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Vanadium oxide (VO x ) thin films were deposited at various substrate temperatures ( T s ) by spray pyrolysis technique using 0.05 M vanadyl acetylacetonate precursor. V 4 O 9 films are formed at T s = 300 °C, while mixed V 2 O 5 phases are formed at higher T s (400 and 500 °C). Annealing in forming gas of V 4 O 9 films shows the formation of higher content of thermochromic VO 2 phase than V 2 O 5 films. V 4 O 9 films show little higher electric resistivity ( ρ ), higher temperature coefficient of resistance ( TCR ), and higher thermal carrier activation energy ( E a ) than V 2 O 5 films. Annealed VO x films show a 2–3 order of magnitude change in ρ , optical transmission switch of 19–39%, and higher E a than the as deposited films. Annealed films deposited at T s = 500 °C presents a high TCR of −4.6%K −1 . Optical absorption, electronic transitions, and energy gaps of the formed VO x phases have been discussed in relation to its electronic band structure. [ABSTRACT FROM AUTHOR]

Abstract: Corundum (hexagonal) structure indium tin oxide (h-ITO) nanocrystals have been synthesized by subjecting an aqueous solution of In and Sn chlorides (Sn/In 8wt.%) to a hydrothermal process followed by annealing at 450°C in forming gas for 1h. The annealing temperature was selected based on thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA) of the dried precipitated powder, which showed a stable weight and phase at temperatures above 420°C. X-ray diffraction (XRD) patterns showed the formation of orthorhombic InOOH precipitates that is transformed, after annealing, into h-ITO nanocrystals with 32nm average crystal size. For nanostructure film deposition, dispersed sols of the prepared nanocrystals were spun coated on glass substrates. The films were densified by UV irradiation, whilst four-probe method was used to measure its sheet resistance. A sheet resistance as low as 10.6kΩ□ have been reached. Scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM) showed that the films have high surface roughness and nanopores. The transmittance spectra of the nanostructure films were measured in the UV–vis–NIR wavelength range. In addition to its low resistivity, nanostructure h-ITO films showed a wide range of transparency. [Copyright &y& Elsevier]