Electrostriction, Electroresistance, and Electromigration in Epitaxial BaTiO₃‑Based Heterostructures: Role of Interfaces and Electric Poling

Ferroelectric materials hold significant promise for potential applications in a number of fields including spintronics and solar energy harvesting. When integrating them into heterostructures, it becomes of crucial importance to master the ferroelectric properties and to determine the influence of adjacent materials (substrates and/or top layers). We studied the role of interfaces on the ferroelectric properties of BaTiO₃-based heterostructures elaborated on 1 atom % Nb:SrTiO₃ (001) and Pt (001) substrates. Poled patterns were found to be more stable in time and shape for sandwich structures when the BaTiO₃ layer is covered by a nonferroelectric oxide layer due to interface screening. Significant topography deformations occur when poling was performed with voltages above a threshold value and were found undoubtedly depending on both the nature of the substrate and the voltage polarity. Maximum deformations occur for negative poling voltages in BaTiO₃ layers grown on Pt (001) and for positive ones for BaTiO₃ grown on 1 atom % Nb:SrTiO₃ (001). In both cases, the step was associated with an increase of the sample resistance. Clockwise and counterclockwise resistance hysteresis loop cycles obtained for BaTiO₃-based heterostructures grown on Pt (001) and on 1 atom % Nb:SrTiO₃ (001), respectively, are understood by oxygen ions and vacancies migration through the oxide layers depending on the substrate nature (oxide or antioxidant metal). The present work provides a global view of ferroelectric thin film behaviors and is important for the understanding of physical phenomena occurring upon poling in nanometric ferroelectric layers.