Combinatorial Study of Surface Pattern Formation in Thin Block Copolymer Films

Abstract

Surface pattern formation in diblock copolymer films is investigated as a function of film thickness $h$ and molecular mass $M$. Smooth films are observed for certain $h$ ranges centered about multiples of the lamellar thickness $L_0$, and we attribute this effect to an increase in the surface chain density with $h$ in the outer brushlike copolymer layer. We also observe apparently stable labyrinthine surface patterns for other $h$ ranges, and the average size of these patterns is found to scale as $\lambda \sim L_0^{-2.5\mathrm{}}$. Hole and island patterns occur for $h$ ranges between those of the labyrinthine patterns and the smooth regions, and their size similarly decreases with $L_0$ and $M$.