Ultraflat Graphene

Graphene, a single atomic layer of carbon connected by sp2 hybridized bonds, has attracted intense scientific interest since its recent discovery. Much of the research on graphene has been directed towards exploration of its novel electronic properties, but the structural aspects of this model two-dimensional system are also of great interest and importance.

Detailed electron-diffraction studies of free-standing graphene monolayers indicate the presence of an intrinsic rippling, with 1-nm-high corrugations normal to the surface appearing over a characteristic lateral scale of 10–25 nm. It has been argued that these corrugations are necessary to stabilize the suspended graphene sheets against thermal instabilities present in ideal two-dimensional systems.

Researchers from University of Columbia have recented published a report in Nature,where they report the fabrication and characterization of high-quality ultraflat graphene monolayers by making use of a mica support that provides atomically flat terraces over large areas. Using high-resolution, non-contact mode atomic force microscopy (AFM) to characterize the morphology, They have found that graphene on mica approaches the limit of atomic flatness. The availability of such a flat substance provides insight into questions of thermodynamic stability for this model two-dimensional system and also a reference material with which to determine the role of ripples in the panoply of observed and predicted phenomena.

Their measurements demonstrate unambiguously that intrinsic ripples in graphene, if they do exist, can be strongly suppressed by interfacial van der Waals interactions when this material is supported on an appropriate atomically flat substrate.