Preparation Of Mg-doped And Zn-doped Lithium Niobate Thin Films And Their Photoelectric Properties

Lithium niobate crystal is an artificial crystal with many excellent characteristics such as electro-optic effect,acousto-optic effect,ferroelectric effect,photorefractive effect and nonlinear optical effect.It is widely used in electro-optic modulators,optical waveguides,photoelectric switches,Holographic storage and optical communications.However,pure lithium niobate crystals are difficult to meet the needs of many applications.Ion doping of lithium niobate crystals can improve the performance of lithium niobate crystals.For example,doping of magnesium ions(Mg²⁺)and zinc ions(Zn²⁺)can improve the electro-optical characteristics of lithium niobate crystals,especially significantly Improve the anti-light damage threshold of lithium niobate crystals,greatly expanding the application range of lithium niobate crystals.Lithium niobate film has received extensive attention from researchers because it has the same excellent properties as lithium niobate crystals.The small size,light weight,and easy preparation of lithium niobate film make it useful in electronic integration and micro-devices.The field has broad prospects.Therefore,this paper selects Mg²⁺and Zn²⁺to dope the lithium niobate film in order to obtain the magnesium-doped and zinc-doped lithium niobate film with excellent electro-optical properties.The research of this paper is mainly divided into the following parts:1.The development history of lithium niobate crystal is reviewed,the defect model of lithium niobate crystal is discussed,and the lithium vacancy defect model is determined as the main intrinsic defect in lithium niobate crystal.At the same time,the development history of lithium niobate film is reviewed,and the influence of various doping ions and substrate materials on the performance of lithium niobate film is discussed,which provides theoretical support for the preparation of magnesium and zinc doped lithium niobate films.2.The high-quality magnesium-doped lithium niobate film（LN:Mg）was deposited by radio frequency magnetron sputtering（RFMS）.The structure,surface morphology and optical properties of the deposited magnesium-doped lithium niobate film were characterized by X-ray diffractometer,Raman spectrometer,scanning electron microscope and ultraviolet-visible spectrometer.The inside of the magnesium-doped lithium niobate film was measured by energy dispersive spectrometer.The weight percentage and mass percentage of each element was test.The results show that the preferred orientation of the LN:Mg film is（012）.The surface of the film is dense and the grain size is uniform.Through analysis,it is found that the average transmittance of the LN:Mg film decreases with the increase of the atomic percentage of the Mg element inside the film.Among them,when the atomic percentage of the Mg element is at least 0.8%,the magnesium-doped lithium niobate film has The transmittance is as high as 89%;by calculating the optical band gap of the film,it is found that the optical band gap of the magnesium-doped lithium niobate film is negatively correlated with the change of the grain size.The crystal grain size of the film can be controlled by changing the deposition conditions,so that the optical band gap of the film can be adjusted from 3.85 e V to 4.04 e V.In addition,through the self-built anti-light damage test platform,the anti-light damage threshold of the LN:Mg film was tested,which is as high as 4.68×10⁴W/cm²,which makes the LN:Mg film have broad application prospects in the manufacture of new optoelectronic devices.3.Lithium niobate films and 2mol%,4mol%,6mol%and 8mol%zinc-doped lithium niobate films（LN:Zn）were deposited at room temperature by radio frequency magnetron sputtering.The doping concentration was discussed and the effect of annealing temperature on film structure and photoelectric properties.By analyzing the XRD results,it is found that the doping concentration and annealing temperature have a significant effect on the structure of the film.The 6mol%Zn-doped LN:Zn film has the most ideal lattice orientation and crystallinity after annealing at 600℃.At the same time,SEM and AFM results show that the 6mol%Zn-doped LN:Zn film has a smooth and dense surface after annealing at 600°C.In addition,the LN:Zn film has good optical transmittance.By calculating the optical band gap of the film,it is found that the optical band gap of the6mol%Zn-doped LN:Zn film decreases with the increase of the grain size.In order to explore the electrical properties of the LN:Zn film,the electrical properties of the 6mol%Zn-doped LN:Zn film were tested using a Hall effect instrument.The results show that the conductivity type of the 6mol%Zn-doped LN:Zn film is n-type,and its resistivity and Hall mobility at room temperature are 1.29×10^-4Ωcm and 129 cm²V^-1s^-1,respectively.This result shows that the conductivity of the 6mol%Zn-doped LN:Zn film is n-type.Lithium zinc niobate films have potential applications in optoelectronic devices.4.The conclusions drawn through experiments and characterization analysis are summarized,the current problems of magnesium-doped and zinc-doped lithium niobate films are proposed,and the application prospects of magnesium-doped and zinc-doped lithium niobate films are prospected.