Page 32 - february_012822.indd
P. 32
TAP TIMES -32- FEBRUARY 2022
Graphene nanoribbons (from 31) The second challenge was to develop a
new technique to directly measure a mag-
This activation step breaks a chemical netic field at the nanometer scale. Luckily,
bond and leaves behind a highly reactive the researchers found that the nitrogen
“sticky end.” atoms substituted in the nanoribbons’
structure actually acted as atomic-scale
New bonds sensors.
Each time two “sticky ends” meet while
the activated molecules spread out on the Characteristic features
surface, the molecules combine to form Measurements at the positions of the ni-
new carbon-carbon bonds. trogen atoms revealed the characteristic
features of a local magnetic field along the
Eventually, the process builds 1D daisy zigzag edge.
chains of molecular building blocks. Final-
ly, a second heating step rearranges the Calculations performed by Louie using
chain’s internal bonds to form a graphene computing resources at the National En-
nanoribbon featuring two parallel zigzag ergy Research Scientific Computing Center
edges. (NERSC) yielded quantitative predictions
of the interactions that arise from the
“The unique advantage of this molecular spin-polarized edge states of the ribbons.
bottom-up technology is that any structur-
al feature of the graphene ribbon, such as Microscopy measurements of the pre-
the exact position of the nitrogen atoms, cise signatures of magnetic interactions
can be encoded in the molecular building matched those predictions and confirmed
block,” said Raymond Blackwell, a co-lead their quantum properties.
author with Fangzhou Zhao, a graduate
student. “Exploring and ultimately developing the
experimental tools that allow rational en-
The next challenge was to measure the gineering of these exotic magnetic edges
nanoribbons’ properties. opens the door to unprecedented oppor-
tunities of carbon-based spintronics,” said
Two additional problems Fischer, referring to next-generation nano-
“We quickly realized that, to not only electronic devices that rely on intrinsic
measure but actually quantify the mag- properties of electrons.
netic field induced by the spin-polarized Custom designs
nanoribbon edge states, we would have Future work will in-
to address two additional problems,” said volve exploring phe-
Fischer, who is also a professor of chemis- nomena associated
try at UC Berkeley. with these proper-
Felix Fischer Steve Louie
ties in custom-de-
First, the team needed to figure out how signed zigzag graphene architectures.
to separate the electronic structure of the This research was supported by the DOE
ribbon from its substrate. Office of Science. NERSC is a DOE Office
of Science user facility located at Berkeley
Fischer solved the issue by using a scan- Lab.— Rachel Berkowitz, lbl.gov
ning tunneling microscope tip to irrevers-
ibly break the link between the graphene
nanoribbon and the underlying metal. Reach more markets with TAP TIMES!
