title: Perpendicular Block Copolymer Microdomains in High Aspect Ratio Templates.
abstract: Perpendicular orientation of lamellar microdomains in a high interaction parameter block copolymer was obtained within high aspect ratio gratings functionalized with a preferential sidewall brush. The experiments used polystyrene-block-polydimethylsiloxane (PS-b-PDMS) with molecular weight 43 kg/mol within trenches made using interference lithography. The perpendicular alignment was obtained for both thermal and solvent annealing, using three different solvent vapors, for a range of film thicknesses and trench widths. A platinum (Pt) layer at the base of the trenches avoided the formation of a wetting layer, giving perpendicular orientation at the substrate surface. The results are interpreted using self-consistent field theory simulation and a Ginzburg-Landau analytic model to map the energies of lamellae of different orientations as a function of the grating aspect ratio and the surface energies of the sidewalls and top and bottom surfaces. The model results agree with the experiment and provide a set of guidelines for obtaining perpendicular microdomains within topographic features.
authors.affiliation: Department of Materials Science and Engineering, Massachusetts Institute of Technology , Cambridge Massachusetts 02139, United States.
authors.forename: Wubin
authors.initials: W
authors.lastname: Bai
authors.affiliation: Department of Materials Science and Engineering, Massachusetts Institute of Technology , Cambridge Massachusetts 02139, United States.
authors.forename: Karim
authors.initials: K
authors.lastname: Gadelrab
authors.affiliation: Department of Materials Science and Engineering, Massachusetts Institute of Technology , Cambridge Massachusetts 02139, United States.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Alexander-Katz
authors.affiliation: Department of Materials Science and Engineering, Massachusetts Institute of Technology , Cambridge Massachusetts 02139, United States.
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Ross
keywords: Block Copolymer; graphoepitaxy; perpendicular orientation; self-assembly; solvent annealing; thermal annealing