Anisotropic coarsening of two-dimensional surface domains in copolymer thin films

We have investigated by scanning force microscopy the growth of surface rel ief structures on thin diblock copolymer films for a infinity x infinity ge ometry (homogeneous substrate) and a L x infinity geometry (heterogeneous s ubstrate). We characterize the growth by a length scale obtained from the c orrelation function describing the fluctuations. Two-dimensional viscous fl ow within a continuous layer dominates the process. On the homogeneous subs trate we find a power law growth with an exponent of alpha = 2/3, while the growth on the stripe pattern in a direction parallel to the stripes is cha racterized by an exponent that is much lower.