Intrinsic ferroelectricity in Y-doped HfO2 thin films

Ferroelectric HfO2-based materials hold great potential for the widespread integration of ferroelectricity into modern electronics due to their compatibility with existing Si technology. Earlier work indicated that a nanometre grain size was crucial for the stabilization of the ferroelectric phase. This constraint, associated with a high density of structural defects, obscures an insight into the intrinsic ferroelectricity of HfO2-based materials. Here we demonstrate that stable and enhanced polarization can be achieved in epitaxial HfO2 films with a high degree of structural order (crystallinity). An out-of-plane polarization value of 50 mu C cm(-2) has been observed at room temperature in Y-doped HfO2(111) epitaxial thin films, with an estimated full value of intrinsic polarization of 64 mu C cm(-2), which is in close agreement with density functional theory calculations. The crystal structure of films reveals the Pca2(1) orthorhombic phase with small rhombohedral distortion, underlining the role of the structural constraint in stabilizing the ferroelectric phase. Our results suggest that it could be possible to exploit the intrinsic ferroelectricity of HfO2-based materials, optimizing their performance in device applications. Hafnium dioxide is of technological interest as it is compatible with silicon; however, previous work indicates that a nanometre grain size is required to generate ferroelectricity. Here ferroelectric Y-doped HfO2 thin films with high crystallinity are grown with large crystal grain sizes, indicating that ferroelectricity is intrinsic.

Automated summary

Ferroelectricity can be achieved in epitaxial HfO2 films with high structural order, indicating that it is an intrinsic property of HfO2-based materials. This discovery has significant implications for optimizing the performance of HfO2-based materials in device applications.