Thickness Effect of Interlayer on the Dielectric Permittivity of BaTiO $_{3}$ /Co/BaTiO $_{3}$ and BaTiO $_{3}$ /Ta/BaTiO $_{3}$ Films

Co and Ta inserted layers with thickness x varied from 0 to 20 nm on the dielectric permittivity of BaTiO 3 (60 nm)/Co(x nm)/BaTiO 3 (60 nm) (BCB) and BaTiO 3 (60 nm)/Ta(x nm)/BaTiO 3 (60 nm) (BTB) films fabricated on glass B270 substrates by the reactive sputtering technique was studied. The dielectric constant is around 7.6 for B270 glass substrate and BaTiO 3 /B270 film. However, it is rapidly raised up to roughly 84.3-89.4 for BCB, and 75.5-88.2 for BTB samples with the thickness of the Co or Ta inserted layer larger than 2 nm. This large enhancement of the dielectric constant could be explained due to the growth mechanism of the metallic inserted layer from island clusters to continuous layer for samples with x roughly near 3 nm, and the conducting property of the metallic inserted layer. The adding of a Co or Ta interlayer redistributes the interface charges between metal and ferroelectric layers, and that enhances both the intrinsic polarization and its dielectric constant. For the magnetic induced dielectric variation, after comparing the variation of the dielectric properties of both Co and Ta inter layers, the magneto dielectric properties in BaTiO 3 /Co/BaTiO 3 films are manifested. This magnetic tunability of the dielectric constant is clearly attributed to the magnetic metallic Co layer in the films. From this study, the magneto dielectric properties are manifested in BTO/Co/BTO films and it has the potential for a ferroic sensor application.