A kind of polymer resistive switching memory material based on dithiol metal complex doping

Abstract

The application discloses a kind of based on dithio metal complex doped polymer resistance change storage material and its preparation method and application, belong to data storage technical field.The storage material is with cadmium halide synthesis complex with bipyridine (Bpy) as ligand, and with polyvinylpyrrolidone (PVP) compound and obtained composite material.Based on the storage performance of pure cadmium complex device is poor, and the switch ratio is only 10 2.32 ~10 3.18 , with halogen from I to SCN, storage performance gradually improves.After being compounded with PVP, Cl base and SCN base device exhibits good ternary storage behavior (ternary yield is 65% and 55%), and the current switch ratio reaches 10 6.13 :10 3.80 :1, and good device stability is shown, and it is expected to be applied to construct high-performance halogen-based memory.Raw material is widely sourced, and the preparation method is simple, and the product has excellent performance, and has significant economic and social benefits.

Description

Technical Field

[0001] This invention belongs to the field of data storage technology, specifically relating to a resistive switching memory material based on disulfide metal complex doped polymer, its preparation method, and its application. Background Technology

[0002] Resistive random access memory (RRAM) has attracted widespread attention due to its advantages such as large capacity, high speed, simple structure, low power consumption, and ease of integration. Currently, exploring ways to achieve high-density storage through RRAM integration, multi-valued storage, miniaturization, and vertical multilayering remains a significant challenge. Multi-level resistive memory refers to information storage where multiple resistive stable states exist. Taking ternary memory as an example, the storage capacity per unit area can be 3... n This means that the unit storage capacity is increased exponentially compared to binary. Compared to methods that increase information storage density by reducing the size of storage devices or using vertical multi-layering of memory structures, applying multi-level memristor memory materials is a simpler and easier approach to implement.

[0003] This invention leverages the conformational isomerism of disulfide metal complexes under external (electric) stimulation, along with the electron-trapping and releasing capabilities and excellent film-forming properties of the organic polymer PVP, to synthesize a multi-level switchable storage material. This invention produces a material with low synthesis cost, simple preparation method, excellent film-forming properties, and suitability for large-scale industrial production, while also exhibiting controllable multi-level switchable storage performance, demonstrating promising application prospects. Summary of the Invention

[0004] The purpose of this invention is to provide a resistive switching memory material based on a disulfide metal complex-doped polymer, its preparation method, and its applications. Using disulfide metal complexes and polyvinylpyrrolidone (PVP) organic polymer materials as raw materials, a multi-level controllable memory storage material is prepared through simple physical mixing. The preparation method is simple, the raw materials are readily available, and it is easy to implement. Furthermore, the preparation process produces no harmful byproducts, making it an environmentally friendly green synthesis.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a resistive switching memory material based on a disulfide metal complex-doped polymer, the mass ratio of the disulfide metal complex to the polymer is 1:3.

[0007] The disulfide metal complex is any one of Cd-Bpy-I, Cd-Bpy-Br, Cd-Bpy-Cl, and Cd-Bpy-SCN; the polymer is polyvinylpyrrolidone.

[0008] The preparation method of the disulfide metal complex includes: using disulfide pyridine as a ligand, reacting it with cadmium halides or halide-like compounds by stirring, cooling and filtering, and evaporating and crystallizing the filtrate to obtain the disulfide metal complex.

[0009] Preparation method: The disulfide metal complex and the polymer are dissolved in a solvent and stirred for 2 hours to obtain the resistive switching memory material based on the disulfide metal complex doped polymer.

[0010] The application of the disulfide metal complex-doped polymer resistive switching memory material in multi-level memristors: The multi-level memristor structure is a sandwich structure of bottom electrode / resistive switching memory layer / top electrode; the bottom electrode is a fluorine-doped indium tin oxide conductive material; the top electrode is an inert metal material; and the resistive switching memory layer is a disulfide metal complex-doped polymer resistive switching memory material.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0012] (1) The resistive switching memory material based on disulfide metal complex doped polymer obtained in this invention can form a uniform and dense thin film on the substrate.

[0013] (2) The resistive switching memory material based on disulfide metal complex doped polymer obtained in this invention exhibits excellent multi-level memory storage performance at room temperature and has good cyclic fatigue resistance.

[0014] (3) All raw materials used in this invention are commercially available; the method does not require a complicated reaction process and is simple to operate. Attached Figure Description

[0015] Figure 1 The diagram shows the crystal structure of disulfide metal complexes, where a, b, c, and d are the crystal structures of I, Br, Cl, and SCN-based disulfide metal complexes, respectively.

[0016] Figure 2 The image shows the infrared spectra of the disulfide metal complex / polymer composite material. From top to bottom, the infrared spectra are those of PVP, the disulfide metal complex, and the composite material.

[0017] Figure 3 This is a structural diagram of a disulfide metal complex / polymer composite device.

[0018] Figure 4 This is a graph showing the IV characteristic curves of a disulfide metal complex / polymer composite (Cd-Bpy-Cl@PVP) device.

[0019] Figure 5 The graph shows the number of cycles required to maintain the disulfide metal complex / polymer composite (Cd-Bpy-Cl@PVP) device in different resistive states.

[0020] Figure 6 The diagram shows the state maintenance time of the disulfide metal complex / polymer composite (Cd-Bpy-Cl@PVP) device in different resistive states. Detailed Implementation

[0021] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0022] Example 1

[0023] First, the disulfide metal complex Cd-Bpy-I was prepared via a volatilization method. 0.2 mmol (0.050 g) of disulfide oxypyridine (Bpy) and 0.2 mmol (0.073 g) of CdI₂ were dissolved in 10 mL of methanol, stirred at room temperature for 2 h, and then filtered to volatilize, yielding yellow crystals. Next, 8.3 mg of Cd-Bpy-I and 25 mg of polyvinylpyrrolidone (PVP) were dissolved in 5 mL of DMF, stirred for 2 h, and filtered to obtain a homogeneous solution. All homogeneous solutions were used to fabricate devices using the following method: First, FTO (20 × 20 mm) was pre-cleaned sequentially with acetone, ethanol, and deionized water under ultrasonic conditions, and then dried in a vacuum drying oven. Second, the above solution was spin-coated onto FTO at 1000 rpm and annealed in a vacuum at 60 °C for 2 h. Finally, silver nanowires were sprayed as the top electrode.

[0024] Example 2

[0025] First, the disulfide metal complex Cd-Bpy-Br was prepared by a volatilization method. 0.2 mmol (0.050 g) of disulfide oxypyridine (Bpy) and 0.2 mmol (0.069 g) of CdBr₂ were dissolved in 10 mL of methanol, stirred at room temperature for 2 h, and then filtered to volatilize, yielding yellow crystals. Next, 8.3 mg of Cd-Bpy-Br and 25 mg of polyvinylpyrrolidone (PVP) were dissolved in 5 mL of LDM, stirred for 2 h, and filtered to obtain a homogeneous solution. The device fabrication method was the same as in Example 1.

[0026] Example 3

[0027] First, the disulfide metal complex Cd-Bpy-Cl was prepared by a volatilization method. 0.2 mmol (0.050 g) of disulfide oxypyridine (Bpy) and 0.2 mmol (0.037 g) of CdCl₂ were dissolved in 10 mL of methanol, stirred at room temperature for 2 h, and then filtered to volatilize, yielding yellow crystals. Next, 8.3 mg of Cd-Bpy-Cl and 25 mg of polyvinylpyrrolidone (PVP) were dissolved in 5 mL of LDM, stirred for 2 h, and filtered to obtain a homogeneous solution. The device fabrication method was the same as in Example 1.

[0028] Example 4

[0029] First, the disulfide metal complex Cd-Bpy-SCN was prepared by a volatilization method. 0.2 mmol (0.050 g) of disulfide oxypyridine (Bpy), 0.2 mmol (0.084 g) of Cd(ClO4)2·6H2O, and 0.4 mmol (0.038 g) of KSCN were dissolved in 30 mL of methanol, stirred at room temperature for 2 h, and then filtered to volatilize, yielding yellow crystals. Next, 8.3 mg of Cd-Bpy-SCN and 25 mg of polyvinylpyrrolidone (PVP) were dissolved in 5 mL of LDM, stirred for 2 h, and filtered to obtain a homogeneous solution. The device fabrication method was the same as in Example 1.

[0030] Product Characterization

[0031] 1. The crystal structure of disulfide metal complexes is as follows: Figure 1 As shown in the figure:

[0032] In Cd-Bpy-I, the Cd atom forms a five-coordinate trigonal bipyramidal configuration with two I atoms and three O atoms on the Bpy ligands. Each ligand consists of one I atom and two Bpy ligands in the equatorial plane, and a second I atom and another Bpy ligand at the apex. Figure 1 a).

[0033] In Cd-Bpy-Br, the Cd atom, along with two Br atoms, three O atoms on the Bpy ligands, and one O atom on H2O, forms a six-coordinate twisted octahedral configuration. One Br atom and three Bpy ligands form the equatorial plane, while the apex position is occupied by another Br atom and one H2O atom. Figure 1 b).

[0034] In Cd-Bpy-Cl, the Cd atom has two coordination modes. One is a six-coordinate octahedral configuration with four Cl atoms and two O atoms on the Bpy ligands. In this configuration, the Cd atom is located at the structural center of the repeating unit, the two Cl atoms and two Bpy ligands are located in the equatorial plane, and the apex is occupied by two more Cl atoms. The other coordination mode is a five-coordinate twisted trigonal bipyramidal configuration with three Cl atoms, one O atom on the Bpy ligand, and one O atom on a methanol molecule. In this configuration, the Bpy ligand sites and two Cl atoms occupy the equatorial plane, and the apex is occupied by another Cl atom and a methanol molecule. Figure 1 c).

[0035] In Cd-Bpy-SCN, the Cd atom forms a six-coordinate octahedral configuration with the N atoms of the two SCN groups, the S atoms of the two SCN groups, and the O atoms of the two Bpy ligands. This Cd atom is located at the structural center of the repeating unit, while the N atoms of the two SCN groups, the S atom of one SCN group, and one Bpy ligand are located in the equatorial plane. The apex is occupied by the S atom of the other SCN group and one Bpy ligand. Figure 1 d).

[0036] Table 1

[0037]

[0038] 2. Infrared spectral characterization:

[0039] from Figure 2 It can be seen that 1642cm -1 The peak at 2940 cm⁻¹ is attributed to the C=O stretching vibration of the tertiary amide in PVP. -1 735cm -1 The peaks at 1295 cm⁻¹ are attributed to the stretching and bending vibrations of long-chain alkanes in PVP, respectively. -1 The peak at 3000–3500 cm⁻¹ belongs to the stretching vibration of CN, while the peak at 3000–3500 cm⁻¹ belongs to the stretching vibration of CN. -1 The strong and broad absorption band between these peaks is generally considered to be the absorption peak of moisture in PVP, which is moisture adsorbed by PVP molecules. Figure 2 a(above)). Taking Cd-Bpy-I as an example, 520cm -1 The peak at 1555 cm⁻¹ is attributed to the stretching vibration of SS in the disulfide pyridine ligand. -1 The peak at 3068 cm⁻¹ is attributed to the stretching vibration of the aromatic ring in the disulfide pyridine ligand. -1 The peak at 570 cm⁻¹ is attributed to the stretching vibration of CH in the disulfide pyridine ligand. -1 700cm -1The peak at that point is attributed to the shift of the pyridine ring bending vibration to higher frequencies after the disulfide pyridine forms a complex. Figure 2 a(middle)); while Cd-Bpy-Br and Cd-Bpy-Cl also involve water molecules and methanol respectively during coordination, which leads to 3000cm -1 The absorption peaks appear at the above positions ( Figure 2 b (middle) Figure 2 c(middle)); For Cd-Bpy-SCN, both the S and N atoms of the thiocyanate group participate in coordination, therefore 2098cm -1 The peak position at 834 cm should be attributed to the stretching vibration of C=N. -1 The peak position at that point should be attributed to the stretching vibration of the CS. Figure 2 (d(middle)). In all the infrared spectra before and after recombination, the characteristic vibrations of the disulfide metal complex and PVP were still present before and after recombination, and no new peak positions were found, indicating that the material recombination of the two was only a physical mixing.

[0040] 3. Multi-level controllable memory storage performance test:

[0041] The IV characteristic curves of the FTO / composite / Ag device were tested in a KEYSIGHT-B2901A single-channel semiconductor parameter tester.

[0042] like Figure 4 As shown, the IV characteristic curves of FTO / complex / Ag were tested within the range of 0V→-5V→0V→5V. During the first scan (-8V→5V, “Sweep 1” and “Sweep 2”), the current initially showed a high-resistance state (OFF state, 8.28×10⁻⁶). - 8 A) As the voltage applied across the device gradually increases, when the voltage reaches 1.39V, the current suddenly jumps to 4.08 × 10⁻⁶. - 4 A indicates that the current state changed from "OFF" to "ON1". Afterward, the voltage continued to increase, and when the external voltage reached 1.87V, the current further increased to 2.90 × 10⁻⁶. -2 A corresponds to the change to the "ON2" state, completing the device's Set process. The "Sweep 2" process is equivalent to a "write" operation in memory. After the write process, even if the device is swept from 5V to 0V ("Sweep 3" process), or even swept back to -8V, the device still maintains a low-resistance state. This also indicates that the device is a ternary WORM memory type. The device exhibits good cycle stability over 100 rounds, and all three resistance states remain stable without significant decay for 2500s. Figure 5 and Figure 6 ).

[0043] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A doped polymer resistive switching memory material based on a dithiolate metal complex, characterized in that: The mass ratio of the dithiol metal complex and the polymer is 1:3; The dithiol metal complex is any one of Cd-Bpy-I, Cd-Bpy-Br, Cd-Bpy-Cl and Cd-Bpy-SCN; and the polymer is polyvinylpyrrolidone. The preparation method of the dithiol metal complex comprises the following steps: taking dithiolopyridine as a ligand, stirring and reacting with a halide or a halide-like compound of cadmium, cooling and filtering, and volatilizing and crystallizing the filtrate to obtain the dithiol metal complex.

2. A method of preparing the dithio-metal complex based polymer doped resistive switching memory material according to claim 1, characterized by: The dithiol metal complex and the polymer are dissolved in a solvent, and stirred for 2 h to obtain the dithiol metal complex doped polymer resistive random access memory material.

3. Application of the dithiol metal complex doped polymer resistive random access memory material in a multi-level memristor according to claim 1.

4. Use according to claim 3, characterized in that: The multi-level memristor structure is a sandwich structure of bottom electrode / resistive random access memory layer / top electrode; the bottom electrode is a fluorine-doped indium tin oxide conductive material; the top electrode is an inert metal material; and the resistive random access memory layer is the dithiol metal complex doped polymer resistive random access memory material.

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