Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Transistor for Plastic Electronics Exhibits the Best of Both Worlds

28.01.2011
In the quest to develop flexible plastic electronics, one of the stumbling blocks has been creating transistors with enough stability for them to function in a variety of environments while still maintaining the current needed to power the devices.

Online in the journal Advanced Materials, researchers from the Georgia Institute of Technology describe a new method of combining top-gate organic field-effect transistors with a bilayer gate insulator. This allows the transistor to perform with incredible stability while exhibiting good current performance. In addition, the transistor can be mass produced in a regular atmosphere and can be created using lower temperatures, making it compatible with the plastic devices it will power.

The research team used an existing semiconductor and changed the gate dielectric because transistor performance depends not only on the semiconductor itself, but also on the interface between the semiconductor and the gate dielectric.

“Rather than using a single dielectric material, as many have done in the past, we developed a bilayer gate dielectric,” said Bernard Kippelen, director of the Center for Organic Photonics and Electronics and professor in Georgia Tech’s School of Electrical and Computer Engineering.

The bilayer dielectric is made of a fluorinated polymer known as CYTOP and a high-k metal-oxide layer created by atomic layer deposition. Used alone, each substance has its benefits and its drawbacks.

CYTOP is known to form few defects at the interface of the organic semiconductor, but it also has a very low dielectric constant, which requires an increase in drive voltage. The high-k metal-oxide uses low voltage, but doesn’t have good stability because of a high number of defects on the interface.

So, Kippelen and his team wondered what would happen if they combined the two substances in a bilayer. Would the drawbacks cancel each other out?

“When we started to do the test experiments, the results were stunning. We were expecting good stability, but not to the point of having no degradation in mobility for more than a year,” said Kippelen.

The team performed a battery of tests to see just how stable the bilayer was. They cycled the transistors 20,000 times. There was no degradation. They tested it under a continuous bias stress where they ran the highest possible current through it. There was no degradation. They even stuck it in a plasma chamber for five minutes. There was still no degradation.

The only time they saw any degradation was when they dropped it into acetone for an hour. There was some degradation, but the transistor was still operational.

No one was more surprised than Kippelen.

“I had always questioned the concept of having air-stable field-effect transistors, because I thought you would always have to combine the transistors with some barrier coating to protect them from oxygen and moisture. We’ve proven ourselves wrong through this work,” said Kippelen.

“By having the bilayer gate insulator we have two different degradation mechanisms that happen at the same time, but the effects are such that they compensate for one another,” explains Kippelen. “So if you use one it leads to a decrease of the current, if you use the other it leads to a shift of the thereshold voltage and over time to an increase of the current. But if you combine them, their effects cancel out.”

“This is an elegant way of solving the problem. So, rather than trying to remove each effect, we took two processes that complement one another and as a result you have a transistor that’s rock stable.”

The transistor conducts current and runs at a voltage comparable to amorphous silicon, the current industry standard used on glass substrates, but can be manufactured at temperatures below 150°C, in line with the capabilities of plastic substrates. It can also be created in a regular atmosphere, making it easier to fabricate than other transistors.

Applications for these transistors include smart bandages, RFID tags, plastic solar cells, light emitters for smart cards – virtually any application where stable power and a flexible surface are needed.

In this paper the tests were performed on glass substrates. Next, the team plans on demonstrating the transistors on flexible plastic substrates. Then they will test the ability to manufacture the bilayer transistors with ink jet printing technologies.

Kippelen’s research team was comprised of Do Kyung Hwang, Canek Fuentes-Hernandez, Jungbae Kim, William J. Postcavage Jr. and Sung-Jin Kim.

The research was supported by Solvay, the Office of Naval Research and the National Science Foundation.

David Terraso | EurekAlert!
Further information:
http://www.gatech.edu

More articles from Materials Sciences:

nachricht Switched-on DNA
20.02.2017 | Arizona State University

nachricht Using a simple, scalable method, a material that can be used as a sensor is developed
15.02.2017 | University of the Basque Country

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Switched-on DNA

20.02.2017 | Materials Sciences

Second cause of hidden hearing loss identified

20.02.2017 | Health and Medicine

Prospect for more effective treatment of nerve pain

20.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>