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Open AccessArticle

Study of the Thermal Annealing on Structural and Morphological Properties of High-Porosity A-WO3 Films Synthesized by HFCVD

1
Doctorado en Nanociencias y Micro-Nanotecnologías, UPIBI, Instituto Politécnico Nacional, Ciudad de México 07340, Mexico
2
Departamento de Biociencias e Ingeniería, CIIEMAD, Instituto Politécnico Nacional, Ciudad de México 07340, Mexico
3
Centro de Investigación en Fisicoquímica de Materiales, ICUAP, Benemérita Universidad Autónoma de Puebla, Edificio VAL.3, Eco Campus Valsequillo, San Pedro Zacachimalpa, Puebla 72960, Mexico
4
Centro de Nanociencias y Micro y Nanotecnologías, Instituto Politécnico Nacional, Ciudad de México 07738, Mexico
*
Authors to whom correspondence should be addressed.
Nanomaterials 2019, 9(9), 1298; https://doi.org/10.3390/nano9091298
Received: 25 July 2019 / Revised: 31 August 2019 / Accepted: 4 September 2019 / Published: 11 September 2019
High-porosity nanostructured amorphous tungsten OXIDE (a-WO3) films were synthesized by a Hot Filament Chemical Vapor Deposition technique (HFCVD) and then transformed into a crystalline WO3 by simple thermal annealing. The a-WO3 films were annealed at 100, 300, and 500 °C for 10 min in an air environment. The films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-Raman spectroscopy, high-resolution transmission electron microscopy (HR-TEM), and UV–vis spectroscopy. Results revealed that the a-WO3 films were highly porous, composed of cauliflower-like structures made of nanoparticles with average sizes of 12 nm. It was shown that the effect of annealing on the morphology of the a-WO3 films leads to a sintering process. However, the morphology is conserved. It was found that at annealing temperatures of 100 °C, the a-WO3 films are of an amorphous nature, while at 300 °C, the films crystallize in the monoclinic phase of WO3. The calculated bandgap for the a-WO3 was 3.09 eV, and 2.53 eV for the film annealed at 500 °C. Finally, the results show that porous WO3 films preserve the morphology and maintain the porosity, even after the annealing at 500 °C. View Full-Text
Keywords: HFCVD; a-WO3; porous tungsten oxide films HFCVD; a-WO3; porous tungsten oxide films
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Cruz-Leal, M.; Goiz, O.; Chávez, F.; Pérez-Sánchez, G.F.; Hernández-Como, N.; Santes, V.; Felipe, C. Study of the Thermal Annealing on Structural and Morphological Properties of High-Porosity A-WO3 Films Synthesized by HFCVD. Nanomaterials 2019, 9, 1298.

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