Block Copolymer Thin Films

Several schemes for developing nanotechnologies hinge upon the ability to create patterns of discrete, chemically distinct domains on the scale of nanometers. Given this paradigm for device production, the possible utility of block copolymers, which spontaneously order into nanoscale domains of uniform size and spacing, as nanolithographic templates has been amply noted. Our work has investigated the thermodynamic effects of spatial confinement on block copolymer assembly. In confined geometries, the nanodomain morphology of lamellae-forming block copolymers is predicted and experimentally found to be a strong function of confinement width, with lamellae contracting or expanding relative to their bulk dimensions in the direction of confinement.

We have employed AFM and TEM experiments in conjunction with theory to create equilibrium morphology diagrams for ultrathin, compositionally symmetric block copolymer films as a function of thickness, molecular weight, and the relevant interfacial energies. Similar confinement effects are seen when sphere-forming block copolymer films are confined in grooves 100-500 nm wide. The high degree of order imposed by the groove walls results in perfect ordering of domains, potentially useful for the fabrication of spatially addressable nanodot arrays for high density magnetic storage or DNA microarrays.

Collaborators:
Prof. Caroline A. Ross (MIT)
Prof. Francesco Stellacci (MIT)

Sponsorship:
MIT Center for Materials Science and Engineering (NSF MRSEC)