Investigation of multilevel data storage in silicon-based polycrystalline ferroelectric tunnel junction

Multilevel data ferroelectric tunnel junction is a breakthrough for further improving the storage density of ferroelectric random access memories. However, the application of these ferroelectric tunnel junctions is limited by high cost of epitaxial perovskite heterostructures, unsatisfactory retention and difficulty of exactly controlling the middle polarization states. In order to overcome the issues, we develop a ferroelectric tunnel junction with smooth ultrathin polycrystalline BiFeO3 (BFO) film. Through controlling the polarization state and oxygen vacancy migration using voltage pulses, we demonstrate that voltage-controlled barrier yields a memristive behavior in the device, in which the resistance variations exceed over two orders of magnitude. And we achieve multi logic states written and read easily using voltage pulses in the device. Especially the device is integrated with the silicon technology in modern microelectronics. Our results suggest new opportunity for ferroelectrics as high storage density nonvolatile memories.