A preparation method of t-Se / Si and BP / t-Se / Si heterojunction photodetectors

Abstract

The application belongs to the technical field of photoelectric detectors, and discloses a preparation method of t-Se / Si and BP / t-Se / Si heterojunction photodetectors. First, a few-layer black phosphorus nanosheet dispersion liquid is prepared, then a trigonal selenium film is deposited on a silicon substrate to construct a t-Se / Si composite structure, and then black phosphorus nanosheets are spin-coated to form a BP / t-Se / Si heterojunction. Electrodes are prepared on the two structures respectively to obtain t-Se / Si and BP / t-Se / Si unit detectors with significantly different photoelectric response characteristics. The two units are arranged and integrated according to a preset pattern to form a patterned detector array. The array has wide spectral response and low dark current characteristics under zero bias, and can be used for non-contact displacement monitoring of precision instruments.

Description

Technical Field

[0001] This application belongs to the field of photodetector technology, specifically relating to a method for fabricating t-Se / Si and BP / t-Se / Si heterogeneous photodetectors. Background Technology

[0002] The precise and safe displacement of core components of high-precision instruments and equipment, such as the objective lens of an optical microscope and the probe of a scanning probe microscope, in three-dimensional space is crucial to ensuring their functionality and equipment lifespan. The risk of these components accidentally colliding with surrounding structures during movement is ever-present, potentially causing irreversible damage and high maintenance costs. Therefore, there is a clear need to develop a low-cost, high-reliability technology capable of real-time, non-contact monitoring of the spatial position of critical components. Existing solutions largely rely on complex photoelectric encoders, laser interferometers, or machine vision-based systems. These solutions typically involve sophisticated mechanical structures, complex optical path designs, or high-performance image processing units, resulting in high overall system costs, large size, and insufficient adaptability to harsh environments or limited installation space, making large-scale application difficult in cost-sensitive fields such as education, research, and general industrial equipment.

[0003] At the materials level, seeking high-performance, process-compatible, and cost-effective photosensitive materials is fundamental to realizing the aforementioned applications. Selenium (Se), as a classic optoelectronic material, possesses a triangular crystal phase (t-Se) with high stability, a moderate band gap (approximately 1.8 eV), and low intrinsic dark current, and has already been used in X-ray detection and some visible light sensors. However, as a three-dimensional semiconductor material, the optoelectronic properties of t-Se, especially its spectral response range, are mainly tunable through doping. Limited tuning methods and the difficulty in achieving broad spectral coverage restrict its applicability in multi-band or specific infrared monitoring scenarios. On the other hand, black phosphorus (BP), as an emerging two-dimensional layered semiconductor, has attracted considerable attention due to its direct band gap adjustable with the number of layers, broad-spectrum light absorption extending from visible light to mid-infrared, and high carrier mobility. However, few-layer black phosphorus nanosheets are extremely sensitive to oxygen and water vapor in the environment, easily degrading and leading to a sharp decline in device performance. Furthermore, black phosphorus nanosheets obtained by conventional liquid phase exfoliation methods often have uneven size and thickness distribution and rough surfaces, resulting in poor uniformity and repeatability of devices constructed based on them, limited interfacial charge transport efficiency, and difficulty in achieving stable, large-scale, controllable fabrication and integration.

[0004] Therefore, in existing technologies, a single material system cannot simultaneously meet the requirements for practical low-cost monitoring applications, such as wide spectral response, high environmental stability, low dark current, and easy patterning integration. Summary of the Invention

[0005] To address the challenges of achieving a balance between broad spectral response, environmental stability, and integrability in existing single-material photodetectors, this application provides a method for fabricating a photodetector based on a black phosphorus / triangular selenium heterostructure. This method, through material composite and structural design, yields a detection unit that combines low dark current, high light response, and good process compatibility, laying the foundation for constructing patterned functional arrays capable of directly converting spatial displacement into electrical signals.

[0006] To achieve the above technical objectives, this application specifically adopts the following technical solution: In one aspect of this application, a method for fabricating t-Se / Si and BP / t-Se / Si photodetectors is provided, comprising the following steps: S1. Deposit a triangular selenium film on a cleaned silicon substrate to form a t-Se / Si composite structure; S2. The few-layer black phosphorus nanosheet dispersion is spin-coated onto the t-Se / Si composite structure and dried to form a BP / t-Se / Si composite structure. The few-layer black phosphorus nanosheet dispersion is prepared by a method including the following steps: mixing black phosphorus powder with anhydrous ethanol to obtain an initial dispersion; stirring and sonicating the initial dispersion; centrifuging the sonicated dispersion and collecting the supernatant to obtain the few-layer black phosphorus nanosheet dispersion. S3. Electrodes are fabricated on the t-Se / Si composite structure and the BP / t-Se / Si composite structure respectively to obtain the t-Se / Si photodetector and the BP / t-Se / Si photodetector respectively.

[0007] In one embodiment, the mass ratio of the black phosphorus powder to the volume of the anhydrous ethanol is 400 mg:40 mL.

[0008] In one embodiment, the initial dispersion of the few-layer black phosphorus nanosheets is first magnetically stirred at 500 rpm for 4 h, and then subjected to ultrasonic treatment.

[0009] In one embodiment, the ultrasonic treatment is performed under ice-water bath conditions, with an ultrasonic power of 240 W, and the operation mode is to stop for 1 second after every 3 seconds of operation, with a total treatment time of 9 hours.

[0010] In one embodiment, the centrifugation process in the preparation of the few-layer black phosphorus nanosheet dispersion includes a first centrifugation and a second centrifugation performed sequentially; the first centrifugation is performed at a speed of 3500 rpm for 30 min; and the second centrifugation is performed at a speed of 5000 rpm for 10 min.

[0011] In one embodiment, the silicon substrate is ultrasonically cleaned sequentially using acetone, anhydrous ethanol, and deionized water, with each cleaning agent lasting 15 minutes.

[0012] In one embodiment, a triangular selenium thin film is deposited using a thermal evaporation method, with process parameters including a chamber vacuum of 1×10⁻⁶. -3 The heating current was initially set to 12.5 A and held for 1 min, then adjusted to 15.5 A and held for 5 min. The thickness of the triangular selenium film was 150-200 nm.

[0013] In one embodiment, the spin-coating parameters in step S2 include: taking 0.1 mL of the few-layer black phosphorus nanosheet dispersion each time, first spin-coating at 50 rpm for 5 s, then spin-coating at 300 rpm for 20 s, and repeating this spin-coating process 20-25 times; the drying is vacuum drying at 40 °C for 4 h.

[0014] In another aspect of this application, t-Se / Si photodetectors and BP / t-Se / Si photodetectors prepared by the above-described preparation method are provided.

[0015] In one embodiment, the BP / t-Se / Si photodetector has a dark current of less than 10 pA for ultraviolet to near-infrared light sources at zero bias voltage.

[0016] In one embodiment, the BP / t-Se / Si photodetector has a signal-to-noise ratio of 35 under 450 nm wavelength illumination.

[0017] In one embodiment, the BP / t-Se / Si photodetector has a photocurrent rise time of 62.6 ms and a fall time of 42.5 ms at zero bias voltage.

[0018] In one embodiment, under zero bias voltage, the photocurrent values ​​of the BP / t-Se / Si photodetector at wavelengths of 450 nm and 808 nm are 12.4 times and 10.5 times the photocurrent values ​​of the t-Se / Si photodetector at the corresponding wavelengths, respectively.

[0019] In another aspect of this application, a patterned photodetector array is provided, comprising a plurality of t-Se / Si photodetectors and BP / t-Se / Si photodetector units, wherein the units are spatially arranged according to a preset pattern.

[0020] In one implementation, the preset pattern is configured such that when a light spot of a specific pattern shines on the array, due to the difference in photocurrent response of different units, the total current or current distribution output by the array can reflect the position, size, or angle change of the light spot on the array.

[0021] The beneficial effects of this application are as follows: This application employs a two-step centrifugation method to separate few-layer black phosphorus nanosheets with relatively uniform size and thickness from a black phosphorus / ethanol dispersion, effectively improving the quality and dispersion stability of the nanosheet material. The obtained black phosphorus nanosheets are then composited with a triangular selenium film prepared by thermal evaporation, exhibiting high flatness and stability, to construct a BP / t-Se / Si heterojunction. This structure fully utilizes the broad-spectrum absorption characteristics of black phosphorus and the low dark current and high stability advantages of triangular selenium, achieving complementary material properties. The photodetector based on this heterojunction exhibits an extremely low dark current of less than 10 pA at zero bias, and its photocurrent response in the 450 nm to 808 nm wavelength range is an order of magnitude higher than that of a single t-Se / Si device, while maintaining a fast response speed.

[0022] Furthermore, by utilizing the significant difference in photocurrent response between the two types of device units, they can be spatially arranged in a specific pattern to construct a patterned detector array. This array can directly convert changes in the position, size, or angle of the light spot projected onto its surface into a distinguishable current signal output. This allows the array system to achieve low-cost, high-sensitivity, non-contact monitoring of the three-dimensional displacement of the object under test without the need for complex optical paths or image processing units, demonstrating excellent application potential in fields such as precision instrument protection and displacement sensing. Attached Figure Description

[0023] Figure 1 These are TEM images of few-layer black phosphorus nanosheets provided in the embodiments of this application; Figure 2 This is a SEM image of the t-Se / Si composite structure provided in the embodiments of this application; Figure 3 This is a SEM image of the BP / t-Se / Si composite structure provided in the embodiments of this application; Figure 4 This refers to the ultraviolet to near-infrared reflectance spectrum of the t-Se / Si and BP / t-Se / Si composite structures provided in the embodiments of this application. Figure 5 This is the It curve of BP / t-Se / Si under zero bias voltage provided in the embodiments of this application; Figure 6 This is a comparison diagram of the current response of BP / t-Se / Si and t-Se / Si photodetectors provided in the embodiments of this application under different wavelength bands; Figure 7 This is a schematic diagram of the three-dimensional displacement response application of the patterned photodetector array provided in the embodiments of this application. Detailed Implementation

[0024] The technical solution of this application will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are only some embodiments of this application, not all embodiments, and are only used to illustrate this application, and should not be regarded as limiting the scope of this application. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] This application addresses the limitations of existing photoelectric detection materials in terms of performance and integrability by providing a solution from material preparation to system application.

[0026] At the materials level, well-dispersed few-layer black phosphorus nanosheets were obtained by optimizing liquid-phase exfoliation and centrifugation parameters. At the device level, a highly flat triangular selenium film was prepared on a silicon substrate using thermal evaporation, and the aforementioned black phosphorus nanosheets were spin-coated onto this substrate to construct a BP / t-Se / Si heterojunction. This structure aims to combine the broad-spectral absorption capability of black phosphorus with the high stability and low dark current characteristics of triangular selenium to form a complementary photodetector unit. Based on this process, two structurally related basic devices can be fabricated in parallel: a t-Se / Si photodetector and a BP / t-Se / Si photodetector.

[0027] These two detectors exhibit significant differences in photocurrent response under the same illumination conditions. Based on this difference, multiple detectors of these two types are further arranged and integrated as basic units according to a preset spatial pattern to form a patterned detector array. The function of this array is to directly map the geometric feature changes of the light spot projected on its surface into a distinguishable, spatially related current signal output, thereby providing a device basis for realizing low-cost precision displacement monitoring.

[0028] In one specific embodiment of this application, a method for fabricating t-Se / Si and BP / t-Se / Si photodetectors is provided, comprising depositing a triangular selenium thin film on a cleaned silicon substrate to form a t-Se / Si composite structure; spin-coating a few-layer black phosphorus nanosheet dispersion onto the t-Se / Si composite structure, and drying it to form a BP / t-Se / Si composite structure; and then fabricating electrodes on the two composite structures respectively to obtain the corresponding photodetectors.

[0029] During the cleaning of the silicon substrate, acetone, anhydrous ethanol, and deionized water were used sequentially for ultrasonic cleaning, with each cleaning agent lasting fifteen minutes.

[0030] The cleaned silicon substrate was used for depositing triangular selenide thin films. Thermal evaporation was employed for deposition, with the cavity vacuum maintained at 1×10⁻⁶ throughout the process. -3 Pa. The heating current was initially set to 12.5 A and maintained for one minute, then adjusted to 15.5 A and maintained for five minutes. This process forms a triangular selenium film with a thickness of 150-200 nm on a silicon substrate, obtaining a t-Se / Si composite structure.

[0031] The preparation of the few-layer black phosphorus nanosheet dispersion was as follows: black phosphorus powder and anhydrous ethanol were mixed at a ratio of 400 mg to 40 mL to obtain an initial dispersion. This initial dispersion was magnetically stirred at 500 rpm for four hours. After stirring, it was ultrasonically treated in an ice-water bath at a power of 240 W, with a cycle of three seconds followed by a one-second pause, for a total treatment time of nine hours. The ultrasonically treated dispersion was then centrifuged at 3500 rpm for thirty minutes, followed by 5000 rpm for ten minutes. The supernatant was collected to obtain the few-layer black phosphorus nanosheet dispersion.

[0032] The prepared few-layer black phosphorus nanosheet dispersion was spin-coated onto the surface of the aforementioned t-Se / Si composite structure. For each spin-coating, 0.1 mL of the dispersion was used, initially spin-coated at 50 rpm for five seconds, then the speed was increased to 300 rpm and spin-coated for twenty seconds. This spin-coating process was repeated twenty to twenty-five times. After spin-coating, the sample was vacuum-dried at 40 ℃ for four hours to form the BP / t-Se / Si composite structure.

[0033] Conductive silver paste was printed as electrodes on the top layer of the fabricated t-Se / Si composite structure and BP / t-Se / Si composite structure, respectively, and dried at room temperature for 30 minutes to finally obtain the t-Se / Si photodetector and the BP / t-Se / Si photodetector.

[0034] In another specific embodiment of this application, a t-Se / Si photodetector and a BP / t-Se / Si photodetector prepared by the above-described method are provided. The BP / t-Se / Si photodetector operates under zero bias voltage conditions and generates a dark current of less than 10 pA when irradiated by a light source in the ultraviolet to near-infrared band. The detector achieves a signal-to-noise ratio of 35 under 450 nm illumination. Regarding the dynamic response of the optical signal, the BP / t-Se / Si photodetector, under zero bias voltage, has a photocurrent rise time of 62.6 ms and a fall time of 42.5 ms. Furthermore, comparing under zero bias voltage and the same illumination conditions, the photocurrent value measured by the BP / t-Se / Si photodetector at 450 nm is 12.4 times that of the t-Se / Si photodetector at the corresponding wavelength; and at 808 nm, its photocurrent value is 10.5 times that of the t-Se / Si photodetector.

[0035] In another specific embodiment of this application, a patterned photodetector array is provided. The array includes multiple t-Se / Si photodetector units and BP / t-Se / Si photodetector units, which are arranged and combined in space according to a preset pattern.

[0036] The preset pattern is configured such that when a light spot of a specific shape illuminates the detector array, the total output current of the entire array or its internal current distribution pattern will change accordingly due to the significant difference in light response between the t-Se / Si units and the BP / t-Se / Si units. This current change can directly reflect information such as the positional shift, size change, or angular rotation of the incident light spot on the array surface, thereby converting optical information into an electrically readable signal.

[0037] In some embodiments, the array pattern is designed as a hollow rectangular frame. The rectangular frame area is composed of BP / t-Se / Si units, while the inner area is composed of t-Se / Si units. An infrared light source is linked to the vertically moving component to be monitored, and the light emitted by the source passes sequentially through a light-shielding plate with a rectangular hollow pattern and a lens, ultimately projecting a clear rectangular frame light spot onto the detector array. Initially, the light spot is small and falls entirely within the inner t-Se / Si region. As the component moves downwards, the light spot enlarges. The enlarged spot boundary touches or covers the outer BP / t-Se / Si region. Because the photocurrent response of the BP / t-Se / Si units is much higher than that of the t-Se / Si units, the total output current of the array increases sharply. This current surge can be used to trigger an alarm device.

[0038] In some embodiments, the array pattern is designed as a snowflake shape. The center and branches of the snowflake shape are composed of BP / t-Se / Si units, and the background area is composed of t-Se / Si units. A light source is linked to a component that can rotate around a fixed point, causing the light source to directly project a light spot that is the same size as the BP / t-Se / Si snowflake pattern in the array, with its center coinciding with the pattern, but whose branches are straight lines without any angle. Initially, the light spot with straight branches falls entirely on the t-Se / Si background area. When the component rotates, the light spot rotates synchronously. When the rotation angle exceeds the allowable error range, the straight branches of the light spot will slide into the BP / t-Se / Si branch area of ​​the array, causing a sharp increase in the array output current and triggering an alarm.

[0039] In some embodiments, the array pattern is used to define a planar working boundary. Specific areas of the array are designated as BP / t-Se / Si cells to represent prohibited or invalid working areas, while the remaining areas are designated as t-Se / Si cells to represent safe working areas. A light source projects a small, laser-like spot directly onto the array. As the monitored component moves within the plane, the spot moves along with it on the array. As long as the spot remains within the t-Se / Si area, the output current remains low. When the component moves beyond the safe boundary, the spot falls into the BP / t-Se / Si area, and the output current increases rapidly, triggering an out-of-bounds alarm. This method is also applicable to devices that require defining a visible or operational area.

[0040] Example 1 400 mg of black phosphorus powder was weighed and added to 40 mL of anhydrous ethanol. The mixture was magnetically stirred at 500 rpm for 4 h to ensure thorough dispersion. The dispersion was then sonicated in an ice-water bath for 9 h at a power of 240 W, with a cycle of 3 seconds of operation followed by a 1-second pause, to peel the bulk black phosphorus powder into smaller nanosheets with fewer layers. The nanosheets were then centrifuged at 3500 rpm for 30 min, followed by 5000 rpm for 10 min. The supernatant was collected to obtain a dispersion of fewer-layered black phosphorus nanosheets. The side length of each nanosheet ranged from 60 to 100 nm. Figure 1 As shown.

[0041] The n-Si substrate (10 x 10 mm, purchased from Jingying Electronics Technology Co., Ltd.) was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 15 min each. The Si substrate was then fixed in a thermal evaporation chamber, and 20 mg of selenium powder (purity ≥99.9%, purchased from Mairuida Technology Co., Ltd.) was added to the evaporation boat. The chamber vacuum was adjusted to 1 x 10 mm. -3First, the heating current was set to 12.5 A and held for 1 min for preheating. Then, it was slowly adjusted to 15.5 A and held for 5 min to obtain a t-Se / Si composite structure, in which the t-Se layer thickness was 150-200 nm, exhibiting extremely high surface smoothness and interface quality. Figure 2 As shown.

[0042] Take 0.1 mL of the black phosphorus nanosheet dispersion prepared above and spin-coat it onto the top layer of the t-Se / Si composite structure. The spin-coating speed was initially set to 50 rpm for 5 s, then to 300 rpm for 20 s, and repeated 20-25 times. After spin-coating, the structure was vacuum-dried at 40 ℃ for 4 h to obtain the BP / t-Se / Si composite structure. Figure 3 As shown, compared to the extremely high flatness of t-Se / Si, the roughness of the top layer of BP / t-Se / Si is significantly improved. Conductive silver paste was printed on the top layers of t-Se / Si and BP / t-Se / Si composite structures, respectively, and dried at room temperature to obtain t-Se / Si photodetectors and BP / t-Se / Si photodetectors.

[0043] Depend on Figure 4 It can be seen that after being combined with a black phosphorus layer, the overall reflectivity of the material decreases significantly in the ultraviolet to near-infrared band. The photoelectric response behavior of the above photodetector was tested using various single-wavelength laser light sources, such as... Figure 5 As shown, the obtained BP / t-Se / Si photodetector operates at 10.75 mW / cm². 2 Under low-power illumination, it exhibits an extremely low dark current level of less than 10 pA in the ultraviolet to near-infrared band, and the photocurrent values ​​in each band are significantly improved compared to t-Se / Si photodetectors, with increases of 12.4 and 10.5 times at 450 nm and 808 nm, respectively. Figure 6 ).

[0044] Example 2 This embodiment specifically illustrates a vertical displacement monitoring device based on the differentiated response characteristics of BP / t-Se / Si and t-Se / Si photodetectors. This device can convert the vertical displacement of a target object into a specific current signal, making it suitable for monitoring vulnerable components of precision instruments, such as optical microscope objectives, that move along the z-axis.

[0045] Reference Figure 7Part a describes a device comprised of an infrared light source, a perforated light-shielding plate, a lens, and a hollow rectangular patterned detector array. The activation or deactivation of the infrared light source is linked to the vulnerable component being monitored, moving accordingly. The perforated light-shielding plate has a hollow rectangular light-transmitting area. The lens is used to focus the light, ensuring a clear light spot. The patterned detector array is composed of t-Se / Si photodetector units and BP / t-Se / Si photodetector units arranged and integrated according to a preset hollow rectangular pattern. The dark areas of the array are composed of BP / t-Se / Si units, and the light areas are composed of t-Se / Si units, together forming a detection surface with a rectangular frame and a rectangular filled area.

[0046] When the device is operating, the light emitted by the linked infrared light source passes sequentially through the rectangular light-transmitting area of ​​the perforated light-shielding plate and the lens, ultimately projecting a clear rectangular wireframe light spot onto the surface of the patterned detector array. Initially, the objective lens is at a safe height, and the projected rectangular light spot is relatively small, falling entirely within the central light-colored area of ​​the detector array, i.e., illuminating only the internal rectangular filled area composed of t-Se / Si units. Since the photocurrent generated by the t-Se / Si units under illumination is relatively low, the total output current of the device remains at a reference level.

[0047] As the objective lens moves downwards, its linkage mechanism changes the relative position between the light source and the optical components, causing the size of the rectangular light spot projected onto the detector array to increase proportionally. During this magnification, the outer frame of the light spot gradually expands outwards. When the objective lens descends to a critical position where it might collide with the stage, the outer frame of the magnified rectangular light spot will just touch or cover the dark rectangular frame region surrounding the detector array, i.e., the region where the BP / t-Se / Si cells are located. The BP / t-Se / Si cells have significantly higher photocurrent response characteristics. Therefore, when the light spot moves from the light-colored t-Se / Si region into the dark BP / t-Se / Si region, the excited BP / t-Se / Si cells in the array will contribute a huge increase in photocurrent, causing a sharp and sudden increase in the total output current of the device.

[0048] The rapidly changing current signal is acquired and processed by subsequent circuitry, immediately triggering an associated audible and visual alarm to promptly alert the operator to stop moving the lens and prevent collisions between the objective lens and the stage. By calibrating the relationship between the spot size and the objective lens height, the device enables precise, real-time, and non-contact safety monitoring of the objective lens's vertical displacement.

[0049] Example 3 This embodiment specifically illustrates an angle monitoring device based on the differentiated response characteristics of BP / t-Se / Si and t-Se / Si photodetectors. This device can convert the rotation angle of a target object around a fixed axis into a specific current signal, making it suitable for monitoring the angular displacement of precision instrument components, such as photogalvanometer probes, that rotate around a fixed point.

[0050] Reference Figure 7 In part b, the device comprises an infrared light source, a light-shielding plate, and a snowflake-patterned detector array. The activation or deactivation of the infrared light source is linked to the rotating component being monitored, moving synchronously with its rotation. The light-shielding plate is used to shape the light emitted by the light source. The patterned detector array is composed of t-Se / Si photodetector units and BP / t-Se / Si photodetector units arranged and integrated according to a preset snowflake pattern. The dark snowflake-shaped areas on the array are composed of BP / t-Se / Si units, and the light-colored background areas are composed of t-Se / Si units. Each branch of the snowflake pattern has a set angle, and this angle range represents the allowable rotation angle error threshold.

[0051] When the device is in operation, the light emitted by the linked infrared light source passes through the light shield and is shaped into a specific snowflake-shaped spot, which is then projected onto the surface of the patterned detector array. This spot is exactly the same size as the dark snowflake-shaped area in the array and coincides with its center, but the key difference is that each snowflake branch of the spot pattern has no angle and appears as a thin straight line.

[0052] Initially, the rotating component (such as the probe) is in the reference orientation. At this time, the projected straight-line branch snowflake-shaped light spot is perfectly aligned with the pattern boundary of the detector array, so that each straight branch of the light spot falls exactly within the t-Se / Si unit region of the light-colored background of the array, completely avoiding the dark, angular BP / t-Se / Si snowflake branch region. Due to the low photocurrent response of the t-Se / Si unit, the output current of the device remains at a stable baseline value.

[0053] When the component begins to rotate around its fixed point, the linkage mechanism drives the infrared light source to rotate synchronously, causing the straight-line branch snowflake light spot projected on the detector array to rotate at the same angle. When the rotation angle is less than the preset allowable safety range (i.e., less than the angle of the light-colored snowflake branch), the rotated straight-line branch of the light spot can still be completely contained within the light-colored background area, illuminating only the t-Se / Si unit, and the output current does not change significantly.

[0054] When the component rotation angle reaches or exceeds the allowable error threshold, the ends of all straight branches of the rotated light spot will cross the boundary between the light background area and the dark snowflake area, falling into the BP / t-Se / Si branch region with a specific angle. BP / t-Se / Si units have significantly higher photocurrent response. Therefore, when the light spot covers a dark area, the excited BP / t-Se / Si units will contribute a huge increase in photocurrent, causing a sharp and sudden increase in the total output current of the device.

[0055] The rapidly changing current signal is acquired and processed by subsequent circuitry, immediately triggering an alarm device to indicate that the rotation angle has exceeded the safe or permissible range. By precisely designing the angle of the snowflake branches on the detector array, this device enables non-contact, real-time monitoring and over-limit alarm of component rotation angle.

[0056] Example 4 This embodiment specifically illustrates a two-dimensional planar displacement monitoring and region delineation device based on the differentiated response characteristics of BP / t-Se / Si and t-Se / Si photodetectors. This device can convert the position coordinates of a target object in a two-dimensional plane into a specific current signal, suitable for monitoring the position of a horizontally moving probe or delineating the effective working field of view of an instrument.

[0057] Reference Figure 7 In section c, the device comprises an infrared light source and a boundary patterned detector array. The activation or deactivation of the infrared light source is linked to the moving part being monitored, moving synchronously with its planar movement. The boundary patterned detector array is rectangular in shape, integrated from t-Se / Si photodetector units and BP / t-Se / Si photodetector units arranged according to a preset "boundary" pattern. Specifically, a separate first BP / t-Se / Si region is set at each of the four corners of the rectangular array; a second BP / t-Se / Si region is set at the geometric center of the rectangular array; apart from these five specific regions, the rest of the rectangular array is entirely composed of t-Se / Si units, i.e., light-colored t-Se / Si regions. These five BP / t-Se / Si regions (the four corner regions and one central region) collectively define the boundary range where entry or ineffective operation is not permitted.

[0058] When the device is working, the linked infrared light source projects a small laser-like spot directly onto the surface of the patterned detector array. The shape of the spot can be set as needed, such as a circle or a square.

[0059] In the initial or normal operating state, the monitored moving part (such as a probe) moves within the permissible two-dimensional working area. At this time, the light spot projected by the linked light source always falls on the light-colored background area composed of t-Se / Si units. Due to the low photocurrent response of the t-Se / Si units, the total output current of the device remains at a stable baseline level.

[0060] When the moving part moves beyond the preset safe or effective working range in the plane, the position of the light spot projected by its linked light source will shift accordingly. When the light spot falls completely or partially into any BP / t-Se / Si region on the array (i.e., one of the four corner regions or the center region), the excited BP / t-Se / Si units will contribute a huge increase in photocurrent due to the significantly higher photocurrent response of the BP / t-Se / Si units, resulting in a rapid and significant increase in the total output current of the device.

[0061] The rapidly increasing current signal is captured and processed by the subsequent monitoring circuit, which can immediately trigger an audible and visual alarm or an actuator to lock the device, thereby indicating that the component has moved into a prohibited area or outside the effective field of view. By precisely designing the shape, size, and position of the BP / t-Se / Si region on the detector array, this device can achieve non-contact, real-time monitoring and boundary crossing alarms of the component's two-dimensional planar position, or be used to clearly define the effective observation or operational field of view boundaries of instruments such as cell counters.

[0062] Although the embodiments of this application have been described above in conjunction with the accompanying drawings, this application is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of this application, and these are all within the scope of protection of this application.

Claims

1. A method for fabricating t-Se / Si and BP / t-Se / Si photodetectors, characterized in that, Includes the following steps: S1. Deposit a triangular selenium film on a cleaned silicon substrate to form a t-Se / Si composite structure; S2. Spin-coating the few-layer black phosphorus nanosheet dispersion onto the t-Se / Si composite structure, and drying it to form a BP / t-Se / Si composite structure; the few-layer black phosphorus nanosheet dispersion is prepared by a method including the following steps: mixing black phosphorus powder with anhydrous ethanol to obtain an initial dispersion; stirring and ultrasonicating the initial dispersion; The ultrasonically treated dispersion was centrifuged, and the supernatant was collected to obtain the few-layer black phosphorus nanosheet dispersion. S3. Electrodes are fabricated on the t-Se / Si composite structure and the BP / t-Se / Si composite structure respectively to obtain the t-Se / Si photodetector and the BP / t-Se / Si photodetector respectively.

2. The method for fabricating t-Se / Si and BP / t-Se / Si photodetectors according to claim 1, characterized in that, The mass ratio of the black phosphorus powder to the volume of the anhydrous ethanol is 400 mg: 40 mL.

3. The method for fabricating t-Se / Si and BP / t-Se / Si photodetectors according to claim 1, characterized in that, In the preparation of the few-layer black phosphorus nanosheet dispersion, the initial dispersion was first magnetically stirred at 500 rpm for 4 h, and then subjected to ultrasonic treatment.

4. The method for fabricating t-Se / Si and BP / t-Se / Si photodetectors according to claim 3, characterized in that, The ultrasonic treatment was performed under ice-water bath conditions, with an ultrasonic power of 240 W. The operation mode was to work for 3 seconds and then stop for 1 second, with a total treatment time of 9 hours.

5. The method for fabricating t-Se / Si and BP / t-Se / Si photodetectors according to claim 1, characterized in that, In the preparation of the few-layer black phosphorus nanosheet dispersion, the centrifugation process includes a first centrifugation and a second centrifugation performed sequentially; the first centrifugation is performed at a speed of 3500 rpm for 30 min; the second centrifugation is performed at a speed of 5000 rpm for 10 min.

6. The method for fabricating t-Se / Si and BP / t-Se / Si photodetectors according to claim 1, characterized in that, When cleaning the silicon substrate, acetone, anhydrous ethanol and deionized water are used to ultrasonically clean the silicon substrate in sequence, and the cleaning time for each cleaning agent is 15 minutes.

7. The method for fabricating t-Se / Si and BP / t-Se / Si photodetectors according to claim 1, characterized in that, Triangular selenium thin films were deposited using a thermal evaporation method. The process parameters included a chamber vacuum of 1×10⁻⁶. -3 The heating current was initially set to 12.5 A and held for 1 min, then adjusted to 15.5 A and held for 5 min. The thickness of the triangular selenium film was 150-200 nm.

8. The method for fabricating t-Se / Si and BP / t-Se / Si photodetectors according to claim 1, characterized in that, The parameters for spin coating in step S2 include: taking 0.1 mL of the few-layer black phosphorus nanosheet dispersion each time, first spin coating at 50 rpm for 5 s, then spin coating at 300 rpm for 20 s, and repeating this spin coating process 20-25 times; the drying is vacuum drying at 40 ℃ for 4 h.

9. A t-Se / Si photodetector or a BP / t-Se / Si photodetector prepared by the preparation method according to any one of claims 1 to 8.

10. A patterned photodetector array, characterized in that, It includes multiple t-Se / Si photodetectors and BP / t-Se / Si photodetector units as described in claim 9, wherein the units are arranged in space according to a preset pattern.

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