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We present a process for nanoscale fabrication of ordered ultra-thin films of conjugated organic molecules. Spatially structured ultra-thin films of sexithiophene (T6) have been obtained on patterned silicon substrates with high geometrical order. By home-built patterning system, we have fabricated patterned silicon substrates using a new parallel oxidation technique. In a relative humidity (RH) controlled environment (from 50% to 80%), a stamp holder is moved by a micrometric screw towards the substrate. The stamp was a metallized polymeric support that replicates compact disk lines. If bias voltage is applied between the substrate and the stamp when they are in contact, the silicon surface is decorated by parallel silicon oxide stripes (pitch = 650nm, width = 100 nm, and height ranging from 2 to 8 nm). On the top of this pattern, ultra-thin films of T6 are successively deposited under high-vacuum conditions. To maximize the effect of patterning on the growth, the amount of evaporated material is kept low enough to cover only 50-60% of the surface. The organic ultra-thin films so deposited mimic the features of the underlying motives. This effect is due to interplay between kinetic parameters of the growth and preferential interactions with the patterned surface. Surface morphology has been characterized by tapping mode AFM in air and studied by Minkowski functionals. Furthermore, picosecond time-resolved fluorescence techniques have been applied to the study of the patterned samples, to investigate an induced structural order on micrometric scale. |