Dynamics of the leveling process of nanoindentation induced defects on thin polystyrene films

Using Atomic Force Microscopy (AFM) we study the effect of nanoindentation induced defects on 50 and 120 nm thick unentangled polystyrene (PS) films, spin cast on silicon (Si) substrates. Indents with residual depths of penetration less than the film thickness level upon heating above the glass transition temperature (T_g) of bulk PS. The resulting leveling process is discussed in terms of a diffusion process driven by the curvature gradient. Calculated diffusivity values are close to the self-diffusivity of bulk PS.