seminar abstracts
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The Center for Chemical Innovation / CaSTL presents: Dr. Harald Ibach Research Center Juelich, Institute of Bio- and Nanosystems Thursday, December 3, 2009 1:00 pm 2201 Natural Sciences II Title: The Metal/Electrolyte Interface - Electric Properties and Structure of Water at    Stepped Gold Surfaces Abstract: More than 170 years after the scientific foundation of electrochemistry by Faraday our understanding of the interface between solids and electrolytes is still rudimentary. While scanning tunneling microscopy has provided us with atomic level information on the in-situ structure of electrodes comparable information on the liquid side is lacking. For example, nearly all investigations concerning the solid/electrolyte interface begin with the characterization of the interface by voltammograms and measurements of the capacitance. Yet, there is still little understanding of these methods in terms of atomic level properties. Our recent experimental result of a dramatic reduction of the Helmholtz-capacitance of stepped gold and silver surfaces therefore came as a total surprise. My presentation discusses these results in the light of existing theoretical models for the structure of water and the electric properties of the interface and in connection with results on vibration spectra of water in the form of ice on stepped gold surfaces. The talk also includes a brief update on the structure and dynamics of metal surfaces in contact with an electrolyte where theory and experiment are in much better shape.   Host: Doug Mills

Chemistry Special Seminar and ISIS   Dr. Ulrich Rant Walter Schottky Institute, Technical University Munich Friday, November 20, 2009 2:00 pm 1201 Natural Sciences II Title: Electrically Switchable DNA Layers for the Label-free Detection and Sizing of Protein Targets on a Chip Abstract:  We introduce a chip-compatible scheme for the label-free detection of proteins in realtime that is based on the electrically driven conformation-switching of DNA oligonucleotides on metal surfaces. The switching behavior is a sensitive indicator for the specific recognition of IgG antibodies, antibody-fragments, and small proteins, which can be detected in quantities of less than 1 amol on the sensor surface. We show how the dynamics of the induced molecular motion can be monitored by measuring the high-frequency switching response as well as by time-resolved fluorescence measurements. When proteins bind to the layer, the increase in hydrodynamic drag slows the switching dynamics, which allows us to determine the size of the captured proteins. We demonstrate the identification of different antibody fragments and small proteins by means of their kinetic fingerprint. The switchDNA method represents a generic approach to simultaneously detect and size target molecules using a single analytical platform. Host:  Rob Corn and Zuzanna Siwy

The Center for Chemical Innovation / CaSTL presents: Shiwei Wu Molecular Foundry Lawrence Berkeley National Laboratory Thursday, October 15, 2009 1:00 pm 2201 Natural Sciences II Title: Optical Spectroscopy and Dynamics of Nanostructures Abstract: Optical microscopy incorporated with spectroscopy is a very powerful approach to study nanostructures. In this talk, I will present a few examples of our recent work in this direction. One is optical characterization of single rare-earth ion doped nanoparticles, which show strong near-infared to visible upconverted photoluminescence. The unique characteristics of these nanoparticles suggest that they could serve as ideal single-molecule probes for bio-imaging. Another is on graphene, a two-dimensional (2D) carbon material and the mother of 1D carbon nanotubes. The 2D confinement of carriers and phonons in graphene leads to many extraordinary electrical, thermal and mechanical properties, as well as optical and optoelectronic properties. I will show you some of our recent findings that include a bright, broadband nonlinear photoluminescence and ultrafast phonon dynamics in gated graphene. Finally, I will describe my recent endeavor in developing a near-field optical microscope that has the capability to study nanostructures towards the spatial and temporal limits.   Host: Wilson Ho

The Center for Chemical Innovation / CaSTL presents: Postdoc Candidate, Hongtao Chen Department of Chemistry Purdue University Thursday, June 4, 2009 1:00 pm 2201 Natural Sciences II Title: A multimodal nonlinear optical microscope and its applications Abstract: Multimodal nonlinear optical microscopy is a valuable tool to study complex biological samples. Here we present an easy-to-operate approach to perform coherent anti-Stokes Raman scattering (CARS), two-photon fluorescence (TPF), second harmonic generation (SHG), and third-harmonic generation (THG) imaging using a single laser source.  Furthermore, inherently nonresonant-background-free CARS is demonstrated by controlling the polarization of three collinearly combined laser beams. This platform allows vibrationally resonant CARS imaging of CH-rich tissues and lipid bodies in live cells, SHG imaging of collagen fibers, multiphoton fluorescence analysis and the four wave mixing (FWM) imaging of gold nanorods. The possible addition of the stimulated Raman scattering (SRS) imaging capability to this platform is also discussed.   Host: Eric Potma

The Center for Chemical Innovation / CaSTL presents: Postdoc Candidate, Hikari Kimura Department of Physics University of California, Berkeley Wednesday, May 27, 2009 1:00 pm 2201 Natural Sciences II Title: Scanning Josephson tunneling microscopy of single crystal Bi2Sr2CaCu2O8+δ from a conventional superconducting tip Abstract: Using a scanning tunneling microscope (STM) with a superconducting tip, STM-based Josephson junctions are implemented to directly probe both the quasiparticle spectrum and the phase of the superconducting condensate via the Josephson Effect. In this talk we present data from Josephson junctions formed between superconducting tips and Bi2Sr2CaCu2O8+δ single crystals. These results clearly show c-axis Josephson tunneling between a conventional superconductor and both overdoped and optimally doped Bi2Sr2CaCu2O8+δ. Josephson measurements at different surface locations yield local values for the Josephson ICRN product, indicating an inhomogeneous structure of the ICRN product in overdoped Bi2Sr2CaCu2O8+δ on a nanometer length scale. Corresponding energy gap measurements were also performed and a surprising inverse correlation was observed between the local ICRN product and the local energy gap. We also discuss Superconductor-Insulator transition in two dimensional disordered thin films which phase diagram shows a similarity to that of the high-Tc superconducting cuprates. Proposed study will be described. This work is supported by DOE Grant No. DE-FG02-05ER46194.   Host: Wilson Ho

The Institute for Surface and Interface Science (ISIS) presents: Dr. Enge G. Wang Institute of Physics Chinese Academy of Sciences Beijing, China Tuesday, March 17, 2009 4:00 pm 4112 Natural Sciences I Title: A step up to self-assembly Abstract: Pattern formation and decay in the early stage of growth is fundamental to many materials physics and chemistry. Understanding the complex interplay between factors that influence the evolution of surface-based nanostructures can be challenging and so computer simulation can play an important role in providing insight. In this talk, I will first introduce a one-, two-, and three-dimensional Ehrlich-Schwoebel (ES) barrier in kinetics-driven growth. Within this framework, I will show how to control the island shape, the island instability, and the film roughness efficiently. Furthermore, I will discuss a novel concept: a true upward adatom diffusion on metal surface, which is beyond the traditional Ehrlich-Schwoebel (ES) barrier model. This process offers new indications as how to use ab initio kinetic Monte Carlo simulation can uncover some of the building regulations of the evolution mechanism down to atomic-scale. Financial support from the NSF, MOST, and CAS of China. Host: Wilson Ho

Joint Condensed Matter / CaSTL Seminar    Dr. Jordan Gerton Department of Physics University of Utah March 4, 2009   4:00 pm 1201 Natural Sciences II Title: Exploring the Limits Apertureless Fluorescence Microscopy  Abstract: Tip-enhanced (apertureless) fluorescence microscopy (TEFM) is a technique that uses the sharp probe tip of an atomic force microscope to enhance the fluorescence signal from a laser-illuminated sample. The signal is enhanced only within several nanometers of the tip apex, which enables fluorescence images with resolution limited only by the tip sharpness. In previous work we showed that resolution as high as ~10 nm can be achieved using sharp silicon probes. The background fluorescence excited directly by the laser beam limits the image contrast for samples with large fluorophore density. However, this background signal can be suppressed by oscillating the AFM tip, thereby modulating the near-field signal, followed by demodulation using a lock-in amplifier. We have explored the limits on image contrast after demodulation and conclude that it should be possible to resolve single fluorophores within a dense molecular network with inter-fluorophore spacing of only ~10 nm. More recently we have begun to investigate carbon nanotube and metal tips, which suppress the local fluorescence signal, but which nonetheless can produce high-resolution images. Finally, we have developed a novel phase-sensitive photon counting technique that can be used to increase image contrast yet further, and which enables near-field tomographical measurements. Host: Phil Collins

The Institute for Surface and Interface Science (ISIS) presents: Michael Springborg Physical and Theoretical Chemistry University of Saarland February 9, 2009 4:00 pm 1114 Natural Sciences I Title: Theoretical Studies of Structural and Electronic Properties of Clusters   Abstract: Clusters contain more than just some few atoms but not so many that they can be considered infinite. By varying their size, their properties can often be varied in a more or less controllable way. Often, however, the precise relation between size and property is largely unknown: the sizes of the systems are below the thermodynamic limit. Theoretical studies of such systems can provide relevant information, although in many cases idealized systems have to be treated. The challenge of such calculations is the combination of the relatively large size of the systems together with an often unknown structure. In this presentation, different theoretical methods for circumventing these problems shall be discussed. They shall be illustrated through applications on various types of clusters. These include isolated metal clusters with one or two types of atoms, metal clusters deposited on a surface, nanostructured HAlO, and semiconductor nanoparticles. Host: Kieron Burke

Department of Chemical Engineering and Materials Science Co-sponsored by The Institute for Surface and Interface Science (ISIS) Dr. Mark C. Hersam Professor Department of Materials Science and Engineering Northwestern University  February 6, 2009 3:00 pm 1300 Donald Bren Hall Title: Preparation and Characterization of Monodisperse Carbon Nanotube Materials and Devices Abstract: Large-scale production of high purity carbon nanotubes has the potential to enable or improve many applications.  Recently, we have developed a scalable and flexible technique for sorting single-walled carbon nanotubes (SWNTs) by their physical and electronic structure using density gradient ultracentrifugation (DGU).  Diameter-sorted metallic SWNTs yield semi-transparent conductive films with tunable optical absorption.  On the other hand, semiconducting SWNTs enable thin film transistors with high switching ratios and drive currents.  Most recently, chiral surfactants have been utilized for DGU-based sorting of SWNT enantiomers.  In all cases, analytical ultracentrifugation measurements allow the SWNT surfactant loading to be quantified and optimized for improved DGU sorting.  This talk will also delineate DGU sorting of double-walled carbon nanotubes (DWNTs).  Since DWNTs possess a buoyant density that is intermediate between SWNTs and multi-walled carbon nanotubes, a two-step DGU process has been developed for high purity DWNTs.  DGU-sorted DWNTs enable characterization of the fundamental properties of DWNTs and yield high performance transparent conductive films. Biography: Dr. Mark C. Hersam 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.  In 1999, he also performed research at the IBM T. J. Watson Research Laboratory under the support of an IBM Distinguished Fellowship. His research interests include single molecule chemistry, nanofabrication, scanning probe microscopy, semiconductor surfaces, and carbon nanomaterials. As a faculty member, Dr. Hersam has received several awards including the Beckman Young Investigator Award (2001), NSF CAREER Award (2001), ARO Young Investigator Award (2005), ONR Young Investigator Award (2005), Sloan Research Fellowship (2005), Presidential Early Career Award for Scientists and Engineers (2005), TMS Robert Lansing Hardy Award (2006), AVS Peter Mark Award (2006), and two Teacher of the Year Awards (2003, 2007). In recognition of his early career accomplishments, Dr. Hersam was directly promoted from assistant professor to full professor with tenure in 2006. In 2007, Dr. Hersam co-founded NanoIntegris, which is a start-up company focused on supplying high performance carbon nanomaterials. Host: Regina Ragan

The Chemical Bonding Center (CBC) and The Institute for Surface and Interface Science (ISIS) present: William A. Goddard, III Charles and Mary Ferkel Professor of Chemistry, Materials Science, and Applied Physics Director, Materials and Process Simulation Center (MSC) California Institute of Technology January 15, 2009 1:00 pm 2201 Natural Sciences II Title:  First Principles Approaches to Design of Materials with applications to Catalysis, Nanoelectronics, Fuel Cells, Superconductivity, and Microelectronics Processing Abstract:  Advances in theoretical and computational chemistry are making it practical to consider fully first principles (de novo) predictions of important systems and processes in the Chemical, Biological, and Materials Sciences.  Our approach to applying first principles to such systems is to build a hierarchy of models each based on the results of more fundamental methods but coarsened to make practical the consideration of much larger length and time scales. Connecting this multi-paradigm multi-scale hierarchy back to quantum mechanics enables the application of first principles to the coarse levels essential for practical simulations of complex systems. We will highlight some recent advances in methodology and will illustrate them with recent applications to problems involving Catalysis, Nanoelectronics, Fuel Cells, and nanotechnology selected from •    Mechanism Organometallic reactions for converting methane to methanol •    Mechanisms Heterogeneous catalysis: oxidation and ammoxidation on multimetal oxides •    Mechanism of dioxygen reduction reaction (ORR) on Pt alloy and non Pt cathodes •    Conductance properties of Nanoelectronic switches and carbon nanotube interconnects  •    Highly excited electronic systems involved in electron etching of materials •    The mechanism underlying superconductivity in cuprates •    Reversible dihydrogen storate at room temperature using Li-MOF and COF systems •    Dendrimer Enhanced Nanotechnology Filtration (DEF) process for low pressure         ultrafiltration (UF) and microfiltration (MF) for remediation of contaminated groundwater. Host: Wilson Ho

ISIS Lunch Lecture Professor Reg Penner Department of Chemistry November 14, 2008 12:00 pm 4112 Natural Sciences I Title: Sniffing Hydrogen with Palladium Nanowires Abstract: A palladium resistor registers the presence of hydrogen gas as an increase in its resistance.  But these devices are slow, insensitive, and they produce erratic readings in the concentration range that coincides with a phase transition of the palladium hydride - near 1-2% at atmospheric pressure.  These problems are solved, to a large extent, by scaling down the size of the palladium resistor to the nanometer scale, and by simultaneously scaling down the dimensions of the palladium grains in the polycrystalline metal.  I'll talk briefly about our unpublished results in this ISIS lunch.

Theoretical Chemistry Seminar Professor Annabella Selloni Princeton University May 9, 2008 2:00 pm 2201 Natural Sciences II Title: Structure and sensitization of titanium dioxide surfaces Abstract: This talk will give an overview of recent theoretical work meant at obtaining insights into issues relevant to TiO2-based photocatalysis. Topics to be discussed include the influence of surface structure on the adsorption of different species, and surface sensitization via adsorbed chromophores  as used in dye sensitized solar cells. Host:  Kieron Burke

Physics Colloquium Dr. Roberto Car Ralph W. Dornte *31 Professor in Chemistry Princeton University May 8, 2008 3:30 pm 101 Rowland Hall Title: Band Alignment and Tunneling Conductance through Long Molecular Wires Abstract: Experiments indicate that the linear, low bias, conductance of devices made by long insulating molecular chains connected to metallic electrodes decays exponentially with the number n of monomers in the molecular chain, according to a simple tunneling law which depends on two parameters, the decay constant and the pre-exponential factor . Understanding how , the contact conductance, and depend on the properties of the molecule, of the electrodes, and of the contacts is an issue of relevant current interest. In this talk I will show that the above tunneling law can be derived under general assumptions from linear response theory within the Kohn Sham density functional formalism. This approach shows that depends on the alignment of the molecular band edges with respect to the Fermi energy of the electrodes, while is directly related to the chemistry of the contacts. Calculations based on this approach will be presented, emphasizing open problems and future perspectives. Host:  Kieron Burke

ISIS Distinguished Lecture Dr. Roberto Car Ralph W. Dornte *31 Professor in Chemistry Princeton University May 5, 2008 4:00 pm 104 Rowland Hall Title: Quantum Water Abstract: Water, the most important liquid on earth, owes its unusual properties to a fluctuating network of hydrogen bonds. This causes adjacent molecules to become strongly correlated and makes this liquid quite different from a simple fluid. Quantum mechanics profoundly affects the behavior of water at the molecular scale. On the one hand it defines the adiabatic dynamics of the electrons which is at the origin of intermolecular correlations. On the other hand also the nuclei, and particularly the protons, need a quantum mechanical treatment as indicated by the large isotope effects that are observed experimentally. In this talk I will review some of the challenges faced by first-principles simulations in this field and will discuss future perspectives. Host:  Reg Penner

The Institute for Surface and Interface Science (ISIS) and The Department of Physics and Astronomy present: Dr. Matthias Bode Center for Nanoscale Materials, Argonne National Laboratory March 5, 2008 4:00 pm 1201 Natural Sciences II Title:  The many faces of magnetism in Fe nanostructures imaged by spin-polarized STM Abstract:  Continuum micromagnetic theory has successfully been used in the past to model spin structures of surfaces and films.  Since this theoretical approach disregards the atomic structure of matter it is expected to breakdown as the spin orientation changes on length scales comparable with the lattice constant.  Only recently, the high lateral resolution of spin-polarized scanning tunneling microscopy (SP-STM) allows to scrutinize continuum micromagnetic theory.  In my talk I will present results which reveal a variety of magnetic domain and spin structures, all obtained on Fe epitaxially grown on single-crystalline tungsten substrates, ranging from magnetic vortices, over stripe domain phases and single domain islands, down to superparamagnetic islands and antiferromagnetic Fe.    The data show that micromagnetic theory is capable of describing the spin structure of domain walls as narrow as a few nanometer. Host: Doug Mills

ISIS Lunch Lecture Professor Alexei A. Maradudin Department of Physics & Astronomy February 7, 2008 12:00 pm 2201 Natural Sciences II Title: Structured surfaces as optical metamaterials Abstract:  If a metamaterial can be defined as a deliberately structured material that possesses physical properties that are not possible in naturally occurring materials, surely deliberately structured surfaces that possess optical properties not found in naturally occurring surfaces can be considered to be optical metamaterials.  Such surfaces can be periodically or randomly structured. Indeed, in the past few years, interest has arisen in optical science in structured surfaces designed to display desirable optical properties that planar surfaces do not possess. After a brief description of such surfaces and their properties, I will describe approaches developed recently by my colleagues and myself to the design of one-and two-dimensional random or deterministic rough surfaces that scatter or transmit light to produce fields that possess specified angular, coherence, spatial, or wavelength properties. In addition I will present a surface structure that produces the negative refraction of a surface plasmon polariton. Finally, I will show how the average over the ensemble of realizations of the surface profile function used in the design of randomly rough surfaces with specified scattering/transmission properties can be replaced in the theory and in experiments by the illumination of a single realization of the random surface by a broadband source.

The Institute for Surface and Interface Science (ISIS) presents: Jim De Yoreo Lawrence Livermore National Laboratory January 14, 2008 4:00 pm 2201 Natural Sciences II Title: “Physical controls on assembly of biomolecular materials”   Abstract: Systematic organization of protein complexes as well as protein-directed formation of inorganic solids enables living organisms to achieve a high density of functionality and create hierarchical materials with unique properties.  Conversely, when these processes proceed without the proper level of control, they often result in disease.   Consequently, developing a fundamental understanding of the thermodynamic and kinetic controls on protein and protein-directed assembly can define new strategies towards both materials synthesis and the treatment of disease.  To develop that understanding, we have used in situ force microscopy, molecular modeling, and X-ray absorption spectroscopy to investigate macromolecular assembly and protein-directed crystallization.       In the first part of the talk, I will present the results of investigations into biomineralization that argue for a change in the paradigm commonly used to explain controls on mineral shape and kinetics.  The results show that small molecules, organic modifiers, and proteins exhibit a wide range of control mechanisms, but in all cases crystal shape is driven kinetically by recognition of the modifiers for the atomic structure at step edges.  While the effects of proteins and peptides on step kinetics are inhibitory at high concentrations, at low levels they act to accelerate the kinetics to a degree that scales with their hydrophobicity.  These results demonstrate the importance of solution structure on mediating protein-surface interactions and reveal the physical mechanisms by which control is established.       In the second portion of this talk, I will show how protein engineering combined with chemical synthesis and scanned probe nanolithography can be used to template deposition and assembly of macromolecules.  In particular, using engineered viruses as adsorbates and a set of alkyl thiol "inks" that act as either protein resists, covalent binders, or reversible linkers, one can direct the adsorption of these viruses into nanoscale arrays that subsequently act as nucleation sources for virus assembly.  By varying surface chemistry, virus concentration, and  solution composition, one can tune the mobility, flux, and interaction potentials that drive assembly.  In situ measurements reveal characteristic growth laws and lead to the hypothesis that templated assembly of macromolecules can be described as the one-dimensional equivalent of colloidal crystallization with tuneable interactions. Host: Greg Weiss

The Institute for Surface and Interface Science (ISIS) presents: Dr. Ofir Alon University of Heidelberg January 11, 2008 2:00 pm 1201 Natural Sciences II Title: “Statics and dynamics of interacting Bose gases: Multi-orbital mean-field and beyond”   Abstract: The necessity to go beyond the popular Gross-Pitaevskii theory to properly describe strongly-interacting cold bosonic atoms, and even weakly-interacting atoms in double- and multi-well traps has by now become well-accepted by the community. We present new theoretical and computational approaches going beyond standard mean-field. These have enabled us to predict new physical phenomena. I discuss fragmentation of repulsive and attractive condensates; a zoo of Mott-insulator phases in optical lattices [thereby going beyond the popular Bose-Hubbard model]; demixing scenarios of bosonic mixtures in optical lattices on various length scales; the pathway to fermionization of trapped cold bosonic systems; interferences in the density of two condensates consisting of identical or different atoms; and how to split a Bose-Einstein condensate. Host: Vladimir Mandelshtam

ISIS Lunch Lecture Professor D. L. Mills Department of Physics & Astronomy December 13, 2007 12:00 pm 1201 Natural Sciences II Title:  Collective Plasmons and Their Influence on the Optical Response of Metallic Nanostructures Abstract:   The presentation will be begin with an elementary discussiom of the origin of the very large enhanced electromagnetic fields often invoked to explain surface enhance Raman scattering (SERS) along with a review of other mechanics which enter. Then we disuss recent studies of the influence of collective plasmons by Ping Chu.

The Institute for Surface and Interface Science (ISIS) presents: Dr. Andreas Heinrich IBM Almaden Research Center December 10, 2007 11:00 am 2111 Frederick Reines Hall Title: Magnetism on the Atomic Scale Abstract: Understanding and controlling the magnetic properties of nanoscale systems is crucial for the implementation of future data storage and computation paradigms. Here we show how the magnetic properties of individual atoms can be probed with a low-temperature, high-field scanning tunneling microscope when the atom is placed on a thin insulator. We find clear evidence of magnetic anisotropy in the spin excitation spectra of individual magnetic atoms embedded in a non-magnetic surface. In extended one-dimensional spin chains, which we build one atom at a time, we find strong spin-coupling into collective quantum-spins, even for the longest chains of length 3.5nm. The spectroscopic results can be understood with the model of spin-excitations in a system with antiferromagnetic coupling, controlled on the atomic scale. High-spin atoms can show an interesting form of the Kondo effect when the magnetic anisotropy places a degenerate, low-spin Kramers-doublet in the ground-state. Host: Ruqian Wu

The Institute for Surface and Interface Science (ISIS) presents: Professor Joanna Aizenberg Gordon McKay Professor of Materials Science Professor of Chemistry and Chemical Biology Harvard University November 5, 2007 3:00 pm 1201 Natural Sciences II Title: Designing organic-inorganic interfaces for controlled crystallization: A bio-inspired approach Abstract: Nature produces a wide variety of exquisite mineralized tissues fulfilling diverse functions, and often from simple inorganic salts.  Organisms exercise a level of molecular control over the physico-chemical properties of inorganic crystals that is unparalleled in today's technology.  This reflects directly or indirectly the controlling activity of biological organic surfaces that are involved in the formation of these materials.  Biomineralization occurs within specific microenvironments, which implies stimulation of crystal formation at certain interfacial sites and relative inhibition of the process at all other sites.  Our approach to artificial crystallization is based on the combination of the two latter concepts: that is, the use of organized organic surfaces patterned with specific initiation domains on a sub-micron scale to study and orchestrate the crystallization process.  This bio-inspired engineering effort made it possible to achieve a remarkable level of control over various aspects of the crystal nucleation and growth, including the precise localization of particles, nucleation density, crystal sizes, morphology, crystallographic orientation, arbitrary  shapes, microstructure, stability and architecture.  The ability to construct large, defect-free, micropatterned single crystals with controlled microporosity; periodic arrays of uniform, oriented crystals or films presenting patterns of crystals offers a new synthetic methodology to materials engineering. Host: Zhibin Guan

Chemical Bonding Center (CBC) and ISIS present: Dr. Erik Muller Center for Functional Nanomaterials Brookhaven National Laboratory October 25, 2007 12:00 pm 2201 Natural Sciences II Title: Electric force microscopy of pentacene transistors and scanning tunneling microscopy of hydrogen dissociation in sodium alanate Abstract: I will discuss results of scanning probe techniques applied to organic semi-conducting devices and model systems for hydrogen storage. First, electric force microscopy is applied to investigate charge traps in pentacene devices. Correlating topography with charge trap distributions and surface potential shows that the trap spatial distribution is not related to topography. Measurements of the trap dynamics support the assertion that the origin of trapping in these devices is chemical in nature. Second, scanning tunneling microscopy is used to investigate hydrogen dissociation catalysis in a promising hydrogen storage material, sodium alanate. Titanium doped aluminum surfaces are used as a model surface for studying the interaction with atomic and molecular hydrogen. The presence of a large population of predicted catalytically active sites are determined. Host: Wilson Ho

The Institute for Surface and Interface Science & the Chemical Bonding Center (ISIS & CBC) present: Kristin L. Wustholz University of Washington October 1, 2007 12:00 pm 2201 Natural Sciences II Title: Dispersive Kinetics from Single Molecules Oriented in Single Crystals of Potassium Acid Phthalate Abstract:  The intermittent emission or "blinking" of single violamine R (VR) and 2',7'- dichlorofluorescein (DCF) molecules incorporated into single crystals of potassium acid phthalate (KAP) is studied using confocal fluorescence microscopy. Blinking dynamics are quantified in terms of switching rates and on- and off-time probability distributions. Mixed crystals of KAP/VR and KAP/DCF consist of photophysical sub-populations with ~40% and ~20% exhibiting persistent emission, respectively, and the remainder demonstrating a broad range of blinking behavior that is well described by a power-law distribution. The blinking dynamics are modeled using Monte Carlo simulations based on a three-level electronic system with the rate constants for population and depopulation of the "dark" state being distributed. No correlation between molecular orientation and blinking dynamics is observed, suggesting that intermolecular electron-transfer is not the origin of the power-law behavior. Alternative origins for this behavior (e.g., conformational flexibility and spectral diffusion) are explored using a combination of experimental and computational techniques Host: Rob Corn

Kohei Uosaki Professor of Physical Chemistry Division of Chemistry Graduate School of Science September 4, 2007 3:00 pm 2201 Natural Sciences II Title: Molecular Structures at Solid/Liquid Interfaces by Sum Frequency Generation Spectroscopy Abstract: To understand the properties and chemical reaction mechanisms at solid/liquid interfaces, it is essential to determine the structure of molecules at the interfaces including water and short-lived reaction intermediates. One needs to use surface specific techniques for this purpose because there is much larger number of molecules in solution. Sum frequency generation (SFG) spectroscopy is an interface-selective probe and has been applied to determine the interfacial molecular structure in many systems, including solid/liquid interfaces. Furthermore, time-resolved surface vibrational spectroscopy to investigate the mechanism of chemical reactions at solid/liquid interfaces based on SFG is possible because short pulse laser is used. We used two SFG systems, one based on a ps Nd:YAG laser and the other based on a Ti:sapphire regenerative amplifier system. We have carried out SFG investigations at a wide variety of interfaces including: 1. SFG intensity of OH stretching vibration at the interfaces between an aqueous electrolyte solution and a quartz surface modified by a self-assembled monolayer (SAM) was found to be very strongly dependent on the terminal group of the SAM and pH and ionic strength of the solution. 2. Interfacial structures of alkylated polyvinylpyridine (Cn-PVP) brushes with various side chain lengths (n = 0, 2, 6, 12) in dry nitrogen, water vapor, liquid water, and aqueous electrolyte solution were investigated by SFG. The conformational order of the side chain depended on the chain length with the highest at hexyl side chain. Molecular conformations of all the brushes became less ordered upon contact with water and were almost completely disordered in liquid water. 3. SFG intensity of the hydrogen-bonded OH bands on TiO2 surface increased after UV illumination, reflecting the increase of orientational order of water as a result of UV induced increase of hydrophilicity of the TiO2 surface. 4. Potential dependent water structures at metal electrodes such as Pt and Au were also studied. References: (1) S. Ye, S. Nihonyanagi and K. Uosaki, PCCP, 3, 3463 (2001). (2) S. Nihonyanagi, D. Miyamoto, S. Idojiri, and K. Uosaki, J. Am. Chem. Soc., 126, 7034 (2004). (3) K. Uosaki, T. Yano, and S. Nihonyanagi, J. Phys. Chem. B, 108, 19086 (2004). (4) S. Nihonyanagi, S. Ye, K. Uosaki, L. Dreesen, C. Humbert, P. Thiry and A. Paremans, Surf. Sci., 573, 11 (2004). (5) H. Noguchi, T. Okada, and K, Uosaki, J. Phys. Chem. B, 110, 15055 (2006). Host: Rob Corn

The Institute for Surface and Interface Science & the Chemical Bonding Center (ISIS & CBC) present: Mats Persson Surface Science Research Centre/Department of Chemistry The University of Liverpool, UK August 27, 2007 3:00 pm 1201 Natural Sciences II Title: Electronic Friction and Excitations in Molecule-Surface Interactions Abstract: A long-standing issue in surface science has been the role of electronic non-adiabaticity in the interactions of atoms and molecules with metal surfaces. The absence of any energy gap for electron-hole pair excitations of a metal substrate results in general of a breakdown of the adiabatic (Born-Oppenheimer) approximation for the electronic motion in response to ionic motion. A key question is whether this electronic non-adiabaticity is sufficiently strong to be important in dynamical processes at surfaces or not. The progress in the theoretical description of the electronic structure of adsorbates using density functional theory has made it possible to calculate the electronic non-adiabatic coupling for more or less realistic systems and we can now address this question in a more quantitative manner. A most elementary case is provided by electron-hole pair damping of adsorbate vibrations, whose theoretical treatment will be the starting point for this talk that will cover theory of electronic adiabaticity in transition state dynamics, hot-electron induced surface chemistry, chemically-induced electronic excitations upon adsorption of atoms and molecules, and exo-electron emission in vibrational de-excitation in scattering from surfaces.

Professor H.-J Freund Director of the Fritz-Haber-Institute of the Max Planck Society, Berlin August 9, 2007 3:00 pm 1201 Natural Sciences II Title: Photochemistry and Metal nanoparticles Abstract:  We are interested in the influence of the finite size of metal particles onto the photochemistry at their surfaces. To this end we prepare Ag nano particles by nucleation and growth on thin oxide (alumina) film surfaces and apply scanning tunneling microscopy not only to unravel their morphology but also to investigate their excited states, i.e. their surface plasmons. Using a photon-STM we are able to do this on individual particles.The goal of our studies is to learn more about the influence of the plasmonic excited states on the photodesorption from the nano particles. We study photodesorption using time of flight mass spectrometry and also quantum state resolved techniques and apply it to NO and Xe.

Wolfgang Knoll Max-Planck-Institute for Polymer Research Mainz, Germany June 20, 2007 1:00 pm 1201 Natural Sciences II Title: Tethered Bimolecular Lipid Membranes-a Novel Model Membrane Platform Abstract:  This contribution summarizes some of our efforts in designing, synthesizing, assembling, and characterizing functional tethered lipid bilayer membranes (tBLMs) as a novel platform for biophysical studies of and with artificial membranes or for sensor development employing, e.g., membrane integral receptor proteins. Chemical coupling schemes based on thiol groups for Au substrates or silanes used in the case of oxide surfaces allow for the covalent and, hence, chemically and mechanically robust attachment of anchor lipids to the solid support, stabilizing the proximal layer of a tethered membrane on the transducer surface. Surface plasmon optics, the quartz crystal microbalance, fluorescence- and IR spectroscopies, and electrochemical techniques are used to characterize the build-up of these complex supramolecular interfacial architectures. We demonstrate, in particular, that bilayers with a specific electrical resistance of better than 10 M_cm2 can be achieved routinely with this approach. The functionalization of the lipid membranes by the incorporation of peptides is demonstrated for the carrier valinomycin which shows in our tBLMs the expected discrimination by four orders of magnitude between the translocation of K+ and Na+ -ions across the hydrophobic barrier. For the synthetic channel-forming peptide M2 the high electrical resistance of the bilayer with the correspondingly low background current allows for the recording of even single channel current fluctuations. >From the many membrane proteins that we reconstituted so far we describe results obtained with the redox-protein Cytochrome c Oxidase. Here, we also use a genetically modified mutant with a his-tag at either the C- or the N-terminus for the oriented attachment of the protein via the NTA/Ni2+ approach. With this strategy, we not only can control the density of the immobilized functional units, we introduce a completely new and alternative concept for the stabilization of lipid bilayers, i.e., the protein-tethered membrane. Our efforts in experimentally characterizing the resulting membrane functions and correlating the data with the structural details of the bilayer architectures are complemented by theoretical studies modeling the electrical and electrochemical response of functional tethered lipid bilayer membranes by extended SPICE simulations.

ISIS Distinguished Lecture: Wolfgang Knoll Max-Planck-Institute for Polymer Research Mainz, Germany June 21, 2007 4:00 pm 1201 Natural Sciences II Title: Nanoscopic Building Blocks from Polymers, Metals, and Semiconductors for Hybrid Assemblies and Nanostructured Materials Abstract:  This contribution summarizes some of our efforts in designing, synthesizing, and characterizing – both structurally and functionally – hybrid aggregates and materials assembled from nanoscopic building blocks of polymers, (noble) metals, and semiconductors (cf. Figure 1) for future applications, e.g., in opto-electronics and for biosensing. Dendrimers are introduced as a novel class of polymers that are strictly monodisperse, hence have all the same molecular mass. In the case of paraphenylene dendrimers that are in addition to their excellent chemical stability also shape-persistent it is thus justified to speak of polymeric objects that can be regarded as building blocks for complex architectures. Noble metals play a particularly exciting role for the fabrication of nanoscopic structures due to their localized plasmonic resonances that can be observed, e.g., in Au particles of different sizes and shapes. Optical field enhancements of up to a factor of 106 have been reported experimentally and predicted theoretically. We will present the fabrication and optical characterization of non-trivial Au colloids prepared in the shape of nano-crescents that exhibit interesting optical properties that might result in novel bio-sensor designs based on single resonant objects. And finally, nanoparticles from semiconducting materials, the quantum dots, will be discussed. The possibility of engineering their bandgap, thus tuning their optical emission properties make them most interesting candidates for various device concepts in opto-electronics and as labels for bio-affinity studies.

The Institute for Surface and Interface Science (ISIS) and CBC present: Professor H. Kumar Wickramasinghe IBM Fellow Professor of Electrical Engineering and Computer Science and The Henry Samueli Endowed Chair University of California, Irvine May 25, 2007 2:00 pm 1114 Natural Sciences I Title: Scanning Probe Microscopy and their Applications to Technology Abstract:  Scanning Probe Microscopes have become essential tools for nanotechnology. We will discuss the development of this field from its very early days. The first part of the talk will focus on the speaker's experiences driving the AFM technology from its infancy into fully hardened instruments for use both within and outside IBM. The second part will describe some recent projects the speaker has initiated and driven. They range from apertureless near-field optics for thermally assisted magnetic recording aimed at extending the super paramagnetic limit in magnetic recording to nanoscale strain measurement to work on a novel x-ray nano-scope, and the  development of an ultra high speed DNA separation technology which can separate DNA strands at speeds that are 10,000 times faster than current micro fluidic separation technologies. Implications for some these technologies will be discussed. Host: Wilson Ho

The Institute for Surface and Interface Science (ISIS) and CBC present: Sergei Smirnov Department of Chemistry and Biochemistry New Mexico State University, Las Cruces, NM May 4, 2007 2:00 pm 4135 Frederick Reines Hall Title: Photoinduced Charge Transfer in Organic Monolayers    Abstract:  Charge transfer and photoinduced charge transfer in particular are in the heart of various applications as well as of many natural phenomena. Studying such phenomena on molecular systems using electrical measurements is often hindered and controlled by poor quality of electrical contacts to molecules. Can electrical properties of molecules be studied without making Ohmic contacts? The bulk of this presentation is dedicated to demonstration of the capacitive coupling approach for investigating intramolecular photoinduced charge transfer.1-6 Molecules in solution and on solid surfaces can be studied and each method offers unique advantages and disadvantages, which will be demonstrated. The latter method is realized with molecules covalently linked to metal oxides.5-8 For small molecules the signal has unexpendingly strong dependence on solvent polarity and even is opposite in sign in the gas phase. The amplitude is maximal in vacuum and declines in accordance with increasing collision frequency dependent on the gas pressure and its mass. Collisions with paramagnetic oxygen induce intersystem crossing to long-lived triplet charge transfer states with the rate close to the half of that for the collision. Other applications originated from exploring chemistry of molecules linked to solid surfaces will be briefly described as well. They are based on using modified nanoporous membranes for biochemical sensinng.9-14 References 1. S. Smirnov, P.A. Liddell, I. Vlassiouk, A.Teslja, D. Kuciauskas, C.L.Braun, A.L. Moore, T. A. Moore, and D. Gust,, J. Phys. Chem. A, 2003, 107, 7567 2. F.-P. Montforts, I. Vlassiouk, S. Smirnov; M. Wedel, J. Porph. Phthal., 2003, 7, 651 3. S. Smirnov, I. Vlassiouk, O.Kutzki, M.Wedel, F.Montforts,  JACS, 2002, 124, 4212 4. I.Vlassiouk, S.Smirnov, O.Kutzki, M.Wedel, F.-P.Montforts, J. Phys. Chem., 2002, 106, 8657 5. Krasnoslobodtsev A., Smirnov S.,  J. Phys. Chem., 2006, 110, 17931 6. Krasnoslobodtsev A., Smirnov S., J. Phys. Chem., 2006, 110, 17941 7. Krasnoslobodtsev A., Smirnov S., Langmuir, 2001, 17, 7539 8. Krasnoslobodtsev A., Smirnov S., Langmuir, 2002, 18, 3181 9. I. Vlassiouk, A.Krasnoslobodtsev, S.Smirnov,M.Germann, Langmuir, 2004, 20 9913 10. I. Vlassiouk, P.Takmakov, S.Smirnov, Langmuir, 2005, 21, 4776 11. I. Vlassiouk, C.-D.Park, S.A.Vail, D. Gust, S. Smirnov, Nano Letters, 2006, 6, 1013 12. V. Szczepanski, I. Vlassiouk, S. Smirnov, J. Membr. Sci., 2006, 281, 587 13. P. Takmakov, I. Vlassiouk, S. Smirnov, Anal. Bioanal. Chem., 2006, 385, 954 14. P. Takmakov, I. Vlassiouk, S. Smirnov, Analyst, 2006, 131, 1248 Host:  Zuzanna Siwy

The Institute for Surface and Interface Science (ISIS) and CBC present: Marat Khafizov Department of Physics and Astronomy and Laboratory for Laser Energetics University of Rochester April 25, 2007 1:00 pm 2201 Natural Sciences II Title: Photoresponse Mechanism in Superconducting Magnesium Diboride Abstract:  Understanding the photoresponse mechanism of materials subject to short optical pulses is important for optimal design of optical detectors. Superconducting detectors offer broadband detection capability from deep infrared to X-rays. Until recently due to low-temperature operations they were developed for astronomical applications only. Recent demonstration of single photon detection in niobium nitride made them attractive for quantum key distribution and some biological applications. Superconductivity in MgB2 is one of the recent discoveries. In this work we study the photoresponse mechanism of this material excited by train of 100-fs wide, 800-nm wavelength optical pulses. First set of experiments employs all-optical time resolved pump probe spectroscopy of thin films. Second set of measurements studies the transient photoimpedance of current-biased microbridge structures. Both experiments allow us to observe the superconducting recovery dynamics in MgB2. Transient photoimpedance measurements demonstrate hot electron resistive and kinetic inductive responses which represent two detection mechanisms. Kinetic inductive responses observed under low optical excitation powers are as fast as 100-ps. Resistive responses observed at high excitation powers in general are longer than 500-ps wide and depend on biasing conditions.   Observed voltage responses make MgB2 as an attractive material for fast superconducting hot electron detectors and mixers. Host: Eric Potma

The Institute for Surface and Interface Science (ISIS) presents: Sergei Smirnov Department of Chemistry and Biochemistry New Mexico State University, Las Cruces, NM May 4, 2007 1:00 pm 4135 Frederick Reines Hall Title:  Charge Transfer in Surface Bound Molecules Abstract:  TBN

Chemical Bonding Center (CBC) and ISIS present: Hans Ågren Theoretical Chemistry Royal Institute of Technology April 13, 2007 2:00 pm 1114 Natural Sciences I Title: Modeling of light-matter interaction of strong laser pulses Abstract:  In this talk I will describe applications in materials science of modeling of non-linear interaction of strong laser pulses. The project is rooted in that novel hybrid materials featuring large non-linearity and multi-photon absorption cross sections are of great interest due to many attractive applications exploiting their response to strong exciting light. These include, for example, ultrahigh-resolution biological imaging using multi-photon confocal microscopy, high-efficiency upconverted lasing for infra-red to visible upconversion, and optical power limiting, where the range of radiation amenable to effective suppression can be extended to the infra-red region. Our research has mostly address organic and organometallic hybrid compounds, but has recently also been extended to quantum dots. These offer the combined advantage of brilliance and photo-resistance of normal quantum dots with the 3-dimensional confocality and penetration of multi-photon excitation, something that can have important applications in fluorescence based experiments in biology. I will highlight the use of multi-scale/multi-physics approaches that combine quantum mechanics with wave mechanics to address optical control of strong laser pulses, in particular pulse propagation in non-linear media. We address the optical transmission from cross sections of multi-photon absorption processes and from considerations of propagation effects, saturation and pulse effects. It is shown that in the non-linear regime it is often necessary to account simultaneously for coherent one-step and incoherent step-wise multi-photon absorption, and for off-resonant excitations even when resonance conditions prevail. We find that the mechanisms for multi-photon absorption are quite different in the different pulse length regimes.

The Institute for Surface and Interface Science (ISIS) presents: Zeev Rosenzweig Professor of Chemistry University of New Orleans Program Director at NSF/Chemistry March 30, 2007 3:00 pm 1201 Natural Sciences II Title:  Luminecent Quantum Dots based Probes in Bioassays Abstract: The presentation will focus on the development of quantum dot based nanoscale probes and their use in various biological assays. The probes are fabricated by the covalent attachment of fluorescent  dyes to the surface of the nanometric quantum dots. This facilitates fluorescence resonance energy transfer (FRET) interactions between the quantum dots and fluorescent dyes. The intriguing photophysical  properties of this system will be discussed in detail. When the fluorescent dyes are attached to the quantum dots through specific linkers it is possible to form probes that will monitor in real time the chemical or enzymatic cleavage of these rationally designed linkers. Recently, we demonstrated this principle in measuring the activity of proteolytic enzymes and the potency of protease inhibitors. These measurements and their implications in the area of cancer diagnostics will be discussed. Short Bio - Prof. Zeev Rosenzweig obtained his doctoral degree in physical chemistry from the Hebrew University of Jerusalem in 1991. His PhD research focused on the development and application of non-linear optical techniques like second harmonic generation for the  analysis of basic surface processes related to catalysis. He then postdoced from 1992 to 1994 with Ed Yeung at Iowa State University where he applied laser based techniques for studying biological samples and from 1994-1995 with Raoul Kopelman at the University of Michigan where he developed submicrometric optochemical sensors for the analysis of  single cells. Prof. Rosenzweig assumed a faculty position in the department of chemistry at the University of New Orleans in 1995. He became a full Professor in 2001. Prof. Rosenzweig received an NSF CAREER award in 1997 to synthesize and apply luminescent nanoparticles for cellular analysis. This has been his research area since then. Prof. Rosenzweig has been serving as a Program Director at NSF/Chemistry since September 2005. He currently leads the Analytical and Surface Chemistry program, lead the international working group of the division and represent the division in several collaborative calls with the department of homeland security.

The Institute for Surface and Interface Science (ISIS) and CBC present: Shiwu Gao Institute of Physics, Chinese Academy of Sciences Department of Physics, Goteborg University, Sweden March 12, 2007 11:00 am 306 Rowland Hall Title: Collective plasmon excitations in low-dimensional nanostructures Abstract:  Collective electron oscillations in nanostructures form localized surface plasmon resonances (LSPR), which exhibit unusual properties in energy, lifetime, optical spectroscopy, and short-time dynamics. In this talk, I will present some of our recent progress in the study of plasmon excitation of artificial nanostructures, whose sizes and shapes are controllable down to atomic precision. With a general introduction, we focus on two model systems: metallic thin films and linear atomic chains, whose excitation spectra were obtained from the linear response theory and the time-dependent local density approximation (LR-TDLDA). The energy dispersion, Landau damping and lifetime, polarization dependences and size effects of surface plasmons are determined. Comparison with classical electrodynamical models are made and discussed whenever possible. At both conceptual and quantitative levels, we elaborate the emergence, the development of collectivity, and quantum characteristics of plasmons at nanometer to atomic scales. Host:  Reg Penner

The Institute for Surface and Interface Science (ISIS) presents: Dr. Yukio Hasegawa The Institute for Solid State Physics The University of Tokyo, Kashiwa, Japan March 14, 2007 11:00 am 306 Rowland Hall Title: Real-space observation of screened potential and the Friedel oscillation by scanning tunneling spectroscopy Abstract:  The electrostatic potential around a single charge in vacuum is described with the Coulomb potential.  If it is situated in a metal, the potential is modified by electrons in the metals. The modification of the potential, called screening, is one of the fundamental phenomena in the condensed matter physics. Using low-temperature scanning tunneling microscopy / spectroscopy (STM/S) we have developed a method for measuring electrostatic potential in high spatial and energy resolutions and performed a real-space observation of the potential around external charges screened by two-dimensional surface electron system.  In the real-space potential mappings, characteristic decay and oscillation in the potential, so-called the Friedel oscillation, were clearly visible around the charges [1].      As a sample having a two-dimensional electron system, we used the Si(111)-÷3¥÷3-Ag surface.  The electron standing wave patterns are observed in tunneling conductance (dI/dV) images and an obtained energy dispersion curve indicates free-electron like behaviors of the electrons.  It has been known that when the surface potential is changed by, for instance, additional Ag adsorption on the surface, an energy level of the surface states shifts accordingly.  Therefore, by measuring the energy level of the surface states by using STS, a potential mapping is obtained. The obtained potential profiles around step edges, where Ag adsorbates are accumulated, were fitted well with theoretically predicted screened potential profiles. If the oscillation in the potential is assumed to be the Friedel oscillation, it should have a period of the half Fermi wavelength of the electron system. The assumption was confirmed by an observation that the potential oscillation has the same period as the electron standing wave at the Fermi level, although  their shapes and phases are different. References [1] , M. Ono, Y. Nishigata, T. Nishio, and T. Eguchi and Y. Hasegawa, Phys. Rev. Lett., 96, 016801 (2006)

Dr. Sascha Sadewasser Division of Solar Energy, Hahn-Meitner Institut Glienicker Str. 100, 14109 Berlin March 23, 2007 3:00 pm 1114 Natural Sciences I TItle:  Kelvin probe force microscopy on semiconductors Abstract:  To improve understanding of semiconductor materials and device functionality detailed studies are required providing information on materials characteristics on the nanometer scale. Kelvin probe force microscopy (KPFM) is a technique based on non-contact atomic force microscopy (NC-AFM) and is well suited for this task as it measures the surface potential with high spatial resolution. We apply a resonance enhanced mode of operation which allows compensating electrostatic forces using detection ac-voltages below 100 mV; thus, the influence of the KPFM tip on the semiconductor is minimized [1]. This talk will first introduce the KPFM method. It will then be demonstrated that for correct height imaging the KPFM method is superior to regular NC-AFM. Depending on the sample bias, even a contrast inversion can be observed in regular NC-AFM topography imaging [2]. Using KPFM, a variation in the surface potential at surface steps of III-V semiconductors is observed. In conjunction with simulations, the density of charged defects was quantitatively determined, corresponding to about 2% of the dangling bonds being charged [3]. For the application to chalcopyrite semiconductors (i.e. Cu(In, Ga)Se2) in thin film solar cells, it is shown that differently oriented facets of single semiconductor grains show a distinct work function [4]. The investigation of grain boundaries in these polycrystalline thin films shows a local band bending due to the presence of charges [5]. However, for an epitaxially grown S3 grain boundary, a charge neutral barrier to majority transport could be identified for CuGaSe2 [6]. [1] Ch. Sommerhalter et al., Appl. Phys. Lett. 75, 286 (1999). [2] S. Sadewasser et al., Phys. Rev. Lett. 91, 266101 (2003). [3] Y. Rosenwaks et al., Phys. Rev. B 70, 085320 (2004). [4] S. Sadewasser et al., Appl. Phys. Lett. 80, 2979 (2002). [5] D. Fuertes Marrón et al., Phys. Rev. B 71, 033306 (2005). [6] S. Siebentritt et al., Phys. Rev. Lett. 97, 146601 (2006).

Henrikas Cesiulis Visiting Associate Professor Louisiana State University Visiting Professor Gordon A and Mary Cain Department of Chemical Engineering February 15, 2007 1:00 pm 1201 Natural Sciences II Title: Electrodeposition and Properties of Tungsten and Molybdenum Alloys with Iron Group Metals Abstract:  A superalloy, or high-performance alloy, is an alloy able to withstand extreme temperatures. Superalloys of the first generation were intended for operation up to 700 °C (973 K). The up-to-date superalloys of the fourth generation are used as single crystals and are extra alloyed, especially with ruthenium. They can operate up to 1100 °C (1373 K). A superalloy's base alloying element is usually Ni, Co or Ni-Fe. Many other elements can be present: Mo, W, Cr, Al, Zr, Nb, Rh and etc. The information dealing with electrodeposition of W alloys from citrate-ammonium baths and electrodeposition of Mo alloys from pyrophosphate baths will be provided and discussed. The attention is paid on the management of bath's composition in order to obtain the alloys having composition close to the composition of intermetallic compounds: Ni4W, Co2W, Fe2W or Ni3Mo. The information about their structure and morphology, and resistance to corrosion will be provided. Also, the information about electrodeposition of ternary and quaternary alloys such as Ni-Fe-W, Co-Ni-W, Co-W-P, Co-Ni-W-P will be provided and perspectives to implement W and Mo alloys into microtechnics will be discussed. In addition, some facts about Lithuania, electrochemistry in Lithuania will be provided. Host:  Reg Penner

Chemical Bonding Center (CBC) and ISIS present: Marlan O. Scully Texas A&M University and Princeton University February 1, 2007 1:00 pm 2201 Natural Sciences II Title: Quantum Control of Light: From Slow Light and Fast CARS to Nuclear x-ray Spectroscopy Abstract: In recent work we have demonstrated strong coherent backward wave oscillation using forward propagating fields only.  This surprising result is achieved by applying laser fields to an ultra-dispersive medium with proper chosen detunings to excite a molecular vibrational coherence that corresponds to a backward propagating wave [1]. The physics then has much in common with propagation of ultra-slow light. Applications of coherent scattering and remote sensing to the detection of bio and chemical pathogens (e.g., anthrax) via Coherent Anti-Raman Scattering together with Femtosecond Adaptive Spectroscopic Techniques (FAST CARS [2]) will be discussed. Furthermore, the interplay between quantum optics (Dicke super and sub-radiant states) and nuclear physics (forward scattering of _ radiation) provides interesting problems and insights into the quantum control of scattered light [3]. Host: Shaul Mukamel ------------------ [1] "Electromagnetically Induced Backscattering," PRL, 97, 113001 (2006). [2] "Towards a FAST CARS Anthrax Detector," Opt. Comm., 244, 423 (2005). [3] "Directed Spontaneous Emission from an Ensemble of N Atoms" PRL, 96, 010501 (2005).

Nancy E. Levinger Department of Chemistry Colorado State University January 17, 2007 1:00 pm 1201 Natural Sciences II Title: What your IR spectrum wouldn't tell you about water Abstract:  Frequently, the IR spectrum of water is used to characterize the structure and strength of the associated hydrogen bond network.  Our recent results show that linear IR spectroscopy alone is insufficient to predict effects on the structure and dynamics of water in different chemical environments based on qualitative assertions regarding the strength of the hydrogen bond network.  Using nonlinear IR pump-probe spectroscopy we examine the dynamics of water in various chemical systems that have nearly identical IR absorption spectra.  The results illustrate that the vibrational lifetimes and orientational relaxation timescales vary dramatically between all the samples.   Nonlinear IR spectroscopies are therefore essential in providing more detailed information about hydrogen bonded systems.

Joint ISIS/CBC Seminar Tigran Shahbazyan Professor of Physics Jackson State University November 17, 2006 2:00 pm 2201 Natural Sciences II Title:  Surface-enhanced Raman scattering on small metal nanoparticles: Microscopic effects Abstract:  Surface-enhanced Raman scattering (SERS) from molecules adsorbed on small metal particles has attracted increasing interest during past two decades. The main SERS mechanism has electromagnetic origin and is due to the strong surface plasmon local field near the metal surface. Recent observations of enormous (up to 1015) enhancement of single-molecule Raman scattering as well as emerging possibilities of nanoparticle-based Raman sensors have prompted a new interest in single particle SERS and, in particular, in finite-size effects in small nanoparticles. Although the classical electromagnetic enhancement is independent of nanoparticle size, quantum corrections due to the discreteness of the electron spectrum (Landau damping) result in the overall weakening of the enhancement for small nanoparticles. On the other hand, this general trend is somewhat remedied by a reduction of the electron screening near nanoparticle surface. The interplay between several quantum-size effects is rather involved and requires a microscopic approach.       In noble-metal nanoparticles, the confining potential has different effect on s-band and d-band electrons. Namely, the spillover of delocalized s-electrons beyond the classical nanoparticle boundary results in an incomplete embedding of s-electron distribution in the background of localized d-electrons whose density profile follows more closely the classical shape. In the absence of d-electron population in the nanoparticle surface layer, the screening of electron gas is reduced. We performed calculations of SERS in small Ag nanoparticles, based on time-dependent local-density approximation, and found that the effect of underscreening in the surface layer leads to stronger surface plasmon local field acting on a molecule located in a close proximity to the metal surface [3]. This results in an additional enhancement of the Raman signal, although the general trend of reduction of SERS in small nanoparticles still dominates. Host:  Shaul Mukamel

Joint ISIS/Physics Condensed Matter Seminar Dr. Konstantin Arutyunov NanoCentre Department of Physics University of Jyvaskyla November 29, 2006 3:00 pm   1114 Natural Sciences I Title: Quantum fluctuations in ultranarrow superconducting nanowires Abstract: Below a certain temperature Tc (typically cryogenic) some materials lose their electric resistance R entering a superconducting state. Following the general trend toward a large scale integration of a greater number of electronic components, it is desirable to use superconducting elements in order to minimize heat dissipation. It is expected that the basic property of a superconductor, i.e., dissipationless electric current, will be preserved at reduced scales required by modern nanoelectronics. However, it is a known fact that there is certain range of temperatures close to the critical one, where a superconductor is in a so called 'resistive state' providing non-zero resitance. Moreover, there are indications that for a certain critical diameter limit of the order of 10 nm, below which a 'superconducting' nanowire is no longer a superconductor in a sense that it acquires a finite resistance even at temperatures close to absolute zero. Method of progressive and nondestructive reduction of effective diameter of a nanowire has been applied to trace evolution of the shape of superconducting transition R(T).  Here we report experimental evidence of superconductivity breakdown in ultranarrow quasi-1D aluminum and tin nanowires. Apart from suppression of superconductivity due to quantum fluctuations , size effects result in modulation of the critical temperature Tc and unusual negative magnetoresistance in the very thinnest samples. The experimental results are in a reasonable agreement with existing theoretical models. References: 1. M. Zgirski, K. P. Riikonen, V. Touboltsev, and K. Arutyunov, Nano Lett. 5, 1029 (2005) 2. A. A. Shanenko, M. D. Croitoru, M. Zgirski, F. M. Peeters and K. Yu. Arutyunov., Phys. Rev. B 74, 052502 (2006)

Joint ISIS/CBC Seminar Professor Thomas Elsaesser Professor of Physics Max Born Institut, Berlin, Germany November 3, 2006 3:00 pm 1201 Natural Sciences II Title: From Terahertz to X-Rays - Ultrafast structural Dynamics in Liquids and Solids Abstract:  The study of ultrafast processes in nature has developed into one of the most exciting areas of science. Powerful experimental techniques such as multidimensional nonlinear spectroscopies as well as ultrafast x-ray diffraction and absorption allow for observing such phenomena in real-time. Presently, there are strong efforts to unravel transient structures on atomic length and femtosecond time scales in order to understand the microscopic interactions governing structural fluctuations, phase transitions, or chemical reactions. In this talk, recent progress in two-dimensional vibrational spectroscopy of hydrogen-bonded liquids, in particular neat water, will be discussed, giving insight into the structural and vibrational dynamics of extended molecular networks. As a second topic, ultrafast lattice dynamics of inorganic and organic solids as monitored by femtosecond x-ray diffraction will be addressed.

The Institute for Surface and Interface Science (ISIS) presents: Michael Grunze, Distinguished Visitor Angewandte Physikalische Chemie Universität Heidelberg October 10, 2006 4:00 pm 104 Rowland Hall Title: "Biological” Surface Science Abstract:  Surface Science evolved from the need to understand interfaces in semiconductor manufacturing and heterogeneous catalysis, and relied heavily on model surfaces mimicking specific aspects of the more complex “real” surfaces of technological relevance. Most methods to characterize the structure and composition of surfaces with atomic precision traditionally required a vacuum environment, if not for the probes used (electrons, ions, atoms...), then to avoid contamination of the surfaces from an ambient atmosphere. Biomedical interfaces were the last thing you would put into your UHV chamber, not only because of  the dire consequences for your vacuum system, but also because the interfaces were too complex to be analysed quantitatively with the concepts derived from inorganic model surfaces. I well remember the first presentations at the annual AVS symposia by Buddy Ratner in which he showed XPS data of explanted implant surfaces and other biomedical devices. Awe and disbelief was a common reaction in the audience. However, the message was clear that interfaces of biotechnological and biomedical relevance need to be better understood to improve the performance of diagnostic platforms and biomedical devices. Since then Biomaterial Interphase science developed into a mature field. In my talk I will discuss two selected examples from our own work in this area to demonstrate the “surface science“ approach to biotechnical problems, and one example where the Interface Science toolbox can help to solve important biological questions. The first part of my talk will be organized according to the dominating forces between artificial surfaces and biological molecules/cells, i.e. surfaces which are repellent, attractive, or are not recognized as foreign in a living organism (stealth surfaces). I will summarize and explain why non-ionic surfaces are negatively charged in aqueous solutions, and that this negative surface charge and the solvation forces determine the adsorption characteristics of the organic surface. The subtle and distance dependent balance between these forces determines under which (external) conditions surfaces adsorb or repel proteins and cells. These “inert” surfaces have wide applications in biotechnology applications, yet they lack the stability in blood to be useful in e.g. cardiovascular applications. Needed for implants is not an “inert” surface coating, but a surface coating which avoids the activation of the complement system (and thus prevents the immune response), and on the other side supports the integration of the implant into the vessel walls without scarring. The solution to this problem is a “stealth surface” which selectively does not adsorb and activate proteins which are involved in the activation of the complement system, or alternatively maintains their native conformation in the adsorbed state. Such a surface is poly(bis(trifluoroethoxy)phosphazene) (Polyzene®-F),  a soft rubber like inorganic polymer with a -[P=N]n- backbone completely substituted by trifluoroethanol side groups, a strictly linear structure and an extreme high molecular weight. The final example demonstrates the impact of synchrotron based microscopy and spectroscopy can have on Functional Genomics. I will give an overview over X-ray microscopy applied to biological specimen, and discuss our results on the chemical and structural analysis of Melanosomes of different phenotype mice. Melanosomes are specialized intracellular membrane bound organelles that produce and store melanin pigment. The composition of melanin and distribution of melanosomes determine the color of many mammalian tissues, including the hair, skin, and iris. However, the presence of melanosomes within a tissue carries potentially detrimental risks related to the cytotoxic indolequinone intermediates produced during melanin synthesis. In order to study melanosomal molecules, including melanin and melanin-related intermediates, we have refined methods allowing spectro-microscopic analysis of purified melanosomes using scanning transmission X-ray microscopy. Here, we present for the first time absorption data for melanosomes ranging from 284-290 eV. High-resolution images of melanosomes at the carbon absorption edge demonstrate that fully melanized mature melanosomes are internally non-homogeneous, suggesting the presence of an organized internal sub-structure. Differences in the absorption spectra  are detectable between samples from three strains of inbred mice known to harbor genetically determined melanosomal differences, DBA/2J, C57BL/6J, and albino, and support a hypothesis that the development of glaucoma in adult mice is related to a deficit in tyrosinase. Host: Reg Penner

The Institute for Surface and Interface Science (ISIS) and  the Department of Physics, Condensed Matter present: Michael Grunze, Distinguished Visitor Angewandte Physikalische Chemie Universität Heidelberg October 11, 2006 4:00 pm 104 Rowland Hall Title: Chemical Nanolithography – from Nanosheets to Pyramids Abstract:   The development of simple and rapid techniques for the site-specific immobilization of single molecules or molecular aggregates is critical in many areas of nanoscience, e.g. for the definition of molecular contacts in ‘molecular electronics’ or the miniaturization of high throughput assays in molecular biology. Different techniques and strategies based on Scanning Probe Microscopies have been developed to chemically pattern substrates on a molecular length scale; they are, however, limited in speed and are difficult to combine with conventional microfabrication techniques. Here we present alternative paths to create molecular nanopatterns by combining electron beam lithography with novel self-assembling materials (SAMs). Since SAMs show specific sensitivity to irradiation, aliphatic and aromatic SAMs have been used as positive and negative electron beam resists, we use them as templates for growing nanostructured polymer brushes of various shapes, for the manufacturing of large and stable membranes with molecular thickness, and as spacers for the preparation of stable and defect free metal/organic monolayer/ metal sandwich structures. Host: Reg Penner

The Institute for Surface and Interface Science (ISIS) and The Department of Physics and Astronomy present: Dr. Ingo Köper Max Planck Institute for Polymer Research September 8, 2006 11:00 am 1201 Natural Sciences II Title: Biomimetic Surface Architectures Abstract:  We try to construct a surface architecture that provides on the one hand a biomimetic model for a biomembrane and is on the other hand simple and robust enough to be used in biosensing applications. Tethered membranes (tBLMs), as the most prominent example, have been proven during the last years to be a powerful and flexible bio-mimetic platform for the study of membrane protein in an artificial, but quasi-natural environment. Based on a lipid bilayer membrane that is coupled via a polymeric spacer group to a solid substrate they provide not only excellent stability but also the necessary conditions for functional incorporation of membrane proteins, especially fluidity and high electrical resistance. We could synthesize, using a generic synthesis approach, several lipids that allow the construction of membrane architectures both on gold as well on silicon surfaces and provide good electrical sealing properties. This enabled us to study the functional incorporation of membrane proteins. Examples for different peptides and proteins will be shown. Furthermore, characterization using a variety of surface analytical tools such as Surface Plasmon Resonance spectroscopy, quartz crystal microbalance or neutron reflectivity are used to characterize and investigate properties of the system. The molecular membrane-"construction kit" offers now the possibility to directly combine microelectronic read-out systems with a biological compound. Applications as biosensors will be discussed. Host:  Zuzanna Siwy

The Institute for Surface and Interface Science (ISIS), Chemical Bonding Center (CBC) and ICAM present: Torsten Meier Professor of Physics Philipps University, Germany July 27, 2006 2:30 pm 1201 Natural Sciences II Title: Ultrafast **Dynamics of Photocurrents in Semiconductor Nanostructures** analyzed by Microscopic Many-Body Theory Abstract: The coherent optical injection and temporal decay of spin and charge currents in semiconductor heterostructures is described on a microscopic basis. The approach includes excitonic effects and many-body Coulomb correlations as well as the carrier LO-phonon coupling on the second-order Born-Markov level. Furthermore, the light-field-induced intraband and interband excitations are treated nonperturbatively. Enhanced damping of the spin current relative to the charge current is obtained as a consequence of Coulomb scattering and a nonmonotonic dependence of the currents on the intensities of the two incident laser beams is predicted. Additionally, the influence of quantum-kinetic memory effects on the coherent transients is investigated. Host: Shaul Mukamel

Mats Persson Surface Science Research Centre/Dept of Chemistry The University of Liverpool June 15, 2006 3:00 pm 2201 Natural Sciences II Title:  Vibronic broadening, charge multi-stability and chemical bond formation on insulating films Abstract:  The recent spectacular progress in carrying out microscopy and spectroscopy of adsorbates on ultrathin, insulating films supported by metal surfaces in a scanning tunnelling junction has opened up a new fascinating field in atomic scale science and has revived the interest in double-barrier tunnelling junctions.  In this talk I will present some highlights of our on-going theoretical work done in collaboration with the experimental group of J. Repp and G. Meyer at IBM Zurich on manipulation and characterization by electron tunnelling in an STM junction of single atoms and molecules adsorbed on ultrathin, polar insulating NaCl films supported by a metal surface. These highlights include: (1) characterization of vibronic effects on electronic states of single Cl vacancies [1]; (2) charge multi-stability of single Au [2] and Ag adatoms; (3) frontier orbital reorganization in a single metallo-organic complex [3]. Our theoretical approach is based on density functional theory of the electronic structure. [1] J. Repp, G. Meyer, S. Paavilainen, F. E. Olsson, and M. Persson, Physical Review Letters 95, 225503 (2005) [2] J. Repp, G. Meyer, S. Paavilainen, F. E. Olsson, and M, Persson, Science 312, 1196 (2006) [3] J. Repp, G. Meyer, F. E. Olsson, and M. Persson, Science 305, 493 (2004)

ISIS Lunch Lecture Zhibin Guan Department of Chemistry University of California, Irvine June 8, 2006 11:45 am 2201 Natural Sciences II Title:   Soft Materials Synthesis: from Nano- to Biomaterials

Dr. Erik Winfree Computer Science, Computation and Neural Systems Caltech University April 28, 2006 3:00 pm 2201 Natural Sciences II Title: Algorithmic self-assembly of DNA Abstract:  Nucleic acids have proven to be remarkably versatile as an engineering material for chemical tasks including the storage of information, catalyzing reactions creating and breaking bonds, mechanical manipulation using molecular motors, and constructing supramolecular structures.  This talk will focus particularly on molecular self-assembly, giving examples of engineered DNA "tiles" that crystallize into two-dimensional sheets, one-dimensional tubes and ribbons, and information-guided patterns such as a Sierpinski triangle and a binary counter.  A theme is how cooperative binding can be used to control nucleation and direct selective tile attachment. Such "algorithmic" self-assembly may provide a bottom-up fabrication method for creating complex, well-defined supramolecular structures that can be used as scaffolds o r templates for applications such as arranging molecular electronic components into active circuits. Host: Regina Ragan

Professor Andrei Slavin St.Petersburg Technical University, Russia May 8, 2006 1:00 pm 2201 Natural Sciences II Abstract:  TBN Host: Chen Tsai

Professor Cynthia Friend Harvard University April 18, 2006 4:00 pm 104 Rowland Hall Title:  Surface Chemistry of Nanostructures:  Materials Synthesis and Chemical Reactivity. Abstract:  TBN Host: John Hemminger

Charles T. Campbell Department of Chemistry & Center for Nanotechnology University of Washington April 11, 2006 4:00 pm 104 Rowland Hall Title: Probing Chemical Reactions at Surfaces: A Few Novel Approaches Abstract:  A few novel approaches will be described for probing the details of chemical reactions occurring at solid surfaces.  These include microcalorimetric methods for measuring adsorption energies on well-defined surfaces and time-resolved SPR microscopy for probing the kinetics of biomolecular binding events at protein and DNA microarrays in high throughput.  Applications of these to elucidate details of surface reactions of importance in catalysis, microelectronics fabrication and biochemistry will be discussed.   First, measurements of the adsorption energies of intermediates in catalytic reaction mechanisms will be described.  Metal - carbon bond energies will be estimated from the adsorption energies of small hydrocarbons on metals like Pt(111).  Next, I will describe measurements of the energetics of thin film growth during MBE on well-defined surfaces of oxides, carbides, semiconductors, polymers and metals.  It will be shown that the adsorption energy of metals atoms is a reasonable predictor of the morphology and chemical reactivity of the thin metal film that evolves.  Finally, I will discuss the use of surface plasmon resonance (SPR) microscopy for high-throughput measurements of the kinetics of protein and ligand binding to microarrays of immobilized proteins or dsDNAs.  Using arrays of proteins spotted on a gold surface in ~100 mm diameter spots, it will be shown that SPR microscopy can be used to simultaneously monitor the kinetics of binding of proteins and even small ligands (<500 Da) to 1028 different protein spots with sensitivity to <0.05 pg (<106 protein molecules) in each array spot with a time resolution of 1 s.  The signals easily be can be quantified into absolute amounts bound per unit area, so that they provide absolute rate constants and binding stoichiometries at each spot. *  Work supported by NSF, DOE-BES Chemical Sciences, the Institute for Systems Biology and Lumera Corp... Host: Rob Corn

Sergei Tretiak Theoretical Division, Center for Nonlinear Studies and Center for Integrated Nanotechnologies Los Alamos National Laboratory April 5, 2006 4:00 pm 104 Rowland Hall Title: Photoprocesses in conjugated polymers and carbon nanotubes: similarities and differences Abstract:  This talk will discuss dynamics and relaxation of photoexcited states in technologically important organic materials (conjugated polymers and carbon nanotubes), investigated using time-dependent density functional theory (TDDFT) and time-dependent Hartree-Fock (TDHF)/semiempirical approaches. These techniques allow following the excited state molecular dynamics trajectories on fs to ns timescales in clusters up to several hundreds of atoms in size. Our analysis identifies specific fast and slow vibrational motions which are coupled to the electronic degrees of freedom. Relaxation of photoexcited states usually results in localization of electronic excitations into the "hot spots" (self-trapped excitons), which leads to the local lattice and torsional distortions and shows up as specific signatures in spectroscopic observables characteristic to molecular conformations. For example, in carbon nanotubes, combined experimental and theoretical study allows for direct observation of non-linear coupling and energy transferbetween vibrational modes mediated by photoexcited dynamics.

Regina Ragan, Assistant Professor Chemical Engineering and Materials Science March 9, 2006 12:00 pm 2201 Natural Sciences II Title:  Self-assembled nanostructures - understanding kinetic and thermodynamic driving forces.

Professor Chaim N. Sukenik Chemistry Department Bar-Ilan University February 17, 2006 2:00 pm 1114 Natural Sciences I Title:  Chemistry at Surfaces: From Self-Assembled Monolayers to Ceramic Thin Films Abstract: Self-Assembled Monolayer (SAM) films can provide surface modification that is both uniform and stable. The direct deposition of functionalized self-assembled monolayers is a simple route to surfaces with customized chemical and physical properties. In situ chemical transformations within an already established monolayer provide a versatile and effective way to install functionality that would otherwise be incompatible with the monolayer-anchoring functionality with which it must coexist prior to SAM formation. SAM modification can also fine-tune monolayer reactivity and provide useful approaches to patterned surfaces which can then be used as templates for further, site specific, surface elaboration. The effective implementation of in situ monolayer chemistry requires reactions that do not compromise monolayer integrity as well as an awareness of the constraints imposed by the organization of the monolayer environment. This presentation will describe a number of examples where functional group chemistry within a self-assembled monolayer film is affected by the constraints of monolayer packing and organization. Examples from carboxylic acid chemistry will be described, along with studies of the influence of the monolayer on both electrophilic and nucleophilic processes. Unexpected behavior in both the yield and selectivity of interfacial chemical processes will be described along with an attempt to understand the extent to which monolayer organization can perturb interfacial properties and processes. Functionalized monolayer surfaces will also be shown to provide a tunable template for the subsequent deposition of ceramic films from aqueous solution under near ambient conditions. We will provide examples of finely controlled metal oxide deposition along with an extension of this chemistry to the surface modification of polymers and polymer composites. Host: Ken Shea

Professor Peter Taborek Department of Physics and Astronomy University of California, Irvine February 23, 2006 2201 Natural Sciences II Title:  Wetting, Drops, and Pinch-off in super and normal fluids Abstract: Topics which I will use as a stimulus for questions and discussion include: 1) An overview of the wetting experiments in our lab which primarily     involve helium on alkali metal surfaces prepared in UHV. 2) Movies of superfluid contact line motion 3) Pictures and movies of  the final stages of droplet break-up 4) Plans for engineering ultra-weak surfaces using laser ablation

Professor Joseph Zyss Molecular Quantum Photonics Laboratory and d'Alembert Institute Ecole Normale Supérieure Cachan, France January 26, 2006 2:00 pm 2201 Natural Sciences II Title:  Advances in Nonlinear Light-Matter Interactions in Molecular Media: from Materials to Single Molecules Abstract: We will first discuss recent results on new nonlinear optical multi-valued optical memories allowing for high density (e.g. with tensorial multiplicity) optical data storage and opening the way towards new possibilities of light steering for functional entities in biological environment. This recent development [1, 2] is at the outcome of over a decade long combined physics and chemistry fundamental research ongoing avenue building-up on interference of multiphoton absorption pathways in relevant molecular systems. Direct implementation of basic symmetry considerations pertaining to molecular symmetry and light polarizations will be shown to govern the practical ability of rotating and displacing molecules by light, down to the single molecular scale. Implementation of multiphoton schemes under the microscope opens-up a wealth of new imaging as well as sensing with high sensitivity and ultimate spatial resolution in conjunction with adequate nonlinear or fluorescent labelling. A powerful approach along this avenue consists in combining coherent and non-coherent multiphoton effects under the confocal microscope with polarization and phase resolution. It allows to map-out with sub-micron resolution, local order parameters of "inhomogeneous" matter up to unprecedented high accuracy (for example 6th order Legendre polynomial in the case of cylindrical symmetry poled polymers) [3,4]. We will particularly emphasize a new imaging scheme which is possibly our most striking and simplest evidence of the direct connection between telecom and life science. It may be viewed as an original "optical patch-clamp" system directly deriving from the linear electro-optic Pockels effect at the tip of a confocal microscope in an interferometric configuration [5]. Preliminary results will be presented, on the way to our basic goal in the realm of biophotonics and neurophysiology which aims at providing direct non-contact dynamical imaging of electric action under a contact-less sub-mW CW level of laser power, in strong contrast with the currently used more aggressive techniques. These are only a few examples that are extracted from the broader emerging field of NanoBiophotonics [6] currently emerging at the interface of Physics, Chemistry and Life Sciences, a challenging area of both fundamental and applied nanoscience where life science goals and information technologies means are joining hands. [1] Encoding multipolar polariztion patterns by optical poling in polymers: towards nonlinear optical memories, S.Bidault, J.Gouya, S.Brasselet, J.Zyss, Optics Express (13), 505(2005) [2] Coherent control of the optical nonlinear and luminescence anisotropies in molecular thin films by multiphoton excitations, S.Bidault, S.Brasselet, J.Zyss, Opt.Lett. 29(11), 1242(2004) [3] Monitoring of Orientation in Molecular Ensembles by Polarization Sensitive Nonlinear Microscopy, V.Le Floc'h,S.Brasselet,J.F.Roch,J.Zyss, J.Phys.Chem.B 107, 12403-12410(2003) [4] In-situ diagnostics of the crystalline nature of single organic nano-crystals by nonlinear microscopy, S.Brasselet, V.Le Floc'h, F.Treussart, J.F.Roch, A.Ibanez , J.Zyss, Phys.Rev.Lett. 92(20), 207401 (2004) [5] Two international patents filed in 2003 under #0310116 and #0310117 by J.Zyss and T.Toury [6] see articles in "Molecular Nanoscience" (dedicated to Daniel Chemla for his 65th birthday), a special issue of Chemical Physics, J.Zyss and C.Shank editors (vol.318/1-2, 15 Nov. 2005) Host: Shaul Mukamel

Professor Paul S. Cremer Department of Chemistry Texas A & M University January 25, 2006 3:00 pm 2201 Natural Sciences II Title: Protein and Polymer Folding on a Chip   Abstract:  We have designed temperature gradient microfluidic devices that allow high throughput, low sample volume assays to be performed on the folding of thermoresponsive polymers and proteins.  These macromolecular systems are insoluble at high temperatures, but become hydrated and unfold as the temperature is decreased in a process analogous to the cold denaturation of proteins.  Our assays enable highly precise measurements to be made rapidly of the physical behavior of the polymers.  The device is specifically used to obtain data on poly (N-isopropylacrylamide) and__-elastin at multiple concentrations in the presence of a variety of ions.  The results indicate that the folding process follows the Hofmeister series.  This series, which dates back to 1888, is a rank ordering of anions and cations based upon their ability to salt-out or salt-in proteins.  It had been historically believed that ions affect macromolecule solubility indirectly through their interactions with bulk water.  This idea has been largely disproved by a variety of characterization techniques over the last decade.  A new theory to explain the mechanism of the Hofmeister effect, however, still needs to be developed.  Microfluidic assays in combination with vibrational sum frequency spectroscopy allowed us to develop a model based solely on the direct interaction of the ions with a macromolecule and its first hydration shell.  In fact, the protein folding properties can be related to a few simple factors: an ion's hydration entropy, its effect on the surface tension of an aqueous interface, and its ability to interact directly with binding sights on a protein. References (1) Yanjie Zhang, Steven Furyk, David E. Bergbreiter, and Paul S. Cremer,  J. Am. Chem. Soc. 127 (2005) 14505-14510 (2) Marc C. Gurau, Soon-Mi Lim, Edward T. Castellana, Fernando Albertorio, Sho Kataoka and Paul S. Cremer, J. Am Chem. Soc. 126 (2004) 10522-10523 (3) Hanbin Mao, Chunmei Li, Yanjie Zhang, David E. Bergbreiter, and Paul S. Cremer  J. Am. Chem. Soc. 125 (2003) 2850-2851 (4) Hanbin Mao, Tinglu Yang, and Paul S. Cremer, J. Am. Chem. Soc. 124 (2002) 4432-4435 Host: John Hemminger

Lorenzo Pavesi Professor of Experimental Physics University of Trento, Italy January 24, 2006 2:00 pm McDonnell Douglas Auditorium Title:  Silicon nanostructures to enable Silicon photonics   Abstract: In this talk, I will review the photonic applications of nanostructured silicon. As we change the dimensionality of silicon very fascinating and new optical properties of the material appear. In particular, light emission starts to be a very efficient process in nanostructured silicon and light emitting diodes with efficiency in excess of 1% have been fabricated. Optical amplification has been also observed when silicon nanocrystals are embedded into a dielectric matrix. This makes the system a potential candidate for laser action. In addition to electronic property variations, nanostructured silicon can be also used as a nanodielectric material, where controlled changes in the refractive index can lead to trapp ing or slow down of photons. Some examples will be discussed where photonic Bloch oscillations, photonic Zener tunnelling and high quality microcavities are demonstrated. All these various phenomena pave the way to a new field of applications for the "old dog" of microelectronics. Host: Chen Tsai

ISIS Lunch Lecture Doug Tobias Department of Chemistry University of California, Irvine November 18, 2005          11:45 pm 1115 Natural Sciences II Title:  Ions at the air-water interface.

The Institute for Surface and Interface Science (ISIS) presents: Professor Claudio Serpico Department of Electrical Engineering Professor of Elettrotecnica University of Naples, Italy October 28, 2005 3:00 pm 1114 Natural Sciences I Title:  Nonlinear Magnetization Dynamics in Nanomagnets Driven by Spin-Polarized Currents. Abstract:  Phenomenological (continuum) description of ferromagnetic materials: the micromagnetics model and the Landau-Lifshitz-Gilbert (LLG) equation. LLG dynamics in uniformly magnetized bodies. The Slonczewski term in LLG equation to model the effect of spin-polarized current injection. Energy balance in spin-torque driven system. Equilibria e self-oscillations. Perturbation approach: spin-torque driven dynamics as a perturbation of conservative (precessional) dynamics. Melnikov technique to study existence, stability and bifurcations of self-oscillatory regimes. Representation and classification of phase portraits. Application of the theory to explain experimentally observed phenomena: 'red shift', 'blue shift' and jumps in self-oscillation frequency. Analysis of thermal stability in spin-torque driven magnetization dynamics. Fokker-Planck equation for the free energy probability distribution. Arrhenius formula for spin-driven dynamics regimes. Quantitative predictions and tentative comparison with experiments. Host: Doug Mills

Dr. Aristide Dogariu College of Optics and Photonics/CREOL University of Central Florida August 1, 2005 11:00 am 4135 Frederick Reines Hall Title:  Statistical Optics at Subwavelength Scales Abstract:  Next generation photonics-based technologies will ultimately rely on novel materials and devices. To assist in this development, optical phenomena in the proximity of material structures are actively studied to advance both fundamental knowledge and experimental capabilities. At subwavelength scales, the statistical properties of optical fields are determined by both propagating and evanescent components and, as a result, characteristics such as first- and second-order statistics as well as the spectral density are all affected. Based on the coherence properties at subwavelength scales, new possibilities exist for surface and subsurface diagnostics. Manipulating the statistical properties of the radiation at these scales provides means for designing novel concepts for robust, integrated sensing techniques with resolution below the propagating light’s wavelength. Host:  Alexei A. Maradudin

The Institute for Surface and Interface Science (ISIS) presents: Professor Reshef Tenne The Drake Family Chair in Nanotechnology Head, Department of Materials and Interfaces Director, Helen and Martin Kimmel Center for Nanoscale Science Weizmann Institute - Israel June 2, 2005 2:00 pm 306 Rowland Hall Title: Inorganic nanotubes and inorganic fullerene-like materials from layered compounds: from concept to applications Abstract: We have proposed in 1992 that nanoparticles of layered compounds will be unstable against folding and close into fullerene-like structures and nanotubes (IF). Initially this hypothesis was realized in WS2, MoS2 and the respective diselenides. Subsequently, nanotubes and fullerene-like structures were prepared from numerous compounds with layered and recently also non-layered structure by various groups. Much progress has been achieved in the synthesis of inorganic nanotubes and fullerene-like nanoparticles of WS2 and MoS2 and many other metal dichalcogenides over the last few years. Synthetic methods for the production of multiwall WS2 nanotubes by sulfidizing WO3 nanoparticles have been described and further progress is underway. A fluidized-bed reactor for the synthesis of up to 100 g/day of fullerene-like WS2 nanoparticles has been established in our lab, and the scaling-up of the synthesis to 100 kg/day and above is under way. The detailed mechanisms for the synthesis of fullerene-like WS2 and MoS2 nanoparticles and nanotubes of these compounds have been elucidated. Substantial progress has been accomplished in the use of such nanoparticles for tribological aUCpplications and lately as nanocomposites, for e.g. impact resilient materials for self-protection. Few testing programs have been undertaken together with different laboratories and major industrial partners and have clearly indicated the usefulness of the fullerene-like WS2 (MoS2) as solid lubricants in various products. These tests indicated that IF-MoS2 and IF-WS2 are heading for large scale applications in the automotive, machining, aerospace, electronics, medical and numerous other kinds of industries. This technology was licensed to "NanoMaterials", which is currently involved in many collaborative development programs. Orders for about 2000 tons/year have been secured and further orders from major industrial partners are expected shortly. Novel applications of inorganic nanotubes and fullerene-like nanoparticles in the fields of catalysis; microelectronics; Li rechargeable batteries; medical and opto-electronics will be presented. Host: Reginald Penner

Margret Giesen Institute of Thin Films and Interfaces Institut fuer Schichten und Grenzflaechen Juelich, Germany May 6, 2005 2:00 pm 1114 Natural Sciences I Title:  The Discovery of Slowness: A scanning tunneling microscopy expedition to the atomic motion at interfaces Abstract:  With the shrinking dimensions of today's device structures it becomes more and more important to consider the problem of the stability of nanostructures on the atomic scale. Among the large number of possible atomic diffusion processes on surfaces those are most important for the stability of nanostructures which have high activation barriers and therefore are scarce at low surface temperatures. Although the scanning tunneling microscope (STM) is capable to image the atomic structure of surfaces, mobile atoms at high temperatures cannot be displayed. In order to gain information on the stability of nanostructures at realistic operation temperatures of devices where atomic motion is too fast to image with the STM, we make use of indirect methods based on thermodynamics models. In this talk an overview is given on experimental data from interfaces in ultrahigh vacuum as well as in electrolyte and how one may analyze STM image series in order to obtain basic information and energy parameters of atomic interface transport processes. Host: Doug Mills

The Institute for Surface and Interface Science (ISIS) and the Department of Chemistry present: Professor Daniel Buttry University of Wyoming May 10, 2005 4:00 pm 104 Rowland Hall Title:  Redox Active Nanoparticles as New Battery Materials Host:  Nien-Hui Ge

The Institute for Surface and Interface Science (ISIS) presents: K.L. Ngai Senior Scientist and Theoretical Consultant Electronic Science & Technology Division Naval Research Laboratory, Washington, D.C. May 13, 2005 2:00 pm 1114 Natural Sciences I Title:   The dispersion of the structural relaxation: a governing factor of the structural relaxation time and glass transition Abstract:  Glass transition by decreasing temperature or increasing pressure occurs when the structural relaxation time, ta, becomes so long that the system falls out of equilibrium.     Theories and models including the celebrated free volume and configurational entropy models explain the glass transition by invoking one quantity or the other that governs the structural relaxation time. However, invariably the dispersion of the structural relaxation is derived either as a parallel consequence independent of ta, or considered as an afterthought.  In no way the dispersion plays any fundamental role in determining ta and other dynamic properties. In this paper, we show these theories and models are untenable because they cannot explain a general experimental fact recently discovered in many glass-formers. The remakable experimental finding from dielectric relaxation data collected at various combinations of temperature and pressure but having the same ta is that they also have exactly the same dispersion. If the dispersion of the structural relaxation is another consequence of a theory or model independent of ta, it is unlikely that both ta and the dispersion can be maintained invariant to the same combinations of temperature and pressure.     On the other hand, the Coupling Model of the speaker can explain the observed properties. Other recent advances of the Coupling Model will be presented. Hosts: Doug Mills and Albert Ye

Professor Qi-Kun Xue Institute of Physics The Chinese Academy of Science, China March 24, 2005 4:00 pm 2111 Frederick Reines Hall Title:  Superconductivity Modulated by Quantum Size Effects Abstract: It is well-known that the electrons confined in a perfectly uniform thin film are quantized into discrete energy levels in the vertical direction, forming standing-wave like eigenstates, known as quantum well states (QWSs). This has been proven to modulate significantly the electronic distribution near the Fermi level (EF), and thus the physical and chemical properties of a thin film material.  We have successfully fabricated ultra-thin Pb films on Si substrates with atomic-scale control of the thickness over a macroscopic area using a low-temperature growth method, and investigated thickness-dependent surface morphology and electronic structure of the films by photoemission spectroscopy and scanning tunnelling microscopy.  An oscillatory superconducting transition temperature was observed when the film is increased by one atomic layer at a time. We demonstrate that this non-monotonic dependence is a spectacular manifestation of the Fabry-Perot modes of electron standing waves, the QWS, in the ultrathin films, which modulate the electron density of states near the Fermi level and electron-phonon coupling, the two factors controlling superconductivity transition. Our work has thus opened the door for quantum engineering of superconductivity and other properties of thin films. In collaboration with Yan-Feng Zhang, Yang Guo, Xin-Yu Bao, Tie-Zhu Han, Zhe Tang, E. G. Wang, Jin-Feng Jia, Zhong-Xian Zhao (IOP), Qian Niu (UT Austin) and Z. Q. Qiu (UC Berkeley) Host:  Wilson Ho

The Institute for Surface and Interface Science (ISIS) presents: Professor Conrad Becker Institute of Physical and Theoretical Chemistry University of Bonn March 3, 2005 1:00 pm   1114 Natural Sciences I Title:  Low temperature STM investigation of thin alumina films on Ni3Al(111) Abstract:  The high temperature oxidation (T = 1000 K) of Ni3Al(111) under ultrahigh vacuum conditions leads to the formation of a thin well-ordered alumina film. This film has been characterized using low temperature scanning tunneling microscopy (LT-STM), spot profile analysis low energy electron diffraction (SPA-LEEED), and scanning tunneling spectroscopy (STS). It was shown that the alumina film exhibits a nanoscopic superstructure (a = 4.16 nm) that is commensurate with the substrate lattice. The apparent topography of the alumina film in STM strongly depends on the bias voltage. This effect can be related to the electronic structure of the film using STS. Most importantly a localized state in the band gap of the alumina has been found that is responsible for contrast reversal observed in STM. Because of the well-ordered structure of the alumina film (and the localized electronic state in particular) the alumina film can be used as a template for the nanostructured growth of metal clusters by physical vapor deposition. In the case of Pd and V the growth leads to particularly well-ordered cluster arrays. Host:  Wilson Ho

The Institute for Surface and Interface Science (ISIS) presents: Dr. Harald Ibach Research Center Jülich ISG3 Jülich, Germany February 18, 2005 3:00 pm 4112 Natural Sciences I Title:  Some remarkable consequences of the thermodynamics of charged  surfaces Abstract:  Surfaces in vacuum are kept at constant (zero) charge, surfaces in contact with an electrolyte are held at constant potential. This seemingly trivial statement has some remarkable, far-reaching consequences. For example the surface tension, by definition the work to create a surface per area is the specific Helmholtz free energy f for surfaces in vacuum. For surfaces in an electrolyte the surface tensions is with  s the specific surface charge. The free energy is a linear function of the potential at the potential of zero charge, the surface tension  g has a maximum there. While this is well known to the community of electrochemists the consequences of the different thermodynamic boundary condition for the nanoworld were hitherto not explored. I show that the facet-to-rough transition in the equilibrium shape of crystals is abrupt in an electrolyte vicinal surfaces in an electrolyte are always unstable with respect to step bunching all activation energies for atom migration and the creation energies to first order depend linearly on the surface charge. This makes all surface transport rate depend exponentially on the charge, i.e. app roximately exponential on the potential.  The well-known effect of electrochemical annealing thereby finds a natural explanation. By using ab initio calculations of dipole moments of defects our analysis provides a quantitative description of experimental data on Ostwald ripening. Host: Doug Mills

The Institute for Surface and Interface Science (ISIS) presents: Dr. Gerald Mahan Department of Physics Pennsylvania State University February 4, 2005 3:00 pm 1114 Natural Sciences I Title:  Phonons in Nanowires and Nanotubes Abstract:  TBN Host:  Doug Mills

The Institute for Surface and Interface Science (ISIS) presents: NanoScience Recruitment Seminar Dr. Kenneth Cooper Department of Physics University of California, Santa Barbara January 21, 2005 3:00 pm 1114 Natural Sciences I Title:  Quantum Coherence and Coupling in Superconducting Josephson Phase Qubits Abstract:  Superconducting circuits based on Josephson tunnel junctions are promising qubit candidates for a quantum computer because their quantum properties can be engineered using conventional microelectronic technology.  I will discuss our recent progress in identifying sources of decoherence in Josephson phase qubits and in coupling multiple qubits for eventual quantum logic operations.  Using a novel few-nanosecond readout technique, we have made the first observation of coherent quantum coupling between a qubit and a microscopic two-level system associated with decoherence in phase qubits.  Experiments on loss mechanisms in classical superconducting resonators also point to environmental two-level systems as a source of qubit decoherence.  These results indicate that qubit performance will greatly benefit from circuit materials improvements.  We have also investigated multi-qubit systems by fabricating pairs of capacitively coupled qubits.  The fast readout technique allows us to perform simultaneous single-shot measurements of the qubits individually and detect time-domain antiphase oscillations between t he two-qubit basis states.  This opens the possibility for the characterization of multi-qubit gates and elementary quantum algorithms once the single-qubit coherence times are improved. Host:  Doug Mills

Michael R. Diehl California Institute of Technology January 7, 2005 3:00 pm 1114 Natural Science I Title: Engineering Functional Multiprotein Assemblies (Exploring Cooperative Biomotor Dynamics with Single Molecule Sensitivity) Abstract: In nature proteins often coordinate in the form of architecturally rich assemblies.  This prevalence is particularly common with linear biomotor proteins, a class of mechanochemical enzymes that use the energy released during nucleotide hydrolysis to produce motion along 1-dimentional polymer tracks.  At a basic level, clustering these Brownian motors into functional groups is known to lead to a non-linear enhancement of movement due to the suppression of the stochastic fluctuations exhibited by individual motors.  Here, we explore such effects through the rational engineering of multi -biomotor protein assemblies, where the molecular nature of intermotor coupling is acutely controlled.   Our approach involves the synthesis of protein-based templates through the in vivo expression of artificial genes.  This synthetic route provides genetic level control over macromolecular architecture, and consequently, discrete control over number of coupled motors, intermotor distance as well as the nature of the elastic interconnects between motors.  The materials approach to supramolecular biophysics adopted here provides unique insight into molecular communication mechanisms that can be used to regulate biomotor transport.  For example, our results demonstrate that coupling several motors along a single polymer backbone leads to an enhancement of motor activity beyond what is gained from generic clustering mechanisms. These mechanisms can be distinguished due to our ability to probe the molecular orchestration that occurs in multi-unit biomotor assemblies with single molecule sensitivity.  Furthermore, the molecular and nanoscale tools developed here should provide generic handles to engineer multiprotein assemblies, and be readily applied to a host of non-motor protein systems. Host:  Doug Mills

Joint ISIS and Condensed Matter Physics Seminar Mats Persson Department of Applied Physics Chalmers/Göteborg Universit December 8, 2004    4:00 pm 1114 Natural Sciences I Title: Control of matter on the atomic scale Abstract: The fiction to control matter on the atomic scale is becoming a reality by the unique capabilities provided by the scanning tunnelling microscope to image, characterize and manipulate single atoms and molecules on surfaces.  A recent milestone has been the ability to control the charge state of a single gold atom on a thin insulating, polar film [Science 305, 493 (2004)]. In this talk, I will present a theory of this charge state control, which is based on density functional calculations and involves inelastic electron tunnelling (IET) attachment. As an introduction, I will also present some of our theory of si ngle molecule vibrational spectroscopy and chemistry, in which IET is also a key mechanism. Host: Doug Mills

The Institute for Surface and Interface Science (ISIS) presents: Sergey A. Nikitov Professor and Deputy Director Institute of Radieengineering and Electronics Russian Academy of Sciences December 3, 2004 2:00 pm 1114 Natural Sciences I Title:  YIG Thin Film-Based Two-Dimensional Magnonic and Magneto-Photonic Crystals Abstract:  Propagation properties of photonic crystals (PCs), stop-bands in particular, depend on the wavelength of the waves involved. Conventional PCs made of opals, colloid particles, nanostructured films, etc., are normally studied in the visible light frequency range. Such PCs when operating in a microwave frequency range must carry large dimensions. In contrast, magnonic crystals (MCs) operating in the same microwave frequency range involve micron size dimensions. The properties of microwave propagation in MCs are closely related to spin waves. In this talk, we report the first experimental realization of such MCs and present the theoretical and experimental results on spin waves propagation. From the practical point of view two-dimensional (2-D) MCs that utilize ferromagnetic waveguide with 2-D inhomogeneities of magnetization is preferred. We have fabricated yttrium-iron-garnet (YIG) film-based MCs in which 2-D arrays of holes are incorporated. The holes diameter and periodicity were chosen close to the half-wavelength of the magnetostatic spin wave (MSW) in order to fulfill Bragg reflection condition. The YIG film dimensions are 1.5 cm x 0.5 cm in area and 5 _m in thickness. The periodic structures of holes were prepared by the photolithography method. Depth of holes was varied from 1.0 to 4.5 _m  in order to ensure sufficient changes in the magnetic parameters of the YIG film. The holes period was varied from 20 to 40 _m. The spin wave spectrum in 2-D periodic structures has been calculated using Landau-Lifshitz equation for magnetization motion, Maxwell's equations with respective boundary conditions at the film surfaces and periodic boundary conditions. It was found that stop bands exist in the spin wave spectrum. The location of stop-band depends on the external magnetic field and the film parameters. Delay-line configurations were fabricated in the YIG film-based 2-D MCs for experimental study of the MSW spectrum. The stop bands for spin waves were found to be tunable by an external magnetic field. In addition, the MSW excitation band in the MC was found to decrease by an order of magnitude. Specifically, the measured bandwidth was reduced from 400 to 50 MHz when the 2-D holes structure was incorporated in the YIG film. Furthermore, the propagation of optical waves in a magnetic waveguide with periodic domain structures, called magneto-photonic crystals (MPC), has been investigated. It is shown that conversion between propagating modes in 2-D periodic domain structures depends strongly on the parameters of the domain structure. Dispersion and anisotropic properties of the interacting modes and the dependence of the intensity of the converted mode on the parameters of the domain structures will be reported. Host: Chen Tsai

The Institute for Surface and Interface Science (ISIS) presents: Andreas Heinrich IBM Almaden Research Center November 18, 2004 4:30 pm 4135 Frederick Reines Hall Title:  The Miracles of inelastic spectroscopy on the atomic scale Abstract:   This  talk  focuses  on  low-temperature  spectroscopic  measurements  with scanning   tunneling   microscopes   (STM)   on  metal  surfaces.  A  brief introduction  is  given  into  the  by  now  well-established  field of STM spectroscopy  of  the  local  density  of  states.  We  will then focus our attention  on  the  more recent development of inelastic spectroscopy where the tunneling electrons give off energy to local excitations. Two examples will be discussed in some detail: 1) Vibrational spectroscopy of CO on Cu (111). This is one of the text book examples  of  vibrational  spectroscopies  studied  extensively  with  many surface science techniques. We will focus our attention on the detection of carbon  isotopes  with  the  STM  and  its use in understanding the hopping mechanism of molecule cascades. 2) Single-atom spin flip spectroscopy. The energy levels of a magnetic atom split  in  an  applied  magnetic  field:  the  Zeeman  splitting. Inelastic tunneling spectroscopy can be used to measure the Zeeman energy one atom at a  time  at T=0.5K and B=7T. When a magnetic atom is coupling strongly with its  environment  (conduction  electrons) the onset of Kondo physics can be observed. Host:  Doug Mills

Professor Nongjian Tao Electrical Engineering, Chemistry & Biochemistry Arizona State University November 22, 2004 4:00 pm 104 Rowland Hall Title:  Wiring Molecules into an Electrical Circuit: From Single Molecule Electronics to Biosensors Abstract: The ability to measure and control current through a single molecule is a basic requirement towards the ultimate goal of building an electronic device using single molecules. It also allows one to read the chemical and biological information of the molecule electronically, which opens the door to chemical and biological sensor applications based on electrical measurement of individually wired molecules. To reliably measure the current, one must: 1) provide a reproducible contact between the molecule and two probing electrodes; 2) find a signature to identify that the measured conductance is due to not only the sample molecules but also a single sample molecule; 3) provide a third gate electrode to control the current; and 4) carry out the measurement in aqueous solutions for biologically relevant molecules in order to preserve their native conformations. We have developed a method to attach a single molecule to two electrodes via covalent bonds and control the current through the molecule with an electrochemical gate. The method allows us to reliably measure single molecule conductance of many systems, including peptides and DNA in aqueous solutions. By simultaneously measuring the conductance and the force required to break a molecule from contacting the electrodes, we can identify how many molecules are involved in the measurements and if the molecules are indeed covalently bonded to two electrodes. We have studied the dependence of the conductance on the gate voltage, sequence, length as well as specific bindings of the molecules with other species. Host:  Reg Penner

The Department of Physics and Astronomy and The Institute for Surface and Interface Science present: Professor Alexei A. Maradudin Research Professor University of California, Irvine November 3, 2004 4:00  pm 1114 Natural Sciences I Title:   The Design of Two-Dimensional Randomly Rough Surfaces with Specified Scattering Properties Abstract: The great majority of theoretical studies of the scattering of waves from randomly rough surfaces have been devoted to the direct problem, in which the surface profile function and its statistical properties are specified, and it is the angular distribution of the intensity of the scattered field and its polarization properties that it sought.  Comparatively little attention has been devoted to the inverse problem, in the usual formulation of which scattering data are provided by experimentalists, and the surface profile function, or some statistical properties of it are sought.  In this talk I consider a somewhat different version of the inverse problem, namely one in which the goal is to design, and ultimately to fabricate, a two-dimensional randomly rough surface that produces a specified angular distribution of the intensity of the field scattered from it.  The approach used to solve this problem is based on the geometrical optics limit of the Kirchhoff approximation for scattering from a Dirichlet surface, but the results are shown to be more generally valid by means of computer simulation calculations.  It is illustrated by applying it to the design of surfaces that scatter light with a constant intensity within various regions of scattering angles and produce no scattering outside these regions; surfaces that act as Lambertian diffusers; and surfaces that produce a scattered field with a specified amplitude correlation function.  Relevant experimental results will also be presented. Host: A. Chernyshev

The Department of Physics and Astronomy and The Institute for Surface and Interface Science present: Dr. Kai Liu Physics Department University of California, Davis June 2, 2004 4:00 pm 1114 Natural Sciences Title: Nanoscale Construction and Magnetic Fingerprinting Abstract:  Nanostructured materials often exhibit novel properties as their physical dimensions become comparable to certain characteristic length scales. However, the ease of fabrication and characterization of such nanostructures often scales inversely with the physical dimensions.  In the first part of my talk, I will present our recent efforts in achieving magnetic nanostructures cost-effectively over macroscopic areas. A combination of techniques, including nanoporous alumina shadow mask, pulsed electrodeposition, sputtering, evaporation, reverse micelle, and lithography methods have been used to realize nanowires, nanodots, core/shell nanoparticles, and other patterned nanostructures. Magnetic and spin-dependent transport properties of these materials will be will be illustrated. In the second half of the talk, I will present a recently developed First-Order Reversal Curve (FORC) technique for characterizing magnetic nanostructures. The method uses a large number of partial hysteresis curves to obtain detailed information about the distribution of magnetic properties of a system. Studies on Co/Pt perpendicularly magnetized thin films will be shown to illustrate the magnetization reversal processes. The macroscopic features observed by FORC are further confirmed by microscopic studies using Transmission X-Ray Microscopy (TXRM).  Our results demonstrate that FORC can potentially be used as a "fingerprinting" tool for magnetic systems. Host:  Doug Mills

Dr. Andreas Berger Hitachi Global Storage Technologies May 7, 2004 3:00 pm 110 Engineering Lecture Hall Title:  The Computer Hard Disk Drive - Nanotechnology on a 100 Dollar Budget Abstract:  Nanotechnology is expected to change and shape our lives in the 21st century. It is, however, not just a far out vision, but actually part of our daily lives already. The computer Hard Disk Drive (HDD), which is found in all Personal Computers and increasingly in consumer electronics applications, is one of the technologies that requires and utilizes nm-scale precision already today. In my talk, I will give a basic introduction into HDD technology and outline some of today's challenges related to the nanometer scale of its components. In detail, I will discuss modern magnetic disk media, in particular the recently introduced Anti-Ferromagnetically Coupled (AFC) media and laminated media, which enable storage densities above 100 Gbits/inch2. Further topics include the product-readiness approaching technology of perpendicular magnetic recording as well as long-term alternative magnetic storage solutions.

Professor Valeriy Sterligov University of Nice May 14, 2004 3:00 pm 2111 Frederick Reines Hall Title:  Studies of the Optical Properties of Nanosized Objects Abstract:  The physics of nanosized structures has grown extensively in the recent past. Nanosized structures are developing very quickly, becaus e many applications in nano-optics, nano-electronics, etc. become more realistic in view of possible applications. In this talk the results of studies of the optical properties of nanosized metallic particles, organized arrays of empty or metal filled nanopores, ordered mesoporous silica films, and colloidal suspensions will be presented. These objects were studied by scattering, reflection, and transmission of volume and surface electromagnetic waves. Host: Alex Maradudin

The Institute for Surface and Interface Science (ISIS) presents: Professor Nicola Manini Department of Physics University of Milan May 3, 2004 3:00 pm 4135 Frederick Reines Hall Title: Hund's Rule Magnetism in C60 Ions? Abstract:  We investigate the occurrence of Hund's rule magnetism in Cn±60  molecular ions, by computing the ground-state spin for all charge states n from -3 to +5. The two competing interactions, electron-vibration (e-v, including Jahn Teller, favoring low spin) and electron-electron (e-e, including Hund-rule exchange, favoring high spin), are accounted for based on ab-initio coupling parameters. The reliability of these couplings is discussed by comparison with photoemis-sion and magnetic resonance experiments. We calculate and classify the static Jahn-Teller distorted states for all n, inclusive of both e-v and e-e effects. We then correct these adiabatic results by including the zero-point energy lowering associated with softening of vibrations at the adiabatic Jahn-Teller minima. Our overall result is that while, like in previous investigations, low-spin states prevail in negative ions, Hund's rule high spin dominates all positive Cn+60  ions. This suggests that Hund-rule magnetism could arise in fullerene cation-based solid compounds, particularly those involving C2+60, such as (AsF6)2 C60. N. Manini1 , A. Bordoni1, P. Gattari1, M. Lueders2, M. Fabrizio2, and E. Tosatti2 1Dipartimento di Fisica, Universit`a di Milano, Via Celoria 16, 20133 Milano, Italy; 2International School for Advanced Studies (SISSA), Via Beirut 4, 34014 Trieste, Italy. Host: Doug Mills

Professor Gerd Bergmann Department of Physics University of Southern California April 9, 2004 3:00 pm 110 Engineering Lecture Hall Title: Induced Spin-Currents in Alkali Films Abstract: In thin alkali films, which are weakly coupled to a ferromagnetic substrate, one observes large spin currents. This is due to the potential difference for spin up and spin down electrons at the interface. The spin current is detected by in situ coverage of alkali films with 1/100 atomic layers of Pb or Au. These impurities possess strong spin-orbit scattering. And they generate a large anomalous Hall effect in the presence of a spin current. Host: Jia Grace Lu