Preparation And Investigation Of Metamaterials Based On Composite Structure Of Au/VO₂ With Plasmon Resonance

Semiconductor oxide vanadium dioxide?VO₂?exhibits a reversible transition from metal phase to insulator phase under the stimulation such as light,electric,heat,and its optical,electrical and magnetic properties make a reversible change,it has attracted serious concern for variety of practical applications,such as smart windows,optical switches,LSPR sensors and memory devices.In recent years,due to the strong dielectric sensitivity,Au triangle nanoparticle array is widely used in LSPR sensors.But LSPR characteristics of the fixed structures are difficult to change,which limit their practical application.The LSPR features of Au triangle nanoparticles are not only related to the structural parameters?such as size,thickness?,but also closely related to the surrounding dielectric environment of nanoparticles.VO₂ is added to the surrounding of the nanoparticle array on the basis of not changing the original nanostructure,utilization of the changed dielectric constant under the phase transition of VO₂ has become a research hot spot.In the paper,a composite metamaterial structure of Au triangle array embedded in VO₂ thin film and another VO₂/Au/VO₂ composite nanotriangle array are fabricated by using the nanosphere lithography technique and the preparation craft of films.And we research the LSPR features of the two composite structures,the FDTD simulation method is used to model the two structures,and the resonance mechanism and the tunability mechanism are analyzed.The microstructure,material ingredient,electrical and optical properties of the composite structures are studied by Field Emission Electron Microscope?FESEM?,four-point probe method,X-ray diffraction?XRD?,Raman spectrometer and UV-visible-near infrared spectrophotometer.The effects of VO₂ phase transition on the LSPR characteristics of the Au triangle nanoparticle array under different composite forms is studied.For the composite structure of Au triangle array embedded in VO₂ thin film,when the thickness of Au triangle nanoparticle array and VO₂ film is 10 nm and 90nm,the absorption peak achieves a large tunability of 56.2%while the VO₂ undergoes a structural transition from metallic phase?m-VO₂?to insulator phase?i-VO₂?.And the large wavelength tunability can be explained by a hybrid electric resonance and magnetic resonance mode from the electromagnetic field distributions at the resonance wavelengths.In this composite structure,the LSPR position changes from the sharp corners to the boundaries of Au triangles,increasing the resonance region and intensity,and the tunability efficiency of LSPR property is improved.Compared to the metal-dielectric?Au/VO₂?and dielectric-metal?VO₂/Au?nanotriangle arrays,a largest wavelength shift of⁴2 nm and a largest transmittance modulation of¹3.2%in the modulator for the sandwich array between the hot-metallic and cold-insulating states are obtained.And the wavelength shift of Au/VO₂ nanotriangle array is larger than that of VO₂/Au array.Based on the calculated electric near-field,the change of dielectric environment at the top VO₂ nanotriangle array is larger than that at the bottom upon the VO₂ phase transition.The results suggest that this architecture is one path for designing a plasmonic structure with tunable resonance responses.The research of resonance characteristic on Au triangle nanoparticle array under different structures from VO₂ material has practical significance for the temperature sensitivity of LSPR sensor.