Ferroelectric and dielectric properties of bismuth ferrite based thin films by Pulsed Laser Deposition

Abstract

BiFeO₃ (BFO) has stimulated a great interest in recent years for its room temperature multiferroic behavior with very high remnant polarization. However, the leakage current of BFO films is very high. To lower the leakage current, we have developed thin films with following target compositions on SrRuO₃ buffered on SrTiO₃ substrate by Pulsed Laser Deposition (PLD): (A) BiFeO₃, (B) 0.88Bi_0.5Na_0.5TiO₃-0.08Bi_0.5K_0.5TiO₃-0.04BaTiO₃, (C) 0.6BiFeO₃-0.4(Bi_0.5K_0.5TiO₃) The phase, growth orientation, microstructural characterization and electrical properties were investigated as a function of deposition parameters. The epitaxial bi-layered 300nm BNT-BKT-BT/BFO thin films (150nm each) exhibited ferroelectric behavior as: 2P_r = 44.0 μC.cm^-2, 2E_c = 200 kV.cm^-1 and K = 140. Thin films with a composition of 0.6BFO-0.4BKT have also been deposited with different oxygen pressures of 300-500 mTorr. Preliminary results of 0.6BFO-0.4BKT films show that the leakage current can be suppressed by about 4 orders of magnitude which in turn improves the ferroelectric and dielectric properties of the films. It is observed that the remnant polarization increases from 8 to 19 μC.cm^-2 as the oxygen pressure is changed from 500 to 300mtorr.