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.