Preparation method of plasmonic micro-nano film of surface acoustic wave hydrogen sensor

Abstract

The application relates to the technical field of surface acoustic wave hydrogen sensors, and discloses a preparation method of a plasmonic micro-nano film of a surface acoustic wave hydrogen sensor, wherein the plasmonic micro-nano film is prepared on a propagation path of a surface acoustic wave device; the plasmonic micro-nano film excites plasmonic resonance effect under specific wavelength illumination, generates hot carriers, and thus actively reduces a dissociation energy barrier of hydrogen on a sensitive film surface, significantly accelerates a hydrogen dissociation, adsorption and diffusion process. Compared with a traditional hydrogen sensor which passively relies on spontaneous dissociation of hydrogen, the response speed and sensitivity are significantly improved. The plasmonic micro-nano film is prepared by using standard semiconductor processes such as photolithography, film plating, peeling and annealing, and has good compatibility and strong consistency with the surface acoustic wave device process, thereby providing a reliable path for large-scale and batch production.

Description

Technical Field

[0001] This invention relates to the field of surface acoustic wave (SAW) hydrogen sensor technology, and specifically to a method for preparing plasmonic micro / nano films for SAW hydrogen sensors. Background Technology

[0002] Currently, research on hydrogen sensing technology mainly focuses on resistive, catalytic combustion, thermal conductivity, and electrochemical types. Among these, except for the electrochemical type, the other types of sensors require heating the sensing element (>300℃) during operation to achieve low-concentration hydrogen detection and rapid response. This poses safety hazards in flammable and explosive application scenarios (such as hydrogen fuel cell vehicles and hydrogen refueling stations). Furthermore, some sensors, because they require an oxygen-rich environment, cannot be used long-term in confined spaces, limiting their application in specific scenarios.

[0003] In recent years, surface acoustic wave (SAW) gas sensors have attracted widespread attention due to their advantages such as high sensitivity, fast response, miniaturization, and room temperature operation. Existing SAW hydrogen sensors typically fabricate palladium as a gas-sensitive film layer along the propagation path of the SAW device, utilizing the dissociation of hydrogen by palladium to achieve adsorption. Changes in parameters such as film mass, conductivity, and viscoelasticity alter the sensor's operating frequency or output energy. However, this mechanism is limited by the dissociation energy barrier of the palladium surface, resulting in a long response time and low sensitivity for low concentrations of hydrogen at room temperature. Although studies have found that using gas-sensitive films with high specific surface area (such as those based on palladium nanoparticles or their composite nanomaterials) can help improve hydrogen detection performance, these materials have poor compatibility with sensor fabrication processes, and performance consistency between devices is difficult to guarantee, thus posing challenges for mass production and commercial application. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a method for fabricating plasmonic micro / nano films for surface acoustic wave (SAW) hydrogen sensors. Unlike traditional palladium films that passively rely on the spontaneous dissociation of hydrogen, the plasmonic micro / nano films introduced in this invention can generate abundant hot carriers under specific wavelength light excitation, lowering the dissociation energy barrier and thus actively promoting the hydrogen dissociation process on the sensitive layer surface, accelerating the diffusion and permeation of hydrogen atoms. The hydrogen sensor proposed in this invention achieves rapid response and high sensitivity while also possessing excellent manufacturability, meeting the demands of large-scale mass production. The plasmonic micro / nano films are fabricated using standard semiconductor processes such as photolithography, deposition, lift-off, and annealing, exhibiting good compatibility and consistency with SAW device processes, providing a reliable path for large-scale, mass production.

[0005] The embodiments of the present invention adopt the following technical solutions:

[0006] In a first aspect, the present invention provides a method for fabricating a plasmonic micro / nano film for a surface acoustic wave (SAW) hydrogen sensor. The SAW hydrogen sensor includes a SAW device and a plasmonic micro / nano film located on the propagation path of the SAW device. The surface of the plasmonic micro / nano film has a periodic micro / nano structure, and the plasmonic micro / nano film excites a plasmonic resonance effect under illumination of a specific wavelength.

[0007] The preparation method includes the following steps:

[0008] A first micro / nano structure mask is fabricated; wherein the first micro / nano structure mask covers the area outside the preset periodic micro / nano structure pattern in the propagation path region of the surface acoustic wave device;

[0009] The material of the substrate thin film is deposited using a coating process, and the material of the first micro-nano structure mask and the substrate thin film covering the first micro-nano structure mask is removed using a stripping process.

[0010] A second micro / nano structure mask is fabricated; wherein the second micro / nano structure mask is conformal to the first micro / nano structure mask.

[0011] Alloy material is deposited using a coating process, and the second micro / nano structure mask and the alloy material covering the second micro / nano structure mask are removed using a stripping process.

[0012] Annealing under a protective atmosphere forms a surface alloy between the alloy material and the substrate film.

[0013] Preferably, a first micro / nano structure mask is prepared by spin-coating photoresist and combining it with a photolithography process; the first micro / nano structure mask covers the area outside the preset periodic micro / nano structure pattern in the propagation path region of the surface acoustic wave device; the photolithography process includes ultraviolet lithography, laser direct writing lithography, or electron beam lithography.

[0014] Preferably, the material used to deposit the substrate film (palladium or platinum) is used, and the material used to remove the photoresist and the substrate film covering the photoresist is used.

[0015] Preferably, a second micro / nano structure mask is prepared by spin-coating photoresist and combining it with a photolithography process; the second micro / nano structure mask is conformal to the first micro / nano structure mask to mask the area outside the preset periodic micro / nano structure pattern in the propagation path region of the surface acoustic wave device; the photolithography process includes ultraviolet lithography, laser direct writing lithography, or electron beam lithography.

[0016] Preferably, an alloy material (at least one of gold, nickel, and copper) is deposited using a coating process, and the photoresist and the alloy material covering the photoresist are removed using a stripping process.

[0017] Preferably, the annealing process is carried out under a protective atmosphere at a temperature of 350-400°C and a holding time of 1 minute to 1 hour, so that a surface alloy is formed between the alloy material and the substrate film.

[0018] Preferably, the plasmonic micro / nano film includes a substrate film and a surface alloy; the substrate film is made of palladium or platinum; the surface alloy uses the material of the substrate film as the substrate, and the alloying material of the surface alloy is at least one of gold, nickel, and copper; thereby forming at least one of palladium-gold alloy, palladium-nickel alloy, and palladium-copper alloy, or forming at least one of platinum-gold alloy, platinum-nickel alloy, and platinum-copper alloy.

[0019] Preferably, the wavelength range of the specific wavelength illumination is 400~1100 nanometers (visible to near-infrared band).

[0020] Preferably, the specific wavelength illumination is provided by one of the following: a laser, a halogen lamp, an incandescent lamp, a light-emitting diode, or an organic light-emitting diode.

[0021] Preferably, the periodic micro / nano structure has a period of 400-1100 nanometers, a height of 50-100 nanometers, and a duty cycle of 0.2-0.8.

[0022] Preferably, the periodic micro / nano structure is a one-dimensional grating structure.

[0023] Preferably, the periodic micro / nano structure is a two-dimensional periodic array structure; the two-dimensional periodic array structure includes a square-arranged circular array structure or a triangular-arranged circular array structure.

[0024] Secondly, the present invention also provides a method for fabricating a plasmonic micro / nano film for a surface acoustic wave (SAW) hydrogen sensor. The SAW hydrogen sensor includes a SAW device and a plasmonic micro / nano film located on the propagation path of the SAW device. The surface of the plasmonic micro / nano film has a random micro / nano structure, and the plasmonic micro / nano film excites a plasmonic resonance effect under illumination of a specific wavelength.

[0025] The preparation method includes the following steps:

[0026] A third micro / nano structure mask is fabricated; wherein the third micro / nano structure mask masks the area outside the propagation path region of the surface acoustic wave device;

[0027] The substrate film and alloy material are deposited sequentially using a coating process, and the third micro / nano structure mask and the substrate film and alloy material covering the third micro / nano structure mask are removed using a stripping process.

[0028] Rapid annealing under a protective atmosphere allows the alloy material to form a surface alloy on the surface of the substrate film, resulting in random micro / nano structures.

[0029] Preferably, a third micro / nano structure mask is prepared by spin-coating photoresist and combining it with photolithography; the third micro / nano structure mask covers the area outside the propagation path region of the surface acoustic wave device; the photolithography process includes ultraviolet lithography, laser direct writing lithography or electron beam lithography.

[0030] Preferably, a substrate thin film (palladium or platinum) and an alloy material (at least one of gold, nickel, or copper) are deposited sequentially using a coating process, and the photoresist and the substrate thin film and alloy material covered on the photoresist are removed using a stripping process.

[0031] Preferably, the rapid annealing process is carried out under a protective atmosphere, with a heating rate of not less than 10°C / second, a temperature of 350~450°C, and a holding time of 1~5 minutes, so that a surface alloy is formed between the alloy material and the substrate film, and random micro / nano structures are formed through the thermal stress effect.

[0032] Preferably, the plasmonic micro / nano film includes a substrate film and a surface alloy; the substrate film is made of palladium or platinum; the surface alloy uses the material of the substrate film as the substrate, and the alloying material of the surface alloy is at least one of gold, nickel, and copper; thereby forming at least one of palladium-gold alloy, palladium-nickel alloy, and palladium-copper alloy, or forming at least one of platinum-gold alloy, platinum-nickel alloy, and platinum-copper alloy.

[0033] Preferably, the wavelength range of the specific wavelength illumination is 400~1100 nanometers (visible to near-infrared band).

[0034] Preferably, the specific wavelength illumination is provided by one of the following: a laser, a halogen lamp, an incandescent lamp, a light-emitting diode, or an organic light-emitting diode.

[0035] Preferably, the surface roughness of the random micro / nano structure is not less than 2 nanometers and the characteristic size distribution is 10~200 nanometers.

[0036] Preferably, the random micro / nano structure is a random nanoparticle or a random island structure.

[0037] This invention provides a surface acoustic wave (SAW) hydrogen sensor based on plasmonic micro / nano films. The core of this SAW hydrogen sensor lies in its sensitivity enhancement mechanism: unlike existing high specific surface area gas-sensitive films (such as palladium nanoparticles and their composites) that rely on physical adsorption, this invention utilizes the photo-induced plasmonic resonance effect to actively lower the dissociation energy barrier, thereby achieving ultrafast response and extremely high sensitivity. Simultaneously, this plasmonic micro / nano film exhibits good compatibility with the fabrication process of SAW devices, providing a reliable path for the large-scale and mass production of SAW hydrogen sensors.

[0038] This invention provides a plasmonic micro / nano film for hydrogen detection. The film, based on palladium or platinum, possesses sensitive adsorption properties for hydrogen. The film undergoes alloying and is designed with micro / nano structures, which can excite plasmonic resonance under specific wavelength light irradiation, thereby effectively reducing the dissociation and adsorption energy barrier of hydrogen and increasing the adsorption and desorption rates of hydrogen in the sensitive film.

[0039] This invention provides a method for preparing the aforementioned plasmonic micro / nano thin films. This method combines standard semiconductor processes such as photolithography, deposition, lift-off, and annealing to ensure good process compatibility between the sensitive film and the surface acoustic wave (SAW) device. The prepared plasmonic micro / nano thin films exhibit consistent hydrogen adsorption performance, and the SAW hydrogen sensor based on these plasmonic micro / nano thin films is suitable for large-scale and mass production. Attached Figure Description

[0040] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0041] Figure 1 A schematic diagram of a surface acoustic wave hydrogen sensor based on plasmonic micro / nano films according to an embodiment of the present invention is shown.

[0042] Figure 2 A micro-display image of a plasmonic micro / nano film according to Embodiment 1 of the present invention is shown;

[0043] Figure 3 The figure shows the gas-sensing test results of the surface acoustic wave hydrogen sensor based on plasmon micro / nano thin films according to Embodiment 1 of the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0045] Figure 1 This diagram illustrates the structure of a surface acoustic wave hydrogen sensor based on plasmon micro / nano films, as proposed in an embodiment of the present invention. (Refer to...) Figure 1As shown, the surface acoustic wave hydrogen sensor based on plasmon micro / nano film includes: a surface acoustic wave device 1 and a plasmon micro / nano film 2 located on the propagation path of the surface acoustic wave device 1; the plasmon micro / nano film 2 is excited by plasmon resonance under a specific wavelength of light 3.

[0046] More specifically: the surface acoustic wave device 1 includes a piezoelectric substrate 11, an input interdigital transducer 12, and an output interdigital transducer 13; a plasmonic micro / nano film 2 is fabricated on the piezoelectric substrate 11 between the input interdigital transducer 12 and the output interdigital transducer 13; the plasmonic micro / nano film 2 is irradiated with light 3 of a specific wavelength to excite the plasmonic resonance effect, thereby significantly improving the response speed and detection sensitivity to hydrogen.

[0047] The following is a detailed description of the surface acoustic wave hydrogen sensor based on plasmonic micro / nano films proposed in this invention through specific embodiments.

[0048] Example 1:

[0049] (1) Fabrication of the first micro / nano structure mask.

[0050] Photoresist was spin-coated onto the surface of the surface acoustic wave (SAW) device at 5000 rpm for 50 seconds to form a photoresist layer approximately 500 nanometers thick. Ultraviolet exposure was then performed using a photomask patterned as a one-dimensional grating structure (800 nm period, 0.5 duty cycle). The total area of ​​the outer frame of the pattern was 1 × 1 mm (the same as the area of ​​the propagation path region of the SAW device). The one-dimensional grating structure was transparent, while other areas were opaque. After exposure, development was performed to remove the photoresist from the exposed areas, thus forming a periodic one-dimensional grating structure pattern consistent with the photomask pattern within the propagation path region of the SAW device (other areas remained opaque to the photoresist).

[0051] (2) The material of the substrate film is deposited by the coating process, and the material of the first micro-nano structure mask and the substrate film covering the first micro-nano structure mask is removed by the stripping process.

[0052] Platinum material was deposited using magnetron sputtering at a power of 100 watts and a deposition rate of 5 nanometers per minute to form a 50-nanometer-thick platinum film. The film was then immersed in acetone for 30 minutes to remove the photoresist layer and the platinum material covering it, resulting in a periodic one-dimensional grating pattern on the remaining platinum film that matches the mask pattern.

[0053] (3) Fabrication of a second micro / nano structure mask.

[0054] Photoresist was spin-coated at 5000 rpm for 50 seconds to form a photoresist layer approximately 500 nanometers thick. Ultraviolet exposure was then performed using a photomask patterned as a one-dimensional grating structure (800 nm period, 0.5 duty cycle). The total area of ​​the outer frame of the pattern was 1 × 1 mm. The one-dimensional grating structure was transparent, while other areas were opaque, corresponding to the platinum thin film pattern. After exposure, development was performed to remove the photoresist from the exposed areas, thus forming a periodic one-dimensional grating structure pattern consistent with the platinum thin film pattern (other areas remained opaque by photoresist).

[0055] (4) The alloy material is deposited by coating process and the second micro-nano structure mask and the alloy material covered on the second micro-nano structure mask are removed by stripping process.

[0056] Gold material was deposited using magnetron sputtering at a sputtering power of 100 watts and a deposition rate of 5 nanometers per minute to form a 5-nanometer-thick gold film. The film was then immersed in acetone for 30 minutes to remove the photoresist layer and the gold material covering it, allowing the remaining gold film to conformally coat the platinum film surface.

[0057] (5) Annealing under a protective atmosphere to form a surface alloy between the alloy material and the substrate film material.

[0058] Place the quartz boat into the tubular furnace and seal it. Connect the gas line, turn on the mechanical pump, and evacuate the furnace tubes to a low vacuum (10). -2 The tube furnace (below the specified value) is filled with high-purity nitrogen. The "vacuum-nitrogen filling" process is repeated at least three times to ensure that oxygen and water vapor are fully removed. Under a continuous, slow nitrogen flow (approximately 50 sccm), the temperature is increased to 400°C at a rate of 5°C / min and held at 400°C for 1 hour. After holding, the heating power is turned off, and the tube furnace is allowed to cool naturally. Nitrogen flow is maintained until the temperature drops below 100°C, ultimately forming a platinum alloy.

[0059] Figure 2 A micro-display image of the plasmonic micro / nano film of Example 1 is shown.

[0060] Hydrogen detection was performed using the surface acoustic wave (SAW) hydrogen sensor prepared in Example 1. The workflow was as follows: The SAW hydrogen sensor was installed in the gas chamber to be tested, ensuring a reliable connection between its lead bonding points and the external measurement circuit. A light-emitting diode (LED) with a center wavelength of 800 nm was used as the excitation source. This light source was fixed outside the gas chamber, with its light outlet aligned with the gas chamber window, ensuring that the light uniformly and perpendicularly illuminated the plasmon micro / nano film region along the propagation path of the SAW hydrogen sensor. During detection, the LED light source was continuously irradiated to activate the plasmon resonance effect of the film; the baseline frequency of the SAW hydrogen sensor in clean air was measured and recorded using an external circuit; the hydrogen gas to be tested was introduced into the gas chamber, the light source was continuously irradiated, and the frequency shift of the SAW hydrogen sensor was monitored in real time; after detection, the hydrogen flow was cut off while the light source was kept irradiated, or clean air was used to purge the gas chamber to accelerate the recovery of the SAW hydrogen sensor to the baseline frequency.

[0061] Figure 3 The gas-sensing test results of the surface acoustic wave (SAW) hydrogen sensor based on plasmonic micro / nano films of Example 1 are shown. It is evident that the SAW hydrogen sensor's response to 1% hydrogen gas under illumination is significantly higher than under no-illumination conditions, indicating that illumination can effectively promote the adsorption and diffusion of hydrogen gas on the surface of the plasmonic micro / nano film, thereby improving the gas-sensing performance of the SAW hydrogen sensor.

[0062] Example 2:

[0063] (1) Fabrication of the first micro / nano structure mask.

[0064] Photoresist was spin-coated onto the surface of the surface acoustic wave (SAW) device at 5000 rpm for 50 seconds to form a photoresist layer approximately 500 nanometers thick. Ultraviolet exposure was then performed using a mask patterned as a two-dimensional square circular array (800 nm period, 400 nm diameter). The total area of ​​the outer frame of the pattern was 1 × 1 mm (the same as the area of ​​the propagation path region of the SAW device). The two-dimensional square circular array was transparent, while other areas were opaque. After exposure, development was performed to remove the photoresist from the exposed areas, thus forming a periodic two-dimensional square circular array pattern consistent with the mask pattern within the propagation path region of the SAW device (other areas remained opaque).

[0065] (2) The material of the substrate film is deposited by the coating process, and the material of the first micro-nano structure mask and the substrate film covering the first micro-nano structure mask is removed by the stripping process.

[0066] Palladium material was deposited using magnetron sputtering at a power of 100 watts and a deposition rate of 5 nanometers per minute to form a 50-nanometer-thick palladium film. The film was then immersed in acetone for 30 minutes to remove the photoresist layer and the palladium material covering it. This resulted in the remaining palladium film forming a periodic two-dimensional square circular array pattern consistent with the photomask pattern.

[0067] (3) Fabrication of a second micro / nano structure mask.

[0068] Photoresist was spin-coated at 5000 rpm for 50 seconds to form a photoresist layer approximately 500 nanometers thick. Ultraviolet exposure was performed using a mask patterned as a two-dimensional square circular array (800 nm period, 400 nm diameter), with a total outer frame area of ​​1 × 1 mm. The two-dimensional square circular array was transparent, while other areas were opaque, corresponding to the palladium film pattern. After exposure, development was performed to remove the photoresist from the exposed areas, thus forming a periodic two-dimensional square circular array pattern consistent with the palladium film pattern (other areas remained opaque).

[0069] (4) The alloy material is deposited by coating process and the second micro-nano structure mask and the alloy material covered on the second micro-nano structure mask are removed by stripping process.

[0070] Gold material was deposited using magnetron sputtering at a sputtering power of 100 watts and a deposition rate of 5 nanometers per minute to form a 5-nanometer-thick gold film. The film was then immersed in acetone for 30 minutes to remove the photoresist layer and the gold material covering it, resulting in a conformal gold film that covers the palladium film surface.

[0071] (5) Annealing under a protective atmosphere to form a surface alloy between the alloy material and the substrate film material.

[0072] Place the quartz boat into the tubular furnace and seal it. Connect the gas line, turn on the mechanical pump, and evacuate the furnace tubes to a low vacuum (10). -2 The tube furnace is filled with high-purity nitrogen. The "vacuum-nitrogen filling" process is repeated at least three times to ensure that oxygen and water vapor are fully removed. Under a continuous, slow nitrogen flow (approximately 50 sccm), the temperature is increased to 350°C at a rate of 5°C / min and held at 350°C for 1 hour. After holding, the heating power is turned off, and the tube furnace is allowed to cool naturally. Nitrogen flow is maintained until the temperature drops below 100°C, ultimately forming a palladium alloy.

[0073] Hydrogen detection was performed using the surface acoustic wave (SAW) hydrogen sensor prepared in Example 2. The workflow was as follows: The SAW hydrogen sensor was installed in the gas chamber to be tested, ensuring a reliable connection between its lead bonding points and the external measurement circuit. A light-emitting diode (LED) with a center wavelength of 650 nm was used as the excitation source. This light source was fixed outside the gas chamber, with its light outlet aligned with the gas chamber window, ensuring that the light uniformly and perpendicularly illuminated the plasmon micro / nano film region along the propagation path of the SAW hydrogen sensor. During detection, the LED light source was continuously irradiated to activate the plasmon resonance effect of the film; the baseline frequency of the SAW hydrogen sensor in clean air was measured and recorded using an external circuit; the hydrogen gas to be tested was introduced into the gas chamber, the light source was continuously irradiated, and the frequency shift of the SAW hydrogen sensor was monitored in real time; after detection, the hydrogen flow was cut off while the light source was kept irradiated, or clean air was used to purge the sensor to accelerate its recovery to the baseline frequency.

[0074] Example 3:

[0075] (1) Fabrication of a third micro / nano structure mask.

[0076] Photoresist was spin-coated onto the surface of the surface acoustic wave (SAW) device at 5000 rpm for 50 seconds to form a photoresist layer approximately 500 nanometers thick. Ultraviolet exposure was then performed using a 1×1 mm square mask (the same area as the propagation path region of the SAW device), with the square transparent and the other areas blocked. After exposure, development was performed to remove the photoresist from the exposed areas, thus forming a propagation path pattern within the SAW device that matches the mask pattern (other areas remain blocked by photoresist).

[0077] (2) The substrate film and alloy material are deposited sequentially using a coating process, and the third micro-nano structure mask and the substrate film and alloy material covered on the third micro-nano structure mask are removed using a stripping process.

[0078] Palladium was deposited using magnetron sputtering at a power of 200 W and a deposition rate of 5 nm / min to form a 5 nm thick palladium film. Gold was then deposited at the same power of 200 W and a deposition rate of 5 nm / min to form a 2 nm thick gold film. The sputtering power in Example 3 was higher than that in Examples 1 and 2, which improved the surface roughness of the prepared film. The film was then immersed in acetone for 30 minutes to remove the photoresist layer, simultaneously removing the palladium and gold materials covering the photoresist layer. This resulted in the remaining gold and palladium films conformally covering the surface acoustic wave (SAW) device's propagation path region.

[0079] (3) Rapid annealing under a protective atmosphere to form a surface alloy and random micro / nano structure on the surface of the alloy material and the substrate film.

[0080] Place it in a rapid annealing furnace, turn on the mechanical pump to evacuate the furnace tubes to a low vacuum (10). - ² (below Torr). Continuously purge with high-purity nitrogen (flow rate approximately 50 sccm) to ensure complete removal of oxygen and water vapor. Maintain a constant nitrogen flow rate and rapidly heat to 400°C at a rate of 20°C / s, holding at 400°C for 1 minute. After holding, turn off the heating power and allow the annealing furnace to cool naturally. Continue nitrogen flow until the temperature drops below 100°C. During this process, the rapid heating and cooling introduce significant thermal stress, further increasing the surface roughness of the film and forming randomly distributed micro / nano structures. Simultaneously, palladium undergoes an alloying reaction with gold, ultimately forming micro / nano films with plasmon resonance properties on the surface.

[0081] Hydrogen detection was performed using the surface acoustic wave (SAW) hydrogen sensor prepared in Example 3. The workflow was as follows: The SAW hydrogen sensor was installed in the test chamber, ensuring a reliable connection between its lead bonding points and the external measurement circuit. Due to the broad plasmon resonance spectrum of the random micro / nano structure, a halogen lamp or white LED could be used as the broadband excitation source. This broadband excitation source should be fixed outside the chamber, with its light outlet aligned with the chamber window, ensuring that the light uniformly and perpendicularly illuminates the plasmon micro / nano film region along the propagation path of the SAW hydrogen sensor. During detection, the broadband excitation source was continuously irradiated to activate the plasmon resonance effect of the film; the baseline frequency of the SAW hydrogen sensor in clean air was measured and recorded using an external circuit; the hydrogen gas to be tested was introduced into the chamber, the broadband excitation source was continuously irradiated, and the frequency shift of the SAW hydrogen sensor was monitored in real time; after detection, the hydrogen flow was cut off while the broadband excitation source remained irradiated, or clean air was used for purging to accelerate the sensor's recovery to the baseline frequency.

[0082] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for fabricating plasmonic micro / nano films for a surface acoustic wave hydrogen sensor, characterized in that, The surface acoustic wave hydrogen sensor includes a surface acoustic wave device and a plasmonic micro / nano film located on the propagation path of the surface acoustic wave device. The surface of the plasmonic micro / nano film has a periodic micro / nano structure. Under illumination of a specific wavelength, the plasmonic micro / nano film excites a plasmonic resonance effect, generating abundant hot carriers and reducing the dissociation energy barrier. The plasmonic micro / nano film includes a substrate film and a surface alloy. The material of the substrate film is palladium or platinum; The surface alloy uses the material of the base film as the matrix, and the alloy material of the surface alloy is at least one of gold, nickel, and copper; The wavelength range of the specific wavelength illumination is 400~1100 nanometers; The preparation method includes the following steps: A first micro / nano structure mask is fabricated; wherein the first micro / nano structure mask covers the area outside the preset periodic micro / nano structure pattern in the propagation path region of the surface acoustic wave device; The material of the substrate thin film is deposited using a coating process, and the material of the first micro / nano structure mask and the substrate thin film covering the first micro / nano structure mask is removed using a stripping process. A second micro / nano structure mask is fabricated; wherein the second micro / nano structure mask is conformal to the first micro / nano structure mask. An alloy material is deposited using a coating process, and the second micro / nano structure mask and the alloy material covering the second micro / nano structure mask are removed using a stripping process. Annealing is performed under a protective atmosphere to form a surface alloy between the alloy material and the material of the substrate film. The holding time for the annealing process is 1 minute to 1 hour, and the annealing temperature is 350 to 400°C.

2. The method for preparing the plasmonic micro / nano film of the surface acoustic wave hydrogen sensor according to claim 1, characterized in that, The specific wavelength illumination is provided by one of a laser, a halogen lamp, an incandescent lamp, a light-emitting diode, or an organic light-emitting diode.

3. The method for preparing the plasmonic micro / nano film of the surface acoustic wave hydrogen sensor according to claim 1, characterized in that, The periodic micro / nano structure has a period of 400-1100 nanometers, a height of 50-100 nanometers, and a duty cycle of 0.2-0.

8.

4. The method for preparing the plasmonic micro / nano film of the surface acoustic wave hydrogen sensor according to claim 3, characterized in that, The periodic micro / nano structure is a one-dimensional grating structure.

5. The method for preparing the plasmonic micro / nano film of the surface acoustic wave hydrogen sensor according to claim 3, characterized in that, The periodic micro / nano structure is a two-dimensional periodic array structure; The two-dimensional periodic array structure includes a square-arranged circular array structure or a triangular-arranged circular array structure.

6. A method for fabricating plasmonic micro / nano films for a surface acoustic wave hydrogen sensor, characterized in that, The surface acoustic wave hydrogen sensor includes a surface acoustic wave device and a plasmonic micro / nano film located on the propagation path of the surface acoustic wave device. The surface of the plasmonic micro / nano film has a random micro / nano structure. The plasmonic micro / nano film is excited by plasmonic resonance under specific wavelength illumination to generate abundant hot carriers and reduce the dissociation energy barrier. The plasmonic micro / nano film includes a substrate film and a surface alloy. The material of the substrate film is palladium or platinum; The surface alloy uses the material of the base film as the matrix, and the alloy material of the surface alloy is at least one of gold, nickel, and copper; The wavelength range of the specific wavelength illumination is 400~1100 nanometers; The preparation method includes the following steps: A third micro / nano structure mask is fabricated; wherein the third micro / nano structure mask covers the area outside the propagation path region of the surface acoustic wave device; The substrate film and alloy material are deposited sequentially using a coating process, and the third micro / nano structure mask and the substrate film and alloy material covering the third micro / nano structure mask are removed using a stripping process. Rapid annealing under a protective atmosphere causes the alloy material and the substrate film to form a surface alloy and random micro / nano structure. The holding time of the rapid annealing is 1 to 5 minutes, the heating rate of the rapid annealing is not less than 10°C / second, and the temperature of the rapid annealing is 350 to 450°C.

7. The method for preparing the plasmonic micro / nano film of the surface acoustic wave hydrogen sensor according to claim 6, characterized in that, The specific wavelength illumination is provided by one of a laser, a halogen lamp, an incandescent lamp, a light-emitting diode, or an organic light-emitting diode.

8. The method for preparing the plasmonic micro / nano film of the surface acoustic wave hydrogen sensor according to claim 6, characterized in that, The surface roughness of the random micro / nano structure is not less than 2 nanometers, and the characteristic size distribution is 10~200 nanometers.

9. The method for preparing the plasmonic micro / nano film of the surface acoustic wave hydrogen sensor according to claim 7, characterized in that, The random micro / nano structure is a random nanoparticle or a random island structure.

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