Researchers at the Ulsan National Institute of Science and Technology (UNIST) in South Korea are on their way towards industrial-scale production of graphene suitable for semiconductors.

Graphene is a one-atom-thick carbon layer that is highly conductive. While graphene’s outstanding electrical properties have made it the focus of many studies since its discovery in 2004, it has not been practical for manufacturing semiconductors.

Pure graphene is a semimetal material that, alone, does not allow the electrical switching needed to make logic devices, such as field-effect transistors. The operation of semiconductor chips is based on such logic devices. The UNIST team is researching ways to make graphene-based logic chips practical.

To address the problem the team has developed a simple but promising way to “dope” graphene: in other words to modify its electrical properties by deliberately inserting impurities. The process involves coupling boron with nitrogen.

Boron doping has shown promise for scaling up graphene production, but boron and carbon atoms are mismatched in size, which makes uniform doping challenging. After the UNIST team paired boron with nitrogen to overcome the mismatch, the combination was easily introduced into graphene. It turns out the resulting boron-carbon-nitride graphene (BCN-graphene) can be efficiently mass-produced.

Current test devices made by using BCN-graphene are less efficient than commercial silicon devices but prove the concept. The experimental device’s switching ability and its potential for scalable production using simple solution processing methods suggest many potential practical uses such as logic devices, water splitting devices and sensors.

Professor Jong-Beom Baek, who leads the UNIST team, says the remaining challenge is fine-tuning its band gap to improve switching performance for real-world semiconductor devices.

 

For further information contact:

Professor/ Director Jong-Beom Baek
Interdisciplinary School of Green Energy/Low-Dimensional Carbon Materials Center
Ulsan National Institute of Science and Technology (UNIST)
Republic of Korea
Email: jbbaek@unist.ac.kr

 

Did you know?

Through 2013, the UNIST team combined “ball-milling”, or grinding, with chemical processes to make several graphene variants that are chemically modified at their edges. These variants are suitable for producing efficient, cost-effective non-metal electrodes in fuel cells. One variant also promises better energy conversion for flexible solar cells.

In June 2013, UNIST reported using ball-milling to produce graphene “nanoplatelets”: nanoscale stacks of graphene discs that are doped with various halogen atoms, including chlorine, bromine and iodine molecules. All of these materials proved to catalyse the reduction of oxygen very efficiently. Since fuel cells rely on this reaction to work, such halogenated materials show promise for use as non-metal fuel cell cathodes, which could lead to less costly mass-produced fuel cells. Until now, most fuel cells have relied on costly platinum electrodes to function.

UNIST researchers also combined ball milling and chemical processes to fix nitrogen molecules in the edges of graphene. This has resulted in a material that offers very good catalytic performance for dye-sensitised solar cells and fuel cells. The material has the ability to replace conventional platinum catalysts for energy conversion.

Lastly, UNIST announced a ball-milling process, this time using sulphur, to produce another metal-free catalyst that offers good efficiency and long-term stability. The research team says its material shows promise for manufacturing low-cost high-efficiency fuel cells.