"By growing graphene directly on silver under vacuum, we provide an atomically pristine surface for advanced graphene-based technologies," says Brian Kiraly. (Credit: Argonne National Laboratory/Flickr)

Engineers grow graphene on silver

Growing graphene on a single-crystal silver substrate could lead to better optical devices and could allow graphene to interface with other 2D materials.

“Silver is a widely used material to enhance optical properties,” says study co-author Mark Hersam, professor of materials science and engineering at Northwestern University.

“More recently, graphene has emerged as a promising platform for optical technologies. With our recent development of a method for growing graphene on silver, we can now exploit the best attributes of both graphene and silver at the same time.”

While graphene is conventionally grown on a metal surface by catalytically decomposing hydrocarbons at elevated temperatures, this method is ineffective for silver substrates because the substrates are chemically inert and have a relatively low melting point.

Using a graphite carbon source, the researchers were able to grow graphene by depositing atomic carbon, rather than a carbon-based molecular precursor, onto the substrate. The growth circumvented the need for a chemically active surface and allowed the researchers to realize graphene growth at lower temperatures.

‘Pristine’ graphene

“Graphene growth and transfer to a variety of substrates has allowed graphene to transform countless scientific fields,” says Brian Kiraly, a Northwestern graduate student in materials science and engineering who worked on the research with Hersam and Nathan Guisinger, a staff scientist at Argonne National Laboratory.

“However, conventional techniques lead to contamination issues and are not compatible with the ultra-clean vacuum environments required for the growth of the latest 2D materials,” he says. “By growing graphene directly on silver under vacuum, we provide an atomically pristine surface for advanced graphene-based technologies.”

The researchers also found the graphene they grew was electronically decoupled from the underlying silver substrate, allowing the intrinsic properties of graphene to be studied and exploited directly on the growth substrate; this characteristic has not been previously observed with graphene grown on other metals.

The researchers observed unique wave-like electron scattering at the graphene’s edges that had previously been observed only on insulating substrates.

2D opportunities

Recent work on integrating graphene with other 2D materials—a step vital for the development of graphene-based circuits and other technologies—has yielded both enhancements of graphene’s properties and the emergence of new properties distinct from isolated graphene.

The development of graphene on silver enables researchers to probe graphene interfaces with a new 2D material, silicene, which is almost exclusively grown on silver.

The Department of Energy and the National Science Foundation funded the research. The study appears in Nature Communications.

Source: Northwestern University