Modulation of Zirconia Ferroelectricity via Crystal Orientation of Pt Electrode Available to Purchase

The origin of ferroelectricity and antiferroelectricity in zirconia (ZrO₂) ultrathin films has become a topic of great interest in recent years. The normal ferroelectricity in ZrO₂ is widely considered to originate from the high-pressure noncentrosymmetric Pca2₁ orthorhombic (o) phase. While the antiferroelectric-like behavior is regarded as the result of a phase transition from the centrosymmetric and paraelectric P4₂/nmc tetragonal (t) phase to the ferroelectric o-phase under electrical loading. This study reports an effective technique to selectively produce a ferroelectric or antiferroelectric ZrO₂ ultrathin film (∼15 nm) without compositional manipulation. The technique is based on tailoring the crystal orientation of the Pt bottom electrode on which the ZrO₂ ultrathin film is deposited. By correlating the results of the XRD, HRTEM, and electric field-polarization (P-E) analyses, it is found that a cubic phase (111)-oriented Pt electrode promotes the textured growth of the ferroelectric o-phase (111) planes in the ZrO₂ ultrathin film; while a random-oriented Pt electrode leads to a t-phase dominated system, resulting in an antiferroelectric-like pinched P-E hysteresis. The modulation of ZrO₂ ferroelectricity via the crystal orientation of the Pt bottom electrode can be achieved with a low thermal budget (< 400 °C), making it highly favorable for process integration and device scaling in a variety of nanoelectronics and nanoelectromechanical applications.