A graduate student at Cornell University, US, has taken a simple way of creating the single atom thick sheets of carbon known as graphene, and looked at how they behave as electromechanical resonators.
The electronic properties of graphenes have attracted much interest, as they are considered suitable for constructing ballistic transistors and other novel electronic components. But their mechanical properties are just as remarkable, according to Scott Bunch, who works in Paul McEuan’s research group at Cornell.
Bunch etched tiny trenches into a wafer of silicon dioxide, and, just as if he were drawing on the wafer with a pencil, spread a thin layer of graphite over the surface. With atomic force microscopy and Raman spectroscopy, Bunch and his colleagues then found trenches spanned by single sheets of graphene. The graphite drawing procedure was invented by Andre Geim at the University of Manchester, UK.
To study the graphene sheets’ mechanical properties, the researchers vibrated them with an electric field, and measured the vibrations with a laser. The results of the experiment show that graphene is one of the stiffest materials around.
“We created a single suspended layer of atoms,” says Bunch. “These sheets of graphene can be used as a strong thin membrane separating two disparate environments such as two different gases or liquids, or even a liquid and gas. You can also use these membranes to detect small pressure differences, or poke a hole in it and study diffusion of atoms and molecules across it.” Mass sensing is another obvious application.
Dan Rugar of IBM Research concurs: “The work by Bunch et al. is remarkable and pioneering. Many researchers, including myself, will be following this type of work closely to see if the use of atomically thin mechanical structures might lead to major advances in the capabilities of nano-mechanical sensors.”
But before practical applications of graphene sheets can be realised, a way must be found to mass-produce the material. The McEuan Group is currently exploring ways to improve the graphene fabrication process.
Bunch et al. – Electromechanical Resonators from Graphene Sheets, Science 315, 490 (2007) (subscription required for full article)
Graphene (from Wikipedia)
Schematic of a suspended graphene resonator. The graphene is in contact with a gold electrode which can be used to electrostatically actuate the resonator. A red laser is used to detect the motion of the resonator by interferometry. Image courtesy of Arend van der Zande.
Article first published in Nanomaterials News.