In search of Pca2₁ phase ferroelectrics

Abstract

In recent years, hafnia-based ferroelectrics have attracted enormous attention, due to their capability of maintaining the ferroelectricity below 10 nm thickness and excellent compatibility to microelectronics flow-line. However, the physical origin of its ferroelectricity is still not fully clear, though it is commonly attributed to a polar Pca21 orthorhombic phase. Its high- temperature paraelectric phases (the tetragonal phase or the cubic phase) do not possess a soft- mode at the Brillouin zone center, thus the ferroelectric distortion has to be explained in terms of trilinear coupling among three phonon modes in the tetragonal phase. It is necessary to explore new materials with possible ferroelectricity due to the polar Pca21 phase, which in turn should be very helpful in evaluating the microscopic theory for ferroelectric hafnia. In this work, based on the idea of material genome initiative, a series of hafnia-like ferroelectrics have been found. Their common features and delicate differences have been discussed in details. Particularly, a promising potential ferroelectric material, Pca21-phase LuOF, is predicted.