Tudy On Periodic Micro/Nano Structure Prepared By Ultra-short Pulse Laser

Surface micro/nanostructuring has great application potential in material modification.The micro/nano structures obviously improve the properties of materials in optics,mechanics,wetting.chemistry and biology.For this reason,various technologies for preparing micro/nano structure have emerged,such as lithography,self-organizing,nanoimprint,electron-beam lithography,etc.,but the preparation process of these technologies often require special processing environment and disposable mask reticle,which increase the processing cost.The birth of ultra-short pulse laser provides a convenient way for us to prepare micro/nano structures.Laser interference and laser-induced periodic surface structures(LIPSS)are widely used in the preparation of periodic micro/nano structure.Silicon and ITO are important semiconductor materials,which are widely used in the field of photoelectric devices.In the paper,the periodic micro/nano structures prepared by laser interference and LIPSS on silicon with crystal phase <100> and ITO film with thickness of 60 nm are discussed,and the factors affecting the morphology characteristics are systematically studied,and the advantages and disadvantages of the two processing technologies are compared.In the paper,first of all,the periodic micro/nano structure on silicon with the period of more than 600 nm is prepared by nanosecond laser two-beam interference ablation assisted with wet-etching method.In the experiment,we observe that the structure depth increases with the increase of laser power and exposure time,but there is a saturation value of the depth,and the maximum depth is about 50 nm,which is related to the skin depth of the laser.Periodic splitting occurs when the exposure time reaches 5s.The finite difference time domain(FDTD)simulation confirms that the formed structure has negative feedback regulation to the interference light field,whichis the main reason of periodic splitting.These results are of great significance for the fabrication of silicon-based micro/nano devices.Secondly,we induce subwavelength structures on ITO film using femtosecond laser with a wavelength of 343 nm.The effects of laser energy and pulse number on the structure morphology are discussed.The result shows that,when the laser power is near-threshold and the pulse number is enough,the subwavelength periodic structure with uniform structure and period less than 100 nm can be prepared;the structure period increases with the decrease of power.The effect of the energy distribution of the focused spot on the induced ripple period is found,and it is verified that changing the energy distribution of the focused spot can change the structure period,which provides a feasible method for the preparation of subwavelength periodic structures with controllable period.These research results have a certain guiding role in the preparation of periodic micro/nano structure by short-pulse laser,providing a one-step rapid maskless preparation method,deepening people's understanding of laser-matter interactions,broadening the application of the two technologies.