Microdomain patterns from directional eutectic solidification and epitaxy

Abstract

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 electrophoresis¹, and island structures used for high-density magnetic recording devices². Block copolymer patterns can also be used for lithography on length scales below 30 nanometres (refs 3,4,5). But for such polymers to prove useful for thin-film technologies, chemically patterned surfaces need to be made substantially defect-free over large areas, and with tailored domain orientation and periodicity. So far, control over domain orientation has been achieved by several routes^6,7,8,9, using electric fields, temperature gradients, patterned substrates and neutral confining surfaces. Here we describe an extremely fast process that leads the formation of two-dimensional periodic thin films having large area and uniform thickness, and which possess vertically aligned cylindrical domains each containing precisely one crystalline lamella. The process involves rapid solidification of a semicrystalline block copolymer from a crystallizable solvent between glass substrates using directional solidification and epitaxy. The film is both chemically and structurally periodic, thereby providing new opportunities for more selective and versatile nanopatterned surfaces.