Growing graphene at room temperature
By By Katherine Bourzac | 03 Feb 2012
A new method makes it possible to directly grow large-area graphene films on plastic, glass, and other substrates at room temperature. Researchers at the Ulsan National Institute of Science and Technology in Korea hope it will provide a simpler way to manufacture graphene electronics with fewer steps and under less stringent conditions.
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| Growing graphene: Carbon atoms diffuse through the grain boundaries in a layer of nickel. When they reach the substrate, they form a polycrystalline film of graphene. Image credit: Soon-Yong Kwon. |
Large graphene films are typically grown on metal at high temperatures, around 1,000 degrees Celsius, then transferred to another surface, for example a sheet of plastic for making a flexible transparent electrode for a touchscreen display.
Researchers led by Soon-Yong Kwon have developed a method called diffusion-assisted synthesis that enables them to grow graphene directly on plastic and glass, eliminating the need for a transfer step. The process, which uses a layer of nickel to facilitate the growth of graphene on an underlying surface, is described in the journal Nature Communications.
They started by evaporating a nickel film onto a substrate at room temperature. Next, they coated the film with a paste of graphite powder in ethanol, then pressed the paste onto the nickel. Nickel has a relatively high solubility for carbon. Once they're in contact, carbon begins to diffuse into the nickel along the grain boundaries of the film.
As the carbon atoms reach the substrate they create a thin film of graphene. The pressure encourages the carbon to move through the nickel, as does some further processing.
The researchers placed the chip into a quartz tube filled with argon gas or air and heated it to temperatures ranging from 25 to 250 degrees Celsius. After one to ten minutes, they removed the chip and etched away the remaining carbon and nickel, leaving behind a film of graphene.
