KR20060055575A - Fabrication method of field emitter electrode using nanosphere lithography - Google Patents

Abstract

Disclosed is a method of manufacturing a field emission emitter electrode that can increase the uniformity of carbon nanotube emitter distribution and control the density of the carbon nanotube emitter using nanosphere lithography. The method of manufacturing a field emission emitter electrode according to the present invention comprises the steps of arranging spherical nanoparticles on a substrate; Depositing gold using the spherical nanoparticles as a deposition mask to form a gold pattern on the substrate; Forming a thiol group on the gold pattern surface; Bonding carbon nanotubes to the gold patterned surface on which the thiol group is formed by self-assembly.

Nanosphere Lithography, Carbon Nanotubes, Field Emission Emitters, Polystyrene Beads

Description

Manufacturing method of field emission emitter electrode using nanosphere lithography {FABRICATION METHOD OF FIELD EMITTER ELECTRODE USING NANOSPHERE LITHOGRAPHY}

1A and 1B are cross-sectional views illustrating a method of manufacturing a field emission emitter electrode using a conventional carbon nanotube-metal composite plating method.

2 to 6 are views for explaining a method of manufacturing a field emission emitter electrode according to an embodiment of the present invention.

7 is a schematic cross-sectional view of a field emission emitter electrode made in accordance with another embodiment of the present invention.

8 and 9 are views for explaining a method of manufacturing a field emission emitter electrode according to another embodiment of the present invention.

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

101: substrate 104: polystyrene beads

110, 110a, 110b: metal patterns 140, 160, 180: carbon nanotubes

150, 185: metal plating layer 170: anodized aluminum film

175: pore

The present invention relates to a method for manufacturing a field emission emitter electrode, and more particularly, a field emission emitter capable of improving the uniformity of the emitter distribution and adjusting the emitter density using a nanosphere lithography method. It relates to a manufacturing method of the electrode electrode.

As nanoscience advances, much research is being conducted on how to arrange regular and fine particles. Reflecting this research trend, a method for producing a desired particle arrangement or layer structure by a bottom-top method has been developed. One such method is nanosphere lithography. According to the nanosphere lithography method, naturally occurring two-dimensional thin films are used to form a continuous array of spherical particles of sub-micrometer size. This continuous array of spherical particles can be used as a deposition mask.

In 1986, Deckman applied spin-coating spherical polystyrene particles, about 0.8 μm in diameter, onto a flat silicon substrate to give a two-dimensional monolayer crystal with a honeycomb structure in which up to 105 polystyrene particles were firmly arranged. It was reported that was prepared. Monolayer crystals formed by this "natural lithography" technique can be used as deposition masks to produce nanoscale patterns of metals, oxides or organic compounds. Van Duyne and co-workers applied polystyrene spherical particles with diameters of several hundred nanometers with a spin coating on mica and glass surfaces to form two-dimensional monolayers and bilayer arrays, and deposited silver as a deposition mask. The deposition mask was then removed to form a pattern of silver particles.

In addition to spherical polystyrene particles, an example of a pattern manufactured using spherical silicon particles has been reported, and an example of preparing an array of particles having a size of about 10 nanometers using protein molecules has been reported. In addition, the nanosphere lithography method may be used to manufacture a thin film for an organic light emitting diode. The nanosphere lithography method has advantages in that the process is simple, inexpensive, and hardly restricted to the applied material, compared to other pattern forming methods.

On the other hand, a field emission display (FED) is a light source based on electron emission in a vacuum, and has a fine tip or emitter that emits electrons by a strong electric field. These emitted electrons are accelerated to the phosphor screen in a vacuum to emit light by exciting the phosphor. The performance of the field emission display is largely dependent on the emitter electrode that emits electrons. Recently, carbon nanotubes (CNTs) have been used as emitter materials having excellent field emission characteristics. Representative carbon nanotube emitter electrode manufacturing methods include a conventional printing method, a method of attaching CNT on the electrode using electrophoresis, and attaching the CNT together with the metal plating layer on the negative electrode using a plating solution in which CNT is dispersed. There are ways.

1 is a cross-sectional view illustrating a method of manufacturing a field emission emitter electrode using a conventional CNT-metal composite plating method. Referring to FIG. 1A, first, a metal layer 12 is formed on a support substrate 11 to prepare a substrate to be plated. The metal layer 12 may be patterned in a line form. Thereafter, the substrate is immersed in a plating solution in which CNTs are dispersed to form a metal plating layer 14 on the metal layer 14 by a method such as electroless plating. At this time, the CNT 16 is attached to the metal layer 12 together with the metal plating layer 14. Thus, a field emission emitter electrode in which CNTs are arranged is produced. However, according to the conventional method of manufacturing the emitter electrode using the composite plating of CNT-metal, the CNT emitter is not uniformly distributed on the metal layer 12, resulting in uneven density of the CNT emitter. This lowers the field emission efficiency and causes a deterioration of the lifetime of the field emission display device. In addition, according to the conventional method, it is difficult to adjust the emitter density to a desired value.

The present invention is to solve the above problems, the object is to implement a high-efficiency field emission using the nanosphere lithography method, to improve the uniformity of the emitter distribution as a whole, the emitter density can be adjusted It is to provide a method for producing a field emission emitter electrode.

In order to achieve the above technical problem, a method of manufacturing a field emission emitter electrode according to an aspect of the present invention comprises the steps of arranging spherical nanoparticles on a substrate; Depositing gold (Au) using the spherical nanoparticles as a deposition mask to form a gold pattern on the substrate; Forming a thiol group on the surface of the gold pattern; Bonding the carbon nanotubes to the gold patterned surface on which the thiol group is formed by self-assembly. Preferably, the spherical nanoparticles are polystyrene bead particles.

According to an aspect of the present invention, the step of bonding the carbon nanotubes by self-assembly on the gold pattern surface, forming a carboxyl group on the carbon nanotubes; Treating the carboxyl group-formed carbon nanotubes with NH ₂ (CH ₂ ) ₂ SH; And providing carbon nanotubes treated with NH ₂ (CH ₂ ) ₂ SH on the gold pattern on which the thiol group is formed, and arranging the carbon nanotubes vertically on the gold pattern surface. In this case, in the step of arranging carbon nanotubes vertically on the surface of the gold pattern, a coupling reagent may be provided on the gold pattern. As the coupling agent, dicyclohexylcarbodiimide (DCC), oxalic acid chloride, or EDC (1- [3- (dimethylamino) propyl] -3-ethylcarbodiimide hydrochloride) may be used.

In addition, the step of forming a thiol group in the gold pattern, the 11-mercapto-1-undecanol (11-mercapto-1-undecanol) solution or 11-mercaptoundi canoic to the substrate on which the gold pattern is formed It may include immersing in an alcohol solution of acid (11-mercaptoundecanoic acid). In addition, the step of forming a carboxyl group on the carbon nanotubes may include the step of applying ultrasonic waves to the carbon nanotubes in a mixed solution of nitric acid and sulfuric acid.

According to another aspect of the present invention, there is provided a method of manufacturing a field emission emitter electrode, comprising: arranging spherical nanoparticles on a substrate; Depositing nickel (Ni) on the substrate using the spherical nanoparticles as a deposition mask to form a nickel pattern; Attaching carbon nanotubes on the nickel pattern using electroplating or electrophoresis to form an emitter of carbon nanotubes. In this case, preferably the spherical nanoparticles are polystyrene bead particles. Forming the carbon nanotube emitter by attaching carbon nanotubes on the nickel pattern may include forming a nickel-carbon nanotube composite plating layer on the nickel pattern.

According to still another aspect of the present invention, there is provided a method of manufacturing a field emission emitter electrode, comprising: arranging spherical nanoparticles on a substrate; Depositing aluminum (Al) using the spherical nanoparticles as a deposition mask to form an aluminum pattern; Anodizing the aluminum pattern to form an anodized aluminum oxide (AOO) film on the aluminum pattern; Attaching carbon nanotubes on the AAO film using electroplating or electrophoresis to form an emitter of carbon nanotubes. In this case, preferably the spherical nanoparticles are polystyrene bead particles.

According to another aspect of the present invention, the forming of the AAO film may include anodizing the aluminum pattern, and etching the anodized aluminum pattern with a phosphoric acid solution. . In addition, attaching carbon nanotubes on the AAO film to form an emitter made of carbon nanotubes may include forming a nickel-carbon nanotube composite plating layer in pores formed in the AAO film. .

The present invention provides a way to improve the uniformity of the emitter distribution and to easily control the emitter density. To this end, a nanosphere lithography method is used to form a uniformly distributed metal pattern on the substrate, and then a carbon nanotube emitter is formed on the metal pattern. Since the uniformity of the metal pattern is very high, the uniformity of the emitter is also very high. In addition, by selecting the spherical nanoparticles of the appropriate size it is possible to obtain the desired metal pattern density, thereby easily controlling the density of the carbon nanotubes.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape and size of elements in the drawings may be exaggerated for clarity, and the elements denoted by the same reference numerals in the drawings are the same elements.

2 to 6 are views for explaining a method of manufacturing a field emission emitter electrode according to an embodiment of the present invention. In this embodiment, after the gold (Au) pattern is formed by nanosphere lithography, a carbon nanotube emitter is formed on the substrate by self-assembly between gold and carbon nanotubes.

First, referring to FIGS. 2A and 2B, a single layer film of polystyrene beads 104 is formed by uniformly applying spherical nanoparticles 104 made of polystyrene bead particles onto a substrate 101. FIG. 2B shows the top view of FIG. 2A. If necessary, a multilayer film of the polystyrene beads 104 may be formed on the substrate 101. The polystyrene beads 104 particles may have diameters of tens to hundreds of nanometers (nm). The diameter of the polystyrene beads may be appropriately selected depending on the desired emitter distribution density. In addition, the substrate 101 is preferably made of a glass substrate and an ITO layer formed thereon. The substrate 101 may be simply made of a glass material.

As a method of applying the polystyrene beads 104 to the substrate 101, there is a method using spin coating or a method of applying a thin layer directly by hand. At this time, it is important to apply the coating uniformly so as to have as few defects as possible. In addition, the polystyrene beads 104 should be well packed. In order to satisfactorily pack the polystyrene beads 104, it is preferable to apply the polystyrene beads 104 by a spin coating method. In addition, the method of evaporating the solvent of the suspension by tilting the polystyrene beads 104 applied on the substrate 101 and packing them by pushing the beads to one side, by dropping the suspension of the polystyrene beads 104 with the dropper, Interactive packing.

3A and 3B, gold (Au) is deposited on the substrate 101 using the polystyrene beads 104 as a deposition mask. Accordingly, as shown in FIG. 3B, a gold pattern 110 is formed on the substrate 101 through the space between the particles of the polystyrene beads 104.

Next, referring to FIGS. 4A and 4B, the polystyrene beads 104 are completely removed using an acid or base solution. As such, when the polystyrene beads 104 are completely removed, a very uniform and regularly distributed gold pattern 110 as shown in FIG. 4B appears on the substrate 101. The portion of the substrate 101 exposed by the gold pattern 110 corresponds to the ITO layer. The spacing or distribution density of the gold pattern 110 formed at this time will vary depending on the size of the polystyrene beads 104 particles. For example, when using 500 nm diameter polystyrene beads 104, the spacing between the gold patterns 110 is about 280 nm and the size of one gold pattern 110 forming a triangle is about 100 nm. Thus, by appropriately adjusting the size of the particles of polystyrene beads 104 used in nanosphere lithography, the distribution density of the gold pattern 110 can be appropriately controlled.

Next, as shown in FIGS. 5A and 5B, the carbon nanotubes 140 are vertically arranged on the surface of the gold pattern 110 using an Au-thiol self assemble reaction. . FIG. 5B is an enlarged view illustrating a bonding portion between the gold pattern 110 and the carbon nanotubes 140 in FIG. 5A. As shown in FIG. 5B, the gold pattern 110 and the carbon nanotubes 140 are connected to -CONH (CH ₂ ) ₂ S-. The detailed procedure of the gold-thiol self-assembly reaction is shown in Figures 6a and 6b.

6A and 6B illustrate a process of vertically coupling the carbon nanotubes 140 to the surface of the gold pattern 110 by a gold-thiol self-assembly reaction. First, referring to FIG. 6A, a single wall carbon nanotube (SWNT) 140 is previously placed in a mixed solution of sulfuric acid and nitric acid, and the SWNT is cut by applying ultrasonic waves at a temperature of 40 ° C. for about 8 hours. . The mixed solution may be prepared by mixing sulfuric acid and nitric acid in a volume ratio of about 3: 1, for example. Accordingly, the carbon nanotubes 140 are cut off to form carboxyl groups (-COOH) at the end of the graphite layer. Thereafter, the carbon nanotubes on which the carboxyl group is formed are treated with NH ₂ (CH ₂ ) ₂ SH. At this time, DCC can be provided to the carbon nanotubes. Accordingly, as shown in FIG. 6A, -CONH (CH ₂ ) ₂ SH is formed in the carbon nanotube.

Meanwhile, a thiol group (-SH) is formed on the surface of the gold pattern 110. That is, 11-mercapto-1-undecanol solution or 11-mercapto-undecanol acid or 11-mercaptoundecanoic acid having the gold pattern 110 formed thereon. In an alcohol solution for 4-12 hours. Accordingly, the surface of the gold pattern 110 has a thiol group.

Thereafter, as illustrated in FIG. 6B, the carbon nanotubes are formed by providing the carbon nanotubes on which the -CONH (CH ₂ ) ₂ SH is formed on the gold pattern 110 having the surface A on which thiol groups are formed. To be coupled on the pattern 110. At this time, to provide a coupling reagent (coupling reagent) such as DCC (dicyclohexylcarbodiimide), oxalic acid chloride or EDC (1- [3- (dimethylamino) propyl] -3-ethylcarbodiimide hydrochloride) to the gold pattern desirable. Accordingly, a plurality of carbon nanotubes 140 are vertically arranged on the surface of the gold pattern 110. As the carbon nanotubes 140 are vertically arranged on the gold pattern 110 formed on the substrate 101, the substrate 101 can be used as an emitter electrode of the field emission device. The vertically arranged carbon nanotubes 140 serve as emitters of the emitter electrode.

According to the above embodiment, since the gold pattern 110 is formed by the nanosphere lithography method, the gold pattern 110 has a very uniform and regular distribution. In addition, by appropriately selecting the size of the polystyrene bead particles used to form the gold pattern 110, the distribution density of the gold pattern 110 can be easily controlled. Therefore, the overall distribution of the carbon nanotube emitters arranged vertically on the gold pattern 110 is also very uniform, and the overall distribution density of the carbon nanotube emitters can be easily controlled. As a result, the emitter electrode manufactured according to the present embodiment can improve the problem of surface resistance and junction resistance to implement high-efficiency field emission.

Next, the manufacturing method of the field emission emitter electrode which concerns on other embodiment of this invention is demonstrated. 7 schematically shows a cross-sectional structure of a field emission emitter electrode prepared according to the other embodiment. Referring to FIG. 7, a metal plating layer (eg, a nickel plating layer) 150 is formed on a nickel pattern 110a formed by using nanosphere lithography, and carbon nanotubes 160 are attached to the metal plating layer 150. It is. The carbon nanotubes 160 attached to the metal plating layer 150 may be emitters of the field emission device. The process for manufacturing the emitter electrode of this structure is as follows.

First, polystyrene bead particles are regularly arranged on the substrate 101 as in the above-described embodiment, and then nickel (Ni) metal is deposited using the bead particles as a deposition mask. Thereafter, when the bead particles are removed, a nickel pattern 110a having a shape similar to that of the gold pattern 110 of FIG. 5 appears on the substrate 101. In this case, the size L of the nickel pattern 110a or the spacing D between the nickel patterns 110a may be adjusted by appropriately selecting the size of the polystyrene beads. Thereafter, electroplating is performed on the nickel pattern 110a so that the composite plating layers 150 and 160 of metal-carbon nanotubes are formed on the nickel pattern 150. For example, when a substrate 101 having a nickel pattern 150 is immersed in a nickel plating solution in which carbon nanotubes are dispersed, and a current is flowed using the substrate 101 as a negative electrode substrate, nickel is formed on the surface of the nickel pattern 150. The plating layer 150 is formed. At this time, the carbon nanotubes 160 are also plated together with the nickel plating layer 150 so that the carbon nanotubes are arranged on the nickel pattern 110a. The carbon nanotubes 160 arranged as described above form an emitter of the field emission device.

Alternatively, carbon nanotubes may be arranged on the nickel pattern 110a by electrophoresis (not shown). That is, the substrate 101 on which the nickel pattern 110a is formed is immersed in an electrolyte in which carbon nanotubes are dispersed, and then voltage is applied using the substrate 101 as a negative electrode substrate. Accordingly, the carbon nanotubes dispersed in the electrolyte are deposited on the nickel pattern 110a by electrophoresis. The carbon nanotubes attached by electrophoresis may be used as emitters of the field emission device.

As described above, even when the carbon nanotube emitter is formed on the nickel pattern 110a by nanosphere lithography using electroplating or electrophoresis, the carbon thiol-self-assembly reaction described above is similar to carbon. The nanotubes are only attached onto the nickel pattern 110a by nanosphere lithography. Therefore, also in this embodiment, a carbon nanotube emitter can be distributed uniformly as a whole and the distribution density can be controlled easily.

Next, the manufacturing method of the field emission emitter electrode which concerns on another embodiment of this invention is demonstrated. In this embodiment, after forming an anodized aluminum oxide (AAO) film pattern by using anodization of aluminum, carbon nanotubes are attached onto the AAO film by electroplating or electrophoresis.

Specifically, first, aluminum spheres are formed on a substrate by performing nanosphere lithography using polystyrene beads. In this embodiment, aluminum (Al) is deposited instead of gold (Au) to form an aluminum pattern having a shape similar to that of the gold pattern 110 shown in FIG. 5. Thereafter, the aluminum pattern is anodized to form a porous Anodized Aluminum Oxide (AOA) film on the Al pattern. For example, an aluminum pattern is immersed in a 3% by weight phosphoric acid solution, and this substrate is used as an anode substrate to apply a voltage of 50V to flow a current of 0.5 A for about 15 minutes to anodize the aluminum pattern. Thereafter, the aluminum pattern is etched with 5% by weight of phosphoric acid at 50 ° C. for about 20 minutes to form an AAO film having aligned pores on the aluminum pattern. 8 is a planar photograph showing the porous AAO membrane thus formed.

Next, carbon nanotubes are attached to the porous AAO membrane using electroplating. For example, when a substrate on which a porous AAO film is formed is immersed in a nickel plating solution in which carbon nanotubes are dispersed, electroplating is performed to form a composite plating layer of nickel-carbon nanotubes in pores on the surface of the AAO film. 9 is a cross-sectional view of an aluminum pattern on which composite plating layers 185 and 180 of nickel-carbon nanotubes are formed. Referring to FIG. 9, an AAO film 170 having aligned pores 175 is formed on the aluminum pattern 110b by nanosphere lithography, and the nickel plating layer 185 and carbon nanotubes are formed in the pores 175. 180 is plated. The carbon nanotubes 180 may be used as emitters of field emission devices. Alternatively, carbon nanotubes may be attached to the porous AAO membrane using electrophoresis.

Also in this embodiment, a carbon nanotube emitter exhibiting a uniform distribution as a whole can be obtained, and the distribution density of the emitter can be easily controlled. In addition, since the carbon nanotube emitter is mainly attached to the aligned pore portion of the AAO membrane, it is possible to further improve the uniformity of the carbon nanotube emitter.

It is intended that the invention not be limited by the foregoing embodiments and the accompanying drawings, but rather by the claims appended hereto. In addition, it will be apparent to those skilled in the art that the present invention may be substituted, modified, and changed in various forms without departing from the technical spirit of the present invention described in the claims.

As described above, according to the present invention, by forming a carbon nanotube emitter using a metal pattern formed by nanosphere lithography, the uniformity of the emitter distribution can be improved, and the spherical nanoparticles used in the nanosphere lithography By appropriately selecting the size, the density of the carbon nanotube emitter can be easily controlled. Therefore, the field emission efficiency can be greatly improved.

Claims (14)

Arranging spherical nanoparticles on the substrate; Depositing gold using the spherical nanoparticles as a deposition mask to form a gold pattern on the substrate; Forming a thiol group on the gold pattern surface; And The method of manufacturing a field emission emitter electrode comprising the step of self-assembling carbon nanotubes on the surface of the gold pattern formed thiol group. The method of claim 1, The spherical nanoparticles are polystyrene bead particles, characterized in that the manufacturing method of the field emission emitter electrode. The method of claim 1, Coupling carbon nanotubes by self-assembly on the gold pattern surface, Forming a carboxyl group on the carbon nanotubes; Treating the carbon nanotubes having the carboxyl group formed with NH ₂ (CH ₂ ) ₂ SH; And Providing the carbon nanotubes treated with NH ₂ (CH ₂ ) ₂ SH on the gold pattern on which the thiol group is formed, and vertically arranging the carbon nanotubes on the surface of the gold pattern. Method of manufacturing the electrode. The method of claim 3, The method of manufacturing a field emission emitter electrode, characterized in that to provide a coupling agent to the gold pattern in the step of arranging carbon nanotubes vertically on the gold pattern surface. The method of claim 4, wherein The coupling agent is a method of producing a field emission emitter electrode, characterized in that the DCC, oxalic acid chloride or EDC. The method of claim 1, Forming a thiol group in the gold pattern, the step of immersing the substrate on which the gold pattern is formed in an alcohol solution of 11-mercapto-1-undicanol solution or 11-mercaptoundi cananoic acid A method for producing a field emission emitter electrode, characterized in that. The method of claim 3, Forming a carboxyl group on the carbon nanotubes, the carbon nanotubes in a mixed solution of nitric acid and sulfuric acid comprising the step of applying ultrasonic waves, characterized in that for producing a field emission emitter electrode. Arranging spherical nanoparticles on the substrate; Depositing nickel using the spherical nanoparticles as a deposition mask to form a nickel pattern on the substrate; And And attaching carbon nanotubes on the nickel pattern using electroplating or electrophoresis to form an emitter made of carbon nanotubes. The method of claim 8, The spherical nanoparticles are polystyrene bead particles, characterized in that the manufacturing method of the field emission emitter electrode. The method of claim 8, Forming an emitter made of carbon nanotubes by attaching carbon nanotubes on the nickel pattern may include forming a nickel-carbon nanotube composite plating layer on the nickel pattern. Method for producing emitter electrode. Arranging spherical nanoparticles on the substrate; Depositing aluminum using the spherical nanoparticles as a deposition mask to form an aluminum pattern on the substrate; Anodizing the aluminum pattern to form an anodized aluminum film on the aluminum pattern; And And attaching carbon nanotubes on the anodized aluminum film using electroplating or electrophoresis to form emitters of the carbon nanotubes. The method of claim 11, The spherical nanoparticles are polystyrene bead particles, characterized in that the manufacturing method of the field emission emitter electrode. The method of claim 11, The forming of the anodized aluminum film may include performing anodization on the aluminum pattern, and etching the anodized aluminum pattern with a phosphoric acid solution. Way. The method of claim 11, Attaching carbon nanotubes on the anodized aluminum film to form an emitter made of carbon nanotubes includes forming a nickel-carbon nanotube composite plating layer in pores formed in the anodized aluminum film. A method for producing a field emission emitter electrode, characterized in that.

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