Palladium-based multilayer film hydrogen sensor based on abnormal Hall effect as well as preparation method and application of palladium-based multilayer film hydrogen sensor

Abstract

The invention relates to the field of hydrogen sensors, in particular to a palladium-based multilayer film hydrogen sensor based on an abnormal Hall effect as well as a preparation method and application of the palladium-based multilayer film hydrogen sensor. The palladium-based multilayer film hydrogen sensor based on the abnormal Hall effect comprises a substrate, a film structure with a Hall rod pattern and an electrode layer which are sequentially arranged from bottom to top, the thin film structure with the Hall rod pattern sequentially comprises a Pd single-layer thin film and a (Co / Pd) X multi-layer thin film from bottom to top, wherein X represents the cycle number of the (Co / Pd) X multi-layer thin film; x is an integer from 1 to 10; in each period of the (Co / Pd) X multilayer film, an arrangement mode that the Co layer is arranged on the lower portion and the Pd layer is arranged on the upper portion is adopted. The palladium-based multilayer film hydrogen sensor based on the abnormal Hall effect has the advantages of being obvious in hydrogen detection current signal, high in environmental gas interference resistance and controllable in hydrogen detection concentration.

Description

Technical Field

[0001] The present invention relates to the field of hydrogen sensors, and in particular to a palladium-based multilayer hydrogen sensor based on an anomalous Hall effect, and a preparation method and application thereof. Background Art

[0002] Hydrogen is a highly efficient energy source with pollution-free and renewable products, and is therefore widely used in various industrial fields such as aviation, chemical industry, and metal smelting. However, since hydrogen molecules are small, colorless, and odorless, they are very likely to leak without being discovered during production, storage, and transportation. At the same time, the ignition point of hydrogen is only 585°C, and when the mixed concentration in the air is between 4% and 75%, it is easy to explode when exposed to open flames. Therefore, in response to hydrogen leaks, the research and development of hydrogen sensors with high sensitivity and fast response time is of great significance for the safe use of hydrogen energy.

[0003] At present, the main categories of hydrogen sensors include metal oxide semiconductor sensors, electrochemical hydrogen sensors, optical fiber hydrogen sensors, surface acoustic wave (SAW) hydrogen sensors, etc. However, existing technologies often have various problems in hydrogen detection: such as interference from other gases (carbon dioxide, methane, oxygen, etc.), resulting in false alarms or reduced accuracy; or high operating temperature leading to increased energy consumption and safety issues; or limited lifespan, after a limited number of cycles, the sensor material will be exhausted or fail with use; or strong environmental dependence, requiring additional calibration in temperature or humidity sensitive environments.

[0004] The detection mechanism of common hydrogen sensors usually relies on the change of hydrogen on the electrical signal, and the change of electrical signal is usually divided into two types: one is the change of the intuitive resistivity / conductivity / current caused by the electron concentration after the sensor surface contacts with hydrogen, thereby performing hydrogen reading detection; the other is the change of hydrogen on the electronic structure of the sensor material, causing the change of the abnormal Hall signal of the sensor, thereby realizing the detection of hydrogen concentration. The first type of hydrogen sensor designed based on the electron concentration mechanism has an extremely fast response speed, but it is very susceptible to interference from other gases or environmental influences, resulting in inaccurate accuracy. The second type of sensor based on electronic structure change basically does not make misjudgments, but this type of sensor has been rarely studied and has great difficulties, such as whether the difference in electrical signals in hydrogen and not in hydrogen is large enough to be distinguished. Therefore, how to design and obtain a hydrogen sensor based on electronic structure change is of great significance. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect and its preparation method and application, aiming to solve the problem that the existing hydrogen sensors are easily interfered by other gases or affected by the environment, thereby causing inaccurate accuracy.

[0006] The technical solution of the present invention is as follows:

[0007] In the first aspect of the present invention, a palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect is provided, which includes a substrate, a thin film structure with a Hall bar pattern, and an electrode layer arranged in sequence from bottom to top;

[0008] The thin film structure with a Hall bar pattern includes a Pd single-layer thin film and (Co / Pd) X multilayer thin films from bottom to top, where X represents the number of periods of the (Co / Pd) X multilayer thin films;

[0009] The X is an integer from 1 to 10;

[0010] In each period of the (Co / Pd) X multilayer thin films, the Co layer is arranged below and the Pd layer is arranged above.

[0011] Optionally, the substrate is a Gd3Sc2Ga3O 12 single crystal substrate or a silicon substrate with a SiO2 layer on its surface; the material of the electrode layer is a conductive metal.

[0012] Optionally, the thickness of the Pd single-layer thin film is 3 to 10 nm; in the (Co / Pd) X multilayer thin films, the thickness of the Co layer is 0.5 to 1.2 nm, and the thickness of the Pd layer is 3 to 10 nm.

[0013] In the second aspect of the present invention, a preparation method of the palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect according to the present invention is provided, which includes the steps:

[0014] S1. Provide a substrate, and deposit a Pd single-layer thin film and (Co / Pd) X multilayer thin films on the substrate in sequence by vacuum magnetron sputtering;

[0015] S2. Use photolithography and etching methods to etch the Pd single-layer thin film and (Co / Pd) X multilayer thin films on the substrate into a thin film structure with a Hall bar pattern;

[0016] S3. Form an electrode layer on the thin film structure with a Hall bar pattern to obtain the palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect.

[0017] Optionally, in step S1, the process of the vacuum magnetron sputtering is: under the condition of introducing argon, set the vacuum degree to be less than or equal to 1×10 -6Torr, the sputtering gas pressure is 3 - 5 mTorr, the sputtering temperature is room temperature, and the sample stage rotation speed is 10 - 40 rpm.

[0018] Optionally, in step S1, the Pd single-layer film and the Pd layer in the (Co / Pd) X multilayer film are both sputtered using a radio frequency power supply. The sputtering power of the radio frequency power supply sputtering is 40 - 60 W, and the sputtering time of the radio frequency power supply sputtering is 1 - 5 min;

[0019] The (Co / Pd) X Co layer in the multilayer film is sputtered using a direct current power supply. The sputtering power of the direct current power supply sputtering is 40 - 60 W, and the sputtering time of the direct current power supply sputtering is 15 - 60 s.

[0020] Optionally, step S2 specifically includes:

[0021] Coating photoresist on the substrate for depositing the Pd single-layer film and the (Co / Pd) X multilayer film, and performing exposure and development processing on the photoresist according to the Hall bar pattern;

[0022] Etching the substrate using ion beam etching, stripping the film not protected by the photoresist, and removing the photoresist to obtain a film structure with a Hall bar pattern.

[0023] Optionally, step S3 specifically includes:

[0024] Coating photoresist on the film structure with the Hall bar pattern, and performing exposure and development processing on the photoresist according to the electrode pattern;

[0025] Depositing electrode material, removing the photoresist, forming a patterned electrode layer, and obtaining the palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect.

[0026] In the third aspect of the present invention, there is provided an application of the palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect of the present invention in detecting hydrogen concentration.

[0027] Optionally, the hydrogen concentration in the external environment is 0.1% - 15%.

[0028] Beneficial effects: For the palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect provided by the present invention, hydrogen will affect the electronic structure of the Pd layer in its structure and cause a change in the anomalous Hall signal, thereby detecting the hydrogen concentration; and by changing the (Co / Pd) XThe number of periods of the multi-layer thin film can regulate the sensitivity of the sensor to the hydrogen concentration. The lower the period, the lower the hydrogen sensitivity, thus enabling the detection of different hydrogen concentrations. The palladium-based multi-layer film hydrogen sensor based on the anomalous Hall effect of the present invention has the advantages of obvious hydrogen detection current signal, strong anti-environmental gas interference, and controllable hydrogen detection concentration. Description of the Drawings

[0029] Figure 1 It is a schematic diagram of depositing a Pd / (Co / Pd)3 thin film structure on a substrate in Example 1.

[0030] Figure 2 It is a schematic diagram of the developed thin film pattern in Example 1.

[0031] Figure 3 It is a schematic diagram of the hydrogen sensor prepared in Example 1.

[0032] Figure 4 It is a schematic diagram of the anomalous Hall effect detection.

[0033] Figure 5 It is a graph of the Hall resistance varying with the magnetic field of the hydrogen sensor prepared in Example 1 under different hydrogen concentrations.

[0034] Figure 6 It is a graph of the Hall resistance varying with the magnetic field of the hydrogen sensor prepared in Example 2 under different hydrogen concentrations.

[0035] Figure 7 It is a graph of the Hall resistance varying with the magnetic field of the hydrogen sensor prepared in Example 3 under different hydrogen concentrations. Detailed Description of the Invention

[0036] The present invention provides a palladium-based multi-layer film hydrogen sensor based on the anomalous Hall effect, its preparation method and application. To make the purpose, technical solution and effect of the present invention clearer and more definite, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] An embodiment of the present invention provides a palladium-based multi-layer film hydrogen sensor based on the anomalous Hall effect, which includes a substrate, a thin film structure with a Hall bar pattern, and an electrode layer arranged in sequence from bottom to top;

[0038] The thin film structure with a Hall bar pattern includes a Pd single-layer thin film and (Co / Pd) X multi-layer thin films from bottom to top, where X represents the number of periods of the (Co / Pd) X multi-layer thin films;

[0039] The X is an integer from 1 to 10 (X is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10);

[0040] The (Co / Pd) X In each period of the multilayer film, the Co layer is arranged below and the Pd layer is arranged above.

[0041] In the embodiment of the present invention, the detection of hydrogen concentration is realized by using the anomalous Hall effect in a hydrogen sensor. The anomalous Hall effect refers to the deflection phenomenon of charge carriers perpendicular to the current and magnetization directions in a magnetic material due to the internal properties of the material, and is usually characterized by the anomalous Hall resistance or anomalous Hall resistivity.

[0042] In the embodiment of the present invention, the palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect mainly detects the change of the anomalous Hall signal due to hydrogen affecting the electronic structure of the Pd multilayer film in its structure, so as to detect the hydrogen concentration; and by changing the (Co / Pd) X The number of periods of the multilayer film can regulate the sensitivity of the sensor to hydrogen concentration. The lower the period, the lower the hydrogen sensitivity, so as to realize the detection of different hydrogen concentrations. Pd, as a hydrogen-active material, can quickly adsorb and dissociate hydrogen, causing lattice expansion and changes in the Pd electron energy band, thus making a rapid electrical signal response to the hydrogen environment. Pd only has a catalytic effect (dissociation and analysis) on hydrogen at normal temperature and pressure, and because hydrogen is a small molecule, the hydrogen atom has a small size, a high diffusion rate, and a strong interaction with the lattice. The palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect provided in the embodiment of the present invention has the advantages of obvious hydrogen detection current signal, strong anti-environmental gas interference, and controllable hydrogen detection concentration.

[0043] The method and principle for the palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect in the embodiment of the present invention to detect hydrogen concentration are as follows: For a thin film structure with a Hall bar pattern, a fixed current I is applied longitudinally, a magnetic field Hz is applied in the direction perpendicular to the thin film structure, the transverse Hall voltage U is measured, and the Hall resistance R = U / I is obtained. According to the Hall resistance signal, the hydrogen concentration in the external environment is fed back, so as to realize the detection of the hydrogen concentration in the external environment.

[0044] In this embodiment, the thin film structure with a Hall bar pattern sequentially includes a Pd single-layer film and a (Co / Pd) X multilayer film from bottom to top, where X represents the (Co / Pd) XThe number of periods of the multi-layer film, X is an integer from 1 to 10, being 1, 2 or 3, 4, 5, 6, 7, 8, 9 or 10. When X is 1, the thin film structure with a Hall bar pattern sequentially includes a multi-layer thin film structure of a Pd layer / Co layer / Pd layer from bottom to top; when X is 2, the thin film structure with a Hall bar pattern sequentially includes a multi-layer thin film structure of a Pd layer / (Co layer / Pd layer)2 from bottom to top; when X is 3, the thin film structure with a Hall bar pattern sequentially includes a multi-layer thin film structure of a Pd layer / (Co layer / Pd layer)3 from bottom to top; when X is other integers, the corresponding thin film structure with a Hall bar pattern can be obtained in the same way. In some preferred embodiments, X is an integer from 1 to 3, and X is 1, 2 or 3.

[0045] In this embodiment, the thin film structure with a Hall bar pattern is a thin film structure in some common shapes in Hall devices, such as rectangular, cross-shaped, square, four-leaf clover-shaped, etc. The different sizes and shapes of the Hall bar pattern have little influence on the detection of hydrogen concentration by the hydrogen sensor of the present application, and can all well regulate the anomalous Hall effect caused by hydrogen on the thin film structure with a Hall bar pattern to achieve the detection of hydrogen concentration.

[0046] In some embodiments, the substrate is a Gd3Sc2Ga3O 12 single crystal substrate or a silicon substrate with a SiO2 layer on its surface. Preferably, the substrate is a Gd3Sc2Ga3O with a (111) crystal orientation and a lattice constant of 12 (GSGG) single crystal substrate.

[0047] In some embodiments, the material of the electrode layer is a conductive metal, which can be Pt, Al or Ru, etc.

[0048] In some embodiments, the thickness of the Pd single-layer thin film is 3 to 10 nm (for example, it can be 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, etc.); the (Co / Pd) XIn the multilayer film, the thickness of the Co layer is 0.5 to 1.2 nm (for example, it can be 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1.0 nm, 1.1 nm, 1.2 nm, etc.), and the thickness of the Pd layer is 3 to 10 nm (for example, it can be 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, etc.). Among them, when the thickness of the Co layer is within the range of 0.5 to 1.2 nm, good perpendicular magnetic anisotropy can be exhibited, and the thinner the Co layer, the lower the hydrogen sensitivity, that is, the inversion of the anomalous Hall signal can be achieved at a lower hydrogen concentration; there is no strict limit on the thickness of the Pd layer, but when the Pd layer is too thin, such as 1.5 nm, the inversion of the anomalous Hall signal cannot be achieved in hydrogen, and in the present invention, the thickness of the Pd layer is limited to 3 to 10 nm.

[0049] An embodiment of the present invention provides a preparation method of the palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect described in any one of the foregoing embodiments, wherein the method includes the steps:

[0050] S1. Provide a substrate, and sequentially deposit a Pd single-layer film and a (Co / Pd) X multilayer film on the substrate by means of vacuum magnetron sputtering;

[0051] S2. Use photolithography and etching methods to etch the Pd single-layer film and the (Co / Pd) X multilayer film on the substrate into a thin film structure with a Hall bar pattern;

[0052] S3. Form an electrode layer on the thin film structure with the Hall bar pattern to obtain the palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect.

[0053] The preparation method provided by the embodiment of the present invention is simple and efficient. First, a Pd single-layer film and a (Co / Pd) X multilayer film are sequentially deposited on the substrate by means of vacuum magnetron sputtering, and then the Pd single-layer film and the (Co / Pd) X multilayer film on the substrate are etched into a thin film structure with a Hall bar pattern (etching the thin film into a Hall bar pattern), that is, a thin film structure with a Hall bar pattern is deposited on the substrate (including a Pd single-layer film and a (Co / Pd) X multilayer film from bottom to top in sequence). Finally, an electrode layer is deposited on the thin film structure to prepare the palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect described in the present invention.

[0054] In step S1, in some embodiments, the process of the vacuum magnetron sputtering is: under the condition of introducing argon, set the vacuum degree to be less than or equal to 1×10 -6Torr, the sputtering pressure is 3 - 5 mTorr (for example, it can be 3 mTorr, 3.5 mTorr, 4 mTorr, 4.5 mTorr, 5 mTorr), the sputtering temperature is room temperature (generally 25 °C), and the rotation speed of the sample stage is 10 - 40 rpm (for example, it can be 10 rpm, 20 rpm, 30 rpm, 40 rpm).

[0055] In some embodiments, the Pd single - layer film and the Pd layer in the (Co / Pd) X multilayer film are both sputtered using a radio - frequency power supply. This is because the thickness of the Co layer is extremely thin (0.5 - 1.2 nm). If the Pd layer is sputtered using a direct - current power supply, the bombardment energy is too large, which easily makes the Co layer discontinuous, so that the film does not exhibit perpendicular magnetic anisotropy, resulting in no obvious anomalous Hall signal. However, when using a radio - frequency power supply for sputtering, the prepared film has perpendicular magnetic anisotropy. The sputtering power of the radio - frequency power supply sputtering is 40 - 60 W (for example, it can be 40 W, 45 W, 50 W, 55 W, 60 W), and the sputtering time of the radio - frequency power supply sputtering is 1 - 5 min (for example, it can be 1 min, 2 min, 3 min, 4 min, 5 min); for the Co layer in the (Co / Pd) X multilayer film, direct - current power supply sputtering can be used. The sputtering power of the direct - current power supply sputtering is 40 - 60 W (for example, it can be 40 W, 45 W, 50 W, 55 W, 60 W), and the sputtering time of the direct - current power supply sputtering is 15 - 60 s (for example, it can be 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, 55 s, 60 s).

[0056] In some embodiments, step S1 specifically includes:

[0057] Providing a substrate, and sequentially depositing a Pd single - layer film and a (Co / Pd) X multilayer film on the substrate in a vacuum magnetron sputtering device. The gas introduced is argon, the vacuum degree is less than or equal to 1×10 -6 Torr, the sputtering pressure is 3 - 5 mTorr, the sputtering temperature is room temperature, the rotation speed of the sample stage is 10 - 40 rpm. When depositing the Pd single - layer film and the Pd layer in the (Co / Pd) X multilayer film, radio - frequency power supply sputtering is used. The sputtering power of the radio - frequency power supply sputtering is 40 - 60 W, and the sputtering time of the radio - frequency power supply sputtering is 1 - 5 min. When depositing the Co layer in the (Co / Pd) X multilayer film, direct - current power supply sputtering is used. The sputtering power of the direct - current power supply sputtering is 40 - 60 W, and the sputtering time of the direct - current power supply sputtering is 15 - 60 s, to obtain a substrate deposited with a Pd single - layer film and a (Co / Pd) X multilayer film.

[0058] In step S2, in some embodiments, step S2 specifically includes:

[0059] Apply photoresist on the substrate for depositing the Pd single-layer film and the (Co / Pd) X multilayer film, and perform exposure and development processing on the photoresist according to the Hall bar pattern;

[0060] Etch the substrate by using ion beam etching, strip the film not protected by the photoresist, and remove the photoresist to obtain a film structure with a Hall bar pattern.

[0061] In step S3, in some embodiments, step S3 specifically includes:

[0062] Apply photoresist on the film structure with the Hall bar pattern, and perform exposure and development processing on the photoresist according to the electrode pattern;

[0063] Deposit electrode materials, remove the photoresist, form a patterned electrode layer, and obtain the palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect.

[0064] In the present invention, the exposure and development processing, ion beam etching, removal of photoresist, deposition of electrode materials, etc. are all conventional techniques in the art and are not limited herein.

[0065] An embodiment of the present invention provides an application of the palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect described in any one of the foregoing embodiments in detecting the hydrogen concentration in the external environment.

[0066] In some embodiments, the hydrogen concentration in the external environment is 0.1% to 15%.

[0067] The present invention will be further described below through specific embodiments.

[0068] Example 1

[0069] This example provides a preparation method for a palladium-based multilayer film hydrogen sensor S1 based on the anomalous Hall effect, which is specifically as follows:

[0070] Step 1: Select a Gd3Sc2Ga3O single crystal substrate with a (111) crystal orientation and a lattice constant of 12 (GSGG), and use a vacuum magnetron sputtering device (AJA Company, USA, model ATC ORION 8) to sequentially deposit a Pd single-layer film and 3 cycles of (Co / Pd)3 multilayer films on the substrate. The gas introduced is argon, and the vacuum degree is set to be less than or equal to 1×10 -6Torr, the sputtering pressure was 3.5 mTorr, the sputtering temperature was room temperature, the rotation speed of the sample stage was 30 rpm, and when depositing the Pd single-layer film and the Pd layer in the (Co / Pd)3 multi-layer film, radio frequency power sputtering was used. The sputtering power of the radio frequency power sputtering was 50 W, and the sputtering time of the radio frequency power sputtering was 3 min. When depositing the Co layer in the (Co / Pd)3 multi-layer film, direct current power sputtering was used. The sputtering power of the direct current power sputtering was 50 W, and the sputtering time of the direct current power sputtering was 25 s. That is, a Pd single-layer film and a (Co / Pd)3 multi-layer film were deposited on the GSGG single crystal substrate, obtaining as Figure 1 the Pd / (Co / Pd)3 film structure shown.

[0071] Step 2: Place the substrate deposited with the Pd / (Co / Pd)3 film structure on a spin coater, and drop RNRN246 negative photoresist on the film structure. Set the rotation speed of the coater to 3000 rad / s and continue for 30 s to spin coat a flat and smooth photoresist with a thickness of about 3 μm on the film structure. Then, place the substrate on a heating table and dry it at 110 °C for 90 s to remove the solvent in the photoresist. Then, use a mask aligner (SUSS MA / BA6 GEN4, Germany) to perform an exposure process on the substrate, so that the Hall-bar pattern on the mask is transferred to the substrate. Then, place the substrate on a heating table and dry it at 110 °C for 90 s to make the photoresist more stable. Then, use NMD-3 2.38% negative photoresist developer to develop the photoresist. Wait until the denatured photoresist is fully dissolved in the developer, and the photoresist remaining on the substrate presents a "cross"-shaped Hall-bar pattern. The schematic diagram of the developed film pattern is as Figure 2 shown, where the long segment is the current-carrying end with a line width of 10 μm, and the short segment is the voltage end with a line width of 5 μm. Finally, place the substrate in an ion beam etching machine for etching. The high-energy ion beam bombards and strips the film not protected by the photoresist, and then removes the photoresist to obtain a film structure with a "cross"-shaped Hall-bar pattern.

[0072] S3: Spin coat the photoresist on the substrate obtained in Step 2. After drying at 100 °C, expose and transfer the electrode pattern on a mask aligner, clean it after development, and use a vacuum magnetron sputtering device to deposit an electrode layer, where the vacuum degree is set to be less than 5×10 -5 Pa; the sputtering power is 50 W, and the direct current sputtering time is 14 min. That is, a Pt layer with a thickness of 40 nm is deposited as the electrode layer on the film structure. After plating the electrode layer, ultrasonically clean the substrate in acetone for 30 s to remove the photoresist, that is, a patterned electrode layer is formed on the film structure, and finally the palladium-based multi-layer film hydrogen sensor S1 based on the anomalous Hall effect is obtained. The schematic diagram of the hydrogen sensor S1 is as Figure 3 shown.

[0073] Example 2

[0074] The preparation method of Example 2 is the same as that of Example 1, except that in the first step, a Pd single-layer film and two cycles of (Co / Pd)2 multilayer films are sequentially deposited on the substrate, and finally a palladium-based multilayer film hydrogen sensor S2 based on the anomalous Hall effect is obtained.

[0075] Example 3

[0076] The preparation method of Example 3 is the same as that of Example 1, except that in the first step, a Pd single-layer film and one cycle of (Co / Pd)1 multilayer film are sequentially deposited on the substrate, and finally a palladium-based multilayer film hydrogen sensor S3 based on the anomalous Hall effect is obtained.

[0077] For the palladium-based multilayer film hydrogen sensors S1 to S3 based on the anomalous Hall effect prepared in the above Examples 1 to 3, a test for detecting the hydrogen concentration performance is carried out. Among them, a mixed gas of hydrogen and nitrogen and its regulation of the hydrogen concentration in the mixed gas are used to simulate the hydrogen concentration in the environment to be detected. A hydrogen generator is used to generate hydrogen, and a high-purity nitrogen (4N) gas cylinder provides nitrogen, and the hydrogen concentration is controlled by a mixed gas control software. It is defined that the hydrogen concentration = hydrogen flow rate / (hydrogen flow rate + nitrogen flow rate), specifically as follows:

[0078] For the palladium-based multilayer film hydrogen sensors S1 to S3 based on the anomalous Hall effect prepared in the above Examples 1 to 3, a mixed gas of hydrogen and nitrogen with different hydrogen concentrations is introduced into the anomalous Hall effect resistance measuring device, and a fixed current I (I = 10 mA) is applied longitudinally to its Hall-bar film structure, and a varying magnetic field Hz is applied in the direction perpendicular to the film structure. The transverse Hall voltage U is measured. The schematic diagram of the anomalous Hall effect detection is as Figure 4 shown. In this way, the corresponding Hall voltage U can be obtained according to the change of the magnetic field Hz. Dividing U by the fixed current I can obtain the Hall resistance R, and finally the Hall resistance curve of the hydrogen sensor changing with the magnetic field can be obtained.

[0079] According to the Hall resistance curves of the hydrogen sensors changing with the magnetic field at different hydrogen concentrations measured, the hydrogen sensitivity point and the anomalous Hall resistance change value of the hydrogen sensor can be obtained. Among them, the hydrogen sensitivity point refers to the hydrogen concentration when the left and right ends of the Hall resistance curve are equal, that is, the hydrogen concentration when the Hall resistance remains unchanged under positive and negative magnetic fields; the calculation method of the anomalous Hall resistance change value is (RH1 - R0) / R0, where R0 is the anomalous Hall resistance at 0% hydrogen concentration, RH1 is the anomalous Hall resistance at the corresponding hydrogen concentration, and the anomalous Hall resistance RAHE = (Hall resistance corresponding to the maximum positive magnetic field - Hall resistance corresponding to the maximum negative magnetic field) / 2.

[0080] For the hydrogen sensor S1 prepared in Example 1, the applied variable magnetic field Hz was -1000 to 1000 Oe, and the Hall resistance curves of the hydrogen sensor with respect to the magnetic field change were measured at hydrogen concentrations of 0%, 4.0%, 7.5%, 7.9%, 8.2%, 9.0%, 10.0%, 11.0%, and 12.0% respectively, as Figure 5 shown. According to Figure 5 it can be seen that as the hydrogen concentration increases, the anomalous Hall signal is reversed, changing from high on the left and low on the right to low on the left and high on the right, and when the hydrogen concentration returns to 0%, the Hall signal can be restored, indicating that the hydrogen sensor can be reused. Moreover, the hydrogen sensitivity of the hydrogen sensor S1 is at a hydrogen concentration of 8.2%, and at the same time, the change value of the anomalous Hall resistance of the hydrogen sensor S1 in hydrogen can reach 180%, ensuring its accuracy and anti-interference ability, and it is not easy to generate errors.

[0081] For the hydrogen sensor S2 prepared in Example 2, the applied variable magnetic field Hz was -400 to 400 Oe, and the Hall resistance curves of the hydrogen sensor with respect to the magnetic field change were measured at hydrogen concentrations of 0%, 1.0%, 2.5%, 2.6%, 3.0%, 3.5%, 4.0%, 5.0%, and 5.5% respectively, as Figure 6 shown. According to Figure 6 it can be seen that as the hydrogen concentration increases, the anomalous Hall signal is reversed, changing from high on the left and low on the right to low on the left and high on the right, and when the hydrogen concentration returns to 0%, the Hall signal can be restored, indicating that the hydrogen sensor can be reused. Moreover, the hydrogen sensitivity of the hydrogen sensor S2 is at a hydrogen concentration of 2.6%, and at the same time, the change value of the anomalous Hall resistance of the hydrogen sensor S2 in hydrogen can reach 206%, ensuring its accuracy and anti-interference ability, and it is not easy to generate errors.

[0082] For the hydrogen sensor S3 prepared in Example 3, the applied variable magnetic field Hz was -300 to 300 Oe, and the Hall resistance curves of the hydrogen sensor with respect to the magnetic field change were measured at hydrogen concentrations of 0%, 0.1%, 0.2%, 0.4%, 0.6%, 1.0%, 1.5%, 2.5%, and 4.0% respectively, as Figure 7 shown. According to Figure 7 it can be seen that as the hydrogen concentration increases, the anomalous Hall signal is reversed, changing from high on the left and low on the right to low on the left and high on the right, and when the hydrogen concentration returns to 0%, the Hall signal can be restored, indicating that the hydrogen sensor can be reused. Moreover, the hydrogen sensitivity of the hydrogen sensor S3 is at a hydrogen concentration of 0.4%, and at the same time, the change value of the anomalous Hall resistance of the hydrogen sensor S3 in hydrogen can reach 175%, ensuring its accuracy and anti-interference ability, and it is not easy to generate errors.

[0083] In addition, it can be seen from the above data that the sensitivity of the palladium-based multilayer film hydrogen sensor provided by the present invention based on the anomalous Hall effect can be adjusted by the number of periods of the (Co / Pd) X multilayer thin films. The lower the number of periods, the lower the hydrogen sensitivity. Among them, the hydrogen sensor with a single period flips at a hydrogen concentration of 0.4% (the left and right sides of the curve are equal), the hydrogen sensor with 2 periods flips at a hydrogen concentration of 2.6%, and the hydrogen sensor with 3 periods flips at a hydrogen concentration of 8.2%.

[0084] In summary, a palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect provided by the present invention includes a substrate, a thin film structure with a Hall bar pattern, and an electrode layer arranged in sequence from bottom to top. Hydrogen affects the electronic structure of the Pd multilayer film in its structure and generates a change in the anomalous Hall signal, thereby detecting the hydrogen concentration; and by changing the (Co / Pd) X number of periods of the multilayer thin films, the sensitivity of the sensor to the hydrogen concentration can be adjusted. The lower the number of periods, the lower the hydrogen sensitivity, so as to realize the detection of different hydrogen concentrations. The palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect of the present invention has the advantages of obvious hydrogen detection current signal, strong resistance to environmental gas interference, and controllable hydrogen detection concentration.

[0085] It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A palladium-based multilayer hydrogen sensor based on the anomalous Hall effect, characterized in that: It includes a substrate, a thin film structure with a Hall bar pattern and an electrode layer which are arranged in sequence from bottom to top; The thin film structure with the Hall bar pattern includes, from bottom to top, a Pd single-layer thin film and a (Co / Pd) X Multilayer film, where X represents (Co / Pd) X The number of cycles of the multilayer film; X is an integer between 1 and 10; The (Co / Pd) X In each period of the multilayer film, the Co layer is arranged at the bottom and the Pd layer is arranged at the top.

2. The palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect according to claim 1, characterized in that: The substrate is Gd3Sc2Ga3O 12 A single crystal substrate or a silicon substrate with a SiO2 layer on the surface; the material of the electrode layer is a conductive metal.

3. The palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect according to claim 1, characterized in that: The thickness of the Pd single-layer film is 3 to 10 nm; the (Co / Pd) X In the multilayer film, the thickness of the Co layer is 0.5 to 1.2 nm, and the thickness of the Pd layer is 3 to 10 nm.

4. A method for preparing a palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect as claimed in any one of claims 1 to 3, characterized in that: Includes steps: S1. Provide a substrate, and sequentially deposit a Pd single-layer film and (Co / Pd) on the substrate by vacuum magnetron sputtering. X Multilayer films; S2, using photolithography and etching methods to remove the Pd single layer film and (Co / Pd) X The multilayer film is etched into a film structure having a Hall bar pattern; S3. Forming an electrode layer on the thin film structure having the Hall bar pattern to obtain the palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect.

5. The method for preparing a palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect according to claim 4, characterized in that: In step S1, the vacuum magnetron sputtering process is as follows: under the condition of introducing argon gas, the vacuum degree is set to be less than or equal to 1×10 -6 Torr, the sputtering gas pressure is 3-5mTorr, the sputtering temperature is room temperature, and the sample stage rotation speed is 10-40rpm.

6. The method for preparing a palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect according to claim 5, characterized in that: In step S1, the Pd single layer film and (Co / Pd) X The Pd layers in the multilayer film are all sputtered by radio frequency power supply, the sputtering power of the radio frequency power supply is 40-60W, and the sputtering time of the radio frequency power supply is 1-5min; The (Co / Pd) X The Co layer in the multilayer film is sputtered by a direct current power supply, the sputtering power of the direct current power supply is 40 to 60 W, and the sputtering time of the direct current power supply is 15 to 60 seconds.

7. The method for preparing a palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect according to claim 4, characterized in that: The step S2 specifically includes: In the deposition of Pd monolayer and (Co / Pd) X A photoresist is coated on a substrate of a multilayer film, and the photoresist is exposed and developed according to a Hall bar pattern; The substrate is etched by ion beam etching, the thin film not protected by the photoresist is peeled off, the photoresist is removed, and a thin film structure with a Hall bar pattern is obtained.

8. The method for preparing a palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect according to claim 4, characterized in that: The step S3 specifically includes: Applying photoresist on the thin film structure having the Hall bar pattern, and exposing and developing the photoresist according to the electrode pattern; The electrode material is deposited, the photoresist is removed, and a patterned electrode layer is formed to obtain the palladium-based multilayer film hydrogen sensor based on the anomalous Hall effect.

9. Use of the palladium-based multilayer hydrogen sensor based on the anomalous Hall effect as claimed in any one of claims 1 to 3 in detecting the hydrogen concentration in an external environment.

10. Use of the palladium-based multilayer hydrogen sensor based on the anomalous Hall effect according to claim 9 in detecting the hydrogen concentration in an external environment, wherein the hydrogen concentration in the external environment is 0.1% to 15%.

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