title: Molecular pathways for defect annihilation in directed self-assembly.
abstract: Over the last few years, the directed self-assembly of block copolymers by surface patterns has transitioned from academic curiosity to viable contender for commercial fabrication of next-generation nanocircuits by lithography. Recently, it has become apparent that kinetics, and not only thermodynamics, plays a key role for the ability of a polymeric material to self-assemble into a perfect, defect-free ordered state. Perfection, in this context, implies not more than one defect, with characteristic dimensions on the order of 5 nm, over a sample area as large as 100 cm(2). In this work, we identify the key pathways and the corresponding free energy barriers for eliminating defects, and we demonstrate that an extraordinarily large thermodynamic driving force is not necessarily sufficient for their removal. By adopting a concerted computational and experimental approach, we explain the molecular origins of these barriers and how they depend on material characteristics, and we propose strategies designed to overcome them. The validity of our conclusions for industrially relevant patterning processes is established by relying on instruments and assembly lines that are only available at state-of-the-art fabrication facilities, and, through this confluence of fundamental and applied research, we are able to discern the evolution of morphology at the smallest relevant length scales-a handful of nanometers-and present a view of defect annihilation in directed self-assembly at an unprecedented level of detail.
authors.affiliation: Materials Science Division, Argonne National Laboratory, Lemont, IL 60439; Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637; School of Polymer Science and Engineering, Chonnam National University, Gwangju 500757, Korea;
authors.forename: Su-Mi
authors.initials: SM
authors.lastname: Hur
authors.affiliation: School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853;
authors.forename: Vikram
authors.initials: V
authors.lastname: Thapar
authors.affiliation: Materials Science Division, Argonne National Laboratory, Lemont, IL 60439; Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637;
authors.forename: Abelardo
authors.initials: A
authors.lastname: Ramírez-Hernández
authors.affiliation: Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637;
authors.forename: Gurdaman
authors.initials: G
authors.lastname: Khaira
authors.affiliation: Materials Science Division, Argonne National Laboratory, Lemont, IL 60439;
authors.forename: Tamar
authors.initials: T
authors.lastname: Segal-Peretz
authors.affiliation: Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637;
authors.forename: Paulina A
authors.initials: PA
authors.lastname: Rincon-Delgadillo
authors.affiliation: Institut für Theoretische Physik, Georg-August-Universität, 37077 Göttingen, Germany; Department of Macromolecular Science, Fudan University, 200433 Shanghai, China.
authors.forename: Weihua
authors.initials: W
authors.lastname: Li
authors.affiliation: Institut für Theoretische Physik, Georg-August-Universität, 37077 Göttingen, Germany;
authors.forename: Marcus
authors.initials: M
authors.lastname: Müller
authors.affiliation: Materials Science Division, Argonne National Laboratory, Lemont, IL 60439; Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637;
authors.forename: Paul F
authors.initials: PF
authors.lastname: Nealey
authors.affiliation: Materials Science Division, Argonne National Laboratory, Lemont, IL 60439; Institute for Molecular Engineering, The University of Chicago, Chicago, IL 60637; depablo@uchicago.edu.
authors.forename: Juan J
authors.initials: JJ
authors.lastname: de Pablo
keywords: copolymer; defect; directed self-assembly; minimum free energy path; string method