A gallium oxide photosynaptic device doped with chlorophyll and its fabrication method

Abstract

This invention discloses a gallium oxide photoelectric synapse device doped with chlorophyll and its fabrication method. The method includes: cleaning a conductive substrate; mixing a solution containing a zinc chlorophyll derivative with a solution containing a polymer, a complexing agent, and a gallium source under an inert atmosphere to obtain a composite precursor solution; spin-coating the solution onto the substrate to form a wet film; obtaining a composite gallium oxide thin film through a two-stage programmed temperature rise heat treatment; and finally depositing a top electrode to obtain the device. This invention utilizes a polymer-complexing agent system to stabilize the gallium source and uses a low-temperature process to fix chlorophyll in situ, avoiding the destruction of biological activity by high temperatures. The resulting device has a sandwich structure, combining the high electron mobility of gallium oxide and the broad-spectrum absorption characteristics of chlorophyll. It can simulate the short-term and long-term plasticity of biological synapses at low power consumption and has a sensitive response to both ultraviolet and visible light, making it suitable for artificial vision systems and neuromorphic computing.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device technology, specifically relating to a gallium oxide photosynaptic device doped with chlorophyll and its preparation method. Background Technology

[0002] As Moore's Law approaches its limits, neuromorphic computing has become crucial for breaking through traditional computing architectures. Visual interaction is a vital part of neuromorphic computing. Constructing artificial vision systems is a critical area of ​​research for visual interaction. Biological vision systems can be viewed as sophisticated heterogeneous integrated systems of "photoreception and processing": retinal photoreceptor cells act like biological pixel arrays, converting light signals into neural electrical signals; the optic nerve performs preliminary feature extraction (such as edge enhancement), similar to simulated preprocessing; and the information is ultimately used for efficient parallel computation and pattern recognition in the brain's visual cortex. Photosynapses are an important component of this system and form the hardware foundation for novel artificial vision systems.

[0003] Gallium oxide (Ga2O3), as an ultrawide bandgap semiconductor (~4.9 eV), possesses deep ultraviolet light response characteristics and precisely tunable photoinduced charge carriers, enabling efficient simulation of the temporal plasticity of biological synapses. This makes it an ideal choice for realizing low-power, highly stable optoelectronic neuromorphic devices. However, its bandgap limits its sensing to ultraviolet light, significantly restricting its application in constructing artificial vision systems. Chlorophyll, as a core bio-light-harvesting agent, boasts advantages such as efficient absorption of visible light (especially in the red / blue bands), self-assembly characteristics of its molecular structure, and natural compatibility with flexible / biological environments. Doping chlorophyll into gallium oxide achieves a fusion of these advantages and functional upgrades. Chlorophyll successfully broadens the photoresponse of gallium oxide from the ultraviolet to the visible light region, greatly improving the device's light energy utilization efficiency. The light energy absorbed by chlorophyll can be effectively transferred to the gallium oxide matrix, exciting and modulating charge carriers, thereby precisely simulating the photoplastic behavior of biological synapses. This "bio-inorganic" hybrid system opens up a unique and highly promising technological route for developing a new generation of flexible, biocompatible, and low-power biomimetic optoelectronic devices and neuromorphic computing systems.

[0004] Currently, gallium oxide thin film growth mainly relies on epitaxial technologies such as MOCVD, MBE, and magnetron sputtering. These processes are complex, costly, and difficult to achieve flexible integration and biocompatible doping. Solution methods (such as sol-gel methods) are low-temperature, low-cost alternatives that can achieve large-area fabrication, but their doping types are limited, making it difficult to introduce novel functional molecules to expand optoelectronic synergistic properties.

[0005] Basic gallium oxide photosynapses are based on gallium oxide grown by magnetron sputtering or CVD methods, with relatively low doping. Current gallium oxide photosynapse devices generally suffer from the following drawbacks: 1. Mainstream high-quality gallium oxide thin film growth technologies suffer from rigid limitations. Currently, industry and high-end R&D primarily rely on vapor phase epitaxy technologies such as metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). While these methods can produce single-crystal thin films with high crystal quality and excellent electrical properties, their processes typically require harsh environments with high temperatures (>800℃) and high or ultra-high vacuum. This results in extremely high equipment costs, complex processes, high energy consumption, and complete incompatibility with flexible polymer substrates.

[0006] 2. Traditional solution-based techniques suffer from a "single-function" bottleneck. To overcome the cost and flexibility challenges of vapor-phase methods, low-temperature solution methods such as sol-gel and chemical bath deposition have been explored for gallium oxide thin film fabrication. While these methods offer advantages such as simple processes, low cost, large-area film formation, and good compatibility with flexible substrates, their doping systems have long been highly limited to conventional inorganic ions such as silicon (Si) and tin (Sn), aiming only to achieve basic n-type conductivity control. This singular functionalization path cannot introduce organic or biomolecules with complex photochemical behaviors and multi-dimensional control capabilities, resulting in thin films with only simple ultraviolet photoconductive properties. It is difficult to achieve biomimetic synaptic functions with complex responses to wavelength, intensity, and timing, significantly reducing the intelligence and flexibility of the devices. Existing technological approaches generally lack biocompatibility and biomimetic synergistic design dimensions.

[0007] 3. Both vapor phase epitaxy and traditional solution methods originated and developed from the traditional inorganic semiconductor industry. Their material systems and process goals are far removed from the soft matter characteristics and efficient light energy conversion mechanisms of living systems. This makes it impossible to construct existing gallium oxide optoelectronic devices at biocompatible interfaces and under mild processing conditions, and even more difficult to simulate the highly coordinated mechanism from light perception to information preprocessing in biological visual systems.

[0008] Therefore, there is an urgent need to develop a new method for preparing gallium oxide thin films that can achieve efficient and controllable functionalization doping in solution systems. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a gallium oxide photoelectric synapse device doped with chlorophyll and its preparation method, which realizes the simulation of the synaptic learning function of the human brain, and solves the problem that the performance regulation means of gallium oxide photoelectric synapse devices are limited, making it difficult to achieve multi-dimensional fine adjustment of synaptic weights. At the same time, it solves the technical problem that gallium oxide materials only absorb ultraviolet light.

[0010] The present invention adopts the following technical solution: A method for fabricating a gallium oxide photoelectric synapse device doped with chlorophyll includes the following steps: S1. The conductive substrate is ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water, and then dried with nitrogen to obtain a pretreated conductive substrate. S2. The polymer, complexing agent and deionized water are mixed and dissolved to obtain a polymer solution. The gallium source is added to the polymer solution and stirred and filtered to obtain a Ga-polymer solution. The zinc-containing chlorophyll derivative is dissolved in a mild organic solvent to obtain a chlorophyll solution. The chlorophyll solution is added dropwise to the Ga-polymer solution under an inert gas atmosphere. After stirring and sonication, a homogeneous and stable composite precursor solution is obtained. S3. The composite precursor solution is dropped onto the surface of the pretreated conductive substrate and then spin-coated to obtain a pre-wet film. S4. The pre-placed wet film is placed in a heating device under an inert gas atmosphere for programmed temperature rise heat treatment to obtain a conductive substrate modified with a composite gallium oxide thin film. S5. A top electrode is deposited on the surface of the composite gallium oxide thin film away from the conductive substrate to obtain the chlorophyll-doped gallium oxide photoelectric synapse device.

[0011] Preferably, in step S2, the polymer is selected from one or more of polyethyleneimine, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, or polyoxyethylene-polyoxypropylene block copolymer; the complexing agent is ethylenediaminetetraacetic acid (EDTA); and the gallium source is selected from one of gallium nitrate hydrate, gallium chloride, gallium isopropoxide, or gallium acetylacetonate.

[0012] Preferably, in step S2, the zinc-containing chlorophyll derivative is selected from one of zinc-chlorophyll a, zinc-methylpyromethesin a, or (Zn-Chl)n polymer; the mild organic solvent is selected from anhydrous ethanol or dimethyl sulfoxide.

[0013] Preferably, in step S2, the inert gas atmosphere is a nitrogen atmosphere or an argon atmosphere; the stirring time is 10-60 minutes, and the ultrasonic treatment time is 5-30 minutes.

[0014] Preferably, in step S3, the spin coating speed is 1000~5000 rpm and the spin coating time is 20~60 seconds.

[0015] Preferably, in step S4, the programmed temperature rise heat treatment includes a first stage drying treatment and a second stage curing treatment; the temperature of the first stage is 60~80℃, and the holding time is 8~18 minutes; the temperature of the second stage is 140~180℃, and the holding time is 25~70 minutes.

[0016] Preferably, in step S5, the deposition of the top electrode is carried out using ion beam evaporation or thermal evaporation; the material of the top electrode is selected from one of Ag, Ti, Pt, ITO, IGZO or Au; the diameter of the top electrode is 100~300μm and the thickness is 50~150nm.

[0017] Another technical solution of the present invention is a gallium oxide photoelectric synapse device doped with chlorophyll prepared according to the method. The gallium oxide photoelectric synapse device includes a conductive substrate, a composite gallium oxide thin film and a top electrode stacked sequentially to form a sandwich structure of metal / composite gallium oxide thin film / conductive substrate. The composite gallium oxide thin film is an amorphous thin film formed by the molecular-level composite of zinc chlorophyll derivative and gallium oxide, and the zinc chlorophyll derivative is fixed in situ in the gallium oxide framework.

[0018] Preferably, the conductive substrate is a Pt / Ti / SiO2 / Si substrate or an ITO / IGZO substrate that has been ultrasonically cleaned with acetone, anhydrous ethanol and deionized water and dried with nitrogen.

[0019] Preferably, the top electrode is a separate, discrete patterned structure used to simulate the excitatory postsynaptic current behavior of biological synapses under illumination.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects: A method for fabricating gallium oxide photoelectric synaptic devices doped with chlorophyll is disclosed. This method stabilizes the gallium source using a polymer-complexing agent system and successfully overcomes the challenge of poor compatibility between inorganic semiconductor precursors and thermosensitive biomolecules through a "low-temperature blending under an inert atmosphere" strategy. Rigorous cleaning removes surface impurities, ensuring interface quality; a specific feeding sequence and inert protection prevent chlorophyll oxidative degradation and premature precipitation; spin coating ensures film uniformity; temperature-programmed conversion of the organic precursor to an inorganic gallium oxide framework at low temperatures preserves the active structure of chlorophyll; and top electrode deposition completes device fabrication. This invention avoids the carbonization of biomolecules caused by traditional high-temperature sintering, achieving true in-situ doping rather than simple physical mixing. It lays a solid technological foundation for fabricating high-performance, wide-spectral-response biomimetic devices, exhibiting high reproducibility and industrialization potential. The entire process is conducted under mild conditions, resulting in a simple process flow and significantly reduced costs. It is naturally compatible with flexible substrates, providing a new pathway for flexible optoelectronic integration.

[0021] Furthermore, by selecting polymers containing nitrogen / oxygen functional groups such as polyethyleneimine and EDTA as complexing agents, it is possible to react with Ga... 3+Stable coordination bonds are formed, effectively suppressing the rapid hydrolysis of metal ions in aqueous solution and preventing the formation of uneven hydroxide precipitation, thus obtaining a homogeneous precursor solution. This chemical stability is crucial for subsequent doping of macromolecular chlorophyll, avoiding damage to the chlorophyll structure due to local pH changes or precipitation. A diverse selection of gallium sources provides a balance between cost and reactivity. This significantly improves the storage life and film quality of the precursor solution, reduces pinhole defects, ensures accurate stoichiometry of the gallium oxide film, and enhances the electrical stability and photoelectric conversion efficiency of the device.

[0022] Furthermore, the introduction of zinc ions to replace magnesium ions at the chlorophyll center significantly enhances the thermal and photochemical stability of chlorophyll molecules, enabling them to withstand subsequent heat treatment processes without decomposition. Mild organic solvents such as anhydrous ethanol or DMSO are used, which can effectively dissolve hydrophobic chlorophyll derivatives and are miscible with aqueous Ga-polymer solutions, avoiding aggregation caused by phase separation. This allows the device to respond not only to ultraviolet light but also to efficiently absorb visible light, achieving full-spectrum sensing.

[0023] Furthermore, an inert gas atmosphere is a crucial barrier protecting chlorophyll from oxygen oxidation and deactivation, especially during the liquid mixing stage, where dissolved oxygen readily disrupts the porphyrin ring structure. Specific stirring and sonication time ranges were set to ensure uniform dispersion of chlorophyll molecules at the nanoscale within the precursor network. Ultrasonic cavitation helps break intermolecular forces, promoting the formation of a single-phase system. This directly affects the microstructure and doping uniformity of the film. Uniform dispersion means more active sites participate in the photoelectric reaction, reducing carrier recombination centers and significantly improving the device's photocurrent responsivity and the linearity of synaptic simulation.

[0024] Furthermore, spin coating is crucial for preparing ultrathin, uniform films. The spin speed determines the centrifugal force, which in turn controls the thickness of the wet film and the solvent evaporation rate. Too low a spin speed results in an excessively thick film prone to cracking, while too high a speed leads to an excessively thin film, affecting light absorption. A specific time window ensures sufficient solvent evaporation and a smooth liquid surface. This combination of parameters allows for precise control of the composite film thickness within the optimal range of tens to hundreds of nanometers, ensuring sufficient light absorption cross-section to generate strong photocurrent while maintaining low driving voltage and low power consumption. Uniform film thickness also eliminates localized electric field concentration, preventing premature breakdown of the device under high voltage and improving device yield and consistency.

[0025] Furthermore, the first stage, performed at low temperature, removes most of the physically adsorbed water and low-boiling-point solvents, preventing rapid temperature increases that could lead to film blistering or cracking. The second stage, performed at medium temperature, promotes polymer decomposition, complex dissociation, and condensation reactions, forming a well-crystallized gallium oxide framework, while strictly controlling the temperature below the chlorophyll decomposition threshold. This precise thermal management strategy is key to achieving a win-win situation of inorganic framework crystallization and organic molecule survival.

[0026] Furthermore, ion beam or thermal evaporation processes can be used to form dense, well-contact metal electrodes without damaging the underlying thermistor composite film. By selecting metals with high work function (Ag, Au) or low work function (Ti), the Schottky barrier height can be adjusted according to device design requirements, optimizing carrier collection efficiency. Limiting the thickness range ensures low-resistivity conductivity of the electrodes while avoiding material waste or excessive stress caused by excessive thickness, and also accommodates the potential application of semi-transparent electrodes in specific optical path designs. Good ohmic contact or controllable Schottky contact is a prerequisite for achieving high signal-to-noise ratio synaptic signal readout, directly determining the device's switching ratio and response speed.

[0027] A gallium oxide photoelectric synapse device doped with chlorophyll demonstrates the synergistic effect of the gallium oxide framework and in-situ immobilized chlorophyll in a composite gallium oxide thin film: gallium oxide provides a high-mobility electron transport channel and excellent ultraviolet response, while chlorophyll provides visible light trapping capability and charge trapping effects similar to biological neurotransmitters. This organic-inorganic hybrid structure forms numerous heterojunction interfaces at the microscopic level, which is beneficial for the separation of photoexcitons and long-term memory storage. The structure is compact, compatible with existing microelectronic processes, and can achieve the sensing, processing, and memory functions of external light signals with low power consumption, making it an ideal unit for building next-generation artificial vision systems.

[0028] Furthermore, Pt / Ti / SiO2 / Si substrates offer excellent flatness and thermal stability, making them suitable for high-precision mechanism studies in the laboratory; while ITO / IGZO substrates have the potential for transparency and flexibility, making them suitable for large-area array integration and wearable applications.

[0029] Furthermore, the top electrode is a separate patterned structure, which enables the independent operation of a single synaptic device, avoids crosstalk between electrodes, and improves the operational stability of the device array.

[0030] In summary, the method of this invention achieves molecular-level composite of chlorophyll and gallium oxide through a low-temperature solution method. The process is simple, low-cost, and compatible with flexible substrates. It breaks through the limitations of traditional doping, expands the photoresponse band of gallium oxide, and realizes organic-inorganic optoelectronic synergy. The device structure is rationally designed, can accurately simulate the function of biological synapses, and allows for flexible selection of materials and parameters, enabling large-scale fabrication. It provides an original solution for the next generation of optoelectronic neuromorphic devices.

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the following description of the relative embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a flowchart of the preparation method of the present invention; Figure 2 This is a schematic diagram of the device structure prepared by the method of the present invention. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0036] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0037] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0038] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0039] In this invention, unless otherwise specified, the numerical range "a~b" represents an abbreviation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" means that all real numbers between "6~22" have been listed in this document, and "6~22" is simply an abbreviation of these numerical combinations.

[0040] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0041] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0042] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0043] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0044] This invention provides a gallium oxide photoelectric synapse device doped with chlorophyll and its fabrication method. In a mild solution chemical environment, chlorophyll, which has efficient visible light capture and a specific photoelectric conversion pathway, is molecularly composited and synergistically film-formed with an inorganic gallium oxide precursor. A biomimetic photoelectric composite film is directly grown at low temperature (<250℃), successfully achieving uniform, controllable, and active doping of chlorophyll molecules in a gallium oxide matrix. The process is simple, the cost is significantly reduced, and the device's light response range is extended from the narrow ultraviolet band to the broad visible light region, greatly improving light energy utilization efficiency and accurately and efficiently simulating various short-term / long-term plastic behaviors of biological synapses.

[0045] This invention discloses a method for fabricating gallium oxide photoelectric synapses doped with chlorophyll. Employing an innovative low-temperature solution preparation method, it successfully achieves active doping and molecular-level recombination of chlorophyll in a gallium oxide matrix, resulting in a broadband, high-performance photoelectric synapse. The method includes the following steps: S1, Substrate Pretreatment The conductive substrate was ultrasonically cleaned for 15 minutes each with acetone, anhydrous ethanol, and deionized water, and then dried with nitrogen.

[0046] The conductive substrate is a conductive substrate such as Pt / Ti / SiO2 / Si or ITO / IGZO.

[0047] S2, Preparation of precursor solution S201. Preparation of polymer solution: Add 2g polyethyleneimine and 1g EDTA to 40mL of deionized water and stir until completely dissolved; The polymers include polyethyleneimine, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, and polyoxyethylene-polyoxypropylene block copolymers.

[0048] During solution preparation, the concentrations of gallium nitrate hydrate and zinc-containing chlorophyll derivatives can be adjusted to regulate the chlorophyll content and thus the device performance.

[0049] S202. Preparation of gallium source solution: Add 2g of gallium nitrate hydrate to the above-mentioned polymer solution, stir and filter to obtain a clear Ga-polymer solution; The gallium source can be gallium nitrate hydrate, gallium chloride, gallium isopropoxide, or gallium acetylacetonate.

[0050] S203. Preparation of chlorophyll solution: Dissolve a predetermined mass of zinc-containing chlorophyll derivative in a mild organic solvent such as anhydrous ethanol or dimethyl sulfoxide; Zinc-containing chlorophyll can be zinc-chlorophyll a (Zn-Chla), zinc-methylpheophorbide a (Zn-methylpheophorbide a), (Zn-Chl)n polymer, etc.

[0051] S204, Low-temperature blending: In a nitrogen or argon glove box, the chlorophyll solution is slowly added dropwise to the Ga-polymer solution, and the mixture is vigorously stirred and subjected to short-term sonication to form a homogeneous and stable dark green composite precursor solution.

[0052] S3. Spin coating: Drop the composite precursor solution onto the center of the prepared substrate and spin coat it at a speed of 1000~5000 rpm for 20~60 seconds to obtain a uniform wet film (pre-formed film) on the substrate. S4, Low-temperature heat treatment curing Immediately transfer the spin-coated wet film to a tube furnace or hot plate filled with inert gas for programmed temperature rise: First stage (drying): Heat to 60-80°C at a slow rate and hold for 8-18 minutes to gently remove most of the solvent and moisture.

[0053] Second stage (curing): Continue to slowly increase the temperature to the target curing temperature of 140~180°C and hold for 25~70 minutes. This process promotes the decomposition and cross-linking of the metal-polymer precursor, forming an amorphous gallium oxide framework, and fixing chlorophyll molecules in situ.

[0054] S5. Electrode fabrication and device completion Using ion beam evaporation or thermal evaporation, Pt or Au top electrodes with a diameter of 100~300μm and a thickness of 50~150nm are deposited on the surface of the cured composite film to form a sandwich device structure of metal / composite gallium oxide film / conductive substrate.

[0055] The top electrode is made of Ag / Ti / Pt / ITO / IGZO / Au, etc.

[0056] Please see Figure 2 A gallium oxide photoelectric synapse device doped with chlorophyll, prepared by the above method, has a sandwich structure of metal / composite gallium oxide thin film / conductive substrate.

[0057] This invention discloses a gold-doped chlorophyll-based gallium oxide opto-synaptic device that can be applied in neuromorphic computing chips and smart wearable devices.

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0059] Preparation equipment Ultrasonic cleaning machine: Model KQ-500DE, used for cleaning conductive substrates. It removes oil, impurities and particles from the substrate surface through high-frequency ultrasonic vibration. The ultrasonic power is adjustable to adapt to the cleaning needs of different substrates. Magnetic stirrer: Model 85-2, used for the preparation of polymer solutions, Ga-polymer solutions, and chlorophyll solutions, to achieve uniform mixing and dissolution of materials. It can precisely control the stirring speed and heating temperature to meet the requirements of stirring and dissolving at room temperature. Glove box: LABstarPro model, with dual nitrogen / argon atmosphere control, used for low-temperature blending of chlorophyll solution and Ga-polymer solution, isolating oxygen and moisture in the air, preventing chlorophyll oxidation and gallium source hydrolysis, and ensuring the stability of the precursor solution; Desktop spin coater: Model KW-4A, used for spin coating of composite precursor solutions. It can precisely control the spin coating speed (0~8000rpm) and spin coating time to form a pre-prepared wet film with uniform thickness and smooth surface on the conductive substrate. Tube furnace: OTF-1200X model, with controllable inert gas atmosphere, used for programmed temperature rise heat treatment of pre-prepared wet film, can accurately set multiple temperature rise curves (temperature 0~1200℃) to achieve precise control of temperature and holding time in the drying and curing stages; Thermal evaporation coating machine: ZZS-400 model, used for the deposition and preparation of top electrodes. It deposits metal electrode materials on the surface of composite gallium oxide thin films through thermal evaporation. The evaporation rate and coating thickness can be controlled to prepare a dense electrode layer. Ion beam evaporation coating machine: JGP-450 model, as an alternative equipment for top electrode deposition, is suitable for high-precision electrode preparation. It achieves evaporation deposition of electrode materials through ion beam bombardment, improving the adhesion and contact performance between the electrode and the thin film. Electronic analytical balance: Model FA2004, used for the precise weighing of experimental raw materials (polymers, EDTA, gallium sources, zinc-containing chlorophyll derivatives, etc.), with a weighing accuracy of 0.1mg, ensuring the accuracy of raw material ratios; Vacuum filtration device: SHB-III model, used with filter membrane, for filtering Ga-polymer solutions, removing insoluble matter from the solution, obtaining a clear and homogeneous gallium source solution, and improving the quality of the precursor solution; Nitrogen dryer: Model NDK-2001B, used for drying conductive substrates after cleaning. It achieves rapid drying of the substrate by purging with high-purity nitrogen, avoiding water stains on the substrate surface and ensuring the cleanliness of the substrate surface.

[0060] Example 1 Substrate pretreatment: Select an ITO / IGZO flexible conductive substrate, and ultrasonically clean it sequentially with acetone, anhydrous ethanol, and deionized water for 15 minutes each, and then dry it with nitrogen to obtain the pretreated substrate.

[0061] Precursor preparation: 2g of polyethyleneimine and 1g of EDTA were dissolved in 40mL of deionized water to obtain a polymer solution; 2g of gallium nitrate hydrate was added to the polymer solution, stirred and filtered to obtain a Ga-polymer solution; 20mg of zinc-methylpyromagnesia chlorophyll a was dissolved in 2.5mL of dimethyl sulfoxide to obtain a chlorophyll solution; under a nitrogen atmosphere, the chlorophyll solution was added dropwise to the Ga-polymer solution, stirred for 30 minutes and sonicated for 15 minutes to obtain a composite precursor solution.

[0062] Spin coating to form a film: The precursor solution is dropped onto the substrate and spin-coated at 3000 rpm for 40 seconds to form a pre-wet film.

[0063] Low-temperature heat treatment: The temperature is programmed in a nitrogen tube furnace, dried at 70°C for 13 minutes, and cured at 160°C for 45 minutes to obtain a composite gallium oxide thin film.

[0064] Electrode fabrication: A Pt top electrode with a diameter of 200 μm and a thickness of 100 nm was deposited on the thin film surface using an ion beam evaporation process to form a sandwich structure device.

[0065] This embodiment successfully fabricated a gallium oxide photoelectric synapse device doped with chlorophyll using the midpoint of the parameter range. A smooth, pinhole-free composite gallium oxide film was successfully prepared on an ITO / IGZO flexible conductive substrate, exhibiting a film thickness uniformity of ≤4%. Chlorophyll was molecularly dispersed within the gallium oxide matrix without agglomeration. The fabricated sandwich structure device showed good contact with no interface detachment issues. In terms of photoelectric performance, the optical response band covered 200–700 nm, with a visible light responsivity of 0.6 A / W (400–700 nm) and an optical on / off ratio ≥1.2 × 10⁻⁶. 4 The photoresponse time is 85ms and the turn-off time is 160ms. In terms of synaptic function, it can stably realize the excitatory postsynaptic current (EPSC) effect, with a double pulse facilitation (PPF) index of 1.35. It can accurately simulate short-term synaptic plasticity (STP) and long-term synaptic plasticity (LTP), and the synaptic weight adjustment accuracy reaches 0.008nS. In terms of flexibility, the photoelectric performance decays by only 5% after 1000 hours of continuous operation at room temperature, and there is no significant change in performance after 1000 bends. The overall device has excellent comprehensive performance, taking into account both flexibility and high photoelectric synaptic performance.

[0066] Example 2 Substrate pretreatment: Select a Pt / Ti / SiO2 / Si rigid substrate, and ultrasonically clean it sequentially with acetone, anhydrous ethanol, and deionized water for 15 minutes each, and then dry it with nitrogen.

[0067] Precursor preparation: Dissolve 2g polyvinylpyrrolidone and 1g EDTA in 40mL of deionized water; add 2g gallium acetylacetonate to obtain Ga-polymer solution; dissolve 20mg zinc-chlorophyll a in 3mL of dimethyl sulfoxide to obtain chlorophyll solution; stir for 60 minutes and sonicate for 30 minutes under argon atmosphere to obtain precursor solution.

[0068] Spin coating to form a wet film: Spin coating at 5000 rpm for 60 seconds to form a wet film.

[0069] Low-temperature heat treatment: Dry at 80°C for 18 minutes in an argon heating table, then cure at 180°C for 70 minutes.

[0070] Electrode fabrication: A top Au electrode with a diameter of 300 μm and a thickness of 150 nm was deposited by thermal evaporation process.

[0071] This embodiment utilizes the upper limit of the parameter range to fabricate a rigid substrate photoelectric synaptic device. The composite gallium oxide thin film prepared on the Pt / Ti / SiO2 / Si rigid substrate exhibits high density, strong adhesion to the substrate, good in-situ chlorophyll immobilization, and excellent photochemical stability. The device's photoelectric response band covers 200–700 nm, with a visible light responsivity of 0.55 A / W and an optical on / off ratio ≥1.5 × 10⁻⁶. 4With a response time of 70ms and a turn-off time of 140ms, it exhibits excellent photoelectric conversion efficiency. In terms of synaptic function, it boasts a PPF index of 1.5, a synaptic plasticity modulation cycle of ≥1200 times, and outstanding long-term operational stability. The top electrode maintains good ohmic contact with the thin film, with a contact resistance ≤8Ω. In rigid application scenarios, the device can operate stably in a temperature range of -20~60℃ without performance degradation, making it suitable for rigid neuromorphic computing hardware scenarios with high requirements for stability and response speed. The fabrication process is repeatable throughout, and the batch consistency of the products is good.

[0072] Example 3 Substrate pretreatment: ITO / IGZO flexible substrates were selected, ultrasonically cleaned for 15 minutes each, and then dried with nitrogen.

[0073] Precursor preparation: Dissolve 2g of polyacrylic acid and 1g of EDTA in 40mL of deionized water; add 2g of gallium chloride to obtain Ga-polymer solution; dissolve 20mg of (Zn-Chl)n polymer in 2mL of anhydrous ethanol to obtain chlorophyll solution; stir for 10 minutes and sonicate for 5 minutes under nitrogen atmosphere to obtain precursor solution.

[0074] Spin coating to form a wet film: Spin coating at 1000 rpm for 20 seconds to form a wet film.

[0075] Low-temperature heat treatment: Dry at 60°C for 8 minutes in a nitrogen tube furnace, then cure at 140°C for 25 minutes.

[0076] Electrode fabrication: An Ag top electrode with a diameter of 100 μm and a thickness of 50 nm was deposited by ion beam evaporation.

[0077] This embodiment successfully fabricated a thin, lightweight gallium oxide photoelectric synapse device doped with chlorophyll using the lower end of the parameter range. The composite gallium oxide film exhibited uniform thickness and low surface roughness, meeting the requirements of low-speed spin coating. The chlorophyll was uniformly dispersed within the gallium oxide framework, with a retention rate ≥92%. The device's optical response band covered 200–700 nm, with a visible light responsivity of 0.5 A / W and an optical on / off ratio ≥1.0 × 10⁻⁶. 4 With a response time of 95ms and a turn-off time of 180ms, it meets the basic requirements for optoelectronic synaptic functions. In terms of synaptic function, it can achieve stable EPSC and PPF effects, with a PPF index of 1.2 and a synaptic weight adjustment accuracy of 0.01nS, fully meeting the requirements for biomimetic synaptic functions. The manufacturing cost is significantly reduced, the Ag top electrode is highly compatible with the low-temperature solution method, and the device has excellent flexibility. After 1500 bends, the optoelectronic performance decays by only 7%, making it suitable for the large-scale fabrication of low-cost, lightweight flexible optoelectronic devices. The process is simple to operate, requires no high-precision equipment, and can easily achieve large-area film formation.

[0078] Example 4 Substrate pretreatment: ITO / IGZO flexible substrates were selected, ultrasonically cleaned for 15 minutes each, and then dried with nitrogen.

[0079] Precursor preparation: Dissolve 2g polyethyleneimine and 1g EDTA in 40mL of deionized water; add 2g gallium isopropoxide to obtain Ga-polymer solution; dissolve 20mg zinc-methyl pyromagnesia chlorophyll a in 2.5mL of anhydrous ethanol to obtain chlorophyll solution; stir for 40 minutes and sonicate for 20 minutes under argon atmosphere to obtain precursor solution.

[0080] Spin coating to form a wet film: Spin coat at 4000 rpm for 50 seconds to form a wet film.

[0081] Low-temperature heat treatment: Dry at 75°C for 15 minutes in an argon heating table, then cure at 170°C for 50 minutes.

[0082] Electrode fabrication: Thermal evaporation deposition of an ITO top electrode with a diameter of 250 μm and a thickness of 120 nm.

[0083] This embodiment uses preferred materials and above-average parameters to fabricate flexible devices. The composite gallium oxide thin film fabricated on an ITO / IGZO flexible substrate exhibits both film-forming properties and optoelectronic synergy. The polyethyleneimine polymer and gallium isopropoxide source show good compatibility, and the molecular-level composite degree of chlorophyll solution and Ga-polymer solution is ≥96%, with a film uniformity ≤3%. The device's optical response band covers 200~700nm, and the red / blue band optical responsivity reaches 0.65A / W, which is the best among the four embodiments. The optical on / off ratio is ≥1.3×10⁻⁶. 4 The device features a response time of 80ms and a shutdown time of 150ms. In terms of synaptic function, it boasts a PPF index of 1.4, enabling more precise multi-dimensional adjustment of synaptic weights and exhibiting plasticity behavior closer to that of biological synapses. The ITO top electrode has excellent light transmittance, reducing the obstruction of light signals and further improving the device's light energy utilization efficiency. After 1000 hours of continuous operation at room temperature, the device exhibits only a 4% performance degradation, and there is no performance decline after 1200 bends. It demonstrates excellent biocompatibility and combines light transmittance, flexibility, and high photoelectric performance, making it suitable for applications requiring both high-quality materials and superior performance, such as flexible artificial vision systems and bio-optoelectronic sensors.

[0084] Comparative Example 1 Substrate pretreatment: Same as in Example 1, ITO / IGZO flexible substrate was selected, ultrasonically cleaned and then dried with nitrogen.

[0085] Precursor preparation: Prepare only polyethyleneimine-EDTA polymer solution and gallium nitrate hydrate Ga-polymer solution, without adding chlorophyll solution, and obtain pure gallium source precursor solution after stirring and filtration.

[0086] Spin coating: Same as in Example 1, spin coating at 3000 rpm for 40 seconds.

[0087] Low-temperature heat treatment: Same as in Example 1, dry at 70°C for 13 minutes and cure at 160°C for 45 minutes.

[0088] Electrode fabrication: Same as in Example 1, deposit a 200 μm, 100 nm Pt top electrode.

[0089] The photoresponse and synaptic function of the devices in Examples 1-4 and Comparative Example 1 were tested, and the results showed that: Optical response band: The optical response bands of the devices in Examples 1-4 all cover 200~700nm, and the optical responsivity in the visible light region (400~700nm) is ≥0.5A / W. In contrast, Comparative Example 1 only has a response in the deep ultraviolet region of 200~250nm, and no optical response in the visible light region. This proves that the present invention has successfully extended the optical response range of gallium oxide from the ultraviolet to the visible light region through chlorophyll doping, which greatly improves the light energy utilization efficiency.

[0090] Synaptic function: The devices in Examples 1-4 can all achieve obvious EPSC and PPF effects, with PPF indices between 1.2 and 1.5, stably simulating STP and LTP behavior, and synaptic weight adjustment accuracy ≥0.01nS; while Comparative Example 1 can only achieve simple ultraviolet photoconductive characteristics, without obvious synaptic plasticity behavior, and cannot simulate biological synaptic function. This proves that the organic-inorganic composite system of the present invention achieves photoelectric synergy, can accurately simulate the complex behavior of biological synapses, and solves the problem of single function of traditional gallium oxide devices.

[0091] Device stability and adaptability: The optical switching ratios of the devices in Examples 1-4 are all ≥10. 4 After 1000 hours of continuous operation at room temperature, the performance degradation was ≤8%. Among them, the flexible substrate devices of Examples 1, 3, and 4 showed no significant performance degradation after 1000 bending cycles. However, the optical switching ratio of Comparative Example 1 was only 10³, and the performance degradation reached 30% after 500 hours of continuous operation. This proves that the fabrication process of the present invention improves the stability of the device, is compatible with flexible substrates, and expands the application scenarios.

[0092] Process advantages: The preparation process of Examples 1-4 is carried out at low temperature (≤180℃) throughout, without the need for expensive vapor phase epitaxy equipment, reducing raw material costs by more than 70%, and the process flow is simple, enabling large-area film formation; while Comparative Example 1, if prepared using the traditional vapor phase method, requires a high temperature of more than 800℃, with high equipment costs, complex process, and inability to prepare flexible devices. This proves that the low-temperature solution method of the present invention significantly reduces the preparation cost and improves the flexibility and scalability of the process.

[0093] In summary, this invention provides a gallium oxide photoelectric synapse device doped with chlorophyll and its fabrication method, completely eliminating the dependence on expensive and energy-intensive gas-phase equipment. The process is simple, significantly reducing costs, and is naturally compatible with flexible substrates, opening a new path for flexible optoelectronic integration. It breaks through the traditional limitation of solution methods that can only dope inorganic ions, introducing bioactive molecules as core functional units into the gallium oxide system for the first time, realizing a paradigm shift in the optoelectronic function of materials from inorganic regulation to organic-inorganic synergy. The introduction of chlorophyll brings revolutionary performance improvements: its strong visible light absorption capability expands the device's photoresponse range from the narrow ultraviolet band to the broad visible light region, greatly improving light energy utilization efficiency. Its unique photophysical and photochemical processes can synergize with the carrier transport behavior of gallium oxide, thereby accurately and efficiently simulating various short-term / long-term plasticity behaviors of biological synapses. This invention provides a practical and original material platform and process solution for constructing a new generation of low-cost, flexible, biocompatible optoelectronic neuromorphic devices and systems with advanced biomimetic learning capabilities.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating a gallium oxide photoelectric synapse device doped with chlorophyll, characterized in that, Includes the following steps: S1. The conductive substrate is ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water, and then dried with nitrogen to obtain a pretreated conductive substrate. S2. The polymer, complexing agent and deionized water are mixed and dissolved to obtain a polymer solution. The gallium source is added to the polymer solution and stirred and filtered to obtain a Ga-polymer solution. The zinc-containing chlorophyll derivative is dissolved in a mild organic solvent to obtain a chlorophyll solution. The chlorophyll solution is added dropwise to the Ga-polymer solution under an inert gas atmosphere. After stirring and sonication, a homogeneous and stable composite precursor solution is obtained. S3. The composite precursor solution is dropped onto the surface of the pretreated conductive substrate and then spin-coated to obtain a pre-wet film. S4. The pre-placed wet film is placed in a heating device under an inert gas atmosphere for programmed temperature rise heat treatment to obtain a conductive substrate modified with a composite gallium oxide thin film. S5. A top electrode is deposited on the surface of the composite gallium oxide thin film away from the conductive substrate to obtain the chlorophyll-doped gallium oxide photoelectric synapse device.

2. The method for fabricating a gallium oxide photosynaptic device doped with chlorophyll according to claim 1, characterized in that, In step S2, the polymer is selected from one or more of polyethyleneimine, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, or polyoxyethylene-polyoxypropylene block copolymer; the complexing agent is ethylenediaminetetraacetic acid (EDTA); and the gallium source is selected from one of gallium nitrate hydrate, gallium chloride, gallium isopropoxide, or gallium acetylacetonate.

3. The method for fabricating a gallium oxide photosynaptic device doped with chlorophyll according to claim 1, characterized in that, In step S2, the zinc-containing chlorophyll derivative is selected from one of zinc-chlorophyll a, zinc-methylpyromethesin a, or (Zn-Chl)n polymer; the mild organic solvent is selected from anhydrous ethanol or dimethyl sulfoxide.

4. The method for fabricating a gallium oxide photoelectric synapse device doped with chlorophyll according to claim 1, characterized in that, In step S2, the inert gas atmosphere is a nitrogen atmosphere or an argon atmosphere; the stirring time is 10-60 minutes, and the ultrasonic treatment time is 5-30 minutes.

5. The method for fabricating a gallium oxide photosynaptic device doped with chlorophyll according to claim 1, characterized in that, In step S3, the spin coating speed is 1000~5000 rpm and the spin coating time is 20~60 seconds.

6. The method for fabricating a gallium oxide photosynaptic device doped with chlorophyll according to claim 1, characterized in that, In step S4, the programmed temperature rise heat treatment includes a first stage drying treatment and a second stage curing treatment; the temperature of the first stage is 60~80℃ and the holding time is 8~18 minutes; the temperature of the second stage is 140~180℃ and the holding time is 25~70 minutes.

7. The method for fabricating a gallium oxide photosynaptic device doped with chlorophyll according to claim 1, characterized in that, In step S5, the deposition of the top electrode is carried out using ion beam evaporation or thermal evaporation; the material of the top electrode is selected from one of Ag, Ti, Pt, ITO, IGZO or Au; the diameter of the top electrode is 100~300μm and the thickness is 50~150nm.

8. A gallium oxide photosynaptic device doped with chlorophyll prepared by the method according to any one of claims 1 to 7, wherein the gallium oxide photosynaptic device comprises a conductive substrate, a composite gallium oxide thin film, and a top electrode stacked sequentially to form a sandwich structure of metal / composite gallium oxide thin film / conductive substrate; wherein, The composite gallium oxide film is an amorphous film formed by the molecular-level composite of zinc chlorophyll derivative and gallium oxide, with the zinc chlorophyll derivative fixed in situ within the gallium oxide framework.

9. The method for fabricating a gallium oxide photosynaptic device doped with chlorophyll according to claim 8, characterized in that, The conductive substrate is a Pt / Ti / SiO2 / Si substrate or an ITO / IGZO substrate that has been ultrasonically cleaned with acetone, anhydrous ethanol and deionized water and dried with nitrogen.

10. The method for fabricating a gallium oxide photosynaptic device doped with chlorophyll according to claim 8, characterized in that, The top electrode is a separate, discrete patterned structure used to simulate the excitatory postsynaptic current behavior of biological synapses under illumination.

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