Polarization evolution in ferroelectric thin films at different electrode interfaces without strain

Abstract

Ferroelectric materials show significant potential for application in ferroelectric random access memory, sensors, and transducers. With the demand for electronic devices scaling down in size, ferroelectrics are being increasingly produced as nanoscale films. However, in ultrathin films, polarization tends to decrease significantly due to depolarization fields caused by incomplete charge screening at the interfaces, which poses challenges for their integration into electronic devices. To address this, we investigated the effects of different electrode and film interfaces, including Nb:SrTiO₃/PbTiO₃ (Nb:STO/PTO), SrRuO₃/PbTiO₃ (SRO/PTO), La_0.7Sr_0.3MnO₃/PbTiO₃ (LSMO/PTO), and LaCoO₃/PbTiO₃ (LCO/PTO). Using aberration-corrected scanning transmission electron microscopy, we analysed these interfaces and found that the PTO films grown on the LSMO and LCO electrode exhibited a sharp increase in polarization, while the PTO film grown on SRO exhibited a marked decrease. Consequently, LSMO/PTO was proven to have the highest polarization, followed by Nb:STO/PTO, with SRO/PTO having the lowest. This behaviour was further confirmed through piezoresponse force microscopy. These findings indicate that ferroelectric polarization at epitaxial interfaces can be fine-tuned through atomic-level control of the interface structure, yielding possibilities for designing nanoscale ferroelectric devices with interfacial properties.