KR20100026102A - Method for growing nanostructure on tip and method for adhering material on tip - Google Patents

Abstract

PURPOSE: A method for growing a nanostructure on a tip and a method for attaching a material on the tip are provided to efficiently and easily transfer the material form exposed liquid to the tip after exposing the liquid including a catalyst for synthesizing the nanostructure. CONSTITUTION: A method for growing a nanostructure on a tip includes the following steps: exposing liquid including a catalyst for synthesizing the nanostructure through a pore(110); transferring the catalyst from the exposed liquid to the tip(120); and growing the nanostructure on the top with the transferred catalyst. The inner surface of the pore has hydrophilic property. The top of a thin film has hydrophobic property. A method for attaching the material on the tip includes a step for exposing the liquid containing the material through the pore and a step for transferring the material from the expose to the tip.

Description

Method for growing nanostructure on tip and method for adhering material on tip

The present disclosure generally relates to a method of growing nanostructures on a tip and a method of attaching material on the tip.

Carbon nanotubes, which are being actively researched recently, are one of the new materials that are expected to be applied. The application of carbon nanotubes as electron emission sources in field emission devices is one of its applications. The field emission device is a device that emits electrons on the surface of the electron emission source to the outside by quantum mechanical tunneling by applying an external electric field to the surface of the electron emission source. Carbon nanotubes have excellent conductivity and electric field concentration effects, and have a low work function, and thus have excellent field emission characteristics. In addition, carbon nanotubes are excellent in chemical resistance and mechanical strength, and thus can be fabricated as an excellent electron emission source.

Recently Chem. Phys. Lett. 292, 567 (1988), J. Kong et al. Chem. Phys Lett. In 296, 195 (1998), a method for forming carbon nanotubes by using Fe and Mo or Fe particles as metals as a catalyst and thermochemical vapor deposition was reported by J. Hafner et al.

Since then, a method of forming carbon nanotubes on a cathode electrode as a field emission source using a metal catalyst has been studied. Applied Phys. Lett. 90, 183109 (2007) to S.H. Heo et al. Disclose a method of forming multi-walled carbon nanotubes on a tungsten tip using a nickel catalyst and applying plasma-promoted chemical vapor deposition.

In a method of growing a nanostructure on a tip according to an embodiment, a solution containing a catalyst for synthesizing the nanostructure is exposed through a pore. The catalyst is transferred from the exposed solution to the tip. The nanostructure is grown on the tip using the catalyst.

In addition, by attaching a material on the tip according to an embodiment, the solution containing the material is exposed through a pore (pore). The material is transferred from the exposed solution to the tip.

Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the disclosed technology is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to fully convey the spirit of the present disclosure to those skilled in the art. In the drawings, the width, thickness, or shape of structures may be enlarged in order to clearly express various layers (or layers), regions, and shapes. When a part of a layer, film, region, etc. is said to be "on or over" another part, this includes not only the other part "on or directly above" but also another part in the middle.

How to attach catalyst on the tip

1 is a flowchart illustrating a method of forming a catalyst on a tip, according to one embodiment. Referring to FIG. 1, at 110 block, a solution comprising a catalyst is exposed through one or more pores. The catalyst is a catalyst for the synthesis of nanostructures. At 120 blocks, the catalyst is formed on the tip by transferring the catalyst from the exposed solution to the tip.

Using this method, it is possible to control the area where the catalyst is formed on the tip. For example, when the tip contacts the solution through the pores, the smaller the area of the pores, the smaller the contact area between the tip and the solution, and thus the smaller the area on which the catalyst is formed. Further, using the above method, no expensive process such as a photolithography process or a process using vacuum equipment is required.

2 and 3 are diagrams for describing a process of exposing a solution including a catalyst through one or more pores, shown in block 110 of FIG. 1, according to an embodiment. Referring to FIGS. 2A and 2B, which show plan and cross-sectional views of the thin film 220, respectively, a thin film 220 having one or more pores 210 is provided. The inner surface 211 of the pores 210 may be hydrophilic, and the upper surface 221 of the thin film 220 may be hydrophobic. In addition, the thin film 220 may include a hydrophilic material 223 (eg, AAO anodic aluminum oxide) and a hydrophobic layer 225 formed on the hydrophilic material 223. AAO is used in the manufacture of various nanostructures, and has the advantage of controlling the size and pitch of the pores 210. The hydrophobic film 225 may be, for example, a fluorocarbon film. The fluorocarbon film may be formed on the AAO using, for example, plasma enhanced chemical vapor deposition (PECVD). The thickness of the fluorocarbon film may be, for example, about 50 nm to about 100 nm. In the drawings, the pores 210 are represented in a circular shape, but unlike the drawings, the pores 210 may have other shapes such as polygons or ellipses. The pores 210 may be provided with nanopores, for example. Nanopores refer to pores whose diameters (the longest distance between the points on the circumference of the cross-sections if the cross-sections of the nano-pores are not circles) are in nanometers or more than 1 nm and less than 100 μm.

Referring to FIG. 3, a thin film 220 having pores 210 is floated on a solution 320 including a catalyst 310 in the form of metal nanoparticles. The inner surface 211 of the pores 210 is hydrophilic, so that the solution 320 may rise to the top of the pores 210 by capillary force, and the upper surface 221 of the thin film 220 is hydrophobic, so that the solution 320 It is prevented from spreading to the upper surface 221 of the thin film 220. Thus, the droplet 320 may be stably present in the pores 210. The catalyst 310 in the form of metal nanoparticles is a catalyst for synthesis of nanostructures. For example, the nanostructures are carbon nanotubes, and the catalyst 310 in the form of metal nanoparticles includes nickel, cobalt, molybdenum, and iron. It may include at least one selected from the group.

4 is a diagram for describing a process of transferring a catalyst from an exposed solution to a tip, illustrated in block 120 of FIG. 1, according to an embodiment. Referring to FIG. 4, the solution 320 is attached to the tip 410 by contacting the tip 410 with the solution 320 including the catalyst 310 in the form of metal nanoparticles. The tip 410 may be a conductive material, and may include, for example, a metal such as tungsten, nickel, aluminum, molybdenum, tantalum, niobium, or an alloy thereof.

The sharp tip 410 can be formed by electrochemically etching the metal wire in a hydroxide solution (eg, potassium hydroxide or sodium hydroxide solution). In one embodiment, a tungsten tip having a diameter of 0.3 mm is placed in a 1.5 molar potassium hydroxide solution and a sharp tungsten tip is applied using an electrochemical etching method that applies voltages of 0 V and 30 V to the solution and the tungsten wire, respectively. Form. The radius of curvature of the tip of the tungsten tip formed in this way may be, for example, 250 nm.

 The solution 320 may be a colloidal solution including the catalyst 310 in the form of metal nanoparticles in one embodiment. The metal nanoparticles may have, for example, a diameter of about 5 nm to about 20 nm. In some other embodiments, the solution 320 may be, for example, an organic solvent or deionized water. The organic solvent may be, for example, isopropyl alcohol (IPA) or hexane (hexane). In another embodiment, the solution 320 may be an electrolyte solution including a catalyst in the form of metal ions.

When the tip 410 is contacted with the solution 320 and then spaced apart, a portion of the solution 320 including the catalyst 310 in the form of metal nanoparticles is transferred to a limited area of the tip 410 and subsequent drying process. When the transferred solution 320 is evaporated, the catalyst 310 in the form of metal nanoparticles dispersed in the transferred solution 320 is attached to the tip 410.

As shown in FIG. 4, the tip 410 is in contact with the exposed solution 320 through one of the pores 210, so that the solution 320 is the tip, unlike when directly contacting the solution 320. Only a limited area of the apex of 410 (eg, hundreds of nm squared) is contacted. In addition, in other embodiments not shown in the figures, the tip 410 may contact the exposed solution 320 through several of the pores 210, in which case the solution may be in contact with the tip of the tip 410. May contact a restricted area.

Thereafter, by drying the solution 320 attached to the tip 410, it is possible to obtain a tip 410 having the catalyst 310 in the form of metal nanoparticles attached only to a limited area of the tip of the tip.

FIG. 5 is a diagram for describing a process of transferring a catalyst from an exposed solution to a tip, shown in block 120 of FIG. 1, according to another embodiment. Referring to FIG. 5, the metal ionic catalyst 510 is attached to the tip 410 from the electrolyte solution 520 in which the metal ions catalyst 510 is dissolved using an electroplating method. It can be reduced to form the catalyst 530 in the form of a metal element. Attaching the metal ions catalyst 510 to the tip 410 and reducing may be performed simultaneously. The catalyst 510 in the form of metal ions may include at least one metal ion selected from the group consisting of nickel ions, cobalt ions, molybdenum ions, and iron ions.

More specifically, a level lower than the first voltage V1 and the first voltage in the electrolyte solution 520 and the tip 410, respectively, in at least a portion of the period during which the tip 410 is in contact with the electrolyte solution 520. Applies a second voltage V2. When the voltages are applied as described above, the catalyst 510 in the form of metal ions included in the electrolytic solution 520 is attached to the tip 410, and receives electrons from the tip 410, which is a conductive material, to form a metal element. Reduced to catalyst 530. When using the method of electroplating, it is possible to control the amount of catalyst 530 attached and reduced to the tip 410 by controlling the current and plating time.

Thereafter, by drying the solution 520 attached to the tip 410, it is possible to obtain the tip 410 with the catalyst 530 attached only to a limited area of the tip of the tip.

FIG. 6 is a view for explaining a process of transferring a catalyst from an exposed solution to a tip, shown in block 120 of FIG. 1, according to another embodiment. Referring to FIG. 6, first, the tip 410 is disposed spaced apart from the solution 620. The solution 620 may be an electrolyte solution including the catalyst 615 in the form of metal ions. The catalyst 615 in the form of metal ions may include at least one metal ion selected from the group consisting of nickel ions, cobalt ions, molybdenum ions, and iron ions.

As shown, a first voltage Va and a second voltage Vb are applied to the solution 620 and the tip 410, respectively. The second voltage Vb has a lower level than the first voltage Va. As such, when the voltages are applied, the catalyst 615 in the form of metal ions included in the solution 620 is released from the solution 620. The catalyst 615 in the form of released metal ions is attached to the tip 610 and receives electrons from the tip 410, which is a conductive material, and is reduced to the catalyst 630 in the form of a metal element. The required voltage difference between the first voltage Va and the second voltage Vb increases as the distance between the tip 410 and the solution 620 increases. For example, the tip 410 and the solution 620 may be spaced apart by 1 μm, and the first and second voltages Va and Vb may be applied to have a voltage difference of 5V. By controlling the time for applying the current and voltages Va and Vb, the amount of catalyst 630 attached and reduced to tip 410 may be controlled.

How to grow nanostructures on tips

7 is a flowchart illustrating a method of growing a nanostructure on a tip, according to one embodiment. Referring to FIG. 7, at 710, a catalyst is attached onto the tip. The method of attaching the catalyst on the tip according to this embodiment is substantially the same as the method of attaching the catalyst on the tip according to one embodiment of the present disclosure described above in connection with FIGS. 1 to 6. Therefore, detailed description of the method of attaching the catalyst on the tip is omitted to avoid duplication. In block 720, the catalyst particles are used to grow the nanostructures on the tip.

8 is a diagram for describing a process of growing a nanostructure on a tip using a catalyst, shown in block 720 of FIG. 7, according to an embodiment. Referring to FIG. 8, nanostructures 810 are grown from various types of catalysts 310, 530 or 630 attached to the tip of the tip 410 described above with reference to FIGS. 1 through 6. The nanostructure 810 may include, for example, carbon nanotubes, nanowires, or nanorods. Hereinafter, a method of forming carbon nanotubes is described as an embodiment of the nanostructure 810. For convenience, the carbon nanotubes will be shown by reference numeral 810.

According to one embodiment, the reaction gas 830 containing a hydrocarbon is introduced into the catalyst particles 310, 530 or 630 to form the carbon nanotubes 810 from the catalyst particles 310, 530 or 630. Hydrocarbons may include carbon monoxide, acetylene, ethylene, ethane, methane, propane or combinations thereof. The carbon nanotube 810 may be formed by, for example, a chemical vapor deposition method using heat, plasma, or microwave as an energy source.

The reaction gas 830 containing the hydrocarbon is decomposed by the heat, plasma, microwave, or the like as an example on the catalyst particles 310, 530, or 630. Carbon atoms separated from the hydrocarbons in the decomposed reaction gas 830 diffuse into the catalyst particles 310, 530 or 630, and the carbon atoms are filled in the catalyst particles 310, 530 or 630. Precipitation occurs when the carbon atoms are filled beyond the solid solubility of carbon in the catalyst particles 310, 530 or 630. The carbon atoms are extracted out of the catalyst particles 310, 530 or 630 by the precipitation reaction. In this case, the extracted carbon atoms may be rearranged at the interface with the catalyst particles 310, 530 or 630 to form the carbon nanotubes 810 on the tip 410. The catalyst particles 310, 530 or 630 may remain on the carbon nanotubes 810 even after the carbon nanotubes 810 are formed.

Nanostructures other than the carbon nanotubes 810 may be formed by a method similar to the method of forming the carbon nanotubes 810 described with reference to FIG. 8. In other words, a predetermined source gas corresponding to the nanostructure may be provided on the metal catalyst particles and decomposed. The nanostructures may be formed by a reaction between the decomposed source gas and the metal catalyst particles. In one embodiment, the silicon carbide nanorods may be formed by a chemical vapor deposition method using a vaporized C6H18Si2 gas as a source gas, and iron particles as the metal catalyst particles. In another embodiment, the silicon oxide nanowires may be formed by evaporation using vaporized SiO gas as the source gas and iron particles as the metal catalyst particles.

By growing the nanostructure 810 on the tip 410 in the above-described manner, it is possible to grow the nanostructure 810 only at the tip of the tip 410 of the limited region to which the catalysts 310, 530, and 630 are attached. have.

Although the above has been described above based on the embodiments of the disclosed technology, those skilled in the art will understand that various modifications and changes can be made without departing from the spirit and scope of the disclosed technology. As an example, the method of attaching a catalyst on the tip as shown in FIGS. 1 to 6 may also be applied when attaching a material other than the catalyst onto the tip. The other material may be, for example, an organic or nanostructure (eg nanoparticles).

1 is a flowchart illustrating a method of forming a catalyst on a tip, according to one embodiment.

 2 and 3 are diagrams for describing a process of exposing a solution including a catalyst through one or more pores, shown in block 110 of FIG. 1, according to an embodiment.

4 is a diagram for describing a process of transferring a catalyst from an exposed solution to a tip, illustrated in block 120 of FIG. 1, according to an embodiment.

FIG. 5 is a diagram for describing a process of transferring a catalyst from an exposed solution to a tip, shown in block 120 of FIG. 1, according to another embodiment.

FIG. 6 is a view for explaining a process of transferring a catalyst from an exposed solution to a tip, shown in block 120 of FIG. 1, according to another embodiment.

7 is a flowchart illustrating a method of growing a nanostructure on a tip, according to one embodiment.

8 is a diagram for describing a process of growing a nanostructure on a tip using a catalyst, shown in block 720 of FIG. 7, according to an embodiment.

Claims (21)

In a method of growing nanostructures on a tip, (a) exposing a solution comprising a catalyst for synthesizing the nanostructure through a pore; (b) transferring the catalyst from the exposed solution to the tip; And (c) growing the nanostructures on the tip using a transferred catalyst How to include. According to claim 1, The step (a) is (a1) providing a thin film in which the pores are formed; And (a2) floating the thin film on the solution; The inner surface of the pores is hydrophilic and the upper surface of the thin film, the upper surface being the tip direction of both sides of the thin film, is hydrophobic According to claim 1, The step (b) (b1) attaching the solution to the tip by contacting the tip with the exposed solution; And (b2) drying the tip to which the solution is attached, thereby obtaining a tip to which the catalyst is attached. According to claim 1, The step (b) (b1) contacting the tip with an exposed solution, the solution being an electrolyte solution, and attaching a catalyst included in the solution, the catalyst being a metal catalyst, to the tip by electroplating; And (b2) drying the tip to which the solution is attached, thereby obtaining a tip to which the catalyst is attached. According to claim 1, The step (b) (b1) disposing the tip spaced apart from the solution, wherein the solution is an electrolyte solution; And (b2) applying a first voltage and a second voltage, wherein the second voltage has a lower level than the first voltage, to the solution and the tip, respectively, so that the catalyst in the form of metal ions included in the solution And are attached to the tip and reduced with a catalyst in the form of a metal element. The method according to any one of claims 1 to 5, The nanostructures comprise carbon nanotubes. The method of claim 6, In performing the process (c), the carbon nanotubes are grown from the catalyst by providing a gas containing a hydrocarbon to the tip. The method according to any one of claims 1 to 5, The catalyst comprises at least one selected from the group consisting of nickel, cobalt, molybdenum and iron. The method according to any one of claims 1 to 5, The tip comprises at least one selected from the group consisting of tungsten, nickel, aluminum, molybdenum, tantalum and niobium. The method according to any one of claims 1 to 5, Wherein the pores are provided with nanopores. In a method of attaching a substance on a tip, (a) exposing a solution comprising the substance through pores; And (b) transferring the material from the exposed solution to the tip How to include. The method of claim 11, wherein The step (a) is (a1) providing a thin film in which the pores are formed; And (a2) floating the thin film on the solution. The method of claim 12, Wherein the inner surface of the pores is hydrophilic and the upper surface of the thin film, the upper surface being the tip direction of both sides of the thin film, is hydrophobic. The method of claim 12, And the hydrophobic film formed on a hydrophilic anodic aluminum oxide (AOA) and an upper surface of the AAO, wherein the upper surface is a surface in the tip direction of both sides of the AAO. The method of claim 14, Wherein said hydrophobic membrane comprises fluorocarbon. The method of claim 11, wherein The step (b) (b1) attaching the solution to the tip by contacting the tip with the exposed solution; And (b2) drying the tip to which the solution is attached, thereby obtaining a tip to which the substance is attached. The method of claim 16, The material is a metal in the form of nanoparticles, and the solution is a colloidal solution in which the material is dispersed. The method of claim 16, The metal ion contained in the solution by applying a voltage lower than the voltage applied to the solution to the tip in at least a portion of the period of time during which the tip is exposed, the solution being an electrolyte solution. The material in form is attached to the tip and reduced to the material in metal element form. The method of claim 11, wherein The step (b) (b1) disposing the tip spaced apart from the solution, the solution being an electrolyte solution; And (b2) applying a first voltage and a second voltage to the solution and the tip, respectively, wherein the second voltage has a lower level than the first voltage, such that the material in the form of metal ions included in the solution is And is released from solution and attached to the tip to reduce the material to a metal element form. The method according to any one of claims 11 to 19, Wherein the pores are provided with nanopores. The method according to any one of claims 11 to 19, The material comprises a catalyst for synthesizing a nanostructure.

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