"Mechanics of Low Dimensional Materials - Plasticity and Fracture", Horacio D. Espinosa, James and Nancy Farley Professor of Mechanical Engineering, Northwestern University. Host: Daniel Lopez

In the past decade, there has been a major thrust to synthesize low dimensional materials exhibiting unique and outstanding physical properties. These nanomaterials are envisioned as building blocks for the next generation of lightweight materials, electronics, sensors, and energy systems. In these applications, identification of size and time dependent mechanical properties is essential. However, such endeavor has proven challenging from both experimental and modeling perspectives. In this presentation, progress in nanoscale mechanical experimentation and modeling, towards accurate identification of plasticity and fracture, will be discussed. Two case studies will be examined. In the first one, the plasticity and time dependent fracture of silver nanowires will be explored by means of in situ electron microscopy testing and molecular modeling. We will show that silver nanowires are very strong and exhibit an unusual Bauschinger effect arising from high surface to volume ratios. Interestingly, we will also show that the same feature can lead to stress-driven atomic surface diffusion, leading to time dependent failure instabilities under constant strain conditions. In a second case study, we will discuss the mechanical properties of graphene oxide, a material presenting functional groups ideal for synthesis of multilayer nanocomposites and membrane filtration films. The effect of chemical functional group type and density on monolayer toughness, stiffness, and strength will be ascertained using a combination of nanomechanics experiments and molecular modeling. Pathways for achieving a several-fold increase in the toughness of graphene oxide monolayers will be examined.

"Intentional Nonlinearity in the Small Scale with Applications to Multi-Frequency Atomic Force Microscopy (AFM) and Mass Sensing", Randi Potekin, Dept of Mechanical Science and Engineering, University of Illinois, Urbana, Host: Daniel Lopez

In recent decades, micro- and nanomechanical resonators have drawn considerable attention due to their high sensitivity, portability and relatively low-cost. They are currently used in a wide variety of applications including precise frequency generation and timekeeping, nanoscale imaging and sensor technology. This presentation will include results of experimental, numerical and analytical investigations of microscale mechanical resonators with applications in atomic force microscopy (AFM) and mass sensing. The focus of this research effort is to exploit nonlinear phenomena in order to enhance existing measurement techniques in AFM and mass sensing. In the first section of the talk, a summary of my work in the area of AFM will be presented in which I consider a new design of the AFM cantilever. The new probe design utilizes internal resonance to passively amplify higher harmonics for use in multi-harmonic AFM. In contrast to other multifrequency AFM techniques, this approach provides multiple channels with strong signal to noise ratios while maintaining the simplicity of a single excitation frequency. I studied the capability of this cantilever to characterize material properties of polymers, bacteria and viruses and found that the internal resonance-based design results in enhanced sensitivity to Young's modulus.

In the second section of the talk, I will present results from a study of a new micromechanical mass sensor design that utilizes amplitude shifts within ultra-wide broadband resonances. The sensor consists of a clamped-clamped beam under harmonic base excitation having a concentrated mass at its center. Interestingly, due to geometric nonlinearity, for sufficiently large base excitation amplitudes there is no theoretically predicted jump-down bifurcation point in the primary resonance curve. Further, the critical excitation level above which there is no theoretical jump-down event is significantly lowered by the presence of the concentrated mass, hence its critical role in the beam design. In practice, a jump-down bifurcation point may occur due to the excitation of higher resonances, perturbations in the initial conditions and/or excitation amplitude caused by noise, or the basin of attraction for the upper branch solution may become impractically small. However, I believe it may be possible to physically realize a critical excitation amplitude above which the bandwidth of the resonance increases substantially. By operating at an excitation amplitude above this critical threshold, the ultra-wide resonant bandwidth can be exploited in a mass-sensing technique based on amplitude tracking.

Dec. 1, 2017

"Non-Equilibrium Materials Discovery: Terahertz Light-Quantum-Tuning of Electronic Phases Hidden by Superconductivity", Jigang Wang, Dept. of Physics & Astronomy, Iowa State University - Ames Laboratory. Host: Haidan Wen

Observation of "sudden" quantum quench of dominant phases without heating of other degrees of freedom in the system can provide transformative opportunities for accessing and controlling new, thermodynamically forbidden, phases of matter. These states are not accessible by traditional adiabatic tuning methods: chemical substitution, temperature, pressure, or magnetic field that reach exotic phases, often with serendipity, via spontaneous coherence. In this talk, I will discuss several examples using terahertz (THz) light-matter coherence for non-adiabatic Hamiltonian design in superconductors which expose new phases and collective modes hidden in equilibrium by the dominant competing SC order. Finally, I will present the outlook for applying the THz quantum control strategy in topological materials and spectroscopy nano-imaging.

Sept 25, 2017

"Entanglements and Discrete Andreev States in Monolayer Organic Superconductor". Abdou Hassanien, Jozef Stefan Institute, Ljubljana, Solveia. Host: Yuan Zhang

Epitaxially grown monolayer of organic superconductor, (BETS)2GaCl4 [where BETS is bis(ethylenedithio)tetraselenafulvalene], on Ag(111) form islands of uniform and mixed stacking of 2-dimensional stripes. A d-wave superconducting gap, of magnitude 2? = 14 meV, is ubiquitously measured on uniform islands while been structurally altered on the inhomogeneous islands. Entanglements of superconducting intra-stripes are manifested by smeared anisotropy of the low energy quasiparticle as well as features of multigaps in their density of states. Despite proximal entanglements, the pronounced coherence peaks indicate well preserved superconducting state. Robust zero bias peaks are detected only at the edges of isolated stripes indicating tunneling into Andreev bound states. These features broaden significantly away from the edges due to quantum interference with nearby discrete states. The interplay between structural parameters and electronic properties makes single layer (BETS)2GaCl4 a unique playground for testing quantum computations.

"Low-cost, high-performance, single-crystal-like device layers and controlled self-assembly of nanostructures within device layers for wideranging energy and electronic applications", Amit Goyal, Director RENEW, The State University of New York. Host: Supratik Guha.

For many energy and electronic applications, single-crystal-like materials offer the best performance. However, in almost all cases, fabrication of single-crystal form of the relevant material is too expensive. In addition, for many applications, very long or wide materials are required, a regime not accessible by conventional single-crystal growth. This necessitates the use of artificially fabricated, large-area, single-crystal-like substrates suitable for heteroepitaxial growth of the relevant advanced material for the electronic or energy application in question. In this talk, details of the fabrication of such substrates will be discussed. Heteroepitaxial growth of nanolaminate multilayers and devices on such substrates using a variety of deposition techniques such as pulsed laser ablation, sputtering, e-beam evaporation, MBE, MOCVD, and chemical solution deposition will be reported upon. Application areas that have been demonstrated via the use of such artificial substrates include – oxide high-temperature superconductors, semiconductor materials (Si, Ge, GaAs, CdTe, Cu2O), ferroelectrics (BaTiO3), multiferroics (BiFeO3), etc. In addition, strain-driven selfassembly of second phase nanomaterials at nanoscale spacings has been demonstrated within device layers. Control of heteroepitaxy in lattice-mismatched systems and the effects of strain on self-assembly will be discussed. Such heteroepitaxial device layers on large-area, singlecrystal-like artificial substrates are quite promising for a range of electrical and electronic applications.

"Visualizing Nanoscale Dynamics in Liquids with High Spatial and Temporal Resolution Using Liquid Cell TEM", See Wee, Center for BioImaging Sciences, National University of Singapore. Host: Jianguo We

Liquid cell transmission electron microscopy is a powerful technique that allows to us visualize phenomena that take place in a liquid environment with the resolving power of a transmission electron microscope (TEM). In this presentation, I will show two examples of how liquid cell TEM can be used to study chemical reactions involving nanoparticles and the dynamics of nanoparticles. First, I will discuss results from experiments where we followed the microstructural evolution of Ag nanocubes as they undergo galvanic replacement with Au ions to understand mechanisms behind hollow structure formation. Second, I will talk about how we can track both the translation and rotation of nanoparticles contained within these liquid cells with temporal resolution of a few milliseconds. Lastly, I will discuss the potential impact of high speed direct electron cameras on the field. In particular, I will touch on the strategies we are developing at the Center for BioImaging Sciences to achieve low electron dose imaging conditions for our experiments and the challenges in working with the large datasets that result from these experiments.

"Four-Dimensional Ultrafast Electron Microscopy", Haihua Liu, Division of Chemistry and Chemical Engineering, California Institute of Technology. Host: Tijana Rajh

The 4D UEM pioneered by Professor Ahmed Zewail at Caltech since 2004 enables scientist to explore ultrafast events and process that occur at the atomic-scale and in femtoseconds, which is 10 orders of magnitude better than that of conventional microscopes limited by the video-camera rate of recording. Now, 4D UEM has been used in the study of ultrafast dynamics from atomic motions during structural dynamics to ultrafast phase transitions, nanomechanical oscillations, chemical bonding dynamics, crystallization dynamics, charge density wave, plasmonics. Dr. Liu is focusing on novel methodology development of 4D UEM and their applications in studying ultrafast dynamics of light-matter interactions.

In this talk, Dr. Liu will introduce the development and progress that he made in 4D UEM, such as ultrafast phase transition dynamics of single particle vanadium dioxide embedded in ensemble, development of diffraction PINEM to improve energy resolution and study near field plasmon dynamics in the infrared range, photon-gating to improve temporal resolution in UEM, 4D multiple cathode UEM.

August 11, 2017

"Nanophotonic materials by design: The case for refractory plasmonics", Urcan Guler, School of Electrical & computer Engineering and Brick Nanotechnology Center, Purdue University. Host: Daniel Lopez

Plasmonics studies the interaction of electric field with free electrons in metallic materials, which results in enhanced optical cross-sections. The field has attracted great attention due to the unprecedented ability to control light and its promise in a vast variety of scientific and technological applications such as sensing, energy harvesting, waveguiding, imaging, data storage, and medical therapies. However, material-related limitations and the strategic knowledge gap in alternative plasmonic materials research have been the major roadblocks. As with many other fields, plasmonics is now evolving into a multidisciplinary research area with a focus on materials development for application-specific requirements. In this talk, I will present a case study on transition metal nitrides as refractory plasmonic materials and their enabling role in applications that impose harsh environmental conditions. Energy harvesting, remote sensing in hot zones, photocatalysis, local heating and photothermal therapy will be discussed as prominent examples among many other opportunities. In the second part, I will discuss future directions for nanophotonic materials by design approach utilizing in situ and operando characterization techniques. Devices pushing the temporal and spatial limits bring new exciting challenges towards multifunctional systems made of nanoscale components. A detailed understanding of nanomaterials and their interfaces is a true challenge that is becoming a necessity to develop highly efficient nanoscale light sources, sensors, modulators, and energy harvesters for self- powered remote components that will form a network of multifunctional devices. Techno- economically feasible, self-sustaining systems will require highly efficient components made of earth abundant and process-compatible materials that can meet multiple environmental requirements often imposed by applications. The interaction of nanomaterials with local chemistry and external stimuli such as electromagnetic field, heat, electric signal, and mechanical load at the nanoscale forms the basis of a multiphysics system pushing the spatiotemporal, spectral, and intensity limits. A combinatorial approach for in situ and operando characterization and development of optical nanodevices for multifunctional systems will transform the internet of intelligent things covering a broad spectrum of arenas from smart cities to intra-body networks. The work will reveal fundamentally new insights to nanoscale phenomena and trigger new research questions both in the field of nanophotonics and other related areas where nanomaterials are the driving force.

August 11, 2017

"Random Access Quantum Information Processors", Srivatsan Chakram Sundar, The University of Chicago. Host: Gary Wiederrecht

Qubit connectivity is an important property of a quantum processor, with an ideal processor having random access -- the ability of arbitrary qubit pairs to interact directly. We describe the implementation of a random access superconducting quantum information processor, demonstrating universal operations on a nine-bit quantum memory, with a single superconducting transmon qubit serving as the central processor. The quantum memory uses the eigenmodes of a linear array of coupled superconducting resonators. The memory qubits are superpositions of vacuum and single-photon states, controlled by a single superconducting transmon coupled to the edge of the array. We show that single transmon charge control, and flux-driven sideband interactions with the cavity modes are sufficient for universal quantum control of the entire multimode manifold. We demonstrate universal gate operations between arbitrary pairs of modes, as well as efficient schemes for generating multi-photon entangled states. The fast and flexible control, achieved with efficient use of cryogenic resources and control electronics, in a scalable architecture compatible with state-of-the-art quantum memories in the form of high-Q 3D microwave cavities, is promising for quantum computation and simulation.

"Quantum dots created by atom manipulation with the scanning tunneling microscope", Dr. Stefan Folsch, Senior Scientist, Paul-Drude-Institut fur Festkorpereletronik. Host: Saw-Wai Hla

Atom manipulation with the scanning tunneling microscope (STM) makes it possible to create ultimately small structures at surfaces. We applied this technique to III-V semiconductor surfaces and found that their electrostatic potential landscape can be precisely designed by the controlled positioning of charged adatoms. In this way, quantum dots (QDs) with identical, deterministic sizes can be created one atom at a time. By using the lattice of the InAs(111)A surface to define the allowed atomic positions, the shape and location of the dots is controlled with effectively zero error. The dots are assembled from +1 charged indium adatoms, leading to the confinement of intrinsic surface-state electrons. This technique enables one to generate ultra-small QDs free of statistical variations in size and shape, providing error-free control of their energy level structure. The discussed results illustrate that atom manipulation in combination with scanning tunneling spectroscopy provides detailed insight into the quantum-physical properties of artificial surface structures at the smallest size scales. Understanding and controlling these properties – and the new kinds of behavior to which they can lead – will be crucial for integrating atomic-scale devices with existing semiconductor technologies.

"Direct Optical Lithogrpahy of Functional Inorganic Nanomaterials", Dmitri Talapin, The University of Chicago. Host: Daniel Lopez

Photolithography is an important manufacturing process that relies on using photoresists, typically polymer formulations, that change solubility when illuminated with ultraviolet light. Here, we introduce a general chemical approach for photoresist-free, direct optical lithography of functional inorganic nanomaterials. The patterned materials can be metals, semiconductors, oxides, magnetic, or rare earth compositions. No organic impurities are present in the patterned layers, which helps achieve good electronic and optical properties.

The conductivity, carrier mobility, dielectric, and luminescence properties of optically patterned layers are on par with the properties of state-of-the-art solution-processed materials. The ability to directly pattern all-inorganic layers by using a light exposure dose comparable with that of organic photoresists provides an alternate route for thin-film device manufacturing.

July 31, 2017

"Quantum and Topological Plasmons in Two Dimension", Dafei Jin, University of California, Berkeley, Host: Daniel Lopez

In the first part of my talk, I will present our observation of quantum-spilling enhanced surface-plasmon absorption at the interface of silver and high-index dielectrics. We show that due to the reduced work function of the high-index dielectrics with respect to the Fermi surface of the metal, conduction electrons can have a significant quantum spilling into the dielectrics. This phenomenon allows for intense interfacial electron-hole pair production along with the surface-plasmon absorption at optical frequencies. The enhancement occurs in the favorable solar-spectrum regime, and so can be helpful for developing high-efficiency energy- harvesting devices.
In the second part of my talk, I will present our recent studies on the topological behaviors of two-dimensional magnetoplasmons in GaAs/AlGaAs heterojunctions and on monolayer graphene. We show that with a modest magnetic field to break the time-reversal symmetry, topologically protected one-way edge states can exist on both the structural boundaries and on magnetic-domain boundaries. These edge states are operable from gigahertz to terahertz frequencies and can potentially be used to develop low-loss high-speed electronic-photonic hybridized devices.
[1] D. Jin et al. Phys. Rev. Lett. 118, 245301 (2017). [2] D. Jin et al. Nature Commun. 7, 13486 (2016). [3] D. Jin et al. Phys. Rev. Lett. 115, 193901 (2015).

July 27, 2017

"Novel X-Ray Imaging Systems Enabled by Nanofabrication", Houxun Miao, National Heart, Lung, and Blood Instittue (NHLBI), National Institutes of Health (NIH), Host: Daniel Lopez.

X-ray imaging accounts for the majority of medical diagnostic procedures in the United States. Sensitivity and resolution are key technical parameters of an x-ray imaging system. Enhancing the sensitivity results in a reduction of the radiation dose, which has attracted a great deal of attention. This talk presents our recent development of an ultra-sensitive x-ray interferometric imaging system enabled by nanofabrication. The development of cost-effective processes to fabricate deep submicron period hard x-ray diffraction gratings will be described. Then special focus will be given to the invention of an x-ray polychromatic far-field interferometer with the fabricated gratings, where preliminary experiments demonstrated more than an order of magnitude improvement of the sensitivity compared to the state-of-the-art grating-based Talbot-Lau interferometry technique. Potential application of the far-field interferometer in digital mammography will be discussed. A universal moiré effect to explain the physics of the polychromatic far-field interferometer and the application of this fundamental optical effect in neutron imaging will be presented. As future perspectives, I will discuss the design of novel x-ray devices and imaging systems for high resolution imaging.

July 26, 2017

"Real-space Investigation of Water at Surfaces: Kinetics, Solvation and Lght Interaction", Prof. Karina Morgenstern, Physical Chemistry I, Ruhr Universitat Bochum, Germany, Host: Saw-Wai Hla

Water is important in all aspects of life and thus there is a broad interest in supported water- ice in areas as diverse as the environmental sciences, electrochemistry, and astrochemistry. However, there is only few experimental evidence about the interaction of individual water molecules with each other or with other molecules. Consequently microscopic details of water dynamics and kinetics need to be unravelled.

In our low-temperature scanning tunnelling microscopy study, we follow the diffusion and cluster formation of water monomers to larger structures of Cu(111) and NaCl(100) surfaces to determine fundamental barriers for water interaction on surfaces. Then we coadsorb functionalized organic molecules and water on Au(111) to investigate the interaction of water molecules with different polar groups and the formation of a solvation shell of the molecules. Finally, we adsorb halogenated hydrocarbons on top of both, amorphous and crystalline water structures (see Figure), in order to unravel the process behind photo induced dissociation of these molecules. The latter study gives insight into chlorine radical formation on top of ice covered nanoparticles that exist in the Earth's upper atmosphere.

July 26, 2017

"Electrical Access to Marginally Protected States in Graphene", Arindam Ghosh, Department of Physics, Indian Institute of Science, Host: Nathan Guisinger

The zigzag (ZZ) edges of both single and bilayer graphene are perfect one dimensional (1D) conductors due to a set of zero energy gapless states that are topologically protected against backscattering. Competing effects of edge topology and electron-electron interaction in these channels have been probed with scanning probe microscopy, which reveals unique local thermodynamic and magnetic properties. A direct evidence of edge-bound electrical conduction, however, has remained experimentally elusive, primarily due to the lack of graphitic nanostructures with low structural and/or chemical edge disorder, as well as a clear understanding of the impact of edge disorder and confinement on electrical transport. In this talk I shall present a new experimental route to observe ballistic edge-mode transport in graphene, created during nanomechanical exfoliation of graphite, which manifests in quantization of conductance close to multiples of e2/h, even at room temperature . I shall elaborate the uniqueness of these current-carrying states in electrically biased bilayer graphene, where the conductance at low temperatures will be shown to possess non-trivial localization properties, as expected from topologically protected edge states in the presence of inter-valley scattering.

July 25, 2017

"From Nanodisk to the Universe", Junjia Ding, Materials Science Division, Argonne National Laboratory, Host: Daniel Lopez

The idea of nanotechnology was introduced more than half of a century ago. Since then, it has been changing people's lives daily, from medicine products to electronic devices. Same for scientific research, with advancing nanofabrication and characterization techniques, researchers are now able to access, analysis and manipulate objects that were inaccessible before. In this talk, three projects with different fabrication techniques implemented will be discussed. Firstly, the investigation of static and dynamic properties of magnetic nanodisks [1] and nanowires [2] prepared by Electron-beam lithography (EBL) will be discussed. Thanks for the highest pattern resolution provided by EBL, new magnetic phenomenon were observed due to the nanoscale geometry effects. Secondly, the fabrication process based on deep ultraviolet (DUV) lithography technique will be discussed. DUV lithography provides opportunities to prepare nanostructures over a relatively large area with a faster processing speed compared to the EBL process. This technique makes the using of magnetic nanostructures in practical applications possible, for example, large area magnonic crystals and nanoscale antidot bio-sensing devices. Furthermore, new pattern transfer techniques, such as selfaligned shadow deposition [3], have been developed taking advantage of the high pattern aspect ratio provided by DUV technique. Last but not least, we will discuss the fabrication process and performance of large array of superconducting transition edge sensor (TES) detectors, which are fabricated for the latest generation cosmic microwave background (CMB) experiment on the South Pole Telescope (SPT- 3G) [4]. The entire fabrication process contains more than 15 steps, including multilayer UV lithography, sputtering deposition, lift-off and etching etc. And these SPT-3G detector arrays were deployed to the South Pole at the end of 2016. Several interesting findings during the optimization of fabrication process will be shared in this talk.

July 21, 2017

"The Use of Electron Ptychography to Implement Efficient Phase Imaging in STEM", Hao Yang, Molecular Foundry, Lawrence Berkeley National Laboratory, Host: Gary Wiederrecht.

Historically, the scanning transmission electron microscope has not been widely used for phase contrast imaging because existing imaging methods including the bright-field (BF) and annular bright field (BF) etc., detect only a fraction of the incident electrons and therefore are inefficient with respect to dose. This limitation has hindered the efficient imaging of light elements in STEM. In my work, by make use a direct electron pixelated detector to record the entire diffraction signal as the electron beam rasterscans across the specimen, and phase information can be extracted using electron ptychography with maximum efficiency. Electron ptychography in the STEM was first demonstrated more than 20 years ago in the context of improving image resolution. At that time, the image field of view was restricted by the limitations of the camera technology. Current commercially available pixelated detectors can operate at a reasonably fast speed on the order of a few hundred to several tens of thousands frames-per-second. The resulting 4D data set is formed of a series of coherent convergent beam diffraction patterns recorded as a function of illuminating probe position. This data set is a very rich source of information. By adapting a previously used method for use with a modern aberration-corrected STEM, high quality, quantitative phase images can be formed simultaneously with other STEM imaging modes such as annular dark field (ADF) imaging. This phase imaging mode has a relatively simple transfer function and also provides an inherent filter of image noise without reducing the signal strength to form high quality phase images. Residual aberrations in the image can be detected and corrected, and three-dimensional information is available post-acquisition without running a tomographic tiltseries of images. In addition, it is also found that the ptychographic phase images can be intuitively interpreted in relatively thick samples where dynamical electron diffraction dominates. These imaging technique developments enable advantageous capabilities for simultaneous imaging of light and heavy elements under low dose conditions. Therefore, our work has opened up exciting opportunities for studying complex nanostructures and hybrid materials systems, for example, studying complex carbon nanostructures for potential drug delivery applications, and halide perovskites based energy materials.

July 20, 2017

"Nano-plasmonics in graphene/hexagonal boron nitride heterostructures", Guangzin Ni, University of California - San Diego, Host: Gary Wiederrecht.

Graphene is proposed as one of the most promising candidates for novel plasmonic devices, owning to its versatile tunability, broadband frequency capability and ultrafast operation speed. In this talk, we present infrared nanooptics studies on graphene that is encapsulated with hexagonal boron nitride (hBN) to forming van der Waals hererostructures. We have uncovered a rich variety of plasmonics effects that may enable functionalities not attainable through bulk metal-based plasmonics. Through direct nano-imaging of plasmonic standing waves we were able to quantify the electronic losses in graphene. By examining the sub picosecond dynamics of plasmons in a unique set of pump-probe spectroscopy apparatus we were able to switch on plasmon on demand [Nature Photonics 10, 244 (2016)]. In addition, we performed nanoimaging studies of graphene/hBN assembling with the presence of a periodic moiré superlattice structures, which yielding rich insights into the electronic phenomena of the hosting material [Nature Materials 14, 1217 (2015)]. Furthermore, we were able to map and characterize plasmonic domain boundaries in graphene that is created by a tunable potential barrier through nearby one-dimensional line-like perturbations [Physics Review Letters 117, 086801 (2016)].

July 19, 2017

"Cavity Magnonics for Quantum Information Processing", Xufeng Zhang, Argonne National Laboratory, Host: Gary Wiederrecht

System hybridization is of great importance in the development of quantum networks because it allows utilization of different techniques in a single system. YIG magnonics is emerging as a promising candidate for hybrid quantum systems recently. As the elementary collective excitation, the interaction of magnon with other information carriers is significantly enhanced by the large spin density in magnetic insulator yttrium iron garnet (YIG). Besides, YIG also provides very long lifetime not only for magnons but also for acoustic phonons, microwave and optical photons. In this talk I will present my recent work on information transduction among different systems using YIG magnonics, and discuss the approach toward bridging superconducting qubits with optical systems using magnon as a quantum transducer to develop fully functional distributed quantum network.

July 19, 2017

July 17, 2017

"Making Room at the Bottom with Advanced Scanning Transmission Electron Microscopy", Yuanyuan Zhu, Pacific Northwest National Laboratory, Host: Tijana Rajh

In his famous lecture in 1959, Richard Feynman stated, "it would be very easy to make an analysis of any complicated chemical substance, all one would have to do would be to LOOK AT it and see where the ATOMS are." In this talk, I will show how can we leverage the advanced Scanning Transmission Electron Microscopy to accelerate the innovations in heterogeneous functional nanomaterials at the fundamental atomistic scale.

Modifying nanoscale materials by trace amounts of foreign elements represents an opportunity to extend their unique functionalities. Currently, much interest is devoted to the functional promotion of layered dichalcogenides, such as MoS2, for diverse applications in electronics, optoelectronics and heterogeneous catalysis. To rationally guide the promotional optimization, insight into the location and bonding geometry of the promoter elements is needed at the level of a single atom. I will show how we combine low-voltage and lowdose aberration-corrected scanning transmission electron microscopy (STEM) with electron energy loss spectroscopy (EELS) to enable the first single-atom sensitive spectroscopic analysis that unambiguously identifies single Co atoms in a promoted industrial-style MoS2 nanocatalyst in its native state. Furthermore, no material is completely static. To truly understand and guide materials design, dynamic behaviors of a functional material system need to be investigated in the presence of corresponding mechanical, electrical, chemical and/or thermal applied fields. Taking gas-solid reaction for instance, it is crucial to understand how the gas molecules affect the scattering of fast electrons contributing to an atomic scale image for better imaging sensitivity and resolvability in reaction relevant gaseous environments. I will show how we evaluated the inelastic-noise-free annular dark-field STEM imaging mode for a directly interpretable observation under the influence of various gaseous environment at different pressure. Using this new environmental STEM (ESTEM), we unambiguously resolved all thirteen cation atomic sites on the surface of a complex oxide catalyst (M1 catalyst) under the working condition. The in situ ESTEM images at different reaction stages under different gas environment were quantified with a sound sampling statistics, via an automated image analysis algorithm developed in house. This combined in situ and big-data microscopy approach revealed a new mechanism of generating catalytic active sites on the surface of a mixed oxide catalyst (M1 catalyst) during oxidative ethane dehydrogenation. This new reaction pathway occurring in 0-, 1-, and 2-dimensional subsystems, points to the fact that the catalytic functionality is not solely described by the properties of an isolated specific site, but requires the control of charge transfer mechanisms and their dynamics in the catalyst bulk. This realization opens new perspectives for tailoring nano-oxide functionalities.

July 10, 2017

"Investigating Interfaces and Surfaces with Transmission Electron Microscopy", Amish B. Shah, D1C Failure Analysis Intel Corporation, Host: Tijana Rajh

Epitaxial superlattices of transition metal oxides can lead to new materials properties due to the proximity of interfaces separated by a few atomic layers. Recent studies involving epitaxial oxide films grown by pulsed laser deposition (PLD) and molecular beam epitaxy (MBE) have led to new phenomena at the interface such as enhanced electrical transport and enhanced magnetic properties, which are not observed in bulk materials. Here, I will show our investigation on the interfaces in superlattices of LaMnO3, SrMnO3, and SrTiO3 films. Surfaces play a key role in the properties of noble metal nanocrystals, which are used in catalysis, medicine, and chemical sensing applications. The shape and size of nanocrystals controls their properties. Nanocrystals enclosed by high-index facets are thought to have higher catalytic properties. However, characterizing high-index facets is challenging due their small size, complex shape, and presence of inward facing facets. Here we present an approach to determine high index facets using streaked Bragg reflections in coherent electron diffraction patterns. We report new high-index facets in trisoctahedra and show the evolution of facets as a function of aging time.

June 23, 2017

June 21, 2017

June 7, 2017

May 3, 2017

April 26, 2017

April 26, 2017

"An overview of wafer processing systems from Osiris: coat-develop, liftoff, cleaning, and mounting tools", Bruce Neufeld, Osiris

Osiris International is a manufacturer of a wide line of wafer processing tools for the semiconductor and MEMs industries. We manufacture coat/develop, liftoff, wafer cleaning, and mounting/demounting tools. This presentation will provide an overview of the company and our line of tools. Tools can be configured from manual to fully automated with features such as variable substrate size, edge bead removal that matches the substrate shape, high thickness uniformity, and no-soak high-pressure liftoff.

April 12, 2017

April 3, 2017

Self-assembly of proteins and inorganic nanoparticles driven by weak interactions opens the door for engineering organic-inorganic analogs of cellular organelles comprised of diverse components and with integrated functionalities. Such systems are fundamentally and technologically attractive due to their uniformity, versatility and simplicity of preparation. To demonstrate such assemblies, we combine CdTe nanoparticles with cytochrome C proteins and observe spontaneous formation of spherical supraparticles with a narrow size distribution containing both components. Assembly was originated from the competition between electrostatic repulsion and non-covalent attractive interactions. Non-covalent interactions between protein and charged NPs lead to drastically different self-assembly behavior previously unseen for each component individually, and which mimics the cooperative assemblies of proteins. Tight packing of nanoscale components enables effective charge and exciton transport in supraparticles and bionic combination of properties as demonstrated by enzymatic nitrate reduction initiated by light absorption in the nanoparticle.

March 29, 2017

March 28, 2017

"Using machine learning to guide materials design and discovery", Max Hutchinson, Citrine Informatics. Host: Maria Chan

Machine learning (ML) encompasses a diverse set of techniques for constructing quantitative models given examples of a phenomenon. In materials informatics, the primary challenge is data scarcity: the space of materials is very high dimensional, and experiments, including those in silico, are relatively expensive. It is therefore especially important to focus experiments on regions of interest and high information density. This talk presents a general experimental design strategy that uses the predictions of machine learning models to select subsequent experimental targets. This technique is benchmarked on a search for high ZT thermoelectric materials, and it accelerates the rate at which extreme values are found by nearly 3x. This technique can be easily applied to other materials design and discovery problems, and the talk will conclude with a demo of optimal experimental design using the Citrination platform.

March 16, 2017

"Plasmonics with low-dimensional carbon materials", H. Grebel, The Electronic Imaging Center and the ECE Department, NJIT. Host: Ani Sumant

Surface Plasmons Polaritons (SPP) is a collective mode that propagates along the surface between a negative and a positive dielectric constants. Some metals, which are surrounded by a dielectric material can sustain plasmonic modes above a certain cut-off wavelength, which is in the visible/near IR range. Metals also exhibit large plasmonic loss in that spectral range. This loss limits the propagation distance of the surface modes. It is better to work at IR wavelengths where the plasmonic losses are much smaller.

Graphene, and its rolled version – the carbon nanotube, have been investigated extensively in recent years. They have exhibited unique properties not shown by their bulk counterparts. In this talk, I will describe examples of plasmic platforms, which are integrated with low-dimensional carbon materials through bio, bio-chemical and onto-electronic applications.

March 6, 2017

"Gravity as a cue for phytoplankton migrations", Anupam Sengupta, ETCH Zurich, Switzerland

Phytoplankton are photosynthetic microbes, that are among ocean's most important organisms. Many species of phytoplankton are motile and gravitactic, i.e., they migrate in response to gravity: upwards towards light during the day, and downwards towards higher inorganic nutrient concentrations at night. Despite the minute size of the individual organisms, their large numbers and their fundamental role as the base of nearly every aquatic food web, makes these some of the largest and most important migrations on earth. Although it has long been recognized that ocean turbulence is a primary determinant of phytoplankton fitness and species succession, much less is known on whether they can actively respond, and rapidly adapt to a turbulent landscape.

In this talk, I will present recent results that illustrate a striking, behavioral response among phytoplankton species, to turbulence-like cues, wherein micron-sized cells rapidly altered their direction of migration within minutes, possibly as a bet hedging strategy to escape the damaging effects of turbulent microzones. I have used a combination of single-cell and population level experiments to zoom into the mechanistic pathway underpinning this active adaptation. Quantitative morphological analysis together with a model of cell mechanics revealed that this behavior was accompanied by a morphological modulation of the cells' fore-aft asymmetry. The minute magnitude of the required modulation, sufficient to invert the cells' preferential swimming direction, highlights the advanced level of control that phytoplankton can exert on their migratory behavior. I will conclude my talk with a brief description of the behavioral response experiments, recently conducted onboard a parabolic flight, and our ongoing efforts to identify the molecular triggers that regulate gravity perception in micro-plankton. Rapid behavioral adaptation offers an uncharted area – one which lies at the rich interface of fluid mechanics, material physics, and microbiology, and promises a fresh perspective to the physiology, signaling, and ecology of some of earth's most important organisms.

March 1, 2017

March 1, 2017

"An Introduction to JST Manufacturing and its Exhausted Workstations", John Greener, JST Manufacturing

Since its founding in 1982, JST's mission has been to design and build efficient-and-cost-effective cleaning and processing products for cleanroom applications and to support these products with superior customer service. JST is a full service design and manufacturing company. Capabilities consist of Process Development and Applications Testing, Engineering Design and Drafting, Manufacturing and Final Test. Our product lines include Wet Processing Equipment, Precision Cleaning, and Cleanroom Accessories and Support Equipment. This presentation will provide an introduction to JST Manufacturing and describe our series of Exhausted Workstations and their applications.

February 15, 2017

"Probing Charge Dynamics in Nano-materials with Nano-tools: Quasi-One Dimensional Percolation Paths in Quantum Dot Solids", Tamar Mentzel, Massachusetts Institute of Technology

By manipulating matter at the nanoscale, we can make new materials (nano-materials) tailored to have desired—and even unconventional--properties, and new measurement tools (nano-tools) with higher sensitivity and precision than any macroscopic tool. In the first portion of my talk, I will discuss one of the simplest examples of a nanomaterial, a lattice of nanocrystals. One challenge in creating nanocrystal solids with desirable properties is to assemble the nanocrystals with sufficient order. For example, until recently, the electronic properties of nanocrystals were dominated by disorder, and their assembly was not controlled adequately for them to be components of nanoscale circuits. I will discuss a novel technique, based on e-beam lithography, for assembling nanocrystal solids with sufficient precision and order to be integrated into nanoscale electronic devices as well as to measure for the first time their intrinsic electronic properties. We find that the charges are carried in quasi-one-dimensional percolation paths, and that the time dynamics of an individual transport channel is described by Levy statistics. This is an essential step toward realizing and exploiting their predicted unconventional charge and spin transport properties, which are key for application in quantum computing and spintronics or for exploring many-body physics. In the second portion of my talk, I will present a novel nano-tool for measuring charge in nanoscale structures. Measuring electrical properties of nanoscale devices is often complicated by the small contact area between the device and the measurement electrodes: The contacts can be unstable or add series resistance. Our nanoscale charge sensor eliminates contact effects. The nanoscale sensor enables a highly sensitive measurement that can detect the motion of a single charge. In turn, that makes it possible to measure electrical conductances as small as 10^-20 Siemens by applying only one volt bias. This is approximately six orders of magnitude more precise than state-of-the-art current-based measurements permit.

February 15, 2017