Nav: Home

Carbon nanotubes self-assemble into tiny transistors

April 05, 2017

Carbon nanotubes can be used to make very small electronic devices, but they are difficult to handle. University of Groningen scientists, together with colleagues from the University of Wuppertal and IBM Zurich, have developed a method to select semiconducting nanotubes from a solution and make them self-assemble on a circuit of gold electrodes. The results were published in the journal Advanced Materials on 5 April.

The results look deceptively simple: a self-assembled transistor with nearly 100 percent purity and very high electron mobility. But it took ten years to get there. University of Groningen Professor of Photophysics and Optoelectronics Maria Antonietta Loi designed polymers which wrap themselves around specific carbon nanotubes in a solution of mixed tubes. Thiol side chains on the polymer bind the tubes to the gold electrodes, creating the resultant transistor.

Patent

'In our previous work, we learned a lot about how polymers attach to specific carbon nanotubes', Loi explains. These nanotubes can be depicted as a rolled sheet of graphene, the two-dimensional form of carbon. 'Depending on the way the sheets are rolled up, they have properties ranging from semiconductor to semi-metallic to metallic.' Only the semiconductor tubes can be used to fabricate transistors, but the production process always results in a mixture.

'We had the idea of using polymers with thiol side chains some time ago', says Loi. The idea was that as sulphur binds to metals, it will direct polymer-wrapped nanotubes towards gold electrodes. While Loi was working on the problem, IBM even patented the concept. 'But there was a big problem in the IBM work: the polymers with thiols also attached to metallic nanotubes and included them in the transistors, which ruined them.'

Solution

Loi's solution was to reduce the thiol content of the polymers, with the assistance of polymer chemists from the University of Wuppertal. 'What we have now shown is that this concept of bottom-up assembly works: by using polymers with a low concentration of thiols, we can selectively bring semiconducting nanotubes from a solution onto a circuit.' The sulphur-gold bond is strong, so the nanotubes are firmly fixed: enough even to stay there after sonication of the transistor in organic solvents.

The production process is simple: metallic patterns are deposited on a carrier , which is then dipped into a solution of carbon nanotubes. The electrodes are spaced to achieve proper alignment: 'The tubes are some 500 nanometres long, and we placed the electrodes for the transistors at intervals of 300 nanometres. The next transistor is over 500 nanometres away.' The spacing limits the density of the transistors, but Loi is confident that this could be increased with clever engineering.

'Over the last years, we have created a library of polymers that select semiconducting nanotubes and developed a better understanding of how the structure and composition of the polymers influences which carbon nanotubes they select', says Loi. The result is a cheap and scalable production method for nanotube electronics. So what is the future for this technology? Loi: 'It is difficult to predict whether the industry will develop this idea, but we are working on improvements, and this will eventually bring the idea closer to the market.'
-end-
Reference: Vladimir Derenskyi, Widianta Gomulya, Wytse Talsma, Jorge Mario Salazar-Rios, Martin Fritsch, Peter Nirmalraj, Heike Riel, Sybille Allard, Ulrich Scherf, Maria A. Loi: On-chip chemical self-assembly of semiconducting Single-Walled Carbon Nanotubes (SWNTs): towards robust and scale invariant SWNTs transistors Advanced Materials, online 5 april 2017

University of Groningen

Related Carbon Nanotubes Articles:

Why modified carbon nanotubes can help the reproducibility problem
Scientists at Tokyo Institute of Technology (Tokyo Tech) conducted an in-depth study on how carbon nanotubes with oxygen-containing groups can be used to greatly enhance the performance of perovskite solar cells.
Tensile strength of carbon nanotubes depends on their chiral structures
Single-walled carbon nanotubes should theoretically be extremely strong, but it remains unclear why their experimental tensile strengths are lower and vary among nanotubes.
New study reveals carbon nanotubes measurement possible for the first time
Swansea University scientists report an entirely new approach to manipulation of carbon nanotubes that allows physical measurements to be made on carbon nanotubes that have previously only been possible by theoretical computation.
Neural networks will help manufacture carbon nanotubes
A team of scientists from Skoltech's Laboratory of Nanomaterials proposed a neural-network-based method for monitoring the growth of carbon nanotubes, preparing the ground for a new generation of sophisticated electronic devices.
Efficient, interconnected, stable: New carbon nanotubes to grow neurons
Carbon nanotubes able to take on the desired shapes thanks to a special chemical treatment, called crosslinking and, at the same time, able to function as substrata for the growth of nerve cells, finely tuning their growth and activity.
OU Researcher determines catalytic active sites using carbon nanotubes
Catalytic research led by University of Oklahoma researcher Steven Crossley has developed a new and more definitive way to determine the active site in a complex catalyst.
Carbon in color: First-ever colored thin films of nanotubes created
A method developed at Aalto University, Finland, can produce large quantities of pristine single-walled carbon nanotubes in select shades of the rainbow.
FEFU scientists reported on toxicity of carbon and silicon nanotubes and carbon nanofibers
Nanoparticles with a wide range of applying, including medicine, damage cells of microalgae Heterosigma akashivo badly.
Making carbon nanotubes as usable as common plastics
By using an inexpensive, already mass produced, simple solvent called cresol, Northwestern University's Jiaxing Huang has discovered a way to make disperse carbon nanotubes at unprecedentedly high concentrations without the need for additives or harsh chemical reactions to modify the nanotubes.
Carbon nanotubes devices may have a limit to how 'nano' they can be
Carbon nanotubes bound for electronics not only need to be as clean as possible to maximize their utility in next-generation nanoscale devices, but contact effects may limit how small a nano device can be, according to researchers at the Energy Safety Research Institute (ESRI) at Swansea University in collaboration with researchers at Rice University.
More Carbon Nanotubes News and Carbon Nanotubes Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.