KR100850266B1 - Carbon nanotubes field emission source comprising noble metal layer and preparation method thereof - Google Patents

Abstract

A carbon nanotube field emission source comprising a noble metal layer and a manufacturing method thereof are provided to enhance thermal conductivity and electrical conductivity by using a noble metal layer as a buffer layer. An Nb layer is formed on an upper surface of a substrate. A noble metal layer is formed on the upper surface of the substrate including the Nb layer. A carbon nanotube is formed on the upper surface of the substrate including the noble metal layer. A heat treatment process for the substrate including the carbon nanotube is performed by using a microwave or an inductive coil. The heat treatment temperature is equal to and less than 400 degrees centigrade. The noble metal layer is composed of one or more elements selected from a group including Au, Ag, Cu, and an alloy comprising one of Au, Ag, and Cu.

Description

Carbon nanotube field emission source comprising a noble metal layer and its manufacturing method {CARBON NANOTUBES FIELD EMISSION SOURCE COMPRISING NOBLE METAL LAYER AND PREPARATION METHOD THEREOF}

1 is a view showing a schematic process diagram of a method for producing a carbon nanotube field emission source according to an embodiment of the present invention.

2A and 2B are 30,000 magnification (FIG. 2A) and 100,000 magnification (FIG. 2B) electron micrographs of a cross section of a state in which a noble metal layer is formed according to an embodiment of the present invention.

Figure 3 is an electron micrograph of the surface of the carbon nanotube layer is formed in accordance with an embodiment of the present invention.

4 is an electron micrograph of a cross section after heat treatment after forming a carbon nanotube layer according to an embodiment of the present invention.

5 is an I-V graph of a carbon nanotube field emission source manufactured according to an embodiment of the present invention.

6 is a light emission photograph of a carbon nanotube field emission source manufactured according to an embodiment of the present invention.

Explanation of symbols of the main parts of the drawings

100: substrate 110: Nb layer

120: precious metal layer 130: airbrush

140: carbon nanotubes

The present invention relates to a carbon nanotube field emission source including a noble metal layer as a buffer layer and a method of manufacturing the same.

Carbon nanotubes have a large aspect ratio, a low work function, high thermal and electrical conductivity, and high chemical stability. Therefore, many studies have been conducted as electron emission sources of electron emitting devices. As a method for producing a carbon nanotube field emission source known to date, a direct growth method, a screen printing method, an electrophoresis method, a spray method, etc. may be mentioned.

The direct growth method is a method of growing carbon nanotubes directly on an electrode using a method such as thermal vapor deposition or chemical vapor deposition. Since carbon nanotubes are grown directly on a substrate used as an electrode, the substrate and carbon nanotubes are grown. Although the adhesive strength between the very good, there is an advantage that can directly control the length, density, diameter, and the like of the carbon nanotubes, there is a limit to the practical use because it is difficult to manufacture a large area emission source. In addition, in order to grow carbon nanotubes with good crystallinity without amorphous carbon materials, temperature conditions of 900 ° C or higher are required.Indium Tin Oxide (ITO) glass, which is a substrate of a field emission source used commercially, has a melting point of about 550 ° C. This has the disadvantage of not being able to use it.

Screen printing is a method of screen printing by mixing carbon nanotubes and pastes on a substrate. The screen printing method is easy to manufacture a large area emission source and has a high bonding strength between carbon nanotubes and a substrate. When the temperature of the emission source is raised, various polymers and organic substances included in the paste are generated, and these materials deteriorate carbon nanotubes, thereby shortening the lifetime of the emission source.

Electrophoresis is a method of depositing an emission source on a substrate by applying a voltage to a solution in which carbon nanotubes are dispersed. In the spray method, a carbon nanotube dispersion solution is sprayed onto a substrate using an airbrush to produce an emission source. That's how. The electrophoresis method and the spray method are easy to manufacture with a large area emission source, do not cause deterioration of carbon nanotubes due to polymers or organic matters, and the manufacturing process is also relatively simple. However, since the adhesion between the carbon nanotubes and the substrate is weak, when the electric field is emitted, a plurality of carbon nanotubes are separated by the applied electric field.

As such, the field emission source using the conventional carbon nanotubes should be free from the strong bonding force between the substrate and the carbon nanotubes, ease of fabrication as a large area emission source, and the generation of materials (polymers, etc.) that deteriorate the emission source and shorten the lifespan. Various conditions are required, and there have been studies on the method of manufacturing the field emission source that can solve the existing problems.

The present invention provides a field emission source of carbon nanotubes and a method for producing the same, which have a strong bond between the substrate and the carbon nanotubes, are easy to manufacture a large area emission source, and which do not use materials that affect the lifetime of the emission source. It aims to provide.

In order to achieve the above object, the present inventors have intensively researched, and have completed the present invention by paying attention to the problem of the prior art when using a spray method using a precious metal layer as a buffer layer.

The present invention provides a method for producing a carbon nanotube field emission source, comprising the step of forming a noble metal layer on the substrate and forming a carbon nanotube on the noble metal layer.

In the present specification, the term 'noble metal' is a metal that is stable in the air, such as gold and silver, which is not rust and has good gloss, and has a higher melting point, excellent stretchability, and poorly soluble in chemicals, as compared with nonmetals. It means a metal having high conductivity and high conductivity.

The present invention provides a method for producing a carbon nanotube field emission source further comprising the step of heat-treating the substrate on which carbon nanotubes are formed using a microwave or an induction coil.

In the preparation of the field emission source according to the present invention, it is preferable to further include the step of forming an Nb layer on the substrate, before the step of forming the noble metal layer, the noble metal layer is Au, Ag, Cu and any of these It is possible to use a layer including any one or more selected from the group consisting of alloys containing one.

It is preferable to disperse the carbon nanotubes used in the preparation in a dispersion solution.

The present invention provides a carbon nanotube field emission source comprising a substrate 100, a noble metal layer 120 formed on the substrate, and a carbon nanotube layer 130 formed on the noble metal layer.

The field emission source according to the present invention may be formed by further forming an Nb layer 110 between the substrate 100 and the noble metal layer 120.

Hereinafter, the configuration of the present invention in more detail.

A schematic process diagram according to an optimal embodiment of the invention is shown in FIG. 1.

The present invention, carbon nanotube field emission, characterized in that comprising the step of forming a noble metal layer 120 on the substrate 100 and the carbon nanotube 130 on the noble metal layer 120 It provides a raw manufacturing method.

Formation of the noble metal layer 120 has an effect of improving the adhesion between the carbon nanotubes and the substrate, and further improve the thermal conductivity and electrical conductivity of the carbon nanotube field emission source. Examples of the precious metal usable for this purpose include Au, Ag, Cu, and the like, and it is also possible to use an alloy including any one or more of the precious metals. In general, Au, Ag, Cu, Al and the like have not only high thermal conductivity and electrical conductivity, but also have good workability, and thus are widely used in the electronics industry. When these metals are in the form of alloys, the melting point is lower than when they consist of one element, and the intrinsic thermal and electrical characteristics of each element are less likely to change. This feature is characterized by including a noble metal layer between the carbon nanotubes and the substrate in accordance with the present invention to produce a field emission source, and then to effect the coating of the metal layer between the walls of the carbon nanotubes and the substrate, It quickly removes heat from the emission source, facilitates the movement of electrons, and the thin metal oxide layer formed on the metal surface during heat treatment acts as a resistance layer, so that it is not a field emission source of carbon nanotubes (metal surface layer). By blocking the emission of electrons in the) can be induced smooth electron emission of the emission source.

In another aspect, the present invention, in the step of forming the noble metal layer 120 on the substrate 100 and the carbon nanotube layer 130 on the noble metal layer, the substrate on which the carbon nanotube layer 130 is formed micro It provides a method for producing a carbon nanotube field emission source further comprising the step of heat treatment using a wave or an induction coil. In the manufacture of the carbon nanotube field emission source according to the present invention, the substrate on which the carbon nanotubes are formed may improve the adhesion between the substrate and the carbon nanotubes by heat treatment and stabilize the precious metal layer used as the buffer layer. At this time, it is preferable to use a microwave or an induction coil as a heat treatment method rather than using a direct contact heating method. Since heat is transferred to the entire substrate by radiant heating or contact heating by electric current, there is a possibility that a difference in thermal expansion between the metal and the substrate occurs during heat treatment, resulting in irregular shape of the metal on the substrate. Inconsistent lengths and densities can cause electrons to be unevenly emitted from the source during field emission. In order to prevent such a problem, it is preferable to use a heat treatment method using a microwave or an induction coil. Since microwaves or induction coils are supplied with heat by the current induced on the surface of the metal at low temperature, only the metal is selectively dissolved, so that the shape of the metal surface can be flattened, and only the surface of the metal is selectively melted. Since it is possible to prevent the substrate from being deformed by heat, there is an advantage that the ITO glass substrate can be used as the substrate. At this time, in consideration of the melting point temperature of the ITO glass substrate, the heat treatment temperature is preferably 400 ° C. or lower.

The heat treatment time is raised as quickly as possible to reach the temperature, it is preferable to maintain the molten metal to be evenly coated along the carbon nanotubes, and then cooled to room temperature as soon as possible. Particularly, in the case of Ag-Cu alloy, the melting point is generally known as 780 ° C., but it is also melted at 400 ° C. or lower in a water torr vacuum in an argon atmosphere. Therefore, the melting point of each noble metal layer is preferably measured at an appropriate temperature after the melting point is accurately measured through a test heat treatment.

In the method of manufacturing a carbon nanotube field emission source according to the present invention, it is more preferable to further include the step of forming the Nb layer 110 on the substrate before the step of forming the noble metal layer. If the Nb layer 110 is formed before the formation of the noble metal layer 120, the strain and stress between the noble metal layer 120 and the substrate 100 may be reduced. It is possible to prevent the precious metal thin film from being damaged by the impact applied to it. The formation of the Nb layer 110 and the noble metal layer 120 such as Au, Ag, Cu, or Ag-Cu alloy may be performed using a magnetron sputtering method, a thermal vapor deposition method, a chemical vapor deposition method, an electroplating method, or the like.

When forming carbon nanotubes, it is preferable to disperse | distribute to a dispersion solution and to use. The use of carbon nanotubes in a dispersed manner is to uniformly form a thin film of carbon nanotubes on a substrate and to form a constant thickness, and to prevent a factor of unstable emission current. This is because carbon nanotubes that are not straight and are not intertwined with each other are a source of unstable emission current due to arcing or uneven length distribution during field emission.

As a dispersion solution of carbon nanotubes, 1,2-dichloroethane (DCE), N, N-dimethylformamide (DMF), tetrahydrofuran (THF), Non-aqueous dispersions such as N-Methyl pyrrolidone (NMP), acetone, isopropyl alcohol, sodium dodecylsulfate (SDS), deoxyribonucleic acid ( Aqueous solutions containing surfactants such as deoxyribonucleic acid (DNA) can be used.

The carbon nanotube layer 130 is preferably formed using the airbrush 140. At this time, conditions such as nozzle diameter, injection pressure, and injection distance of the spray equipment, and the concentration and amount of the carbon nanotube solution are used. And the thickness and uniformity of the thin film according to the type of the solution. It is possible for a person skilled in the art to control the desired thin film thickness and uniformity without undue experimentation.

Hereinafter, the present invention will be described in more detail with reference to the following examples. The following examples describe the embodiments of the present invention, but the present invention is not limited thereto.

Example

(Example 1)

ITO (Indium Titanium Oxide) substrate was sequentially immersed in acetone, ethyl alcohol, trichloroethylene (TCE), deionized water (Deionized Water) to perform ultrasonic cleaning. Subsequently, an Nb layer 110 having a thickness of 30 nm was deposited under Ar atmosphere using a magnetron sputter on the substrate 100, and then the Ag layer 120 was deposited at a thickness of 300 nm. Electron micrographs of the cross section of the Nb layer and Ag layer are shown in Figure 2a (x 30,000) and Figure 2b (x 100,000).

Multi-walled carbon nanotube powder with a diameter distribution in nm and tens of micrometers in a nitrogen atmosphere chamber of 10 _-3 Torr was heated to about 1000 ° C. to primarily amorphous carbon material and poorly crystalline carbon nanotubes. After removing the mixture, the DCE (1,2-dichloro ethane) solution was mixed in 0.1mg / ml ratio (carbon nanotube 10mg, DCE 100ml), and then dispersed in individual carbon nanotubes by ultrasonication and centrifugation for 30 hours. And heat-treated at 1000 ° C. for 10 minutes. After that, the carbon nanotubes, amorphous carbon materials, and catalysts are separated by centrifugation of the catalyst metals from the carbon nanotubes by ultrasonic treatment of the amorphous carbon material and the catalyst metals used in the synthesis of carbon nanotubes. The metal was sunk and removed to prepare a carbon nanotube dispersion.

100 ml of the prepared carbon nanotube dispersion was used to form a carbon thin film on the Ag layer using the air brush 140. (Ar gas is used, air pressure 1.5 bar) An electron micrograph of the surface is shown in FIG.

The carbon nanotube thin film was placed in the chamber of the heater and the chamber atmosphere temperature was raised to 400 ° C. for 10 minutes using a microwave or an induction coil while maintaining the vacuum at atmospheric pressure in an inert gas Ar atmosphere (actual precious metal layer The temperature was about 700 ° C.), and then maintained for 5 minutes, followed by heat treatment and cooling to room temperature (vacuum degree of the chamber was 760 Torr, working gas Ar, reaching temperature for 10 minutes, holding temperature for 5 minutes, and decreasing to room temperature for 10 minutes). The field emission source was prepared by removing carbon nanotubes not adhered to the metal through the adhesive tape and arranging the lying carbon nanotubes perpendicular to the substrate. An electron micrograph of the field emission source cross section after the heat treatment is completed is shown in FIG. 4. The I-V graph of the prepared carbon nanotube field emission source is shown in FIG.

(Example 2)

A carbon nanotube field emission source was prepared in the same manner as in Example 1 except that the Ag layer was deposited to a thickness of 100 nm.

(Example 3)

A carbon nanotube field emission source was prepared in the same manner as in Example 1 except that the Ag layer was deposited to a thickness of 500 nm.

(Example 4)

A carbon nanotube field emission source was prepared in the same manner as in Example 1 except that the Nb layer was deposited to a thickness of 10 nm.

(Example 5)

A carbon nanotube field emission source was prepared in the same manner as in Example 1, except that the Nb layer was deposited to a thickness of 10 nm and the Ag layer was deposited to a thickness of 100 nm.

(Example 6)

A carbon nanotube field emission source was prepared in the same manner as in Example 1 except that the Nb layer was deposited at 10 nm and the Ag layer was deposited at 500 nm.

(Example 7)

A carbon nanotube field emission source was prepared in the same manner as in Example 1 except that the Nb layer was deposited to a thickness of 50 nm.

(Example 8)

A carbon nanotube field emission source was prepared in the same manner as in Example 1 except that the Nb layer was deposited at 50 nm and the Ag layer was deposited at 100 nm.

(Example 9)

A carbon nanotube field emission source was prepared in the same manner as in Example 1 except that the Ag layer was deposited at 50 nm and the Ag layer was deposited at 500 nm.

In the carbon nanotube field emission source prepared in Examples 1 to 9, the carbon nanotubes were uniformly bonded, and it was confirmed visually that the adhesion with the substrate was excellent. The field emission source obtained in Example 1 (see FIG. 4). Unlike the conventional electrophoretic and spray methods, the field emission source produced according to the present invention does not cause any drop of carbon nanotubes even when used, and thus the field emission source deteriorates due to poor adhesion of carbon nanotubes. It was confirmed that the problem of shortening the life was solved.

It can be seen from the IV graph shown in FIG. 5 that the current density of 1.5 mA / cm ² is obtained when the turn-on voltage is 1.6 V / µm and the voltage is 3.0 V / µm, and uniform electron emission is induced.

In addition, it can be seen from the emission picture of FIG. 6 that the field emission source is uniformly and uniformly formed on the entire substrate.

The carbon nanotube field emission source manufactured according to the present invention, by using the precious metal layer as a buffer layer, not only has excellent thermal conductivity and electrical conductivity, but also induces uniform electron emission on the metal surface. The adhesion between the substrates is improved to solve the problem of falling of carbon nanotubes, which is a problem of the field emission source manufactured by the conventional electrophoresis and spray methods. In addition, when a heating method using a microwave or an induction coil, etc. is used, since a low process temperature can be used, since it does not affect a glass substrate, it is very practical. In addition, the problem of deteriorating the characteristics of the electron emission source does not occur at all, and the manufacturing method is easy to solve all the problems of the existing screen printing method, direct growth method, etc., it can be used very usefully It is expected.

Claims (14)

As a method for producing a carbon nanotube field emission source, Forming an Nb layer over the substrate; Forming a noble metal layer on the substrate on which the Nb layer is formed; A method for producing a carbon nanotube field emission source, comprising the step of forming a carbon nanotube on an upper substrate on which a noble metal layer is formed. The method of claim 1, Method for producing a carbon nanotube field emission source further comprises the step of heat-treating the substrate on which the carbon nanotubes are formed using a microwave or an induction coil The method of claim 2, The heat treatment temperature is a method for producing a carbon nanotube field emission source, characterized in that 400 ℃ or less. delete The method of claim 1, The noble metal layer is a method for producing a carbon nanotube field emission source, characterized in that the layer containing any one or more selected from the group consisting of Au, Ag, Cu and an alloy containing any one of these. The method of claim 1, The carbon nanotube is a method for producing a carbon nanotube field emission source, characterized in that using the carbon nanotube dispersed in a dispersion solution. The method of claim 6, The dispersion solution is a carbon nanotube field emission source, characterized in that the non-aqueous dispersion solution selected from the group consisting of 1,2-dichloroethane, tetrahydrofuran, N-methyl pyrrolidone, acetone, isopropyl alcohol. . The method of claim 6, The dispersion solution is a carbon nanotube field emission source, characterized in that the aqueous solution containing a sodium dodecyl sulfate, deoxyribonucleic acid surfactant. The method of claim 6, Forming the carbon nanotubes is a method for producing a carbon nanotube field emission source, characterized in that performed using an air brush. The method of claim 1, The substrate is a method for producing a carbon nanotube field emission source, characterized in that the ITO glass substrate. Board; An Nb layer formed on the substrate; A precious metal layer formed on the Nb layer; And A carbon nanotube layer formed on the noble metal layer; Carbon nanotube field emission source characterized in that consisting of. delete The method of claim 11, The substrate is a carbon nanotube field emission source, characterized in that the ITO glass substrate. The method of claim 11, The noble metal layer is a carbon nanotube field emission source, characterized in that the layer consisting of any one selected from the group consisting of Au, Ag, Cu and an alloy containing any one of these.

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