Poster abstracts 2017

ODD numbers present in session A (wednesday). EVEN numbers present in session B (thursday)
The posters should be up throughout the duration of the meeting. 

The recommended poster format is A0 (landscape or portrait). 

Gaetano Calogero: Atomistic large-scale simulations of transport in ballistic graphene

posted 15 Aug 2017, 02:33 by Peter Boggild

Gaetano Calogero , Nick P. Rübner, Peter Bøggild, Mads Brandbyge
Danish Technical University (DTU Nanotech), Center for Nanostructured Graphene.DK-2800 Kgs. Lyngby, Denmark

Graphene exhibits astonishing mesoscopic effects hosting massless Dirac quasiparticles that can travel with little scattering and behave like light rays. Mean free paths of up to 28 mm have been reached at low temperature [1], while ballistic transport in the micrometre scale has become accessible even at room temperature. Electrons in such devices undergo negative refraction when passing p-n junctions and can be manipulated by external electromagnetic fields, paving the way to a new concept of electronics based on the principles of optics [2]. One interesting perspective is a “2D Dirac fermion microscope” (DFM), where electron guns, tunable lenses, deflectors, and detectors are combined in a graphene “vacuum chamber” to image different types of targets [3]. We aim at performing multi-scale simulations of ballistic graphene devices starting from atoms, combining density functional theory (DFT) and large-scale tight-binding (TB) models in a non-equilibrium Green’s functions (NEGF) framework. As an application, we use a NEGF+TB model to reproduce key features of electron transport in a DFM, such as electron beam collimation, deflection and scattering off circular p-n junctions. For targets with size larger than the Fermi wavelength (mesoscopic limit), our results resemble those of semiclassical simulations, but quantum coherence leads to a richer emission and reflection structure which may be utilized to extract more detailed information.

1. Banszerus et al. Nano Letters 16, 1387 (2016)
2. Chen et al. Science 353, 1522 (2016)
3. Bøggild et al. Nature Communications 8, 15783 (2017)

Gaetano Calogero is currently a PhD student at the Danish Technical University (DTU), in the Theoretical Nanoelectronics group led by Prof. M. Brandbyge. He is primarily interested in theory and multi-scale atomistic simulations of ballistic graphene nanoelectronics. He received his B.S. degree in Physics from University of Catania (IT) in 2013, with a thesis on the role of basis sets on the unfolding of supercell bandstructures. He got his M.S. degree in Physics from the same university (2015), after spending a research period of 5 months as Erasmus+ student at the Debye Institute of Utrecht University (NL), where he worked on density functional theory simulations of atomic force microscopy of nitrogen-doped graphene.

Razieh Sahraei: Novel magnetic poly(vinyl alcohol)/modified gum tragacanth/graphene oxide hydrogel beads with daul activity for removal of cationic and anionic dyes from water

posted 9 Aug 2017, 04:33 by Peter Boggild

Razieh Sahraei, Mousa Ghaemy
Polymer Research Laboratory, Department of Chemistry, University of Mazandaran, Babolsar, Iran

The objective of this work is the preparation of effective magnetic biosorbent beads with the high surface area from a low-value abundant biopolymer (Katira, GT) and graphene oxide (GO) for the removal of dyes from the water. For this aim, magnetic hydrogel beads based on poly(vinyl alcohol)/poly(2-Acrylamido-2-methyl-1-propanesulfonic acid-co-1-vinyl imidazole)-g-gum tragacanth/graphene oxide were prepared by instantaneous gelation method in boric acid solution followed by cross-linking with glutaraldehyde (GA). The prepared magnetic beads with good mechanical stability (97.18%) were used as an effective adsorbent for removal of both cationic (crystal violet, CV) and anionic (congo red, CR) dyes from aqueous solution. The specific surface area and average pore diameter of magnetic beads (with a spherical shape and an average diameter of 3.0 mm) was 283.84 m2/g and 4.2767 ᵒA, respectively. The total pore volume was 0.0303 mL/g and the porosity based on a skeletal density of 0.5 g mL was 0.0149 per gram of sample.
The maximum adsorption capacities were found 94.0 and 101.74 mg g-1 for CV and CR, respectively. Therefore, advantages such as biocompatibility, easy preparation and separation, inexpensiveness, chemical stability, high adsorption, reusability, and having functional groups with dual activities make these magnetic beads attractive and broadly applicable in the removal of various pollutants simultaneously from water, wastewater, and for column applications [1-3].

1.Zhang Y, Liu Y, Wang X, Sun Z, Ma J, Wu T, Xing F, and Gao J, Carbohydr. Polym., 101, 392-400, 2014.
2.Jiang W, Wang W, Pan B, Zhang Q, Zhang W, and Lv L, ACS Appl. Mater. Interfaces, 6(5), 3421-3426, 2014.
3.Pour Z.S, and Ghaemy M, RSC Adv., 5(79), 64106-64118, 2015.

I am Razieh Sahraei, PhD student of Polymer Chemistry at University of Mazandaran, Babolsar, Iran. I received my MSc. degree in the field of applied-polymer chemistry from University of Tehran in 2013. My research is mainly focused at Synthesis and characterization of nanocomposite adsorbents based on gum tragacanth and graphene oxide for water treatment applications. I am at present pursuing the last year of my doctoral research as a visiting researcher in Malmö University, Department of Biomedical Science, Sweden.  I am interested in different concepts of waste water treatment, synthesis and characterization of functional polymers, synthesis of nanostructures, graphene-based materials, polymeric smart hydrogels, and polymeric nanofiltration membranes. 

Sanjoy K. Mahatha: Evidence of out-of-plane metallic band dispersion in commensurate charge density wave of 1T-TaS2

posted 9 Aug 2017, 03:49 by Peter Boggild

Sanjoy K. Mahatha, Arlette S. Ngankeu, Kevin Guilloy, Marco Bianchi, Charlotte E. Sanders, Kai Rossnagel, Jill Miwa, and Philip Hofmann
Department of Physics and Astronomy, Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus C, Denmark

The 1T polymorph of layered transition metal dichalcogenide compound TaS2 undergo phase transition towards low temperature with a periodic structural distortion where the electrons organize themselves in regular pattern which is widely known as charge density wave (CDW) [1]. The commensurate CDW phase of 1T-TaS2 has widely been treated as a quasi two-dimensional phenomenon that coexist with a Mott insulating state. However, recent theoretical calculations predicted the coexistence of CDW phase with a nearly one-dimensional metallic dispersion perpendicular to the crystal planes. In this presentation, I will show the angle-resolved photo emission spectroscopy results which confirms the existence of this metallic band [2]. The experimental band width of this metallic band is in excellent agreement with the predicted stacking order of CDW between the adjacent layers and its periodicity along c axis.
1. K. Rossnagel, J. Phys.: Condens. Matter 23, 213001 (2011).
2. Arlette S. Ngankeu, Kevin Guilloy, Sanjoy K. Mahatha, Marco Bianchi, Charlotte E. Sanders, Kai Rossnagel, Jill A. Miwa, and Philip Hofmann, arxiv1705.00455.

Sanjoy Kr.  Mahatha is currently a Postdoc of Department of Physics and Astronomy at the University of Aarhus. His primary interest lies in studying the growth and electronic structure of two-dimensional Dirac materials and transition metal dichalcogenides. He received his M.Sc. degree in Physics from The University of Burdwan (2006) and a Ph.D. in Experimental Physics (2013) from Calcutta University where he studied the electronic structure of two-dimensional materials and metal overlayers using angle-resolved photoemission. After finishing his Ph.D, he spent little more than 3 years as a postdoctoral researcher in ISM-CNR and in the Elettra Synchrotron, Trieste, Italy studying the electronic structure of silicene and multilayer Si film on Ag(111) and quantization effects in magnetic thin films. His awards include TRIL fellowship awarded by ICTP for carrying out post-doctoral research work at Elettra - Sincrotrone Trieste (2013), MRSI Young Scientist Award (2012) and Best Poster Award in “JSPS-DST Asian Academic Seminar 2010”.

Aran Garcia-Lekue: Tuning the properties of graphene nanoribbons via chemical modification

posted 7 Aug 2017, 01:29 by Peter Boggild   [ updated 15 Aug 2017, 08:20 ]

Donostia International Physics Center (DIPC), San Sebastian, Spain
Ikerbasque, Basque Foundation for Science, Bilbao, Spain


Armchair Graphene Nanoribbons (AGNRs) are one-dimensional stripes of graphene with a width-dependent electronic bandgap[1], which makes them suitable for applications in carbon-based nanoelectronics. AGNRs can be effectively produced by on-surface reaction of halogenated bianthracene (DBBA) monomers, a synthesis technique providing atomic control on the dimension and edge structure of the ribbons[2]. Furthermore, the electronic structure of the AGNRs can also be tuned by chemical modification of the precursors.
Here, we report on the properties of 7-AGNRs periodically doped with boron pairs on Au(111). Our density functional theory (DFT) based findings are compared with scanning tunneling microscopy (STM) and angle-resolved photoemission (ARPES) data. We find that the di-boron backbone reduces the band gap of the nanoribbon, and induces the formation of a new conduction band near the Fermi level. Furthermore, it is possible to grow structures formed by pristine segments separated by regions doped with B pairs. We have studied the properties of such boron defects as scattering centers, and found that they provide large effective barriers for the propagation of electrons in the valence band (VB), but are nearly transparent for the immediately lower energy band (VB-1) due to the different symmetry of both bands. As a result, the VB gives rise to clearly identifiable quantized levels in the pristine regions, with a remarkable agreement between theory and experiment[3].

[1] Son et al., Phys. Rev. Lett. 97, 216803 (2006)
[2] Cai et al., Nature 466, 470 (2010)
[3] Carbonell-Sanroma et al., Nano Letters 17, 50 (2017)

Aran Garcia-Lekue is currently an Ikerbasque Research Fellow at Donostia International Physics Center (DIPC). Her research line is focused on the simulation of electron transport at the nanoscale, and on the theoretical investigation of electron processes at nanostructured surfaces. In the last years, she has been very active in the study of electronic and transport properties of graphenic nanostructures. She received his PhD degree in Physics from the University of the Basque Country UPV/EHU (Spain). After finishing her Ph.D, she held postdoctoral positions at the Surface Science Research Center (SSRC) of the University of Liverpool (UK) and at the Berkeley National Laboratory (US). She joined DIPC as a Gipuzkoa Research Fellow Gipuzkoa in 2007, and became an Ikerbasque Research Fellow in 2012.

Kristen Kaasbjerg: Symmetry protection against quasiparticle scattering in disordered monolayer transition-metal dichalcogenides

posted 2 Aug 2017, 04:25 by info admin

Kristen Kaasbjerg (1), Johannes H. J. Martiny (1), Tony Low (2), and Antti-Pekka Jauho (1)

1) Center for Nanostructured Graphene (CNG), Dept. of Micro- and Nanotechnology,
Technical University of Denmark, Denmark

2) Department of Electrical and Computer Engineering, University of Minnesota, USA

Two-dimensional (2D) monolayers of transition metal dichalcogenides (TMDs; MX2) are promissing candidates for spin- and valley-based electronic devices. In order to realize their apparent potential for valleytronics application, long valley lifetimes are required. However, atomic vacancies which are among the most common types of atomic disorder in 2D TMDs, are expected to limit the achievable valley lifetimes.

Here, we demonstrate that besides the spin-valley coupling which partially protects the valley degree of freedom against intervalley scattering as illustrated in Fig. 1, the symmetry and position of atomic disorder give rise to additional selection rules. As shown in Fig. 1, K, K' scattering by disorder with threefold rotational symmetry (C3), e.g., atomic vacancies, is forbidden by symmetry, except in the conduction band for M-centered disorder.

We propose to verify our predictions with Fourier transfrom scanning tunneling spectroscopy (FT-STS) which provides direct access to the available scattering channels in q space. For this purpose, we calculate the FT-STS and QPI spectra using an atomistic DFT approach for two archetypal TMDs: the direct gap, small spin-orbit split MoS2, and the indirect gap, large spin-orbit split WSe2. In both cases, the K, K' conduction-band intervalley FT-STS peak is completely absent for X vacancies while appearing clearly for M vacancies, thus suggesting an alternative explanation for its conspicious absence in experiments [1,2].

1. H. Liu, J. Chen, H. Yu, F. Yang, L. Jiao, G.-B. Liu, W. Ho, C. Gao, J. Jia, W. Yao, and M. Xie, "Observation of intervalley quantum interference in epitaxial monolayer tungsten diselenide," Nature Commun. 6, 8180 (2015).
2. M. Yankowitz, D. McKenzie, and B. J. LeRoy, "Local spectroscopic characterization of spin and layer polarization in WSe2," Phys. Rev. Lett. 115, 136803 (2015).

Kristen Kaasbjerg is a researcher at the Center for Nanostructured Graphene at DTU where he is working on theoretical quantum transport in 2D materials and their nanostructures.

Jack Alexander-Webber: Engineering oxide interfaces for graphene electronics

posted 2 Aug 2017, 01:49 by info admin

Department of Engineering, University of Cambridge, United Kingdom

Reliable and controlled interfacing with conventional dielectrics or barrier films remains a critical issue for 2D materials. Early attempts to grow atomic-layer deposited (ALD) layers directly on graphene resulted in inhomogeneous film growth. However, frequently used seed layers can negatively affect the as-grown interface. Here we present a detailed study of ALD Al2O3 nucleation on chemical vapour deposited (CVD) graphene films. By optimizing precursor exposure to promote Al2O3 nucleation, we show high-quality, dense ALD films directly on graphene without the need for seed layers [1]. These techniques have been shown to be suitable to grow sub-nanometre Al2O3 tunnel junctions directly on graphene for spintronic devices [2]. Film thicknesses of 90nm can virtually eliminate gate hysteresis for CVD graphene-based field-effect devices [3]. In addition, unintentional doping is significantly reduced and the room temperature field-effect mobility of encapsulated devices greatly increases. These results are relevant for 2D materials integration with conventional thin film and ultra-large-scale integration technologies.

1. Aria et al. ACS Appl. Mater. Interfaces 8, 30564 (2016)
2. Martin et al. ACS Nano 8, 7890 (2014)
3. Alexander-Webber et al. 2D Materials 4, 011008 (2017)

Jack Alexander-Webber holds Research Fellowship from the Royal Commission for the Exhibition of 1851 and is a Junior Research Fellow of Churchill College Cambridge. He graduated from Royal Holloway, University of London in 2009 with an MSci in Physics. After a summer studentship working for the National Physical Laboratory he began his DPhil in the group of Prof Robin Nicholas at the University of Oxford. His doctoral research was on the properties of low-dimensional nanostructures such as graphene, carbon nanotubes and III-V semiconductors with a particular focus on high magnetic field effects studied both in Oxford and at the European Magnetic Field Laboratory facilities in Grenoble and Toulouse. After completing his DPhil in 2013, Jack undertook an EPSRC Doctoral Prize fellowship at Oxford. He is currently working in the group of Prof Stephan Hofmann in the Department of Engineering at the University of Cambridge. His current research interests lie in developing scalable techniques to integrate low-dimensional nanomaterials in electronic and optoelectronic device applications.

Hyewon Du: The introduction of straightforward fabrication technique to improve device performance at graphene/2D semiconductor junction

posted 2 Aug 2017, 01:38 by info admin   [ updated 2 Aug 2017, 01:39 ]

Hyewon Du(1), Kunsik An(2), Taekwang Kim(1), Somyeong Shin(1), Seonyeong Kim(1), Minho Song(1), Changhee Lee(2) and Sunae Seo(1)

(1) Department of Physics, Sejong University, Seoul, 143-747, South Korea
(2) Department of Electrical and Computer Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826

Graphene as a contact metal can be integrated with two-dimensional semiconductor (2D-SC) through the van der Waals interaction without the breakage of covalent bonds. This undamaged contact provides an atomically sharp interface by hindering Fermi-level pinning. [1] The lower Schottky barrier height has been often reported in Molybdenum disulfide (MoS2), the most common n-type 2D-SC, with graphene than other conventional metals. [2] Unfortunately, the typical fabrication methods involved with lithography and etching process accompany undesired deterioration such as defects and various residues on graphene surface. It obstructs electron injection at graphene/SC junction and results in the degradation of device performance such as contact resistance and mobility.
Here, we introduced Oxidation Scanning Probe Lithography (o-SPL) [3] to integrate multilayer MoS2 transistor with graphene electrode. This technique reduces graphene damage and contamination by minimizing necessary process. With the analysis of AFM, Raman and electrical transport, we could confirm the improved device performance. 

[1] Yuan Liu, et al. “Van der Waals Heterostructures and Devices” Nat Rev Mater, 1, 16042 (2016)
[2] Yuan Liu, et al. “Toward Barrier Free Contact to Molybdenum Disulfide Using Graphene Electrodes” Nano Lett, 15 (5), 3030-3034 (2015)
[3] Satoru Masubuchi, et al. “Atomic Force Microscopy Based Tunable Local Anodic Oxidation of Graphene” Nano Lett, 11 (11), 4542-4546 (2011)

Hyewon Du is currently a PHD student at the department of Physics, Sejong University, Korea. Her research interests are mainly focused on the device fabrication and investigation of electrical characterization in graphene/2D semiconductor heterojunctions such as graphene/MoS2 and graphene/pentacene.

Nicole Nagy: The Fabrication of Copper-Carbon Nanotube Composites for Global Interconnects

posted 2 Aug 2017, 01:36 by info admin

Nicole Nagy, Katharina Lilienthal, Benjamin Uhlig

Interconnects, Center Nanoelectronic Technologies (CNT), Fraunhofer Institute for Photonic Microsystems (Fraunhofer IPMS), Dresden

Due to its promising physical and electrical properties Cu-CNT composite could be the future material for metallization in semiconductor technologies. The aim of the work described in this talk is to take a closer look on the integration of Cu-CNTs from lab to fab, along with the consideration of material restrictions in terms of CMOS compatibility. For the formation of the composite by wet methods there are two common ways. The first is conventional Cu plating from acidic baths driven by current (electrochemical deposition, ECD). ECD is carried out either in acidic CuSO4 or organic Cu(CH3COO)2 baths and it needs a conductive layer for charge carrier transport, which limits its application [1]. The second approach is electroless Cu deposition, which is done from basic baths by catalytic reaction (ELD). Often used ELD baths consist of tartrate as chelating agent and formaldehyde (a CMR substance) as reducing agent [2]. The substitution of formaldehyde leads to limited alternatives for chelating agents. Glyoxylic acid in combination with EDTA is well known, less toxic and has additional advantages [3]. Another choice to be made is the catalyst material, which has to face the same material restrictions. In general, there is a strong dependency between the alignment of the CNTs on the substrate and the applicability of these two methods. The effects of various substance combinations, growth properties of CNTs, and other parameters on composite formation performance will be shown.

[1] Subramaniam et al. One hundred fold increase in current carrying capacity in a carbon nanotube–copper composite. Nat. Commun. 4:2202 doi: 10.1038/ncomms3202 (2013).
[2] Paunovic, M. ELECTROLESS DEPOSITION OF COPPER. In Schlesinger, M. and Paunovic, M. (Ed.) Modern Electroplating. 5th ed. Hoboken: John Wiley & Sons, Inc. 2010, pp. 433-446.
[3] Wang et al. Metallization of multi-walled carbon nanotubes with copper by an electroless deposition process. Electrochemistry Communications 6 (2004) pp. 1042–1044.

Nicole Nagy is currently working on ECD processes for semiconductor technologies and on metallization of carbon nanotubes within the EU project CONNECT at Fraunhofer IPMS-CNT in Dresden. She received her M.Sc. degree in chemical engineering from University of Applied Sciences Dresden in 2015. 

Anjan Mukherjee: An Imprinting Technique to Fabricate Embedded Single GaAs Nanowire(NW)/Graphene Hybrid Devices

posted 25 Jul 2017, 04:18 by info admin

Anjan Mukherjee(1), Dong-chul kim(1,2), Hoyeol Yun(3), Miri Seo(4), Jung Tae Nam(5), Keun Soo Kim(5), Sang Wook Lee(4), A. Mazid Munshi(2), Dasa L. Dheeraj(2), Bjørn-Ove Fimland(1,2), Helge Weman(1,2)

(1) Department of Electronic Systems, Norwegian University of Science and Technology, NO-7491, Trondheim, Norway
(2) Crayonano As, Otto Nielsens vei 12, NO-7052, Trondheim, Norway
(3) School of Physics, Konkuk University, 143 071, Seoul, Republic of Korea
(4) Department of Physics, Ewha Womans University,120 750, Seoul, Republic of Korea
(5) Department of physics and Graphene Research Institute, Sejong University, 143 747, Seoul, Republic of Korea 

Compared to present thin film/graphene optoelectronic devices[1], semiconductor NW/graphene hybrid devices can show additional interesting properties such as light trapping and polarization dependent absorption etc. GaAs is one of the most important lll-V semiconductor NW structure with a high potential for high efficiency solar cells[2] and photo-detectors[3]. In addition, using graphene as highly conducting and transparent electrode could lead to enhance the absorption efficiency of single GaAs NW optoelectronic devices as well as enable basic NW contact studies through a fermi level tunning of the graphene. 
In this report, we present the fabrication process of single GaAs NW/graphene hybrid devices with a planar junction configuration. A position-controlled micro transfer and imprinting technique that enables us to choose a single NW (or graphene) selectively on a target graphene (or a single NW) for high quality junction has been developed. Both GaAs NW/graphene bottom-and top-contact devices will be presented. For the fabrication of the first approch, we utilized the weak nature of adhesion between a polymer resist and a hydrophobic surface. For graphene/single NW top- contact devices, a key issue is how to make single NW embedded in a flat-surfaced structure, which is critical for the successful transfer of graphene on top of the NWs. Using a curable photo- resist layer, single NW could be transferred and imprinted for the embedded NW structure.                       

[1] Xiaoqiang Li et al., Nano Energy, 16(2015) 310-319
[2] Sander A. Mann et al., Nature Nanotechnology, 11(2016) 1071-1075
[3] FuX. W. et al., Appl. Phys. Lett, 100(2012) 223114

Anjan Mukherjee is currently a PhD student at the Department of Electronic Systems, Norwegian University of Science and Technology(NTNU). He received his MSc. degree from Indian Institute of Technology Delhi(IITD) in 2015. His research is mainly focused at graphene/nanowire devices for optoelectronic applications. 

Mohammad Hassan Ramezan zadeh: Iron oxide reinforced carbon nanotubes as promising nanofillers for biosensing applications of polymer films

posted 21 Jul 2017, 01:51 by info admin

Mohammad Hassan Ramezan zadeh, Majid Seifi

Department of Physics, Faculty of Science, University of Guilan, Rasht 41335, Iran

Carbon nanotubes (CNTs) have been widely investigated owing to their exceptionally structural and physicochemical properties which make them great candidates for numerous applications, such as, hydrogen storage, capacitors, sensors, biomarkers etc. [1, 2].
We have studied the influence of single walled carbon nanotubes coated with iron oxide nanoparticles (SWCNT-iron oxide nanocomposites) on the electrochemical properties of 2- dimensional polymer matrices and applied them as the frontier materials in electrochemical biosensors.
In the present study, first, we synthesized SWCNT-iron oxide nanocomposites by following  a same methodology reported previously [3], and then used them as nanofillers in gelatin films to make them applicable materials for electrochemical sensing in different branches, such as food industry, high-tech packaging, new medicine, biomedical devices, agricultural industry etc. 
This novel work could increase the different real-life applications of electrochemical biosensors for modern mankind as well as the over-increasing elderly population health care issues.

1. Irina V. Zaporotskova, et al. "Carbon nanotubes: Sensor properties. A review." Modern Electronic Materials 2.4 (2016): 95-105.
2. Xiaoxing Zhang, et al. "Mechanism and Application of Carbon Nanotube Sensors in SF6 Decomposed Production Detection: a Review." Nanoscale research letters 12.1 (2017): 177.
3. Mohammad Hassan Ramezan zadeh, et al. "Preparation and study of the electrical, magnetic and thermal properties of Fe 3 O 4 coated carbon nanotubes." Chinese Journal of Physics (2017).

I am developing new apparatuses about increasing polymers' structural, physical and biological properties by using carbon nanotubes and nanoparticles. Polymers such as chitosan, PVA, etc. The applications are supposed to be in various regions like biomedical, medical, life, food and environmental sciences.

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