【introduction】

In today‘s big data era, the huge amount of data requires the next-generation non-volatile memory (NVM) technology to have the characteristics of large storage capacity and fast read and write speed. Resistive random access memory (RRAM), magnetic random access memory (MRAM), phase change memory (PCM) and other new NVM applications are born, showing the advantages of permanent storage and fast read and write speed. The device realizes information storage and output through the switch resistance state, and the nanometer size makes it possible for high density and large-scale integration.

As a non-volatile storage device with broad application prospects, memristors can effectively simulate synaptic structures and enable neuromorphic systems, so they have received extensive attention. In recent years, two-dimensional materials have been widely used in memristors because of their unique advantages, which not only improves the performance of memristors, but also promotes memristors in flexible electronics, low power consumption, high temperature equipment, neuromorphic calculation And other developments.

【Achievement Introduction】

Recently, based on the rapid development of two-dimensional material memristors , Professor Yan Xiaobing of Hebei University and Professor Zhang Han (co-corresponding author) of Shenzhen University summarized the application of two-dimensional materials in memristors and their physical switching mechanism, and The existing challenges and development prospects were discussed. First, the author discusses the current status of graphene and its derivatives, transition metal sulfides (TMDs), and other two-dimensional material-based memristors, including BN, black phosphorus, and perovskite. Subsequently, the three physical switching mechanisms of memristors were summarized and discussed. Finally, the application of two-dimensional materials in the field of memristors is summarized, and future research directions are proposed. The review was published on Materials Horizons with the title " Current Status and Prospects of Memristor Based on Novel 2D Materials " .

【Graphic introduction】

Figure 1. Overview of 2D material-based memristor and its switching mechanism

Figure 2. Bipolar switching characteristics of Ag / GO / ITO devices

(a, b) Optical photo and IV curve of Ag / GO / ITO device;

(c) The IV curve of the Ag / GO / ITO device, in which the GO film annealing temperature is 20 ° C, the inset is a schematic diagram of the device;

(d) The retention characteristic curve of the device.

Figure 3. Basic characteristics of graphene electrode memristors

(a, b) MLG transferred on a glass substrate and the optical picture after assembly into a device;

(c, d) Bipolar RS characteristic curve of linear and nonlinear on-state MLG / TaO y / Ta 2 O 5–x / MLG devices;

(e) Polymer assisted peeling MoS 2 diagram and its IV curve;

Figure 4. Basic characteristics of Ag / MoS 2 / Ag / MoS 2 / Ag memristor

(ac) Ag / MoS 2 / Ag / MoS 2 / Ag memristor diagram (a) and its room temperature IV curve (b), (c) is the IV curve in logarithmic coordinates

(d, e) The basic IV curve (d), ( e) of MoO x / MoS 2 memory is its capacitance and resistance;

(f) IV curves of memristors of different TE materials;

(g) Schematic and cross-sectional diagrams of GMG devices;

(h) Measuring equipment and corresponding pictures;

(i) Typical switching characteristic curve of GMG device;

(j) A high durability of 2 × 10 ⁷ can be obtained with a pulse width of 1 μm ;

(k, l) At V g = 40 V, the principle diagram and local IV curve of the memristor;

(m, n) The tunability curve of memristors and the typical IV curve of GB memristors bisected by different V g

Figure 5. Basic characteristics of Pd / WS 2 / Pt memristive devices

(a, b) Classic IV characteristic curve and comparison with operating current reported in other literatures;

(c) 13 ns opening speed;

(d) 14 ns closing speed.

Figure 6. Basic characteristics of MoTe2 based memristors

(a) MoTe 2 vertical device diagram and optical and SEM images;

(b) IV curve of Mo 0.96 W 0.04 Te 2 RRAM device after electroforming ;

(c) Correspondence between V set value and material thickness.

Figure 7. Basic characteristics of BN -based memristors

(a, b) Structural diagram of Ti / thin h-BN / Cu device and classic IV curve of memristor;

(c, d) IV curves of the response of bipolar and unipolar switches in single-layer h-BN crossbar switching devices;

(e, f) IV curves of single-layer h-BN devices based on Au foil and Ni foil.

Figure 8. Basic characteristics of perovskite-based memristors

(a) Schematic diagram of the formation and fracture of Ag CFs;

(b, c) Schematic diagram of IV curve and energy level of Ag / CH 3 NH 3 PbI 3-x Cl x / FTO under illumination .

Figure 9. Basic characteristics of GaSe -based memristors

(a, b) The IV curve of the Ag / GaSe / Ag device and the 50th data cycle curve;

(c) The fitting result of the IV curve in Figure (a);

(d) Energy level diagram of Ag / GaSe metal semiconductor junction.

Figure 10. Wire switching mechanism of Ti / thin h-BN / Cu memristor

(a) The IV curve of the BN device indicates that it has a bipolar RS;

(b, c) Electron energy loss spectroscopy (EELS) cross-sectional analysis of the device‘s original position (LRS) and GB / CF position.

Figure 11. Physical switching mechanism of Ag TE / hBN / Cu memristor

(a) TEM image of conductive filament;

(b, c) STEM image and EDS diagram of the device in low resistance state;

(d, e) The TEM image of the conductive filament and the corresponding HRTEM image when the Cu bottom electrode is not fully contacted;

(f, g) HRTEM image of Ag conductive filaments, schematic diagram of conductive filament growth of h-BN based devices.

Figure 12. Ag physical switching mechanism of AZA device

(a) The fitting result of IV curve

(b, c) TEM image and element distribution image of AZA device;

Figure 13. Physical switching mechanism of Ag / GaSe / Ag memristor

(a) The original state of V ds = 0;

(b) The growth process of Ga vacant conductive filaments;

(c) The source and drain are connected through conductive filaments;

(d) The breaking process of conductive filaments.

Figure 14. Physical switching mechanism of Ag / MoO x / MoS 2 / Ag memristor

(ac) Schematic diagram of MoO x / MoS 2 memristor, SEM image and XPS analysis diagram;

(d) The degree of oxidation of surface Mo;

(eg) EDS line scan profile;

(hj) Schematic diagram of the physical switching mechanism of the GMG device.

Figure 15. Physical switching mechanism of WS 2 based memristor

(a, b) TEM images of WS 2 nanosheets and films in LRS ;

(c) W atom line analysis of the regions corresponding to Figures a and b.

Figure 16. Physical switching mechanism of Al / Ti 3 C 2 T x / Pt memristor

(ad) The fitting curve of LRS and HRS and the corresponding IV curve;

(e) Oxidation of Ti 3 C 2 T x to TiO 2 ;

(fh) There are atomic holes in the white dot area, but not in the yellow dot area. Figures g and h are the corresponding line profiles;

(io) XPS depth profile of Ti 3 C 2 T x sheet in its original state and under LRS;

(p) Oxygen content curves of HRS and LRS at different depths of Ti 3 C 2 T x flakes.

Figure 17. Physical switching mechanism of W / MoS 2 / p-Si memristor

(a) The left picture shows the energy band structure of a single layer of MoS 2 with local potential fluctuations , and the right picture shows the MoS 2 SiO 2 interface with suspended Si-O bonds ;

(b) Schematic diagram of the physical switching mechanism of the MoS 2 / p-Si junction.

【Summary】

This paper summarizes the application of two-dimensional materials such as graphene, TMDs, BN, black phosphorus, perovskite, and GaSe in the field of memristors, and analyzes the structure and characteristics of their two-dimensional systems. Memristors based on 2D materials have multiple physical switching mechanisms, including conductive filaments, atomic vacancies, and electron trapping and detachment mechanisms. In addition, the research of memristors has a significant impact on brain-like computing and artificial intelligence. Memristors based on 2D materials have broad development prospects in the future.

Original link: Current Status and Prospects of Memristor Based on Novel 2D Materials ( Mater. Horiz. , 2020, DOI: 10.1039 / C9MH02033K.)

【Team introduction / Corresponding author profile】

Professor Yan Xiaobing, Deputy Dean, Distinguished Professor and Doctoral Supervisor of School of Electronic Information Engineering, Hebei University. He is a senior member of IEEE in the United States, and has two levels of Jieqing and three, three, and three talents in Hebei Province. He has long been engaged in research on memristors. He has published more than 60 papers with the first and corresponding authors, including Adv. Mater., Adv. Funct. Mater., Adv. Sci., Mater. Horiz. And other authoritative magazines. Director of Chinese young science and technology workers, winner of the May 4th Medal of Hebei Youth, Standing Committee of Hebei Youth Federation. He has won the Huo Yingdong Young Teacher Award and the Hebei Youth Science and Technology Award.

Professor Zhang Han, male, born in 1984, is a distinguished professor of Shenzhen University, director of Shenzhen Black Phosphorus Engineering Laboratory, and a doctoral tutor. Fellow of the American Optical Society, "Excellent Youth" of the Funding Committee, "Recognized Scientist (2018/2019)" of Clarivate, and Guangdong‘s leading science and technology personnel He has long been engaged in research on low-dimensional materials and optoelectronic devices, and has published more than 100 papers in the first area of the Chinese Academy of Sciences as corresponding authors, including 2 Physics Reports, 1 PNAS, 2 Science Advance, and 6 Nature Communications. The papers have been cited more than 26,000 times. The H factor is 85. Professor Zhang Han serves as the editor-in-chief / editor of several SCI journals, the secretary-general of the China Laser Youth Editorial Committee, and the vice-chairman of the second presidium of the National Optical Youth Academic Forum. Scientific research achievements have won the second prize of the Ministry of Education Natural Science Award, the China Industry-University-Research Cooperation Innovation Award, China‘s Top Ten Progress in Optics, the Guangdong Ding Ying Science and Technology Award, the Shenzhen Youth Science and Technology Award, and the Shenzhen Natural Science Award.

The research group recruits excellent post-doctors and researchers. Welcome to submit your resume to 506180626 (at) 163.com; 947935449 (at) qq.com. Requirements: Optics, chemistry, biology and other sciences and engineering, published 1-2 SCI papers, under 35 years old; those engaged in two-dimensional nanomaterials are preferred.

Literature recommendation:

1. Self-Assembled Networked PbS Distribution Quantum Dots for Resistive Switching and Artifcial Synapse Performance Boost of Memristors. (Adv. Mater. DOI: 10.1002 / adfm.201705320)

2. Memristor with Ag-cluster-doped TiO2 films as artificial synapse for Neuroinspired computing. (Adv. Funct. Mater. DOI: 10.1002 / adfm.201705320)

3. Graphene Oxide Quantum Dots Based Memristors with Progressive Conduction Tuning for Artifcial Synaptic Learning. (Adv. Funct. Mater. DOI: 10.1002 / adfm.201803728)

4. Designing carbon conductive filament memristor devices for memory and electronic synapse applications. (Mater. Horiz. DOI: 10.1039 / C9MH01684H)

5. The Rise of 2D Photothermal Materials beyond Graphene for Clean Water Production. (Adv. Sci. DOI: 10.1002 / advs.201902236);

6. Nonlayered Tellurium Nanosheets: Facile Liquid‐Phase Exfoliation, Characterization, and Photoresponse with High Performance and Enhanced Stability. Adv. Funct. Mater. 2018, 28 (16), 1705833–1705844. Https://doi.org/10.1002/ adfm.201705833

Information source: material cattle