Study On The Micro-nano Structure Design Of The Crystal Surface And The Performance Of The LYSO Scintillator

Scintillator is the core functional material of scintillation detection system,which can convert high-energy particles and high-energy rays that cannot be directly detected into visible light or near-ultraviolet light to be received by subsequent photodetectors,so as to realize the detection of high-energy particles or high-energy rays.Light output is an important performance of scintillator,which will directly affect the detection efficiency and sensitivity of scintillation detection system.The inorganic scintillator has the advantages of high stopping power,high luminous efficiency,good linear energy response and radiation resistance to charged particles.However,due to the high refractive index of inorganic scintillators,a large part of the scintillator light is completely reflected at the exit surface.This part of the light will be limited to the interior of the scintillator and cannot be absorbed by the photodetector,which greatly reduces the light output.In this paper,two-dimensional photonic crystal structures were introduced into the LYSO scintillator,and the properties of the scintillator were improved by using nano-period structures to regulate scintillation light.The main work and conclusions are as follows.（1）By analyzing the light extraction principle of photonic crystals,three types of nano-period structures of nanospheres,air holes and dielectric columns were designed.Based on the strict coupling wave analysis method,the designed photonic crystal structures were simulated and the structural parameters were optimized.The results show that a good light extraction effect is obtained when the period of the nanoarray is close to the central luminescence wavelength of the LYSO scintillator.（2）Monolayer SiO₂/PS nano-sphere periodic array was prepared on the surface of LYSO scintillator by colloidal crystal self-assembly method,and TiO₂ layer was conformed deposited on the surface of nano-sphere by magnetron sputtering technology.This method is simple and easy to prepare two-dimensional photonic crystals in large area.TiO₂-air hole periodic array was prepared on the surface of LYSO scintillator by electron beam lithography combined with ion beam etching technology.The photonic crystal prepared by this method has regular structure arrangement and accurate size.（3）After introducing of a 420nm diameter monolayer SiO₂ spheres array and a100nm thickness TiO₂ conformal layer on the surface of LYSO scintillator,under the dual action of the unique whispering gallery mode and periodic array diffraction of the nanometer sphere periodic array,the light extraction efficiency was improved by 193%and the energy resolution was improved by 10.3%.After introducing a monolayer PS spheres array with a diameter of 415nm and a TiO₂ layer with a thickness of 85nm,the optical extraction ground increased by 184%.After introducing square TiO₂-air hole periodic array photonic crystal plate on the surface of LYSO scintillator,the scintillation light is coupled with the high-refractive index periodic array structure,which enables more scintillation light to enter the nanocycle structure,and the light extraction is improved by 53.5%and the energy resolution by 43%.