Edge profile of relief 2D domains at the free surface of smectic copolymer thin films

Ultrathin (≃1000 Å) ordered films of symmetric diblock copolymers deposited on a plane solid substrate exhibit relief domains at their free surface. Their height is equal to the period L of the lamellar stacking (L=310 Å). The thickness profile at the edge of the domains has been investigated using atomic force microscopy. Its shape, independent of the domain size, is close to the theoretical prediction for the free surface of a smectic liquid crystal above a single dislocation. However, its lateral extension appears to be larger than expected by a factor of 20; the effect of the polymer/air surface tension is qualitatively invoked.