Graphene is an ultra-thin sheet of carbon atoms that is attractive for a wide range of applications because of its remarkable electronic, structural and thermal properties. Its successful integration into future high-performance electronic device architectures requires the fabrication of patterned graphene sheets in a well-controlled, cost-effective way. Gui Yu and colleagues at the Chinese Academy of Sciences in Beijing have now demonstrated how graphene oxide sheets obtained using a low-cost, up-scalable solution method can be patterned using a simple, yet versatile approach based on a common surface-treatment technique and spin-coating.1

Fig. 1: Graphene oxide electrodes for nanoelectronic applications can be created by patterning the wettability of a surface to allow graphene oxide from solution to stick to the desired areas.

The researchers’ technique is based on patterning the wettability of a substrate through ultraviolet ozone treatment using a patterned shadow mask. By making a ‘wettable’ pattern on the surface, Yu and his co-workers were able to get graphene oxide in solution to stick to the patterned areas (see image). In the ‘dewetted’ areas, the graphene oxide solution could be easily cleared by traditional spin-coating, leaving the desired pattern of graphene oxide behind. These graphene oxide-bearing areas were then made highly conductive by thermal reduction.

According to Yu, the method is not only very simple, but also very effective. “With our patterning technique, both the position and the shape of the reduced graphene oxide can be strictly controlled by the mask.” Yu further notes that this procedure is applicable to many kinds of metals, including gold, silver, copper and aluminum. Using previous approaches, the deposition of graphene oxide on metal surfaces has been difficult because of the lack of specific forces to bind the graphene oxide to the surface, such as electrostatic interactions.

Turning to the fabrication of low-resistance electrodes in nanoelectronics devices, the researchers showed in a series of proof-of-principle experiments that the graphene oxide deposited on metal by their method forms excellent source and drain electrodes suitable for use in high-performance organic field-effect transistors. As Yu explains, this is because reduced graphene oxide greatly lowers the contact resistance and facilitates charge injection into organic semiconductors. The researchers further demonstrated the versatility of their preparation method by fabricating flexible transparent conducting graphene films and sensors on polyethylene terephthalate — a widely applied substrate for flexible electronics.