Microsphere Assisted Laser Fabrication Of Nanohole Arrays On Silicon And Sapphire Substrates And Its Applications

Nanohole arrays have been widely used in solar cells,light-emitting devices,electrochemical energy storage,nanophotonics and sensors because of their excellent physical,chemical,photoelectric properties.With the development of nano-machining technology,the processing methods of nanohole arrays are gradually improved,but there are still some problems such as expensive processing equipment(focused ion beam processing),only can processing conductive materials(electrochemical processing).At present,the nanohole array can be fabricated on the substrate by laser irradiation.This method can quickly achieve nanohole array with low cost and low environmental requirements.However,there are obvious ablative sputters around the nanoholes,and the geometric accuracy of the nanoholes is poor.In addition,the relationship between nanohole size and laser processing parameters,microsphere size and material,as well as the optimal structure size of nanohole array in different practical applications need further study.Therefore,in view of the above problems,this paper will carry out the following four aspects of research content:(1)The parameters of laying single-layer microspheres were optimized.By single factor method,three main factors affecting the arrangement of microspheres were optimized one by one: the ratio of water to absolute ethanol(Prop),the solubility of sodium dodecyl sulfonate solution(SDS)and the amount of SDS added.The experimental results show that when the Prop of SDS is 1:1,the concentration of SDS is 6 wt%,and the amount of SDS is 1 ml,the tightly aligned single-layer microspheres can be obtained.(2)Experimental study of microsphere-assisted infrared picosecond laser processing of nanohole arrays.Using silicon and sapphire as processing substrate materials,respectively,the effects of laser energy,the diameter of polystyrene microspheres,and the gold film on the substrate surface on the morphology and size of nanoholes were studied.The experimental results show that as the laser energy and microsphere diameter increase,the hole diameter and hole depth gradually increase.When the laser energy is 30-35 μJ and the diameter of the microspheres is 1.0 μm,a nanohole array with a good morphology can be obtained on silicon substrates.The nanohole has a hole size range of 350-550 nm and a depth range of 60-100 nm.When the laser energy is 160-180 μJ,the diameter of the microspheres is 1.5 μm,nanoholes array can be obtained on sapphire substrates with a hole diameter of 350-450 nm and a depth of about 50 nm;(3)The thin gold film on the substrate can obviously reduce the molten material and debris on the surface of the substrate,while the gold film can improve the internal profile of the nanohole.Under the same processing parameters,the hole size of the gold film assisted microspheres on the surface of the silicon wafer increases about 1/10.(4)Optimization of structural parameters of nanohole array in silicon solar cell applications.Through the design of single factor experiments,the optimal sizes of the diameter,depth and spacing of the nanoholes were obtained.The simulation results show that when the hole depth,the hole diameter and the hole spacing of the cylindrical hole are 250 nm,300 nm and 50 nm respectively,and the hole depth,the hole diameter and the hole spacing of the conical hole are 250 nm,400 nm and 30 nm respectively,the optical absorption efficiency of the nanohole array used in the silicon solar cell can be significantly improved in the near ultraviolet and visible light band,and the maximum optical absorption efficiency is about 2.6 times.(5)The structural parameters of the nanohole array on the GaN-based LEDs sapphire substrate were optimized.Through the design of orthogonal experiments,the effects of the depth,diameter and spacing on light extraction efficiency were analyzed.The size of the nanopore is optimized,and the maximum light emitting efficiency of the LEDs is obtained.When the pore depth,pore diameter,and space distance of the cylindrical pores are 140 nm,300 nm,and 70 nm,respectively,the light extraction efficiency is enhanced by 1.82 times.When the hole depth of the tapered hole is 180 nm,the pore diameter is 360 nm,and the pitch is 10 nm,the light extraction efficiency is increased by 1.70 times.