McGroddy Prize: Ferroelectricity in ultrathin binary oxides

Ferroelectricity remains a very active field of research even after a century after its discovery due to the intriguing underlying physics and potential for practical applications. The last decade has seen a significant shift towards Hafnium oxide based ferroelectrics. Distinct from prototypical and mostly perovskite based counterparts, ferroelectric hafnium oxide is polycrystalline and can be achieved in thin films (<5 nm) without worrying about an epitaxial substrate. I will discuss how mixed phases can be achieved in such ultrathin Hafnium oxide films. The mixed phase configuration, where polar phases are stabilized within a non-polar matrix, leads to a state of frustrated polarization and locally stable negative capacitance. In addition, ultra thin (<3nm) films show stronger distortion than their thicker counterparts -- again, in contrast to what has been seen in perovskite films. The enhanced distortion alludes to a new way of achieving polar phases in binary oxides. I will give two examples.