Nano Lett.http://doi.org/hp4 (2012)

Finding a facile route for the growth of large-area graphene sheets seems to be the most important challenge before this material can be used in commercial electronic devices. But what should not be underestimated is the necessity of patterning these large sheets in a scalable way. TaeYoung Kim and colleagues demonstrated a patterning technique based on the so-called evaporation-induced self-assembly method. A single layer of graphene was laid on a substrate and placed in a poly(methyl methacrylate) (PMMA) solution. A cylinder was then rolled on the surface while the PMMA evaporated. During the rolling, the contact line between the cylinder, PMMA and graphene alternated between pinning and capillarity, effectively leaving equidistant stripes of non-evaporated PMMA, which protected the underlying graphene. Finally, simple plasma etching of the unprotected graphene and removal of the left-over PMMA left equidistant stripes of graphene behind. The team fabricated field-effect transistors using the graphene stripes and observed characteristics comparable with those of commercial devices. The approach is possibly the simplest non-lithographic technique proposed so far, and could lead to easily scalable patterning of large-area graphene.