Ferroelectric properties of Sr2Bi4Ti5O18 thin films

Bi-based layered ferroelectric thin films of ${\mathrm{Sr}}_{\mathrm{2}}{\mathrm{Bi}}_{\mathrm{4}}{\mathrm{Ti}}_{\mathrm{5}}{\mathrm{O}}_{\mathrm{18}}$ (SBTi) were prepared by pulsed-laser deposition. The $c$ -axis-oriented SBTi films were grown on ${\mathrm{SrRuO}}_{\mathrm{3}}$ seeded ${\mathrm{Pt/TiO}}_{\mathrm{2}}{\mathrm{/SiO}}_{\mathrm{2}}\mathrm{/Si}$ substrates while polycrystalline SBTi films were grown on ${\mathrm{Pt/TiO}}_{\mathrm{2}}{\mathrm{/SiO}}_{\mathrm{2}}\mathrm{/Si}$ substrates. The measurements of ferroelectricity revealed that the direction of spontaneous polarization was not along the $c$ axis since the polarization of $c$ -axis-oriented films was much less than that of randomly oriented films. There was no significant degradation of switchable charge at least up to ${10}^{11}$ cycles for the randomly oriented films, suggesting that, even with Ti which was widely accepted to contribute to the fatigue of ${\mathrm{Pb(Zr, Ti)O}}_{\mathrm{3}},$ SBTi showed superior fatigue characteristics. The randomly oriented films also showed excellent retention characteristics after ${10}^5 \mathrm{s}.$