Description:DESCRIPTION:
Field of the invention:
The present disclosure generally relates to the technical field of gas sensing technology and, in specific relates to a method for detecting nitric oxide (NO) gas through a deposition of molybdenum disulphide (MoS2) thin films using radiofrequency (RF) sputtering and optimizes the film thickness for enhanced gas sensing performance.
Background of the invention:
Nitric oxide gas is a frequent chemical gas emission in factories, and the concentration of the gas over 1 ppm (parts per million) can cause irreversible harm to the respiratory system of a human body. For example, the presence of NO gas can also be employed as an expired air marker for individuals with lung tissue infection and gastrointestinal disorders, at a concentration of ppb. Therefore, it is possible to manage NO gas. Gas detection with ultra-high sensitivity is extremely significant in both industry and clinical practice. Generally, the NO is a colourless gas, and one of the most harmful oxidizing gases in the atmosphere. The Nitric oxide gas is a by-product of various sectors, including metal etching, agriculture, human waste, and cars.

The limit for NO gas in the atmosphere is less than 50 ppm. However, prolonged exposure to NO gas can lead to cardiovascular issues, dizziness, fainting, throat etching, and impaired brain cell function. Moreover, the NO gas also have a significant impact on the vascular and immunological systems. Excessive NO gas levels can harm the ecosystem by causing acid rain, atmospheric growth, and ozone depletion. Therefore, this effort aims to design and develop a gas sensor for detecting NO gas using molybdenum disulphide for gas sensing applications.

In recent years, ambient gases have affected the electrical properties of nanostructured materials such as graphene, metal oxides, thin films, and polymers. The electrical resistance of nanostructured materials may vary based on the gases used. Semiconductor materials provide sufficient reactive sites for redox processes, allowing for easy measurement of resistance fluctuations. Two-dimensional MoS2 materials are known for their high surface-to-volume ratio and superior semiconductor properties. These materials are ideal for building high-performance gas sensors. However, molybdenum disulphide (MoS2) nanostructured thin films show potential for detecting a variety of hazardous gas pollutants.

Nowadays, in the market, gas sensors can be electrochemical, optical, or semiconductor. Thin-film semiconductor gas sensors are the most cost-effective, compact, and power-efficient option. The detection of gas sensors is primarily determined by the sensitivity and selectivity criteria, which are boosted by using a suitable qualities. MoS2 has a large surface volume ratio and band gap, making it ideal for gas sensing. In addition to gas sensors, MoS2 is used in electronics, optoelectronics, and lithium-ion batteries.

In existing technology, a nitrogen dioxide sensor based on molybdenum disulphide is known. The molybdenum disulphide is configured to set up a source electrode and drain electrode for sensing material, set up an ultraviolet filter above the molybdenum disulphide material, and the sensor both sides set up gaseous input and output channel, and the lead wire of the source electrode and drain electrode stretches out from the sensor on both sides, and under ultraviolet illumination, NO2 is diffused to the MoS2 surface, allowing MoS2 to transfer electrons into the NO2 gas. However, the gas sensor might not detect the NO2 gas sensor and might not measure the change in electrical conductivity of MoS2.

Therefore, there is a need for a method for detecting nitric oxide (NO) gas through the deposition of molybdenum disulphite (MoS2) thin films using radiofrequency (RF) sputtering and optimizes the film thickness for enhanced gas sensing performance. There is also a need for a method that integrated with MoS2 thin films with a thickness optimized for NO gas detection (around 60 nm), allows for sensitive detection of NO gas molecules.

There is also a need for a method that leverages the unique properties of MoS2 thin films, with tow-dimensional nanomaterial for gas sensing applications. Further, there is also a need for a method that utilizes radiofrequency (RF) sputtering, and scalable thin-film deposition techniques, which facilitate cost-effective mass production.
Objectives of the invention:
The primary objective of the invention is to provide a method for detecting nitric oxide (NO) gas through the deposition of molybdenum disulphite (MoS2) thin films using radiofrequency (RF) sputtering and optimizes the film thickness for enhanced gas sensing performance.

Another objective of the invention is to provide a method that integrated with MoS2 thin films with a thickness optimized for NO gas detection (around 60 nm), allows for sensitive detection of NO gas molecules.

The other objective of the invention is to provide a method that leverages the unique properties of MoS2 thin films, with tow-dimensional nanomaterial for gas sensing applications.

The other objective of the invention is to provide a method that utilizes radiofrequency (RF) sputtering, and scalable thin-film deposition techniques, which facilitate cost-effective mass production.

Yet another objective of the invention is to provide a method that exhibits a rapid response time (around 16 seconds) upon exposure to NO gas, making it suitable for real-time monitoring applications.

Further objective of the invention is to provide a method that utilized thin films and potentially compatible flexible substrates allows for the development of miniaturized and portable NO gas sensing devices.
Summary of the invention:
The present disclosure proposes molybdenum disulphide (MoS2) films of various thicknesses used to detect nitric oxide (NO) gases. The following presents a simplified summary in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview. It is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

In order to overcome the above deficiencies of the prior art, the present disclosure is to solve the technical problem to provide a method for detecting nitric oxide (NO) gas through a deposition of molybdenum disulphide (MoS2) thin films using radiofrequency (RF) sputtering and optimizes the film thickness for enhanced gas sensing performance.

According to an aspect, the invention provides a method for detecting nitric oxide. At one step, deposits a molybdenum disulphide (MoS2) thin film onto a substrate using a radio frequency (RF) sputtering process. The substrate is selected from a group consisting of silicon wafers, alumina (Al2O3), and other materials compatible with the RF sputtering process. In one embodiment, the RF power is configured to set within a range of 100 watts (W) to 500 W to achieve the desired film growth rate and properties.

At another step, the MoS2 thin film is exposed to the nitric oxide (NO) gas at an operating temperature of about 40 ?C. At another step, measures a change in electrical properties of the MoS2 thin film upon exposure to NO gas. Further, at another step, the correlates the change in the electrical properties measured to the presence of NO gas. In one embodiment, the change in the electrical properties indicates the presence of NO gas with improved sensitivity compared to MoS2 thin film with non-optimized thickness.

In one embodiment, the MoS2 thin film is deposited by a method selected from the group consisting of radiofrequency (RF) sputtering and other suitable thin-film deposition techniques. In one embodiment, the thickness of the MoS2 thin film ranges from 20 nm, 40 nm, and 60 nm (nanometre). In one embodiment, the thickness of the MoS2 thin film is selected from a range of thicknesses for optimized NO gas sensing sensitivity.

In one embodiment, the method is configured to utilize scanning electron microscopy (SEM) to analyse the morphology surface of the deposited MoS2 thin film, ensuring the film is uniform, continuous, and free of detects. In one embodiment, the method is configured to utilize X-ray diffraction (XRD) to determine the crystalline structure of the MoS2 thin film, verifying the MoS2 as the desired crystalline phase for optimal gas sensing performance.

Further, objects and advantages of the present invention will be apparent from a study of the following portion of the specification, the claims, and the attached drawings.
Detailed description of drawings:
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, explain the principles of the invention.

FIG. 1 illustrates a flowchart of a method for detecting nitric oxide, in accordance to an exemplary embodiment of the invention.

FIG. 2A illustrates a block diagram of fabrication steps of molybdenum disulphide (MoS2) based gas sensor, in accordance to an exemplary embodiment of the invention.

FIG. 2B illustrates a schematic view of nitric (NO) gas based on MoS2 thin film, in accordance to an exemplary embodiment of the invention.

FIG. 3 illustrates a schematic view of an experimental setup for NO gas sensor measurement, in accordance to an exemplary embodiment of the invention.

FIGs. 4A-4C illustrate graphical representations of X-ray diffusion patterns of MoS2 film deposited at various thickness of 20 nm, 40 nm, and 60 nm, in accordance to an exemplary embodiment of the invention.

FIGs. 5A-5C illustrate graphical representations of morphology of MoS2 thin film thickness of 20 nm, 40 nm, and 60 nm after post annealing at obtained temperature, in accordance to an exemplary embodiment of the invention.

FIGs. 6A-6C illustrate graphical representations of a current-voltage characteristics of MoS2 based sensor for various thickness in the presence of NO gas with different thickness of 20 nm, 40 nm, and 60 nm, in accordance to an exemplary embodiment of the invention.

FIG. 7 illustrates a schematic view of the MoS2 during charge density changes in the presence of NO gas, in accordance to an exemplary embodiment of the invention.

FIGs. 8A-8C illustrate graphical representations of resistance transients of the MoS2 films with difference thickness and temperatures in the presence of NO gas, in accordance to an exemplary embodiment of the invention.

FIG. 9 illustrates a graphical representation of the influence of MoS2 film thickness and temperature on NO gas sensor sensitivity, in accordance to an exemplary embodiment of the invention.

FIG. 10 illustrates a graphical representation of the influence of the MoS2 film thickness and NO gas sensor response, in accordance to an exemplary embodiment of the invention.

FIG. 11 illustrates a graphical representation of the response time for MoS2 films at different thickness for 103 ppm NO gas detection, in accordance to an exemplary embodiment of the invention.
Detailed invention disclosure:
Various embodiments of the present invention will be described in reference to the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps.

The present disclosure has been made with a view towards solving the problem with the prior art described above, and it is an object of the present invention to provide a method for detecting nitric oxide (NO) gas through a deposition of molybdenum disulphide (MoS2) thin films using radiofrequency (RF) sputtering and optimizes the film thickness for enhanced gas sensing performance.

According to an exemplary embodiment of the invention, FIG. 1 refers to a flowchart 100 of a method for detecting nitric oxide. At step 102, deposits a molybdenum disulphide (MoS2) thin film onto a substrate using a radio frequency (RF) sputtering process. The substrate is selected from a group consisting of silicon wafers, alumina (Al2O3), and other materials compatible with the RF sputtering process. In one embodiment, the RF power is configured to set within a range of 100 watts (W) to 500 W to achieve the desired film growth rate and properties.

At step 104, the MoS2 thin film is exposed to the nitric oxide (NO) gas at an operating temperature of about 40 ?C. At step 106, measures a change in electrical properties of the MoS2 thin film upon exposure to NO gas. At step 108, the correlates the change in the electrical properties measured to the presence of NO gas. In one embodiment, the change in the electrical properties indicates the presence of NO gas with improved sensitivity compared to MoS2 thin film with non-optimized thickness.

In one embodiment, the MoS2 thin film is deposited by a method selected from the group consisting of radiofrequency (RF) sputtering and other suitable thin-film deposition techniques. In one embodiment, the thickness of the MoS2 thin film ranges from 20 nm, 40 nm, and 60 nm (nanometre). In one embodiment, the thickness of the MoS2 thin film is selected from a range of thicknesses for optimized NO gas sensing sensitivity.

In one embodiment, the method is configured to utilize scanning electron microscopy (SEM) to analyse the morphology surface of the deposited MoS2 thin film, ensuring the film is uniform, continuous, and free of detects. In one embodiment, the method is configured to utilize X-ray diffraction (XRD) to determine the crystalline structure of the MoS2 thin film, verifying the MoS2 as the desired crystalline phase for optimal gas sensing performance.

According to another exemplary embodiment of the invention, FIG. 2A refers to a block diagram 202 of fabrication steps of molybdenum disulphide (MoS2) based gas sensor. According to another exemplary embodiment of the invention, FIG. 2B refers to a schematic view 204 of nitric (NO) gas based on MoS2 thin film. In one embodiment herein, the several deposition techniques are utilized for the preparation of MoS2 thin films, including mechanical exfoliation, chemical vapour deposition, and molecular beam epitaxy. However, cost and poor scalability were constraints for the deposition techniques. Radio-frequency (RF) sputtering is chosen for depositing MoS2 films because it has better control over the thickness, ion density and quality of the thin films being deposited than other known deposition technologies. If the diameter of the target is a high dimension with high purity, RF sputtering deposits thin coatings with uniform deposition over a vast region. The MoS2 sputtering target (imported) having dimensions of 2-inch diameter with 3 mm thickness supported backing copper plate having thickness 2mm was used in the study. P-type silicon wafers were used after cutting wafer into size 1.5 cm x 1.5 cm.

Well-cleaned Silicon (Si) substrate uses RCA-1 and RCA-2 cleaning techniques followed by nitrogen air purging to remove surface wet drops (chemicals utilized for this treatment were hydrogen peroxide, ammonium hydroxide, hydrogen chloride and DI water at a temperature of 75 °C). The well-cleaned Si substrates were placed on the substrate holder in the vacuum chamber, followed by pumping using a turbo molecular and rotary vacuum pump. The sputtering chamber was evacuated to a pressure of 1.5 X 10-5 mbar before the sputtering process, and argon gas was utilized for igniting the plasma. Pre-sputtering in an argon gas ambience was carried out to remove surface contamination from the target surface before actual MoS2 film deposition to ensure that the target is free of contaminants. Argon gas is introduced at a flow rate of 15 SCCM, and the partial pressure of argon during sputtering is 1.2 X 10-2 mbar.

Substrates are maintained at a temperature of 250 °C to promote surface diffusion and proper adhesion of the condensed film particle. RF power used was 22.5 W at a constant substrate rotation speed of 1 rpm. Different thickness of films is obtained according to deposition time and allowed to reach room temperature. As deposited, MoS2 films were subjected to heat treatment to improve crystallinity at a temperature of 700 °C for 60 min with argon ambience in a muffle furnace. DC sputtering was used for depositing conducting contacts such as aluminium film and gold film deposition using a current of 100 mA followed by heat treatment at a temperature of 100 °C for 30 min.

According to another exemplary embodiment of the invention, FIG. 3 refers to a schematic view 300 of an experimental setup for NO gas sensor measurement. In one embodiment herein, the analyte gas (nitric oxide) was tested using MoS2 based gas sensor in a chamber that has been specifically designed for this purpose. Specifically, this equipment is equipped with two mass flow control valves to feed two different analyte gases into the test chamber. The vacuum within the chamber was monitored by a Pirani gauge that measures the level of vacuum in pressures. A temperature controller (substrate and sample temperature) was used to pre-heat samples to the required temperature. In order to test the response of analyte gas, contacts have been taken from the sample electrodes and attached to a parameter analyser. After each measurement with the analyte gas, the sample was exposed to the ambient air in the test chamber (for sensitivity calculations).

The flow rate of the analyte gas was fixed at 50 SCCM. After taking, measurement analyte gas valve is closed and vented by opening the vent valve once the measurement within the chamber is complete, and the process repeats. To carry out the study, nitric oxide gas with a concentration of 103 (one hundred and three) parts per million (ppm) was utilized.

According to another exemplary embodiment of the invention, FIGs. 4A-4C refer to graphical representations (402, 404, 406) of X-ray diffusion patterns of MoS2 film deposited at various thickness of 20 nm, 40 nm, and 60 nm. In one embodiment herein, the XRD pattern for samples deposited on silicon substrates having a different thickness. The XRD patterns of all the deposited films acquired a crystalline nature. As the thickness of the samples increases, phase changes have been observed. The MoS2 film with thickness range from at least 20 nanometre (nm), 40 nm, and 60 nm, which has a hexagonal crystal structure, which is consistent with previous findings. The reflection of planes (002), (101), (103), and (107) was observed at diffraction angles of 14.42o, 32.98o, 38.76o, and 61.7o. The silicon peak is located at the value of 69.18o and is also marked in the pattern.

According to another exemplary embodiment of the invention, FIGs. 5A-5C refer to graphical representations (502, 504, 506) of morphology of MoS2 thin film thickness of 20 nm, 40 nm, and 60 nm after post annealing at obtained temperature. In one embodiment herein, the scanning electron microscopy is the surface morphology of films was observed using a scanning electron microscope. Due to charging effects, the surface topography appears rough. The MoS2 thin film thickness of 20 nm, 40 nm, and 60 nm after a post annealing. The MoS2 thin film is changed variability based on the annealing temperature, thereby forming white particles on the MoS2 thin film with different thickness.

According to another exemplary embodiment of the invention, FIGs. 6A-6C refer to graphical representations (602, 604, 606) of a current-voltage characteristics of MoS2 based sensor for various thickness in the presence of NO gas with different thickness of 20 nm, 40 nm, and 60 nm. In one embodiment herein, the adsorption of gas depends on the conductivity of the MoS2 layer. Here, we investigated the adsorption of NO gas onto MoS2 monolayers of 20 nm, 40 nm, and 60 nm thickness films and measured the conductivity of the films. In the first step, the 20 nm film was examined with atmospheric air in a gas examination chamber. The current–voltage (I–V) characteristics were measured with a parameter analyser in linear voltage sweep mode with a step of 0.1 in the biasing voltage range from - 20 V to +20 V.

Then, nitric oxide gas was purged with a concentration of 103 ppm maintained at a flow rate of 50 SCCM using a mass flow controller (MFC). It is observed that nonlinear behaviour was present in the V–I characteristics of MoS2 films with and without analyte gas. It is speculated that a Schottky contact was formed between the film and electrodes. Due to the presence of Al/Au contacts, the same procedure was applied to 40 and 60 nm MoS2 films and measured the electrical parameters. The large current variation was observed in the 20 nm film compared to other film thicknesses.

According to another exemplary embodiment of the invention, FIG. 7 refers to a schematic view 702 of the MoS2 during charge density changes in the presence of NO gas. In one embodiment herein, the nitric oxide gas sensing studies have been done using a MoS2 film having a thickness of 20 nm, 40 and 60 nm. It involves initial oxygen gas molecules adsorbed on the surface of the MoS2 due to the presence of dangling bonds. The adsorbed O2 molecules are converted to O2–as per Eq. (1). The oxygen molecules dissociate at a specific temperature and adsorb onto the MoS2 thin film surface, resulting in the formation of the characteristic O2 or O depending on the temperature of the surface.

Both kinds of oxygen drain electrons from the conduction band of the semiconductor, resulting in the formation of the depletion zone in the MoS2 thin film. Because of their high electronegative characteristics, when NO gas was introduced into the chamber, the NO gas molecules captured the electrons and formed NO-, as described in Eq. (2). When NO is allowed into test chamber, the charge density changes at the surface of MoS2. As a result, NO gas molecules react more quickly, which leads to increase in sensitivity of the sensor.
(1)
(2)
The resistance and conductance of the gas sensor have been reported by several studies on the sensor’s sensitivity. In this case, the sensitivity is stated in terms of resistance (for oxidizing gases).
S= R_g/R_a (3)
where, Rg is resistance with analyte gas, and Ra is resistance without gas (atmospheric air). Sensitivity studies have been done on different thick samples of MoS2, and it is temperature dependant. From the previous experimental efforts, theoretical studies had played a key role for forecasting how well the proposed materials will perform in gas sensing applications.

According to another exemplary embodiment of the invention, FIGs. 8A-8C refer to graphical representations (802, 804, 806) of resistance transients of the MoS2 films with difference thickness and temperatures in the presence of NO gas. In on embodiment herein, the first principles studies, NO gas adsorption is strong within the MoS2 monolayer among CO, CO2, NH3, NO2, CH4, H2O, N2, O2, and SO2 gases. As a result of charge transfer reactions between analyte gas molecules and the MoS2 film surface, hence the resistance of the MoS2 films changes at different temperatures. The resistance variation on MoS2 films with a thickness of 20 nm, 40 nm, and 60 nm. As the temperature increased, the responsiveness of the resistance of the MoS2 film drops consistently with NO concentration of 103 parts per million (ppm) at a fixed flow rate has been investigated.

According to another exemplary embodiment of the invention, FIG. 9 refers to a graphical representation 902 of the influence of MoS2 film thickness and temperature on NO gas sensor sensitivity. In one embodiment herein, the temperature influence on sensor response. While calculating the sensors gas response, the operating temperature is crucial. At low temperatures, some sensors produce high responses, but at higher temperatures, other sensors produce high responses. As a result, the effect of the operating temperature on the sensitivity of thin films is being explored with the goal of reducing the operating temperature to the smallest achievable value. A constant resistance value for a sensor is defined as the temperature at which the resistance of the sensor reaches a constant value, designated as the operating temperature.

The gas sensitivity experiments were carried out at temperatures ranging from ambient temperature to 65 °C, having a ramp of 5 °C. The results reveal that at a temperature of 40 °C, sensitivity is very much promising and results in an increase in its sensitivity. It is also clear from the results that the sensitivity of films decreases as the working temperature increases. The highest peak values are observed at specific temperatures known as optimal temperatures, and the values decrease as the temperature is raised further. This explains why the correlations between sensitivity and temperature for semiconductor metal oxide gas sensors take on the shape of a volcano.

The ideal temperature was found to be 40 °C, while the reaction at surrounding temperatures was reducing in manner. It has been discovered that the maximal sensitivity of 145.15 for NO gas was achieved at an operating temperature of 40 °C for a 60 nm MoS2 film. It indicates that the chemical reactivity is good at optimized temperature. It has also been understood that rise and fall in sensitivity correspond to the adsorption and desorption of the gas, respectively. It was also reported that surface porosity, surface area as well as the faster rate of NO oxidation at 40 °C for a film indicate a higher sensitivity. Also, the highest sensitivity of 40 nm thick MoS2 film to NO gas was observed to be 76.50 percent and the maximum sensitivity of a 20 nm MoS2 film to NO gas was observed to be 19.4 percent at 40 °C.

According to another exemplary embodiment of the invention, FIG. 10 refers to a graphical representation 1002 of the influence of the MoS2 film thickness and NO gas sensor response. In one embodiment herein, the thickness influence on sensor response. The size, shape, thickness, morphology, and hybrid structure of the MoS2 film have a significant impact on the gas sensing capabilities of the device. Among all sensing properties, the impact of thickness is one of the crucial to optimize. In order to accomplish this, MoS2 thin films, with thicknesses ranges are 20 nm, 40 nm, and 60 nm, have been deposited using RF sputtering. The sensitivity test revealed that all thin film samples reacted to sense NO gas in ascending order. Moreover, all parameters such as flow rate, ppm level of gas, and temperature were maintained fixed in the gas testing chamber.

In one embodiment herein, the relationship between the thicknesses of the MoS2 sensing layer and the sensitivity of the NO gas sensor. In this study, it was discovered that the highest sensitivity of a 20 nm MoS2 film to NO gas was 22.87 percent, whereas the maximum sensitivity of a 40 nm MoS2 film with a Si substrate was 76.50 percent. The highest sensitivity, however, was obtained using a 60 nm MoS2 film, which had a sensitivity of 145.15 for nitric oxide gas. Even at low temperatures, all thin films exhibit high sensitivity. In addition, it was discovered that the sensitivity of the films and the thickness of the films are both exactly proportional to one another in the presence of the NO gas.

According to another exemplary embodiment of the invention, FIG. 11 refers to a graphical representation 1102 of the response time for MoS2 films at different thickness for 103 ppm NO gas detection. In one embodiment herein, the two parameters are crucial while measuring the response of any gas sensor, namely response time and recovery time. Measuring response time is the time required to achieve 90 percent of its maximum gas response after introducing analyte gas into the test chamber, whereas the recovery time is the time required for the sensor to achieve 10 percent of its maximum gas response after analysed gas is completely removed from the test chamber. In the present study analysing the sensor response time of the slope from the measured data, the sensor response time of 16 seconds was observed.

The results for response times in thin film samples with various thicknesses, which also shows the variation in gas response as a function of time in seconds for MoS2 films of various thicknesses. Moreover, the MoS2 thin film with a 20 and 40 nm thickness layer has the same response time of 17 seconds. During testing, a constant flow rate of NO gas was maintained throughout experiments. These results indicate that MoS2 devices with a 60 nm thickness had greater response even at low temperatures than other devices reported. A fast response time is necessary for real-world situations when compared to recovery time.

In one embodiment herein, the film thickness is a significant parameter for ‘‘thin film’’ sensors, as it impacts their primary operational properties, such as sensor responsiveness, rate of response and working temperature among others. The RF-magnetron sputtering of MoS2 films of various thicknesses (20 nm, 40 nm, and 60 nm) has been successfully deposited to detect nitric oxide (NO) gas, resulting in the detection of NO gas at very high sensitivity. The synthesis of MoS2 was validated by using X-ray diffraction and SEM measurements.

The MoS2 film surface reactions determine the sensitivity, whereas the gas diffusion process occurs within the gas sensing material. The different MoS2 thickness films produced various sensitivities. The high responsiveness to NO gas at a concentration of 103 ppm and a fast response time of 16 seconds, coated films with a thickness of 60 nm had a slow recovery time compared to other response times. As a result, the MoS2 based gas sensor exemplifies a diverse approach to constructing an optimistic, simple, and low-cost sensor for detecting NO gas in our environment.

Numerous advantages of the present disclosure may be apparent from the discussion above. In accordance with the present disclosure, the proposed method that integrated with MoS2 thin films with a thickness optimized for NO gas detection (around 60 nm), allows for sensitive detection of NO gas molecules. The proposed method that that leverages the unique properties of MoS2 thin films, with tow-dimensional nanomaterial for gas sensing applications.

The proposed method utilizes radiofrequency (RF) sputtering, and scalable thin-film deposition techniques, which facilitate cost-effective mass production. The proposed method that exhibits a rapid response time (around 16 seconds) upon exposure to NO gas, making it suitable for real-time monitoring applications. The proposed method utilized thin films and potentially compatible flexible substrates allows for the development of miniaturized and portable NO gas sensing devices.

It will readily be apparent that numerous modifications and alterations can be made to the processes described in the foregoing examples without departing from the principles underlying the invention, and all such modifications and alterations are intended to be embraced by this application.
, Claims:CLAIMS:
I / We Claim:
1. A method for detecting nitric oxide (NO) gas, comprising:
depositing a molybdenum disulphide (MoS2) thin film onto a substrate using a radio frequency (RF) sputtering process;
exposing the MoS2 thin film to NO gas at an operating temperature of about 40 ?C;
measuring a change in electrical properties of the MoS2 thin film upon exposure to NO gas; and
correlating the change in the electrical properties measured to the presence of NO gas.
2. The method as claimed in claim 1, wherein the substrate is selected from a group consisting of silicon wafers, alumina (Al2O3), and other materials compatible with the RF sputtering process.
3. The method as claimed in claim 2, wherein the RF power is configured to set within a range of 100 watts (W) to 500 W to achieve the desired film growth rate and properties.
4. The method as claimed in claim 1, wherein the thickness of the MoS2 thin film is selected from a range of thicknesses for optimized NO gas sensing sensitivity.
5. The method as claimed in claim 1, wherein the MoS2 thin film is deposited by a method selected from the group consisting of radiofrequency (RF) sputtering and other suitable thin-film deposition techniques.
6. The method as claimed in claim 1, wherein the change in the electrical properties indicates the presence of NO gas with improved sensitivity compared to MoS2 thin film with non-optimized thickness.
7. The method as claimed in claim 1, wherein the thickness of the MoS2 thin film ranges from 20 nm, 40 nm, and 60 nm (nanometre).
8. The method as claimed in claim 1, wherein the method is configured to utilize scanning electron microscopy (SEM) to analyze the morphology surface of the deposited MoS2 thin film, ensuring the film is uniform, continuous, and free of detects.
9. The method as claimed in claim 1, wherein the method is configured to utilize X-ray diffraction (XRD) to determine the crystalline structure of the MoS2 thin film, verifying the MoS2 as the desired crystalline phase for optimal gas sensing performance.