Banca de QUALIFICAÇÃO: FRANCISCO DE ASSIS ARAÚJO BARROS

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE: FRANCISCO DE ASSIS ARAÚJO BARROS
DATA: 13/07/2026
HORA: 08:30
LOCAL: Auditório do PPGQ
TÍTULO: Influence of plasma doping on monoclinic γ-WO₃ thin films: investigation of structural, morphological, and topographical properties
PALAVRAS-CHAVES: Ar/H2/N2 plasma treatment. N doping, oxygen vacancies. Lattice distortion. Surface properties.
PÁGINAS: 44
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Físico-Química
RESUMO:

This study demonstrated an efficient and environmentally friendly approach to doping monoclinic γ-WO₃ thin films with nitrogen and oxygen vacancy defects via sputtering, using a hybrid Ar/H₂/N₂ plasma under various time and mild conditions. The monoclinic phase of γ-WO₃ was obtained by a modified polymer precursor synthesis method, deposited onto FTO via drop casting, followed by heat treatment. This study investigates the structural, morphological, and topographical evolution of monoclinic γ-WO₃ thin films. X-ray diffraction analysis revealed the presence of the monoclinic phase of γ-WO₃ in the electrodes of both the pure and doped thin films. Doping does not cause peak broadening and preserves phase purity. The reliability indices R_p and R_wp obtained from the Ritveld refinement signal the distortion of the crystal lattice with significant voluminous expansion and readjustment in the β angle to adapt to the stresses in the lattice after plasma treatment. Raman spectroscopy analysis confirmed the presence of lower valence W⁵⁺ ions, as well as displacements and changes in the intensities of the characteristic vibrations in the γ−WO₃ films after plasma exposure, which signify changes in the coordination environment of the W atom after plasma treatment via sputtering. The reduction in FWHM width suggests a restructuring and improvement of the original symmetry and crystallinity following plasma treatment. Morphological analysis (SEM) suggests that doping induces a morphological rearrangement and reveals multilayered aggregates of irregular sizes. The sizes of the nanocrystals decrease progressively from FTO|WO₃ (∽112.9 nm) to the FTO|W-60 sample (∽59.1 nm), in addition to a reduction in film thickness due to the compaction of the nanocrystals as doping increases. On the other hand, 2D and 3D topographical analysis of the local surface (AFM) reveals high roughness for pristine FTO|WO₃ (RMS ∽12.96 nm). The doped samples exhibit smoother and finer peaks, revealing a reduction in the roughness of the doped films, particularly for FTO|W-10 (RMS ∽3.695 nm). These results demonstrate that N doping and oxygen vacancies synergistically modulate the properties of monoclinic γ-WO₃ films. In addition, the results indicate that the use of a hybrid Ar/H₂/N₂ plasma is suitable for the beneficial modification of monoclinic γ-WO₃ films, paving the way for their promising use in energy storage systems.

MEMBROS DA BANCA:
Presidente - 756.***.***-91 - GERALDO EDUARDO DA LUZ JUNIOR - UESPI
Interno - 2363808 - EDMILSON MIRANDA DE MOURA
Interno - 2351244 - JEAN CLAUDIO SANTOS COSTA
Interno - 1714193 - JOSE MILTON ELIAS DE MATOS
Externo ao Programa - 6276167 - ROMULO RIBEIRO MAGALHÃES DE SOUSA
Externo à Instituição - 027.***.***-64 - REJANE MARIA PEREIRA DA SILVA - UESPI