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Invited speakers 2019

Marija Drndic: Once upon a time, there was a 2D nanopore

posted 2 May 2019, 03:42 by Peter Boggild   [ updated 2 May 2019, 03:44 ]

Department of Physics & Astronomy, University of Pennsylvania, Philadelphia, PA 

When molecules are driven through 2D nanopores in solution, they can changethe ion current flow through the pore, from which molecule’s physical and chemical properties can be inferred (1). DNA, proteins and other biomolecules can be analyzed in this way. Nanopores are optimal when they are thin because signal increases with decreased pore thickness, and because pores sense a smaller part of the passing molecule. Pores or vacancies in the sub-nm diameter range, can be envisioned for allowing passage of water molecules but blocking salt ions for efficient water desalination (2). Nanopores can also be integrated with nearby FETs to sense both the ionic and electronic currents (3). The temporal, spatial resolution and sensitivity in nanopore experiments have been improved over the last few years thanks to advanced materials, device designs and electronics. 

G. Danda, M. Drndic, Current Opinion in Biotechnology, 55C, 124 (2019).
J.P. Thiruraman et al., Nano Letters 18 (3), 1651 (2018).
W. Parkin, M. Drndic, ACS Sensors 3 (2), 313 (2018).

Marija Drndic is the Fay R. and Eugene L. Langberg Professor in the Department of Physics and Astronomy at the University of Pennsylvania. She received her MPhil from Cambridge University, AB, AM and PhD from Harvard University, all in Physics, and was a Pappalardo Fellow at MIT, before joining Penn in 2003. Her work on cold atom manipulation, and nanocrystal electronics was recognized by the Presidential Young Investigator Award, the Alfred Sloan Fellowship, the DARPA Young Faculty Award, the ONR Young Investigator, and the NSF Career Award. In 2013 she was named the APS Fellow “for development of novel nanofabrication methods for graphene nanoelectronics and fast biomolecular analysis in solution”. She also received several teaching awards, including the Edmund J. and Louise W. Kahn Award for Distinguished Teaching. Drndic lab focuses on nanoscale structures in the areas of experimental condensed matter physics, nanoscience and nanotechnology. The group is known for their studies of fundamental physical properties of low-dimensional and small-scale structures and the development of their device applications.

Kasper Pedersen: Non-Innocent Approaches to 2D Conductive Magnets

posted 1 May 2019, 07:48 by Peter Boggild   [ updated 1 May 2019, 07:49 ]

Department of Chemistry, Technical University of Denmark, kastp@kemi.dtu.dk , www.kemi.dtu.dk/pedersen 

Metal-organic frameworks (MOFs) constitute a new family of designer-materials where metal ion nodes are connected by organic spacer molecules (ligands) to form a rigid framework. The combination of both inorganic and organic building blocks results in virtually endless possibilities for properties tuning and a structural diversity that surpasses all other materials. Nearly all of these materials are however intrinsically insulating and the observation of interesting magnetic phenomena is hampered by the large spatial separation between the constituent metal ions. In this talk I will present our synthetic approaches to 2D metal-organic networks in which magnetic ordering and high electrical conductivity coexist. The combination of reducing transition metal ions and p-conjugated organic linkers facilitates strong p-d conjugation, which results in significant electron and spin densities on the bridging ligands and thereby providing high electron mobility as well as high magnetic ordering temperatures. This synthetic principle, benefitting from ligand redox non-innocence, proffers new possibilities for e.g. synthetically tunable 2D magnetic conductors of relevance for molecular spintronics.

Kasper S. Pedersen obtained his PhD in inorganic chemistry from the University of Copenhagen in 2014. He thereafter received a DFF-Sapere Aude Research Talent grant to pursue postdoctoral research in Bordeaux and Montreal. He returned to Denmark in 2017 as facilitated by a VILLUM Young Investigator starting grant. Since 2017 he has been a group leader and an assistant professor at the Department of Chemistry, Technical University of Denmark. His research group focuses on synthetic inorganic chemistry and materials discovery including novel types of metal-organic 2D materials, porous materials, and  spin-orbit entangled materials. 

Aitor Mugarza: Tailoring structural and electronic properties of graphene nanostructures with atomic precision

posted 1 May 2019, 07:40 by Peter Boggild   [ updated 1 May 2019, 07:50 ]

Atomic manipulation and Spectroscopy group, Catalan Institute of Nanoscience and Nanotechnology, ICN2, ES

Nanostructuring graphene confers multiple functionalities to this material, making it attractive to very diverse applications in electronics, molecular sensing and filtering. For instance, semiconducting gaps can be induced by reducing its dimensions to the nanometer scale, whereas introducing pores of similar sizes turns impermeable graphene into the most efficient molecular sieve membrane. In both cases, the interesting scale for applications is below 3-5 nm, a regime where bottom-up synthesis can be particularly efficient. 

Here I report different on-surface methods to grow graphene quantum dots with controlled shape and edge structure [1], periodic arrays of nanoribbons with lengths exceeding 100 nm [2], and nanoporous graphene sheets that combine 1 nm size ribbons and pores [3]. Their novel electronic states are correlated with the particular atomic structures by using STM. Their potential application in devices is illustrated by gate modulated transport measurements in nanoporous graphene sheets.

[1] S. O. Parreiras et al., 2D Mater., 4 25104 (2017).
[2] C. Moreno et al., Chem. Commun. 54, 9402 (2018).
[3] C. Moreno et al, Science (80-. ). 360, 199 (2018).Catalan Institute of Nanoscience and Nanotechnology

Professor Aitor Mugarza received his PhD in Physics both at the University of Basque Country. After his doctoral studies, he worked at the Lawrence Berkeley National Laboratory, USA, and at the Materials Science Institute of Barcelona (ICMAB) as a Marie Curie Fellow. He is currently ICREA research professor and group leader at the Catalan Institute of Nanoscience and Nanotechnology (ICN2). He is author of 65+ articles, and of 45+ invited talks at international conferences, universities and schools in the field of electronic and magnetism in low dimensional materials. His current research interest is focused on the bottom-up synthesis of 2D organic and hybrid materials and the engineering of their quantum properties.

Saverio Russo: The new silicon

posted 30 Apr 2019, 08:15 by Peter Boggild   [ updated 30 Apr 2019, 08:15 ]

Quantum Systems and Nanomaterials group, Physics Department, University of Exeter, UK. 

The coexistence of semiconducting properties and a stable oxide dielectric suitable for transistor applications are some of the key aspects beyond the success of Silicon. The leap to future imperceptible, wearable and flexible applications is now held back by the lack of mechanical flexibility inherent to a Silicon wafer. The development of sensing and computing on textile fibres(1) and biological tissues poses stringent constrains on the mechanical properties of materials in addition to their optical and electrical characteristics. The discovery of 2D semiconductors characterized by an unprecedented combination of physical properties is enabling a wide range of fundamental and applied science discoveries. However, the lack of a 2D system with a mechanically flexible oxide suitable for transistor, memory, light emitting and sensing devices has been holding back the true potential of these novel systems. In this talk I will present the discovery of a mechanically flexible and air stable high-k oxide obtained from the photo-oxidation of the atomically thin semiconductor HfS2. Hence I will show how spatially controlled photo-oxidation can be used to engineer specific strain patterns in a two-dimensional semiconducting sheet, leading to an unprecedented tailoring of the energy bandgap. I will discuss, how these strain fields can be used to generate built-in electric fields necessary to observe inverse charge-funnelling(2) that is the funnelling of photo-excited charges away from the excitation area towards regions where they can be efficiently separated and collected. Finally I will review the use of this novel mechanically flexible oxide in layered transistors, memories, light emitting devices and photodetectors(3)

[1] E. Torres et al., Nature Flexible Electronics 2, 25 (2018)

[2] De Sanctis A. et al., Nature Communications 9, 1652 (2018)

[3] Peimyoo, N. et al., Science Advances 5, eaau0906 (2019)

Saverio Russo is Associate Professor and academic leader of the Quantum Systems and Nanomaterials group in the Physics Department at the University of Exeter in the United Kingdom. Following a master in Physics at the University of Pisa (Italy) and a master in Materials Engineering from the Katholieke Universiteit Leuven (Belgium), he received the PhD degree in Physics from the Kavli Institute of Nanoscience Delft in the Netherlands in 2007 for pioneering studies on electron transport in hybrid structures. He has joined the University of Exeter in 2010, after securing a JSPS fellowship at the University of Tokyo (Japan). His research focusses on fundamental and applied science of emerging quantum systems to include 2D materials, and his scientific discoveries have regularly been featured by broad audience media to include BBC, NBC, The Guardian, etc.  

Yong P. Chen: Manipulating Dirac Cones - from twisted bilayer graphene to hybridized topological insulator

posted 30 Apr 2019, 06:18 by Peter Boggild

Purdue University; WPI-AIMR; and Aarhus University

In 2013, we reported synthesis of twisted bilayer graphene (tBLG) by chemical vapor deposition (CVD), and observation of new low energy Raman modes in the tBLG, resonantly enhanced when photon energy matches the energy of van Hove singularities formed with two overlapping and offset Dirac cones from the two twisted graphene layers [1]. Using gate-tunable Raman spectroscopy and transport measurements in CVD-synthetic as well as mechanically stacked/exfoliated tBLG, we have studied electron-phonon coupling and other interesting band structure physics with two offset Dirac cones whose separation in momentum or energy may be tuned by twisting and electric field [2]. More recently, we showed that tuning the thickness and in-plane magnetic field may drive a ultrathin film of topological insulator into perhaps a simpler and more tunable analog of graphene (or analog of a Weyl semimetal in 2D) possessing two non-degenerate Dirac cones with field tunable separation [3].

[1] Rui He*, Ting-Fung Chung*, Conor Delaney, Courtney Keiser, Luis A. Jauregui, Paul M. Shand, C. C. Chancey, Yanan Wang, Jiming Bao, and Yong P. Chen (*equal contribution), "Observation of Low Energy Raman Modes in Twisted Bilayer Graphene", Nano Letters 13, 3594 (2013)

[2] Ting-Fung Chung, Rui He, Tai-Lung Wu, Yong P. Chen, "Optical Phonons in Twisted Bilayer Graphene with Gate-Induced Asymmetric Doping", Nano Letters 15, 1203 (2015); Ting-Fung Chung, Yang Xu, Yong P. Chen, "Transport measurements in twisted bilayer graphene: Studies of electron-phonon coupling and Landau level crossing", Physical Review B 98, 035425 (2018)

[3] Yang Xu, Guodong Jiang, Ireneusz Miotkowski, Rudro R. Biswas, and Yong P. Chen, "Tuning insulator-semimetal transitions in 3D topological insulator thin films by inter-surface hybridization and in-plane magnetic fields", arXiv:1904.03722

Yong P. Chen leads the “Quantum Matter and Devices Laboratory” that makes, measures and manipulates diverse quantum matter ranging from 2D/topological/hybrid quantum materials to atomic quantum gases, with potential applications such as energy, sensing and quantum technologies. He received a BSc and MSc in mathematics from Xi’an Jiaotong University and MIT, a PhD in electrical engineering from Princeton University, and did a physics postdoc at Rice University. He is a Professor of Physics and Astronomy and Professor of Electrical & Computer Engineering at Purdue University and the Inaugural Director of Purdue Quantum Science and Engineering Institute (PQSEI), a principal investigator in WPI-AIMR International Materials Research Center in Tohoku, Japan, and recently selected as a 2019 Villum Investigator in Denmark hosted at Aarhus University. Chen is a recipient of young investigator awards from NSF, DOD and ACS, an IBM faculty award, and Horiba Award, and is an elected Fellow of American Physical Society (APS).

Cinzia Casiraghi: Water-based and biocompatible 2D-inks for all-inkjet printed devices

posted 30 Apr 2019, 04:31 by Peter Boggild

School of chemistry, University of Manchester, M13 9PL, UK

In this talk I will review ink-jet printable formulations made of 2D materials and their use in heterostructure-based electronics. The talk will present research conducted at the interface between chemistry and electrical engineering: we have developed a general formulation engineering approach to achieve highly concentrated, and inkjet printable water-based 2D crystal formulations, which also provide optimal film formation for heterostructure fabrication [1]. I will provide specific examples of all-inkjet printed devices, such as large area arrays of photosensors on plastic [1], programmable logic memory devices [1], strain sensors on paper [2] and capacitors [3]. If time allows, I will also present the first Hall bar measurements made on printed graphene films.
[1] McManus et al, Nature Nanotechnology, 2017, doi:10.1038/nnano.2016.281.
[2] Casiraghi et al, Carbon, 2018, 129, 462.
[3] Worsley et al, ACS Nano, 2019, 13 , 54.

Prof Cinzia Casiraghi graduated in Nuclear Engineering from Politecnico di Milano (Italy) and received her PhD in Electrical Engineering from the University of Cambridge (UK) in 2006. She was awarded with the Oppenheimer Research Fellowship, followed by the Humboldt Fellowship and the prestigious Kovalevskaja Award (1.6M Euro). In 2008 she became Junior Professor at the Physics Department of the Free University Berlin (Germany). In 2010 she joined the School of Chemistry, at the University of Manchester (UK). Her current research work is focused on the development of 2D inks and their applications in printed electronics, thermoelectrics, and biomedical applications. Furthermore, she is leading expert on Raman spectroscopy, used to characterise a wide range of carbon-based nanomaterials. She authored and co-authored more than 80 peer reviewed articles, collecting more than 22k citations (h-index = 44). She also served as chairperson and program committee member on top international conferences (eg Graphene Week, MRS, etc). She is recipient of the Leverhulme Award in Engineering (2016) and the Marlow Award (2014), given by the Royal Society of Chemistry in recognition of her meritorious contributions in the development of Raman spectroscopy for characterisation of carbon nanostructures.

Aleksandra Radenovic: Nanoscopy of 2D materials

posted 30 Apr 2019, 04:25 by Peter Boggild   [ updated 30 Apr 2019, 04:26 ]

Jean Comtet, Evgenii Glushkov, Vytautas Navikas, Jiandong Feng and Aleksandra Radenovic
Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland

In this talk, I will detail our strategy on how to translate nanoscopy techniques into the field of materials science. We have developed and applied different modalities of nanoscopy techniques that provide unique insights about the type and density of defects together with the spectral characterization at locations determined with nanometre-scale precision. We focus on defects hosted in two classes of 2D materials: hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDs), such as MoS2, WS2, MoSe2, WSe2, and MoTe2. Defects hosted in 2D materials such as h-BN and TMDs are particularly interesting due to their single photon emission. SP emitters are stable concerning transfer onto other substrates, opening the possibility of integrating them into more complex nanophotonic devices and paving the way for future semiconductor quantum information processing technologies. 
Transmission electron microscopy and scanning probe microscopy can provide atomic resolution. However, both techniques require strict sample preparation protocols and are not optimal for fast in-situ operation or applications requiring the characterization of large areas. In contrast, Nanoscopy can operate in –situ under ambient conditions and is compatible with the probing of defect chemistry and dynamics in different pH environments and under different solvents. We also demonstrated the high-content characterization of 2D materials using silicon nitride waveguides as imaging platforms that allow integration of more complex nanophotonic circuits.

Aleksandra Radenovic received her master's degree in physics from the University of Zagreb in 1999 before joining Professor Giovanni Dietler's Laboratory of Physics of Living Matter in 2000 at University of Lausanne. There she earned her Doctor of Sciences degree in 2003. In 2003 she was also awarded a research scholarship for young researchers from the Swiss Foundation for Scientific Research which allowed her to spend 3 years as a postdoctoral fellow at the University of California, Berkeley (2004-2007). Before joining EPFL as Assistant Professor in 2008 she spent 6 months at NIH and Janelia Farm. In 2010 she received the ERC starting grant and in 2015 SNSF Consolidator grant. Her group is interested in using novel nanomaterials and single molecule experimental techniques to study fundamental questions at nanoscale. 

Aravind Vijayaraghavan: Capacitive pressure and touch sensors with suspended graphene-polymer heterostructure membranes

posted 30 Apr 2019, 04:21 by Peter Boggild   [ updated 30 Apr 2019, 07:14 ]

I will present the fabrication and characterization of a suspended graphene/polymer heterostructure membrane spanning a large array of micro-cavities each up to 30 µm in diameter with 100 %  
yield.[1] Such membrannes are then employed in a capacitive pressure sensor covering an area of just 1 mm2, showing reproducible pressure transduction under static and dynamic loading up to pressures of 250 kPa, and in good agreement with calculations. Next, I will demonstrate a novel strained membrane transfer and optimizing the sensor architecture. This enables suspended structures with less than 50 nm of air dielectric gap, giving a pressure sensitivity of 123 aF/Pa per mm2 over a pressure range of 0 to 100 kPa.[2] Lastly, we demonstrate a touch-mode capacitive pressure sensor (TMCPS) incorporating a SU-8 spacer grid structure.[3] This results in a partially suspended membrane configuration, which produces reproducible deflection, even after exposing the membrane to pressures over 10 times the operating range. The device shows a pressure sensitivity of 27.1 ± 0.5 fF/Pa over a pressure range of 0.5 kPa to 8.5 kPa. I will describe our ongoing work to develop a fully transparent, flexible, multi-touch, force-touch capacitive sensor interface, and commercialisation efforts through the new spin-out Atomic Mechanics Ltd. and discuss the future of graphene-based pressure and touch sensors. 
1. Berger, et al. Nanoscale 2016 2. Berger, et al. Nanoscale 2017 3. Berger, et al. 2D Materials 2017

Dr. Aravind Vijayaraghavan is a Reader in Nanomaterials in the School of Materials and the National Graphene Institute at The University of Manchester. He leads the Nano-functional Materials Group (www.nanofunc.com) and his research involves the science and technology of graphene and 2-dimensional materials, particularly for applications in composites, sensors and biotechnology. He was previously a post-doctoral research fellow at Massachusetts Institute of Technology, USA and an Alexander von Humboldt Fellow at Karlsruhe Institute of Technology, Germany. He obtained his MEng (2002) and PhD (2006) from Rensselaer Polytechnic Institute, USA and his BTech (2000) from the Indian Institute of Technology - Madras, India. He has published over 80 papers in international peer reviewed journals and delivered over 60 presentations at international conferences. Dr. Vijayaraghavan is also a leader in science communication and won the 2013 Joshua Phillips Award for Innovation in Science Engagement and was Science Communicator in Residence at the 2013 Manchester Science Festival. He has also been awarded a Royal Society Pairing Scheme Award (2013) and a British Science Association Media Fellowship (2017). He has delivered over 40 public lectures. He is the founder of two spin-out companies, Grafine Ltd. (www.gra-fine.com) and Atomic Mechanics Ltd. (www.atomic-mechanics.com) which commercialise applications of graphene in the fields of composites and sensors respectively. 

Olga Kazakova: Graphene sensors for ultrasensitive environmental monitoring

posted 30 Apr 2019, 04:19 by Peter Boggild   [ updated 30 Apr 2019, 04:26 ]

Quantum Detection, NPL, Teddington, UK 

We demonstrate proof-of-concept graphene sensors for environmental monitoring of ultralow concentration NO2 in complex environments. Robust detection in a wide and environmentally relevant range of NO2concentrations, 10−154 ppb, was achieved, highlighting the great potential for graphene-based NO2sensors, with applications in environmental pollution monitoring, portable devices, automotive and mobile sensors for a global real-time monitoring network. The measurements were performed in a complex environment, combining NO2/synthetic air/water vapour, traces of other contaminants, and variable temperature in an attempt to fully replicate the environmental conditions of a working sensor. It is shown that the performance of the graphene-based sensor can be affected by co-adsorption of NO2and water at low temperatures (≤70 °C). However, the sensitivity to NO2 increases significantly when the sensor operates at 150 °C and the cross-selectivity to water, SO2, and CO is minimized. Additionally, it is demonstrated that single-layer graphene exhibits two times higher carrier concentration response upon exposure to NO2than bilayer graphene. 

[1] Ch. Melios, et al., ACS Sensors. 3, 1666 (2018)

Olga Kazakova received the Ph.D. degree in Solid State Physics from Institute of Crystallography, Russian Academy of Science in 1996. 
In 1999 – 2002, she was a first postdoctoral researcher and then an Assistant Professor at Chalmers University of Technology, Gothenburg, Sweden. Since 2002, she has been working at the National Physical Laboratory. Her research interests include functional (electronic, optical, structural) nanoscale studies of 2D materials; development of novel Scanning Microscopy techniques; novel sensors for Life Science and metrological applications. She is an author of ca 160 peer-refereed publications and had above 130 presentations at scientific conferences, e.g. ca 60 invited talks and seminars.  
She was a recipient of the numerous national and international awards, including Intel European Research and Innovation Award (2008), NPL Rayleigh Award and Serco Global Pulse Award (2011). She is a Fellow of Institute of Physics. 

Email: olga.kazakova@npl.co.uk 

Vittorio Pellegrini: Graphene-based electrodes for high-power Li-ion batteries

posted 30 Apr 2019, 04:15 by Peter Boggild   [ updated 30 Apr 2019, 04:27 ]

Director IIT Graphene Labs, Istituto Italiano di Tecnologia, Genova (Italy), Co-founder of Bedimensional S.p.A

In this talk I will first show that a novel laminated silicon-graphene heterostructure provides superior performance as anode nanomaterial in half and full Li-ion cells [1]. It is composed by dispersing carbon-coated polycrystalline silicon nanoparticles in between a few parallel oriented few-layers graphene flakes leading to high capacity values of around 1000 mAh/g at current values up to 3.5 A/g. On the cathode side, I will address a Lithium Iron Phosphate (LFP)-graphene nanohybrid obtained by a direct LFP crystal colloidal synthesis on few-layer graphene (FLG) flakes produced by LPE [2] offering a specific capacity exceeding 110 mAh/g at 20 C, with no electrode damaging. On Lithium Sulphur batteries, I will present a facile, non-aggressive and environmentally friendly strategy to perform a sulfur carbon composite material by simply dry a dispersion of elemental sulfur and graphene in ethanol solvent. The sample powder shows a suitable micrometric morphology exhibits a rate capability with a stable trend till current rate of 2C, a Coulombic efficiency approaching 100% for 300 cycles at the current rate of C/4 (420 mA g-1) and long cycle life up to 500 cycles delivering about 600 mAhg-1 at 2C (3350 mA g-1) [3].

[1] S. Palumbo, L. Silvestri, V. Pellegrini et al. ACS Appl. Energy Mater., 2 1793 (2019)
[2] G. Longoni, et al., Nano Energy 51 656 (2018).
[3] L. Carbone, V. Pellegrini et al. submitted.

Vittorio Pellegrini holds a PhD degree in condensed matter physics and he is currently a 
research scientist at the Istituto Italiano di Tecnologia (IIT) in Genova and director of the IIT Graphene Labs. He is the head of division energy, composites and production of the European flagship project on graphene. He is also leader of the graphene flagship work-package energy storage. His current interests focus on the exploitation of twodimensional crystals for energy devices and for applications in composites. Vittorio Pellegrini has published more than 180 peer-reviewed papers and he is co-inventor of several patents. He gave more than 100 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 Italian National Research Council in 2008. He is cofunder of the start-up BeDimensional (www.bedimensional.it). He has published several articles for the general public in newspapers and scientific magazines and routinely gives talks at science festivals and at other public events.

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