A multi-level resistive random access memory based on tunable resistive switching behavior of covalent organic polymer thin film material and a preparation method thereof

Abstract

The application discloses a multilevel resistive switching memory based on a covalent organic polymer thin film material and a preparation method thereof. The multilevel resistive switching memory material is a covalent organic polymer thin film which is prepared by Schiff base condensation reaction with 1,3,6,8-tetra(4-aminophenyl)pyrene and triformylphloroglucin as reaction monomers. An ITO / 2DP PyTTA+Tp‑n / Ag sandwich structure memory device is prepared. In the reaction process, the memory device shows adjustable resistive switching behavior storage performance by adjusting the volume ratio of the mixed solvent. The covalent organic polymer thin film can be used as a novel multilevel resistive switching memory material with adjustable resistive switching behavior. The memory device shows the characteristics of flexibility, low cost, high switching current ratio, low turn-on voltage, high stability and the like in the aspects of device preparation and performance, and is suitable for memory devices under a wide range of conditions.

Description

Technical Field

[0001] This invention belongs to the field of memory technology, specifically relating to a multi-level resistive switching memory based on a covalent organic polymer thin film with adjustable resistive switching behavior and its fabrication method. Background Technology

[0002] Resistive random access memory (RRAM) can reversibly switch between high-resistance and low-resistance states under external (electrical) stimulation. It boasts advantages such as large capacity, high speed, simple structure, low power consumption, and ease of integration, and is considered the most promising next-generation non-volatile memory. The rapid development of information technology has led to an explosive growth in the amount of information people have, demanding that memory stores even more information. Multilevel memory can effectively solve the congestion bottleneck between information processors and main memory, significantly increasing storage density. Currently, only a few materials can realize multilevel memristor storage, and research on multilevel RRAM materials is still in its early stages, far from meeting the enormous demands of future ultra-high-density information storage. Compared to binary unit storage, multilevel RRAM not only has two resistive storage states (0 and 1), but its storage capacity can be increased by up to 3... n This means that the unit storage capacity is increased by hundreds of millions of times 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 storage materials is a simpler and easier approach to implement.

[0003] This invention relates to a multilevel resistive switching memory (RSM) with tunable resistive switching behavior, based on the in-situ deposition of covalent organic polymer thin films on a substrate (ITO conductive glass) through polymerization with different mixed solvent ratios. The thin film material is synthesized using a simple and controllable solvothermal method, resulting in a smooth surface with low roughness. The resistive switching behavior is controlled by altering the mixed solvent ratio during the reaction. This invention produces a low-cost, high-current-to-voltage, low-threshold multilevel RSM material suitable for large-scale industrial production, demonstrating promising application prospects. Summary of the Invention

[0004] Based on the above analysis, the present invention will be further described in detail with reference to the accompanying drawings.

[0005] The purpose of this invention is to provide a multilevel resistive switching memory (RSM) with tunable resistive switching behavior based on a covalent organic polymer thin film and its fabrication method. 1,3,6,8-tetratetra(4-aminophenyl)pyrene (PyTTA) and trialdehyde phloroglucinol (Tp) are used as monomers, and the RSM is prepared via a simple Schiff base condensation reaction to produce a multilevel RSM material 2DP with tunable resistive switching behavior.PyTTA+Tp-n Its preparation method is simple, the raw materials are readily available, and it is easy to implement. Moreover, there are no harmful byproducts in the preparation process, making it an environmentally friendly green synthesis.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A multi-level resistive switching memory material based on tunable resistive switching behavior of a covalent organic polymer thin film, namely a covalent organic polymer thin film 2DP. PyTTA+Tp-n (n=01, 02, or 03), the device structure based on this covalent organic polymer film is as follows: Figure 6 As shown. This device has a sandwich structure, with the bottom electrode being, but not limited to, ITO conductive glass, and the middle memristor material being a covalent organic polymer thin film 2DP. PyTTA+Tp-n (n=01, 02 or 03), the top electrode can be, but is not limited to, Ag.

[0007] The preparation method of the covalent organic polymer thin film material is as follows: Figure 1 As shown: Under N2 atmosphere, PyTTA and Tp were dissolved in a mixed solvent of dimethylacetamide and o-dichlorobenzene, and then the substrate (ITO conductive glass) and the catalyst acetic acid were added, followed by ultrasonic treatment; after three vacuum degassing-gas charging cycles, the reactor was placed in an oven at 120 ℃ and reacted for 3-5 days; after the reaction was completed, the substrate was transferred to dimethylacetamide or o-dichlorobenzene and soaked for 12-24 h, and finally dried in a vacuum oven at 90-120 ℃.

[0008] Furthermore, a multi-level resistive switching memory based on a covalent organic polymer thin film material is provided. This multi-level resistive switching memory uses a covalent organic polymer thin film as the resistive switching storage layer to fabricate the multi-level resistive switching memory with adjustable resistive switching behavior. The multi-level resistive switching memory has a sandwich structure of a bottom electrode / resistive switching storage layer / top electrode. The bottom electrode is indium tin oxide conductive glass; the top electrode is a silver inert metal material; and the resistive switching storage layer is a covalent organic polymer thin film material. The preparation method of the covalent organic polymer thin film includes: using 1,3,6,8-tetra(4-aminophenyl)pyrene and trialdehyde phloroglucinol as monomers, a covalent organic polymer thin film is synthesized via a Schiff base condensation reaction.

[0009] Furthermore, the method for preparing the multilevel resistive switching memory includes the following steps: adding 1,3,6,8-tetra(4-aminophenyl)pyrene and trialdehyde phloroglucinol to a mixed solvent, placing ITO conductive glass into a reaction vessel, adding a catalyst, and carrying out a solvothermal polymerization reaction under a nitrogen atmosphere to obtain a covalent organic polymer thin film material with ITO conductive glass as the substrate, and then preparing a silver electrode on the covalent organic polymer thin film material to obtain the multilevel resistive switching memory with adjustable resistive switching behavior.

[0010] Furthermore, the mixed solvent is a mixture of o-dichlorobenzene and dimethylacetamide, with a volume ratio of o-dichlorobenzene:dimethylacetamide = 1:1 to 1:9; the catalyst is acetic acid with a concentration of 3 to 12 M; the reaction temperature of the solvothermal polymerization reaction is 90 to 120 °C, and the reaction time is 6 to 72 h. The resistive switching behavior is controlled by changing the ratio of the mixed solvent during the reaction.

[0011] The significant advantages of this invention are: (1) The covalent organic polymer material obtained in this invention can form a uniform and dense film on the substrate.

[0012] (2) The covalent organic polymer material obtained by the present invention exhibits adjustable resistance switching behavior under different mixed solvent ratios, especially exhibiting multi-level memory storage performance when the mixed solvent ratio is 7:3 (dimethylacetamide: o-dichlorobenzene).

[0013] (3) All raw materials used in this invention are readily available; the synthesis method is simple to operate; the device has excellent performance and strong cycle stability. Attached Figure Description

[0014] Figure 1 The resulting covalent organic polymer material 2DP PyTTA+Tp-n A schematic diagram of the synthesis of (n=01, 02 or 03).

[0015] Figure 2 The resulting covalent organic polymer material 2DP PyTTA+Tp-n Infrared spectra of (n=01, 02 or 03).

[0016] Figure 3 The resulting covalent organic polymer material 2DP PyTTA+Tp-n Raman spectra of (n=01, 02 or 03).

[0017] Figure 4 The resulting covalent organic polymer material 2DP PyTTA+Tp-n UV absorption spectra of (n=01, 02 or 03).

[0018] Figure 5 The resulting covalent organic polymer material 2DP PyTTA+Tp-n Scanning electron microscope images (n=01, 02 or 03).

[0019] Figure 6 The resulting covalent organic polymer material 2DP PyTTA+Tp-n Device structure diagram (n=01, 02 or 03).

[0020] Figure 7 The resulting covalent organic polymer material 2DP PyTTA+Tp-n(n=01, 02 or 03) Device at room temperature IV Characteristic curve test graph.

[0021] Figure 8 The resulting covalent organic polymer material 2DP PyTTA+Tp-n (n=01, 02 or 03) The number of cycles the device maintains in high and low resistance states at room temperature. Detailed Implementation

[0022] 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.

[0023] Example 12DP PyTTA+Tp-01 Preparation of polymer films: 1) Under a nitrogen atmosphere, PyTTA (22.6 mg) and Tp (10.9 mg) were dissolved in o-dichlorobenzene ( o In a mixed solvent of DCB and dimethylacetamide (DMAc) (2 mL, V DMAc :V o-DCB =1:1), ultrasonic treatment for 5 min; 2) Add ITO conductive glass and acetic acid (6 M, 200 μL) as catalyst to the above mixture and sonicate for 5 min; 3) After three vacuum degassing-gas-charging cycles, the reactor was placed in an oven at 120 ℃ and reacted for 3 days; 4) After the reaction is complete, the substrate is transferred to o-dichlorobenzene and soaked for 1 day to remove unreacted raw materials and other impurities; 5) The above film was dried in a vacuum oven at 90°C to obtain 2DP grown on ITO conductive glass. PyTTA+Tp-01 Polymer thin film materials.

[0024] Example 22DP PyTTA+Tp-02 Preparation of polymer films: 1) Under a nitrogen atmosphere, PyTTA (22.6 mg) and Tp (10.9 mg) were dissolved in o-dichlorobenzene ( o In a mixed solvent of DCB and dimethylacetamide (DMAc) (2 mL, V DMAc :V o-DCB =7:3), ultrasonic treatment for 5 min; 2) Add ITO conductive glass and acetic acid (6 M, 200 μL) as catalyst to the above mixture and sonicate for 5 min; 3) After three vacuum degassing-gas-charging cycles, the reactor was placed in an oven at 120 ℃ and reacted for 3 days; 4) After the reaction is complete, the substrate is transferred to o-dichlorobenzene and soaked for 1 day to remove unreacted raw materials and other impurities; 5) The above film was dried in a vacuum oven at 90°C to obtain 2DP grown on ITO conductive glass. PyTTA+Tp-02 Polymer thin film materials.

[0025] Example 32DP PyTTA+Tp-03 Preparation of polymer films: 1) Under a nitrogen atmosphere, PyTTA (22.6 mg) and Tp (10.9 mg) were dissolved in o-dichlorobenzene ( o In a mixed solvent of DCB and dimethylacetamide (DMAc) (2 mL, V DMAc :V o-DCB =9:1), ultrasonic treatment for 5 min; 2) Add ITO conductive glass and acetic acid (6 M, 200 μL) as catalyst to the above mixture and sonicate for 5 min; 3) After three vacuum degassing-gas-charging cycles, the reactor was placed in an oven at 120 ℃ and reacted for 3 days; 4) After the reaction is complete, the substrate is transferred to o-dichlorobenzene and soaked for 1 day to remove unreacted raw materials and other impurities; 5) The above film was dried in a vacuum oven at 90°C to obtain 2DP grown on ITO conductive glass. PyTTA+Tp-03 Polymer thin film materials.

[0026] Figure 2 For the prepared 2DP PyTTA+Tp-n The Fourier transform infrared spectrum. Figure 2 Analysis shows that 2DP PyTTA+Tp-n In (n=01, 02, 03), at 1635cm -1 The vibrational absorption peak at (-CHO) disappears, and at 1618 cm⁻¹... -1 An absorption peak at C=N appears.

[0027] Figure 3 For the prepared 2DP PyTTA+Tp-n The Raman spectrum. For Figure 3 Analysis shows that 2DP PyTTA+Tp-n In (n=01, 02, 03), at 1593cm -1 The absorption is attributed to the stretching vibration of -NH2 at 1245 cm⁻¹. -1 The absorption is attributed to the stretching vibration of CO.

[0028] Figure 4 For the prepared 2DP PyTTA+Tp-n The UV-Vis absorption spectrum. For Figure 4 Analysis shows that, compared to the UV absorption spectra of the two monomers, the 2DP after polymerization... PyTTA+Tp-n (n=01, 02, 03) The ultraviolet absorption bands broaden, and the degree of conjugation is enhanced.

[0029] Figure 5 For the prepared 2DP PyTTA+Tp-n Scanning electron microscope image. For Figure 5 Analysis shows that the thin film surface is relatively flat and smooth, which is conducive to electron transfer and transport.

[0030] Example 42DP PyTTA+Tp-n Fabrication and Evaluation of Polymer Thin Film-Based Multilevel Resistive Switching Memory Devices (n=01, 02, 03) 1) Device fabrication: The 2DP PyTTA+Tp-n Polymer thin films are used as resistive switching active layers to construct multi-level resistive switching memory devices, the device structure of which is as follows: Figure 6 As shown, it includes a bottom electrode, a middle resistive switching active layer, and a top electrode, namely ITO / 2DP. PyTTA+Tp-n / Ag, where Ag is coated onto 2DP by vapor deposition. PyTTA+Tp-n On polymer films.

[0031] 2) Device Evaluation: The electrical performance of the memory was measured using a KEYSIGHT B2911A digital source meter. Specifically, a certain bias range (-5 V to 5 V) was applied, and a scan was performed under the condition of limiting the current to 0.5 A. When the voltage reached the threshold voltage, the current suddenly increased, and the resistance changed from a high resistance state (HRS) to a low resistance state (LRS). This process is called "writing," and the voltage at this time is the turn-on voltage (V). set During the voltage reverse scan, the current suddenly decreases, and the resistance changes from a low-resistance state (LRS) back to a high-resistance state (HRS). This process is called "reading," and the voltage at this time is the reset voltage (V). reset ).

[0032] like Figure 7 As shown in Figure a, the ITO / 2DP test was performed. PyTTA+Tp-01 / Ag within the range of 0V→+5V→0V→-5V IV The characteristic curve shows that when the applied voltage exceeds the threshold voltage (Vths = +1.16 V), the device changes from a low conductivity state (ON1) to a high conductivity state (ON2) and exhibits binary WORM storage behavior, with an ON / OFF current switching ratio of 10. 4.8 / 1.

[0033] like Figure 7 As shown in Figure b, the ITO / 2DP test was performed. PyTTA+Tp-02 / Ag within the range of 0V→+5V→0V→-5V IV The characteristic curves show that when the applied voltage exceeds the threshold voltage (Vths = +1.14 V), the device transitions from the off state to a low conductivity state (ON1). Subsequently, when the applied voltage reaches +1.73 V, the device transitions to a high conductivity state (ON2) and exhibits ternary WORM storage behavior, with an ON2 / ON1 / OFF current switching ratio of 10. 5.0 / 10 2.5 / 1.

[0034] like Figure 7 As shown in Figure c, the ITO / 2DP test is performed. PyTTA+Tp-03 / Ag within the range of 0V→-5V→0V→+5V→0V IV The characteristic curves show that in the negative voltage scanning region, when the applied voltage exceeds the threshold voltage (Vths = -1.01 V), the device changes from a low conductivity state (ON1) to a high conductivity state (ON2); in the positive voltage scanning region, when the applied voltage exceeds the threshold voltage (Vth = +4.57 V), the device changes from a high conductivity state (ON2) to a low conductivity state (ON1). It also exhibits binary RRAM storage behavior, with an ON / OFF current switching ratio of 10. 2.9 / 1.

[0035] Table 1 shows a comparison of device performance based on the polymerization of covalent organic polymer films with different mixed solvent ratios. PyTTA+Tp-n (n=01, 02, 03) The keto-enol isomer ratio in the polymer film can be controlled by the reaction solvent. When the mixed solvent ratio is V DMAc :V o-DCB At a ratio of 7:3, the keto-enol isomer ratio is the lowest (~2.70). When a voltage stimulus is applied, more enol configurations in the polymer film are converted to keto configurations, thereby promoting efficient charge transfer in the polymer.

[0036] Table 1 Based on 2DP PyTTA+Tp-n Summary of performance of multi-level resistive random access memory (n=01, 02, 03)

[0037] like Figure 8 As shown, ITO / 2DP PyTTA+Tp-n The / Ag device exhibited good stability over 105 cycles.

[0038] In summary, this invention utilizes the polymerization of covalent organic polymer thin films in different mixed solvent ratios to form in-situ films on a substrate (ITO conductive glass), thereby fabricating a multi-level resistive switching memory with adjustable resistive switching behavior. This thin film material is synthesized using a simple and controllable solvothermal method, resulting in a smooth surface with low roughness. The resistive switching behavior is controlled by altering the mixed solvent ratio during the reaction. This invention produces a low-cost, high-current-to-current ratio, low-turn-on voltage, and industrially suitable multi-level resistive switching memory material with adjustable resistive switching behavior (specific performance parameters are shown in Table 1), demonstrating promising application prospects.

[0039] 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 multi-level resistive switching memory based on the adjustable resistive switching behavior of a covalent organic polymer thin film material, characterized in that: A covalent organic polymer thin film is used as the resistive switching memory layer to fabricate a multi-level resistive switching memory with adjustable resistive switching behavior; the multi-level resistive switching memory has a sandwich structure of bottom electrode / resistive switching memory layer / top electrode; the bottom electrode is indium tin oxide conductive glass. The top electrode is made of silver inert metal; the resistive switching memory layer is made of covalent organic polymer thin film material; the preparation method of the covalent organic polymer thin film includes: using 1,3,6,8-tetra(4-aminophenyl)pyrene and trialdehyde phloroglucinol as monomers, the covalent organic polymer thin film is synthesized by Schiff base condensation reaction; the covalent organic polymer contains keto-enol isomers, and the keto-enol isomer ratio is 2.

70.

2. A method for fabricating a multi-level resistive switching memory with adjustable resistive switching behavior as described in claim 1, characterized in that: Includes the following steps: 1,3,6,8-tetra(4-aminophenyl)pyrene and trialdehyde phloroglucinol were added to a mixed solvent, and ITO conductive glass was placed in a reaction vessel. A catalyst was then added, and a solvothermal polymerization reaction was carried out under a nitrogen atmosphere to obtain a covalent organic polymer thin film material based on ITO conductive glass. Silver electrodes were then fabricated on the covalent organic polymer thin film material to obtain the multi-level resistive switching memory with adjustable resistive switching behavior.

3. The preparation method according to claim 2, characterized in that: The mixed solvent is a mixture of o-dichlorobenzene and dimethylacetamide, with a volume ratio of o-dichlorobenzene:dimethylacetamide = 3:

7.

4. The preparation method according to claim 2, characterized in that: The catalyst is acetic acid with a concentration of 3-12M.

5. The preparation method according to claim 2, characterized in that: The reaction temperature for solvothermal polymerization is 90~120℃, and the reaction time is 6-72 h.

6. The preparation method according to claim 2, characterized in that: The behavior of the resistor switch can be controlled by changing the ratio of the mixed solvent during the reaction process.

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