A method for fabricating integrated single-molecule devices based on electropolymerization

Abstract

This application provides a method for fabricating integrated single-molecule devices based on electropolymerization. The method involves etching to form a nanoscale controllable array of graphene point electrodes, using amide bonds to anchor monomers at the graphene edges, and then connecting single conductive polymer chains between the graphene electrode pairs via electrochemical polymerization to form conductive polymer-graphene single-molecule devices. This method employs a "static electrode, dynamic molecule" strategy, offering advantages such as high success rate and the ability to mass-produce arrayed devices. Furthermore, it can fabricate devices with bottom gates as needed, thereby integrating single-molecule electronic devices to achieve specific logic functions. The performance of single-molecule electronic devices fabricated using this method is significantly improved compared to those constructed using traditional methods, exhibiting excellent gate controllability and achieving device integration.

Description

Technical Field

[0001] This application relates to the field of single-molecule electronic devices, and in particular to a method for preparing integrated single-molecule devices based on electropolymerization. Background Technology

[0002] Given that traditional semiconductor devices will eventually reach their physical limits, how to utilize novel materials to overcome the limits of Moore's Law has become a crucial research topic. Single-molecule electronics aims to achieve the functionality of macroscopic devices using a single molecule. To connect single molecules to macroscopic devices, single-molecule electronics has undergone two developmental stages: exploring device fabrication methods and studying molecular properties. Currently, numerous prototype devices have emerged in the field of single-molecule science, but these devices all face the same challenge in their path to industrial application: how to achieve efficient and stable integration of single-molecule functional devices. The fabrication of single-molecule devices can be broadly divided into dynamic and static devices. A representative example of dynamic devices is the scanning tunneling microscope's fracture joint, which uses the up-and-down movement of the probe tip to pick up a single molecule. Static devices, such as graphene single-molecule devices, mainly rely on numerous channels within the device that match the molecular size to achieve connection. Analyzing these devices, dynamic devices have a higher connection success rate because they can achieve electrode width matching molecular width, while static devices can be fabricated on a large scale, better meeting the requirements of current chips. Therefore, combining the two can achieve a high success rate in fabricating integrated single-molecule devices.

[0003] Conductive polymers are a class of one-dimensional materials with excellent semiconductor properties. Their intrinsic conductivity is low, but after oxidative doping, they exhibit high conductivity, making them promising candidates for applications in electronic chips. Conductive polymers, such as polypyrrole and polythiophene, can be polymerized in situ at relatively low electrolysis voltages, which can precisely address the difficulties faced by the aforementioned single-molecule devices.

[0004] First, building blocks such as pyrrole enable the specific self-growth of graphene ends, improving atom utilization. Second, conductive polymers exhibit good conductivity, allowing for the realization of field-effect transistor performance through doping. Finally, molecular chains of different lengths exhibit similar properties, ensuring the uniformity of the device array. This project utilizes in-situ electrochemical polymerization of conductive polymers to achieve the goal of "static electrodes and dynamic molecules," thus combining the advantages of both static and dynamic devices to fabricate highly stable, high-success-rate, and highly integrated single-molecule devices. Furthermore, by designing molecular and device structures, single-molecule electronic devices with different performance characteristics and applications can be obtained, such as field-effect transistors and light-emitting diodes. Summary of the Invention

[0005] To address the challenges of integrating single-molecule electronic devices, this method provides a technique for preparing integrated graphene monomolecules using the electropolymerization of conductive polymers. This technique enables the efficient fabrication of arrayed graphene monomolecule functional devices. Monolayer graphene obtained through chemical vapor deposition can be transferred in batches onto silicon wafers. Integrated graphene devices are then obtained by photolithography and thermal evaporation. Electron beam lithography and oxygen plasma etching techniques are used to obtain integrated electrode pairs with nanoscale gaps. Conductive polymer monomers are covalently bonded to the edges of the graphene electrode pairs. Using an electrochemical workstation, polymer monomers are added for in-situ electropolymerization to obtain integrated conductive polymer graphene monomolecule devices. Depending on the specific requirements, the molecular bridge structure and device structure can be changed to construct functional devices such as field-effect transistors.

[0006] The technical solution adopted in this invention is:

[0007] To achieve the above objectives, the integrated conductive polymer graphene single-molecule electronic device uses nanoscale graphene point electrode pairs as electrodes and achieves single-molecule connection through electropolymerization to obtain a graphene single-molecule device.

[0008] The specific technical solution for preparing the graphene point electrode pair is as follows:

[0009] (1) Preparation of high-quality graphene on a substrate;

[0010] (2) Laying metal electrodes on graphene;

[0011] (3) Nanoscale graphene triangular point electrode pairs are obtained by pattern exposure and etching.

[0012] The graphene required for preparing the graphene triangular point electrodes is a single-layer graphene grown by CVD. The graphene is transferred to a substrate using a wet process. Electrodes are deposited on the substrate, integrating the graphene into the circuit. PMMA is spin-coated onto the surface of the graphene block, and two quadrilateral patterns are created using electron beam exposure. After development, the patterns are etched using oxygen plasma to obtain a pair of graphene point electrodes with carboxyl groups at the edges, nanoscale gaps, and protected by PMMA. The substrate includes, but is not limited to, atomically flat SiO2 / Si, h-BN, or mica. The source-drain current is measured using a semiconductor parameter analyzer at a source-drain bias voltage of 50 mV, and the current is reduced to the noise level (pA level) to ensure that each electrode pair is open-circuited. When electrode conduction occurs, a gradient voltage from 0V to 20V is used for burn-off. The graphene triangular point electrodes have a single controllable electrode gap at the edge, with a spacing of 1-10 nm, and the electrode ends are capped with carboxyl groups for subsequent processes. The metal electrode consists of Cr as an adhesion layer, Au as a conductive layer, and SiO2 as a protective layer. The adhesion layer has a thickness of 6–8 nm, the conductive layer has a thickness of 60–80 nm, and the protective SiO2 layer has a thickness of 40–60 nm.

[0013] In this invention, the performance of a field-effect transistor is achieved by adding a gate in the process. The gate material used includes, but is not limited to, titanium and gold, and the dielectric layer includes, but is not limited to, hafnium oxide and lanthanum fluoride. Preferably, the solid gate of the field-effect transistor is a 40 nm Ti electrode and a 10 nm hafnium oxide dielectric layer, or a 40 nm Au electrode and an 80 nm lanthanum fluoride dielectric layer.

[0014] This invention provides a method for achieving monomolecular linkage through electropolymerization, the specific technical solution of which is as follows:

[0015] (1) Modify molecular anchor points at the edge of graphene;

[0016] (2) Electropolymerize the molecular building blocks between graphene point electrode pairs;

[0017] (3) Only a single molecule is connected between the control electrode pairs.

[0018] The molecular linking process involves modifying the carboxyl ends of graphene with anchor molecules, using amide or ester bonds. The anchor molecules used are various conductive polymers and modified molecules containing amino or hydroxyl terminals, including but not limited to compounds containing pyrrole, thiophene, aniline, and substituted aromatic units. For anchor molecules with amino or hydroxyl terminals, a triangular graphene point electrode device containing carboxyl groups is immersed in a solution of the target molecule, a dehydrating agent is added, and under inert gas protection, a stable amide or ester bond is formed at room temperature. Using a dual potentiostat, with a graphene point electrode pair as the working electrode, a silver wire coated with AgCl as the reference electrode, and a platinum wire as the counter electrode, the molecular building blocks are electropolymerized between the electrodes. The molecular building blocks used are various conductive polymers and modified conductive polymer molecules, including but not limited to compounds containing pyrrole, thiophene, aniline, and substituted aromatic units. A graphene triangular point electrode device containing anchor molecules is immersed in a solution of molecular building blocks. Electropolymerization is performed under inert gas protection using a dual potentiostat, connecting individual molecular chains between graphene point electrode pairs with a conductivity in the nS range. A voltage divider resistor, such as 500 MΩ, is included between the graphene electrode and the working electrode. This resistor reduces the voltage at the graphene terminals, thereby stopping the reaction and achieving the connection of single polymer molecules. The applied voltage includes, but is not limited to, 0.3-1.0 V on one side and -0.5-0 V on the other. The electrolyte is applied to the device surface through a microfluidic pool made of polysiloxane (PDMS). The pool sidewalls have openings, allowing the reference electrode and counter electrode to be inserted into the solution.

[0019] In this invention, the stable amide or ester bond connection is achieved by linking anchor molecules to the graphene edge through amide or ester bonds. The 0.4-micron PMMA on the surface of the graphene device has a shape consistent with the graphene edge, thus protecting the graphene surface. The solvent used in the process of linking anchor molecules to carboxyl groups includes, but is not limited to, formamide. The dehydrating agent includes, but is not limited to, dicyclohexylcarbodiimide, N,N-diisopropylcarbodiimide, or 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloric acid. The catalyst includes, but is not limited to, 1-hydroxybenzotriazole (HOBT). The base includes, but is not limited to, triethylamine. The inert gas is nitrogen or argon.

[0020] In this invention, the solution used in the electropolymerization process includes, but is not limited to, an acidic buffer solution with TsONa as the electrolyte; a mixture of an acidic buffer solution and ethanol with TsONa as the electrolyte; and ionic liquids, including but not limited to 1-butyl-3-methylimidazolium tetrafluoroborate.

[0021] In this invention, the molecular anchor point comprises any one of the compounds having the structure shown in Formula A.

[0022]

[0023] Formula A

[0024] The molecular anchor point comprises any one of the compounds having the structure shown in Formula B.

[0025]

[0026] Formula B

[0027] The molecular anchor point comprises any one of the compounds having the structure shown in Formula C.

[0028]

[0029] Formula C

[0030] Wherein, R1 is a spacer group selected from... or n and m are integers from 0 to 3, R2 is an amino or hydroxyl group, and the pyrrole, thiophene or aniline structure can be modified by any group.

[0031] In this invention, the molecular building blocks comprise any one of the compounds having the structure shown in Formula D, wherein the pyrrole ring can be modified by any group.

[0032]

[0033] Formula D

[0034] Alternatively, the molecular building block may comprise any one of the compounds having the structure shown in Formula E, wherein the thiophene ring may be modified by any group.

[0035]

[0036] Formula E

[0037] Alternatively, the molecular building blocks may comprise any one of the compounds having the structure shown in Formula F, wherein the aniline ring may be modified by any group.

[0038] .

[0039] Formula F

[0040] Furthermore, in this invention, the graphene single-molecule device achieves the function of a light-emitting diode by protecting the core molecule with polysiloxane during the manufacturing process.

[0041] In this invention, the graphene single-molecule device achieves simultaneous electropolymerization connection of multiple devices by connecting different devices in parallel to a dual potentiostat.

[0042] The technical effects of this invention are:

[0043] This invention proposes a novel method for fabricating integrated single-molecule devices based on electropolymerization. The method first fabricates a nanoscale, controllable array of graphene point electrodes using an etching process. Then, monomer anchors are used to modify the graphene edges using amide bonds. Finally, electrochemical polymerization is employed to connect single conductive polymer chains between the graphene electrode pairs, ultimately constructing a conductive polymer-graphene single-molecule device. This approach offers advantages such as high success rate, large-scale array fabrication capability, and the ability to fabricate devices with bottom-gate structures according to specific needs, thereby achieving the integration of single-molecule electronic devices and specific logic functions. Compared to single-molecule devices fabricated using traditional methods, the single-molecule electronic devices fabricated using this method exhibit significantly improved performance, demonstrating excellent gate control characteristics and successfully achieving efficient device integration. Attached Figure Description

[0044] To clearly and intuitively illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments of this application are briefly described below. Obviously, the drawings in the following description are merely some embodiments of this application; those skilled in the art can obtain other embodiments based on these drawings.

[0045] Figure 1 This is a flowchart illustrating the fabrication process of a single-molecule conductive polymer electronic device.

[0046] Figure 2 A flowchart illustrating the process of achieving monomolecular linkage through electropolymerization.

[0047] Figure 3 Electron micrograph of the fabrication process of a single-molecule conductive polymer electronic device.

[0048] Figure 4 This is a flowchart illustrating the fabrication process of a single-molecule conductive polymer field-effect transistor.

[0049] Figure 5 This is a scanning electron micrograph of a single-molecule conductive polymer field-effect transistor.

[0050] Figure 6 A schematic diagram of a device for achieving monomolecular linkages in electropolymerization.

[0051] Figure 7 The connection process is monitored by a dual potentiostat.

[0052] Figure 8 The transfer curve is shown for a polyEDOT single-molecule field-effect transistor.

[0053] Figure 9 An electroluminescent image of a polypyrrole monomolecule device. Detailed Implementation

[0054] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments. Unless otherwise specified, the methods described are conventional methods. Unless otherwise specified, the raw materials are all available from publicly available commercial sources.

[0055] (1) Preparation of nanoscale graphene point electrode pairs

[0056] First, a 25 μm thick copper sheet is treated with glacial acetic acid for 20 minutes to remove the surface oxide layer and contaminants. After cleaning, the copper sheet is placed in a tube furnace at a temperature of 16 cm. 3 ·min –1 Annealing was performed at 1055 °C for 1 h under a hydrogen atmosphere, followed by reducing the hydrogen flow rate to 8 cm. 3 ·min –1 And add 1.6 cm 3 ·min –1 Methane was added, and the temperature was lowered after 25 minutes. At this point, a single layer of graphene had grown and covered the copper sheet. PMMA 950 was spin-coated onto the graphene-coated copper sheet at 4000 rpm, and the sheet was dried at 180 °C for 2 minutes. Subsequently, the copper substrate was etched away with a FeCl3 hydrochloric acid solution, transferring the graphene onto the PMMA film. A 1.5 × 1.5 cm silicon wafer (SiO2 thickness of 3000 Å) was cut and treated with Piranha solution (concentrated sulfuric acid to hydrogen peroxide volume ratio of 7:3) for 4 hours to remove contaminants from the silicon wafer surface and modify it to be hydrophilic. The PMMA film with graphene was transferred onto the silicon wafer, annealed in air at 380 °C for 2 minutes, and the film was removed to obtain a silicon wafer with a single layer of graphene attached.

[0057] Mark patterns were etched onto a silicon wafer using a mask-photolithography method (AR-P 5350 photoresist, baked at 120 ℃ for 3 min, and developed with AR300-26). An 8 nm thick layer of Cr and 80 nm thick Au was then deposited as markers using thermal evaporation. Subsequently, a 15 μm wide photoresist protective layer array was fabricated on the graphene using the same mask-photolithography method. The remaining graphene was etched away using plasma oxygen etching (RIE), and the photoresist was washed away with acetone to obtain graphene nanostrips. An 8 nm thick layer of Cr and 80 nm thick Au was then deposited onto the silicon wafer as electrodes using the same mask-photolithography method. Finally, the graphene was divided into 15 × 6 μm arrays using mask-photolithography and RIE, resulting in an array of 250 graphene transistors.

[0058] A 0.4 μm layer of PMMA was spin-coated onto a graphene transistor device at 1500 rpm and baked at 190 °C for 2 min. A dashed pattern was then exposed on the graphene surface using electron beam lithography. Under monitoring of the feedback current, the exposed area was etched using oxygen plasma for 5 s to obtain graphene point electrodes with nanoscale gaps protected by PMMA. The source-drain current was measured using a semiconductor parameter analyzer at a source-drain bias voltage of 50 mV, and the current was reduced to the noise level (pA level) to ensure that each electrode pair was open-circuited. When electrode conduction occurred, a gradient voltage from 0 V to 20 V was used for burn-off. Since PMMA served as the polishing layer for graphene etching, its shape is considered to be essentially consistent with that of graphene, exposing only the edges while protecting the surface, thus creating conditions for subsequent single-molecule bonding. Figure 1 The diagram illustrates the fabrication process of the above-mentioned devices. Figure 3 This is the final structure diagram of the device.

[0059] To fabricate graphene field-effect transistors, a bottom gate and dielectric layer must be prepared on a silicon wafer before transferring graphene. The gate pattern is etched onto the silicon wafer using a mask-photolithography method. An 8 nm thick layer of Cr and an 80 nm thick layer of Au are deposited using thermal evaporation to form the bottom gate, followed by the deposition of a 100 nm thick layer of lanthanum fluoride as the dielectric layer. Using this as a substrate, the graphene field-effect transistor is obtained after steps including graphene transfer. Figure 4 The diagram illustrates the fabrication process of the above-mentioned devices. Figure 5 This is the final structure diagram of the device.

[0060] (2) Achieving monomolecular linkage through electropolymerization ( Figure 2 ).

[0061] Example 1: Fabrication of a single-molecule polypyrrole device

[0062] For the graphene-based device platform obtained above, pyrrole groups were modified onto the graphene edges via a dehydration reaction using amide bonds. The prepared graphene electrode was immersed in a formamide solution of 2-aminomethylpyrrole, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloric acid (EDCI), 1-hydroxybenzotriazole (HOBT), and triethylamine were added. The reaction was carried out at room temperature for 2 hours. After the reaction was completed, the electrode was rinsed with deionized water and ethanol, and dried with high-purity nitrogen to obtain a graphene triangular point electrode pair with pyrrole groups at the ends.

[0063] A liquid cell made of polysiloxane (PDMS) was attached to the top of the device. 40 μL of buffer solution containing pyrrole monomers (0.1 M TsONa, 0.01 M pyrrole, pH 2 phosphate buffer) was injected into the reaction chamber of the liquid cell. A CHI730 dual potentiostat was used, with graphene electrodes on both sides as working electrodes. A 500 MΩ resistor was connected in series across the graphene electrodes and linked to the instrument via a probe. A silver wire coated with AgCl served as the reference electrode, and a platinum wire as the counter electrode, which was inserted into the solution through the side wall of the liquid cell. Figure 6 The potential of the right electrode WE1 was set at 0.45 V in the electrolysis region, and the potential of the left electrode WE2 was set at -0.45 V in the intrinsic region. Electropolymerization was carried out for approximately 20 seconds. The instrument can simultaneously output the current value I1 of the left electrode and the current value I2 of the right electrode. When a symmetry break occurs in the current value, it indicates that the monomolecule connection is successful. Figure 7 At this point, stop applying voltage to complete the connection.

[0064] Example 2: Fabrication of a single-molecule poly(3,4-ethylenedioxythiophene) (PEDOT) device

[0065] For the graphene-based device platform obtained above, pyrrole groups were modified onto the graphene edges via a dehydration reaction using amide bonds. The prepared graphene electrodes were immersed in a formamide solution of 2-aminomethyl-3,4-ethylenedioxythiophene, and EDCI, HOBT, and triethylamine were added. The reaction was carried out at room temperature for 2 h. After the reaction, the electrodes were rinsed with deionized water and ethanol, and dried with high-purity nitrogen to obtain graphene triangular point electrode pairs with pyrrole groups at the ends.

[0066] A liquid cell made of polysiloxane (PDMS) was attached to the top of the device. 40 μL of buffer solution containing dimeric EDOT monomer (0.1 M TsONa, 0.01 M dimeric EDOT, pH=2 phosphate ethanol mixed buffer) was injected into the reaction chamber of the liquid cell. A CHI730 dual potentiostat was used, with graphene on both sides as working electrodes. A 500 MΩ resistor was connected in series on both sides of the graphene and linked to the instrument via a probe. A silver wire coated with AgCl was used as the reference electrode, and a platinum wire as the counter electrode, inserted into the solution through the sidewall of the liquid cell. The potential of the right electrode WE1 was set at 0.35 V in the electrolytic region, and the potential of the left electrode WE2 was set at -0.35 V in the intrinsic region. Electropolymerization was carried out for approximately 20 s. The instrument could simultaneously output the current value I1 of the left electrode and the current value I2 of the right electrode. When a symmetrical abrupt change occurred in the current value, it indicated successful monomolecular connection. At this point, the applied voltage was stopped, and the connection was completed.

[0067] Example 3: Fabrication of monomolecular polyaniline devices

[0068] For the graphene-based device platform obtained above, pyrrole groups were modified onto the graphene edges via a dehydration reaction using amide bonds. The prepared graphene electrodes were immersed in a formamide solution of p-diaminobenzene, and EDCI, HOBT, and triethylamine were added. The reaction was carried out at room temperature for 2 h. After the reaction was completed, the electrodes were rinsed with deionized water and ethanol, and dried with high-purity nitrogen to obtain graphene triangular point electrode pairs with pyrrole groups at the ends.

[0069] A liquid pool made of polysiloxane (PDMS) was attached to the top of the device. 40 μL of a solution containing dimeric EDOT monomers (a mixture of 0.1 M TsONa, 0.01 M aniline, ethanol, and water) was injected into the reaction chamber of the liquid pool. A CHI730 dual potentiostat was used, with graphene electrodes on both sides as working electrodes. A 500 MΩ resistor was connected in series across the graphene electrodes and linked to the instrument via a probe. A silver wire coated with AgCl served as the reference electrode, and a platinum wire as the counter electrode, inserted into the solution through the sidewall of the liquid pool. The potential of the right electrode WE1 was set at 0.5 V in the electrolytic region, and the potential of the left electrode WE2 was set at -0.2 V in the intrinsic region. Electropolymerization was carried out for approximately 20 s. The instrument simultaneously output the current values ​​I1 of the left electrode and I2 of the right electrode. When a symmetrical breakpoint occurred in the current value, it indicated successful monomolecular connection. At this point, the applied voltage was stopped, and the connection was complete.

[0070] Example 4: Fabrication of a single-molecule polythiophene device

[0071] For the graphene-based device platform obtained above, pyrrole groups were modified onto the graphene edges via a dehydration reaction using amide bonds. The prepared graphene electrodes were immersed in a formamide solution of C-[2,2'-dithiophenyl-5-ylmethyl]amine, and EDCI, HOBT, and triethylamine were added. The reaction was carried out at room temperature for 2 h. After the reaction was completed, the electrodes were rinsed with deionized water and ethanol, and dried with high-purity nitrogen to obtain a graphene triangular point electrode pair with pyrrole groups at the ends.

[0072] A liquid cell made of polysiloxane (PDMS) was attached to the top of the device. 40 μL of an ionic liquid solution containing 2,2'-dithiophene monomer (0.01 M dithiophene, 1-butyl-3-methylimidazolium tetrafluoroborate) was injected into the reaction chamber of the liquid cell. A CHI730 dual potentiostat was used, with graphene electrodes on both sides as working electrodes. A 500 MΩ resistor was connected in series on both sides of the graphene electrodes and linked to the instrument via a probe. A silver wire coated with AgCl was used as the reference electrode, and a platinum wire as the counter electrode, inserted into the solution through the sidewall of the liquid cell. The potential of the right electrode WE1 was set at 0.9 V in the electrolytic region, and the potential of the left electrode WE2 was set at 0 V in the intrinsic region. Electropolymerization was carried out for approximately 20 s. The instrument could simultaneously output the current value I1 of the left electrode and the current value I2 of the right electrode. When a symmetrical breakpoint occurred in the current value, it indicated successful monomolecular connection. At this point, the applied voltage was stopped, and the connection was completed.

[0073] To improve the efficiency of connecting single molecules, eight pairs of resistors were connected in parallel at each end of the PCB circuit board, and then connected to eight graphene electrodes via copper wires and conductive silver paste. This enabled the simultaneous connection of eight devices, achieving the integration of 250 single-molecule polypyrrole devices on a single device. The connection speed of the devices is linked to the number of parallel resistors, and large-scale industrial integration can be achieved by increasing the number of parallel resistors.

[0074] (3) Electrical testing of single-molecule heterojunctions

[0075] The fabricated single-molecule device was tested for electrical properties of the single-molecule heterojunction using an Agilent 4155C semiconductor parametric analyzer and an ST-500 probe station. The probe was attached to the corresponding source, drain, and gate electrodes of the device, and a bias voltage ranging from -1.0 to 1.0 V was set. The measured conductivity values ​​were in the nA range, demonstrating the transport performance of the single-molecule polypyrrole device.

[0076] The probe was attached to the corresponding source, drain, and gate electrodes of the device. The bias voltage was set to 0-1.0 V, and the gate voltage to 0-1.0 V. The transfer curve of the single-molecule field-effect device was measured, demonstrating its superior field-effect transistor performance. Figure 8 ).

[0077] (4) Luminescence test of single-molecule heterojunction

[0078] A polysiloxane precursor was dropped onto the surface of a single-molecule device, and then a thin cover glass was placed on the liquid surface and cured at 50 °C for two days to obtain a single-molecule light-emitting diode.

[0079] The probe is attached to the corresponding source, drain, and gate electrodes of the device, and a bias voltage of 4.0 V is set. The diode is then imaged using an integrated photoelectric detection system with ultra-high spatiotemporal resolution. Single-molecule devices emit electroluminescence under high voltage, which is observed in a dark environment. Figure 9The light spot shown in image a; obtained in a mercury lamp environment. Figure 9 The device structure diagram shown in b, when combined with the two, can prove that the luminescent point is located in the region of the single polymer molecule, thus proving its electroluminescent performance.

Claims

1. A method for fabricating integrated single-molecule devices based on electropolymerization, characterized in that: A method for obtaining a graphene monomolecular device by using nanoscale graphene point electrode pairs as electrodes and achieving monomolecular connection through electropolymerization; the method for achieving monomolecular connection through electropolymerization includes the following steps: (1) Modify molecular anchor points at the edge of graphene; (2) Electropolymerize the molecular building blocks between graphene point electrode pairs; (3) Only a single molecule is connected between the control electrode pairs.

2. The method for fabricating integrated single-molecule devices based on electropolymerization as described in claim 1, characterized in that: The electrodes connected to the molecules are nanoscale graphene point electrode pairs, which form a circuit through metal electrodes; the flat substrate includes, but is not limited to, atomically flat SiO2 / Si, h-BN or mica. The preparation method of the graphene point electrode pair includes the following steps: (1) Preparation of high-quality graphene on a substrate; (2) Laying metal electrodes on graphene; (3) Graphene triangular point electrode pairs are achieved through pattern exposure and etching.

3. The method for fabricating integrated single-molecule devices based on electropolymerization as described in claim 2, characterized in that: The graphene required for preparing the graphene triangular point electrode is a single-layer graphene grown by CVD. The graphene is transferred to the substrate by a wet process; the electrode is deposited on the substrate to incorporate the graphene into the circuit. PMMA was spin-coated onto the surface of a graphene block, and two quadrilateral patterns were exposed using an electron beam. After development, the patterns were etched using oxygen plasma to obtain a graphene point electrode pair with carboxyl groups at the edges, nanoscale gaps, and protected by PMMA. The source and drain current is measured by a semiconductor parameter meter when the source and drain bias voltage is 50 mV. The current is reduced to the noise level to ensure that each pair of electrodes is disconnected. When the electrodes are conducting, a gradient voltage from 0V to 20V is used to burn them off.

4. The method for fabricating integrated single-molecule devices based on electropolymerization as described in claim 2, characterized in that: The graphene triangular point electrode has a single controllable electrode gap at its edge, with a spacing of 1-10 nm, and the electrode end is capped with a carboxyl group for subsequent processes.

5. The method for fabricating integrated single-molecule devices based on electropolymerization as described in claim 2, characterized in that: The metal electrode is composed of Cr as an adhesion layer, Au as a conductive layer, and SiO2 as a protective layer. The adhesion layer has a thickness of 6–8 nm, the conductive layer has a thickness of 60–80 nm, and the protective SiO2 layer has a thickness of 40–60 nm.

6. The method for fabricating integrated single-molecule devices based on electropolymerization as described in claim 1, characterized in that: A method for connecting single molecules to point electrode pairs via electropolymerization includes modifying the carboxyl ends of graphene with anchor molecules, the connection being an amide bond or an ester bond; using a dual potentiostat, with the graphene point electrode pair as the working electrode, a silver wire coated with AgCl as the reference electrode, and a platinum wire as the counter electrode, the molecular building blocks are electropolymerized between the electrodes; wherein: The molecular anchor point has an amino or hydroxyl end, and the core includes, but is not limited to, structures that can undergo electropolymerization such as pyrrole, thiophene, aniline, and polycyclic aromatic hydrocarbons; for anchor molecules with amino or hydroxyl ends, a graphene triangular point electrode device containing a carboxyl group is immersed in a solution of the target molecule, a dehydrating agent is added, and under the protection of an inert gas, a stable amide bond and ester bond are formed at room temperature. The molecular building blocks include, but are not limited to, structures that can be electropolymerized, such as pyrrole, thiophene, aniline, and polycyclic aromatic hydrocarbons. Graphene triangular point electrode devices with anchor molecules at their ends are immersed in a solution of the molecular building blocks, and electropolymerization is carried out under inert gas protection using a dual potentiostat to connect individual molecular chains between graphene point electrode pairs, with a conductivity in the nS range.

7. The method for fabricating integrated single-molecule devices based on electropolymerization as described in claim 6, characterized in that: The molecular anchor point includes any one of the compounds having the structure shown in Formula A. Formula A The molecular anchor point comprises any one of the compounds having the structure shown in Formula B. Formula B The molecular anchor point comprises any one of the compounds having the structure shown in Formula C. Formula C Wherein, R1 is a spacer group selected from... or n and m are integers from 0 to 3, R2 is an amino or hydroxyl group, and the pyrrole, thiophene or aniline structure can be modified by any group.

8. The method for fabricating integrated single-molecule devices based on electropolymerization as described in claim 6, characterized in that: The stable amide or ester bond connection is achieved by linking anchor molecules to the graphene edge through amide or ester bonds. The 0.4-micron PMMA on the surface of the graphene device has a shape consistent with the graphene edge, thus protecting the graphene surface. The solvents used in the process of linking anchor molecules to carboxyl groups include, but are not limited to, formamide. The dehydrating agents include, but are not limited to, dicyclohexylcarbodiimide, N,N-diisopropylcarbodiimide, or 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloric acid. The catalysts include, but are not limited to, 1-hydroxybenzotriazole (HOBT). The base includes, but is not limited to, triethylamine. The inert gas is nitrogen or argon.

9. The method for fabricating integrated single-molecule devices based on electropolymerization as described in claim 6, characterized in that: The solutions used in the electropolymerization process include, but are not limited to, acidic buffer solutions with TsONa as the electrolyte; mixtures of acidic buffer solutions and ethanol with TsONa as the electrolyte; and ionic liquids, including but not limited to 1-butyl-3-methylimidazolium tetrafluoroborate.

10. The method for fabricating integrated single-molecule devices based on electropolymerization as described in claim 6, characterized in that: The molecular building blocks comprise any one of the compounds having the structure shown in Formula D, wherein the pyrrole ring can be modified by any group. Formula D Alternatively, the molecular building block may comprise any one of the compounds having the structure shown in Formula E, wherein the thiophene ring may be modified by any group. Formula E Alternatively, the molecular building blocks may comprise any one of the compounds having the structure shown in Formula F, wherein the aniline ring may be modified by any group. Formula F The molecular building block may comprise any of any compound having the structure shown in Formula F, wherein the aniline ring may be modified by any group.

11. The method for fabricating integrated single-molecule devices based on electropolymerization as described in claim 6, characterized in that: In the electropolymerization method, a voltage divider resistor with a resistance of 500 MΩ is included between the graphene electrode and the working electrode. The voltage at the graphene end is reduced by the resistor, thereby stopping the reaction and realizing the connection of single-molecule polymers. The applied voltage includes, but is not limited to, 0.3-1.0 V on one side and -0.5-0 V on the other side. The electrolyte is applied to the device surface through a microfluidic liquid pool made of polysiloxane. The sidewall of the liquid pool has openings to allow the reference electrode and the counter electrode to contact the solution.

12. The method for fabricating integrated single-molecule devices based on electropolymerization as described in claim 1, characterized in that: The graphene single-molecule device achieves the performance of a field-effect transistor by adding a gate in the process; the gate material used includes, but is not limited to, titanium and gold, and the dielectric layer includes, but is not limited to, hafnium oxide and lanthanum fluoride.

13. The method for fabricating integrated single-molecule devices based on electropolymerization as described in claim 1, characterized in that: The graphene single-molecule device achieves the function of a light-emitting diode by protecting the core molecule with polysiloxane during the manufacturing process.

14. The method for fabricating integrated single-molecule devices based on electropolymerization as described in claim 1, characterized in that: The graphene single-molecule device achieves simultaneous electropolymerization connection of multiple devices by connecting different devices in parallel to a dual potentiostat.

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