  The surface morphologies of poly(chloro-p-xylylene) films were measured using
atomic force microscopy and analyzed within the frame work of the dynamic
scaling theory. The evolution of polymer films grown with fixed experimental
parameters showed drastic changes of dynamic roughening behavior, which involve
unusually high growth exponent (beta = 0.65+-0.03) in the initial growth
regime, followed by a regime characterized by beta~0, and finally a crossover
to beta = 0.18+-0.02 in a steady growth regime. Detailed scaling analysis of
the surface fluctuation in Fourier space in terms of power spectral density
revealed a gradual crossover in the global roughness exponent, analogous to a
phase transition between two equilibrium states, from a morphology defined by
alpha=1.36+-0.13 to the other morphology characterized by alpha=0.93+-0.04 as
the film thickness increases. Our experimental results which significant
deviate from the well established descriptions of film growth clearly exhibit
that the dynamic roughening of polymer film is deeply affected by strong
molecular interactions and relaxations of polymer chains.
