Ferroelectric polarization switching kinetics process in Bi _0.9La_0.1FeO₃ thin films

Bi_0.9La_0.1FeO₃ (BLFO) thin films with the thickness of ∼500 nm were deposited on (001) oriented SrTiO₃ substrate with 30 nm LaNiO₃ as buffer layer. The switching kinetics process of ferroelectric BLFO thin films was investigated by using pulse voltages. The result shows that one dimension and two dimensions are the prior grown modes of BLFO domains in the polarization switching process. The dimensionality of the domain growth n increases linearly with applied voltage, and the grown model varies from 1 D (n = 1, implies needlelike growth) to 2 D (n = 2, planar growth) with electric pulses increasing. This is explained due to the increase in the density of nucleating domains at high fields where sideway growth is limited. The higher value of n can be an indication of non-homogeneous distribution of domain nuclei. Under all our experimental conditions that the switching time t_sw is instrumentally limited and therefore the intrinsic switching time of ferroelectric BLFO films is smaller than several nanoseconds. This very short polarization switching time can be explained as a switching mechanism controlled by nucleation rate. Considering the domain walls de-pinning and thermal disturbance, the saturated polarization increases with the temperature increasing under the same input voltage which in turn affects the he switching transient current and switching time.