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  • Yunqi Liu, Chinese Academy of Sciences, Inst. Chemistry
  • Cosmin Roman, Mikro- und Nanosysteme, ETH Zürich
  • Sergey Kubatkin, Chalmers University of Technology
  • Pagona Papakonstantinou, University of Ulster
  • Wenping Hu, Chinese Academy of Sciences, Inst. Chemistry
  • Baohang Han, Chinese Academy of Sciences, Natl. Center for Nanoscience and Tech.
  • Jesper Nygård, Nanoscience Center, University of Copenhagen
  • Antti Pekka Jauho, Technical University of Denmark
  • Xiaohui Qiu, Chinese Academy of Sciences, Natl. Center for Nanoscience and Tech.
  • Daniel Engstrøm, DTU Nanotech, Technical University of Denmark
  • Jun Yan, DTU Physics, Technical University of Denmark
  • Klaus Bo Mogensen, DTU Nanotech, Technical University of Denmark
  • Jörg R Jinscheck, DTU CEN, Technical University of Denmark 
  • Jin Sue, Chalmers University of Technology

More will be added...


Holey carbon

Pristine graphene has no band gap making device applications tedious. This problem can be avoided by cutting graphene into nanoribbons, or by considering bilayer graphene in external fields.  We have suggested a yet another way of engineering the graphene band-structure [1]:  introduce a regular array of holes ("an antidot lattice").  This structure is, at least theoretically, highly promising, however the challenge is to fabricate these structures. In this colloquium we review the physical properties of graphene antidot lattices, discuss its theoretical modeling, give an update of what has been achieved in the lab, and speculate on future device applications, e.g., in spintronics or thermoelectrics.

[1] Graphene Antidot Lattices - Designed Defects and Spin Qubits, Thomas G. Pedersen, Christian Flindt, Jesper Pedersen, Niels Asger Mortensen, Antti-Pekka Jauho, and Kjeld Pedersen, Phys. Rev. Lett. 100, 136804 (2008); arXiv:0802.4019; see also Nature
Research highlights, April 17 (2008).

Antti Pekka Jauho, DTU Nanotech,  Tech. Univ. Denmark and Dept. of Appl. Physics, Aalto, Finland

Antti-Pekka Jauho holds a Ph.D from Cornell University (1982) and he joined DTU in 1992. He is currently Professor of Theoretical Nano-technology at DTU Nanotech, and con-currently Finland Distinguisehd Professor at Aalto University, Finland. His research interests encompass theoretical modeling of electronic, optical and transport properties of nanoscale structures, often in far-from equilibrium conditions. He has used extensively non-equilibrium Green's functions as the theoretical tool, and he is a co-author of a widely used text-book on the topic. In recent years his interests have turned to modeling of carbon-based nanostructures, usually in collaboration with DFT specialists.


Graphene for electrochemical biosensors and fuel cell devices

An important feature of graphene, has been its edges, where interesting electrocatalytic properties and direct wiring with biomolecules (proteins, enzymes) can develop. Recently we integrated vertical grahene sheets into a platform using a one-step microwave plasma enhanced chemical vapour deposition approach, for elucidating the electrocatalytic properties of graphene edges. This work has created a new class of graphene based electrodes for a wide range of applications in the electroanalytical, biosensing, energy storage/conversion sectors and could essentially compete their vertically aligned carbon nanotubes counterparts. The application of graphene nanosheets as a promising support material for developing next-generation advanced Pt based fuel cells has also been established [2]. In the talk I will also discuss the synthesis of Reduced Graphene Oxide / Platinum supported electrocatalysts (Pt/RGO) employing a fast and eco-friendly microwave assisted polyol process. This hybrid material Pt/RGO shows excellent electrocatalytic activity and CO-poisoning tolerance for the methanol oxidation reaction (MOR), outperforming the commercial Pt/C electrocatalysts. Our experimental observations have demonstrated that the presence of residual oxygen groups on RGO play a vital role on the removal of carbonaceous species from the Pt sites.

[1] Shang N et al, Advanced Functional Materials, 18 (2008) 3506. [2] Shang N, et al The Journal of Physical Chemistry C 114 (2010) 15837. [3] Sharma S, et al accepted, The Journal of Physical Chemistry C.

Papakonstantinou Pagona, Nanotech. and Integrated BioEngineering Centre, Univ. Ulster, UK

After doctoral studies at Queen’s University of Belfast on magneto-optical materials and postdoctoral research on fs direct laser micro-deposition at IESL in Crete, Pagona moved to the University of Ulster in 1998 embarking on a new research programme addressing the synthesis and comprehensive characterisation of diamond like carbon. Over the last eight years, her research interests have focused on the fabrication and functionalization of low dimensional carbon based nanomaterials (graphene, carbon nanotubes, diamond nanorods), the characterization of their unique physical and physicochemical properties and the demonstration of these materials in energy and biological sensing areas. Research efforts are also been directed on the introduction of atomic scale defects in carbon nanotubes and graphene through plasma and chemical approaches in order to alter the physical and chemical properties of the carbon nanostructures. In many cases a comprehensive understanding of the properties of carbon based materials has been obtained by probing their local atomic environment using high resolution synchrotron based spectroscopies. Pagona has published more than 70 papers in peer review Journals and has attracted funding from EC (DESYGN-IT), INVEST-NI, Royal Society, Royal Academy of Engineering, Industry (GSK) and Science and Technology Research Council. Currently she serves on the following committees: Diamond Synchrotron Facility, EPSRC College, National Access Programme (SFI) at Tyndall Institute in Cork.

Quantum dots, spin-orbit coupling and splitting of entangled electrons in nanotubes and wires

Quantum dots are devices where a small number of electrons can either be trapped or participate in single-electron transport, controlled by electrostatic gates. During the last decade it has become clear that the most ideal, textbook-like quantum dots can be made from carbon nanotubes while semiconductor nanowires occasionally offer materials properties that result in new physical phenomena. 

Various ways of detecting and manipulating single electron spins in quantum dots is of great current interest, e.g. in the context of quantum information processing. For instance, a coupling of the orbital motion and the spin of electrons would allow for rapid spin control using electric fields (local electrostatic gates) rather than external magnetic fields. While such a spin-orbit interaction is basically absent in flat graphene, it has recently turned out that the curvature of cylindrical nanotubes results in a strong effect, contrary to all prior expectations that were based on assumptions from carbon flatland.

Going beyond single electron physics, the notion of quantum entanglement between pairs of particles holds prospects for radically new electronic devices and as well as fundamental quantum-on-a-chip experiments. We demonstrate the controlled spatial splitting of Cooper pairs from a superconductor into two separate quantum dots. This discovery was made simultaneously in carbon nanotubes and in semiconductor nanowires.

Jesper Nygård, Nanoscience Center, University of Copenhagen

JN is associate professor of experimental physics at the Niels Bohr Institute and the Nano-Science Center, University of Copenhagen, where he runs the Nanoscale Quantum Electronics group. JN has worked on carbon electronics since the first carbon nanotubes arrived in Copenhagen in 1998. His current interests cover quantum devices, growth of semiconductor and carbon materials, molecular electronics, and novel types of biosensors. JN is head of the nanophysics/condensed matter section of the Niels Bohr Institute and currently acts as director of the Nano-Science Center, an interdisciplinary research center involving around 150 staff and students.

Carbon nanotubes

Carbon nanotubes can be used to improve the performance of chemical analysis systems, due to a strong interaction between the hydrophobic nanotubes and organic molecules, such as proteins. Other research groups typically buy the carbon nanotubes in the form of powder, dissolve it in a porous polymer and fills it into fluidic channels, where it is used as a stationary phase for chromatography.

Here, the carbon nanotubes are grown on the substrate inside glass-based microfluidic channels, which is a much faster and more efficient way of fabricating the devices, compared to manual filling of the carbon nanotube powder. Electroosmotic flow (EOF) is being used for pumping of the liquid in the microchannels. The carbon nanotube forest is grown in an array of micrometer sized pillars in order to reduce the conductivity of the nanotube forest throughout the channel. This makes it possible to apply an electric field strength of more than 2 kV/cm without bubble formation from electrolysis of the aqueous buffer solution. This is more than 1 order of magnitude higher than what other groups have achieved and is necessary in order to obtain a high flow rate during the chemical analysis.

Klaus Bo Mogensen, DTU Nanotech, Tech. Univ. Denmark

Klaus B. Mogensen is working in the field of Lab-on-a-chip and received his Ph.D. in 2002 on micro-fabricated glass-based separation systems with integrated planar waveguides for optical detection from the Technical University of Denmark.  He is currently employed as an assoc. prof. at DTU Nanotech and is mainly working on integration of carbon nanotubes with microfluidic devices for electrochromatography applicarions. This work is a part of a larger EU project 'Technotubes'.

Plasmons in graphene from first principles: Effects of
semiconducting and metallic substrates

Collective electronic excitations are of fundamental interest in
graphene, due to its twodimensional and halfmetallic
nature[1]. The understanding of these plasmons will in turn bridge the gap between graphene and nanoplasmonics[2], en emerging field with one of the aims being to develop plasmon enhanced imaging and sensing techniques. For many applications of graphene, the substrate plays a crucial role and should be considered as part of the device. Here we investigate the role of substrates on the plasmon excitations of graphene. Our first principles calculations show that, the substrates have a profound influence on the plasmonic excitations even for weakly coupled graphene/substrate systems. The plasmons are significantly damped by a semiconducting SiC(0001) substrate and completely quenched by a metallic Al(111) substrate, in particular in the long wavelength limit. The strong damping of the plasmons occurs despite the fact that the singleparticle band structure of graphene is completely unaffected by the substrates illustrating the nonlocal nature of the effect.

[1] A. H. Castro Neto, F. Guinea, N. M. R. Peres, K. S. Novoselov and A. K. Geim, Rev. Mod. Phys. 81, 109 (2009).
[2] S. A. Maier, Plasmonics: Fundamentals and Applications (Springer, New York, 2007)

Jun Yan, DTU Physics, Technical University of Denmark

After PhD studies (20042009)
from Institute of Physics, Chinese Academy of Sciences (CAS), Jun Yan joined CAMD, DTU in 2009 as a postdoc. Her PhD work focused on theoretical modeling of electronic excitations especially plasmon excitations, in metallic nanoand atomic systems using timedependent density functional theory (TDDFT). The work aims at a microscopic understanding of plasmons concerning their formation and development from single atoms, their collective nature and dynamics in time and space, and the influence of quantum confinement effects at atomic scale. During her stay in DTU, she has implemented linear density response function in the GPAW code. It enables one to calculate optical and dielectric properties of bulk, surfaces, thin films and clusters. This work aims at engineering and exploring new material for solar cell applications. Her interests include first principle calculations of electronic structure and electronic excitations of solids and nanostructures using DFT and TDDFT as well as theoretical implementation and massive parallel computing.

Vertically aligned CNT growth on microfabricated silicon heater with integrated temperature control

Optimisation of carbon nanotube growth is at best cumbersome and time consuming. Uncontrolled changes in the growth conditions from experiment to experiment, such as local flow and temperature variations make it difficult to draw conclusions as to the effect of growth parameters without a significant statistical basis. The use of MEMS microheaters is a novel method to reduce the thermal mass of the heater, to achieve a continuous temperature distribution and to grow carbon nanotubes [1] or nanowires [2] in a location that allow accurate and convenient inspection. In this study vertically aligned carbon nanotubes were grown along a temperature gradient on a silicon microheater in order to investigate the carbon nanotube activation energy. Through a four point measurement of the silicon conductivity in the heated region the temperature could be measured accurately during growth. Finite element simulations of the microheater was used to determine the temperature along the silicon heater and from the carbon nanotube growth rate as a function of temperature the growth activation energy was determined with great accuracy.

[1] Englander O, Christensen D and Lin L 2003 Applied Physics Letters 82 4797-4799
[2] Mølhave K, Wacaser B A, Petersen D H, Wagner J B, Samuelson L and Bøggild P 2008 Small 4 1741–1746

Daniel S. Engstrøm, DTU Nanotech, Tech. Univ. Denmark and Materials Department, Imperial College London, UK

After receiving his M.Sc. from the Technical University of Denmark Daniel S. Engstrøm carried out his PhD at DTU Nanotech and the University of Cambridge (2007-2010) before starting as a post doctoral research associate at Imperial College London. His researched has focused on growth studies and integration of carbon nanotubes and graphene in microsystems. Methods for wafer scale integration of carbon nanotubes on AFM tips for high aspectratio scans and high durability is one area of interest. He has also carried growth optimization of grapehen and vertically aligned single wall carbon nanotubes and has grown carbon nanotubes on microfabricated silicon heaters for investigations of carbon nanotube growth kinetics.

 More will be added...