Preparation and electrical properties of BiFeO₃ films by RF magnetron sputtering

Mn-substituted BiFeO₃(BFO) thin films were prepared by r.f. magnetron sputtering under an Ar/O₂ mixture of various deposition pressures at room temperature. The effects of the deposition pressure and annealing temperature on the crystallization and electrical properties of BFO films were investigated. X-ray diffraction patterns revealed that BFO films were crystallized for films annealed above 500 °C. BFO films annealed at 550 °C for 5 min in N₂ atmosphere exhibited the crystallized perovskite phase. The (Fe+Mn)/Bi ratio decreased with an increase in the deposition pressure due to the difference of sputtering yield. The grain size and surface roughness of films increased with an increase in the deposition pressure. The dielectric constant of BFO films prepared at various conditions shows 127-187 at 1 kHz. The leakage current density of BFO films annealed at 500 °C was approximately two orders of magnitude lower than that of 550 oC. The leakage current density of the BFO films deposited at 10-30 m Torr was about 5×10^-6-3×10^-2 A/cm² at 100 kV/cm. Due to the high leakage current, saturated P-E curves were not obtained in BFO films. BFO film annealed at 500 °C exhibited remnant polarization(2Pr) of 26.4 μC/cm² at 470 kV/cm.