Bismuth ferrite bilayered thin films of different constituent layer thicknesses

Bilayered thin films consisting of (Bi0.90La0.10)(Fe0.85Zn0.15)O-3 and (Bi0.90La0.10)(Fe0.90Zn0.10)O-3 layers have been fabricated by radio frequency sputtering. Both multiferroic layers are well retained in these bilayers. Their leakage current, multiferroic properties, and fatigue behavior are largely dependent on the thicknesses of (Bi0.90La0.10)(Fe0.85Zn0.15)O-3. With an increase of the thickness in the (Bi0.90La0.10)(Fe0.85Zn0.15)O-3 layer, the leakage current density of bilayers is degraded due to different grain growth modes and an increase in oxygen vacancies, the dielectric constant (epsilon(r)) becomes larger due to the introduction of (Bi0.90La0.10)(Fe0.85Zn0.15)O-3 with a high epsilon(r) value, and their magnetic properties are deteriorated with increasing the thickness ratios of (Bi0.90La0.10)(Fe0.85Zn0.15)O-3 with a weaker magnetization. All bilayers exhibit a good ferroelectric behavior regardless of varying thicknesses of the (Bi0.90La0.10)(Fe0.85Zn0.15)O-3 layer, while their coercive field decreases with increasing the thickness of the (Bi0.90La0.10)(Fe0.85Zn0.15)O-3 layer. An anomalous enhancement in switchable polarization is demonstrated by these bilayers, owing to the involvement of space charges accumulated at the interfaces between two constituent layers. (C) 2011 Elsevier B.V. All rights reserved.