Development of Strategies to Improvement Ordering and Perpendicular Alignment of Cylinder Phase Block Copolymers Used as
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1032-I14-38
Development of Strategies to Improvement Ordering and Perpendicular Alignment of Cylinder Phase Block Copolymers Used as Templates for Bit Patterned Media Seth Garrett1, Vincent Franco1, Timothy Snowden1, Chris Redden1,2, Vishal Warke1,2, and Martin Gerard Bakker1,2 1 Chemistry, The University of Alabama, Box 870336, Tuscaloosa, AL, 35487-0336 2 Center for Materials for Information Technologies, The University of Alabama, Tuscaloosa, AL, 35487-0209 ABSTRACT The development of patterned media for high density information storage requires the development of methods for cheaply creating patterns in the 20-40 nm range. Cylinderical phase block copolymers self-assemble on this length scale to give the desired patterns. However, use on noble metal capped magnetic phases of such cylinder forming phases needs a thin orienting layer to align the cylinders perpendicular to the substrate surface. Random copolymers of similar composition to the block copolymer provide an appropriate orienting layer. By attachment of a thiol group to the random co-polymer, the random copolymer will be covalently bound to a platinum or gold surface allowing the formation of a suitably thin orienting layer. Synthesis of such thiol-functionalized polystyrene-polymethylmethacrylate random co-polymers is reported. The synthesis uses a novel two-step route starting with commercially available polystyrene-polymethylmethacrylate random copolymer. INTRODUCTION There is considerable interest in the development of bit patterned media as a potential pathway to higher information storage density. Concurrently, there is also interest is establishing the viability of graded media to decrease the switching field of perpendicular media. Proof of concept of such media requires magnetically isolated individual graded nanopillars or other nanostructures. The size distribution of such nanopillars must be relatively narrow, and the nanopillars must be fabricated over areas sufficiently large to enable study of the switching properties by a variety of methods. The maximum column diameter for which a nanopillar is expected to switch as a single domain, depends upon the hardness of the media used, but estimates for L10 iron/platinum alloys range from 4 nm up to approximately 15-20 nm. The use of block co-polymer nanolithography as a method of generating the desired patterns is an approach that has been receiving considerable attention[1-3]. We and others have been focusing on the use of cylindrical phase block co-polymers, i.e. those in which the minority domain selforganizes into hexagonally ordered arrays of cylinders within a continuous phase of the majority
domain. For such materials to be used as pattern generators for perpendicular bit patterned media requires that the cylinders orient perpendicular to the substrate surface. Unfortunately, the most common orientation for such block co-polymer phases is parallel to the substrate surface. Among a number of methods of overcoming this orienting tendency is to use an orienting layer of random co-polymer[
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