University of Illinois at Urbana-Champaign engineers have developed what they say is a one-step method to pattern graphene using a stencil mask and oxygen plasma reactive-ion etching.

The sequence to create polymer-free graphene patterning. Image Credit University of Illinois College of EngineeringWith their method they are able to deliver a polymer-free direct transfer to almost any flexible substrate. Although there have been strides in developing graphene films that are large and uniform with CVD (chemical vapor deposition) with a variety of precursors and catalyst substrates, the researchers' method eliminates the need for the post-synthesis processing that creates interconnects, channels for transistors, or terminals, all of which have stalled the use of graphene in a wider range of applications.

The team’s approach is a scalable graphene patterning technique that is performed using a stencil mask fabricated with a laser cutter. Using the same shadow mask technique that is used for contact metal deposition, they are able to create graphene patterns directly on flexible substrates without the need for organic solvents or polymeric transfer layers. They say this results in a contamination-free pattern.

Not only are stencil masks said to be easily and rapidly manufactured for repeatable rapid prototyping, they also are reusable, which allows for a cost-effective pattern replication system. The CAD designed stencil mask is cut with a laser cutter. The mask is then aligned on the as-grown CVD graphene on copper foil, following by the exposed graphene region being removed by oxygen plasma. The patterned graphene then can be laminated on a flexible substrate, then the copper foil is etched.