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)center dot 5H(2)O), iron(III) nitrate nonahydrate (Fe(NO3)(3)center dot 9H(2)O), 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.