Controlling The Orientation Of Diblock Copolymer Microstructures Thomas P. Russell, Paul Mansky and Elbert Huang, University of Massachusetts, Amherst, MA; Craig J.Hawker, IBM Almaden Research Center, San Jose, CA; Sushil K. Satija, NIST, Gaithersburg, MD

In thin films, the orientation of the microstructure of diblock copolymers is controlled, dominantly, by the specific interactions of the segments of the blocks with the air and substrate interfaces. Precise control over these interactions has been achieved by end-anchoring a random copolymer to the substrate where the components of the block and random copolymers are identical. By adjusting the composition of the random copolymer, the interactions between the block copolymer and substrate can be balanced. On such a "neutral" substrate there is a preferential orientation of the copolymer microstructure normal to the plane of the substrate. Herein, results from small angle neutron scattering, which probes the in-plane correlations in the concentration, and neutron reflectivity, which probes concentration variations normal to the surface, are shown as a function of the composition of the random copolymer and as a function of the thickness of the block copolymer film. Periodic variations in the total integrated small angle neutron scattering reflect the variations in the orientation of the block copolymer microdomains and demonstrate the conditions under which surface neutrality is achieved. On a neutral surface, film thickness is shown to be the controlling factor.