Kyoung-Cheol Kwon

Flexible conductive-bridging random-access-memory cell vertically stacked with top Ag electrode, PEO, PVK, and bottom Pt electrode

Flexible conductive-bridging random-access-memory (RAM) cells were fabricated with a cross-bar memory cell stacked with a top Ag electrode, conductive polymer (poly(n-vinylcarbazole): PVK), electrolyte (polyethylene oxide: PEO), bottom Pt electrode, and flexible substrate (polyethersulfone: PES), exhibiting the bipolar switching behavior of resistive random access memory (ReRAM). The cell also exhibited bending-fatigue-free nonvolatile memory characteristics: i.e., a set voltage of 1.0 V, a reset voltage of -1.6 V, retention time of >1 × 10(5) s with a memory margin of 9.2 × 10(5), program/erase endurance cycles of >10(2) with a memory margin of 8.4 × 10(5), and bending-fatigue-free cycles of ∼1 × 10(3) with a memory margin (I(on)/I(off)) of 3.3 × 10(5).

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.

Biological Synapse Behavior of Nanoparticle Organic Memory Field Effect Transistor Fabricated by Curing

The p-type channel of a nanoparticle organic memory field effect transistor (NOMFET) was fabricated by evaporating a thin Au layer, curing at 700 °C, and evaporating pentacene. The resulting NOMFET showed a facilitating ac-pulse drain current after programming and a depressing ac-pulse drain current after erasing that mimicked the behavior of biological synapses. The facilitating and depressing current ratio could be adjusted by using the program or erase voltage; i.e., the facilitating current increased with the program voltage, and the depressing current ratio increased with the erase voltage.

Fabricated nonvolatile memory with Ag nano-crystals embedded in PVK

We have been researching the polymer nonvolatile memory-cell based on electrical bi-stability. The polymer nonvolatile memory-cell was the 4F² embedded with Ag nano-crystals in conductive polymer. The structure of polymer nonvolatile memory-cell was PVK(poly(N-vinylcarbazole) / Ag nano-crystals / PVK between the Al electrodes. The Ag nano-crystals were formed by using the curing process after evaporate several nanometers of Ag layer. The polymer nonvolatile memory-cell embedded with Ag nano-crystals showed the memory magin(ratio of I<inf>on</inf> to I<inf>off</inf>) is ∼5.0×10¹. The retention time is more than 10⁵ seconds.