High contrast thermochromic switching in vanadium dioxide (VO2) thin films deposited on indium tin oxide substrates

Abstract

Vanadium dioxide thin films with excellent thermochromic switching properties were deposited on indium tin oxide (ITO)-coated glass substrates with the RF magnetron sputtering technique. Reversible transmission switching of these films from as much as 65% to near zero at 2500nm, with contrast ratios of more than 3000, was observed. These films compare favorably to those deposited on glass slides, and, in particular, show a resistivity drop of nearly 2 orders of magnitude upon switching to the metallic state. Inducing the metal–insulator transition by electrical current through the ITO layer lowers the transition temperature by 4–7°C, as compared to traditional heating of the sample by a heating plate. The presence of an ITO sublayer also seems to result in smaller grain size and slightly broader hysteresis in VO2 films.