A research team headed by Prof. Patrick Han and Prof. Taro Hitosugi at the Advanced Institute of Materials Research (AIMR), Tohoku University discovered a new bottom-up fabrication method that produces defect-free graphene nanoribbons (GNRs) with periodic zigzag-edge regions. This method, which controls GNR growth direction and length distribution, is a stepping stone towards future graphene-device fabrication by self-assembly.
Graphene, with its low dimensionality, high stability, high strength, and high charge-carrier mobility, promises to be a revolutionary material for making next-generation high-speed transistors. Moreover, graphene's properties are predicted to be directly controllable by its structure.
Graphene nanoribbons are fabricated by molecular assembly on a Cu(111) substrate. On this surface system, GNRs on grow in six azimuthal directions exclusively. White lines in the inset highlight the zigzag edges of a ribbon.
Credit: Patrick Han
For example, recent works have demonstrated that the bandgap of armchair GNRs is controlled by the ribbon width. However, the property-tailoring capabilities of other edge conformations (e.g., the zigzag edge is predicted by theory to have magnetic properties) have not been tested, because their defect-free fabrication remains a major challenge.
"Previous strategies in bottom-up molecular assemblies used inert substrates, such as gold or silver, to give molecules a lot of freedom to diffuse and react on the surface," says Han. "But this also means that the way these molecules assemble is completely determined by the intermolecular forces and by the molecular chemistry." Currently, there is no molecule that can assemble to produce zigzag-edge GNRs.
To target the zigzag edge, the AIMR team used a copper surface—a substrate more reactive than gold or silver—to introduce new substrate-to-molecule interactions, in addition to the intermolecular interactions. The effects of this strategy were demonstrated using a precursor molecule known to form armchair-edge GNRs.
On copper, scanning tunneling microscope images revealed a molecular assembly that is entirely different than that on gold or silver, yielding GNRs with periodic zigzag-edge regions. Future directions include the assessment of other reactive surfaces for bottom-up GNR fabrication, and the determination of the property-tailoring effects of the GNR edges shown in this work.
Moreover, the surface reactivity of the copper substrate also has a profound effect on both the GNR length distribution and surface growth direction. Unlike previous assemblies, the current method produces shorter ribbons, only in six surface azimuthal directions. These features could be exploited for making single graphene interconnections between prefabricated structures by self-assembly.
"Diffusion-controlled assemblies, as seen on gold and silver, produce bundles of long GNRs. These methods are good for making interconnect arrays, but not single connections", Han says. "Our method opens the possibility for self-assembling single graphene devices at desired locations, because of the length and of the direction control."
Patrick Han, Kazuto Akagi, Filippo Federici Canova, Hirotaka Mutoh, Susumu Shiraki, Katsuya Iwaya, Paul S. Weiss, Naoki Asao, Taro Hitosugi, "Bottom-Up Graphene-Nanoribbon Fabrication Reveals Chiral Edges and Enantioselectivity", ACS Nano, 2014, in press DOI: 10.1021/nn5028642
Prof. Patrick Han
Advanced Institute for Materials Research, Tohoku University
(about Public Relations)
Public Relations & Outreach office, Advanced Institute for Materials Research, Tohoku University
TEL: +81 22 217 6146
The Advanced Institute for Materials Research (AIMR) at Tohoku University is one of nine World Premier International Research Center Initiative (WPI) Program established with the support of the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT), aimed at developing world-class research bases in Japan. After its establishment in 2007, AIMR has been active in conducting research activities and creating new systems in order to become a global center for materials science. Since 2012, AIMR has also been conducting fundamental research by finding connections between materials science and mathematics.
Learn more at http://www.wpi-aimr.tohoku.ac.jp
Yasufumi Nakamichi | Eurek Alert!
Simple processing technique could cut cost of organic PV and wearable electronics
06.12.2016 | Georgia Institute of Technology
InLight study: insights into chemical processes using light
05.12.2016 | Fraunhofer-Institut für Lasertechnik ILT
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
06.12.2016 | Materials Sciences
06.12.2016 | Medical Engineering
06.12.2016 | Power and Electrical Engineering