| Block copolymer thin films have been demonstrated to serve as useful templates for the fabrication of nanopatterned arrays of metals, semiconductors, or dielectrics, potentially leading to improved performance in a wide array of applications, including (to name only a few) MOS decoupling capacitors, data storage devices, and separation membranes. Realization of the full potential of these materials in this arena, however, has been impeded by a lack of precise control over the ordering of the block copolymer nanodomains and a poor understanding of the effects of topological defects on that order. Herein is presented a combined top-down/bottom-up approach for creating highly ordered arrays of cylinder-forming diblock copolymers, with the cylinders lying in the film plane. The technique employed, graphoepitaxy, involves confining a monolayer of the cylinder domains within long channels, one cylinder repeat-spacing deep, that are etched into the substrate. By annealing the monolayer films above the copolymer order-disorder transition temperature and subsequently cooling slowly, the kinetic hindrances to achieving equilibrium structures are circumvented. The thermodynamic limitations on the perfection of translational and orientational ordering within these arrays, primarily due to thermal defect generation, are discussed and compared with theoretical predictions. The repulsion of topological defects in these arrays from the edges of the confining channels is measured, and it is found that this effect can be described mathematically by considering the forces arising from the lattice strain imposed by these defects. Additionally, a description is presented of the defect structures in films of cylinder-forming block copolymers where the cylinder axes are perpendicular to the film plane, and the polydispersity of copolymer domain sizes that results. These experimental results compare favorably with those from a self-consistent mean field theory simulation of a similar system. |
