researchers from the national research nuclear university mephl in russia have created a new means for purifying graphene that has a high stability to ozonation through the high-temperature sublimation of silicon carbide (sic). this avoids the need for treating graphene with thermal annealing, plasma stripping or chemical solvents that could dull its properties.

researchers have created graphene that is resistant to ozone. (wikimedia commons)

to create graphene, as outlined in a recent phys.org article, for nanoelectronic devices, a polymeric coating is placed on graphene and peeled off. this could leave a residue that pollutes the graphene and alters its electric conductivity.

the graphene that researchers created with sublimated sic was able to stay in contact with ozone, a common and highly reactive polymer used to strip residue that can deteriorate graphene, for nearly 10 minutes before losing its properties. normal graphene can only last 3-4 minutes under ozone.

through computer simulations, researchers discovered that the buildup of graphene on the sic substrate was “smooth” and this made it less susceptible to the reactivity of ozone.

in a report published in carbon, the researchers stated:

“we present an experimental study of time dependent ozone treatment on post-process epitaxial graphene using both electron transport measurements and resonant micro-raman spectroscopy. we focus on a systematic analysis of residual polymer decomposition on the epitaxial graphene on sic substrate.

“it was found that graphene could be effectively cleaned by ultraviolet (uv)/ozone treatment after nanofabrication from residual lithographic polymers. this procedure improves the charge carrier mobility, almost by a factor of two for strongly contaminated samples, decreases the doping level and does not introduce defect inside the graphene lattice. it was found that epitaxial sic graphene is extremely stable when exposed to radical oxygen atoms.

“we ascribe this effect to the substrate topography, which significantly affects the graphene stability under uv/ozone treatment. our calculations reveal that surface roughness of the sic substrate can change the energy gain from epoxy group adsorption by a few tenths of electron volts.”

this new discovery could lead to an industrial cleansing process for graphene with more stable electronic properties and less reactive to oxygen-free radicals.