Scaling Behavior of Anisotropic Organic Thin Films Grown in High Vacuum

Roughness scaling properties of sexithienyl thin films are investigated by scanning force microscopy as a function of the substrate deposition temperature. The correlation length of the surface fluctuations follows the behavior of the average domain size, increasing exponentially with temperature from submicron to micron scales. Self-affinity is exhibited on 3 orders of magnitude of the spatial frequencies when the morphology changes from grain aggregates to lamellae. The decay with temperature of the roughness scaling exponent \ensuremath{\alpha} from 1 to 0.7 suggests a transition from diffusion-limited growth to a strong adsorption regime.