Vanadium pentoxide thin films are prepared by the sol-gel route by dissolving V 2 O 5 powder (99.5% purity) in H 2 O 2 solution. The solution is spin-coated on glass substrates for optical (UV-VIS-NIR) and XRD analysis, and on ITOcoated glass substrates for electrochromic measurements. The samples are then annealed at 150 C for 1 hour. The resulting films have a yellow-orange color, typical of polycrystalline V 2 O 5 . XRD measurements have shown that after annealing in air at 400 C the structure of the films has a c-axis preferred orientation, the (0 0 1)-type planes lying parallel to the substrate. SEM analysis revealed a smooth surface. The films' optical and physical constants (n, a, Eg, the thickness d and the mean thickness inhomogeneity s) are calculated using a simple and accurate method based on the transmission spectrum alone. The films' electrochromism is studied using cyclic voltammetry (CV) and chronoamperometry in propylene carbonate solution containing 1 mol=l LiClO 4 . The films show reversible multichromism (yellow-green-blue) upon Li þ ion insertion=extraction. The absorbance of films colored at three different potentials is measured in the UV-VIS-PIR wavelength range, and this study shows that the changes in the optical absorption are consistent with the film color changes. Finally, the optical and electrochromic properties of the films prepared by this method are compared with those of our sputtered films already studied and with other works.
Nanocrystalline TiO 2 thin films were prepared by spin coating on covered glass substrates with an indium tin oxide (ITO) layer. The structural, electrochromic and optical properties of the films were investigated. The films are crystallized predominantly in the anatase phase with lattice parameters a ¼ b ¼ 0.378 nm and c ¼ 0.958 nm. The crystallite size was found to be of the order of 14 nm. The films showed reversible coloration=bleaching cycles as demonstrated by cyclic voltametry and current-time transients. The transmission of the blue colored films decreased and their absorption edge was less sharp and shifted to higher wavelengths as a result of the intercalation of Li þ ions.
The lithiated/delithiated vanadium pentoxide films deposited by sol-gel spin coating on indium tin oxide-coated glass substrates were analyzed by sputter-induced photon spectroscopy, X-ray diffraction, and optical absorption techniques. First, it is shown that the crystalline structure of where Li + ion is the host material and x the molar intercalation fraction.During the intercalation reaction, the vanadium atoms are considered to be partially reduced from V 5+ to V 4+ formal oxidation state, when 0 ≤ x ≤ 1. 6 The insertion/deinsertion processes of Li ions into V 2 O 5 matrix are often accompanied by electronic structure changes. V 2 O 5 as base material is semiconductor characterized by an energy gap and Na x V 2 O 5 10 deposited by physical vapor deposition technique.Note that these results were obtained by photoelectron spectroscopy (XPS and UPS). Concerning the deposition methods, they were listed by Granquist. 11 Besides, the properties of V 2 O 5 films show strong dependence on the synthesis procedures. Furthermore, the intercalation of lithium ions into V 2 O 5 leads to several changes in the electronic structure and optical and electrical properties. Hence, various electroanalytical techniques [12][13][14] have been used to explain the mechanisms of Li intercalation into this oxide.Using X-ray diffraction (XRD), optical absorption spectroscopy, and sputter-induced photon spectroscopy (SIPS) techniques, we investigate in this study the effect of Li insertion and deinsertion on the host lattice of V 2 O 5 thin film prepared by sol-gel spin coating procedure.The structure and optical absorption properties of clean, intercalated, and deintercalated V 2 O 5 films are discussed. The luminescence spectra resulting from 5 keV Kr + ion bombardment are also reported. The observed lines are all identified, and their intensities before and after
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