Fabrication And Optical Property Of Two-dimensional VO₂/SiO₂ Composite Photonic Crystal Structure

Vanadium dioxide?VO₂?has been intensively studied for its fantastic property of a reversible phase transition between a semiconducting state and a metallic state.There is an abrupt change in the infrared?IR?transmittance while maintaining in the visible range during the semiconductor-to-metal transition?SMT?.But the plane VO₂film has a problem of low transmittance and un-tunable.The two-dimensional?2D?periodic nanostructures based on monolayer colloidal crystals?MCC?can be viewed as 2D photonic crystals forbids propagation of certain wavelengths of visible light.This two-dimensional structure has the effect of enhanced transmission.The VO₂ and2D periodic nanostructures are combined to form a two-dimensional nanocomposite structure.By changing the condition of preparing VO₂ to realize the tunable of light response.This paper use self-assembly method to prepare single-layer SiO₂ sphere array simply and efficiently.We demonstrated a tunable photonic nanostructure,which is composed of vanadium dioxide?VO₂?thin film and silicon dioxide?SiO₂?ordered nanosphere arrays.The vanadium films were sputtered on two-dimensional?2D?SiO₂sphere arrays.VO₂ thin films were prepared by rapid thermal annealing?RTA?method with different oxygen flow rates.The close packed VO₂ shell formed a continuous surface,the composition of VO₂ films in the structure changed when the oxygen flow rates increased.The 2D VO₂/SiO₂ composite photonic crystal structure exhibited transmittance trough tunability and near infrared?NIR?transmittance modulation.When the oxygen flow rate increased from 3 slpm to 4 slpm,the largest transmittance trough can be regulated from 904 nm to 929 nm at low temperature,the transmittance troughs also appear blue shift when the VO₂ phase changes from insulator to metal.The composite nanostructure based on VO₂ films showed visible transmittance tunability,which would provide insights into the glass color changing in smart windows.We proposed a metamaterial absorber which is aimed to achieve a multiple broadband absorption and tunable absorption peak in the near-infrared region.The absorber is based on VO₂ semi-shell coated on the top of silica nano-particle array supported on the gold-reflective layer.Measured results show that the absorber has the multiple broadband with the absorption magnitudes more than 95%in the near infrared region.The absorption peaks can be tuned through the VO₂ phase transition from metallic phase to insulator phase in the short wavelength?before?=1500 nm?,when VO₂ is at the metallic state,an absorption band appears in the long wavelength?after?=1500 nm?.The optical properties of the structure are simulated by the finite difference time domain?FDTD?method.The simulation results closely match those of measured.The absorption intensity becomes stronger and absorption peaks have red shift with the increase of thickness of VO₂ semi-shell.The distribution diagram of the simulated electric field shows that the absorption occurs at the junction of the spherical shell and the interior of the sphere.