Multi-level resistive switching in hafnium-oxide-based devices for neuromorphic computing

Abstract

In the growing area of neuromorphic and in-memory computing, there are multiple reviews available. Most of them cover a broad range of topics, which naturally comes at the cost of details in specific areas. Here, we address the specific area of multi-level resistive switching in hafnium-oxide-based devices for neuromorphic applications and summarize the progress of the most recent years. While the general approach of resistive switching based on hafnium oxide thin films has been very busy over the last decade or so, the development of hafnium oxide with a continuous range of programmable states per device is still at a very early stage and demonstrations are mostly at the level of individual devices with limited data provided. On the other hand, it is positive that there are a few demonstrations of full network implementations. We summarize the general status of the field, point out open questions, and provide recommendations for future work.

Electrolyte Influence on Properties of Ultra-Thin Anodic Memristors on Titanium

“…Following the TEM analysis, a hybrid interfacial resistive switching mechanism is proposed, where only partial filaments are formed. The crystalline protrusions observable in the figure act as preferential paths for the partial filament formation [42,43]. They do not reach all the way through the oxide, so there is no full filamentary switching.…”

“…The partial filaments, therefore, simulate an effective bottom electrode. Interfacial memristors exhibit resistive switching due to O species migration, including ions and vacancies, that are distributed through the entire interface [13,36,42,43]. This switching mechanism is based on the Schottky-like barrier formation, which can be modulated by varying the O species concentration [36,44].…”

“…The presence of an electric field increases the concentration of vacancies at the interface, reducing the barrier height and thus transitioning the device to a low resistance state. Conversely, the concentration of O vacancies decreases due to the electric field reversal, resulting in an increased barrier height, reverting the device to a high resistance state [36,42]. The initial electron trapping at the Pt/oxide interface is reported to create a negatively charged layer, prompting the accumulation of O vacancies in the nearby depletion zone to counterbalance this charge [13,36].…”

“…The initial electron trapping at the Pt/oxide interface is reported to create a negatively charged layer, prompting the accumulation of O vacancies in the nearby depletion zone to counterbalance this charge [13,36]. The different asymmetry of the I-U sweep for the memristor prepared in the PB and CB can be explained by different depletion dynamics and the amount of O vacancies in the Schottky barrier, which could be a result of phosphate incorporation into the oxide [13,36,42].…”

Flexible Artificial Mechanoreceptor Based on Microwave Annealed Morphotropic Phase Boundary of HfxZr1‐xO2 Thin Film

“…Particularly, the relationship between electrical properties and the Hf to Zr composition ratio has been thoroughly investigated in earlier reports. [18][19][20]47,48] Interestingly, at a particular threshold of zirconium content, abrupt changes in the material's piezoelectric and dielectric properties were seen. The MPB, or morphotropic phase barrier, is what causes this.…”