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2015
Santos, L., P. Wojcik, J. V. Pinto, E. Elangovan, J. Viegas, L. Í. Pereira, R. Martins, and E. Fortunato, "Structure and Morphologic Influence of WO3 Nanoparticles on the Electrochromic Performance of Dual-Phase a-WO3/WO3 Inkjet Printed Films", Advanced Electronic Materials, pp. n/a-n/a, 2015. AbstractWebsite

The optimization of tungsten trioxide (WO3) nanoparticles produced via hydrothermal synthesis for application in electrochromic (EC) devices is reported. The structure and morphology of the nanoparticles are controlled by changing the acidity of the aqueous solvent added to the sol-gel precursor (peroxopolytungstic acid) during synthesis. Orthorhombic hydrated WO3 nanorods or monoclinic WO3 nanoslabs are obtained when HCl is added, while synthesis only in aqueous medium results in a mixture of both types of polymorphs. Dual-phase thin films are processed by inkjet printing deposition of the nanoparticles in flexible polyethylene terephthalate substrate with indium tin oxide coating (ITO PET) followed by the deposition of the precursor solution. When compared with purely amorphous tungsten oxide films, the dual phase ones present higher optical densities and improved capacity, and cyclability stability. The best results, obtained for orthorhombic hydrated nanoparticles (ortho-WO3·0.33H2O), are due to its high surface area and improved conductivity. Additionally, the ex situ X-ray diffraction (XRD) lithiation studies show evidence of a higher distortion of the monoclinic when compared with the orthorhombic crystallographic structure, which contribute to the inferior EC performance. These results validate the use of inkjet printing deposition with low processing temperatures for EC dual-phase thin films containing optimized nanoparticles which are compatible with low-cost substrates.

2013
Santos, R., J. Loureiro, A. Nogueira, E. Elangovan, J. V. Pinto, J. P. Veiga, T. Busani, E. Fortunato, R. Martins, and I. Ferreira, "Thermoelectric properties of V2O5 thin films deposited by thermal evaporation", Applied Surface Science, vol. 282, pp. 590-594, 2013. AbstractWebsite
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2012
Figueiredo, V., E. Elangovan, R. Barros, J. V. Pinto, T. Busani, R. Martins, and E. Fortunato, "{p-Type Cu x O Films Deposited at Room Temperature for Thin-Film Transistors}", Journal of Display Technology, vol. 8, no. 1, pp. 41–47, 2012. Abstract

Thin-films of copper oxide @Cu OA were sputtered from a metallic copper (Cu) target and studied as a function of oxygen partial pressure @O??A. A metallic Cu film with cubic structure obtained from 0{%} O?? has been transformed to cubic CuPO phase for the increase in O?? to 9{%} but then changed to monoclinic CuO phase (for O?? PS7). The variation in crystallite size (calculated from x-ray diffraction data) was further substantiated by the variation in grain size (surface microstruc- tures). The Cu O films produced with O?? ranging between 9{%} and 75{%} showed p-type behavior, which were successfully applied to produce thin-film transistors.