Spinodal dewetting of thin polymer films

Dewetting of polystyrene films on a silicon substrate is investigated as a function of film thickness h. We observe the nucleation of holes in the early stage of dewetting for relatively thick films (h > 100 Angstrom), as observed previously, but the breakup of thinner films occurs through the growth of uniformly distributed surface undulations ("spinodal dewetting"). The average amplitude delta h of these undulations increases exponentially up to the film rupture point where delta h becomes comparable to h, as predicted by a capillary wave instability model.