Interfacial Nb-substitution induced anomalous enhancement of polarization and conductivity in BaTiO₃ ferroelectric tunnel junctions

Using density functional theory (DFT) method combined with non-equilibrium Green’s function approach, we systematically investigated the structural, ferroelectric and electronic transport properties of Pt/BaTiO₃/Pt ferroelectric tunnel junctions (FTJ) with the interface atomic layers doped by charge neutral Nb_Ti substitution. It is found that interfacial Nb_Ti substitution will produce several anomalous effects such as the vanishing of ferroelectric critical thickness and the decrease of junction resistance against tunneling current. Consequently, the thickness of the ferroelectric thin film (FTF) in the FTJ can be reduced, and both the electroresistance effect and sensitivity to external bias of the FTJ are enhanced. Our calculations indicate that the enhancements of conductivity and ferroelectric distortion can coexist in FTJs, which should be important for applications of functional electronic devices based on FTJs