Preparation Method of a Room Temperature Mid-Wave Infrared Van der Waals Heterojunction Linear Array Detector

Abstract

A method for preparing a room-temperature mid-wave infrared van der Waals heterojunction linear detector according to the present invention comprises the following steps: mechanically exfoliating a first single-crystal two-dimensional material; transferring the first single-crystal two-dimensional material to PDMS; transferring the first single-crystal two-dimensional material adhered to the PDMS thin sheet to a first silicon wafer; etching the first single-crystal two-dimensional material; transferring the etched first single-crystal two-dimensional material to a second silicon wafer; preparing a PDMS thin sheet adhered with a narrow-bandgap single-crystal two-dimensional material; heating the second silicon wafer, and the PDMS thin sheet placed obliquely expands when heated, driving the narrow-bandgap single-crystal two-dimensional material to gradually cover and contact the single-crystal two-dimensional material from one side to the other side until a heterojunction is formed between the first single-crystal two-dimensional material and the narrow-bandgap single-crystal two-dimensional material; preparing the heterojunction; forming a linear structure to complete the device preparation. The present invention can prepare a room-temperature mid-wave infrared van der Waals heterojunction linear detector with high sensitivity and high uniformity.

Description

Technical Field

[0001] The invention belongs to the technical field of mid-infrared signal detection, and in particular relates to a method for preparing a room-temperature mid-wave infrared van der Waals heterojunction array detector. Background Art

[0002] Room temperature medium wave infrared photoelectric detector is an infrared detector that can work at room temperature. It is mainly used to detect radiation in the medium wave infrared band. The working principle of this detector is to use photoelectric technology to convert the infrared radiation emitted by the object into an electrical signal, so that the infrared information that cannot be directly perceived by the human eye can be detected and analyzed. Among them, room temperature medium wave infrared photoelectric detection can reduce the dependence on ambient light or auxiliary lighting sources, and has the ability to work all day. Using room temperature medium wave infrared detectors to image the target has the characteristics of low power consumption, strong concealment, high sensitivity, and accurate recognition. With the improvement of target detection requirements, it is urgent to develop high-performance room temperature infrared detectors. They have important application value in medical detection, meteorological remote sensing, aerospace detection and other fields. Target detection requires the use of a certain scale of detectors to obtain infrared images of the target. The detector scale can be divided into unit, linear array and planar array devices. When acquiring the target image based on the unit detector, it is necessary to make the unit device perform two-dimensional scanning in the plane to obtain an image of a certain resolution. When acquiring the target image based on the linear array detector, the device needs to perform one-dimensional scanning in the direction perpendicular to the linear array, which greatly shortens the imaging time compared to the unit device. When acquiring target images based on a planar array detector, staring imaging can be achieved. Therefore, while ensuring device performance, increasing the number of device pixels as much as possible, while enhancing device performance and uniformity, can significantly improve target detection capabilities.

[0003] Narrow-bandgap van der Waals layered material detectors have excellent properties such as low dark current, high light absorption, and high mobility. They show the advantages of high responsivity, fast response, and high detection rate. They are suitable for the preparation of medium-wave infrared photodetectors, such as black phosphorus-based room-temperature medium-wave infrared photodetectors, but the technical bottleneck of large-size single-crystal black phosphorus preparation needs to be broken through. The preparation of multi-pixel medium-wave infrared devices based on narrow-bandgap van der Waals layered materials is the direction of future development and a hot topic of current research. In addition, the uniformity between pixels affects the imaging quality. High uniformity is conducive to reducing image noise, and achieving highly uniform pixel devices is the key to improving imaging quality. Therefore, the use of large-size single-crystal two-dimensional materials to prepare high-quality, uniform narrow-bandgap heterojunction array detectors is conducive to realizing sensitive detection of room-temperature medium-wave infrared.

[0004] Although chemical vapor deposition can achieve the preparation of large-sized materials and further fabricate multi-pixel array devices, the large-sized materials grown by it are wide-bandgap transition metal chalcogenides, and the response range of the fabricated devices is from visible to near-infrared bands, unable to achieve mid-wave infrared detection. Thermal evaporation can grow large-sized narrow-bandgap semiconductor materials, but the fabricated materials are polycrystalline materials with a large number of grain boundaries and defects, which is not conducive to carrier transport. The fixed-point transfer technology fabricates devices by transferring mechanically exfoliated single-crystal materials, but the conventional fixed-point transfer technology focuses on the development of new devices, and the fabricated devices are single-pixel devices. Although pixel stitching can be achieved through multiple fixed-point transfers, since different pixels come from different single-crystal samples and factors such as thickness are inconsistent, the pixel uniformity is poor. In addition, mechanical movements driven by manual or stepper motors will cause the generation of bubbles or material defects at the heterojunction interface, hindering the transport of carriers at the heterojunction and resulting in the degradation of the optoelectronic response of van der Waals layered material devices. It can be seen that although linear array detectors can be fabricated through multiple transfers of heterojunctions at present, it is difficult to control the uniformity of material thickness, interface contact quality, etc. At the same time, the heterojunction preparation method using mechanical pressing and other methods is prone to problems such as bubbles and material wrinkles, resulting in poor heterojunction interface quality.

[0005] Currently, in room-temperature mid-wave infrared linear array detectors, it is necessary to improve the uniformity and area of single-crystal materials after mechanical exfoliation to achieve large-area coverage while maintaining high optoelectronic response performance, and it is necessary to have a technology that can precisely control the transfer and positioning of single-crystal materials to ensure the consistency of each pixel in the multi-pixel array and the performance of the overall device, and study and implement a bubble-free and high-quality heterojunction interface preparation technology to promote the effective transport of carriers and improve the optoelectronic response performance of the device.

[0006] Therefore, it is particularly important to develop a new preparation method for fabricating linear array devices of room-temperature mid-wave infrared detectors. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation method for a room-temperature mid-wave infrared van der Waals heterojunction linear array detector in view of the problems in the prior art.

[0008] To this end, the above object of the present invention is achieved by the following technical solutions:

[0009] A preparation method for a room-temperature mid-wave infrared van der Waals heterojunction linear array detector includes the following steps:

[0010] S1, mechanically exfoliate the first single-crystal two-dimensional material;

[0011] S2, transfer the first single-crystal two-dimensional material to PDMS;

[0012] S3. Transfer the first single-crystalline two-dimensional material pasted with the PDMS sheet to the first silicon wafer to obtain the first single-crystalline two-dimensional material on the first silicon wafer;

[0013] S4. Etch the first single-crystalline two-dimensional material;

[0014] S5. Transfer the etched first single-crystalline two-dimensional material to the second silicon wafer;

[0015] S6. Repeat steps S1 - S2 to prepare a PDMS sheet pasted with a single-crystalline two-dimensional material having a narrow bandgap;

[0016] S7. Place the PDMS sheet obliquely, lower the PDMS sheet until it stops before one side of the single-crystalline two-dimensional material with a narrow bandgap contacts the first single-crystalline two-dimensional material in step S5. Heat the second silicon wafer. The obliquely placed PDMS sheet expands when heated, driving the single-crystalline two-dimensional material with a narrow bandgap to gradually cover and contact the single-crystalline two-dimensional material from one side to the other. Maintain the temperature of the second silicon wafer constant until the heterojunction between the first single-crystalline two-dimensional material and the single-crystalline two-dimensional material with a narrow bandgap is formed;

[0017] S8. After the second silicon wafer is cooled to room temperature, the PDMS sheet shrinks. Lift the PDMS sheet to obtain the heterojunction between the first single-crystalline two-dimensional material and the single-crystalline two-dimensional material with a narrow bandgap on the second silicon wafer;

[0018] S9. Use electron beam lithography and metal deposition techniques to define electrode patterns on the heterojunction, and form a line array structure through an etching process to complete the device preparation.

[0019] While adopting the above technical solutions, the present invention can also adopt or combine the following technical solutions:

[0020] As a preferred technical solution of the present invention: the first single-crystalline two-dimensional material is MoS2, and the single-crystalline two-dimensional material with a narrow bandgap is BP.

[0021] As a preferred technical solution of the present invention: in step S4, the etched first single-crystalline two-dimensional material is square.

[0022] As a preferred technical solution of the present invention: in step S5, use a PPC thin film to pick up the etched first single-crystalline two-dimensional material and transfer it to the second silicon wafer to obtain a two-dimensional material sample on the second silicon wafer.

[0023] As a preferred technical solution of the present invention: in step S7, the included angle between the obliquely placed PDMS sheet and the first single-crystalline two-dimensional material is 5°. After the temperature of the second silicon wafer is slowly heated to 50 °C, keep the temperature constant until the heterojunction is formed

[0024] As a preferred technical solution of the present invention: Step S9 specifically includes: spin-coating PMMA on the second silicon wafer, exposing the electrode window on the heterojunction by electron beam lithography, preparing the electrode by thermal evaporation, and removing the PMMA by soaking in acetone; spin-coating PMMA on the second silicon wafer, exposing the etching window by electron beam lithography, removing the exposed area of the heterojunction by reactive ion etching, and removing the PMMA by soaking in acetone to form a room-temperature mid-wave infrared van der Waals heterojunction linear detector.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] A preparation method of a room-temperature mid-wave infrared van der Waals heterojunction linear detector of the present invention uses a temperature-assisted method to prepare a room-temperature mid-wave infrared van der Waals heterojunction linear detector. During the preparation process, by adjusting the temperature of the silicon wafer and the tilt angle of the PDMS, the temperature of the tilted PDMS is further regulated. The precise transfer and contact of two-dimensional materials are realized by the small-angle tilt of the PDMS thin sheet and the expansion and contraction characteristics of the PDMS, and the preparation of a large-size, high-quality and uniform two-dimensional material heterojunction is achieved. In the preparation method of a room-temperature mid-wave infrared van der Waals heterojunction linear detector of the present invention, the PDMS contacts the silicon wafer at a small angle, and the two-dimensional material slowly adheres to the silicon wafer through the thermal expansion of the PDMS, avoiding problems such as material wrinkles and bubbles caused by manually or mechanically driving the PDMS to press down. Utilizing the characteristic of the tilted PDMS thin sheet expanding when heated, the contact area is gradually expanded from one side to the other side along a specific direction until the two-dimensional material is completely covered. This step-by-step covering method helps to reduce the generation of bubbles and wrinkles, improve the quality and uniformity of the van der Waals vertical structure, and ensure uniform and defect-free contact between the van der Waals vertical structures.

[0027] At the same time, in the present invention, PDMS-assisted dry transfer is adopted. Through the good stability of the PDMS material, by slowly raising and lowering its temperature, the expansion and contraction of the PDMS thin sheet are precisely controlled, thereby realizing the precise manipulation and transfer of two-dimensional materials. In addition, by adjusting the tilt angle of the PDMS, during the expansion process, the contact area is slowly expanded from one side to the other side along a specific direction, which can avoid the generation of two-dimensional materials and the existence of bubbles at the heterojunction surface. By this method, a room-temperature mid-wave infrared van der Waals heterojunction linear detector with high sensitivity and high uniformity can be prepared, improving the responsivity of the detector, helping to maintain the stability and reliability of the detector, increasing the operating temperature of the detector, thereby expanding its application range under various environmental conditions, improving the imaging quality, and enhancing the overall performance of the detector. In the preparation of a room-temperature mid-wave infrared van der Waals heterojunction linear detector of the present invention, temperature-assisted PDMS thin sheets are used to prepare large-area van der Waals layered structures, which have the advantages of avoiding contamination, precisely controlling the contact area, and compatibility.

[0028] PDMS has good chemical stability and biocompatibility. It can be compatible with a variety of two-dimensional materials, including different material combinations such as MoS2 / BP heterojunctions, which provides the possibility for the preparation of multifunctional van der Waals heterostructures.

[0029] The preparation method of a room-temperature mid-wave infrared van der Waals heterojunction linear detector of the present invention has broad application prospects in many fields such as microfluidic chip manufacturing, flexible electronic devices, medical devices, electronic appliances, environmental monitoring, and tissue engineering. Description of the Drawings

[0030] Figure 1 It is a flowchart of the preparation method of a room-temperature mid-wave infrared van der Waals heterojunction linear detector of the invention;

[0031] Figure 2 It is a schematic diagram of the preparation method of a room-temperature mid-wave infrared van der Waals heterojunction linear detector of the present invention. Detailed Description of the Invention

[0032] The present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.

[0033] The preparation method of a room-temperature mid-wave infrared van der Waals heterojunction linear detector of the present invention includes the following steps:

[0034] S1, mechanically exfoliate the first single-crystalline two-dimensional material;

[0035] S2, transfer the first single-crystalline two-dimensional material to PDMS to obtain the first single-crystalline two-dimensional material pasted on the PDMS thin sheet;

[0036] S3, transfer the first single-crystalline two-dimensional material pasted on the PDMS thin sheet to the first silicon wafer to obtain the first single-crystalline two-dimensional material located on the first silicon wafer;

[0037] S4, etch the first single-crystalline two-dimensional material;

[0038] S5, transfer the etched first single-crystalline two-dimensional material to the second silicon wafer;

[0039] S6, repeat steps S1 - S2 to prepare a PDMS thin sheet pasted with a narrow-bandgap single-crystalline two-dimensional material;

[0040] S7. Adjust the angle of the PDMS sheet until the angle between the single-crystalline two-dimensional material with a narrow bandgap and the first single-crystalline two-dimensional material in step S5 is 5°. Lower the PDMS sheet until it stops before the single-crystalline two-dimensional material with a narrow bandgap contacts the first single-crystalline two-dimensional material in step S5. Heat the second silicon wafer. The PDMS sheet expands when heated, driving the single-crystalline two-dimensional material with a narrow bandgap to slowly cover and contact the single-crystalline two-dimensional material from one side to the other along a specific direction. Keep the temperature of the second silicon wafer constant to maintain the contact state between the PDMS sheet and the two-dimensional material until a heterojunction is formed between the first single-crystalline two-dimensional material and the single-crystalline two-dimensional material with a narrow bandgap; wherein, the specific direction refers to the small-angle inclination direction of the PDMS sheet.

[0041] S8. After the second silicon wafer is cooled to room temperature, the PDMS sheet shrinks. Lift the PDMS sheet to obtain a heterojunction of the first single-crystalline two-dimensional material and the single-crystalline two-dimensional material with a narrow bandgap on the silicon wafer.

[0042] S9. Use electron beam lithography and metal deposition techniques to define electrode patterns on the heterojunction, and form a line array structure through an etching process to complete the device preparation.

[0043] The beneficial effects of the present invention are as follows: The preparation method of the room-temperature mid-wave infrared van der Waals heterojunction line array detector of the present invention is a temperature-assisted preparation method for a room-temperature mid-wave infrared van der Waals heterojunction line array detector. In the present invention, in order to solve the problem in the prior art that large-size single-crystalline two-dimensional materials with a narrow bandgap cannot be realized, and currently, BP cannot achieve large-size single-crystalline preparation and it is difficult to form line array or array devices. By making the PDMS contact the silicon wafer at a small angle, and through the thermal expansion of the PDMS, the two-dimensional material slowly adheres to the silicon wafer from one side to the other along a specific direction, avoiding problems such as material wrinkles and bubbles caused by manually or mechanically driving the PDMS to press down. Through this method, a room-temperature mid-wave infrared van der Waals heterojunction line array detector with high sensitivity and high uniformity can be prepared. Example 1

[0044] As Figure 1 - Figure 2 shown, a preparation method of a room-temperature mid-wave infrared van der Waals heterojunction line array detector of the present invention specifically includes the following steps:

[0045] In step S1, it specifically includes the following steps:

[0046] S1.1. Cut the PDMS with a scalpel to obtain a PDMS sheet with a size of 20 mm × 8 mm × 160 μm. Place the PDMS sheet in the middle of a clean glass slide, and one end of the PDMS is fixed with blue tape. Among them, PDMS, that is, polydimethylsiloxane, is a synthetic silicone rubber commonly used in laboratory and industrial applications.

[0047] S1.2. Take a certain number of single-crystal thin flakes of MoS₂ two-dimensional material and place them on the blue tape. Fold and paste the blue tape, repeat the folding and pasting 5 - 10 times, so that the first single-crystal two-dimensional material MoS₂ covers a certain area on the blue tape.

[0048] In step S2, it specifically includes the following steps:

[0049] S2.1. Paste the blue tape with the first single-crystal two-dimensional material MoS₂ onto the PDMS thin film in step S1, gently press it with the thumb for 1 minute, and then quickly tear off the blue tape with the two-dimensional material from one end where the blue tape is fixed.

[0050] S2.2. Directly observe the two-dimensional material sample on the PDMS thin film under the microscope, select the two-dimensional material sample with regular shape and appropriate thickness, and then use a scalpel to cut and remove the excess PDMS near the sample.

[0051] Step S3. Paste the remaining PDMS thin film with the first single-crystal two-dimensional material MoS₂ sample onto a clean first silicon wafer to obtain a larger-sized first single-crystal two-dimensional material MoS₂ on the first silicon wafer.

[0052] In step S4, spin-coat PMMA on the first silicon wafer and use electron beam lithography to expose the window of the part to be etched, and remove the exposed area through reactive ion etching, leaving a rectangular first single-crystal two-dimensional material MoS₂ sample. Among them, PMMA, the full name is polymethyl methacrylate, is a polymer with wide applications.

[0053] In step S5, use the PPC thin film to pick up the etched rectangular two-dimensional material sample and transfer it to a new second silicon wafer to obtain a rectangular two-dimensional material sample on the second silicon wafer. Among them, PPC is poly(propylene carbonate), which is a polymer material.

[0054] In step S6, copy steps S1 - S2, and the two-dimensional material used in the process is changed to a single-crystal two-dimensional material BP with a certain narrow bandgap. Among them, BP refers to black phosphorus, which is a two-dimensional semiconductor material.

[0055] In step S7, slowly approach the remaining PDMS thin film with the narrow-bandgap two-dimensional material sample to the second silicon wafer prepared in step S5 at an inclination angle of 5°, and at the same time align the narrow-bandgap single-crystal two-dimensional material BP with the rectangular two-dimensional material sample in step S5.

[0056] Slowly lower the inclined PDMS thin film mechanically, and stop lowering when the contact area covers the aligned two-dimensional material sample.

[0057] Slowly increase the temperature of the second silicon wafer to 50 °C, and then keep the temperature constant. When the temperature increases, due to the thermal expansion of the PDMS sheet, the contact area slowly expands from one side to the other in one direction until the contact area completely covers the single-crystalline two-dimensional material BP with a narrow bandgap. After reaching the required temperature, it is necessary to keep the temperature constant to maintain the contact state between the PDMS sheet and the two-dimensional material until the heterojunction is formed.

[0058] Slowly increase the temperature of the silicon wafer to 50 °C. During this process, the PDMS sheet will expand due to heat. Since the thermal expansion coefficient of PDMS is usually 150 - 200 ppm / K, this means that for every 1 °C increase in temperature, the length or volume of PDMS will increase by 0.15% to 0.2%. As the temperature rises, the expansion of the PDMS sheet will cause the contact area to slowly expand until it completely covers the single-crystalline two-dimensional material BP with a narrow bandgap. This step is crucial for ensuring the quality of the heterojunction because it needs to ensure uniform and defect-free contact between MoS2 and BP.

[0059] Although the current bottom-up growth method can achieve the growth of large-area two-dimensional sheets, seamlessly merging these sheets to form a large-area continuous film with well-controlled layer thickness and lattice orientation remains a challenge. In this application, the temperature-assisted PDMS sheet helps to solve these problems and can achieve a high-quality and uniform interface while preparing the heterojunction of large-area narrow-bandgap materials.

[0060] In step S8, slowly lower the temperature to room temperature and slowly lift the PDMS sheet to obtain a large-size and uniform two-dimensional material heterojunction sample on the silicon wafer.

[0061] In step S9, spin-coat PMMA on the second silicon wafer and use electron beam lithography to expose the electrode window on the heterojunction. Prepare the electrode by thermal evaporation and soak in acetone to remove PMMA. Spin-coat PMMA on this second silicon wafer and use electron beam lithography to expose the etching window, remove the exposed area of the heterojunction by reactive ion etching, and soak in acetone to remove PMMA to form a room-temperature mid-wave infrared van der Waals heterojunction linear detector.

[0062] The above specific embodiments are used to explain and illustrate the present invention. They are only the preferred embodiments of the present invention and do not limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and scope of the claims of the present invention fall within the protection scope of the present invention.

Claims

1. A preparation method of a room-temperature mid-wave infrared van der Waals heterojunction linear detector, comprising the following steps: S1, mechanically exfoliating a first single-crystal two-dimensional material, S2, transferring the first single-crystal two-dimensional material to PDMS; S3, transferring the PDMS thin sheet pasted with the first single-crystal two-dimensional material to a first silicon wafer to obtain the first single-crystal two-dimensional material located on the first silicon wafer; S4, etching the first single-crystal two-dimensional material; S5, transferring the etched first single-crystal two-dimensional material to a second silicon wafer; S6, replicating steps S1 - S2 to prepare a PDMS thin sheet pasted with a single-crystal two-dimensional material with a narrow bandgap; S7, placing the PDMS thin sheet obliquely, lowering the PDMS thin sheet until it stops before one side of the single-crystal two-dimensional material with a narrow bandgap contacts the first single-crystal two-dimensional material in step S5, heating the second silicon wafer, and the obliquely placed PDMS thin sheet expands when heated, driving the single-crystal two-dimensional material with a narrow bandgap to gradually cover and contact the single-crystal two-dimensional material from one side to the other side, and maintaining the temperature of the second silicon wafer constant until the heterojunction between the first single-crystal two-dimensional material and the single-crystal two-dimensional material with a narrow bandgap is formed; S8, after the second silicon wafer is cooled to room temperature, the PDMS thin sheet shrinks, lifting the PDMS thin sheet to obtain a heterojunction between the first single-crystal two-dimensional material and the single-crystal two-dimensional material with a narrow bandgap located on the second silicon wafer, and obtaining a large-size and uniform two-dimensional material heterojunction sample located on the silicon wafer; S9, using electron beam lithography and metal deposition techniques to define electrode patterns on the heterojunction, and forming a linear structure through an etching process to complete the device preparation; wherein, the first single-crystal two-dimensional material is MoS2, and the single-crystal two-dimensional material with a narrow bandgap is BP; In step S7, the included angle between the obliquely placed PDMS thin sheet and the first single-crystal two-dimensional material is 5°, and after the temperature of the second silicon wafer is slowly heated to 50 °C, the temperature is maintained constant until the heterojunction is formed.

2. The preparation method of the room-temperature mid-wave infrared van der Waals heterojunction linear detector according to claim 1, characterized in that: In step S4, the etched first single-crystal two-dimensional material is square.

3. The preparation method of the room-temperature mid-wave infrared van der Waals heterojunction linear detector according to claim 1, characterized in that: In step S5, a PPC thin film is used to pick up the etched first single-crystal two-dimensional material and transfer it to the second silicon wafer to obtain a two-dimensional material sample located on the second silicon wafer.

4. The preparation method of the room-temperature mid-wave infrared van der Waals heterojunction linear detector according to claim 1, characterized in that: Step S9 specifically includes: spin-coating PMMA on the second silicon wafer and using electron beam lithography to expose electrode windows on the heterojunction, preparing electrodes through thermal evaporation, and soaking in acetone to remove PMMA; spin-coating PMMA on the second silicon wafer and using electron beam lithography to expose etching windows, removing the exposed area of the heterojunction through reactive ion etching, and soaking in acetone to remove PMMA to form a room-temperature mid-wave infrared van der Waals heterojunction linear detector.

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