Giant tunnel electroresistance with PbTiO3 ferroelectric tunnel barriers

The persistency of ferroelectricity in ultrathin films allows their use as tunnel barriers. Ferroelectric tunnel junctions are used to explore the tunneling electroresistance effect-a change in the electrical resistance associated with polarization reversal in the ferroelectric barrier layer-resulting from the interplay between ferroelectricity and quantum-mechanical tunneling. Here, we use piezoresponse force microscopy and conductive-tip atomic force microscopy at room temperature to demonstrate the resistive readout of the polarization state through its influence on the tunnel current in PbTiO3 ultrathin ferroelectric films. The tunnel electroresistance reaches values of 50 000% through a 3.6 nm PbTiO3 film.