A group of scientists from MEPhI and a series of foreign universities has developed an industrial technology for the purification of graphene, which has higher stability under the influence of aggressive oxygen free radicals. This discovery is of the crucial importance for the development of nanoelectronics.

Graphene is crystalline carbon film  with the thickness of one atom. Thanks to its unique characteristics (special electronic properties, high conductivity, transparency for light, an ability for mechanical stretching and others), graphene is a promising material, which is in high demand in nanoelectronics.

In the manufacturing of various nanoelectronic devices polymeric covering is applied on graphene, and then peeled off. The remains of that coating "pollute" graphene, lowering the mobility of charge carriers in it. Different treatment methods (thermal annealing, plasma stripping and chemical solvents) can remove the polymer residues, but they make the quality of graphene worse. For example, in one of the most common purification methods ozone, which has high reactivity, is used. However, under the influence of ozone not only polymeric residue is destroyed, but defects appear in graphene, which lead to the deterioration of its characteristics. Scientists from MEPhI have managed to obtain graphene with a very high stability to ozonation using high-temperature sublimation of silicon carbide (SiC). The obtained graphene maintains contact with ozone for more than 10 minutes, while ordinary graphene loses its properties in only three or four minutes under such conditions. The results of the research have been published in the prestigious scientific journal, Carbon.

For further studying of the phenomenon, scientists from Greece, France and Sweden were attracted. With the help of computer modeling the experts were able to figure out the reasons of SiC-graphene increased stability under the impact of aggressive oxygen free radicals. The new graphene's abnormal stability turned out to be associated with the low roughness of epitaxial graphene on SiC-substrate (epitaxy is a natural buildup of one crystalline material upon the surface of another).

"It was found out that the usual ‘rough' graphene is more vulnerable because of the presence of convex areas; these areas show high reactivity to the formation of epoxy groups, which destroy its integrity," Konstantin Katin, Assistant Professor of the Department of Condensed Matter Physics at the MEPhI Institute of Nanotechnology in Electronics, Photonics, and Spintronics said. "The results show that the technological process for the production of industrial graphene with improved characteristics can involve the nanofabrication of graphene on the basis of silicon carbide with its subsequent ozonation. Ozonation itself is an effective way of clearing graphene obtained in any way. The only limitation on the purification techniques has to do with the possible roughness of the graphene sheet: it should be practically perfectly smooth," Mikhail Maslov, Assistant Professor of the Department of Condensed Matter Physics, said.

The scientists’ discovery will become a basis for perspective technologies to purify high-quality industrial graphene with stable electronic characteristics.