Hydrogen gas sensor and method for manufacturing the same

Abstract

To provide a hydrogen gas sensor equipped with a small-sized hydrogen gas sensor element operated at room temperature and having high sensitivity, and its manufacturing method.SOLUTION: The hydrogen gas sensor includes a graphene element 30 including a graphene thin film 13 terminated with zigzag ends and having palladium nanoparticles 21 vapor-deposited on a surface thereof, a vacuum container in which the graphene element 30 is installed, a hydrogen gas introduction unit that selectively introduces hydrogen gas into the evacuated vacuum container, an electrical resistance measurement unit that measures an electrical resistance of the graphene element 30, and a hydrogen gas detection unit that detects the hydrogen gas introduced into the vacuum container by the hydrogen gas introduction unit based on the electrical resistance.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a hydrogen gas sensor and a method for manufacturing the same, and particularly to a hydrogen gas sensor using a nanoscale graphene element and a method for manufacturing the same.

Background Art

[0002] Hydrogen has attracted attention as a next-generation energy source that is essential for achieving a carbon-neutral society. In addition, hydrogen gas is considered useful in medical and disease diagnosis scenarios.

[0003] On the other hand, hydrogen has disadvantages such as exploding in a wide concentration range in the atmosphere of 4 to 75% and having high permeability to substances, which can deteriorate steel materials. However, since it is colorless, odorless, and tasteless, it cannot be perceived by humans.

[0004] Therefore, it is important to check for hydrogen leakage and measure hydrogen concentration at each stage of hydrogen production, storage, transportation, and utilization.

[0005] Conventionally, as a hydrogen gas sensor capable of performing precise concentration measurement, there is a sensor using a mass spectrometry method, but there is a problem that the device becomes large.

[0006] On the other hand, for smaller sensors mainly for leak detection, there are those that detect a change in the electrical resistance of a metal oxide semiconductor due to an oxidation-reduction reaction with hydrogen, those that detect a change in the electrical resistance of a platinum wire due to the combustion of hydrogen gas, and those that detect from a change in the thermal conductivity of a gas. However, since all of them operate at a high temperature of several 100°C, in addition to high power consumption, there is also a risk of explosion depending on the hydrogen gas concentration.

[0007] Therefore, the development of a small and low-power hydrogen gas sensor element that operates even at room temperature is expected.

[0008] For example, Non-Patent Document 1 discloses a hydrogen gas sensor element using graphene with palladium (Pd) nanoparticles deposited on its surface. Pd is known as a metal that absorbs hydrogen. Such a hydrogen gas sensor element can be used at room temperature because it can detect changes in the physical properties of Pd due to its reaction with hydrogen through graphene. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] Rakesh Kumar, Shweta Malik, BR Mehta, "Interface induced hydrogen sensing in Pd nanoparticle / graphene composite layers," Sensors and Actuators B: Chemical Volume 209 , 31 March 2015, Pages 919-926. [Overview of the project] [Problems that the invention aims to solve]

[0010] However, conventional hydrogen gas sensor elements, such as those disclosed in Non-Patent Document 1, can only detect hydrogen concentrations down to about tens of ppm, which presents a challenge in that they cannot perform the highly sensitive hydrogen gas detection required in recent years.

[0011] The present invention has been made to solve these conventional problems, and aims to provide a hydrogen gas sensor equipped with a small, highly sensitive hydrogen gas sensor element that operates at room temperature, and a method for manufacturing the same. [Means for solving the problem]

[0012] To solve the above problems, the hydrogen gas sensor according to the present invention is a hydrogen gas sensor (50) for detecting hydrogen gas, comprising: a graphene element (30) having a graphene thin film (13) terminated with a zigzag end and having palladium nanoparticles (21) deposited on its surface; a vacuum vessel (56) in which the graphene element is installed; a hydrogen gas introduction unit (51, 52, 53, 54) for selectively introducing the hydrogen gas into the vacuum vessel which has been evacuated; an electrical resistance measuring unit (61) for measuring the electrical resistance of the graphene element; and a hydrogen gas detection unit (62) for detecting the hydrogen gas introduced into the vacuum vessel by the hydrogen gas introduction unit based on the electrical resistance.

[0013] With this configuration, the hydrogen gas sensor according to the present invention can detect hydrogen gas with high sensitivity approaching 1 ppm using a small, room-temperature operating graphene element.

[0014] Furthermore, the hydrogen gas sensor according to the present invention may be configured such that the hydrogen gas detection unit determines that a concentration of hydrogen gas higher than the concentration corresponding to the predetermined threshold has been detected when the difference between the electrical resistance of the graphene element in a vacuum and the electrical resistance of the graphene element when the hydrogen gas is introduced into the vacuum container by the hydrogen gas introduction unit exceeds a predetermined threshold.

[0015] With this configuration, the hydrogen gas sensor according to the present invention can detect hydrogen gas at a concentration higher than a predetermined concentration based on the difference between the electrical resistance of the graphene element in a vacuum and the electrical resistance of the graphene element when hydrogen gas is introduced into a vacuum vessel.

[0016] Furthermore, the hydrogen gas sensor according to the present invention may further include a graphene element comprising a conductive substrate (12) and an oxide film (11) formed on the surface of the conductive substrate, wherein the graphene thin film is formed on the surface of the oxide film, and the hydrogen gas detection unit may be configured to change the concentration according to a predetermined threshold by changing the gate voltage applied to the conductive substrate.

[0017] With this configuration, the hydrogen gas sensor according to the present invention can change the sensitivity when detecting the presence or absence of hydrogen gas by changing the gate voltage applied to the conductive substrate of the graphene element.

[0018] Further, the hydrogen gas sensor according to the present invention may be configured such that the hydrogen gas detection unit calculates the rate of change of the electrical resistance corresponding to the concentration of the hydrogen gas and estimates the concentration of the hydrogen gas based on the rate of change.

[0019] With this configuration, the hydrogen gas sensor according to the present invention can estimate the concentration of hydrogen gas based on the rate of change of the electrical resistance of the graphene element with respect to the change in the concentration of hydrogen gas in the vacuum container.

[0020] Further, the manufacturing method according to the present invention is a manufacturing method for manufacturing the hydrogen gas sensor described in any one of the above, and is configured to form the zigzag end of the graphene element by hydrogen plasma etching.

[0021] With this configuration, the manufacturing method according to the present invention can manufacture a hydrogen gas sensor capable of detecting hydrogen gas with high sensitivity approaching 1 ppm at room temperature by forming the zigzag end of the graphene element by hydrogen plasma etching.

Effects of the Invention

[0022] The present invention provides a hydrogen gas sensor including a small and highly sensitive hydrogen gas sensor element that operates at room temperature, and a manufacturing method thereof.

Brief Description of the Drawings

[0023] [Figure 1] It is a diagram for explaining the end structure of graphene. [Figure 2] (a) is a schematic diagram showing the Dirac cone of graphene and the gate voltage dependence of electrical resistance, and (b) is a graph showing the electronic state density of the vicinity of the zigzag end of graphene and the bulk graphene. [Figure 3] This figure shows structural examples of nanoscale graphene elements terminated with zigzag ends: (a) shows an array of zigzag graphene nanoribbons, (b) shows a zigzag graphene nanomesh, and (c) shows a zigzag graphene nanosnake. [Figure 4] This is a diagram (part 1) illustrating a method for manufacturing a Pd-modified graphene element included in a hydrogen gas sensor according to an embodiment of the present invention. [Figure 5] This is a diagram (part 2) illustrating a method for manufacturing a Pd-modified graphene element included in a hydrogen gas sensor according to an embodiment of the present invention. [Figure 6] This figure illustrates a Pd-modified graphene element included in a hydrogen gas sensor according to an embodiment of the present invention. [Figure 7] This graph shows the results of measuring the electrical resistance of a Pd-modified graphene element while varying the hydrogen gas concentration. [Figure 8] This graph shows the gate voltage dependence of the electrical resistance of a Pd-modified graphene element, measured in a vacuum and in hydrogen gas at a concentration of 18 ppm. [Figure 9] This is a schematic diagram showing the configuration of a hydrogen gas sensor according to an embodiment of the present invention. [Modes for carrying out the invention]

[0024] Hereinafter, embodiments of the hydrogen gas sensor and its manufacturing method according to the present invention will be described with reference to the drawings.

[0025] The hydrogen gas sensor according to this embodiment uses a nanoscale graphene element (hereinafter also referred to as a "Pd-modified graphene element") on which palladium (Pd) nanoparticles have been deposited as a hydrogen gas sensor element to detect hydrogen gas.

[0026] Figure 1 illustrates the end structure of graphene. Reflecting its honeycomb structure, graphene has end structures such as zigzag ends (left side of Figure 1), armchair ends (right side of Figure 1), or a regular or random mixture of these. The properties of graphene are influenced by this end structure. This influence becomes particularly pronounced when the end structure occupies a large proportion of the whole, such as in nanoribbons.

[0027] As shown in Figure 2(a), graphene has a linear energy dispersion (Dirac cone) that intersects at a charge neutral point called the Dirac point, and the Fermi energy (E) is affected by the field effect due to the gate voltage. F The conductivity can be greatly manipulated by controlling ). At the Dirac point, the density of electronic states is zero, so E F When the point is near the Dirac point, the electrical resistance increases.

[0028] At the armchair ends, the symmetry between the two equivalent sublattices that make up the honeycomb lattice, sublattices A and B, is preserved, whereas near the zigzag ends, the symmetry is broken. As a result, at the armchair ends, electronic states essentially equivalent to those of bulk graphene appear, while at the zigzag ends, electronic states localized to the edge (zigzag edge states) appear.

[0029] Figure 2(b) is a graph showing the density of electronic states near the zigzag edge of graphene and of bulk graphene (partially modified from Figure 6b in Tomohiro Matsui, Hideki Sato, Kazuma Kita, Andre EB Amend, and Hiroshi Fukuyama, "Hexagonal Nanopits with the Zigzag Edge State on Graphite Surfaces Synthesized by Hydrogen-Plasma Etching," The Journal of Physical Chemistry C 2019, Volume 123, Issue 36 Pages 22665-22673). Near the zigzag edge, EF Around 0 meV, corresponding to this point, a peak structure clearly indicating a zigzag edge state appears.

[0030] Figures 3(a) to 3(c) show examples of nanoscale graphene device structures terminated with zigzag ends.

[0031] The left side of Figure 3(a) shows an array of zigzag graphene nanoribbons (zGNRA), which are nanoscale ribbon-shaped graphene with zigzag ends. The center side of Figure 3(a) shows how approximately 10 nm in size Pd nanoparticles are attached to the entire surface of the zGNRA. The right side of Figure 3(a) is a magnified view of the area enclosed by the rectangle in the center side, showing how the Pd nanoparticles are selectively attached to the zigzag ends.

[0032] Figure 3(b) shows the zigzag graphene nanomesh (zGNM), which is the network structure of zGNRs. Figure 3(c) shows the zigzag graphene nanosnake (zGNS), which is a meandering structure of zGNRs.

[0033] The manufacturing method for the Pd-modified graphene element 30 of the hydrogen gas sensor of this embodiment will be described below with reference to Figures 4 to 6, using a Pd-modified zGNRA element having zGNRA as an example.

[0034] First, a graphene thin film 13 of any thickness is formed on a conductive substrate 12 on which an oxide film 11 is formed on its surface (step i).

[0035] Here, the conductive substrate 12 is a semiconductor such as silicon (Si), or a metal. The oxide film 11 is an oxide film of the semiconductor (e.g., SiO2) or an oxide film of the metal. For the graphene thin film 13, for example, cleaved graphene can be used.

[0036] Next, a resist film 15a is applied onto the oxide film 11 containing the graphene thin film 13 (step ii).

[0037] Next, a linear slit 14 is formed at a desired position in the resist film 15a to form a resist mask 15 on the graphene thin film 13 (step iii).

[0038] More specifically, the side of the conductive substrate 12 coated with the resist film 15a is irradiated with light or an electron beam to expose the resist film 15a and form a linear slit 14. The resist film 15a with the slit 14 formed becomes the resist mask 15. The length and width of the slit 14 can be adjusted as appropriate according to the specifications (length, width) of the GNRA being manufactured.

[0039] Next, the graphene thin film 13 is etched in the depth direction through the slit 14 of the resist mask 15 to the oxide film 11 (step iv).

[0040] This etching is performed using CHF3 plasma etching. After etching, grooves 16 are formed in the oxide film 11 in the depth direction. The depth of the grooves 16 is arbitrary. In Figure 4, the depth of the grooves 16 reaches about halfway through the thickness of the oxide film 11, but it may also reach the conductive substrate 12.

[0041] Next, the resist mask 15 is removed (step v).

[0042] Next, the graphene thin film 13 is etched in the plane direction of the conductive substrate 12 using the groove 16 as a nucleus (anisotropic etching) (step vi).

[0043] This etching is performed using hydrogen plasma etching. Through this etching process, the graphene thin film 13 is etched into equiangular hexagonal shapes using the grooves 16 as nuclei.

[0044] Since the graphene thin film 13 between the etched equiangular hexagons becomes a GNR, the etching is terminated when the graphene thin film 13 between the equiangular hexagons reaches the desired width. The GNR formed by this hydrogen plasma etching has a structure terminated at a zigzag edge.

[0045] Next, the graphene thin film 13 is completely removed by etching, leaving only the GNRs in the desired areas (step vii). After step vii is completed, zGNRA 20 is finished.

[0046] Next, electrodes 22 and 23 are formed at both ends of zGNRA20, as schematically shown in Figure 6.

[0047] Next, a Pd film approximately 1 nm thick is vacuum deposited onto zGNRA20. The vacuum deposition of the Pd film takes 5 × 10⁻¹⁰ -4 The process is started at a pressure of less than Pa. This causes Pd nanoparticles 21, slightly larger than 10 nm in size, to adhere to the zGNRA 20, as schematically shown in Figure 6, completing the Pd-modified zGNRA element.

[0048] In the above explanation, electrodes 22 and 23 are formed on both ends of zGNRA20 before the Pd film is vacuum-deposited onto zGNRA20. However, this order can be reversed. That is, after step vii is completed, the Pd film may be vacuum-deposited onto zGNRA20 before the electrodes 22 and 23 are formed on both ends of zGNRA20.

[0049] When fabricating a Pd-modified graphene element 30, for example, an element having a zGNM or zGNS structure, in step iii, instead of a linear slit 14, a round hole or alternating parallel slits may be formed in the resist film 15a.

[0050] Specifically, as shown in Figure 6, the Pd-modified graphene element 30 includes a conductive substrate 12, an oxide film 11 formed on the surface of the conductive substrate 12, a graphene thin film 13 formed on the surface of the oxide film 11 and terminated with a zigzag edge, and Pd nanoparticles 21 deposited on the surface of the graphene thin film 13. A gate voltage Vg is applied to the conductive substrate 12 as needed.

[0051] Figure 7 is a graph showing the results of measuring the electrical resistance of a Pd-modified graphene element 30 installed inside a vacuum-filled vacuum chamber, while varying the concentration of hydrogen gas introduced into the vacuum chamber.

[0052] Electrical resistance measurements were performed between electrodes 22 and 23 using the measurement system shown in Figure 6, with the gate voltage Vg set to 0V. The Pd-modified graphene element 30 used for the measurement was a 2- or 3-layer graphene Pd-modified zGNRA element with 12 ribbons of approximately 240 nm width in parallel.

[0053] This measurement is performed by repeatedly introducing hydrogen gas into a vacuum chamber in which a Pd-modified graphene element 30 is installed, and then evacuating the hydrogen gas from the vacuum chamber. Specifically, approximately 18 ppm of hydrogen gas is introduced into the vacuum chamber during the 300-second period from 0 to 300 seconds, approximately 10 ppm of hydrogen gas during the 300-second period from 500 to 800 seconds, and approximately 2 ppm of hydrogen gas during the 300-second period from 1000 to 1300 seconds. In this specification, the hydrogen concentration (ppm) is based on atmospheric pressure.

[0054] The graph in Figure 7 shows the rate of change of the electrical resistance R of the Pd-modified graphene element 30 {(R-Rs) / Rs} × 100 (%), with the electrical resistance Rs of the Pd-modified graphene element 30 as the reference value, at the start times of three hydrogen gas introductions (0 seconds, 500 seconds, and 1000 seconds).

[0055] From these measurement results, it was found that the electrical resistance R of the Pd-modified graphene element 30 decreases when the Pd-modified graphene element 30 is exposed to hydrogen gas. This is the opposite behavior to the hydrogen gas sensor element disclosed in Non-Patent Literature 1, in which the electrical resistance increases when exposed to hydrogen gas. It should be noted that the hydrogen gas sensor element in Non-Patent Literature 1 is measured in atmospheric pressure, whereas the Pd-modified graphene element 30 in this embodiment is measured in a vacuum. Therefore, it is thought that this difference in behavior is due to the presence of gases other than hydrogen, such as oxygen and nitrogen, in atmospheric pressure, while only hydrogen gas is present in a vacuum.

[0056] Furthermore, it was found that the rate of change of the electrical resistance R of the Pd-modified graphene element 30 is linearly related to the hydrogen concentration when the time the Pd-modified graphene element 30 is exposed to hydrogen gas is constant.

[0057] Furthermore, while conventional hydrogen gas sensor elements, such as those disclosed in Non-Patent Document 1, can only detect hydrogen concentrations down to several hundred ppm, the Pd-modified graphene element 30 of this embodiment can detect hydrogen concentrations approaching 1 ppm when measured in a vacuum as described above.

[0058] Figure 8 is a graph showing the gate voltage dependence of the electrical resistance of a Pd-modified graphene element 30, similar to the one used in the measurement shown in Figure 7, measured in vacuum and in hydrogen gas at a concentration of 18 ppm. Here, vacuum is defined as 10 -3 It is Pa.

[0059] According to the measurement results in Figure 8, the gate voltage that gives the peak electrical resistance in 18 ppm hydrogen gas is higher than the gate voltage that gives the peak electrical resistance in a vacuum. This indicates that the graphene thin film 13 of the Pd-modified graphene element 30 is held-doped by the hydrogen gas. This is different behavior from the hydrogen gas sensor element described in Non-Patent Literature 1, in which it is thought that the graphene is doped with electrons by the hydrogen gas.

[0060] Furthermore, the peak electrical resistance value in 18 ppm hydrogen gas is lower than the peak value of the gate voltage dependence of electrical resistance in a vacuum.

[0061] In other words, when the Pd-modified graphene element 30 is exposed to hydrogen gas, the graphene thin film 13 is held doped, and the peak value of the gate voltage dependence of the electrical resistance decreases, resulting in a lower electrical resistance compared to when it is in a vacuum.

[0062] Furthermore, the gate voltage applied to the conductive substrate 12 may be changed. For example, when the gate voltage is 20V, the difference in electrical resistance of the Pd-modified graphene element 30 between a vacuum and 18ppm hydrogen gas is approximately 0.015kΩ. On the other hand, when the gate voltage is 0V, the difference in electrical resistance of the Pd-modified graphene element 30 between a vacuum and 18ppm hydrogen gas is approximately 0.03kΩ.

[0063] Therefore, in the gate voltage range of 0 to 25V, it is desirable to set the gate voltage to 0V, where the difference in electrical resistance is large, in terms of the accuracy of electrical resistance measurement, and the accuracy of electrical resistance measurement can be further improved by setting the gate voltage to a negative value.

[0064] Furthermore, by changing the gate voltage, the sensitivity for detecting the presence or absence of hydrogen gas can also be altered.

[0065] For example, when the threshold for the difference in electrical resistance is 0.015 kΩ, the following can be observed: When the gate voltage is 20 V and the difference in electrical resistance is 0.015 kΩ or more, the presence or absence of hydrogen gas with a concentration of 18 ppm or more can be detected. When the gate voltage is lower than 20 V and the difference in electrical resistance is 0.015 kΩ or more, the presence or absence of hydrogen gas with a predetermined concentration lower than 18 ppm can be detected. Conversely, when the gate voltage is higher than 20 V and the difference in electrical resistance is 0.015 kΩ or more, the presence or absence of hydrogen gas with a predetermined concentration higher than 18 ppm can be detected.

[0066] The following describes an example of the specific configuration of the hydrogen gas sensor 50 in this embodiment.

[0067] As shown in Figure 9, the hydrogen gas sensor 50 mainly comprises, for example, a variable leak valve V1, a first vacuum pump 52, a second vacuum pump 53, a vacuum vessel 56 in which a Pd-modified graphene element 30 is installed, an operating unit 57, a display unit 58, and a control unit 60.

[0068] The vacuum vessel 56 is connected to the first vacuum pump 52 via a valve V2 and a second vacuum pump 53.

[0069] The first vacuum pump 52 is connected to the exhaust port side of the second vacuum pump 53. The first vacuum pump 52 is, for example, a dry pump, a rotary pump, or a membrane pump. The second vacuum pump 53 is, for example, a turbomolecular pump.

[0070] The variable leak valve V1 is installed on the intake side of the vacuum chamber 56. A test gas, which may contain hydrogen gas, is drawn into the vacuum chamber 56 via the variable leak valve V1. The test gas is, for example, a gas present in any piping or container, or outside air.

[0071] Furthermore, the vacuum vessel 56 is equipped with a vent valve V3, which allows nitrogen gas or other gases to be introduced into the vacuum vessel 56 via the vent valve V3 as needed when hydrogen gas detection is complete.

[0072] Furthermore, the first vacuum pump 52 is equipped with a vent valve V4, which allows air, nitrogen gas, or other substances to be introduced into the first vacuum pump 52 via the vent valve V4 when the operation of the first vacuum pump 52 has ended.

[0073] The open / closed state of each valve V1 to V4 is controlled by the control unit 60 in response to user input to the operation unit 57. Furthermore, the number of vacuum pumps and valves is not limited to the configuration shown in Figure 9, and can be changed as appropriate depending on the device configuration.

[0074] The control unit 60 includes an electrical resistance measuring unit 61 and a hydrogen gas detection unit 62.

[0075] The electrical resistance measuring unit 61 is configured to measure the electrical resistance of the Pd-modified graphene element 30. For example, as shown in Figure 6, the electrical resistance measuring unit 61 measures the DC electrical resistance between electrodes 22 and 23 when a predetermined gate voltage is applied to the conductive substrate 12.

[0076] The following describes an example of a procedure for detecting hydrogen gas using the hydrogen gas sensor 50 of this embodiment.

[0077] First, the variable leak valve V1, vent valves V3 and V4 are closed, and valve V2 is opened to evacuate the vacuum chamber 56 using the second vacuum pump 53 and the first vacuum pump 52 in series until the pressure falls below a predetermined level. Here, the "predetermined pressure" is preferably 0.01 Pa or less, which is lower than the partial pressure of hydrogen in the atmosphere.

[0078] Next, the electrical resistance measuring unit 61 measures the electrical resistance Rv of the Pd-modified graphene element 30 in a vacuum.

[0079] Next, the variable leak valve V1 is opened to draw a predetermined amount of test gas into the vacuum vessel 56, and hydrogen gas detection by the Pd-modified graphene element 30 in the vacuum vessel 56 is started. At this time, the degree to which the variable leak valve V1 is opened may be automatically adjusted according to the pressure of the vacuum gauge P attached to the vacuum vessel 56.

[0080] In other words, the variable leak valve V1, the first vacuum pump 52, and the second vacuum pump 53 constitute a hydrogen gas introduction unit that selectively introduces hydrogen gas into the vacuumed vacuum vessel 56.

[0081] Next, the hydrogen gas detection unit 62 detects the hydrogen gas introduced into the vacuum container 56 by the hydrogen gas introduction unit based on the electrical resistance R of the Pd-modified graphene element 30 measured by the electrical resistance measurement unit 61.

[0082] In other words, the electrical resistance measuring unit 61 measures, for example, the electrical resistance Rv of the Pd-modified graphene element 30 in a vacuum below a predetermined pressure, and the electrical resistance R of the Pd-modified graphene element 30 when hydrogen gas is introduced into a vacuum container 56 that has been evacuated to below a predetermined pressure by the hydrogen gas introduction unit.

[0083] For example, the hydrogen gas detection unit 62 determines that it has detected a concentration of hydrogen gas higher than the concentration corresponding to a predetermined threshold when the difference between the electrical resistance Rv and the electrical resistance R exceeds a predetermined threshold. As already mentioned, the hydrogen gas detection unit 62 can change the concentration corresponding to the predetermined threshold by changing the gate voltage applied to the conductive substrate 12.

[0084] As already mentioned, the rate of change of the electrical resistance of the Pd-modified graphene element 30 is linearly related to the hydrogen gas concentration. For this reason, the hydrogen gas detection unit 62 may calculate the rate of change of the electrical resistance R based on the electrical resistance Rv as {(R-Rv) / Rv} × 100 (%) and estimate the hydrogen concentration according to the calculated rate of change of electrical resistance.

[0085] The display unit 58 displays the detection result from the hydrogen gas detection unit 62, that is, whether or not there is hydrogen gas at a concentration higher than a predetermined concentration, or an estimated value of the hydrogen concentration.

[0086] As described above, the hydrogen gas sensor 50 according to this embodiment has a configuration in which a Pd-modified graphene element 30, which is a graphene thin film 13 terminated at a zigzag end and on which Pd nanoparticles 21 are deposited on the surface, is installed inside a vacuum chamber 56.

[0087] As a result, the hydrogen gas sensor 50 according to this embodiment can detect hydrogen gas with high sensitivity approaching 1 ppm using a compact, room-temperature operating Pd-modified graphene element 30.

[0088] Furthermore, the hydrogen gas sensor 50 according to this embodiment can detect hydrogen gas at a concentration higher than a predetermined concentration based on the difference between the electrical resistance Rv of the Pd-modified graphene element 30 in a vacuum and the electrical resistance R of the Pd-modified graphene element 30 when hydrogen gas is introduced into the vacuum container 56.

[0089] Furthermore, the hydrogen gas sensor 50 according to this embodiment can change the sensitivity of detecting the presence or absence of hydrogen gas by changing the gate voltage applied to the conductive substrate 12 of the Pd-modified graphene element 30.

[0090] Furthermore, the hydrogen gas sensor 50 according to this embodiment can estimate the hydrogen gas concentration based on the rate of change of the electrical resistance R of the Pd-modified graphene element 30 in response to a change in the hydrogen gas concentration in the vacuum container 56.

[0091] Furthermore, the manufacturing method according to this embodiment allows for the production of a hydrogen gas sensor 50 that can detect hydrogen gas with high sensitivity approaching 1 ppm at room temperature by forming a zigzag edge of the Pd-modified graphene element 30 by hydrogen plasma etching. [Explanation of symbols]

[0092] 11 Oxide film 12 Conductive substrate 13 Graphene Thin Film 20 zGNRA 21 nanoparticles 22,23 electrode 30 Pd-modified graphene elements (graphene elements) 50 Hydrogen gas sensor 52. First Vacuum Pump 53. Second Vacuum Pump 56 Vacuum container 57 Operation section 58 Display section 60 Control Unit 61 Electrical resistance measurement section 62 Hydrogen gas detection unit V1 Variable Leak Valve

Claims

1. A hydrogen gas sensor (50) for detecting hydrogen gas, A graphene element (30) comprising a graphene thin film (13) terminated at a zigzag end and having palladium nanoparticles (21) deposited on its surface, A vacuum vessel (56) in which the graphene element is installed inside, Hydrogen gas introduction units (51, 52, 53, 54) for selectively introducing the hydrogen gas into the vacuum-filled vacuum container, An electrical resistance measuring unit (61) for measuring the electrical resistance of the graphene element, A hydrogen gas sensor comprising a hydrogen gas detection unit (62) that detects the hydrogen gas introduced into the vacuum container by the hydrogen gas introduction unit based on the electrical resistance.

2. The hydrogen gas sensor according to claim 1, characterized in that the hydrogen gas detection unit determines that a concentration of hydrogen gas higher than the concentration corresponding to the predetermined threshold has been detected when the difference between the electrical resistance of the graphene element in a vacuum and the electrical resistance of the graphene element when the hydrogen gas is introduced into the vacuum container by the hydrogen gas introduction unit exceeds a predetermined threshold.

3. The graphene element further comprises a conductive substrate (12) and an oxide film (11) formed on the surface of the conductive substrate, wherein the graphene thin film is formed on the surface of the oxide film. The hydrogen gas sensor according to claim 2, characterized in that the hydrogen gas detection unit changes the concentration according to a predetermined threshold by changing the gate voltage applied to the conductive substrate.

4. The hydrogen gas sensor according to claim 1, characterized in that the hydrogen gas detection unit calculates the rate of change of the electrical resistance according to the concentration of the hydrogen gas and estimates the concentration of the hydrogen gas based on the rate of change.

5. A manufacturing method for producing the hydrogen gas sensor described in any one of claims 1 to 4, A manufacturing method characterized by forming the zigzag edge of the graphene element by hydrogen plasma etching.

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