Kinetics of growth of islands and holes on the free surface of thin diblock copolymer films

When prepared on a silicon wafer and annealed above the glass transition temperature $T_{\rm g}$, symmetric, diblock copolyumers of poly(styrene-b-butylmethacrylate), P(S-b-BMA), exhibit a multilayer structure parallel to the substrate and islands (or holes) are formed on the free surface of the films. In situ interference microscopy has been used to follow the kinetics of growth of these islands or holes. It is shown that the kinetics of growth depends on the initial density of islands (or holes) : at 140 $^\circ{\rm C}$, for intermediate annealing times, there is no time-evolution of the free surface for dilute systems while for more concentrated ones, the size distribution function of islands or holes verifies a scaling law versus time. For longer annealing times at 170 $^\circ{\rm C}$, the ultimate behavior of the copolymer film is to eliminate islands or holes by allowing the permeation of the copolymer molecules into the inner layers of the film