Intrinsic RESET Speed Limit of Valence Change Memories

Abstract

During the past decade, valence change memory (VCM) has been extensively studied due to its promising features, such as a high endurance and fast switching times. The information is stored in a high resistive state (HRS) and a low resistive state (LRS). It can also be operated in two different writing schemes, namely a unipolar switching mode (LRS and HRS are written at the same voltage polarity) and a bipolar switching mode (LRS and HRS are written at opposite voltage polarities). VCM, however, still suffers from a large variability during writing operations and also faults occur, which are not yet fully understood and, therefore, require a better understanding of the underlying fault mechanisms. In this study, a new intrinsic failure mechanism is identified, which prohibits RESET times (transition from LRS to HRS) faster than 400 ps and possibly also limits the endurance. We demonstrate this RESET speed limitation by measuring the RESET kinetics of two valence change memory devices (namely Pt/TaO x /Ta and Pt/ZrO x /Ta) in the time regime from 50 ns to 50 ps, corresponding to the fastest writing time reported for VCM. Faster RESET times were achieved by increasing the applied pulse voltage. Above a voltage threshold it was, however, no longer possible to reset both devices. Instead a unipolar SET (transition from HRS to LRS) event occurred, preventing faster RESET times. The occurrence of the unipolar SET is attributed to an oxygen exchange at the interface to the Pt electrode, which can be suppressed by introducing an oxygen blocking layer at this interface, which also allowed for 50 ps fast RESET times.

Endurance of 2 Mbit Based BEOL Integrated ReRAM

“…This results in a voltage divider where the totally applied voltage V tot splits up into the voltage dropping over the periphery V per and the voltage dropping over the ReRAM cell V cell . This voltage V cell is crucial with regard to the switching process, as the switching time depends exponentially on it [28]. According to the voltage divider, V cell can be calculated to…”

“…Between these two states, a change in V cell of about 0.2 V can be observed. Since it has been demonstrated that a decrease of V cell by 0.1 V can increase the RESET time by one order of magnitude [28], this huge variance in V cell leads to a strongly varying switching behavior from cell to cell and from cycle to cycle. up.…”

“…But, in comparison with the experiment, this increase in is too low. Thus, we propose to consider and investigate additional effects like diffusion, thermodiffusion or an additional oxygen exchange at the AE in future works [20] [34] [28]. Furthermore, in our model, so far, we assumed N cell to be constant.…”

High On/Off Ratio Carbon Quantum Dot–Chitosan Biomemristors with Coplanar Nanogap Electrodes

“…A memristor (or ReRAM), with its fast switching speed, 14 multilevel data storage, 15 and low power consumption, 16 provides an exceptional platform for the next generation of nanoelectronics. 17 Numerous materials, including inorganic, 18,19 organic, 20 and hybrid nanocomposites, 21 have been utilized in memristive systems. Biomolecules have an excellent potential to be engaged in producing cost-effective memories due to their non-toxicity, environmentally benign nature, compatibility with various flexible substrates, natural abundance, and ease of fabrication.…”

“…Numerous materials, including inorganic, , organic, and hybrid nanocomposites, have been utilized in memristive systems. Biomolecules have an excellent potential to be engaged in producing cost-effective memories due to their non-toxicity, environmentally benign nature, compatibility with various flexible substrates, natural abundance, and ease of fabrication.…”