Chapter 6 - Thermodynamics of Phase Stability and Ferroelectricity From First Principles

Abstract

The current understanding and key insights obtained from first-principles computational studies on the origins of ferroelectricity in pure and doped HfO2 are summarized. After identifying the potential polar phases of HfO2, a Gibbs free energy model is used to investigate the influence of diverse physical factors that lead to the emergence of the polar phases. Specifically, it is shown that finite size effects, mechanical strains, and the electric field all play a role in the stabilization of the polar orthorhombic phase observed experimentally. The effects of chemical factors (i.e., dopants and oxygen vacancies) are also treated in detail through the systematic applications of density functional theory methods, and the results of an extensive screening to identify dopants that are most favorable in promoting ferroelectricity are reported. Remaining research gaps are highlighted, which may serve to motivate future research work.