Two-dimensional homojunction structure and preparation method and application thereof

Abstract

The invention belongs to the related technical field of photoelectric devices, and discloses a two-dimensional homojunction structure and a preparation method and application thereof, and the method comprises the steps: S1, depositing silicon nitride on a substrate to obtain a silicon nitride substrate; and S2, preparing a two-dimensional material homojunction on the silicon nitride substrate by using a chemical vapor deposition reaction method so as to obtain a two-dimensional homojunction structure. The silicon nitride is deposited on the substrate, and the two-dimensional material homojunction is grown on the silicon nitride substrate through a chemical vapor deposition method, so that a two-dimensional material homojunction / silicon nitride material structure is prepared through a one-step chemical reaction method, and the material preparation operation process and period are obviously simplified; the problems that an existing mechanical stripping method cannot be expanded, and a chemical doping method is difficult to accurately control are solved.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic device technology, and more specifically, relates to a two-dimensional homojunction structure, its preparation method and application. Background Technology

[0002] Neuromorphic computing, with its high parallel processing capabilities and low data transfer losses, shows great promise, and artificial synaptic devices, as its core hardware module, have attracted much attention. Among them, opto-synaptic devices are a new type of electronic / optoelectronic device that simulates the function of biological synapses. They utilize optical and / or electrical signals as stimuli to achieve plasticity similar to biological synapses, meaning that the connection strength (synaptic weight) can continuously change according to the history of the input signal. Opto-synaptic devices are one of the most promising technological routes in the post-Moore's Law era and the era of artificial intelligence. Through the ingenious interaction between light and matter, they directly simulate biological learning and memory functions at the hardware level, aiming to solve the fundamental bottleneck of current computing technology in processing visual information. Opto-synapses can integrate visual sensing and signal processing functions, achieving efficient conversion between optical and electrical signals, and possess advantages such as high bandwidth, low crosstalk, low power consumption, and no RC delay.

[0003] However, current mainstream optoelectronic synaptic devices generally suffer from insufficient reliability and incompatibility with CMOS processes, which severely restricts their large-scale fabrication and on-chip integration applications. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a two-dimensional homojunction structure, its preparation method and application, which aims to solve the problem of difficult preparation of existing optoelectronic synaptic devices.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a two-dimensional homojunction structure is provided, comprising the following steps: S1, deposit silicon nitride on the substrate to obtain a silicon nitride substrate; S2, a two-dimensional homojunction is prepared on a silicon nitride substrate using a chemical vapor deposition reaction to obtain a two-dimensional homojunction structure.

[0006] Furthermore, firstly, photoresist is uniformly spin-coated onto a silicon nitride substrate, and after baking, it is exposed and developed using a photolithography machine to form an array pattern. Then, using a chemical vapor deposition reaction method, in a tube furnace, the reaction source is placed upstream of the reaction, and the developed substrate is placed downstream of the reaction. The substrate is heated to the reaction temperature to grow a two-dimensional homojunction on the silicon nitride substrate to obtain a two-dimensional homojunction structure.

[0007] Furthermore, the temperature upstream of the reaction is 150℃~350℃.

[0008] Furthermore, the downstream temperature of the reaction is 650℃~800℃.

[0009] The present invention also provides a two-dimensional homojunction structure prepared by the preparation method of the two-dimensional homojunction structure as described above, wherein the two-dimensional homojunction structure includes a substrate, a silicon nitride layer and a two-dimensional material homojunction layer arranged from bottom to top.

[0010] The present invention also provides a two-dimensional homojunction photoelectric synapse device, the photoelectric synapse device comprising the two-dimensional homojunction structure as described above and a metal electrode disposed on the two-dimensional homojunction layer.

[0011] Furthermore, photosynaptic devices exhibit increased current under visible light irradiation, while conversely, they exhibit decreased current under ultraviolet light irradiation.

[0012] Furthermore, depending on the different values ​​of light irradiation power, photoelectric synaptic devices are used to convert multi-valued time-series optical signals into characteristic currents in order to extract the temporal characteristics of the optical signals.

[0013] Furthermore, photoelectric synaptic devices exhibit different photosynaptic characteristics under light irradiation; photoelectric synaptic devices exhibit different photoresponse characteristics at different light wavelengths.

[0014] The present invention also provides an application of the two-dimensional material homojunction photoelectric synapse device described above in the sensing and preprocessing of visible light and ultraviolet light signals.

[0015] In summary, compared with the prior art, the two-dimensional homojunction structure, its preparation method, and its application provided by this invention have the following beneficial effects: 1. This invention deposits silicon nitride on a substrate and grows a two-dimensional homojunction on the silicon nitride substrate by chemical vapor deposition. This achieves the one-step chemical reaction method to prepare a two-dimensional homojunction / silicon nitride material structure, which significantly simplifies the material preparation process and cycle. It solves the problems of non-scalability of existing mechanical exfoliation methods and difficulty in precise control of chemical doping methods, meets the needs of large-scale device production and high-integration applications, and reduces the cost of batch preparation.

[0016] 2. This invention utilizes the synergistic effect of silicon dangling bonds, nitrogen vacancies, and homojunctions of two-dimensional materials in the silicon nitride layer to achieve stable positive and negative photoelectric responses, significantly improving the environmental stability and long-term operational reliability of photoelectric synaptic devices, and overcoming the shortcomings of insufficient reliability of existing two-dimensional materials and perovskite-based synaptic devices. At the same time, the fabrication process adopts mature chemical vapor deposition, photolithography, evaporation and other technologies, which are highly compatible with CMOS processes, providing favorable conditions for on-chip integration of devices.

[0017] 3. The photoelectric synaptic device prepared in this invention exhibits a positive response of increased current under visible light and a negative response of decreased current under ultraviolet light. It is a novel photoelectric synapse with dual-color light discrimination capability, breaking through the limitation of the single response mode of traditional photoelectric synaptic devices. This characteristic enables the photoelectric synaptic device to directly distinguish light signals of different wavelengths without the need for additional filtering modules. At the same time, it can realize the conversion of multi-valued time-series light signals into characteristic currents based on the difference in light power, and can efficiently extract the time features of light signals, providing new hardware support for multimodal signal processing and optical information encoding in neuromorphic computing.

[0018] 4. This invention can grow various two-dimensional material homojunctions / silicon nitride arrays on silicon nitride substrates by controlling the type of materials through chemical vapor deposition. In addition, this method can also prepare large-area two-dimensional material homojunctions / silicon nitride. Attached Figure Description

[0019] Figure 1 In Example 1 of this invention, image a is a light microscope image of the WSe2 homojunction array grown on a silicon nitride substrate by chemical vapor deposition; image b is a WSe2 homojunction / silicon nitride 3D structure in Example 1 of this invention. SEM images of the 3 arrays; Figure 2 In Example 1 of this invention, 'a' refers to the WSe2 homojunction / silicon nitride 3. AFM images of the array are shown in Figure 3; b is a magnified AFM image of a localized WSe2 homojunction / silicon nitride. Figure 3 In Figure a, the Raman spectrum of the WSe2 homojunction / silicon nitride in Example 1 of this invention is shown; in Figure b, the Raman spectrum of the WSe2 homojunction / silicon nitride in Example 3 is shown. Intensity-mapped scan images of Raman peaks in a 3-array; Figure 4 This is an optical mirror image of the WSe2 homojunction / silicon nitride photosynapse device constructed in Embodiment 3 of the present invention; Figure 5 This is a current-time response curve of the WSe2 homojunction / silicon nitride photosynapse device constructed in Embodiment 3 of the present invention under different visible light wavelengths; Figure 6 This is a current-time response curve of the WSe2 homojunction / silicon nitride photoelectric synapse device constructed in Embodiment 3 of the present invention under different optical powers; Figure 7 This is a graph showing the current-time response curves of the WSe2 homojunction / silicon nitride positive and negative photosynaptic device constructed in Embodiment 4 of the present invention under visible light and ultraviolet light irradiation. Figure 8This is a graph showing the current-time response curves of the WSe2 homojunction / silicon nitride positive and negative photosynaptic device constructed in Embodiment 4 of the present invention under visible light and ultraviolet light irradiation. Figure 9 In this invention, 'a' is the 10 constructed in embodiment 5. a) Optical mirror image of a 10WSe2 homojunction / silicon nitride array; b) is a 10 Current intensity diagram of a 10WSe2 homojunction / silicon nitride array device; Figure 10 This is a schematic diagram of the positive and negative light responses of the photoelectric synaptic device prepared by the present invention; Figure 11 a and b in the figure are schematic diagrams of the operation of the photoelectric synaptic device prepared in the present invention in shallow trap and deep trap states, respectively. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0021] This invention provides a method for preparing a two-dimensional homojunction structure, the method comprising the following steps: S1, deposit silicon nitride on the substrate to obtain a silicon nitride substrate.

[0022] The thickness of the silicon nitride deposition is approximately 100 nanometers.

[0023] S2, Two-dimensional homojunctions are prepared on silicon nitride substrates using chemical vapor deposition to obtain two-dimensional homojunction structures.

[0024] Specifically, firstly, photoresist is uniformly spin-coated onto a silicon nitride substrate, and after baking, it is exposed and developed using a photolithography machine to form an array pattern. Then, using a chemical vapor deposition reaction method, in a tube furnace, the reaction source is placed upstream of the reaction, and the developed substrate is placed downstream of the reaction. The substrate is heated to the reaction temperature to grow a two-dimensional homojunction on the silicon nitride substrate to obtain a two-dimensional homojunction structure.

[0025] The upstream temperature of the reaction is 150℃~350℃. The downstream temperature of the reaction is 650℃~800℃.

[0026] Please see Figure 10 and Figure 11The present invention also provides a two-dimensional homojunction structure prepared by the method described above. The two-dimensional homojunction structure includes, from bottom to top, a substrate, a silicon nitride layer, and a two-dimensional material homojunction layer.

[0027] The present invention also provides a two-dimensional homojunction photoelectric synapse device, the photoelectric synapse device comprising the two-dimensional homojunction structure as described above and a metal electrode disposed on the two-dimensional homojunction layer.

[0028] Please see Figure 10 and Figure 11 Photosynaptic devices exhibit increased current under visible light irradiation, while decreasing current under ultraviolet light irradiation. Visible light excites carrier separation in a two-dimensional homojunction, simultaneously exciting silicon dangling bonds in silicon nitride to capture a small number of electrons, resulting in a positive synaptic response. Ultraviolet light excites carrier separation in a two-dimensional homojunction, simultaneously exciting nitrogen vacancies in silicon nitride to capture a large number of electrons, resulting in a negative synaptic response.

[0029] Depending on the light irradiation power, photoelectric synaptic devices are used to convert multi-valued time-series optical signals into characteristic currents, extracting the temporal characteristics of the optical signals. Photoelectric synaptic devices exhibit different photosynaptic characteristics under light irradiation. They also exhibit different photoresponse characteristics at different light wavelengths. Under visible light irradiation, photoelectric synaptic devices exhibit a positive response photosynaptic characteristic with increased current. Under ultraviolet light irradiation, they exhibit a negative response photosynaptic characteristic with decreased current.

[0030] The material of the metal electrode is Pt, Ti, W, Au, Ru, Al, Ta, or Cr.

[0031] The present invention also provides an application of the two-dimensional material homojunction photoelectric synapse device described above in the sensing and preprocessing of visible light and ultraviolet light signals.

[0032] The present invention will be further described in detail below with reference to specific embodiments.

[0033] Example 1 Example 1 of this invention utilizes chemical vapor deposition to grow a WSe2 homojunction on a silicon nitride substrate. The specific preparation method includes the following steps: (1) A clean silicon wafer is used as the substrate, and a 100 nm thick silicon nitride layer is deposited on the substrate.

[0034] (2) Photoresist is uniformly spin-coated onto the obtained silicon nitride substrate, and after baking, it is exposed and developed by a photolithography machine to form an array pattern.

[0035] (3) WO3 is deposited on the substrate with the array pattern developed using a coating machine. The thickness of the WO3 deposition is 4 nm. After deposition, the photoresist is dissolved using an organic solvent.

[0036] (4) The flow rate ratio in the tubular furnace Argon and hydrogen gases were used to place elemental selenium powder upstream of a tube furnace, and the upstream reaction temperature was set to 350 °C. WO3 and a silicon nitride substrate coated with a WO3 array were placed downstream of the tube furnace, and the downstream reaction temperature was set to 800 °C. After the reaction was completed, the furnace was allowed to cool naturally to room temperature to obtain the reaction product WSe2 homojunction / silicon nitride array.

[0037] Results analysis: The results and basic characterization of the WSe2 homojunction / silicon nitride array prepared in Example 1 are as follows: Figure 1 , Figure 2 and Figure 3 As shown. Figure 1 Image 'a' in the image shows an optical mirror image of a WSe2 homojunction array grown on a silicon nitride substrate. Figure 1 Figure b shows a SEM image of a WSe2 homojunction / silicon nitride array, which shows that the WSe2 homojunction / silicon nitride is grown uniformly. Figure 2 AFM characterization quantitatively described the uniform thickness distribution of the WSe2 homojunction / silicon nitride array. The thickness of the multilayer region was approximately 4.8 nm, and the thickness of the monolayer region was approximately 0.8 nm. Figure 3 In the image, 'a' represents the Raman spectrum of the WSe2 homojunction. Figure 3 In this context, 'b' represents the 249 cm⁻¹ of the WSe2 homojunction array. -1 Intensity mapping scans of the Raman peaks showed that the Raman peak intensity in the monolayer region was higher than that in the multilayer region, and the peak intensity distribution was more uniform. As the characterization results above indicate, the WSe2 homojunction array grown on the silicon nitride substrate using this strategy exhibits excellent quality and uniformity.

[0038] Example 2 In Example 2 of this invention, MoSe2 homojunction / silicon nitride arrays, WS2 homojunction / silicon nitride arrays, and MoS2 homojunction / silicon nitride arrays were prepared using the same steps as in Example 1. The difference from Example 1 lies in the adjustment of the reaction source material and the reaction temperature.

[0039] Example 3 A photoelectric synaptic device was constructed using the WSe2 homojunction / silicon nitride material obtained in Example 1 of this invention. The resulting two-dimensional homojunction / silicon nitride photoelectric synaptic device comprises, from bottom to top, a substrate, a silicon nitride layer, a two-dimensional homojunction layer, and a metal electrode. Specifically, a Cr / Au layer was deposited as an electrode in both the few-layer and multi-layer regions of the WSe2 homojunction / silicon nitride, with the Au film having a thickness of 40 nm and the Cr film having a thickness of 10 nm. This device configuration allows for effective measurement of the photoelectric performance of the homojunction region. Figure 4 Optical mirror images of the fabricated WSe2 homojunction / silicon nitride photosynaptic device are shown.

[0040] Figure 5 The current-time response curves of the photoelectric synaptic device under different visible light wavelengths were shown. At the initial moment of photoexcitation, the current corresponding to each wavelength showed a rapid pulse-like jump; then, during the continuous light application, the current showed a slow and stable increase; after the light source was removed, the current did not drop rapidly to the dark state current, and had a relatively long retention time, which is consistent with the dynamic response characteristics of the photoelectric synaptic device; and the response amplitudes corresponding to different visible light wavelengths (532nm green light, 455nm blue light, and 625nm red light) were significantly different. Figure 6 The current response curves of this photoelectric synaptic device over time at a wavelength of 532nm and different optical powers are shown. As the optical power increases, the amplitude of the current response gradually increases. This characteristic indicates that the photoelectric synaptic device can achieve multi-valued modulation of the current response through differences in optical power, and can convert light signals of different intensities into corresponding characteristic currents, matching the needs of multi-valued signal encoding in neuromorphic computing.

[0041] Example 4 The WSe2 homojunction / silicon nitride obtained in Example 1 of this invention is used to construct positive and negative photoelectric synapse devices. Figure 7 The current-time response curves of the synaptic device under visible and ultraviolet light irradiation are shown. Under continuous visible light irradiation, the current changes with a positive upward trend and gradually stabilizes, reflecting the positive response characteristics of the synaptic device under visible light. Under continuous ultraviolet light irradiation, the current changes with a negative downward trend and remains in the negative growth range, reflecting the negative response characteristics of the synaptic device under ultraviolet light. Visible light excites carrier separation in the homojunction of the two-dimensional material while simultaneously exciting silicon dangling bonds in silicon nitride to capture a small number of electrons, resulting in a positive synaptic response. Ultraviolet light excites carrier separation in the homojunction of the two-dimensional material while simultaneously exciting nitrogen vacancies in silicon nitride to capture a large number of electrons, resulting in a negative synaptic response.

[0042] Figure 8The current-time response curves of this synaptic device under visible light and ultraviolet light irradiation for 1 second are shown. Under visible light irradiation for 1 second, the current rapidly increases positively after photoexcitation, and gradually decreases after the visible light source is removed, exhibiting the typical "excitation-relaxation" dynamic process of a photosynapse. Under ultraviolet light irradiation for 1 second, the current rapidly decreases negatively after photoexcitation, also following the "excitation-relaxation" law, and the response direction is completely opposite to that under visible light. These curves visually verify the core advantages of this two-dimensional homojunction / silicon nitride synaptic device: it possesses dual-color differentiated response capabilities for visible and ultraviolet light, and can achieve rapid dynamic response to short-pulse light signals, matching the application requirements of photosynapses in optical signal sensing, encoding, and neuromorphic computing.

[0043] Example 5 The WSe2 homojunction / silicon nitride array obtained in Example 1 of this invention is used to construct an optoelectronic array device. Figure 9 Figure 'a' shows a 10x10 WSe2 homojunction / silicon nitride array device. The array device also exhibits different light responses to visible and ultraviolet light. Figure 9 Figure b shows the current intensity of 100 optoelectronic devices under dark conditions, visible light illumination, and ultraviolet light illumination. The data shows that the current values ​​of these 100 devices are concentrated in the dark, increase significantly and remain concentrated under visible light illumination, and similarly decrease significantly and remain concentrated under ultraviolet light illumination. This indicates that the fabricated array possesses excellent positive and negative light responsivity and uniformity.

[0044] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a two-dimensional homojunction structure, characterized in that, The steps are as follows: S1, deposit silicon nitride on the substrate to obtain a silicon nitride substrate; S2, a two-dimensional homojunction is prepared on a silicon nitride substrate using a chemical vapor deposition reaction to obtain a two-dimensional homojunction structure.

2. The method for preparing a two-dimensional homojunction structure as described in claim 1, characterized in that: First, photoresist is uniformly spin-coated onto a silicon nitride substrate. After baking, the substrate is exposed and developed using a photolithography machine to form an array pattern. Then, using a chemical vapor deposition reaction method, in a tube furnace, the reaction source is placed upstream of the reaction, and the developed substrate is placed downstream of the reaction. The substrate is heated to the reaction temperature to grow a two-dimensional homojunction on the silicon nitride substrate to obtain a two-dimensional homojunction structure.

3. The method for preparing a two-dimensional homojunction structure as described in claim 2, characterized in that: The upstream temperature of the reaction is 150℃~350℃.

4. The method for preparing a two-dimensional homojunction structure as described in claim 3, characterized in that: The downstream temperature of the reaction is 650℃~800℃.

5. A two-dimensional homojunction structure prepared by the method for preparing a two-dimensional homojunction structure according to any one of claims 1-4, characterized in that: The two-dimensional homojunction structure includes a substrate, a silicon nitride layer, and a two-dimensional material homojunction layer arranged from bottom to top.

6. A two-dimensional material homojunction photoelectric synapse device, characterized in that: The photoelectric synaptic device includes the two-dimensional homojunction structure as described in claim 5 and a metal electrode disposed on the two-dimensional homojunction layer.

7. The two-dimensional homojunction photoelectric synapse device as described in claim 6, characterized in that: Photosynaptic devices exhibit increased current under visible light irradiation, while conversely, they exhibit decreased current under ultraviolet light irradiation.

8. The two-dimensional homojunction photoelectric synapse device as described in claim 6, characterized in that: Depending on the different values ​​of light irradiation power, photoelectric synaptic devices are used to convert multi-valued time-series optical signals into characteristic currents in order to extract the temporal characteristics of the optical signals.

9. The two-dimensional homojunction photoelectric synapse device as described in claim 6, characterized in that: Photosynaptic devices exhibit different photosynaptic properties under light irradiation; photosynaptic devices exhibit different photoresponse properties under different light wavelengths.

10. The application of a two-dimensional material homojunction photoelectric synaptic device according to any one of claims 6-9 in the sensing and preprocessing of visible light and ultraviolet light signals.

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