Preparation Of Plasma-controlled VO₂-based Thin Films And Their Intelligent Photoresponsive Behavio

Vanadium dioxide（VO₂）is a special photoelectric material with thermochromic behavior.When it is lower than the phase transition temperature（T_C=68℃）,it is a monoclinic phase with non-metallic insulation characteristics and can penetrate infrared light;When the ambient temperature is higher than the phase transition temperature,the crystal structure will change into tetragonal rutile phase,which has metal conductivity.At this time,most of the infrared light is reflected.This phase transition characteristic makes VO₂ have broad application prospects in the fields of intelligent window,laser protection and photoelectric switch.However,the theoretical phase transition temperature of VO₂ is 68℃,which is much higher than the room temperature.If the practical application must reach the phase transition temperature through external heating,its application in optoelectronics is greatly limited.At the same time,the solar light utilization rate of VO₂ materials is low,especially in the visible light part,which is one of the core problems in the development of VO₂ in the application fields such as intelligent windows.Aiming at the above two problems,this paper proposes a strategy of using double glow plasma discharge to pre bombard the substrate surface and induce the growth of VO₂ films through the vacancy defect structure generated by activation.The main research work is as follows:（1）The process parameters of double glow plasma pretreatment of quartz substrate surface are studied,and the effects of different pretreatment power on the substrate surface are compared.The results show that appropriate pretreatment can etch the substrate surface to form a large number of defects and provide stress induction for VO₂ growth.Atomic force microscope（AFM）was used to study the change law of surface roughness of the substrate before and after pretreatment,and 150 W was the best pretreatment power.From the SEM table/section results of the sample,the film formed after pretreatment is dense and uniform,has stronger adhesion with the matrix,and has no obvious interface;The phase structure of VO₂ thin films was studied by X-ray diffraction（XRD）to explore the effect of annealing temperature on the growth of the films.The results show that the films are composed of VO₂（M2）phase at 550℃without impurity phase.At the same time,the effect of residual stress on the growth of VO₂ films was studied by XRD.The results show that there is a stress of 785.42 MPa in VO₂ lattice after pretreatment.（2）The electrical and optical properties of the films were analyzed by four probe resistance test and UV-vis-NIR spectrum.It was found that the phase transition amplitude increased before and after near-infrared light regulation,and the phase transition temperature decreased to 39.4℃,and the utilization of sunlight was also improved.（3）The generation law of surface vacancy defect structure in the process of plasma bombardment is simulated by molecular dynamics,and the growth mechanism of VO₂ thin films is studied.The results show that the relationship between vacancy defects and interstitial atoms in the process of simulated pre sputtering and the number of bombardment times is confirmed theoretically.It is possible that a large number of vacancy defects will be produced in the process of plasma bombardment to induce the directional growth of VO₂ thin films.（4）Through the design of VO₂ based composite films,Zn O/VO₂ and Zn O/VO₂/Zn O multilayer composite films were prepared by magnetron sputtering technology,and the process optimization parameters of VO₂ based multilayer composite films were obtained.The photoelectric performance test showed that the Zn O transition layer could play a good role in increasing the transmittance on the basis that the phase transition performance was not affected.The UV response behavior of VO₂ based multilayer composite films was studied by water contact angle.The results show that the composite films can regulate the contact angle after being excited by UV light.The laser protection properties of single VO₂ film and Zn O/VO₂ composite film are compared.The results show that VO₂ can reflect infrared light,but there is dissociation phenomenon affected by light energy.The multilayer composite film will have potential application value in the field of laser protection.