Enhancement of Ferroelectric Properties of Superlattice-Based Epitaxial BiFeO₃ Thin Films via Substitutional Doping Effect

Although there is considerable interest in BiFeO₃ owing to its versatile physical properties, which make it suitable for a wide range of applications, its high leakage current is a significant limitation. Among various methods for reducing the leakage current, substitution with transition-metal or rare-earth elements is widely recognized as the most effective approach. Herein, to enable in-depth studies of the physical properties of BiFeO₃, high-quality epitaxial BiFeO₃ thin films with a low leakage current must be formed. However, owing to the difficulty of controlling the element doping when pulsed laser deposition is used for epitaxial thin-film growth, studies on substitutional doping based on epitaxial BiFeO₃ thin films have not been systematically carried out. In this regard, we establish an innovative approach for overcoming the high leakage current of BiFeO₃ by fabricating artificially engineered superlattice-based epitaxial BiFeO₃ thin films in which there is a significant reduction of the leakage current. The control of the element doping in epitaxial BiFeO₃ thin films is easily regulated precisely at the atomic-scale level. The results of this study strongly suggest that superlattice-based epitaxial BiFeO₃ thin films can be a cornerstone for exploring the reliable fundamental physical properties of substitutional doping in epitaxial BiFeO₃ thin films.