An arrayed neural network with artificially designed boundaries based on two-dimensional materials, its preparation method and application

Abstract

The present invention discloses an arrayed neural network with artificially designed boundaries based on two-dimensional materials, as well as its preparation method and application. Its preparation method includes the following steps: 1) growing a single-crystal transition metal compound thin film on a substrate by vapor deposition; 2) transferring the thin film described in step 1) to a substrate with a dielectric layer; 3) irradiating the thin film on the substrate with a dielectric layer in step 2) with a laser according to a specified path to obtain a sample of a specified heterostructure; 4) coating the source and drain electrodes on the surface of the sample of the specified heterostructure by electron beam or thermal evaporation, thereby obtaining an arrayed neural network with artificially designed boundaries based on two-dimensional materials. Due to the sub-nanometer thickness, artificially modulated boundaries, and controllably generated surface defects, the present invention effectively reduces the Schottky barrier between the metal and the electrode, thereby reducing the turn-on voltage and reducing its energy consumption to the level of the human brain.

Description

Technical Field

[0001] The present invention relates to an arrayed neural network with artificially designed boundaries based on two-dimensional materials, a preparation method and application thereof, and belongs to the field of nanotechnology. Background Art

[0002] Neuromorphic computing aims to emulate the biological brain, mimicking its efficiency, versatility, and resilience. Synapses are key components of information transmission and processing in the brain. Synaptic plasticity, the ability of synapses to change their connection strength in response to neural activity, is considered the biological basis of learning and memory. Subnanoscale two-dimensional heterojunctions are promising flexible, transparent electronic devices. In recent years, synaptic devices based on two-dimensional layered materials have been shown to perform well in neuromorphic computing systems, such as electronic synapses and neurons. Advanced two-dimensional in-plane synaptic devices operate based on grain boundaries, whose formation is always random and uncontrollable. Furthermore, synaptic devices that can accurately mimic the learning and cognitive processes in biological systems remain very limited, let alone achieve the low power consumption of the human brain. Controllability and low energy consumption of synaptic devices are fundamental to the development of artificial neural networks and are two of the most critical issues. Furthermore, to be integrated with visual systems, synaptic devices must exhibit a sensitive response to light dose, but achieving dual optical and electrical modulation in existing devices remains difficult. Summary of the Invention

[0003] The purpose of the present invention is to provide an arrayed neural network with artificially designed boundaries based on two-dimensional materials, as well as a preparation method and application thereof.

[0004] The present invention uses a specific laser to scan transition metal chalcogenides (such as molybdenum disulfide and tungsten disulfide) to form a designated boundary, thus forming a multi-field modulated synapse with an artificially designed boundary. This method not only can simultaneously simulate short-range and long-range plasticity on the same device, particularly the stimulation frequency-dependent plasticity (SRDP) and stimulation time-dependent plasticity (STDP) that are the basis of artificial neural networks, but can also be modulated by light and gate voltage. In addition, the device has very low energy consumption (≤20pJ per conversion), similar to that of the human brain, showing the potential for realizing the electrical and optical aspects of biological memory learning and image recognition processes.

[0005] The present invention provides a method for preparing an arrayed neural network with artificially designed boundaries based on two-dimensional materials, comprising the following steps:

[0006] 1) growing a single crystal transition metal compound thin film on a substrate by vapor deposition;

[0007] 2) transferring the thin film described in step 1) onto a substrate having a dielectric layer;

[0008] 3) irradiating the thin film on the substrate having the dielectric layer in step 2) with a laser along a specified path to obtain a sample of a specified heterostructure;

[0009] 4) The source and drain electrodes are deposited on the surface of the sample of the designated heterostructure by electron beam or thermal evaporation, thereby obtaining an arrayed neural network with artificially designed boundaries based on two-dimensional materials.

[0010] In the above preparation method, the substrate in step 1) is a SiO2 / Si substrate;

[0011] The transition metal compound in the single crystal transition metal compound film is molybdenum disulfide;

[0012] The thickness of the single crystal transition metal compound thin film may be 0.5 to 10 nm, specifically 0.7 nm, 0.5 to 0.7 nm, 0.7 to 10 nm, 0.5 to 1 nm or 0.5 to 5 nm.

[0013] In the above-mentioned preparation method, the preparation method of the single crystal transition metal compound thin film comprises the following steps:

[0014] a1) placing the substrate in deionized water, acetone, and isopropyl alcohol for ultrasonic cleaning in sequence, then drying with nitrogen, placing the substrate in a double-ended open-ended quartz boat containing a transition metal oxide (preferably molybdenum trioxide), and placing the boat in a high-temperature tube furnace reaction chamber;

[0015] b1) placing a quartz boat filled with a chalcogen (preferably sulfur powder) in another heating zone at the upper end of the substrate gas flow;

[0016] c1) After purging with argon in a tube furnace, introduce 5 sccm of argon. After the gas flow stabilizes, heat the chalcogen and transition metal oxide (silicon wafer) separately to grow a monolayer of transition metal chalcogen compound on the substrate. When the chalcogen is sulfur powder and the transition metal oxide is molybdenum trioxide, heat the chalcogen and molybdenum trioxide (silicon wafer) to ~130-140°C and ~645-655°C, respectively, and maintain the constant temperature for 5-10 minutes.

[0017] In the above preparation method, in step 2), the transfer method adopts wet transfer;

[0018] The substrate with the dielectric layer is a substrate with a silicon dioxide oxide layer.

[0019] In the above preparation method, the wet transfer comprises the following steps:

[0020] a2) spin-coating a layer of polymethyl methacrylate (PMMA) on the single crystal thin film synthesized on the silicon wafer in step 1), and heating on a heating table at 180° C. for 2 minutes to dry;

[0021] b2) placing the PMMA-coated silicon wafer in deionized water or potassium hydroxide solution and allowing it to stand until the PMMA is peeled off the silicon wafer;

[0022] c2) After rinsing the peeled PMMA several times with clean water, stick it on a new substrate with a dielectric layer (preferably a silicon wafer with silicon oxide), heat it on a heating table at 180°C for 2 minutes to dry it, let it cool, and then put it in 70°C acetone for about 30 minutes to dissolve the PMMA, and then obtain the transferred film.

[0023] In the above preparation method, in step 3), the laser irradiation along a specified path includes the following steps:

[0024] a3) Determine the scan image, set the laser power and laser scanning speed; the laser power is 1 to 1000 kW / mm 2 , specifically 11kW / mm 2 , 1~11kW / mm 2 11~1000kW / mm 2 or 1~500kW / mm 2 The laser scanning speed may be 1 μm / s to 100 m / s, specifically 10 μm / s, 1 μm / s to 1 m / s, or 1 μm / s to 50 m / s. In a specific embodiment, the wavelength of the laser may be 532 nm.

[0025] b3) placing the thin film on the substrate with the dielectric layer in step 2) at the starting point of the scanning image, and scanning the thin film using laser scanning software according to the laser power and laser scanning speed in a3).

[0026] In the present invention, after the laser irradiates along a specified path, the area scanned retains the crystal structure of the transition metal chalcogenide, but significant surface defects are generated. When the transition metal chalcogenide is molybdenum disulfide, the generated defects are sulfur defects. The unscanned areas remain unchanged, with few or no surface defects.

[0027] In the above-mentioned preparation method, the material of the source electrode is titanium;

[0028] The material of the drain electrode is gold.

[0029] In the above-mentioned preparation method, the method of preparing the electrode using the electron beam or thermal evaporation method includes the following steps:

[0030] a4) spin-coating a photoresist on the surface of the sample of the designated heterostructure obtained in step 3); when the photoresist is specifically 4% PMMA, the spin-coating rate is 600-5000 r / min, specifically 2500 r / min, 600-2500 r / min, 2500-5000 r / min, or 3000-4000 r / min;

[0031] b4) etching the source electrode pattern and the drain electrode pattern at the electrodes at both ends of the sample processed in step a4) by electron beam exposure or photolithography;

[0032] c4) depositing the source electrode and the drain electrode on the source electrode pattern and the drain electrode pattern by electron beam evaporation or thermal evaporation; preferably, when electron beam evaporation is used, when the sample is a molybdenum disulfide heterostructure, first evaporating a titanium or cadmium electrode with a thickness of 1 to 50 nm (specifically 20 nm), and then evaporating a gold electrode with a thickness of 1 to 100 nm (specifically 50 nm);

[0033] d4) After peeling off the evaporated layer, the source electrode and the drain electrode are obtained.

[0034] The present invention also provides the arrayed neural network with artificially designed boundaries based on two-dimensional materials, which is prepared by the above-mentioned preparation method.

[0035] The arrayed neural network with artificially designed boundaries based on two-dimensional materials described in the present invention is used to prepare artificial synaptic devices.

[0036] The present invention has the following advantages:

[0037] The present invention uses a heterojunction made by laser processing a single layer of transition metal chalcogenide for artificial synaptic devices. Due to the sub-nanometer thickness, artificially modulated boundaries, and controllably generated surface defects, the Schottky barrier between the metal and the electrode is effectively reduced, thereby reducing the turn-on voltage and reducing its energy consumption to the level of the human brain. At the same time, the movement of controllable surface defects enables this device to well simulate the short-term and long-term plasticity of the synapse, especially SRDP and STDP, allowing this device to effectively simulate the memory and forgetting process. In addition, the controllability of gate voltage and light stimulation enables this device to achieve multi-field regulation, realize vertical and horizontal dual integration, and simultaneously realize image recognition simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the structure of the artificial synapse device in Example 1 of the present invention.

[0039] Figure 2 This is the short-term synaptic plasticity of the artificial synaptic device in Example 1 of the present invention.

[0040] Figure 3 This is the long-term synaptic plasticity of the artificial synaptic device in Example 1 of the present invention.

[0041] Figure 4 This is the STDP synaptic plasticity of the artificial synaptic device in Example 1 of the present invention.

[0042] Figure 5 This is the SRDP synaptic plasticity of the artificial synaptic device in Example 1 of the present invention.

[0043] Figure 6 1 is the gate voltage modulation characteristic of the artificial synaptic device in Example 1 of the present invention.

[0044] Figure 7 1 is the optical modulation characteristic of the artificial synapse device in Example 1 of the present invention. DETAILED DESCRIPTION

[0045] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0046] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] Example 1

[0049] 1. A silicon wafer with a single layer of molybdenum disulfide (300 nm thick oxide layer) was grown using chemical vapor deposition as follows:

[0050] a1) placing the substrate in deionized water, acetone, and isopropyl alcohol for ultrasonic cleaning in sequence, then drying with nitrogen, placing the substrate in a double-ended open-ended quartz boat containing a transition metal oxide (preferably molybdenum trioxide), and placing the boat in a high-temperature tube furnace reaction chamber;

[0051] b1) placing a quartz boat filled with a chalcogen (preferably sulfur powder) in another heating zone at the upper end of the substrate gas flow;

[0052] c1) After purging with argon in a tube furnace, introduce 5 sccm of argon. After the gas flow stabilizes, heat the chalcogen and transition metal oxide (silicon wafer) separately to grow a monolayer of transition metal chalcogen compound on the substrate. When the chalcogen is sulfur powder and the transition metal oxide is molybdenum trioxide, heat the chalcogen and molybdenum trioxide (silicon wafer) to ~130-140°C and ~645-655°C, respectively, and maintain the constant temperature for 5-10 minutes.

[0053] 2. The silicon wafer with a single layer of MoS2 (300nm thick silicon wafer, the thickness of the single layer of MoS2 is 0.7nm) is wet-transferred to a new 300nm thick silicon wafer as follows:

[0054] a2) spin-coating a layer of polymethyl methacrylate on the single crystal thin film synthesized on the silicon wafer in step 1, and heating on a heating table at 180° C. for 2 minutes to dry;

[0055] b2) placing the polymethyl methacrylate-coated silicon wafer in deionized water or potassium hydroxide solution and allowing it to stand until the polymethyl methacrylate is peeled off from the silicon wafer;

[0056] c2) After rinsing the peeled polymethyl methacrylate with clean water several times, it is attached to a new substrate with a dielectric layer, heated on a heating table at 180°C for 2 minutes to dry it, allowed to cool, and then placed in 70°C acetone for about 30 minutes to dissolve the polymethyl methacrylate, thereby obtaining the transferred film.

[0057] 3. Use 532nm laser to follow the specified path, use TANGO translation stage and control software, and transmit the laser at 11kW / mm 2 The sample surface was scanned with a power of 1000 nm and a rate of 10 μm / s to obtain a sample with a specified heterostructure.

[0058] a3) Determine the scan image, set the laser power and laser scanning speed (preferably 11kW / mm 2 , 10 μm / s);

[0059] b3) placing the thin film on the substrate with the dielectric layer in step 2 at the starting point of the scanning image, and scanning the thin film using laser scanning software according to the laser power and laser scanning speed in a3).

[0060] 4. 4% PMMA (polymethacrylate) was spin-coated onto the sample surface and exposed using an electron beam geometries system (NPGS) to create source and drain patterns. Subsequently, 20nm Ti / 50nm Au were deposited onto the sample surface using electron beam evaporation to create an artificial synaptic device based on a MoS2 in-plane heterostructure.

[0061] The electron beam evaporation method comprises the following steps: a4) spin coating a photoresist on the surface of the sample of the specified heterostructure obtained in step 3; when the photoresist is specifically 4% polymethyl methacrylate, the spin coating rate is 2500 r / min;

[0062] b4) etching the source electrode pattern and the drain electrode pattern at the electrodes at both ends of the sample processed in step a4) by electron beam exposure or photolithography;

[0063] c4) depositing the source electrode and the drain electrode on the source electrode pattern and the drain electrode pattern by electron beam evaporation or thermal evaporation; preferably, when electron beam evaporation is used, when the sample is a molybdenum disulfide heterostructure, first depositing a 20 nm titanium electrode and then depositing a 50 nm gold electrode;

[0064] d4) After peeling off the evaporated layer, the source and drain electrodes are prepared.

[0065] The schematic diagram of the artificial synaptic device based on the MoS2 in-plane heterostructure prepared above is as follows: Figure 1 As shown, the direction of the heterojunction boundary line is controllable and can be fabricated in an array. Electrical properties were then measured on a Casecade Microtech MPS150 probe station and an Agilent B1500 semiconductor parameter analyzer.

[0066] The short-term plasticity and long-term plasticity of the synaptic device are respectively as follows Figure 2 and Figure 3 As shown. At this time, the drain voltage is 20V and the gate voltage is 0V. Figure 2 It can be seen that the current and relaxation time increase monotonically with the light intensity. Figure 3 It can be seen that the transition from short-term plasticity to long-term plasticity can be achieved on a single device.

[0067] The STDP and SRDP synaptic characteristics of the synaptic device are shown as follows: Figure 4 and Figure 5 As shown, the drain voltage is 20V and the gate voltage is 0V. Figure 4 It can be seen that the device has STDP plasticity and can realize brain-like computing.

[0068] The gate voltage modulation characteristics of the synaptic device are as follows: Figure 6 As shown. Figure 6 As can be seen from the figure, the device has a third terminal and can be integrated vertically.

[0069] The synaptic device is photometrically modulated. Figure 7 As shown. Figure 6 As can be seen from the figure, the device is sensitive to light measurement and can be used for image recognition. It is a photoelectric dual-mode device.

[0070] Of course, the present invention can also have many embodiments, without departing from the spirit and essence of the present invention.

[0071] Those skilled in the art may make various corresponding changes and modifications based on the disclosure of the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an arrayed neural network with artificially designed boundaries based on two-dimensional materials, comprising the following steps: 1) Growing single-crystalline transition metal compound thin films on a substrate by vapor deposition; 2) transferring the thin film described in step 1) onto a substrate having a dielectric layer; 3) irradiating the thin film on the substrate with the dielectric layer in step 2) with a laser along a specified path to obtain a sample of a specified heterostructure; After the laser is irradiated along a specified path, the transition metal chalcogenide region scanned by the laser still maintains the crystal structure of the transition metal chalcogenide and defects are generated on the surface; the crystal structure of the transition metal chalcogenide region not scanned by the laser remains unchanged; the transition metal chalcogenide scanned by the laser and the transition metal chalcogenide not scanned by the laser form a heterostructure; 4) The source and drain electrodes are deposited on the surface of the sample of the specified heterostructure by electron beam or thermal evaporation, thereby obtaining an arrayed neural network with artificially designed boundaries based on two-dimensional materials.

2. The preparation method according to claim 1, wherein: The substrate in step 1) is a SiO2 / Si substrate; The transition metal compound in the single crystal transition metal compound film is molybdenum disulfide; The thickness of the single crystal transition metal compound film is 0.5-10 nm.

3. The preparation method according to claim 1 or 2, characterized in that: The method for preparing the single crystal transition metal compound thin film comprises the following steps: a1) ultrasonically cleaning the substrate in deionized water, acetone, and isopropyl alcohol in sequence, then drying with nitrogen gas. The substrate is then placed in a double-ended open-ended quartz boat containing a transition metal oxide, and placed in a high-temperature tube furnace reaction chamber. b1) placing a quartz boat filled with chalcogen in another heating zone at the upper end of the substrate gas flow; c1) After purging with argon in a tube furnace, 5 seem of argon is introduced. After the gas flow stabilizes, the chalcogen and the transition metal oxide are heated separately to grow a monolayer of transition metal chalcogen compound on the substrate; wherein, when the chalcogen is sulfur powder and the transition metal oxide is molybdenum trioxide, the chalcogen and molybdenum trioxide are heated to approximately 130-140°C and approximately 645-655°C, respectively, and maintained at this temperature for 5-10 minutes.

4. The preparation method according to claim 1 or 2, characterized in that: In step 2), the transfer method is wet transfer; The substrate with the dielectric layer is a substrate with a silicon dioxide oxide layer.

5. The preparation method according to claim 4, characterized in that: The wet transfer comprises the following steps: a2) Spin-coating a layer of polymethyl methacrylate on the single crystal film synthesized on the silicon wafer in step 1) and heating on a heating table at 180°C for 2 minutes to dry; b2) placing the polymethyl methacrylate-coated silicon wafer in deionized water or potassium hydroxide solution and allowing it to stand until the polymethyl methacrylate is peeled off the silicon wafer; c2) After rinsing the peeled polymethyl methacrylate several times with clean water, it is attached to a new substrate with a dielectric layer and dried by heating it on a heating table at 180°C for 2 minutes. After cooling, it is placed in 70°C acetone for about 30 minutes to dissolve the polymethyl methacrylate, and then the transferred film is obtained.

6. The preparation method according to claim 1 or 2, characterized in that: In step 3), the laser irradiation along the designated path includes the following steps: a3) Determine the scan image, set the laser power and laser scanning speed, the laser power is 1~1000kW / mm 2 , the laser scanning speed is 10μm / s~1m / s; b3) The thin film on the substrate with the dielectric layer in step 2) is placed at the starting point of the scanning image, and the thin film is scanned by laser scanning software according to the laser power and laser scanning speed in a3).

7. The preparation method according to claim 1, wherein: The material of the source electrode is titanium; The material of the drain electrode is gold.

8. The preparation method according to claim 1 or 7, characterized in that: The method for preparing the source electrode and the drain electrode by using the electron beam or thermal evaporation method comprises the following steps: a4) Spin-coating a photoresist on the surface of the sample of the specified heterostructure obtained in step 3); when the photoresist is specifically 4% polymethyl methacrylate, the spin-coating speed is specifically 600-5000 r / min; b4) etching the source electrode pattern and the drain electrode pattern at the electrodes at both ends of the sample processed in step a4) by electron beam exposure or photolithography; c4) depositing the source electrode and the drain electrode on the source electrode pattern and the drain electrode pattern by electron beam evaporation or thermal evaporation; when electron beam evaporation is used, when the sample is a molybdenum disulfide heterostructure, first evaporating a titanium or cadmium electrode with a thickness of 1 to 50 nm, and then evaporating a gold electrode with a thickness of 1 to 100 nm; d4) After peeling off the evaporated layer, the source electrode and the drain electrode are manufactured.

9. The arrayed neural network with artificially designed boundaries based on two-dimensional materials prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the arrayed neural network with artificially designed boundaries based on two-dimensional materials as claimed in claim 9 in the preparation of artificial synaptic devices.

Images