The impact of charge compensated and uncompensated strontium defects on the stabilization of the ferroelectric phase in HfO2.

Different dopants with their specific dopant concentration can be utilized to produce ferroelectric HfO2 thin films. In this work, it is explored for Sr in a comprehensive first-principles study. Density functional calculations reveal structure, formation energy, and total energy of the Sr related defects in HfO2. We found the charge compensated defect with an associated oxygen vacancy SrHfVO to strongly favour the non-ferroelectric, tetragonal P42/mnc phase energetically. In contrast, the uncompensated defect without oxygen vacancy SrHf favours the ferroelectric, orthorhombic Pca21 phase. According to the formation energy, the uncompensated defect can form easily under oxygen rich conditions in the production process. Low oxygen partial pressure existing over the lifetime promotes the loss of oxygen leading to VO, and thus, the destabilization of the ferroelectric, orthorhombic Pca21 phase is accompanied by an increase of the leakage current. This study attempts to fundamentally explain the stabilization of the ferroelectric, orthorhombic Pca21 phase by doping. [ABSTRACT FROM AUTHOR]