| Near infrared absorbers have many applications in the optoelectronic field.In particular,imaging,communications,energy devices all need near infrared broadband absorber.At present,researchers have carried out a series of work for the purpose of achieving high-efficiency broadband absorption.With the development of infrared technology,optical switches and information storage have put forward new requirements for near infrared,broadband,and tunable absorbers,but the current near infrared absorbers have some problems such as narrow absorption bandwidths and unchangeable absorption performance,which cannot meet the requirements.Near infrared absorber structures mainly include ultra-thin planar multilayer structures and surface pattern array structures.The preparation process of the absorber with surface pattern array structure requires photolithography technology,which is not easy to manufacture in large batch,while the preparation of ultra-thin multilayer structures is much easy.Therefore,the near infrared broadband tunable absorber based on the ultra-thin planar multilayer structure has more engineering and practical prospects.To solve the narrow absorption bandwidths and unchangeable absorption performance problems.This thesis uses ultrathin planar multilayer film structures as research basis,and uses near infrared broadband tunable absorption based on epsilon-near-zero property of ITO film and phase change property of VO2 film as research road.A series of research work have been carried out on the theoretical analysis of the epsilon-near-zero material achieve light absorption,the deposition and property research of VO2 film,the deposition and property research of ITO film,the design and fabrication and mechanism research of near-infrared wide absorber,etc.The main research results are as follows:(1)Based on the Fresnel reflection equation of the multilayer film structure,verifying the feasibility of introducing the epsilon-near-zero film to improve the absorption of absorber.Two near-infrared absorber structures were designed(Ti O2/ITO,VO2/Hf O2/V1-xWxO2/ITO).VO2 film and V1-xWxO2 film with high quality were prepared by magnetron sputtering.XPS diffraction patterns determines the actual W doping amount of V1-xWxO2 film is 2.38%.The crystal phase structure,morphology,optical and phase change properties of VO2 and V1-xWxO2 film were studied comprehensively.The V1-xWxO2 film has a greater dielectric loss.The phase transition temperature Tc of VO2 and V1-xWxO2 film are 72.37?and 41.42?,and the cooling efficiency of W doping is 13.00?/%.(2)ITO films,Ti O2film,Hf O2 film were prepared were prepared by magnetron sputtering,pulsed laser deposition and electron beam evaporation respectively.The influence of oxygen flow on the microstructure,photoelectric and near-zero dielectric properties of ITO thin films were explored.The oxygen flow rate adjusts the photoelectric properties of the ITO film by changing oxygen defects.The permittivity profile of the ITO film and the lossless dielectric films were obtained by the two-layer gradient model and Cauchy model.The ITO film with 2 sccm oxygen flow rate has epsilon-near-zero property in the near-infrared wavelength.(3)Based on the permittivity of the single-layer films,the near-infrared broadband absorber(64 nm Ti O2/283 nm 1.5 sccm-ITO/286 nm 2 sccm-ITO)were designed and fabricated by the transmission matrix model and vacuum deposition device.The absorption of ITO-based near-infrared broadband absorber was higher than 90%in range of 1340?1890 nm and the absorption peak is 97.41%.The broad-band perfect absorption could still be maintained with incident rises to 70°.The absorption maps and the electric field distribution show that most of the absorption of the absorber is located in the 1.5 sccm-ITO film.This result provides a new idea for the absorber design.(4)The influence of single and double-layer VO2 film,epsilon-near-zero film and thickness on the absorption performance of the absorber were explored by the transmission matrix model.The near-infrared broadband tunable absorber with the structure of 20 nm V1-xWxO2,50 nm Hf O2,20 nm VO2,283 nm 1.5 sccm-ITO,20 nm Ag film structure was designed.When the temperature is-25?,the absorption was higher than 90%in range of 1670?1915 nm and the absorption peak is 91.84%;when the temperature is 40?,the absorption was higher than 90%in range of 1420?2000nm and the absorption peak is 99.71%;When the temperature is 100?,the absorption was higher than 90%in range of 1160?1420 nm and the absorption peak is 95.58%.The absorber has a narrow band absorption peak at 888 nm and has good filtering performance.The broad-band perfect absorption could still be maintained when the incident up to 60°.(5)The absorption mechanism of the above-mentioned absorber structure was explored by the absorption maps and the electric field distribution.Based on the epsilon-near-zero of ITO films,the double-layers VO2 film structure can combine the absorption advantages of a single-layer VO2 film and enhance its performance.Because the main absorption of the absorber mainly occurs in the ultra-thin V1-xWxO2 film and VO2 film,the absorber has good angular insensitivity property. |
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