Self-driven photoelectric synaptic device and preparation method thereof
By using low-work function metal electrodes and WS2/graphene Schottky junction in the photodetector, self-driven photodetection under zero bias and biological synaptic plasticity simulation under positive bias are achieved, solving the problems of high energy consumption and lack of optical information interaction in traditional photodetectors.
Patent Information
- Application Number
- CN202510295330.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-13
- Publication Date
- 2025-06-13
Smart Images
Figure CN120152403A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of photodetectors, and particularly to a self-driven photoelectric synaptic device and a preparation method thereof. Background Art
[0002] Traditional photodetectors rely on external power supplies for driving, and their high energy consumption characteristics are difficult to meet the requirements of low-power edge computing devices; at the same time, traditional synaptic devices (such as memristors and transistors) are mostly regulated based on electrical signals and lack the direct interaction ability with optical information, which limits their applications in optically controlled neuromorphic computing. Summary of the Invention
[0003] In view of the above problems, the present invention overcomes at least one deficiency and provides a self-driven photoelectric synaptic device and a preparation method thereof.
[0004] A self-driven photoelectric synaptic device includes a substrate, a first metal electrode layer and a second metal electrode layer formed on the upper surface of the substrate, and further includes a WS 2 layer (tungsten disulfide layer) and a graphene layer. One end of the graphene layer is connected to the first metal electrode layer, and the other end is disposed on the substrate. One end of the WS 2 layer is connected to the second metal electrode layer, and the other end is stacked above the graphene layer.
[0005] In the device of the present application, the WS 2 layer and the graphene layer form a Schottky junction (vertical stacking structure), and a strong built-in electric field is formed by using the difference in their work functions to achieve efficient carrier separation under zero bias voltage. Self-driven photoelectric detection can be realized under zero bias voltage, solving the high energy consumption problem of traditional photodetectors; at the same time, due to the PPC (positive photoconductivity) effect of the WS 2 layer, the device can simulate biological synaptic plasticity under positive bias voltage, providing a new solution for the fields of photoelectric detection and neuromorphic computing.
[0006] In one embodiment of the present invention, the first metal electrode layer is a drain electrode, and the second metal electrode layer is a source electrode.
[0007] In one embodiment of the present invention, the materials of the first metal electrode layer and the second metal electrode layer are nickel.
[0008] Nickel is a metal with a low work function, which can form an ohmic contact between the WS 2 layer and the second metal electrode.
[0009] In one embodiment of the present invention, the thickness of the first metal electrode layer is 30 nm to 70 nm, and the thickness of the second metal electrode layer is 30 nm to 70 nm.
[0010] In one embodiment of the present invention, the WS2 The thickness of the layer is 1 nm to 50 nm, and the thickness of the graphene layer is 1 nm to 50 nm.
[0011] In one embodiment of the present invention, the substrate is SiO 2 / Si substrate, the substrate includes an Si layer and an SiO layer located on the upper surface of the Si layer. 2 layer.
[0012] The present application also discloses a preparation method of a self-driven optoelectronic synaptic device, including the following steps: S1, using the mechanical exfoliation method to exfoliate WS 2 and graphene crystals onto the PDMS film respectively, and a WS layer and a graphene layer are formed on the PDMS film; 2 layer and graphene layer; S2, using photolithography to form a first metal electrode layer and a second metal electrode layer on the SiO 2 / Si substrate; S3, using a transfer platform to attach a part of the PDMS film with the graphene layer obtained in step S1 to the substrate and another part to one end of the first metal electrode layer, and adjusting the temperature of the transfer platform to the first set temperature and maintaining the first set time. After peeling off the PDMS film, one end of the graphene layer is connected to the first metal electrode layer, and the other end is disposed on the substrate; S4, using a transfer platform to attach a part of the PDMS film with the WS 2 layer obtained in step S1 to the first metal electrode layer and another part to the graphene layer, and adjusting the temperature of the transfer platform to the second set temperature and maintaining the second set time. After peeling off the PDMS film, one end of the graphene layer is connected to the second metal electrode layer, and the other end is stacked above the graphene layer. The graphene layer and the WS 2 layer form a WS 2 -graphene heterojunction; S5, performing an annealing operation to obtain a self-driven optoelectronic synaptic device.
[0013] In one embodiment of the present invention, the first set temperature is 50°C to 70°C, and the first set time is 2 minutes to 5 minutes; the second set temperature is 50°C to 70°C, and the second set time is 2 minutes to 5 minutes; the annealing operation is annealing at 130°C to 170°C for 10 minutes to 20 minutes in a vacuum environment.
[0014] Preferably, the first set temperature is 60°C, the first set time is 3 minutes; the second set temperature is 60°C, the second set time is 3 minutes; the annealing operation is annealing at 150°C for 15 minutes in a vacuum environment.
[0015] In one embodiment of the present invention, the materials of the first metal electrode layer and the second metal electrode layer are nickel; the thickness of the first metal electrode layer is 30 nm to 70 nm, and the thickness of the second metal electrode layer is 30 nm to 70 nm.
[0016] Preferably, the thickness of the first metal electrode layer is 50 nm, and the thickness of the second metal electrode layer is 50 nm.
[0017] In one embodiment of the present invention, the WS 2 layer has a thickness of 1 nm to 50 nm, and the graphene layer has a thickness of 1 nm to 50 nm.
[0018] In one embodiment of the present invention, in step S1, the mechanical exfoliation method includes the following steps: A1. Place the bulk crystal on the Scotch tape, fold the Scotch tape several times so that the bulk crystal on the Scotch tape is torn into thinner crystal flakes, and then lay the Scotch tape with the crystal flakes flat on the glass slide and fix it; A2. Place a PDMS film with a thickness of about 1.5 mm on another glass slide; A3. Stick the blue film on the Scotch tape with the crystal flakes obtained in step A1, then tear off the blue film, and then stick the blue film on the PDMS film in step A2, and gently press the blue film to make it closely fit with the PDMS film; A4. Lift the blue film to separate it from the PMDS film, leaving a small amount of crystal flakes on the PDMS film. Observe the material color through an optical microscope and select the PDMS film with crystal flakes of appropriate thickness (1 nm to 50 nm).
[0019] When the bulk crystal is WS 2 , the WS 2 layer formed on the PDMS film can be obtained by the above mechanical exfoliation method; when the bulk crystal is a graphene crystal, the graphene layer formed on the PDMS film can be obtained by the above mechanical exfoliation method.
[0020] In one embodiment of the present invention, in step S2, the specific steps of forming the first metal electrode layer and the second metal electrode layer include: B1. Immerse the substrate in acetone solution, isopropanol solution, and deionized water respectively. After each immersion, perform ultrasonic cleaning for 5 minutes, and then dry it with high-purity nitrogen; B2. Uniformly coat the photoresist on the substrate processed in step B1 to form a photoresist layer; B3. Perform pre-baking treatment on the structure obtained in step B2 to remove the solvent in the photoresist; B4. Use a maskless lithography machine to expose the structure processed in step B3, and write a preset electrode pattern into the photoresist layer; B5. Immerse the structure processed in step B4 in a developer for development to form a desired photoresist electrode pattern; B6. Bake the structure with the photoresist electrode pattern; B7. Perform metal evaporation on the baked structure to form a preliminary metal layer on the substrate; B8. Use a stripping solution to dissolve and remove the photoresist electrode pattern and strip the excess metal film in the preliminary metal layer, and form a first metal electrode layer and a second metal layer on the substrate that are consistent with the structure of the photoresist electrode pattern.
[0021] The beneficial effects of the present invention are: By using a metal with a low work function as the electrode layer material in this application, based on the Schottky junction (vertical stacking structure) formed by the WS 2 layer and the graphene layer, a new optoelectronic device that exhibits different functions under different bias voltages is prepared. This device can achieve self-driven photodetection at zero bias voltage, solving the high energy consumption problem of traditional photodetectors; at the same time, due to the PPC (positive photoconductivity) effect of the WS 2 layer, the device can simulate biological synaptic plasticity under positive bias voltage, providing a new solution for the fields of photodetection and neuromorphic computing. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 is a schematic structural diagram of a self-driven optoelectronic synaptic device according to an embodiment of the present invention; Figure 2 is an optical image of the driven optoelectronic synaptic device; Figure 3 is the I-V curve of the driven optoelectronic synaptic device under different optical power densities, where λ = 635 nm; Figure 4 is the optical response I-T curve of the driven optoelectronic synaptic device under different optical power densities at VDS = 0 V; Figure 5 is the optical response I-T curve of the driven optoelectronic synaptic device triggered by double optical pulses at 635 nm; Figure 6 is the graph of the change relationship of the PPF index of the driven optoelectronic synaptic device with the pulse interval.
[0023] 1. Graphene layer; 2. WS 2 layer; 31. First metal electrode layer; 32. Second metal electrode layer; 10. Substrate; 11. Si layer; 12. SiO 2 layer. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. Usually, the components of the embodiments of this application described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.
[0025] As Figure 1 and Figure 2 shown, a self-driven optoelectronic synaptic device includes a substrate 10, a first metal electrode layer 31 and a second metal electrode layer 32 formed on the upper surface of the substrate, and further includes a WS 2 layer 2 (tungsten disulfide layer) and a graphene layer 1. One end of the graphene layer 1 is connected to the first metal electrode layer 31, and the other end is disposed on the substrate 10. One end of the WS 2 layer 2 is connected to the second metal electrode layer 32, and the other end is stacked above the graphene layer 1.
[0026] In this embodiment, the first metal electrode layer 31 is a drain electrode, and the second metal electrode layer 32 is a source electrode.
[0027] In this embodiment, the materials of the first metal electrode layer 31 and the second metal electrode layer 32 are nickel. Nickel is a metal with a low work function, which can form an ohmic contact between the WS 2 layer and the second metal electrode.
[0028] In this embodiment, the thickness of the first metal electrode layer 31 is 50 nm, and the thickness of the second metal electrode layer 32 is 50 nm.
[0029] In this embodiment, the thickness of the WS 2 layer 2 is 1 nm to 50 nm, and the thickness of the graphene layer 1 is 1 nm to 50 nm.
[0030] As Figure 1 shown, in this embodiment, the substrate 10 is a SiO 2 / Si substrate, and the substrate includes an Si layer 11 and an SiO 2 layer 12 located on the upper surface of the Si layer.
[0031] This application uses a metal with a low work function as the electrode layer material, and based on the Schottky junction (vertical stacking structure) formed by the WS 2 layer and the graphene layer, a new optoelectronic device that exhibits different functions under different bias voltages is prepared. This device can achieve self-driven photoelectric detection at zero bias voltage, solving the high energy consumption problem of traditional photodetectors; at the same time, due to the WS 2Due to the PPC (positive photoconductivity) effect of the layer, the device can simulate biological synaptic plasticity under a positive bias voltage, providing a new solution for the fields of photodetection and neuromorphic computing.
[0032] This embodiment also discloses a preparation method of a self-driven optoelectronic synaptic device, including the following steps: S1, Using the mechanical exfoliation method to exfoliate WS 2 and graphene crystals onto the PDMS film respectively, forming WS 2 layers and graphene layers on the PDMS film; S2, Using photolithography to form a first metal electrode layer and a second metal electrode layer on the SiO 2 / Si substrate; S3, Using a transfer platform to attach a part of the PDMS film with a graphene layer obtained in step S1 to the substrate and another part to one end of the first metal electrode layer, and adjusting the temperature of the transfer platform to the first set temperature and maintaining it for the first set time. After peeling off the PDMS film, one end of the graphene layer is connected to the first metal electrode layer, and the other end is disposed on the substrate; S4, Using a transfer platform to attach a part of the PDMS film with a WS 2 layer obtained in step S1 to the first metal electrode layer and another part to the graphene layer, and adjusting the temperature of the transfer platform to the second set temperature and maintaining it for the second set time. After peeling off the PDMS film, one end of the graphene layer is connected to the second metal electrode layer, and the other end is stacked above the graphene layer. The graphene layer and the WS 2 layer form a WS 2 -graphene heterojunction; S5, Performing an annealing operation to obtain a self-driven optoelectronic synaptic device.
[0033] In actual application, the first set temperature is 50°C - 70°C, the first set time is 2 minutes - 5 minutes; the second set temperature is 50°C - 70°C, the second set time is 2 minutes - 5 minutes; the annealing operation is annealing at 130°C - 170°C for 10 minutes - 20 minutes in a vacuum environment. In this embodiment, the first set temperature is 60°C, the first set time is 3 minutes; the second set temperature is 60°C, the second set time is 3 minutes; the annealing operation is annealing at 150°C for 15 minutes in a vacuum environment.
[0034] In this embodiment, in step S1, the mechanical exfoliation method includes the following steps: A1, Placing the bulk crystal on the Scotch tape, folding the Scotch tape several times so that the bulk crystal on the Scotch tape is torn into thinner crystal flakes, and then laying the Scotch tape with the crystal flakes flat on the glass slide and fixing it; A2. Place a PDMS film with a thickness of about 1.5 mm on another glass slide; A3. Stick the blue film on the Scotch tape with the crystal flake obtained in step A1, then tear off the blue film, and then stick the blue film on the PDMS film in step A2, and gently press the blue film to make it closely fit with the PDMS film; A4. Lift the blue film to separate it from the PMDS film, leaving a small amount of crystal flakes on the PDMS film. Observe the material color through an optical microscope and select the PDMS film with crystal flakes of appropriate thickness (1 nm - 50 nm).
[0035] When the bulk crystal is WS 2 layers formed on the PDMS film can be obtained by the above mechanical exfoliation method; when the bulk crystal is a graphene crystal, graphene layers formed on the PDMS film can be obtained by the above mechanical exfoliation method. 2 In this embodiment, in step S2, the specific steps of forming the first metal electrode layer and the second metal electrode layer include:
[0036] B1. Immerse the substrate in acetone solution, isopropyl alcohol solution, and deionized water respectively, and perform ultrasonic cleaning for 5 minutes each time after immersion to remove surface impurities and organic substances, ensure the cleanliness of the substrate surface, and then dry it with high-purity nitrogen; B2. Uniformly coat the photoresist on the substrate processed in step B1 to form a photoresist layer; B3. Perform pre-baking treatment on the structure obtained in step B2 to remove the solvent in the photoresist; B4. Use a maskless lithography machine to expose the structure processed in step B3, and write the preset electrode pattern through the photoresist layer; B5. Put the structure processed in step B4 into the developer for development to form the required photoresist electrode pattern; B6. Perform hardening treatment on the structure with the photoresist electrode pattern; B7. Perform metal evaporation treatment on the structure after hardening treatment to form a preliminary metal layer on the substrate; B8. Use a stripping solution (such as acetone, N-methylpyrrolidone, etc.) to dissolve and remove the photoresist electrode pattern and strip the excess metal film in the preliminary metal layer to form a first metal electrode layer and a second metal layer on the substrate with the same structure as the photoresist electrode pattern.
[0037] Figures 3 to 6 The advantages of the self-driven optoelectronic synaptic device in this embodiment are referred to Figures 3 to 6 It can be seen that: 1. It has high-performance optoelectronic response: Figure 3The I-V curve of photocurrent of the self-driven optoelectronic synaptic device in this embodiment under different 635 nm laser powers (the abscissa is voltage and the ordinate is current). Excellent optoelectronic performance of the device under bias voltage can be extracted from the data in the figure: the responsivity R is as high as 2.49 A / W, the external quantum efficiency EQE reaches an astonishing 488.8%, and the detectivity D* is 5.1×10 11 Joens。
[0038] 2. With self-driven optoelectronic response: Figure 4 For the device under 0 V bias voltage, the photocurrent response I-T curve (the abscissa is time and the ordinate is current) of the self-driven synaptic device in this embodiment under different optical powers. The optical performance parameters can be calculated to reach a maximum of R = 0.36 A / W, EQE = 71.3%, and D* = 1.1×10 12 Joens, showing excellent self-powered performance.
[0039] This self-driven characteristic enables the device to have broad application prospects in low-power and self-powered systems.
[0040] 3. With biomimetic synaptic plasticity simulation: Under positive bias voltage, the device shows the ability to simulate the plasticity of biological synapses. Figure 5 The photocurrent response I-T curve triggered by double optical pulses of the device in this embodiment at 635 nm (the abscissa is time and the ordinate is current), which is a paired-pulse facilitation (PPF) test for evaluating the synaptic performance of the device. Each pulse width is 2 s and the interval time is 2 s; Figure 6 The relationship between the PPF index and the pulse interval (the abscissa is time; the ordinate is Paired-Pulse Facilitation Index). It is found from the test that as the optical pulse time interval Δt increases, the PPF coefficient gradually decreases, indicating that the memory effect of the device will weaken with the extension of the training interval. This dynamic characteristic highly coincides with the learning and forgetting mechanism of biological synapses, successfully realizing the biomimetic simulation of the neural double-pulse facilitation behavior. This means that the device can learn and remember input signals like biological synapses, providing a basis for neuromorphic computing.
[0041] The above are only the preferred embodiments of the present invention, and thus do not limit the patent protection scope of the present invention. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention, directly or indirectly applied in other related technical fields, shall be included in the protection scope of the present invention by the same token.
Claims
1. A self-driven optoelectronic synaptic device, characterized in that: It includes a substrate, a first metal electrode layer and a second metal electrode layer formed on the upper surface of the substrate, and also includes a WS2 layer and a graphene layer, one end of the graphene layer is connected to the first metal electrode layer, and the other end is arranged on the substrate, one end of the WS2 layer is connected to the second metal electrode layer, and the other end is stacked on the graphene layer.
2. The self-driven optoelectronic synaptic device according to claim 1, characterized in that: The first metal electrode layer is a drain electrode, and the second metal electrode layer is a source electrode.
3. The self-driven optoelectronic synaptic device according to claim 1, characterized in that: The materials of the first metal electrode layer and the second metal electrode layer are nickel.
4. The self-driven optoelectronic synaptic device according to claim 3, characterized in that: The thickness of the first metal electrode layer is 30 nm to 70 nm, and the thickness of the second metal electrode layer is 30 nm to 70 nm.
5. The self-driven optoelectronic synaptic device according to claim 1, characterized in that: The thickness of the WS2 layer is 1 nm to 50 nm, and the thickness of the graphene layer is 1 nm to 50 nm.
6. The self-driven optoelectronic synaptic device according to claim 1, characterized in that: The substrate is a SiO2 / Si substrate, and the substrate comprises a Si layer and a SiO2 layer located on the upper surface of the Si layer.
7. A method for preparing a self-driven optoelectronic synaptic device, characterized in that: The steps include: S1, using a mechanical exfoliation method to peel off WS2 and graphene crystals onto the PDMS film, respectively, to form a WS2 layer and a graphene layer on the PDMS film; S2, forming a first metal electrode layer and a second metal electrode layer on the SiO2 / Si substrate by photolithography; S3, using a transfer platform to attach a portion of the PDMS film with the graphene layer obtained in step S1 to the substrate and the other portion to one end of the first metal electrode layer, and adjusting the temperature of the transfer platform to a first set temperature and maintaining it for a first set time, after the PDMS film is peeled off, one end of the graphene layer is connected to the first metal electrode layer, and the other end is set on the substrate; S4, using a transfer platform to attach a portion of the PDMS film with the WS2 layer obtained in step S1 to the first metal electrode layer, and the other portion to the graphene layer, and adjusting the temperature of the transfer platform to a second set temperature and maintaining the second set time, after peeling off the PDMS film, one end of the graphene layer is connected to the second metal electrode layer, and the other end is stacked on the graphene layer, and the graphene layer and the WS2 layer form a WS2-graphene heterojunction; S5, performing annealing operation to obtain a self-driven optoelectronic synaptic device.
8. The method for preparing a self-driven optoelectronic synaptic device according to claim 7, characterized in that: The first set temperature is 50°C~70°C, and the first set time is 2 minutes~5 minutes; the second set temperature is 50°C~70°C, and the second set time is 2 minutes~5 minutes; the annealing operation is annealing at 130°C~170°C in a vacuum environment for 10 minutes~20 minutes.
9. The method for preparing a self-driven optoelectronic synaptic device according to claim 7, characterized in that: The materials of the first metal electrode layer and the second metal electrode layer are nickel; the thickness of the first metal electrode layer is 30nm-70nm, and the thickness of the second metal electrode layer is 30nm-70nm.
10. The method for preparing a self-driven optoelectronic synaptic device according to claim 7, characterized in that: The thickness of the WS2 layer is 1 nm to 50 nm, and the thickness of the graphene layer is 1 nm to 50 nm.