SUBMICRON PERIODIC STRUCTURES PRODUCED ON POLYMER SURFACES WITH POLARIZED EXCIMER LASER ULTRAVIOLET-RADIATION

In many applications, a controlled submicron-level roughening of surfaces is desired. For the first time, pure laser-induced periodic structures (without any ablation or any larger structure) of submicron size (spacing and amplitude of 0.2 mum) are developed on polymer surfaces (poly(ethylene terephthalate), poly(butylene terephthalate), polystyrene, polycarbonate, etc.) by irradiation with one thousand pulses of the polarized beam of an excimer laser (193 and 248 nm). Fluence is below the ablation threshold and must be chosen in a narrow window which depends on the polymer and the wavelength. The obtained relief is observed by SEM, TEM and characterized by ellipsometry. Structures are obtained also by irradiation of thin films (2000 angstrom) coated on silicon wafers. The mechanism of ripple formation involves a surface wave. Owing to the simplicity of this irradiation procedure large-scale surface treatments are possible. Surface properties like friction, adhesion, and so on, can be very much improved.