Resistive Switching Effect in BiFeO3 Nano-Islands

Abstract

With a revolution in mobile devices and the increasing demand for higher data storage density, non-volatile memory technologies have rapidly developed. Among various non-volatile memories, resistive random access memory (ReRAM) based on metal oxide has been emerging as a promising alternative to flash memory due to its high speed, long retention, good endurance, low operating voltage, and high scalability. However, gaining a high memory performance and overcoming the scaling limitations would still impose a significant challenge and require nanoscale device structure, reliable resistive switching (RS) materials, and cost-effective device architectures. To realize high density resistive random access memory (ReRAM) compatible with cross-point stack structure, highly nonlinear bistable current-voltage (I-V) characteristics is necessary. Here, we report highly nonlinear bistable I-V characteristics in a BiFeO3 (BFO) nano-island arrays. We explored the local charge conduction and ferroelectric polarization in highly-oriented ferroelectric BFO nano-islands by using conductive atomic force microscopy and piezoresponse force microscopy. A mosaic nano-crystalline BFO nano-island grown on a Nb-doped SrTiO3 substrate, which has pinned downward polarization, exhibits both bipolar resistive switching with resistance ratio of 4,420 and nonlinear behavior with nonlinearity factor α of 1,100 in low resistance state. Such high resistance ratio and nonlinearity factor suggest that our BFO nano-islands can be extended to an N × N array of N = 3,740 corresponding to ~107 bits. Therefore, our BFO nano-island showing both high resistance ratio and nonlinearity factor offers a simple and promising building block of high density ReRAM.