Tech Briefs Magazine - October 2021 - 22

Electrical/Electronics
der Waals zinc-oxide magnet - from a
solution of graphene oxide, zinc, and
cobalt. A few hours of baking in a conventional
lab oven transformed the mixture
into a single atomic layer of zinc-oxide
with a smattering of cobalt atoms sandwiched
between layers of graphene. In a
final step, the graphene is burned away,
leaving behind just a single atomic layer of
cobalt-doped zinc-oxide.
To confirm that the resulting 2D film is
just one atom thick, the team conducted
scanning electron microscopy experiments
to identify the material's morphology
and transmission electron microscopy
(TEM) imaging to probe the material
Co
O
Zn
atom by atom. The x-ray experiments
characterized the 2D material's magnetic
parameters under high temperature.
Additional x-ray experiments verified
the electronic and crystal structures of
the synthesized 2D magnets. TEM was
used to image the 2D material's crystal
structure and chemical composition.
The graphene-zinc-oxide system be -
comes weakly magnetic with a 5 to 6 percent
concentration of cobalt atoms. In -
creasing the concentration of cobalt
atoms to about 12 percent results in a
very strong magnet. A concentration of
cobalt atoms exceeding 15 percent shifts
the 2D magnet into an exotic quantum
Illustration of the one-atom-thin 2D magnet. Red represents cobalt atoms, blue represents oxygen
atoms, and yellow represents zinc atoms. (Credit: Berkeley Lab)
state of " frustration, " whereby different
magnetic states within the 2D system are
in competition with each other. And
unlike previous 2D magnets, which lose
their magnetism at room temperature
or above, the researchers found that the
new 2D magnet not only works at room
temperature but also at 100 °C (212 °F).
When a computer is commanded to
save a file, that information is stored as
a series of ones and zeroes in the computer's
magnetic memory such as the
magnetic hard drive or a flash memory.
And like all magnets, magnetic memory
de vices contain microscopic magnets
with two poles - north and south -
the orientations of which follow the
direction of an external magnetic field.
Data is written or encoded when these
tiny magnets are flipped to the desired
directions.
Zinc oxide's free electrons could act as
an intermediary that ensures the magnetic
cobalt atoms in the new 2D device continue
pointing in the same direction -
and thus stay magnetic - even when the
host (in this case, the semiconductor zinc
oxide) is a nonmagnetic material.
The new material - which can be
bent into almost any shape without
breaking and is a million times thinner
than a sheet of paper - could help
advance the application of spin electronics
or spintronics, a new technology that
uses the orientation of an electron's spin
rather than its charge to encode data.
For more information, contact Theresa
Duque at tnduque@lbl.gov; 510-495-2418.
Insulation Material Enables More Efficient Electricity
Distribution
High-voltage direct current cables can more efficiently transport electricity over long distances.
Chalmers University of Technology, Gothenburg, Sweden
o transition to a world powered by
renewable energy, efficient long-distance
transport of electricity is essential,
since the supply - renewable energy
sources such as wind and solar farms, as
well as hydroelectric dams - is often
located far from cities, where most of
the demand exists.
T
High-voltage direct current (HVDC)
cables are the most efficient means of
transporting electricity over long distances.
HVDC cables with an insulation
layer can be buried underground or on
the seabed, allowing for considerable
22
Cov
expansion of networks. During transport,
as little energy as possible should
be lost. One way to reduce transmission
losses is by increasing the direct
current voltage level.
However, an increase in the transmission
voltage adversely affects the
insulation of a HVDC cable. The re -
sulting higher electric field stresses
could be handled if the electrical conductivity
of the insulation material was
reduced sufficiently. Researchers have
developed a new insulation material
up to three times less conductive,
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ToC
offering significant improvements to
the properties and performance of
such cables.
The basis of the new material is polyethylene,
which is already used for
insulation in existing HVDC cables.
Now, by adding very small amounts -
5 parts per million - of the conjugated
polymer known as poly(3-hexylthiophene),
the researchers were able to
lower the electrical conductivity by up
to three times
The additive, also known as P3HT, is
a widely studied material and given the
Tech Briefs, October 2021

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Tech Briefs Magazine - October 2021

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