Photoelectric synapses and visual units made of two-dimensional materials assisted by gas adsorption

Abstract

The present application relates to the field of semiconductor technology. The present application provides a two-dimensional material photoelectric synapse and visual unit based on gas adsorption assistance, wherein the photoelectric synapse includes a plurality of photoelectric heterojunction units arranged in an array, each of which has a Ta2NiSe5 / SnS2 structure, wherein the Ta2NiSe5 / SnS2 structure has a preset bandgap structure, and the Ta2NiSe5 / SnS2 structure enables each of the photoelectric heterojunction units to store a preset duration of photocurrent generated by the light pulse after receiving N light pulses of a preset wavelength, where N is a natural number greater than or equal to 1. The photoelectric synapse has a Ta2NiSe5 / SnS2 structure, and the Ta2NiSe5 / SnS2 structure improves the photocurrent retention performance of the photoelectric synapse by regulating the carrier transport behavior by utilizing the physical adsorption of water and oxygen molecules in the air.

Description

Technical Field

[0001] The present application relates to the field of optoelectronic technology, and in particular to a two-dimensional material optoelectronic synapse and visual unit based on gas adsorption assistance. Background Art

[0002] In recent years, the rise of brain-like computing architectures, with their outstanding characteristics such as high efficiency, low power consumption and high fault tolerance, indicates that they are expected to surpass the traditional constraints of von Neumann architecture on computing power. In application fields such as computer vision, brain-like computing circuits based on traditional silicon-based technology have shown great application potential. However, these circuits usually require multiple transistors to simulate the functions of a single neuron, and their operating wavelengths are limited, which greatly limits the progress towards higher density integration and lower power consumption operation.

[0003] Two-dimensional materials have attracted extensive attention in the field of brain-like computing devices due to their unique physical properties, excellent wide-band detection capabilities, and naturally passivated interfaces that are conducive to large-scale integration. The research and application of two-dimensional materials are developing rapidly, and their application value in electronics, optoelectronics, catalysis, energy storage, solar cells, sensors, biomedicine, etc. has also been deeply explored and important progress has been made. For example, progress in the synthesis and preparation of two-dimensional materials has laid a solid material foundation for the research and application of two-dimensional materials. In addition, breakthroughs have also been made in the large-scale preparation process of memory and transparent and flexible devices based on two-dimensional materials.

[0004] Two-dimensional materials have broad application prospects in brain-like computing. Their unique properties, such as high electron mobility, excellent mechanical flexibility and transparency, make them have great potential in manufacturing high-performance, low-power electronic devices. In particular, in the construction of neuromorphic computing systems that simulate the functions of the human brain, two-dimensional materials can be used to manufacture artificial synapses and neurons to achieve efficient information processing and learning capabilities. With the deepening of research on two-dimensional materials, they are expected to play an increasingly important role in the field of brain-like computing and promote the development of related technologies. Summary of the invention

[0005] Some embodiments of the present application provide a two-dimensional material photoelectric synapse based on gas adsorption assistance, including: a plurality of photoelectric heterojunction units arranged in an array, each of the photoelectric heterojunction units having a Ta2NiSe5 / SnS2 structure, wherein the Ta2NiSe5 / SnS2 structure has a preset band gap structure, and the Ta2NiSe5 / SnS2 structure enables each of the photoelectric heterojunction units to store a preset duration of photocurrent generated by the light pulses after receiving N light pulses of a preset wavelength, where N is a natural number greater than or equal to 1.

[0006] In some embodiments, after each of the photoelectric heterojunction units receives the Nth light pulse of a preset wavelength, the photocurrent generated by the light pulse satisfies the following relationship: ,in, represents the photocurrent intensity after the Nth light pulse ends at time T, T is the light pulse period, P represents the percentage of the photocurrent intensity reduced to the current photocurrent peak intensity after the first light pulse ends at time T, It represents the peak intensity of the photocurrent generated by each light pulse itself, and N represents the number of light pulses.

[0007] In some embodiments, the value of P ranges from 5% to 80%.

[0008] In some embodiments, the peak intensity of the photocurrent accumulated by each light pulse is greater than the peak intensity of the photocurrent accumulated by the previous light pulse.

[0009] In some embodiments, the Ta2NiSe5 / SnS2 structure includes Ta2NiSe5 flakes and SnS2 flakes, and the Ta2NiSe5 flakes and SnS2 flakes at least partially overlap.

[0010] In some embodiments, the thickness of the Ta2NiSe5 thin film is 20-50 nm, and the thickness of the SnS2 thin film is 8-15 nm.

[0011] In some embodiments, the preset wavelengths include wavelengths of three colors: red, green, and blue.

[0012] In some embodiments, N is a natural number greater than or equal to 30.

[0013] In some embodiments, the preset duration of photocurrent storage is 1-50 seconds.

[0014] An embodiment of the present application also provides a visual unit, comprising a two-dimensional material photoelectric synapse based on gas adsorption assistance as described in any one of the above.

[0015] Compared with the related art, the above solution of the embodiment of the present application has at least the following beneficial effects:

[0016] The present application provides a two-dimensional photoelectric synapse and a display unit based on gas adsorption assistance. The present application provides a novel gas adsorption-assisted persistent photoelectric synapse, which has a Ta2NiSe5 / SnS2 structure.

[0017] The structure improves the photocurrent retention performance of the photoelectric synapse by regulating the carrier transport behavior through the physical adsorption of water and oxygen molecules in the air. The photoelectric synapse is composed of a ternary narrow bandgap material and a binary chalcogenide compound, and the photoelectric synapse has excellent photoelectric synapse performance in the ultraviolet to near-infrared band. First, through the carefully designed interface bandgap structure, the transport characteristics of photogenerated carriers are successfully regulated, so that the photoelectric synapse has a significant photoconductivity gain. Secondly, the physical adsorption of water and oxygen molecules in the environment on the inherent sulfur vacancies in the binary chalcogenide compound effectively prolongs the lifetime of the carriers. The photoelectric synapse not only enhances the response to light signals, but also significantly improves the ability of light signals to regulate synaptic plasticity, thus providing an important technical foundation for the development of new high-efficiency optoelectronic devices and brain-like computing systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present application, and together with the specification, are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0019] Figure 1 A schematic diagram of the structure of a photoelectric synapse provided in some embodiments of the present application;

[0020] Figure 2 A schematic diagram of a photovoltaic heterojunction unit structure provided for some embodiments of the present application;

[0021] Figure 3 A schematic diagram comparing the photocurrent generated by the photoelectric synapse provided in some embodiments of the present application and a general photodetector after receiving a light signal;

[0022] Figure 4 A schematic diagram of a photoelectric synapse generating a photocurrent after receiving multiple light pulses at different powers provided in some embodiments of the present application;

[0023] Figure 5 A schematic diagram of the display results of the photoelectric synapse provided in some embodiments of the present application;

[0024] Figure 6 Schematic diagram of the preparation process of Ta2NiSe5 / SnS2 heterojunction photoelectric synapse provided in some embodiments of the present application.

[0025] Description of reference numerals:

[0026] Photoelectric synapse 100 , photoelectric heterojunction unit 10 , substrate 1 , thin sheet 2 formed of binary chalcogenide compound, thin sheet 3 formed of ternary narrow bandgap material, drain electrode 4 , source electrode 5 . DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0028] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0029] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0030] It should be understood that although the terms first, second, third, etc. may be used to describe in the embodiments of the present application, these should not be limited to these terms. These terms are only used to distinguish. For example, without departing from the scope of the embodiments of the present application, the first may also be referred to as the second, and similarly, the second may also be referred to as the first.

[0031] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such product or device. In the absence of more restrictions, the elements defined by the sentence "comprises a" do not exclude the presence of other identical elements in the product or device including the elements.

[0032] The present application is described in detail below with reference to the accompanying drawings.

[0033] like Figure 1 , Figure 2As shown, the embodiment of the present application provides a photoelectric synapse 100, in particular, a two-dimensional photoelectric synapse based on gas adsorption assistance, the photoelectric synapse 100 includes a plurality of photoelectric heterojunction units 10 arranged in an array, each of the photoelectric heterojunction units 10 includes a substrate 1, a thin sheet 2 formed by a binary chalcogenide compound, a thin sheet 3 formed by a ternary narrow bandgap material, a drain electrode 4 and a source electrode 5; wherein the binary chalcogenide compound uses SnS2, and the ternary narrow bandgap material uses Ta2NiSe5, so that each of the photoelectric heterojunction units 10 has a Ta2NiSe5 / SnS2 structure, the Ta2NiSe5 / SnS2 structure includes a Ta2NiSe5 thin sheet and a SnS2 thin sheet, and the Ta2NiSe5 thin sheet and the SnS2 thin sheet at least partially overlap. Optionally, the thickness of the Ta2NiSe5 thin sheet is 20-50 nm, and the thickness of the SnS2 thin sheet is 8-15 nm. Among them, the Ta2NiSe5 / SnS2 structure forms a preset bandgap structure through multiple experiments. The Ta2NiSe5 / SnS2 structure enables each of the photoelectric heterojunction units to store the photocurrent generated by the N light pulses for a preset time length after receiving N light pulses of a preset wavelength (ultraviolet to near-infrared), and the photocurrent will not disappear immediately due to the cessation of the N light pulses. The preset storage time length is at least greater than the pulse period T of the N light pulses, and N is a natural number greater than or equal to 1.

[0034] like Figure 2 , Figure 3 As shown, the gate current V GS Under the action of the switch, a light pulse V of a certain wavelength (for example, a wavelength of 375nm-1550nm) is input at a fixed frequency to one or several or all of the photoelectric heterojunction units 10 in the photoelectric synapse 100. M , the wavelengths received by the same photoelectric heterojunction unit 10 are the same, and the wavelengths received by different photoelectric heterojunction units 10 may be the same or different. The photoelectric heterojunction unit 10 receives a light pulse V M After that, a corresponding photocurrent I0 of corresponding intensity will be generated. The Ta2NiSe5 / SnS2 structure enables each of the photoelectric heterojunction units 10 to receive a light pulse V of a preset wavelength. M After that, the photocurrent generated by the light pulse can be stored for a preset time, that is, when the light pulse V is modulated M After the end, the photocurrent generated in the photoelectric heterojunction unit 10 slowly decreases, and the next modulated light pulse V M Before the arrival of the light pulse, there will still be a certain amount of photocurrent, thus forming a memory function, and after N light pulses, significant characteristic information can be formed. M After the photocurrent ends, it also ends immediately, and there is no storage effect on the photocurrent, such as Figure 3 shown.

[0035] In some embodiments, after each of the photoelectric heterojunction units 10 receives the Nth light pulse of a preset wavelength and the end time T, the photocurrent generated by the light pulse satisfies the following relationship: ,in, represents the photocurrent intensity after the Nth light pulse ends at time T, T is the light pulse period, P represents the percentage of the photocurrent intensity reduced to the current photocurrent peak intensity after the first light pulse ends at time T, represents the peak intensity of the photocurrent generated by each light pulse itself, and N represents the number of light pulses. Figure 3 As shown in the figure, when the first light pulse ends, the photocurrent intensity generated by the light pulse does not drop to zero immediately, but slowly decreases until the next light pulse is received. At this time, after a period of time T, the photocurrent drops to P times the peak photocurrent intensity, that is, Then the second light pulse is received, and the starting point of the photocurrent intensity is I 1. The peak value of the photocurrent intensity generated by the second light pulse is I 20 = I 0+ I 1. When the second light pulse ends, the photocurrent intensity generated by the light pulse will not drop to zero immediately, but will slowly decrease until the next light pulse is received. At this time, the time elapsed is one cycle T, and the photocurrent intensity is , and so on, the peak value of the photocurrent intensity generated by the Nth light pulse is I N0 = I 0+(N-1) PI 0, therefore, the accumulated photocurrent intensity after each light pulse is greater than the accumulated photocurrent intensity after the previous light pulse. After N light pulses, the photocurrent intensity can still be maintained Taking into account the losses of various factors, after the Nth light pulse ends at time T, the photocurrent intensity generated by the light pulse satisfies the following relationship: . It has sufficient strength to characterize characteristic information in a specific application scenario, such as in the visual field, which means that visual information still exists in the photoelectric heterojunction unit 10 without the need for additional storage devices to store the information.

[0036] In some embodiments, according to experimental verification, the frequency of modulating the light pulse irradiation can control the value range of P. Optionally, the value range of P is 5%-80%. If it is lower than 5%, the characteristic information is not obvious and the application effect cannot be achieved. If it is higher than 80%, the irradiation frequency of the light pulse needs to be increased, which increases the difficulty of modulating the light pulse. Generally, the smaller the light pulse period T, the larger the value of P.

[0037] In some embodiments, Figure 4 As shown, a light pulse V of a certain wavelength is input at a fixed frequency to one or several or all of the photoelectric heterojunction units 10 in the photoelectric synapse 100. M For example, input the wavelengths of red, green, and blue colors respectively. Each color light pulse is transmitted at a different power (for example, 2 W-13 W) Continuously input 10-50 light pulses, for example, input 30 light pulses, from Figure 4 It can be seen that in the pulse input stage at a certain power, for example, 30 light pulses are input, the intensity of the photocurrent generated gradually increases, and after the 30 light pulses end, the photocurrent slowly decreases and still has a certain intensity of photocurrent for a period of time. This shows that the photoelectric synapse 100 of the present application has a memory effect on the photocurrent generated by the received light pulse. The photocurrent can be stored for a preset time of 1-50 seconds, for example, at least 30 seconds.

[0038] Further, such as Figure 5 As shown, a light pulse V of a certain wavelength is input at a fixed frequency to one or several or all of the photoelectric heterojunction units 10 in the photoelectric synapse 100. M For example, the wavelengths of red, green and blue are input respectively to form a display result of H. When 30 light pulses are continuously input, the boundaries between the three colors of red, green and blue are distinct and the display is clear. Within 30 seconds after the light pulse ends, the display result of H can still be seen clearly, indicating that the optoelectronic synapse 100 of the present application has a memory effect on the photocurrent generated by the received light pulse.

[0039] like Figure 6 As shown, the present application provides a preparation process of a Ta2NiSe5 / SnS2 heterojunction photoelectric synapse, comprising the following steps:

[0040] Step a: Prepare SiO2 / Si substrate.

[0041] Prepare a P-type highly doped silicon wafer with 300 nm thick SiO2, clean it with acetone, anhydrous ethanol, and deionized water, and then blow dry it with a nitrogen gun. Deep clean the SiO2 by oxygen plasma treatment for 1 minute, as in step (i).

[0042] Step b: Preparation of Ta2NiSe5 / SnS2 heterojunction.

[0043] Ta2NiSe5 and SnS2 flakes were prepared by mechanical exfoliation, and then stacked to form a heterojunction by directional transfer technology. The Ta2NiSe5 / SnS2 heterojunction was then heated at 80 degrees for 20 minutes to allow the two materials to fit tightly together and form a high-quality van der Waals interface, as shown in steps (ii) and (iii).

[0044] Step c: Preparation of metal electrodes.

[0045] Spin-coat the photoresist on the Ta2NiSe5 / SnS2 heterojunction, use UV lithography to form patterns at both ends of Ta2NiSe5 and SnS2, and then use thermal evaporation to deposit 20 and 80 nm of Ti and Au to form drain-source electrodes. Remove the photoresist and excess metal through a demolding process. Then anneal the device at 200 degrees in a nitrogen atmosphere for 20 minutes to repair the lattice defects formed between the material and the electrode, reduce the contact resistance, and improve the device performance. Such as steps (iv) and (vii).

[0046] The present application optimizes the Ta2NiSe5 / SnS2 barrier so that the thickness of the Ta2NiSe5 sheet is 20-50 nm, and the thickness of the SnS2 sheet is 8-15 nm. As a result, the Ta2NiSe5 / SnS2 heterojunction can use the interface barrier to block the photogenerated holes to produce a significant grating pressure effect, so that the electrons circulate back and forth in the material, and there is a significant current even after the light is removed. The surface defects of SnS2 are used to capture photoelectrons, further enhancing the circulation of electrons, thereby greatly improving the data storage capability. The physical adsorption of water and oxygen molecules in the environment on the inherent sulfur vacancies in binary chalcogenides effectively prolongs the life of the carriers.

[0047] The present application also provides a visual unit, comprising the two-dimensional material photoelectric synapse based on gas adsorption assistance as described in any one of the above. Figure 5As shown, the gas adsorption-assisted two-dimensional material photoelectric synapse of the present application can simulate the ability of the human eye to recognize multiple colors. The present application applies a bias voltage to the Ta2NiSe5 / SnS2 heterostructure to operate it in a photoconductive mode, thereby simulating the postsynaptic membrane potential changes produced by the visual nerve cells of the human eye when perceiving light signals. Through the regulation of the gate voltage pulse, the light signal can be finely processed and manipulated to achieve efficient extraction of image features. When 30 light pulses of different colors are input into the photoelectric synapse, the photoelectric synapse can realize the function of three-primary color imaging based on different responses to various color light signals. This feature enables our photoelectric synapse to not only simulate the visual processing mechanism of the human eye, but also play an important role in the field of image recognition and processing.

[0048] The present application provides a two-dimensional material photoelectric synapse and a display unit based on gas adsorption assistance. The present application provides a new type of gas adsorption-assisted persistent photoelectric synapse, which has a Ta2NiSe5 / SnS2 structure. The Ta2NiSe5 / SnS2 structure improves the photocurrent retention performance of the photoelectric synapse by regulating the carrier transport behavior by physical adsorption of water and oxygen molecules in the air. The photoelectric synapse is composed of a ternary narrow bandgap material and a binary chalcogenide compound, and the photoelectric synapse has excellent photoelectric synapse performance in the ultraviolet to near-infrared band. First, through the carefully designed interface bandgap structure, the transmission characteristics of the photogenerated carriers are successfully regulated, so that the photoelectric synapse has a significant photoconductivity gain. Secondly, the physical adsorption of water and oxygen molecules in the environment on the inherent sulfur vacancies in the binary chalcogenide compound is used to effectively extend the life of the carrier. The photoelectric synapse not only enhances the response to the light signal, but also significantly improves the ability of the light signal to regulate the synaptic plasticity, thereby providing an important technical basis for the development of new high-efficiency photoelectric devices and brain-like computing systems.

[0049] The present application provides an application of a gas-assisted enhanced optoelectronic synaptic device in the preparation of a high-performance brain-like computing chip. The present application prepares an optoelectronic synapse based on a van der Waals heterojunction formed by SnS2 and Ta2NiSe5 with intrinsic gas adsorption sites, and utilizes the physical adsorption of water and oxygen molecules in the air to enhance the persistent photoconductivity effect, thereby simulating the neuroelectrochemical behavior of human retinal cells. The device can be used in the field of computer vision, and can realize the simultaneous perception, storage, and calculation processes, thereby reducing the power consumption of the chip and improving the accuracy and speed of target recognition.

[0050] Finally, it should be noted that: each embodiment in this specification is described by way of example, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other. For the system or device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0051] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A two-dimensional photoelectric synapse based on gas adsorption assistance, characterized in that ,include: A plurality of photoelectric heterojunction units are arranged in an array, each of the photoelectric heterojunction units having a Ta2NiSe5 / SnS2 structure, wherein the Ta2NiSe5 / SnS2 structure has a preset bandgap structure, and the Ta2NiSe5 / SnS2 structure enables each of the photoelectric heterojunction units to store a preset duration of photocurrent generated by N light pulses of a preset wavelength after receiving the light pulses, where N is a natural number greater than or equal to 1.

2. The gas adsorption-assisted two-dimensional material optoelectronic synapse according to claim 1, characterized in that After each of the photoelectric heterojunction units receives the Nth light pulse of the preset wavelength, the photocurrent generated by the light pulse satisfies the following relationship: ,in, represents the photocurrent intensity after the Nth light pulse ends at time T, T is the light pulse period, P represents the percentage of the photocurrent intensity reduced to the current photocurrent peak intensity after the first light pulse ends at time T, It represents the peak intensity of the photocurrent generated by each light pulse itself, and N represents the number of light pulses.

3. The gas adsorption-assisted two-dimensional material optoelectronic synapse according to claim 2, characterized in that ,The value range of P is 5%-80%.

4. The gas adsorption-assisted two-dimensional material optoelectronic synapse according to claim 1, characterized in that , the peak intensity of the photocurrent generated by the accumulation of each light pulse is greater than the peak intensity of the photocurrent generated by the accumulation of the previous light pulse.

5. The gas adsorption-assisted two-dimensional material optoelectronic synapse according to claim 1, characterized in that The Ta2NiSe5 / SnS2 structure includes Ta2NiSe5 flakes and SnS2 flakes, and the Ta2NiSe5 flakes and SnS2 flakes at least partially overlap.

6. The gas adsorption-assisted two-dimensional material optoelectronic synapse according to claim 5, characterized in that , the thickness of the Ta2NiSe5 thin film is 20-50 nm, and the thickness of the SnS2 thin film is 8-15 nm.

7. The gas adsorption-assisted two-dimensional material optoelectronic synapse according to claim 1, characterized in that , the preset wavelengths include wavelengths of three colors: red, green, and blue.

8. The gas adsorption-assisted two-dimensional material optoelectronic synapse according to claim 1, characterized in that , N is a natural number greater than or equal to 30.

9. The gas adsorption-assisted two-dimensional material optoelectronic synapse according to claim 1, characterized in that , the preset duration of the photocurrent storage is 1-50 seconds.

10. A visual unit, characterized in that , including the gas adsorption-assisted two-dimensional material photoelectric synapse as described in any one of claims 1-9.

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