A bridged tungsten oxide nanowire device and its preparation method and use

Abstract

The present invention relates to the technical field of electronic devices, and in particular to a bridged tungsten oxide (WO3) nanowire device and a preparation method and use thereof. The bridged WO3 nanowire device comprises an insulating substrate, a forked electrode, and a patterned WO3 nanowire, wherein the forked electrode is arranged on the upper surface of the insulating substrate, the patterned WO3 nanowire grows on the forked electrode and the upper surface of the insulating substrate where the forked electrode is located, part of the patterned WO3 nanowire forms electrical contact with the forked electrode, and the tops of adjacent patterned WO3 nanowires are randomly bridged to form a stable conductive channel. The device is prepared by in-situ growth on the forked electrode substrate by a vapor transport deposition method, and the method is simple and efficient. Without an external heater, the device can realize efficient self-heating by utilizing the Joule heat generated under high voltage, and realize gas-sensitive response and detection of NO2 at a lower power consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic devices, and in particular to a bridged tungsten oxide nanowire gas sensor device and a preparation method thereof, as well as an application thereof in realizing low-power consumption NO2 gas molecule detection in a self-heating mode. Background Art

[0002] Due to its abundant surface oxygen vacancies and multiple stable substoichiometric phases, WO3 has excellent catalytic activity and gas-sensing properties, and is an important type of gas-sensing material. WO3 gas sensors are widely used in the identification and detection of various gas pollutants. Similar to other oxide (SnO2, ZnO, In2O3, etc.) gas sensors, WO3 gas sensors usually need to be heated to 150-350°C to desorb the air (O2, H2O, etc.) adsorbed on the sensor surface (exposing active sites) and generate new active oxygen ions (O2 - , O - ) to regulate the response and recovery of the sensor to different target gases. Therefore, oxide (including WO3) sensors usually need to integrate heaters. On the one hand, it increases the sensor preparation process and limits the substrates that can be used by the sensor. On the other hand, the introduction of heaters also greatly increases the power consumption of the sensor (heated to 300°C, the power consumption of a micro-hot stage with a lateral size of about 100μm is about 20mW, and the power consumption of a ceramic wafer substrate of about 2mm is about 0.4W). Power consumption is an important indicator that restricts the application of gas sensors in Internet of Things monitoring. Reducing the power consumption of the sensor to μW (10 -6 W) level, it will greatly promote the in-depth application of gas sensors in smart cities, smart agriculture, park grid monitoring and other fields.

[0003] Sensor self-heating occurs when the sensitive layer doubles as a heating layer. Under high bias voltage (power), the sensor generates Joule heating, raising the temperature of the sensitive layer and activating the sensor's response to the gas being measured. Compared to nanoparticles and nanosheets, quasi-one-dimensional nanowires combine a high surface area (facilitating adsorption of gas molecules) with single-crystal carrier transport / heating channels, making them more suitable for self-heating testing and maintaining the thermal stability of the sensitive layer. In 2016, the applicant reported a single SnO2 nanowire device with a suspended structure. The suspended structure (except for the electrode contacts at both ends, the nanowire is not in contact with the substrate) effectively blocks the dissipation of Joule heat generated by self-heating to the substrate, and can efficiently localize the Joule heat generated by self-heating in the nanowire. The nanowire can be heated to 250°C at a low power of 13μW. The average power consumption can be further reduced to about 36pW by short pulse heating (10μs on, 3s off) [Nanoscale Thermal Management of Single SnO2 Nanowire: pico-Joule Energy Consumed Molecule Sensor, ACS Sensors, 1 (2016) 997]. Although single suspended nanowire devices provide a solution to reduce sensor power consumption, they still have the following shortcomings: First, the equipment required to prepare single suspended nanowire devices (electron beam exposure or focused ion beam) is expensive and the process is complex (first growing the nanowires, then dispersing the grown nanowires in a solution, and then dispersing them on a substrate with interdigitated electrodes, and then undergoing multi-step focused ion beam or electron beam exposure and sputtering); second, the device preparation yield is low, making it difficult to achieve engineering batch preparation of the devices. Summary of the Invention

[0004] One of the objectives of the present invention is to provide a bridged WO3 nanowire device. The sensor does not require an external heater and can achieve efficient self-heating by utilizing the Joule heat generated by the sensitive layer under high bias voltage, thereby realizing NO2 gas-sensitive response and detection at low power consumption.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions: a bridged WO3 nanowire device, comprising an insulating substrate and two interdigitated electrodes with tooth-like structures arranged opposite to each other on the upper surface of the insulating substrate, the tooth-like structures of the interdigitated electrodes being arranged opposite to each other and staggered to form a serpentine channel; the material of the interdigitated electrodes is a precious metal; the interdigitated electrodes and the upper surface of the insulating substrate where the interdigitated electrodes are located are provided with a plurality of patterned tungsten film area units, a plurality of randomly oriented WO3 nanowires are grown on the surface of the tungsten film area units, and the WO3 nanowires of adjacent tungsten film area units are randomly crossed and bridged in space to form a conductive channel.

[0006] As a further improvement of the bridged WO3 nanowire device:

[0007] Preferably, the insulating substrate is made of one of alumina ceramics, zirconia ceramics, quartz glass, and a silicon wafer with a SiO2 insulating layer.

[0008] Preferably, the material of the interdigital electrodes is Pt or Au.

[0009] Preferably, the interdigitated electrode includes two or more electrode teeth arranged side by side, the width t21 of the electrode teeth perpendicular to the extension direction thereof is 1-1000 μm, the width t22 of the serpentine channel is 10-100 μm, the width w20 between the farthest ends of the electrode teeth arranged side by side in the same interdigitated electrode is 1-10 mm, and the width h20 between the farthest ends of the two oppositely arranged interdigitated electrodes in the extension direction of the electrode teeth is 1-10 mm.

[0010] Preferably, the shape of the tungsten film region unit is a strip, a rectangle or a square, and the interval t31 between adjacent tungsten film region units is 1-10 μm.

[0011] A second object of the present invention is to provide a method for preparing the above-mentioned bridged WO3 nanowire device, comprising the following steps:

[0012] Step 1: on the insulating substrate, obtaining interdigital electrodes by photolithography, magnetron sputtering, electron beam evaporation or screen printing;

[0013] Step 2: On the interdigital electrodes and the upper surface of the insulating substrate where the interdigital electrodes are located, a patterned tungsten film area unit is set by photolithography or a mask plate process, and then the interdigital electrode substrate covered with the photoresist or mask is placed in a vacuum chamber, and a 400-500nm tungsten film is evaporated on the set tungsten film area unit by magnetron sputtering or electron beam evaporation. The sample is taken out, and the photoresist film or mask plate is removed to obtain a patterned tungsten film seed layer, guiding the growth of WO3 nanowires only in the area where the seed layer is located;

[0014] Step 3: Place the substrate with the patterned tungsten film seed layer in step 2 into a ceramic boat, place 0.1-2g of WO3 powder next to the substrate in the ceramic boat, heat the tube furnace to 800-900°C under a vacuum of 0.01-10Pa, and keep it warm for 3-20 hours to obtain a bridged WO3 nanowire device.

[0015] The preparation method of bridging WO3 nanowire devices is further improved:

[0016] Preferably, the specific steps of setting the patterned tungsten film area unit in step 2 are as follows:

[0017] The specific steps of setting the patterned tungsten film area unit in step 2 are as follows: spin coating a photoresist film on the interdigitated electrode substrate, baking and curing it, using photolithography or laser direct writing to depict an orderly arranged pattern, exposing and developing to obtain the patterned tungsten film area unit;

[0018] Alternatively, a metal mask provided with ordered through holes is taken and placed closely on the interdigital electrode substrate, with the through holes on the metal mask forming patterned tungsten film area units.

[0019] The third object of the present invention is to provide a use of the above-mentioned bridged WO3 nanowire device in detecting 0.1-5ppm NO2 gas in an environment.

[0020] Further improvement of the use of WO3 nanowire devices as bridges in detecting 0.1-5ppm NO2 gas in the environment:

[0021] Preferably, the detection process includes the following steps: self-heating the bridged WO3 nanowire device, and controlling the voltage at both ends of the bridged nanowire device not to be higher than the fuse voltage V melt By regulating the voltage across the bridge nanowire device to control the power of Joule heat generated by self-heating, the temperature of the nanowire device can be regulated and the electrical response of the device to different concentrations of NO2 can be activated.

[0022] Preferably, the fuse voltage V melt The test method is as follows: in an air atmosphere, an external heater is used to control the temperature of the bridge nanowire device to room temperature ~ 350 ° C, the current I of the bridge nanowire device is measured at different voltages V, and the change curve of the bridge nanowire device resistance R with the self-heating power P is recorded, where R = V / I, P = V×I; as the voltage across the bridge nanowire device further increases, the nanowire device will generate more Joule heat, and the voltage when the bridge nanowire device melts is recorded as V melt .

[0023] The beneficial effects of the present invention compared to the prior art are:

[0024] 1) This invention discloses the following technical solution: By using a mask or photolithography process to create a patterned tungsten film region, tungsten film is evaporated within this region to form a patterned tungsten film seed layer, guiding the growth of WO3 nanowires only in the seed layer region. Then, through vapor transport deposition, WO3 nanowires are grown in the region coated with the tungsten film seed layer. By controlling the nanowire growth parameters (temperature, oxygen partial pressure, and time), the desired length for bridging adjacent nanowires is achieved, resulting in a bridged WO3 nanowire device. The technical solutions employed in this invention (patterning, evaporation, and vapor transport deposition) all belong to conventional micro-nanoetching processes. Through a single nanowire growth pass, bridged nanowire devices can be obtained "in situ." Furthermore, this solution can achieve efficient, mass-produced arrays of bridged nanowire devices on wafer-scale substrates through conventional overlay processes (masking or photolithography), addressing the bottleneck of single suspended nanowire device fabrication. The simple technical solution of this invention can also be extended to the efficient, in situ fabrication / integration of other metal oxide bridged nanowire devices, addressing the bottleneck of low-power bridged nanowire device fabrication.

[0025] 2) The bridged WO3 nanowires proposed in this invention are partially grown on the tungsten film on the interdigital electrodes. The base of the nanowire forms a stable electrical contact with the interdigital electrodes through the tungsten film. No continuous WO3 film forms between the interdigital electrodes, and carriers are conducted solely through the path of "interdigital electrode - WO3 nanowire above - (single or multiple) bridged nanowires - WO3 nanowire - bottom interdigital counter electrode," forming a stable conductive path. The nanowires contact the substrate only through their root cross-sections. This extremely small contact interface effectively suppresses the dissipation of Joule heat generated by self-heating to the substrate, localizing the Joule heat generated by self-heating within the bridged nanowires. This results in efficient self-heating, raising the effective temperature of the sensor to approximately 300°C with a self-heating power consumption of 0.13μW. Further reductions in device size and the number of bridged nanowires (reducing the volume of the heating element) are expected to further reduce gas sensor power consumption.

[0026] 3) The technical solution of the present invention first uses an external heater to control the temperature of the bridge nanowire device. As the voltage across the device increases, the Joule heat in the nanowire device increases, thereby effectively raising the temperature of the nanowire device, thereby achieving the purpose of activating the gas-sensitive response. As the voltage across the device further increases, the nanowire device generates more Joule heat, which may cause the device to fuse, and the voltage V at the time of fuse is recorded. melt When no external heater is needed, the bridged WO3 nanowire device is self-heated, and there is no need to design an additional microheater to control the sensor temperature. The sensor temperature can be controlled by controlling the sensor voltage, providing a solution for subsequent sensor monitoring applications in grid-based Internet of Things. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The structure diagram of the bridged WO3 nanowire device of the present invention is shown in FIG. The meanings of the symbols in the figure are as follows: 1. insulating substrate; 2. interdigitated electrodes; 3. tungsten film region unit; 4. WO3 nanowire.

[0028] Figure 2 The image of the bridged WO3 nanowire device of the present invention (a) is a graphically grown WO3 nanowire, and the top of the nanowire bridges the prescription frame portion as shown in FIG. Figure 2 (b) shown.

[0029] Figure 3 Schematic diagrams of the structures of Example 2 (bridged WO3 nanowire device) and the comparative example and the NO2 response characteristics under self-heating (a, b), as well as schematic diagrams of the device conductive channel (c, d). Figure 3 (e) is the gas-sensing response characteristic test of the tungsten oxide bridge nanowire device of Example 2 to 5 ppm NO2 at different bias voltages (different self-heating power consumption); Figure 3 (f) is the gas-sensing response characteristic test of the comparative example tungsten oxide bridge nanowire device to 5ppm NO2 at different bias voltages (different self-heating power consumption); Figure 3 (g) Sensitivity test of the tungsten oxide bridged nanowire device prepared in Example 2 and Comparative Example to 5 ppm NO2 under different bias voltages; Figure 3 (h) is the sensitivity test of the tungsten oxide bridged nanowire device prepared in Example 2 and the comparative example to 5 ppm NO2 at different self-heating powers;

[0030] Figure 4 This is the relationship between the resistance of the device of Example 2 in air and the temperature (the temperature is controlled by an external heater, the device bias is 5V, and the self-heating effect is negligible at this time) and the driving voltage under self-heating conditions.

[0031] Figure 5 This is the dynamic response curve of the device of Example 2 to 0.1-3 ppm NO2 at a bias voltage of 200 V (self-heating power consumption of 0.13 μW). DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] Step 1: Take 0.2g of absorbent cotton, wash it with deionized water and ethanol 2-3 times, and dry it at 80℃ for 24h;

[0035] Step 2: Weigh 5g of tungsten powder, add 80ml of 30% H2O2 and 4ml of deionized water, react at room temperature for about 72h, remove excess hydrogen peroxide with 80ml of ethanol, and let it stand for about 48h to obtain a peroxypolytungstic acid precursor solution;

[0036] Step 3: Immerse the absorbent cotton obtained in step 1 into the peroxy polytungstate precursor, take out the absorbent cotton after adsorption for 24 hours, wash it with anhydrous ethanol several times, and bake it in an oven at 80°C for 24 hours;

[0037] Step 4: Place the precursor cotton composite material of step 3 into a tube furnace, heat it from room temperature to 600° C. at a heating rate of 1° C. / min in air, and keep it warm for 1-10 hours to obtain WO3 nanoparticles.

[0038] Example 2

[0039] Step 1: Alumina ceramic is selected as an insulating substrate, and noble metal interdigital electrodes are coated on the ceramic substrate by screen printing / sputtering, thereby preparing a plurality of insulating substrates coated with interdigital electrodes for standby use;

[0040] Step 2: A copper / nickel metal mask is placed on the surface of the insulating substrate where the noble metal interdigital electrodes and the noble metal interdigital electrodes are located. The metal mask is provided with orderly arranged square micrometer holes with a diameter of 90 μm and a spacing of 35 μm, which penetrate the metal mask. The insulating substrate with the mask is placed in a vacuum chamber, and a tungsten thin film of approximately 500 nm is deposited on the metal mask where the micrometer holes are located. The metal mask is removed to obtain an orderly tungsten thin film array deposited on the insulating substrate.

[0041] Step 3: Place the WO3 nanoparticles prepared in Example 1 and the ordered tungsten thin film array prepared in Step 2 into a vacuum tube furnace, with the WO3 placed in the center of the tube furnace and the ordered tungsten thin film array placed 4-5 cm from the center. The vacuum tube furnace is heated to 900°C and the chamber vacuum is approximately 13 Pa for 3 hours, until the ordered tungsten thin film array turns dark blue, thereby obtaining a bridged WO3 nanowire device.

[0042] The process of preparing tungsten oxide bridge nanowire devices by the above method is as follows: Figure 1 As shown, the tops of the nanowires in the adjacent areas are randomly bridged to form a conductive channel; the optical microscope of the product prepared in step 3 shows the results as shown in FIG. Figure 2 As shown, the tungsten film area unit is a square with a side length of 90 μm and a spacing between adjacent tungsten film area units of 35 μm.

[0043] Comparative Example

[0044] This comparative example provides a method for preparing a gas sensor of bridged WO3 nanowires, comprising the following steps:

[0045] Step 1: Alumina ceramic is selected as an insulating substrate, and noble metal interdigital electrodes are coated on the ceramic substrate by screen printing / sputtering, thereby preparing a plurality of insulating substrates coated with interdigital electrodes for standby use;

[0046] Step 2: depositing a tungsten thin film of about 500 nm on the surface of the noble metal interdigital electrode and the insulating substrate where the noble metal interdigital electrode is located, thereby obtaining a tungsten thin film deposited on the insulating substrate;

[0047] Step 3: Place the WO3 nanoparticles prepared in Example 1 and the tungsten film prepared in Step 2 into a vacuum tube furnace, with the WO3 placed in the center of the tube furnace and the tungsten film placed 4-5 cm from the center. The vacuum tube furnace is heated to 900°C and the chamber vacuum is approximately 13 Pa for 3 hours, until the surface of the tungsten film turns dark blue, thereby obtaining a bridged WO3 nanowire device.

[0048] Example 2: Schematic diagram of preparing tungsten oxide bridge nanowire device Figure 3 As shown in (a), Figure 3 (a) shows that this method uses a patterned W film as the seed layer for nanowire growth. In the prepared tungsten oxide bridge nanowire device, part of the nanowire array grows on the interdigital electrodes, and the roots of the nanowires form a stable electrical contact with the interdigital electrodes. There is no continuous WO3 film between the interdigital electrodes. The schematic diagram of the device conductive channel is shown in Figure 2. Figure 3 As shown in (c), the bridge nanowire device conducts carriers through the "interdigital electrode-bridge nanowire-interdigital electrode". The gas-sensitive response characteristics of the tungsten oxide bridge nanowire device of Test Example 2 to 5ppm NO2 under different bias voltages (different self-heating power consumption) are tested. Figure 3 (e) is shown. Figure 3 (e) As can be seen, the sensor's baseline resistance in air drops dramatically as the driving voltage across the device increases, indicating that the self-heating effect becomes apparent and the device temperature gradually rises (the resistance of a semiconductor device decreases with increasing temperature). Simultaneously, the NO2 response sensitivity gradually increases, and the device recovery rate accelerates. This demonstrates that, without the use of an external heater, the device can significantly increase the sensor's operating temperature, thereby improving both NO2 response sensitivity and response / recovery rate by utilizing the Joule heat generated within the device at high driving voltage.

[0049] The schematic diagram of the comparative example preparation of tungsten oxide bridge nanowire device is shown in FIG. Figure 3 As shown in (b), this comparative example directly uses a continuous W film (non-patterned) as a seed layer. After the WO3 nanowires are grown by vapor transport, the W film is thermally oxidized to form a continuous WO3 film. The interdigitated electrodes are in direct contact with the continuous WO3 nanowires to form a conductive channel. Figure 3As shown in (d), in addition to the "interdigital electrode-bridge nanowire-interdigital electrode", the carriers are mainly transmitted through the bottom WO3. The gas-sensitive response characteristics of the comparative tungsten oxide bridge nanowire device to 5ppm NO2 under different bias voltages (different self-heating power consumption) are tested, as shown in Figure 5. Figure 3 (f) is shown. Figure 3 (f) It can be seen that the baseline resistance of the comparative device in air is 2-3 orders of magnitude lower than that of the embodiment device (because the W film seed layer in the embodiment is continuous, thus forming a bottom carrier conduction layer). As the driving voltage across the device increases, the baseline resistance of the sensor in air decreases and the response sensitivity of NO2 increases, indicating that the device can also operate in self-heating mode, but the self-heating gas-sensing effect is significantly lower than that of the embodiment.

[0050] The sensitivity of the tungsten oxide bridged nanowire devices prepared in Example 2 and the comparative example to 5ppm NO2 was tested under different bias voltages. The results are as follows: Figure 3 (g) As shown; The sensitivity of the tungsten oxide bridged nanowire device prepared in Example 2 and the comparative example to 5ppmNO2 was tested at different self-heating powers. The results are shown in FIG. Figure 3 (h) Figure 3 (g) and 3(h) show that the sensitivity of both devices increases with the increase of self-heating power consumption (temperature). The device of Example 2 has a sensitivity of up to 24.6 to 5ppmNO2 at a low power consumption of 0.13μW, while the sensitivity of the comparative device to 5ppmNO2 is only 6.7 at a power consumption of 0.44μW.

[0051] In summary Figure 3 It can be seen that the tungsten oxide bridge nanowire device of Example 2 has a higher response sensitivity to the self-heating (>100V) of NO2 than the comparative example device, and the self-heating power consumption of the tungsten oxide bridge nanowire device of Example 2 is much lower than that of the comparative example. By setting a graphic bridge nanowire device, the loss of the self-heating function can be reduced, and efficient self-heating can be achieved.

[0052] The baseline resistance of the tungsten oxide bridge nanowire device prepared in Example 2 was tested in air at different self-heating voltages and different external heating temperatures. Under self-heating conditions, the actual temperature of the nanowire is difficult to measure directly. By comparing the changes in resistance under self-heating and external heating (at a known temperature), the temperature generated by self-heating can be estimated (semiconductor devices are similar to thermistors, in that resistance is a function of temperature. Therefore, the temperature can be measured by calibrating the resistance-temperature relationship). The results are shown in Figure 2. Figure 4As shown, the local temperature of the tungsten oxide bridge nanowire device prepared in Example 2 can reach an estimated 300°C at a bias of 200V as the external heating temperature / voltage increases. The resistance decreases, and the magnitude of the decrease in resistance due to self-heating and external heating matches that of the device, consistent with the device's intrinsic resistance-temperature characteristics. This indicates that increasing the voltage can generate sufficient Joule heating from the bridge nanowire itself, raising the local temperature and reducing device heating power consumption.

[0053] Figure 5 The gas-sensitive response test of Example 2 to 0.1-3ppm NO2 gas under an applied voltage of 200V is shown. Figure 5 It can be seen that Example 2 of the present invention can test 100ppb NO2 gas at extremely low power consumption. The quasi-one-dimensional nanowires take into account both high surface area and single-crystal carrier transport / heating channels, which not only ensures the sensitivity of self-heating, but also ensures the stability of self-heating. At the same time, the preparation method is also compatible with existing micro-nano processing (masks, photolithography, evaporation, sputtering, annealing), so it can be standardized and integrated on a large scale to obtain large-scale, repeatable, and batch preparation of smaller bridge nanowire devices, thereby solving the bottleneck of existing single suspended nanowire device devices and being suitable for other nanowire devices that can be integrated in situ. It will greatly promote the in-depth application of gas sensors in smart cities, smart agriculture, park grid monitoring and other fields.

[0054] Those skilled in the art will appreciate that the foregoing descriptions are merely specific embodiments of the present invention, and not exhaustive. It should be noted that numerous variations and modifications are possible for those skilled in the art, and all such variations and modifications that do not exceed the scope of the claims should be considered within the scope of protection of the present invention.

Claims

1. A bridged WO3 nanowire device, characterized in that: The invention comprises an insulating substrate (1) and two interdigital electrodes (2) with tooth-like structures arranged opposite to each other on the upper surface of the insulating substrate (1), wherein the tooth-like structures of the interdigital electrodes (2) arranged opposite to each other are arranged opposite to each other and staggered to form a serpentine channel; the material of the interdigital electrodes (2) is a noble metal; the interdigital electrodes (2) and the upper surface of the insulating substrate (1) where the interdigital electrodes (2) are located are provided with a plurality of patterned tungsten film area units (3); a plurality of randomly oriented WO3 nanowires (4) are grown on the surface of the tungsten film area units (3); the WO3 nanowires (4) of adjacent tungsten film area units (3) are randomly crossed and bridged in space to form a conductive channel; The method for preparing the bridged WO3 nanowire device comprises the following steps: Step 1, obtaining interdigital electrodes on the insulating substrate by photolithography, magnetron sputtering, electron beam evaporation or screen printing; Step 2: On the interdigital electrodes and the upper surface of the insulating substrate where the interdigital electrodes are located, a patterned tungsten film area unit is set by photolithography or mask plate process, and then the interdigital electrode substrate covered with photoresist or mask is placed in a vacuum chamber, and a 400-500nm tungsten film is evaporated on the set tungsten film area unit by magnetron sputtering or electron beam evaporation, and the sample is taken out, and the photoresist film or mask plate is removed to obtain a patterned tungsten film seed layer, and the WO3 nanowire is guided to grow only in the area where the seed layer is located; Step 3: Place the substrate with the patterned tungsten film seed layer in step 2 into a ceramic boat, place 0.1-2 g of WO3 powder next to the substrate in the ceramic boat, heat the tube furnace to 800-900°C under a vacuum of 0.01-10 Pa, and keep warm for 3-20 hours to obtain a bridged WO3 nanowire device.

2. The bridged WO3 nanowire device according to claim 1, characterized in that: The material of the insulating substrate (1) is one of alumina ceramics, zirconium oxide ceramics, quartz glass, and a silicon wafer with a SiO2 insulating layer.

3. The bridged WO3 nanowire device according to claim 1, characterized in that: The material of the interdigital electrodes (2) is Pt or Au.

4. The bridged WO3 nanowire device according to claim 1, characterized in that: The interdigitated electrode (2) comprises two or more electrode teeth arranged side by side, the width t21 of the electrode teeth in a direction perpendicular to the extension direction thereof is 1-1000 μm, the width t22 of the serpentine channel is 10-100 μm, the width w20 between the farthest ends of the electrode teeth arranged side by side in the same interdigitated electrode (2) is 1-10 mm, and the width h20 between the farthest ends of two interdigitated electrodes (2) arranged opposite to each other in the extension direction of the electrode teeth is 1-10 mm.

5. The bridged WO3 nanowire device according to claim 1, characterized in that: The shape of the tungsten film region unit (3) is a rectangle or a square, and the spacing t31 between adjacent tungsten film region units (3) is 1-10 μm.

6. The bridged WO3 nanowire device according to claim 1, characterized in that: The specific steps of setting the patterned tungsten film area unit in step 2 are as follows: spin coating a photoresist film on the interdigitated electrode substrate, baking and curing it, using photolithography or laser direct writing to depict an orderly arranged pattern, exposing and developing to obtain a patterned tungsten film area unit; Alternatively, a metal mask provided with ordered through holes is taken and the metal mask is closely attached to the interdigital electrode substrate, and the through hole portions on the metal mask constitute a patterned tungsten film area unit.

7. Use of the bridged WO3 nanowire device according to any one of claims 1 to 6 for detecting 0.1-5 ppm NO2 gas in an environment.

8. The use of the bridged WO3 nanowire device according to claim 7, characterized in that: The method comprises the following steps: self-heating the bridge WO3 nanowire device, and controlling the voltage at both ends of the bridge nanowire device not to be higher than the fuse voltage V melt By adjusting the voltage across the bridge nanowire device, the power of Joule heat generated by self-heating can be controlled, thereby achieving temperature regulation of the nanowire device and activating the electrical response of the device to different concentrations of NO2.

9. The use of the bridged WO3 nanowire device according to claim 8, characterized in that: The fuse voltage V melt The test method is as follows: in an air atmosphere, an external heater is used to control the temperature of the bridge nanowire device to room temperature to 350°C, the current I of the bridge nanowire device under different voltages V is tested, and the change curve of the resistance R of the bridge nanowire device with the self-heating power P is recorded, where R = V / I, P = V×I; as the voltage across the bridge nanowire device is further increased, the nanowire device will generate more Joule heat, and the voltage when the bridge nanowire device is melted is recorded as V melt .

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