A kind of organic vertical source-gate transistor nitrogen dioxide sensor and its preparation method

Abstract

The application relates to a kind of organic vertical source-gate transistor nitrogen dioxide sensors and preparation methods thereof, and belongs to the technical field of sensor preparation.The device includes a substrate, a gate electrode is arranged on the substrate, a dielectric layer is wrapped around the gate electrode, a semiconductor layer is arranged above and on one side of the dielectric layer, a source electrode and a drain electrode are arranged above the semiconductor layer, the source electrode is above the gate electrode, the drain electrode is on the side of the gate electrode, and the semiconductor layer, the substrate are below the drain electrode, the semiconductor layer between the source electrode and the gate electrode forms a depletion-type conductive channel, the material of the source electrode is different from the material of the drain electrode, the source electrode forms a Schottky contact, and the drain electrode forms an ohmic contact.The production cost is low, green and environmentally friendly, and high sensitivity, high stability and long service life can be achieved in an atmospheric environment.

Description

Technical Field

[0001] This invention relates to a nitrogen dioxide sensor based on an organic vertical source-gate transistor and its fabrication method, belonging to the field of sensor fabrication technology. Background Technology

[0002] With the advent of the Internet of Things (IoT) era, the user-friendliness and portability of electronic products are receiving increasing attention. Simultaneously, to protect the natural environment and humanity, developing low-cost, high-efficiency, and low-loss gas sensing devices for monitoring pollutant gases, especially harmful and toxic gases, has become an urgent research direction. In daily life, people directly or indirectly release many harmful gases into the atmosphere, such as methane, nitric oxide, nitrogen dioxide, ammonia, sulfur dioxide, and hydrogen sulfide, sometimes even endangering lives. Among various gas sensors, sensors based on organic field-effect transistors (OFETs) have attracted considerable attention due to their lightweight, flexibility, and low material / processing costs. Compared to resistive devices, OFET gas sensors offer advantages such as high sensitivity, room temperature operation, ease of integration, and independent multi-parameter selection. Furthermore, OFETs can function as signal converters and amplifiers. Therefore, organic field-effect transistors are widely used as unit components in high-performance sensors and have consistently garnered significant attention in the field of gas sensors. However, most reports on nitrogen dioxide sensors based on organic field-effect transistors focus primarily on developments in the semiconductor field, neglecting the issues of high drive voltage and high losses.

[0003] Organic source-gate transistors (OSGTs) have attracted increasing attention as an emerging transistor device due to their unique characteristics. Compared with traditional OFETs, they offer advantages such as low power consumption, high gain, high bias stability, greater tolerance to geometric changes, and resistance to short-channel effects. These characteristics make OSGTs an important candidate device for easily manufactured displays, biomedical sensors, and IoT wearable electronics, especially in these fields where low power consumption, high performance, high efficiency, and low cost manufacturability are crucial.

[0004] As is well known, the dielectric layer is a crucial component of organic field-effect transistors. Current solution preparation methods largely utilize toxic reagents such as chlorobenzene, chloroform, and anisole. Exploring an in-situ oxidation process for the gate electrode is a vital step towards achieving green manufacturing. Meanwhile, doping the organic layer with the dielectric layer is a simple and effective measure to improve the performance and stability of transistor devices. Furthermore, the polarized functional groups of naturally occurring high-k dielectric materials are also an effective factor in achieving high sensitivity in sensors. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of traditional organic field-effect transistor gas sensors and provide a nitrogen dioxide sensor based on organic vertical source-gate transistors and its fabrication method, which has a simple fabrication process, low production cost, is environmentally friendly, and can achieve high sensitivity, high stability, and long lifespan in atmospheric environments.

[0006] The technical solution of the present invention is as follows:

[0007] A nitrogen dioxide sensor based on an organic vertical source-gate transistor includes a substrate, a gate electrode on the substrate, a dielectric layer surrounding the gate electrode, a semiconductor layer above the dielectric layer and on one side, a source electrode and a drain electrode above the semiconductor layer, the source electrode being above the gate electrode and the drain electrode being on the side of the gate electrode, and the semiconductor layer and the substrate being below the drain electrode. The semiconductor layer between the source electrode and the gate electrode forms a depletion-type conductive channel. The source electrode material and the drain electrode material are different. The source electrode forms a Schottky contact and the drain electrode forms an ohmic contact.

[0008] Preferably, the semiconductor layer is composed of a mixture of soluble organic semiconductor material and natural high-k dielectric material, wherein the mass percentage of natural high-k dielectric material is 1% to 10% of the organic semiconductor layer.

[0009] Further preferred soluble organic semiconductor materials include one of poly(3-hexylthiophene) (P3HT), Tips-pentacene, siloxane-containing polyisoprene derivatives, and the PBTTT series (PBTTT-C14, PBTTT-C12).

[0010] Further preferred natural high-k dielectric materials include one of silk fibroin, egg white protein, and gelatin.

[0011] Preferably, the dielectric layer is a high-k dielectric layer formed by the natural oxide of the gate electrode, specifically an aluminum oxide dielectric layer formed by the oxidation of the aluminum electrode.

[0012] Preferably, the dielectric layer thickness is 5-10 nm, and the dielectric layer thickness is the same around the gate electrode.

[0013] Preferably, the thickness of the semiconductor layer is 25–100 nm.

[0014] Preferably, the drain electrode material is a metal nanowire, and the material is one of iron nanowire, copper nanowire, silver nanowire, gold nanowire, aluminum nanowire, nickel nanowire, cobalt nanowire, manganese nanowire, cadmium nanowire, indium nanowire, tin nanowire, tungsten nanowire, and platinum nanowire.

[0015] Preferably, the source electrode material is metallic carbon nanotubes or graphene. The source and drain electrode materials are different; the source electrode forms a Schottky contact, and the drain electrode forms an ohmic contact.

[0016] Preferably, the gate electrode is an aluminum electrode.

[0017] Preferably, unlike traditional field-effect transistor structures, in this source-gate transistor structure, the gate electrode completely overlaps and covers the source electrode vertically, and the area of ​​the gate electrode is larger than that of the source electrode. Besides covering the overlapping source electrode, it also overlaps with the semiconductor layer between the source and drain electrodes. Furthermore, the drain electrode and the gate electrode do not overlap vertically at all; they are on the same horizontal plane, and the drain electrode is located to the side of the gate electrode.

[0018] A method for fabricating a nitrogen dioxide sensor based on an organic vertical source-gate transistor includes the following steps:

[0019] ① Clean the substrate using detergent, acetone solution, deionized water and isopropanol solution, and then dry it with nitrogen gas;

[0020] ② Fabricate a gate electrode on the substrate surface;

[0021] ③ The gate electrode is prepared by high-temperature annealing oxidation or ultraviolet ozone atmosphere annealing oxidation to form a natural dielectric layer;

[0022] ④ The natural high-k dielectric material and the soluble organic semiconductor material are ultrasonically mixed in proportion, and the semiconductor layer is prepared on the dielectric layer using the mixed solution;

[0023] ⑤ A drain electrode is fabricated on the semiconductor layer on the side of the gate electrode to form an ohmic contact with the semiconductor layer. Then, a source electrode is fabricated on the semiconductor layer above the gate electrode to form a Schottky contact with the semiconductor layer and to form a semiconductor depletion region.

[0024] Preferably, in step ③, during high-temperature annealing oxidation and ultraviolet ozone annealing oxidation, the annealing temperature is between 300℃ and 500℃, with the optimal effect being around 350℃.

[0025] Furthermore, in step ④, the semiconductor layer is prepared by one of the following methods: spin coating, roll coating, drop coating, embossing, printing, or spraying.

[0026] Furthermore, in steps ② and ⑤, the gate electrode, source electrode, and drain electrode are prepared by one of the following methods: vacuum thermal evaporation, magnetron sputtering, plasma-enhanced chemical vapor deposition, screen printing, printing, or spin coating.

[0027] The beneficial effects of this invention are as follows:

[0028] I. The nitrogen dioxide sensor fabricated in this invention is an organic vertical source-gate transistor (OST) nitrogen dioxide sensor. The OST has fundamental differences and advantages compared to traditional organic field-effect transistors (OFETs). By constructing a Schottky barrier between the source electrode and the semiconductor, the OST exhibits a smaller saturation voltage and saturation current, resulting in low-loss characteristics. Simultaneously, the OST has a larger output resistance, leading to higher intrinsic gain. Furthermore, the conduction path of the OST is affected by the source voltage but less by the gate voltage, resulting in better gate bias stability. Finally, by constructing a Schottky barrier, the conductive channel exists below the source electrode rather than between the source and drain electrodes, thus providing superior resistance to short-channel effects and greater tolerance to geometric changes at the channel.

[0029] Second, because bio-high-k dielectric materials contain a large number of polarizing groups, such as carboxyl, aldehyde, and sulfur-containing groups, the responsivity of nitrogen dioxide is significantly improved and the detection concentration lower limit is lowered after introducing a certain amount of bio-high-k dielectric material into the organic semiconductor layer. In organic vertical source-gate transistors, the larger the semiconductor depletion layer capacitance, the smaller the saturation voltage. By mixing organic materials and bio-high-k dielectric materials, the saturation voltage of the device can be significantly reduced, power consumption can be lowered, and device stability can be improved, making it more suitable for wearable electronic devices.

[0030] Third, in organic source-gate transistors, by constructing a vertical structure, the diffusion distance of nitrogen dioxide to the conductive channel is much smaller than that in traditional organic field-effect transistors. Therefore, organic vertical source-gate transistor nitrogen dioxide sensors have a faster gas-sensing response speed.

[0031] Fourth, in this organic vertical source-gate transistor, the dielectric layer is obtained by high-temperature oxidation and ultraviolet ozone oxidation of the gate electrode. The natural oxidation method eliminates the use of toxic reagents such as chlorobenzene, toluene, chloroform and anisole in the traditional dielectric layer processing. At the same time, compared with traditional dielectric materials, it reduces complex processes such as extraction and refining, saving manpower and resources. In addition, most importantly, the dielectric layer formed by natural oxidation has a clean metal / dielectric layer interface at the atomic level, thereby reducing electric field loss and making it more conducive to the realization of low-power device functions.

[0032] Fifth, by mixing organic materials and biological high-k dielectric materials, the metal-semiconductor contact can be effectively improved, effectively preventing semiconductor damage during electrode deposition. This enhances the stability of the organic source-gate transistor nitrogen dioxide sensor.

[0033] 6. Because the diffusion distance of nitrogen dioxide to the conductive channel in an organic source-gate transistor is much smaller than that in a conventional organic field-effect transistor, the organic source-gate transistor nitrogen dioxide sensor has a faster gas-sensing response speed.

[0034] Meanwhile, organic vertical source-gate transistors are fundamentally different from traditional organic field-effect transistors in terms of working principle and fabrication process. The transformation from organic field-effect transistors to organic vertical source-gate transistors cannot be achieved simply by building a Schottky barrier. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of the present invention;

[0036] In the figure: 1-substrate, 2-gate electrode, 3-dielectric layer, 4-semiconductor layer, 5-source electrode, 6-drain electrode, 7-depletion-type conductive channel;

[0037] Figure 2 This is the gas response time-current curve of the nitrogen dioxide sensor in Implementation Case 1. Detailed Implementation

[0038] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0039] Example 1

[0040] A nitrogen dioxide sensor based on organic vertical source-gate transistors, such as Figure 1 The diagram shows a bottom-gate top-contact structure, including a substrate, a gate electrode on the substrate, a dielectric layer surrounding the gate electrode, a semiconductor layer above the dielectric layer and on one side, a source electrode and a drain electrode above the semiconductor layer, with the source electrode above the gate electrode and the drain electrode on the side of the gate electrode. Below the drain electrode are the semiconductor layer and the substrate. The semiconductor layer between the source and gate electrodes forms a depletion-type conductive channel. The source and drain electrode materials are different. The source electrode forms a Schottky contact, and the drain electrode forms an ohmic contact. The gate electrode completely overlaps and covers the source electrode vertically, and its area is larger than that of the source electrode. Besides covering the overlapping source electrode, it also overlaps with the semiconductor layer between the source and drain electrodes. The drain electrode does not overlap and covers the gate electrode vertically; they are on the same horizontal plane, and the drain electrode is on the side of the gate electrode.

[0041] like Figure 1The diagram shows a bottom-gate top-contact structure. The materials and thicknesses of each layer are as follows: the gate electrode is an aluminum electrode; the dielectric layer is a natural alumina dielectric layer formed by high-temperature oxidation of the gate electrode; the dielectric layer around the gate electrode has the same thickness of 7 nm; the drain electrode is a silver nanowire; the source electrode is a carbon nanotube; and the semiconductor layer is a mixture of poly(3-hexylthiophene) (P3HT) and egg white protein (5% by mass) with a thickness of 30 nm. This structure enables a high-sensitivity and high-stability organic vertical source-gate transistor nitrogen dioxide sensor.

[0042] The method for fabricating the above-mentioned nitrogen dioxide sensor based on organic vertical source-gate transistors includes the following steps:

[0043] ① Clean the substrate using detergent, acetone solution, deionized water and isopropanol solution, and then dry it with nitrogen gas;

[0044] ② Fabricate a gate electrode on the substrate surface;

[0045] ③ The gate electrode is prepared by high-temperature annealing oxidation to form a natural dielectric layer; the annealing temperature is 350℃;

[0046] ④ The natural high-k dielectric material egg white protein is ultrasonically mixed with a soluble organic semiconductor material in a certain proportion, and the semiconductor layer is prepared on the dielectric layer using the mixed solution; the semiconductor layer is prepared by one of the conventional methods of spin coating, roll coating, drop film, embossing, printing or spraying.

[0047] ⑤ A drain electrode is fabricated on the semiconductor layer on the side of the gate electrode, forming an ohmic contact with the semiconductor layer. Then, a source electrode is fabricated on the semiconductor layer above the gate electrode, forming a Schottky contact with the semiconductor layer and constructing a semiconductor depletion region. The gate electrode, source electrode, and drain electrode are fabricated using one of the following conventional methods: vacuum thermal evaporation, magnetron sputtering, plasma-enhanced chemical vapor deposition, screen printing, printing, or spin coating.

[0048] like Figure 2 As shown, the organic vertical source-gate transistor gas sensor constructed using the method of this embodiment exhibits a responsivity more than 10 times that of a conventional organic field-effect transistor at the same gas concentration. This demonstrates that this structure can effectively improve the gas response characteristics of the gas sensor, such as sensitivity.

[0049] Example 2

[0050] An organic vertical source-gate transistor-based nitrogen dioxide sensor is disclosed, featuring a bottom-gate top-contact structure as shown in Example 1. The difference lies in the materials and thicknesses of each layer: the gate electrode is an aluminum electrode; the dielectric layer is a natural oxide layer formed by ultraviolet ozone treatment of the gate electrode, with a thickness of 5 nm; the drain electrodes are all copper nanowires; the source electrode is graphene; and the semiconductor layer is a mixture of Tips-pentacene and silk fibroin (10% by mass), with a thickness of 30 nm. This structure enables a high-sensitivity, long-lifetime organic vertical source-gate transistor gas sensor. The fabrication method is as follows:

[0051] ① Clean the substrate using detergent, acetone solution, deionized water and isopropanol solution, and then dry it with nitrogen gas;

[0052] ② Fabricate a gate electrode on the substrate surface;

[0053] ③ A dielectric layer is prepared on the gate electrode by ultraviolet ozone treatment; the annealing temperature is 350℃;

[0054] ④ The silk fibroin and organic materials are ultrasonically mixed in a specific ratio. A semiconductor layer is then prepared on the dielectric layer using the mixed solution.

[0055] ⑤ Fabricate source and drain electrodes on an organic semiconductor layer.

[0056] Example 3

[0057] An organic vertical source-gate transistor-based nitrogen dioxide sensor is disclosed, featuring a bottom-gate, top-contact structure as shown in Example 1. The difference lies in the materials and thicknesses of each layer: the gate electrode is an aluminum electrode; the dielectric layer is a natural oxide layer formed by high-temperature oxidation of the gate electrode, with a thickness of 10 nm; the drain electrodes are all copper nanowires; the source electrode is a carbon nanotube; and the semiconductor layer is a mixture of Tips-pentacene and egg white protein (6% by mass), with a thickness of 50 nm. This structure enables a high-sensitivity, long-lifetime organic vertical source-gate transistor gas sensor. The fabrication method is as follows:

[0058] ① Clean the substrate using detergent, acetone solution, deionized water and isopropanol solution, and then dry it with nitrogen gas;

[0059] ② Fabricate a gate electrode on the substrate surface;

[0060] ③ A dielectric layer is prepared on the gate electrode by high-temperature natural oxidation; the annealing temperature is 300℃;

[0061] ④ The egg white protein and organic materials are ultrasonically mixed in a specific ratio. A semiconductor layer is then prepared on the dielectric layer using the mixed solution.

[0062] ⑤ Fabricate source and drain electrodes on an organic semiconductor layer.

[0063] Example 4

[0064] An organic vertical source-gate transistor (OST) nitrogen dioxide sensor is disclosed, featuring a bottom-gate, top-contact structure as shown in Example 1. The difference lies in the materials and thicknesses of each layer: the gate electrode is an aluminum electrode; the dielectric layer is a natural oxide layer formed by high-temperature oxidation of the gate electrode; the drain electrodes are all copper nanowires; the source electrode is graphene; and the semiconductor layer is a mixture of siloxane-containing polyisoprene derivatives and egg white protein (8% by mass), with a thickness of 80 nm. This structure enables a highly sensitive and stable organic vertical source-gate transistor gas sensor. The fabrication method is as follows:

[0065] ① Clean the substrate using detergent, acetone solution, deionized water and isopropanol solution, and then dry it with nitrogen gas;

[0066] ② Fabricate a gate electrode on the substrate surface;

[0067] ③ A dielectric layer is prepared on the gate electrode by high-temperature natural oxidation annealing; the annealing temperature is 500℃;

[0068] ④ The egg white protein and organic materials are ultrasonically mixed in a certain proportion; a semiconductor layer is prepared on the dielectric layer using the mixed solution;

[0069] ⑤ Fabricate source and drain electrodes on an organic semiconductor layer.

[0070] Example 5

[0071] An organic vertical source-gate transistor (OST) nitrogen dioxide sensor is disclosed, featuring a bottom-gate, top-contact structure as shown in Example 1. The difference lies in the materials and thicknesses of each layer: the gate electrode is an aluminum electrode; the dielectric layer is a natural oxide layer formed by ultraviolet ozone treatment of the gate electrode; the drain electrodes are all copper nanowires; the source electrode is graphene; and the semiconductor layer is a mixture of siloxane-containing polyisoprene derivatives and egg white protein (3% by mass), with a thickness of 100 nm. This structure enables a highly sensitive and stable organic vertical source-gate transistor gas sensor.

[0072] ① Clean the substrate using detergent, acetone solution, deionized water and isopropanol solution, and then dry it with nitrogen gas;

[0073] ② Fabricate a gate electrode on the substrate surface;

[0074] ③ A dielectric layer is prepared on the gate electrode by ultraviolet ozone treatment;

[0075] ④ The egg white protein and organic materials are ultrasonically mixed in a certain proportion, and the resulting solution is used to prepare a semiconductor layer on the dielectric layer;

[0076] ⑤ Fabricate source and drain electrodes on an organic semiconductor layer.

[0077] Example 6

[0078] An organic vertical source-gate transistor-based nitrogen dioxide sensor is disclosed, featuring a bottom-gate, top-contact structure as shown in Example 1. The difference lies in the materials and thicknesses of each layer: the gate electrode is an aluminum electrode; the dielectric layer is a natural oxide layer formed by ultraviolet ozone treatment of the gate electrode; the drain electrodes are all copper nanowires; the source electrode is a carbon nanotube; and the semiconductor layer is a mixture of poly(3-hexylthiophene) (P3HT) and egg white protein (3% by mass), with a thickness of 25 nm. This structure enables a highly sensitive and stable organic vertical source-gate transistor gas sensor. The fabrication method is as follows:

[0079] ① Clean the substrate using detergent, acetone solution, deionized water and isopropanol solution, and then dry it with nitrogen gas;

[0080] ② Fabricate a gate electrode on the substrate surface;

[0081] ③ A dielectric layer is prepared on the gate electrode by ultraviolet ozone treatment;

[0082] ④ The egg white protein and organic materials are ultrasonically mixed in a certain proportion, and the resulting solution is used to prepare a semiconductor layer on the dielectric layer;

[0083] ⑤ Fabricate source and drain electrodes on an organic semiconductor layer;

[0084] Example 7

[0085] An organic vertical source-gate transistor (OST) nitrogen dioxide sensor is disclosed, featuring a bottom-gate, top-contact structure as shown in Example 1. The difference lies in the materials and thicknesses of each layer: the gate electrode is an aluminum electrode; the dielectric layer is a natural oxide layer formed by ultraviolet ozone treatment of the gate electrode; the drain electrodes are all copper nanowires; the source electrode is a carbon nanotube; and the semiconductor layer is a mixture of poly(3-hexylthiophene) (P3HT) and egg white protein (10% by mass), with a thickness of 40 nm. This structure enables a highly sensitive and stable organic vertical source-gate transistor gas sensor.

[0086] ① Clean the substrate using detergent, acetone solution, deionized water and isopropanol solution, and then dry it with nitrogen gas;

[0087] ② Fabricate a gate electrode on the substrate surface;

[0088] ③ A dielectric layer is prepared on the gate electrode by ultraviolet ozone treatment;

[0089] ④ The egg white protein and organic materials are ultrasonically mixed in a certain proportion, and the resulting solution is used to prepare a semiconductor layer on the dielectric layer;

[0090] ⑤ Fabricate source and drain electrodes on an organic semiconductor layer.

[0091] Example 8

[0092] An organic vertical source-gate transistor-based nitrogen dioxide sensor is disclosed, featuring a bottom-gate top-contact structure as shown in Example 1. The difference lies in the materials and thicknesses of each layer: the gate electrode is an aluminum electrode; the dielectric layer is a natural oxide layer formed by high-temperature oxidation of the gate electrode; the drain electrodes are all copper nanowires; the source electrode is graphene; and the semiconductor layer is a mixture of poly(3-hexylthiophene) (P3HT) and egg white protein (1% by mass), with a thickness of 50 nm. This structure enables a highly sensitive organic vertical source-gate transistor gas sensor. The fabrication method is as follows:

[0093] ① Clean the substrate using detergent, acetone solution, deionized water and isopropanol solution, and then dry it with nitrogen gas;

[0094] ② Fabricate a gate electrode on the substrate surface;

[0095] ③ A dielectric layer is prepared on the gate electrode by high-temperature natural oxidation;

[0096] ④ The egg white protein and organic materials are ultrasonically mixed in a certain proportion, and the resulting solution is used to prepare a semiconductor layer on the dielectric layer;

[0097] ⑤ Fabricate source and drain electrodes on an organic semiconductor layer.

[0098] Example 9

[0099] An organic vertical source-gate transistor-based nitrogen dioxide sensor is disclosed, featuring a bottom-gate, top-contact structure as shown in Example 1. The difference lies in the materials and thicknesses of each layer: the gate electrode is an aluminum electrode; the dielectric layer is a natural oxide layer formed by high-temperature oxidation of the gate electrode; the drain electrodes are all copper nanowires; the source electrode is a carbon nanotube; and the semiconductor layer is a mixture of poly(3-hexylthiophene) (P3HT) and gelatin (2% by mass), with a thickness of 50 nm. This structure enables a highly sensitive organic vertical source-gate transistor gas sensor. The fabrication method is as follows:

[0100] ① Clean the substrate using detergent, acetone solution, deionized water and isopropanol solution, and then dry it with nitrogen gas;

[0101] ② Fabricate a gate electrode on the substrate surface;

[0102] ③ A dielectric layer is prepared on the gate electrode by high-temperature natural oxidation;

[0103] ④ The egg white protein and organic materials are ultrasonically mixed in a certain proportion, and the resulting solution is used to prepare a semiconductor layer on the dielectric layer;

[0104] ⑤ Fabricate source and drain electrodes on an organic semiconductor layer.

[0105] Example 10

[0106] An organic vertical source-gate transistor-based nitrogen dioxide sensor is disclosed, featuring a bottom-gate top-contact structure as shown in Example 1. The difference lies in the materials and thicknesses of each layer: the gate electrode is an aluminum electrode; the dielectric layer is a natural oxide layer formed by ultraviolet ozone treatment of the gate electrode; the drain electrodes are all copper nanowires; the source electrode is graphene; and the semiconductor layer is a mixture of poly(3-hexylthiophene) (P3HT) and egg white protein (3% by mass), with a thickness of 80 nm. This structure enables a highly sensitive organic source-gate transistor gas sensor. The fabrication method is as follows:

[0107] ① Clean the substrate using detergent, acetone solution, deionized water and isopropanol solution, and then dry it with nitrogen gas;

[0108] ② Fabricate a gate electrode on the substrate surface;

[0109] ③ A dielectric layer is prepared on the gate electrode by ultraviolet ozone treatment;

[0110] ④ The egg white protein and organic materials are ultrasonically mixed in a certain proportion, and the resulting solution is used to prepare a semiconductor layer on the dielectric layer.

[0111] ⑤ Fabricate source and drain electrodes on an organic semiconductor layer.

[0112] Example 11

[0113] A nitrogen dioxide sensor based on an organic vertical source-gate transistor is disclosed, featuring a bottom-gate top-contact structure as shown in Example 1. The difference lies in the semiconductor layer, which is a mixture of PBTTT-C14 and egg white protein (5% by mass), with a thickness of 60 nm. The drain electrode material is iron nanowire.

[0114] Example 12

[0115] A nitrogen dioxide sensor based on an organic vertical source-gate transistor is disclosed, featuring a bottom-gate top-contact structure as shown in Example 1. The difference lies in the semiconductor layer, which is a mixture of PBTTT-C12 and silk fibroin (4% by mass) with a thickness of 50 nm. The drain electrode material is gold nanowire.

Claims

1. A nitrogen dioxide sensor based on an organic vertical source-gate transistor, characterized in that, The device includes a substrate, a gate electrode on the substrate, a dielectric layer surrounding the gate electrode, a semiconductor layer above the dielectric layer and on one side, a source electrode and a drain electrode above the semiconductor layer, the source electrode above the gate electrode and the drain electrode on the side of the gate electrode, and a semiconductor layer and substrate below the drain electrode. The semiconductor layer between the source electrode and the gate electrode forms a depletion-type conductive channel. The source electrode material and the drain electrode material are different. The source electrode forms a Schottky contact and the drain electrode forms an ohmic contact. The semiconductor layer is a mixture of soluble organic semiconductor material and natural high-k dielectric material, with the natural high-k dielectric material accounting for 1% to 10% of the semiconductor layer by mass. The gate electrode completely overlaps and covers the source electrode in the longitudinal direction, and the area of ​​the gate electrode is larger than that of the source electrode. The drain electrode does not overlap and cover the gate electrode in the longitudinal direction. The drain electrode and the gate electrode are on the same horizontal plane, and the drain electrode is on the side of the gate electrode.

2. The nitrogen dioxide sensor based on organic vertical source-gate transistors according to claim 1, characterized in that, Soluble organic semiconductor materials include poly(3-hexylthiophene), Tips-pentabenzene, siloxane-containing polyisoprene derivatives, and one of the PBTTT series; Natural high-k dielectric materials include one of the following: silk fibroin, egg white protein, and gelatin.

3. The nitrogen dioxide sensor based on organic vertical source-gate transistors according to claim 1, characterized in that, The dielectric layer is an aluminum oxide dielectric layer formed by the oxidation of aluminum electrodes; The dielectric layer thickness is 5-10 nm, and the dielectric layer thickness is the same around the gate electrode.

4. The nitrogen dioxide sensor based on organic vertical source-gate transistors according to claim 1, characterized in that, The thickness of the semiconductor layer is 25–100 nm.

5. The nitrogen dioxide sensor based on organic vertical source-gate transistors according to claim 1, characterized in that, The drain electrode material is one of the following: iron nanowires, copper nanowires, silver nanowires, gold nanowires, aluminum nanowires, nickel nanowires, cobalt nanowires, manganese nanowires, cadmium nanowires, indium nanowires, tin nanowires, tungsten nanowires, and platinum nanowires. The source electrode material is metallic carbon nanotubes or graphene; the gate electrode is an aluminum electrode.

6. A method for fabricating a nitrogen dioxide sensor based on an organic vertical source-gate transistor as described in any one of claims 1-5, characterized in that, Includes the following steps: ① Clean the substrate using detergent, acetone solution, deionized water and isopropanol solution, and then dry it with nitrogen gas; ② Fabricate a gate electrode on the substrate surface; ③ The gate electrode is prepared by high-temperature annealing oxidation or ultraviolet ozone atmosphere annealing oxidation to form a natural dielectric layer; ④ The natural high-k dielectric material and the soluble organic semiconductor material are ultrasonically mixed in proportion, and the semiconductor layer is prepared on the dielectric layer using the mixed solution; ⑤ A drain electrode is fabricated on the semiconductor layer on the side of the gate electrode to form an ohmic contact with the semiconductor layer. Then, a source electrode is fabricated on the semiconductor layer above the gate electrode to form a Schottky contact with the semiconductor layer and to form a semiconductor depletion region.

7. The method for fabricating a nitrogen dioxide sensor based on an organic vertical source-gate transistor according to claim 6, characterized in that, In step ③, during high-temperature annealing oxidation or ultraviolet ozone annealing oxidation, the annealing temperature is 300℃-500℃.

8. The method for fabricating a nitrogen dioxide sensor based on an organic vertical source-gate transistor according to claim 7, characterized in that, In step ④, the semiconductor layer is prepared by one of the following methods: spin coating, roll coating, drop film, embossing, printing, or spraying; in steps ② and ⑤, the gate electrode, source electrode, and drain electrode are prepared by one of the following methods: vacuum thermal evaporation, magnetron sputtering, plasma-enhanced chemical vapor deposition, screen printing, printing, or spin coating.

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