Study On The Structure And Properties Of SiO_x Thin Films Irradiated By Laser

Low dimensional silicon structure can imporve the internal quantum efficiency of silicon light emission.Nanocrystalline-silicon embedded in silicon dioxide has good thermal stability,high compatibility with silicon-based semiconductor technology,possessing good application prospect.The most effective preparation method of this system is annealing of SiO_x.Compared with furnace annealing,laser annealing has the advantages of fast processing speed and controllable processing area.In the paper,the structural characteristics and luminescent properties of SiO_x films after laser annealing are studied.The formation mechanism of the structure of SiO_x films after annealing is analyzed,and the structural changes of SiO_x films irradiated by electron beam at different temperatures are observed by in-situ transmission electron microscopy.This study provides a reliable basic theory for the application of laser irradiation technology in silicon based devices and has great research potential.The main contents and conclusions are as follows:(1)By laser irradiating the SiO_x film with different power densities,it is found that SiO_x could form nanosilicon when the laser power density is greater than 1.0×10~7W/cm~2.SiO_x film produces bumps,spherical cavities and point damage morphologies after laser annealing due to the characteristics of the laser energy and the defects of the SiO_x.The size distribution and crystallization characteristics of SiO_x film after laser annealing are obtained by Raman spectroscopy:the grain size is related to the laser power density and annealing time;it takes time for the formation of grains;the crystallinity is related to the depth of the film.According to the fluorescence spectrum of SiO_x after laser annealing,the luminous peak of SiO_x after annealing is located near700 nm.(2)The cross-section samples of SiO_x films parallel to and perpendicular to the laser processing direction are prepared by FIB,and the structural characteristics of the cross-section samples in different directions were compared by transmission electron microscopy.According to the characteristics of Gaussian distribution of laser energy and EDS and EELS spectrum,the microstructure of SiO_x film after laser annealing is divided into five parts:melting zone,cladding zone,porous silica zone,silicon crystallization zone and substrate zone.(3)The in-situ transmission electron microscope was used to observe the structural changes of SiO_x with temperature under different densities of electron beam irradiation.Under high temperature and high density electron beam irradiation,the formation of nanocrystalline-silicon and pores was clearly observed.The generation of holes in SiO_xis the interaction of temperature and electron beam irradiation.Temperature is the main factor that makes SiO_x phase separate.Electron beam irradiation can speed up the phase separation process of SiO_x.Under the irradiation of high density electron beam,SiO_xhas a damage threshold temperature.Below this temperature,electron beam irradiation can accelerate the formation of grains;above this temperature,electron beam irradiation will damage SiO_x.It is difficult for SiO_x to form porous structure only by thermal annealing,and the formation of porous structure requires higher density of energy.