A single-molecule memristor based on dipole control and its preparation method

Abstract

The present invention relates to the technical field of electronic devices, and in particular to a single-molecule electrical memristor based on dipole control and a preparation method thereof, wherein the molecular electrical memristor comprises a molecular heterojunction, wherein the molecular heterojunction is formed by connecting a dipole molecule and a graphene point electrode through an amide bond, wherein the dipole molecule comprises an amide structure based on a carbazole nitrogen-containing heterocyclic unit, and under the action of an external electric field, the side chain chemical bond of the dipole molecule can rotate rapidly, changing the size and direction of the dipole moment in the molecule, prompting the molecule to switch rapidly and stably between different resistance states, significantly improving the read and write speed of the memristor; and stably maintaining its storage state under power-off conditions, ensuring the long-term stability and reliability of the memristor function. The preparation method thereof comprises a process of introducing a dipole molecule to form an amide bond between the dipole molecule and the graphene point electrode, and the preparation method is simple to operate, mild in conditions, and conducive 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 electrical memristor based on dipole control and a preparation method thereof. Background Art

[0002] Memristor is a nonlinear resistor with memory function. It combines the characteristics of resistance, capacitance and inductance, and is the link between magnetic flux and charge. Memristor has the non-volatile property of maintaining its state after power failure, which makes it show great application potential in fields such as information storage, logical operations and neural networks. The non-volatile property of memristor is mainly achieved through its resistance change mechanism, which relies on ionic effect and electronic effect.

[0003] Using organic molecules to construct memristors provides a potential solution for the miniaturization of semiconductor devices and has attracted much attention. Although some progress has been made in the research on molecular memristors, there are still problems such as weak reversibility, slow switching speed, 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:

[0006] A single-molecule electrical memristor based on dipole control, comprising a molecular heterojunction, wherein the molecular heterojunction is formed by connecting a dipole molecule and a graphene point electrode via an amide bond;

[0007] Wherein, the structural formula of the dipole molecule is as follows:

[0008] .

[0009] By introducing a single dipole molecule, a conductive pathway 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, and its side chain can reversibly rotate relative to the main chain around 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.

[0010] The charge distribution of the side chain groups and the main chain of the dipole molecule is uneven. Under the action of an external electric field, the chemical bonds of the side chain of the dipole molecule can rotate rapidly, changing the size and direction of the dipole moment within the molecule, and prompting the molecule to switch rapidly and stably between different resistance states. This process is based on the rapid rotation ability of the molecular side chain under the action of an electric field, reducing the delay in the electron transmission process and significantly improving the read and write speed of the memristor. At the same time, due to the dynamic regulation of the dipole moment within the molecule, the reversibility and stability of the resistance state switching are further ensured.

[0011] The distance between the oxygen atom on the double bond of the side chain of the dipole molecule and the hydrogen atom in carbazole satisfies the van der Waals radius formed by hydrogen bonding. The hydrogen bonding effect maintains the stability of the molecular conformation, resulting in a high energy barrier between the different orientations of the side chains of the dipole molecule, and can maintain a stable memory state at room temperature, avoiding state instability caused by thermal motion.

[0012] Preferably, X in the dipole molecular structure is an alkynyl-containing group.

[0013] Preferably, the alkynyl-containing group is any one of the following structural formulas:

[0014] , , , .

[0015] Preferably, X in the dipole molecule structural formula is as follows:

[0016] .

[0017] Preferably, X in the dipole molecule structural formula is as follows:

[0018] .

[0019] Preferably, the graphene point electrode is a triangular electrode.

[0020] Preferably, the gap between the top ends of the graphene point electrodes is 1 nm to 10 nm.

[0021] Preferably, the graphene point electrodes are array electrodes, and the graphene point electrodes are arranged on a graphene electrode layer.

[0022] Preferably, the graphene electrode layer is in a strip shape with a width of 5nm to 100nm.

[0023] In order to achieve the second purpose, the technical solution adopted by the present invention is:

[0024] A method for preparing an electric memristor, for preparing any of the above-mentioned single-molecule electric memristors based on dipole control, comprising a process of forming an amide bond between a dipole molecule and a graphene point electrode, comprising the following steps:

[0025] S100, dissolving the dipolar compound and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloric acid in a pyridine solution to obtain a mixed solution;

[0026] Wherein, the molar ratio of the dipolar compound to 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloric acid is 1:(20-40);

[0027] 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.

[0028] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0029] The present invention provides a single-molecule electrical memristor based on dipole control and a preparation method thereof. A single dipole molecule is introduced to connect it to a graphene point electrode through an amide bond to form a molecular heterojunction. The molecular heterojunction is a conductive path. An electric field is used to stimulate the side chain of the dipole molecule to reversibly rotate relative to the main chain about a CN bond as an axis, thereby regulating the molecular conformation and changing the molecular conductivity behavior.

[0030] Under the action of an external electric field, the chemical bonds of the dipole molecular side chains can rotate rapidly, changing the size and direction of the dipole moment within the molecule, causing the molecule to switch rapidly and stably between different resistance states. This process is based on the ability of the molecular side chains to rotate rapidly under the action of an electric field, reducing the delay in the electron transmission process and significantly improving the read and write speed of the memristor. At the same time, due to the dynamic regulation of the dipole moment within the molecule, the reversibility and stability of the resistance state switching are further ensured.

[0031] 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 memristor function.

[0032] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0034] Figure 1 It is a schematic diagram of the structure of a single-molecule memristor based on dipole control provided in Example 2 of the present invention.

[0035] 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.

[0036] Reference numerals:

[0037] 1. Silicon wafer; 2. Molecular heterojunction; 21. Dipolar molecule; 22. Graphene point electrode. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0039] 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.

[0040] Example 1 Preparation of dipolar compounds.

[0041] The molecular structure of a dipolar compound is shown below:

[0042] ;

[0043] Its synthetic route is as follows:

[0044]

[0045] The specific process is as follows:

[0046] 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 injected at 0°C, stirred at room temperature for 45 minutes, and then pyridine-2-carbonyl chloride (2.04 g, 14.40 mmol) was added at 0°C, stirred at 0°C for 10 minutes, and then the temperature was raised to room temperature and continued to stir for 2 hours. The reaction was quenched with water, and the mixture was extracted with dichloromethane (20 mL×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 (the volume ratio of silica gel to petroleum ether / dichloromethane was 1:1) to obtain a white solid compound I.

[0047] Compound Ⅰ (4.29g, 0.01 mol) and p-aminophenyl boronate hydrochloride (4.34g, 0.025 mol) were added to a 500 mL three-necked flask, THF (250 mL) was added as solvent, and then 2 mol / L potassium carbonate (K2CO3) solution (37.5 mL) and methyl trioctyl ammonium chloride (0.5g) were added, magnetic stirring and argon gas were passed, and the oil bath was heated to 75°C; then tetrakistriphenylphosphine palladium (PdPPh3)4 (0.05g) was added, and after reflux reaction for 24 hours, the filter cake was filtered and collected with a funnel, and the filter cake was washed three times with distilled water (100mL). Finally, the filter cake was vacuum dried at 80°C for 24 hours to obtain compound Ⅱ.

[0048] The compound II synthesized above is dissolved in acetonitrile to obtain an acetonitrile solution of compound II, and then the same molar number of concentrated hydrochloric acid solution is added dropwise. After the reaction is completed, the solvent is removed by rotary evaporation to obtain a solid dipole compound in the form of a pyridinium cation salt.

[0049] Among them, the dipole compound uses carbazole as the main molecular chain and connects the side chain containing pyridinium cations with CN bonds to form a dynamic dipole molecule. Under the action of an external electric field, the pyridinium cation undergoes a 360° reversible rotation around the CN bond as the axis, thereby changing the direction of the dipole moment inside the molecule and realizing dynamic regulation of the electron transmission path. The larger electronegativity of the pyridinium cation can enhance the molecular polarity, increase the dipole moment, and further enhance the responsiveness of the molecule in the electric field. Through this molecular structure design, the molecular dipole moment can be quickly adjusted by using an external electric field, thereby changing the charge transmission path, accurately regulating the resistance state of the molecule, and realizing the memristor function. In addition, through the diversified design of the side chain structure, such as changing the length of the side chain, the substitution group, etc., the performance of the electric memristor can be flexibly adjusted so that it can be optimized according to specific application requirements.

[0050] Example 2 Preparation of single-molecule memristor based on dipole control.

[0051] like Figure 1 As shown, it is a schematic diagram of the structure of a single-molecule memristor based on dipole control provided in this embodiment, including 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.

[0052] The preparation process of the single-molecule memristor based on dipole control provided by the present invention is as follows:

[0053] 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 glue. 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 with the back side facing down in a freshly prepared ferric chloride solution. After being immersed in a hydrochloric acid solution and a deionized water solution for 30 minutes, the graphene layer was transferred to a silicon wafer, and the glue was removed by heating at 120°C for 8 minutes using an acetone solution to obtain a single layer of graphene film.

[0054] Strips with a width of 40 μm and a length of 200 μm are photoetched on the graphene film using ultraviolet photoresist, and the strips are exposed by ultraviolet light. The strip portions to be retained are selected for protection with photoresist, and the remaining portions are removed by a developer, thereby exposing the graphene layer under the photoresist. The exposed graphene layer is placed in an oxygen plasma etcher for oxygen plasma etching for 50 seconds, and the residual photoresist is removed with acetone to obtain a graphene strip-silicon wafer.

[0055] 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 are evaporated, and the sample is taken out and rinsed with acetone solution to obtain a gold electrode-graphene strip-silicon wafer;

[0056] Among them, the gold electrodes in the gold electrode-graphene strip-silicon wafer are located on the strip, with a total of 169 pairs of gold electrodes forming a gold electrode array.

[0057] A layer of PMMA was spin-coated on the gold electrode-graphene strip-silicon wafer, and heated at 180°C for 2 minutes for curing. Then, an electron beam exposure machine was used to etch dotted lines on the gold electrode-graphene strip-silicon wafer to obtain graphene array point electrodes. The graphene array point electrodes were tested for continuity using a source meter and a probe station. The dotted lines are located between each pair of gold electrodes, with a total length of 60μm, each dotted line segment is 150nm long, and the interval is 40nm.

[0058] The graphene array point electrodes after dotted line etching are developed using a methyl isobutyl ketone solution diluted with isopropyl alcohol (the volume ratio of isopropyl alcohol to methyl isobutyl ketone is 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.

[0059] A dipole molecule is introduced between the graphene point electrodes, and 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 clamped with tweezers, washed three times with acetone and ultrapure water, and gently blown dry with a nitrogen stream to obtain a single-molecule memristor based on dipole control.

[0060] 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.

[0061] The positive and negative values ​​and magnitude of the bias voltage applied to the source graphene point electrode and the drain graphene point electrode are controlled, and the current response characteristic curve of the dipole molecule under the external electric field is tested using a probe station and a semiconductor parameter instrument, and the conductivity information is encoded to realize the memristive function of the molecular device.

[0062] Test conditions: temperature range: 80 K ~ 300 K, source-drain voltage range: -1 ~ 1 V, interval 5 mV.

[0063] The results are as follows Figure 2As shown, the IV curve of the single-molecule electrical 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 0.8 V, showing a typical memristor 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 the transmission of charges. On the contrary, when a reverse voltage is applied, the direction of the electric field is reversed, from the drain to the source, 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.

[0064] 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 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: ； The structural formula of X is .

2. The single-molecule memristor based on dipole control as claimed in claim 1, characterized in that: The graphene point electrode is a triangular electrode.

3. The single-molecule memristor based on dipole control as claimed in claim 2, characterized in that: The gap between the top ends of the graphene point electrodes is 1 nm to 10 nm.

4. 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.

5. The single-molecule memristor based on dipole control as claimed in claim 4, characterized in that: The graphene electrode layer is in strip shape with a width of 5nm to 100nm.

6. A method for preparing an electric memristor, characterized in that: A method for preparing a single-molecule memristor based on dipole control as claimed in any one of claims 1 to 5, 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 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); Wherein, the molecular structure formula of the dipole compound is as follows: ； 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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