Systematic study of ferroelectric, interfacial, oxidative, and doping effects on conductance of Pt/BaTiO 3/Pt ferroelectic tunnel junctions

Abstract

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 BaTiO 3-based ferroelectric tunnel junctions (Pt/BaTiO 3/Pt). The ferroelectric effect reduces the tunneling conductance compared to nonferroelectric BaTiO 3 due to the large decay rate of the Δ5 (p y and d yz) band. The TiO 2-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. © 2012 American Physical Society.