Epitaxial BiFeO3 thin films on Si

${\mathrm{BiFeO}}_3$ was studied as an alternative environmentally clean ferro/piezoelectric material. $200\text{-}\mathrm{nm}$ -thick ${\mathrm{BiFeO}}_3$ films were grown on $\mathrm{Si}$ substrates with ${\mathrm{SrTiO}}_3$ as a template layer and ${\mathrm{SrRuO}}_3$ as bottom electrode. X-ray and transmission electron microscopy studies confirmed the epitaxial growth of the films. The spontaneous polarization of the films was $\sim 45\mu \mathrm{C}∕{\mathrm{cm}}^2$ . Retention measurement up to several days showed no decay of polarization. A piezoelectric coefficient $\left(d_{33}\right)$ of $\sim 60\mathrm{pm}∕\mathrm{V}$ was observed, which is promising for applications in micro-electro-mechanical systems and actuators.