. In addition, NDs possess uniform dimensions (~2-8 nm in diameter per particle) and material stability that are coupled with observed biocompatibility in vitro and in vivo. Furthermore, NDs can be batch purified and functionalized for scalable and high yield processing. Among other functional groups, NDs also possess an abundance of surface-bound carboxyl groups which are conducive towards facile, application-dependent molecular linking/conjugation onto the diamond surface. Furthermore, NDs can be functionalized with additional chemical species to enable direct drug conjugation. Our previous studies have confirmed robust drug binding to NDs through transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) coupled with in vitro tracking of cellular internalization and quantitative demonstration of bio-amenable cell response through quantitative real time polymerase chain reaction (RT-PCR) assays of inflammatory and apoptosis-regulating gene expression programs. Towards the broadening of ND applicability in clinically-significant treatment scenarios, recent work pertaining to the in vivo validation of ND-based treatment of drug-resistant tumors as well as implantable/localized wound healing will be discussed.

Bio: Dr. Dean Ho is currently an Associate Professor in the Departments of Biomedical Engineering and Mechanical Engineering in the Robert R. McCormick School of Engineering and Applied Science, and member of the Robert H. Lurie Comprehensive Cancer Center of Northwestern University where he directs the Laboratory for Nanoscale Biotic-Abiotic Systems Engineering (N-BASE). Dr. Ho is investigating the fabrication of nanodiamond-based technologies for drug delivery as well as localized and targeted chemotherapy using novel nanomaterial devices.

Dr. Ho's research has garnered news coverage on the CNN and NPR homepages, Reuters, Yahoo, and The Chicago Tribune, among other international news outlets. Dr. Ho has also appeared on the National Geographic Channel program 'Known Universe' which aired domestically and internationally. Dr. Ho is currently Editor-in-Chief of the Journal of the Association for Laboratory Automation, and serves on the Editorial Boards of Nanomedicine: Nanotechnology, Biology and Medicine, the Journal of Biomedical Nanotechnology, and Journal of Nanotechnology Law and Business. He is a recipient of the National Science Foundation CAREER Award, Wallace H. Coulter Foundation Early Career Award for Translational Research, Phase 2 Coulter Translational Research Award, and V Foundation for Cancer Research V Scholars Award. In addition, Dr. Ho was a recipient of the John G. Bollinger Outstanding Young Manufacturing Engineer Award of the Society of Manufacturing Engineers, attendee of the National Academy of Engineering Frontiers of Engineering Symposium, and received the Distinguished Young Alumnus Award from the UCLA School of Engineering and Applied Science.

May 03, 2011

Takhee Lee
Engineering
Molecular Nanoelectronics Lab
Gwangju Institute of Science and Technology, Korea

Streaming Video
Molecular Transistors and Organic Memory Devices
Field-effect transistors (FETs) rely on the gated electrostatic modulation of the channel charge by changing the relative position of the conduction and valance bands with respect to the electrodes. In molecular-scale devices, a longstanding challenge has been the ability to create a true three-terminal device that operates in this manner. In this talk, I will demonstrate a direct electrostatic modulation of orbitals in a molecular transistor configuration, with both effective gate control and enhanced resonant coupling of the orbitals to the source and drain electrodes. Individual molecules are connected to source and drain electrodes with a bottom-gate control electrode in a FET configuration. We have examined two prototype molecules: the control, octanedithiol with an alkyl σ-backbone as a saturated aliphatic molecule, and the active device, benzenedithiol with a delocalized π-electron aromatic ring as a conjugated molecule. We observed the transport barrier for molecular transistors shifted to a lower bias as a more negative VG is applied, indicating that the molecular transistors behave as a p-type-like tunneling devices. Inelastic electron tunneling spectroscopy was also performed, to verify the identity of the molecules in the junction, and to determine the amount of orbital coupling.

In the second part of the talk, our recent research on the organic non-volatile memories will be briefly discussed. I will puts special focus on important strategies to realize more practical memory devices in terms of memory performance enhancement, high density integration, and advanced architectural concepts. And, if time is allowed, I will also briefly discuss other research results on nanoscale logic circuits and graphene-electrode optoelectronic devices.



Figure. (Left) SEM images and schematic of a molecular transistor. (Right) Cross-sectional TEM image and schematic of three-dimensionally stacked organic resistive memory devices.

Bio: Dr. Takhee Lee received his B.S., M.S. and Ph.D. degrees in physics from Seoul National University, Korea, and Purdue University in 1992, 1994, and 2000, respectively. After working as a postdoctoral fellow with Prof. Mark Reed at Yale University from 2000 to 2004, he became an assistant professor in Materials Science and Engineering at Gwangju Institute of Science and Technology (GIST), Korea, and he has been a professor since 2010. His research interests include molecular and organic electronics (molecular transistors, memories, etc.), nanowire and graphene based electronics. Dr. Lee has published more than 130 scientific articles, 8 book chapters, 6 review articles, and has won Nano-Korea Researcher Award (2007), Minister of Education, Science and Technology Award (2008, 2010), Prime Minister Award (2010), and Scientist of the Month Award (2010) of Korea.

April 12, 2011

Xiangfeng Duan
Chemistry and Biochemistry
Duan Group, Hetero-integrated Nanostructures and Nanodevices
University of California, Los Angeles

Streaming Video
Rational Design and Nanoscale Integration of Multifunctional Nanostructures
Our research focuses on the rational design and nanoscale integration of highly complex inorganic nanostructures through chemical synthesis and/or physical assembly. A strong emphasis is placed on the hetero-integration of multi-composition, multi-structure and multi-function at nanoscale, with an aim to create a new generation of integrated nanosystems with unique functions or unprecedented performances that can break the boundaries of traditional technologies. In this seminar, I will discuss two recent examples. In a first example, I will discuss our ongoing effort in using chemical synthesis to hetero-integrate a nanoscale photovoltaic device with two redox catalysts in a single nanostructure to form a freestanding photoelectrochemical nanodevice. Our studies shows that such freestanding photoelectrochemical nanodevices can be used as highly efficient photocatalysts to harness solar energy and make use of photogenerated carriers on site to drive both thermodynamically downhill and uphill reactions, which may lead to exciting opportunities in artificial photosynthesis and solar fuel production. In a second example, I will briefly describe our recent effort in using a physical assembly approach to integrate graphene with a self-aligned nanowire gate to enable graphene transistors with unprecedented speed.

BIO: Dr. Duan is an Assistant Professor at UCLA. He received the B.S degree in chemistry from University of Science and Technology and China in 1997; M.A. degree in chemistry and Ph.D. degree in physical chemistry from Harvard University in 1999 and 2002, respectively. From 2002 to 2008, he was a Founding Scientist, Principal Scientist and Manager of Advanced Technology at Nanosys Inc., a nanotechnology startup founded based partly on his doctoral research. In 2008, he joined Department of Chemistry and Biochemistry, University of California, Los Angeles. Dr. Duan's research focuses on fundamental studies of functional nanostructures and nanodevices, and the exploration of their potential for future electronics, energy science and biomedical science. Dr. Duan has published over 50 technical papers in leading scientific journals, and holds more than 50 patents or patent applications.
April 05, 2011

Mark C. Hersam
Materials Science and Engineering
Northwestern University

Streaming Video
Chemically functionalized carbon nanomaterials
Carbon nanomaterials have attracted significant attention due to their potential to improve applications such as transistors, transparent conductors, solar cells, batteries, and biosensors. This talk will highlight our latest efforts to develop strategies for purifying, functionalizing, and assembling carbon nanomaterials into functional devices. For example, we have recently developed and commercialized a scalable technique for sorting surfactant-encapsulated single-walled carbon nanotubes (SWCNTs) by their physical and electronic structure using density gradient ultracentrifugation (DGU). The resulting monodisperse SWCNTs enhance the performance of thin film transistors, infrared optoelectronic devices, and transparent conductors. The DGU technique also enables multi-walled carbon nanotubes to be sorted by the number of walls, and solution phase graphene to be sorted by thickness, thus expanding the suite of monodisperse carbon nanomaterials. By extending our DGU efforts to carbon nanotubes and graphene dispersed in biocompatible polymers (e.g., DNA, Pluronics, Tetronics, etc.), new opportunities have emerged for monodisperse carbon nanomaterials in biomedical applications.

In addition to these solution-phase approaches, this talk will also discuss vacuum compatible methods for functionalizing the surfaces of carbon nanomaterials. For example, a suite of perylene-based molecules form highly ordered self-assembled monolayers (SAMs) on graphene via gas-phase deposition in ultra-high vacuum. Due to their noncovalent bonding, these SAMs preserve the superlative electronic properties of the underlying graphene while providing uniform and tailorable chemical functionality. In this manner, disparate materials (e.g., high-k gate dielectrics) can be seamlessly integrated with graphene, thus enabling the fabrication of capacitors, transistors, and related electronic/excitonic devices. Alternatively, via aryl diazaonium chemistry, functional polymers can be covalently grafted to graphene. In addition to presenting opportunities for graphene-based chemical and biological sensing, covalent grafting allows local tuning of the electronic properties of the underlying graphene.