Defect Annihilation Pathways in Directed Assembly of Lamellar Block Copolymer Thin Films

Journal Article · 17 September 2018 · ACS Nano

DOI: https://doi.org/10.1021/acsnano.8b04202 · OSTI ID:1487452

Hur, Su -Mi  ^[1]; Thapar, Vikram ^[2]; Ramírez-Hernández, Abelardo  ^[3]; Nealey, Paul F.  ^[4]; de Pablo, Juan J.  ^[4]

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1. Chonnam National Univ., Gwangju (Korea)
2. Chonnam National Univ., Gwangju (Korea); The Univ. of Chicago, Chicago, IL (United States)
3. Argonne National Lab. (ANL), Argonne, IL (United States); The Univ. of Texas at San Antonio, San Antonio, TX (United States)
4. The Univ. of Chicago, Chicago, IL (United States); Argonne National Lab. (ANL), Argonne, IL (United States)

Defects in highly ordered self-assembled block copolymers represent an important roadblock toward the adoption of these materials in a wide range of applications. This work examines the pathways for annihilation of defects in symmetric diblock copolymers in the context of directed assembly using patterned substrates. Past theoretical and computational studies of such systems have predicted minimum free energy pathways that are characteristic of an activated process. However, they have been limited to adjacent dislocations with opposite Burgers vectors. By relying on a combination of advanced sampling techniques and particle-based simulations, this work considers the long-range interaction between dislocation pairs, both on homogeneous and nanopatterned substrates. As illustrated here, these interactions are central to understanding the defect structures that are most commonly found in applications and in experimental studies of directed self-assembly. More specifically, it is shown that, for dislocation dipoles separated by several lamellae, multiple consecutive free energy barriers lead to effective kinetic barriers that are an order of magnitude larger than those originally reported in the literature for tightly bound dislocation pairs. Furthermore, it is also shown that annihilation pathways depend strongly on both the separation between dislocations and their relative position with respect to the substrate guiding stripes used to direct the assembly.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1487452
• Journal Information: ACS Nano, Journal Name: ACS Nano Journal Issue: 10 Vol. 12; ISSN 1936-0851
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English