title: Sequential Nanopatterned Block Copolymer Self-Assembly on Surfaces.
abstract: Bottom-up self-assembly of high-density block-copolymer nanopatterns is of significant interest for a range of technologies, including memory storage and low-cost lithography for on-chip applications. The intrinsic or native spacing of a given block copolymer is dependent upon its size (N, degree of polymerization), composition, and the conditions of self-assembly. Polystyrene-block-polydimethylsiloxane (PS-b-PDMS) block copolymers, which are well-established for the production of strongly segregated single-layer hexagonal nanopatterns of silica dots, can be layered sequentially to produce density-doubled and -tripled nanopatterns. The center-to-center spacing and diameter of the resulting silica dots are critical with respect to the resulting double- and triple-layer assemblies because dot overlap reduces the quality of the resulting pattern. The addition of polystyrene (PS) homopolymer to PS-b-PDMS reduces the size of the resulting silica dots but leads to increased disorder at higher concentrations. The quality of these density-multiplied patterns can be calculated and predicted using parameters easily derived from SEM micrographs of corresponding single and multilayer patterns; simple geometric considerations underlie the degree of overlap of dots and layer-to-layer registration, two important factors for regular ordered patterns, and clearly defined dot borders. Because the higher-molecular-weight block copolymers tend to yield more regular patterns than smaller block copolymers, as defined by order and dot circularity, this sequential patterning approach may provide a route toward harnessing these materials, thus surpassing their native feature density.
authors.affiliation: Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2, Canada.|National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, AB T6G 2M9, Canada.
authors.forename: Cong
authors.initials: C
authors.lastname: Jin
authors.affiliation: Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2, Canada.|National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, AB T6G 2M9, Canada.
authors.forename: Brian C
authors.initials: BC
authors.lastname: Olsen
authors.affiliation: National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, AB T6G 2M9, Canada.|Department of Electrical and Computer Engineering, University of Alberta , Edmonton, Alberta T6G 2G8, Canada.
authors.forename: Nathanael L Y
authors.initials: NL
authors.lastname: Wu
authors.affiliation: Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2, Canada.|National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, AB T6G 2M9, Canada.
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Luber
authors.affiliation: Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2, Canada.|National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, AB T6G 2M9, Canada.
authors.forename: Jillian M
authors.initials: JM
authors.lastname: Buriak