Reducing hysteresis in Pb(Mg0.33Nb0.67)O3–PbTiO3 thin-film heterostructures by electronic contact engineering

This study demonstrates the importance of electronic contacts in obtaining low hysteresis in Pb(Mg0.33Nb0.67)O3–PbTiO3 (PMN-PT) based thin-film ferroelectric/piezoelectric devices. Our results show that the electronic contact significantly affects both the polarization and displacement responses: capacitors with a PMN-PT layer directly in contact with a metallic La-doped BaSnO3 (LBSO) electrode layer exhibit strong hysteresis. In contrast, nearly ideal relaxor ferroelectric responses with significantly reduced hysteresis were observed for capacitors with an ultrathin metallic SrRuO3 layer between the LBSO and the PMN-PT. To explain the observed hysteresis differences, we employed a phenomenological model that assumed the presence of a dielectric layer at the LBSO/PMN-PT interface. This model qualitatively describes the measured polarization loops and attributes the increased hysteresis to processes of charge exchange across the interfacial dielectric layer. We speculate that the dielectric layer is primarily due to the initial growth layer of the PMN-PT film rather than to extended screening in the LBSO layer, as the thickness of the interfacial dielectric layer as derived from the model differs significantly from the Thomas–Fermi screening length of LBSO. Furthermore, we present band diagrams to provide qualitative insight into how charge exchange across the interfacial dielectric layer impacts the band structure and hysteresis of the PMN-PT heterostructure.