Preparation method and application of MoS2-based two-dimensional semiconductor photoelectric material
By constructing a surface-hydroxylated Mo2C(OH)4 MXene heterojunction on the MoS2 surface, the problems of weak light absorption, short carrier lifetime, and high contact barrier of MoS2-based optoelectronic devices were solved, and the optoelectronic performance of high photoresponsivity, wide spectral response, and low dark current was improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-17
- Publication Date
- 2026-04-07
AI Technical Summary
Existing MoS2-based optoelectronic devices suffer from problems such as weak light absorption, short carrier lifetime, easy trapping of carriers by defect states, and the formation of a Schottky barrier due to Fermi level mismatch when in contact with metal electrodes, resulting in low photoresponsivity, insufficient sensitivity, and slow response time.
A monolayer of MoS2 was grown by chemical vapor deposition, and the Mo2Ga2C precursor was etched by a fluoride-containing acidic solution to obtain a surface-hydroxylated Mo2C(OH)4 MXene suspension, which was then coated onto the MoS2 surface to form a heterojunction. The photogenerated carrier transport was optimized by Mo atom bridging and van der Waals interactions.
It significantly improves photoresponsivity and light absorption capacity, broadens the spectral response range, reduces dark current, forms an efficient photogenerated carrier separation channel, and enhances photoelectric performance.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of optoelectronic material preparation, and in particular to a method for preparing MoS2-based two-dimensional semiconductor optoelectronic materials and their applications. Background Technology
[0002] Optoelectronic devices are core components of the modern information industry, playing an indispensable role in fields such as optical communication, sensing and imaging, and energy. Currently, commercially available photodetectors are mostly based on traditional semiconductor materials such as silicon (Si) and indium gallium arsenide (InGaAs). However, these traditional materials are facing performance bottlenecks: Si-based detectors are limited by their intrinsic bandgap, resulting in a narrow detection spectral range that cannot meet the requirements of full-spectrum detection; while III-V semiconductors (such as InGaAs) have excellent performance, their raw materials are rare and some are toxic, leading to high costs, and they typically need to operate in harsh low-temperature environments, which limits their widespread application in low-power, portable devices.
[0003] With the advent of the post-Moore's Law era, the strategic demand for continuous miniaturization and high performance of devices is becoming increasingly urgent. Two-dimensional (2D) semiconductor materials, due to their atomic-level thickness, perfect surface without dangling bonds, excellent optoelectronic properties, and inherent flexibility, are widely recognized as ideal platforms for constructing next-generation ultrathin, high-speed, and low-power optoelectronic devices. Among many 2D materials, molybdenum disulfide (MoS2), as a typical transition metal chalcogenide (TMD), exhibits enormous application potential. In particular, monolayer MoS2 is a direct bandgap semiconductor, where the excitation of photogenerated carriers does not require phonon assistance, thus exhibiting high photoelectric conversion efficiency. Furthermore, the absence of dangling bonds on the MoS2 surface allows for stacking and assembly with any material via van der Waals forces, thereby overcoming the stringent requirements for lattice matching in traditional heterojunction fabrication.
[0004] However, intrinsic MoS2 still has several inherent defects when applied to high-performance optoelectronic devices: 1) It has weak light absorption, and its atomic-level thickness limits its interaction with light; 2) It has a short carrier lifetime, and photogenerated electron-hole pairs are prone to recombination; 3) Defect states (such as sulfur vacancies) easily trap carriers, leading to persistent photoconductivity and affecting the device's response speed; 4) When in contact with metal electrodes, it often forms a high Schottky barrier due to Fermi level mismatch, which hinders the effective injection and extraction of carriers and increases the contact resistance.
[0005] To overcome these problems, researchers have tried various modification strategies, such as chemical doping and interface engineering. While these have improved the performance of MoS2-based optoelectronic devices to some extent, they have not fundamentally solved key issues such as narrow spectral response range, low photoresponsivity and sensitivity, and high dark current. Therefore, developing a new structure and method that can fundamentally improve the optoelectronic properties of MoS2 is a pressing technical challenge in this field. Summary of the Invention
[0006] One of the objectives of this invention is to provide a method for preparing MoS2-based two-dimensional semiconductor optoelectronic materials, in order to solve the problem that optoelectronic devices in the prior art cannot simultaneously achieve high responsivity and fast response time, and the detection range cannot reach the theoretical estimate.
[0007] This invention is achieved through the following technical solution: a method for preparing a MoS2-based two-dimensional semiconductor optoelectronic material, comprising: a) using chemical vapor deposition under inert gas protection, with MoO3 and sulfur as precursors, to grow a monolayer of MoS2 on a predetermined substrate; b) etching Mo2Ga2C precursor powder with an acidic solution containing fluoride to obtain Mo2CT. x Intermediate, then the Mo2CT x The intermediate was subjected to ultrasonic exfoliation under an oxygen atmosphere and an ice-water bath to obtain a monolayer Mo2C(OH)4MXene suspension with hydroxyl groups on the surface; c) The monolayer Mo2C(OH)4MXene suspension was coated onto the surface of the monolayer MoS2 and then subjected to heat treatment to form a heterojunction.
[0008] Furthermore, the reaction temperature for chemical vapor deposition is 700~900℃.
[0009] Furthermore, the amount of MoO3 used is 2.3~6.5 mg, the amount of sulfur used is 100~200 mg, and the reaction growth time is 10~60 min.
[0010] Furthermore, the acidic solution containing fluoride is prepared by dissolving LiF in hydrochloric acid or sulfuric acid.
[0011] Furthermore, the concentration of hydrochloric acid is 5~15 M, the etching reaction temperature is 20~60℃, and the reaction time is 10~30h.
[0012] Furthermore, the ultrasonic ablation treatment time is 1~5 hours.
[0013] Furthermore, in obtaining Mo2CT x After the intermediate and before ultrasonic stripping, the process also includes a step of centrifuging and washing the intermediate at a speed of 5000~12000 rpm.
[0014] Further, in step b), after ultrasonic stripping, the obtained suspension is further subjected to low-speed centrifugation to extract the supernatant containing a monolayer of Mo2C(OH)4 MXene, wherein the low-speed centrifugation speed is 1000~5000 rpm.
[0015] Furthermore, the coating method is spin coating.
[0016] Furthermore, the heat treatment temperature is 80~120℃, and the time is 100~15 h.
[0017] Furthermore, after step a) and before step c), the step of constructing source and drain electrodes on the monolayer MoS2 surface is also included.
[0018] In another aspect, the present invention provides a MoS2-based two-dimensional semiconductor optoelectronic material, which is prepared according to the preparation method described above. The structure comprises: a monolayer MoS2 layer grown on a substrate; and a monolayer Mo2C(OH)4MXene layer with hydroxyl groups as surface functional groups covering the monolayer MoS2 layer; wherein the monolayer Mo2C(OH)4MXene layer and the monolayer MoS2 layer form a heterojunction interface through van der Waals interactions.
[0019] Furthermore, the substrate is selected from at least one of SiO2 / Si, indium tin oxide (ITO), fluorine-doped tin oxide (FTO), or sapphire.
[0020] Another aspect of the present invention provides an application of a MoS2-based two-dimensional semiconductor optoelectronic material. The material prepared according to the above-mentioned method for preparing a MoS2-based two-dimensional semiconductor optoelectronic material has the following applications: (1) application in photodetectors; (2) application in optical signal reception.
[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0022] 1. This invention prepares Mo2C(OH)4 MXene, which shares Mo atoms with MoS2, and has an atomic layer composition of Mo-C-Mo, with transition metal Mo atoms located on the surface. The bridging effect of Mo atoms makes Mo2CT x MXene forms a more compact heterojunction with MoS2, optimizing the photogenerated carrier transport dynamics.
[0023] 2. This invention introduces hydroxyl (–OH) end groups onto the surface of Mo2C through ultrasonic exfoliation in both aqueous and oxygen atmospheres. This alters the density of states and Fermi level of Mo2C, endowing it with unique electronic tunability. The enhanced coupling between the material and light through these surface polar groups promotes the separation and transport of photogenerated carriers, significantly improving photoelectric response performance. Compared to other types of end groups, hydroxyl groups reduce the density of states (DOS) of Mo2C. x The work function of MXene forms an ohmic contact, eliminating the Schottky contact barrier at the heterojunction interface.
[0024] 3. The heterojunction photodetector prepared by this invention exhibits extremely high photoresponsivity, reaching 8.49 × 10⁻⁶ at 550 nm. 5 The A / W ratio and specific detectivity are as high as 8.2 × 10⁻⁶ at 550 nm. 14 Jones's performance far surpasses that of existing MoS2-based optoelectronic devices, resulting in a significant improvement in optoelectronic performance.
[0025] 4. This invention successfully broadens the response range from the visible light region of MoS2 to the near-infrared region (up to 1000 nm), solving the core defect of MoS2's large band gap and inability to respond to low-energy photons. Furthermore, by introducing metallic Mo2C(OH)4 MXene, not only is the light capture enhanced, but more importantly, the type II band alignment and ohmic contact formed by it with MoS2 construct a highly efficient photogenerated carrier separation channel, which greatly suppresses electron-hole pair recombination. This achieves a synergistic enhancement of light absorption and carrier separation efficiency, resulting in an effective broadening of the spectral response range.
[0026] 5. Due to the formation of high-quality ohmic contacts and efficient charge transport, the dark current of the device is suppressed to an extremely low level (10). -14 (A-level), laying the foundation for achieving high signal-to-noise ratio and high detectivity. Furthermore, the oxygen atmosphere ultrasonic exfoliation method proposed in this invention is the key to preparing surface hydroxyl-functionalized Mo2C MXene, and the process is controllable. Moreover, the overall preparation method is compatible with existing semiconductor micro-nano fabrication processes, providing the possibility for large-scale production. Attached Figure Description
[0027] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:
[0028] Figure 1 This is a schematic diagram of the fabrication technology route for MoS2-based two-dimensional semiconductor optoelectronic materials provided in Embodiment 1 of the present invention.
[0029] Figure 2 This is an X-ray diffraction pattern provided in Embodiment 1 of the present invention.
[0030] Figure 3 This is a scanning electron microscope image of the precursor MAX phase Mo2Ga2C provided in Embodiment 1 of the present invention.
[0031] Figure 4 This is a scanning electron microscope image of a single layer of MoS2 provided in Embodiment 1 of the present invention.
[0032] Figure 5 This is a transmission electron microscope image of a heterojunction provided in Embodiment 1 of the present invention.
[0033] Figure 6 The Raman spectrum of monolayer MoS2 provided in Embodiment 1 of the present invention.
[0034] Figure 7 This is a structural model diagram of the MoS2 crystal provided in Embodiment 1 of the present invention.
[0035] Figure 8 This is the band structure diagram of a single-layer MoS2 provided in Embodiment 1 of the present invention.
[0036] Figure 9 This is a projected density of states diagram of a single-layer MoS2 provided in Embodiment 1 of the present invention.
[0037] Figure 10 The structural model diagram of Mo2C(OH)4 MXene provided in Embodiment 1 of the present invention is shown.
[0038] Figure 11 The band structure diagram of Mo2C(OH)4 MXene provided in Embodiment 1 of the present invention.
[0039] Figure 12 This is the density of states diagram of Mo2C(OH)4 MXene provided in Example 1 of the present invention.
[0040] Figure 13 This is a band structure mechanism diagram of the Mo2C(OH)4MXene / MoS2 heterojunction provided in Embodiment 1 of the present invention.
[0041] Figure 14 The optical absorption spectrum of the Mo2C(OH)4MXene / MoS2 heterojunction provided for the experimental example of this invention.
[0042] Figure 15 The fluorescence spectrum of the Mo2C(OH)4MXene / MoS2 heterojunction provided as an experimental example of the present invention. Detailed Implementation
[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.
[0044] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated herein by reference to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail. The terms “comprising,” “including,” “having,” “containing,” etc., as used herein are open-ended terms, meaning that they include but are not limited to. Unless the context clearly indicates otherwise, the expressions “a” and “an” as used herein include plural references. It should be noted that “first,” “second,” etc., are used merely for convenience of description and distinction and should not be construed as indicating or implying relative importance. The term “about” as used herein indicates a range of ±20% of the following numerical value. In some embodiments, the term “about” indicates a range of ±10% of the following numerical value. In some embodiments, the term “about” indicates a range of ±5% of the following numerical value.
[0045] Example 1
[0046] Figure 1 A schematic diagram of the fabrication technology route for MoS2-based two-dimensional semiconductor optoelectronic materials provided in this embodiment. The diagram shows two core technology paths in this embodiment: (1) using chemical vapor deposition (CVD) to fabricate MoS2-based two-dimensional semiconductor optoelectronic materials. x (1) Using S powder as raw material, a monolayer MoS2 was prepared on the substrate under high temperature and argon (Ar) protection; (2) Using the MAX phase material Mo2Ga2C as a precursor, liquid phase etching was performed by LiF and HCl solution, and then Mo2CT was obtained by centrifugation. x Finally, Mo2CT x The supernatant was spin-coated onto the surface of a monolayer MoS2 and dried to form the final heterojunction. The preparation method of the Mo-atom-bridged Mo2C(OH)4MXenes / monolayer-MoS2 Van der Waals heterojunction optoelectronic material in this embodiment specifically includes the following steps:
[0047] 1. Place 4.2 mg of MoO3 powder in a quartz boat and place the quartz boat in a multi-temperature zone CVD tube furnace;
[0048] 2. Place the SiO2 / Si substrate face down on top of the quartz boat containing MoO3 powder from step 1;
[0049] 3. Place 150 mg of sulfur powder in a quartz boat and place it upstream of a multi-temperature zone tubular furnace. The temperature of different zones in the tubular furnace can be independently controlled.
[0050] 4. The temperature of the center of the tube furnace is raised to 800℃ at a rate of 5℃ / min and held at that temperature. At the same time, the temperature zone where the S powder is located is heated to 200℃ at a rate of 5℃ / min. The reaction is carried out for 30 min. High-purity argon is introduced as a protective gas during the process. After the reaction is completed, the mixture is naturally cooled to room temperature to obtain monolayer-MoS2 grown on SiO2 / Si substrate.
[0051] 5. Constructing a MoS2 transistor: The Au electrode is transferred to the MoS2 nanosheet obtained in step 4 to obtain the source and drain electrodes of the detector. The Si sheet is used as the gate to obtain the MoS2 transistor channel.
[0052] 6. Add 2 g LiF to 20 ml of 9 M hydrochloric acid solution and stir with a magnetic stirrer for 1 h to mix thoroughly, to obtain solution 1;
[0053] 7. Add 2 g of Mo2Ga2C powder to solution 1, adjust the temperature of the magnetic stirrer to 40℃, and stir for 20 h to obtain suspension 2;
[0054] 8. The suspension 2 obtained in the above steps is centrifuged and washed at 8000 rpm, and then washed three times with deionized water to obtain Mo2CT. x Suspension 3;
[0055] 9. Place the suspension 3 obtained in the above steps in an ice-water bath and ultrasonically exfoliate it in an oxygen atmosphere for 2 hours to obtain suspension 4;
[0056] 10. Centrifuge the above suspension 4 at 3000 rpm for 2 hours. The resulting monolayer-Mo2CT... x Store the supernatant for later use;
[0057] 11. The monolayer-Mo2CT obtained in step 9 x The supernatant was spin-coated onto the surface of the monolayer-MoS2 transistor channel obtained in step 5 and dried in a vacuum drying oven at 100°C for 12 h to obtain a Mo2C(OH)4MXene / monolayer-MoS2 Van der Waals heterojunction grown on a SiO2 / Si substrate.
[0058] Figure 2 The X-ray diffraction (XRD) patterns of Mo2C(OH)4MXene and the final product Mo2C(OH)4MXene / MoS2 prepared in this embodiment are shown. As can be seen from the figures, the lower Mo2C(OH)4MXene pattern shows a sharp (002) crystal plane diffraction peak at approximately 8°, indicating the successful preparation of MXene with a well-defined layered structure. The upper heterojunction pattern not only retains the characteristic peaks of MXene but also shows diffraction peaks belonging to MoS2, proving that the two phases, MoS2 and Mo2C(OH)4MXene, coexist in the final product, successfully constructing the composite material.
[0059] Figure 3 This is a scanning electron microscope (SEM) image of the precursor MAX phase Mo2Ga2C in this embodiment. The image shows the multilayer "accordion" structure of the precursor MAX phase Mo2Ga2C, which is an important morphological feature for successful etching.
[0060] Figure 4 The image shows a scanning electron microscope (SEM) image of the monolayer MoS2 prepared by CVD in this embodiment. As can be seen from the image, the monolayer MoS2 exhibits a typical triangular morphology and uniform size, indicating high growth quality.
[0061] Figure 5 The image shows a transmission electron microscope (TEM) image of the heterojunction in this embodiment. As can be seen from the image, the Mo2C(OH)4 MXene nanosheets are tightly bonded to MoS2, forming a clear heterojunction interface.
[0062] Figure 6 The Raman spectrum of the monolayer MoS2 prepared in this embodiment is shown. The image clearly shows the region located at approximately 387 cm⁻¹. -1 and 405 cm -1 The two characteristic peaks at the location correspond to the in-plane vibration modes (E) of monolayer MoS2. 1 The characteristic peaks (A1g) and out-of-plane vibration mode (A1g) are strong evidence that MoS2 is a monolayer, ensuring the monolayer characteristics of the MoS2 material used in this invention. Furthermore, the characteristic peak frequency difference for a monolayer is 17.4 ≤ ∆ω ≤ 20.0 cm⁻¹. -1 In this embodiment, the frequency difference between the two characteristic peaks is 18 cm⁻¹. -1 Less than 25 cm of bulk material -1 The peak positions match those of monolayer MoS2, indicating that monolayer MoS2 was successfully synthesized.
[0063] Figure 7The diagram shows a structural model of the MoS2 crystal prepared in this embodiment. The diagram shows its layered structure consisting of three layers of S-Mo-S atoms connected by covalent bonds, with the layers stacked by van der Waals forces.
[0064] Figure 8 The band structure of monolayer MoS2, calculated using first-principles calculations, is shown. The calculations demonstrate that the valence band top and conduction band bottom of monolayer MoS2 are aligned at k-points, exhibiting characteristics of a direct bandgap semiconductor. This is beneficial for the effective excitation of photogenerated electron-hole pairs, forming the theoretical basis for its excellent optoelectronic properties. It can be seen that the spin-up and spin-down bands of MoS2 are essentially overlapping, and MoS2 is a direct bandgap semiconductor, with both the conduction band bottom and valence band top located at k-points. Specific values are shown in Table 1: the bandgap is 2.087 eV, slightly larger than that of bulk materials; the conduction band potential is -3.897 eV; and the valence band potential is -5.985 eV.
[0065] Table 1. Band structure of MoS2: band gap, conduction band level, valence band level, Fermi level.
[0066]
[0067] Figure 9 The projected density of states (PDOS) spectrum of monolayer MoS2, calculated using first-principles calculations, is shown. This spectrum reveals that the valence band top (VBM) is primarily contributed by the d orbitals of Mo atoms and the p orbitals of S atoms, while the conduction band bottom (CBM) is primarily contributed by the d orbitals of Mo atoms.
[0068] Figure 10 A structural model of Mo2C(OH)4MXene, one of the core materials in this embodiment, is shown. The model demonstrates that hydroxyl (-OH) functional groups are uniformly distributed across the upper and lower surfaces of the two-dimensional atomic layers of Mo2C. The presence of these hydroxyl functional groups effectively modulates the work function of MXene, enabling it to form ohmic contacts with MoS2 rather than Schottky contacts. This is the key to solving the high contact barrier problem in this invention.
[0069] Figure 11 The band structure of Mo2C(OH)4MXene, calculated using first-principles calculations, is shown. As can be seen from the figure, its bands cross the Fermi level (E - E_VBM, HSE = 0 eV), exhibiting metallic or half-metallic characteristics and excellent conductivity, making it an ideal charge transport layer.
[0070] Figure 12The density of states spectrum of Mo₂C(OH)₄MXene, calculated using first-principles calculations, is shown. This spectrum reveals a high density of electronic states near the Fermi level, primarily contributed by the d orbitals of the Mo atom, further confirming its excellent electrical conductivity.
[0071] Figure 13 The diagram shows the mechanism of this heterojunction. It illustrates that by controlling the surface end groups, a suitable work function and band structure are obtained, which is beneficial for photogenerated electrons to migrate along specific paths and promote electron-hole separation.
[0072] Example 2
[0073] The preparation method in this embodiment is largely the same as that in Example 1, except that:
[0074] In steps 1 and 4: the amount of MoO3 powder used was 4.2 mg, and the amount of sulfur powder used was 100 mg. During CVD growth, the central high-temperature zone was heated to 700°C at a rate of 5°C / min, and the low-temperature zone containing the sulfur powder was heated to 100°C at a rate of 5°C / min. The reaction time was 30 min.
[0075] In step 2: the substrate is made of ITO conductive glass.
[0076] In steps 6 and 7: Weigh 2 g of LiF powder and add it to 30 ml of 9 M hydrochloric acid solution, stir for 1 h; add 2 g of Mo2Ga2C powder, and stir the reaction at 60 °C for 20 h.
[0077] In step 8: the centrifugal washing speed is 12000 rpm, and the product is washed 3 times with deionized water.
[0078] In step 9: the ultrasonic ablation time is 2 hours.
[0079] In step 10: the low-speed centrifugation speed is 5000 rpm and the time is 2 h.
[0080] In step 11: the vacuum drying temperature is 100℃ and the time is 12 h.
[0081] Example 3
[0082] The preparation method in this embodiment is largely the same as that in Example 1, except that:
[0083] In steps 1 and 4: the amount of MoO3 powder used was 2.3 mg, and the amount of sulfur powder used was 100 mg. During CVD growth, the central high-temperature zone was heated to 700℃ at a rate of 2℃ / min, and the low-temperature zone containing the sulfur powder was heated to 100℃ at a rate of 2℃ / min. The reaction time was 10 min.
[0084] In steps 6 and 7: Weigh 1 g of LiF powder and add it to 5 ml of 5 M hydrochloric acid solution, and stir for 0.5 h; add 1 g of Mo2Ga2C powder and stir the reaction at 20 °C for 10 h.
[0085] In step 8: the centrifugal washing speed is 5000 rpm, and the product is washed once with deionized water.
[0086] In step 9: the ultrasonic ablation time is 1 hour.
[0087] In step 10: the low-speed centrifugation speed is 1000 rpm and the time is 1 h.
[0088] In step 11: the vacuum drying temperature is 80℃ and the time is 10 h.
[0089] Example 4
[0090] The preparation method in this embodiment is largely the same as that in Example 1, except that:
[0091] In steps 1 and 4: the amount of MoO3 powder used was 4.2 mg, and the amount of sulfur powder used was 200 mg. During CVD growth, the central high-temperature zone was heated to 900℃ at a rate of 8℃ / min, and the low-temperature zone containing the sulfur powder was heated to 300℃ at a rate of 8℃ / min. The reaction time was 30 min.
[0092] In step 2: the substrate is FTO conductive glass.
[0093] In steps 6 and 7: Weigh 5 g of LiF powder and add it to 50 ml of 15 M hydrochloric acid solution, and stir for 3 h; add 5 g of Mo2Ga2C powder and stir the reaction at 40 °C for 30 h.
[0094] In step 8: the centrifugal washing speed is 8000 rpm, and the product is washed 3 times with deionized water.
[0095] In step 9: the ultrasonic ablation time is 2 hours.
[0096] In step 10: the low-speed centrifugation speed is 5000 rpm and the time is 1 h.
[0097] In step 11: the vacuum drying temperature is 100℃ and the time is 12 h.
[0098] Example 5
[0099] The preparation method in this embodiment is largely the same as that in Example 1, except that:
[0100] In steps 1 and 4: the amount of MoO3 powder used was 6.5 mg, and the amount of sulfur powder used was 200 mg. During CVD growth, the central high-temperature zone was heated to 900℃ at a rate of 8℃ / min, and the low-temperature zone containing the sulfur powder was heated to 300℃ at a rate of 8℃ / min. The reaction time was 60 min.
[0101] In steps 6 and 7: Weigh 5 g of LiF powder and add it to 50 ml of 15 M hydrochloric acid solution, stir for 3 h; add 5 g of Mo2Ga2C powder, and stir the reaction at 60 °C for 30 h.
[0102] In step 8: the centrifugal washing speed is 12000 rpm, and the product is washed 5 times with deionized water.
[0103] In step 9: the ultrasonic ablation time is 5 hours.
[0104] In step 10: the low-speed centrifugation speed is 5000 rpm and the time is 5 h.
[0105] In step 11: the vacuum drying temperature is 120℃ and the time is 15 h.
[0106] Experimental Example
[0107] Photoelectric performance testing and effect verification.
[0108] To verify the performance of the Mo2C(OH)4 MXene / monolayer MoS2 van der Waals heterojunction optoelectronic material prepared by the method disclosed in this invention, the devices prepared in Examples 1-5 were subjected to optoelectronic performance tests and compared with the control devices containing only monolayer MoS2.
[0109] 1. Structural characterization:
[0110] The morphology and crystal structure of the material were characterized using atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy, and scanning / transmission electron microscopy (SEM / TEM). The results are shown in the figure in Example 1, confirming the successful preparation of the material.
[0111] 2. Optical performance:
[0112] The optical properties of the material were tested using a UV-Vis-NIR spectrophotometer and a fluorescence spectrometer. The results are attached. Figure 14 and 15As shown, compared with pure monolayer MoS2, the heterojunction material prepared in this invention exhibits significantly enhanced light absorption and severe quenching of fluorescence signal. This indicates that the introduction of Mo2C(OH)4MXene not only increases light absorption but, more importantly, constructs a highly efficient charge separation channel, greatly suppressing the recombination of photogenerated electron-hole pairs, thus laying the foundation for excellent photoelectric conversion performance.
[0113] Figure 14 The absorption spectra of pure monolayer MoS2 and the Mo2C(OH)4 MXene / MoS2 heterojunction prepared in this embodiment are shown. As can be seen from the figure, compared with pure MoS2, the light absorption intensity of the Mo2C(OH)4 MXene / MoS2 heterojunction is significantly enhanced throughout the ultraviolet-visible region. This result indicates that the introduction of MXene effectively improves the light-trapping ability of the composite system, which is the basis for subsequent improvements in photoelectric performance.
[0114] Figure 15 The fluorescence (PL) spectra of pure monolayer MoS2 and the Mo2C(OH)4 MXene / MoS2 heterojunction prepared according to this invention are shown. It can be seen that compared with the strong fluorescence emission peak of pure MoS2, the fluorescence intensity of the Mo2C(OH)4 MXene / MoS2 heterojunction exhibits significant quenching. This fluorescence quenching phenomenon is direct evidence of the effective separation and removal of photogenerated electron-hole pairs, indicating that efficient charge transfer occurs at the heterojunction interface, greatly suppressing carrier recombination and thus improving the internal quantum efficiency.
[0115] 3. Photoelectric detection performance:
[0116] The performance parameters of the Mo2C(OH)4 MXene / monolayer-MoS2 Van der Waals heterojunction photodetector were obtained by testing with a B1500A semiconductor tester.
[0117] The LEDs used for testing mainly included three wavelengths: 450 nm, 541 nm, and 715 nm. The spot diameter was 3 mm, which is much larger than the length and width of the device channel.
[0118] The prepared Mo₂C(OH)₄ MXene / MoS₂ van der Waals heterojunction was used in a photodetector, capable of responding to a spectrum in the 380 nm–1000 nm range and driven by ultra-low bias voltages of 0.1 mV and 0.1 V. The photoresponsivity and specific detectivity reached 8.49 x 10⁻⁶. 5 A / W and 8.2x10 14Jones (@550 nm) has a power of 98 A / W and 5.2 x 10¹¹ Jones at 1000 nm. The input power is 3.52 mW·cm⁻¹. -2 Under irradiation by a 550 nm laser, 10 -14 Ultra-low dark current on the order of A. At V ds At 0.5 V, the responsivity is achieved, which is superior to previously reported MoS2-based photodetectors. The photocurrent rises rapidly under laser irradiation and then decays sharply when the laser is turned off, indicating that the photogenerated carrier mobility is improved in this heterojunction. The photodetector exhibits fast responsivity and short response time at different laser wavelengths (450, 550, and 1000 nm), demonstrating its effectively broadened spectral response characteristics. The photoelectric properties of samples obtained from different embodiments are shown in Table 2.
[0119] Table 2. Photoelectric properties of samples obtained from different embodiments
[0120]
[0121] The photoelectric response performance of the device was tested using a semiconductor parameter tester (B1500A) and LED light sources of different wavelengths (e.g., 450 nm, 550 nm, 715 nm and 1000 nm).
[0122] Test results show that the heterojunction photodetector prepared in this invention exhibits unexpected technical effects:
[0123] (1) Wide spectrum response: The device can respond to a wide range of spectra from ultraviolet to near infrared (380 nm-1000 nm), effectively solving the technical defect that pure MoS2 is only sensitive to visible light.
[0124] (2) Ultra-high sensitivity: Under 550 nm wavelength illumination, the device's photoresponsivity reaches 8.49 × 10⁻⁶. 5 A / W, with a specific detectivity as high as 8.2 × 10⁻⁶. 14 Jones. Even in the near-infrared band at 1000 nm, the photoresponsivity and specific detectivity still reach 98 A / W and 5.2 × 10⁻⁶, respectively. 11 Jones. These values are far superior to most photodetectors based on pure MoS2 or other MoS2 heterojunctions reported in the literature.
[0125] (3) Extremely low dark current: Under no-light conditions, the dark current of the device is as low as 10 -14 The A-level noise level significantly reduces device noise and is key to achieving high specific detectivity.
[0126] (4) Fast response: The device exhibits fast photocurrent rise and fall edges and short response time under different wavelength illumination on and off, indicating that the ohmic contact formed at the heterojunction interface effectively promotes the rapid transport and extraction of charge carriers.
[0127] In summary, this invention, through rational design, combines surface-hydroxylated Mo2C(OH)4 MXene with monolayer MoS2, constructing a high-quality heterojunction using Mo atomic bridging and van der Waals interactions. This heterojunction not only broadens the spectral response range and enhances light absorption, but also fundamentally solves the problems of severe carrier recombination and high contact barriers in traditional MoS2-based optoelectronic devices by forming ohmic contacts and efficient charge separation interfaces, thereby achieving a significant improvement in key performance indicators such as photoresponsivity and specific detectivity.
[0128] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing a MoS2-based two-dimensional semiconductor optoelectronic material, characterized in that, The preparation method includes: a) Using chemical vapor deposition, under inert gas protection, with MoO3 and sulfur as precursors, a monolayer of MoS2 is obtained by reaction growth on a pre-set substrate. b) Etching the Mo2Ga2C precursor powder with an acidic solution containing fluoride to obtain Mo2CT x Intermediate, then the Mo2CT x The intermediate was subjected to ultrasonic ablation under oxygen atmosphere and ice-water bath conditions. A monolayer Mo2C(OH)4 MXene suspension with hydroxyl groups as surface functional groups was obtained; c) The monolayer Mo2C(OH)4MXene suspension is coated onto the surface of the monolayer MoS2, and then heat-treated to form a heterojunction.
2. The method for preparing MoS2-based two-dimensional semiconductor optoelectronic materials according to claim 1, characterized in that, The reaction temperature for the chemical vapor deposition method is 700~900℃.
3. The method for preparing MoS2-based two-dimensional semiconductor optoelectronic materials according to claim 1 or 2, characterized in that, The amount of MoO3 used is 2.3~6.5 mg. The amount of sulfur used is 100-200 mg. The reaction growth time is 10~60 min.
4. The method for preparing MoS2-based two-dimensional semiconductor optoelectronic materials according to claim 1, characterized in that, The acidic solution containing fluoride is prepared by dissolving LiF in hydrochloric acid or sulfuric acid.
5. The method for preparing MoS2-based two-dimensional semiconductor optoelectronic materials according to claim 4, characterized in that, The concentration of the hydrochloric acid is 5-15 M. The etching reaction temperature is 20~60℃, and the reaction time is 10~30 h.
6. The method for preparing MoS2-based two-dimensional semiconductor optoelectronic materials according to claim 1, characterized in that, The ultrasonic ablation process takes 1 to 5 hours.
7. The method for preparing MoS2-based two-dimensional semiconductor optoelectronic materials according to claim 1, characterized in that, In obtaining Mo2CT x After the intermediate and before ultrasonic stripping, the process also includes a step of centrifuging and washing the intermediate at a speed of 5000~12000 rpm.
8. The method for preparing MoS2-based two-dimensional semiconductor optoelectronic materials according to claim 1, characterized in that, In step b), after ultrasonic stripping, the obtained suspension is further subjected to low-speed centrifugation to extract the supernatant containing a monolayer of Mo2C(OH)4 MXene, wherein the low-speed centrifugation speed is 1000~5000 rpm.
9. A MoS2-based two-dimensional semiconductor optoelectronic material, characterized in that, The two-dimensional semiconductor optoelectronic material is prepared according to the preparation method described in any one of claims 1 to 8. Its structure includes: A monolayer MoS2 layer grown on a substrate; and a monolayer Mo2C(OH)4 MXene layer covering the monolayer MoS2 layer with hydroxyl groups as surface functional groups; The monolayer Mo2C(OH)4 MXene layer and the monolayer MoS2 layer form a heterojunction interface through van der Waals interactions.
10. An application of a MoS2-based two-dimensional semiconductor optoelectronic material, characterized in that, The two-dimensional semiconductor optoelectronic material is prepared according to the preparation method described in any one of claims 1 to 8. Including the following applications: (1) Applications in photodetectors; (2) Application in optical signal reception.