Nanoscaling of microdomain spacings in thin films of cylinder-forming block copolymers

We present first quantitative measurements of the characteristic lateral dimensions in thin films of cylinder-forming block copolymers. Using a metrological scanning force microscope and tailor-made image analysis, we map out lateral distances with subnanometer accuracy. Microdomain spacings change in a systematic way as a function of the film thickness and as a function the lateral cylinder bending. We show that in very thin films the unit cell is stretched perpendicular to the plane of the film resulting in lateral distances smaller than those in bulk. The changes are distinct, although small, and can be rationalized within the framework of the strong segregation theory of block copolymers.