A water-soluble polymer-based protonic memristor and preparation thereof

Abstract

The application discloses a water-soluble polymer-based proton-type memristor and a preparation method thereof. The memristor has a sandwich structure and is sequentially composed of a top electrode, an inorganic resistive switching functional layer, an organic resistive switching functional layer and a bottom electrode. The top electrode is a metal active electrode, the bottom electrode is indium tin oxide (ITO), the inorganic resistive switching functional layer is a metal oxide film, and the organic resistive switching functional layer is a doping system composed of a water-soluble polymer and a doping material. The preparation process of the proton-type memristor is reliable and stable. The obtained memristor has the characteristics of high biocompatibility and green environmental protection. The device performance consistency and environmental dependence are improved, and the simulation of bionic synaptic plasticity is greatly improved. The device can be controlled by using a low voltage, has low power consumption, and has a good bidirectional current modulation effect, so that the device provides a possibility for further enriching synaptic functions and designing flexible wearable devices.

Description

Technical Field

[0001] This invention belongs to the fields of organic optoelectronic materials and neuromorphic hardware manufacturing, specifically relating to a proton-type memristor based on a water-soluble polymer and its preparation. Background Technology

[0002] The advent of the information age has led to a rapid increase in the amount of data to be processed. Traditional von Neumann architectures, involving separate processing and storage units, result in slow data movement rates and high energy consumption, making current semiconductor technology unable to meet future demands for ultra-high-density storage. In this context, emerging memory devices have emerged. Memristors are a new type of device with advantages such as low power consumption, high switching speed, good retention, high durability, and scalability. Memristors exhibit non-linear resistance changes, enabling dynamic conductance adjustment, and are considered one of the most promising candidates for future non-volatile memory technology.

[0003] Neurons in the human brain are closely connected through synapses. In the transmission of information in the human brain, synapses play a variety of complex signal processing roles such as computation, adaptation, memory and learning. Analogous to the human brain, memristors can process high-energy-efficiency neuromorphic computing tasks in real time, and therefore have great development potential. The ion migration mechanism involved is similar to the transmission of neurotransmitters at human brain synapses, which gives memristors an inherent advantage in simulating bionic synaptic plasticity.

[0004] The performance of memristors is closely related to the choice of resistive switching layer material. Inorganic semiconductor memristors mostly use metal oxide materials as resistive switching layers; while traditional organic semiconductor memristors have slow ion transport, resulting in small conductance changes, which affects the simulation of biomimetic synaptic plasticity. In addition, the low carrier mobility and large charge injection barrier make it difficult to control the performance of the device.

[0005] Wei Rongshan's research group previously published a paper on the simulation of neural synapses using memristors. They primarily used PEDOT:PSS, a conductive polymer with electrical properties similar to biomolecules, as the memory medium. By doping PEDOT:PSS with a small amount of PVP, they altered the conductivity range of the Ag / PEDOT:PSS / Ta structure memristor. This memristor can simulate learning behaviors such as short-term plasticity (STP), long-term plasticity (LTP), pulse frequency-dependent plasticity (SRDP), and pulse time-dependent plasticity (STDP). However, this memristor requires an external stimulus of 2V to complete the response, with a response current ranging from 100-850μA. While it can achieve basic simulations of synaptic plasticity, such as the curve of stable current changing with the number of pulses, it lacks simulation of higher-level functions of the human brain. Furthermore, the device has high power consumption, making it unsuitable for application in large-scale neural circuits. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing memristors in terms of excessive current consumption by providing a proton-type memristor based on a water-soluble polymer and its fabrication. This memristor can generate a conductivity response under low-voltage external stimulation, with the conductivity response at the pA level. In terms of simulating synaptic plasticity, this memristor has a biphasic current effect, and the biphasic current can be effectively adjusted by changing the pulse voltage and pulse width, thereby realizing various biomimetic simulations and enriching synaptic plasticity.

[0007] The technical solution of this invention is as follows: a proton-type memristor based on a water-soluble polymer, the memristor having a "sandwich" structure, consisting sequentially of a top electrode, an inorganic resistive switching layer, an organic resistive switching layer, and a bottom electrode. The top electrode is a metal active electrode (such as Al, Cu, etc.) used for connection to ground; the bottom electrode is indium tin oxide (ITO), with a sheet resistance of approximately 10 Ω / sq; the inorganic resistive switching layer is a metal oxide thin film (such as AlO₂). x HfO x TaO x (etc.) are used to provide oxygen vacancies for the device, and the oxygen vacancy migration mechanism is used to assist proton migration and increase the conductivity change of the device; the organic resistive switching functional layer is a doping system based on water-soluble polymers. The doping material can be selected from one or more of the following materials: organic oligomers, small molecule materials, metal nanoparticles, and nano-carbon materials (carbon quantum dots, graphene oxide, carbon nanotubes). Water-soluble polymers have the characteristics of water solubility, dispersion, flocculation, and thickening. The doping system of water-soluble polymers can effectively reduce the response current of the device.

[0008] Furthermore, this proton-type memristor has a biphase current effect, and the biphase current can be adjusted by changing the pulse voltage and pulse width.

[0009] Furthermore, the water-soluble polymer is a polymer material containing a large number of hydrophilic groups and readily forming an aqueous solution system, specifically selected from polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, or carboxymethyl cellulose; the doping material can be a triphenylamine-pyrrolopyrroledione amphiphilic molecule.

[0010] The preparation method of the above-mentioned proton-type memristor based on water-soluble polymer is as follows:

[0011] (1) Prepare a doping system by mixing water-soluble polymers with doped materials as a mixed solute;

[0012] (2) Dissolve the prepared solute in deionized water and let it stand at room temperature for later use;

[0013] (3) Clean the glass substrate with indium tin oxide bottom electrode sputtered by magnetron sputtering, blow it dry with high-purity nitrogen, and put it into an electric heating drying oven to dry.

[0014] (4) Ultraviolet ozone sterilization glass substrate;

[0015] (5) Spin-coat the solution obtained in step (2) onto a glass substrate to form an organic resistive switching functional layer;

[0016] (6) Place the device with the spin-coated organic resistive switching functional layer in a vacuum drying oven to dry;

[0017] (7) A metal oxide film is grown on the organic resistive switching layer as an inorganic resistive switching functional layer by means of vacuum thermal evaporation, atomic layer deposition or magnetron sputtering.

[0018] (8) Annealing in a vacuum thermal evaporation equipment;

[0019] (9) After placing the electrode mask above the device, place it in a vacuum thermal evaporation equipment to evaporate the metal active electrode;

[0020] (10) Place the device with the top electrode deposited under a vacuum thermal evaporation equipment for annealing, and then take it out to obtain the memristor.

[0021] Furthermore, in step (1), the mass fraction ratio of the water-soluble polymer to the doped material is 2-4:1.

[0022] Furthermore, in step (5), the spin coating speed for preparing the organic resistive switching functional layer based on the solution of the water-soluble polymer doping system is 4000 rpm, the spin coating time is 30 s, and the thickness of the spin-coated film is 25-35 nm.

[0023] Furthermore, in step (6), the drying time is 20-30 minutes and the drying temperature is set at 60-100℃.

[0024] Furthermore, in step (7), when a metal oxide thin film is grown by vacuum thermal evaporation as an inorganic resistive switching functional layer, the vacuum level is controlled at 5×10⁻⁶. -4 -7×10 -4 pa, evaporation rate is The evaporation frequency is 50-55Hz, and the thickness is controlled at 10-20nm using a quartz crystal oscillator.

[0025] Furthermore, in step (8), the annealing time is 20-30 minutes, and the vacuum degree is controlled at 5×10⁻⁶. -4 Below pa.

[0026] Furthermore, in step (9), the vacuum degree is controlled at 5 × 10⁻⁶ during the deposition of the metal active electrode. -4 -7×10 -4 pa, evaporation rate is The evaporation frequency is 2000-2200Hz, and the thickness is controlled at 120-140nm using a quartz crystal oscillator.

[0027] Furthermore, in step (10), the annealing time is 20-30 minutes, and the vacuum degree is controlled at 5×10⁻⁶. -4 Below pa.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. The proton-type memristor disclosed in this application can generate a conductance response under a low voltage external stimulus of 0.2-1V, and the response current operates at 100-900pA. Compared with the memristors in the prior art, the overall power consumption is significantly reduced.

[0030] 2. In the proton-type memristor disclosed in this application, the inorganic resistive switching functional layer is a grown metal oxide thin film. The introduction of oxygen vacancies compensates for the deficiency of proton source caused by factors such as dry environment in the proton-type memristor, thereby reducing the environmental dependence of the device and improving the performance consistency of the device.

[0031] 3. Doping is an effective method for regulating device performance. This application mainly utilizes the characteristic that polyvinylpyrrolidone (PVPy) is suitable for water-soluble doping systems and selects it as a water-soluble polymer. It also selects the organic oligomer triphenylamine-pyrrolopyrroledione amphiphilic molecule (DPP) as a doping material and introduces a molecular-level nano-floating gate, so that the charge trapping mechanism of the memristor controls the proton migration and enhances the conductivity change rate range of the device. The synergistic effect of the two mechanisms can realize dynamic conductivity regulation and generate a biphase current effect, so that the pulse voltage can more accurately modulate the synaptic simulation. The advanced simulation of synaptic plasticity can be completed with high sensitivity at a voltage of 0.2V.

[0032] 4. The proton-type memristor prepared in this application has a biphasic current effect, and the biphasic current can be effectively regulated by changing the pulse voltage and pulse width, thereby realizing a variety of biomimetic simulations, such as simulating the Ebbinghaus learning curve of the human brain, high / low-pass filters, selective memory and forgetting, etc. It is confirmed that this regulation can enrich synaptic plasticity, and the regulation method is simple and repeatable, providing a more practical approach for the development of low-power flexible smart wearable devices and biocompatible and environmentally friendly neuromorphic circuits. Attached Figure Description

[0033] Figure 1 This is a device structure diagram of a proton-type memristor based on water-soluble polymer (PVPy), 1-top electrode, 2-inorganic resistive switching functional layer, 3-organic resistive switching functional layer, 4-bottom electrode;

[0034] Figure 2 The image shows the IV electrical performance curve of the memristor under 1V voltage stimulation.

[0035] Figure 3The image shows the IV electrical performance curve of the memristor under -1V voltage stimulation.

[0036] Figure 4 Diagram showing the bidirectional current and pulse voltage modulation of the memristor artificial synapse;

[0037] Figure 5 This is a diagram showing the bidirectional current and pulse voltage modulation of the artificial synapse of a memristor. Detailed Implementation

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0039] Example 1: Fabrication of a proton-type memristor based on a water-soluble polymer

[0040] During preparation, the laboratory temperature was maintained at around 25°C and the indoor humidity was maintained at around 22%.

[0041] The main preparation steps are as follows:

[0042] (1) Selection of water-soluble polymer and dopant: In this embodiment, polyvinylpyrrolidone (PVPy) with a molecular weight of 1,300,000 is preferred as the water-soluble polymer and the organic oligomer triphenylamine-pyrrolopyrroledione amphiphilic molecule (DPP) is preferred as the dopant. The two are mixed to prepare the solute, and the mass fraction ratio of PVPy to DPP is 4:1.

[0043] (2) Dissolve the prepared solute in 1 mL of deionized water and let it stand at room temperature for 24 hours before use;

[0044] (3) For glass substrates with indium tin oxide bottom electrodes sputtered by magnetron sputtering, ultrasonic cleaning was performed for 10 minutes each in an ultrasonic cleaner with acetone, ethanol and deionized water, and the glass substrates were dried with high-purity nitrogen gas and placed in an electric heating drying oven at 120°C for 20 minutes.

[0045] (4) Expose the dried glass substrate to ultraviolet ozone for 5 minutes;

[0046] (5) Spin-coat the solution obtained in step (2) onto the bottom electrode to form an organic resistive switching functional layer. The spin-coating speed is 4000 rpm, the spin-coating time is 30 s, and the thickness of the spin-coated film is 25-35 nm.

[0047] (6) Place the device with the spin-coated organic resistive switching functional layer in a vacuum drying oven and dry at 80°C for 20 min;

[0048] (7) The inorganic resistive switching functional layer of the device is preferably a metal oxide AlO.x 1≤x≤3, specifically, the metal oxide thin film is grown on the organic resistive switching functional layer by vacuum thermal evaporation, with the vacuum degree controlled at 5×10. -4 pa, evaporation rate is The evaporation frequency is 50Hz, and the thickness is controlled at 10-20nm using a quartz crystal oscillator.

[0049] (8) After the inorganic resistive switching functional layer has grown well, anneal it for 20-30 minutes in a vacuum thermal evaporation equipment, with the vacuum degree controlled at 5×10. -4 Below pa;

[0050] (9) After placing the electrode mask above the device, place it in a vacuum thermal evaporation equipment to deposit the metal active electrode. Al electrodes are preferred here, and the vacuum degree is controlled at 5×10⁻⁶. -4 pa, evaporation rate is The evaporation frequency is 2000Hz, and the thickness is controlled at 120-140nm using a quartz crystal oscillator.

[0051] (10) To ensure the smooth morphology of the thin film and the electrode, after the top electrode is deposited, the device is annealed for another 20-30 minutes in a vacuum thermal evaporation apparatus, with the vacuum degree controlled at 5×10⁻⁶. -4 Below pa, the complete memristor device can be obtained by removing it.

[0052] Figure 1 This is a device structure diagram of a proton-type memristor based on a water-soluble polymer (PVPy). From top to bottom, the structure consists of four parts: top electrode 1, inorganic resistive switching layer 2, organic resistive switching layer 3, and bottom electrode 4. The top electrode 1 is an aluminum electrode, and the inorganic resistive switching layer 2 is AlO₂. x The organic resistive switching functional layer 3 is composed of PVPy-doped DPP, and the bottom electrode 4 is indium tin oxide.

[0053] To simulate synaptic function, an external voltage is used as an excitation to stimulate a memristor device. The two electrodes at the ends serve as the anterior and posterior synapses, respectively. The current level is equivalent to the synaptic weight, and changes and modulation of the current level represent the simulation of synaptic plasticity. This exhibits characteristics similar to biological synapses. Therefore, different input voltages can be used to stimulate the device to simulate the excitation and inhibition of biological synapses.

[0054] Figure 2 The image shows the IV electrical performance of the proton-type memristor after five consecutive stimulations at 1V. Under stimulation with a step size of 0.05, the device exhibits a characteristic that the conductivity increases with the number of scans, which is a simulated biological synapse characteristic of positive excitation. The current response is between 200pA and 1nA, indicating that the device has low power consumption switching characteristics in the positive range.

[0055] Figure 3 The image shows the IV electrical performance of the proton-type memristor after five consecutive stimulations at -1V. Under stimulation with a step size of 0.05, the device exhibits a characteristic that the conductivity level decreases with the increase of the number of scans, i.e., the negative suppression characteristic of the device. The current response is between 200pA and 300pA, indicating that the device has low power consumption switching characteristics in the negative range.

[0056] Figure 4 The fabricated proton-type memristor exhibits biphase current characteristics that can be adjusted by varying the pulse voltage. The biphase current consists of electrically mediated (B1) and ion-mediated (A1) currents, which can be modulated by the pulse amplitude, varying between 0.2V and 1V, with a fixed pulse width of 100ms. As shown in the figure, the biphase currents of the device gradually increase with increasing pulse voltage amplitude, demonstrating good adjustability.

[0057] Figure 5 The fabricated proton-type memristor exhibits biphase current characteristics that can be adjusted by varying the pulse voltage. The biphase current can be modulated by the pulse width, which varies between 100 and 900 ms, while the voltage amplitude is fixed at 0.5 V, resulting in a current around 400 pA. As the pulse voltage width increases, the electrical conductivity remains constant, while the ion-mediated conductivity gradually increases. Therefore, both the ion-mediated and electrical-mediated PSC components can be well adjusted by changing the pulse.

[0058] In this embodiment, PVPy was selected for device fabrication due to its good environmental stability, ease of processing, suitable conductivity, and non-toxicity. Due to hydrogen bonding or complexation, it is suitable as a water-soluble polymer doping system, further enabling the modulation of memristor performance. Furthermore, it can generate a conductive response under low-voltage (0.2-1V) external stimulation, with the conductivity response at the pA level. In simulating synaptic plasticity, this memristor exhibits a biphasic current effect, which can be effectively adjusted by varying the pulse voltage and pulse width, thereby achieving various biomimetic simulations and enriching synaptic plasticity. This provides possibilities for the development of low-power flexible smart wearable devices and biocompatible, environmentally friendly neuromorphic circuits.

[0059] In the modulation of synaptic plasticity, this memristor exhibits a biphasic current effect, which can be effectively adjusted by changing the pulse voltage and pulse width. This provides possibilities for various biomimetic simulations, such as simulating the Ebbinghaus forgetting curve of the human brain, high-pass or low-pass filters, and selective learning and memory applications. These findings demonstrate that this modulation can enrich synaptic plasticity, and the modulation method is simple and repeatable. It provides a more practical approach for the development of low-power flexible smart wearable devices and biocompatible, environmentally friendly neuromorphic circuits.

[0060] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A proton-type memristor based on a water-soluble polymer, characterized in that, This memristor has a "sandwich" structure, consisting sequentially of a top electrode, an inorganic resistive switching layer, an organic resistive switching layer, and a bottom electrode. The top electrode is a metal active electrode, the bottom electrode is indium tin oxide, and the inorganic resistive switching layer is a metal oxide thin film. The organic resistive switching layer is a doped system based on a water-soluble polymer. The water-soluble polymer is a polymer material containing a large number of hydrophilic groups that easily forms an aqueous solution system, specifically selected from polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, or carboxymethyl cellulose. The dopant material is a triphenylamine-pyrrolopyrroledione amphiphilic molecule. This proton-type memristor exhibits a biphase current effect, which can be adjusted by changing the pulse voltage and pulse width; it can also generate a conductance response under low voltage external stimulation of 0.2-1V, with a current response of 100-900 pA.

2. The method for preparing a proton-type memristor based on a water-soluble polymer as described in claim 1, characterized in that, Specifically, it includes the following steps. (1) Prepare a doping system mixed with water-soluble polymer and doped material, wherein the mass fraction ratio of water-soluble polymer to doped material is 2-4:1; (2) Dissolve the prepared solute in deionized water and let it stand at room temperature until needed; (3) Clean the glass substrate with indium tin oxide bottom electrode sputtered by magnetron sputtering, blow it dry with high-purity nitrogen, and put it into an electric heating drying oven to dry. (4) Ultraviolet ozone sterilization glass substrate; (5) Spin-coat the solution obtained in step (2) onto a glass substrate to form an organic resistive switching functional layer; (6) Place the device with the spin-coated organic resistive switching functional layer in a vacuum drying oven to dry; (7) A metal oxide thin film is grown on the organic resistive switching layer as an inorganic resistive switching functional layer by means of vacuum thermal evaporation, atomic layer deposition or magnetron sputtering; (8) Annealing in a vacuum thermal evaporation equipment; (9) After placing the electrode mask above the device, place it in a vacuum thermal evaporation equipment to evaporate the metal active electrode; (10) Place the device with the top electrode deposited under a vacuum thermal evaporation equipment for annealing, and then take it out to obtain the memristor.

3. The method for preparing a proton-type memristor based on a water-soluble polymer as described in claim 2, characterized in that, In step (5), the spin coating speed for preparing the organic resistive switching functional layer based on the solution of the water-soluble polymer doping system is 4000 rpm and the spin coating time is 30 s. The thickness of the spin-coated film is 25-35 nm.

4. The method for preparing a proton-type memristor based on a water-soluble polymer as described in claim 2, characterized in that, In step (7), when vacuum thermal evaporation is used to grow a metal oxide thin film as an inorganic resistive switching functional layer, the vacuum level is controlled at 5×10⁻⁶. -4 -7×10 -4 The evaporation rate is 0.08-0.1 Å / S, the evaporation frequency is 50-55 Hz, and the thickness is controlled at 10-20 nm using a quartz crystal oscillator.

5. A method for preparing a proton-type memristor based on a water-soluble polymer as described in claim 2, characterized in that, In step (8), the annealing time is 20-30 minutes, and the vacuum degree is controlled at 5×10. -4 Below Pa.

6. The method for preparing a proton-type memristor based on a water-soluble polymer as described in claim 2, characterized in that, In step (9), the vacuum degree is controlled at 5×10 during the deposition of the metal active electrode. -4 -7×10 -4 The evaporation rate is 0.4-0.5 Å / S, the evaporation frequency is 2000-2200 Hz, and the thickness is controlled at 120-140 nm using a quartz crystal oscillator.

7. The method for preparing a proton-type memristor based on a water-soluble polymer as described in claim 2, characterized in that, In step (10), the annealing time is 20-30 minutes, and the vacuum degree is controlled at 5×10. -4 Below Pa.

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