Welcome to the CarbOnlineHagen 2021 homepage. We brought 12 top-class speakers to your home or office in 2020 and 2021 a time where we need to interact more and better to keep 2D science in motion, all for free. We hope you enjoyed it. All talks from 2021 are non online (see www.youtube.com/nanoclips), and they can also be seen by scrolling further down this page. 

Keynote speakers 
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CVD graphene: Past, Present, and Future                     
Rodney Ruoff, UNIST, KR (Opening Lecture)


Emerging properties of amorphous layered membranes (carbon and boron-nitride)
Stephan Roche, ICN2, ES

Watch tutorial on polycrystalline graphene here

Engineering Deformed Graphene Membranes: From confined charges to Valley Filters and Moire Structures
Nancy Sandler, University of Ohio, US


Hydrodynamic Conductivity and Viscosity in Bilayer and Monolayer Graphene
James Hone, Columbia University, US


Bilayer graphene – a tunable 2D semiconductor for quantum electronics
Christoph Stampfer, RTWH Aachen University, DE


One atom thin Capillaries: Confined Water, Ion and Gas flows
Radha Boya, Univ. Manchester, UK


Nanophotonics with phonon polaritons in 2Dmaterials
Rainer Hillenbrand
, NanoGune, ES



What are 2D Materials good for? 
Eric Pop, Stanford University, US

Programme may be subject to change - More speakers may be added

CarbOnlineHagen? In 2020, the Carbonhagen conference series (2010-2019) was revived as "CarbOnlineHagen" to support the research community during the lockdown in Spring 2020. In 2021 we are back. 

Format? The format is simple. A 40 minute talk is given by a hand-picked invited speaker, whose research we are excited about. Moderators will collect and answer questions during the talk, and there will be 20 minutes of open discussion with the speaker after that.  

Registration? Registration is free, but required to get a link to the event. 

Organisers? The meeting is organised by DTU Physics, Technical University of Denmark, chaired by Prof. Peter Bøggild. Contact us at info@carbonhagen.com. 

Eric Pop: What are 2D Materials Good For?

posted 26 Apr 2021, 09:58 by Peter Boggild

Eric Pop (2021 - April 26 - 16.00 CET, GMT+1)                        

Electrical Engineering, Materials Science & Engineering, and SystemX Alliance
Stanford University, Stanford CA 94305, U.S.A. Contact: epop@stanford.edu

This talk will present an electrical engineer’s (biased) perspective for what 2D materials could be good for. For example, they may be good for applications where their ultrathin nature and lack of dangling bonds give them distinct advantages, such as flexible electronics [1] or DNA-sorting nanopores [2]. They may not be good for applications where conventional materials work well, like in transistors thicker than a few nanometers. I will focus on the case of 2D materials for 3D heterogeneous integration of electronics, which presents significant advantages for energy-efficient computing [3]. In this context, 2D materials could be monolayer transistors with ultralow leakage [4] (taking advantage of larger band gaps than silicon), and they could play a role in high-density data storage [5]. For example, recent results from our group have shown monolayer transistors with record performance [6,7], which cannot be achieved with sub-nanometer thin conventional semiconductors. I will also describe some less conventional applications, using 2D materials as highly efficient thermal insulators [8] and as thermal transistors [9]. These could enable control of heat in “thermal circuits” analogous with electrical circuits. Combined, these studies reveal fundamental limits and some unusual applications of 2D materials, which take advantage of their unique properties.

[1] A. Daus et al., arXiv:2009.04056 (2020)
[2] J. Shim et al. Nanoscale 9, 14836 (2017)
[3] M. Aly et al., Computer 48, 24 (2015)
[4] C. Bailey et al., EMC (2019)
[5] C. Neumann et al. Appl. Phys. Lett. 114, 082103 (2019)
[6] C. English et al., IEDM, Dec 2016
[7] C. McClellan et al. ACS Nano 15, 1587 (2021)
[8] S. Vaziri et al., Science Adv. 5, eaax1325 (2019)
[9] A. Sood et al. Nature Comm. 9, 4510 (2018).

Eric Pop is a Professor of Electrical Engineering (EE) and Materials Science & Engineering (by courtesy) at Stanford. He was previously on the faculty of UIUC (2007-13) and worked at Intel (2005-07). His research interests are at the intersection of electronics, nanomaterials, and energy. He received his PhD in EE from Stanford and three degrees from MIT (MEng and BS in EE, BS in Physics). His honors include the Presidential Early Career Award (PECASE), Young Investigator Awards from the Navy, Air Force, NSF and DARPA, and several best paper and best poster awards with his students. In 2018, he was named one of the world’s Highly Cited Researchers by Web of Science. He is an Editor of 2D Materials, has served as General Chair of the Device Research Conference, and on program committees of VLSI, IEDM, APS, and MRS conferences. In his spare time he tries to avoid injuries while snowboarding and in a past life he was a DJ at KZSU 90.1 FM, from 2000-04. Additional information about the Pop Lab is available online at http://poplab.stanford.edu.

YouTube Video

Rainer Hillenbrand: Nanophotonics with phonon polaritons in 2D materials

posted 22 Apr 2021, 10:29 by Peter Boggild   [ updated 26 Apr 2021, 09:36 ]

Rainer Hillenbrand (2021 - April 22 - 11:00 CET, GMT+1)                

University of the Basque Country

Phonon polaritons - light coupled to optical lattice vibrations - in 2D materials exhibit ultra-short wavelengths, long lifetimes and strong field confinement, which allow for manipulating infrared light at the nanometer scale. Here, we discuss real-space nanoimaging studies of ultra-confined infrared phonon polaritons, essentially in thin hexagonal boron nitride layers and nanostructures, using scattering-type scanning near-field optical microscopy (s-SNOM) and nanoscale infrared Fourier transform (nano-FTIR) spectroscopy. We visualize and analyze phonon polaritons in nanoscale waveguides and resonators, as well as propagation with anomalous wavefronts when the (effective) in-plane permittivity of the 2D material is strongly anisotropic. Particularly, we will demonstrate that phonon polaritons can be utilized to achieve vibrational strong coupling with nanoscale amounts of organic molecules.

Rainer Hillenbrand is Ikerbasque Research Professor and Nanooptics Group Leader at the nanoscience research center CIC nanoGUNE BRTA in San Sebastian (Basque Country, Spain), and a Joint Professor at the University of the Basque Country. He is also co-founder of the company neaspec GmbH (Germany), which develops and manufactures near-field optical microscopes. From 1998 to 2007 he worked at the Max-Planck-Institute for Biochemistry (Martinsried, Germany), where he led the Nano-Photonics Research Group from 2003 to 2007. He obtained his PhD degree in physics from the Technical University of Munich in 2001. Hillenbrand pioneered the development of infrared near-field nanoscopy and nanospectroscopy, and its applications in nanophotonics, polaritonics, materials sciences and soft matter sciences. In 2014 he received the Ludwig-Genzel-Price “for the design and development of infrared near-field spectroscopy and the application of the novel spectroscopy method in different fields of natural sciences”.

YouTube Video

Radha Boya: One atom thin capillaries: Confined water, Ion and Gas flows

posted 22 Apr 2021, 10:28 by Peter Boggild   [ updated 22 Apr 2021, 10:32 ]

Radha Boya (2021 - April 22 - 10:00 CET, GMT+1)        

Condensed Matter Physics Group, The University of Manchester and National Graphene Institute
Manchester M13 9PL, United Kingdom

It has been an aspiring goal to controllably fabricate nanopores and capillaries with dimensions approaching the size of small ions and water molecules. But surface roughness makes it challenging to produce capillaries with precisely controlled dimensions at this spatial scale. We have developed a method for fabrication of one atom thin, smooth angstrom (Å) scale capillaries through van der Waals assembly of two-dimensional (2D)-materials [1-5]. These capillaries can be envisaged as if individual atomic planes are removed from a bulk layered crystal leaving behind flat voids of a chosen height. A core strand of the work that I will present is the development of Angstrom-capillaries as a platform to probe intriguing molecular-scale phenomena experimentally, including: water flow under extreme atomic-scale confinement [5], complete steric exclusion of ions [3,5], voltage gating of ion flows [4] translocation of DNA [6], and specular reflection and quantum effects in gas reflections off a surface [2]. I will discuss and compare these gas flows to that in atomic-scale apertures, created from missing tungsten (W) sites in freestanding (WS2) monolayers, which show fast helium flow [7].

[1] B. Radha et al., Molecular transport through capillaries made with atomic-scale precision. Nature 538, 222 (2016).
[2] A. Keerthi et al., Ballistic molecular transport through two-dimensional channels, Nature, 558, 420 (2018).
[3] A. Esfandiar et al., Size effect in ion transport through angstrom-scale slits. Science 358, 511 (2017).
[4] T. Mouterde et al., Molecular streaming and voltage gated response in Angstrom scale channels. Nature 567, 87 (2019).
[5] K. Gopinadhan et al., Complete ion exclusion and proton transport through monolayer water. Science 363, 145 (2019).
[6] W. Yang et al., Advanced Materials 2007682, (2021).
[7] J. Thiruraman et al., Gas flows through atomic-scale apertures, Science Advances 6, eabc7927, (2020).

Prof. Radha Boya is a Professor, Royal Society University Research and Kathleen Ollerenshaw fellow at the University of Manchester (UoM). She completing her PhD in India and worked as a post-doctoctoral fellow in Northwestern University, United States. She has secured a series of highly prestigious international research fellowships, Mari-Curie fellowship, Kathleen Ollerenshaw fellowship, Royal society university research fellowship that have enabled her to rapidly build her research profile in the United Kingdom. Radha has 49 peer-reviewed publications, written two book chapters and has three patents. She was awarded as RSC Marlow award, UNESCO-L’Oréal International Rising Talent, L’Oréal UK & Ireland women in science fellow, and was recognized as an inventor of MIT Technology Review's global "Innovators under 35"

YouTube Video

(2021) Christoph Stampfer: Bilayer graphene – a tunable 2D semiconductor for quantum electronics

posted 18 Apr 2021, 08:55 by Peter Boggild   [ updated 26 Apr 2021, 09:35 ]

Christoph Stampfer (2021 - March 22 - 16:00 CET, GMT+1)         

JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany

Graphene and bilayer graphene (BLG) are attractive platforms for quantum circuits. This has motivated substantial efforts in studying quantum dot (QD) devices based on graphene and BLG. The major challenge in this context is the missing band-gap in graphene, which does not allow to confine electrons by means of electrostatics. A widely used approach to tackle this problem was to introduce a hard-wall confinement by etching the graphene sheet. However, the influence of edge disorder, turned out to be a roadblock for obtaining clean quantum devices. The problem of edge disorder can be circumvented in clean BLG, thanks to the fact that this material offers a tunable band-gap (up to 150 meV) in the presence of a perpendicularly applied electric field, a feature that allows introducing electrostatic soft confinement in BLG.Here we present gate-controlled single, double, and triple dot operation in electrostatically gapped BLG. We show a remarkable degree of control of our devices, which allows the implementation of gate-defined electron-hole and electron-electron double-dot systems, where single-electron occupation becomes possible. Also in the single dot regime, we reach the very few electron/hole regime, extract excited state energies and investigate their evolution in a parallel and perpendicular magnetic field. Finally, we will show data on ultra-clean BLG quantum dots allowing investigating the spin-valley coupling in bilayer graphene.

Christoph Stampfer is Professor of Experimental Solid State Physics at the RWTH Aachen University and researcher at the Forschungszentrum Jülich. His primary interests include graphene and 2D materials research, quantum transport, and micro electromechanical systems. He holds a Dipl.-Ing. Degree in Technical Physics from the TU Vienna (Austria) and a Ph.D. in Mechanical Engineering from the ETH Zurich (Switzerland). He was a staff member at the Institute for Micro and Nano Systems of the ETH Zurich from 2003 to 2007 and staff member of the Solid State Laboratory (Ensslin-Group at ETH Zurich) from 2007 to 2009. From 2009 till 2013 he was JARA-FIT Junior Professor at the RWTH Aachen and the Forschungszentrum Jülich. He has been awarded with an ERC Starting Grant to work on "Graphene Quantum Electromechanical Systems" in 2011, was a member of the Young Scientist community of the World Economic Forum and received in 2018 an ERC Consolidator Grant to work on “2D Materials for Quantum Technologies”.

YouTube Video

James Hone: Hydrodynamic Conductivity and Viscosity in Bilayer and Monolayer Graphene

posted 9 Mar 2021, 06:47 by Peter Boggild

James Hone (2021 - March 8 - 15:00 CET, GMT+1)          

Columbia University, Dept. of Mechanical Engineering New York NY USA  


Hydrodynamic electronic transport occurs when carrier-carrier collisions constitute the dominant scattering mechanism. This talk will present two recent studies of hydrodynamic behaviour in monolayer and bilayer graphene. I will first describe our work establishing bilayer graphene a model hydrodynamic semiconductor, in which carrier-carrier collisions play a dominant role over a wide range of temperature and carrier density. Remarkably, a simple model captures the complex interplay between carrier-carrier scattering and conventional dissipative scattering. This model consists of a universal Coulomb drag contribution that dominates at charge neutrality and decays with increasing density, and a non-universal dissipative contribution corresponding to collective motion of the electron-hole plasma. We compare this model to electrical transport measurements of ultraclean bilayer graphene encapsulated within hBN, with dual gates providing independent control over carrier density and bandgap. At charge neutrality, these samples show electron-hole limited conductivity over a wide temperature range. A single set of fit parameters provides quantitative agreement with experiments at all densities, temperatures, and gaps measured, allowing for separate extraction of the electron-hole and dissipative contributions. Our work provides the first complete description of electronic transport in bilayer graphene and provides an intuitive understanding for electron-hole limited transport across a wide range of parameters. In the second part of the talk, I will describe a new approach to determine the viscosity of electrons in graphene using geometrical magnetoresistance (MR) in a Corbino disk. In the degenerate limit where Fermi energy EF is much higher than thermal energy kBT, the shear viscosity scales unexpectedly with 1/T. As kBT approaches EF, we for the first time observe a crossover to a T2 dependence in monolayer graphene, signifying a quantum critical Dirac fluid. Remarkably, viscosity in the entire EF −T phase space is described by a universal expression considering both finite-momentum and zero-momentum modes. These results provide valuable insight into electron hydrodynamics, and the new probe of viscosity developed here can be directly employed in other systems of interest such as twisted bilayer graphene.

James Hone is currently Wang Fong-Jen Professor of Mechanical Engineering at Columbia University, and director of PAS3, Columbia’s Materials Science Research and Engineering Center (MRSEC).  He received his BS in physics from Yale in 1990, and PhD in experimental condensed matter physics from UC Berkeley in 1998, and did postdoctoral work at the University of Pennsylvania and Caltech, where he was a Millikan Fellow.  He joined the Columbia faculty in 2003.   


(2021) Nancy Sandler: Engineering Deformed Graphene Membranes: From confined charges to Valley Filters and Moire Structures

posted 4 Mar 2021, 03:46 by Peter Boggild   [ updated 9 Mar 2021, 06:45 ]

Department of Physics and Astronomy, and Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio, USA.
*e-mail: sandler@ohio.edu

As an atomically thin membrane, graphene is a highly flexible material, a property that provides the opportunity to use strain engineering to control its electronic properties. Wrinkled or rippled graphene, either suspended or on a substrate, reveals inhomogeneous charge distributions originated by underlying strain fields that affect electron dynamics. Scanning tunneling microscopy (STM) measurements on deformed samples demonstrated electron confinement with peculiar charge distributions that break sublattice symmetry. The phenomena that differentiate carbon atoms in each unit cell results in local valley currents with essential applications in the field of valleytronics, i.e., the manipulation of the valley degree of freedom for electronic purposes. Because valley filtering properties in these structures are highly dependent on the type of deformation considered, it is crucial to identify the relevant factors determining the optimal operation and detection of valley currents. While local and extended deformations confine charges, the fold geometry serves as an electronic wave-guide, as revealed in recent transport measurements.

Furthermore, we showed that fold structures provide filtering in broader energy ranges and exhibit robust features against geometrical parameter variations and incident current directions. However, designing proper geometries is not enough to isolate valley states, fully embedded in the continuum that makes graphene a semimetal. Taking the strained membrane into the Quantum Hall regimes allows the separation of these states from the continuum and provides the flexibility of positioning them at different locations in the sample. More exciting is the possibility of developing band structure engineering protocols by designing substrates able to induce specific periodic strain patterns. Our recent studies reveal that Moire structures' characteristic features appear in images of electronic charge distributions of graphene samples deposited on regular arrays of deformations. These systems exhibit narrow bands at low energies reminiscent of those observed in twisted bilayer structures, suggesting the possibility for the emergence of novel correlated physics in single graphene membranes. 

Professor Nancy Sandler is a faculty in the Department of Physics and Astronomy at Ohio University (OU), in Athens, Ohio, USA. She is a member of the Nanoscale and Quantum Phenomena Institute (NQPI) and science editor of its newsletter and member of the Editorial College at SciPost. Prof. Sandler's research focuses on novel low-dimensional materials' electronic properties and the effects of strong correlations. She is active in outreach and education activities serving as a board member in the Margaret Boyd Scholar Program, a leadership program for women undergraduates at OU, and as the physics science director in the NSF-funded NOYCE teacher fellowship program. A native of Argentina, she obtained her Lic. en Ciencias Fisicas degree from the Universidad Nacional de Buenos Aires. She continued her studies at the University of Urbana-Champaign in Illinois, USA, where she received her Ph.D. in theoretical physics (1998). After holding postdoctoral positions at ENS and Orsay (France) and Brandeis and BU (USA), she joined the Ohio University faculty in 2005. She was a visiting professor at the Dahlem Center for Complex Quantum Systems at Freie Universitat, Berlin, Germany (2012-13), and is currently a visiting faculty in the Department of Physics at the Technical University of Denmark (DTU) and the Niels Bohr Institute at the University of Copenhagen, Denmark.



(2021) Stephan Roche: Emerging properties of amorphous layered membranes (carbon and boron-nitride)

posted 15 Feb 2021, 12:01 by Peter Boggild   [ updated 9 Mar 2021, 06:48 ]

Catalan Institute of Nanoscience Nanotechnology, Campus UAB, Bellaterra, Spain
ICREA, Institució Catalana de Recerca i Estudis Avancats, Spain

Formidable progress has been recently achieved in the fabrication and characterization of disordered materials with unprecedented properties. In this context, particular forms of disordered graphene (reduced graphene oxides), obtained by chemical exfoliation techniques, have been found suitable to improve the performances of composite materials, with application in energy. Moreover, the recent demonstrated possibility to synthesize wafer-scale two-dimensional amorphous carbon monolayers and boron-nitride, structurally dominated by sp2 hybridization has initiated a new platform of low-dimensional materials to explore as alternative forms of membranes with enhanced chemical reactivity which could serve as coating materials. The excellent physical properties of the mentioned materials derive from the nature and degree of their disorder which, controlled at the fabrication level, represents the key ingredient to tune their physical/chemical properties for specific target applications. In this respect, new fabrication strategies to modify the degree of disorder and a systematic theoretical characterization of the impact of the material structural quality on the ultimate performance is urgent. Here, I will present the results of our theoretical investigation of systematic analysis of the structural and vibrational properties of amorphous carbon and boron nitride monolayers as a function of the structural quality of the material, showing how disorder results in a tunable thermal conductivity and electrical conductivity varying by orders of magnitude. In particular, I will identify how energy is dissipated in this material by a systematic analysis of emerging vibrational modes whose localization increases with the loss of spatial symmetries. Our simulations provide some recipe to design most suitable "amorphous graphene" based on the target applications such as ultrathin heat spreaders, energy harvesters or insulating thermal barriers. The unprecedented properties of amorphous boron nitride will be also discussed in the context of recent discovery of their ultralow dielectric coefficient, which provides an exceptional material for further boosting interconnects technologies in advanced nanoelectronics.

ICREA Prof. Stephan Roche is working at the Catalan Institute of Nanosciences and Nanotechnology-ICN2 and BIST. He leads the "Theoretical and Computational Nanoscience" group which focuses on physics of Dirac materials (graphene & topological insulators), 2D materials-based van der Waals heterostructures and amorphous matter. He pioneered the development of linear scaling quantum transport approaches enabling simulations of billion atoms-scale disordered models. He studied Theoretical Physics at ENS and got PhD (1996) at Grenoble University (France); worked in Japan, Spain & Germany; was appointed as assistant Prof. in 2000, CEA Researcher in 2004 and joined ICREA in 2009. He received the Friedrich Wilhelm Bessel prize from the Alexander von Humboldt Foundation (Germany). He is one of the founder of the Graphene Flagship initiative, currently workpackage (spintronics) and Division (fundamental science) leader.

TUTORIAL: Review of Polycrystalline Graphene Properties
Professor Stephan Roche is also offering a tutorial, "Review on Polycrystalline Graphene Properties", at 14.00 CET, 1 hour before his main talk. Please register HERE.  

Stephan Roche: Review of Polycrystalline Graphene Properties

YouTube Video

Stephan Roche: Emerging properties of amorphous layered membranes (carbon and boron-nitride)

YouTube Video

(2021) Rodney S Ruoff: CVD graphene: Past, Present, and Future

posted 15 Feb 2021, 11:57 by Peter Boggild   [ updated 9 Mar 2021, 06:48 ]

Director, Center for Multidimensional Carbon Materials (CMCM)
Institute for Basic Science (IBS) Center on the UNIST Campus)
UNIST Distinguished ProfessorDepartments of Chemistry and Materials Science,School of Energy Science and Chemical EngineeringUlsan National Institute of Science & Technology (UNIST)Ulsan 689-798, Republic of Koreahttp://cmcm.ibs.re.kr/http://www.unist.ac.kr/ruofflab@gmail.comhttps://en.wikipedia.org/wiki/Rodney_S._Ruoff

I’ll attempt to present some history of CVD growth of graphene, particularly on metal foils, describe some current research and near-term goals, and then look to the future while outlining several goals that merit consideration. The reader might consider these articles below prior to my presentation. (i) The large area single crystal metal foils (Cu, Ni, Co, Pd, Pt) we make by ‘colossal grain growth’ (Science, 2018: doi.org/10.1126/science.aao3373) allow (ii) growing “truly single layer and single crystal graphene” (no adlayers-no regions having 2 layers, 3 layers, etc.; Advanced Materials 2019: doi.org/10.1002/adma.201903615), (iii) obtaining large area, epitaxial, AB-stacked bilayer graphene on single crystal Cu-Ni(111) foils (Nature Nanotechnology: doi.org/10.1038/s41565-019-0622-8), and using this AB-stacked BLG to make (iv) fluorinated single layer diamond (“F-diamane”, Nature Nanotechnology: doi.org/10.1038/s41565-019-0582-z). (v) Why do wrinkles (and folds) appear in single layer graphene with some metal foil substrates and not others—it’s the interplay between adhesion (friction) and deadhesion (Advanced Materials, 2018: doi.org/10.1002/adma.201706504, Advanced Materials 2019: doi.org/10.1002/adma.201903615; “fold-free single crystal graphene”: submitted). 

The compressive strain we discovered in wrinkle-free (its epitaxial!) single layer graphene on the Cu(111) surface can (vi) ‘drive’ certain chemical reactions that do not occur for wrinkled and “not compressively strained” graphene regions (Advanced Materials, 2018: doi.org/10.1002/adma.201706504; and see more detail in Chemistry of Materials: doi.org/10.1021/acs.chemmater.9b01729). (vii) We invented a method to measure the intrinsic stiffness (that is, Young’s modulus), and the fracture strength and toughness of centimeter-scale single layer graphene (Advanced Materials 2018: doi.org/10.1002/adma.201800888) and so we discuss the meaning of our measured values and of this method of measuring tensile-loading mechanics of macroscale ultrathin samples for future studies. We have (viii) folded an A5 sheet of ultrathin polycarbonate film that is ‘laminated’ to an A5-size sheet of single layer graphene 12 times (for fun!), and 10 times to generate samples whose mechanics we could explore by 3-point bending tests. Significant stiffening, strengthening, and toughening results from the graphene folds embedded in this composite sample that has 210 = 1024 layers of embedded graphene, and 1023 folds (Advanced Materials 2018: doi.org/10.1002/adma.201707449). Support from the Institute for Basic Science (IBS-R019-D1) is appreciated.

Rodney S. Ruoff, UNIST Distinguished Professor (The Departments of Chemistry, Materials Science, and The School of Energy Science and Chemical Engineering), directs the Center for Multidimensional Carbon Materials (CMCM), an Institute for Basic Science Center (IBS Center) located at the Ulsan National Institute of Science and Technology (UNIST) campus. Prior to joining UNIST in 2014, he was the Cockrell Family Regents Endowed Chair Professor at the University of Texas at Austin from September, 2007. He earned his Ph.D. in Chemical Physics from the University of Illinois-Urbana in 1988, and was a Fulbright Fellow in 1988-89 at the Max Planck Institute für Strömungsforschung in Göttingen, Germany. He was at Northwestern University from January 2000 to August 2007, where he was the John Evans Professor of Nanoengineering and director of NU’s Biologically Inspired Materials Institute. He has authored or co-authored about 500 peer-reviewed publications related to chemistry, physics, materials science, mechanics, and biomedical science. Rod is a Fellow of the Materials Research Society, the American Physical Society, the American Association for the Advancement of Science, and the Royal Society of Chemistry. He is the recipient of the 2014 Turnbull Prize from the MRS, the 2016 SGL Skakel Award from the American Carbon Society, the James C. McGroddy Prize for New Materials from the American Physical Society in 2018, and has been named a “Citation Laureate” (Clarivate Analytics) for many years. For further background on some of his research see: http://en.wikipedia.org/wiki/Rodney_S._Ruoff . [If of interest: Google Citation H-index 161, I-10 Index 503, 41 publications cited > 1000 times and 10 > 5000 times. A ‘highly cited researcher’ in Chemistry, Physics, and Materials Science, since such statistics have been reported by Thomson Reuters (and more recently by Clarivate Analytics).]

YouTube Video

(2020) Mark Hersam: Atomically Thin Neuromorphic Computing Materials and Devices

posted 15 Feb 2021, 11:55 by Peter Boggild

Department of Materials Science and Engineering, Northwestern University, USA
2220 Campus Drive, Evanston, IL 60208-3108, USA 
m-hersam@northwestern.edu; http://www.hersam-group.northwestern.edu/

The exponentially improving performance of conventional digital computers has slowed in recent years due to the speed and power consumption issues that are largely attributable to the von Neumann bottleneck (i.e., the need to transfer data between spatially separate processor and memory blocks). In contrast, neuromorphic (i.e., brain-like) computing aims to circumvent the limitations of von Neumann architectures by spatially co-locating processor and memory blocks or even combining logic and data storage functions within the same device. In addition to reducing power consumption in conventional computing, neuromorphic devices also provide efficient architectures for emerging applications such as image recognition, machine learning, and artificial intelligence [1]. With this motivation in mind, this talk will explore the opportunities for atomically thin materials in neuromorphic devices. For example, by combining p-type single-walled carbon nanotube thin films with n-type transition metal dichalcogenides, gate-tunable diodes have been realized, which show anti-ambipolar transfer characteristics that are suitable for artificial neurons, competitive learning, and spiking circuits [2]. In addition, by exploiting field-driven defect motion mediated by grain boundaries in monolayer MoS2, gate-tunable memristive phenomena have been achieved, which enable hybrid memristor/transistor devices (i.e., “memtransistors”) that concurrently provide logic and data storage functions [3]. The planar geometry of memtransistors further allows multiple contacts to the channel region that mimic the behavior of biological neurons such as heterosynaptic responses [4]. Overall, this work introduces new foundational circuit elements for neuromorphic computing in addition to providing alternative pathways for studying and utilizing the unique charge transport characteristics of atomically thin materials and heterostructures [5].

[1] V. K. Sangwan, et al., Nature Nanotechnology, DOI: 10.1038/s41565-020-0647-z (2020).
[2] M. E. Beck, et al., Nature Communications, 11, 1565 (2020).
[3] V. K. Sangwan, et al., Nature Nanotechnology, 10, 403 (2015).
[4] V. K. Sangwan, et al., Nature, 554, 500 (2018).
[5] D. Jariwala, et al., Nature Materials, 16, 170 (2017).

Mark C. Hersam is the Walter P. Murphy Professor of Materials Science and Engineering and Director of the Materials Research Center at Northwestern University. He also holds faculty appointments in the Departments of Chemistry, Applied Physics, Medicine, and Electrical Engineering. He 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 (UK) in 1997, and a Ph.D. in Electrical Engineering from UIUC in 2000. His research interests include nanomaterials, nanomanufacturing, scanning probe microscopy, nanoelectronic devices, and renewable energy. Dr. Hersam has received several honors including the Presidential Early Career Award for Scientists and Engineers, TMS Robert Lansing Hardy Award, AVS Peter Mark Award, MRS Outstanding Young Investigator, U.S. Science Envoy, MacArthur Fellowship, and eight Teacher of the Year Awards. An elected member of the National Academy of Inventors, Dr. Hersam has founded two companies, NanoIntegris and Volexion, which are commercial suppliers of nanoelectronic and battery materials, respectively. Dr. Hersam is a Fellow of MRS, AVS, APS, AAAS, SPIE, and IEEE, and also serves as an Associate Editor of ACS Nano.

Mark Hersam

(2020) Sarah Haigh: Atomic Imaging enabling 2D heterostructure development: Studies of bend, twist, and point defects

posted 15 Feb 2021, 11:54 by Peter Boggild

University of Manchester

This talk aims to demonstrate how atomic resolution transmission electron microscope imaging is being used to support and enable the development of 2D materials and their heterostructures. The possibility to create new ‘designer’ materials by stacking together atomically thin layers extracted from layered materials with different properties has opened up a huge range of opportunities, from new optoelectronic phenomena [1], modifying and enhancing electron interactions in moire superlattices [2], to creating a totally new concept of designer nanochannels for molecular or ionic transport [3]. The impressive progress being achieved in the field crucially depends on knowledge of the atomic structure of these heterostructures, which in many cases can only be analysed by transmission electron microscopy (TEM) techniques. In this talk I will try to illustrate this statement with some of our recent work. For example, plan view imaging of point defect dynamics in graphene encapsulated monochalcogenides, GaSe and InSe (Fig. 2) [4]. 

Cross sectional imaging allows analysis and also prediction of the 
microstructures produced when 2D van der Waals material (graphite, boron nitride, MoSe2) are subjected to mechanical deformation [5]. We find that above a critical thickness the materials exhibit numerous twin boundaries and for large bend angles these can contain nanoscale regions of local delamination (Fig.1). Such features are proposed to be important in determining how easily the material can be thinned by mechanical or liquid exfoliation.[5] We finally demonstrate study of twisted bilayer structures of semiconducting transition metal chalcogenides where we see unexpected structural relaxation, different to that observed in bilayer graphene. Complementary scanning tunnelling measurements show that such reconstruction creates strong piezoelectric textures, opening a new avenue for engineering of 2D material properties [6].

[1] Zultak, Nature Communications 11 (1), 1-6 (2020)
[2] R. Krishna-Kumar, Science 357, 181-184 (2017)
[3] B. Radha et al. Nature 538, 222–225 (2016) and Keerthi, et al Nature 558 (7710), 420-424. (2018) 
[4] Hopkinson et al ASC Nano 13 (5), 5112-5123 (2019)
[5] Rooney et al 9, Nature Communications, 9, 3597, (2018)  
[6] Weston et al Nature Nanotechnology, in press (2020).

Sarah Haigh is Professor of Materials in the Department of Materials at University of Manchester, Director of the Electron Microscopy Centre (the largest in the UK), and Deputy Director of the BP International Centre for Advanced Materials. Her group applies advanced transmission electron microscopy (TEM) techniques to understand nanomaterial performance and she holds an ERC Starter Grant developing in situ TEM techniques with 2D heterostructures. 

Sarah Haigh

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