JP2005097113A - Method and device for producing carbon nanowall - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new method for producing carbon nanowalls, and to provide a device suitable for performing the method. <P>SOLUTION: A gaseous starting material 32 at least comprising carbon as a constitutive element is introduced into a reaction chamber 10. The reaction chamber 10 is provided with a diode parallel plate capacitive coupling plasma (CCP)-generating mechanism 20 including a first electrode 22 and a second electrode 24. In this way, electromagnetic waves such as RF (Radio Frequency) waves are applied to form a plasma atmosphere 34 in which the gaseous starting material 32 is converted into plasma. On the other hand, in a radical generation chamber 41 provided at the outside of the reaction chamber 10, a radical source gas 36 at least comprising hydrogen is cracked by RF waves, or the like, to generate a hydrogen radical 38. The hydrogen radical 38 is injected inside the plasma atmosphere 34, and carbon nanowalls are formed on the surface of a substrate 5 arranged on the second electrode 24. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a structure mainly composed of carbon and having a predetermined fine structure, and an apparatus used for the method.

A structure (carbon nanostructure) that is mainly composed of carbon and has a predetermined microstructure is known. Such carbon nanostructures include fullerenes, carbon nanotubes, and the like. Patent Document 1 below describes carbon nanostructures called carbon nanowalls. In Patent Document 1, for example, a microwave is applied to a mixture of CH ₄ and H ₂ to form carbon nanowalls on a sapphire substrate coated with a nickel iron catalyst. Patent Document 2 relates to a technique for forming a thin film or performing microfabrication by injecting radicals into plasma. Patent Document 3 relates to a technique for measuring the concentration of radicals.
US Patent Application Publication No. 2003/0129305 JP-A-9-137274 Japanese Patent Laid-Open No. 10-102251

  One object of the present invention is to provide a novel method for producing carbon nanowalls. Another object of the present invention is to provide a manufacturing apparatus suitable for carrying out such a manufacturing method. Another object of the present invention is to provide a method for producing carbon nanowalls, which can easily control properties and / or characteristics. Moreover, it is providing the manufacturing apparatus suitable for implementation of this manufacturing method.

  The present inventors have found that carbon nanowalls can be produced by supplying radicals from the outside of the plasma atmosphere in a plasma atmosphere in which a raw material containing carbon as a constituent element is turned into plasma.

That is, in the carbon nanowall manufacturing method provided by this application, a plasma atmosphere in which a source material containing at least carbon as a constituent element is turned into plasma is formed in at least a part of the reaction chamber. Radicals generated outside the atmosphere are injected into the plasma atmosphere. And carbon nanowall is formed in the surface of the base material arrange | positioned in this reaction chamber.
According to such a manufacturing method, one or more conditions among the composition, supply amount, etc. of radicals injected into the plasma atmosphere are made independent of one or more other manufacturing conditions, or the other manufacturing. It can be adjusted in relation to the conditions. That is, the degree of freedom in adjusting the manufacturing conditions is higher than when radical injection from the outside is not performed. This means that carbon having properties (for example, wall thickness, height, formation density, smoothness, surface area, etc.) and / or properties (for example, electrical characteristics such as field emission characteristics) according to the purpose. This is advantageous from the viewpoint of producing nanowalls.

The “carbon nanowall” according to this application is a carbon nanostructure having a two-dimensional extension. A typical example of the carbon nanowall obtained by the above production method is a carbon nanostructure having a wall-like structure rising from the surface of the substrate in a substantially constant direction. Note that fullerenes (C _{60 and the} like) can be regarded as zero-dimensional carbon nanostructures, and carbon nanotubes can be regarded as one-dimensional carbon nanostructures. The “plasma atmosphere” refers to an atmosphere in which at least a part of a substance constituting the atmosphere is ionized (that is, in a plasma state).

In one preferred embodiment of the manufacturing method disclosed herein, the plasma atmosphere is formed by converting the raw material into plasma in a reaction chamber. Alternatively, the source material may be converted into plasma outside the reaction chamber, and the plasma may be introduced into the reaction chamber to form a plasma atmosphere in the reaction chamber.
Radicals are injected into the plasma atmosphere from the outside of the atmosphere. It is preferable to decompose the radical source material outside the reaction chamber to generate radicals, which are then injected into the plasma atmosphere in the reaction chamber. Alternatively, the radical source material may be decomposed inside the reaction chamber and outside the plasma atmosphere, and radicals generated thereby may be injected into the plasma atmosphere.

A preferred method for generating radicals from a radical source material includes a method of irradiating the radical source material with electromagnetic waves. As the electromagnetic wave used in this method, either microwave or high frequency (UHF wave, VHF wave or RF wave) can be selected. It is particularly preferable to irradiate VHF waves or RF waves. According to such a method, for example, by changing the frequency and / or input power, the decomposition strength (radical generation amount) of the radical source material can be easily adjusted. Therefore, there is an advantage that it is easy to control the production conditions of carbon nanowalls (such as the amount of radicals supplied into the plasma atmosphere).
Here, as is well known, “microwave” refers to an electromagnetic wave of about 1 GHz or more. The “UHF wave” refers to an electromagnetic wave of about 300 to 3000 MHz, the “VHF wave” refers to an electromagnetic wave of about 30 to 300 MHz, and the “RF wave” refers to an electromagnetic wave of about 3 to 30 MHz.
As another preferred method for generating radicals from a radical source material, a method of applying a DC voltage to the radical source material can be mentioned. It is also possible to employ a method of irradiating the radical source material with light (eg, visible light or ultraviolet light), a method of irradiating an electron beam, a method of heating the radical source material, or the like. Alternatively, a member having a catalytic metal may be heated, and a radical source material may be brought into contact with the member (that is, by heat and catalytic action) to generate radicals. As the catalyst metal, one or more selected from Pt, Pd, W, Mo, Ni and the like can be used.

The radical injected into the plasma atmosphere preferably contains at least a hydrogen radical (that is, a hydrogen atom; hereinafter, sometimes referred to as “H radical”). It is preferable to decompose a radical source material containing at least hydrogen as a constituent element to generate H radicals and inject the H radicals into a plasma atmosphere. Particularly preferred as such a radical source material is hydrogen gas (H ₂ ).

  As the raw material, various substances having at least carbon as a constituent element can be selected. Only one kind of substance may be used, or two or more kinds of substances may be used in an arbitrary ratio. An example of a preferable raw material is a substance (hydrocarbon or the like) containing at least carbon and hydrogen as constituent elements. As another example of a preferable raw material, a substance (fluorocarbon or the like) having at least carbon and fluorine as constituent elements can be given.

  In one preferred embodiment of the production method disclosed herein, based on the concentration of at least one radical in the reaction chamber (for example, the concentration of at least one radical among a carbon radical, a hydrogen radical, and a fluorine radical), Adjust at least one of the carbon nanowall production conditions. Examples of production conditions that can be adjusted based on such radical concentration include the amount of raw material supplied, the intensity of plasma of the raw material (the severity of the plasma conditions), the amount of radicals (typically H radicals) injected, etc. Is mentioned. Such production conditions are preferably controlled by feeding back the radical concentration. According to such a production method, it is possible to more efficiently produce carbon nanowalls having properties and / or characteristics according to the purpose.

Moreover, according to this invention, the apparatus which manufactures carbon nanowall on the surface of a base material is provided. The apparatus includes a reaction chamber in which a source material containing at least carbon is supplied and the base material is disposed. Further, plasma discharge means for converting the raw material in the reaction chamber into plasma is included. Further, it includes a radical generation chamber to which a predetermined radical source material (typically, a radical source material having at least hydrogen as a constituent element) is supplied. Also included is a radical generating means for generating radicals from the radical source material in the radical generating chamber. The radical generated by the radical generating means can be introduced into the reaction chamber.
According to such a manufacturing apparatus, one or two or more conditions among the composition, supply amount, etc. of radicals introduced into the reaction chamber are changed to other one or two or more carbon nanowall manufacturing conditions (for example, plasma conditions of the raw material). And can be adjusted independently of the other manufacturing conditions. That is, the carbon wall production conditions can be adjusted with a high degree of freedom. Such a manufacturing apparatus is suitable as an apparatus for carrying out any of the carbon nanowall manufacturing methods described above.

In a preferred aspect of the manufacturing apparatus, the radical generating means is configured to irradiate the radical generating chamber with microwaves, UHF waves, VHF waves, or RF waves. This radical generating means is preferably configured as an inductively coupled plasma (ICP) generating mechanism. Alternatively, the radical generating means may be configured such that a member having a catalyst metal (Pt, Pd, W, Mo, Ni, etc.) is disposed facing the radical generation chamber and the catalyst metal member can be heated. Good. For example, it can be set as the structure which has arrange | positioned the wavy Ni wire (catalyst metal member) inside the radical generation chamber. H ₂ as a radical source material is introduced and brought into contact with a heater in which a current is passed through the wire. Thereby, H radicals can be generated by the catalytic action of Ni. The heating temperature of the catalyst metal can be, for example, about 300 to 800 ° C., and is usually preferably about 400 to 600 ° C. The plasma discharge means is preferably configured as a capacitively coupled plasma (CCP) generating mechanism.

  In another preferred embodiment of the above production apparatus, the radical generating means can introduce a radical into the reaction chamber from a radical introduction port provided to expand toward the carbon nanowall formation surface of the substrate. It is configured. In another preferred embodiment, a plurality of radical introduction ports are dispersedly arranged at positions facing the carbon nanowall formation surface of the substrate arranged in the reaction chamber. According to such a configuration, it is possible to more efficiently form carbon nanowalls on the formation surface. In the case where the carbon nanowall is formed in a relatively wide range of the substrate, the effect of such a configuration is particularly well exhibited.

  The carbon nanowall manufacturing apparatus disclosed herein can further include a concentration measuring means for measuring the concentration (density) of carbon radicals in the reaction chamber. The measuring means includes emission line emitting means for emitting the radical emission line (that is, the carbon atom emission line) into the reaction chamber. Also included is a light receiving means for receiving a light emitting line emitted from the emitting means. According to the apparatus having such a configuration, the production conditions can be more accurately adjusted based on the concentration of carbon radicals in the reaction chamber. Alternatively, the concentration of carbon radicals in the reaction chamber can be managed with higher accuracy. Accordingly, it is possible to efficiently produce carbon nanowalls having properties and / or characteristics according to the purpose. The emission line emitting means can be configured to emit an emission line specific to a carbon radical (carbon atom) by adding appropriate energy to a gas containing at least carbon as a constituent element, for example.

  The manufacturing apparatus may further include a concentration measuring unit that measures the concentration of H radicals (hydrogen atoms) in the reaction chamber. Further, a concentration measuring means for measuring the concentration of fluorine radicals (fluorine atoms) in the reaction chamber can be provided. Such a measuring unit may include a light emitting line emitting unit that emits a light emitting line corresponding to the type of radical to be measured, and a light receiving unit that receives the light emitting line emitted from the emitting unit. it can.

  The manufacturing apparatus includes a control unit that adjusts at least one carbon nanowall manufacturing condition based on a radical concentration measurement result by the measurement mechanism. Examples of manufacturing conditions that can be adjusted based on the measurement results include: the amount of raw material supplied, the plasma intensity of the raw material, the amount of radicals (typically H radicals) injected, the amount of radical source material supplied, the radicals The radicalization strength of the source material can be increased. Such production conditions are preferably controlled by feeding back the measurement result of the radical concentration. According to such a production method, it is possible to more efficiently produce carbon nanowalls having properties and / or characteristics according to the purpose.

  Hereinafter, preferred embodiments of the present invention will be described in detail. It should be noted that technical matters other than the contents particularly mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters for those skilled in the art based on the prior art. The present invention can be carried out based on the technical contents disclosed in the present specification and the common general technical knowledge in the field.

As the raw material used for the production of the carbon nanowall, various substances having at least carbon as a constituent element can be selected. Examples of elements that can form the raw material together with carbon include one or more selected from hydrogen, fluorine, chlorine, bromine, nitrogen, oxygen, and the like. Examples of preferable source materials include source materials substantially composed of carbon and hydrogen, source materials substantially composed of carbon and fluorine, and source materials substantially composed of carbon, hydrogen and fluorine. . Saturated or unsaturated hydrocarbon (for example, CH ₄ ), fluorocarbon (for example, C ₂ F ₆ ) and the like can be preferably used. A linear, branched or cyclic molecular structure can be used. Usually, it is preferable to use a source material (source gas) that exhibits a gaseous state at normal temperature and pressure. Only one type of material may be used as the source material, or two or more types of materials may be used in any proportion. The type (composition) of the raw material used may be constant throughout the carbon wall manufacturing stage (for example, the growth process), or may vary depending on the manufacturing stage. Depending on the properties (for example, wall thickness) and / or characteristics (for example, electrical characteristics) of the target carbon nanostructure, the type (composition) of the raw material used, the supply method, etc. can be appropriately selected. .

As the radical source material, a material having at least hydrogen as a constituent element can be preferably used. It is preferable to use a radical source material (radical source gas) that exhibits a gaseous state at normal temperature and pressure. A particularly preferred radical source material is hydrogen gas (H ₂ ). In addition, a substance that can generate H radicals by decomposition, such as hydrocarbon (CH ₄ or the like), can be used as the radical source substance. Only one type of material may be used as the radical source material, or two or more types of materials may be used in any proportion.

In the manufacturing method disclosed herein, radicals are injected into a plasma atmosphere in which the source material is turned into plasma. As a result, the plasma of the raw material and radicals (typically H radicals) are mixed. Carbon nanowalls are formed (grown) by the carbon deposited on the base material from the mixed region. Examples of the base material that can be used include a base material in which at least a region where carbon nanowalls are formed is made of a material such as Si, SiO ₂ , Si ₃ N ₄ , GaAs, or Ai ₂ O ₃ . The whole base material may be comprised with the said material. In the said manufacturing method, carbon nanowall can be directly produced on the surface of the said base | substrate, without using especially catalysts, such as nickel iron. A catalyst (typically a transition metal catalyst) such as Ni, Fe, Co, Pd, or Pt may be used. For example, a thin film of the catalyst (for example, a film having a thickness of about 1 to 10 nm) may be formed on the surface of the substrate, and carbon nanowalls may be formed on the catalyst coating. The external shape of the base material to be used is not particularly limited. Typically, a plate-like base material (substrate) is used.

<First embodiment>
One structural example of the carbon nanowall (carbon nanostructure) manufacturing apparatus according to this application is shown in FIG. The apparatus 1 includes a reaction chamber 10, plasma discharge means 20 that generates plasma in the reaction chamber 10, and radical supply means 40 connected to the reaction chamber 10.

The plasma discharge means 20 is configured as a parallel plate capacitively coupled plasma (CCP) generating mechanism. The first electrode 22 and the second electrode 24 constituting the plasma discharge means 20 of the present embodiment both have a substantially disc shape. These electrodes 22 and 24 are disposed in the reaction chamber 10 so as to be substantially parallel to each other. Typically, the first electrode 22 is disposed on the upper side and the second electrode 24 is disposed on the lower side thereof.
A power supply 28 is connected to the first electrode (cathode) 22 via a matching network 26. These power supply 28 and matching circuit 26 allow RF waves (for example, 13.56 MHz), UHF waves (for example, 500 MHz), VHF waves (for example, 27 MHz, 40 MHz, 60 MHz, 100 MHz, 150 MHz), or microwaves (for example, 2.45 GHz). ) Can be generated. In this embodiment, at least an RF wave can be generated.
The second electrode (anode) 24 is disposed in the reaction chamber 10 away from the first electrode 22. The distance between the electrodes 22 and 24 can be set to about 0.5 to 10 cm, for example. In this example, it was about 5 cm. The second electrode 24 is grounded. At the time of manufacturing the carbon nanowall, the substrate (base material) 5 is disposed on the second electrode 24. For example, the substrate 5 is disposed on the surface of the second electrode 24 so that the surface of the base material 5 on which the carbon nanowall is to be manufactured is exposed (opposite the first electrode 22). The second electrode 24 incorporates a heater 25 (for example, a carbon heater) as a substrate temperature adjusting means. The temperature of the substrate 5 can be adjusted by operating the heater 25 as necessary.

  The reaction chamber 10 is provided with a raw material inlet 12 through which a raw material (raw material gas) can be supplied from a supply source (not shown). In a preferred embodiment, the inlet 12 is arranged so that the source gas can be supplied between the first electrode (upper electrode) 22 and the second electrode (lower electrode) 24. Further, the reaction chamber 10 is provided with a radical inlet 14 through which radicals can be introduced from a radical supply means 40 described later. In a preferred embodiment, the inlet 14 is arranged so that radicals can be introduced between the first electrode 22 and the second electrode 24. Further, the reaction chamber 10 is provided with an exhaust port 16. The exhaust port 16 is connected to a vacuum pump (not shown) or the like as pressure adjusting means (pressure reducing means) for adjusting the pressure in the reaction chamber 10. In a preferred embodiment, the exhaust port 16 is disposed below the second electrode 24.

  The radical supply means 40 includes a radical generation chamber 41 and a radical generation means 50 that generates radicals from the radical source material in the radical generation chamber 41. This radical generating means 50 is configured as an inductively coupled plasma (ICP) generating mechanism. For example, the coil 52 can be arranged around the radical generation chamber 41. In this example, a coil 52 was formed by spirally winding a quarter inch copper tube around the radical generating chamber 41 formed by using a quartz tube having an inner diameter of 26 mm and a length of 20 mm. . The coil 52 can be cooled by running water or the like. A power source 58 is connected to the radical generating means 50 (coil 52) through a matching circuit 56. Thereby, at least one of an RF wave (13.56 MHz), a UHF wave (for example, 500 MHz), and a VHF wave (for example, 100 MHz) can be generated. In this embodiment, at least an RF wave can be generated. Note that microwaves (eg, 2.45 GHz) may be directly introduced to generate plasma, thereby generating radicals. In this case, the coil 52 can be omitted.

  The radical generation chamber 41 is provided with a radical source inlet 42 through which a radical source material 36 can be introduced from a supply source (not shown). The radical generation chamber 41 is connected to the radical inlet 14 of the reaction chamber 10. In a preferred embodiment, a radical introduction port 42 is provided on one end side in the longitudinal direction of the tubular radical generation chamber 41, the other end side is connected to the radical introduction port 14 of the reaction chamber 10, and a coil 52 is disposed therebetween. Yes. In this embodiment, the radical generation chamber 41 is arranged on the side of the reaction chamber 10, but the position of the radical generation chamber is not limited to this. For example, it may be arranged above the reaction chamber or below. Or it can also be set as the structure which has arrange | positioned (accommodated) the radical generating chamber inside the reaction chamber.

Using the apparatus 1 having such a configuration, for example, carbon nanowalls can be manufactured as follows.
That is, the base material 5 is set on the second electrode 24, and a gaseous source material (source gas) 32 is supplied from the source inlet 12 to the reaction chamber 10 at a predetermined flow rate. Further, a gaseous radical source material (radical source gas) 36 is supplied from the radical source inlet 42 to the radical generation chamber 41 at a predetermined flow rate. A vacuum pump (not shown) connected to the exhaust port 16 is operated, and the internal pressure of the reaction chamber 10 (total pressure of the partial pressure of the raw material gas and the partial pressure of the radical source gas) is adjusted to about 10 to 1000 mTorr.
In addition, the ratio of the preferable supply amounts of the source gas and the radical source gas may vary depending on the type (composition) of those gases, the properties and characteristics of the target carbon nanowall, and the like. For example, when a hydrocarbon or fluorocarbon having 1 to 3 carbon atoms is used as the source gas and hydrogen gas is used as the radical source gas, the ratio of the supply amount of the source gas / radical source gas (for example, the temperature is set to the same level). (The ratio of the flow rate at the time) can be supplied in the range of 2/98 to 60/40. This supply ratio is preferably in the range of 5/95 to 50/50, more preferably in the range of 10/90 to 30/70.

  And RF power of about 13.56 MHz and 5 W to 2 KW, for example, is input from the power supply 28. Thereby, the source gas 32 is mainly converted into plasma between the first electrode 22 and the second electrode 24 to form a plasma atmosphere 34. Further, RF power of about 13.56 MHz and about 10 to 1000 W is input from the power source 58, for example. As a result, the radical source gas 36 in the radical generation chamber 41 is decomposed to generate radicals 38. The generated radicals 38 are introduced into the reaction chamber 10 from the radical inlet 14 and injected into the plasma atmosphere 34. Thereby, the plasma of the source gas constituting the plasma atmosphere 34 and the radicals 38 injected from the outside are mixed. In this way, carbon nanowalls can be grown on the surface of the substrate 5 disposed on the second electrode 24. At this time, it is preferable to keep the temperature of the substrate 5 at about 100 to 800 ° C. (more preferably about 200 to 600 ° C.) using the heater 25 or the like.

<Second embodiment>
The second embodiment is an example in which the configuration of the radical supply means is different from the apparatus of the first embodiment. Hereinafter, members having the same functions as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.
As shown in FIG. 2, the radical supply means 40 provided in the apparatus 2 according to this embodiment has a plasma generation chamber 46 above the reaction chamber 10. The plasma generation chamber 46 and the reaction chamber 10 are partitioned by a partition wall 44 provided to face the carbon nanowall formation surface of the substrate 5. A power source 28 is connected to the partition wall 44 via the matching circuit 26. That is, the partition wall 44 in this embodiment also functions as the first electrode 22. In addition, the apparatus 2 includes high-frequency applying means 60 that applies an RF wave, a VHF wave, or a UHF wave between the wall surface of the plasma generation chamber 46 and the partition wall 44. Thereby, the plasma 33 can be generated from the radical source gas 36. In the high frequency applying means 60 shown in FIG. 2, reference numeral 62 indicates an AC power source, reference numeral 63 indicates a bias power source, and reference numeral 64 indicates a filter.
Ions generated from the plasma 33 disappear at the partition walls 44 and are neutralized to become radicals 38. At this time, the neutralization rate can be increased by appropriately applying an electric field to the partition wall 44. Moreover, energy can also be given to the neutralized radical. A large number of through holes are dispersed in the partition wall 44. These through holes become a large number of radical inlets 14, radicals 38 are introduced into the reaction chamber 10, diffused as they are, and injected into the plasma atmosphere 34. As shown in the figure, these inlets 14 are arranged so as to extend in the surface direction of the upper surface of the substrate 5 (the surface facing the first electrode 22, that is, the carbon nanowall forming surface).
According to the apparatus 2 having such a configuration, the radicals 38 can be introduced more uniformly in a wider range in the reaction chamber 10. Thus, carbon nanowalls can be efficiently formed in a wider range (area) of the substrate 5. In addition, carbon nanowalls having a more uniform structure (properties, characteristics, etc.) at each part in the plane direction can be formed. According to the present embodiment, one or more of these effects can be realized.

The partition wall 44 may be formed by coating a surface with a material having high catalytic function such as Pt, or such a material itself. By applying an electric field between the partition wall 44 having such a configuration and the plasma atmosphere 34 (typically, applying a negative bias to the partition wall 44), ions in the plasma atmosphere 34 are accelerated, and the partition wall 44 is sputtered. To do. Thereby, atoms (such as Pt) or clusters having a catalytic function can be injected into the plasma atmosphere 34.
In the process of forming the carbon nanowall, radicals (typically H radicals) 38 injected from the plasma generation chamber 46, radicals and / or ions containing at least carbon generated in the plasma atmosphere 34, and as described above An atom or cluster having a catalytic function generated and injected by sputtering of the partition wall 44 is used. Thereby, atoms, clusters or fine particles having a catalytic function can be deposited inside and / or on the surface of the obtained carbon nanowall. Since carbon nanowalls having such atoms, clusters or fine particles can exhibit high catalytic performance, they can be applied as electrode materials for fuel cells.

  In addition, although the apparatus 2 shown in FIG. 2 is comprised so that the plasma 33 may be produced | generated from the radical source gas 36 with a high frequency, it is good also as a structure which produces | generates this plasma 33 with a microwave. For example, as in the apparatus 3 shown in FIG. 3, a waveguide 47 for introducing the microwave 39 is provided above the plasma generation chamber 46. Then, a microwave is introduced into the plasma generation chamber 46 from the quartz window 48 using the slot antenna 49 to generate high-density plasma 332. The plasma 332 can be diffused into the plasma generation chamber 46 (plasma 334) and radicals 38 can be generated therefrom. In FIG. 3, the plasma discharge means 20 is partially omitted. A bias can be appropriately applied to the partition 44 shown in FIG. For example, a bias is applied between the plasma 334 in the plasma generation chamber 46 and the partition 44 or between the plasma atmosphere 34 and the partition 44 in the reaction chamber 10. The direction of the bias is variable as appropriate. A configuration in which a negative bias can be applied to the partition wall 44 is preferable.

FIG. 4 shows another configuration example of the apparatus having the radical introduction port 14 provided so as to spread toward the carbon nanowall formation surface. As shown in the figure, the radical supply means 40 provided in the apparatus 4 has a radical generation chamber 41 and a radical diffusion chamber 43 into which the radical 38 generated in the radical generation chamber 41 is introduced. The radical diffusion chamber 43 is provided in a cylindrical shape on the outer periphery of the reaction chamber 10 via a partition wall 44. The radical 38 can be introduced into the reaction chamber 10 from the radical inlet 14 provided in each part of the partition wall 44 (that is, spread in the circumferential direction of the base material 5).
Alternatively, like the apparatus 6 shown in FIG. 5, the plasma generation chamber 46 in the configuration of the apparatus 2 (see FIG. 2) may be continuously provided from the upper side to the outer periphery of the reaction chamber 10. By adopting such a configuration, radicals 38 can be supplied from a wider area (the entire side and upper part) and injected into the plasma atmosphere 34. In FIG. 5, a part of the high frequency applying means 60 and the plasma discharging means 20 is not shown. These devices 4 and 6 (see FIGS. 4 and 5) can be configured so that a bias can be appropriately applied to the partition wall 44, as in the device 3 shown in FIG. In the apparatus 6, a bias may be applied to the partition wall 44 located at any position in the upper part and the periphery of the reaction chamber 10.

<Third embodiment>
The third embodiment is an example in which radical concentration measuring means is provided in the apparatus of the first embodiment. Hereinafter, members having the same functions as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. As shown in FIG. 6, the apparatus 7 according to the present embodiment is provided with radical concentration measuring means 70 for measuring the concentration of C radicals (carbon atoms) in the reaction chamber 10. The measurement means 70 includes a light emission line emitter 72 as light emission line emission means for emitting a light emission line 75 (for example, a light emission line having a wavelength of 296.7 nm) specific to a carbon atom (carbon radical) into the reaction chamber 10; And a light receiver 74 as light receiving means for receiving (detecting) the light emission line 75. The light emission line 75 emitted from the light emission line emitter 72 passes between the first electrode 22 and the second electrode 24 and reaches the light receiver 74. Or you may comprise so that the light emission line 75 inject | emitted from the injector 72 may pass the other location in the reaction chamber 10, and may reach the light receiver 74. FIG. For example, as indicated by a virtual line in FIG. 6, the light emitting line 75 can pass through the second electrode 24 (exhaust port 16 side) and reach the light receiver 74.

  The emission line 75 of carbon atoms is absorbed according to the concentration of carbon radicals (carbon atoms) existing between the emitter 72 and the light receiver 74. Therefore, for example, the intensity of the light emission line 75 detected by the light receiver 74 at an arbitrary measurement time and the light emission line 75 detected by the light receiver 74 when substantially no carbon radical is present in the path of the light emission line 75. From the difference in intensity, the concentration (density) of carbon radicals at the measurement time can be grasped. Further, by controlling the manufacturing conditions so that the detected intensity of the light emission line 75 is maintained at the same level as that at the start of manufacturing, for example, fluctuations in the carbon radical concentration during manufacturing can be suppressed. By monitoring the concentration of carbon radicals in this way, the concentration of carbon radicals in reaction chamber 10 and / or other production conditions can be adjusted more accurately. For example, a carbon radical concentration detection signal detected by the light receiver 74 is sent to a control circuit 76 connected to a source gas supply amount adjustment mechanism (for example, a solenoid valve) (not shown), and the intensity of this signal falls within a predetermined range. Thus, the supply amount of the source gas 32 can be adjusted. Thus, by setting it as the structure which can adjust manufacturing conditions according to the radical density | concentration in reaction chamber, the carbon nanowall which has the property and / or characteristic according to the objective can be manufactured more efficiently. For example, improvement of carbon nanowall yield, improvement of shape (property) accuracy, improvement of shape (property) reproducibility, saving of use amount of source gas and / or radical source gas, and easier control of production conditions One or more effects can be realized.

In addition, the apparatus 7 can be configured to include radical concentration measuring means 70 configured to measure the concentration of H radicals (hydrogen atoms) in the reaction chamber 10. In this case, a light emission line emitter 72 that emits a light emission line 75 unique to hydrogen atoms (H radicals) and a light receiver 74 that detects the light emission line 75 are used. Alternatively, the concentration of F radicals (fluorine atoms) in the reaction chamber 10 by a light emission line emitter 72 that emits a light emission line 75 unique to fluorine atoms (fluorine radicals) and a light receiver 74 that detects the light emission line 75. It is good also as a structure provided with the radical concentration measuring means 70 comprised so that it might measure. Further, it may be configured to include a radical concentration measuring means 70 for measuring the concentration of C ₂ radical in the same manner. In this way, a configuration including the radical concentration measuring means 70 having the light emitting line emitter 72 that emits the light emitting line 75 corresponding to the type of radical to be measured and the light receiver 74 that detects the light emitting line 75, and can do. For example, a measuring means capable of measuring the concentration of at least one radical among C, C ₂ , H, F, CF ₃ , CF ₂ and CF can be provided. You may provide the some measurement means which can measure 2 or more types among these.

  Note that a radical concentration measuring means having an emission line emitter that emits an emission line unique to hydrogen atoms (H radicals) and a light receiver that detects the emission line is used to change the concentration of H radicals in the radical generation chamber 41. You may provide so that it can measure. Alternatively, such H radical concentration measuring means may be provided so that the concentration of H radicals in the plasma generation chamber 46 or the radical diffusion chamber 43 can be measured.

Next, an experimental example in which a carbon nanostructure is manufactured using the above-described apparatus 1 and an experimental example in which the characteristics of the obtained carbon nanostructure are evaluated will be described.
<Experimental example 1>
In this experimental example, C ₂ F ₆ was used as the source gas 32. Hydrogen gas (H ₂ ) was used as the radical source gas 36. As the substrate 5, a silicon (Si) substrate having a thickness of about 0.5 mm was used. The silicon substrate 5 does not substantially contain a catalyst (such as a metal catalyst).
The silicon substrate 5 was set on the second electrode 24 so that the (100) surface thereof faced the first electrode 22 side. C ₂ F ₆ (raw material gas) 32 was supplied from the raw material inlet 12 to the reaction chamber 10, and hydrogen gas (radical source gas) 36 was supplied from the radical source inlet 42. Further, the gas in the reaction chamber 10 was exhausted from the exhaust port 16. Then, supply amounts (flow rates) of the source gas 32 and the radical source gas 36 so that the partial pressure of C ₂ F ₆ in the reaction chamber 10 is about 20 mTorr, the partial pressure of H ₂ is about 80 mTorr, and the total pressure is about 100 mTorr. ) And exhaust conditions were adjusted.
While supplying the raw material gas 32 under these conditions, RF power of 13.56 MHz and 100 W is input from the power source 28 to the first electrode 22, and the raw material gas (C ₂ F ₆ ) 32 in the reaction chamber 10 is irradiated with RF waves. did. As a result, the source gas 32 was turned into plasma, and a plasma atmosphere 34 was formed between the first electrode 22 and the second electrode 24. Further, while supplying the radical source gas 36 under the above conditions, 13.56 MHz and 50 W RF power is input from the power source 58 to the coil 52, and an RF wave is applied to the radical source gas (H ₂ ) 36 in the radical generation chamber 40. Irradiated. H radicals thus generated were introduced into the reaction chamber 10 from the radical inlet 14. In this way, carbon nanostructures were grown (deposited) on the (100) surface of the silicon substrate 5. In this experimental example, the growth time of the structure was set to 2 hours. Meanwhile, the temperature of the substrate 5 was maintained at about 500 ° C. by using a heater 25 and a cooling device (not shown) as needed.

<Experimental Examples 2 to 4>
The conditions for generating radicals (here, H radicals) 38 were changed from those in Experimental Example 1. That is, the RF input power from the power source 58 to the coil 52 was set to 100 W (Experimental Example 2), 200 W (Experimental Example 3), and 400 W (Experimental Example 4), respectively. In other respects, a carbon nanostructure was produced on the (100) plane of the silicon substrate 5 in the same manner as in Experimental Example 1.
The above experimental conditions are summarized in Table 1. The “pressure ratio” represents the ratio of the partial pressure of the source gas / radical source gas supplied to the apparatus (that is, the ratio of the supply amount).

The structures formed in Experimental Examples 1 to 4 were observed with a scanning electron microscope (SEM). 7 to 10 are SEM images obtained by observing the structures formed in Experimental Examples 1 to 4 from the upper surface. 11 to 14 are SEM images obtained by observing each structure from a cross section, and FIGS. 15 to 18 are SEM images obtained by observing each structure at a higher magnification. FIG. 19 is an SEM image of the structure according to Experimental Example 4 observed from a cross section at a higher magnification than that in FIG. 20 is an SEM image obtained by observing the structure according to Experimental Example 4 from the upper surface at a higher magnification than that in FIG.
As can be seen from these figures, according to Experimental Examples 1 to 4, a two-dimensional carbon sheet (carbon nanowall) was formed almost perpendicularly to the (100) plane of the substrate 5. The average thickness (average thickness of the carbon sheet) of the carbon nanowalls formed in these experimental examples was about 10 to 30 nm. The shape (property) of the carbon nanowall was greatly different depending on the conditions for generating H radicals (RF input power from the power source 58 to the coil 52). Further, under the conditions of Experimental Examples 1 to 4, the influence of the H radical generation condition on the height of the carbon nanowall was relatively small. That is, the average height of the carbon nanowalls formed in these experimental examples was about 300 nm. These observation results suggest that the shape of the obtained carbon nanowall can be controlled by adjusting the amount of H radicals generated (the amount of H radicals supplied to the reaction chamber 10).

<Experimental Examples 5-8>
In Experimental Example 4, the time for growing the structure on the substrate was 0.5 hour (Experimental Example 5), 1 hour (Experimental Example 6), 2 hours (Experimental Example 7), and 3 hours (Experimental Example 8). did. In other respects, a carbon nanostructure was produced on the (100) plane of the silicon substrate 5 in the same manner as in Experimental Example 4. These experimental conditions are summarized in Table 2. Experimental example 7 has substantially the same conditions as experimental example 4.

The structures formed in Experimental Examples 5 to 7 were observed with SEM. 21 to 24 are SEM images obtained by observing the structures formed in Experimental Examples 5 to 7 from the upper surface. 25 to 28 are SEM images obtained by observing the cross section of each structure.
As can be seen from these figures, the properties of the structure formed on the substrate 5 differ depending on the growth time. As well shown in FIGS. 25 to 28, the height of the structure increases as the growth time increases. As shown in FIG. 29, under the conditions of Experimental Examples 5 to 8, a substantially linear relationship (proportional relationship) was observed between the length of the growth time and the height of the structure.

<Experimental Examples 9 to 10>
C ₂ F ₆ (Experimental Example 9) or CH ₄ (Experimental Example 10) was used as the source gas 32, and the carbon nanostructure was formed on the (100) plane of the silicon substrate 5 under the same conditions as in Experimental Example 4 for the other points. The body was made. These experimental conditions are summarized in Table 3. Note that Experimental Example 9 has substantially the same conditions as Experimental Example 4.

FIG. 30 shows an SEM image obtained by observing the structure formed in Experimental Example 9 from the upper surface, and FIG. 31 shows an SEM image obtained by observing the structural body formed by Experimental Example 10 from the upper surface. The carbon nanowall (FIG. 30) according to Experimental Example 9 produced using fluorocarbon (here, C ₂ F ₆ ) as a source gas has an average wall thickness of about 10 to 30 nm. On the other hand, the carbon nanowall (FIG. 31) according to Experimental Example 10 produced using hydrocarbon (here, CH ₄ ) as a source gas has an average wall thickness of about several nm. Thus, when C ₂ F ₆ was used as the source gas, carbon nanowalls with clearly thicker walls were formed than when CH ₄ was used as the source gas. The wall thickness can be controlled by the amount of C ₂ F ₆ . In addition, the carbon nanowall according to Experimental Example 9 and the carbon nanowall according to Experimental Example 10 are different in shape at points other than the thickness (for example, the flatness of the wall). These observation results suggest that the properties of the obtained carbon nanowall can be controlled by appropriately selecting the type and / or composition of the source gas.

<Experimental example 11>
A voltage was applied to the carbon nanowall obtained in Experimental Example 9 to evaluate the electron emission characteristics. The result is shown in FIG. As shown in the figure, when the electric field strength is about 5.5 to 6 V / μm or more, the measurement current rapidly increased. This result suggests that the carbon nanowall obtained in Experimental Example 9 can be useful as a constituent material of a field emission electron source (electrode). Moreover, the surface of such a carbon nanowall can be coated with Pt or the like to form a structure that exhibits highly efficient catalytic action. Thus, the carbon nanowall provided with a catalyst can be applied to, for example, an electrode of a fuel cell.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
For example, the manufacturing apparatus shown in FIGS. 1 to 6 can be configured such that a high frequency (for example, 400 KHz, 1.5 MHz, 13.56 MHz, etc.) can be applied to the second electrode (lower electrode) 24. According to this configuration, it is possible to control the energy of incident charged particles. FIG. 33 and FIG. 34 schematically show a specific example of a configuration in which a high frequency is applied to the second electrode 24. Reference numeral 242 in FIG. 33 denotes an AC power source that generates a high frequency of, for example, 400 KHz, 1.5 MHz, or 13.56 MHz. Moreover, the code | symbol 244 in FIG. 34 is AC power supply which generate | occur | produces the high frequency of 13.56 MHz, for example. Reference numeral 246 in the figure is an AC power source that generates a high frequency of, for example, 400 KHz. A low pass filter 248 is connected between these power supplies 244 and 246. Note that a DC power supply may be used instead of the AC power supply 246.
In addition, the technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

It is a schematic diagram which shows the manufacturing apparatus which concerns on 1st Example. It is a schematic diagram which shows the manufacturing apparatus which concerns on 2nd Example. It is a schematic diagram which shows the manufacturing apparatus which concerns on the modification of 2nd Example. It is a schematic diagram which shows the manufacturing apparatus which concerns on the modification of 2nd Example. It is a schematic diagram which shows the manufacturing apparatus which concerns on the modification of 2nd Example. It is a schematic diagram which shows the manufacturing apparatus which concerns on 3rd Example. It is the SEM image which observed the structure formed by Experimental example 1 (RF input power; 50W) from the upper surface. It is the SEM image which observed the structure formed by Experimental example 2 (RF input power; 100W) from the upper surface. It is the SEM image which observed the structure formed by Experimental example 3 (RF input power; 200W) from the upper surface. It is the SEM image which observed the structure formed by Experimental example 4 (RF input power; 400 W) from the upper surface. 4 is an SEM image obtained by observing a cross section of a structure formed in Experimental Example 1. FIG. 10 is an SEM image obtained by observing a cross section of a structure formed in Experimental Example 2. 10 is an SEM image obtained by observing a cross section of a structure formed in Experimental Example 3. 10 is an SEM image obtained by observing a cross section of a structure formed in Experimental Example 4. 4 is an SEM image obtained by observing a cross section of a structure formed in Experimental Example 1. FIG. 10 is an SEM image obtained by observing a cross section of a structure formed in Experimental Example 2. 10 is an SEM image obtained by observing a cross section of a structure formed in Experimental Example 3. 10 is an SEM image obtained by observing a cross section of a structure formed in Experimental Example 4. 10 is an SEM image obtained by observing a cross section of a structure formed in Experimental Example 4. 10 is an SEM image obtained by observing the structure formed in Experimental Example 4 from the upper surface. It is the SEM image which observed the structure formed by Experimental example 5 (growth time; 0.5 hour) from the upper surface. It is the SEM image which observed the structure formed by Experimental example 6 (growth time; 1 hour) from the upper surface. It is the SEM image which observed the structure formed by Experimental example 7 (growth time; 2 hours) from the upper surface. It is the SEM image which observed the structure formed by Experimental example 8 (growth time; 3 hours) from the upper surface. 10 is an SEM image obtained by observing a cross section of a structure formed in Experimental Example 5. 10 is an SEM image obtained by observing a cross section of a structure formed in Experimental Example 6. 10 is an SEM image obtained by observing a cross section of a structure formed in Experimental Example 7. 10 is an SEM image obtained by observing a cross section of a structure formed in Experimental Example 8. It is a characteristic view which shows the growth rate of a structure. Experimental Example 9 (source gas; C ₂ F ₆₎ a structure formed by a SEM image observed from above. Experimental Example 10 (raw material gas; CH ₄₎ is a SEM image obtained by observing the cross section of the structures formed by. 10 is a characteristic diagram showing an electron emission characteristic of a structure formed in Experimental Example 9. FIG. It is a schematic diagram which shows an example of the structure which applies a high frequency to a 2nd electrode. It is a schematic diagram which shows the other example of the structure which applies a high frequency to a 2nd electrode.

Explanation of symbols

1, 2, 3, 4, 6, 7 Carbon nanowall production equipment 5 Substrate (base material)
DESCRIPTION OF SYMBOLS 10 Reaction chamber 14 Radical inlet 20 Plasma discharge means 22 1st electrode 24 2nd electrode 25 Heater 26 Matching circuit 28 Power supply 32 Source gas (source material)
34 Plasma atmosphere 36 Radical source gas (radical source material)
38 radical 40 radical supply means 41 radical generation chamber 43 radical expansion chamber 44 partition 50 radical generation means 52 coil 56 matching circuit 58 power supply 70 radical concentration measurement means 72 light emission emitter (light emission emission means)
74 Light receiver (light receiving means)
76 Control circuit (control means)

Claims (16)

  At least a part of the reaction chamber is formed with a plasma atmosphere in which a source material containing at least carbon as a constituent element is turned into plasma, and radicals generated outside the atmosphere are injected into the plasma atmosphere to enter the reaction chamber. A method for producing carbon nanowalls, wherein carbon nanowalls are formed on the surface of a substrate.   The method according to claim 1, wherein the radical is generated by decomposing a radical source material outside the reaction chamber.   The radical is generated by irradiating the radical source material with microwaves, UHF waves, VHF waves or RF waves and / or bringing the radical source material into contact with a heated catalyst metal. The method of claim 2.   The method according to claim 1, wherein the radical includes a hydrogen radical.   The method according to any one of claims 1 to 3, wherein a radical source material containing at least hydrogen as a constituent element is decomposed to generate hydrogen radicals, and the hydrogen radicals are injected into the plasma atmosphere. .   The method according to claim 1, wherein the raw material contains at least carbon and hydrogen as constituent elements.   The method according to any one of claims 1 to 5, wherein the raw material contains at least carbon and fluorine as constituent elements.   Based on the concentration of at least one kind of radicals among carbon radicals, hydrogen radicals and fluorine radicals in the reaction chamber, at least one of the supply amount of the source material, the plasma intensity of the source material and the injection amount of the radicals The method according to claim 1, wherein the conditions are controlled. An apparatus for producing carbon nanowalls on the surface of a substrate,
A reaction chamber in which a source material containing at least carbon is supplied and the base material is disposed;
Plasma discharge means for converting the raw material in the reaction chamber into plasma;
A radical generation chamber to which a radical source material is supplied; and
Radical generating means for generating radicals from the radical source material in the radical generating chamber,
The carbon nanowall manufacturing apparatus comprised so that the radical produced | generated by the said radical generation means can be introduce | transduced into the said reaction chamber.   The radical generation means realizes at least one of irradiating the radical generation chamber with microwaves, UHF waves, VHF waves, or RF waves and heating the catalyst metal provided facing the radical generation chamber. The apparatus of claim 9, wherein the apparatus is configured to obtain.   The radical generating means is configured to be able to introduce radicals into the reaction chamber from a radical introduction port provided so as to spread toward a carbon nanowall formation surface of the base material. The apparatus according to 9 or 10. A concentration measuring means for measuring the concentration of carbon radicals in the reaction chamber;
The measurement means includes: an emission line emitting means for emitting the radical emission line into the reaction chamber; and a light receiving means for receiving the emission line emitted from the emission means. The device described in 1. A concentration measuring means for measuring the concentration of hydrogen radicals in the reaction chamber;
The measuring means includes: an emission line emitting means for emitting the radical emission line into the reaction chamber; and a light receiving means for receiving the emission line emitted from the emission means. The device described in 1. A concentration measuring means for measuring the concentration of fluorine radicals in the reaction chamber;
The measurement means includes: an emission line emitting means for emitting the radical emission line into the reaction chamber; and a light receiving means for receiving the emission line emitted from the emission means. The device described in 1.   Based on the measurement result of the radical concentration by the measuring means, at least one of the following conditions: source material supply amount, source material plasmaization intensity, radical injection amount, radical source material supply amount and radical source material radicalization intensity The apparatus according to claim 12, further comprising control means for controlling   The plurality of radical introduction ports are dispersedly arranged at positions facing the carbon nanowall formation surface of the base material arranged in the reaction chamber. Equipment.