KR20110075841A - Hydrogen sensor and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A manufacturing method of hydrogen sensor is provided to precisely sense hydrogen by improving the reaction reproducibility that the hydrogen sensor reacts to hydrogen. CONSTITUTION: A manufacturing method of hydrogen sensor comprises a step of arranging transition metal or an alloy film on a surface of an elastic board and a step of forming a nanogap on the thin film by adding tensile force to the elastic board. The thin film is stretched toward a tensile force applying direction when the tensile force is applied.

Description

Hydrogen sensor and manufacturing method

The present invention relates to a hydrogen sensor and a method of manufacturing the same, and more particularly to a method of manufacturing a hydrogen sensor using a transition metal or an alloy thin film thereof.

Hydrogen energy is recyclable and has an advantage of not causing environmental pollution, and research on this is being actively conducted.

However, if the hydrogen gas leaks more than 4% in the atmosphere, there is a risk of explosion, there is a problem that it is difficult to be widely applied to real life unless safety is secured in use.

Therefore, along with the study on the utilization of hydrogen energy, the development of a hydrogen gas detection sensor (hereinafter, simply referred to as a 'hydrogen sensor') that can detect the leakage of hydrogen gas at the time of actual use is being progressed in parallel.

Hydrogen sensors developed to date include ceramic / semiconductor sensors (contact combustion, piezoelectric and semiconductor thick film), semiconductor element sensors (MISFET, MOS), optical sensors and electrochemical (Potentiometric / Amperometric). .

In the case of ceramic / semiconductor type sensors, the change in electrical conductivity that occurs when gas comes into contact with the surface of the ceramic semiconductor is often used, and most of them are used by heating in the air, and thus stable metal oxides (ceramic, SnO2, ZnO, Fe2O3) Mainly used. However, there is a disadvantage that it is impossible to detect a high concentration of hydrogen gas saturated with a high concentration of hydrogen gas.

In the case of the contact combustion type, the sensor output is proportional to the gas concentration, the detection accuracy is high, and the detection temperature is changed by the ambient temperature or humidity. It has the advantage of less impact. However, the disadvantage is that the operating temperature must be high and it is not selectable.

In addition, optical sensors using semiconductor device-type sensors (MISFET, MOS) and gas-coloured materials whose light transmittance changes with hydrogen adsorption use palladium which adsorbs hydrogen gas well, and are repeatedly exposed to high concentration of hydrogen gas. In case of performance deterioration.

Lastly, the electrochemical gas sensor is an apparatus that measures the current flowing through the external circuit by oxidizing or reducing the detected gas electrochemically. Can be. Despite the various gas detection capabilities, the manufacturing method has the disadvantage of being complicated and difficult.

Recent materials used as hydrogen sensing technology for sensors include Pd thin film sensors, semiconductors such as MISFETs, carbon nanotube sensors, and titania nanotube sensors (F. Dimeo et al., 2003 Annual Merit Review). However, despite their respective advantages, their performance is still insignificant in terms of detectable initial hydrogen concentration, reaction time, sensing temperature, and driving power consumption. .

Conventionally developed technology uses a graphite layer to form a place where Pd can be generated by using a reaction of palladium (Pd) with hydrogen, and the hydrogen is introduced into the functionalized substrate of the palladium particles. A technique using a phenomenon in which the electrical resistance is reduced by the expansion of the Pd lattice to be formed like wires connected to each other has been proposed (Penner et al. Science 293 (2001) 2227-2231). Here, by experimentally confirming the lattice expansion of Pd by hydrogen adsorption, the electrical signals were detected by arranging Pd nanoparticles in the form of non-contiguous wires. However, there are disadvantages in that the manufacturing method is complicated and the minimum detection concentration is high.

The hydrogen gas detection sensor using a Pd thin film is commonly used because of its excellent hydrogen detection capability compared to a sensor manufactured using other materials. Conventionally, in the case of such a hydrogen sensor, a method of inflating a lattice by applying a strong force to the Pd particles by sputtering and vapor deposition, etc. adheres to the substrate, but this result has an effect that the connection does not last after hydrogen exposure. Since the amount of expansion is reduced by the bonding force with the substrate, the sensitivity to hydrogen is not large. In addition, in the case where the Pd particles are not adhered to the substrate, when hydrogen exposure is interrupted after the Pd lattice expands during hydrogen exposure, reproducibility is poor because the Pd particles are not restored to the initial state due to the bonding force between Pd. Furthermore, these hydrogen sensors using Pd particles have a problem that the initial resistance value changes when only hydrogen is reacted at high concentration and the hydrogen exposure is stopped.

As described above, the conventional hydrogen sensors supplement the problems of the existing hydrogen sensors to some extent, but are not an alternative to the conventional sensors in the problems of sensing ability, sensitivity, stability, and fast reaction time at low concentration.

Therefore, studies on materials and structures capable of optimizing hydrogen detection performance are ongoing, and attempts to improve hydrogen detection performance using nanomaterials continue.

As a representative nanomaterial, palladium has a property of reacting with hydrogen irrespective of the surrounding environment, and when the hydrogen gas is chemically absorbed, the lattice constant increases, thereby increasing resistance when applying current.

Using these phenomena, studies of solid-state hydrogen sensors that react only with hydrogen using palladium nanowires that have maximized surface area have been actively conducted. The hydrogen sensor using palladium nanowires detects hydrogen using a phenomenon in which the resistance value of palladium nanowires is changed depending on the presence or absence of hydrogen.

Specifically, when hydrogen is not present, palladium nanowires have a nanogap, which shows high resistance. When hydrogen is present, the hydrogen gap is absorbed and expands in volume, and the nanogap is filled by volume expansion. The resistance is reduced, and the principle of detecting the concentration of hydrogen by measuring the change in the resistance value is applied to the sensor.

Palladium nanowire manufacturing methods developed so far include a method using a Highly Oriented Pyrolytic Graphite (HOPG) template, a method using E-beam lithography (EBL), and a method using di-electrophoresis (DEP).

The method using the HOPG template is a method of producing palladium nanowires electrochemically to the nano-mould of the substrate, but the manufacturing process is complicated, takes a long time, and the resistance value of the palladium nanowires produced by the manufacturing process error is constant It was difficult to have the disadvantage of low production yield.

In addition, the method using the ELB has a disadvantage in that the method for forming palladium nanowires electrochemically after nano-patterning on the substrate, the production yield is low, the manufacturing cost is expensive.

Similarly, the method using DEP also forms a layer of nanowire material on a substrate and supplies a high frequency alternating current power through a metal electrode to manufacture nanowires, but the manufacturing process is complicated and uniform palladium nano There was a disadvantage in that production yield was low because the wire could not be produced.

Accordingly, there is a need to newly develop a new manufacturing process that can easily and easily manufacture a palladium hydrogen sensor having a nano gap shape while maintaining the hydrogen sensing performance of the palladium metal.

In order to solve the above-mentioned problems of the prior art, an object of the present invention is to replace the conventional electrochemical method of manufacturing a hydrogen sensor with a complicated manufacturing method, a long time, and a low production yield, and thus it is simple in a short time. An object of the present invention is to provide a new method of manufacturing a hydrogen sensor that can produce a cheaply manufactured hydrogen sensor.

In addition, another object of the present invention to eliminate the influence of the error of the manufacturing process, and to increase the reproducibility of the hydrogen sensor reacts to the hydrogen to provide an ultra low-cost high-performance hydrogen sensor capable of precisely detecting hydrogen and its manufacturing method I would like to.

Hydrogen sensor manufacturing method according to an aspect of the present invention for achieving the above object is a step of disposing a transition metal or its alloy thin film on the surface of the elastic substrate; And forming a nanogap in the thin film disposed on the surface of the elastic substrate by applying a tensile force to the elastic substrate, wherein upon application of the tensile force, the thin film is stretched in the direction in which the tensile force is applied, The nano-gap is compressed in the vertical direction of the direction in which the tensile force is applied, and upon recovery of the tensile force, the thin film is compressed again in the direction in which the tensile force is recovered and at the same time again in the vertical direction in the direction in which the tensile force is recovered. It characterized in that to form.

Preferably, the elastic substrate may have a Poisson's ratio of 0.3 to 0.7.

Preferably, the tensile force may be applied so that the elastic substrate is stretched by 1.05 to 1.50 times.

Preferably, the transition metal may be at least one selected from Pd, Pt, Ni, Ag, Ti, Fe, Zn, Co, Mn, Au, W, In, Al expandable by hydrogen, and the alloy is Pd -Ni, Pt-Pd, Pd-Ag, Pd- Ti, Pd-Fe, Pd-Zn, Pd-Co, Pd-Mn, Pd-Au, Pd-W, Pt-Ni, Pt-Ag, Pt-Ag And all transition metal alloys expandable by at least one hydrogen selected from Pt-Ti, Fe-Pt, Pt-Zn, Pt-Co, Pt-Mn, Pt-Au, and Pt-W.

Preferably, the transition metal and the alloy is to use Pd and its alloy.

Preferably, the elastic material may use natural rubber, synthetic rubber, or polymer.

Preferably, the synthetic rubber may be any one selected from the group consisting of butadiene rubber, isoprene rubber, chloroprene rubber, nitrile rubber, polyurethane rubber, and silicone rubber, the silicone rubber is PDMS (polydimethylsiloane) Can be.

Preferably, the tensile force may be repeatedly applied to the elastic substrate one or more times.

Preferably, the tensile force may act in one or more directions on the elastic substrate.

Preferably, the tensile force may be repeatedly applied in a first direction, a second direction perpendicular to the first direction, and a third direction forming a direction different from the first direction and the second direction.

Preferably, the second direction in which the tensile force is applied forms an angle of 90 ° with the first direction, and the third direction in which the tensile force is applied is greater than ± 0 ° or ± 90 ° with the first direction and the second direction. An angle of less than ° can be achieved.

Preferably, the elastic substrate may have a width of 0.1 to 2m, a length of 0.1 to 2m, and a thickness of 0.15 to 1.5m.

Preferably, the method of manufacturing the hydrogen sensor may further comprise the step of heat-treating the transition metal or the alloy thin film formed with the plurality of nanogap.

Preferably, the method of manufacturing the hydrogen sensor may further comprise the step of ion milling the transition metal or the alloy thin film formed with the plurality of nanogap.

In addition, the hydrogen sensor according to another aspect of the present invention comprises a substrate made of an elastic material; A transition metal or an alloy thin film disposed on the surface of the substrate and having a plurality of nanogaps formed by a tensile force applied to the substrate; And electrodes formed at both ends of the thin film.

The hydrogen sensor manufacturing method of the present invention is a conventional hydrogen sensor manufacturing method (semiconductor type, catalytic combustion type, field effect transistor) type, electrolyte type (electrochemical type), optical fiber type, piezoelectric type, thermoelectric type, etc. having a complicated process. Or commercially available hydrogen sensors (contact combustion hydrogen sensors, palladium alloy and hotplate coupled hydrogen sensors, Pd / Ag alloy solid-state hydrogen sensors, Pd gate FET hydrogen sensors, etc.) in large, expensive and inconvenient manners. Alternatively, by applying a physical tensile force to a substrate on which palladium or an alloy thin film is disposed, the thin film can be processed into a nanogap that can sense hydrogen gas, thereby providing a high performance hydrogen sensor at a low cost in a short time. Can mass produce.

In addition, the manufacturing method of the hydrogen sensor of the present invention is a conventional method of manufacturing a hydrogen sensor having a complex process (semiconductor type, catalytic combustion type, FET (field effect transistor) type, electrolyte type (electrochemical), optical fiber type, piezoelectric type, Unlike thermoelectric, etc., palladium or an alloy thin film thereof may be placed on an elastic substrate, the elastic substrate may be tensioned, and the thin film disposed on the substrate may be stretched in the tensile force acting direction and compressed in the vertical direction. have. Therefore, it is possible to easily form a transition metal having a nano gap or a thin film by imposing a physical strain by a simple method of applying a tensile force to the elastic substrate. Therefore, a cheap and high-performance hydrogen sensor having a change in the resistance value according to the change in the hydrogen concentration can be manufactured in large quantities, and through this, it is possible to significantly improve the yield of the hydrogen sensor production.

In addition, unlike the conventional hydrogen sensor formed on a substrate made of an inelastic material, such as a silicon oxide substrate, a sapphire substrate, or a glass substrate, the hydrogen sensor of the present invention may be disposed by placing a transition metal or an alloy thin film thereof on a substrate surface made of an elastic material. By being made, the hydrogen sensor has its own elasticity and can be freely installed in various spaces in which hydrogen may leak, thereby widening the use of the hydrogen sensor.

The hydrogen sensor manufacturing method of the present invention replaces the complicated conventional method of producing palladium nanowires using a mass process such as lithography, and places a transition metal or an alloy thin film on the elastic substrate, and stretches the elastic substrate in a specific direction. This allows the mass production of hydrogen sensors with nanogap.

The thin film disposed on the substrate is stretched in the tension force action direction and compressed in the vertical direction. In addition, when the tensile force applied to the elastic substrate is recovered again, the thin film is compressed in the direction in which the tensile force is recovered and at the same time again in the vertical direction.

Therefore, the method of manufacturing the hydrogen sensor of the present invention imposes a physical strain on the palladium or its alloy thin film by a simple method of applying a tensile force to the elastic substrate, thereby producing a hydrogen sensor having a nano gap inexpensively and easily in a short time Will be adopted.

When the nanogap is formed in the transition metal or the alloy thin film as described above, the nanogap has a high resistance value because the current does not flow smoothly. However, under hydrogen atmosphere, the surrounding hydrogen is absorbed to increase the lattice constant of the transition metal or its alloy thin film, and as the volume increases, the nano gap is filled so that the current flows smoothly, thereby having a low resistance value. . The hydrogen concentration can be measured by measuring a change in resistance value depending on the presence or absence of such hydrogen gas.

Hereinafter, a method of manufacturing the hydrogen sensor of the present invention and a hydrogen sensor manufactured according to the present invention will be described in detail with reference to the accompanying drawings.

First, in order to manufacture the hydrogen sensor of the present invention, a transition metal or an alloy thin film thereof is disposed on an elastic substrate.

In this case, the substrate serves as a substrate on which the thin film serving as a sensor unit for detecting hydrogen is disposed, and when strain is applied in the process of manufacturing a hydrogen sensor, transferring the strain to the thin film disposed on the substrate. Play a role.

The substrate is made of an elastic material that can be stretched in that direction when a tensile force is applied, and can be restored to its original shape when the tensile force is removed again.

Referring to FIG. 1, when tensioning an elastic material in the longitudinal direction (x direction), as is commonly seen in an elastic material, the elastic material is in the longitudinal direction unless there is any condition other than the tensile strain component in the longitudinal direction. It is expected that the contraction in the transverse direction (y direction) will occur as it increases. The shrinkage strain in the lateral direction (y direction) is contracted while maintaining a constant ratio with the longitudinal tensile strain. When the tensile force applied to the stretched elastic material is recovered or the elastic material is compressed in the uniaxial direction, a tensile strain occurs in the transverse direction, and at the same time as the tension between the transverse tensile strain and the longitudinal shrinkage change rate. It is deformed while maintaining a constant ratio. The value of a certain ratio of the transverse tensile strain and the longitudinal shrinkage change is defined as the poisson's ratio of the elastic material.

As shown in FIG. 1, when a tensile force is applied to an elastic material, palladium or an alloy thin film disposed to be integrally coupled to the surface thereof is integrally deformed according to the deformation of the elastic material, and the aspect of the deformation is a tensile force. When this is applied, the film is stretched in the x direction and contracted in the y direction, and when the tensile force is recovered, the film contracts in the x direction and is stretched in the y direction.

2A to 2D, a physical strain may be imposed on the thin film 110 integrally bonded to the surface of the elastic substrate 120 by a simple method of applying a tensile force to the elastic substrate. The imparted palladium or alloy thin film 110 thereof, as shown in FIGS. 2A and 2D, vertically intersect to form a nanogap 11.

Since the tensile force applied to the elastic substrate 120 is transmitted to the palladium or its alloy thin film 110 as it is, the tension of the thin film 110 by the Poisson's ratio of the elastic substrate 120 The ratio of tension and shrinkage in the direction (x direction) or the shrinkage direction (y direction) is determined.

In the method of manufacturing the hydrogen sensor of the present invention, the thin film is stretched in the x direction in which the tensile force is applied, and simultaneously contracted in the y direction, which is perpendicular to the direction in which the tensile force is applied. Therefore, it is necessary to adjust the magnitude of the tensile force acting on the elastic substrate 120 in consideration of the physical strain acting on the thin film 110 and the efficient formation of the nanogap 11 by the strain. For this reason, the elastic substrate 120 preferably has a Poisson's ratio of 0.2 to 0.8, more preferably a Poisson's ratio of 0.3 to 0.7, and a Poisson's ratio of 0.5 most preferred is poisson's ratio.

In addition, the tensile force acting on the elastic substrate 120 comprehensively considers the characteristics of the elastic substrate and the thickness, material and properties of the transition metal or its alloy thin film formed integrally on the surface of the elastic substrate, The elastic substrate 120 is preferably stretched so that the nanogap 11 may be uniformly formed on the thin film 110, and most preferably, the elastic substrate 120 is stretched by 1.05 to 1.50 times. Do.

The transition metal or the alloy thin film 110 is disposed on the substrate 120. In this case, the present invention is not limited to the type of transition metal, and various transition metals or alloy thin films thereof expandable by hydrogen may be used. ,

Preferably, the transition metal may be at least one selected from Pd, Pt, Ni, Ag, Ti, Fe, Zn, Co, Mn, Au, W, In, Al expandable by hydrogen.

In addition, the alloy is Pd-Ni, Pt-Pd, Pd-Ag, Pd- Ti, Pd-Fe, Pd-Zn, Pd-Co, Pd-Mn, Pd-Au, Pd-W, Pt-Ni, Pt- Ag, Pt-Ag, Pt-Ti, Fe-Pt, Pt-Zn, Pt-Co, Pt-Mn, Pt-Au, Pt-W can be all transition metal alloys expandable by at least one hydrogen . For example, in the case of Pd-Ni or Pd-Au alloys, Pd acts as a catalyst in the reaction with hydrogen, and Ni or Au reduces the lattice constant of Pd, thus producing hydrogen sensors made of Pd-Ni or Pd-Au alloys. It increases the durability and shortens the reaction time with hydrogen.

More preferably, the transition metals and alloys use Pd and its alloys.

Meanwhile, any method commonly used in the art may be used as the method of disposing the transition metal or the alloy thin film 110 on the substrate 120, and examples thereof include sputtering and evaporation. Physical vapor deposition such as (evaporation), and chemical vapor deposition such as chemical vapor deposition (CVD) and atomic layer deposition (ALD) may be used.

The material usable as the elastic substrate 120 may be stretched in the direction when a tensile force is applied, and any material that may be restored to its original shape when the tensile force is removed again may be used. For example, natural rubber, Synthetic rubbers or polymers.

Examples of the synthetic rubber include butadiene-based rubber, isoprene-based rubber, chloroprene-based rubber, nitrile-based rubber, polyurethane-based rubber, or silicone-based rubber, and preferably disposed on a substrate because of low interfacial free energy. PDMS (polydimethylsiloane), which is an elastic material having good durability, may be used for molding a transition metal or an alloy thereof, and in addition to the PDMS, a polyimide polymer material, a polyurethane polymer material, and a fluorocarbon Fluorocarbon-based polymers, acrylic polymers, polyaniline-based polymers, and polyester-based polymers are also suitable for elasticity if they can transfer tensile force to thin films made of transition metals or their alloys. Can be used after adjustment.

When a tensile force is applied to the elastic substrate 120 on which the transition metal or the alloy thin film 110 is disposed, as described above, the thin film 110 is stretched in the x direction to which the tensile force is applied and simultaneously in the y direction. It is contracted and subjected to physical strain to form the nanogap 11. In this case, even when a tensile force is applied even once, the nanogap 11 may be formed in the thin film. However, in consideration of the directionality and the uniformity when the nanogap 11 is formed, it acts on the elastic substrate 120. It is preferable that the tensile force to act is repeated one or more times.

In addition, the application of the tensile force may be simply applied in one specific direction, but is not limited thereto. As shown in FIG. 3, the ductility of the alloy may be due to the metal component added to the preparation of the palladium alloy. In the case of increasing, a tensile force may be applied in one or more directions, for example, two or three directions, to facilitate the formation of nanogaps in the thin film.

When the tensile force is applied in the three directions, at least one time in a first direction, a second direction perpendicular to the first direction, and a third direction forming a direction different from the first direction and the second direction. Repeatedly, it is possible to effectively concentrate the strain acting on the thin film, thereby forming a nano gap in the transition metal or its alloy thin film, wherein the second direction to which the tensile force is applied is 90 and the first direction An angle of ° and a third direction in which the tensile force is applied effectively concentrate the strain acting on the thin film when the first direction and the second direction have an angle greater than ± 0 ° or less than ± 90 °. Can be.

On the other hand, the thickness of the transition metal or the alloy thin film is preferably in the range of 1nm to 100㎛. The thickness of the transition metal or its alloy thin film is related to whether or not nanogap is effectively formed in the thin film when the tensile force is applied to the substrate and removed. The thinner the thickness, the more nanogaps can be created. However, if the thickness is too thin, when the tensile force is repeatedly applied to the substrate, the transition metal or its alloy thin film may be physically damaged and torn. Therefore, the thickness of the thin film is preferably 1 nm to 100 μm so as to effectively create a nano gap in the thin film and to withstand the applied tensile force, and the elastic properties of the elastic substrate and the physical properties of the transition metal or alloy thin film thereof. In consideration of the above, the thickness of the thin film is more preferably 3 nm to 100 nm, and most preferably 5 nm to 15 nm.

In addition, the substrate is not limited in size, but when combining the convenience of applying a tensile force to the substrate and the size of the manufactured hydrogen sensor, etc., from a practical point of view, a width of 0.1 to 2m, 0.1 to 2m It is preferred to have a length and a thickness of 0.15 to 1.5 m.

Referring to FIG. 4, the transition metal or the alloy thin film, in which the nanogap is formed in the above-described manner, exhibits high resistance because current does not flow smoothly due to the nanogap when hydrogen is not present. However, under the hydrogen atmosphere, the hydrogen is absorbed to expand the volume, and the nano gaps are filled with the volume expansion, thereby having a low resistance. Accordingly, the concentration of hydrogen may be sensed by measuring the change in the resistance value and using the thin film having the nanogap formed as a hydrogen sensing unit.

The nano-gap can be freely controlled by the tensile force applied to the substrate and the direction of the force, the nano-gap is filled as the transition metal or its alloy expands by absorbing hydrogen in a hydrogen atmosphere, In consideration of the limit of sensing hydrogen through a change in the resistance value, it is preferred to have a width of 1 nm to 10 μm.

In addition, the thin film having the nano-gap as described above can be maximized by ion milling. A method of ion milling a thin film having such a nanogap includes a method of ion milling the upper part of the substrate on which the thin film is formed, and more preferably, a nano gap after applying a resin layer on the substrate on which the thin film is formed. There is a method of forming a resin layer pattern so as to expose only a thin film portion having a portion, and after the exposed thin film is ion milled, the resin layer is removed.

In addition, the mechanical properties may be increased by heat-treating the transition metal or the alloy thin film having the nanogap. The heat treatment method includes a method in which the substrate on which the thin film is formed is heat treated in a furnace.

The thin film having the plurality of nanogaps formed thereon forms electrodes by depositing conductive metals at both ends in a direction parallel to the direction in which the nanogap is formed to apply current. In this case, the nano-gap thin film and the electrode are electrically connected to each other. The current is applied to one of the electrodes thus formed (I +) and at the same time the voltage is measured (V +), and the current (I-) and voltage (V-) output from the other electrode are measured, and the two-terminal measurement method (quasi It is possible to measure the resistance change according to the change of hydrogen concentration by using -two prove method.

As described above, after the tensile force is applied to the elastic substrate on which the transition metal or the alloy thin film is disposed to form a nanogap, the hydrogen sensor having the electrode formed by depositing a conductive metal on the thin film has a resistance value depending on the presence or absence of hydrogen gas. It has a different characteristic, through which the hydrogen concentration can be measured.

As shown in Figure 2a, the hydrogen sensor 10 according to an embodiment of the present invention comprises a substrate 120 made of an elastic material; A transition metal or an alloy thin film 110 disposed on a surface of the substrate 120 and having a plurality of nanogaps 111 formed by a tensile force applied to the substrate 120; And electrodes 130 formed at both ends of the thin film.

Referring to FIG. 4, when the hydrogen sensor 10 is exposed to hydrogen gas, the partial pressure of H ₂ around the Pd thin film having a nanogap becomes higher than the partial pressure of hydrogen inside the Pd thin film, and the hydrogen molecule is Pd. In order to lower the interfacial energy of the thin film surface, it is adsorbed on the Pd thin film surface and dissociated into H atoms. The difference in hydrogen partial pressure inside and outside the Pd thin film acts as a driving force for dissociated H atoms to diffuse into the Pd thin film. Penetrates into PdHx. At this time, the lattice constant increases due to H atoms entering the invasive sites.

Accordingly, the hydrogen sensor 10 has a low lattice constant under a hydrogen atmosphere, and thus, when the volume expands, the nano gaps 11 are filled by the volume expansion. By measuring such a change in resistance value, the concentration of hydrogen may be detected using the thin film having the nanogap formed as a hydrogen sensing unit.

Unlike the conventional hydrogen detection sensor, the hydrogen sensor manufactured according to the above method can measure room temperature and has a small size, thereby reducing power consumption.

Accordingly, the hydrogen sensor of the present invention can satisfy the essential requirements as a sensor for reducing reaction time and driving stable while satisfying characteristics of low cost, miniaturization, low power consumption, and room temperature operation.

Hereinafter, the present invention will be described in detail with reference to a preferred embodiment so that those skilled in the art can easily practice the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

Manufacturing example  One

Pd was deposited using a sputter on a PDMS substrate 120 having a width of 20 mm, a length of 10 mm, and a thickness of 0.75 mm. At this time, the Pd thin film 110 has a thickness of 7.5 nm and is disposed on the substrate 120 in a size of 15 mm in width and 10 mm in length.

Subsequently, the tensile force was applied to the substrate 120 five times to extend the horizontal length of the substrate 120 to 25 mm, and then the tensile force was removed.

2A to 2D, it can be seen that the Pd thin film 110 is processed to have a nano gap by applying a tensile force as described above.

Hydrogen sensor is electrically connected to the thin film 110 and the electrode 130 on the PDMS substrate 120 by depositing Au electrodes on both ends of the thin film 110, the nano-gap 111 is formed through the above process by the sputtering method (10) was prepared.

Manufacturing example  2

The hydrogen sensor 10 was manufactured in the same manner as in Preparation Example 1, except that the thickness of the Pd thin film 110 was 10 nm and was deposited on the elastic substrate 120.

Manufacturing example  3

A hydrogen sensor 10 was manufactured in the same manner as in Preparation Example 1 except that the thickness of the Pd thin film 110 was 12 nm and was deposited on the elastic substrate 120.

Manufacturing example  4

Pd was deposited using a sputter on a PDMS substrate 120 having a width of 20 mm, a length of 10 mm, and a thickness of 0.75 mm. At this time, the Pd thin film 110 has a thickness of 6 nm and is disposed on the substrate 120 in a size of 15 mm in width and 10 mm in length.

Subsequently, the tensile force was applied to the substrate 120 in the horizontal direction (first direction) to increase the horizontal length of the substrate 120 to 25 mm, and then the tensile force was removed to restore the original size.

The tensile force is applied to the substrate 120 to which the tensile force is applied in the first direction in a diagonal direction (second direction) connecting upper right and lower left, so that the substrate 120 is stretched to 1.25 times the diagonal length of the circle. After working, the substrate was returned to its original size.

Subsequently, the tensile force is applied to the substrate 120 exerted with the tensile force in the second direction in a diagonal direction (third direction) connecting the upper left and the lower right to extend the substrate 120 by 1.25 times the original diagonal length. After applying the tensile force, the substrate was restored to its original size.

The nanogap 11 was formed in the thin film 110 disposed on the surface of the substrate 120 by repeatedly applying the tensile force five times in the first, second, and third directions.

Hydrogen sensor is electrically connected to the thin film 110 and the electrode 130 on the PDMS substrate 120 by depositing Au electrodes on both ends of the thin film 110, the nano-gap 111 is formed through the above process by the sputtering method (10) was prepared.

Experimental Example 1

In order to evaluate the characteristics of the hydrogen sensor manufactured according to the above production example, a system 20 capable of measuring using a quasi-two prove method was manufactured and used.

An IV measuring apparatus as shown in FIG. 5, centering on the hydrogen sensor 10 of the manufacturing example, a reaction flow 210, MFC (Mass Flow Controller) 220 for adjusting the flow rate of gas of H ₂ and N ₂ . ), The voltage of the sensor, the current application device 230, and the gas tank 240.

The reaction chamber 210 in which the hydrogen sensor 10 is mounted in the system 20 seals the hydrogen gas and the sensor with the outside when the sensor reacts, and the H ₂ and N ₂ gases are transferred through the MFC 220. The amount is precisely controlled to create the desired ratio of hydrogen gas concentration. The adjusted H ₂ gas reacts with the hydrogen sensor in the reaction chamber 230, and the electrical signal for the change of the sensor is measured through the voltage and current applying device 230.

These measurements were carried out at room temperature and atmospheric pressure, and after mounting the Pd thin film hydrogen sensor 10 having the nanogap 11 in the reaction chamber 210 connected with an external current application device, H ₂ and N ₂ were mixed in the chamber. The difference in resistance was measured by changing a potential difference by applying a current of 100 nA while flowing the prepared gas.

FIG. 6A is a graph showing a result of measuring a change in resistance value at a hydrogen concentration of 4% (40000 ppm) by attaching the hydrogen sensor 10 manufactured in Preparation Example 1 to the system 20 of FIG. 6. 6b is a graph showing current values measured when the hydrogen sensor of Preparation Example 1 is exposed to a hydrogen concentration of 0 to 4%.

6A and 6B, the hydrogen sensor 10 of Preparation Example 1 suddenly changed resistance in about 1 second (one point on the graph means 1 second) at a hydrogen concentration of 4%, the upper explosion limit. It can be seen that the resistance value decreases to zero immediately after removing hydrogen in the reaction chamber 210, so that it can act as a precision hydrogen sensor that can detect the change in hydrogen concentration on-off. have.

6C is a hydrogen sensor manufactured in Preparation Example 2, and FIG. 6D is a hydrogen sensor prepared in Preparation Example 3, respectively, mounted on the system 20 of FIG. This graph shows the result of measuring.

Referring to Figure 6c, it can be seen that the hydrogen sensor of Preparation Example 2 can also act as a precision hydrogen sensor that can detect the change in the concentration of hydrogen of 0 to 4% on-off.

Referring to FIG. 6D, it can be seen that the hydrogen sensor of Preparation Example 3 may also act as a hydrogen sensor by showing a change in current value according to a change in hydrogen concentration.

7A to 7C show the hydrogen sensor 10 manufactured in Preparation Example 4 in the system 20 of FIG. 6 to 1% (10000 ppm), 0.5% (5000 ppm), and 0.05 (500 ppm), respectively. This graph shows the result of measuring the resistance change while changing the hydrogen concentration.

Referring to FIG. 7A, it can be seen that a sudden change in resistance occurs in about 1 second at 1% (10,000 ppm) hydrogen concentration, which is 1/4 of the upper explosion limit concentration (4%). That is, it shows that hydrogen gas can be detected at a much higher speed than the conventional hydrogen sensor element, and it can be seen that it has very good durability without changing the magnitude of the signal even after several repetitions.

In addition, when the hydrogen in the reaction chamber 210 is removed, the resistance value increases rapidly in about 1 to 2 seconds, and it can be seen that it has a fast recovery speed.

Referring to FIG. 7B, even when the hydrogen concentration was reduced to 0.5% (5,000 ppm), a sudden resistance change appeared in about 2 to 3 seconds, and it was found that hydrogen could be detected at a high speed. The sensitivity was measured at 700%, indicating that the hydrogen sensor of the present invention showed excellent performance in detecting hydrogen gas.

In addition, referring to FIG. 7C, even in the amount of initial detection hydrogen, which is the most important element of the sensor, hydrogen gas is detected in about 3 to 5 seconds at a concentration of 0.05% (500 ppm) of hydrogen, and a very small amount of hydrogen is immediately detected. It showed characteristics. In addition, the resistance value increased in 1 second when hydrogen was removed, indicating a fast recovery rate (300% sensitivity).

On the other hand, Figure 8a is a graph showing the current value measured when exposing the hydrogen sensor having a Pd thin film thickness of 16nm in the air according to another embodiment of the present invention, Figure 8b is a hydrogen sensor having a Pd thin film thickness of 14nm in the air It is a graph showing the change of the current value with time when exposing. As shown in FIG. 8A, when the Pd thin film is thick at 16 nm, it can be seen that the Pd thin film operates in the air with an ON sensor which does not fall to zero. On the other hand, in the case of FIG. 8 / b, where the thickness of the Pd thin film is 14 nm, the basic resistance falls to zero, and it can be seen that it operates as an on-off sensor in the air after several initial reactions.

On the other hand, Figure 9a according to another embodiment of the present invention is a picture showing a mechanism when the hydrogen sensor is exposed to nitrogen or in the air, Figure 9b is a time when the hydrogen sensor having a Pd thin film thickness of 14nm in the air at the time It is a graph showing the change of current value. As shown in Figure 9a, when the Pd thin film is formed in the nano-cracks due to the tension is present in the ON state that the basic resistance does not drop to 0, when exposed to hydrogen, the resistance is reduced by expansion and hydrogen is removed Later it turns out to be in the OFF state as it changes to thermodynamic equilibrium, acting as an ON-OFF sensor. As an example of this, when the hydrogen sensor having a thickness of 8 nm of Pd thin film is exposed to nitrogen, a change in current value with time is shown.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the technical idea of the present invention, and it is obvious that the present invention belongs to the appended claims. Do.

As described above, the present invention is different from the conventional method of producing a hydrogen sensor of a complex electrochemical method, which takes a long time and a low production yield. By applying a tensile force, the thin film can be processed into a form having a nano-gap that can detect the hydrogen gas, there is an advantage that can mass-produce a high-performance hydrogen sensor at a low cost in a short time.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an explanatory view showing an embodiment in which an elastic substrate and a transition metal or alloy thin film thereof disposed on an elastic substrate are applied when a tensile force is applied to the elastic substrate on which the palladium thin film is disposed.

2A is a perspective view of a hydrogen sensor according to an embodiment of the present invention.

2B is a micrograph (about 1000 times) of a palladium thin film having a nano gap formed thereon.

2C is a micrograph (about 50 times) of a palladium thin film having a nano gap formed thereon.

FIG. 2D is a 3D stereoscopic image of a palladium thin film with nanogaps formed. FIG.

FIG. 3 is an explanatory diagram showing a shape change of a substrate on which a palladium thin film is formed when a tensile force is sequentially applied and removed in one direction or more.

4 is an explanatory diagram illustrating a change in a resistance value of a hydrogen sensor according to an embodiment of the present invention depending on the presence of hydrogen.

5 is a schematic diagram of a system for measuring the hydrogen detection capability of the hydrogen sensor of the present invention.

FIG. 6A is a graph illustrating a result of measuring a resistance value by changing a hydrogen concentration in a range of 0% to 4% (40000 ppm) by installing a hydrogen sensor according to an exemplary embodiment of the present invention.

6B is a graph showing current values measured when the hydrogen sensor according to an embodiment of the present invention is exposed to a hydrogen concentration of 0 to 4%.

FIG. 6C is a graph illustrating a result of measuring a resistance value by changing a hydrogen concentration in a range of 0% to 4% (40000 ppm) by installing a hydrogen sensor according to an exemplary embodiment of the present invention.

6D is a graph showing a current value measured when the hydrogen sensor according to an embodiment of the present invention is mounted in a measurement system and exposed to a hydrogen concentration of 0 to 4%.

FIG. 7A is a graph illustrating a result of measuring a resistance change at a concentration of 10000 ppm hydrogen gas by attaching a hydrogen sensor according to an exemplary embodiment of the present invention to the hydrogen detection system of FIG. 6.

7B is a graph illustrating a result of measuring a resistance change at a concentration of 5000 ppm hydrogen gas by attaching a hydrogen sensor according to an exemplary embodiment of the present invention to the hydrogen detection system of FIG. 6.

7C is a graph illustrating a result of measuring a resistance change at a concentration of 500 ppm hydrogen gas by attaching a hydrogen sensor according to an embodiment of the present invention to the hydrogen detection system of FIG. 6.

8A is a graph showing a current value measured when a Pd thin film 16 nm hydrogen sensor according to another embodiment of the present invention is mounted in a measurement system and exposed to air.

8B is a graph showing a change in current value with time when a hydrogen sensor having a Pd thin film thickness of 14 nm is exposed to air.

9A is a diagram of a mechanism that occurs when a Pd thin film hydrogen sensor is repeatedly exposed to hydrogen.

9B is a graph showing a change in current value with time when a hydrogen sensor having a Pd thin film thickness of 8 nm is exposed in hydrogen.

<Explanation of symbols for the main parts of the drawings>

10: hydrogen sensor 110: palladium or its alloy thin film

111: nano gap 120: substrate

130 electrode 20 hydrogen sensor measurement system

210: reaction chamber 220: MFC (Mass flow controller)

  230: current voltage application device 240: gas tank

Claims (18)

Disposing a transition metal or an alloy thin film thereof on the surface of the elastic substrate; And Applying a tensile force to the elastic substrate to form a nanogap in the thin film disposed on the surface of the elastic substrate; Including, Upon application of the tensile force, the thin film is stretched in the direction in which the tensile force is applied, and simultaneously compressed in the vertical direction in the direction in which the tensile force is applied, Upon recovery of the tensile force, the thin film is compressed again in the direction in which the tensile force is recovered and at the same time forms the nanogap by tensioning again in the direction perpendicular to the direction in which the tensile force is recovered. . The method of claim 1, wherein the transition metal is at least one selected from Pd, Pt, Ni, Ag, Ti, Fe, Zn, Co, Mn, Au, W, In, and Al. .        The method of claim 1, wherein the alloy is Pd-Ni, Pt-Pd, Pd-Ag, Pd- Ti, Pd-Fe, Pd-Zn, Pd-Co, Pd-Mn, Pd-Au, Pd-W, Pt Hydrogen sensor characterized in that at least one selected from -Ni, Pt-Ag, Pt-Ag, Pt-Ti, Fe-Pt, Pt-Zn, Pt-Co, Pt-Mn, Pt-Au, Pt-W Manufacturing method.       The method of claim 1, wherein the transition metal is Pd, and the alloy is a Pd alloy. The method of claim 1, And said substrate has a Poisson's ratio of 0.3 to 0.7. The method of claim 1, The tensile force is a method of manufacturing a hydrogen sensor, characterized in that applied to the elastic substrate to be stretched by 1.05 to 1.50 times The method of claim 1, The elastic material is a method of producing a hydrogen sensor, characterized in that using natural rubber, synthetic rubber, or polymer. The method of claim 7, wherein The synthetic rubber is any one selected from the group consisting of butadiene rubber, isoprene rubber, chloroprene rubber, nitrile rubber, polyurethane rubber, and silicone rubber. The method of claim 8, The silicon-based rubber is a manufacturing method of a hydrogen sensor, characterized in that the polydimethylsiloane (PDMS). The method of claim 1, The tensile force is a method of manufacturing a hydrogen sensor, characterized in that the elastic substrate is repeated one or more times. The method of claim 1, The tensile force is a manufacturing method of a hydrogen sensor, characterized in that acting in more than one direction on the elastic substrate. The method of claim 11, The tensile force is repeatedly applied in a first direction, a second direction perpendicular to the first direction, and a third direction forming a direction different from the first direction and the second direction. Way.         The method of claim 1, wherein a thickness of the transition metal or an alloy thin film thereof satisfies a range of 1 nm to 100 µm. The method of claim 1, The elastic substrate is a method of manufacturing a hydrogen sensor, characterized in that having a width of 0.1 to 2m, a length of 0.1 to 2m, and a thickness of 0.15 to 1.5m. The method of claim 1, And heat-treating the transition metal or the alloy thin film having the nanogap formed therein. The method of claim 1, And ion milling the transition metal or the alloy thin film having the nanogap formed thereon. The method of claim 1, The formed nano gap has a width of 1nm to 10㎛ method for producing a hydrogen sensor. A substrate made of an elastic material; 18. A transition metal or alloy thin film thereof having a plurality of nanogaps formed by any one of claims 1 to 17; And Electrodes formed at both ends of the thin film; Hydrogen sensor comprising a.

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