Vacuum-Driven Orientation of Nanostructured Diblock Copolymer Thin Films.

Panda, Aum Sagar; Lee, Yi-Chien; Hung, Chen-Jung; Liu, Kang-Ping; Chang, Cheng-Yen; Manesi, Gkreti-Maria; Avgeropoulos, Apostolos; Tseng, Fan-Gang et al. · ACS Nano · 2022

basic_science · Level V

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Abstract

This work aims to demonstrate a facile method for the controlled orientation of nanostructures of block copolymer (BCP) thin films. A simple diblock copolymer system, polystyrene-<i>block</i>-polydimethylsiloxane (PS-<i>b</i>-PDMS), is chosen to demonstrate vacuum-driven orientation for solving the notorious low-surface-energy problem of silicon-based BCP nanopatterning. By taking advantage of the pressure dependence of the surface tension of polymeric materials, a neutral air surface for the PS-<i>b</i>-PDMS thin film can be formed under a high vacuum degree (∼10<sup>-4</sup> Pa), allowing the formation of the film-spanning perpendicular cylinders and lamellae upon thermal annealing. In contrast to perpendicular lamellae, a long-range lateral order for forming perpendicular cylinders can be efficiently achieved through the self-alignment mechanism for induced ordering from the top and bottom of the free-standing thin film.