Expanded Thermochromic Color Changes in VO_2 Thin Film Devices Using Structured Plasmonic Metal Layers

摘要

We investigate metallic thin films on VO_2 and show that the magnitude of the reflected color change in that visible portion of the spectrum as VO_2 undergoes the insulating to metallic phase transition can be controlled by changing the type of metal, the thickness of the metal and by patterning the metal at the nano scale. We consider the role of surface plasmas in the metal film and show that in the near infrared, the magnitude of the reflectivity increase for metal coated VO_2 films, but decrease for uncoated VO_2 thin films. This is explained in the context of Fresnel equations and considering the large change in the imaginary part of the dielectric constant as the VO_2 changes state from the insulating to metallic phase.