News & Events

Speaker: Professor Alexandr Marchenko
Affiliation: Institute of Physics of National Academy of Sciences of Ukraine
Abstract Details: The results of STM/AFM/SEM investigations of 2D-films and interfaces with molecule and intramolecular resolution will be presented. Atomically flat surfaces (graphite, reconstructed Au(111), MoS2 and mica) are used as the substrates. The main attention will be focused on possible applications of obtained nanostructures for design of externally controlled interfaces, molecular matrixes for selective adsorption, electroluminescence devices and devices for nanotribology.
About the Speaker: Institute of Physics of National Academy of Sciences of Ukraine 1 Pierre et Marie Curie University (Paris, France), CEA Saclay2
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Speaker: Professor Junichiro Kono
Affiliation: Departments of Electrical & Computer Engineering, Physics & Astronomy, and Materials Science & NanoEngineering, Rice University
Abstract Details: Strong resonant light-matter coupling in a cavity setting is an essential ingredient in cavity-QED-based quantum information processing as well as explorations of new ground states in strongly light-driven condensed matter. This talk will first describe our recent observation of cooperative ultrastrong light-matter coupling in a two-dimensional electron gas in a high-Q terahertz cavity in a quantizing magnetic field, demonstrating a record-high cooperativity [1]. The electron cyclotron resonance peak exhibited splitting into the lower and upper polariton branches with a magnitude that is proportional to the square-root of the electron density, a hallmark of cooperative vacuum Rabi splitting. Additionally, we have obtained clear and definitive evidence for the vacuum Bloch-Siegert shift due to the breakdown of the rotating-wave approximation [2]. The second part of this talk will present one-dimensional microcavity exciton polaritons in a thin film of aligned carbon nanotubes [3] embedded in a Fabry-Perot cavity, also exhibiting cooperative ultrastrong light-matter coupling with unusual continuous controllability over the coupling strength through polarization rotation [4]. These experiments open up a variety of new possibilities to combine the traditional disciplines of many-body condensed matter physics and cavity-based quantum optics. 1. Q. Zhang et al., Nature Physics 12, 1005 (2016). 2. X. Li et al., Nature Photonics 12, 324 (2018) 3. X. He et al., Nature Nanotechnology 11, 633 (2016). 4. W. Gao et al., Nature Photonics 12, 362 (2018).
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Speaker: Professor Park Hyung Gyu
Affiliation: Department of Mechanical and Process Engineering, Swiss Federal Institute of Technology (ETH) Zurich
Abstract Details: Fast mass transport inside and across nanoscale graphitic surfaces such as carbon nanotubes and graphene, respectively, forms the basis of Carbon Nanofluidic phenomena and poses potential applications in energy and clean technologies. This talk will review the existing paradigm of the fast transport in carbon nanotube conduits with a proposal of a new scaling relation to answer a question, “how fast is fast?”, followed by our story of shifting the paradigm with a recognition that having a nearly frictionless channel could be equivalent to having no channel but only openings. Synthesis, transfer, perforation and device integration of graphene enable altogether to prepare an atomically thin porous membrane for the embodiment of this new concept. Transport physics across the 2D pores points to an ultimate permeation of fluids (both in molecular and viscous transport regimes) as well as emergence of a high-permeation membrane. The high-permeation membranes are in need of proper applications in membrane technology, for which this talk introduces our active endeavors of utilizing the porous graphene and imposing substantial selectivity to it. The talk ends with a brief overview and outlook of my faculty research portfolio, Nanoscience for Energy Technology and Sustainability.
About the Speaker: Hyung Gyu Park is a tenured, Associate Professor of Nanoscience for Energy Technology and Sustainability in the Department of Mechanical and Process Engineering at Swiss Federal Institute of Technology (ETH) Zurich. He received B.S. and M.S. in Mechanical Engineering from Seoul National University, Seoul, Korea, in 1998 and 2000, respectively. Following, he received Ph.D. from University of California at Berkeley, CA, U.S.A., by carrying out research projects in collaboration with Lawrence Livermore National Laboratory (LLNL), CA, U.S.A.: (a) development of micro fuel-cell system and (b) mass transport phenomena in carbon nanotubes. After continued academic training at LLNL as a postdoctoral research staff member, he joined ETH Zurich in 2009. His research interest at ETH Zurich encompasses syntheses of carbon nanomaterials and 2D material, fundamental transport physics at nanometer scale, nanomanufacturing towards multiscale integration, and nanotechnology solutions for our sustainable growth such as addressing energy and water sustainability issues. He received R&D Magazine 2010 R&D 100 Award and Editor’s Choice Award, U.S.A., in recognition of his contribution to “Ultrapermeable Carbon Nanotube Membranes”. He holds senior adjunct researcher position at Eawag (Swiss Federal Institute of Aquatic Science and Technology), Switzerland, and adjunct professorship at KAIST (Korean Advanced Institute of Science and Technology), visiting professorship at Sungkyunkwan University (Department of Energy Science), and guest professorship at Seoul National University (Department of Mechanical and Aerospace Engineering) supported by KNRF (Brain Pool).
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Speaker: Yang Guang (??)
Affiliation: Beijing Normal University
Abstract Details: Recently, two dimensional materials like graphene and phosphorene have been attracting great attention for its possible application in new electronics. My doctoral work focus on the tailoring magnetic and electronic properties of graphene, phosphorene and the single-layer form of phosphorene allotropes. By means of two different large scale quantum Monte-Carlo methods, we propose that relatively weak interactions can lead to remarkable edge magnetism in the phosphorene nanoribbons. The ground state constrained path quantum Monte-Carlo simulations reveal strong ferromagnetic correlations along the zigzag edges, and the finite temperature determinant quantum Monte-Carlo calculations show a high Curie temperature up to room temperature. We argue that the change of the topological structure that induced by the natural strong anisotropy in phosphorene is the key to understand the enhancement of the edge ferromagnetism compared with that of the isotropic case, namely graphene. Thus the strain-tuning of edge magnetism in zigzag graphene nanoribbons is also proposed. Most recently, another stable monolayer of a new phosphorus allotrope with a direct gap, called green phosphorene, has been predicated. Using the first principle density functional theory calculations, we find that it can sustain a tensile strain limit in the armchair direction up to 35% and reveal the nature of its more puckered structure. Moreover, the direct-indirect band gap transition happens under appropriate strain. These works may open up to new possibilities of engineering further electronic and spintronic devices.
About the Speaker: I am a doctoral student from Beijing Normal University under the direction of Prof. Tianxing Ma in condensed matter physics. During my doctoral period, I have worked on tailoring the magnetic properties of 2D materials, especially graphene and phosphorene using quantum Monte Carlo simulations. Last year, I got an opportunity to cooperate with Prof. Xihong Peng as a short-term visitor at Arizona State University. During that time, I did some research on tuning the electronic properties of green phosphorene using the first principle density functional theory calculations.
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Speaker: Professor Andreas J. Heinrich
Affiliation: Director, Center for Quantum Nanoscience, Institute for Basic Science, Seoul Department of Physics, Ewha Womans University, Seoul, Korea
Abstract Details: The scanning tunneling microscope is an amazing tool because of its atomic-scale spatial resolution. This can be combined with the use of low temperatures, culminating in precise atom manipulation and spectroscopy with microvolt energy resolution. In this talk we will apply these techniques to the investigation of the quantum spin properties of magnetic atoms sitting on thin insulating films. We will start our exploration with the understanding of the quantum spin states (also called the magnetic states) of these adsorbates. To measure these states, we combined scanning tunneling with x-ray absorption spectroscopy and found amazing agreement of those vastly different techniques (Science 2014, PRL 2015). Next, we will investigate the lifetimes of excited states. Surprisingly, we find lifetimes that vary from nanoseconds to hours, a truly amazing consequence of the quantum states of different adsorbates. Finally, we will explore the superposition of quantum states which is inherent to spin resonance techniques. We recently demonstrated the use of electron spin resonance on single Fe atoms on MgO (Science 2015). This technique combines the power of STM of atomic-scale spectroscopy with the unprecedented energy resolution of spin resonance techniques, which is about 10,000 times better than normal spectroscopy.
About the Speaker: Heinrich is a world-leading researcher in the field of quantum measurements on the atomic-scale in solids. He pioneered spin excitation and single-atom spin resonance spectroscopy with scanning tunneling microscopes – methods that have provided high-resolution access to the quantum states of atoms and nanostructures on surfaces. He has a track record of outstanding publications and invited talks and has established a strong network of global collaborations. As a consequence, Heinrich’s work has received extensive media coverage worldwide. Heinrich received his Masters (Diplom) degree in 1994 and his doctorate in 1998 in physics at Georg-August University in Goettingen, Germany. Heinrich then spent 18 years in IBM Research, which uniquely positioned him to bridge the needs of industrial research and the academic world. This unique environment gave Heinrich extensive experience in presenting to corporate and political leaders, including the president of Israel and the IBM Board of Directors. Heinrich became a distinguished professor of Ewha Womans University in August 2016 and started the Center for Quantum Nanoscience (QNS) of the Institute for Basic Science (IBS) in January 2017. Under his leadership, QNS focuses on exploring the quantum properties of atoms and molecules on clean surfaces and interfaces with a long-term goal of quantum sensing and quantum computation in such systems. Heinrich is a fellow of the American Physical Society and the American Association for the Advancement of Sciences and a member of the German Physical Society and the Korean Physical Society.
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Speaker: Professor Shisheng Lin
Affiliation: College of Microelectronics, College of Information Science & Electronic Engineering, Zhejiang University
Abstract Details: Shisheng Lin 1 College of Microelectronics, College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou, China 2: State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, China The electrons in graphene behave as Dirac Fermions and have a very high mobility. The linear electronic band structure of graphene and the low density of states near the Dirac points allow that the Fermi level of graphene is highly tunable. The junction formed by graphene and semiconductor is ultrashallow and near the graphene layers. Those merits make graphene/semiconductor heterostructure highly efficient for optoelectronic devices. The van der Waals Schottky diodes is highly tunable based on that the Fermi level of graphene is highly tunable, which has been demonstrated by the Raman spectroscopy measurements. We have achieved a high performance graphene/GaAs solar cell with a power conversion efficiency of 18.5%. The simulation and experimental work demonstrate that a power conversion efficiency over 30% can be finely reached in the near future for the graphene/semiconductor van der Waals heterostructure system. We will also summarize our progress on graphene/semiconductor heterostructure based photodetectors, light emitting diodes and nanogenerators . References: 1, Z. Q. Wu, Y. H. Lu, W. L. Xu, Y. J. Zhang, J. F. Li, S. S. Lin*, Surface plasmon enhanced graphene/p-GaN heterostructure light-emittingdiode by Ag nano-particles, Nano Energy 30, 362 (2016). 2, S. S. Lin*, Z. Q. Wu, X. Q. Li, Y. J. Zhang, S. J. Zhang, P. Wang, R. Panneerselvam, J. F. Li*, Stable 16.2% Efficient Surface Plasmon-Enhanced Graphene/GaAs Heterostructure Solar Cell, Adv Energy Mater, 6, 1600822 (2016). 3, X. Q. Li, W. C. Chao, S. J. Zhang, Z. Q. Wu, P. Wang, Z. J. Xu, H. S. Chen, W. Y. Yin, H. K. Zhong, S. S. Lin*, 18.5% efficient graphene/GaAs van der Waals heterostructure solar cell, Nano Energy, 9, 310 (2015). 4, Z. J. Xu, S. S. Lin*, X. Q. Li, S. J. Zhang, Z. Q. Wu, W. L. Xu, Y. H. Lu, S. Xu, Monolayer MoS2/GaAs heterostructure self-driven photodetector with extremely high detectivity, Nano Energy, 23, 89, (2016). 5, H. K. Zhong, J. Xia, F. C. Wang, H. S. Chen, H. A. Wu, S. S. Lin*, Graphene-Piezoelectric Material Heterostructure for Harvesting Energy from Water Flow, Adv. Functional Mater. 27, 1604226 (2017)
About the Speaker: Prof. Shisheng Lin leads a pioneering group in the department of information science and electronic engineering in Zhejiang University. He implements the novel physics carried by novel materials into the traditional devices and create high performance optoelectronic and electronic devices. He has achieved high performance two-dimensional materials based solar cells, photodetectors and light emitting diodes. Professor Lin has demonstrated the possibility of fabrication of two-dimensional SiC, SiC2 and silicon doped graphene, which provides a solution for band gap engineering of graphene. Professor Lin leads the systematic research on 2D materials based heterostructure solar cells and has achieved 18.5% efficient graphene/semiconductor heterostructure solar cells. Professor Lin has created the unique novel graphene nanogenerator through interacting a water droplet with the graphene and the functional substrate, which can be potentially used in various kinds of sensors.
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Speaker: Assistant Professor Gong Xiao
Affiliation: Electrical and Computer Engineering, NUS
Abstract Details: Future electron systems would require large-scale heterogeneous integration where advanced transistors and devices with new materials can be reliably manufactured on a common substrate. Such heterogeneous integration will enable interconnections between various circuit components such as RF, optoelectronic, photonic, and spintronic devices. Enormous benefits can be derived in terms of functionality, cost and power per function, and system optimization, in a future where such benefits can no longer be attained by complementary metal-oxide-semiconductor (CMOS) scaling. These, in turn, will significantly aid in the advancement of more-than-Moore applications, including the Internet of Things, next-generation communications, and wearable and flexible technology. This talk would cover recent research progress to drive the vision of heterogeneous integration to address CMOS scaling challenges, including advanced transistors using various novel materials for low power and high performance applications, photonic devices, and the heterogeneous integration of different types of semiconductor devices.
About the Speaker: Dr. Gong Xiao is an Assistant Professor in the ECE Department of the National University of Singapore (NUS) since January, 2017. His research interest includes transistors with high mobility channels and advanced structures, emerging steep slope transistors, photonic devices, and integration of logic and high speed circuits. He has more than 120 publications in international journals and conferences, including 16 invited papers, 10 papers in the International Electron Devices Meeting (IEDM), and 10 papers in the VLSI Symposium. His work has been widely reported by various high-profile magazines such as IEEE Spectrum, Compound Semiconductors, Semiconductor Today, and etc.
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Speaker: Dr. Ksenia Makarenko
Affiliation: Department of Chemistry, NUS
Abstract Details: Downscaling of conventional semiconductor electronics becomes more and more challenging. Despite the large number of proposed functional building blocks, e.g., metallic nanoparticles (NPs), semiconductor nanocrystals or individual molecules, reliable contacting of such structures to electrical circuitry has proven to be a challenging task. We developed a novel bottom-up approach for the fabrication of high-quality single-electron transistors (SETs) that can easily be contacted electrically in a controllable manner. Our approach employs self-assembly of a single Au NP, acting as a SET, to Au NRs, forming the electrical leads to macroscopic electrodes. Thus, the nanoscale junctions between the nanoobject of interest (viz. the Au NP SET) and the electrical contacts are already formed in the NP/NR solution before dispersing the bottom-up formed assemblies on the substrate. The SETs, with organic molecules (1,8-octanedithiol, OPE3) acting as tunnelling barriers, are controlled by a source-drain voltage applied between the leads and a gate voltage applied to the substrate (working as a back gate). Low-temperature electron transport measurements reveal exemplary single-electron tunnelling characteristics. We also show that the SET behaviour can be significantly changed, post-fabrication, using molecular exchange of the tunnel barriers, demonstrating tunability of the assemblies. Moreover, we characterize electron transport through a parallel metallic SET system. The double island also forms a nanoscale hybrid interferometer, where we studied coherent electron transport through organic molecular layers. We observed indications that transport through the self-assembled monolayers can indeed be quantum coherent if we are in the right operating regime. The present results form a promising proof-of-principle of the versatility and high-quality of bottom-up nanoelectronics, and controlled fabrication of (quantum-coherent) nanoelectronic devices.
About the Speaker: Research Fellow, Department of Chemistry, NUS
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Speaker: Associate Professor Elbert Chia
Affiliation: School of Physical and Mathematical Sciences, NTU
Abstract Details: I will demonstrate the ultrafast dynamics of spin injection and spin-to-charge conversion in topological materials. First, in a ferromagnet/topological insulator (Co/Bi2Se3) bilayer, we find a giant spin-mediated terahertz emission dominates its dynamical response. Locked to the Cobalt magnetization direction, the giant THz emission enables unprecedented tracking of the dynamical spin-charge conversion and its dependence on external device parameters that include temperature and layer thickness. For example, this allows us to identify the timescale of spin-to-charge conversion as ~0.12 ps, that sets a technological speed limit of spin-to-charge conversion processes in topological insulators, and pave the way for designing the next generation high-speed spintronic devices based on topological insulators. Second, in a ferromagnet/monolayer 2D transition metal dichalcogenide (Co/1L-MoS2) bilayer, we demonstrate efficient spin injection into a atomically thin semiconductor --- previously thought to be too inefficient and impractical --- by injecting strongly out-of-equilibrium sub-picosecond spin current pulses, and overcome the crippling problem of impedance mismatch to obtain a massive spin transfer. On top of intrinsically allowing for the transport and processing of highly time-compressed information, the giant ultrafast spin currents in semiconductors we find here naturally overcome the biggest challenge against full integration of charge and spin electronics.
About the Speaker: Elbert Chia is an Associate Professor of the School of Physical and Mathematical Sciences, Division of Physics and Applied Physics, at the Nanyang Technological University which he joined in 2007. In his research, he uses and develops ultrafast pump-probe spectroscopy as well as THz time-domain spectroscopy to probe the ultrafast quasiparticle dynamics in strongly correlated electron systems, low-temperature condensed matter physics, and penetration depth studies of unconventional superconductors. His research has covered a number of physical systems such as high-temperature superconductors (cuprates and pnictides), graphene-based materials, topological insulators, 2D transition metal dichalcogenides, organometallic halide perovskites. Elbert received his B.Sc (Hons) 1st Class, in Mathematics from University of Auckland, New Zealand, then Postgraduate Diploma of Education (Secondary) with Distinction from the National Institute of Education, NTU. Dr Chia then obtained his MS and Ph.D. degrees in Physics from the University of Illinois at Urbana-Champaign, USA, and was a G. T. Seaborg Postdoctoral Fellow in Los Alamos National Laboratory, USA.
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Speaker: Dr. Yutsung Tsai
Affiliation: Center for Complex Quantum Systems in University of Texas, Austin
Abstract Details: Heterostructures are artificially engineered systems that consist of two or more dissimilar semiconductor junctions. Scientists have developed many combinations of heterostructures like Si/SiGe, GaAs/AlGaAs, ZnS/CdSe, and HgTe/CdTe for high-speed electronic and optoelectronic devices by tailoring those vertical multijunctions through quantum confinement. In recent years, the emergence of transition metal dichalcogenides (TMDs) has opened new frontiers in heterostructure research. In particular, their monolayer form not only enables optoelectronic application with their direct-gap band structure, but also provides a myriad of possibilities through vertical stacking due to their van der Waals (vdW) interactions between layers. On the other hand, although vertically stacked TMDs optoelectronic heterostructures have been demonstrated extensively, atomically-thin two-dimensional (2D) TMDs lateral multijunctions beyond two heterojunctions have only been explored sparingly; this has limited the development of 2D optoelectronics. In this talk, I would like to present recently achieved lateral 2D TMDs multijunctions about the growing method, their heterostructures, optoelectronic properties, and the photo-generated carrier transport mechanism. My motivation of developing these multijunctions as nano-optoelectronic platforms for quantum information, photovoltaics, and light-induced superconductivity will then be revealed and discussed. This critical development will be the building block for more advanced 2D optoelectronic architecture.
About the Speaker: Dr. Yutsung Tsai received his PhD in Physics from the State University of New York at Buffalo in 2015 and have been working as a postdoctoral research fellow at the Center for Complex Quantum Systems in University of Texas at Austin for the past two years. He has participated in condensed matter experimental research in seven labs since his undergraduate training and become a believer for “better collaboration makes better research.” The PhD students and undergraduate students mentored by him advocated his devotion by acquiring advanced experimental skills like atomic force microscopy, micro-Raman compact mapping and appearing as first authors of publications on Nature Nanotechnology. His current professional interests focus on optoelectronic semiconductors, particularly two-dimensional transition metal dichalcogenides (2D TMDs) lateral multijunctions MX2/M’X’2/MX2 (M=W, Mo; X=S, Se) for photovoltaic applications. He recently observed photo-generated carriers trapped by nanoscale quantum confined structures that was manifested by 100-fold photoconductivity at M’X’2 junction. This discovery enables innovative technology, for example, harvesting these trapped photo-generated carriers for solar cell use.
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