Monomolecular electric memristor based on dipole control and preparation method thereof

Abstract

The invention relates to the technical field of electronic devices, in particular to a monomolecular electric memristor based on dipole control and a preparation method thereof.The monomolecular electric memristor comprises a molecular heterojunction, and the molecular heterojunction is formed by connecting dipole molecules and graphene point electrodes through amido bonds; the dipole molecule comprises an amide structure based on a carbazole nitrogen-containing heterocyclic ring unit, under the action of an external electric field, a side chain chemical bond of the dipole molecule can rapidly rotate, the size and direction of an intramolecular dipole moment can be changed, the molecule can be rapidly and stably switched among different resistance states, and the read-write speed of the memristor is remarkably improved; the storage state is stably kept under the power-off condition, and the long-term stability and reliability of the memristor function are ensured. The preparation method comprises the processes of introducing dipole molecules and forming amido bonds between the dipole molecules and the graphene point electrode, and the preparation method is simple and convenient to operate, mild in condition and beneficial to large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic devices, and in particular to a single-molecule memristor based on dipole control and a preparation method thereof. Background Art

[0002] A memristor is a nonlinear resistor with memory, combining the properties of resistance, capacitance, and inductance. It serves as the link between magnetic flux and charge. Its nonvolatile nature, retaining its state after power failure, holds great potential for applications in information storage, logic operations, and neural networks. The nonvolatile nature of a memristor is primarily achieved through its resistance change mechanism, which relies on ionic and electronic effects.

[0003] Using organic molecules to construct memristors offers a potential solution for miniaturizing semiconductor devices and has attracted considerable attention. Although research on molecular memristors has made some progress, they still face challenges such as weak reversibility, slow switching speeds, and poor stability. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the related art. To this end, the first object of the present invention is to provide a single-molecule memristor based on dipole control; the second object of the present invention is to provide a method for preparing the memristor.

[0005] In order to achieve the first purpose, the technical solution adopted by the present invention is: A single-molecule memristor based on dipole control, comprising a molecular heterojunction, wherein the molecular heterojunction is composed of a dipole molecule and a graphene point electrode connected by an amide bond; Wherein, the structural formula of the dipole molecule is as follows: .

[0006] By introducing a single dipole molecule, a conductive path is constructed between it and the graphene point electrode through an amide bond. The dipole molecule contains an amide structure based on a nitrogen-containing heterocyclic unit of carbazole. Its side chain can undergo reversible rotation relative to the main chain with the CN bond as the axis under the stimulation of an external electric field, thereby regulating the molecular conformation and changing the molecular conductivity behavior.

[0007] The charge distribution of the side chains and main chain of this dipole molecule is uneven. Under the influence of an external electric field, the chemical bonds of the dipole side chains can rotate rapidly, changing the magnitude and direction of the intramolecular dipole moment and enabling the molecule to switch between different resistance states quickly and stably. This process, based on the molecular side chains' ability to rotate rapidly under the influence of an electric field, reduces delays in electron transmission and significantly improves the read and write speed of the memristor. Furthermore, the dynamic regulation of the intramolecular dipole moment further ensures the reversibility and stability of the resistance state switching.

[0008] The distance between the oxygen atom on the double bond of the dipole molecule's side chain and the hydrogen atom in carbazole satisfies the van der Waals radius of hydrogen bonding. This hydrogen bonding maintains the molecular conformation, resulting in a high energy barrier between different orientations of the dipole molecule's side chains. This allows for a stable memory state at room temperature, avoiding instability caused by thermal motion.

[0009] Preferably, X in the dipole molecular structure is an alkynyl-containing group.

[0010] Preferably, the alkynyl-containing group is any one of the following structural formulas: 、 、 、 .

[0011] Preferably, X in the dipole molecular structure is as follows: .

[0012] Preferably, X in the dipole molecular structure is as follows: .

[0013] Preferably, the graphene point electrode is a triangular electrode.

[0014] Preferably, the gap between the top ends of the graphene point electrodes is 1 nm to 10 nm.

[0015] Preferably, the graphene point electrodes are array electrodes, and the graphene point electrodes are arranged on a graphene electrode layer.

[0016] Preferably, the graphene electrode layer is in a strip shape with a width of 5 nm to 100 nm.

[0017] In order to achieve the second purpose, the technical solution adopted by the present invention is: A method for preparing a memristor, for preparing any of the above-mentioned single-molecule memristors based on dipole control, comprising forming an amide bond between a dipole molecule and a graphene dot electrode, comprising the following steps: S100, dissolving the dipolar compound and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride in a pyridine solution to obtain a mixed solution; wherein the molar ratio of the dipolar compound to 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:(20-40); S200, placing the graphene dot electrode in the mixed solution, reacting in an inert gas atmosphere for 36 hours to 72 hours, so that the dipole molecule and the graphene dot electrode are connected through an amide bond, and then cleaning and drying to obtain a single-molecule memristor based on dipole control.

[0018] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: The present invention provides a single-molecule memristor based on dipole control and a preparation method thereof. By introducing a single dipole molecule, it is connected to a graphene point electrode through an amide bond to form a molecular heterojunction. The molecular heterojunction serves as a conductive path. The electric field is used to stimulate the side chain of the dipole molecule to undergo reversible rotation relative to the main chain about the CN bond as the axis, thereby regulating the molecular conformation and changing the molecular conductivity behavior.

[0019] Under the influence of an external electric field, the chemical bonds in the dipolar molecular side chains rotate rapidly, changing the magnitude and direction of the intramolecular dipole moment and enabling the molecule to switch quickly and stably between different resistance states. This process, based on the molecular side chains' ability to rotate rapidly under the influence of an electric field, reduces delays in electron transmission and significantly improves the read and write speed of the memristor. Furthermore, the dynamic regulation of the intramolecular dipole moment further ensures the reversibility and stability of the resistance state switching.

[0020] Since the intramolecular hydrogen bond interaction can ensure the existence of a high energy barrier between the different orientations of the dipole molecular side chains, it can stably maintain its storage state under power-off conditions, ensuring the long-term stability and reliability of the memristive function.

[0021] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 Schematic diagram of the structure of a single-molecule memristor based on dipole control provided in Example 2 of the present invention.

[0024] Figure 2 This is the voltage-current curve region of the single-molecule memristor based on dipole control provided in Example 2 of the present invention.

[0025] Reference numerals: 1. Silicon wafer; 2. Molecular heterojunction; 21. Dipolar molecule; 22. Graphene dot electrode. DETAILED DESCRIPTION

[0026] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0027] In the following examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all available from commercial sources unless otherwise specified.

[0028] Example 1 Preparation of dipolar compounds.

[0029] The molecular structure of a dipolar compound is shown below: ; Its synthetic route is as follows: The specific process is as follows: 2,7-Dibromocarbazole (3.90 g, 12 mmol) and sodium hydride (NaH) (0.860 g, 36 mmol) were added to a two-necked flask. 30 mL of dry tetrahydrofuran (THF) was added at 0°C and stirred at room temperature for 45 minutes. Pyridine-2-carbonyl chloride (2.04 g, 14.40 mmol) was then added at 0°C. The mixture was stirred at 0°C for 10 minutes, then warmed to room temperature and stirred for another 2 hours. The reaction was quenched with water and extracted with dichloromethane (20 mL x 3). The organic phase was dried over anhydrous magnesium sulfate and the solvent was removed by rotary evaporation. The residue was purified by silica gel column chromatography (silica gel: petroleum ether / dichloromethane, volume ratio 1:1) to afford Compound I as a white solid.

[0030] Compound I (4.29 g, 0.01 mol) and p-aminophenylboronic acid hydrochloride (4.34 g, 0.025 mol) were placed in a 500 mL three-necked flask. THF (250 mL) was added as the solvent. A 2 mol / L potassium carbonate (K2CO3) solution (37.5 mL) and methyltrioctyl ammonium chloride (0.5 g) were then added. The mixture was stirred magnetically and purged with argon. The mixture was heated to 75°C in an oil bath. Tetrakistriphenylphosphine palladium (PdPPh3)4 (0.05 g) was then added. After reflux for 24 hours, the mixture was filtered and the filter cake collected. The filter cake was washed three times with distilled water (100 mL). Finally, the filter cake was dried under vacuum at 80°C for 24 hours to yield Compound II.

[0031] The compound II synthesized above is dissolved in acetonitrile to obtain an acetonitrile solution of compound II, and then a concentrated hydrochloric acid solution of the same molar number is added dropwise. After the reaction is completed, the solvent is removed by rotary evaporation to obtain a solid dipolar compound in the form of a pyridinium cation salt.

[0032] The dipolar compound uses carbazole as the molecular backbone and side chains containing pyridinium cations connected by C-N bonds, forming a dynamic dipolar molecule. Under the influence of an external electric field, the pyridinium cation undergoes a reversible 360-degree rotation around the C-N bond, thereby changing the direction of the dipole moment within the molecule and dynamically regulating the electron transfer path. The large electronegativity of the pyridinium cation enhances the molecular polarity and increases the dipole moment, further improving the molecule's responsiveness to electric fields. This molecular structure design allows the molecular dipole moment to be rapidly modulated using an external electric field, thereby altering the charge transfer path and precisely controlling the molecule's resistance state to achieve a memristive function. Furthermore, by varying the side chain structure, such as by varying the length and substituent groups, the performance of the memristor can be flexibly adjusted, enabling optimization based on specific application requirements.

[0033] Example 2 Preparation of single-molecule memristor based on dipole control.

[0034] like Figure 1 As shown, it is a schematic structural diagram of a single-molecule memristor based on dipole control provided in this embodiment, comprising a silicon wafer 1 and a molecular heterojunction 2, wherein the molecular heterojunction 2 is loaded on the silicon wafer 1, and the molecular heterojunction 2 is composed of a dipole molecule 21 and a graphene point electrode 22 connected by an amide bond.

[0035] The preparation process of the single-molecule memristor based on dipole control provided by the present invention is as follows: A single layer of graphene was obtained on a copper sheet by chemical vapor deposition, and the single layer of graphene was fixed to a quartz sheet with transparent adhesive. Polymethyl methacrylate (PMMA) was spin-coated using a spin coater, initially at 500 rpm for 10 s, then at 4000 rpm for 40 s. A heating stage was used to heat at 180°C for 2 minutes. The graphene on the back of the copper sheet was etched using oxygen plasma. After 50 seconds of etching, it was cut into 1 cm × 1 cm squares. The copper sheet was placed face down in a freshly prepared ferric chloride solution and soaked in a hydrochloric acid solution and a deionized water solution for 30 minutes. The graphene layer was then transferred to a silicon wafer and the adhesive was removed by heating at 120°C for 8 minutes in an acetone solution to obtain a single layer of graphene film.

[0036] Strips with a width of 40 μm and a length of 200 μm were photoetched on the graphene film using ultraviolet photoresist. The strips were exposed to ultraviolet light, and the portion of the strip to be retained was selected for protection with photoresist. The remaining portion was removed with a developer, thereby exposing the graphene layer under the photoresist. The exposed graphene layer was placed in an oxygen plasma etcher for oxygen plasma etching for 50 seconds, and the remaining photoresist was removed with acetone to obtain a graphene strip-silicon wafer.

[0037] Spin-coat photoresist on the graphene strip-silicon wafer, heat at 110°C for 3 minutes, photolithography the electrodes using a photolithography machine, and then evacuate the thermal resistance evaporation coating machine to a vacuum of about 5×10 -5 After Pa, chromium with a thickness of 8nm to 10nm and gold with a thickness of 60nm to 80nm were evaporated, and the sample was taken out and rinsed with acetone solution to obtain a gold electrode-graphene strip-silicon wafer; Among them, the gold electrodes in the gold electrode-graphene strip-silicon wafer are located on the strips, with a total of 169 pairs of gold electrodes forming a gold electrode array.

[0038] A layer of PMMA was spin-coated on a gold electrode-graphene strip-silicon wafer and cured on a hot plate at 180°C for 2 minutes. An electron beam lithography system was then used to etch dotted lines on the gold electrode-graphene strip-silicon wafer to create graphene array point electrodes. This was then tested for continuity using a source meter and a probe station. The dotted lines were located between each pair of gold electrodes, with a total length of 60 μm, each 150 nm long, and separated by 40 nm intervals.

[0039] The graphene array point electrodes after dotted line etching were developed using a methyl isobutyl ketone solution diluted with isopropyl alcohol (the volume ratio of isopropyl alcohol to methyl isobutyl ketone was 1:3), and then etched using oxygen plasma reactive ion etching (RIE) technology to obtain graphene point electrodes with a gap of 1 nm to 10 nm.

[0040] A dipole molecule is introduced between the graphene point electrodes. The process is as follows: the dipole compound obtained in Example 1 and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloric acid are weighed at a molar ratio of 1:30, placed in a clean two-necked flask, and 10 ml of pyridine solution is injected into the flask with a syringe to obtain a mixed solution; a silicon wafer loaded with graphene point electrodes is placed in the mixed solution, reacted in a dark nitrogen atmosphere for 48 hours, and then the sample is carefully picked up with tweezers, washed three times with acetone and ultrapure water, and gently blown dry with a nitrogen flow to obtain a single-molecule memristor based on dipole control.

[0041] Using Agilent 4155C semiconductor tester and ST-500 probe station, the external electric field strength was set in the range of -1 to 1V to test the current response characteristics of the single-molecule memristor based on dipole control.

[0042] By controlling the positive and negative values ​​and magnitude of the bias voltage applied to the source and drain graphene point electrodes, a probe station and a semiconductor parameter analyzer are used to test the current response characteristic curve of the dipole molecule under an external electric field, and the conductivity information is encoded to realize the memristive function of the molecular device.

[0043] Test conditions: Temperature range: 80 K to 300 K, source-drain voltage range: -1 to 1 V, interval 5 mV.

[0044] The results are as follows Figure 2 As shown, the IV curve of the single-molecule memristor based on dipole control provided by the present invention has obvious electrical hysteresis, and a resistance transition can occur between voltages of 0.6 and 0.8V, demonstrating typical memristive function. When a forward voltage is applied, the electric field is directed from the source to the drain, causing the current state to switch from a low resistance state to a high resistance state, and the molecular resistance decreases. This change is speculated to be due to the rotation of the side chain under the action of the electric field, making the direction of the dipole moment more conducive to charge transfer. Conversely, when a reverse voltage is applied, the direction of the electric field is reversed, from the drain to the source, and the current state recovers from a high resistance state to a low resistance state, and the molecular resistance increases, indicating that the molecular side chain can reversibly rotate back to the initial state, thereby realizing the dipole control of the molecular memristor.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A single-molecule memristor based on dipole control, characterized in that: It includes a molecular heterojunction, wherein the molecular heterojunction is formed by connecting a dipole molecule and a graphene point electrode via an amide bond; Wherein, the structural formula of the dipole molecule is as follows: 。 2. The single-molecule memristor based on dipole control as claimed in claim 1, characterized in that: X in the dipole molecular structure is an alkynyl-containing group.

3. The single-molecule memristor based on dipole control as claimed in claim 2, characterized in that: The alkynyl-containing group is any one of the following structural formulas: 、 、 、 。 4. The single-molecule memristor based on dipole control as claimed in claim 1, characterized in that: X in the dipole molecular structure is as follows: 。 5. The single-molecule memristor based on dipole control as claimed in claim 1, characterized in that: X in the dipole molecular structure is as follows: 。 6. The single-molecule memristor based on dipole control as claimed in claim 1, characterized in that: The graphene point electrode is a triangular electrode.

7. The single-molecule memristor based on dipole control as claimed in claim 6, characterized in that: The gap between the top ends of the graphene point electrodes is 1 nm to 10 nm.

8. The single-molecule memristor based on dipole control as claimed in claim 1, characterized in that: The graphene point electrodes are array electrodes, and the graphene point electrodes are arranged on the graphene electrode layer.

9. The single-molecule memristor based on dipole control as claimed in claim 8, characterized in that: The graphene electrode layer is in strip shape with a width of 5nm to 100nm.

10. A method for preparing an electric memristor, characterized in that: A method for preparing a dipole-controlled single-molecule memristor according to any one of claims 1 to 9, comprising forming an amide bond between a dipole molecule and a graphene point electrode, comprising the following steps: S100, dissolving the dipolar compound and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloric acid in a pyridine solution to obtain a mixed solution; Wherein, the molar ratio of the dipolar compound to 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloric acid is 1:(20-40); S200, placing the graphene dot electrode in the mixed solution, reacting in an inert gas atmosphere for 36 hours to 72 hours, connecting the dipole molecule to the graphene dot electrode through an amide bond, and then washing and drying to obtain a single-molecule memristor based on dipole control.

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