Research On The Preparation By Magnetron Sputtering And Etching Modification Of Vanadium Oxide Thin Films

Vanadium dioxide（VO₂）will undergo phase transition from the monoclinic（M）phase in semiconductor state at low temperature to the rutile tetragonal（R）phase in metal state at high temperature which is reversible near 68℃（340 K）.When the structure changes,the physical property such as electrical,optical and magnetic properties will all change.It is functional material with unique phase transition characteristics.The research on VO₂ based thin film for smart window has been developing rapidly in recent years.At present,the practical application of VO₂ based thin film for smart window still faces two major problems:（1）Higher visible light transmittance(T_lum)and higher sunlight modulation efficiency(ΔT_sol)can not be realized at the same time;（2）The phase transition temperature is much higher than room temperature.Aiming at these two problems,thesis has carried out the following work:（1）The effect of acid etching treatment time on VO₂ films was studied.Vanadium dioxide thin films with the same thickness were prepared by magnetron sputtering,then treated with acid etching for different time,and then tested The result showed that with the increase of acid etching time,the visible light transmittance continued to increase,and the sunlight modulation ability first increased and then decreased.Both of them could be maintained at a high level at the same time,but the phase transition temperature of vanadium dioxide film showed an upward trend,and the loop width showed a widening trend.When the acid etching time was 45 s,T_lum was increased to47.6%,meeting the daylighting requirements of VO₂ thin film for smart window.When the acid etching time was 30 s,ΔT_sol could reach 18.5%,much higher than 10.0%required.When the etching time was 60 s,ΔT_sol was 16.9%,which was still higher than16.7%that before acid etching treatment.Moderate acid etching treament could effectively improve the visible light transmittance and sunlight modulation ability of vanadium dioxide thin films at the same time.（2）The effect of VO₂ film thickness on acid etching treatment was studied.Considering the influence of film thickness on the optical propertiy of vanadium dioxide films,vanadium dioxide films with different thicknesses were prepared by magnetron sputtering,then treated with acid etching for the same time,and then tested.The result showed that vanadium dioxide films with different thickness could effectively improve the solar modulation efficiency and visible light transmittance on the original basis through moderate acid etching treatment,but the phase transition temperature still showed an upward trend and the loop width still showed a widening trend after the acid etchng treatment.In addition,the etched VO₂ film samples have obvious advantages in optical properties compared with the non etched samples with similar thickness.Among the experimental samples,theΔT_sol of sample ST2 could reach 19.6%,while T_lum was 34.4%,and T_lum of sample ST8 could reach 69.0%,ΔT_solwas 10.3%.（3）The effect of acid etching treatment on metal element doped VO₂ films was studied.Considering that doping metal elements can reduce the phase transition temperature and loop width of vanadium dioxide thin films,iron（Fe）doped Vanadium dioxide thin films and tungsten（W）doped vanadium dioxide thin films with the same thickness were prepared by magnetron sputtering,then treated with acid etching for different time and then tested.The effect of acid etching treatment on improving visible light transmittance and sunlight modulation efficiency was also applicable to doped vanadium dioxide films,and the phase transition temperature and loop width were reduced.Among the experimental samples,the T_lum of sample SF4 doped with iron was42.3%,theΔT_sol was 16.5%,and the phase transition temperature was 49.0℃,the T_lumof SW3 doped with tungsten was 53.4%,theΔT_sol was 16.2%,and the phase transition temperature was 32.2℃.