Dual-mode event camera of PMN-PT-based photoelectric detector and preparation method of dual-mode event camera

Abstract

The invention belongs to the field of intelligent photoelectric detectors, and particularly discloses a dual-mode event camera of a PMN-PT-based photoelectric detector and a preparation method of the dual-mode event camera, array electrodes are deposited in an auxiliary mode through a mask, a relaxor ferroelectric PMN-PT photoelectric detector is constructed, and the dual-mode photoresponse characteristic is shown; at 0V, typical symmetric peaks caused by the pyroelectric effect can be seen from visible light to near-infrared bands; under a proper bias voltage, under excitation of 405nm laser, a light response waveform is converted into a square mainly based on a bulk photovoltaic effect; a PMN-PT-based photoelectric detector is used for constructing an event camera, bias voltage is applied to start the camera when a vehicle passes by, image capture is performed on the vehicle by using a photovoltaic effect, and the problem of high energy consumption of a traditional camera is solved.

Description

Technical Field

[0001] The invention relates to the field of intelligent photoelectric detection devices, in particular to a dual-mode event camera of a PMN-PT based photoelectric detector and a preparation method thereof. Background Art

[0002] The rapid development of artificial intelligence (AI) applications urgently requires low-power, multifunctional, highly compact and integrated smart photodetectors, which requires innovations in both smart photosensitive materials and device architectures. At the Curie temperature (Tc), the presence of spontaneous polarization in ferroelectrics can introduce a variety of physical effects, such as piezoelectric effect, inverse piezoelectric effect, pyroelectric effect and bulk photovoltaic effect, showing potential for application in multifunctional devices and opening up opportunities for smart imaging applications. In the field of road traffic imaging, traditional cameras are kept on for a long time because they need to monitor road traffic conditions at all times, which is a huge challenge to the performance and energy consumption of the camera.

[0003] Therefore, a dual-mode event camera for low-energy consumption and long-life road monitoring is designed to solve the above problems. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a dual-mode event camera of a PMN-PT based photoelectric detector and a preparation method thereof.

[0005] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0006] One of the technical solutions of the present invention is a method for preparing a dual-mode event camera of a PMN-PT based photodetector, comprising the following steps:

[0007] S1. Lay two copper foils flat on the upper and lower end faces of the relaxor ferroelectric single crystal PMN-PT, respectively, and connect them with the wires drawn from the DC voltage regulator to form a closed loop; immerse the PMN-PT in a glass dish containing silicone oil, place the glass dish on a hot plate, adjust the temperature of the hot plate to raise the temperature of the silicone oil to 60°C, check the continuity of the circuit with a multimeter before polarization, and after confirming that the circuit is connected, use a DC voltage regulator to perform DC polarization on the PMN-PT: apply a working voltage of 1kV, and slowly increase the voltage from 0V to 1kV within 3min. The polarization process lasts for 17min. After the polarization is completed, reduce the voltage from 1kV to 0V within 3min, take out the PMN-PT from the silicone oil, and use ethanol and deionized water to remove the residual silicone oil on the surface of the PMN-PT to obtain a polarized PMN-PT;

[0008] S2, using a copper mesh as a mask, depositing a Cr layer and an Au layer in sequence at intervals on both ends of the polarized PMN-PT upper end surface, removing the copper mesh from the top of the PMN-PT, forming a Cr / Au array electrode on the PMN-PT upper end surface, and obtaining a PMN-PT-based photodetector;

[0009] S3, bonding the PMN-PT based photodetector wires to the PCB board;

[0010] S4. Integrate the PCB board loaded with PMN-PT based photodetectors into the intelligent light detection module to obtain a dual-mode event camera.

[0011] Furthermore, the electric field strength of the PMN-PT during DC polarization is 2 kV / mm.

[0012] Furthermore, the thickness of the Cr array electrode is 15 nm, and the thickness of the Au array electrode is 65 nm.

[0013] Furthermore, the length*width*height of the PMN-PT is 1 cm*1 cm*0.5 mm, and the crystal orientation is

[111] .

[0014] Preferably, the copper mesh is a square-hole copper mesh with a pore size of 230 μm.

[0015] The principle of the present invention is: the polarization intensity of the ferroelectric relaxation single crystal PMN-PT will be affected by temperature changes, causing PMN-PT to be very sensitive to periodic laser irradiation. The two processes of laser turning on and off will cause the temperature of PMN-PT to rise or fall, which will have opposite effects on the polarization intensity. The amount of charges bound on the crystal surface will change, generating pyroelectric current. The pyroelectric effect generated based on temperature changes can make the detection range of the PMN-PT detector extend from the visible to the near-infrared band, and can effectively detect approaching vehicles on the road.

[0016] The second technical solution of the present invention is a dual-mode event camera using a PMN-PT-based photodetector prepared by the above method.

[0017] Compared with the prior art, the present invention constructs a relaxor ferroelectric PMN-PT photodetector through mask-assisted deposition of array electrodes, and exhibits dual-mode light response characteristics; at 0V, typical symmetrical peaks caused by the pyroelectric effect can be seen from the visible light to the near-infrared band; under appropriate bias voltage, under 405nm laser excitation, the light response waveform is transformed into a square dominated by the bulk photovoltaic effect; the PMN-PT-based photodetector is used to construct an event camera, and when a vehicle passes by, a bias voltage is applied to start the camera, and the image of the vehicle is captured using the bulk photovoltaic effect, solving the problem of high energy consumption of traditional cameras. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the polarization device of PMN-PT.

[0019] Figure 2 The polarizing microscope image of PMN-PT is shown in the figure, and the inset image is the polarizing microscope image of PMN-PT when it is not polarized.

[0020] Figure 3 This is the IV curve of PMN-PT under 405nm laser irradiation with the change of power.

[0021] Figure 4 It curves of PMN-PT with different bias voltages applied to PMN-PT under periodic irradiation of 405nm laser.

[0022] Figure 5 It curves of PMN-PT after different bias voltages are applied to PMN-PT under periodic irradiation of 532nm laser.

[0023] Figure 6 It curves of PMN-PT after different bias voltages are applied to PMN-PT under periodic irradiation of 980nm laser.

[0024] Figure 7 is the transmission spectrum of PMN-PT, and the inset is the IV curve of PMN-PT under 532 nm laser irradiation.

[0025] Figure 8 Schematic diagram of PMN-PT wire bonding to PCB board.

[0026] Fig. 9 This is a picture of the intelligent light detection module.

[0027] Fig.10 Schematic diagram of the working logic of the dual-mode event camera and the three different working stages of the event camera. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the invention.

[0029] Example 1

[0030] This embodiment exemplarily demonstrates a method for preparing a dual-mode event camera of a PMN-PT based photodetector. First, a PMN-PT based photodetector is prepared, and then the PMN-PT based photodetector is integrated into an intelligent light detection module to construct a dual-mode event camera.

[0031] like Figure 1As shown, this embodiment uses a relaxor ferroelectric single crystal PMN-PT with a length*width*height of 1cm*1cm*0.5mm and a crystal orientation of

[111] ; two copper foils are respectively flatly attached to the upper and lower end surfaces of the relaxor ferroelectric single crystal PMN-PT, and connected to the wires drawn from the DC voltage regulator to form a closed loop; PMN-PT is immersed in a glass dish with silicone oil, and the glass dish is placed on the hot stage, and the temperature of the hot stage is adjusted to make the temperature of the silicone oil rise to 60°C. Before polarization, a multimeter is used to check the continuity of the circuit to confirm that the circuit is connected. After the passage, a DC voltage stabilizer was used to apply an electric field of 2 kV / mm to the PMN-PT for DC polarization: a working voltage of 1 kV was applied, and the voltage was slowly increased from 0 V to 1 kV within 3 min. The polarization process lasted for 17 min. After the polarization was completed, the voltage was reduced from 1 kV to 0 V within 3 min. The PMN-PT was taken out from the silicone oil, and the residual silicone oil on the surface of the PMN-PT was removed by ethanol and deionized water in turn to obtain the polarized PMN-PT. The polarization effect was verified by observing the polarizing microscope image of the PMN-PT, as shown in FIG. Figure 2 As shown in the figure, compared with the unpolarized polarizing microscope image, the existence of ferroelectric domains can be clearly seen on the surface of the polarized PMN-PT, proving that polarization has an effect, providing conditions for the introduction of the pyroelectric effect of the PMN-PT crystal. Afterwards, a square hole copper mesh with an aperture size of 230μm was used as a mask, and a 15nm thick Cr layer and a 65nm thick Au layer were sequentially deposited at intervals on both ends of the upper end face of the polarized PMN-PT. The copper mesh was removed from the top of the PMN-PT, and a Cr / Au array electrode was formed on the upper end face of the PMN-PT to obtain a PMN-PT-based photodetector.

[0032] This example tests the IV curve of the PMN-PT based photodetector under 405nm laser irradiation. Figure 3 As shown, an attenuation plate is used to adjust the laser power incident on the PMN-PT crystal. Under the same bias voltage, the photocurrent generated by the device increases with the increase of the incident light power, showing a photosensitivity characteristic. At a bias voltage of 5V, the maximum photocurrent can reach 7.6nA.

[0033] This example studies the transient photoresponse characteristics of PMN-PT based photodetectors under periodic 405nm laser irradiation. Figure 4As shown in the figure, with the increase of bias voltage, the working mechanism of PMN-PT gradually changes from being dominated by pyroelectric effect to being dominated by bulk photovoltaic effect. When the bias voltage is 1V, the coexistence of pyroelectric effect and bulk photovoltaic effect can be observed. At the moment of laser incidence, a negative pyroelectric spike is generated due to temperature change, and then the response current rises to a stable value under the action of bulk photovoltaic effect. After the laser is removed, a positive pyroelectric spike is generated due to the recovery of PMN-PT polarization intensity, and finally the current returns to the same value as the dark current. When the bias voltage increases from 0V to 5V, the response current waveform changes from a symmetrical pyroelectric spike to a square wave waveform, so the detection mode conversion can be achieved by adjusting the bias voltage of PMN-PT.

[0034] The pyroelectric effect generated by temperature change makes PMN-PT still show symmetrical pyroelectric spikes (0V bias) under 532nm and 980nm laser irradiation. Figure 5 and Figure 6 However, when the applied bias voltage is increased to 5 V, the response current waveform of PMN-PT still does not change significantly, which is different from the performance of PMN-PT under 405 nm laser irradiation, indicating that the dual-mode detection of PMN-PT is also related to the wavelength of the incident laser.

[0035] In this example, the transmission spectrum of PMN-PT is measured. Figure 7 As shown, PMN-PT has a low transmittance to light in the 405nm band, and a high transmittance to light in the 532nm to near-infrared band, corresponding to two different experimental phenomena. The inset is the IV curve of PMN-PT under 532nm laser irradiation. It can be seen that the incident light power has no significant effect on the measured IV curve, which further illustrates that PMN-PT crystal has almost no absorption of laser in the 532nm to near-infrared band, thus proving that the generation of bulk photovoltaic effect is related to PMN-PT's absorption of laser.

[0036] Bond the PMN-PT based photodetector wires to the PCB board, such as Figure 8 As shown, the electrodes of the PMN-PT are connected to the electrodes of the PCB board by aluminum wires, which can prevent the PMN-PT electrodes from being further damaged, facilitate multiple tests, make the performance more stable, and facilitate the integration of the PMN-PT chip into the smart device optical module. It should be noted that the PCB board of this embodiment can directly use the same type of PCB board in the field; Fig. 9As shown, the PCB board loaded with PMN-PT-based photodetectors is integrated into the intelligent light detection module to obtain a dual-mode event camera; the PCB board and the intelligent light detection module are customized using the Jialichuang platform after the circuits are designed by ourselves, and the corresponding components are purchased in the Jialichuang Mall. The names of the components, packaging processes and corresponding bit numbers in the module (the packaging processes and bit numbers are marked in brackets) are as follows: thick film resistor 10kΩ±1% 100mW (0603, R41, R40, R19, R27, R14, R55, R51, R50, R49, R48, R47, R46, R45, R44, R39, R38, R37, R35, R22, R17, R6, R3), 0603 red light is bright (0603, D4, D3), DC power socket inner diameter: 3mm outer diameter: 6mm [plug-in] (plug-in, P15), [plug-in] 1x5P spacing: 2.54mm straight plug (plug-in, P=2.54mm, P16), Type-B female curved plug [US] (plug-in, U13, U11), input 20V output 3.3V 800mA (SOT-223, U10), 100nF ±10% 50V (0603, CP2, CP1, C70, C65, C63, C59, C56, C55, C50, C49, C48, C47, C46, ​​C45, C42, C41, C37, C36, C33, C32, C31, C30, C29, C26, C24, C18, C17, C16, C15, C14, C13, C12, C11, C10, C9, C8, C7, C4, C3, C2), 1kΩ ±1% 100mW thick film resistor (0603, R56, R54, R43, R42, R34 , R33, R32, R31, R29, R28, R26, R25, R24, R23, R21, R20, R18, R16, R15, R13, R12, R11, R10, R9, R8, R7, R4, R2), USB to serial port chip CH340 (SOP-8, U12), self-ejecting MicroSD card (TF card) holder (SMD, U5), 10MΩ±1% 100mW thick film resistor (0603, R63), 2N7002 (SOT-23, Q2, Q1), 4.7kΩ±1% 100mW thick film resistor (0603, R62, R61), thin film resistor 249kΩ±0.1% 100mW (0603, R66, R53), 10nF ± 10% 50V (0603, C40, C34), REF5025AIDR (SOIC-8, U8), 8MHz ± 10ppm 20pF YSX530GA (SMD5032-2P, Y1), AD7606BSTZ-4RL (LQFP-64_10x10, U2), OPA2171AID (SOIC-8, U3, U1), [Plug-in] Pitch: 2.54mm 1x8P straight-insert square pin (plug-in, P = 2.54mm, P2, P1), 8pF 50V (0603, C61, C60), pitch 2.54mm flat dial, raised 4-position DIP switch [DIP] (plug-in, SW1), 22uF ± 20% 25V (0805, C64, C62, C58, C52, C51, C44, C43, C39, C38, C28, C23, C21, C20, C19, C6, C5, C1), STM32F103VET6 (LQFP-100 (14x14), U9), 32.768kHz ± 20ppm 12.5pF (SMD3215-2P, Y2), MCP6002T-I / SN (SOIC-8, U14), Thin Film Resistor 768kΩ±1% 100mW (0603, R52), 33pF±5% 50V (0603, C71, C69, C68, C67, C66), 18pF±5% 50V (0603, C54, C53), DAC8562SDGSR (VSSOP-10-0.5mm, U4), Thick Film Resistor 100MΩ±5% 100mW (0603, R64), 100kΩ±1 % 100mW thick film resistor (0603, R67, R65), Battery base for battery: CR1220 (SMD, BT1), Voltage: 1kV Current: 1A (SMA (DO-214AC), D2, D1), 10Ω ± 1% 100mW thick film resistor (0603, R59, R58, R30, R5, R1), 1uF ± 10% 50V (0603, C27, C25, C22), LT1962EMS8#TRPBF (MSOP-8, U6), Inner hole SMA elbow [plug-in] (plug-in, RF1), 3.81mm 1x8P row number: 1P number per row: 8

plug-in

[0037] In order to verify the performance of the dual-mode event camera prepared in this embodiment, the dual-mode event camera is used for road vehicle monitoring.

[0038] Fig.10 The figure is a schematic diagram of the working logic of the dual-mode event camera and the corresponding three different working stages. The pyroelectric current signal generated by the PMN-PT will first be converted into a voltage signal, and then sent to the MCU chip for logic judgment after digital-to-analog conversion: when there is no vehicle approaching, the PMN-PT detector does not respond, and the dual-mode event camera is in standby mode; when a vehicle approaches, the pyroelectric effect of the PMN-PT is triggered, and when the output pyroelectric voltage is greater than the set threshold, a 5V bias voltage will be applied to the PMN-PT chip, so that the pyroelectric effect switches to the bulk photovoltaic effect, and the image of the approaching vehicle is captured. Therefore, when there is no vehicle, the dual-mode event camera can be in a 0V standby state, and when a vehicle passes by, the event camera is started to capture the vehicle image, which greatly saves energy compared to traditional cameras working day and night.

[0039] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a dual-mode event camera based on a PMN-PT photodetector, characterized in that: The following steps are involved: S1. Lay two copper foils flat on the upper and lower end faces of the relaxor ferroelectric single crystal PMN-PT, respectively, and connect them with the wires drawn from the DC voltage regulator to form a closed loop; immerse the PMN-PT in a glass dish containing silicone oil, place the glass dish on a hot plate, adjust the temperature of the hot plate to raise the temperature of the silicone oil to 60°C, check the continuity of the circuit with a multimeter before polarization, and after confirming that the circuit is connected, use a DC voltage regulator to perform DC polarization on the PMN-PT: apply a working voltage of 1kV, and slowly increase the voltage from 0V to 1kV within 3min. The polarization process lasts for 17min. After the polarization is completed, reduce the voltage from 1kV to 0V within 3min, take out the PMN-PT from the silicone oil, and use ethanol and deionized water to remove the residual silicone oil on the surface of the PMN-PT to obtain a polarized PMN-PT; S2, using a copper mesh as a mask, depositing a Cr layer and an Au layer in sequence at intervals on both ends of the polarized PMN-PT upper end surface, removing the copper mesh from the top of the PMN-PT, forming a Cr / Au array electrode on the PMN-PT upper end surface, and obtaining a PMN-PT-based photodetector; S3, bonding the PMN-PT based photodetector wires to the PCB board; S4. Integrate the PCB board loaded with PMN-PT based photodetectors into the intelligent light detection module to obtain a dual-mode event camera.

2. The method for preparing a dual-mode event camera of a PMN-PT based photodetector according to claim 1, characterized in that: The electric field strength of the PMN-PT during DC polarization is 2 kV / mm.

3. The method for preparing a dual-mode event camera of a PMN-PT based photodetector according to claim 1, characterized in that: The thickness of the Cr array electrode is 15 nm, and the thickness of the Au array electrode is 65 nm.

4. The method for preparing a dual-mode event camera of a PMN-PT based photodetector according to claim 1, characterized in that: The length*width*height of the PMN-PT is 1 cm*1 cm*0.5 mm, and the crystal orientation is [111].

5. The method for preparing a dual-mode event camera of a PMN-PT based photodetector according to claim 1, characterized in that: The copper mesh is a square-hole copper mesh with a pore size of 230 μm.

6. A dual-mode event camera of a PMN-PT based photodetector prepared by the method according to any one of claims 1 to 5.

Images