CaBi₂Ta₂O₉ ferroelectric thin films prepared by pulsed laser deposition

Abstract

Thin films of CaBi₂Ta₂O₉ (CBT) were deposited on Pt/TiO₂/SiO₂/Si substrates using the pulsed laser deposition technique at temperatures ranging from 500 to 700° C. The presence of (115) and (0010) orientations confirm the phase formation at the lower temperature (500° C). Microstructure evolution of CBT films with oxygen pressure of 100-200 mTorr at a substrate temperature of 650° C shows that the films deposited at lower pressure have a relatively smaller grain size and less surface roughness. The films grown at 650° C exhibited a maximum polarization of (2P_m) 17 µ C/cm², remanent polarization of (2P_r) 8 µ C/cm² and coercive field of (E_c) 128 kV/cm, with fatigue endurance up to 10¹⁰ switching cycles. The higher dielectric constant (~115 at 100 kHz) with a relatively lower dissipation factor (0.02) at higher growth temperature (700° C) was explained by the increased grain size. The higher leakage current density (~10^-7 A/cm²) at higher deposition temperature is attributed to the interfacial diffusion of the film and the substrate.