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.