Research On Preparation And Phase Transition Properties Of Silicon-based Vanadium Oxide Thin Films

Vanadium dioxide?VO₂?has been extensively studied in the past few decades due to its metal-insulator transition?MIT?under the triggering conditions of heat,electricity,light,etc.MIT is accompanied by sudden and large changes in electrical and optical properties,making VO₂ a promising material for electrical,optical switching and modulation applications.We can use thermal,optical,electrical and other external excitation to control the phase transition of the vanadium oxide film,so that the VO₂ film exhibits both transmissive and non-transmissive states for far-infrared light waves,and realizes modulation of far-infrared light waves.In order to realize the application of VO₂film in the far-infrared modulation device,the VO₂ film should meet the following three performance requirements:?1?the insulating state has a high far-infrared transmittance;and?2?a large far-infrared modulation amplitude;?3?a narrow hysteresis width.This gives the device good stability and reliability,high response rate and efficiency.Compared with thermally induced MIT modulation devices,electro–induced MIT modulation devices can be better compatible with high-speed electronic systems.It is also important to study the electro-induced phase transition properties of VO₂ films.In order to prepare a good VO₂film with far-infrared modulation performance,this paper has done the following work based on the research status:?1?Alumina?Al₂O₃?film was prepared on a high purity Si substrate by using atomic layer deposition?ALD?as a buffer layer for growing VO₂ film.The introduction of Al₂O₃buffer layer significantly enhances the thermal-induced MIT properties of VO₂ film.The experimental results show that when Al₂O₃ buffer layer's thickness increases to 40nm and VO₂ film is 300nm,the amplitude modulation is largely increased from 51.2%to 71.3%at 390 cm^-1 and from 18.0%to 40.2%at 280 cm^-1,and the hysteresis loop width is reduced from 18.5°C to 11.8°C.?2?The effect of Al₂O₃ buffer layer on VO₂ film was studied in depth.The effect of Al₂O₃ buffer layer thickness and VO₂ film thickness on phase transition characteristics was studied.The experimental results show that the thicker the thickness of Al₂O₃ buffer layer is,the better the MIT performance of VO₂ film gets.Under the same thickness of Al₂O₃ buffer layer,and the thickness of VO₂ film is within a certain interval,the thinner the thickness,the better the phase transformation performance,indicating that the optimization of the buffer layer for VO₂ film decreases with the increase of film thickness.?3?VO₂ film was prepared on ITO glass,and ITO glass was used as the bottom electrode to study the electro-induced MIT characteristics of VO₂ film in the vertical direction.The experimental results show that the thickness of VO₂ film affects its electro-induced MIT performances,and the change trend of its electro-induced MIT property is closely related to its thermal-induced MIT properties and crystallization.