Study On The Band Gap Characteristics And Edge Electronic States Of Silicon Thin Film Structures On Silicon Oxid

Silicon is an indirect band gap semiconductor with low luminous efficiency.The energy band structure of many silicon oxides is a direct band gap structure,but the band gap is wide.Nano-silicon crystals are grown on silicon oxide,keeping the direct band gap structure of silicon oxide,and introducing edge electronic States to reduce the band gap of silicon crystal films on silicon oxide for luminescence and photovoltaics.In this paper,the band gap characteristics and edge electronic states of silicon thin films on silicon oxide are studied.By combining physical experiments and simulation calculation,the edge electronic states are introduced by growing silicon thin films on silicon oxide,which keeps the direct band gap characteristics of silicon oxide and reduces its energy band gap.In the experimental part,silicon crystal films on silicon oxide were prepared by pulsed laser deposition,and their morphological characteristics were observed by optical microscope and transmission electron microscope.After that,the silicon thin film on silicon oxide was characterized,and the photoluminescence spectrum of the silicon thin film on silicon oxide was measured under the excitation of different power Ar ion lasers.When the power of the Ar ion laser reaches more than 4m W,there is a strong luminescence peak at 775nm（1.6e V）on the edge electronic state of the silicon crystal thin film sample on silicon oxide.A quantum platform with photoluminescence intensity varying with the excitation power of Ar ion laser was observed on the silicon crystal film on silicon oxide.Among them,the excitation regions of the luminescent quantum platform are obvious at 0.5～1mw,1.5～2mw and 4～6mw.The edge electronic state of silicon crystal thin film on silicon oxide acts as a quantum storage,in which excited electrons are isolated for a long time to produce a luminescent quantum platform.In the theoretical calculation part,density functional theory is used to study the interface model ofα-cristobalite with different thickness and Si/Si O₂ with different silicon oxide layer thickness through first principles.The filmα-square Shi Ying with different thickness is a direct band gap semiconductor material with high band gap.By growing a silicon crystal film on the surface and introducing edge electronic states,the energy band gap at the Si/Si O₂ interface is reduced,while the direct band gap characteristics are maintained.Theα-square Shi Ying thickness decreases from2.887nm to 1.047nm,and theα-square Shi Ying band gap of the film increases from5.233e V to 5.927e V.The thickness of silicon oxide decreased from 2.887nm to1.047nm,and the band gap of Si/Si O₂ interface increased from 1.62e V to 1.782e V.The change of electronic state structure of Si/Si O₂ interface caused by the change of silicon oxide layer thickness is similar to that caused by the change of filmα-cristobalite thickness.In the energy band structure of Si/Si O₂ interface,Dirac vertebra is formed near G point,and the energy band gap of silicon oxide is effectively reduced by introducing edge electronic states.The energy band of silicon oxide with energy band gap above 5e V is reduced to 1～2ev,which is beneficial to luminescence and photovoltaic applications.The imaginary part of the dielectric function at the Si/Si O₂interface has a dielectric peak around 4.5e V.With the decrease of the thickness of the silicon oxide layer at the Si/Si O₂ interface,the dielectric peak slightly moves to the high energy direction,and the peak value of the dielectric peak increases continuously.Near6e V,the change trend of refractive index of Si/Si O₂ interface appears inflection point,and it maintains transparency at high energy.There is an absorption peak at the Si/Si O₂interface near 6e V,and the peak of the absorption coefficient at the Si/Si O₂ interface also increases significantly with the decrease of the thickness of the silicon oxide layer,and the peak position moves to the high energy direction,resulting in a blue shift.In this study,a new two-dimensional nanomaterial structure is designed,in which silicon quantum disks are embedded in amorphous silicon oxide.The energy bandgap of the silicon quantum disk in the amorphous silicon oxide is regulated by changing the overall thickness of the silicon quantum disk in the amorphous silicon oxide.As the overall thickness of silicon quantum disks in amorphous silicon oxide increases from0.4nm to 1.2nm,the energy bandgap of silicon quantum disks embedded in amorphous silicon oxide gradually decreases,from 4.018e V to 1.415e V,showing a significant quantum confinement effect.The peaks of the imaginary dielectric peak and absorption peak of the dielectric function imaginary part of the silicon quantum disk embedded in amorphous silicon oxide decrease with the decrease of the overall thickness of the silicon quantum disk embedded in amorphous silicon oxide,and the peak position blue shifts to the high energy direction,and the non-After the overall thickness of the embedded silicon quantum disk in crystalline silicon oxide decreases,a double peak is produced.Afterwards,the energy bandgap of the silicon quantum disk in the amorphous silicon oxide is regulated by changing the diameter of the silicon quantum disk in the amorphous silicon oxide.As the diameter of silicon quantum disks decreases from1.22nm to 0.41nm,the energy bandgap of amorphous silicon oxide embedded silicon quantum disks increases from 0.515e V to 4.556e V.There is a dielectric peak at 4.4e V for the silicon quantum disk embedded in the amorphous silicon oxide with a diameter of 1.2nm.As the diameter of silicon quantum disks decreases,the dielectric peak of silicon quantum disks embedded in amorphous silicon oxide decreases continuously and moves to the right.The silicon quantum disk embedded in amorphous silicon oxide with a diameter of 1.2nm has an absorption peak at 4.5e V,at which point the absorption capacity for ultraviolet light and visible light is the largest.This paper concludes that by growing silicon thin film on silicon oxide,the edge electronic state can be introduced to maintain its direct band gap and reduce the forbidden band width.And by controlling the thickness of the silicon oxide layer of the silicon crystal film on silicon oxide,the overall thickness of the silicon quantum disk in the amorphous silicon oxide,and the diameter of the silicon quantum disk in the amorphous silicon oxide,the electronic properties of the silicon crystal film on silicon oxide can be effectively regulated.State structure and optical properties,adjust the band gap of silicon crystal thin film material on silicon oxide to enter the range of 1-2e V,and obtain silicon-based light-emitting materials.