Highly infrared sensitive VO2 nanowires for a nano-optical device

Abstract

Recent studies on the electronic, magnetic and optical properties of VO₂ (vanadium dioxide) materials have motivated the exploration of one dimensional VO₂ nanowires. First principles calculations were performed to investigate the structural, electronic, magnetic and optical properties of the monoclinic (M) and rutile (R) phases of VO₂ nanowires. The monoclinic phase shows semiconducting behaviour with a band gap of 1.17 eV, whereas the rutile phase of VO₂ nanowires behaves as a spin gapless semiconducting material, as band lines cross the Fermi level due only to up spin contribution. The monoclinic structure of VO₂ nanowires is found to be paramagnetic and the rutile structure shows ferromagnetic half metal behavior. The conductivity calculation for VO₂ nanowires shows the metal–insulator transition (MIT) temperature to be 250 K. The possible mechanism of VO₂ nanowires to be used as smart windows has been discussed, as the nanowires are highly sensitive in the infrared (IR) region. Interestingly, at low temperature, the VO₂ monoclinic structure allows infrared light to be transmitted, while VO₂ with the rutile phase blocks light in the IR region. Furthermore, we adsorbed CO₂, N₂ and SO₂ gas molecules on 1D VO₂ monoclinic nanowire to investigate their interaction behaviour. It was observed that the absorption and transmission properties of VO₂ dramatically change upon the adsorption of CO₂ and SO₂ gas molecules, which is likely to open up its application as an optical gas sensor.