Quantum Dots for Resistive Switching Memory and Artificial Synapse

Abstract

Memristor devices for resistive-switching memory and artificial synapses have emerged as promising solutions for overcoming the technological challenges associated with the von Neumann bottleneck. Recently, due to their unique optoelectronic properties, solution processability, fast switching speeds, and low operating voltages, quantum dots (QDs) have drawn substantial research attention as candidate materials for memristors and artificial synapses. This review covers recent advancements in QD-based resistive random-access memory (RRAM) for resistive memory devices and artificial synapses. Following a brief introduction to QDs, the fundamental principles of the switching mechanism in RRAM are introduced. Then, the RRAM materials, synthesis techniques, and device performance are summarized for a relative comparison of RRAM materials. Finally, we introduce QD-based RRAM and discuss the challenges associated with its implementation in memristors and artificial synapses.

Keywords: artificial synaptic device; quantum dot; resistive switching; switching mechanism.

Figure 1

(a) Comparison between von Neumann architecture and neuromorphic architecture [25]. Copyright 2023, MDPI. (b) Schematic illustration of carrier dynamics (generation, separation/transport, and recombination in QDs) [26]. Copyright 2020. Wiley Online Library. (c) Schematic illustration of QD color conversion layer on GaN-based blue micro-LEDs [27]. Copyright 2021, ACS Publications. (d) Illustration of Al/CdSe-PVP/Al resistive memory device along with TEM image of synthesized QDs and I–V curve [28]. Copyright 2022, ACS Publications. (e) Preparation of Eu/CdTe QD nanostructure and sensing mechanism for tetracycline [29]. Copyright 2020, Elsevier.

Figure 6

(a) Schematic of Al/ZnO/Pt device structure investigated in our research. (b) Cross-sectional HR-TEM images of Al/ZnO/Pt device [112]. Copyright 2022, Elsevier. (c) Device structure of glucose-based RRAM. (d) Photograph of glucose film with thickness information on glass substrate and synthesized solution [113]. Copyright 2018, Wiley Online Library. (e) Schematic showing cross-section of 2D material-based vertical RRAM. (f) Cross-sectional bright-field TEM image of as-prepared RRAM cell [114]. Copyright 2017, nature.com.

Figure 2

(a) Results of analysis of core–shell structure with high-resolution transmission electron microscopy (HR-TEM). Determination of crystal structure based on HR-TEM images of individual CdSe/CdS particles, shown in Panels (a.1) and (a.3), and the resulting Fourier transformations, shown in Panels (a.2) and (a.4), respectively, superimposed on the corresponding simulated diffraction patterns. The jems software program was used to simulate the diffraction patterns. (b) Model of CdSe/CdS QDs (tOA: thickness of oleylamine ligand shell; tS: thickness of CdS shell; dcore: diameter of CdSe core; dparticle: diameter of particle that is unequivocally detectable with TEM and SAXS; dparticle-OA: diameter of particle, including organic shell) [42]. Copyright 2020, nature.com. (c) Sustainable route for green synthesis of GQD from cellulose [43]. Copyright 2019, Wiley Online Library. (d) Synthesis scheme for InP/ZnSe/ZnS QDs using indium and zinc halides, tris(diethylamino)phosphine, zinc carboxylates, tri-n-octylphosphine selenide, and sulfide in oleylamine and 1-octadecene [44]. Copyright 2022, ACS Publications. (e) Mechanism of oxidative (OX) gelation of thioglycolic acid-capped QD film (sol film) submerged in TNM solution [45]. Copyright, 2013.

Figure 3

(a) Surface-engineering strategies for QDs for end-applications: capping layers with oleophilic ligands, water-soluble surface layers with hydrophilic ligands, versatile tether functionalities via selective reactions or interactions, and bio-functionalities for targeting or therapeutic applications [75]. Copyright 2017, Elsevier. (b) Quantum dot shapes considered [76]. Copyright 2006, American Physical Society.

Figure 4

(a) Schematic of TiN/WO_X/FTO device. (b) Cross-sectional TEM image. DC I–V curves of TiN/WO_X/FTO RRAM device with different CC (compliance current) conditions. (c) I–V curves with varying CC (10 µA, 100 µA, 1 mA, and 5 mA) [4]. Copyright 2024, Elsevier. (d) Applied voltage pulse (black trace) and measured current (red trace) waveform for SET operation. The applied pulse has a pulse width of 2.7 ns, and the device switches in about 700 ps. (e) I–V plot of the data in (d) shows a change in resistance with the applied pulse. (f) Applied voltage pulse (black trace) and measured current (blue trace) waveform for RESET operation. (g) I–V plot of the data in (f) shows a change in resistance with the applied pulse [89]. Copyright 2024, nature.com.

Figure 5

RS memory operation of a Co/SiO_X/TiN cell. Filament morphologies based on observations of Co CBRAM in (a) pristine state, (b,c) HRS, and (d) LRS [95]. Copyright 2023, ACS Publications. Schematic of oxygen migration in TiN/WO_X/FTO device: (e) initial state; (f,g) set and reset processes [4]. Copyright 2024, Elsevier. (h) Schematic illustration of RS behavior in pyramid-structured device. Nucleation and growth of the nickel (Ni) filament occur predominantly at the tip due to the locally accelerated Joule heating and facile hole injection, which result from the tip-enhanced electric field. (i) Energy diagram of reduction reactions at anode interface of nickel oxide (NiO) pyramid-structured RRAM [96]. Copyright 2021, Elsevier.

Figure 7

(a) Schematic illustration of CsPbBr3 QD-based RRAM device fabrication via all-solution process. (b) Atomic force microscope image showing topography of CsPbBr3 QDs’ arrays with height profile of surface. (c) Cross-sectional scanning electron microscope image showing side view of Ag/PMMA/CsPbBr3 QDs/PMMA/ITO device. (d) Typical I–V plot of the device; inset shows photograph of the as-prepared device. The photoresponse curve of the RRAM device in the HRS was measured at 0.5 V with UV light pulse stimulation. (e) Illustration of RS in the initial state, (f) during the SET process under dark conditions, and (g) during the SET process under UV illumination. (h) Schematic illustration of CsPbBr3 QD-based logic OR device. (i) Typical I–V characteristics of ITO/PMMA/CsPbBr3/PMMA/Ag-structured device measured in the dark or under a UV lamp. (j) Photoresponse curve of the RRAM device in HRS, measured at 0.5 V with UV light pulse stimulation [152]. Copyright 2018, Wiley Online Library.

Figure 8

(a) Schematic showing imitation of a synaptic neural structure through device synaptic plasticity. (b) EPSC gain values in response to different programming pulse amplitudes [174]. Copyright 2024, ACS Publications. (c,d) PPF characteristics of TiN/ZnO/NiO/Pt device: statistical distribution of PPF as a function of interval time [175]. Copyright 2023, Elsevier. (e) Pulse schematic for STDP. (f) Result of planar STDP measurement [176]. Copyright 2024, Wiley Online Library. (g,h) Cycle-to-cycle multiple potentiation and depression curves; (i) deep neural network simulation framework for MNIST pattern recognition; (j) pattern recognition accuracy of synaptic device over 10 consecutive epochs [175]. Copyright 2023, Elsevier.