Enhanced Ferroelectric Stability by Interface Engineering
Ferroelectric materials are characterized by a spontaneous polarization that can be switched by external electric field. This property is important for various technological applications such ferroelectric random access memories. However, when ferroelectric film thickness is reduced down to a nanoscale the ferroelectric polarization may become unstable due to strong depolarization fields and interface effects. Nebraska MRSEC researchers in collaboration with their colleagues at Universities of Wisconsin and Michigan have predicted and demonstrated that interface engineering may be efficiently used to stabilize ferroelectric polarization at the nanoscale. Using sophisticated first-principles calculations and advanced fabrication and characterization techniques the researchers showed that deposition of a two-unit cell thick non-ferroelectric strontium titanate layer at the interface enhances the polarization of ferroelectric barium titanate layer, making it switchable by an applied electric filed. This discovery provides a new insight into the switching and retention behavior of thin-film ferroelectric materials and paves the way to atomic scale property engineering in ferroelectric-based electronic devices. This work was partly supported by the Nanoelectronics Research Initiative of Semiconductor Research Corporation.
Caption: Experimental observation of enhanced polarization of a barium titanate thin film. Left images have the same contrast indicating that polarization of barium titanate is not switched by electric field. Right images have different contrast indicating that the interface engineered film can be switched by an electric field.