A SF-based memristor with reversible negative photoelectric effect and a method for preparing the same

Abstract

The present invention belongs to the field of bioelectronics and neuromorphic computing technology, and relates to a SF-based memristor with a reversible negative photoelectric effect and a preparation method thereof, wherein SF@WS is spin-coated on the upper surface of a conductive layer. 2 After suspension, drying forms SF@WS 2 layer, and then deposit the electrode layer to obtain a SF-based memristor with a reversible negative photoelectric effect. 2 The solution was prepared by adding WS to the SF solution. 2 The invention solves the problems of poor cycle stability, short data retention time and irreversibility of negative photoelectric memristor in existing SF-based memristor, and realizes reversible regulation of device resistance with light intensity, long data retention time and good cycle stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of bioelectronics and neuromorphic computing, and relates to a SF-based memristor with a reversible negative photoelectric effect and a preparation method thereof. Background Art

[0002] As one of the most important ways to perceive environmental information, the visual system receives 80% of external information. The human visual system can not only perceive and process information at the same time, but also respond positively and negatively in different situations. Bionic visual systems consisting of sensing, memory and processing units have gradually developed to simulate the human visual system. However, the structural separation of memory and computing leads to data delay and power consumption, which is completely different from the human visual system. Integrating sensing, processing and storage functions into one device is one of the effective strategies to solve the above problems and obtain an ideal artificial visual system. The structure and working mechanism of photoelectric memristors are similar to those of neural synapses. They have the comprehensive functions of sensing, memory and computing and have been proven to be an ideal strategy for building artificial visual neural systems. Most photoelectric memristors increase charge carriers under the stimulation of light, resulting in a decrease in the resistance value of the device, showing a positive photoelectric effect; some are negative photoelectric memristors whose resistance value increases when the device is exposed to light.

[0003] So far, the materials that have achieved the photoelectric effect are mainly concentrated on organic and inorganic materials. However, these materials have problems such as difficulty in degradation and poor biocompatibility, which limits their application in bioelectronics, implantable devices, etc. Since biomaterial-based memristors have good biocompatibility, biodegradability, sustainability, etc., they have natural advantages in the field of neuromorphic computing. Silk fibroin (SF) derived from natural silk is a structurally adjustable and environmentally friendly biomaterial, which has become a biomemristor construction material that is expected to be applied in practice.

[0004] Reference 1 (Adv. Funct. Mater., 2012(22), 4493-4499.) demonstrated for the first time that a memristor with SF film as the functional layer and ITO and Al as the electrode layers exhibited non-volatile resistance switching behavior, with a data retention time of 10 3 s, and the transition of its resistance state is mainly achieved by the carrier capture / removal caused by the oxidation and reduction process of SF.

[0005] In the SF-based memristor device prepared in Reference 2 (Adv. Funct. Mater., 2015(25), 3825-3831.), by applying different scanning voltages to the device, the high resistance state (HRS) and low resistance state (LRS) can be switched back and forth. Based on this resistance switching, charge information can be stored, and a long retention time (> 4500s) is also shown. Subsequent ultra-lightweight memristors and transparent transient bio-memristors prepared based on SF have shown good performance, indicating that SF-based memristors have broad application prospects.

[0006] Reference 3 (Adv. Sci, 2018, 5, 1800714.) successfully constructed the first protein-based light-adjustable bio-memristor by doping carbon dots (CDs) in SF films. The set voltage was effectively adjusted by applying ultraviolet illumination to the device, which laid the foundation for promoting the development of light-adjustable bio-based memristors.

[0007] Reference 4 (Adv. Funct. Mater., 2019, 1904777.) used silver nanoclusters (AgNCs) and bovine serum albumin (BSA) to modify SF, significantly improving the memristive performance of SF. AgNCs@BSA acts as an electron potential well to change the transmission behavior of charged particles in the SF film to achieve resistive state switching. This silk composite memristor can achieve a stable erasing process of 100 times and shows unique synaptic characteristics and synaptic learning ability.

[0008] Reference 5 (Adv. Funct. Mater., 2022, 2101139.) prepared a volatile memristor with low set voltage by doping silver nitrate in SF film, which showed good cycle stability (> 100 cycles). Different from the traditional non-volatile SF-based memristor, this volatile SF-based memristor reduces silver ions in situ into uniformly dispersed silver nanoparticles through tyrosine residues in SF, providing a stable current path for stable resistance switching operation.

[0009] Reference 6 (ACS Applied Nano Materials, 2024, 7 (12), 14684-14694.) prepared a non-volatile memristor with ITO / SF-GO / Al structure by doping graphene oxide (GO) into SF, which can achieve 100 stable cycles and good retention time (10 4 s).

[0010] Although the above-mentioned SF-based memristors have made certain progress, the existing SF-based memristors are all positive photoelectric memristors, and negative photoelectric SF-based memristors have not yet been successfully produced.

[0011] In addition, current negative photomemristors based on other materials still maintain the negative photomemristive effect after the light stimulus is removed, that is, they are not reversible and the resistance state cannot be restored from a high resistance state to a low resistance state.

[0012] Therefore, it is necessary to propose a SF-based memristor with reversible negative photoelectric effect and a preparation method thereof. Summary of the invention

[0013] The purpose of the present invention is to solve the problems existing in the prior art and to provide a SF-based memristor with a reversible negative photoelectric effect and a preparation method thereof.

[0014] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0015] A SF-based memristor with a reversible negative photoelectric effect is composed of an electrode layer, a memristor functional layer and a conductive layer in sequence. The memristor functional layer is a SF@WS2 layer, and the SF@WS2 layer is a SF film doped with WS2. WS2 has the photosensitivity of strong light absorption and rapid carrier migration, is easy to process, and can promote the regular arrangement of SF molecules.

[0016] As the preferred technical solution:

[0017] As described above, the SF-based memristor with a reversible negative photoelectric effect can change the resistance of the device by adjusting the light intensity, thereby realizing a reversible negative photoelectric effect. When the light intensity increases from 0 to 12.7 W / m 2 When the light is on, the set voltage of the SF-based memristor with a reversible negative photoelectric effect increases, and the resistance value also increases; when the light is removed, the resistance value of the SF-based memristor with a reversible negative photoelectric effect recovers; the negative photoelectric memristors in the prior art cannot achieve a reversible negative photoelectric effect. The present invention prepares a memristor with such characteristics for the first time, filling the gap in the prior art.

[0018] As described above, in a SF-based memristor with a reversible negative photoelectric effect, the content of WS2 in the SF@WS2 layer is 1~5wt%, and the crystallinity of the SF@WS2 layer is 35~50%.

[0019] The SF-based memristor with reversible negative photoelectric effect as described above has a data retention time greater than 8×10 3s, the average set voltage of the 1st to mth cycle period is 0.66~1V, the standard deviation is 0.045~0.2V, and m is 200~300, that is, 200~300 stable erasing processes can be achieved; the SF-based memristor in the prior art not only does not have a negative photoelectric effect, but also has the problems of poor cycle stability (only about 100 stable erasing processes can be achieved at most) and short data retention time, which limits its application in the fields of sensing, storage and computing integration and wearable flexible devices. The present invention solves this problem.

[0020] As described above, the SF-based memristor with a reversible negative photoelectric effect has an electrode layer thickness of 100~120nm, a SF@WS2 layer thickness of 30~40nm, and a conductive layer thickness of 185nm~0.05mm; the electrode layer is an Ag or Al electrode layer, and the conductive layer is an ITO (indium tin oxide) or PET (polyethylene terephthalate)-ITO film.

[0021] The present invention also provides a method for preparing an SF-based memristor with a reversible negative photoelectric effect. After spin coating an SF@WS2 solution on the upper surface of a conductive layer, drying to form an SF@WS2 layer, and then depositing an electrode layer, the SF-based memristor with a reversible negative photoelectric effect is obtained, wherein the SF@WS2 solution is obtained by adding a WS2 dispersion to an SF solution. The preparation process of the SF solution is as follows: boiling silkworm cocoons twice in a Na2CO3 aqueous solution (the mass fraction of Na2CO3 is 0.5wt%), washing with deionized water to obtain SF, and then dissolving SF in a lithium bromide aqueous solution (concentration is 9-9.3mol / L), and sequentially centrifuging, filtering, dialyzing and concentrating (i.e., concentrating the SF solution to a required concentration at 4°C) to obtain a SF solution.

[0022] As the preferred technical solution:

[0023] In the method for preparing a SF-based memristor with a reversible negative photoelectric effect as described above, after the SF@WS2 solution is spin-coated on the upper surface of the conductive layer and before drying, the upper surface is immersed in an ethanol aqueous solution.

[0024] As described above, a preparation method of a SF-based memristor with a reversible negative photoelectric effect, the content of WS2 in the SF@WS2 layer is 1~5wt%, the concentration of the SF solution is 2.0~3.0wt%; WS2 is a nanoscale sheet structure, the diameter of WS2 is 400~700nm, the volume concentration of the ethanol aqueous solution is 75~90%, the immersion time is not less than 30min, and the size of WS2, the concentration of the ethanol aqueous solution and the immersion time jointly affect the crystallinity of the SF@WS2 layer.

[0025] As described above, in the preparation method of a SF-based memristor with a reversible negative photoelectric effect, the immersion time is 30 to 60 minutes and the drying time is 30 to 40 minutes; within the immersion time range selected by the present invention, the crystallinity of the obtained SF@WS2 layer is relatively high, and the crystallinity of the obtained SF@WS2 layer does not change much if the immersion time is further extended.

[0026] As described above, in the preparation method of a SF-based memristor with a reversible negative photoelectric effect, spin coating of the SF@WS2 solution is divided into two stages. The spin coating speed of the first stage is 500~600rpm, and the spin coating time is 5~10s; the spin coating speed of the second stage is 2000~2500rpm, and the spin coating time is 25~30s.

[0027] In the method for preparing a SF-based memristor with a reversible negative photoelectric effect as described above, the electrode layer is deposited by thermal evaporation, electron beam evaporation or magnetron sputtering.

[0028] Principle of the invention:

[0029] The SF-based memristor of the present invention has a reversible negative photoelectric effect because the memristor functional layer is a SF@WS2 layer, and the SF@WS2 layer is a SF film doped with WS2. There are abundant sulfur vacancies in WS2, and sulfur atoms are easily separated from the lattice and migrate under the action of voltage, resulting in the formation of sulfur vacancies. In the absence of light, when a positive voltage is applied to the top electrode, positively charged sulfur vacancies (V S + ), while V S + By capturing electrons and converting them into V S , experience V S + + e - =V S reaction; however, V S + The migration rate is greater than V S The formation of V S + A large amount of accumulation occurs and a conductive connection is formed between the two electrodes, resulting in an increase in conductivity and the memristor switching from HRS to LRS. Under photoelectric synergistic stimulation, in addition to the above process, light also causes sulfur vacancies to lose electrons and transfer back to a positively charged state, resulting in V S + hv = V S + + e - reaction; at the same time, it leads to the polarization of WS2, and the reaction WS2 + hv = WS2 (e - +h +); As a result, a large number of electrons and holes are generated in the functional layer. The high concentration of carriers makes the Coulomb scattering between carriers non-negligible. The electrons generated by the polarization of WS2 can return to the electrode. At the same time, as the above reaction proceeds, the Coulomb blockade effect caused by the generation of electrons is enhanced, blocking the injection channel of electrons and inhibiting the formation of the conductive path. This causes the resistance value of the memristor to increase after exposure to light, resulting in a negative photoelectric effect. The above results show that under a single electrical stimulation, the device realizes resistance switching through the formation and breakage of the sulfur vacancy conductive channel. Once the memristor is stimulated by photoelectric synergy, a large number of charge carriers are generated, which affects the potential barrier at the interface. At the same time, the Coulomb blockade effect and electron scattering are enhanced, inhibiting the generation of the conductive channel, resulting in a higher resistance switching voltage. After the light is removed, the process of sulfur vacancies losing electrons is reduced, the number of electrons and holes generated in the functional layer is also reduced, and the reduction in carrier concentration leads to the weakening of Coulomb blockade and electron scattering, so that the formation of the conductive channel returns to normal, the original conductive state is restored, and a reversible negative photoelectric effect is achieved.

[0030] The SF-based memristor of the present invention can realize multiple stable erasing processes, because the main components of the SF solution are water, protein, amino acid and some metal ion impurities, etc., among which amino acid as an amphoteric electrolyte has the function of capturing and releasing protons, but the crystallinity of pure SF is low, resulting in poor memristive performance. The doped WS2 is a sheet structure with a nanometer size. The smaller size is conducive to the uniform dispersion of WS2 in the solution, making the prepared functional layer more uniform and smooth, and improving the performance stability of the functional layer. After adding WS2 to the SF solution, the ethanol aqueous solution is used for treatment to effectively promote SF crystallization, make the SF molecular arrangement more regular, thereby reducing leakage paths and invalid defects, improving carrier mobility, and improving the stability and durability of the device to a certain extent. In addition, the SF molecules after WS2 and ethanol post-treatment are arranged regularly, reducing the free volume of the molecules at the microscopic scale and reducing the volume of the membrane at the macroscopic scale, which is conducive to reducing the power consumption of the device and improving the ion transmission performance of the functional layer, thereby giving the device better electrical properties, such as good stability and durability, long data retention time, etc.

[0031] Beneficial effects:

[0032] (1) The SF-based memristor of the present invention can exhibit a negative photoelectric effect under light stimulation, that is, the resistance value increases, and when the light is removed, its resistance value can be restored, achieving reversibility. This feature fills the gap in the prior art that negative photoelectric memristors cannot achieve reversibility.

[0033] (2) Compared with the SF-based memristor in the prior art, the SF-based memristor of the present invention has higher cycle stability and data retention performance; by optimizing the composition and crystallinity of the SF@WS2 layer, multiple (200~300 times) stable erasing processes from a high resistance state to a low resistance state are achieved.

[0034] (3) The SF-based memristor of the present invention also has unique synaptic characteristics and synaptic learning capabilities, and can simulate the perception, processing and storage functions of human eye neurons, realizing the integrated function of sensing, storage and computing. This feature makes the SF-based memristor of the present invention have broad application prospects in the fields of bioelectronics, implantable devices, artificial vision systems and neuromorphic computing. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The resistance switching behavior of the SF-based memristor with reversible negative photoelectric effect in Example 1 at the 1st to 300th cycle (under dark conditions);

[0036] Figure 2 The SF-based memristor with reversible negative photoelectric effect of Example 1 is subjected to light intensity of 0 W / m 2 , 4.6W / m 2 、6.0W / m 2 、12.7W / m 2 The resistance switching behavior under the condition of (the arrow in the figure indicates the direction of change of the curve);

[0037] Figure 3 The SF-based memristor with reversible negative photoelectric effect of Example 1 is subjected to a light intensity of 6.0 W / m 2 The photocurrent response under light conditions (grey area is under light conditions, white area is under dark conditions). DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0039] In the following embodiments, the SF-based memristor changes from HRS to LRS and then from LRS to HRS as one cycle; the cyclic test process from HRS to LRS and then from LRS to HRS is as follows: in a dark environment, gradually increase the voltage from 0V to make the SF-based memristor change from HRS to LRS, and then gradually reduce the voltage to 0V to make the SF-based memristor change from LRS to HRS.

[0040] The following are the test methods for the relevant performance indicators in each embodiment:

[0041] Size of WS2: The WS2 dispersion was dropped onto a copper grid to prepare a sample. A JEOL JEM-2100 transmission electron microscope was used to measure the size of the WS2 material at an accelerating voltage of 200 kV.

[0042] Crystallinity: WAXD testing was carried out at the BL15U1 beamline of the Shanghai Synchrotron Radiation Source, and the test results were processed and calculated using Peakfit software.

[0043] HRS resistance, LRS resistance, and initial values ​​of the set voltage: tested using Keithley's 4200A-SCS semiconductor tester; the original resistance of the SF-based memristor is the HRS resistance; in the first cycle, the resistance of the SF-based memristor when it changes from HRS to LRS is the LRS resistance (after the first cycle, the resistance at this time is used as the reference), and the voltage at this time is the initial value of the set voltage.

[0044] Data retention time: At 25°C and 0.1MPa, the memristor characteristics of the SF-based memristor were measured in DC mode using a Keithley 4200A-SCS semiconductor tester. Under a bias voltage of 0.1V, the time for which the resistance of the SF-based memristor remained stable under LRS was measured, which was the data retention time.

[0045] Example 1

[0046] A method for preparing a SF-based memristor with a reversible negative photoelectric effect, the specific steps are as follows:

[0047] (1) Preparation of materials;

[0048] Silkworm cocoons: Origin: Guiyang City, Guizhou Province;

[0049] Na2CO3 aqueous solution: mass fraction 0.5wt%;

[0050] Deionized water;

[0051] Lithium bromide aqueous solution: concentration 9.3 mol / L;

[0052] WS2 dispersion: The manufacturer is Nanjing Xianfeng Nanomaterial Technology Co., Ltd., the concentration is 1 mg / ml, the diameter of WS2 nanosheets is 400~700nm, and the thickness is 1-10 layers;

[0053] Conductive layer: ITO film, manufactured by South China Xiangcheng Technology Co., Ltd., square resistance ≤ 6 ohms / square centimeter, thickness 185nm, transmittance ≥ 84%;

[0054] Ethanol aqueous solution: volume concentration is 80%;

[0055] Electrode layer: Ag electrode layer, thickness is 100nm;

[0056] (2) Preparation of SF@WS2 solution;

[0057] (2.1) Boil the silkworm cocoons twice in a Na2CO3 aqueous solution and wash with deionized water to obtain SF, then dissolve the SF in a lithium bromide aqueous solution, centrifuge, filter, dialyze and concentrate (at 4°C) to obtain a 2.5 wt% SF solution;

[0058] (2.2) Add WS2 dispersion to SF solution to obtain SF@WS2 solution;

[0059] (3) Preparation of SF-based memristors with reversible negative photoelectric effect;

[0060] First, SF@WS2 solution was spin-coated on the upper surface of the conductive layer at a speed of 500 rpm for 5 seconds, and then SF@WS2 solution was spin-coated on the upper surface of the conductive layer at a speed of 2500 rpm for 30 seconds. The layer was then immersed in an ethanol aqueous solution for 30 minutes and dried for 40 minutes to form a SF@WS2 layer with a thickness of 40 nm, a crystallinity of 45%, and a WS2 content of 2 wt%. Then, an electrode layer was deposited on the SF@WS2 layer by thermal evaporation to obtain a SF-based memristor with a reversible negative photoelectric effect.

[0061] The HRS resistance of the SF-based memristor with reversible negative photoelectric effect is 130Ω, the LRS resistance is 70Ω, and the initial value of the set voltage is 0.65V. The average set voltage of the SF-based memristor with reversible negative photoelectric effect from the 1st to the 300th cycle is 0.67V, and the standard deviation is 0.045V. One set voltage is obtained in each cycle, and the average set voltage and standard deviation are obtained by processing all the set voltages.

[0062] Data retention time of SF-based memristor with reversible negative photoelectric effect is 1.2×10 4 s; when the light intensity increases from 0 to 12.7W / m 2 When the light is removed, the set voltage of the SF-based memristor with reversible negative photoelectric effect increases from the initial value to 1.47V, and the resistance increases to 1100Ω; when the light is removed, the resistance of the SF-based memristor with reversible negative photoelectric effect recovers.

[0063] The resistance switching behavior of the SF-based memristor with reversible negative photoelectric effect during the 1st to 300th cycles is shown in Figure 2. Figure 1 As shown, from Figure 1It can be seen that only under electrical stimulation, the SF-based memristor with reversible negative photoelectric effect can achieve 300 stable erase and write processes, indicating that the SF-based memristor has good cycle stability.

[0064] The SF-based memristor with reversible negative photoelectric effect is exposed to light at 0W / m 2 , 4.6W / m 2 、6.0W / m 2 、12.7W / m 2 The resistance switch behavior under Figure 2 As shown, from Figure 2 It can be seen that as the light intensity increases from 0W / m 2 , 4.6W / m 2 、6.0W / m 2 Gradually increase to 12.7W / m 2 The set voltage of the SF-based memristor increases steadily from 0.65V, 0.97V, 1.19V to 1.47V. The SF-based memristor with reversible negative photoelectric effect is 2 The photocurrent response under Figure 3 As shown, from Figure 3 It can be seen that under extended light exposure time, the resistance of the SF-based memristor does not change significantly. After the light is removed, the resistance of the SF-based memristor recovers immediately. When the light is applied again, the resistance of the SF-based memristor increases immediately. After the light is removed again, the resistance of the SF-based memristor recovers immediately, indicating that the SF-based memristor has a reversible negative photoelectric effect.

[0065] Example 2

[0066] A method for preparing a SF-based memristor with a reversible negative photoelectric effect, the specific steps are as follows:

[0067] (1) Preparation of materials;

[0068] Silkworm cocoons: Origin: Guiyang City, Guizhou Province;

[0069] Na2CO3 aqueous solution: mass fraction 0.5wt%;

[0070] Deionized water;

[0071] Lithium bromide aqueous solution: concentration 9.3 mol / L;

[0072] WS2 dispersion: The manufacturer is Nanjing Xianfeng Nanomaterial Technology Co., Ltd., the concentration is 1 mg / ml, the diameter of WS2 nanosheets is 400~700nm, and the thickness is 1-10 layers;

[0073] Conductive layer: ITO film, manufactured by South China Xiangcheng Technology Co., Ltd., square resistance ≤ 6 ohms / square centimeter, thickness 185nm, transmittance ≥ 84%;

[0074] Ethanol aqueous solution: volume concentration is 85%;

[0075] Electrode layer: Al electrode layer, thickness is 100nm;

[0076] (2) Preparation of SF@WS2 solution;

[0077] (2.1) The silkworm cocoons were boiled twice in a Na2CO3 aqueous solution and washed with deionized water to obtain SF, which was then dissolved in a lithium bromide aqueous solution and centrifuged, filtered, dialyzed and concentrated (at 4°C) to obtain a 2.4 wt% SF solution;

[0078] (2.2) Add WS2 dispersion to SF solution to obtain SF@WS2 solution;

[0079] (3) Preparation of SF-based memristors with reversible negative photoelectric effect;

[0080] First, SF@WS2 solution was spin-coated on the upper surface of the conductive layer at a speed of 500 rpm for 10 seconds, and then SF@WS2 solution was spin-coated on the upper surface of the conductive layer at a speed of 2500 rpm for 30 seconds. The layer was then immersed in an ethanol aqueous solution for 30 minutes and dried for 40 minutes to form a SF@WS2 layer with a thickness of 32 nm, a crystallinity of 50%, and a WS2 content of 2 wt%. Then, an electrode layer was deposited on the SF@WS2 layer by thermal evaporation to obtain a SF-based memristor with a reversible negative photoelectric effect.

[0081] The HRS resistance of the SF-based memristor with reversible negative photoelectric effect is 125Ω, the LRS resistance is 65Ω, and the initial value of the set voltage is 0.65V; the average set voltage of the SF-based memristor with reversible negative photoelectric effect from the 1st to the 280th cycle is 0.66V, with a standard deviation of 0.05V, and a stable erase and write process of 280 times can be achieved;

[0082] Data retention time of 10 s for SF-based memristor with reversible negative photoelectric effect 4 s; when the light intensity increases from 0 to 12.7W / m 2 When the light is removed, the set voltage of the SF-based memristor with reversible negative photoelectric effect increases from the initial value to 1.41V, and the resistance increases to 1050Ω; when the light is removed, the resistance of the SF-based memristor with reversible negative photoelectric effect recovers.

[0083] Example 3

[0084] A method for preparing a SF-based memristor with a reversible negative photoelectric effect, the specific steps are as follows:

[0085] (1) Preparation of materials;

[0086] Silkworm cocoons: Origin: Tongxiang City, Zhejiang Province;

[0087] Na2CO3 aqueous solution: mass fraction 0.5wt%;

[0088] Deionized water;

[0089] Lithium bromide aqueous solution: concentration 9.3 mol / L;

[0090] WS2 dispersion: The manufacturer is Nanjing Xianfeng Nanomaterial Technology Co., Ltd., the concentration is 1 mg / ml, the diameter of WS2 nanosheets is 400~700nm, and the thickness is 1-10 layers;

[0091] Conductive layer: ITO film, manufactured by South China Xiangcheng Technology Co., Ltd., square resistance ≤ 6 ohms / square centimeter, thickness 185nm, transmittance ≥ 84%;

[0092] Ethanol aqueous solution: volume concentration is 85%;

[0093] Electrode layer: Ag electrode layer, thickness is 110nm;

[0094] (2) Preparation of SF@WS2 solution;

[0095] (2.1) The silkworm cocoons were boiled twice in a Na2CO3 aqueous solution and washed with deionized water to obtain SF, which was then dissolved in a lithium bromide aqueous solution and centrifuged, filtered, dialyzed and concentrated (at 4°C) to obtain a 2.3 wt% SF solution;

[0096] (2.2) Add WS2 dispersion to SF solution to obtain SF@WS2 solution;

[0097] (3) Preparation of SF-based memristors with reversible negative photoelectric effect;

[0098] First, SF@WS2 solution was spin-coated on the upper surface of the conductive layer at a speed of 550 rpm for 8 s, and then SF@WS2 solution was spin-coated on the upper surface of the conductive layer at a speed of 2300 rpm for 27 s. The layer was then immersed in an ethanol aqueous solution for 45 min and dried for 30 min to form a SF@WS2 layer with a thickness of 35 nm, a crystallinity of 35%, and a WS2 content of 2.5 wt%. An electrode layer was then deposited on the SF@WS2 layer using an electron beam method to obtain a SF-based memristor with a reversible negative photoelectric effect.

[0099] The HRS resistance of the SF-based memristor with reversible negative photoelectric effect is 140Ω, the LRS resistance is 75Ω, and the initial value of the set voltage is 0.7V; the average set voltage of the SF-based memristor with reversible negative photoelectric effect from the 1st to the 240th cycle is 0.72V, and the standard deviation is 0.055V, which can achieve 240 stable erase and write processes;

[0100] The data retention time of SF-based memristor with reversible negative photoelectric effect is 9.9×10 3 s; when the light intensity increases from 0 to 12.7W / m 2 When the light is removed, the set voltage of the SF-based memristor with reversible negative photoelectric effect increases from the initial value to 1.55V, and the resistance increases to 1200Ω; when the light is removed, the resistance of the SF-based memristor with reversible negative photoelectric effect recovers.

[0101] Example 4

[0102] A method for preparing a SF-based memristor with a reversible negative photoelectric effect, the specific steps are as follows:

[0103] (1) Preparation of materials;

[0104] Silkworm cocoons: Origin: Guiyang City, Guizhou Province;

[0105] Na2CO3 aqueous solution: mass fraction 0.5wt%;

[0106] Deionized water;

[0107] Lithium bromide aqueous solution: concentration is 9 mol / L;

[0108] WS2 dispersion: The manufacturer is Nanjing Xianfeng Nanomaterial Technology Co., Ltd., the concentration is 1 mg / ml, the diameter of WS2 nanosheets is 400~700nm, and the thickness is 1-10 layers;

[0109] Conductive layer: PET-ITO film, manufactured by South China Xiangcheng Technology Co., Ltd., with a square resistance of 5 ohms / square centimeter, a thickness of 0.05 mm, and a transmittance of ≥80%;

[0110] Ethanol aqueous solution: volume concentration is 85%;

[0111] Electrode layer: Ag electrode layer, thickness is 120nm;

[0112] (2) Preparation of SF@WS2 solution;

[0113] (2.1) Boil the silkworm cocoons twice in a Na2CO3 aqueous solution and wash with deionized water to obtain SF, then dissolve the SF in a lithium bromide aqueous solution, centrifuge, filter, dialyze and concentrate (at 4°C) to obtain a 3 wt% SF solution;

[0114] (2.2) Add WS2 dispersion to SF solution to obtain SF@WS2 solution;

[0115] (3) Preparation of SF-based memristors with reversible negative photoelectric effect;

[0116] First, SF@WS2 solution was spin-coated on the upper surface of the conductive layer at a speed of 500 rpm for 5 seconds, and then SF@WS2 solution was spin-coated on the upper surface of the conductive layer at a speed of 2000 rpm for 25 seconds. The layer was then immersed in an ethanol aqueous solution for 30 minutes and dried for 35 minutes to form a SF@WS2 layer with a thickness of 40 nm, a crystallinity of 40%, and a WS2 content of 5 wt%. Then, an electrode layer was deposited on the SF@WS2 layer by magnetron sputtering to obtain a SF-based memristor with a reversible negative photoelectric effect.

[0117] The HRS resistance of the SF-based memristor with reversible negative photoelectric effect is 200Ω, the LRS resistance is 90Ω, and the initial value of the set voltage is 0.9V. The average set voltage of the SF-based memristor with reversible negative photoelectric effect from the 1st to the 200th cycle is 0.92V, and the standard deviation is 0.065V, which can achieve a stable erase and write process of 200 times.

[0118] Data retention time of SF-based memristor with reversible negative photoelectric effect is 1.01×10 4 s; when the light intensity increases from 0 to 12.7W / m 2 When the light is removed, the set voltage of the SF-based memristor with reversible negative photoelectric effect increases from the initial value to 1.8V, and the resistance increases to 1700Ω; when the light is removed, the resistance of the SF-based memristor with reversible negative photoelectric effect recovers.

[0119] Example 5

[0120] A method for preparing a SF-based memristor with a reversible negative photoelectric effect, the specific steps are as follows:

[0121] (1) Preparation of materials;

[0122] Silkworm cocoons: Origin: Tongxiang City, Zhejiang Province;

[0123] Na2CO3 aqueous solution: mass fraction 0.5wt%;

[0124] Deionized water;

[0125] Lithium bromide aqueous solution: concentration is 9 mol / L;

[0126] WS2 dispersion: The manufacturer is Nanjing Xianfeng Nanomaterial Technology Co., Ltd., the concentration is 1 mg / ml, the diameter of WS2 nanosheets is 400~700nm, and the thickness is 1-10 layers;

[0127] Conductive layer: PET-ITO film, manufactured by South China Xiangcheng Technology Co., Ltd., with a square resistance of 5 ohms / square centimeter, a thickness of 0.05 mm, and a transmittance of ≥80%;

[0128] Ethanol aqueous solution: volume concentration is 90%;

[0129] Electrode layer: Al electrode layer, thickness is 120nm;

[0130] (2) Preparation of SF@WS2 solution;

[0131] (2.1) Boil the silkworm cocoons twice in a Na2CO3 aqueous solution and wash with deionized water to obtain SF, then dissolve the SF in a lithium bromide aqueous solution, centrifuge, filter, dialyze and concentrate (at 4°C) to obtain a 2 wt% SF solution;

[0132] (2.2) Add WS2 dispersion to SF solution to obtain SF@WS2 solution;

[0133] (3) Preparation of SF-based memristors with reversible negative photoelectric effect;

[0134] First, SF@WS2 solution was spin-coated on the upper surface of the conductive layer at a speed of 600 rpm for 10 s, and then SF@WS2 solution was spin-coated on the upper surface of the conductive layer at a speed of 2500 rpm for 30 s. The layer was then immersed in an ethanol aqueous solution for 60 min and dried for 40 min to form a SF@WS2 layer with a thickness of 35 nm, a crystallinity of 40%, and a WS2 content of 3 wt%. Then, an electrode layer was deposited on the SF@WS2 layer by thermal evaporation to obtain a SF-based memristor with a reversible negative photoelectric effect.

[0135] The HRS resistance of the SF-based memristor with reversible negative photoelectric effect is 180Ω, the LRS resistance is 80Ω, and the initial value of the set voltage is 0.75V; the average set voltage of the SF-based memristor with reversible negative photoelectric effect from the 1st to the 210th cycle is 1V, and the standard deviation is 0.055V, which can achieve 210 stable erase and write processes;

[0136] Data retention time of 10 s for SF-based memristor with reversible negative photoelectric effect 4 s; when the light intensity increases from 0 to 12.7W / m 2When the light is removed, the set voltage of the SF-based memristor with reversible negative photoelectric effect increases from the initial value to 1.65V, and the resistance increases to 1300Ω; when the light is removed, the resistance of the SF-based memristor with reversible negative photoelectric effect recovers.

[0137] Example 6

[0138] A method for preparing a SF-based memristor with a reversible negative photoelectric effect is basically the same as that of Example 5, except that: in step (3), there is no immersion in an ethanol aqueous solution, and the crystallinity of the SF@WS2 layer is 32%.

[0139] The HRS resistance of the SF-based memristor with reversible negative photoelectric effect is 200Ω, and the initial value of the set voltage is 0.9V. The average set voltage of the SF-based memristor with reversible negative photoelectric effect from the 1st to the 210th cycle is 0.77V, with a standard deviation of 0.2V, and a stable erase and write process of 210 times can be achieved.

[0140] Data retention time of SF-based memristor with reversible negative photoelectric effect is 8×10 3 s; when the light intensity increases from 0 to 12.7W / m 2 When the light is removed, the set voltage of the SF-based memristor with reversible negative photoelectric effect increases from the initial value to 1.62V, and the resistance increases to 1200Ω; when the light is removed, the resistance of the SF-based memristor with reversible negative photoelectric effect recovers.

Claims

1. A SF-based memristor with reversible negative photoelectric effect, characterized in that: It is composed of an electrode layer, a memristor functional layer and a conductive layer in sequence, wherein the memristor functional layer is a SF@WS2 layer, and the SF@WS2 layer is a SF film doped with WS2; The content of WS2 in the SF@WS2 layer is 1-5wt%, and the crystallinity of the SF@WS2 layer is 35-50%; When the light intensity increases from 0 to 12.7W / m 2 When the light is on, the set voltage of the SF-based memristor with a reversible negative photoelectric effect increases, and the resistance value also increases; when the light is removed, the resistance value of the SF-based memristor with a reversible negative photoelectric effect recovers.

2. The SF-based memristor with reversible negative photoelectric effect according to claim 1, characterized in that: Data retention time of SF-based memristor with reversible negative photoelectric effect is greater than 8×10 3 s, the average set voltage of the 1st to mth cycles is 0.66~1V, the standard deviation is 0.045~0.2V, and m is 200~300.

3. The SF-based memristor with reversible negative photoelectric effect according to claim 1, characterized in that: The thickness of the electrode layer is 100-120 nm, the thickness of the SF@WS2 layer is 30-40 nm, and the thickness of the conductive layer is 185 nm-0.05 mm; The electrode layer is an Ag or Al electrode layer, and the conductive layer is an ITO or PET-ITO film.

4. A method for preparing a SF-based memristor with a reversible negative photoelectric effect, characterized in that: After spin coating the SF@WS2 solution on the upper surface of the conductive layer, drying it to form a SF@WS2 layer, and then depositing the electrode layer, a SF-based memristor with a reversible negative photoelectric effect is obtained, wherein the SF@WS2 solution is obtained by adding WS2 dispersion to the SF solution.

5. The method for preparing a SF-based memristor with a reversible negative photoelectric effect according to claim 4, characterized in that: After the SF@WS2 solution was spin-coated on the upper surface of the conductive layer and before drying, it was immersed in an ethanol aqueous solution.

6. The method for preparing a SF-based memristor with a reversible negative photoelectric effect according to claim 5, characterized in that: The content of WS2 in the SF@WS2 layer is 1-5wt%, and the concentration of the SF solution is 2.0-3.0wt%; WS2 is a nanoscale flaky structure, the diameter of WS2 is 400-700nm, the volume concentration of the ethanol aqueous solution is 75-90%, and the immersion time is not less than 30min.

7. The method for preparing a SF-based memristor with a reversible negative photoelectric effect according to claim 6, characterized in that: The soaking time is 30 to 60 minutes, and the drying time is 30 to 40 minutes.

8. The method for preparing a SF-based memristor with a reversible negative photoelectric effect according to claim 7, characterized in that: Spin coating of SF@WS2 solution is divided into two stages. The spin coating speed of the first stage is 500-600 rpm, and the spin coating time is 5-10 s; the spin coating speed of the second stage is 2000-2500 rpm, and the spin coating time is 25-30 s.

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