Production of Periodic Nano-structure by Laser on Polyimide Surface

A 200nm space-and-width linear periodic structures in a large area have been produced on polyimide films using a polarized beam of Nd:YAG 4th harmonic laser irradiation.The linear direction is parallel to the polarization direction. The periodicity of lines depends mostly on the laser wavelength and the angle of incidence, it can be indicated with Λ=λ/(n-sinϕ), while the depth of lines depends mostly on fluences of light. With the increasing of the fluences, the depth of the lines increases. The best periodic lines could be obtained in the condition of wavelength of 266nm, angle of incidence of 20° and fluences of 30mJ/cm². LIPS was formed by repeated heating and cooling the polymer surface following the intensity distribution caused by interference of reflected surface electromagnetic wave and incoming polarized laser beam. Consequently, after certain amount of continuous pulse, periodic ripple structures were formed and then the incident waves were waveguided by the corrugated structures initially formed to deveop line structures . We also found that a few photo-oxidation reactions took place on film surface during the proass of formation of LIPS which may have some influences on the formation of LIPS. 5