Nitrogen dioxide sensor based on organic vertical source gate transistor and preparation method thereof

Abstract

The invention relates to a nitrogen dioxide sensor based on an organic vertical source gate transistor and a preparation method thereof, and belongs to the technical field of sensor preparation. The device comprises a substrate, a gate electrode is arranged on the substrate, a dielectric layer wraps the periphery of the gate electrode, semiconductor layers are arranged above the dielectric layer and on one side face, a source electrode and a drain electrode are arranged above the semiconductor layers, the source electrode is arranged above the gate electrode, the drain electrode is arranged on the side face of the gate electrode, and the semiconductor layer and the substrate are arranged below the drain electrode. The semiconductor layer between the source electrode and the gate electrode forms a depletion type conducting channel, the material of the source electrode is different from that of the drain electrode, the source electrode forms Schottky contact, the drain electrode forms ohmic contact, the production cost is low, environmental protection is achieved, and high sensitivity, high stability and long service life can be achieved in the atmospheric environment.

Description

Technical Field

[0001] The invention relates to a nitrogen dioxide sensor based on an organic vertical source-gate transistor and a preparation method thereof, belonging to the technical field of sensor preparation. Background Art

[0002] With the advent of the Internet of Things era, the humanization and portability of electronic products are increasingly valued. At the same time, in order to protect the natural environment and humans, the development of 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 life, people directly or indirectly release a lot of harmful gases into the atmosphere, such as methane, nitric oxide, nitrogen dioxide, ammonia, sulfur dioxide, and hydrogen sulfide, which sometimes even endanger their lives. Among various gas sensor devices, sensors based on organic field effect transistors (OFETs) have attracted much attention due to their advantages such as light weight, flexibility, and low material / process costs. Compared with resistive devices, OFET gas sensors have the advantages of high sensitivity, room temperature operation, easy integration, and independent multi-parameters to improve selectivity. In addition, OFETs can be used as signal converters and amplifiers. Therefore, organic field effect transistors are widely used as unit elements of high-performance sensors and have always attracted much attention in the field of gas sensors. However, most reports on nitrogen dioxide sensors based on organic field effect transistors focus on the development of the semiconductor field, while ignoring the problems of high driving voltage and high loss.

[0003] Organic source-gate transistors (OSGTs) are an emerging transistor device that has attracted increasing attention due to their unique device properties. Compared with traditional OFETs, they have 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 source-gate transistors an important candidate for easy-to-manufacture 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 we all know, the dielectric layer is an important component of organic field-effect transistors. At present, the solution preparation mostly uses a large amount of toxic reagents such as chlorobenzene, chloroform and anisole. Exploring an in-situ oxidation process for the gate electrode has become an important part of realizing green technology. At the same time, doping the organic layer with the dielectric layer is a simple and effective measure to improve the performance and stability of transistor devices. At the same time, the polarization functional group of natural high-k dielectric materials is also an effective factor in achieving high sensitivity of sensors. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of traditional organic field effect transistor gas sensors and provide a nitrogen dioxide sensor based on an organic vertical source-gate transistor and a preparation method thereof which has simple preparation process, low production cost, is green and environmentally friendly, and has high sensitivity, high stability, and long life in an atmospheric environment.

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

[0007] A nitrogen dioxide sensor based on an organic vertical source-gate transistor comprises 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, the semiconductor layer and 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 source electrode material is different from the drain electrode material, the source electrode forms a Schottky contact, and the drain electrode forms an ohmic contact.

[0008] Preferably, the semiconductor layer is formed by mixing a soluble organic semiconductor material with a natural high-k dielectric material, and the mass proportion of the natural high-k dielectric material is 1% to 10% of the organic semiconductor layer.

[0009] Further preferably, the soluble organic semiconductor material includes one of poly 3-hexylthiophene (P3HT), Tips-pentacene, a polyisoprene derivative containing siloxane, and a PBTTT series (PBTTT-C14, PBTTT-C12).

[0010] Further preferably, the natural high-k dielectric material includes one of silk fibroin, egg white protein and gelatin.

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

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

[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, different from the traditional field effect transistor structure, in this source-gate transistor structure, the gate electrode completely overlaps and covers the source electrode in the vertical direction, and the gate electrode area is larger than the source electrode area, and in addition to covering and overlapping the source electrode, it also overlaps with the semiconductor layer between the source and drain electrodes. The drain electrode and the gate electrode do not overlap at all in the vertical 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.

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

[0019] ① Clean the substrate with detergent, acetone solution, deionized water and isopropanol solution, and blow dry with nitrogen after cleaning;

[0020] ②Prepare the gate electrode on the substrate surface;

[0021] ③ Preparing a natural dielectric layer by subjecting the gate electrode to high temperature annealing oxidation or ultraviolet ozone atmosphere annealing oxidation;

[0022] ④ Ultrasonic mixing of natural high-k dielectric material and soluble organic semiconductor material in proportion, and using the mixed solution to prepare a semiconductor layer on the dielectric layer;

[0023] ⑤ Prepare a drain electrode on the semiconductor layer on the side of the gate electrode to form an ohmic contact with the semiconductor layer, and then prepare a source electrode on the semiconductor layer above the gate electrode to form a Schottky contact with the semiconductor layer and 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°C and 500°C, with the best effect being around 350°C.

[0025] Furthermore, in step ④, the semiconductor layer is prepared by a method selected from the group consisting of spin coating, roller coating, drip coating, embossing, printing or spraying.

[0026] Furthermore, in steps ② and ⑤, the gate electrode, the source electrode and the drain electrode are prepared by a method selected from the group consisting of vacuum thermal evaporation, magnetron sputtering, plasma enhanced chemical vapor deposition, screen printing, printing or spin coating.

[0027] The beneficial effects of the present invention are:

[0028] 1. The nitrogen dioxide sensor prepared by the present invention is an organic vertical source-gate transistor nitrogen dioxide sensor, in which the organic vertical source-gate transistor is essentially different and has advantages over the traditional organic field-effect transistor. The source-gate transistor has a smaller saturation voltage and saturation current by constructing a Schottky barrier between the source electrode and the semiconductor, so that the device has the characteristics of low loss. At the same time, since the organic source-gate transistor has a larger output resistance, the device has a higher intrinsic gain. In addition, the source-gate transistor is affected by the source voltage on the conductive channel and has little to do with the gate voltage, so that the prepared device has better gate bias stability. Finally, by constructing a Schottky barrier, the conductive channel of the device exists under the source electrode instead of between the source and drain electrodes, so it has excellent resistance to short channel effects and has greater tolerance to geometric changes at the channel.

[0029] Second, because biological high-k dielectric materials contain a large number of polarized groups, such as carboxyl, aldehyde, and sulfur-containing groups, after a certain amount of biological high-k dielectric materials are introduced into the organic semiconductor layer, the responsiveness of nitrogen dioxide is significantly improved, and the lower limit of detection concentration is lower; the larger the semiconductor depletion layer capacitance in the organic vertical source-gate transistor, the smaller the saturation voltage. By mixing organic materials and biological high-k dielectric materials, the saturation voltage of the device can be significantly reduced, the power consumption can be reduced, the stability of the device can be improved, and it is more conducive to the application of wearable electronic devices.

[0030] 3. In organic source-gate transistors, by constructing a vertical structure, the diffusion distance of nitrogen dioxide to reach the conductive channel is much shorter than that in traditional organic field-effect transistors. Therefore, the organic vertical source-gate transistor nitrogen dioxide sensor has a faster gas-sensitive response speed.

[0031] 4. 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 process; at the same time, compared with traditional dielectric materials, it reduces complex process such as extraction and refining, saving manpower and material resources; in addition, the most important point is that the dielectric layer formed by natural oxidation has a clean metal / dielectric layer interface at the atomic layer level, thereby reducing electric field loss and being more conducive to the realization of low-power device functions.

[0032] 5. By mixing organic materials and biological high-k dielectric materials, the metal-semiconductor contact can be effectively improved, effectively eliminating the semiconductor damage caused by the electrode evaporation process, thereby improving the stability of the organic source-gate transistor nitrogen dioxide sensor.

[0033] 6. Since the diffusion distance of nitrogen dioxide to reach the conductive channel in an organic source-gate transistor is much shorter than that in a traditional organic field-effect transistor, the organic source-gate transistor nitrogen dioxide sensor has a faster gas-sensitive response speed.

[0034] At the same time, organic vertical source-gate transistors are fundamentally different from traditional organic field-effect transistors in terms of working principles and preparation processes. The transition from organic field-effect transistors to organic vertical source-gate transistors cannot be achieved simply by constructing a Schottky barrier. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It 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 conductive channel;

[0037] Figure 2 It is the gas response time-current curve of the nitrogen dioxide sensor in implementation case 1. DETAILED DESCRIPTION

[0038] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings, but is not limited thereto.

[0039] Example 1

[0040] A nitrogen dioxide sensor based on an organic vertical source-gate transistor, such as Figure 1 The bottom gate top contact structure is shown, including a substrate, a gate electrode is provided on the substrate, a dielectric layer is wrapped around the gate electrode, a semiconductor layer is provided above and on one side of the dielectric layer, a source electrode and a drain electrode are provided above the semiconductor layer, the source electrode is above the gate electrode, the drain electrode is on the side of the gate electrode, the semiconductor layer and 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 source electrode material is different from the drain electrode material, 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 in the vertical direction, and the gate electrode area is larger than the source electrode area. In addition to covering the overlapping source electrode, it also overlaps with the semiconductor layer between the source and drain electrodes. The drain electrode and the gate electrode do not overlap at all in the vertical 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.

[0041] like Figure 1The bottom gate top contact structure is shown, and the materials and thicknesses of each layer are as follows: the gate electrode is an aluminum electrode, the dielectric layer is a natural oxide layer aluminum oxide dielectric layer formed by high-temperature oxidation of the gate electrode, the dielectric layer thickness around the gate electrode is the same, the dielectric layer thickness is 7nm, 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), and the semiconductor layer thickness is 30nm. This structure can realize a highly sensitive and stable organic vertical source-gate transistor nitrogen dioxide sensor.

[0042] The method for preparing the above-mentioned organic vertical source-gate transistor-based nitrogen dioxide sensor comprises the following steps:

[0043] ① Clean the substrate with detergent, acetone solution, deionized water and isopropanol solution, and blow dry with nitrogen after cleaning;

[0044] ②Prepare the gate electrode on the substrate surface;

[0045] ③ Preparing a natural dielectric layer by high-temperature annealing and oxidation of the gate electrode; the annealing temperature is 350° C.;

[0046] ④ Ultrasonic mixing of natural high-k dielectric material egg white protein and soluble organic semiconductor material in proportion, and using the mixed solution to prepare a semiconductor layer on the dielectric layer; the semiconductor layer is prepared by a method of existing conventional dynamic spin coating, roller coating, dripping, embossing, printing or spraying.

[0047] ⑤ Prepare a drain electrode on the semiconductor layer on the side of the gate electrode to form an ohmic contact with the semiconductor layer, and then prepare a source electrode on the semiconductor layer above the gate electrode to form a Schottky contact with the semiconductor layer and a semiconductor depletion region. The gate electrode, source electrode, and drain electrode are prepared by one of the existing conventional 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 by the method of this embodiment has a responsiveness more than 10 times that of a conventional organic field effect transistor at the same gas concentration, indicating that the structure can effectively improve the sensitivity and other gas response characteristics of the gas sensor.

[0049] Example 2

[0050] A nitrogen dioxide sensor based on an organic vertical source-gate transistor is a bottom-gate top-contact structure. Its structure is as shown in Example 1, except that the materials and thicknesses of each layer are as follows: 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 thickness of the dielectric layer is 5nm, the drain electrode is copper nanowires, the source electrode is graphene, and the semiconductor layer is a mixture of Tips-pentacene and silk protein (mass proportion is 10%), with a thickness of 30nm. This structure can realize a high-sensitivity, high-life organic vertical source-gate transistor gas sensor. The preparation method is as follows:

[0051] ① Clean the substrate with detergent, acetone solution, deionized water and isopropanol solution, and blow dry with nitrogen after cleaning;

[0052] ②Prepare the gate electrode on the substrate surface;

[0053] ③ Preparing a dielectric layer on the gate electrode by ultraviolet ozone treatment; the annealing temperature is 350° C.;

[0054] ④Ultrasonically mix the silk fibroin and the organic material in proportion. Use the mixed solution to prepare a semiconductor layer on the dielectric layer;

[0055] ⑤ Prepare source electrode and drain electrode on the organic semiconductor layer.

[0056] Example 3

[0057] A nitrogen dioxide sensor based on an organic vertical source-gate transistor is a bottom-gate top-contact structure. Its structure is as shown in Example 1, except that the materials and thicknesses of each layer are as follows: 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 thickness of the dielectric layer is 10nm, the drain electrode is 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 50nm. This structure can realize an organic vertical source-gate transistor gas sensor with high sensitivity and long life. The preparation method is as follows:

[0058] ① Clean the substrate with detergent, acetone solution, deionized water and isopropanol solution, and blow dry with nitrogen after cleaning;

[0059] ②Prepare the gate electrode on the substrate surface;

[0060] ③ Preparing a dielectric layer on the gate electrode by high temperature natural oxidation; the annealing temperature is 300° C.;

[0061] ④Ultrasonically mix the egg white protein and the organic material in proportion. Use the mixed solution to prepare a semiconductor layer on the dielectric layer;

[0062] ⑤ Prepare source electrode and drain electrode on the organic semiconductor layer.

[0063] Example 4

[0064] A nitrogen dioxide sensor based on an organic vertical source-gate transistor is a bottom-gate top-contact structure. Its structure is as shown in Example 1, except that the materials and thicknesses of each layer are as follows: 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 electrode is copper nanowires, the source electrode is graphene, and the semiconductor layer is a mixture of a polyisoprene derivative containing siloxane and egg white protein (8% by mass), with a thickness of 80nm. This structure can realize an organic vertical source-gate transistor gas sensor with high sensitivity and high stability. The preparation method is as follows:

[0065] ① Clean the substrate with detergent, acetone solution, deionized water and isopropanol solution, and blow dry with nitrogen after cleaning;

[0066] ②Prepare the gate electrode on the substrate surface;

[0067] ③ Preparing a dielectric layer on the gate electrode by high temperature natural oxidation annealing; the annealing temperature is 500° C.;

[0068] ④ Ultrasonic mixing the egg white protein and the organic material in proportion; using the mixed solution to prepare a semiconductor layer on the dielectric layer;

[0069] ⑤ Prepare source electrode and drain electrode on the organic semiconductor layer.

[0070] Example 5

[0071] A nitrogen dioxide sensor based on an organic vertical source-gate transistor is a bottom-gate top-contact structure. Its structure is as shown in Example 1, except that the materials and thicknesses of each layer are as follows: 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 electrode is copper nanowires, the source electrode is graphene, and the semiconductor layer is a mixture of a polyisoprene derivative containing siloxane and egg white protein (3% by mass), with a thickness of 100nm. This structure can realize an organic vertical source-gate transistor gas sensor with high sensitivity and high stability.

[0072] ① Clean the substrate with detergent, acetone solution, deionized water and isopropanol solution, and blow dry with nitrogen after cleaning;

[0073] ②Prepare the gate electrode on the substrate surface;

[0074] ③ Preparing a dielectric layer on the gate electrode by ultraviolet ozone treatment;

[0075] ④ Ultrasonic mixing the egg white protein and the organic material in proportion, and using the mixed solution to prepare a semiconductor layer on the dielectric layer;

[0076] ⑤ Prepare source electrode and drain electrode on the organic semiconductor layer.

[0077] Example 6

[0078] A nitrogen dioxide sensor based on an organic vertical source-gate transistor is a bottom-gate top-contact structure. Its structure is as shown in Example 1, except that the materials and thicknesses of each layer are as follows: 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 electrode is 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 25nm. This structure can realize an organic vertical source-gate transistor gas sensor with high sensitivity and high stability. The preparation method is as follows:

[0079] ① Clean the substrate with detergent, acetone solution, deionized water and isopropanol solution, and blow dry with nitrogen after cleaning;

[0080] ②Prepare the gate electrode on the substrate surface;

[0081] ③ Preparing a dielectric layer on the gate electrode by ultraviolet ozone treatment;

[0082] ④ Ultrasonic mixing the egg white protein and the organic material in proportion, and using the mixed solution to prepare a semiconductor layer on the dielectric layer;

[0083] ⑤Prepare source electrode and drain electrode on the organic semiconductor layer;

[0084] Example 7

[0085] A nitrogen dioxide sensor based on an organic vertical source-gate transistor is a bottom-gate top-contact structure. Its structure is as shown in Example 1, except that the materials and thicknesses of each layer are as follows: 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 electrode is 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 40nm. This structure can realize an organic vertical source-gate transistor gas sensor with high sensitivity and high stability.

[0086] ① Clean the substrate with detergent, acetone solution, deionized water and isopropanol solution, and blow dry with nitrogen after cleaning;

[0087] ②Prepare the gate electrode on the substrate surface;

[0088] ③ Preparing a dielectric layer on the gate electrode by ultraviolet ozone treatment;

[0089] ④ Ultrasonic mixing the egg white protein and the organic material in proportion, and using the mixed solution to prepare a semiconductor layer on the dielectric layer;

[0090] ⑤ Prepare source electrode and drain electrode on the organic semiconductor layer.

[0091] Example 8

[0092] A nitrogen dioxide sensor based on an organic vertical source-gate transistor is a bottom-gate top-contact structure. Its structure is as shown in Example 1, except that the materials and thicknesses of each layer are as follows: 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 electrode is 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 50nm. This structure can achieve high sensitivity, a high-sensitivity organic vertical source-gate transistor gas sensor. The preparation method is as follows:

[0093] ① Clean the substrate with detergent, acetone solution, deionized water and isopropanol solution, and blow dry with nitrogen after cleaning;

[0094] ②Prepare the gate electrode on the substrate surface;

[0095] ③ Preparing a dielectric layer on the gate electrode by high temperature natural oxidation;

[0096] ④ Ultrasonic mixing the egg white protein and the organic material in proportion, and using the mixed solution to prepare a semiconductor layer on the dielectric layer;

[0097] ⑤ Prepare source electrode and drain electrode on the organic semiconductor layer.

[0098] Example 9

[0099] A nitrogen dioxide sensor based on an organic vertical source-gate transistor is a bottom-gate top-contact structure. Its structure is as shown in Example 1, except that the materials and thicknesses of each layer are as follows: 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 electrode is a copper nanowire, 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 50nm. This structure can achieve high sensitivity, a highly sensitive organic vertical source-gate transistor gas sensor. The preparation method is as follows:

[0100] ① Clean the substrate with detergent, acetone solution, deionized water and isopropanol solution, and blow dry with nitrogen after cleaning;

[0101] ②Prepare the gate electrode on the substrate surface;

[0102] ③ Preparing a dielectric layer on the gate electrode by high temperature natural oxidation;

[0103] ④ Ultrasonic mixing the egg white protein and the organic material in proportion, and using the mixed solution to prepare a semiconductor layer on the dielectric layer;

[0104] ⑤ Prepare source electrode and drain electrode on the organic semiconductor layer.

[0105] Example 10

[0106] A nitrogen dioxide sensor based on an organic vertical source-gate transistor is a bottom-gate top-contact structure. Its structure is as shown in Example 1, except that the materials and thicknesses of each layer are as follows: 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 electrode is 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 80nm. This structure can achieve high sensitivity, a high-sensitivity organic source-gate transistor gas sensor. The preparation method is as follows:

[0107] ① Clean the substrate with detergent, acetone solution, deionized water and isopropanol solution, and blow dry with nitrogen after cleaning;

[0108] ②Prepare the gate electrode on the substrate surface;

[0109] ③ Preparing a dielectric layer on the gate electrode by ultraviolet ozone treatment;

[0110] ④ Ultrasonic mixing the egg white protein and the organic material in proportion, and using the mixed solution to prepare a semiconductor layer on the dielectric layer;

[0111] ⑤ Prepare source electrode and drain electrode on the organic semiconductor layer.

[0112] Embodiment 11

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

[0114] Example 12

[0115] A nitrogen dioxide sensor based on an organic vertical source-gate transistor is a bottom-gate top-contact structure, and its structure is as shown in Example 1, except that the semiconductor layer 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 invention comprises 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, the semiconductor layer and 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 source electrode material is different from the drain electrode material, the source electrode forms a Schottky contact, and the drain electrode forms an ohmic contact.

2. The organic vertical source-gate transistor-based nitrogen dioxide sensor according to claim 1, characterized in that: The semiconductor layer is a mixture of a soluble organic semiconductor material and a natural high-k dielectric material, and the mass of the natural high-k dielectric material accounts for 1% to 10% of the semiconductor layer.

3. The organic vertical source-gate transistor-based nitrogen dioxide sensor according to claim 1, characterized in that: Soluble organic semiconductor materials include poly-3-hexylthiophene, Tips-pentacene, polyisoprene derivatives containing siloxane, and one of the PBTTT series; The natural high-k dielectric material includes one of silk fibroin, egg white protein, and gelatin.

4. The organic vertical source-gate transistor-based nitrogen dioxide sensor according to claim 1, characterized in that: The dielectric layer is a gate natural oxide high-k dielectric layer, specifically an aluminum oxide dielectric layer formed by oxidation of an aluminum electrode; The thickness of the dielectric layer is 5-10nm, and the thickness of the dielectric layer around the gate electrode is the same.

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

6. The organic vertical source-gate transistor-based nitrogen dioxide sensor according to claim 1, characterized in that: 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; The source electrode material is metallic carbon nanotube or graphene; the gate electrode is an aluminum electrode.

7. The organic vertical source-gate transistor-based nitrogen dioxide sensor according to claim 1, characterized in that: The gate electrode completely overlaps and covers the source electrode in the vertical direction, and the area of ​​the gate electrode is larger than that of the source electrode. The drain electrode and the gate electrode do not overlap and cover each other in the vertical direction at all, the drain electrode and the gate electrode are in the same horizontal plane, and the drain electrode is on the side of the gate electrode.

8. A method for preparing a nitrogen dioxide sensor based on an organic vertical source-gate transistor according to any one of claims 1 to 7, characterized in that: The following steps are involved: ① Clean the substrate with detergent, acetone solution, deionized water and isopropanol solution, and blow dry with nitrogen after cleaning; ②Preparing a gate electrode on the substrate surface; ③ Preparing a natural dielectric layer by subjecting the gate electrode to high temperature annealing oxidation or ultraviolet ozone atmosphere annealing oxidation; ④ Ultrasonic mixing of natural high-k dielectric material and soluble organic semiconductor material in proportion, and using the mixed solution to prepare a semiconductor layer on the dielectric layer; ⑤ Prepare a drain electrode on the semiconductor layer on the side of the gate electrode to form an ohmic contact with the semiconductor layer, and then prepare a source electrode on the semiconductor layer above the gate electrode to form a Schottky contact with the semiconductor layer and a semiconductor depletion region.

9. The method for preparing a nitrogen dioxide sensor based on an organic vertical source-gate transistor according to claim 8, characterized in that: In step ③, during high temperature annealing oxidation or ultraviolet ozone annealing oxidation, the annealing temperature is between 300°C and 500°C, with the best effect being around 350°C.

10. The method for preparing a nitrogen dioxide sensor based on an organic vertical source-gate transistor according to claim 8, characterized in that: In step ④, the semiconductor layer is prepared by a method selected from the group consisting of spin coating, roller coating, dripping, embossing, printing or spraying; in steps ② and ⑤, the gate electrode, source electrode and drain electrode are prepared by a method selected from the group consisting of vacuum thermal evaporation, magnetron sputtering, plasma enhanced chemical vapor deposition, screen printing, printing or spin coating.

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