Synthesis and Characterization of Polycrystalline Bifeo3 Deposited by Sol-Gel Technique

A thin film of BiFeO3 (BFO) was fabricated on an FTO/glass substrate using the sol-gel method and applying a sequential layered deposition process. The raw materials used in the starting solution were bismuth nitrate pentahydrate (Bi(NO3)3·5H2O), iron(III) nitrate nonahydrate (Fe(NO3)3·9H2O), and ethylene glycol (HOCH2CH2OH) as solvent. A 5 mol% excess of bismuth was used to compensate for its volatility during high-temperature annealing. Structural analysis by High-Resolution X-Ray Diffraction and Raman Spectroscopy indicated that the film exhibits a rhombohedral distorted perovskite structure without impure phases. Raman spectroscopic analysis showed 13 Raman phonon active modes (4A1 + 9E) corresponding to the rhombohedral structure R3c. The morphological study using Scanning Electron Microscopy (SEM) revealed a surface formed by agglomerations of grains with a certain degree of porosity. The thickness of the BFO film obtained from the cross-sectional image indicated an approximate thickness of 555 nm. Analysis of XPS spectra revealed the coexistence of Fe2+/Fe3+ ions in the film. The optical study showed that the film has a maximum transmittance of 66% in the visible region. The estimated value of E_g was 2.33 eV, which is consistent with those reported for BFO thin films by other researchers. In our study, it was found that the leakage current is a consequence of oxygen vacancies induced mainly by the volatilization of Bi and the presence of Fe2+ ions.