  Nonvolatile bipolar resistive switching has been observed in an Au/BiFeO3/Pt
structure, where a Schottky contact and a quasi-Ohmic contact were formed at
the Au/BiFeO3 and BiFeO3/Pt interface, respectively. By changing the polarity
of the external voltage, the Au/BiFeO3/Pt is switched between two stable
resistance states without an electroforming process. The resistance ratio is
larger than two orders of magnitude. The resistive switching is understood by
the electric field - induced carriers trapping and detrapping, which changes
the depletion layer thickness at the Au/BiFeO3 interface.
