A three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires and its preparation method

Abstract

The present invention is a three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires and a preparation method thereof. The device is composed of a nanowire array distributed on a substrate, a source electrode and a drain electrode distributed at both ends of the array, and an ion glue as a gate electrode between the source electrode and the drain electrode; the preparation method first uses an electrofluidic printer to prepare ITO nanowires, which are used as channel materials for synaptic devices; then, metal electrodes are evaporated on the ITO nanowires that have been annealed at high temperature as source electrodes and drain electrodes, and finally, the ion glue is used as a gate electrode to prepare a three-terminal artificial synaptic device. The present invention has simple process, simple operation, low cost, energy saving and environmental protection, and is suitable for large-scale production, which provides useful guidance for material selection and device design in the field of neuromorphic computing.

Description

Technical Field

[0001] The invention belongs to the field of microelectronics, and specifically relates to a three-terminal artificial synapse device based on digitally controllable printed ITO nanowires and a preparation method thereof. Background Art

[0002] In the 1950s, John McCarthy proposed the concept of artificial intelligence (AI). With the successful creation of "AlphaGo", AI technology has attracted more attention. At present, the implementation of AI is still based on the von Neumann architecture, which separates computing from storage, cannot achieve parallel computing, and has high power consumption. With the advent of the era of big data and artificial intelligence, a new computing system is urgently needed to replace the von Neumann architecture.

[0003] In a complex environment, the human brain can easily identify various objects through calculations. It has lower power consumption, higher computing efficiency and fault tolerance than current digital computers. The energy required to complete cognitive tasks is only ~20W, which is equivalent to household lights. The human brain can achieve efficient and parallel computing mainly due to ~10 15 Synaptic connections ~10 11 The synapse is the link between the front and back neurons. Its connection strength (i.e., synaptic weight) can be controlled by various ions (such as Ca 2+ 、Na + and K + The concentration changes of the neurons (such as ) can be precisely regulated, and this property is called synaptic plasticity. Synaptic plasticity is an important basis for the brain to realize cognition, learning and other functions. Therefore, the development of electronic devices with neural synaptic functions (artificial synaptic devices) is of great significance to the hardware realization of neuromorphic computing systems, and then to replace the computing systems of von Neumann architecture.

[0004] In recent years, scientists have used two-terminal resistive devices (such as memristors, phase change memories, atomic switches, etc.) and three-terminal field effect transistors (such as ion / electronic hybrid synaptic transistors, ferroelectric synaptic transistors, etc.) to simulate neural synapses, all of which have achieved the functions of biological neural synapses to a certain extent. Compared with two-terminal artificial synaptic devices, three-terminal devices can simultaneously realize signal transmission and modulation. Three-terminal artificial synaptic devices based on two-dimensional materials, oxide semiconductors, organic semiconductors, etc. have been widely reported. The document "Chitosan-Based Polysaccharide-Gated Flexible Indium Tin Oxide Synaptic Transistor with Learning Abilities" (see the American academic journal "ACS Applied Materials & Interfaces" 2018, Vol. 10, pp. 16881-16886) reports a method for preparing an ITO-based three-terminal artificial synaptic device using a sputtering method. However, the sputtering method has high cost, high energy consumption, cumbersome process, and complex operation. Summary of the invention

[0005] In view of the shortcomings of current technology, the present invention proposes a three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires and a preparation method thereof. The device is composed of a nanowire array distributed on a substrate, a source and a drain are distributed at both ends of the array, and an ion glue is used as a gate between the source and the drain; the preparation method first uses an electrofluidic printer to prepare ITO nanowires, which are used as channel materials for synaptic devices; then, metal electrodes are evaporated on the ITO nanowires that have been annealed at high temperature as source and drain, and finally, the ion glue is used as a gate to prepare a three-terminal artificial synaptic device. The present invention has simple process, simple operation, low cost, energy saving and environmental protection, and is suitable for large-scale production, which provides useful guidance for material selection and device design in the field of neuromorphic computing.

[0006] The technical solution of the present invention is as follows:

[0007] A three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires, the device comprises: a nanowire array is distributed on the surface of a substrate, a metal electrode is distributed on the surfaces of both ends of the nanowire array, and an ion glue layer is attached to the nanowire array between the two metal electrodes;

[0008] The substrate is Si / SiO2, Al2O3 or glass.

[0009] The material of the nanowire array is ITO, the diameter of the nanowire is 100-6000nm, the length is 0.01-20cm, and the spacing between the nanowires is 10-2000μm.

[0010] The metal in the metal electrode is gold, silver, aluminum or titanium / gold; the thickness of the metal electrode is 60-200nm.

[0011] The ion glue is chitosan, PVA or PVDF-HFP / [EMIM][TFSI], and has a thickness of 0.05-500 μm.

[0012] The method for preparing a three-terminal artificial synaptic device based on digitally controllable printing of ITO nanowires comprises the following steps:

[0013] (1) ultrasonically cleaning the substrate with deionized water, isopropanol, acetone, and anhydrous ethanol in sequence, and then blowing the surface dry with nitrogen;

[0014] (2) adding polyvinyl pyrrolidone, indium nitrate hydrate and stannous chloride dihydrate to a mixed solvent, and magnetically stirring at 20 to 70° C. for 0.5 to 24 hours to obtain a precursor solution;

[0015] The mixed solvent is composed of N, N-dimethylformamide and anhydrous ethanol, with a mass ratio of N, N-dimethylformamide: anhydrous ethanol = 1-20:1; a mass ratio of polyvinyl pyrrolidone: indium nitrate hydrate = 1:1-4, and a mass ratio of stannous chloride dihydrate: indium nitrate hydrate = 1:1-20; the mass concentration of polyvinyl pyrrolidone in the precursor solution is 5%-20%;

[0016] (3) using an electrofluidic printer to print the precursor solution prepared in step (2) into ITO nanowires;

[0017] (4) annealing the ITO nanowires printed in step (3) at high temperature in air, and taking them out after the temperature drops to room temperature;

[0018] (5) using a mask plate, evaporating metal electrodes on the surfaces of both ends of the ITO nanowires obtained in step (4) to serve as source and drain electrodes;

[0019] (6) Using ion glue as a gate, stick it on the nanowire between the source and drain of the sample obtained in step (5) to obtain a three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires.

[0020] When printing is performed using an electrofluidic printer in step (3), a high voltage of 0.5 to 3 kV is applied to the syringe needle, the distance from the syringe needle to the substrate is set to 0.5 to 8 mm, the liquid flow rate of the syringe is set to 1 to 250 nL / min, and the moving speed of the substrate is set to 50 to 1000 mm / s.

[0021] In step (4), the printed nanowires are annealed at a temperature of 300 to 700° C. in air for 30 to 240 minutes to finally obtain ITO nanowires.

[0022] The essential features of the present invention are:

[0023] The method used in the current technology for preparing ITO-based three-terminal artificial synaptic devices is sputtering, which is costly, energy-intensive, cumbersome in process, and complex in operation. In comparison, the synaptic device prepared by the method of the present invention can achieve the same function, simulating various synaptic plasticities such as excitatory postsynaptic current (EPSC), double pulse facilitation (PPF), pulse voltage-dependent plasticity (SVDP), and pulse number-dependent plasticity (SNDP). However, the present invention has simple process, easy operation, low cost, energy conservation and environmental protection, and is suitable for large-scale production, and is of great significance in material selection and device design in the field of neuromorphic computing.

[0024] The beneficial effects of the present invention are:

[0025] The present invention uses digitally controllably printed ITO nanowires to prepare a three-terminal artificial synaptic device for the first time, and uses an electrofluidic printer to directly print ITO nanowires on a substrate as a conductive channel. The prepared synaptic device can simulate synaptic plasticity, such as excitatory postsynaptic current (EPSC), double pulse facilitation (PPF), pulse voltage-dependent plasticity (SVDP), pulse number-dependent plasticity (SNDP), pulse frequency-dependent plasticity (SFDP), etc.; the present invention obtains ITO nanowires with stable chemical properties and good photoelectric properties by reasonably controlling parameters such as precursor concentration, solute ratio, printing parameters and annealing conditions, and then prepares an ITO-based three-terminal artificial synaptic device. Compared with an ITO-based three-terminal artificial synaptic device prepared by a sputtering method, the synaptic device prepared by the method of the present invention can achieve the same function and can simulate multiple synaptic plasticities such as EPSC, PPF, SVDP and SNDP, but the present invention has simple process, simple operation, low cost, energy saving and environmental protection, and is suitable for large-scale production, which provides useful guidance for material selection and device design in the field of neuromorphic computing. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of a three-terminal artificial synapse device in the present invention;

[0027] Figure 2 is an optical microscope image of the ITO nanowires in Example 1;

[0028] Figure 3 is an optical microscope picture of the ITO nanowire array in Example 1;

[0029] Figure 4is the excitatory postsynaptic current (EPSC) of the three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires in Example 1;

[0030] Figure 5 It is the double pulse facilitation (PPF) of the three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires in Example 1;

[0031] Figure 6 The pulse voltage dependent plasticity (SVDP) of the three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires in Example 1;

[0032] Figure 7 The pulse number dependent plasticity (SNDP) of the three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires in Example 1;

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments, but is not limited thereto. DETAILED DESCRIPTION

[0034] The three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires described in the present invention is composed of: a nanowire array is distributed on the surface of a substrate, a metal electrode is distributed on the surfaces of both ends of the nanowire array, and an ion glue layer is attached to the nanowire array between the two metal electrodes.

[0035] Example 1

[0036] (1) The Si / SiO2 substrate was ultrasonically cleaned with deionized water, isopropanol, acetone, and anhydrous ethanol for 30 minutes, and then its surface was blown dry with nitrogen gas;

[0037] (2) preparing a mixed solvent by mixing two reagents in a mass ratio of N,N-dimethylformamide:anhydrous ethanol=20:1; dissolving reagents in a mass ratio of polyvinyl pyrrolidone:indium nitrate hydrate=1:1.2 and stannous chloride dihydrate:indium nitrate hydrate=1:6.5 in the mixed solvent, and stirring at 50°C for 6 hours using a magnetic stirrer to prepare a precursor solution required for printing; the mass concentration of polyvinyl pyrrolidone in the precursor solution is 10.4%;

[0038] (3) using an electrofluidic printer to print the precursor solution prepared in step (2) into ITO nanowires, wherein a high voltage of 0.65 kV is applied to the syringe needle, the distance from the syringe needle to the substrate is set to 2.5 mm, the liquid flow rate of the syringe is set to 50 nL / min, and the moving speed of the substrate is set to 250 mm / s;

[0039] (4) annealing the printed sample in step (3) at 500° C. in air for 120 min to obtain ITO nanowires;

[0040] (5) using a mask, evaporating two 80 nm thick gold electrodes spaced apart from each other on the surface of the ITO nanowires obtained in step (4) as source and drain electrodes;

[0041] (6) a poly(vinylidene fluoride-co-hexafluoropropylene) / 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide ion glue (PVDF-HFP / [EMIM][TFSI] ion glue (thickness of about 200 μm) prepared by mixing poly(vinylidene fluoride-co-hexafluoropropylene), 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide and acetone in a mass ratio of 1:4:7 is attached to the surface of the ITO nanowire between the source and the drain in the device of step (5) as a gate, thereby obtaining a three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires;

[0042] (7) Using a semiconductor analyzer, the electrical performance of the three-terminal artificial synaptic device in step (6) is tested, and the device's simulation of synaptic plasticity is explored by adjusting the input pulse voltage.

[0043] By optimizing the experimental parameters, a three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires was successfully prepared. Figure 1 It is a schematic diagram of the structure of the three-terminal artificial synaptic device in the present invention, including a substrate, an ITO nanowire channel, a metal source and drain, and an ion glue gate covered on the ITO nanowire. An electrofluid printer is used to directly print the ITO nanowire on the Si / SiO2 substrate as the conductive channel of the three-terminal artificial synaptic device, the ion glue is used as the gate, and evaporated gold is used as the source and drain of the device. Figure 2 and Figure 3 Optical microscope images of the ITO nanowires and nanowire arrays in Example 1 are shown respectively. The total length of the nanowires is about 2 cm. The figure is an enlargement of a part of the area. It can be seen that the nanowires are continuous, straight and neatly arranged, with a spacing of about 100 μm and a diameter of about 1500 nm.

[0044] Figure 4-Figure 7 The performance of synaptic devices tested using Keithley's 4200A-SCS semiconductor analyzer is demonstrated, including: Figure 4 It is the excitatory postsynaptic current (EPSC) of the three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires in Example 1 when the gate voltage is 3V and the drain voltage is 0.005V. It can be seen that when a certain pre-pulse stimulation is applied, the device can measure EPSC. Figure 5It is the double pulse facilitation (PPF) of the three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires in Example 1 when the gate voltage is 3V and the drain voltage is 0.005V. The duration of a single pulse is fixed at 50ms, and the time interval between two stimuli is 100ms. When the second stimulus is applied, the subsequent current is significantly stronger than the current generated by the first stimulus. Figure 6 It is the pulse voltage-dependent plasticity (SVDP) of the three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires in Example 1. The duration of a single pulse is fixed at 50ms, and the amplitude of the pulse is gradually increased (0.1, 0.5, 1, 1.5, 2, 2.5 and 3V). It can be seen that EPSC gradually increases with the increase of the pulse voltage amplitude. Figure 7 The pulse number-dependent plasticity (SNDP) of the three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires in Example 1 is fixed. The duration (50ms), pulse interval (50ms) and pulse amplitude (3V) of a single pulse are fixed, and the number of pulses in each group is changed (gradually increasing from 1 to 10). It can be seen that EPSC gradually increases with the increase in the number of pulses. The above data all illustrate that the three-terminal artificial synaptic device prepared by the present invention can simulate the function of biological neural synapses, that is, compared with the ITO-based three-terminal artificial synaptic device prepared by the sputtering method, the synaptic device prepared by the method of the present invention can achieve the same function, but the method of the present invention is simple in process, easy to operate, low in cost, energy-saving and environmentally friendly, and suitable for large-scale production.

[0045] Example 2

[0046] (1) The Si / SiO2 substrate was ultrasonically cleaned with deionized water, isopropanol, acetone, and anhydrous ethanol for 30 minutes, and then its surface was blown dry with nitrogen gas;

[0047] (2) preparing a mixed solvent by mixing two reagents in a mass ratio of N,N-dimethylformamide:anhydrous ethanol=10:1; dissolving reagents in a mass ratio of polyvinyl pyrrolidone:indium nitrate hydrate=1:2 and stannous chloride dihydrate:indium nitrate hydrate=1:10 in the mixed solvent, and stirring for 12 hours at 40° C. using a magnetic stirrer to prepare a precursor solution required for printing; the mass concentration of polyvinyl pyrrolidone in the precursor solution is 11%;

[0048] (3) using an electrofluidic printer to print the precursor solution prepared in step (2) into ITO nanowires, wherein a high voltage of 1.1 kV is applied to the syringe needle, the distance from the syringe needle to the substrate is set to 2 mm, the liquid flow rate of the syringe is set to 60 nL / min, and the moving speed of the substrate is set to 200 mm / s;

[0049] (4) annealing the printed sample in step (3) at 550° C. in air for 60 min to obtain ITO nanowires;

[0050] (5) using a mask, evaporating two 120 nm thick gold electrodes spaced apart from each other on the surface of the ITO nanowires obtained in step (4) as source and drain electrodes;

[0051] (6) a poly(vinylidene fluoride-co-hexafluoropropylene) / 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide ion glue (PVDF-HFP / [EMIM][TFSI] ion glue (thickness of about 200 μm) prepared by mixing poly(vinylidene fluoride-co-hexafluoropropylene), 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imide and acetone in a mass ratio of 1:4:7 is attached to the surface of the ITO nanowire between the source and the drain in the device of step (5) as a gate, thereby obtaining a three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires;

[0052] (7) Using a semiconductor analyzer, the electrical performance of the three-terminal artificial synaptic device in step (6) is tested, and the device's simulation of synaptic plasticity is explored by adjusting the input pulse voltage.

[0053] Example 3

[0054] (1) The glass substrate was ultrasonically cleaned with deionized water, isopropanol, acetone and anhydrous ethanol for 30 minutes respectively, and then the surface was blown dry with nitrogen gas;

[0055] (2) preparing a mixed solvent by mixing two reagents with a mass ratio of N,N-dimethylformamide:anhydrous ethanol=6:1; dissolving reagents with a mass ratio of polyvinyl pyrrolidone:indium nitrate hydrate=1:2 and stannous chloride dihydrate:indium nitrate hydrate=1:20 in the mixed solvent, and stirring for 12 hours at 25° C. using a magnetic stirrer to prepare a precursor solution required for printing; the mass concentration of polyvinyl pyrrolidone in the precursor solution is 9%;

[0056] (3) using an electrofluidic printer to print the precursor solution prepared in step (2) into ITO nanowires, wherein a high voltage of 1.3 kV is applied to the syringe needle, the distance from the syringe needle to the substrate is set to 4 mm, the liquid flow rate of the syringe is set to 30 nL / min, and the moving speed of the substrate is set to 500 mm / s;

[0057] (4) annealing the printed sample in step (3) at 400° C. in air for 180 min to obtain ITO nanowires;

[0058] (5) using a mask, evaporating two 120 nm thick titanium / gold electrodes spaced apart from each other on the surface of the ITO nanowires obtained in step (4) as source and drain electrodes;

[0059] (6) attaching the prepared chitosan ion glue (thickness of about 15 μm) to the surface of the ITO nanowire between the source and drain in the device of step (5) as a gate, to obtain a three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires;

[0060] (7) Using a semiconductor analyzer, the electrical performance of the three-terminal artificial synaptic device in step (6) is tested, and the device's simulation of synaptic plasticity is explored by adjusting the input pulse voltage.

[0061] Matters not covered by the present invention are known technologies.

Claims

1. A three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires, characterized by The device is composed of: a nanowire array is distributed on the surface of a substrate, a metal electrode is distributed on the surfaces of both ends of the nanowire array, and an ion glue layer is attached to the nanowire array between the two metal electrodes; The material of the nanowire array is ITO, the diameter of the nanowire is 100-6000nm, the length is 0.01-20cm, and the spacing between the nanowires is 10-2000μm; The substrate is Si / SiO2, Al2O3 or glass; The metal in the metal electrode is gold, silver, aluminum or titanium / gold; the thickness of the metal electrode is 60 to 200 nm; The ionic glue is chitosan, PVA or PVDF-HFP / [EMIM][TFSI], and has a thickness of 0.05 to 500 μm; The method for preparing a three-terminal artificial synaptic device based on digitally controllable printing of ITO nanowires comprises the following steps: (1) ultrasonically cleaning the substrate with deionized water, isopropanol, acetone, and anhydrous ethanol in sequence, and then blowing the surface dry with nitrogen; (2) adding polyvinyl pyrrolidone, indium nitrate hydrate and stannous chloride dihydrate to a mixed solvent, and magnetically stirring at 20 to 70° C. for 0.5 to 24 hours to obtain a precursor solution; The mixed solvent is composed of N, N-dimethylformamide and anhydrous ethanol, with a mass ratio of N, N-dimethylformamide: anhydrous ethanol = 1-20:1; a mass ratio of polyvinyl pyrrolidone: indium nitrate hydrate = 1:1-4, and a mass ratio of stannous chloride dihydrate: indium nitrate hydrate = 1:1-20; the mass concentration of polyvinyl pyrrolidone in the precursor solution is 5%-20%; (3) using an electrofluidic printer to print the precursor solution prepared in step (2) into ITO nanowires; (4) annealing the ITO nanowires printed in step (3) in air, and taking them out after the temperature drops to room temperature to obtain ITO nanowires; (5) using a mask plate, evaporating metal electrodes on the surfaces of both ends of the ITO nanowires obtained in step (4) to serve as source and drain electrodes; (6) using ion glue as a gate and attaching it to the nanowire between the source and drain of the sample obtained in step (5) to obtain a three-terminal artificial synaptic device based on digitally controllable printed ITO nanowires; When printing is performed using an electrofluid printer in step (3), a high voltage of 0.5 to 3 kV is applied to the syringe needle, the distance from the syringe needle to the substrate is set to 0.5 to 8 mm, the liquid flow rate of the syringe is set to 1 to 250 nL / min, and the moving speed of the substrate is set to 50 to 1000 mm / s; The annealing conditions described in step (4) are: annealing the printed nanowires at a temperature of 300 to 700° C. in air for 30 to 240 minutes.

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