High contrast thermochromic switching in vanadium dioxide (VO 2 ) thin films deposited on indium tin oxide substrates

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 2500 nm, 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 VO 2 films.