A first-principles study on ferroelectric phase formation of Si-doped HfO2 through nucleation and phase transition in thermal process

We have investigated ferroelectric phase formation of Si-doped HfO2 through nucleation and phase transition in the thermal process by first-principles simulation. For the nucleation process from amorphous HfO2 in the thin film during thermal annealing, the tetragonal phase can be thermodynamically preferred with the effects of dopant and surface energy and temperature for which entropy is directly calculated from phonon spectrum calculations. During cooling down, the diffusionless phase transition from the tetragonal to ferroelectric phase takes place by atomic displacement and the transition to the monoclinic phase is suppressed by the high kinetic activation barrier. The phase transition process from the tetragonal phase to the ferroelectric phase is directly confirmed by ab initio molecular-dynamics simulation.