Tunable optical properties of nano-Au on vanadium dioxide

The optical properties of Au nanoparticles deposited on thermochromic thin films of VO₂ are investigated using spectroscopy. A localized modification on the transmittance spectrum of VO₂ film is formed due to the presence of Au nanoparticles which exhibit localized surface plasmon resonance (LSPR) in the visible-near IR region. The position of the modification wavelength region shows a strong dependence on the Au mass thickness and shifts toward the red as it increases. On the other hand, it was found that the LSPR of Au nanoparticles can be thermally tunable because of the thermochromism of the supporting material of VO₂. The LSPR wavelength, λ_SPR, shifts to the blue with increasing temperature, and shifts back to the red as temperature decreases. A fine tuning is achieved when the temperature is increased in a stepwise manner.