Myung-JIn Song

Electro-Forming and Electro-Breaking of Nanoscale Ag Filaments for Conductive-Bridging Random-Access Memory Cell using Ag-Doped Polymer-Electrolyte between Pt Electrodes

Ag-doped polymer (polyethylene oxide: PEO) conductive-bridging-random-access-memory (CBRAM) cell using inert Pt electrodes is a potential electro-forming free CBRAM cells in which electro-forming and electro-breaking of nanoscale (16~22-nm in diameter) conical or cylindrical Ag filaments occurs after a set or reset bias is applied. The dependency of the morphologies of the Ag filaments in the PEO polymer electrolyte indicates that the electro-formed Ag filaments bridging the Pt cathode and anode are generated by Ag+ ions drifting in the PEO polymer electrolyte toward the Pt anode and that Ag dendrites grow via a reduction process from the Pt anode, whereas electro-breaking of Ag filaments occurs through the oxidation of Ag atoms in the secondary dendrites and the drift of Ag+ ions toward the Pt cathode. The Ag doping concentration in the PEO polymer electrolyte determines the bipolar switching characteristics; i.e., the set voltage slightly decreases, while the reset voltage and memory margin greatly increases with the Ag doping concentration.

Nanoscale CuO solid-electrolyte-based conductive-bridging-random-access-memory cell operating multi-level-cell and 1selector1resistor

Nanoscale (∼28 nm) non-volatile multi-level conductive-bridging-random-access-memory (CBRAM) cells are developed by using a CuO solid-electrolyte, providing a Vset of ∼0.96 V, a Vreset of ∼−1.5 V, a ∼1 × 102 memory margin, ∼3 × 106 write/erase endurance cycles with 100 μs AC pulse, ∼6.63 years retention time at 85 °C, ∼100 ns writing speed, and multi-level (four-level) cell operation. Their non-volatile memory cell performance characteristics are intensively determined by studying material properties such as crystallinity and poly grain size of the CuO solid-electrolyte and are found to be independent of nanoscale memory cell size. In particular, the CuO solid-electrolyte-based CBRAM cell vertically connecting with p/n/p-type oxide (CuO/IGZO/CuO) selector shows the operation of 1S(selector)1R(resistor), demonstrating a possibility of cross-bar memory-cell array for realizing terabit-integration non-volatile memory cells.