Ferroelectric properties of SrRuO3∕BaTiO3∕SrRuO3 ultrathin film capacitors free from passive layers

Structural studies on ultrathin $\mathrm{Sr}\mathrm{Ru}{\mathrm{O}}_3∕\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_3∕\mathrm{Sr}\mathrm{Ru}{\mathrm{O}}_3$ capacitors, with $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_3$ thicknesses of between $5\mathrm{nm}$ and $30\mathrm{nm}$ , show well-defined interfaces between ferroelectric $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_3$ and electrode $\mathrm{Sr}\mathrm{Ru}{\mathrm{O}}_3$ layers. In these capacitors, we cannot observe any extrinsic electrical effects due to either the formation of an insulating interfacial passive layer or passive-layer-induced charge injection. Such high-quality interfaces result in very good fatigue endurance, even for the $5\mathrm{nm}$ thick $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_3$ capacitor.