Position sensitive detector based on plasmon hot electron capture and preparation method thereof

Abstract

The invention belongs to the technical field of optoelectronic devices, and discloses a position sensitive detector based on plasmon hot electron capture and a preparation method thereof. The position sensitive detector comprises a silicon substrate, a gold nanorod layer and a molybdenum disulfide layer from bottom to top, and the molybdenum disulfide layer is obtained by adopting a liquid phase stripping method and spin coating. The preparation method comprises the following steps: (1) carrying out impurity removal and cleaning treatment on a silicon substrate; (2) carrying out surface treatment on the silicon substrate to enable the surface of the silicon substrate to carry hydroxyl; (3) preparing a gold nanorod solution; (4) putting the silicon substrate carrying the hydroxyl group into the gold nanorod solution, standing, taking out, cleaning and drying to obtain a gold nanorod layer / silicon substrate; (5) adding molybdenum disulfide into the SDBS aqueous solution, uniformly stirring, and ultrasonically stripping to obtain a suspension; and centrifuging the suspension, taking supernate obtained after centrifugation, and spin-coating the supernate on the gold nanorod layer / silicon substrate to obtain a target product. According to the invention, position detection with high sensitivity and broadband response is realized.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic device technology, specifically relating to a position-sensitive detector based on plasmonic thermionic capture and its fabrication method. Background Technology

[0002] With the rapid development of precision measurement, optical sensing, and automation technologies, the demand for high-performance photoelectric detection devices in the Chinese market is becoming increasingly urgent. Position-sensitive detectors, as a typical photoelectric detection device, are widely used in space exploration, angle measurement, and micro-displacement detection. The rapid advancement of science and technology has led to increasingly higher requirements for the resolution, stability, and response speed of position-sensitive detectors in applications such as high-precision ultrafast detection and high-sensitivity position detection. Position-sensitive detectors based on the lateral photovoltaic effect (LPE) have become a research hotspot in the field of position-sensitive detection due to their unique advantages, including non-contact operation, no blind zone, direct signal detection, high responsivity, and no need for external voltage drive.

[0003] However, traditional position-sensitive detectors often suffer from low position sensitivity and limited spectral response range. Although researchers have attempted to improve sensitivity characteristics by applying external modulation in recent years, the results often lead to decreased device stability and increased manufacturing costs, failing to meet practical application requirements. In recent years, the excellent light-trapping ability and local electromagnetic field focusing characteristics of plasmonic nanomaterials have attracted attention, providing a new approach to overcoming the performance bottlenecks of traditional position-sensitive detectors. When noble metal nanostructures are photoexcited, conduction band electrons undergo surface plasmon resonance, subsequently generating high-energy hot electrons through a relaxation process. This enhances local light absorption intensity, directly converting the captured light energy into heat energy, thereby improving photoelectric conversion efficiency. Moreover, the injection of surface plasmon hot electrons can overcome the absorption limitations of conventional semiconductor band gaps, expanding the spectral response range of position-sensitive detectors. Previously, researchers conducted a series of studies on plasmon hot electron position-sensitive detectors, but the fabricated devices only achieved a sensitivity of approximately 160 mV / mm, far below the theoretical prediction. Research has found that the main reason for this problem is that the hot electrons generated by the plasmon nanomaterials are not effectively captured. Therefore, it remains extremely challenging to efficiently capture hot electrons and develop a position-sensitive detector with excellent performance such as high position sensitivity, large spectral response range, and self-powered operation. Summary of the Invention

[0004] To address the problems of low sensitivity and limited spectral response range in existing position-sensitive detectors, the present invention aims to provide a position-sensitive detector based on plasmonic thermionic capture and its fabrication method.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A position-sensitive detector based on plasmonic hot electron capture, wherein the position-sensitive detector comprises, from bottom to top, a silicon substrate, a gold nanorod layer and a molybdenum disulfide layer, wherein the molybdenum disulfide layer is obtained by liquid phase exfoliation and spin coating.

[0006] Preferably, the silicon substrate is N-type 111 crystal orientation with a resistivity of 35~55 Ω·cm.

[0007] Preferably, the aspect ratio of the gold nanorods is between 1 and 7.

[0008] Preferably, the thickness of the molybdenum disulfide layer is 10~20 nm.

[0009] The method for fabricating the position-sensitive detector based on plasmon hot electron capture includes the following steps: (1) Clean the silicon substrate to remove impurities; (2) The silicon substrate obtained in step (1) is subjected to surface treatment to make its surface carry hydroxyl groups; (3) Preparation of gold nanorod solution; (4) Place the silicon substrate with hydroxyl groups obtained in step (2) into the gold nanorod solution in step (3), let it stand, take it out, clean it, and blow it dry to obtain the gold nanorod layer / silicon substrate. (5) Add molybdenum disulfide to SDBS aqueous solution, stir evenly, and ultrasonically peel off to obtain a suspension; centrifuge the suspension, take the supernatant obtained after centrifugation, and spin coat it onto the gold nanorod layer / silicon substrate obtained in step (4) to obtain a position-sensitive detector based on plasmonic hot electron capture; wherein, the raw material ratio is molybdenum disulfide: SDBS aqueous solution = (0.5g~2g): 100mL, the concentration of SDBS aqueous solution is 0.001~0.02mol / L, and the spin coating conditions are: first low-speed spin coating and then high-speed spin coating, and the rotation speed of low-speed spin coating is 500~1000rpm and the spin coating time is 5~20s, and the rotation speed of high-speed spin coating is 1100~2000rpm and the spin coating time is 30~60s.

[0010] Preferably, the process of step (1) is as follows: immerse the silicon substrate in an HF solution with a mass concentration of 10~30% for 10~30 minutes to remove the natural oxide layer on the surface, and then immerse the silicon substrate in acetone, anhydrous ethanol and water in sequence for ultrasonic cleaning for 10~30 minutes to obtain the cleaned silicon substrate.

[0011] Preferably, in step (2), the present invention uses a piranha solution to treat the silicon substrate. The treatment process is as follows: concentrated sulfuric acid and 30% hydrogen peroxide are mixed in a volume ratio of 7:3 to obtain a piranha solution. The silicon substrate obtained in step (1) is immersed in the piranha solution at 80°C for 30-60 minutes, and then ultrasonically cleaned in water for 10-30 minutes to obtain a silicon substrate with hydroxyl groups on the surface.

[0012] Preferably, in step (3), the present invention uses the silver-induced seedless method to prepare the gold nanorod solution. The volume parts are in mL and the mass parts are in mg. The preparation process is as follows: 7000-10000 parts by mass of CTAB powder are added to 200-250 parts by volume of water at 20-40℃ and stirred until fully dissolved to form a growth solution; then 30-40 parts by mass of HAuCl4 powder, 0.9-5.4 parts by volume of 8-12mM AgNO3 solution, and 100-150 parts by mass of hydroquinone powder are added to it and stirred continuously until colorless; then 0.01-0.03 parts by volume of 16-18mM NaBH4 ice-water mixture solution is added and stirred to make it uniform; then the solution is kept at a constant temperature of 20-40℃ for more than 12 hours; the above solution is centrifuged and purified to remove CTAB to obtain the gold nanorod solution.

[0013] Preferably, in step (4), the settling time is 24~72h, ultrasonic cleaning is performed in water, and nitrogen is used for drying.

[0014] Preferably, in step (5), ultrasonic ablation is performed in cold water below 20°C for 3 to 6 hours.

[0015] The underlying principle of this invention is as follows: The efficiency of hot electron capture is affected by the height of the Schottky barrier between the nanometal and the semiconductor, as well as the energy loss caused by scattering during electron transfer. Molybdenum disulfide (MoD) has the advantages of high absorption rate, high interlayer carrier mobility, and tunable band structure, and it also has a parallel band structure, which can effectively suppress carrier scattering, making it an excellent material for capturing and transporting hot electrons. This invention uses gold nanorods to generate plasmonic hot electrons and MoD as a hot electron capture layer. By modifying the metal nanorod structure with MoD and adjusting the thickness of the MoD layer, the high light absorption and high carrier mobility of MoD optimize the hot electron capture efficiency of the device, thus fabricating a high-sensitivity, fast-response, wide-band position-sensitive photodetector.

[0016] Beneficial effects: (1) Molybdenum disulfide has stable chemical properties, which can effectively maintain the stability of position-sensitive detectors; (2) The position-sensitive detector of the present invention has an adjustable response band. The absorption peak can be changed by adjusting the aspect ratio of the gold nanorods, thereby achieving the control of the device response band. (3) The position-sensitive detector of the present invention has a position sensitivity of 290.3mV / mm under laser excitation at a wavelength of 635nm; (4) The position-sensitive detector of the present invention has a wide spectral response range and good response in the 405~980 nm band; In summary, this invention breaks through the bottleneck problem that has long plagued the development of position sensitivity detectors, and achieves position detection with high sensitivity and wide-band response. Attached Figure Description

[0017] Figure 1 SEM images of gold nanorod solutions prepared with different amounts of silver nitrate solution.

[0018] Figure 2 Absorption spectra of gold nanorod solutions prepared with different amounts of silver nitrate solution.

[0019] Figure 3 : A schematic diagram of the sensitivity testing system for a position-sensitive detector, in which 1 is a laser, 2 is a convex lens, 3 is a three-dimensional displacement platform, 4 is a device electrode, and 5 is a six-and-a-half-digit digital multimeter.

[0020] Figure 4 The graph shows the relationship between the lateral photovoltage and the laser spot position of the position-sensitive detector prepared in Example 1 under different wavelength laser irradiation conditions, with an addition of 1.44 mL of silver nitrate solution. The lower left inset is a comparison graph of the lateral photovoltage and the laser spot position of the position-sensitive detectors prepared in Example 1 and Control Example 1 under 635 nm wavelength laser irradiation.

[0021] Figure 5 Comparison of lateral photovoltage and laser spot position of the position-sensitive detectors prepared in Example 1, Comparative Example 2 and Comparative Example 3 under 635nm wavelength laser irradiation, with an addition of 1.44mL of silver nitrate solution.

[0022] Figure 6 The response time of the position-sensitive detector obtained in Example 1 was measured under the condition that 1.44 mL of silver nitrate solution was added.

[0023] Figure 7 The response time of the position-sensitive detector obtained in Comparative Example 2 was compared with that of silver nitrate solution with an addition volume of 1.44 mL.

[0024] Figure 8 The response time of the position-sensitive detector obtained in Comparative Example 3 was compared with that obtained with 1.44 mL of silver nitrate solution. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the described embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0026] Example 1

[0027] A method for fabricating a position-sensitive detector based on plasmonic hot electron trapping, comprising the following steps: (1) Immerse the silicon substrate (N-type 111 crystal orientation, resistivity 35~55Ω·cm) in a 20% HF solution for 15 minutes to remove the natural oxide layer on the surface. Then, immerse the silicon substrate in acetone, anhydrous ethanol and deionized water in sequence for ultrasonic cleaning for 15 minutes to obtain the cleaned silicon substrate. (2) Surface treatment of silicon substrate using piranha solution: Concentrated sulfuric acid and 30% hydrogen peroxide were mixed in a volume ratio of 7:3 to obtain piranha solution; the silicon substrate obtained in step (1) was immersed in piranha solution at 80°C for 30 min, and then ultrasonically cleaned in deionized water for 15 min to obtain a surface-carrying hydroxyl group OH. - Silicon substrate; (3) Preparation of gold nanorod solution by silver-induced seedless method: 8.0395 g of CTAB powder was added to 224.4 mL of water at 30 °C and stirred until fully dissolved to obtain the growth solution; then 35.9 mg of HAuCl4 powder was added; 0.9 mL, 1.44 mL, 2.7 mL, 3.6 mL, 4.5 mL, and 5.4 mL of AgNO3 solution (10 mM concentration) and 133.1 mg of hydroquinone powder were added respectively, and the mixture was stirred continuously with a magnetic stirrer until colorless. Then 22.8 μL of 17.05 mM NaBH4 ice-water mixture solution was added and stirred for 5 min to make it uniform. The solution was then stored at 30 °C for 20 h. The above solution was centrifuged (6000 r / m, 30 min each time, repeated 3 times) to remove CTAB and obtain gold nanorod solution. (4) Take the hydroxyl group OH obtained in step (2) - The silicon substrate was placed in the gold nanorod solution obtained in step (3) and left to stand for 48 hours. After being taken out, it was ultrasonically cleaned with deionized water and dried with nitrogen to obtain gold nanorods / silicon substrate. (5) Molybdenum disulfide was removed by liquid phase exfoliation method assisted by sodium dodecylbenzenesulfonate (SDBS): 100 mL of SDBS aqueous solution with a concentration of 0.002 mol / L was prepared, 1 g of molybdenum disulfide powder was added to it, and the mixture was stirred evenly. Then it was placed in cold water at 15℃ and ultrasonically treated for 6 h to remove molybdenum disulfide nanosheets. After ultrasonic treatment, the resulting suspension was centrifuged at 2000 rpm for 30 min to remove the unexfoliated part. The supernatant obtained after centrifugation is molybdenum disulfide / SDBS. The supernatant was spin-coated onto the gold nanorods / silicon substrate obtained in step (4) to obtain a molybdenum disulfide layer with a thickness of 10 nm. The spin-coating conditions were: first low-speed spin-coating and then high-speed spin-coating. The low-speed spin-coating speed was 1000 rpm and the spin-coating time was 10 s. The high-speed spin-coating speed was 1500 rpm and the spin-coating time was 30 s. After spin-coating, the target position sensitive detector was obtained.

[0028] Figure 1 SEM images of gold nanorod solutions prepared with different amounts of silver nitrate solution. Figure 1 It can be seen that when preparing gold nanorod solutions using the silver-induced seedless method, the aspect ratio of the gold nanorods increases with the increase of AgNO3 solution. The aspect ratios of the gold nanorods corresponding to 0.9 mL, 1.44 mL, 2.7 mL, 3.6 mL, 4.5 mL, and 5.4 mL AgNO3 solutions are approximately 1, 1.2, 1.7, 2, 3.4, and 6.7, respectively.

[0029] Figure 2 Absorption spectra of gold nanorod solutions prepared with different amounts of silver nitrate solution. Figure 2 It can be seen that as the amount of silver nitrate solution increases (the aspect ratio of the gold nanorods increases), its longitudinal absorption peak red-shifts.

[0030] Compare with Example 1 The difference from Example 1 is that step (5) is omitted, while everything else is the same as in Example 1, with 1.44 mL of silver nitrate solution added.

[0031] In this comparative example 1, a control position sensitive detector 1, namely a gold nanorod / silicon substrate, was prepared without a molybdenum disulfide hot electron trapping layer.

[0032] Compare with Example 2 The difference from Example 1 is that, in step (5), the SDBS aqueous solution is changed to 0.004 mol / L, while the rest is the same as in Example 1.

[0033] In this control example 2, a control position sensitive detector 2 was prepared.

[0034] Compare with Example 3 The difference from Example 1 is that, under the condition that the amount of silver nitrate solution added is 1.44 mL, step (5) uses atomic layer deposition technology to prepare a molybdenum disulfide hot electron trapping layer, and the specific steps are as follows: Using gaseous molybdenum hexacarbonyl (Mo(CO)6) and hydrogen sulfide (H2S) as reaction precursors, the flow rate of carrier gas N2 was adjusted to 150 sccm, the heating temperature of the reaction chamber was 350℃ and the gas pressure was 20 Pa. One cycle was formed by introducing Mo(CO)6 for 0.5s → rinsing with N2 for 5s → introducing H2S for 1s → rinsing with N2 for 5s. The cycle was repeated several times until a molybdenum disulfide layer with a thickness of 10 nm was deposited on the gold nanorod / silicon substrate obtained in step (4), thus obtaining the control position sensitive detector 3.

[0035] Sensitivity test Figure 3 This is a schematic diagram of a position-sensitive detector sensitivity testing system. In the attached diagram, 1 represents a laser, 2 a convex lens (focal length 1 cm), 3 a three-dimensional displacement platform, 4 a device electrode, and 5 a 6.5-digit multimeter. The distances between the laser and the convex lens, and between the convex lens and the three-dimensional displacement platform, are all 50 cm. The two device electrodes are two silver paste electrodes with a diameter of less than 50 μm added to the surface of the device using conductive silver paste. Figure 3 As shown, a series of lasers with wavelengths from 405nm to 980nm are fixed on a laser holder. Two silver paste electrodes are connected to a digital multimeter via wires. The position of the incident laser spot is adjusted by operating a three-dimensional displacement platform. The relationship between the spot position and the output lateral light voltage is measured. The midpoint of the two silver paste electrodes is defined as the origin, and the corresponding spot position is 0.

[0036] Figure 4 The graph shows the relationship between the lateral photovoltage and the laser spot position of the position-sensitive detector prepared in Example 1 under different wavelength laser irradiation conditions, with an added silver nitrate solution of 1.44 mL. The lower left inset is a comparison of the lateral photovoltage and laser spot position of the position-sensitive detectors prepared in Example 1 and Control Example 1 under 635 nm wavelength laser irradiation. Figure 4 As shown, the lateral photovoltage is relatively large under 635nm wavelength laser excitation, while Figure 2 The plasmon absorption peak of the gold nanorods is also located at 635 nm, indicating that the spectral response of the device corresponds to the absorption spectrum of the material. Calculations show that the position-sensitive detector prepared in this invention achieves a position sensitivity of 290.3 mV / mm under 635 nm wavelength laser irradiation, while the position-sensitive detector without the molybdenum disulfide hot electron trapping layer (prepared in Control Example 1) has a sensitivity of only 158.1 mV / mm. This demonstrates that the molybdenum disulfide layer effectively traps the hot electrons emitted by the plasmons of the gold nanorods, further improving the sensitivity of the position-sensitive detector.

[0037] Figure 5 The image shows a comparison of the lateral photovoltage and laser spot position of the position-sensitive detectors prepared in Examples 1, 2, and 3 under 635 nm laser irradiation, with a silver nitrate solution addition of 1.44 mL. As a control, the photovoltages of the position-sensitive detectors prepared using different parameters (Example 2) and methods (Example 3) were all lower than those in Example 1, indicating that the high-quality molybdenum disulfide nanosheets prepared by the SDBS-assisted liquid-phase exfoliation method can effectively capture plasmonic hot electrons, improving the performance of the position-sensitive detectors, with the best effect observed at an SDBS solution concentration of 0.002 mol / L.

[0038] Response characteristic test The testing equipment is basically the same Figure 3 The difference lies in the following: a chopper (converting a constant laser beam into a pulsed laser beam) is placed between the laser and the convex lens, and a digital oscilloscope is used instead of a six-and-a-half-digit multimeter; the distance between the chopper and the laser is 10 cm, and the distance between the chopper and the convex lens is 40 cm. During testing, two silver paste electrodes are connected to the digital oscilloscope via wires, and the response time of the position-sensitive detectors obtained in Example 1, Comparative Example 2, and Comparative Example 3 is measured under the condition that 1.44 mL of silver nitrate solution is added. The rise time of the device is defined as the time interval during which the photovoltage rises from 10% to 90% of its peak value, and the fall time is defined as the time interval during which the photovoltage falls from 90% to 10% of its peak value.

[0039] The response time of the position-sensitive detector obtained in Example 1 under 635nm wavelength laser illumination is as follows: Figure 6 As shown, its rise time is 74μs and its fall time is 90μs, which can meet the requirements for rapid position detection.

[0040] The response times of the position-sensitive detectors obtained in Comparative Example 2 and Comparative Example 3 under 635nm wavelength laser illumination are as follows: Figure 7 , 8 As shown, their response times are all greater than those of the position-sensitive detector obtained in Example 1, indicating that the molybdenum disulfide nanosheets prepared by the SDBS-assisted liquid-phase exfoliation method capture plasmonic hot electrons at a faster rate, and the obtained plasmonic hot electron position-sensitive detector has better performance.

Claims

1. A position-sensitive detector based on plasmonic thermionic trapping, characterized in that: The position-sensitive detector comprises, from bottom to top, a silicon substrate, a gold nanorod layer, and a molybdenum disulfide layer, wherein the molybdenum disulfide layer is obtained by liquid phase exfoliation and spin coating.

2. The position-sensitive detector based on plasmonic thermionic trapping as described in claim 1, characterized in that: The silicon substrate is N-type with a 111 crystal orientation and a resistivity of 35~55 Ω·cm.

3. The position-sensitive detector based on plasmon thermionic trapping as described in claim 1, characterized in that: The aspect ratio of the gold nanorods is between 1 and 7.

4. The position-sensitive detector based on plasmon thermionic electron capture as described in claim 1, characterized in that: The thickness of the molybdenum disulfide layer is 10~20 nm.

5. A method for fabricating a position-sensitive detector based on plasmon hot electron trapping as described in any one of claims 1 to 4, characterized in that, The steps are as follows: (1) Clean the silicon substrate to remove impurities; (2) The silicon substrate obtained in step (1) is subjected to surface treatment to make its surface carry hydroxyl groups; (3) Preparation of gold nanorod solution; (4) Place the silicon substrate with hydroxyl groups obtained in step (2) into the gold nanorod solution in step (3), let it stand, take it out, clean it, and blow it dry to obtain the gold nanorod layer / silicon substrate. (5) Add molybdenum disulfide to SDBS aqueous solution, stir evenly, and ultrasonically peel off to obtain a suspension; centrifuge the suspension, take the supernatant obtained after centrifugation, and spin coat it onto the gold nanorod layer / silicon substrate obtained in step (4) to obtain a position-sensitive detector based on plasmonic hot electron capture; wherein, the raw material ratio is molybdenum disulfide: SDBS aqueous solution = (0.5g~2g): 100mL, the concentration of SDBS aqueous solution is 0.001~0.003mol / L, and the spin coating conditions are: first low-speed spin coating and then high-speed spin coating, and the rotation speed of low-speed spin coating is 500~1000rpm and the spin coating time is 5~20s, and the rotation speed of high-speed spin coating is 1100~2000rpm and the spin coating time is 30~60s.

6. The method for fabricating a position-sensitive detector based on plasmon hot electron trapping as described in claim 5, characterized in that, Step (1) involves immersing the silicon substrate in a 10-30% HF solution for 10-30 minutes to remove the natural oxide layer on the surface. Then, the silicon substrate is ultrasonically cleaned in acetone, anhydrous ethanol, and water for 10-30 minutes to obtain the cleaned silicon substrate.

7. The method for fabricating a position-sensitive detector based on plasmon hot electron trapping as described in claim 5, characterized in that, Step (2) involves surface treatment of the silicon substrate using a piranha solution. The treatment process is as follows: concentrated sulfuric acid and 30% hydrogen peroxide are mixed in a volume ratio of 7:3 to obtain a piranha solution. The silicon substrate obtained in step (1) is immersed in the piranha solution at 80°C for 30-60 minutes, and then ultrasonically cleaned in water for 10-30 minutes to obtain a silicon substrate with hydroxyl groups on its surface.

8. The method for fabricating a position-sensitive detector based on plasmon hot electron trapping as described in claim 5, characterized in that, Step (3) Gold nanorod solution was prepared using the silver-induced seedless method. The volume parts were expressed in mL and the mass parts in mg. The preparation process was as follows: 7000-10000 parts by mass of CTAB powder were added to 200-250 parts by volume of water at 20-40℃ and stirred until fully dissolved to form a growth solution. Then, 30-40 parts by mass of HAuCl4 powder, 0.9-5.4 parts by volume of 8-12 mM AgNO3 solution, and 100-150 parts by mass of hydroquinone powder were added to the solution and stirred until colorless. Then, 0.01-0.03 parts by volume of 16-18 mM NaBH4 ice-water mixture solution was added and stirred to make it uniform. The solution was then stored at a constant temperature of 20-40℃ for more than 12 hours. The solution was centrifuged and purified to remove CTAB, and the gold nanorod solution was obtained.

9. The method for fabricating a position-sensitive detector based on plasmon hot electron trapping as described in claim 5, characterized in that, In step (4), the settling time is 24~72h, ultrasonic cleaning is performed in water, and nitrogen is used to dry the water.

10. The method for fabricating a position-sensitive detector based on plasmon hot electron trapping as described in claim 5, characterized in that, In step (5), ultrasonic ablation is performed in cold water below 20°C for 3-6 hours.

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