Pulsed laser deposition of ferroelectric Sr4Bi4Ti7O24 thin films

Ferroelectric thin films of Sr4Bi4Ti7O24 (SBTi) were prepared on Pt-coated Si substrates by pulsed laser deposition (PLD). Crystallinity of the films was analyzed by X-ray diffraction (XRD), which indicated that the films were consisted of (001)- and (100)-oriented grains. Surface of the films was dense and crack-free, and no large droplets were observed by atomic force microscopy (AFM). Scanning electron microscopy (SEM) measurements revealed that the interface between Pt bottom electrode and film was sharp and thickness of the column-like grown thin films was about 700 nm. At an applied electrical field of 140 kV/cm, the films showed good hysteresis loop with remnant polarization (2Pr) and coercive field (2Ec) of 8.1 μC/cm2 and 37.5 kV/cm, respectively. Good fatigue-free property with ∼10% decrease of nonvolatile polarization up to 2.2×109 switching cycles was exhibited experimentally.