Quantum materials cut closer than ever

Date:
September 13, 2021
Source:
Technical University of Denmark
Summary:
A new method designs nanomaterials with less than 10-nanometer
precision.

It could pave the way for faster, more energy-efficient electronics.



FULL STORY ==========================================================================
DTU and Graphene Flagship researchers have taken the art of patterning nanomaterials to the next level. Precise patterning of 2D materials
is a route to computation and storage using 2D materials, which can
deliver better performance and much lower power consumption than today's technology.


==========================================================================
One of the most significant recent discoveries within physics and material technology is two-dimensional materials such as graphene. Graphene is
stronger, smoother, lighter, and better at conducting heat and electricity
than any other known material.

Their most unique feature is perhaps their programmability. By creating delicate patterns in these materials, we can change their properties dramatically and possibly make precisely what we need.

At DTU, scientists have worked on improving state of the art for more
than a decade in patterning 2D materials, using sophisticated lithography machines in the 1500 m2 cleanroom facility. Their work is based in DTU's
Center for Nanostructured Graphene, supported by the Danish National
Research Foundation and a part of The Graphene Flagship.

The electron beam lithography system in DTU Nanolab can write details down
to 10 nanometers. Computer calculations can predict exactly the shape and
size of patterns in the graphene to create new types of electronics. They
can exploit the charge of the electron and quantum properties such as
spin or valley degrees of freedom, leading to high-speed calculations
with far less power consumption. These calculations, however, ask for
higher resolution than even the best lithography systems can deliver:
atomic resolution.

"If we really want to unlock the treasure chest for future quantum
electronics, we need to go below 10 nanometers and approach the atomic
scale," says professor and group leader at DTU Physics, Peter Bo/ggild.



==========================================================================
And that is excactly what the researchers have succeeded in doing.

"We showed in 2019 that circular holes placed with just 12-nanometer
spacing turn the semimetallic graphene into a semiconductor. Now we
know how to create circular holes and other shapes such as triangles,
with nanometer sharp corners. Such patterns can sort electrons based
on their spin and create essential components for spintronics or
valleytronics. The technique also works on other 2D materials. With these supersmall structures, we may create very compact and electrically tunable metalenses to be used in high-speed communication and biotechnology,"
explains Peter Bo/ggild.

Razor-sharp triangle The research was led by postdoc Lene Gammelgaard,
an engineering graduate of DTU in 2013 who has since played a vital role
in the experimental exploration of 2D materials at DTU: "The trick is to
place the nanomaterial hexagonal boron-nitride on top of the material
you want to pattern. Then you drill holes with a particular etching
recipe," says Lene Gammelgaard, and continues: "The etching process
we developed over the past years down-size patterns below our electron
beam lithography systems' otherwise unbreakable limit of approximately
10 nanometers. Suppose we make a circular hole with a diameter of
20 nanometers; the hole in the graphene can then be downsized to 10
nanometers.

While if we make a triangular hole, with the round holes coming from
the lithography system, the downsizing will make a smaller triangle with
self- sharpened corners. Usually, patterns get more imperfect when you
make them smaller. This is the opposite, and this allows us to recreate
the structures the theoretical predictions tell us are optimal."


==========================================================================
One can e.g. produce flat electronic meta-lenses -- a kind of
super-compact optical lens that can be controlled electrically at very
high frequencies, and which according to Lene Gammelgaard can become
essential components for the communication technology and biotechnology
of the future.

Pushing the limits The other key person is a young student, Dorte
Danielsen. She got interested in nanophysics after a 9th-grade internship
in 2012, won a spot in the final of a national science competition
for high school students in 2014, and pursued studies in Physics and Nanotechnology under DTU's honors program for elite students.

She explains that the mechanism behind the "super-resolution"
structures is still not well understood: "We have several possible
explanations for this unexpected etching behavior, but there is still
much we don't understand. Still, it is an exciting and highly useful
technique for us. At the same time, it is good news for the thousands of researchers around the world pushing the limits for 2D nanoelectronics
and nanophotonics." Supported by the Independent Research Fund Denmark,
within the METATUNE project, Dorte Danielsen will continue her work on extremely sharp nanostructures. Here, the technology she helped develop,
will be used to create and explore optical metalenses that can be tuned electrically.

========================================================================== Story Source: Materials provided by
Technical_University_of_Denmark. Original written by Tore Vind
Jensen. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Dorte R. Danielsen, Anton Lyksborg-Andersen, Kirstine E. S. Nielsen,
Bjarke S. Jessen, Timothy J. Booth, Manh-Ha Doan, Yingqiu
Zhou, Peter Bo/ ggild, Lene Gammelgaard. Super-Resolution
Nanolithography of Two- Dimensional Materials by Anisotropic
Etching. ACS Applied Materials & Interfaces, 2021; 13 (35): 41886
DOI: 10.1021/acsami.1c09923 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210913135701.htm

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