WO2008084951A1

WO2008084951A1 - Method for coating carbon nanotube and products thereof

Info

Publication number: WO2008084951A1
Application number: PCT/KR2008/000092
Authority: WO
Inventors: Seung Hun Huh; Doh Hyung Riu
Original assignee: Seung Hun Huh; Doh Hyung Riu
Priority date: 2007-01-08
Filing date: 2008-01-08
Publication date: 2008-07-17
Also published as: WO2008084951B1

Abstract

Disclosed herein are a method for coating carbon nanotubes on a substrate and products manufactured thereby. The method comprises spraying a carbon nanotube-containing material on a substrate at a speed of at least 30 m/sec to form a carbon nanotube-containing film on the substrate. According to the method, it is possible to easily obtain films that have strong chemical bonds between a substrate and CNT particles, contain no separate binder resin, have a high dangling bond density higher than that of a tubular material used as a raw material, leading to high conductivity, by allowing CNT fragments, open at one end, to grow vertically or horizontally relative to the substrate, and are useful in field emission devices. Also, novel films having excellent properties, such as durability, conductivity and plasma corrosion resistance, can be manufactured by depositing CNTs in combination with metallic, ceramic and/or semiconductor materials.

Description

[DESCRIPTION]

[invention Title]

METHOD FOR COATING CARBON NANOTUBE AND PRODUCTS THEREOF

[Technical Field]

The present invention relates to a method for forming a carbon nanotube-containing film on a substrate and products thereof, and more particularly to a method of forming a carbon nanotube-containing film using an aerosol deposition process and a carbon nanotube-containing deposited film formed thereby, which has novel physical properties.

[Background Art] Methods of coating carbon nanotubes (hereinafter, referred to as "CNTs") on a substrate are largely classified into four categories. The first method is chemical vapor deposition (CVD) , in which a catalyst is deposited on a substrate, and then a hydrocarbon precursor is broken down while CNTs grow on the catalyst portion. Most of the CNTs grow at the catalyst portion in a direction vertical to the substrate. Such CNT films are frequently used as field emission devices (FEDs) . However, there are problems in that the vertically grown CNTs tend to fall down, and in that the temperature of the substrate must be kept high.

The second method comprises dispersing CNTs in a polymer, and then coating the dispersion on a substrate. This method is very inexpensive, and thus is currently used by many companies. However, this method is difficult to use commercially due to problems associated with the worsening of the physical properties of the CNTs dispersed in the polymer and with the durability and contamination of the polymer itself.

The third method comprises chemically treating CNTs to make a highly dispersed CNT solution, adding thereto various additives, such as polymers, to make ink, and printing the ink on a substrate. This method is highly advantageous for CNT interconnects, but fails to obtain the inherent physical properties of CNTs due to problems associated with weak bonds (Van der Waals bonds) between the substrate and the CNTs and with a binder.

The fourth method is a method in which a CNT-dispersed solution such as that described in the third method is sprayed on a substrate using an air brush under atmospheric pressure, thus forming a film. Like the third method, the fourth method has problems associated with weak bonds between the substrate and the CNTs and with a binder.

Accordingly, there is an urgent need to develop a method of forming a CNT film, having direct chemical bonds between the substrate and CNTs and between CNT and CNT, most preferably without using any binder. [Disclosure] [Technical Problem]

The present invention has been made in order to solve the above-described problems occurring in the prior art, and it is an object of the present invention to provide a method of forming a tubular material-containing film, which has novel physical properties and can be used directly in the electronic material field, the method comprising forming direct bonds between a substrate and the tubular material at room temperature using an inexpensive process without using any polymer binder.

Another object of the present invention is to provide a tubular material-containing deposited film, which has a direct bond between a substrate and a tubular material, and has a dangling bond density higher than that of the tubular material used as a raw material, and thus is useful in field emission devices.

Still another object of the present invention is to provide a tubular material-containing deposited film that has high dangling bond density, and thus does not require a separate mechanical cutting or chemical opening process.

[Technical Solution]

To achieve the above objects, the present invention provides a method of forming a carbon nanotube-containing film on a substrate, the method comprising spraying a carbon nanotube-containing material on the substrate at a speed of at least 10 m/sec.

The above method according to the present invention may also comprise forming on the upper surface of the substrate a mask having a given pattern, and forming said film according to the mask pattern. Alternatively, the inventive method may also comprise forming a resist pattern on the surface of the substrate through photolithography, and patterning said film into a given shape. In another aspect, the present invention provides a method for coating a carbon nanotube film, the method comprising the steps of: aerosolizing a carbon nanotube- containing material; and spraying the aerosolized material on a substrate at a speed of at least 30 m/sec to form a film on the substrate.

In the above method according to the present invention, the carbon nanotube-containing material may further comprise at least one material selected from tubular material, nanoparticle material, nanowire material, nanorod material, nanobelt material and powdery material. Also, the carbon nanotube-containing material may be impurity-doped carbon nanotube material.

In the present invention, the spraying step is preferably carried out using a nozzle, and the space around the outlet of the nozzle is preferably maintained at a pressure of less than 100 torr. In the present invention, the carbon nanotube- containing material may be a material having a chemically modified surface or a material ground through a grinding step.

In the present invention, the aerosolizing step can be carried by introducing carrier gas.

In still another aspect, the present invention provides a carbon nanotube-containing coating film, which: (a) contains no separate binder resin; and (b) contains a large number of carbon nanotube fragments, which are hollow and open at least at one end.

In the present invention, the film may contain, in addition to the carbon nanotubes, at least one other component .

In the present invention, said other component may be at least one material selected from tubular material, nanoparticle material, nanowire material, nanorod material, nanobelt material and powdery material.

In still another aspect, the present invention provides a method for forming a carbon nanotube-containing film on a substrate, the method comprising the steps of: supplying external carrier gas into the space in which a carbon nanotube-containing material is located, to aerosolize the material; and spraying the aerosolized material into the space in which a substrate is located, in a vacuum to form a film on the substrate, wherein the film-forming step comprises intermittently opening and closing the substrate- containing space and the material-containing space so as to increase the strength of the vacuum in the substrate- containing space, thus increasing the collision speed of the aerosolized material.

[Advantageous Effects]

According to the present invention, it is possible to easily obtain films, which have strong chemical bonds between a substrate and CNT particles by aerosolizing CNTs and allowing the CNT aerosol to collide with the substrate at high speed, contain no separate binder resin, have a high dangling bond density higher than that of the tubular material used as a raw material, leading to high conductivity, by allowing CNT fragments, open at one end, to grow vertically or horizontally to the substrate, and are useful in field emission devices. Also, novel films having excellent properties, such as durability, conductivity and plasma corrosion resistance, can be manufactured by depositing CNTs in combination with metallic, ceramic and/or semiconductor materials. In addition, the films of the present invention can be formed into a given pattern and can be used as interconnects due to their high conductivity.

[Description of Drawings] FIG. 1 is a schematic diagram showing a continuous flow manufacturing (CFM) system according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a pulse flow manufacturing (PFM) system according to an embodiment of the present invention. FIG. 3 is a schematic diagram showing a pulse flow manufacturing (PFM) system according to another embodiment of the present invention.

FIG. 4 is a schematic diagram showing a pulse flow manufacturing (PFM) system according to still another embodiment of the present invention.

FIG. 5 is a scanning electron microscope (SEM) photograph of the surface of a silicon substrate, obtained after carbon nanotubes were deposited on the silicon substrate using the system of FIG. 1 according to the present invention.

FIG. 6 is a scanning electron microscope (SEM) photograph of the surface of a silicon substrate, observed after carbon nanotubes were deposited on silicon substrate using the system of FIG. 2 according to the present invention. FIG. 7 is a scanning electron microscope (SEM) photograph of the surface of a silicon substrate, observed after a mixture of yttria (Y₂O₃) powder with carbon nanotubes was deposited on a substrate using the system of FIG. 2 according to the present invention. FIG. 9 is a scanning electron microscope (SEM) photograph of the surface of a silicon substrate, observed after a mixture of copper (Cu) powder with carbon nanotubes was deposited on a substrate using a pulse method according to the present invention.

FIG. 9 is a scanning electron microscope (SEM) photograph of the surface of a silicon substrate, observed after carbon nanotubes were deposited on a substrate using the system of FIG. 2 according to the present invention.

FIG. 10 shows the results of measurement of field emission properties for the carbon nanotube-deposited film of FIG. 9. The photograph in FlG. 10 shows that the carbon nanotube film having RGB fluorescent materials formed thereon emits white light during field emission.

FIG. 11 shows the results of field emission properties of a deposited film, formed from a mixture of ITO (indium tin oxide) powder and carbon nanotubes using the system of FIG. 4.

FIG. 12 is a scanning electron microscope (SEM) photograph of a interconnect pattern, obtained by previously breaking carbon nanotubes into fragments, depositing the fragments on a silicon substrate, having a patterned photoresist thereon, using the system of FIG. 2, and dissolving the resist with a solvent to remove the resist.

FIG. 13 shows a voltage-current curve measured using an atomic force microscope (AFM) , having two tips, for the micrometer-sized interconnect obtained in connection with FIG. 10. description of important reference numerals in the figures> 10, 100 and 1000: material supply units; 20, 200 and 2000: deposition units;

1, 91 and 991: raw material powder;

2, 92 and 992: porous filter membranes; 3, 93 and 993: carrier gases;

4, 94 and 994: gas transport pipes;

5, 95 and 995: first opening/closing means;

5', 95' and 995': second opening/closing means;

6, 96 and 996: aerosol particulates; 7, 97 and 997: aerosol supply pipes;

8, 98 and 998: nozzles; 9: joining means; 11: chamber; 80: blowing means; 90: flow control means; 15, 915 and 1915: substrate holder; 16, 916 and 1916: substrates;

17, 917 and 1917: substrate-moving means; and

18, 918 and 1918: gas vent ports.

[Best Mode] As used herein, the term "tubular material" means a hollow elongated tube-shaped structure, the diameter of which ranges from the nanometer scale to the micrometer scale, and which is not specifically limited.

In the present invention, the tubular material may be doped with a small amount of an impurity according to any conventional method, in which an example of the impurity may be boron or phosphorus, but the scope of the present invention is not limited thereto.

Also, the carbon nanotube film of the present invention may comprise, in addition to carbon nanotubes, at least one component which is deposited, coated or blended with the carbon nanotubes.

In the present invention, a tubular material such as

CNT material is made to collide with a substrate in the vapor phase at a rate of more than about 30 m/sec, so as to form direct chemical bonds between CNTs and the substrate and between CNTs. Thus, according to the present invention, a novel CNT film different from those formed through the prior methods can be obtained. The formation of particle-particle bonds in metal nanoparticles by physical collision is explained well in Huh et. al., Appl. Phys. Lett. 91, 093118,

2007.

In the present invention, the CNT-substrate adhesion can be explained by a principle similar thereto. That is, if a CNT having kinetic energy higher than a critical value collides with a substrate, the kinetic energy locally changes to strong thermal energy, which is sufficient to induce chemical bonds between the substrate and the CNT. The case where another CNT is deposited on the deposited CNT can also be explained by a similar principle. However, when observed in detail, this collision mechanism completely differs from the collision mechanism of metal nanoparticles. That is, CNTs have no crystal plane, unlike nanoparticles, and have a hollow elongated hollow structure. If CNT collides with a substrate at high energy, the CNT is readily broken lengthwise due to excessive collision energy, such that it is divided into several fragments. At the broken CNT portions, the dangling bonds of carbon atoms are created, and such dangling bonds allow new chemical bonds between the broken CNTs and between the substrate and the CNT to be readily created. However, unlike the case of general spherical powders, CNTs are difficult to form into a thick film. This is because even if CNTs are broken, they are hollow and have bent portions, and thus the uniformity of the CNT film decreases as the CNTs are deposited on the CNT film. In the process in which CNTs bond to the substrate, most of the CNTs are arranged in the direction parallel to the substrate, but some CNT fragments are driven into the film, and are thus arranged in the direction vertical to the substrate. The deposition time is preferably about 10-20 minutes when the particle collision speed is between 10² m/s and 10" m/s. The particle collision speed is preferably at least 30 m/s, and more preferably 10² m/s to 10³ m/s in terms of coating adhesion and deposition rate. If the particle collision rate is higher than 10³ m/s, carbon nanotubes will be completely broken, or carbon nanotubes, which have already been bonded to the substrate, can be damaged or desorbed. The particle collision speed is determined by pump capacity and nozzle design, and the pump capacity and nozzle design suitable for obtaining the desired particle collision speed can be easily determined by any person having ordinary knowledge in the art . In the present invention, a carbon nanotube film consisting of a plurality of layers, for example, 1-5 layers, can be formed. Also, when a powdery material, such as metal powder or ceramic powder, and carbon nanotube, are deposited at the same time, a film having a thickness of more than 1 mm can be formed at a deposition rate of a few um/min. This is because the powdery material is advantageous for the bonding between crystal planes upon collision, compared to the tubular material. In this state, carbon nanotubes enter spaces between powder grains. Thus, if the material that is deposited in a mixture with the carbon nanotube material is transparent conductive oxide powder, such as ITO (indium tin oxide) , FTO (F-doped tin oxide) or ZnO, it can impart various new physical properties, such as improved durability and increased conductivity, to a film, while it can maintain film transparency.

Also, if ceramic powder having good abrasion resistance, such as Y₂O₃, is aerosolized in a mixture with carbon nanotubes, the insulating powder can be imparted with conductivity. Also, if nanowires, such as ZnO, are deposited in a mixture with carbon nanotubes, the conductivity of a ZnO film can be increased, and it is possible to manufacture a film having increased durability when it is used as a field emission device.

Moreover, if a mixture of carbon nanotubes with powdery materials is used in a film manufacturing process, a film having sufficient adhesion and deposition rate can be manufactured even when the collision speed is between 30 m/s and 50 m/s.

In the present invention, a good deposited film can be obtained regardless of the kind of substrate, because carbon nanotubes are deposited on the substrate using strong collision energy. That is, in the present invention, it is possible to use all kinds of substrates, including a plastic substrate, a metal substrate, a ceramic substrate and an Si substrate.

This indicates that, in the present invention, a carbon nanotube film is formed through a mechanism completely different from the prior methods for manufacturing carbon nanotube films. The carbon nanotube film produced in the present invention differs structurally from the carbon nanotubes that are used as raw materials for forming the film. In general, carbon nanotubes are closed at the ends thereof, and to order to open the ends of the carbon nanotubes, a separate post-treatment process, such as mechanical chemical treatment or thermal treatment, must be carried out. However, in the present invention, even when carbon nanotubes closed at the ends are used, at least one end of the carbon nanotubes in the deposited film is opened. When carbon nanotubes in the film produced according to the present invention are observed with high-resolution TEM, some of the carbon nanotubes are seen to be completely broken, and thus are present in the form of fragments rather than tubes . This is thought to be because carbon nanotubes are broken upon collision in the present invention and, at the same time, form a film. Also, in the carbon nanotube film according to the present invention, the carbon nanotubes are generally arranged in a direction parallel to the substrate, but some of the carbon nanotubes are arranged in a direction vertical to the substrate. The carbon nanotube film according to the present invention has strong chemical bonds between the substrate and CNTs and between CNT and CNT. Thus, the carbon nanotube film having such a structure shows high field emission, which was impossible in the prior carbon nanotube film, and in addition, it has a very small number of pores therein, that is, has high density. This CNT film could not be provided using the prior CVD and printing methods .

In the formation of aerosol particles for use in the deposition method of the present invention, at least one other component, in addition to the tubular material, may, if necessary, be used to form aerosol particles. Examples of the other component may include, but are not limited to, metals, TCO (ITO, FTO (F-doped tin oxide), etc.), oxide-based superconductive materials, lead titanate zirconate, barium titanate, ferrites, alumina, titania, zirconia, silica, MgB₂, CeF₂, CoO, NiO, MgO, silicon nitride, aluminum nitride, silicon carbide, apatite minerals, semiconductor materials, such as C, Si, Ge, GaN, GaAs, GaP, InP, InAs, ZnS, CdS, CdSe, ZnO, MgO, SiO₂, CdO, SiC, B₄C, Si₃N₄ and In₂O₃, and other ceramic and insulating materials.

Also, when polymer-based powder is dispersed and deposited together with CNTs, a polymer-CNT composite film can be formed.

Such materials may be powdery or linear, and when they are nanosized materials, they include nanoparticles, nanowires, nanorods, nanobelts, nanotubes and the like. In the present invention, in the process of accelerating the tubular material at high speed to form a film, reactive gas may be introduced in the deposition process in order to chemically change doped metal or other components or to reduce defects in the tubular material. In other words, carrier gas for aerosolization is conventionally used in a deposition process, but in the present invention, carrier gas can be replaced with reactive gas that enables a chemical reaction to occur, or such reactive gas can be used together with carrier gas . In the present invention, the aerosolized tubular material collides with the substrate at high speed, and thus is open at least at one end. In the present invention, separate energy for cutting the carbon nanotubes is not required, because the carbon nanotubes are cut during the process of forming the film by the collision of the carbon nanotubes. Thus, a thick and uniform deposited film consisting of small CNT fragments can be formed.

As described below, a process of physically modifying carbon nanotube raw material in advance so as to be used as interconnects, etc., may be carried out in the present invention.

Herein, the physical modification may be, for example, a method of breaking both ends of the carbon nanotube raw material to make an open structure, and may also include a process of cutting the carbon nanotubes through ball milling. If necessary, the tubular material can also be chemically pretreated to modify the surface thereof. Examples of chemical pretreatment may include a method of modifying the surface of the tubular material through acid treatment . This physical or chemical pretreatment of the tubular material can be carried out according to any known method.

FIG. 1 is a schematic diagram showing a continuous flow manufacturing (CFM) system according to an embodiment of the present invention. In order for the tubular material to be aerosolized and made to collide with a substrate at high speed as described above, the system comprises two chambers, that is, an aerosol chamber 1 and a deposition chamber 12.

In the aerosol chamber 1, a carbon nanotube material is introduced through the bottom of the aerosol chamber 1. External carrier gas 3 is metered into the aerosol chamber through a flow control unit 4. The carrier gas is sprayed on the carbon nanotube material through a connecting tube 5. Due to the gas spraying, the carbon nanotube particles are dispersed in the vapor phase to form carbon nanotube aerosol 9. The produced carbon nanotube aerosol passes through an aerosol transport pipe 10 and is sprayed into the deposition chamber 12 at high speed through a nozzle 11 at the top of the pipe 10. The carbon nanotube aerosol, sprayed at high speed, collides with a silicon substrate 14 and is deposited on the substrate. The silicon substrate is fixed to a substrate holder 15, which can adjust the distance between the substrate and the nozzle through a holder height- adjusting unit 16. Gases in the chamber are continuously vented through a vent unit 17. The acceleration of the carbon nanotube aerosol increases with the increase in gas vent rate (pumping rate) through the vent unit, and is maximized at the time point at which the aerosol is discharged from the nozzle. Meanwhile, the substrate can be designed such that it is moveable along the x-, y- and z-axis using a piezoelectric material or a driving device such as a motor. Alternatively, the driving device may also be connected with the nozzle unit, such that the nozzle unit can be movably operated.

In the present invention, if necessary, a mask having a given pattern may be placed on the upper surface of the substrate, such that a film having the desired pattern can be formed on the surface of the substrate.

Moreover, a process of coating the carbon nanotube on a substrate, having a photoresist pattern formed on the surface thereof by photolithography, and then etching the photoresist film according to a conventional lift-off method, can also be carried out.

The carbon nanotube-containing film, formed according to a series of such methods, satisfies conditions where: (a) it does not comprise separate binder resin; and (b) it comprises carbon nanotubes, which are hollow and open at least at one end.

In the present invention, the bonding ability between CNTs and the substrate is the best, particularly when the carbon nanotubes are deposited in 1-5 layers (on the basis of horizontally deposited carbon nanotubes) . That is, the number of deposited layers is preferably 1-5, and if the number of the deposited layers is excessively high, the bonding ability between the carbon nanotubes will decrease, and thus the deposited carbon nanotubes will be readily detached. However, as described below, thin CNT films obtained in the present invention can be used in many industrial applications, such as field emission devices. [Mode for Invention]

FIG. 2 is a schematic diagram showing a pulse flow manufacturing (PFM) system according to another embodiment of the present invention. The system of FIG. 1 performs deposition using a continuous high-speed gas/CNT beam, whereas the system of FIG. 2 performs the deposition of CNTs using an intermittent pulse beam. To obtain the intermittent pulse beam, a method of intermittently blocking the supply of external carrier gas, or a method of intermittently blocking the spray of a sample dispersed in the vapor phase, can be carried out. Alternatively, these two methods may also be simultaneously or sequentially applied.

Referring to FIG. 2, the system comprises a material supply unit 10 and a deposition chamber 20. The material supply unit 10 comprises a gas transport pipe 4 for introducing external carrier gas (including a simple carrier gas or reactive gas) , and an aerosol chamber for dispersing raw material powder 1 to make gaseous particulates 6, and transporting the particulates 6 through a transport pipe 7.

As shown in FIG. 2, the material supply unit 10 and the deposition chamber can be joined with each other by a separate joining means 9.

In the system of FIG. 2, the material supply unit 10 includes the joining means for joining it with the deposition chamber, and the aerosol chamber 11 contains the raw material powder 1 and includes a porous filter membrane 2 in the upper space thereof. To introduce the carrier gas 3 into the chamber 11, the gas transport pipe 4 is provided with a separate opening/closing means (first opening/closing means 5) , and the gaseous sample transport pipe 7 is also provided with a separate opening/closing means (second opening/closing means 5' ) . Thus, the carrier gas can be introduced in the form of a pulse, so that the dispersed gaseous material can be produced in the form of a pulse, or the aerosol particulates can collide with the substrate 16 in the form of a pulse.

In other words, the carrier gas 3 passes through the first opening/closing means 5 and enters the aerosol chamber 11 in the form of a pulse through the gas transport pipe 4. At this time, the gas introduced in the pulse is instantaneously blown toward the opposite side thereof to aerosolize the raw material powder 1. At this time, nondispersed masses are filtered through the porous filter membrane 2, and only the fine aerosol material particles pass through the porous filter membrane 2, are discharged through the aerosol transport pipe 7, and are finally accelerated into the deposition unit 200 through the nozzle 8 at the top of the aerosol transport pipe 7. That is, the aerosol particulates, supplied through the aerosol transport pipe 7, are accelerated and deposited on the substrate 16 fixed to the substrate holder 5. The substrate holder can be provided such that it is movable upward and downward by a substrate- moving unit 17.

The aerosol transport pipe 7 may be provided with the second opening/closing means. In the present invention, the first and second opening/closing means can cooperatively operate. For example, after the carrier gas is introduced by opening the first opening/closing means, the first opening/closing means is closed, and the second opening/closing means is opened, such that the aerosolized material can be introduced into the deposition chamber through the transport pipe 7. However, in the present invention, while the first opening/closing means is opened, the second opening/closing means may also be opened, such that the raw material can be introduced into the deposition chamber. In an alternative embodiment of the present invention, only the second opening/closing means is provided in the system, without the first opening/closing means, such that the raw material can be introduced in the form of a pulse by the operation of the second opening/closing means. The introduced gas is vented through gas vent ports 18. Outside the material supply unit 10, a separate sample container (not shown) may also be provided, such that, when the raw material in the material supply unit 10 is insufficient, the sample can be continuously or discontinuously supplied in the material supply unit.

In the conventional deposition process, a vacuum pump is provided in the deposition unit, but the vacuum pump is not shown in FIGS. 2 to 4.

In the present invention, as described above, a piezoelectric material may be added to the substrate, such that the substrate is precisely movable along the x-, y- and z-axes.

FIG. 3 shows a system according to another embodiment of the present invention, which comprises the material supply unit 100 and the deposition chamber 200, like the system shown in FIG. 2. However, the material supply unit 100 and the deposition chamber 200 do not comprise a separate joining means, and are connected with each other through a pipe 97 for transporting the dispersed gaseous material.

In this system, the structure of the deposition chamber 200 is almost identical to the deposition chamber 20 shown in FIG. 2.

In the material supply unit 100, external carrier gas 93 is introduced through a gas transport pipe 94. The flow rate of the supplied gas is adjusted by a flow control unit 90. In the material supply unit 100, raw material powder 91 is contained, and this raw material powder 91 disperses in the vapor phase by a blowing means 80 provided in the material supply unit 100. The dispersed gaseous powder passes through a porous filter membrane 92, and only finely dispersed particles 96 exist in the upper layer portion of the material supply unit. If an opening/closing means 95' provided in the material transport pipe 97 is not opened, the concentration of the dispersed gaseous particles 96 becomes constant after a given amount of time. Herein, the dispersed gaseous particles having uniform concentration are accelerated into the deposition chamber 200 in the form of a pulse through the material transport pipe and a nozzle 98 due to a pressure differential that exists when an opening/closing means 95' provided in the material transport pipe 97 is opened. Likewise in this case, a material container (not shown) may also be provided outside the material supply unit 100, such that, when the material in the material supply unit 100 is insufficient, the material can be continuously or discontinuously supplied into the material supply unit 100. FIG. 4 shows a system according to another embodiment of the present invention. As in the case of FIG. 3, the system comprises a material supply unit 1000 and a deposition chamber 2000, which are connected with each other through an aerosol transport pipe 997. The material supply unit 1000 contains raw material powder 991, and external carrier gas 993 enters the material supply unit 1000. At the same time, the carrier gas 993 enters the material supply unit 1000, preferably in the form of a pulse, as a result of the opening and closing of a first opening/closing means 995 provided in a gas transport pipe 994. The introduced pulse-type carrier gas is sprayed through the gas transport pipe 993. Preferably, the carrier gas is sprayed away from the gas transport pipe 993, such that it can reach the location of the raw material powder 991, so that it can be sprayed directly on the raw material powder 991 to disperse the raw material 991 in the vapor phase. The gaseous material powders pass through a porous filter membrane 992, and only fine particulates are moved to the upper layer portion of the material supply unit, and then are introduced into the deposition chamber 2000 in the form of a pulse through the material transport pipe 997 and a nozzle 998 due to pressure differential. Herein, the material transport pipe may be provided with a separate opening/closing means (second opening/closing means 995' ) . The pressure of the material supply unit 1000 is controlled by a separate flow control valve (not shown) . Also, a material container may be provided outside the material supply unit, such that, when the material in the material supply unit is insufficient, the material can be continuously or discontinuously supplied into the material supply unit. FIG. 5 is a scanning electron microscope (SEM) photograph of the surface of a substrate, on which a CNT film has been formed using the experimental system of FIG. 1 through the aerosol deposition method.

Herein, the spray speed of the CNT aerosol was about 100-500 m/s, and the time taken for deposition was 5-10 minutes. As the substrate, a silicon substrate having a thickness of 0.5 mm was used. The pressure in the aerosol chamber was 500-700 torr, and the pressure in the deposition chamber was 5-10 torr.

FIG. 6 is a SEM photograph showing CNT fragments adhered to a substrate. The original length of the CNTs ranged from a few micrometers to a few tens of micrometers, whereas the photograph clearly shows that the CNTs were broken into fragments. Most of the CNT fragments were arranged parallel to the substrate, but some of the CNT fragments were arranged vertical to the substrate. Also, it can be seen that the formed CNT film consists of 1-5 layers and has a very high density.

FIG. 7 is a scanning electron microscope photograph of a substrate surface having formed thereon a CNT film, formed by mixing Y₂O₃ powder with CNTs and forming the CNT film from the mixture using the system of FIG. 1 in the same conditions as in FIG. 5. As can be seen in FIG. 7, CNTs were fixed well between Y₂O3 powder grains .

FIG. 8 is a scanning electron microscope photograph of a substrate surface having formed thereon a CNT film, formed by mixing Cu powder with CNTs and forming the CNT film from the mixture using the system of FIG. 1 in the same conditions as in FIG. 7. As can be seen in FIG. 8, the mixture of CNTs and Cu powder was deposited on the substrate. FIG. 9 is a SEM photograph of a CNT film manufactured using the system of FIG. 2. As can be seen in FIG. 9, the film was very uniform and compact. In this experiment, the speed of the CNT aerosol was about 100-500 m/s, and the time taken for deposition was 5-10 minutes. As the substrate, a 0.5-mm-thick glass substrate having ITO coated thereon was used, the pressure of gas introduced was 3-4 atm, and the pressure in the deposition chamber was about 5-20 Torr. The pulse period was 5 sec (rest period: 4 sec, and deposition period: 1 sec) , and the deposit ion chamber was maintained in a vacuum state. FIG. 10 shows the results of a field emission test on the CNT film manufactured in FlG. 9. As can be seen in FIG. 10, the field emission was started at about 2 V/urn, and the CNT film showed a very high field emission current density of 3 mA/cm² at 4 V/μm. This is an excellent field emission property, because a film having a field emission current density of 0.1 mA/cm² is known to be applicable to field emission devices. This indicates that the CNT film manufactured in the present invention is very superior to the prior film with respect to field emission properties. As the substrate, an ITO substrate having a sheet resistance of 5 Ω/D was used.

The photograph in FIG. 10 shows that, when RGB (Red, Green and Blue) fluorescent materials and electrodes were sequentially formed on the CNT film deposited on the ITO substrate, field emission electrons were released, and the fluorescent materials emitted light due to the released electrons. As can be seen in the photograph, a white light source could be obtained, and the CNT film manufactured in the present invention can be used in a backlight unit. Any person skilled in the art will appreciate that the CNT film manufactured in the present invention may also be used in FED displays by embodying RGB fluorescent materials into separate pixels using this principle.

FIG. 11 shows the results of a field emission test on a CNT film formed by mixing ITO powder (size: about 1 μm) with CNT powder at a weight of 10:1 and then depositing the mixture on a substrate using the system of FIG. 3. As can be seen in FIG. 11, the field emission was started at about 2 V/μm, and the CNT film showed a very high field emission current density of about 0.3 mA/cm² at 4 V/μm. This current value was reduced compared to that of a pure CNT film, but CNTs were stably fixed between the ITO powder grains . In this experiment, the pressure in the aerosol chamber was about 1.5 atm, and the pressure in the deposition chamber was about 5-15 Torr. The pulse period was 5 sec (rest period: 4 sec, and deposition period: 1 sec) , and the deposition chamber was maintained in a vacuum state.

These results suggest that the inventive method of forming a film using a tubular material is also useful for the formation of various films, including ceramic-CNT composite films, metal-CNT film, semiconductor-CNT films, and insulator-CNT composite films. Particularly, the above examples show that the inventive CNT film can be deposited together with ITO powder, and thus can be used as a transparent conductive film.

FIG. 12 is a SEM photograph showing t.hat CNTs were deposited on a substrate, having a resist pattern formed by photolithography, and that CNTs interconnects were formed from the deposited film using a lift-off method. The liftoff method is a method in which a resist and CNTs deposited on the resist are removed using a suitable solvent (acetone herein) , such that only CNTs deposited in polymer trenches remain. FIG. 12 (a) shows the case where the polymer trench linewidth is 2 um, FIG. 12 (b) shows the case where the trench linewidth is 300 nm, and FIG. 12 (c) shows the case where the trench linewidth is 200 nm. Herein, the deposition process was carried out using the pulse method of FIG. 2. As can be seen in FIG. 12, a CNT pattern having a linewidth of less than 100 nm could be manufactured (FIG. 12 (c) ) . The CNT interconnects remained adhered to the substrate even in a liquid ultrasonic cleaning process following the lift-off process, and in a solvent removal process based on jet blowing. This suggests that strong chemical bonds between CNTs and the substrate and between CNT and CNT were formed despite the lack of adhesive agent. Such strong chemical bonds are physical properties that could not be expected in the prior CNT films (obtained using CVD, polymer dispersion, and ink brushing methods, etc.). In order to manufacture such fine CNT interconnects, a CNT breaking process, such as ball milling, can be used. The reasons therefor are broadly classified into two categories. The first reason is that, as shown in FIGS. 5 and 6, CNTs are broken if the high-speed CNT beam collides with the substrate. If CNTs are previously broken, the energy required for cutting the CNTs can be reduced, and thus a good quality film can be formed in an easier manner. The second reason is that long CNTs are difficult to introduce into the trenches of the photoresist pattern, particularly when ultrafine CNT interconnects, for example, CNT interconnects having a linewidth of 200 nm, are manufactured. Thus, in order to obtain good-quality interconnects, CNTs smaller than the trench linewidth should be used, or CNTs cut into short lengths should be used. In order to obtain such patterned interconnects, another method similar to the method described in connection with FIG. 12 can also be used, in which the deposition of CNTs is carried out using a mask patterned according to a given interconnect pattern. FTG. 13 shows the results of T-V measurement conducted using an AFM tip for the CNT interconnect (FIG. lla) having a linewidth on the micrometer scale, manufactured as shown in FIG. 10. The CNT interconnect showed electrical conductivity of about 10^~2 Ω/cm. This value is a markedly improved property in view of the fact that the prior polymer-dispersed CNT film shows an electrical conductivity of 100 Ω/cm. Also, this value is a property value, which cannot be obtained in any CNT interconnect known in the prior art.

Such good field emission properties and electrical conductivity are because direct chemical bonds between the substrate and CNTs and between CNT and CNT were formed without an organic material or binder. Such properties cannot be shown in a CNT network structure, in which CNTs are simply physically contacted with each other.

When CNTs are deposited in a mixture with nanoparticles, a CNT-nanoparticle composite film has many defects. Thus, the quality of the deposited film can be improved by applying energy (energy, electron beam energy, microwave, etc.), that is, through light annealing.

If necessary, the tubular material may also be chemically pretreated to modify the surface thereof. Methods for carrying out the chemical pretreatment may include a method of modifying the surface of the tubular material through acid treatment, etc.

This physical or chemical pretreatment of the tubular material can be carried out according to any known method.

In short, according to the present invention, if the tubular material is, for example, CNT material, a CNT- containing structure or film in a form different from the prior film can be obtained by allowing CNT powder or CNT- mixed powder to collide with a substrate in a continuous or pulse form at a speed of 30 m/sec so as to directly induce substrate-CNT bonds, CNT-CNT bonds, CNT-mixture bonds, or substrate-CNT-mixture bonds . Accordingly, a novel type of film can be formed, a patterning process using the film is possible, and physical properties, including improved field emission properties and high electrical conductivity, can be provided.

According to the present invention, it is possible to easily obtain films that have strong chemical bonds between a substrate and CNT particles by aerosolizing CNTs and allowing the CNT aerosol to collide with the substrate at high speed, contain no separate binder resin, have a high dangling bond density higher than that of the tubular material used as a raw material, leading to high conductivity, by allowing CNT fragments, open at one end, to grow vertically or horizontally relative to the substrate, and are useful in field emission devices. Also, novel films having excellent properties, such as durability, conductivity and plasma corrosion resistance, can be manufactured by depositing CNTs in combination with metallic, ceramic and/or semiconductor materials. In addition, the films of the present invention can be formed into a given pattern and can be used as interconnects due to their high conductivity.

[industrial Applicability] The carbon nanotube-containing film manufactured according to the present invention is a useful invention, which can be used in various applications, including field emission devices, light-emitting devices, display devices and conductive interconnects.

Claims

[CLAIMS]

[Claim l]

A method for forming a carbon nanotube-containing film on a substrate, the method comprising spraying a carbon nanotube-containing material on the substrate at a speed of more than 30 m/sec.

[Claim 2] The method of Claim 1, wherein the spraying step is intermittently carried out.

[Claim 3]

The method of Claim 1, which comprises forming on the upper surface of the substrate a mask having a given pattern, and forming said film according to the mask pattern.

[Claim 4]

The method of Claim 1, which comprises forming a resist pattern on the surface of the substrate by photolithography, and forming said film on the substrate into a given pattern.

[Claim 5]

A method for forming a carbon nanotube film on a substrate, the method comprising the steps of: aerosolizing a carbon nanotube-containing material; and spraying the aerosolized material on the substrate at a speed of at least 30 m/sec to form a film.

[Claim β] The method of Claim 5, wherein the material further comprises at least one material selected from the group consisting of tubular material, nanoparticle material, nanowire material, nanorod material, nanobelt material and powdery material .

[Claim 7]

The method of Claim 1 or 5, wherein the material is impurity-doped carbon nanotube material .

[Claim 8]

The method of Claim 1 or 5, wherein the spraying step is carried out using a nozzle, and a space around the outlet of the nozzle is maintained at a pressure of less than 100 torr.

[Claim 9]

The method of Claim 1 or 5, wherein the material is a material having a chemically modified surface.

[Claim 10]

The method of Claim 1 or 5, wherein the material is a material ground through a grinding step.

[Claim 11]

The method of Claim 5, wherein the aerosolizing step is carried out by introducing carrier gas.

[Claim 12]

A carbon nanotube-containing coating film, which: (a) comprises no separate binder resin; and (b) comprises a large number of carbon nanotube fragments, which are hollow and open at least at one end.

[Claim 13]

The carbon nanotube-containing coating film of Claim 12, which comprises, in addition to carbon nanotubes, at least one other component.

[Claim 14]

The carbon nanotube-containing coating film of Claim 13, wherein the other component is at least one material selected from the group consisting of tubular material, nanoparticle material, nanowire material, nanorod material, nanobelt material and powdery material.

[Claim 15]

A method for forming a carbon nanotube-containing film on a substrate, the method comprising the steps of: supplying external carrier gas into a space, in which a carbon nanotube-containing material is located, to aerosolize the material; and spraying the aerosolized material into a space, in which the substrate is located, in a vacuum to form a film on the substrate, wherein the film forming step comprises intermittently opening and closing the substrate-containing space and the material-containing space so as to increase the strength of the vacuum in the material-containing space, thus increasing the collision velocity of the aerosolized material.