Improved ferroelectricity in Mn-doped HfO₂ (111) epitaxial thin films through controlled doping and substrate orientation

Doped HfO₂ as an emerging ferroelectric material, holds considerable promise for non-volatile memory applications. Epitaxial growth of doped HfO₂ thin films is widely adopted as an effective technique for revealing the intrinsic ferroelectric properties. In this study, based on systematic structural, chemical and electrical investigations, the influences of Mn doping and substrate orientation on ferroelectric properties of Mn-doped HfO₂ epitaxial thin films are investigated. The results demonstrate that Mn-doped HfO₂ thin films with orthorhombic phase can be epitaxially grown along 111 out-of-plane direction on both SrTiO₃ (001) and (110) substrates, and 10% Mn-doping significantly stabilizes the orthorhombic polar phase and enhances the ferroelectric polarization. Interestingly, compared to the films on SrTiO₃ (001) substrate, the better crystallinity and reduction of oxygen vacancy amount in Mn-doped HfO₂ films grown on the SrTiO₃ (110) substrate are observed, which enhance the remanent polarization and reduce the coercive field. It provides an effective approach for the controllable regulation of defects and the enhancement of intrinsic ferroelectricity in HfO₂-based materials.