Enhanced energy storage properties in relaxor Pb(Mg1/3Nb2/3)O3-PbTiO3 thin-film capacitors by incorporating buffer layers

Recently, relaxor ferroelectric thin-film capacitors have attracted considerable attention for energy storage applications since their slim-type polarization–electric field hysteresis loops can yield large recoverable energy density (Wrec) and high efficiency (η). In this work, we study the effects of buffer layers on energy storage properties of 0.93Pb(Mg1/3Nb2/3)O3-0.07PbTiO3 (PMN-PT) thin-film capacitors with a 5 nm-thick SrTiO3 (STO) and LaAlO3 (LAO) films. The energy storage properties of Pt/PMN-PT/SrRuO3 (SRO) capacitors are found to be significantly changed by incorporating the STO or LAO buffer layer at the top Pt/PMN-PT interface, while inserting the buffer layer at bottom PMN-PT/SRO interface shows negligible effects on the electrical properties. Specifically, with the STO buffering, the breakdown field is dramatically increased in the Pt/STO/PMN-PT/SRO capacitor due to the existence of an internal field in the STO, which prevents the growth of electrical trees from the bottom SRO to the top Pt electrode, and a large Wrec of ∼48.91 J/cm3, more than three times of that of the PMN-PT capacitor, is achieved. However, buffered by the LAO, the Pt/LAO/PMN-PT/SRO capacitor exhibits a reduced relaxor character, which may be ascribed to a pinning effect of nanodomains associated with the charged LAO/PMN-PT interface. As a result, both Wrec and η are significantly lowered, compared to the non-buffered PMN-PT capacitor. These results provide physical insights into the modulation of relaxor and dielectric behaviors by designing the characteristics of buffer layers, demonstrating a way for enhancing energy storage properties in thin-film capacitors.