Epitaxial growth of BiFeO3 thin films by LPE and sol–gel methods (original) (raw)
2004, Journal of Magnetism and Magnetic Materials
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Growth of BiFeO3 thin films by chemical solution deposition: the role of electrodes
Physical chemistry chemical physics : PCCP, 2017
BiFeO3 (BFO) thin films were grown by chemical solution deposition on a range of electrodes to determine their role in controlling the phase formation and microstructure of the films. The crystallization on oxide electrodes followed the sequence: amorphous → Bi2O2(CO3) → perovskite, while those on Pt crystallized directly from the amorphous phase. IrO2 electrodes promoted perovskite phase formation at the lowest temperature and LaNiO3 additionally induced local epitaxial growth. All compositions exhibited fully coherent Fe-rich precipitates within the grain interior of the perovskite matrix, whereas the incoherent Bi2Fe4O9 second phase was also observed at the grain boundaries of BFO grown on Pt electrodes. The latter could be observed by X-ray diffraction as well as transmission electron microscopy (TEM) but coherent precipitates were only observed by TEM, principally evidenced by their Z contrast in annular dark field images. These data have pronounced consequences for the extende...
Preparation and Characterization of BiFeO 3 Thin Films by Sol-Gel Route
Synthesis of the precursors, using research grade materials and locally available facilities, is optimized in order to obtain a suitable sol for BiFeO 3. The optimally synthesized BiFeO 3 sol is then spun onto Cu and glass substrates to obtain films of thickness 100-300nm. Films are studied with the help of XRD, VSM, SEM, and Spectroscopic Ellipsometry. X-ray diffraction results show the formation of BiFeO 3 even in the as-deposited samples. However, some secondary phases were also present with high intensity. After annealing at 300 o C, secondary phases became less intense but could not be completely eliminated. Another BiFeO 3 sol was prepared by changing the solvents and by controlled addition of sodium oleate as ligand. Thin films, prepared using this sol, are single phased even in the as-deposited form. (110) preferred orientation of these BiFeO 3 thin films is achieved after annealing at 300 o C. Ferroelectric switching with a phase angle of 180 o is observed as a function of externally applied electric field. Ferromagnetic properties are also observed in these BiFeO 3 thin films. Dense nanostructure with uniformly distributed grains ~ 100 nm is observed by scanning electron microscope. Optical results show absorption in the blue and green region with a band gap ~ 2.7 eV. Dielectric constants of the films show dispersion in the range of 100Hz-1MHz. These results demonstrate that careful use of solvents and ligands can result in pure BiFeO 3 sol and then thin films; a promising candidate for memory and photovoltaic applications.
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