Molecular graphene,first system designer electrons

Molecular graphene, the first system of designer electrons

11:24 PM, 18th March 2012
Molecular graphene, the first system of designer electrons
Specific hexagonal pattern of carbon monoxide molecules (black/red) has on free-flowing electrons (orange/yellow) atop a copper surface. Ordinarily, the electrons behave as simple plane waves but the electrons are repelled by the carbon monoxide molecules, placed here in a hexagonal pattern.

MENLO PARK, US: Researchers from Stanford University and the US Department of Energy’s SLAC National Accelerator Laboratory have created the first-ever system of ‘designer electrons’- exotic variants of ordinary electrons with tunable properties that may ultimately lead to new types of materials and devices.

“The behaviour of electrons in materials is at the heart of essentially all of today’s technologies. We’re now able to tune the fundamental properties of electrons so they behave in ways rarely seen in ordinary materials,” said Hari Manoharan, Associate Professor, Stanford University.

Their first examples, reported in Nature, were hand-crafted, honeycomb-shaped structures inspired by graphene, a pure form of carbon that has been widely heralded for its potential in future electronics. Initially, the electrons in this structure had graphene-like properties; for example, unlike ordinary electrons, they had no mass and traveled as if they were moving at the speed of light in a vacuum. But researchers were then able to tune these electrons in ways that are difficult to do in real graphene.

To make the structure, which Manoharan calls molecular graphene, the scientists use a scanning tunneling microscope to place individual carbon monoxide molecules on a perfectly smooth copper surface. The carbon monoxide repels the free-flowing electrons on the copper surface and forces them into a honeycomb pattern, where they behave like graphene electrons.

To tune the electrons’ properties, the researchers repositioned the carbon monoxide molecules on the surface; this changed the symmetry of the electron flow. In some configurations, electrons acted as if they had been exposed to a magnetic or electric field. In others, researchers were able to finely tune the density of electrons on the surface by introducing defects or impurities. By writing complex patterns that mimicked changes in carbon-carbon bond lengths and strengths in graphene, the researchers were able to restore the electrons’ mass in small, selected areas.

“One of the wildest things we did was to make the electrons think they are in a huge magnetic field when, in fact, no real field had been applied,” said Manoharan. The Stanford team calculated the positions where carbon atoms in graphene should be to make its electrons believe they were being exposed to magnetic fields ranging from zero to 60 Tesla, more than 30 per cent higher than the strongest continuous magnetic field ever achieved on Earth. The researchers then moved carbon monoxide molecules to steer the electrons into precisely those positions, and the electrons responded by behaving exactly as predicted, as if they had been exposed to a real field.

“Our new approach is a powerful new test bed for physics. Molecular graphene is just the first in a series of possible designer structures. We expect that our research will ultimately identify new nanoscale materials with useful electronic properties,” said Manoharan.

© SLAC National Accelerator Laboratory News

0 Comments

Login

Your Comments (Up to 2000 characters)
Please respect our community and the integrity of its participants. WOC reserves the right to moderate and approve your comment.

Related News


Making hydrogen fuel cells practical and cost effective

FLORIDA, US: Hydrogen fuel cells, like those found in some ‘green’ vehicles, have a lot of promise as an alternative fuel source, but maki ...

Read more
Fluor awarded FEMA contract to support national emergency recovery efforts

IRVING, US: Fluor Corporation has been awarded a contract by the Department of Homeland Security’s Federal Emergency Management Agency (FEMA) to ...

Read more
Novozymes wins biofuels leadership award

BAGSVAERD, DENMARK: Novozymes wins the biofuels leadership award, a recognition for leadership in the area of sustainable biofuels at the World Biofue ...

Read more
BASF appoints Dr Ramachandran as Asia Pacific’s Crop Protection head

LUDWIGSHAFEN, GERMANY: BASF has appointed Dr Raman Ramachandran as Senior Vice President of the company’s Crop Protection division for the Asia ...

Read more
New material discovered, absorbs wide range of light with high efficiency

MASSACHUSETTS, US: Researchers at Massachusetts Institute of Technology (MIT) have found a way to use metamaterials to absorb a wide range of light wi ...

Read more
Momentive to close epoxies Wesseling plant in Germany

COLUMBUS, US/ WESSELING, GERMANY: Momentive Specialty Chemicals announced the closure of its Wesseling site, Germany. This action will better align Eu ...

Read more