Preparation And Optical Property Of Vanadium Oxide Thin Films

In this thesis,vanadium oxide thin films were prepared by two methods,i.e.thermal oxidation of sputtered Vanadium films and DC reactive magnetron sputtering of Vanadium oxides.The influence of experimental parameters such as thermal oxidation temperature,sputtering current and Ar/O₂ flow ratio on the phase composition,surface morphology and optical transmittance of Vanadium oxide films were studied.And the dependence of the transmittance at 1000 nm on temperature was investigated.The transmittance contrast factor and the thermal-induced phase transition temperature of the films were analyzed at 20℃（Room temperature）and 90℃.As to the thermal oxidation method,the metallic Vanadium films were prepared at different sputtering currents,then they were subjected to thermal oxidation at different temperatures（150℃,250℃,350℃,450℃）.The phase composition,surface morphology and transmittance of the films were characterized by XRD,SEM,AFM and UV-Vis spectrophotometer.The results are as follows:1、The metallic V films prepared at low sputtering currents had good optical transmittance.The grain size of the metallic Vanadium films increased and the transmittance decreased with the increase of sputtering current.2、After the heat treatment of the metallic Vanadium film at low thermal oxidation temperatures（150℃,250℃）,there was no vanadium oxide phase appeared in the XRD pattern.After 350℃thermal oxidation,the oxide peaks of different valence states V were observed,which were mainly VO₂ and V₂O₃ phases.After hot oxidation at 450℃,the films exhibited preferential orientation growth on VO₂（011）planes.3、The transmittance of the metallic Vanadium films obtained at sputtering current of0.15A and 0.20A after thermal oxidation at 450℃for two hours was 64%and 50%at 1000nm,respectively.And the thermal-induced phase transition temperature was about 60℃and70℃,respectively.The Vanadium oxide films were also prepared with different Ar/O₂（1S 50:1,2S 40:1,3S 30:1）fiow ratio using DC reactive magnetron sputtering method,and the thermal oxidation was carried out as well.The surface morphology and the transmittance of the Vanadium oxide films were characterized by SEM and UV-Vis spectrophotometer.The results are as follows:1、As the Ar/O₂ flow ratio was reduced,the grain shape of the film evolved from round pack to block,and then to long strip.Grain size increased significantly from≤100nm to500nm.2、The transmittance in the visible-near infrared region of 1S,2S,3S samples reached70%,and the transmittance contrast ratios at 1000 nm were 75%,79%and 83%,respectively.The thermal-induced phase transition temperature was about 70°C,60°C,and 50°C,respectively.Compared with the Vanadium oxide films by thermal oxidation,Vanadium oxide thin films fabricated using magnetron sputtering at Ar/O₂ of 30:1 exhibit better comprehensive property,i.e.high transmittance at low temperature while low transmittance at high temperature for the lights with wavelength of 1000 nm,the transmittance contrast ratio at1000 nm being 83%,thermal-induced phase transition temperature being 50°C.