Flexible nitrogen dioxide gas sensor based on tungsten disulfide and method of making the same

Abstract

This application provides a flexible nitrogen dioxide gas sensor based on tungsten disulfide and its fabrication method. The sensor includes a flexible substrate, a flexible electrode, and a tungsten disulfide sensitive film. The flexible electrode is disposed on the same plane of the flexible substrate, and the source and drain adopt an arrayed interdigitated electrode structure. The tungsten disulfide sensitive film covers the channel region between the source and drain, and there is a gap between it and the gate. When a gate voltage is applied, the gate modulates the carrier concentration in the tungsten disulfide channel of the tungsten disulfide sensitive film through a lateral electric field, thereby adjusting the sensitivity to nitrogen dioxide detection. The fabrication process is simplified, and high sensitivity, fast recovery, and flexible wearable adaptation are achieved simultaneously without material modification or external assistance.

Description

Technical Field

[0001] This application relates to the field of sensors, and more particularly to a flexible nitrogen dioxide gas sensor based on tungsten disulfide and its preparation method. Background Technology

[0002] Nitrogen dioxide gas sensors are used to detect the concentration of nitrogen dioxide gas. Existing nitrogen dioxide gas sensors still have the following problems: (1) Nitrogen dioxide gas sensors have an inherent defect of incomplete recovery of nitrogen dioxide at room temperature, resulting in poor recovery performance and limiting their practical application. Existing solutions mainly rely on material modification methods such as heterostructure construction, ultraviolet light assistance, or element doping, which increase the complexity of the device and the manufacturing cost.

[0003] (2) The correlation mechanism between the electrode design and device recovery performance of nitrogen dioxide gas sensor is unclear, and the selection of electrode geometric parameters (such as width and spacing) lacks systematic matching with the gas-sensitive characteristics of tungsten disulfide. Summary of the Invention

[0004] The following is an overview of the topics described in detail in this article.

[0005] The purpose of this application is to at least partially solve one of the technical problems existing in the related technologies. The embodiments of this application provide a flexible nitrogen dioxide gas sensor based on tungsten disulfide and its preparation method.

[0006] An embodiment of the first aspect of this application provides a flexible nitrogen dioxide gas sensor based on tungsten disulfide, comprising: Flexible substrate; A flexible electrode is disposed on the same plane of the flexible substrate. The flexible electrode includes a gate, a source, and a drain. The source and the drain adopt an arrayed interdigitated electrode structure. Tungsten disulfide sensitive film, the tungsten disulfide sensitive film covers the channel region between the source and the drain, and there is a gap between it and the gate; Specifically, when a gate voltage is applied, the gate modulates the carrier concentration in the tungsten disulfide channel of the tungsten disulfide sensitive film through a lateral electric field, thereby adjusting the sensitivity to nitrogen dioxide detection.

[0007] According to certain embodiments of the first aspect of this application, the array interdigital electrode structure is provided with four interdigital electrode units, each interdigital electrode unit comprising six electrode fingers, wherein the ratio of the width of the electrode fingers to the interdigital spacing is 2:1, the width of the electrode fingers is 200 μm, the length is 700 μm, and the interdigital spacing is 100 μm.

[0008] According to certain embodiments of the first aspect of this application, the tungsten disulfide sensitive film has 1 to 5 tungsten disulfide layers, and the thickness of the tungsten disulfide sensitive film ranges from 0.7 nm to 3.5 nm.

[0009] According to certain embodiments of the first aspect of this application, the width of the gap between the tungsten disulfide channel and the gate ranges from 5 μm to 10 μm.

[0010] According to certain embodiments of the first aspect of this application, the gap between the tungsten disulfide channel and the gate is filled with air or an insulating layer is deposited.

[0011] According to certain embodiments of the first aspect of this application, the flexible substrate is made of polyethylene terephthalate or polyethylene naphthalate.

[0012] An embodiment of the second aspect of this application, a method for fabricating a flexible nitrogen dioxide gas sensor based on tungsten disulfide, includes: A support layer is formed by spin-coating a support layer material onto the surface of a silicon wafer substrate with a single layer of tungsten disulfide. After etching away the silicon substrate, the composite film is retrieved using a flexible substrate, and the support layer is removed by dissolving it with acetone to obtain the tungsten disulfide sensitive film. A polyimide mask layer is coated on the surface of the tungsten disulfide sensitive film, and a hollow pattern is formed by laser patterning. A flexible electrode is formed by depositing an electrode based on the hollow pattern using a sputtering coating instrument, thereby obtaining a flexible nitrogen dioxide gas sensor.

[0013] According to certain embodiments of the second aspect of this application, the preparation of a tungsten disulfide layer includes: using sulfur powder and tungsten trioxide powder as precursors, reacting them in a high-temperature tube furnace under an argon atmosphere to obtain a tungsten disulfide layer.

[0014] According to certain embodiments of the second aspect of this application, the preparation of a tungsten disulfide layer includes: using tungsten hexacarbonyl and hydrogen sulfide as precursors, and obtaining a tungsten disulfide layer by plasma-assisted decomposition.

[0015] According to certain embodiments of the second aspect of this application, the support layer material is polymethyl methacrylate, polycarbonate, or polystyrene.

[0016] The above-described approach offers at least the following advantages: By integrating a high-quality monolayer tungsten disulfide film grown by chemical vapor deposition onto a flexible PET substrate via a non-destructive wet transfer process, and employing a coplanar gate structure, the channel carrier concentration is actively controlled by a lateral electric field, thereby achieving high sensitivity, rapid recovery, and flexible wearable adaptation without material modification or external assistance. The use of a coplanar field-effect transistor structure integrates all electrodes and the tungsten disulfide sensitive film onto the same plane of the flexible substrate, simplifying the fabrication process. Without introducing heteromaterials, dopants, or external assistance, good recovery performance can be achieved simply by combining specific interdigital electrode geometry parameters. Attached Figure Description

[0017] The accompanying drawings are used to provide a further understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0018] Figure 1 This is a structural diagram of a flexible nitrogen dioxide gas sensor based on tungsten disulfide; Figure 2 This is a structural diagram of the flexible electrode of a flexible nitrogen dioxide gas sensor; Figure 3 This is a SEM image of a flexible nitrogen dioxide gas sensor; Figure 4 This is the AFM diagram of a flexible nitrogen dioxide gas sensor; Figure 5 This is the Raman spectral characterization of the flexible nitrogen dioxide gas sensor; Figure 6 This is a PL characterization diagram of a flexible nitrogen dioxide gas sensor; Figure 7 This is the response / recovery curve of a flexible nitrogen dioxide gas sensor; Figure 8 This is a dynamic response curve of a flexible nitrogen dioxide gas sensor; Figure 9 This is a graph showing the relationship between the sensitivity of a flexible nitrogen dioxide gas sensor and the nitrogen dioxide concentration. Figure 10 This is a graph showing the selectivity test results of a flexible nitrogen dioxide gas sensor; Figure 11 This is a step-by-step diagram of the fabrication method for a flexible nitrogen dioxide gas sensor. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0020] It should be noted that although functional modules are divided in the device schematic diagram and a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the device or the order in the flowchart. The terms "first," "second," etc., in the specification, claims, or the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0021] Nitrogen dioxide gas sensors are used to detect the concentration of nitrogen dioxide gas. Existing nitrogen dioxide gas sensors still have the following problems: (1) Performance improvement depends on material modification, which increases device complexity and manufacturing cost.

[0022] Intrinsic WS2 sensors inherently exhibit incomplete recovery of nitrogen dioxide at room temperature. To overcome this defect, existing technologies commonly employ material modification techniques such as heterostructure construction (e.g., WS2 / SnSe2, WS2 / PbS), UV-assisted activation, elemental doping (e.g., Nd, Ni, Pd), or noble metal modification (e.g., Au, Pt). While these methods can improve recovery performance to some extent, they introduce additional heteromaterials, doping elements, or external auxiliary devices, increasing device structural complexity, fabrication difficulty, and manufacturing costs. Furthermore, UV-assisted methods are unsuitable for passive sensing scenarios without external power supply.

[0023] (2) The recovery problem of large-area WS2 devices in nitrogen dioxide gas sensing.

[0024] While chemical vapor deposition (CVD) can achieve large-area fabrication of WS2, current research on large-area WS2 devices mainly focuses on photodetectors or field-effect transistors, and has not yet been applied to NO2 gas sensors. In particular, the recovery performance of large-area devices remains a problem, namely, how to achieve rapid and complete gas desorption within a large sensing area, and there is a lack of optimization schemes for the recovery performance of large-area devices.

[0025] (3) The correlation mechanism between electrode pattern design and device recovery performance is missing.

[0026] Interdigitated electrodes are a conventional electrode structure in WS2 gas sensors, but in existing technologies, the selection of electrode geometric parameters (finger width, spacing, finger width / spacing ratio, etc.) often follows a fixed pattern, lacking a systematic matching of the gas-sensing characteristics of WS2.

[0027] To address the above issues, embodiments of this application provide a flexible nitrogen dioxide gas sensor based on tungsten disulfide and a method for its fabrication.

[0028] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0029] Reference Figure 1 A flexible nitrogen dioxide gas sensor based on tungsten disulfide includes: a flexible substrate 3, a flexible electrode 1, and a tungsten disulfide sensitive film 2.

[0030] The flexible electrode 1 is disposed on the same plane as the flexible substrate 3. The flexible electrode 1 includes a gate, a source, and a drain. The source and drain adopt an arrayed interdigitated electrode structure. The tungsten disulfide sensitive film 2 covers the channel region between the source and drain and has a gap with the gate.

[0031] The sensor adopts a coplanar structure, that is, the gate, source, drain and tungsten disulfide sensitive film 2 are all located on the same surface of the flexible substrate 3.

[0032] The flexible substrate 3, made of polyethylene terephthalate or polyethylene naphthalate, provides mechanical support for the entire device. The substrate size is 10 mm × 10 mm. Of course, in other embodiments, the substrate size can be set according to actual production requirements.

[0033] The flexible substrate 3 is replaced with polyethylene terephthalate (PET) instead of polyethylene naphthalate (PEN). PEN, like PET, is a polyester material, but it offers superior heat resistance (glass transition temperature of approximately 120°C), better barrier properties, and higher mechanical strength. In applications requiring slightly higher process temperatures or long-term stability, PEN can be an effective alternative to PET, and its surface properties are similar to PET, eliminating the need for significant adjustments to the wet transfer process parameters for tungsten disulfide films.

[0034] The gate is made of a conductive material (such as silver).

[0035] Reference Figure 2 The source and drain adopt an array interdigitated electrode structure. The array interdigitated electrode structure is set with four interdigitated electrode units, each containing 6 electrode fingers. The ratio of the width of the electrode fingers to the spacing between the fingers is 2:1. The width of the electrode fingers is 200μm, the length is 700μm, and the spacing between the fingers is 100μm.

[0036] The tungsten disulfide sensitive film 2 has 1 to 5 tungsten disulfide layers, and its thickness ranges from 0.7 nm to 3.5 nm. It is prepared by chemical vapor deposition and transferred to the substrate surface, covering the channel region between the source and drain electrodes, and maintaining a certain gap with the gate. The width of the gap between the tungsten disulfide channel and the gate ranges from 5 μm to 10 μm. The gap between the tungsten disulfide channel and the gate is filled with air or deposited with an insulating layer.

[0037] When a gate voltage is applied, the gate modulates the carrier concentration in the tungsten disulfide channel of the tungsten disulfide sensitive film 2 through a lateral electric field, thereby actively adjusting the sensitivity to nitrogen dioxide detection; at the same time, the interdigitated electrode structure effectively increases the contact area between the sensitive material and the electrode, improving the response signal intensity.

[0038] The flexible nitrogen dioxide gas sensor was prepared using the following method.

[0039] Reference Figure 11 A method for fabricating a flexible nitrogen dioxide gas sensor based on tungsten disulfide includes the following steps: A support layer is formed by spin-coating a support layer material onto the surface of a silicon wafer substrate with a single layer of tungsten disulfide. After etching away the silicon substrate, the composite film is retrieved using a flexible substrate 3, and the support layer is removed by dissolving it with acetone to obtain the tungsten disulfide sensitive film 2. A polyimide mask layer is coated on the surface of a tungsten disulfide sensitive film 2, and a hollow pattern is formed by laser patterning. A flexible electrode 1 is formed by depositing an electrode based on the hollow pattern using a sputtering coating instrument, thereby obtaining a flexible nitrogen dioxide gas sensor.

[0040] The support layer material is polymethyl methacrylate (PMMA), polycarbonate, or polystyrene. Polycarbonate (PC) or polystyrene (PS) is used instead of PMMA as the support layer in the wet transfer process. PC and PS have higher glass transition temperatures, reducing organic residues during transfer, which can be removed subsequently using solvents such as chloroform. This approach only replaces the support layer material, keeping the overall transfer process unchanged, and yields a cleaner tungsten disulfide film surface.

[0041] Specifically, the tungsten disulfide sensitive film 2 is prepared as follows.

[0042] High-quality monolayer tungsten disulfide films were prepared by chemical vapor deposition (CVD). Sulfur powder and tungsten trioxide powder were used as precursors, and the reaction was carried out in a high-temperature tube furnace under an argon atmosphere to obtain the tungsten disulfide layer.

[0043] On the other hand, the preparation of the tungsten disulfide layer includes: using tungsten hexacarbonyl and hydrogen sulfide as precursors, and obtaining the tungsten disulfide layer through plasma-assisted decomposition. A tungsten disulfide thin film is directly grown at low temperature on a flexible substrate 3 using plasma-enhanced chemical vapor deposition (PECVD). PECVD can directly deposit a tungsten disulfide thin film on the surface of a flexible substrate 3 (such as polyimide PI, PEN) at relatively low temperatures (200~400°C) through plasma-assisted decomposition of precursors (such as tungsten hexacarbonyl and hydrogen sulfide). The advantage of this approach is its high process integration and the elimination of subsequent transfer steps. However, it requires optimization of plasma parameters (deposition temperature, RF power, gas flow rate ratio) to control the number of film layers and crystal quality. Continuous and uniform multilayer or near-monolayer tungsten disulfide thin films can be obtained. Although its gas-sensing performance may be slightly inferior to that of single-crystal thin films grown by high-temperature CVD, it is still sufficient for effective detection of nitrogen dioxide.

[0044] Reference Figure 3 Scanning electron microscopy (SEM) images show that the prepared tungsten disulfide film has a clear outline and a complete triangular domain morphology. (Refer to...) Figure 4 Atomic force microscopy (AFM) measurements showed a film thickness of 0.85 nm, consistent with the characteristics of a monolayer film. (Refer to...) Figure 5 Raman spectroscopy revealed the characteristic peak of the E¹²g mode in monolayer tungsten disulfide at 350.2 cm⁻¹. - ¹, The A_g mode is located at 417.2 cm. - ¹. Reference Figure 6 Photoluminescence (PL) spectroscopy showed that the emission peaks for monolayer, bilayer, and multilayer films were located at 1.98 eV, 1.95 eV, and 1.85 eV, respectively. These characterization results demonstrate that the chemical vapor deposition process is stable and reliable, and can produce high-quality monolayer tungsten disulfide films.

[0045] Specifically, the sensor assembly and fabrication are as follows.

[0046] Based on obtaining a high-quality monolayer tungsten disulfide thin film, it was transferred to a flexible PET substrate using a wet transfer technique. The specific process was as follows: First, polymethyl methacrylate (PMMA) was spin-coated onto the surface of a silicon wafer with a monolayer of tungsten disulfide as a support layer. After etching to remove the silicon substrate, the composite film was retrieved using a PET substrate. Finally, the PMMA support layer was removed by dissolving it in acetone. Subsequently, flexible interdigitated electrodes were fabricated on the surface of the tungsten disulfide thin film as source and drain electrodes using a laser patterning mask combined with sputtering deposition: A polyimide mask layer was coated on the surface of a glass slide, and after ultraviolet laser patterning to form a hollow pattern, silver electrodes were deposited using a sputtering deposition machine to obtain a complete flexible tungsten disulfide coplanar field-effect transistor gas sensor.

[0047] For example, a single-layer tungsten disulfide thin film is prepared by chemical vapor deposition.

[0048] The preparation of a monolayer tungsten disulfide thin film using chemical vapor deposition (CVD) is as follows: Weigh out 100 mg of sulfur powder and 10 mg of tungsten trioxide (WO3) powder using an analytical balance, and spread them evenly in two graphite boats. Place the graphite boat containing WO3 in the central heating zone of a tube furnace, and place the graphite boat containing sulfur powder upstream of the tube furnace, 17 cm away from the WO3. Place the growth substrate (such as a silicon wafer) downstream, approximately 1 cm directly above the graphite boat.

[0049] Before heating, the furnace tube was purged three times with 100 sccm of argon gas to remove residual gas. Then, under an argon atmosphere of 80 sccm, the furnace temperature was raised to 900℃ at a rate of 50℃ / min and held for 5 minutes. After holding, it was allowed to cool naturally to room temperature. The grown substrate was then removed, yielding a monolayer tungsten disulfide film.

[0050] For example, a flexible transistor gas sensor based on tungsten disulfide is fabricated.

[0051] Step 1: A wet transfer technique is used to transfer the tungsten disulfide (TDS) film grown on a silicon wafer to a flexible PET substrate. First, polymethyl methacrylate (PMMA) is spin-coated as a support layer onto the silicon wafer with grown TDS. The spin-coating parameters are: first, a low spin speed of 600 rpm for 10 s, followed by a high spin speed of 1500 rpm for 30 s, to ensure a uniform coating of PMMA solution on the TDS film. The sample is then placed in an 80°C drying oven for 30 min to allow the PMMA film to fully cure. After curing, cracks are made along the edges of the film around the sample to allow the subsequent etching solution to effectively penetrate the silicon wafer surface. The dried and scratched PMMA / WS2 sample is then immersed in a sodium hydroxide (NaOH) solution for etching to remove the silicon substrate. After etching, the PMMA / WS2 film floats on the NaOH surface. The PMMA / WS2 film floating on the liquid surface was carefully retrieved using a frosted glass plate and rinsed in deionized water. This process was repeated three times, 10 minutes each time, to ensure complete removal of the NaOH etching solution. After rinsing, the PMMA / WS2 film was retrieved using a flexible PET substrate and placed on a hot plate at 120°C for 10 minutes to remove excess moisture and initially fix the film onto the PET substrate. The PMMA / WS2 / PET sample fixed on the PET substrate was then immersed in acetone solution for 15 minutes, followed by rinsing with deionized water for 10 minutes. This process was repeated three times to ensure complete removal of PMMA. Finally, the sample was allowed to air dry naturally, and then placed on a hot plate and heated at 100°C for 5 minutes to thoroughly remove any residual moisture from the sample surface, resulting in the transferred WS2 / PET composite substrate.

[0052] Step Two: First, low-viscosity polyimide is uniformly coated onto the surface of a glass slide to obtain a smooth, bubble-free, uniform film. Then, using an ultraviolet laser processing system equipped with a 355 nm wavelength laser, the polyimide film is laser-patterned under parameters of 1.85 W laser power, 100 kHz repetition rate, and 50 μs pulse width to prepare a polyimide mask with interdigitated electrode cutouts. Using this pre-patterned polyimide as a mask, metallic silver electrodes are deposited on a WS2 / PET composite flexible substrate using a sputtering deposition system. This polyimide mask integrates the cutout patterns of interdigitated source / drain electrodes and lateral gates, allowing the entire silver electrode structure to be fabricated simultaneously in a single sputtering deposition, ultimately resulting in a structurally complete flexible tungsten disulfide coplanar field-effect transistor gas sensor.

[0053] It should be noted that the finger width of 200 μm and the spacing of 100 μm (finger width / spacing ratio 2:1) of the interdigitated electrodes in this embodiment are optimal parameters selected through preliminary experiments. It is understood that, while maintaining this finger width / spacing ratio essentially unchanged, proportionally scaling the electrode size (e.g., finger width 100 μm, spacing 50 μm, or finger width 300 μm, spacing 150 μm), or appropriately adjusting the absolute size within the allowable range of the flexible substrate 3, can still achieve similar gas-sensing performance. Therefore, the above parameters should not be construed as a strict limitation of the present invention, but rather as providing a feasible implementation method.

[0054] Specifically, the gas-sensing performance of this flexible nitrogen dioxide gas sensor was tested as follows.

[0055] The gas-sensing performance of the prepared flexible nitrogen dioxide gas sensor was tested at room temperature. (Refer to...) Figure 7 The sensor exhibits a 248% responsivity to 100 ppm nitrogen dioxide, with a response time of 95 s and a recovery time of 166 s, demonstrating high responsivity and good recoverability. (Reference) Figure 8 The sensor exhibits good concentration-dependent response behavior in the nitrogen dioxide concentration range of 20 ppm to 100 ppm, with sensitivity increasing with increasing concentration, reaching 30.34% at 20 ppm and 248% at 100 ppm, exhibiting typical n-type semiconductor response behavior. (Reference) Figure 9 The correlation coefficient R² for the concentration-sensitivity linear fit was 0.97, indicating that the sensor has good linearity. (Refer to...) Figure 10 Selectivity tests showed that the response to nitrogen dioxide was 248%, which was significantly higher than that of ammonia (NH3) (22.9%), hydrogen sulfide (H2S) (36.03%) and nitrogen (N2) (8.32%), demonstrating excellent selective recognition ability.

[0056] This flexible nitrogen dioxide gas sensor based on tungsten disulfide has the following advantages.

[0057] Without introducing heterogeneous materials, dopants, or external aids, good recovery performance can be achieved simply by combining specific interdigital electrode geometry parameters. It should be noted that the existing biomimetic wood sensor was tested at a concentration of 10 ppm (recovery time 403 seconds), and since the concentrations are different, direct comparison of absolute values ​​is not appropriate. However, this flexible nitrogen dioxide gas sensor achieves a recovery time of 166 seconds at 100 ppm, indicating that its recovery capability is feasible within the practical application concentration range.

[0058] A coplanar field-effect transistor structure is adopted, integrating all electrodes (gate, source, and drain) on the same surface of a flexible PET substrate, simplifying the fabrication process. Compared with the traditional back-gate structure, the coplanar structure eliminates the need for double-sided processing, allowing for completion in a single photolithography step, making it more suitable for mass production on flexible substrate 3. Existing biomimetic wood sensors rely on delignification and tilted sputtering, resulting in complex processes and difficulties in ensuring substrate consistency; heterojunction solutions require multiple solution spin-coating steps. This embodiment employs a process combining PET thin film and CVD growth with wet transfer, offering better compatibility with existing semiconductor production lines. The sensor exhibits good linearity (R²=0.97) within a concentration range of 20ppm to 100ppm, and its selectivity for NO2 is significantly better than that for NH3, H2S, and N2. These properties were achieved without any material modification of WS2, demonstrating the feasibility and simplicity of the device structure optimization path.

[0059] By integrating a high-quality monolayer tungsten disulfide (WS2) film grown by chemical vapor deposition onto a flexible PET substrate via a non-destructive wet transfer process and employing a coplanar gate structure, the channel carrier concentration is actively controlled by a lateral electric field. This achieves high sensitivity, rapid recovery, and flexible wearable adaptation without material modification or external assistance. Specifically, the monolayer WS2 film prepared by CVD exhibits high crystal quality (0.85 nm AFM thickness, precise Raman characteristic peaks, and standard photoluminescence peak positions), overcoming the challenges of numerous defects in liquid-phase exfoliation and the inability to scale up mechanical exfoliation. Through optimized wet transfer processes and laser patterned mask sputtering electrode technology, a coplanar field-effect transistor structure was successfully constructed on the flexible PET substrate. This resulted in a sensor with a responsivity of up to 248% for 100 ppm nitrogen dioxide at room temperature, a response time of only 95 s, and a recovery time of 166 s, demonstrating excellent overall performance superior to existing flexible resistive WS2 sensors. This sensor exhibits high sensitivity in the range of 20 ppm to 100 ppm. It exhibits excellent linearity (R²=0.97) within the ppm concentration range, and its selectivity for nitrogen dioxide far exceeds that for NH3, H2S, and N2. Furthermore, the single WS2 material system avoids the instability problem of heterojunction interfaces, ensuring long-term stability. In addition, the coplanar structure places all electrodes on the same surface, simplifying the fabrication process. Meanwhile, the flexible PET substrate gives the device the mechanical flexibility to bend, which meets the comprehensive requirements of wearable electronic devices for room temperature operation, low power consumption, high sensitivity, and flexible integration. This provides a nitrogen dioxide detection solution with great application potential for environmental monitoring and medical diagnosis.

[0060] The above is a detailed description of the preferred embodiments of this application, but this application is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this application, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A flexible nitrogen dioxide gas sensor based on tungsten disulfide, characterized in that, include: Flexible substrate; A flexible electrode is disposed on the same plane of the flexible substrate. The flexible electrode includes a gate, a source, and a drain. The source and the drain adopt an arrayed interdigitated electrode structure. Tungsten disulfide sensitive film, the tungsten disulfide sensitive film covers the channel region between the source and the drain, and there is a gap between it and the gate; Specifically, when a gate voltage is applied, the gate modulates the carrier concentration in the tungsten disulfide channel of the tungsten disulfide sensitive film through a lateral electric field, thereby adjusting the sensitivity to nitrogen dioxide detection.

2. The flexible nitrogen dioxide gas sensor based on tungsten disulfide according to claim 1, characterized in that, The array interdigitated electrode structure is provided with four interdigitated electrode units, each containing 6 electrode fingers. The ratio of the width of the electrode finger to the interdigital spacing is 2:

1. The width of the electrode finger is 200μm, the length is 700μm, and the interdigital spacing is 100μm.

3. The flexible nitrogen dioxide gas sensor based on tungsten disulfide according to claim 1, characterized in that, The tungsten disulfide sensitive film has 1 to 5 tungsten disulfide layers, and the thickness of the tungsten disulfide sensitive film ranges from 0.7 nm to 3.5 nm.

4. The flexible nitrogen dioxide gas sensor based on tungsten disulfide according to claim 1, characterized in that, The width of the gap between the tungsten disulfide channel and the gate ranges from 5 μm to 10 μm.

5. The flexible nitrogen dioxide gas sensor based on tungsten disulfide according to claim 1, characterized in that, The gap between the tungsten disulfide channel and the gate is filled with air or an insulating layer is deposited.

6. The flexible nitrogen dioxide gas sensor based on tungsten disulfide according to claim 1, characterized in that, The flexible substrate is made of polyethylene terephthalate or polyethylene naphthalate.

7. A method for fabricating a flexible nitrogen dioxide gas sensor based on tungsten disulfide, characterized in that, include: A support layer is formed by spin-coating a support layer material onto the surface of a silicon wafer substrate with a single layer of tungsten disulfide. After etching away the silicon substrate, the composite film is retrieved using a flexible substrate, and the support layer is removed by dissolving it with acetone to obtain the tungsten disulfide sensitive film. A polyimide mask layer is coated on the surface of the tungsten disulfide sensitive film, and a hollow pattern is formed by laser patterning. A flexible electrode is formed by depositing an electrode based on the hollow pattern using a sputtering coating instrument, thereby obtaining a flexible nitrogen dioxide gas sensor.

8. The method for fabricating a flexible nitrogen dioxide gas sensor based on tungsten disulfide according to claim 7, characterized in that, The preparation of tungsten disulfide layer includes: using sulfur powder and tungsten trioxide powder as precursors, reacting them in a high-temperature tube furnace under an argon atmosphere to obtain tungsten disulfide layer.

9. The method for fabricating a flexible nitrogen dioxide gas sensor based on tungsten disulfide according to claim 7, characterized in that, The preparation of tungsten disulfide layers includes: using tungsten hexacarbonyl and hydrogen sulfide as precursors, and obtaining tungsten disulfide layers through plasma-assisted decomposition.

10. The method for fabricating a flexible nitrogen dioxide gas sensor based on tungsten disulfide according to claim 7, characterized in that, The support layer material is polymethyl methacrylate, polycarbonate, or polystyrene.

Images