Influence of Thermal Annealings in Argon on the Structural and Thermochromic Properties of $$\mathrm{MoO}_{3}$$ MoO 3 Thin Films

Abstract

The effect of thermal annealing in an inert atmosphere (argon) on the structural and thermochromic properties of \(\hbox {MoO}_{3}\) thin films was investigated. \(\hbox {MoO}_{3}\) thin films were deposited by thermal evaporation in vacuum of \(\hbox {MoO}_{3}\) powders. X-ray diffraction patterns of the films showed the presence of the monoclinic Magneli phase \(\hbox {Mo}_{9}\hbox {O}_{26}\) for annealing temperatures above \(250\,{^{\circ }}\hbox {C}\). Absorbance spectra of the films annealed in argon indicated that their thermochromic response increases with the annealing temperature in the analyzed range (23 \({^{\circ }}\hbox {C}\)–300 \({^{\circ }}\hbox {C}\)), a result opposite to the case of thermal annealings in air, for which case the thermochromic response shows a maximum value around 200 \({^{\circ }}\)C–225 \({^{\circ }}\)C and decreases for higher temperatures. These results are explained in terms of a higher density of oxygen vacancies formed upon thermal treatments in inert atmospheres.