Encapsulation layers keep carbon nanotube transistors stable in open air
Individual transistors made from carbon nanotubes are faster and more energy efficient than those made from other materials. Going from a single transistor to an integrated circuit full of transistors, however, is a giant leap.
“A single microprocessor has a billion transistors in it,” said Northwestern Engineering’s Mark Hersam. “All billion of them work. And not only do they work, but they work reliably for years or even decades.”
When trying to make the leap from an individual, nanotube-based transistor to wafer-scale integrated circuits, many research teams, including Hersam’s, have met challenges. For one, the process is incredibly expensive, often requiring billion-dollar cleanrooms to keep the delicate nano-sized components safe from the potentially damaging effects of air, water, and dust. Researchers have also struggled to create a carbon nanotube-based integrated circuit in which the transistors are spatially uniform across the material, which is needed for the overall system to work.
Now Hersam and his team have found a key to solving all these issues. The secret lies in newly developed encapsulation layers that protect carbon nanotubes from environmental degradation.
Supported by the Office of Naval Research and the National Science Foundation, the research appears online in Nature Nanotechology on September 7. Tobin J. Marks, the Vladimir N. Ipatieff Research Professor of Chemistry in the Weinberg College of Arts and Sciences and professor of materials science and engineering in the McCormick School of Engineering, coauthored the paper. Michael Geier, a graduate student in Hersam’s lab, was first author.
“One of the realities of a nanomaterial, such as a carbon nanotube, is that essentially all of its atoms are on the surface,” said Hersam, the Walter P. Murphy Professor of Materials Science and Engineering. “So anything that touches the surface of these materials can influence their properties. If we made a series of transistors and left them out in the air, water and oxygen would stick to the surface of the nanotubes, degrading them over time. We thought that adding a protective encapsulation layer could arrest this degradation process to achieve substantially longer lifetimes.”
Hersam compares his solution to one currently used for organic light-emitting diodes (LEDs), which experienced similar problems after they were first realized. Many people assumed that organic LEDs would have no future because they degraded in air. After researchers developed an encapsulation layer for the material, organic LEDs are now used in many commercial applications, including displays for smartphones, car radios, televisions, and digital cameras. Made from polymers and inorganic oxides, Hersam’s encapsulation layer is based on the same idea but tailored for carbon nanotubes.
To demonstrate proof of concept, Hersam developed nanotube-based static random-access memory (SRAM) circuits. SRAM is a key component of all microprocessors, often making up as much as 85 percent of the transistors in the central-processing unit in a common computer. To create the encapsulated carbon nanotubes, the team first deposited the carbon nanotubes from a solution previously developed in Hersam’s lab. Then they coated the tubes with their encapsulation layers.
Using the encapsulated carbon nanotubes, Hersam’s team successfully designed and fabricated arrays of working SRAM circuits. Not only did the encapsulation layers protect the sensitive device from the environment, but they improved spatial uniformity among individual transistors across the wafer. While Hersam’s integrated circuits demonstrated a long lifetime, transistors that were deposited from the same solution but not coated degraded within hours.
“After we’ve made the devices, we can leave them out in air with no further precautions,” Hersam said. “We don’t need to put them in a vacuum chamber or controlled environment. Other researchers have made similar devices but immediately had to put them in a vacuum chamber or inert environment to keep them stable. That’s obviously not going to work in a real-world situation.”
Hersam imagines that his solution-processed, air-stable SRAM could be used in emerging technologies. Flexible carbon nanotube-based transistors could replace rigid silicon to enable wearable electronics. The cheaper manufacturing method also opens doors for smart cards — credit cards embedded with personal information to reduce the likelihood of fraud.
Read more: Realizing Carbon Nanotube Integrated Circuits
The Latest on: Carbon Nanotube Integrated Circuits
[google_news title=”” keyword=”Carbon Nanotube Integrated Circuits” num_posts=”10″ blurb_length=”0″ show_thumb=”left”]
via Google News
The Latest on: Carbon Nanotube Integrated Circuits
- News tagged with carbon nanotubeon November 27, 2023 at 4:00 pm
Skoltech scientists have found a way to improve the most widely used technology for producing single-walled carbon nanotube films—a promising material for solar cells, LEDs, flexible and ...
- Carbon Nanotube MOSFETs With Controlled Polarityon November 15, 2023 at 4:00 pm
Researchers. The team at the University of California, San Diego, in collaboration with the Taiwan Semiconductor Manufacturing Company, has recently created new carbon nanotube ...
- Integrated circuits based on a 2D semiconductor operating at GHz frequencieson November 13, 2023 at 4:00 pm
While past studies have demonstrated the potential of these materials in individual transistors, their use for developing entire integrated circuits (ICs ... than the CMOS technology as well as the ...
- Carbon nanotube–based MOSFETs doped using a scalable techniqueon November 9, 2023 at 4:01 pm
Researchers at the University of California, San Diego, and the Taiwan Semiconductor Manufacturing Company recently developed new carbon nanotube metal-oxide- semiconductor field-effect transistors ...
- Carbon Nanotube and Graphene Device Physicson June 14, 2023 at 2:07 am
Explaining the properties and performance of practical nanotube devices ... focus the important details of carbon solid-state physics to understand the ground rules of carbon transistors and the ...
- Carbon nanotubes – what they are, how they are made, what they are used foron March 21, 2022 at 8:59 am
This makes them highly attractive for numerous applications. Schematic of how graphene could roll up to form a carbon nanotube. Carbon is the fourth-most-abundant element in the universe and, ...
- Sew-able Carbon Nanotube Thread Could Spin A Lot Of Awesomeon September 28, 2021 at 5:35 pm
Well, we watch-less ones have something to look forward to, because a group of graduate students at Rice University have created extremely strong conductive thread woven from carbon nanotubes ...
- carbon nanotubeon October 3, 2019 at 5:00 pm
the devices can rely on an efficient energy source that easily integrated with the human body. Scientists have developed a flexible conductive material made up of carbon nanotubes, cross-linked ...
- Carbon Nanotube stock illustrationson January 12, 2018 at 5:58 pm
Atom molecule macro structure layer superconductor development vector illustration. carbon nanotube stock illustrations 3D nanotechnololy graphene texture cyberspace. Nano fiber... 3D nanotechnololy ...
- Carbon Nanotube Manufacturers and Supplierson September 10, 2017 at 9:58 am
The narrower the diameter of the nanotube, the more its intrinsic properties depends upon its specific type. Here is an overview of the most important and largest manufacturers and suppliers of carbon ...
via Bing News