Explains why the polar orthorhombic Pca21 phase of HfO2, responsible for its ferroelectricity, can be stabilized over the more stable non-polar monoclinic phase. Combining compressive biaxial strain in the higher-density (111) crystallographic orientation with yttrium doping and oxygen vacancies increases the structural flexibility around tri-coordinated oxygen atoms and lowers the phase-transition stress. Learners see how first-principles calculations connect crystal orientation, defect chemistry, and bonding to the emergence of robust ferroelectricity in a CMOS-compatible oxide.
A first-principles density functional theory study of how biaxial strain orientation and doping stabilize the polar ferroelectric orthorhombic (Pca21) phase of hafnium oxide (HfO2) relative to its st…