Low temperature rf-sputtered thermochromic VO2 films on flexible glass substrates

¹Physics Department, University of Crete, P.O. Box 2208, 71003 Heraklion, Crete, Greece

²Institute of Electronic Structure & Laser (IESL), Foundation for Research and Technology (FORTH) Hellas, P.O. Box 1385, Heraklion 70013, Crete, Greece

³School of Applied Mathematical and Physical Sciences, National Technical University of Athens, GR 157 80, Zografou Campus, Athens, Greece

Adv. Mater. Lett., 2017, 8 (7), pp 757-761

DOI: 10.5185/amlett.2017.6934

Publication Date (Web): May 23, 2017

Copyright © IAAM-VBRI Press

E-mail: mgagas@iesl.forth.gr

Abstract

The high deposition temperature of the order of 400 ^oC and more is requirement for the growth of the thermochromic phase of vanadium dioxide (VO₂), limits the type of substrates that one may grow them on only to rigid ones. In this work, thermochromic VO₂ films were successfully deposited on flexible Corning® Willow® glass substrates, without the use of a buffer layer, by rf sputtering at a substrate temperature of 300 ^oC, one of the lowest for this technique ever reported. The critical transition temperature of 80 nm thin films was T_c = 50.7 ^oC, transmittance hysteresis width was ΔT = 12.1 ^oC, while the modulation of the transmittance at λ = 2000 nm measured at 25 ^oC and 90 ^oC was around 36%, leading to a solar modulation of ΔTr_sol = 5%. In addition, an increase in transmittance at λ = 600nm (visible region) of 4% was observed before and after heating, while integrated luminous transmittance remained almost constant at Tr_lum = 34%. The thermochromic and luminous characteristics of the VO₂ films deposited on flexible glass are comparable to those deposited on rigid glass substrates. The deposition of thermochromic VO₂ film on flexible glass substrates by sputtering technique opens up a new window for thermochromic applications on flexible substrates.

Keywords

Thermochromic VO₂, rf sputtering, flexible glass substrate, low deposition temperature