In-situ differential optoelectronic synapse device and its storage-computing integrated method

Abstract

The application belongs to the technical field of cross technology of semiconductor optoelectronic devices, multiferroic materials and neuromorphic computing, and specifically discloses an in-situ differential optoelectronic synapse device and a memory-computing integrated method thereof; the method is: grounding the first electrode and the second electrode, applying a voltage on the bottom electrode, changing the polarization direction of the ferroelectric domain of the bismuth ferrite film layer, taking the polarization direction of the ferroelectric domain as a weight sign in a neural weight, and realizing the setting of a nonvolatile synapse weight; removing or reducing the voltage on the bottom electrode, irradiating a light spot above the bismuth ferrite film layer, adjusting the light spot position, reading the differential current between the first electrode and the second electrode as a weight value in the neural weight, and realizing the reading operation. The application realizes memory-computing integration.

Description

Technical Field

[0001] This application belongs to the interdisciplinary fields of semiconductor optoelectronic devices, multiferroic materials and neuromorphic computing, and more specifically, relates to an in-situ differential optoelectronic synaptic device and its in-memory computing method. Background Technology

[0002] With the rapid development of artificial intelligence and machine vision, neuromorphic vision systems that integrate perception (photosensing) and computation (synaptic weighting) have become a research hotspot. In the hardware implementation of convolutional neural networks (CNNs) and spiking neural networks (SNNs), differential signal reading and positive / negative weight mapping are the core functions for achieving high-precision image recognition. However, existing optoelectronic in-memory computing technologies face the dual challenges of structural complexity and implementation difficulties in realizing this core function.

[0003] However, the current mainstream technical solutions suffer from the following irreconcilable contradictions: The contradiction between unipolar devices and the demands of bipolar computing: Traditional opto-synaptic devices (such as photodiodes / transistors based on silicon, perovskite, or two-dimensional materials) are essentially unipolar devices. Under illumination, they typically generate only a single-polarity photocurrent signal (usually positive). However, the convolutional kernel operations of neural networks require a complete linear spatial mapping, needing both positive weights representing excitation and negative weights representing inhibition. Existing technologies cannot generate positive and negative signals in situ within a single device, necessitating the introduction of extremely complex external solutions.

[0004] The high hardware overhead bottleneck in implementing differential functionality: To simulate negative weights and implement differential operations, existing technologies have had to employ cumbersome physical solutions. The most common approach is to use a dual-device pair structure, which uses two identical devices to store the positive and negative weights respectively. The effective weight is obtained by calculating the current difference between the two devices through complex external readout circuitry. This approach not only doubles the hardware area but also introduces severe device matching problems. Due to variations in manufacturing processes, it is difficult for two physically separate devices to maintain completely identical electrical characteristics, leading to a significant decrease in computational accuracy. Furthermore, the bias circuitry and operational amplifier circuitry used to maintain this differential pair are extremely complex, greatly increasing the system's static power consumption and design complexity.

[0005] The lack of multiphysics manipulation capabilities: Existing optoelectronic device materials (such as silicon and organic semiconductors) typically possess only a single photoelectric conversion function. They lack the ability to coordinate responses to multiple physical fields, including light, electricity, magnetism, and force. This means that existing devices struggle to simultaneously control the "sign" (positive or negative) and "value" (magnitude) of weights through simple physical mechanisms (such as a single voltage pulse or a change in the position of a light spot). To achieve similar functionality, complex heterojunction structures or additional control electrodes are often required, leading to cumbersome device fabrication processes and hindering large-scale integration.

[0006] In summary, existing opto-synaptic devices, limited by the single functional properties and physical mechanisms of materials, cannot directly output positive and negative differential signals in simple physical structures. Current technologies have to rely on paired, complex device structures and expensive peripheral circuits to synthesize differential signals. This not only contradicts the original intention of in-memory computing to pursue high density and low power consumption, but also becomes a key bottleneck restricting the development of neuromorphic computing hardware. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this application is to provide an in-situ differential opto-synaptic device and its in-memory computing method. This aims to solve the problem that existing opto-synaptic devices are limited by the properties of unipolar materials, and must rely on differential pair structures and complex peripheral circuits to achieve positive and negative weight calculations, making it difficult to achieve both high-density integration and low-power, high-efficiency computing.

[0008] The first aspect of this application relates to an in-situ differential photoelectric synapse device, comprising: a substrate, a bottom electrode and a bismuth ferrite thin film layer disposed sequentially from bottom to top, a first electrode and a second electrode symmetrically distributed about the bottom electrode, a photomask and a differential readout circuit; The bottom electrode is used to apply a voltage signal, generating a polarization potential difference between the bottom electrode and the first electrode and the second electrode, thereby controlling the polarization direction of the ferroelectric domains in the bismuth ferrite thin film. The bismuth ferrite thin film layer is used to generate the polarization of ferroelectric domains under the action of polarization voltage difference, and the polarization direction of the ferroelectric domains is used as the weight symbol in the neural weight to realize the setting of non-volatile synaptic weight; at the same time, it is used to generate the bulk photovoltaic effect under the illumination of the incident light spot, changing the first potential difference between the bottom electrode and the first electrode, and the second potential difference between the bottom electrode and the second electrode. The photomask is used to adjust the position of the light spot on the surface of the bismuth ferrite thin film layer, thereby adjusting the magnitude of the first potential difference and the second potential difference, and thus adjusting the magnitude of the output current of the first electrode and the second electrode; The differential readout circuit is used to calculate the differential current by subtracting the output currents of the first and second electrodes, which is then used as the weight value in the neural weights to realize the readout operation.

[0009] In some implementations, the neural weights are: ; in, , is the weight symbol, determined by the polarization direction of the ferroelectric domains, and is not volatilely stored; The position of the light spot is determined by a function and can be adjusted in real time. This is a normalization function for the light spot position. It is 0 when the light spot is between the first and second electrodes, and decreases as the spot gets closer to the first electrode. The closer the value is to -1, the closer it is to the second electrode. The closer the value is to +1.

[0010] In some embodiments, when the first and second electrodes are grounded and a positive voltage pulse is applied to the bottom electrode, the ferropolarization direction of the bismuth ferrite thin film is upward and the weight sign is negative; when the first and second electrodes are grounded and a negative voltage pulse is applied to the bottom electrode, the ferropolarization direction of the bismuth ferrite thin film is downward and the weight sign is positive.

[0011] In some implementations, when the polarization direction of the ferroelectric domains in the bismuth ferrite thin film is upward and the weight sign is negative, if the light spot moves from the first electrode to the position between the first and second electrodes, the light spot is closer to the first electrode, and the efficiency of the first electrode in collecting electrons is greater than that of the second electrode. The unit of the weight is negative, and the weight gradually decreases, tending to 0, which represents the neuron changing from an inhibited state to a resting state. If the light spot moves from the second electrode to the position between the first and second electrodes, the light spot is closer to the second electrode, and the efficiency of the second electrode in collecting electrons is greater than that of the first electrode. The unit of the weight value is positive, and the weight gradually increases, tending to 0, which represents the neuron changing from an excited state to a resting state. When the polarization direction of the ferroelectric domains in the bismuth ferrite thin film is downward and the weight sign is positive, if the light spot moves from the first electrode to the position between the first and second electrodes, the light spot is closer to the first electrode, and the efficiency of the first electrode in collecting holes is greater than that of the second electrode. The weight value is positive, and the weight gradually decreases, tending to 0, which is manifested as the neuron changing from an excited state to a resting state. If the light spot moves from the second electrode to the position between the first and second electrodes, the light spot is closer to the second electrode, and the efficiency of the second electrode in collecting holes is greater than that of the first electrode. The weight value is negative, and the weight gradually increases, tending to 0, which is manifested as the neuron changing from an inhibited state to a resting state.

[0012] In some embodiments, the bismuth ferrite thin film layer is or doped and modified , or ;in, , .

[0013] In some embodiments, the first electrode and the second electrode are selected from at least one of ITO, FTO, graphene, and AZO, and the dimensions of a single first electrode and the second electrode are [missing information]. The thickness is 30nm~150nm; the electrode spacing between the first and second electrodes is 10. ~50 .

[0014] In some embodiments, the substrate is quartz glass, sapphire glass, , , It is one of the following: a flexible polymer and a thickness of 0.3 mm to 1.0 mm.

[0015] The second aspect of this application relates to a memory computing method for an in-situ differential opto-synaptic device, comprising the following steps: The first and second electrodes are grounded, and a positive or negative voltage is applied to the bottom electrode to change the polarization direction of the ferroelectric domains in the bismuth ferrite film. The polarization direction of the ferroelectric domains is used as the weight symbol in the neural weight to realize the setting of non-volatile synaptic weights. By removing or reducing the voltage on the bottom electrode, a light spot is used to irradiate the bismuth ferrite film layer. By adjusting the position of the light spot, the differential current between the first electrode and the second electrode is read and used as the weight value in the neural weight to realize the reading operation.

[0016] In some implementations, the neural weights are: ; in, , is the weight symbol, determined by the polarization direction of the ferroelectric domains, and is not volatilely stored; The position of the light spot is determined by a function and can be adjusted in real time. This is a normalization function for the light spot position. It is 0 when the light spot is between the first and second electrodes, and decreases as the spot gets closer to the first electrode. The closer the value is to -1, the closer it is to the second electrode. The closer the value is to +1.

[0017] In some implementations, when the polarization direction of the ferroelectric domains in the bismuth ferrite thin film is upward and the weight sign is negative, if the light spot moves from the first electrode to the position between the first and second electrodes, the light spot is closer to the first electrode, and the efficiency of the first electrode in collecting electrons is greater than that of the second electrode. The unit of the weight is negative, and the weight gradually decreases, tending to 0, which represents the neuron changing from an inhibited state to a resting state. If the light spot moves from the second electrode to the position between the first and second electrodes, the light spot is closer to the second electrode, and the efficiency of the second electrode in collecting electrons is greater than that of the first electrode. The unit of the weight value is positive, and the weight gradually increases, tending to 0, which represents the neuron changing from an excited state to a resting state. When the polarization direction of the ferroelectric domains in the bismuth ferrite thin film is downward and the weight sign is positive, if the light spot moves from the first electrode to the position between the first and second electrodes, the light spot is closer to the first electrode, and the efficiency of the first electrode in collecting holes is greater than that of the second electrode. The weight value is positive, and the weight gradually decreases, tending to 0, which is manifested as the neuron changing from an excited state to a resting state. If the light spot moves from the second electrode to the position between the first and second electrodes, the light spot is closer to the second electrode, and the efficiency of the second electrode in collecting holes is greater than that of the first electrode. The weight value is negative, and the weight gradually increases, tending to 0, which is manifested as the neuron changing from an inhibited state to a resting state.

[0018] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: This application provides an in-situ differential photoelectric synapse device that breaks through the limitation of traditional photoelectric devices that can only generate unidirectional (positive polarity) signals. Through a unique symmetrical electrode structure and differential readout mechanism, the device can generate differential current signals with positive and negative polarities in situ according to the spatial position of the incident light spot. The device has a simple structure.

[0019] This application provides an in-situ differential opto-synaptic device, in which the polarization of ferroelectric domains enables weighted non-volatile storage, and the photoresponse enables computation, truly realizing the integration of storage and computation with low power consumption.

[0020] This application provides an in-situ differential photoelectric synapse device, which can reproduce the excitation-inhibition function of the biological nervous system by adjusting the flipping direction of the ferroelectric domains at the physical level, providing an ideal basic hardware for building highly biomimetic neural networks. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the in-situ differential photoelectric synapse device provided in the embodiments of this application.

[0022] Figure 2(a) is a schematic diagram of the photogenerated carrier transport mechanism in the polarization direction of the actual three-terminal BFO ​​device provided in the embodiment of this application.

[0023] Figure 2(b) is a schematic diagram of the photogenerated carrier transport mechanism of the actual three-terminal BFO ​​device with the polarization direction downward provided in the embodiment of this application.

[0024] Figure 3 This is a schematic diagram of the differential circuit structure provided in the embodiments of this application.

[0025] Figure 4 This is a flowchart of the in-memory computing workflow provided in the embodiments of this application. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0027] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. In this application, the symbol " / " indicates that the related objects are in an "or" relationship, for example, A / B means A or B.

[0028] In this application, the terms “first” and “second” are used to distinguish different objects, rather than to describe a specific order of objects.

[0029] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0030] In the description of the embodiments in this application, unless otherwise stated, "multiple" means two or more.

[0031] The embodiments of this application are described below with reference to the accompanying drawings.

[0032] like Figure 1 As shown, this application provides an in-situ differential photoelectric synapse device, comprising: Substrate, selected from quartz glass, sapphire glass, (STO) (LAO) It contains at least one of a flexible polymer and has a thickness of 0.3 mm to 1.0 mm; Bottom electrode: disposed on the substrate, selected from... (SRO) At least one of (LNO), Pt and ITO is used as a back gate common modulation electrode (BE) to apply a positive or negative voltage thereon to regulate the polarization direction of the ferroelectric domains of the bismuth ferrite thin film. Bismuth ferrite thin film layer: deposited on the bottom electrode, with a thickness of 100nm~500nm, chemical formula is or doped and modified , , ,in, , This is used to set the non-volatile synaptic weights when the first electrode E1 and the second electrode E2 are grounded, based on the change in the positive or negative voltage applied to the bottom electrode, the polarization direction of its ferroelectric domains changes, thereby changing the direction of the built-in electric field. The polarization direction of its ferroelectric domains is used as the weight sign. Specifically, when a positive voltage pulse is applied to the bottom electrode, the polarization direction of its ferroelectric domains is upward, and the weight sign is negative; when a negative voltage pulse is applied to the bottom electrode, the polarization direction of its ferroelectric domains is downward, and the weight sign is positive. It is also used to generate a bulk photovoltaic effect when incident light shines on its surface, changing the first potential difference between the bottom electrode and the first electrode, and the second potential difference between the bottom electrode and the second electrode; The specific mechanism is implemented as follows: When the device is in the polarization-up (P↑) state, a built-in electric field (E↓) is formed inside the ferroelectric thin film, pointing from the top electrode to the bottom electrode. Driven by this electric field, photogenerated electron-hole pairs undergo efficient separation: holes drift along the electric field direction to the bottom electrode, while electrons are transported against the electric field direction to the top electrode. When the light spot is positioned near the E1 electrode region, the concentration of photogenerated carriers below E1 is significantly higher than that in the E2 region, forming a lateral concentration gradient. This gradient drives electrons to diffuse laterally in the top electrode plane, resulting in a greater electron current amplitude collected by the E1 electrode than that collected by the E2 electrode. According to the definition of the galvanometer reference direction (inflow electrode is positive), the electron outflow electrode exhibits a negative current; therefore, |I E1| > |I E2|, and both are negative. Similarly, when the light spot is close to E2, the current amplitude of the E2 electrode is greater than that of the E1 electrode, and both are negative.

[0033] When the device is in polarization downward (P In the ) state, the spontaneous polarization vector inside the ferroelectric thin film reverses, causing the direction of the built-in electric field to point from the bottom electrode to the top electrode (E). Driven by this reverse built-in electric field, the separation and transport paths of photogenerated carriers are reversed: carrier separation: photogenerated electrons drift along the direction of the electric field to the bottom electrode (BE), while photogenerated holes are transported against the direction of the electric field and accumulate at the interface of the top electrodes (E1 and E2). When the light spot is positioned near the E1 electrode region, the concentration of photogenerated holes below E1 is significantly higher than that in the E2 region, forming a lateral concentration gradient. This gradient drives the lateral diffusion of holes in the top electrode plane, making the hole current collected by the E1 electrode significantly higher than that of the E2 electrode. According to the definition of the galvanometer reference direction (inflow electrode is positive), hole inflow into the electrode (or equivalent electron outflow) is a positive current. Therefore, IE1 and IE2 are both positive, and IE1 > IE2. Similarly, when the light spot is close to E2, the current amplitude of the E2 electrode is greater than that of the E1 electrode, and both are positive.

[0034] A photomask is a patterned metal mask structure based on a transparent substrate. It utilizes laser direct writing technology to fabricate micron-scale transparent windows (i.e., areas without metal coverage) on a thick metal film. This metal layer acts as a light-shielding layer, defining the effective irradiation area of ​​the incident light spot. The position of the photomask is adjusted by mechanically adjusting its position, thereby adjusting the magnitude of the first and second potential differences, and consequently, the output current of the first and second electrodes. Two parallel elongated electrodes (first electrode E1 and second electrode E2): formed on the upper surface of a bismuth ferrite thin film layer, the electrode material is selected from at least one of ITO, FTO, graphene and AZO (aluminum-doped zinc oxide), and the size of a single electrode is... The spacing between adjacent electrodes is 10. ~50 The electrode thickness is 30nm~150nm; The first electrode E1 and the second electrode E2 are symmetrically or quasi-symmetrically distributed about the bottom electrode BE; and the first electrode E1 and the second electrode E2 are usually grounded or suspended to form a potential difference with the bottom electrode. The differential readout circuit is used to amplify the output current of the first electrode E1 and the second electrode E2, calculate the differential current, and realize the readout operation.

[0035] Mechanism introduction: The bismuth ferrite thin film layer is used to implement the weight sign bit and weight value bit separation storage mechanism. In this application, the neural weight is decomposed into two parts: weight sign bit and weight value bit, which are stored and regulated by different physical mechanisms, as shown in Table 1. Table 1

[0036] The physical mechanism of bismuth ferrite thin film layer as weighted sign bit storage: the weights of traditional optoelectronic synaptic devices rely on real-time light intensity modulation, and the weight information is lost after power is turned off; while this application utilizes the potential energy curve of BFO crystal to form a double potential well structure, with polarization upward ( ) and polarization downward ( The two potential wells are two stable lowest energy states with an energy barrier (usually >1 eV) between them. The thermal perturbation energy at room temperature is only ~0.026 eV, which cannot overcome the barrier. Therefore, the polarization state can be maintained stably for a long time without the need for external energy. Accelerated aging tests estimate that the maintenance time is >10 years.

[0037] Among them, ferropolarization enables the pre-setting of non-volatile weights: This application utilizes the ferroelectric polarization direction of BFO ( and Preset device weighting sign: When the polarization of ferroelectric domains is upward The weight sign is negative; when the polarization of the ferroelectric domains is downward... The weight sign is positive, the polarization state can be maintained for more than 10 years, realizing true non-volatile synaptic weights, and the static storage power consumption is 0.

[0038] Bulk photovoltaic effect enhances differential signal: The bulk photovoltaic effect (BPVE) of BFO can generate a photogenerated voltage higher than the bandgap voltage (theoretically reaching the polarization field). (Carrier mean free path), compared with the traditional photovoltaic effect, BPVE does not depend on the PN junction and can generate directional photocurrent in a uniform material; in the device structure of this application, BPVE works synergistically with the transverse electric field to significantly enhance the differential current amplitude of the first electrode E1 and the second electrode E2. Neural weight mapping relationship: ; in, It is determined by the polarization direction of the ferroelectric domains and is non-volatile; The position of the light spot is determined by a function and can be adjusted in real time. The value is a normalization function for the position of the light spot. It is 0 when the light spot is in the center. The closer the light spot is to the first electrode E1, the closer its value is to -1. The closer the light spot is to the second electrode E2, the closer its value is to +1.

[0039] As shown in Figure 2(a), when the polarization direction of the ferroelectric domains in the bismuth ferrite thin film is upward and the weight sign is negative, if the light spot moves from the first electrode to the position between the first and second electrodes, the light spot is closer to the first electrode, and the efficiency of the first electrode in collecting electrons is greater than that of the second electrode. The unit of the weight is negative, and the weight gradually decreases and tends to 0, which is manifested as the neuron changing from an inhibited state to a resting state. If the light spot moves from the second electrode to the position between the first and second electrodes, the light spot is closer to the second electrode, and the efficiency of the second electrode in collecting electrons is greater than that of the first electrode. The unit of the weight value is positive, and the weight gradually increases and tends to 0, which is manifested as the neuron changing from an excited state to a resting state.

[0040] As shown in Figure 2(b), when the polarization direction of the ferroelectric domains in the bismuth ferrite thin film is downward and the weight sign is positive, if the light spot moves from the first electrode to the position between the first and second electrodes, the light spot is closer to the first electrode, and the efficiency of the first electrode in collecting holes is greater than that of the second electrode in collecting holes. The weight value is positive, and the weight gradually decreases and tends to 0, which is manifested as the neuron changing from an excited state to a resting state. If the light spot moves from the second electrode to the position between the first and second electrodes, the light spot is closer to the second electrode, and the efficiency of the second electrode in collecting holes is greater than that of the first electrode in collecting holes. The weight value is negative, and the weight gradually increases and tends to 0, which is manifested as the neuron changing from an inhibited state to a resting state.

[0041] like Figure 3 As shown, the differential readout circuit in the in-situ differential photosynaptic device provided in this application is used to generate weighted numerical bits using a differential structure: Spatial light modulation principle: When the incident light spot moves along the direction of the first electrode E1 to the first electrode E2 on the surface of the BFO functional layer, the charge carriers are shifted towards the first electrode E1 or the second electrode E2 under the action of the built-in electric field (polarization field + external bias field), and the collection ratio of photogenerated charge carriers changes: light spot position - weight value mapping. Differential current signal: ; in, The device response coefficient (related to BFO thickness and doping concentration) The polarization symbol for ferroelectric polarization is (+1 or -1, non-volatile). The position function of the light spot is (-1 to +1, continuously adjustable). The incident light power; like Figure 3 As shown; the differential readout circuit includes: Dual-channel transimpedance amplifier (TIA): converts the photocurrent of the first electrode E1 and the second electrode E2 into voltage signals respectively; Differential subtractor: Calculates the difference between two voltages and outputs a signed analog differential voltage; Optional operational transconductance amplifier (OTA): converts differential voltage back into current signal to drive subsequent neuromorphic circuitry; The output signal satisfies: Where G is the adjustment coefficient; Channel resistance; This refers to the output voltage. In summary, the polarization write and read operations are shown in Table 2; Table 2

[0042] The symbol / value separation modulation demonstration is shown in Figure 2(a) and Figure 2(b). Taking the weighted symbol and value separation normalization control of a single device as an example, and setting a threshold for the absolute value of the output current to be greater than 1nA, as shown in Table 3. Table 3

[0043] like Figure 4 As shown, this application provides an in-situ differential opto-synaptic device in-memory computing method, including the following steps: The first electrode E1 and the second electrode E2 are grounded. When a positive or negative voltage pulse is applied to the bottom electrode, the polarization direction of the ferroelectric domains in the bismuth ferrite thin film is changed. The polarization direction of the ferroelectric domains is used as the weight symbol to realize the setting of non-volatile synaptic weights. By removing or reducing the voltage on the bottom electrode, a light spot is used to irradiate the bismuth ferrite thin film layer. By adjusting the position of the light spot, the differential current between the first electrode E1 and the second electrode E1 is read to achieve the reading operation.

[0044] On the other hand, this application provides a method for fabricating an in-situ differential photoelectric synapse device, specifically including the following steps: Step S1: Substrate preparation A 0.5 mm thick quartz glass substrate was selected and ultrasonically cleaned with acetone, isopropanol, and deionized water for 10 minutes each. It was then dried with nitrogen and treated with oxygen plasma for 5 minutes to enhance the surface hydrophilicity. A 20 nm Pt metal layer was deposited by magnetron sputtering as the bottom electrode BE. Step S2: Functional layer deposition A 300 nm thick substrate was grown using pulsed laser deposition (PLD). (BFO) thin film; deposition conditions: laser wavelength 248 nm, energy density 2 J / L. The frequency is 5Hz, the substrate temperature is 650℃, and the oxygen pressure is 10Pa. Further annealing: Anneal at 650℃ for 30 minutes to improve crystallization quality; Step S3: Electrode Patterning The rotation thickness is 1.5. Positive photoresist (AZ5214), UV exposure (365nm, 150mJ / The first and second electrode regions are patterned by development. Step S4: Electrode deposition A 50nm thick ITO electrode was deposited by magnetron sputtering, and two side-by-side electrodes were formed by lift-off process; the resistivity was reduced by annealing at 400℃ for 30 minutes. Step S5: Etching the bottom electrode BE window pattern The rotation thickness is 1.5. Positive photoresist (AZ5214), UV exposure (365nm, 150mJ / The bottom electrode region is patterned by development; then, a 300nm thick layer is etched into this region using ICP etching. (BFO) exposes the underlying Pt metal layer bottom electrode, completing the device fabrication.

[0045] In summary, this application has the following advantages compared with the prior art: This application provides an in-situ differential photoelectric synapse device that breaks through the limitation of traditional photoelectric devices that can only generate unidirectional (positive polarity) signals. Through a unique symmetrical electrode structure and differential readout mechanism, the device can generate differential current signals with positive and negative polarities in situ according to the spatial position of the incident light spot. The device has a simple structure.

[0046] This application provides an in-situ differential opto-synaptic device, in which the polarization of ferroelectric domains enables weighted non-volatile storage, and the photoresponse enables computation, truly realizing the integration of storage and computation with low power consumption.

[0047] This application provides an in-situ differential photoelectric synapse device, which can reproduce the excitation-inhibition function of the biological nervous system by adjusting the flipping direction of the ferroelectric domains at the physical level, providing an ideal basic hardware for building highly biomimetic neural networks.

[0048] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0049] Furthermore, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0050] Furthermore, the mathematical concepts mentioned in the embodiments of this application, such as symmetry, equality, parallelism, and perpendicularity, are all limitations relative to the current technological level, rather than absolute and strict mathematical definitions. Slight deviations are allowed, and approximations of symmetry, equality, parallelism, and perpendicularity are all acceptable.

[0051] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. An in-situ differential photoelectric synapse device, characterized in that, It includes a substrate, a bottom electrode and a bismuth ferrite thin film layer arranged sequentially from bottom to top, a first electrode and a second electrode symmetrically distributed about the bottom electrode, a mask and a differential readout circuit; The bottom electrode is used to apply a voltage signal, generating a polarization potential difference between the bottom electrode and the first electrode and the second electrode, thereby controlling the polarization direction of the ferroelectric domains in the bismuth ferrite thin film. The bismuth ferrite thin film layer is used to generate the polarization of ferroelectric domains under the action of polarization voltage difference, and the polarization direction of the ferroelectric domains is used as the weight symbol in the neural weight to realize the setting of non-volatile synaptic weight; at the same time, it is used to generate the bulk photovoltaic effect under the illumination of the incident light spot, changing the first potential difference between the bottom electrode and the first electrode, and the second potential difference between the bottom electrode and the second electrode. The photomask is used to adjust the position of the light spot on the surface of the bismuth ferrite thin film layer, thereby adjusting the magnitude of the first potential difference and the second potential difference, and thus adjusting the magnitude of the output current of the first electrode and the second electrode; The differential readout circuit is used to calculate the differential current by subtracting the output currents of the first electrode and the second electrode, and use it as the weight value in the neural weight to realize the readout operation. The neural weights are: ; in, , is the weight symbol, determined by the polarization direction of the ferroelectric domains, and is not volatilely stored; The position of the light spot is determined by a function and can be adjusted in real time. This is a normalization function for the light spot position. It is 0 when the light spot is between the first and second electrodes, and decreases as the spot gets closer to the first electrode. The closer the value is to -1, the closer it is to the second electrode. The closer the value is to +1.

2. The in-situ differential photosynapse device according to claim 1, characterized in that, When the first and second electrodes are grounded and a positive voltage pulse is applied to the bottom electrode, the ferropolarization direction of the bismuth ferrite thin film is upward, and the weight sign is negative; when the first and second electrodes are grounded and a negative voltage pulse is applied to the bottom electrode, the ferropolarization direction of the bismuth ferrite thin film is downward, and the weight sign is positive.

3. The in-situ differential photosynapse device according to claim 1, characterized in that, When the polarization direction of the ferroelectric domains in the bismuth ferrite thin film is upward and the weight sign is negative, if the light spot moves from the first electrode to the position between the first and second electrodes, the light spot is closer to the first electrode, and the efficiency of the first electrode in collecting electrons is greater than that of the second electrode. The unit of the weight is negative, and the weight gradually decreases, tending to 0, which is manifested as the neuron changing from an inhibited state to a resting state. If the light spot moves from the second electrode to the position between the first and second electrodes, the light spot is closer to the second electrode, and the efficiency of the second electrode in collecting electrons is greater than that of the first electrode. The unit of the weight is positive, and the weight gradually increases, tending to 0, which is manifested as the neuron changing from an excited state to a resting state. When the polarization direction of the ferroelectric domains in the bismuth ferrite thin film is downward and the weight sign is positive, if the light spot moves from the first electrode to the position between the first and second electrodes, the light spot is closer to the first electrode, and the efficiency of the first electrode in collecting holes is greater than that of the second electrode. The weight value is positive, and the weight gradually decreases, tending to 0, which is manifested as the neuron changing from an excited state to a resting state. If the light spot moves from the second electrode to the position between the first and second electrodes, the light spot is closer to the second electrode, and the efficiency of the second electrode in collecting holes is greater than that of the first electrode. The weight value is negative, and the weight gradually increases, tending to 0, which is manifested as the neuron changing from an inhibited state to a resting state.

4. The in-situ differential photosynapse device according to claim 1, characterized in that, The bismuth ferrite thin film layer is or doped and modified , or ;in, , .

5. The in-situ differential photosynapse device according to claim 1 or 4, characterized in that, The first and second electrodes are selected from at least one of ITO, FTO, graphene, and AZO, and the dimensions of a single first and second electrode are as follows: The thickness is 30nm~150nm; the electrode spacing between the first and second electrodes is 10. ~50 .

6. The in-situ differential photosynapse device according to claim 1, characterized in that, The substrate is quartz glass, sapphire glass, , , It is one of the following: a flexible polymer and a thickness of 0.3 mm to 1.0 mm.

7. A memory computing method based on the in-situ differential photoelectric synaptic device according to any one of claims 1 to 6, characterized in that, Includes the following steps: The first and second electrodes are grounded, and a positive or negative voltage is applied to the bottom electrode to change the polarization direction of the ferroelectric domains in the bismuth ferrite film. The polarization direction of the ferroelectric domains is used as the weight symbol in the neural weight to realize the setting of non-volatile synaptic weights. By removing or reducing the voltage of the bottom electrode, a light spot is used to irradiate the bismuth ferrite thin film layer. By adjusting the position of the light spot, the differential current between the first electrode and the second electrode is read and used as the weight value in the neural weight to realize the reading operation.

8. The in-memory computing method according to claim 7, characterized in that, The neural weights are: ； in, , is the weight symbol, determined by the polarization direction of the ferroelectric domains, and is not volatilely stored; The position of the light spot is determined by a function and can be adjusted in real time. This is a normalization function for the light spot position. It is 0 when the light spot is between the first and second electrodes, and decreases as the spot gets closer to the first electrode. The closer the value is to -1, the closer it is to the second electrode. The closer the value is to +1.

9. The in-memory computing method according to claim 7 or 8, characterized in that, When the polarization direction of the ferroelectric domains in the bismuth ferrite thin film is upward and the weight sign is negative, if the light spot moves from the first electrode to the position between the first and second electrodes, the light spot is closer to the first electrode, and the efficiency of the first electrode in collecting electrons is greater than that of the second electrode. The unit of the weight is negative, and the weight gradually decreases, tending to 0, which is manifested as the neuron changing from an inhibited state to a resting state. If the light spot moves from the second electrode to the position between the first and second electrodes, the light spot is closer to the second electrode, and the efficiency of the second electrode in collecting electrons is greater than that of the first electrode. The unit of the weight is positive, and the weight gradually increases, tending to 0, which is manifested as the neuron changing from an excited state to a resting state. When the polarization direction of the ferroelectric domains in the bismuth ferrite thin film is downward and the weight sign is positive, if the light spot moves from the first electrode to the position between the first and second electrodes, the light spot is closer to the first electrode, and the efficiency of the first electrode in collecting holes is greater than that of the second electrode. The weight value is positive, and the weight gradually decreases, tending to 0, which is manifested as the neuron changing from an excited state to a resting state. If the light spot moves from the second electrode to the position between the first and second electrodes, the light spot is closer to the second electrode, and the efficiency of the second electrode in collecting holes is greater than that of the first electrode. The weight value is negative, and the weight gradually increases, tending to 0, which is manifested as the neuron changing from an inhibited state to a resting state.

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