Microwave-Assisted Hydrothermal Synthesis of BiFe_xCr_1–xO₃ Ferroelectric Thin Films

We synthesize ferroelectric BiFe_xCr_1–xO₃ thin films by microwave-assisted hydrothermal synthesis on (111) oriented Nb-doped SrTiO₃ substrates. Bi­(NO₃)₃, Fe­(NO₃)₃, Cr­(NO₃)₃, and KOH are used in the precursor solution, along with deionized water. Combination of Raman and X-ray photoelectron spectroscopies confirmed the incorporation of chromium into the rhombohedral structure of BiFeO₃. The effect of deposition time on the surface morphology and the ferroelectric properties of the films are analyzed. This reveals that if the deposition goes on beyond completion of the reaction (10 min at 120 W), the ferroelectric properties of the film deteriorate due to stoichiometry changes. Through piezoresponse force microscopy, we show that Cr significantly deteriorates the film retention, which cannot be recovered by thermal annealing.