Last year, Jannick Meyer at the Max Plank Institute for Solid State Research in Stuttgart and pals discovered that single sheets of graphene are gently rippled, like the rolling hills of New England. That’s a puzzle because graphene behaves like a perfect 2D crystal. So how do these ripples form and what role do they play in the crystal properties of the material?
One possibility is that thermal fluctuations cause the wrinkles, in other words, that graphene buckles as it heats up. But today, Rebecca Thompson-Flagg and buddies at the University of Texas at Austin present another idea.
They say that heat is an unlikely to be the cause because the stiffness of graphene ought to ensure that ripples of the observed size vibrate at a frequency of 10^11 Hz. However, Meyer’s observations only make sense if the ripples are static.
Instead, Thompson-Flagg suggests that the ripples are formed by the adsorption of OH molecules at random sites throughout the crystal. In other words, the graphene wrinkles when it’s damp.
They’ve simulated the shape of a damp graphene and the ripples exactly match those seen by Meyer.
That’s an interesting result but not quite a slam dunk. For that, we’ll need to see what graphene looks like and how it behaves when no OH is present.
Ref: arxiv.org/abs/0807.2938: Rippling of Graphene