News & Events

Speaker: Chen Jian-Hao
Affiliation: Peking University
Abstract Details: The problem of unconventional magnetism in materials without d and f electrons has attracted continuous attention. In particular, a lot of efforts have been devoted to understand the origin and effects of magnetic moments induced in graphene with structure defects such as missing carbon atoms, absorption of light atoms such as hydrogen or fluorine. We have measured the magnetoresistance (MR) of graphene at low temperature with in-situ hydrogenation in ultra-high vacuum environment. Large negative MR was found in hydrogenated graphene which could be tuned by carrier density and sample temperature. Depending on the density of adsorbed atomic hydrogen and carrier density, large linear negative MR was found which did not saturate up to 9 Tesla. Such negative MR could be the manifestation of local moments created by atomic hydrogen adsorbed on graphene.
About the Speaker: Dr. Jian-Hao Chen obtained his PhD in Physics under the supervision of Prof. Ellen Williams at the University of Maryland (USA) in 2009. Thereafter, he worked as a Research Fellow in the nanoelectronics group of Prof. Michael Fuhrer at University of Maryland and in Prof. Alex Zettl’s group at University of California at Berkeley. Since March 2013 he joined Peking University as an Associate Professor and Principal Investigator of the Laboratory for Nanoelectronics and In-Situ Quantum Transport. His present research is focused on studying the physics and applications of low-dimensional electronic materials and its nanostructures, manipulation of material properties at the atomic scale, and in-situ quantum electrical transport in ultra-high vacuum environment. His peer-reviewed publications include three articles in Nature Physics, one article in Nature Nanotechnology and three articles in Physical Review Letters.
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Speaker: Vladimir Falko
Affiliation: University of Manchester, UK
Abstract Details: We present the evolution of electronic band structure of InSe and other III-VI semiconductors) films, from stoichiometric mono-layer to multilayer films, and trace consequences of these changes for optical properties of these 2D materials. This study is based on the ab initio DFT and related multi-orbital tight-binding model analysis of the electronic band structure and wave functions in the two-dimensional N-layer InSe crystals. We find that the conduction band edge electron mass in few-layer InSe is quite light (comparable to Si), which suggests opportunities for high-mobility devices and the development of nanocircuits. In contrast, the valence band in mono-, bi- and trilayer InSe is flat, opening possibilities for strongly correlated hole gases in p-doped systems.
About the Speaker: Professor Vladimir Falko is professor of theoretical physics and Research Director of the National Graphene Institute at the University of Manchester, and one of the UK's leading condensed matter theorists. He obtained his doctoral degree at the Institute for Solid State Physics (Russian Academy of Science), followed by postdoctoral experience at Max-Planck-Institute in Stuttgart and Oxford University. Prior to joining the University of Manchester, V. Falko served for 19 years at Lancaster University where he was Distinguished Professor and Head of Theory Division of its Physics Department. Falko was responsible for many advances in the theory of localisation and quantum transport in mesoscopic systems, and made substantial contributions towards the understanding of electronic and optical properties of graphene, including the discovery of bilayer graphene. His current research interests include modelling graphene-based electronic and optoelectronic systems and developing theories of electronic and optical properties of various atomically thin two-dimensional crystals and their heterostructures. His has received a Humboldt Fellowship, an EPSC Advanced Fellowship, ERC Advanced Investigator and Synergy Grants, and the Royal Society Wolfson Foundation Research Merit Award. Falko played a pivotal role in building up the European research community in graphene and two-dimensional materials by initiating the Graphene Week conference series and by being one of the organisers and leaders of the European Graphene Flagship Project. From 2014, he is the founding Editor-in-Chief of the IoP Journal 2D Materials (with 2016 IF of 9.6)."
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Speaker: Dr. Marco Polini
Affiliation: Italian Institute of Technology, Italy
Abstract Details: Graphene sheets encapsulated between crystals of hexagonal boron nitride host a unique two-dimensional (2D) electron system, whereby electrons suffer minimal scattering against acoustic phonons and practically no scattering against long-range disorder (unless gated very close to the charge neutrality point) [1-4]. Above liquid nitrogen temperatures, these electron liquids are expected to display local equilibrium enabled by strong electron-electron interactions and viscosity-dominated hydrodynamic transport [5-8]. In this talk I will report on results of combined theoretical and experimental work [9] showing unambiguous evidence for this long-sought transport regime. In particular, I will discuss how high-quality doped graphene sheets above liquid nitrogen temperatures exhibit negative non-local resistance near current injection points and whirlpools in the spatial current pattern [6,9,10]. Measurements of these non-local electrical signals enable to extract the value of the kinematic viscosity of the two-dimensional massless Dirac fermion liquid in graphene, which is found to compare well with many-body theoretical predictions [6]. Finally, I will also discuss the subtle connection between negative non-local resistances and current whirlpools [10]. References [1] A.S. Mayorov et al., Nano Lett. 11, 2396 (2011). [2] L. Wang et al., Science 342, 614 (2013). [3] T. Taychatanapat et al., Nature Phys. 9, 225 (2013). [4] A. Woessner et al., Nature Mater. 14, 421 (2015). [5] M. Polini and G. Vignale, The quasiparticle lifetime in a doped graphene sheet.  In No-nonsense physicist: an overview of Gabriele Giuliani's work and life (eds. M. Polini, G. Vignale, V. Pellegrini, and J.K. Jain) (Edizioni della Normale, Pisa, 2016). [6] I. Torre, A. Tomadin, A.K. Geim, and M. Polini, Phys. Rev. B 92, 165433 (2015). [7] A. Principi, G. Vignale, M. Carrega, and M. Polini, Phys. Rev. B 93, 125410 (2016). [8] L. Levitov and G. Falkovich, Nature Phys. 12, 672 (2016). [9] D. Bandurin, I. Torre, R.K. Kumar, M. Ben Shalom, A. Tomadin, A. Principi, G.H. Auton, E. Khestanova, K.S. NovoseIov, I.V. Grigorieva, L.A. Ponomarenko, A.K. Geim, and M. Polini, Science 351, 1055 (2016). [10] F.M.D. Pellegrino, I. Torre, A.K. Geim, and M. Polini, Phys. Rev. B 94, 155414 (2016).
About the Speaker: Marco Polini graduated in Physics in 1999 from the University of Pisa (Italy) and received his Ph.D. in Physics in January 2003 from the Scuola Normale Superiore (Pisa, Italy). He is a Senior Scientist at the Istituto Italiano di Tecnologia (Italian Institute of Technology) in Genoa (Italy), where he leads the Theory and technology of 2D materials group. He also holds a contract professorship at the Scuola Normale Superiore (Pisa, Italy). He has co-authored more than 140 publications in peer-reviewed international journals including Science, Nature Materials, Nature Nanotechnology, Nature Photonics, Nature Communications, and Physical Review Letters and he is a coauthor of the book Many-body physics in condensed matter systems (Edizioni della Normale, Pisa, 2006). He has carried out research at the University of Texas at Austin (USA), at the Zhejiang Normal University (China), at the Chinese Academy of Sciences in Beijing (China), at Purdue University (USA), at the University of Missouri-Columbia (USA), at Texas ;M University (USA), at the Kavli Institute for Theoretical Physics in Santa Barbara (USA), at the University of New South Wales (Australia), at the Cambridge Graphene Center (UK), at the Graphene Research Center in Singapore, at the Massachusetts Institute of Technology (USA), and at the University of Manchester (UK). In 2010 he was awarded with the prestigious italian grant FIRB - Futuro in Ricerca
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Speaker: Dr. Vittorio Pellegrini
Affiliation: Istituto Italiano di Tecnologia (Italian Institute of Technology, Genoa
Abstract Details: In this talk I shall present our recent progresses on the large-scale production of graphene, two-dimensional crystals and related composites for industrial applications. I will discuss different graphene compounds and related applications such reinforced coatings for electrical cables [1], plastic frames for glasses [2], motorcycle helmets [3], foldable biodegradable plastic [4], cellulosic graphene biocomposites sensors [5], and reinforced plastic components for robotics [6,7]. In the last part of the talk I will focus on energy conversion and storage [8] and, particularly, on our recent progresses on graphene-silicon Li-ion batteries [9,10,11]. References In collaboration with Baldassari Cavi s.r.l. (http://www.baldassaricavi.it) In collaboration with Luxottica s.p.a (http://www.luxottica.com/en) In collaboration with Momodesign s.r.l. (http://www.momodesign.com/en/) P. Cataldi, et al., Adv. Electronic Materials 1, 1500224 (2015). P. Cataldi et al. Adv. Electronic Materials (2016). E. Lago et al. RSC Adv. 6, 97931 (2016) P. Toth et al to be submitted F. Bonaccorso, et al., Science 347, 1246501 (2015). H. Sun et al. Journal of Materials Chemistry A (2016). J. Hassoun, et al. Nano Lett. 14, 4901 (2014). E. Greco et al. to be submitted
About the Speaker: Vittorio Pellegrini is a scientist at the Italian Institute of Technology (IIT) in Genova and director of the IIT Graphene Labs. He is the chair of the executive committee of the European flagship project on graphene. He is also the Italian representative of the flagship and leader of the graphene flagship work-package ENERGY STORAGE. Vittorio Pellegrini has published more than 160 peer-reviewed papers. He gave more than 60 invited/keynote talks. He was Fellow of the Italian Academy at Columbia University (USA) in 2008, Winner of Campisano prize for condensed matter physics of the CNR in 2008. Director of the CNR international schools on low-dimensional system in 2008, 2010 and 2011. He has been the coordinator and local coordinator of several european and national projects. Vittorio Pellegrini is also active in scientific divulgation. He has published several articles for the general public in Italian newspapers and routinely gives talks at science festivals and at other public events. He is co-funder of the start-up BeDimensional (www.bedimensional.it)
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Speaker: Dr. Liu Song
Abstract Details: Controlled growth of two-dimensional transition metal dichalcogenide (TMD) lateral heterostructures would enable ondemand tuning of electronic and optoelectronic properties in this new class of materials. Previous compositional modulations in lateral TMD heterostructures have been considered to depend solely on the growth chronology. We show that in-plane diffusion can play a significant role in the chemical vapor deposition of MoS2/WS2 lateral heterostructures leading to a variety of nontrivial structures whose composition does not necessarily follow the growth order. Optical, structural, and compositional studies of TMD crystals captured at different growth temperatures and in different diffusion stages suggest that compositional mixing versus segregation are favored at high and low growth temperatures, respectively. The observed diffusion mechanism will expand the realm of possible lateral heterostructures, particularly ones that cannot be synthesized using traditional methods"
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Speaker: Lee Chuen Neng
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Speaker: Antonio Castro Neto
Affiliation: CA2DM, NUS
Abstract Details: Curious about what such a title means or in what research in 2D materials and inter-galactic exploration have in common? If so, do participate in this seminar where the CA2DM director will share his vision for the future of 2D materials -- in general and in the context of our research centre -- from a broad perspective that spans fundamental science, applications, and societal impact. 'Space: the final frontier...' This is the ultimate target for CA2DM in its mission: to explore new scientific concepts, to seek out new 2D materials and create disruptive technologies, to boldly go where no other research centre has gone before. (*) Refreshments will be provided after the seminar.
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Speaker: Mustafa Çulha
Affiliation: Yeditepe University, Turkey
Abstract Details: Boron nitride nanotubes (BNNTs) are considered as structural analogues of carbon nanotubes (CNTs) and claimed to be more superior than CNTs since they resist to high temperature and harsh chemical conditions, possess high hydrogen storage capacity and unique electronic properties. Several synthesis methods such as arc-discharge, chemical vapor deposition (CVD) or laser ablation using amorphous boron, boric acid, borazine or CNTs as starting materials have recently been reported. However, all these approaches are far from the desired outcomes such as uniformity, low cost and high yield. In our on going effort, the BNNTs were synthesized starting from a commodity boron compound, colemanite, under ammonia atmosphere and iron (III) oxide as catalyst at relatively low temperatures. Figure 1 shows the SEM and TEM images of the BNNTs. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that BNNTs were at uniform structure with 10-30 nm outside diameter and 5-nm-wall-width. The synthesized BNNTs were investigated for their use in medical and biomedical applications such as gene and drug delivery, and tissue scaffolds after their toxicity evaluations. The results show that these nontoxic materials are good candidates for novel medical and biomedical applications as emerging novel materials. The financial support from The Scientific and Technological Research Council of Turkey (TUBITAK) (Project no: 112M480) is gratefully acknowledged
About the Speaker: Professor Mustafa Culha obtained his Ph.D. in chemistry from the University of Tennessee-Knoxville in 2002. Then, he joined to Advanced Biomedical Research Group as a post-doctoral researcher at Oak Ridge National Laboratory (2002-2003) before joining to Schering-Plough Corporation. In 2004, he accepted a faculty position in Genetics and Bioengineering Department of Yeditepe University, Istanbul,Turkey. The utility of spectroscopic techniques such as surface-enhanced Raman scattering (SERS) toshed light onto living-nonliving interactions, development of novel detection and diagnostic tools for medical and biomedical applications are ongoing research projects in his laboratories. He authored ofmore than 70 papers in refereed international journals, several book chapters and patents in the area of bioanalytical chemistry, and nanotechnology. He is the editor of a special issue for Surface-enhanced Raman Scattering of Journal of Nanotechnology, and NanoBio special issue for Journal of Nanoparticle Research.He is on the editorial board of Applied Spectroscopy.
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Speaker: Wang Zhuo
Abstract Details: Impressive properties arise from the atomically-thin nature of transition metal dichalcogenide 2D materials. However, being atomically thin limits their optical absorption or emission. Hence, enhancing their photoluminescence (PL) and second harmonic generation (SHG) by plasmonic nanostructures is critical for integrating these materials in optoelectronic and photonic devices. Typical PL enhancement from transition metal dichalcogenides is hundred-fold, with recent enhancement of thousand-fold achieved by simultaneously enhancing absorption, emission and directionality of the system. By suspending WSe2 flakes onto sub-20 nm wide trenches in gold substrate, we report a giant PL enhancement of ~20,000-fold (Nature Communications, 7, 11283, 2016). It is attributed to an enhanced absorption of the pump laser due to the lateral gap plasmons confined in the trenches and the enhanced Purcell factor by the plasmonic nanostructure. In addition, significant enhancement of SHG in WSe2 due to the plasmon-enhanced light-matter interaction has also been observed. The work demonstrates the feasibility of giant PL and SHG enhancement in WSe2 with judiciously designed plasmonic nanostructures and paves a way towards the implementation of plasmon-enhanced transition metal dichalcogenide photodetectors, sensors and emitters.
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Speaker: Aaron Thean
Affiliation: Department of Electrical & Computer Engineering, NUS
Abstract Details:

As the industry scales deep into the the sub-10nm technology nodes in the next decade, the need to maintain chip-level energy budget with increasing circuit density motivates the search for new materials and new transistor technologies. As the industry explores beyond Silicon materials for transistors, there are enormous recent learning on how 3-D materials like III-V and Ge bring advantages over traditional silicon, as well as new challenges. As devices with these novel materials are scaled into sub deca-nanometer dimensions, issues due to low channel density of states, narrow band-gap, and defects become major limitations. At the same time, the need for a ultra low-energy switch for low operating supply voltage, prompts us to investigate steep-subthreshold swing devices like tunnel FETs (TFETs). In turn, requiring us to integrate novel heterostructures to enable more effective tunnel junctions. However, this also highlighted new detractors like interface defects.

With the advent of 2-D crystals of Transition Metal Dichalcogenides (TMDs) and their 2-D Van Der Waal (VdW) Heterostructures, new possibilities in tunnel juctions for TFETs are revealed. In this talk, we will first discuss the challenges of scaling 3D semiconductor from MOSFETs to TFETs. We will then look at how 2-D TMDs may address these issues, while bringing new challenges. In addition, we will review challenges related to large-area growth of TMDs and possibilities for new logic technology applications.

About the Speaker:

Aaron Voon-Yew Thean is a Professor of Electrical and Computer Engineering at the National University of Singapore. He is also a consulting Fellow to IMEC, a Nano-electronic Research Center, based in Belgium. Prior to joining NUS in 2016, Aaron served as IMEC’s Vice President of Logic Technologies Research and the Director of the Logic Devices Research. Working with major industry partners like Intel, TSMC, Samsung, Globalfoundries, Qualcomm, he directed the research and development of advanced materials, device, and design technologies ranging from 7nm to Beyond CMOS technologies, 2-D materials to Spintronics.  Before joining imec in 2011, he worked at Qualcomm Inc. San Diego, CA USA, IBM-New York, and Motorola-Austin Texas. Aaron graduated in 2001 from the University of Illinois at Champaign-Urbana, USA, where he received his B.Sc. (Highest Honors), M.Sc., and Ph.D. in Electrical Engineering. He has published over 300 technical papers and holds more than 50 U.S. patents. He is also serving as an Editor of the IEEE Electron Device Letters. Among his notable recognitions include the 2014 Compound Semiconductor Industry Innovation award, Best R&D Collaboration Award from Samsung Electronics, and 2010 Young Alumni Achievement Award UIUC. Most recently, Aaron has been recognized by NRF as a Returning Singaporean Scientist.

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