Teams of Korean scientists have developed groundbreaking techniques that could bring forward the application of graphene.

Graphene is a layer of carbon with the thickness of one carbon atom and in which the atoms are arranged in a tight honeycomb structure.

The structure, which forms graphite when congregated in multiple layers, has some unique properties that have led to its being touted as a “miracle material” that could replace a number of widely used materials.

Graphene’s tensile strength is 200 times greater than that of steel, while its heat conductivity ― the ability to transfer heat ― is 100-fold greater than that of copper.

In addition, electron mobility across a graphene sheet is 140 times higher than that displayed by silicon materials that form the basis of the semiconductor and electronics industries.

Despite such properties, the use of graphene-based materials has been hampered by the high production costs and limitations in handling graphene.

Recent developments from Korea’s scientific community, however, could speed up wider application of graphene materials, with two teams of local researchers developing new methods for producing graphene semiconductors and for observing the size and distribution of graphene segments.

The graphene semiconductor production method, developed by a team led by Ulsan National Institute of Science and Technology’s Jun Yong-seok and Seoul National University’s Park Yung-woo, treats graphene with hydrogen molecules to produce n-type semiconductors.

In n-type semiconductors, the conductivity is provided by electrons that are not bound to the nucleus of the constituent atoms.

The team found that exposing graphene with missing carbon atoms to pressurized hydrogen gas gives the graphene the characteristics of an n-type semiconductor.

The team’s experiments showed that hydrogen molecules break into two hydrogen atoms in the presence of graphene and that the process was more pronounced when the graphene had missing carbon atoms.

The two hydrogen atoms then cause the double bond between carbon atoms, with one of the hydrogen atoms going on to bond with the resulting opening while the other gives the graphene the properties of an n-type semiconductor.

“Developing core technologies is not only important for the semiconductor industry but also for securing a lead in the diverse applications of graphene from flexible solar cells,” Jun said in a statement.

“Succeeding in producing n-type semiconductors simply by exposing (graphene) to hydrogen gas, the research is expected to contribute to developing low-cost, high-efficiency semiconductor materials.”

While Jun and Park focused on developing graphene with semiconducting properties, professor Lee Young-hee of Sungkyunkwan University and his team succeeded in developing a groundbreaking method for observing graphene structures.

While smaller graphene structures need to be connected together to form larger sheets, observing the edges of the fragments and their distribution at the same time has been impossible due to the small size of graphene structures.

The method developed by Lee and his team, however, allows both the edges and distribution of graphene structures using optical microscope.

In the method, the graphene is placed on copper plates, and exposed the graphene to oxidizing agents.

The team discovered that the process results in the oxidation of the edges and also that the copper plate underneath the graphene is oxidized, leaving copper oxide in a pattern that is observable with optical microscopes.

According to Lee, the new method will allow researchers who do not have access to expensive transmission electron microscopes to conduct research concerning graphene, and offer a cost-effective way for related processes to be monitored in the industry.

By Choi He-suk  (cheesuk@heraldcorp.com)