Generation And Application Of Micro Structures On Monocrystalline Silicon Fabricated By Femtosecond Laser Irradiation And Wet Etching

As an important single crystal material of non-metallic elements,monocrystalline silicon has excellent thermal conductivity,long-term and high-quality service performance,and is widely used in MEMS,solar cells,infrared detectors and other fields.Among them,the related research shows that the surface of single crystal silicon solar cells with micro nano structure can enhance the absorption of light and improve the conversion efficiency.However,monocrystalline silicon has the characteristics of high brittleness and low plasticity,which is a typical difficult to machine material.Wet etching can achieve efficient processing of monocrystalline silicon,but it has low controllability and complex process.Femtosecond laser has unique advantages in the fabrication of surface micro/nano structures due to its high peak power and small heat affected zone.However,there are few reports on the fabrication of complex micro array structures on monocrystalline silicon surface by combining femtosecond laser with wet etching.In this study,we proposed to use femtosecond laser to process monocrystalline silicon in air and deionized water,and then used KOH solution to wet etch it,so as to realize the processing of monocrystalline silicon surface micro array structure.The optical properties(transmittance,reflectivity and absorptivity)and surface characteristics(hydrophilicity)of monocrystalline silicon with micro structure were detected and analyzed.The research contents and results of this paper are of great significance to reveal the femtosecond laser processing mechanism of monocrystalline silicon in different environments,to obtain the change rule of monocrystalline silicon surface morphology after femtosecond laser wet etching,and to improve the optical properties and surface characteristics of monocrystalline silicon surface.In this paper,the femtosecond laser ablation threshold of monocrystalline silicon in air and deionized water was studied by calculation method,and the single point ablation of monocrystalline silicon was carried out in two kinds of environment,and the morphology change rule of ablated micropores was analyzed.EDS was used to detect the element distribution in the ablated area of monocrystalline silicon surface after femtosecond laser processing in two environments.The SiO2 content around the ablated micropores obtained in deionized water environment was lower.Secondly,the influence of etching temperature and KOH etching solution content on the morphology of silicon after wet etching was studied.Under the etching temperature of 80?,the mass fraction of etching solution of 30%and the introduction of ultrasound,the wet etching of smooth pits was realized.The variation of the morphology of the ablation holes with the increase of the etching time was analyzed.The ablation holes with different laser power,pulse number and defocusing amount were wet etched in 10,11,12,13 and 14 min.At the same time,the etched holes in deionized water were wet etched,and the complete inverted pyramid etched pits were obtained at the laser power of 12.861mW.Finally,the single inverted pyramid etch pits were processed into inverted pyramid array according to different spacing.Compared with the single crystal silicon with unprocessed microstructure,the reflectivity of single crystal silicon with inverted pyramid array is reduced to less than 5%,and the absorptivity is increased to more than 95%.At the same time,groove arrays and grid arrays with different spacing were fabricated on the surface of monocrystalline silicon.After wet etching,V-shaped micro groove arrays and positive pyramid arrays were obtained.Among them,the reflectivity of V-groove array silicon decreases to less than 5%,and the absorptivity increases to more than 95%;The contact angle of the V-groove array with a spacing of 30 ?m is 4.556°,Super hydrophilic surface was obtained.