Growth and characterization of excimer laser-ablated BaBi₂Nb₂O₉ thin films

Abstract

The pulsed-laser ablation technique has been employed to deposit polycrystalline thin films of layered-structure ferroelectric BaBi₂Nb₂O₉ (BBN). Low-substrate-temperature growth (T_s=400° C) followed by ex situ annealing at 800° C for 30 min was performed to obtain a preferred orientation. Ferroelectricity in the films was verified by examining the polarization with the applied electric field and was also confirmed from the capacitance-voltage characteristics. The films exhibited well-defined hysteresis loops, and the values of saturation (P_s) and remanent (P_r) polarization were 4.0 and 1.2 µ C/cm², respectively. The room-temperature dielectric constant and dissipation factor were 214 and 0.04, respectively, at a frequency of 100 kHz. A phase transition from a ferroelectric to paraelectric state of the BBN thin film was observed at 220° C. The dissipation factor of the film was observed to increase after the phase transition due to a probable influence of dc conduction at high temperatures. The real and imaginary part of the dielectric constant also exhibited strong frequency dispersion at high temperatures.