Toward a Low-Temperature Route for Epitaxial Integration of BiFeO3 on Si

• Published in: Journal of physical chemistry. C 2019-05, Vol.123 (19), p.12203-12210
• Main Authors: Plokhikh, Aleksandr V, Karateev, Igor A, Falmbigl, Matthias, Vasiliev, Alexander L, Lapano, Jason, Engel-Herbert, Roman, Spanier, Jonathan E
• Format: Article
• Language: English
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.8b12486

Epitaxial thin-film growth enables novel functionalities, particularly if significant barriers to integration with existing technologies, scalability and excessive temperature of films, can be addressed. Here, we demonstrate a step toward addressing both challenges by combining hybrid molecular beam epitaxy and atomic layer deposition to epitaxially integrate BiFeO3 on Si wafers via a SrTiO3 metamorphic buffer layer. The solid–solid transformation of atomic-layer-deposited amorphous Bi–Fe–O films into epitaxial BiFeO3 thin films is investigated by in situ annealing utilizing transmission electron microscopy. The amorphous Bi–Fe–O layer undergoes a very complex crystallization process, encompassing phenomena such as reorientation, recrystallization, and grain growth. Our in situ transmission electron microscopy study revealed that a growth front of epitaxial crystallites emerged from the interface with the (001)-oriented SrTiO3 as temperature increased, whereas randomly oriented BiFeO3 crystallites formed simultaneously away from the interface. Structural rearrangement and recrystallization of crystallites took place at temperatures below 400 °C. At the final stage, above 400 °C, epitaxial crystallites larger than 60 nm merged into a single crystalline film. Our results demonstrate that this approach permits high-quality epitaxial integration of BiFeO3 thin films at back-end-of-line-compatible temperatures below 500 °C on metamorphic SrTiO3 buffer layers on Si.