Solvent-Induced Ordering in Thin Films of Diblock Copolymer/Homopolymer Mixtures

Using solvent evaporation, long-range lateral order over many square microns has been achieved in mixtures of homopolymers with asymmetric diblock copolymers having a cylindrical microdomain morphology. Arrays of cylindrical microdomains ~20 nm in diameter with average separation distances of ~40 nm with near-perfect hexagonal packing in films several tenths of a micron in thickness were found. These results point to a simple route to produce nanoscopic templates for the generation of addressable media. (S. H. Kim, M. J. Misner, M. Kimura, T. Xu and T. P. Russell, "Highly Oriented and Ordered Arrays from Block Copolymers Via Solvent Evaporation," Adv. Mats. 16(3), 226-231 (2004).).

Flash Memory

Block copolymers, two distinct polymers joined at one end, self-assemble into well-defined, well-ordered arrays of nanoscopic domains where the type of domain (spheres, cylinders or sheets) depends on the relative volume fraction of the components. For spincoated films, by balancing the interactions of each block with the substrate, by attaching random copolymers to the underlying substrate to mediate interfacial interactions. the With cylindrical domains, by removing one of the block, e.g. by exposure to ultraviolet radiation, a densely packed array of nanopores (1.2 Terapores/in2) is produced in a crosslinked thin polymer films that serves as templates where, as shown in the image, using established ion beam etching techniques pattern transfer. This simple process is being used by IBM to produce arrays of floating gates in flash memory. (IBM Press Release (2004)).