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Technique boosts graphene (Berkeley Lab) and UC Berkeley have de-
nanoribbons’ potential veloped a method to stabilize the edges of
graphene nanoribbons and directly mea-
BERKELEY, Calif. — Ever since gra- sure their unique magnetic properties.
phene – a thin carbon sheet just one-
atom thick – was discovered more Carbon atoms substitution
than 15 years ago, the wonder mate- The team co-led by Felix Fischer and
rial became a workhorse in materials Steven Louie, both faculty scientists in
science research. Berkeley Lab’s Materials Sciences Division,
found that by substituting some of the car-
Exotic magnetic properties bon atoms along the ribbon’s zigzag edges
From this body of work, other research- with nitrogen atoms, they could discretely
ers learned that slicing graphene along tune the local electronic structure without
the edge of its honeycomb lattice creates disrupting the magnetic properties.
one-dimensional zigzag graphene strips or
nanoribbons with exotic magnetic proper- This subtle structural change further en-
ties. abled the development of a scanning
probe microscopy technique for measur-
Many researchers have sought to harness ing the material’s local magnetism at the
nanoribbons’ unusual magnetic behavior atomic scale.
into carbon-based, spintronics devices that
enable high-speed, low-power data stor- “Prior attempts to stabilize the zigzag edge
age and information processing technolo- inevitably altered the electronic structure
gies by encoding data through electron of the edge itself,” said Louie, who is also a
spin instead of charge. professor of physics at UC Berkeley.
“This dilemma has doomed eff orts to ac-
cess their magnetic structure with ex-
perimental techniques, and until now rel-
egated their exploration to computational
models,” he added.
Guidance from theoretical models
Guided by theoretical models, Fischer and
Louie designed a custom-made molecular
building block featuring an arrangement
Local magnetic ordering along zigzag edge states (red and blue of carbon and nitrogen atoms that can be
arrows) in nitrogen-doped graphene nanoribbons induces a split-
ting in energy of the nitrogen atom’s electrons. mapped onto the precise structure of the
(Felix Fischer/Berkeley Lab) desired zigzag graphene nanoribbons.
Making realworld devices To build the nanoribbons, the small mo-
But because zigzag nanoribbons are high- lecular building blocks are fi rst deposited
ly reactive, researchers have grappled with onto a fl at metal surface, or substrate.
how to observe and channel their exotic Next, the surface is gently heated, activat-
properties into a real-world device. ing two chemical handles at either end of
each molecule.
Now, as reported in Nature, researchers at next page
Lawrence Berkeley National Laboratory
