Microdomain patterns from directional eutectic solidification and epitaxy

Creating a regular surface pattern on the nanometre scale is important for many technological applications, such as the periodic arrays constructed by optical microlithography that are used as separation media in electrophore sis(1), and island structures used for high-density magnetic recording devi ces(2). Block copolymer patterns can also be used for lithography on length scales below 30 nanometres (refs 3-5). But for such polymers to prove usef ul for thin-film technologies, chemically patterned surfaces need to be mad e substantially defect-free over large areas, and with tailored domain orie ntation and periodicity. So far, control over domain orientation has been a chieved by several routes(6-9), using electric fields, temperature gradient s, patterned substrates and neutral confining surfaces. Here we describe an extremely fast process that leads the formation of two-dimensional periodi c thin films having large area and uniform thickness, and which possess ver tically aligned cylindrical domains each containing precisely one crystalli ne lamella. The process involves rapid solidification of a semicrystalline block copolymer from a crystallizable solvent between glass substrates usin g directional solidification and epitaxy. The film is both chemically and s tructurally periodic, thereby providing new opportunities for more selectiv e and versatile nanopatterned surfaces.