Manipulating ripples could pave way for strain-based graphene electronics

Washington, July 27 (ANI): Scientists from the University of California Riverside (UCR) have manipulated ripples in graphene, which would enable the development of strain-based graphene electronics.

Graphene is nature's thinnest elastic material and displays exceptional mechanical and electronic properties.

Its one-atom thickness, planar geometry, high current-carrying capacity and thermal conductivity make it ideally suited for further miniaturizing electronics through ultra-small devices and components for semiconductor circuits and computers.

But one of graphene's intrinsic features is ripples, similar to those seen on plastic wrap tightly pulled over a clamped edge.

Induced by pre-existing strains in graphene, these ripples can strongly affect graphene's electronic properties, and not always favorably.

If the ripples can be controlled, however, they can be used to advantage in nanoscale devices and electronics, opening up a new arena in graphene engineering: strain-based devices.

UC Riverside's Chun Ning Lau and colleagues now report the first direct observation and controlled creation of one- and two-dimensional ripples in graphene sheets.

Using simple thermal manipulation, the researchers produced the ripples, and controlled their orientation, wavelength and amplitude.

"When the graphene sheets are stretched across a pair of parallel trenches, they spontaneously form nearly periodic ripples," Lau explained.

"When these sheets are heated up, they actually contract, so the ripples disappear. When they are cooled down to room temperature, the ripples re-appear, with ridges at right angle to the edges of the trenches," she added.

The unusual thermal contraction of graphene had been predicted theoretically, but Lau's lab is the first to demonstrate and quantify the phenomenon experimentally.

Because graphene is both an excellent conductor and the thinnest elastic membrane, the ripples could have profound implications for graphene-based electronics.

"This is because graphene's ability to conduct electricity is expected to vary with the local shape of the membrane," Lau said.

"For instance, the ripples may produce effective magnetic fields that can be used to steer and manipulate electrons in a nanoscale device without an external magnet," she added.

Lau's experimental system, which involved a stage inside a scanning electron microscope (SEM) with a built-in heater, thermometer and several electrical feed-throughs, enabled her to image graphene while it was being heated and explore the interplay between graphene's mechanical, thermal and electrical properties.

"Our result has important implications for controlling thermally induced stress in graphene electronics," Lau said.

"Our ability to control and manipulate the ripples in graphene sheets represents the first step towards strain-based graphene engineering," she added. (ANI)