A neuromorphic device with light shielding effect and its preparation method

Abstract

This invention belongs to the field of semiconductor technology and discloses a neuromorphic device with a light-shielding effect and a method for its preparation. This invention breaks with the traditional light-quenching methods of neuromorphic devices by introducing an electrolyte layer, significantly improving the device's photostability and helping it maintain normal operation under strong light without interference. The invention is highly applicable because it utilizes the exciton-quenching effect of the electrolyte layer, achieving the same effect on photogenerated excitons generated by most organic semiconductor layers. The process is simple and compatible with existing neuromorphic device fabrication techniques.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to a neuromorphic device with light shielding effect and a preparation method thereof. Background Art

[0002] Traditional chips use the von Neumann architecture, in which computing and storage functions are separated. The CPU reads data from memory, performs calculations, and then writes the results back to memory. Memory access speeds cannot keep up with the CPU's data processing speed, leading to an increasingly serious memory wall problem. This is why neuromorphic chips have emerged. By drawing on the brain's information processing and storage methods, neuromorphic chips feature integrated computing and storage, and are highly parallel. Consequently, neuromorphic chips offer significant advantages in terms of computing power, energy consumption, and efficiency for intelligent computing.

[0003] The basic unit of a neuromorphic chip is a neuromorphic device. By simulating the transmission, processing, and storage of information through biological synapses, neuromorphic devices can achieve integrated storage and computing capabilities. Currently, neuromorphic devices can be divided into three-terminal devices and two-terminal devices. Three-terminal devices mainly include field-effect transistors and ferroelectric transistors, while two-terminal devices include phase-change memory and memristors. Organic field-effect transistors have become a research focus due to their simple fabrication process, high compatibility of device materials, integration with flexible devices, and excellent electrical performance.

[0004] Due to their non-volatile nature, organic field-effect transistor (OFET) memories can simulate various synaptic behaviors, such as EPSCs, IPSCs, PPFs, and LTP / LTD, in artificial neuromorphic research. Currently, OFETs utilize charge trapping to store information. However, in their applications, they are inevitably exposed to light. Due to the photosensitivity of organic semiconductors, the resulting photoelectric response can reduce the transistor's current switching ratio or shift the transistor's threshold voltage, leading to photoelectric interference and even device failure. The photogenerated exciton processes in organic semiconductors include (i) light absorption, (ii) exciton diffusion, (iii) exciton dissociation, and (iv) free carrier transport or exciton destruction. To suppress the OFET's photoelectric response, the current approach is to synthesize organic semiconductors with large band gaps and low trap densities to inhibit the exciton dissociation process. However, these approaches suffer from poor applicability and limited light suppression. Therefore, the study of OFETs with light-shielding properties is of great significance.

[0005] In view of this, the present invention provides a neuromorphic device with light shielding effect and a preparation method thereof.

[0006] Through the above analysis, the problems and defects of the existing technology are as follows:

[0007] In the application of organic field-effect transistors, they are inevitably exposed to light environments. Due to the photosensitivity of organic semiconductors, the photoelectric response of the transistor will reduce the current switching ratio of the transistor or cause the threshold voltage of the transistor to shift, which will lead to photoelectric interference or even device failure. Summary of the Invention

[0008] In response to the problems existing in the prior art, the present invention provides a neuromorphic device with light shielding effect and a preparation method thereof.

[0009] The present invention is implemented as follows: a neuromorphic device with a light shielding effect includes a gate, a gate insulating layer, a hole capture layer, an organic semiconductor layer, a source electrode, a drain electrode, and an electrolyte layer.

[0010] Furthermore, the electrolyte layer is located directly above the organic semiconductor layer and between the source and drain electrodes, or directly below the organic semiconductor layer and directly above the hole capture layer, or directly above the gate insulating layer and directly below the hole capture layer.

[0011] Furthermore, the hole capture layer material is alq3 (8-hydroxyquinoline aluminum), and the electrolyte material is chitosan.

[0012] Furthermore, the electrolyte layer has exciton quenching capability.

[0013] Furthermore, the organic semiconductor material is pentacene.

[0014] Furthermore, the electrode material is metallic copper, the insulating layer material is SiO2 with a thickness of 50 nm, and the gate material is Si.

[0015] Furthermore, except for the electrolyte layer, all other layers of the device are prepared by vacuum evaporation coating.

[0016] Furthermore, the electrolyte layer is prepared by a drop coating method.

[0017] A method for preparing a neuromorphic device with light shielding effect comprises the following steps:

[0018] Step 1: ultrasonically clean the Si / SiO2 substrate and dry it;

[0019] Step 2: vacuum evaporating a hole capture layer, an organic semiconductor layer, and an electrode in sequence;

[0020] Step 3: drop-coating chitosan solution as the electrolyte layer;

[0021] Step 4: Conduct electrical property tests and light shielding effect tests.

[0022] Furthermore, the size of the cleaned Si / SiO2 substrate is 2cm×2cm.

[0023] Furthermore, the vacuum evaporation hole capture layer material is AlQ3, the film thickness is 50nm, and the evaporation rate is The evaporation temperature was 240°C and the vacuum degree was controlled at 5×10 -4 Pa below, the substrate is rotated during the evaporation process.

[0024] Furthermore, the vacuum-evaporated organic semiconductor layer is Pentacene, the film thickness is 30 nm, and the evaporation rate is The evaporation temperature should not exceed 195℃ and the vacuum degree should be controlled at 5×10 -4 Pa below, the substrate is rotated during the evaporation process.

[0025] Furthermore, the vacuum evaporation electrode material is Cu, the electrode thickness is 50nm, and the evaporation rate is The evaporation current was 140A and the vacuum degree was controlled at 5×10 -4 Pa, the substrate is not rotated during the evaporation process.

[0026] Furthermore, the drop coating material is a chitosan solution, the chitosan solution is ultrasonicated for 3 hours, and then annealed at 110° C. for 10 minutes after drop coating.

[0027] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0028] First, in view of the technical problems existing in the above-mentioned prior art and the difficulty of solving these problems, this paper closely combines the technical solutions to be protected by the present invention and the results and data during the research and development process, and analyzes in detail and in depth how the technical solutions of the present invention solve the technical problems and some creative technical effects brought about by solving the problems. The specific description is as follows:

[0029] Due to the photosensitivity of their organic semiconductor layers, the current applications of organic field-effect transistors (OFETs) are inevitably limited to low-light environments. To address this technical issue, the main approach currently employed is to synthesize semiconductor layers with wide bandgap and low trap density to mitigate the effects of light on the electrical performance of OFETs. However, this approach suffers from poor applicability and light-shielding effectiveness, and it struggles to simultaneously achieve the advantages of high carrier mobility and high photostability. The present invention, however, utilizes the exciton-quenching effect of a chitosan electrolyte layer by drop-coating a neuromorphic device, thereby imparting excellent light-shielding effectiveness while retaining the device's inherent high carrier mobility and high on / off ratio. Test data show that the electrical performance of the device with the chitosan electrolyte layer under strong light is comparable to that of the device without the chitosan electrolyte layer under dark conditions. This demonstrates that the present invention, by drop-coating the chitosan electrolyte layer, enables neuromorphic devices to maintain excellent light-shielding performance without compromising their inherent transistor performance.

[0030] Second, considering the technical solution as a whole or from the perspective of the product, the technical effects and advantages of the technical solution to be protected by the present invention are described in detail as follows:

[0031] The neuromorphic device fabricated by the present invention, by adding a chitosan electrolyte layer, can achieve a light-shielding effect directly through the exciton quenching effect of the electrolyte layer. This light-shielding effect is superior to that of conventional light-suppressing transistor devices, and therefore the present invention is expected to be applicable under various lighting conditions without limitation. Furthermore, the technical solution of the present invention is highly applicable, as the light-shielding effect achieved through the exciton quenching effect of the chitosan electrolyte layer is applicable to the vast majority of organic field-effect transistor devices. Finally, the technical solution proposed by the present invention is simple to manufacture and compatible with existing neuromorphic device fabrication processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a flow chart of a neuromorphic device with light shielding effect and a method for preparing the same provided by an embodiment of the present invention.

[0033] Figure 2-4 Schematic diagrams of three structures of neuromorphic devices with light shielding effect provided by embodiments of the present invention. Figure 2 In the structure, the electrolyte layer is located above the organic semiconductor and between the source and drain electrodes; Figure 3 In the structure, the electrolyte layer is located below the organic semiconductor; Figure 4 In the structure, the electrolyte layer is located below the charge trapping layer.

[0034] Figure 54 is a transfer characteristic curve diagram of a neuromorphic device with light shielding effect provided by an embodiment of the present invention.

[0035] Figure 6 3 is a graph showing the ratio of currents of a neuromorphic device with light shielding effect under three conditions provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] In order to enable those skilled in the art to fully understand how to implement the present invention, this section provides an explanatory embodiment that expands on the technical solutions of the claims.

[0038] The present invention provides a neuromorphic device with a light shielding effect, which comprises a gate, a gate insulating layer, a hole capture layer, an organic semiconductor layer, a source electrode, a drain electrode, and an electrolyte layer.

[0039] The electrolyte layer provided by the present invention is located directly above the organic semiconductor layer and between the source and drain electrodes, or directly below the organic semiconductor layer and directly above the hole capture layer, or directly above the gate insulating layer and directly below the hole capture layer.

[0040] The hole capture layer material provided by the present invention is alq3 (8-hydroxyquinoline aluminum), and the electrolyte material is chitosan.

[0041] The electrolyte layer provided by the present invention has the ability to quench excitons.

[0042] The organic semiconductor material provided by the present invention is pentacene.

[0043] The electrode material provided by the present invention is metallic copper, the insulating layer material is SiO2 with a thickness of 50nm, and the gate material is Si.

[0044] Except for the electrolyte layer, all other layers of the device provided by the present invention are prepared by vacuum evaporation coating.

[0045] The electrolyte layer provided by the present invention is prepared by a drop coating method.

[0046] like Figure 1 As shown, the present invention provides a method for preparing a neuromorphic device with light shielding effect, comprising the following steps:

[0047] S101, ultrasonically cleaning the Si / SiO2 substrate and drying it;

[0048] S102, vacuum evaporating a hole capture layer, an organic semiconductor layer, and an electrode in sequence;

[0049] S103, drop-coating chitosan solution as the electrolyte layer;

[0050] S104, conducting electrical property test and light shielding effect test.

[0051] The size of the cleaning Si / SiO2 substrate provided by the present invention is 2cm×2cm.

[0052] The vacuum evaporation hole capture layer material provided by the present invention is alq3, the film thickness is 50nm, and the evaporation rate is The evaporation temperature was 240°C and the vacuum degree was controlled at 5×10 -4 Pa below, the substrate is rotated during the evaporation process.

[0053] The vacuum-evaporated organic semiconductor layer provided by the present invention is Pentacene, the film thickness is 30nm, and the evaporation rate is The evaporation temperature should not exceed 195℃ and the vacuum degree should be controlled at 5×10 -4 Pa below, the substrate is rotated during the evaporation process.

[0054] The vacuum evaporation electrode material provided by the present invention is Cu, the electrode thickness is 50nm, and the evaporation rate is The evaporation current was 140A and the vacuum degree was controlled at 5×10 -4 Pa, the substrate is not rotated during the evaporation process.

[0055] The drop coating material provided by the present invention is a chitosan solution, the chitosan solution is ultrasonicated for 3 hours, and then annealed at a temperature of 110° C. for 10 minutes after drop coating.

[0056] See also Figure 2-4 As shown, the present invention provides a neuromorphic device with a light-shielding effect. The device structure includes a gate electrode, a gate insulating layer covering the gate electrode, a hole-trapping layer formed on the gate insulating layer, an organic semiconductor layer formed on the hole-trapping layer, and source / drain electrodes and an electrolyte layer formed on both sides of the surface region of the organic semiconductor layer. Specifically, the electrolyte layer is located directly above the organic semiconductor layer and between the source / drain electrodes, or directly below the organic semiconductor layer and directly above the hole-trapping layer, or directly above the gate insulating layer and directly below the hole-trapping layer.

[0057] In this example, a 50nm heavily doped silicon wafer is used as the gate electrode and gate insulation layer; an organometallic compound AlQ3 is used as a hole-trapping layer with a thickness of 50nm; a 30nm thick layer of pentacene is evaporated on the hole-trapping layer to serve as a p-type organic semiconductor layer; metallic copper is then evaporated on both sides of the p-type semiconductor conductive channel as source and drain electrodes; and a chitosan electrolyte is drop-coated in the conductive channel between the source and drain electrodes as a light-quenching material.

[0058] The chitosan electrolyte is prepared by using acetic acid as a solvent and preparing a solution from chitosan. In actual preparation, the laboratory room temperature is maintained at about 25°C.

[0059] The specific steps for preparing the neuromorphic device in this example are as follows:

[0060] Step (1): preparing a chitosan polymer solution with a concentration of 0.02 g / ml, and ultrasonicating the solution in an acetic acid solvent for 3 h to uniformly disperse the chitosan polymer solution;

[0061] Step (2): Cut a heavily doped silicon wafer with 50nm of silicon dioxide on the surface into 2cm×2cm pieces. Ultrasonic cleaning is performed with decon solution and deionized water for 30min each at a frequency of 100kHz. The liquid on the surface of the wafer is then blown away with high-purity nitrogen to ensure a clean surface. The wafer is then dried in an oven at 80°C for 30min.

[0062] Step (3): placing the substrate dried in step (2) in a UV ozone machine for 10 minutes;

[0063] Step (4): vacuum evaporation is performed on the substrate surface treated in step (3) using a vacuum evaporation source. The hole capture layer is made of AlQ3 with a film thickness of 50 nm and a deposition rate of The evaporation temperature was 240°C and the vacuum degree was controlled at 5×10 -4 Pa below, the substrate is rotated during the evaporation process; the p-type organic semiconductor layer is vacuum evaporated on the hole capture layer, the organic semiconductor layer is pentacene, the film thickness is 30nm, and the evaporation rate is The evaporation temperature should not exceed 195℃ and the vacuum degree should be controlled at 5×10 -4 Pa below, the substrate is rotated during the evaporation process; the metal electrode Cu is continuously evaporated on both sides of the pentacene surface, using a vacuum evaporation source, the electrode thickness is 50nm, and the evaporation rate is The evaporation current was 140A and the vacuum degree was controlled at 5×10 -4 Pa, the substrate is not rotated during the evaporation process.

[0064] Step (5): After the evaporation in step (4) is completed, chitosan electrolyte solution is drop-coated on the surface of the pentacene film between the metal electrodes and annealed at a temperature of 110° C. for 10 minutes.

[0065] Step (6): After the above device preparation steps are completed, its electrical properties are characterized by Keithley 2636B semiconductor analyzer, and the transfer curve drawn by data processing is as follows Figure 5 shown.

[0066] Figure 5 is the device's V DS = -5V transfer characteristic curve, as the gate voltage increases, the current of the device gradually increases, from 0V to 10 -11 A increases to 10 when -30V -7 A, on / off ratio about 10 4 , indicating that the device has good p-type transistor characteristics.

[0067] Figure 6 The main purpose is to verify the light quenching effect of the device. Initially, when no electrolyte layer was added to the device under dark conditions, by scanning the hysteresis curve of the device, we found that the ratio of the output current before hysteresis to the output current after hysteresis was about 1:1. Afterwards, when the device was exposed to light, the hysteresis curve was scanned again, and it was found that the ratio of the output current before hysteresis to the output current after hysteresis had changed significantly. When the reading voltage was -15V, the ratio of the hysteresis current before and after was 22.23. When the reading voltage was -20V, the ratio of the hysteresis current before and after was 29.34. When the reading voltage was -25V, the ratio of the hysteresis current before and after was 17.38. Comparing before and after illumination, it was found that the current of the device had changed significantly. Finally, when we added an electrolyte layer to the device, such as Figure 6 As shown in the figure, even under light conditions, the before-after ratio of the device's hysteresis current is still around 1:1.

[0068] All test results show that the present invention uses chitosan electrolyte as a dielectric drop-coated on the surface of the organic semiconductor channel, which can quench light, improve the photostability of the neuromorphic device, and avoid the device operating under light conditions. The electrical performance of the device is disturbed by photogenerated excitons, which affects the normal working state of the device, thereby making the device have good anti-light interference function.

[0069] In order to prove the creativity and technical value of the technical solution of the present invention, this section provides application examples of the claimed technical solution on specific products or related technologies.

[0070] The excellent light shielding effect demonstrated by the test results of the embodiments of the present invention is expected to enable the application of this technical solution in a variety of products.

[0071] 1. Transparent and wearable electronic devices: These products are often exposed to natural light and therefore require high light stability.

[0072] 2. Biochemical sensors. Biochemical sensors are easily affected by noise signals in light environments, and their application scenarios are often limited to low-light environments.

[0073] 3. OLED driving circuit: The driving circuit based on organic field effect transistor is easily affected by the light interference of OLED, which reduces the reliability of the circuit.

[0074] The technical solution of the present invention is expected to be applied to the above-mentioned products to help them achieve light shielding effects.

[0075] The embodiments of the present invention have achieved some positive results during the development or use process, and indeed have great advantages over the existing technology. The following content describes them in conjunction with data, charts, etc. from the experimental process.

[0076] like Figure 6 As shown, without the addition of an electrolyte layer, under dark conditions, the output current hysteresis ratio was 1:1. After the device was exposed to light, the ratio of the output current hysteresis changed significantly at all gate voltages. At 15V, the ratio became 22.23, at a reading voltage of -20V, the ratio became 29.34, and at a reading voltage of -25V, the ratio became 17.38. Comparisons before and after illumination demonstrate that the device's electrical performance undergoes a significant change under the influence of light. Subsequently, by adding an electrolyte layer to the device and placing it under the same illumination environment, the measured output current hysteresis ratio was 1:1, demonstrating that the device's electrical performance was unaffected by light, indicating that the neuromorphic device with the chitosan electrolyte layer has excellent light shielding effects.

[0077] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A neuromorphic device with light shielding effect, characterized in that: The neuromorphic device comprises a gate, a gate insulating layer, a hole capture layer, an organic semiconductor layer, a source electrode, a drain electrode, and an electrolyte layer; the electrolyte layer is located directly above the organic semiconductor layer and between the source and drain electrodes, or directly below the organic semiconductor layer and directly above the hole capture layer, or directly above the gate insulating layer and directly below the hole capture layer; The hole capture layer material is AlQ3 (8-hydroxyquinoline aluminum), the electrolyte layer material is chitosan; and the electrolyte layer has exciton quenching capability.

2. The neuromorphic device with light shielding effect according to claim 1, wherein: The material of the organic semiconductor layer is pentacene.

3. The neuromorphic device with light shielding effect according to claim 1, wherein: The source and drain electrode material is metallic copper, the insulating layer material is SiO2 with a thickness of 50 nm, and the gate material is Si.

4. The neuromorphic device with light shielding effect according to claim 1, wherein: Except for the electrolyte layer, all other layers of the device are prepared by vacuum evaporation coating; the electrolyte layer is prepared by drop coating.

5. A method for preparing a neuromorphic device with light shielding effect according to any one of claims 1 to 4, characterized in that: The method for preparing the neuromorphic device with light shielding effect comprises the following steps: Step 1: ultrasonically clean the Si / SiO2 substrate and dry it; Step 2: vacuum evaporating a hole capture layer, an organic semiconductor layer, and an electrode in sequence; Step 3: drop-coating chitosan solution as the electrolyte layer; Step 4: Conduct electrical property tests and light shielding effect tests.

6. The method for preparing a neuromorphic device with light shielding effect according to claim 5, wherein: The size of the cleaned Si / SiO2 substrate is 2cm×2cm.

7. The method for preparing a neuromorphic device with light shielding effect according to claim 5, wherein: The vacuum evaporation hole capture layer material is AlQ3, the film thickness is 50nm, the evaporation rate is 0.1Å / s, the evaporation temperature is 240°C, and the vacuum degree is controlled at 5×10 -4 Pa below, the substrate is rotated during the evaporation process; the vacuum evaporated organic semiconductor layer material is Pentacene, the film thickness is 30nm, the evaporation rate is 0.2Å / s, the evaporation temperature cannot exceed 195°C, and the vacuum degree is controlled at 5×10 -4 Pa below, the substrate is rotated during the evaporation process.

8. The method for preparing a neuromorphic device with light shielding effect according to claim 5, wherein: The vacuum deposition electrode material is Cu, the electrode thickness is 50nm, the deposition rate is 0.5Å / s, the deposition current is 140A, and the vacuum degree is controlled at 5×10 -4 Pa, the substrate is not rotated during the evaporation process.

9. The method for preparing a neuromorphic device with light shielding effect according to claim 5, wherein: The chitosan solution was ultrasonicated for 3 h and then annealed at 110° C. for 10 min after drop coating.

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