$\mathrm{Hf}{\mathrm{O}}_2$ thin films are recognized as pivotal materials for next-generation ferroelectric memories, and extensive experimental efforts have been dedicated to defect-engineering $\mathrm{Hf}{\mathrm{O}}_2$-based systems towards tailored ferroelectric properties. However, the microscopic mechanisms through which excess electrons modulate the defect states and doping behavior in $\mathrm{Hf}{\mathrm{O}}_2$ remain not fully understood, which has slowed progress in the field. To fill this gap, we investigate the interaction mechanisms between aliovalent dopants and oxygen vacancies ($V_{\mathrm{O}}$) in $\mathrm{Hf}{\mathrm{O}}_2$ by subspace corrected (PBE+$U$ functional) density functional theory simulations. Our results reveal that the extra charge introduced by trivalent dopants forms a small polaron localized on a tricoordinated oxygen atom, producing a deep empty defect state within the $\mathrm{Hf}{\mathrm{O}}_2$ band gap. This deep defect state can interact with the excess electrons generated by oxygen vacancies, thereby enhancing the stability of the three-coordinated oxygen vacancy ($V_{\mathrm{O}3}$) configuration compared to the four-coordinated one ($V_{\mathrm{O}4}$). The introduction of $V_{\mathrm{O}4}$ lowers the local polarization-switching barrier near a statistical accumulation of vacancies by 13%, while $V_{\mathrm{O}3}$ produces a more pronounced reduction of 60%, corresponding to a minimum barrier of 0.12eV/u.c. The stabilized $V_{\mathrm{O}3}$ center effectively reduces the ferroelectric switching barrier in the $\mathrm{Pca}{2}_1$ phase by promoting reduced atomic displacements and lattice distortions, significantly decreasing the coercive field of $\mathrm{Hf}{\mathrm{O}}_2$. These findings provide critical insights for advancing the fundamental understanding of $\mathrm{Hf}{\mathrm{O}}_2$ materials and establishing design guidelines for constructing defect-tolerant ferroelectric devices through targeted defect engineering.

Close

PrevNext

View figure in article

• Defects
• Density of states
• Doping effects
• Electronic structure
• Ferroelectricity
• DFT+U
• First-principles calculations