A Tunable Vertical Monolayer Memristor and Its Preparation Method

Abstract

The present invention relates to the technical field of molecular electronic devices, and provides a vertically tunable single-molecule film memristor and a preparation method thereof. The memristor provided by the present invention includes: a conductive metal source electrode, a single-molecule module, a single-layer graphene drain electrode, a liquid ion gate electrode, and a conductive metal gate electrode; the single-molecule module extends in the vertical direction, and the bottom end of the single-molecule module is connected to the conductive metal source electrode; the top end of the single-molecule module is connected to the single-layer graphene drain electrode; the graphene drain electrode is connected to the liquid ion gate electrode; the liquid ion gate electrode is connected to the conductive metal gate electrode; the liquid ion gate electrode is used to control the working mode of the single-molecule module. By adding two modules, namely a single-molecule module and a liquid ion gate electrode, the present invention obtains a vertically tunable single-molecule film memristor with a high switching ratio, a high rectification ratio, and a tunable working window.

Description

Technical Field

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

[0002] In the past half century or more, the rapid development of the integrated circuit industry has accelerated the pace of humanity'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 advent 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 for traditional information storage devices, such as a sharp decline in material performance, a sharp increase in device power consumption, and a steep increase in system integration difficulty. 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 with molecules as the charge transport path have the advantages of small size, low power consumption, and easier integration, and are considered to be one of the most promising technical routes for developing storage functional devices in the "post-Moore era".

[0003] A memristor is one of the four basic elements of circuit theory. Its resistance value can be changed by applying an electrical signal and can maintain this state after power-off, thus realizing non-volatile storage. Memristors have excellent characteristics such as low power consumption, stable tunability, high-density storage, and integration of storage and computing, making them promising for applications in multiple fields such as reconfigurable circuits, logic circuits, and non-volatile memories. It can also be used to simulate the basic functions of neurons to build a more efficient neural network. Different from traditional semiconductor storage technologies, single-molecule film memristors are not restricted by physical laws such as short-channel effects and quantum tunneling effects, which is more conducive to breaking through the bottleneck of the von Neumann architecture. At the same time, single-molecule film memristors have the advantages of good miniaturization, fast operating speed, and large storage density, and are 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. For this purpose, the present invention provides a tunable vertical single-molecule film memristor and a preparation method thereof to obtain a vertical single-molecule film memristor with a high switching ratio, a high rectification ratio, and a tunable working window.

[0005] The present invention provides a tunable vertical single-molecule film memristor, including: a conductive metal source electrode, a single-molecule module, a drain electrode, a liquid ion gate, and a conductive metal gate;

[0006] The drain electrode includes a conductive metal drain electrode and a single-layer graphene drain electrode;

[0007] The single-molecule module extends in the vertical direction, and the bottom end of the single-molecule module is connected to the conductive metal source electrode;

[0008] The top end of the single-molecule module is connected to the single-layer graphene drain electrode;

[0009] The single-layer graphene drain electrode is connected to the liquid ion gate electrode;

[0010] The liquid ion gate electrode is connected to the conductive metal gate electrode;

[0011] The liquid ion gate electrode is used to control the working mode of the single-molecule module;

[0012] The conductive metal drain electrode is connected to the single-layer graphene drain electrode;

[0013] The conductive metal drain electrode is connected to the liquid ion gate electrode.

[0014] According to a tunable vertical single-molecule film memristor provided by the present invention, the body of the single-molecule module is a nitroxide radical molecule, and the structural formula is as follows:

[0015]

[0016] Wherein, R1 is a nitroxide radical, R2 is a sulfur-containing group, and n = 8-14.

[0017] According to a tunable vertical single-molecule film memristor provided by the present invention, R1 includes the following structures:

[0018] Or ;

[0019] R2 includes the following structures:

[0020] , And Any one of them.

[0021] According to a tunable vertical single-molecule film memristor provided by the present invention, the condensing agent of the liquid ion gate electrode is one of tetrabutylammonium bis(trifluoromethylsulfonyl)imide or diethylmethyl(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide.

[0022] According to a tunable vertical single-molecule film memristor provided by the present invention, the conductive metal source electrode is any one of Au, Ag, and Pt, and the conductive metal gate electrode is any one of Au, Ag, and Pt.

[0023] According to the present invention, a tunable vertical single-molecule film memristor is provided. Under a negative bias voltage, the nitroxide 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 single-layer graphene drain and the interface of the negatively charged single-molecule self-assembled film is enhanced, resulting in an increase in conductance to a high conductance state, and this high conductance state can still be maintained when the bias voltage decreases. Under a positive bias voltage, the nitroxide 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 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 transport and causes the conductance of the device to decrease and switch to a low conductance state.

[0024] The present invention also provides a preparation method for a tunable vertical single-molecule film memristor, comprising the following steps:

[0025] S100: Prepare a substrate, where the upper layer of the substrate is a SiO2 layer and the lower layer of the substrate is a semiconductor Si layer;

[0026] S200: Prepare a conductive metal gate on the upper surface of the SiO2 layer, and etch a blind hole in the center of the substrate, with the blind hole penetrating through the SiO2 layer until reaching the semiconductor Si layer;

[0027] S300: Prepare a conductive metal source on the upper surface of the Si layer within the blind hole;

[0028] S400: Self-assemble the single-molecule module on the conductive metal source to obtain a semi-finished device;

[0029] S500: Cover the surface of the semi-finished device with a single layer of graphene, such that the top of the blind hole is completely covered, and etch away the excess graphene, leaving a circular graphene covering the blind hole to obtain a single-layer graphene drain;

[0030] S600: Prepare a conductive metal drain on the single-layer graphene drain;

[0031] S700: Drop the liquid to cover the single-layer graphene drain and part of the conductive metal gate to obtain a liquid ion gate.

[0032] According to the preparation method for a tunable vertical single-molecule film memristor provided by the present invention, in step S200, a deposition technique is used to prepare the conductive metal gate; in step S600, a deposition technique is used to prepare the conductive metal drain.

[0033] According to the preparation method for a tunable vertical single-molecule film memristor provided by the present invention, in step S300, a coating technique is used to prepare the conductive metal source.

[0034] According to a preparation method of a tunable vertical single-molecule film memristor provided by the present invention, the graphene drain electrode in S700 is prepared by chemical vapor deposition-wet transfer method.

[0035] One or more of the above technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0036] 1. The present invention provides a new working mechanism for a single-molecule film memristor based on redox and interfacial interactions. 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-tetramethylpiperidine-1-oxyl radical) or PTIO (2-Phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl; 3-oxo-2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl) group can form Au-S, Ag-S, Pt-S chemical bonds with the conductive metal source electrode, so that the self-assembled single-molecule film can be stably linked with the conductive metal source electrode; the other terminal R1 group is TEMPO or PTIO, and a stable contact is formed between the self-assembled single-molecule film and the monolayer graphene through non-covalent interactions. At the same time, under a negative bias voltage, the R1 radical group gains electrons and undergoes a reduction reaction to transform into an anionic state, and the non-covalent interaction between the π electron cloud of the graphene drain electrode and the negatively charged molecular film interface is enhanced. This strong interfacial coupling effect significantly improves the electron tunneling efficiency, making the device conductance increase to a high conductance state and still maintain this high conductance state when the bias voltage decreases; under a positive bias voltage, 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 the graphene, resulting in a weakening of the non-covalent interaction between the graphene and the positively charged molecular film interface, presenting a weak interfacial coupling effect, hindering electron transport, and reducing the device conductance to switch to a low conductance state. This mechanism realizes a vertical single-molecule film memristor with a rectifying function through the reversible switching of the strength of the interfacial coupling between the molecule and the graphene by an external electric field, and has an ultra-high on-off ratio and rectification ratio.

[0037] 2. The present invention provides a single-molecule-membrane memristor with a controllable working window. By utilizing the interaction between the molecular membrane and the graphene electrode and the regulation of the graphene interface charge by the liquid ion gate, a wide-range regulation of the working window of the single-molecule-membrane memristor is achieved. Applying a positive gate voltage causes positive ions to accumulate on the graphene surface, enhancing the interaction between the R1 group in the negative charge state and graphene, thereby promoting the transition of the device from the low-conductance state to the high-conductance state and narrowing the working window of the memristor; conversely, applying a negative gate voltage causes negative ions to accumulate on the graphene surface, inhibiting the interaction between the R1 group in the negative charge state and graphene, thereby delaying the transition of the device from the low-conductance state to the high-conductance state and broadening the working window of the memristor. Based on redox, strong and weak interface coupling effects, and the liquid ion gate, a reversible regulation of the working window of the single-molecule-membrane memristor is jointly achieved, enabling its memristive working window to vary between 0.5V and 1.5V.

[0038] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0040] Figure 1 It is a side view of the structural schematic diagram of a controllable vertical single-molecule-membrane memristor provided by the present invention.

[0041] Figure 2 It is a flowchart of the preparation method of a controllable vertical single-molecule-membrane memristor provided by the present invention.

[0042] Figure 3 It is the current-voltage characteristic curve of the vertical single-molecule-membrane memristor in Example 1 of the present invention.

[0043] Figure 4 It is the current-voltage characteristic curve of the vertical single-molecule-membrane memristor under gate voltage regulation in Example 1 of the present invention.

[0044] Figure 5 It is the current-voltage characteristic curve of the vertical single-molecule-membrane memristor in Example 2 of the present invention

[0045] Reference numerals:

[0046] 1. Conductive metal source; 2. Single-molecule module; 3. Monolayer graphene drain; 4. Conductive metal drain; 5. Liquid ion gate; 6. Conductive metal gate. Detailed implementation manners

[0047] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope 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.

[0048] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationships indicated by the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation to the embodiments of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0049] In the description of the embodiments of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "connected" and "coupled" 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 directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific situations.

[0050] In the embodiments of the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0051] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0052] The following is combined with Figures 1 to 5 to describe the present invention.

[0053] As Figure 1 shown, Figure 1 is a schematic side view of the structure of a tunable vertical single-molecule film memristor. It includes: a conductive metal source electrode 1, a single-molecule module 2, a drain electrode, a liquid ion gate 5, and a conductive metal gate 6;

[0054] The drain electrode includes a conductive metal drain electrode 4 and a single-layer graphene drain electrode 3;

[0055] 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 electrode 1;

[0056] The top end of the single-molecule module 2 is connected to the single-layer graphene drain electrode 3;

[0057] The single-layer graphene drain electrode 3 is connected to the liquid ion gate 5;

[0058] The liquid ion gate 5 is connected to the conductive metal gate 6;

[0059] The liquid ion gate 5 is used to control the working mode of the single-molecule module 2;

[0060] The conductive metal drain electrode 4 is located above the single-layer graphene drain electrode 3. The outer diameter of the conductive metal drain electrode 4 needs to be greater than the diameter of the single-layer graphene drain electrode 3, and the inner diameter of the conductive metal drain electrode 4 is smaller than the diameter of the single-layer graphene drain electrode 3.

[0061] The conductive metal drain electrode 4 is connected to the liquid ion gate 5.

[0062] The present invention adopts an innovative molecular system and utilizes the strong and weak interfacial coupling effect unique to a few free radical systems to realize a single-molecule memristive functional device with a high on-off ratio and rectifying characteristics. The conductance change amplitude reaches 10 4 , far exceeding that of traditional molecular memristors (usually < 102 ), achieving a high on - off ratio; the asymmetric interface design combined with the redox - state - dependent energy - level alignment realizes unidirectional current conduction (conducting under negative bias and cutoff under positive bias), and the rectification ratio can reach 10 4 orders of magnitude. Different from the functions of other single - molecule - film memristors, the present invention utilizes the strong and weak interface coupling effect and the liquid ion - gate voltage to realize a wide - range regulation of the working window of the memristor. A working window adjustment from 1.5 V to 0.5 V can be achieved with only a gate - voltage change range of ±2 V. The narrow working window is the basis for realizing low - power - consumption devices.

[0063] Traditional metal - oxide memristors rely on the migration of oxygen vacancies and have problems such as high writing voltage (>3 V) and poor durability. Through molecular - scale interface - coupling regulation, the present invention avoids the randomness of ion migration and significantly improves reliability and energy efficiency.

[0064] Different from traditional molecular - system (viologen - based system, mechanically interlocked molecular system) memristors: The single - molecule - film memristor of viologen - based compounds utilizes molecular redox and intermolecular dimerization to achieve a high on - off ratio and rectification ratio. It does not involve the coupling between the molecular film and the graphene electrode, but adjusts the electron - tunneling efficiency through energy - level matching with graphene. At the same time, the viologen system is easily affected by the environment (such as humidity), the formation of dimers leads to a reduced response speed, the viologen molecules are relatively rigid, the configuration change is limited, and the on - off ratio is lower than that of the TEMPO system. Compared with the methyl - viologen - based system, the redox potential of TEMPO / PTIO radicals is more stable, and the non - covalent interaction is less sensitive to humidity / temperature, suitable for operation in a wide environmental range. In addition, the single - molecule - film memristor of the mechanically interlocked molecular system utilizes molecular redox and intramolecular electrostatic interactions to achieve a high on - off ratio and rectification ratio, and does not involve the coupling between the molecular film and the graphene electrode.

[0065] Specifically, the main body of the single - molecule module 2 is a nitroxide radical molecule, and the structural formula is as follows:

[0066]

[0067] Among them, R1 is a nitroxide radical, R2 is a sulfur - containing group, and n = 8 - 14.

[0068] Among them, R1 includes the following structures:

[0069] or ;

[0070] The R1 group at the molecular end is TEMPO or PTIO, and the self - assembled single - molecule film forms a stable contact with the single - layer graphene through non - covalent interaction.

[0071] R2 includes the following structures:

[0072] , and Any one of .

[0073] 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 .

[0074] 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.

[0075] 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.

[0076] 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.

[0077] like Figure 2 As shown, the present invention also discloses a method for preparing a controllable vertical monolayer memristor, comprising the following steps:

[0078] 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;

[0079] 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;

[0080] S300: preparing a conductive metal source electrode 1 on the upper surface of the Si layer in the blind hole;

[0081] S400: self-assembling the single molecule module 2 on the conductive metal source 1 to obtain a semi-finished device;

[0082] S500: Cover 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 etch away the excess graphene, leaving a circular graphene covering the blind hole;

[0083] S600: Fabricate a conductive metal drain 4 on the circular graphene;

[0084] S700: Drop the liquid to cover the single-layer graphene drain 3 and part of the conductive metal gate 6, obtaining a liquid ion gate 5.

[0085] Before step S100, a pretreatment operation can also be performed: after cutting the substrate into a suitable size, ultrasonically clean it in a piranha solution for 20 - 30 minutes. Among them, the piranha solution is obtained by mixing 35% H2O2 and concentrated sulfuric acid in a volume ratio of 3:7. The pretreatment operation can effectively clean the impurities on the substrate surface, making its surface clean and pollution-free.

[0086] Among them, the thickness of the SiO2 layer is 50 - 130 nm, and there is no special limitation on the thickness of the semiconductor Si layer.

[0087] The metal materials of the conductive metal drain 4, conductive metal source 1, and conductive metal gate 6 are obtained by evaporation. Optionally, first deposit 5 - 10 nm of Cr, and then evaporate 75 - 90 nm of Au, Ag, or Pt. The thicknesses of the conductive metal drain 4, conductive metal source 1, and conductive metal gate 6 are 80 - 100 nm.

[0088] The main body of the conductive metal gate is semi-circular ring-shaped, with an outer diameter of 200 - 250 μm and an inner diameter of 170 - 230 μm; the main body of the conductive metal drain 4 is semi-circular ring-shaped, with an outer diameter of 110 - 190 μm and an inner diameter of 50 - 110 μm; the single-layer graphene drain 3 is circular, with a diameter of 50 - 160 μm; the conductive metal source 1 is circular, with a diameter of 1 - 3 μm;

[0089] The single-layer graphene is prepared by chemical vapor deposition (CVD), transferred to the substrate using dry or wet methods, and further fabricated into a single-layer graphene drain 3 with a diameter of 50 - 160 μm through photolithography and oxygen or argon plasma etching.

[0090] In addition, the outer diameter of the conductive metal drain needs to be greater than the diameter of the single-layer graphene drain, and the inner diameter of the conductive metal drain is less 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 directly above the center of the conductive metal source (i.e., the center of the blind hole) vertically; 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.

[0091] Example 1

[0092] The body of the single-molecule module 2 in Example 1 is a nitroxide radical molecule, and its structural formula is as follows:

[0093]

[0094] A1

[0095] The synthesis process of compound A1 is as follows:

[0096] Dissolve (6 mmol), (1 mmol) and sodium hydride (2 mmol) in dimethylformamide (DMF). The mixture is stirred overnight at room temperature. After the reaction is completed, DMF is removed under reduced pressure to obtain a crude product. The crude product is dissolved in ethyl acetate again, and the desired product is separated by silica gel column chromatography . Dissolve (1 mmol) and potassium thioacetate (2 mmol) in dimethylformamide (DMF). The mixture is stirred overnight at room temperature. DMF is removed under reduced pressure. The crude product is dissolved in ethyl acetate again and adsorbed on silica gel. is separated by silica gel column chromatography .

[0097] The preparation method process of a tunable vertical single-molecule film memristor with compound A1 as the body of the single-molecule module 2 is as follows:

[0098] S1: Substrate pretreatment. Take an N-type doped silicon wafer Si / SiO2 (manufacturer: Silicon Valley Microelectronics Co., Ltd., USA) with a SiO2 thickness of 100 nm and a resistivity of 0.001 - 0.004 Ω·cm. Cut the silicon wafer into 2 cm × 2 cm, place it in a piranha solution and heat it at 100 °C for 1 hour, and then ultrasonically clean it in ultrapure water for 20 minutes to obtain a clean silicon wafer.

[0099] S2: Prepare the conductive metal gate 6. Under the conditions of a super-clean yellow light room, 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 with a spin coater and dry it. Then, perform local exposure with the pattern of the conductive metal drain on the mask, and then develop, fix, and blow dry. Subsequently, deposit 10 nm of Cr and 90 nm of Au successively at the above-mentioned developed pattern as the conductive metal drain 4. Finally, soak and rinse the photoresist on the graphene drain with hot acetone. Among them, the Cr layer is an adhesion layer between the Au layer and the substrate. The main part of the conductive metal gate is semi-circular, with an outer diameter of 200 μm and an inner diameter of 170 μm, and the gate test site is led out;

[0100] S3: Prepare blind holes. Under the conditions of a super-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, perform local exposure using the blind hole pattern on the mask plate, and then develop, fix, and blow dry. Among them, the blind hole is set at the center of the circle of the above-mentioned gate semi-ring, and the diameter of the blind hole is 3 μm. Subsequently, etch the blind hole where the photoresist has been removed with BOE solution until the semiconductor substrate layer under the SiO2 layer is completely exposed. Take out the etched device, rinse it with ultrapure water, and blow dry.

[0101] S4: Prepare the conductive metal source electrode 1. Use the vacuum magnetron sputtering coating technology to deposit a 10-nm-thick Cr layer and an 87-nm-thick Au layer successively on the upper surface of the semiconductor substrate layer at the bottom of the blind hole to obtain the conductive metal source electrode 1. Finally, soak it in hot acetone and rinse off the surface photoresist. Thus, a semi-finished device containing the conductive metal source electrode is obtained.

[0102] S5: Prepare a self-assembled monolayer. Dissolve compound A1 in an ultra-dry ethanol solvent to prepare a molecular solution of compound A1 with a molar concentration of 0.5 mmol / L. After soaking the semi-finished device prepared above in the molecular solution for more than 5 hours, wash it with ultra-dry ethanol and blow dry. Thus, a self-assembled monolayer is formed on the conductive metal source electrode 1, and the thickness of the self-assembled monolayer is about 3 nm.

[0103] S6: Prepare the single-layer graphene drain electrode 3:

[0104] S61: Grow a graphene film on a copper foil. 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 can also be used.

[0105] S62: Spin-coat a layer of polymethyl methacrylate (PMMA) on the graphene film to obtain a multi-layer structure of PMMA-graphene-copper foil-graphene. Subsequently, etch off the graphene on the back with oxygen or argon plasma to obtain a three-layer structure of PMMA-graphene-copper foil.

[0106] S63: Paste slender tapes around the four edges of the PMMA surface to facilitate subsequent transfer.

[0107] S64: Immerse the PMMA surface upward in a ferric chloride solution so that the underlying copper foil reacts with the ferric chloride solution and dissolves until the copper foil is completely removed, leaving only the double-layer structure of PMMA-graphene. Among them, the ferric chloride solution is a mixed solution of ferric chloride powder, water, and hydrochloric acid. The present invention does not particularly limit the mass concentration of the ferric chloride solution, as long as the purpose of the present invention can be achieved. Exemplarily, the concentration of the ferric chloride solution is 15%-45%, and PH = 3 ± 0.1.

[0108] S65: Immerse the PMMA-graphene bilayer structure successively in three hydrochloric acid solutions with gradually decreasing concentration gradients for more than 10 minutes each for cleaning, and finally immerse it in pure deionized water for more than 15 minutes for cleaning before taking it out. Exemplarily, the volume fractions of the three hydrochloric acid solutions with gradually decreasing concentration gradients can be 15%, 5%, and 0.1% in sequence.

[0109] S66: Take out the semi-finished device with the single-molecule film already assembled in step S65, drop a little isopropyl alcohol (IPA) on the semi-finished device to remove water, then attach the cleaned single-layer graphene to the surface of the semi-finished device, and after drying, remove the excess graphene and tape at the edges; after standing for several days to make the graphene fit more tightly to the upper surface of the device, immerse the semi-finished device with the PMMA-graphene bilayer structure attached in hot acetone at 70 - 80 °C for 5 minutes to remove PMMA, take it out, rinse it with clean acetone and then dry it. At this time, a semi-finished device with a single-layer graphene attached is obtained.

[0110] S67: Under the conditions of a 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 perform local exposure using the pattern of the single-layer graphene drain on the mask, and then develop, fix, and dry. Then etch away the graphene outside the circular single-layer graphene drain with oxygen or argon plasma, and finally soak and rinse the photoresist on the graphene drain with hot acetone. Thus, 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 120 μm;

[0111] S7: Prepare the conductive metal drain 4. Under the conditions of a 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 perform local exposure using the pattern of the conductive metal drain on the mask, and then develop, fix, and dry. Subsequently, deposit 10 nm of Cr and 90 nm of Au successively at the developed pattern as the conductive metal drain 4, and finally soak and rinse the photoresist on the graphene drain with hot acetone. Among them, the main part of the conductive metal drain is two semi-circular rings opposite to the two circular graphene drains, 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 140 μm, the inner diameter is 100 μm, and each of the two semi-circular conductive metal drains 4 leads out a leakage electrode test site.

[0112] S8: Prepare the liquid ion gate 5. Cover the liquid ion gate 5 on the device surface. 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, and finally a vertical single-molecule film memristor is obtained.

[0113] In Example 1, using an Agilent-4155C semiconductor tester and an ST-500 probe station, the current-voltage characteristic curve of the current of the single-molecule film memristor varying with the source-drain voltage was tested in the room-temperature atmosphere. The results are as Figure 3 and Figure 4 shown.

[0114] Specifically, Figure 3 is the current-voltage characteristic curve of the vertical single-molecule film memristor in Example 1. Figure 4 is the current-voltage characteristic curve of the vertical single-molecule film memristor under gate voltage regulation in Example 1.

[0115] The device has a high switching ratio at -1.2 V, up to 10 4 ; it has a high rectification ratio in I- 2V / I +2V (in the range of +2 V and -2 V around the switching voltage), also up to 10 4 . After dropping a liquid ion gate on the device, by applying different gate voltages V G on the conductive metal gate electrode, current-voltage characteristic curves with different widths of the working window can be obtained. A V G of ±2 V enables the working window of this single-molecule film memristor to be adjustable in the range of ~0.5 V to ~1.5 V.

[0116] Example 2

[0117] The body of the single-molecule module 2 in Example 2 is a nitroxide radical molecule, and its structural formula is as follows:

[0118]

[0119] A2

[0120] The synthesis process of compound A2 is as follows:

[0121] Dissolve (6 mmol), (1 mmol) and sodium hydride (2 mmol) in dimethylformamide (DMF). The mixture is stirred overnight at room temperature. After the reaction is completed, DMF is removed by reduced pressure to obtain a crude product. The crude product is dissolved in ethyl acetate again, and the desired product is separated by silica gel column chromatography. Dissolve (1 mmol) and potassium thioacetate (2 mmol) in dimethylformamide (DMF). The mixture is stirred overnight at room temperature. Remove DMF by reduced pressure. The crude product is dissolved in ethyl acetate again and adsorbed on silica gel. is obtained by silica gel column chromatography.

[0122] Example 2 The preparation method process of a tunable vertical single-molecule film memristor is completely the same as that of Example 1 except that compound A1 is replaced by compound A2.

[0123] In Example 2, an Agilent-4155C semiconductor tester and an ST-500 probe station were used to test the current-voltage characteristic curve of the current of the single-molecule film memristor varying with the source-drain voltage at room temperature in the atmosphere. The results are as Figure 5 shown. The device has a high switching ratio at -1.2 V, up to 10 4 ; in I -2V / I +2V it has a high rectification ratio, also up to 10 4 .

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

[0125] In addition, although the operations of the method of the present disclosure are described in a specific order in the drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. On the contrary, the steps depicted in the flowchart may be changed in the order of execution. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step for execution, and / or one step may 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 may be embodied in one device. Conversely, the features and functions of one device described above may be further divided and embodied by multiple devices.

[0126] 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 specification.

Claims

1. A tunable vertical single-molecule film memristor, characterized in that, Comprising: A conductive metal source electrode, a single-molecule module, a drain electrode, 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 the vertical direction, and the bottom end of the single-molecule module is connected to the conductive metal source electrode; The top end of the single-molecule module is connected to the single-layer graphene drain electrode; The single-layer graphene drain electrode 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 electrode is connected to the liquid ion gate.

2. The adjustable vertical single-molecule film memristor according to claim 1, wherein The body of the single-molecule module is a nitroxide radical molecule, and the structural formula is as follows: Wherein, R1 is a nitroxide radical, R2 is a sulfur-containing group, and n = 8 - 14.

3. The adjustable vertical single-molecule film memristor according to claim 2, characterized in that, R1 includes the following structure: or ; R2 includes the following structure: , and any one of them 4. A tunable vertical single-molecule film memristor according to claim 1, characterized in that, The liquid of the liquid ion gate is an ion-containing elemental liquid or solution.

5. The adjustable vertical single-molecule film memristor according to claim 1, wherein The conductive metal source electrode is any one of Au, Ag, and Pt; the conductive metal gate is any one of Au, Ag, and Pt.

6. The adjustable vertical single-molecule film memristor according to claim 2, characterized in that, Under a negative bias voltage, the nitroxide radical obtains electrons and undergoes a reduction reaction to transform into an anion state. The π electron cloud of the single-layer graphene drain electrode and the non-covalent interaction at the interface of the negatively charged single-molecule self-assembled film are enhanced, resulting in an increase in conductance to a high-conductance state, and this high-conductance state can still be maintained when the bias voltage decreases; under a positive bias voltage, the nitroxide radical loses electrons and undergoes an oxidation reaction to transform into a cation state. The π electron cloud of the single-layer graphene drain electrode and the non-covalent interaction at the interface of the positively charged single-molecule self-assembled film are weakened, presenting a weak interface coupling effect, which hinders electron transport and causes the device conductance to decrease and switch to a low-conductance state.

7. A preparation method of a tunable vertical single molecular layer memristor, characterized in that, For preparing a tunable vertical single-molecule film memristor as described in any one of claims 1 - 6, comprising the following steps: S100: Prepare a substrate, the upper layer of the substrate is a SiO2 layer, and the lower layer of the substrate is a semiconductor Si layer; S200: Prepare a conductive metal gate on the upper surface of the SiO2 layer, and etch a blind hole in the center of the substrate, and the blind hole penetrates through the SiO2 layer until the semiconductor Si layer; S300: Prepare a conductive metal source electrode on the upper surface of the semiconductor Si layer in the blind hole; S400: Self-assemble the single-molecule module on the conductive metal source electrode to obtain a semi-finished device; S500: Cover 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 etch away the excess graphene, leaving a circular graphene covering the blind hole to obtain a single-layer graphene drain electrode; S600: Prepare a conductive metal drain electrode on the single-layer graphene drain electrode; S700: Drop the liquid to cover the single-layer graphene drain electrode and part of the conductive metal gate to obtain a liquid ion gate.

8. The preparation method of a tunable vertical single-molecule film memristor according to claim 7, wherein In step S200, a deposition technique is used to prepare the conductive metal gate; in step S600, a deposition technique is used to prepare the conductive metal drain electrode.

9. The preparation method of a tunable vertical single-molecule film memristor according to claim 7, characterized in that, In step S300, a coating technique is used to prepare the conductive metal source electrode.

10. The preparation method of a tunable vertical single-molecule film memristor according to claim 7, wherein The graphene drain terminal electrode in S700 is prepared by chemical vapor deposition - wet transfer method.

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