Real-time monitoring of the surface relief formation on azo-polymer films upon near-field excitation

We use near-field optical microscopy to investigate the early state formation of photo-induced topographical structures on the free surface of azobenzene-containing polymers. The near-field technique is employed to monitor in real time the mass migration during the embossing of the surface of 50/50 copolymer films of polymethacrylate and polymethacrylate containing 3-methyl-4'-pentyloxy-azobenzene units. The dynamic of surface relief formation induced by light have been investigated as a function of the sample temperature. Furthermore, a formula derived from Navier-Stokes equations for classical laminar flow has been used to fit the mass displacement data during the embossing process. Excellent agreements between the experimental data and the fitting formula have been found for all the temperature considered.