WO2017176018A1

WO2017176018A1 - Hydrogen gas sensor and method for manufacturing same

Info

Publication number: WO2017176018A1
Application number: PCT/KR2017/003642
Authority: WO
Inventors: 신흥주; 임영진; 서준영
Original assignee: 울산과학기술원
Priority date: 2016-04-06
Filing date: 2017-04-03
Publication date: 2017-10-12
Also published as: KR20180119151A; KR20170114963A; KR102013825B1

Abstract

The present invention relates to a hydrogen gas sensor and a method for manufacturing the same. A hydrogen gas sensor may be provided that includes: a pair of electrode parts disposed on a substrate and facing each other at a predetermined distance; a carbon nano-wire disposed between the electrode parts and supported by the electrode parts; and hydrogen detection particles disposed on a surface of the carbon nano-wire. The hydrogen detection particles are disposed in the form of an island on the surface of the carbon nano-wire and are disposed locally on the surface of the carbon nano-wire, and the particle diameter of the hydrogen detection particles is 1 nm to 500 nm.

Description

【Specification】

[Name of invention]

Hydrogen gas sensor and its manufacturing method

Technical Field

The present invention relates to a hydrogen gas sensor and a method of manufacturing the same, and more particularly, to manufacture a floating-type carbon nanowire hydrogen gas sensor to build a low-cost high-sensitivity sensor by depositing palladium nanoparticles locally on carbon nanowires by an electroplating method. It is about a method.

Background Art

In general, hydrogen is a promising renewable energy in the future, and it is expected to solve the problem of finite and environmental pollution of fossil fuel which is widely used now, and it is expected that the era of popularization of hydrogen energy will open.

However, hydrogen is an explosive gas, and more than 4% is present in the air, and there is a risk of explosion, so an initial detection of hydrogen gas is required.

However, conventionally developed hydrogen detection sensors are not only complicated production process, but also need to develop a new type of sensor having high efficiency and high sensitivity to overcome the commercial viability due to low yield.

In order to make up for the shortcomings of commercially available hydrogen detection sensors, development of nanotechnology-based gas sensors has been actively conducted as in Patent Registration No. 10-0655640 (December 4, 2006).

Nanomaterials have characteristics such as quantum confinement effects and very high surface to volume rat io that are not seen in materials larger than micrometers. Not only is it possible to develop a sensor with sensitivity, selectivity, and quick response, but it is also advantageous for miniaturization and portable device development due to its small size.

In addition, researches on shape control and integration of nanomaterials are being actively conducted to maximize the effect of the high volume to surface area ratio of nanomaterials, and nanowires, which are one-dimensional nanomaterials of nanomaterials, have a high volume to surface area ratio, By measuring the change in resistance across the wire The change in electrical conductivity can be detected and is actively used as a sensor material.

In addition, if the nanowires are processed in the form of legs separated from the substrate, that is, notary type, the high surface area of the nanowires can be maximized and the transfer efficiency of external materials to the nanowires can be maximized to improve sensor performance. It can have the advantage of minimizing the influence of heat, contaminants, etc. of the substrate.

However, currently introduced airborne nanostructure fabrication method has a disadvantage that the process is complex, difficult to control the size and shape, and the yield is low.

In order to overcome this problem, the carbon-MEMS process, which consists of photolithography and polymer pyrolys is process, which is a semiconductor batch process, can be used to produce a notary floating carbon nanowire. Techniques have been developed.

Due to the nature of the photolithography process, it is easy to control the size and shape of nanowires, and high volume reduction occurs during the polymer pyrolysis process, so that micro-sized polymer structures can be processed into nano-sized carbon structures without the use of complex and expensive nano-fabrication equipment. Can be.

In addition, a hydrogen detection sensor was developed by depositing a palladium (Pal adium, Pd) thin film, which is a hydrogen sensing material, on an airborne carbon nanostructure made of carbon-mess using E-beam evaporat ion. It became.

At this time, palladium is a material whose electrical conductivity changes according to the external hydrogen concentration, and thus the hydrogen concentration can be measured by measuring the resistance change of palladium, and the resistance between the electrode portions supporting the airborne carbon nanowires on which the palladium thin film is deposited is measured. By measuring, the hydrogen concentration can be measured.

However, in order to coat palladium, a precious metal, on the surface of carbon nanowires, it is expensive to deposit palladium over the entire substrate. Also, due to the thin thickness of the palladium thin film, it is easily saturated by hydrogen gas and thus detects high concentration hydrogen gas. Had a difficult problem. [Content of invention]

[Problem to solve]

The present invention is to solve the above problems by depositing spherical palladium nanoparticles having various sizes locally on carbon nanowires using a small amount of palladium compared to the conventional electron beam deposition method, the hydrogen saturation state at high hydrogen concentration It is not an object of the present invention to provide a hydrogen gas sensor and a method of manufacturing the same, which can detect hydrogen at a concentration, and can construct a low cost and high sensitivity sensor.

[Measures of problem]

In one embodiment of the present invention, a pair of electrode portions disposed on a substrate and opposed to each other at predetermined intervals, positioned between the electrode portions, supported by the electrode portion, carbon nanowires, and the surface of the carbon nanowires Hydrogen sensing particles located in; The hydrogen sensing particles are located in the island form on the surface of the carbon nanowires, are located locally on the surface of the carbon nanowires, the particle size of the hydrogen sensing particles is 1 to 500 nm It provides a hydrogen gas sensor.

More specifically, the electrode unit may be a carbon electrode unit. In the present specification, the portion of the electrode portion described as the carbon electrode portion is described by taking an example of the electrode portion material, and the electrode portion material is not limited to carbon. The hydrogen sensing particles may be located on the surface of the carbon nanowires in the form of primary particles.

The hydrogen sensing particles may be located on the surface of the carbon nanowires in the form of secondary particles in which primary particles are collected.

The particle diameter of the secondary particles may be 10 to 500 nra.

The area in which the hydrogen sensing particles are located may be 90 to 100 areas> 100 area% of the total surface area of the carbon nanowires.

The hydrogen detecting particles may be palladium particles.

The specific surface area of the hydrogen detecting particles may be 0.5 to 250 ra ² / g.

The carbon nanowires may have a diameter of about 100 nm to about 500 nm. In another embodiment of the present invention, the high-sensitivity sensor caps and the high-density sensor caps located on the substrate, the high-sensitivity sensor caps and high-concentration sensor caps, each independently, facing each other at a predetermined interval A pair of electrode units; Carbon nanowires disposed between the electrode portions and supported by the electrode portions; And hydrogen sensing particles located on the surface of the carbon nanowires, wherein the hydrogen sensing particles in the high sensitivity sensor mode are located in an island form on the surface of the carbon nanowires and are locally located on the surface of the carbon nanowires. The particle diameter is 1 to 10 nm, the hydrogen-sensing particles in the high concentration sensor mode, is located in the island shape on the surface of the carbon nanowires, is located locally on the surface of the carbon nanowires, the particle diameter is greater than 10 nm and 500 It provides a hydrogen gas sensor of nm.

The area where the hydrogen sensing particles are located may be 90 to 100 area% with respect to 100 area% of the total surface of the carbon nanowires in the high sensitivity sensor mode. With respect to 100% of the total surface area of the carbon nanowires for high concentration, the area where the hydrogen detecting particles are located may be 90 to 100 area ¾>.

The specific surface area of the hydrogen detecting particles in the high sensitivity sensor mode may be 25 to 250 m ² / g.

The specific surface area of the hydrogen detecting particles in the high concentration sensor mode may be 0.5 to 25 m ² / g.

In another embodiment of the present invention, a pair of carbon electrode parts facing each other at a predetermined interval; Located between the carbon electrode portion, preparing a support comprising a carbon nanowires supported by the carbon electrode portion; and among the support, the hydrogen sensing particles locally on the surface of the carbon nanowires by electroplating method It provides a method of manufacturing a hydrogen gas sensor comprising the step of depositing.

Locally depositing hydrogen sensing particles on the surface of the carbon nanowires by electroplating in the support; wherein an electrolyte is placed on the carbon nanowires, and the electrolyte is a palladium plating solution having a concentration of 10 nM to 100 RAM. ₂ PdC, Sodium tetrachloropalladate).

Of the support, the surface of the carbon nanowires by electroplating In the step of locally depositing hydrogen sensing particles, a working electrode is connected to the carbon electrode portion and carbon nanowires, and a counter electrode and a reference electrode are immersed in a palladium plating solution. After positioning, electroplating can be performed.

The electroplating method may include a palladium seed forming step and a palladium seed growing step, and the palladium seed forming step may be performed at a higher voltage and a shorter time condition than the palladium seed growing step.

The electroplating method may include forming a palladium seed step and a palladium seed growth step, and alternately performing the palladium seed formation step and the palladium seed growth step a plurality of times to form palladium particles in the form of secondary particles. Locally depositing hydrogen sensing particles on the surface of the carbon nanowires of the support by electroplating, further comprising the step of annealing the carbon nanowires on which the hydrogen sensing particles are deposited in a vacuum or inert gas environment. Can be.

Preparing a support including a carbon nanowires positioned between the pair of carbon electrode portions facing each other at the predetermined intervals and supported by the carbon electrode portion,

Preparing a substrate, forming an insulating layer on the substrate, and forming a photoresist microwire connecting the pair of photoresist electrode portions and the pair of photoresist electrode portions by photolithography on the insulating layer. The support may be prepared by a method including pyrolyzing the pair of photoresist electrode portions and the photoresist microwires and converting the pair of carbon electrode portions and carbon nanowires. .

[Effects of the Invention]

Effects of the hydrogen gas sensor and the manufacturing method according to an embodiment of the present invention are as follows.

First, the airborne carbon nanowires formed integrally with the electrode part are manufactured using the carbon-MEMS process, which is a batch MEMS process, and thus has a high yield and low cost manufacturing effect.

Secondly, the shape of the photomask, the amount of secondary exposure and the pyrolysis process conditions Since the shape of the carbon nanowires is determined by, the carbon nanowire structure having various sizes can be manufactured as necessary.

Third, by using palladium in a small amount compared to the conventional electron beam deposition method, by depositing palladium nanoparticles locally on carbon nanowires, it is possible to build a high-sensitivity hydrogen gas sensor at low cost.

Fourth, spherical palladium nanoparticles are deposited on carbon nanowires, and the gas sensor sensitivity is high due to a relatively high volume-to-surface area ratio at the same thickness as compared to the conventional thin film type.

Fifth, palladium nanoparticles of various sizes are deposited on carbon nanowires, so that hydrogen cannot be saturated even at high hydrogen concentrations.

Sixth, as the size of the palladium nanoparticles increases, the reaction to low concentrations of hydrogen gas decreases, but it is not saturated even at high concentrations of hydrogen. Therefore, after integrating a plurality of carbon nanowires on one chip, palladium nanoparticles of various sizes suitable for low and high concentrations of hydrogen can be selectively deposited on each carbon nanowire so that low and high concentrations can be deposited. Hydrogen can be measured with one chip.

[Brief Description of Drawings]

1 is an exemplary view briefly showing a process of manufacturing a hydrogen gas sensor according to an embodiment of the present invention.

2 is an exemplary photograph showing a pair of photoresist electrode portions and a photoresist microwire structure before pyrolysis and a pair of carbon electrode portions and carbon nanowire structures after pyrolysis according to an embodiment of the present invention. 3 is an exemplary view showing a state of depositing palladium on carbon nanowires by an electroplating method according to an embodiment of the present invention.

4 is an exemplary view showing a state in which palladium is deposited on carbon nanowires according to a voltage by electroplating according to an embodiment of the present invention. FIG. 5 is a graph showing a change in measurement current according to an applied voltage of airborne carbon nanowires before and after deposition of palladium nanoparticles according to an exemplary embodiment of the present invention. Figure 6 is a graph showing the rate of change according to the hydrogen concentration of the hydrogen gas sensor according to an embodiment of the present invention.

7 is a schematic diagram of a hydrogen sensing sensor having a plurality of sensor heads and SEM photographs of the respective heads.

8 is an exemplary view illustrating a current flow after palladium nanoparticles are deposited according to an embodiment of the present invention, and a change in measurement current according to an applied voltage of airborne carbon nanowires before and after palladium nanoparticle deposition and for a plurality of modules. The graph shown.

9 is a graph of a resistance change rate according to a change in hydrogen concentration of a hydrogen detecting sensor having a plurality of sensor modules.

[Specific contents to carry out invention]

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in the present specification and claims should be construed to be limited to ordinary or dictionary meanings. No, the inventor should be interpreted as meanings and concepts corresponding to the technical idea of the present invention, based on the principle that the concept of terms can be properly defined in order to explain his invention in the best way.

Therefore, the embodiments described in the present specification and the configuration shown in the drawings are only the most preferred embodiments of the present invention, and do not represent all of the technical idea of the present invention. It should be understood that there may be variations.

In one embodiment of the present invention, a pair of carbon electrode portions disposed on a substrate and opposed to each other at predetermined intervals; Carbon nanowires disposed between the carbon electrode portions and supported by the carbon electrode portions; And hydrogen sensing particles positioned on the surface of the carbon nanowires, wherein the hydrogen sensing particles are positioned in an island form on the surface of the carbon nanowires, and are locally located on the surface of the carbon nanowires, and have a particle diameter of the hydrogen sensing particles. It provides a hydrogen gas sensor that is 1 to 500 nm.

The hydrogen detecting particles may be palladium particles.

In the following description, the part referring to palladium is Specific examples of the hydrogen sensing particles have been described, but are not limited to palladium.

More specifically, as described in detail in the following examples, looking at Figure 4 it can be seen that the diameter of the palladium particles from several nanometers to several hundred nanometers.

The hydrogen sensing particles may be located on the surface of the carbon nanowires in the form of primary particles.

The particle size of the primary particles may be 1 to 10 nm level. This range has the significance of increasing hydrogen sensitivity.

Alternatively, the hydrogen sensing particles may be located on the surface of the carbon nanowires in the form of secondary particles in which primary particles are collected.

The particle diameter of the secondary particles may be 10 to 500 ran. This range has the significance of not being saturated with high concentrations of hydrogen.

Such primary particles or secondary particles may be determined by the electroplating method described below.

Depending on the particle size of the hydrogen-sensing particles (for example, palladium) to be plated and the area where the hydrogen-sensing particles are located on the carbon wire, there may be a difference in the sensitivity and the concentration of sensing the hydrogen of the sensor. This can be adjusted according to the desired specifications.

The formation process of more specific hydrogen sensing particles will be described in detail in the manufacturing method described later.

The area where the hydrogen sensing particles are located may be 90 to 100 area% with respect to 100 area% of the total surface of the carbon nanowires. The area ratio of the hydrogen sensing particles occupying the surface of the carbon nanowire may also affect the specification of the sensor. The range is determined to be a range that can be used as a real commercial sensor.

More specifically, referring to FIG. 4, the area where the parallax particles coat the carbon nanowires can be adjusted. However, in order to utilize as a hydrogen sensor, the higher the ratio of current flowing through the palladium nanoparticles, the greater the change in resistance to hydrogen, so that the surface of the carbon nanowire is more than 90% palladium. It may be desirable to coat.

The specific surface area of the hydrogen detecting particles may be 0.5 to 250 m ² / g. This range is when the diameter of the hydrogen sensing particles is 1 to 500 nm, the smaller the diameter of the hydrogen sensing particles, the larger the specific surface area. As the specific surface area increases, the rate of change of resistance of the hydrogen sensing particles according to reaction or absorption of hydrogen on the surface of the hydrogen sensing particles increases, thereby improving sensitivity.

In another embodiment of the present invention, the high-sensitivity sensor caps and the high-density sensor caps located on the substrate, the high-sensitivity sensor caps and high-concentration sensor caps, each independently, facing each other at a predetermined interval A pair of carbon electrode portions; Carbon nanowires disposed between the carbon electrode portions and supported by the carbon electrode portions; And hydrogen sensing particles positioned on the surface of the carbon nanowires, wherein the hydrogen sensing particles in the high sensitivity sensor module are located in an island form on the surface of the carbon nanowires and are locally located on the surface of the carbon nanowires. , The particle diameter is 1 to 10 nm, the hydrogen-sensing particles in the high concentration sensor mode, is located in the island shape on the surface of the carbon nanowires, is located locally on the surface of the carbon nanowires, the particle diameter is 10 nm to 500 nra It provides a hydrogen gas sensor.

The hydrogen gas sensor may include a plurality of modules.

More specifically, the sensor module may include high sensitivity sensor modules and high concentration sensor modules. This may be divided according to the particle diameter of the hydrogen sensing particles to be plated on each carbon nanowire.

For example, in the case of using hydrogen particle having a small particle size, it is possible to detect a small concentration of hydrogen with high sensitivity, but because the amount of hydrogen detection particle is small, it can be easily saturated.

On the contrary, in the case of using the hydrogen-sensing particles having a large particle size, since the volume of the hydrogen-sensing particles is large, the resistance change may be insufficient for a small concentration of hydrogen, but may be effective in detecting high concentrations of hydrogen. With respect to the total surface area 100 ¾ of the carbon nanowires in the high sensitivity and high concentration sensor mode, the area where the hydrogen sensing particles are located may be 90 to 100 area%. This range is achieved through carbon nanowires and palladium nanoparticles. Increased current flow rate Increases the ratio of the current flowing through the palladium nanoparticles to increase hydrogen sensitivity by increasing the effect of resistance change of the palladium nanoparticles reacting with hydrogen on the overall resistance.

The specific surface area of the hydrogen detecting particles in the high sensitivity sensor mode may be 25 to 250 m ² / g. This range can be effective to speed up the reaction with high sensitivity.

More specifically, the higher the specific surface area, the higher the rate of change of resistance due to hydrogen reaction and absorption on the surface. The hydrogen absorption is determined by the surface area, and the resistance to change due to the hydrogen absorption is a property related to the volume of the nanoparticles, so the greater the volume-to-surface area ratio, the greater the effect of reaction on the surface. Therefore, sensitivity and reaction speed can be improved.

The specific surface area of the hydrogen detecting particles in the high concentration sensor mode may be 0.5 to 25 m ² / g. This range is not easily saturated even at high concentrations of hydrogen and may be effective for detecting high concentrations of hydrogen.

More specifically, the larger the specific surface area ratio, the greater the sensitivity, but since the actual volume is reduced, it can be easily saturated with hydrogen. Therefore, if the specific surface area ratio decreases, that is, the size of the nanoparticles increases, the resistance change may occur even with a high concentration of hydrogen even with a loss in sensitivity.

In another embodiment of the present invention, a pair of carbon electrode parts facing each other at a predetermined interval; Preparing a support including a carbon nanowire positioned between the carbon electrode parts and supported by the carbon electrode parts; And locally depositing hydrogen sensing particles on the surface of the carbon nanowires by electroplating in the support.

The support may be prepared by various conventional methods.

However, it may be prepared through the photoresist method as described below, and will be described in detail.

A pair of carbon electrode portions opposed to each other at predetermined intervals; Located between the carbon electrode portion, supported by the carbon electrode portion Preparing a support comprising a carbon nanowire; The step of preparing a substrate; Forming an insulating layer on the substrate; Forming a photoresist microwire connecting the pair of photoresist electrode portions and the pair of photoresist electrode portions by photolithography on the insulating layer; The support may be prepared by a method including a step of thermally decomposing the pair of photoresist electrode parts and the photoresist microwires, and converting the pair of carbon electrode parts and carbon nanowires.

Hereinafter, a specific manufacturing method including a drawing using the photoresist will be described with reference to the accompanying drawings.

According to one embodiment of the present invention, the airborne carbon nanowire structure formed integrally with a pair of electrode portions supporting carbon nanowires is manufactured using carbon-MEMS, so that a high yield and low cost can be manufactured, and carbon is more conventional. By depositing spherical palladium nanoparticles locally on the nanowire, a small amount of palladium can be used to build a highly sensitive sensor at low cost.

Accordingly, airborne carbon nanowire hydrogen gas sensors in which palladium nanoparticles of various sizes are deposited may be manufactured to prevent hydrogen saturation at high hydrogen concentration.

First, referring to FIG. 1, in step (a), the insulating layer 11 is formed on the upper surface of the silicon wafer 10.

At this time, the formation of the insulating layer (11) is carried out by thermal oxidation (thermal oxidat ion) deposition, the silicon wafer (10) having an element symbol of Si by applying a heat of 800 ~ 1200 ^° C., The insulating layer 11 whose element symbol is Si0 ₂ is formed by vapor deposition on the upper surface of the silicon wafer 10. Here, the thickness of the insulating layer 11 to be deposited is 0.1 ~ 10 卿 can be formed by selectively selecting the thickness according to the thickness of the silicon wafer 10 and the measuring capacity of the sensor.

Next, in step (b), a pair of photoresist electrode portions 21 and the pair of photoresist are photolithographically formed on the insulating layer 11 of the silicon wafer 10 formed by the step (a). The photoresist microwires 22 connecting the electrode portions 21 are formed. In the photolithography, when ultraviolet rays are irradiated to the substrate coated with the photosensitive resin through a photomask, the pattern engraved on the photomask is transferred to the photoresist and developed to form a pattern on the substrate.

Step (b) consists of a plurality of steps, which are described in more detail as follows.

First, in step (b-1), the photoresist layer 20 is formed by applying photoresist on the insulating layer 11 formed by step (a).

In this case, SU-8 is used as the photoresist material to be applied to the insulating layer 11, and the photoresist is evenly applied on the insulating layer 11 by spin coating, and on the insulating layer 11. The photoresist layer 20 is formed.

Here, the thickness of the photoresist layer 20 to be formed is 5 ~ 100 kPa, the thickness is selectively selected according to the measuring capacity of the sensor.

Next, in step (b-2), the first photomask 31 having the perforated area of the pair of electrode portions formed on the photoresist layer 20 formed by the step (b-1) is perforated. Thereafter, ultraviolet rays are irradiated to carry out the first exposure. In this case, the primary exposure is to perform exposure with sufficient energy such that optical deposition (Polymer i zat ion) is performed to the bottom of the photoresist layer 20 floating on the region of the photoresist layer 20. Desirable

Next, in step (b-3), a region where the photoresist microwire position is formed on the photoresist layer 20 where the pair of electrode regions are first exposed by the step (b-2) is perforated. After the secondary photomask 32 is placed, secondary exposure is performed with ultraviolet rays.

At this time, the photoresist microwires 22 connecting the pair of photoresist electrode portions 21 are formed in the form of micro-sized wires. It is preferable to adjust the dose so that only the upper portion of the polymerization is carried out, the thickness of the photoresist microwire 22 can be adjusted according to the ultraviolet exposure energy.

Next, in step (b-4), the exposure is performed by steps (b-2) and (a-3). The photoresist layer 20 except for the region is developed and removed, and the pair of photoresist electrode portions 21 and the photoresist electrode portions 21 are formed on the insulating layer 11 of the silicon wafer 10. Photoresist microwires 22 are formed to connect them.

At this time, the airborne photoresist microwires 22 and the photoresist microwires made of a photoresist material polymerized using a developer capable of selectively etching portions other than the optically evaporated portions irradiated with ultraviolet rays ( A pair of photoresist electrode portion 21 structures supporting 22 are formed.

Next, in the step (c), the pair of photoresist electrode portions 21 and the photoresist microwires 22 formed on the insulating layer 11 are thermally decomposed by the step (b). It converts into the carbon electrode part 41 and the carbon nanowire 42.

At this time, the pair of photoresist electrode portions 21 and the photoresist microwires 22 structure of the polymerized photoresist material are accommodated in a chamber, and the inner atmosphere of the chamber is 500 ° C. or higher in a vacuum or inert gas environment. A polymer pyrolysis step of heating to temperature is carried out.

The pair of photoresist electrode portions 21 and the photoresist microwires 22 structure through the polymer pyrolysis process generate a shape change due to volume reduction, and FIG. The structure of the photoresist electrode portion 21 and the photoresist microwire 22 is shown, and the structure of the pair of photoresist electrode portion 21 and the photoresist microwire 22 after thermal decomposition is shown.

As shown in FIG. 2, the pair of photoresist electrode portions 21 and the photoresist microwires 22 structures are reduced by about 80% in volume compared to the volume before pyrolysis.

Here, the pyrolysis process may control the volume reduction of the pair of photoresist electrode portions 21 and the photoresist microwires 22 structures according to conditions such as time, temperature, heating rate, cooling rate, injection gas, and the like. have. Therefore, the size and exposure of the photomask for polymer microfabrication Energy shape and polymer pyrolysis conditions can be adjusted to control the shape of the final carbon nanowires.

At this time, the size of the photoresist microwire is a diameter ~ number, the length is a few ~ hundreds, the interval between the conducting wafer and the notarized photoresist microwire is selected to be produced from 1 to several hundred, carbon nanowires through the pyrolysis process The size of the dome is several tens of nm ~ several, the length is several hundreds of mi, the distance between the substrate and the wire hundreds of nm to hundreds.

Next, in step (d), palladium nanoparticles are locally formed on the surfaces of the carbon nanowires 42 of the pair of carbon electrode portions 41 and the carbon nanowires 42 converted by the step (c). To deposit.

In this case, as shown in FIG. 3, the deposition of palladium nanoparticles is performed by electroplating, and the electroplating is performed by using a counter electrode as a counter electrode (Counter electrode: 1) and a reference electrode as a reference for measuring electrode potential. 2) A working electrode (3) is required for the purpose of flowing an electric current in the sample when generating an electrode reaction, in which platinum (Platinum, Pt) is used as the counter electrode (1), Silver chloride (Silver / Silver chloride, Ag / AgCl) is used as a reference electrode (2), and a working electrode (3) is in contact with one or both sides of the pyrolyzed carbon electrode portion 41, A voltage (electricity) is applied to the carbon electrode 42 to deposit the palladium nanoparticles 50 on the carbon nanowires 42 exposed to the palladium plating solution (electrolyte) by electrochemical deposition.

Looking in more detail, the plating solution (Na ₂ PdCl ₄ , Sodium tetrachloropalladate) of the notarized carbon nanowires 42 on the insulating layer 11 of the silicon wafer 10 manufactured according to an embodiment of the present invention Immersed in, and the working electrode (3) in contact with one or both carbon electrodes 41, the counter electrode (1) made of platinum and the reference electrode (2) made of silver-silver chloride are carbon nanowires (42) and Electroplating is performed by applying a voltage (electricity) to the working electrode (3) while being immersed in the palladium plating solution.

At this time, the concentration of the palladium plating solution is to proceed to ΙΟηΜ ~ lOOraM Preferably, as the concentration of the palladium plating solution is increased, palladium nanoparticles may be formed faster and particles larger than the nano size may be formed.

The size and spacing of the palladium nanoparticles vary with the voltage and deposition time of the working electrode 3.

Referring to FIG. 4 (a), one embodiment of the present invention first applies a high voltage of −0.8 V to the working electrode 2 for 5 seconds to form palladium nanoparticles on a surface of carbon having relatively low electrochemical activity. After the deposition is formed, a voltage of −0.2 V is applied for 20 seconds to limit the growth rate of the deposited palladium nanoparticles 50 to form palladium nanoparticles of relatively small size on the carbon nanowires 42.

4 (b) shows that palladium nanoparticles 50 are applied to the carbon nanowires 42 by applying a voltage of −0.8 V to the working electrode 2 for 5 seconds and then applying a voltage of −0.2 V for 80 seconds. Palladium nanomiZip is deposited by secondary deposition of these, and Figure 4 (c) is a voltage of -0.8 V to the working electrode (2) for 5 seconds, and then successively applying a voltage of -0.2V for 120 seconds The palladium nanoparticles 50 were deposited on the carbon nanowires 42 by applying a voltage of -0.8V to 10 seconds and finally to a voltage of -0.2V to 60 seconds.

Referring to (b) of FIG. 4, after first deposition by applying a voltage of −0.8 V to the working electrode 2 for 5 seconds, a voltage of −0.2 V is applied for 80 seconds to palladium to the carbon nanowires 42. Nanoparticles 50 are second deposited. In this case, it can be seen that a relatively large amount of palladium nanoparticles are formed on the carbon nanowires at regular intervals.

Next, referring to FIG. 4C, FIG. 4C shows the working electrode 2 for 5 seconds.

After applying a voltage of -0.8 V, successively -0.2V voltage for 120 seconds, -0.8V voltage for 10 seconds, -0.2V voltage for 60 seconds and then palladium nano to carbon nanowires 42 It is a shape in which the particles 50 were deposited. In this case, it can be seen that large-sized palladium nanoparticles are continuously formed along the outer circumferential surface of the carbon nanowires.

As such, the size and spacing of the palladium nanoparticles may be controlled by the voltage and deposition time of the working electrode 3. In addition, in one embodiment of the present invention in order to further increase the adhesion (adhes ion) between the palladium nanoparticles (50) and the carbon nanowires 42 deposited by the electrochemical (electroplating) method in a vacuum or inert gas environment Annealing can be performed at temperatures above 100 ^° C.

FIG. 5 is a graph showing changes in voltage and current of a notary-type carbon nanowire before and after deposition of palladium nanoparticles according to an embodiment of the present invention. Referring to FIG. 5, in the airborne carbon nanowire hydrogen gas sensor manufactured according to an exemplary embodiment of the present invention, palladium nanoparticles 50 are deposited on carbon nanowires 42 to form carbon nanowires 42. The overall electrical resistance is reduced. The decrease in the electrical resistance of the carbon nanowires is because the electrical resistance of the palladium nanoparticles 50 is lower than that of the carbon nanowires 42.

In the airborne carbon nanowires according to an embodiment of the present invention, the current flows not only through the carbon nanowires 42 but also through the palladium nanoparticles 50. The electrical resistance of the floating carbon nanowires also changes, and based on this, hydrogen can be detected.

Figure 6 is a graph showing the resistance change rate according to the hydrogen concentration of the airborne carbon nanowire hydrogen gas sensor according to an embodiment of the present invention, as shown in Figure 6 airborne type manufactured by one embodiment of the present invention The carbon nanowire hydrogen gas sensor can be observed that the electrical resistance changes according to the hydrogen concentration.

Figure 7 (a) is a schematic image of two airborne carbon nanowires coated with palladium nanoparticles of different sizes integrated on one chip. Figure 7 (b) is an electron microscopy image of two airborne carbon nanowires coated with different sized palladium nanoparticles on one chip.

More specifically, the size and spacing of the palladium nanoparticles depend on the voltage of the working electrode and the deposition time. The nanowire (NW 1) of FIG. 7 is a nanowire having palladium nanoparticles of several nanometer size deposited by applying a voltage of −1.2 V to a working electrode for 5 seconds and then applying a voltage of 0.8 V for 5 seconds in succession. to be.

Nanowire 2 in FIG. 7 applies a voltage of −1.2 V to the working electrode for 5 seconds. After the addition, a voltage of -0.8 V was applied for 25 seconds to deposit nanoscale palladium nanoparticles of tens of nanometers in size. However, the size of the parallax nanoparticles is determined by the resistance of the carbon nanowires, the concentration of the palladium solution, the applied voltage and time of the electroplating.

Fig. 7 (c, d) is a side and top electron microscope image. FIG. 7 (e) is an electron microscope image of nanowire (X1) coated with small size (a few nanometers) of palladium nanoparticles. 7 (f) An electron microscope image of Nanowire 2 (X2) coated with large size (tens of nanometers) of palladium nanoparticles.

Figure 8 (a) is a schematic image of the current flow in the airborne carbon nanowires coated with palladium nanoparticles. FIG. 8 (b) is a voltage-current graph before and after palladium nanoparticle deposition (bare carbon nanowi re).

It can be seen that depositing the palladium nanoparticles enjoys the overall resistance of the carbon nanowires. When palladium nanoparticles are deposited on carbon nanowires, the overall resistance of the nanowires is reduced. In addition, since current flows bypassed to palladium nanoparticles having high electrical conductivity compared to carbon nanowires having low electrical conductivity, the overall resistance of the carbon nanowires coated with palladium nanoparticles is sensitively changed due to the change of the external hydrogen concentration. This becomes possible.

Figure 9 is a ^'and the resistance change ratio graph according to the hydrogen concentration of the hydrogen sensor. Figure 9 (a) is for the nanowire 1 (NW 1), Figure 9 (b) is for the nanowire 2 (NW 2). The green shadows represent hydrogen environments of 5, 3.5, 2.5, 1, 0.1%, 700, 500, 200, 100, 80, 50, 30, 20, and 10 ppm, respectively.

As described above, when the size of the palladium nanoparticles is small (NW1), high sensitivity hydrogen sensing is possible, but saturation occurs at a relatively low hydrogen concentration (Fig. 9 (a)), and when the palladium nanoparticles are large (NW2) Hydrogen gas can be measured without saturation even in hydrogen (Fig. 9 (b)).

The present invention is not limited to the above embodiments and can be manufactured in various forms, and a person of ordinary skill in the art without changing the technical spirit or essential features of the present invention It will be appreciated that it may be embodied in other specific forms. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

[Explanation of code]

1: counter electrode

2: reference electrode

3: working electrode

10 Silicon Wafer

11 insulation layer

20. Photoresist layer

21: photoresist electrode portion

22 ： Photoresist Microwire

31 ： The first photomask

32 ： Second photomask

41 ： Third small bran pole

42 ： carbon nanowires

50: palladium nanoparticle

Claims

[Claim]

[Claim 11

A pair of electrode portions disposed on the substrate and opposed to each other at predetermined intervals; Carbon nanowires disposed between the electrode portions and supported by the electrode portions; And

Hydrogen sensing particles located on the surface of the carbon nanowires; The hydrogen sensing particles are located in the island form on the surface of the carbon nanowires, and are located locally on the surface of the carbon nanowires,

The particle diameter of the hydrogen detecting particles is 1 to 500 nm hydrogen gas sensor.

[Claim 2]

The method of claim 1,

The hydrogen detecting particle is a hydrogen gas sensor that is located on the surface of the carbon nanowires in the form of primary particles.

[Claim 3]

The method of claim 1,

The hydrogen detecting particle is a hydrogen gas sensor that is located on the surface of the carbon nanowires in the form of secondary particles, the primary particles are collected.

[Claim 4]

The method of claim 1,

The particle size of the secondary particles is 10 to 500 nm hydrogen gas sensor.

[Claim 5]

The method of claim 1,

Hydrogen gas sensor with respect to the area of the carbon nanowire electrode surface 100>, wherein the area of the hydrogen sensing particles is 90 to 100% by area.

[Claim 6]

The method of claim 1,

The hydrogen detecting particle is a hydrogen gas sensor that is palladium particles.

[Claim 7]

In that U term,

Specific surface area of the hydrogen sensing particles is that of 0.5 to 250 m ² / g Hydrogen gas sensor.

[Claim 8]

The method of claim 1,

The carbon nanowires have a diameter of 100 to 500 nm.

【Claim 9】.

It comprises a high sensitivity sensor cap and a high concentration sensor cap located on the substrate,

The high-sensitivity sensor modules and high-concentration sensor hair, each independently, a pair of electrode parts facing each other at a predetermined interval; Carbon nanowires disposed between the electrode portions and supported by the electrode portions; And a hydrogen sensing location on the surface of the carbon nanowires;

Hydrogen sensing particles in the high-sensitivity sensor mode, is located in the island shape on the surface of the carbon nanowires, is located locally on the surface of the carbon nanowires, the particle diameter is 1 to 10 nm,

Hydrogen-sensing particles in the high concentration sensor mode, is located in the form of islands on the surface of the carbon nanowires, locally located on the surface of the carbon nanowires, the particle diameter is more than 10 nm and 500 nm hydrogen gas sensor.

[Claim 10]

The method of claim 9,

Hydrogen gas sensor with respect to 100% by area of the total surface of the carbon nanowires in the high-sensitivity sensor mode, the area of the hydrogen sensing particles is 90 to 100 area%.

[Claim 11]

According to that 19,

Hydrogen gas sensor with respect to the total surface area 100% by area of the carbon nanowires for high concentration, the area where the hydrogen sensing particles are located is 90 to 100% by area.

[Claim 12]

The method of claim 9,

Hydrogen gas sensor that the specific surface area of the hydrogen detecting particles in the high sensitivity sensor mode is 25 to 250 m ² / g.

[Claim 13]

The method of claim 9,

Hydrogen gas sensor is a specific surface area of the hydrogen detecting particles in the high concentration sensor mode is 0.5 to 25 m ² / g.

[Claim 14]

A pair of carbon electrode portions opposed to each other at a predetermined interval; Preparing a support including a carbon nanowire positioned between the carbon electrode parts and supported by the carbon electrode parts; And

The method of manufacturing a hydrogen gas sensor comprising the step of locally depositing hydrogen sensing particles on the surface of the carbon nanowires by the electroplating method of the support.

[Claim 15]

The method of claim 14,

Locally depositing hydrogen sensing particles on the surface of the carbon nanowires in the support by electroplating;

Wherein the electrolyte is placed on the carbon nanowires, the electrolyte is a method of producing a hydrogen gas sensor (Na ₂ PdC, Sodium tetrachloropalladate) of ΙΟηΜ -OOmM concentration.

[Claim 16]

The method of claim 15,

Locally depositing hydrogen sensing particles on the surface of the carbon nanowires by electroplating in the support;

A working electrode is connected to the carbon electrode and the carbon nanowires, and a counter electrode and a reference electrode are positioned by immersing in a palladium plating solution and performing electroplating. Manufacturing method of gas sensor.

[Claim 17]

The method of claim 16,

The electroplating method,

Palladium seed formation step; And growing a palladium seed; The palladium seed forming step; is a method of manufacturing a hydrogen gas sensor to be carried out at a higher voltage and shorter time conditions than the palladium seed growth step

[Claim 18]

The method of claim 17,

The electroplating method is,

Palladium seed formation step; And growing a palladium seed; wherein the palladium seed forming step and the palladium seed growing step are alternately performed a plurality of times to form palladium particles in the form of secondary particles.

[Claim 19]

The method of claim 14,

And annealing the carbon nanowires on which the hydrogen sensing particles are deposited in a vacuum or inert gas environment.

[Claim 20]

15. The method of claim 14, further comprising: a pair of carbon electrode portions facing each other at the predetermined intervals; Preparing a support including a carbon nanowire positioned between the carbon electrode parts and supported by the carbon electrode parts;

Preparing a substrate;

Forming an insulating layer on the substrate;

Forming a photoresist microwire connecting the pair of photoresist electrode portions and the pair of photoresist electrode portions by photolithography on the insulating layer; And

Pyrolyzing the pair of photoresist electrode portions and photoresist microwires, and converting the pair of carbon electrode portions and carbon nanowires to prepare a support by a method including a hydrogen gas sensor. .