Ozone sensor based on etched indium tin oxide film and preparation method and application thereof

Abstract

The invention belongs to the technical field of sensing, and particularly relates to an ozone sensor based on an etched indium tin oxide film as well as a preparation method and application of the ozone sensor. The preparation method comprises the following steps: etching an ITO layer on the surface of ITO glass by using laser to obtain a patterned ITO film resistance device (the resistance is 0.1-5 k omega); the ITO film resistance device is loaded into a plasma etching machine, and Aramp is carried out; carrying out H2 plasma etching to obtain an ITO film resistance device with a rough surface and rich surface defects; and carrying out annealing aging treatment in air and then cooling to prepare the ozone sensor based on the etched indium tin oxide film. The sensor can detect trace O3 in the environment with high sensitivity in a self-heating mode, has the characteristics of low power consumption, high selectivity, humidity interference resistance and long-term stability, and meets the O3 detection requirements of indoor and outdoor environments. The problems that a sensing substrate of an existing O3 sensor is opaque and the preparation process is complex (a heater needs to be integrated) are solved, and the O3 sensor has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the field of sensing technology, and particularly to an ozone sensor based on an etched indium tin oxide film, a preparation method thereof, and an application in detecting trace ozone in the environment. Background Art

[0002] Ozone (O3) is a strong oxidant. Near-surface O3 can cause serious damage to the human nervous system, eyes, nose, throat, and respiratory tissues. Research shows that ozone exposure increases the risk of premature death caused by heart or lung diseases. In recent years, the air quality in China has continued to improve. However, the problem of O3 pollution in the country and key regions has shown an intensifying trend. Developing new O3 monitoring technologies to empower the O3 pollution prevention and control battle with science and technology is crucial for public health.

[0003] Indium tin oxide (ITO) is one of the most widely used n-type transparent conductive oxides (TCOs) to date. ITO glass is widely used in fields such as solar cells, LEDs, mobile phones, and flat panel displays. In addition, ITO is also an important gas-sensitive material. Under a heating state, ITO has a good electrical response to O3.

[0004] Although gas (including O3) sensors based on metal oxide semiconductors (including ITO) have advantages such as small size, low cost, fast response, and easy integration, the preparation of semiconductor gas sensors first requires obtaining nanometer powders with controllable composition, size, and morphology; after mixing with binders, pore formers, and solvents, a sensitive material slurry is obtained; then, the slurry is coated on a special sensing substrate plated with interdigital electrodes and micro heaters by means of screen printing, microspraying, etc. After aging, a sensor with stable properties is obtained. Although this solution can independently regulate the characteristics of the sensitive film and the operating temperature, it also has the following defects: First, the device preparation process is relatively complex and costly, which is not conducive to the large-scale application of sensors; second, conventional silicon-based and ceramic sensing substrates are usually opaque, and it is difficult to make such devices into transparent sensors; third, existing oxide sensors need to integrate heaters, which limits the use of flexible substrates and also significantly increases the complexity of device preparation and the power consumption of sensors. Summary of the Invention

[0005] One of the purposes of the present invention is to solve the problems of complex device preparation process, device opacity, and high sensor power consumption existing in existing oxide semiconductor (ITO) gas sensors, and to provide an ozone sensor based on an etched indium tin oxide film. Using conventional ITO glass as the raw material, a patterned ITO film resistance unit is etched by laser engraving, and then an etched ITO film resistance device is obtained by Ar&H2 plasma etching. After low-temperature air annealing, a highly sensitive ozone sensor capable of detecting trace O3 in the environment in a self-heating mode is obtained.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A preparation method of an ozone sensor based on an etched indium tin oxide film, comprising the following steps: Step 1: Use a short-pulse laser to etch the indium tin oxide conductive layer of the ITO glass to obtain a patterned ITO film resistance unit arranged in an array. Then, use a short-pulse laser to cut and separate adjacent patterned ITO film resistance units to obtain a patterned ITO film resistance device for use. The patterned ITO film resistance device includes an insulating glass and a patterned ITO film resistance unit on the insulating glass. The patterned ITO film resistance unit includes two independently arranged ITO electrodes and an ITO serpentine resistance wire connecting the two ITO electrodes. The resistance of the ITO resistance wire is 0.1 - 5 kΩ; Step 2: Place the patterned ITO film resistance device in an etching machine and perform Ar&H2 plasma etching on the ITO electrodes and the ITO resistance wire to obtain an etched ITO film resistance device with a rough surface and rich in surface defects; Step 3: Anneal and age the etched ITO film resistance device in air and then cool it to prepare an ozone sensor based on an etched indium tin oxide film.

[0007] As a further improvement to the preparation method of the ozone sensor based on an etched indium tin oxide film: Preferably, in Step 1, the indium tin oxide conductive layer is an In2O3 film with a Sn mass fraction of 5 - 15%, the film thickness is 100 - 500 nm, and the sheet resistance is 6 - 20 Ω.

[0008] Preferably, the insulating glass is ordinary glass or quartz glass, and the thickness is 30 - 300 μm. The thinner the insulating glass, the lower the power consumption of the sensor.

[0009] Preferably, in Step 1, the ITO resistance wire is arranged in a serpentine bend or a serpentine coil, and adjacent ITO resistance wires are arranged at equal intervals.

[0010] Preferably, the ITO resistance wire is arranged in a serpentine bend. The width W0 of the ITO resistance wire is 5 - 200 µm, the distance W1 between adjacent bend segments is 10 - 200 μm, and the length l1 of each bend segment in the ITO resistance wire is 1 - 3 mm; the ITO electrode is square, the length l2 is 1.4 - 3.5 mm, and the width W2 is 0.5 - 2 mm.

[0011] Preferably, when the indium tin oxide conductive layer of the ITO glass is etched with short-pulse laser in step 1, the scanning etching path of the laser is controlled by a program; the wavelength of the short-pulse laser is ultraviolet light of 355 nm or green light of 532 nm, the laser pulse width is from fs to ps, the repetition frequency of the laser is 10–100 kHz, the power of the laser device is 0.1–5 W, the diameter of the laser spot focused on the ITO glass surface is 10–50 μm, and the laser scanning speed is 100 - 2000 mm / s.

[0012] Preferably, in step 2, the etching machine is a plasma etching machine or a reactive ion etching machine, the radio frequency of the etching machine is 13.56 MHz, the power is 100–300 W, the etching time is 0.5 - 2 h, and the Ar&H2 gas is a mixed gas of high-purity Ar and H2, and the volume ratio of H2 in the mixed gas is 1–5%.

[0013] Preferably, in step 3, the temperature of the annealing and aging treatment is 300–450 °C, and the time is 0.5 - 24 h.

[0014] The second object of the present invention is to provide an ozone sensor based on an etched indium tin oxide film prepared by the preparation method of the ozone sensor based on an etched indium tin oxide film described in any one of the above.

[0015] The third object of the present invention is to provide an application of the above ozone sensor based on an etched indium tin oxide film in detecting trace ozone, including the following steps: Step 21, study the relationship between the temperature of the ozone sensor based on an etched indium tin oxide film and the driving power (regulated by the sensor driving voltage), and regulate the self-heating temperature of the sensor; within the working temperature range where the sensitive film is not burned out and stably self-heated, regulate the working temperature of the sensor by regulating the self-heating power, and study the electrical response of the sensor to 1000 ppb O3 at different working temperatures ( R g / R a ), where, R g 、 R a are the resistance values of the sensor in the air background with O3 and without O3 respectively, obtain the working temperature corresponding to the maximum response value of the sensor to O3, and record it as the optimal working temperature; Step 22, at the optimal working temperature in step 21, test the electrical response of the sensor to 10 - 1000 ppb O3 ( R g / R a ), obtain the corresponding relationship curve between the O3 response of the sensor and the O3 concentration, and record it as the response characteristic curve; Step 23: At the optimal working temperature in Step 21, record the resistance values of the sensor in an air background and an environment with O3 gas successively to obtain the response value of the sensor. R g / R a , and then analyze the concentration of O3 in the current environment according to the response characteristic curve calibrated in Step 22.

[0016] The beneficial effects of the present invention compared with the prior art are as follows: 1) The present invention provides a preparation process of an ozone sensor based on etched indium tin oxide film. First, a patterned ITO film resistance unit with an array arrangement is obtained by laser etching, and then the patterned ITO film resistance unit is obtained after cutting; for the ozone sensor based on etched indium tin oxide film, the high visible light transmittance characteristic of the transparent conductive indium tin oxide glass is retained, and the device is visible light transparent, overcoming the bottleneck of the opacity of conventional oxide semiconductor gas sensors and meeting the requirements for O3 detection in future transparent electronics systems. By designing the resistance of the ITO resistance wire, the resistance of the ITO film device (to match the driving circuit voltage and current system) and the efficient self-heating of the film device (reducing the dissipation of joule heat generated by self-heating) can be taken into account.

[0017] Then, the patterned ITO film resistance device is subjected to Ar&H2 plasma etching to obtain an ITO sensitive film rich in surface defects, making the conventional ITO film exhibit excellent O3 response characteristics. Then annealing and aging are carried out, and finally an ozone sensor based on etched indium tin oxide film is prepared.

[0018] 2) In the ozone sensor prepared by the present invention, the ITO resistance wire is arranged in a serpentine bend or a serpentine coil. By reducing the resistance area of the ITO resistance wire, thinning the thickness of the glass substrate or using pulse heating, the sensitive area (serpentine resistance) can be quickly heated to 150–250°C at a lower driving power consumption, realizing a highly sensitive and rapid response to ppb-level O3 in the environment.

[0019] 3) The preparation process of the present invention is simple, without multiple processes such as ITO nanopowder synthesis, slurry preparation, and coating. Laser etching and plasma treatment are compatible with conventional micro-nano etching processes. The batch preparation cost is low and the device consistency is good. Directly using low-cost industrial ITO glass as raw material is conducive to the large-scale production and application of the sensor.

[0020] 4) Compared with conventional four-pin oxide sensors (two pins for measuring the resistance of the sensitive film and two pins for heater control to regulate the working temperature of the sensor, with an insulating ceramic isolating the sensitive film from the heater), the ozone sensor based on etched indium tin oxide film does not require an integrated external heater, has a simple structure (two-electrode structure), there is no isolation between the sensitive film and the insulating glass, and the ITO sensitive film also serves as the heating layer. The working temperature of the sensor (150–250 °C) is regulated by driving power through the ITO sensitive film (serpentine resistor). The device can directly regulate the working temperature of the sensitive film through the self-heating mode, thereby regulating the sensor's response to O3; the advantage of self-heating is fast heat conduction rate, low heat dissipation, and low power consumption.

[0021] 5) The present invention also provides an application of the ozone sensor based on etched indium tin oxide film. By studying the relationship between the sensitive film temperature and the driving power of the ozone sensor based on etched indium tin oxide film under different driving powers, the self-heating temperature of the sensor is regulated to obtain the working temperature at which the sensor has the maximum response value to O3, denoted as the optimal working temperature; at the optimal working temperature, the electrical response of the sensor to 10 - 1000 ppb O3 is tested. R g / R a A response characteristic curve is formed; during actual testing, at the optimal working temperature, the resistance values of the sensor in the air background and in the O3 gas environment are recorded successively to obtain the response value of the sensor. R g / R a Corresponding to the response characteristic curve, the concentration of O3 in the current environment is analyzed. Brief Description of the Drawings

[0022] Figure 1 It is a schematic diagram and a physical diagram of the preparation process of the ozone sensor based on etched indium tin oxide film of the present invention.

[0023] Figure 2 It is the geometric size of the ITO film resistance in the ITO sensor of the present invention.

[0024] Figure 3 It is the morphology and X-ray diffraction pattern of the ordinary ITO sensor 1 (without Ar&H2 plasma etching) prepared in Comparative Example 1 and the etched ITO ozone sensor 1 prepared in Example 1 (Ar&H2 plasma etching for 60 min), where (a) and (b) are scanning electron microscope SEM images, (c) and (d) are atomic force microscope AFM images, and (e) is the X-ray diffraction XRD pattern.

[0025] Figure 4For the etched ITO ozone sensor 1 prepared in Example 1, the central peak temperature of the sensor and the infrared thermal imaging photos at different driving powers (adjusting the driving voltage across the sensor).

[0026] Figure 5 The resistance response curves of the ordinary ITO sensor 1 prepared in Comparative Example 1, the ordinary ITO sensor 2 prepared in Comparative Example 2, and the etched ITO ozone sensor 1 prepared in Example 1 to 1 ppm O3 at a self-heating temperature of 180°C.

[0027] Figure 6 The response characteristics of the ordinary ITO sensor 1 prepared in Comparative Example 1 and the etched ITO ozone sensor 1 prepared in Example 1 to O3: (a) The responses of the two sensors to 1 ppm O3 at different operating temperatures; (b) The response and recovery characteristic curves of the two sensors to 25–1000 ppb O3 at 180°C; (c) The relationship curve between the O3 response and the O3 concentration of the two sensors at 180°C; (d) The selectivity of the two sensors to the responses of various gases at 180°C; (e) The humidity dependence characteristics of the etched ITO ozone sensor 1 of Example 1 to 1 ppm O3 at 180°C; (f) The long-term stability of the responses of the two sensors to 1 ppm O3 at 180°C.

[0028] Figure 7 The response characteristics of the etched ITO ozone sensor 1 prepared in Example 1 in the pulse heating mode (peak temperature of 180°C, adjusting the duty cycle of the sensor driving voltage) to 1 ppm O3: (a) Dynamic response curve; (b) The responses and power consumptions of the sensor to 1 ppm O3 at different duty cycles.

[0029] Figure 8 The test results of the ozone response uniformity of the ITO film resistance unit array (18×12 = 216) prepared in batches by the preparation method of the present invention and the corresponding etched ITO ozone sensors: (a) The ITO glass engraved pattern (the ITO film in the dark area is retained, and the ITO film in the light area is etched away by laser to expose the glass substrate), the 18×12 sensor array, the size and physical diagram of a single film resistance device; (b) The size comparison diagram of the ITO sensor (transparent) prepared by the present invention with the existing MEMS sensors, the Japanese Fis, and the Zhengzhou Weisheng MQ131 O3 sensor; (c) The response characteristics of the ozone sensors selected at different positions in the same batch to 1 ppm O3 at a self-heating temperature of 180°C. Detailed implementation manners

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] Embodiment 1 This embodiment provides a preparation method for an ozone sensor based on an indium tin oxide film, which specifically includes the following steps: S1. Take ITO glass. The structure of this ITO glass includes an indium tin oxide conductive layer and ordinary glass. The thickness of the indium tin oxide conductive layer is 185 nm, the Sn mass fraction is 10%, and the sheet resistance is 10 Ω; the thickness of the ordinary glass is 300 μm.

[0032] After cleaning the surface of the ITO glass with anhydrous ethanol and drying it, use short-pulse laser to etch the indium tin oxide conductive layer of the ITO glass. Use a laser control system to control the laser to travel along the designed etching path to obtain a patterned ITO film resistance unit arranged in an array; then use short-pulse laser for cutting to separate adjacent patterned ITO film resistance units to obtain a patterned ITO film resistance device for use; The short-pulse laser is an ultraviolet laser with a wavelength of 355 nm, a laser pulse width of 1 ps, a laser repetition frequency of 50 kHz, a laser power of 1.2 W, a laser spot diameter of 20 μm, and a laser scanning speed of 500 mm / s. Repeat 3 to 5 times until the indium tin oxide conductive layer in the set area is completely etched away; The prepared patterned ITO film resistance device is as Figure 2 shown, and includes insulating glass and a patterned ITO film resistance unit on the insulating glass. The patterned ITO film resistance unit includes two independently arranged ITO electrodes and an ITO resistance wire connecting the two ITO electrodes. The resistance of the ITO resistance wire is 0.56 kΩ; the ITO resistance wire is arranged in a serpentine bend. The width W0 of the ITO resistance wire is 100 µm, the distance W1 between adjacent bend segments is 100 μm, and the length l1 of each bend segment in the ITO resistance wire is 1 mm; the ITO electrode is square as a whole, with a length l2 of 1.4 mm and a width W2 of 0.5 mm.

[0033] S2. Load the patterned ITO film resistance device into a plasma etching machine and perform Ar&H2 plasma etching on the ITO substrate. The plasma radio frequency is 13.56 MHz, the power is 150 W, and the etching time is 1 h. The Ar&H2 gas is high-purity Ar containing 5% by volume of H2 to obtain an etched ITO film resistance device with a rough surface and rich surface defects; S3. Anneal and age the etched ITO film resistor device in air. The annealing and aging temperature is 450 °C and the time is 3 h, then cool it to obtain the ozone sensor 1 based on the etched indium tin oxide film, denoted as the etched ITO ozone sensor 1.

[0034] Comparative Example 1 This comparative example provides a preparation method of a common ITO sensor. The specific steps refer to Example 1, except that the Ar&H2 plasma treatment in step S2 is not carried out, and only steps S1 and S3 are carried out. The common ITO sensor 1 is obtained.

[0035] Comparative Example 2 This comparative example provides a preparation method of a common ozone sensor. The specific steps refer to Example 1, and the difference is that: in step S2, Ar&H2 plasma etching is not carried out, but the patterned ITO film resistor device obtained in step S1 is placed in a tube furnace for Ar&H2 atmosphere annealing. The Ar&H2 gas flow rate is 100 sccm, the heating rate of the tube furnace is 5 °C / min, and it is heated from room temperature to 450 °C and maintained at this temperature for 5 hours. After the heat preservation is completed, it is naturally cooled to room temperature to obtain the ITO film resistor device annealed in Ar&H2 atmosphere; S3. Anneal and age the above device in air. The annealing and aging temperature is 450 °C and the time is 3 h, then cool it to obtain the common ITO sensor 2.

[0036] Example 2 This example provides a preparation method of an ozone sensor based on indium tin oxide film. The specific steps refer to Example 1, except that the power of Ar&H2 plasma etching in step S2 is 100 W and the etching time is 0.5 h, and the other processing parameters are the same. Finally, the ozone sensor 2 based on the etched indium tin oxide film is obtained, denoted as the etched ITO ozone sensor 2.

[0037] Example 3 This example provides a preparation method of an ozone sensor based on indium tin oxide film. The specific steps refer to Example 1, except that the power of Ar&H2 plasma etching in step S2 is 300 W and the etching time is 2 h, and the other processing parameters are the same. Finally, the ozone sensor 3 based on the etched indium tin oxide film is obtained, denoted as the etched ITO ozone sensor 3.

[0038] Example 4 This embodiment provides a method for preparing an ozone sensor based on indium tin oxide film. The specific steps refer to Embodiment 1, with the only difference being that the width W0 of the ITO resistance wire is 100 µm, the distance W1 between adjacent bent segments is 100 µm, and the length l1 of each bent segment in the ITO resistance wire is 2.1 mm; the ITO electrode is square as a whole, with a length l2 of 2.1 mm and a width W2 of 2.4 mm, and the other parameters are the same. Finally, an ozone sensor 4 based on etched indium tin oxide film is fabricated, denoted as etched ITO ozone sensor 4.

[0039] Embodiment 5 This embodiment provides a method for preparing an ozone sensor based on indium tin oxide film. The specific steps refer to Embodiment 1, with the only difference being that the width W0 of the ITO resistance wire is 100 µm, the distance W1 between adjacent bent segments is 100 µm, and the length l1 of each bent segment in the ITO resistance wire is 3.1 mm; the ITO electrode is square as a whole, with a length l2 of 3.5 mm and a width W2 of 2.0 mm, and the other parameters are the same, and the other parameters are the same. Finally, an ozone sensor 5 based on etched indium tin oxide film is fabricated, denoted as etched ITO ozone sensor 5.

[0040] Embodiment 6 This embodiment provides an application of an ozone sensor based on etched indium tin oxide film, which specifically includes the following steps: Step 21: By adjusting the sensor driving voltage, study the relationship between the temperature and driving power of the etched ITO ozone sensor 1 prepared based on Embodiment 1, and control the self-heating temperature of the sensor; within the working temperature range where the sensitive film (serpentine resistance wire area) is not burned out and stably self-heated, adjust the working temperature of the sensor by controlling the self-heating power, and study the electrical response of the sensor to 1000 ppb O3 at different working temperatures ( R g / R a ) where, R g 、 R a are the resistance values of the sensor under O3 and air backgrounds respectively, and obtain the working temperature when the sensor has the maximum response value to O3, denoted as the optimal working temperature; after testing, the temperature of the etched ITO ozone sensor 1 has a highly linear correlation with the sensor power consumption, and its power consumption is 350 mW at the optimal working temperature (180 °C), and the maximum working temperature (stable working serpentine resistance wire is not burned out) can reach 250 °C; Step 22: At the optimal working temperature in Step 21, test the electrical response of the ITO sensor to different concentrations of O3 in the range of 10 - 1000 ppb R g / R a , where R g and R a are the resistance values of the sensor under O3 and air background respectively, and the response characteristic curve of the sensor to O3 at different driving powers (self-heating temperatures) is obtained; the test results show that the response value of the sensor to 25 ppb of trace ozone can reach 1.5, and the response value to 1 ppm of ozone concentration can reach 5.2. The change of the sensor resistance with ozone concentration conforms to the sensing characteristics of n-type metal oxide semiconductors, and it shows a high degree of linear correlation above and below 200 ppb of ozone concentration; Step 23: At the optimal operating temperature in Step 21, record the resistance values of the sensor in the air background and in the environment with O3 gas successively to obtain the response value of the sensor R g / R a , and then analyze the concentration of O3 in the current environment according to the response characteristic curve calibrated in Step 22.

[0041] Performance test: 1) Figure 1 is the flow chart for preparing the ozone sensor based on indium tin oxide film in the present invention. The specific process is as follows: ① Use laser etching to engrave the patterned ITO film resistance unit to obtain the patterned ITO film resistance device; ② Perform Ar&H2 plasma etching on the ITO electrode and ITO resistance wire to obtain the etched ITO film resistance device with a rough surface and rich surface defects (after treatment, part of In2O3 is reduced to In, and the originally transparent ITO film becomes darker and the transmittance becomes worse); ③ Anneal in a low-temperature (300–450 °C) air atmosphere, and the ITO film becomes transparent again.

[0042] The ozone sensor of the present invention can be applied to the real-time on-line monitoring of indoor O3 concentration. The ozone sensor is integrated into a smart device and installed on the ceiling of an office with an ozone ultraviolet disinfection lamp. When the ultraviolet disinfection lamp in the office is started (ozone will be generated and diffused into the environment), the portable smart device can collect the resistance change of the ozone sensor in real time, and convert it into the real-time ozone concentration in the environment through the corresponding relationship between the concentration and the resistance change of the ozone sensor, and then transmit it to the mobile phone end via Bluetooth. Through the pre-adapted WeChat mini-program, the real-time monitoring of the ozone concentration in the working environment can be realized, and when the safety concentration threshold is exceeded, the user interface will flash a danger sign in real time.

[0043] 2) Figure 2It is a schematic diagram of the geometric dimensions of the patterned ITO film resistance unit in the O3 sensor of the present invention. The patterned ITO film resistance unit consists of square electrodes at opposite ends and serpentine resistance wires connecting the two square electrodes; the width W0 of the serpentine resistance wire is 5–200 µm, the spacing W1 between adjacent bent segments of the serpentine resistance wire is 10–200 µm, and the length l1 of each bent segment in the serpentine resistance wire is 1–3 mm; the length l2 of the square electrode is 1.4–3.5 and is equal to the width of the ITO glass, and the width W2 is 0.5–2 mm. The total resistance of the sensor is 0.1–5 kΩ (mainly determined by the width and length of the serpentine resistance wire).

[0044] 3) Figure 3 It is the morphology and XRD pattern of the ITO film on the ozone sensors prepared in Comparative Example 1 and Example 1, where (a) and (b) are scanning electron microscope SEM images, (c) and (d) are atomic force microscope AFM images, and (e) is the X-ray diffraction XRD pattern. From Figure 3 the comparison of the electron microscope images of the film layers on the sensors prepared in Example 1 and Comparative Example 1, it can be seen that the surface of the patterned ITO film (Comparative Example 1) only subjected to laser etching is dense and flat, which is not conducive to the adsorption of gas molecules to be measured and charge exchange. Therefore, the electrical response is weak; while the ITO (Example) treated with Ar&H2 plasma has a rough surface and is rich in various defects, which is conducive to the adsorption of target gas molecules and electrical detection.

[0045] 4) Figure 4 It is the central peak temperature of the sensitive area and its infrared thermal imaging photo of the etched ITO ozone sensor 1 prepared in Example 1 at different driving powers (adjusting the driving voltage across the sensor).

[0046] From Figure 4 it can be seen that as the driving power increases, the central temperature of the sensitive area increases accordingly; at a high driving power of ~450 mW, the temperature of the sensitive area can be higher than 200 °C. The optimized layout of the ITO sensing / heating wire in the sensitive area enables the sensor to achieve efficient self-heating at lower power consumption, and the infrared camera photo confirms that the Joule heat generated by self-heating is mainly concentrated in the (serpentine resistance) sensitive area.

[0047] 5) Figure 5 It is the resistance response curves of the ordinary ITO sensor 1 prepared in Comparative Example 1, the ordinary ITO sensor 2 prepared in Comparative Example 2, and the etched ITO ozone sensor 1 prepared in Example 1 to 1 ppm O3 at 180 °C.

[0048] Comparative Examples 1 and 2 and the O3 sensor of Example 1 have the same ITO pattern size. At the same working temperature (controlling the driving power of the sensor), the response of Comparative Example 1 (without Ar&H2 plasma etching) to 1 ppm O3 is negligible, and the response of Comparative Example 2 (annealing in Ar&H2 atmosphere) to O3 is also weak. In contrast, the example has a high response to 1 ppm O3, indicating that the conventional ITO film (with a flat and dense surface) itself has a weak response to O3. Ar&H2 plasma treatment can effectively generate active sites, enabling the ITO thin-film device to have gas-sensing response characteristics comparable to those of ITO particles.

[0049] 6) Figure 6 Response characteristics of the ordinary ITO sensor 1 prepared in Comparative Example 1 and the etched ITO ozone sensor 1 prepared in Example 1 to O3: (a) Responses of the two sensors to 1 ppm O3 at different working temperatures; (b) Response and recovery characteristic curves of the two sensors to 25–1000 ppb O3 at 180 °C; (c) Relationship curve between O3 response and O3 concentration of the two sensors at 180 °C; (d) Selectivity of the two sensors to various gases at 180 °C; (e) Humidity dependence characteristic of the etched ITO ozone sensor 1 to 1 ppm O3 at 180 °C; (f) Long-term stability of the responses of the two sensors to 1 ppm O3 at 180 °C.

[0050] It can be seen from Figure 6 that temperature has a great influence on the O3 response. The sensor has almost no response to O3 below 130 °C, indicating that O3 detection requires heating the device. By adjusting the self-heating driving power of the sensor and heating the sensor to 180 °C, the response of the device to O3 can be activated. At this working temperature, the device has a fast response and recovery time (~1 min) to O3. The etched ITO ozone sensor 1 prepared in Example 1 has excellent selectivity, anti-humidity interference characteristics and long-term stability, meeting the requirements for O3 detection in indoor and outdoor environments. In addition, the device has an obvious response to low-concentration O3 of 25 ppb, meeting the requirements for O3 monitoring in the national standards "Ambient Air Quality Standard" and "Indoor Air Ozone Hygiene Standard".

[0051] 7) Figure 7 Response characteristics of the etched ITO ozone sensor 1 prepared in Example 1 to 1 ppm O3 in pulse mode (peak temperature is 180 °C, adjusting the duty cycle of the sensor driving voltage): (a) Dynamic response curve; (b) Responses and power consumptions of the sensor to 1 ppm O3 at different duty cycles.

[0052] It can be seen from Figure 7It can be seen that the etched ITO ozone sensor 1 prepared in Example 1 is subjected to pulsed self-heating (periodically starting and stopping heating). When the sensor is at the peak temperature of 180 °C and the duty cycle of the heating waveform is reduced to 10%, the average power consumption of the sensor is reduced by one order of magnitude. Although the response value of the device decreases, the device still has an obvious response to O3. When the duty cycle is 3%, the average power consumption of the device can be reduced to less than 20 mW, which is comparable to the power consumption of MEMS devices, facilitating the application of the sensor in future Internet of Things grid monitoring.

[0053] 8) Figure 8 The ozone response uniformity test results of the ITO film resistor unit array (18×12 = 216) prepared in batches by the preparation method of the present invention and the corresponding etched ITO ozone sensor are as follows: (a) The ITO glass is engraved with a pattern (the ITO film in the dark area is retained, and the ITO film in the light area is etched away by laser to expose the glass substrate), an 18×12 sensor array, the size and physical diagram of a single film resistor device; (b) The size comparison diagram of the ITO sensor (transparent) prepared by the present invention with the existing MEMS sensor, Japanese Fis, and Zhengzhou Weisheng MQ131 O3 sensor; (c) The response characteristics of the ozone sensor selected at different positions in the same batch to 1 ppm O3 at 180 °C.

[0054] From Figure 8 It can be seen that the preparation method of the present invention meets the requirement of batch preparation of devices with uniform performance. Using commercial ITO glass (side length 2.5 cm) as the substrate, through laser etching, scribing, plasma etching, and air annealing, 216 ozone sensors are obtained. Compared with commercial O3 sensors (Japanese Fis, Zhengzhou Weisheng MQ131), the sensors prepared by the present invention have a simple preparation process, small size, transparency, low batch preparation cost, and good device consistency.

[0055] 9) The self-heating temperature and power consumption relationship of the etched ITO ozone sensors 2, 3, 4, and 5 prepared in Examples 2, 3, 4, and 5 are respectively tested, and the gas sensing performance of the sensors to 1 ppm trace ozone gas at the optimal working temperature is tested. The results are as follows: Due to the reduction of the processing time and power consumption, the change of the ITO film of the etched ITO ozone sensor 2 is small. The resistance of the serpentine ITO resistance wire in the sensitive area is ~0.56 kΩ, and its power consumption-temperature relationship is close to that of the untreated Comparative Example 1, and its response value of 2.1 is also higher than that of Comparative Example 1.

[0056] With the increase of time and processing power consumption, the ITO film of the etched ITO ozone sensor 3 changes greatly, and large particles appear on the surface. The resistance of the serpentine ITO resistance wire in its sensitive area reaches ~2.5 kΩ. It can reach a higher temperature at the same power consumption, but it is more likely to burn out. Its response value reaches 3.3, and it also realizes a high response to 1 ppm trace ozone.

[0057] For the etched ITO ozone sensor 4, after the area of the sensitive layer is enlarged to 2.1×2.1 mm 2 the total length of the serpentine electrodes in its sensitive area increases, so the serpentine resistance wire in its sensitive area increases and reaches 3.2 kΩ. A larger voltage needs to be applied under the same power consumption. And due to the increased area, the temperature of the device is lower than that of Comparative Example 1 under the same power consumption. Therefore, the power consumption to reach the optimal working temperature is 460 mW. Although the power consumption increases at the optimal working temperature, its response value to 1 ppm ozone reaches 3.6, which is also higher than that of Comparative Example 1; In the etched ITO ozone sensor 5, the area of the sensitive area is further enlarged, and the power consumption at the optimal working temperature of the sensor further increases to 600 mW. However, its response value to 1 ppm ozone is 2.9, which is also higher than that of Comparative Example 1, and the concentration monitoring of ambient O3 can also be realized.

[0058] Those skilled in the art should understand that the above are only several specific embodiments of the present invention, rather than all embodiments. It should be noted that many variations and improvements can be made by those of ordinary skill in the art. All variations or improvements that do not exceed the scope of the claims should be regarded as the protection scope of the present invention.

Claims

1. A preparation method of an ozone sensor based on an etched indium tin oxide film, characterized in that, It includes the following steps: Step 1: Use short-pulse laser to etch the indium tin oxide conductive layer of ITO glass to obtain a patterned ITO film resistor unit arranged in an array. Then use short-pulse laser to cut and separate adjacent patterned ITO film resistor units to obtain a patterned ITO film resistor device for standby; The patterned ITO film resistor device includes an insulating glass and a patterned ITO film resistor unit on the insulating glass. The patterned ITO film resistor unit includes two independently arranged ITO electrodes and an ITO resistance wire connecting the two ITO electrodes. The resistance of the ITO resistance wire is 0.1 - 5 kΩ; Step 2: Place the patterned ITO film resistor device in an etching machine and perform Ar&H2 plasma etching on the ITO electrodes and the ITO resistance wire to obtain an etched ITO film resistor device with a rough surface and rich in surface defects; Step 3: Anneal and age the etched ITO film resistor device in air and then cool it to obtain an ozone sensor based on the etched indium tin oxide film.

2. The preparation method of the ozone sensor based on an etched indium tin oxide film according to claim 1, wherein, In Step 1, the indium tin oxide conductive layer is an In2O3 film with a Sn mass fraction of 5 - 15%, the film thickness is 100 - 500 nm, and the sheet resistance is 6 - 20 Ω.

3. The preparation method of the ozone sensor based on an etched indium tin oxide film according to claim 1, wherein, The insulating glass is ordinary glass or quartz glass with a thickness of 30 - 300 μm.

4. The preparation method of the ozone sensor based on an etched indium tin oxide film according to claim 1, characterized in that, In Step 1, the ITO resistance wire is arranged in a serpentine bend or a serpentine coil, and adjacent ITO resistance wires are arranged at equal intervals.

5. The preparation method of the ozone sensor based on an etched indium tin oxide film according to claim 4, characterized in that, The ITO resistance wire is arranged in a serpentine bend. The width W0 of the ITO resistance wire is 5 - 200 µm, the distance W1 between adjacent bend segments is 10 - 200 μm, and the length l1 of each bend segment in the ITO resistance wire is 1 - 3 mm; the ITO electrode is square, with a length l2 of 1.4 - 3.5 mm and a width W2 of 0.5 - 2 mm.

6. The preparation method of the ozone sensor based on an etched indium tin oxide film according to claim 1, characterized in that, When using short-pulse laser to etch the indium tin oxide conductive layer of ITO glass in Step 1, the scanning etching path of the laser is controlled by a program; the wavelength of the short-pulse laser is ultraviolet light of 355 nm or green light of 532 nm, the laser pulse width is from fs to ps, the repetition frequency of the laser is 10 - 100 kHz, the power of the laser device is 0.1 - 5 W, the diameter of the laser spot focused on the ITO glass surface is 10 - 50 μm, and the laser scanning speed is 100 - 2000 mm / s.

7. The preparation method of the ozone sensor based on an etched indium tin oxide film according to claim 1, characterized in that, In Step 2, the etching machine is a plasma etching machine or a reactive ion etching machine. The radio frequency of the etching machine is 13.56 MHz, the power is 100 - 300 W, the etching time is 0.5 - 2 h, and the Ar&H2 gas is a mixed gas of high-purity Ar and H2. The volume ratio of H2 in the mixed gas is 1 - 5%.

8. The preparation method of the ozone sensor based on the etched indium tin oxide film according to claim 1, wherein, In Step 3, the temperature of the annealing and aging treatment is 300 - 450 °C, and the time is 0.5 - 24 h.

9. An ozone sensor based on an etched indium tin oxide film prepared by the preparation method of the ozone sensor based on an etched indium tin oxide film according to any one of claims 1 - 8.

10. Use of the ozone sensor based on an etched indium tin oxide film as described in claim 9 in detecting trace ozone, characterized in that, It includes the following steps: Step 21: Study the relationship between the temperature and driving power of an ozone sensor based on an etched indium tin oxide film, and regulate the self-heating temperature of the sensor; within the working temperature range where the sensitive film does not burn out and has stable self-heating, regulate the working temperature of the sensor by adjusting the self-heating power, and study the electrical response of the sensor to 1000 ppb O3 at different working temperatures. R g / R a , where R g and R a are the resistance values of the sensor in air backgrounds with and without O3 respectively, and obtain the working temperature corresponding to the maximum O3 response value of the sensor, denoted as the optimal working temperature. Step 22: At the optimal working temperature in Step 21, test the electrical response of the sensor to O3 with concentrations ranging from 10 to 1000 ppb R g / R a , and obtain the corresponding relationship curve between the O3 response and the O3 concentration of the sensor, which is denoted as the response characteristic curve; Step 23: At the optimal operating temperature in Step 21, record the resistance values of the sensor in the air background and in the environment with O3 gas successively to obtain the response value of the sensor R g / R a , and then analyze the concentration of O3 in the current environment according to the response characteristic curve calibrated in Step 22.

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