Ferroelectricity in the Al doped HfO2

Recently, hafnia (HfO2)-based ferroelectrics have attracted much attention due to their unique features such as superior ferroelectricity at an ultra-thin thickness, large coercive electric field, and compatibility with the standard silicon process platform. In this work, the growth of ferroelectric HfO2 thin films through Al doping have been demonstrated. Structural analysis showed that non-centrosymmetric polar orthorhombic phase HfO2 have been observed after doping Al. Interestingly, the ferroelectricity was shown to be dependent on the Al composition, where the remnant polarization as high as 2Pr = 22.9 & mu;C/cm2 was obtained in HfO2 thin film with a 5.0 mol% Al doping. The mechanisms of structural transition to ferroelectric orthorhombic-phase owing to oxygen vacancies and generation of oxygen vacancies benefiting from Al doping were further studied by density functional theory calculations. The results shown in this work provide insights into the formation of ferroelectric HfO2 due to Al doping and further offer a simple way for controlled fabrication of ferroelectric HfO2 thin films.