A spectral shift type hydrogen sensor and a method for manufacturing the same

Abstract

The application discloses a spectrum shift type hydrogen sensor and a preparation method thereof, and comprises a silicon substrate, a suspended micro-bridge formed by local etching and releasing of the silicon substrate, and a nanowire array arranged on the suspended micro-bridge, wherein the nanowire sensitive structure in the nanowire array comprises, from inside to outside, a gold core, a palladium shell layer coated on the periphery of the gold core, an air gap located outside the palladium shell layer, an annular gold shell layer arranged around the air gap, and a porous alumina filling layer reserved in the final device and filled outside the annular gold shell layer; a temperature control circuit is connected with the suspended micro-bridge and used for controlling the working temperature of the suspended micro-bridge; wherein the nanowire sensitive structure is subjected to plasmonic resonance spectrum peak displacement under the action of hydrogen, the air gap and the annular gold shell layer form a radial coupling cavity for amplifying the readout amplitude of the spectrum peak displacement. The application can realize high-sensitivity, fast-recovery and high-stability hydrogen spectrum detection.

Description

Technical Field

[0001] This invention relates to a spectral shift type hydrogen sensor and its fabrication method, belonging to the technical field of hydrogen sensing and micro / nano photonic devices. Background Technology

[0002] Hydrogen possesses high energy density, clean combustion products, and wide availability, making it a promising candidate for applications in hydrogen-powered transportation, energy storage, power systems, petrochemicals, and semiconductor manufacturing. However, hydrogen diffuses rapidly, has a low ignition energy, and a wide explosive limit range, meaning that leaks can easily lead to combustion or explosions. Therefore, developing highly sensitive, reliable hydrogen sensors suitable for long-term online operation is of great significance.

[0003] Existing hydrogen sensors mainly include resistive, electrochemical, thermal conductivity, and optical types. Among them, optical hydrogen sensors have advantages such as intrinsically safe detection, resistance to electromagnetic interference, remote readout, and suitability for operation in complex environments. Palladium and its alloys are often used as hydrogen-sensitive layers due to their reversible adsorption and hydrogenation properties. When hydrogen acts on palladium or palladium alloy nanostructures, it causes changes in their dielectric constant, plasmon resonance conditions, and local electromagnetic field distribution, resulting in peak shifts in the reflection, transmission, or scattering spectra.

[0004] Existing technologies still generally suffer from the following problems: the local field enhancement capability of single palladium nanostructures or ordinary palladium alloy nanostructures is limited, the hydrogen-induced peak shift amplitude is relatively small, and the low-concentration detection and high-resolution readout capabilities are insufficient; the palladium hydrogen absorption and dehydrogenation processes are prone to hysteresis and slow recovery, which affects repeatability and stability during cyclic detection; conventional planar devices have weak thermal isolation capabilities, and environmental temperature fluctuations can easily cause signal drift, making it difficult to balance fast recovery and low-power operation; some template-assisted nanostructures require template removal or secondary transfer after fabrication, which can easily introduce problems such as morphological damage, structural inconsistency, and decreased packaging reliability. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a spectral shift type hydrogen sensor and its preparation method, which can achieve highly sensitive, fast-recovery, and highly stable hydrogen spectral detection. To achieve the above objective, this invention employs the following technical solution:

[0006] In a first aspect, the present invention provides a spectral shift type hydrogen sensor, comprising:

[0007] Silicon substrate;

[0008] Suspended microbridges are formed by localized etching of the silicon substrate;

[0009] A nanowire array is disposed on the suspended microbridge. The nanowire sensitive structure in the nanowire array, from the inside out, includes: a gold core, a palladium shell layer covering the periphery of the gold core, an air gap located outside the palladium shell layer, an annular gold shell layer disposed around the air gap, and a porous alumina filling layer retained in the final device. The porous alumina filling layer fills the outside of the annular gold shell layer.

[0010] A temperature control circuit, connected to the suspended microbridge, is used to control the operating temperature of the suspended microbridge;

[0011] The nanowire sensitive structure undergoes a plasmonic resonance spectral peak shift under the action of hydrogen gas, and the air gap forms a radial coupling cavity with the annular gold shell layer to amplify the readout amplitude of the spectral peak shift.

[0012] In conjunction with the first aspect, the suspended microbridge may optionally be a cantilever beam structure or a bridge structure.

[0013] In conjunction with the first aspect, optionally, the diameter of the gold core is 50-70 nm, the thickness of the palladium shell is 3-5 nm, the width of the air gap is 10 nm, and the thickness of the annular gold shell is 20 nm.

[0014] In conjunction with the first aspect, optionally, the porous alumina filling layer is formed by anodizing an aluminum layer with a thickness of 200-500 nm.

[0015] In conjunction with the first aspect, optionally, the porous alumina filling layer serves as a support layer and stabilizing layer for the nanowire sensitive structure in the final device.

[0016] In conjunction with the first aspect, optionally, the temperature control circuit includes a heating resistor, a temperature sensing resistor, and a feedback control unit disposed on the suspended microbridge.

[0017] The feedback control unit adjusts the heating power of the heating resistor based on the temperature signal measured by the temperature measuring resistor, so that the nanowire sensitive structure is maintained at the set operating temperature.

[0018] In conjunction with the first aspect, optionally, the set operating temperature is used to promote the dehydrogenation of the palladium shell.

[0019] In a second aspect, the present invention provides a method for preparing the spectral shift type hydrogen sensor described in the first aspect, comprising:

[0020] S1, depositing a gold underlayer and an aluminum layer on the surface of a silicon substrate;

[0021] S2, the aluminum layer is anodized and the pores are enlarged to form a porous alumina template;

[0022] S3, gold nuclei are formed by depositing gold in the porous alumina template channels;

[0023] S4, a palladium shell layer is formed on the outer periphery of the gold core;

[0024] S5, enlarge the pores of the template after the palladium shell layer is formed to form an air gap located on the outside of the palladium shell layer;

[0025] S6, an annular gold shell layer is formed on the surface of the hole wall outside the air gap;

[0026] S7. The silicon substrate is micromachined to form a suspended microbridge, and a temperature control circuit is integrated to obtain the spectral shift type hydrogen sensor.

[0027] In conjunction with the second aspect, optionally, the thickness of the gold base layer in step S1 is 10 nm, the thickness of the aluminum layer is 200–500 nm; the diameter of the gold core in step S3 is 50–70 nm; the thickness of the palladium shell layer in step S4 is 3–5 nm; the width of the air gap in step S5 is 10 nm; and the thickness of the annular gold shell layer in step S6 is 20 nm.

[0028] In conjunction with the second aspect, optionally, the annular gold shell layer described in step S6 is formed by chemical plating after activating the surface of the hole wall, and the porous alumina filling layer is retained in the final device after step S7.

[0029] Compared with the prior art, the beneficial effects achieved by the spectral shift type hydrogen sensor and its preparation method provided in this embodiment of the invention include:

[0030] This invention includes: a silicon substrate; a suspended microbridge formed by local etching of the silicon substrate; and a nanowire array disposed on the suspended microbridge. The suspended microbridge provided by this invention can effectively isolate the nanowire sensing structure from the silicon substrate, reduce heat diffusion to the substrate, and reduce the heating power consumption of the temperature control circuit. The suspended structure of the suspended microbridge of this invention can reduce the influence of substrate stress on the sensitive area, which helps to improve the mechanical stability and signal consistency of the sensor.

[0031] The nanowire sensitive structure in the nanowire array of this invention comprises, from the inside out: a gold core, a palladium shell layer surrounding the gold core, an air gap located outside the palladium shell layer, an annular gold shell layer surrounding the air gap, and a porous alumina filling layer. This invention uses the gold core as the internal plasmon resonance center and the palladium shell layer as the hydrogen-sensitive layer. The direct contact between the gold core and the palladium shell layer can convert the hydrogen-induced dielectric constant change into a change in resonance conditions. The annular gold shell layer, together with the gold core and the palladium shell layer, constitutes a coaxial plasmon coupling system. The air gap provides a precise nanometer-scale radial coupling distance, amplifying the hydrogen-induced spectral resonance peak shift amplitude and improving the sensor's detection sensitivity and resolution for low-concentration hydrogen.

[0032] The nanowire sensing structure of this invention exhibits plasmon resonance spectral peak shift under the influence of hydrogen gas. The air gap and the annular gold shell form a radial coupling cavity, which amplifies the readout amplitude of the spectral peak shift. The radial coupling cavity formed by the air gap and the annular gold shell can strongly confine the local electromagnetic field to the gap region where the palladium shell is located, causing a significant shift in the spectral peak position due to a small dielectric change in the palladium shell. Compared with sensors without air gaps or double-layer gold structures, the peak shift readout amplitude of this invention can be improved by several times, which is beneficial for signal identification in subsequent spectral demodulation systems.

[0033] In this invention, the porous alumina filling layer is retained in the final device and fills the outer side of the annular gold shell layer. As a natural porous template, the porous alumina layer not only provides mechanical support and a confined growth environment for the nanowire sensitive structure, preventing the nanowires from collapsing or agglomerating, but the porous structure also allows hydrogen to diffuse rapidly to the surface of the palladium shell layer. At the same time, as a thermal isolation auxiliary layer, it further reduces the heat loss of the suspended microbridge. Retaining the porous alumina filling layer also avoids the structural damage and process complexity caused by removing the template in traditional processes, and improves the consistency and long-term stability of device fabrication.

[0034] The temperature control circuit provided by this invention is connected to a suspended microbridge and is used to control the operating temperature of the suspended microbridge. By performing closed-loop temperature regulation on the sensitive area, this invention can effectively suppress spectral baseline drift caused by ambient temperature fluctuations and ensure the output stability of the sensor in a wide temperature range. Setting an appropriate operating temperature can promote the rapid desorption of hydrogen in the palladium shell, significantly shorten the recovery time of the sensor after hydrogen removal, and improve the repeatability and reliability of cyclic detection.

[0035] In summary, the spectral shift type hydrogen sensor provided by this invention has the advantages of high sensitivity, large peak shift readout amplitude, fast recovery speed, small baseline drift, good structural stability, and suitability for chip integration, which can meet the actual needs of the field of hydrogen energy safety monitoring for high-performance hydrogen sensors. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the overall structure of a spectral shift type hydrogen sensor provided in Embodiment 1 of the present invention;

[0037] Figure 2 This is an axial schematic diagram of a single nanowire sensitive structure in a spectral shift type hydrogen sensor provided in Embodiment 1 of the present invention;

[0038] Figure 3 This is a schematic diagram of the radial cross-section of a single nanowire sensitive structure in a spectral shift type hydrogen sensor provided in Embodiment 1 of the present invention;

[0039] Figure 4 This is a process flow diagram of a method for preparing a spectral shift type hydrogen sensor provided in Embodiment 2 of the present invention.

[0040] In the picture:

[0041] 1. Silicon substrate; 2. Suspended microbridge; 3. Gold base layer; 4. Porous alumina filling layer; 5. Gold core;

[0042] 6. Palladium shell; 7. Air gap; 8. Ring-shaped gold shell; 9. Heating resistor. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0044] Example 1:

[0045] like Figure 1 As shown, this embodiment provides a spectral shift type hydrogen sensor, including: a silicon substrate 1, a suspended microbridge 2 formed by local etching of the silicon substrate, a nanowire array disposed on the suspended microbridge 2, and a temperature control circuit connected to the suspended microbridge 2.

[0046] like Figure 1 As shown, the nanowire array consists of multiple nanowire sensitive structures arranged at a certain period. Figure 2 and Figure 3 As shown, each nanowire sensing structure, viewed from the radial section, consists of, from the inside out: a gold core 5, a palladium shell 6 surrounding the gold core 5, an air gap 7 located outside the palladium shell 6, a ring-shaped gold shell 8 surrounding the air gap 7, and a porous alumina filling layer 4 retained in the final device. The porous alumina filling layer 4 fills the outside of the ring-shaped gold shell 8, encapsulating all the nanowire sensing structures in the nanowire array together, serving both as the outer medium of each nanowire and as the continuous substrate of the entire sensing array.

[0047] In some embodiments, the nanowire array is arranged in a regular hexagonal pattern, and the array density is optimized according to the target working band and the spectral readout system, for example, the aperture spacing is 100-200 nm.

[0048] The suspended microbridge 2 is formed by local etching of the silicon substrate 1. The function of the suspended microbridge 2 is to thermally isolate the sensor sensitive area from the silicon substrate, reduce the heat conduction between the nanowire sensitive area and the silicon substrate, so that the temperature control circuit can maintain the constant temperature of the sensitive area with lower power consumption; at the same time, the suspended structure can also buffer the influence of substrate stress on the sensitive area, which helps to improve the mechanical stability and signal consistency of the sensor.

[0049] In this embodiment, the suspended microbridge 2 is a cantilever beam structure fixed at one end, or a bridge structure fixed at both ends and supported at both ends.

[0050] Preferably, the suspended microbridge 2 is formed by partial release from the silicon substrate 1 using silicon micromachining technology.

[0051] The temperature control circuit includes a heating resistor 9 mounted on the suspended microbridge 2, a temperature sensing resistor, and a feedback control unit. The feedback control unit adjusts the heating power of the heating resistor 9 based on the temperature signal measured by the temperature sensing resistor, thereby maintaining the nanowire array at the set operating temperature.

[0052] The set operating temperature is usually chosen to be a value that can promote the dehydrogenation of the palladium shell without being too high, so as to shorten the recovery time of the sensor after the hydrogen is removed and improve the stability of the cycle detection.

[0053] In this embodiment, the operating temperature is set to 40–80°C.

[0054] In this embodiment, the dimensions of each structural layer are as follows:

[0055] Gold nucleus 5 diameter: 50-70 nm;

[0056] Palladium shell layer 6 thickness: 3–5 nm;

[0057] Air gap 7 width: 10nm;

[0058] The ring-shaped gold shell layer is 20 nm thick.

[0059] The thickness of the aluminum layer in the porous alumina filling layer 4 is 200–500 nm.

[0060] The porous alumina filling layer 4 is formed by anodic oxidation of the deposited aluminum layer and is completely retained in the final device, serving as a support and stabilizing layer for the nanowire sensitive structure.

[0061] Specifically, the porous alumina filling layer 4 serves as a support layer for the nanowire sensitive structure in the device. Since the nanowires are extremely thin, they are prone to collapsing or breaking during the bending of the suspended microbridge or subsequent encapsulation process without rigid support. The continuous skeleton structure of the porous alumina provides mechanical constraints and support for each nanowire, enabling the nanowire array to maintain an upright and uniform shape.

[0062] Specifically, the porous alumina filling layer 4 serves as a stabilizing layer for the nanowire-sensitive structure in the device. In traditional processes, the porous alumina template is often dissolved and removed, causing the nanowires to lose their fixation and collapse. This invention intentionally retains the porous alumina template, improving the long-term structural stability of the device and the consistency of batch production. In addition, the low thermal conductivity of porous alumina also contributes to thermal isolation and reduces heating power consumption.

[0063] When the sensor is working, incident light illuminates the nanowire array region. Since the distance between the gold core 5 and the annular gold shell 8 is only the width of the air gap 7, extremely strong plasmon radial coupling is formed between the two metal layers, and the electric field energy is highly confined within the air gap where the palladium shell 6 is located.

[0064] In a hydrogen-free air environment, the palladium shell is in a metallic state with a known dielectric constant, and the plasmon resonance peak is located at the initial wavelength λ0.

[0065] When hydrogen is present in the environment, hydrogen molecules rapidly diffuse through the nanopores of the porous alumina filling layer 4 to the surface of the palladium shell layer 6. After absorbing hydrogen, the palladium shell layer 6 undergoes a phase transition or a change in its dielectric constant, forming palladium hydride. This significant change in the material's complex dielectric constant alters the effective refractive index of the radial coupling cavity between the gold core 5 and the annular gold shell layer 8, causing a shift in the position of the plasmon resonance peak, denoted as Δλ. Since the electric field energy is mainly concentrated in the air gap 7 and the palladium shell layer 6 region, even a small change in the dielectric constant of the palladium shell layer 6 can cause a large Δλ. Therefore, the radial coupling cavity formed by the air gap 7 and the annular gold shell layer 8 amplifies the spectral peak shift readout amplitude. By measuring Δλ using a high-resolution spectrometer and pre-calibrating the relationship between Δλ and hydrogen concentration, quantitative detection of hydrogen concentration is achieved.

[0066] In this embodiment, the externally arranged annular gold shell layer, together with the gold core and palladium shell layer, constitutes a coaxial plasmon coupling system. The air gap can provide a precise nanometer-scale radial coupling distance, amplifying the amplitude of the hydrogen-induced spectral resonance peak shift, and improving the sensor's detection sensitivity and resolution for low-concentration hydrogen. The radial coupling cavity formed by the air gap and the annular gold shell layer can strongly confine the local electromagnetic field to the gap region where the palladium shell layer is located, causing a significant shift in the spectral peak position due to the small dielectric change of the palladium shell layer. Compared with sensors without air gaps or double-layer gold structures, the peak shift readout amplitude of this embodiment can be improved by several times, which is beneficial to the signal recognition of the subsequent spectral demodulation system.

[0067] Meanwhile, the temperature control circuit keeps the nanowire array at the set operating temperature, which can eliminate the interference of ambient temperature fluctuations on the dielectric constant and resonance peak position of the palladium shell, effectively suppress spectral baseline drift caused by ambient temperature fluctuations, and ensure the output stability of the sensor in a wide temperature range. It can also promote the rapid dehydrogenation of the palladium shell after hydrogen removal, significantly shorten the recovery time of the sensor after hydrogen removal, prepare for the next detection, and improve the repeatability and reliability of cyclic detection.

[0068] Example 2:

[0069] Based on the spectral shift type hydrogen sensor provided in Embodiment 1, this embodiment provides a method for preparing a spectral shift type hydrogen sensor.

[0070] like Figure 4 As shown, the specific steps include the following:

[0071] S1: Deposit a gold underlayer and an aluminum layer on the surface of a silicon substrate.

[0072] A silicon wafer is selected as the silicon substrate 1, and a gold underlayer 3 and an aluminum layer are deposited on its surface. The thickness of the gold underlayer 3 is preferably 10 nm, and the thickness of the aluminum layer is preferably 200–500 nm.

[0073] The gold base layer 3 is formed by magnetron sputtering, electron beam evaporation or thermal evaporation, and the aluminum layer is formed by magnetron sputtering or evaporation.

[0074] S2: The aluminum layer is anodized and the pores are expanded to form a porous alumina template.

[0075] The aluminum layer is anodized to form a regularly arranged porous alumina layer. Then, a first pore enlargement process is performed to ensure uniform pore diameter, and the pore size is adjusted to the required dimensions to obtain a template structure suitable for subsequent metal deposition.

[0076] In some embodiments, anodizing of the aluminum layer is performed by applying a suitable voltage in an oxalic acid or phosphoric acid electrolyte, followed by a first pore-expanding process using a phosphoric acid solution.

[0077] S3: Gold nuclei are formed by depositing gold within the pores of a porous alumina template.

[0078] Using the gold substrate 3 as a conductive layer, gold was deposited in the porous alumina template pores by electrochemical deposition to form the gold core 5.

[0079] By controlling the deposition time and current density, the diameter of gold core 5 was controlled within the range of 50–70 nm.

[0080] S4: A palladium shell is formed around the gold core.

[0081] The template after the gold core 5 is formed undergoes a second pore enlargement, creating a first annular deposition space between the outer periphery of the gold core 5 and the pore wall; then palladium is deposited in this space to form a palladium shell layer 6 covering the outer periphery of the gold core 5. The thickness of the palladium shell layer 6 is 3–5 nm.

[0082] S5: Expand the pores in the template after the palladium shell is formed to create an air gap on the outside of the palladium shell.

[0083] The template after forming the palladium shell layer 6 is subjected to a third pore enlargement, creating a second annular gap between the outer surface of the palladium shell layer 6 and the pore wall. This gap serves as the air gap 7. The width of the air gap 7 is controlled to be 10 nm.

[0084] S6: A ring-shaped gold shell layer is formed on the surface of the hole wall outside the air gap.

[0085] The inner wall surface of the channel after step S5 is activated, and then gold is deposited on the surface of the channel using a chemical plating method to form a ring-shaped gold shell layer 8.

[0086] The thickness of the annular gold shell layer 8 is controlled to be 20nm.

[0087] Before electroless plating, a gold seed layer needs to be formed on the inner wall surface of the channel to ensure uniform deposition.

[0088] In some embodiments, the activation treatment of the inner wall surface of the channel includes: sensitization and activation with a tin salt or palladium salt solution.

[0089] S7: Micromachining is performed on the silicon substrate to form a suspended microbridge, and a temperature control circuit is integrated to obtain a spectral shift type hydrogen sensor.

[0090] The silicon substrate 1 is micromachined to form a suspended microbridge 2. A heating resistor 9 and a temperature sensing resistor 10 are then fabricated on the suspended microbridge 2 and connected to a feedback control circuit to obtain the final device. Throughout the process, the porous alumina template is not removed and remains as a filler layer in the final device.

[0091] In some embodiments, micromachining of the silicon substrate 1 includes back-side deep silicon etching or front-side release processes. Heating resistors 9 and temperature sensing resistors are fabricated on the suspended microbridges 2 by sputtering platinum or nickel-chromium alloy and then patterning them using photolithography.

[0092] Example 3:

[0093] This embodiment verifies the structural advantages of the spectral shift type hydrogen sensor provided in Embodiment 1 by setting up a comparison sample.

[0094] In this embodiment, a set of process parameters for a spectral shift type hydrogen sensor provided in Embodiment 1 are selected, specifically: gold base thickness 10nm, aluminum layer thickness 300nm, gold core diameter 60nm, palladium shell layer thickness 4nm, air gap width 10nm, annular gold shell layer thickness 20nm, and nanowire array period 120nm.

[0095] The sensor prepared using these parameters typically responds to 1% hydrogen-containing air as follows: peak shift of approximately 35 nm, response time to reach 90% stable peak shift of <2 seconds, recovery time to return to within 90% of baseline of <5 seconds, and initial baseline drift of less than 2 nm after 100 cycles of testing.

[0096] The comparison samples include:

[0097] Comparison sample 1 contains only gold / palladium core-shell nanowires, without a ring-shaped gold shell layer and air gaps;

[0098] Comparative sample 2 has a gold / palladium core-shell and a ring-shaped gold shell layer, but the porous alumina filling layer was removed after preparation.

[0099] In contrast, sample 3 fabricated a nanowire array on a conventional planar silicon substrate without using suspended microbridges and closed-loop temperature control.

[0100] The sensor manufactured in this embodiment and the comparison sample were tested for hydrogen response.

[0101] The test conditions were room temperature and 1% hydrogen-containing air. The spectral peak shift, response time, recovery time, and baseline drift after multiple cycles were recorded.

[0102] Compared to sample 1, which exhibits a peak shift of less than 5 nm under the same hydrogen concentration, indicating low sensitivity, the sensor fabricated in this embodiment shows a significantly greater peak shift than sample 1. This demonstrates that the air gap and the annular gold shell contribute to plasmon enhancement.

[0103] Compared to the sample with its collapsed 2-nanometer wire array, poor device consistency, and large baseline drift, the sensor fabricated in this embodiment exhibits a more stable baseline and better device consistency, indicating that retaining the porous alumina filling layer is beneficial for structural stability and mass production.

[0104] Compared to sample 3, which had a recovery time >30 seconds and a baseline drift >10 nm for every 10°C change in ambient temperature, the sensor manufactured in this embodiment has a shorter recovery time and smaller output signal fluctuations under different ambient temperatures, demonstrating the combined advantages of the suspended microbridge and closed-loop temperature control.

[0105] In summary, the spectral shift type hydrogen sensor provided by this invention has the advantages of high sensitivity, large peak shift readout amplitude, fast recovery speed, small baseline drift, good structural stability, and suitability for chip integration, which can meet the actual needs of the field of hydrogen energy safety monitoring for high-performance hydrogen sensors.

[0106] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A spectral shift type hydrogen sensor, characterized in that, include: Silicon substrate; Suspended microbridges are formed by localized etching of the silicon substrate; A nanowire array is disposed on the suspended microbridge. The nanowire sensitive structure in the nanowire array, from the inside out, includes: a gold core, a palladium shell layer covering the periphery of the gold core, an air gap located outside the palladium shell layer, an annular gold shell layer disposed around the air gap, and a porous alumina filling layer retained in the final device. The porous alumina filling layer fills the outside of the annular gold shell layer. A temperature control circuit, connected to the suspended microbridge, is used to control the operating temperature of the suspended microbridge; The nanowire sensitive structure undergoes a plasmonic resonance spectral peak shift under the action of hydrogen gas, and the air gap forms a radial coupling cavity with the annular gold shell layer to amplify the readout amplitude of the spectral peak shift.

2. The spectral shift type hydrogen sensor according to claim 1, characterized in that, The suspended microbridge is a cantilever beam structure or a bridge structure.

3. The spectral shift type hydrogen sensor according to claim 1, characterized in that, The diameter of the gold core is 50-70 nm, the thickness of the palladium shell is 3-5 nm, the width of the air gap is 10 nm, and the thickness of the annular gold shell is 20 nm.

4. The spectral shift type hydrogen sensor according to claim 1, characterized in that, The porous alumina filling layer is formed by anodizing an aluminum layer with a thickness of 200-500 nm.

5. The spectral shift type hydrogen sensor according to claim 4, characterized in that, The porous alumina filling layer serves as a support and stabilizing layer for the nanowire sensitive structure in the final device.

6. The spectral shift type hydrogen sensor according to claim 1, characterized in that, The temperature control circuit includes a heating resistor, a temperature sensing resistor, and a feedback control unit disposed on the suspended microbridge. The feedback control unit adjusts the heating power of the heating resistor based on the temperature signal measured by the temperature measuring resistor, so that the nanowire sensitive structure is maintained at the set operating temperature.

7. The spectral shift type hydrogen sensor according to claim 6, characterized in that, The set operating temperature is used to promote the dehydrogenation of the palladium shell.

8. A method for preparing a spectral shift type hydrogen sensor according to any one of claims 1 to 7, characterized in that, include: S1, depositing a gold underlayer and an aluminum layer on the surface of a silicon substrate; S2, the aluminum layer is anodized and the pores are enlarged to form a porous alumina template; S3, gold nuclei are formed by depositing gold in the porous alumina template channels; S4, a palladium shell layer is formed on the outer periphery of the gold core; S5, enlarge the pores of the template after the palladium shell layer is formed to form an air gap located on the outside of the palladium shell layer; S6, an annular gold shell layer is formed on the surface of the hole wall outside the air gap; S7. The silicon substrate is micromachined to form a suspended microbridge, and a temperature control circuit is integrated to obtain the spectral shift type hydrogen sensor.

9. The method according to claim 8, characterized in that, In step S1, the thickness of the gold base layer is 10 nm, and the thickness of the aluminum layer is 200–500 nm; in step S3, the diameter of the gold core is 50–70 nm; in step S4, the thickness of the palladium shell layer is 3–5 nm; in step S5, the width of the air gap is 10 nm; and in step S6, the thickness of the annular gold shell layer is 20 nm.

10. The method according to claim 8, characterized in that, The annular gold shell layer described in step S6 is formed by chemical plating after activating the surface of the hole wall. After step S7, the porous alumina filling layer is retained in the final device.

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