Synergistic effect of strain and oxygen vacancy on the ferroelectric properties of hafnium oxide-based ferroelectric films

Abstract

In this paper, a multiphase coexistence phase field model considering mobile oxygen vacancy is established to investigate the synergistic effect of strain and oxygen vacancy on the ferroelectric properties of hafnium oxide-based ferroelectric films. Uniform strain introduced by flat substrate and heterogeneous strain caused by miscut substrate are considered. Our study demonstrates that whether the HfO2 film is under flat substrate-induced strain or miscut substrate-induced strain, the regulation of oxygen vacancy concentration on the ferroelectric phase transition and domain switching of the film is double-sided. When the oxygen vacancy concentration is 1 × 1020 cm−3, the film under 1.2 % uniform strain reaches a maximum remanent polarization of 0.36 C/m2. The optimal concentration interval of oxygen vacancy can be widened by −1.2 % flat substrate-induced uniform strain or 6° and 8° miscut substrate-induced heterogeneous strain. These results embodied the synergistic relationship between oxygen vacancy and strain in regulating the ferroelectric properties of hafnium-oxide based films, which offers guidance for us to understand the phase transition behavior of hafnium-based ferroelectric films and to optimize the electric properties of thin films in device applications.