Dielectric Property of a Large‐Scale Transferred Single‐Crystal BaTiO ₃ Film Prepared Using a Water‐Soluble Sacrificial Buffering Layer

Abstract The process of transferring inorganic single crystal thin films by using a water‐soluble sacrificial layer, especially Sr ₃ Al ₂ O ₆ , has attracted much attention for its potential application to flexible devices and to the investigation of the properties of thin films without strain originated from a substrate. However, single‐crystal thin films of BaTiO ₃ , the best‐known dielectric material, are difficult to transfer. In this study, to prepare a large‐scale single‐crystal BaTiO ₃ thin film, the mismatch strain between the objective film and a substrate is reduced by introducing a buffering layer. Sr ₃ Al ₂ O ₆ with partial substitution of Sr to Ba is utilized as a water‐soluble sacrificial layer for the lattice matching to BaTiO ₃ . A large‐scale transferred single‐crystal BaTiO ₃ thin film succeeded in preparing of over 5 mm × 5 mm by using a sacrificial (Ba,Sr) ₃ Al ₂ O ₆ layer. The high crystallinity of single‐crystal BaTiO ₃ is maintained during the transfer process, and a very low dielectric loss (tan δ < 0.1) of the transferred BaTiO ₃ is estimated. The dielectric constant ε _r of the transferred BaTiO ₃ film is lower than that of BaTiO ₃ /SrRuO ₃ /(100)SrTiO ₃ and almost the same as that of the c axis of BaTiO ₃ single crystal with a low tan δ value of ≈0.1. These results suggest that reducing the mismatch strain by introducing a buffering layer of (Ba,Sr) ₃ Al ₂ O ₆ is effective for the production of large‐scale transferred single‐crystal thin films.