Vacuum-Driven Orientation of Nanostructured Diblock Copolymer Thin Films
Aum Sagar Panda, Yi-Chien Lee, Chen-Jung Hung, Kang-Ping Liu, Cheng-Yen Chang, Gkreti-Maria Manesi, Apostolos Avgeropoulos, Fan‐Gang Tseng, Fu‐Rong Chen, Rong‐Ming Ho
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-block-polydimethylsiloxane (PS-b-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-b-PDMS thin film can be formed under a high vacuum degree (∼10–4 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.