Multi Spectral Switchable Infra-Red Reflectance Resonances in Highly Subwavelength Partially Oxidized Vanadium Thin Films

TL;DR

This paper demonstrates switchable, passively tunable infrared reflectance resonances in highly subwavelength partially oxidized Vanadium thin films, enabling applications in multispectral imaging and thermal management.

Contribution

It introduces a novel multilayer Vanadium film structure exhibiting temperature and oxidation-duration tunable infrared resonances, modeled effectively with transfer matrix methods.

Findings

Infrared resonances can be switched with temperature at 68°C.

Resonance wavelengths are passively tunable by oxidation duration.

Model accurately captures dual reflectance resonances.

Abstract

Phase transition materials are promising for realization of switchable optics. In this work, we show reflectance resonances in the near-infrared and long-wave infrared wavelengths in highly subwavelength partially oxidized Vanadium thin films. These partially oxidized films consist of a multilayer of Vanadium dioxide and Vanadium as shown using Raman spectroscopy and four-probe measurements. As Vanadium dioxide is a phase transition material that shows insulator to metal phase transition at 68 C, the observed infra-red resonances can be switched with temperature into a high-reflectance state. The wavelength of these resonances are passively tunable as a function of the oxidation duration. The obtained reflectance resonance at near-infrared wavelength red shifts from 1.78 um to 2.68 um with increasing oxidation duration while the long-wavelength infrared resonance blue shifts from 12.68 um to 9.96 um. To find the origin of the reflectance resonances, we model the reflectance spectra as a function of the oxidation duration using the transfer matrix method. The presented model captures the dual reflectance resonances reasonably well. These passive wavelength-tunable and switchable resonances with easy to fabricate lithography-free multilayer structure will be useful for multispectral applications such as camouflage, spectral selective microbolometer, and thermal management.