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Organizing Committee
Symposium Organizer:
Ho Bum Park (Hanyang University, Korea)
Antonio Politano (University of Calabria, Italy)
Enrich Drioli (University of Calabria (Italy) & Hanyang University (Korea))
Francesco Canganella (Science and Technology Counsellor, Embassy of Italy)
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Contents
Welcome Address ................................................................................................................ 4
Venue ........................................................................................................................................ 5
List of Speakers .................................................................................................................... 7
Program Timetable .............................................................................................................. 8
Presentation Schedule ....................................................................................................... 9
Abstracts ................................................................................................................................ 11
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Welcome Address
Dear participants,
It is with a great pleasure to welcome you all to the Korea-Italy Bilateral Symposium on Beyond Graphene at Hanyang University, Korea. This unique symposium between two countries will provide a friendly platform for renowned researchers to discuss their new findings and ideas on graphene and any other rising two-dimensional materials, and build a lasting collaboration to encourage synergy in research.
We have prepared an exciting program for participants to freely discuss their research in oral presentations. After the program, a dinner banquet is planned for all speakers.
On behalf of organizing committee, we appreciate the support and help of the co-organizers who made this wonderful symposium a success. We hope everyone will enjoy this fulfilling and inspiring event.
Welcome to Korea!
Yours sincerely,
Young Moo Lee
Hanyang University
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Venue
Address: Fusion Tech Center (FTC) 402, Hanyang University, Haengdang 1-dong, Seongdong-gu, Seoul, South Korea Route from Hotel Plaza
By taxi (recommended): the address is Hanyang University, FTC building, expected cost of the fare: 15,000 KRW (approximately $15)
By Subway: Take Line 2 (Green line) towards Wangsimni, get off at Hanyang University station, 2nd exit, follow the path shown in the map
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Seoul Subway Map
Seoul Metro website (http://www.seoulmetro.co.kr/eng/)
Seoul Tour website (http://english.seoul.go.kr/)
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List of Speakers
Affiliation Name
Sungkyunkwan University Young Hee Lee
Hanyang University Ho Bum Park
Sungkyunkwan University Dongmok Whang
KAIST Sang Ouk Kim
Hanyang University Danil W. Boukhvalov
Sungkyunkwan University Jae-Young Choi
Hanyang University Jun-Hyung Cho
University of Calabria Antonio Politano
IIT Francesco Bonaccorso
NEST Miriam S. Vitiello
University of Padova Gaetano Granozzi
NEST Stefan Heun
University of Calabria & Hanyang University
Enrico Drioli
CNR Maurizio Peruzzini
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Program Timetable
09:00–09:30 Registration 09:30–09:40 OpeningRemarks H.E.MarcodellaSeta,AmbassadorofItaly;PresidentYoungMooLee,HYU 09.40–10:10 Thereisplentyofroomat2D‐layeredmaterials
Prof.YoungHeeLee,SKKU 10:10–10:40 Theendlessatlasoftwo‐dimensionalmaterials“beyondgraphene”: statusandprospect
Dr.AntonioPolitano,UniversityofCalabria 10:40–11:10 Nanoscaleassembly&chemicalmodificationofgraphene‐basedmaterials
ProfessorSangOukKim,KAIST 11:10–11:40 Grapheneandother2Dcrystalsforenergyand(opto)electronicapplications Dr.FrancescoBonaccorso,IIT 11:40–12:10 Competingtopologicalstatesin2Dorganometallichoneycomblattice
Prof.Jun‐HyungCho,HYU 12:10–12:40 Terahertzphotodetectionmediatedbynovelbi‐dimensionalnano‐materials
Dr.MiriamS.Vitiello,NEST
12:40–14:00 LunchBreak(6thFl.HIT) 14:00–14:30 Asurfacesciencebaseddrivinglicensebeyondgraphene Prof.GaetanoGranozzi,UniversityofPadova 14:30–15:00 Monolayergraphenewithcontrolledcrystallinity:fromamorphoustosingle
crystalline Prof.DongmokWhang,SKKU
15:00–15:30 Synthesisoflarge‐areasinglecrystallinegrapheneoncopperfoildrivenbyabnormalgraingrowth Prof.Jae‐YoungChoi,SKKUandProf.HoBumPark,HYU
15:30–16:00 Phosphorene,anew2Dplaygroundchallengingchemicalfunctionalization Dr.MaurizioPeruzzini,CNR 16:00–16:15 CoffeeBreak 16:15–16:45 Chemicalpropertiesofphosphorene:insightfromDFTcalculations
Prof.DanilW.Boukhvalov,HYU 16:45–17:15 Prospectsforhydrogenstorageingraphene Dr.StefanHeun,NEST 17:15–17:45 Compositegrapheneandbeyondgraphenemembranes
Prof.EnricoDrioli,UniversityofCalabria&HYU 17:45–18:15 Maximizingtherightstuff:roleof2Dmaterialsonmembraneworld Prof.HoBumPark,HYU 18:15–18:30 ClosingRemark Prof.FrancescoCanganella,ScienceandTechnologyCounsellor,EmbassyofItaly
18:30–20:00 Banquet(6thFl.AdminBldg)
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Presentation Schedule <Oral Session 1 – 3>
Chair: Prof. Dongmok Whang
9:40 ~ 10:10 Thereisplentyofroomat2D‐layeredmaterialsProf.YoungHeeLee,SKKU
10:10 ~ 10:40 Theendlessatlasoftwo‐dimensionalmaterials“beyondgraphene”:statusandprospect Dr.AntonioPolitano,UniversityofCalabria
10:40 ~ 11:10 Nanoscaleassembly&chemicalmodificationofgraphene‐basedmaterials ProfessorSangOukKim,KAIST
<Oral Session 4 – 6>
Chair: Dr. Antonio Politano
11:10 ~ 11:40 Grapheneandother2Dcrystalsforenergy and(opto)electronicapplications Dr.FrancescoBonaccorso,IIT
11:40 ~ 12:10 Competingtopologicalstatesin2DorganometallichoneycomblatticeProf.Jun‐HyungCho,HYU
12:10 ~ 12:40 Terahertzphotodetectionmediatedbynovelbi‐dimensionalnano‐materials Dr.MiriamS.Vitiello,NEST
<Oral Session 7 – 10>
Chair: Prof. Ho Bum Park
14:00 ~ 14:30 Asurfacesciencebaseddrivinglicensebeyondgraphene Prof.GaetanoGranozzi,UniversityofPadova
14:30 ~ 15:00 Monolayergraphenewithcontrolledcrystallinity:fromamorphoustosinglecrystalline Prof.DongmokWhang,SKKU
15:00 ~ 15:30 Synthesisoflarge‐areasinglecrystallinegrapheneoncopperfoildrivenbyabnormalgraingrowth Prof.Jae‐YoungChoi,SKKUandProf.HoBumPark,HYU
15:30 ~ 16:00 Phosphorene,anew2Dplaygroundchallengingchemicalfunctionalization Dr.MaurizioPeruzzini,CNR
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<Oral Session 11 – 14>
Chair: Prof. Enrico Drioli
16:15 ~ 16:45 Chemicalpropertiesofphosphorene:insightfromDFTcalculationsProf.DanilW.Boukhvalov,HYU
16:45 ~ 17:15 ProspectsforhydrogenstorageingrapheneDr.StefanHeun,NEST
17:15 ~ 17:45 Compositegrapheneandbeyondgraphenemembranes Prof.EnricoDrioli,UniversityofCalabria&HYU
17:45 ~ 18:15 Maximizingtherightstuff:roleof2DmaterialsonmembraneworldProf.HoBumPark,HYU
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Abstracts
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There is plenty of room at 2D-layered materials
Young Hee Lee*
Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon, 440-746, Korea
*E-mail: [email protected]
Motivated by graphene which has exotic Dirac-particle like feature with extremely high mobility at room temperature but still limited by the zero bandgap feature, other types of 2D materials such as insulating hexagonal-BN monolayer and semiconducting layered transition metal dichalcoginides (LTMDs) have been intensively focused as a new class of transparent and flexible materials, which can be used as essential components of transistors for soft electronics. While large-area graphene is available in a meter-scale, synthesis of large area monolayer h-BN and LTMDs are still a long way to realize. These materials have known to exhibit exotic physical and chemical phenomena which have never been accessed so far with 3D materials. I will demonstrate some key concepts of 2D materials why they differ from 3D and show some examples of some new phenomena that emerge uniquely in 2D materials in this talk. We will also demonstrate that thin MoTe2 revealed a reversible phase transition from 2H to 1T’ at around 650-900 oC depending on Te-rich conditions. We will further demonstrate that the phase transition of MoTe2 can be provoked by several robust parameters such as laser irradiation and strain. The problematic Ohmic contact was realized by phase patterning of the contact area at source and drain positions with laser irradiation. We further demonstrate that even the phase transition temperature can be reduced to room temperature by applying a tensile strain of ~0.2%. 1. Keum and Cho et al., Bandgap opening in few-layered monoclinic MoTe2 ', Nature Phys. 11, 482-486 (2015) 2. Cho et al., ' Phase patterning for ohmic homojunction contact in MoTe2 ', Science 349, 625-628 (2015) 3. Kim et al., ‘Dense dislocation arrays embedded in grain boundaries for high-performance bulk thermoelectrics',
Science 348, 109-114 (2015) 4. Lee et al., ‘Selective amplification of primary exciton in MoS2 monolayer', Phys. Rev. Lett. 115, 226801 (2015) 5. Perello et al., ' High-performance n-type black phosphorus transistors with type control via thickness and contact-
metal engineering ', Nature Comm. 6, 1~8 (2015)
Coulomb interaction
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The endless atlas of two-dimensional materials “beyond graphene”
: Status and prospect
Antonio Politano
University of Calabria, Department of Physics, cubo 31/C 87036 Rende (CS) Italy Two-dimensional (2D) materials had a groundbreaking impact on science and technology. Their use for the fabrication of nanodevices strongly depends on their electronic band gap. As an example, the gapless spectrum of graphene avoids the effective switching of its conductivity in electronic devices and, moreover, the achievement of a high ON-OFF ratio. Thus, there is a continuous effort in the search of novel materials with finite and direct band gaps. Nature provides a variety of layered materials “beyond graphene” (semimetals, semiconductors, insulators) 1 with electronic band gaps going from the infrared to the ultraviolet. The synthesis of novel 2D materials, such as transition-metal dichalcogenides (MoS2 , WS2, MoSe2, WSe2), 2D carbides, IV-VI compounds or atomically thin elemental materials (silicene, germanene, phosphorene, stanene) promises a revolutionary step-change. Such innovative 2D materials allow combining flexibility and transparency with an existing electronic band gap. A 2D material is characterized by the following properties: (i) strong in-plane bonds, (ii) highly crystalline atomic planes and (iii) van der Waals interactions between atomically-thin planes in the normal direction (i.e. missing dangling bonds). The absence of dangling bonds between the planes and the weak van der Waals interaction enable the isolation of single-unit-cell-thickness flakes by mechanical or chemical exfoliation of a parental bulk crystal 2. In addition, recently other classes of innovative materials have emerged. In particular, topological insulators (TIs) combine the presence of bulk band gap with surface states forming a Dirac cone as for graphene3. Their peculiar band structure enable (i) the control of electron flow and (ii) the reduction of low-frequency noise in TI-based electronic devices. The recent advent of additional novel topological phases of matter, such as Dirac and Weyl semimetals, will be also discussed. 1. P. Miro, M. Audiffred, and T. Heine, Chem. Soc. Rev. 43, 6537 (2014). 2. M. Buscema, J. O. Island, D. J. Groenendijk, S. I. Blanter, G. A. Steele, H. S. J. van der Zant, and A.
Castellanos-Gomez, Chem. Soc. Rev. 44, 3691 (2015). 3. A. Politano, V. M. Silkin, I. A. Nechaev, M. S. Vitiello, L. Viti, Z. S. Aliev, M. B. Babanly, G. Chiarello, P.
M. Echenique, and E. V. Chulkov, Phys. Rev. Lett. 115, 216802 (2015).
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Nanoscale assembly & chemical modification of graphene based materials
Sang Ouk Kim
National Creative Research Initiative Center for Multi-Dimensional Directed Nanoscale Assembly
Department of Materials Science & Engineering, KAIST 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
E-mail: [email protected] Graphene based materials, such as carbon nanotubes and graphene attract enormous research attention for their outstanding material properties along with molecular scale dimension. Optimized utilization of the graphene based materials in many different application fields inevitably requires the subtle controllability of their structures and properties. In this presentation, our recent research works associated to nanoscale assembly and chemical modification of graphene based nanomaterials will be presented [1, 2]. Carbon nanotubes and graphene can be efficiently assembled into various three-dimensional structures via various self-assembly principles. The resultant carbon assembled structures with extremely large surface and high electro-conductivity are potentially useful for energy storage/conversion, catalysis and so on. In particular, aqueous dispersion of graphene oxide shows liquid crystalline phase, whose spontaneous molecular ordering is useful for fiber spinning or nanoporous material production [3-5]. In addition, the substitutional doping of graphitic carbon with B- or N- was achieved via pre- or post-synthetic treatment. The resultant chemically modified graphene based nanostructures with tunable workfunction and remarkably enhanced surface activity could be employed for organic solar cells, nanocomposite generators and dopant specific unzipping process for improved functionalities and device performances [6, 7]. 1. S. H. Lee, D. H. Lee, W. J. Lee, S. O. Kim, Advanced Functional Materials 21 (2011), 1338 - Invited Feature
Article. 2. U. N. Maiti, W. J. Lee, J. M. Lee, Y. T. Oh, .J. Y. Kim, J. E. Kim, J. Shim, T. H. Han, S. O. Kim, Advanced
Materials 26 (2014), 40 - 25th Anniversary Article. 3. J. E. Kim, T. H. Han, S. H. Lee, J. Y. Kim, C. W. Ahn, J. M. Yun, S. O. Kim, Angewandte Chemie International
Edition 50 (2011), 3043. 4. J. Y. Kim, S. O. Kim, Nature Materials 13 (2014), 325 - News & Views. 5. U. N. Maiti, J. Lim, K. E. Lee, W. J. Lee, S. O. Kim, Advanced Materials 26 (2014), 615. 6. K. I. Park, M. Lee, Y. Liu, S. Moon, G. T. Hwang, G. Zhu, J. E. Kim, S. O. Kim, D. K. Kim, Z. L. Wang, K. J.
Lee, Advanced Materials 24(2012), 2999. 7. J. Lim, U. N. Maiti, N. Y. Kim, R. Narayan, W. J. Lee, D. S. Choi, Y. Oh, J. M. Lee, G. Y. Lee, S. H. Kang, H.
Kim, Y. H. Kim, S. O. Kim, Nature Communications 7 (2016), 10364.
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Graphene and other 2D crystals for energy and (opto)electronic applications
Francesco Bonaccorso
Istituto Italiano di Tecnologia, Graphene Labs, Via Morego 30, 16163 Genova, Italy
Email: [email protected]
Graphene, thanks to its excellent material properties, has the opportunity to improve the performance of existing devices or enable new ones1-6 that are also environmentally friendly.7 Graphene is just the first of a new class of two dimensional (2D) crystals, derived from layered bulk crystals.2 The assembly of such 2D crystals (heterostructures) will provide a rich toolset for the creation of new, customized materials.1,2
A key requirement for applications such as flexible (opto)electronics and energy storage and conversion is the development of industrial-scale, reliable, inexpensive production processes,2 while providing a balance between ease of fabrication and final material quality with on-demand properties.
Liquid-phase exfoliation2 is offering a simple and cost-effective pathway to fabricate various 2D crystal-based (opto)electronic and energy devices, presenting huge integration flexibility compared to conventional methods. Here, I will present an overview of graphene and other 2D crystals for flexible and printed (opto)electronic and energy applications, starting from solution processing of the raw bulk materials,2 the fabrication of large area electrodes3 and their devices integration.6-12
1. A. C. Ferrari, et al., Nanoscale, 7, 4598-4810 (2015). 2. F. Bonaccorso, et al., Materials Today, 15, 564-589, (2012). 3. F. Bonaccorso, et. al., Nature Photonics 4, 611-622, (2010). 4. F. Bonaccorso, Z. Sun, Opt. Mater. Express 4, 63-78 (2014). 5. G. Fiori, et al., Nature Nanotech 9, 768-779, (2014). 6. F. Bonaccorso, et. al., Science, 347, 1246501 (2015). 7. G. Calogero, et al., Chem. Soc. Rev. 44, 3244-3294 (2015). 8. J. Hassoun, et al. Nano Lett. 14, 4901-4906 (2014). 9. F. Bonaccorso, et al. Adv. Funct. Mater. 25, 3870-3880 (2015). 10. P. Cataldi, et al. Adv. Electr. Mater. 1, DOI: 10.1002/aelm.201500224 (2015). 11. S. Casaluci, et al. Nanoscale 8, 5368-5378 (2016). 12. H. Sun, et al., J. Mater. Chem. A DOI: 10.1039/C5TA08553E (2016).
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Competing topological states in 2D organometallic honeycomb lattice
Jun-Hyung Cho
Department of Physics, Hanyang University
Since the discovery of the quantum Hall effect, the concept of topological order has become a subject of major interest in contemporary condensed matter physics. Kane and Mele revealed that graphene, a two-dimensional (2D) honeycomb lattice of carbon atoms, opens a gap by spin-orbit coupling (SOC) and realizes a topologically nontrivial state called the quantum spin Hall (QSH) state, giving rise to a quantized response of a transverse spin current to an applied in-plane electric field. This discovery triggers a huge amount of activities in exploring 2D or three-dimensional topological insulators that possess robust helical conducting edge or surface states on the boundary of bulk insulators. This peculiar helical state is topologically protected from elastic backscattering by time-reversal symmetry, and hence offers fascinating playgrounds for applications in spintronics and quantum computation devices. Here, using first-principles calculations, we show that a 2D hexagonal triphenyl-lead lattice composed of only main group elements is susceptible to a magnetic instability, characterized by a considerably more stable antiferromagnetic (AFM) insulating state rather than the topologically nontrivial quantum spin Hall state proposed recently. Even though this AFM phase is topologically trivial, it possesses an intricate emergent degree of freedom, defined by the product of spin and valley indices, leading to Berry curvature-induced spin and valley currents under electron or hole doping. Furthermore, such a trivial band insulator can be tuned into a topologically nontrivial matter by the application of an out-of-plane electric field, which destroys the AFM order, favoring instead ferrimagnetic spin ordering and a quantum anomalous Hall state with a nonzero topological invariant. These findings further enrich our understanding of 2D hexagonal organometallic lattices for potential applications in spintronics and valleytronics.
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Terahertz photodetection mediated by novel bi-dimensional nano-materials
Miriam Serena Vitiello*
NEST, CNR-Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, Pisa (Italy)
The ability to convert light into an electrical signal with high efficiencies and controllable dynamics is a major need in photonics and optoelectronics. In the Terahertz (THz) frequency range, with its exceptional application possibilities in high data rate wireless communications, security, night-vision, biomedical or video-imaging and gas sensing, detection technologies providing efficiency and sensitivity performances that can be “engineered” from scratch, remain elusive [1]. These key priorities prompted in the last decade a major surge of interdisciplinary research, encompassing the investigation of different technologies in-between optics and microwave electronics, different physical mechanisms and a large variety of material systems [1,2] offering ad-hoc properties to target the expected performance and functionalities.
The talk will provide an overview on our recent developments on THz photodetectors from graphene [1] to novel and fascinating 2D material systems, never exploited before for any active THz device, as black phosphorus and topological insulators (TI). By exploiting the inherent electrical and thermal in-plane anisotropy of a flexible thin flake of black-phosphorus (BP), we devised plasma-wave, thermoelectric and bolometric nano-detectors with a selective, switchable and controllable operating mechanism [3,4]. All devices operates at room-temperature and are integrated on-chip with planar nanoantennas, which provide remarkable efficiencies through light-harvesting in the strongly sub-wavelength device channel. The achieved selective detection (5-8 V/W responsivity) and sensitivity performances (signal-to-noise ratio of 500), are here exploited to demonstrate the first concrete application of a phosphorus-based active THz device, for pharmaceutical and quality control imaging of macroscopic samples, in real-time and in a realistic setting.
As a very intriguing alternative, we explored TIs which represent a novel quantum state of matter, characterized by edge or surface-states, showing up on the topological character of the bulk wave-functions. Allowing electrons to move along their surface, but not through their inside, they emerged as an intriguing material platform for the exploration of exotic physical phenomena, somehow resembling the graphene Dirac-cone physics, as well as for exciting applications in optoelectronics, spintronics, nanoscience, low-power electronics and quantum computing. Investigation of topological surface states (TSS) is conventionally hindered by the fact that, in most of experimental conditions, the TSS properties are mixed up with those of bulk-states. We devised a novel tool to unveil TSS and to probe related plasmonic effects. By engineering Bi2Te(3-x)Sex stoichiometry, and by gating the surface of nanoscale field-effect-transistors, exploiting thin flakes of Bi2Te2.2Se0.8 or Bi2Se3, we recently provided the first demonstration of room-temperature Terahertz (THz) detection mediated by over-damped plasma-wave oscillations on the “activated” TSS of a Bi2Te2.2Se0.8 flake [5]
1. F.H.L. Koppens, T. Mueller, Ph. Avouris, A.C. Ferrari, M.S. Vitiello, and M. Polini “Photodetectors based on graphene, other two-dimensional materials, and hybrid systems”, Nature Nanotech. 9, 780 (2014).
2. M. S. Vitiello et al. “One dimensional semiconductor nanostructures: An effective active-material for terahertz detection” APL Materials, 3, 026104 (2015).
3. L. Viti et al. “Black Phosphorus Terahertz photodetectors” Advanced Materials, 27, 5567 (2015). 4. L.Viti et al. “Efficient Terahertz detection in black-phosphorus nano-transistors with selective and controllable
plasma-wave, bolometric and thermoelectric response” Scientific Reports, (2016). 5. L. Viti et al. “Plasma-Wave Terahertz Detection Mediated by Topological Insulators Surface States”, Nano
Letters (2016) DOI: 10.1021/acs.nanolett.5b02901.
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A Surface Science based driving license beyond graphene
Gaetano Granozzi and Stefano Agnoli
Surface Science and Catalysis Group, Department of Chemical Sciences, University of Padova, Italy
The field of ultrathin 2D films has been developing well before the great acceleration given by the
astonishing properties associated to the isolation of graphene. It was already well acknowledged within the community of Surface Science that many innovative properties were reachable by exploiting matter in 2D.[1] Since the historical article by Novoselov and Geim,[2] a tremendous race has been initiated where the main focus was on the understanding of the many innovative properties of graphene. Since then, the forefront of research on graphene, mainly pushed by the very active materials science community, has progressed toward a second generation of graphene-based materials that, very simplistically, can be divided into two main categories: chemically modified graphene and 3D architectures based on 2D graphene layers. The contribution of Surface Science to such second generation graphene systems has been recently outlined. [3] Nowadays, we are facing the third generation of graphene-related materials: getting out from the restricted territory of graphene, the whole realm of the 2D materials is now considered. In this context, again Surface Science is taking the lead of the play.
In particular, heterostructures made up by 2D materials, obtained by following the methodology and tools of Surface Science, are emerging as a test ground for new physics and new chemistry, and represent a treasure trove for innovative applications in electronics, sensors, photovoltaics. [4]
Actually, the rational combination of different nanosheets provides a way to control in a surgical way the physicochemical properties of the assembled 2D heterostructures and sometimes it allows even inducing totally new properties. However, basic research is only at the beginning of its journey into this multi-material flatland. Actually, one major obstacle toward the full comprehension of heterostructures and in particular for a fundamental understanding of structure-activity relationships, is represented by the complex methods needed for producing highly perfect interfaces with low defectivity, extreme purity, and atomic scale control of structural properties. In this contribution, we present what is going on in the Surface Science and Catalysis group of the University of Padova in the field of the synthesis under ultra high vacuum conditions, e.g. physical and chemical vapor deposition, of different types of vertically stacked heterojunctions such as WSe2/graphene and WS2/h-BN,[5] as well as in-plane graphene/h-BN nanojunctions.[6] These systems have been investigated in situ without using any transfer method or exposing them to the atmosphere, by means of advanced spectroscopy and microscopy techniques, in order to determine their pristine electronic and structural properties. In addition, we report the results of a study where an aerosol processing enables the preparation of hierarchical graphene/MoS2 nanocomposites where nitrogen-doped crumpled graphene nanosacks wrap finely dispersed MoS2 nanoparticles.[7] The activity of these materials is tested toward the photoelectrochemical production of hydrogen, obtaining seven times more efficient materials with respect to single MoS2, because of the formation of p-n MoS /graphene nanojunctions, which allow an efficient charge carrier separation. 1. for an historical perspective on ultrathin films see: G. Granozzi , S. Agnoli, Ultrathin Oxide Films, Chapter in
Surface and Interface Science, Vol. 4, pp 585-690, Wiley-VCH (2014) 2. K.S. Novoselov et al. Science 204, 306, 666 3. S. Agnoli and G. Granozzi, Second generation graphene: Opportunities and challenges for surface science 4. Surf. Sci. 609 (2013) 1–5 5. A. K Geim et al. Nature 2013, 499, 419-425 6. M. Cattelan et al. Chem. Mater., 2015, 27, 4105–4113 7. S. Nappini et al. Adv. Func. Mater. 2016, doi10.1002/adfm.201503591 8. F. Carraro et al. ACS Appl. Mater. Interfaces 2015, 7, 25685−25692
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Monolayer graphene with controlled crystallinity: from amorphous to single-crystalline
Dongmok Whang
School of Advanced Materials Science and Engineering, SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 16419, Korea
Large-area graphene has been grown by catalytic chemical vapor deposition (CVD) on various metal substrates. However, the uniform growth of graphene with controlled crystallinity over wafer-scale areas remains a challenge toward the commercial realization of various electronic, photonic, mechanical, and other devices based upon the outstanding properties of graphene. In this talk, control of crystallinity during the catalytic growth of single-atom-thick 2D carbon layer will be presented. A hydrogen-terminated germanium (Ge) substrate is a promising candidate for the growth of carbon monolayer, because of (i) its reasonably good catalytic activity for the catalytic decomposition of carbon atoms on the surface, (ii) the extremely low solubility of carbon in Ge even at its melting temperature, enabling growth of complete carbon monolayer. In particular, the anisotropic atomic arrangement of single crystal Ge surface enables uniform growth of single-crystal monolayer graphene [1]. Etch-free dry transfer and possible applications of the obtained carbon monolayers will also be discussed.
1. Lee, J.-H. et al. Wafer-Scale Growth of Single-Crystal Monolayer Graphene on Reusable Hydrogen-Terminated Germanium. Science 344, 286-289 (2014).
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Synthesis of large-area single crystalline graphene on copper foil driven by abnormal grain growth
Jae-Young Choi1 and Ho Bum Park2
1School of Advanced Materials Science and Engineering, SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 16419, Korea
2Department of Energy Engineering, Hanyang University, Seoul 04763, Korea
[email protected] or [email protected]
Chemical vapor deposition (CVD) using transition metal is the most promising way to produce large-size monolayer
graphene. However, the graphene from the CVD method has usually numerous structural defects which cause to
degrade its outstanding physical properties. Thus, it would be a great challenge to prepare high-quality graphene sheet
without such structural defects, for promising applications. Recently, there have been many studies on the preparation
of single crystal graphene to improve the quality, but most of them are far away from the practical way. Here we show
large-area, single crystal graphene sheet on modified copper film with the most preferred lattice orientation by using
a thermal annealing method. In this study, we show the way to convert polycrystalline copper film into single
crystalline one, derived from unexpected abnormal grain growth (AGG) followed by recrystallization. By using (111)
oriented copper film, large-area, high-quality graphene has been successfully prepared with time efficiency,
particularly with no significant grain boundaries (GBs), confirmed by Raman, optical microscopy after UV/ozone
treatment, and scanning tunneling microscope (STM). The absence of such GBs in the graphene sheet led to a high
carrier mobility of ~12,000 cm2/Vs on SiO2/Si wafer.
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Phosphorene, a new 2D playground challenging chemical functionalization
Maurizio Peruzzini
Consiglio Nazionale delle Ricerche - Istituto di Chimica dei Composti Organo-Metallci, Sesto Fiorentino (Florence), Italy
At ambient temperature and pressure, black phosphorus (BP) is the most stable and unreactive polymorphic form of elemental phosphorus. BP was discovered more than one century ago1, but, most likely due to his inertness, its chemistry was marginally explored in comparison to the white and the red phosphorus allotropes. The global interest for BP exploded in 2014, when it was demonstrated being its layered structure exfoliated forming a 2D sheet with an honeycomb hexagonal network.2 The new material was called phosphorene and it can be considered the all-P cousin of graphene for the close related affinity of the two materials.
We have demonstrated that high quality phosphorene flakes could be prepared and stabilized using DMSO under sonication.3 With respect to graphene, the presence of phosphorene lone pairs on each phosphorus, should results in a higher reactivity, thus making phosphorene functionalization more feasible avoiding the harsh conditions necessary for graphene. As shown in scheme, we are going to play with phosphorene either chemically, using small molecules, nanoparticles and extended systems, either physically using the high pressure. The goal is to use functionality innovative advanced 2D materials by implanting phosphorene derivatives into different device platforms addressed to applications in material science, catalysis, microelectronics and optoelectronic devices. Our final aim is to demonstrate the feasibility of a chain-of-value based on phosphorene platform from synthesis to device realization and implementation.
Acknowledgements: The author thank the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 670173) for funding the project PHOS FUN “Phosphorene functionalization: a new platform for advanced multifunctional materials” through an ERC Advanced Grant. Thanks are given to my coworkers: M. Serrano-Ruiz, M. Caporali, A. Ienco, G. Manca, S. Interlandi, E. Passaglia, S. Heun, s. Toffanin for their valuable help.
1) P. W. Bridgman, J. Am. Chem. Soc.,1914, 36, 1344 – 1363. 2) H. Liu, A. T. Neal, Z. Zhu, Z. Luo, X. Xu, D. Tomanek, P. D. Ye, ACS Nano 2014, 8, 4033-4041; K. Li, Y. J. Yu, G .J. Ye, Q. Q. Ge, X. D. Ou, H. Wu, D. L. Feng, X. H. Chen, Y. B. Zhang, Nat. Nanotechnol. 2014, 9, 372-377. 3) M. Serrano-Ruiz, M. Caporali, A. Ienco, V. Piazza, S. Heun, M. Peruzzini Adv. Materials Interf., 2016, 3, 1500441.
22
Chemical properties of phosphorene: Insight from DFT calculations
Danil W. Boukhvalov
Department of Chemistry, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Republic of Korea
In contrast to graphene phosphorene is not flat layer and instead single π out-of-plane orbital but initially distorted anisotropic structure with out-of-plane σ-orbital with lone pair of electrons. This difference in atomic and electronic structure provides completely different chemical properties of phosphorene.
We perform a systematic first-principles study of phosphorene in the presence of typical monovalent (hydrogen, fluorine) and divalent (oxygen) impurities. The results of our modeling suggest a decomposition of phosphorene into weakly bonded one-dimensional (1D) chains upon single- and double-side hydrogenation and fluorination. In spite of a sizable quasiparticle band gap, fully hydrogenated phosphorene found to be dynamically unstable. In contrast, full fluorination of phosphorene gives rise to a stable structure, being an indirect gap semiconductor with the band gap of 2.27 eV. We also show that fluorination of phosphorene from the gas phase is significantly more likely than hydrogenation due to the relatively low energy barrier for the dissociative adsorption of F2 compared to H2. At low concentrations, monovalent impurities tend to form regular atomic rows phosphorene, though such patterns do not seem to be easily achievable due to high migration barriers. Oxidation of phosphorene is shown to be a qualitatively different process. Particularly, we observe instability of phosphorene upon oxidation, leading to the formation of disordered amorphous-like structures at high concentrations of impurities. [1]
Another set of modellings is about nitrogen- and boron-doped phosphorene. It demonstrates the tendency toward formation of highly ordered structures. Nitrogen doping leads to the formation of -N-P-P-P-N- lines. Further transformation to -P-N-P-N- lines across the chains of phosphorene occurs with increasing band gap and increasing nitrogen concentration, which coincides with the decreasing chemical activity of N-doped phosphorene. In contrast to the case of nitrogen, boron atoms prefer to form -B-B- pairs with the further formation of -P-P-B-B-P-P- patterns along the phosphorene chains. The low concentration of boron dopants converts the phosphorene from a semiconductor into a semimetal with the simultaneous enhancement of its chemical activity. Co-doping of phosphorene by both boron and nitrogen starts from the formation of -B-N- pairs, which provide flat bands and the further transformation of these pairs to hexagonal BN lines and ribbons across the phosphorene chains. [2]
Our calculations also consider the effect features in electronic and atomic structure of phosphorene to physisorption of gases on the surface of phosphorene and black phosphorous. Modelling of CO adsorption demonstrate significant difference with adsorption of same gas on metal substrate, and also valuable changes in electronic structure of phosphorene after adsorption of CO and tendency to clusterization with further formation of layered structure with appearance of CO-CO interactions via phosphorene substrate. [3]
1. D. W. Boukhvalov, A. N. Rudenko, D. A. Prishchenko, V.G. Mazurenko, M. I. Katsnelson “Chemical modifications and stability of phosphorene with impurities: A first principles study” Chem. Phys. Phys. Chem. 17, 15209-15217 (2015).
2. D. W. Boukhvalov “Atomic and electronic structure of nitrogen- and boron-doped phosphorene” Phys. Chem. Chem. Phys. 17, 27210-27216 (2015)
3. A. Politano, M.S. Vitiello, L. Viti, J. Hu, Z.Q. Mao, J. Wei, G. Chiarello and D. W. Boukhvalov “Unusually strong lateral interaction in the CO overlayer in phosphorene-based systems” (submitted).
23
Prospects for hydrogen storage in graphene
S. Heun
NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, 56127 Pisa, Italy
The realization of innovative hydrogen storage materials has worldwide strategic importance. Graphene has recently attracted attention as a promising hydrogen storage medium. Indeed, graphene is lightweight, chemically stable, and exhibits attractive physico-chemical properties for hydrogen adsorption. Furthermore, the interaction between hydrogen and graphene can be controlled by chemical functionalization.
The energetics of the chemisorption of hydrogen on graphene can be modified by the local curvature of the graphene sheet. Based on scanning tunneling microscopy (STM) we report on site-selective adsorption of atomic hydrogen on convexly warped regions of monolayer graphene grown on SiC(0001). This system exhibits an intrinsic curvature owing to the interaction with the substrate [1]. We show that at low coverage hydrogen is found on convex areas of the graphene lattice [2]. No hydrogen is detected on concave regions. These findings are in agreement with theoretical models which suggest that both binding energy and adsorption barrier can be tuned by controlling the local curvature of the graphene lattice. This curvature-dependence combined with the known graphene flexibility may be exploited for storage and controlled release of hydrogen at room temperature.
Theoretical studies regarding metal atoms (e.g. Ti) deposited on graphene suggest that such materials can adsorb up to 8 wt% gravimetric density of hydrogen. We investigate the deposition of Ti on graphene and its potential for hydrogen storage [3]. The Ti atoms form small islands (diameter ~ 10 nm). The Ti-covered graphene was exposed to molecular hydrogen, and the hydrogen desorption dynamics was measured by thermal desorption spectroscopy. Our data demonstrate the stability of hydrogen binding at room temperature and show that the hydrogen desorbs at moderate temperatures – both ideally matching technical requirements for hydrogen storage. First principle calculations clarify the multi-bonding state between hydrogen and the graphene-supported Ti clusters [4]. To further increase the hydrogen uptake of these samples, we employ controlled surface modifications to increase the active surface for hydrogen adsorption by decreasing the size of the Ti-islands and increasing their density [5].
1. S. Goler, C. Coletti, V. Piazza, P. Pingue, F. Colangelo, V. Pellegrini, K. V. Emtsev, S. Forti, U. Starke, F. Beltram,
and S. Heun, Carbon 51, 249 (2013). 2. S. Goler, C. Coletti, V. Tozzini, V. Piazza, T. Mashoff, F. Beltram, V. Pellegrini, and S. Heun: J. Phys. Chem. C
117, 11506 (2013). 3. T. Mashoff, M. Takamura, S. Tanabe, H. Hibino, F. Beltram, and S. Heun: Appl. Phys. Lett. 103, 013903 (2013). 4. K. Takahashi, S. Isobe, K. Omori, T. Mashoff, D. Convertino, V. Miseikis, C. Coletti, V. Tozzini, and S. Heun, J.
Phys. Chem. C, submitted. 5. T. Mashoff, D. Convertino, V. Miseikis, C. Coletti, V. Piazza, V. Tozzini, F. Beltram, and S. Heun: Appl. Phys.
Lett. 106, 083901 (2015).
24
Composite graphene and beyond graphene membranes
E. Drioli a,b,c*, A. Gugliuzza,a A. Politanod
aInstitute on Membrane Technology-National Research Council (ITM-CNR), Via Pietro Bucci 17C, Rende (CS),
87036, Italy bDepartment of Environmental and Chemical Engineering, University of Calabria, Via Pietro Bucci, 33C,
Rende (CS), 87036, Italy cWCU Energy Engineering Department, College of Engineering, Hanyang University, Korea
bDepartment of Physics, University of Calabria, Via Pietro Bucci, 33C, Rende (CS), 87036, Italy
*Presenting author: [email protected]
Many areas around the globe suffer the scarcity of clean and fresh water as well as the access to adequate sanitation due to the exponential increase in the world’s population and industrial activities over the last decades. Current state-of-the-art technology allows for the provision of refresh water by processing seawater and brackish water by means of membrane operations and in particularly reverse osmosis plants. Though the reverse osmosis is 10 folds more efficient than thermal processes, it is not yet an intensely competitive technology from an energetic point of view, especially for those countries that suffer important energy shortages (1). Also, seasonal variations in seawater quality as well as sensitivity to fouling, scaling and brine disposal make the RO-process necessary to the integration with pre-treatment steps, such as nanofiltration, and post-treatment steps, such as membrane distillation and membrane crystallization. Nanofiltration takes advantages of reducing hardness and total dissolved solid with a recover factor up to 50% and energy saving of 25-30%. Membrane Distillation and Crystallization are envisaged as suited processes to handle the brine problems, taking advantages of production of ultra-pure, desalted and demineralized water as well as concentration of aqueous salts or inorganic acids up to high concentrations, and crystallization (2). Despite the sustainability of integrated membrane processes, there is still a great demand for advanced materials, which can yield more efficient production of clean and safe water while reducing the energy need to produce it. The choice of 2D layered materials for the fabrication of advanced membranes appears to be a reliable route for allocating in the same device complementary functions, including mass, charge and energy transport (3). Herein, the potentiality of graphene and 2D materials beyond graphene in water processing is discussed. Nanopores, local defects and wrinkling in graphene sheets as well as the insertion of functional groups in the pore edges or between the stacked layers are discerned with the membrane ability to let water pass through, but also to stop pollutants and salts at the interface according to size exclusion, chemical and electrostatic interactions and Donnan’s exclusion mechanisms. Electronical features are also examined in relation to the possibility to realize devices for self-sustainable energy recovery, production and storage. Finally, perspectives on the future of 2D electronic materials beyond graphene, including phosphorene, silicene, and other transition metal dichalcogenide, are discussed with an emphasis to the synthesis, characterization and production of nanoporous desalination membranes through which water flow and ion filtering can be regulated (4-7).
1) E. Drioli, L. Giorno, Comprehensive membrane science and engineering, Amsterdam; London: Elsevier Science, 2010, ISBN: 978-0444532046
2) E. Drioli, A. Ali, F. Macedonio, CA Quist-Jensen, Minerals, Energy and Water from the Sea: A New Strategy for Zero Liquid Discharge in Desalination, JSM Environ Sci Ecol 3 (2015), 1018
3) A. Gugliuzza, L. Giorno, E. Drioli, Graphene membranes in: Encyclopedia of Membranes, (E. Drioli, L. Giorno), SpringerReference, 2016 ISBN: 978-3-662-44325-5.
4) S. P. Surwade, S. N. Smirnov, I. V. Vlassiouk, R. R. Unocic, G. M. Veith, S, Dai, S. M. Mahurin, Water desalination using nanoporous single-layer graphene, Nature Nanotechnology, 10 (2015), 459.
5) B. Mi, Science, Graphene Oxide Membranes for Ionic and Molecular Sieving, Science, 343 (2014), 740. 6) X. Li, H. Zhu, Two-dimensional MoS2: Properties, preparation, and applications, J. Materiomics, 1 (2015),
33 7) W. Li, Y. Yang, J. K. Weber, G. Zhang, R. Zhou, Tunable, Strain-Controlled Nanoporous MoS2, Filter for
Water Desalination, ACS NANO, in press (2016), DOI: 10.1021/acsnano.5b05250
25
Maximizing the right stuff: role of 2D materials in the membrane world
Ho Bum Park
Department of Energy Engineering, Hanyang University, Seoul 04763, Korea
Recently, breakthroughs in materials synthesis, coupled with increasing demands for energy-efficient separations in applications ranging from water purification to petroleum refining and chemicals production, have sparked a surge in new approaches to designing separation membranes. However, membranes suffer a ubiquitous, pernicious tradeoff: highly permeable membranes lack selectivity and vice versa. Elusive combinations of both high permeability and high selectivity are beginning to emerge as fundamental design rules for membrane materials become more refined. Concepts from nature are being applied to break the permeability/selectivity tradeoff. Here, we review the history of the permeability/selectivity tradeoff, state-of-the-art approaches to membrane materials design to overcome the tradeoff, and factors other than permeability and selectivity that govern membrane performance and, in turn, influence membrane design. Among many candidate materials, membranes utilizing nanoporous one-dimensional and two-dimensional materials are emerging as attractive candidates for applications in molecular separations and related areas. Such nanotubular and nanolayered 2D materials include carbon nanotubes, metal oxide nanotubes, layered zeolites, porous layered oxides, layered aluminophosphates, and porous graphenes. With their unique shape, size and structure, they possesses transport properties that are advantageous for membrane and thin film applications. These materials also have very different chemistry from more conventional porous 3D materials, due to the existence of a large, chemically active, external surface area. This feature also necessitates the development of innovative strategies to process these materials into membrane and thin films with high performance. This presentation provide the comprehensive review of this emerging materials. 1. H. W. Yoon, Y. H. Cho, H. B. Park "Graphene-based membranes: status and prospects", Phylosophical
Transactions A, 374.2060 (2016) 2. H. B. Park "Graphene-based membranes - a new opportunity for CO2 separation", Taylor & francis, Carbon
Management, 251-253 (2014) 3. H. W. Kim, H. W. Yoon, B. M. Yoo, J. S. Park, K. Gleason, B. D. Freeman, H. B. Park "High-Performance CO2-
philic Graphene Oxide Membranes in the Wet-Conditions", Chem. Commun., 50, 13563 (2014) 4. M. J. Yoo, H. W. Kim, B. M. Yoo, H. B. Park "Highly soluble polyetheramine-functionalized graphene oxide and
reduced graphene oxide both in aqueous and non-aqueous solvents", Carbon, 75, 149-160 (2014) 5. H. D. Lee, H. W. Kim, Y. H. Cho, H. B. Park "Experimental Evidence of Rapid Water Transport through Carbon
Nanotubes Embedded in Polymeric Desalination Membranes", Small, 10(13), 2653-2660 (2014) 6. H. W. Kim, H. W. Yoon, S. Yoon, B. M. Yoo, B. K. Ahn, Y. H. Cho, H. J. Shin, H. Yang, U. Paik, S. Kwon, J. Choi,
H. B. Park "Selective Gas Transport Through Few-Layered Graphene and Graphene Oxide Membranes", Science, 342, 91-95 (2013)
7. B. M. Yoo, H. J. Shin, H. W. Yoon, H. B. Park "Graphene and Graphene Oxide and Their Uses in Barrier Polymers", J. Appl. Polym. Sci. 131(1), 39628 (2014)
