Artificial visual memory device with selective memory and method of making and use thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TIANJIN UNIV
- Filing Date
- 2022-11-16
- Publication Date
- 2026-06-09
Smart Images
Figure CN115835653B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of artificial vision technology, specifically relating to an artificial visual memory device with selective memory, its preparation method, and its application. Background Technology
[0002] Humans acquire a vast amount of information from the external environment daily, with 80% of this information perceived through the retina, highlighting the crucial role of vision in human life. This has led to increasing research into artificial vision systems, which form the basis for the development of artificial intelligence and amorphous electronics. Artificial vision systems generally require photoreceptors and neuromorphic devices, consistent with the human visual system. In visual processing, optical information is first captured by the retina, converting light signals into electrical signals. Subsequently, the optic nerve transmits the information to the cerebral cortex cells in the form of electrical or chemical signals. Finally, humans respond specifically to the optical information.
[0003] In recent years, simulating artificial vision devices with sensing, processing, and memory functions has become a research hotspot. However, while currently developed optical image sensors can quickly sense and process information to some extent, this process generates a large amount of redundant information and consumes a lot of energy. Single-function photoelectric detection devices can only recognize information and cannot perform memory functions. Single-function storage devices, although capable of storing information, have poor adjustment capabilities and cannot perform processing functions, thus generating a large amount of useless information and wasting storage space. If artificial vision devices could identify the importance of information and decide whether to store it, thus performing preprocessing of signal information, this would greatly reduce the space occupied by unimportant information, while improving preprocessing efficiency and reducing energy consumption. Summary of the Invention
[0004] To address the shortcomings of existing technologies, the present invention aims to provide an artificial visual memory device with selective memory. The PMMA layer of this artificial visual memory device, acting as a tunneling layer, can control the slow capture of charge, thereby controlling the amount of charge captured. This allows for control of the growth of the source-drain current, representing the memory level, thus simulating human selective memory. It possesses a very strong source-drain current regulation capability, realizing transient, short-term, and long-term memory. It simulates the selective memory of human vision: transient memory is activated when the matter is unimportant, short-term memory is activated when the matter is slightly important, and long-term memory is activated when the matter is very important.
[0005] Another object of the present invention is to provide a method for preparing the above-mentioned artificial visual memory device with selective memory.
[0006] Another object of the present invention is to provide the application of the above-mentioned PMMA layer as a tunneling layer to regulate source leakage current.
[0007] The objective of this invention is achieved through the following technical solution.
[0008] An artificial visual memory device with selective memory includes: a substrate, a PMMA layer, an organic semiconductor layer, a source, and a drain. The PMMA layer covers the substrate, the organic semiconductor layer covers the PMMA layer, the source and drain are spaced apart and both located on the organic semiconductor layer, and the thickness of the PMMA layer is at least 4 nm.
[0009] In the above technical solution, the thickness of the PMMA layer is 4-100 nm, preferably 4-15 nm, and the thickness of the organic semiconductor layer is 8-12 nm.
[0010] In the above technical solution, the substrate is a silicon wafer loaded with a silicon dioxide layer, and the silicon dioxide layer is located on the side of the substrate used for connection with the PMMA layer.
[0011] The method for fabricating the above-mentioned artificial visual memory device includes the following steps:
[0012] 1) A two-dimensional molecular crystal is transferred onto a controlled charge trapping number substrate to form an organic semiconductor layer on the controlled charge trapping number substrate, wherein the controlled charge trapping number substrate is a substrate covered with the PMMA layer, and the method for preparing the controlled charge trapping number substrate is: coating PMMA on the substrate to obtain a PMMA layer on the substrate;
[0013] In step 1), the method of coating PMMA on the substrate is as follows: PMMA and a first solvent are mixed to obtain a coating solution, the coating solution is coated on the substrate, and annealed at 100-120°C for 1-2 hours.
[0014] In the above technical solution, the coating is spin coating.
[0015] In the above technical solution, the spin coating speed is 2500-3500 r / min, and the spin coating time is 30-40 s.
[0016] In the above technical solution, the first solvent is chlorobenzene, and the concentration of PMMA in the coating solution is 1-20 mg / mL.
[0017] In step 1), the substrate is cleaned with oxygen plasma at a power of 80-90W for 10-15 minutes before coating.
[0018] In step 1), the organic semiconductor layer is a two-dimensional molecular crystal with a thickness of 2 to 3 molecules.
[0019] In the above technical solution, the method for preparing the two-dimensional molecular crystal is as follows: an organic semiconductor, a surfactant, and a second solvent are mixed to obtain an organic semiconductor solution, the organic semiconductor solution is dropped onto glycerol as a liquid substrate, and after the second solvent evaporates, a two-dimensional molecular crystal is formed on the liquid surface of the glycerol.
[0020] In step 1), the method for transferring the two-dimensional molecular crystal onto the controlled charge capture number substrate is as follows: the PMMA layer of the controlled charge capture number substrate is oriented toward and in contact with the two-dimensional molecular crystal on the liquid surface of glycerol, so that the two-dimensional molecular crystal adheres to the PMMA layer, and the glycerol on the surface of the two-dimensional molecular crystal is rinsed with water.
[0021] In the above technical solution, the concentration of the organic semiconductor in the organic semiconductor solution is 0.5 mg / mL, the second solvent is chlorobenzene, the organic semiconductor is 2,6-bis(4-octylphenyl)-dithieno[3,2-b:2',3'-d]thiophene (DTT-8), the surfactant is tetrabutylammonium bromide (TBAB), and the ratio of the organic semiconductor to the surfactant is 1:2 by mass.
[0022] In the above technical solution, the evaporation time of the second solvent is at least 12 hours.
[0023] In the above technical solution, the temperature of the atmospheric environment in which the two-dimensional molecular crystal is formed is 16℃.
[0024] In the above technical solution, the volume of the organic semiconductor solution is 50 μL.
[0025] 2) A source and a drain are disposed on the organic semiconductor layer.
[0026] The aforementioned PMMA layer is used as a tunneling layer to regulate source leakage current.
[0027] The advantages of this invention are:
[0028] 1. The preparation method of this invention has the advantages of simple and efficient design, inexpensive raw materials, and low synthesis cost; it also has high universality and good reproducibility.
[0029] 2. The artificial visual memory device with selective memory obtained by this invention has good field-effect performance, good photoresponse performance, good photosynaptic performance and good photomemory performance, high repeatability and good stability.
[0030] 3. The artificial visual memory device with selective memory prepared by the present invention can realize the switching of different working modes, and can realize three modes: instantaneous memory, short-term memory and long-term memory. Attached Figure Description
[0031] Figure 1 The thickness (a) and mean square roughness (b) of the PMMA layer obtained in Example 1 are shown.
[0032] Figure 2 An optical microscope is used to transfer two-dimensional molecular crystals onto a substrate with controlled charge trapping quantity. In the image, a is an optical microscope image, b is a polarization optical microscope image, and c is a polarization optical microscope image after being rotated 45°.
[0033] Figure 3 XRD image of a two-dimensional molecular crystal;
[0034] Figure 4 AFM images of the thickness and roughness of a two-dimensional molecular crystal;
[0035] Figure 5 TEM (inset) and selected electron diffraction images of two-dimensional molecular crystals;
[0036] Figure 6 A photograph of an artificial visual memory device with selective memory;
[0037] Figure 7 A schematic diagram of the structure of an artificial visual memory device with selective memory;
[0038] Figure 8 The transfer characteristic curve of an artificial visual memory device with selective memory;
[0039] Figure 9 The diagram shows the structure and photoresponse performance of an artificial visual memory device with selective memory. In the diagram, a is the structural diagram of the artificial visual memory device under ultraviolet light pulse stimulation, b is the transfer curve of the artificial visual memory device under stimulation of different light intensities, c is the threshold voltage of the artificial visual memory device under stimulation of different light intensities, d is the photosensitivity of the artificial visual memory device under stimulation of different light intensities and different gate voltages, e is the photoresponsivity of the artificial visual memory device under stimulation of different light intensities and different gate voltages, and f is the specific detectivity of the artificial visual memory device under stimulation of different light intensities and different gate voltages.
[0040] Figure 10The image shows the photosynaptic performance of an artificial visual memory device with selective memory, where a is the EPSC response, b is the PPF response, c is the PPF exponent under different time intervals of continuous light pulse stimulation, d is the source-drain current under different number of light stimulations, e is the source-drain current under different light intensity stimulations, and f is the source-drain current under different light duration stimulations.
[0041] Figure 11 For the source and drain current of artificial visual memory devices with selective memory;
[0042] Figure 12 For the source and drain current of artificial visual memory devices with selective memory;
[0043] Figure 13 For the source and drain current of artificial visual memory devices with selective memory;
[0044] Figure 14 For the source and drain current of artificial visual memory devices with selective memory;
[0045] Figure 15 The diagram shows (a) a schematic diagram of the device in Example 2, (b) a transfer curve, and (c) a curve showing the change of source and drain current over time.
[0046] Figure 16 The following are the parameters of the artificial visual memory device in Example 3: (a) thickness of the PMMA layer, (b) mean square roughness of the PMMA layer, (c) transfer curve, and (d) source-drain current variation curve over time.
[0047] Figure 17 The following are the parameters of the artificial visual memory device in Example 4: (a) thickness of the PMMA layer, (b) mean square roughness of the PMMA layer, (c) transfer curve, and (d) source-drain current variation curve over time.
[0048] Figure 18 The following are the parameters of the artificial visual memory device in Example 5: (a) thickness of the PMMA layer, (b) mean square roughness of the PMMA layer, (c) transfer curve, and (d) source-drain current variation curve over time.
[0049] Figure 19 The following are the parameters of the artificial visual memory device in Example 6: (a) thickness of the PMMA layer, (b) mean square roughness of the PMMA layer, (c) transfer curve, and (d) source-drain current variation curve over time.
[0050] Figure 20 The following are the parameters of the artificial visual memory device in Example 7: (a) thickness of the PMMA layer, (b) mean square roughness of the PMMA layer, (c) transfer curve, and (d) source-drain current variation curve over time.
[0051] Figure 21 This refers to the number of light exposures required for artificial visual memory devices with different PMMA thicknesses to achieve the same source-leakage current level under the same light intensity. Detailed Implementation
[0052] The technical solution of the present invention will be further described below with reference to specific embodiments.
[0053] The drug purchase sources in the following examples are as follows:
[0054] (2,6-Di(4-octylphenyl)-dithiopheno[3,2-b:2',3'-d]thiophene)(DTT-8), purity: >99%, purchased from Shanghai Daran Chemical Co., Ltd.
[0055]
[0056] PMMA (polymethyl methacrylate), purity: Mw~120000, purchased from Sigma-Aldrich.
[0057]
[0058] Octadecyltrichlorosilane (OTS), purity: >99%, purchased from Sigma-Aldrich.
[0059] Chlorobenzene, purity: >99%, purchased from Sigma-Aldrich.
[0060] Acetone, purity: analytical grade, purchased from: Tianjin Jiangtian Chemical Co., Ltd.
[0061] Isopropanol, purity: analytical grade, purchased from: Tianjin Kemeo Chemical Reagent Co., Ltd.
[0062] n-Hexane, purity: analytical grade, purchased from: Lianyungang Bohua (Shanghai) Pharmaceutical Chemicals Co., Ltd.;
[0063] Chloroform, purity: analytical grade, purchased from Tianjin Jiangtian Chemical Co., Ltd.
[0064] Silicon wafer: A silicon dioxide layer is loaded on the silicon wafer (area: 4cm²). 2 The silicon dioxide layer is 300nm thick and was purchased from the 46th Research Institute of China Electronics Technology Group Corporation.
[0065] Oxygen plasma cleaner: Zepto 116457, Germany.
[0066] The silicon wafers described below should be cleaned before use. The cleaning steps include: sequentially sonicating with water, acetone, and isopropanol for 10 minutes each, and then drying the silicon wafers with a nitrogen gun.
[0067] Example 1
[0068] like Figure 7 As shown, an artificial visual memory device with selective memory includes: a substrate, a PMMA layer, an organic semiconductor layer, a source, and a drain. The PMMA layer covers the substrate, the organic semiconductor layer covers the PMMA layer, and the source and drain are spaced apart and both located on the organic semiconductor layer. The PMMA layer has a thickness of 10.8 nm, the organic semiconductor layer has a thickness of 9.52 nm, and the substrate is a silicon wafer loaded with a silicon dioxide layer, the silicon dioxide layer being located on the side of the substrate used for connection with the PMMA layer.
[0069] The organic semiconductor layer serves as both a charge transport layer and a photosensitive layer, while the PMMA layer functions as both a tunneling layer and a barrier layer.
[0070] The method for fabricating the artificial visual memory device in Example 1 includes the following steps:
[0071] 1) Preparation of two-dimensional molecular crystals: The method for preparing two-dimensional molecular crystals is as follows: an organic semiconductor, a surfactant, and a second solvent are mixed and sonicated for 20 min to obtain an organic semiconductor solution. 25 mL of glycerol is placed in a weighing bottle with a diameter of 60 mm and a height of 30 mm. 50 μL of the organic semiconductor solution is slowly dropped onto the glycerol as a liquid substrate using a pipette. After waiting for 12 h in an atmospheric environment, the second solvent evaporates, and two-dimensional molecular crystals are formed on the surface of the glycerol. The concentration of the organic semiconductor in the organic semiconductor solution is 0.5 mg / mL, the second solvent is chlorobenzene, the organic semiconductor is 2,6-bis(4-octylphenyl)-dithiophene[3,2-b:2',3'-d]thiophene (DTT-8), and the surfactant is tetrabutylammonium bromide (TBAB). The ratio of organic semiconductor to surfactant by mass is 1:2. The atmospheric temperature for forming two-dimensional molecular crystals is 16 °C.
[0072] Two-dimensional molecular crystals are transferred onto a controlled charge capture number substrate, which serves as an organic semiconductor layer. The controlled charge capture number substrate is a substrate covered with a PMMA layer. The method for preparing the controlled charge capture number substrate is as follows: PMMA and chlorobenzene as the first solvent are mixed and stirred at 70°C and 1000 r / min for 12 h. The mixture is then filtered through a 220 μm filter to obtain a coating solution with a PMMA concentration of 3 mg / mL. The substrate is then cleaned with oxygen plasma at 80 W power for 10 min to facilitate the formation of more Si-OH bonds, which serve as charge capture centers. 50 μL of the coating solution is dropped onto the substrate and allowed to stand for 10 s. The substrate is then spin-coated at 3000 r / min for 30 s and annealed at 120°C in a vacuum drying oven for 2 h to evaporate the first solvent, resulting in a PMMA layer on the substrate, thus obtaining the controlled charge capture number substrate.
[0073] The method for transferring a two-dimensional molecular crystal onto a controlled charge capture number substrate is as follows: the PMMA layer of the controlled charge capture number substrate is inverted onto the two-dimensional molecular crystal with the liquid surface of glycerol facing it. The PMMA layer contacts the two-dimensional molecular crystal on the liquid surface of glycerol, and the two-dimensional molecular crystal adheres to the PMMA layer. Then, the controlled charge capture number substrate is removed with tweezers, and the glycerol on the surface of the two-dimensional molecular crystal is rinsed with water.
[0074] 2) A source and a drain are set on an organic semiconductor layer. Both the source and the drain are rectangular gold electrodes of 400nm×100nm. The rectangular gold electrodes are picked up with a probe dipped in gallium indium alloy and transferred to the surface of a two-dimensional molecular crystal.
[0075] The PMMA layer obtained in Example 1 has a thickness of 10.8 nm and a mean square roughness of 0.318 nm. Figure 1 As shown.
[0076] Optical microscopes used to transfer two-dimensional molecular crystals onto substrates that control charge trapping quantity, such as... Figure 2 As shown, Figure 2 Image a is an optical microscope image of a two-dimensional molecular crystal. As can be seen from the image, the surface of the two-dimensional molecular crystal is smooth and flat, without cracks or steps, indicating that it is a high-quality crystal. Figure 2 Images b and c are polarized light microscope images of the two-dimensional molecular crystal. As can be seen from the images, when the two-dimensional molecular crystal is rotated 45°, the crystal's color changes significantly and uniformly, demonstrating its single-crystal properties. The microscope images prove that the two-dimensional molecular crystal is a high-quality single crystal.
[0077] The XRD image of the two-dimensional molecular crystal prepared in Example 1 is as follows: Figure 3As shown in the figure, “2DMCs DTT-8”, the smooth baseline and sharp diffraction peaks indicate that this two-dimensional molecular crystal has a high degree of crystallinity. Furthermore, these diffraction peaks are consistent with those reported in previous literature (Chem. Commun., 2013, 49, 6483-6485). Figure 3 The positions of the diffraction peaks of the two-dimensional molecular crystal (DTT-8) in the literature correspond one-to-one.
[0078] AFM thickness and roughness images of two-dimensional molecular crystals are shown below. Figure 4 As shown, the TEM and selected electron diffraction images of the two-dimensional molecular crystal are as follows: Figure 5 As shown. The fine structure of the two-dimensional molecular crystal was observed using a transmission electron microscope. From Figure 5 The smooth and flat surface of the crystal is clearly visible. The selected area electron diffraction pattern shows that the two-dimensional molecular crystal has highly ordered diffraction spots without any impurities, both of which prove that the two-dimensional molecular crystal is a high-quality single crystal.
[0079] Based on the above, the source and drain electrodes (channel size 400μm × 100μm; source and drain sizes are 400μm × 100μm each) need to be pre-fabricated on another silicon wafer. The fabrication method is as follows:
[0080] Step 1: Clean the silicon wafer.
[0081] Step 2: Place the silicon wafer in an oxygen plasma cleaner and clean it at 80W for 10 minutes. Dry the cleaned wafer under vacuum at 90℃ for 60 minutes. In a sealed environment, heat the wafer from 90℃ to 120℃. During this heating process, drop octadecyltrichlorosilane (OTS) around the silicon wafer (silica layer facing upwards). Maintain the temperature at 120℃ for 2 hours, then cool to room temperature (20-25℃). The ratio of the volume fraction of the sealed environment, the volume fraction of the added octadecyltrichlorosilane, and the area fraction of the silicon dioxide layer on one side of the silicon wafer is 196:1:78.5. The unit of volume fraction is cm³. 3 Volume fractions are expressed in μL, and area fractions are expressed in cm². 2 .
[0082] Step 3: The silicon wafer obtained in Step 2 is ultrasonicated with hexane, chloroform and isopropanol for 10 minutes each in sequence, and then dried with a nitrogen gun.
[0083] Step 4: Attach a circular copper metal mask to the silicon wafer. The mask has a 400nm × 100nm rectangular array of cutouts. Then, thermally deposit gold on the silicon wafer with the mask attached to form a 120nm thick gold layer. Place the silicon wafer with the mask attached into the evaporation chamber and fix it to the substrate of the evaporation chamber. Turn on the cooling circulating water-vacuum system and wait until the vacuum level in the evaporation chamber reaches 1.0 × 10⁻⁶. -6 Maintain for 30 minutes after mbar, to Au was evaporated at a rate that resulted in a Au deposition thickness of 120 nm.
[0084] The silicon wafer after thermally depositing gold was removed, and the mask on its surface was removed with tweezers to obtain a rectangular gold electrode array of 400nm×100nm.
[0085] The above-mentioned artificial visual memory device with selective memory is shown in the photograph. Figure 6 As shown.
[0086] The artificial visual memory device prepared in this embodiment was tested:
[0087] The transfer curves of an artificial visual memory device with selective memory were tested using a Keithley 4200. The transfer curves refer to the transfer curves at a fixed source-drain voltage (V). DS At -60V, the source-drain current varies with the gate voltage (V). GS The variation curve of (10~-60V). The test results are shown in Table 1. Figure 8 As shown.
[0088] Table 1
[0089]
[0090] The results above show that artificial visual memory devices with selective memory have good field-effect performance and a high on / off ratio, and therefore have high application value.
[0091] like Figure 9 As shown in Figure a, an artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. A 365nm ultraviolet light source was used to align with the artificial visual memory device, and the ultraviolet light source was turned on at 37.3μW·cm⁻¹. -2 226μW·cm -2 278μW·cm -2 and 334 μW·cm -2 Irradiate with light intensity and test its transfer curve. For example... Figure 9 As shown in Figure b, with the increase of laser power intensity, the transfer curve shifts upward, the source-drain current increases, and the threshold voltage shifts in the positive direction. Under illumination conditions, such as Figure 9As shown in c, the maximum threshold voltage variation can reach 36V. Figure 9 As shown in d, the maximum photosensitivity (P) can reach 1×10 7 ,like Figure 9 As shown in e, the maximum photoresponsivity (R) can reach 450 AW. -1 ,like Figure 9 As shown in f, the maximum specific detectivity (D) * Up to 7×10 15 These data demonstrate that artificial visual memory devices with selective memory possess excellent light response characteristics, forming the basis for simulating the human visual system.
[0092] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. A 365nm ultraviolet light source was aimed at the artificial visual memory device, and the ultraviolet light source was turned on at 42.35μW·cm⁻¹. -2 After being exposed to ultraviolet light for 1 second, the illumination is turned off. During this process, the artificial visual memory device generates typical excitatory postsynaptic currents (EPSCs) under ultraviolet light irradiation, such as... Figure 10 As shown in a (the time range for turning on the ultraviolet light source is as follows) Figure 10 (The time corresponding to the bulge of the upper curve in a). Figure 10 Figure 'a' illustrates that the artificial visual memory device generates typical excitatory postsynaptic currents under ultraviolet light irradiation. When light shines on the artificial visual memory device, the current can be seen to rise rapidly, and then slowly decay after the light stimulus is removed.
[0093] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. A 365nm ultraviolet light source was aimed at the artificial visual memory device, and the ultraviolet light source was turned on at 42.35μW·cm⁻¹. -2 The light source was irradiated for 1 second and then turned off. After 10 seconds, the ultraviolet light source was turned on again at 42.35 μW·cm⁻¹. -2 The light intensity is applied for 1 second and then turned off. During this process, the artificial visual memory device generates typical excitatory postsynaptic currents under ultraviolet light irradiation, such as... Figure 10 As shown in b (the time range for turning on the ultraviolet light source is as follows) Figure 10 (The time corresponding to the bulge of the upper part of curve b). Figure 10 Figure b illustrates the paired pulse facilitation (PPF) behavior of an artificial visual memory device stimulated by two identical consecutive light pulses.
[0094] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. A 365nm ultraviolet light source was aimed at the artificial visual memory device, and the ultraviolet light source was turned on at 42.35μW·cm⁻¹. -2The light source was irradiated for 1 second and then turned off. After t1 seconds, the ultraviolet light source was turned on again at 42.35 μW·cm⁻¹. -2 The light intensity was irradiated for 1 second and then turned off, with t1 = 1, 2, 6, 8, 10, 20, and 50 seconds. The PPF index for different t1 values is as follows: Figure 10 As shown in c, Figure 10 Figure c shows the PPF index under different time intervals of continuous light pulse stimulation. It can be seen that the larger the time interval, the smaller the PPF index, which is similar to the human memory pattern.
[0095] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. A 365nm ultraviolet light source was aimed at the artificial visual memory device, and the ultraviolet light source was turned on at 42.35μW·cm⁻¹. -2 The device is exposed to light of intensity C times, each lasting 1 second, with an interval of 5 seconds between adjacent exposures. Where C = 10, 20, and 30. The source-drain current of the artificial visual memory device under different light exposure times is as follows: Figure 10 As shown in d.
[0096] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. A 365nm ultraviolet light source was aimed at the artificial visual memory device, and the ultraviolet light source was turned on at 42.35μW·cm⁻¹. -2 ( Figure 10 10% of e), 226 μW·cm -2 ( Figure 10 30% of e), 278 μW·cm -2 ( Figure 10 50% of e) and 334 μW·cm -2 ( Figure 10 Irradiation for 1 second with 70% of the light intensity of e. The source and drain currents of artificial visual memory devices under different light intensities are as follows: Figure 10 As shown in e.
[0097] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. A 365nm ultraviolet light source was aimed at the artificial visual memory device, and the ultraviolet light source was turned on at 42.35μW·cm⁻¹. -2 The light intensity was applied for 1s, 2s, 3s, 4s, and 5s, respectively. The source and drain currents of the artificial visual memory device under different illumination times are as follows: Figure 10 As shown in f.
[0098] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. Under atmospheric conditions at 20°C, a 365nm ultraviolet light source was used to align with the device, with the light source turned on at 42.35 μW·cm⁻¹. -2 After 10 seconds of illumination with light intensity, the source and leakage currents of the artificial visual memory device after 10 seconds of illumination are as follows: Figure 11 As shown. Figure 11 As shown, this artificial visual memory device with selective memory exhibits long-term memory behavior under ultraviolet light irradiation, with a memory time of up to 12,000 seconds, thus realizing the important function of memory in artificial visual systems.
[0099] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. Under atmospheric conditions at 20°C, a 365nm ultraviolet light source was used to align the device with the light source at 15.5 μW·cm⁻¹. -2 The device was exposed to light of varying intensity multiple times, with each exposure lasting 1 second and an interval of 5 seconds between adjacent exposures. During the test, the source and leakage currents of the artificial visual memory device were as follows: Figure 12 As shown, artificial visual memory devices exhibit different memory modes under varying degrees of ultraviolet light irradiation, namely transient response, short-term memory, and long-term memory. (Transient response is defined as the source-drain current decaying to 90-100% of the maximum current. Short-term memory is defined as the source-drain current decaying to 10-90% of the maximum current. Long-term memory is defined as the source-drain current decaying to 0-10% of the maximum current.)
[0100] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. Under atmospheric conditions at 20°C, a 365nm ultraviolet light source was used to test the source-leakage current of the device. The ultraviolet light source was turned on at 15.5 μW·cm⁻¹. -2 Irradiate with light intensity for 5 seconds, and after the source-leakage current decays to 0, turn on the ultraviolet light source at 37.3 μW·cm⁻¹. -2 Irradiate with light intensity for 5 seconds, and after the source-leakage current decays to 0, turn on the ultraviolet light source at 42.35 μW·cm⁻¹. -2 Irradiation intensity was applied for 5 seconds. During this process, the source and leakage currents of the artificial visual memory device were as follows: Figure 13 As shown. Figure 13As shown, the artificial visual memory device exhibits three different operating modes under ultraviolet light pulse stimulation: optical switching, optical synapse, and optical memory. When the light intensity is low, the source-drain current level is low, and the decay rate is the fastest, with complete decay occurring in 96 seconds. When the light intensity is moderate, the source-drain current level is high, and the decay rate is slower, taking 1142 seconds to completely decay. When the light intensity is high, the source-drain current level is high, and it has not completely decayed even after 3837 seconds.
[0101] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. Under atmospheric conditions at 20°C, a 365nm ultraviolet light source was used to target the artificial visual memory device. The following operation was performed 10 times, with a +30V gate voltage applied after each operation to erase the device. Each operation consisted of: turning on the ultraviolet light source at 15.5μW·cm⁻¹. -2 The device is exposed to light at the specified intensity 20 times, with each exposure lasting 5 seconds and an interval of 10 seconds between each exposure. During this process, the source-drain current of the artificial visual memory device is as follows: Figure 14 As shown. Figure 14 As shown, the artificial visual memory device with selective memory underwent ten cyclic tests under three working modes, showing almost no degradation and demonstrating good cyclic stability.
[0102] Example 2
[0103] A device is fabricated using a method essentially the same as that in Example 1, except that this example does not include a PMMA layer; instead, an organic semiconductor layer is directly fabricated on the substrate, and its structure is as follows. Figure 15 As shown in a.
[0104] Tests revealed that the threshold voltage of the device's transfer curve shifted positively, indicating that electrons were being captured by the substrate. Figure 15 As shown in b.
[0105] The device was mounted on a Keithley 4200 probe stage and, under atmospheric conditions at 20°C, irradiated 10 times with a 365nm ultraviolet light source. Each irradiation consisted of the following steps: the ultraviolet light source was turned on at 15.5 μW·cm⁻¹. -2 The device was exposed to light at the same intensity for 5 seconds. The interval between any two consecutive exposures was 10 seconds. Under the same light intensity, the device exhibited only optical storage characteristics, such as... Figure 15 As shown in c.
[0106] Example 3
[0107] An artificial visual memory device is prepared in a manner that is basically the same as that in Example 1, except that the thickness of the PMMA layer is 2.5 nm and the concentration of PMMA in the coating solution is 0.5 mg / mL.
[0108] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. Under atmospheric conditions at 20°C, the device was irradiated 10 times with a 365nm ultraviolet light source. Each irradiation cycle consisted of: the ultraviolet light source being turned on at 15.5 μW·cm⁻¹. -2 The device was exposed to light at the same intensity for 5 seconds, with a 10-second interval between each subsequent exposure. Tests revealed that under the same light intensity, the device only exhibited optical storage characteristics, such as... Figure 16 As shown in d. The thickness of the PMMA layer, the mean square roughness of the PMMA layer, and the transfer curve are shown in Figure d. Figure 16 As shown in a, b, and c.
[0109] Example 4
[0110] An artificial visual memory device is prepared in a manner that is basically the same as that in Example 1, except that the thickness of the PMMA layer is 4 nm and the concentration of PMMA in the coating solution is 1 mg / mL.
[0111] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. Under atmospheric conditions at 20°C, the device was irradiated 10 times with a 365nm ultraviolet light source. Each irradiation cycle consisted of: the ultraviolet light source being turned on at 15.5 μW·cm⁻¹. -2 The device was exposed to light of high intensity for 5 seconds, with a 10-second interval between each subsequent exposure. Tests revealed that under the same light intensity, the artificial visual memory device exhibited photosynaptic and optical storage characteristics, such as… Figure 17 As shown in d. The thickness of the PMMA layer, the mean square roughness of the PMMA layer, and the transfer curve are shown in Figure d. Figure 17 As shown in a, b, and c.
[0112] Example 5
[0113] An artificial visual memory device is prepared in a manner that is basically the same as that in Example 1, except that the thickness of the PMMA layer is 13.5 nm and the concentration of PMMA in the coating solution is 5 mg / mL.
[0114] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. Under atmospheric conditions at 20°C, the device was irradiated 10 times with a 365nm ultraviolet light source. Each irradiation cycle consisted of: the ultraviolet light source being turned on at 15.5 μW·cm⁻¹. -2 The device was exposed to light of high intensity for 5 seconds, with a 10-second interval between each subsequent exposure. Tests revealed that under the same light intensity, the artificial visual memory device exhibited photosynaptic and optical storage characteristics, such as… Figure 18 As shown in d. The thickness of the PMMA layer, the mean square roughness of the PMMA layer, and the transfer curve are shown in Figure d. Figure 18 As shown in a, b, and c.
[0115] Example 6
[0116] An artificial visual memory device is prepared in a manner that is basically the same as that in Example 1, except that the thickness of the PMMA layer is 28.8 nm and the concentration of PMMA in the coating solution is 10 mg / mL.
[0117] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. Under atmospheric conditions at 20°C, the device was irradiated 10 times with a 365nm ultraviolet light source. Each irradiation cycle consisted of: the ultraviolet light source being turned on at 15.5 μW·cm⁻¹. -2 The device was exposed to light of high intensity for 5 seconds, with a 10-second interval between each subsequent exposure. Tests revealed that under the same light intensity, the artificial visual memory device exhibited photosynaptic and optical storage characteristics, such as… Figure 19 As shown in d. The thickness of the PMMA layer, the mean square roughness of the PMMA layer, and the transfer curve are shown in Figure d. Figure 19 As shown in a, b, and c.
[0118] Example 7
[0119] An artificial visual memory device is prepared in a manner that is basically the same as that in Example 1, except that the thickness of the PMMA layer is 72.7 nm and the concentration of PMMA in the coating solution is 20 mg / mL.
[0120] An artificial visual memory device with selective memory was mounted on a Keithley 4200 probe stage. Under atmospheric conditions at 20°C, the device was irradiated 136 times with a 365nm ultraviolet light source. Each irradiation consisted of the following steps: the ultraviolet light source was turned on at 15.5 μW·cm⁻¹. -2 The device was exposed to light at the same intensity for 5 seconds, with a 10-second interval between each subsequent exposure. Tests revealed that under the same light intensity, the artificial visual memory device exhibited characteristics of optical switching, photosynapses, and optical storage, such as… Figure 20 As shown in d.
[0121] The artificial visual memory devices from Examples 3-7 were mounted on a Keithley 4200 probe stage. Under atmospheric conditions at 20°C, a 365nm ultraviolet light source was used to irradiate the devices multiple times until the source-leakage current reached 1*102. -7 A, where each irradiation is as follows: the ultraviolet light source is turned on at 15.5 μW·cm⁻¹.-2 Irradiation intensity was applied for 5 seconds. The interval between two consecutive irradiations was 10 seconds. Statistical analysis of examples 3-7 showed that the source-leakage current of the artificial visual memory devices under the same light intensity reached 1*102. -7 The number of times A needs to be illuminated, such as Figure 21 As shown in the figure, as the thickness of the PMMA layer increases, more light is required to achieve charge capture, indicating that the PMMA layer plays a blocking role.
[0122] The transfer curves of the artificial visual memory devices with selective memory obtained in Examples 2-7 were tested using a Keithley 4200. The transfer curve refers to the curve obtained at a fixed source-drain voltage (V). DS At -60V, the source-drain current varies with the gate voltage (V). GS The variation curve of (10~-60V) is shown in Table 2. The test results are shown in Table 2.
[0123] Table 2
[0124]
[0125] This invention relates to an artificial visual memory device with three different operating modes that can be switched to meet information processing needs under different circumstances. When external information is unimportant, an instantaneous response mode can be used; when the external information is slightly important, a short-term memory mode can be used; and when the external information is very important, a long-term memory mode can be used. This allows for pre-processing of new information, reducing the storage space occupied during information processing and improving storage space utilization efficiency. This paves the way for the development of multifunctional, high-performance artificial visual memory devices.
[0126] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.
Claims
1. An artificial visual memory device with selective memory, characterized in that, include: The device comprises a substrate, a PMMA layer, an organic semiconductor layer, a source electrode, and a drain electrode. The PMMA layer covers the substrate, and the organic semiconductor layer covers the PMMA layer. The source electrode and the drain electrode are spaced apart and both located on the organic semiconductor layer. The thickness of the PMMA layer is 4~15 nm, and the thickness of the organic semiconductor layer is 8~12 nm. The organic semiconductor layer serves as a charge transport layer and a photosensitive layer, and the PMMA layer serves as a tunneling layer and a blocking layer. Artificial visual memory devices exhibit different memory modes under different numbers of ultraviolet light irradiation, namely transient response, short-term memory and long-term memory. Transient response is when the source-drain current decays to 90-100% of the maximum current, short-term memory is when the source-drain current decays to 10-90% of the maximum current, and long-term memory is when the source-drain current decays to 0-10% of the maximum current.
2. The artificial visual memory device according to claim 1, characterized in that, The substrate is a silicon wafer loaded with a silicon dioxide layer, which is located on the side of the substrate used for connection with the PMMA layer.
3. The method for preparing the artificial visual memory device according to any one of claims 1 to 2, characterized in that, Includes the following steps: 1) A two-dimensional molecular crystal is transferred onto a controlled charge trapping number substrate to form an organic semiconductor layer on the controlled charge trapping number substrate, wherein the controlled charge trapping number substrate is a substrate covered with the PMMA layer, and the method for preparing the controlled charge trapping number substrate is: coating PMMA on the substrate to obtain a PMMA layer on the substrate; 2) A source and a drain are disposed on the organic semiconductor layer.
4. The preparation method according to claim 3, characterized in that, In step 1), the method for coating PMMA on the substrate is as follows: PMMA and a first solvent are mixed to obtain a coating solution, the coating solution is coated on the substrate, and annealed at 100-120 °C for 1-2 h.
5. The preparation method according to claim 3, characterized in that, In step 1), the organic semiconductor layer is a two-dimensional molecular crystal with a thickness of 2 to 3 molecules.
6. The preparation method according to claim 4, characterized in that, The coating is spin-coating, the spin-coating speed is 2500-3500 r / min, the spin-coating time is 30-40 s, the first solvent is chlorobenzene, and the concentration of PMMA in the coating solution is 1-20 mg / mL.
7. The preparation method according to claim 4, characterized in that, In step 1), the substrate is cleaned with oxygen plasma at a power of 80-90 W for 10-15 min before coating.
8. The preparation method according to claim 3, characterized in that, The method for preparing the two-dimensional molecular crystal is as follows: an organic semiconductor, a surfactant, and a second solvent are mixed to obtain an organic semiconductor solution. The organic semiconductor solution is dropped onto glycerol, which serves as a liquid substrate. After the second solvent evaporates, a two-dimensional molecular crystal is formed on the liquid surface of the glycerol.
9. The preparation method according to claim 3, characterized in that, In step 1), the method for transferring the two-dimensional molecular crystal onto the controlled charge capture number substrate is as follows: the PMMA layer of the controlled charge capture number substrate is oriented toward and in contact with the two-dimensional molecular crystal on the liquid surface of glycerol, so that the two-dimensional molecular crystal adheres to the PMMA layer, and the glycerol on the surface of the two-dimensional molecular crystal is rinsed with water.
10. The preparation method according to claim 8, characterized in that, The concentration of the organic semiconductor in the organic semiconductor solution is 0.5 mg / mL, the second solvent is chlorobenzene, the organic semiconductor is 2,6-bis(4-octylphenyl)-dithiophene[3,2-b:2',3'-d]thiophene, the surfactant is tetrabutylammonium bromide, the ratio of the organic semiconductor to the surfactant is 1:2 by mass, the evaporation time of the second solvent is at least 12 h, and the atmospheric temperature for the formation of the two-dimensional molecular crystal is 16 ℃.