Research On Design And Application Of Infrared Switch Based On Electrically Driven Phase Transition Of Vanadium Dioxide Film

Vanadium dioxide(VO₂)has unique metal-insulator phase transition(MIT)characteristics,which can be effectively controlled by multiple physical fields.It is this characteristic that makes VO₂ have a broad application prospect in the field of high-speed switching devices.There are some outstanding issues demanding resolution for future application—the relatively high phase transition temperature of VO₂ films(about 68?),the multiphase coexisting of vanadium oxide,the unsettled phase transition mechanism and the high modulation threshold,et al.Therefore,improving the infrared switching characteristics of thin films to improve practicability,reducing the threshold of phase transition to improve energy saving efficiency,are the key problems to be solved in the current switching devices.In view of the above problems,based on the electrically induced metal-insulator transition(E-MIT)of VO₂ thin film,two kinds of physical fields,temperature and electric field,can be conveniently loaded on VO₂ thin film by rational device design,and an VO₂infrared switching device with self-regulating temperature control was designed.In this thesis,VO₂ thin film was prepared by polymer-assisted deposition.Metal layers were patterned based on UV nanosecond laser cutting technology and home-made micro-mask.The properties of VO₂thin films were characterized,including elemental valence state,lattice structure,optical and electrical properties.The surface morphology and optical properties of VO₂ films with different thickness were studied to clarify the effect of thickness on the surface morphology and optical properties of VO₂.Furthermore,the change of domain fraction of VO₂ thin films in transition phase was detected by variable temperature Raman spectroscopy,revealing that the sudden change of infrared transmittance can be interpreted as the macroscopic expression of the percolation threshold in the metal domain fraction of vanadium dioxide,which is about 1/3.In view of the problem of high modulation voltage of E-MIT,the self-regulating temperature control was integrated,which was achieved by micro heater,to reduce the potential barrier of E-MIT by applying a stable thermal field.Furthermore,the electric field intensity was enhanced by controlling the distance between the interfinger-electrodes,and the reversible phase transition characteristics and infrared modulation of the devices under different applied voltages were analyzed.On this basis,this thesis proposed an effective method for thermoelectric co-regulation of phase transition.By utilizing the advantages of E-MIT and controlling the device at the percolation threshold,the as-designed infrared switch can achieve the high-speed control of MIT,thus achieving performance optimization under multi-field control.Compared with the single thermal field regulation,fast regulation was achieved,and the response time was increased by up to 95%.Compared with single electric field regulation,low voltage regulation is realized,and the regulation voltage is reduced by 82.5%with same response time.The thermoelectric co-regulated infrared switching device proposed in this thesis not only provides an effective method for infrared switching control,but also provides a new way for the development of phase change devices based on VO₂ thin film sensors integrating multiple physical field response modes.