Modulation of Zirconia Ferroelectricity via Crystal Orientation of Pt Electrode

Abstract

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.