Designing High‐Performance Storage in HfO₂/BiFeO₃ Memristor for Artificial Synapse Applications

Abstract

using artificial synapses is an essential step to accomplish the neuromorphic computing system. [9,10] Formerly, artificial synapses were realized by complementary metal-oxide-semiconductor (CMOS) circuitry containing dozens of electronic components. [11] However, many electronic components result in complicated architecture and high energy consumption. As comparison, two-terminal memristors, especially resistive random access memory and phase change random access memory, that recently entered our field of vision have been widely discussed as artificial synapses owing to their structures which is similar to that of synapses and the reproducible tuning of resistance. [12][13][14][15][16] Also, for an ideal synapse device it is better to meet these requirements, such as symmetric potentiation-depression characteristics, 5-bit/cell analog levels, and high non-volatility with ≈100 conductance ON/OFF ratio. They are the key points we need to take into account. [17,18] In particular, HfO 2 -based memristors have been demonstrated as a leading alternative as synapse in virtue of its distinctive superiority, such as simple structure, <10 ns switching speed, <10 pJ power consumption, multilevel ability, and compatibility with CMOS fabrication process. [19][20][21] However, the resistance contrast (ON/OFF ratio) of HfO 2 -based memristors ranges from ≈40 to ≈150. [22] Considering the resistance fluctuation of these memristors across a silicon wafer, larger ON/OFF ratio is needed to guarantee high recognition accuracy (>97%). [23] Recently, several works were reported on improvement of the memristors' performance with thin interfacial layer. [24][25][26] As one of the most important multiferroic materials, bismuth iron oxide with perovskite structure has come into notice for its potential in multifunctional device applications. [27] Moreover, BiFeO 3 (BFO) has attracted much attention because it possesses superior characteristics of resistance switching (RS) such as large ON/OFF ratio in some researches. [28] It is also confirmed that BFO can be applied in bi-layer design memristor to significantly improve RS characteristics, [29] which gives inspiration to insert BFO thin film as the goal of high device performances.In this work, ultrathin BFO film was inserted to fabricate Pt/BFO/HfO 2 /TiN memristor to improve the RS characteristic of HfO 2 -based memristor. The material characterization and RS behavior were systemically analyzed. The role of the inserting BFO layer on the RS behavior was evaluated and the RS mechanism triggered by inserting BFO film was explored.HfO 2 -based memristors that remembers the history of the current that has passed through them have attracted great interest for use as artificial synapses in neuromorphic systems. However, the low resistance contrast exhibited by HfO 2 -based memristors seriously decreases their recognition accuracy. By inserting a 2 nm BiFeO 3 layer a large memory window of 10 4 and remarkable pulse endurance of 10 8 cycles are achieved. Multilevel storage capability is also d...

HfO2‐Based Memristor as an Artificial Synapse for Neuromorphic Computing with Tri‐Layer HfO2/BiFeO3/HfO2 Design

“…It possibly can be explained that the sufficient oxygen vacancies in BFO inserting film will accelerate the formation of CFs, which results in the reduction of the V Forming . [ 31 ] Figure 1c presents the typical bipolar RS curves of both memristive devices. The I–V curves of both devices were measured for 100 consecutive cycles under the same voltage range (from −2 to +2 V) with the compliance current (C.C.)…”

Electrolyte-Dependent Modification of Resistive Switching in Anodic Hafnia

“…Redox-based random access memories (ReRAMs), as a new generation of memories more progressive than FLASH technology, and dynamic random access memories (DRAM) are some of the most common applications [ 1 , 2 , 3 ]. Additionally, memristors are used as building blocks for neuromorphic architectures [ 4 ] such as artificial synapses [ 5 ] and logic circuits due to the possibility of multilevel switching to implement a fuzzy behavior [ 6 , 7 , 8 ]. Due to their reported high stability, memristors are also used for various sensing applications [ 9 ].…”

“…Generally, CF formation is regarded as the active mechanism based on partial reduction of solid electrolyte forming local oxygen deficient regions with their charge compensated by electrons [ 15 ]. However, there is a possibility that mobile cations are accompanying this process, including other species that can be trapped inside the memristive layer [ 3 , 7 , 10 , 16 ].…”

Memristors based on TiOx/HfOx or AlOx/HfOx Multilayers with Gradually Varied Thickness

“…[10,11] Also, multilevel storage capability have been achieved through a bilayer structure. [12,13] Unfortunately, simultaneous realization of the forming-free, self-compliance, and multilevel storage capability characteristics, which is necessary to meet the demands of practical applications for memristors, has been not reported for HfO 2 -based memristors so far.…”