Investigation of switching uniformity in resistive memory via finite element simulation of conductive-filament formation

Abstract

Herein, we present simulations of conductive filament formation in resistive random-access memory using a finite element solver. We consider the switching material, which is typically an oxide, as a two-phase material comprising low- and high-resistance phases. The low-resistance phase corresponds to a defective and conducting region with a high anion vacancy concentration, whereas the high-resistance phase corresponds to a non-defective and insulating region with a low anion-vacancy concentration. We adopt a phase variable corresponding to 0 and 1 in the insulating and conducting phases, respectively, and we change the phase variable suitably when new defects are introduced during voltage ramp-up for forming. Initially, some defects are embedded in the switching material. When the applied voltage is ramped up, the phase variable changes from 0 to 1 at locations wherein the electric field exceeds a critical value, which corresponds to the introduction of new defects via vacancy generation. The applied voltage at which the defects percolate to form a filament is considered as the forming voltage. Here, we study the forming-voltage uniformity using simulations, and we find that for typical planar-electrode devices, the forming voltage varies significantly owing to the stochastic location of the initial defects at which the electric field is “crowded.” On the other hand, a protruding electrode can improve the switching uniformity drastically via facilitating the deterministic location of electric-field crowding, which also supported by the reported experimental results.

High-Quality Single-Crystalline β-Ga2O3 Nanowires: Synthesis to Nonvolatile Memory Applications

“…The switching mechanism is more likely to be dominated by the filament formation mechanism based on our preliminary material characterization results of the switching material and also the detailed analysis of the bipolar switching curve. The fundamental resistive switching phenomenon of VCM metal oxide materials is explained by the formation and rupture of conductive filaments constructed by oxygen vacancies, defects, ion migration between electrodes through the grain boundaries, and so on [18,[36][37][38]. Hsu et al (2012) reported resistive switching through oxygen vacancy filament formation in a core-shell Au/Ga 2 O 3 single nanowire, though a low density of oxygen vacancies in the Ga 2 O 3 shell was perceived.…”

“…This process is also recognized as trap-controlled SCLC (TC-SCLC). As the applied bias voltage crosses the voltage called the trap-filled limited voltage (V TFL ), the I-V curve corresponds to the trap-free SCLC (TF-SCLC) [19,37]. During this period, all the traps are filled, and the excess electrons are free to conduct electricity between electrodes, so the conductive filament is formed to produce an LRS state.…”

Continual Learning Electrical Conduction in Resistive‐Switching‐Memory Materials

“…Moreover, finite element simulations were carried out to study the distribution of forming voltage for 206 runs of HfO 2 ‐based RS devices with planar electrodes, and for 196 runs of HfO 2 ‐based RS devices with protruding electrodes. [ 37 ] A narrower forming voltage distribution was disclosed by the device models with protruding electrodes, indicating that the filament can be formed at predetermined locations (the electric‐field crowding location). Furthermore, the cumulative distribution of resistance for pristine state and HRS for few tens of oxide‐based RS devices were explored using compact modeling.…”

Intact Metal/Metal Halide van der Waals Junction Enables Reliable Memristive Switching with High Endurance

“…When the voltage is applied, the Ag atoms in the EVC can easily migrate into the FAPbI3 layer through chemical bonding to participate in forming the CFs. As the number of the operation cycles increases, the more migration of metal atoms can occur 39,40 . At the end, permanent metal filaments that cannot be ruptured cause the failure of switching in the EVC devices.…”

“…As the number of operation cycles increases, more migration of the metal atoms can occur. [44,45] Finally, permanent metal filaments that cannot be ruptured cause switching failure in EVC devices. In this regard, the dramatically improved endurance of the vdWC device is owing to the well-defined van der Waals heterojunction with relatively high activation energy for Ag atom penetration, which prevents the formation of permanent CFs.…”