Adjustable vertical monomolecular film memristor and preparation method thereof

Abstract

The invention relates to the technical field of molecular electronic devices, and provides an adjustable vertical monomolecular film memristor and a preparation method thereof. The memristor provided by the invention comprises a conductive metal source electrode, a single molecule module, a single-layer graphene drain electrode, a liquid ion grid electrode and a conductive metal grid electrode, the monomolecular module extends in the vertical direction, and the bottom end of the monomolecular module is connected with the conductive metal source electrode; the top end of the single-molecule module is connected with the single-layer graphene drain electrode; the graphene drain electrode is connected with the liquid ion grid electrode; the liquid ion grid is connected with the conductive metal grid; and the liquid ion grid is used for controlling the working mode of the single-molecule module. The vertical monomolecular film memristor with a high switch ratio, a high rectification ratio and an adjustable working window is obtained by adding the monomolecular module and the liquid ion grid.

Description

Technical Field

[0001] The invention relates to the technical field of molecular electronic devices and provides an adjustable vertical single-molecule film memristor and a preparation method thereof. Background Art

[0002] Over the past half century, the rapid development of the integrated circuit industry has accelerated the pace of mankind's progress from the information age to the artificial intelligence age. Traditional information storage devices based on semiconductor integrated circuits have also played an irreplaceable role in the field of information technology. However, with the arrival of the limit of size miniaturization, the traditional method of semiconductor integrated circuits to achieve high integration and high data processing capabilities by directly reducing the channel size faces huge challenges, resulting in a series of problems such as a sharp decline in material performance, a surge in device power consumption, and a sharp increase in the difficulty of system integration for traditional information storage devices. Therefore, in the era of artificial intelligence, the requirements for miniaturization, integration, and low power consumption of electronic devices have promoted the development of molecular electronics. Different from traditional silicon-based microelectronic devices, molecular electronic devices that use molecules as charge transfer pathways have the advantages of small size, low power consumption, and easier integration. They are considered to be one of the most promising technical routes for the development of "post-Moore era" storage functional devices.

[0003] Memristor is one of the four basic elements in circuit theory. Its resistance value can be changed by an applied electrical signal and can maintain this state after power failure, thus realizing non-volatile storage. Memristor has excellent characteristics such as low power consumption, stable and adjustable, high-density storage and storage-computing integration, making it promising for application in multiple fields such as reconfigurable circuits, logic circuits, and non-volatile memory. It can also be used to simulate the basic functions of neurons and build more efficient neural networks. Different from traditional semiconductor storage technology, single-molecule film memristor is not restricted by physical laws such as short channel effect and quantum tunneling effect, which is more conducive to breaking through the bottleneck of von Neumann architecture. At the same time, single-molecule film memristor has the advantages of good miniaturization, fast operation speed, and high storage density, and is expected to break through the storage density limit. 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 present invention provides an adjustable vertical monolayer memristor and a preparation method thereof, so as to obtain a vertical monolayer memristor with high switching ratio, high rectification ratio and adjustable working window.

[0005] The present invention provides a controllable vertical monomolecular film memristor, comprising: a conductive metal source, a monomolecular module, a drain, a liquid ion gate and a conductive metal gate; The drain electrode includes a conductive metal drain electrode and a single-layer graphene drain electrode; The single molecule module extends in a vertical direction, and the bottom end of the single molecule module is connected to the conductive metal source electrode; The top of the single-molecule module is connected to the single-layer graphene drain; The single-layer graphene drain is connected to the liquid ion gate; The liquid ion gate is connected to the conductive metal gate; The liquid ion gate is used to control the working mode of the single molecule module; The conductive metal drain electrode is connected to the single-layer graphene drain electrode; The conductive metal drain is connected to the liquid ion gate.

[0006] According to the present invention, a controllable vertical monomolecular film memristor is provided, wherein the main body of the monomolecular module is a nitroxide free radical molecule, and the structural formula is as follows: Among them, R1 is a nitroxide free radical, R2 is a sulfur-containing group, and n=8~14.

[0007] According to the present invention, a controllable vertical monolayer memristor R1 includes the following structure: or ; R2 includes the following structure: , and Any of .

[0008] According to an adjustable vertical monolayer memristor provided by the present invention, the condensing agent of the liquid ion gate is one of tetrabutylammonium bis(trifluoromethylsulfonyl)imide or diethylmethyl(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide.

[0009] According to an adjustable vertical monolayer memristor provided by the present invention, the conductive metal source is any one of Au, Ag and Pt, and the conductive metal gate is any one of Au, Ag and Pt.

[0010] According to an adjustable vertical single-molecule film memristor provided by the present invention, under a negative bias voltage, the nitroxide free radical obtains electrons, undergoes a reduction reaction and is converted into an anionic state, and the non-covalent interaction between the π electron cloud of the single-layer graphene drain and the interface of the negatively charged single-molecule self-assembled film is enhanced, so that the conductivity is increased to a high-conductivity state, and the high-conductivity state can still be maintained when the bias voltage is reduced; under a positive bias voltage, the nitroxide free radical loses electrons, undergoes an oxidation reaction and is converted into a cationic state, and the non-covalent interaction between the π electron cloud of the single-layer graphene drain and the interface of the positively charged single-molecule self-assembled film is weakened, presenting a weak interface coupling effect, which hinders electron transmission and reduces the device conductivity to switch to a low-conductivity state.

[0011] The present invention also provides a method for preparing a controllable vertical monolayer memristor, comprising the following steps: S100: preparing a substrate, wherein the upper layer of the substrate is a SiO2 layer, and the lower layer of the substrate is a semiconductor Si layer; S200: preparing a conductive metal gate on the upper surface of the SiO2 layer, and etching a blind hole in the center of the substrate, the blind hole penetrating the SiO2 layer to the semiconductor Si layer; S300: preparing a conductive metal source electrode on the upper surface of the Si layer in the blind hole; S400: self-assembling the single-molecule module on the conductive metal source electrode to obtain a semi-finished device; S500: covering the surface of the semi-finished device with a single layer of graphene so that the top of the blind hole is completely covered, and etching away excess graphene to leave a circular graphene covering the blind hole, thereby obtaining a single layer of graphene drain; S600: preparing a conductive metal drain on the single-layer graphene drain; S700: dripping the liquid to cover the single-layer graphene drain and part of the conductive metal gate to obtain a liquid ion gate.

[0012] According to a method for preparing an adjustable vertical monolayer memristor provided by the present invention, a deposition technique is used to prepare a conductive metal gate in step S200; and a deposition technique is used to prepare a conductive metal drain in step S600.

[0013] According to a method for preparing a controllable vertical monolayer memristor provided by the present invention, in step S300, a conductive metal source is prepared by using a coating technology.

[0014] According to a method for preparing a controllable vertical monolayer memristor provided by the present invention, the graphene drain electrode in S700 is prepared by a chemical vapor deposition-wet transfer method.

[0015] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: 1. The present invention provides a new working mechanism of a monolayer memristor based on redox and interface effects. In the present invention, the terminal R2 group of the molecular system containing TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxide; 2,2,6,6-tetramethylpiperidinyl-1-oxyl) or PTIO (2-Phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl; 3-oxo-2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl) groups can form Au-S, Ag-S, Pt-S chemical bonds with the conductive metal source, so that the self-assembled monolayer can be stably linked to the conductive metal source; the other terminal R1 group is TEMPO or PTIO, and the self-assembled monolayer forms a stable contact with the monolayer graphene through non-covalent interaction. At the same time, under negative bias, the R1 radical group obtains electrons, undergoes a reduction reaction and turns into an anion state, and the non-covalent interaction between the π electron cloud of the graphene drain and the negatively charged molecular film interface is enhanced. This strong interface coupling significantly improves the electron tunneling efficiency, causing the device conductivity to increase to a high conductivity state, and can still maintain this high conductivity state when the bias is reduced; under positive bias, the molecular structure and charge distribution change again, and there is a large steric hindrance in the charge transfer between nitrogen atoms and graphene, resulting in a weakened non-covalent interaction between graphene and the positively charged molecular film interface, showing a weak interface coupling effect, which hinders electron transfer and reduces the device conductivity to a low conductivity state. This mechanism achieves a vertical single-molecule film memristor with both rectification function by regulating the strength of the interface coupling between molecules and graphene through an external electric field, with an ultra-high switching ratio and rectification ratio.

[0016] 2. The present invention provides a single-molecule film memristor with adjustable working window, which utilizes the interaction between the molecular film and the graphene electrode and the regulation of the graphene interface charge by the liquid ion gate to achieve a wide range of regulation of the working window of the single-molecule film memristor. Applying a positive gate voltage will cause positive ions to gather on the graphene surface, enhance the interaction between the R1 group in the negative charge state and the graphene, thereby promoting the transition of the device from a low conductivity state to a high conductivity state, and narrowing the working window of the memristor; conversely, applying a negative gate voltage will cause negative ions to gather on the graphene surface, inhibit the interaction between the R1 group in the negative charge state and the graphene, thereby delaying the transition of the device from a low conductivity state to a high conductivity state, and widening the working window of the memristor. Based on redox, strong and weak interface coupling, and liquid ion gate, the reversible regulation of the working window of the single-molecule film memristor is achieved together, so that its memristor working window can be changed between 0.5V and 1.5V.

[0017] 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

[0018] 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.

[0019] Figure 1 It is a side view of a structural schematic diagram of an adjustable vertical monolayer memristor provided by the present invention.

[0020] Figure 2 It is a flow chart of a method for preparing an adjustable vertical single-molecule film memristor provided by the present invention.

[0021] Figure 3 4 is a current-voltage characteristic curve of the vertical single-molecule film memristor in Example 1 of the present invention.

[0022] Figure 4 This is a current-voltage characteristic curve of the vertical monolayer memristor under gate voltage regulation according to Example 1 of the present invention.

[0023] Figure 5 is a current-voltage characteristic curve of the vertical monolayer memristor in Example 2 of the present invention Reference numerals: 1. Conductive metal source; 2. Single molecule module; 3. Single-layer graphene drain; 4. Conductive metal drain; 5. Liquid ion gate; 6. Conductive metal gate. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the present invention will be clearly and completely described below. 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.

[0025] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0026] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0027] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0028] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0029] Combine the following Figures 1 to 5 The present invention is described.

[0030] like Figure 1As shown, Figure 1 This is a schematic side view of the structure of a controllable vertical monomolecular film memristor, including: a conductive metal source 1, a monomolecular module 2, a drain, a liquid ion gate 5 and a conductive metal gate 6; The drain electrode includes a conductive metal drain electrode 4 and a single-layer graphene drain electrode 3; The single molecule module 2 extends in the vertical direction, and the bottom end of the single molecule module 2 is connected to the conductive metal source 1; The top of the single-molecule module 2 is connected to the single-layer graphene drain 3; The single-layer graphene drain 3 is connected to the liquid ion gate 5; The liquid ion gate 5 is connected to the conductive metal gate 6; The liquid ion gate 5 is used to control the working mode of the single molecule module 2; The conductive metal drain 4 is located above the single-layer graphene drain 3 , the outer diameter of the conductive metal drain 4 needs to be larger than the diameter of the single-layer graphene drain 3 , and the inner diameter of the conductive metal drain 4 is smaller than the diameter of the single-layer graphene drain 3 .

[0031] The conductive metal drain electrode 4 is connected to the liquid ion gate electrode 5 .

[0032] The present invention adopts an innovative molecular system and utilizes the strong and weak interface coupling effect that only a few free radical systems have to realize a single-molecule memristor functional device with high switching ratio and rectification characteristics. The conductance change amplitude is up to 10 4 , far exceeding traditional molecular memristors (usually <10 2 ), achieving a high on-off ratio; the asymmetric interface design combined with the redox-dependent energy level alignment achieves unidirectional current conduction (negative bias conduction, positive bias cutoff), and the rectification ratio can reach 10 4 Different from the functions of other single-molecule film memristors, the present invention utilizes strong and weak interface coupling and liquid ion gate voltage to achieve a wide range of control of the memristor operating window. The gate voltage variation range of only ±2V can achieve the adjustment of the operating window from 1.5V to 0.5V. The narrow operating window is the basis for realizing low-power devices.

[0033] Traditional metal oxide memristors rely on oxygen vacancy migration and have problems such as high write voltage (>3V) and poor durability. The present invention avoids the randomness of ion migration through molecular scale interface coupling regulation and significantly improves reliability and energy efficiency.

[0034] Different from the traditional molecular system (viologen system, mechanical interlocking molecular system) memristor: the single-molecule film memristor of viologen compounds uses molecular redox and dimerization between molecules to achieve high switching ratio and rectification ratio, without involving the coupling between the molecular film and the graphene electrode, but by matching the energy level with the graphene, thereby adjusting the electron tunneling efficiency. At the same time, the viologen system is easily affected by the environment (such as humidity), and the formation of dimers leads to a decrease in response speed. The viologen molecules are relatively rigid, the configuration changes are limited, and the switching ratio is lower than the TEMPO system. Compared with the system based on methyl viologen, the redox potential of TEMPO / PTIO radicals is more stable, and the non-covalent interaction is less sensitive to humidity / temperature, which is suitable for operation in a wide range of environments. In addition, the single-molecule film memristor of the mechanical interlocking molecular system uses molecular redox and electrostatic interactions within the molecule to achieve high switching ratio and rectification ratio, and does not involve the coupling between the molecular film and the graphene electrode.

[0035] Specifically, the main body of the single molecule module 2 is a nitroxide free radical molecule, and the structural formula is as follows: Among them, R1 is a nitroxide free radical, R2 is a sulfur-containing group, and n=8~14.

[0036] Wherein, R1 comprises the following structure: or ; The R1 group at the end of the molecule is TEMPO or PTIO, and the self-assembled monolayer film forms a stable contact with the monolayer graphene through non-covalent interaction.

[0037] R2 includes the following structure: , and Any one of .

[0038] The R2 group at the other end of the molecule can form Au-S, Ag-S, or Pt-S chemical bonds with the conductive metal source 1 , so that the self-assembled monolayer can be stably linked to the conductive metal source 1 .

[0039] Specifically, the liquid of the liquid ion gate is a simple liquid or solution containing ions, for example, tetrabutylammonium bis(trifluoromethylsulfonyl)imide or diethylmethyl(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide ionic liquid.

[0040] Under negative source-drain voltage, the R1 group gains electrons, undergoes a reduction reaction, and the free radicals are converted to negative charges. The non-covalent interaction between graphene and the negatively charged molecular film interface is enhanced, which increases the device conductivity and can still maintain this high conductivity state when the bias voltage is reduced; under positive source-drain voltage, the R1 group loses electrons and undergoes an oxidation reaction, and the free radicals on the oxygen atom are converted to positive charges on the nitrogen atom. At this time, the molecular structure and charge distribution change again, and there is a large steric hindrance in the charge transfer between the nitrogen atom and graphene, which leads to a weakened non-covalent interaction between graphene and the positively charged molecular film interface, which reduces the device conductivity. This mechanism realizes a vertical single-molecule film memristor with a rectifying function.

[0041] Specifically, the conductive metal source 1 is any one of Au, Ag and Pt, and the conductive metal gate 6 is any one of Au, Ag and Pt.

[0042] like Figure 2 As shown, the present invention also discloses a method for preparing a controllable vertical monolayer memristor, comprising the following steps: S100: preparing a substrate, wherein the upper layer of the substrate is a SiO2 layer, and the lower layer of the substrate is a semiconductor Si layer; S200: preparing a conductive metal gate 6 on the upper surface of the SiO2 layer, and etching a blind hole in the center of the substrate, the blind hole penetrating the SiO2 layer to the semiconductor Si layer; S300: preparing a conductive metal source electrode 1 on the upper surface of the Si layer in the blind hole; S400: self-assembling the single molecule module 2 on the conductive metal source 1 to obtain a semi-finished device; S500: Covering the surface of the semi-finished device with a single layer of graphene so that the top of the blind hole is completely covered, and etching away excess graphene to leave a circular graphene covering the blind hole; S600: preparing a conductive metal drain electrode 4 on the circular graphene; S700: dripping the liquid to cover the single-layer graphene drain 3 and part of the conductive metal gate 6 to obtain a liquid ion gate 5.

[0043] Before step S100, a pretreatment operation can be performed: after the substrate is cut into a suitable size, ultrasonic cleaning is performed in a piranha solution for 20-30 minutes. The piranha solution is a mixture of 35% H2O2 and concentrated sulfuric acid in a volume ratio of 3:7. The pretreatment operation can effectively clean impurities on the surface of the substrate, making its surface clean and pollution-free.

[0044] The thickness of the SiO2 layer is 50-130 nm, and there is no special restriction on the thickness of the semiconductor Si layer.

[0045] The metal materials of the conductive metal drain 4, the conductive metal source 1, and the conductive metal gate 6 are obtained by evaporation. Optionally, 5-10 nm of Cr is first plated, and then 75-90 nm of Au, Ag or Pt is evaporated. The thickness of the conductive metal drain 4, the conductive metal source 1, and the conductive metal gate 6 is 80-100 nm.

[0046] The conductive metal gate body is in the shape of a semicircle, with an outer diameter of 200-250 μm and an inner diameter of 170-230 μm; the conductive metal drain 4 body is in the shape of a semicircle, with an outer diameter of 110-190 μm and an inner diameter of 50-110 μm; the single-layer graphene drain 3 is in the shape of a circle, with a diameter of 50-160 μm; the conductive metal source 1 is in the shape of a circle, with a diameter of 1-3 μm; The single-layer graphene is prepared by chemical vapor deposition (CVD), transferred to a substrate by dry or wet method, and further prepared by photolithography and oxygen or argon plasma etching to form a single-layer graphene drain electrode 3 with a diameter of 50-160 μm.

[0047] In addition, the outer diameter of the conductive metal drain needs to be larger than the diameter of the single-layer graphene drain, and the inner diameter of the conductive metal drain is smaller than the diameter of the single-layer graphene drain; the single-layer graphene drain 3 will completely cover the blind hole, and its center is located vertically above the center of the conductive metal source (i.e., the center of the blind hole); the liquid ion gate 5 completely covers the single-layer graphene drain 3 and part of the conductive metal gate 6, and finally a vertical single-molecule film memristor is obtained.

[0048] Example 1 The main body of the single molecule module 2 in Example 1 is a nitroxide free radical molecule, and the structural formula is as follows: A1 The synthesis process of compound A1 is as follows: Will (6mmol), (1 mmol) and sodium hydride (2 mmol) were dissolved in dimethylformamide (DMF). The mixture was stirred at room temperature overnight. After the reaction was completed, DMF was removed by decompression to obtain a crude product. The crude product was again dissolved in ethyl acetate and the desired product was isolated by silica gel column chromatography. .Will (1 mmol) and potassium thioacetate (2 mmol) were dissolved in dimethylformamide (DMF). The mixture was stirred at room temperature overnight. DMF was removed by decompression. The crude product was dissolved again in ethyl acetate and adsorbed on silica gel. It was separated by silica gel column chromatography to obtain .

[0049] The preparation method of a controllable vertical monomolecular film memristor based on the main body of the compound A1 monomolecular module 2 is as follows: S1: Substrate pretreatment: Take an N-type doped silicon wafer Si / SiO2 (manufacturer: Silicon Valley Microelectronics Co., Ltd., USA) with a SiO2 thickness of 100nm and a resistivity of 0.001-0.004Ω·cm. Cut the silicon wafer into 2cm×2cm pieces, put it into piranha solution and heat it at 100℃ for 1 hour, and then ultrasonically clean it in ultrapure water for 20 minutes to obtain a clean silicon wafer.

[0050] S2: Prepare a conductive metal gate 6. Under the condition of a super-clean yellow light room, use a coating machine to spin-coat a layer of ultraviolet photoresist (AR-P-5350) on the upper surface of the oxide layer of the above-mentioned clean silicon wafer, and dry it. Then use the pattern of the conductive metal drain on the mask to perform local exposure, and then develop, fix, and blow dry. Subsequently, 10nm of Cr and 90nm of Au are successively evaporated at the above-mentioned developed pattern as a conductive metal drain 4, and finally the photoresist on the graphene drain is soaked and washed away with hot acetone. Among them, the Cr layer is the adhesion layer between the Au layer and the substrate, and the main part of the conductive metal gate is semi-circular, with an outer diameter of 200μm and an inner diameter of 170μm, and an external gate test site is introduced; S3: Prepare blind holes. Spin a layer of ultraviolet photoresist (AR-P-5350) on the surface of the semi-finished device prepared above under ultra-clean yellow light conditions and dry it. Then use the blind hole pattern on the mask to perform local exposure, then develop, fix and blow dry. Among them, the blind hole is set at the center of the semi-circular circle of the above-mentioned gate, and the diameter of the blind hole is 3μm. Subsequently, BOE solution is used to etch the blind hole where the photoresist is removed until the semiconductor substrate layer under the SiO2 layer is completely exposed. The etched device is taken out and rinsed with ultrapure water and blown dry.

[0051] S4: Prepare a conductive metal source 1, and use vacuum magnetron sputtering coating technology to coat a 10nm thick Cr layer and an 87nm thick Au layer on the upper surface of the semiconductor substrate layer at the bottom of the blind hole to obtain a conductive metal source 1. Finally, soak and rinse the surface photoresist with hot acetone to obtain a semi-finished device containing a conductive metal source.

[0052] S5: Prepare a self-assembled monolayer, dissolve compound A1 in an ultra-dry ethanol solvent, and prepare a molecular solution of compound A1 with a molar concentration of 0.5 mmol / L. Soak the semi-finished device prepared above in the molecular solution for more than 5 hours, wash it with ultra-dry ethanol, and then blow it dry. So far, a self-assembled monolayer is formed on the conductive metal source 1, and the thickness of the self-assembled monolayer is about 3 nm.

[0053] S6: Preparation of single-layer graphene drain 3: S61: growing a graphene film on a copper foil by chemical vapor deposition, wherein the copper foil is a Cu(111) foil. The deposition and growth method of the graphene film includes but is not limited to chemical vapor deposition, and methods such as molecular beam epitaxy technology can also be used.

[0054] S62: Spin-coat a layer of polymethyl methacrylate (PMMA) on the graphene film to obtain a multilayer structure of PMMA-graphene-copper foil-graphene, and then etch away the graphene on the back side with oxygen or argon plasma to obtain a three-layer structure of PMMA-graphene-copper foil.

[0055] S63: Stick thin tape around the edges of the PMMA surface to facilitate subsequent transfer.

[0056] S64: Soak the PMMA surface facing upward in a ferric chloride solution, so that the copper foil at the bottom reacts with the ferric chloride solution and dissolves until the copper foil is completely removed, leaving only a double-layer structure of PMMA-graphene. The ferric chloride solution is a mixed solution of ferric chloride powder, water and hydrochloric acid. The present invention has no particular limitation on the mass concentration of the ferric chloride solution, as long as the purpose of the present invention can be achieved. For example, the concentration of the ferric chloride solution is 15%-45%, and the pH is 3±0.1.

[0057] S65: The PMMA-graphene double-layer structure is sequentially placed in three hydrochloric acid solutions with decreasing concentration gradients for soaking and cleaning for more than 10 minutes, and finally, is soaked and cleaned in pure deionized water for more than 15 minutes before being taken out. For example, the volume fractions of the three hydrochloric acid solutions with decreasing concentration gradients may be 15%, 5%, and 0.1% respectively.

[0058] S66: Take out the semi-finished device with assembled monolayer prepared in step S65, add a little isopropyl alcohol (IPA) on the semi-finished device to remove water, then bond the cleaned single-layer graphene to the surface of the semi-finished device, remove excess graphene and tape on the edge after drying; after standing for a few days to allow the graphene to fit more closely to the upper surface of the device, soak the semi-finished device with PMMA-graphene double-layer structure in hot acetone at 70-80°C for 5 minutes to remove PMMA, take it out, rinse it with clean acetone and blow it dry, and obtain the semi-finished device with bonded single-layer graphene.

[0059] S67: Under the condition of ultra-clean yellow light room, a layer of ultraviolet photoresist (AR-P-5350) is spin-coated on the surface of the semi-finished device prepared above and dried, and then the pattern of the single-layer graphene drain on the mask is used for local exposure, and then developed, fixed, and blown dry. Then, the graphene other than the circular single-layer graphene drain is etched away with oxygen or argon plasma, and finally the photoresist on the graphene drain is soaked and washed away with hot acetone, so that a semi-finished device with a single-layer graphene drain installed is obtained. Among them, the diameter of the single-layer graphene drain 3 is 120μm; S7: Prepare the conductive metal drain 4. Under the condition of ultra-clean yellow light room, spin-coat a layer of ultraviolet photoresist (AR-P-5350) on the upper surface of the semi-finished device prepared above and dry it, then use the pattern of the conductive metal drain on the mask to perform local exposure, then develop, fix and blow dry. Subsequently, 10nm of Cr and 90nm of Au are successively evaporated at the above-mentioned developed pattern as the conductive metal drain 4, and finally the photoresist on the graphene drain is soaked and washed away with hot acetone. Among them, the main part of the conductive metal drain is a semi-ring with two circular graphene drains facing each other, and the conductive metal drain partially covers the outer circle of the single-layer graphene drain. The outer diameter of the conductive metal drain is 140μm and the inner diameter is 100μm. The two semi-circular conductive metal drains 4 each have an external drain electrode test site.

[0060] S8: Prepare a liquid ion gate 5, and cover the liquid ion gate 5 on the surface of the device. The liquid ion gate 5 completely covers the single-layer graphene drain 3 and the conductive metal drain 4, and partially covers the conductive metal gate 6, so as to finally obtain a vertical single-molecule film memristor.

[0061] In Example 1, the current-voltage characteristic curve of the single-molecule film memristor is tested at room temperature using an Agilent-4155C semiconductor tester and an ST-500-probe station. The results are as follows: Figure 3 and Figure 4 shown.

[0062] Specifically, Figure 3 Graph showing the current-voltage characteristic of the vertical single-molecule film memristor in Example 1. Figure 4 This is a current-voltage characteristic curve of the vertical monolayer memristor under gate voltage regulation of Example 1.

[0063] The device has a high on / off ratio of up to 10 at -1.2V. 4 ; in I- 2V / I +2V (within the range of +2V and -2V around the switching voltage) with a high rectification ratio, which can also reach 10 4 After dropping the liquid ion gate on the device, different gate voltages V are applied to the conductive metal gate electrode. G, the current-voltage characteristic curves of different widths of the working window can be obtained. ±2V V G This enables the single-molecule film memristor to achieve an adjustable operating window in the range of ~0.5V to ~1.5V.

[0064] Example 2 The main body of the single molecule module 2 in Example 2 is a nitroxide free radical molecule, and the structural formula is as follows: A2 The synthesis process of compound A2 is as follows: Will (6mmol), (1 mmol) and sodium hydride (2 mmol) were dissolved in dimethylformamide (DMF). The mixture was stirred at room temperature overnight. After the reaction was completed, DMF was removed by decompression to obtain a crude product. The crude product was again dissolved in ethyl acetate and the desired product was isolated by silica gel column chromatography. .Will (1 mmol) and potassium thioacetate (2 mmol) were dissolved in dimethylformamide (DMF). The mixture was stirred at room temperature overnight. DMF was removed by decompression. The crude product was dissolved again in ethyl acetate and adsorbed on silica gel. It was separated by silica gel column chromatography to obtain .

[0065] The preparation method of Example 2 for preparing a controllable vertical monolayer memristor is completely consistent with that of Example 1 except that Compound A1 is replaced by Compound A2.

[0066] In Example 2, the current-voltage characteristic curve of the single-molecule film memristor is tested in the room temperature atmosphere using an Agilent-4155C semiconductor tester and an ST-500-probe station. The results are as follows: Figure 5 The device has a high on / off ratio of up to 10 at -1.2V. 4 ; in I -2V / I +2V With high rectification ratio, it can also reach 10 4 .

[0067] 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.

[0068] In addition, although the operation of the method of the present disclosure is described in a particular order in the accompanying drawings, this does not require or imply that these operations must be performed in this particular order, or that all the operations shown must be performed to achieve the desired result. On the contrary, the steps depicted in the flow chart can change the order of execution. Additionally or alternatively, some steps can be omitted, multiple steps can be combined into one step for execution, and / or one step can be decomposed into multiple steps for execution. It should also be noted that the features and functions of two or more devices according to the present disclosure can be embodied in one device. Conversely, the features and functions of a device described above can be further divided into being embodied by multiple devices.

[0069] Although the present disclosure has been described with reference to several specific embodiments, it should be understood that the present disclosure is not limited to the specific embodiments disclosed. The present disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended description.

Claims

1. A controllable vertical monolayer memristor, characterized in that: include: Conductive metal source, single molecule module, drain, liquid ion gate and conductive metal gate; The drain electrode includes a conductive metal drain electrode and a single-layer graphene drain electrode; The single molecule module extends in a vertical direction, and the bottom end of the single molecule module is connected to the conductive metal source electrode; The top of the single-molecule module is connected to the single-layer graphene drain; The single-layer graphene drain is connected to the liquid ion gate; The liquid ion gate is connected to the conductive metal gate; The liquid ion gate is used to control the working mode of the single molecule module; The conductive metal drain electrode is connected to the single-layer graphene drain electrode; The conductive metal drain is connected to the liquid ion gate.

2. The controllable vertical monolayer memristor according to claim 1, characterized in that: The main body of the single molecule module is a nitroxide free radical molecule, and the structural formula is as follows: Among them, R1 is a nitroxide free radical, R2 is a sulfur-containing group, and n=8~14.

3. The controllable vertical monolayer memristor according to claim 2, characterized in that: R1 includes the following structure: or ; R2 includes the following structure: , and Any of .

4. The controllable vertical monolayer memristor according to claim 1, characterized in that: The liquid of the liquid ion gate is a simple liquid or solution containing ions.

5. The controllable vertical monolayer memristor according to claim 1, characterized in that: The conductive metal source is any one of Au, Ag and Pt; the conductive metal gate is any one of Au, Ag and Pt.

6. The controllable vertical monolayer memristor according to claim 2, characterized in that: Under negative bias, the nitroxide free radical gains electrons and undergoes a reduction reaction to transform into an anionic state. The non-covalent interaction between the π electron cloud of the monolayer graphene drain and the negatively charged single-molecule self-assembled film interface is enhanced, causing the conductivity to increase to a high conductivity state, and the high conductivity state can still be maintained when the bias is reduced; under positive bias, the nitroxide free radical loses electrons and undergoes an oxidation reaction to transform into a cationic state. The non-covalent interaction between the π electron cloud of the monolayer graphene drain and the positively charged single-molecule self-assembled film interface is weakened, showing a weak interface coupling effect, which hinders electron transmission and reduces the device conductivity to a low conductivity state.

7. A method for preparing a controllable vertical monolayer memristor, characterized in that: The method for preparing a controllable vertical monolayer memristor as claimed in any one of claims 1 to 6 comprises the following steps: S100: preparing a substrate, wherein the upper layer of the substrate is a SiO2 layer, and the lower layer of the substrate is a semiconductor Si layer; S200: preparing a conductive metal gate on the upper surface of the SiO2 layer, and etching a blind hole in the center of the substrate, the blind hole penetrating the SiO2 layer to the semiconductor Si layer; S300: preparing a conductive metal source electrode on the upper surface of the semiconductor Si layer in the blind hole; S400: self-assembling the single-molecule module on the conductive metal source electrode to obtain a semi-finished device; S500: covering the surface of the semi-finished device with a single layer of graphene so that the top of the blind hole is completely covered, and etching away excess graphene to leave a circular graphene covering the blind hole, thereby obtaining a single layer of graphene drain; S600: preparing a conductive metal drain on the single-layer graphene drain; S700: dripping the liquid to cover the single-layer graphene drain and part of the conductive metal gate to obtain a liquid ion gate.

8. The method for preparing a controllable vertical monolayer memristor according to claim 7, characterized in that: In step S200 , a conductive metal gate is prepared by using a deposition technique; in step S600 , a conductive metal drain is prepared by using a deposition technique.

9. The method for preparing a controllable vertical monolayer memristor according to claim 7, characterized in that: In step S300 , a conductive metal source is prepared using a coating technique.

10. The method for preparing a controllable vertical monolayer memristor according to claim 7, characterized in that: The graphene drain electrode in S700 is prepared by chemical vapor deposition-wet transfer method.

Images