Investigation of the mesoscopic contact mechanics of sexithienyl thin films

We demonstrate that the mechanical properties of self-affine fractal thin films can be investigated on mesoscopic scale with an atomic force microscope. Sexithienyl films have been studied by acquiring load-displacement curves with flat micrometric tips. It is shown that the mechanical response of these samples strongly depends on their surface morphology, the contact stiffness varying an order of magnitude upon small but significative changes of fractal parameters. This indicates a general route to tailor films properties at the stage of their deposition and growth.