Evolution of structures and optical properties of vanadium oxides film with temperature deposited by magnetron sputtering

Abstract

In this study, mid infrared optical modulation property of VOx films with temperature was researched. VOx film which contain both VO2 and V2O5 was deposited on Al2O3 substrate by radio frequency magnetron sputtering. The mid infrared transmittance undergoes two reductions when increasing the temperature to 590 °C, the first reversible reduction around 68 °C as the phase transition of VO2 and the second irreversible gradually reduction starting around 350 °C because the oxidation state changed from V2O5 to VO2. The transmittance increased from 5.49% to 70.29% when cooling the temperature around 54℃. The film has the reversible 64% optical modulation around 60 °C during the second thermal cycling and keep stable even increased the temperature higher than 550 °C. The difference caused by high temperature thermal cycling in surface morphology structures, and chemical composition, were characterized by AFM, XRD, Raman, and XPS. The process of phase transition and the oxidation state changed during the thermal cycles were monitored with temperature dependent Raman spectra. This study provides new information about the transition between different structures and oxidation states of VOx film and a good candidate for infrared thermochromic window.