In the decade since graphene was first synthesized, researchers have been preoccupied about overcoming the fact that the material lacks an inherent band gap, which limits its potential in digital logic applications.
While researchers have been reasonably successful at engineering a band gap into graphene in the lab, there is another looming show stopper: How robust is the material when facing real-world environments?
Now researchers from AMO GmbH in Germany and Spain-based Graphenea SE have demonstrated a sophisticated encapsulation technique that they claim is easily reproducible and should allow graphene devices in normal atmosphere to last for several months.
What typically is the death knell for graphene is partly the result of the environment and also the impurities in the production process. As far as the environment is concerned, moisture or oxygen causes the problem. From the production side, the residue from lithography processes adhere to the graphene and change its doping level unintentionally.
The doping levels change the properties that make graphene so attractive in the first place—such as its conductivity and its optical properties. As a result, all the great capabilities that graphene is heralded for are largely lost.
In research published in the Royal Society of Chemistry journal Nanoscale, the team first identified this problem and then devised their encapsulation technique to overcome it.
The researchers applied their encapsulation technique to field-effect devices using aluminum oxide, an encapsulation material that is often used in making organic light-emitting diodes (OLEDs).
To a technique known in the business as passivation, in which a light coat of a protective oxide is used to create a shell against corrosion, the researchers added a bit of a wrinkle. They were able to grow the oxide layer using an oxidized layer of aluminum that served as as the seed for further growth. This new twist to the passivation technique managed to stabilize the device characteristics over several months when stored and measured in ambient atmosphere.
The researchers believe that this development serves as a major step torward getting graphene devices into real-world applications.
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.