Energy preference of uniform polarization switching for HfO2 by first-principle study

In this work, the pathways for polarization switching of hafnium oxide (HfO2) orthorhombic phase were simulated via density functional theory. The energy barriers vary from 30.7 to 69.3 meV/atom depending on the transition states taken in the process of polarization switching. With further analysis, it is found that the pathway via transition state of the Pbcm phase is suitable for the domain-wall motion mechanism for polarization switching but bears the highest energy barrier. On the other hand, the pathways via the tetragonal-like transition state with the lowest energy barrier suggest the uniform switching mechanism. For HfO2 films composed of different sizes of grains, a uniform switching and domain-wall motion mechanism could be activated in small and large grains.