A strain-enhanced multi-sensory fusion optoelectronic synapse device, a preparation method and application thereof

Abstract

The application belongs to the technical field of two-dimensional material devices, and discloses a strain-enhanced multi-sensory fusion optoelectronic synapse device and a preparation method and application thereof. The optoelectronic synapse device comprises, from bottom to top, an insulating layer, an electrode and a functional layer. The material of the functional layer is an in-plane polarization two-dimensional ferroelectric material, and the functional layer is applied with a tensile strain along the direction of its own polar axis. The optoelectronic synapse device simulates the perception of visual information through the photoconductivity effect of the functional layer and simulates the sense of touch through the tensile strain. The synergistic effect of the photoconductivity effect and the tensile strain significantly enhances the persistent photoconductivity (PPC) of the synapse device, and the enhancement processing of a fingerprint image is realized through the characteristics of the device. At the same time, by applying the tensile strain along a specific direction, the in-plane polarization intensity is significantly improved, the constraint of the depolarization field is avoided, the stability and performance of the ferroelectric device are improved, and a new way for improving the performance of the optoelectronic synapse device is provided.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of two-dimensional material devices, and more particularly relates to a strain-enhanced multi-sensory fusion optoelectronic synapse device and a preparation method and application thereof. BACKGROUND

[0002] The multi-sensory system of human beings realizes high-level cognitive learning and environmental perception by integrating visual, auditory and tactile information. The multi-sensory fusion artificial neural system simulates the operation mechanism of the biological nervous system, and its development is crucial for the progress of bionic systems and human-computer interaction technology. Among all the information obtained by human beings, visual information accounts for more than 80%, and tactile information contains multi-dimensional information related to object contact. The fusion of these two senses induces cross-modal synaptic plasticity, which has great significance in the simulation of artificial intelligence.

[0003] In recent years, most of the multi-sensory fusion researches on the combination of vision and touch are based on the integration of tactile sensors and artificial synapses. The physical separation of sensors and processors will cause additional loss in the information transmission process. Therefore, designing a high-performance device with sensing and processing using advanced integrated design and methods is becoming a key direction for low-power neuromorphic sensing systems. In order to realize the fusion perception of vision and touch under the premise of simplifying the structure, breakthroughs need to be sought in material properties.

[0004] In order to realize the fusion sensing of vision and touch in multi-functional artificial systems, the functional layer material not only needs to have photoresponse and piezoelectricity, but also needs to be able to memorize and process visual and tactile information. Under this background, two-dimensional ferroelectric materials have become an ideal choice, which is expected to promote the development of vision-tactile integrated artificial synapse devices in artificial intelligence systems. SUMMARY

[0005] In view of the above defects or improvement needs of the prior art, the application provides a strain-enhanced multi-sensory fusion optoelectronic synapse device and a preparation method and application thereof, which aims to realize the fusion perception of vision and touch under the premise of simplifying the structure.

[0006] To achieve the above-mentioned purpose, according to one aspect of the application, a strain-enhanced multi-sensory fusion optoelectronic synapse device is provided, which comprises an insulating layer, an electrode and a functional layer arranged from bottom to top, the material of the functional layer is an in-plane polarization two-dimensional ferroelectric material, and the functional layer is applied with a tensile strain along the direction of its own polar axis; the optoelectronic synapse device simulates the perception of visual information through the photoconductive effect of the functional layer, and simulates the touch through the tensile strain.

[0007] Further, the material of the functional layer is any one of mechanically exfoliated NbO I2, NbOCl2, NbOBr2, and the thickness is 20-40 nm.

[0008] Further, the material of the insulating layer is any one of SiO2, Al2O3, HfO2, ZrO2, and the thickness is 0-200 nm.

[0009] Further, the material of the electrode is gold, palladium or platinum, and the thickness is 60 nm.

[0010] Further, the functional layer is further provided with an insulating encapsulation layer, and the material of the insulating encapsulation layer is mechanically exfoliated two-dimensional layered material h-BN, and the thickness is 10-20 nm.

[0011] Further, the adjustment of the tensile strain is achieved by controlling the deposition thickness of the step structure composed of the insulating layer and the electrode and the channel width between the electrodes, the thickness of the step structure is 50-250 nm, and the channel width is 1-5 μm.

[0012] The application further provides a preparation method of the strain-enhanced multi-sensory fusion optoelectronic synapse device.

[0013] (1) obtaining a required pattern on the surface of a hard substrate by using an electron beam lithography process;

[0014] (2) sequentially depositing the insulating layer and the electrode on the surface of the hard substrate;

[0015] (3) sequentially transferring the functional layer and the encapsulation layer to the electrode by using a low-dimensional transfer platform, and thus obtaining the synapse device.

[0016] Further, in the transfer process, the functional layer is first attached to the surface of the electrode, and then pressure is gradually applied to the functional layer, so that the channel bottom formed between the functional layer and the electrode is completely attached, thereby generating a tensile strain.

[0017] The application further provides an application of the strain-enhanced multi-sensory fusion optoelectronic synapse device in an artificial intelligence system.

[0018] Overall, compared with the prior art, the strain-enhanced multi-sensory fusion optoelectronic synapse device, the preparation method and the application provided by the application mainly have the following beneficial effects:

[0019] 1. The material of the functional layer is an in-plane polarization two-dimensional ferroelectric material, and a tensile strain is applied along the polarization axis direction of the functional layer, the perception of visual information is simulated through the photoconductive effect of the functional layer, and the sense of touch is simulated by applying a tensile strain in a specific direction of the functional layer, the synergistic effect of the photoconductive effect and the tensile strain significantly enhances the persistent photoconductivity (PPC) of the synaptic device, and the enhancement processing of the fingerprint image is realized through the characteristics of the device. At the same time, by applying a tensile strain in a specific direction, the in-plane polarization intensity is significantly improved, while the depolarization field is avoided, the stability and performance of the ferroelectric device are improved, and a new way is provided for the performance improvement of the optoelectronic synaptic device, especially in the fields of neuromorphic visual perception and visual information preprocessing, which has great application potential.

[0020] 2. Compared with the common three-terminal floating gate and heterojunction device structures in current research, the structure design is simplified, the ferroelectric, piezoelectric and photoelectric characteristics of the functional layer are combined, and the photoelectric synaptic characteristics are successfully simulated by using a simple two-terminal structure, and the synaptic performance is effectively optimized.

[0021] 3. The device is prepared by evaporating the electrode first and then transferring the two-dimensional material, which effectively avoids the damage of metal atoms to the contact interface between the two-dimensional material and the electrode when the electrode is directly evaporated on the two-dimensional material, avoids the Fermi level pinning effect, and helps to form good contact between the metal and the two-dimensional material, thereby facilitating the preparation of a photoelectric synaptic device with better performance.

[0022] 4. The application utilizes the synergistic effect of strain and light to effectively improve the PPF index and persistent photoconductivity (PPC) and other photoelectric synaptic performances, and by applying the characteristics of the strain photoelectric synaptic device to the image processing of the optical sensor fingerprint, the image quality can be greatly improved, and the application potential of multi-modal sensory integration in multi-functional artificial neural systems is demonstrated. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a structure diagram of a strain-enhanced multi-sensory integrated photoelectric synaptic device provided by the application;

[0024] Figure 2 is an optical image of the device in embodiment 1 of the application;

[0025] Figure 3 is the P2 Raman peak of the strain and non-strain regions of the two-dimensional material NbOI2 in embodiment 1 of the application;

[0026] Figure 4 is a second harmonic total intensity diagram of the non-strain and strain regions of the two-dimensional material NbOI2 in embodiment 1 of the application;

[0027] Figure 5I-V curves of strain-free (top) and strained (bottom) devices in Example 1 of the present invention ds -V ds Cyclic hysteresis curves

[0028] Figure 6 PPF exponential fitting functions of strained and strain-free NbO I2 devices in Example 1 of the present invention

[0029] Figure 7 Current responses of strained and strain-free NbO I2 devices to different number of 532 nm light pulses in Example 1 of the present invention

[0030] Figure 8 Photocurrent fitting curves of strained and strain-free NbO I2 devices in Example 1 of the present invention

[0031] Figure 9 Processing effects of the same original fingerprint image (a-b) using synaptic characteristics of strained (e-f) and strain-free (c-d) NbO I2 devices in Example 1 of the present invention and their gray value distribution statistics. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present 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 only used to explain the present invention and should not be used to limit the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] The present invention provides a strain-enhanced multi-sensory fusion optoelectronic synaptic device, which comprises, from bottom to top, an insulating layer, an electrode, a functional layer and an insulating packaging layer, the material of the functional layer is an in-plane polarization two-dimensional ferroelectric material, and the functional layer is applied with tensile strain along its own polar axis direction; the optoelectronic synaptic device simulates the perception of visual information through the photoconductivity effect of the functional layer, and simulates the sense of touch through tensile strain.

[0034] The material of the functional layer is any one of mechanically exfoliated NbO I2, NbO Cl2 or NbO Br2, and the thickness is 20-40 nm.

[0035] The material of the insulating layer is any one of SiO2, Al2O3, HfO2 or ZrO2, and the thickness is 0-200 nm.

[0036] The material of the electrode is gold, palladium or platinum, and the thickness is 60 nm.

[0037] The material of the insulating encapsulation layer is a mechanically exfoliated two-dimensional layered material h-BN, and the thickness is 10-20 nm. The insulating encapsulation layer is used to protect the functional layer sensitive to water and oxygen, so as to avoid the reaction of the functional layer with water and oxygen in the environment. For the functional layer with environmental stability, the insulating encapsulation layer is not needed.

[0038] The adjustment of the tensile strain is realized by controlling the deposition thickness of the step structure composed of the insulating layer and the electrode and the channel width between the electrodes, the thickness of the step structure is 50-250 nm, and the channel width is 1-5 μm.

[0039] The application further provides a preparation method of the strain-enhanced multi-sensory fusion optoelectronic synapse device.

[0040] (1) The required pattern is prepared on the surface of the hard substrate by using an electron beam lithography process.

[0041] (2) The insulating layer and the electrode are sequentially deposited on the surface of the hard substrate.

[0042] (3) The functional layer and the encapsulation layer are sequentially and fixedly transferred to the electrode by using a low-dimensional transfer platform, and the synapse device is obtained.

[0043] The deposition method of the insulating layer includes but is not limited to an e-beam evaporation and a magnetron sputtering film coating process. The deposition method of the electrode includes but is not limited to an e-beam evaporation and a thermal evaporation film coating process. In a glove box with extremely low oxygen and water content, the low-dimensional transfer platform is used to transfer the functional layer to the electrode surface along a specific direction, so as to increase the non-centrosymmetry of the crystal structure. In the transfer process, the functional layer is first slightly attached to the electrode surface, and then the pressure of the PDMS is gradually increased, so that the functional layer is completely attached to the bottom of the channel, so that the tensile strain is generated. If the functional layer is easily affected by the water and oxygen environment, the encapsulation layer is transferred to the electrode surface to protect the functional layer from the environment; if the functional layer is stable, the encapsulation layer is not needed to be transferred.

[0044] The application further provides an application of the strain-enhanced multi-sensory fusion optoelectronic synapse device in an artificial intelligence system.

[0045] The application is further described in detail in the following specific embodiments.

[0046] Embodiment 1

[0047] The embodiment 1 provides a strain-enhanced multi-sensory fusion optoelectronic synapse device, and the device structure is as shown in Figure 1 and Figure 2As shown in the figure, the material of the insulating layer is SiO2, and the thickness is 140 nm; the material of the bottom electrode is Cr / Au, and the thickness is 10 / 50 nm; the material of the functional layer is NbOI2, and the thickness is 30 nm; the material of the encapsulation layer is h-BN, and the thickness is 15 nm.

[0048] The preparation method of the strain-enhanced multi-sensory fusion optoelectronic synaptic device provided in this embodiment 1 is as follows:

[0049] (1) Photoetching pattern on clean silicon oxide / silicon substrate: spin-coat a layer of PMMA according to the parameters (speed: 600 r / min, time: 5 s; speed: 1000 r / min, time: 10 s; speed: 4000 r / min, time: 60 s), and then dry (5 min at 150°C). Expose the pattern by electron beam lithography process, and the channel width is 3 μm. Dissolve the exposed PMMA with developer to obtain the desired pattern;

[0050] (2) On the pattern surface prepared in step (1), deposit the insulating layer SiO2 by electron beam evaporation process, the thickness is 140 nm, and the speed is 0.05 nm / s; deposit the electrode layer Cr by thermal evaporation process, the thickness is 10 nm, and the speed is 0.03 nm / s; deposit the electrode layer Au by thermal evaporation process, the thickness is 50 nm, and the speed is 0.03 nm / s. Then dissolve the excess PMMA in acetone (60°C, 5 min);

[0051] (3) Sequentially transfer the functional layer and the encapsulation layer to the step surface prepared in step (2): in a glove box with extremely low water and oxygen content, use a low-dimensional transfer platform to accurately transfer the mechanically exfoliated two-dimensional material NbOI2 to the electrode surface, and ensure that the polar axis is perpendicular to the specific direction of the channel. First, NbOI2 is slightly attached to the electrode surface, and then by gradually applying pressure to the PDMS, it is deformed downward, so that NbOI2 completely fits the bottom of the channel. After this process is completed, the sample needs to be heated to 80°C and kept for 5 minutes. Then, transfer h-BN to the surface of NbOI2, as in the previous step. It should be noted that the area of h-BN should be larger than that of NbOI2 to protect NbOI2 from the water and oxygen environment.

[0052] Result analysis

[0053] The strain characterization and performance characterization of the strain-enhanced multi-sensory fusion optoelectronic synaptic device prepared in this example 1 are as shown in the figure. Figures 3-8

[0054] Figure 3 ​P2 Raman peaks of the unstrained (light curve) and strained (dark curve) regions of the two-dimensional material NbOI2 are shown. The Raman spectrum shows that the P2 Raman peak of the channel region exhibits a significant shift compared to the unstrained region, which proves the formation of strain. The tensile strain applied along the polar axis of NbOI2 increases the polar displacement of Nb atoms, intensifies the non-centrosymmetry, and thus enhances the second harmonic signal. Figure 4 The variation of the total second harmonic intensity with the polarization angle of the excitation light beam (λ SHG = 525 nm) is shown, which shows that the second harmonic intensity of the strained region is significantly higher than that of the unstrained region. The shift of the Raman peak and the enhancement of the second harmonic fully prove the generation of channel strain.

[0055] In order to study the influence of the synergistic effect of strain and light on the performance of the device, an unstrained NbOI2 device is constructed by transferring the electrode for comparison. Figure 5 The I ds -V ds curves of the two devices in the dark state are shown, which show the memristive curves of multiple cycles, indicating that the device has ferroelectric memristive behavior. Due to the tensile strain along the polar axis, the spontaneous polarization of NbOI2 is enhanced, so the strained NbOI2 device has a larger hysteresis window compared with the unstrained device. Figure 6 The relationship between the PPF index obtained by fitting with a double exponential function and the pulse interval is shown. Compared with the unstrained device, the PPF index of the strained device is significantly improved from 116% to 180%. Figure 7 The current decay processes of the strained and unstrained NbOI2 devices after responding to different numbers of light pulses under 532 nm light pulses are shown, which shows that the strained device has better memory effect of photocurrent. In order to verify the superiority of multi-modal perception in specific information processing compared with single-mode perception, the application research of optical fingerprint image processing is carried out.

[0056] Figure 8 The relationship between photocurrent and light intensity of the NbOI2 device in the strained and unstrained states is shown, and a power law fitting is performed. Figure 9 The strained device shows better effect in enhancing the complete (e in FIG. 14B) and partial (f in FIG. 14C) fingerprint images compared with the unstrained device (c and d in FIG. 14A), and the ridges and valleys of the fingerprint become more obvious. Figure 9 Figure 9 Figure 9

[0057] Example 2

[0058] ​​​The strain enhanced ferroelectric polarized optoelectronic synapse device was prepared by using the same steps as in Example 1, except that one of Al2O3, HfO2, ZrO2, etc. was deposited by a magnetron sputtering process.

[0059] Example 3

[0060] The strain enhanced ferroelectric polarized optoelectronic synapse device was prepared by using the same steps as in Example 1, except that one of NbOCl2, NbOBr2, etc. was used as the functional layer.

[0061] Example 4

[0062] The strain enhanced ferroelectric polarized optoelectronic synapse device was prepared by using the same steps as in Example 1, except that the tensile strain size was adjusted by changing the thickness of the insulating layer (0-200 nm) and the channel width (1-5 μm).

[0063] Those skilled in the art will easily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A strain-enhanced multi-sensory fusion opto-synaptic device, characterized in that: The photoelectric synaptic device includes an insulating layer, electrodes, and a functional layer arranged from bottom to top. The material of the functional layer is an in-plane polarized two-dimensional ferroelectric material, and the functional layer is subjected to tensile strain along its own polar axis. The photoelectric synaptic device simulates the perception of visual information through the photoconductive effect of the functional layer and simulates tactile sensation through tensile strain. The material of the functional layer is any one of mechanically exfoliated NbOI2, NbOCl2, and NbOBr2; the tensile strain is adjusted by controlling the deposition thickness of the stepped structure composed of the insulating layer and the electrode and the channel width between the electrodes, wherein the thickness of the stepped structure is 50 nm - 250 nm and the channel width is 1 μm - 5 μm.

2. The strain-enhanced multi-sensory fusion photosynaptic device as described in claim 1, characterized in that: The thickness of the functional layer is 20 nm - 40 nm.

3. The strain-enhanced multi-sensory fusion photosynaptic device as described in claim 1, characterized in that: The insulating layer is made of any one of SiO2, Al2O3, HfO2, or ZrO2, and its thickness is 0 nm - 200 nm.

4. The strain-enhanced multi-sensory fusion photosynaptic device as described in claim 1, characterized in that: The electrode is made of gold, palladium, or platinum and has a thickness of 60 nm.

5. The strain-enhanced multi-sensory fusion optosynaptic device as described in claim 1, characterized in that: An insulating encapsulation layer is also provided on the functional layer. The material of the insulating encapsulation layer is a mechanically peeled two-dimensional layered material h-BN with a thickness of 10 nm to 20 nm.

6. A method for fabricating a strain-enhanced multi-sensory fusion opto-synaptic device according to any one of claims 1-5, characterized in that, The method includes the following steps: (1) The desired pattern is prepared on the surface of a hard substrate using electron beam lithography. (2) The insulating layer and the electrode are sequentially deposited on the surface of the hard substrate; (3) The functional layer and the encapsulation layer are sequentially transferred to the electrode using a low-dimensional transfer platform to obtain the synaptic device.

7. The method for fabricating the strain-enhanced multi-sensory fusion opto-synaptic device as described in claim 6, characterized in that: During the transfer process, the functional layer is first attached to the electrode surface, and then pressure is gradually applied to the functional layer so that the bottom of the channel formed between the functional layer and the electrode is completely attached, thereby generating tensile strain.

8. The application of the strain-enhanced multi-sensory fusion optosynaptic device according to any one of claims 1-5 in an artificial intelligence system.

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