Abstract
Highly nonlinear bistable current-voltage (I–V) characteristics are necessary in order to realize high density resistive random access memory (ReRAM) devices that are compatible with cross-point stack structures. Up to now, such I–V characteristics have been achieved by introducing complex device structures consisting of selection elements (selectors) and memory elements which are connected in series. In this study, we report bipolar resistive switching (RS) behaviours of nano-crystalline BiFeO3 (BFO) nano-islands grown on Nb-doped SrTiO3 substrates, with large ON/OFF ratio of 4,420. In addition, the BFO nano-islands exhibit asymmetric I–V characteristics with high nonlinearity factor of 1,100 in a low resistance state. Such selector-free RS behaviours are enabled by the mosaic structures and pinned downward ferroelectric polarization in the BFO nano-islands. The 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.
Highlights
Nonlinear bistable current-voltage (I–V) characteristics are necessary in order to realize high density resistive random access memory (ReRAM) devices that are compatible with cross-point stack structures
This increase in the out-of-plane lattice constant arises either from compressive stress imposed through a large lattice mismatch with the Nb-doped SrTiO3 (Nb):STO substrate (0.390 nm) or from volume expansion of the lattice induced by the formation of oxygen vacancies[25]
We explored the local charge conduction and ferroelectric polarization in highly-oriented, mosaic-structured ferroelectric BFO nano-islands arrays grown on Nb:STO bottom electrodes by using conductive atomic force microscopy and piezoresponse force microscopy
Summary
Nonlinear bistable current-voltage (I–V) characteristics are necessary in order to realize high density resistive random access memory (ReRAM) devices that are compatible with cross-point stack structures. Up to now, such I–V characteristics have been achieved by introducing complex device structures consisting of selection elements (selectors) and memory elements which are connected in series. Selector-free memory cell significantly reduces the leakage current in the idle state and cell-to-cell disturbance enabling larger array size and lower process complexity, in which both highly nonlinear and bistable I–V characteristics are required[15,16,17,18,19]
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