Systematic study of ferroelectric, interfacial, oxidative, and doping effects on conductance of Pt/BaTiO3/Pt ferroelectic tunnel junctions

Using the nonequilibrium Green's function method combined with density functional theory, we systematically study the ferroelectric, interfacial, oxidative, and doping effects on electron transport of BaTiO3-based ferroelectric tunnel junctions (Pt/BaTiO3/Pt). The ferroelectric effect reduces the tunneling conductance compared to nonferroelectric BaTiO3 due to the large decay rate of the Delta 5 (p(y) and d(yz)) band. The TiO2-terminated interface shows a better tunneling conductance than the BaO-terminated interface since electrons mainly transport through the Ti-3d-O-p bonding state. Interfacial oxidation strongly reduces the conductance due to trapping of electrons and interfacial charge localization by additional O ions, while Nb doping enhances the conductance due to the delocalized distribution of charges on orbitals of the transport channel. Our studies provide a useful guide to practical applications of tunnel junctions with ferroelectric barriers.