Competing phases of HfO₂ in applied electric field: A first principles insight

The recent discovery of ferroelectricity in doped HfO₂ thin films has generated intense experimental and theoretical interest, with a particular focus on the precise nature of the HfO₂ ferroelectric phase and the factors promoting the observation of ferroelectric switching. In this talk, I present first principles results and analysis to demonstrate how phases of HfO₂ evolve under applied electric field as a function of field magnitude and direction. In particularly, the symmetry breaking of yttrium dopants is shown to open new reaction pathways for structural transformation, leading to an electric-field-driven transition from a metastable nonpolar tetragonal phase to the polar ferroelectric orthorhombic phase. The implications of the results for interpreting recent experimental observations will be discussed.