Epitaxial growth of BiFeO3 films on TiN under layers by sputtering deposition.

BiFeO₃/TiN/MgO (001) films have been prepared by magneton sputtering, where TiN serves as a conductive under layer. X-ray diffraction profiles and cross-sectional transmission electron microscopy images reveal that not only (001)-epitaxial BiFeO₃ films are obtained, but also both tetragonal and rhombohedral phases co-exist in BiFeO3 films. Their crystallographic relationship is shown as following: tetragonal- BiFeO₃ (001) [100]//TiN (001) [100]//MgO (001) [100] and rhombohedral-BiFeO₃ (001) [100]//TiN (001) [100]//MgO (001) [100]. Besides, an oxidized TiN layer (~ 20 nm) has also been detected between BiFeO₃ and TiN layers and its formation may originate from oxygen inter-diffusion from BiFeO₃ layer. Despite of the existence of the oxidized TiN layer, it does not affect the epitaxial growth of BiFeO3 films. On the other hand, the coercivity electric field obtained in ferroelectric loop of BiFeO3 is greatly enhanced to 49 MV/cm due to the existence of oxidized TiN layer. [ABSTRACT FROM AUTHOR]