Graphene structuration by self-assembly of high-χ block copolymers

Large-area graphene is not suitable for digital logic applications because its bandgap is zero. Graphene structuration into sub-10nm width nanoribbons (GNRs) can open up a bandgap (>0.4eV) for operational nanoelectronics devices such as field-effect transistors (FETs). However, fabricating circuits with sub-10nm aligned GNR arrays remains a technological challenge. Block copolymer (BCP) self-assembly is a highly promising nanolithography technique in terms of throughput, cost and high resolution patterning. We fabricated 8nm width (w) GNRs using cylinder forming BCP thin films of polystyrene-block-polydimethylsiloxane (PS-b-PDMS). The fabrication includes the direct spin-coating on graphene and a thermal treatment to trigger the self-assembly. By using an O2 plasma etching, a triple functionality is achieved: the PS matrix is removed, the PDMS block is oxidized and the PDMS pattern is transferred into graphene. The lithographic mask is finally removed out by wet etching and dedicated hydrogen plasma. AFM and Raman spectroscopy are used to demonstrate the formation of GNRs since w correspond to the width of the PDMS block of the BCP. The method presented could be generalise to fabricate other graphene nanostructures which could be employed to design FETs and photodetectors.