Electric polarization and phase transitions in Y-doped hafnia

Hafnia-based thin films show robust ferroelectricity at nanoscale sizes and are compatible with current Si-based technology, which provides tremendous opportunities in nanoelectronics, but bulk Hafnia is not ferroelectric or polar. The polar, ferroelectric Pca2₁ phase is however stabilized in bulk by Yttrium doping [1]. Here, we study the properties of bulk Y-doped hafnia using molecular dynamics with machine learning. It is shown that the stability of polarized phase is tunable by the Y concentration, which further affects the properties of ferroelectricity and piezoelectricity in bulk HfO₂:Y. In particular we study electromechanical coupling in Y-doped HfO₂.

[1] X. Xu, F. T. Huang, Y. Qi, S. Singh, K. M. Rabe, D. Obeysekera, J. Yang, M. W. Chu, and S. W. Cheong, Kinetically stabilized ferroelectricity in bulk single-crystalline HfO₂:Y, Nat. Mater. 20, 826 (2021).