A mercaptopyridine-based cadmium complex-doped polymer resistive switching memory material

Abstract

The present invention discloses a thiopyridine-based cadmium complex-doped polymer resistive random access memory material, its preparation method, and application, belonging to the field of data storage technology. The storage material is a composite material prepared by synthesizing a cadmium thiocyanate complex using 2-thiopyridine (2Spy) and 4-thiopyridine (4Spy) as ligands and compounding it with polyvinylcarbazole (PVK). The FTO / Cd-4Spy@PVK / Ag device exhibits ternary RRAM storage behavior, with an ON2 / ON1 / OFF state current ratio of 10 6.10 :10 3.33 :1, V Set1 / V Set2 The ratios of the active layer traps to the binary RRAM type are 1.27 / 1.87, with a ternary yield of 61%. At 100°C, the storage behavior transforms into a binary RRAM type due to shallow traps in the active layer. The device exhibits excellent stability under 365 nm ultraviolet radiation, providing a new strategy for the fabrication of high-performance memories that are resistant to high temperatures and UV radiation.

Description

Technical Field

[0001] The present invention belongs to the technical field of data storage, and in particular relates to a mercaptopyridine-based cadmium complex-doped polymer resistive storage material, a preparation method thereof, and an application thereof. Background Art

[0002] The era of rapidly expanding information volumes places higher demands on next-generation high-density data storage, and multi-level memory is the most practical approach to breaking the von Neumann bottleneck. To achieve high-density data storage, research into novel materials is crucial. Due to the tunable structure of metal complexes, subtle structural modifications and design can significantly enhance resistive switching behavior. However, these materials also have limitations, and the device fabrication process often faces challenges such as poor device morphology, poor reproducibility, and complex synthesis.

[0003] This invention combines a cadmium complex of mercaptopyridine as a good charge-trapping site with the electron-trapping and photoelectric properties of the organic polymer PVK to produce a multi-level switchable memory material. This material, produced by the invention, features low synthesis cost, simple preparation methods, excellent film-forming properties, and suitability for large-scale industrial production. It also exhibits controllable multi-level switchable memory performance and has promising application prospects. Summary of the Invention

[0004] The present invention aims to provide a thiopyridine-based cadmium complex-doped polymer resistive switching memory material, its preparation method, and its application. Using a thiopyridine-cadmium complex and polyvinylcarbazole (PVK) as raw materials, a simple physical mixing method is used to prepare a multi-level controllable memory material. The preparation method is simple, the raw materials are readily available, and the material is easy to implement. Furthermore, the preparation process is free of harmful products, making it an environmentally friendly green synthesis.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The mass ratio of the cadmium complex of mercaptopyridine to the polymer in the resistive switching memory material doped with a cadmium complex of mercaptopyridine is 1:3.

[0007] The cadmium complex of mercaptopyridine is any one of Cd-2Spy and Cd-4Spy; and the polymer is polyvinylcarbazole.

[0008] The preparation method of the cadmium complex of mercaptopyridine comprises: using mercaptopyridine as a ligand, stirring and reacting with cadmium thiocyanate, cooling and filtering, and volatilizing and crystallizing the filtrate to obtain the cadmium complex of mercaptopyridine; the mercaptopyridine is any one of 2-mercaptopyridine and 4-mercaptopyridine.

[0009] Preparation method: dissolving the cadmium complex of mercaptopyridine and a polymer in a solvent and stirring for 2 hours to obtain the mercaptopyridine-based cadmium complex-doped polymer resistive switching memory material.

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

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] (1) The organic polymer composite material obtained by the present invention can form a uniform and dense thin film on a substrate.

[0013] (2) The organic polymer composite material obtained by the present invention exhibits excellent multi-level ultraviolet radiation-resistant memory storage performance at room temperature and has good cyclic fatigue resistance.

[0014] (3) The raw materials used in the present invention can be obtained commercially; the method does not require a complicated reaction process and is simple to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The crystal structure diagram of the obtained cadmium complex of mercaptopyridine, where a and b are the crystal structures of Cd-2Spy and Cd-4Spy, respectively.

[0016] Figure 2 1 is the infrared spectrum of the obtained cadmium complex of pyrithione / polymer composite material, and the figure shows the infrared spectra of PVK, cadmium complex of pyrithione, and composite from top to bottom.

[0017] Figure 3 Schematic diagram of the structure of the obtained mercaptopyridine cadmium complex / polymer composite device.

[0018] Figure 4 This is a test diagram of the IV characteristic curve of the obtained mercaptopyridine cadmium complex / polymer composite material (Cd-2Spy@PVK) device.

[0019] Figure 5 This is a graph showing the state maintenance cycle times of the obtained mercaptopyridine cadmium complex / polymer composite material (Cd-2Spy@PVK) device in different resistance states.

[0020] Figure 6 This is a diagram of the state maintenance time of the obtained mercaptopyridine cadmium complex / polymer composite material (Cd-2Spy@PVK) device in different resistance states.

[0021] Figure 7 The IV characteristic curve test diagram of the obtained mercaptopyridine cadmium complex / polymer composite material (Cd-2Spy@PVK) device after irradiation with ultraviolet radiation for 12h and 24h. DETAILED DESCRIPTION

[0022] In order to make the contents of the present invention easier to understand, the technical solutions of the present invention are further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0023] Example 1

[0024] The cadmium complex of mercaptopyridine, Cd-2Spy, was prepared by a volatilization method. 0.2 mmol (0.084 g) of Cd(ClO4)2·6H2O, 0.4 mmol (0.038 g) of KSCN, and 0.4 mmol (0.044 g) of 2-mercaptopyridine (2Spy) were dissolved in 30 mL of methanol, stirred at room temperature for 2 h, and then filtered to evaporate the solution, yielding yellow crystals. Next, 8.3 mg of Cd-2Spy and 25 mg of polyvinylcarbazole (PVK) were dissolved in 5 mL of DMF, stirred for 2 h, and filtered to obtain a homogeneous solution. Devices were fabricated from these homogeneous solutions using the following method: First, a FTO (20 × 20 mm) substrate was pre-cleaned with acetone, ethanol, and deionized water, respectively, under ultrasonication, and dried in a vacuum oven. Next, the solution was spin-coated onto the FTO substrate at 1000 rpm and annealed in a vacuum oven at 60°C for 2 h. Finally, silver nanowires were spray-coated as the top electrode.

[0025] Example 2

[0026] First, the cadmium complex of mercaptopyridine, Cd-4Spy, was prepared by a volatilization method: 0.2 mmol (0.084 g) of Cd(ClO4)2·6H2O, 0.4 mmol (0.038 g) of KSCN, and 0.4 mmol (0.044 g) of 4-mercaptopyridine (4Spy) were dissolved in 30 mL of methanol. The mixture was stirred at room temperature for 2 hours, then filtered and evaporated to obtain yellow crystals. Next, 8.3 mg of Cd-4Spy and 25 mg of polyvinylcarbazole (PVK) were dissolved in 5 mL of DMF, stirred for 2 hours, and filtered to obtain a homogeneous solution. The device preparation method was the same as in Example 1.

[0027] Product Characterization

[0028] 1. The crystal structure of the cadmium complex of mercaptopyridine is as follows Figure 1 As shown in the figure:

[0029] The Cd atom in Cd-2Spy forms a typical hexacoordinated octahedral structure with the N atoms of two SCN groups and the S atoms on four 2Spy ligands. Two 2Spy ligands and two SCN groups are located on the equatorial plane, and the other two 2Spy ligands are located at the two vertices.

[0030] The Cd atom in Cd-4Spy has two coordination modes: one is a tetrahedral structure formed by a Cd atom with two S atoms from the 4Spy ligands, one S atom from the SCN group, and another N atom from the SCN group; the other is a hexahexahedral structure formed by a Cd atom with two N atoms from the SCN groups and four S atoms from the other SCN groups. These two different coordination environments are bridged by two SCN groups, forming a symmetrical structure centered on the hexahexahedral Cd atom.

[0031] Table 1

[0032]

[0033]

[0034] 2. Infrared spectrum characterization:

[0035] from Figure 2 It can be seen that 2936cm -1 , 740cm -1 The peaks at 1324 cm-1 are attributed to the stretching vibration and bending vibration of the long-chain alkane in PVK. -1 The peak at 1597 cm is attributed to the stretching vibration of CN. -1 、1481cm -1 、1441cm -1 It is attributed to the vibration of the benzene ring skeleton on the carbazole group in PVK. 2600cm -1 The weak peak at 2097 cm is the characteristic stretching vibration of the thiol group; the stretching vibration peak corresponding to the SCN group in Cd-4Spy is located at 2097 cm -1 and 879cm -1 In Cd-2Spy, it is 2016cm -1 and 811cm -1 879cm -1 and 811cm -1 The corresponding peak position is the stretching vibration of CS in the SCN group. The reason for the large difference in peak position is that in Cd-2Spy, only the N atom of SCN participates in the coordination. In all infrared spectra before and after the composite, the characteristic vibrations of the disulfide metal complex and PVP still exist before and after the composite, and basically no new peak position is found (3396cm in Cd-2Spy@PVK). -1The new peak at 2Spy is derived from the migration of the thiol proton to the N atom on the pyridine ring after the coordination of the 2Spy ligand, which indicates that the composite of the two materials is just a physical mixture.

[0036] 3. Multi-level controllable memory storage performance test:

[0037] The IV characteristic curves of the FTO / composite / Ag device were measured using a KEYSIGHT-B2901A single-channel semiconductor parameter tester.

[0038] like Figure 4 As shown in the figure, the IV characteristic curves of FTO / composite / Ag were tested within the range of 0V→-5V→0V→5V. In the first sweep process (-8V→5V, “Sweep 1” and “Sweep 2”), the current started to be in a high resistance state (OFF state, 1.54×10 - 7 A), as the voltage applied across the device gradually increases, when the voltage reaches 1.18V, the current suddenly jumps to 4.08×10 - 4 A, indicating that the current state changes from "OFF" state to "ON1" state. After that, the voltage continues to increase, and when the external voltage reaches 1.87V, it is observed that the current further increases to 2.90×10 -2 A, corresponds to the change into the "ON2" state, completing the Set process of the device. The "Sweep 2" process is equivalent to the "write" operation in the 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 shows that the device is a ternary RRAM storage type. The device has good cycling stability for 100 rounds, and all three resistance states can remain stable without significant attenuation for 2500s ( Figure 5 and Figure 6 Moreover, even after 12h and 24h of UV radiation, its performance did not show significant attenuation and it could still maintain the ternary resistive switching behavior ( Figure 7 ).

[0039] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A thiopyridine-based cadmium complex-doped polymer resistive switching memory material, characterized by: The mass ratio of the cadmium complex of mercaptopyridine to the polymer is 1:3; The cadmium complex of mercaptopyridine is any one of Cd-2Spy and Cd-4Spy; the polymer is polyvinylcarbazole; The preparation method of the cadmium complex of mercaptopyridine comprises: using mercaptopyridine as a ligand, stirring and reacting with cadmium thiocyanate, cooling and filtering, and volatilizing and crystallizing the filtrate to obtain the cadmium complex of mercaptopyridine; the mercaptopyridine is any one of 2-mercaptopyridine and 4-mercaptopyridine.

2. A method for preparing the mercaptopyridine-based cadmium complex-doped polymer resistive switching memory material according to claim 1, characterized in that: The cadmium complex of mercaptopyridine and the polymer are dissolved in a solvent and stirred for 2 hours to obtain the mercaptopyridine-based cadmium complex-doped polymer resistive switching memory material.

3. An application of the mercaptopyridine-based cadmium complex-doped polymer resistive memory material as claimed in claim 1 in a multi-level memristor.

4. The use according to claim 3, characterized in that: The multi-level memristor structure is a sandwich structure of bottom electrode / resistive storage 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 storage layer is a thiopyridine-based cadmium complex-doped polymer resistive storage material.

Images