Roughness-induced fluid interface fluctuations due to polar and apolar interactions

We investigate substrate roughness-induced fluctuations on liquid films in the presence of polar (exponential) and apolar (van der Waals) interactions in the complete wetting regime. The liquid/vapor interface roughness ampli tude sigma(w) increases rapidly with film thickness epsilon above a critica l thickness epsilon(c) for which the film is stable (or it does not rupture due to presence of polar interactions), and it reaches a maximum at a thic kness epsilon(m) slightly larger than epsilon(c) if polar and apolar compon ents are of comparable strength and for small polar potential ranges. As th e strength of the polar interaction decreases with respect to the apolar; b ehavior characteristic of that of apolar interactions within the Derjaguin approximation is recovered for moderate film thicknesses (epsilon > epsilon (m)); sigma(w)proportional to zeta(-2) with zeta the healing length. [S1063 -651X(99)11701-X].