Hexagonal boron nitride packaged two-dimensional metal sulfide photoelectric detector and preparation method thereof

Abstract

The invention relates to the field of photoelectric detector structures of electrical devices, and discloses a hexagonal boron nitride packaged two-dimensional metal sulfide photoelectric detector and a preparation method thereof. The chemical inert surface provided by the hexagonal boron nitride (h-BN) not only can effectively prevent environmental degradation, but also can improve the interface quality between the two-dimensional metal sulfide material and the base material, and obviously reduces charge scattering caused by the surface roughness and defects of the traditional base material, thereby realizing more efficient charge transmission. Experimental results show that an atom smooth surface brought by h-BN / MoS2 / h-BN packaging promotes efficient transmission of charge carriers to a great extent, and the photoelectric property of the two-dimensional metal sulfide material is remarkably enhanced. By eliminating the surface roughness caused by the substrate and reducing the defect state to the maximum extent, the h-BN effectively reduces charge carrier scattering, and the responsiveness and photocurrent measurement are further enhanced. The h-BN packaging also plays a key role in inhibiting exciton annihilation, and is crucial for improving the photoelectric property.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric detector structures of electrical devices, and in particular to a photoelectric detector of hexagonal boron nitride encapsulated two-dimensional metal sulfide and a preparation method thereof. Background Art

[0002] With the rapid development of two-dimensional materials, especially two-dimensional metal sulfide materials such as MoS2, their applications in electronic and optoelectronic devices have attracted widespread attention. However, the performance of two-dimensional metal sulfide devices is often affected by factors such as surface roughness, environmental degradation and interface defects, which limits their performance in practical applications. Traditional substrates and packaging materials often cannot provide a sufficiently flat surface, which increases the charge scattering effect, thereby reducing the migration efficiency of charge carriers and ultimately affecting the optoelectronic performance of the device.

[0003] To solve this problem, researchers began to explore high-quality packaging materials. Hexagonal boron nitride (h-BN) has attracted much attention due to its excellent chemical inertness, thermal stability, and atomically flat surface. h-BN can not only effectively prevent the degradation of two-dimensional metal sulfide materials in the environment, but also significantly improve the interface quality between the material and the substrate. The flat surface structure of h-BN reduces the scattering effect of charge carriers and promotes efficient charge transfer, thereby improving the responsiveness and optoelectronic performance of the device.

[0004] In addition, h-BN encapsulation can also effectively suppress exciton annihilation, which is one of the key factors in improving the optoelectronic performance of two-dimensional metal sulfide devices. By providing an ideal atomically flat surface, h-BN has shown great potential and has played a significant role in improving the performance of two-dimensional metal sulfide devices. Therefore, the research and application of two-dimensional metal sulfide material devices based on h-BN encapsulation technology not only has important academic value, but also has broad market prospects. Summary of the invention

[0005] The purpose of the present invention is to solve the problems existing in the prior art, provide a photoelectric detector based on a two-dimensional metal sulfide material encapsulated by hexagonal boron nitride (h-BN), and disclose a specific preparation method. By using h-BN as the encapsulation material, the present invention can achieve an atomically flat surface, significantly enhance the photoelectric performance of the two-dimensional metal sulfide material device, reduce charge scattering, improve charge transfer efficiency, and inhibit exciton annihilation, ensuring that the prepared device has high photoelectric responsiveness and fast response speed.

[0006] In order to achieve the above technical objectives, the present invention is implemented by the following technical solutions: a method for preparing a photoelectric detector of hexagonal boron nitride encapsulated two-dimensional metal sulfide, comprising the following steps: 1) Pre-treat the substrate, transfer the hexagonal boron nitride material to be transferred to the substrate surface by mechanical stripping, select a hexagonal boron nitride material with a flat surface, a thickness of 0.7-20 nm and no residual glue bubbles, and form a hexagonal boron nitride material / substrate structure; 2) Peel off the two-dimensional metal sulfide material on the blue film and paste it repeatedly to control the thickness to 0.7~20nm to form a two-dimensional metal sulfide material / blue film structure; 3) Bonding the polydimethylsiloxane (PDMS) film to a glass slide to obtain a PDMS / glass slide structure; 4) The two-dimensional metal sulfide material to be transferred is transferred onto the PDMS film by mechanical peeling to form a glass slide / PDMS / two-dimensional metal sulfide material structure, and the excess PDMS film is cut off with the two-dimensional metal sulfide material to be transferred as the center; 5) Fixing the glass slide with the two-dimensional metal sulfide material in the substrate slot of the transfer platform, and placing the substrate on the sample holder of the transfer platform; 6) By controlling the bonding and separation rates of the transfer platform, the two-dimensional metal sulfide material is separated from the PDMS and bonded to the side of the hexagonal boron nitride material on the substrate; 7) Transferring the two prepared gold films to both ends of the two-dimensional metal sulfide material structure obtained in the previous step; 8) Peel off the hexagonal boron nitride material on the blue film and paste it repeatedly to control the thickness to 0.7~20nm to form a hexagonal boron nitride material / blue film structure; 9) Laminating the PDMS film on a glass slide to obtain a PDMS / glass slide structure; 10) The hexagonal boron nitride material to be transferred is transferred to the PDMS film by mechanical peeling to form a glass slide / PDMS / hexagonal boron nitride material structure, and the excess PDMS film is cut off with the hexagonal boron nitride material to be transferred as the center; 11) Fix the glass slide with hexagonal boron nitride material in the substrate slot of the transfer table, and place the substrate on the sample holder of the transfer table; 12) By controlling the bonding and separation rates of the transfer platform, the hexagonal boron nitride material is separated from the PDMS and bonded to one side of the two-dimensional metal sulfide material on the substrate, forming a hexagonal boron nitride material / two-dimensional metal sulfide material / hexagonal boron nitride material / substrate structure, thus completing the preparation.

[0007] The hexagonal boron nitride encapsulated two-dimensional metal sulfide photoelectric detector prepared by the above preparation method has a hexagonal boron nitride material layer, a two-dimensional metal sulfide material layer, a hexagonal boron nitride material layer and a gold film arranged in sequence on a substrate.

[0008] The beneficial effects of the present invention are: (1) A simple photoelectric detection device was prepared by designing the h-BN / MoS2 / h-BN structure. The atomically flat surface provided by the h-BN package significantly enhanced the light absorption ability and charge transfer efficiency. Compared with traditional photodetectors, the prepared photodetector has excellent detection ability and stability, and also has a fast response speed, showing good application prospects.

[0009] (2) Compared with traditional two-dimensional metal sulfide material devices, the two-dimensional metal sulfide material encapsulated by h-BN can effectively reduce the influence of deep energy level defect states, ensure that carriers will not be captured by deep energy level defects, thereby improving the generation and migration efficiency of photogenerated carriers, so that the final optoelectronic device has a higher responsiveness and faster response speed.

[0010] (3) By using h-BN packaging technology on the surface of two-dimensional metal sulfide materials, the good interface properties of h-BN can effectively improve the photocurrent of the photodetector and enhance the device's responsiveness and detection rate.

[0011] (4) The gold electrode on the prepared photodetector is in van der Waals contact with the two-dimensional metal sulfide material. This form of transfer contact will not cause adverse doping to the junction, has good contact, and will not change the properties of the junction.

[0012] (5) The hexagonal boron nitride material and the two-dimensional metal sulfide material can be transferred using a transfer platform, which can accurately transfer the material to any position on the target substrate. The force is evenly applied during the transfer process to avoid the formation of new wrinkles.

[0013] (6) Pre-treating the PDMS film with an ultraviolet ozone cleaning machine can reduce the viscosity of the PDMS and the adsorption of impurities on the surface of the material. After successfully transferring the hexagonal boron nitride material and the two-dimensional metal sulfide material, the residual glue on the surface of the hexagonal boron nitride material and the two-dimensional metal sulfide material after transfer can be greatly reduced.

[0014] (7) The disclosed h-BN / MoS2 / h-BN structure photodetector has a simple preparation process and low preparation cost. It is expected to become a feasible choice for low-cost photodetection or other functional applications in the future, providing new ideas for the development of related fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a flow chart of the preparation of a h-BN / MoS2 / h-BN structure photoelectric detector in an embodiment of the present invention; Figure 2 is a microscope photograph of the h-BN / MoS2 / h-BN structure prepared in an embodiment of the present invention; Figure 3is the Raman spectrum data of the h-BN / MoS2 / h-BN structure and MoS2 / h-BN prepared in the embodiment of the present invention; Figure 4 It is a light response test diagram of the photoelectric detectors of MoS2 / h-BN structure and h-BN / MoS2 / h-BN structure prepared in the embodiments of the present invention; Figure 5 is a graph showing the relationship between the performance improvement ratio of the photodetector prepared in an embodiment of the present invention before and after h-BN encapsulation and the light intensity; Figure 6 30 days and 60 days after the re-evaluation of the light response of the photodetector prepared in the embodiment of the present invention and the relationship between the light intensity. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0017] A method for preparing a photoelectric detector based on h-BN / MoS2 / h-BN, the steps are as follows: Step 1, pre-treat the silicon (thickness 500μm) / silicon oxide (thickness 285nm) substrate (clean the surface with propanol after wafer cutting, then clean the surface with deionized water, and use a nitrogen gun to blow dry the substrate) to obtain a silicon-based substrate with a clean surface, and use a mechanical peeling method to peel off the layered sample from the hexagonal boron nitride (h-BN) bulk crystal with tape, observe the sample under an optical microscope, and select h-BN with a flat surface, a thickness of about 10nm and no residual glue bubbles, and tear it to the surface of the silicon-based substrate to obtain an h-BN / substrate structure.

[0018] Step 2: peel off the two-dimensional metal sulfide material MoS2 onto the blue film and paste it repeatedly until its thickness reaches about 10nm to form a MoS2 / blue film.

[0019] Step 3, cut the polydimethylsiloxane PDMS into small pieces of 0.5 cm*2 cm, peel off the film on its surface, and make it fit on the glass slide.

[0020] Step 4: Use UV Ozone to treat the PDMS surface, then repeatedly paste the blue film / two-dimensional metal sulfide material, transfer the MoS2 on the blue film to the PDMS, find a few layers of uniform, wrinkle-free MoS2 under a microscope, and cut the PDMS film into 0.3cm*0.3cm squares with a blade centered on the transferred MoS2. After cutting off the excess film, a certain width must be reserved between the material boundary and the film boundary, so that the two-dimensional metal sulfide material is as close to the center of the cut film as possible to facilitate subsequent transfer.

[0021] Step 5, fix the glass slide with the two-dimensional metal sulfide material in the substrate slot of the transfer platform, and place the substrate on the sample holder of the transfer platform. The function of the transfer platform is to find the MoS2 previously observed under the microscope and align it with the substrate to be transferred. The glass slide with the two-dimensional metal sulfide material is fixed in the substrate slot of the transfer platform, and the silicon-based substrate is adsorbed on the sample holder of the transfer platform. The transfer platform can be slowly raised and lowered, and the minimum distance of the rise and fall is adjusted to 0.1μm, so that the two-dimensional metal sulfide material can be slowly attached to the substrate surface.

[0022] Step 6, first find the MoS2 to be transferred on the transfer platform and align it with the h-BN / substrate structure to be transferred. During the transfer process, the bonding process is maintained at a uniform speed. After complete bonding, they are separated at a uniform speed to avoid rapid separation that causes the material to be torn or leaves a large amount of bubbles and residual glue, thereby obtaining a MoS2 / h-BN / substrate structure.

[0023] Step 7: Attach a 200-mesh copper mesh to the silicon wafer, place it in a high vacuum electron beam evaporation coating instrument, evaporate 150 nm thick gold, remove the copper mesh, and use a fine needle with a needle tip diameter of 1 μm to cut the gold film into 600 μm × 70 μm strip films to prepare two strips of gold film. On the MoS2 / h-BN / substrate structure, use a fine needle with a needle tip diameter of 15 μm to transfer the strip gold film obtained in the previous step to the two ends of the two-dimensional metal sulfide material, and the distance between the two transferred strip gold films is 3 μm.

[0024] Step 8, peel off the hexagonal boron nitride material h-BN onto the blue film, and paste it repeatedly until its thickness reaches about 10nm to form h-BN / blue film.

[0025] Step 9, cut the PDMS into small pieces of 0.5 cm*2 cm, peel off the film on its surface, and make it fit on the glass slide.

[0026] Step 10, treat the PDMS surface with UV Ozone, then repeatedly paste the blue film / hexagonal boron nitride material, transfer the block h-BN on the blue film to the PDMS, find a few layers of uniform, wrinkle-free h-BN under a microscope, and cut the PDMS film into 0.3cm*0.3cm squares with a blade centered on the transferred h-BN. After cutting off the excess film, a certain width must be reserved between the material boundary and the film boundary so that the hexagonal boron nitride material is as close to the center of the cut film as possible to facilitate subsequent transfer.

[0027] Step 11, fix the glass slide with the hexagonal boron nitride material in the substrate slot of the transfer platform, and place the substrate on the sample holder of the transfer platform.

[0028] Step 12, first find the h-BN to be transferred on the transfer platform and align it with the MoS2 / h-BN / substrate structure to be transferred. During the transfer process, the bonding process is maintained at a uniform speed. After complete bonding, they are separated at a uniform speed to avoid rapid separation that causes the material to be torn or leaves a large amount of bubbles and residual glue, and finally a photoelectric detector with a h-BN / MoS2 / h-BN / substrate structure is obtained.

[0029] Figure 2 This is a microscope photograph of the single-layer h-BN / MoS2 / h-BN structure prepared in this embodiment. After transferring a few layers of h-BN to a silicon-based substrate by mechanical peeling, a few layers of MoS2 were transferred to h-BN by PDMS, and then a few layers of h-BN were transferred to MoS2 / h-BN by PDMS to obtain the structure.

[0030] Figure 3 The Raman spectra of the MoS2 / h-BN structure and h-BN / MoS2 / h-BN structure prepared in this example are shown at 385 cm -1 and 407cm -1 There are two sharp peaks at , corresponding to E1 2g (in-plane) and A 1g (Out-of-plane) vibration mode. It can be seen that the crystal structure of MoS2 is preserved after encapsulation.

[0031] Figure 4 The light response test diagram of the photodetectors of the MoS2 / h-BN structure and h-BN / MoS2 / h-BN structure prepared in this embodiment. The increased current after illumination is mainly contributed by the photogenerated carriers. At this time, the response time of the MoS2 / h-BN structure rising and falling is measured to be 0.538ms and 3.43ms respectively, and the response time of the h-BN / MoS2 / h-BN structure rising and falling is 23.1μs and 99.6μs respectively, and the response speed is significantly faster.

[0032] Figure 5 The light power-dependent responsivity of the photodetectors of the MoS2 / h-BN structure and the h-BN / MoS2 / h-BN structure prepared in this embodiment is compared. It can be seen from the figure that the two structures show similar trends in responsivity with light power, indicating that the light response is dominated by MoS2, while the responsivity of h-BN / MoS2 / h-BN is higher, which is due to the atomically smooth surface provided by the h-BN encapsulation. By eliminating the surface roughness caused by the substrate and minimizing the defect states, the charge carrier scattering is significantly reduced, which leads to more efficient charge transfer in the MoS2 layer in the h-BN / MoS2 / h-BN structure, effectively improving the performance of the device.

[0033] Figure 6The light power dependence responsivity of the photodetector of the h-BN / MoS2 / h-BN structure prepared in this embodiment is compared after 30 days and 60 days of storage with that when it was just prepared. It can be seen from the figure that after 30 days, a slight decrease in performance was observed, which may be due to the residual oxygen or moisture molecules trapped between the interfaces during the packaging process, which may cause slight degradation of MoS2. At 60 days, the performance is basically the same as that of 30 days, indicating that the packaging effectively protects the device from environmental factors and effectively improves the stability of the device.

[0034] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the contents disclosed by the present invention should be included in the protection scope recorded in the claims.

Claims

1. A method for preparing a photoelectric detector of hexagonal boron nitride encapsulated two-dimensional metal sulfide, characterized in that: The steps include: Step 1, pre-treating the substrate, selecting a hexagonal boron nitride material with a flat surface, a thickness of 0.7-20 nm and no residual glue bubbles, and transferring the hexagonal boron nitride material to be transferred to the substrate surface by a mechanical stripping method to form a hexagonal boron nitride material / substrate structure; Step 2, peeling off the two-dimensional metal sulfide material on the blue film, pasting repeatedly, controlling the thickness to be 0.7-20 nm, and forming a two-dimensional metal sulfide material / blue film structure; Step 3, laminating a polydimethylsiloxane (PDMS) film on a glass slide to obtain a PDMS / glass slide structure; Step 4, transferring the two-dimensional metal sulfide material to be transferred onto the PDMS film by a mechanical peeling method to form a two-dimensional metal sulfide material / PDMS / glass slide structure, and cutting off excess PDMS film with the two-dimensional metal sulfide material to be transferred as the center; Step 5, fixing the glass slide with the two-dimensional metal sulfide material in the substrate slot of the transfer platform, and placing the substrate on the sample holder of the transfer platform; Step 6, by controlling the bonding and separation rates of the transfer platform, the two-dimensional metal sulfide material is separated from the PDMS and bonded to the top surface of the hexagonal boron nitride material on the substrate; Step 7, preparing two gold films and transferring them to both ends of the two-dimensional metal sulfide material having the structure obtained in step 6; Step 8, peeling the hexagonal boron nitride material onto the blue film, pasting repeatedly, controlling the thickness to be 0.7-20 nm, and forming a hexagonal boron nitride material / blue film structure; Step 9, laminating the PDMS film on a glass slide to obtain a PDMS / glass slide structure; Step 10, transferring the hexagonal boron nitride material to be transferred onto the PDMS film by a mechanical peeling method to form a hexagonal boron nitride material / PDMS / glass slide structure, and cutting off excess PDMS film with the hexagonal boron nitride material to be transferred as the center; Step 11, fix the glass slide with the hexagonal boron nitride material in the substrate slot of the transfer table, and place the substrate on the sample holder of the transfer table; Step 12, by controlling the bonding and separation rates of the transfer platform, the hexagonal boron nitride material is separated from the PDMS and bonded to one side of the two-dimensional metal sulfide material on the substrate to form a hexagonal boron nitride material / two-dimensional metal sulfide material / hexagonal boron nitride material / substrate structure, thus completing the preparation.

2. The method for preparing the photoelectric detector of hexagonal boron nitride encapsulated two-dimensional metal sulfide according to claim 1, characterized in that: In step 2, the two-dimensional metal sulfide material is MoS2.

3. The method for preparing the photoelectric detector of hexagonal boron nitride encapsulated two-dimensional metal sulfide according to claim 1, characterized in that: In step 4, before transferring the two-dimensional metal sulfide material onto the PDMS film, the surface of the PDMS film needs to be treated using a UV Ozone cleaning machine.

4. The method for preparing the photoelectric detector of hexagonal boron nitride encapsulated two-dimensional metal sulfide according to claim 1, characterized in that: In step 4, the two-dimensional metal sulfide material transferred to the PDMS film is uniform and wrinkle-free, with a thickness of 0.7 to 10 nm and a layer number of 1 to 25 layers.

5. The method for preparing the photoelectric detector of hexagonal boron nitride encapsulated two-dimensional metal sulfide according to claim 1, characterized in that: In step 6, when transferring the two-dimensional metal sulfide material, the glass slide is lowered at a uniform speed so that the two-dimensional metal sulfide material adheres to the top surface of the hexagonal boron nitride material on the target substrate, and the adhered state is maintained. Then, the glass slide is lifted at a uniform speed so that the two-dimensional metal sulfide material is completely transferred to the surface of the target hexagonal boron nitride material.

6. The method for preparing a photoelectric detector of hexagonal boron nitride encapsulated two-dimensional metal sulfide according to claim 1, characterized in that: In step 7, a 200-mesh copper mesh is attached to the silicon wafer, and the wafer is placed in a high vacuum electron beam evaporation coating apparatus to evaporate 150 nm thick gold. The copper mesh is removed, and the gold film is cut into 600 μm × 70 μm strip films with a fine needle with a needle tip diameter of 1 μm to prepare two strips of gold films. The distance between the two transferred strips of gold films is 1 to 10 μm.

7. The method for preparing a photoelectric detector of hexagonal boron nitride encapsulated two-dimensional metal sulfide according to claim 1, characterized in that: In step 10, the surface of the PDMS film needs to be treated with UV Ozone before the hexagonal boron nitride material is transferred onto the PDMS film.

8. The method for preparing a photoelectric detector of hexagonal boron nitride encapsulated two-dimensional metal sulfide according to claim 1, characterized in that: In step 10, the hexagonal boron nitride material transferred to the PDMS film is uniform and wrinkle-free, with a thickness of 0.7 to 20 nm and 1 to 25 layers.

9. The method for preparing a photoelectric detector of hexagonal boron nitride encapsulated two-dimensional metal sulfide according to claim 1, characterized in that: In step 12, when transferring the two-dimensional metal sulfide material, the glass slide is lowered at a uniform speed so that the hexagonal boron nitride material adheres to one side of the two-dimensional metal sulfide material on the target substrate, and the adhered state is maintained. Then, the glass slide is lifted at a uniform speed so that the hexagonal boron nitride material is completely transferred to the surface of the target two-dimensional metal sulfide material.

10. A hexagonal boron nitride encapsulated two-dimensional metal sulfide photodetector prepared by the method according to any one of claims 1 to 9, characterized in that: The photodetector comprises a substrate and a hexagonal boron nitride material layer, a two-dimensional metal sulfide material layer and a hexagonal boron nitride material layer arranged in sequence on the substrate, wherein gold films are arranged on both sides of the hexagonal boron nitride material layer on the two-dimensional metal sulfide material layer.

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