Authors: Geon Gug Yang, Chan Woo Lee, Jin Goo Kim, In Ho Kim, Kyu Hyo Han, Jang Hwan Kim, Hee Jae Choi, Dong Won You, Hyeong Min Jin, Sang Ouk Kim
Published: 2025-02-13
Source: Full article
AbstractVertically aligned nanopatterns of high Flory‐Huggins parameter (χ) block copolymers (BCPs) are desirable for effective pattern transfer of sub‐10‐nm scale self‐assembled morphologies. To this end, BCP thin film is required to interface with neutralized surface energy at both substrate and free‐surface, among which neutralization of top free‐surface is generally more difficult without well‐defined substrate geometry. Therefore, various types of top‐coat layers have been developed, many of which, however, require complex synthetic processes or specifically designed equipment. In this work, a surface energy‐tailored reduced graphene oxide (rGO) top‐coat layer capable of achieving neutral surface conditions for high‐χ BCPs is presented. The surface energy of rGO can be precisely controlled by straightforward thermal reduction to attain neutral surface energy conditions for high‐χ BCPs. The versatile processability of rGO introduces intriguing features in top‐coat layers, facilitating area‐selective nanopatterning or multilayer stacked independently self‐assembled nanopatterning. Additionally, a large area rGO top‐coat layer is successfully implemented on various types of substrate materials, over which directed self‐assembly (DSA) of high‐χ BCPs can be attained for highly aligned vertical nanopatterns of sub‐10‐nm scale lamellar morphologies.