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

Emmanouil Gagaoudakis1, 2*, Giannis Michail2, Elias Aperathitis2, Ioannis Kortidis2, Vassilios Binas2, Marianthi Panagopoulou3, Yannis S. Raptis3, Dimitris Tsoukalas3, George Kiriakidis1,2

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

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 Tc = 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 ΔTrsol = 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 Trlum = 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

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