Broadband photoelectric detector based on polystyrene nano-microsphere array and preparation method

Abstract

The invention discloses a broadband photoelectric detector based on a polystyrene nanometer microsphere array and a preparation method, and belongs to the technical field of photoelectric detectors. The broadband photoelectric detector is composed of a silicon / silicon dioxide substrate, a gold electrode, a light absorption layer black phosphorus and polystyrene nanometer microspheres from bottom to top in sequence; the polystyrene nanometer microspheres are of a hexagonal close-packed structure and cover a half area of the surface of the black phosphorus absorption layer, light energy is focused on the black phosphorus absorption layer through the lens effect, optical absorption is enhanced, a temperature gradient difference is generated, and diffusion and migration of carriers are promoted to form electric signals. At the same time, the preparation of the broadband mid-infrared photoelectric detector with high performance and high stability is realized through the synergistic effect of the lens effect of the nanometer microspheres and the broadband spectrum absorption of the black phosphorus.

Description

Technical Field

[0001] This invention belongs to the field of photodetector technology, specifically relating to a broadband photodetector based on a polystyrene nanosphere array and its fabrication method. Background Technology

[0002] Wideband photodetectors, as core devices for optical signal sensing and conversion, have irreplaceable application value in many fields such as optical communication, environmental monitoring, biomedical diagnosis, and military reconnaissance. Among them, the mid-infrared band is an important atmospheric window, providing additional thermal information compared to the visible light band, and is of great value in medical detection, meteorological remote sensing, and aerospace exploration. However, this band cannot be directly perceived by the human eye. Therefore, developing mid-infrared photodetectors with high responsivity, wide spectral response range, room temperature stability, and controllable manufacturing costs is of significant research importance and value. Photothermoelectric (PTE) detectors are renowned for their ultra-wideband response due to their Seebeck effect-based operating mechanism. Furthermore, PTE detectors have many advantages, such as low noise, no need for cooling devices, no need for external power supplies, and no need for modulation choppers, making them suitable for infrared and terahertz detection.

[0003] In recent years, black phosphorus (BP), a two-dimensional material, has become an ideal material for constructing high-performance mid-infrared detectors due to its tunable direct bandgap, high carrier mobility, low dark current, and broad spectral response in the mid-infrared range. However, a single black phosphorus light absorption layer still faces the problem of limited optical absorption efficiency in practical applications, resulting in device responsivity and detectivity that cannot meet the requirements of high-performance applications. Traditional solutions address the bottleneck of insufficient light absorption efficiency by constructing structures such as nanoantennas and aperture arrays to capture and focus light energy, thereby improving photoelectric conversion efficiency. However, existing microstructure fabrication processes often involve complex steps such as precision photolithography and etching, which not only increases device fabrication costs but may also introduce interface defects, affecting device stability. Therefore, we developed a structural design strategy that is simple, low-cost, and can efficiently enhance the light absorption performance of black phosphorus-based detectors. By utilizing the lens effect of nanospheres to enhance local optical absorption, a local temperature gradient difference is generated, ultimately constructing a broadband photothermal-electric mid-infrared detector. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a broadband photodetector based on a polystyrene nanosphere array and its fabrication method. Through the synergistic effect of the lens effect of the nanospheres and the broadband absorption of black phosphorus, a high-performance and highly stable broadband mid-infrared photodetector is fabricated.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A broadband photodetector based on a polystyrene nanosphere array comprises, from bottom to top, a silicon / silica substrate, a gold electrode, a black phosphorus absorption layer, and polystyrene nanospheres. The polystyrene nanospheres, arranged in a hexagonal close-packed structure, cover half of the surface of the black phosphorus absorption layer. Through the lens effect, they focus light energy onto the black phosphorus absorption layer, enhancing optical absorption and generating a temperature gradient difference, which promotes carrier diffusion and migration to form an electrical signal.

[0006] This invention provides a method for fabricating a broadband photodetector based on a polystyrene nanosphere array, specifically including the following steps: (1) The silicon wafer coated with silicon dioxide film was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water in sequence, dried with nitrogen gun, and then the surface hydrophobicity was optimized by ozone ultraviolet treatment. (2) Two gold electrodes were prepared on both ends of the surface of a silicon dioxide thin film by electron beam evaporation; (3) A uniform black phosphorus film is transferred to both ends of the electrode by mechanical peeling and transfer. (4) A layer of PS nanospheres was deposited on the substrate by nanosphere self-assembly and transferred to the black phosphorus surface by PDMS tape.

[0007] Furthermore, in step (1), the ultrasonic cleaning time is 5-10 min, and the ozone ultraviolet treatment time is 15-30 min.

[0008] Further, in step (2), two gold electrodes are symmetrically arranged at both ends of the silicon dioxide film surface, with a distance of 500 μm between the two electrodes, an electrode length of 1 mm, and a width of 200 μm. After the electrodes are homogenized, photolithographically and developed, they are rinsed with IPA for 60 seconds to remove the developer. An 80 nm thick gold layer is deposited by electron beam evaporation. The substrate is then inverted in acetone stripper to remove the remaining photoresist, resulting in two gold electrodes with a spacing of 500 μm, a length of 1 mm, and a width of 200 μm.

[0009] Furthermore, step (3) the transfer of the black phosphorus absorption layer specifically involves: Place the black phosphorus crystal block on 3M tape and fold and tear it repeatedly 7 times. Gently press the peeled black phosphorus onto the surface of the PDMS heat release tape to transfer the black phosphorus to the PDMS substrate for use. The PDMS film with black phosphorus was fixed directly above the middle area of ​​the two electrodes by fine-tuning the transfer platform. The PDMS was slowly lowered to make it fully adhere to the substrate. After heating the substrate platform to 120°C, the extension arm was slowly raised to transfer the black phosphorus onto the electrodes.

[0010] Furthermore, step (4) specifically includes: Add 85% ethanol dispersant to the polystyrene nanosphere suspension and mix thoroughly by ultrasonication for 10 minutes. Monolayer nanospheres were spread onto the liquid surface using a syringe at an angle of approximately 60° via a micro-push injection method. After the microspheres were retrieved using a glass slide, they were baked at a low temperature of 50°C to form a hexagonal close-packed structure on the glass slide. The array of nanospheres on a glass slide was adhered using double-sided PDMS tape. The nanospheres were then transferred to half of the black phosphorus surface using a mechanical transfer system and an optical microscope to obtain the broadband photodetector.

[0011] Furthermore, the detector prepared by the above method has a wide spectral response in the 3-7 μm band, with a photocurrent of up to 560 nA at a bias voltage of 0.01 V, a responsivity of 320 mA / W at a wavelength of 3.7 μm, a rise time of 360 μs, and a fall time of 310 μs.

[0012] Compared with the prior art, the beneficial effects of the present invention are: This invention abandons the traditional complex microstructure preparation steps such as precision photolithography and etching, and adopts simple processes such as nanosphere self-assembly and mechanical transfer. It does not require expensive equipment and complex processes, which reduces the preparation cost and technical threshold and facilitates mass production. This invention achieves precise, directional, and regionalized transfer of nanosphere arrays through processes such as PDMS thermal release tape transfer and low-temperature baking, while avoiding the introduction of interface defects and ensuring the structural integrity and operational stability of the device. The tight adhesion between black phosphorus and the electrodes and microsphere layers further enhances the long-term operational reliability of the device. This invention allows for flexible optimization of the optical and electrical performance of the device by changing the size of the nanospheres, adjusting the coverage concentration, and controlling the thickness of the black phosphorus film, thus adapting to different waveband detection requirements and exhibiting strong scalability. Furthermore, the invention features a specially designed non-full-coverage structure where the microspheres cover half of the black phosphorus surface, ensuring enhanced light absorption due to the lens effect while optimizing the device's electrical performance through the contrast effect of the uncovered area. Simultaneously, the hexagonal close-packed structure of the nanospheres maximizes focusing efficiency. This invention utilizes the wide-band absorption characteristics of black phosphorus material (2-10 μm) and combines them with the lens focusing effect of polystyrene nanospheres to achieve effective detection in the mid-infrared band (3-7.5 μm), covering key atmospheric windows and meeting the needs of multiple application scenarios. At the same time, the lens effect of the nanospheres can focus light energy onto the black phosphorus absorption layer, significantly enhancing the local light field intensity and reducing light energy loss. This solves the problem of limited optical absorption efficiency of a single black phosphorus absorption layer and lays the foundation for high response performance. The detector fabricated using the method of this invention exhibits a wide spectral response in the 3-7 μm band, with a maximum photocurrent of 560 nA at a bias voltage of 0.01 V, a responsivity of 320 mA / W at a wavelength of 3.7 μm, a rise time of 360 μs, and a fall time of 310 μs. It balances high sensitivity with rapid detection capability, meeting the requirements of high-performance applications. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 The image shows the simulation results of the optical lens focusing effect of the polystyrene microspheres of this invention at a mid-infrared wavelength of 3.6 μm. Figure 3 Optical transmittance for different degrees of polystyrene nanosphere coverage; Figure 4 Microscopic images of mechanically transferred polystyrene; Figure 5 The optical transmittance of black phosphorus material in the mid-infrared band; Figure 6 This is a diagram showing the wideband operating characteristics of a photodetector. Figure 7 The photoelectric response speed of a broadband photodetector; Figure 8 This refers to the responsivity of a broadband photodetector. Detailed Implementation

[0014] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of this invention and does not strictly limit the scope of protection specifically claimed by this invention.

[0015] Example 1 like Figure 1 As shown, a broadband photodetector based on a polystyrene nanosphere array is composed of a silicon / silica substrate, a gold electrode, a black phosphorus absorption layer, and polystyrene nanospheres from bottom to top. The polystyrene nanospheres are arranged in a hexagonal close-packed structure covering half of the surface of the black phosphorus absorption layer. Through the lens effect, light energy is focused onto the black phosphorus absorption layer, enhancing optical absorption and generating a temperature gradient difference, which promotes carrier diffusion and migration to form an electrical signal.

[0016] The above-mentioned method for fabricating a broadband photodetector based on a polystyrene nanosphere array specifically includes the following steps: (1) The silicon wafer coated with silicon dioxide film was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water in sequence, dried with nitrogen gun, and then the surface hydrophobicity was optimized by ozone ultraviolet treatment. (2) Two gold electrodes are symmetrically arranged at both ends of the silicon dioxide film surface, with a distance of 500 μm between the two electrodes, an electrode length of 1 mm and a width of 200 μm. After the electrodes are coated, photolithographically and developed, they are rinsed with IPA for 60 seconds to remove the developer. An 80 nm thick gold layer is deposited by electron beam evaporation. The substrate is then inverted in acetone stripper to remove the remaining photoresist, resulting in two gold electrodes with a spacing of 500 μm, a length of 1 mm and a width of 200 μm. (3) The uniform black phosphorus film is transferred to both ends of the electrode by mechanical peeling and transfer, specifically as follows: Place the black phosphorus crystal block on 3M tape and fold and tear it repeatedly 7 times. Gently press the peeled black phosphorus onto the surface of the PDMS heat release tape to transfer the black phosphorus to the PDMS substrate for use. The PDMS film with black phosphorus was fixed directly above the middle area of ​​the two electrodes by fine-tuning the transfer platform. The PDMS was slowly lowered to make it fully adhere to the substrate. After heating the substrate platform to 120°C, the extension arm was slowly raised to transfer the black phosphorus onto the electrodes. (4) Add 85% ethanol dispersant to the polystyrene nanosphere suspension and mix evenly by ultrasonication for 10 minutes; Monolayer nanospheres were spread onto the liquid surface using a syringe at an angle of approximately 60° via a micro-push injection method. After the microspheres were retrieved using a glass slide, they were baked at a low temperature of 50°C to form a hexagonal close-packed structure on the glass slide. The array of nanospheres on a glass slide was adhered using double-sided PDMS tape. The nanospheres were then transferred to half of the black phosphorus surface using a mechanical transfer system and an optical microscope to obtain the broadband photodetector.

[0017] Figure 2 The figure shows the Comsol simulation results of the optical lens focusing effect of polystyrene microspheres at a mid-infrared wavelength of 3.65 μm in this embodiment. As can be seen from the figure, due to the optical lens effect of the nanospheres, the light field intensity below each sphere is significantly enhanced, thereby improving the optical absorption of the black phosphorus material below and causing a significant increase in temperature, which helps to form a temperature difference.

[0018] Figure 3 To measure the optical transmittance of different polystyrene nanosphere coverage levels in this embodiment, different concentrations of polystyrene nanospheres were covered on the sample surface. A coverage concentration of 100% indicates that the test area is filled with a single layer of nanospheres, while 150% indicates that some nanospheres are stacked to form a two-layer structure. The test results show that the optical transmittance is significantly reduced due to the optical enhancement absorption caused by the focusing effect of the nanospheres.

[0019] Figure 4The image shows a microscopic optical image of polystyrene transferred mechanically in this embodiment. As can be seen from the image, by combining the self-assembly method and the mechanical transfer process, PDMS thermal release tape can be used to achieve the batch and regional directional transfer of polystyrene microspheres.

[0020] Figure 5 The optical transmittance spectrum of black phosphorus material in the mid-infrared band in this embodiment clearly shows that black phosphorus has an optical absorption rate of >20% in the 3-7μm band, exhibiting broad spectral absorption characteristics in this band, which helps to achieve effective detection of optical signals in the mid-infrared band.

[0021] Figure 6 The wide-band operating characteristics of the photodetector in this embodiment are clearly shown. The detector has a wide-band detection characteristic of 3-7 μm, and the photocurrent can reach up to 560 nA under a bias voltage of 0.01 V.

[0022] Figure 7 The figure shows the photoelectric response speed of the wideband photodetector in this embodiment. As can be seen from the figure, the rise time and fall time of the detector are 360 ​​and 310 μs, respectively.

[0023] Figure 8 The responsivity of the broadband photodetector in this embodiment is in the 3-7 μm band. Since black phosphorus has strong optical absorption characteristics at 3.7 μm, the responsivity of this photodetector at 3.7 μm can reach 320 mA / W.

[0024] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A wide-band photodetector based on polystyrene nanosphere array, characterized in that, From bottom to top, it is composed of silicon / silicon dioxide substrate, gold electrode, black phosphorus absorption layer and polystyrene nanospheres; the polystyrene nanospheres in hexagonal close-packed structure cover half of the surface of the black phosphorus absorption layer, focus light energy on the black phosphorus absorption layer through lens effect, enhance optical absorption and generate temperature gradient difference, promote carrier diffusion and migration to form an electrical signal.

2. The method for preparing a wide-band photodetector based on polystyrene nanosphere array according to claim 1, characterized in that: Specifically comprising the following steps: (1) The silicon wafer coated with a thin film of silicon dioxide is sequentially cleaned with acetone, anhydrous ethanol and deionized water, dried by nitrogen gun, and the surface hydrophobicity is optimized by ozone ultraviolet treatment; (2) Two gold electrodes are prepared on both ends of the silicon dioxide thin film surface by electron beam evaporation; (3) A uniform black phosphorus film is transferred to both ends of the electrodes by mechanical peeling and transferring method; (4) A layer of PS nanosphere layer is deposited on the substrate by nanosphere self-assembly method, and then transferred to the surface of the black phosphorus sample by polydimethylsiloxane (PDMS) thermal release tape.

3. The method of claim 2, wherein the method comprises: 3-1) providing a substrate; 3-2) providing a polystyrene nanosphere array on the substrate; 3-3) providing a first electrode on the polystyrene nanosphere array; 3-4) providing a second electrode on the polystyrene nanosphere array; and 3-5) providing a light source. The ultrasonic cleaning time in step (1) is 5-10 min, and the ozone ultraviolet treatment time is 15-30 min.

4. The method for fabricating a broadband photodetector based on a polystyrene nanosphere array according to claim 2, characterized in that: In step (2), the two gold electrodes are symmetrically arranged at both ends of the silicon dioxide thin film surface, the distance between the two electrodes is 500μm, the electrode length is 1mm, and the electrode width is 200μm. After the electrode is treated by uniform coating, photoetching and developing, it is washed with IPA for 60 seconds to remove the developing solution, and then 80nm thick gold is deposited by electron beam evaporation. Then, the substrate is inverted in acetone stripper to remove the remaining photoresist, and two gold electrodes with a distance of 500μm, a length of 1mm and a width of 200μm are obtained.

5. The method of claim 2, wherein the polystyrene nanosphere array-based wideband photodetector is prepared by the following steps: (1) preparing a polystyrene nanosphere array on a substrate; (2) depositing a metal film on the polystyrene nanosphere array; and (3) removing the polystyrene nanospheres from the metal film to form a metal nanowire array. The black phosphorus absorption layer transfer in step (3) is specifically: Place the black phosphorus crystal block on the 3M tape and fold it repeatedly for 7 times. Then, gently press the peeled black phosphorus on the surface of the PDMS thermal release tape, so that the black phosphorus is transferred to the PDMS substrate. Fix the PDMS film with black phosphorus on the two electrodes in the middle area above by fine adjustment of the transfer platform. Slowly lower the PDMS to completely adhere to the substrate. Heat the substrate platform to 120℃, then slowly raise the extension arm to transfer the black phosphorus to the electrode.

6. The method of claim 2, wherein the polystyrene nanosphere array-based wideband photodetector is prepared by the following steps: (1) preparing a polystyrene nanosphere array on a substrate; (2) depositing a metal film on the polystyrene nanosphere array; and (3) removing the polystyrene nanospheres from the metal film to form a metal nanowire array. The step (4) specifically includes: Add 85% ethanol dispersant to the polystyrene nanosphere suspension, mix uniformly by ultrasonic machine for 10 min; Use a syringe to spread a single layer of nanospheres on the liquid surface at an angle of about 60° by microinjection method. Then, use a glass slide to fish the nanospheres, and bake them at 50℃ to form a hexagonal close-packed structure on the glass slide; Use double-sided PDMS tape to stick the nanosphere array on the glass slide, and cover half of the black phosphorus surface with the nanospheres by mechanical transfer system and optical microscope to obtain the wide-band photodetector.

7. The method for preparing a wide-band photodetector based on polystyrene nanosphere array according to any one of claims 2-6, characterized in that: The prepared detector has wide spectral response characteristics in the 3-7 μm wave band, the photocurrent can be up to 560 nA under 0.01 V bias voltage, the responsivity at 3.7 μm wavelength is 320 mA / W, the rise time is 360 μs, and the fall time is 310 μs.

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