Pulsed laser deposition of Mo-V-O thin films for chromogenic applications

Mo-V-O thin films were prepared by pulsed laser deposition (PLD) technique at an oxygen pressure of 13.3 Pa and room temperature on glass and Indium tin oxide (ITO)/glass substrates from (MoO3)(1 - x)(V2O5)(x) (x = 0, 0.09, 0.17,0.23, 0.29) targets. We studied the effect of V2O5 counterpart on the growth characteristics of Mo-V-O thin films and coloring switching properties including thermochromic, gasochromic, photochromic and electrochromic. Surface morphology, surface chemical states, optical and electrochemical properties were examined using atomic force microscope (AFM), field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), UV-Vis spectroscopy and electrochemical impedance spectroscopy (EIS). Morphological characterizations illustrated porous cauliflower-like surface for the thin films and a columnar growth was observed in which surface roughness varied by x. XPS spectra showed that Mo surface composition for all the samples are Mo6+ and V composition at x = 0.09 is a combination of V4+ and V5+ states. At the other stoichiometries the main state was V5+. Moreover, XPS and EDS revealed that V:Mo molar ratio in a deposited film is smaller than in the target used for. It was found that there is a relation between the vanadium valance states and the optical band gap as well as chromogenic properties. (C) 2016 Elsevier B.V. All rights reserved.