KR101491206B1 - Method of manufacturing Emitter for Field Emission and Field Emission Device manufactured by using the same - Google Patents

Abstract

A method of manufacturing an emitter for field emission is provided. A method of manufacturing a field emission emitter includes the steps of preparing a substrate, forming a metal adhering layer on the substrate, forming a carbon nanotube film on the metal adhesion layer, And annealing the carbon nanotubes to increase the adhesion between the substrate and the carbon nanotubes. Therefore, the carbon nanotube density can be controlled by controlling the average particle size of the metal adhesion layer, and the adhesion strength between the substrate and the carbon nanotubes can be improved by heating the carbon nanotubes formed on the metal adhesion layer.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing an emitter for field emission and a field emission device using the field emission device,

The present invention relates to a method for manufacturing an emitter for field emission, and more particularly, to a method for manufacturing a field emission emitter using carbon nanotubes and a field emission device manufactured using the method.

Field Emission Device is a light source based on electron emission in a vacuum, and has been attracting attention as a next generation light source in various lighting fields and display devices.

Generally, a field emission device includes a field emission emitter electrode having a plurality of fine tips or emitters for emitting electrons by a strong electric field. The performance of such a field emission device is mainly determined by the emitter electrode capable of emitting electrons.

In recent years, carbon nanotubes (CNTs) have been used as emitters in order to improve the field emission characteristics. Carbon-based materials including carbon nanotubes having excellent electron conductivity are excellent in conductivity and field concentration effect, have low work function and excellent field emission characteristics, and can be easily driven at a low voltage and can be made large-sized. Therefore, a field emission device ) As an ideal electron emission source.

In the method of manufacturing an electron emission source including carbon nanotubes, carbon nanotube direct growth, carbon nanotube paste, solution-based spraying, or electrophoresis are used as a method of manufacturing a cathode substrate.

Conventionally, when the carbon nanotube emitter is formed, the adhesion force between the cathode substrate and the carbon nanotubes is not strong, so that the density of the carbon nanotubes is low and the electric conductivity is low, so that the carbon nanotubes are easily detached from the substrate upon electron emission So that electrical arcing is caused and eventually stable driving for a long time is difficult. Further, when the distance between the carbon nanotubes is too close, there is a problem that a canceling effect due to electric field interference occurs.

Korean Patent Laid-Open No. 10-2006-0024725 (Mar. 17, 2006) discloses a method of manufacturing a field emission emitter electrode comprising a step of applying a conductive polymer on a surface to which carbon nanotubes are adhered and a heat treatment for curing the conductive polymer Lt; / RTI > In this case, the adhesion strength of the carbon nanotubes can be improved, but the density of the carbon nanotubes can not be controlled.

Therefore, there is a need to manufacture a field emission emitter in which the density of carbon nanotubes is controlled and adhesion between the substrate and the carbon nanotubes is improved.

SUMMARY OF THE INVENTION The present invention provides a field emission emitter in which the density of carbon nanotubes is controlled and adhesion between a substrate and carbon nanotubes is improved.

According to an aspect of the present invention, there is provided a method of manufacturing a semiconductor device, Forming a metal adhesion layer on the substrate; Forming a carbon nanotube film on the metal adhesion layer; And annealing the substrate on which the carbon nanotube film is formed to increase the adhesion between the substrate and the carbon nanotubes.

The surface free energy of the metal adhesion layer is reduced by heat treating the metal adhesion layer before the step of forming the carbon nanotube film on the metal adhesion layer.

The heat treatment of the metal adhesion layer is characterized in that the average grain of the metal adhesion layer is grown to a size of 0.5 탆 to 50 탆.

The step of forming the metal adhesion layer on the substrate may have an average particle size of the metal adhesion layer of 1 nm to 10 nm.

The step of heating the substrate on which the carbon nanotube film is formed is performed in a vacuum atmosphere or a reducing atmosphere.

The metal adhesion layer is formed from a group consisting of Ni, Fe, Co, Cu, Ag, Au, Pd, Pt, Zn, Sn, Pb, Cr, Ti, Ta, Al, In, W, Si, Mo, And may include any one selected.

The carbon nanotube film is produced by vacuum-filtering a carbon nanotube solution onto a polymer membrane.

And activating the carbon nanotubes to vertically align the carbon nanotubes with the substrate after the step of increasing the adhesion between the substrate and the carbon nanotubes.

The method may further include the step of coating the carbon nanotubes with a metal oxide after the step of increasing the adhesion between the substrate and the carbon nanotubes.

The metal oxide may be one selected from the group consisting of Ni, Fe, Cu, Co, Ag, Ti, Zn, Rh, Sn, Cd, Cr, Be, Pd, In, Pt, Au, Si, W, Mo, Al, May be any one selected from oxides.

According to another aspect of the present invention, there is provided a method of fabricating a carbon nanotube film, comprising: forming a metal adhesion layer on a substrate and then heat treating the metal adhesion layer to form a metal adhesion layer; An emitter formed by heat-treating the substrate on which the carbon nanotube film is formed, and vertically aligning the carbon nanotube by activating the carbon nanotube; A base substrate formed under the emitter; A target layer formed on the upper portion of the emitter; And an upper substrate formed on the target layer.

As described above, according to the present invention, the metal adhesion layer is formed between the substrate and the carbon nanotubes and then heat-treated at a certain temperature, thereby improving electrical conductivity and adhesion of the emitter.

In addition, by adjusting the average grain size of the metal adhesion layer, the distance between the carbon nanotubes is optimized to minimize the decrease of the field emission effect due to the electric field interference between the carbon nanotubes, and the electric field enhancement factor can be greatly improved have.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

FIGS. 1 to 5 are cross-sectional views illustrating a method of manufacturing a field emission emitter according to an embodiment of the present invention.
6 is a schematic view of an emitter manufactured by a method for manufacturing a field emission emitter according to an embodiment of the present invention.
7 is a cross-sectional view of a field emission device including an emitter manufactured by the method for manufacturing a field emission emitter according to an embodiment of the present invention.
8 is an SEM image of the field emission emitters of Production Example 1 and Comparative Example 1. Fig.
9 is a graph showing the field emission JE curves of the field emission emitters of Production Example 1 and Comparative Example 1. Fig.
10 is a graph showing the current density of the emitter for field emission according to Production Example 1 with time.
11 to 13 are SEM images obtained in the manufacturing method of the field emission emitters according to Production Examples 1 to 3.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Like reference numerals designate like elements throughout the specification. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Example  One

FIGS. 1 to 5 are cross-sectional views illustrating a method of manufacturing a field emission emitter according to an embodiment of the present invention.

Referring to FIG. 1, first, a substrate 100 is prepared. The substrate 100 may have various shapes depending on the type of the emitter. For example, in the case of a point type emitter, the substrate 100 may be in the form of a rod or wire. The substrate 100 may be formed of a material selected from the group consisting of Ni, Fe, Co, Cu, Ag, Au, Pd, Pt, Zn, Sn, Pb, Cr, Ti, Ta, Al, In, W, Si, Mo, As shown in FIG.

Referring to FIG. 2, a metal adhesion layer 200 is formed on the substrate 100. The average grain size of the metal deposition layer 200 as deposited can be nanometer size, for example, several to several tens nanometers in size. For example, the average grain size of the metal adhesion layer 200 may be between 1 nm and 10 nm. The metal adhesion layer 200 may be formed using sputtering, thermal evaporation, electrophoresis, paste printing, or electroplating. The metal adhesion layer 200 may be formed of any one of Ni, Fe, Co, Cu, Ag, Au, Pd, Pt, Zn, Sn, Pb, Cr, Ti, Ta, Al, In, W, Si, Mo, And may include any one selected from the group consisting of.

Referring to FIG. 3, the metal adhesion layer 200 is heat-treated to reduce the surface free energy of the metal adhesion layer 200. The surface free energy of the metal adhesion layer 200 affects the density of the carbon nanotubes formed in the metal adhesion layer 200, which will be described later in the process steps.

The smaller the average particle size of the metal adhesion layer 200 is, the more thermodynamically unstable the surface free energy is. Therefore, when the particles of the metal deposition layer 200 are grown by the heat treatment, the surface free energy can be reduced.

The average grain size of the metal deposition layer 210 grown by the heat treatment may be in the range of several micrometers to several tens micrometers, preferably 0.5 micrometers to 50 micrometers, for example. If the mean grain size of the grain growth metal adhesion layer 210 is grown to a size of less than 0.5 탆, the surface free energy of the metal adhesion layer is still high, The density of the carbon nanotubes formed increases, and the field emission effect can be reduced due to the electric field interference between the carbon nanotubes. If the average grain size of the grain-grown metal adhesion layer 210 is increased to a size exceeding 50 m, the surface free energy of the metal adhesion layer is too low to cause the carbon nanotubes There may be a limit to increasing the density.

The heat treatment of the metal adhesion layer 200 may be performed at a temperature higher than a temperature at which grain growth of the metal adhesion layer 200 occurs. For example, if the Ni adherent layer is heat-treated at a temperature of 300 ° C or higher, grain growth of the Ni adherent layer can be caused.

However, according to the embodiment, if it is not necessary to control the density of the carbon nanotubes, the heat treatment step of the metal deposition layer 200 may be omitted.

Referring to FIG. 4, a carbon nanotube film 300 is formed on the grain-grown metal deposition layer 210. Next, the adhesion of the substrate 100 and the carbon nanotubes 310 is increased by heating the substrate 100 on which the carbon nanotube film 300 is formed.

For example, the carbon nanotube film 300 may be prepared by vacuum-filtering a carbon nanotube solution onto a polymer membrane. Specifically, a polymer membrane is prepared. The polymer membrane may include a plurality of pores. The polymer membrane may be a mixed cellulose ester (MCE) membrane or a polyvinyl difluoride (PVDF) membrane. Next, the carbon nanotube solution is vacuum filtered on the polymer membrane. The carbon nanotube solution may include carbon nanotubes and a surfactant. The surfactant may comprise sodium dodecyl sulfate (SDS). The SDS remaining in the vacuum-filtered carbon nanotubes is removed by using distilled water or the like or removed by heat treatment. Then, the polymer membrane is removed from the substrate 100. For example, the polymer membrane may be dissolved using acetone or the like to leave only the carbon nanotube film 300.

The step of heat-treating the substrate 100 on which the carbon nanotube film 300 is formed may be performed in an air atmosphere, a vacuum atmosphere, or a reducing atmosphere such as hydrogen.

The heat treatment of the substrate 100 on which the carbon nanotube film 300 is formed may be heated to the melting point of the metal adhesion layer 200 material. However, since the carbon nanotubes 310 may be damaged when heated to a temperature higher than a certain temperature in the air, the temperature may be limited to about 650 ° C. On the other hand, since the possibility of damaging the carbon nanotubes 310 is small in a vacuum atmosphere or a reducing atmosphere, the metal adhesion layer material can be heated to the melting point temperature. Therefore, when the heat treatment is performed in a vacuum atmosphere or a reducing atmosphere, it is possible to heat at a higher temperature than in the case of heat treatment in air, which has the advantage that the adhesion force can be further strengthened.

As the temperature of the substrate 100 on which the carbon nanotube film 300 is formed is increased, the carbon nanotubes 310 are bonded to the metal deposition layer. As a result, Can be increased.

5, after the step of increasing the adhesion between the substrate 100 and the carbon nanotubes 310, the carbon nanotubes 310 are activated by activating the carbon nanotubes 310, . For example, the carbon nanotubes 310 may be vertically aligned by activating the carbon nanotubes 310 using an elastomer.

Meanwhile, a step (not shown) of coating a metal oxide on the carbon nanotubes 310 may be further performed. The coating method can be carried out by various conventional methods. The metal oxide may be one selected from the group consisting of Ni, Fe, Cu, Co, Ag, Ti, Zn, Rh, Sn, Cd, Cr, Be, Pd, In, Pt, Au, Si, W, Mo, Al, May be any one selected from oxides. The carbon nanotubes 310 are coated with a metal oxide to provide the carbon nanotubes 310 with resistance in an oxidizing atmosphere. In addition, since the carbon nanotubes 310 have a solid structure, the carbon nanotubes 310 can not be easily released during the field emission, and the lifetime can be increased.

6 is a schematic view of an emitter manufactured by a method for manufacturing a field emission emitter according to an embodiment of the present invention. The carbon nanotube 310 is formed on the metal wire 110 coated with the metal adhesion layer.

7 is a cross-sectional view of a field emission device including an emitter manufactured by the method for manufacturing a field emission emitter according to an embodiment of the present invention.

Referring to FIG. 7, the emitter 400 is formed by forming a metal adhesion layer on a substrate 100 and then heat-treating the metal adhesion layer 210 to form a grain-grown metal adhesion layer 210, The carbon nanotube film 310 may be formed by vertically aligning the carbon nanotube film 310 by activating the substrate.

The base substrate 500 is formed under the emitter 400. The base substrate 500 may include a conductive material to serve as a cathode substrate.

The target layer 600 is formed on the upper portion of the emitter 400. The target layer 600 may include a fluorescent material to emit visible light or may include a metallic material to emit X-rays. The metal material may be any one selected from the group consisting of W, Cu, Mo, Co, Cr, Te, Ag, and alloys thereof.

The upper substrate 700 is formed on the target layer 600. The upper substrate 700 may include a conductive material to serve as an anode substrate.

Further, a spacer (not shown) may be further formed between the emitter 400 and the target layer 600 to serve as a support.

Manufacturing example  One

Thereby manufacturing a field emission emitter according to an embodiment of the present invention.

First, Ni was electroplated on a Cu wire having a diameter of 1.24 mm to form a Ni-coated Cu wire.

On the other hand, a multi-walled carbon nanotube (MWCNT) having a diameter of 5 nm to 9 nm was prepared. 30 mg of MWCNT was added to 100 mL of distilled water together with 1 wt% of sodium dodecyl sulfate (SDS) to prepare a carbon nanotube solution. The carbon nanotube solution was subjected to low energy ball milling for 3 hours and then ultrasonicated at 300 W for 30 minutes. The carbon nanotube solution was vacuum-filtered through a mixed cellulose ester (MCE) membrane having a diameter of 47 mm to form a carbon nanotube film. The MCE membrane was then dissolved in acetone to remove. Then, the carbon nanotube film was soaked in pure acetone three times to remove residual MCE from the carbon nanotube film.

The formed carbon nanotube film was moved to the top of Ni-coated Cu wire, dried at room temperature, and then the wire formed with the carbon nanotube film was heat-treated at about 400 ° C for 30 minutes in air.

As a result, all of the carbon nanotubes are attached to the upper surface of the wire, and the carbon nanotubes are laid on the surface of the wire. Therefore, the carbon nanotubes were vertically aligned by activating the carbon nanotubes by using a polydimethylsiloxane (PDMS) elastomer.

Manufacturing example  2

Before the step of moving the formed carbon nanotube film to the upper portion of the Ni-coated Cu wire, the same procedure as in Production Example 1 was performed except that the Ni-coated Cu wire was heated to 400 ° C, Was prepared.

Manufacturing example  3

Before the step of moving the formed carbon nanotube film to the upper portion of the Ni-coated Cu wire, the same procedure as in Production Example 1 was performed except that the Ni-coated Cu wire was heated to 800 ° C, Was prepared.

Comparative Example  One

A field emission emitter was manufactured in the same manner as in Production Example 1 except that pristine Cu wire was used instead of Ni coated Cu wire.

Hereinafter, exemplary embodiments of the present invention will be described in order to facilitate understanding of the present invention. It should be understood, however, that the following examples are intended to aid in the understanding of the present invention and are not intended to limit the scope of the present invention.

Experimental Example

8 is an SEM image of the field emission emitters of Comparative Example 1 and Production Example 1. Fig. The top surfaces (a) to (c) of the field emission emitter of Comparative Example 1 and the top surfaces (d) to (f) of the field emission emitter of Production Example 1 were measured with an SEM image.

8 (a) to 8 (c), CuO nanowires and carbon nanotubes are present on the upper surface of the emitter.

8 (d) to 8 (f), carbon nanotubes are present on the upper surface of the emitter.

Therefore, the number of carbon nanotubes per unit area is higher than that in the case where the Ni-adherent layer is present, and the density of the carbon nanotubes is high.

9 is a graph showing the field emission J-E curves of the field emission emitters of Comparative Example 1 and Production Example 1. Fig.

9 (a), in Comparative Example 1, the J-E curve of the emitter for field emission in the case of heating the carbon nanotube film attached on the top of the pristine Cu wire and in the case of not heating was measured. The turn-on fields of the carbon nanotube film when heated and not heated are 1.39 V / 탆 and 3.67 V / 탆, respectively. It can be seen that when the carbon nanotube film is heated, the turn-on electric field value is rather increased. This is because, when the carbon nanotube film attached to the top of the pristine Cu wire is heated, the carbon nanotubes are burned by the catalytic oxidation of Cu, and the CuO nanowires and some carbon nanotubes remain. Therefore, the density of the carbon nanotubes is lowered and the turn-on electric field value is increased.

Referring to FIG. 9 (b), the J-E curves of the field emission emitters when the carbon nanotube films adhered on the Ni coated Cu wires were heated and when they were not heated were measured. The turn-on field of the carbon nanotube film when heated and not heated is 1.73 V / m and 0.81 V / m, respectively. It can be seen that when the carbon nanotube film is heated, the turn-on electric field value decreases. Therefore, it can be seen that the number of carbon nanotubes strongly adhered to the Ni adhesion layer is increased by the heat treatment process.

10 is a graph showing the current density of the emitter for field emission according to Production Example 1 with time.

Referring to FIG. 10, when a current of ² mA (167 mA / cm ² ) flows under an electric field of 6.7 V / 탆, the current abruptly decreases in the early stage and then slowly decreased to half of the initial value by 25 hours thereafter. The current was maintained for 40 hours when a current of 0.72 mA (60 mA / cm < ² >) was applied under an electric field of 6.7 V / Therefore, it can be seen that the lifetime of the carbon nanotube emitter is improved by the Ni adhesion layer.

11 to 13 are SEM images obtained in the manufacturing method of the field emission emitters according to Production Examples 1 to 3.

Figs. 11 (a), 12 (a) and 13 (a) are top images of a Ni-coated Cu wire before lamination of carbon nanotube films.

Figs. 11 (b), 12 (b) and 13 (b) are top views of the emitter for field emission according to Production Examples 1 to 3.

Referring to Figs. 11 (a), 12 (a) and 13 (a), the average particle size of the Ni-adhered layer is about 10 nm when the Ni-adherent layer is not heat- And about 100 m when heat-treated at 800 [deg.] C. 11 (b), 12 (b) and 13 (b), the larger the average particle size of the adhesion layer, that is, the higher the heat treatment temperature of the Ni adhesion layer, As shown in Fig.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the present invention is not limited to the disclosed exemplary embodiments, and various changes and modifications may be made by those skilled in the art without departing from the scope and spirit of the invention. Change is possible.

100: substrate 110: wire coated with a metal adhesion layer
200: metal deposition layer 210: particle deposition metal deposition layer
300: Carbon nanotube film 310: Carbon nanotube
400: Emitter 500: base substrate
600: target layer 700: upper substrate

Claims (11)

Preparing a substrate;
Forming a metal adhesion layer on the substrate;
Annealing the metal adhering layer to reduce the surface free energy of the metal adhering layer;
Attaching a carbon nanotube film on the metal adhesion layer; And
And annealing the substrate having the carbon nanotube film attached thereto to increase the adhesion between the substrate and the carbon nanotube,
Wherein the step of forming the metal adhesion layer on the substrate comprises the steps of:
The heat treatment of the metal adhesion layer is characterized in that the average particle of the metal adhesion layer is grown to a size of 0.5 to 50 탆,
Wherein the carbon nanotube film is manufactured by vacuum-filtering a carbon nanotube solution onto a polymer membrane. delete delete delete The method according to claim 1,
Wherein the step of heating the substrate to which the carbon nanotube film is attached is performed in a vacuum atmosphere or a reducing atmosphere. The method according to claim 1,
The metal adhesion layer is formed from a group consisting of Ni, Fe, Co, Cu, Ag, Au, Pd, Pt, Zn, Sn, Pb, Cr, Ti, Ta, Al, In, W, Si, Mo, Wherein the emitter layer is formed on the surface of the substrate. delete The method according to claim 1,
After the step of increasing the adhesion between the substrate and the carbon nanotubes,
And activating the carbon nanotubes to vertically align the carbon nanotubes with respect to the substrate. The method according to claim 1,
After the step of increasing the adhesion between the substrate and the carbon nanotubes,
And coating a metal oxide on the carbon nanotubes. 10. The method of claim 9,
The metal oxide may be one selected from the group consisting of Ni, Fe, Cu, Co, Ag, Ti, Zn, Rh, Sn, Cd, Cr, Be, Pd, In, Pt, Au, Si, W, Mo, Al, Wherein the oxide is one selected from the group consisting of oxides, nitrides, nitrides, nitrides, nitrides, and nitrides. delete

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