New Flexible, Transparent Transistors made of Nanotubes

The ability to create flexible, transparent electronics could lead to a host of novel applications, such as e-paper and electronic car windshields. Now, scientists have constructed a transistor made of a network of nanotubes that may serve as an essential component in a trans-flex device.

Such devices require two main components: light displays and current-controlling transistors. While scientists have found that OLEDs and LCDs work well as light displays, finding a truly transparent and flexible transistor material is still an open area. Usually, these transistors consist of metallic nanowires.

Recently, researchers from Hanyang University in Seoul have constructed a thin film transistor made of networked single-walled carbon nanotubes (SWNTs) on a glass substrate. While it’s not the first thin film transistor made of SWNTs, it has the advantage of allowing a high density of SWNTs to be grown under lower temperatures than normally required.

Most significantly, the method shows that nanotubes can offer a practical choice for fabricating transparent, thin film electronics such as flat-panel displays and future opto-electronics devices.

“This works shows that we are able to build a transistor with thin films of SWNTs, rather than with single SWNTs,” coauthor Wanjun Park told PhysOrg.com. “It means that we have an easier fabrication method for building electronic devices made of nanotubes, without the need to individually control each single tube.”

In a recent issue of Nanotechnology, the researchers explained how the SWNT network can be arranged through a technique called chemical vapor deposition. In this method, the substrate is pre-patterned with catalysts to avoid the need for etching, and the nanotubes can be directly deposited on the substrate. By enhancing this technique with the use of a water plasma, the scientists were able to grow the nanotubes at significantly lower temperatures than in previous methods.

Due to the high SWNT density on the substrate, the nanotubes intersected with each other to form a continuous conductive path. However, for nanotubes above a critical percolation threshold (a measure of connectivity), there was no conductance. In this way, the SWNTs act like semiconductors, providing the basis for the on-off switching in the transistor.

In the future, the scientists plan to make improvements to the nanotube transistors by increasing their mobility and further understanding the complex configuration of the nanotube networks.

“These results are just the beginning,” Park said. “The technology needs lower temperatures for semiconducting SWNT growth, as well as higher transistor performance for real applications. But SWNT is a very robust material with outstanding electrical properties. It can be expected to be one of the candidates for a future electronic material.”

More information: Bae, Eun Ju, Min, Yo-Sep, Kim, Un Jeong, and Park, Wanjun. “Thin film transistors of single-walled carbon nanotubes grown directly on glass substrates.” Nanotechnology 18 (2007) 495203 (4pp).

Copyright 2007 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

Related stories:

Novel memory device is set to rival transistor-switched silicon-based memory
Working with an international group of researchers, Professor Gehan Amaratunga has produced a novel memory device which is set to rival transistor-switched silicon-based memory.
Carbon Nanotubes Compromise the Functions of Certain Protozoa, Study Shows
A new study by researchers from the University of Waterloo in Ontario, Canada, hints that carbon nanotubes may be toxic to microorganisms. When cultures of a certain key protozoan, a single-cell organism, were exposed to the nanotubes their ability to ingest and digest bacteria was hindered.
Sandia researcher examines the physics of carbon nanotubes
Carbon nanotubes, described as the reigning celebrity of the advanced materials world, are all the rage. Recently researchers at Rice University and Rensselaer Polytechnic Institute used them to make the “blackest black” — the darkest known material, reflecting only 0.045 percent of all light shined on it.
New Properties Discovered for Nanotube Sheets
A team of nanotechnologists at The University of Texas at Dallas, along with Brazilian collaborators, have discovered that sheets of carbon nanotubes can produce bizarre mechanical properties when stretched or uniformly compressed. These unexpected but highly useful properties could be used for such applications as making composites, artificial muscles, gaskets or sensors. The team’s findings are reported in the April 25 issue of the journal Science.
Memory in artificial atoms
Nanophysicists have made a discovery that can change the way we store data on our computers. This means that in the future we can store data much faster, and more accurate. Their discovery has been published in the scientific journal Nature Physics.
Physicists show electrons can travel over 100 times faster in graphene than in silicon
University of Maryland physicists have shown that in graphene the intrinsic limit to the mobility, a measure of how well a material conducts electricity, is higher than any other known material at room temperature. Graphene, a single-atom-thick sheet of graphite, is a new material which combines aspects of semiconductors and metals.
IBM researchers quell nanoscale interference
IBM researchers have discovered a way to use graphite effectively in building nanoelectonic circuits vastly smaller than those in silicon-based computer chips.
New kind of transistor radios shows capability of nanotube technology
Carbon nanotubes have a sound future in the electronics industry, say researchers who built the world’s first all-nanotube transistor radios to prove it.

News discussion:

Nanotechnology news