Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
  • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
  • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
  • G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
  • G01N27/127—Composition of the body, e.g. the composition of its sensitive layer comprising nanoparticles
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/0004—Gaseous mixtures, e.g. polluted air
  • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
  • G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
  • G01N33/0036—General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
  • G01N33/005—H2

Definitions

• the present invention relates to a hydrogen sensor and a method for manufacturing the same, and more particularly, to a hydrogen sensor using a transition metal or an alloy thin film thereof and a method for manufacturing the same.
• Hydrogen energy is recyclable and has the advantage of not causing environmental pollution, and research on this is being actively conducted.
• Hydrogen sensors developed to date include ceramic / semiconductor sensors (contact combustion, thermoelectric and semiconductor thick film sensors), semiconductor element sensors (MISFET, MOS), optical sensors and electrochemical (Po ten tiome) trie / Amperometric) sensor.
• the change in the heat of combustion generated by the oxidation reaction generated by the contact of the combustible gas on the sensor surface is detected.
• the sensor output is proportional to the gas concentration, the detection accuracy is high, and the ambient temperature or humidity is detected. There is a merit that there is little influence.
• the disadvantage is that the operating temperature must be high and it is not selectable.
• the electrochemical sensor is an apparatus that measures the current flowing through the pseudo circuit by oxidizing or reducing the gas to be detected electrochemically.
• the electrochemical sensor can be classified into electrostatic potential, galvanic cell type, and ion electrode type according to the measuring principle.
• 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, semiconductor sensors in MISFETs, carbon nano-levers, and titania nano-levers (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 sensitivity and driving power consumption.
• Pd can be formed by using a graphite layer through reaction of palladium (Pd) with hydrogen, and the palladium particles thus formed are introduced as hydrogen enters the functionalized substrate.
• Pd palladium
• a technique using the 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).
• the Pd nanoparticles were arranged in the form of a non-contiguous wire to detect an electrical signal.
• the manufacturing method is complicated and the minimum detection concentration is high.
• Hydrogen gas detection sensor using Pd thin film is commonly used because the hydrogen detection ability is significantly superior to the sensor made using other materials.
• a method of inflating a lattice by applying a strong force to the Pd particles by sputtering and vapor deposition, etc. closely adheres to the substrate, but the amount of expansion is reduced by the bonding force with the substrate. The sensitivity was not so great.
• bonding Pd particles to the substrate Otherwise, if hydrogen exposure is increased after the Pd lattice expands during hydrogen exposure, reproducibility is poor because the Pd lattice is not restored to the initial state due to the bonding force between Pds.
• these hydrogen sensors using Pd particles have a problem in that the initial resistance value changes when only hydrogen is reacted at high concentration and the hydrogen exposure is stopped.
• 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.
• palladium has the property of reacting with hydrogen regardless of the surrounding environment, and when the hydrogen gas is chemically absorbed, the lattice constant increases, thereby increasing the resistance when applying a current.
• the hydrogen sensor using palladium nanowires detects hydrogen using a phenomenon in which the resistance value of the palladium nanowires changes depending on the presence or absence of hydrogen.
• the palladium nanowire manufacturing methods developed so far include a method using a HighIy Oriented Pyrolytic Graphite (HOPG) template, a method using E-beam lithography (EBL), and a method using di_electrophoresis (DEP).
• HOPG HighIy Oriented Pyrolytic Graphite
• EBL E-beam lithography
• DEP di_electrophoresis
• the method using the HOPG template is a method of manufacturing palladium nanowires electrochemically to the nano-mould of the substrate, but the production process is complicated, takes a long time, due to the error of manufacturing process, It was difficult to have a constant resistance value, so the number of production was low.
• the method using the EBL has a disadvantage in that the method of forming palladium nanowires electrochemically after the nano patterning on the substrate or the number of production is low, the manufacturing cost is expensive.
• 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 complicated manufacturing process and uniform palladium nanoparticles. There was a disadvantage in that the number of production was low because wires could not be produced.
• the present invention has been made to solve the above problems of the prior art, and one object thereof is to replace the conventional hydrogen sensor manufacturing method which is complicated, time-consuming, and low in production, and is simple in a short time.
• the present invention provides a method for manufacturing a new hydrogen sensor and a hydrogen sensor for producing a hydrogen sensor that can be manufactured at low cost.
• a novel hydrogen sensor manufacturing method comprising the steps of forming a transition metal or an alloy thin film on the surface of the elastic substrate; Applying a tensile force to the elastic substrate to form a plurality of nanogaps in the alloy thin film formed on the surface of the substrate, and when the tensile force is applied, the thin film is stretched in the direction in which the tensile force is applied The thin film is compressed in a direction perpendicular to the direction in which the tensile force is applied, and when the tensile force is recovered, the thin film is recompressed in the direction in which the tensile force is recovered and is stretched again in a direction perpendicular to the recovery direction to form the nanogap.
• the transition metal is Pd, Pt, Ni, Ag, Ti, Fe, Zn, Co, Mn, It may be selected from Au, W, In and Al.
• the alloy is Pd-Ni, Pt-Pd, Pd-Ag, Pd—Ti, Pd-Fe, Pd-Zn, Pd— Co, Pd—Mn, Pd— Au, Pc ⁇ W, Pt—Ni, Pt-Ag, Pt-Ag, Pt-Ti, Fe-Pt, Pt-Zn, Pt-Co, Pt-Mn, Pt-Au and Pt—W can be selected.
• the transition metal is Pd
• the alloy may be a Pd alloy.
• the surface of the elastic substrate satisfies 0.90 ⁇ x ⁇ 0.94
• Pd x Nii-x alloy thin films may be formed.
• the elastic substrate may be used having a Poisson's ratio of 0.2 ⁇ 8.8.
• the tensile force may be applied to extend the elastic substrate by 1.05 to 1.50 times.
• the elastic substrate may be made of natural rubber, synthetic rubber or polymer.
• the tensile force may be repeatedly applied to the elastic substrate one or more times.
• the tensile force may be applied to the elastic substrate in one or more directions.
• the tensile force repeats 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. Can be authorized.
• the thickness of the thin film may be about 1 nm to about 100 zm. In one embodiment, the nanogap may be formed at intervals of about 1 nm to 10 zm.
• the method may further include heat treating the transition metal or the alloy thin film having the nano gap formed therein.
• the method may further include ion milling the transition metal or the alloy thin film having the nanogap formed therein.
• a novel method of manufacturing a hydrogen sensor comprising the steps of preparing an elastic substrate; Forming a Pd or Pd alloy thin film having an ⁇ phase on the elastic substrate; Exposing the thin film to a hydrogen-containing gas at a predetermined concentration to change the thin film of ⁇ phase into a thin film of ⁇ phase to form a nanogap in the thin film due to volume expansion; And increasing the exposure to the hydrogen-containing gas to change the ⁇ -phase thin film back to the ⁇ -phase thin film.
• the method may further include heat treating the thin film converted into the ⁇ phase.
• the method may further include milling the thin film converted to the ⁇ phase.
• the hydrogen concentration may be 2 to 15% when the hydrogen-containing gas is exposed.
• the thickness of the thin film may be in the range of about 1 nm to about 100 zm.
• a hydrogen sensor includes a substrate made of an elastic material; A thin film of a transition metal or an alloy thereof formed on a surface of the substrate; An electrode is formed at both ends of the thin film, and the thin film includes a plurality of nanogaps formed by a tensile force applied to the substrate.
• a hydrogen sensor includes a substrate made of an elastic material; The substrate A thin film of Pd or Pd alloy formed on the surface of the film; Electrodes formed at both ends of the thin film, characterized in that the thin film includes a plurality of nano-gaps formed by the method using the phase change.
• the hydrogen sensor manufacturing method of the present invention is a conventional hydrogen sensor manufacturing method having a complex process (semiconductor type, catalytic combustion type, FET (field effect transistor) type electrolyte type (electrochemical type), optical fiber type, piezoelectric type, thermoelectric type, etc. ) Or a commercially available hydrogen sensor with a large, expensive, and inconvenient manner (contact hydrogen news, hydrogen-sensed palladium alloy and hot plate coupled hydrogen sensor, Pd / Ag alloy solid-state hydrogen sensor, Pd gate FET hydrogen sensor) The .
• a physical gap is applied to a substrate on which a transition metal (for example, palladium) or an alloy thin film thereof (for example, Pd—Ni alloy thin film) is disposed, and the thin film has a nanogap capable of detecting hydrogen gas.
• a transition metal for example, palladium
• an alloy thin film thereof for example, Pd—Ni alloy thin film
• the high performance hydrogen sensor can be mass-produced at low cost in a short time.
• a transition metal or an alloy thin film thereof is disposed on an elastic substrate, the elastic substrate is tensioned, and is disposed on the substrate.
• the thin film may be stretched in the direction of the tensile force action and simultaneously compressed in the vertical direction. 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, it is possible to manufacture a large amount of cheap and high-performance hydrogen sensor having a change in resistance value according to the change of hydrogen concentration, thereby significantly improving the number of hydrogen sensor manufactured.
• the hydrogen sensor of the present invention arranges a transition metal or an alloy thin film on a surface of a substrate made of an elastic material.
• the hydrogen sensor itself has elasticity and can be freely installed in various spaces in which hydrogen may leak, thereby expanding the range of utilization of the hydrogen sensor.
• 1 is an explanatory diagram showing an embodiment in which a transition metal or an alloy thin film thereof disposed on an elastic substrate and the elastic substrate is deformed when a tensile force is applied to the elastic substrate on which the palladium thin film is disposed.
• 2 is a perspective view of a hydrogen sensor according to an embodiment of the present invention.
• FIG. 3 is a photograph showing a palladium thin film formed nano-gap, (a) is a micrograph of about 1000 times, (b) is a micrograph of about 50 times, (c) is a 3D stereoscopic image.
• FIG. 4 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 or more directions.
• FIG. 5 is an explanatory diagram illustrating a change in the resistance value of the hydrogen sensor according to an embodiment of the present invention according to the presence or absence of hydrogen.
• FIG. 6 is a schematic diagram of a system for measuring the hydrogen detection capability of the hydrogen sensor of the present invention.
• FIG. 7 is a view showing a change in the resistance value and the current value measured at various hydrogen concentrations after mounting the hydrogen sensor in the measurement system according to an embodiment of the present invention.
• FIG. 8 is a view showing a change in resistance at various hydrogen concentrations after the hydrogen sensor is mounted in a hydrogen detection system according to an embodiment of the present invention, (a) measuring the change in resistance at the concentration of 100 ppm hydrogen gas. It is a graph showing one result, (b) is a graph showing the result of measuring the resistance change at a concentration of 5000 ppm hydrogen gas, (c) is a graph showing the result of measuring the resistance change at a concentration of 500 ppm hydrogen gas.
• FIG. 9 is a diagram showing a current value measured when the Pd thin film hydrogen sensor according to an embodiment of the present invention is mounted on a measurement system and exposed to air vapor, and (a) measures a hydrogen sensor having a thickness of 16 nm Pd thin film.
• FIG. 10 is a diagram showing a mechanism that occurs when a Pd thin film hydrogen sensor is repeatedly exposed to hydrogen and a change in current value with time when a hydrogen sensor having a Pd thin film thickness of 8 nm is exposed to hydrogen deposition.
• FIG. 11 is a view schematically showing two methods of forming a Pd x Ni 1-x thin film on a substrate according to an embodiment of the present invention.
• FIG. 12 is a perspective view of a hydrogen sensor according to an embodiment of the present invention.
• FIG. 13 is an SEM image photograph of a Pd x N- x alloy thin film having a nano gap formed thereon.
• FIG. 15 is a graph showing a current value measured when a hydrogen sensor having a Pd 93 Ni 7 alloy thin film having a thickness of 7.5 nm according to an embodiment of the present invention is mounted in a measurement system and exposed to nitrogen gas.
• FIG. 16 is a graph showing a current value measured when a hydrogen sensor having a 7.5 nm thick Pd 93 Ni 7 alloy thin film according to an embodiment of the present invention is mounted in a measurement system and exposed to air vapor.
• FIG. 17 is a graph showing a current value measured when a hydrogen sensor having a Pd93Ni 7 alloy thin film having a thickness of 8 nm is mounted in a measurement system and exposed to air.
• FIG. 18 is a graph showing a current value measured when a hydrogen sensor having a Pd 93 Ni 7 alloy thin film having a thickness of 10 nm is mounted in a measurement system and exposed to air vapor.
• FIG. 18 is a graph showing a current value measured when a hydrogen sensor having a Pd 93 Ni 7 alloy thin film having a thickness of 10 nm is mounted in a measurement system and exposed to air vapor.
• 19 is a graph showing a current value measured when a hydrogen sensor having a Pd 93 Ni 7 alloy thin film having a thickness of llnm is mounted in a measurement system and exposed to air.
• 20 is a graph showing a current value measured when a hydrogen sensor having a Pd 93 Ni 7 alloy thin film having a thickness of 10 nm is mounted in a measurement system and exposed to nitrogen gas deposition.
• FIG. 21 is a graph showing a current value measured when a hydrogen sensor having a Pd93Ni 7 alloy thin film having a thickness of llnm is mounted in a measurement system and exposed to nitrogen gas.
• FIG. 22 is a graph of current values measured when a hydrogen sensor having a Pd thin film having a thickness of 7.5 nm is mounted on a measurement system as a comparative example of the present invention and exposed to nitrogen gas.
• FIG. 23 is a graph of current values measured when a hydrogen sensor having a Pd thin film having a thickness of 7.5 nm as a comparative example of the present invention is mounted in a measurement system and exposed to air.
• 24 is a view illustrating a manufacturing process of a hydrogen sensor according to an embodiment of the present invention.
• 25 is a 0M image photograph of a 10-nm-thick Pd thin film manufactured according to an embodiment of the present invention.
• FIG. 26A is a graph showing changes in current values measured when a Pd thin film having a thickness of lOnm is exposed to 0.5 to 4% hydrogen concentration
• FIG. 25B is a 0.5 to 4 Pd thin film having a thickness of llnm. It is a graph showing the change of the measured current value when exposed to% hydrogen concentration.
• FIG. 27 is a graph showing changes in current values measured when a Pd thin film having a thickness of 10.5 nm is exposed to 2% hydrogen concentration in air.
• the hydrogen sensor manufacturing method of the present invention replaces the complicated conventional method of producing palladium nanowires using a MEMS process such as lithography, and places a transition metal or an alloy thin film thereof on an elastic substrate, and places the elastic substrate in a specific direction. By stretching, hydrogen sensors with nanogap can be produced in large quantities.
• the thin film disposed on the substrate is stretched in the tensile force action direction and compressed in the vertical direction.
• the thin film is compressed in the direction in which the tensile force is recovered and is stretched again in the vertical direction.
• a physical strain is imposed on a transition metal such as palladium or an alloy thin film thereof by a simple method of imposing a tensile force on an elastic substrate, and thus, nanogap is cheap and easy in a short time.
• a hydrogen sensor having can be prepared.
• a hydrogen sensor having a nanogap may be manufactured using a phase change of the parallax.
• the nanogap When the nanogap is formed in the transition metal or the alloy thin film as described above, since the current does not flow smoothly due to the nanogap, it has a high resistance value. However, in the 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. do. Hydrogen concentration can be measured by measuring a change in resistance value depending on the presence or absence of such hydrogen gas.
• a transition metal or an alloy thin film thereof is disposed on an elastic substrate.
• 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.
• the elastic material when tensioning an elastic material in the longitudinal direction (X direction), as is commonly seen in an elastic material, the elastic material is a longitudinal material as long as there is no condition other than the component in the longitudinal strain in the longitudinal direction. It is expected that shrinkage in the transverse direction (y direction) will occur as the stretch in the direction. In addition, the shrinkage strain in the lateral direction (y direction) is contracted while maintaining a constant ratio with the longitudinal tensile strain.
• the tensile force applied to the stretched elastic material is recovered or the elastic material is compressed in the uniaxial direction, tensile strain occurs in the transverse direction, and at the time of tensioning between the transverse tensile strain and the longitudinal shrinkage change. Deformation is made while maintaining the same ratio as.
• the ratio of a certain ratio between the transverse tensile strain and the longitudinal shrinkage change is defined as the Poisson's ratio of the elastic material.
• a parallax or an alloy thin film disposed 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.
• this is applied, it is stretched in the X direction and contracted in the y direction, and when the tensile force is recovered, it is contracted in the X direction and is stretched in the y direction.
• FIG. 2 which shows a hydrogen sensor according to an embodiment of the present invention
• it is physically attached to a 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.
• a nanogap 11 is formed in the parallax or its alloy thin film 110 to which strain can be imposed and the physical strain is imposed, as shown in FIG. 3.
• the tensile direction of the thin film 110 by the Poisson's ratio of the elastic substrate 120 ( X direction), or the ratio of tension and shrinkage in the shrinking direction (y direction) is determined.
• the thin film is stretched in the X direction in which the tensile force is applied, and is contracted in the y direction in the vertical direction of the direction in which the tensile force is applied.
• the elastic substrate 120 preferably has a Poisson's ratio of 0.2 to 0.8, more preferably has a Poisson's ratio of 0.3 to 0.7, and most preferably has a Poisson's ratio of five.
• the elastic substrate 120 is preferably stretched, and the elastic substrate 120 is 1.05 to 1.50 times as large. Most preferably applied to stretch.
• the transition metal or the alloy thin film 110 is disposed on the substrate 120.
• 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.
• the transition metal may be selected from Pd, Pt, Ni, Ag, Ti, Fe, Zn, Co, Mn, Au, W, In and Al, which are expandable by hydrogen.
• the alloy is Pd-Ni, Pt-Pd, Pd-Ag, Pd-Ti, Pd- Fe, Pd- Zn, Pd-Co, Pd-Mn, Pd-Au, Pd-W, Pt expandable by hydrogen -Ni, Pt- Ag, Pt- Ag, Pt-Ti, Fe-Pt, Pt-Zn, Pt-Co, Pt- Mn, Pt-Au, Pt- W can be selected.
• Pd acts as a catalyst in reaction with hydrogen
• Ni or Au reduces the lattice constant of Pd, which leads to the durability of hydrogen sensors made of Pd-Ni or Pd-Au alloys.
• the transition metals and alloys use Pd and its alloys.
• the method for disposing the transition metal or the alloy thin film 110 on the substrate 120 a method commonly used in the art may be used.
• physical vapor deposition methods such as sputtering and evaporation, chemical vapor deposition (CVD), atomic layer deposition (ALD) and the like may be used.
• any material that can be stretched in the direction when a tensile force is applied, and can be restored to its original shape when the tensile force is removed again can be used. Rubber, synthetic rubber, or polymers.
• the synthetic rubber examples include butadiene-based rubber, isoprene-based rubber, chloroprene-based rubber, nitrile-based rubber, polyurethane-based rubber, or silicone-based rubber, preferably having low interfacial free energy on the substrate.
• PDMS polydimethylsiloane
• Fluorocarbon polymers, acrylic polymers, polyaniline polymers, polyester polymers, etc. can also transfer tensile forces to thin films made of transition metals or their alloys. If possible, the elasticity can be adjusted appropriately.
• the thin film 110 is stretched in the X direction to which the tensile force is applied and simultaneously in the y direction.
• the nanogap 11 may be formed in the thin film.
• the tensile force to act is repeated one or more times.
• the application of the tensile force may be applied in only one specific direction, but is not limited thereto.
• the tensile force in one or more directions, for example, two directions, three directions May be applied to facilitate the formation of nanogap in the thin film.
• the tensile force is applied in the three directions, the 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.
• the second direction may be that the tensile force applied is at an angle in the first direction and 90 °, the third direction being applied with the tensile force in the first direction and the low 12-direction and the ⁇ 0 ⁇ greater than or ⁇ 90 °
• the angle is smaller, the strain applied to the thin film can be effectively concentrated.
• the thickness of the transition metal or its alloy thin film is preferably in the range of lnm to 100/100.
• the thickness of the transition metal or its alloy thin film is removed by applying a tensile force to the substrate. This is related to whether or not nano gaps are effectively generated in the thin film. 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.
• the thickness of the thin film is preferably in the range of Inm to 100 / ⁇ so as to effectively create the nanogap 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.
• the thickness of the thin film is more preferably 3 nm to 100 nm, and most preferably 5 nm to 15 nm.
• 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 0.1 to 10 cm in width, 0.1 to 20 cm It is preferred to have a length of and a thickness of 0.01 to 1 cm.
• the transition metal or the alloy thin film in which the nanogap is formed in the same manner as described above may exhibit high resistance because current does not flow smoothly due to the nanogap.
• the hydrogen is absorbed to expand the volume, and the nano gaps are filled with the volume expansion, thereby having a low resistance. Therefore, by measuring the change in the resistance value, the concentration of hydrogen can be detected using the thin film having the nanogap formed as a hydrogen sensing unit.
• the nano-gap can be freely controlled by the tensile force and the direction of the force applied to the substrate, the nano-gap is filled as the transition metal or its alloy expands by absorbing hydrogen in a hydrogen atmosphere, Considering the threshold value for detecting hydrogen through the change in the resistance value through this, it is preferable to have a width of lnm to 10 ⁇ .
• a thin film having such a nanogap can maximize its surface area by subsequent milling.
• the method of ion milling a thin film having such a nanogap may be performed by milling the upper part of the substrate on which the thin film is formed as described above, and more preferably, after applying the resin layer on the substrate on which the thin film is formed, the nano There is a method of forming a resin layer pattern to expose only a thin film portion having a gap, followed by milling the exposed thin film, and then removing the resin layer.
• the mechanical properties may be increased by heat-treating the transition metal or the alloy thin film having the nanogap.
• a heat treatment method includes a method of heat treating a substrate on which the thin film is formed 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. At this time, the thin film electrode and the nanogap is formed is electrically connected to, each other. The current is applied to one of the electrodes thus formed (1+) and the voltage is measured (V +) and the current (I-) and voltage (V-) output from the other electrode are measured.
• the quasi-two prove method can be used to measure the resistance change according to the hydrogen concentration change.
• the hydrogen sensor having the electrode formed by depositing a conductive metal on the thin film has a resistance according to the presence or absence of hydrogen gas. It has the property of varying values, which makes it possible to measure the hydrogen concentration.
• the hydrogen sensor 10 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 11 formed by a tensile force applied to the substrate 120; And electrodes 130 formed at both ends of the thin film.
• the hydrogen partial pressure around the Pd thin film having a nanogap (H 2 partial pressure) is higher than the hydrogen partial pressure within the Pd thin film, a hydrogen molecule
• H 2 partial pressure the hydrogen partial pressure within the Pd thin film
• a hydrogen molecule In order to lower the interfacial energy of the Pd thin film surface, it is adsorbed on the surface of the Pd thin film and dissociated into H atoms.
• the difference in the partial pressure of hydrogen inside and outside the Pd thin film acts as a driving force for the dissociated H atoms to diffuse into the Pd thin film, and the diffused H atoms are invasive sites of a lattice (fee, face centered cubic) structure formed by a—phase Pd atoms. Penetrates into PdHx. this The lattice constant increases due to H atoms entering the invasive sites.
• 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.
• the concentration of hydrogen may be detected using the thin film having the nanogap formed as a hydrogen sensing unit.
• the hydrogen sensor manufactured according to the above method can measure room temperature and has a small size, thereby reducing power consumption.
• the hydrogen sensor of the present invention can satisfy the essential requirements as a sensor for reducing reaction time and stable driving while satisfying characteristics of low cost, miniaturization, low power consumption, and room temperature operation.
• 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.
• the Pd thin film 110 had a thickness of 7.5 nm and was disposed on the substrate 120 in a size of 15 mm in width and 10 mm in length.
• 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.
• the tensile force was applied as described above to form a nanogap in the Pd thin film 110.
• the Au electrode is sputtered on both ends of the thin film 110 having the nanogap 11 formed thereon, and the thin film 110 and the electrode 130 are electrically connected to the PDMS substrate 120.
• Hydrogen sensor 10 was prepared.
• 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 set to 10 nm and the elastic substrate 120 was formed.
• the hydrogen sensor 10 was manufactured in the same manner as in Production Example 1, with the Pd thin film 110 having a thickness of 12 nm and having been formed on the elastic substrate 120.
• 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.
• the Pd thin film 110 had a thickness of 6 nm and was disposed on the substrate 120 in a size of 15 mm in width and 10 mm in length.
• the tensile force was applied to the substrate 120 in the transverse 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.
• Tensile force is applied to the substrate 120 exerted by the tensile force in the first direction in a diagonal direction (second direction) connecting the upper right and lower sides, so that the substrate 120 is stretched by 1.25 times the original diagonal length. After applying, the substrate was restored to its original size again.
• 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.
• the Au electrode is sputtered on both ends of the thin film 110 having the nanogap 11 formed thereon, and the thin film 110 and the electrode 130 are electrically connected to the PDMS substrate 120.
• Hydrogen sensor 10 was prepared.
• the system is an IV measuring device as shown in FIG. About the sensor 10, the reaction chamber 210, the mass flow controller (MFC) 220 which regulates the flow rate of the gas of H 2 and N 2 , the voltage of the sensor, the current applying 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 with the outside when the sensor reacts, and the H 2 and N 2 gas are transferred through the MFC 220 in an amount thereof. This precise control is responsible for producing the desired concentration of hydrogen gas.
• the adjusted H 2 gas is reacted with the hydrogen sensor in the reaction chamber 210, and the electrical signal for the change of the sensor at this time is measured through the voltage and current application device 230.
• FIG. 7 (a) shows the result of measuring the change in resistance value at a hydrogen concentration of 4% (40000 ppm) by mounting the hydrogen sensor 10 manufactured in Preparation Example 1 to the system 20 of FIG. 6.
• 7B 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%.
• the hydrogen sensor 10 of Preparation Example 1 is only 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 abrupt change in resistance is observed, and the resistance value increases as soon as the hydrogen is removed in the reaction chamber 210, and it can act as a precision hydrogen sensor that can detect the change in hydrogen concentration on off. Able to know.
• Figure 7 (c) is a hydrogen sensor manufactured in Preparation Example 2
• Figure 7 (d) is a hydrogen sensor produced in Preparation Example 3 is mounted to the system 20 of Figure 6, respectively, hydrogen concentration change
• the graph shows the result of measuring the change of resistance value or current value.
• the hydrogen sensor of Preparation Example 2 can also act as a precision hydrogen sensor that can detect the change in hydrogen concentration of 0 to 4% on-off
• Figure 7 Referring to (d) of, the hydrogen sensor of Preparation Example 3 also shows a change in the current value according to the change in the hydrogen concentration, it can be seen that it can act as a hydrogen sensor.
• FIG. 8 shows that the hydrogen sensor 10 prepared in Preparation Example 4 is mounted to the system 20 of FIG. 6, respectively, at 1% (10000 ppm) (a), 0.5% (5000 ppm) (b), and 0.05 (500).
• the graph shows the result of measuring the resistance change while changing the hydrogen concentration up to ppm) (c).
• FIG. 9A is a graph illustrating a current value measured when a hydrogen sensor having a Pd thin film thickness of 16 nm is exposed to air according to another manufacturing example of the hydrogen sensor of the present embodiment
• FIG. 9B Is a graph showing the change of current value with time when a hydrogen sensor having a Pd thin film thickness of 14 nm is exposed to air.
• the Pd thin film is thick at 16 nm. In this case, it can be seen that the ON resistance does not fall to zero, and it works in the air chamber.
• FIG. 9A the Pd thin film is thick at 16 nm.
• FIG. 10 is a graph showing the change in the current value with respect to the mechanism when the hydrogen sensor of the present embodiment is exposed to nitrogen or air vapor and the hydrogen sensor having a Pd thin film thickness of 8nm in the air.
• the basic resistance remains in an ON state where the basic resistance does not drop to 0, and when exposed to hydrogen, the resistance decreases due to expansion and hydrogen is removed.
• thermodynamic equilibrium state changes to the thermodynamic equilibrium state and turns to the OFF state to operate as an ON-OFF sensor.
• the hydrogen sensor having a thickness of 8 nm of Pd thin film is exposed to nitrogen gas, it shows a change in current value with time.
• the hydrogen sensor was manufactured using a transition metal or an alloy thereof.
• the hydrogen sensor is manufactured using a Pd x Nh- x alloy thin film among transition metal alloys in more detail. Since the present embodiment is substantially the same as that described in Example A, except that the Pd x Nh- x alloy thin film is formed on the elastic substrate, redundant descriptions are omitted.
• a Pd x Nh- x alloy thin film is formed on an elastic substrate.
• the alloy thin film can be formed by various methods, and in this embodiment, is formed according to the following method. That is, referring to FIG. 11, two methods of forming the Pd x N- x alloy thin film according to the present embodiment are schematically illustrated.
• two targets (Pd, Ni) are positioned in parallel, and the sample holder portion is dilute, passing over two targets alternately in time, Pd and Ni Is deposited on the substrate in the form of a layer by layer.
• the two targets are inclined so that the plasma from the two targets is overlapped at the lower side of the sample holder.
• the sample holder is rotating so that two target materials are evenly deposited on the substrate. Since both materials are deposited at the same time, Pd and Ni form an alloy or solid solution, unlike the above method.
• the present invention is not limited to the deposition method as described above. That is, the Pd x Ni 1-x alloy deposition method is merely an exemplary invention for depositing a Pd x Nh- x alloy on a substrate, and the present invention is not limited to a specific deposition method of Pd x Ni 1-x alloy. For example, as described in Example A, sputtering, chemical vapor deposition, atomic layer deposition, and the like can be used.
• FIG. 12 is a perspective view of a hydrogen sensor 10 according to the present embodiment, comprising: a substrate 120 made of an elastic material; A Pd x Ni 1-x alloy thin film (110) formed 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.
• a Pd x Ni 1-x alloy thin film satisfying 0.85 ⁇ x ⁇ 0.96 is formed on the substrate 120 of this embodiment.
• a Pd x Ni 1-x alloy thin film having a predetermined composition ratio is formed in place of the Pd thin film commonly employed in the conventional hydrogen sensor. The specific reason is as follows.
• the Pd x Nh- x alloy thin film is used instead of the Pd thin film, a phase transition phenomenon that is different from the exposed hydrogen concentration does not occur. It has been found that the same problem can be improved.
• the Pd x N x alloy thin film 110 that satisfies 0.85 ⁇ x ⁇ 0.96 is formed on the elastic substrate 120. If the molar ratio X is less than 0.85, a problem of lowering the reaction amount due to exposure of hydrogen due to excessive Ni content occurs. If the molar ratio X exceeds 0.96, the problem of phase transition as described above is caused. More preferably, the molar ratio is 0.90 ⁇ x ⁇ 0.94.
• a nanogap 111 is formed in the alloy thin film 110 formed on the surface of the substrate by applying a tensile force to the elastic substrate 120.
• the other Poisson's ratio, the material of the elastic substrate, the tensile force applied to the elastic substrate, the number of times of applying the tensile force, the thickness of the alloy thin film in the tensile force direction, the width of the nanogap, and the like are the same as those of Example A described above, and thus redundant descriptions are omitted.
• the hydrogen sensor manufactured according to the present embodiment 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 stable driving while satisfying characteristics of low cost, miniaturization, low power consumption, and room temperature operation.
• a Pd x Ni 1-x (but 0.85 ⁇ x ⁇ 0.96) alloy was deposited on a PDMS substrate having a width of 20 mm, a length of 10 mm, and a thickness of 0.75 mm by sputtering. At this time, the PdxNii-x thin film was made to have a thickness of 7.5nm, placed on a substrate with a size of 15mm horizontal, 10mm vertical.
• FIG. 13 is an SEM image photograph of a Pd x Nh- x alloy thin film having a nano gap formed according to the above process.
• FIG. 14 is an optical image photograph of a Pd x Ni 1-x alloy thin film having a nano gap formed therein.
• Pd was deposited using a sputter on a PDMS substrate having the same size as above.
• the Pd thin film had a thickness of 7.5 nm and was disposed on a substrate with a size of 15 mm in width and 10 mm in length.
• the tensile force was applied to the substrate five times, the horizontal length of the substrate was increased to 25 mm, and then the tensile force was removed to form a nano gap in the Pd thin film.
• Au electrodes were sputtered on both ends of the thin film on which the nanogap was formed, thereby manufacturing a hydrogen sensor in which the thin film and the electrode were electrically connected to the PDMS substrate.
• Example A In order to evaluate the characteristics of the hydrogen sensor manufactured according to the above, as in Example A, the system 20 of FIG. 6, which can be measured using a two-terminal measurement method, was used. Since the present system has been described in Embodiment A, the description thereof is omitted.
• Measurements using the system were conducted at phase silver and atmospheric pressure, and the nano-gap PdxNii thin-film hydrogen sensor 10 was mounted in a reaction chamber 210 connected to a pseudo current applying device, and then H 2 and N 2 were mixed in the chamber. The intensity of the current was measured while keeping the voltage at 0.1V.
• the lowest hydrogen detection concentration is about 0.08%. As shown in FIG. In this case, the lowest hydrogen detection concentration is 0.66%, which is very low.
• FIGS. 17 to 19 show hydrogen detection concentrations when the thickness of the thin film is formed at 8 nm, 10 nm, and ll nm, respectively, and the hydrogen sensor is exposed to air in the reaction chamber 210.
• the lowest hydrogen detection concentration is lower than in FIG. That is, in FIG. 17, the lowest hydrogen detection concentration was 0.65%, that is, 6500 ppm, and in FIG. 18, the lowest hydrogen detection concentration was about 0.45%.
• the lowest hydrogen detection concentration was 500 ppm. It can be seen that. That is, it can be seen that as the thickness of the thin film of the composition is increased, hydrogen of lower concentration can be detected.
• FIGS. 20 and 21 illustrate hydrogen detection concentrations when the thickness of the thin film is 10 nm and ll nm, respectively, and the hydrogen sensor is exposed to a nitrogen atmosphere in the reaction chamber 210.
• the lowest hydrogen detection concentration is about 0.01%
• the lowest hydrogen detection concentration is about 0.05% in FIG. 21, which is lower than that in air deposition.
• the lowest hydrogen detection concentration was 0.4%. As shown, the lowest hydrogen detection concentration is 1.2% when exposed to air vapor, and the lowest hydrogen detection concentration is higher than that of the Pd x Nh- x alloy having the composition according to the present invention.
• the phase transition phenomenon due to hydrogen exposure is suppressed, compared with the hydrogen sensor to which the Pd thin film is applied. It can be seen that it is possible to detect extremely lower concentrations of hydrogen.
• Example A and B a tensile force was applied to the elastic substrate to form a nanogap in the thin film formed on the substrate, and hydrogen was detected using the nanogap.
• the hydrogen gap is detected by forming a nano gap through a mechanism other than the application of phosphorus tension.
• description of the part which overlaps with Example A, B is abbreviate
• FIG. 24 is a view showing a hydrogen sensor manufacturing process according to this embodiment.
• the elastic substrate 10 is first provided in the same manner as in the embodiment.
• the elastic substrate 10 serves to accept the expansion as it is when the Pd or Pd alloy thin film formed thereon is subjected to volume expansion by a phase change in a subsequent process, thereby promoting nanogap formation in the thin film. .
• the present invention is not particularly limited to the composition and type of the elastic substrate 10, and any elastic material that can accommodate the volume expansion and contraction caused when the phase change of the Pd or Pd alloy thin film formed on the substrate is used as it is. It is possible. For example, similarly to Example A, B, it can provide using a natural rubber, a synthetic rubber, or a polymer.
• a Pd or Pd alloy thin film 30 having an ⁇ phase is formed on the elastic substrate 10.
• a method for forming the Pd or Pd alloy thin film 30 any method commonly used in the art can be used, and sputtering, chemical vapor deposition (CVD) and the like can be used in the same manner as in the above embodiment.
• the thickness of the formed thin film 30 is related to whether or not nanogap is effectively generated in the thin film 30 during the ⁇ ⁇ 3 phase change of the thin film 30 in a subsequent process. That is, the thinner the thickness, the more nanogaps can be created. Therefore, in order to effectively create a nanogap in the thin film, as in the above embodiment, the thickness of the thin film 30 is preferably in the range of lnm to 100 / zm, more preferably in the range of 3nm to 100nm, most preferably. 5 nm to 15 nm.
• the Pd alloy thin film is selected from Pd_Ni, Pd-Pt, Pd-Ag, Pd- Ti, Pd-Fe, Pd-Zn, Pd-Co, Pd-Mn, Pd-Au, and Pd-W. It may be a thin film of species, more preferably, a Pd—Ni thin film.
• the formed ⁇ -phase thin film 30 is exposed to a hydrogen-containing gas at a predetermined concentration. Due to the exposure of the hydrogen-containing gas, the ⁇ -phase thin film 30 formed on the substrate 10 gradually changes into the ⁇ -phase thin film 30.
• the volume expansion occurs in the thin film 30 in accordance with the hydrogen absorption, the elastic substrate 10 of the lower portion to accommodate the volume expansion of the thin film (30).
• a nano gap is formed in the thin film 30 phase-changed into the ⁇ phase according to volume expansion, and may have a width of approximately lnm to 10 / mm 3.
• the hydrogen-containing gas is exposed to the hydrogen concentration is preferably in the range of 2 to 15%. This is because a phase change of the thin film 30 easily occurs in this concentration range.
• the thin film 30 having the nanogap may be subjected to ion milling to increase its surface area, or may be heat treated to increase its mechanical properties.
• the ⁇ -phase Pd thin film to be obtained was formed on the PDMS substrate with a thickness of 10 nm and llnm, respectively, having a size of 15 mm and 10 mm.
• the ⁇ -phase Pd thin films formed on each of the PDMS substrates were exposed to a hydrogen-containing gas having a 10% hydrogen concentration, respectively, and the thin film was phase-changed into ⁇ -phase. Subsequently, the hydrogen-containing gas exposure was increased to switch the thin film phase back to the ⁇ phase.
• FIG. 25 is an OM (Optical Microscope) image photograph of a 10 nm thick Pd thin film prepared by the above process. As shown in FIG. 25, in the case of the Pd thin film manufactured by the above process, a nano gap is formed therein, and thus, it may be easily used as a hydrogen sensor.
• OM Optical Microscope
• the Au electrode was sputtered on both ends of the thin film where the nanogap was formed through the above process to prepare a hydrogen sensor in which the Pd thin film and the electrode were electrically connected to the PDMS substrate.
• the I-V measuring apparatus and the apparatus shown in FIG. 6, which can be measured using the two-terminal measuring method, were used as in the above-described embodiment.
• FIG. 26 (a) is a graph showing a change in current value measured when a Pd thin film having a thickness of 10 nm is exposed to 0.5-4% hydrogen concentration
• FIG. 26 (b) shows 0.5-4% hydrogen of a Pd thin film having a thickness of llnm. This graph shows the change in the measured current value when exposed to concentration. As shown in FIGS.
• Fig. 27 is a graph showing the change of the measured current value when exposing a Pd thin film having a thickness of 10.5 nm to 2% hydrogen concentration in air vapor, and in this case, it has a current value when exposed to hydrogen gas, but the current value when hydrogen is removed. This decreases to 0, indicating that the change in hydrogen concentration can be detected on-off.

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