WO2004060799A1

WO2004060799A1 - Method and apparatus for producing halogen atom containing fullerene

Info

Publication number: WO2004060799A1
Application number: PCT/JP2003/016994
Authority: WO
Inventors: Rikizo Hatakeyama; Takamichi Hirata; Yasuhiko Kasama; Kenji Omote
Original assignee: Ideal Star Inc.
Priority date: 2002-12-31
Filing date: 2003-12-26
Publication date: 2004-07-22
Also published as: TW200422255A; JPWO2004060799A1; AU2003292705A1

Abstract

A method and an apparatus enabling to produce a halogen atom containing fullerene at higher yield are disclosed. The apparatus comprises a vacuum chamber (501), a gas supply port (502) for supplying a halogen gas into the vacuum chamber (501), a means for producing a plasma (an RF antenna (503)), a means for bringing a fullerene into the plasma (a fullerene oven (504)), a deposition plate (505) for depositing a halogen atom containing fullerene thereon, and a magnetic filter (506) arranged between the means for bringing a fullerene into the plasma and the deposition plate (505).

Description

Description Production method and production equipment for halogen-containing fullerenes

The present invention relates to a method and an apparatus for producing a halogen-containing fullerene. Background art

Non-patent document 1

Journal of Plasma and Fusion Science Vol. 75, No. 8, P. 927-933 (August 1999)

Non-patent document 2

Thin Solid Films Vol. 386 P. 286-290 (2001)

Non-Patent Document 1 proposes a technique shown in FIG. 3 as a technique for producing an endohedral fullerene.

This technology is to produce endohedral fullerenes by injecting fullerenes into a plasma stream in which atoms to be included are ionized in a vacuum vessel and depositing the endohedral fullerenes on a deposition plate located downstream of the plasma stream. .

According to this technique, it is possible to produce endohedral fullerenes at a low temperature and with good yield.

However, this technique has a problem that the encapsulation rate is not good at the center of the deposition plate. In other words, the endohedral fullerene is deposited almost entirely on the radially outer portion of the plasma flow, and the endohedral fullerene is hardly deposited on the radially inner side of the plasma flow.

In recent years, various usefulness of endohedral fullerenes has attracted attention, and a technique for producing endohedral fullerenes with higher yield has been desired.

Non-Patent Document 2 proposes a technique of depositing fullerene fluoride on a substrate by generating a plasma by introducing a CF ₄ gas into a chamber.

However, the film deposited in this technique is not an endohedral fullerene but a chemically modified fullerene. W

Two

An object of the present invention is to provide a method and an apparatus for producing a halogen-containing endohedral fullerene that can produce an endohedral fullerene with higher yield. Disclosure of the invention

In the method for producing a halogen atom-containing fullerene of the present invention, a halogen gas is introduced into a vacuum vessel to generate plasma, form a plasma flow, introduce fullerene into the plasma or plasma flow, and further pass through a magnetic filter. Then, the endohedral fullerenes are deposited on a deposition plate disposed downstream of the plasma flow. An apparatus for producing a halogen atom-containing fullerene according to the present invention includes a vacuum vessel, a gas inlet for introducing a halogen gas into the vacuum vessel, a means for generating plasma containing a negatively charged halogen atom, Means for introducing fullerene into the plasma, a deposition plate for depositing the endohedral fullerene, and a magnetic filter provided between the deposition plate and the plasma.

(Action)

For the for encapsulating, for example, fluorine atom in the present invention, plasma is generated by introducing the fluorocarbon gas (C _m F _n gas) in the vacuum chamber. When CF ₄ gas is used, CF ₃ + and F— exist in the plasma.

Alternatively, a halogen gas or a compound thereof and an inert gas are introduced into a vacuum vessel. In this case, the plasma contains a positively charged inert gas and a negatively charged halogen gas.

For plasma generation, plasma having a high energy component can be obtained by using, for example, an RF (Radio Frequency) antenna.

When fullerene is introduced into this plasma, electrons in the fullerene are knocked out. In particular, the plasma according to the present invention is an ionized plasma and has a high plasma energy, so that electrons are easily knocked from fullerene. As a result, high density fullerene ions (eg, C ₆₀ +) are obtained.

It is preferable that a permanent magnet or an electromagnet is arranged outside the vacuum vessel to confine the plasma and to provide directionality. This also creates a plasma flow. In the present invention, a magnetic filter is provided between the plasma and the deposition plate. By passing through the magnetic filter, only positively charged fullerene ions and negatively charged halogen ions will flow downstream of the plasma flow.

As a result, endohedral fullerene can be deposited with a high yield by the interaction of positive and negative ions.

It is preferable that the deposition plate be a plurality of divided plates that are concentrically divided. The radius of the central deposition plate is R + 5 mm or less, where R is the radius of the plasma generation hole, and film formation is performed while applying a bias voltage to the central deposition plate. It is preferable for improving the yield.

An arbitrary bias voltage is applied to each of the deposition plates.

The fullerene is C ₆ . It is characterized by being. C _6. C ₆ has more C atoms than fullerene, which has a larger diameter. Although encapsulation is difficult, in the present invention, encapsulation can be easily achieved in high yield even with C ₆₀ .

The method is characterized in that a bias voltage Δaρ of 120 V × Δφ & ρ + 5 V is applied to the central deposition plate.

A cylinder having a diameter 2.5 to 3.0 times the inner diameter of the plasma flow is provided in the middle of the plasma flow.

A cooling means for cooling the wall of the vacuum vessel at least downstream from the downstream end of the cylinder is provided. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a conceptual view showing an apparatus for producing an endohedral fullerene according to an embodiment of the present invention.

FIG. 2 is a front view showing the deposition plate of FIG.

FIG. 3 is a conceptual diagram illustrating a conventional technology for producing an endohedral fullerene.

(Explanation of code)

5 0 1 Vacuum container

5 0 2 Gas inlet 5 0 3 RF antenna

5 0 4 Fullerene

5 0 5 5 0 5 a 5 0 5 b 5 0 5 c

5 0 6 Magnetic filter

5 0 7 Magnet

509, 509a, 509b, 55 00 99 cc bias voltage applying means

5 1 0 Exhaust pump

5 1 1 Magnet

5 1 2 Wire mesh

5 1 3 Tube Best Mode for Carrying Out the Invention

FIG. 1 shows an apparatus for producing an endohedral fullerene according to an embodiment of the present invention.

A vacuum vessel 501, a gas inlet 502 for introducing, for example, a fluorocarbon gas CF ₄ into the vacuum vessel 501, a means for generating plasma (RF antenna 503), and A means for introducing fullerene (fullerene oven 504), a deposition plate 505 for depositing the encapsulated fullerene, and a magnetic filter 506 provided between the plate and the plasma. Have.

Hereinafter, this device will be described in detail.

In the embodiment of FIG. 1, a plasma is generated by discharge fluorocarbon gas CF _4. The generation of plasma ionized by CF ₃ ⁺ and F— is performed by an RF (Radio Frequency) antenna 503. The RF antenna 503 preferably uses an inductive coupling type. There is also a method of using a flat plate such as a spiral type, but in this case, the problem arises that the material of the antenna or attached dirt floats in the vacuum vessel, causing the generation of plasma and the formation of encapsulated fullerenes to deteriorate. I do.

Also, the halogen gas or its compound to be included and the inert gas may be introduced from the gas inlet. In this case, the RF antenna 503 generates a plasma composed of a positively charged inert gas and a negatively charged halogen gas.

The generated plasma has a magnet 507, for example, where the S and N poles cross outside the vacuum vessel 501. It is confined axially within the vacuum vessel 501 along a uniform magnetic field (B = 2-7 kG) formed by permanent magnets or electromagnets arranged next to each other. The charged particles are neutralized and lost when colliding with the inner wall of the vacuum container 501, but the loss of the charged particles can be prevented by providing magnetic force lines near the inner wall.

The value obtained by adding the Larmor radius (about 5 mm) of the ions constituting the plasma to the radius of the RF antenna 503 is the radius of the plasma flow. Therefore, the radius of the plasma flow can be arbitrarily selected to an appropriate size according to the size of the apparatus by changing the radius of the RF antenna.

A cooling means (not shown) is provided on the outer periphery of the vacuum vessel 501. By cooling the inner wall of the vacuum vessel 501 with cooling means, neutral gas molecules are trapped (adsorbed on the inner surface). By trapping neutral gas molecules on the inner wall, a plasma containing no impurities can be generated, and a highly pure endohedral fullerene can be formed on the deposition plate 505.

It is preferable to provide a cylinder 5 13 around the plasma flow. When the cylinder 513 is provided, it is preferable to cool at least the inner wall of the vacuum vessel 501 between the downstream end of the cylinder 513 and the deposition plate 505. The temperature of the inner wall of the vacuum vessel 501 is preferably equal to or lower than room temperature, and more preferably equal to or lower than o ° C. At such a temperature, trapping of neutral gas molecules is facilitated, and it becomes possible to obtain a higher-purity endohedral fullerene.

When the cylinder 513 is provided so as to cover the plasma flow in the middle of the plasma flow 508, the cylinder 513 is ripened to 400 to 65 ° C. Fullerene that has not been ionized in the plasma after being introduced into the cylinder 5 13 and adheres to the inner surface of the cylinder is sublimated again. If the temperature of the cylinder 5 13 is lower than 400 ° C, re-sublimation is not performed efficiently, and if the temperature is higher than 65 ₀ C, C ₆₀ is re-sublimated excessively, so halogen C _60, which does not contribute to the formation of endohedral fullerene by reaction with atoms, increases, and there is a problem that C ₆₀ is not used efficiently. Therefore, it is preferable that the temperature of the cylinder 513 is set at 400 to 65 ° C.

More preferably, the temperature is 480 to 62 ° C. When the temperature is lower than 480 ° C, the density of fullerene ions decreases, and the yield of endohedral fullerene decreases. Exceeds 62 ° C The amount of neutral fullerene that is not ionized increases, and the encapsulation rate decreases.

The inner diameter of the cylinder 513 is preferably 2.5 to 3.0 times the diameter of the plasma flow 508. More preferably, it is 2.7 to 2.8 times. If it is less than 5, the interaction between the plasma flow 508 and the cylinder 5 13 becomes large, the plasma retention is reduced, and the yield of endohedral fullerene is reduced. If it exceeds 3.0, the duration of the plasma will be shortened, and the yield of endohedral fullerene will be reduced.

The introduction speed of the fullerene may be controlled by the temperature rise rate of the fullerene oven 504. The temperature rise rate is preferably 100 ° C./min or more. The upper limit is the temperature rise rate at which bumping does not occur.

An upstream end of the tube 5 1 3, the distance 1 u between the RF antenna 50 3 (1.5 to 2.0) is preferably set such that ^{X (π DH 2/4)} . DH is the diameter of the RF antenna 503. By setting the value to 1 u, the cylinder 5 13 can be prevented from being affected by heat from the RF antenna 503, and can maintain stable plasma over time.

The deposition plate 505 is divided concentrically as shown in FIG. In the example shown in FIG. 2, the plate is divided into three plates 505a, 505b, and 505c. In other words, the central deposition plate 505a is circular, and a ring-shaped deposition plate 505b, which is electrically insulated from the deposition plate 505a, is provided around the periphery of the deposition plate 505a. 505 c is arranged. The number of deposition plates is not limited to three. Each of the deposition plates 505a, 505b, and 505c is provided with bias applying means 509a, 509b, and 509c so that a bias voltage can be independently applied. The shape of the deposition plate is not limited to a circular or circular ring as long as the shape of the vacuum vessel is not limited, and may be, for example, a square to square ring or other shapes.

The radius of the central deposition plate 505a is preferably R + 5 mm, where R is the radius of the RF antenna 503. There is a low probability that endohedral fullerenes will be formed outside the area of R + 5 mm on the deposition plate. It is preferable to reduce the size of the manufacturing apparatus from the viewpoint of improving the degree of background vacuum and shortening the evacuation time.From the viewpoint of using the generated plasma without waste and miniaturizing the manufacturing apparatus, Centrally located It is preferable that the radius of the divided plate be R + 5 mm or less. However, even when the deposition voltage is not divided and the entire plate is set to the same bias voltage, it is possible to form the endohedral fullerene by optimizing the deposition conditions.

The radius of the plasma flow confined by the magnetic field of the magnetic field strength B is larger than the radius of the RF antenna generating the plasma by the Larmor radius _{RL of the} ions constituting the plasma. Is inversely proportional to B, for example, B = 0. 3 T, under conditions of plasma temperature 250 0 ° C is, C _6. _{R L = 4. 0 mm,} F is R _L = 1. 0 mm _N CI is R _L = 1. 4 mm is... And can be estimated. Therefore, it is preferable to design the size of the deposition plate based on R + 5 mm in consideration of the applicable range of the manufacturing conditions such as the magnetic field strength and the plasma temperature.

A bias voltage is applied to the central deposition plate 505a. It is preferable to apply a negative bias voltage. As a result, the velocity of the halogen ions, which are the target atoms, is reduced, and the interaction with the fullerene ions is increased, so that the target atoms are easily included. However, even when a floating state is applied without applying a bias voltage to the central deposition plate 505a, it is possible to form the endohedral fullerene by optimizing the deposition conditions. '

When a bias voltage is applied to the central deposition plate 505a, the encapsulation rate is increased by controlling the bias voltage so that fullerene ions have a distribution having a peak at the center of the plasma flow 508. be able to. The optimum bias voltage varies depending on the atoms to be included, the type of fullerene, and other film formation conditions, but may be determined in advance by experiments.

A halogen element as encapsulated target atom, when using a C ₆₀ as fullerenes, the deposition plate 505 a of the central portion, it is preferable to apply a bias voltage one 20V rather phi & [rho Ku + 5 V. One 18ν≤φap≤OV is particularly preferred.

Similarly to the central deposition plate 505a, the outer deposition plates 505b and 505c may be set to either the floating potential state or the bias voltage application. Even when both of the outer deposition plates 506b and 506c are in a floating state, the same amount of endohedral fullerene is deposited on the deposition plate 505b as in the conventional method. Therefore, the increase in the yield on the central deposition plate 505a was Rate is higher.

Of course, if the density of fullerene ions in the portion corresponding to the deposition plate 505b becomes low due to the change of the film formation conditions, a bias voltage is also applied to the deposition plate 505b to reduce the density of the fullerene ions. Even if it is high, The spatial distribution of plasma may be measured during film formation using an ion measurement probe, and the bias voltage applied to the deposition plates 505b and 505c may be automatically controlled by a computer. The same applies to the automatic control of the application to the deposition plate 505a.

The vacuum vessel 501 is provided with a pump 510 so that the inside of the vacuum vessel 501 can be evacuated to a vacuum.

Examples of the fullerene in the present invention include C _n (n = 60, 70, 74, 82, 84).

If the relationship between the distance 1 d from the downstream end of the cylinder 5 13 to the accumulation plate 505 and the length 1 c of the cylinder 5 13 is 1 d ≥ 21 c, the accumulation plate The concentration of neutral fullerene in the film deposited on 505 can be further reduced. That is, the concentration of the endohedral fullerene in the film can be further increased. The magnetic filter 506 is composed of, for example, a magnet 511 and a wire mesh 512 arranged outside the vacuum vessel 501. The magnetic filter 506 is set to pass only the ions of the atoms to be included and the ions of fullerene, and reflect or restrict the other ions, that is, electrons, and the positively charged inert gas or CF ₃ ^+. Have been. The magnet 5 11 may be either a permanent magnet or an electromagnet. If an electromagnet is used, the strength of the magnetic field can be changed in accordance with the halogen gas to be included and the inert gas introduced from the gas inlet 502.

In addition, the magnetic filter 506 has a double structure, and one of the magnetic filters reflects or restricts electrons, and the other filter reflects or restricts positively charged inert gas or CF ₃ ^+. You may.

(Example 1)

Using the apparatus shown in FIG. 1, fluorine-containing C ₆₀ (hereinafter, referred to as “F @ C ₆ ”) fullerene was formed.

In this example, the vacuum vessel 501 has a diameter of 100 mm and a length of 1200 mm. Using.

In this example, an RF antenna having a diameter of 20 mm was used.

CF ₄ gas was introduced into the vacuum vessel 501 from the gas introduction port 502 to generate plasma.

Note that the vacuum chamber 501, and 1 X 10- ⁴ P a, the magnetic field intensity B is set to B = 0. 3 T.

Next, fullerene was introduced from the fullerene oven 504.

On the other hand, a three-division type deposition plate 505 was used. The diameter of the central deposition plate 505a was 14 mm, the diameter of the outer deposition plate 505b was 32 mm, and the diameter of the outer deposition plate 505c was 5 Omm.

Δ φ ap = —5 V was applied as a bias voltage Δ ap (= a ρ-φ s) to the central deposition plate 505a. The deposition plates 505b and 505c were at floating potential. Note that Δφap is a DC voltage, and φs is a plasma space potential. When the ion distribution in the course of film formation was measured using an ion measurement probe, it was found that C ₆₀ ⁺ ions were concentrated in the central region.

After the film was formed for 30 minutes, the thin film containing endohedral fullerene (F @ C _{6 in} this example) deposited on the deposition plate was analyzed. In the central part of the deposition plate 505a, a high content of endohedral fullerene was formed. In addition, a deposition film containing endohedral fullerene was observed on the deposition plate 505b outside the center.

(Example 2)

In this example, the endohedral fullerene was deposited by changing the bias value on the central deposition plate in the range of 120 V to +10 V.

Excellent yields were shown in the range of −20 Δ ρ <+5 V. A better yield was shown in the range of −18ν≤Δφαρ≤0V. Industrial applicability

According to the present invention, it is possible to increase the yield of endohedral fullerenes.

Claims

The scope of the claims

1Halogen gas was introduced into the vacuum vessel to generate plasma and form a plasma flow, fullerene was introduced into the plasma or the plasma flow, and further passed through a magnetic filter and placed downstream of the plasma flow. A method for producing a halogen atom-encapsulated fullerene, comprising depositing an endohedral fullerene on a deposition plate.

2. The method according to claim 1, wherein the plasma flow is formed by a magnet.

3. The fullerene is C ₆ . 3. The method for producing a halogen atom-encapsulated fullerene according to claim 1 or 2, wherein:

4. The method for producing a halogen atom-encapsulated fullerene according to any one of claims 1 to 3, wherein a bias voltage is applied to the deposition plate.

5. The deposition plate is divided into a plurality of concentric deposition plates, the radius of the deposition plate at the center is not more than the radius of the plasma flow, and a bias voltage is applied to the deposition plate at the center. 5. The method for producing a halogen atom-encapsulated fullerene according to claim 1, wherein the deposition is performed.

6. A halogen atom according to any one of claims 1 to 5, wherein a bias voltage m ap of 120 V × Δφ & ρ + 5 V is applied to the central deposition plate. Manufacturing method of endohedral fullerene.

7. The method for producing a halogen atom-encapsulated fullerene according to any one of claims 1 to 6, wherein the plasma is generated by an RF antenna.

8. A gas inlet for introducing a halogen gas into the vacuum vessel, a means for generating plasma, a means for introducing fullerene into the plasma, a deposition plate for depositing endohedral fullerene, An apparatus for producing a halogen atom-encapsulated fullerene, comprising: a magnetic filter provided between a deposition plate and the plasma.

9. The apparatus for producing fullerene containing halogen atoms according to claim 8, wherein the deposition plate comprises a plurality of deposition plates divided concentrically.

10. Vias for applying an arbitrary bias voltage to each of the deposition plates 10. The apparatus for producing a halogen atom-containing fullerene according to claim 9, further comprising a source applying means.

11. The apparatus for producing a halogen atom-encapsulated fullerene according to claim 10, wherein the bias applying means is variable.

12. The bias is such that a bias voltage Δφap of 20 V × Δφ & ρ + 5 V is applied to a centrally located deposition plate. 11. The apparatus for producing fullerene containing halogen atoms according to any one of 1 to 11.

13. The inner radius of the deposition plate disposed at the center is not more than R + 5 mm, where R is the radius of the plasma generating hole of the plasma generating means. The apparatus for producing a halogen atom-encapsulated fullerene according to any one of the above.

14. The apparatus for producing fullerene containing halogen atoms according to any one of claims 8 to 13, wherein the plasma generating means is RF antenna.

15. The method according to any one of claims 8 to 14, wherein a cylinder having a diameter of 2.5 to 3.0 times the inner diameter of the plasma flow is provided in the middle of the plasma flow. Equipment for producing fullerenes containing halogen atoms.

16. The apparatus for producing a halogen atom-encapsulated fullerene according to claim 15, wherein cooling means for cooling at least a wall of the vacuum vessel at a downstream side from a downstream end of the cylinder is provided.