KR100746586B1 - Coating and implant Method of surface of Carbon Nanotube with Fe by using Helicon Plasma - Google Patents

Abstract

The present invention improves the electrical conductivity of carbon nanotubes by coating and implanting iron (Fe) on carbon nanotubes using helicon plasma and treating carbon nanotubes with hydrogen gas to change the SP ² structure to SP ³ structure. The present invention relates to a method of coating and implanting iron (Fe) on a surface of carbon nanotubes of the present invention, comprising: vaporizing ferrocene (Fe (C ₅ H ₅ ) ₂ ), a metal powder, in a bubbler with heat; Injecting the vaporized vapor into a plasma generating device together with hydrogen gas to generate a plasma; And concentrating the generated plasma on the surface of the carbon nanotubes.

The present invention constituted as described above improves the electrical conductivity of carbon nanotubes by coating and implanting iron on the surface of carbon nanotubes, thereby improving the electrical conductivity of carbon nanotubes of carbon nanoparticles used in FED, FET, nanoelectronic devices and circuits, and nanotube diodes. Good release.

Carbon nanotube, plasma, iron, coating

Description

Coating and implant method of surface of Carbon Nanotube with Fe by using Helicon Plasma}

1 is a schematic diagram schematically showing a configuration of coating and implanting iron (Fe) on carbon nanotubes using a helicon plasma device according to the present invention,

2 is an EDX spectrum of carbon nanotubes coated and implanted with iron according to the present invention,

3 and 4 are FE-SEM spectral photographs of carbon nanotubes coated and implanted with iron according to the present invention,

5 is a TEM spectrum photograph of carbon nanotubes coated and implanted with iron according to the present invention.

The present invention relates to a method for coating and implanting iron (Fe) on the surface of carbon nanotubes using a helicon plasma, and more specifically, to coating and implanting iron (Fe) on the surface of carbon nanotubes using a helicon plasma. The present invention relates to a method of improving the electrical conductivity of carbon nanotubes by treating carbon nanotubes with hydrogen gas and changing the SP ² structure to the SP ³ structure.

Carbon nanotubes were discovered by Dr. Ijima of Japan in 1991 and are new nanomaterials with a wide range of applications due to their unique structural and excellent physical and chemical properties.

These carbon nanotubes have a hollow tube shape in which the carbon surface of the hexagonal honeycomb structure made by combining one carbon atom with three other carbon atoms is rounded. The diameter of the tube is very small, ranging from several nanometers to tens of nanometers (one billionth of a meter), and the length is several microns to tens of microns. This high length / diameter ratio increases the field enhancement factor of the carbon nanotubes, making it easy to release electrons even at low electric fields, and making the surface area per unit area very large. It has strength and chemical stability. Depending on the angle at which the carbon surface is curled, it may be an electrical conductor (Armchair structure) such as a metal or a semiconductor (Zigzag structure). Such carbon nanotubes are electron emission sources of field-emission displays (FEDs), field-effect transistors (FETs), nanoelectronic devices and circuits, nanotube diodes, secondary battery electrodes, hydrogen Applications include storage fuel cells, AFM / STM (tips of atomic force microscopy), sensors, and high performance composites.

As a manufacturing method for carbon nanotubes having the above characteristics, "Method of manufacturing single-walled carbon nanotubes" of Korean Patent Application No. 1999-0008897 is "Arc discharge is generated between two carbon electrodes in a gas atmosphere, and the carbon In the method for producing a single-walled carbon nanotube which generates soot containing single-walled carbon nanotubes by evaporating the electrode, a metal-added carbon electrode in which two or more metals are added to one or both sides as the two carbon electrodes is used. And a method for producing a single-walled carbon nanotube characterized in that an alternating arc discharge is generated by applying an alternating voltage between the two carbon electrodes. Korean Patent Application No. 2002-0012949 discloses a "first electrode. And arranging a second electrode mainly composed of a carbon material in the air or in air, wherein the first electrode and the Generating an arc discharge by applying a voltage between the two electrodes, evaporating the carbon material of the second electrode by the arc discharge to generate soot including nanocarbon, and soot including the nanocarbon It discloses a method for producing nanocarbon, characterized in that it comprises a step of recovering the, "Korean Patent Application No. 2003-0040461" forms a pattern on the surface-treated substrate by a photolithography method and chemical self-assembly thereon A method of forming a pattern of carbon nanotubes by laminating carbon nanotubes in a single layer and a multilayer using a method is disclosed.

However, the above-described invention and the like merely improve the manufacturing method of carbon nanotubes, and there is no disclosed invention for a method for improving the electrical conductivity in the physical properties of carbon nanotubes.

Therefore, the inventors of the present invention further improve the electrical conductivity of the properties of carbon nanotubes, which are being actively studied in various applications worldwide due to the excellent physical properties as described above, and thus, FED, FET, nanoelectronic devices and circuits, and nanotube diodes. The present invention was completed by improving the electrical conductivity by coating and implanting carbon nanotubes while studying to improve the functionalities of carbon nanotubes applied to many fields.

An object of the present invention is to solve the problems such as the emission (emission) generated by the electrical conductivity of the carbon nanotubes, by coating and implanting iron (Fe) on the carbon nanotubes and by treating the carbon nanotubes with hydrogen gas It is to provide a method for improving the electrical conductivity of carbon nanotubes.

In order to achieve the above object, the present invention provides a metallic carbon nanotube coated with and coated with iron (Fe).

In another aspect, the present invention comprises the step of vaporizing the metal powder ferrocene (ferrocene; Fe (C ₅ H ₅ ) ₂ ) in a bubbler to heat; Injecting the vaporized vapor into a plasma generating device together with hydrogen gas to generate a plasma; And it provides a method for coating and implanting Fe on the surface of the carbon nanotubes consisting of the step of collecting the generated plasma on the surface of the carbon nanotubes.

Hereinafter, the present invention will be described in more detail.

According to the present invention, in order to coat and implant iron (Fe) on the carbon nanotubes, a small amount of metal powder called ferrocene is placed in a bubbler, and the vaporization state is maintained by maintaining the vaporization temperature of the metal at 100 ° C. It is injected into the chamber (chamber) at the same time with the hydrogen gas to generate a plasma while maintaining a constant pressure.

The hydrogen gas is preferably injected into the chamber with the ferrocene vapor at 900 to 1100 sccm. If it is injected below 900 sccm, the effect of hydrogen gas injection is inferior. If it is injected above 1100 sccm, it is not preferable because it adversely affects proper coating and implant of iron.

The carbon nanotubes are placed on a substrate holder in the chamber and a DC bias of a constant voltage is applied to collect ion plasmas on the substrate holder, thereby ionizing the carbon nanotubes held in the substrate holder. Implant the plasma.

The plasma condition is preferably 13.56 MHz RF power 500 W, the magnetic field is maintained for 30 minutes by generating a Helicon plasma (Helicon Plasma) at 300 to 600 G.

As described above, the present invention coats and implants iron (Fe) on carbon nanotubes using a helicon plasma, in which hydrogen gas is injected and treated at the same time. This is a well-known next-generation FED plasma treatment with hydrogen gas, the structure of carbon nanotubes that had SP² structure is changed to the SP³ structure has been reported that the field emission is good, using hydrogen gas as a carrier gas pressure Can be used while adjusting.

As described above, whether iron (Fe) is coated and implanted on the carbon nanotubes according to the present invention can be confirmed through FE-SEM, EDX spectrum, and TEM.

As described above, the present invention improves the conductivity by coating and implanting iron on carbon nanoparticles, thereby improving carbon nanoparticles used in FED, FET, nanoelectronic devices and circuits, nanotube diodes, and the like. It improves the problem of tip growth of particles. In addition, by providing carbon nanoparticles with excellent conductivity, the carbon nanoparticles can be applied to new materials.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings, but the present invention is not limited thereto.

<Example 1>

Helicon plasma generator

Helicon plasma is basically composed of discharge tube, high frequency source, antenna, parallel magnetic field applying coil, impedance matching, vacuum device and interferometer.

The high frequency source uses ENI products with a maximum output power of 3 kW with a frequency of 13.56 MHz and is installed in a shielding room to prevent the interference of electromagnetic waves generated by the RF system. Installed outside.

The antenna is a device for generating plasma by transmitting RF power in a discharge box. In this embodiment, the antenna is installed in a Nagoya type-III type.

The length of the straight portion of the antenna is composed of a straight portion having a length of 150 mm and four semicircles having a diameter of 140 mm to satisfy the conditions under which Landau damping can effectively occur. The straight and semicircular sections were made of 3 mm thick and 25 mm wide copper plates. The joints were welded with silver, and the overlapping copper plates constituting the antenna were insulated with epoxy plates and the corners were insulated with heat shrink tubes.

The Helmholtz coil manufactured to apply a uniform magnetic field in the discharge tube in the axial direction has a center radius of 20 cm, and wound by winding 100 times a copper tube having a hole of 2.2 × 2.2 mm² for cooling on a 6 × 6 mm² cross section and bonding it with epoxy. Two bundles of coils were designed and manufactured to be 20cm away from the center. The strength of the magnetic field applied to the Helmholtz coil can be up to 600 G, but the magnetic field was maintained at 400 G in order to maintain a stable plasma state.

The equipment used for impedance matching of RF plasma is ENI's automatching network and uses a vacuum variable capacitor of Model UCSXF 2000-12S from Joslyn Jennings with a maximum capacity of 2200 pF. It was.

A vacuum was created using mechanical pumps, diffusion pumps, and NV-8 thermopile type vacuum gauges from Hastings Instruments, and the CO flow rate was controlled by a mass flow controller. Was adjusted. The pressure inside the chamber was maintained at 3.0 × 10 ⁻² torr, and the injection amount of CO gas was injected at 300 sccm using a flow meter.

The substrate structure inside the chamber has a heating unit capable of heating up to 1000 ° C. using SiC filaments at the bottom and protrudes between the filaments of the thermocouple. In order to accelerate the plasma ions to the sample by applying a negative voltage to the substrate holder, a ceramic ring was insulated between the substrate holder and the heating unit, and a circuit was configured to apply a DC bias to the substrate holder.

<Example 2>

After injecting 1 g of ferrocene metal powder into the bubbler, the bubbler was maintained at a vaporization temperature of the metal at 100 ° C. to form a vapor state, and then 10 cm in diameter and 50 cm in length according to Example 1, such as 1000 sccm of hydrogen gas. The plasma was generated while being injected into the chamber of the helicon plasma source while maintaining the total pressure to be 10 ⁻² torr. Carbon nanotube samples were placed on a substrate holder in the chamber and ion plasmas were collected on the substrate holder by applying a negative DC bias of -30V. The plasma conditions were 13.56 MHz RF power 500 W, the magnetic field was 400 G to generate a helicon plasma and maintained for 30 minutes to coat and implant the iron ions on the carbon nanotube samples held in the substrate holder.

<Example 3>

The same procedure as in Example 2 was carried out except that hydrogen gas injected with ferrocene vapor was 800 sccm.

<Example 4>

The same procedure as in Example 2 was carried out except that hydrogen gas injected with ferrocene vapor was 900 sccm.

Example 5

The same procedure as in Example 2 was carried out except that hydrogen gas injected with ferrocene vapor was 1100 sccm.

<Example 6>

The same procedure as in Example 2 was carried out except that hydrogen gas injected with ferrocene vapor was 1200 sccm.

<Example 7>

Except for maintaining the total pressure of the helicon plasma generator chamber to be 2x10 ^-2 torr was the same as in Example 2.

<Example 8>

Except for maintaining the total pressure of the helicon plasma generator chamber to be 3x10 ^-2 torr was the same as in Example 2.

Experimental Example 1

Analysis of iron (Fe) implanted in carbon nanotubes.

The carbon nanotubes prepared according to Example 2 were examined for iron coating and implant through EDX spectrum, FE-SEM, and TEM, and the results are shown in FIGS. 2 to 5.

Figure 2 is an EDX spectrum of the carbon nanotubes prepared according to Example 2, as can be seen in this figure, the iron (Fe) component is found in the carbon nanotubes prepared according to one embodiment of the present invention, carbon It was found that iron was coated and implanted on the nanotubes.

3 and 4 are FE-SEM spectra of the carbon nanotubes prepared according to Example 2, it can be seen that the nano-sized iron particles are coated on the surface of the carbon nanotubes, as shown in FIG. In addition, it can be seen that the surface of the carbon nanotubes prepared according to Example 2 in FIG. 4 is consistent with the results obtained when the surface of the carbon nanotubes is hydrogenated according to a conventional method. It is as if the nano-scale particles appear as nodes along the tube, and this phenomenon is seen as a kind of carbon nanotubes as NCNTs (Nodular cabon nanotues). Analysis of the Raman spectral data of the NCNT demonstrates that the diamond structure (SP 3) has a higher electron state density than the SP 2 structure of carbon nanotubes.

5 is a TEM spectrum picture of the carbon nanotubes prepared according to Example 2, it can be seen that the iron nanoparticles implanted on the surface and the inside of the carbon nanotubes prepared according to Example 2.

Experimental Example 2

Measurement of electrical conductivity

As a result of testing the electrical conductivity of the iron-coated and implanted carbon nanotubes according to Examples 2 to 8, the carbon-coated and nano-implanted carbon nanotubes were significantly improved in electrical conductivity compared to conventional carbon nanotubes. .

The present invention constituted as described above improves the electrical conductivity of carbon nanotubes by coating and implanting iron on carbon nanotubes, thereby eliminating problems of nanosystems such as emission that carbon nanotubes have, such as FED, FET, Good emission of carbon nanoparticles used in nanoelectronic devices, circuits, nanotube diodes, and the like. In addition, by providing carbon nanoparticles with excellent conductivity, the carbon nanoparticles can be applied to new materials.

Claims (6)

delete Vaporizing ferrocene (Ferocene; Fe (C ₅ H ₅ ) ₂ ), which is a metal powder, with heat in a bubbler; Injecting the vaporized vapor into a plasma generating device together with hydrogen gas to generate a plasma; And The method of coating and implanting iron (Fe) on the surface of the carbon nanotubes, characterized in that consisting of the step of collecting the plasma generated on the surface of the carbon nanotubes. The carbon nanotube of claim 2, wherein the plasma generator uses a helicon plasma generator comprising a discharge tube, a high frequency source, an antenna, a parallel magnetic field applying coil, an impedance matching device, a vacuum device, and an interferometer. Coating and implanting iron (Fe) on the surface. 3. The method of claim 2, wherein the hydrogen gas is injected into the chamber with the ferrocene vapor at 900 to 1100 sccm. 3. The method of claim 2, wherein the pressure inside the plasma generator chamber is maintained within a range of 1 × 10 ⁻² torr to 3 × 10 ⁻² torr. . According to claim 3, wherein the high frequency source is installed in a shielding room (shielding room) with a frequency generator having a maximum output of 2 to 4 kW of frequency 10 to 15 MHz, The antenna is a device for generating a plasma by transmitting RF power in the discharge box, the length of the straight portion of the antenna has a straight portion and a diameter of a length that satisfies the condition that can effectively occur Landau damping (Landau damping) Consists of four semicircles, the overlapping and corner portions of the copper plate constituting the antenna are insulated, The discharge tube is installed inside the Helmholtz coil manufactured to apply a uniform magnetic field in the axial direction, An impedance matching device and a vacuum forming device of the plasma are installed, The holder for holding the substrate inside the chamber is provided with a heating unit (heating unit) that can be heated to 1000 ℃ using SiC filament to protrude between the filament of the thermocouple, The substrate holder is a method for coating and implanting iron (Fe) on the surface of the carbon nanotubes, characterized in that the circuit is configured to apply a DC bias.

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