Dewetting dynamics of thin polystyrene films from sputtered silicon and gold surfaces

Using atomic force microscopy (AFM) we study the dynamics of the dewetting process of polystyrene (PS) films from, (i) atomically smooth silicon (Si) wafers; (ii) sputtered (rough) Si surfaces; and (iii) sputtered (rough) gold (Au) surfaces. Deviations from the circular geometry of the developed dry patches are observed when sputtered surfaces are used as substrates and they are more pronounced for the Au surfaces. It is concluded that the dry patch shape is affected by both the roughness and the nature of the substrate. Kinetic measurements performed using Si surfaces as substrates show that the dewetting rate decreases with substrate roughness. The dewetting dynamics of unentangled PS from Au surfaces shows no deviation from kinetic laws, established for Si substrates. That is the radius of the dry patch scales linearly with time and the dewetting rate is proportional to the ratio of the surface energy over the viscosity of the polymer. PS dewets faster from Au than from a Si surface. A comparison of the dewetting rates of PS from the two surfaces (Si and Au) is found to be in relatively good agreement with respective contact angle measurements.