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 An gstrom), as observed previously, but the breakup of thinner films occu rs through the growth of uniformly distributed surface undulations ('' spinodal dewetting''). The average amplitude delta h of these undulati ons increases exponentially up to the film rupture point where delta h becomes comparable to h, as predicted by a capillary wave instability model.