Nanoscale ring-shaped conduction channels with memristive behavior have been observed in the BiFeO₃ (BFO) nanodots prepared by the ion beam etching. At the hillside of each individual nanodot, a ring-shaped conduction channel is formed. Furthermore, the conduction channels exhibit memristive behavior, i.e., their resistances can be continuously tuned by the applied voltages. More specifically, a positive (negative) applied voltage reduces (increases) the resistance, and the resistance continuously varies as the repetition number of voltage scan increases. It is proposed that the surface defects distributed at the hillsides of nanodots may lower the Schottky barriers at the Pt tip/BFO interfaces, thus leading to the formation of ring-shaped conduction channels. The surface defects are formed due to the etching and they may be temporarily stabilized by the topological domain structures of BFO nanodots. In addition, the electron trapping/detrapping at the surface defects may be responsible for the memristive behavior, which is supported by the surface potential measurements. These nanoscale ring-shaped conduction channels with memristive behavior may have potential applications in high-density, low-power memory devices.
Keywords: BiFeO3; memristors; nanodots; ring-shaped conduction channels.