Picosecond laser fabrication of nanostructures on ITO film surface assisted by pre-deposited Au film

Abstract

With greater optical penetration depth and lower ablation threshold fluence, it is difficult to directly fabricate large scales of laser-induced periodic surface structures (LIPSSs) on indium–tin–oxide (ITO) films. This study proposed an approach to obtain optimized LIPSSs by sputtering an Au thin film on the ITO film surface. The concept behind the proposal is that the upper layer of the thin Au film can cause surface energy aggregation, inducing the initial ripple structures. The ripples deepened and become clear with lower energy due to optical trapping. The effective mechanism of Au film was analyzed and verified by a series of experiments. Linear sweep, parallel to the laser polarization direction, was performed using a Nd:VAN laser system with 10-ps Q-switched pulse, at a central wavelength of 532 nm, with a repetition rate of 1 kHz. The complete and clear features of the nanostructures, obtained with the periods of approximately 320 nm, were observed on ITO films with proper laser fluence and scanning speed. The depth of ripples was varying in the range of 15–65 nm with clear and coherent ITO films. The preferred efficiency of fabricating nanostructures and the excellent results were obtained at a scanning speed of 2.5 mm/s and a fluence of 0.189 J/cm². In this way, the ablation and shedding of ITO films was successfully avoided. Thus, the proposed technique can be considered to be a promising method for the laser machining of special nonmetal films.