Preparation Of Silicon Nanowires By Metal-assisted Chemical Etching And Its Optical Properties

Semiconductor silicon is widely used as the most important semiconductor material because of its stable properties,easy purification,large storage capacity and other advantages.The quantum confining effect and small size effect of silicon nanostructure make it have excellent optical properties,electrical properties and photoelectric conversion properties.It has a wide range of applications in the fields of display devices,sensors,photodetectors,new energy and so on.The optical properties of silicon nanowires have always been the research focus of scientific researchers.The research of this property can promote the optimization of silicon based optical devices.Use a metal auxiliary chemical etching of silicon nanowires prepared,first of all,silicon nanowires samples by SEM,the two-step method,the different concentration of silver ion(0.005 M,0.01 M,0.015 M),different etching time(15 min?75 min),different oxidant H₂O₂concentration(0.3 M?0.9 M),different etching temperature(10??70?)on silicon nanowire morphology.The results show that the silver ion concentration does not affect the length of the silicon nanowires,but when the silver ion concentration is 0.005 M,it will cause a tree branch structure.When the silver ion concentration is 0.01 M and 0.015 M,the greater the silver ion concentration,the silicon nanowire The smaller the diameter and density;within a certain etching time range,the etching time is positively correlated with the length of the silicon nanowires generated,and the average etching rate is 1.14?m/min;the greater the concentration of oxidant H₂O₂,the more thorough the reaction is,and the generated silicon The longer the nanowire is,the limit will be reached when the H₂O₂ concentration is 0.9 M;The rise of the etching temperature will also make the reaction more complete,thereby making the silicon nanowires longer,but when the temperature reaches 70?,the structure of the silicon nanowires will be destroyed.Moreover,during the reaction,some Ag⁺will diffuse to the sidewalls of the silicon nanowires to initiate new etching,so that the sidewalls of the silicon nanowires form silicon nanoparticle bumps.We have studied three optical properties of silicon nanowires,namely,anti-reflection property,photoluminescence property and Raman spectrum.In a certain etching time,the silver ion concentration and the etching time increase can reduce the reflectivity in the visible light range.When the oxidant H₂O₂ concentration increases,the reflectivity first decreases and then increases,and the smaller the visible light wavelength,the better the anti-reflection effect.After the etched silicon nanowire is excited at 279 nm,an emission peak can appear at about 700 nm.In a certain etching time,the concentration of silver ions decreases and the etching time is prolonged,which can increase the photoluminescence intensity.The oxidant H₂O₂ When the concentration increases,the photoluminescence intensity first increases and then decreases,which is related to the effective exposure area of the silicon nanowires and the rough nanoparticle protrusions on the sidewalls of the silicon nanowires.The polished silicon wafers have a Raman peak at?=520 cm^-1.When the silicon wafers are etched into silicon nanowires,the longer the etching time,the longer the Raman The more the peak position shifts,and the phenomenon of asymmetric broadening is shown,which proves that the longer the etching time can make the diameter of the silicon nanoparticles on the sidewalls of the silicon nanowires become smaller.